JPH04276751A - Production of phase shift mask - Google Patents

Abstract

PURPOSE:To lower the approaching effect at the time of plotting with electron beams by dividedly forming the apertures of a light shielding layer on which phase shifters are required and apertures of a light shielding layer on which the phase shifters are not required. CONSTITUTION:The light shielding layer 2 is provided on a transparent substrate 1 and the light shielding layer 2 of the apertures 4 on which the phase shifters 8 are required is removed; thereafter, a phase shift layer 5 is provided on the substrate 1. The phase shift layer 5 and light shielding layer 2 of the apertures 7 on which the phase shifters 8 are not required are then partially removed. Namely, the apertures 4 of the light shielding layer 2 on which the phase shifters 8 are required and the apertures 7 of the light shielding layer 2 on which the phase shifters 8 are not required are dividedly formed. The light shielding layer 2 is exposed and, therefore, the etching stops when the etching of the phase shift layer 5 is finished at the time of forming the apertures 7 of the light shielding layer 2 on which the phase shifters 8 are not required. Further, the unetched parts of the phase shift layer 5 act as masking patterns at the time of etching the light shielding layer 2.

Description

[Detailed description of the invention] [Industrial application field]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase shift mask used as an original image for a reduction projection exposure apparatus for producing LSIs and the like.

0002

[Prior Art] Conventionally, when creating a phase shift mask, Japanese Patent Application Laid-Open Nos. 62-67514 and 2-211451
For example, C
A resist sensitive to electron beams, that is, an electron beam resist, is applied onto the light shielding layer such as r, and a masking pattern of the light shielding pattern is formed by exposing with an electron beam lithography system, and the light shielding layer is partially etched. After forming all the necessary light-shielding patterns by removing
There is a method in which a phase shift layer is provided on a substrate with all the necessary light-shielding patterns as described above, and only the phase shift layer is partially removed to form a phase shifter. The transparent substrate is manufactured by a method in which a thickness difference is provided in the transparent substrate by partially removing the exposed transparent substrate to a predetermined thickness.

0003

However, as the pattern to be formed becomes finer, there has been a problem that the pattern cannot be formed accurately due to the proximity effect during electron beam lithography.

[0004] The transparent substrate is an optical glass mainly made of SiO2, such as quartz glass, and the phase shift layer (phase shifter) is also made of, for example, SOG (spin-on glass), sputtering, or CVD (chemical vapor deposition). Since the phase shift layer is mainly made of SiO2 produced by a phase growth method, etc., the following problems occur in the step of patterning the phase shift layer.

In the method of forming a phase shifter by partially removing only the phase shift layer, since the boundary between the phase shift layer and the transparent substrate is of the same type, the phase shift layer is partially removed in this step. There has been a problem in that it is difficult to control the etching process, i.e., etching only the phase shift layer and not etching the transparent substrate.

Further, in the method of providing a transparent substrate with a difference in plate thickness, there is a problem in that it is difficult to stop the progress of etching after a predetermined thickness has been etched.

[0007]

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned problems, and includes providing a light-shielding layer on a transparent substrate, and removing the light-shielding layer from an opening on which a phase shifter is required. After that, a phase shift layer is provided on the substrate, and then a phase shifter partially removes the phase shift layer and the light shielding layer in unnecessary openings thereon.

[0008]

[Operation] According to the manufacturing method of the present invention, by separately forming an opening in the light-shielding layer on which the phase shifter is necessary and an opening in the light-shielding layer on which the phase shifter is unnecessary, Proximity effects during line drawing are reduced.

Furthermore, when the phase shifter forms an unnecessary opening in the light shielding layer thereon, when the phase shift layer is etched, the light shielding layer is exposed and the etching is stopped. In other words, the light shielding layer functions as an etching stopper. Next, when etching the light shielding layer, the etching of the light shielding layer is stopped when the etching reaches the transparent substrate. In other words, the transparent substrate acts as an etching stopper.

Furthermore, the unetched portions of the phase shift layer serve as a masking pattern during etching of the light shielding layer. Due to the above-described effects, a good phase shift mask pattern can be formed.

[0011]

EXAMPLES Examples of the present invention will be described below with reference to FIGS. 1 to 12, but it goes without saying that the present invention is not limited to these examples.

An example of the pattern of the phase shift mask is shown in FIG. FIG. 1 is a cross-sectional view of a phase shift mask, in which a light shielding pattern 9 and a phase shifter 8 are formed on a transparent substrate 1.
is formed. A in Fig. 2 shows the amplitude of the light immediately after passing through the mask when coherent light is transmitted (the horizontal axis in Fig. 2 corresponds to the AB direction in Fig. 1), and B in Fig. 2 shows the amplitude of the light when coherent light is transmitted through the mask. C in FIG. 2 indicates the intensity of light when the pattern is projected onto the wafer using a reduction exposure device.

It can be seen from FIG. 2 that the phase shift mask of the present invention has the same optical characteristics as those of the conventional phase shift mask. 3 to 11 are cross-sectional views showing the manufacturing method according to the present invention in the order of steps.

A photomask blank (with a Cr layer as a light shielding layer 2 formed on a transparent substrate 1 made of quartz glass)
Electron beam resist (manufactured by Chisso Co., Ltd., product name: PBS) was applied on top of the 5-inch square, 0.09-inch thick) manufactured by Toppan Printing Co., Ltd.
) 3 was applied to a thickness of approximately 5000 Å (see Figure 3).
.

First, the opening pattern of the light-shielding layer on which the phase shifter is required is created using a raster scan type electron beam lithography system on the photomask blank shown in FIG. 3 formed with an electron beam resist. , acceleration voltage 10Kv,
Drawing was performed at a dose of about 2 μC/cm 2 , and a pattern was obtained after development using a dedicated developer (see FIG. 4). After prescribed baking and descum processing, the Cr film, which is a light-shielding film, was etched with an aqueous solution of cerium ammonium nitrate and perchloric acid, and the phase shifter formed the required pattern of openings 4 on it (Fig. (see 5).

Next, the electron beam resist was removed, and then a phase shift layer 5 of about 3850 Å made of SiO2 to serve as a phase shifter was formed by RF magnetron sputtering (see FIG. 6).

Further, on the phase shift layer 5, a negative type electron beam resist 6 (manufactured by Shipley Microelectronics, trade name: SAL-601 ER7) is applied to a thickness of about 10,000 Å.
Spin coating was performed to a thickness of (
(See Figure 7).

Using the above-mentioned electron beam lithography system, the phase shifter performs lithography on the unnecessary portion of the light-shielding layer other than the opening 7 at an acceleration voltage of 10 Kv and a dose of approximately 2.5 μC/cm 2 to form a predetermined pattern. After baking and developing with a special developer, a pattern was obtained (see FIG. 8).

Using the pattern of the electron beam resist 6 as a masking pattern, the phase shift layer made of SiO2 was etched using a parallel plate type reactive etching apparatus using C2F6 and O2 gas at a power of 100.
W for about 15 minutes (see Figure 9).

[0020] After that, etching of Cr, which is a light shielding film, is performed using Cl
2 and O2 gas and a power of 100 W for about 10 minutes (see FIG. 10). At this time, electron beam resist 6
Although it has dry etching resistance, it has become quite thin and cannot be said to function sufficiently as a masking pattern, but the SiO2 pattern functions as a masking pattern instead.

After etching, the electron beam resist 6 was peeled off and cleaned, thereby completing a phase shift mask in which a light shielding pattern 9 and a phase shifter 8 were formed on the transparent substrate 1 (see FIG. 11). A plan view of this pattern is shown in FIG.

【Effect of the invention】

As described above, according to the manufacturing method of the present invention, the opening of the light-shielding layer on which the phase shifter is necessary and the opening of the light-shielding layer on which the phase shifter is not necessary are separately formed. By doing so, the proximity effect during electron beam lithography is reduced.

Furthermore, when the phase shifter forms an unnecessary opening in the light shielding layer thereon, when the phase shift layer is etched, the light shielding layer is exposed and the etching is stopped. When etching the light shielding layer, the etching of the light shielding layer is stopped when the etching reaches the transparent substrate. Further, since the unetched portion of the phase shift layer, that is, the phase shifter, acts as a masking pattern when etching the light shielding layer, a good phase shift mask can be easily manufactured.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of a phase shift mask manufactured according to the present invention.

[Figure 2] The amplitude of the light immediately after passing through the phase shift mask when coherent light is transmitted through the mask, the amplitude of the light when the pattern is projected onto the wafer with a reduction projection exposure device, and the amplitude of the light when the pattern is projected onto the wafer using a reduction projection exposure device. FIG. 2 is an explanatory diagram showing the amplitude of light when the pattern is projected onto a wafer by the apparatus.

FIG. 3 is a cross-sectional view showing an embodiment of the manufacturing method of the present invention in order of steps.

FIG. 4 is a cross-sectional view showing an embodiment of the manufacturing method of the present invention in order of steps.

FIG. 5 is a cross-sectional view showing an example of the manufacturing method of the present invention in order of steps.

FIG. 6 is a cross-sectional view showing an embodiment of the manufacturing method of the present invention in order of steps.

FIG. 7 is a cross-sectional view showing an embodiment of the manufacturing method of the present invention in order of steps.

FIG. 8 is a cross-sectional view showing an embodiment of the manufacturing method of the present invention in order of steps.

FIG. 9 is a cross-sectional view showing an example of the manufacturing method of the present invention in order of steps.

FIG. 10 is a cross-sectional view showing an embodiment of the manufacturing method of the present invention in the order of steps.

FIG. 11 is a cross-sectional view showing an embodiment of the manufacturing method of the present invention in order of steps.

FIG. 12 is a plan view of an embodiment of a pattern of a phase shift mask according to the present invention.

[Explanation of symbols]

1 Transparent substrate 2 Light shielding layer 3 Electron beam resist 4 Opening 5 on which a phase shifter is required
Phase shift layer 6 Electron beam resist 7 Unnecessary opening 8 on which the phase shifter is placed
Phase shifter 9 light shielding pattern

Claims (1)

[Claims] 1. A light-shielding layer is provided on a transparent substrate, and after removing the light-shielding layer from an opening on which a phase shifter is required, a phase shift layer is provided on the substrate, and then a phase shifter is not required on it. 1. A method for manufacturing a phase shift mask, comprising partially removing a phase shift layer and a light shielding layer in an opening.