JPH05166697A - Method and apparatus for alignment - Google Patents

Abstract

PURPOSE:To align a substrate having no reference for alignment such as orientation flats and notches on the basis of a specified reference position. CONSTITUTION:In order to form pattern regions PA on a substrate 1 in a specified array, marks 24 and 25 for reference are provided in a position asymmetric with respect to a specific axis of coordinates of the pattern region array. Or a pattern region for reference is formed in such a position. The position of these reference marks or the reference pattern region is detected, and the substrate is shifted so that the relative deviation from the position with which the substrate is to be aligned will be a specified value. This makes it unnecessary to provide a substrate with notches such as an orientation flat, minimizing the distortion which may occur in a substrate during processing operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aligner for an exposure apparatus for manufacturing semiconductor devices, and more particularly to aligning a wafer not provided with a positioning reference such as an orientation flat or notch with a predetermined reference position. It is related to the device.

[0002]

2. Description of the Related Art A conventional device of this type is shown in FIG.
A substrate (wafer) provided with a notch portion such as an orientation flat or a notch as shown in (b) is aligned, and its configuration is generally as shown in FIG. 8 (c). That is, the wafer 1 is placed on the wafer holder 6 rotatably supported by the rotation shaft 7 of the rotating mechanism such as the motor 8 so that the center of the wafer 1 and the rotation center of the motor 8 are substantially aligned with each other. A light flux is emitted from a plurality of light sources 2 and 3 (the number of light sources may be one) to the peripheral portion. These light fluxes are normally shielded by the peripheral portion of the wafer 1, but when the cutout portion of the wafer 1 is located at the light flux position, the light flux is not shielded by the wafer,
The light is received by light receivers 4 and 5 arranged at positions facing the light sources 2 and 3 with the wafer 1 interposed therebetween. The light amount signals detected by the light receivers 4 and 5 are input to the position detection unit 31, and information regarding the position of the cutout portion of the wafer is output to the control unit 33 based on each light amount signal. The control unit 33 outputs a signal to the rotation control unit 32 so as to rotate the wafer by a predetermined amount based on the position information of the cutout portion.

In the apparatus having the above-mentioned structure, the wafer is rotated while the peripheral portion of the wafer 1 is being irradiated with the light flux, and the change in the light quantity of the light flux detected by the photodetectors 4 and 5 is examined to determine the position of the orientation flat or notch. Was detected and the wafer was pre-aligned. The rotation mechanism such as the motor 8 or the wafer holder 6 is provided with a position measuring device such as a rotary encoder so that the rotation amount (rotation angle) of the wafer can be measured.

FIGS. 9A and 9B are diagrams showing the relationship between the rotation angle θ of the wafer having an orientation flat and the output of the light amount signal detected by the photodetectors 4 and 5, respectively. For example, in FIG. 8, the rotation angle θ when the wafer 1 is placed and fixed on the wafer holder 6 is set to zero, and the rotation control unit 32 rotates the wafer 1 in the direction of the arrow while monitoring the rotation angle θ. At that time, the light flux is emitted from the light sources 2 and 3 to the peripheral portion of the wafer 1, and the light receiver 4 first receives the light flux with the movement of the orientation flat. While the orientation flat passes through the portion of the light beam (for the photodetector 4, the rotation angle θ ₁
From θ ₂ to θ _2, the rotation angle θ ₃ to θ ₄ for the photodetector 5
(Between), the light amount signals are obtained from the light receivers 4 to 5.
After the output is started to be detected by the light receiver 4, the rotation angle in the middle (the middle of the rotation angle θ ₁ and the rotation angle θ ₄ ) is calculated while the output is not detected by the light receiver 5, and this position is set to the orientation flat. The center position of. While monitoring with a position measuring device such as a rotary encoder, based on the obtained rotation angle and considering the relationship between the positions of the light sources 2 and 3 and the light receivers 4 and 5 and the position where the orientation flat should be aligned. Rotate the wafer to align.

FIG. 9C is a diagram showing the relationship between the rotation angle θ of the wafer having a notch and the output of the light amount signal detected by the light receiver 4 or 5. In this case, the peak position of the signal becomes the position of the notch, and the alignment of this notch is the same as in the case of a wafer having an orientation flat.

[0006]

Generally, in order to form a circuit element on a wafer, it is necessary to go through several steps. When a wafer having a notch such as an orientation flat or a notch is used, There is a problem in that the wafer is distorted (non-linear distortion is generated) due to the notch as the process progresses. Further, in the apparatus (stepper) for exposing the wafer,
As a method of aligning wafers (each exposure area) when performing overlay exposure, the positions of several arbitrary exposure areas are measured, and the positions of other exposure areas are analogized based on that position and based on the results. In some cases, a method of performing superposition exposure by using the above method is used. In this method, since overlay exposure is performed based on the assumption that the arrangement of each exposure area on the wafer is linear, non-linear distortion of the wafer caused by the notch directly leads to deterioration of alignment accuracy. .. To avoid errors due to this non-linear distortion,
It is conceivable to use a circular wafer with no notches.

However, the conventional technique as described above can be applied only to a wafer provided with a notch such as an orientation flat or a notch. That is, in the case of a wafer having no notch in the peripheral portion, the light receiving portion cannot receive the light flux, and thus the alignment in the conventional device is impossible. The present invention has been made in view of the above problems, and a device for performing pre-alignment with high accuracy even on a wafer without an orientation flat or notch (circular wafer),
And to provide a method.

[0008]

In order to solve the above problems, according to the present invention, a substrate (1) on which a pattern area (PA) is formed in a predetermined characteristic array is provided with a predetermined reference point (O '). In the method of aligning with respect to, in forming a pattern area (PA) of a characteristic array on the substrate (1), array coordinates of the pattern area (PA) are set, and a specific axis of the coordinates is set. Forming at least one pair of fiducial marks (24, 25) at asymmetric and asymmetrical design locations;
The reference mark (24, 2) is formed at a position unique to the reference point (O ′).
5) Detecting the existence position of the mark (24, 25) by detecting the position; a direction in which the relative deviation between the detected existence position and the reference point (O ′) becomes a predetermined value. And the step of moving the substrate (1).

Further, in the method of aligning the substrate (1) on which the pattern areas (PA) are formed with a predetermined characteristic array with respect to a predetermined reference point (O '), When forming the pattern area (PA), at least one area (27) of the pattern area (PA)
Substrate (1) under different design arrangement conditions from the characteristic arrangement
A step of forming above; a step of detecting the existing position of the area (27) by detecting an area (27) formed under different arrangement conditions at a position unique to the reference point (O ′); The substrate (1) is oriented in such a direction that the relative deviation between the detected existing position and the reference point (O ′) becomes a predetermined value.
And the step of moving.

Further, in the apparatus for aligning the substrate (1) on which the pattern area (PA) is formed with a predetermined characteristic array with respect to a predetermined reference point (O '), the characteristic array When forming the pattern area (PA), the array coordinates of the pattern area (PA) are set, and at least one pair of reference marks (24, 25) are provided at design positions asymmetric with respect to a specific axis of the coordinates. A stage (6) for holding the formed substrate (1); a detection means (11, 35) which is arranged in a unique positional relationship with the reference point (O ') and detects the existence position of the reference mark (24, 25). ) And ;; drive means (8) for moving the stage (6) in a direction such that the relative deviation between the detected existing position and the reference point (O ′) becomes a predetermined value. ..

Further, in an apparatus for aligning a substrate (1) on which a pattern area (PA) is formed with a predetermined characteristic array with respect to a predetermined reference point (O '), the characteristic array When forming the pattern area (PA), at least one area (27) of the pattern area (PA)
A stage (6) for holding a substrate (1) formed under a design arrangement condition different from a characteristic arrangement; a reference point (O ')
By detecting the regions (27) which are arranged in a unique positional relationship with and are formed under different arrangement conditions, the regions (2
Detection means (11, 35) for detecting the existing position of 7);
It is assumed that a driving means (8) for moving the stage (6) in a direction such that the relative deviation between the detected existing position and the reference point (O ′) becomes a predetermined value is provided.

[0012]

According to the present invention, when the pattern area is previously formed on the substrate to be aligned with respect to the reference point, a mark or pattern area serving as a reference for alignment is provided, and the position where the mark or pattern area exists. Since the relative deviation between the reference point and the above-mentioned reference point is obtained and the board is moved in the direction so that this relative deviation becomes a predetermined value, there is no need to provide a special reference for alignment such as orientation flat on the board. In this way, the substrates can be aligned.

[0013]

1 is a diagram showing a schematic configuration of an alignment apparatus according to an embodiment of the present invention. The wafer 1 is transferred from a storage case (not shown) onto a wafer holder 6 for pre-alignment, and a pre-alignment pin 2 as shown in FIG.
By driving 1, 22, 23 in the direction of the arrow,
The center O of the wafer 1 and the center (rotation axis) O ′ of the holder 6 are aligned and held so as to substantially coincide with each other. At that time, a minute offset (positional deviation in the two-dimensional direction) and a rotational deviation with respect to a predetermined position to be aligned remain on the wafer 1. The holder 6 is axially supported by the motor 8 and can be rotated by the rotation control unit 34.
Further, the CCD 11 is arranged at a position conjugate with the surface of the wafer 1 via the lenses 9 and 10, and the output signal from the CCD 11 is two-dimensionally analyzed by the position detection unit 35. If the CCD is for observing the entire surface of the wafer at a time, the IT connected to the CCD 11
It is observed as shown in FIG. On the wafer 1 shown in FIG. 3, the circuit pattern areas PA have already been transferred in a predetermined array, and when the array coordinates XY of this pattern area PA are set with the center O as the origin, with respect to the X axis. Positioning marks 24 and 25 are disposed at asymmetrical positions (however, the positions are line-symmetrical with respect to the Y axis). The marks 24 and 25 are detected by the CCD 11, and the position detector 35 analyzes the positions of the marks 24 and 25 with respect to the center O ′. As for the image information on the wafer 1 detected by the CCD, the two-dimensional position of each pixel of the CCD and the information on the presence / absence of an image at that position are stored in the memory in the position detecting unit 35 in association with each other. There is.
Therefore, it is possible to select and process arbitrary data from the detected image information. Based on the position of this mark, the position where the outer peripheral portion of the array of the pattern area PA is present is further obtained, and the accurate rotational deviation (rotation angle) and offset are obtained. The rotation deviation of the wafer 1 is corrected by the rotation control unit 34, and the wafer 1 is transferred onto the wafer holder 15 by the wafer loader 19. Wafer loader 19 is drive unit 2
0 and the wafer loader control unit 36 accurately conveys the wafer 1 onto the wafer holder 15. Regarding the offset, the offset amount is determined by the main controller 37 from the position detector 35.
The precise alignment at the time of exposure is performed by correcting the offset amount on the wafer holder 15.

Next, a method of detecting the marks 24 and 25 will be described with reference to FIG. This is to check the positions of the marks 24 and 25 with respect to the holder center O ′ based on the designed positions of the marks 24 and 25. Incidentally, if the positions of the marks 24 and 25 with respect to the wafer center O and the position with respect to the holder center O ′ match, the wafer alignment is completed. Considering the coordinate axes X and Y with the center O as the origin on the wafer 1, the marks 24,
The 25 design positions are represented by (-x, y) and (x, y), respectively. As described above, the marks 24 and 25 are located in line symmetry with respect to the Y axis and asymmetric with respect to the X axis. In this case, the position detector 35 considers the circle 26 at a distance of radius | y | from the holder center O ′,
A tangent line A _n tangent to this circle 26 is set. Each tangent line A
The image information in the regions B _n and B _n ′ in the vicinity of the positions on _n that are separated from each contact by ± x is analyzed. That is, the data for m pixels of the CCD are added in the longitudinal direction of the marks 24 and 25 to make one point of data, and the pixel l in the Y direction is added.
The data is processed for the range of the number to obtain the coordinate position of the mark. The image information detected by the CCD is displayed in the area B ₁ ,
FIG. 5 shows an example of signals obtained when processing is performed on B _i , B _j and B ₁ ′, B _i ′, B _j ′. Area B ₁ , B _j
, B ₁ ′ and B _j ′ do not have the marks 24 and 25 in the detection region, the signal waveform is almost flat, but in the regions B _i and B _i ′, the marks 24 and 25 exist in the detection region. Therefore, the bottom signal is detected.

The center O'of the mark obtained by the above method
And the mark position on the design (mark is center O '
Existing position with respect to the wafer)
The offset in the direction can be obtained. The subscript n may be set to n> 2πy / l, and the number of pixels m to which data is added may be set to be smaller than the number of pixels in the longitudinal direction of the marks 24 and 25. In addition, mark 2
Since the arrangements of 4 and 25 are associated with the lattice directions of the crystals in the wafer, the marks are formed in advance before forming the pattern area on the wafer.

In the above-mentioned embodiment, the case where the alignment is performed by using the alignment marks other than the pattern regions arranged on the wafer in consideration of the material orientation of the wafer (crystal lattice direction) is described. It was However, if there is no such restriction, the above marks 24 and 25 are not necessary if the array itself of the pattern area is asymmetric with respect to one specific coordinate axis of the array coordinates. For example, as shown in FIG. 6A, the pattern areas 27 are provided so that the arrangement of the pattern areas is asymmetric with respect to the X axis. In this case, it is not necessary to set the circle 26 as described above, and the circle 26 shown in FIG.
A straight line passing through the center O'of the holder as shown in (b) is set. Then, in the vicinity of both ends of this straight line, the pattern area 2
For the area near the position corresponding to 7 (especially the outer peripheral portion),
The width of the detection range 1 with respect to the area B _n is widened, or
Alternatively, as shown in FIG. 6C, two areas B _i1 and
B _i2, and B _i1 ', B _i2' by dividing the may detect the position of the outer periphery of the pattern region 27 which is arranged asymmetrically. Then, when the area 27 is detected, for example, the waveforms of the signals obtained for the areas B _i1 , B _i2 and B _i1 ′, B _i2 ′ are as shown in FIG. 7, and the position where the pattern area 27 exists can be obtained. it can. The position of the pattern area 27 and the position of the designed pattern area 27 (area 27
From the center O ′), it is possible to determine the wafer rotational displacement amount and offset. Further, by averaging the positions of the straight line portions on the outer circumference of the pattern, it is possible to know the outer circumference position with high accuracy. Further, in the above case, a plurality of bottom signals are output from the pattern portion as shown in FIG. 7, but only flat signals are output in the portion where the pattern does not exist, so the outer peripheral portion is recognized as the position of the bottom signal at both ends of the waveform. can do.

Further, in order to detect the image on the wafer, C
Although the entire area is observed using a CD, a partial area on the wafer is observed using a line sensor or the like, and the observation area is sequentially moved by rotating the wafer by a predetermined angle. Therefore, it may be configured to observe almost the entire region.

[0018]

As described above, according to the present invention, the substrate can be easily aligned with respect to a predetermined reference without specially providing a reference for alignment such as an orientation flat or a notch on the outer periphery of the substrate. It becomes possible. In addition, since there are no notches in the substrate, it is possible to minimize distortion of the substrate due to heat treatment or the like. Further, a substrate having no orientation flat or notch is effective because there is little uneven coating of the photosensitive agent.

In addition, if the images formed on the substrate are asymmetrically arranged and used, it is not necessary to provide special alignment marks, and the space for arranging the circuit pattern area and the throughput can be improved. In terms of efficiency.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of an alignment apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a state of centering a wafer using three pins.

FIG. 3 is a diagram showing an array of circuit patterns on a wafer to be aligned.

FIG. 4 is a diagram showing a method of detecting image information on a wafer to be aligned.

5 is a diagram showing a signal of image information detected by the method shown in FIG.

6A is a diagram showing another example of an arrangement of circuit patterns on a wafer to be aligned, and FIGS. 6B and 6C are other diagrams for detecting image information on the wafer to be aligned. Diagram showing the method

7 is a diagram showing a signal of image information detected by the method shown in FIG.

8A and 8B are views showing the shape of a substrate adapted to a conventional alignment device, and FIG. 8C is a diagram showing a schematic configuration of a conventional alignment device.

FIG. 9 is a diagram showing a relationship between a rotation angle of a wafer and an output of a detected signal when a conventional alignment device is used.

[Explanation of symbols]

 1 wafer 6 wafer holder 8 motor 11 CCD 19 wafer loader 24,25 wafer mark PA, 27 pattern area 34 rotation controller 35 position detector 37 main controller

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location H01L 21/68 G 8418-4M

Claims (8)

[Claims] 1. A method of aligning a substrate on which pattern regions are formed in a predetermined characteristic array with respect to a predetermined reference point, wherein the pattern regions in the characteristic array are formed on the substrate. At this time, the array coordinates of the pattern area are set, and at least 1 is set at a design position asymmetric with respect to the specific axis of the coordinates.
Forming a pair of reference marks; detecting the reference position at the reference point by detecting the reference mark at a position unique to the reference point; detecting the presence position and the reference point And moving the substrate in a direction such that the relative deviation of the substrate becomes a predetermined value. 2. The alignment method according to claim 1, wherein the reference mark is different from the pattern area. 3. A method of aligning a substrate, on which pattern areas are formed in a predetermined characteristic array, with respect to a predetermined reference point, wherein when forming the pattern areas in the characteristic array, Forming at least one region of the pattern region on the substrate under a design arrangement condition different from the characteristic arrangement; a region formed under the different arrangement condition at a position unique to the reference point Detecting the existence position of the area by detecting the value; and moving the substrate in a direction such that the relative deviation between the detected existence position and the reference point becomes a predetermined value. An alignment method comprising: and. 4. The alignment method according to claim 3, wherein the position to be detected in the areas formed under the different arrangement conditions is a position where the outer peripheral portion of the area exists. 5. An apparatus for aligning a substrate, on which pattern areas are formed in a predetermined characteristic array, with respect to a predetermined reference point, when the pattern areas in the characteristic array are formed. A stage for setting array coordinates of regions and holding a substrate on which at least one pair of reference marks is formed at an asymmetrical design position with respect to a specific axis of the coordinates; and a stage having a unique positional relationship with the reference points. A detection unit that is disposed and that detects the existing position of the reference mark; a driving unit that moves the stage in a direction such that the relative deviation between the detected existing position and the reference point becomes a predetermined value. An alignment device characterized by comprising. 6. An apparatus for aligning a substrate, on which pattern areas are formed in a predetermined characteristic array, with respect to a predetermined reference point, when the pattern areas are formed in the characteristic array. A stage for holding a substrate in which at least one of the regions is formed under a design arrangement condition different from the characteristic arrangement; and a stage arranged in a unique positional relationship with the reference point and formed under the different arrangement condition. Detecting means for detecting the existing position of the area by detecting the present area; and moving the stage in a direction such that the relative deviation between the detected existing position and the reference point becomes a predetermined value. A positioning device comprising: a driving unit. 7. The detection means detects the image information of at least a part of the substrate and analyzes the information to obtain the existence position of the pattern region or the reference mark. The alignment device according to items 5 and 6. 8. The alignment apparatus according to claim 5, wherein the calculation means determines at least one of a rotation amount of the substrate and a shift amount of the substrate as the relative deviation.