JPH0229655A - Resist pattern forming method - Google Patents

Abstract

PURPOSE:To form patterns with good accuracy even if sizes are very small by embedding the inter-pattern spaces of a 2nd resist with resin layers and further, patterning the 1st resin layer by RIE with the resin layers as a mask. CONSTITUTION:The lower layer resist 4 is coated on a substrate surface to about the thickness at which the surface is fattened and this resist is heat- treated to prevent mixing thereof with the upper layer resist 5. The upper layer resist 5 is then relatively thinly coated thereon. Further, the upper layer resist 5 is patterned by lithography. An SiO2 layer which is, for example, SOG6 is coated thereon so as to be thickly deposited between the patterns. After the PIE of a fluorine system is applied over the entire surface, the SiO2 layer on the resist pattern is removed and in succession, the upper layer resist 5 and the lower layer resist 4 are etched by the RIE of an oxygen system with the SiO2 layer remaining between the patterns as a mask. The patterns reversed of the patterns of the upper layer resist 5 are formed on the lower layer resist 4 by this treatment. The fine patterns are thus formed.

Description

[Detailed Description of the Invention] [Summary] The present invention relates to a resist pattern forming method using a multilayer resist method, which is unaffected by substrate level differences, and which improves accuracy even when the dimensions between patterns are minute (pattern pattern formation method). The purpose of the present invention is to provide a resist pattern forming method in which a first resist layer is applied to a substrate surface so that the surface is flat, and a second resist layer is selectively applied thereon. Includes a step of applying a resin layer and performing full painting/double-etching to fill in the gaps between the patterns of the second resist with the resin layer, and further patterning the first resin layer by RIH using the resin layer as a mask. It is composed of

[Industrial application field]

The present invention relates to a method for forming a resist pattern, and particularly to the formation of a fine pattern by a multilayer resist method.

In semiconductor integrated circuits, patterns become finer as the density increases, and line width and line spacing (line and spacing) increase.
el (abbreviated as L/S below), and lithography technology is required to form patterns of 5 μm or smaller, but on the other hand, the unevenness of the substrate surface has become extremely large due to multilayer wiring structures, etc. This makes fine patterning of resist difficult.

In other words, a resist layer coated on an uneven surface will inevitably have a large thickness, but in order to increase the resolution of the transferred image, it is necessary to increase the numerical aperture of the optical system, and it is necessary to increase the numerical aperture of the optical system. In this case, the depth of focus becomes shallow, making it impossible to expose the thick resist layer uniformly in the depth direction. Therefore, a resist pattern obtained by developing this resist pattern has low dimensional accuracy.

[Conventional technology]

A processing method called a multilayer resist method has been developed as a method to deal with this situation. The process is as shown in FIG. 2, and an example of the process of the conventional multilayer resist method will be described below with reference to the drawing.

First, fat in the figure is referred to. For example, a polycrystalline St (polySt) layer 2 is partially formed on the surface of the substrate 1, and the PSG
With the structure covered with layer 3, lower layer resist 4 is applied thickly enough to eliminate the step difference, and the surface is made flat. This lower layer resist is a carbon-based polymer compound.

A Sto or silicone resin layer is applied thereon as an intermediate layer 7, and an upper resist 5 is further applied thereon, and only the upper resist is patterned first. The upper resist layer, like the lower resist layer, is a carbon-based polymer compound and has photosensitivity to enable patterning by lithography.

Next, as shown in the same figure (bl), the intermediate layer is selectively etched using the pattern of the upper resist as a mask.The processing method is reactive ion etching (R) using fluorine-based plasma.
In IE), the silicon-based material which is the intermediate layer is etched exclusively.

Using the intermediate layer pattern formed by the above process as a mask, the lower resist layer is selectively etched to form a lower resist pattern as shown in FIG. 3(C). The processing method is RIE using oxygen plasma, and the carbon-based lower resist layer is etched exclusively, but because of the anisotropy characteristic of RWE, the thick lower resist layer is also patterned into a shape that matches the etching mask.

As explained above, in the multilayer resist method, a pattern precisely formed on a relatively thin upper resist layer is successively inherited (therefore, a pattern matching the mask pattern is also formed on a relatively thick lower resist layer). It is possible.

[Problem to be solved by the invention]

In photoresist patterning, whether positive or negative, the resist pattern tends to be thinner than the pattern set on the photomask.

One reason for this is that in areas with high pattern density, it is difficult to remove the resist in narrow areas between patterns, and even under such conditions, if you try to remove the resist reliably, it is difficult to remove the resist in the narrow areas between the patterns. A portion of the resist will also be lost.

In addition, even apart from such circumstances, if exposure/development processing is performed with the idea that no resist should be left in the area where resist should be removed, the resist pattern will become thinner ( Furthermore, even when patterning the underlying resist by RIE, which is characterized by anisotropy, the selectively etched area tends to be larger than the area defined by the mask, so the thinning of the pattern is even more significant. Become.

Therefore, in order to realize a pattern with an L/S of 0.5 μm, it is necessary to modify the mask pattern in advance to set the line width to 0.6 μm and the line spacing to 0.4 μm. is the super-ultraviolet g-line (λ”436 nm
), making lithography using ultra-ultraviolet light extremely difficult.

The purpose of the present invention is to provide fine pattern lamination lithography,
It is an object of the present invention to provide a resist pattern forming method using a multilayer resist method in which the resist between patterns can be reliably removed without narrowing the width of the pattern formed on the lower resist layer below a predetermined value, and the L/S is 0.5 μm. It is an object of the present invention to provide a method for forming a resist pattern with the same ease as in the prior art.

[Means to solve the problem]

In order to achieve the above object, a typical embodiment of the present invention performs the following processing.

First, a lower resist layer is applied to the surface of the substrate to a thickness that makes the surface flat, and this is heat-treated to prevent it from mixing with the upper resist layer, and an upper layer resist is applied relatively thinly. Furthermore, the upper resist layer is patterned by lithography.

On top of that, a layer of Sin, which is SOG, for example, is applied so as to be thickly deposited between the patterns, and then fluorine-based RIE is applied.
is applied to the entire surface to remove the Sin1 layer on the resist pattern, and then the upper resist layer and the lower resist layer are etched by oxygen-based RIE using the SiO□ layer remaining between the patterns as a mask.

Through the above process, a pattern that is an inversion of the pattern of the upper resist is formed in the lower resist.

[For production]

In the above process, by applying SOG and etching the entire surface, 300 layers are left to fill in the gaps between the patterns of the upper resist. This process is equivalent to patterning 300 layers, and If the resist pattern is formed negative, the pattern of 300 layers is reversed and formed positive.

Since it is easy to dry-etch resists such as SOG and novolak, which have Sing as their main component, by changing the etching speed, the lower resist layer can be patterned using the 300-layer pattern as a mask.

The line spacing in the 300-layer pattern corresponds to the line width in the upper resist pattern, so narrowing the line spacing in the 300-layer pattern means narrowing the line width in the upper resist pattern, that is, increasing the line spacing. As a result, obstacles to resist pattern formation by photolithography are reduced, making it possible to form finer patterns compared to conventional multilayer resist methods.

〔Example〕

FIG. 1 is a schematic cross-sectional view showing the steps of an embodiment of the present invention.

The steps of the embodiment will be described below with reference to the drawings.

As shown in FIG. 18), the P S Gl! Substrate 1 coated with 3
A lower resist 4 is applied over the entire surface using a spin code. The purpose of the process in this embodiment is to form a pattern in the lower resist layer that will serve as a mask for selectively etching this PSG layer.

For example, BCR (trade name: Tokyo Ohka Type) is suitable as the lower layer resist, but the surface tends to become flat after application.
Any material can be used as long as it functions as a mask when performing RIB processing on the PSG layer.

When the lower layer resist is applied to such an extent that the surface irregularities are eliminated, the thickness will be 2 to 3 μm. Note that the photosensitive properties of the lower resist layer do not need to be a particular problem, but the photosensitive groups are destroyed during baking and may cause pinholes, so it is better not to have photosensitivity.

After heat-treating this at 250 to 300° C., an upper resist 5 is applied and patterned. As in the case of ordinary photolithography, a novolac positive type resist is used as the upper layer resist, but since the lower layer resist is heat-treated, the two do not mix and there is no chemical influence. The thickness of the upper resist layer is preferably about 0.2 to 1.0 μm, although it is better to be thinner from the viewpoint of lithography accuracy, since it also determines the thickness of 300 layers as described later.

This state is shown in FIG. 1 (bl).

As already mentioned, the pattern formed on the upper resist layer is a negative pattern that is the inverse of the pattern to be formed on the lower resist layer.

300 layers 6 are then applied by means of a spin cord. S.O.
Examples of G include OCD Type-7 (trade name).

Tokyo Ohka type) is suitable, but it is also possible to use a fluid material such as silicone resin, which has a different etching speed in dry etching than carbon-based resist. However, as shown in Figure C1, it is desirable that the flow characteristics be such that it accumulates between the patterns of the upper resist, and it is unsuitable that it remains only at the corners of the stepped portions.

The entire surface of the substrate coated with SOG is etched using a fluorine-based RIB.The reaction gas is CF, CHF3°CBrF*
etc., and the processing conditions were a pressure of 0.2 Torr.

The high frequency power is 300 mW. This dry etching is performed until the surface of the upper layer pattern 5 appears, as shown in FIG. 1 (dl).

Next, when the etching conditions are changed and RIB is performed using only O2 as a reactive gas, the upper resist between the SOG patterns and the lower resist not covered by SOG are etched away, and the lower resist is exposed as shown in Figure 1 +81. A pattern is formed. Processing conditions are pressure 0.02-0.005
The pattern of this lower resist layer may be the same as that of the F series except for Torr, and the pattern of this lower resist layer is an inversion of the pattern of the upper resist layer, and they have a positive/negative relationship with each other.

The process of the embodiment is thus completed, and the PSGjii3 is selectively etched using the formed lower resist pattern as a mask.This is also normally performed by fluorine-based RIE.

〔Effect of the invention〕

As explained above, in the multilayer resist method of the present invention, the pattern is reversed, so in the resist pattern that is finally formed, it is possible to make the size of the part where the resist is removed between the patterns narrower. Furthermore, the characteristics of the multilayer resist method, in which a relatively thick lower resist layer is precisely patterned based on a pattern precisely formed by photolithography on a relatively thin upper resist layer, are not impaired.

According to the present invention, it is now possible to form a pattern with an L/S of 0.5 μm using ultraviolet g-line (λ = 436 nm) or by lithography,
Lithography has made it possible to form finer patterns.

5 is the upper layer resist, 6 is SOG.

7 is middle class It is.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the steps of the embodiment, and FIG. 2 is a schematic cross-sectional view showing the steps of the conventional technology. 4 is a lower resist layer; Fig. 4 is a schematic cross-sectional diagram showing the process of the example; Fig. 4 is a schematic cross-sectional diagram showing the process of the prior art;

Claims (1)

[Scope of Claims] A step of applying a first resist onto the surface of the substrate so that the surface is flat, and applying a second resist onto the first resist layer without mixing it with the first resist. a step of patterning the second resist layer by applying a resin, which has a different etching speed in dry etching than the first or second resist, onto the substrate after the step; a step of etching the entire surface of the resin layer by dry etching; using the resin layer left by the etching process as a mask, the second resist layer and the second resist layer are coated so as to fill the gaps between the patterns; 1. A resist pattern forming method comprising the step of selectively etching one resist layer by anisotropic dry etching.