Non-Damage Probing and Analysis of ILD Damage at Scrub Marks

Transcription

1 2004 Southwest Test Workshop Non-Damage Probing and Analysis of ILD Damage at Scrub Marks Jun Yorita, T.Haga, Y.Hirata, S.Shimada* ( yorita-jun@sei.co.jp) Electronics Materials R&D Laboratories *Analysis Technology Research Center Sumitomo Electric Industries, LTD. June 7, 2004 J.Yorita 1

2 Contents Introduction to LIGA Probing Technology - Industrial Requirement for Probing Low-k k Devices - LIGA Process & LIGA Probe Development of Low-Load Load Contact Probes - Basic Characteristic of LIGA Probe - Analysis of ILD Damage and Scrub Action - Simulation of ILD Damage - Proposal of Contact Probes for Low-k k Devices Conclusions June 7, 2004 J.Yorita 2

3 Industrial Requirement for Probing Low-k k Devices Low and Stable Load Probing - Low-k k materials are more fragile - Low and stable probe load is desired to minimize damage to Low-k k materials Low and Stable Contact Resistance - High frequency and high power applications require severe contact resistance control Finer Pitch - Roadmap to 100µm m pitch requires revolutionary probing approach June 7, 2004 J.Yorita 3

4 LIGA Process & LIGA Probe 1) X-ray Lithography Irradiation <What is LIGA?> (Lithographie-Galbvanoformung-Abformung) SR(X-ray) X-ray Mask POGO Type Probe Development 2) Electroforming Electroforming Removal of Resist Resist Metal for Array(C4), LCD etc. <Advantages> - Little Dispersion of Spring Constant (±15%(3σ)) - Any Form is Possible (Tip/Spring/Support) - High Hardness/Toughness - Good Electric Resistance (1.3x10-7 Ωm) June 7, 2004 J.Yorita 4

5 Development of Low-Load Load Contact Probes June 7, 2004 J.Yorita 5

6 Experiment Condition(1) Probe Samples- <Scrub Type Probe> for Al Pad <Basic Characteristic> Overdrive, Scrub Length vs Contact Load R1µm 55 4µm Trapezoidal Tip (µ-edmed( EDMed) June 7, 2004 J.Yorita 6

7 Experiment Condition(2) ILD Samples- <CMOS Image Sensor> (*Since we couldn t t come low-k k devices to hand, we chose CMOS image sensor with fragile ILD directly under Al Pads.) Al Pad SEM Image of Electrode Pad (Modulus of ILD : 2.5GPa) June 7, 2004 J.Yorita 7

8 Analysis of ILD Damage(1) Trapezoidal Tip- R1µm 55 4µm Trapezoidal Tip (µ-edmed( EDMed) Trivial Flaws! Probe Tip Al Pad June 7, 2004 J.Yorita 8

9 Analysis of ILD Damage(2) ILD Section Observation- SIM Image of ILD Section after Probing Forward Trivial Flaws! Cracks!(Crevasse!) Crevasse!) 30mN 20mN High Contact Resistance 0mN Non-Damage Probing Range (NDPR) : Very Narrow! How Do Cracks Occur? June 7, 2004 J.Yorita 9

10 Outline of Analysis of Scrub Action Conceptual Figure of Analysis of Scrub Action in SEM Chamber Stage (Actuator) Before TD Just TD Tester Probe Electrode Pad Under TD e-gun Camera After TD E-SEM Analysis of Scrub Action June 7, 2004 J.Yorita 10

11 Analysis of ILD Damage(3) How Do Cracks Occur?- Forward Forward Scrub Only Trivial Flaws! After Return Return Trivial Flaws on Scrub Surface : - Occur in Forward Scrub Action. - Don t t Increase in Backward Scrub Action. June 7, 2004 J.Yorita 11

12 Simulation Technology of LIGA Probe <Spring-action Simulation> OD (MPa) <Scrub-Action Simulation> (MPa) Before OD Scrub After OD Backward It is Possible to : - Simulate Scrub Action and Estimate ILD Damage. - Design Low-load Contact Probes for Low-k k Devices. June 7, 2004 J.Yorita 12

13 Simulation of ILD Damage(1) -Trapezoidal Tip- <TD Model on ILD> Mises Stress) Al SiO 2 (MPa) Forward - Maximum Stress Occurs at Forward Scrub Action. - Rear Edge of Probe Tip Makes Strong Stress to ILD. It is Suggested that Contact Probes for ILD Shouldn ouldn t Have Sharp Edge at Tip. June 7, 2004 J.Yorita 13

14 Development of Low-Load Load Contact Probes <New Probe Tip Design> Fixed Radius Tip as a Simple Model (Spring Design isn t t Changed) <Initial Contact Resistance> (for Al Pad) R10µm Low Contact Resistance Initial Contact Resistance is Equal. June 7, 2004 J.Yorita 14

15 Analysis of ILD Damage(4) Fixed Radius Tip- No Trivial Flaw! Forward 0mN 20mN 50mN High Contact Resistance NDPR Spreads! - There is No Trivial Flaws on Al Pad! - Non-Damage Probing Range(NDPR) Spreads! It is Suggested that Tip Form is More Important than Probe Load to Non-Damage Probing. June 7, 2004 J.Yorita 15

16 Analysis of ILD Damage(5) Why is Small Damage?- Depth Profile at Al Scrub Cantilever LIGA Probe (Trapezoid Tip) LIGA Probe (Fixed Radius Tip) nm Pad Surface Substrate > Forward Metal Thickness - Low-Load Load LIGA Probes Scrub the Pad Surface Thinly. - There is No Substrate Atom in Scrub Surface. June 7, 2004 J.Yorita 16

17 Simulation of ILD Damage(2) -Fixed Radius Tip- <TD Model on ILD> Mises Stress) <Mises Stress vs Contact Load> (MPa) Forward Al SiO 2 Si At Fixed Radius Tip, ILD Stress at Forward Scrub Cuts Down. But at Fix Radius Tip : - Much Debris May Adhere to Tip. - Contact Load May Rise & NDPR May Become Narrow. June 7, 2004 J.Yorita 17

18 Simulation of ILD Damage(3) Advanced Tip Design- <Advanced Tip Design> Cleaning-Free Tip <Mises Stress vs Contact Load> R5µm R2µm R5µm Forward - Advanced Tip Have Higher Stress than Fixed Radius Tip. - At Advanced Tip, ILD Stress is Changed Sharply. We ll Optimize Tip Form with the Performance of Non-Damage and Cleaning-Free. June 7, 2004 J.Yorita 18

19 Simulation of ILD Damage(4) Probing Low-k k Devices- Low-k k Devise (*There are more fragile materials at the lowest layer) <Low-k k ILD> Al SiO 2 SiOC Cu SiN <TD Model on Low-k k Materials> Mises Stress(@100µm_OD) <Mises Stress/Modulus vs Contact Load> Low-k Si (MPa) Forward Using This Simulation Technology, It is Possible to Propose the Suitable Contact Probes for Low-k k Devices. June 7, 2004 J.Yorita 19

20 Conclusions We clarified that tip form is more important than probe load to non- damage probing. Moreover, we succeeded in realizing wide NDPR. Probes with wide NDPR absorb height dispersion of electrode pad in devices and that the wafer probing is complete without ILD breakdown. Moreover, we think that probes with wide NDPR are also available for probing Low-k k devices. The following two points are very important for probing Low-k k devices; It is necessary to use the contact probes with little dispersion in tip form and spring properties. From this point of view, LIGA probes are very advantageous. It is necessary to design low-load load contact probes on the basis of exact simulation and investigation of scrub action. June 7, 2004 J.Yorita 20

21 Spare

22 Simulation of ILD Damage Inclination of Trapezoidal Tip- <Inclination TD Model> (10 degrees in a back side) Mises Stress(@Maximum Stress) Forward <Mises Stress vs Contact Load> Al SiO 2 (MPa) Si Trapezoidal Tip Form is Sensitive to the Inclination of Probe. June 7, 2004 J.Yorita 22

23 Simulation of ILD Damage Advanced Tip Design- <Maximum Stress> Forward Al <Mises Stress vs Contact Load> SiO 2 Si (MPa) <Load : 47mN> Forward Because of Ever-changing Tip Radius to Contact Al Pad, ILD Stress is Changed Sharply. June 7, 2004 J.Yorita 23

24 Sharpening of LIGA Probe Tip µ-electro Discharge Machining(µ-EDM) Discharge Electrode Probe Tip Oil Probe Tip Scrub Mark 20µm Shaving Forward 48µm SEM Micrograph of Discharge Scar June 7, 2004 J.Yorita 24

25 Simulation of scrub action Why do Adhesion and Accumulation of Debris Occur? Al Contact Wiping Action of Truncated Pyramid Tip (Conventional MEMS Probe Tip Fabricated by Si Micro Machining) Forward Backward 4µm Initial Adhesion of Al Debris Occurs at Backward Scrub Action. Al Debris Increase the Debris Adhesion at Next Contact. Backward Scrub Action is Useless for Electrical Contact. June 7, 2004 J.Yorita 25

26 Cutting Tool Simulation Technology 3D Machining Simulation Tool IGETARROY Debris (Shaving) Tool Cutting Tool 3mm For Cutting Tool Shape Design & Cutting Condition Analysis Scrub Simulation June 7, 2004 J.Yorita 26

27 Ni Grain Size Control <Grain TEM Photograph> Conventional Material 1μm Hardness:Hv New Material Grain Size Uniformity along Thickness Average grain size (nm) New Material XRD Measurement (Wilson Method) Seed Layer SideThickness (µm) Top 0.1μm Miniaturization of Grain Size High hardness: up to Hv600 Good Uniformity June 7, 2004 Hardness:Hv620 J.Yorita 27