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標題: The Variation of Bulk Microdefect for Heavy Boron Doped Czochralski Silicon Crystal after Simulated Process Thermal Cycles
作者: Yi, Kang Meng
關鍵字: bulk microdefect;磊晶;gettering;oxygen;heavy doped boron.;去疵;矽晶內部微缺陷;氧;重摻硼
出版社: 精密工程研究所
重摻Cz矽晶片廣泛的被用來當p/p+ epi wafer的基板。然而重摻硼矽晶圓經過熱處理後,會產生大量的內部缺陷,且內部缺陷在長磊晶的過程中極易延伸生長至磊晶層內,有害於後續的元件製造,因此瞭解重摻硼矽晶片內部微觀缺陷種類的改變及如何創造出相當寬敞的無缺陷表層便值得深入去探討。在本研究中,我們模擬磊晶和CMOS高溫製程的熱歷程而設計出二階段和三階段熱處理,來研究重摻硼矽晶圓內部缺陷和無缺陷區的形成。並與先前本實驗室輕摻硼重要結果做比較。
隨著摻雜硼原子濃度的增加會增強氧凝聚物的析出,因而會縮短氧凝聚物群的消失與疊差的產生所需之孕核時間。重摻硼矽晶片經低溫孕核短時間(0~4小時),試片內部缺陷種類即以疊差為主。同時隨著硼摻雜濃度的增加, 盤狀氧凝聚物因為更多硼原子的參與,體積會變得較為肥胖短小,圍繞在盤狀析出物周圍的應力降低,試片內部缺陷經過高溫熱處理後便轉變成為短胖的疊差。
複晶矽膜沉積不影響試片內部缺陷的種類, 但複晶矽膜沉積的過程會增強矽晶片內凝結核的成長,疊差密度會略微增加,也因而不易創造出足夠寬敞的無缺陷區,因此氧含量高的重摻硼矽晶片並不適合用來生長複晶矽膜層。

The P- epitaxy on heavy boron doped wafer has been well employed in power MOS device for reducing vertical on-resistance and also provide effective latch-up hardening for advanced CMOS technology. However, the micro-defect generated from the substrate greatly affects the quality of epitaxial layer. To control the density of bulk micro-defect as well as to create a comfortable denuded zone is an important research subject of applying heavy boron doped substrate for IC manufacture. In this resear- ch, a systematical two-step (low — high) and three-step (high-low- high) anneals was carried out to investigate the bulk-micro -defect (BMD) for B+ Cz silicon. Some important information described as follows were obtained.
The increase of boron concentration enhanced the oxygen precipitation. The high density of stacking faults was observed with much short nucleation annealing. The feature of etched stacking faults in heavy boron doped silicon is much plump (more less like elliptic shape) than that in light boron doped silicon. The feature of the bulk defects in the heavy doped silicon is different from that of the light doped silicon, in upon with the annealing time and annealing temperature.
The denuded zone generated after two-step anneal is not easy to be observed, A long high temperature annealing prior to the two-step anneal is needed. 1150 ℃ annealing up to 4 hours can generate a denuded zone size of about 20 um. The wet ambient can provide a much wide denuded zone than dry N2 anneal.
The poly-silicon film deposition process reduce the denuded zone size drastically for the medium to high oxygen concentration silicon used in this research. Therefore, it is not appropriated to use the poly film as back side gettering for high oxygen concentration wafers.
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