JPH01297648A - Production of semiconductor device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Regarding the single-layer silylation process, a resist pattern with a high aspect ratio is formed on a semiconductor processing substrate using photolithography technology, with the aim of improving pattern accuracy and reducing processing steps. In the single-layer silylation process, a novolak-based positive resist layer made of a mixture of the photosensitive agent naphthoquinone azide and Talezol novolank or phenol novolac resin was formed on the semiconductor processing substrate, and selectively exposed to ultraviolet light. After that, while heating the resist layer or heating under reduced pressure, the wavelength is 400 nm.
A resist pattern is formed by exposing the entire surface to deep ultraviolet rays of less than m, followed by conventional silylation treatment and later reactive ion etching with oxygen ions.

[Industrial application field]

The present invention relates to improvements in the monolayer silylation process.

2. Description of the Related Art Thin film formation technology and photolithography are often used to form semiconductor integrated circuits such as ICs and LSIs, and fine conductor patterns and electrode patterns are formed on substrates to be processed.

In other words, regarding the wiring pattern, silicon (S
A resist is coated on a thin film made of a wiring forming material formed on a substrate to be processed, such as i), and a photomask is used to perform reduction projection exposure of ultraviolet rays to create a resist pattern. Fine patterns are created by etching or dry etching.

On the other hand, there is a significant demand for larger capacities in semiconductor integrated circuits, and this is achieved by miniaturizing unit elements.As a result, patterns are becoming increasingly finer, and submicron patterns are being put into practical use, as well as three-dimensional wiring. It is being done.

That is, after forming a conductor line on the substrate to be processed, an insulating layer is formed on this, and the conductor line is formed on this insulating layer in a direction perpendicular to the direction in which the conventional conductor line is formed, and the upper and lower Three-dimensional wiring is formed by connecting conductor lines through via holes.

In this case, the surface of the insulating layer is uneven due to the conductor line formed below, and since a fine pattern is to be formed on this surface, it is necessary to form a resist pattern with a high aspect ratio.

[Conventional technology]

As mentioned above, isotropic development such as the conventional wet development is not suitable for forming fine patterns on a substrate with steps, and reactive ion etching is not suitable. It is necessary to perform anisotropic development using anisotropic etching such as RIE (abbreviated as RIE), and the following development process has been put into practical use in this regard.

■ Single layer silylation process, ■ Two layer (Bi-1 level) process, ■ Three layer (T
ri-1 level) process, where (2) is to coat a resist on the substrate to be processed, selectively expose the resist to change the quality of the photosensitive agent constituting the resist, and then react it with a silicone compound. This process imparts dry etching resistance by silylation, and is a process in which a fine pattern is obtained as a result of etching by RIH performed in an oxygen (0□) gas atmosphere, leaving the silylated portions.

① is a resin liquid that is easily etched by RIE (hereinafter abbreviated as 0.-RIE) performed in an 0.2 gas atmosphere, such as phenol novolac resin, and is flattened by spin-coding (lower resist), and then a conventional method is applied on top of this. is coated with photoresist (upper layer resist). After forming a resist pattern on the upper layer resist by exposure and development, use this resist pattern as a mask to apply oxygen to the lower layer [/cyst].
, - This is a process of obtaining a fine pattern by performing RIE.

(2) is an intermediate layer that is difficult to be etched by OX plasma but is etched by fluorine (F2) gas or chlorine (Cβ2) gas after planarization with a resin layer that is easily etched by 02-RIE (lower layer resist I-). A resist pattern is formed on the upper layer by selective exposure and development, and the intermediate layer is dry-etched using this as a mask. This is a process in which a fine pattern is obtained by etching the lower resist layer by 0□-RIE using as a mask.

As described above, various processes have been put into practical use, but the single-layer silylation process (2) is considered to be the most effective method because it requires fewer processing steps.

However, this process also has its problems.

Taking as an example the commonly used novolac positive resist TSMR-8900 (manufactured by Tokyo Ohka Corporation), the processing steps will be explained with reference to FIG. 2 as follows.

This resist uses tetrahydroxybenzophenone as a sensitizer, and uses naphthoquinone diazide-5 as a photoreceptor.
- It is a photosensitizer made by adding an ester to sulfonyl chloride, and is mixed with Talesol Novolank resin.

In FIG. 2, the cresol novolak resin is shown as (11), and the photosensitizer naphthoquinone azide is shown as (2).

In this structural formula (2), R represents tetrahydroxybenzophenone.

This figure 2 shows how the resist changes during pre-exposure, exposure, and silylation.
The exposed area and the unexposed area are shown separately for the n+ g line).

That is, before exposure, there is no change in resin (1) and photosensitizer (2), but when exposed to ultraviolet light, resin (1) remains unchanged, but photosensitizer (2) is activated and becomes nitrogen (N2). ) separates to form a ketene intermediate, which takes up water from the atmosphere and transforms into indenecarboxylic acid (3).

On the other hand, the unexposed area remains unchanged as shown in (1) and (2).

Next, the entire surface of the resist layer is silylated by spraying the vapor of hexamethyldisilazane (abbreviated as HMDS), an organosilicon compound.
) is a trimethylsilyl group (-3i
(Me) 3) Resin (1) and indenecarboxylic acid (3) are silylated to become (4) and (5) due to substitution with (Me is a methyl group).

In this case, since both silylated (4) and (5) have excellent resistance to O ions, they act as a mask, and the resist in the unexposed area is supposed to be etched, but the problem is that even in the unexposed area, the resist is etched. Since the resin (cresol novolak resin) has an OH group, it is silylated, and as it is, it is resistant to 0 ions even in the unexposed region.

Therefore, the entire surface layer of the resist (approximately 1,000 layers) was dry-etched using carbon tetrafluoride (CF) gas to remove the silylated material in the unexposed area, and then the silylated material in the exposed area was removed by dry etching. ), 02-R using (5) as a mask
IE is performed to form a fine pattern with a high aspect ratio.

However, the thickness of the resist layer formed on the substrate to be processed is as thin as about 1000 layers, and when the resist layer is thinned by etching the entire surface with CF and gas, it may be partially eroded and its reliability may be impaired. was the problem.

[Problem to be solved by the invention]

As mentioned above, according to the silylation process, not only the exposed area but also the unexposed area is silylated, so it is necessary to remove the silylated part in the unexposed area, and therefore the selectivity for O,-RIE is The problem is that this decreases.

[Means to solve the problem]

The above problem can be solved by forming a novolac-based positive resist layer on the semiconductor substrate and selecting the After the exposure, the resist layer is heated or heated under reduced pressure,
The entire surface is exposed to deep ultraviolet light with a wavelength of 4000 m or less, followed by conventional silylation treatment and later O,-RIE.
The problem can be solved by doing the following.

[Effect]

In the present invention, the photosensitizer activated by ultraviolet irradiation is unstable in an environment without moisture, and reacts with the cresol or phenol nophorac resin activated by deep ultraviolet irradiation to form an ester bond with the resin. , this conjugate takes advantage of the fact that it is easily dry etched by 02-RIB.

FIG. 1 is an explanatory diagram of the monolayer silylation process according to the present invention.

Here, the state before exposure and the state after exposure of the exposed area and the unexposed area are the same as in FIG. 2.

That is, naphthoquinone azide, which is a photosensitizer, is used for G-line (wavelength: 436 nm) or i-line (wavelength: 3651 m).
It is activated by ultraviolet irradiation and separates nitrogen (N2) to form a ketene intermediate, but this is unstable and takes in moisture from the atmosphere to form indene carboxylic acid.

On the other hand, cresol novolak resin does not change even when exposed to ultraviolet rays.

In addition, the naphthoquinone azide in the unexposed area is of course left untouched.
It is.

Next, the selectively exposed resist is heated or heated under reduced pressure while being exposed to far ultraviolet light (Deep UV rays) with a wavelength of 400 nm or less.
The entire surface is irradiated with UV).

The reason for heating or heating under reduced pressure is to remove water from around the resist.

That is, naphthoquinone azide is exposed to ultraviolet light.

On the other hand, cresol or phenol novolac resin (hereinafter referred to as cresol novolac resin for simplicity) is activated by full-surface irradiation with far ultraviolet rays, and the two react (6
) forms an ester bond as shown in

In addition, indenecarboxylic acid (3) in the exposed area is left as is\
remains unchanged.

Next, when silylation is performed using hexamethyldisilazane (HMDH), the OH group of the talesol novolank resin (1) in the exposed area and the OH group of the indenecarboxylic acid (3)
The group is a trimethylsilyl group (-3i (CII3) s)
However, silylation is not performed because there is no OH group in the unexposed portion of the ester bond (6).

Therefore, the unexposed areas are etched by the O, -RIH development process, but the exposed areas are not etched.

From the above, the conventional process of removing the silylated layer in the unexposed area using CF or gas is not necessary, thereby improving reliability and making it possible to form a highly accurate pattern.

〔Example〕

Example 1: Novolac-based positive resist (product name KP) on St wafer
R-820. Kodak) was spin-coded to a film thickness of 1.2 μm, placed on a hot plate, and heated to 100°C.
Pre-baked for 90 seconds.

Then, projection exposure was performed using a reduction projection exposure machine with a numerical aperture of 0.35 using g-line ultraviolet light.

After exposure, the wafer was placed on a hot plate at 110° C., and while being heated, the entire surface was exposed to deep ultraviolet rays for 120 seconds using a xenon-mercury (Xs-11g) lamp.

Next, a silylation process was performed for 300 seconds in a 90°C oven filled with hexamethyldisilazane (HMDS) vapor, and then dry development was performed by O,-RIE. As a result, the pattern accuracy was good and the aspect ratio was We were able to obtain a high resist pattern.

Example 2: After pre-baking the novolak positive resist using the same process as in Example 1, the wafer was placed in a vacuum dryer, and
0. After being irradiated with far ultraviolet rays using an Xe-Hg lamp for 120 seconds under reduced pressure to I Torr, the sample was taken out, and then silylation treatment and dry development using O,-RIE were performed in the same manner as in Example 1. As a result, the pattern accuracy was improved. It was possible to obtain a resist pattern with good characteristics and a high aspect ratio.

〔Effect of the invention〕

By implementing the present invention, a pattern with a high aspect ratio can be formed with high reliability in a small number of steps by preventing silylation of an unexposed region in a single-layer silylation process.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a single-layer silylation process according to the present invention, and FIG. 2 is an explanatory diagram of a conventional single-layer silylation process. Ward 1

Claims (1)

[Claims] In a single-layer silylation process for forming a resist pattern with a high aspect ratio on a semiconductor substrate using photolithography, a photosensitive material formed by mixing naphthoquinone azide with a cresol novolac or phenol novolac resin. A novolac-based positive resist layer is formed on the semiconductor substrate to be processed, selectively exposed to ultraviolet light, and then the entire surface is exposed to deep ultraviolet light having a wavelength of 400 nm or less while heating or heating under reduced pressure. . A method for manufacturing a semiconductor device, comprising: successively performing conventional silylation treatment, and then performing reactive ion etching using oxygen ions to form a resist pattern.