JPS63232432A - Pattern formation - Google Patents

Abstract

PURPOSE:To form a pattern with high accuracy by conducting alignment and exposure in a state in which a film mainly comprising nitrogen and titanium and having thickness of 42 nm or less is formed under a photoresist layer. CONSTITUTION:Alignment and exposure are performed under the state in which a film mainly comprising nitrogen and titanium and thickness of 42 nm or less is formed under a photoresist layer. That is, it is preferable that reflectivity at the time of alignment extends over 20% or more and it is desirable that reflectivity at the time of exposure inversely extends over 20% or less in reduction projection exposure. Since He-Ne laser beams having a wavelength of 633 nm are used as beams for alignment and the G beams of an ultrahigh pressure mercury lamp having a wavelength of 436 nm as beams for exposure, the thickness of a TiON film satisfying both conditions of reflectivity of 20% or more to beams having the wavelength of 633 nm and reflectivity of 20% or less to beams having the wavelength of 436 nm is brought to 42 nm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a pattern forming method for forming a pattern on a photoresist layer by aligning and exposing the photoresist layer.

[Summary of the invention]

The present invention uses the above-described pattern forming method by performing alignment and exposure with a film containing nitrogen and titanium as main components and having a thickness of 42 nm or less formed under the photoresist layer. This allows highly accurate pattern formation.

[Conventional technology]

Fine patterns such as wiring of semiconductor devices are formed by photolithography and etching.

However, when attempting to form wiring or the like using a material with a high reflectance such as AI, dielectric condensation occurs in the photoresist layer due to reflection by the AI during photolithography. Therefore, in such a case, a highly accurate pattern cannot be formed.

For this reason, Japanese Patent Application Laid-Open No. 61-185928 discloses a film that has an anti-reflection function and that does not damage the pattern after forming a pattern on AI etc. (a removable film containing nitrogen and titanium as main components) A pattern forming method is disclosed in which the resist layer is exposed to light after a film is formed under the resist layer to a thickness of about 1,000.

[Problem that the invention seeks to solve]

Incidentally, in order to microfabricate semiconductor devices and increase their integration, the exposure of the resist layer has come to be performed by reduction projection exposure.

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

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

However, if a film mainly composed of nitrogen and titanium is formed with a thickness of about 1,000 as in the conventional example described above, the reflectance of the wafer, etc. to the alignment light is low, and the alignment mark on the wafer is cannot be detected with high precision. Therefore,
It is not possible to form a pattern with high precision by aligning the wafer with high precision.

[Means for solving problems]

The pattern forming method according to the present invention is characterized in that alignment and exposure are performed while a film containing nitrogen and titanium as main components and having a thickness of 42 nm or less is formed under a photoresist layer.

[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.

〔Example〕

An embodiment of the present invention applied to the formation of At wiring in a semiconductor device will be described below, but prior to the explanation of this embodiment,
First, the experimental results leading to the present invention will be explained.

In this experiment, we first used Al-5ill with a thickness of 1.0 μm.
The Si substrate with the surface formed on it was placed in a batch type sputtering device, and after vacuum evacuation and heating baking, Ar65cc/min, Nt6Tcc/min and 0!1.5
Ti was sputtered by introducing c c for 7 minutes.

As a result of this sputtering, the thickness was reduced to 30 mm.
Al
-5i film. Figure 2 shows these four types of Ti.
The reflectance spectrum of the 0N film is shown. This change in reflectance depending on wavelength is thought to be due to light interference.

By the way, in reduction projection exposure, the reflectance during alignment is 20
It is preferable that the reflectance at the time of exposure is 20% or more.
The inventor of the present application has empirically found that it is preferably less than %.

In FIG. 1, in FIG. 2, the wavelengths at which the reflectance is 20% on the high wavelength side and the low wavelength side are shown by broken lines, and the wavelengths at which the reflectance is the lowest are shown by solid lines. Therefore, in the region between the two broken lines, the reflectance is 20% or less, and in the other regions, the reflectance is 20% or more.

On the other hand, in the current reduction projection exposure apparatus, He-Ne laser light with a wavelength of 633r++w is used as alignment light, and G-line of an ultra-high pressure mercury lamp with a wavelength of 436nm is used as exposure light, both over a wide range. It is used.

Therefore, from FIG. 1, it can be seen that the thickness of TiONM that satisfies both conditions of having a reflectance of 20% or more for light with a wavelength of 633 nm and a reflectance of 20% or less for light with a wavelength of 436 nm is 42 nm or less. Ru.

Therefore, as an embodiment of the present invention, a Ti0N film having a thickness of 50nw and having a reflectance of approximately 20% for light with a wavelength of 436n@
A photoresist layer was patterned on the film. As a result, a pattern with a width of 11,000 nm or less was successfully formed without being affected by reflected light from the substrate side.

Note that light with a shorter wavelength than He-Ne laser light, such as He-Cd laser light, is used as alignment light.
In addition, even in exposure equipment that uses light with a wavelength shorter than the G-line of an ultra-high pressure mercury lamp as exposure light, such as excimer laser light, the thickness of the Ti0N film must be appropriately selected, including a range of 20 nm or less. It can be easily seen from FIG. 1 that both alignment and exposure can be performed satisfactorily by this method.

〔Effect of the invention〕

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. It is also possible to perform highly accurate pattern formation.

[Brief explanation of drawings]

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

Claims (1)

[Claims] A pattern forming method in which the pattern is formed on the photoresist layer by aligning a photoresist layer and a pattern to be formed on the photoresist layer and exposing the photoresist layer to light, comprising: A pattern forming method characterized in that the alignment and the exposure are performed in a state where a film containing titanium as a main component and having a thickness of 42 nm or less is formed under the photoresist layer.