硅酸盐学报

AlN单晶氢化物气相外延生长技术研究进展

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张电 ¹ , 朱容昕 ¹ , 杨晓凤 ¹ , 刘一军 ²

硅酸盐学报 | 综合评述 2024,52(5): 1761-1777

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硅酸盐学报 |综合评述 2024 , 52 (5) : 1761 -1777

AlN单晶氢化物气相外延生长技术研究进展

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张电¹, 朱容昕¹, 杨晓凤¹, 刘一军²

作者信息

^1．西安建筑科技大学材料科学与工程学院，西安 710055

^2．蒙娜丽莎集团有限公司，广东佛山 528211

通讯作者:

张电（1978—），男，博士，讲师。

杨晓凤（1978—），女，副教授。

作者简介:

张电（1978—），男，博士，讲师。

Research Progress of Hydride Vapor Phase Epitaxy Technology for AlN Single Crystal

Dian ZHANG¹, Rongxin ZHU¹, Xiaofeng YANG¹, Yijun LIU²

Affiliations

^1.College of Materials Science and Engineering, Xi'an University of Architecture and Technology, Xi'an 710055, Shaanxi, China

^2.Monalisa Group Co., LTD, Foshan 528211, Guangdong, China

Corresponding Author:

ZHANG Dian (1978—), male, Ph.D., Lecturer. E-mail: zhangdian@xauat.edu.cn;

YANG Xiaofeng (1978—), female, Associate Professor. xiaofeng96@163.com

ZHANG Dian (1978—), male, Ph.D., Lecturer. E-mail: zhangdian@xauat.edu.cn

出版时间: 2024-05-20 doi: 10.14062/j.issn.0454-5648.20230714

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摘要

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氮化铝（AlN）晶体具有超宽禁带、深紫外透明、高热导率、高声速以及高温稳定等优异特能，成为当前半导体领域的关键前沿材料之一。它是氮化镓（GaN）基功率半导体器件和深紫外光电器件的理想衬底，也是深紫外光电器件和声表面波器件领域的关键材料。经过1960年代至今的漫长发展历程，AlN晶体生长相关技术种类繁多，但长期以来缺少较为系统的综述。本文介绍了AlN晶体的晶体结构以及主要的性质、应用场景和要求；对AlN晶体生长技术简要分类，重点阐述氢化物气相外延法（HVPE），从原理、生长区结构、温度、气氛、衬底、工艺、应用技术以及优劣势等层面梳理研究进展；最后，指出当前HVPE AlN技术面临的主要挑战。

关键词

氮化铝晶体 / 半导体 / 晶体生长 / 氢化物气相外延法

Abstract

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Aluminum nitride (AlN) crystal is one of the key frontier materials in semiconductors due to its superior properties such as ultra-wide band gap, deep ultraviolet transparency, high thermal conductivity, high sound velocity, and high temperature stability. AlN is an ideal substrate for gallium nitride (GaN)-based power semiconductor devices and deep ultraviolet photoelectronic devices, and is also a key material in deep ultraviolet photoelectronic and surface acoustic wave devices.

Different AlN crystal growth related technologies have been developed since 1960s. Among them, a PVT AlN crystal technology is relatively mature, and several manufacturers are able to provide 2 inch AlN wafers. However, a high growth temperature (i.e., 2 300 ℃) used in this PVT AIN technology makes the growth of larger PVT AlN wafer extremely hard, and induces some impurities doping and relevant absorption in the ultraviolet region. Moreover, PVT AlN is hard to fulfill controlled doping. These factors and extremely high cost restrict the application.

Hydride vapor phase epitaxy (HVPE) is considered an alternative to PVT AlN due to its potential advantages in terms of large-area wafer preparation, controlled doping and cost. Recent studies dealt with the preparation HVPE AlN. This review briefly introduced the crystal structure and fundamental properties, application scenarios, and requirements of AlN crystals. The growth technologies of AlN crystals were concisely categorized, and the HVPE method was elaborated in terms of principle, structure of the growth zone, temperature, atmosphere, substrates, process, application technology, advantages, and disadvantages. In addition, the main challenges for HVPE AlN technology were also proposed.

The structural factors of HVPE growth zone (i.e., the horizontal or vertical configuration, the location and direction of gas outlet, the position and direction of substrate, and the size of the growth chamber) are coupled with process factors (i.e., flow rate, pressure and temperature), resulting in complicated flow and temperature fields. A reasonable flow field can create a uniform laminar flow pattern on the substrate surface, which is crucial for epitaxy, crystal quality and uniformity. For instance, a horizontal HVPE system, in which the gas flow direction is horizontal and perpendicular to the substrate surface, can produce a mirror-like AlN epilayer on a c-plane sapphire substrate at 1 100 ℃ with a growth rate of 1.1 μm·h^-1 and obtain FWHM of planes (0002) and () as low as 40 arcsec and 45 arcsec, respectively.

A higher growth temperature can accelerate chemical reaction on the substrate surface and epitaxy. Meanwhile, a high temperature can significantly increase the migration rate of active Al and N atoms in the growth plane, thus promoting two-dimensional growth and crystal quality. HVPE AlN epilayers grown at 1 550 ℃ with a growth rate of about 20 μm·h^-1 can obtain a FWHM of planes (0002) and () of 102 arcsec and 219 arcsec, respectively.

The V/III ratio affects the concentration of growth atoms, diffusion distance, reaction rate and growth mode, significantly affecting the crystal quality and surface morphology of HVPE AlN. In general, the V/III ratio of HVPE AlN growth process ranges from 10 to 300. AlN film grown under V/III ratio of 150 can obtain FWHM values of planes (0002) and () of 64 arcsec and 648 arcsec, respectively. When the V/III ratio is 150 and 300, the threading dislocation (TD) density can reach 8.9×10⁶ cm^-2 and 5.9×10⁷ cm^-2, respectively.

The materials, crystal orientation and polarity of substrate are a basis for the crystal quality, morphology and performance of HVPE AlN epilayer. Except for commonly used sapphire, Si and SiC substrate, GaN or AlN templates are used to further reduce TD density. Especially, an association of patterned substrates with a lateral epitaxial overgrowth technology is proven as an effective way in reducing TD density.

The optimization of growth process, such as surface nitridation of the substrate, buffer layer growth, adjustment of growth procedures, etc., is also investigated to improve the crystal quality of HVPE AlN epilayers.

As an alternative to PVT AlN wafers, HVPE AlN wafers can enter into application only if an effective lift-off technology is established. There are only three processes, namely, chemical etching, mechanical lift-off, and self-seperation methods.

This review also introduces HTCVD AlN technique, which is developed and can be regarded as a prototype or a variant of HVPE AlN. It also has the same advantages as HVPE AlN. Moreover, HTCVD AlN can grow at 1 700 ℃ and avoid harmful Si and O doping of AlN crystal, which happens in HVPE AlN process, leading to a significant promotion of AlN crystal quality. In addition, the HTCVD also adopts a safe Ar carrier and a solid AlCl₃ source instead of explosive H₂ and corrosive HCl and Cl₂.

Summary and prospects

There are still some problems in HVPE AlN that need to be solved in the future.

The most promising application of HVPE AlN is a large-area free-standing substrate, but the prerequisite for its realization is the development of effective lift-off technology. It is a long-standing challenge and a technical barrier for HVPE AlN application. A fundamental technological tactics to solve the lift-off problem is an idea regarding substrate technology, such as using patterned substrates with a large depth ratio, using template or buffer layers made of two-dimensional materials, or using the both.

Little work on HVPE AlN epilayers with a diameter of 2 inches, a thickness of 100 μm and a TD density of 10⁶ cm^-2 has been reported yet due to the limitations of heteroepitaxy and growth temperatures below 1 400 ℃. The coupled temperature and flow fields as well as the position of the gas-solid interface can affect the uniformity and crystal quality of the AlN epilayers. A problem is an intense stress field caused by heteroepitaxy, which varies with the size of the epilayer. HVPE AlN epilayers with a thickness of several microns can crack, and those with a thickness of several tens of microns can cause a substrate fracture. A solution to the stress problem also can be innovative substrate technologies such as patterned substrates and two-dimensional material buffer layers.

In addition, achieving n-type and p-type doping in HVPE AlN with a high carrier concentration and a high mobility remains a challenge. Specific issues such as nonpolar surface epitaxy and parasitic reactions also need further studies.

Key words

aluminum nitride crystal / semiconductor / crystal growth / hydride vapor phase epitaxy

引用本文

张电, 朱容昕, 杨晓凤, 刘一军. AlN单晶氢化物气相外延生长技术研究进展. 硅酸盐学报, 2024 , 52 (5) : 1761 -1777 . DOI: 10.14062/j.issn.0454-5648.20230714

Dian ZHANG, Rongxin ZHU, Xiaofeng YANG, Yijun LIU. Research Progress of Hydride Vapor Phase Epitaxy Technology for AlN Single Crystal[J]. Journal of the Chinese Ceramic Society, 2024 , 52 (5) : 1761 -1777 . DOI: 10.14062/j.issn.0454-5648.20230714

基金

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陕西省重点研发计划一般项目(2024GX-YBXM-329)
广东省大尺寸陶瓷薄板企业重点实验室开放课题(KFKT2022001)

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2024年第52卷第5期

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文章信息

doi: 10.14062/j.issn.0454-5648.20230714

接收时间：2023-09-14
首发时间：2026-10-22
出版时间：2024-05-20

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出版历史

收稿日期：2023-09-14
修回日期：2023-10-18

基金

陕西省重点研发计划一般项目(2024GX-YBXM-329)

广东省大尺寸陶瓷薄板企业重点实验室开放课题(KFKT2022001)

作者信息

^1．西安建筑科技大学材料科学与工程学院，西安 710055

^2．蒙娜丽莎集团有限公司，广东佛山 528211

通讯作者:

张电（1978—），男，博士，讲师。

杨晓凤（1978—），女，副教授。

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20230714

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2种不同金属材料的力学参数

科 Family	属数 Number of genus	种数 Number of species	占总种数比例 Percentage of total species (%)	属 Genus	种数 Number of species	占总种数比例 Percentage of total species (%)
鹅膏菌科Amanitaceae	2	11	5.26	鹅膏菌属 Amanita	10	4.78
小菇科 Mycenaceae	2	12	5.74	丝盖伞属 Inocybe	5	2.39
多孔菌科 Polyporaceae	8	14	6.70	蜡蘑属 Laccaria	5	2.39
红菇科 Russulaceae	3	23	11.00	小皮伞属 Marasmius	6	2.87
				小菇属 Mycena	11	5.26
				光柄菇属 Pluteus	5	2.39
				红菇属 Russula	17	8.13
				栓菌属 Trametes	5	2.39

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