JPH08160625A - Photolithography method - Google Patents

Abstract

PURPOSE: To manufacture a board having a desired pattern in a short time by constituting the photosensitive process with the first process forming the desired pattern on a space modulation element with the first light and the second process projecting the pattern formed on the spatial modulation element on the resist layer on the board with the second light. CONSTITUTION: A pattern forming device is constituted of a space modulation element 2 storing a circuit pattern, a pattern drawing device 1 writing the desired circuit pattern on the spatial modulation element 2, and a pattern exposing device 3 reading the circuit pattern written on the spatial modulation element 2 and projecting it on a board 4. The desired pattern is formed on the spatial modulation element 2 by the first light in the first process, and the pattern formed on the spatial modulation element 2 is projected to a resist layer on the board 4 by the second light in the second process. A masking original film recording the pattern is not required to be prepared.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a photolithography method.

[0002]

2. Description of the Related Art A printed wiring board is a copper foil on an insulating substrate on which electrical wiring for connecting circuit components is formed.
Widely used in various electronic devices. As the insulating substrate, in addition to hard materials such as a paper phenol resin laminated plate and a paper epoxy resin laminated plate, a polymer film such as polyimide or polyester is used. The latter is generally called a flexible printed circuit board, and by making use of its thinness and flexibility, it plays a major role in making electronic devices thinner, smaller, and higher in density. The wiring pitch is about 100μ for connecting the driver of the liquid crystal display.
m has been put to practical use.

When manufacturing such a printed wiring board, as shown in FIG.
As shown in FIG. 1, first, a circuit pattern is created from a design drawing, and a film original plate on which the circuit pattern is formed is manufactured by using a photograph or a light spot drawing machine. Then, the printed wiring board is manufactured by etching the copper foil on the insulating substrate using the film original plate as a photomask.

[0004]

However, the above-mentioned conventional structure has a problem that a printed wiring board cannot be rapidly manufactured because it is necessary to manufacture a film original plate on which a circuit pattern is formed in advance. . In particular, when a design change is required, a new film original plate has to be manufactured again, which is troublesome.

Further, since it is necessary to secure a place for storing the film original plate in a clean room and prepare a stocker so that a desired film original plate can be immediately taken out, it is necessary to store and manage it. I have a problem.

[0006]

In order to solve the above-mentioned problems, a photolithography method according to the invention of claim 1 comprises a step of exposing a resist layer on a substrate to a desired pattern, and a resist which has been exposed. In the photolithography method including a developing step of developing the layer and an etching step of etching the substrate using the resist layer remaining after the development as a mask, in the above-mentioned exposing step, a desired pattern is formed by the spatial modulation element with the first light. And the second step of projecting the pattern formed on the spatial modulation element onto the resist layer on the substrate by the second light.

In order to solve the above-mentioned problems, a photolithography method according to a second aspect of the present invention is the photolithography method of the first aspect, characterized in that a spatial modulator having a pattern self-holding function is used. I am trying.

In order to solve the above-mentioned problems, a photolithography method according to a third aspect of the present invention is the photolithography method according to the first aspect, characterized in that laser light is used as the first light.

In order to solve the above-mentioned problems, the photolithography method according to a fourth aspect of the present invention is the photolithography method according to the second aspect, wherein the spatial modulation element comprises a photoconductor layer and a surface stabilizing layer. The liquid crystal layer including a dielectric liquid crystal and a pair of transparent electrodes sandwiching the liquid crystal layer are provided.
An AC voltage is applied between the transparent electrodes in the step, and an AC voltage is not applied between the transparent electrodes in the second step.

[0010]

According to the structure of claim 1, in the first step,
A desired pattern is formed on the spatial modulation element by the first light. Then, in the second step, the pattern formed on the spatial modulation element is projected onto the resist layer on the substrate by the second light. Thereby, the resist layer can be exposed to a desired pattern. Therefore, it is not necessary to prepare a film original plate for a mask on which a pattern is recorded, and a substrate having a desired pattern can be manufactured in a short time. Moreover, since the pattern formed on the spatial light modulator can be freely rewritten, it is possible to immediately respond to the change of the pattern accompanying the design change. Further, since the pattern formed on the spatial modulation element can be managed by a computer as numerical data, it can be managed and stored much more easily than a film original plate.

According to the configuration of claim 2, since the spatial modulation element having the pattern self-holding function is used, in addition to the effect of claim 1, the pattern can be stored in the spatial modulation element for a long period of time.

According to the structure of claim 3, since laser light is used as the first light, in addition to the function of claim 1,
It is possible to accurately form a fine pattern. As a result, a substrate having a desired pattern can be manufactured with a high yield.

According to the structure of claim 4, in addition to the function of claim 2, since the alternating voltage is applied between the transparent electrodes in the first step, the pattern can be written in the liquid crystal layer, and the second step. Since no AC voltage is applied between the transparent electrodes, the boundary of the pattern projected on the resist becomes clear. This improves the definition and accuracy of the pattern.

[0014]

The first embodiment of the present invention will be described below with reference to FIGS.

As shown in FIG. 1, the pattern forming apparatus of this embodiment includes a spatial modulation element 2 for storing a circuit pattern,
It comprises a pattern drawing device 1 for writing a desired circuit pattern on the spatial modulation element 2 and a pattern exposure device 3 for reading the circuit pattern written on the spatial modulation element 2 and projecting the read circuit pattern on the substrate 4. .

The pattern drawing apparatus 1 includes an XY movable stage 11 on which the spatial modulation element 2 is mounted (the XY plane is perpendicular to the paper surface), and He for writing a circuit pattern on the spatial modulation element 2.
-Ne laser 12 (oscillation wavelength 0.633 μm) and a circuit pattern are designed, and He-Ne laser 12
A CAD (computer-aided design) machine 5 for controlling the He-Ne laser 12 and the XY movable stage 11 so as to draw a circuit pattern on the spatial modulation element 2 with the laser light (first light) from A power source 6 for applying an AC voltage to the modulation element 2 is provided.

As shown in FIG. 2, the spatial modulation element 2 includes, in order from the glass substrate 21a, a transparent electrode 22a, a photoconductor layer 23, a light shielding layer 24, a dielectric mirror layer 25, and a light modulation layer for storing a circuit pattern. Liquid crystal layer 26 as a transparent electrode 22
b, the glass substrate 21b is laminated. H
The laser light from the e-Ne laser 12 is the glass substrate 2
It is incident from 1a.

The spatial modulator 2 is specifically made of, for example, the following materials. The transparent electrodes 22a and 22b are
Each has a structure in which an oxide of indium and tin (ITO) and tin oxide (SnO ₂ ) are laminated. The photoconductor layer 23 is made of amorphous silicon (a-Si: H). The light shielding layer 24 is made of amorphous silicon-germanium (a-SiGe: H). The dielectric mirror layer 25 has a structure in which titanium dioxide (TiO ₂ ) and silicon dioxide (SiO ₂ ) are alternately laminated. The liquid crystal layer 26 is a surface-stabilized ferroelectric liquid crystal (S) having a self-alignment memory function (so-called memory property).
SFLC).

The pattern exposure apparatus 3 (FIG. 1) includes a mercury lamp 31, and a condenser lens 32 that collects divergent light (second light) from the mercury lamp 31 and converts it into parallel light.
Of the light transmitted through the UV-IR cut filter 33 and the UV-IR cut filter 33 that cuts UV (ultraviolet) and IR (infrared) from parallel light, only linearly polarized light is directed to the spatial modulation element 2. Of the return light from the spatial modulation element 2, the polarization beam splitter 34 that transmits only the light whose polarization plane is rotated according to the circuit pattern written in the spatial modulation element 2 and the polarization beam splitter 34 is transmitted. And a projection lens 35 that projects the reflected light onto the substrate 4.

The substrate 4 is composed of an insulating substrate, a copper foil formed on the insulating substrate, and a resist coated on the copper foil.

In the above structure, first, the CAD machine 5 of the pattern drawing apparatus 1 designs a desired circuit pattern. Then, the transparent electrodes 22a and 2 of the spatial light modulator 2
An alternating voltage from the power source 6 is applied between the power source 6 and the 2b. In this state, by controlling the He-Ne laser 12 and the XY movable stage 11 with the CAD machine 5, the He-Ne-
A circuit pattern is drawn on the spatial modulation element 2 with laser light from the Ne laser 12 (first step).

When the spatial modulation element 2 is irradiated with the laser light from the glass substrate 21a side, the impedance of the portion of the photoconductor layer 23 irradiated with the laser light is lowered. Therefore, the voltage drop in the photoconductor layer 23 is reduced, and the voltage from the power source 6 is applied to the portion of the liquid crystal layer 26 in contact with the photoconductor layer 23. As a result, the alignment state of liquid crystal molecules in the liquid crystal layer 26 changes. In other words, the liquid crystal layer 26
The circuit pattern is recorded on the spatial modulation element 2 by changing the orientation of the liquid crystal molecules according to the circuit pattern.

When the surface-stabilized ferroelectric liquid crystal having a self-orientation memory function is adopted for the liquid crystal layer 26, after the circuit pattern is recorded on the spatial modulation element 2, the power source 6 for applying an alternating voltage to the spatial modulation element 2 is used. Turn off.

The circuit pattern written in the spatial modulation element 2 is read out by the pattern exposure device 3 and the substrate 4
(2nd step). That is, the divergent light from the mercury lamp 31 containing the light of the photosensitive wavelength of the resist is condensed by the condenser lens 32 and converted into parallel light. For parallel light, unnecessary UV and IR components are UV-
After being cut by the IR cut filter 33, it enters the polarization beam splitter 34. The polarization beam splitter 34 allows the spatial modulation element 2 to output only linearly polarized light.
Reflected in the direction of. Then, the return light from the spatial modulation element 2 enters the polarization beam splitter 34 again.

The plane of polarization of the linearly polarized light incident on the spatial modulation element 2 from the glass substrate 21b side is rotated according to the orientation of the liquid crystal molecules of the liquid crystal layer 26. The light whose polarization plane is rotated passes through the polarization beam splitter 34. The light transmitted through the polarization beam splitter 34, that is, the spatial modulation element 2
The circuit pattern read from is projected on the substrate 4 in a reduced size by the projection lens 35. As a result, the resist on the substrate 4 is exposed according to the circuit pattern.

After that, a known photolithography process, that is, development of a resist and etching for removing an unnecessary copper foil by using the remaining resist as a mask are performed, so that a desired circuit pattern is formed on the insulating substrate. It is possible to obtain a printed wiring board formed by.

According to the pattern forming apparatus of this embodiment, a desired printed wiring board can be directly produced from numerical data such as CAD data representing a circuit pattern as shown in FIG. It eliminates the need for original film. Therefore, the manufacturing period of the printed wiring board can be significantly shortened. Therefore, the cost of the printed wiring board can be reduced. Moreover, it is possible to quickly respond to the design change of the circuit pattern.

Further, since the circuit pattern can be stored as numerical data, the circuit pattern can be managed much more easily by using a computer such as the CAD machine 5 as compared with the conventional film original plate.

Furthermore, the liquid crystal layer 26 of the spatial modulation element 2
By adopting the surface-stabilized ferroelectric liquid crystal having the self-orientation memory function, it is possible to form a circuit pattern having excellent definition and precision. As a result, it becomes possible to manufacture the printed wiring board with a high yield.

The fineness and precision of the circuit pattern are influenced by the operation mode of the liquid crystal layer 26 in the spatial modulation element 2. That is, the intensity of the laser light (writing light) exhibits a Gaussian distribution, as shown in FIG. For this reason,
When the liquid crystal layer 26 is operated in the electric field control type birefringence mode in which the liquid crystal molecules respond in proportion to the electric field strength, when the laser light from the He—Ne laser 12 is irradiated to an arbitrary position of the spatial modulation element 2, The impedance of the photoconductor layer 23 changes according to the intensity of the laser light, as shown in FIG. As a result, the intensity of the projection light (readout light) obtained by the pattern exposure apparatus 3 also changes according to the intensity of the laser light at the time of writing, as shown in FIG. The boundary of the circuit pattern becomes unclear. As a result, the definition and accuracy of the circuit pattern are reduced.

On the other hand, when the surface-stabilized ferroelectric liquid crystal having a self-alignment memory function is adopted for the liquid crystal layer 26, the electric field strength is the same as in the electric field control type birefringence mode while the electric field is applied. The liquid crystal molecules respond in proportion to, but when the application of the electric field is stopped, the part where the electric field strength is above a certain threshold value is in the bright state, and the part where the electric field strength is below the certain threshold value is in the dark state. As a result, the intensity of the projection light (readout light) obtained by the pattern exposure device 3 does not depend on the intensity of the laser light at the time of writing, as shown in FIG. The boundaries of the pattern become clear. This improves the definition and accuracy of the circuit pattern.

The second embodiment of the present invention will be described below with reference to FIG. For convenience of explanation, members having the same functions as those of the members shown in the drawings of the above-described embodiments are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 5, the pattern forming apparatus of the present embodiment is provided with a pattern drawing apparatus 1'for fixing a spatial modulation element 2 and writing a circuit pattern by scanning a laser beam. It differs from the previous embodiment.

The pattern drawing apparatus 1'is based on the CAD machine 5 for designing a circuit pattern, the He-Ne laser 12 for writing the circuit pattern in the spatial modulation element 2, and the numerical data of the circuit pattern designed by the CAD machine 5. An optical modulator 62 that modulates the laser light from the He-Ne laser 12, a rotating polygon mirror 63 that scans the laser light from the optical modulator 62, and a laser light from the rotating polygon mirror 63 is applied to the spatial modulation element 2. And an illuminating optical system including a relay lens 64, a cylindrical lens 65, a relay lens 66, and a rotating galvanometer mirror 67.

In the above structure, first, a desired circuit pattern is designed by the CAD machine 5 of the pattern drawing apparatus 1 '. Then, an AC voltage from the power supply 6 is applied between the transparent electrodes 22a and 22b of the spatial light modulator 2. In this state, the laser light from the He-Ne laser 12 is modulated by the optical modulator 62 based on the numerical data of the circuit pattern designed by the CAD machine 5. Light modulator 6
The laser light from 2 is scanned by the rotating polygon mirror 63, and the spatial modulation element 2 is irradiated with the optical system from the relay lens 64 to the rotating galvanometer mirror 67. As a result, a circuit pattern is drawn on the spatial modulation element 2 with the laser light from the He-Ne laser 12.

Thereafter, a desired circuit pattern is formed on the substrate 4 and a printed wiring board is obtained in the same manner as in the above embodiment.

In the present embodiment, the spatial modulation element 2 is fixed, and the spatial modulation element 2 is scanned by laser light.
Since the circuit pattern is written on the
The circuit pattern can be written quickly and accurately. Therefore, the definition and accuracy of the circuit pattern are further improved.

Although the formation of the circuit pattern by the pattern forming apparatus has been described in the above embodiments, the present invention is not limited to this, and the photolithography method of this embodiment can be applied to various pattern formations.

[0039]

As described above, in the photolithography method according to the first aspect of the present invention, the photolithography step includes the first step of forming a desired pattern on the spatial modulation element by the first light and the spatial modulation element. And a second step of projecting the formed pattern on the resist layer on the substrate by the second light.

According to this, since it is not necessary to prepare a film original plate, a substrate having a desired pattern can be manufactured in a short time. Moreover, since the pattern formed on the spatial light modulator can be freely rewritten, it is possible to immediately respond to the change of the pattern accompanying the design change. Further, since the pattern formed on the spatial light modulator can be managed by a computer as numerical data, there is an effect that it can be managed and stored much more easily than a film original plate.

As described above, the photolithography method according to the invention of claim 2 is the photolithography method of claim 1, wherein the spatial modulation element having a pattern self-holding function is used.

According to this, in addition to the effect of the first aspect, there is an effect that the pattern can be stored in the spatial modulation element for a long time.

As described above, the photolithography method according to the invention of claim 3 is the photolithography method of claim 1, wherein the laser light is used as the first light.

According to this, in addition to the effect of the first aspect, it is possible to form a fine pattern with high precision, and thus it is possible to produce a substrate having a desired pattern with a high yield.

As described above, the photolithography method according to the invention of claim 4 is the photolithography method of claim 2, wherein the spatial modulation element comprises a photoconductor layer and a surface-stabilized ferroelectric liquid crystal. The liquid crystal layer and the pair of transparent electrodes sandwiching these liquid crystal layers are provided, and an AC voltage is applied between the transparent electrodes in the first step, and an AC voltage is not applied between the transparent electrodes in the second step.

According to this, in addition to the effect of claim 2, the boundary of the pattern projected on the resist becomes clear.
This has the effect of improving the definition and accuracy of the pattern.

[Brief description of drawings]

FIG. 1 illustrates a first embodiment of the present invention, and is a schematic configuration diagram of a pattern forming apparatus.

FIG. 2 is a vertical cross-sectional view showing the configuration of a spatial modulation element used in the pattern forming apparatus of FIG.

3A and 3B are explanatory views showing a method for manufacturing a printed wiring board by the pattern forming apparatus of FIG.

FIG. 4 is an explanatory diagram showing an effect when a liquid crystal layer made of a surface-stabilized ferroelectric liquid crystal is used for the spatial modulation element of FIG.

FIG. 5 illustrates a second embodiment of the present invention and is a schematic configuration diagram of a pattern forming apparatus.

FIG. 6 is an explanatory diagram showing a conventional method for manufacturing a printed wiring board.

[Explanation of symbols]

 2 Spatial Modulation Element 4 Substrate 12 He-Ne Laser 22a Transparent Electrode 22b Transparent Electrode 23 Photoconductor Layer 26 Liquid Crystal Layer 31 Mercury Lamp

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Claims (4)

[Claims] 1. A photosensitive step of exposing a resist layer on a substrate to a desired pattern, a developing step of developing the exposed resist layer, and an etching step of etching the substrate using the resist layer remaining after development as a mask. In the photolithography method including the above, the exposing step includes a first step of forming a desired pattern on the spatial modulation element by the first light, and a pattern formed on the spatial modulation element on the substrate by the second light. A second step of projecting onto a resist layer, the photolithography method. 2. The photolithography method according to claim 1, wherein a spatial modulation element having a pattern self-holding function is used. 3. The photolithography method according to claim 1, wherein laser light is used as the first light. 4. A spatial modulation element comprises a photoconductor layer, a liquid crystal layer made of surface-stabilized ferroelectric liquid crystal, and a pair of transparent electrodes sandwiching these layers. In the first step, a space is provided between the transparent electrodes. The photolithography method according to claim 2, wherein an alternating voltage is applied and no alternating voltage is applied between the transparent electrodes in the second step.