JP2005093720A - Aligner and exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aligner that can form such a pattern with a small line width that exceeds the limit of an optical system without lowering productivity. <P>SOLUTION: Light generated by a light source 2 is given to an object 6 to be processed through a mask 4 wherein an opening with a specified pattern is formed, and the specified pattern is transferred to the object 6. Such an aligner 1 is provided with a means 9 to move the mask 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exposure apparatus and an exposure method.

In an exposure apparatus that has been used conventionally, it has been difficult to reduce the line width of a pattern transferred to a photoresist formed on a substrate (wafer) due to the limit of the performance of an optical system.
In such an exposure apparatus, when trying to obtain a thin line width that exceeds the performance limit of the optical system, for example, a method of shortening the wavelength of the light source or a large NA (lens numerical aperture). It was necessary to use an optical system. That is, it is necessary to further enhance the performance of the optical system.

  On the other hand, when it is assumed that a positive type photoresist is used as the photoresist formed on the substrate, for example, by performing the exposure process twice, the range not irradiated with light is narrowed. A method is also known in which the line width of a pattern finally obtained on a wafer is narrowed so as to exceed the performance limit of the optical system (see Non-Patent Document 1).

Specifically, first, as shown in FIG. 7A, a mask 43 having a predetermined pattern is provided on a wafer 41 coated with a photoresist 42 in a chamber where a first exposure process is performed. As shown in FIG. 7B, the entire surface of the mask 43 is exposed to transfer a predetermined pattern to the photoresist 42 by the first exposure.
In the photoresist 42, the white portion 44 indicates a portion irradiated with light by the first exposure.

Next, the wafer 41 to which the predetermined pattern transferred by the first exposure is transferred by a transfer system (not shown) is transferred to the chamber where the mask 43 is provided at a position different from the first exposure process. Then, by exposing the entire surface again, a predetermined pattern by the second exposure is transferred to the photoresist 42 as shown in FIG. 7C.
In the photoresist 42, a hatched portion 45 indicates a portion irradiated with light by the second exposure.

  As a result, in the photoresist 42, the exposed range is widened and the unexposed range 46 is narrowed by the portion 44 exposed in the first exposure step and the portion 45 exposed in the second exposure step.

  Therefore, after that, the part 44 exposed in the first exposure process and the part 45 exposed in the second exposure process are removed by immersing the wafer 41 in the developer as shown in FIG. 7D. In addition, a photoresist 47 having a narrow line width pattern can be formed on the wafer 41.

In this way, by performing the exposure process twice by shifting the mask 43, it is possible to form a line width that is narrow enough to exceed the limit of the performance of the optical system.
Nikkei Sangyo Shimbun (Nikkei Telecon 21), July 10, 2003, morning edition, page 6, “Semiconductor exposure, misaligned irradiation, Tokyo Denki University, with a line width of 80 nm”

  However, when such a method of performing the exposure process twice is used (see Non-Patent Document 1 above), for example, the wafer 41 from the chamber in which the first exposure process is performed to the chamber in which the second exposure process is performed. Transfer time and the time required to align the mask and wafer in each exposure process, etc., so throughput (processing amount per unit time) cannot be increased and productivity is reduced. End up.

  Therefore, in addition to such a method of performing the exposure process twice, it is required that a pattern with a thin line width exceeding the limit of the performance of the optical system can be formed without reducing the productivity. It was.

  Further, in the case of a general exposure apparatus, in the case of forming a pattern whose thickness changes (for example, a lens shape), it is necessary to perform exposure several times by shifting the mask and changing each time. However, as in the case of the method of performing the above-described two exposure steps, the throughput cannot be increased and the productivity is lowered.

  In view of the above, the present invention provides an exposure apparatus and an exposure method that can form a pattern with a thin line width that exceeds the limit of an optical system without reducing productivity.

  The present invention moves a mask in an exposure apparatus that irradiates a workpiece with light generated from a light source through a mask in which a predetermined pattern of openings is formed, and transfers the predetermined pattern to the workpiece. A means is provided.

According to the exposure apparatus according to the present invention described above, since the means for moving the mask is provided, when performing exposure, the mask can be moved by driving the means for moving the mask. .
Since the exposed area can be moved by moving the mask, for example, it is possible to narrow the non-exposed area in one exposure step, change the amount of exposure light depending on the location, and the like. .

  The exposure method according to the present invention moves a mask when a predetermined pattern is transferred to the workpiece by irradiating the workpiece with light through a mask in which openings of a predetermined pattern are formed. To.

  According to the exposure method according to the present invention described above, when a predetermined pattern is transferred to a workpiece by irradiating the workpiece with light through a mask in which openings of the predetermined pattern are formed, Since the mask is moved, the exposed area can be moved according to the movement of the mask. Thereby, for example, it is possible to narrow the exposed area in one exposure step, change the amount of exposure light depending on the location, and the like.

  According to the exposure apparatus of the present invention, even when a pattern with a thin line width exceeding the limit of the performance of the optical system can be formed without lowering the throughput, it is possible to perform with high performance and productivity. A high exposure apparatus can be provided.

  According to the exposure method of the present invention, even when a pattern with a thin line width exceeding the performance of the optical system is formed, it can be formed without reducing the throughput. Productivity can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

First, an embodiment of an exposure apparatus of the present invention will be described with reference to FIG.
The exposure apparatus of the present embodiment is a light reduction projection type exposure apparatus.
The exposure apparatus 1 includes a light source (for example, a mercury lamp) 2 that emits light of a predetermined wavelength, a lens (condenser lens) 3 that condenses the light emitted from the light source 2 and converts it into parallel light, and a predetermined light A mask (glass mask) 4 in which an opening of the pattern is formed, a projection lens 5 for reducing the light transmitted through the mask 4 at a predetermined magnification, and a workpiece provided so as to correspond to the projection lens 5 That is, it comprises a stage 7 on which a substrate (wafer) 6 is placed. The stage 7 is provided with a loader (not shown) for moving the stage 7.
The size of the opening of the predetermined pattern formed in the mask 4 is, for example, 2 to 10 times the actual size, and is configured to be reduced to 1/2 to 1/10 times by the projection lens 5. .

  In the exposure apparatus 1 having such a configuration, the light emitted from the light source 2 is converted into parallel by the condenser lens 3 and irradiates the mask 4, and only the transmitted light that is not blocked by the mask 4 is transmitted by the projection lens 5. The wafer 6 that has been reduced in size and placed on the stage 7 is irradiated. Reference numeral 8 denotes a shot portion when the light transmitted through the projection lens 5 is irradiated on the wafer 6.

In the exposure apparatus 1 of the present embodiment, means 9 for moving the mask 4 is particularly provided on the mask 4.
In the present embodiment, the means 9 for moving the mask 4 includes, for example, an actuator 10 that generates vibration, and a drive shaft 11 that transmits the vibration generated by the actuator 10 to the mask 4. The mask 4 is vibrated. It is comprised so that.

  Specifically, as shown in FIG. 1B, the drive shaft 11 is connected to both ends of a mask holder 23 on which the mask 4 is set, and the actuator 10 is connected to one end of one drive shaft 11 and the other drive shaft is connected. A shaft retainer 24 is provided at one end. Although not shown, a shaft retainer is also provided in the actuator 10. Further, the mask holder 23 is configured such that the mask 4 can be taken in and out so that the mask 4 can be exchanged according to the pattern to be obtained.

  Here, the shaft retainer 24 has a configuration using a high-precision bearing, although not shown, so as not to rattle when the mask 4 (mask holder 23) is vibrated.

  Further, the mask 4 and the mask holder 23 need to be fixed so that there is no backlash. That is, when there is a backlash between the mask 4 and the mask holder 23, the shape of the pattern obtained may be distorted. In order to solve such a problem, it is desirable to provide the mask holder 23 with a means for mechanically fixing the mask 4 after the mask 4 is set in the mask holder 23. As such means, for example, the same means as in the case of a conventional exposure apparatus may be used, but it is necessary to be able to withstand vibration.

  Further, both the mask holder 23 and the drive shaft 11 need to be fixed so that there is no backlash. In other words, it is necessary to mechanically fix the mask holder 23 and the drive shaft 11 so that there is no displacement between the mask holder 23 and the drive shaft 11 due to mechanical stress during vibration. In this case, for example, a method of fixing using screws, or the mask holder 23 and the drive shaft 11 may be integrated.

With this configuration, when the actuator 10 is vibrated by operating a drive mechanism (not shown), the vibration is transmitted to the mask holder 23 through the drive shaft 11 and the mask holder 23 is vibrated. In accordance with the vibration of the mask holder 23, the mask 4 set on the mask holder 23 also vibrates.
At this time, since one side of the drive shaft 11 is fixed by the shaft presser 24, there is no blurring or the like when the actuator 10 is driven.

  The vibration direction is changed depending on the direction of the pattern to be obtained. For example, if the pattern has a vertically long shape, it vibrates in the horizontal direction, and if the pattern has a horizontally long shape, it vibrates in the vertical direction.

  Thereby, for example, if the mask 4 is caused to vibrate when irradiated with light (exposure light) from the light source 2, a photoresist (not shown) on the wafer 6 according to the vibration of the mask 4. The pattern to be transferred can be changed. That is, the exposed area can be moved in accordance with the movement of the vibration of the mask 4.

Thus, according to the exposure apparatus 1 of the present embodiment, since the means 9 for vibrating the mask 4 is provided, the mask 4 can be vibrated by vibrating the actuator 10 constituting the means 9. .
Accordingly, if the mask 4 is combined and vibrated when irradiating light (exposure light), the region to be exposed can be moved according to the vibration of the mask 4. Then, by controlling the movement of the vibration of the mask 4, for example, it is possible to move the exposed area and narrow the unexposed area in one exposure process.

Therefore, in such an exposure apparatus 1, for example, when trying to obtain a pattern with a thin line width exceeding the limit of the performance of the optical system, the mask is shifted twice for the first time and the second time. Even if the exposure process (see FIG. 7) is not performed, it is possible to move the exposed area and narrow the unexposed area in one exposure process.
In this case, for example, the wafer transport time from the place where the first exposure is performed to the place where the second exposure is performed or the second exposure process occurs when the exposure process is performed twice. Since the time required for aligning the mask and the wafer can be reduced, a pattern with a narrow line width can be obtained without reducing the throughput.

  Next, an embodiment of an exposure method according to the present invention using such an exposure apparatus 1 will be described with reference to the drawings.

First, a wafer 6 loaded from a carrier (not shown) is transferred into a chamber provided with the exposure apparatus 1 having the above-described configuration via a transfer system (not shown) and placed on the stage 7 of the exposure apparatus 1. . At this time, the mask 4 in which the opening of the predetermined pattern is already formed is set at a predetermined position, and the mask 4 and the wafer 6 are aligned by driving a control unit (not shown).

  In this embodiment, when the wafer 6 is placed on the stage 7 and irradiated with light (exposure light) from the light source 2, in this embodiment, a driving mechanism (not shown) is operated to mask The means 9 for moving 4 is driven. That is, by vibrating the actuator 10, the vibration is transmitted from the drive shaft 11 to the mask 4 so that the mask 4 is vibrated.

Here, how the mask 4 is vibrated will be described with reference to FIG.
2A shows the shape of the pattern to be finally obtained on the wafer 6, and FIG. 2B shows the relationship between the vibration amount of the mask 4 and the vibration time for obtaining such a shape. Is shown. Moreover, in FIG. 2B, the point X has shown the center position of a vibration. The parts corresponding to those in FIG.
For example, as shown in FIG. 2A, when a pattern 15 having a square cross section is to be obtained on the wafer 6, the mask 4 is vibrated with a predetermined vibration amount W in the horizontal direction, for example, as shown in FIG. 2B. Such vibration is repeated for a predetermined time H.
The vibration amount W is calculated in advance from the shape of the pattern to be obtained, for example.

Hereinafter, a specific operation when the mask 4 is vibrated in this way will be described with reference to FIG.
The exposed area is shown in white.
Initially, as shown in FIG. 3A, the mask 4 is at one end (for example, the left end), and has a predetermined vibration amount + W. Here, exposure is performed for a certain period of time. At this time, a region 17 not covered with the mask 4 is exposed in the photoresist 16.

  Then, after a certain period of time, as shown in FIG. 3B, the mask 4 vibrates (moves) to the other end (for example, the right end) and reaches a predetermined vibration amount −W as shown in FIG. 3C. Then, the vibration of the mask 4 is stopped again, and the exposure process is performed for a predetermined time. At this time, a region 18 of the photoresist 16 that is not covered with the mask 4 is exposed.

  Thereafter, the mask 4 vibrates again to the left end until reaching a predetermined vibration amount + W, and such vibration to the left end and right end is repeated for a predetermined time H.

  In this manner, the line width is narrow on the wafer 6 due to the region 17 exposed when the mask 4 is vibrated to the left end and the region 18 exposed when the mask 4 is vibrated to the right end. A region 19 that is not exposed can be formed.

  Thereafter, the wafer 6 is transferred to a chamber where the developing process is performed by a transfer system (not shown), and the developing process is performed. In the development process, the region 17 exposed when the above-described mask 4 is vibrated to the left end and the region 18 exposed when the mask 4 is vibrated to the right end are removed, whereby FIG. As shown in FIG. 3D, a rectangular pattern 15 having a narrow line width can be formed on the photoresist 16 on the wafer 6.

As described above, the vibration amount (amplitude) varies depending on the line width of the pattern to be finally obtained (for example, small when the line width of the pattern is thick and large when the line width is thin), but the amplitude of vibration. If becomes too large, the entire surface of the wafer 6 is exposed.
In such a case, the shape of the pattern finally formed on the photoresist 16 on the wafer 6 may be distorted. Therefore, the vibration amount (amplitude) of vibration is, for example, about several tens of nm on the wafer 6. It is desirable to do.

In addition, if the frequency is large, the entire optical system is shaken. Even in such a case, there is a possibility that the shape of the pattern finally formed on the photoresist 16 on the wafer 6 may be distorted. Therefore, it is desirable to make the frequency as small as possible.
Specifically, it is sufficient that there is at least one vibration within the light irradiation time from the light source 2. For example, when the light irradiation time is 2 seconds, the frequency is 0.5 Hz or more. .

Further, when the number of vibrations is small, for example, in the case of forming the patterns (15, 20) as shown in FIGS. 2A and 5A, the dull short-wave vibration (motion) at the rising and falling portions of the vibration. ).
In such a case, a portion of the photoresist 16 that is not sufficiently irradiated with light is formed, and after the development process, the photoresist 16 is formed below the pattern formed on the photoresist 16 on the wafer 6. It will remain.
In order to avoid such a problem, for example, at a rising part and a falling part of the vibration, the light is irradiated for a sufficiently long time, or the light from the light source 2 is moved while the mask 4 is moving. Stop the irradiation. Further, the number of vibrations can be increased.

  Further, if the irradiation of light from the light source 2 is terminated at a position in the middle of vibration, there is a possibility that the shape of the pattern finally formed on the wafer 6 may be distorted. In order to avoid such a problem, an integer number of vibrations may be performed within the light irradiation time. For example, as described above, when the light irradiation time is 2 seconds, 0. Light irradiation may be performed at an integer multiple of 5 Hz or more.

  The light irradiation time is a time during which the photoresist 16 on the wafer 6 is completely irradiated with the photoresist 16 other than the pattern to be obtained. This is because if the irradiation time is shorter than that, unnecessary photoresist 16 may remain on the wafer 6 after the development process.

As described above, according to the exposure method of the present embodiment, the mask 4 is vibrated when the predetermined pattern drawn on the mask 4 is transferred to the photoresist 16 on the wafer 6. The area to be exposed can be moved according to the movement of the vibration.
Thereby, the area | region to be exposed can be moved by one exposure process, and the area | region which is not exposed can be narrowed.

  Therefore, in such an exposure apparatus 1, for example, when trying to obtain a pattern with a thin line width exceeding the limit of the performance of the optical system, the mask is shifted twice for the first time and the second time. Even if the exposure process (see FIG. 7) is not performed, it is possible to move the exposed area and narrow the unexposed area in one exposure process.

  In this case, for example, as in the method of performing the second exposure process, the wafer transport time from the place where the first exposure is performed to the place where the second exposure is performed, or by performing the second exposure process. Since the time required for alignment between the mask and the wafer can be reduced, it is possible to form a pattern with a thin line width exceeding the limit of the performance of the optical system without reducing the throughput.

In the present embodiment, as shown in FIG. 2A, as a pattern to be finally obtained, a pattern 15 having a quadrangular cross-sectional shape has been described. However, as shown in FIG. In the case of the pattern 20 having a narrower line width, the mask 4 is vibrated as shown below.
That is, as shown in FIG. 4B, the mask 4 is vibrated with a predetermined vibration amount (amplitude) W in the horizontal direction, for example, and such vibration is repeated for a predetermined time H. At this time, the vibration amount (amplitude) W is increased as compared with the case shown in FIG. 2B.

  As described above, by increasing the vibration amount W as compared with the case shown in FIG. 2B, the unexposed area can be further narrowed, and a thinner line width can be obtained when the exposed part is removed by the development process. It becomes possible to form the pattern.

Further, unlike the shape shown in FIGS. 2A and 4A, when forming a pattern whose thickness changes as shown in FIGS. 5A and 6A, the mask 4 is vibrated as shown below.
For example, as shown in FIG. 5A, when forming a pattern 21 having a cross-sectional shape in which the upper part is flat and both sides are rounded, the mask 4 is vibrated with a predetermined vibration amount W as shown in FIG. 5B. Repeat the vibration for a predetermined time H. At this time, the mask 4 is vibrated at a constant speed.

Specifically, the mask is vibrated at a constant speed until it reaches the vibration amount −W from the vibration amount + W, reaches the predetermined vibration amount −W, and again starts to vibrate in the opposite direction. The mask 4 is vibrated at a constant speed until the predetermined vibration amount + W is reached.
Then, such vibration movement is repeated for a predetermined time H.

  6A, even in the case of the trapezoidal cross-sectional pattern 22, the mask 4 is vibrated with a predetermined vibration amount W as shown in FIG. Try to repeat. At this time, the mask 4 is vibrated by changing the vibration speed.

Specifically, the vibration speed of the mask 4 is gradually increased from the vibration amount + W to the state where the vibration amount −W is reached, and after passing through the center position, before reaching the predetermined vibration amount −W, The vibration speed of the mask 4 is gradually decreased.
Next, the vibration speed of the mask 4 is gradually increased until the predetermined vibration amount −W is reached and the vibration of the mask 4 starts in the opposite direction and then reaches the predetermined vibration amount + W again. After passing the position, before the predetermined vibration amount + W is reached, the vibration speed of the mask 4 is gradually decreased.
Then, such vibration movement is repeated for a predetermined time H.

  When the thickness of the pattern finally obtained on the wafer 6 is deformed in this way, the amount of vibration (amplitude) of the mask 4 varies depending on the shape, but the mask is, for example, about several tens nm to several μm. It is desirable to vibrate 4.

In this way, even when the thickness of the pattern to be obtained changes, by changing the vibration movement of the mask 4, the mask can be shifted as in the prior art, and the irradiation time of each light can be reduced. It is possible to form the film in a single exposure process without changing the exposure process many times.
In this case, it is possible to reduce, for example, the wafer transfer time, the time required for alignment between the mask and the wafer, etc., which has occurred when performing a plurality of exposure steps, and the thickness can be reduced without reducing the throughput. A deformed pattern shape can be formed.

  In the embodiment described above, the mask 4 is moved by vibrating the mask 4, but the mask 4 is vibrated simply by moving the mask 4 without vibrating the mask 4. As in the case, it is possible to obtain an effect of narrowing the region exposed in one exposure step.

As described above, when the mask 4 is moved, the process shown in FIG. 3A to the process shown in FIG. 3C are performed only once. That is, the mask 4 is simply moved from the state where the left end predetermined vibration amount + W is reached until the right end predetermined vibration amount −W is reached.
At this time, for example, the photoresist 16 is exposed in a state where the predetermined vibration amount + W is reached and in a state where the predetermined vibration amount −W is reached. As a result, a non-exposed region 191 having a narrow line width can be formed on the wafer 6 by the region 171 exposed before the movement and the region 181 exposed after the movement.

  Accordingly, as in the case where the mask 4 is vibrated, the exposed area can be moved and the unexposed area can be narrowed in a single exposure step, so that the performance of the optical system can be reduced without reducing the throughput. It is possible to form a pattern having a thin line width exceeding the limit of the above.

  In the above-described embodiment, as the exposure apparatus 1, for example, the size of the opening of the predetermined pattern formed in the mask 4 is 2 to 10 times the actual size, and the projection lens 5 reduces the size to 1/2 to 1. Although the case of the light reduction projection type exposure apparatus 1 configured to be reduced to / 10 times has been described, the exposure apparatus 1 is not limited to such a configuration, and is formed on the mask 4, for example. The present invention can also be applied to an exposure apparatus having a configuration in which the opening size of the predetermined pattern is an actual size and the projection lens 5 is not provided.

  In the exposure apparatus 1 of the above-described embodiment, the configuration in which the mask 4 is vibrated only in the horizontal direction is shown. However, when the pattern to be obtained has a complicated pattern, The orientation of the wafer 6 can be changed.

  That is, when the pattern to be obtained has, for example, a vertically long shape and a horizontally long shape, the portion of the vertically long pattern is formed by vibrating the mask 4 in the horizontal direction as it is. This portion is formed by rotating the wafer 6 in the horizontal direction after rotating the wafer 6 in the horizontal direction, for example, by 90 degrees with respect to the mask 4.

In this way, by configuring the direction of the wafer 6 to be changed with respect to the mask 4, even if the pattern to be obtained is a complicated pattern, the unexposed area can be narrowed in one exposure process. Is possible.
As a result, as in the case of the configuration in which the mask 4 is vibrated only in the horizontal direction, it is possible to form a pattern with a thin line width that exceeds the limit of the performance of the optical system without reducing the throughput.

  The present invention is not limited to the above-described embodiment, and various other configurations can be taken without departing from the gist of the present invention.

A, B It is the schematic block diagram which shows one Embodiment of the exposure apparatus which concerns on this invention, and the concrete perspective view of the principal part. A and B are a diagram showing one form of a pattern to be finally obtained, and a diagram showing a relationship between a vibration amount of a mask and a vibration time for forming this pattern. AD is a specific explanatory view of the vibration movement of the mask. A and B are diagrams showing another form of the pattern to be finally obtained, and a diagram showing the relationship between the amount of vibration of the mask and the vibration time for forming this pattern. A and B are diagrams showing still another form of the pattern to be finally obtained, and a diagram showing the relationship between the amount of vibration of the mask and the vibration time for forming this pattern. A and B are diagrams showing still another form of the pattern to be finally obtained, and a diagram showing the relationship between the amount of vibration of the mask and the vibration time for forming this pattern. A to D are explanatory diagrams of a method of performing an exposure process twice.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Exposure apparatus, 2 ... Light source, 3 ... Condenser lens, 4 ... Mask, 5 ... Projection lens, 6 ... Wafer, 7 ... Stage, 9 ... Mask 10 ... actuator, 11 ... drive shaft, 23 ... mask holder, 24 ... shaft retainer

Claims (6)

In an exposure apparatus that irradiates a workpiece with light generated from a light source through a mask in which openings of a predetermined pattern are formed, and transfers the predetermined pattern to the workpiece.
An exposure apparatus comprising means for moving the mask.   2. The exposure apparatus according to claim 1, wherein the means for moving the mask is configured to vibrate the mask.   3. The exposure apparatus according to claim 2, wherein a direction of the workpiece can be changed with respect to the mask.   The exposure apparatus according to claim 1, wherein a reduction lens is provided between the mask and the workpiece. When the workpiece is irradiated with light through a mask in which openings of a predetermined pattern are formed, and the predetermined pattern is transferred to the workpiece,
An exposure method, wherein the mask is moved.   6. The exposure method according to claim 5, wherein the mask is vibrated when the predetermined pattern is transferred to the workpiece.

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