JP4433715B2 - Raster drawing method and photomask manufacturing method - Google Patents

Description

  The present invention relates to a raster drawing method for irradiating a spot beam to draw a desired pattern, a photomask manufacturing method using the same, and a photomask for manufacturing a photomask for manufacturing a semiconductor device, and more particularly scanning. The present invention relates to a raster drawing method for avoiding a reduction in the dimensional accuracy of a drawing pattern due to a dimensional variation in a direction, a photomask manufacturing method using the same, and a photomask.

2. Description of the Related Art Conventionally, in manufacturing a photomask used in a semiconductor wafer process, an apparatus that scans a spot beam and draws a desired pattern on a mask blank by turning the beam on and off is used. In general, this method is called a raster method, and an electron beam or a laser beam is used.
A normal mask refers to a substrate in which an actual size semiconductor LSI pattern is applied to a substrate such as glass or the like, or a pattern that is four times or five times the original size is drawn on a mask blank. The latter is called a reticle. With the recent miniaturization, most masks are of the reticle type.

  With an electron beam, the beam is scanned by deflecting the beam with a magnetic field, and with a laser beam, the beam is scanned with an optoacoustic element or a rotating mirror. Further, drawing is performed by moving the stage in a direction perpendicular to the scanning direction.

  As an exposure method, a mask blank is first fixed on a stage that can move on the vertical axis and the horizontal axis. Then, scanning is performed at a certain distance, and exposure is performed on the mask blank. At this time, in the case of a multi-beam using many spot beams, each beam is scanned and exposed simultaneously.

  The pattern scanned at this fixed distance and exposed is used as a basic unit. Then, after irradiating the basic unit, the mask blank is moved. Similarly, after scanning the beam and irradiating the basic unit, the mask blank is moved. In this manner, multiple exposure is performed by repeating irradiation for each unit by scanning the beam and moving the mask blank, and drawing of the entire mask blank is completed. Therefore, the basic unit is repeated in the mask blank, and drawing is performed with this cycle.

A predetermined pattern is formed on the mask as follows.
The electron beam is patterned by controlling on / off of the beam on the stage according to a predetermined pattern by deflection and simultaneously scanning the mask by another deflection.

  Laser beams are often used as multi-beams. In this case, one beam is divided into a plurality of laser beams by a beam splitter. Thereafter, on / off of the progress of each beam is controlled according to a predetermined pattern by an acoustooptic device or the like, and a pattern is formed by simultaneously scanning the mask with another acoustooptic device or a rotating mirror.

However, the following problems occur due to the mask drawing as described above.
That is, by scanning the beam, dimensional variations due to the scanning position occur.
The electron beam causes aberration blur, and the laser beam causes variations in pattern dimensions due to the lens and optical path difference.
In the case of multi-beams, variations between beams due to light splitting or optical path differences become dimensional variations.

In order to avoid such dimensional variations, the object to be processed (mask blank or the like) is irradiated N times in a scan direction with a shift of 1 / N of the scanning distance.
By shifting in the scanning direction, dimensional variations between scans and variations in connection are averaged.
Further, in the multi-beam, by shifting in the direction perpendicular to the scanning direction so that different laser beams overlap each other, the intensity variation between the beams is averaged, and the size variation is averaged.

  FIG. 5 is a diagram for explaining an example of this overlapping method for multi-beams using laser light. The scanning direction of the unit pattern of the exposure is defined as the Y axis, and the direction in which a plurality of beams perpendicular to this is aligned is defined as the X axis. Accordingly, in scanning / exposure of one unit pattern, a linear pattern in which a plurality of beams are arranged in the Y-axis direction is exposed. The length in the X-axis direction on the mask blank of one unit pattern is LX, and the length in the Y-axis direction is LY (scanning distance). First, in the first exposure, after the first unit pattern 11 is exposed for the first time, the one unit pattern is repeatedly exposed so as to be in contact with each other in the X-axis direction and the Y-axis direction, and the first multi-face pattern is applied. Next, with respect to the first unit pattern 11, the second unit pattern 12 is exposed by shifting by LX / 2 in the X-axis direction and LY / 4 in the Y-axis direction. Multifaceted. Next, the first unit pattern 11 is exposed by shifting the unit pattern 13 for the third time by shifting LX × (3/4) in the X-axis direction and LY / 2 in the Y-axis direction. , Make a third facet. Next, the first unit pattern 11 is exposed by shifting the unit pattern 14 for the fourth time by shifting LX / 4 in the X-axis direction and LY × (3/4) in the Y-axis direction. , Make a fourth facet. As a result, the multifaceted pattern is overwritten four times.

  FIG. 6 is an explanatory view schematically showing an example of the dimension distribution of the beam overwritten on the mask blank in this way. FIG. 6A is an explanatory diagram of a legend showing a beam size distribution, in which the pattern length is one scanning distance 1, the arrow is the scanning direction 2, and the pattern separator is the scanning line. The connection 3 and the number schematically show the dimension 4 at the scanning position.

  In the present specification, the “beam pattern” refers to a linear pattern corresponding to one beam exposed in an overlapping manner in one unit pattern.

  FIG. 6B is an explanatory diagram of a dimensional distribution in which different beams are shifted by ¼ of the scanning distance and exposed four times. Here, the beam pattern indicated by BEAM1 is exposed with the laser beam A for the first multi-surface imposition, and with the second multi-surface exposure, the scanning is shifted by 1/4 of the scanning distance, and is exposed with the laser beam B. The exposure is performed with the laser beam C by shifting the second scanning by 2/4 and the laser beam D by shifting the fourth scanning by 3/4. These four beams are exposed on the same beam pattern, but are shown in parallel in the figure for explanation. The dimensions of the result of scanning and overlapping (the sum of the dimensions of the superimposed beams) are shown in the right part of the figure. The average dimension is 27. Further, when the variation in the scanning direction of the dimension is viewed by RANGE, the maximum value is 34 and the minimum value is 22, so that it is 12. Similarly, the beam pattern indicated by BEAM2 is exposed by laser beams B, C, D, and A, the average of the dimensions is 27, and the variation in the scanning direction is 12. The beam pattern indicated by BEAM3 is exposed by laser beams C, D, A, and B, the average dimension is 27, the variation in scanning direction is 12, and the beam pattern indicated by BEAM4 is laser beams D, A, B, and C. The average of the dimensions is 27 and the variation in the scanning direction is 12. Therefore, the average dimension variation of BEAM1 to BEAM4 is 0, and the average variation of each BEAM in the scanning direction is 12.

  That is, it can be seen that the dispersion between the beams is averaged by mixing the four types of beams.

As described above, it is possible to reduce the unevenness by averaging the variations by drawing different beams in a superimposed manner. When drawing by shifting the beam, it is necessary to draw in a consistent manner so that a predetermined pattern of the mask does not deviate. However, drawing in this way is very limited due to the function of the device. Since it cannot be set arbitrarily, the reduction of such variation is also limited.
Japanese Patent Application No. 2002-219224

  The present invention has been made in view of the above-described problems. A raster drawing method for improving the dimensional accuracy of a pattern to be drawn, in which multiple drawing can be increased to an arbitrary multiple, and the amount of misalignment can be set without limitation. It is an object of the present invention to provide a photomask manufacturing method and a photomask.

The present invention has been made to solve the above problems, a first aspect of the invention, the mask blank for a photomask having a predetermined pattern Ru is formed, in a raster drawing method for drawing by scanning a laser spot beam, Drawing Separately from multiple drawing using the apparatus , a plurality of pattern data obtained by cutting out a predetermined pattern in advance and a pattern data cut out by shifting the cutting position of the predetermined pattern are prepared, and the pattern data is directly used as a drawing apparatus. predetermined pattern sets the coordinate of the pattern data so as to overlap consistent with, by overlap drawing, at different start position of drawing the pattern data, the variation of the beam in a predetermined pattern on the photomask Is a raster drawing method characterized in that is averaged.

The invention of claim 2 of the present invention, the mask blank, a predetermined pattern is drawn by the beam, the photomask manufacturing method of manufacturing a photomask and developed, laser drawing method of a writing method is placing serial to claim 1 The photomask manufacturing method is characterized by the above.

  According to the laser drawing method according to claim 1 of the present application, a plurality of pattern data in which a predetermined pattern data and a predetermined pattern are shifted are prepared in advance before drawing. In other words, the number of times of multiple drawing can be increased to an arbitrary multiple of the setting on the apparatus, and the amount of deviation can be set arbitrarily. For this reason, the ERROR component due to the apparatus can be further averaged, and the dimensional accuracy of the drawing pattern can be improved.

Further, according to the drawing method according to claim 1, and draw over in pattern data by shifting the position of the predetermined pattern of multiple, variation in dimension is averaged in a predetermined pattern on the photomask. Before drawing, the data of the predetermined pattern and a plurality of pattern data in which the position of the predetermined pattern is shifted are prepared in advance, so the data can be simply drawn on the device as it is, and the overlay drawing of the raster drawing is the amount of deviation There is no limit to the number of times, and a drawing method in which dimensional variations are further averaged can be obtained.

According to the photomask producing method according to claim 2, draws a predetermined pattern on the mask blank according to the method of rendering claim 1 Symbol placement, since the production of photomasks, it is possible to improve the dimensional accuracy of the pattern of the photomask It becomes possible.

  A raster drawing method, a photomask manufacturing method, and a photomask of the present invention will be described below in detail based on an embodiment.

Before drawing, a plurality of pattern data in which a predetermined pattern data and a predetermined pattern position are shifted are prepared in advance. First, drawing is performed with data of a predetermined pattern, and further drawing is performed with pattern data in which the position of the predetermined pattern is shifted so that the predetermined pattern coincides and overlaps on the mask blank.
This may be performed multiple times.

Thus, to draw over the pattern data obtained by shifting the positions of a plurality of predetermined patterns, variation in dimension is averaged in a predetermined pattern on the photomask.

  In addition, since a plurality of pattern data in which the position of the predetermined pattern and the position of the predetermined pattern are shifted are prepared in advance before drawing, it is only necessary to draw the data as it is with the apparatus, and multiple drawing can be performed with an amount of deviation. There is no limit.

  By drawing as described above, the present invention is a raster drawing method for improving the dimensional accuracy of a pattern to be drawn, which can set the number of deviations to an arbitrary multiple, and can set the deviation without limitation, and the drawing method using the same The photomask manufacturing method will be described in detail with reference to the drawings.

FIG. 1 shows an example of a predetermined mask pattern and a predetermined mask pattern created by shifting the position. In order to create data whose position is shifted from the data of a predetermined mask pattern, CAD is usually used to display the predetermined mask pattern data on the screen and the end of the area where the pattern is shifted (usually lower left and upper right) Can be created by specifying and specifying the pattern. FIG. 5A shows a predetermined mask pattern, FIG. 5B shows a predetermined pattern shifted in position, and FIG. 4C shows a predetermined pattern drawn by superimposing both patterns.
It is assumed that the exposed portion is described as PATTERN DATA.

Patterns A and B have the same exposure part but different cut-out surfaces. Therefore, when drawing with a beam, the drawing start position (drawing starts from the end with data) is different. The place where the ERROR component (variation) due to the device of the above appears on a predetermined pattern is different. As a prerequisite, the time overlap drawing, a predetermined pattern itself (in this case, the portion that says PATT ER N DATA) as overlap match, sets the coordinates of the pattern data. In addition, when data of a predetermined pattern and data of patterns whose positions are shifted are prepared and prepared n times, when drawing is repeated n times, each pattern is drawn with an intensity of 1 / n of the amount of energy required for drawing. Do.

  Note that, when performing multiple drawing using the present application, drawing by only an apparatus using a conventional technique and the multiple drawing of the present application are usually performed in combination. For example, the pattern A shown in FIG. 1 is subjected to multiple drawing using a drawing apparatus, and then further multiple drawing is performed using the pattern B. If multiple drawing using a drawing apparatus is performed four times, it is possible to draw eight times in combination with the overlapping drawing of the present application.

  FIG. 2 shows numerically the ERROR component (dimensional variation) when four laser beams are subjected to multiple exposure four times and A and B are drawn. In this example, the RANGE is 12. As shown in the figure, the value of the ERROR component obtained by superimposing A and B is improved to RANGE2.

  FIG. 3 schematically shows the distribution of dimensions of patterns A and B. The larger the bubble, the greater the deviation from the average dimension. The pattern A having an inclination tends to be averaged by overlapping A and B, and the inclination is eliminated.

  As described above, in the raster drawing method of the present invention, a pattern with reduced dimensional variation can be drawn. Therefore, at least a predetermined pattern is drawn on the mask blank by the raster drawing method of the present invention and developed to produce a photomask. By doing so, a photomask with reduced dimensional variations can be manufactured.

  Furthermore, by manufacturing in this way, it is possible to provide a photomask with reduced dimensional variations as compared with the prior art.

  Examples of the present invention will be specifically described below.

Pattern data A comprising PILINE of LINE having a width of about 30 μm and 2 μm was prepared. For this, data of pattern B in which the cut surface is shifted by 9/16 of the scanning distance was created. These were drawn with Alta3000 manufactured by ETEC using a multi-laser beam. Normally, drawing is performed by shifting the number of overlaps to 8 times in the scanning direction by setting the apparatus. FIG. 4A shows the dimensional variation of the pattern A when drawn in this way. In the figure, ◯ indicates that the dimension is smaller than the average value, and ○ indicates that the dimension is larger than the average value. In addition, the larger the circle mark, the larger the value (absolute value). The variation RANGE was 0.037 μm and 3σ was 0.022 μm. Next, FIG. 4B shows the dimensional variation when the pattern A and the pattern B are overwritten. Since each pattern is similarly drawn by setting the apparatus, in this case, the number of overlaps is substantially 16 times and the drawing is shifted by 1/16 in the scanning direction.
RANGE was 0.024 μm, and 3σ was improved to 0.011 μm. Further, the pattern A had a tendency to appear in an oblique direction, and the size distribution was less likely to be uneven.

It is explanatory drawing which showed typically the example of the predetermined mask pattern which concerns on the example of embodiment of the method of this invention, and the mask pattern produced by shifting this position. It is explanatory drawing which showed typically the ERROR component (dimensional variation) which drawn the mask pattern which concerns on the embodiment of the method of this invention. It is explanatory drawing which showed typically the ERROR component (dimensional variation) which drawn the mask pattern which concerns on the embodiment of the method of this invention. It is explanatory drawing which showed typically the Example of the line pattern drawn by the method of this invention It is explanatory drawing which shows the method of multiple exposure. It is explanatory drawing which showed typically an example of intensity distribution of a beam.

Explanation of symbols

1 .... Distance of one scanning 2 .... Direction of scanning 3 .... Connection of scanning 4 .... Dimension 11 .... First unit pattern 12 .... Second one Unit pattern 13... Third unit pattern 14... Fourth unit pattern

Claims (2)

The mask blank for a photomask having a predetermined pattern Ru is formed, in a raster drawing method for drawing by scanning a laser spot beam, apart from the multiple writing using the writing apparatus, pattern data preliminarily cut a predetermined pattern When the pattern data cut out by shifting the cutout position of the predetermined pattern in advance a plurality prepared, their pattern data, sets the coordinate of pattern data so as to overlap to match a predetermined pattern by directly drawing device A raster drawing method characterized in that , by overlapping drawing , the drawing start positions of the respective pattern data are made different, and beam variations in a predetermined pattern on the photomask are averaged.   A photomask manufacturing method for manufacturing a photomask by drawing a predetermined pattern on a mask blank with a beam and developing the photomask, wherein the drawing method is the laser drawing method according to claim 1. .