JPH04359419A - Compound semiconductor substrate - Google Patents

Abstract

PURPOSE:To easily manufacture a substrate having a mask alignment mark of predetermined shape and size by a method wherein the mask-alignment mark is made on a GaAs substrate by a low-pressure organic metal vapor-phase epitaxial growing method. CONSTITUTION:A mask alignment mark is made on a GaAs substrate 1 by low-pressure organic metal vapor-phase epitaxial growing method. For instance, on a part of the GaAs substrate 1 exposed through a window corresponding to a predetermined mask-alignment pattern of a silicon nitride film made to adhere to the GaAs substrate 1, GaAs selective-growing layers 4, 5 are formed by a low-pressure MOVPE method. Thus, the GaAs epitaxially grown layer which selectively formed on the GaAs substrate 1 becomes a plane of cleavage such that the angle made by a side face of the epitaxial growing layer 4 and an upper face of the GaAs substrate 1 is 125 degrees, whereby the shape and size of the mask-alignment mark constituted by the epitaxial growing layer can accurately be grasped.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound semiconductor substrate provided with mask alignment marks used in manufacturing compound semiconductor devices.

0002

[Background Art] When manufacturing a semiconductor device, mask alignment marks (alignment marks...positioning marks) that are pre-formed on the substrate of the semiconductor device, and individual marks for each of a plurality of photomasks that are sequentially used. It is well known that successive photomask patterns can be correctly formed on the substrate of a semiconductor device by aligning the alignment marks formed on the substrate. The same applies to semiconductors. As mentioned above, the mask alignment marks that should be formed in advance on the substrate of a compound semiconductor device are conventionally patterned using photolithography technology on a thin film of photoresist deposited on a GaAs substrate. After that, GaAs
Mask alignment marks were formed on the GaAs substrate by subjecting the GaAs substrate to wet etching means or dry etching means.

0003

[Problems to be Solved by the Invention] By the way, when wet etching means is applied to a GaAs substrate to form mask alignment marks,
Since the etching of the GaAs substrate proceeds not only in the depth direction but also in the width direction of the substrate, the deformation of the mark formed on the GaAs substrate becomes large and the alignment accuracy decreases. If the substrate is anisotropically etched using a dry etching method, such as reactive ion etching, it is possible to prevent the marks formed on the GaAs substrate from deforming, but the line width is narrower than the pattern width. Since it is difficult to form mask alignment marks well, it has been desired to develop a compound semiconductor substrate on which mask alignment marks are formed without the above-mentioned defects.

0004

SUMMARY OF THE INVENTION The present invention provides a compound semiconductor substrate in which mask alignment marks are formed on a GaAs substrate by low pressure organometallic vapor phase epitaxial growth.

[0005]

[Operation] Since the mask alignment marks formed on the GaAs substrate by the reduced pressure organic metal vapor phase epitaxial growth method have a predetermined shape and size, the mask alignment marks on the GaAs substrate are sequentially used in the fabrication of semiconductor devices. Facilitates correct alignment of photomask patterns.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific details of the compound semiconductor substrate of the present invention will be explained in detail with reference to the accompanying drawings. Figure 1 shows Ga
A partial perspective view showing a state in which a mask alignment mark pattern is formed on a thin film of silicon nitride deposited on an As substrate. FIG. 2 is an explanatory diagram of the process of manufacturing a compound semiconductor substrate of the present invention. FIG. FIG. 2 is a perspective view of a portion of a GaAs substrate in which mask alignment marks are formed by low-pressure organometallic vapor phase epitaxial growth. 1 in Figures 1 to 3
is a GaAs substrate used as a compound semiconductor substrate. Further, in the figure, 2 is a SiNx (silicon nitride) film, and 3 is a pattern of mask alignment marks formed on the silicon nitride thin film 2. The single crystal GaAs substrate 1 is
In the following description, it is assumed that the crystal plane is used in the state shown in the figure. here,
How the compound semiconductor substrate of the present invention is manufactured will be explained with reference to FIGS. 2(a) to 2(f). First, as shown in FIG. 2(a), a GaAs substrate 1 is coated with, for example, 1,000 layers by, for example, plasma CVD.
A thin film 2 of silicon nitride with a thickness of angstroms is deposited.

After a photoresist film is deposited on the silicon nitride thin film 2 as described above, the photoresist film is exposed to a pattern of predetermined mask alignment marks and developed. Using the photoresist film as an etching mask, the silicon nitride film 2 is dry-etched using, for example, a plasma etching method, as shown in FIG.
As shown in (b), a window 3 corresponding to a pattern of a predetermined mask alignment mark is opened in the silicon nitride film 2. Then, as shown in FIG. FIG. 1 shows this state as a perspective view, but only one mask alignment mark pattern is shown in FIG. 1 for simplicity of illustration. As illustrated in FIG. 1 or FIG. 2(b), a silicon nitride film 2 deposited on a GaAs substrate 1 has a window 3 corresponding to a predetermined mask alignment mark pattern. Next, Ga
An epitaxially grown layer of GaAs is formed in a portion of a silicon nitride film 2 deposited on an As substrate 1 exposed by a window 3 corresponding to a pattern of predetermined mask alignment marks.

The portion of the GaAs substrate 1 exposed by the window 3 corresponding to the pattern of the predetermined mask alignment mark of the silicon nitride film 2 deposited on the GaAs substrate 1 by the low pressure MOVPE method is coated as described above. To form a selective growth layer of GaAs, for example, TMG-AsH is used.
Growth pressure...10 Torr by three-system reduced pressure MOVPE method
By performing selective growth of GaAs at a growth temperature of 650 degrees Celsius, a V/III ratio of 75, and a total flow rate of 500 sccm, the GaAs substrate 1 exposed by the window 3 corresponding to the mask alignment mark pattern described above is grown. A GaAs epitaxial growth layer is well formed in the portion. The epitaxial growth layer of GaAs selectively grown on the GaAs substrate 1 as described above looks like the one shown with reference numeral 4 in FIGS. 2(c) and 2(d) when viewed from the side in the direction of the arrow Y in FIG. The angle between the side surface of the GaAs epitaxial growth layer and the top surface of the GaAs substrate 1 is 125.
Since the cleavage plane is a degree cleavage plane, the shape and dimensions of the GaAs epitaxial growth layer selectively grown on the GaAs substrate 1 can be accurately grasped. In addition, the GaAs substrate 1
When the epitaxial growth layer of GaAs selectively grown on the top is viewed from the side in the direction of the arrow X in FIG.
) is in the state shown by reference numeral 5.

When the silicon nitride film 2 shown in FIGS. 2(c) and 2(e) is removed by applying a wet etching method or a dry etching method, for example, the silicon nitride film 2 shown in FIG. 2(c) and (e) is removed.
As shown in d) and (f), a compound semiconductor substrate is obtained in which mask alignment marks are formed on a GaAs substrate by metal organic vapor phase epitaxial growth. FIG. 3 is a perspective view of the state shown in FIGS. 2(d) and 2(f). In the compound semiconductor substrate of the present invention, in which mask alignment marks are formed on a GaAs substrate by low-pressure organometallic vapor phase epitaxial growth, a predetermined semiconductor device can be manufactured by a normal epitaxial growth process for semiconductor device manufacturing. . In order to fabricate a compound semiconductor substrate on which a mask alignment mark is formed using the low-pressure organometallic vapor phase epitaxial growth method of the present invention, a silicon nitride film is left only on a portion of the wafer, a mask alignment pattern is formed, and a semiconductor device is fabricated. Mask alignment marks may be formed at the same time as the epitaxial film for production is grown.

0010

Effects of the Invention As is clear from the above detailed explanation, the compound semiconductor substrate of the present invention has mask alignment marks formed on a GaAs substrate by the low-pressure organometallic vapor phase epitaxial growth method. Since the angle between the side surface of the layer and the top surface of the GaAs substrate 1 is a cleavage plane of 125 degrees,
The shape and dimensions of the GaAs epitaxial growth layer selectively grown on the GaAs substrate 1 can be accurately grasped, and a compound semiconductor substrate having a mask alignment mark of a predetermined shape and dimension can be easily obtained, thereby solving the conventional problems described above. In other words, when wet etching is applied to a GaAs substrate to form mask alignment marks, G
Corrosion of the aAs substrate progresses not only in the depth direction but also in the width direction of the substrate, resulting in significant deformation of the marks formed on the GaAs substrate, reducing alignment accuracy. On the other hand, when a dry etching method is used, it is difficult to accurately form a mask alignment mark in a line width narrower than the pattern width. With the compound semiconductor substrate of the invention, mask alignment marks can be formed using the same MOVPE equipment as the epitaxial film growth equipment for semiconductor device production, so RIE equipment and other expensive equipment are not required to produce the mask alignment marks. You also have the advantage of not having to do this.

[Brief explanation of drawings]

FIG. 1 is a partial perspective view showing a state in which a mask alignment mark pattern is formed on a silicon nitride thin film deposited on a GaAs substrate.

FIG. 2 is an explanatory diagram of the process of manufacturing a compound semiconductor substrate of the present invention.

FIG. 3 is a perspective view of a portion of a GaAs substrate in which mask alignment marks are formed by low-pressure organometallic vapor phase epitaxial growth.

[Explanation of symbols]

Claims (1)

[Claims] 1. A compound semiconductor substrate in which mask alignment marks are formed on a GaAs substrate by low pressure organometallic vapor phase epitaxial growth.