JPH0822113A - Manufacture of phase shift mask - Google Patents

Abstract

PURPOSE:To manufacture a shifter part with high accuracy for a phase shift mask in which the shifter is formed by engraving a substrate. CONSTITUTION:(a) A Cr light-shielding film 2 is patterned on a synthetic quartz substrate 1, and (b) the area except for the phase shifter part is coated with a resist pattern 3 such as AZ1350. (c) Then phosphorus ions are implanted in the whole surface of the synthetic quartz substrate 1 to 1700Angstrom depth by using the resist pattern 3 as a mask under 100 to 200kV accelerating voltage. (d) The substrate 1 is put in a dry etching chamber 5 to etch the doped layer 6 with etchant gas such as CF4 while the substrate is irradiated with beams of ArF laser 4. (e) The resist pattern 3 is peeled off to obtain a phase shifter 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a phase shift mask.

[0002]

2. Description of the Related Art A phase shift mask is considered promising for high integration of memories and the like as one method of super-resolution exposure. It is known that the Levenson type is particularly effective. There are two types of Levenson-type phase shift masks: a method in which a thin film is formed on a phase shifter to obtain a phase difference, and a method in which a substrate in the phase shifter is dug down by etching to obtain a phase difference.

The method of digging down the phase shifter has great advantages as compared with the method of forming a thin film in that the step of forming a thin film can be omitted and the strength such as cleaning resistance is excellent. However, in forming a step, it is necessary to etch a uniform amount of a homogeneous material without a stopper,
Depth control is extremely difficult. As a method for solving this problem, Japanese Patent Application Laid-Open No. 4-42154 discloses a method in which ions are implanted into a shifter portion to a predetermined depth so as to increase the etching rate difference from a portion where ions have not reached. I have. However, in this method, an etching rate ratio of several times can be obtained only in the case of wet etching, and there is almost no effect in the case of dry etching, and application to a fine pattern is difficult.

[0004]

As described above, the conventional method has a problem that the phase shifter cannot be formed with good controllability in manufacturing a phase shift mask of a type in which a phase shifter portion is dug. SUMMARY OF THE INVENTION An object of the present invention is to provide a phase shift mask of the type in which a phase shifter portion is dug, which solves the problems of the conventional method.

[0005]

In order to solve the above-mentioned problems, a method of manufacturing a phase shift mask according to the present invention comprises the steps of: patterning a light-shielding film on a transparent glass substrate; A step of forming a pattern, a step of ion-implanting the entire surface of the substrate using the resist pattern as a mask, and irradiating the substrate with light having a wavelength that is absorbed by a portion modified by the ion implantation on the substrate Etching the substrate.

[0006]

The ion implantation technique is a technique of implanting ions accelerated by an electric field into a substrate, and the implantation depth can be accurately controlled by controlling the acceleration voltage. During this ion implantation, crystal defects, dangling bonds, etc. occur on the substrate. On the other hand, the synthetic quartz substrate for the mask is 19
Although it has a transmittance of 90% or more for light having a wavelength longer than 0 nm, the transmittance in the ultraviolet region is significantly reduced by ion implantation of phosphorus, boron or the like. Therefore, if the surface is irradiated with ultraviolet rays after ion implantation of phosphorus, boron, etc., the density of crystal defects and dangling bonds is further increased, and the etching rate is increased as compared with a synthetic quartz substrate which has not been implanted. .

The present invention utilizes this fact to form a phase shifter for a phase shift mask. Prior to digging down the phase shifter portion by etching, impurities such as phosphorus and boron are doped to the phase shifter portion to a depth that gives a predetermined shift amount. Thereafter, etching is performed while irradiating with ultraviolet light. In the injection layer, the crystal structure is destroyed by the absorption of ultraviolet light, and the etching rate is significantly increased. On the other hand, the ultraviolet ray is transmitted in a portion deeper than the injection layer, so that the etching rate is rapidly reduced. Therefore, it becomes easy to control etching at a predetermined step. In the present invention, since the effect is exerted not only by wet etching but also by dry etching, fine patterns can be dealt with without any trouble.

[0008]

EXAMPLES Examples in which the present invention is applied to the production of a Levenson-type phase shift mask for ArF exposure will be described in detail with reference to the drawings.

FIGS. 1A to 1E are schematic views showing each step of an embodiment of the present invention.

A Cr light-shielding film 2 is patterned on a synthetic quartz substrate 1 (a), and portions other than the phase shifter forming portion are AZ1350.
(B). Subsequently, phosphorus ^ions (P ²⁺ ) are applied to the entire surface of the synthetic quartz substrate 1 at an accelerating voltage of 100 to 200 kV by using the resist pattern 3 as a mask.
Inject to a depth of 700A (angstrom) (c). Synthetic quartz substrate 1 is dry-etched in chamber 5
Then, the doping layer 6 is etched with an etchant gas such as CF ₄ while irradiating an ArF laser 4 (d), and the resist pattern 3 is peeled off to obtain a phase shifter 7 (e).

In the present invention, since the etching rate of the doping layer 6 is 10 times or more higher than the etching rate of the portion deeper than the doping layer, the etching depth can be controlled very easily. In the conventional phase shift mask, the phase error was 10 degrees or more, but in the present embodiment, a phase shift mask with an accurate phase error of 5 degrees or less was obtained.

In the above embodiment, phosphorus is used as doping ions, but ions such as boron and silicon may be used.

In the above embodiment, a phase shift mask for ArF exposure has been described. However, a mask for another wavelength can be manufactured by changing the depth of ion doping.

In the above embodiment, the ArF laser is used as the ultraviolet light to be irradiated at the time of etching. However, the ArF laser is not necessarily used, and a mercury lamp or a deuterium lamp may be used.

In the above embodiment, the resist is AZ1.
Although 350 is used, any resist may be used as long as it absorbs light irradiated during etching.

[0016]

As described above, according to the method of the present invention, a phase shifter by a method of digging a substrate can be manufactured with high accuracy.

[Brief description of drawings]

FIG. 1 is a schematic view of a manufacturing process showing an example to which the present invention is applied.

[Explanation of symbols]

 Reference Signs List 1 synthetic quartz substrate 2 Cr light-shielding thin film 3 resist pattern 4 ArF laser 5 dry etching chamber 6 doping layer 7 phase shifter

Claims (1)

[Claims] 1. A step of patterning a light-shielding film on a transparent glass substrate, a step of forming a predetermined resist pattern on the light-shielding film, and a step of ion-implanting the entire surface of the substrate using the resist pattern as a mask. And a step of etching the substrate while irradiating the substrate with light having a wavelength that is absorbed by a portion modified by the ion implantation.