JP2003295460A - Projection exposure method and projection exposure apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately perform projection exposure on an inclined surface having a large step amount. A plurality of projection optical systems arranged at equal pitches are provided in a projection optical system unit, and the projection optical system unit forms equal-size erect images at different positions of a pattern of a mask. Project at the same time. While keeping the relative position of the wafer 10 and the mask 20 constant, the wafer 1
When the mask 0 and the mask 20 are moved, the projection exposure area of each projection optical system relatively moves on the wafer 10 to perform scanning. Each projection optical system includes a concave mirror and a combination lens. The combination lens consists of a concave lens made of a single optical glass and a concave lens made of a different optical glass.
Achromatic convex lens composed of various types of lenses.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure method and a projection exposure apparatus for projecting and exposing a wiring pattern of a semiconductor device, and more particularly to a projection exposure method and a projection exposure method suitable for projection exposure on an inclined surface having a large step amount. The present invention relates to an exposure apparatus.

[0002]

2. Description of the Related Art In recent years, the mounting of semiconductor devices on a printed wiring board has been rapidly increased in density. Higher density is supported by a technique of directly providing wiring for connecting to a printed wiring board on a chip surface of a semiconductor device, and such a technique is called a wafer process package (WPP). There is.

FIG. 17 is a diagram showing the basic structure of a wafer process package. FIG. 18 is a flow chart showing the outline of the manufacturing process of the wafer process package. The process of forming the semiconductor circuit 2 and the bonding pad 3 on the surface of the silicon substrate 1 is the same as that of a conventional semiconductor package using a lead frame and a wire bonder. The periphery of the bonding pad 3 is
It is covered with an inorganic insulating film 4 such as SiO ₂ . In FIG. 18, these steps are omitted.

In the wafer process package, an organic insulating film 5 such as photosensitive polyimide (PIQ) is formed on the insulating film 4 (step 101). Then, after forming a hole in the portion of the bonding pad 3 in the insulating film 5 (steps 102 to 103), a stress relaxation layer 6 is further formed on the insulating film 5 (steps 104 to 1).
05). Then, Cu / Ni wiring 7 is formed on the surface of the stress relaxation layer 6 from the bonding pad 3 (step 10).
6-112). Further, the wiring protective film 8 of polyimide or the like is formed except for the portion where the solder balls 9 are installed (steps 113 to 114), and the solder balls are mounted (steps 115 to 117). Finally, after reflowing (step 118), dicing is completed (step 11).
9).

The thickness of the stress relaxation layer 6 is generally 75 μm or more, and the thicker the stress relaxation effect when the semiconductor device is mounted on the printed wiring board, the higher the effect. In addition, Cu / Ni from the bonding pad 3 to the surface of the stress relaxation layer 6
Resist coating process for forming the wiring 7 (step 1
The resist applied in 07) has a thickness of about 10-18 μm.
m, and the film thickness variation is about 8 μm.

[0006]

In the manufacturing process of the wafer process package shown in FIG. 18, a wiring pattern exposing process for forming the Cu / Ni wiring 7 from the bonding pad 3 to the surface of the stress relaxation layer 6 ( In step 108), a precise pattern must be transferred to the resist having a thickness of about 10 to 18 μm applied to the surface of the stress relaxation layer 6 having a slope of 75 μm or more.
It is an object of the present invention to accurately perform projection exposure on such an inclined surface having a large step amount.

Further, in the hole pattern exposure step (step 103) for forming a hole in the insulating film 5 at the portion of the bonding pad 3, the target pattern formed in the previous step is used to align the wafer and the mask. Need to be done accurately.

The exposure apparatus used in the previous step is a step-and-repeat type reduction projection exposure apparatus. This reduction projection exposure apparatus uses a mask pattern called a reticle of 4 times or 5 times, and is equipped with a high precision XY stage of laser length measurement feedback. The positions of the reticle and the wafer are independently detected and aligned. Therefore, the reticle alignment pattern is not transferred to the target pattern on the wafer.

FIG. 19A is a diagram showing the arrangement of target patterns, and FIG. 19B is a diagram showing a typical target pattern. A scribe line region 13 for dicing is provided between the semiconductor chips 11 on the wafer, and the target pattern 12 is provided in the scribe line region 13. The size of the target pattern 12 that can be inserted into the scribe line region 13 is limited, and the width W of the target pattern is generally 70 μm.
m or less. Furthermore, since a number of test circuits for evaluating electrical characteristics are installed in the scribe line area 13,
There is little free space where the target pattern 12 can be installed.

An object of the present invention is to accurately align the exposure surface and the mask by using the target pattern provided in the scribe line area.

Further, in the hole pattern exposure step (step 103), there is a constraint that the peripheral portion of the wafer should not be exposed. On the other hand, in order to increase the number of semiconductor chips to be acquired, it is necessary to expose the wafer to the edge. FIG. 20 is a diagram showing an unexposed area. FIG. 20 shows an example in which the exposure shot size is twice the semiconductor chip size (area four times), and the square portion surrounded by the thick line in the figure shows the exposure shot range. As shown in FIG. 20, when the range of the exposure shot is set to the edge of the wafer 1, the non-exposure region is included in the range of the exposure shot in the peripheral portion of the wafer.

In order to expose a wide range without exposing the non-exposure area, a method of matching the exposure shot size with the semiconductor chip size or a method of exposing the front surface of the wafer at one time can be considered. However, the method of matching the exposure shot size and the semiconductor chip size is
The number of exposure shots increases significantly and throughput decreases. On the other hand, the method of collectively exposing the front surface of the wafer is
Although the put is improved, a huge projection optical system larger than the wafer size is required.

An object of the present invention is to expose a wide range without exposing an unexposed area.

[0014]

The main features of the present invention for solving the above problems are as follows. (1) Using a projection optical system including a concave mirror and a combination lens including a concave lens made of a single optical glass and an achromatic lens made of three types of different optical glasses, a mask pattern of equal magnification is used. The erect image is projected onto the exposure surface, the exposure surface and the mask are moved relative to the projection optical system, and the equi-magnification erect image of the mask pattern is scanned on the exposure surface.

By using a projection optical system having a concave mirror and a combination lens, the number of necessary lenses is reduced, and light absorption and reflection by the lenses are reduced. Also,
The chromatic aberration is corrected by the achromatic convex lens, and projection exposure using more wavelengths becomes possible. Therefore, high-contrast projection exposure can be performed with high illuminance.
Further, the configuration of the concave mirror and the combination lens enables projection exposure with a deep depth of focus. Therefore, it is possible to accurately perform projection exposure on an inclined surface having a large step amount.

Further, an equal-magnification erect image of the mask pattern is projected onto the exposure surface, and the exposure surface, the mask, and the projection optical system are moved relative to each other to form an equal-magnification erect image of the mask pattern on the exposure surface. By scanning, a wide range can be exposed without exposing the unexposed area.

(2) An equal-magnification erect image at different positions of the mask pattern is simultaneously projected by using a plurality of projection optical systems.
By projecting equal-magnification erect images at different positions of the mask pattern at the same time, the required number of scans can be reduced and throughput can be improved.

(3) A transparent plate whose both surfaces are parallel is inserted into the optical path, and the angle of the inserted transparent plate is adjusted to adjust the position of the equi-magnification erect image of the mask pattern. By using the transparent plate inserted in the optical path, it is possible to accurately adjust the position of the erect image of the same size of the mask pattern.

(4) Before projecting an equal-size erect image of the mask pattern onto the exposure surface, the alignment pattern provided on the exposure surface and the alignment pattern provided on the mask are independently detected. Then, based on the detection results of both, the relative position error between the exposure surface and the mask is corrected.

Since the pattern for alignment of the exposure surface and the pattern for alignment of the mask are independently detected to correct the relative position error between the exposure surface and the mask, the alignment pattern provided in the scribe line area is corrected. Using this target pattern, the exposure surface and the mask can be accurately aligned.

(5) Before projecting an equal-magnification erect image of the mask pattern onto the exposure surface, a pattern formed on the exposure surface is detected by using a detection optical system provided on the exposure surface for detecting an alignment pattern. Position, the center position of the detected pattern is moved to the center position of the detection optical system that detects the alignment pattern provided on the exposure surface, and the alignment pattern provided on the exposure surface is detected. The Z-direction position of the detected pattern is detected by using the detection optical system for detecting the Z-direction position having the same center position as the center position of the detection optical system to be detected, and based on the detection result of the Z-direction position of the detected pattern. Then, the Z direction position of the exposure surface is adjusted.

After the center position of the pattern is moved to the center position of the detection optical system for detecting the alignment pattern provided on the exposure surface, the center of the detection optical system for detecting the alignment pattern provided on the exposure surface. By using the detection optical system for detecting the Z-direction position at the same center position as the position, the Z-direction error of the surface of the wafer on which the pattern with a large step amount is formed is detected by detecting the Z-direction position of the pattern.
It can always be detected accurately under the same conditions.

(6) The projection image of the slit pattern installed at the height of the mask surface is converted into the slit pattern installed at the height of the exposure surface by using a projection optical system for projecting an equal-magnification erect image of the mask pattern. By projecting and detecting the amount of light that has passed through the slit pattern installed at the height of the exposure surface,
A projection image position error of a projection optical system that projects an equal-size erect image of the mask pattern is detected, and the angle of the transparent plate inserted in the optical path is adjusted based on the detection result of the projection image position error.
By adjusting the angle of the transparent plate to correct the projection image position error of the projection optical system, the overlay accuracy of the projected and exposed patterns can be improved.

(7) Using a projection optical system for projecting an erect image of the mask pattern at the same magnification, the projected image of the slit pattern installed at the height of the mask surface is converted into the slit pattern installed at the height of the exposure surface. By projecting and detecting the amount of light that has passed through the slit pattern installed at the height of the exposure surface,
Detects the projected image position of the slit pattern installed at the height of the mask surface, based on the detection result of the projected image position, the projected image position of the slit pattern installed at the height of the mask surface,
After matching the position of the slit pattern installed at the height of the exposure surface, the position of the slit pattern installed at the height of the exposure surface is detected by the detection optical system that detects the alignment pattern provided on the exposure surface. Then, the position of the slit pattern installed at the height of the mask surface is detected by the detection optical system that detects the alignment pattern provided on the mask,
The relative position error of both detection optical systems is corrected based on the detection results of both.

Since the relative position error between the detection optical system for detecting the alignment pattern provided on the exposure surface and the detection optical system for detecting the alignment pattern provided on the mask is corrected, the exposure surface and the mask are corrected. It is possible to improve the alignment accuracy with respect to and the overlay accuracy of the projected and exposed patterns.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a schematic configuration of a projection exposure apparatus according to an embodiment of the present invention. The base 90a is installed on the vibration isolation unit 90b.
A guide 90e is installed on the base 90a, and a wafer Y stage 95 is mounted on the guide 90e. Similarly, a guide 95a is also provided on the Y stage 95.
Is installed, and an X for wafer is placed on the guide 95a.
A stage 94 is mounted. A θ stage 93 is installed on the X stage 94, and a Z / tilt stage 92 is installed on the θ stage 93. And the wafer 10
A wafer chuck 91, which is equipped with, is installed on a Z / tilt stage 92. Wafer chuck 91
By the X stage 94, the Y stage 95, the Z / tilt stage 92, and the θ stage 93.
By moving in the Z direction, the θ direction, and the tilt direction, the wafer 10 is aligned and the focus is adjusted.

A support 90c is installed on the base 90a, and a support 90d is further installed on the support 90c. The projection optical system unit 40 is fixed to the pillar 90c, and the exposure illumination unit 30 is fixed to the pillar 90d. The projection optical system unit 40 includes a wafer detection optical system 71, a mask detection optical system 76, and a Z sensor 8
0 is attached.

A guide 90f is installed on the column 90c, and a mask Y stage 97 is mounted on the guide 90f. Similarly, the guide 97a is also installed on the Y stage 97, and the mask X stage 96 is mounted on the guide 97a. A mask holder 98 is installed on the X stage 96, and the mask 20 is fixed to the mask holder 98. The mask holder 98 is moved by the X stage 96 and the Y stage 97.
The mask 2 is moved by being moved in the X direction and the Y direction.
Alignment of 0 is performed.

The exposure illumination light emitted from the exposure illumination unit 30 to the mask 20 passes through the mask 20 and enters the projection optical system unit 40. Projection optical system unit 4
0 indicates the projected image of the pattern of the mask 20 on the wafer 10
Project to.

The projection optical system unit 40 is used for the wafer 10
In order to accurately perform projection exposure on a sloped surface having a large step difference formed on the surface of the substrate, (1) a projection optical system having a deep focal depth, and (2) an autofocus mechanism suitable for a sloped surface having a large step difference. is necessary. Further, in order to expose a resist having a large film thickness, it is necessary to perform projection exposure with high illuminance and high contrast.

In a projection optical system using a lens, the larger the field size, the larger the number of lenses and the thickness of the lens. Reflection of light on the surface of the lens and absorption of light inside the lens reduce the amount of light, and scattered light reaches the wafer surface and lowers contrast. Therefore, in order to perform projection exposure with high illuminance and high contrast, a projection optical system that is small in size, has a small number of lenses, and is capable of exposing a wide range is required.

FIG. 2 is a diagram showing a schematic configuration of a projection optical system according to an embodiment of the present invention. Generally, a mercury lamp is used as a light source for exposure. The wavelengths of light from a mercury lamp that contribute to exposure are g-line (436 nm) and h-line (4
04 nm) and i-line (365 nm). Therefore, in this embodiment, in order to obtain higher illuminance, g
A projection optical system for an erect image of the same size, which can use three wavelengths of line, h line, and i line, is used.

In the projection optical system unit 40, a plurality of projection optical systems arranged at equal pitches are provided. Each projection optical system includes triangular mirrors 41a and 41b, combination lenses 42a and 42b, NA diaphragms 43a and 43b, concave mirrors 44a and 44b, XY correction plates 45a and 45b, and an exposure area diaphragm 46. The combination lenses 42a and 42b are lens barrels 48a and 48b, respectively.
Concave mirrors 44a and 44b are attached to the tips of the movable parts of the lens tubes 48a and 48b, respectively. The lens barrels 48 a and 48 b are supported by a support block 47.

The basic characteristic of the projection optical system according to this embodiment is that the combination lenses 42a and 42b and the concave mirror 44 are used.
It is determined by the machining accuracy of a and 44b and the relative position. Therefore, the optical precision adjustment is performed for each of the lens barrels 48a and 48b. FIG. 3 is a diagram showing relative positions of the projection optical system according to the embodiment of the present invention. In the present embodiment, as an example, G = 49.5 mm and H = 75.
mm, J = 45 mm, K = 1 mm, L = 450 mm.

In FIGS. 2 and 3, the illumination light for exposure incident from the mask surface is reflected by the triangular mirror 41a, passes through the combination lens 42a and the NA diaphragm 43a, and reaches the concave mirror 44a. The illumination light reflected by the concave mirror 44a reaches the triangular mirror 41a through the NA diaphragm 43a and the combination lens 42a. The illumination light reflected by the triangular mirror 41a passes through the XY correction plate 45a and forms an image on the first image forming surface. The concave mirror 44a is arranged on the first pupil plane, and the mask surface and the first imaging plane are arranged symmetrically with respect to the first pupil plane.

An exposure area diaphragm 46 is installed on the first image plane, and the illumination light that has passed through the exposure area diaphragm 46 passes through the XY correction plate 45b and is reflected by the triangular mirror 41b. The concave mirror 44b is reached through the NA diaphragm 43b. The illumination light reflected by the concave mirror 44b reaches the triangular mirror 41b through the NA diaphragm 43b and the combination lens 42b. The illumination light reflected by the triangular mirror 41b forms an image on the second image forming surface. Concave mirror 44
b is located on the second pupil plane, and the wafer surface is located on the second imaging plane. The first image plane and the wafer plane (second image plane) are arranged symmetrically with respect to the second pupil plane.

If a concave mirror is used instead of a lens in the projection optical system, chromatic aberration due to the difference in wavelength of illumination light does not occur. Therefore, projection exposure using more wavelengths becomes possible. However, the concave mirror has spherical aberration, and if it is left as it is, a focus position error occurs depending on the radius method of the spot of the illumination light and the circumferential direction. Therefore, in this embodiment, the focus position error is corrected by the combination lens.

FIG. 4 is a diagram showing a configuration of a combination lens and a concave mirror according to an embodiment of the present invention. The combination lenses 42a and 42b are composed of a concave lens 51 made of a single optical glass and a convex lens 52. The convex lens 52 is an achromat lens composed of three types of lenses 53, 54, 55 made of different optical glasses. In the present embodiment, as an example, the thickness and radius of curvature of each lens and concave mirror 44a, 44b are: G = 49.5 mm, G1 = G2 = G3 = G5 = 9 mm, G4 = 13.5 mm, R1 = 120. 4005 mm, R2 = 125.0000 mm, R3 = −312.1953 mm, R4 = 627.4278 mm, R5 = −82.9404 mm, R6 = −108.3667 mm R7 = −606.28777 mm.

The lens 51 and the lens 54 have a refractive index of 1.43986 for the g-line, a refractive index of 1.44187 for the h-line, and a refractive index of 1.4452 for the i-line.
3, the refractive index of the lens 53 for the g-line is 1.5275
8, the refractive index for the h line is 1.53116, the refractive index for the i line is 1.53718, the refractive index of the lens 55 for the g line is 1.52984, and the refractive index for the h line is 1.5.
3447, the refractive index for the i-line is 1.54252.

The combination lenses 42a and 42b are movable in the optical axis direction within the lens barrels 48a and 48b, and the focus position and the projection position can be adjusted by adjusting the distance between the lenses forming the combination lenses 42a and 42b. The magnification can be adjusted. When adjusted to the design position in the above example, the best focus gives a perfect magnification of 1.
Asymmetrical aberrations such as magnification and coma are zero.

According to the present embodiment, the focus position error caused by the concave mirror is corrected by the combination lens, and the convex lens of the combination lens is made an achromat convex lens composed of three kinds of lenses made of different optical glasses. , Chromatic aberration can be corrected.

FIG. 5 is a diagram showing a ray trace of the projection optical system according to the embodiment of the present invention. This is an example in which the field size is 48 mm in diameter (image height is 24 mm).
The solid line shows the case where the numerical aperture NA is -0.06 (rad), and the broken line shows the case where the numerical aperture NA is 0.06 (rad). Figure 5
Therefore, when the numerical aperture NA is ± 0.06 and the field size is 48 mm in diameter, the spread range of the light beam is 66 mm in diameter.
It turns out that it fits within.

A light beam from a point having a distance of 24 mm in the image height direction on the mask surface (distance 0 in the optical axis direction) forms an image on a point having a distance of -24 mm in the image height direction on the first image forming surface, and the wafer surface (second bonding). Image plane)
The image is formed at a point at a distance of 24 mm in the image height direction. That is, the image obtained on the first imaging plane is an equal-magnification inverted image, and the image obtained on the wafer surface (second imaging plane) is an equal-magnification erect image. Therefore,
The projection optical system according to the present embodiment can project an erect image of equal magnification.

According to the above-described embodiments, the concave mirror and the combination lens are used together to project an equal-magnification erect image, so that the number of necessary lenses is reduced and light absorption and reflection by the lenses are reduced. . In addition, chromatic aberration can be corrected by an achromatic lens and all wavelengths of g-line, h-line and i-line can be used. Therefore, high-contrast projection exposure can be performed with high illuminance. Further, the configuration of the concave mirror and the combination lens enables projection exposure with a deep depth of focus. Therefore, it is possible to accurately perform projection exposure on an inclined surface having a large step amount.

Regarding the autofocus mechanism,
For an inclined surface with a large amount of step difference, the real-time autofocus mechanism used in the reduction projection exposure apparatus is not suitable. At the same pattern position, the autofocus measurement value shows the same value. Therefore, when autofocus measurement is performed after recognizing the pattern position, the measurement becomes discrete, but by approximating the measured value to a flat surface or a curved surface, it is possible to perform autofocus on an inclined surface having a large step amount. .

FIG. 6 is a diagram showing a projection exposure area of the projection optical system according to the embodiment of the present invention. Since the projection optical system uses a concave mirror, the projection-exposureable area is a semicircle.
The range of the predetermined distance E from the center line of the circle in the semicircle is excluded from the projection exposure possible region because the boundary line of the triangular mirrors 41a and 41b is shaded. The exposure area diaphragm 46 is
A trapezoidal projection exposure area as shown in FIG. 6 is set from the projection exposure possible areas. In the present embodiment, as an example, A = 39 mm, B = 43 mm, C = 47 mm, D =
9.5 mm, E = 4.5 mm, R = 24 mm (diameter 48
mm). The exposure area diaphragm 46 is installed on the first image plane and is movable in the XY directions. The position of the projection exposure area can be adjusted by moving the exposure area diaphragm 46 in the XY directions.

FIG. 7 is a diagram for explaining the operation of the projection optical apparatus according to the embodiment of the present invention. The projection optical system unit 40 is provided with a plurality of projection optical systems, and the projection optical systems are arranged at equal pitches. FIG. 7 shows an example in which six projection optical systems are provided. In FIG. 1, while keeping the relative position of the wafer 10 and the mask 20 constant, Y
Wafer 10 and mask 20 by stages 95 and 97
Is moved in the Y direction, the projection exposure area of each projection optical system moves relatively on the wafer 10 to perform scanning. In the example of FIG. 7, the first exposure provides a completely exposed range that is completely exposed, a half exposed range that is intermediately exposed, and an unexposed range that is not exposed. In FIG. 6, the portion of the projection exposure area scanned by the area of width A is the complete exposure range of the first scanning, and the portion of the projection exposure area scanned by the remaining area is the half-exposure range of one scanning. .

Next, the wafers 10 and the mask 20 are moved by a half pitch in the X direction perpendicular to the scanning direction by the X stages 94 and 96. The moving distance is the same as the dimension B shown in FIG. Then, while keeping the relative position of the wafer 10 and the mask 20 constant, the wafers 10 and the mask 20 are moved in the Y direction by the Y stages 95 and 97, and the second scanning is performed. In the second scanning, the unexposed range of the first scanning is completely exposed, the half-exposure range of the first scanning is overlaid, and the completely exposed range of the first scanning is not exposed. The half-exposure range of the first scan is exposed in the second scan in an overlapping manner, so that it is finally completely exposed.
As a result, the entire surface of the wafer 10 is uniformly exposed in two scans.

Although FIG. 7 shows an example in which six projection optical systems are provided in the projection optical system unit 40, five or less or seven or more projection optical systems may be provided. Also,
The number of scans can be changed by changing the pitch at which each projection optical system is arranged. If you reduce the number of scans,
Throughput is improved, but the number of projection optical systems required is large. Conversely, increasing the number of scans reduces throughput, but reduces the number of projection optical systems required.

According to the present embodiment, the entire surface of the wafer can be exposed by scanning once or several times. Therefore,
A small projection optical system can be used to expose a wide range without exposing the unexposed area.

FIG. 8 is a diagram for explaining the operation of the XY correction plate. The XY correction plates 45a and 45b are made of transparent plates whose both surfaces are parallel to each other. The transparent plate forming the XY correction plates 45a and 45b has a refractive index of N ₂ , and the XY correction plates 45a and 4b
When 5b is tilted by an angle θ1 from the direction perpendicular to the optical axis,
The displacement amount X of the projected image position is as shown in FIG.

FIG. 9 is a diagram showing the relationship between the angle of the XY correction plate and the amount of displacement of the projected image position. The solid line in FIG. 9 is the g line (43
6 nm), the broken line is the case of h line (404 nm). From FIG. 9, it can be seen that the displacement amount of the projected image position changes in proportion to the angle of the XY correction plate for both the g line and the h line.

FIG. 10 shows X according to an embodiment of the present invention.
It is a figure which shows the angle adjustment mechanism of a Y correction plate. The screw 62 is attached to the rotary shaft of the pulse motor 61, and the screw 6
A nut 63 is engaged with the shaft 2. XY correction plate 4
5a and 45b are L-shaped leaf springs 65 by the attachment 67.
Is attached to. One end of the leaf spring 65 has a nut 63
, And the other end is fixed by a fixture 66. When a pulse is supplied to the pulse motor 61 and the pulse motor 61 rotates, the nut 63 moves and the leaf spring 65 displaces, and the angles of the XY correction plates 45a and 45b change.

The stopper 64 limits the moving range of the nut 63. The reference position of the leaf spring 65 is set by pressing the nut 63 against the stopper 64 with a predetermined torque when the power is turned on. Then, the XY correction plate 45
The angles a and 45b are adjusted by the number of pulses supplied to the pulse motor 61 from the state where the leaf spring 65 is at the reference position.

According to the present embodiment, the XY correction plate 45
By adjusting the angles of a and 45b, the projected image position of the projection optical system can be adjusted in the XY directions. By controlling the number of pulses supplied to the pulse motor 61, the angles of the XY correction plates 45a and 45b can be adjusted accurately.

FIG. 11 is a diagram showing a schematic structure of an exposure illumination unit according to an embodiment of the present invention. The illumination light generated by the mercury lamp 31 is condensed by the condenser lens group 32.
Reflected by mirrors 33a and 33b through a and 32b, fly-eye lenses 34a and 34b and diaphragms 35a and 35b.
The light is emitted from the illumination lenses 36a and 36b.
The fly-eye lenses 34a and 34b are for making the illuminance distribution of the illumination light uniform.

According to this embodiment, illumination light can be supplied to two projection optical systems using one mercury lamp. Further, by making the cross-sectional shape of the fly-eye lenses 34a and 34b rectangular, it is possible to effectively form a rectangular illumination area.

In the exposure step, first, the mask 20 is supplied from the mask loader (not shown) to the mask holder 98 of the projection exposure apparatus of FIG. 1, and the X stage 9 for the mask is used.
The mask 20 is positioned by the 6 and Y stage 97. After the positioning of the mask 20 is completed, the mask detection optical system 76 detects the alignment pattern provided on the mask 20. As with the wafer, the alignment pattern uses the target pattern shown in FIG. 19B and is installed at a position corresponding to the scribe line region of the wafer. This method, unlike a reduction projection exposure apparatus or a general exposure apparatus, does not require the insertion of a special dedicated pattern for alignment, and facilitates mask production.

In the detection of the target pattern by the mask detection optical system 76, only the coordinates of the target pattern with respect to the coordinate system of the X stage 96 and the Y stage 97 on which the mask 20 is mounted are recognized. It does not adjust the position. By detecting the target pattern of two or more points, the mask 20 is detected from the detection result.
XY position error, rotation error, tilt error, XY pitch error, etc. are calculated.

Next, the wafer 10 is supplied from the wafer loader (not shown) to the wafer chuck 91 of the projection exposure apparatus of FIG. Then, the Z sensor 80 detects Z direction errors at a plurality of points on the surface of the wafer 10.

FIG. 12 is a diagram showing a schematic configuration of a wafer detection optical system and a Z sensor according to an embodiment of the present invention. The wafer detection optical system 71 includes a light source 72, a beam splitter 73, an objective lens 74, and a detector 75. The light from the light source 72 is reflected by the beam splitter 73, passes through the objective lens 74, and is applied to the wafer 10. The light reflected on the surface of the wafer 10 passes through the objective lens 74 and the beam splitter 73, and is detected by the detector 75 including a CCD camera or the like.

On the other hand, the Z sensor 80 comprises a slit illumination light source 81, mirrors 82 and 83, and a detector 84. The slit-shaped light from the slit illumination light source 81 is reflected by the mirror 82 and is applied to the wafer 10. At this time, the irradiation position of the slit-shaped light is accurately aligned with the central position of the wafer detection optical system 71.
The light reflected on the surface of the wafer 10 is reflected by the mirror 83 and detected by the detector 84 including a one-dimensional CCD sensor or the like.

In FIG. 12, first, the XY position of the step pattern 14 formed on the surface of the wafer 10 is detected by the wafer detection optical system 71, and the X stage 94 for the wafer is detected.
Then, the Y stage 95 is moved to align the center position of the step pattern 14 with the center position of the wafer detection optical system 71. Then, the Z sensor 80 detects the position of the step pattern 14 in the Z direction. The Z direction position is detected for a plurality of step patterns having the same specifications on the wafer 10, and the Z / tilt stage 92 is driven based on the detection result to adjust the Z direction position and tilt of the wafer 10.

According to the present embodiment, the Z-direction error on the surface of the wafer on which the pattern having a large amount of step difference is formed can be detected accurately under the same conditions.

After the adjustment of the position and the inclination of the wafer 10 in the Z direction is completed, the wafer detection optical system 71 operates the wafer 10
The target pattern provided in the scribe line area is detected. In the detection of the target pattern, the coordinates of the target pattern with respect to the coordinate system of the X stage 94 and the Y stage 95 on which the wafer 10 is mounted are recognized. By detecting two or more target patterns, the XY position error, rotation error, orthogonality error, XY scale error, etc. of the wafer 10 are calculated from the detection result.

The rotation error of the wafer 10 is corrected by driving the θ stage 93 so as to match the rotation error of the mask 20. The XY position error of the wafer 10 is corrected by moving the X stage 94 and the Y stage 95 for the wafer so as to match the XY position error of the mask 20. The correction of the Y scale error of the wafer 10 is
This is performed by correcting the position of the Y stage 95 during the scanning operation so as to match the scale of the mask 20. The X scale error and the orthogonality error of the wafer 10 are corrected by adjusting the angles of the XY correction plates 45a and 45b in the projection optical system. By these corrections, the relative position between the projected image of the mask 20 and the wafer 10 is completely corrected. These correction operations are performed simultaneously with the scanning exposure described in FIG. When there is no Y scale error, the mask Y stage 97 and the wafer Y stage 95 move in perfect synchronization.

According to the present embodiment, the target pattern of the wafer and the target pattern of the mask are independently detected to correct the relative position error between the wafer and the mask, so that they are provided in the scribe line region. Using the target pattern for alignment, the exposure surface and the mask can be accurately aligned.

In the projection exposure apparatus shown in FIG. 1, when the relative position between the wafer detection optical system 71 and the mask detection optical system 76 changes over time, the alignment accuracy between the wafer and the mask decreases, and projection exposure is performed. The superposition accuracy of the pattern is reduced. Further, even if the projected image position of the projection optical system unit 40 changes with time, the overlay accuracy of the projected and exposed patterns decreases.

FIG. 13 is a diagram for explaining a method of correcting the projected image position according to the embodiment of the present invention. The reference mask 77 is movably installed in synchronization with the mask 20 at the same position as the height of the mask surface of the mask 20. Also, wafer 1
The reference mask 78 is movably installed in synchronization with the wafer 10 at the same position as the height of the surface of 0. Reference mask 78
A photo sensor 79 is movably installed below the wafer in synchronization with the wafer 10. The exposure illumination unit 30 and the projection optical system unit 40 move to the center positions of the reference masks 77 and 78 in the vicinity of the stroke end of scanning by the Y-suges 95 and 97 of the projection exposure apparatus of FIG. Note that FIG.
Then, Z between the wafer chuck 91 and the X stage 94
The tilt stage 92 and the θ stage 93 are omitted.

FIG. 14A is a top view of a reference mask according to an embodiment of the present invention, and FIG. 14B is an enlarged view of each slit pattern of the reference mask. Reference mask 77, 7
8 is composed of a plurality of slit patterns corresponding to the number of projection optical systems in the projection optical system unit 40. A plurality of photosensors 79 are provided corresponding to each slit pattern.

In FIG. 13, the illumination light emitted from the exposure illumination unit 30 and passing through the slit pattern of the reference mask 77 forms a projected image of the slit pattern on the surface of the reference mask 78 by the projection optical system unit 40. .
The projected image of the formed slit pattern is the reference mask 78.
It is detected by the photo sensor 79 through the slit pattern of. When the X stage 94 and the Y stage 95 for the wafer are moved, the output of the photo sensor 79 changes according to the movement. The output of the photo sensor 79 becomes maximum when the projected image position of the slit pattern of the reference mask 77 and the position of the slit pattern of the reference mask 78 match. FIG. 15 is a diagram showing an example of the output of the photo sensor. The projected image position of the slit pattern of the reference mask 77 can be easily calculated from the output waveform of the photo sensor 79 as shown in FIG.

Next, with the projected image position of the slit pattern of the reference mask 77 and the position of the slit pattern of the reference mask 78 aligned, the X stages 94 and 96 and the Y stages 95 and 97 are moved in synchronization. Then, the wafer detection optical system 71 detects the pattern position of the reference mask 77,
The mask detection optical system 76 detects the pattern position of the reference mask 78. From these detection results, the relative position error between the wafer detection optical system 71 and the mask detection optical system 76 is calculated, and the correction amount is determined.

From the output of each photosensor 79,
The projection image position error between the projection optical systems in the projection optical system unit 40 and the projection magnification error of each projection optical system are calculated.
If the projection image position error between the projection optical systems or the projection magnification error between the projection optical systems deviates from the specified value, correction is performed by adjusting the angles of the XY correction plates 45a and 56b in the projection optical system.

According to the present embodiment, the relative position error between the wafer detection optical system and the mask detection optical system can be detected and corrected, so that the alignment accuracy between the wafer and the mask is improved. Further, it is possible to detect and correct a projection image position error between the projection optical systems in the projection optical system unit and a projection magnification error of each projection optical system. Therefore, the overlay accuracy of the projected and exposed patterns can be improved.

In this embodiment, the reference mask 7 is used.
7,78 slit pattern and photo sensor 79
Although a plurality of optical projection units are provided corresponding to the number of projection optical systems in the projection optical system unit 40, only a smaller number than the number of projection optical systems in the projection optical system unit 40 are provided, and the X stage 94 and the Y stage for the wafer are provided. By moving the stage 95, the projected images of the slit pattern by each projection optical system may be sequentially detected.

FIG. 16 is a diagram showing a schematic configuration of a projection exposure system according to an embodiment of the present invention. The projection exposure system includes a coating device 100, a projection exposure device 200, a developing device 300, an overlay accuracy measuring device 400, and an overlay error analyzing device 500. As the projection exposure apparatus 200, the projection exposure apparatus shown in FIG. 1 is used.

The overlay accuracy measuring device 400 measures the overlay error of the pattern projected by the projection exposure device 200 and developed by the developing device 300. The overlay error analysis device 500 is the overlay accuracy measurement device 400.
From the measurement result of 1 and the exposure condition of the projection exposure apparatus 200, the correction amount of each correction item such as pitching / rolling correction, XY scaling correction, tilt correction, rotation offset correction, and XY offset correction is determined and fed back to the projection exposure apparatus 200. To do.

A particularly important correction item is pitching / rolling correction. This is the Y stage 9 for wafers.
5 and the XY position error of the projected image due to the pitching / rolling error during the scanning operation of the mask Y stage 97, which changes non-linearly depending on the scanning position. For such a non-linear position error, a correction data table corresponding to each scanning position is created, and correction is performed between the data using an interpolation formula.

According to the present embodiment, the pattern overlay accuracy can be further improved.

In the embodiment described above, the projection optical system unit is fixed, and the wafer and the mask are moved to move the wafer and the mask relative to the projection optical system unit. Alternatively, the projection optical system unit may be moved with the mask fixed.

[0081]

The present invention has the following effects. (1) It is possible to accurately perform projection exposure on an inclined surface having a large step amount, and without exposing an unexposed area,
A wide range can be exposed.

(2) Further, by projecting the same-size erect images at different positions of the mask pattern at the same time, the required number of scans can be reduced and the throughput can be improved.

(3) Furthermore, by adjusting the angle of the transparent plate inserted in the optical path, the position of the equi-magnification erect image of the mask pattern can be adjusted accurately.

(4) Furthermore, by detecting the alignment pattern of the exposure surface and the alignment pattern of the mask independently of each other and correcting the relative position error between the exposure surface and the mask, By using the alignment target pattern provided in, the exposure surface and the mask can be accurately aligned.

(5) Further, after moving the center position of the pattern to the center position of the detection optical system for detecting the alignment pattern provided on the exposure surface, the alignment pattern provided on the exposure surface is detected. By detecting the Z direction position of the pattern by using the detection optical system for detecting the Z direction position at the same center position as the center position of the detection optical system,
An error in the Z direction on the surface of the wafer on which a pattern having a large amount of step difference is formed can be detected with high accuracy under the same conditions.

(6) Further, using a projection optical system for projecting an equal-magnification erect image of the mask pattern, the projected image of the slit pattern set at the height of the mask surface is slit at the height of the exposure surface. The projection image position error of the projection optical system that projects an equal-size erect image of the mask pattern is detected by detecting the amount of light that has passed through the slit pattern installed at the height of the exposure surface. By adjusting the angle of the transparent plate inserted in the optical path based on the detection result of the position error, it is possible to improve the overlay accuracy of the projected and exposed patterns.

(7) Further, using a projection optical system for projecting an equal-magnification erect image of the mask pattern, the projected image of the slit pattern set at the height of the mask surface is slit at the height of the exposed surface. The projected image position of the slit pattern installed at the height of the mask surface is detected by detecting the amount of light that has passed through the slit pattern installed at the height of the exposure surface by projecting onto the pattern, and the detection result of the projected image position is obtained. Based on this, after matching the projected image position of the slit pattern installed at the height of the mask surface with the position of the slit pattern installed at the height of the exposure surface, the alignment pattern provided on the exposure surface is detected. The height of the mask surface is detected by the detection optical system that detects the position of the slit pattern installed at the height of the exposure surface with the detection optical system and detects the alignment pattern provided on the mask. By detecting the position of the installed slit pattern and correcting the relative position error between both detection optical systems based on the detection results of both, the alignment accuracy between the exposure surface and the mask can be improved, and the projection exposure It is possible to improve the overlay accuracy of the formed patterns.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a schematic configuration of a projection optical system according to an embodiment of the present invention.

FIG. 3 is a diagram showing a relative position of a projection optical system according to an embodiment of the present invention.

FIG. 4 is a diagram showing a configuration of a combination lens and a concave mirror according to an embodiment of the present invention.

FIG. 5 is a diagram showing a ray trace of a projection optical system according to an embodiment of the present invention.

FIG. 6 is a diagram showing a projection exposure area of the projection optical system according to the embodiment of the present invention.

FIG. 7 is a diagram illustrating an operation of the projection optical device according to the embodiment of the present invention.

FIG. 8 is a diagram for explaining the operation of the XY correction plate.

FIG. 9 is a diagram showing a relationship between an angle of an XY correction plate and a displacement amount of a projected image position.

FIG. 10 is a diagram showing an angle adjustment mechanism for an XY correction plate according to an embodiment of the present invention.

FIG. 11 is a diagram showing a schematic configuration of an exposure illumination unit according to an embodiment of the present invention.

FIG. 12 is a diagram showing a schematic configuration of a wafer detection optical system and a Z sensor according to an embodiment of the present invention.

FIG. 13 is a diagram illustrating a method of correcting a projected image position according to an embodiment of the present invention.

FIG. 14A is a top view of a reference mask according to an embodiment of the present invention, and FIG. 14B is an enlarged view of each slit pattern of the reference mask.

FIG. 15 is a diagram showing an example of an output of a photo sensor.

FIG. 16 is a diagram showing a schematic configuration of a projection exposure system according to an embodiment of the present invention.

FIG. 17 is a diagram showing a basic structure of a wafer process package.

FIG. 18 is a flowchart showing an outline of a manufacturing process of a wafer process package.

19A is a diagram showing the arrangement of target patterns, and FIG. 19B is a diagram showing a typical target pattern.

FIG. 20 is a diagram showing an unexposed area.

[Explanation of symbols]

10 ... Wafer, 20 ... Mask, 30 ... Exposure illumination unit, 40 ... Projection optical system unit, 41a, 41b ... Triangular mirror, 42a, 42b ... Combination lens, 43a,
43b ... NA diaphragm, 44a, 44b ... Concave mirror, 45a,
45b ... XY correction plate, 46 ... Exposure area diaphragm, 51 ... Concave lens, 52 ... Convex lens, 71 ... Wafer detection optical system, 7
6 ... Mask detection optical system, 77, 78 ... Reference mask, 80
... Z sensor

Continued front page    (72) Inventor Takuro Hosoe             Hitachi Electronics, 3-16-3 Higashi, Shibuya-ku, Tokyo             Engineering Co., Ltd. (72) Inventor Ryoji Nemoto             Hitachi Electronics, 3-16-3 Higashi, Shibuya-ku, Tokyo             Engineering Co., Ltd. F-term (reference) 2H097 BA01 GB01 KA03 KA28 KA38                       LA09

Claims (14)

[Claims] 1. A projection optical system comprising a concave mirror, a concave lens made of a single optical glass, and a combination lens including an achromatic convex lens made of three kinds of lenses made of different optical glasses is used to form a mask pattern. Projection exposure characterized by projecting an equal-magnification erect image onto the exposure surface, moving the exposure surface and the mask relative to the projection optical system, and scanning the exposure surface with the equal-magnification erect image of the mask pattern. Method. 2. The projection exposure method according to claim 1, wherein a plurality of projection optical systems are used to simultaneously project equal-magnification erect images at different positions of the mask pattern. 3. A position of an equal-magnification erect image of a mask pattern is adjusted by inserting a transparent plate whose both surfaces are parallel to each other in the optical path and adjusting an angle of the inserted transparent plate. 1. The projection exposure method according to 1. 4. An alignment pattern provided on the exposure surface and an alignment pattern provided on the mask are detected independently of each other before projecting an equal-magnification erect image of the mask pattern onto the exposure surface. The projection exposure method according to claim 1, wherein the relative position error between the exposure surface and the mask is corrected based on the detection results of both. 5. A projection optical system for detecting a pattern formed on an exposure surface by using a detection optical system for detecting an alignment pattern provided on the exposure surface before projecting an equal-magnification erect image of the mask pattern onto the exposure surface. Detects the position, moves the center position of the detected pattern to the center position of the detection optical system that detects the alignment pattern provided on the exposure surface, and detects the alignment pattern provided on the exposure surface The Z direction position of the detected pattern is detected using the detection optical system for detecting the Z direction position at the same center position as the center position of the detection optical system, and based on the detection result of the Z direction position of the detected pattern. The projection exposure method according to claim 4, wherein the Z-direction position of the exposure surface is adjusted. 6. A projection optical system for projecting an equal-magnification erect image of a mask pattern is used to project a projected image of a slit pattern installed at the height of the mask surface onto a slit pattern installed at the height of the exposure surface. Then, by detecting the amount of light that has passed through the slit pattern installed at the height of the exposure surface, the projection image position error of the projection optical system that projects the 1x erect image of the mask pattern is detected. 4. The projection exposure method according to claim 3, wherein the angle of the transparent plate inserted in the optical path is adjusted based on the detection result. 7. A projection optical system for projecting an equal-magnification erect image of a mask pattern is used to project a projected image of a slit pattern installed at the height of the mask surface onto a slit pattern installed at the height of the exposure surface. Then, by detecting the amount of light that has passed through the slit pattern installed at the height of the exposure surface, the projected image position of the slit pattern installed at the height of the mask surface is detected, and based on the detection result of the projected image position, Detection optics that detects the alignment pattern provided on the exposure surface after matching the projected image position of the slit pattern installed at the height of the mask surface with the position of the slit pattern installed at the height of the exposure surface The system detects the position of the slit pattern installed at the height of the exposure surface and detects the alignment pattern provided on the mask.The detection optical system is installed at the height of the mask surface. Detecting the position of the slit pattern, based on both the detection result, the projection exposure method according to claim 4, wherein the correcting the relative positional error of both detection optical system. 8. A concave mirror made of a single optical glass and a combination lens including an achromatic convex lens made up of three kinds of lenses made of different optical glasses are provided, and an erect image of a mask pattern of equal magnification is exposed. A projection optical system for projecting onto the exposure surface, an exposure surface and a mask, and means for moving the projection optical system relative to each other to scan an erect image of the mask pattern on the exposure surface. Projection exposure system. 9. The projection exposure apparatus according to claim 8, further comprising a plurality of the projection optical systems. 10. The projection exposure apparatus according to claim 8, further comprising: a transparent plate provided in the optical path, both surfaces of which are parallel to each other, and an angle adjusting unit for adjusting an angle of the transparent plate. 11. A first detection optical system for detecting an alignment pattern provided on an exposure surface, and a first detection optical system for detecting an alignment pattern provided on a mask independently of the first detection optical system. 2 detection optical system, based on the detection results of the first and second detection optical system,
9. The projection exposure apparatus according to claim 8, further comprising means for correcting a relative position error between the exposure surface and the mask. 12. A third detection optical system, which has the same center position as that of the first detection optical system and detects the Z-direction position of the exposure surface, and a detection result of the third detection optical system. The projection exposure apparatus according to claim 11, further comprising means for adjusting the Z direction position of the exposure surface based on the above. 13. A first slit pattern provided at a height of a mask surface, a second slit pattern provided at a height of an exposure surface, and projection of the first slit pattern by the projection optical system. 9. The projection exposure apparatus according to claim 8, further comprising a detection unit that detects the amount of light whose image has passed through the second slit pattern. 14. A first slit pattern provided at a height of a mask surface, a second slit pattern provided at a height of an exposure surface, and projection of the first slit pattern by the projection optical system. A detecting means for detecting an amount of light whose image has passed through the second slit pattern, wherein the angle adjusting means adjusts an angle of the transparent plate based on a detection result of the detecting means. Item 11. The projection exposure apparatus according to item 10.