JP2007219240A - Contact exposure method and contact exposure apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a contact exposure method and an apparatus for obtaining a uniform exposure pattern with less unevenness by imparting simple alteration even when a conventional contact exposure apparatus using a light source having variance in luminance energy or irradiation direction. <P>SOLUTION: The contact exposure apparatus includes a mask holder 12 holding a mask 11 where an exposure pattern is formed; a wafer stage 22 holding a transparent substrate 21 coated with a resist; an moving mechanism 30 for adhesion for changing relative positions of the mask holder 12 and the wafer stage 22 and tightly adhering the mask 11 to the transparent substrate 21, and a light source 15 for irradiating the mask with light for exposure, wherein a moving mechanism 17 to 19 for exposure for relatively moving the light source 15 in a direction perpendicular to the irradiation direction of the light is provided on the mask holder 12 and the wafer stage 22. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a contact exposure method and a contact exposure apparatus that perform exposure by irradiating light onto a mask in a state where a mask on which an exposure pattern is formed is in close contact with a substrate (wafer) coated with a resist. It is related with the contact exposure method and contact exposure apparatus which apply | coat and expose.

  The optical waveguide is formed by applying a resist on a transparent substrate such as a lithium niobate wafer, exposing a pattern by contact exposure, and processing by photoetching or the like. Contact exposure is performed by irradiating the mask with ultraviolet rays or the like in a state where the mask on which the exposure pattern is formed is in close contact with the transparent substrate coated with the resist. The formation of an optical waveguide using contact exposure is described in Patent Document 1 and the like, and is well known, so detailed description thereof is omitted here.

  Also in the manufacture of optical waveguides, pattern miniaturization and high precision are required. For example, an error range of +0.15 μm and −0.25 μm is required for a line width of 3 μm, and a Y of 0.5 μm is required. The resolution of the branch tip diameter is required.

  When exposing the transparent substrate, the light that has passed through the mask is absorbed by the resist film, exposing the resist film, and the light that has not been absorbed passes through the transparent substrate and is reflected by the bottom surface of the transparent substrate and the surface of the wafer stage. Then, the light passes again through the transparent substrate and enters the resist film to expose the resist film. The light irradiated to the mask is not completely parallel to the irradiation direction and has a component that does not enter perpendicularly to the transparent substrate. The light tilted by θ from the vertical direction with respect to the transparent substrate having the thickness d is reflected by the bottom surface of the transparent substrate and is incident on the resist film again. The position is 2dθ / n (n is the refractive index of the transparent substrate). Deviation occurs and blurs the exposure pattern. This blur causes a reduction in resolution.

Japanese Patent Laid-Open No. 2005-266739

  A relatively inexpensive contact exposure apparatus has large variations in illuminance and irradiation direction in the exposure range due to cost constraints of the optical system of the exposure light source. For this reason, the exposure pattern is blurred due to variations in the exposure amount, the thickness of the transparent substrate and the inclination of the irradiation direction, and the resulting resist pattern is deteriorated.

  FIG. 1 is a diagram for explaining this problem. As shown in FIG. 1A, among the light irradiated from the irradiation port 1 of the ultraviolet light source toward the mask 2, the light incident on the shielding unit 3 is reflected there, and the light incident on the transmission unit 4 is The resist film 5 is absorbed to expose the resist film 5, and the light that has not been absorbed passes through the transparent substrate 6, is reflected by the bottom surface of the transparent substrate 6 and the surface of the wafer stage 7, and again passes through the transparent substrate 6. Passes through and enters the resist film 5 to expose the resist film 5. For example, light that is tilted to the right as it travels exposes the edge portion of the shield 3 that is in contact with the right side of the transmission part 4 of the mask 2 to cause blur, and light that tilts to the left as it travels is masked The edge part of the shielding part 3 in contact with the left side of the second transmission part 4 is exposed to cause blurring.

  As described above, the light emitted from the irradiation port 1 of the exposure light source has unevenness in illuminance and variation in the irradiation direction. Therefore, as shown in FIG. 1A, the reflected light concentrates on the edge portion P of the shielding portion 3 on the right side of the transmission portion 4 of the mask 2 and the exposure amount increases, but the transmission portion 4 of the mask 2 increases. In the edge portion Q of the right shielding portion 3, there may be a phenomenon in which the reflected light is dispersed and the exposure amount does not increase so much. When such an exposure pattern is reversed and developed, a resist pattern 8 is formed in the portion of the transmissive portion 4 and a residue 9 is formed on the edge portion P of the shielding portion 3 on the right side of the transmissive portion 4 of the mask 2 from which the resist is to be removed. Occurs. On the other hand, no residue is generated in the edge portion Q of the shielding portion 3 on the right side of the transmission portion 4 of the mask 2 from which the resist is to be removed. This causes a reduction in the resolution of the resist pattern and degrades the shape of the waveguide formed on the transparent substrate.

  The location where the influence of the exposure amount variation and the variation in the irradiation direction appears and the extent thereof vary depending on the size and shape of the transmission part of the mask and the surface state of the wafer stage, and are not constant. For this reason, there is a problem that it is difficult to adjust to the optimum exposure conditions.

  The present invention solves such a problem, and even in the case of a conventional contact exposure apparatus using a light source having a variation in exposure amount and a variation in irradiation direction, it is uniform with little unevenness only by performing a simple modification. An object is to realize a contact exposure method and apparatus capable of obtaining an exposure pattern.

  In order to achieve the above object, the contact exposure method and apparatus of the present invention relatively moves a light source that emits light for exposure with respect to a mask and a transparent substrate in close contact with each other.

  That is, the contact exposure method of the present invention is a contact exposure method in which a mask on which an exposure pattern is formed is brought into close contact with a transparent substrate coated with a resist, and light from a light source is irradiated onto the mask and the transparent substrate. During the exposure, the light source is moved relative to the mask and the transparent substrate that are in close contact with each other in a direction perpendicular to the light irradiation direction.

  Further, the contact exposure apparatus of the present invention changes the relative position between the mask holder that holds the mask on which the exposure pattern is formed, the wafer stage that holds the transparent substrate coated with the resist, and the mask holder and the wafer stage, A contact exposure apparatus comprising: an adhesion moving mechanism for bringing the mask into close contact with the transparent substrate; and a light source for irradiating the mask with light to expose the exposure pattern onto the resist applied to the wafer. And an exposure moving mechanism for moving the light source relative to the mask holder and the wafer stage in a direction perpendicular to a light irradiation direction.

  According to the present invention, since the light source is moved relative to the mask and the transparent substrate, the unevenness of the exposure amount and the variation in the irradiation direction are averaged, and the resist residue remains only on one edge. This can be avoided, the exposure conditions can be easily adjusted, and a desired resist pattern can be easily obtained.

  It is only necessary to move the light source relative to the mask and the transparent substrate that are in close contact, either by moving the light source with the mask and the transparent substrate fixed, or by moving the mask and the transparent substrate with the light source fixed, You may move both.

  In the contact exposure apparatus, since the irradiation range of light from the light source is generally wider than the exposure range of the mask, the closely contacted mask and the transparent substrate move relatively so as to fall within this irradiation range.

  According to the present invention, the quality of an exposure pattern (resist pattern) can be improved and the processing accuracy of an optical waveguide and the like can be improved with a simple configuration in which a light source is moved relative to a mask and a transparent substrate that are in close contact with each other. Can do.

  FIG. 2 is a diagram showing a schematic configuration of a contact exposure apparatus according to an embodiment of the present invention. As shown in the figure, the contact exposure apparatus of the embodiment irradiates the mask 11 with a mask holder 12 that holds a mask 11, a wafer stage 22 that holds a transparent wafer (transparent substrate) 21 such as a lithium niobate wafer, and the mask 11. And an ultraviolet ray source (lamp) 15 that outputs ultraviolet rays. The ultraviolet light source 15 is held by the support 16. The mask holder 12 is provided with a double ring-shaped gasket 13, and a space between the double rings of the gasket 13 is connected to an intake port S 1 of the vacuum pump 20 through a gas path 14. When the pressure in the gas path 14 is reduced by the vacuum pump 20 with the mask 11 in contact with the gasket 13, the mask 11 is vacuum-sucked and held by the mask holder 12. The mask 11 can be fixed to the mask holder 12 by a method other than vacuum suction. Further, the mask holder 12 can be moved in the vertical direction by a Y-axis moving mechanism (not shown).

  The surface of the wafer stage 22 has a groove connected to the air inlet S2 of the vacuum pump 20 through the gas path 29, and when the pressure inside the gas path 29 is reduced by the vacuum pump 20 with the transparent wafer 21 placed thereon. The transparent wafer 21 is vacuum-sucked and held on the wafer stage 22. The wafer stage 22 is held on the stage base 25 via a ball bearing 23, the orientation of the mounting surface of the wafer stage 22 can be adjusted, and the wafer stage 22 can be fixed in the direction adjusted by the stage fixing knob 24. Yes. The stage base 25 is held by the XZθ adjustment mechanism 30. Thereby, the stage base 25, that is, the wafer stage 22, can adjust the position of the XZ axis in two axes by operating the Z axis adjustment knob 26 and the X axis adjustment knob 28, and operates the θ axis adjustment knob 27. Thus, the rotational position in the plane perpendicular to the Y axis can be adjusted.

  The above configuration is the same as the conventional example. In the present embodiment, a light source moving mechanism including a crankshaft 17 connected to the exposure light source 15 and a cam 18 connected to the crankshaft 17 is provided. The cam 18 is rotated by a shaft 19 connected to a motor shaft via a reduction gear, and the exposure light source 15 reciprocates in the left-right direction with respect to the column 16 as the cam 18 rotates.

  When performing exposure, the mask 11 on which the exposure pattern is formed is held on the mask holder 12 by the above method. Next, the transparent wafer 21 is placed on the wafer stage 22 and held by vacuum suction. Then, the mask holder 12 is lowered by the Y-axis moving mechanism to bring the mask 11 close to the transparent wafer 21, and the marks are matched by the XZθ adjusting mechanism 30 while checking the alignment mark of the mask 11 and the transparent wafer 21 with a microscope or the like. Thus, the position and rotation θ of the wafer stage 22 in the XZ axis direction are adjusted. Thereafter, the mask holder 12 is further lowered to bring the mask 11 into contact with the transparent wafer 21. At this time, since the wafer stage 22 is held on the stage base 25 via the ball bearings 23, the orientation of the wafer stage 22 is adjusted so that the transparent wafer 21 is along the surface of the mask 11, so that the fixed knob 24 is thereafter used. To fix the orientation of the wafer stage 22.

  In this state, the cam 18 is rotated to move the ultraviolet ray source 15 in the left-right direction, and the mask 11 is irradiated with ultraviolet rays from the ultraviolet ray source 15 so that the pattern of the mask 11 is applied to the resist applied on the surface of the transparent wafer 21. To expose. During this time, the mask 11 is vacuum-sucked to the mask holder 12 and the transparent wafer 21 is kept vacuum-sucked to the wafer stage 22.

  After the exposure, the mask holder 12 is raised by the Y-axis moving mechanism, and the mask 11 and the transparent wafer 21 are separated. Since the mask 11 is vacuum-sucked to the mask holder 12 and the transparent wafer 21 is vacuum-sucked to the wafer stage 22, it can be separated.

  As described above, since the exposure is performed while moving the ultraviolet ray source 15 in the left-right direction, the unevenness of the light amount distribution on the mask 12 and the variation in the direction of the ultraviolet ray emitted from the ultraviolet ray source 15 are averaged. The edge portion of the pattern has a similar shape regardless of the position of the mask 11. Moreover, the contact exposure apparatus of this embodiment can be realized by adding a mechanism for moving the ultraviolet light source 15 to the existing contact exposure apparatus.

  FIG. 3 is a diagram for explaining a method of moving the ultraviolet ray source 15 relative to the mask 11. In general, an irradiation range 40 of ultraviolet rays from the ultraviolet source 15 that can be used for exposure is defined, and the irradiation range 40 is considerably larger than the transmission range 41 of the mask 11. Here, although the transmission range 41 is shown as a circle, it may be a square or the like. Therefore, in this embodiment, as shown in FIG. 3A, the center of the transmission range 41 is actually moved so as to move relative to the ultraviolet irradiation range 40 like a movement path 42. The irradiation range 40 is moved with respect to the transmission range 41.

  The movement path 42 can be variously modified. For example, as shown in FIG. 3B, even if the movement path 42 is square by combining two-way linear movements, As shown in C), the movement path 42 may be circular. However, in the case of FIG. 3B, the light source moving mechanism that moves the ultraviolet ray source 15 in two directions of the X axis and the Z axis is used. In the case of FIG. A light source moving mechanism that moves so as to draw is necessary.

  As mentioned above, although the Example of this invention was described, it cannot be overemphasized that various modifications are possible.

  For example, it is possible to move the mask 11 and the transparent wafer 21 that are in close contact with the ultraviolet ray source 15 fixed, and in that case, the XZθ moving mechanism 30 can be used. Further, in the embodiment, the two-dimensional movement is realized by moving the ultraviolet ray source 15 in the left-right (X-axis) direction and moving the closely contacted mask 11 and transparent wafer 21 in the Z-axis direction using the XZθ moving mechanism 30. It is also possible to do.

  The present invention can be applied to any contact exposure method and apparatus using a transparent substrate as well as a contact exposure method and apparatus used for manufacturing an optical waveguide.

  The present invention can be applied to any apparatus as long as it is a contact exposure apparatus. Currently, almost no new model has been developed, but a contact exposure apparatus that has been used for a long time and is still widely used. It can also be realized by modification.

It is a figure explaining the influence of the variation in the irradiation direction of an exposure light beam. It is a figure which shows schematic structure of the contact exposure apparatus of the Example of this invention. It is a figure explaining the method of the relative movement of the ultraviolet-ray source with respect to a mask.

Explanation of symbols

11 Mask 12 Mask Holder 15 UV Source (Lamp)
16 Strut 17 Crankshaft 18 Cam 20 Vacuum Pump 21 Wafer 22 Wafer Stage 29 Gas Path

Claims (2)

A contact exposure method in which a mask on which an exposure pattern is formed is brought into close contact with a transparent substrate coated with a resist, and light from a light source is applied to the mask and the transparent substrate.
A contact exposure method, wherein the light source is moved in a direction perpendicular to a light irradiation direction with respect to the mask and the transparent substrate in close contact during exposure. A mask holder for holding a mask on which an exposure pattern is formed;
A wafer stage for holding a transparent substrate coated with a resist;
A moving mechanism for close contact that changes the relative position of the mask holder and the wafer stage, and closes the mask to the transparent substrate;
A light source for irradiating the mask with light to expose the resist applied to the wafer with the exposure pattern, and a contact exposure apparatus comprising:
A contact exposure apparatus comprising an exposure moving mechanism that moves the light source relative to the mask holder and the wafer stage in a direction perpendicular to a light irradiation direction.

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