JP4591039B2 - Measuring method of front and back pattern deviation of double-sided mask and creating method of double-sided mask - Google Patents

Description

  The present invention relates to a method for measuring a shift in position coordinates (in the plane direction) of a pattern on both sides of a double-sided mask having patterns on both front and back surfaces of a transparent substrate, and also a double-sided mask using the measurement method. It relates to the creation method.

  Conventionally, the method of measuring the deviation (in the plane direction) of the patterns on both sides in a double-sided mask having patterns on both the front and back sides of the transparent substrate is the center of gravity of the pattern on each side from the distance from the end face of the substrate to the pattern on each side And the rotational component were obtained, and the deviation between the pattern on the front surface and the pattern on the back surface was measured from the difference between them.

  However, since the end face has roughness, the center of gravity cannot be obtained accurately even if the distance from the end face is measured. In addition, since the corners of the end face are rounded, it is difficult to measure coordinates with a coordinate microscope, and there is a problem that measurement errors increase.

  In manufacturing a double-sided mask, in order to control the overlay deviation between the back surface pattern and the front surface pattern at a high level, high accuracy is required for measurement of the overlay displacement. (See Patent Document 1 and Patent Document 2).

The known literature is described below.
Japanese Patent Laid-Open No. 2-93457 Japanese Patent Laid-Open No. 3-271738

  The present invention has been made in view of the above-described problems, and provides a method for measuring a shift of a pattern on both sides of a double-sided mask with high accuracy, and a pattern on a front surface and a back surface using the measurement method. It is an object of the present invention to provide a method for creating a double-sided mask in which the patterns are superimposed with high accuracy.

SUMMARY OF THE INVENTION The present invention has been made for the purpose of solving such problems, and the invention according to claim 1 of the present invention is directed to the pattern on one side and the other side of a double-sided mask in which patterns are formed on both the front and back sides of a transparent substrate. In the method of measuring the pattern deviation, a measurement pattern and a main pattern are formed on the first metal thin film layer on the surface of the transparent substrate, and then the second metal thin film layer is formed on the back surface of the transparent substrate. When the pattern is formed, first, a measurement opening that allows the measurement pattern to be visually recognized from the back surface through the transparent substrate is formed in the second metal thin film layer on the back surface, and the measurement opening is measured. Measuring the position shift of the measurement pattern with respect to a point, rotating the double-sided mask 180 degrees in a horizontal plane, and again measuring the position shift of the measurement pattern with respect to the measurement point of the measurement opening. The error due to the measuring device is offset, a resist resin is applied on the second metal thin film layer, and the main pattern and the measurement auxiliary pattern of the second metal thin film layer are applied to the resist resin at the measured positions. The position of the pattern of the second metal thin film layer is corrected and drawn using a shift amount, the resist resin is developed, the position shift of the measurement auxiliary pattern with respect to the measurement pattern is measured, and the measurement The measurement of the position shift of the measurement pattern with respect to the measurement point of the opening measures the relative position of the measurement point of the measurement opening and the measurement point of the measurement pattern, and the measurement point of the measurement opening The coordinates of the measurement points of the measurement pattern are calculated as relative positions of the double-sided mask.

The invention according to claim 2 of the present invention is the method for producing a double-sided mask in which a pattern is formed on both front and back surfaces of a transparent substrate , wherein the measurement pattern and the main pattern are provided on the first metal thin film layer on the surface of the transparent substrate. And forming the second metal thin film layer pattern on the back surface of the transparent substrate , first, the second metal thin film layer on the back surface is passed through the transparent substrate from the back surface for the measurement. A step of forming a measurement opening capable of visually recognizing the pattern, and measurement of a position shift of the measurement pattern with respect to a measurement point of the measurement opening , and the double-sided mask is rotated 180 degrees in a horizontal plane Measuring the deviation of the position of the measurement pattern with respect to the measurement point of the measurement opening again to offset the error caused by the measurement device; and applying a resist resin on the second metal thin film layer Process and the resist main pattern and the measurement auxiliary pattern of the resin to the second metal thin film layer, by using the shift amount of the position the measurement of the second gold
Correcting and drawing the position of the pattern of the metal thin film layer, developing the resist resin, measuring the positional deviation of the auxiliary measurement pattern with respect to the measurement pattern, and then etching the second A step of forming a pattern of the metal thin film layer, and a step of measuring a displacement of the position of the measurement pattern with respect to the measurement point of the measurement opening includes measuring the measurement point of the measurement opening and the measurement pattern. A method for producing a double-sided mask, comprising: measuring a relative position of a measurement point and calculating coordinates of the measurement point of the measurement pattern as a relative position with respect to the measurement point of the measurement opening .

  As described above, according to the present invention, it is possible to measure the deviation between the front surface pattern and the back surface pattern due to the rotational deviation of the front and back surfaces of the double-sided mask and the deviation in the XY direction with high accuracy. A double-sided mask with a small pattern deviation can be created.

  FIG. 1 is a view for explaining the structure of a measurement pattern in a double-sided mask to be measured by the method for measuring the front / back pattern deviation of a double-sided mask according to claim 1 of the present invention. (A) is a top view of the pattern of an upper surface, (b) is a sectional side view, (c) is a top view of the pattern of the lower surface of a reference figure. When the double-sided mask is set on the coordinate microscope, the upward surface is the upper surface pattern and the downward surface is the lower surface pattern (see FIG. 1B).

  A measurement point A is set in the measurement pattern a (5) of the lower surface pattern, and a measurement opening b (8) is provided in the upper surface pattern so that the measurement point A can be viewed from the upper surface. A measurement point B is defined in the measurement opening b of the upper surface pattern.

  The material of the pattern formed on the double-sided mask according to the present invention is not particularly limited as long as the coordinates of the pattern can be measured at the time of measuring the deviation, but FIG. The case where a metal thin film layer is used is shown.

  Note that the position of the measurement point A is preferably far from the center of rotation in order to increase the change in position when a rotational deviation occurs and reduce the measurement error.

  FIG. 2 is a diagram for explaining a method of measuring the front / back pattern deviation of the double-sided mask according to claim 1 of the present invention.

  When the lower surface pattern rotates θ with respect to the upper surface pattern and is shifted by a in the X direction and by b in the Y direction, the measurement point A (xa, ya) moves to the coordinates of A ′ (xa ′, ya ′). However, in the figure, the origin of coordinates is set at the center of the top surface.

When the deviation between the measurement points A and A ′ of the measurement pattern a on the lower surface is (xA, yA),
xA = xa′−xa = f (θ) + a
yA = ya′−ya = g (θ) + b
The relationship holds.

Here, f (θ) and g (θ) are functions for converting the rotational component of the shift from the measurement point A to A ′ into an orthogonal coordinate component, and can be obtained from the coordinates of the measurement point A by a trigonometric function. it can.

The formula is described below.
f (θ) = ± [SQRT {(xa * xa) + (ya * ya)}] cos {| arctan (ya / xa) | ± θ} −xa
g (θ) = ± [SQRT {(xa * xa) + (ya * ya)}] sin {| arctan (ya / xa) | ± θ} −ya
Note that ± is determined by the direction of rotation and the sign of the coordinates.

  Since a, b, and θ are independent of each other, if xA and yA are known, theoretically, a, b, and θ can be obtained by solving simultaneous equations with two or more measurement points.

  The deviation (xA, yA) between the measurement points A and A ′ of the measurement pattern a on the lower surface is determined by measuring the measurement point B (xb, yb) of the upper surface measurement opening b by using a coordinate microscope aligned with the coordinate axis of the upper surface pattern. And by measuring the relative position of the measurement point A ′ (xa ′, ya ′) of the measurement pattern a on the lower surface.

  However, since the measurement value includes a measurement error, the obtained solution may be deviated from the true value, and it is difficult to solve an equation including a trigonometric function.

FIG. 3 is a process diagram for explaining an example of a method for producing a double-sided mask according to the present invention. As described above, the pattern may be formed of any material as long as the coordinates of the pattern can be measured at the time of measuring the deviation (for example, the pattern can be formed by unevenness on the transparent substrate. However, the case where a metal thin film layer is used is demonstrated as an example here.

  The transparent substrate 1 uses borosilicate glass or quartz glass. Each of the above-mentioned glasses has a difference in thermal expansion coefficient, and the latter quartz glass has a much smaller thermal expansion coefficient, so it is used for a high-precision photomask. It is preferable to select according to the required dimensional accuracy. The metal thin film layer 2 is formed by laminating a single layer or a plurality of layers made of chromium, chromium oxide, molybdenum silicide or the like. The metal thin film layer 2 is formed by a method such as a vacuum deposition method or a sputtering method. Next, the resist resin 3 is applied to one surface (front surface) of the double-sided mask blank using a spin coater (see step (a)).

  Next, the main pattern 4 and the measurement pattern 5 are drawn on the resist layer on the surface of the double-sided mask blank. According to the pattern data file management name (data file name) and the drawing procedure file (hereinafter referred to as JOB file) in which the position coordinates are recorded, the resist resin is exposed to form pattern figures, and the development process, etching A photomask in which a pattern including the main pattern 4 and the measurement pattern 5 is formed is obtained through the process and the process of peeling the resist layer (see process (b)).

  Next, a metal thin film layer 6 is formed on the back surface, and a resist resin 7 is applied (see step (c)).

  An alignment pattern (not shown) and a measurement opening 18 are drawn on the back surface of the double-sided mask blank. A pattern is exposed to form a figure, and after a development process, an etching process, and a resist layer peeling process, a photomask having an alignment pattern and a measurement opening 8 is formed (see processes (d) and (e)). ).

The mask is set on the coordinate microscope with the measurement opening 8 facing upward. At this time, the front surface is the bottom surface and the back surface is the top surface.

  FIG. 4 shows a state visually recognized from the measurement opening 8 on the upper surface. As shown in FIG. 4, the four points of the measurement pattern on the lower surface (front surface) can be visually recognized through the transparent substrate from the opening on the upper surface. Reference diagrams will be referred to in the following description.

  If four measurement points XA, XB, XC, and XD are set in the measurement opening and four measurement points A, B, C, and D are set in a specific arrangement in the measurement pattern, the correlation of the respective coordinates is set. Therefore, since the rotational deviation θ, the X-direction deviation a, and the Y-direction deviation b can be calculated individually, they can be easily obtained without solving the equations. Further, since the error due to the measurement can be reduced because it is obtained from the average of a plurality of measurement points, it can be obtained with higher accuracy.

  The four measurement points A, B, C, and D are set so that the center point of a rectangle (square or rectangle) connecting the four points A, B, C, and D of the measurement pattern coincides with the origin of the coordinate axis. Set at the four corners of the bottom surface. At this time, A and B, C and D are symmetric with respect to the Y axis, respectively, and A and C, B and D are symmetric with respect to the X axis. Similarly, measurement points XA, XB, XC, and XD of the measurement opening are placed on the upper surface (back surface).

  When the lower surface pattern rotates θ with respect to the upper surface pattern and is shifted by a in the X direction and b in the Y direction, the four measurement points A, B, C, and D of the measurement pattern on the lower surface (front surface) are With respect to the upper surface, they move to A ′, B ′, C ′, and D ′, respectively, due to the rotational deviation θ, the X-direction deviation a, and the Y-direction deviation b.

  The coordinates of A ′, B ′, C ′, and D ′ of the measurement points of the measurement pattern on the lower surface are measured using a coordinate microscope that is aligned with the coordinate axis of the upper surface pattern. The coordinates can be calculated as relative positions with respect to the four measurement points XA, XB, XC, and XD of the measurement opening on the upper surface. Let A ′ (xa, ya), B ′ (xb, yb), C ′ (xc, yc), and D ′ (xd, yd), respectively.

When the distance xab in the X direction and the distance yab in the Y direction between A ′ and B ′ are obtained from the respective coordinates, the rotational deviation θ is
arctan (yab / xab)
Can be obtained. Similarly, since the rotational deviation θ can be obtained from B′D ′, C′D ′, and C′A ′, the average value of these is the rotational deviation θ.

If the lower surface pattern is shifted upward with respect to the upper surface pattern, the displacement in the Y direction is
{(Ya + yb) / 2 + (yc + yd) / 2} / 2
Can be obtained.

If the lower surface pattern is shifted to the right with respect to the upper surface pattern, the displacement in the x direction is
{(Xa + xc) / 2 + (xb + xd) / 2} / 2
Can be obtained.

  If the coordinate microscope has an apparatus-specific measurement error, the error is canceled by rotating the mask 180 ° in the horizontal plane and using the average value with the value calculated in the same manner as the measurement value. Measurement accuracy can be further increased.

  Again, a resist resin 9 is applied to the back surface of the double-sided mask blank (see step (f)).

  The main pattern 20 and the auxiliary measurement pattern 21 are drawn by a method of correcting the amount of misalignment between the measured patterns on both sides and aligning with the alignment pattern. The auxiliary measurement pattern 21 is arranged on a straight line connecting the centroids of the diagonal measurement openings so that it can be used in the same manner as the measurement points of the measurement openings. If there is no function for correcting the deviation on the apparatus, the alignment pattern reading position coordinates in the JOB file relating to drawing may be changed. That is, it is a method for correcting the shift by converting the shift into a shift in the position coordinates of the alignment pattern registered in the JOB file and aligning the mask with the shift in the shift coordinates (see step (g)). .

  The back surface pattern is developed (see step (h)).

The position offset of the front and back patterns, by using the measurement pattern 5 of the measuring auxiliary patterns 21 and the lower surface, the upper surface, through the transparent substrate, and measuring the bottom surface of the position coordinates of the measurement pattern 5, the measurement From the difference between the coordinates of the position that should be designed with respect to the measurement auxiliary pattern 21 and the coordinates of the actually measured position of the measurement pattern 5, the rotational component and the orthogonal coordinate component of the shift Is calculated to measure the front / back pattern deviation of the double-sided mask .

  As a result of the measurement, after confirming that there is no problem in the misalignment between the front surface pattern and the back surface pattern, etching and peeling of the resist layer are performed to complete the double-sided mask of the present invention (see step (i)).

  However, in the case where a deviation of the superposition of the front surface pattern and the back surface pattern occurs, the cause of the occurrence of the deviation is investigated and countermeasures are taken, and after removing the resist layer, the process returns to the step (f) and the process is performed again. (F) The subsequent processing is performed. As described above, the double-sided mask with high overlay accuracy of the desired front and back double-sided patterns is completed by the double-sided mask production method of the present invention.

It is a figure which shows the structure of the measurement pattern in the measuring method of the shift | offset | difference of the front and back pattern of the double-sided mask of this invention, (a) is a top view, (b) is a sectional side view. It is a schematic diagram which shows the relationship between the shift | offset | difference of the pattern of the front and back in a double-sided mask of this invention, a rotation shift | offset | difference, and the shift | offset | difference of an XY direction. It is a figure which shows the process of the creation method of the double-sided mask of this invention. It is a schematic diagram which shows an example of the method of calculating | requiring the shift | offset | difference of the pattern of both surfaces in the double-sided mask of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transparent substrate 2 ... Metal thin film layer 3 of surface (lower surface) ... Resist resin 4 of surface (lower surface) ... Main pattern 5 of surface (lower surface) ... Measurement pattern 6 of surface (lower surface) ... Metal of back surface (upper surface) Thin film layer 7... Resin resin 8 on the back surface (upper surface) 18... Alignment pattern and measurement opening 9 on the back surface (upper surface) Resist resin 10 on the back surface (upper surface) 20 Main pattern 11 and 21 on the back surface (upper surface) ... back surface (upper surface) measurement auxiliary pattern 13 ... upper surface measurement point (B)
12 ... Measurement point on the bottom surface (A)

Claims (2)

In the method of measuring the deviation of the pattern on one side and the pattern on the other side of the double-sided mask with patterns formed on both sides of the transparent substrate ,
When forming the measurement pattern and the main pattern on the first metal thin film layer on the surface of the transparent substrate, and then forming the pattern of the second metal thin film layer on the back surface of the transparent substrate,
First, in the second metal thin film layer on the back surface, a measurement opening that can visually recognize the measurement pattern from the back surface through the transparent substrate is formed,
Measure the deviation of the position of the measurement pattern with respect to the measurement point of the measurement opening,
The double-sided mask is rotated 180 degrees in a horizontal plane, and the error of the measurement pattern is offset by measuring the deviation of the position of the measurement pattern with respect to the measurement point of the measurement opening, thereby the second metal thin film layer Apply resist resin on top,
The main pattern of the second metal thin film layer and the measurement auxiliary pattern are drawn on the resist resin by correcting the position of the pattern of the second metal thin film layer using the measured displacement amount, and Develop resist resin,
Measure the displacement of the measurement auxiliary pattern with respect to the measurement pattern,
The measurement of the positional deviation of the measurement pattern with respect to the measurement point of the measurement opening measures the relative position between the measurement point of the measurement opening and the measurement point of the measurement pattern, A method for measuring the front / back pattern deviation of a double-sided mask, wherein the coordinates of the measurement point of the measurement pattern are calculated as a relative position to the measurement point . In the method of creating a double-sided mask with a pattern formed on both sides of the transparent substrate ,
Forming a measurement pattern and a main pattern on the first metal thin film layer on the surface of the transparent substrate;
Next, when forming the pattern of the second metal thin film layer on the back surface of the transparent substrate,
First, forming a measurement opening in the second metal thin film layer on the back surface through which the measurement pattern can be viewed through the transparent substrate;
Measure the deviation of the position of the measurement pattern with respect to the measurement point of the measurement opening,
Rotating the double-sided mask 180 degrees in a horizontal plane and again measuring the deviation of the position of the measurement pattern with respect to the measurement point of the measurement aperture, thereby offsetting the error caused by the measurement device;
Applying a resist resin on the second metal thin film layer;
The main pattern of the second metal thin film layer and the auxiliary pattern for measurement are drawn on the resist resin by correcting the position of the pattern of the second metal thin film layer using the measured displacement amount.
And developing the resist resin;
Measuring a positional deviation of the auxiliary measurement pattern with respect to the measurement pattern;
Next, the step of forming a pattern of the second metal thin film layer by etching,
The step of measuring the shift of the position of the measurement pattern with respect to the measurement point of the measurement opening measures the relative position between the measurement point of the measurement opening and the measurement point of the measurement pattern, and the measurement opening A method for producing a double-sided mask, comprising a step of calculating coordinates of measurement points of the measurement pattern as relative positions with respect to measurement points of a part .

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