JPH05291702A - Manufacture of semiconductor laser - Google Patents
Manufacture of semiconductor laserInfo
- Publication number
- JPH05291702A JPH05291702A JP11972192A JP11972192A JPH05291702A JP H05291702 A JPH05291702 A JP H05291702A JP 11972192 A JP11972192 A JP 11972192A JP 11972192 A JP11972192 A JP 11972192A JP H05291702 A JPH05291702 A JP H05291702A
- Authority
- JP
- Japan
- Prior art keywords
- layer
- ingap
- algaas
- diffraction grating
- mask layer
- 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.)
- Granted
Links
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 17
- 239000004065 semiconductor Substances 0.000 title claims abstract description 6
- 229910000980 Aluminium gallium arsenide Inorganic materials 0.000 claims abstract description 43
- 238000005530 etching Methods 0.000 claims abstract description 23
- 229920002120 photoresistant polymer Polymers 0.000 claims abstract description 21
- 229910001218 Gallium arsenide Inorganic materials 0.000 claims abstract description 16
- 238000005253 cladding Methods 0.000 claims description 11
- 239000000758 substrate Substances 0.000 claims description 5
- 230000004888 barrier function Effects 0.000 claims description 4
- 101100240461 Dictyostelium discoideum ngap gene Proteins 0.000 claims description 3
- 239000013078 crystal Substances 0.000 abstract description 23
- 230000010355 oscillation Effects 0.000 description 7
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 6
- 238000000034 method Methods 0.000 description 6
- 230000003287 optical effect Effects 0.000 description 6
- 230000008878 coupling Effects 0.000 description 4
- 238000010168 coupling process Methods 0.000 description 4
- 238000005859 coupling reaction Methods 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 2
- 229910005540 GaP Inorganic materials 0.000 description 2
- 240000002329 Inga feuillei Species 0.000 description 2
- FTWRSWRBSVXQPI-UHFFFAOYSA-N alumanylidynearsane;gallanylidynearsane Chemical compound [As]#[Al].[As]#[Ga] FTWRSWRBSVXQPI-UHFFFAOYSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 2
- 229910052794 bromium Inorganic materials 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 241000824268 Kuma Species 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 238000000862 absorption spectrum Methods 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052792 caesium Inorganic materials 0.000 description 1
- TVFDJXOCXUVLDH-UHFFFAOYSA-N caesium atom Chemical compound [Cs] TVFDJXOCXUVLDH-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000003776 cleavage reaction Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- HZXMRANICFIONG-UHFFFAOYSA-N gallium phosphide Chemical compound [Ga]#P HZXMRANICFIONG-UHFFFAOYSA-N 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 1
- 230000010365 information processing Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 230000031700 light absorption Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000002488 metal-organic chemical vapour deposition Methods 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 229910052701 rubidium Inorganic materials 0.000 description 1
- IGLNJRXAVVLDKE-UHFFFAOYSA-N rubidium atom Chemical compound [Rb] IGLNJRXAVVLDKE-UHFFFAOYSA-N 0.000 description 1
- 230000007017 scission Effects 0.000 description 1
- 238000001039 wet etching Methods 0.000 description 1
Landscapes
- Semiconductor Lasers (AREA)
- Diffracting Gratings Or Hologram Optical Elements (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】アルミニウムガリウムヒ素（以
下、ＡｌＧａＡｓという。）／ガリウムヒ素（以下、Ｇ
ａＡｓという。）結晶を用いた分布帰還型レーザ（以下
ＤＦＢレーザという）の製造において、高さのある良好
な形状の回折格子の形成と、前記回折格子を埋め込む再
成長で、均一で良質な結晶を形成することとを可能にす
る製造工程の改良に関する。[Field of Industrial Application] Aluminum gallium arsenide (hereinafter referred to as AlGaAs) / gallium arsenide (hereinafter referred to as G)
It is called aAs. ) In manufacturing a distributed feedback laser (hereinafter referred to as a DFB laser) using a crystal, a uniform and good-quality crystal is formed by forming a diffraction grating having a good height and regrowth of the diffraction grating. The present invention relates to an improvement in a manufacturing process that enables
【０００２】[0002]
【従来の技術】ＤＦＢレーザは、高速直接変調下でも単
一縦モードで発振する、へき開面を必要としないため集
積化に適する、温度や駆動電流によって発振波長を連続
的に変化できる、回折格子の周期により発振波長を精密
に設定できる等の特徴を持つ。特に、短波長帯（波長
０．７〜０．９μｍ）で発振するＤＦＢレーザは、光情
報記録、光情報処理、光応用計測等で極めて有用なもの
であるが、近年、原子標準発振器用として、ルビジウム
（Ｒｂ）やセシウム（Ｃｓ）等の光吸収線に合わせた波
長０．７８〜０．８５２μｍ帯等の半導体レーザが励起
用光源として注目されている。2. Description of the Related Art A DFB laser oscillates in a single longitudinal mode even under high-speed direct modulation, does not require a cleavage plane, and is suitable for integration. It can continuously change the oscillation wavelength by temperature or driving current. It has the feature that the oscillation wavelength can be set precisely by the cycle of. In particular, a DFB laser that oscillates in a short wavelength band (wavelength 0.7 to 0.9 μm) is extremely useful for optical information recording, optical information processing, optical applied measurement, etc. , Semiconductor lasers having a wavelength range of 0.78 to 0.852 μm, which are aligned with light absorption lines such as rubidium (Rb) and cesium (Cs), are attracting attention as excitation light sources.
【０００３】励起用光源としては、吸収スペクトル幅が
狭いため、通常のファブリペロー型の半導体レーザでは
縦モードの単一性と安定性に欠けることから、上に述べ
た特徴を有したＤＦＢレーザの要求が高まってきてい
る。波長０．７〜０．９μｍ帯で発振する半導体レーザ
の製造には通常ＡｌＧａＡｓ／ＧａＡｓ系の結晶が用い
られ、単一縦モードで発振するＤＦＢレーザを製造する
ためには、波長選択性を持たせるために、発光する活性
層の近傍に回折格子を埋め込む技術が必要になる。As a pumping light source, since the absorption spectrum width is narrow, an ordinary Fabry-Perot type semiconductor laser lacks unity and stability of a longitudinal mode. Therefore, a DFB laser having the above-mentioned characteristics is used. The demand is increasing. AlGaAs / GaAs crystals are usually used for manufacturing a semiconductor laser that oscillates in a wavelength range of 0.7 to 0.9 μm, and a wavelength selectivity is required for manufacturing a DFB laser that oscillates in a single longitudinal mode. In order to achieve this, a technique for burying a diffraction grating near the active layer that emits light is required.
【０００４】以下、上で述べた短波長帯で発振するＤＦ
Ｂレーザの従来の製造方法（例えば、小島、野田、光
永、藤原、久間 ：電子通信学会技術研究報告 ＯＱＥ
８５（１９８５）−３７）を図を用いて説明する。図２
は、従来の技術によるＤＦＢレーザの製造方法を示す断
面模式図である。Hereinafter, the DF that oscillates in the short wavelength band described above
Conventional manufacturing method of B laser (eg, Kojima, Noda, Mitsunaga, Fujiwara, Kuma: IEICE Technical Report OQE
85 (1985) -37) will be described with reference to the drawings. Figure 2
FIG. 3 is a schematic sectional view showing a method of manufacturing a DFB laser according to a conventional technique.
【０００５】図２（ａ）は１回目の結晶成長を示す断面
模式図で、ｎ−ＧａＡｓ基板１上に、ｎ−ＧａＡｓバッ
ファ層２、ｎ型のアルミニウムガリウムヒ素（以下、Ａ
ｌＧａＡｓという。）クラッド層３、ＡｌＧａＡｓ活性
層４、ｐ−ＡｌＧａＡｓバリア層５、ｐ−ＡｌＧａＡｓ
ガイド層６を順次成長する。FIG. 2A is a schematic cross-sectional view showing the first crystal growth, in which an n-GaAs buffer layer 2, an n-type aluminum gallium arsenide (hereinafter referred to as A) is formed on an n-GaAs substrate 1.
It is called lGaAs. ) Cladding layer 3, AlGaAs active layer 4, p-AlGaAs barrier layer 5, p-AlGaAs
The guide layer 6 is sequentially grown.
【０００６】図２（ｂ）は、二光束干渉露光を示す断面
模式図で、ｐ−ＡｌＧａＡｓガイド層６上に、フォトレ
ジスト８を塗布し、Ｈｅ−Ｃｄレーザビーム９（波長３
２５０オングストローム）を用いた二光束干渉露光を行
う。このときの設定は、１次の回折格子は周期が短かす
ぎて露光が困難であるため、通常２次以上の周期が用い
られる。FIG. 2B is a schematic cross-sectional view showing the two-beam interference exposure, in which a photoresist 8 is coated on the p-AlGaAs guide layer 6 and a He-Cd laser beam 9 (wavelength 3).
Two-beam interference exposure using 250 Å) is performed. At this time, the first-order diffraction grating has a too short cycle and exposure is difficult, so that the second-order or higher-order cycle is usually used.
【０００７】図２（ｃ）は、現像後の状態を示す断面模
式図で、設定した周期でフォトレジスト８のパターンが
形成される。FIG. 2C is a schematic sectional view showing the state after development, in which the pattern of the photoresist 8 is formed at a set cycle.
【０００８】図２（ｄ）は、エッチングを示す断面模式
図で、フォトレジスト８のパターンをマスクとし、例え
ば硫酸系のエッチング液を用いて、下のｐ−ＡｌＧａＡ
ｓガイド層６をエッチングし、回折格子を形成する。こ
のとき、フォトレジスト８のパターンとｐ−ＡｌＧａＡ
ｓガイド層６との密着は、硫酸系等のエッチング液に対
して弱いために、フォトレジスト８のパターン下にサイ
ドエッチングが進行し、高さのある回折格子を形成する
ことは困難である。FIG. 2 (d) is a schematic cross-sectional view showing etching, using the pattern of the photoresist 8 as a mask and using, for example, a sulfuric acid-based etching solution, the p-AlGaA below is formed.
The s guide layer 6 is etched to form a diffraction grating. At this time, the pattern of the photoresist 8 and p-AlGaA
Since the close contact with the s guide layer 6 is weak with respect to an etching solution such as a sulfuric acid-based solution, side etching progresses under the pattern of the photoresist 8 and it is difficult to form a high diffraction grating.
【０００９】図２（ｅ）は、２回目の結晶成長を示す断
面模式図で、パターン化されたフォトレジスト８を除去
した後、ｐ−ＡｌＧａＡｓクラッド層１２、ｐ−ＧａＡ
ｓコンタクト層１１を順次成長し、回折格子を埋め込
む。このとき、回折格子を形成したｐ−ＡｌＧａＡｓガ
イド層６は、酸化されやすいアルミ（以下Ａｌという）
を含んでいるために、均一で良質な結晶を成長すること
は困難である。また、光の閉じ込め構造上、ｐ−ＡｌＧ
ａＡｓクラッド層１２は、Ａｌを最も多く含むため、後
工程でのエッチング等で空気中にさらされることは避け
られないので素子の信頼性の点から好ましくない。FIG. 2 (e) is a schematic cross-sectional view showing the second crystal growth. After removing the patterned photoresist 8, the p-AlGaAs cladding layer 12 and p-GaA are formed.
The s contact layer 11 is sequentially grown to fill the diffraction grating. At this time, the p-AlGaAs guide layer 6 having the diffraction grating formed thereon is easily oxidized by aluminum (hereinafter referred to as Al).
Therefore, it is difficult to grow a uniform and high-quality crystal. In addition, due to the light confinement structure, p-AlG
Since the aAs clad layer 12 contains the largest amount of Al, it is unavoidable that it is exposed to the air by etching or the like in a later step, which is not preferable from the viewpoint of device reliability.
【００１０】[0010]
【発明が解決しようとする課題】従来の技術では、パタ
ーン化されたフォトレジスト８をマスクにして直接ｐ−
ＡｌＧａＡｓガイド層６をエッチングするために、サイ
ドエッチングの進行によって高さのある回折格子の形成
が困難である。そのため、充分な光結合が得られず、単
一縦モード発振の歩留りが低下するばかりか、発振しき
い値が上昇するといった問題が生じやすい。一般的に２
次以上の回折格子を用いるため、１次の回折格子と同等
な光結合を得るためには高さのある回折格子が必要にな
る。また、酸化されやすいｐ−ＡｌＧａＡｓガイド層６
に形成した回折格子上に直接Ａｌ組成比の高いｐ−Ａｌ
ＧａＡｓクラッド層１２を成長するため、膜厚の不均一
性や、表面の凹凸などの異常成長が起こりやすく、良質
な結晶を得るのは困難である。さらに、上部に位置する
ｐ−ＡｌＧａＡｓクラッド層１２は、電流狭窄や、光の
閉じ込め構造等の形成のために後工程でエッチングする
必要があり、この時点で界面が酸化され、素子化してか
らの劣化など信頼性に問題が生じやすい。本発明の目的
は、これら製造工程上及び、レーザ素子化してからの特
性上の課題を解決することにあり、高さのある回折格子
を形成でき、成長時に良質な結晶が得られ、さらに、そ
の埋め込まれた結晶は後工程で酸化の恐れのない製造方
法を提供することにある。According to the conventional technique, the patterned photoresist 8 is used as a mask to directly p-type the photoresist.
Since the AlGaAs guide layer 6 is etched, it is difficult to form a high diffraction grating due to the progress of side etching. As a result, sufficient optical coupling cannot be obtained, and the yield of single longitudinal mode oscillation is likely to decrease and the oscillation threshold value tends to increase. Generally 2
Since a diffraction grating of the order or higher is used, a diffraction grating having a height is required to obtain optical coupling equivalent to that of the diffraction grating of the first order. In addition, the p-AlGaAs guide layer 6 which is easily oxidized
P-Al with a high Al composition ratio directly on the diffraction grating
Since the GaAs clad layer 12 is grown, it is difficult to obtain a good quality crystal because the film thickness becomes nonuniform and abnormal growth such as surface irregularities easily occurs. Further, the p-AlGaAs clad layer 12 located on the upper side needs to be etched in a later step in order to form a current constriction, a light confinement structure, and the like. Problems such as deterioration easily occur in reliability. An object of the present invention is to solve these problems in the manufacturing process and in the characteristics after the laser device is formed, a diffraction grating having a height can be formed, and a good quality crystal can be obtained during growth. The embedded crystal is to provide a manufacturing method which is free from the risk of oxidation in the subsequent process.
【００１１】[0011]
【課題を解決するための手段】ｐ−ＡｌＧａＡｓガイド
層６に回折格子を形成する際、フォトレジスト８とｐ−
ＡｌＧａＡｓガイド層６との間にインジウムガリウムリ
ン（以下、ＩｎＧａＰという）マスク層７を介し、フォ
トレジスト８とＩｎＧａＰマスク層７とＡｌＧａＡｓガ
イド層６との間の２種類のエッチング液に対する密着性
を利用して、エッチングを行うことにより、高さのある
ＡｌＧａＡｓ回折格子の形成を実現する。When a diffraction grating is formed in a p-AlGaAs guide layer 6, a photoresist 8 and a p-AlGaAs guide layer 6 are formed.
Utilizing the adhesiveness between the photoresist 8 and the InGaP mask layer 7 and the AlGaAs guide layer 6 with respect to two kinds of etching liquids via the indium gallium phosphide (hereinafter referred to as InGaP) mask layer 7 between the AlGaAs guide layer 6 and the AlGaAs guide layer 6. Then, etching is performed to realize the formation of a high AlGaAs diffraction grating.
【００１２】また、２回目の結晶成長では、上記のパタ
ーン化されたｐ−ＩｎＧａＰマスク層７を回折格子上に
残したまま、同組成のｐ−ＩｎＧａＰクラッド層１０、
ｐ−ＧａＡｓコンタクト層１１を成長し、回折格子を埋
め込む。このとき、回折格子上に残したｐ−ＩｎＧａＰ
マスク層７のパターンは、同じ結晶であるため、ｐ−Ｉ
ｎＧａＰクラッド層１０の成長を円滑にし、均一で良質
な結晶の成長が容易に達成される。In the second crystal growth, the patterned p-InGaP mask layer 7 is left on the diffraction grating and the p-InGaP cladding layer 10 having the same composition,
The p-GaAs contact layer 11 is grown and the diffraction grating is embedded. At this time, p-InGaP left on the diffraction grating
Since the pattern of the mask layer 7 is the same crystal, p-I
The growth of the nGaP cladding layer 10 is smoothed, and uniform and high-quality crystal growth is easily achieved.
【００１３】そして、この手段を用いれば、高さのある
回折格子が容易に形成でき、上部クラッド層にＩｎＧａ
Ｐを用いることにより、均一で良質な結晶が形成でき、
しかもＡｌを含んでいないため、後工程での酸化による
劣化等のない信頼性の高いレーザ素子が得られる。By using this means, a diffraction grating having a height can be easily formed, and InGa can be formed in the upper cladding layer.
By using P, uniform and high quality crystals can be formed,
Moreover, since it does not contain Al, it is possible to obtain a highly reliable laser element which is free from deterioration due to oxidation in the subsequent process.
【００１４】[0014]
【作用】本発明によるＡｌＧａＡｓ／ＧａＡｓ系ＤＦＢ
レーザの製造方法では、ｐ−ＡｌＧａＡｓガイド層６に
回折格子を形成する際、通常パターン化されたフォトレ
ジスト８をマスクとし、直接エッチングしていたのに対
し、間にｐ−ＩｎＧａＰマスク層７を介することで各層
間の各エッチング液に対する密着性の強さと２段階に分
けたウェットエッチングの特性を利用して高さのある回
折格子が形成できる。したがって、２次以上の回折格子
でも強い光結合が得られ、ＤＦＢレーザとして、単一縦
モード発振の歩留り向上が期待できる。また、回折格子
を埋め込む結晶成長では、回折格子の形成時に用いたパ
ターン化されたｐ−ＩｎＧａＰマスク層７を残したまま
同じ結晶であるｐ−ＩｎＧａＰクラッド層１０を成長す
るので、成長時の加熱下において、ＩｎＧａＰのマスト
ランスポートによる回折格子表面のパッシベーションが
なされ、円滑に均一な結晶が形成できる。さらに、上部
クラッド層中にＡｌを含んでいないため、電流狭窄や、
光の閉じ込めを目的とした後のエッチング工程等で酸化
など、レーザ素子の特性に悪影響を及ぼす要因が除去で
きる。Operation: AlGaAs / GaAs DFB according to the present invention
In the method of manufacturing a laser, when the diffraction grating is formed in the p-AlGaAs guide layer 6, the photoresist 8 which is normally patterned is used as a mask for direct etching, whereas the p-InGaP mask layer 7 is interposed therebetween. Through the interposition, a strong diffraction grating can be formed by utilizing the strength of adhesion to each etching solution between the layers and the characteristics of wet etching divided into two stages. Therefore, strong optical coupling can be obtained even with a diffraction grating of the second or higher order, and improvement in the yield of single longitudinal mode oscillation can be expected as a DFB laser. In the crystal growth for embedding the diffraction grating, the p-InGaP clad layer 10 of the same crystal is grown while leaving the patterned p-InGaP mask layer 7 used for forming the diffraction grating. Below, the surface of the diffraction grating is passivated by InGaP mass transport, and a smooth and uniform crystal can be formed. Further, since the upper clad layer does not contain Al, current confinement and
It is possible to remove a factor that adversely affects the characteristics of the laser element, such as oxidation, in a subsequent etching process for the purpose of confining light.
【００１５】[0015]
【実施例】以下、図面を参照しつつ、本発明の一実施例
に関するＤＦＢレーザの製造方法について説明する。図
１は本発明の一実施例であるＤＦＢレーザの製造方法に
関する断面模式図である。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A DFB laser manufacturing method according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of a method for manufacturing a DFB laser according to an embodiment of the present invention.
【００１６】図１（ａ）は１回目の結晶成長を示す断面
模式図で、ｎ−ＧａＡｓ基板１上にｎ−ＧａＡｓバッフ
ァ層２、ｎ−ＡｌＧａＡｓクラッド層３、ＡｌＧａＡｓ
活性層４、ｐ−ＡｌＧａＡｓバリア層５、ｐ−ＡｌＧａ
Ａｓガイド層６、ｐ−ＩｎＧａＰマスク層７（ＧａＡｓ
に格子整合）を例えば、ＭＯＶＰＥ、ＭＢＥ装置等を用
いて順次成長する。このとき、ｐ−ＩｎＧａＰマスク層
７は、回折格子の周期にパターン化することを考え、膜
厚は２００〜３００オングストローム程度とする。FIG. 1A is a schematic cross-sectional view showing the first crystal growth, in which an n-GaAs buffer layer 2, an n-AlGaAs cladding layer 3 and an AlGaAs are formed on an n-GaAs substrate 1.
Active layer 4, p-AlGaAs barrier layer 5, p-AlGa
As guide layer 6, p-InGaP mask layer 7 (GaAs
Lattice matching) is sequentially grown using, for example, a MOVPE or MBE apparatus. At this time, considering that the p-InGaP mask layer 7 is patterned in the period of the diffraction grating, the film thickness is set to about 200 to 300 angstroms.
【００１７】図１（ｂ）は二光束干渉露光を示す断面模
式図で、ｐ−ＩｎＧａＰマスク層７の上に、フォトレジ
スト８を５００オングストローム程度の厚さに塗布し、
Ｈｅ−Ｃｄレーザビーム９（波長３２５０オングストロ
ーム）を用いて露光する。このとき、設定する回折格子
の周期は１次のとき１１００〜１３００オングストロー
ムと短く困難であるので、２次（２２００〜２６００オ
ングストローム）以上の周期にする。FIG. 1B is a schematic cross-sectional view showing two-beam interference exposure, in which a photoresist 8 is applied on the p-InGaP mask layer 7 to a thickness of about 500 angstroms.
Exposure is performed using a He-Cd laser beam 9 (wavelength 3250 angstrom). At this time, the period of the diffraction grating to be set is as short as 1100 to 1300 Å for the first order, which is difficult. Therefore, the period of the second order (2200 to 2600 Å) is set.
【００１８】図１（ｃ）は、フォトレジスト８の現像後
の状態を示す断面模式図で、設定した周期で、パターン
が形成される。FIG. 1C is a schematic sectional view showing the state of the photoresist 8 after development, and a pattern is formed at a set cycle.
【００１９】図１（ｄ）は、１回目のエッチングを示す
断面模式図で、フォトレジスト８のパターンをマスクに
して、例えば臭素系のエッチング液を用いて、ｐ−Ｉｎ
ＧａＰマスク層７をｐ−ＡｌＧａＡｓガイド層６の表面
が露呈する程度にエッチングし、パターン化する。この
とき、臭素系のエッチング液に対しては、フォトレジス
ト８とｐ−ＩｎＧａＰマスク層７との密着が強いため
に、ｐ−ＡｌＧａＡｓガイド層６の表面が露呈する前に
ｐ−ＩｎＧａＰマスク層７が消滅するようなサイドエッ
チングの進行はない。FIG. 1D is a schematic cross-sectional view showing the first etching. Using the pattern of the photoresist 8 as a mask, for example, a bromine-based etching solution is used to p-In.
The GaP mask layer 7 is etched and patterned to such an extent that the surface of the p-AlGaAs guide layer 6 is exposed. At this time, since the photoresist 8 and the p-InGaP mask layer 7 are strongly adhered to the bromine-based etching solution, the p-InGaP mask layer 7 is exposed before the surface of the p-AlGaAs guide layer 6 is exposed. There is no progress of side etching that disappears.
【００２０】図１（ｅ）は、２回目のエッチングを示す
断面模式図で、フォトレジスト８を除去後、パターン化
されたｐ−ＩｎＧａＰマスク層７をマスクにして、例え
ば硫酸系のエッチング液を用いてｐ−ＡｌＧａＡｓガイ
ド層６をエッチングし、回折格子を形成する。このと
き、パターン化されたｐ−ＩｎＧａＰマスク層７はほと
んどエッチングされず、エッチングを適度な時間で停止
すれば、回折格子上に、パターン化されたｐ−ＩｎＧａ
Ｐマスク層７が残った状態になる。ここで、ｐ−ＩｎＧ
ａＰマスク層７と、ｐ−ＡｌＧａＡｓガイド層６とは結
晶成長によるものであるため密着が強く、高さのある良
好な形状の回折格子が形成できる。FIG. 1E is a schematic cross-sectional view showing the second etching. After removing the photoresist 8, using the patterned p-InGaP mask layer 7 as a mask, a sulfuric acid-based etching solution, for example, is used. The p-AlGaAs guide layer 6 is etched by using it to form a diffraction grating. At this time, the patterned p-InGaP mask layer 7 is hardly etched, and if the etching is stopped in a proper time, the patterned p-InGaP mask layer 7 is patterned.
The P mask layer 7 remains. Where p-InG
Since the aP mask layer 7 and the p-AlGaAs guide layer 6 are formed by crystal growth, they are strongly adhered to each other, and a high-shaped diffraction grating having a good shape can be formed.
【００２１】図１（ｆ）は、２回目の結晶成長を示す断
面模式図で、パターン化されたｐ−ＩｎＧａＰマスク層
７を残したまま、同じ結晶である、ｐ−ＩｎＧａＰクラ
ッド層１０、ｐ−ＧａＡｓコンタクト層１１を順次成長
する。このとき、パターン化されたｐ−ＩｎＧａＰマス
ク層７を残しているため、成長時の加熱下において、Ｉ
ｎＧａＰのマストランスポートによる回折格子表面のパ
ッシベーションがなされ、ｐ−ＩｎＧａＰクラッド層１
０の成長が円滑に進み、均一で、表面が鏡面状態の良質
な結晶が得られる。FIG. 1 (f) is a schematic cross-sectional view showing the second crystal growth. The p-InGaP cladding layers 10 and p, which are the same crystal, with the patterned p-InGaP mask layer 7 remaining. -The GaAs contact layer 11 is sequentially grown. At this time, since the patterned p-InGaP mask layer 7 remains, I
The surface of the diffraction grating is passivated by mass transport of nGaP, and the p-InGaP cladding layer 1 is formed.
Growth of 0 proceeds smoothly, and a high quality crystal having a uniform and mirror-like surface is obtained.
【００２２】[0022]
【発明の効果】第１に、本発明によるＤＦＢレーザの製
造工程においては、フォトレジストのマスクだけでは高
さのある良好な形状のＡｌＧａＡｓ回折格子の形成が困
難なことから、間にＩｎＧａＰ層を介し、さらにエッチ
ング液を切り替える２段階のエッチングを取り入れるこ
とで、高さのある良好な形状のＡｌＧａＡｓ回折格子の
形成でき、２次以上の回折格子でも充分な光の結合が得
られ、単一縦モード発振の歩留り向上、発振しきい値の
低減等、ＤＦＢレーザ素子の高性能化が実現できる。First, in the process of manufacturing the DFB laser according to the present invention, it is difficult to form an AlGaAs diffraction grating having a good height with a photoresist mask alone. By adopting two-stage etching in which the etching solution is switched through, an AlGaAs diffraction grating with a good height can be formed, and sufficient light coupling can be obtained even with a diffraction grating of a second or higher order, and a single vertical It is possible to realize high performance of the DFB laser device such as improvement of yield of mode oscillation and reduction of oscillation threshold.
【００２３】第２に、回折格子形成時に用いたＩｎＧａ
Ｐ層のパターンをそのまま残して上部のクラッド層を同
じＩｎＧａＰで形成することで、従来まで困難であっ
た、酸化しやすいＡｌＧａＡｓ回折格子上の再成長を容
易なものにし、均一で良質な上部の結晶層が得られる。Second, InGa used for forming the diffraction grating
By forming the upper cladding layer with the same InGaP while leaving the pattern of the P layer as it is, re-growth on the AlGaAs diffraction grating, which has been difficult to oxidize, which has been difficult until now, can be facilitated, and a uniform and high-quality upper layer can be formed. A crystalline layer is obtained.
【００２４】第３に、従来まで上部クラッド層の材料と
して、ＡｌＧａＡｓを用いていたのに対し、本発明では
Ａｌを含まないＩｎＧａＰを用いることにより、後工程
や素子化してからの酸化の心配が無いため、信頼性の高
いレーザ素子が製造可能である。Third, while AlGaAs has been used as the material for the upper clad layer in the past, the use of InGaP that does not contain Al in the present invention may cause oxidation in a later step or after device formation. Since it does not exist, a highly reliable laser element can be manufactured.
【００２５】[0025]
【図１】本発明の一実施例を示す断面模式図である。FIG. 1 is a schematic sectional view showing an embodiment of the present invention.
【図２】ＤＦＢレーザの従来の製造方法を示す断面模式
図である。FIG. 2 is a schematic sectional view showing a conventional method for manufacturing a DFB laser.
１ ｎ−ＧａＡｓ基板 ２ ｎ−ＧａＡｓバッファ層 ３ ｎ−ＡｌＧａＡｓクラッド層 ４ ＡｌＧａＡｓ活性層 ５ ｐ−ＡｌＧａＡｓバリア層 ６ ｐ−ＡｌＧａＡｓガイド層 ７ ｐ−ＩｎＧａＰマスク層 ８ フォトレジスト ９ Ｈｅ−Ｃｄレーザビーム １０ ｐ−ＩｎＧａＰクラッド層 １１ ｐ−ＧａＡｓコンタクト層 １２ ｐ−ＡｌＧａＡｓクラッド層。 1 n-GaAs substrate 2 n-GaAs buffer layer 3 n-AlGaAs cladding layer 4 AlGaAs active layer 5 p-AlGaAs barrier layer 6 p-AlGaAs guide layer 7 p-InGaP mask layer 8 photoresist 9 He-Cd laser beam 10 p -InGaP clad layer 11 p-GaAs contact layer 12 p-AlGaAs clad layer.
Claims (1)
Ａｓバッファ層（２）、ｎ−ＡｌＧａＡｓクラッド層
（３）、ＡｌＧａＡｓ活性層（４）、ｐ−ＡｌＧａＡｓ
バリア層（５）、ｐ−ＡｌＧａＡｓガイド層（６）、ｐ
−ＩｎＧａＰマスク層（７）を順次成長する段階と、 前記ｐ−ＩｎＧａＰマスク層（７）の上に、フォトレジ
スト（８）を塗布し、露光することにより所定の周期を
もつ回折格子を作るためのレジストパターンを形成する
段階と、 第１のエッチング液を用いて、レジストパターンが形成
されたｐ−ＩｎＧａＰマスク層（７）を前記ｐ−ＡｌＧ
ａＡｓガイド層（６）の上面までエッチングし、ｐ−Ｉ
ｎＧａＰマスク層（７）のパターンを形成する段階と、 前記パターン化されたｐ−ＩｎＧａＰマスク層（７）を
マスクとして、第２のエッチング液を用いて前記ｐ−Ａ
ｌＧａＡｓガイド層（６）をエッチングし、回折格子を
形成する段階と、 前記パターン化されたｐ−ＩｎＧａＰマスク層（７）を
残したまま、ｐ−ＩｎＧａＰクラッド層（１０）、ｐ−
ＧａＡｓコンタクト層（１１）を順次成長する段階とか
らなる半導体レーザの製造方法。1. An n-Ga substrate (1) on which an n-Ga substrate is formed.
As buffer layer (2), n-AlGaAs cladding layer (3), AlGaAs active layer (4), p-AlGaAs
Barrier layer (5), p-AlGaAs guide layer (6), p
A step of sequentially growing an InGaP mask layer (7), and a photoresist (8) applied on the p-InGaP mask layer (7) and exposed to form a diffraction grating having a predetermined period. And forming a resist pattern on the p-InGaP mask layer (7) using the first etching solution.
Etch to the upper surface of the aAs guide layer (6) and p-I
forming a pattern of the nGaP mask layer (7), and using the patterned p-InGaP mask layer (7) as a mask, using the second etchant to form the p-A
Etching the lGaAs guide layer (6) to form a diffraction grating, and leaving the patterned p-InGaP mask layer (7), p-InGaP clad layer (10), p-
A method of manufacturing a semiconductor laser, comprising a step of sequentially growing a GaAs contact layer (11).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4119721A JP2987253B2 (en) | 1992-04-13 | 1992-04-13 | Manufacturing method of semiconductor laser |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4119721A JP2987253B2 (en) | 1992-04-13 | 1992-04-13 | Manufacturing method of semiconductor laser |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05291702A true JPH05291702A (en) | 1993-11-05 |
| JP2987253B2 JP2987253B2 (en) | 1999-12-06 |
Family
ID=14768480
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4119721A Expired - Lifetime JP2987253B2 (en) | 1992-04-13 | 1992-04-13 | Manufacturing method of semiconductor laser |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2987253B2 (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010067639A (en) * | 2008-09-08 | 2010-03-25 | Fujitsu Ltd | Semiconductor device, and method for manufacturing the same |
| JP2011211004A (en) * | 2010-03-30 | 2011-10-20 | Fujitsu Ltd | Method of manufacturing optical semiconductor element |
| JP2012018987A (en) * | 2010-07-06 | 2012-01-26 | Fujitsu Ltd | Optical semiconductor element, method of manufacturing the same, and optical device |
-
1992
- 1992-04-13 JP JP4119721A patent/JP2987253B2/en not_active Expired - Lifetime
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2010067639A (en) * | 2008-09-08 | 2010-03-25 | Fujitsu Ltd | Semiconductor device, and method for manufacturing the same |
| JP2011211004A (en) * | 2010-03-30 | 2011-10-20 | Fujitsu Ltd | Method of manufacturing optical semiconductor element |
| JP2012018987A (en) * | 2010-07-06 | 2012-01-26 | Fujitsu Ltd | Optical semiconductor element, method of manufacturing the same, and optical device |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2987253B2 (en) | 1999-12-06 |
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