4H-SiC外延层中堆垛层错与衬底缺陷的关联性研究

doi:10.15541/jim20180443

摘要/Abstract

摘要：

本研究探讨了同质外延生长的4H-SiC晶片表面堆垛层错(SF)的形貌特征和起因。依据表面缺陷检测设备KLA-Tencor CS920的光致发光(PL)通道和形貌通道的特点, 将SF分为五类。其中I类SF在PL通道图中显示为梯形, 在形貌图中不显示; II类SF在PL通道图中显示为三角形, 且与I类SF重合, 在形貌图中显示为胡萝卜形貌。III-V类SF在PL通道图中均显示为三角形, 在形貌图中分别显示为胡萝卜、无对应图像或三角形。研究结果表明, I类SF起源于衬底的基平面位错(BPD)连线, 该连线平行于<1$\bar{1}$00>方向, 在生长过程中沿着<11$\bar{2}$0>方向移动, 形成基平面SF。II类和大部分的III-IV类SF起源于衬底的BPD, 其中一个BPD在外延过程中首先转化为刃位错(TED), 并在外延过程中延<0001>轴传播, 其余BPD或由TED分解形成的不全位错(PDs)在(0001)面内传播形成三角形基平面SF。其余的III-V类SF起源于衬底的TED或其它。II-III类SF在形貌通道中显示为胡萝卜, 而IV类SF不显示, 主要区别在于外延过程中是否有垂直于(0001)面的棱镜面SF与表面相交。上述研究说明减少衬底的BPD, 对减少外延层中的SF尤为重要。

关键词: 碳化硅, 同质外延, 位错, 堆垛层错

Abstract:

The morphology and causes of stacking faults (SF) in homoepitaxial layers of 4H-SiC were studied. According to characteristics of PL images and morphology images of 4H-SiC five kinds of SFs have been defined. In the PL images, the morphologies of SF I and SF II-V are trapezoidal and triangular, respectively. SF II lays inside the area of SF I. In the morphology images, SF I and IV are not seen, SF II-III are carrot shaped and SF V is triangular respectively. The results show that SF I is a kind of base plane SF which originates from the base plane dislocation (BPD) lines of the substrate, parallel to <1$\bar{1}$00> direction and moving along <11$\bar{2}$0> direction during epitaxial growing. SF II and most of SF III-IV originate from BPDs in substrate. One BPD converts into threading dislocation during epitaxial growing and propagates to the surface along <0001> direction, while other BPDs or partial dislocations originating from threading dislocation propagate in (0001) plane to form triangular base plane SFs. The rest of SF III-IV and SF V originate from TED or other defects in substrate. SF II-III display carrots morphology because a prism SF plane perpendicular to the (0001) plane is formed to intersect with surface during epitaxial growing process. SF IV is not seen in the morphology image because no prism SF plane is formed to intersect with surface. All results demonstrated that reducing BPDs of the substrate is especially important for reducing SFs in the epitaxial layers.

Key words: SiC, homoepitaxial, dislocation, stacking fault

中图分类号:

郭钰, 彭同华, 刘春俊, 杨占伟, 蔡振立. 4H-SiC外延层中堆垛层错与衬底缺陷的关联性研究[J]. 无机材料学报, 2019, 34(7): 748-754.

GUO Yu, PENG Tong-Hua, LIU Chun-Jun, YANG Zhan-Wei, CAI Zhen-Li. Correlation between Stacking Faults in Epitaxial Layers of 4H-SiC and Defects in 4H-SiC Substrate[J]. Journal of Inorganic Materials, 2019, 34(7): 748-754.

图/表 9

图1 CS920检测SF的图像(a)激发波长为355nm的PL通道图和(b)形貌通道图

Fig. 1 SF images tested by CS920 (a) PL images excited by 355 nm wavelength; (b) morphology images

图2 I类和II类SF的起因和繁衍特征, <11$\bar{2}$0>方向是晶体生长的下台阶方向, D1~D6标记平行条纹的移动距离, H1~H6标记外延层的去除厚度

Fig. 2 Originations and propagations of SF I and SF II<11$\bar{2}$0> is the direction of lower steps of crystal growth. D1-D6 are the moving distances of BPD lines. H1-H6 are the removing thickness of epitaxial layers

表1 图2中平行条纹移动的距离D和外延层去除厚度H的对应关系

Table 1 Relationship of moving distance D of BPD lines and removing thickness H of epitaxial layers in Fig. 2

No.	1	2	3	4	5	6
Moving distance of BPD lines, D/μm	33	57	44	94	60	39
Removing thickness, H/μm	2.3	4	3.1	6.6	4.2	2.7

表2 二次离子质谱(SIMS)检测衬底和外延层中的N含量

Table 2 Nitrogen concentration in substrate and epitaxial layers tested by SIMS

Test position	Substrate	Epitaxial layers
N concentration	8×10¹²	<10¹⁰

图3 (a) SF I; (b) SF II; (c)~(d) SF III; (e)~(f) SF IV的繁衍规律示意图

Fig. 3 Propagation diagrams of (a) SF I, (b) SF II, (c)-(d) SF III, and (e)-(f) SF IV

图4 III类SF的起因和繁衍特征, <11$\bar{2}$0>方向是晶体生长的下台阶方向, D1~D4标记胡萝卜尾部的移动距离, H1~H4标记外延层的去除厚度

Fig. 4 Originations and propagations of SF III<11$\bar{2}$0> is the direction of lower steps of crystal growth. D1-D4 are the moving distances of BPD lines. H1-H4 are the removing thickness of epitaxial layers

图5 IV类SF起因和繁衍特征, <11$\bar{2}$0>方向是晶体生长的下台阶方向, H1~H6标记外延层的去除厚度, L1~L8是三角形底边长度, W1~W8是三角形顶点到底边的垂直距离

Fig. 5 Originations and propagations of SF IV<11$\bar{2}$0> is the direction of lower steps of crystal growth. H1~H6 are the removing thickness of epitaxial layers. L1~L8 are bottom lengths of triangle defects. W1~W8 are widths of triangle defects

表3 图3中平行条纹移动的距离D和外延层去除厚度H的对应关系

Table 3 Relationship of the moving distance D of BPD lines and the removing thickness H of epitaxial layers in Fig. 3

No.	1	2	3	4
Moving distance of BPD lines, D/μm	102	53	23	61
Removing thickness, H/μm	7.1	3.7	1.6	4.3

表4 图5中平行条纹移动的距离D、外延层去除厚度H、三角形缺陷宽度W和底边长度L的对应关系表

Table 4 Relationship of the moving distance D of BPD lines, the removing thickness H of epitaxial layers and width of trianagle defects W with bottom lengths of triangle defects in Fig. 3

No.	1	2	3	4	5	6	7	8
Moving distance of BPD lines, D/μm	34	-	36	-	50	-	-	-
Removing thickness, H/μm	2.4	3.8	2.5	12.9	3.5	2.9	-	-
With triangle defects, W/μm	85	51	85	49.0	85	35	85	35
Bottom lengths of triangle defects, L/μm	105	63	90	52	60	25	110	45

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