【発明の詳細な説明】[Detailed description of the invention]
本発明はウエハ等の半導体材料を熱処理するた
めの反応管の改良に関する。
一般に、ダイオードやトランジスタ等の半導体
を製造するには、種々の熱処理が施され、中でも
半導体材料としてのシリコンウエハの酸化処理工
程、拡散処理工程は重要である。
ところで、従来、上述したシリコンウエハ等の
半導体材料を熱処理するには、拡散炉と呼ばれる
電気炉内に装填され外周をコイル状発熱体で囲繞
した石英ガラス製反応管を用いて行なつている。
しかしながら、石英ガラスは1050℃付近で歪を生
じ、高温長時間使用すると、熱変形を起こして彎
曲するため、内部に載置すると半導体材料の出し
入れ作業が非常に困難となる問題があつた。ま
た、石英ガラス製反応管自体を高純度化しても、
拡散炉内のナトリウムやカルシウム等のアルカリ
金属やその他の化合物が外周面に付着すると、高
温で使用した場合、失透してボロボロに亀裂して
使用できなくなる。
このようなことから、石英ガラスに代つて珪素
を含む炭化珪素、或いは炭化珪素単体の反応管が
提案されている。しかしながらこれらの反応管は
純度的に石英ガラス製反応管に及ばず、しかも耐
スポーリング性、耐酸化性が劣るという難点もあ
つた。
本発明は上記欠点を解消するためになされたも
ので、石英ガラス製反応管本体の超高純度性を保
持しつつ、熱変形、外域不純物による劣化を防止
し、均熱性の良好な熱処理用反応管を提供しよう
とするものである。
以下、本発明の一実施例を図面を参照して説明
する。
図中１は一端に半導体材料の出し入れとガス供
給を兼ねた大径の開口部２ａ、他端にガス排出の
ための小径の開口部２ｂを有する石英ガラス製反
応管本体である。そして、この反応管本体１の加
熱部外域には耐熱製セラミツク管としての高純度
化処理されたカーボン管３が密着して配置され、
更に前記反応管本体１の外周には石英ガラス保護
管４が前記カーボン管３を密接包囲するように取
付けられている。なお、石英ガラス保護管４で包
囲されたカーボン管３の両端部には該保護管４の
内壁面と離間しており、この空間に例えば石英ガ
ラスウールの緩衝部５を介在させることによりカ
ーボン管３を保護管４内に支持固定している。ま
た、前記保護管４内に減圧状態に保持されてい
る。
このような構成によれば、石英ガラス製反応管
本体１内にシリコンウエハを載置した状態で電気
炉内に装填し、シリコンウエハを熱処理する場
合、反応管本体１の加熱部外域には耐熱性の優れ
たカーボン管３が配置され、該カーボン管３が耐
熱性の劣る反応管本体１に対して骨格（フレー
ム）として作用するため、反応管本体１の変形を
防止できる。その結果、反応管本体１内に載置す
るシリコンウエハの出し入れ作業を長期間円滑に
行なうことができる。
また、カーボン管３を包囲し、反応管本体１の
外周に石英ガラス保護管４を取付けることによつ
て、電気炉内のナトリウム、カルシウムなどの不
純物が反応管本体１外周面の加熱帯域に付着する
のを阻止でき、その結果、石英ガラス製反応管本
体１の失透、亀烈発生を防止でき、長寿命化を達
成できる。
更に、カーボン管３を包囲する石英ガラス保護
管４内を減圧にすれば、該カーボン管３の酸化を
防止できると共に、該保護管３と反応管本体１で
形成される空間のガスが熱膨張して圧力上昇し、
破裂するのを防止できる。しかも、カーボン管３
の両端部とこれを包囲する石英ガラス保護管４の
内壁面の間に隙間を形成し、この隙間に石英ガラ
スウールの緩衝部５を設ければ、カーボンと石英
ガラスの間の熱張差による相互の応力発生を吸収
でき、石英ガラス保護管４の破損を防止できる。
更にまた、石英ガラス保護管４で包囲される耐
熱性セラミツク管としてカーボン管３を用いれ
ば、カーボンは石英ガラスの熱伝導度0.003Cal／
cm・sec・℃より格段に大きく、0.22〜0.38Cal／
cm・sec・℃程度であるため、発熱体からの熱を
反応管本体１の軸方向に分散させる役目を果た
し、均熱長を長くできる。その結果、反応管本体
１内のシリコンウエハ等の半導体材料を均一加熱
できる。
次に、本発明の熱処理用反応管の効果を立証す
るための実験例を示す。
石英ガラス製反応管本体１の寸法を内径160mm
φ、全長2300mmとし、この外域に配置されるカー
ボン管３の寸法を内径168mm、外径178mm、全長
1500mmとし、更に石英ガラス保護管４の寸法を外
径182mm、全長1520mmとして熱処理用反応管（重
量490ｇ）を構成し、この反応管本体１内にシリ
コンウエハを載置し1240℃の温度で40時間熱処理
した。こうした熱処理を11回行なつた後の曲り度
合、ツブレ割合、均熱長、及び失透状態を調べた
ところ、下記表の如き結果となつた。なお、曲り
測定は、彎曲部の最大位置での度合より求め、ツ
ブレ割合は管を軸と直角方向に切断した断面にお
ける短軸と長軸の差より求め、均熱長は1240±
0.1℃の範囲内にある領域の長さとして求めた。
また、表中の比較例は石英ガラス製の単一管から
なる従来の反応管を例にしたものである。
The present invention relates to improvements in reaction tubes for heat treating semiconductor materials such as wafers. In general, various heat treatments are performed to manufacture semiconductors such as diodes and transistors, and among them, oxidation treatment and diffusion treatment of silicon wafers as semiconductor materials are important. Conventionally, heat treatment of semiconductor materials such as the silicon wafers described above has been carried out using a quartz glass reaction tube that is placed in an electric furnace called a diffusion furnace and whose outer periphery is surrounded by a coiled heating element.
However, quartz glass becomes distorted at around 1050°C, and when used at high temperatures for long periods of time, it will thermally deform and become curved, making it extremely difficult to insert and remove semiconductor materials when placed inside. Furthermore, even if the quartz glass reaction tube itself is made highly purified,
If alkali metals such as sodium and calcium or other compounds in the diffusion furnace adhere to the outer circumferential surface, when used at high temperatures, they will devitrify and crumble and crack, making them unusable. For this reason, reaction tubes made of silicon carbide containing silicon or silicon carbide alone have been proposed in place of quartz glass. However, these reaction tubes were not as pure as quartz glass reaction tubes, and they also had the disadvantage of being inferior in spalling resistance and oxidation resistance. The present invention was made in order to eliminate the above-mentioned drawbacks, and it is possible to prevent thermal deformation and deterioration due to external impurities while maintaining the ultra-high purity of the quartz glass reaction tube body, and to provide a heat treatment reaction with good thermal uniformity. It is intended to provide a tube. Hereinafter, one embodiment of the present invention will be described with reference to the drawings. In the figure, reference numeral 1 denotes a reaction tube body made of quartz glass, which has a large diameter opening 2a for taking in and out of semiconductor material and gas supply at one end, and a small diameter opening 2b for discharging gas at the other end. A highly purified carbon tube 3 as a heat-resistant ceramic tube is placed in close contact with the outside of the heating section of the reaction tube body 1.
Furthermore, a quartz glass protection tube 4 is attached to the outer periphery of the reaction tube body 1 so as to closely surround the carbon tube 3. Note that both ends of the carbon tube 3 surrounded by the quartz glass protection tube 4 are spaced apart from the inner wall surface of the protection tube 4, and by interposing a buffer portion 5 of quartz glass wool in this space, the carbon tube 3 is supported and fixed within the protective tube 4. Further, the protective tube 4 is maintained in a reduced pressure state. According to such a configuration, when a silicon wafer is placed inside the quartz glass reaction tube body 1 and the silicon wafer is loaded into an electric furnace and the silicon wafer is heat-treated, the area outside the heating part of the reaction tube body 1 is provided with a heat-resistant material. Since the carbon tube 3 having excellent heat resistance is disposed and acts as a frame for the reaction tube body 1 having poor heat resistance, deformation of the reaction tube body 1 can be prevented. As a result, the work of loading and unloading silicon wafers placed into the reaction tube main body 1 can be carried out smoothly for a long period of time. In addition, by surrounding the carbon tube 3 and attaching a quartz glass protection tube 4 to the outer periphery of the reaction tube body 1, impurities such as sodium and calcium in the electric furnace can adhere to the heating zone on the outer circumferential surface of the reaction tube body 1. As a result, devitrification and cracking of the quartz glass reaction tube main body 1 can be prevented, and a longer life can be achieved. Furthermore, by reducing the pressure inside the quartz glass protection tube 4 surrounding the carbon tube 3, oxidation of the carbon tube 3 can be prevented, and the gas in the space formed by the protection tube 3 and the reaction tube body 1 can be thermally expanded. and the pressure increases,
It can prevent it from bursting. Moreover, carbon tube 3
If a gap is formed between both ends of the carbon and the inner wall surface of the quartz glass protection tube 4 that surrounds it, and a buffer section 5 of quartz glass wool is provided in this gap, the thermal tension between the carbon and the quartz glass will be reduced. Mutual stress generation can be absorbed, and damage to the quartz glass protection tube 4 can be prevented. Furthermore, if the carbon tube 3 is used as a heat-resistant ceramic tube surrounded by the quartz glass protective tube 4, carbon has a thermal conductivity of 0.003 Cal/
Much larger than cm・sec・℃, 0.22 to 0.38 Cal/
Since it is approximately cm·sec·°C, it serves to disperse the heat from the heating element in the axial direction of the reaction tube body 1, and the soaking length can be increased. As a result, semiconductor materials such as silicon wafers within the reaction tube body 1 can be heated uniformly. Next, an experimental example will be shown to prove the effectiveness of the heat treatment reaction tube of the present invention. The inner diameter of the quartz glass reaction tube body 1 is 160 mm.
φ, total length is 2300 mm, and the dimensions of carbon tube 3 placed in this outer area are inner diameter 168 mm, outer diameter 178 mm, and total length.
1500 mm, and the dimensions of the quartz glass protective tube 4 were 182 mm in outer diameter and 1520 mm in total length to constitute a reaction tube for heat treatment (weight 490 g). A silicon wafer was placed inside this reaction tube body 1 and heated at a temperature of 1240°C for 40 minutes. Heat treated for hours. After carrying out such heat treatment 11 times, the degree of bending, proportion of fringing, soaking length, and state of devitrification were investigated, and the results were as shown in the table below. The bending measurement is determined from the degree at the maximum position of the curved part, the curvature rate is determined from the difference between the short axis and long axis in a cross section of the pipe cut perpendicular to the axis, and the soaking length is 1240±
It was determined as the length of the area within a range of 0.1℃.
Furthermore, the comparative examples in the table are examples of conventional reaction tubes consisting of a single tube made of quartz glass.
【表】
なお、本発明に係る熱処理用反応管は上記実施
例の如く耐熱性セラミツク管としてカーボン管を
用いる形態に限定されず、高純度のアルミナ管、
炭化珪素管、金属シリコン管、窒化珪素管等で形
成してもよい。
本発明に係る熱処理用反応管は上記実施例の如
く半導体材料の熱処理に利用する場合に限らず、
他の材料の熱処理にも同様に適用できる。
以上詳述した如く、本発明によれば石英ガラス
製反応管本体の超高純度性を保持しつつ、その短
所である熱変形、外域不純物による劣化を防止
し、更に均熱性を向上した高寿命、高性能の熱処
理用反応管を提供できるものである。[Table] Note that the reaction tube for heat treatment according to the present invention is not limited to the form in which a carbon tube is used as a heat-resistant ceramic tube as in the above embodiment, but also a high-purity alumina tube,
It may also be formed of a silicon carbide tube, a metal silicon tube, a silicon nitride tube, or the like. The heat treatment reaction tube according to the present invention is not limited to being used for heat treatment of semiconductor materials as in the above embodiments.
It can be similarly applied to heat treatment of other materials. As detailed above, according to the present invention, while maintaining the ultra-high purity of the quartz glass reaction tube main body, it can prevent its disadvantages such as thermal deformation and deterioration due to external impurities, and has a long life with improved thermal uniformity. , it is possible to provide a high-performance reaction tube for heat treatment.
【図面の簡単な説明】[Brief explanation of drawings]
図は本発明の一実施例を示す熱処理用反応管の
断面図である。
１……石英ガラス製反応管本体、３……カーボ
ン管（耐熱性セラミツク管）、４……石英ガラス
保護管、５……石英ガラスウールの緩衝部。
The figure is a sectional view of a heat treatment reaction tube showing an embodiment of the present invention. 1... Reaction tube body made of quartz glass, 3... Carbon tube (heat-resistant ceramic tube), 4... Quartz glass protection tube, 5... Buffer section made of quartz glass wool.