JPS5815537B2 - chemical etching method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a chemical etching method suitable for, for example, printed wiring, and is particularly intended to obtain a method in which the occupancy of conductors in the object to be etched is high.

In conventional printed wiring, a conductor layer 12 is formed on the entire surface of an insulating substrate 11, as shown in FIG. form.

The resist layer 13 is formed by, for example, screen printing or photography.

Thereafter, the conductor layer 12 was chemically etched using the resist layer 13 as a mask.

In this case, as shown in FIG. 2, the portion of the conductor layer 12 that is not masked by the resist layer 13 is not only etched in the direction perpendicular to the plate surface, and in the Y direction in FIG. It is also etched in the direction along the X direction in FIG.

This etching in the direction along the plate surface is called side etching, and the speed of this side etching is the same speed as the etching speed in the direction perpendicular to the plate surface (in the Y direction in the figure). Conductor layer 12
The side surface is a concave curved surface with an arcuate cross section.

Originally, it is desirable that the pattern be etched from the edge of the resist layer 13 at right angles to the conductor layer.
The side etched portions 15 shown in the figures are not preferred.

If such side etched portions 15 exist, it becomes difficult to narrow the width of the conductor layer pattern 16 formed by etching, and it becomes difficult to form the conductor layer pattern 16 in a fine pattern with high density. Become.

An object of the present invention is to provide a chemical etching method that enables the formation of fine patterns with high density.

According to this invention, an etching-resistant mask layer is formed in a predetermined pattern on an object to be etched, and the object to be etched is chemically etched using the mask layer as a mask.

A re-etched corrosion-resistant layer is formed on the side etched surfaces generated by the chemical etching, and then the object to be etched is etched again using the mask layer and the corrosion-resistant layer as a mask.

This process is repeated as necessary.

By doing this, the etching process is not performed all at once, and a corrosion-resistant layer is formed on the side-etched area as soon as it is etched to the extent that it is etched, thereby preventing the side-etching area from becoming larger and forming a fine, high-density pattern. It is also possible to form

By the way, in order to form a corrosion-resistant layer on the side-etched surface, make sure that the light does not reach the part of the object to be etched that is in contact with the mask layer, and form a positive type photoresist layer on the entire surface including the side-etched part and the mask layer. Utilizing the fact that the side-etched portion becomes a shadow of the previous mask layer during subsequent exposure, a corrosion-resistant layer is formed on the side-etched surface, leaving the positive type photoresist.

Generally, the mask layer is made of photoresist and is often light-transmissive, and in such cases it no longer functions as a mask, so it is necessary to make it act as an optical mask when exposing a positive type photoresist. The mask layer can be treated in advance to block light.

Next, an embodiment of the chemical etching method according to the present invention will be described.

First, as shown in FIG. 1, for example, a conductor layer formed on the entire surface of an insulating substrate 11 is used as an object to be etched, and an etching-resistant mask layer 13 is formed in a predetermined pattern on the object to be etched 12. do.

This mask layer is, for example, Kodak's KMERl so-called Kodak micro etch resist, which is a rubber-based negative type photosensitive resin that hardens in the exposed areas when exposed to light.

This resist is generally optically transparent.

The mask layer 13 is formed into a predetermined pattern using such a resist, and has a thickness of, for example, 5 μm.

The thickness of the conductor layer 12 is, for example, 30μ.

The conductor layer 12 is etched using the mask layer 13 as a mask, and the etching depth is, for example, approximately half the thickness of the conductor layer 12.

The situation is shown in Figure 3.

By this etching, side etched portions 17 are formed.

A corrosion-resistant layer is formed on the side etched surface of this side etched portion 17.

To form this corrosion-resistant layer, the mask layer 13 of the object 12 to be etched is
A light blocking means is provided to prevent light from reaching the portion in contact with.

For example, a light blocking layer is formed on the mask layer 13.

As the light blocking layer, light absorbing particles such as carbon fine particles are adsorbed.

As shown in FIG. 4, a liquid 24 in which carbon black is dispersed in a photoresist developer or paraffin hydrocarbon is placed in a container 23, and a mask layer 13 is formed in the liquid 24 as shown in FIG. A sample 25 is placed therein, and an ultrasonic wave is made to enter the container 23 from below the container 23 using an ultrasonic transducer 26, that is, into the liquid 24.

This is a so-called ultrasonic bath, and when the liquid is a developer or paraffin hydrocarbon liquid in which carbon black is dispersed, and when ultrasonic waves are applied to the liquid, the carbon black agglomerates are dispersed into fine particles. The fine particles are uniformly adsorbed as a layer on the surface of the mask layer 130.

In this way, the carbon particles are distributed in various parts, especially in the mask layer 13.
The carbon particles collide with the surface many times, and the carbon particles are adsorbed as a layer.

If the mask layer 13 is formed and placed in the ultrasonic bath while the rubber resist mask layer 13 is still swollen due to development, carbon particles will be better absorbed.

If the mask layer 13 is simply immersed flatly in a liquid in which card black is dispersed without applying ultrasonic waves, the carbon particles will not adhere to the mask layer 13 uniformly, but will harden and adhere.
It also becomes easy to peel off.

The carbon black preferably has small particles of 0.5 μm or less.

It is also possible to attach carbon black to the mask layer 13 with a brush, but in that case there is a risk of damaging the mask layer 13.

Deposition of carbon black using an ultrasonic bath is for example 3
A sufficiently uniform carbon black layer can be obtained by carrying out this process for about 0 seconds.

In the above manner, as shown in FIG.
After depositing the photoresist layer 13 on the mask layer 13, etching is performed as shown in FIG. As shown in FIG. 6, the conductor layer 12,
It also adheres to the mask layer 13 and side etched portions 17.

Next, the photoresist layer 27 is exposed by irradiating half-line light perpendicularly to the substrate 11, and only the portion irradiated with the light is melted away by development, and the conductor of the side etched portion 17 is removed as shown in FIG. A corrosion-resistant layer 18 made of a photoresist layer 27 is formed only on the surface of the layer 120, that is, on the side etching surface 21 and the surface of the mask layer 13 on the conductor layer side.

Thereafter, using the mask layer 13 and the corrosion-resistant layer 18 as masks, the old conductor layer 12 on which the corrosion-resistant layer 18 has been formed is etched in the same manner as described above to obtain a desired conductor pattern 22 as shown in FIG. 8, for example.

Furthermore, if necessary, an insulating layer 28 may be formed on the surface of the conductor pattern 22 as shown in FIG.

As light-absorbing particles, in addition to carbon particles, silver particles, mercury sulfide, chromium sulfide, etc. can also be used.

In this way, by performing the etching in two rounds and forming one layer of the corrosion-resistant layer 18 during the first etching, the depth of the side etching, that is, the length of the side etching in the direction along the surface of the mask layer 130, can be reduced. The width of the conductor pattern 220 is approximately half that of the case shown in FIG. 2, and the width of the conductor pattern 220 is wider than that shown in FIG.

After the layer 20 of light-absorbing particles was formed on the surface of the mask layer 13 in this way, it was etched, and then a positive type photoresist was applied. Instead of adsorbing such photoimage particles, a dye, such as a lipophilic dye such as red or black, may be diffused into the mask layer 13.

This diffusion can be achieved by mixing a dye that absorbs light at the wavelength at which the positive type photoresist layer 27 is sensitive to, for example, paraffin hydrocarbons or benzene hydrocarbons, and adding the mask layer 27 to the solution.
3 is immersed, for example, for about 2 hours or more to disperse the dye into the mask layer 13.

The subsequent treatment can be carried out in the same manner as described above for adsorption of carbon black.

Alternatively, as shown in FIG. 10, the surface of the conductor layer 12 may be coated with a solvent-soluble black color or a light-absorbing paint that absorbs short wavelength light, such as acrylic paint or vinyl paint containing pigments such as carbon black or other colors. forming a layer 29;
A photoresist layer 31 is formed thereon.

This) first resist layer 31 is selectively exposed to light to form a mask layer 13 as shown in FIG. The conductor layer 12 is removed and then etched to etch a portion of the conductor layer 12 into the state shown in FIG.

Thereafter, as described above, a positive type photoresist layer 27 is formed to form a corrosion-resistant layer, and further etching is performed again in the same manner as in the previous example.

In this case, when side etching is performed in the first etching, the light absorbing layer 29 on the back surface of the mask layer 13 is made of a material that remains adsorbed to the mask layer and cannot be peeled off by the N etching solution.

Therefore, the processing shown in FIGS. 6 and 7 can be performed.

Further, to form the corrosion-resistant layer 18, for example, after performing the first etching as shown in FIG. 3, a positive type resist layer 27 is formed as shown in FIG.

In this case, as the positive type first resist layer 27, one that is photosensitive at the wavelength of light absorbed by the first mask layer 13 is used.

In this way, the positive type resist layer 27 is not exposed to light in the portions shaded by the mask layer 13, so that by developing it, a corrosion-resistant layer 18 is obtained as shown in FIG.

Although the light blocking layer 29 is formed of paint as shown in FIG. 10, a metal layer that is not corroded by the etching solution for the conductor layer 12 which is the object to be etched may be used instead.

That is, in FIG. 10, for example, aluminum is used as the light blocking layer 29 and copper is used as the conductive layer 12, and the aluminum layer 29 is formed on the conductive layer 12 to a thickness sufficient to block light, for example, several microns or more. , and a resist layer 31 thereon.
As described above, the mask layer 3 is formed on the resist layer 31 as shown in FIG. 29 was etched as shown in Figure 12, and then etched with nitric acid or Fe(NO3)s.
The conductor layer 12 is etched to the middle of its thickness using an etching solution such as etching solution (FIG. 13).

Next, as described with reference to FIG. 6, a positive type resist layer 27 is formed and exposed.

At this time, since the aluminum layer 29 is not etched when etching the conductor layer 12, the aluminum layer 29 remains in the side etched portion 17, and the light is blocked by the aluminum layer in the side etched portion. Form the corrosion-resistant layer 18 in the same manner as described above.
You can do it.

As described above, according to the chemical etching method according to the present invention, it is possible to form relatively wide conductor patterns even in fine patterns in close proximity to each other, and also to form relatively thick conductor patterns. be able to.

For example, when the width of the mask layer 130 is 80μ and the interval between the mask layers 130, that is, the width of the etched portion is 20μ, that is, when forming a conductor pattern at a pitch of 0.1 mm, the thickness of the conductor layer 12 is about 30μ. By etching the material in two steps as in the previous example, it was possible to reduce the resistance value of the conductor pattern 22 to about 1/2 compared to the conventional case where etching was performed only in two steps. .

Moreover, mask alignment only needs to be done once, and even fine patterns can be formed with high precision.

A positive type photoresist layer can be formed in close contact with the side etched portion, and from this point of view as well, fine patterns can be formed thickly.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional views for explaining the conventional chemical etching method, FIG. 3 is a cross-sectional view showing the first etching state in this invention, and FIG. 4 is a mask layer with light-absorbing fine particles. 5 is a sectional view showing a state in which a light absorption layer has been formed. FIG. Fig. 7 is a cross-sectional view showing an example in which a corrosion-resistant layer is formed using a positive type photoresist layer, Fig. 8 is a cross-sectional view showing a state in which the second etching process is applied to Fig. 7, and Fig. 9 is a cross-sectional view showing an example of a corrosion-resistant layer formed with a positive type photoresist layer. FIG. 10 is a cross-sectional view showing a state in which a light blocking layer is formed, and FIGS. 11 to 13 are cross-sectional views showing steps of chemical etching in the case where a light blocking layer is formed. It is a diagram. 11: Insulating substrate, 12: Conductor layer as an object to be etched, 13
: Etching resistant mask layer, 17: Side etching portion, 18: Corrosion resistant layer, 28: Insulating layer, 29: Light blocking layer.

Claims (1)

[Scope of Claims] 1. A step of forming an etching-resistant mask layer of a predetermined pattern on an object to be etched, a step of chemically etching the object to be etched using the mask layer as a mask, and a mask layer of the object to be etched. After the light shielding step to prevent light from reaching the part in contact with the object and the above chemical etching, a positive type photoresist layer is formed, exposed and developed to form a positive type photoresist layer on the side-etched surface of the object to be etched. A chemical etching method comprising the steps of forming an etching-resistant and corrosion-resistant layer while leaving a resist layer, and then chemically etching the object to be etched again using the mask layer and the corrosion-resistant layer as a mask. 2. The chemical etching method according to claim 1, wherein the light blocking step is a step of forming a light-absorbing fine particle layer on the surface of the mask layer. 3. The chemical etching method according to claim 1, wherein the light blocking step is a step of diffusing dye into the mask layer. 4. The light blocking step includes forming a light blocking layer between the object to be etched and the mask layer, and then forming the mask layer and removing the light blocking layer while being masked by the mask layer. A chemical etching method according to claim 1, comprising: 5. The chemical etching method according to claim 4, wherein the light blocking layer is a layer containing a black dye that absorbs light. 6. The chemical etching method according to claim 4, wherein the light blocking layer is a conductive layer and is made of a material that is resistant to corrosion when etching the object to be etched.