JP6415360B2 - Method for manufacturing silicon carbide single crystal substrate - Google Patents
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- JP6415360B2 JP6415360B2 JP2015049224A JP2015049224A JP6415360B2 JP 6415360 B2 JP6415360 B2 JP 6415360B2 JP 2015049224 A JP2015049224 A JP 2015049224A JP 2015049224 A JP2015049224 A JP 2015049224A JP 6415360 B2 JP6415360 B2 JP 6415360B2
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- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 title claims description 69
- 229910010271 silicon carbide Inorganic materials 0.000 title claims description 67
- 239000000758 substrate Substances 0.000 title claims description 65
- 239000013078 crystal Substances 0.000 title claims description 64
- 238000000034 method Methods 0.000 title claims description 26
- 238000004519 manufacturing process Methods 0.000 title claims description 11
- 239000007789 gas Substances 0.000 claims description 68
- 238000009832 plasma treatment Methods 0.000 claims description 19
- 238000005498 polishing Methods 0.000 claims description 14
- 238000000992 sputter etching Methods 0.000 claims description 10
- 238000004140 cleaning Methods 0.000 claims description 9
- 239000011261 inert gas Substances 0.000 claims description 6
- 230000004075 alteration Effects 0.000 claims 1
- 238000007517 polishing process Methods 0.000 claims 1
- 238000005530 etching Methods 0.000 description 25
- 229910052731 fluorine Inorganic materials 0.000 description 10
- 239000011737 fluorine Substances 0.000 description 10
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 9
- 238000001020 plasma etching Methods 0.000 description 9
- 230000003746 surface roughness Effects 0.000 description 9
- 229910052736 halogen Inorganic materials 0.000 description 8
- 230000003749 cleanliness Effects 0.000 description 7
- 150000002367 halogens Chemical class 0.000 description 7
- 230000009257 reactivity Effects 0.000 description 7
- 239000000460 chlorine Substances 0.000 description 6
- 229910052801 chlorine Inorganic materials 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 3
- 239000007795 chemical reaction product Substances 0.000 description 3
- 229910003460 diamond Inorganic materials 0.000 description 3
- 239000010432 diamond Substances 0.000 description 3
- 239000010408 film Substances 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 3
- 238000004544 sputter deposition Methods 0.000 description 3
- -1 Cl 2 Chemical compound 0.000 description 2
- 150000001804 chlorine Chemical class 0.000 description 2
- 239000002019 doping agent Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- NBVXSUQYWXRMNV-UHFFFAOYSA-N fluoromethane Chemical compound FC NBVXSUQYWXRMNV-UHFFFAOYSA-N 0.000 description 2
- 235000012431 wafers Nutrition 0.000 description 2
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 description 1
- BSYNRYMUTXBXSQ-UHFFFAOYSA-N Aspirin Chemical compound CC(=O)OC1=CC=CC=C1C(O)=O BSYNRYMUTXBXSQ-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 239000006061 abrasive grain Substances 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 150000002221 fluorine Chemical class 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 238000009616 inductively coupled plasma Methods 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 229910052740 iodine Inorganic materials 0.000 description 1
- 239000011630 iodine Substances 0.000 description 1
- 238000005468 ion implantation Methods 0.000 description 1
- 230000001678 irradiating effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- 238000002230 thermal chemical vapour deposition Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
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- Drying Of Semiconductors (AREA)
Description
本発明は、炭化珪素（ＳｉＣ）単結晶基板の表面に存在する加工変質部やイオン損傷部が除去され、かつその除去処理に伴う残渣や表面荒れが無く、清浄性及び平坦性に優れた表面を有する炭化珪素単結晶基板の製造方法に関するものである。 The present invention is a surface excellent in cleanliness and flatness, in which a work-affected part and an ion-damaged part existing on the surface of a silicon carbide (SiC) single crystal substrate are removed, and there is no residue or surface roughness associated with the removal process. The present invention relates to a method for manufacturing a silicon carbide single crystal substrate having the following.
炭化珪素（ＳｉＣ）は、耐熱性及び機械的強度に優れ、物理的、化学的に安定なことから、耐環境性半導体材料として注目されている。また、近年、高周波高耐圧電子デバイス等の基板としてＳｉＣ単結晶基板の需要が高まっている。 Silicon carbide (SiC) has attracted attention as an environmentally resistant semiconductor material because it is excellent in heat resistance and mechanical strength and is physically and chemically stable. In recent years, the demand for SiC single crystal substrates as substrates for high-frequency, high-voltage electronic devices has increased.
ＳｉＣ単結晶のインゴットからＳｉＣ単結晶基板を加工する工程は、先ず前記インゴットをスライスしてウエハ状に切り出す工程と、所定の厚さまで荒削りする研削工程と、基板の両面を平坦かつ鏡面に仕上げる研磨工程と、上記各工程で基板に付着した汚れを除去する洗浄工程と、加工工程で導入された表面加工変質部を除去する工程とからなる。 The process of processing a SiC single crystal substrate from an SiC single crystal ingot is a process of first slicing the ingot into a wafer, a grinding process of roughing to a predetermined thickness, and polishing to finish both sides of the substrate to a flat and mirror surface. A process, a cleaning process for removing dirt adhered to the substrate in each of the above processes, and a process for removing the surface-processed altered portion introduced in the processing process.
このようなＳｉＣ単結晶基板を用いて、電力デバイス、高周波デバイス等を作製する場合には、通常基板上に熱ＣＶＤ法（熱化学蒸着法）と呼ばれる方法を用いてＳｉＣ薄膜をエピタキシャル成長させたり、イオン注入法により直接ドーパントを打ち込んだりするのが一般的である。 When producing a power device, a high-frequency device, etc. using such a SiC single crystal substrate, a SiC thin film is epitaxially grown on a normal substrate using a method called a thermal CVD method (thermochemical vapor deposition method) In general, a dopant is directly implanted by an ion implantation method.
この際、ＳｉＣ単結晶基板の表面に、上記加工変質部が残存していると、正常なエピタキシャル成長を阻害したり、打ち込まれたドーパントの活性化率が低下したりする等の問題が発生することが知られており、さらに、その変質部が電流のリークパスになり、デバイスの性能を落とすこと等も考えられる。 At this time, if the above-mentioned altered part remains on the surface of the SiC single crystal substrate, problems such as inhibiting normal epitaxial growth or reducing the activation rate of the implanted dopant may occur. Further, it is conceivable that the altered portion becomes a current leakage path, which degrades the performance of the device.
通常、ＳｉＣ単結晶基板の表面は、ダイヤモンド砥粒等による研磨加工による仕上げがされているが、近年のデバイスの微細化に伴い、さらに表面の平坦化が求められているため、メカノケミカル研磨等も行われている。このような基板の表面には、研磨による加工変質部が数百ｎｍ存在し、これが十分に除去されていないと、上記のような問題を引き起こすことが想定される。 Usually, the surface of the SiC single crystal substrate is finished by polishing with diamond abrasive grains, etc., but with the recent miniaturization of devices, further planarization of the surface is required, so mechanochemical polishing, etc. Has also been done. On the surface of such a substrate, there are several hundred nanometers of damaged portions due to polishing, and if this is not sufficiently removed, it is assumed that the above-described problems are caused.
このため、従来においては、Ｓｉとの反応性が高いフッ素系反応性ガスを用いたエッチングにより、この加工変質部を取り除いていた。このフッ素系反応性ガスは、酸化シリコンや窒化シリコン等の絶縁膜のエッチングにも用いられる、半導体プロセスにおいては、一般的なガスである。しかしながら、加工変質部の除去にこのようなフッ素系反応性ガスを用いると、ＳｉＣ単結晶基板の表面にフロロカーボン系の反応生成物が残渣として残ることがあり（非特許文献１）、一度このような残渣が生じてしまうと、その後に酸素ガスプラズマ処理あるいはＲＣＡ洗浄等の表面清浄化処理を行っても除去することが難しい。 For this reason, conventionally, this work-affected zone has been removed by etching using a fluorine-based reactive gas that is highly reactive with Si. This fluorine-based reactive gas is a general gas in a semiconductor process that is also used for etching an insulating film such as silicon oxide or silicon nitride. However, when such a fluorine-based reactive gas is used to remove the work-affected part, a fluorocarbon-based reaction product may remain as a residue on the surface of the SiC single crystal substrate (Non-patent Document 1). If such a residue is generated, it is difficult to remove even if a surface cleaning treatment such as oxygen gas plasma treatment or RCA cleaning is performed thereafter.
そこで、このような問題を解決するために、フッ素系反応性ガスに替えて塩素系反応性ガスを用いる方法が発明されている（特許文献１）。この塩素系反応性ガスは、同じハロゲン系ガスではあるが、フッ素系反応性ガスよりも反応性が低く、加工変質部除去後にカーボン系の反応生成物が表面に残らないので、最終的に表面品質が高くなり、プロセスガスとして優れている。この塩素系反応性ガスを用いることで、表面粗さを表すマイクロラフネスＲａ値がＲａ＝０．３ｎｍと比較的良好な表面が得られるようになった。 In order to solve such problems, a method of using a chlorine-based reactive gas instead of a fluorine-based reactive gas has been invented (Patent Document 1). Although this chlorine-based reactive gas is the same halogen-based gas, the reactivity is lower than that of the fluorine-based reactive gas, and the carbon-based reaction product does not remain on the surface after removal of the work-affected part. High quality and excellent as process gas. By using this chlorine-based reactive gas, a relatively good surface can be obtained with a microroughness Ra value representing surface roughness of Ra = 0.3 nm.
しかしながら、並行平板型の電極を有する反応性イオンエッチング装置を用いる限り、高周波のマイクロ波を用いることが出来ず、また、イオンフラックスとイオンエネルギーとをそれぞれ独立に制御することができないことから、この塩素系反応性ガスを用いたエッチングの効果は限定的であった。 However, as long as a reactive ion etching apparatus having parallel plate type electrodes is used, high-frequency microwaves cannot be used, and ion flux and ion energy cannot be controlled independently. The effect of etching using a chlorine-based reactive gas was limited.
そこで、本発明者らは、表面粗さＲａ値においてより優れた清浄性及び平坦性を達成するための方法について鋭意検討した結果、意外にも、反応性がよりマイルドなＨＩガスを用い、この低い反応性をプラズマ密度の高さで補うことにより、より優れた清浄性及び平坦性を有するＳｉＣ単結晶基板を製造することができることを見出し、本発明を完成した。 Therefore, as a result of earnestly examining the method for achieving better cleanliness and flatness in the surface roughness Ra value, the present inventors surprisingly used a HI gas with milder reactivity. The present inventors have found that a SiC single crystal substrate having better cleanliness and flatness can be produced by supplementing low reactivity with high plasma density, and completed the present invention.
従って、本発明の目的は、マイクロ波で励起した反応性プラズマガスを用いた、清浄性及び平坦性に優れた表面を有するＳｉＣ単結晶基板の製造方法を提供するものである。 Accordingly, an object of the present invention is to provide a method for producing a SiC single crystal substrate having a surface excellent in cleanliness and flatness using a reactive plasma gas excited by microwaves.
即ち、本発明は、以下の通りである。
(1) 炭化珪素単結晶インゴットからスライス加工により切り出し、表面研磨加工を行って得られた研磨加工後の炭化珪素単結晶基板について、その表面に存在する加工変質部を除去して炭化珪素単結晶基板を製造する方法において、前記研磨加工後の炭化珪素単結晶基板表面の加工変質部をマイクロ波でプラズマ化させたＨＩガスによるＨＩプラズマ処理により除去することを特徴とする炭化珪素単結晶基板の製造方法。
(2) 炭化珪素単結晶インゴットからスライス加工により切り出し、表面研磨加工を行って得られた研磨加工後の炭化珪素単結晶基板について、その表面に存在する加工変質部を除去して炭化珪素単結晶基板を製造する方法において、前記研磨加工後の炭化珪素単結晶基板表面の加工変質部を不活性ガスを用いたスパッタエッチングで除去した後、このスパッタエッチング処理後の炭化珪素単結晶基板表面のイオン損傷部をマイクロ波でプラズマ化させたＨＩガスによるＨＩプラズマ処理により除去することを特徴とする炭化珪素単結晶基板の製造方法。
(3) 前記ＨＩプラズマ処理の後に、マイクロ波でプラズマ化させたＯ2ガスによる表面清浄化処理を行うことを特徴とする前記(1)又は(2)に記載の炭化珪素単結晶基板の製造方法。
That is, the present invention is as follows.
(1) For a silicon carbide single crystal substrate after polishing, obtained by slicing from a silicon carbide single crystal ingot and performing surface polishing, the work-affected portion existing on the surface is removed to remove the silicon carbide single crystal In the method for manufacturing a substrate, the altered portion of the surface of the silicon carbide single crystal substrate after the polishing is removed by HI plasma treatment using HI gas that has been made into plasma by microwaves. Production method.
(2) For a silicon carbide single crystal substrate after polishing, obtained by slicing from a silicon carbide single crystal ingot and performing surface polishing, the work-affected portion existing on the surface is removed to remove the silicon carbide single crystal In the method of manufacturing a substrate, after removing the altered portion of the polished silicon carbide single crystal substrate surface by sputter etching using an inert gas, the ions on the silicon carbide single crystal substrate surface after the sputter etching treatment are removed. A method for producing a silicon carbide single crystal substrate, wherein the damaged portion is removed by HI plasma treatment using HI gas that has been made plasma by microwaves.
(3) The silicon carbide single crystal substrate according to the above (1) or (2), wherein after the HI plasma treatment, a surface cleaning treatment with O 2 gas plasmified by microwaves is performed. Method.
この発明によれば、ＳｉＣ単結晶基板の表面に存在する加工変質部あるいはイオン損傷部が除去され、かつ、その除去処理に伴う残渣や表面荒れが無く、清浄性及び平坦性に優れた表面を有するＳｉＣ単結晶基板を作成することが可能である。 According to the present invention, a work-affected portion or an ion-damaged portion existing on the surface of the SiC single crystal substrate is removed, and a surface excellent in cleanliness and flatness without residue and surface roughness accompanying the removal treatment is obtained. It is possible to produce a SiC single crystal substrate having the same.
先ず、ＳｉＣ単結晶のインゴットからＳｉＣ単結晶基板を加工する工程についての概略を説明する。ＳｉＣ単結晶のインゴットを作製後、それをスライスして、ウエハ状の基板に切り出し、所定の厚さまで荒削りを行う。その後、基板の両面を平坦かつ鏡面に仕上げるための研磨を行い、続いて、基板に付着した汚れを除去するための洗浄を行う。最後に、上記各工程で基板に導入された表面加工変質部を除去する工程となるが、この工程が、本発明が対象としている工程である。 First, the outline about the process of processing a SiC single crystal substrate from a SiC single crystal ingot is explained. After producing the SiC single crystal ingot, it is sliced, cut into a wafer-like substrate, and roughed to a predetermined thickness. Thereafter, polishing is performed to finish both surfaces of the substrate to a flat and mirror surface, followed by cleaning to remove dirt attached to the substrate. Finally, it becomes a step of removing the surface-processed deteriorated portion introduced into the substrate in each of the above steps, and this step is a step targeted by the present invention.
本発明では、反応性ガスを用いたエッチングによってＳｉＣ単結晶基板表面の加工変質部を除去する際に、使用するガス種とプラズマ密度とを考慮したものである。ＳｉＣに対してエッチング性を有するガスとしては、ＣＦ4、ＣＨＦ3等のフッ素系反応性ガスやＣｌ2、ＨＣｌ、ＨＢｒ、ＨＩ等のフッ素以外のハロゲン元素を含むハロゲン系反応性ガスがある。フッ素系反応性ガスでは、Ｆに起因するフロロカーボン系の反応生成物が表面に残り、それが残渣になるため、Ｆを含まないハロゲン系反応性ガスでのエッチングを試み検討した。 In the present invention, the type of gas to be used and the plasma density are taken into account when removing the work-affected portion on the surface of the SiC single crystal substrate by etching using a reactive gas. Examples of the gas having etching property with respect to SiC include a fluorine-based reactive gas such as CF 4 and CHF 3 and a halogen-based reactive gas containing a halogen element other than fluorine such as Cl 2 , HCl, HBr, and HI. In the case of a fluorine-based reactive gas, a fluorocarbon-based reaction product resulting from F remains on the surface and becomes a residue. Therefore, etching with a halogen-based reactive gas containing no F was studied.
そして、フッ素以外のハロゲン元素を含むハロゲン系反応性ガスとして塩素系反応性ガスを用いた場合には、前述の通り、表面粗さＲａ値において比較的良好な結果が得られたことと、そのエッチング効果が限定的であったことを考慮し、特に、ハロゲン系反応性ガスとして更に反応性の低いヨウ素系反応性ガスのＨＩガスを用い、このＨＩガスの反応性の低さをプラズマ密度で補うことに着眼して検討を行った結果、マイクロ波でプラズマ化させたＨＩガスを用いるＨＩプラズマ処理であれば、加工変質部やイオン損傷部を除去した後の表面に殆ど残渣が残らず、表面粗さＲａ値により優れたＳｉＣ単結晶基板を製造できることを見出した。これは、ＨＩガスが他のハロゲン水素化物に比べて反応性がよりマイルドであって表面がより平坦に仕上がり、また、この反応性の低さをプラズマ密度の高さで補って所定のエッチングが達成されたものと考えられる。因みに、並行平板型の電極でプラズマを発生させる際によく使われる周波数が１３．５６MHzであるのに比べて、２．４５ＧＨｚのマイクロ波ではプラズマ密度を約２０，０００倍上げられるためであり、マイクロ波の方がより高いプラズマ密度でＳｉＣ単結晶基板表面の加工変質部やイオン損傷部を効率良くエッチングできたものと考えられる。 And, when using a chlorine-based reactive gas as a halogen-based reactive gas containing a halogen element other than fluorine, as described above, relatively good results were obtained in the surface roughness Ra value, Considering that the etching effect was limited, in particular, HI gas of iodine-based reactive gas having lower reactivity was used as the halogen-based reactive gas, and the low reactivity of this HI gas was expressed by the plasma density. As a result of investigating to supplement, as a result of HI plasma treatment using HI gas that has been plasmatized by microwaves, almost no residue remains on the surface after removal of the work-affected part and ion-damaged part, It has been found that a SiC single crystal substrate having an excellent surface roughness Ra value can be produced. This is because the HI gas has a milder reactivity than other halogen hydrides and the surface finishes more flat, and this low reactivity is compensated for by the high plasma density to achieve a predetermined etching. It is thought that it was achieved. By the way, compared to the frequency of 13.56 MHz that is often used when generating plasma with parallel plate electrodes, the plasma density can be increased by about 20,000 times in the microwave of 2.45 GHz. It is considered that the microwave was able to efficiently etch the work-affected part and the ion-damaged part on the surface of the SiC single crystal substrate with a higher plasma density.
また、上記ＳｉＣ単結晶基板表面の加工変質部をＡｒ、Ｈｅ、Ｎｅ等の不活性ガスによるスパッタエッチング処理で除去した後、このスパッタエッチング処理後のイオン損傷部をマイクロ波でプラズマ化させたＨＩガスによるＨＩプラズマ処理で除去すれば、更に表面品質（マイクロラフネス）Ｒａ値が良くなることも確認した。 Moreover, after removing the altered portion of the SiC single crystal substrate surface by a sputter etching process using an inert gas such as Ar, He, Ne, etc., the ion-damaged part after the sputter etching process is turned into plasma by microwaves. It was also confirmed that the surface quality (microroughness) Ra value was further improved if the gas was removed by HI plasma treatment with gas.
更に、以上のようにしてＳｉＣ単結晶基板表面の加工変質部をＨＩプラズマ処理で除去した後に、あるいは、スパッタエッチング処理で加工変質部を除去した後のイオン損傷部をＨＩプラズマ処理で除去した後に、マイクロ波でプラズマ化させたＯ2ガスを用いるＯ2プラズマ処理による表面清浄化処理を行うと、残渣をほぼ完全に除去することができることも確認した。なお、ＳｉＣ単結晶基板の表面は化学的に安定であり、Ｏ2プラズマ処理後の表面に酸化膜による干渉色が観察されなかったことからも、Ｏ2プラズマ処理後の表面が酸化膜で覆われていることは認められなかった。 Further, after removing the damaged portion of the SiC single crystal substrate surface by HI plasma processing as described above, or after removing the damaged portion of the SiC single crystal substrate surface by HI plasma treatment after removing the damaged portion by sputter etching processing. It has also been confirmed that the residue can be removed almost completely when surface cleaning is performed by O 2 plasma treatment using O 2 gas that has been plasmatized by microwaves. The surface of the SiC single crystal substrate is chemically stable, O 2 from the interference color due to oxide film on the surface after the plasma treatment was observed, covering the surface oxide film after O 2 plasma treatment It was not recognized that
本発明において使用する反応性イオンエッチング装置としては、反応性ガスのＨＩガスをマイクロ波でプラズマ化してエッチングする装置であり、例えば、プラズマ源として磁場コイルを利用した電子サイクロトロン共鳴プラズマ(ECP; Electron Cyclotron resonance Plasma)、磁場コイルを利用したヘリコン波励起プラズマ(HWP; Helicon Wave Plasma)、アンテナ内挿型等の誘導結合型プラズマ(ICP; Inductively Coupled Plasma)、スロットアンテナ等を利用したマイクロ波励起表面波プラズマ(SWP; Surface Wave Plasma)等を備えた装置を例示することができ、これらの反応性イオンエッチング装置によれば１０11〜１０13/cm-3という高いプラズマ密度を達成することができる。 The reactive ion etching apparatus used in the present invention is an apparatus that performs etching by converting a reactive gas HI gas into plasma with microwaves. For example, an electron cyclotron resonance plasma (ECP) using a magnetic coil as a plasma source is used. Cyclotron resonance plasma), Helicon Wave Plasma (HWP) using magnetic coil, Inductively Coupled Plasma (ICP) such as antenna insertion type, Microwave excitation surface using slot antenna, etc. An apparatus equipped with a wave plasma (SWP; Surface Wave Plasma) can be exemplified, and according to these reactive ion etching apparatuses, a high plasma density of 10 11 to 10 13 / cm −3 can be achieved. .
ここで、ＨＩガスをプラズマ源とする反応性イオンエッチング装置を用いた場合の本発明のＨＩプラズマ処理について、その原理を説明すると、図１において、ＳｉＣ単結晶基板１が反応チャンバー２内にセットされており、発振器３で発信されたマイクロ波はインピーダンス整合器４でインピーダンスがマッチングされて反応チャンバー２内に導入され、また、反応性ガスのガスボンベ５からはＨＩガスが反応チャンバー２内に導入され、前記反応チャンバー２内でＨＩガスにマイクロ波が照射されて発生したプラズマによりＳｉＣ単結晶基板１の表面がエッチングされる。なお、符号６は、反応チャンバー２内のガスを排気させる排気ポンプである。
Here, the principle of the HI plasma processing of the present invention using a reactive ion etching apparatus using HI gas as a plasma source will be described. In FIG. 1, the SiC single crystal substrate 1 is set in the reaction chamber 2. The microwave transmitted from the
本発明において、ＨＩガスを用いるＨＩプラズマ処理の際のエッチング条件としては、ＨＩガスをプラズマ化させるマイクロ波の周波数領域が好ましくは４３３．０５〜４３４．７９MHz、９０２〜９２８MHz、２．４〜２．５GHz、５．７２５〜５．８７５GHz、２４〜２４．２５GHz、６１〜６１．５GHz、又は、１２２〜１２３GHzであり、エッチング時の圧力が通常１０Pa以上５０Pa以下、好ましくは１０Pa以上３０Pa以下であり、ガス流量が通常１０cm3/分以上５０cm3/分以下、好ましくは２０cm3/分以上３０cm3/分以下であり、前記マイクロ波の入力パワーが通常０．５W/cm2以上１．０W/cm2以下、好ましくは１．０W/cm2である。この条件は、エッチング後の残渣の発生を極力避けるために、エッチングのスパッタ性を高め、かつ生産性を落とさない程度にＳｉＣに対して適度なエッチング速度を持たせるという観点から設定されたものであり、この際のＳｉＣに対するエッチング速度は毎分８０〜９０ｎｍである。 In the present invention, as the etching conditions for the HI plasma treatment using HI gas, the microwave frequency region for converting the HI gas into plasma is preferably 433.05 to 434.79 MHz, 902 to 928 MHz, 2.4 to 2 5 GHz, 5.725 to 5.875 GHz, 24 to 24.25 GHz, 61 to 61.5 GHz, or 122 to 123 GHz, and the pressure during etching is usually 10 Pa to 50 Pa, preferably 10 Pa to 30 Pa. The gas flow rate is usually 10 cm 3 / min to 50 cm 3 / min, preferably 20 cm 3 / min to 30 cm 3 / min, and the microwave input power is usually 0.5 W / cm 2 to 1.0 W / min. cm 2 or less, preferably 1.0 W / cm 2 . This condition was set from the viewpoint of increasing the sputterability of etching in order to avoid generation of residues after etching as much as possible, and giving an appropriate etching rate to SiC to the extent that productivity is not reduced. In this case, the etching rate for SiC is 80 to 90 nm per minute.
また、不活性ガスによるスパッタエッチング処理時のエッチング条件としては、エッチング時の圧力が通常１０Pa以上５０Pa以下であり、ガス流量が通常１０cm3/分以上５０cm3/分以下であり、スパッタの入力パワーが通常０．２W/cm2以上１．０W/cm2以下である。特に、不活性ガスとしてＡｒガスを用いた場合のエッチング条件としては、エッチング時の圧力が１０Pa以上２０Pa以下、Ａｒ流量が２０cm3/分以上３０cm3/分以下、スパッタの入力パワーが０．２５W/cm2以上１．０W/cm2以下であるのがよい。 Etching conditions for sputter etching with an inert gas are that the pressure during etching is usually 10 Pa or more and 50 Pa or less, the gas flow rate is usually 10 cm 3 / min or more and 50 cm 3 / min or less, and the sputtering input power There is usually 0.2W / cm 2 more than 1.0W / cm 2 or less. In particular, the etching conditions when using Ar gas as the inert gas are as follows: the etching pressure is 10 Pa or more and 20 Pa or less, the Ar flow rate is 20 cm 3 / min or more and 30 cm 3 / min or less, and the sputtering input power is 0.25 W. It is good that it is not less than / cm 2 and not more than 1.0 W / cm 2 .
そして、マイクロ波でプラズマ化させたＯ2ガスを用いるＯ2プラズマ処理によって表面清浄化処理を行う際の処理条件としては、Ｏ2ガスをプラズマ化させるマイクロ波の周波数領域が好ましくは４３３．０５〜４３４．７９MHz、９０２〜９２８MHz、２．４〜２．５GHz、５．７２５〜５．８７５GHz、２４〜２４．２５GHz、６１〜６１．５GHz、又は、１２２〜１２３GHzであり、処理時の圧力が通常１０Pa以上１００Pa以下、好ましくは４０Pa以上５０Pa以下であり、Ｏ2流量が通常１０cm3/分以上５０cm3/分以下、好ましくは３０cm3/分以上４０cm3/分以下であり、また、前記マイクロ波の入力パワーが通常０．５W/cm2以上１．０W/cm2以下、好ましくは１．０W/cm2である。 Then, as the frequency region of microwaves to plasma of O 2 gas is preferably processing conditions when performing the surface cleaning treatment by O 2 plasma treatment using O 2 gas were plasma in microwave 433.05 ˜434.79 MHz, 902 to 928 MHz, 2.4 to 2.5 GHz, 5.725 to 5.875 GHz, 24 to 24.25 GHz, 61 to 61.5 GHz, or 122 to 123 GHz, and the pressure during processing is It is usually 10 Pa or more and 100 Pa or less, preferably 40 Pa or more and 50 Pa or less, and the O 2 flow rate is usually 10 cm 3 / min or more and 50 cm 3 / min or less, preferably 30 cm 3 / min or more and 40 cm 3 / min or less. input power of the wave normal 0.5 W / cm 2 or more 1.0 W / cm 2 or less, preferably 1.0 W / cm 2.
以下、実施例及び比較例に基づいて、本発明の内容を具体的に説明する。
〔実施例１〕
ＳｉＣ単結晶インゴットからウエハ状にスライスし、粒径の大きいダイヤモンド研磨剤から順次粒径を小さくして研磨していき、最終的に平均粒径１μｍのダイヤモンド研磨剤で研磨した後のＳｉＣ単結晶基板を調製した。
得られたＳｉＣ単結晶基板を、プラズマ源としてＨＩガスを備えた反応性イオンエッチング装置の反応チャンバー内にセットし、この反応チャンバー内にＨＩガスを導入すると共に２．４５ＧＨｚのマイクロ波を照射し、プラズマ化させたＨＩガスによるマイクロ波プラズマエッチングであるＨＩプラズマ処理を実施した。エッチング条件は、ガス流量が３０cm3/分で、エッチング時の真空度が１３Paで、また、２．４５ＧＨｚのマイクロ波の入力パワーが１．０W/cm2であった。この場合は、表面に残渣は殆ど見られず、Ｒａ値はＲａ＝０．１nmと良好であり、この実施例１のＨＩプラズマ処理により清浄性及び平坦性に優れた表面を有するＳｉＣ単結晶基板が得られた。
Hereinafter, based on an Example and a comparative example, the content of this invention is demonstrated concretely.
[Example 1]
The SiC single crystal is sliced into wafers from a SiC single crystal ingot, polished with a diamond particle having a large particle size, and then polished with a diamond particle having an average particle size of 1 μm. A substrate was prepared.
The obtained SiC single crystal substrate was set in a reaction chamber of a reactive ion etching apparatus equipped with HI gas as a plasma source, and HI gas was introduced into the reaction chamber and a 2.45 GHz microwave was irradiated. Then, HI plasma processing, which is microwave plasma etching using plasmaized HI gas, was performed. The etching conditions were such that the gas flow rate was 30 cm 3 / min, the degree of vacuum during etching was 13 Pa, and the microwave input power of 2.45 GHz was 1.0 W / cm 2 . In this case, almost no residue is observed on the surface, the Ra value is as good as Ra = 0.1 nm, and the SiC single crystal substrate has a surface excellent in cleanliness and flatness by the HI plasma treatment of Example 1. was gotten.
〔実施例２〕
実施例１で用いたのと同様の表面状態を有するＳｉＣ単結晶基板に、不活性ガスとしてＡｒガスを用いたスパッタエッチング処理を行い、ＳｉＣ単結晶基板表面の加工変質部の除去を行った。この際の具体的なエッチング条件は、Ａｒガスのガス流量が２０cm3/分で、エッチング時の真空度が１５Paで、スパッタの入力パワーが０．２５W/cm2であった。
その後、実施例１の場合と同じ条件でＨＩプラズマ処理によるマイクロ波プラズマエッチングを行った。
上記のスパッタエッチング処理及びＨＩプラズマ処理によりＳｉＣ単結晶基板の表面の荒れあるいは残渣が除去されており、Ｒａ値もＲａ＝０．０９nmと極めて良好であった。
[Example 2]
The SiC single crystal substrate having the same surface state as that used in Example 1 was subjected to sputter etching using Ar gas as an inert gas to remove the work-affected portions on the surface of the SiC single crystal substrate. Specific etching conditions at this time were an Ar gas gas flow rate of 20 cm 3 / min, a degree of vacuum during etching of 15 Pa, and a sputtering input power of 0.25 W / cm 2 .
Thereafter, microwave plasma etching by HI plasma treatment was performed under the same conditions as in Example 1.
The surface roughness or residue of the SiC single crystal substrate was removed by the above-described sputter etching treatment and HI plasma treatment, and the Ra value was also very good at Ra = 0.09 nm.
〔実施例３〕
実施例１によって得られたＳｉＣ単結晶基板の表面に、更に、２．４５ＧＨｚのマイクロ波でプラズマ化させたＯ2ガスを用いたＯ2プラズマ処理による表面清浄化処理を実施した。処理条件としては、Ｏ2のガス流量が４０cm3/分で、処理時の真空度が５０Paで、２．４５ＧＨｚのマイクロ波の入力パワーが１．０W/cm2であり、Ｒａ値も実施例１の場合に比べてＲａ＝０．０８nmと更に改善された。
Example 3
The surface of the SiC single crystal substrate obtained in Example 1 was further subjected to surface cleaning treatment by O 2 plasma treatment using O 2 gas that was plasmatized with a microwave of 2.45 GHz. The processing conditions are as follows: O 2 gas flow rate is 40 cm 3 / min, vacuum degree during processing is 50 Pa, microwave input power of 2.45 GHz is 1.0 W / cm 2 , and Ra value is also an example. Compared to the case of 1, Ra = 0.08 nm was further improved.
〔比較例１〕
比較例１として、２．４５ＧＨｚのマイクロ波でプラズマ化させたフッ素系反応性ガス（ＣＦ4とＯ2の混合ガス）を用いてマイクロ波プラズマエッチングを行った。この際のエッチング条件は、ＣＦ4ガスのガス流量が２０cm3/分で、Ｏ2ガスのガス流量が４０cm3/分で、エッチング時の真空度が５０Paで、２．４５ＧＨｚのマイクロ波の入力パワーが０．２５W/cm2であった。この比較例１で得られたＳｉＣ単結晶基板の表面の表面粗さＲａ値はＲａ＝１．４８nmであり、実施例１で得られたＳｉＣ単結晶基板の表面状態に比べ、明らかに劣るものであった。
[Comparative Example 1]
As Comparative Example 1, microwave plasma etching was performed using a fluorine-based reactive gas (mixed gas of CF 4 and O 2 ) that was plasmatized with a microwave of 2.45 GHz. The etching conditions are as follows: CF 4 gas flow rate is 20 cm 3 / min, O 2 gas flow rate is 40 cm 3 / min, the degree of vacuum during etching is 50 Pa, and 2.45 GHz microwave input. The power was 0.25 W / cm 2 . The surface roughness Ra value of the surface of the SiC single crystal substrate obtained in Comparative Example 1 is Ra = 1.48 nm, which is clearly inferior to the surface state of the SiC single crystal substrate obtained in Example 1. Met.
本発明によれば、ＳｉＣ単結晶基板の表面に存在する加工変質部やイオン損傷部が反応性穏やかにかつ効率良く除去され、その除去処理に伴う残渣や表面荒れが無く、清浄性及び平坦性に優れた表面を有するＳｉＣ単結晶基板を作成することができる。そのため、このようなＳｉＣ単結晶基板上に電子デバイスを形成すれば、デバイスの特性が向上することが期待される。 According to the present invention, process-affected parts and ion-damaged parts existing on the surface of a SiC single crystal substrate are reactively and efficiently removed, and there are no residues and surface roughness associated with the removal process, and cleanliness and flatness. A SiC single crystal substrate having an excellent surface can be produced. Therefore, if an electronic device is formed on such a SiC single crystal substrate, it is expected that the characteristics of the device will be improved.
１…炭化珪素単結晶基板、２…反応チャンバー、３…発振器、４…インピーダンス整合器、５…反応ガスボンベ、６…排気ポンプ。 DESCRIPTION OF SYMBOLS 1 ... Silicon carbide single crystal substrate, 2 ... Reaction chamber, 3 ... Oscillator, 4 ... Impedance matching device, 5 ... Reaction gas cylinder, 6 ... Exhaust pump.
Claims (3)
前記研磨加工後の炭化珪素単結晶基板表面の加工変質部をマイクロ波でプラズマ化させたＨＩガスによるＨＩプラズマ処理により除去することを特徴とする炭化珪素単結晶基板の製造方法。 A silicon carbide single crystal substrate is manufactured by removing a damaged portion on the surface of a polished silicon carbide single crystal substrate obtained by slicing from a silicon carbide single crystal ingot and performing surface polishing. In the way to
A method for producing a silicon carbide single crystal substrate, comprising removing a process-affected portion on the surface of the silicon carbide single crystal substrate after the polishing by HI plasma treatment using HI gas that has been made into plasma by microwaves.
前記研磨加工後の炭化珪素単結晶基板表面の加工変質部を不活性ガスを用いたスパッタエッチングで除去した後、このスパッタエッチング処理後の炭化珪素単結晶基板表面のイオン損傷部をマイクロ波でプラズマ化させたＨＩガスによるＨＩプラズマ処理により除去することを特徴とする炭化珪素単結晶基板の製造方法。 A silicon carbide single crystal substrate is manufactured by removing a damaged portion on the surface of a polished silicon carbide single crystal substrate obtained by slicing from a silicon carbide single crystal ingot and performing surface polishing. In the way to
After the polishing alteration of the silicon carbide single crystal substrate surface after the polishing process is removed by sputter etching using an inert gas, ion-damaged portions of the silicon carbide single crystal substrate surface after the sputter etching treatment are plasma-generated by microwaves. A method for producing a silicon carbide single crystal substrate, wherein the removal is performed by HI plasma treatment with a fluorinated HI gas.
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