JPH0812870B2 - Method for manufacturing semiconductor device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a semiconductor device.

[Conventional technology]

FIG. 2 is a cross-sectional view showing a conventional method for manufacturing a semiconductor device, and for a semiconductor device having a multi-step recess structure, it is shown in FIGS. In these figures, (1) is a substrate such as gallium arsenide, (2),
(3) and (4) are semiconductor active layers sequentially formed on the substrate (1), a spacer layer such as a silicon nitride (SiN) film, a resist layer, and (5) are openings formed in the resist layer (4). , (6) is a recess formed in the semiconductor active layer (2),
(7) is a step formed in the recess (6), and (8) is a gate electrode metal for forming a gate. Note that a transistor is formed by providing a source and a drain at places not shown in the left and right of FIG. 2 (G).

Next, the manufacturing process will be described. First, FIG. 2 (A)
Forming a semiconductor active layer (2) on the substrate (1),
Further, a spacer layer (3) and a resist layer (4) are successively laminated thereon, and then, an opening (5) is formed in the resist layer (4) by photolithography. Next, the spacer layer (3) exposed at the opening (5) is subjected to etching such as reactive ion etching (RIE) using the resist layer (4) as a mask to select as shown in FIG. After the removal, the spacer layer (3) is used as a mask to form a recess (6) having a width A in the semiconductor active layer (2) as shown in FIG. Then, as shown in FIG. 6D, side etching is selectively performed only on the spacer layer (3) to remove a portion close to the recess (6), and etching using the spacer layer (3) as a mask is performed. To do. At this time, the recess (6) is expanded to the width B as shown in FIG.
The step (7) is formed on the bottom surface of the recess (6) by further excavating the place where the recess (6) has already been formed in the step of FIG. Then, as shown in FIG. 6F, the gate electrode metal is vapor-deposited on the resist layer (4) and on the bottom surface of the recess (6) corresponding to the lower side of the opening (5) in the figure, and then the resist layer (by lift-off method). 4) and the gate electrode metal (8) above it are removed, leaving the necessary gate electrode (8) at the bottom of the recess (6), resulting in the state shown in FIG.

[Problems to be Solved by the Invention]

In a semiconductor device having a recess structure, its element performance is greatly influenced by the width of the recess region, that is, the width of the recess after expansion, and whether or not this width can be obtained as desired depends on the amount of side etching of the spacer. Although it can be controlled, since the conventional semiconductor device manufacturing method is performed as described above, it is difficult to control the side etching amount well when the spacer side etching is performed by wet etching. If dry etching is performed, the resist layer is also etched and thinned, so that the gate electrode metal on the resist layer is connected to that on the bottom surface of the recess, and during lift-off, the gate electrode metal left on the bottom surface of the recess is There was a problem that deformation such as protrusions occurred.

The present invention has been made to solve the above problems, and provides a method of manufacturing a semiconductor device in which the side etching amount of the spacer layer can be easily controlled and the thickness of the resist layer is less reduced by etching. The purpose is to

[Means for solving the problem]

In the method for manufacturing a semiconductor device according to the present invention, after forming a protective film on a resist layer having an opening laminated on a spacer layer, etching of the protective film and side etching of the spacer layer from the opening are performed. The spacer layers are side-etched at the same time until the protective film is completely removed by etching.

[Action]

In the method for manufacturing a semiconductor device according to the present invention, since the side etching of the spacer layer is performed simultaneously until the protective film is entirely removed by etching, the side etching amount of the spacer layer is determined by the etching rate of the spacer layer and the protective film The amount is determined by the etching rate ratio and the thickness of the protective film. Further, since the resist layer is protected by the protective film, the reduction in film thickness due to etching is small.

Example of Invention

An embodiment of the present invention will be described below. FIG. 1 is a cross-sectional view showing a method of manufacturing a semiconductor device according to an embodiment of the present invention, and FIGS. 1A to 1C show the manufacturing process of a semiconductor device having a multi-step recess structure. In these figures, (1) to (6) are the same as in the case of FIG. (9) is a resist layer (4)
It is a protective film formed of titanium (Ti) or the like on the top and the bottom of the recess (6).

Next, the manufacturing process will be described. First, FIG. 2 (A)
The manufacturing steps similar to those of the conventional example of (C) are performed. As a result, it becomes as shown in FIG. Next, titanium or the like is vapor-deposited from above in the figure, and a protective film (9) is formed on the resist layer (4) and the bottom surface of the recess (6) as shown in FIG. 1 (B).
To form. In the next step, when the side etching of the spacer layer (3) is performed until the protective film (9) is entirely removed by etching, the side etching amount of the spacer layer (3) becomes a desired amount, (9) is formed to have an appropriate thickness according to the ratio of the etching rate of the spacer layer (3) and the etching rate of the protective film (9). The protective film (9) is made of a material having a relatively small etching rate, and accordingly, the protective film (9) on the bottom surface of the recess (6) needs to be thick enough to reach the spacer layer (3). It doesn't happen. Subsequently, the etching of the protective film (9) and the side etching of the spacer layer (3) are simultaneously performed by using the dry etching method. This is because the protective film (9) is entirely exposed as shown in FIG. 1 (C). Do until removed. At this time, since the resist layer (4) is protected by the protective film (9), the film thickness is not significantly reduced. Whether or not the protective film (9) has been removed is determined by providing a protective film having the same material and the same thickness (not shown) separately from the chip to be the product.
The change in color of the portion can be detected by a method of monitoring from the window of the etching device. FIG. 1 (C) corresponds to the state of FIG. 2 (D), and thereafter, FIG. 2 (E)-
A semiconductor device is manufactured by the same process as shown in (G).

Since the adhesive force between the spacer layer (3) and the resist layer (4) is weak, when the wet etching method is used for the side etching of the spacer layer (3), the etching liquid, which is an etchant, may be impregnated. However, since the dry etching method is used in this embodiment, there is no such problem.

Further, in the above embodiment, SiN is used for the spacer layer, but SiO
₂ , SiON, etc. may be used. Further, the side etching of the spacer layer was performed by RIE, but plasma etching,
Alternatively, it may be performed by reactive ion beam etching (RIBE).

〔The invention's effect〕

As described above, according to the present invention, since the protective film is formed on the resist layer and the side etching of the spacer layer is simultaneously performed until the protective film is completely removed by etching, the side etching of the spacer layer is performed. The amount is determined by the ratio of the etching rate of the spacer layer to the etching rate of the protective film and the thickness of the protective film. Therefore, the protective film is formed to have an appropriate thickness and the removal of the protective film by etching is monitored. As a result, the side etching amount of the spacer layer can be easily controlled, and the resist layer is protected by the protective film, so that there is an effect that the reduction in the film thickness of the resist amount due to etching is reduced.

[Brief description of drawings]

1 is a sectional view showing a method of manufacturing a semiconductor device according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a method of manufacturing a conventional semiconductor device. In the figure, (1) is a substrate, (2) is a semiconductor active layer,
(3) is a spacer layer, (4) is a resist layer, (5) is an opening, (6) is a recess, (7) is a step, (8) is a gate electrode metal, and (9) is a protective film. . In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A step of sequentially laminating a spacer layer and a resist layer on a semiconductor active layer formed on a substrate, a step of forming an opening in the resist layer, and etching the spacer layer by etching using the resist layer as a mask. The step of selectively removing, the step of forming a recess in the semiconductor active layer by etching using the spacer layer as a mask, the step of forming a protective film on the resist layer and the bottom surface of the recess, and the etching of the protective film At the same time, a step of side etching the spacer layer until the protective film is completely removed, a step of expanding the concave portion by etching with the spacer layer as a mask and forming a step, and a step of forming a step on the resist layer. And a step of depositing a gate electrode metal on the bottom surface of the recess, and removing the gate electrode metal on the resist layer by a lift-off method. The method of manufacturing a semiconductor device comprising the step of.