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IFTLE 169 EMPC – Grenoble part 3: Fine Pitch RDL; Handling Ultra-thin Die; Backside Passivation as Stress Compensation

Leti / ST Micro – Interposer Fine Pitch RDL

Passive interposers redistribute the electrical lines from the attached upper dies down to the organic substrate through μPillars, RDL, TSVs and solder bumps, thus somehow acting as a pitch adapter between dies and substrate.

Backside RDL on a passive interposer can be created by either damascene integration or “conventional”  integration as shown in the figure below.

Damascene approach mainly consists in full wafer copper plating over etched trenches followed by a CMP, allowing to retrieve at the end, a fully planarized surface. This integration allows an easy access to sub-micron line/space widths but at a higher cost, mainly due to CMP steps.

leti 1

Leti / ST Micro have investigated investigate the minimum pitch that could be achieved with the conventional approach. Under their conditions they were able to achieve 8um l/s with high uniformity and reproducibility.

BESI/IMEC – Handling Ultra-thin Die

The use of ultra thin die (thickness less than 50um) requires specially designed handling solutions due to their fragility and flexibility.

BESI and IMEC have examined several tape types (UV vs thermal release), ejection systems, die size (5 x 5mm; 40um thick) and bump configurations.

Click to view full screen.

Click to view full screen.

They also examined both face up and face down to the wafer tape:

Besi 2

Their conclusions include: (1) proper dice/grind and stress relief needed to maximize die strength; (2) some UV tapes resulted in residues; (3) thermal release tapes gave larger process window; (4) stable and reliable picking of ultra-thin die can be achieved with throughputs greater than 3000 units per hour using several different hardware, maerial, process combinations.

SPTS – Low Temp Via Reveal Passivation with Stress Compensation

2.5 and 3DIC wafers require backside processing including thinning to reveal the TSV, passivation, RDL and creation of copper pillar connections. Before the wafer reveal process CMOS devices are usually temp bonded to carriers (Si or glass) and thinned to ca. 50um. The temperature stability of the temporary bonding adhesive sets a limit on the upper temp of subsequent processing steps. The current goal for this temperature would be ca. 190 C.

The backside passivation also serves to maintain the bow of the thinned wafers to a manageable level (ca. ~ 10mm) to allow subsequent processing steps. Full thickness 300mm wafers (770um) typically have incoming bow in the range of 100 – 200um. If thinned to  50um and released from the carrier the 300mm wafer would show a bow of several cm making them unprocessable and potentially lead to cracking after debond. Backside passivation stress can be tailored to compensate for the incoming wafer bow. CMOS cu/low-K wafers usually show tensile stress and thus backside stresses must be net tensile to compensate.

Compressively stressed SiN films generally give the best diffusion barrier properties. For the via reveal passivation stack compressive SiN with stress of – 100 MPa was used.

SiO films deposited using TEOS based chemistry is tunable from -200 to +200 MPa, but are must be taken since tensile SiO has a limited thickness cracking threshold.

SPTS

TEOS Cracking Threshold (left) and SiN Electrical Characteristics

The final solution was to develop a 190 C SiN film with a tensile stress of +200 MPa and a cracking threshold of 7um (deposited onto compressive SiN barrier).

For all the latest on 3DIC and advanced packaging, stay linked to IFTLE…

 

Hope to see you all at this years RTI ASIP. It is the 10th Anniversary of this 3D focused meeting.

RTI ASIP

 

 

IFTLE 168 EMPC Part 2: FC Market; BLR of BoP WLCSPs; Chip Embedding; Temp Stability of Molding Compounds

Yole – FC Market & Tech Trends

Rozalia Beica, newly appointed CTO of Yole Developpement, examined the FC marketplace. The FC market is currently growing at CAGR of 19% as a result of expanded use in memory, consumer electronics and mobile phones. In 2012 bumping capacity of 14MM 300mm equiv. was in place accounting for 81% of all “mid end” capacity.

FC technology is being reshaped by the demand for Cu pillar bumping (CPB) and microbumps which are both quickly becoming mainstream. CPB is expected to show 35% CAGR over the period 2010 – 2018.

FC capacity is expected to grow in the next 5 years in response to demand from (1) 28nm CMOS application processor (APE) and baseband (BB) applications;(2) next gen DDR memory and (3) 2.5/3DIC.

FC Bumping and CPB Forecast 2010 – 2018 (Click to view full screen)

FC Bumping and CPB Forecast 2010 – 2018
(Click to view full screen)

 

ASE – Board Level Reliability of BoP WLCSPs

There hsas been reduction of  the production cost for WLCSP packages for the past years. Today, many OSATs are working on further cost reduction with customized WLCSP package designs that are optimized for specific market needs.

For example, omitting the UBM layer on smaller WLCSP devices can reduce costs and may still meet the market requirement on package quality and reliability. Omitting the UBM requires 25% less process steps, from 4-mask process to 3-mask process.

ASE reports on the BLR performance of a 3-mask bump on polymer (BoP) WLCSP design vs  a 4-mask BoP WLCSP design for 0.4mm and 0.5mm ball pitch using  tin/silver/copper ( SAC) and SACNi (Ni doping) solders and reports on failure analysis.

WLCSP (a) 4 mask process with UBM; (b) 3 mask process without UBM; (c) failure modes for 3 mask process (Click to view full screen)

WLCSP (a) 4 mask process with UBM; (b) 3 mask process without UBM; (c) failure modes for 3 mask process
(Click to view full screen)

 

The polymer material can be polyimide (PI) or Polybenzobisoxazole (PBO) with thickness of  5um to 7.5um. In most BOP WLCSP packages, ASE states that PBO is the preferred material for better stress compliance, and hence better board level reliability.

For 3-mask WLCSP design, there is no UBM. The solder ball is directly attached to the redistribution layer, using polymer 2 to define the pad opening. Therefore, the electrolytic plating copper thickness for RDL needs to be sufficiently thick to avoid any problems due to Cu consumption during SnxCuy intermetallic (IMC) formation during thermal ageing. For these reasons the Cu RDL thickness is increased from 4um, on 4-mask WLCSP, to about 8um on the 3 mask process to ensure a reliable solder joint. the thickness of polymer-2 also needs to increase to 12um polymer-2 thickness to ensure line coverage. A 12um thick polymer-2 layer creates processing challenge for PI or PBO, and the thermal stress or residual stress after high temperature curing needs to be carefully controlled to guarantee the integrity of package structure.

After board level reliability test, failure analysis was performed to confirm the failure mode. The failure modes were classified as failed at PCB side Mode A, failed at component side Mode B and solder fracture Mode C. In the failure analysis, we found that BLR failure modes are governed by shear rate applied to the tested samples. High shear rate test, like drop test, tended to fail at the component side with IMC fracture (Mode B2) or residual solder on pad (Mode B3). But, for slow shear rate test, like temperature cycling test, the fail tended to occur at the solder joint (Mode C). They concluded that 3-mask the WLCSP does not change the failure mode in either temperature cycling test or drop test.

They conclude:

- BLR temperature cycling performance is governed by the WLCSP device size (DNP). The bigger the DNP, the worse temperature cycling lifetime. This was evident for both solder materials used in this study, even though the larger device has a larger solder joint size, and there was a larger difference between SAC405 devices than SACNi devices.

-  In general, the 3-mask WLCP has worse BLR performance than 4-mask WLCSP.

-  SACNi solder gives improved BLR Drop test performance (characteristic life, and first fails) for both 4-mask and 3-mask WLCSP devices.

-  They found the same failure mechanism and failure modes on 3-mask WLCSP as 4-mask WLCSP.

 

Chip Embedding at IMS

Ultra-thin chips (less than 50 μm thick) can be assembled by either on flexible films; i.e. chip-on-foil technology or by embedding them inside the foil. Initial work by the Institute for Microelectronics Stuttgart (IMS CHIPS) dealt with attempts to glue attach Chipfilm dies onto flexible foil substrates. They have now described research with less than  20μm thickness die with a two polymer (BCB and PI) ultra-thin chip imbedding approach.

Polymers used for embedding should be flexible and at the same time strong enough to keep the chip firmly embedded. To achieve an optimal solution for the desired process IMS used a combination of polymers where BCB serves as the embedding polymer for ultra-thin chips and the PI as the  reinforcement polymer. The X sectional structure is shown below.

Two Polymer Embedding of Ultra-thin Chips

Two Polymer Embedding of Ultra-thin Chips

The PI reinforcement layer provides strong yet bendable reinforcement for the entire chip stack. The BCB embedding polymer provides excellent electrical properties, low moisture absorption, compatibility with the interconnect metals and fine pitch patterning compatibility.  The process flow is shown below. An initial “adhesion lowering layer” is initially coated on the wafer to allow for package removal once the process is complete.

IFTLE 167 IARPA Trusted Integrated Chips program (TIC); The Apple A7

Halloween

In the US, we are approaching Oct 31, the day for pumpkins and witches. Hannah and Madeline wish all IFTLE readers a Happy Halloween.

H and M

IARPA Trusted Integrated Chips

At the IEEE 3DIC in San Francisco Dan Radack of IDA [Institute of Defense Analysis] recently gave an update on the  IARPA trusted Integrated Chip Program known as TIC

Background

From 19996 – 2006 the IC Fab at Ft Meade was used to fabricate ICs required for Govt. programs. It was mothballed 5-6 years ago. From 2003 to present the Govt. has used so called “trusted foundries” but they found that they were not able to provide everything that the Govt. needed.

With all of the top foundries now situated outside the US or owned by non US entities, there was a need for a new way of ensuring secure state of the art chip procurement. This certainly dovetailed with the interest in cyber security i.e. how to prevent counterfeits and the vision of needing more-than-Moore technology (i.e. sensors in a 3D chip stack) in the future.

Trusted Integrated Chips program TIC

In the summer of 2011 The Intelligence Advanced Research Projects Activity (IARPA) announced its  Trusted Integrated Chips program. TIC features what IARPA calls “split-manufacturing,” where fabrication of new chips is divided into Front-End-of-Line (FEOL) manufacturing consisting of transistor layers to be fabricated by offshore state-of-the-art” foundries lines and Back-End-of-Line (BEOL) development that would be fabricated by trusted U.S. facilities.

In this approach, the design intention is not disclosed to the FEOL fabricators. “FEOL circuit fabrication to the point of only the first metallization layer can be used to obfuscate the design and performance of an integrated chip thereby protecting the intellectual property of the designer. Alternately, circuit obfuscation can be realized through a chip integration strategy whereby only partial circuits are fabricated on any single chip but when integrated with other chips or wafers in a US manufacturing or packaging facility, a complete safe and secure circuit or system can be realized,” IARPA stated.

According to IARPA, the vision of the TIC Program is to ensure that the United States can:

• obtain the highest performance possible in integrated circuits;

• obtain near 100% assurance that designs are safe and secure — not compromised with malicious circuitry;

• ensure security of designs, capability, and performance while simultaneously protecting intellectual property; and

• realize secure systems combining advanced CMOS with other high value chips.

The TIC program is examining  a number of split-manufacturing concepts in the following areas:

• Mixed Signal                       • Photonics-CMOS                       • MEMS-CMOS

• Power-CMOS                      • RF CMOS                                  • Memory-CMOS

• Josephson Junctions-CMOS                    • Other systems integrated with CMOS

The five-year program was divided into three phases with the development and demonstration of split-manufacturing starting at the 130 nm technology node in Phase 1. It is anticipated that the TIC Program performers will scale the development of their capabilities to the 22 nm node at the end of a five-year period in Phase 3.

Sandia National Laboratories was selected to coordinate the FEOL and BEOL processing with Multi-Project Wafer runs carried out by the University of Southern California/Information Sciences Institute (USC/ISI) using their MOSIS service.

6 organizations did design of CMOS circuits in the MPW multi project wafer. Global foundries performed the front end work and  IBM Burlington fabricated the interconnect layers. Each of the 6 designers then capped the structure with their heterogeneous layer.

NGAS, Cornell, Lucent, Raytheon Vision systems, CMU, Stanford

Raytheon capped with focal plane array for vision system

Carnegie Mellon – cap with piezoelectric MEMS containing digital, analog and smart SRAM

Bell Labs / Lucent – cap in photonics layer

Northrup Grumman – InP mm wave circuits

Cornell – FPGA with ultrasonic comm. Cap

Stanford – cap with materials and ReRam (resistive RAM)

The program is now moving to 65 nm. The move to 28nm will be June or 2014

Details on the Apple A7

The Apple A7 is a PoP 64-bit SoC designed by Apple.  It first appeared in the iPhone 5S, which was introduced in September 2013. Apple states that it is up to twice as fast and has up to twice the graphics power compared to its predecessor, the Apple A6. The A7 is a 64-bit 1.3GHz dual-core CPU coupled with what’s believed to be a Power VR G6430 GPU. The A7 is manufactured by Samsung on a high-κ metal gate (HKMG) 28 nm process and the chip includes over 1 billion transistors on a die 102 mm2 in size.

A7

Fellow blogger Dick  James from Chipworks has sent the first shots of the PoP processor. He comments that  “”It looks as though there is some degree of bowing in the top package, and there is an interface layer between the two packages. Another surprise is silver wire in the Elpida DRAM package..the pitch of the TMV (through mold via) between the top and bottom packages is 0.35mm. Ball pitch on the base is 0.4mm. There are 3 rows of TMVs for a total of 456. Ball count on the base is 34 x 38 = 1292.”

Cross section of the A7 is shown below.

PoP

For all the latest on 3DIC and advanced packaging, stay linked to IFTLE.

IFTLE 166 IEEE 3DIC Conf part 1; 3DIC panel discussion; Ginti; Novati

The IEEE 3D System Integration Conference  met recently in SF to hold their 4th annual symposium. The conference which is held on a rotational basis in USA, Europe and Asia was chaired by Professor Paul Franzon of NC State Univ and yours truly (IFTLE i.e. Phil Garrou). What makes this conference different than other conferences with 3D emphasis is the concerted effort to bring all phases of the required 3D infrastructure together including processing, design, thermal and test.

Invited keynote talks included Maaike Visser Taklo of SINTEF discussing the European eBrains program which is looking at using 3D to integrate MEMS into heterogeneous stacks for, amongst other things,  bio and medical applications. Mitsu Koyanagi updated the group on activities at Tohoku University including their spin out of Ginti [Global Integration Initiative]. Bob Patti, CTO of Tezzaron which recently acquired the old Sematech fabs in Austin updated us on Tezzaron / Novati activities and Avi Bar-Cohen of DARPA brought us up to date on the DARPA ICECool programs.

Panel Discussion on Remaining 2.5/3D Obstacles

panel

Jan Vardaman of TechSearch moderated a panel entitled “Progress and Remaining Obstacles for 3D ICs and 2.5D HVM” which consisted of Bob Patti, CTO, Tezzaron, Prof Mitsumasa Koyanagi, Tohoku University; Dr Dimitrios Velenis, IMEC; Doug Anberg, Vice President,  Ultratech (a stepper manufacturer) and Dr Dongkai Shangguan, CEO of the  National Center for Advanced Packaging  (NCAP) in  China.

When panel members were asked about remaining material and equipment issues, Koyanagi discussed the issue of exposure tools pointing out that mask aligners did not have enough accuracy and needed very expensive 13” masks. His recommendation was i-line steppers such as Cannon.

When discussing imaging for interposers, Patti reported that interposers are by definition required to be quite large and are having trouble since current retical fields are i.e. 26 x 31mm. Anberg pointed out that in the next few years you will see 2-3X the retical field , but the cost will be more expensive optics.

Both Koyanagi and Velenis pointed out the need for better bond/debond yields and better thin die handling. Patti indicated that Tezzaron / Novati avoids that issue by doing their thinning after F2F wafer bonding so the bottom wafer becomes the carrier and is not ever removed.

All agreed that cost remains the number 1 obstacle to HVM and most agreed that improved yield and increased throughput were needed.

The interposer discussion, as with most other conferences, centered around whether silicon, glass or laminate would be the best choice. Patti offered that glass while a useful interposer material would require a major infusion of capital to get it off the ground. IFTLE as we have before, commented that glass will not enter the realm of being a real option till the flat panel display industry recognizes the opportunity and begins to address it.

Koyanagi offered that he did not see the silicon interposer market developing in Japan because the Japanese companies could not compete with TSMC.  Tohoku Univ has spun out a startup company Ginti for small volume 2.5/3D production.

GINTI

GINTI, which stands for the Global Integration Initiative, has been spun out of Tohoku University with Professor Mitsu Koyanagi as CEO. With a complete line of 200 and 300mm equipment their goal is to become a one stop shop for prototype and small volume concept, design, fabrication and testing of designs that need TSV and/ or 2.5D interposers. A base-line process is set up for pilot production which is capable of using commercial / customized 2D chips.

Koyanagi (left) and Hasegawa pose with  300mm wafer of 3DIC.

Koyanagi (left) and Hasegawa pose with 300mm wafer of 3DIC.

Tezzaron / Novati

IFTLE has previously discussed the Tezzaron purchase of SVTC (former Sematech fabs in Austin) [ see IFTLE 146, “TSMC Apple Rumors; Gartner OSAT Mkt Numbers; Novati”].

http://electroiq.com/insights-from-leading-edge/2013/05/iftle-146-tsmc-apple-rumors-gartner-osat-mkt-numbers-novati/

During his invited presentation “A Perspective on Manufacturing 2.5/3D” CTO Bob Patti indicated that from his perspective vendors have become much more “3D aware.”

Dave Chapman and Bob Patti - Tezzaron

Dave Chapman and Bob Patti – Tezzaron

Tezaron memory technology consists of a both a controller layer and an IO layer as shown below.

Tezzaron 1

Patti reports their current capacity is 12K 300mm wafers/mo going to 26K by 2016. He announced that Novati will become a US trusted foundry later this year.

Of special interest was Bobs remark that he sees future power conversion being done on the interposer.

As an aside… Patti specifically called out new New Mexico process engineers Walter White and lab technician Jesse Pinkman as having been invaluable in both fund-raising and 3DIC process development. “Their love of Chemistry and their trust in basic Scientific principles  has brought a new enthusiasm to our whole process development team” Chapman added “…there have been several instances while walking through the fab I have actually overheard Pinkman shouting out, “Yeah  Mr. White…Yeah  SCIENCE!” His enthusiasm is contagious.

Tezz 2

For all the latest on 3DIC and advanced packaging, stay linked to IFLE.

IFTLE 165 Semicon Taiwan contd: DRAM Consolidation, Smartphone Mkt; Packaging Materials Forecast

Semicon Taiwan 2013 consisted of several programs of interest to the IC packaging community. Taking a look at the Market Trends Forum chaired by Dr Burn Lin of TSMC.

DRAM Status – Charlie Chan –  Morgan Stanley

During their discussions on the financial status of the DRAM industry, Morgan Stanley showed a great slide depicting consolidation in the DRAM memory business over the last decade.

Click to view full screen.

Click to view full screen.

Even though memory content still favors desktop/PC over tablet/smart phone the cross over point for mobile applications appears to be within the next month.

Click to view full screen.

Click to view full screen.

Smartphones – Guadois – UBS

Nicolas Gaudois Managing Director of UBS Investment Research looked at the “ The End of the High End Smartphones Run.”

UBS projects smartphones to be a maturing market with smartphone sales now > 50% of the US market. They estimate US mid to high end smartphones (> $300)  YoY unit growth of 15% in ’13E, 8% in ’14E and 5% in ’15E .

Smartphones have been the main growth engine for the semis industry out of the financial crisis. Communications accounted for 57% of TSMC revenues in 2Q13 and 51% for UMC. UBS assumes single-digit YoY revenue growth for the cellular phones industry implies similar levels for wireless semis. “This implies a longer term slowdown in semiconductor revenues growth – until more application drivers emerge.”

UBS expects to see late 2014 14nm finFET production at Intel, TSMC and Samsung.

UBS sees DRAM usage split equally between PC and mobile markets and the NAND flash demand split between mobile phones and solid state drives.

Click to view full screen.

Click to view full screen.

SEMI Packaging Materials Outlook – Dan Tracy – SEMI

The SEMI Packaging Materials forecast is shown below.

Click to view full screen.

Click to view full screen.

1. Includes PBGA, PPGA, LGA, and CSP laminate substrates and flex BGA and CSP substrates; 3. Includes die attach film (tape) materials; 4. Includes solder balls and wafer level package dielectrics

The Pacific region accounting for ~ 95% of the total market!

Click to view full screen.

Click to view full screen.

For all the latest in 3D-IC and advanced packaging, stay linked to IFTLE…

IFTLE 164 Semicon Taiwan part 2; GlobalFoundries Manocha Interview

By Garrou

Over the past few years, SEMICON Taiwan has been a conference where significant new advances in packaging technology, especially 3D-IC, have been revealed. There were no such revelations this year.

The Advanced Packaging Technology Symposium was chaired by Mike Liang, resident of Amkor Taiwan.  The 3D-IC Technology Forum and the embedded Technology Forum were chaired by Chair  Ho-Ming Tong, General Manager & Chief R&D Officer for  ASE.

FC and WLP Continue to Expand

At the Advanced packaging symposium, Vardaman of TechSearch reported that FC and WLP growth , driven by mobile products, will increase from 15% of the pie in 2012 to 21% of the pie by 2017.

TS 1

Moving to copper pillar because bump pitch is limited to ~ 130um. Cu pillar bump pitch can go to < 100um. Most are looking at NCP/NCF underfill solutions.

Corning Updates Capabilities for Glass Interposers

At the 3DIC technology symposium Shorey of Corning updated their progress in the area of glass interposers. Working on 100 to 300mm wafers and 500mm panels (100 – 700um thick) some typical results are shown below.

corning 1

Looks like current minimums at 20um TSV on 50um pitch with wafer thicknesses of 100um. Max via densities greater than 250 TSV/mm. Warpage looks better on glass than on silicon.

Click to view full screen.

Click to view full screen.

Unimicrons look at Panel Level Technology

At the Embedded Technology Forum Hu of Unimicron looked at panel level embedded technology. They offer the following comparison of WLP technology on silicon to “panel level packaging”

UM 1

(Note: IFTLE does not agree with the density capability assumptions in either category)

Two processes are evolving for embedded passive panel level processing as shown in the slide below.

UM 2

Key Process Items include (a)  Component placement accuracy; (b) Interface Adhesion with Dielectric Layer and (c) Warpage Control.

On interesting concept is the embedding of the SI interposed into the substrate as shown below. Reportedly less testing steps would be required and certainly thin wafer handling would be reduced.

 

Click to view full screen.

Click to view full screen.

GF’s CEO Agit Manocha on stacked die, 450mm and consolidation

Ed Spurling of Semi Manuf. & Design posted a interesting interview with GlobalFoundries CEO Agit Manocha. Manocha indicates that GF will be moving from 20 to 14nm in mid 2014 with a finfet product.

He reports that GF is working with multiple assembly houses and memory supplier partners to develop 2.5/3D technology which will be available for 28, 22 and 14nm.

He does not see 450mm being mainstream till 2020.

80% of the worlds IC production is now in moderate to high risk zones for natural disasters. GF has their production ( New York, Germany and Singapore) in the 20% low risk zone.

Moving to the 20 NAND 14 noted Manocha supports those who say there will be very few players left. He indicates TSMC, GF, Samsung and Intel. That’s it…four !

More coverage of SEMICON Taiwan is coming in the next few weeks.

For all the latest on 3D-IC and advanced packaging, stay linked to IFTLE.

IFTLE 163 Consolidation, The Leading Edge, EMPC Grenoble part 1

By Garrou

Consolidation Continues

We have spoken about consolidation many times in IFTLE. Most recently in IFTLE 148, “The Future of Packaging: A Look From 50,000 Feet” we predicted significant consolidation for both equipment and materials suppliers.  To be honest, this has been focused on the front end equipment suppliers buying up their back end brethren. What happened this week was even more significant.

The $29B merger of Applied Materials with fellow front end equipment supplier Tokyo Electron was an all-stock merger, which, if allowed by the courts, will create a global powerhouse in semiconductor and display manufacturing technology. The company will have a new name, dual headquarters in Tokyo and Santa Clara, a dual listing on the Tokyo Stock Exchange and NASDAQ, and will be incorporated in the Netherlands. Under the terms of the deal, AMAT shareholders will own 68% of the new company and TEL shareholders 32%. Tetsuro Higashi, chairman, president and CEO of TEL, will serve as chairman of the new company, while Gary Dickerson, president and CEO of AMAT, will serve as chief executive officer of the new company.

As we said in IFTLE 148, it’s all about the economics. By cutting duplicated R&D and sharing the same platforms, the companies expect to achieve $250 million in annualized run-rate operating synergies by the end of the first year, rising to $500 million in the third year.

We should not view this as “Fait accomplis” because I’m sure the antitrust paperwork is being filed as we speak by their remaining competitors.

The Leading Edge

When I started this blog as “Perspectives From the Leading Edge” back in 2008 in Semiconductor International, I noted that we would be focused on the leading edge  because “that’s where the money is made.” Further evidence of that came from IC Insights last week when they provided the headline “Leading edge technology to be responsible for entire 2013 increase in pure-play foundry sales.” [link]

It appears that 51% of TSMC’s revenue and 50% of GlobalFoundries’ sales in 2013 are expected to be from ≤45nm processing.

In 2012, only TSMC, GlobalFoundries, and UMC had significant sales of ≤45nm technology.  In 2013, TSMC is expected to have about 4x the dollar volume sales at ≤45nm as compared to GlobalFoundries and about 12x the ≤45nm sales of UMC ($10.33 billion for TSMC, $2.53 billion for GlobalFoundries, and $0.89 billion for UMC).  In contrast, SMIC only entered initial production of its 45nm technology in early 2012, more than three years after TSMC first put its 45nm process into production and is forecast to sell only $0.22 billion of ≤45nm technology this year.  In fact, only 22% of UMC’s 2013 revenue and 11% of SMIC’s 2013 sales are forecast to come from devices having ≤45nm feature sizes, which is why their revenue per wafer is so low as compared to TSMC and GlobalFoundries.

IC Insights contends that all of the increase in pure-play foundry sales in 2013 is expected to be due to ≤28nm feature size device sales. “ While the >28nm pure-play foundry market is expected to decline 3% in 2013,  leading-edge ≤28nm is forecast to triple this year.  Not only is essentially all the of pure-play foundry market growth forecast to come from leading-edge production, most of the profits that will be realized are also expected to come from the finer feature size sales.”

Click to view full screen.

Click to view full screen.

Despite continued rumors of process and yield problems in the 28nm TSMC fab, TSMC is forecast to have about $6.33 billion in sales of 28nm devices in 2013and as a result, TSMC is expected to hold a 78% share of the pure-play foundry industry’s $8.10 billion of ≤28nm sales this year.

EMPC Grenoble

The recent European Microelectronics Packaging Conference, EMPC, was held in Grenobe Fr. We will be taking a look at some of the key papers from the conference over the next few weeks.

IMEC

IMEC  reported on electrical characterizations done to identify the impact of typical 3D processes on CMOS devices. They report on studies done to assess the effects induced by TSV, wafer thinning and stacking.

The Figure below shows measurements done for PFET transistors ( 2 channel lengths (50nm and 300nm) with TSV of 5um diameter). They conclude that the longer channel is more sensitive to TSV presence, i.e. at a distance of 5um from TSV center, they measure ION variation of 7% in the case of 300nm channel and 2.5% variation in case of 50nm channel. NFET transistors are less sensitive to TSV proximity. At a distance of 5um from TSV center, they measure a max ION variation of 2.5%. Similar to PFET, NFET transistors with longer channels are also more sensitive to TSV proximity.

Click to view full screen.

Click to view full screen.

No relevant change in the device drive current and therefore no major effect induced by the thinning or stacking processes.

For all the latest in 3DIC and advanced packaging, stay linked to IFTLE.

IFTLE 161 Semicon Suss Workshop part 2: GF, Amkor, Nanium

Finishing up our look at the Suss Technology workshop at SEMICON West.

Nanium

Ricardo Gai, head of eWLB engineering at Nanium gave a presentation on wafer level fan out packaging, FO WLP. Nanium, headquartered in Portugal, is derived from the following bloodlines:

Click to view full screen.

Click to view full screen.

Nanium has been in 300mm HVM of  FO WLP since Q3 2010 and has shipped more than 350MM packages. For a complete discussion of eWLB see IFTLE 124, “Status and the Future of eWLB.”

Process Challenges with eWLB:

  • Warpage

- Warpage and shape changes during processing; stiffness is a key parameter to control;

- Equipment modifications are required to handle FO-WLP wafers

- hardware – new end effectors and new chuck sealing

- software – upgrades for warpage handling

  • Die-Shift – In case of complex devices like (Multichip SiP), mask aligners are not capable of overlay requirements and a stepper is required.

Multi-Layer RDL for multilayer RDL the overlay must be smaller than the die shift. This also requires stepper technology.

Click to view full screen.

Click to view full screen.

Fine RDL Line Width / Space and Fine Ball Pitch – - better resist technology is necessary to achieve L/S = 10/10

  • Cost Pressures

- more die per carrier by using smaller edge exclusion zone

- larger substrate sizes

– 300mm and large panel processing to reduce costs.

  • Future Challenges:

- thinner substrates will require temp bonding and front side protection

GlobalFoundries

Jon Greenwood of GlobalFoundries gave a presentation on 2.5/3D readiness for HVM. Global Foundries is dedicated to support the Collaborative Partner Model:

Click to view full screen.

Click to view full screen.

They are creating a supply chain where GF is responsible for the wafer processing and backside integration (BSI) and assembly is owned by the OSAT partners.

Click to view full screen.

Click to view full screen.

As we have discussed before [see IFTLE 142, “GlobalFoundries2.5 / 3D at 20nm…” ] 2.5D interposer work is ongoing in Singapore and 3D activity is in NY. In June 2013, they announced a certified set of design flows for 2.5D interposers. As the next slide shows, by 2015 they hope to offer TSV “in all nodes.”

Click to view full screen.

Click to view full screen.

Greenwood announced that GF thinks their 2.5D and 3D packaging capabilities are proven and their primary focus moving forward is yield and COO reduction.

Amkor Ron Huemoeller Sr VP of Advanced Product Development at Amkor presented their position on 3D/2.5D Market readiness.

Design capability status – established

- Mass production of optical sensors since 2008

- Worlds first fully integrated MCM TSV product started production in 2011

- System integrated architecture proven on many platforms such as:

- multiple logic on Si  interposers

- logic + memory on Si interposers

- memory / memory stack

- memory / logic combination

Manfacturing Capability

- fine pitch Cu pillar in HVM

- wafer thinning equipment and infrastructure in place

- TSV etch equipment and infrastructure well-established

- Backside passivation – equipment and infrastructure well-established

- Backside bumping – equipment and infrastructure well-established

- wafer support – equipment and infrastructure in place but still needs improvement

Click to view full screen.

Click to view full screen.

- Assembly can be done chip-on-substrate, chip-on-wafer or chip-on-chip

- more work is needed on testing memory prior to committing to package stack.

Memory

- End customer chooses memory supplier (only primary memory sources today)

- Receive as KGM on tape and reel

- receiving 2, 4 die stacks in wide IO format

Amkor now sees interposer use reaching “value markets” post 2015.

Click to view full screen.

Click to view full screen.

For all the latest in 3DIC and advanced packaging, stay linked to IFTLE.

IFTLE 160 ECTC 2013 Part 4: Shinko, TSMC, RTI and Dow Corning

Finishing up our look at the presentations at ECTC 2013 in Las Vegas.

Shinko and CEA Leti detailed their presentation entitled “Warpage Control of Silicon Interposer for 2.5D Package Applications.”

Large silicon-interposers when attached to an organic substrate can cause significant warpage problems. Shinko / Leti examined several warpage control techniques including:

- Using a  “chip first process” where chips are mounted on the interposer first  vs “chip last process” where the silicon-interposer is mounted on the organic substrate first and chips are mounted onto the interposer last.

- using various underfill resins.

- using Sn-57Bi solder and thus lowering peak temperature 45-90 degree C. This reduced warpage after reflow to 75% of that using SAC305.

Comparison of warpage using different assembly sequences is shown below.

Click to see full screen.

Click to see full screen.

Warpage of silicon-interposer using three types of underfills (shown below) for  0 level assembly (micro bumps) is shown below. Maximum warpage using U.F. A1, A2 and A3 were 108, 123 and 132mm, respectively. The lowest warpage was obtained at using U.F. A1. With U.F.A3, solder bump open failures were observed. The authors conclude that “… using underfill material with low Tg and high storage modulus for 0 level leads to high reliability.”

Click to see full screen.

Click to see full screen.

TSMC and customer Xilinx presented “Reliability Evaluation of a CoWoS-enabled 3D IC Package” which used FEA to study the thermo-mechanical response of the interposer-based package during thermal cycle reliability stressing. Focus was especially on the fatigue failures of the C4 and BGA joints. Experimental data collected on CoWoS test vehicles were used to validate the FEM models. Parametric study of key package material and geometric parameters was performed to analyze their effects on C4 bump thermal cycle reliability. Package materials of interest include UF (underfill), lid and substrate, and the geometric parameters include lid thickness and C4 bump scheme.
Results showed that the CoWoS package using AlSiC lid has better C4 bump life than the CoWoS package using Cu lid.  While a  thicker lid has the higher stiffness and better co-planarity, the higher constraint from the thicker lid induces higher stress inside the package which negatively impacts  C4 bump fatigue and the micro-bump Ti/Al delamination.

C4 bump layer underfill with Tg of 70 C or 120 C, were studied. The underfill with lower Tg has higher driving force to C4 bump fatigue. When temperature is above Tg, the underfill has much lower Young’s Modulus which has much lower capability to protect C4 bump; and therefore the underfill with lower Tg has higher driving force to C4 bump fatigue. On the contrary, the underfill with lower Tg has lower driving force to Ti/Al delamination in the micro-bump structure. TheC4 underfill with lower stiffness can play as a buffer layer and results in lower driving force to Ti/Al delamination in microbump.

Click to see full screen.

Click to see full screen.

IMEC reported on “Key Elements for Sub-50μm Pitch Micro Bump Processes.”
Scaling the ubump pitch from hundreds to a few tens of microns is not straightforward. Several process parameters need to be taken into account to allow a reliable Cu(Ni)Sn ubumping process. One of the challenges for fine pitch Cu(Ni)Sn stacking is to obtain a high bump uniformity. The non uniformity prevents Cu and Sn from having good contact and subsequent intermetallic formation and increases the risk of underfill entrapment.

A bump scheme that offers better margin for alignment error is better based on a scheme where the size of top die bumps is smaller than the size of the bottom pads. For example it is better to achieve  20μm pitch with 7.5μm bump on 12.5μm pad than with 10μm bump and pad because  equal bump and pad diameter can tolerate only 2μm misalignment whereas the  7.5μm/12.5μm bump/pad can tolerate 5μm. This is a significant difference when working close to the stacking tool’s limit of alignment accuracy.

Details on the plasma treatments necessary when attempting to plate into these fine featured plating resists are also discussed.

RTI  detailed a process for the fabrication and bonding of 100 and 200um  thick silicon interposers with filled 4:1 AR copper filled TSVs and front side and backside multilevel metal copper/ thin film polymer  routing layers in their presentation ”Fabrication and Testing of Thin Silicon Interposers with Multilevel Front side and Backside Metallization and Cu-filled TSVs.”

Click to see full screen.

Click to see full screen.

For most applications, the desired thickness for Si interposers is below the thickness at which unsupported wafers can be safely handled through the necessary fabrication processes (i.e. 100 -200um). In these cases a temporary wafer support system, consisting of a carrier wafer and a layer of a temporary adhesive, must be used.

3M’s Wafer Support System (3M WSS™) and Brewer Science’s WaferBOND 9001™ were the temporary bond materials selected in the RTI program. Multilevel metal was done on either side of the interposer using polymer thin film dielectrics. The front side of the device wafers was patterned with two layers of Cu and three layers of polyimide (HD-4100 from HD Micro). After frontside patterning, the wafers were bonded face-down to temporary carrier wafers coated with temporary adhesive. Backgrinding and CMP were used to thin the wafers to a nominal thickness of 100 um. After thinning, a backside Cu routing pattern was formed between two layers of either  BCB 4024-40 (Dow Chemical), HD-8930 (polybenzo-bisoxazole [PBO] HD Microsystems), with curing temperatures of 250˚C and 200˚C, respectively, at or below the temperature limit of the temporary adhesive. The polyimide that we used for the front side MLM structure has a recommended cure temperature of 375 C which would be incompatible with any currently offered temporary adhesive.

Both the 3M and the Brewer wafer bonding solutions were found to be compatible with the processing of the different spin-on dielectric materials used to fabricate frontside and backside MLM structures. Successful debonding of the carriers was done both at the wafer level before dicing and at the die level after dicing and bonding to a substrate.

In both, the 100um and 200um interposer thicknesses with 25um or 50um diameter TSV respectively, an annealing step was found to be successful in preventing Cu from extruding from the TSVs during the subsequent polymer curing steps. Electrical testing before and after thermal cycling showed the high yield and stability of all of the interposer structures irrespective of the dielectric materials choice.

For all the latest in 3DIC and advanced packaging, stay linked to IFTLE…

IFTLE 159 Semicon Suss Wkshp part 1: Material Suppliers; IEEE 3DIC Program

Am I the only one who missed Semicon West?

I had a full week of workshops and 1-on-1 meetings set up for Semicon West, but due to the Korean crash, United canceled my Sunday flight and rebooks me for Tuesday night (I’m a million mile flier, so imagine the service the peons got!) then my replacement Delta flight was cancelled on Monday again with no seats on flights into SF, Oakland or San Jose till late Tuesday. I finally concluded some things are simply not meant to be.

The Suss technology forum that I helped set up and was set to moderate went on without me so I’d still like to cover some of the materials that were presented there.

Let’s look first at the material suppliers.

Lord

Le of Lord gave a presentation on their photo definable silica filled epoxy “solder brace” material which they propose to use as a final passivation in a standard WLP redistribution process.

We are shown data concluding that the “solder brace” shows better thermal cycling reliability (-40 to +125 C) and drop test results then an unidentified “PI” , but without clear understanding the identity of the PI and all the design dimensions involved (such as thickness of the screen printed epoxy vs the spun PI) it is hard to draw any substantial conclusions from the data.

Since screen printing is not a usual unit operation in a standard redistribution process this might be a barrier to acceptance for such a filled product.

Click to view full screen.

Click to view full screen.

Brewer Science

Smith of Brewer Science detailed the separation technologies available for their ZoneBond Process. The temporary adhesive ring of the ZoneBond process can be removed either by immersing the temp bonded wafer on a perforated carrier in a solvent bath as shown below:

Click to view full screen.

Click to view full screen.

Or,  by trimming the narrow bonded ring post fabrication to release the device wafer, where:

-          Debonding occurs at room temperature.

-          Separation occurs at the carrier-to-adhesive interface, not the adhesive-to-device interface.

-          Device is mounted in the film frame and is firmly supported on a vacuum chuck during debonding.

This allows higher-temperature-capable adhesives

-          Thermally stable in bonded pair to 240°-260°C (depends on processing parameters)

Click to view full screen.

Click to view full screen.

Dow Corning

Ho of Dow Corning presented their new silicone based bi-layer temporary bonding solution. Their Bond/Debond Process Flow is shown below.

- Spin-coat bi-layer (release and adhesive layer)

- Room temperature bonding / debonding

- post-bonding cure on hot plate

- no plasma or lasers necessary

- fast mechanical debonding

Click to view full screen.

Click to view full screen.

Dow Chemical

Gallagher of Dow Chemical detailed their photo and laser patternable plating resists and dielectrics for WLP and 3D TSV.

Their Novolac (positive) and Acrylate (negative) resists are capable of a brad thickness range.

Click to view full screen.

Click to view full screen.

Their Cyclotene (BCB) dielectrics are laser patternable and their Intervia (epoxy) dielectrics show excellent vertical sidewalls. They also highlighted BCB as a temporary bonding solution which shows high thermal stability during backside processing ( , 1% weight loss at 300 C per hr) and clean RT mechanical peel-off debonding.

Suss

Lutter, of Suss, compared the temporary bonding solutions that Suss supports focusing on the room temp mechanical debonding solutions.

Click to view full screen.

Click to view full screen.

The mechanical release at RT is described as follows:

Click to view full screen.

Click to view full screen.

Zonebond and several other solutions show excellent TTV (2-3um) after thinning to 50um.

Click to view full screen.

Click to view full screen.

Flex frame tape is a key to good debonding and cleaning . The principle of Suss debonding is shown below.

Click to view full screen.

Click to view full screen.

IEEE 3DIC

The IEEE’s premier 3DIC conference is on tap for the USA again this year. The conference will be held in San Francisco the first week of October. You can register here [link]

Let’s take a look at the program:

Click to view full screen.

Click to view full screen.

Wednesday, October 2nd  – Free Tutorials!

13.00 – 14.00 Tutorials: 2.5/3DIC Players, Products & Markets, Rozalia Beica – Yole Developpement

14.00 – 15.00 Tutorials: 3DIC – Prof. Mitsu Koyanagi, Tohoku University

15.00 – 16.00 Tutorials: Design for 3DIC, Prof. Paul Franzon – NCSU

16.00 – 17.00 Tutorials: TSV and Interposer Design for High Performance and Low Noise,  Kim- Kaist

17.00 – 18.00 Tutorials: Monolithic 3DIC, Zvi Orbach

Thursday, October 3rd

08.30 – 09.45: Keynote Speaker: Prof. M. Taklo, SINTEF, Title:” E Brains”

09.45 – 10.15: Invited Talk I “ 3DIC Activity at Tohoku “  Prof. Mitsu Koyanagi, Tohoku University

13.00 – 13.30: Invited Talk II – “A Perspective on Manufacturing 2.5/3D”  Robert Patti, Tezzaron

17.00 – 18.00: Panel Session “Progress and Outlook for 3D ICs and 2.5D Systems -

Moderator: Jan Vardaman, TechSearch

Friday, October 4th

08.30 – 09.00: Invited talk III “The DARPA ICECool Program”  Avi BarCohen, DARPA

Hope to see you all there.

For all the latest in 3DIC and advanced packaging, stay linked to IFTLE.