WO2014206296A1 - 基片刻蚀方法 - Google Patents

基片刻蚀方法 Download PDF

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Publication number
WO2014206296A1
WO2014206296A1 PCT/CN2014/080722 CN2014080722W WO2014206296A1 WO 2014206296 A1 WO2014206296 A1 WO 2014206296A1 CN 2014080722 W CN2014080722 W CN 2014080722W WO 2014206296 A1 WO2014206296 A1 WO 2014206296A1
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Prior art keywords
etching
substrate
gas
etching method
etching step
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PCT/CN2014/080722
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English (en)
French (fr)
Inventor
李成强
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北京北方微电子基地设备工艺研究中心有限责任公司
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Publication of WO2014206296A1 publication Critical patent/WO2014206296A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B25/00—Single-crystal growth by chemical reaction of reactive gases, e.g. chemical vapour-deposition growth
    • C30B25/02—Epitaxial-layer growth
    • C30B25/18—Epitaxial-layer growth characterised by the substrate
    • C30B25/186—Epitaxial-layer growth characterised by the substrate being specially pre-treated by, e.g. chemical or physical means
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02002—Preparing wafers
    • H01L21/02005—Preparing bulk and homogeneous wafers
    • H01L21/02008—Multistep processes
    • H01L21/0201—Specific process step
    • H01L21/02019—Chemical etching
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/40—AIIIBV compounds wherein A is B, Al, Ga, In or Tl and B is N, P, As, Sb or Bi
    • C30B29/403—AIII-nitrides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/005—Processes
    • H01L33/0062—Processes for devices with an active region comprising only III-V compounds
    • H01L33/0066—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound
    • H01L33/007—Processes for devices with an active region comprising only III-V compounds with a substrate not being a III-V compound comprising nitride compounds
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/20—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular shape, e.g. curved or truncated substrate

Definitions

  • the present invention relates to the field of microelectronics, and in particular to a substrate etching method. Background technique
  • PSS Plasma Sapp Substrates
  • GaN GaN
  • the surface of the substrate is usually etched by ICP technology to form a desired pattern, and an GaN film is grown on the surface of the etched substrate by an epitaxial process.
  • ICP ICP technology
  • an epitaxial process The better the flatness of the bottom of the trench of the substrate obtained by the etching process, the more favorable the subsequent epitaxial process, the higher the crystal quality of the epitaxial GaN film.
  • the PSS etching process includes two steps, namely: a main etching step and an over etching step.
  • the main etching step is used to control the etching rate and the etching selectivity of the process.
  • the typical process parameters range from: 3 to 5 mT in the chamber of the reaction chamber; 2000-2400W; bias power range is 100 ⁇ 300 W; BC1 3 flow range is 50 ⁇ 150sccm.
  • the over-etching step is used to adjust the morphology of the substrate.
  • the typical process parameters range from: 1.5 to 2 mT in the chamber of the reaction chamber; the excitation power ranges from 1400 to 2000 W; The range is 2100 ⁇ 700W; the flow range of BC1 3 is 30 ⁇ 100sccm.
  • the above PSS etching process inevitably has the following problems in practical applications: First, in the main etching step, since only BC1 3 is used as an etching gas, the type of etching gas is single, resulting in the above PSS etching process. The process adjustment window is smaller, thus lowering Low process flexibility.
  • the present invention is directed to at least one of the technical problems existing in the prior art, and proposes a substrate etching method which not only improves the flexibility of the process, but also improves the flatness of the bottom of the substrate groove.
  • a substrate etching method comprising the steps of: a main etching step, introducing an etching gas and an auxiliary gas into the reaction chamber, and turning on the excitation power source and the bias power source to engrave the substrate Etching a predetermined etching depth, wherein the auxiliary gas comprises a fluoride gas;
  • the etching gas is introduced into the reaction chamber, and the excitation power source and the bias power source are turned on to adjust the groove topography of the substrate.
  • the fluoride gas comprises one or more of a hydrogen trifluorocarbonate, a hydrofluorocarbon, a nitrogen trifluoride, and a fluorocarbon compound.
  • the etching gas includes boron chloride.
  • the flow rate of the etching gas is in a range 80 ⁇ 100sccm.
  • the flow rate of the auxiliary gas ranges from 5 to 20 sccm.
  • the excitation power output excitation power ranges from 1400 to 2000W.
  • the chamber pressure of the reaction chamber ranges from 1.5 to 2.5 mT.
  • the bias power output bias power ranges from 100 to 400 Wo.
  • the flow rate of the etching gas is in a range
  • the chamber pressure of the reaction chamber ranges from 1.5 to 2 mT.
  • the excitation power output excitation power ranges from 1400 to 2000W.
  • the bias power supply output bias power ranges from 500 to 700 W.
  • a fluoride gas as an auxiliary gas is introduced into the reaction chamber while an etching gas is introduced into the reaction chamber. Due to the large electronegativity of fluoride ions in the ionized particles of fluoride gas, it is advantageous to displace more radicals and reduce the concentration of high-energy ions to make free radicals and energetic ions in the ionized particles. The balance of the ratio can increase the chemical etching on the bottom of the trench of the substrate, reduce the physical etching, and thereby reduce the groove formed at the corner of the sidewall of the trench and the bottom, and improve the flatness of the bottom of the trench.
  • the reaction chamber is introduced as a supplement.
  • the gas-enriched fluoride gas also increases the process conditioning window, which increases process flexibility.
  • 1A is a scanning electron micrograph of the bottom of a trench obtained by etching a substrate by an existing etching method
  • Figure 1B is an enlarged view of a region I in Figure 1A;
  • FIG. 2 is a flow chart of a substrate etching method according to an embodiment of the present invention.
  • 3A is a scanning electron micrograph of a trench sidewall obtained by etching the substrate etching method provided by the embodiment of the present invention.
  • Fig. 3B is a cross-sectional view showing the side wall of the trench obtained by etching the substrate by the etching method of the embodiment of the present invention. detailed description
  • FIG. 2 is a flow chart of a substrate etching method according to an embodiment of the present invention. Referring to Figure 2, the method includes the following steps:
  • an etching gas and an auxiliary gas are introduced into the reaction chamber, and an excitation power source (for example, a radio frequency power source) is turned on, and an excitation power source is applied to the reaction chamber to excite the etching gas in the reaction chamber to form a plasma.
  • the bias power supply is turned on, and the bias power supply applies bias power to the substrate to etch the substrate until the substrate is etched to a predetermined etch depth.
  • an etching gas is introduced into the reaction chamber, and the excitation power source and the bias power source are turned on to adjust the groove topography of the substrate.
  • the etching gas includes BC1 3 (boron chloride).
  • the etching gas includes BC1 3 ; the auxiliary gas includes a fluoride gas, and the fluoride gas includes CHF 3 (carbon trifluorocarbonate), CHF (hydrogen fluoride), NF 3 (three One or more of nitrogen fluoride) and S X Fy (fluorosulfur compound).
  • the fluoride gas includes CHF 3 (carbon trifluorocarbonate), CHF (hydrogen fluoride), NF 3 (three One or more of nitrogen fluoride) and S X Fy (fluorosulfur compound).
  • the value range of the process parameters of the main etching step is: the flow rate of the etching gas is in the range of 80 to 100 sccm; the flow rate of the auxiliary gas is in the range of 5 to 20 sccm; and the excitation power of the excitation power source is in the range of 1400 to 2000 W;
  • the chamber pressure of the chamber ranges from 1.5 to 2.5 mT; the bias power output of the bias power supply ranges from 100 to 400 W.
  • the etching gas includes BC1 3
  • the over-etching step uses a smaller etching gas flow rate, a lower chamber pressure, and a bias power relative to the main etching step to adjust the substrate.
  • the groove topography that is, the groove sidewall profile and the angle of inclination.
  • the value range of the process parameters of the over-etching step is: the flow rate of the etching gas is in the range of 40 to 70 sccm; the chamber pressure of the reaction chamber is in the range of 1.5 to 2 mT; and the excitation power output of the excitation power source is in the range of 1400. ⁇ 2000W;
  • the bias power output of the bias power supply ranges from 500 to 700W.
  • the substrate etching method provided by the embodiment of the present invention is compared with the prior art substrate etching method by an etching experiment.
  • both the embodiment of the present invention and the prior art use a 12-inch ICP device, and
  • the process parameters of the main etching step of the embodiment of the present invention and the prior art are as shown in Table 1 below.
  • the difference between the two embodiments of the present invention and the prior art includes at least: First, in the prior art substrate etching method, it only reverses in the main etching step. BC1 3 should be introduced into the chamber. It was found through experiments that the ionized particles formed by BC1 3 ionization under glow discharge have more BC1 X particles and less C1 radicals. The proportion of high-energy ions that cause physical etching is higher than the proportion of free radicals that are chemically etched, which makes the density of ion current sputtered to the bottom of the trench larger, at the sidewalls and bottom of the trench.
  • a groove is formed at the corner, which causes the bottom of the groove of the substrate to be uneven, which adversely affects the subsequent epitaxial process and reduces the quality of the epitaxial film.
  • a fluoride gas for example, CHF 3
  • an etching gas is introduced into the reaction chamber. Due to the large electronegativity of fluoride ions in the ionized particles of fluoride gas, it is advantageous to displace more C1 radicals and reduce the concentration of high-energy ions, thereby increasing the chemistry of the bottom of the substrate trench.
  • Etching and reducing physical etching can further reduce the grooves formed at the corners of the sidewalls and the bottom of the trench, improve the flatness of the bottom of the trench, and thereby improve the quality of the epitaxial film in the subsequent epitaxial process. It can be seen from the comparison experiment that the trench obtained by etching by the etching method provided by the embodiment of the present invention has no groove at the corner of the sidewall and the bottom, and the bottom of the trench has high flatness, as shown in FIG. 3A. 3B and 3B are respectively a scanning electron micrograph and a cross-sectional view of a trench obtained by etching the substrate etching method provided by the embodiment of the present invention.
  • the prior art substrate etching method uses only BC1 3 as an etching gas, the type of etching gas is single, which results in a small process adjustment window of the PSS etching process, thereby reducing process flexibility.
  • the substrate etching method provided by the embodiment of the present invention can increase the process adjustment window by introducing a fluoride gas as an auxiliary gas into the reaction chamber while introducing an etching gas into the reaction chamber. This increases the flexibility of the process.
  • the excitation power ranges from 2000 to 2400 W
  • the excitation power ranges from 1400 to 2000 W, that is, the implementation of the present invention
  • a substrate etching method is provided, in which the main etching step uses a lower excitation power, which can further reduce the proportion of high-energy ions in the ionized particles.
  • the flatness of the bottom of the trench can be further improved.
  • the chamber pressure of the reaction chamber is in the range of
  • the chamber pressure of the reaction chamber ranges from 1.5 to 2.5 mT, that is, the substrate etching method provided by the embodiment of the present invention, and the main etching step thereof
  • the lower chamber pressure which not only increases the free path of the active particles in the ionized particles, enhances the effective reaction of the active ions, but also facilitates the discharge of the etching reactant deposited on the sidewalls and the bottom of the trench. Thereby, the deposition amount of the etching reactant can be reduced, and the groove formed at the corner of the sidewall and the bottom of the trench can be further reduced.
  • the substrate etching method provided by the embodiment of the present invention passes through the etching gas into the reaction chamber in the main etching step, and also introduces fluorine as an auxiliary gas into the reaction chamber.
  • the gas at the same time, preferably, the groove formed at the corners of the sidewalls of the trench and the bottom can be reduced by using a lower excitation power and/or chamber pressure, thereby improving the bottom of the trench.
  • the flatness is further beneficial to improve the quality of the epitaxial film in the subsequent epitaxial process. Exemplary embodiments, however, the invention is not limited thereto. Various modifications and improvements can be made by those skilled in the art without departing from the spirit and scope of the invention. These modifications and improvements are also considered to be within the scope of the invention.

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Abstract

本发明提供的基片刻蚀方法，其包括以下步骤：主刻蚀步骤，向反应腔室通入刻蚀气体和辅助气体，并开启激励电源和偏压电源，以对基片刻蚀预定刻蚀深度，其中，所述辅助气体包括氟化物气体；过刻蚀步骤，向反应腔室内通入所述刻蚀气体，并开启激励电源和偏压电源，以调节基片的沟槽形貌。本发明提供的基片刻蚀方法，其不仅可以提高工艺的灵活性，而且还可以提高基片沟槽底部的平整性。

Description

基片刻蚀方法 技术领域
本发明涉及微电子技术领域， 特别涉及一种基片刻蚀方法。 背景技术
PSS ( Patterned Sapp Substrates , 图形化蓝宝石基片 ） 技术是目前 普遍釆用的一种提高 GaN (氮化镓） 基 LED器件的出光效率的方法。 在进行 PSS工艺的过程中， 其通常釆用 ICP技术刻蚀基片表面， 以形 成需要的图形， 再釆用外延工艺在刻蚀后的基片表面上生长 GaN薄膜。 刻蚀工艺所获得的基片沟槽底部的平整性越好，越有利于后续的外延工 艺， 外延 GaN薄膜的晶体质量越高。
目前， 在釆用电感辆合等离子体 ( Inductively Coupled Plasma, 以 下简称 ICP ) 设备对基片表面进行刻蚀时， 例如， 在釆用 12英寸 ICP 设备进行刻蚀时， 通常釆用 BC13 (氯化硼） 作为刻蚀气体， 且 PSS刻 蚀工艺包括两个步骤， 即： 主刻蚀步骤和过刻蚀步骤。 其中， 主刻蚀步 骤用于控制工艺的刻蚀速率和刻蚀选择比，其典型的工艺参数的取值范 围为： 反应腔室的腔室压力的范围在 3~5mT ; 激励功率的范围在 2000-2400W； 偏压功率的范围在 100~300 W ; BC13 的流量范围在 50~150sccm。 过刻蚀步骤用于调节基片形貌， 其典型的工艺参数的取值 范围为： 反应腔室的腔室压力的范围在 1.5~2mT; 激励功率的范围在 1400-2000W； 偏压功率的范围在 2100~700W； BC13 的流量范围在 30~100sccm。
上述 PSS刻蚀工艺在实际应用中不可避免地存在以下问题： 其一， 在主刻蚀步骤中， 由于仅釆用 BC13作为刻蚀气体， 刻蚀气 体的种类单一， 导致上述 PSS 刻蚀工艺的工艺调节窗口较小， 从而降 低了工艺的灵活性。
其二， 在进行主刻蚀步骤时， 由于 BC13在辉光放电的条件下离化 生成的离化粒子， 其所含的 BC1X粒子的数量较多， 而 C1 自由基的数量 较少，导致起物理刻蚀作用的高能离子所占比例高于起化学刻蚀作用的 自由基所占比例， 这使得溅射至沟槽底部的离子流的密度较大， 并且由 于沟槽侧壁会将溅射至其上的离子流朝向侧壁与底部的拐角处反射，导 致该拐角处因离子流的密度增大而受到更多的刻蚀，从而随着刻蚀时间 的积累， 最终在该拐角处形成凹槽 （如图 1A 中的矩形框 I以及图 1B 中的矩形框 I 的放大图所示）， 这会导致基片沟槽的底部不平整， 从而 给后续的外延工艺带来不良影响， 降低外延薄膜的质量。 发明内容
本发明旨在至少解决现有技术中存在的技术问题之一，提出了一种 基片刻蚀方法， 其不仅可以提高工艺的灵活性， 而且还可以提高基片沟 槽底部的平整性。
为实现本发明的目的而提供一种基片刻蚀方法， 包括以下步骤： 主刻蚀步骤， 向反应腔室通入刻蚀气体和辅助气体， 并开启激励电 源和偏压电源， 以对基片刻蚀预定刻蚀深度， 其中， 所述辅助气体包括 氟化物气体；
过刻蚀步骤， 向反应腔室内通入所述刻蚀气体， 并开启激励电源和 偏压电源， 以调节基片的沟槽形貌。
其中， 所述氟化物气体包括三氟氢化碳、 氟氢化碳、 三氟化氮和氟 石克化合物中的一种或多种。
优选地， 在所述主刻蚀步骤和过刻蚀步骤中， 所述刻蚀气体包括氯 化硼。
优选地， 在所述主刻蚀步骤中， 所述刻蚀气体的流量范围在 80~100sccm。
优选地， 在所述主刻蚀步骤中， 所述辅助气体的流量范围在 5~20sccm。
优选地， 在所述主刻蚀步骤中， 所述激励电源输出激励功率的范围 在 1400~2000W。
优选地， 在所述主刻蚀步骤中， 所述反应腔室的腔室压力的范围在 1.5~2.5mT。
优选地， 在所述主刻蚀步骤中， 所述偏压电源输出偏压功率的范围 在 100~400Wo
优选地， 在所述过刻蚀步骤中， 所述刻蚀气体的流量范围在
40~70sccm。
优选地， 在所述过刻蚀步骤中， 所述反应腔室的腔室压力的范围在 1.5~2mT。
优选地， 在所述过刻蚀步骤中， 所述激励电源输出激励功率的范围 在 1400~2000W。
优选地， 在所述过刻蚀步骤中， 所述偏压电源输出偏压功率的范围 在 500~700W。
本发明具有以下有益效果：
本发明提供的基片刻蚀方法， 在主刻蚀步骤中， 在向反应腔室通入 刻蚀气体的同时， 向该反应腔室通入作为辅助气体的氟化物气体。 由于 氟化物气体的离化粒子中， 氟离子的电负性较大， 这有利于置换出更多 的自由基， 且减小高能离子的浓度， 以使离化粒子中的自由基与高能离 子的比例平衡， 从而可以增加对基片沟槽底部的化学刻蚀、 减少物理刻 蚀， 进而可以减小在沟槽侧壁与底部的拐角处形成的凹槽， 提高沟槽底 部的平整性， 从而有利于提高后续的外延工艺中的外延薄膜的质量。 而 且， 通过在向反应腔室通入刻蚀气体的同时， 向该反应腔室通入作为辅 助气体的氟化物气体， 还可以增大工艺调节窗口， 从而可以提高工艺的 灵活性。 附图说明
图 1A为釆用现有的刻蚀方法刻蚀基片获得的沟槽底部的扫描电镜 图；
图 1B为图 1A中的区域 I的放大图；
图 2为本发明实施例提供的基片刻蚀方法的流程框图；
图 3 A为釆用本发明实施例提供的基片刻蚀方法刻蚀获得的沟槽侧 壁的扫描电镜图； 以及
图 3B为釆用本发明实施例提供的基片刻蚀方法刻蚀获得的沟槽侧 壁的剖面图。 具体实施方式
为使本领域的技术人员更好地理解本发明的技术方案，下面结合附 图来对本发明提供的基片刻蚀方法进行详细描述。
图 2为本发明实施例提供的基片刻蚀方法的流程框图。请参阅图 2， 该方法包括以下步骤：
主刻蚀步骤， 向反应腔室通入刻蚀气体和辅助气体， 并开启激励电 源 （例如射频电源）， 激励电源向反应腔室施加激励功率， 以使反应腔 室内的刻蚀气体激发形成等离子体； 开启偏压电源， 偏压电源向基片施 加偏压功率， 以使等离子体刻蚀基片， 直至对基片刻蚀预定刻蚀深度。
过刻蚀步骤， 向反应腔室内通入刻蚀气体， 并开启激励电源和偏压 电源， 以调节基片的沟槽形貌。 其中， 刻蚀气体包括 BC13 (氯化硼）。
在主刻蚀步骤中， 刻蚀气体包括 BC13; 辅助气体包括氟化物气体， 所述氟化物气体包括 CHF3 (三氟氢化碳）、 CHF (氟氢化碳）、 NF3 (三 氟化氮）和 SXFy (氟硫化合物） 中的一种或多种。 优选地， 主刻蚀步骤 的工艺参数的数值范围为： 刻蚀气体的流量范围在 80~100sccm; 辅助 气体的流量范围在 5~20sccm ; 激励电源输出的激励功率的范围在 1400-2000W; 反应腔室的腔室压力的范围在 1.5~2.5mT; 偏压电源输出 的偏压功率的范围在 100~400W。
在过刻蚀步骤中， 刻蚀气体包括 BC13， 过刻蚀步骤相对于主刻蚀 步骤釆用较小的刻蚀气体流量、较低的腔室压力和偏压功率， 用以调节 基片的沟槽形貌， 即， 调节沟槽侧壁形貌及倾斜角度。 优选地， 过刻蚀 步骤的工艺参数的数值范围为： 刻蚀气体的流量范围在 40~70sccm; 反 应腔室的腔室压力的范围在 1.5~2mT; 激励电源输出的激励功率的范围 在 1400~2000W; 偏压电源输出的偏压功率的范围在 500~700W。
下面通过刻蚀实验对本发明实施例提供的基片刻蚀方法和现有技 术的基片刻蚀方法进行比较， 在该刻蚀实验中， 本发明实施例和现有技 术均使用 12英寸 ICP设备， 并且， 本发明实施例和现有技术的主刻蚀 步骤的工艺参数如下述表 1所示。
表 1
Figure imgf000006_0001
由表 1可知，本发明实施例与现有技术相比，二者的区别至少包括: 其一， 就现有技术的基片刻蚀方法而言， 其在主刻蚀步骤中仅向反 应腔室内通入 BC13， 通过实验发现， 由 BC13在辉光放电的条件下离化 生成的离化粒子， 其所含的 BC1X粒子的数量较多， 而 C1 自由基的数量 较少，导致起物理刻蚀作用的高能离子所占比例高于起化学刻蚀作用的 自由基所占比例， 这使得溅射至沟槽底部的离子流的密度较大， 在沟槽 侧壁与底部的拐角处形成凹槽， 从而导致基片沟槽的底部不平整， 进而 给后续的外延工艺带来不良影响， 降低了外延薄膜的质量。 而本发明实 施例提供的基片刻蚀方法， 其在主刻蚀步骤中， 在向反应腔室通入刻蚀 气体的同时， 通入作为辅助气体的氟化物气体（例如 CHF3 )。 由于氟化 物气体的离化粒子中， 氟离子的电负性较大， 这有利于置换出更多的 C1 自由基， 且减小高能离子的浓度， 从而可以增加对基片沟槽底部的 化学刻蚀、 减少物理刻蚀， 进而可以减小在沟槽侧壁与底部的拐角处形 成的凹槽， 提高沟槽底部的平整性， 从而有利于提高后续的外延工艺中 的外延薄膜质量。 通过该对比实验可知， 釆用本发明实施例提供的刻蚀 方法刻蚀获得的沟槽在侧壁与底部的拐角处没有凹槽，沟槽的底部具有 较高的平整性， 如图 3A和 3B所示， 其中， 图 3A和 3B分别为为釆用 本发明实施例提供的基片刻蚀方法刻蚀获得的沟槽的扫描电镜图和剖 面图。
其二， 由于现有技术的基片刻蚀方法仅釆用 BC13作为刻蚀气体， 刻蚀气体的种类单一， 导致上述 PSS 刻蚀工艺的工艺调节窗口较小， 从而降低了工艺的灵活性。 而本发明实施例提供的基片刻蚀方法， 其通 过在向反应腔室通入刻蚀气体的同时，向其内还通入作为辅助气体的氟 化物气体， 以此可以增大工艺调节窗口， 从而可以提高工艺的灵活性。
其三， 在现有技术的主刻蚀步骤中 ， 激励功率的范围在 2000-2400W , 而在本发明实施例的主刻蚀步骤中， 激励功率的范围在 1400-2000W , 即， 本发明实施例提供基片刻蚀方法， 其主刻蚀步骤釆 用较低的激励功率， 这可以进一步减少离化粒子中高能离子所占比例， 以使高能离子和自由基的比例趋于平衡，从而可以进一步提高沟槽底部 的平整性。
其四， 在现有技术的主刻蚀步骤中， 反应腔室的腔室压力的范围在
3~5mT; 而在本发明实施例的主刻蚀步骤中， 反应腔室的腔室压力的范 围在 1.5~2.5mT， 即， 本发明实施例提供的基片刻蚀方法， 其主刻蚀步 骤釆用较低的腔室压力， 这不仅可以增大离化粒子中活性粒子的自由 程， 增强活性离子的有效反应， 而且还有利于排出沉积在沟槽侧壁和底 部的刻蚀反应物， 从而可以减少刻蚀反应物的沉积量， 进而可以进一步 减小在沟槽侧壁与底部的拐角处形成的凹槽。
综上所述， 本发明实施例提供的基片刻蚀方法， 其通过在主刻蚀步 骤中， 向反应腔室通入刻蚀气体的同时， 还向该反应腔室通入作为辅助 气体的氟化物气体， 与此同时， 优选地， 还可以通过釆用较低的激励功 率和 /或腔室压力， 减小在沟槽侧壁与底部的拐角处形成的凹槽， 从而 可以提高沟槽底部的平整性，进而有利于提高后续的外延工艺中的外延 薄膜质量。 的示例性实施方式， 然而本发明并不局限于此。 对于本领域内的普通技 术人员而言， 在不脱离本发明的精神和实质的情况下， 可以做出各种变 型和改进， 这些变型和改进也视为本发明的保护范围。

Claims

UP-141834-98 要 求 书
1. 一种基片刻蚀方法， 其特征在于， 包括以下步骤：
主刻蚀步骤， 向反应腔室通入刻蚀气体和辅助气体， 并开启激励电源和 偏压电源，对基片刻蚀预定刻蚀深度，其中，所述辅助气体包括氟化物气体； 过刻蚀步骤， 向反应腔室内通入所述刻蚀气体， 并开启激励电源和偏压 电源， 以调节基片的沟槽形貌。
2. 如权利要求 1 所述的基片刻蚀方法， 其特征在于， 所述氟化物气体 包括三氟氢化碳、 氟氢化碳、 三氟化氮和氟硫化合物中的一种或多种。
3. 如权利要求 1 所述的基片刻蚀方法， 其特征在于， 在所述主刻蚀步 骤和过刻蚀步骤中， 所述刻蚀气体包括氯化硼。
4. 如权利要求 1 所述的基片刻蚀方法， 其特征在于， 在所述主刻蚀步 骤中， 所述刻蚀气体的流量范围在 80~100sccm。
5. 如权利要求 1 所述的基片刻蚀方法， 其特征在于， 在所述主刻蚀步 骤中， 所述辅助气体的流量范围在 5~20sccm。
6. 如权利要求 1 所述的基片刻蚀方法， 其特征在于， 在所述主刻蚀步 骤中， 所述激励电源输出激励功率的范围在 1400~2000W。
7. 如权利要 1 所述的基片刻蚀方法， 其特征在于， 在所述主刻蚀步骤 中， 所述反应腔室的腔室压力的范围在 1.5~2.5mT。
8. 如权利要求 1 所述的基片刻蚀方法， 其特征在于， 在所述主刻蚀步 骤中， 所述偏压电源输出偏压功率的范围在 100~400W。
9. 如权利要求 1 所述的基片刻蚀方法， 其特征在于， 在所述过刻蚀步 骤中， 所述刻蚀气体的流量范围在 40~70sccm。
10. 如权利要求 1所述的基片刻蚀方法， 其特征在于， 在所述过刻蚀步 骤中， 所述反应腔室的腔室压力的范围在 1.5~2mT。
11. 如权利要求 1所述的基片刻蚀方法， 其特征在于， 在所述过刻蚀步 骤中， 所述激励电源输出激励功率的范围在 1400~2000W。
12. 如权利要求 1所述的基片刻蚀方法， 其特征在于， 在所述过刻蚀步 骤中， 所述偏压电源输出偏压功率的范围在 500~700W。
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