JPH11149152A - Grounding method and photomask blanks - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grounding method and a photomask blanks used in the method which can surely prevent the retaining of an electron on a photomask blanks caused by an electron beam, which does not spoil the appearance quality of a photomask to be manufactured, and which does not cause contamination in a device used in processing process after lithographic process in electron beam exposure and lithography using an electron beam exposing and lithographing device. SOLUTION: This is the grounding method for preventing the retaining of the electron on the photomask blanks 100 caused by the irradiation of the electron beam in the electron beam exposing and lithographing device. Conductive metallic layers 130 and 135 are provided on the back surface opposed to a surface where a light shielding layer 120 is provided and on an end face, and the light shielding layer is electrically connected with the grounding line 170 of the exposing and lithographing device through the conductive metallic layer on the back surface of the photomask blanks by using the photomask blanks whose conductive metallic layer on the back surface is electrically connected with the light shielding layer through the conductive metallic layer on the end face.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the manufacture of a photomask used in the manufacture of semiconductor devices such as ICs and LSIs, and more particularly, to the patterning of a photomask in electron beam exposure drawing for manufacturing a photomask. The present invention relates to a grounding method capable of reliably preventing electrons from staying on a photomask blank in which a resist is applied on a light-shielding layer to be formed, and a photomask blank used in the grounding method.

[0002]

2. Description of the Related Art A photomask is used as an original when forming a circuit pattern of a semiconductor element such as an IC or an LSI, and is formed of a light-shielding layer mainly composed of chromium, molybdenum or the like on a substrate of quartz or the like. A pattern is arranged. Usually, as shown in FIG. 5, it is manufactured by processing a photomask blank in which a light-shielding layer mainly composed of chromium, molybdenum or the like is provided on one surface of a substrate such as quartz. The method of manufacturing the photomask shown in FIG. 5 will be briefly described here. First, a light-shielding layer 520 mainly composed of chromium, molybdenum or the like is formed on substantially one surface of a substrate 510 (FIG. 5A) made of quartz glass or the like (FIG. 5B). Line (436n
m) and a resist 530 sensitive to ionizing radiation such as an ultraviolet ray such as an i-ray (365 nm) or an electron beam (FIG. 5C), and then a g-ray, an i-ray, an electron beam, etc. corresponding to the resist 530 are applied. Resist 5 using ionizing radiation 540 of
30 is selectively exposed and drawn in a predetermined pattern shape.
(FIG. 5D) Next, a developing process is performed to form a resist pattern.
In the case of a positive resist, the exposed resist portion is removed to form a resist pattern. (FIG. 5
(E)) In the case of a negative resist, since the exposed resist portion is hardened, the unexposed resist portion is removed by a developing process to form a resist pattern. Next, a baking process and a descum process are performed as necessary, and the light-shielding layer 520 exposed according to the resist pattern is formed.
After etching (corrosion) to form a pattern formed of a light shielding layer (FIG. 5F), the resist film 530 is removed, and a cleaning process or the like is performed to obtain a photomask 500. (FIG. 5 (g)) The light-shielding layer 520 was a single-layer film, a two-layer film having a chromium oxide layer on the surface, and a similar chromium oxide layer was provided on the first and third layers. A three-layer film or the like is used. The exposure / drawing method in the photomask manufacturing method shown in FIG. 5 includes an electron beam exposure / exposure method in which a resist portion provided on a light-shielding layer of a photomask blank is exposed and drawn with an electron beam using graphic data. Although a drawing apparatus is mainly used, in recent years, a drawing apparatus or the like which performs drawing by light exposure using excimer KrF light using graphic data has been used.

When electron beam exposure / drawing is performed by an electron beam exposure / drawing apparatus, a photomask blank in which a photosensitive resist is applied to one surface of an electron beam is set in a cassette, and this is set in a drawing apparatus. This is performed while being held on the XY moving stage, but if the electrons supplied by the irradiated electron beam stay in the photomask blanks, the accuracy of exposure and drawing is reduced. Say) must be prevented. Therefore, generally, as shown in FIG. 4, the conductive pins 457 of the cassette 450 penetrate the resist 440 of the photomask blank 400, and
0 and the light shielding layer 420 and the cassette 450
The electron supplied to the photomask blanks 400 by the electron beam through the cassette 450 flows to the ground line 470 of the electron beam exposure / drawing apparatus via the cassette 450 to prevent the accumulation of the electrons. However, in the case of this method for preventing the accumulation of electrons, the resist penetrates, so that residues of the resist and peeling of the light shielding layer occur. For this reason, these may adhere to the exposure / drawing area and hinder exposure / drawing, resulting in poor quality. In addition, even when these remain in the outer peripheral portion of the photomask blank and do not hinder exposure / drawing, there are steps of resist development, light-shielding layer etching, cleaning, etc. after exposure / drawing, and these may cause quality defects. Had to cause. In addition, these have caused contamination of the equipment used in the process. In addition, the contact between the conductive pin 457 and the light-shielding layer 420 is electrically unstable, and in some cases, the electric resistance is increased, and electrons are not sufficiently emitted.
Electrons are repelled by the staying electrons staying at 00 and the drawing accuracy may be significantly deteriorated, which has been a problem.

[0004]

Further, with the miniaturization and high density of semiconductor elements, the demand for finer and higher precision photomask patterns is strict, and electron beam exposure / drawing using an electron beam exposure / drawing apparatus. Also, there is an increasing demand for improved exposure and drawing accuracy and improved appearance quality. Under such circumstances, in electron beam exposure / drawing using an electron beam exposure / drawing apparatus, it has been required to reliably prevent electrons from staying on photomask blanks due to electron beams. The present invention corresponds to this, and in electron beam exposure / drawing using an electron beam exposure / drawing apparatus, the retention of electrons on a photomask blank by an electron beam can be reliably prevented, and the appearance quality of a photomask to be produced can be reduced. An object of the present invention is to provide a grounding method which does not hinder and does not cause contamination in an apparatus used in a processing step after drawing. At the same time, it is intended to provide a photomask blank used for the grounding method.

[0005]

According to the grounding method of the present invention, a photomask blank in which an electron beam-sensitive resist is applied on a light shielding layer for forming a picture of a photomask is held on an XY moving stage. In an electron beam exposure / drawing apparatus that performs exposure / drawing by irradiating a controlled electron beam, a grounding method for preventing stagnation of electrons on the photomask blank due to irradiation of the electron beam, wherein the light-shielding layer is A conductive metal layer is provided on the back surface facing the provided surface and the end surface, and the conductive metal layer on the back surface is electrically connected to the light-shielding layer via the conductive metal layer on the end surface. Characterized in that a light-shielding layer and a ground line of an exposure / writing apparatus are electrically connected to each other via a conductive metal layer on the back surface of the photomask blank using the photomask blanks described above. A. The electron beam exposure / drawing apparatus described above is characterized in that the photomask blanks are set in a cassette and the cassette is held on a stage. Further, the photomask blank of the present invention is a photomask blank used for electron beam exposure drawing, provided with a conductive metal layer on the back surface and the end face, and via the conductive metal layer on the end face, The conductive metal layer on the back surface is electrically connected to a light-shielding layer for forming a picture of a photomask.
In the above, the conductive metal layer on the back surface and the end surface is mainly made of the same substance as the light-shielding layer for forming the picture of the photomask.

[0006]

According to the grounding method of the present invention having such a structure, in the electron beam exposure / drawing using the electron beam exposure / drawing apparatus, it is possible to reliably prevent the accumulation of electrons on the photomask blanks due to the electron beam. This makes it possible to provide a grounding method that does not impair the appearance quality of a photomask to be manufactured and does not cause contamination in an apparatus used in a processing step after drawing. Specifically, as a photomask blank, a conductive metal layer is provided on the back surface and the end surface thereof, and the pattern of the conductive metal layer on the back surface and the pattern of the photomask are provided via the conductive metal layer on the end surface. Use what is electrically connected to the light shielding layer to form,
This is achieved by electrically connecting the light-shielding layer and the ground line of the exposure / writing apparatus via a conductive metal layer on the back surface of the photomask blank. That is, by using a photomask blank in which the conductive metal layer on the back surface and the light-shielding layer for forming the pattern of the photomask are electrically connected via the conductive metal layer on the end surface, The back surface can reliably contact the ground line of the exposure / writing apparatus, and as a result, the electrical connection between the light shielding layer and the ground line of the exposure / writing apparatus can be ensured. Further, unlike the conventional method shown in FIG. 4, there is no need to penetrate the resist by the conductive pins 457 of the cassette 450, and the residue of the resist and peeling of the light shielding film are eliminated. For this reason, a stable photomask can be obtained as the appearance quality.

[0007] The photomask blank of the present invention, by adopting such a structure, makes it possible to carry out the grounding method of the present invention. It is possible to reliably prevent stagnation of electrons on the photomask blanks due to electron beams in electron beam exposure drawing. In addition, a photomask to be manufactured is stable in appearance quality. In addition, the conductive metal layer provided on the back surface and the end surface is mainly made of the same material as the light-shielding layer for forming the pattern of the photomask, so that workability is improved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a grounding method according to the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining an example of an embodiment of a grounding method according to the present invention, and is a cross-sectional view showing a state where a photomask blank 100 is held and placed on a cassette 150. In FIG. 1, 100 is a photomask blank,
100A is the front surface, 100B is the back surface, 100C is the end surface, 1
10 is a glass substrate, 120 is a light shielding layer, 130 and 135 are conductive metal layers, 140 is a resist, 150 is a cassette, 155 is a support pin, 160 is a stage, and 170 is a ground line. In the grounding method shown in FIG. 1A, a photomask blank 100 in which an electron beam-sensitive resist 140 is applied on a light shielding layer 120 for forming a pattern of a photomask is set in a cassette 150, In addition, the cassette 150 is held on an XY moving stage, and is irradiated with a controlled electron beam to perform exposure and drawing. ) Is a grounding method for preventing Then, as the photomask blank 100, a conductive metal layer is provided on the back surface 100B and the end surface 100C facing the surface on which the light-shielding layer 120 is provided, and the back surface 100B is provided via the conductive metal layer 135 on the end surface 100C. And a light shielding layer 120 for forming a picture of a photomask is electrically connected to the conductive metal layer 130, and is electrically connected to a ground line 170 of an exposure / drawing apparatus (not shown). The conductive metal layer 13 on the back surface 100B of the photomask blank 100 is attached to the support pins 155 of the cassette 150 which are securely connected.
0 to make photomask blanks 10
0 is supported. Although not shown, the entire photomask blank 100 is held and fixed so that pressure is applied to the support pins 155. The side of the support pin 155 that is in contact with the photomask blank 100 may have a round shape, but is not limited thereto. Thereby, the light-shielding layer 120 is formed on the conductive metal layer 1 on the end face 100C.
35, via the conductive metal layer 130 on the back surface 100B,
It is securely connected electrically to the cassette 150, and furthermore, is securely connected electrically to the ground line 170 of the exposure / drawing apparatus. The conductive metal layer 130 on the back surface 100B of the photomask blank 100 and the conductive metal layer 135 on the end face 100C may be made of the same material or different materials. Further, the conductive metal layers 130, 135
May be the same material as the light shielding layer. Conductive metal layer 13
What is essential is that the materials 0 and 135 have conductivity and good processability, but from the viewpoint of workability, it is preferable to use the same substance as the light shielding layer 120 as a main component. FIG. 1 (a)
In the example shown in FIG.
The conduction between the conductive metal layer 130B and the cassette 150 is performed via the support pins 155, but the back surface 100B
The conduction between the conductive metal layer 130 and the cassette 150 is not limited to this.

As a grounding method, as shown in FIG.
A method in which the photomask blanks 100 are directly held on the stage 160 without using the step 50 may be used. Again,
The conductive metal layer 130 on the back surface 100B of the photomask blank 100 and the ground line 170 of the apparatus are easily and electrically connected easily.

Next, a photomask blank of the present invention will be described with reference to the drawings. 2A and 2B show an example of an embodiment of a photomask blank. FIG. 2A is a cross-sectional view in the width direction, and FIG. 2B is an enlarged view of a portion B0 in FIG. 2A. FIG. In FIG. 2, 100 is a photomask blank, 100A is a front surface, 100B is a back surface, 100C is an end surface, 110 is a glass substrate, 120 is a light shielding layer, 123 is a first layer, 125 is a second layer, and 130, 1
35 is a conductive metal layer. The photomask blank 100 shown in FIG. 2 is a photomask blank used for electron beam exposure drawing, and has conductive metal layers 130 and 135 on its back surface 100B and end surface 100C, respectively.
And the conductive metal layer 130 on the back surface 100B and the conductive metal layer 135 on the back surface 100B via the conductive metal layer 135 on the end surface 100C.
Light-shielding layer 1 for forming a pattern of a 00A photomask
20 are electrically connected. The glass substrate 110 needs to be transparent to exposure light at the time of manufacturing a semiconductor element, but when ultraviolet light such as g-line (436 nm) or i-line (365 nm) is used as exposure light. Usually, quartz glass is used. The light-shielding layer 120 needs to have a light-shielding property with respect to exposure light at the time of manufacturing a semiconductor element, and preferably has a better processability. g
When ultraviolet light such as line (436 nm) or i-line (365 nm) is used as the exposure light, it is usually a single layer mainly composed of chromium, molybdenum, or the like, or a multilayer structure formed from a plurality of types of metals. Is used. The light-shielding layer 120 in the example shown in FIG. 2 includes a first layer 123 and a second layer 125.
The first layer 123 is a metal chromium layer, and the second layer 125 is a chromium oxynitride layer. However, the present invention is not particularly limited to this. The conductive metal layers 130 and 135 are not particularly limited as long as they are conductive and have good processability. From the viewpoint of workability, the same or the same material as the light shielding layer 220, that is, the same material is used. Those which are mainly used are preferred. The back 100B
The conductive metal layer 130 and the conductive metal layer 135 on the end face 100C may be made of the same material or different materials.

Next, an example of manufacturing a photomask when performing exposure and drawing using the photomask blank 100 shown in FIG. 2 and the grounding method shown in FIG. 1 will be described. FIG. 3 is a cross-sectional view illustrating a manufacturing process of the photomask.
FIGS. 3A to 3C simply show the steps of manufacturing the photomask blank 100 shown in FIG. First, a glass substrate 110 for preparing a photomask blank is prepared. (FIG. 3 (a)) After cleaning the glass substrate 110, one surface (front surface)
Then, a light-shielding layer 120 for forming a pattern of a photomask is formed. The film formation of the light shielding layer 120 is performed by sputtering, vapor deposition, or the like. Sputtering, vapor deposition, and the like usually involve the wraparound of the end face 110C of the glass substrate 110, and a film is formed on a part of the end face 110C. Next, conductive metal layers 130 and 135 are formed on the surface (back surface) of the glass substrate 110 opposite to the side on which the light shielding layer 120 is provided, in the same manner as the film formation of the light shielding layer 120. (FIG. 3C) The conductive metal layers 130 and 135 are not particularly limited, but are preferably the same as or similar to the light shielding layer 120 from the viewpoint of workability. That is, in the case of a light-shielding layer mainly composed of chromium, a conductive metal layer mainly composed of chromium is preferable. Similarly, a conductive metal layer 130 is formed on a part of the end face 110C of the glass substrate 110 by wraparound.
20 and a conductive metal thin film 130, the surface 1
The light shielding layer 120 of 10A and the conductive metal layer 130 of the back surface 110B are electrically connected. Here, the formation of the conductive metal layers 130 and 135 is performed at one time, but it is not always necessary to perform them at once. Thus, the photomask blank 100 shown in FIG. 2 is manufactured.
Next, a resist 140 having photosensitivity to an electron beam is formed on the light shielding layer 120 by coating. (FIG. 3D) Thereafter, the photomask blanks 100 are set and held in a cassette 150 (not shown) of the electron beam lithography apparatus (FIG. 3E).
XY moving stage of electron beam lithography system (not shown)
Place it on the top and perform electron beam exposure drawing. After the exposure and drawing, the glass substrate 110 (FIG. 3 (f)) is developed to form a resist pattern 140A (FIG. 3 (g)), and then the resist pattern 140A is used as an etching resistant mask to shield the surface of the photomask blank 100 from light. The layer 120 is first etched (FIG. 3 (h)), and then the conductive metal layers 130, 135 on the back and end surfaces are etched. (FIG. 3 (i)) In FIG. 3 (f), reference numeral 145 denotes an exposure drawing unit. In the process shown in FIG. 3, since the negative type resist was used, the exposed / drawn portion was hardened by exposure / drawing, and only this portion was left to form a pattern by development. However, when the positive type resist was used, the exposed / drawn portion was formed. Only the part thus formed is dissolved and removed by development to form a pattern. By etching, a pattern portion of the photomask is formed, and all of the conductive metal layer 130 on the back surface of the photomask blank and the conductive metal layer 135 at the end are removed. The order of etching the light-shielding layer 120 and the conductive metal layers 130 and 135 may be performed separately by spray etching on the front and back of the substrate, or substantially simultaneously by dipping. After this, resist 1
The photomask 200 is obtained by removing 40 (145).
(FIG. 3 (j)) In the fabrication of a photomask by this method, the grounding of the photomask blanks during electron beam exposure and drawing can be ensured, and quality problems due to the grounding in the conventional method and the subsequent steps. The problem of contamination of the apparatus does not occur.

[0012]

EXAMPLES Further, examples will be described. The photomask blank has the same structure as that of the embodiment shown in FIG. 2, and has a glass substrate of 6.35 mm thick, 6 inches square.
Using a chrome layer 10 as a light shielding layer.
In this embodiment, a multi-layered light-shielding layer composed of two layers of a chromium oxide layer 200 and a chromium oxide layer 200 is provided. On the light-shielding layer of the photomask blank of the example, a positive resist EBR9 HS-31 (manufactured by Toray Industries, Inc.) was provided to a thickness of 5500 mm, and then FIG.
After being set in a cassette as shown in (a), an electron beam exposure / drawing apparatus MebesIV (Perkin Elmer)
), Electron beam diameter 0.25μmφ, current value 60μ
In A, a large number of line patterns having a line width of 2 μm and a pitch of 4 μm were drawn in a wide range, developed and etched, and a photomask was fabricated. Then, the photomask was inspected. No defect in drawing position accuracy due to stagnation (charge-up) of electrons on the blanks was observed, and no influence on quality based on a conventional grounding method was observed.

[0013]

As described above, according to the present invention, in electron beam exposure / drawing using an electron beam exposure / drawing apparatus, it is possible to reliably prevent stagnation (charge-up) of electrons on a photomask blank by an electron beam. It is possible to provide a grounding method. At the same time, it has become possible to provide photomask blanks used for the grounding method.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of an embodiment of a grounding method according to the present invention.

FIG. 2 is a sectional view showing an example of an embodiment of a photomask blank of the present invention.

FIG. 3 is a view showing a manufacturing process of a photomask using the grounding method of the present invention and a photomask blank of the present invention.

FIG. 4 is a view for explaining a conventional grounding method and a conventional photomask blank.

FIG. 5 is a process chart for explaining a photomask manufacturing process.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Photomask blanks 100A Front surface 100B Back surface 100C End surface 110 Glass substrate 110A Surface 110B Back surface 110C End surface 120 Light shielding layer 130, 135 Conductive metal layer 140 Resist 140A Resist pattern 145 Exposure drawing unit 150 Cassette 155 Support pin 160 Stage 170 Ground line 200 Photomask 400 Photomask blanks 410 Glass substrate 420 Light shielding layer 440 Resist 450 Cassette 460 Stage 470 Ground line 500 Photomask 510 Substrate 520 Light shielding layer 530 Resist 540 Ionizing radiation

Claims (4)

[Claims] 1. A photomask blank in which an electron beam-sensitive resist is applied on a light-shielding layer for forming a pattern of a photomask is held on an XY moving stage and irradiated with a controlled electron beam. An electron beam exposure / drawing apparatus for performing exposure / drawing, a grounding method for preventing the accumulation of electrons on a photomask blank due to irradiation with an electron beam, a back surface facing a surface provided with the light shielding layer, and an end surface A photomask blank in which a conductive metal layer on the back surface and the light-shielding layer are electrically connected to each other via a conductive metal layer on an end face, A grounding method, wherein a light-shielding layer is electrically connected to a grounding line of an exposure / writing apparatus via a conductive metal layer on a back surface of the mask blank. 2. An electron beam exposure / drawing apparatus according to claim 1, wherein the photomask blanks are set in a cassette.
A grounding method, wherein the cassette is an electron beam exposure / drawing apparatus of a type held on a stage. 3. A photomask blank used for electron beam exposure drawing, wherein a conductive metal layer is provided on a back surface and an end surface thereof, and via a conductive metal layer on the end surface.
A photomask blank, wherein a conductive metal layer on a back surface and a light shielding layer for forming a pattern of a photomask are electrically connected. 4. The photomask blank according to claim 4, wherein the conductive metal layer on the back surface and the end surface is mainly made of the same substance as a light-shielding layer for forming a picture of a photomask.