JPS5947480B2 - Manufacturing method of semiconductor device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a semiconductor device.

This method is particularly useful for manufacturing semiconductor lasers as described below. 3. In the following, a description will be given using a semiconductor laser as an example.

In recent years, a structure in which multiple semiconductor layers are formed on a substrate with band-shaped grooves, as shown in Figure 1, has been proposed as a highly reliable semiconductor laser with stable horizontal orientation (
Patent application 1983-60009). 3 To give a specific example, in FIG. 1, 1 is a substrate crystal, which is an n-GaAs substrate, and 2
3 is a band-shaped groove, and 3 is a second semiconductor layer, for example, n-Gal-
xAlx layer (x:: 0.3) 4 is the first semiconductor layer and G
aAs active layer, 5 is a third semiconductor layer such as p-Gal
-yAlyAs layer (y″■■0.3~0.4), 6 is the fourth semiconductor layer, which is an n-GaAs layer, 7 is a selective diffusion region of Zn, which is a p-type impurity, 8 and 9 are ohmic In this structure, light is mainly distributed in the layer 4, but on both sides of the strip groove 2, some of the light seeps into the GaAs substrate 1, causing a loss. A difference in complex refractive index occurs, and a light trapping effect appears.
This effect is determined by the layered structure of the element, so
The laser oscillation state becomes stable with respect to current and light intensity.
In this laser, the relative position of the Zn diffusion region 7 and the band-shaped groove 2 is adjusted to an accuracy of about 2 μm or less so that current flows effectively and evenly to the active layer located above the band-shaped groove 2. Therefore, in the photolithography process in laser device manufacturing, some kind of index is required as a mark for mask alignment.

Conventionally, as an indicator of this, a hole with sufficient depth was prepared separately from the band-shaped groove 2 so that the groove would not be completely filled even when crystal growth was performed. A film was formed so that the position of the substrate groove could be determined after growth.

However, in such a method, the figure used as the alignment mark does not remain in the same shape and is easily deformed, making it difficult to accurately align the masks in the photo-etching process. An object of the present invention is to eliminate the drawbacks of conventional methods and to provide a manufacturing method for manufacturing the semiconductor laser with high precision.

The following means will be used to achieve the above objectives.

Focusing on the fact that semiconductor lasers are composed of multilayer crystal films with different compositions, we selected a chemical etching solution to selectively etch only the desired specific crystal growth layer, thereby etching a partial region of the crystal wafer. The growth layer is removed to expose band-shaped grooves (a plurality of grooves, preferably at least two or more) formed on the substrate crystal surface, and this is used as an index for accurate mask alignment in the photolithography process. This paper proposes a new manufacturing method with characteristics. As a result, we were able to significantly improve accuracy in laser device manufacturing. Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 2 is used in a photolithography process, which is an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a method of forming a mask alignment index. Reference numerals 1, 3, 4, 5, and 6 in the figure are the layers explained in FIG. 1. The thickness of each is approximately 4 times the n-type GaAs substrate 1
00μm) n-type Gal-XAlxAs layer 3 (x=0.3
) approx. 0.4 μm) GaAs active layer 4 approx. 0.1 μM. p-type Ga,-YAlyAs layer 5 about 2 μM, . The n-type GaAs layer 6 has a thickness of about 1 μm. The band-shaped grooves 2 have a width of about 6 μm, a depth of about 1 μm, and are formed in parallel at intervals of 400 Itm. To form alignment marks, first, as shown in Figure 2a, an etching mask 1 is applied to the crystal surface, leaving only a portion.
Apply Apiezon wax as 0. Next, as shown in Figure b, the grown layer is etched to the middle of the first layer, which is the second semiconductor layer of n-Ga, -XAlxAs3, by a chemical etching method. The etching solution used was phosphoric acid:hydrogen peroxide:ethylene glycol=1:1:3 (etching rate: 0.6 μm/Mm at 20° C.). Next, as shown in c, the first layer of Gal. Using an etching solution that selectively etches only xAlxAs, n-
The Ga, -XAlxAs layer 3- is removed to expose the band-shaped groove formed on the substrate crystal surface. Gal-XAlxAs
Fluoric acid was used as the etching solution for selectively etching only the wafer, and the reaction was heated to about 70° C. in order to speed up the reaction. Etching time is 20 to 60 minutes. Thereafter, in the laser manufacturing process, this band-shaped groove on the exposed substrate crystal surface is used as an index for mask alignment in photolithography.

As a result, it has become possible to match the relative positions of the band-shaped groove of the semiconductor laser device shown in FIG. 1 and the Zn diffusion portion with high accuracy. FIG. 3 is a histogram showing how much the mask alignment error has been improved.

Figure a shows the result obtained by the conventional method in which a figure of a SlO2 oxide film is formed on the substrate surface and the position of the substrate groove is indicated after the growth of each semiconductor layer. Figure b shows the result obtained by the present method. As is clear from this, in the conventional method, the mask alignment error largely varied around ±4 μm, but with the present method, this could be improved to about ±2 μm or less. According to the present invention, the accuracy of device fabrication is improved, and as a result, the device characteristics,
The device manufacturing yield was significantly improved.

Further, the present invention can also be applied to alignment of a semiconductor device in which a semiconductor layer is formed on a semiconductor substrate.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a highly reliable and laterally stable semiconductor laser in a direction perpendicular to the direction of light propagation, and FIG. 2 is a mask for a photolithography process, which is an embodiment of the present invention. FIGS. 3A and 3B, which are diagrams showing a method of forming alignment indices, are histograms showing a comparison of mask alignment errors when using the conventional method and the method of the present invention.

Claims (1)

[Claims] 1. On the surface of a semiconductor substrate provided with a plurality of band-shaped grooves,
In the manufacturing process of a semiconductor device having a structure in which a semiconductor layer is formed, a band-shaped groove is formed in the semiconductor substrate by removing at least a portion of the semiconductor layer in a partial region of the semiconductor substrate in which the semiconductor layer is formed. 1. A method of manufacturing a semiconductor device, characterized in that the groove is exposed and the groove is used as an alignment index.