【発明の詳細な説明】[Detailed description of the invention]
［産業上の利用分野］
本発明は半導体製造装置の構造部材として用い
られるステンレス鋼部材に関し、詳細には高品
質・高性能製品を製造するために必要な高清浄性
の半導体製造装置においてガスや純水の供給系、
排気系或は反応室等の構成部材に用いることがで
きる耐ガス放出性に優れた表面処理ステンレス鋼
部材に関するものである。
［従来の技術］
半導体産業界における技術の発展は近年特に目
ざましいものがあり、高性能製品が製造される様
になつている。例えば半導体記憶素子の配線間隔
はミクロン、更にはサブミクロンの精度まで要求
される様になつている。このため配線上に微粒子
や細菌等が付着しただけでも回路がシヨートする
おそれがあり、半導体の製造段階で使用されるガ
スや純水（以下ガス等ということがある）も超高
純度であることが必要とされる。その為従来は導
入ガス自体を高純度化することに努力が払われて
きたが、それだけでは不十分であり、半導体製造
装置におけるガス等の供給系、排出系、或は反応
室の系路を構成する材料の表面に吸着している不
純物ガスの量を少なくすることや、この様な構成
材料自体からの不純ガスの放出をできる限り抑制
することが重要であると考えられる様になつてき
た。このため構成材料の材質としては、半導体記
憶素子の大容量化に伴なう溶接機会が増加しても
不都合がなく、耐食性も他の素材に比べて良好な
ステンレス鋼材が注目される様になつた。
また構成材料は不純物成分の溶出を抑制すると
いう観点から、ガス等との接触面積がなるべく小
さくなる様に内表面を平滑化することが必要であ
る。更に材料表面を加工処理した場合に変質層が
残存するようなものであるとガス等が変質層に吸
着されて清浄性を損うおそれがあるので、この様
な変質層を除去し同時に平滑化処理も兼ねる電解
研摩処理を施こしたステンレス鋼部材が使用され
ている。尚不純ガスの放出量を更に抑制すること
を目的として、電解研摩処理に付した後で非晶質
のNi−Ｐ系合金を無電解メツキしたステンレス
鋼部材も実用化されはじめている。
［発明が解決しようとする問題点］
しかしながら電解研摩処理の後に非晶質のNi
−Ｐ系合金を無電解めつきする場合は一般に非常
に複雑な製造工程を要し、その為めつきコストが
高くなるという問題があつた。
本発明はこの様な事情に鑑みてなされたもので
あつて、半導体製造装置におけるガス系路の構成
材料としてガス放出量の低減化に優れ且つ安価な
ステンレス鋼部材を提供しようとするものであ
る。
［問題点を解決する為の手段］
本発明は電解研摩処理を施こしたステンレス鋼
部材表面に膜厚：75Å以上の非晶質酸化皮膜を形
成したことを要旨とするものである。
［作用］
本発明は上記の様に構成されるが、要するに電
解研摩処理により平滑化したステンレス鋼は、大
気等の酸化性ガス雰囲気中で加熱酸化処理するこ
とにより、一定膜厚以上の非晶質酸化皮膜を形成
し、ガス放出量が著しく減少することを見出し本
発明を完成したものである。
本発明者らは種々の酸化加熱処理条件でステン
レス鋼の表面に酸化皮膜を形成し、各供試材の耐
ガス放出量を調査した。その結果、後述する実施
例に示す様に膜厚：75Å以上の非晶質性酸化皮膜
が形成されたものは耐ガス放出性が極めて良好で
あることを知見した。その理論的根拠を見出した
訳ではないが、酸化皮膜が結晶質の場合は耐ガス
放出性は改善されず、また非晶質酸化皮膜であつ
ても膜圧が75Å未満の場合は薄すぎて良好な耐ガ
ス放出性が得られなかつた。ステンレス鋼表面に
膜厚：75Å以上の非晶質性酸化皮膜を形成する方
法としては、大気中等の酸化性雰囲気中で加熱処
理する方法が例示される。加熱温度は酸化性雰囲
気の種類により異なるが、例えば大気中の場合
は、後述する実施例に示す様に220〜280℃が望ま
しく、また加熱時間は加熱温度にもよるが一般に
１分以上が望ましい。加熱温度が220℃未満の場
合は温度が低すぎて非晶質酸化皮膜の膜厚が十分
でなく、一方加熱温度が580℃を越えると酸化皮
膜は結晶質として生成する傾向にある。また加熱
時間が１分未満の場合は、加熱温度にもよるが一
般に酸化皮膜の生成が不十分で膜厚が薄く良好な
耐ガス放出性が得られない傾向にある。
以下実施例について説明するが本発明は下記実
施例に限定されるものではなく、前・後記の趣旨
に徴して適宜設計変更することは本発明の技術範
囲に含まれる。
［実施例］
外径：12.7mm、肉厚：１mm、長さ：２ｍの
SUS316Lステンレス鋼管の内面をH2SO4−
H3PO4水溶液を用いて電解研摩を施こしたもの
及び機械研摩を施したもの（いずれも表面粗度は
Rnax．0.4〜0.6μｍに調整した）を、第１表（左
欄）に示す加熱酸化処理条件で大気中加熱酸化処
理を施こして試験材とした。
[Industrial Application Field] The present invention relates to stainless steel members used as structural members of semiconductor manufacturing equipment, and more specifically, the present invention relates to stainless steel members used as structural members of semiconductor manufacturing equipment, and more particularly, to stainless steel members used as structural members of semiconductor manufacturing equipment. Pure water supply system,
The present invention relates to a surface-treated stainless steel member with excellent gas release resistance that can be used for structural members of exhaust systems, reaction chambers, etc. [Prior Art] Technological developments in the semiconductor industry have been particularly remarkable in recent years, and high-performance products are being manufactured. For example, the wiring spacing of semiconductor memory elements is now required to have micron or even submicron accuracy. For this reason, even if particles or bacteria adhere to the wiring, there is a risk of circuit failure, and the gases and pure water (hereinafter referred to as gas, etc.) used in the semiconductor manufacturing stage must also be of ultra-high purity. is required. For this reason, efforts have been made to improve the purity of the introduced gas itself, but this alone is insufficient, and the gas supply system, exhaust system, or reaction chamber system in semiconductor manufacturing equipment has to be improved. It has come to be considered important to reduce the amount of impurity gas adsorbed on the surface of the constituent materials and to suppress the release of such impurity gases from the constituent materials themselves as much as possible. . For this reason, stainless steel is attracting attention as a material for its construction because it is not inconvenient even when the number of welding opportunities increases due to the increase in the capacity of semiconductor memory elements, and it also has better corrosion resistance than other materials. Ta. In addition, from the viewpoint of suppressing the elution of impurity components, the inner surface of the constituent materials must be smoothed so that the contact area with gas etc. is as small as possible. Furthermore, if a degraded layer remains after processing the surface of the material, gases etc. may be adsorbed to the degraded layer and impair cleanliness, so such a degraded layer must be removed and smoothed at the same time. Stainless steel parts are used that have been subjected to an electrolytic polishing treatment that also serves as a treatment. In order to further suppress the amount of impurity gas released, stainless steel members that are subjected to electrolytic polishing treatment and then electrolessly plated with an amorphous Ni--P alloy are beginning to be put into practical use. [Problems to be solved by the invention] However, after electrolytic polishing treatment, amorphous Ni
Electroless plating of -P alloys generally requires a very complicated manufacturing process, which poses the problem of high plating costs. The present invention has been made in view of these circumstances, and it is an object of the present invention to provide an inexpensive stainless steel member that is excellent in reducing the amount of gas released and can be used as a constituent material for gas lines in semiconductor manufacturing equipment. . [Means for Solving the Problems] The gist of the present invention is to form an amorphous oxide film with a thickness of 75 Å or more on the surface of a stainless steel member that has been subjected to electropolishing treatment. [Function] The present invention is configured as described above, but in short, stainless steel smoothed by electrolytic polishing is heated and oxidized in an oxidizing gas atmosphere such as the atmosphere to form an amorphous film with a certain thickness or more. The present invention was completed based on the discovery that a fine oxide film is formed and the amount of gas released is significantly reduced. The present inventors formed an oxide film on the surface of stainless steel under various oxidative heat treatment conditions, and investigated the gas release resistance of each test material. As a result, as shown in the Examples described below, it was found that those in which an amorphous oxide film with a thickness of 75 Å or more was formed had extremely good gas release resistance. I have not found any theoretical basis for this, but if the oxide film is crystalline, gas release resistance will not be improved, and even if the oxide film is amorphous, if the film thickness is less than 75 Å, it will be too thin. Good gas release resistance could not be obtained. An example of a method for forming an amorphous oxide film with a thickness of 75 Å or more on the surface of stainless steel is a method of heat treatment in an oxidizing atmosphere such as the air. The heating temperature varies depending on the type of oxidizing atmosphere, but for example in the air, it is preferably 220 to 280°C as shown in the examples below, and the heating time is generally preferably 1 minute or more, although it depends on the heating temperature. . When the heating temperature is less than 220°C, the temperature is too low and the thickness of the amorphous oxide film is insufficient, whereas when the heating temperature exceeds 580°C, the oxide film tends to form as a crystalline film. In addition, if the heating time is less than 1 minute, although it depends on the heating temperature, the formation of the oxide film is generally insufficient and the film thickness tends to be thin and good gas release resistance cannot be obtained. Examples will be described below, but the present invention is not limited to the following examples, and it is within the technical scope of the present invention to make appropriate design changes in accordance with the spirit of the above and below. [Example] Outer diameter: 12.7mm, wall thickness: 1mm, length: 2m
The inner surface of the SUS316L stainless steel pipe is H 2 SO 4 −
Electrolytic polishing using H 3 PO 4 aqueous solution and mechanical polishing (surface roughness is
Rnax ． (adjusted to 0.4 to 0.6 μm) was subjected to heat oxidation treatment in the air under the heat oxidation treatment conditions shown in Table 1 (left column) to prepare a test material.
【表】【table】
【表】
上記第１表の耐ガス放出性欄において○及び×
の印はそれぞれ
○：優れている、×：悪い
を意味する。
上記各試験材より採取した小片における酸化皮
膜の結晶性を低入射角反射電子線回折により調査
した。また上記各試験材の一方側管端を閉じると
共に他方側のバルブ経由で真空ポンプに接続さ
せ、真空引きを行ないながらリボンヒータにより
管部を200℃にして30時間保持した後、室温に戻
した。その後10時間の真空引きで１×10-10Torr.
／Ｓが達成されるか否かにより耐ガス放出性の
良否を調べた。以上の結果を第１表（右欄）に併
せて示す。
第１表から明らかな様に、本発明例No.1〜９
はいずれも電解研摩後適切な条件で酸化処理して
いるので75Å以上の膜厚で非晶質酸化皮膜が形成
されており、耐ガス放出性が優れていた。
一方No.11及び12は非晶質酸化皮膜が形成される
ものの、No.11は加熱温度が低いため、またNo.12は
加熱時間が短いためにいずれも酸化皮膜の膜厚が
薄く耐ガス放出性が悪かった。No.13は加熱温度が
高すぎるため、酸化皮膜は結晶質となり耐ガス放
出性が悪かつた。No.14は酸化処理を施こさないた
め酸化皮膜の膜厚が薄く耐ガス放出性が悪かつ
た。No.15及び16は機械研摩を施こしたため酸化皮
膜は結晶質であり、耐ガス放出性が悪かつた。
［発明の効果］
本発明は上記の様に構成されているから耐ガス
放出性の優れた半導体製造装置用ステンレス鋼部
材を安価に提供できることとなつた。[Table] ○ and × in the gas release resistance column of Table 1 above
The marks mean ○: excellent, ×: bad. The crystallinity of the oxide film in the small pieces collected from each of the above test materials was investigated by low incidence angle reflected electron beam diffraction. In addition, one tube end of each of the above test materials was closed and connected to a vacuum pump via a valve on the other side, and the tube section was heated to 200 °C with a ribbon heater and held for 30 hours while drawing a vacuum, and then returned to room temperature. . After that, 1×10 -10 Torr was vacuumed for 10 hours.
The quality of gas release resistance was examined based on whether /S was achieved. The above results are also shown in Table 1 (right column). As is clear from Table 1, invention examples No. 1 to 9
In both cases, an amorphous oxide film was formed with a thickness of 75 Å or more because it was oxidized under appropriate conditions after electrolytic polishing, and it had excellent gas release resistance. On the other hand, although an amorphous oxide film is formed in No. 11 and 12, the heating temperature for No. 11 is low, and the heating time for No. 12 is short, so both have thin oxide films and are resistant to gas. Release properties were poor. In No. 13, the heating temperature was too high, so the oxide film became crystalline and had poor gas release resistance. Since No. 14 was not subjected to oxidation treatment, the oxide film was thin and its gas release resistance was poor. Since Nos. 15 and 16 were mechanically polished, the oxide film was crystalline and had poor gas release resistance. [Effects of the Invention] Since the present invention is configured as described above, it is possible to provide a stainless steel member for semiconductor manufacturing equipment with excellent gas release resistance at a low cost.