JPS6152973B2 - - Google Patents

Description

Detailed Description of the Invention [Summary] Among the field regions to be exposed by deflecting the main deflector, an area equivalent to one field is assumed at the center position of an area consisting of four field areas, and within that area, providing a plurality of alignment marks near the periphery of the area and near the boundary dividing the four field areas;
Positioning is performed using the positioning marks.
Thereafter, the XY stage on which the semiconductor wafer is placed is moved to sequentially expose the four field regions using the main deflector.

This will further speed up the electron beam exposure process.

[Industrial application field]

The present invention relates to an electron beam exposure method, and more particularly to an improved mark alignment method.

Among electron beam exposure methods, a direct exposure method in which a pattern is directly drawn on a semiconductor wafer can form a pattern with particularly high precision, and is therefore often used for forming conductive wiring layers of integrated circuit chips.

However, since the direct exposure method requires more time for exposure processing than the mask transfer exposure method, there is a desire to shorten the processing time.

[Problems to be solved by conventional technology and invention]

FIG. 3 shows a schematic diagram of an electron beam exposure apparatus, in which 21 is an electron gun, 22 is a projection lens system, and 23 is a projection lens system.
is the main deflector, 24 is the sub-deflector,
The semiconductor wafer 25 is placed on an XY stage 26. This XY stage 26 moves every time one field area is exposed, but the movement is
The laser wavelength is reflected by a reflecting mirror 27 attached to the stage 26, measured by a laser length measuring device 28, the moving distance is calculated by an electronic computer 29, and the value is given to the drive mechanism 30 for operation. I'm letting you do it.

In addition, one field region is exposed by deflecting the main deflector 23, and one sub-field region generated by deflecting the main deflector 23 is exposed by deflecting the sub-deflector 24, thus exposing the semiconductor wafer. The entire surface has been exposed to light.

On the other hand, even in the conventional ultraviolet exposure method, which transfers images from a mask all at once, alignment is carefully performed using alignment marks, but the above-mentioned direct exposure method using an electron beam allows for much more precise alignment. In order to require Further, the field is exposed while repeating the positioning using the positioning mark for each field area, thereby maintaining highly accurate exposure.

FIG. 4 shows an example of a conventional mark pattern in which alignment marks are formed for each field.
After forming two rectangular marks 2 and aligning with the rectangular marks, that field is exposed, and then the XY stage is moved to an adjacent field and the same operation is repeated again.

However, repeating alignment for each field requires a lot of processing time, and the long processing time of the direct exposure method has traditionally been considered a drawback.

On the other hand, integrated circuits have become highly integrated, such as LSIs and super LSIs, and chips have become larger.Therefore, it has become impossible to use one semiconductor chip as one field due to the problem of exposure equipment. be.

The present invention aims to reduce such problems and shorten the exposure processing time.

[Means for solving problems]

The purpose of this is to create a plurality of fields in a region corresponding to one field located at the center of an area consisting of four field regions of the sample, near the periphery of the region corresponding to one field, and near the boundaries of the four field regions. alignment marks are formed, the sample is aligned based on the alignment marks, and then the sample is moved to sequentially expose the four field regions without alignment. This is achieved by an electron beam exposure method.

[Effect]

That is, in the present invention, an area corresponding to one field is assumed to be at the center position of an area consisting of four field areas among the field areas to be exposed by deflecting the main deflector. Then, within that area, a plurality of alignment marks are provided near the area and near the boundaries dividing the four field areas, and after alignment is performed using the alignment marks, the semiconductor wafer is mounted. placed
Move the XY stage to each field area. Then, each of the four field regions is sequentially exposed by the main deflector.

This will further speed up electron beam exposure and reduce the number of processing steps.

〔Example〕

Hereinafter, embodiments will be described in detail with reference to the drawings.

FIG. 1 shows a field area provided with alignment marks according to the present invention, where an area consisting of four adjacent fields a, b, c, and d is defined as one area, and a field located at the center of this area is defined as one area. Then, 1
Four alignment rectangular marks 12 are formed around a region m having an area corresponding to one field. This rectangular mark 12 is formed on the boundary dividing the four field regions described above where a predetermined pattern is not provided, and its dimensions are approximately 10 μm in both vertical and horizontal widths.
A concave shape with a step difference of about 1 μm is formed by etching in the previous process.

In this way, four adjacent fields a,
The regions b, c, and d are treated as one region, and the alignment rectangular marks 12 are formed at the above-mentioned positions in that region, and the semiconductor wafer with such a plurality of regions is exposed to an electron beam exposure apparatus. of
Place it on the XY stage. Then, using the facet surface of such a semiconductor wafer, the semiconductor wafer is aligned in advance.

Next, the position of the XY stage is moved by the drive mechanism to align the position of the electron beam to the m area at the center of any area of the four field areas as shown in FIG. Then, a detector detects the reflected electron signal of the irradiated electron beam, determines the X and Y coordinates of the four marks, and adjusts the error to accurately align the marks. Such errors are calculated by an electronic computer and adjusted by correcting the deflector.

After accurate positioning using the four positioning rectangular marks in area m, the position of the XY stage is moved by the drive mechanism to move the main deflector and sub deflector in field area a. Then, it is deflected and exposed.

Next, field regions b, c, and d are subjected to exposure processing only by moving the position of the XY stage without alignment. After completing the exposure of the four field areas a, b, c, and d in this way, the position of the XY stage is moved to another area consisting of the next four field areas, and the same operation is repeated again.

Even if such an exposure method is used, the moving distance of the XY stage within the four field regions mentioned above is, for example, about 2 to 3 mm, which is accurately monitored by a laser length measuring device. In addition, the positional error is at most about 0.1 μm, allowing highly accurate exposure.

Further, FIG. 2 is a diagram for explaining the advantages of the exposure method according to the present invention. When forming alignment marks according to the present invention and performing exposure processing, if the divided area 11 shown in FIG. The positioning mark prevents overlap with the necessary pattern inside the semiconductor chip. Therefore, it is possible to easily handle and process a semiconductor chip with a large area extending over four field regions, and to perform exposure processing on a semiconductor chip with an area corresponding to one field region. The same pattern accuracy is maintained, and its practical value is extremely high.

Note that the above is an example in which the alignment mark is provided on the boundary of the field area, but if the positions of the required patterns overlap, the alignment mark may be moved to the vicinity of the boundary.

〔Effect of the invention〕

As is clear from the description of the embodiments above, according to the present invention, alignment can be completed once in four field areas, instead of four times in the conventional method, and the number of steps for exposure processing can be reduced. , which is useful for improving the operating efficiency of electron beam exposure equipment.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a field area provided with alignment marks according to the present invention;
FIG. 2 is a diagram of a field region explaining the advantages of the alignment mark according to the present invention, FIG. 3 is a schematic diagram of an electron beam exposure apparatus, and FIG. 4 is a diagram of a field region provided with a conventional alignment mark. FIG. In the figure, 12 is an alignment mark, a,
b, c, and d are four field regions, m is a field region forming alignment marks, 23 is a main deflector, 24 is a sub-deflector, 25 is a semiconductor wafer, and 26 is an XY stage.

Claims (1)

[Claims] 1. Within a region equivalent to one field located at the center of an area consisting of four field regions of the sample, a plurality of alignments are performed near the periphery of the region equivalent to one field and near the boundaries of the four field regions. forming marks, aligning the sample based on the alignment marks, and then moving the sample to perform alignment without performing alignment.
An electron beam exposure method characterized in that exposure within two field regions is sequentially performed.