JP2653072B2 - Pattern formation method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photolithography technique in microfabrication techniques such as semiconductor device manufacturing. More specifically, the present invention relates to formation of a resist pattern in photolithography and a pattern forming material therefor.

2. Description of the Related Art In recent years, with the development of semiconductor device manufacturing technology, photolithography technology has been required to have a fine processing technology on the order of 0.5 μm. This 0.5
As a technology that exceeds the order of microns,
Exciter laser steppers, X-ray steppers, or direct writing electron beam exposure apparatuses are being developed as new apparatuses to shorten the wavelength and increase the aperture of conventional steppers. Also, various methods have been proposed and attempted in the resist process technology. For example, multilayer resist method (MLR method), anti-reflection coating method (ARC
Method, contrast enhancement method (CEL method), portable conformable method (PCM method), image reversal method (IR method), and the like.

Problems to be Solved by the Invention However, there is a limit in increasing the aperture and shortening the wavelength of a conventional stepper, making it difficult to manufacture a mask with an X-ray stepper, and having a low throughput with a direct writing type electron beam exposure apparatus. For that reason, excimer laser steppers are currently the most promising. However, excimer laser steppers also have problems. As represented by the following Rayleigh equation, R = kλ / NA …… R: resolution, k: constant (0.6 to 0.8) λ: exposure wavelength, NA: numerical aperture of lens To improve resolution at the same wavelength If this is the case, the NA must be increased, but as the NA is increased, there is a disadvantage that the depth of focus (FD) becomes shallow as shown in the equation.

FD = λ / (NA) ² … On the other hand, as described above, various methods have been tried in the resist process technology. All of the methods have an effect of covering the depth of focus degradation in the photolithography process, There were problems such as the complexity of the process and the small effect of increasing the depth of focus, which was not very practical.

That is, the conventional resist process technology cannot sufficiently cope with the shallow depth of focus associated with a shorter wavelength and a larger aperture in an excimer stepper.

The present invention relates to a pattern forming material such as a photoresist process developed in view of the above-described drawbacks of the conventional resist process and a pattern forming material therefor, and to an exposure apparatus having a small depth of focus such as an excimer laser stepper. An object of the present invention is to provide a resist process technology capable of sufficiently exhibiting performance.

Means for solving the problems The pattern forming method of the present invention, on a substrate such as a semiconductor substrate, an organic material whose chemical substance changes by the first exposure,
A step of applying an organic coating material containing an organic material whose chemical substance changes by the second exposure to form an organic thin film, and a step of selectively exposing the vicinity of the surface of the organic thin film by the first exposure, A step of exposing the entire surface of the organic thin film by the second exposure, and a step of developing the exposed organic thin film to form a pattern.

Further, the organic coating material which is a pattern forming material used in the present invention, an organic material whose main composition is composed of an alkali-soluble resin, and furthermore, an organic material composed of an aromatic azide compound which chemically changes at the wavelength of the first exposure, And an organic material composed of a diazo compound that chemically changes at the wavelength of the second exposure.

Effects The pattern forming method and the pattern forming material of the present invention enable a resist process having only the advantages of the MLR method, the CEL method, the PCM method, and the IR method. That is, in the first exposure step, only the vicinity of the surface of the organic thin film is used, and selectively exposed to, for example, far ultraviolet light (for example, KrF excimer laser light; 248 nm) to modify only the surface of the organic thin film. Here, the modified portion has a property of absorbing the wavelength of the second exposure. Next, as the second exposure, the entire surface is exposed to light having a wavelength having a good transmittance to the organic thin film (for example, g-line; 436 nm), and only the portion which has already been denatured by the first exposure is left organic. The thin film is developed and removed. That is, by using the resist pattern forming method and the pattern forming material of the present invention,
Since only a very thin portion near the surface of the organic thin film is selectively exposed in the first exposure, the advantages of the MLR method are adopted. In addition, the selectively exposed portion selectively absorbs the wavelength of the second exposure, thereby exhibiting an adhesion mask effect in the CEL method. Further, by selectively forming the light absorption pattern on the organic thin film, the advantage of the PCM method is included. Furthermore, the effect of the IR method can be taken in by forming a pattern by the second overall exposure.

Therefore, the effect of the pattern forming method and the pattern forming material of the present method is particularly large in a region where the pattern formation is very fine, for example, in the region of submicron pattern formation or less.

EXAMPLES Hereinafter, examples of the pattern forming method and the pattern forming material of the present invention will be described with reference to process cross-sectional views.

First, as shown in FIG. 1, an arbitrary substrate (for example,
The main composition is composed of an alkali-soluble resin (for example, phenol novolak resin) on a semiconductor substrate 1, and a diazo compound (for example, 1,2-naphthoquinonediazidosulfonic acid chloride) and an aromatic azide compound (for example, , 2-phenylamino-5-azidobenzoic acid) to form an organic thin film 2 having a thickness of 1 to 2 μm. Next, as the first exposure, far ultraviolet light (for example, KrF excimer laser light)
3 to selectively expose the vicinity of the surface of the organic thin film 2 (FIG. 2). Here, reference numeral 4 denotes a photomask for performing selective exposure. At this time, since the main composition forming the organic thin film 2 largely absorbs far ultraviolet light, only the surface layer of the organic thin film 2 having a thickness of about 0.1 to 0.2 μm is selectively exposed in a pattern. Thus, an extremely thin exposed portion 5 is formed only on the surface. Therefore, in this step, as in the case of the multi-layer resist, the same effect can be obtained as in the case where a thin resist is overlaid and applied and only the upper resist is selectively exposed. That is, the apparatus can be used for high-resolution exposure with a small depth of focus, and a high-resolution and sharp fine pattern of 0.5 μm or less can be obtained (FIG. 3).

Here, the aromatic azide compound (for example, 2-phenylamino-5-azidobenzoic acid) undergoes a photochemical reaction with far ultraviolet light (for example, excimer laser light), and its color becomes
The color changes from green to black according to the exposure time. That is,
The extremely thin exposed portion 5 only on the surface forms a colored portion 6 by coloring of the compound. At this time, the coloring portion 6
All light having a wavelength of at least 450 nm or less is absorbed (FIG. 4). Therefore, if the entire exposure is performed in the second exposure using light 7 having a wavelength longer than the above-mentioned far ultraviolet light, for example, light having a wavelength of 450 nm or less (for example, g-line 436 nm), only the uncolored portion 8 of the organic thin film 2 is selected. This means that the exposure has been completed (FIG. 5).
That is, in this process, the three effects of the CEL method, the PCM method, and the IR method have been incorporated at once.

Finally, by developing the organic thin film with a developing solution (for example, an aqueous solution of a quaternary amine compound such as tetramethylammonium hydroxide), only the uncolored portion 8 is removed, and the resist pattern 9 remains only in the colored portion 6. As with the IR method, a high-resolution pattern of about 0.5 μm opposite to the mask pattern can be obtained (FIG. 6).

In the above embodiments, an example in which KrF excimer laser light is used as light for the first exposure and g-ray is used as light for the second exposure has been described. However, a photosensitive agent forming an organic coating material is used. The wavelengths of the first and second exposures can be arbitrarily changed depending on the combination of the light absorption ranges of the diazo compound and the aromatic azide compound.

Also, an example in which a colored portion is selectively formed only in an exposed portion has been described. Conversely, an organic thin film in which a colored portion is entirely formed in advance is used, and the vicinity of the surface of the organic thin film is determined by the wavelength of the first exposure. Except that the pattern is reversed even when using a method of decoloring only the exposed part,
It is clear that the same effect can be obtained.

Further, the light for the first exposure is not limited to the excimer laser light, but may be an X-ray, an electron beam, an ion beam, or the like. The light for the second exposure is not limited to the g-ray, but may be i-line, visible light, or the like. Light rays, soft X-rays and the like may be used.

In the method of the present invention, only the surface of the organic thin film is used for the first pattern exposure, so that the exposure apparatus can be sufficiently used even when the aperture is increased, the wavelength is shortened, and the depth of focus is reduced. There is a great effect that the device resolution can be fully exhibited.

That is, only one application step is required as compared with the conventional multilayer resist (MLR method) process. Furthermore, since the development process is performed only once, the process is greatly simplified.

In addition, the pattern forming method of the present invention does not require a heat treatment step as compared with the conventional image reverse (IR method) process, so that the process stability is good.

Further, the pattern forming method of the present invention does not require a photobleaching film on the resist upper surface unlike the conventional contrast enhancement (CEL) process, so that the exposure time is greatly reduced and the contrast is sufficiently obtained. Only one time.

Furthermore, conventional anti-reflective coating (ARC method)
Compared with the process, only the vicinity of the surface of the organic thin film is exposed, and the light for exposure does not reach the lower portion of the organic thin film.

In addition, the pattern forming method of the present invention can form a high-contrast patterned light-absorbing layer on the resist surface without applying two layers, compared to the conventional portable coformable (PCM) process. There are effects such as the resolution of the resist pattern can be greatly improved.

Effect of the Invention As described above, the pattern forming method and the pattern forming material of the present invention can be applied to an exposure apparatus having a small depth of focus, such as an excimer laser stepper, without significantly improving the conventional photoresist process technology. There is a feature that a sufficiently high resolution can be obtained when applied to an apparatus. Therefore, when ultra-fine processing is required in various devices including semiconductor devices in the future, the effect thereof will be significant.

[Brief description of the drawings]

1 to 6 are process cross-sectional views for explaining a pattern forming method according to one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... board | substrate, 2 ... organic thin film, 3 ... far ultraviolet light (for example, excimer laser light), 4 ... photomask, 5 ... exposure part, 6
... Colored section, 7... Second exposure light (eg g-line light), 8
... Uncolored part, 9... Resist pattern.

Claims (6)

(57) [Claims] An organic material which is converted into a substance which does not pass through the second exposure by a chemical reaction of the chemical substance by the first exposure on the substrate and the chemical substance by the second exposure, and thereafter the developing treatment Forming an organic thin film by applying one layer of an organic coating material containing an organic material capable of forming a pattern, and selectively exposing the vicinity of the surface of the organic thin film by the first exposure. Selectively forming a layer that does not allow the light of the exposure to pass, a step of exposing the entire surface of the organic thin film in the second exposure, and a step of forming a pattern by developing the organic thin film that has been entirely exposed. A pattern forming method, comprising: 2. The pattern forming method according to claim 1, wherein the wavelength of the first exposure light is shorter than the wavelength of the second exposure light. 3. The pattern forming method according to claim 1, wherein the light for the first exposure is excimer laser light in a far ultraviolet region. 4. The method according to claim 1, further comprising the step of: reacting a chemical substance by a first exposure on the substrate with a photoreaction to change the organic substance into a substance which passes through the second exposure;
A step of applying an organic coating material including an organic material capable of forming a pattern by a development process after a chemical substance undergoes a photoreaction by exposure to form an organic thin film; Selectively forming a layer through which light of the second exposure passes by selectively exposing the first exposure, and exposing the entire surface of the organic thin film by the second exposure;
A pattern forming method, comprising a step of developing the organic thin film which has been entirely exposed to form a pattern. 5. The pattern forming method according to claim 4, wherein the wavelength of the first exposure light is shorter than the wavelength of the second exposure light. 6. The pattern forming method according to claim 4, wherein the light for the first exposure is excimer laser light in a far ultraviolet region.