JP2004095906A - Device and method for alignment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and method for alignment by which the deflection and deformation of an object to be aligned, such as the mask etc., can be detected. <P>SOLUTION: The device aligns a wafer (W) and a mask (110) used for executing prescribed treatment on the wafer (W) with each other. The device is provided with moving devices (102, 103, and 104) which changes the relative position between the wafer (W) and mask (110) and a reader (108) which reads an alignment mark provided on the wafer (W) through an opening for alignment provided on the mask (110). The device is also provided with a controller (101) which changes the relative position between the wafer (W) and the mask (110) based on the relative position between the opening for alignment and alignment mark read by means of the reader (108). The controller (101) stores the position of the edge of the opening for alignment at prescribed timing, and judges whether the position of the edge newly read from the reader (108) deviates from a prescribed permitted limit by comparing the newly read position of the edge with the stored position of the edge. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
[Industrial applications]
The present invention relates to an exposure apparatus or an ion implantation apparatus used for semiconductor manufacturing or the like, and more particularly, to an improvement in an apparatus for aligning a wafer with an exposure / ion implantation mask.
[0002]
[Prior art]
In a manufacturing process of a semiconductor device, a plurality of chip regions are set on a silicon wafer, and manufacturing processes such as exposure and ion implantation are sequentially performed on each chip region.
[0003]
In order to form a pattern on each chip region on a wafer, a method called proximity exposure or proximity exposure, in which a mask on which a mask pattern for exposure is formed is exposed close to the wafer, is used.
[0004]
In this proximity exposure, since the position of the wafer and the position of the mask must be correctly aligned, it is necessary to accurately perform the alignment before the exposure step. As an alignment method, both the wafer mark provided on the wafer and the mask mark provided on the mask are imaged by the imaging means, and the relative position between the wafer and the mask is detected from the positional relationship between the two. As such a positioning technique, for example, Japanese Patent Application Laid-Open No. 9-139333 discloses a positioning method to which an oblique detection method is applied (Patent Document 1). According to the oblique detection method, since there is no need to arrange a positioning means on the optical axis of the exposure light for exposure, there is no need to evacuate the positioning means during exposure, and alignment is performed even during exposure. This makes it possible to improve throughput.
[0005]
[Patent Document 1]
JP-A-9-139333
[0006]
[Problems to be solved by the invention]
However, since the mask is extremely thin, typically about 10 μm, the mask may bend during exposure or ion implantation, and the mask pattern may not be correctly aligned with the chip region of the wafer.
[0007]
That is, even if the wafer and the mask are correctly aligned at the beginning of the exposure or the like, in the exposure process or the ion implantation process, the temperature of the mask becomes high due to radiation heat of exposure light or collision of ions with the mask. This temperature causes the mask to deform and bend. In the alignment by the oblique detection method, the position of the mask mark provided on the mask and the wafer mark on the wafer are observed obliquely, so even if the mask is slightly bent, accurate alignment may not be possible. was there. Further, since the gap between the mask and the wafer is usually extremely small, that is, several μm to 50 μm, there is a possibility that the mask may come into contact with the wafer if the deformation of the mask is large.
[0008]
[Means for Solving the Problems]
Therefore, an object of the present invention is to provide a positioning device and a positioning method capable of detecting a deflection of a positioning target such as a mask.
[0009]
In order to achieve the above object, a positioning device according to the present invention includes a reading device that reads a mark provided on a positioning target, and a storage unit that stores a position of the mark read by the reading device at a predetermined timing. And comparing the position of the mark read by the reading device with the position of the mark stored in the storage unit to determine whether the position of the mark read by the reading device deviates from a predetermined allowable range. And a comparison / determination unit for performing the determination.
[0010]
According to the above configuration, the position of the mark on the object read by the reading device is stored in the storage unit, the position of the newly read mark is compared with the position of the stored mark, and the position of the read mark is compared. It is determined whether or not the position is within a predetermined allowable range when viewed from the position of the stored mark. If the object is deformed and the distance to the reader changes, the position of the mark on the object also changes, so that the bending and deformation of the object can be reliably detected by this configuration.
[0011]
Note that the change in the mark position due to the bending / deformation of the object is more greatly observed when the direction of the bending / deformation of the object is different from the direction from the reading device to the mark position. Although it is suitable for the so-called oblique detection method, the mark shape changes even in the vertical detection method in which the direction of deflection / deformation of the object and the direction from the reader to the mark position are substantially parallel. By detecting the change in the position, the positioning technique can be applied.
[0012]
In the present invention, the “positioning target object” may be, for example, a mask in an exposure apparatus or an ion implantation apparatus, but is not particularly limited to its name or application as long as it is an object whose deformation is to be detected. .
[0013]
In the present invention, the “reading device” is sufficient if it can convert a change in the position of the mark into an electric signal in a form that can be identified, and is a means such as a camera that reads a two-dimensional image. May be a line sensor that reads an image while scanning one-dimensionally.
[0014]
In the present invention, the “mark” is not particularly limited in its shape and size, but corresponds to an opening provided on a mask as an object in a device that requires alignment between a wafer and a mask. .
[0015]
Further, in the present invention, the “predetermined timing” is not limited, and it is conceivable that the reading is performed at the start of the work or periodically during the middle of the work. This is because the purpose is to detect bending / change of the target object from the timing.
[0016]
In the present invention, the "permissible range" can be variously set in accordance with the accuracy required to achieve the purpose of alignment. For example, in the case of an exposure apparatus or an ion implantation apparatus, the term refers to a range of a positional shift in an object such that a shift in a pattern or an ion implantation position does not affect performance. Such a range is set, for example, in an experiment performed in advance.
[0017]
Here, the storage unit stores the position of the mark at the initial timing of the operation. This storage unit may be an external removable storage device or a temporary storage device such as an internal RAM or cache memory. The position of the mark may be stored as an image of the mark itself, or may be stored as a numerical value corresponding to the detected position. The contents to be stored can be changed as appropriate according to the specifications of the reading device.
[0018]
The determining unit performs a predetermined emergency process when determining that the value deviates from the allowable range. Here, the predetermined emergency processing includes, for example, outputting a warning signal, for example, when the alignment apparatus is used for an exposure apparatus or an ion implantation apparatus, exposure processing, or interruption of the ion implantation processing. No. Since the deviation from the allowable range indicates that the bending and deformation of the object are relatively large, it is possible to notify the user by issuing a warning signal. For example, based on a warning signal, a warning is given by means that can be perceived by the user, such as turning on (flashing) a lamp, generating a warning sound, or displaying a warning on a display.
[0019]
Further, the present invention is an alignment device for performing alignment between a wafer and a mask for performing a predetermined process on the wafer, and a moving device that changes a relative position between the wafer and the mask. A reading device that reads an alignment mark provided on a wafer through an alignment opening provided on a mask, and a wafer and a mask based on a relative position between the alignment opening and the alignment mark read by the reading device. And a control device for changing a relative position of the control signal. Then, the control device stores the position of the edge of the alignment opening at a predetermined timing, compares the position of the edge newly read from the reading device with the position of the stored edge, and reads the position of the edge newly read by the reading device. It is determined whether or not the position of the edge has deviated from a predetermined allowable range.
[0020]
According to the above configuration, the control device stores the edge position of the alignment opening on the mask read by the reading device at a predetermined timing, and stores the edge position of the newly read opening and the stored opening position. Compare with the edge position of the part. Then, it is determined whether the newly read edge position of the opening is within a predetermined allowable range when viewed from the stored edge position of the opening. If the mask bends and deforms and the distance to the reading device changes, the edge position of the opening on the mask also changes, so that the mask can reliably detect the bending and deformation of the mask.
[0021]
The change in the edge position of the opening due to the bending / deformation of the mask is more greatly observed when the direction of the bending / deformation of the mask is different from the direction from the reader to the position of the opening. The alignment is suitable for the so-called oblique detection method, but the shape of the opening changes even in the vertical detection method in which the direction of the bending and deformation of the mask and the direction from the reader to the edge position of the opening are almost parallel. Therefore, the alignment technique can be applied by detecting a change in the shape of the opening.
[0022]
Here, for example, the control unit stores the position of the edge read by the reading device at a predetermined timing, the position of the edge read by the reading device, and the position of the edge stored in the storage unit. And a comparison / determination unit that determines whether the position of the read edge deviates from a predetermined allowable range.
[0023]
Further, the control device may store the position of the edge at an initial timing of the process processing on the wafer. However, it may be stored at any timing during the processing. This is because the purpose is to detect the deflection / deformation of the mask from a certain reference timing.
[0024]
Further, the control device may perform a predetermined emergency process when it is determined that it is out of the allowable range. The predetermined emergency processing includes, for example, the following. First, a warning signal may be output. Since the deviation from the allowable range indicates that the deflection and deformation of the mask are relatively large, it is possible to notify the user by issuing a warning signal. For example, based on a warning signal, a warning is given by means that can be perceived by the user, such as turning on (flashing) a lamp, generating a warning sound, or displaying a warning on a display. Thereby, the user can recognize that the mask should be replaced.
[0025]
Further, the control device may be configured to interrupt the subsequent processing on the wafer when it is determined that the deviation is out of the allowable range. Deviating from the permissible range means that the deflection and deformation of the mask is relatively large, and if the production is continued as it is, only inaccurate patterning and ion implantation can be performed, so it is inappropriate to continue the subsequent process. It is.
[0026]
In this case, the interrupted process may be an exposure process or an ion implantation process, but may be another process. This is a case where the present invention is applied to an exposure apparatus or an ion implantation apparatus. The exposure apparatus may be an ultraviolet exposure apparatus, an electron beam lithography apparatus, an electron beam exposure apparatus, an X-ray exposure apparatus, or the like, which performs 1: 1 or reduced projection.
[0027]
The alignment method of the present invention includes a step of reading a position of a mark provided on an alignment target at a predetermined timing, a step of storing a position of the read mark, and a step of storing a position of a newly read mark. The method includes a step of comparing the stored position of the mark and a step of determining whether the position of the newly read mark deviates from a predetermined allowable range.
[0028]
Further, the alignment method of the present invention is an alignment method for aligning a wafer with a mask for performing a predetermined process on the wafer, and is provided on the mask at a predetermined timing. Reading an alignment mark provided on the wafer through the alignment opening provided, and storing a position of an edge of the alignment opening at a predetermined timing. Then, during the execution of the process, a step of reading a new edge position, a step of comparing the newly read edge position with the stored edge position, and a step of determining the position of the newly read edge Determining whether or not the position is outside the allowable range, and when the position of the newly read edge is within the allowable range, the relative position between the newly read alignment opening and the alignment mark is determined. Changing the relative position between the wafer and the mask on the basis of this.
[0029]
The alignment apparatus and the alignment method of the present invention can be used, for example, by incorporating them into a part of an exposure apparatus or an ion implantation apparatus of a manufacturing apparatus used for semiconductor manufacturing or the like.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<First embodiment>
In the first embodiment of the present invention, the alignment apparatus and method of the present invention are applied to an exposure apparatus in semiconductor manufacturing.
[0031]
FIG. 1 shows a schematic diagram of a manufacturing apparatus according to the first embodiment of the present invention. As shown in FIG. 1, in the manufacturing apparatus 1, a process chamber 10, a work chamber 12, a mask chamber 13, and a pre-alignment chamber 14 are connected to a loader chamber 11 by gate valves 15, 16, 17, and 18, respectively. It is configured. The gate valves 15, 18 between the pre-alignment chamber 14 and the process chamber 10, which are almost always kept in a vacuum state together with the loader chamber 11, may be omitted.
[0032]
The pressure of the process chamber 10, the loader chamber 11, the work chamber 12, the mask chamber 13, and the pre-alignment chamber 14 can be reduced to a degree of vacuum suitable for the semiconductor manufacturing process by a suction unit (not shown). The loader chamber 11 is provided with a loader 20 including an arm 21 and a hand 22.
[0033]
The work chamber 12 stores a plurality of silicon wafers mounted in a cassette (not shown). In the mask chamber 13, a stencil mask (not shown) in which an exposure pattern for exposing the wafer is recorded is stored corresponding to the exposure pattern. The pre-alignment chamber 14 includes a direction adjusting mechanism for turning the wafer carried from the work chamber 12 and the stencil mask carried from the inside of the mask chamber 13 in substantially constant directions. This pre-alignment is performed using a notch (see FIG. 4) provided in the wafer and the stencil mask. The notch may be V-shaped or the like. The process chamber 10 is a place where the alignment device according to the present invention is provided, and is provided with a process unit 10a for performing wafer exposure and ion implantation.
[0034]
FIG. 2 shows a configuration diagram of the exposure apparatus 100 provided in the process section 10a. As shown in FIG. 2, the exposure apparatus 100 includes a control device 101, a drive circuit 102, a drive mechanism 103, a stage 104, an electrostatic chuck 105, reading devices 106A, BC, and an exposure illumination device 109. . Each of the reading devices 106A / B / C includes a detection illumination device 107 and a camera 108, respectively.
[0035]
The control device 101 is a computer device, and is configured to be able to execute the alignment method of the present invention according to a predetermined software program (see FIG. 10). That is, a drive signal (digital signal) corresponding to the positional deviation indicated by the reading result of the reading device 106 and a drive signal (digital signal) for step-feeding can be output. Specifically, the control device 101 functions as a functional block as shown in FIG. 3 and includes a storage unit 1011, a comparison determination unit 1013, and a control unit 1014. The storage unit 1011 is an internal memory such as a RAM, but may be configured to store information in the external memory 1012. As the external memory 1012, various storage media such as a fixed disk and a memory card can be used regardless of whether they are detachable.
[0036]
The drive circuit 102 is configured to receive a drive signal and convert the drive signal into a drive pulse for moving the stage 104. That is, the drive circuit 102 outputs a drive pulse for moving the stage 104 by the movement amount indicated by the drive signal in accordance with the specification of the drive mechanism 103.
[0037]
The driving mechanism 103 includes a mechanism for moving by a relatively large moving amount such as a step feed, and a fine movement mechanism for correcting displacement. The former includes a driving mechanism in the X-axis direction in the horizontal direction of the drawing, a driving mechanism in the Y-axis direction in the depth direction of the drawing, and a driving mechanism in the Y-axis direction A drive mechanism in the Z-axis direction is provided, and the stage 104 can be moved in each direction by a movement amount corresponding to the drive pulse. The latter includes, for example, a piezoelectric element or the like, and is configured to finely move the stage 104 in the X-axis direction, the Y-axis direction, the Z-axis direction, and around each axis. That is, the relative position between the stage 104 and the stencil mask 110 attached by the electrostatic chuck 105 can be changed.
[0038]
The stage 104 temporarily holds the wafer W by means of a suction chuck or the like (not shown) (for example, an electrostatic chuck, a vacuum chuck in the atmosphere, or a mechanical gripping mechanism) in order to removably mount the wafer W. It can be fixed. When the wafer W is exchanged, the temporary fixing is released, the loader 20 removes the wafer W, and the wafer W newly transported by the loader 20 is correctly placed, so that the temporary fixing can be performed again. Has become.
[0039]
The electrostatic chuck 105 can temporarily fix the stencil mask 110 temporarily by electrostatic force. Instead of the electrostatic chuck 105, various suction chucks (for example, a magnet chuck or a vacuum chuck in the case of air), a gripping mechanism, and other known temporary fixing means may be used depending on the type of the exposure apparatus. Good.
[0040]
In each of the reading devices 106A, B, and C, the detection illuminating device 107 is configured to emit detection light having a spectrum suitable for image capturing at a light amount suitable for image capturing. For example, as the detection illumination device 107, a configuration in which a halogen lamp and a reflection plate are stacked, an LED, a laser device, and the like are applied. The camera 108 has a configuration capable of capturing a two-dimensional image, for example, a CCD camera or the like capable of capturing a micro area such as an alignment mark with an objective lens in an enlarged manner. With these configurations, each of the reading devices 106A, B, and C can simultaneously read the alignment marks at different positions on the mask 110 at the same time.
[0041]
Note that a transport device of a reading device (not shown) may be provided so that the reading position of each of the reading devices 106A, B, and C can be changed. Of course, if the relative positional relationship between the pattern area and the alignment mark on the mask 110 is set to be the same for all the masks, the positions of these readers 106A, 106B, and 106C are set with respect to the electrostatic chuck 105. It may be fixed. If the position of the reading device is fixed in this manner, a transport device becomes unnecessary, and the need to transport the reading device every time a mask mark is read is eliminated, thereby improving the throughput.
[0042]
The illumination device 109 is configured to be able to emit ultraviolet rays, X-rays, or electron beams to a pattern region on the mask 110. These ultraviolet rays, X-rays, or electron beams emitted from the illumination device 109 are irradiated onto the wafer with the area thereof being limited by the pattern area of the mask 110, so that the resist material applied on the wafer can be exposed. .
[0043]
FIG. 4 is a perspective view illustrating a relative position between the stencil mask 110 and the wafer W. FIG. 5 is a plan view of the stencil mask 110, and FIG. 6 is a plan view centering on a predetermined chip area of the wafer W.
[0044]
The stencil mask 110 used in the present embodiment is configured such that a pattern region 111 is formed in a membrane portion 113 surrounded by a peripheral portion 114. The pattern region 111 is formed in a rectangular shape in this embodiment. Then, mask marks (openings) 112A and 112B are formed at one end of the pattern region 111, and another mask mark 112C is formed at one end of the side opposite to the side. Further, two global alignment marks 115 are formed in the peripheral portion 114. The stencil mask 110 is provided with a notch, so that pre-alignment is possible.
[0045]
The stencil mask 110 is mainly made of, for example, silicon and includes a peripheral portion 114 having a diameter of 4 inches and a thickness of 0.5 mm and a membrane portion 113 having a thickness of about 10 μm. Further, a pattern area 111 and a mask mark 112 corresponding to the exposure pattern are formed.
[0046]
In addition, in the case of an exposure apparatus using, for example, ultraviolet rays, X-rays, etc., it is also possible to use a magnetic material as a stencil mask. For example, the material may be used, and the material is not limited to this embodiment. When a magnetic material is used, a magnet chuck may be used as the chuck.
[0047]
The silicon wafer W is provided with a plurality of chip areas CA. Wafer marks WMA and WMB are formed at one end of one side of the chip area, and another wafer mark WMC is formed at one end of the opposite side. . When exposure is performed, a resist is applied to the chip area CA. In FIGS. 4 and 6, only the chip area CA to be exposed is shown by hatching. However, the exposure apparatus changes the relative position between the wafer and the mask so that different chip areas become exposure targets. It has become. The wafer W is provided with a notch, and the notch enables pre-alignment.
(motion)
Next, an operation in the configuration of the manufacturing apparatus will be described with reference to a flowchart shown in FIG.
[0048]
First, the stencil mask 110 is transported (S1). First, the gate valve 17 is opened and the loader 20 moves to the position 20b. The loader 20 operates the arm 21 to selectively place the stencil mask 110 for exposure on the hand 22. Next, the gate valve 18 is opened, the loader 20 on which the stencil mask 110 is mounted moves to the position 20c, and the stencil mask 110 is pre-aligned. That is, the mask is aligned in a certain direction using the notch (see FIGS. 4 and 5) provided in the peripheral portion 114 of the stencil mask 110. Next, the gate valve 15 is opened, and the hand 22 of the loader 20 on which the pre-aligned stencil mask 110 is placed again moves to the position 20d and enters the process section 10a. Inside the processing unit 10 a, the loader 20 positions the stencil mask 110 below the electrostatic chuck 105 of the exposure apparatus 100. At this position, the electrostatic chuck 105 is operated to attract the stencil mask 110. Next, the stencil mask 110 is positioned by a mechanism (not shown) using the global alignment mark 115 (see FIGS. 4 and 5). By this operation, the stencil mask 110 is temporarily fixed at a position where it can be aligned with the wafer by the alignment apparatus according to the present invention later.
[0049]
Next, an initial value of a mark for performing the alignment method according to the present invention is obtained (S2). That is, the position of the mask mark 112 is stored after the mask 110 is temporarily fixed. As shown in FIGS. 4 and 5, mask marks 112A, 112B, and 112C, which are openings, are arranged on the mask 110. The position of each of these, specifically, the position of the edge of the opening is stored.
[0050]
In FIG. 7, an image taken by the camera 108 is shown in the lower part of the view of one mask mark 112 as viewed from directly above the mark, with the cross-sectional view taken from the side thereof being interrupted. As shown in the lower part of FIG. 7, an image including the edge of the mask mark 112 is captured by the camera 108 and stored in the storage unit 1011. In this way, the initial image of the mask mark 112 is stored as it is to store the position. Further, the edge portion may be extracted by a known image processing technique such as edge enhancement, and the edge edge may be stored as an image or as a coordinate value from a reference point.
[0051]
Next, the wafer W is transferred onto the stage 104 (S3). After the gate valve 16 is opened, the loader 20 operates to extend the arm 21 and move to the position 20a. Next, the loader 20 places one of the wafers stored in the work chamber 12 on the hand 22. Next, the gate valve 18 is opened, the loader 20 on which the wafer W is mounted moves to the position 20c, and the wafer W is pre-aligned. That is, the notch provided at one end of the wafer W aligns the wafer W in a certain direction. Next, the gate valve 15 is opened, the hand 22 of the loader 20 on which the pre-aligned wafer W is mounted again moves to the position 20d, and enters the processing unit 10a. Inside the process unit 10a, the loader 20 places the wafer W on the stage 104 of the exposure apparatus 100. The wafer W is positioned using a predetermined mark on the wafer W while the suction chuck (not shown) is operated and the wafer W is fixed. As a result, it becomes possible to perform the alignment with the stencil mask 110 later.
[0052]
Since the mask 110 and the wafer W are temporarily fixed in a pre-aligned state by the above steps, the operation shifts to the exposure operation (S4 to S4).
[0053]
First, the control device 101 causes the stage 104 to step forward to the position of the chip area CA to be exposed (S4). As a result, the chip regions of the mask 110 and the wafer W substantially overlap each other.
[0054]
In this state, each of the reading devices 106A, B, and C reads image data including the corresponding mask mark 112 and wafer mark WM for alignment (S5).
[0055]
FIG. 7 shows how the mask mark 112 on the mask 110 and the wafer mark WM on the wafer W overlap at this time. The detection light from the detection illumination device 107 irradiates each mask mark 112 and also reaches the wafer W through the opening thereof. Since the detection light is obliquely incident on the mask surface, a shadow SA is generated on the wafer W by the edge of the mask mark 112. The edge of the mask mark 112 becomes clearer due to the shadow SA. Further, since the mask mark 112 and the wafer mark WM are almost aligned by the positioning in the steps S1 and S3 as described above, the wafer mark WM can be viewed from the opening of the mask mark 112.
[0056]
The control device 101 calculates the relative position deviation between the mask 110 and the wafer W and the gap between the stencil mask 110 and the wafer W from the image data including the mask mark 112, the wafer mark WM, and the shadow SA obtained in step S5. Then, the stage 104 is driven in a direction to correct the same (S6). That is, the shift Δ between the central axis of the mask mark 112 (indicated by a dashed line) and the line direction of the wafer mark WM and the length D of the shadow SA are calculated and obtained. As shown in FIG. 6, three wafer marks WM are provided around the chip area CA, and at least one of them (WMC) has a line direction different from that of the other marks. If the positional deviation of the wafer mark WM from the mask mark 112 is measured, the X-axis direction, the Y-axis direction, and the rotation angle can be corrected so that all the wafer marks WM correctly match the central axis of each mask mark 112. Can be calculated. Known techniques can be applied to this calculation. Similarly, a deviation from the set value of the gap d between the stencil mask 110 and the wafer W at each location is also obtained based on the length D of the shadow SA. The controller 101 outputs a drive signal so as to compensate for the calculated deviation in the X-axis direction, the Y-axis direction, and the rotation angle θ and the deviation in the Z-axis direction. The relative position between the wafer and the wafer W is corrected.
[0057]
Next, the mask mark 110 and the wafer mark WM are re-read in order to check whether the deviation is within the allowable range due to the correction of the relative position between the mask 110 and the wafer W (S7). A check is made at 101 (S8), and if it is outside the allowable range, the process returns to S6.
[0058]
If it is determined that the position is within the allowable range in the step S8, the alignment processing for the chip area CA ends, and the process shifts to the exposure processing (S10). That is, exposure light is emitted from the exposure illumination device 109, and the exposure light whose area is limited through the pattern area 111 exposes the resist material or the like applied to the chip area CA on the wafer W.
[0059]
When the exposure processing is completed, the control device 101 determines whether or not the chip area CA to be exposed next exists on the wafer W (S11). If the chip area CA to be exposed next remains (S11: Y), the control device 101 outputs a drive signal for step-feeding, and moves the stage 104 until the next chip area CA substantially overlaps the pattern area 111 of the mask 110. It is transported (S12).
[0060]
Although not shown, when the exposure of all the chip areas of one wafer W is completed, the chuck of the wafer W is released, the exposed wafer W is returned to the work chamber 13 by the loader 20, and the cassette is loaded into the cassette. If an unexposed wafer W remains, the next wafer W is exposed. More specifically, step S13 described below (however, in this case, the image data is only the mask) and S14 are performed.
[0061]
Now, in the exposure apparatus, the temperature of the mask 110 increases due to radiant heat, radiant heat, and conductive heat of the exposure light. Here, since the membrane portion 113 is very thin, about 10 μm, the high temperature causes bending and deformation gradually.
[0062]
FIG. 8 is a cross-sectional view of the membrane portion 113 when the flexure / deformation occurs as described above. In FIG. 8, the original surface of the membrane portion 113 is indicated by a chain line, and the distance between the surface and the surface of the wafer W is d0. However, as a result of the mask being bent or deformed, the distance from the wafer W surface is increased (d1) or decreased (d2). If the flexure / deformation of the membrane portion 113 is increased, a pattern formed by exposure may be distorted, or a part of the membrane portion 113 may come into contact with the wafer W. Therefore, in the positioning device according to the present embodiment, this is prevented by the following method.
[0063]
That is, as shown in FIG. 9, when the mask 110 is bent or deformed by heat, the position (or shape) of the apparent contour of the mask pattern in an image obtained by imaging the mask mark on the mask fluctuates. . For example, when the membrane unit 113 is located at the reference initial position 113-0, the positions of the edges Xa, Xb, Ya, and Yb in the image obtained by imaging the mask mark 112 are Xa0, Xb0, Ya0, It is assumed that the shape is a rectangle surrounded by Yb0. If the membrane 113 is deformed by heat from the position 113-0 to the position 113-1, and the distance to the wafer W is increased, the edges Xa and Xb of the mask mark 112 obtained by imaging the same. , Ya, and Yb move to positions surrounded by Xa1, Xb1, Ya0, and Yb0. On the other hand, if the membrane portion 113 is deformed from the position of 113-0 to the position of 113-2 and approaches the wafer W, the edges Xa, Xb, Ya, and Yb of the mask mark 112 obtained by imaging it are It moves to a position surrounded by Xa2, Xb2, Ya0, and Yb0. Here, assuming that the fluctuation amounts of 113-1 and 113-2 are the limit values that can be correctly patterned, it is assumed that the mask marks edges Xa and Xb are included in the region TR surrounded by the oblique lines in FIG. 9 on the image. That is, the exposure can be performed correctly.
[0064]
Therefore, in the present embodiment, it is determined as follows whether or not the edge of the newly captured mask mark falls within the allowable range TR. First, when the stage 104 is driven such that the new chip area CA faces the pattern area 111 of the mask 110, the control device 101 first operates the reading devices 106A, B, and C to operate the image including the mask mark 112 and the wafer mark WM. The data is read (S13). This step is the same as the above-described step S5, and at the same time, data of positional deviation between the mask and the wafer required for the next exposure is obtained. The comparison determination unit 1013 compares the position of the edge Xa of the read mask mark 112 with the position Xa0 of the edge of the mask mark 112 stored in the storage unit 1011 in step S2, and indicates the position of the edge Xa as indicated by the oblique lines in FIG. It is determined whether it is within the allowable range TR (S14).
[0065]
Strictly, the shape of the mask mark 112 (opening) is also deformed by the deformation of the membrane portion 113 of the stencil mask 110, but the size of the mask mark 112 is less than 0.1 mm, and the size of the membrane of the stencil mask 110 is small. Since the deformation is negligible compared to the entire portion 113, the deformation can be ignored, and the change in the mask mark 112 in the camera field of view due to the deformation of the membrane portion 113 can be considered as a change in the horizontal position as shown in FIG. . Therefore, in the present embodiment, step S14 is performed by observing a change in the position of the edge Xa on the side where the shadow SA occurs.
[0066]
If the stencil mask 110 is shifted in the field of view due to a cause other than the deformation of the membrane 113 (for example, if the stencil mask 110 moves with respect to the electrostatic chuck 105), the process can be continued. It is. In the case of such a displacement due to the deformation other than the deformation of the membrane portion 113, it can be geometrically obtained from the mutual relationship between the displacement of the three edges 112A, 112B, and 112C with respect to the initial position. A step of making a determination by subtracting such an influence may be added.
[0067]
Various methods can be applied for comparing the positions of the edges. For example, in the present embodiment, since two-dimensional image data is captured, subtraction operation is performed between the image data before exposure stored in the storage unit 1011 and the newly captured image data. If the positions of the two have not changed, the portion corresponding to the edge of the mask mark in the output of the subtracted image data and the portion corresponding to the shadow SA remain at zero level. If the position of the edge of the newly acquired mask mark has changed from the position of the edge of the mask mark in the previously recorded image data, a luminance level at a pixel having a difference in pixel level appears. By extracting a pixel component in which a certain level appears, a deviation from the position of the original mask mark can be detected.
[0068]
When the position of the edge of the mask mark falls within the allowable range TR (S14: Y), the degree of the bending and deformation of the mask 110 is allowable, and the process shifts to the normal alignment processing and exposure processing (S6 to S13). . On the other hand, when the position of the edge of the mask mark is out of the allowable range (S14: N), it can be determined that the mask 110 has been deformed beyond the limit due to heat, and the subsequent exposure processing is interrupted.
[0069]
Here, when the control device 101 determines that the deformation of the mask exceeds the limit, it outputs a warning signal. The warning signal is transmitted to the user as lighting or blinking of a predetermined lamp, generation of a warning sound, or display of a warning message on a display. The user may operate the manufacturing apparatus 1 to change the mask 110 to a new mask when these warnings are issued.
[0070]
When the deformation of the mask exceeds the allowable range TR, the control device 101 stores the position of the chip area CA, and starts the alignment and exposure using the newly loaded mask from the chip area CA at the position. Is preferred.
[0071]
When a warning signal is output, the mask may be automatically discarded, a mask having the same pattern may be taken out of the mask chamber 13 and set in the exposure apparatus 100 again.
[0072]
Further, in the present embodiment, the oblique detection method is employed, and the mask mark 112 can be read even during the exposure, so that the edge position Xa is taken in during the exposure and the comparison with the initial edge position Xa0 is performed for a predetermined time. It may be repeated for each interval to determine whether the edge position is within the allowable range during step S10. Alternatively, it may be determined whether the edge position is within the allowable range before the step S11 after the exposure is completed.
[0073]
As described above, according to the first embodiment, the control device reads the mask mark every time the exposure processing is performed, detects the change in the edge position with respect to the initial mask mark, and determines the degree of deformation of the mask. It is possible to accurately determine that the mask is bent or deformed by the heat in the processing. Therefore, exposure of the mask in a state where the deformation of the mask exceeds the allowable range is prevented, and the yield in semiconductor manufacturing can be improved.
<Second embodiment>
In the second embodiment of the present invention, the positioning apparatus and method according to the present invention are applied to an ion implantation apparatus.
[0074]
The ion implantation apparatus 200 according to the second embodiment is provided in the process chamber 10 in the manufacturing apparatus 1 like the exposure apparatus 100 according to the first embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.
[0075]
The manufacturing apparatus 1 is the same as in the first embodiment. However, the mask 110 stored in the mask chamber 13 is not an exposure mask for forming a pattern, but a mask for limiting a position where ions are implanted during ion implantation. For example, in a thin film transistor, when introducing impurities in a source region and a drain region in a semiconductor region, a pattern that masks a region other than these regions is formed.
[0076]
FIG. 11 shows a schematic diagram of a manufacturing apparatus according to the second embodiment. As shown in FIG. 11, the ion implantation apparatus 200 includes a control device 101, a driving circuit 102, a driving mechanism 103, a stage 104, an electrostatic chuck 105, a reading device 106A, B, C, an ion source 120, a mass separator. 121 and an acceleration coil 122. The configuration other than the ion source 120, the mass separator 121, and the acceleration coil 122 is the same as that of the first embodiment.
[0077]
The ion generation source 120 is a part for generating ions used for implantation and extracting the ions as a beam. ⁺ , P ⁺ , AS ⁺ It generates ions and the like. The mass separator 121 separates only desired ions from a plurality of types of ions based on the mass of atoms and selectively emits them. The acceleration coil 122 accelerates the selected ions to a predetermined speed.
[0078]
The stencil mask 110 and the wafer W are the same as in the first embodiment except that the mask 110 has a mask pattern for ion implantation.
[0079]
Next, the operation in the second embodiment will be described with reference to the flowchart shown in FIG. Basically, it is the same as the first embodiment. However, this embodiment is different from the first embodiment in that an ion implantation process is performed instead of the exposure process.
[0080]
That is, the stencil mask 110 is conveyed (S21), the initial mask mark position is stored (S22), the wafer is conveyed (S23), the first chip is fed (S24), three wafer marks are read (S25), and the position is shifted. Is the same as that of the first embodiment up to the correction (S26).
[0081]
When the alignment between the chip area CA and the mask 210 is completed, an ion implantation process is performed (S30). That is, the ion generator 120 is driven to eject ions, the ions are selected by the mass separator 121, the ions are accelerated by the acceleration coil 122, and the ions are ejected toward the mask 110. The area of the ions is limited by the mask pattern, and ions are implanted only into a desired area (for example, a source area or a drain area) on the chip area CA.
[0082]
When the ion implantation is completed for one chip area CA, the subsequent steps, that is, determination of the presence / absence of the next chip (S31), step feed (S32), new reading of the edge position of the mask mark (S33), and the edge within the allowable range The determination as to whether or not is included (S34) is performed according to the first embodiment.
[0083]
That is, when the position of the edge of the mask mark falls within the allowable range TR (S34: Y), the degree of the bending and deformation of the mask 110 is allowable, so that the process shifts to the normal alignment processing and the ion implantation processing (S25). To S33). On the other hand, when the position of the edge of the mask mark is out of the allowable range TR (S34: N), it can be determined that the mask 210 is deformed beyond the limit due to heat, and the subsequent ion implantation processing is interrupted. .
[0084]
As in the first embodiment, when the control device 101 determines that the deformation of the mask exceeds the limit, the control device 101 outputs a warning signal or replaces the mask.
[0085]
As described above, according to the second embodiment, the control device reads the mask mark each time the ion implantation process is performed, detects the change in the edge position with respect to the initial mask mark, and determines the degree of deformation of the mask. It can be accurately determined that the mask is bent or deformed by the heat in the ion implantation process. Therefore, ion implantation is performed in a state where the deformation of the mask exceeds the allowable range, and the yield in semiconductor manufacturing can be improved.
[0086]
In particular, in the ion implantation process, the temperature of the mask surface is significantly increased due to ions colliding with the mask surface. By applying the alignment apparatus and method according to the present invention to such an ion implantation apparatus, it is possible to accurately detect the deformation of the mask.
[0087]
【The invention's effect】
As described above, according to the present invention, the position of a mark or an opening at a predetermined timing is stored, and this is compared with the position of a newly read mark or an opening to determine whether or not the position is within an allowable range. Therefore, it is possible to reliably detect the deflection of the alignment target such as a mask.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a manufacturing apparatus according to a first embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of an exposure apparatus according to the first embodiment of the present invention.
FIG. 3 is a functional block diagram of a control device according to the first embodiment.
FIG. 4 is a perspective view showing a relationship between a stencil mask and a wafer according to the first embodiment of the present invention.
FIG. 5 is a plan view of the stencil mask according to the first embodiment of the present invention.
FIG. 6 is a partial plan view of the silicon wafer according to the first embodiment of the present invention.
FIG. 7 is an explanatory diagram illustrating a basic operation of the positioning device according to the present invention.
FIG. 8 is a diagram for explaining bending and deformation of a mask due to heat.
FIG. 9 is a diagram illustrating a change in the shape of a mask mark when the mask is deformed by heat.
FIG. 10 is a flowchart illustrating an operation of the exposure apparatus according to the first embodiment of the present invention.
FIG. 11 is a schematic configuration diagram of an ion implantation apparatus according to a second embodiment of the present invention.
FIG. 12 is a flowchart illustrating an operation of the ion implantation apparatus according to the second embodiment of the present invention.
[Explanation of symbols]
CA: Chip area
TR: allowable range
WMA, WMB, WMC: Wafer mark
101 ... Control device
102 ... Drive circuit
103 ... Drive mechanism
104 ... stage
105 ... Electrostatic chuck
106A, B, C ... reading device
107 ... Detection illumination device
108 ... Camera
110, 210 ... Stencil mask
112A, 112B, 112C ... Mask mark

Claims (10)

A reading device that reads a mark provided on the alignment target;
A storage unit that stores the position of the mark read by the reading device at a predetermined timing;
The position of the mark read by the reading device is compared with the position of the mark stored in the storage unit, and the position of the mark read by the reading device is out of a predetermined allowable range. And a comparison / determination unit that determines whether or not the position is determined. The alignment device according to claim 1, wherein the storage unit stores the position of the mark at an initial timing of an operation. The positioning device according to claim 1, wherein the determination unit performs a predetermined emergency process when determining that the value deviates from the allowable range. An alignment apparatus for performing alignment between a wafer and a mask for performing a predetermined process on the wafer,
A moving device that changes a relative position between the wafer and the mask,
A reading device that reads an alignment mark provided on the wafer through an alignment opening provided on the mask,
A control device that changes a relative position between the wafer and the mask based on a relative position between the alignment opening and the alignment mark read by the reading device,
The control device stores the position of the edge of the alignment opening at a predetermined timing, compares the position of the edge newly read from the reading device with the stored position of the edge, and newly reads the edge. A positioning device that determines whether or not the position of the edge is out of a predetermined allowable range. The control device includes:
A storage unit that stores the position of the edge read by the reading device at a predetermined timing,
The position of the edge read by the reading device is compared with the position of the edge stored in the storage unit, and it is determined whether the position of the read edge deviates from a predetermined allowable range. The positioning apparatus according to claim 4, further comprising: The alignment device according to claim 4, wherein the control device stores the position of the edge at an initial timing of processing on the wafer. The positioning device according to claim 4, wherein the control device performs a predetermined emergency process when it is determined that the control device deviates from the allowable range. The positioning apparatus according to claim 1, wherein the positioning apparatus is used for an exposure apparatus or an ion implantation apparatus. Reading a mark provided on the alignment target at a predetermined timing;
Storing the read position of the mark;
Comparing the position of the newly read mark with the stored position of the mark;
Determining whether the position of the newly read mark deviates from a predetermined allowable range. An alignment method for performing alignment between a wafer and a mask for performing a predetermined process on the wafer,
At a predetermined timing, reading an alignment mark provided on the wafer through an alignment opening provided on the mask; and storing an edge position of the alignment opening at the predetermined timing. ,
Furthermore, when the processing is performed, a step of reading the position of the edge newly, and a step of comparing the position of the newly read edge with the stored position of the edge,
Determining whether the position of the newly read edge deviates from a predetermined allowable range;
When the position of the newly read edge is within the allowable range, the relative position between the wafer and the mask is determined based on the relative position between the newly read alignment opening and the alignment mark. Changing the position.

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