Online Semi-radius Probe Tip Cleaning and Reshaping

Transcription

1 Online Semi-radius Probe Tip Cleaning and Reshaping Authors: Sam McKnight and Michael Agbesi IEEE SW Test Workshop 1

2 Agenda Acknowledgements Background info Setup and measurement technique Contact resistance results Cleaning recipe parameters to consider Silicone vs polymer based materials Summary Future work IEEE SW Test Workshop 2

3 Acknowledgements Jack Courtney John Cartier Steve Duda Les Griffith Rob Holwager Glen Langsman Josh Pendergast IEEE SW Test Workshop 3

4 Basic cantilever probe types IEEE SW Test Workshop 4

5 Why Semi-radius? Lower pad damage in general for today s soft aluminum Approximately same scrub length as flat tip while reducing the amount of material removed from base material Equivalent contact resistance to flat or full radius tip Reflectivity similar to flat tip for prober and probe metrology alignment (easier to align to vs. full radius material) IEEE SW Test Workshop 5

6 Bonding Semi radius tips Pad opening shown is 29X29 microns - running out of room! IEEE SW Test Workshop 6

7 The problem with Semi- radiused probes Variable tip geometry using standard material cleaning solutions No insitu solution non silicone based Either flat tip or radiused tip solution but no semi-radiused solution IEEE SW Test Workshop 7

8 Traditional way to maintain semi-radius probe tips Use elastomeric abrasive i.e. polymer based material continues to radius tips Remove periodically to reshape (put a flat back on it) IEEE SW Test Workshop 8

9 The solution Two part cleaning insitu Abrasive material for flat tip SiC Elastomeric material for radius tip and removes stringers (contact pad and cleaning detritus) IEEE SW Test Workshop 9

10 Two basic cleaning mediums Two part cleaning insitu Solid Abrasive material for flat tip SiC (Silicon Carbide) Elastomeric material for radius tip and removes stringers (contact pad detritus) Order is important see data IEEE SW Test Workshop 10

11 Typical recipes 5-10 up/down touchdowns on each medium SiC abrasive removes all detritus down to base material (flat tip) Elastomeric abrasive -removes probing/cleaning detritus (radius tip) Use same OD as with product for SiC, OD + 30% for elastomeric (typical) - pitch dependant Move to new location between Up/Down cycles IEEE SW Test Workshop 11

12 Polymer based abrasive clean Before clean After clean IEEE SW Test Workshop 12

13 Contact resistance - Elastomeric Elastomeric cleaner 50um OD 25C clean freq 100 die Wafer average 0.59 ohms Cres(ohms) Min Max Average Cleaning cycle Test # Each "test" represents 25 contacts (190K data points total) opens removed from average data all CRES charts IEEE SW Test Workshop 13

14 Contact resistance silicon carbid SIC abrasive 50um OD 25C clean freq 100 die Cres(ohms) Wafer average 0.10 ohms Min Max Average Cleaning cycle Test # IEEE SW Test Workshop 14

15 Contact resistance dual clean JEM elsatomeric & SIC abrasive 50um OD 25C clean freq 100 die Each "test" represents 25 contacts (190K data points) Wafer average 0.40 ohms opens removed from average data Cres(ohms) Min Max Average Test # S. McKnight 05/02/2007 Cleaning cycle IEEE SW Test Workshop 15

16 Contact resistance setup and measurement technique TEL P12XLN 25C, Maximum z velocity Probe 50 micron pitch 1X25 tungsten rhenium material, 20 micron nominal tip diameter ~ 1gf/mil spring rate 50 micron overdrive from first touch (contacts were within 9 microns from first to last touch) 100 touchdowns between cleans Relative measurement not 4 point All data nulled path or bulk resistance removed 300mm wafer 1.2 micron as deposited aluminum blanket deposition IEEE SW Test Workshop 16

17 Measurement circuit Test stimulus 10 ma forcing current 5V clamp Min - Max - Average data collected plus raw data Keithley based matrix switch and source/measurement unit VI source Contact under test Return path Shorted wafer Note: actual return path pins = 24 IEEE SW Test Workshop 17

18 Polymer based abrasive clean SiC abrasive Probe tip Abraded area largest area expose to cleaning medium IEEE SW Test Workshop 18

19 SiC clean Typical flat tip Silicon Carbide abrasive 3µm IEEE SW Test Workshop 19

20 Recipe Considerations Probe characteristics Tip diameter Tip length Taper Spring rate Material Cleaning order Lowest CRES use SIC last Maximum particulate removal use Elastomeric last IEEE SW Test Workshop 20

21 Sequence and motion (use animation) Elastomeric material SIC material IEEE SW Test Workshop 21

22 Benefits Low cost solution use existing materials Comparable CRES to SiC material Non Silicone Uniform tip shape throughout life of probe Longer probe life IEEE SW Test Workshop 22

23 Detractor Die Size limited effectively cut cleaning area in half IEEE SW Test Workshop 23

24 142 mm 155 mm Cleaning summary Flat material Radius material Semi-Radius tip + = IEEE SW Test Workshop 24

25 142 mm 155 mm Future work Evaluate even lower cost materials Look for extension to other probe technologies i.e. Cobra, metrology usage Maximize cleaning medium lifetime Larger cleaning plate Thank you! Questions? IEEE SW Test Workshop 25