JPS6151825A - Forming method of resist pattern - Google Patents

Abstract

PURPOSE:To do positively edging of a resist and taper-forming and to form precisely a pattern with a desired shape, by irradiating radioactive rays hardening at least the surface portion of the resist thereon, and by heat-treating the resist. CONSTITUTION:On a substrate 1 consisting of a silicon wafer 11 and an SiO2 film 12, a pattern is formed with a resist 2, on which radioactive rays 3 are irradiated. At this time, the surface of the resist 2 is hardened to fix the resist position approximately, and the sections 21 bonding with the substrate 1 is fixed. Then the resist 2 is heat-treated. A desired resist pattern is formed, in which round portions 22 are formed at edges of steps and taper portions 22 are formed due to contracting action. The SiO2 film 12 is etched away to form a contact hole 4. Since durability of the resist 2 has been improved, the side walls 23 of the resist 2 is never made rough on etching. The resist 2 such as thermosetting novolak resin resist is preferably used and ultraviolet rays are irradiated as the radioactive rays 3.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Object of the Invention [Field of Industrial Application] The present invention relates to a resist pattern forming method for forming a pattern on a substrate using a resist.

Techniques of this type are used, for example, in the production of electronic components, for example in the production of semiconductors.

[Conventional technology]

As is well known, the pattern forming method using a resist involves forming a resist on a substrate, using this resist as a mask, etching the portions not covered by the resist using an appropriate etching means, and then removing the resist to form a desired pattern. I am getting .

At this time, in order to obtain a desired pattern shape, it may be necessary to closely control the cross-sectional shape of the resist pattern. One possible example of this is the need to make the resist steps rounded or tapered. For example, when forming a contact hole in an insulating film on a semiconductor substrate, RI E (1'!eactive
When using reactive ion etching (reactive ion etching), due to the anisotropy of RIE etching, the step of hole a becomes steep as shown schematically in Figure 2 (Ell), and when a wiring is formed on top of it, the height of the wiring becomes There is a risk that the step coverage will deteriorate and the reliability of the wiring will decrease.Therefore, as shown in Fig. 2 (011), the step of resistor (b) is rounded or tapered in advance to reflect this in the hole. It has been considered to avoid this problem by making the hole a tapered. In addition, in order to give the Et final pattern a desired shape, it may become necessary to round or taper the steps of the resist pattern in various cases.

As a method for controlling the shape of the resist pattern as described above, a technique has been proposed in which the resist is heat treated before etching. This is because if the resist is post-baked at an appropriate temperature, the shoulders of the resist steps are expected to become rounded or slightly tapered due to the heat. By selecting appropriate temperature conditions accordingly, we were able to successfully round or taper the shoulders of the resist steps. This is thought to be due to the heat shrinkability of the resist.

However, if the above-mentioned method is used alone, the entire resist may sag, especially in the horizontal direction from the state shown by the broken line in resist b as shown in FIG. This causes problems such as poor reproducibility of resist patterning accuracy. In addition, this method simply heat-treats the resist to make the shoulder part sag, so it is difficult to predict how the resist will sag, that is, how rounded or tapered it will be. Therefore, the controllability of the resist shape is poor. Further, if only heat treatment is performed, there is a problem in the resistance of the resist, and when RIE is used, the resistance of the resist to RIE is poor, and as a result, sidewall roughness as shown in FIG. 4 may occur in the resist. This roughness affects the object to be etched, causing roughness on the sidewalls of the etched pattern of the object to be etched, making it particularly difficult to apply to the formation of fine patterns (such as minute contact holes). (In addition, in resist b in Figs. 3 and 4,
(hatching omitted).

[Problem that the invention seeks to solve]

The problems to be solved by the present invention are that the width between the resist lines changes due to lateral sag due to heat treatment, that the controllability of the resist shape is poor, and that the accuracy of patterning is reduced due to these. Moreover, due to the poor resistance of the resist, the resist and the object to be etched become rough.

The present invention solves these problems and makes it possible to reliably form rounded and tapered resists, thereby making it possible to form patterns in desired shapes with high patterning accuracy, and to improve resist resistance (
The purpose of the present invention is to obtain a resist pattern forming method that can prevent roughening of the resist sidewalls and substrate sidewalls during patterning by improving RIE resistance, heat resistance, etc., and can be effectively applied to fine pattern formation. .

(B) Structure of the invention, [Means for solving the problems] In order to solve the above problems, in the present invention, a pattern is formed on a substrate using a resist, and at least the surface of the resist is Technological measures are employed to irradiate the resist with curing radiation and then heat treat the resist.

[Action of the invention]

As described above, in the resist pattern forming method of the present invention, prior to the heat treatment of the resist, radiation is irradiated to harden at least the surface of the resist, so that the resist surface is hardened in advance. As a result, even if heat treatment is performed next to round off the shoulder portion of the step, lateral sagging is unlikely to occur because the surface is hardened. Therefore, changes in the resist width can be prevented, and formation of unintended patterns (for example, contact holes that are too small) can be avoided. Since the resist position is almost fixed by hardening the surface, the problem of poor controllability of the resist shape is also solved, making it possible to form a desired pattern. Therefore, the precision of patterning is excellent. In addition, the resistance of the resist is improved by hardening the surface, and the side walls of the resist are prevented from becoming rough even when subjected to heat treatment or later etching by RIE, etc., so that the object to be etched is not roughened. This makes it possible to effectively apply the method to fine pattern formation.

As described above, according to the resist pattern forming method of the present invention, it is possible to eliminate problems when heat-treating the resist, such as when rounding or tapering the steps of the resist in order to give the desired shape to the desired pattern. can. In other words, it is possible to reliably form roundness or taper in the resist without changing the resist width, thereby enabling pattern formation with desired properties with high patterning accuracy, and by improving resist resistance, it is possible to prevent roughness and etching of the resist sidewalls during pattern unraveling. This method has the effect that it can prevent the sidewalls of etched patterns on objects from becoming rough, and can therefore be effectively applied to the formation of fine patterns.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. This embodiment takes as an example the case where a contact hole is formed in a SiO□ insulating film on a silicon wafer, and the present invention is applied to the formation of a resist pattern in that case.

First, an overview of the resist pattern forming method according to this example will be explained.

As shown in FIG. 1(a), a pattern is formed using a resist 2 on a substrate 1 (in this example, consisting of a silicon wafer 11 and an SiOz film 12 thereon). This resist 2 is exposed to radiation 3 that hardens at least the surface of the resist 2.
irradiate. As will be described in detail later, in this example, a thermosetting resin resist is used as the resist 2, and the resist 2 is irradiated with ultraviolet rays, particularly ultraviolet rays in the deep UV range.

This radiation irradiation hardens the surface of the resist 2. As a result, the resist position is almost determined, and for example, the bonded portion with the base 1 indicated by reference numeral 21 in the figure is fixedly determined.

Next, the resist 2 is heat-treated as shown in FIG. It is formed.

The pattern on the substrate 1 is formed by etching away the portion of the 5iOz film 12 that is not masked by the resist 2, as shown in FIG. 1 (C1). In this example, a contact hole 4 is formed. However, even when an anisotropic etching method such as RIE is used, the roundness 22 or taper 23 is formed in the resist 2 during the heat treatment process (FIG. 1(b)), so the contact hole 4 is
Also, reflecting this, the side wall 41 has a tapered shape.

Therefore, the problem of reduced wiring reliability due to steep contact holes 4 is reliably solved.

In addition, the resistance of the resist 2 is improved due to the surface hardening by the radiation 3 and the heat treatment, and the side walls 23 of the resist 2 are not roughened even during etching such as RIH, so that the roughness of the resist 2 is not caused by contact. Hall 4 side wall 41
Since there is no influence on the contact hole 4, the contact hole 4 does not become rough. Therefore, it can be effectively applied to the formation of minute contact holes, and can be advantageously applied to the formation of other fine patterns.

In detail, this embodiment has the following specific configuration.

As described above, the base body 1 is made up of a silicon wafer 11 and a SiO□ film 12, and a pattern (contact hole 4) is formed in this SiO□ film 12.

As the resist 2, a thermosetting resin type was used, and in this example, a novolac resin type resist or a polyvinylphenol resin type resist was used. After forming a pattern using such a resist material, ultraviolet rays were irradiated as radiation 3. The irradiation conditions were a wavelength of 254 n.
The zero-order heat treatment was performed by irradiating the entire surface of the wafer with ultraviolet rays in the Deep UV region of 1.2 J/cj for 1 to 10 minutes at a density of 1.2 J/cj, followed by convection beta at 250° C. for 30 minutes.

It is thought that in this example, the crosslinking reaction of the resist polymer progresses and hardens due to radiation irradiation prior to heat treatment. As a result of curing, heat resistance is improved and pattern flow of the resist 2 (pattern deformation due to flow of the resist) is prevented even in the subsequent high temperature beta.

In this example, only the resist surface was hardened by the radiation vA3, but the crosslinking density also increased inside the resist 2 due to the high temperature beta, and the entire resist 2 was hardened to an insoluble and infusible state.
It is thought that the resistance is improved, that is, it is considered that both the curing process by radiation and the heat treatment process work together to improve the resistance of the resist 2.

In this example, etching was performed by RIE after heat treatment, and the RIE resistance was good, with almost no roughness occurring on the sidewall 23 of the resist 2, and therefore no roughness occurred on the sidewall 41 of the contact hole 4 formed. A hole 4 with a beautiful shape was obtained without any problems.

As described above, in this example, the deformation of the resist pattern is prevented by curing the resist surface with radiation, and the taper (or rounding effect) of the resist 2 is achieved by balancing the curing with the thermal curing effect (shrinkage effect) caused by heat treatment. ) Formation can be performed reliably, and due to the effect of improved resistance such as RIE resistance, precise etching that is faithful to the resist pattern can be performed, and a tapered pattern with the desired shape can be obtained. .

Naturally, the present invention is not limited to this example, and can be carried out using various resists and appropriately selecting the radiation that hardens at least the surface of the resist. Various means can also be used for the treatment process. Moreover, the present invention is widely applicable to the formation of electronic materials and other pattern formation using resists.

(c) Effects of the invention As mentioned above, the resist pattern forming method of the present invention includes:
It has the advantage that it can prevent pattern deformation caused by heat treatment, has good resistance, and can be effectively applied to the formation of fine patterns.

[Brief explanation of the drawing]

FIG. 1 (81, BL, (C) is a schematic side cross-sectional view showing an embodiment of the present invention in the order of steps. FIGS. 2 to 4 are schematic side cross-sectional views for explaining the background art. 1... aH4c, 11... silicon wafer, 12...
...S i O2 film, 2... resist, 3... radiation. Patent Applicant Sony Corporation Agent Patent Attorney Takazuki Noriseki Figure 1 Figure 2 Ca) (b) Figure 3 Figure 4

Claims (1)

[Claims] 1. A method for forming a resist pattern, which comprises forming a pattern on a substrate using a resist, irradiating the resist with radiation that hardens at least the surface of the resist, and then heat-treating the resist.