JPS62124454A - Hetero junction type gas sensor - Google Patents

Abstract

PURPOSE:To obtain a good sensing characteristic for a combustible gas by providing many gas introducing holes by etching to the joint surface of an n-type oxide semiconductor and p-type oxide semiconductor in such a manner that the gas contacts said surface. CONSTITUTION:The joint part is made of an Li-doped NiO film having 1mum thickness as the p-type oxide semiconductor 1 and a ZnO film having 2mum thickness as the n-type oxide semiconductor to a 1mmX2mm size and the gas introducing holes 3 sized 10mum square and 2mum depth are formed at 15mum pitch thereto by reactive ion etching from above the semiconductor 1. A positive bias voltage is impressed to such element in the forward direction of a diode formed of the semiconductors 1 and 2 to operate the same. The combustible gas reacts with gaseous oxygen adsorbed to the joint part when the gas arrives at the joint part of the semiconductors 1 and 2 through the holes 3. The electrostatic potential in the joint part is then changed and the current flowing in the joint part changes. As a result, the concn. of the cmbustible gas is known from the current flowing in the joint part.

Description

【発明の詳細な説明】 （浬業上の第１」用分野） 本発明は小型にして消費電力が小さく、かつ高感度なガ
スセンサに関するものである。DETAILED DESCRIPTION OF THE INVENTION (First field of application in the industry) The present invention relates to a gas sensor that is small in size, has low power consumption, and is highly sensitive.

（従来技術及び発明が解決しょうとする問題点）従来の
ガスセンサは第１表に示すように電気抵抗式と非電気抵
抗式に大別さｎる。現在商品化されているものは、はと
んどが電気抵抗式でこれらはＳ”ｏ２＋　ＺｎＯなどの
ｎ型の歌化物半導体材料で素子を作り、その電気抵抗値
からガス濃度を知る方式である。電気抵抗式のガスセン
サ素子の大きな欠点は４００℃前後の筒温でのみ動作す
ることで消費電力が大きく、他の機能を持つセンナある
いは制御用の集積（ロ）路などとの集積化を阻む原因と
なっている。(Prior Art and Problems to be Solved by the Invention) Conventional gas sensors are broadly classified into electrical resistance type and non-electrical resistance type, as shown in Table 1. Currently, most of the commercially available devices are electrical resistance type, in which the element is made of an n-type compound semiconductor material such as S''O2+ ZnO, and the gas concentration is determined from the electrical resistance value. The major disadvantage of electrical resistance type gas sensor elements is that they operate only at a cylinder temperature of around 400°C, which consumes a lot of power, which prevents integration with sensors with other functions or control integration paths. It is the cause.

ま之非也気抵抗式はガスの吸着や反応などによる半導体
の仕事関数全直接的あるいは間接的にガス検出に利用す
る方式で、具体的には金属／半導体接合ダイオードと金
楓ゲート膜を用いたＭＯ８ＦＥＴ七ンサがあセンサ槁／
半導体接合ダイオードセンサはＰｄ　／　ＣｄＳ　ｆｆ
ｉはじめとしてＰｔ／Ｔｉ１ｔ、Ｐｔ／Ｔｉ１ｔなどを
用いた素子が提案されているが、これらはＰｄ　、　Ｔ
ｉ　’（通過てきるＨ２ガスが主な感知ガスである。ま
た金属ゲート膜を用い友ＭＯ８ＦＥＴセンサは５ｉＦＥ
Ｔの耐熱性から動作温度が約１５０℃までとおさえられ
ているためＨ２，ＣＯなどの反応性の高いガスに限られ
ており、１足応答特性にも問題が残されている（文献１
）。The non-resistance type is a method that uses the work function of a semiconductor through gas adsorption or reaction, either directly or indirectly, for gas detection. Specifically, it uses a metal/semiconductor junction diode and a gold maple gate film. There was MO8FET seven sensors/
Semiconductor junction diode sensor is Pd/CdS ff
Initially, elements using Pt/Ti1t, Pt/Ti1t, etc. have been proposed, but these are Pd, T
i' (H2 gas passing through is the main sensing gas. Also, the companion MO8FET sensor using a metal gate film is 5iFE
Due to the heat resistance of T, the operating temperature is limited to about 150°C, so it is limited to highly reactive gases such as H2 and CO, and there are still problems with the one-foot response characteristics (Reference 1).
).

酸化物半導体に関するヘテロ接合全応用した例としては
湿度センサがある（文献２）ｏこｎは焼結体全慎械的に
互層したもので、焼結した粒子間に水分が入ることによ
るイオン電流の増加全利用したもので、感度は優れてい
るが安定性に問題がある。An example of a full application of heterojunctions for oxide semiconductors is a humidity sensor (Reference 2). An oxide semiconductor is a sintered body in which the entire layer is carefully alternated, and an ionic current is generated when moisture enters between the sintered particles. Although the sensitivity is excellent, there are problems with stability.

（問題点金牌決するための手段） 不発明の目的は、酸化物半導体のへテロ接合が安定性の
悪い湿度センサにしか利用されない構造的欠陥−ｅｍ決
した新しい構造の各種可燃性ガスセンサ全提供すること
ＶＣある。(Means for determining the problem) The purpose of the invention is to provide all kinds of flammable gas sensors with new structures that eliminate the structural defect in which heterojunctions of oxide semiconductors are used only for unstable humidity sensors. There is a thing called VC.

不発明は酸化物半導体のへテロ接合を用い友ガスセンサ
において、ｎ型酸化物半導体とｐＷ鍍化物牛導体の接合
面にガスが接触するエラに多数のガス導入穴をエツチン
グにニジ設けることを最も主要な特徴とする。従来技術
とは各種可燃性ガス（及び湿度）を安定に高感度に感知
できる点が異なる。In a gas sensor using a heterojunction of an oxide semiconductor, it is most important to provide a large number of gas inlet holes by etching in the gills where gas comes into contact with the junction surface of the n-type oxide semiconductor and the pW chloride conductor. Main characteristics. It differs from conventional technology in that it can stably and highly sensitively sense various flammable gases (and humidity).

次に実施例について説明する。Next, an example will be described.

第１図は本発明の第一の実施例を説明する図であって、
（イ）は平面図、（ロ）は断面図金示す。図において１
はｐ型酸化物半導体（ＬｉｉドープしたＮｉＯ）、Ｚ　
ｕ　ｎ型酸化物半導体（ＺｎＯ）、３は反応性イオンエ
ツチングにより形成したガス導入穴、４はリード線、５
はｐ型酸化物半導体とオーミックな接合を形成する電極
、６はＳｔ基板、７はヒータ、８はｎ型酸化物半導体と
オーミックな接合を形成する電極、９はＳｉＱ熱酸化膜
（Ｓｔｏｗ）を示す。FIG. 1 is a diagram illustrating a first embodiment of the present invention,
(a) is a plan view, and (b) is a cross-sectional view. In the figure 1
is a p-type oxide semiconductor (Lii-doped NiO), Z
u n-type oxide semiconductor (ZnO), 3 is a gas introduction hole formed by reactive ion etching, 4 is a lead wire, 5
is an electrode that forms an ohmic contact with a p-type oxide semiconductor, 6 is an St substrate, 7 is a heater, 8 is an electrode that forms an ohmic contact with an n-type oxide semiconductor, and 9 is a SiQ thermal oxide film (Stow). show.

これを動作するにはｐギ酸化物半導体１とｎ型酸化物半
導体２とで形成するダイオードの順方向に正のバイアス
電圧を与える。口」゛燃性ガスがガス導入穴３全通して
ｐギ酸化物半導体１とｎ型酸化物半導体２の接合部に達
すると接合部に吸着してい友酸素ガスと反応し接合部の
静電ポテンシャルが変化して、接合部を流れる電流が変
化する。この結果、接合部を流れる電流により可燃ガス
の濃度を知ることができる。ｐギ酸化物半導体１として
厚さ１μｍのＬｉミラドープ７ｊＮｉＯ＠、ｎ型酸化物
半導体２として厚さ２μｍＺｎＯ膜でｌツ×２＃の寸法
で接合を作ｐ、ｐ型酸化物半導体１の上から、反応性イ
オンエツチング１０μｍ角深さ２μｍのガス導入穴３’
ｉ１５μｍピッチで作製する。To operate this, a positive bias voltage is applied in the forward direction of the diode formed by the p-type oxide semiconductor 1 and the n-type oxide semiconductor 2. ``When the flammable gas passes through the gas introduction hole 3 and reaches the junction between the p-type oxide semiconductor 1 and the n-type oxide semiconductor 2, it is adsorbed to the junction and reacts with friendly oxygen gas, increasing the electrostatic potential of the junction. changes, causing a change in the current flowing through the junction. As a result, the concentration of combustible gas can be determined from the current flowing through the joint. A junction was made with a dimension of 1×2# using a 1 μm thick Li mira-doped 7jNiO@ as the p-type oxide semiconductor 1 and a 2 μm-thick ZnO film as the n-type oxide semiconductor 2. Reactive ion etching 10μm square 2μm deep gas introduction hole 3'
It is manufactured with a pitch of 15 μm.

この素子による可燃性ガスの感知特性を第２図に示す。Fig. 2 shows the sensing characteristics of combustible gas by this element.

（素子温度１００℃である。）図において■。は大気中
の素子電流、工はガス雰囲気中の素子の電流を示ｉ。(The element temperature is 100°C.) In the figure, ■. is the device current in the atmosphere, and d is the device current in the gas atmosphere.

このＬつなガス導入穴と接合部全加熱するヒータを設け
た構造になっているため、従来、湿度のみを不安定に感
知してい九へテロ接合が可燃性ガス＠度を感知できるよ
うになつ九。Because the structure includes this L-shaped gas inlet hole and a heater that heats the entire joint, the 9-heterojunction can now sense flammable gas, whereas conventionally only humidity was sensed unstablely. Natsu9.

〔実施子タリ２　〕 第３図は本発明の第二の実施例を説明する図であって、
１０は表面に１０μｍの５ｉＣｈｔ付は友方位（１００
）のＳｉウエノ”ｔエチレンジアミンとピロカテコール
の混合液で異方性エツチングして作製し几ダイヤフラム
の空間である。１１は素子の出力の対する演算、ヒータ
の温度条件等を制御する集積回路である。その他の符号
は、第１図の場合と同様のものを示す。ｎ型酸化物半導
体２としてＡＬｆドープしたＺｎＯ１ｐ型酸化物型環化
物半導てＬｉｆｆ１ドープしｆｃ　ＣｕＯｆ、それぞれ
スノくツタ法に工り１＋ｍＸ１．５ｍの寸法で作製する
。[Embodiment 2] FIG. 3 is a diagram illustrating a second embodiment of the present invention,
10 has 5iCht of 10 μm on the surface is a friend direction (100
) is the space of a diaphragm produced by anisotropic etching with a mixture of ethylenediamine and pyrocatechol. 11 is an integrated circuit that controls calculations for the output of the element, temperature conditions of the heater, etc. .Other symbols are the same as those in Fig. 1.As the n-type oxide semiconductor 2, an ALf-doped ZnO1, a Liff1-doped ZnO, a Liff1-doped fc, and a CuOf, respectively. Manufactured with dimensions of 1+m x 1.5m.

この後、ｎ型酸化物半導体の上面から５μ角のガス導入
穴ヲ１０μｍピッチで設ける。ヒータ７及びその上の素
子はダイヤスラムに＝９形成され几空間の上の１０μｍ
の５ｉＯ１膜のみで支えられており、ヒータの熱は集積
回路１１に伝達しにくい構造となっている。Thereafter, gas introduction holes of 5 μm square are provided at a pitch of 10 μm from the upper surface of the n-type oxide semiconductor. The heater 7 and the element above it are formed in a diamond slam with a distance of 10 μm above the space.
The integrated circuit 11 is supported only by the 5iO1 film, and has a structure in which heat from the heater is difficult to transfer to the integrated circuit 11.

このような構造になっているからヒータ温度があげられ
、ガス導入穴の効果と合わせ高感度に可燃性ガスの感知
が可能となる。第４図にその結果を示す。ここに工。は
大気中の素子電流、■はガス雰囲気中の素子電流である
。この結果から明らかなように従来、湿度センサとして
しか用いられなかつｔヘテロ接合のセンサが可燃性ガス
ガスセンサとして使用できる改善があつｔ。With this structure, the heater temperature can be raised, and in combination with the effect of the gas introduction hole, combustible gas can be sensed with high sensitivity. Figure 4 shows the results. Engineering here. is the device current in the atmosphere, and ■ is the device current in the gas atmosphere. As is clear from these results, there has been an improvement in that a heterojunction sensor, which has conventionally been used only as a humidity sensor, can now be used as a combustible gas sensor.

（発明の効果） 以上説明した工うに本発明のガスセンサに：れば、ｎ型
酸化物半導体とｐ型酸化物半導体のｐｎ接合において接
合部よ＃）深い位置まで多数のガス導入穴を設け、ヒー
タで加熱する構造であるから、Ｈ２，ＣＯ，メタン、エ
タン、グロバン。(Effects of the Invention) According to the above-described method, in the gas sensor of the present invention, a large number of gas introduction holes are provided deep into the pn junction between an n-type oxide semiconductor and a p-type oxide semiconductor, and Since the structure is heated with a heater, H2, CO, methane, ethane, and globan are used.

イソプロピレン等の可燃性ガスに対して良好な感知特性
が得られる効果がある。This has the effect of providing good sensing characteristics for flammable gases such as isopropylene.

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

第１図は本発明の特徴を表わす第一の実施例で（イ）は
上面図、に）ノは断面図、第２因は第一の実施例による
効果を示すデータ、第３図は第二の実施例を示すもので
（イ）は上面図、（ロ）は前面図、第４図は第二の実施
例による効果を示すデータである。 １・・・・・・ｐ型酸化物半導体 ２・・・・・ｎＷ＃化物半導体 ３・・・・・・ガス導入穴 ４・・・・・・リード線 ５・・・・・・ｐ型酸化物半尋体のオーミック電極６・
・・・・・Ｓｉ基板 ７・・・・・・ヒータ ８・・・・・・ｎ型酸化物半導体のオーミック電極９・
・・・・・熱酸化Ｓｉｎ、膜 ｌＯ・・・・・・ダイヤフラムの空間 １１・・・・・・集積回路 参考文献 （１）高山、酒井；セ／す技術ｖｏ１．４　、　ｍ１３
ｐ　３９〜４３　（１９８４） （２）中村、池尻、宮山、河本、柳田；日本化学会誌１
９８５　（６）　Ｐ１１５４〜１１５９特許出願人　　
日本電イキ電話株式会社第１図 ９−一−だ１＼ＭＡえイ乙５１０２月５己第２図 第３図 ］］ （ロ） 第４図 素手５毘／’Ｌ　（’Ｃ）Figure 1 is a first embodiment showing the features of the present invention, (a) is a top view, (b) is a sectional view, the second factor is data showing the effect of the first embodiment, and Figure 3 is a top view. Embodiment 2 is shown in which (a) is a top view, (b) is a front view, and FIG. 4 is data showing the effects of the second embodiment. 1...p-type oxide semiconductor 2...nW# compound semiconductor 3...gas introduction hole 4...lead wire 5...p-type Oxide semicircular ohmic electrode 6.
...Si substrate 7 ... Heater 8 ... N-type oxide semiconductor ohmic electrode 9
...Thermal oxidation of Sin, film lO...Diaphragm space 11...Integrated circuit references (1) Takayama, Sakai; Center Technology vol. 1.4, m13
p 39-43 (1984) (2) Nakamura, Ikejiri, Miyayama, Kawamoto, Yanagita; Journal of the Chemical Society of Japan 1
985 (6) P1154-1159 patent applicant
Nippon Denki Denwa Co., Ltd. Fig. 1 9-1-da 1\MA Ei Otsu 510 February 5 self Fig. 2 Fig. 3]] (b) Fig. 4 Bare hand 5 bi/'L ('C)

Claims (1)

【特許請求の範囲】[Claims] ｎ型の酸化物半導体とｐ型酸化物半導体からなるｐｎ接
合において、いずれか一方の酸化物半導体側から接合部
を通つて深い位置まで及ぶ多数のガス導入穴と、前記接
合部を加熱するヒータとを具備することを特徴とするヘ
テロ接合型ガスセンサ。In a pn junction consisting of an n-type oxide semiconductor and a p-type oxide semiconductor, a large number of gas introduction holes extending from one of the oxide semiconductors to a deep position through the junction, and a heater that heats the junction A heterojunction gas sensor comprising: