Precipitation of Oxygen and Intrinsic Gettering in Silicon
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PRECIPITATION OF OXYGEN AND INTRINSIC GETTERING IN SILICON
W. K. TICE IBM General Technology Division, Essex Junction, T. Y. TAN IBM Research Division, Yorktown Heights,
NY
VT
05452
10598
ABSTRACT In this review, dislocations introduced by prismatic punching at SiO precipitate sites in Czochralski silicon are shown to ac? as metal adsorption centers. Conditions necessary to localize SiO2 precipitate and dislocation complexes in wafer regions remote from semiconductor devices are discussed. This localization achieves an intrinsic gettering effect. The application of the intrinsic gettering mechanism to bipolar and MOS device technologies is shown to improve device performance and leakage limited yields.
INTRODUCTION Recently, it has been shown that the amount and distribution of oxygen in single crystal silicon wafers can have a profound influence on semiconductor device behavior and yields. This review deals with the mechanism of oxygen precipitation and consequent dislocation generation in silicon. The effects of localizing such SiO2 precipitate-dislocation complexes (SiO2 PDC) in wafer regions remote from active semiconductor devices is discussed in terms of bipolar device leakage limited yields (LLY) and MOS storage time. It will be shown that such regions perform a gettering role, thereby enhancing device performance and yields. The subject will be treated in the following sequence: 1.
Introduction of oxygen during Czochralski
2.
Evidence for heterogeneous
3.
Growth of SiO2 precipitates.
4.
Prismatic punching of dislocations by a compressive misfit stress field introduced into the silicon matrix by differential contraction between precipitates and matrix during wafer cooling.
5.
Adsorption of metallic impurities by SiO2 PDC.
6.
Localization of SiO2 PDC in wafer regions remote from active devices
(CZ)
crystal growth.
nucleation of SiO2 precipitates in
silicon.
to achieve an intrinsic gettering effect. 7.
Experimental results showing beneficial results of intrinsic gettering on semiconductor device yields/performance.
368 INTRODUCTION OF OXYGEN INTO SILICON During silicon single crystal growth using the CZ method, the quartz crucible and silicon undergo the reaction: [1-4]
Si + Sio2 -*2SiO
At typical crystal pulling temperatures (-1412 °C), SiO is volatile and passes out of the liquid-solid interface. This results in a nonhomogeneous distribution of oxygen at the crystal-liquid interface, giving a nonuniform distribution across the boule diameter. Depletion of SiO during crystal pulling can also lead to nonuniform oxygen distribution along the length of the silicon 3 boule. Typical oxygen concentrations for a single crystal are 2-20 x 1017 at./cm . The oxygen is
present initially in
Si-O-Si bound interstitial
form, which
gives an infrared absorption band at 9 pm [5,6]. NUCLEATION OF OXIDE PRECIPITATES The possibility of SiO2 precipitation due to decomposition of silicon-oxygen solid solution had been discussed by Patel in 1964 [7]. Later, Batavin [8J published curves of oxygen
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