JPH0410208B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an alignment device for a transfer device.

Conventionally, transfer devices have been used to align the mask and wafer relative to each other at the alignment position, that is, based on the alignment optical system, and then clamp them together to prevent their relative positions from shifting, and then set the exposure position, that is, for exposure. There are two types: one in which the optical system is moved to the base of the optical system, and the other in which the alignment position is made to match the exposure position and after alignment is completed, the alignment optical system is retracted and exposure is performed.

However, in the former case, even if a positional shift occurs between the wafer and mask when they are moved to the exposure position, this cannot be easily corrected, and in the latter case, it is necessary to evacuate the alignment optical system. Therefore, there is a drawback that the mechanical strength and accuracy of the alignment optical system become unstable.

These drawbacks become noticeable in so-called step-and-repeat exposure systems. Here, the step-and-repeat method is a method in which the exposure area is set smaller than the wafer size, and the entire wafer is exposed by moving the wafer or mask and exposing each small area. In the method,
In the former case, the wafer or mask needs to move back and forth between the alignment position and the exposure position multiple times, and in the latter case, the alignment optical system needs to be retracted each time each area is exposed, so the unit time A problem arises in that the number of processing operations per unit, so-called throughput, cannot be increased.

Furthermore, in recent years, in order to form patterns with narrower line widths on wafers, in addition to exposure using visible light and the like, transfer techniques using X-rays with extremely short wavelengths have been researched. For example, when transferring a pattern using the proximity method in which the mask and wafer are placed slightly apart, the time required to irradiate X-rays, including the sensitivity of the resist applied to the wafer, is the so-called transfer time, which is the exposure time for visible light, etc. The problem is that it becomes extremely long. When performing transfer using X-rays in this manner, the X-ray source and the alignment optical system are naturally placed at separate positions. Therefore, as mentioned earlier, the relative position of the mask and wafer is adjusted at the alignment position, and the wafer and mask are moved to the exposure position, that is, the X-ray irradiation position, while being clamped at that relative position, and transfer is performed. It turns out. Hold the wafer and mask in this state for a long time (for example, 1 to 10 minutes).
During the irradiation with X-rays, the relative positions of the wafer and mask may shift due to mechanical fluctuations such as the wafer mounting stage clamp. If one end shifts during transfer, an accurately positioned pattern can no longer be transferred onto the wafer. As a result, there has been a drawback in that the use of X-rays to transfer patterns with narrower line widths is not fully utilized.

In addition, even in the latter method, that is, a method in which the alignment position and exposure position are matched and the alignment optical system is inserted and removed, the mechanical The relative positions of the mask and wafer may shift due to fluctuations or the like.

In view of the above circumstances, the present invention is capable of relatively aligning a mask and a wafer (subject to be transferred), and then maintaining the relative position at the time of alignment during the transfer operation without using a temporary clamp or the like. This was done for the purpose of providing such an alignment position.

In order to achieve this object, the present invention includes mask holding means 21 and 22 having a mechanism for holding a mask 25 on which a predetermined pattern is formed and for moving the mask slightly; movable stages 7, 11, 14 that hold the transferred substrate 15; drive means 8, 31 that relatively moves the moving stage and the mask holding means two-dimensionally; Alignment detection means 40, 4 are configured to detect the positional relationship with a predetermined area on the mask from above the mask, and are set to be retracted from above the pattern on the mask during the transfer operation.
2, 43, and controls the driving means based on the detection result of the alignment detecting means to align and transfer the pattern of the mask with a predetermined area on the transfer target substrate. The beam from the coherent light source 31 is divided and irradiated to each of the reflecting member 27 provided on a part of the mask holding means and the reflecting member 26 provided on a part of the moving stage, and the beam from the two reflecting members is irradiated separately. A single light wave interferometer 32 that directly measures the relative distance between the mask holding means and the moving stage by directly interfering each reflected beam.
and; prior to the transfer operation, the alignment detecting means 40, 42, and 43 detect a deviation from the alignment state between the pattern of the mask 25 and a predetermined area of the transfer target substrate 15, and the alignment state is achieved. The mask holding means 21, 22 and the moving stage 7,
The measured value of the relative distance to 11 and 14 is measured using a light wave interferometer 3.
Means 103, 104 for reading and storing from 2
and control means 100, 101, 102 for controlling the driving means 8, 13 so that the measured value of the light wave interferometer 32 always matches the value stored in the storage means 103, 104 during the transfer operation. This is to prevent deviation from the aligned state due to slight movement of the mask holding means 21, 22 or the moving stages 7, 11, 14 during the transfer operation.

One embodiment of the present invention will be described below with reference to the drawings. In this embodiment, the alignment device of the present invention is applied to a proximity exposure device.

In FIG. 1, a column 2 is mounted on a base 1 so as to be movable in the x-axis direction (left and right in the figure) via a bearing 3, and the column 2 is moved by a motor 4 fixed on the base 1. It is designed to be driven via a feed screw 4a. A y-axis stage 7 is mounted on the column 2 via rolling elements 6 such as bearings and rollers.
is mounted so as to be movable in the y-axis direction (perpendicular to the plane of the drawing) and is driven by a y-axis motor 8 fixed to the column 2. Furthermore, an x-axis stage 11 is mounted on the y-axis stage 7 so as to be movable in the x-axis direction via rolling elements 12.
It is designed to be driven by an x-axis motor 13 fixed on the axis stage 7. A wafer stage 14 for mounting a wafer 15 is fixed on the x-axis stage 11, and this wafer stage 14
is a leveling mechanism for correcting the taper of the wafer 15 itself and creating a gap between the wafer 15 and a mask (described later) 25, and an x-axis stage 1.
The wafer orientation mechanism has a wafer orientation mechanism for correcting an error in the rotation direction of the wafer 15 with respect to the rotation direction of the wafer 15.

The column 2 has an upper extension portion 2a, which includes a mask holder 21 for attaching a mask 25 and a mask orientation mechanism 2 for correcting rotational errors when attaching the mask 25.
2 is provided, and the mask holder 21 is rotatable with respect to the column extension 2a by a mask orientation mechanism 22 within the x- and y-axis planes including the respective movement directions of the x- and y-axis stages 11 and 7. It is said that

The above x-axis stage 11 and column extension part 2a
Planar reflection mirrors 26 and 27 for position detection in the x-axis direction are attached to the ends of the mirrors, respectively.
Although not shown, each end has a y mark.
A plane reflective mirror for axial position detection is also installed.

Furthermore, a side length laser light source 31 and a laser light wave interferometer 32 are fixed to the end of the column 2. Between the laser light source 31 and the x-axis stage 11,
A half mirror 33 and a reflecting mirror 34 are arranged between the interferometer 32 and the column 2, respectively.
Another reflective mirror 36 is arranged above the mirrors 33 and 34 at a position relative to the mirror 27. The laser light source 31 and the interferometer 32 are connected to a side length circuit 35 that determines the relative distance between the mirrors 26 and 27. A part of the laser beam from the laser light source 31 passes through the half mirror 33 and is reflected by the reflection mirror 26, and is reflected by the mirrors 33 and 34.
The light is reflected downward and to the left and reaches the laser interferometer 32. On the other hand, the remainder of the laser beam reflected by the half mirror 33 is directed to the right by the mirror 36, and to the right by the mirror 27.
It is reflected to the left by the mirror 36, reflected again to the left by the mirror 34, and reaches the interferometer 32.
By comparing both incident lights in the side length circuit 35, the relative distance between the x-axis stage 11 and the column, that is, the wafer 15 and the mask 25 is determined, and the determined distance value is input to the control device 50. The relative distance between the wafer 15 and the mask 25 is determined in the same manner in both the x-axis direction and the y-axis direction. Therefore, the output signal of the length measuring circuit is transmitted to the mirror 26.
and the relative distance of mirror 27 in the x-axis direction (for example, the distance from mirror 26 to mirror 27)
This value corresponds to the relative distance between the wafer 15 and the mask 25 in the x-axis direction. Also,
Since the relative distance in the y-axis direction is also determined by a similar length measuring circuit, the relative two-dimensional position of the wafer 15 and the mask 25 (for example, the coordinate value of the wafer 15 with respect to the mask 25) is finally measured.

On the other hand, an alignment optical system 40 for observing alignment marks provided on each of the mask 25 and the wafer 15 is fixed to a base 41 that is integrated with the base 1 above the mask holder 21. The observation light is input to a mark detection section 42 provided on the side and converted into an electrical signal representing the position of each mark. Then, the positional deviation processing unit 43 detects the direction and amount of deviation of each mark on the wafer 15 and the mask 25 based on the input of the electric signal, and generates a signal corresponding to the deviation between both marks. Therefore, this signal represents the amount of deviation between the mask 25 and the wafer 15.

Here, the wafer 15 and mask 2 handled by the mark detection section 42 and the positional deviation processing section 43
An example of the mark on 5 will be explained based on FIG. As shown in FIG. 2, marks M and M' are provided on the mask 25 at a predetermined distance apart, and a rectangular mark W is provided on the wafer 15 so as to be sandwiched between the marks M and M'. (In addition, the shaded part of each mark in the figure is, for example, a reflective part that reflects light.) Then, as described above, the marks M, M' and mark W are observed simultaneously by the alignment optical system 40, and the mark The detection section 42, for example, scans a laser spot in the direction of arrow S in FIG. 2, and photoelectrically detects the reflected light from each mark. At this time, the mark detection section 42 generates, for example, a high level signal at each mark, and a low level signal at the intervals a and b. Based on the input of this signal, the positional deviation processing section 43 detects the sizes of the gaps a and b, and generates a signal corresponding to the direction and amount of deviation between the marks M, M' and the mark W. Alternatively, an image input device such as an ITV may be used as the mark detection section 42, and the shift of the mark may be determined based on the image scanning signal.

Note that the marks on the wafer 15 and the mask 25 are provided, for example, as shown in FIG. 4. Each stage 11,
Two marks are made for one transfer area P so that alignment can be performed in the moving directions x and y of 7.
Wx and Wy are provided. Of course, two corresponding MM'a and MM'y are also provided on the mask 25 having the area Q where the circuit pattern is drawn. In the case of this device, the wafer 15 moves within the xy plane with respect to the mask 25, and marks are made in each transfer area.
MM′X and mark Wx and mark MM′y and mark
Transfer is performed with the Wys matched or superimposed. By aligning the mark MM' and the mark W in this way, the pattern of the mask 25 matches the pattern formed in the area P by, for example, the first transfer.

Returning to FIG. 1 again, a light source 46 that generates energy rays such as visible light and X-rays for transfer is provided on the base 41 at a position apart from the alignment optical system 40 along the moving direction of the column 2. It is being The light source 46 is moved to the wafer 15 by a drive unit 47.
Irradiation of light beams, X-rays, etc. to the area is controlled. Drive part 4
7 includes, for example, a shutter control circuit that blocks light from an aperture through which light rays and the like pass. The positional deviation processing section 43 and the length measuring circuit 35 are connected to a control device 50, which controls the motors 4, 8 and 1.
3. Connected to the drive section 47. This control device 50 controls the driving and state detection of each section based on instructions from a computer 51 that performs predetermined control and data transfer and storage.

FIG. 3 is a block diagram for explaining the control device 50 in detail. Regarding the control device 50, only the configuration for driving the x-axis and y-axis stages 11 and 7 is shown as a block diagram.
A signal D ₁ corresponding to the amount of deviation in the x-axis direction between the wafer 15 and the mask 25 generated in the positional deviation processing unit 43,
A signal corresponding to the relative distance in the x-axis direction between the mask 25 and the wafer 15 measured by the length measurement circuit 35
D ₂ , a signal D ₃ corresponding to the amount of deviation between the mask 25 and the wafer 15 in the y-axis direction, and a signal D ₄ corresponding to the relative distance in the y-axis direction are input to the arithmetic processing circuit 100 .

This arithmetic processing circuit 100 exchanges information regarding positioning with the computer 51, and sends and receives signals D ₁ ,
Based on the input of _D3 , a signal is sent to the drive circuits 101 and 102 of each of the motors 8 and 13 for servo control so that the amount of deviation between the mask 25 and the wafer 15 in the x-axis and y-axis directions is equal to or less than a predetermined value. Operation of outputting, storing or reading values of the relative distances between the mask ₂₅ and the wafer 15 in the x-axis and y- _axis directions in the X memory 103 and the Y memory 104, respectively, based on the input of the signals D 2 and D 3 control. In addition, X memory 1
It goes without saying that the memory 03 and the Y memory 104 may be internal memories of the computer 51.

Next, the operation of this embodiment will be explained with reference to FIGS. 1 and 3.

First, the column 2 is moved by the drive motor 4, and the mask 25 is positioned below the alignment optical system 40. Next, alignment optical system 40
using the mask 25 and the x and y axis stages 11 and 7.
Correct the rotational deviation in the x and y directions. This correction is performed by the orientation mechanism 22 by observing dedicated marks provided at two locations on the mask 25, for example. This prevents the mask pattern from being printed diagonally onto the wafer 15.

Next, the wafer 15 is set on the wafer stage 14, and the gap between the wafer 15 and the mask is
Make adjustments. Although not shown, this gap setting is performed using a proximity sensor or the like.

Subsequently, as shown in FIG.
The x-axis stage 1 is moved so that the marks W used at two corresponding locations on the
1 and y-axis stage 7 by motors 13 and 8, respectively.
move by. Then, the rotational deviation of the wafer 15 with respect to the mask 25 is detected by the alignment optical system 4.
0, mark detection section 42 and positional deviation signal processing section 4
3, and the orientation mechanism on the wafer stage 14 rotates the wafer 15 to correct this deviation.

Next, move the x-axis and y-axis stages 11 and 7,
The mask 25 is aligned for each of a plurality of transfer areas on the wafer 15. For this purpose, the computer 51
A signal from the length measuring circuit 35 indicates the relative position with respect to the mask 25 in each area of the wafer 15 that has been printed for the first time.
D ₂ and signal D ₄ are stored in advance through the arithmetic circuit 100 as two-dimensional positions corresponding to each region. Note that the plurality of two-dimensional positions written in the pre-calculator 51 will be designated positions from now on. First, wafer 1
The computer 51 outputs information on the corresponding designated position to the arithmetic processing circuit 100 for one area on the screen 5 . At this time, the arithmetic processing circuit 100
Based on the signal D ₂ and the signal D ₄ of 5, the mask 25
The drive circuits 101 and 102 are controlled so that the relative position of the wafer 15 is equal to the designated position.
As a result, the pattern of the mask 25 almost matches the pattern formed in one transfer area of the wafer 15, but if there is a slight deviation when the wafer 15 is placed, it will not be completely aligned at this specified position. There is no guarantee that there will be consistency.

At the specified position, the mark on the mask 25
MM′ and the mark W on the wafer 15 are simultaneously observed by the alignment optical system 40, and the mark detection unit 4
2 and the positional deviation processing unit 43 detect the amount of positional deviation of the wafer 15 with respect to the mask 25, and the controller 50 uses signals D ₁ and D ₃ corresponding to this deviation amount.
The drive circuits 101 and 103 of stage 1 are controlled.
1 and 7 and apply servo so that the amount of positional deviation in the x-axis direction and the y-axis direction becomes zero. When the amount of positional deviation between the wafer 15 and the mask 25 reaches a preset tolerance value, for example, the distances a and b shown in FIG.
The information on the stage positions of the stages 11 and 7 read at that time, that is, the signals D ₂ and D ₄ is sent to the arithmetic processing circuit 100, and the signal D ₂ is sent to the X memory 103.
As X ₁ , signal D ₄ is written to Y memory 104 as Y ₁ . Then, the computer 51 outputs information regarding the next specified position to the arithmetic processing circuit 100, and the above-described operation is repeated.

The above scanning is repeated for all of the designated position information of the stages 11 and 7 that has been stored in advance in the computer 51, and marks are marked for each designated position.
The relative positions of the x-axis stage 11 and the y-axis stage 7, which are accurately recognized by marks MM' and mark W, are stored in the X memory 103 and the Y memory 104 as (X ₂ , Y ₂ ), (X ₃ , Y ₃ )... still,
The position information stored in each of the memories 103 and 104 will be referred to as matching positions corresponding to each area on the wafer 15.

As described above, once all alignment positions of the x-axis stage 11 and y-axis stage 7 with respect to the mask 25 have been stored in the memories 103 and 104, the column 2 is moved by the motor 4, and the mask 25 is placed at the light source. 46.

Next, the computer 51 outputs a transfer start command to the arithmetic processing section 100. Based on this command, one of the matching position information stored in each memory 103 and 104, for example (X ₁ , Y ₁ ), is taken into the arithmetic processing unit 100 . Then, the arithmetic processing unit 100 receives the signals D ₂ , D ₄ and matching position information (X ₁ ,
Y ₁ ), and control the drive circuits 101 and 102 that move the x-axis and y-axis stages 11 and 7 so that the difference becomes zero, for example. That is, using the information (X ₁ , Y ₁ ) as a reference value, the relative positions of the wafer 15 and the mask 25 are controlled so as to always match this reference value. Therefore, each stage 11, 7
Even if mechanical fluctuations occur for some reason in the wafer 15 and its feeding mechanism, the relative positions of the wafer 15 and the mask 25 are always maintained in alignment.

When the pattern of the mask 25 is aligned with one area on the wafer 15 in this way, the computer 51 issues a command to the drive section 47 of the light source 46 via the control device 50 to start irradiating the transfer illumination light or energy beam. The pattern is transferred to one area on the wafer 15 by irradiating the mask 25 for a predetermined period of time. Note that during transfer, the drive circuit 1 is always
01 and 102 work to keep the aligned position.
Thereafter, the illumination of the light source 46 is stopped, and the X memory 1
03, information on the next matching position (X ₂ , Y ₂ ) is taken into the arithmetic processing circuit 100 from the Y memory 104. Then, each stage 11, 7 is moved as described above, and the pattern of the mask 25 is similarly transferred to the next area on the wafer 15. In this manner, the pattern of the mask 25 is aligned with the pattern in each area on the wafer 15 and sequentially transferred based on the information of each alignment position stored in each memory 103, 104.

In the alignment apparatus according to the embodiment of the present invention described above, when each alignment position is determined and stored, each stage 11, 7 is moved near the designated position,
For example, the mark MM′x shown in FIG. 4 in the x direction
The mark detection unit 42 photoelectrically detects the coincidence of the mark Wx and the mark Wx and generates a pulse signal.
Configure. When the arithmetic processing circuit 100 receives this pulse signal, the signal from the length measuring circuit 35 is
D ₂ may be stored in the X memory 103. Of course, the same applies to the y direction.

FIG. 5 is an explanatory diagram showing the configuration of another transfer device using the alignment device according to the present invention. 1st
The difference from the configuration shown in the figure is that the position of the mask 25 is fixed relative to the base 1, and the alignment optical system 4
0. The light source 46 is movable with respect to the base 41. For this purpose, the mount 61 that fixes the alignment optical system 40 and the light source 46 to the mount 61 so as not to spatially interfere with each other is attached to the base 41.
It is moved in the left and right direction in FIG. 5 by a feed screw 62 which is suspended by bearings 63 and 64 fixed to. This movement is controlled by a motor 65 which functions similarly to motor 4 shown in FIG. On the other hand, the mask holder 21 that holds the mask 25 and the mask orientation mechanism 22 are attached to an arm 60 that is integrated with the base 1. Then, the x-axis and y-axis stages 11 and 7 move two-dimensionally relative to the base 1. Regarding other configurations,
Since it is the same as FIG. 1, the explanation will be omitted.

In addition, the mark detection section 42 and the driving section 4 of the light source 46
7. The control system shown in FIGS. 1 and 3 is used as is for controlling the motors 8, 13, etc. The positioning operation in this case is the same as described above, but the difference is that during transfer to the wafer 15, the control device 50 drives the motor 65 instead of the motor 4 shown in FIG. It is to control.

By configuring the transfer device as in this example,
Since it is not necessary to mount the x-axis and y-axis stages 11 and 7, which require mechanical safety, on the column 2, a stage with sufficiently high mechanical strength and safety can be used. As a result, there is an advantage that alignment accuracy is improved.

According to the embodiment described above, it is not necessary to retreat the alignment optical system every time the wafer 15 is exposed, and the mechanical safety of the alignment optical system can be improved. The positional deviation between the mask 25 and the wafer 15 during movement can be set to about the resolution of the Loese interferometer during exposure. Since the alignment optical system 40 and the light source 46 are separated, there is no interference between them, and each can be provided with sufficient mechanical margin to form a highly accurate optical system.
Furthermore, the throughput during alignment and exposure can be increased.

In addition, as another configuration of the transfer device, as shown in FIG.
7, only the alignment optical system 40 is movable in the horizontal direction in the figure, and the light source 46 is disposed above the mask 25 so as to be vertically movable. When using the alignment optical system 40, the light source 46 may be retracted upward, and during transfer, the alignment optical system 40 may be retracted horizontally to move the light source 46 downward to a predetermined position. Furthermore, it goes without saying that the present invention can also be used in other exposure apparatuses, such as step-and-repeat type projection exposure apparatuses.

As described above, according to the present invention, the relative positional deviation between the mask and the transferred object is directly detected by a single interferometer. Therefore, the alignment status between the mask and the transferred object can be monitored with high precision based only on a single length measurement output, and the positional deviation that occurs during exposure transfer operation is completely eliminated with an extremely simple configuration. You can get the desired effect. Therefore, in the manufacture of semiconductor devices such as ICs, patterns with narrower line widths can be managed with good yield. Furthermore, if the member that holds the mask or transferred object is servo-controlled based on the length measurement output of this interferometer, even if the absolute position of the mask or transferred object moves slightly, the relative The positional relationship will not shift at all. Therefore, pattern shake due to slight movement of the device that occurs during the transfer operation is reduced, and pattern transfer with extremely high resolution becomes possible. Furthermore, in devices with alignment systems that do not allow simultaneous observation of the mask and the transferred object during the transfer operation,
Another effect is that accurate resolution is guaranteed even if the transfer time is long.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the present invention, and FIG.
3 is a block diagram of the control device 50, FIG. 4 is a perspective view showing the wafer mark and mask mark,
FIG. 5 is an explanatory diagram corresponding to FIG. 1 showing another embodiment of the present invention. [Description of symbols of main parts], 7, 11...Movement stage, 15...Wafer, 25...Mask, 2
6, 27...Mirror, 31...Laser light source, 32
...Laser interferometer, 35...Length measurement circuit.

Claims (1)

[Scope of Claims] 1. A mask holding means that holds a mask on which a predetermined pattern is formed and has a mechanism for slightly moving the mask, and a moving stage that holds a transfer target substrate onto which the pattern of the mask is transferred. , the moving stage and the mask holding means are relatively 2
A driving means for dimensional movement, detecting the positional relationship between the pattern of the mask and a predetermined area on the transfer target substrate from above the mask, and retracting from above the pattern of the mask during the transfer operation. and an alignment detecting means for setting, and controlling the driving means based on the detection result of the alignment detecting means to transfer the pattern of the mask in alignment with a predetermined area on the transfer target substrate. In the apparatus, a beam from a coherent light source is divided and irradiated to each of a reflecting member provided on a part of the mask holding means and a reflecting member provided on a part of the moving stage, and a beam from the two reflecting members is irradiated. a single light wave interferometer that directly measures the relative distance between the mask holding means and the moving stage in the direction of the two-dimensional movement by directly interfering each reflected beam of the transfer operation; , the alignment detecting means detects a deviation from the aligned state between the pattern of the mask and the predetermined area of the transfer target substrate, and the alignment between the mask holding means and the moving stage is determined when the aligned state is achieved. means for reading and storing measured values of relative distances from said light wave interferometer; and means for reading and storing measured values of relative distances from said light wave interferometer; a control means for controlling a driving means, and a transfer apparatus characterized in that the transfer apparatus is characterized in that the transfer apparatus is provided with a control means for controlling a driving means, and is characterized in that deviation from the alignment state caused by slight movement of the mask holding means or the moving stage during the transfer operation is prevented. Alignment device. 2. The transfer target substrate has a plurality of the predetermined regions that can be matched with the pattern of the mask, and the driving means generates information on a designated position where the pattern of the mask and each of the predetermined regions substantially match, and the light wave. Claim 1, wherein the movable stage is moved in steps based on the measured value by an interferometer, and the movable stage is slightly moved in order to sequentially correct misalignment during the transfer operation. Alignment device for transfer device.