1. 5/24/2001 1 Plasma Assisted Controllable Bonding SFR Workshop May 24, 2001 Yonah Cho, Chang-Han Yun, and Nathan Cheung Berkeley, CA 2001 GOAL: To establish plasma recipes and bonding data for Si, oxide, and metal surfaces

2. 5/24/2001 2 New Applications of Plasma Enhanced Bonding Systems Integration Metal polymer Enhanced Adhesion between low k /metal Metal Precleaned wafers stored as bonded pair Si Particle/contaminant free storage Debond SOI Technology

3. 5/24/2001 3 Capacitance + V- V0 p-Si accumulation inversion as cleaned plasma exposed Plasma Induced Surface Charge Both n-Si and p-Si surface are + charged after plasma exposure. V sweep > 1000V Surface Charge Density > 10 12 /cm 2 Technics Plasma Etcher Vacuum O2O2 Pr = 220 mtorr P = 150 W wafer + + + - + + - - - - Surface Charge Analyzer Data

4. 5/24/2001 4 Surface Charge Control: e - Bombardment Vacuum V Capacitance + V- V0 accumulation inversion After e- bombardment plasma exposed Complete neutralization by e- bombardment PIII Chamber with ECR plasma source Ar + - + + + + + - - - - - + + - - - - - V wafer = +50 V dc I wafer =.17 A Surface Charge Analyzer Data p-Si

5. 5/24/2001 5 Proposed Bonding Model O H O O H H H Si O O O H O O H H H OO Hydrophilic Bonding Plasma Enhanced Bonding ++ -- ++ ++ Interaction between Partial charges (  + and  -) due to high  x (electronegativity): O-H: 1.2, N-H: 0.8, C-H:0.3 Ref: I.N. Levine, Physical Chemistry ++++++++++++++ ++++++++++++++ ++ -- ++ -- ++ -- ++ ++ -- ++ -- ++ -- ++ Enhanced interaction between surface charge and H 2 O

6. 5/24/2001 6 Surface Dependent Bonding Strength  f (Si) Double side plasma Single side plasma No plasma  max (mJ/m 2 )

7. 5/24/2001 7 Bonding Kinetics E a = 0.58 eV Plasma enhanced bonding E a >> HL bonding (E a ~ 0.05 eV) Arrehenius Plot HL bonding at RT Time Dependent Bonding Strength,  (t)

8. 5/24/2001 8 Hydrophobic Hydrophilic 3000 2500 2000 1500 1000 500 0 100200 300 400 500600 700 800900 Bonding Energy (mJ/m 2 ) Annealing Temperature ( o C) Bonding Energy vs. Temperature O 2 plasma Tong et al. APL 64, 625 (94) Accomplishments Established SCA technique to monitor surface charge Transient and steady-state bonding kinetics studied Bias mode demonstrated as a control variable for surface charge

9. 5/24/2001 9 2002 and 2003 Goals 2002:Demonstrate polymer surface modification with plasma implantation or surface treatment. 2003:Demonstrate concomitant plasma treated deposition surfaces as effective diffusion barrier. Surface Layer Si Substrate Plasma treatment Deposition Modified Surface + + + + - - - - + + - - -