JPH10242497A - Infrared detector - Google Patents

Infrared detector

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Publication number
JPH10242497A
JPH10242497A JP9047873A JP4787397A JPH10242497A JP H10242497 A JPH10242497 A JP H10242497A JP 9047873 A JP9047873 A JP 9047873A JP 4787397 A JP4787397 A JP 4787397A JP H10242497 A JPH10242497 A JP H10242497A
Authority
JP
Japan
Prior art keywords
infrared detector
protective film
film
mesa
electric charge
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.)
Pending
Application number
JP9047873A
Other languages
Japanese (ja)
Inventor
Akira Ajisawa
昭 味澤
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NEC Corp
Original Assignee
NEC Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by NEC Corp filed Critical NEC Corp
Priority to JP9047873A priority Critical patent/JPH10242497A/en
Publication of JPH10242497A publication Critical patent/JPH10242497A/en
Pending legal-status Critical Current

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Abstract

PROBLEM TO BE SOLVED: To provide an infrared detector which reduces a surface leakage current in a mesa part and whose characteristic is excellent in the infrared detector which uses an HgCdTe crystal and which is of a mesa-type structure. SOLUTION: A p-HgCdTe layer 2 is formed on an n-HgCdTe layer 1, a protective film 3 having a positive fixed electric charge is formed on the surface of a mesa-type structure in which a p-n junction is isolated by an etching operation, and a protective film 4 which does not have a fixed electric charge is formed on the protective film 1 having the positive fixed electric charge. Since the anodic oxide film 3 having the positive fixed electric charge is formed on an etched wall surface and an etched bottom face which are damaged and whose crystallinity is bad, electrons are induced near the boundary between the film and the crystal protective film due to the influence of the positive fixed electric charge, and an inversion region is formed in the region of the p-HgCdTe layer 2. As a result, the p-n junction is moved to the inside from the damaged region, and a surface leakage current can be reduced.

Description

【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION

【0001】[0001]

【発明の属する技術分野】本発明は禁制帯幅の狭い半導
体、特にHgを含む化合物半導体を用いた赤外線検出器
に関するものである。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared detector using a semiconductor having a narrow band gap, particularly a compound semiconductor containing Hg.

【0002】[0002]

【従来の技術】一般に赤外線検出器においては禁制帯幅
の狭い半導体を用いたものが高感度であることが知られ
ている。特に検出部分にpn接合を有する光起電力型素
子(フォトダイオード)は各素子を二次元に配列した構
成をもつ配列型赤外線検出器を比較的容易に形成するこ
とができ、暗視カメラ等の赤外線撮像装置に適用でき有
効である。その代表的なものにHgCdTe結晶を用い
た赤外線検出器がある。この検出器の特性は主に光を吸
収する領域の結晶性と表面近傍でのpn接合状態により
支配されている。光を吸収する領域はn−HgCdTe
の方がp−HgCdTeよりもキャリアのライフタイム
が長く結晶性に優れているため、一般にはp on n
構造の方が特性が良いとされている。また近年HgCd
Te結晶へのドーピング技術が発展してきたため、エピ
タキシャル結晶成長の際にpn接合を形成し、その後メ
サエッチングを行うことによりpn接合分離を行うメサ
形状のHgCdTeフォトダイオードが主流になってき
ている。この方法は従来のイオン注入による方法に比
べ、pn接合界面自体にダメージが入らないという点で
優れている。
2. Description of the Related Art It is generally known that an infrared detector using a semiconductor having a narrow band gap has high sensitivity. In particular, a photovoltaic element (photodiode) having a pn junction in a detection portion can relatively easily form an arrayed infrared detector having a configuration in which each element is two-dimensionally arranged. It can be applied to an infrared imaging device and is effective. A typical example is an infrared detector using a HgCdTe crystal. The characteristics of this detector are mainly governed by the crystallinity of the light absorbing region and the pn junction state near the surface. The light absorbing region is n-HgCdTe
Is longer in p-HgCdTe and has better crystallinity than p-HgCdTe.
It is said that the structure has better characteristics. In recent years, HgCd
Since the doping technology for Te crystal has been developed, a mesa-shaped HgCdTe photodiode in which a pn junction is formed during epitaxial crystal growth and then a pn junction is separated by performing mesa etching has become mainstream. This method is superior to the conventional ion implantation method in that the pn junction interface itself is not damaged.

【0003】この素子の基本的な構造を図3に示す。n
−HgCdTe1上に形成されたp−HgCdTe2を
レジスト等のマスクを用いメサエッチングを行いpn接
合を分離する。その後、全面に固定電荷をもたないZn
S保護膜4を堆積しコンタクトホールを開けp側電極6
を形成することにより素子は完成する(n側電極に関し
てはここでは省略した)。
FIG. 3 shows the basic structure of this device. n
-Mesa etching is performed on p-HgCdTe2 formed on HgCdTe1 using a mask such as a resist to separate a pn junction. After that, Zn having no fixed charge on the entire surface
An S protective film 4 is deposited, a contact hole is opened, and a p-side electrode 6 is formed.
Is completed (the n-side electrode is omitted here).

【0004】メサ型構造のHgCdTeフォトダイオー
ドに関しては、特開昭63−250136号公報に記載
された半導体装置の製造方法がある。これはn on
p構造を用いている点で前述した従来例とは異なるが、
メサ形状の表面保護膜として陽極硫化膜、窒化膜、Zn
S膜等の固定電荷をもたない膜を用いている点で類似し
ている。
[0004] As for the HgCdTe photodiode having a mesa structure, there is a method of manufacturing a semiconductor device described in Japanese Patent Application Laid-Open No. 63-250136. This is non
Although it differs from the conventional example described above in that a p-structure is used,
Anodic sulfide film, nitride film, Zn as mesa-shaped surface protection film
It is similar in that a film having no fixed charge such as an S film is used.

【0005】[0005]

【発明が解決しようとする課題】この赤外線検出器の特
性は、前述したようにn−HgCdTe1の結晶性以外
にも表面の特性、特にpn接合近傍での表面の特性に大
きく支配される。図3に示した従来の構造ではメサを形
成する際にエッチングを行うため、pn接合が表面に露
出している領域ではエッチングによって入ったダメージ
により、表面リーク電力の増大など表面特性を劣化させ
ることが大きな問題となっている。特にこのフォトダイ
オードを二次元に配列し赤外線カメラに適用する場合な
どは、メサ構造の制御性、微細化が要求されるためイオ
ンミリング等のドライエッチングを用いる必要があり、
エッチングによって表面に与えるダメージが表面特性の
劣化に及ぼす影響は特に重大な問題となる。例えばHg
CdTeとの界面準位密度の小さな表面特性の優れた保
護膜を用いたとしても、結晶側にダメージが入っている
ので何ら解決にもならない。
As described above, the characteristics of the infrared detector are largely governed by the surface characteristics, particularly the surface characteristics near the pn junction, in addition to the crystallinity of n-HgCdTe1. In the conventional structure shown in FIG. 3, since etching is performed when a mesa is formed, in a region where a pn junction is exposed on the surface, damage caused by etching may deteriorate surface characteristics such as an increase in surface leakage power. Is a major problem. Especially when the photodiodes are arranged two-dimensionally and applied to an infrared camera, it is necessary to use dry etching such as ion milling because controllability of the mesa structure and miniaturization are required.
The effect of the damage given to the surface by the etching on the deterioration of the surface characteristics is a particularly serious problem. For example, Hg
Even if a protective film having a small interface state density with CdTe and having excellent surface characteristics is used, there is no solution because the crystal side is damaged.

【0006】本発明の目的は、メサエッチングによる表
面ダメージが表面特性に影響を及ぼすことのない、特性
の優れたフォトダイオードよりなる赤外線検出器を提供
することにある。
SUMMARY OF THE INVENTION An object of the present invention is to provide an infrared detector comprising a photodiode having excellent characteristics so that surface damage due to mesa etching does not affect surface characteristics.

【0007】[0007]

【課題を解決するための手段】本発明の赤外線検出器
は、n−HgCdTe層上にp−HgCdTe層が形成
され、エッチングによりpn接合が分離されたメサ型構
造の表面に正の固定電荷をもつ保護膜が形成され、前記
正の固定電荷をもつ保護膜の上に固定電荷をもたない保
護膜が形成されていることを特徴とする赤外線検出器で
あり、また、前記正の固定電荷をもつ保護膜が陽極酸化
膜あるいは光酸化膜であることを特徴とする赤外線検出
器であり、また、前記固定電荷をもたない保護膜がZn
S膜あるいは窒化膜であることを特徴とする赤外線検出
器である。
According to the infrared detector of the present invention, a positive fixed charge is applied to the surface of a mesa structure in which a p-HgCdTe layer is formed on an n-HgCdTe layer and a pn junction is separated by etching. An infrared detector, wherein a protective film having no fixed charge is formed on the protective film having the positive fixed charge. Wherein the protective film having a fixed charge is an anodic oxide film or a photo-oxide film, and the protective film having no fixed charge is Zn.
An infrared detector characterized by being an S film or a nitride film.

【0008】本発明の赤外線検出器の特徴を図2を用い
て説明する。ここでは正の固定電荷をもつ保護膜として
陽極酸化膜が用いられている。n−HgCdTe1上の
p−HgCdTe2をイオンミリング等のドライエッチ
ングによりpn接合を分離する。エッチングの壁面、底
面は結晶にダメージが入っており結晶性は非常に悪く、
このままの状態ではpn接合とダメージ領域の重なる部
分ではpn間での表面リーク電流が非常に大きい。これ
に正の固定電荷をもつ陽極酸化膜を形成する。正の固定
電荷の影響で結晶の保護膜との界面近傍には電子が誘起
され、p−HgCdTe2の領域では反転領域5が形成
される。その結果、pn接合はダメージ領域より内部に
移動し前述した表面リーク電流を低減することができ
る。
The features of the infrared detector according to the present invention will be described with reference to FIG. Here, an anodic oxide film is used as a protective film having a positive fixed charge. A pn junction is separated from p-HgCdTe2 on n-HgCdTe1 by dry etching such as ion milling. The walls and bottom of the etching are damaged and the crystallinity is very poor.
In this state, the surface leakage current between the pns is very large in the portion where the pn junction and the damaged region overlap. An anodic oxide film having a positive fixed charge is formed thereon. Electrons are induced in the vicinity of the interface between the crystal and the protective film due to the influence of the positive fixed charge, and an inversion region 5 is formed in the region of p-HgCdTe2. As a result, the pn junction moves from the damaged region to the inside, and the above-described surface leakage current can be reduced.

【0009】[0009]

【発明の実施の形態】本発明の赤外線検出器の動作およ
び特性を製造方法と共に図1、図2を用いて具体的に説
明する。GaAs基板上にCdTeバッファ層を介して
(図1では省略した)n−HgCdTe1、p−HgC
dTe2のMBE法により順次エピタキシャル成長させ
る。このとき各層の極性は成長の際の不純物ドーピング
によって行う。また各層の厚さはCdTeバッファ層が
5μm 、n−HgCdTe1が10μm 、p−HgCd
Te2が3μm である。成長終了後、20μm 径のレジ
ストパターンを形成し、イオンミリングによりメサ型の
構造を形成する。エッチング深さは4μm とし、pn接
合が分離できるようにする。次に水酸化カリウムとエチ
レングリコールと水の混合液を用い陽極酸化膜を0.1
μm 形成し、メサ上面の陽極酸化膜をエッチングによっ
て落とし、約18μm 径のコンタクト部を形成する。更
に表面の絶縁を確実に行うため、Eガン蒸着によりZn
S保護膜4を0.5μm 堆積し、先程と同様にメサ上面
部に約15μm 径のコンタクト部を形成し、その部分に
p側電極6としてTi/Auを蒸着、パターニングを行
い素子は完成する。
DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation and characteristics of an infrared detector according to the present invention will be described in detail with reference to FIGS. N-HgCdTe1, p-HgC on a GaAs substrate via a CdTe buffer layer (omitted in FIG. 1)
The epitaxial growth is performed sequentially by the MBE method of dTe2. At this time, the polarity of each layer is determined by impurity doping during growth. The thickness of each layer is 5 μm for the CdTe buffer layer, 10 μm for n-HgCdTe1, and p-HgCd.
Te2 is 3 μm. After the growth is completed, a resist pattern having a diameter of 20 μm is formed, and a mesa structure is formed by ion milling. The etching depth is set to 4 μm so that the pn junction can be separated. Next, using a mixed solution of potassium hydroxide, ethylene glycol and water, the anodic oxide film is
Then, the anodic oxide film on the upper surface of the mesa is removed by etching to form a contact portion having a diameter of about 18 μm. Furthermore, in order to ensure the insulation of the surface, Zn is deposited by E gun evaporation.
An S protective film 4 is deposited to a thickness of 0.5 .mu.m, a contact portion having a diameter of about 15 .mu.m is formed on the upper surface of the mesa as before, and Ti / Au is deposited and patterned as a p-side electrode 6 on the portion to complete the device. .

【0010】次に本発明の赤外線検出器の動作、特性に
ついて説明する。裏面あるいは表面より入射した赤外光
はそのほとんどがn−HgCdTe1で吸収され光電変
換されキャリア(この場合はホール)を発生する。この
キャリアが拡散し、p−HgCdTe2により形成され
ているpn接合に到達し、p側電極6を介して信号とし
て出力される。本発明のようなメサ型構造の赤外検出器
の特性に影響を与える主な暗電流は、前述したようにn
−HgCdTe1で発生する拡散電流とメサ壁面部の表
面リーク電流である。本発明では基本的にはp on
n構造を用いているためn−HgCdTe1でのキャリ
アのライフタイムは長く拡散電流は小さい。また本発明
では作用の項でも述べたように、ダメージが入っている
エッチング面は正の固定電荷をもつ陽極酸化膜で覆われ
ているため、p−HgCdTe2のエッチング面は電子
が誘起され反転領域5が形成されている。その結果、p
n接合はダメージ領域より内部に移動し前述した表面リ
ーク電流を低減することができる。
Next, the operation and characteristics of the infrared detector of the present invention will be described. Most of the infrared light incident from the back surface or the front surface is absorbed by n-HgCdTe1 and photoelectrically converted to generate carriers (in this case, holes). This carrier diffuses, reaches a pn junction formed by p-HgCdTe2, and is output as a signal via the p-side electrode 6. The main dark current that affects the characteristics of the infrared detector having the mesa structure as in the present invention is n as described above.
The diffusion current generated in HgCdTe1 and the surface leakage current of the mesa wall. In the present invention, p on is basically used.
Since the n-structure is used, the carrier lifetime in n-HgCdTe1 is long and the diffusion current is small. In the present invention, as described in the section of the operation, the damaged etched surface is covered with the anodic oxide film having a positive fixed charge, so that the etched surface of p-HgCdTe2 is induced by electrons, and 5 are formed. As a result, p
The n-junction moves inward from the damaged region and can reduce the above-described surface leakage current.

【0011】このようにHgCdTe結晶を用いたメサ
型構造の赤外線検出器に関わる本発明は、メサ部分での
表面リーク電流を低減した優れた特性の赤外線検出器を
提供するものである。
The present invention, which relates to a mesa-type infrared detector using a HgCdTe crystal as described above, provides an infrared detector having excellent characteristics with reduced surface leakage current at the mesa portion.

【0012】本実施の形態では正の固定電荷をもつ膜と
して陽極酸化膜を固定電荷のない保護膜としてZnS膜
を用いているが、陽極酸化膜の代わりに光酸化膜を、Z
nS膜の代わりに窒化膜を用いても得られる効果は全く
同様である。製造方法に関しては、光酸化膜は加熱した
オゾン雰囲気中に一定時間曝すことにより形成され、ま
た窒化膜はプラズマCVD法により形成することが可能
である。
In this embodiment, an anodic oxide film is used as a film having a positive fixed charge, and a ZnS film is used as a protective film having no fixed charge.
The effect obtained by using a nitride film instead of the nS film is exactly the same. Regarding the manufacturing method, the photo-oxide film can be formed by exposing it to a heated ozone atmosphere for a certain time, and the nitride film can be formed by a plasma CVD method.

【0013】また本実施の形態ではエピタキシャル成長
させる基板としてGaAs基板を用いているがHgCd
Te層が成長可能であればこれに限るものではない。
In this embodiment, a GaAs substrate is used as a substrate for epitaxial growth, but HgCd
It is not limited to this as long as the Te layer can be grown.

【0014】[0014]

【発明の効果】以上説明したように、本発明の赤外線検
出器では、メサ型の構造を用いた場合でも、メサ壁面で
の表面リーク電流を低減でき、優れた特性が得られる赤
外線検出器を提供するものである。
As described above, in the infrared detector according to the present invention, even when a mesa structure is used, a surface leak current on the mesa wall surface can be reduced, and an infrared detector having excellent characteristics can be obtained. To provide.

【図面の簡単な説明】[Brief description of the drawings]

【図1】本発明の赤外線検出器の実施例を説明するため
の図である。
FIG. 1 is a diagram for explaining an embodiment of an infrared detector according to the present invention.

【図2】本発明の赤外線検出器の動作を説明するための
図である。
FIG. 2 is a diagram for explaining the operation of the infrared detector of the present invention.

【図3】従来例を示す図である。FIG. 3 is a diagram showing a conventional example.

【符号の説明】[Explanation of symbols]

1 n−HgCdTe 2 p−HgCdTe 3 陽極酸化膜 4 ZnS保護膜 5 反転領域 6 p側電極 Reference Signs List 1 n-HgCdTe 2 p-HgCdTe 3 anodic oxide film 4 ZnS protective film 5 inversion region 6 p-side electrode

Claims (5)

【特許請求の範囲】[Claims] 【請求項1】n−HgCdTe層上にp−HgCdTe
層を有し、p−HgCdTe層をエッチングすることに
よりpn接合が分離されたメサ型構造の表面に正の固定
電荷をもつ保護膜を有し、さらに前記正の固定電荷をも
つ保護膜の上に固定電荷をもたない保護膜を有すること
を特徴とする赤外線検出器。
1. A p-HgCdTe layer on an n-HgCdTe layer.
A protective film having a positive fixed charge on the surface of the mesa structure in which the pn junction is separated by etching the p-HgCdTe layer, and further comprising a protective film having the positive fixed charge. An infrared detector having a protective film having no fixed charge.
【請求項2】前記正の固定電荷をもつ保護膜が陽極酸化
膜であることを特徴とする請求項1記載の赤外線検出
器。
2. The infrared detector according to claim 1, wherein said protective film having a positive fixed charge is an anodic oxide film.
【請求項3】前記正の固定電荷をもつ保護膜が光酸化膜
であることを特徴とする請求項1記載の赤外線検出器。
3. The infrared detector according to claim 1, wherein said protective film having a positive fixed charge is a photo-oxide film.
【請求項4】前記固定電荷をもたない保護膜がZnS膜
であることを特徴とする請求項1記載の赤外線検出器。
4. The infrared detector according to claim 1, wherein said protective film having no fixed charge is a ZnS film.
【請求項5】前記固定電荷をもたない保護膜が窒化膜で
あることを特徴とする請求項1記載の赤外線検出器。
5. The infrared detector according to claim 1, wherein said protective film having no fixed charge is a nitride film.
JP9047873A 1997-03-03 1997-03-03 Infrared detector Pending JPH10242497A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP9047873A JPH10242497A (en) 1997-03-03 1997-03-03 Infrared detector

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP9047873A JPH10242497A (en) 1997-03-03 1997-03-03 Infrared detector

Publications (1)

Publication Number Publication Date
JPH10242497A true JPH10242497A (en) 1998-09-11

Family

ID=12787508

Family Applications (1)

Application Number Title Priority Date Filing Date
JP9047873A Pending JPH10242497A (en) 1997-03-03 1997-03-03 Infrared detector

Country Status (1)

Country Link
JP (1) JPH10242497A (en)

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Effective date: 19990608