Ag Sinter Joining for WBG Interconnects

Transcription

1 2016 3D-PEIM, June 14, 2016 Ag Sinter Joining for WBG Interconnects Katsuaki Suganuma, Shoji Nagao, Toru Sugahara, Hao Zhang, and Jinting Jiu ISIR, Osaka University, Osaka, Japan SiC Cu Si 3 N 4 Ag SMB Phone: , suganuma@sanken.osaka-u.ac.jp

2 Introduction Wide band gap power device Die-bonding for power electronics Sinter joining Outline - Ag sinter joining - Thermal stability and its improvement - Ag film stress migration bonding - Low temperature sintering mechanism Ceramic substrate Summary and future

3 WBG benefits and market 3 Benefits: Energy consumption reduction Si SiC Bandgap Size reduction (ev) Breakdown Less or no voltage cooling (MV/cm) High frequency Thermal conductivity (W/m K) etc. Home & Office Renewable energy (million yen) 350, ,000 WBG market growth WBG device 250, , ,000 SiC-FET GaN Transportation 100,000 50,000 0 SiC-SBD From Fuji Keizai Industry

4 SiC power devices in market 4 SiC-SBD inverter Toshiba FCV Toyota Mitsubishi Electric SiC-SBD Toyota ~ 40 % energy loss reduction ~ 1/5 size reduction..etc. Air conditioner Power conditioner Mitsubishi Electric Fuji Electric

5 Heat New generation power interconnections 5 Ag sinter joining Stress migration bonding Pure Zn soldering Active metal brazing Ag sinter joining Si 3 N 4, AlN, Al 2 O 3 T j = 250 ºC Molding compound SiC Heat spreader Insulator Electrode materials Bonding method Wire/ribbon/planer bonding Cu or Al? Plating or other oxidation/reaction protection? Resistance to severe thermal cycles : exposure & oxidation resistant interface design

6 Old sinter joining 6 K. Suganuma, et al; J. Amer. Ceram. Soc., 66 (1983), c117 Beginning of FGM Very high pressure: 100 MPa/1GPa

7 Ag sinter joining with hybrid paste 7 at C in air with no/low-pressure High bonding strength > 40 MPa High thermal conductivity > 140 W/mK Excellent heat shock resistance : ºC K. Suganuma et al., Microelectronics Reliability 52 (2012) 375.

8 Resistivity (x10-6 Ω cm) Low temperature & no pressure at 200 ºC Micron/submicron hybrid paste Nanoparticles paste Temperature (ºC) 5 x 10-6 Ω cm K.Suganuma, et al, Microelectronics Reliability 52 (2012) 375

9 Shear Strength (MPa) Low temperature, no pressure, O 2 is needed! 9 Ag metallization is the best (Cu) 239(Au) Ag O 2 is required (Ag) Au 10 Cu Sintering Temperature ( ) Cu Cu Ag Au M. Kuramoto, et al, IEEE Trans CPMT, 33[4](2010), 801 Ag Ag S. Sakamoto, et al, J Mater Sci: Mater Electron, 24[4](2013),

10 SiC p addition and metallization effect in heat exposure ºC Ag(SiC p )/Ti/Cu 250 ºC 350 ºC Initial 150 ºC 250 ºC 350 ºC SiCp addition stabilize sintered microstructure Ti underlayer has a great effect to avoid degradation

11 Imide-based nano-composite molding SiC SBD Nano-composite mold material Al wire R R R R Si O O Si O O Si O Si O O O Si O O Si O Si O O Si R R R R Ag sinter paste -50 ~250, 500 cycles No pressure, min As-molded No change on SiC-SBD NEDO funded project in collaboration with Nippon Shokubai, Funaki-labo.

12 Delamination after thermal cycles Initial After thermal cycles Sn-Pb solder Hybrid Ag paste Ag nanoparticle paste and Au-12Ge solder also failed by delamination.

13 Ag thin film stress migration bonding SMB SiC 1μm thick Ag film can make prefect bonding Ag plating Si/SiC chip Cu Si 3 N 4 Ag SMB Surface Ag Substrate at 250 ºC in air with no pressure Si Ag Si Hillocks Si C. Oh, et al, Appl. Phys. Letters, 104(2014),

14 Joining temperature and substrate effects 14 Si 250 SiC 250 Mo 300 Ti 350 C.M.Oh, et al: J Mater Sci: Mater Electron (2015) 26:2525

15 Low temperature Ag sinter joining mechanism Ag nanoparticles in amorphous Ag Ag Self-generation of nanoparticles realizes to low temperature bonding

16 Ag-O liquid formation along G.B C Ag-O liquid can be formed in Ag film G.B. under high PO 2 Assal et. Al, J. Am. Ceram. Soc. 80, (1997). 16 presented at TMS2016

17 Self-healing of Ag sinter joint layer 17 Initial h h b a Specimen Notch 10mm under the support of NEDO in collaboration with DENSO Corp.

18 18 Ceramic substrate fracture after thermal cycles -40 ⁰C ~ 200 ⁰C / 500 cycles

19 Typical substrate die-attach materials 19 Thermal conductivity (W/m K) Thermal expansion (x10-6 /K) Strength* (MPa) Fracture toughness (MPa m 1/2 ) ΔT (Degree) Table Selected properties Al 2 O 3 AlN Si 3 N 4 Cu Al Ag Ni * 0.2 proof stress for metals Previously proposed structure Si 3 N 4 Cu Problems: SiC Although it survives up to 300 ⁰C High cost of Si 3 N 4 Poor thermal conductivity of Si 3 N 4 Oxidation of Cu etc.

20 DBA invented from TEM 20 Al/ceramic interfaces were direct and clean. IGBT with DBA was released in 1998 Pressure casting set-up Last proof given to engineers

21 DBA can survive up to 300 temperature cycles 21 after - 40 ~ 300 /110 cycles AlN Ni plating Ni-1%P electroless plating Ni electroplating In collaboration with Siemens, Showa Denko, Uyemura Senju Metals Presented at TMS2016 Al Ni plated Al heat spreader Al cooling plate

22 Electroplated Ni is better ~ 300 / 110 cycles presented at TMS2016

23 Ag sintered die-attach and Al/AlN interfaces ~ 200 / 100 cycles Si Al Ag Ni AlN 100 μm Al 10 μm Ni electroplating presented at TMS2016

24 Summary The Ag sinter joining is one of the most promising die-attach methods for WBG applications. SiC submicron particles addition improves durability up to 250 ºC. The imid based molding nano composite exhibits excellent thermal/power cycling stability with a Ag porous interlayer. Sintering Ag at low temperature in air can be achieved by self-generated Ag nanostructure with oxygen. Ag-O formation in grain boundary has a key role for low temperature joining with Ag. DBA has potentials up to 300 C. Al Acknowledgement The power interconnection was supported by a Grant-in -Aid for Scientific Research (S), no Transfer mold test was carried out under the support of NEDO in collaboration with Nippon Shokubai and Prof. Funaki. Self-healing of Ag bond layer was carried out under the support of NEDO in collaboration with DENSO Coop. AlN Al cooling plate

25 25 Thank you! Suganuma Labo. ISIR Osaka Univ.