JP2570730B2 - Pattern forming method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a pattern on a photoresist layer by aligning and exposing a photoresist layer.

[Summary of the Invention] The present invention is directed to a pattern forming method as described above, wherein a film containing nitrogen and titanium as main components and containing oxygen and having a thickness of 42 nm or less is formed under a photoresist layer. By performing alignment and exposure in the above, a highly accurate pattern can be formed.

[Conventional technology]

A fine pattern such as a wiring of a semiconductor device is formed by photolithography and etching. However,
If an attempt is made to form a wiring or the like with a material having a high reflectance such as A1, in photolithography, halation occurs in the photoresist layer due to reflection by A1. Therefore, in such a case, a highly accurate pattern cannot be formed.

For this purpose, JP-A-61-185928 discloses a film containing nitrogen and titanium as a main component as a film which has an antireflection function and can be removed without damaging this pattern after forming a pattern on A1 or the like. There is disclosed a pattern forming method in which a resist layer is exposed in a state in which the resist layer is formed under a resist layer with a thickness of about 1000 °.

[Problems to be solved by the invention]

Incidentally, in order to achieve high integration by fine processing of a semiconductor device, exposure of a resist layer has been performed by reduction projection exposure.

In this reduced projection exposure, the entire surface of the resist layer formed on the wafer is exposed by repeating step-and-repeat. Therefore, in the reduction projection exposure, precise alignment exposure must be performed. For this purpose, the position of the wafer is detected from alignment marks on the wafer, and the projection image of the mask is aligned with the wafer.

Incidentally, the alignment mark on the wafer is detected by irradiating the wafer with light different from the light used for exposure, that is, light having a wavelength that does not expose the resist layer, and detecting the reflected light. Therefore, in this case, it is preferable that the reflectance of the wafer or the like is high, contrary to the case of the exposure.

However, when a film containing nitrogen and titanium as main components is formed with a thickness of about 1000 mm as in the above-described conventional example, the reflectance of the wafer or the like to alignment-like light is low, and the alignment mark on the wafer is high. It cannot be detected with accuracy. Therefore, it is not possible to perform high-precision pattern formation by performing wafer positioning with high accuracy.

[Means for solving the problem]

The pattern forming method according to the present invention includes performing alignment and exposure in a state where a film containing nitrogen and titanium as main components and containing oxygen and having a thickness of 42 nm or less is formed under a photoresist layer. Features.

[Action]

In the pattern forming method according to the present invention, the reflectance for alignment light is 20% or more, and the reflectance for exposure light is 20% or less.

〔Example〕

Hereinafter, one embodiment of the present invention applied to the formation of the A1 wiring of the semiconductor device will be described, but prior to the description of this embodiment,
First, experimental results leading to the present invention will be described.

In this experiment, first, a Si substrate having a 1.0-μm-thick Al-Si film formed on its surface was placed in a batch-type sputtering apparatus, evacuated and heated and baked.
/ Min, N ₂ 67 cc / min and O ₂ 1.5 cc / min were introduced to perform Ti sputtering.

And by this sputtering, the thickness is 30,
Four types of TION of 50, 58 and 80 nm were formed on the Al-Si film. FIG. 2 shows the reflectance spectra of these four types of TION films. It is considered that the reason why the reflectance changes depending on the wavelength is due to light interference.

By the way, in reduction projection exposure, the reflectivity at the time of alignment is 20
% Is preferable, and the reflectance at the time of exposure is 20%
The inventors of the present application have empirically found that the following is preferable.

FIG. 1 shows, in FIG. 2, wavelengths having a reflectance of 20% on the high wavelength side and low wavelength side by broken lines, and wavelengths having the lowest reflectance by solid lines. Therefore, the reflectance is 20% or less in a region between the two broken lines, and the reflectance is 20% or more in other regions.

On the other hand, in the current reduction projection exposure apparatus, He-Ne laser light having a wavelength of 633 nm is used as alignment light, and G line of an ultra-high pressure mercury lamp having a wavelength of 436 nm is used as exposure light, respectively. Used.

Therefore, from FIG. 1, the reflectance for light having a wavelength of 633 nm is 2
It can be seen that the thickness of the TiON film that satisfies both the conditions of not less than 0% and the reflectivity for light having a wavelength of 436 nm of not more than 20% is not more than 42 nm.

Thus, as an example of the present invention, a photoresist layer was patterned on a 50 nm-thick TION film having a reflectance of about 20% for light having a wavelength of 436 nm. As a result, width 1.0
Patterning of μm or less was favorably formed without being affected by the reflected light from the substrate side.

In an exposure apparatus such as an excimer laser beam, which uses light having a shorter wavelength than the G-line of an ultra-high pressure mercury lamp as light for exposure, the thickness of the TiON film is appropriately selected to include a region of 20 nm or less. It can be easily seen from FIG. 1 that both the alignment and the exposure can be performed satisfactorily.

〔The invention's effect〕

In the pattern forming method according to the present invention, the reflectance for alignment light is 20% or more, and the reflectance for exposure light is 20% or less. Can also be performed with high precision, and highly accurate pattern formation can be performed.

[Brief description of the drawings]

FIG. 1 and FIG. 2 are graphs showing the relationship among the thickness, wavelength, and reflectance of the TiON film.

Claims (1)

(57) [Claims] 1. A pattern forming method for aligning a photoresist layer with a pattern to be formed on the photoresist layer and exposing the photoresist layer to form the pattern on the photoresist layer, comprising the steps of: Wherein the alignment and the exposure are performed in a state where a film containing oxygen as a main component and containing oxygen and having a thickness of 42 nm or less is formed under the photoresist layer.