JPH0131292B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma etching method, and more particularly to an improvement in a method of etching a substrate to be processed by exposing it to plasma using a capacitive plasma etching apparatus.

When a negative resist is used as a photosensitive film in electron beam exposure, X-ray exposure, deep ultraviolet exposure, or ultraviolet exposure, after exposure, the negative resist layer is developed in a solution to form a negative. When the resist pattern is formed, the negative and
On the substrate surface from which the resist should be completely removed,
There is a phenomenon in which an extremely thin negative resist layer remains, called scum. Therefore, when wet etching is performed on the substrate surface using the negative resist pattern as a mask in a subsequent step, there is a problem that the etching is inhibited by the scum. Therefore, when forming a mask pattern using a negative resist, the pattern is usually formed by solution development, and then the substrate surface is ashed in air or oxygen plasma, which is called a de-scum treatment. This adds the work of removing only the scum on the board.

In the conventional day scum treatment, as shown in the cross-sectional view of FIG. The substrates 3 to be processed, on which a negative resist pattern has been formed by the above-mentioned exposure and development method on a light-shielding film made of chromium or the like, are inserted side by side, and a pressure of, for example, about 1 Torr is applied in the plasma etching container. Humidified air is supplied to the upper power supply side electrode 4 from a high frequency power source 5 via a capacitor 6 at a frequency of, for example, 13.56 [MHz] 100 to 150.
A high frequency power of about [W] is supplied, the lower ground side electrode 7 is grounded 8, and plasma is generated in the plasma etching container 1. Then, the substrate 3 to be processed is exposed to the plasma, the negative resist layer on the substrate 3 is ashed, and the substrate 3 to be processed is
This method completely removed the negative resist scum adhering to the glass surface. (9 in the figure)
10 indicates an insulating stand, 10 indicates a gas inlet, and 11 indicates a vacuum exhaust port. ) However, in the conventional day scum processing method described above, since a conductive chromium layer is deposited as a light shielding film on the main surface of the substrate 3 to be processed, the power supply to the upper part of the substrate 3 to be processed is The electric field concentrates on the end face near the side electrode 4, plasma concentration occurs near the end face, and the temperature of the surface of the substrate to be processed in contact with the discharge region 12 rises. Therefore, the ashing rate of the negative resist by the plasma in this region increases significantly, and at the time when all the scum on the substrate 3 to be processed is removed, the negative resist in contact with the discharge region 12 increases.
The resist pattern is significantly reduced compared to other areas.

As mentioned above, in the conventional day scum processing method, hard materials such as chrome masks are used to cause variations in the dimensions of the negative resist pattern.
There was a problem that the manufacturing yield of the mask decreased.

In order to eliminate the above-mentioned problems, the present invention provides a plasma etching method in which a capacitive cylindrical plasma etching apparatus is used, and a substrate to be processed is placed vertically in plasma for etching. To provide a plasma etching method that prevents plasma concentration from occurring in contact with the etching material and achieves uniform etching.

That is, the present invention uses a capacitive cylindrical plasma etching apparatus having a power supply side electrode on the top and a ground side electrode on the bottom, and a substrate to be processed whose main surface is coated with a conductive film is placed vertically in the plasma. In the plasma etching method, a composite plate in which a conductive film is adhered to an insulating plate is placed side by side on the back side of the substrate to be processed, and the upper end of the conductive film of the composite plate is attached to the substrate to be processed. The etching is performed by arranging the electrode closer to the power supply side electrode than the upper end of the electrode.

Hereinafter, the present invention will be described in which a light-shielding film made of chromium is provided on a glass substrate, a negative resist layer coated on the light-shielding film is exposed to light such as an electron beam, a solution phenomenon is performed, and then post-baking is performed. An example method shown in FIG. 2 is used to remove scum from a substrate to be processed, which is a chrome mask substrate with a negative resist pattern formed on the chrome film. The details will be explained using a front view a, a front view b taken along arrow A-A′, a longitudinal sectional view of another embodiment shown in FIG. 3, and a longitudinal sectional view of still another embodiment shown in FIG. explain.

That is, in one embodiment of the present invention, FIGS.
For example, 1000 to 2000 on the entire back surface as shown in
Two quartz plates 14 having a corrosion-resistant metal film 13 made of gold or the like formed by a method such as sputtering or vapor deposition with a thickness of about [Å],
The substrate mounting groove 16 formed on the main surface of the quartz plate 14 is placed so that the upper end of the substrate 15 to be processed is at least 20 mm lower than the upper end of the quartz plate 14, as indicated by l in the figure. A substrate holding jig 17 is used, which is connected by being inclined toward the back side at an angle that allows holding the substrate 14 to be processed. Then, the substrate to be processed 15 is mounted in the substrate mounting groove 16 of the substrate holding jig 17, the substrate holding jig 17 is inserted into a plasma etching container having the above-described structure, and the substrate to be processed 15 is placed in the plasma. Atching the negative resist while directly exposing it to.

In another embodiment of the present invention, as shown in FIG. 3 showing a cross section of a portion thereof, at least an insulating plate 18 made of glass, plastic, or the like is made as thin as possible while maintaining strength. A metal film 13 with a thickness of about 1000 to 2000 [Å] with corrosion resistance is deposited on the entire surface of one side, and has approximately the same width as the substrate 15 to be processed, for example, and has an upper end surface position as indicated by l in the figure. The composite plate 19 is sized so that the upper end of the metal film on the substrate 15 to be processed is at least 20 mm higher than the upper end of the substrate 15 to be processed. Then, with the composite plate stacked on the back side of the substrate 15 to be processed, it is inserted into the substrate insertion grooves 21 and 21' of the substrate holding jig 20 made of quartz or the like, and the substrate holding jig 20 is subjected to plasma etching. Place it in a container and perform etching.

Furthermore, in another embodiment of the present invention, as shown in a partial cross-sectional view in FIG. A composite plate 1 consisting of an insulating plate 18 having approximately the same width and having a wedge-shaped lower end.
9', and insert the composite plate 19' into the upper substrate insertion groove 21 of the substrate holding jig 20 into which the substrate 15 to be processed is inserted, using its wedge-shaped part to the back side of the substrate 15 to be processed. Plasma etching is performed with the device inserted tightly. When the composite plate 19' is inserted into the back side of the substrate 15 to be processed as described above, its upper end is at least 20 mm from the upper end of the substrate 15 to be processed, as shown by l in the figure.
It is formed to a size that is more than [mm] high.

By the method shown in the above three embodiments, the mask substrate to be processed, which has a light-shielding film made of a conductive film such as chromium, is subjected to the above-mentioned cylindrical plasma treatment.
When placed in an etching container and subjected to plasma ashing under the conditions described above, the plasma
Since the electric field is concentrated at the upper end of the metal film of the composite plate closest to the power supply side electrode at the upper part of the etching apparatus, plasma concentration occurs in the vicinity and does not occur in the region in contact with the substrate to be processed. Since the base of the composite plate is an insulating plate made of glass or plastic with high thermal resistance, the temperature rise in the area in contact with the discharge does not affect the temperature distribution on the surface of the substrate to be processed. The temperature becomes uniform over the entire main surface of the substrate to be processed, and uniform ashing is achieved. For example, in a plasma etching chamber having an inner diameter of about 10 [inches], a plurality of negative resist patterns having the same dimensions are formed on the entire main surface by the method of the present invention.
After the day scum treatment of the mask substrate is performed, the pattern width deviation is approximately 0.05 to 0.15 [μm], which is significantly improved compared to the deviation of 0.2 to 0.4 [μm] obtained by the conventional method.

In the above embodiments, the present invention was explained in the case where a chrome mask substrate was used as the substrate to be processed, but the method of the present invention can also be applied to a mask substrate using another conductive film as a light-shielding film or a semiconductor substrate. It is also effective when used as a processed substrate.

Further, in the above embodiment, an example in which the present invention is applied to plasma etching has been described, but the method of the present invention is of course effective in plasma etching as well.

As explained above, according to the present invention, the substrates to be processed are placed side by side in a capacitive cylindrical plasma etching apparatus, and the substrates to be processed are etched uniformly over the entire main surface of the substrates while being directly exposed to plasma. Since etching is performed, the efficiency and yield of plasma etching can be improved when manufacturing photo masks or semiconductor devices.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional plasma ashing method, Fig. 2 is a front view a and a sectional view b taken along the line A-A' in an embodiment of the plasma ashing method of the present invention, and Fig. 3 is a sectional view of an embodiment of the plasma ashing method of the present invention. FIG. 4 is a longitudinal cross-sectional view of still another embodiment of the plasma ashing method of the present invention. In the figure, 1 is a plasma etching container, 2
17 and 20 are substrate holding jigs, 3 and 15 are substrates to be processed, 4 is a power supply side electrode, 5 is a high frequency power source,
6 is a capacitor, 7 is a grounding side electrode, 8 is grounding, 9
10 is an insulating stand, 10 is a gas inlet, 11 is a vacuum exhaust port, 12 is a plasma concentration area, 13 is a metal film, 1
4 is a quartz plate, 16 is a board mounting groove, 18 is an insulating plate,
19 and 19' are composite plates, 21 and 21' are substrate insertion grooves, and l is the height from the upper end of the substrate to be processed to the upper end of the composite plate.

Claims (1)

[Claims] 1 Using a capacitive cylindrical plasma etching device with a power supply side electrode on the top and a ground side electrode on the bottom, the substrate to be processed, which has a conductive film deposited on its main surface, is placed upright in the plasma and etched. In the plasma etching method, a composite plate in which a conductive film is adhered to an insulating plate is placed side by side on the back side of the substrate to be processed, and the upper end of the conductive film of the composite plate is placed above the upper end of the substrate to be processed. A plasma etching method characterized in that etching is performed by arranging the electrode close to the power supply side electrode.