Low Alpha Materials and Metrology in the IC Indust……

1、Low Alpha Materials and Metrology in the IC IndustryCurrent Status and Future RequirementsDr. Brett M. Clark, HoneywellJeff Wilkinson, MedtronicJuly 25, 20052LBCF WorkshopClark & Wilkinson, 2005Outline Soft errors & IC development Current Status-MaterialswTypes wPurity / Activity requirement

2、s-MetrologywAlpha emissivitywInstrument capability Future Requirements-Material specificationswChanges on the horizonwPurity /Activity requirements become more stringent-MetrologywImprovements3LBCF WorkshopClark & Wilkinson, 2005Integrated Circuits and Soft Error Upsets Energetic particles depos

3、iting energy/charge in critical nodes Radioisotopes in component materials Cosmic 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 subst

4、rateIon pathDepletion zone4LBCF WorkshopClark & Wilkinson, 2005IC Materials Overview 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-

5、0.0002 hr 1 cm 2:2006 Primary alpha emitters-210Pb in Pb/Sn solders-U & ThMaterial purity critical to reliability Low Alpha Material Specification0.00010.0010.010.119901995200020052010Yearcts/hr/cm2 5LBCF WorkshopClark & Wilkinson, 2005Current Material Challenges: Contamination Any material

6、with U and/or Th above 1 ppb Some 99.99% materials fail-Sn, In Possible contaminants-Refractory 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

7、 contamination hazard until proven otherwiseActivity vs U & Th concentration0.0000.0010.0020.0030.0040.00500.0020.0040.0060.0080.01Concentration (ppm)Alpha/hr/cm2Uranium (ppm)Thorium (ppm)cumulative6LBCF WorkshopClark & Wilkinson, 2005Current Instrumentation Capability Industry uses Gas Prop

8、ortional Counters-Area :1000 cm2 -Geometry: 2-Background- 2-3 cph optimal, 4-6 nominal-No energy spectroscopy capabilitywLimited ability to identify contamination sources 0.002 analysis requires 7 days counting time for 20% RSDCurrent instrumentation incapable of timely analysis Ordela 8600Alpha Sci

9、ences 19507LBCF WorkshopClark & Wilkinson, 2005Precision/Counting Time trade offPrecision vs Counting time1000 sq cm, BG = 4 cph01020304050012345678910Time (days)% RSD0.0010.0028LBCF WorkshopClark & Wilkinson, 2005Counting time determined by detector sizeDetector Area vs Count TimeBG = 4 cph

10、, RSD = 20%01000200030004000012345Time (days)Area (sq cm)0.0020.0019LBCF WorkshopClark & Wilkinson, 2005Alpha counting rates relative to backgroundSample Signal and Background Noise 010203040500100200300HourCounts0.02BG0.002S/N = 5.2S/N = 1.1Solution: Increase signal and/or decrease noise 10LBCF

11、 WorkshopClark & Wilkinson, 2005Background effect on counting time Background vs Count TimeArea =1000 sq cm, 30% RSD00.511.522.533.544.5502468Time (Days)Counter background (cph)0.0020.0010.000211LBCF WorkshopClark & Wilkinson, 2005Material Requirements - Future 0.001 hr 1 cm 2 material in ma

12、nufacturing Technology roadmaps: 0.0002 hr 1 cm 2 in 2006-2 s from 1 square meter area per hour! With current measurement technology this would take 228 days to measure with 20% relative precision Where is the specification bottom? -Design dependent-Where influences other than cosmic are insignifica

13、nt Measurement times compatible with manufacturing schedules Instrumentation improvement required 12LBCF WorkshopClark & Wilkinson, 2005Instrumentation for the Future Measure increasingly low activity levels in timely manner without loss of precision Increase signal/noise ratio-Increase detector

14、 area without increasing background Optimum solution S/N requires background0.5 cph Current progress-Large area Si detectors-Cr-39 hole counting Low background facilities-Eliminate cosmic component-Enable higher purity materials in detector constructionwDecrease detector background-Assess detector q

15、uality-Validate production methods and materialsSignificant opportunity for improvement 13LBCF WorkshopClark & Wilkinson, 2005Best case 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 s