JPS627692B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, mainly for high-frequency, high-output transistors, to facilitate mask alignment, shorten mask alignment time, and find optimal etching thereafter. The present invention relates to a method for manufacturing a semiconductor device.

Conventionally, in order to improve the high frequency characteristics of a high frequency transistor, it is necessary to reduce the base width, base resistance, collector capacitance, etc. Therefore,
Manufacturing high-frequency transistors requires high-precision processing technology. As a technique for this processing, a photoetching technique using a photomask is conventionally known, and it is possible to process a minute pattern of several micrometers.

However, in order to improve the high-frequency characteristics of high-frequency transistors, a micropattern of about 1μ is required, but there are constraints such as mask alignment accuracy and overetching. Even if a photomask with the same characteristics is made, it is difficult to transfer the same accuracy of the photomask onto the wafer due to the accuracy of the alignment marks, overetching, etc. when photoengraving the photolithography onto the wafer.

This invention was made in view of the above points, and it is possible to perform mask alignment by using a monitor pattern for finding the optimum etching in the photoetching process and a mask having a group of alignment marks on the monitor pattern. The object of the present invention is to provide a method for manufacturing a semiconductor device that is easy and allows optimal etching.

FIG. 1 is a plan view showing an example of a photomask used in the present invention.
A pattern of a transistor to be manufactured is placed therein, a bar-shaped monitor pattern 3 of a required width is placed therein, and an alignment mark group 4 is placed in a part of the monitor pattern portion 3.

FIG. 2 is a plan view showing a semiconductor wafer photoengraved using the photomask 1 shown in FIG. This is a photolithography transfer of Group 4. The monitor pattern 6 at this time is designed to have sufficient dimensions to enable visual observation of when etching, which will be described later, has reached an optimal stage. The alignment mark group 7 includes alignment marks for general mask alignment, high precision mask alignment, and pitch shift detection of the mask itself.

FIG. 3 is an enlarged partial cross-sectional view taken along the - line in FIG. 2, in which a mask as shown in FIG. Shows the state after exposure and development.

FIG. 4 shows a state in which the oxide film 9 has been ideally etched using the photoresist film 10 of FIG. 3 as a mask.

FIG. 5 shows a state where over-etching occurs during the conventional etching process. In order to prevent such overetching from occurring, the present invention uses a monitor pattern 6 to ensure that while the hydrofluoric acid, which is an etching solution, is etching the oxide film 9, the hydrofluoric acid is well adapted to the oxide film 9. However, when the surface of the wafer 8 is exposed as shown in FIG. 4, the etching can be stopped in the optimum etching state by visually observing that the hydrofluoric acid does not blend into the wafer 8 and is repelled. Such visual observation is difficult in the pattern portion of a practical semiconductor element such as a transistor because the pattern is minute, and a monitor pattern of a required size is required.

As explained above, in this invention, since a monitor pattern with the required dimensions is provided, it is possible to visually observe the just etching.Furthermore, since a group of alignment marks are provided in the monitor pattern section, the position of the alignment mark can be searched for when aligning the mask. This makes it possible to shorten mask alignment time and perform highly accurate etching.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of a photomask used in the present invention, FIG. 2 is a plan view showing a semiconductor wafer photoengraved using the photomask shown in FIG. 1, and FIG. 3 is a plan view showing the - line in FIG. 4 is a cross-sectional view showing the oxide film on the wafer ideally etched using the photoresist film of FIG. 3 as a mask, and FIG. FIG. 3 is a sectional view showing the ivy state. In the figure, 1 is a mask, 3 and 6 are monitor patterns, 4 and 7 are alignment mark groups, 5 and 8 are semiconductor wafers, 9 is an insulating film, and 10 is a photoresist film. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In a method for manufacturing a semiconductor device that includes a step of etching with hydrofluoric acid through a photoresist film formed in a desired pattern by photolithography on an insulating film formed on a semiconductor wafer, an opening of a desired size is formed in the photoresist film. Using a mask that forms a monitor pattern and a group of alignment marks on a part of the monitor pattern forming area, the hydrofluoric acid is repelled by the semiconductor wafer to confirm that the etching of the insulating film in the monitor pattern area is completed. 1. A method for manufacturing a semiconductor device, characterized by making it possible to visually observe and recognize the mask alignment, and facilitating mask alignment.