JPH04276752A - Production of optical mask and method for correcting defect thereof - Google Patents

Abstract

PURPOSE:To allow the formation of desired patterns by constituting the above method in such a manner that the mask generated with a defect only in the phase shifter part can be corrected and to eliminate the need for repeating the process for producing mask up to a light shielding material. CONSTITUTION:The phase shifter part 10 is formed by forming the pattern of the light shielding material 6 selectively on a mask substrate 1, depositing a permeable film 7 over the entire surface on the mask substrate 1, applying a negative resist 8 on the permeable film 6, exposing the negative resist 8 from the rear surface of the mask substrate to expose the resist and developing the resist, then etching the permeable film 7 with the remaining negative resist as a mask 9.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an optical mask, and more specifically, to a method of manufacturing an optical mask used in phase shift exposure for the purpose of improving resolution. 2. Description of the Related Art As LSIs have become faster and more highly integrated in recent years, fine lithography technology has been required. Phase shift exposure technology is an exposure technology that meets such demands. In the phase shift exposure method, as shown in FIG. 5, a phase shifter section 10 that shifts the phase of light by 180 degrees is created in a part of the gap between the Cr light shielding film 6 attached to the mask substrate.
When light beams whose phases are shifted by 180 degrees as in 5 and 26 are combined to form a composite wave 27, the portion 27' becomes sharper due to light interference compared to the case where ordinary light beams having the same phase are combined. Therefore, when exposure is performed using this method, the intensity 28 on the photosensitive object rises steeply at the portion 28', so that a fine pattern is created. Although the phase shift exposure method is based on an excellent principle for creating fine patterns, it is necessary to establish this as a technology that actually enables fine lithography.

0002

[Prior Art] In the phase shift exposure method, (
As shown in c), there is a method of inverting the phase using a shifter pattern portion 4a protruding from the chrome pattern 5. In the conventional manufacturing method of a phase shift mask for making this shifter pattern, as shown in FIG. 6(a),
A chromium film 2 and a shifter film 3 are deposited on a mask substrate 11,
As shown in (b) of the same figure, the shifter film 3 is etched to form a shifter pattern 4, and then, as shown in (c) of the same figure, the exposed portion of the chromium film 2 is etched using the shifter pattern 4 as a mask. Then, side etching is further performed to the back side of the shifter pattern 4 to form a chrome pattern 5.

0003

[Problems to be Solved by the Invention] In the conventional phase shift mask manufacturing method, defects such as chipping of the shifter pattern 4 and chrome pattern 5 occur in the step (c) of FIG. 6, or defects occur in the step (a) of FIG. If defects existing in patterns 4 and 5 are discovered in step (c), it is extremely difficult to correct the defects in the mask. It was also impossible to recreate only the defective phase shifter sections 4 and 5 by reprocessing. Therefore, when a defect occurs, it is necessary to repeat the mask manufacturing process shown in FIGS. 6(a) to 6(c) for all of the large number of patterns 4.5 made on one mask substrate. .

Therefore, the present invention makes it possible to repair a mask in which a defect occurs only in the phase shifter portion, thereby making it possible to create a desired pattern, and also eliminates the need to repeat the mask manufacturing process up to the formation of the light shielding material. The purpose is to

[0005]

[Means for Solving the Problems] A method for manufacturing an optical mask according to the present invention includes selectively forming a pattern of light shielding material on a mask substrate, and further depositing one or more types of transmitting film on the entire surface of the mask substrate. , a negative resist is applied on the transparent film, exposed from the back side of the mask substrate to expose the negative resist and developed, and then the remaining negative resist is used as a mask to etch the transparent film to form a phase shifter section. It is characterized by the formation of

[0006]Furthermore, in the optical mask defect repair method according to the present invention, defects are detected in a plurality of phase shifter portions formed by the above method, and when a defect is found,
A mask layer is formed on the mask substrate so as to selectively expose the defective phase shifter portion, the defective phase shifter portion is removed using the mask layer as a mask, and then a new transparent film is formed on the entire surface. After that, a new permeable film is formed in the region including the phase shifter part that was removed by the lift-off method.
Subsequently, the negative resist coating step of the above method is performed again.

FIG. 1 is a diagram explaining the principle of the present invention. First, in the method of the present invention, a mask pattern is formed using a light shielding material 6 such as Cr. The mask pattern at this time is normal CVD
After forming a film by a method such as , sputtering, etc., it is produced by an etching method using a normal resist or the like. If a defect such as a chip in the mask pattern is discovered at this stage,
Defects can be easily repaired by selectively depositing Cr on that portion. Subsequently, an inorganic transparent film 7 is deposited to a thickness such that a phase difference of π (180°) occurs in the exposure light (see FIG. 1(a)). Thereafter, a negative resist 8 is applied to the front surface (see FIG. 1(b)), and when the back side is exposed and developed, a resist pattern 9 remains where the mask pattern of the light shielding material 6 is not present (see FIG. 1(b)). and,
Using the resist pattern 9 as a mask, the inorganic transparent film 7 is selectively removed by etching to complete the phase shifter section 10 (FIG. 1(d)). In this method, if a defect is detected in the shifter section 10, only the defect in the shifter section 10 shown in FIG.
The repair method of forming the shifter portion 10 can be carried out by the methods shown in ) to (d). Furthermore, instead of rebuilding the entire shifter section 10, the pattern can be corrected by applying Cr to defective parts such as chips.

An example of a method for modifying the phase shifter section is shown in FIG. In the figure, 10 is a phase shift pattern having a defective portion 10a, and 11 is an etching stop layer used if necessary. When a defect 10a (see (a) in FIG. 2) occurs in the phase shifter section 10, as a method for repairing the defect, a positive resist 12 is applied and selectively areas including the phase shifter 10 where the defect 10a is present are coated. A mask 12 made of a resist that is exposed on the back side (see FIG. 2(a)) and remains unexposed.
a (see FIG. 2(b))
The inorganic transparent film 7 is selectively deposited by lift-off by selectively removing 0 and removing the mask 12a, and then the negative resist 9 is deposited.
Similarly to c) and (d), back exposure, resist pattern formation, and etching of the inorganic transparent film 7 can be performed. Note that 11 is an etching stop layer that is used if necessary. In FIG. 3, the amplitude of the light transmitted through the optical mask in FIG. 1(d) is shown by a solid line. The dotted line indicates the amplitude of light without the phase shifter section 10.

[0009]

According to the invention according to claim 1, the pattern of the light shielding film 6 is completed before forming the phase shifter portion (see FIG. 1). Therefore, there is no need to form the light shielding film 6 by side etching, and if there is a defect in the phase shifter section 10, only that defect can be corrected. Further, according to the present invention, since the negative resist 8 is used, alignment between the light shielding film 6 and the resist mask is unnecessary during back exposure. If there is a defect in the phase shifter section, the defect can be easily corrected by repeating the method of claim 1 (claim 2).

0010

Embodiment FIG. 4 is a block diagram of an embodiment of the present invention. A mask pattern 21 is formed using Cr, chromium oxide, or the like on a quartz glass substrate 20 as usual. Afterwards, SiN is deposited to a thickness of ~500 Å as an etching stop layer 22, and SiO2 (23) is deposited on top of this as a shifter material to a thickness of 4700 Å (λ/
2(n-1), λ (G line): 4358 Å, n: 1.46
) (see FIG. 4(a)). Then, a negative resist (not shown) is applied and the back side is exposed. Thereafter, only SiO2 (23) is removed by etching, and the negative resist is peeled off to complete the optical mask shown in FIG. 4(b). In the figure, m is the reduction projection ratio, m = 5, and by performing G-line exposure, the size of the window of the mask pattern 21 is 1.1 μm, and the size of the phase shifter section 10 is 0.7 μm.
An optical mask is produced in which the distance between the phase shifter section 10 and the mask pattern 21 is 0.2 μm.

[0011]

As explained above, since the present invention is a method for manufacturing a phase shift mask in which defects in the phase shifter portion can be corrected, a defect-free mask can be manufactured. Furthermore, since the method of the present invention does not perform side etching of the light shielding material, the pattern can be formed with high precision.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention.

FIG. 2 is an explanatory diagram of a defect repair method.

FIG. 3 is a diagram showing the amplitude of light transmitted through the optical mask of FIG. 1;

FIG. 4 is an explanatory diagram of an example.

FIG. 5 is an explanatory diagram of a phase shift exposure method.

FIG. 6 is an explanatory diagram of a conventional optical mask manufacturing method.

[Explanation of sign]

1 Mask substrate 6 Cr light shielding film 7 Transparent film 8 Negative resist 9 Resist pattern 10 Phase shifter section

Claims (2)

[Claims] 1. Forming a pattern of light-shielding material having selective openings on a mask substrate, further depositing one or more types of transparent film on the entire surface of the mask substrate, and applying a negative resist on the transparent film. Then, the negative resist is exposed to light from the back side of the mask substrate, developed, and then the transparent film is etched using the remaining negative resist corresponding to the opening as a mask to form a phase shifter portion. A method for manufacturing an optical mask characterized by: 2. Defects are detected in the plurality of phase shifter parts formed by the method of claim 1, and if a defect is found, the phase shifter part having the defect is selectively exposed on the mask substrate. forming a mask layer so as to remove the defective phase shifter portion using the mask layer as a mask;
Next, after forming a new transmission film on the entire surface, a new transmission film is formed in the area including the phase shifter portion removed by a lift-off method, and then the negative resist coating step of claim 1 is performed again. A method for repairing defects in optical masks.