JPH04342128A - Etching method - Google Patents

Abstract

PURPOSE:To easily and surely remove a multilayer resist mask. CONSTITUTION:A mask which is constituted of a lower-layer resist 13 and a stopper layer 14 is formed on a polysilicon film 12 as a substratum layer. The polysilicon film is etched by using the mask; after that, an organic film 16 is formed on the whole surface. When an etching operation is performed under a condition that the etch rate of the organic film 16 is nearly equal to that of the stopper layer 14, the stopper layer 14 is removed without causing damage to an SiO2, film 11. As a result, the stopper layer is removed by a dry etching operation, and it is possible to prevent particles from being produced. The organic film 16 and the lower-layer resist 13 can be removed easily by an oxygen plasma treatment or the like.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching method using a multilayer resist mask, and more particularly to the removal of a multilayer resist mask.

0002

2. Description of the Related Art A multilayer resist process is attracting attention as a method that allows fine and accurate processing without being affected by differences in level of a substrate. Dry etching using a multilayer resist mask is becoming essential in lithography processes on the order of 0.35 μm with the advent of excimer laser steppers. Examples of methods for forming a multilayer resist mask include anisotropic etching of the lower resist using a SiO2 mask (1988 Autumn Applied Physics Lectures, p. 552, 6a-L-6), and anisotropic etching of the resist using low-temperature etching. Processing (1988 Autumn Applied Physics Lectures No. 4
p. 96, 28a-G-4) and many others have been reported.

0003

However, there has been no report on a method for removing the stopper layer (or intermediate layer) of a multilayer resist mask. In multilayer resist masks, SOG (Spin
On Glass) is used, but if the underlying resist is simply treated with oxygen plasma after dry etching the underlying layer, the lift-off method will cause the stopper layer to peel off in areas with narrow pattern widths, but there is a problem in that it will cause particles to be generated. There is.

[0004] Furthermore, when attempting to remove the stopper layer with hydrofluoric acid or the like, a problem arises in that the underlying layer is also etched.

[0005] The present invention was devised in view of these conventional problems, and aims to provide an etching method that can easily and reliably remove a multilayer resist mask.

[0006]

[Means for Solving the Problems] Therefore, the present invention provides a multilayer resist mask, which is constructed by patterning and forming at least a stopper layer on a lower resist layer, and patterning the lower resist layer using the stopper layer as a mask. In the method of etching the base layer of the lower resist using the base layer, after etching the base layer, an organic film is formed on the entire surface, and then the stopper layer of the multilayer resist mask is etched at an etching rate substantially equivalent to that of the organic film. The solution is to remove it.

[0007]

[Operation] After etching the base layer using a multilayer resist mask, an organic film is formed on the entire surface, making it possible to prevent the base of the organic film from being damaged by the etching performed in the next process. Become. Furthermore, by removing the organic film and the stopper layer at approximately the same etching speed, the lower resist layer is exposed, but this lower resist layer and organic film can be easily removed by conventionally known methods such as oxygen plasma treatment. becomes possible.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the etching method according to the present invention will be explained below based on the embodiments shown in the drawings.

In this embodiment, first, as shown in FIG. 1, on a SiO2 film 11 formed on a silicon substrate 10,
Polysilicon (n+-Poly) doped with phosphorus (P)
A Si) film 12 is formed as a base layer, a positive photoresist is applied thereon, and this is heated (hard baked) to 200° C. or higher to form a lower resist 13. Next, a stopper layer (or intermediate layer) 14 made of, for example, SOG is applied onto the lower resist 13. Next, stopper layer 1
4, a resist pattern 15 is formed using photoresist.

Next, using this resist pattern 15 as a mask, the stopper layer 14 is etched, for example, under the following conditions.

○ Etching gas and its flow rate CHF3...
85SCCM O2...7SCCM ○Ambient pressure...50 mTorr ○Output...1000W Next, the lower resist 13 is subjected to reactive ion etching (RIE) using the patterned stopper layer 14 as a mask. Furthermore, the conditions for this RIE are as follows:
It is as follows.

○ Etching gas and its flow rate O2...50
SCCM ○Atmospheric pressure...50mTorr ○Output...1000W Through this reactive ion etching, the upper resist pattern 15 is removed as shown in the figure.

Then, reactive ion etching of the polysilicon film 12 is performed using the stopper layer 14 and the lower resist layer 13 as a mask (FIG. 3). The conditions for this reactive ion etching are as shown below.

○ Etching gas and its flow rate Hydrogen bromide (
HBr)...50SCCM ○Atmospheric pressure...10 mTorr ○Output...300W Thereafter, an organic film 16 made of, for example, resist is formed over the entire surface as shown in FIG.

Next, reactive ion etching is performed under conditions such that both the organic film 16 and the stopper layer 14 are etched at approximately the same etching rate. The etching conditions are as shown below.

○Etching gas and its flow rate CHF3...
85SCCM O2...50SCCM ○Atmospheric pressure...50mTorr ○Output...800W During this etching, the SiO2 film 11, which is the base of the polysilicon film 12, is covered with the organic film 16, so it is not etched at all and the inorganic It becomes possible to remove the stopper layer 14 made of the material (FIG. 5).

After that, the remaining organic film 16 and lower resist layer 13 can be removed by performing plasma etching using a well-known gas system mainly containing oxygen.

As described above, in this embodiment, the SiO2 film 11 exposed by etching is covered with the organic film 16, so that the stopper layer 14 can be removed without causing damage.

The polysilicon film 12 patterned as shown in FIG. 6 can be used, for example, as a well-shaped gate electrode.

Although the embodiments have been described above, the present invention is not limited thereto, and various design changes can be made in accordance with the gist of the configuration.

For example, in the above embodiment, polysilicon is used as the underlayer, but other materials may of course be used.

Further, in the above embodiment, SOG was used as the stopper layer, but in addition, PSG, P-SiN,
A silicon-based material containing silicon (Si) such as polysilicon may also be used. Furthermore, although the above embodiment uses a three-layer resist structure, a two-layer resist structure may also be used. In this case, a resist containing silicon (Si) or the like may be used as the stopper layer.

[0023]

As is clear from the above description, the etching method according to the present invention has the effect of easily and reliably removing a multilayer resist mask.

In particular, this has the effect of facilitating the removal of the stopper layer, which has been difficult in the past.

[0025] Furthermore, there is an effect of preventing the generation of particles accompanying the removal of the multilayer mask.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing steps in an embodiment of the present invention.

FIG. 2 is a sectional view showing steps in an embodiment of the present invention.

FIG. 3 is a sectional view showing steps in an embodiment of the present invention.

FIG. 4 is a sectional view showing steps in an embodiment of the present invention.

FIG. 5 is a sectional view showing steps in an embodiment of the present invention.

FIG. 6 is a sectional view showing steps in an embodiment of the present invention.

[Explanation of symbols]

11...SiO2 film, 12...polysilicon film (base layer),
13... Base resist, 14... Stopper layer, 15... Resist pattern, 16... Organic film.

Claims (1)

[Claims] 1. At least a stopper layer is patterned and formed on a lower resist, and a base layer of the lower resist is formed using a multilayer resist mask configured by patterning the lower resist using the stopper layer as a mask. The etching method is characterized in that after etching the base layer, an organic film is formed on the entire surface, and then the stopper layer of the multilayer resist mask is removed at an etching rate substantially equal to that of the organic film. .