JPH0141256B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a semiconductor device having a stack of two or more types of semiconductor layers on a semiconductor substrate, such as a semiconductor laser device, a semiconductor light emitting device, etc.
The present invention relates to an improvement in a method of etching different semiconductor layers.

Hereinafter, the case of a semiconductor laser device will be explained as an example.

[Prior art]

FIG. 1 is a sectional view showing the main stages of a conventional method for forming etching grooves perpendicular to the layer direction in a semiconductor stack formed on a semiconductor substrate. On a gallium arsenide (GaAs) substrate 1, a first clad layer 2 consisting of gallium aluminum arsenide [Ga _1-X Al _X As, O<x<1], which is a first semiconductor layer, is the semiconductor layer of
An active layer 3 made of GaAs and a second cladding layer 4 made of Ga _{1-X Al} It is. First, as shown in FIG. 1a, the second cladding layer 4 is
A photoresist film 5 is formed on the photoresist film 5, and a fine etching groove 6 is formed in the photoresist film 5, as shown in FIG. 1B. Thereafter, as shown in FIG. 1c, using this photoresist film 5 as a mask, the second cladding layer 4, the active layer 3, and the first After sequentially etching the cladding layer 2 to form an etching groove 7, the photoresist film 5 was removed, as shown in FIG. 1d, and the etching process was completed.

However, the etching speed when forming the groove 7 by dry etching is lower than that of the cladding layers 2 and 4.
Since Ga _{1-X Al} As a result, smooth etched groove sidewalls could not be obtained.

[Summary of the invention]

This invention has been made in view of the above-mentioned points, and it is possible to remove the step formed on the side wall of the etching groove due to dry etching by wet etching using an appropriate etching solution, thereby forming a fine pattern. The present invention provides a method for etching a semiconductor by which an etching groove can be formed with smooth sidewalls.

[Embodiments of the invention]

FIG. 2 is a cross-sectional view showing the main stages of an embodiment of the present invention, in which the same reference numerals as in the conventional example indicate the same parts. First, an etching groove 7 is formed in the dry etching process in exactly the same manner as in the conventional example shown in FIGS. 1a, b, and c. At this time, as described above, a stepped portion is generated on the side wall of the etching groove. In this example, the photoresist film 5 is not removed at this stage, and using this as a mask, dry etching is performed at a slow etching speed, and the remaining convex layer, in this example the first semiconductor layer, is Ga _1-X Al. Using an etching solution that selectively etches only _XAs , such as hydrofluoric acid or a hydrofluoric acid aqueous solution, the first cladding layer 2, which is the first semiconductor layer, and the second cladding layer are etched, as shown in FIG. 2a. After wet etching is performed until there is no step difference between the active layer 3 and the active layer 3, which is the second semiconductor layer, to obtain an etched groove 7a with smooth sidewalls, the photoresist film 5 is etched as shown in FIG. The process of this example is completed by removing.

Note that this invention is applicable to various combinations of semiconductor substrates and semiconductor laminates, including indium phosphide (InP), indium gallium arsenic phosphorus (InGaAsP), and not only GaAs and Ga _1-X Al _X As. Of course, the semiconductor laminated structure is not limited to the laser element structure of the above example.

〔Effect of the invention〕

As explained above, when etching different types of semiconductor layers of a semiconductor device having a stacked body consisting of two or more types of semiconductor layers, there is a dry etching method that allows vertical etching sidewalls to be obtained, and this dry etching method. By simply combining this method with a selective wet etching method for removing steps caused by differences in etching speed, fine, vertical etched grooves with smooth side walls can be easily obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the main stages of a conventional method for forming etching grooves perpendicular to the layer direction of a semiconductor stack, and FIG. 2 shows the main stages of an embodiment of the present invention. FIG. In the figure, 1 is a semiconductor substrate, 2 and 4 are Ga _1-X
Cladding layer (first semiconductor layer) consisting of Al _x As,
3 is an active layer (second semiconductor layer) made of GaAs,
7 and 7a are etching grooves. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. For a semiconductor device in which a stacked body having at least first and second semiconductor layers of different types is formed on a semiconductor substrate, a direction perpendicular to the plane of each layer across the first and second semiconductor layers. In forming the etching groove of the above, the etching groove of the required depth is formed by dry etching, and the etching rate of the dry etching for the first semiconductor layer is set to the second etching rate.
The method further comprises a step of removing a step formed on the side wall of the etching groove by wet etching using an etching solution that selectively etches only the first semiconductor layer. A method for etching semiconductors.