LowAlphaMaterialsandMetrologyintheICIndustry

1、low alpha materials and metrology in the ic industrycurrent status and future requirementshttp:/ workshopclark & wilkinson, 2005outline soft errors & ic development current status-materialswtypes wpurity / activity requirements-metrologywalpha emissivitywinstrument capability future requirements-mat

2、erial specificationswchanges on the horizonwpurity /activity requirements become more stringent-metrologywimprovements3lbcf workshopclark & wilkinson, 2005integrated circuits and soft error upsets energetic particles depositing energy/charge in critical nodes radioisotopes in component materials cos

3、mic ray contributions microelectronic design trends -flip chip -smaller geometries/decreasing line widths-increased vulnerability to soft error mechanismssoft errors = significant issue in the future +-n dopedp doped substrateion pathdepletion zone4lbcf workshopclark & wilkinson, 2005ic materials ov

4、erview high purity metals and alloys-cu, al, ta, w, ti, pb, sn, ag, ru range in purity from 99.99% to 99.9999% alpha activity requirements-0.02 hr 1 cm 2 : early 1990s-0.01 hr 1 cm 2 : late 1990s-0.002 hr 1 cm 2: 2001-0.0002 hr 1 cm 2:2006 primary alpha emitters-210pb in pb/sn solders-u & thmaterial

5、 purity critical to reliability low alpha material specification0.00010.0010.010.119901995200020052010yearcts/hr/cm2 5lbcf workshopclark & wilkinson, 2005current material challenges: contamination any material with u and/or th above 1 ppb some 99.99% materials fail-sn, in possible contaminants-refra

6、ctory materials and ceramics-abrasives -atmospheric dust and debris-commercial metals & alloys all stages of manufacturing & processing must be controlled & monitored assume any material is an alpha contamination hazard until proven otherwiseactivity vs u & th concentration0.0000.0010.0020.0030.0040

7、.00500.0020.0040.0060.0080.01concentration (ppm)alpha/hr/cm2uranium (ppm)thorium (ppm)cumulative6lbcf workshopclark & wilkinson, 2005current instrumentation capability industry uses gas proportional counters-area :1000 cm2 -geometry: 2-background- 2-3 cph optimal, 4-6 nominal-no energy spectroscopy

8、capabilitywlimited ability to identify contamination sources 0.002 analysis requires 7 days counting time for 20% rsdcurrent instrumentation incapable of timely analysis ordela 8600alpha sciences 19507lbcf workshopclark & wilkinson, 2005precision/counting time trade offprecision vs counting time1000

9、 sq cm, bg = 4 cph01020304050012345678910time (days)% rsd0.0010.0028lbcf workshopclark & wilkinson, 2005counting time determined by detector sizedetector area vs count timebg = 4 cph, rsd = 20%01000200030004000012345time (days)area (sq cm)0.0020.0019lbcf workshopclark & wilkinson, 2005alpha counting

10、 rates relative to backgroundsample signal and background noise 010203040500100200300hourcounts0.02bg0.002s/n = 5.2s/n = 1.1solution: increase signal and/or decrease noise 10lbcf workshopclark & wilkinson, 2005background effect on counting time background vs count timearea =1000 sq cm, 30% rsd00.511

11、.522.533.544.5502468time (days)counter background (cph)0.0020.0010.000211lbcf workshopclark & wilkinson, 2005material requirements - future 0.001 hr 1 cm 2 material in manufacturing technology roadmaps: 0.0002 hr 1 cm 2 in 2006-2 s from 1 square meter area per hour! with current measurement technolo

12、gy this would take 228 days to measure with 20% relative precision where is the specification bottom? -design dependent-where influences other than cosmic are insignificant measurement times compatible with manufacturing schedules instrumentation improvement required 12lbcf workshopclark & wilkinson

13、, 2005instrumentation for the future measure increasingly low activity levels in timely manner without loss of precision increase signal/noise ratio-increase detector area without increasing background optimum solution s/n requires background0.5 cph current progress-large area si detectors-cr-39 hol

14、e counting low background facilities-eliminate cosmic component-enable higher purity materials in detector constructionwdecrease detector background-assess detector quality-validate production methods and materialssignificant opportunity for improvement 13lbcf workshopclark & wilkinson, 2005best cas

15、e scenario background vs count timearea =10000 sq cm, 10% rsd00.511.522.533.544.5502468time (days)counter background (cph)0.0020.0010.0002large area - zero background - high precision 14lbcf workshopclark & wilkinson, 2005conclusions ic improvements continue to require lower activity materials as material activity decreases, contamination risk increases current instrumentation has signific