JPH02312291A - Manufacture of semiconductor laser - Google Patents

Abstract

PURPOSE:To improve a semiconductor laser of this design in dimensional accuracy and reproducibility by a method wherein a vertical plane used for the resonator mirror of a semiconductor laser and an inclined plane used for deflection are processed through a dry etching method using hydrocarbon gas. CONSTITUTION:An insulating film of silicon dioxide or silicon nitride is formed on the surface of a semiconductor laser crystal substrate 1, a window is provided to the film 2, and a groove 11 provided with vertical side faces 11a and 11b is formed on the surface of the substrate 1 through a reactive ion etching method using a mixed gas of hydrogen and methane or ethane as an etching gas and the film 2 as a mask. Then, the etching mask is removed, and side walls 6a and 6b provided with inclined planes are formed through a reactive etching method, using an insulating film 13 of silicon dioxide or silicon nitride provided with a window which covers the side wall 11a of the groove 11 but does not cover the other side wall 11b as a mask and hydrocarbon gas such as methane or ethane not mixed with hydrogen as an etching gas. As mentioned above, a semiconductor laser of this design is formed through a dry etching method, so that it is improved in dimensional accuracy and reproducibility.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a method for manufacturing a surface-emitting semiconductor laser that integrates a reflecting surface that deflects the emitted light of the semiconductor laser in a direction perpendicular to the surface of a substrate. It is something.

[Conventional technology]

Figure 5 shows, for example, Liu and Walbor, Applied Physics Letters No. 46 JL No. 2°p.
115-117 (1985) ((Z, L, Liau
and J.N., Walpole.

Applied Physics Letters,
Vol, 46. No, 2. p, 115-117 (19
85) is a perspective view of the conventional surface-emitting semiconductor laser shown in ), in which l is an n-EnP substrate, 3 is a Ga1nAsP active layer, 4 is a p-InP cladding layer,
16 is the p-electrode Au/Zn (gold/zinc), 17 is the n-electrode Au/Sn (gold/tin), 18 is the radiation surface (45 degrees) reflecting mirror, and 9 is the laser beam emitted from the semiconductor laser. be.

Next, a method for manufacturing this conventional surface-emitting type semiconductor laser will be explained using FIG. 6.

First, on an n-1nP substrate 1, an n-Ga InAsP stop etch layer 19, an n-1nP buffer layer 2, a Ga1n
AsP active layer 3, p-1nP cladding II4, p-1n
Phosphorsilicate glass (PSG) 21 is applied as an etching mask to the wafer on which the P cap layer 20 has been grown, and a window is opened.

Then, with the first etching solution, p-1nP camp N
20. Machining and notching the p-rnP cladding N4, and
The Ga1nAsP active layer 3 is etched with an etching solution to form a groove 11 having vertical sides.

Furthermore, one phosphosilicate glass (PSG) on this groove 11
Remove a part of the mask 21 and use the etching liquid again.
If etching is performed in the same manner, a shape with a stepped cross section will be obtained.

Next, the phosphosilicate glass (PSG) mask 21 is removed, the wafer is placed in a furnace, and hydrogen (H2) and phosphine (PH3) are removed.
) When heat treatment is performed at 740° C. in an atmosphere, the step shape becomes smooth due to the mass transport phenomenon and becomes paraboloidal. Titanium
) and gold (Au) were deposited on this paraboloid to fabricate the reflecting mirror 18, and Au/Z was deposited for the p-electrode and n-electrode, respectively.
By depositing n16 and A u /5n17, a surface emitting type semiconductor laser is completed. The laser beam emitted from the active layer 3 is transmitted through the parabolic reflecting mirror (45 degree reflecting mirror) 1B.
It is reflected by the wafer and taken out in a direction perpendicular to the wafer.

[Problem to be solved by the invention]

Since the conventional surface-emitting type semiconductor laser is manufactured as described above, the shape of the parabolic reflector depends on the thickness of the n-InP buffer layer 2, the p-1nP cladding layer 4, and the p-1nP cap Jii 20. However, crystals have problems with reproducibility, and because a chemical etching method is used for processing, there are problems with variations in shape.

This invention was made to solve the above-mentioned problems, and it is a surface-emitting semiconductor that can produce a good reflective surface with high dimensional accuracy even if the layer thickness of the laser crystal changes. The purpose of this invention is to provide a method for manufacturing a laser.

[Means to solve the problem]

The method for manufacturing a surface-emitting semiconductor laser according to the present invention processes the vertical plane for the resonator mirror and the 45-degree plane for deflection of the semiconductor laser without using chemical etching and using hydrocarbon-based gas as the etching gas. This is done by dry etching using.

[Effect]

In this invention, since the laser resonator mirror and the deflecting mirror are formed by dry etching, it is possible to obtain products with high dimensional accuracy and excellent reproducibility.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is an n-1nP substrate, 2 is an nT n
P buffer layer, 3 is Ga1nAsP active layer, 4 is p-
InP cladding layer, 5 is P Ga1nAsP cap layer, 6 is 45 degree reflective surface, 7 is gold/chromium for p-1 electrode (
8 is gold/nickel/gold-germanium (Au/N)/AuGe) for an n-electrode, and 9 is a laser beam emitted from a semiconductor laser.

m-V group compound semiconductors such as InP and GaAs, and Ga 1
Mixed crystal semiconductors such as 'nAs and Ga InAs P are etched using methane (CH4) or ethane Cc using a silicon dioxide (SiO□) or silicon nitride (SiNx) film as an etching mask.
When reactive ion etching is performed using a mixed gas of a hydrocarbon gas such as tH&) and hydrogen (H2) as an etching gas, a groove having vertical sidewalls can be formed. At this time, the silicon dioxide (Si0,) JJi of the mask is not etched, and a hydrocarbon-based polymer is formed on the crotch.

In addition, methane (CH
4) Alternatively, if only a hydrocarbon gas such as ethane (CZ H&) is used, not only the ■-V group compound semiconductor but also the silicon dioxide (SiO□) film is etched. At this time, the Si0g film not only decreases in film thickness, but also undergoes etching in the lateral direction from the edge and recedes, so that the side walls of the groove of the II[-V group compound semiconductor have an inclined angle. This is particularly noticeable when the edge of the SiO□ film has an inclined angle.

The present invention utilizes the etching characteristics of this IV group compound semiconductor, and a manufacturing method according to an embodiment of the present invention will be described below with reference to FIG.

First, an n-1nP buffer layer 2 is placed on an n-1nP substrate 1.
, Ga1nAsP active layer 3, p-1nP cladding layer 4,
After epitaxially growing the p-GaInAsP layer cap 5 and processing the Ga1nAsP active layer 3 into a stripe shape, next to the active layer, [nPN with a large refractive index and forbidden band width] is regrown, and a buried structure (Bu
A wafer for a semiconductor laser is manufactured.

A silicon dioxide (SiO□) film 10 is deposited on this wafer as a dry etching mask by plasma chemical vapor deposition (P
- CVD), etc., and the window is opened using photolithography (photoengraving) technology (FIG. 2(a)).

Next, using a reactive ion etching method using a mixed gas of ethane (Cz Hb ) and hydrogen (H2) as an etching gas, vertical etching is performed to a depth that etches a part of the p-1nP cladding layer 4. Side wall 11a, Ilb
A groove 11 having a diameter is formed (FIG. 2(b)).

Next, using a buffered fluoric acid (BHF) solution, SiO□l!
The hydrocarbon polymer 12 produced on the JIO mask during etching is removed together with the SiO□ film 10. Furthermore, one side wall 11a of the groove 11 is covered, and the other side wall 11b is covered.
A new SiO□ film 13 with a window opened so as not to remain on the film is formed as an etching mask using P-CVD or photolithography technology. This time, only methane (CH4) gas was used as the etching gas, without mixing hydrogen, to etch deeper than the Ga1nAs active layer 3, and to take advantage of the receding of the silicon dioxide (Sin) film 13 due to lateral etching. Then, the inclined side walls 6a and 6b are manufactured (FIG. 2 (cut)).

After that, a film 7 such as Au that reflects laser light is formed on the inclined side wall 6a facing the Ga1nAsP active layer 3 (
In the figure, this reflective film 7 also serves as a p-electrode and is fabricated at one time). One of the semiconductor laser resonator mirrors is formed using the vertical surface of the groove obtained by dry etching, and the other mirror is formed by separating the other end.

In this example, a reactive ion etching apparatus is used as described above, and a hydrocarbon gas is used as a reactive gas for etching the semiconductor material of the -V group compound. By using etching rates that are similar to each other, a good deflection reflecting surface and a laser resonator end face with excellent reproducibility can be obtained, and a surface-emitting type semiconductor laser can be easily obtained.

Incidentally, in the above embodiment, the case where reactive ion etching was used as the dry etching method was described, but reactive ion beam etching (Reactive
ton beam etching) method and ECR (El
ectron Cyclotron Re5onanc
Other dry etching methods such as e) etching method may be used, and similar effects can be expected by using hydrocarbon gas.

Furthermore, in the above embodiment, a case was described in which a mixed gas of ethane (C2H, ) and hydrogen (H2) was used as the etching gas for the -th etching, and methane (CH4) was used for the second etching. A mixed gas of methane and hydrogen may be used for the first etching, and ethane may be used for the second etching.

Furthermore, in the above embodiments, an example of an InP-based semiconductor laser was shown, but the present invention is also applicable to GaAs or other semiconductor lasers.
-V group compound semiconductor lasers can also be similarly applied. Further, although the laser structure has been described as a buried type, the present invention can of course be applied to lasers with other structures, as well as distributed feedback (DFB) lasers, etc., and the same effects as described above can be expected.

Furthermore, in the above embodiment, a case was described in which the flow rate of the etching gas was not changed during the second etching.
If the flow rate of the etching gas is continuously increased during etching, it is possible to fabricate a side wall 14 having a curvature in the depth direction, as shown in another embodiment of the present invention shown in FIG. be.

Further, as shown in still another embodiment of the present invention shown in FIG.
5, it is also possible to give a curvature to the shape of the formed side wall.

It goes without saying that the side walls having these curvatures can be used as reflective surfaces with a lens effect, and can be applied to desired optical elements.

Furthermore, in the above embodiment, one of the resonant mirrors of the semiconductor laser was fabricated by cleavage, but it may also be formed by dry etching, or by attaching a high reflection film to the cleavage plane etc., the output power in the surface direction is may be increased.

〔Effect of the invention〕

As described above, according to the present invention, the laser resonator end face and the deflection slope are formed using reactive ion etching of the ■-V group compound semiconductor material, and carbonization is added to the etching gas of the semiconductor material. Using hydrogen-based gas,
In addition, because we used an etching mask with an etching rate close to that of semiconductor materials, we were able to obtain a good deflection reflecting surface with excellent reproducibility, and the effect of easily obtaining a surface-emitting semiconductor laser. There is.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional side view showing a surface-emitting semiconductor laser obtained according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a method for manufacturing a surface-emitting semiconductor laser according to an embodiment of the present invention. FIG. 3 is a cross-sectional side view showing a surface-emitting type semiconductor laser obtained according to another embodiment of the present invention, FIG. 4 is a schematic perspective view showing a manufacturing method according to still another embodiment of the present invention, and FIG. 6 is a perspective view showing a surface emitting type semiconductor laser obtained according to the conventional example, and FIG. 6 is an explanatory view showing a method of manufacturing the surface emitting type semiconductor laser according to the conventional example. 1 is InP substrate, 2 is n-InP buff 77 layers, 5iOz
3 is a Ga1nAsP active layer, 4 is a p-InP cap layer, 6 is a 45 degree reflective surface, 7 is a p-electrode, 8 is an n-electrode, and 9 is a laser beam. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) In a method for manufacturing a surface-emitting semiconductor laser that integrates a semiconductor laser and a reflective surface that deflects the emitted light in a direction perpendicular to the substrate surface and extracts the emitted light, a silicon dioxide film is applied to the surface of the semiconductor laser crystal substrate. Alternatively, the substrate surface is formed by forming an insulating film such as a silicon nitride film, opening a window in the film, using the film as an etching mask, and performing reactive ion etching using methane or a mixed gas of ethane and hydrogen as the etching gas. a step of forming a groove with side walls perpendicular to the etching mask; a step of removing the etching mask; and an insulating film such as a silicon dioxide or silicon nitride film having a window that covers one side wall of the groove and does not cover the other side wall. and forming a side wall with an inclined surface by reactive ion etching using a hydrocarbon gas such as methane or ethane that does not contain hydrogen as an etching mask, and converting the inclined surface into a reflective surface. A method for manufacturing a semiconductor laser, comprising manufacturing a semiconductor laser.