JPH04372113A - Formation of circuit pattern - Google Patents

Abstract

PURPOSE:To prevent instability in resist sensitivity and deterioration in pattern caused by ruggedness on a wafer by depositing a thin organic film over a wafer having a ruggedness zone, by heating it to blacken, and by coating it with photoresist for exposure/development. CONSTITUTION:For circuit patterning of a wafer 1 by photolithography, a thin organic film is deposited over the wafer having a ruggedness zone before coating with a photoresist 3, and this organic film is heated to blacken. Thereafter, the above-mentioned blackened organic film 8 is coated with a photoresist 3, which undergoes exposure and development. For example, the top of a layer 2 to be etched is sprayed with a solution of novolac resin dissolved in a solvent such as ethylcellosolveacetate through a spray to coat the wafer 1. Next, a film is novolac resin is blackened by heating up to about 300 deg.C. It is preferable that the postblackening thickness of a resin film is 0.2mum or less.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to IC manufacturing technology.
More specifically, the present invention relates to a method of forming an IC circuit pattern on a wafer substrate such as silicon by a photolithography process. In recent years, as ICs have become more highly integrated, element structures have become finer, and accordingly, it has become necessary to form finer patterns more accurately.

0002

2. Description of the Related Art In a conventional photolithography process, as shown in FIG.
A photoresist 3 is applied directly onto the film 2 provided above to be etched. However, in this case, as shown in FIG. 1, the light irradiated onto the photoresist 3 passes through the resist 3 and is reflected from the film 2, or is reflected on the upper surface of the resist 3, resulting in a phenomenon in which the light travels back and forth within the resist 3. there were. At this time, when the phases of the incident light 5 and the reflected light 6 are opposite, the lights cancel each other out and the effective incident light decreases. On the other hand, when the light 5 and the light 6 are in the same phase, they strengthen each other and the amount of effective incident light increases. Therefore, the relationship between resist sensitivity and resist film thickness is as shown in FIG. In Figure 2, at the maximum peak point A of the relationship curve, the phase of the incident light and the reflected light are opposite, so the amount of exposure required for exposure is large; conversely, at the minimum peak point B, the phase of the incident light and the reflected light is opposite. Since they are the same and strengthen each other, the amount of exposure required for exposure is reduced.

FIG. 3 shows that a suitable layer 7, such as (polysilicon, aluminum, silicon oxide), etc. is deposited on the wafer.
As a result, the film 2 becomes uneven, which causes the incident light 4 to be reflected to an unplanned location. In this case, halation occurs and the pattern deteriorates. I don't like it because it can cause irritation.

0004

As described above, in the conventional method of forming a circuit pattern by photolithography, the pattern dimensions of the resist become unstable due to standing waves caused by reflection from the wafer substrate. Further, there is a problem that the resist sensitivity becomes unstable or the pattern deteriorates due to the reflection of the incident light due to the unevenness of the film 2 to be etched on the wafer. Therefore, the present invention solves the problems of the prior art, that is, when forming a circuit pattern on a wafer by photolithography, instability of resist sensitivity and pattern deterioration due to unevenness on the wafer occur. The purpose of the present invention is to provide a method for forming a circuit pattern.

[0005]

[Means for Solving the Problems] According to the present invention, when forming a circuit pattern on a wafer by photolithography, prior to coating a photoresist, a step of forming a thin organic film on a wafer having uneven portions is performed. , a method for forming a circuit pattern is provided, which includes the steps of heating the organic film to blacken it, and applying a photoresist on the blackened organic film, exposing and developing it.

That is, according to the present invention, as shown in FIG. 4, a suitable layer 7 (for example, polysilicon,
A light-absorbing layer 8 is formed over the film 2 to be etched on a suitable wafer substrate 1 (for example a silicon substrate) having an aluminum, silicon oxide film), and then a photoresist film 3 is formed.

[0007]

[Operation] In the present invention, as shown in FIG. 4, the patterned incident light 4 is absorbed by the blackened light absorption layer 8, so that the problem caused by reflection as in the prior art described above can be solved. can be prevented.

[0008]

EXAMPLES Examples of the present invention will be described below with reference to the drawings, but it goes without saying that the technical scope of the present invention is not limited to the following examples.

FIGS. 5-12 illustrate embodiments of the present invention. Figure 5
1 shows the initial state of a wafer in an example of the method for forming a circuit pattern according to the present invention, in which a layer forming a step (for example, polysilicon,
aluminum, silicon oxide film) 7 is provided,
A layer 2 to be etched (for example, polysilicon, aluminum, silicon oxide) is formed thereon.

FIG. 6 shows that on the layer 2 to be etched,
1 is a diagram illustrating a process of forming an organic film 2 according to the present invention, in which a solution of a novolac resin dissolved in a solvent such as ethyl cellosolve acetate is applied to a wafer by spraying according to a conventional method. A thin organic film 9 of novolac resin can be formed by spraying the novolac resin solution into a sufficiently thin spray. As the material of the organic film, any material can be used as long as it has the property of turning black when heated.In addition to novolac resin, for example, novolac-based positive resist (Az-1350 (Shipley), OFPR) −
800 (Tokyo Ohka)), etc. can be used. The thickness of the organic film 9 is not particularly limited, but the thickness after blackening in the next step is preferably 0.2 μm or less, and 0.05 to 0.0 μm.
More preferably, the thickness is 1 μm.

In FIG. 7, a wafer having an organic film 9 coated in the previous step is heated to blacken the film. For example, when a novolac resin is used, a step is shown in which the novolac resin film 9 is blackened by heating, for example, to a temperature of about 300°C. In FIG. 7, 8 indicates a blackened layer.

FIG. 8 shows a typical photoresist, for example, Zi.
A process of forming a resist layer 3 by applying R-9000 (trade name, manufactured by Nippon Zeon) (i-line positive resist whose main component is novolak resin) is shown. The type of resist used does not matter at all in the present invention.

FIG. 9 is a diagram showing a resist pattern 10 formed by subjecting the photoresist layer to normal exposure and development. According to the present invention, since there is no influence of reflection of incident light, a good pattern can be formed.

FIG. 10 shows the resist pattern 1 obtained above.
For example, the blackened novolac resin 8 is etched by anisotropic etching using O2 plasma according to the method of the present invention.
Etching is performed using the resist pattern 10 as a mask. The anisotropic etching may be performed by RIE or ECR.

FIG. 11 shows the blackened novolac resin layer 8 formed in the previous step.
After etching a part of the layer 2 to be etched,
Using the remaining resist 10 and the blackened novolac resin layer 8 as a mask, etching is performed by dry etching such as RIE or ECR or wet etching using hydrofluoric acid, and further, the remaining photoresist and the blackened organic film are removed by oxygen plasma. A circuit pattern as shown in FIG. 12 can be formed.

FIG. 13 shows a film thickness of 0.15 μm according to the present invention.
Film thickness of photoresist (ZiR-9000) and Eth exposure time (m
・Sec) (Example) and the relationship obtained in the same manner except that no blackened novolac resin film was provided (
It is a graph diagram showing a comparative example).

[0017]

As explained above and as shown in the graph diagram of FIG. 13, according to the present invention, when forming a circuit pattern on a wafer substrate by a photolithography process, it is possible to prevent the irregularities on the wafer substrate from forming. Since the problem of reflection can be effectively prevented, the resist sensitivity can be stabilized, and a good and reliable circuit pattern without the problem of pattern deterioration can be formed.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing the behavior of incident light in a conventional photolithography process.

FIG. 2 is a drawing schematically showing the relationship between the exposure amount required for resist exposure and the resist film thickness in a conventional example.

FIG. 3 is a diagram illustrating a conventional example showing a state of reflection of light on a step.

FIG. 4 is a drawing schematically showing the situation of incident light in photolithography of the present invention.

FIG. 5 is a diagram showing an initial state of a wafer in an embodiment of the present invention.

FIG. 6 is a drawing showing a state of coating an organic film in an example of the present invention.

FIG. 7 is a drawing showing a blackened state of an organic film in an example of the present invention.

FIG. 8 is a drawing showing the coating state of a photoresist film in an example of the present invention.

FIG. 9 is a drawing showing the state of a photoresist film after exposure and development in an example of the present invention.

FIG. 10 is a drawing showing the state after the blackened organic film is removed in an example of the present invention.

FIG. 11 is a drawing showing the state after etching in an embodiment of the present invention.

FIG. 12 is a drawing schematically showing a circuit pattern formed in an example of the present invention.

FIG. 13 is a graph showing the relationship between Eth exposure time and resist film thickness in an example of the present invention.

[Explanation of symbols]

1...Wafer substrate 2...Layer to be etched 3...Resist 4...Incoming light 5... Incident light in resist 6...Light reflected on the top surface of the resist 7...Layer forming a step 8...Blackened novolak resin 9...Novolac resin 10...Resist pattern

Claims (5)

[Claims] Claim 1: When forming a circuit pattern on a wafer by photolithography, prior to applying photoresist, there is a step of forming a thin organic film on the wafer having uneven parts, and heating the organic film to blacken it. 1. A method for forming a circuit pattern, comprising the steps of: applying a photoresist on the blackened organic film, exposing it to light, and developing it. 2. The method according to claim 1, wherein the organic film is formed by coating using a spray. 3. The method according to claim 1, wherein the organic film is a phenolic resin film. [Claim 4] The thickness of the blackened organic film is 0.2μ.
The method according to any one of claims 1 to 3, which is less than or equal to m. 5. The method according to claim 1, wherein the blackened organic film is removed by anisotropic etching.