LRP equipment characterisation at low temperatures and application to polysilicon bipolar emitter processing
| Autor: | C. Parkes, Harold Gamble, F Ruddell, B M Armstrong |
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| Rok vydání: | 1990 |
| Předmět: |
Materials science
Silicon business.industry Polysilicon depletion effect Doping Bipolar junction transistor technology industry and agriculture chemistry.chemical_element Chemical vapor deposition engineering.material Condensed Matter Physics Electronic Optical and Magnetic Materials Monocrystalline silicon Polycrystalline silicon chemistry Materials Chemistry engineering Optoelectronics Electrical and Electronic Engineering business Common emitter |
| Zdroj: | Semiconductor Science and Technology. 5:765-770 |
| ISSN: | 1361-6641 0268-1242 |
| Popis: | A plasma-stimulated LPCVD rapid thermal processor has been developed. This processor is capable of operation in the limited reaction processing (LRP) regime and offers sequential in situ processes such as silicon deposition, plasma oxidation and interface pre-cleaning. Incident power with wavelength greater than 1.1 mu m is absorbed by free carriers and therefore sample doping density has a strong effect on the temperature-time profile obtained. It has been shown experimentally that heavily doped n-type samples reach higher temperature than lightly doped samples and exhibit faster ramp up times. The doping dependence is not so strongly observed for p-type samples. However, in general p-type samples do not attain as high a temperature as n-type samples. This is believed to be due to an additional absorption band for n-type silicon centred around wavelengths of 2.3 mu m. Direct monitoring of the process wafer is considered essential for accurate temperature-time profiles. The system has been used to fabricate n-p-n polycrystalline silicon emitter bipolar transistors. Transistors which received an in situ CF4 plasma pre-clean prior to polysilicon deposition exhibited gains similar to reference long emitter devices. The results were characterised by excellent uniformity across the samples indicating a clean, well controlled interface between the polysilicon and the silicon. This is highly important if LRP systems are to be applied to low-temperature epitaxy and heterojunction production on silicon. Transistors which received an in situ plasma clean, plasma oxidation followed by polysilicon deposition schedule exhibited higher gains. This supports the theory that the thin tunnellable oxide between the polycrystalline and monocrystalline silicon is responsible for the increased gain in the polysilicon emitter devices. |
| Databáze: | OpenAIRE |
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