JPH10172960A - Ashing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove organic residues, by setting a substrate to be processed on the substrate stage of a parallel plane-type plasma ashing device where a distance between electrodes is a specified value, and executing plasma ashing with gas containing oxygen. SOLUTION: A confronted electrode 14 operates as a gas shower head and it can uniformly supply gas containing oxygen to the processed substrate 11. Gas containing oxygen can be supplied from a gas nozzle which is separately provided. The confronting electrode 14 of a substrate stage 12 is stored in a chamber 16 and it is controlled to desired pressure by a vacuum pump and a pressure control means. The inter-electrode distance Gp between the substrate stage 12 and the confronting electrode 14 can be fixed or can finely be adjusted to the range of Gp=10±3mm. The adjusting means of the inter-electrode distance Gp can be a mechanical method by hydraulic and pneumatic fluid cylinder or that by a gear.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ashing method used in a manufacturing process of a semiconductor device and the like, and more particularly, to a method for removing an organic residue, that is, a so-called scum after an organic layer such as a resist mask is patterned by a developing process or the like. The present invention relates to an ashing method for removing with high accuracy.

[0002]

2. Description of the Related Art In a process of manufacturing a semiconductor device such as an LSI, a resist pattern is formed on a layer to be etched when an electrode wiring material, an interlayer insulating film, and the like are etched, and the resist pattern is used as an etching mask. Is etched. The formation of the resist pattern is usually performed by applying a resist film on the layer to be etched, selectively irradiating the resist film with UV light or the like, exposing the resist film, and patterning with a developer. A positive resist removes the exposed portion of the resist film, and a negative resist removes the unexposed portion of the resist film.

In developing a resist film, it is desirable that the resist film is faithfully patterned in accordance with the selectively exposed shape. In many cases, resist residues remain. It has been pointed out that the cause of the scum is an imbalance in the exposure intensity, an interaction between the underlying etched layer and the resist film, and the like. The problem based on this scum will be described with reference to FIGS.

[0004] For example, a positive resist film 2 is applied and formed on the layer 1 to be etched, and exposure light 3 is selectively irradiated by a stepper or the like (FIG. 5A). Develop with a developer,
The resist pattern 4 having the opening width a is formed by eluting the irradiated portion of the exposure light 3. A scum 5 which is a development residue remains between the resist patterns 4 (FIG. 5B). When the layer 1 to be etched is etched using the resist pattern 4 as an etching mask, the space width b at the bottom of the layer to be etched becomes narrower than the desired space width a, and the negative pattern conversion difference ba resulting from the scum 5 is obtained. Occurs (FIG. 5C).

[0005] In order to avoid such a pattern conversion difference, a step called descum may be inserted. Fig. 6 (a)
This will be described with reference to FIGS. When the scum 5 after the resist film development shown in FIG. 6A is removed, the scum 5 is usually applied by a down-flow microwave plasma ashing apparatus. However, under normal ashing conditions, the ashing rate is as high as 1000 nm to 5000 nm / min, and it is difficult to set the descum time. At the same time as the scum 5, the resist pattern 4 is reduced in film thickness or receded, and the desired opening width a is reduced. (FIG. 6B) When the layer 1 to be etched is etched using the resist pattern 4 as an etching mask, the space width c of the layer 1 to be etched becomes larger than the desired space width a, and the pattern conversion difference is increased. ca occurs (FIG. 6C).

For this reason, descum is performed under ashing conditions in which the ashing rate of the microwave plasma ashing apparatus is suppressed, but in this case, the uniformity of the ashing rate is not as good as about ± 4.5 to 6.0%, and is improved. Is desired. An example of a conventional descum condition using a microwave plasma ashing apparatus is shown below. O ₂ 40-60 sccm Pressure 100-200 Pa Microwave power 400-1000 W (2.45 GH
z) Temperature of substrate to be processed 110 to 130 ° C. Ashing rate 60 to 90 nm / min Uniformity of ashing rate in the surface of the substrate to be processed ± 4 to 6%

[0007]

SUMMARY OF THE INVENTION The present invention has been proposed in view of the above-mentioned problems of the prior art. That is, an object of the present invention is to provide an ashing method for uniformly removing organic residues such as scum after developing a resist film without generating a pattern conversion difference or the like.

[0008]

An ashing method according to the present invention is proposed to solve the above-mentioned problems. In an ashing method for a substrate having an organic residue on its surface, the method comprises the steps of: Distance between 7mm and 1
It is set on a substrate stage of a parallel plate type plasma ashing apparatus of 3 mm or less, and plasma ashing is performed with a gas containing oxygen.

At this time, the pressure of the gas containing oxygen is increased to 150
It is desirable to control the pressure to not less than Pa and not more than 250 Pa. As an organic residue, after developing the resist pattern,
It can be suitably applied when removing scum and the like remaining between the resist patterns. In the ashing method of the present invention, the organic residue can be removed, and the surface of the underlying substrate can be subjected to a hydrophilic treatment.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic sectional view showing a configuration example of a parallel plate type plasma ashing apparatus applied to the ashing method of the present invention. The substrate 11 to be processed is placed on a substrate stage 12, and is heated to a desired temperature by a heating means 13 such as a heater. This substrate stage 12 is set to the ground potential. Substrate stage 1
A counter electrode 14 connected to an RF power supply 15 via a blocking capacitor is disposed opposite to the counter electrode 2 to form a so-called parallel plate type etching apparatus of an anode couple type. The counter electrode 14 also serves as a gas shower head, and can uniformly supply a gas containing oxygen to the substrate 11 to be processed. The gas containing oxygen may be supplied from a separately provided gas nozzle. Substrate stage 1
2. The counter electrode 14 and the like are housed in the chamber 16 and are controlled to a desired pressure by a vacuum pump and pressure control means (not shown).

A feature of this parallel plate type plasma ashing apparatus is a distance Gp between the substrate stage 12 and the counter electrode 14, which can be fixed or finely adjusted within a range of Gp = 10 ± 3 mm. The means for adjusting the inter-electrode distance Gp is not shown, but may be a hydraulic cylinder such as hydraulic or pneumatic,
Any of a mechanical method using a gear or the like may be used. In FIG. 1, illustration of the details of the apparatus such as the loading / unloading means for the substrate 11 to be processed and the gas pressure control means is omitted.

Next, a scum ashing method using the parallel plate type plasma ashing apparatus shown in FIG. 1 is shown in FIG.
This will be described with reference to (a) to (d).

First, as shown in FIG. 2A, a positive resist film 2 is applied on a substrate to be etched having a layer 1 to be etched, for example, a wafer having a diameter of 6 inches.
The exposure light 3 is selectively exposed by, for example, i-line (365 nm). The material of the layer 1 to be etched is not particularly limited, and examples thereof include SiO ₂ and polycrystalline silicon.

PEB (Post Exposure B)
After the aking, the resist pattern 4 having an opening width a is formed by developing with a developing solution. The scum 5 remains on the surface of the layer to be etched 1 at the bottom of the resist pattern 4 (FIG. 2B). Up to this step, a conventional method may be used.

Thereafter, the substrate to be processed shown in FIG.
The scum 5 was set on the substrate stage 12 of the parallel plate type plasma ashing apparatus shown in FIG. O ₂ 1000-2000 sccm Pressure 150-200 Pa RF power 40-60 W (13.56M
Hz) Target substrate temperature 110-130 ° C. Distance between electrodes Gp 10 ± 3 mm Ashing rate 50-70 nm / min

As a result, as shown in FIG. 2 (c), the scum 5 was efficiently removed without causing a decrease in the film thickness of the resist pattern 4. Thereafter, the substrate to be processed shown in FIG. 2C is unloaded from the parallel plate type plasma ashing apparatus,
For example, an etching target layer 1, for example, an SiO ₂ layer is patterned by an ECR plasma etching apparatus. In the layer to be etched 1, a pattern having an opening width a in which the opening width a of the resist pattern 4 was faithfully transferred was formed.
(D)). The opening pattern formed in the layer 1 to be etched can be used, for example, as a connection hole.

Further, the Si of the substrate to be processed shown in FIG.
The surface of the layer to be etched 1 such as O ₂ is converted into a hydrophilic surface by this plasma ashing. Therefore, when wet etching is performed in the next step, the wettability with an etching solution is excellent, and generation of bubbles and the like can be suppressed. Therefore, even in the case of wet etching, patterning faithful to the opening width of the resist pattern 4 can be performed.

Under the aforementioned plasma ashing conditions,
For example, the distance G between the electrodes when the pressure is fixed at 175 Pa
FIG. 3 shows the relationship between p and the uniformity of the ashing rate.
As is clear from the figure, the distance Gp between the electrodes is 10 ± 3 m.
It can be seen that in the case of m, the uniformity of the ashing rate in the surface of the substrate to be processed is a good value of ± 2% or less. On the other hand, when the distance Gp between the electrodes exceeds 10 ± 3 mm, the ashing rate uniformity becomes ± 2% or more, and the removal of the scum 5 is insufficient or the resist pattern 5 is reduced in film thickness. As a result, a situation occurs where a pattern conversion difference occurs in the shape of the layer 1 after etching.

FIG. 4 shows the relationship between the gas processing pressure and the uniformity of the ashing rate when the distance between the electrodes is fixed to 10 mm, for example, under the above-mentioned plasma ashing conditions. As is apparent from FIG.
It can be seen that in the case of 0 to 250 Pa, the uniformity of the ashing rate in the surface of the substrate to be processed is a good value of ± 2% or less. On the other hand, when the pressure exceeds the range of 150 to 250 Pa, the uniformity of the ashing rate becomes ± 2% or more, the removal of the scum 5 is insufficient, or the resist pattern 5
Film loss occurs. As a result, a pattern conversion difference occurs in the shape of the layer 1 to be etched after the etching. This tendency is observed when the distance Gp between the electrodes is 10 ± 3 mm.
The same result was obtained within the range.

As described above, the ashing method of the present invention has been described in detail. However, the present invention is not limited to this embodiment, and various embodiments are possible. For example, although the positive resist for i-line is exemplified as the resist film, it can be applied to scum removal after development of various positive and negative resists corresponding to g-line, excimer laser, or electron beam exposure. It is. In addition to the photosensitive resist, it can be suitably used for removing an etching residue of a polyimide film or a lower-layer planarizing film in a multilayer resist. As the organic residue, in addition to the scum and the etching residue, it may be used for cleaning a substrate to be processed having various kinds of organic contamination on the surface.

As the ashing gas, various additive gases such as O ₃ , NH ₃ , CO or rare gas may be mixed and used in addition to oxygen alone. Other etching conditions, such as gas flow rate and RF power, are design items that should be determined to be optimal values according to the diameter of the substrate to be used, the volume in the chamber of the etching apparatus, and the like.

[0022]

As is apparent from the above description, according to the ashing method of the present invention, organic residues such as scum after development of a resist film can be removed with good uniformity without generating a pattern conversion difference. Is possible.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration example of a parallel plate type plasma ashing apparatus employed in an ashing method of the present invention.

FIG. 2 is a schematic sectional view showing the ashing method of the present invention in the order of steps.

FIG. 3 is a graph showing the uniformity of an inter-electrode distance and an ashing rate.

FIG. 4 is a graph showing gas processing pressure and ashing rate uniformity.

FIG. 5 is a schematic sectional view showing a problem of a conventional ashing method in the order of steps.

FIG. 6 is a schematic cross-sectional view showing another problem of the conventional ashing method in the order of steps.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Layer to be etched, 2 ... Resist film, 3 ... Exposure light, 4
... resist pattern, 5 ... scum, 11 ... substrate to be processed,
12: substrate stage, 13: heating means, 14: counter electrode, 15: RF power supply, 16: chamber

Claims (4)

[Claims] 1. An ashing method for a substrate having an organic residue on its surface, comprising: setting the substrate to be processed on a substrate stage of a parallel plate type plasma ashing apparatus having a distance between electrodes of 7 mm or more and 13 mm or less; An ashing method characterized by performing plasma ashing with a gas containing gas. 2. The pressure of the gas containing oxygen is 150 Pa
2. The ashing method according to claim 1, wherein the pressure is controlled to be not less than 250 Pa. 3. The ashing method according to claim 1, wherein the organic residue is scum remaining between the resist patterns after developing the resist pattern. 4. The ashing method according to claim 1, wherein the organic residue is removed by plasma ashing, and the surface of the substrate is subjected to a hydrophilic treatment.