JPS63316437A - Formation of photoresist pattern - Google Patents

Abstract

PURPOSE:To form an ultrafine photoresist pattern of high accuracy and high sharpness on a substrate having a stepped part by a method wherein a second photoresist layer as an upper layer is exposed by far ultraviolet rays and is heat-treated additionally. CONSTITUTION:A first photoresist layer 11 whose surface 11a to be photosensitive to far ultraviolet rays is nearly flat is formed on a substrate 1 having a stepped part 2 on the surface; a second photoresist layer 12 capable of absorbing the far ultraviolet rays is formed on the layer. A required pattern is exposed onto the second photoresist layer 12, and this layer is developed to form the pattern; while the first photoresist layer 11 is being heated especially, it is exposed by the far ultraviolet rays by making use of the second patterned photoresist layer 12 as a mask and is developed; the pattern is formed. By this setup, the photoresist pattern of high accuracy and high definition, i.e. with pattern sharpness, can be formed surely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of forming a photoresist pattern used as a mask for various microfabrication processes, for example, in the manufacturing process of various semiconductor devices.

[Summary of the invention]

In the present invention, a first photoresist layer sensitive to far ultraviolet rays and having a substantially flat surface is formed on a substrate having unevenness, that is, a step, on the surface, and a second photoresist layer that absorbs far ultraviolet rays is formed on this first photoresist layer. forming a second photoresist layer, patterning the second photoresist layer by exposing and developing the desired pattern, and using the patterned second photoresist layer as a mask, the first photoresist layer is heated without particular heating. The photoresist pattern is exposed to deep ultraviolet rays and developed to form a pattern. In this way, it is possible to reliably form a photoresist pattern with high precision and sharpness, that is, with good pattern cut.

[Conventional technology]

In the manufacturing process of various semiconductor devices such as high-density large-scale integrated circuits LSI, ultra-fine resist patterns are required for various purposes, such as as a resist for dry etching such as reactive ion etching RIE, or as a resist for selective ion implantation.

In forming this photoresist pattern, most of the photoresist patterns have unevenness, that is, a step, on the surface of the substrate to which they are adhered due to various manufacturing steps. When there are steps on the surface to which the photoresist is adhered, the conventional method of forming a resist pattern by simply applying a single layer of photoresist H with a uniform thickness, exposing it to light, and developing it can be difficult. It is difficult to obtain highly accurate and sharp ultrafine patterns due to reflected light, uneven coating, and uneven exposure due to the presence of steps.

On the other hand, for example, published by Kogyo Kenkyukai, Electronic Materials 4.198
A two-layer resist method is known, which is also described on page 6, page 47. This method is based on a structure in which two resist layers are laminated, and the step on the substrate surface is filled with the lower first resist layer to flatten the surface, and the second photoresist layer is deposited on top of this. By coating, a flat second resist layer with a uniform thickness and a relatively thin thickness is formed, and this second resist layer is exposed and developed in a desired pattern to form a pattern. There is a method of patterning the first resist layer by, for example, reactive ion etching in oxygen plasma (hereinafter referred to as 02-RIE), that is, anisotropic etching, using this as a mask. In this case, the upper second resist layer is patterned by the optical photographic technique using exposure and development as described above, but as described above, this upper second resist layer has a uniform thickness. Since it is a flat layer with a relatively small thickness, it is possible to form fine patterns with high precision and sharpness, and along with this, the second resist layer was used as a mask and patterned by 02-RIH. It is said that a fine pattern with high accuracy and sharpness can also be obtained from the pattern of the first resist layer.

However, when using this method, in practice, the upper second resist layer is eroded during the 02-RIH operation of the lower first resist layer using the upper second resist layer as a mask, so the ultra-fine resist layer is eroded. There are problems with applying it to patterns.

Furthermore, in the above-mentioned two-layer resist method, a so-called DeepV resist sensitive to far ultraviolet rays (Deep UV) is used as the lower first resist layer, and a positive-type Deep UV absorbing resist is used as the second resist layer above this. Using a large regular positive type photoresist, this second resist is exposed and developed in a required pattern to form a pattern, and then this patterned second resist layer that has a high absorption of UV is optically exposed. Deep UV exposure is performed on the entire surface of this as a mask, and the underlying first resist layer is exposed to a pattern in which the pattern of the second resist Ii is reversed, and then this first resist layer is developed. There is a so-called PCM method in which patterning is performed.

However, even with this method, a problem may arise in that the underlying first photoresist layer, which is exposed using the second photoresist layer as a mask, suffers from pattern breakage. Furthermore, when the photoresist pattern thus formed is used as an etching mask and the substrate is processed by dry etching such as RIE, the continuous external resist forming the first photoresist layer below is generally used for dry etching. There is a problem that because of the poor resistance to etching, so-called thinning occurs in the resist pattern when dry etching the substrate, making it difficult to process ultra-fine patterns with high accuracy and sharpness.

[Problem that the invention seeks to solve]

The present invention solves the above-mentioned problems and makes it possible to form an ultra-fine photoresist pattern with high precision and sharpness on a substrate having steps, and also allows dry etching of the substrate using this photoresist pattern as a resist. Provided is a method for forming a photoresist pattern that can reliably perform microfabrication.

[Means for solving problems]

As shown in FIG. 1A, the present invention includes a first photoresist layer (11) of a positive type exposed to deep UV (200 to 260 nm) on a substrate (1) having a step (2).
) is coated on the first photoresist layer (11) by burying the step (2) so that the surface (lla) becomes a substantially flat surface. (350 to 450 nm) normal, for example, positive type second photoresist layer (12)
As shown in FIG. 1B, the second photoresist layer (12) is exposed to the required pattern and developed to remove unnecessary portions, that is, windows (12w).
A process of patterning by drilling and using this second photoresist 7B (12) as a mask
The first photoresist layer (11), which is the lower layer exposed through the window (12w) of the second resist layer (12), is exposed to light by irradiating the entire surface of the mask. In the invention, this Deepl
At the same time as the JV is exposed, the substrate (1) is heated by the heating means (13).
), therefore, the second resist layer (12) is heated, and the second resist layer (12) is heated by this Deep UV irradiation and heating.
Photo-curing, or curing, is performed on the photoresist layer (12). Next, as shown in FIG. 1C, the first photoresist layer (11) is developed to form a window (12).
Predetermined patterning is performed by forming a window (Ilw) corresponding to w). In this way, a desired photoresist pattern is obtained.

[Effect]

As described above, in the present invention, when the first photoresist layer (11) is exposed to Deep UV, that is, the second photoresist 1 (12) is exposed to Deep UV.
Since heating is performed at the same time as pUV irradiation, the adhesion between both layers (11) and (12) in the second photoresist layer (12) is improved, and this resist layer (12) is When the lower first photoresist Ji (11) is treated with gπ light as an exposure mask, the exposure pattern for the photoresist layer (11) can be reliably formed as a close contact pattern, and the second photoresist layer (12) can be The first photoresist layer (11) formed with a pattern can be patterned with high precision and sharpness. Then, as in the present invention, the second
When heating the photoresist layer (12) at the same time as Deep UV exposure, the curing is effectively performed, so that the subsequent photoresist pattern can be used as an etching resist for microfabrication of the substrate (11, for example, by dry etching). In this case, the heat resistance of the second photoresist layer (12) is improved, so that its function as a resist is improved, and thereby fine patterns can be formed with high accuracy and sharpness.

〔Example〕

An example of the method for forming a photoresist pattern according to the present invention will be described in more detail with reference to FIG.

In this example, the substrate (11 is, for example, a semiconductor substrate (I
A) Workpiece such as 5i02 on top! (IB) is deposited and has a step (2) on the surface (la).

First, as shown in FIG. 1A, a substrate (
On the surface (la) of 11, a positive type DeepHV photoresist exhibiting photosensitivity to DeepUV, such as P
A photoresist layer (11) made of MM8 (polymethyl methacrylate) is applied so as to fill the step (2) and make the surface substantially flat, and is subjected to the required drying process as usual. This first photoresist layer (11
) with a relatively thin and uniform thickness on a flat surface (lla) that absorbs the eepHV and emits normal ultraviolet light (350 ~
A positive photoresist, such as a naphthoquinone diazide resist, which is exposed to light at a wavelength of 450 nm is applied.

Thereafter, as shown in FIG. 1B, for example, a reduction projection exposure device is used to perform a required pattern exposure by irradiating ultraviolet rays using a mercury lamp as a light source, and development processing is performed to form a pattern, and a required window <12w) is formed.

Next, using this patterned second resist layer (12) as an exposure mask, the entire surface is irradiated with deep ultraviolet light, and at the same time, heat treatment is performed using the heating means (13). The heating during this exposure is, for example, 100 to 200° C. for 10 minutes. In this way, the second resist Ji (12
) is cured, and the first photoresist layer (
11) is improved, and the heat resistance of the second resist 7 Vi (12) itself is improved. Also, by this exposure to deep ultraviolet rays, the second photoresist layer (12)
In the part where there is, the second lid of this! - The far ultraviolet rays in the resist hJg (12) are absorbed and this second photoresist layer (12) is absent in the window (12w).
) The first photoresist l1 (11) is exposed only under ).

Next, this first photoresist layer (11) is developed, and windows (l1
The first photoresist layer (11) on which the pattern w) is formed is patterned.

As shown in the first diagram, the substrate (11 processed layers (IB))
Then, using the photoresist layers (12) and (11) as a mask, anisotropic dry etching is performed by, for example, RIE to selectively remove the photoresist layers (12) and (11) to form a desired pattern.

〔Effect of the invention〕

As described above, according to the present invention, the upper second photoresist layer (12) is exposed to deep ultraviolet light and subjected to heat treatment to form the photoresist (15) (12).
By causing curing to occur in
It was possible to improve the heat resistance of the film itself, and at the same time, it was possible to improve the adhesion of the underlying first photoresist layer (11).

Therefore, the exposure pattern on the first photoresist layer (ll) can be performed with high accuracy and sharpness, and furthermore, due to the improvement in the heat resistance of the second photoresist layer (12) itself, for example, The resistance to processing such as dry etching is improved, and reliable patterning and therefore ultra-fine processing can be performed.

Further, according to the present invention, heating is performed simultaneously when the second photoresist layer (12) is irradiated with deep ultraviolet light, that is, when the first photoresist Ji (11) in the lower layer is exposed. When irradiating far ultraviolet light and heating at the same time, compared to performing each treatment in separate steps,
Curing of the second photoresist layer (12), that is, improvement in heat resistance and improvement in the adhesion of the interface between both Ji (11) and (12) can be performed more effectively. Moreover, by performing the heating and exposure, that is, irradiation with far ultraviolet light, at the same time, the desired second photoresist layer (
12) Improved resistance to dry etching and both layers (
Since it is possible to improve the adhesion between 11) and (12), its practical benefits are great.

[Brief explanation of the drawing]

FIGS. 1A to 1D are enlarged cross-sectional views in each step of an example of the method for forming a photoresist pattern according to the present invention. (11 is a substrate, (1)) and (12) are first and second photoresists 1-1 (2) are steps.

Claims (1)

[Claims] A step of forming a first photoresist layer with a substantially flat surface that is sensitive to deep ultraviolet rays on a substrate having steps, and a step of forming a first photoresist layer that absorbs deep ultraviolet rays on the first photoresist layer. 2
forming a photoresist layer; exposing and developing the second photoresist layer to pattern it; and heating the first photoresist using the second photoresist layer as a mask. 1. A method for forming a photoresist pattern, comprising the step of exposing to light.