JPS5949688B2 - Anodization method - Google Patents
Anodization methodInfo
- Publication number
- JPS5949688B2 JPS5949688B2 JP15818776A JP15818776A JPS5949688B2 JP S5949688 B2 JPS5949688 B2 JP S5949688B2 JP 15818776 A JP15818776 A JP 15818776A JP 15818776 A JP15818776 A JP 15818776A JP S5949688 B2 JPS5949688 B2 JP S5949688B2
- Authority
- JP
- Japan
- Prior art keywords
- oxide film
- thickness
- epitaxial layer
- uniform
- anodic oxidation
- 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
Links
- 238000000034 method Methods 0.000 title claims description 30
- 238000002048 anodisation reaction Methods 0.000 title description 3
- 230000003647 oxidation Effects 0.000 claims description 16
- 238000007254 oxidation reaction Methods 0.000 claims description 16
- 238000007743 anodising Methods 0.000 claims description 12
- 239000004065 semiconductor Substances 0.000 claims description 12
- 239000000758 substrate Substances 0.000 claims description 11
- 239000010407 anodic oxide Substances 0.000 claims description 4
- 239000010410 layer Substances 0.000 description 38
- 238000009826 distribution Methods 0.000 description 8
- 239000013078 crystal Substances 0.000 description 7
- 230000005684 electric field Effects 0.000 description 5
- 230000007547 defect Effects 0.000 description 4
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 3
- 230000001681 protective effect Effects 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000012808 vapor phase Substances 0.000 description 2
- FEWJPZIEWOKRBE-JCYAYHJZSA-N Dextrotartaric acid Chemical compound OC(=O)[C@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-JCYAYHJZSA-N 0.000 description 1
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 description 1
- XSTXAVWGXDQKEL-UHFFFAOYSA-N Trichloroethylene Chemical group ClC=C(Cl)Cl XSTXAVWGXDQKEL-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
- 235000002906 tartaric acid Nutrition 0.000 description 1
- 239000011975 tartaric acid Substances 0.000 description 1
- 238000004506 ultrasonic cleaning Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Weting (AREA)
- Formation Of Insulating Films (AREA)
- Junction Field-Effect Transistors (AREA)
Description
【発明の詳細な説明】
本発明は、陽極処理方法、更に詳しくは、主として半導
体ウェーハ、特に半絶縁性基板上に形成されてなるエピ
タキシャル層の厚さを均一制御す３る場合に適用される
陽極酸化方法を用いた陽極処理方法に関するものである
。DETAILED DESCRIPTION OF THE INVENTION The present invention is applied to an anodizing method, and more specifically, to uniform control of the thickness of an epitaxial layer formed on a semiconductor wafer, especially a semi-insulating substrate. The present invention relates to an anodizing method using an anodizing method.
一般、半絶縁性ＣａＡｓ結晶基板上にエピタキシャル成
長せしめたｎ層上に形成するショットキー障壁型ＦＥＴ
の如き半導体素子の製造工程にお３いて、半導体基板上
に結晶成長せしめたエピタキシャル層の厚さを均一制御
する場合に陽極酸化法が適用される。Generally, a Schottky barrier FET is formed on an n-layer epitaxially grown on a semi-insulating CaAs crystal substrate.
In the manufacturing process of semiconductor devices, anodization is applied to uniformly control the thickness of an epitaxial layer grown on a semiconductor substrate.
ここで、陽極酸化法は、電解液の正電極に酸化しようと
する試料を接続し、負電極として白金等を用いて電解す
ることにより、前記試料に酸化膜を成長させる方法であ
る。例えば、半絶縁性ＣａＡｓ結晶基板上に気相法で形
成されるｎ型エピタキシャル層の厚さはＣａＡｓウェー
ハ内でぱらつきが大きいために、該ｎ型エピタキシャル
層上に形成されるショットキーバリヤー型ＦＥＴのピン
チオフ電圧のばらつきが大きくなム該ピンチオフ電圧を
一定にするためには前記エピタキシャル層の厚さを均一
にする必要がある。従来、半絶縁性基板に形成された不
均一な厚さのエピタキシャル層を均→ヒする陽極酸化法
として次のような工程が施行されてきた。即ち、先ず暗
状態において１回の陽極酸化によりエピタキシ・ヤル層
上に形成された不均一な厚さを有する酸化膜を除去して
、前記エピタキシャル層を均一な厚さにする。上記工程
において、除去すべきエピタキシャル層が厚い場合には
、１回の陽極酸化法で前記エピタキシャル層を均Ｈヒし
ようとすると前記エピタキシャル層の厚い部分の表面が
荒れてくるという欠点があつた。例えば、半絶縁性基板
上に気相法でエピタキシャル成長せしめたＣａＡｓウェ
ーハの場合に於て、エピタキシャル層上に約２２００λ
以上の厚さの酸化膜が形成されると該エピタキシャル層
の表面が荒れる。また、第１図の如く、暗状態における
陽極酸化工程と酸化膜除去工程を繰り返しエピタキシャ
ル層２を均一な厚さに調節する場合には、１回目の陽極
酸化工程と酸化膜除去工程によりエピタキシャル層３の
部分を除去したときに、前記エピタキシャル層２の一部
の領域２ａが既に均一な厚さになつている場合がある。Here, the anodic oxidation method is a method in which a sample to be oxidized is connected to a positive electrode of an electrolytic solution, and an oxide film is grown on the sample by electrolyzing the sample using platinum or the like as a negative electrode. For example, since the thickness of an n-type epitaxial layer formed by a vapor phase method on a semi-insulating CaAs crystal substrate varies greatly within the CaAs wafer, Schottky barrier type FETs formed on the n-type epitaxial layer In order to keep the pinch-off voltage constant, it is necessary to make the thickness of the epitaxial layer uniform. Conventionally, the following process has been carried out as an anodic oxidation method for leveling an epitaxial layer of non-uniform thickness formed on a semi-insulating substrate. That is, first, an oxide film having a non-uniform thickness formed on the epitaxial layer is removed by one-time anodic oxidation in a dark state, so that the epitaxial layer has a uniform thickness. In the above process, when the epitaxial layer to be removed is thick, there is a drawback that the surface of the thick portion of the epitaxial layer becomes rough when attempting to homogenize the epitaxial layer with a single anodic oxidation process. For example, in the case of a CaAs wafer epitaxially grown on a semi-insulating substrate by the vapor phase method, approximately 2200λ
If an oxide film with a thickness greater than that is formed, the surface of the epitaxial layer becomes rough. In addition, as shown in FIG. 1, when the epitaxial layer 2 is adjusted to have a uniform thickness by repeating the anodic oxidation process and the oxide film removal process in a dark state, the epitaxial layer 2 is When the portion 3 is removed, some regions 2a of the epitaxial layer 2 may already have a uniform thickness.
このような時に、２回目の陽極酸化工程を施行して、残
存エピタキシャル層２の厚い部分を除去する際に推、前
記エピタキシャル層２の一部の領域２ａに高電界がかか
り、該領域２ａ上に結晶欠陥４力膚出し、該領域４上に
はＦＥＴ等のデバイスを作ることができなくなるるとい
う欠点があつた。本発明の目的は、前記従来の欠点を除
去した新規な陽極処理方法を提供することにある。In such a case, when performing the second anodic oxidation step to remove a thick portion of the remaining epitaxial layer 2, a high electric field is applied to a part of the region 2a of the epitaxial layer 2, causing a high electric field to be applied on the region 2a. There was a drawback that crystal defects were exposed in the region 4, making it impossible to fabricate devices such as FETs on the region 4. SUMMARY OF THE INVENTION An object of the present invention is to provide a new anodizing method that eliminates the drawbacks of the conventional methods.
本発明によれば、半絶縁性又は絶縁性半導体基板上に成
長し、かつ不均一な厚さ分布を有し、しかも雪崩れブレ
イクダウン時における空乏層幅に比較して厚く形成され
たエピタキシヤル層を有する半導体ウエーハの前記エピ
タキシヤル層の厚さを薄くかつ均一に制御する陽極処理
方法において、暗状態で前記エピタキシヤル層上に形成
される薄い酸化膜の光干渉色分布を観察し、その結果、
（１）、前記半導体ウエーハ上における光干渉色分布が
少なくとも一部の領域において不均一化している場合に
前記酸化膜を除去し、光照射状態で前記エピタキシヤル
層上に極めて薄い酸化膜を形成し、その後暗状態で前記
エピタキシヤル層の厚さが均一になるまで陽極酸化を続
行することを特徴とする陽極処理方法、又は（２）、前
記半導体ウエーハ上における光干渉色分布が均一な場合
に、前記酸化膜を除去し、前記半導体ウエーハ上におけ
る光干渉色分布が不均一になるまで暗状態における陽極
酸化膜形成工程と酸化膜除去工程を繰り返し、前記干渉
色分布が不均一になつた後で前記（１）の方法を施行す
ることを特徴とする陽極処理方法、が与えられる。According to the present invention, an epitaxial layer is grown on a semi-insulating or insulating semiconductor substrate, has a non-uniform thickness distribution, and is thicker than the depletion layer width at the time of avalanche breakdown. In an anodizing method for controlling the thickness of the epitaxial layer of a semiconductor wafer having a thin and uniform layer, the light interference color distribution of a thin oxide film formed on the epitaxial layer is observed in a dark state, and its result,
(1) If the light interference color distribution on the semiconductor wafer is non-uniform in at least some regions, the oxide film is removed and an extremely thin oxide film is formed on the epitaxial layer under light irradiation. and then continuing anodic oxidation in a dark state until the thickness of the epitaxial layer becomes uniform, or (2) when the light interference color distribution on the semiconductor wafer is uniform. Then, the oxide film was removed, and the anodic oxide film forming step and oxide film removal step in a dark state were repeated until the light interference color distribution on the semiconductor wafer became non-uniform, and the interference color distribution became non-uniform. An anodizing method is provided, which is characterized in that the method (1) above is subsequently carried out.
この様な本発明によれば、以下に記述する２つの効果が
実現可能である。According to the present invention, the following two effects can be achieved.
第１に、暗状態での陽極酸化法を用いてエピタキシヤル
層上に形成される酸化膜の光干渉色分布を観察する工程
が導入された。その結果、該光干渉色が前記エピタキシ
ヤルウエーハ上で不均一になるまで酸化膜形成工程と酸
化膜除去工程が繰り返されるので、従来の暗状態におけ
る１回の陽極酸化工程で酸化膜を形成した場合に比較し
てエピタキシヤルウエーハの表面の荒れが少なくなる。
第２に、暗状態で形成された酸化膜の光干渉色分布がエ
ピタキシヤルウエーハ上の一部の領域で不均一になつた
ときに、前記酸化膜を除去した後、光照射状態で前記エ
ピタキシヤル層上に極めて薄い保護用酸化膜を形成する
ことにより、暗状態の陽極酸化工程での結晶欠陥露出を
防止することができる。次に本発明をその良好な一実施
例について図面を参照しながら詳細に説明しよう。First, a step was introduced to observe the light interference color distribution of an oxide film formed on an epitaxial layer using a dark anodic oxidation method. As a result, the oxide film formation process and oxide film removal process are repeated until the light interference color becomes non-uniform on the epitaxial wafer, so that the oxide film is formed in a single anodic oxidation process in the conventional dark state. The surface roughness of the epitaxial wafer is reduced compared to the case where the surface of the epitaxial wafer is roughened.
Second, when the light interference color distribution of the oxide film formed in the dark state becomes non-uniform in some areas on the epitaxial wafer, after removing the oxide film, the epitaxial By forming an extremely thin protective oxide film on the coating layer, it is possible to prevent crystal defects from being exposed during the dark anodic oxidation process. Next, a preferred embodiment of the present invention will be explained in detail with reference to the drawings.
本発明の具体的な一実施例として、半絶縁性のＧａＡｓ
基板１１上にエピタキシヤル成長せしめた２×１０１７
Ｃｆ１Ｌ−３の不純物濃度と約０．４〜０．４６μの厚
さを有するｎ型エピタキシヤル層に陽極酸化法を適用し
て均一な厚さに前記ｎ層１２を制御する場合について図
面を用いて説明する。As a specific embodiment of the present invention, semi-insulating GaAs
2×1017 epitaxially grown on the substrate 11
The drawings are used to explain the case where the n-layer 12 is controlled to have a uniform thickness by applying anodization to an n-type epitaxial layer having an impurity concentration of Cf1L-3 and a thickness of about 0.4 to 0.46μ. I will explain.
先ず、該エピタキシヤルウエーハの前洗浄工程施行（ト
リクレン煮沸及びメチルエチルケトン超音波洗浄を各々
５分間で３回繰り返す）後、第２図に示す如く、水と酒
石酸とエチレングリコールからなる陽極酸化液を用いて
、暗状態における陽極酸化工程を施行し、約１０００λ
の厚さを有する酸化膜１５を形成させる。First, after performing a pre-cleaning process on the epitaxial wafer (repeating boiling with trichlorethylene and ultrasonic cleaning with methyl ethyl ketone three times for 5 minutes each), as shown in Figure 2, an anodizing solution consisting of water, tartaric acid, and ethylene glycol was used. Then, an anodic oxidation process was carried out in the dark, and about 1000λ
An oxide film 15 having a thickness of .
該酸化膜１５に消費される ＣａＡｓの厚さは約７００
λである。このとき、該エピタキシヤルウエーハ表面に
形成された酸化膜１５の干渉色を観察すると該エピタキ
シヤルウエーハ内では一様になつている。なぜなら、前
記酸化膜１５の厚さが均一であるからである。よつて酸
化膜１５を濃塩酸で除去した後に、暗状態で２度目の陽
極酸化工程を施行して第３図に示す如く最大厚約７５０
λ（ＧａＡｓの消費される膜厚約５２０λ）の酸化膜１
６を第３図の如く形成する。酸化膜１６の一部の領域１
６ａでは場所によつて酸化膜厚が変化しているので、酸
化膜厚に応じて光干渉色の変化している様子が観察され
る。即ち、前記領域１６ａ直下のエピタキシヤル膜１２
ａの厚さは雪崩れブレイクダウン時における空乏層幅に
等しくなつている。再び前記酸化膜１６を除去した後に
、光照射状態の陽極酸化法により約２００λの厚さを有
する保護用酸化膜１７を第４図の如く形成する。さらに
第４図の如く暗状態で酸化膜１８（最大厚：８００Ａ）
を形成する。最後に、これらの酸化膜１７及び１８を除
去すれば、第５図の如く、エピタキシヤル層１２の領域
は約０．２７μ、また１２ａの領域は約０．２６μとほ
ぼ均一な厚さに制御することができた。しかも、本発明
を用いることにより、エピタキシヤル層１２の一部の領
域１２ａの表面に結晶欠陥が露出することを防止するこ
とができた。以上、本発明の実施例として、陽極酸化法
と共に特定の材料、特定の不純物濃度と厚さを有する半
導体ウエーハ、特定の陽極酸化液及び特定の酸化膜エツ
チング液を用いて説明したが本発明の技術思想から明ら
かなように上記実施例に限定されることなく、本発明は
半絶緑性又は絶緑性結晶基板上に成長せしめたエピキタ
シヤル層の厚さを制御する場合に応用される陽極酸化法
に全て適用されることはいうまでもない。The thickness of CaAs consumed in the oxide film 15 is approximately 700 mm.
It is λ. At this time, when observing the interference color of the oxide film 15 formed on the surface of the epitaxial wafer, it is found to be uniform within the epitaxial wafer. This is because the thickness of the oxide film 15 is uniform. Therefore, after removing the oxide film 15 with concentrated hydrochloric acid, a second anodic oxidation process was performed in a dark state to obtain a maximum thickness of about 750 mm as shown in FIG.
Oxide film 1 of λ (film thickness consumed by GaAs is approximately 520λ)
6 is formed as shown in FIG. Partial region 1 of oxide film 16
In 6a, since the oxide film thickness changes depending on the location, it is observed that the light interference color changes depending on the oxide film thickness. That is, the epitaxial film 12 directly under the region 16a
The thickness of a is equal to the depletion layer width at the time of avalanche breakdown. After removing the oxide film 16 again, a protective oxide film 17 having a thickness of about 200λ is formed as shown in FIG. 4 by anodic oxidation under light irradiation. Furthermore, as shown in Fig. 4, the oxide film 18 (maximum thickness: 800A) is
form. Finally, by removing these oxide films 17 and 18, the thickness of the epitaxial layer 12 is approximately 0.27μ, and the thickness of the epitaxial layer 12a is approximately 0.26μ, as shown in FIG. We were able to. Moreover, by using the present invention, it was possible to prevent crystal defects from being exposed on the surface of a part of the region 12a of the epitaxial layer 12. The embodiments of the present invention have been described using a specific material, a semiconductor wafer having a specific impurity concentration and thickness, a specific anodic oxidation solution, and a specific oxide film etching solution in conjunction with an anodizing method. As is clear from the technical concept, the present invention is not limited to the above-mentioned embodiments, but the present invention is an anodizing method applied to control the thickness of an epitaxial layer grown on a semi-green or non-green crystal substrate. Needless to say, all laws apply.
即ち本発明は、例えば、リード型ダイオードに使用され
るｎ゛− ｎ ー−ｎ＋＋ の如き３層構造のｎ゛領域
の厚さを薄くかつ均一に制御する場合、或いはローハイ
ロ一型インパツトダイオードに使用されるｎ− −ｎ−
ｎ −ーｎ゛゛ の如き４層構造の端部（頂部）のｎ−
領域の厚さを薄くかつ均一に制御する場合等にも適用す
ることができ、一般に本発明は、厚さを薄くしかも均一
に制御しようとする表面層の電界の強さがその下の層に
かかつている電界のそれよりも十分に高い場合に、拡張
して適用することができる。That is, the present invention is useful, for example, when controlling the thickness of the n region of a three-layer structure such as n-n-n++ used in a leaded diode to be thin and uniform, or in a low-high-low type impact diode. used n- -n-
n- at the end (top) of a four-layer structure such as n--n゛゛
The present invention can also be applied to cases where the thickness of a region is to be controlled thinly and uniformly, and in general, the present invention is applicable when the electric field strength of the surface layer whose thickness is to be controlled thinly and uniformly is applied to the layer below it. It can be extended and applied when the electric field is sufficiently higher than that of the applied electric field.
第１図は従来の処理方法を説明するための半導体ウエー
ハの断面図、第２図乃至第５図は本発明に係る陽極処理
方法の一実施例を説明するための半導体ウエーハの断面
図である。
１，１１・・・・・・基板、２，２ａ，３，１２，１２
ａ・・・・・・エピタキシヤル層、４・・・・・・露出
した結晶欠陥層、１５，１６，１６ ａ，１８ ・・・
・・・暗状態で形成された酸化膜、１ １・・・・・・
光照射状態で形成された保護用酸化膜。FIG. 1 is a cross-sectional view of a semiconductor wafer for explaining a conventional processing method, and FIGS. 2 to 5 are cross-sectional views of a semiconductor wafer for explaining an embodiment of an anodizing method according to the present invention. . 1, 11...Substrate, 2, 2a, 3, 12, 12
a...Epitaxial layer, 4...Exposed crystal defect layer, 15, 16, 16 a, 18...
...Oxide film formed in the dark, 1 1...
A protective oxide film formed under light irradiation.
Claims (1)
工程と、前記エピタキシャル成長層の暗状態での陽極酸
化を少なくとも１回行なうことにより厚さの不均一な陽
極酸化膜を形成する工程と、この平均一化した陽極酸化
膜を除去した後、光照射状態での陽極酸化により前記エ
ピタキシャル成長層の表面に新たな酸化膜を形成する工
程と、前記新たな酸化膜を形成した状態で暗状態での陽
極酸化を行なつて前記エピタキシャル成長層の一部を陽
極酸化膜に変換し、もつて前記エピタキシャル成長層の
厚さをほぼ均一にする工程とを有することを特徴とする
陽極処理方法。1. A step of growing a semiconductor epitaxial growth layer on a substrate, a step of anodizing the epitaxial growth layer in a dark state at least once to form an anodic oxide film with a non-uniform thickness, and After removing the oxidized anodic oxide film, a new oxide film is formed on the surface of the epitaxial growth layer by anodic oxidation under light irradiation, and anodic oxidation in the dark with the new oxide film formed. A method for anodizing, comprising the step of converting a part of the epitaxial growth layer into an anodic oxide film, thereby making the thickness of the epitaxial growth layer substantially uniform.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15818776A JPS5949688B2 (en) | 1976-12-28 | 1976-12-28 | Anodization method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15818776A JPS5949688B2 (en) | 1976-12-28 | 1976-12-28 | Anodization method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5382267A JPS5382267A (en) | 1978-07-20 |
| JPS5949688B2 true JPS5949688B2 (en) | 1984-12-04 |
Family
ID=15666161
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP15818776A Expired JPS5949688B2 (en) | 1976-12-28 | 1976-12-28 | Anodization method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5949688B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59224176A (en) * | 1983-06-03 | 1984-12-17 | Nec Corp | Manufacture of field effect transistor |
-
1976
- 1976-12-28 JP JP15818776A patent/JPS5949688B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5382267A (en) | 1978-07-20 |
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