中子嬗变掺杂直拉硅退火温度与目标电阻率的关系

由于中子辐照诱生的施主(简称中照施主)的产生,使得中子嬗变掺杂直拉硅(NTDCZ Si)的退火行为比较复杂。采用中子嬗变掺杂区熔硅(NTDFZ Si)或者CZ Si热处理消除热施主的退火工艺不能获得真实的目标电阻率。本文研究了NTDCZ Si退火温度与电阻率变化的关系,提出了获得准确目标电阻率的退火温度,讨论了中照施主的产生和消除条件。     

NTDCZSi中辐照施主的研究

本文对中子嬗变掺杂直拉硅(NTDCZSi)中辐照施主(ID)的退火行为和性质进行了研究,并探讨了不同中子辐照剂量和氧、碳含量对辐照施主形成的影响。首次报道了低于750℃热处理所产生的施主平台现象,并分别利用低温Hall测量和透射电镜对其进行了研究。结果表明,ID在禁带中产生～20meV的浅施主能级,其电活性起源于硅和二氧化硅沉淀的界面态。     

NTDCZSi内吸除技术的研究

利用中子嬗变掺杂(NTD)技术制备的CZSi(NTDCZSi)片在高温退火时,由于辐照缺陷与直拉硅中杂质氧的相互作用,可以加速内吸除(IG)效应的实现,获得理想的表面清洁区和体内吸杂区.本文探讨了将NTD技术与IG技术相结合的问题,并讨论了NTDCZSi IG效应机理.     

直拉硅单晶的中子嬗变掺杂

本文研究了直拉硅单晶(CASi)中子嬗变掺杂(NTD)的可行性、径向电阻率均匀性以及NTDCZSi内吸除效应的机理,证明了NTDCZSi是半导体器件的优良的新衬底材料.     

NTDCZSi中与氧有关的PL谱

中子嬗变掺杂直拉硅单晶在１０５０－１１００℃６ｈ退火时，体内产生以较大辐照缺陷为核心的氧沉淀和衍生的二次缺陷。光致发光在０．７６－１．０００ｅＶ范围出现了ＰＬ峰，而非中照的ＣＺＳｉ在相同条件下退火却滑以检测出明显的ＰＬ峰。     

中子嬗变掺杂硅（NTD—Si）的实用化是电力半导体器件发展的突破口之一

评述了30年前第一批用中子嬗变掺杂硅单晶(即无条纹硅)制造高电压、大电流整流管和晶闸管的报道。由此介绍硅材料的中子嬗变掺杂技术原理、发展进程，指出NTD硅的实用化成为电力半导体器件向大电流(大直径)、高电压方向发展的一个重要突破口。     

含氮CZ硅力学行为研究

用抗弯强度方法测定不同含氮量的原生和经550℃,750℃及900℃不等时热处理后直拉硅(NCZ-Si)的力学性能变化,结合红外光谱分析热处理过程氧、氮含量及形态的改变,认为在含氮直拉硅中,氮是以聚集在位错周围的氮氧硅络合物及氮氧硅沉淀初期微粒等多种形式钉扎位错的。     

含氮直拉硅中氧沉淀及伴生缺陷的特征

氧沉淀吸杂工艺的应用使直拉硅中氧的沉淀及伴生缺陷的形成及其微观结构成为热门的研究课题。氮因有钉扎位错,增加硅片强度的作用而引起重视,并在实际应用中收到了良好的效果,本工作用TEM和HREM研究了氮在直拉硅中沉淀相及其伴生缺陷的特征,并和不含氮的样品进行了对比。所用材料为N型无位错直拉硅单晶,含5.5×10~(17)cn~(-3)的氧和8.4×10~(15)cm~(-3)的氮,经过450℃64小时+750℃223小时+1050℃3小时三步退火处理。IR分析表明此时样品中53％的氧和100％的氮已消失,样品减薄到3μm后,用Ar~+减薄成电镜试样,在JEM-200cx上进行TEM和HREM观察。     

微氮硅单晶中的空洞型原生缺陷

研究了掺氮和不掺氮直拉硅单晶中,空洞型原生缺陷(voids)的分布行为和其退火性质.从两种晶体不同位置取样,观察与大尺寸voids相关的流水花样缺陷(FPD)沿晶体轴向的分布,然后在1050～1250℃下Ar气中退火不同时间.实验结果表明在掺氮直拉硅中与较大尺寸voids相关的FPD缺陷的密度大量减少,其体内这种FPD缺陷的退火行为与不掺氮直拉硅一样,在高温下才能被有效的消除.这表明在直拉硅中掺氮可以抑制大尺寸的voids的产生,而且掺氮硅中voids的内壁也有氧化膜存在.     

微氮硅单晶中的空洞型原生缺陷

研究了掺氮和不掺氮直拉硅单晶中,空洞型原生缺陷(voids)的分布行为和其退火性质.从两种晶体不同位置取样,观察与大尺寸voids相关的流水花样缺陷(FPD)沿晶体轴向的分布,然后在1050～1250℃下Ar气中退火不同时间.实验结果表明在掺氮直拉硅中与较大尺寸voids相关的FPD缺陷的密度大量减少,其体内这种FPD缺陷的退火行为与不掺氮直拉硅一样,在高温下才能被有效的消除.这表明在直拉硅中掺氮可以抑制大尺寸的voids的产生,而且掺氮硅中voids的内壁也有氧化膜存在.     

Generation lifetime improvement on MOS capacitor by fast neutron enhanced intrinsic gettering technique

Minority-carrier generation lifetime of MOS capacitors was improved by performing a fast neutron enhanced intrinsic gettering (NEIG) technique on the Czochralski (CZ) silicon wafers on which the devices were fabricated. With NEIG, the minority-carrier generation lifetime was possibly to be elevated high to 822 μs.It was shown that the NEIG method can be used to substitute for the conventional three-step H-L-H (H: high temperature annealing for a long time, L: low temperature annealing for a long time) intrinsic gettering method to have equivalent or better electrical properties but saving the processing time.     

Impact of phosphorus gettering parameters and initial iron level on silicon solar cell properties

We have studied experimentally the effect of different initial iron contamination levels on the electrical device properties of p‐type Czochralski‐silicon solar cells. By systematically varying phosphorus diffusion gettering (PDG) parameters, we demonstrate a strong correlation between the open‐circuit voltage (V_oc) and the gettering efficiency. Similar correlation is also obtained for the short‐circuit current (J_sc), but phosphorus dependency somewhat complicates the interpretation: the higher the phosphorus content not only the better the gettering efficiency but also the stronger the emitter recombination. With initial bulk iron concentration as high as 2 × 10¹⁴ cm⁻³, conversion efficiencies comparable with non‐contaminated cells were obtained, which demonstrates the enormous potential of PDG. The results also clearly reveal the importance of well‐designed PDG: to achieve best results, the gettering parameters used for high purity silicon should be chosen differently as compared with for a material with high impurity content. Finally we discuss the possibility of achieving efficient gettering without deteriorating the emitter performance by combining a selective emitter with a PDG treatment. Copyright © 2012 John Wiley & Sons, Ltd.     

Performance improvements of solar-grade crystalline silicon by continuously variable temperature phosphorous gettering process using a porous silicon layer

The Continuously Variable Temperature Phosphorous Gettering process using a Porous Silicon Layer (PSL-CVTPG) was proposed. PSL-CVTPG process can getter unwanted impurities from Solar-Grade silicon (SOG-Si) wafers and upgrade photovoltaic properties of solar cells more efficiently than conventional Constant Temperature Phosphorus Gettering process using a Porous Silicon Layer (PSL-CTPG). The resistivity, and mobility of majority carriers, and the effective lifetime of minority carriers were evaluated; the results showed that under certain conditions, the gettering effect of the PSL-CVTPG is better than that of the optimum PSL-CTPG. By orthogonal experiments, the optimum PSL-CVTPG conditions were found to be 900 °C/60 min+750 °C/60 min. PSL-CVTPG and CTPG processes under their respective optimum gettering conditions were used in the fabrication of solar cells, and cells based on SOG-Si wafers purified by the PSL-CVTPG process exhibited an amelioration in photovoltaic performances.     

Surface gettering of background impurities and defects in GaAs wafers

The first data on surface gettering of background impurities and defects from the bulk of single-crystal undoped GaAs(111) wafers are reported. The wafers were 1.6 mm thick, with an initial electron density of (1–3)×10¹⁵ cm^?3 and a mobility of 1500–2000 cm²/(V s) at room temperature. The wafers were cut from single crystals grown by the Czochralski method from a nonstoichiometric As-enriched Ga-As melt. Gettering was carried out during thermal treatment of the wafers in hydrogen at 400–850°C, with the preliminary deposited layer of Y or SiO₂ 1000 Å thick. As a result of gettering, the charge carrier density decreased to 10⁸–10¹⁰ cm^?3, while the mobility increased to 7000 cm²/(V s).     

Si substrate structure for solid-state color imagers

Si substrate structure for a low-noise MOS-type color imager was proposed. Photodiodes fabricated in a p-well suppress noise due to spurious red and infrared sensitivity, blooming, and smear, Furthermore, defects are diminished by optimized three-step intrinsic gettering and a new plural ion implantation method. Defects include those due to the defect nuclei inherent in a Si substrate grown by the Czochralski method and those due to high-dose boron-ion implantation for a low-resistance well layer.     

空位对普通和掺氮直拉硅单晶中氧沉淀形核的作用

研究了普通直拉(CZ)硅单晶和掺氮直拉(NCZ)硅单晶在氩气氛下进行1250℃/50s的快速热处理(RTP)后,再经600～1000℃的不同温区内的缓慢升温处理和1000℃保温处理后的氧沉淀行为.研究表明,由RTP引入的空位在700～800℃间缓慢升温退火时对CZ硅中氧沉淀形核的促进作用最显著,而在800～900℃间缓慢升温退火时对NCZ硅中氧沉淀形核的促进作用最显著;在800以上,氮促进氧沉淀形核的作用比空位更强.此外,提出了适用于CZ和NCZ硅片的基于高温RTP和低温缓慢升温热处理的内吸杂工艺.     

Erbium-doped silicon epilayers grown by liquid-phase epitaxy

A careful analysis of the features of the spectroscopic properties of Er-doped and undoped epitaxial silicon films grown by liquid-phase epitaxy at 950 °C in silicon-saturated indium melts shows that threading dislocations work as effective gettering sites for erbium and oxygen. The last impurity is incorporated in the epitaxial film by back diffusion from the Czochralski substrate during the growth. The photoluminescence emitted by these films appears to be related to the dislocation and is enforced by the presence of erbium-oxygen complexes. Fiz. Tekh. Poluprovodn. 33, 642–643 (June 1999) Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor.     

Phosphorus gettering of iron by screen‐printed emitters in monocrystalline Czochralski silicon wafers

In this paper, we demonstrate single‐sided screen‐printed emitters in thin monocrystalline Czochralski silicon (Cz‐Si) wafers with an improved gettering of iron compared with conventional double‐sided POCl₃ emitters. The phosphorus dopant pastes used have to be chosen carefully to provide a sufficiently low emitter sheet resistance and to avoid iron contamination. The iron concentration is determined in a non‐destructive way from the minority carrier lifetime obtained by quasi‐steady‐state photoconductance measurements, down to levels not yet demonstrated for screen‐printed emitters. In addition, the well‐known metastable boron–oxygen complexes in Cz‐Si have been transferred into a stable state by light‐induced degradation prior to these measurements. Copyright © 2012 John Wiley & Sons, Ltd.     

热处理气氛对直拉硅单晶中体缺陷的影响

研究了五种不同的热处理气氛对直拉硅中氧沉淀及其诱生缺陷的影响.实验结果表明,经过低-高退火处理的硅片继续在五种不同的气氛中高温退火,氧沉淀会部分溶解,其溶解量与热处理气氛没有明显的关系,但不同气氛中处理的硅片中体缺陷(BMDs)的分布不同.并对此现象的机理进行了讨论,认为热处理气氛影响了硅片中点缺陷的分布从而影响到BMDs的分布.此研究对集成电路生产中内吸杂工艺的保护气氛的选择有指导意义.     

热处理气氛对直拉硅单晶中体缺陷的影响

研究了五种不同的热处理气氛对直拉硅中氧沉淀及其诱生缺陷的影响.实验结果表明,经过低-高退火处理的硅片继续在五种不同的气氛中高温退火,氧沉淀会部分溶解,其溶解量与热处理气氛没有明显的关系,但不同气氛中处理的硅片中体缺陷(BMDs)的分布不同.并对此现象的机理进行了讨论,认为热处理气氛影响了硅片中点缺陷的分布从而影响到BMDs的分布.此研究对集成电路生产中内吸杂工艺的保护气氛的选择有指导意义.