JPH03105344A - Manufacture of optical mask and method for correcting the same - Google Patents

Abstract

PURPOSE:To improve the control of film thickness and to fix a light transmissivity independently of the film thickness control by forming a regist layer opening its formation area on a mask base, evapolating a phase shifter material by ion beam assisting evapolation method and removing the resist layer. CONSTITUTION:A light shielding mask having light transmitting parts 12a, 12b is formed on an optical mask base 10 consisting of synthesized quartz or the like by using a chrome film 12. The whole surface is coated with EB resist by spin coating method and the coated surface is prebaked. Then an aperture 14a is formed on the resist layer 14 laminated on the transmission part 12a forming a phase shifter by electron beam exposure. The correct the mask, a defective oxide film part is opened and the film is removed by etching. The accurate evapolation film of a SiO2 oxide film 16 is evapolated on the whole surface by on-beam assisting evapolation method while controlling rigid film thickness. When the layer 14 is removed, the film 16 formed on the layer 16 is lifted off and the film 16 to be the phase shifter is formed on the transmission part 12a.

Description

[Detailed Description of the Invention] [Summary] This invention relates to an optical mask manufacturing method for manufacturing an optical mask for a projection exposure apparatus used for manufacturing a semi-dedicated apparatus, and an optical mask repair method for modifying the manufactured optical mask. To provide a method for manufacturing an optical mask in which the film thickness of a phase shifter is well controlled and light transmittance does not differ depending on the presence or absence of a phase shifter, and a method for repairing an optical mask by which defects in the phase shifter can be easily repaired. A method for manufacturing an optical mask in which a phase shifter for inverting the phase of exposure light is formed in a phase shifter formation region of an optical mask substrate, the resist layer having the phase shifter type region opened on the optical mask substrate. A step of depositing a phase shifter material using the resist layer as a mask by an ion beam assisted vapor deposition method, and a step of removing the resist layer. [Above field of application] This invention is half 8! The present invention relates to an optical mask manufacturing method for manufacturing an optical mask for a projection exposure apparatus used for manufacturing body equipment, and an optical mask repair method for modifying the manufactured optical mask. In the recent development of ultra-LSIs, submicron to half-micron pattern formation has become necessary to realize ultra-high 1N stacking. For example, 0.8um for 4M-DRAM, 0.5-0.6μm for 16M-DRAM
The design rule is 0.3 for 64M-DRAM.
It becomes a μm design rule. In order to achieve such miniaturization, a reduction projection exposure system (stepper), which has excellent mass productivity and ease of use, is used in the ring graphing process to define the pattern.The performance of this reduction projection exposure system is In order to push the limits of resist materials and resist processes, improvements are being made, but one method to further improve the performance limits of reduction projection exposure equipment is called phase shift phosphorography, which forms a phase shifter on an optical mask (reticle). Phase shift lithography is a technology that improves the light intensity and contrast of a projected image by manipulating the phase of light passing through an optical mask.In phase shift lithography, adjacent light beams of an optical mask are A phase shifter that inverts the phase of light is provided on one side of the light transmitting section.Since the transmitted light has opposite phases between adjacent light transmitting sections, the light intensity becomes almost zero at the boundary between the light transmitting sections, improving contrast. [Conventional technology] Figures 5 and 6 show conventional optical masks used in phase shift phosphorography.

In the optical mask shown in FIG. 5, an oxide (5 (S t O)) 44 as a phase shifter is formed on an optical mask substrate 40 made of quartz via a nitride film (SiN) 42. A chromium film 46 serving as a light shielding mask is formed thereon.Adjacent light transmitting portions 46a of the chromium film 46,
46b is oxidized to a thickness that inverts the phase by 180 degrees only on one light transmitting portion 46b [44]. In the optical mask shown in FIG. 5, oxidized M44, which becomes a phase shifter, is formed on the entire surface by sputtering or CVD, and then an unnecessary light transmitting part 46a is etched away by R fine processing. Nitride WA42 is oxide film 4
4 is provided as an etching stopper when removing it by etching. In the optical mask shown in FIG. 6, a nitride film 42 is formed on the entire surface of an optical mask substrate 40 made of quartz, and a chromium film 46 serving as a light shielding mask is formed on this nitride film 42. Adjacent light transmitting portion 46a of chrome WA46
, 46b is formed with an SOG film 48 having a thickness that inverts the phase by 180 degrees. In the optical mask shown in FIG. 6, SOGJ 48 is applied by Subin coating, and then the pond part is etched away by Ifi 4 [II processing, leaving SOG IIA 48 on the light transmitting part 46a. The nitride film 42 is provided as an etching stopper when removing the SOGM 48 by etching.

[Problems to be Solved by the Invention] However, in the conventional optical masks shown in FIGS. 5 and 6, the optical mask substrate 40 and the oxidation 84 as a phase shifter are
The refractive index of the nitride film 42 or SOG film 42 is almost the same, but the refractive index of the nitride film 42 sandwiched between them is significantly different, so that the transmitted light undergoes multiple reflections, and the light transmittance varies depending on the presence or absence of a phase shifter. , there was a problem that the dimensional accuracy of the pattern deteriorated. In addition, optical masks are required to be perfectly good products with no defects such as missing mask patterns or phase shifters, but it is difficult to make defect-free optical masks in one go.
It is desirable to be able to correct defects in the phase shifter. However, in the conventional optical mask shown in FIG. 5, it is difficult to correct only the oxide film 44 because chromium [46 is formed on the oxide M44, which is the phase shifter. It is. SOGJl4, which is also a phase shifter in the optical mask shown in Figure 6,
8 is applied by subin coat,
It is difficult to repair defects by forming the SOG film 48 only on a portion. Furthermore, in the conventional optical mask shown in FIG. 5, the oxide film 44, which is a phase shifter, is formed by sputtering or CVD.
There was a problem in that it was difficult to control the film thickness. Further, even with the conventional optical mask shown in FIG. 6, there is a problem in that it is difficult to control the film thickness due to film thinning during curing after forming the SOG film 48, which is a phase shifter, by spin coating. The present invention has been made in consideration of the above circumstances, and includes a method for manufacturing an optical mask in which the film thickness of the phase shifter is well controlled and the light transmittance does not differ depending on the presence or absence of the phase shifter, and it is easy to correct defects in the phase shifter. The purpose of this study is to provide a method for modifying optical masks that can be performed in a variety of ways. [Means for Solving the Problems] The above object provides a method for manufacturing an optical mask in which a phase shifter for inverting the phase of exposure light is formed in a phase shifter forming region of an optical mask substrate. The method includes the steps of: forming a resist layer in which the phase shifter formation region is open; using the resist layer as a mask, depositing a phase shifter material by ion beam assisted deposition; and removing the resist layer. This is achieved by a unique optical mask manufacturing method. The above object also provides a method for repairing an optical mask for repairing a phase shifter formed on an optical mask substrate, in which a resist layer is formed on the optical mask substrate in which a phase shifter forming region including a defective phase shifter to be repaired is opened. a step of forming;
using the resist layer as a mask to remove the defective phase shifter by etching; using the resist layer as a mask, depositing a phase shifter material by ion beam assisted deposition; and removing the resist layer. This is achieved by an optical mask modification method characterized by the following. [Function] According to the method for manufacturing an optical mask of the present invention, the film thickness of the phase shifter is well controlled, and the light transmittance does not differ depending on the presence or absence of the phase shifter. Further, according to the optical mask repair method of the present invention, only the defective phase shifter can be selectively removed and repaired without affecting other phase defects.

[Example] A method for manufacturing an optical mask according to an example of the present invention will be explained using FIG. The optical mask substrate 10 is a 127 mm square, 2.3 mm thick substrate made of, for example, synthetic quartz. A chromium film 1 with a thickness of 80 nm is placed on the optical mask substrate 10 as a light-shielding mask.
2 is formed. Adjacent light transmitting portions 12a and 12b are opened in the chromium film 12. In this embodiment, immediately after forming the phase shifter in the light transmitting part 12a, a resist layer 14 of EB resist is formed on the entire surface of the chromium film 12 (FIG. 1(a)). Coat to a thickness of 1 μm, and then pre-bake at 180°C for 30 minutes. Next, the resist layer 14 on the light transmitting part 12a that forms the phase shifter is exposed to 160 μC/c by electron beam exposure.
m'', and an opening 14 is formed in the resist layer 14 by the phenomenon.
a (Fig. 1(b)).

Next, oxidized WA (SiO2) 16 is deposited on the entire surface by ion beam assisted deposition (FIG. 1(C)). The ion beam assisted deposition method performs deposition while irradiating the surface to be deposited with an ion beam, and by bombarding the surface with ions during deposition, it is possible to form a dense deposited film. The ion beam assisted vapor deposition apparatus will be explained using FIG. 2.

The vacuum 4!20 is evacuated using a vacuum pump connected to the vacuum exhaust port 22. The vacuum pump continues to pump the vacuum chamber 20 so that the pressure inside the vacuum chamber 20 is always maintained at a constant level even when gas is introduced or vapor deposition is performed. A substrate support plate 24 for fixing the optical mask substrate 10 is provided above the vacuum chamber 20. A monitor glass 26 for measuring film thickness is provided on the substrate support plate 24. The direction of the light emitted from the light source 28 is bent by two mirrors and is incident on the monitor glass 26. The direction of the light reflected by the monitor glass 26 is bent by a mirror 31 and enters a light receiver 30. The film thickness controller 32 controls the vaporization on the monitor glass 26 based on the light reception signal from the light receiver 30.
The thickness of the film is measured, and when it is detected that the deposited film has reached a predetermined thickness, the deposition is stopped.

At the bottom of the vacuum chamber 20 is an evaporation source 3 containing materials to be evaporated.
4 is listed. Further, an ion gun 36 for irradiating an ion beam is provided at the bottom of the vacuum chamber 20. The gas to be irradiated is the gas inlet 3 below the ion gun 36.
It flows in from 6a. A neutralizer 36b is provided above the ion gun 36 to electrically neutralize the emitted ions.

Using this ion beam assisted vapor deposition system, the oxide film 16 is
The method for forming the will be explained in detail.

First, vacuum! M20 is evacuated using a vacuum pump connected to the vacuum exhaust port 22 to maintain a vacuum level of 5 x 10-'Torr. Next, oxygen gas is introduced from the gas inlet 36a. At this time, continue to exhaust with the vacuum pump,
Make sure to keep the pressure in the vacuum chamber 20 constant. In this state, the evaporation source 34 is heated by an electron beam, and the fused silica or synthetic quartz in the evaporation source 34 is evaporated. At the same time, from the ion gun 36, for example, 20
An oxygen ion beam of μA/cm2 is applied to the optical mask substrate 1.
Irradiate toward 0. Note that the optical mask substrate 1 is
0 may be left at room temperature or may be heated to about 80 to 110°C.

The film thickness of the oxidized Y416 as a phase shifter is strictly controlled by the film thickness controller 32. When the exposure wavelength is λ and the refractive index at the exposure wavelength is n, the thickness of the oxidized v416 is d=λ/2(n-1).

For example, in a general g-line stepper, λ=0.4358μ
m, and the thickness d of the oxide film 16 is approximately 0.47 μm.
The film thickness of the oxide film 16 is set to 0 by the JII thickness controller 32.
, 47 μm, the ion beam assisted deposition is terminated by closing the shutter, etc.

Next, when the resist layer 14 is removed, the oxide film 16 on the resist layer 14 is lifted off, and an oxide film 16 as a phase shifter is formed on the light transmitting part 12a (see FIG.
))． As described above, according to this embodiment, the oxide film as a phase shifter is formed by the ion beam assisted vapor deposition method.
A dense oxide film is formed, and a phase shifter with precisely controlled film thickness can be formed. Furthermore, in this example, since the oxide film serving as the phase shifter is in direct contact with the optical mask substrate, multiple reflections due to differences in refractive index do not occur, and there is no difference in light transmittance due to the presence or absence of the phase shifter.

Next, a method for repairing an optical mask, which is another embodiment of the present invention, will be explained with reference to FIG. The same reference numerals are given to the same top elements as in FIG. 1, and the explanation thereof will be omitted.

In this embodiment, a nitride film 18 is provided between the optical mask substrate 10 and the chromium film 12 as an etching stopper. An oxide film 16 was formed as a phase shifter on one of the light transmitting parts 12a of the chromium film 12, but as shown in FIG.
Let us explain how to correct 6' as an example. First, a resist layer 14 is formed on the entire surface, and only the phase shifter formation region containing the defective oxide film 16' to be repaired is opened (FIG. 3(b)). Next, using the resist layer 14 as a mask, detect the defect.
6' is removed by etching (FIG. 3(C)).

Since the nitride film 18 is formed on the optical mask substrate 10, the optical mask substrate 10 is not etched.

Next, a silicon dioxide film (Si.O2) 16 is deposited on the entire surface by the ion beam assisted deposition method described above (Fig. 3(d)).
．． Next, when the resist layer 14 is removed, the oxide film l6 on the resist layer 14 is lifted off, and a repaired oxide film l6 as a phase shifter is formed on the light transmitting portion 12a (FIG. 3(d)). In this way, according to this embodiment, even if there is a defect in a part of the phase shifter of the optical mask, it is possible to selectively remove and repair only the defective phase shifter without affecting other phase shifters. can.

In the above embodiment, the nitride film 18 as an etching stopper was inserted between the optical mask substrate 10 and the chromium film 12, but as shown in FIG. You may also insert 11118. The present invention is not limited to the above embodiments, and various modifications are possible. For example, it goes without saying that the materials for the optical mask substrate, phase shifter, light shielding mask, resist layer, etching stopper, etc. are not limited to those in the above embodiments. 3 is a cross-sectional view of a process for repairing an optical mask according to another embodiment of the present invention, FIG. 4 is a cross-sectional view showing a specific example of an optical mask pond, and FIGS. It is a cross-sectional view of an optical mask. [Effects of the Invention] As described above, according to the method for manufacturing an optical mask of the present invention,
The film thickness of the phase shifter is well controllable, and it is possible to manufacture an optical mask in which the light transmittance does not differ depending on the presence or absence of the phase shifter. Further, according to the optical mask repair method of the present invention, only a defective phase shifter can be selectively removed and repaired without affecting other phase shifters.

[Brief explanation of drawings]

FIG. 1 is a process cross-sectional view of a method for manufacturing an optical mask according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of an ion beam assisted vapor deposition apparatus. 12b...Light transmitting portion 14...Resist layer 16...Oxide film 16'...Defective oxide film 18...Nitride film 20...Vacuum chamber 22...Vacuum exhaust port 24... Substrate support plate 26... Monitor glass 28... Two light sources, 31... Mirror 30... Light receiver 32... Film thickness controller 34... Evaporation source 36... Ion gun 36a... Gas inlet 36b... Neutralizer 40... Optical mask substrate 42... Nitride film 44... Oxide film 46... Kumu films 46a, 46b... Light transmitting portion 48... SOGWA Applicant Fujitsu Ltd.

Claims (1)

[Scope of Claims] 1. A method for manufacturing an optical mask in which a phase shifter for inverting the phase of exposure light is formed in a phase shifter formation region of an optical mask substrate, wherein the phase shifter formation region is provided with an opening on the optical mask substrate. manufacturing an optical mask, comprising: forming a resist layer; using the resist layer as a mask, depositing a phase shifter material by ion beam assisted deposition; and removing the resist layer. Method. 2. The method according to claim 1, wherein the phase shifter material is a material having substantially the same refractive index as the optical mask substrate, and the phase shifter is in direct contact with the optical mask substrate. Method of manufacturing an optical mask. 3. The method of manufacturing an optical mask according to claim 1 or 2, wherein the optical mask substrate is quartz and the phase shifter material is SiO_2. 4. An optical mask repair method for repairing a phase shifter formed on an optical mask substrate, the step of forming a resist layer on the optical mask substrate in which a phase shifter forming region containing a defective phase shifter to be repaired is opened; , using the resist layer as a mask, etching away the defective phase shifter; using the resist layer as a mask, depositing a phase shifter material by ion beam assisted deposition; and removing the resist layer. A method for repairing an optical mask, comprising: 5. The method of repairing an optical mask according to claim 4, wherein the optical mask substrate is quartz and the phase shifter material is SiO_2.