JP2001092103A - Method and device for manufacturing photomask and method of manufacturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a photomask by which an original plate pattern can be formed with high precision and in a short time. SOLUTION: The original plate pattern 27 is formed on data by increasing the size of a circuit pattern 35 β times, a parent pattern 36 is formed on data by increasing the size of the original plate pattern 27 α times and then parent patterns P1 to PN are formed on data by dividing the parent pattern 36 horizontally and vertically into α pieces. The parent patterns P1 to PN are respectively drawn unmagnifiedly on a substrate by using an electron beam drawing or the like to produce master reticles R1 to RN. Then, a working reticle 34 is produced by transferring reduced images of the parent patterns of the master reticles R1 to RN on the substrate while connecting screens by using an optical reduction stepper of 1/α reduction rate. Transferred positions or the like of the reduced images of the parent is corrected so that errors of image formation characteristic of an exposing device using the working reticle 34 are canceled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a semiconductor integrated circuit,
The present invention relates to a method and an apparatus for manufacturing a photomask used as an original pattern when manufacturing a micro device such as a liquid crystal display element or a thin film magnetic head by using a lithography technique. Further, the present invention relates to a method for manufacturing a device using such a photomask.

[0002]

2. Description of the Related Art When a device such as a semiconductor integrated circuit is manufactured, a circuit pattern to be formed is enlarged by, for example, about 4 to 5 times. A transfer method is used in which the image is projected onto a substrate to be exposed such as a wafer or a glass plate via a reduction projection optical system. An exposure apparatus is used for transferring such a photomask pattern, and a photomask used in a step-and-repeat type reduction projection exposure apparatus is also called a reticle.

Conventionally, such a photomask has been manufactured by drawing an original pattern on a predetermined substrate using an electron beam drawing apparatus or a laser beam drawing apparatus. That is, after forming a mask material on the substrate and applying a resist, the original pattern is drawn using an electron beam drawing apparatus or a laser beam drawing apparatus. Thereafter, the original pattern was formed by the mask material by developing the resist and performing an etching process or the like. In this case, assuming that the reduction magnification of the reduction projection type exposure apparatus using the photomask is 1 / β, the original pattern drawn on the photomask may be a pattern obtained by enlarging the device pattern by β times. The drawing error by the drawing apparatus is reduced to approximately 1 / β times on the device. Therefore, a device pattern can be formed with a resolution substantially equal to 1 / β times the resolution of the drawing apparatus.

[0004]

As described above, conventionally, an original pattern of a photomask has been drawn by an electron beam drawing apparatus or a laser beam drawing apparatus. These drawing apparatuses draw the original pattern directly based on drawing data from a control computer. However, recent devices such as LSIs have a large area, and the degree of fineness and integration have been increasingly improved. Therefore, the original pattern of a photomask required for the exposure has also been increased in area,
And it is miniaturized. Further, as a photomask, a reticle provided with a correction pattern for preventing unnecessary pattern transfer for double exposure, and a so-called phase shift reticle provided with a phase shifter between adjacent patterns may be used. However, these special photomasks tend to have a larger amount of drawing data than other photomasks. Thus, the drawing data required by the drawing apparatus for manufacturing the photomask is enormous.

For this reason, the writing time required for writing an original pattern of one photomask by the writing apparatus has recently been increasing to about 10 to 24 hours. Such an increase in the drawing time contributes to an increase in the manufacturing cost of the photomask. In this regard, in the electron beam writing apparatus, it is necessary to correct the proximity effect due to the influence of back scattering peculiar to the electron beam, and further to correct the uneven electric field around the substrate due to the charging of the surface of the substrate. For this reason, in order to draw an original pattern as designed, it is necessary to measure errors in the drawing position and the like in advance under various conditions, and to perform complicated correction with high accuracy and stability at the time of drawing. However, as described above, it is difficult to continuously perform such a complicated correction with high accuracy and stability during a very long drawing time, which causes a drawback that a drawing position drifts during drawing. was there. It is also possible to perform the calibration by interrupting the drawing, but this has the disadvantage that the entire drawing time is further lengthened.

Further, the characteristics such as the resolving power of a resist for an electron beam have not been improved so much, and it is considered that the characteristics will not be rapidly improved in the future. Therefore, if the pattern rules of semiconductor devices and the like become further finer in the future, the drawing time of the original pattern of one photomask becomes too long, and the resolution of the electron beam resist approaches the limit, so that the required drawing accuracy is reduced. There is a risk that it will not be available. Also, the amount of drawing data in the control computer is
It is becoming enormous that it is difficult to use in one drawing.

On the other hand, a laser beam drawing apparatus draws an original pattern by using a laser beam in an ultraviolet region, and can use a resist capable of obtaining a higher resolution as compared with an electron beam drawing apparatus. There is an advantage that there is no effect. However, the resolution of a laser beam writing apparatus is inferior to that of an electron beam writing apparatus. Also, in a laser beam drawing apparatus, since the original pattern is directly drawn, the amount of drawing data is enormous and data processing is becoming difficult, and the drawing time becomes extremely long. The required drawing accuracy may not be obtained due to the drift of the position.

When a photomask is actually mounted on a projection exposure apparatus and the pattern of the photomask is projected onto a substrate such as a wafer via a projection optical system, distortion or the like remains in the projection optical system. In this case, there is a disadvantage that a distorted image is exposed on the substrate and an overlay error or the like occurs. Further, since the imaging characteristics such as distortion of the projection optical system are slightly different for each projection exposure apparatus, it is desirable to be able to correct the projected image of each projection exposure apparatus if possible.

In view of the above, it is a first object of the present invention to provide a method for manufacturing a photomask capable of forming an original pattern with high accuracy and in a short time. Further, the present invention provides a method of manufacturing a photomask capable of substantially correcting the image forming characteristic when a predetermined image forming characteristic of a projection image of a projection exposure apparatus using the photomask is deteriorated. This is a second object.

It is a third object of the present invention to provide a manufacturing apparatus capable of performing such a method for manufacturing a photomask. It is a fourth object of the present invention to provide a device manufacturing method capable of forming a device pattern with higher accuracy by using such a photomask manufacturing method.
The purpose of.

[0011]

According to a method of manufacturing a photomask according to the present invention, in a method of manufacturing a photomask (34) having a transfer pattern (27) formed thereon, the transfer pattern (27) is enlarged. The divided pattern is divided into a plurality of patterns of parent masks (R1 to RN), and a reduced image of the pattern of the plurality of parent masks (R1 to RN) is screen-connected to the surface of the photomask substrate (4). The transfer is performed sequentially while performing the following.

According to the present invention, when manufacturing the photomask, for example, a thin film of a mask material is formed on a substrate (4) of the photomask, and a photosensitive material such as a photoresist is formed thereon. Material is applied. Thereafter, a reduced image of a pattern of a plurality of parent masks was transferred onto the photosensitive material by a step-and-repeat method or a step-and-scan method using, for example, an optical reduction projection type exposure apparatus. Thereafter, the photosensitive material is developed. Then, a desired transfer pattern (original pattern) is formed by performing etching or the like using the remaining photosensitive material pattern as a mask.

At this time, assuming that the reduction magnification of, for example, an optical exposure apparatus for manufacturing the photomask is 1 / α (α is an integer greater than 1 or a half integer), the transfer pattern (27) That is, the original pattern is enlarged by α times, and the enlarged parent pattern (36) is divided vertically and horizontally into, for example, α × α parent mask patterns. Reduction ratio is 1/5
If it is double (α = 5), 25 × 5 × 5 parent masks are prepared. As a result, the pattern formed on each parent mask becomes a part of the parent pattern obtained by enlarging the original pattern by α times. Therefore, the drawing data amount of the pattern of each parent mask is reduced to about 1 / α ^{2 of the} conventional one. , The minimum line width is α times the conventional value. Therefore, the pattern of each parent mask can be drawn with a small drift and high accuracy in a short time using, for example, a conventional electron beam drawing apparatus or laser beam drawing apparatus. Further, the writing error by the writing apparatus is reduced to 1 / α on the photomask, so that the accuracy of the original pattern is further improved. Further, once the parent masks are manufactured, the pattern of the parent masks can be transferred onto the substrate of the photomask at high speed by a step-and-repeat method or the like. In this case, the manufacturing time can be greatly reduced as compared with the conventional method of individually drawing by a drawing apparatus.

In this case, when sequentially transferring the reduced images of the patterns of the plurality of parent masks (R1 to RN) onto the surface of the substrate (4), the purpose of the photomask (the type of the exposure apparatus used, etc.) It is preferable to use a batch exposure type reduction projection exposure apparatus or a scanning exposure type reduction projection type exposure apparatus in accordance with (1). For example, if the photomask is a step
When used in a scanning exposure type reduction projection exposure apparatus such as an AND scan method, a parallelogram-shaped distortion (so-called skew error) or the like may occur in a projected image. In this case, it is difficult to correct the skew error in the batch exposure type. Therefore, when transferring the pattern of a plurality of parent masks onto the substrate of the photomask, the skew error is offset by using a scanning exposure type projection exposure apparatus. By giving such a distortion, the distortion when the photomask is used can be reduced, so that the overlay error and the like are reduced.

When sequentially transferring the reduced images of the patterns of the plurality of parent masks (R1 to RN) onto the surface of the substrate (4), the projection optical system (42) of the projection exposure apparatus using the photomask. ) According to at least one of the non-rotationally symmetric aberration and the distortion characteristic.
It is desirable to correct the imaging characteristics (transfer position, magnification, distortion, etc.) of the reduced image of the pattern (RN).

As described above, when the amount of change in the predetermined image forming characteristic of the exposure apparatus using the photomask is known in advance, the pattern of each parent mask is screen-connected on the substrate of the photomask. When transferring the image, by adjusting the transfer position, magnification, distortion, etc. of the pattern image of each parent mask so as to offset the fluctuation amount of the imaging characteristics, finally using the photomask The distortion and the like of the device pattern to be exposed are reduced, and the overlay accuracy and the like are improved.

In this regard, many photomasks are manufactured, and these photomasks are mixed and
There are also cases where a plurality of projection exposure apparatuses are used in a match system or the like. In this case, the average characteristics such as the distortion characteristics of the projection images of at least two projection exposure apparatuses that are to use the photoresists are set so that good overlay accuracy can be obtained in each projection exposure apparatus. Accordingly, it is desirable to adjust the transfer position, image characteristics, and the like when the patterns of the respective parent masks are connected and transferred.

Next, it is desirable that the photomask is further used in reduced projection. The photomask is used in, for example, 1 / β-fold (β is an integer greater than 1 or a half-integer) reduced projection, and the reduction magnification of an exposure apparatus for manufacturing the photomask is 1 / α. Times (α is β
Is an integer greater than 1 or a half-integer in the same manner as in (1), the pattern writing error of each parent mask is reduced to 1 / (α · β) times on the device pattern to be finally exposed. . Therefore, even in the case where the minimum line width of the device pattern is supposed to be １ ／ of the current line width, the pattern of each parent mask can be easily formed with the necessary accuracy using an electron beam lithography system or a laser beam lithography system. In addition, drawing can be performed in a short time. Therefore, even if the pattern rule is further miniaturized, a desired device pattern can be exposed with necessary accuracy.

Next, a photomask manufacturing apparatus according to the present invention includes a mask storage device (16-18) for storing a plurality of masks (R1-RN), and one mask selected from the mask storage device. Stage, a projection optical system (3) for projecting a reduced image of a mask pattern on the mask stage onto a photomask substrate (4), and the projection optical system A substrate stage (6) for positioning on a plane perpendicular to the optical axis of the system, and a mask on the mask stage (2) for screen joining of reduced images of the plurality of mask patterns on the substrate. And an alignment system (14A, 14B) for performing alignment with the substrate on the substrate stage (6).

By using such a photomask manufacturing apparatus, the photomask manufacturing method of the present invention can be performed. In this case, as an example, the mask storage device
A plurality of parent masks (R1 to RN) each having a pattern obtained by dividing a pattern obtained by enlarging a pattern (27) of a photomask to be manufactured are stored. As a result, the parent masks are exchanged at high speed, and exposure can be performed in a short time.

Further, according to the device manufacturing method of the present invention, in the device manufacturing method for forming a predetermined pattern on the substrate (W), the first pattern (27) obtained by enlarging the predetermined pattern is further added. A plurality of parent mask patterns (P1 to P
N), and the first pattern (27) is formed by reducing and projecting a plurality of patterns of the parent mask onto a predetermined substrate (4) while sequentially performing screen joining, for actual exposure. A photomask (34) is manufactured, and a reduced image of the pattern of the photomask for actual exposure is transferred onto the substrate (W).

According to the present invention, the magnification from the device pattern formed on the substrate (W) to the first pattern (27) is β times (β is an integer larger than 1, a half integer, etc.). ), If the magnification from the first pattern to the second pattern (36) is α times (α is an integer greater than 1 or a half-integer like β, the line width of the pattern of the parent mask is It becomes α · β times the line width of the pattern of the device. Accordingly, if the line width drawing error when writing the pattern of the parent mask with an electron beam drawing apparatus or the like is Δd, the line width error of the pattern of the device is approximately Δd /
Since it is reduced to (α · β), the pattern of the device can be formed with extremely high precision.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a manufacturing process of the photomask of this embodiment. In FIG. 1, the photomask to be manufactured in this embodiment is a working reticle 34 used when actually manufacturing a semiconductor device. . The working reticle 34 is formed by forming an original pattern 27 for transfer from chromium (Cr), molybdenum silicide (MoSi ₂ or the like), or another mask material on one surface of a light-transmitting substrate made of quartz glass or the like. It is. Two alignment marks 24A and 24B are formed so as to sandwich the original pattern 27.

Further, the working reticle 34 is 1 / β-fold (β is an integer greater than 1 or a half-integer, for example, 4, 5, or 6)). That is, in FIG. 1, after exposing a reduced image 27W of 1 / β times the original pattern 27 of the working reticle 34 to each shot area 48 on the wafer W coated with the photoresist, development, etching, and the like are performed. By
A predetermined circuit pattern 35 is formed in each shot region 48. In this example, the non-rotationally symmetric aberration of the projected image of the projection exposure apparatus and the imaging characteristics such as distortion characteristics are measured in advance, and the measurement results are used when manufacturing the working reticle 34 as described later. You. Hereinafter, the working reticle 3 as the photomask of this example
An example of the manufacturing method 4 will be described.

In FIG. 1, first, a circuit pattern 35 of a certain layer of a finally manufactured semiconductor device is designed. The width of the orthogonal side of the circuit pattern 35 is dX, dY.
Various line-and-space patterns and the like are formed in the rectangular area of FIG. In this example, the circuit pattern 35 is multiplied by β, and the width of the orthogonal side is β · dX, β ·
An original pattern 27 composed of a rectangular area of dY is created on image data of a computer. β times is the reduction ratio (1/1 /) of the projection exposure apparatus in which the working reticle 34 is used.
β). It should be noted that when reverse projection is performed, the image is inverted and enlarged.

Next, the original pattern 27 is multiplied by α (α is an integer greater than 1 or a half-integer, such as 4, 5, or 6 as an example) so that the width of the orthogonal side is α · β.・ D
Parent pattern 36 consisting of rectangular areas of X, α, β, dY
Is created on the image data, and the parent pattern 36 is divided vertically and horizontally into α pieces, respectively, so that α × α pieces of parent patterns P1,
.., PN (N = α ² ) are created on the image data. FIG. 1 shows a case where α = 5. Note that the division number α of the parent pattern 36 does not necessarily need to match the magnification α from the original pattern 27 to the parent pattern 36. Then, those parent patterns Pi (i = 1
To N) to generate drawing data for an electron beam drawing apparatus (or a laser beam drawing apparatus or the like can also be used), and transfer the parent patterns Pi at the same magnification onto a master reticle Ri as a parent mask.

For example, when manufacturing the first master reticle R1, a thin film of a mask material such as chromium or molybdenum silicide is formed on a light transmissive substrate such as quartz glass, and an electron beam is formed thereon. After applying the resist, an equal-magnification image of the first parent pattern P1 is drawn on the electron beam resist using an electron beam drawing apparatus. Thereafter, after the electron beam resist is developed, etching, resist stripping, and the like are performed to form the parent pattern P1 in the pattern region 20 on the master reticle R1. At this time, alignment marks 21A and 21B composed of two two-dimensional marks are formed on master reticle R1 in a predetermined positional relationship with respect to parent pattern P1. Similarly, the parent pattern Pi and the alignment marks 21A and 21B are formed on the other master reticles Ri using an electron beam drawing apparatus or the like. These alignment marks 21A and 21B are used for positioning when screen joining is performed later.

As described above, in this embodiment, since each parent pattern Pi to be drawn by the electron beam drawing apparatus (or the laser beam drawing apparatus) is a pattern obtained by enlarging the original pattern 27 by α times, the amount of each drawing data is , Is reduced to about 1 / α ^{2 as} compared with the case where the original pattern 27 is directly drawn.
Furthermore, the minimum line width of the parent pattern Pi is
.Times. (For example, 5 times, 4 times, or the like) as compared with the minimum line width of each of the parent patterns Pi. Can be drawn. Further, once the N master reticles R1 to RN are manufactured, the necessary number of working reticles 34 can be manufactured by repeatedly using them as described later, so that the master reticles R1 to RN are manufactured. Time is not a big burden.

That is, these N master reticles Ri
Reduced image PIi of 1 / α times the parent pattern Pi (i = 1 to 1)
The working reticle 34 is manufactured by transferring N) while performing screen splicing. FIG.
FIG. 2 shows an optical reduction projection type exposure apparatus used in manufacturing the working reticle 34. In FIG. 2, at the time of exposure, an exposure light source, a fly-eye lens for uniformizing the illuminance distribution, an illumination system aperture stop, a reticle blind Exposure light IL is applied to the reticle on the reticle stage 2 from an illumination optical system 1 including a (variable field stop) and a condenser lens system. On the reticle stage 2 of this example, i
The (th) master reticle Ri (i = 1 to N) is placed. The exposure light may be a bright line such as an i-line (wavelength 365 nm) of a mercury lamp or KrF (wavelength 248 n).
m), ArF (wavelength 193 nm), or F ₂ (wavelength 157 nm) excimer laser or the like can be used.

The image of the pattern in the illumination area of the master reticle Ri is reduced by the projection optical system 3 at a reduction ratio of 1 / α (α
Is projected onto the surface of the substrate 4 for the working reticle 34, for example. The substrate 4 is a light transmissive substrate such as quartz glass, and a thin film of a mask material such as chromium or molybdenum silicide is formed on a pattern region 25 (see FIG. 4) on the surface thereof. Alignment marks 24A and 24B are formed so as to sandwich the two two-dimensional marks for alignment.
A photoresist is applied to the surface of the substrate 4 so as to cover the mask material. Hereinafter, the optical axis A of the projection optical system 3
The description will be made by taking the Z axis parallel to X, the X axis parallel to the plane of FIG. 2, and the Y axis perpendicular to the plane of FIG. 2 in a plane perpendicular to the Z axis.

First, the reticle stage 2 positions the master reticle Ri thereon on the XY plane. The position of the reticle stage 2 is measured by a laser interferometer (not shown), and the operation of the reticle stage 2 is controlled by the measured value and control information from the main control system 9. On the other hand, the substrate 4 is held on a substrate holder (not shown) by vacuum suction, and the substrate holder is fixed on the sample table 5.
The sample stage 5 is fixed on an XY stage 6. The sample stage 5 adjusts the surface of the substrate 4 to the image plane of the projection optical system 3 by controlling the focus position (position in the optical axis AX direction) and the tilt angle of the substrate 4 by an autofocus method. The XY stage 6 positions the sample table 5 (substrate 4) on the base 7 in the X direction and the Y direction by, for example, a linear motor method.

A movable mirror 8 m fixed on the upper part of the sample table 5,
The X- and Y-coordinates and the rotation angle of the sample table 5 are measured by the laser interferometer 8 disposed opposite thereto, and the measured values are supplied to the stage control system 10 and the main control system 9. As shown in FIG. 3, the movable mirror 8m is a general term for the X-axis movable mirror 8mX and the Y-axis movable mirror 8mY. The stage control system 10 controls the operation of the linear motor and the like of the XY stage 6 based on the measured values and the control information from the main control system 9.

In this embodiment, a reticle library 16 having a shelf shape is arranged on the side of the reticle stage 2, and the master reticle R 1 and N reticle R 1 are placed on the N support plates 17 sequentially arranged in the Z direction in the reticle library 16. RN are mounted. These master reticles R1 to RN
Is a reticle (parent mask) on which parent patterns P1 to PN obtained by dividing the parent pattern 36 of FIG. 1 are respectively formed. The reticle library 16 is supported by a slide device 18 so as to be movable in the Z direction. A reticle loader 19 provided between the reticle stage 2 and the reticle library 16 and having an arm that is rotatable and movable in a predetermined range in the Z direction. Is arranged. After the main control system 9 adjusts the position of the reticle library 16 in the Z direction via the slide device 18, the main control system 9 controls the operation of the reticle loader 19,
Between the desired support plate 17 in the reticle library 16 and the reticle stage 2, the desired master reticle R1
It is configured to be able to deliver RNs. In FIG. 2, the ith master reticle Ri in the reticle library 16 is placed on the reticle stage 2.

A storage device 11 such as a magnetic disk device is connected to the main control system 9, and the storage device 11 stores an exposure data file. The exposure data file includes the mutual positional relationship and alignment information of the master reticles R1 to RN, and data of the imaging characteristics of a projection image (projection optical system) of a projection exposure apparatus using the working reticle manufactured in this example. Is recorded.

At the time of exposing the substrate 4 of this embodiment, the substrate 4
When exposure of the reduced image of the first master reticle R1 to the upper first shot area is completed, the next shot area on the substrate 4 moves to the exposure area of the projection optical system 3 by the step movement of the XY stage 6. . In parallel with this, the master reticle R1 on the reticle stage 2 is returned to the reticle library 16 via the reticle loader 19,
The next master reticle R2 to be transferred is placed on the reticle stage 2 from the reticle library 16 via the reticle loader 19. Then, after the alignment is performed, the reduced image of the master reticle R2 is projected and exposed on the shot area on the substrate 4 via the projection optical system 3, and the remaining image on the substrate 4 is thereafter subjected to a step-and-repeat method. Exposure of the reduced images of the corresponding master reticles R2 to RN is sequentially performed on the shot areas.

Although the projection exposure apparatus shown in FIG. 2 is of a batch exposure type, a scanning exposure type reduction projection type exposure apparatus such as a step-and-scan method may be used instead. In the scanning exposure type, at the time of exposure, the master reticle and the substrate 4 are synchronously scanned with respect to the projection optical system 3 at a reduction ratio. By using a scanning exposure type exposure apparatus, there are cases where errors (such as skew errors) that are difficult to correct with a batch exposure type can be corrected as described later.

Now, as described above, the master reticle R1
When exposing the reduced image of the RN on the substrate 4, it is necessary to perform screen joining (joining) between adjacent reduced images with high accuracy. For this purpose, each master reticle Ri (i =
1 to N) and the corresponding shot area (referred to as Si) on the substrate 4 must be aligned with high accuracy. For this alignment, the projection exposure apparatus of this example is provided with an alignment mechanism for a reticle and a substrate.

FIG. 3 shows the reticle alignment mechanism of the present embodiment. In FIG. 3, a light-transmissive reference mark member 12 is fixed near the substrate 4 on the sample stage 5, and is placed on the reference mark member 12. At predetermined intervals in the X direction, for example, a cross 1
A pair of reference marks 13A and 13B are formed. The exposure light IL is provided at the bottom of the reference marks 13A and 13B.
Mark 1 on the projection optical system 3 side with the illumination light branched from
An illumination system for illuminating 3A and 13B is provided. At the time of alignment of the master reticle Ri, by driving the XY stage 6 of FIG. 2, as shown in FIG.
In order that the centers of the reference marks 13A and 13B on the reference mark member 12 substantially coincide with the optical axis AX of the projection optical system 13,
The reference marks 13A and 13B are positioned.

As an example, two cross-shaped alignment marks 21A and 2A are arranged so as to sandwich the pattern region 20 on the pattern surface (lower surface) of the master reticle Ri in the X direction.
1B is formed. The interval between the reference marks 13A and 13B is set substantially equal to the interval between the reduced images of the alignment marks 21A and 21B by the projection optical system 3, and the center of the reference marks 13A and 13B almost coincides with the optical axis AX as described above. In this state, by illuminating from the bottom side of the reference mark member 12 with illumination light having the same wavelength as the exposure light IL, the enlarged images of the reference marks 13A and 13B by the projection optical system 3 are respectively aligned with the alignment marks 21A of the master reticle Ri. , 21B.

These alignment marks 21A, 21
Mirrors 22A and 22B for reflecting illumination light from the projection optical system 3 side in the ± X direction are disposed above B, and T is received so as to receive the illumination light reflected by the mirrors 22A and 22B.
Alignment sensors 14A and 14B of a TR (through the reticle) type and an image processing type are provided.
Each of the alignment sensors 14A and 14B includes an imaging system and a two-dimensional imaging device such as a CCD camera, and the imaging device captures images of the alignment marks 21A and 21B and the corresponding reference marks 13A and 13B. The imaging signal is supplied to the alignment signal processing system 15 in FIG.

The alignment signal processing system 15 performs image processing on the picked-up signal, and aligns the X and Y directions of the alignment marks 21A and 21B with respect to the images of the reference marks 13A and 13B.
The amount of displacement in the direction is obtained, and these two sets of displacements are supplied to the main control system 9. The main control system 37 positions the reticle stage 2 so that the two sets of positional deviation amounts are symmetrical to each other and each falls within a predetermined range. As a result, the alignment marks 21A and 21B, and thus the parent pattern Pi (see FIG. 1) in the pattern area 20 of the master reticle Ri are positioned with respect to the reference marks 13A and 13B.

In other words, the center (exposure center) of the reduced image of the master pattern Pi of the master reticle Ri by the projection optical system 3 is substantially positioned at the center (almost the optical axis AX) of the reference marks 13A and 13B. The sides orthogonal to the contour of the pattern Pi (the contour of the pattern area 20) are set in parallel with the X axis and the Y axis, respectively. In this state, the main control system 9 in FIG. 2 stores the coordinates (XF ₀ , YF ₀ ) of the sample table 5 in the X direction and the Y direction measured by the laser interferometer 8, thereby aligning the master reticle Ri. finish. Thereafter, any point on the sample stage 5 can be moved to the exposure center of the parent pattern Pi.

In FIG. 2, an alignment sensor 23 of an off-axis system and an image processing system is also provided on the side surface of the projection optical system PL to detect the position of a mark on the substrate 4. The alignment sensor 23 illuminates the test mark with non-photosensitive broadband illumination light on the photoresist, and converts the image of the test mark into a CCD camera or the like.
An image is taken by a two-dimensional image sensor, and an image signal is supplied to an alignment signal processing system 15. The alignment sensor 23
The distance (baseline amount) between the detection center of the reference mark and the center (exposure center) of the projected image of the pattern of the master reticle Ri is obtained in advance by using a predetermined reference mark on the reference mark member 12, and the main control system 9 Is stored within.

As shown in FIG. 3, for example, two cross-shaped alignment marks 24A,
24B are formed. And the master reticle R
After the alignment of i, the XY stage 6 is driven to sequentially move the reference marks 13A and 13B of FIG. 3 and the alignment marks 24A and 24B on the substrate 4 to the detection area of the alignment sensor 23 of FIG. Then, the amounts of displacement of the reference marks 13A and 13B and the alignment marks 24A and 24B with respect to the detection center of the alignment sensor 23 are measured. These measurement results are supplied to the main control system 9, and using these measurement results, the main control system 9 uses the coordinates of the sample stage 5 when the centers of the reference marks 13A and 13B coincide with the detection centers of the alignment sensor 23. (XP ₀ , YP ₀ ) and the coordinates (XP ₁ , YP ₀ ) of the sample table 5 when the center of the alignment marks 24A, 24B coincides with the detection center of the alignment sensor 23.
₁ ) Ask for. Thus, the alignment of the substrate 4 is completed.

As a result, the reference marks 13A and 13B
X direction between the center and the center of the alignment marks 24A and 24B
Direction, the interval in the Y direction is (XP₀-XP₁, YP₀-Y
P₁). Therefore, the master reticle Ri
(XF ₀, YF₀) For
And the interval (XP₀-XP₁, YP₀-YP₁) Minutes
4 by driving the XY stage 6 of FIG.
As shown in FIG.
The center (exposure center) of the projected images of marks 21A and 21B
The center of the alignment marks 24A and 24B of the plate 4 (the substrate
4 center) can be matched with high accuracy. This state
From the state, the XY stage 6 of FIG.
Moving in the Y direction, the center on the substrate 4
The parent putter of master reticle Ri at desired position
A reduced image PIi of the image Pi can be exposed.

That is, FIG. 4 shows a state in which the parent pattern Pi of the i-th master reticle Ri is reduced and transferred onto the substrate 4 via the projection optical system 3. In FIG.
A rectangular pattern area 25 surrounded by sides parallel to the X-axis and the Y-axis around the center of the alignment marks 24A and 24B on the surface of the surface is virtually set in the main control system 9. The size of the pattern area 25 is the size of the parent pattern 3 in FIG.
6 is reduced to 1 / α times the size of the pattern area 2
5 are equally divided into α pieces in the X direction and the Y direction, respectively, and shot areas S1, S2, S3,..., SN (N =
α ² ) is virtually set. Shot area Si (i =
1 to N) are set to the positions of the reduced image PIi of the i-th parent pattern Pi when the parent pattern 36 of FIG. 1 is temporarily reduced and projected via the projection optical system 3 of FIG.

If the projection exposure apparatus using the working reticle 34 of this embodiment has an ideal image forming characteristic of the projected image, the main control system 9 drives the XY stage 6 of FIG. , The center of the i-th shot area Si on the substrate 4 is aligned with the exposure center of the reduced image PIi of the master pattern Pi of the master reticle Ri obtained by the above alignment. After that, the main control system 9 starts emission of the exposure light source in the illumination optical system 1 of FIG. 2 and exposes a reduced image of the parent pattern Pi to the shot area Si on the substrate 4. In FIG. 4, the reduced image of the parent pattern already exposed in the pattern area 25 of the substrate 4 is indicated by a solid line, and the unexposed reduced image is indicated by a dotted line.

Thus, the reduced images of the parent patterns P1 to PN of the N master reticles R1 to RN in FIG.
By sequentially exposing the corresponding shot areas S1 to SN on the substrate 4, the reduced images of the respective parent patterns P1 to PN are exposed while performing screen splicing with the reduced images of the adjacent parent patterns. Thus, the projection image 26 obtained by reducing the parent pattern 36 of FIG. 1 by 1 / α is exposed on the substrate 4. Thereafter, by developing the photoresist on the substrate 4 and performing etching, peeling off of the remaining resist pattern, and the like, the projected image 26 on the substrate 4 becomes
The working reticle 34 is completed with the original pattern 27 as shown in FIG.

When exposing one substrate 4, the substrate 4 is fixed on the sample table 5 regardless of the exchange of the master reticle Ri, and the position is accurately measured by the laser interferometer 8. Have been. Accordingly, the positional relationship between the reference marks 13A, 13B and the substrate 4 does not change during the exposure of one substrate 4, so that when exchanging the master reticle Ri, the master reticle Ri is moved with respect to the reference marks 13A, 13B. It is not always necessary to detect the positions of the alignment marks 24A and 24B on the substrate 4 for each master reticle.
Also in this case, the parent pattern Pi on each master reticle Ri is aligned with the reference marks 13A and 13B,
Stage control system 10 monitored by laser interferometer 8
Exposure is performed while maintaining a mutual accurate positional relationship. Therefore, it goes without saying that the joining accuracy between the patterns is also high.

The alignment marks 24A and 24B need not always be formed on the substrate 4 in advance. At this time, when the master pattern of the master reticle Ri is connected to the substrate 4 and reduced and transferred as described above, predetermined marks (for example, alignment marks 21A and 21B) on each master reticle Ri are also reduced and transferred. When transferring the reduced image of the parent pattern of the adjacent master reticle, the position of the latent image of the mark is detected, and based on the detection result, the transfer position of the reduced image of the parent pattern of the adjacent master reticle is corrected. It may be.

When, for example, a dense pattern and an isolated pattern are formed on the original pattern 27 of FIG. 1, only a dense pattern is formed on one master reticle Ra among the master reticles R1 to RN. Only one isolated pattern may be formed on one master reticle Rb. At this time, the exposure condition such as the best illumination condition and the image formation condition is different between the dense pattern and the isolated pattern. Therefore, each time the master reticle Ri is exposed, the exposure condition, that is, the illumination optical system 1 is adjusted in accordance with the parent pattern Pi. The shape and size of the aperture stop, the coherence factor (σ value), the numerical aperture of the projection optical system 3, and the like may be optimized. At this time, when the parent pattern Pi is a dense pattern (periodic pattern), a modified illumination method is adopted, and the shape of the secondary light source is formed into a ring shape or a plurality of local light sources substantially equidistant from the optical axis of the illumination optical system. What is necessary is just to define in an area. Further, in order to optimize the exposure condition, an optical filter (a so-called pupil filter) for blocking exposure light in a circular region centered on the optical axis, for example, is inserted or removed near the pupil plane of the projection optical system 3 or projected. A so-called progressive focus method (flex method) in which the image plane of the optical system 3 and the surface of the substrate 4 are relatively vibrated within a predetermined range may be used together.

The above-described progressive focus method may be adopted by using the parent mask as a phase shift mask and setting the σ value of the illumination optical system to, for example, about 0.1 to 0.4. Further, the photomask is not limited to a mask including only a light-shielding layer such as chrome, and may be a phase shift mask such as a spatial frequency modulation type (Shibuya-Levenson type), an edge enhancement type, and a halftone type. . In particular, in the spatial frequency modulation type and the edge emphasis type, since the phase shifter is patterned so as to overlap the light-shielding pattern on the mask substrate, for example, a parent mask for the phase shifter is separately prepared.

Next, a case where the image forming characteristic of the projected image of the projection exposure apparatus using the working reticle 34 deviates from an ideal state will be described. Assuming that the projection exposure apparatus shown in FIG. 7 using the working reticle 34 is of a batch exposure type, a certain degree of non-rotationally symmetric aberration or distortion remains in the imaging characteristics of the projection optical system 42. It may be possible. Here, in the imaging characteristics of the projection optical system 42, as shown in FIG. 5A, a lattice-like ideal image 28 shown by a dotted line is replaced with a pincushion-type (or barrel-type) projected image 29 shown by a solid line. It is assumed that some distortion remains.

In FIG. 5A, the optical axis A of the projection optical system is shown.
The distance from X1 to 29a point on the projected image 29 r, and the distance from the optical axis AX1 to 28a point on the corresponding ideal image 28 to r _0, the distortion D at a distance r
(R) is represented by the following equation. D (r) = (r−r ₀ ) / r (1) Accordingly, the amount of displacement of the projected image 29 with respect to the ideal image 28 at the distance r is substantially rD (r).

In this case, in this example, as shown in FIG.
When projecting a reduced image of the parent pattern Pi of the i-th master reticle Ri on the substrate 4, the exposure position is shifted laterally from the original shot area Si in the X direction and the Y direction so as to cancel the distortion. .

FIG. 5B shows a shot area S on the substrate 4.
The sequence of 1, S2,..., SN is shown again, and FIG.
It is assumed that a reduced image PI5 of the corresponding parent pattern is projected onto the original shot area S5. in this case,
Assuming that the distance from the center of the shot area S5 to the optical axis AX1 of the projection optical system to be used is r, the projection position of the shot area S5 when reduced projection is performed by 1 / β times the projection optical system. The amount of displacement in the radial direction is (r / β) D (r / β) from equation (1). When the exposure position of the reduced image PI5 is shifted by δ (r) with respect to the shot area S5 in advance, the shift amount by the projection optical system is δ (r) / β. Therefore, the conditions for canceling out the distortion with this displacement amount are as follows.

Δ (r) / β = − (r / β) D (r / β) (2) From the equation (2), the displacement δ (r) is as follows. δ (r) = − r · D (r / β) (3) In this equation, a minus sign when D (r / β) is a positive value indicates that the reduced image PI5 is displaced in the optical axis AX direction. Means to let. Similarly, for example, also in the shot area S7, the exposure position of the corresponding reduced image PI7 is shifted so as to satisfy Expression (3), and the reduced image is similarly shifted in other shot areas. In the shot area S13 on the optical axis AX1, the reduced image P
There is no need to change the position of I13. by this,
The distortion in FIG. 5A is canceled out, and the ideal image 2
8 is exposed.

As can be seen from FIG. 5 (a), in the partial area where the distance from the optical axis AXI is r in the projected image 29, the magnification is also changed by Δβ (r), and A non-rotationally symmetric distortion is also generated. Therefore, the projection optical system 3 of the projection exposure apparatus of FIG. 4 is provided with a correction mechanism for driving a predetermined lens element in the projection optical system 3, for example, so that the projection magnification and distortion can be controlled within a predetermined range. It is desirable to keep. For example, when exposing the reduced image PI5 to the shot area S5 in FIG. 5B, the exposure position is set to δ using the projection exposure apparatus in FIG.
(R) as well as the corresponding magnification error Δβ
The magnification of the projection optical system 3 is corrected so as to cancel (r / β), and the distortion characteristic of the projection optical system 3 is also corrected so as to cancel the corresponding partial distortion as much as possible. This makes it possible to offset the distortion shown in FIG. 5A with higher accuracy as a whole.

Next, assuming that the projection exposure apparatus shown in FIG. 7 is of a scanning exposure type such as a step-and-scan method, the image forming characteristics of the projected image are as shown in FIG. A case where a so-called skew error in which a rectangular ideal image 30 shown by a dotted line becomes a parallelogram projected image 31 shown by a solid line remains will be described. In FIG. 6A,
The center of the projected image 31 is the same as the center 35 of the ideal image 30, but the projected image 31 is distorted by an angle φ clockwise with respect to the Y axis which is an axis in the scanning direction with respect to the ideal image 30. This is an error peculiar to the scanning exposure method (an example of non-rotationally symmetric aberration) that occurs when the scanning direction between the reticle and the substrate to be exposed is shifted. 31a is shifted laterally by δX1 in the −X direction with respect to the ideal partial image 30a, and is distorted into a parallelogram by an angle φ.

In this case, in this example, in FIG. 4, as a projection exposure apparatus for sequentially projecting reduced images of the master patterns of the master reticles R1 to RN onto the substrate 4, a step-and-scan in which the Y direction is the scanning direction. A projection exposure apparatus of the type is used. Then, for example, the partial image 31 of FIG.
When exposing the reduced image PI21 of the master pattern of the master reticle R21 corresponding to a, the imaging characteristics are corrected so as to offset the errors of the lateral shift amount δX1 and the angle φ.

The dotted line array 32 in FIG. 6B shows an array of designed shot areas on the substrate 4.
In FIG. 6, the reduced image PI21 of the parent pattern is placed on the designed shot area S21 corresponding to the partial image 30a in FIG.
Shall be projected. In this case, the shot area S
Since the lateral shift amount when the projection optical system 21 is reduced and projected by 1 / β times by the projection optical system is δX1, the shot area S21
When the exposure position of the reduced image PI21 is displaced by δX2, the amount of displacement by the projection optical system is −δX2 / β (the minus sign is due to reverse projection). Therefore, the lateral shift amount δX1
The conditions for canceling are as follows.

-ΔX2 / β = -δX1 (4) From the equation (4), the positional deviation amount δX2 is β · δX1. Further, in this example, when exposing the reduced image PI21, the scanning direction is set to the Y direction, and the scanning direction between the master reticle and the substrate 4 is shifted, so that the reduced image PI21 is exposed.
Are distorted counterclockwise with respect to the Y axis by an angle φ. Similarly, in the other shot areas, the exposure position of the corresponding reduced image is shifted laterally and distorted by an angle φ counterclockwise with respect to the Y axis. As a result, the skew error in FIG. 6A is substantially canceled, and the ideal image 30 is exposed.

Next, an example of the operation when performing exposure using the working reticle 34 of FIG. 1 manufactured as described above will be described. FIG. 7 shows the working reticle 3
FIG. 7 shows a main part of a reduction projection type exposure apparatus equipped with a reticle stage 4. In FIG. 7, a reduction magnification 1 / β (β) is provided on the lower surface of a working reticle 34 held on a reticle stage (not shown).
5 or 4), the wafer W is arranged via the projection optical system 42. A photoresist is applied to the surface of the wafer W, and the surface is held so as to match the image plane of the projection optical system 42. The wafer W is held on a sample stage 43 via a wafer holder (not shown).
It is fixed on the Y stage 44. The XY stage 44 is driven based on the coordinates measured by the moving mirrors 45mX and 45mY on the sample table 43 and the corresponding laser interferometer, thereby positioning the wafer W.

Further, the reference marks 47A,
The reference mark member 46 on which the 47B is formed is fixed, and the alignment marks 24A and 24B are formed so as to sandwich the pattern region 25 of the working reticle 34 in the X direction.
Above the reticle, alignment sensors 41A and 41B for reticle alignment are arranged. Again, in this case,
Reference marks 47A and 47B, alignment mark 24
The working reticle 34 is aligned with respect to the sample table 43 using the A, 24B and the alignment sensors 41A, 41B. Thereafter, when performing overlay exposure, alignment of each shot area 48 on the wafer W is performed using a wafer alignment sensor (not shown). Then, after sequentially positioning the shot area 48 to be exposed on the wafer W to the exposure position, the pattern area 25 of the working reticle 34 is irradiated with exposure light IL1 such as excimer laser light from an illumination optical system (not shown). Thus, the original pattern 27 in the pattern region 25
27W obtained by reducing the image at a reduction ratio of 1 / β
8 is exposed. After exposing the reduced image of the original pattern 27 on each shot area on the wafer W in this way, the wafer W is developed and a process such as etching is performed, so that the semiconductor A circuit pattern for a layer of the device is formed.

As a projection exposure apparatus for exposing the working reticle 34, a scanning projection type reduction projection exposure apparatus such as a step-and-scan method may be used. It should be noted that the present invention is not limited to the above-described embodiment, and can take various configurations without departing from the spirit of the present invention.

[0066]

According to the photomask manufacturing method of the present invention, since the patterns of the plurality of parent masks are each a part of a pattern obtained by enlarging the pattern for transfer, for example, an electron beam drawing apparatus or a laser beam drawing method. By using an apparatus or the like, writing can be performed with a small amount of drawing data and a small drift amount in a short time. In addition, since the writing error of the parent mask is reduced by the reduction ratio of the pattern of the parent mask, a transfer pattern (original pattern) can be formed with high accuracy. Furthermore, since these parent masks are manufactured once and can be used repeatedly, there is an advantage that individual master patterns can be formed with high precision and in a short time even when a large number of photomasks are manufactured.

When sequentially transferring the reduced images of a plurality of parent mask patterns onto the surface of the substrate, a batch projection type reduction projection exposure apparatus or a scanning exposure type reduction projection device is used depending on the use of the photomask. When using the projection type exposure apparatus properly, for example, by correcting the imaging characteristic of the pattern of the parent mask so as to cancel in advance the error or the like of the imaging characteristic that is expected to occur depending on the application, the expected value is obtained. Error of the imaging characteristics can be corrected.

Further, when sequentially transferring the reduced images of the patterns of the plurality of master masks onto the surface of the substrate, at least the non-rotationally symmetric aberration and distortion characteristics of the projection optical system of the projection exposure apparatus using the photomask are determined. In the case where the imaging characteristics of the reduced image of the pattern of the parent mask are respectively corrected according to one of them, when the predetermined imaging characteristics of the projection optical system using the photomask are deteriorated, the imaging characteristics are deteriorated. Since the image characteristics can be substantially corrected, the overlay accuracy and the like are improved.

Further, when the photomask is further used in reduced projection, the magnification of the pattern of the parent mask becomes larger than that of the device pattern to be finally manufactured. The influence of a drawing error of an electron beam drawing apparatus or the like for drawing a pattern is further reduced, and a pattern of the device can be formed with higher accuracy.

According to the photomask manufacturing apparatus of the present invention, the photomask manufacturing method of the present invention can be implemented. According to the device manufacturing method of the present invention, since the photomask manufacturing method of the present invention is used, a device pattern can be formed with higher accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a manufacturing process of a working reticle (photomask) according to an example of an embodiment of the present invention;

FIG. 2 is a partially cut-away configuration diagram showing an optical reduction projection exposure apparatus used in manufacturing the working reticle in one example of the embodiment.

FIG. 3 is a perspective view of a part of the projection exposure apparatus of FIG. 2 showing a case where alignment of a master reticle is performed;

4 is a perspective view of a main part showing a case where a reduced image of a master pattern of a master reticle is projected onto a substrate 4 in the projection exposure apparatus of FIG.

FIG. 5A is a view showing an example of an error of an imaging characteristic of a projection exposure apparatus using a working reticle manufactured in the embodiment, and FIG. 5B is for canceling the error of the imaging characteristic. FIG. 9 is a diagram showing a method of correcting the imaging characteristics of a reduced image of the parent pattern on the working reticle.

6A is a view showing another example of an error of the imaging characteristic of the projection exposure apparatus using the working reticle manufactured in the embodiment, and FIG. 6B is for canceling the error of the imaging characteristic. FIG. 4 is a diagram showing a method for correcting the imaging characteristics of a reduced image of a parent pattern on the working reticle in order to perform the above operation.

FIG. 7 is a perspective view showing a main part of a projection exposure apparatus that projects a pattern of a working reticle manufactured in the embodiment on a wafer.

[Explanation of symbols]

R1 to RN Master reticle (parent mask) P1 to PN Divided parent pattern 3 Projection optical system 4 Working reticle substrate S1 to SN Shot area on substrate 4 5 Sample table 6 XY stage 9 Main control system 13A, 13B Reference Mark 14A, 14B Alignment sensor for reticle 16 Reticle library 18 Slider 19 Reticle loader 21A, 21B Alignment mark for master reticle 24A, 24B Alignment mark for substrate 27 Original pattern 35 Circuit pattern 36 Parent pattern

Claims (7)

[Claims] 1. A method of manufacturing a photomask on which a transfer pattern is formed, wherein a pattern obtained by enlarging the transfer pattern is divided into a plurality of parent mask patterns, and the pattern is formed on a surface of the photomask substrate. A method of manufacturing a photomask, wherein a plurality of reduced images of the pattern of the parent mask are sequentially transferred while performing screen joining. 2. A method according to claim 1, wherein when sequentially reducing images of a plurality of patterns of said parent mask on a surface of said substrate, a batch exposure type reduction projection exposure apparatus is used according to a use of said photomask.
2. The method for manufacturing a photomask according to claim 1, wherein a scanning exposure type reduction projection type exposure apparatus is selectively used. 3. A non-rotationally symmetric aberration and distortion characteristic of a projection optical system of a projection exposure apparatus using the photomask when sequentially transferring a plurality of reduced images of the pattern of the parent mask onto the surface of the substrate. 3. The method of manufacturing a photomask according to claim 1, wherein the image forming characteristics of the reduced image of the pattern of the parent mask are respectively corrected according to at least one of the following. 4. The method for manufacturing a photomask according to claim 1, wherein the photomask is further used in a reduced projection. 5. A mask storage device for storing a plurality of masks, a mask stage on which one mask selected from the mask storage device is mounted, and a reduced image of a mask pattern on the mask stage. A projection optical system for projecting onto a substrate for a photomask, a substrate stage for positioning the substrate on a plane perpendicular to the optical axis of the projection optical system, and screen joining of reduced images of the plurality of mask patterns. An apparatus for manufacturing a photomask, comprising: a mask on the mask stage and an alignment system for positioning the substrate on the substrate stage so as to perform on the substrate. 6. A plurality of parent masks each having a pattern obtained by dividing a pattern obtained by enlarging a pattern of a photomask to be manufactured is formed in the mask storage device. 6. The photomask manufacturing apparatus according to 5. 7. A method for manufacturing a device for forming a predetermined pattern on a substrate, wherein a second pattern obtained by further expanding the first pattern obtained by expanding the predetermined pattern is used as a pattern of a plurality of parent masks. Dividing and projecting a plurality of patterns of the parent mask onto a predetermined substrate while sequentially performing screen joining to produce a photomask for actual exposure on which the first pattern is formed; A method of transferring a reduced image of a pattern of a photomask for use on the substrate.