JPH11133588A - Exposure mask and exposure device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the remaining of a resist on a metal thin plate due to the exposure of positioning marks without causing troubles for positioning of an exposure mask and a metal thin plate. SOLUTION: In the exposure mask 1, an optical layer 6 which transmits visible rays but absorbs UV rays is formed in the positioning mark part 5. The optical layer 6 is a polyimide film and the layer 6 is adhered to the non- pattern face of the exposure mask 1 with a transparent adhesive layer. Further, in the exposure device, a metal thin plate with a photoresist film formed is exposed to UV rays to form a pattern except for the positioning marks by using the exposure mask 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure mask and an exposure apparatus for irradiating ultraviolet rays to a thin metal plate having a surface coated, electrodeposited, or laminated with a photoresist to print a mask pattern on the photoresist film. .

[0002]

2. Description of the Related Art As shown in a lead frame for a semiconductor integrated circuit, there is a product in which a thin metal plate processed by photo-etching or die-pressing is partially plated. As a method of partially plating a metal sheet that has already been processed, for example, a photoresist film is formed on the surface of the processed metal sheet, and after irradiating exposure light including ultraviolet rays through an exposure mask, developing A method of forming a plating pattern on a metal surface and plating the partially exposed metal surface. The photoresist film used here generally responds to light having a wavelength of 450 nm or less, and has high sensitivity to light having a short wavelength such as ultraviolet light.

In the above process, when exposing the plating pattern to the photoresist film, it is necessary to align the already processed metal sheet and the exposure mask. As an alignment method, for example, an alignment mark is provided on each of the thin metal plate and the exposure mask, two alignment marks are imaged using an imaging camera such as a CCD, and the mark image is processed by an image processing apparatus. Processing is performed to detect the amount of displacement, and adjust the position of the thin metal plate or the exposure mask.

FIG. 5 shows an example of the alignment mark.
FIG. 5 is an external perspective view of an exposure mask and a thin metal plate. As shown in the figure, for example, as shown in the drawing, the alignment mark between the metal thin plate 7 and the exposure mask 1 is provided with an alignment mark 8 formed by drilling a few mm square on one metal thin plate 7, and the other exposure mask 1 A cross-shaped alignment mark 5 larger than the perforation dimension of the thin metal plate is provided. When aligning the positions of the metal thin plate 7 and the exposure mask 1, the metal thin plate 7 and the exposure mask 1 are opposed to each other, and the metal thin plate 7 is provided on the exposure mask 1 at the center of the alignment mark 8 formed by the perforation provided in the metal thin plate 7. So that the cross-shaped alignment mark 5 is located,
The position of the exposure mask 1 or the thin metal plate 7 is adjusted.

[0005] The alignment marks 5 and 8 are provided in the margins of the sheet metal 7 as shown in the figure. On the other hand, the blank portion of the metal sheet 7 is also used as a current-carrying electrode in partial plating of the metal sheet. Accordingly, in order to prevent the plating pattern formed by the photoresist film from being formed in the blank portion, for example, when the photoresist film formed on the thin metal plate is a negative type, the mask pattern corresponding to the blank portion of the thin metal plate is usually as shown in FIG. As shown in the drawing, the solid portion is kept black to block ultraviolet exposure to the margin.

[0006]

In the above situation, when the exposure mask is irradiated with ultraviolet rays and the plating pattern is exposed on the photoresist film, as shown in FIG. 7, the alignment mark provided on the exposure mask becomes a thin metal plate. A phenomenon occurs in which the photoresist film formed on the surface of the photoresist film 7 is baked in the positioning hole 8 and the photoresist film remains in the positioning hole even after developing the resist film. When plating is performed on the metal thin plate in this state, the residue of the photoresist film becomes insulation resistance between the plating electrode and the metal thin plate, and affects quality such as plating thickness. Also,
When the residue of the photoresist film adheres to the plating electrode, the work load such as cleaning increases.

In order to avoid the above-mentioned adverse effects, it is possible to arrange the position of the alignment mark away from the energized electrode portion of the thin metal plate. However, in recent years, there has been a tendency to minimize the margin in order to reduce material costs. Therefore, the interference between the alignment mark and the conductive electrode portion can no longer be avoided. Further, the exposure light beam may be masked so as not to irradiate the alignment mark portion with ultraviolet rays. However, exposure by an illumination light source for imaging the alignment mark is inevitable. An object of the present invention is to provide an exposure mask and an exposure apparatus capable of effectively preventing a resist residue on a metal sheet due to exposure of an alignment mark portion in order to solve the above-described problem.

[0008]

As means for solving the above-mentioned problems, it is necessary to eliminate the resist remaining due to the exposure of the alignment mark portion without causing any trouble in the alignment between the exposure mask and the thin metal plate. is there. In other words, the problem can be solved by providing a material that transmits visible wavelengths of the illumination light source used in the imaging device for the alignment mark but does not transmit ultraviolet light for exposing the photoresist film to the alignment mark portion of the exposure mask. I understood. Therefore, the present inventors have conducted various tests, and by using an exposure mask and an exposure apparatus having the following configuration,
The problem has been solved.

That is, in the exposure mask according to the present invention, an optical layer that transmits visible light and absorbs ultraviolet light is provided on the alignment mark portion, and the optical layer includes: As described in claim 2, it is a polyimide film, and further, as described in claim 3, the optical layer is adhered to the non-pattern surface of the exposure mask using a transparent adhesive layer. . Furthermore, the exposure apparatus of the present invention uses the exposure mask according to claim 1, 2, or 3 to apply a pattern excluding an alignment mark to a thin metal plate on which a photoresist film is formed by using an ultraviolet ray. It was configured to expose.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An exposure mask and an exposure apparatus according to the present invention will be described in detail with reference to the drawings of the embodiments.

(Structure of Exposure Mask) First, the structure of the exposure mask of the present invention will be described. FIG. 1 is a plan view of an exposure mask of the present invention. In the figure, 1 is an exposure mask,
2 is a transparent substrate of the exposure mask, 3 is a mask pattern portion, 4 is a black solid portion corresponding to a blank portion of a thin metal plate, and 5 is an alignment mark provided on the black solid portion. The exposure mask 1 is provided on one surface of a hard glass plate having a thickness of 1 to 5 mm,
A mask pattern is formed of a silver salt emulsion or a thin film of hard chromium, and the mask pattern surface is brought into close contact with a metal sheet on which a photoresist film has been formed during exposure.

The thin metal plate is located in a region (rectangular shape shown by a broken line) inside the solid black portion 4 of the exposure mask 1, and the alignment marks 5 are provided in at least two places inside the region.
In the exposure mask of the present embodiment, alignment marks are respectively arranged substantially diagonally on the mask pattern portion, and the alignment marks and the alignment marks formed by perforations provided in advance in the thin metal plate are overlapped to adjust the position. This makes it possible to match the product shape processed on the metal thin plate with the mask pattern of the exposure mask.

FIG. 2 is a sectional view of the exposure mask 1 taken along line AA.
2 shows a cross section of a thin metal plate adhered to the exposure mask. In FIG. 2, reference numeral 1 denotes an exposure mask, and 7 denotes a thin metal plate. On the surface of the exposure mask 1 facing the metal sheet 7,
A mask pattern portion 3, a solid black portion 4, and an alignment mark 5 are formed. An optical layer 6 is provided on the other surface of the exposure mask 1 so as to cover the alignment mark portion 5. The optical layer 6 is made of a material that transmits visible light and absorbs ultraviolet light.
A μm polyimide film is adhered to a transparent glass substrate 2 constituting an exposure mask using a transparent adhesive layer having a thickness of 2 to 10 μm.

On the other hand, the metal sheet 7 facing the exposure mask 1
In order to allow the alignment marks 5 formed on the exposure mask 1 to be seen through, the alignment marks 8
Is provided. Further, a photoresist film 9 is formed on the metal sheet 7 so as to cover the entire surface including the hole of the alignment mark 8 formed by the perforation. The back surface of the photoresist film, which is not opposed to the exposure mask 1, is previously exposed and exposed by an exposure device (not shown). This is to prevent plating on the back surface of the thin metal plate.

(Operation of Exposure Mask) Next, the operation of the exposure mask 1 having the above configuration will be described. First, the operation in aligning the metal thin plate and the exposure mask will be described with reference to the drawings. FIG. 3 is a schematic configuration diagram showing an example of a mechanism for aligning the thin metal plate and the exposure mask in an exposure apparatus for exposing and printing a mask pattern on the photoresist film of the thin metal plate 7. In the figure, reference numeral 1 denotes the above-described exposure mask, 10 denotes a mask holding frame for fixing the exposure mask 1, and 7 denotes a thin metal plate on which a photoresist film is formed. As a mechanism for aligning the metal thin plate 7 and the exposure mask 1, first, there is provided an illumination light source 11 and an imaging camera 13 for imaging alignment marks formed on the metal thin plate 7 and the exposure mask 1, respectively. A set of imaging devices is provided.

The image signals of the alignment marks photographed by the two sets of image pickup devices are input to an image processing device 14 for detecting the amount of displacement between the alignment marks of the thin metal plate 7 and the alignment marks of the exposure mask 1. I do. The displacement amount of the alignment mark detected by the image processing device 14 is
A mask holding frame driving device, which is applied to a mask holding frame driving device (not shown) and drives the mask holding frame 10 fixing the exposure mask 1 back and forth, right and left, or rotationally, to adjust the position of the exposure mask 1 with respect to the thin metal plate 7. Have been.

When aligning the position of the metal thin plate 7 with the exposure mask 1, first, the illumination light source 11 provided on the back side of the metal thin plate 7 is turned on. The alignment marks on the exposure mask 1 are illuminated through the perforations provided in the thin plate 7. At the same time, a combined image of the alignment mark 5 of the exposure mask 1 and the alignment mark 8 formed by piercing the thin metal plate 7 is captured by the imaging camera 13 provided on the exposure mask 1 side. At this time, the illumination light 12 emitted from the illumination light source 11 is preferably a visible light that does not include ultraviolet light or an infrared light. The ultraviolet light included in the illumination light 12 emitted from the illumination light source 11 is:
It is desirable to cut it using an ultraviolet absorption filter (not shown).

The illuminating light 12 that has passed through the alignment mark 8 formed by the perforation of the thin metal plate 7 is, as shown by a broken line in FIG.
The alignment mark portion 5 of the exposure mask 1 is irradiated, and the transparent glass substrate 2 and the optical layer 6 that transmits visible light are further irradiated.
And enters the imaging camera 13. Imaging camera 13
Are focused on the alignment mark 5 of the exposure mask 1 and the alignment mark 8 formed by perforating the thin metal plate 7, and a composite image of these is captured by the imaging camera 13.

The composite image signal of the two alignment marks captured by the image capturing camera 13 is input to the image processing device 14, where the contrast is adjusted to a binary image signal.
On the basis of the binary image signal, a shift amount between the perforation of the thin metal plate 7 and the alignment mark of the exposure mask 1 is detected.
A position adjustment amount of the exposure mask 1 is calculated based on the shift amount, and a mask holding frame driving device (not shown) is driven to move the mask holding frame 10 to which the exposure mask 1 is fixed,
The position of the exposure mask 1 is adjusted. When the alignment between the metal thin plate 7 and the exposure mask 1 is completed, the metal thin plate 7 is brought into close contact with the exposure mask 1, and the mask pattern is exposed on the photoresist film 9 formed on the metal thin plate 7.

(Structure and Operation of Exposure Apparatus) FIG. 4 is a schematic sectional view showing an example of the exposure apparatus of the present invention. In the figure, reference numeral 1 denotes an exposure mask, and the exposure mask 1 is fixed to a mask holding frame 10. On the other hand, the metal sheet 7 on which the photoresist film is formed is brought into close contact with the exposure mask 1 fixed to the mask holding frame 10 by means not shown. The exposure apparatus 20 includes an exposure light source 21 at a predetermined distance from the exposure mask 1, and an exposure light beam 22 including ultraviolet rays emitted from the exposure light source 21 around the exposure light source 21. Is provided with a light reflection plate 23 for efficiently and uniformly irradiating the light toward the exposure mask 1.

The exposure of the mask pattern to the photoresist film 9 formed on the metal thin plate 7 is performed by an exposure light source 21 provided in an exposure device 20. As the exposure light source 21 of the present embodiment, a xenon lamp, a low-pressure mercury lamp,
A high-pressure mercury lamp, an ultra-high-pressure mercury lamp, or the like is used, and the wavelength is 25.
A light beam including ultraviolet rays such as 3 nm, 365 nm, 406 nm, and 435 nm is passed through the exposure mask 1 and the metal sheet 7.
Irradiate the photoresist film formed on the substrate. When the exposure mask 1 is irradiated with the ultraviolet light having the above-mentioned wavelength, a light pattern corresponding to the mask shape is applied to the photoresist film 9 of the thin metal plate 7 in the mask pattern portion 3 of the exposure mask 1, and the mask pattern is printed.

On the other hand, in the alignment mark portion 5 of the exposure mask 1, as shown in FIG. 2, an optical layer that absorbs the ultraviolet rays by 90% or more is provided on the exposure light source side of the exposure mask 1. Ultraviolet rays emitted from the light source 21 for exposure to the exposure mask 1 are absorbed in the optical layer 6 and the alignment marks 5 of the exposure mask 1 are not printed on the photoresist film 9 formed on the thin metal plate 7. .
1 and 2, a solid black portion 4 is provided around the mask pattern portion 3, and as a result,
The margins of the metal sheet are not irradiated with ultraviolet light for curing the photoresist film.

After the exposure of the mask pattern is completed using the exposure device 20 in the above-described procedure, the thin metal plate is sent to a developing step to develop the photoresist film. As described above, no development residue of the photoresist film including the alignment mark is generated in the blank portion of the thin metal plate exposed to the mask pattern using the exposure mask and the exposure apparatus of the present invention. Therefore, it is possible to eliminate poor contact of the plating electrode in the plating process in the subsequent step, thereby preventing variation in plating thickness, and further eliminating unnecessary work such as removal of dirt due to adhesion of the photoresist film to the plating electrode. become.

(Other Embodiments) In the exposure apparatus shown in the above embodiment, as shown in FIG. 3, an illumination light source used for aligning a thin metal plate and an exposure mask is provided on the back side of the thin metal plate. Is provided between the imaging camera 13 and the exposure mask 1, a half mirror inclined at 45 ° is provided, and illumination light is emitted toward the half mirror to illuminate the alignment mark of the exposure mask and the metal thin plate. A coaxial epi-illumination method may be used. In that case, illumination light including ultraviolet light can be used as the illumination light.

Because, as shown in FIG. 2, the optical layer 6 for absorbing ultraviolet light is provided at the alignment mark portion of the exposure mask, which is the passage of the illumination light, as shown in FIG.
The illumination light passing through the alignment mark portion causes the alignment mark portion 8 to be formed by a perforation provided in the metal sheet 7.
The photoresist film is not irradiated with ultraviolet rays, so that the alignment mark of the exposure mask is not printed on the photoresist film. Further, as another configuration of the exposure apparatus, the arrangement of the illumination light source and the imaging camera used for alignment between the metal thin plate and the exposure mask can be exchanged.

Further, the above-described exposure mask and exposure apparatus of the present invention can be used not only for etching and plating of a lead frame for a semiconductor integrated circuit, but also for photo-etching, electroforming, and liquid crystal of a semiconductor integrated circuit and a printed wiring board. It should be noted that the present invention can be used in various fields such as a process for processing a color filter and an electrode of a display device and a plasma display, and a process for manufacturing a shadow mask for a color CRT.

[0027]

As described above in detail, in the exposure mask of the present invention, as described in claim 1, an optical layer that transmits visible light and absorbs ultraviolet light is provided at the alignment mark portion. It is possible to prevent the exposure of the alignment mark portion from being exposed to the photoresist film without hindering the transmission of the alignment illumination light source in the exposure apparatus and efficiently absorbing the ultraviolet light contained in the mask pattern exposure light beam. . Further, in the exposure mask of the present invention, in addition to the first aspect of the present invention, since the optical layer is formed of a polyimide film, the efficiency of ultraviolet absorption is high and the durability of the optical layer is excellent. Further, in the exposure mask of the present invention, in addition to the first or second aspect of the present invention, the optical layer is adhered to a non-pattern surface of the exposure mask using a transparent adhesive material layer. An optical layer that transmits visible light and absorbs ultraviolet light can be easily formed on an exposure mask without damage.

Further, according to a fourth aspect of the present invention, there is provided an exposure apparatus, comprising irradiating an ultraviolet ray using the exposure mask according to the first, second or third aspect of the present invention to align the position. Since the pattern excluding the mark is exposed on the photoresist film formed on the metal thin plate, no resist remains on the alignment mark portion of the metal thin plate. This has the effect of preventing an increase in contact resistance and always obtaining a stable plating thickness.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of an exposure mask of the present invention.

FIG. 2 is a partial cross-sectional view of the exposure mask shown in FIG.

FIG. 3 is a schematic configuration diagram of an exposure mask alignment mechanism.

FIG. 4 is a schematic sectional view showing an example of an exposure apparatus.

FIG. 5 is an external perspective view of an exposure mask and a thin metal plate.

FIG. 6 is a plan view showing an example of an alignment mark of an exposure mask.

FIG. 7 is a perspective view showing an example of remaining resist at the alignment mark portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exposure mask 2 Transparent glass substrate 3 Mask pattern part 4 Solid black part 5 Alignment mark 6 Optical layer 7 Metal thin plate 8 Alignment mark by perforation 9 Photoresist film 10 Mask holding frame 11 Illumination light source 12 Illumination light 13 Imaging camera 14 Image processing device 20 Exposure device 21 Exposure light source 22 Exposure light beam 23 Light reflector

Claims (4)

[Claims] 1. An exposure mask, wherein an optical layer that transmits visible light and absorbs ultraviolet light is provided on the alignment mark portion. 2. The exposure mask according to claim 1, wherein the optical layer is a polyimide film. 3. The exposure mask according to claim 1, wherein the optical layer is attached to a non-pattern surface of the exposure mask using a transparent adhesive layer. 4. An exposure mask according to claim 1, 2 or 3, which is irradiated with ultraviolet rays to expose a pattern excluding an alignment mark to a photoresist film formed on a thin metal plate. Exposure apparatus characterized by the above-mentioned.