JP2595935B2 - Surface cleaning method - Google Patents
Surface cleaning methodInfo
- Publication number
- JP2595935B2 JP2595935B2 JP28035285A JP28035285A JP2595935B2 JP 2595935 B2 JP2595935 B2 JP 2595935B2 JP 28035285 A JP28035285 A JP 28035285A JP 28035285 A JP28035285 A JP 28035285A JP 2595935 B2 JP2595935 B2 JP 2595935B2
- Authority
- JP
- Japan
- Prior art keywords
- silicon
- silicon oxide
- cleaning
- oxide film
- substrate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Landscapes
- Drying Of Semiconductors (AREA)
- Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
- Cleaning Or Drying Semiconductors (AREA)
Description
【発明の詳細な説明】 〔産業上の利用分野〕 本発明はシリコン表面の清浄化方法に関する。Description: TECHNICAL FIELD The present invention relates to a method for cleaning a silicon surface.
近年高速バイポーラ素子、マイクロ波用素子あるいは
超格子構造素子などへの応用を目的としてこれまでのシ
リコン薄膜成長技術に比べ、より低温で成長が行なわ
れ、従って不純物分布を乱すことがほとんどないという
特徴を有する高真空内でのシリコン分子線成長（SiMB
E）技術が盛んに研究開発されている。In recent years, compared with conventional silicon thin film growth technology, it has been grown at lower temperatures for application to high-speed bipolar devices, microwave devices or superlattice structure devices, etc., so that the impurity distribution is hardly disturbed. Molecular beam growth (SiMB) in high vacuum with
E) Technology is actively researched and developed.
この様なシリコン分子線成長技術において、単結晶シ
リコン基板表面の清浄度によってその上に成長するシリ
コン膜の結晶性が大きく左右される。従って基板表面の
清浄化方法については、これまでにも数々の方法が検討
されてきた。たとえば、日本電子工業進行協会による
「シリコン新デバイスに関する調査研究報告書１（昭和
57年３月）」52ページから66ページに「Siの分子線成長
技術」と題して発表された報告においては表面清浄化の
ための第１の方法として高真空中で高温加熱する方法、
第２の方法としてイオンビームで基板表面をスパッタす
る方法、第３の方法としてガリウムビームを照射する方
法、さらに第４の方法としてレーザ照射を行なう方法が
示されている。In such a silicon molecular beam growth technique, the crystallinity of a silicon film grown thereon is greatly affected by the cleanliness of the surface of the single crystal silicon substrate. Accordingly, a number of methods for cleaning the substrate surface have been studied. For example, the Japan Electronic Industry Progress Association, "Survey and Research Report 1 on New Silicon Devices (Showa
(March, 1957) ”from page 52 to page 66, entitled“ Si Molecular Beam Growth Technology ”, the first method for surface cleaning is to heat at high temperature in a high vacuum.
A method for sputtering a substrate surface with an ion beam as a second method, a method for irradiating a gallium beam as a third method, and a method for performing laser irradiation as a fourth method are described.
また、最近では見方、井上、高須により、第30回応用
物理学関係連合講演会講演予稿集（昭和58年４月）502
ページに「超高真空中ウエハー清浄化（２）」と題して
発表された講演において、基板洗浄時に表面に形成され
た薄い酸化シリコン膜上にさらにシリコンを極薄く堆積
し、710℃という低温で極薄シリコン膜が薄い酸化膜と
反応し、両方が共に蒸発し清浄な表面が得られるという
方法が第５の方法として示された。また、相崎、辰巳、
津屋により第45回応用物理学会学術講演会講演予稿集
（昭和59年10月）651ページに「SiMBEの欠陥密度低減−
オゾン処理と成長速度依存性」と題して発表された講演
において新たな第６の方法として、洗浄の途中で洗浄溶
液中にオゾンを含むガスを導入し、表面の保護酸化膜と
シリコン基板界面の汚染を減少させるという方法が示さ
れた。Recently, the viewpoints, Inoue, and Takasu, Proceedings of the 30th Joint Lecture Meeting on Applied Physics (April 1983) 502
In a lecture entitled "Wafer Purification in Ultra-High Vacuum (2)", a very thin layer of silicon was deposited on a thin silicon oxide film formed on the surface during substrate cleaning, and the temperature was reduced to 710 ° C. A fifth method is described in which an ultra-thin silicon film reacts with a thin oxide film, and both evaporate together to obtain a clean surface. Also, Aizaki, Tatsumi,
Tsuya's 45th Annual Meeting of the Japan Society of Applied Physics (Oct. 1984), page 651, "Reduction of defect density in SiMBE-
In a lecture entitled "Ozone treatment and growth rate dependence", a new method was introduced in which a gas containing ozone was introduced into the cleaning solution during cleaning, and the interface between the protective oxide film on the surface and the silicon substrate interface was removed. Methods have been shown to reduce contamination.
以上述べた第１、第３、第４、第５、第６の方法で
は、いずれもシリコン基板をあらかじめ洗浄溶液中で洗
浄しているので、この洗浄段階での清浄化程度が最終的
なウエハー清浄化程度に影響を与える。第６の方法で
は、オゾンの効果によりかなりの汚染が除去でき（10
0）面ではシリコン分子線成長によるシリコンエピタキ
シャル膜中の欠陥をなくすことができるが、（111）面
では、いまだに102cm-2程度の欠陥がのこる。また、第
２の方法では超高真空内で表面をエッチングでき汚染除
去には有効であるがスパッタによって表面に大きなダメ
ージを与えこれを回復させるために高温熱処理を必要と
する、という欠点があった。In the first, third, fourth, fifth, and sixth methods described above, since the silicon substrate is previously cleaned in the cleaning solution, the degree of cleaning in this cleaning step is the final wafer. Affects the degree of cleaning. In the sixth method, considerable pollution can be removed by the effect of ozone (10
On the (0) plane, defects in the silicon epitaxial film due to silicon molecular beam growth can be eliminated, but on the (111) plane, defects of about 10 2 cm −2 still exist. In the second method, the surface can be etched in an ultra-high vacuum, which is effective in removing contamination. However, there is a disadvantage that high-temperature heat treatment is required to recover the surface by damaging the surface by sputtering. .
本発明の目的は、この様な従来の欠点を除去せしめ
て、シリコン分子線により十分良好な結晶性を有するエ
ピタキシャル成長膜を得ることができるような、あるい
はこれに限らず一般の集積回路の製造工程等においても
適用できる表面清浄化方法を提供することにある。An object of the present invention is to eliminate such conventional drawbacks and to obtain an epitaxially grown film having sufficiently good crystallinity by a silicon molecular beam, or to a general integrated circuit manufacturing process. It is another object of the present invention to provide a method for cleaning a surface which can be applied to a method such as the above.
本発明は、少なくとも表面にシリコンを有する基板の
表面清浄化処理方法において、真空内で該シリコン表面
を露出させ、酸素分子線及び紫外光を照射してシリコン
の表面を酸化シリコン層とし、その後加熱して該酸化シ
リコン層を蒸発させることを特徴とする表面清浄化方法
である。The present invention provides a method for cleaning a surface of a substrate having silicon on at least the surface, exposing the silicon surface in a vacuum, irradiating an oxygen molecular beam and ultraviolet light to turn the silicon surface into a silicon oxide layer, and then heating the silicon surface. And evaporating the silicon oxide layer.
次に本発明の実施例について図面を参照して説明す
る。通常のシリコンウエハーは第１図（ａ）に示す様に
シリコン基板10の表面には厚さ10数Åの自然酸化シリコ
ン膜20が形成され、この酸化シリコン膜20の表面に炭素
等の汚染不純物30が存在し、また酸化シリコン膜20とシ
リコン基板10との界面にも炭素等の汚染不純物31が存在
している。Next, embodiments of the present invention will be described with reference to the drawings. In a normal silicon wafer, as shown in FIG. 1A, a natural silicon oxide film 20 having a thickness of more than 10 mm is formed on the surface of a silicon substrate 10, and contaminant impurities such as carbon are formed on the surface of the silicon oxide film 20. There is also a contaminant impurity 31 such as carbon at the interface between the silicon oxide film 20 and the silicon substrate 10.
次に28％アンモニア水と30％過酸化水素水と水とを1:
4:20の比率で混合し、沸騰した溶液中でシリコンウエハ
ーを５分ないし10分間洗浄するとアンモニア水のエッチ
ング作用と過酸化水素水の酸化シリコン膜形成作用とが
繰り返し作用することにより、第１図（ｂ）に示す様に
酸化シリコン膜20は除去され、新たに表面に炭素等の汚
染不純物がごくわずかしか存在しない良質の酸化シリコ
ン膜21が厚さ10Å程度形成される。このとき酸化シリコ
ン膜20とシリコン基板10との界面に存在した炭素等の汚
染不純物31は、大部分除去されるが一部は残存しまた新
たに付着することによって洗浄前に比べると少なくはな
るがあいかわらず存在する。さらに、空気中にさらされ
ることにより表面には汚染物32として炭素が付着する。Next, 28% ammonia water, 30% hydrogen peroxide water and water are used as 1:
When mixed at a ratio of 4:20 and the silicon wafer is washed in a boiling solution for 5 to 10 minutes, the etching action of the ammonia water and the action of forming the silicon oxide film in the hydrogen peroxide solution are repeatedly performed. As shown in FIG. 1B, the silicon oxide film 20 is removed, and a new high-quality silicon oxide film 21 having a very small amount of contaminant impurities such as carbon is formed at a thickness of about 10 mm. At this time, the contaminant impurities 31 such as carbon present at the interface between the silicon oxide film 20 and the silicon substrate 10 are mostly removed, but partly remains and newly adhered, so that they are less than before cleaning. There exists without a return. Furthermore, carbon is attached to the surface as a contaminant 32 by being exposed to the air.
次に、10-10Torr程度の良好な真空度の真空容器中に
て、短時間、例えば１分ないし２分、600℃ないし850℃
に加熱すると、第１図（ｃ）に示す様に前記酸化シリコ
ン膜21の表面から炭素（汚染物32）が脱離する。さら
に、850℃以上に加熱すると、第１図（ｄ）に示す様に
酸化シリコン膜21が蒸発する。しかし、界面に存在した
炭素汚染物31は脱離せず表面に残存する。この状態で、
基板温度を成長温度である400℃ないし800℃に下げ、分
子線成長を行なうと表面に残存する炭素汚染物31を核と
して結晶欠陥が発生する。この炭素汚染物31を除去する
ためには、基板温度を1200℃以上に上げて表面でシリコ
ンのサーマルエッチングを起こし、表面を削らなければ
ならない。しかし、このような高温に上げると基板のド
ーピングプロファイルを変えてしまい分子線成長の大き
な長所である低温成長という特徴が失われる。Next, in a vacuum vessel having a good degree of vacuum of about 10 −10 Torr, for a short time, for example, 1 minute to 2 minutes, 600 ° C. to 850 ° C.
Then, carbon (contaminant 32) is desorbed from the surface of the silicon oxide film 21 as shown in FIG. 1 (c). Further, when heated to 850 ° C. or higher, the silicon oxide film 21 evaporates as shown in FIG. However, the carbon contaminants 31 existing at the interface do not desorb and remain on the surface. In this state,
When the substrate temperature is lowered to a growth temperature of 400 ° C. to 800 ° C. and molecular beam growth is performed, crystal defects are generated with carbon contaminants 31 remaining on the surface as nuclei. In order to remove the carbon contaminants 31, the substrate temperature must be raised to 1200 ° C. or more to cause thermal etching of silicon on the surface, thereby shaving the surface. However, when the temperature is raised to such a high temperature, the doping profile of the substrate is changed, and the characteristic of low temperature growth, which is a great advantage of molecular beam growth, is lost.
そこで、表面の保護酸化シリコン膜21を除去した後、
基板温度を500℃以上に保ち表面に酸素分子線を照射し
ながら低圧水銀ランプより2537Åと1849Åの２波長の紫
外光をあてると、第１図（ｅ）に示す様に表面層は酸化
シリコン層40となる。このとき次に示すような反応が進
み表面が酸化される。Therefore, after removing the protective silicon oxide film 21 on the surface,
When the substrate temperature is kept at 500 ° C or higher and the surface is irradiated with molecular oxygen beams and ultraviolet light of two wavelengths of 2537 ° and 1849 ° is irradiated from a low-pressure mercury lamp, the surface layer becomes a silicon oxide layer as shown in FIG. 1 (e). It will be 40. At this time, the following reaction proceeds and the surface is oxidized.
O2＋ｈν１→Ｏ＋Ｏ Ｏ＋O2→O3 O3＋ｈν２→Ｏ＊＋O2 Si＋2O＊→SiO2 （λ１＝1849Å，λ２＝2537Å） この酸化シリコン層40は、基板温度を850℃以上にす
ると蒸発し、結果として基板表面層がエッチングされた
ことになる。このとき表面上に残存する炭素等の汚染物
も表面から脱離し、きわめて清浄な表面が得られる。O 2 + hν 1 → O + O O + O 2 → O 3 O 3 + hν 2 → O * + O 2 Si + 2O * → SiO 2 (λ 1 = 1849 °, λ 2 = 2537 °) The silicon oxide layer 40 has a substrate temperature of 850 ° C. or higher. Then, it evaporates, and as a result, the substrate surface layer is etched. At this time, contaminants such as carbon remaining on the surface are also detached from the surface, and an extremely clean surface is obtained.
次に、この表面清浄化法を実際にシリコン分子線成長
に用いた例についてさらに具体的に説明する。面方位が
（111）で比抵抗が10〜20Ω・cmであるＰ型シリコン基
板を、28％アンモニア水と30％過酸化水素水と水とを1:
4:20の比率で混合し、これを沸騰させた溶液中で10分間
洗浄し、次いで10-10Torrの超高真空内で前記第５の方
法であるシリコン予備堆積法を用いて清浄化温度780℃
で表面の酸化膜をとった後、基板温度を成長温度である
650℃に下げ、成長室に装着されている石英製のノズル
より酸素分子線を10分間照射する。酸素分圧は1x10-8To
rrに保つ。このとき同時に、合成石英のビューイングポ
ートを通して350Wの低圧水銀ランプより2537Åと1849Å
の２波長の紫外光を基板に照射する。このような操作を
行なうことによって表面上に30Åの酸化シリコン膜が形
成される。ここで、再び前記第５の方法であるシリコン
予備堆積法を用いて清浄化温度780℃で表面の酸化シリ
コン膜を除去する。このときの効果を、その後のシリコ
ン分子線成長膜の結晶欠陥密度により評価した結果を第
１表に示す。すなわち、第１表は1.0μｍ厚のシリコン
分子線成長後の試料を通常用いられているジルトルエッ
チングにより結晶欠陥密度を求めた結果である。Next, an example in which this surface cleaning method is actually used for silicon molecular beam growth will be described more specifically. A P-type silicon substrate having a plane orientation of (111) and a specific resistance of 10 to 20 Ω · cm is prepared by mixing 28% ammonia water, 30% hydrogen peroxide water and water with 1:
Mix at a ratio of 4:20, wash it in the boiling solution for 10 minutes, and then use the fifth method, silicon pre-deposition, in an ultra-high vacuum of 10 −10 Torr to achieve a cleaning temperature. 780 ℃
After removing the oxide film on the surface, the substrate temperature is the growth temperature
The temperature is lowered to 650 ° C, and a molecular oxygen beam is irradiated from a quartz nozzle mounted in the growth chamber for 10 minutes. Oxygen partial pressure is 1x10 -8 To
Keep at rr. At the same time, 2537W and 1849Å from a 350 W low-pressure mercury lamp through a synthetic quartz viewing port
The substrate is irradiated with two wavelengths of ultraviolet light. By performing such an operation, a silicon oxide film of 30 ° is formed on the surface. Here, the silicon oxide film on the surface is removed again at a cleaning temperature of 780 ° C. by using the silicon pre-deposition method which is the fifth method. Table 1 shows the results of evaluating the effect at this time based on the crystal defect density of the silicon molecular beam growth film. That is, Table 1 shows the results of determining the crystal defect density of a sample after growing a silicon molecular beam having a thickness of 1.0 μm by the commonly used zirtol etching.
第１表の結晶欠陥密度の値より、本発明の方法と従来
の方法とを比較して本発明の方法がすぐれていることが
わかる。 The values of the crystal defect density in Table 1 show that the method of the present invention is superior to the conventional method by comparing the method of the present invention with the conventional method.
なお、本実施例ではシリコンウエハーを対象とした
が、本発明の方法は表面にのみシリコンが存在するSOS
（Silicon on Sapphire）基板や更に一般にSOI（Silico
n on Insulator）基板等にも当然適用できる。In this example, a silicon wafer was used, but the method of the present invention is applied to an SOS in which silicon exists only on the surface.
(Silicon on Sapphire) substrates and more generally SOI (Silico on Sapphire)
n on Insulator) Of course, it can also be applied to substrates and the like.
また、以上の説明では本発明をシリコン分子線成長技
術における清浄化法に適用した場合を例にとって説明し
たが、これに限られるものではなく集積回路製造等のウ
エハー処理工程に広く一般的に適用できる。In the above description, the case where the present invention is applied to a cleaning method in a silicon molecular beam growth technique is described as an example. However, the present invention is not limited to this, and is widely applied to wafer processing steps such as integrated circuit manufacturing. it can.
以上、詳細に述べた通り、本発明はシリコン表面に酸
素分子線と紫外光を照射し、表面層を酸化シリコン層と
し、しかる後この酸化シリコン層を蒸発させることによ
ってシリコン表面をエッチングするものであり、シリコ
ン分子線成長法によりエピタキシャル膜を形成すると結
晶欠陥の極めて少ない良質の膜を得ることができ、さら
に分子線成長法に限らず一般の集積回路の製造工程にも
適用できる効果を有するものである。As described above in detail, the present invention irradiates a silicon surface with an oxygen molecular beam and ultraviolet light to form a silicon oxide layer on the surface layer, and then etches the silicon surface by evaporating the silicon oxide layer. Yes, when an epitaxial film is formed by the silicon molecular beam growth method, a high-quality film with very few crystal defects can be obtained, and further, the effect is applicable not only to the molecular beam growth method but also to a general integrated circuit manufacturing process. It is.
第１図（ａ），（ｂ），（ｃ），（ｄ），（ｅ）は本発
明の一実施例を工程順に示すシリコンウエハーの模式断
面図である。 図において、10……シリコン基板、20……酸化シリコン
膜、21……洗浄後の酸化シリコン膜、30,32……酸化シ
リコン表面の炭素等の汚染不純物、31……酸化シリコン
膜とシリコン基板との界面に存在する炭素等の汚染不純
物、40……酸素分子線と紫外光を照射することによって
形成された酸化シリコン膜。1 (a), 1 (b), 1 (c), 1 (d) and 1 (e) are schematic sectional views of a silicon wafer showing an embodiment of the present invention in the order of steps. In the figure, 10: silicon substrate, 20: silicon oxide film, 21: silicon oxide film after cleaning, 30, 32 ... contaminant impurities such as carbon on the silicon oxide surface, 31 ... silicon oxide film and silicon substrate 40, a silicon oxide film formed by irradiating an oxygen molecular beam and ultraviolet light.
Claims (1)
表面清浄化方法において、真空内で該シリコン表面を露
出させ、酸素分子線及び紫外光を照射してシリコンの表
面を酸化シリコン層とし、その後加熱して該酸化シリコ
ン層を蒸発させることを特徴とする表面清浄化方法。In a method for cleaning a surface of a substrate having silicon on at least the surface, the silicon surface is exposed in a vacuum and irradiated with an oxygen molecular beam and ultraviolet light to turn the silicon surface into a silicon oxide layer. And evaporating the silicon oxide layer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28035285A JP2595935B2 (en) | 1985-12-13 | 1985-12-13 | Surface cleaning method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28035285A JP2595935B2 (en) | 1985-12-13 | 1985-12-13 | Surface cleaning method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS62139335A JPS62139335A (en) | 1987-06-23 |
| JP2595935B2 true JP2595935B2 (en) | 1997-04-02 |
Family
ID=17623804
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP28035285A Expired - Fee Related JP2595935B2 (en) | 1985-12-13 | 1985-12-13 | Surface cleaning method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2595935B2 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS649621A (en) * | 1987-07-01 | 1989-01-12 | Fujitsu Ltd | Surface treatment of semiconductor substrate |
| JPH04107922A (en) * | 1990-08-29 | 1992-04-09 | Fujitsu Ltd | Semiconductor cleaning liquid and cleaning method therewith |
| US5282925A (en) * | 1992-11-09 | 1994-02-01 | International Business Machines Corporation | Device and method for accurate etching and removal of thin film |
| JP2836576B2 (en) * | 1996-05-15 | 1998-12-14 | 日本電気株式会社 | Method for manufacturing semiconductor device |
-
1985
- 1985-12-13 JP JP28035285A patent/JP2595935B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62139335A (en) | 1987-06-23 |
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