A study of in-situ doped polysilicon emitters for deep submicron bipolar transistors
A study of in-situ doped polysilicon emitters for deep submicron bipolar transistors
This thesis investigates the use of in-situ phosphorus doped polysilicon emitter contacts in deep submicron bipolar transistors. The effects of different ex-situ and in-situ cleans prior to polysilicon deposition on the electrical characteristics of low thermal budget bipolar transistors are investigated. Emitter contact deposition in a cluster tool is also compared with deposition in a LPCVD furnace. SIMS results show that an in situ hydrogen bake in a cluster tool gives an extremely low oxygen dose at the interface of 6.3x1013cm-2. This compares with 7.7x1014 and 2.9x1015cm-2 for an ex-situ. HF etch and deposition in a cluster tool or a LPCVD furnace respectively. TEM shows that the in-situ hydrogen bake results in single-crystal silicon with a high density of defects, including dislocations and twins. The ex-situ HF etch gives polycrystalline silicon for deposition in both a cluster tool and a LPCVD furnace. The single-crystal silicon emitter contact has an extremely low emitter resistance of 21Ω.μm2 in spite of the high defect density and the light emitter anneal of 30s at 900oC. This compares with emitter resistances of 151 and 26Ω.μm2 for the polycrystalline silicon contacts produced using an ex-situ HF etch and deposition in a cluster tool or a LPCVD furnace respectively.
The in-situ hydrogen bake is applied in the fabrication of deep sub-micron bipolar transistors. Transistors with in-situ phosphorus doped single-crystal silicon emitters have an almost ideal base current even at a very small emitter geometry. The base current ideality factor varies from 1.009 at an emitter geometry of 0.46x1.03μm2 to 1.016 at an emitter geometry of 0.25x1.08μm2. In contrast, in conventional arsenic implanted polysilicon emitters deposited in a LPCVD furnace, the base current ideality factor degrades from 1.13 to 1.99 on scaling the emitter size from 0.47x1.03μm2 to 0.25x1.07μm2. The in-situ hydrogen bake gives a very low interface oxygen dose of 5.3x1013cm-2, which correlates well with a very low emitter resistance of 6.6 Ω.μm2.
University of Southampton
1999
Abdul Rahim, Ahmad Ismat
(1999)
A study of in-situ doped polysilicon emitters for deep submicron bipolar transistors.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
This thesis investigates the use of in-situ phosphorus doped polysilicon emitter contacts in deep submicron bipolar transistors. The effects of different ex-situ and in-situ cleans prior to polysilicon deposition on the electrical characteristics of low thermal budget bipolar transistors are investigated. Emitter contact deposition in a cluster tool is also compared with deposition in a LPCVD furnace. SIMS results show that an in situ hydrogen bake in a cluster tool gives an extremely low oxygen dose at the interface of 6.3x1013cm-2. This compares with 7.7x1014 and 2.9x1015cm-2 for an ex-situ. HF etch and deposition in a cluster tool or a LPCVD furnace respectively. TEM shows that the in-situ hydrogen bake results in single-crystal silicon with a high density of defects, including dislocations and twins. The ex-situ HF etch gives polycrystalline silicon for deposition in both a cluster tool and a LPCVD furnace. The single-crystal silicon emitter contact has an extremely low emitter resistance of 21Ω.μm2 in spite of the high defect density and the light emitter anneal of 30s at 900oC. This compares with emitter resistances of 151 and 26Ω.μm2 for the polycrystalline silicon contacts produced using an ex-situ HF etch and deposition in a cluster tool or a LPCVD furnace respectively.
The in-situ hydrogen bake is applied in the fabrication of deep sub-micron bipolar transistors. Transistors with in-situ phosphorus doped single-crystal silicon emitters have an almost ideal base current even at a very small emitter geometry. The base current ideality factor varies from 1.009 at an emitter geometry of 0.46x1.03μm2 to 1.016 at an emitter geometry of 0.25x1.08μm2. In contrast, in conventional arsenic implanted polysilicon emitters deposited in a LPCVD furnace, the base current ideality factor degrades from 1.13 to 1.99 on scaling the emitter size from 0.47x1.03μm2 to 0.25x1.07μm2. The in-situ hydrogen bake gives a very low interface oxygen dose of 5.3x1013cm-2, which correlates well with a very low emitter resistance of 6.6 Ω.μm2.
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Published date: 1999
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Local EPrints ID: 463934
URI: http://eprints.soton.ac.uk/id/eprint/463934
PURE UUID: 595f9e12-7f2e-47ba-a1bf-1f585c4c5574
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Date deposited: 04 Jul 2022 20:59
Last modified: 04 Jul 2022 20:59
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Author:
Ahmad Ismat Abdul Rahim
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