JP3357206B2 - Method for manufacturing phase shift mask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a phase shift mask having a phase shifter pattern on a substrate. In particular, the present invention relates to a method for manufacturing a phase shift mask suitable for manufacturing a so-called lower shifter type Levenson type phase shift mask of a type in which a light shielding material pattern is located downstream of a phase shifter pattern with respect to a traveling direction of projection exposure light.

[0002]

2. Description of the Related Art As a photomask used in a projection exposure apparatus such as a stepper, there is known a phase shift mask capable of transferring a high-resolution pattern by giving a phase difference to projection exposure light passing through the photomask. ing. Various types of phase shift masks have been conventionally proposed.

For example, a Levenson type phase shift mask having a structure in which a transparent film for inverting the phase of exposure light is provided in one of a pair of adjacent openings for forming a pattern on a mask, a pattern to be formed, Self-aligned phase shifter with a phase shift mask with an auxiliary pattern with a phase shifter below the resolution limit at the periphery of the mask, or a structure with a phase shifter overhang formed by overetching after forming a chromium pattern on the substrate There is a shift mask and the like.

The phase shift masks having the above-described structures have a Cr (chromium) pattern and a shifter pattern provided on a substrate. Apart from this structure, a phase shift mask formed only by a shifter pattern has the following features. A transmission type phase shift mask, a halftone type phase shift mask, and the like are also known. A transmission type phase shift mask is a phase shift mask that separates a pattern by utilizing the fact that light intensity becomes zero at a boundary between light transmitted through a transparent portion and light transmitted through a phase shifter. Therefore, it is also called a shifter edge type phase shift mask.

A halftone type phase shift mask is formed by forming a so-called semi-transparent phase shifter pattern having partial transparency with respect to projection exposure light on a substrate and forming it at a boundary of the phase pattern. This is a phase shift mask that separates a pattern at a portion where the light intensity is zero.

Among the various phase shift masks as described above, a lower shifter type Levenson type phase shift mask having a structure shown in FIG. 5 is known. In this phase shift mask, a phase shifter layer 2 which is a layer including a phase shifter pattern formed in a desired pattern is formed on a surface layer (a lower surface layer in the figure) of a transparent substrate 1 and the phase shifter layer 2 is formed. A light shielding material pattern 3a is formed in a desired pattern shape on the upper side (the lower position in the figure). When a transfer image is formed on an object to be exposed, for example, a wafer 20 using this phase shift mask, the exposure light R
To expose a light image formed by the light shielding material pattern 3 a on the wafer 20. In the figure, the light shielding member shielding portion K corresponding to the pattern 3a is formed, the shifter transparent portion T _S corresponding to the light transmitting portion of the portion where the substrate 1 is left is formed and removed substrate 1 by etching non shifter transparent portion T _H are formed corresponding to the light transmitting portion of the portions.

In terms of a transferred image formed on the wafer 20, the width of the shifter translucent portion T _S on the mask is a, and the width of the shifter translucent portion T _S on the wafer 20 is a ′. At this time, it is desirable that a = a ′. Also, the width of the non-shifter transparent portion T _H on the mask is b, the wafer 2
0 the width of the non-shifter transparent portion T _H of the on time of the b ',
It is desirable that b = b ′. However, as shown in FIG. 5, when the edge of the recess 2a of the edge and the phase shifter of the light shielding material pattern 3a that defines a non-shifter transparent portion T _H are coincident, b> b 'become possible That is, the transfer width is generally narrow. this is,
Primarily, it believed to be caused by the exposure light R ₀ incident on the non-shifter transparent portion T _H from the oblique direction. In other words, exposure light R ₀ incident from an oblique direction, the non-shifter transparent portion T _H after passing through the phase shifter pattern
Since reaching the, because interference between the exposure light reaching the non-shifter transparent portion T _H without passing through the phase shifter pattern is generated, the light intensity on the wafer 4 is decreased.

Conventionally, the non-shifter light-transmitting portion T _H as described above
In order to avoid the phenomenon of the transfer image narrowing in the above, a method is known in which the side wall of the concave portion 2a of the phase shifter pattern is etched away to form a side-etched portion E as shown in FIG. By providing the side etch portion E, the obliquely incident exposure light _R0 can be prevented from passing through the phase shifter pattern, so that the transfer image can be prevented from being narrowed.

Conventionally, the side etch portion E as described above is
For example, it is formed by the method shown in FIG. That is, as in the step (j), the substrate 1 is dug down into a desired pattern by etching using the light-shielding material pattern 3a and the resist pattern 5a formed on the transparent substrate 1 as a mask to form the phase shifter layer 2, and further the step (k) )like,
The side wall of the concave portion 2a of the phase shifter pattern is laterally etched by wet etching to form a side-etched portion E.

[0010]

However, the conventional side etching method as described above has a problem as shown in FIG. That is, as shown in FIG.
When a resist pattern 5a having a desired pattern is formed on the transparent substrate 1 by drawing by electron beam exposure and subsequent development processing, residual resist or dust G (hereinafter simply referred to as resist residual) is left on the substrate 1. May appear. If etching is performed to form the phase shifter layer 2 on the substrate 1 in this state, the portion of the substrate 1 hidden by the remaining resist G remains without being etched, and a so-called remaining shifter N is generated (step j). ).

[0011] Thereafter, when the side etching by wet etching, the shifter although sidewall of portion having no remaining N is successfully side-etched, the side wall portion is shifter remaining N exists, shifter residual
The side edge by etching
Not Ji (step k, where in fact be part of the N etching
Is ). Thus, the side where there is the shifter remaining N
Side wall is equivalent to side etch E as desired
Side-etched portion is not obtained for (step l). With a phase shift mask having such a side etch defect, a highly precise transfer image cannot be obtained on a wafer. Further, the once formed side-etch defect is almost impossible to correct, and significantly reduces the yield in the manufacturing process of the phase shift mask.

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a phase shift mask in which a side etch portion needs to be formed in a phase shifter. The purpose is to be able to.

[0013]

To achieve the above object, according to an aspect of, the method of manufacturing a phase shift mask according to the present invention, a resist pattern is formed on the phase shifter for film, light-shielding material
In a method for manufacturing a phase shift mask in which a phase shifter pattern having a desired pattern is formed by performing an etching process on a phase shifter film using a pattern and a resist pattern as a mask, the phase shifter film is shielded from light.
A shifter etching step of forming a phase shifter pattern by etching using the material pattern and the resist pattern as a mask, and a shifter defect inspection step of inspecting the phase shifter pattern for defects after the shifter etching step. A defect on the phase shifter pattern that has been repaired, and a sidewall of the phase shifter pattern after the shifter defect correction step.
And a side etching step of the light-shielding material pattern and the resist pattern with d <br/> etching as a mask to form a side-etched portion, the shifter defect inspection process, a phase shifter
-Shifter residue generated at the sidewall of the pattern
Is illuminated from the back side, and the surface pattern is
Reads information and stores pattern data for electron beam exposure drawing
Shifters , including discovering by comparing
In the defect repair process, an ion beam is irradiated by FIB processing.
To remove the shifter residue
Before the shifter etching process.
Phase shift mask material doubles as phase shifter film
Substrate, light shielding material pattern and resist pattern in that order
And a shifter defect inspection process,
After shifter defect repair process and side etching process
Light on the substrate on which the phase shifter pattern is formed
Lower shifter type level
It is characterized by manufacturing a Nson-son type phase shift mask .

The phase shifter film may be formed on a transparent substrate made of quartz or the like separately from the substrate, or may be formed by forming an appropriate thickness on the surface of a transparent substrate made of quartz or the like. It can also be used as a phase shifter film.

In the shifter defect inspection step, for example, a shifter residue generated in a sidewall portion of the phase shifter pattern is found. In the shifter defect repair process,
For example, the shifter residue is removed. The inspection method for performing the shifter defect inspection step is not limited to a specific method, but can be performed using, for example, image processing using a CCD camera. Also, the repair method for performing the shifter defect repair step is not limited to a specific method, but may be, for example, an FIB (Forcus).
ed Ion Beam) processing. This F
The IB process is a process of irradiating a shifter defect, for example, a shifter remaining portion, with an ion beam in a predetermined gas atmosphere to scrape off the shifter remaining portion by a chemical reaction.

The method of manufacturing the phase shift mask according to the present invention can be most effectively applied to a lower shifter type Levenson type phase shift mask. The lower shifter type Levenson-type phase shift mask is a type in which a light-shielding material pattern is projected when a projection exposure light is applied to an exposure target through a completed phase shift mask to form a transfer image on the exposure target. This is a phase shift mask of a type located downstream of the phase shifter pattern with respect to the traveling direction of the exposure light.

[0017]

The phase shifter pattern is formed on the phase shifter film by the shifter etching step. When a phase shifter film is formed separately from the transparent substrate, a phase shifter pattern is formed on the phase shifter film. On the other hand, when the surface layer of the transparent substrate is also used as the phase shifter film, a phase shifter pattern is formed on the surface layer of the transparent substrate. The phase shift mask (workpiece before completion) on which the phase shifter pattern is formed is inspected in a shifter inspection step for the presence or absence of a defect, particularly, for the presence of a remaining shifter or the like. If there is any remaining shifter, etc., the remaining shifter is removed in the shifter defect repair process,
Thereafter, a side etching process is performed to form a side-etched portion. When the side etching is performed, the remaining portion of the shifter is always removed, so that the side etch portion is always formed reliably.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for manufacturing a phase shift mask according to the present invention will be described with reference to FIGS. First, as shown in FIG. 1A, a light-shielding material film 3 and a first resist film 4 are sequentially laminated on a transparent substrate 1 by a well-known film forming technique to produce a phase shift mask blank. Each of the above films is formed of, for example, the following materials. Transparent substrate 1: Quartz Light shielding material film 3: Any one of Cr, CrO, CrN, CrON, etc. or a composite film thereof

Next, after a pattern latent image is formed on the first resist film 4 by drawing by electron beam exposure, it is developed to form a first resist pattern 4a (FIG. 1).
(B)) Further, a light shielding material pattern 3a having a predetermined pattern is formed from the light shielding material film 3 by etching (FIG. 1).
(C)) Then, the first resist pattern 4a is further removed (FIG. 2D). As the etching of the light shielding material film 3, for example, wet etching using a mixed solution of ceric ammonium nitrate and perchloric acid, dry etching using a chlorine-based gas, or the like is used. The first resist pattern 4a is peeled off using, for example, oxygen plasma or sulfuric acid.

Thereafter, a second resist film 5 for a shifter is applied (FIG. 2E), and a desired second resist pattern 5a is formed by drawing and developing by electron beam exposure.
Is formed (FIG. 2F). And then CF ₄ or C ₂
The surface layer of the substrate 1 was etched by well-known dry etching using a reactive gas such as F ₆ to form a desired phase shifter pattern, that is, the phase shifter layer 2 was formed (FIG. 3G). At this time, a shifter residue N may be generated in a portion where the resist residue G exists. In the present embodiment, the shifter defect inspection process (FIG. 3)
In (h)), the shifter defect inspection device 7 inspects the presence or absence of the remaining shifter N.

The shifter defect inspection apparatus 7 is not limited to a specific structure, but may use, for example, an inspection system as shown in FIG. In this inspection system, a mask work-in-progress 8 to be tested is illuminated from behind by a lamp 9, and the front side of the mask work-in-process 8 is read and scanned by a CCD camera 10. Reference numeral 11 indicates a condenser lens. The surface pattern information of the in-process mask 8 read by the CCD camera 10 is compared with pattern data for electron beam exposure drawing, and as a result of the comparison, the existence of the remaining shifter N and its coordinate position are determined.

When the location of the remaining shifter N is known, FIG.
As shown in (i), the shifter defect correcting device 12 corrects, ie, removes, the remaining shifter N. The shifter defect correction device 12 is, for example, a FIB (Fo)
The remaining portion N of the shifter is scraped off by rcused Ion Beam) processing. That is, the shifter remaining portion N is irradiated with an ion beam in a predetermined gas atmosphere to scrape off the shifter remaining portion N by a chemical reaction (FIG. 4 (j)).

Thereafter, the concave portion 2a of the phase shifter pattern is side-etched by isotropic etching, for example, wet etching with hydrofluoric acid or dry etching to form a side-etched portion E (FIG. 4 (k)). At the time of this side etching process, since the remaining shifter portion N has been completely removed, the side etch portion E is reliably formed even where the remaining shifter portion N was. Thereafter, the resist pattern 4a is removed using oxygen plasma, sulfuric acid, or the like, and a cleaning process is performed to complete a lower shifter type Levenson-type phase shift mask (FIG. 4 (l)).

Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the embodiments and can be variously modified within the technical scope described in the claims. For example, in the lower shifter type Levenson type phase shift mask shown in FIG. 4 (l), the surface layer of the transparent substrate 1 is used as the phase shifter layer 2, but the phase shifter layer is separately formed on the transparent substrate 1. The film may be formed.

[0025]

According to the method of manufacturing a phase shift mask according to the present invention, a defect of a phase shifter pattern, for example, a remaining shifter is searched for during the manufacturing of the phase shift mask and further corrected. By performing the etching process, the side-etched portion can always be reliably formed in the concave portion of the phase shifter pattern. Therefore, when a transfer image is formed on an object to be exposed by the phase shift mask, the transfer image can be formed with extremely high precision.

[0026]

[Brief description of the drawings]

FIG. 1 is a view schematically showing a part of one embodiment of a method for manufacturing a phase shift mask according to the present invention.

FIG. 2 is a view schematically showing a manufacturing process of the phase shift mask following FIG. 1;

FIG. 3 is a view schematically showing a manufacturing process of the phase shift mask continued from FIG. 2;

FIG. 4 is a manufacturing process of a phase shift mask subsequent to FIG. 3;
It is a figure which shows typically the completed lower shifter type Levenson type phase shift mask.

FIG. 5 is a diagram schematically showing a transfer state using a lower shifter type Levenson type phase shift mask.

FIG. 6 is an enlarged view showing a main part of the phase shift mask shown in FIG. 5;

FIG. 7 is a view schematically showing main steps of a conventional method for manufacturing a phase shift mask.

FIG. 8 is a perspective view showing an example of an apparatus for performing a shifter defect inspection step.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transparent substrate 2 phase shifter layer 2 a recess of phase shifter pattern 3 light shielding material film 3 a light shielding material pattern 4 first resist film 4 a first resist pattern 5 second resist film 5 a second resist pattern 7 shifter defect inspection device 9 lamp 10 CCD Camera 11 Condenser lens 12 Shifter defect correction device

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-301195 (JP, A) JP-A-6-43626 (JP, A) JP-A-4-136854 (JP, A)

Claims (1)

(57) [Claims] 1. A phase shifter pattern having a desired pattern is formed by forming a resist pattern on a phase shifter film and performing an etching process on the phase shifter film using the light shielding material pattern and the resist pattern as a mask. A method for manufacturing a phase shift mask, comprising: forming a phase shifter film with a light shielding material pattern and a resist pattern.
Etching process using a mask as a mask to form a phase shifter pattern, a shifter defect inspection process that inspects the phase shifter pattern for defects after the shifter etching process, and corrects defects on the phase shifter pattern that were found After the shifter defect correcting step, the side wall of the phase shifter pattern is replaced with the light shielding material pattern and the resist pattern after the shifter defect correcting step.
And a side etching process for forming the side-etched portion is etched as a mask, the shifter defect inspection process, rhino phase shifter pattern
Lights the remaining shifter generated in the door from the back
Read the surface pattern information from the surface with a camera,
Comparison with pattern data for electron beam exposure drawing
, The shifter defect repairing process includes the ion beam
The system by irradiating it and shaving it off by a chemical reaction.
This is a process for removing the residual foot, and the phase shift mask material before the shifter etching process
Is a substrate that also serves as a phase shifter film,
And the resist pattern is laminated in that order,
And shifter defect inspection process, shifter defect repair process and
Phase shifter pattern
The light shielding material pattern is laminated on the substrate with
Lower shifter type Levenson type phase shift mask
A method for manufacturing a phase shift mask.