JP4134664B2 - Semiconductor optical device and manufacturing method thereof - Google Patents

Description

半導体レーザ素子Ｃの基板の反り量δ(デルタ)が、裏面研磨後において１００マイクロメートル(μｍ)程度である場合、この基板に働く応力は、式(１)から、８５Ｐａ・ｍとなる。よって、半導体レーザ素子１における酸化アルミニウム膜１２の厚さをｔとすると、
【００７５】
１．５×１０⁸Ｐａ×３５０×１０^-9メートル(ｍ)
＋ １．５×１０⁷Ｐａ×７×１０^-6メートル(ｍ)
−１×１０⁸Ｐａ×ｔ ≦ ８５ Ｐａ・ｍ ・・・ (２)
が得られる。これを整理すると
ｔ ≧ ０．７２ マイクロメートル(μｍ)
となる。
【００７６】
第１の実施の形態の半導体光素子における酸化アルミニウム膜１２がより厚い場合、基板２は凸型に反ることとなる。本発明者の知見によれば、基板２が凸型に反った場合にも、その反り量δを１００マイクロメートル以下にする必要がある。基板２が凸型に反り、その反り量δが１００マイクロメートル(μｍ)であったとすると、応力が−８５Ｐａ・ｍとなるため、
【００７７】
−８５ Ｐａ・ｍ ≦ １．５×１０⁸Ｐａ×３５０×１０^-9メートル(ｍ)
＋ １．５×１０⁷Ｐａ×７×１０^-6メートル(ｍ)
−１×１０⁸Ｐａ×ｔ ・・・ (３)
を整理すると、
ｔ ≦ ２．４２ マイクロメートル(μｍ)
となる。
【００７８】
したがって、酸化アルミニウム膜１２の厚さｔが０．６８マイクロメートル以上２．３８マイクロメートル以下であれば、基板２の反り量δを１００マイクロメートル以下にできる。また、酸化アルミニウム膜１２の厚さｔが１．６マイクロメートルのときに、全応力が０になる。半導体レーザ素子１においては、酸化アルミニウム膜１２は０．６８マイクロメートル以上２．３８マイクロメートル以下の厚さを有することが好適である。
【００７９】
本発明者は、半導体レーザ素子５１における導電体層５２についても同様の検討を行った。以下、その結果について説明する。ＳｉＯ₂膜およびＢＣＢ樹脂膜に加え、電極１４を構成する金属についても応力を求める。すなわち、Ｔｉ膜、Ｐｔ膜、およびＡｕ膜の単位厚さ当りの応力σ(シグマ)は、
【００８０】
・Ｔｉ膜：−６×１０⁸ Ｐａ
・Ｐｔ膜：１×１０⁹ Ｐａ
・Ａｕ膜：２×１０⁷ Ｐａ
である。
【００８１】
本発明者の実験によれば、成膜装置１００を用いてＣｒ膜をＩｎＰ基板上に形成する場合、イオンビーム電流が６５ミリアンペア程度以下であると引っ張り応力が働き、６５ミリアンペア程度を超えると圧縮応力が働く。Ｃｒ膜に働く単位厚さ当りの応力σは、イオンビーム電流を１００ミリアンペアであるとき、−５×１０⁸ Ｐａである。
【００８２】
発明者は、以上のようにして求めた応力σの値を用いて、上記の式(２)および(３)と同様に計算を行っている。この結果として、導電体層５２の好適な厚さは９８ナノメートル以上４３８ナノメートル以下であることが得られている。特に、導電体層５２の厚さを３６０ナノメートルとすれば、全応力を０とすることができる。半導体レーザ素子５１を製造する際には、導電体層５２の厚さが９８ナノメートル以上４３８ナノメートル以下となるように成膜時間が調整される。
【００８３】
以上、幾つかの実施形態を参照しながら、本発明に係る半導体光素子を説明したが、本発明はこれらに限定されることなく、種々の変形が可能である。例えば、本発明に係る半導体光素子は、ＤＦＢ型の半導体レーザ素子に限らず、ＤＢＲ(Distributed Bragg Reflector)型半導体レーザ素子、半導体光増幅素子であることができる。また、半導体光増幅素子又は半導体レーザ素子と、この素子からの光を変調する半導体変調器とが同一チップ内に設けられて構成される光集積素子であってもよい。
【００８４】
酸化アルミニウム膜１２および導電体層５２の好適な厚さの検討結果について説明したが、上に示した結果は、例示である。製造する素子を構成する絶縁膜および樹脂部の厚さ、基板の直径および材質に基づいて上記の説明と同様の検討を行って、酸化アルミニウム膜１２又は導電体層５２厚さを決定する必要がある。
【００８５】
また、導電体層５２をＣｒから構成し、イオンビーム支援成膜法により形成する場合には、イオンビーム電流により、Ｃｒ膜内の単位厚さ当りの応力σ(シグマ)を調整できる。応力σ(シグマ)により、酸化アルミニウム膜１２又は導電体層５２といった応力補償層としての好適な厚さは変わる。
【００８６】
樹脂部１３は、ＢＣＢ樹脂に限らず、ポリイミドから構成されてもよい。ポリイミドからなる樹脂膜をＩｎＰ基板に単独に形成すると、ポリイミドを塗布した後のベークの際にポリイミドが収縮するため、ＩｎＰ基板は凹型に反ることとなる。したがって、半導体レーザ素子１の樹脂部をポリイミドから構成する場合にも、基板２には凹型に反るよう応力が掛かることになる。しかしながら、半導体レーザ素子１は、酸化アルミニウム膜１２を有しているため、基板２の反りが軽減される。
【００８７】
第１の実施形態においては、絶縁膜１１を介することなく、半導体メサ部１０上に酸化アルミニウム膜１２を直接形成するようにしてもよく、第３の実施形態のおいては半導体メサ部１０上に樹脂部１３を直接に形成することができる。
【００８８】
酸化アルミニウム膜１２および導電体層５２を形成する際、成膜装置１００において、Ａｒイオンを基板２に照射するようにしたが、Ａｒイオンに限らず、酸素イオンを照射するようにしてもよい。
【００８９】
第３の実施形態における導電体層５２はＣｒから構成されたが、タンタル(Ｔａ)、およびモリブデン(Ｍｏ)のいずれから構成されてもよい。また、これら３つの金属のうち２種類又は３種類からなる多層膜であってもよい。このような導電体層を構成する場合には、半導体光素子が形成される基板と同じ基板上にイオンビーム支援成膜法により当該導電体層を成膜し、導電体層となるべき膜に２次元的な圧縮応力が働くよう成膜条件を最適化する必要がある。また、導電体層５２は、Ｔｉ膜を備えることができる。電極がＴｉ膜を備える場合には、２つのＴｉ膜が基板上に設けられる。上層Ｔｉ膜の膜厚は下層Ｔｉ膜の厚さより大きい。この理由は、下層Ｔｉ膜がＡｕのマイグレーションに対するストッパ膜の機能を発揮できる程度の厚さを備えれば十分であるからであり、下層Ｔｉ膜の膜厚はＡｕ膜よりも薄いけれども、上層Ｔｉ膜は、下層Ｔｉ膜の膜厚程度では機能せず、半導体チップの反りを低減できる程度の膜厚を有することが必要であるからである。このことを例示的に説明すれば、下層Ｔｉ膜の厚さは５０ナノメートル程度であり、一方、上層Ｔｉ膜の厚さは、基板の反りを補償するために、８１ナノメートル(８１０オングストローム)以上であることが好ましい。また、上層Ｔｉ膜の厚さは、基板の反りを適切に補償するために、３６５ナノメートル(３６５０オングストローム)以下であることが好ましい。
【００９０】
さらに、イオンビーム支援成膜装置は、上述の成膜装置１００に限定されることはない。成膜装置１００のイオン源１２０は、フィラメントからの電子線によりガスをイオン化する構成を備えるが、冷陰極型またはプラズマ陰極型のイオン源であってよい。また、導電体層５２は、イオンビーム支援成膜法でなく、スパッタ法により成膜されてよい。成膜条件は、導電体層となるべき膜に２次元的な圧縮応力が働くよう成膜条件を予め求めることが必要である。
【００９１】
例えば、基板が反っていると、フォトリソグラフィにおいて露光精度が悪化する。また、チップ化工程の前に、基板の裏面を研磨する際に基板が割れてしまうこともある。さらに、チップ化工程においては、基板を劈開する際に基板面内で均一な力を加えることができなくなり、劈開できない部分が生じたり、チップが欠けたりしてしまう場合もある。しかしながら、本実施の形態によれば、基板の反りを低減できる構成を有する半導体光素子、及び半導体光素子の製造方法が提供される。
【００９２】
好適な実施の形態において本発明の原理を図示し説明してきたが、本発明は、そのような原理から逸脱することなく配置および詳細において変更され得ることは、当業者により認識される。すなわち、本実施の形態に示された構成は例示であり、本発明は、本実施の形態に開示された特定の構成に限定されるものではない。例えば、本実施の形態では、これに限定されるものではない。したがって、特許請求の範囲及びその精神の範囲から来る全ての修正および変更に権利を請求する。
【００９３】
【発明の効果】
以上説明したように、本発明に係る半導体光素子によれば、基板の反りを低減できる構成を有する半導体光素子、及び半導体光素子の製造方法が提供される。
【図面の簡単な説明】
【図１】図１は、第１の実施形態による半導体レーザ素子を示す概略図である。
【図２】図２(Ａ)及び図２(Ｂ)は、第２の実施形態による半導体レーザ素子の製造工程を示す図である。
【図３】図３(Ａ)及び図３(Ｂ)は、第２の実施形態による半導体レーザ素子の製造工程を示す図である。
【図４】図４(Ａ)及び図４(Ｂ)は、第２の実施形態による半導体レーザ素子の製造工程を示す図である。
【図５】図５(Ａ)及び図５(Ｂ)は、第２の実施形態による半導体レーザ素子の製造工程を示す図である。
【図６】図６(Ａ)及び図６(Ｂ)は、第２の実施形態による半導体レーザ素子の製造工程を示す図である。
【図７】図７(Ａ)及び図７(Ｂ)は、第２の実施形態による半導体レーザ素子の製造工程を示す図である。
【図８】図８は、酸化アルミニウム膜を形成するに好適な成膜装置の構成を示す概略図である。
【図９】図９は、第３の実施形態の半導体レーザ素子を示す概略図である。
【図１０】図１０(Ａ)及び図１０(Ｂ)は、第３の実施形態の半導体レーザ素子の製造工程を示す図である。
【図１１】図１１(Ａ)及び図１１(Ｂ)は、第３の実施形態の半導体レーザ素子の製造工程を示す図である。
【図１２】図１２(Ａ)及び図１２(Ｂ)は、第３の実施形態の半導体レーザ素子の製造工程を示す図である。
【図１３】図１３は、第５の実施形態の半導体レーザ素子を示す概略図である。
【図１４】図１４は、第５の実施形態の半導体レーザ素子を示す平面図である。
【図１５】図１５(Ａ)は、凹形に反る基板における反り量δの定義を示す図であり、図１５(Ｂ)は、凸形に反る基板における反り量δの定義を示す図である。
【符号の説明】
１,５１・・・半導体レーザ素子、２・・・基板、３・・・バッファ層、３ａ・・・回折格子、４・・・クラッド層、５・・・活性層、６・・・クラッド層、７・・・キャップ層、８・・・コンタクト層、９・・・電流狭窄部、１０ａ・・・第１メサ、１０ｂ・・・第２メサ、１０・・・半導体メサ部、１１・・・絶縁膜、１２・・・酸化アルミニウム膜、１３・・・樹脂部、１４・・・電極、１５・・・電極、３０・・・バッファ膜、３１,３２,３３・・・マスク層、３４・・・レジストマスク層、４０・・・クラッド膜、５０・・・活性層膜、５２・・・導電体層、６０・・・クラッド膜、７０・・・キャップ膜、８０・・・コンタクト膜、９０・・・半導体埋込層、１００・・・成膜装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor optical device and a method for manufacturing the semiconductor optical device.
[0002]
[Prior art]
In an optical communication system that provides high-speed optical communication, semiconductor optical elements such as semiconductor laser elements are required to operate at high speed as the communication speed increases. This semiconductor optical device has a semiconductor optical waveguide including an active layer, and trenches provided on both sides of the semiconductor optical waveguide.
[0003]
[Problems to be solved by the invention]
In order to operate the semiconductor optical device at higher speed, it is necessary to reduce the parasitic capacitance in the semiconductor optical device. The inventor has considered a structure in which a semiconductor optical waveguide of a semiconductor optical element is embedded with a resin body in order to reduce parasitic capacitance. When a semiconductor optical device having this structure is manufactured, a resin body that embeds the semiconductor optical waveguide portion is formed on the substrate. Since the resin body is formed to a height that is approximately the same as the height of the semiconductor optical waveguide, the resin is applied to a thickness of about several microns. Therefore, the resin body cannot be made thinner. In addition, after the resin is applied, the entire substrate is subjected to heat treatment in order to cure the resin body. By this heat treatment, the resin body shrinks. The force due to the thick resin body is transmitted to the substrate, and the substrate warps in a concave shape. Since the warpage of the substrate has various adverse effects, it is required to reduce the amount of warpage of the substrate.
[0004]
Therefore, an object of the present invention is to provide a semiconductor optical device having a configuration capable of reducing the warpage of the substrate, and a method for manufacturing the semiconductor optical device.
[0005]
[Means for Solving the Problems]
One aspect of the present invention relates to a semiconductor optical device. The semiconductor optical device includes a substrate, a semiconductor mesa portion, and a resin body. The semiconductor mesa portion includes an active layer composed of a III-V group compound semiconductor and is provided on the substrate. The resin body is provided on the substrate so as to embed the semiconductor mesa portion, and acts to warp the substrate. Therefore, the substrate of this semiconductor optical device is warped. However, the semiconductor optical device further includes a thin film provided between the resin body and the semiconductor mesa portion. Since the thin film is provided so as to weaken the force applied to the substrate by the resin body, the warpage of the substrate of the semiconductor optical device can be reduced.
[0006]
  The semiconductor optical device includes a substrate, a semiconductor mesa portion, a resin body, and a thin film. The semiconductor mesa portion includes an active layer composed of a III-V group compound semiconductor and is provided on the substrate. The resin body is provided so as to embed the semiconductor mesa portion. The thin film includes an aluminum oxide film, and the aluminum oxide film is provided between the resin body and the semiconductor mesa portion.In the aluminum oxide film, a compressive stress is generated so as to compensate for the tensile stress generated in the resin body due to thermal contraction during the formation of the resin body.The aluminum oxide film is useful for weakening the force that the resin body applies to the substrate. Therefore, the warpage of the substrate of this semiconductor optical device is reduced.
[0007]
The semiconductor optical device can further include an insulating silicon compound film between the thin film and the semiconductor mesa portion. By providing such an insulating silicon compound film, the mesa portion can be protected, so that the reliability of the semiconductor optical device can be improved. Although the addition of the insulating silicon compound film serves to increase the warpage of the substrate, the thin film serves to weaken the force applied to the substrate by the insulating silicon compound film and the resin body.
[0008]
  The semiconductor optical device of the present invention includes a substrate, a semiconductor mesa portion, a resin body, an electrode,Conductor filmIs provided. In this semiconductor optical device, the semiconductor mesa portion is provided on the substrate and includes an active layer composed of a III-V compound semiconductor. The resin body is provided on the substrate so as to embed the semiconductor mesa portion, and acts to warp the substrate. The electrode is disposed on the resin body and the semiconductor mesa portion and is electrically connected to the semiconductor mesa portion.Conductor filmIs disposed on the resin body and the semiconductor mesa portion,The conductive film is subjected to compressive stress so as to compensate for the tensile stress generated in the resin body due to thermal contraction during the formation of the resin body.. Therefore,Conductor filmIs useful for reducing the warpage of the substrate of the semiconductor optical device.The conductor film is made of one or more elements of chromium, tantalum, and molybdenum. These metals and their alloys are useful for reducing the warpage of the substrate of the semiconductor optical device.
[0010]
The semiconductor optical device of the present invention can further include an insulating silicon inorganic compound film between the resin body and the semiconductor mesa portion. By providing such an inorganic insulating film, the mesa portion can be protected, so that the reliability of the semiconductor optical device can be improved. The amount of warpage of the substrate is reduced by the conductor layer.
[0011]
The substrate may be an InP semiconductor substrate, and the semiconductor mesa portion preferably further includes a cladding layer and a diffraction grating. The cladding layer serves to confine light in the active layer. The diffraction grating is provided to optically couple with the active layer. According to this structure, a semiconductor laser device in which the warpage of the substrate is reduced is provided.
[0012]
  Another aspect of the present invention is a method for manufacturing a semiconductor optical device. This method includes (a) a step of forming a semiconductor mesa portion having an active layer made of a III-V group compound semiconductor on a substrate, and (b) a step of forming an aluminum oxide film on the semiconductor mesa portion and the substrate. And (c) forming a resin body on the aluminum oxide film.In this manufacturing method, the aluminum oxide film is formed under film forming conditions that generate a compressive stress that compensates for the tensile stress generated by thermal shrinkage when forming the resin body when the film is formed alone on the substrate..
[0013]
In the manufacturing method that does not include the step of forming the aluminum oxide film, the warpage of the substrate increases due to the shrinkage of the resin body after the step of forming the resin body. However, since the aluminum oxide film is formed between the resin portion and the mesa portion, the warpage of the substrate caused by the resin body is reduced.
[0014]
  In this manufacturing method, the aluminum oxide film is preferably formed by an ion beam assisted film formation method.When the aluminum oxide film is formed by an ion beam assisted film formation method, a film capable of reducing the warpage of the substrate generated in the resin body can be formed. In the ion beam assisted film formation method, when the ion beam energy is adjusted, the stress of the thin film to be formed changes, so that the warpage of the substrate can be reduced.
[0015]
A method of manufacturing a semiconductor optical device includes: (a) a step of forming a semiconductor mesa portion having an active layer composed of a III-V compound semiconductor on a substrate; and (b) a semiconductor mesa portion under predetermined film forming conditions. And a step of forming an aluminum oxide film on the substrate, and (c) a step of forming a resin body on the aluminum oxide film. The predetermined condition is determined so that a two-dimensional compressive stress is generated when an aluminum oxide film is independently formed on the substrate. When the aluminum oxide film is formed under these film formation conditions, the warpage of the substrate caused by the resin body can be reduced.
[0016]
A method of manufacturing a semiconductor optical device includes: (a) a step of forming a semiconductor mesa portion having an active layer made of a III-V group compound semiconductor on a substrate; and (b) a step of forming a semiconductor mesa portion on the substrate on which the semiconductor mesa portion is formed. A step of forming a resin body, (c) a step of forming a metal film on the resin body and the semiconductor mesa portion, and (d) a step of forming an electrode electrically connected to the semiconductor mesa portion from the metal film, (e) forming a conductive film composed of one or more elements of chromium, tantalum, and molybdenum on the resin body and the semiconductor mesa portion; and (f) forming a conductor from the conductive film; . After the step of forming the resin body, the substrate warps due to the shrinkage of the resin body. However, after the conductive film is formed on the resin body and the semiconductor mesa portion, the warpage of the substrate caused by the resin body is reduced. In the method for manufacturing a semiconductor optical device, if the conductive film is formed by an ion beam assisted film formation method, a film capable of reducing the warpage of the substrate caused by the resin body can be formed.
[0017]
  A method for manufacturing a semiconductor optical device includes: (a) a step of forming a semiconductor mesa portion having an active layer made of a III-V compound semiconductor on a substrate; and (b) a substrate formed after the semiconductor mesa portion is formed. A step of forming a resin body thereon; (c) a step of forming a metal film on the resin body and the substrate; and (d) a conductive film composed of one or more elements of chromium, tantalum, and molybdenum. Forming on the resin body and the substrate, (e) forming a conductor from the conductive film, and (f) forming an electrode electrically connected to the semiconductor mesa portion from the metal film, . ThisIn this manufacturing method, when a conductive film is formed alone on a substrate, the film can be formed so as to generate a two-dimensional compressive stress that compensates for the tensile stress generated by thermal shrinkage when forming the resin body. Form with conditions.After the step of forming the resin body, the substrate warps due to the shrinkage of the resin body. However, when the conductive film is formed under the above film formation conditions, the warpage of the substrate caused by the resin body is reduced after the conductive film is formed over the resin body and the semiconductor mesa portion. In the method for manufacturing a semiconductor optical device, if the conductive film is formed by an ion beam assisted film formation method, a film capable of reducing the warpage of the substrate caused by the resin body can be formed.
[0018]
  The method for manufacturing a semiconductor optical device of the present invention can further include a step of forming another metal film on the metal film after the step of forming the metal film.Metal filmIs formed by electron beam evaporation.
[0019]
When a metal film is deposited on a resin body by a film forming method using high energy particles, a leakage current may occur at the interface of the resin body exposed to the high energy particles. However, electron beam evaporation prevents an increase in leakage current. In electron beam evaporation, if the acceleration voltage of the electron beam is increased to bring the stress of the metal film within a desired range, a damage layer is formed on the sidewall of the semiconductor mesa due to the high energy of the electron beam. Sometimes. This damaged layer may be a path for flowing a leak current. In order to prevent a leak path from being formed, an insulating film is formed around the mesa by a CVD method such as a low-damage thermal CVD (atmospheric pressure CVD) method.
[0020]
In a metal film formed using high energy particles, a damage layer may be formed on the semiconductor surface of the contact layer due to the high energy particles, and the contact resistance between the metal electrode and the semiconductor layer may increase. In order to prevent this increase, an electrode film such as Ti or Ti / Pt / Au is formed in advance by a vapor deposition method using low energy particles, and an electrode film such as Cr is formed on the electrode film by an ion beam assisted vapor deposition method. It is preferable to form.
[0021]
In addition, for the resin layer, 8.01 × 10^-17When an electrode film is formed on the surface of the resin layer by a film forming method using high energy particles exceeding Joule (500 eV), the C—C bond of the resin is broken, and a weak layer is formed on the surface of the resin layer in terms of structure. May be. The adhesion of the electrode to the layer in which the C—C bond is broken is lowered, and it is not preferable to apply the film forming method using the high energy particles to the device. Therefore, after forming an electrode film on the resin layer by a film forming method using low energy particles, it is desirable to form a metal film by an ion beam assisted film forming method as a stress relaxation layer. Since the stress of the metal film formed by the ion beam assisted deposition method is determined by the ion current and the acceleration voltage, it is necessary to form the metal film under the condition of the ion current that can obtain an appropriate stress at a low acceleration voltage. There is.
[0022]
The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, embodiments of a DFB (Distributed Feedback) type semiconductor laser device for optical communication will be described with reference to the accompanying drawings, thereby disclosing a semiconductor optical device and a method for manufacturing the semiconductor optical device of the present invention. Where possible, the same parts are denoted by the same reference numerals.
[0024]
(First embodiment)
FIG. 1 is a schematic view showing a semiconductor laser device according to an embodiment of the present invention. The semiconductor laser element 1 includes a substrate 2, a semiconductor mesa unit 10, an insulating film 11, a thin film such as an aluminum oxide film 12, a resin body 13, a first electrode 14, and a second electrode 15. The thin film can be, for example, an insulating film. Examples of the substrate 2 include III-V compound semiconductor substrates such as n-type InP semiconductor substrates. The semiconductor mesa unit 10 is provided on the substrate 2. The insulating film 11 is provided so as to cover the substrate 2 and the side surface of the semiconductor mesa unit 10. The aluminum oxide film 12 is provided on the insulating film 11. The resin body 13 is provided on the aluminum oxide film 12. The electrode 14 is disposed on the resin portion 13 and is provided so as to be electrically connected to the semiconductor mesa portion 10. The electrode 15 is provided on the back surface of the substrate 2. In order to obtain the semiconductor laser element 1, a wafer on which a plurality of elements are formed is divided into substrates 2.
[0025]
The semiconductor mesa unit 10 is provided on the buffer layer 3 provided on the substrate 2, the cladding layer 4 provided on the buffer layer 3, the active layer 5 provided on the cladding layer 4, and the active layer 5. The clad layer 6, the cap layer 7 provided on the clad layer 6, the contact layer 8 provided on the cap layer 7, and a current confinement portion 9 are provided. In the semiconductor mesa unit 10, the cladding layer 4, the active layer 5, and the cladding layer 6 are stacked on the substrate to form a stacked unit. The stacked portion has a side surface extending along a predetermined axis. The current confinement portion 9 is provided on the substrate adjacent to the stacked portion, and acts as an electrical barrier that guides current to the stacked portion. A diffraction grating 3 a is provided on the boundary surface between the buffer layer 3 and the cladding layer 4.
[0026]
For the above layers 3 to 8 and the current confinement portion 9, if materials and dopants are exemplified
-Substrate 2: n-type InP substrate
Buffer layer 3: n-type (Si doped) InP
Clad layer 4: n-type (Si-doped) InP
Active layer 5: undoped GaInAsP
Clad layer 6: p-type (Zn-doped) InP
Cap layer 7: p-type (Zn-doped) InP
Contact layer 8: p-type (Zn-doped) InGaAs
Current constriction 9: high resistance (Fe doped) InP
It is.
[0027]
The active layer 5 may include an MQW (Multi-Quantum Well) structure or an SQW (Single Quantum Well) structure. The wavelength of the photoluminescence light of the active layer 5 can be about 1.55 μm. Further, since the cladding layers 4 and 6 are made of InP, they have a larger band gap energy and a smaller refractive index than the active layer 5. Therefore, the clad layers 4 and 6 serve as a clad layer for confining light in the active layer 5 and also as a barrier layer for confining carriers in the active layer 5.
[0028]
Since the current confinement part 9 is composed of Fe-doped InP as described above, it has a higher resistivity than the cladding layers 4 and 6 and the active layer 5. For this reason, the current confinement part 9 works to guide the current to the active layer 5.
[0029]
The electrode 14 is provided so as to be electrically connected to the contact layer 8 of the semiconductor mesa unit 10. The electrode 14 is composed of a laminate composed of, for example, a titanium (Ti) layer, a platinum (Pt) layer, and a gold (Au) layer. In a preferred embodiment, a metal layer such as a Ti layer or a Pt layer can be formed by an electron beam evaporation method. According to the electron beam evaporation method, the stress acting on the electrode 14 can be reduced. The contact layer 8 has a carrier concentration such that ohmic contact between the electrode 14 and the contact layer 8 can be easily realized. The electrode 15 formed on the back surface of the substrate 2 is in ohmic contact with the substrate 2.
[0030]
In the semiconductor laser element 1, the insulating layer 11 is made of silicon oxide (SiO₂) And an insulating silicon compound film. SiO₂When the film is deposited alone on the InP substrate, the InP substrate warps in a concave shape. This phenomenon is caused by SiO₂It shows that tensile stress is working in the film. Therefore, even when applied to the semiconductor laser device 1, SiO 2₂A tensile stress is generated in the film.
[0031]
The resin portion 13 is provided to reduce the capacitance of the semiconductor laser element 1 and protect the semiconductor mesa portion 10. In the semiconductor laser element 1, the resin portion 13 is made of a photosensitive resin such as bisbenzocyclobutene (BCB) resin or polyimide resin. For example, the BCB film shrinks during baking. When the BCB film is formed alone on the InP substrate, the tensile stress generated in the BCB film warps the InP substrate into a concave shape. Therefore, even if the BCB film is applied to the semiconductor laser element 1, a tensile stress is generated in the resin portion 13.
[0032]
Referring to FIG. 1, an aluminum oxide film 12 is provided between the insulating film 11 and the resin portion 13. In a preferred embodiment, the aluminum oxide film 12 is formed by an ion beam assisted film formation method. The conditions for forming the aluminum oxide film 12 are determined so that compressive stress is generated in the aluminum oxide film formed on the same type of substrate as the substrate 2. That is, the substrate warps in a convex shape. Therefore, the tensile stress generated in the insulating film 11 and the resin portion 13 is partially canceled by the aluminum oxide film 12. In other words, the aluminum oxide film 12 functions as a stress compensation layer that compensates for the stress generated in the insulating film 11 and the resin portion 13. Therefore, such an aluminum oxide film 12 is useful for reducing the warpage of the substrate 2.
[0033]
(Second Embodiment)
A method of manufacturing a semiconductor laser device according to an embodiment of the present invention will be described with reference to the drawings. In the second embodiment, a case where the semiconductor laser device 1 of the first embodiment is manufactured will be described.
[0034]
(First epitaxial process)
A substrate 2 such as a semiconductor substrate, for example, an n-type InP wafer is prepared. The substrate 2 may have a thickness of 300 to 400 micrometers (μm) and a diameter of about 50 millimeters (mm). A buffer film 30 is formed on the substrate 2 as shown in FIG.
[0035]
(Diffraction grating forming process)
Referring to FIG. 2B, the diffraction grating 3 a is formed on the buffer film 30. The diffraction grating 3 a is obtained by forming periodic stripe-shaped recesses in the surface layer portion of the buffer film 30. The period of the diffraction grating 3 a is determined based on the wavelength of the laser light to be emitted from the semiconductor laser element 1.
[0036]
(Second epitaxial process)
Referring to FIG. 3A, a cladding film 40, an active layer film 50, and a cladding film 60 are formed on the buffer film 30 on which the diffraction grating 3a is formed. These films are grown epitaxially. For the epitaxial growth, an organic metal vapor phase epitaxy (OMVPE) can be used. Illustrating the material, dopant, and thickness of the semiconductor films 30, 40, 50, 60,
[0037]
-Substrate 2: n-type InP wafer
Buffer film 30: Si-doped InP, 300 nanometers (nm)
Clad film 40: Si-doped InP, thickness 550 nanometers
Active layer film 50: undoped GaInAsP, thickness 300 nm
Clad film 60: Zn-doped InP, thickness 200 nanometers
It is.
[0038]
(First mesa formation process)
Referring to FIG. 3B, a semiconductor stripe 10a is formed. The semiconductor stripe 10a is formed as follows. A mask layer 31 is formed on the cladding film 60. The mask layer 31 is preferably a hard mask made of an insulating silicon inorganic compound film. Etching is performed using a bromomethanol solution using the mask layer 31 to obtain the semiconductor stripe 10a. The semiconductor stripe 10 a has a clad layer 4, an active layer 5, and a clad layer 6. After the etching process, the semiconductor stripe 10a is formed in the first region on the main surface of the buffer layer 30, and there are second and third regions on both sides of the first region. The buffer film 30 is exposed in the region. In order to form the semiconductor stripe 10a, an etching gas (CH_Four/ H₂Or CH_Four/ H₂/ Cl₂) Can be applied.
[0039]
(Semiconductor embedded layer formation process)
Referring to FIG. 4A, the semiconductor stripe 10 a is buried with the semiconductor buried layer 90. The semiconductor buried layer 90 is used when a current confinement portion is formed in a later process. The semiconductor buried layer 90 is grown by OMVPE with Fe-doped InP on the side surfaces of the substrate 2 and the semiconductor stripe 10a. After the semiconductor buried layer 90 is grown, the mask layer 31 is removed.
[0040]
(Third epitaxial process)
Referring to FIG. 4B, a cap film 70 and a contact film 80 are formed on the semiconductor stripe 10 a and the semiconductor buried layer 90. Illustrating the materials, dopants, and thicknesses of these films,
[0041]
Cap film 70: Zn-doped InP, thickness 200 nanometers
Contact film 80: Zn-doped InGaAs, 500 nanometers
It is.
[0042]
(Second mesa formation process)
Referring to FIG. 5A, a semiconductor mesa unit 10 is formed. The semiconductor mesa unit 10 is formed as follows. That is, first, the mask layer 32 is formed on the contact film 80. Using the mask layer 32, the buffer film 30, the semiconductor buried layer 90, the cap film 70, and the contact film 80 are wet etched until the substrate 2 is exposed. In order to etch the buffer film 30, the semiconductor buried layer 90, and the cap film 70 made of InP, a mixed liquid of hydrochloric acid and pure water can be used as an etching liquid. Further, in order to etch the contact film 80 made of InGaAs, a mixed solution of sulfuric acid, hydrogen peroxide solution and pure water can be used.
[0043]
The semiconductor mesa portion 10 was formed by etching. The semiconductor mesa unit 10 includes a semiconductor stripe 10 a including an active layer 5 extending in a predetermined axial direction, a buffer layer 3 formed from a buffer film 30, a cap layer 7 formed from a cap film 70, and a contact film 80. The contact layer 8 is formed, and the current confinement portion 9 is formed from the semiconductor buried layer 90.
[0044]
The contact film 80, the cap film 70, the clad film 60, the active layer film 50, the clad film 40, and the buffer film 30 are etched to form trenches extending in a predetermined axial direction, and the semiconductor mesa is formed by these trenches. The part 10 may be defined.
[0045]
(Insulating film formation process)
Referring to FIG. 5B, an insulating film 11 is formed so as to cover the semiconductor mesa unit 10 and the substrate 2. The insulating film 11 is formed by, for example, a CVD method. The thickness of the insulating film 11 is about 350 nanometers, for example. The insulating film 11 is made of SiO.₂Insulating silicon inorganic compound such as silicon nitride or silicon oxynitride. Materials such as SiN and SiON are also films that apply tensile stress.
[0046]
(Aluminum oxide film formation process)
Referring to FIG. 6A, a thin film such as an aluminum oxide film 12 is formed on the insulating film 11. Subsequently, a procedure for forming an aluminum oxide film using an ion beam assisted film forming apparatus will be described.
[0047]
FIG. 8 is a schematic view showing an ion beam assisted film forming apparatus for forming the aluminum oxide film 12. The film forming apparatus 100 includes a vacuum chamber 101, a vacuum pump 102 connected to the vacuum chamber 101, and a main valve 103 provided between the vacuum chamber 101 and the vacuum pump 102. The film forming apparatus 100 also includes a substrate holder 111 that holds the substrate 2, a raw material holder 112 that holds the raw material S, and a shutter provided between the substrate holder 111 and the raw material holder 112 inside the vacuum chamber 101. 110 and a filament 113 as a generation source of the electron beam E1 irradiated to the raw material S. The film forming apparatus 100 also includes a cylinder 141 in which a gas serving as an ion beam source is filled outside the vacuum chamber 101, and a flow rate controller 142 that controls the flow rate of the gas from the cylinder 141. The cylinder 141 includes argon (Ar) gas or oxygen (O₂) Filled with gas. The flow rate controller 142 includes a mass flow rate regulator 142a and a pressure regulator 142b. Further, the film forming apparatus 100 includes an ion source 120 that ionizes a gas from the cylinder 141 and supplies the gas to the substrate 2. A power supply 131 is connected to the ion source 120. The power source 131 includes a variable voltage source 131a and an ammeter 131b. The counter electrode (not shown) is provided so as to face the filament, and is used to accelerate the electron flow from the filament. The gas is ionized by the electron flow, and the ionized gas is accelerated by an acceleration electrode (not shown) and reaches the substrate 2.
[0048]
Using the film forming apparatus 100, the aluminum oxide film 12 is formed as follows. The substrate 2 on which the insulating film 11 is formed is attached to the substrate holder 111, and Al₂O_ThreeA raw material S such as pellets is supplied to the raw material holder 112. 2 × 10 in the vacuum chamber 101^-2After evacuating to a degree of vacuum of about Pa, the raw material S is heated. The heating is performed by causing a predetermined current to flow through the filament 113 and radiating an electron beam Es from the filament 113 to the raw material S. By heating, from raw material S to Al₂O_ThreeAre released. Ar gas is supplied from the cylinder 141 at a predetermined flow rate, and a predetermined ion beam current is supplied from the power source 131 to the ion source 120. With this current, Ar ions are emitted from the ion source 120. When the shutter 110 is opened, an aluminum oxide film is formed on the substrate 2.
[0049]
The growth conditions such as the current flowing to the filament 113, the Ar gas flow rate, the ion beam current, the degree of vacuum in the vacuum chamber 101, and the film formation time are determined when the aluminum oxide film is formed on a substrate substantially equivalent to the substrate 2. It is determined so that a two-dimensional compressive stress is generated in the aluminum oxide film. Equivalent substrate means that the material, thickness and diameter are approximately equal to substrate 2.
[0050]
(Resin part forming process)
A process of forming the resin portion 13 will be described with reference to FIG. A BCB resin is applied on the aluminum oxide film 12. When this BCB resin is subjected to heat treatment, the BCB resin is cured. Examples of the heat treatment conditions include a heat treatment temperature of about 250 degrees Celsius (° C.) and a heat treatment time of about 1 hour. In the BCB resin, the resin portion 13 is formed so as to bury the semiconductor mesa portion 10 covered with the aluminum oxide film 12 and the insulating film 11. For example, the thickness of the BCB resin is preferably adjusted so that the thickness after the heat treatment is about 7 micrometers (μm). Thus, the process for forming the resin portion 13 is completed.
[0051]
(Electrode formation process)
As shown in FIG. 7A, a mask layer 33 is formed on the resin portion 13. The mask layer 33 has an opening 33a in a portion where an electrode is to be formed. Using the mask layer 33, the resin portion 13, the aluminum oxide film 12, and the insulating film 11 are etched to form an opening for an electrode. The contact layer 8 is exposed at the bottom of the opening. For example, plasma etching can be used, and CF_Four(Or SF₆) And O₂Such a process gas can be used for etching the resin portion 13. In order to etch the aluminum oxide film 12, Ar and Cl₂Mixed gas or Cl₂In order to etch the insulating film 11, CF can be used as an etching gas._FourCan be used as an etching gas.
[0052]
After removing the mask layer 33, a resist mask layer is formed. The resist mask layer has, for example, the same opening as the electrode shape. With the resist mask layer left, a metal film such as a Ti film, a Pt film, and an Au film is sequentially deposited by electron beam. If the film thickness of each layer is illustrated, the thickness of the Ti film and the Pt film is about 50 nanometers, and the thickness of the Au film is about 450 nanometers. After the deposition, when the resist mask layer 34 is lifted off, the electrode 14 is obtained as shown in FIG. The Ti film is used to prevent migration of Au into the semiconductor region.
[0053]
Next, the back surface of the substrate 2 is polished to a thickness of about 100 micrometers, for example. An electrode 15 is formed on the back surface of the substrate. Since a large number of semiconductor laser elements 1 are formed on the substrate 2, the substrate 2 is cleaved and separated into individual semiconductor laser elements 1.
[0054]
According to the above manufacturing method, the aluminum oxide film 12 is formed between the insulating film 11 and the resin portion 13. In the present embodiment, the aluminum oxide film 12 is formed by an ion beam assisted film formation method. The film forming conditions are determined so that a two-dimensional compressive stress is generated in the aluminum oxide film when the aluminum oxide film is independently formed on the same substrate as the substrate 2. The aluminum oxide film 12 works so as to partially cancel the force exerted on the substrate by the insulating film 11 and the resin portion 13. By this function, the warpage of the substrate 2 is reduced.
[0055]
(Third embodiment)
FIG. 9 is a schematic view showing the semiconductor laser device of the third embodiment, and shows a semiconductor laser device 51 having a resin embedding portion. The semiconductor laser element 51 is different from the semiconductor laser element 1 of the first embodiment in that it has a conductor layer made of chromium (Cr) and does not have the aluminum oxide film 12.
[0056]
The semiconductor laser element 51 will be described in detail with reference to FIG. The semiconductor laser element 51 includes a substrate 2, a semiconductor mesa unit 10, an insulating film 11, a resin unit 13, an electrode 14, an electrode 15, and a conductor layer 52. The substrate 2 is made of n-type InP. The semiconductor mesa unit 10 is provided on the substrate 2. The insulating film 11 covers the upper surface of the substrate 2 and the side surface of the semiconductor mesa unit 10. The resin portion 13 is provided on the insulating film 11. The electrode 14 is electrically connected to the semiconductor mesa unit 10 and disposed on the resin unit 13. The conductor layer 52 can be provided on the resin portion 13 and / or the electrode 14. The electrode 15 is provided on the back surface of the substrate 2.
[0057]
The semiconductor mesa unit 10 in the third embodiment has the same configuration as that of the semiconductor laser device 1 in the first embodiment. The insulating film 11, the resin portion 13, the electrode 14, and the electrode 15 have the same structure as that of the semiconductor laser device 1 of the first embodiment.
[0058]
The conductor layer 52 is made of, for example, Cr. The conductor layer 52 is formed by, for example, an ion beam assisted film formation method. The conductor layer 52 is formed under such a condition that when the conductive film is deposited on a substrate substantially equivalent to the substrate 2, a two-dimensional compressive stress acts on the conductive film. That is, this substrate warps in a convex shape. Therefore, the conductor layer 52 cancels a part of the force exerted on the substrate by the insulating film 11 and the resin portion 13. The amount of warping of the substrate 2 is reduced.
[0059]
Referring to FIG. 9, the conductor layer 52 is formed in substantially the same planar shape as the electrode 14. Although the conductor layer 52 is locally provided on the substrate 2, the conductor layer 52 can be provided almost entirely on the substrate 2 and in a region different from the region where the electrode 14 is formed. Can be formed. The warp of the substrate 2 is also reduced by the conductor layers of these forms.
[0060]
(Fourth embodiment)
Subsequently, a method for manufacturing the semiconductor laser element 51 will be described. As in the first embodiment, the first epitaxial process, the diffraction grating forming process, the second epitaxial process, the first mesa forming process, the semiconductor buried layer forming process, the third epitaxial process, and the second mesa forming process are performed. Carry out in order. As shown in FIG. 10A, an insulating film forming step is performed as in the first embodiment without forming an aluminum oxide film. The insulating film 53 is formed by the insulating film forming step. After the insulating film forming step, the resin portion forming step is performed as in the first embodiment. By the resin portion forming step, the resin portion 13 is formed on the insulating film 11 as shown in FIG.
[0061]
As shown in FIG. 11A, the resin portion 54 and the insulating film 53 are etched to form openings 53 a and 54 a in the insulating film 53 and the resin portion 54. The openings 53 a and 54 a reach the contact layer 8. As shown in FIG. 11B, the mask layer 55 is formed after the openings 53a and 54a are formed. The mask layer 55 can be formed from a resist. The mask layer 55 has an opening 55a. As shown in FIG. 12A, after the mask layer 55 is formed, a metal film 56 such as a Ti film, a Pt film, and an Au film and a conductive film 57 such as a Cr film are formed on the contact layer 8 and the mask layer 55. Evaporate sequentially. For this vapor deposition, the film forming apparatus 100 shown in FIG. 8 can be used. The Cr film is preferably deposited while irradiating the substrate 2 with Ar ions. The Ar ion irradiation conditions are determined so that a compressive stress acts on the Cr film when a Cr film is formed on the same substrate as the substrate 2 alone. The Ti film, Pt film, and Au film are preferably deposited without irradiating the substrate 2 with Ar ions.
[0062]
In the vapor deposition process, a Ti film, a Pt film, and an Au film to be electrodes and a Cr film to be a conductor layer were formed. When the mask layer is lifted off after the deposition, as shown in FIG. 12B, an electrode 56a and a conductor layer 57a are obtained.
[0063]
Next, the substrate 2 is polished from the back surface until the thickness of the substrate 2 reaches about 100 micrometers. An electrode 15 is formed on the polished back surface. In order to obtain the semiconductor laser element 51, the substrate 2 is cleaved.
[0064]
In the present embodiment, the metal layer and the conductive layer are formed by a single lift-off process, but the present invention is not limited to such an embodiment. For example, the metal layer lift-off process can be performed separately from the conductive layer lift-off process. Therefore, the metal layer can be formed to have a shape different from that of the conductive layer, and can be formed in a different region from the conductive layer. Further, the order of the metal film forming step and the conductive film forming step can be interchanged. Furthermore, the order of the metal layer forming step and the conductive layer forming step can be interchanged. In addition, the order of these four steps is set within a range that satisfies the restriction that the metal layer forming step is performed after the metal film forming step and the conductive layer forming step is performed after the conductive film forming step. Can be replaced.
[0065]
(Fifth embodiment)
FIG. 13 is a schematic view showing a semiconductor laser device according to another embodiment of the present invention. FIG. 14 is a plan view showing the semiconductor laser device shown in FIG. As in the third embodiment, the semiconductor laser element 51a includes a conductor layer made of chromium (Cr). The semiconductor laser element 51a includes a substrate 2, a semiconductor mesa unit 10, an insulating film 11, a resin unit 13, an electrode 14a, an electrode 15, and a conductor layer 52a. The semiconductor mesa unit 10 is provided on the main surface of the substrate 2. The semiconductor laser element 51 a has a pair of trench grooves 53, and a resin portion is provided on the trench grooves 53 and the contact layer 8. The electrode 14 a is electrically connected to the semiconductor mesa unit 10 and is disposed on the resin unit 13. The conductor layer 52a is provided on the resin portion 13 and the electrode 14a. The conductor layer 52a is made of, for example, Cr. The conductor layer 52a is formed by, for example, an ion beam assisted film formation method. A part of the force exerted on the substrate by the insulating film 11 and the resin portion 13 is canceled out by the conductor layer 52a. The amount of warping of the substrate 2 is reduced.
[0066]
Referring to FIG. 14, the conductor layer 52a is formed in substantially the same planar shape as the electrode 14a. The conductor layer 52a is provided in a substantially half region of the surface of the resin body 13. According to the conductor layer of this form, the warp of the substrate 2 is reduced. Since the resin body 13 is provided under the conductor layer 52a, the conductor layer 52a having a large area can be provided with an increase that does not cause a practical problem of the parasitic capacitance of the electrode of the semiconductor laser. More specifically, when the semiconductor laser element 51a is divided into two parts by a plane that intersects the main surface of the substrate 20 and passes through the semiconductor mesa unit 10, the conductor layer 52a is divided into one region. And provided on the semiconductor mesa unit 10. The conductor layer 52 a is provided between the pair of trench grooves 53, and extends over one of the pair of trench grooves 53 in one divided portion of the semiconductor laser element 51 a. . As a preferred embodiment, the conductor layer 52a is provided on a region of 70% or more and 90% or less of the surface area of one of the divided portions of the semiconductor laser element 51a. On the other divided part of the semiconductor laser element 51a, the conductor layer 52a does not extend from the semiconductor mesa 10 beyond the trench groove 53. Further, the resin portion may not be provided on the other divided portion of the semiconductor laser element 51a. The conductor layer 52a can be formed in a region different from the region where the electrode 14 is formed.
[0067]
(Sixth embodiment)
In this embodiment, the amount of warpage of the substrate is considered. The semiconductor laser element C is manufactured according to the manufacturing method described in the first embodiment except for the step of forming the aluminum oxide film. As the substrate for the semiconductor laser element C, an n-type InP substrate having a thickness of about 400 micrometers and a diameter of about 50 millimeters is used. An insulating film having a thickness of 350 nanometers is provided on the semiconductor mesa portion and the substrate. A resin portion having a thickness of 7 micrometers is formed on the insulating film. The substrate is polished so that the thickness is about 100 micrometers. The semiconductor laser element C has the same configuration as that of the semiconductor laser element 1 of the first embodiment except that the semiconductor laser element C does not have the aluminum oxide film 12.
[0068]
After the substrate was polished, the amount of warpage δ of the substrate was measured. The amount of warpage δ (delta) of the substrate was found to be 180 micrometers. The warpage amount δ (delta) is defined as shown in FIGS. 15 (A) and 15 (B). 15A and 15B show the substrate S and the film F. FIG. The film F is formed on the substrate S. A film F indicates a semiconductor mesa portion, an insulating film, a resin portion, and an electrode of the semiconductor laser element C.
[0069]
In the manufacturing method of the semiconductor laser element C, after forming an electrode on the back surface of the substrate, the substrate is cleaved by applying a predetermined pressure to the substrate. When a relatively large amount of warpage δ is generated on the substrate, pressure is not applied evenly, so that a portion that is not cleaved may be generated or a chip obtained by cleaving may be lost. According to the knowledge of the present inventor, if the absolute value of the warpage amount δ (delta) is 100 micrometers or less in an InP substrate having a diameter of 50 mm, chip chipping can be sufficiently prevented and the entire substrate surface is cleaved. Is possible.
[0070]
Further, the warpage of the substrate not only affects the cleavage but also adversely affects photolithography. After the resin portion 13 is formed, a mask layer 33 for providing a contact hole for the electrode 14 is formed. At this time, if the substrate 2 is warped by about 100 micrometers, the positional accuracy of the mask layer 33 is different between the central portion and the peripheral portion of the substrate 2. According to the knowledge of the present inventor, when the amount of warpage δ (delta) of the substrate 2 is so large as to exceed 100 micrometers, the mask layer 33 formed in the central portion of the substrate 2 is formed with high positional accuracy. The mask layer 33 formed on the peripheral portion of the substrate 2 may be shifted by about 1 micrometer. Since the width of the semiconductor stripe 10a is 1 to several micrometers, if the position of the mask layer is shifted by about 1 micrometer, the contact resistance of the electrode is greatly affected. If the amount of warp δ of the substrate 2 is 100 micrometers or less, the positional accuracy of the mask layer 33 can be made uniform within the surface of the substrate 2.
[0071]
In order to reduce the warpage amount δ (delta) of the substrate to 100 micrometers or less, the inventor conducted the following investigation. On the same substrate as the substrate 2, SiO₂A film, a BCB resin film, and an aluminum oxide film were formed separately. The aluminum oxide film was formed using the film forming apparatus 100, and the ion beam current at the time of forming the aluminum oxide film was 5 milliamperes and the acceleration energy voltage was 40V. When the warpage amount δ (delta) was measured for each substrate and the stress σ per unit thickness of the film was determined, the following results were obtained.
[0072]
・ SiO₂Membrane: 1.5 × 10⁸ Pa
-BCB film: 1.5 × 10⁷ Pa
Aluminum oxide film: -1 x 10⁸ Pa
According to the knowledge of the present inventor, it is known that the stress in the formed aluminum oxide film greatly depends on the ion beam current. Suitable film forming conditions for the aluminum oxide film can be obtained by adjusting the ion beam current.
[0073]
The stress σ (sigma) per unit thickness was calculated using the following equation (1). The positive sign indicates tensile stress and the negative sign indicates compressive stress.
[0074]
[Expression 1]

When the warpage amount δ (delta) of the substrate of the semiconductor laser element C is about 100 micrometers (μm) after the back surface polishing, the stress acting on the substrate is 85 Pa · m from the equation (1). Therefore, when the thickness of the aluminum oxide film 12 in the semiconductor laser element 1 is t,
[0075]
1.5 × 10⁸Pa x 350 x 10^-9Meter (m)
+ 1.5 × 10⁷Pa x 7 x 10^-6Meter (m)
-1 x 10⁸Pa × t ≦ 85 Pa · m (2)
Is obtained. If you organize this
t ≧ 0.72 micrometers (μm)
It becomes.
[0076]
When the aluminum oxide film 12 in the semiconductor optical device of the first embodiment is thicker, the substrate 2 warps in a convex shape. According to the knowledge of the present inventor, even when the substrate 2 warps in a convex shape, the warpage amount δ needs to be 100 micrometers or less. If the substrate 2 warps in a convex shape and its warpage amount δ is 100 micrometers (μm), the stress becomes −85 Pa · m,
[0077]
−85 Pa · m ≦ 1.5 × 10⁸Pa x 350 x 10^-9Meter (m)
+ 1.5 × 10⁷Pa x 7 x 10^-6Meter (m)
-1 x 10⁸Pa × t (3)
Organize
t ≤ 2.42 micrometers (μm)
It becomes.
[0078]
Therefore, when the thickness t of the aluminum oxide film 12 is 0.68 micrometers or more and 2.38 micrometers or less, the warpage amount δ of the substrate 2 can be made 100 micrometers or less. Further, when the thickness t of the aluminum oxide film 12 is 1.6 micrometers, the total stress becomes zero. In the semiconductor laser device 1, the aluminum oxide film 12 preferably has a thickness of 0.68 micrometers or more and 2.38 micrometers or less.
[0079]
The inventor conducted the same examination on the conductor layer 52 in the semiconductor laser element 51. The results will be described below. SiO₂In addition to the film and the BCB resin film, stress is also obtained for the metal constituting the electrode 14. That is, the stress σ (sigma) per unit thickness of the Ti film, Pt film, and Au film is
[0080]
Ti film: -6 x 10⁸ Pa
・ Pt film: 1 × 10⁹ Pa
Au film: 2 × 10⁷ Pa
It is.
[0081]
According to the experiments by the present inventors, when the Cr film is formed on the InP substrate using the film forming apparatus 100, the tensile stress works when the ion beam current is about 65 milliamperes or less, and the compression occurs when the ion beam current exceeds about 65 milliamperes. Stress works. The stress σ per unit thickness acting on the Cr film is −5 × 10 5 when the ion beam current is 100 mA.⁸ Pa.
[0082]
The inventor uses the value of the stress σ obtained as described above to perform the calculation in the same manner as the above formulas (2) and (3). As a result, the preferred thickness of the conductor layer 52 is 98 nm or more and 438 nm or less. In particular, if the thickness of the conductor layer 52 is 360 nanometers, the total stress can be reduced to zero. When the semiconductor laser element 51 is manufactured, the film formation time is adjusted so that the thickness of the conductor layer 52 is not less than 98 nanometers and not more than 438 nanometers.
[0083]
The semiconductor optical device according to the present invention has been described above with reference to some embodiments. However, the present invention is not limited to these, and various modifications can be made. For example, the semiconductor optical device according to the present invention is not limited to a DFB type semiconductor laser device, but may be a DBR (Distributed Bragg Reflector) type semiconductor laser device or a semiconductor optical amplifier device. Further, it may be an optical integrated device in which a semiconductor optical amplifying element or a semiconductor laser element and a semiconductor modulator for modulating light from this element are provided in the same chip.
[0084]
Although the examination result of the suitable thickness of the aluminum oxide film 12 and the conductor layer 52 was demonstrated, the result shown above is an illustration. It is necessary to determine the thickness of the aluminum oxide film 12 or the conductor layer 52 by performing the same examination as described above based on the thickness of the insulating film and the resin portion constituting the element to be manufactured, the diameter and material of the substrate. is there.
[0085]
When the conductor layer 52 is made of Cr and formed by ion beam assisted film formation, the stress σ (sigma) per unit thickness in the Cr film can be adjusted by the ion beam current. A suitable thickness as a stress compensation layer such as the aluminum oxide film 12 or the conductor layer 52 varies depending on the stress σ (sigma).
[0086]
The resin portion 13 is not limited to BCB resin, and may be made of polyimide. If a resin film made of polyimide is formed alone on an InP substrate, the polyimide contracts during baking after the polyimide is applied, so that the InP substrate warps in a concave shape. Therefore, even when the resin portion of the semiconductor laser element 1 is made of polyimide, the substrate 2 is subjected to stress so as to warp in a concave shape. However, since the semiconductor laser element 1 has the aluminum oxide film 12, the warp of the substrate 2 is reduced.
[0087]
In the first embodiment, the aluminum oxide film 12 may be formed directly on the semiconductor mesa unit 10 without using the insulating film 11. In the third embodiment, on the semiconductor mesa unit 10. The resin part 13 can be directly formed.
[0088]
In forming the aluminum oxide film 12 and the conductor layer 52, the substrate 2 is irradiated with Ar ions in the film forming apparatus 100. However, not only Ar ions but oxygen ions may be irradiated.
[0089]
The conductor layer 52 in the third embodiment is made of Cr, but may be made of any one of tantalum (Ta) and molybdenum (Mo). Moreover, the multilayer film which consists of two types or three types among these three metals may be sufficient. In the case of forming such a conductor layer, the conductor layer is formed by ion beam assisted film formation on the same substrate as the substrate on which the semiconductor optical element is formed, and the film to be the conductor layer is formed. It is necessary to optimize the film forming conditions so that a two-dimensional compressive stress works. The conductor layer 52 can include a Ti film. When the electrode includes a Ti film, two Ti films are provided on the substrate. The film thickness of the upper Ti film is larger than the thickness of the lower Ti film. This is because it is sufficient that the lower layer Ti film has a thickness that can exert the function of the stopper film against the migration of Au. Although the lower layer Ti film is thinner than the Au film, the upper layer Ti film This is because the film does not function as much as the thickness of the lower layer Ti film and needs to have a thickness that can reduce the warpage of the semiconductor chip. Explaining this exemplarily, the thickness of the lower Ti film is about 50 nanometers, while the thickness of the upper Ti film is 81 nanometers (810 angstroms) to compensate for the warpage of the substrate. The above is preferable. The thickness of the upper Ti film is preferably 365 nanometers (3650 angstroms) or less in order to appropriately compensate for the warpage of the substrate.
[0090]
Further, the ion beam assisted film forming apparatus is not limited to the film forming apparatus 100 described above. The ion source 120 of the film forming apparatus 100 has a configuration in which a gas is ionized by an electron beam from a filament, but may be a cold cathode type or a plasma cathode type ion source. Further, the conductor layer 52 may be formed by a sputtering method instead of the ion beam assisted film formation method. Regarding the film formation conditions, it is necessary to obtain the film formation conditions in advance so that a two-dimensional compressive stress acts on the film to be the conductor layer.
[0091]
For example, if the substrate is warped, the exposure accuracy deteriorates in photolithography. In addition, the substrate may be broken when the back surface of the substrate is polished before the chip forming step. Further, in the chip forming process, when the substrate is cleaved, a uniform force cannot be applied within the substrate surface, and a portion that cannot be cleaved may be generated or the chip may be chipped. However, according to the present embodiment, a semiconductor optical device having a configuration capable of reducing the warpage of the substrate and a method for manufacturing the semiconductor optical device are provided.
[0092]
While the principles of the invention have been illustrated and described in preferred embodiments, those skilled in the art will recognize that the invention can be modified in arrangement and detail without departing from such principles. That is, the configuration shown in the present embodiment is an exemplification, and the present invention is not limited to the specific configuration disclosed in the present embodiment. For example, the present embodiment is not limited to this. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.
[0093]
【The invention's effect】
As described above, the semiconductor optical device according to the present invention provides a semiconductor optical device having a configuration capable of reducing the warpage of the substrate, and a method for manufacturing the semiconductor optical device.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a semiconductor laser device according to a first embodiment.
FIG. 2A and FIG. 2B are views showing a manufacturing process of the semiconductor laser device according to the second embodiment.
FIGS. 3A and 3B are views showing a manufacturing process of the semiconductor laser device according to the second embodiment. FIGS.
FIGS. 4A and 4B are views showing a manufacturing process of the semiconductor laser device according to the second embodiment.
FIGS. 5A and 5B are views showing a process for manufacturing a semiconductor laser device according to the second embodiment. FIGS.
FIGS. 6A and 6B are views showing a manufacturing process of the semiconductor laser device according to the second embodiment.
FIGS. 7A and 7B are views showing a manufacturing process of the semiconductor laser device according to the second embodiment. FIGS.
FIG. 8 is a schematic diagram showing a configuration of a film forming apparatus suitable for forming an aluminum oxide film.
FIG. 9 is a schematic view showing a semiconductor laser device according to a third embodiment.
FIGS. 10A and 10B are views showing a process for manufacturing the semiconductor laser device of the third embodiment. FIGS.
FIGS. 11A and 11B are views showing a manufacturing process of the semiconductor laser device of the third embodiment. FIGS.
FIGS. 12A and 12B are views showing a process for manufacturing the semiconductor laser device of the third embodiment. FIGS.
FIG. 13 is a schematic view showing a semiconductor laser device according to a fifth embodiment.
FIG. 14 is a plan view showing a semiconductor laser device according to a fifth embodiment.
FIG. 15A is a diagram showing a definition of a warpage amount δ in a substrate that warps in a concave shape, and FIG. 15B shows a definition of a warpage amount δ in a substrate that warps in a convex shape. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,51 ... Semiconductor laser element, 2 ... Substrate, 3 ... Buffer layer, 3a ... Diffraction grating, 4 ... Cladding layer, 5 ... Active layer, 6 ... Cladding layer 7 ... cap layer, 8 ... contact layer, 9 ... current confinement portion, 10a ... first mesa, 10b ... second mesa, 10 ... semiconductor mesa portion, 11 ... -Insulating film, 12 ... Aluminum oxide film, 13 ... Resin part, 14 ... Electrode, 15 ... Electrode, 30 ... Buffer film, 31, 32, 33 ... Mask layer, 34 ... Resist mask layer, 40 ... Clad film, 50 ... Active layer film, 52 ... Conductor layer, 60 ... Clad film, 70 ... Cap film, 80 ... Contact film , 90... Semiconductor buried layer, 100.

Claims (8)

A substrate,
A semiconductor mesa portion including an active layer made of a III-V compound semiconductor and provided on the substrate;
A resin body provided to embed the semiconductor mesa portion;
A thin film provided between the resin body and the semiconductor mesa portion;
With
The thin film includes an aluminum oxide film ;
A semiconductor optical device in which a compressive stress is generated in the aluminum oxide film so as to compensate for a tensile stress generated in the resin body due to thermal contraction during the formation of the resin body . The semiconductor optical device according to claim 1 , further comprising an insulating silicon compound film between the thin film and the semiconductor mesa portion. A substrate,
A semiconductor mesa portion provided on the substrate and including an active layer made of a III-V compound semiconductor;
A resin body provided on the substrate so as to embed the semiconductor mesa portion;
An electrode disposed on the resin body and electrically connected to the semiconductor mesa unit;
A conductor film disposed on the resin body and composed of one or more elements of chromium, tantalum, and molybdenum;
A semiconductor optical device in which a compressive stress is generated in the conductor film so as to compensate for a tensile stress generated in the resin body due to thermal contraction during the formation of the resin body . Forming a semiconductor mesa portion having an active layer composed of a III-V compound semiconductor on a substrate;
Forming an aluminum oxide film on the semiconductor mesa portion and the substrate;
Forming a resin body on the aluminum oxide film;
With
A method of manufacturing a semiconductor optical device, wherein the aluminum oxide film is formed under a film forming condition that generates a compressive stress that compensates for a tensile stress generated by thermal contraction during the formation of the resin body when the aluminum oxide film is formed alone on a substrate. . The method for manufacturing a semiconductor optical device according to claim 4 , wherein the aluminum oxide film is formed by an ion beam assisted film formation method. Forming a semiconductor mesa portion having an active layer composed of a III-V compound semiconductor on a substrate;
Forming a resin body on the substrate after the semiconductor mesa portion is formed;
Forming a metal film on the resin body and the substrate;
Forming a conductive film composed of one or more elements of chromium, tantalum, and molybdenum on the resin body and the substrate;
Forming a conductor from the conductive film;
Forming an electrode electrically connected to the semiconductor mesa portion from the metal film,
When the conductive film is formed on the substrate alone , the conductive film can be formed so as to generate a two-dimensional compressive stress that compensates for the tensile stress generated in the resin body due to thermal contraction when the resin body is formed. A method of manufacturing a semiconductor optical device, which is formed under film conditions . The method of manufacturing a semiconductor element according to claim 6, wherein the conductive film is formed by an ion beam assisted film formation method. After the step of forming the metal film, further comprising the step of forming another metal film on the metal film,
The method of manufacturing a semiconductor optical device according to claim 6 , wherein the metal film is formed by an electron beam evaporation method.

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