{"title":"Thermal stress relaxation phenomenon through forming the interstitial region in CZ silicon pulled with rapid and slow cooling heat shields","authors":"Takao Abe","doi":"10.1016/j.pcrysgrow.2022.100579","DOIUrl":null,"url":null,"abstract":"<div><p><span><span>This review article aims to clarify a mechanism of point defects formation in a CZ Si crystal through an experimental arrangement using the two kinds of heat shields with different slow-pulling periods. Point defects in a melt grown </span>silicon<span> crystal have been studied for a long time. The author and his co-researchers have reported about “Mechanism for generating interstitial atoms by thermal stress during silicon crystal growth” [in Progress in Crystal Growth and Characterization of Materials, </span></span><strong>66</strong><span> (2019) 36-46]. The experimental arrangement includes constant growing, changing pulling rate and finally detaching crystals from the melt. The two types of heat shields were used to change the cooling history of the grown crystals, for changing a temperature gradient at a bulk part in the grown crystal, </span><em>G</em><sub>b</sub>. In order to prove that the formation of an interstitial region or a boundary of vacancies (Vs)/interstitials (Is) in a silicon crystal is a phenomenon of relaxing thermal stress, the author explains that a <em>G</em><sub>b</sub> in a crystal forms thermal stress and causes some silicon atoms at lattice positions to move to the closest interstitial sites to relax the stress. The author defines a new term of metastable interstitial atom, I’, or I's as the plural of I’. The I’ coexists with the metastable vacancy V’ from where the I’ is displaced. The plural of V’ is defined to be V's. The author defines the above state to be a complex (I’+ V’), or (I ’+ V’)s as the plural of (I’+ V’), and explains that the (I’+ V’) s convert to Is and form the Is region. The (I’+ V’) is considered as the Frenkel pair-like complex.</p><p>The crystals were firstly pulled with a high pulling rate, and the pulling rate was consequently decreased to a slow one. Then the crystals were pulled with the slow constant pulling rate for different periods making different cooling processes. Finally, the grown crystals were detached from the melt and cooled rapidly. Characterization of defects, such as Vs, Is, and defect-free (D-F) regions were identified in X-ray topographs (XAOP(s)). Wafer lifetime mapping (WLTM(s)) allows confirming dislocation loop (DL) regions. The results show that the Is are generated depending on the pulling period of the slow pulling and the shapes of the heat shields. The Is and DL regions are formed in a region at temperatures near the melting point. The Is form an Is region through a defect-free (D-F) region, forming the Vs/Is boundary. When the thermal stress weakens, the DL region changes to the Is region; the Is region changes to the D-F region; and the D-F region changes to the Vs region. Temperature gradient distribution is induced toward various directions at different parts of the growing crystal depending on the different slow-pulling periods. The temperature gradient, <em>G</em><sub>b</sub>, includes a temperature gradient from the cooled region shaded by the heat shield to the growth interface and a temperature gradient from the upper surface cooled during the long-time growth to the growth interface. The <em>G</em><sub>b</sub> exceeding a certain threshold at near the melting point forms thermal stress, generating Is to relax the stress.</p></div>","PeriodicalId":409,"journal":{"name":"Progress in Crystal Growth and Characterization of Materials","volume":"68 3","pages":"Article 100579"},"PeriodicalIF":4.5000,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Progress in Crystal Growth and Characterization of Materials","FirstCategoryId":"88","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0960897422000225","RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CRYSTALLOGRAPHY","Score":null,"Total":0}
引用次数: 0
Abstract
This review article aims to clarify a mechanism of point defects formation in a CZ Si crystal through an experimental arrangement using the two kinds of heat shields with different slow-pulling periods. Point defects in a melt grown silicon crystal have been studied for a long time. The author and his co-researchers have reported about “Mechanism for generating interstitial atoms by thermal stress during silicon crystal growth” [in Progress in Crystal Growth and Characterization of Materials, 66 (2019) 36-46]. The experimental arrangement includes constant growing, changing pulling rate and finally detaching crystals from the melt. The two types of heat shields were used to change the cooling history of the grown crystals, for changing a temperature gradient at a bulk part in the grown crystal, Gb. In order to prove that the formation of an interstitial region or a boundary of vacancies (Vs)/interstitials (Is) in a silicon crystal is a phenomenon of relaxing thermal stress, the author explains that a Gb in a crystal forms thermal stress and causes some silicon atoms at lattice positions to move to the closest interstitial sites to relax the stress. The author defines a new term of metastable interstitial atom, I’, or I's as the plural of I’. The I’ coexists with the metastable vacancy V’ from where the I’ is displaced. The plural of V’ is defined to be V's. The author defines the above state to be a complex (I’+ V’), or (I ’+ V’)s as the plural of (I’+ V’), and explains that the (I’+ V’) s convert to Is and form the Is region. The (I’+ V’) is considered as the Frenkel pair-like complex.
The crystals were firstly pulled with a high pulling rate, and the pulling rate was consequently decreased to a slow one. Then the crystals were pulled with the slow constant pulling rate for different periods making different cooling processes. Finally, the grown crystals were detached from the melt and cooled rapidly. Characterization of defects, such as Vs, Is, and defect-free (D-F) regions were identified in X-ray topographs (XAOP(s)). Wafer lifetime mapping (WLTM(s)) allows confirming dislocation loop (DL) regions. The results show that the Is are generated depending on the pulling period of the slow pulling and the shapes of the heat shields. The Is and DL regions are formed in a region at temperatures near the melting point. The Is form an Is region through a defect-free (D-F) region, forming the Vs/Is boundary. When the thermal stress weakens, the DL region changes to the Is region; the Is region changes to the D-F region; and the D-F region changes to the Vs region. Temperature gradient distribution is induced toward various directions at different parts of the growing crystal depending on the different slow-pulling periods. The temperature gradient, Gb, includes a temperature gradient from the cooled region shaded by the heat shield to the growth interface and a temperature gradient from the upper surface cooled during the long-time growth to the growth interface. The Gb exceeding a certain threshold at near the melting point forms thermal stress, generating Is to relax the stress.
本文旨在通过两种不同慢拉周期的隔热层的实验布置,阐明czsi晶体中点缺陷的形成机制。熔体生长硅晶体中的点缺陷已经被研究了很长时间。作者和他的合作研究人员报道了“硅晶体生长过程中热应力产生间隙原子的机制”[在晶体生长和材料表征中的进展,66(2019)36-46]。实验安排包括恒定生长,改变拉速,最后从熔体中分离晶体。利用这两种类型的热屏蔽来改变生长晶体的冷却历史,从而改变生长晶体中块体部分的温度梯度。为了证明硅晶体中空位区或空位边界(Vs)/空位边界(Is)的形成是一种热应力松弛现象,作者解释了晶体中的一个Gb形成热应力,使晶格位置的一些硅原子移动到最近的空位位置以松弛应力。作者定义了一个亚稳态间隙原子的新名词I',或I's作为I'的复数形式。I '与亚稳空位V '共存,I '从那里被移开。V'的复数形式被定义为V's。作者将上述状态定义为复合体(I ' + V '),或者(I ' + V ')的复数形式(I ' + V '),并解释了(I ' + V ')转化为Is,形成Is区域。(I ' + V ')被认为是Frenkel对样复合体。首先以较高的拉拔速率对晶体进行拉拔,随后拉拔速率逐渐降低到较慢的拉拔速率。然后以缓慢恒定的拉拔速率对晶体进行不同周期的拉拔,形成不同的冷却过程。最后,生长的晶体从熔体中分离出来并迅速冷却。缺陷的表征,如v、i和无缺陷(D-F)区域在x射线地形图中被识别(XAOP(s))。晶圆寿命映射(WLTM(s))允许确认位错环(DL)区域。结果表明,慢拉过程的拉拔周期和隔热板的形状决定了热阻的产生。i区和DL区是在接近熔点的温度下形成的。通过无缺陷区(D-F)形成一个Is区,形成Vs/Is边界。当热应力减弱时,DL区变为Is区;Is区变为D-F区;D-F区变为v区。随着慢拉周期的不同,生长晶体不同部位的温度梯度分布也不同。温度梯度Gb包括从隔热罩遮蔽的冷却区域到生长界面的温度梯度和从长时间生长过程中冷却的上表面到生长界面的温度梯度。在熔点附近超过一定阈值的Gb形成热应力,产生Is使应力松弛。
期刊介绍:
Materials especially crystalline materials provide the foundation of our modern technologically driven world. The domination of materials is achieved through detailed scientific research.
Advances in the techniques of growing and assessing ever more perfect crystals of a wide range of materials lie at the roots of much of today''s advanced technology. The evolution and development of crystalline materials involves research by dedicated scientists in academia as well as industry involving a broad field of disciplines including biology, chemistry, physics, material sciences and engineering. Crucially important applications in information technology, photonics, energy storage and harvesting, environmental protection, medicine and food production require a deep understanding of and control of crystal growth. This can involve suitable growth methods and material characterization from the bulk down to the nano-scale.