Study on microprobe processing by LIGA on Si

Transcription

1 Study on microprobe processing by LIGA on Si Fundamental study for 3-D 3 D mold -Report 1-1 Teppei Kimura, JEM Japan (Japan Electronic Materials Corp.) Tadashi Hattori Himeji Institute of Technology in San Diego Better Probing Products 1

2 A potential new technology for probing super-fine fine-pitch LCD drivers with Au bumps 2

3 Outline Introduction Experimental Procedures Results Conclusions 3

4 Problem Background Conventional cantilever probe cards may not achieve the pitch requirement in the near future. Need New fabrication process to achieve the finer pitch probing. 4

5 LIGA Features LIGA : Lithographie thographie, Galvanoformung und Abformung High aspect ratio : > 20 High accuracy : < 0.5 um High uniformity 5

6 Purpose Requirements for probing LCD drivers Fine pitch ( < 35um ) Good contact with gold bump Minimal bump damage Low cost 6

7 Concept of 3-D 3 D Micro Probe Processing LIGA process Pros High aspect ratio & High accuracy Con High processing cost per mask Si anisotropic etching Pro Can form sloped shape with only 1 standard UV mask Con Limit on probe tip shape Combination 3-D D micro probe 7

8 Design target of 3-D 3 D probe Probe model by Ni electroforming 1200um 20um 50um 180um 8

9 Process concept Resist Sloped shape Si Si SiO 2 Preparation for etching Si anisotropic etching 9

10 Process concept Thick resist X-ray lithography Si Si Plating seed layer Thick resist preparation X-ray lithography 10

11 Process concept Ni structure Ni electroforming Si Ni electroforming Resist and substrate removal 11

12 Experimental procedures Si anisotropic etching X-Ray lithography Ni electroforming & Lapping 12

13 Si anisotropic etching Resist Slope formation for 3-D mold SiO2 SiO2 Si Resist 1. Photo resist formation 2. UV lithography Si SiO2 Si 3. SiO2 layer removal SiO2 A Si Si 4. Si anisotropic etching A Process step of Si anisotropic etching Cross section of A-A A 13

14 Si anisotropic etching Top Slope Bottom Photograph of slope Depth (um) Solution :TMAH(20%) Temp : 85 deg Time (h) Etching rate 14

15 X-ray lithography Thick resist preparation on mold Walls Slope Slope Photograph of substrate Enlarged view 15

16 X-ray lithography New Subaru Radiation Facility Characteristics of X-ray X lithography Wavelength Storage energy nm 1.5 GeV 16

17 X-ray lithography X-ray Mask Processes X-ray lithography Si mold with thick resist 200um Surface view after lithography Development Process step of X-ray X lithography 17

18 Electroforming & lapping 400um Probe array after electroforming Probe array after lapping 18

19 Results 19

20 Probes Side view 50um 180um 20um Bottom view 40um pitch SEM photograph of micro probe 20

21 Contact force vs Overdrive 4 Contact force [mn] Slope = 0.1 gf/mil Overdrive [µm] 21

22 Contact resistance vs Overdrive Contact Resistance [Ω] Overdrive [µm] Pad Material :Au Current :50mA 22

23 Conclusions 23

24 Conclusions 1. Micro probe with 3-D 3 D shape is manufactured by combining the processes of LIGA and Si anisotropic etching um of allowable probe tip deflection 3. Satisfactory electrical contact within 10um to 70um overdrive can be obtained D D micro probe has the potential to be used for probing super-fine fine-pitch LCD drivers with gold pads. 24

25 What are the next steps? 1. Continue to evaluate the probes Mechanical contact test (scrub, wear) Electrical test (Cres( vs. No of touchdowns) Cleaning process and frequency 2. Reduce pitch (<25 um) 3. Finalize assembly process 25