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Improved Yield on Bipolar Device Products

IP.com Disclosure Number: IPCOM000046830D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Case, S: AUTHOR [+4]

Abstract

This article defines the optimum oxygen precipitation range to provide minimum device leakage characteristics for bipolar devices. The optimum oxygen precipitation range for maximum leakage limited yield is 9-15 PPMA. Below 9 PPMA, the amount of oxygen precipitation is insufficient to getter impurities found in device processing. Above 15 PPMA, the excessive precipitation weakens the silicon lattice, making the wafer susceptible to plastic deformation (warpage) and associated slip. The following table shows the effects of oxygen precipitation on electrical test yield. (Image Omitted) The oxygen precipitation size and density also affect leakage limited yield. For optimum yields, a small but dense precipitation morphology is required.

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Improved Yield on Bipolar Device Products

This article defines the optimum oxygen precipitation range to provide minimum device leakage characteristics for bipolar devices. The optimum oxygen precipitation range for maximum leakage limited yield is 9-15 PPMA. Below 9 PPMA, the amount of oxygen precipitation is insufficient to getter impurities found in device processing.

Above 15 PPMA, the excessive precipitation weakens the silicon lattice, making the wafer susceptible to plastic deformation (warpage) and associated slip. The following table shows the effects of oxygen precipitation on electrical test yield.

(Image Omitted)

The oxygen precipitation size and density also affect leakage limited yield. For optimum yields, a small but dense precipitation morphology is required. To achieve the desired oxygen precipitation range, crystal anneals in the range of 600-800OEC must be performed to create adequate nucleation sites for oxygen precipitation. The anneals are the controlling factor in determining the oxygen precipitation rate. The oxygen precipitation test used to determine optimum oxygen precipitation range is as follows: Precipitation Test __________________

(Image Omitted)

1. Measure interstitial oxygen content. 2. Insert wafers into furnace at 825 C.OE Hold for 1 minute; oxygen ambient of 1.5 1/m. 3. Ramp furnace to 925 at 5 /min. At 925 C add 3% HCl (50 cc/min) to oxygen ambient (1.5 1/min) for 10

minutes. Shut off HCl and continue flow for 15

minutes. Cha...