JPS58106545A - Exposing method - Google Patents

Abstract

PURPOSE:To prevent a drop of exposure accuracy, and also to elevate positioning accuracy, by providing a resist through a spacer film on a semiconductor substrate on which a marker is provided, executing positioning by use of this marker, and thereafter, exposing the resist. CONSTITUTION:On the surface of a silicon wafer 21, a positioning marker 22 is formed by use of an anisotropic wet etching technique. Subsequently, a photoresist 23 is spin-coated as a spacer film. Thereafter, by using a sputter vapor- depositing method, a silicon film 24 is covered as a transfer film, and on this silicon film 24, an electric beam resist 25 is coated. As for said marker 22, a pyramidical shape which is scarcely affected by the spacer is more effective, but any projecting shape can be used. According to this exposing method, attenuation and scattering of an electron, an ion, light or X-rays in a multilayer structure consisting of the spacer film, the transfer film, etc. can be reduced, therefore, the positioning accuracy utilizing the positioning marker can be elevated remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to improvements in exposure methods using light, electron beams, X-rays, and the like.

Technical background of the invention and its problemsRecently, Journal of 5science and
Technolog) r+1 PI 620 (197
As shown in 9), a technology has been developed to form highly accurate grooves even when there are irregularities on the substrate to be processed.

In this technique, first, as shown in FIG. 1(a), a spacer film 3 is spin-coated onto a workpiece 2 provided on a substrate 1.
Transfer blade side 4 and resist 5 are applied to this spacer film 3.

Here, since the spacer film 3 is formed on the workpiece 2 by spin coating, its surface becomes substantially flat regardless of the irregularities of the substrate 1. If the thickness of the spacer film 3 is small, the unevenness of the substrate will appear on the surface of the spacer material, so in order to ensure the flatness of the spacer film surface, the thickness of the spacer M3 should normally be 2 to 3 [μm]. to snatch For the transfer film 4, a material is selected that can be used as a mask when processing the spacer film 3 by a reactive ion etching method, an ion beam etching method, or the like.

Next, as shown in FIG. 1(b), the Renost 5 is
After exposure and development, the entire transfer film 4 is etched using the resist 5 as a mask. Then, the spacer film 3 is etched using the transfer film 4 as a mask, and then the material 2 to be etched is etched using the spacer film 3 as a mask. Thereafter, by removing the transfer film 3, the workpiece 2 is processed into a desired iR pattern as shown in FIG. 1(C). Here, as mentioned above, the resist 5 is formed on a flat surface without being affected by the unevenness of the substrate 1. Therefore, good exposure can be performed without causing deterioration of the exposure characteristics due to the unevenness of the substrate 11. In this way, the multilayer structure method using the spacer film 3, transfer film 4, and resist 5 is an excellent technique that allows exposure without being affected by the unevenness of the substrate 11. Note that the transfer film 4 may be used depending on the combination of the resist 5 and the spacer film 3.

However, in the above-mentioned multilayer structure type exposure method, there was a problem in alignment. This problem will be explained using FIG. 2 and taking electron beam exposure as an example. A concave or convex positioning marker is used for positioning, and in this case, a convex marker 6 is used. A marker 6 provided on the substrate 1 is scanned with an electron beam 7, and the position of the pattern to be exposed is determined based on the signal of reflected electrons 8 generated from the marker 6. In this case, if a thick multilayer structure exists in the soil of the marker 6, that is, a spacer film 3 and a transfer film 4, the electron beam 7 is attenuated and scattered within the multilayer structure before reaching the marker 6. The reflected electrons 8 received are similarly attenuated and scattered within the multilayer structure. As a result, the intensity and contrast of the backscattered electrons decrease, making highly accurate positioning difficult. Note that this problem also occurs in light exposure, X-ray exposure, and ion beam exposure.

Purpose of the Invention An object of the present invention is to reduce attenuation and scattering of electrons, ions, light, or X-rays within a multilayer structure such as a spacer film or a transfer film, thereby contributing to improving alignment accuracy. The object of the present invention is to provide an exposure method.

Summary of the Invention The gist of the present invention is to determine the influence of the relationship between the height of the marker and the thickness of the spacer film on signal generation, and to define the relationship between the height of the marker and the thickness of the spacer film under appropriate conditions. The object of this invention is to solve the problem of the decrease in alignment accuracy. That is, when forming a spacer film by the spin coating method, if the thickness of the spacer film 13 is made smaller than the height of the convex marker 12 provided on the substrate 11 as shown in FIG. Membrane J
3 is formed and the original form of Ma 5-Ichiriki 12 is maintained as it is. This spacer film 1
3. When a thin transfer film 14 and an electron beam resist 15 are deposited on the substrate and alignment is performed by electron beam scanning, the signal intensity and contrast are dramatically improved compared to the conventional method shown in FIG. , it was found that the alignment accuracy was significantly improved. In this case, the exposure accuracy of the resist 15 was sufficiently high compared to the conventional method that does not use the transfer film 13. As shown in FIG. 4, even if the thickness of the spacer film 13 is smaller than the height of the marker 12 and the total thickness of the spacer film 13 and the transfer film 14 is larger than the height of the marker 12, the conventional position The alignment accuracy has been greatly improved. Furthermore, in the case of a multilayer structure system that does not use the transfer film 14 as shown in Figure $5, the thickness M of the spacer film 13 may be made smaller than the height of the marker 12.

The present invention focuses on such points, and a spacer film (6) whose thickness is smaller than the height of the marker, or a spacer film and a transfer film, is formed on a semiconductor substrate provided with a convex alignment marker. After that, a photosensitive, charged particle sensitive, or X-ray sensitive resist was provided on the spacer film or transfer film, and after the markers were aligned with each other, the resist was exposed to light in a desired pattern. It's a method.

Effects of the Invention According to the present invention, it is possible not only to prevent a decrease in exposure accuracy due to unevenness of the substrate to be processed, but also to prevent electrons, ions, light, or X
Since line attenuation and scattering can be reduced, alignment accuracy using all alignment markers can be greatly improved.

Embodiment of the Invention FIGS. 6(a) to 6(C) are cross-sectional views showing an exposure process according to an embodiment of the invention. First, as shown in FIG. 6(a), an alignment marker 22 with a height of 3 [μm] is formed on the surface of a silicon wafer 21 having a surface orientation of (100) using an anisotropic wet etching technique. Next, Fig. 6 (b
As shown in ), photoresist 23 (product name 0FPR-800, manufactured by Tokyo Ohka) was used as a suction film, with a total film thickness of 2 [μm].
Rotate and apply.

Next, as shown in FIG. 6(e), a silicon film 24 with a thickness of 0.2 [μm] is deposited as a transfer film using sputter deposition, and an electron beam resist (PMMA) 25f film is deposited on this silicon film 24. Apply only 0.4 [μm] thick. Next, when the marker 22 was scanned using an electron beam with an accelerating voltage of 20 [K■] to detect the marker, the signal strength and contrast were improved to twice that of the conventional method.

Note that the present invention is not limited to the embodiments described above. For example, as the marker, a pyramid shape is effective because it is less affected by the spacer, but any convex shape may be used. ! In addition, in exposure using charged particles such as electron beam exposure, the spacer film, transfer film, and renost are insulating, which causes misalignment due to charge-up. In this case, it is necessary to provide a conductive film on the resist. It's fine. It goes without saying that the present invention can also be applied not only to electron beam exposure but also to light exposure, X-ray exposure, and ion beam exposure. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

FIGS. 1(a) to 5(c) are cross-sectional views showing a conventional exposure method using a multilayer structure method, FIG. 2 is a cross-sectional view for explaining the problems of the conventional method, and FIGS. The figures are sectional views for explaining the present invention in detail, and Figures 6(a) to (
C) is a sectional view showing an exposure process according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 11... Substrate, 12... Marker, 13... Spacer PIK, 14... Transfer film M, 15-Resist, 21... Silicon wafer, 22... Marker,
23... Photoresist, 24... Silicon m, 2
5...Electron beam resist. Applicant's agent Patent attorney Takehiko Suzue 9- Figure 3 Figure 4 Figure 5

Claims (3)

[Claims] (1) providing a spacer film or a spacer film and a transfer film having a thickness smaller than the height of the marker on a semiconductor substrate provided with a convex alignment marker;
The present invention is characterized by comprising a step of providing a photosensitive, charged particle-sensitive or X-ray-sensitive resist on the spacer film or transfer film, and a step of exposing the resist in a desired pattern after positioning using the marker. exposure method. (2) The exposure method according to claim 1, wherein the total thickness of the spacer film and the transfer film is smaller than the height of the marker. (3) The exposure method according to claim 1, characterized in that the shape of the marker is a pyramid.