JP2006047564A - Photomask and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photomask having an alignment mark for a photomask where a scanning track by an electron beam does not remain as a defect in a phase shift mask comprising a multilayer film which requires a plurality of times of exposure steps, and to provide a method for manufacturing the photomask. <P>SOLUTION: The phase shift mask is formed by scanning an alignment groove with an electron beam, the groove patterned in a halftone film by using an alignment mark for a photomask, and then patterning a light shielding film by exposure to an electron beam to remove the scanning track. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a semiconductor device and a manufacturing method thereof, and more particularly, to a photomask used in a lithography process for transferring a pattern shape onto a substrate and a manufacturing method thereof.

  With the recent miniaturization of the semiconductor process, in the exposure process of the wafer process, a technique for improving the resolution using a phase shift mask is required along with the shortening of the exposure wavelength of the exposure machine. Typical examples of phase shift masks include halftone masks, Levenson masks, and chromeless masks, but most of them are processes that are almost multiple times that of creating a normal mask when forming a mask pattern. Cost. This is because the pattern of each layer is formed separately. Therefore, the alignment of each layer pattern is shifted and the original performance of the pattern may not be obtained. As process miniaturization progresses, it is necessary to reduce this misalignment. For example, in the case of a tritone mask formed of a halftone pattern and a chromium pattern, the misalignment between the halftone pattern and the chromium pattern is minimized. It is necessary to keep it at a minimum. When creating a tritone mask, alignment of a halftone pattern and a chrome pattern is performed using alignment marks in the periphery of the main pattern.

  A conventional photomask alignment mark and photomask manufacturing method will be described below. 4 and 5 show the mask structures of halftone masks and tritone masks and their light intensities among the resolution enhancement techniques used when forming a fine pattern.

  FIG. 4 shows the structure of a conventional halftone phase shift mask and its light intensity. 4A is a schematic view illustrating a planar structure of a conventional halftone phase shift mask, and FIG. 4B is a schematic view illustrating a cross-sectional structure of the conventional halftone phase shift mask. FIG. 4C is a graph showing the light intensity of a conventional halftone phase shift mask.

  As shown in FIG. 4A and FIG. 4B, it is composed of a synthetic quartz glass 7 and a halftone film 6 formed of MoSi or the like whose central portion is cut by patterning. .

  In the halftone mask, the phase of the light passing through the halftone film 6 is reversed, so that the resolution is improved by taking advantage of the steep profile of the light intensity passing through the glass 7. However, as shown in FIG. 4C, the light intensity distribution in which the curve with the transmittance of 5% becomes steep is shown. Also, a structure has been considered in which the resolution is further improved by increasing the transmittance of the halftone film to increase the amount of transmitted light. However, when the transmittance of the halftone film is increased, the amount of transmitted light increases so that an undesirable light distribution called side lobe 9 is generated, making it difficult to form a desired pattern. A curve with a transmittance of 20% shows a large side lobe 9.

  A structure that suppresses the side lobe is a tritone mask.

  FIG. 5 shows the structure of a conventional tritone mask type phase shift mask and its light intensity. That is, FIG. 5A is a schematic view illustrating the planar structure of a conventional tritone mask type phase shift mask, and FIG. 5B illustrates the cross-sectional structure of the conventional tritone mask type phase shift mask. FIG. 5C is a graph showing the light intensity of the conventional tritone mask type phase shift mask.

  As shown in FIG. 5A and FIG. 5B, the synthetic quartz glass 7, the halftone film 6 formed of MoSi or the like, the center part of which is cut by patterning, are provided thereon. The light shielding film 8 is formed.

  As shown in FIG. 5C, the tritone mask has a structure in which a light shielding film 8 such as Cr is further added to the halftone mask, and the light shielding film 8 suppresses the generation of the side lobe 9. It is possible to employ a halftone film 6 having a high transmittance.

  FIG. 6 is a schematic view illustrating the planar structure of a photomask in which conventional photomask alignment marks are arranged. As shown in the figure, a plurality of photomask alignment marks 10 are arranged along the upper inner circumference of the mask, and stepper alignment marks 2 are arranged along the inner circumference of the mask. A stepper exposure region 30 is provided at the center of the mask. In the stepper exposure region 30, a plurality of main patterns 50 are evenly arranged vertically and horizontally, and each main pattern 50 is partitioned by a scribe line 40.

  In a tritone mask in which separate patterns are formed on a multilayer film as a structure that achieves both resolution enhancement and sidelobe suppression as described above, the relative positions of the patterns in each layer must be maintained with high accuracy. Therefore, a photomask alignment mark is necessary.

  However, the conventional photomask manufacturing method having the photomask alignment mark structure has a problem that the scan mark of the alignment mark by the electron beam is patterned as a defect.

  FIG. 7 is a schematic diagram illustrating an enlarged structure around an alignment mark of a conventional photomask. The electron beam is scanned on the photomask alignment mark 11 arranged outside the stepper exposure region 3 of the photomask.

  FIG. 7A is a schematic view illustrating an enlarged planar structure around the alignment mark of a conventional photomask. A rectangular quartz glass 70 is formed, and a patterned halftone film 60 such as MoSi is formed thereon. In the halftone film 60, the region of the photomask alignment mark is removed by etching to form a groove. On the halftone film 60, a light shielding film 80 such as patterned Cr is formed.

  FIG. 7B is a schematic view illustrating the cross-sectional structure taken along the line B-B ′ of FIG. As shown in the figure, a halftone film 60 and a light shielding film 80 from which an alignment mark region has been removed by etching are laminated on a quartz glass 70. The width Wb of the halftone film 60 and the light shielding film 80 that are removed by etching is equal to the original width of the alignment mark.

  FIG. 7C is a schematic view illustrating the cross-sectional structure taken along the line C-C ′ of FIG. As can be seen from the figure, a halftone film 60 and a light shielding film 80 from which the alignment mark region has been removed by etching are laminated on a quartz glass 70. The width Wc of the halftone film 60 and the light shielding film 80 that has been removed by etching is significantly wider than the original width of the alignment mark.

  Scanning of the alignment mark by the electron beam is performed in a state where a resist is applied, and thereafter, development and etching processes are performed. If no electron beam scan trace remains in the resist, the desired cross section is preserved as shown in FIG. 7B showing the cross section BB ′ of FIG.

  However, if the scan trace of the electron beam is left on the resist, the alignment mark pattern is disturbed as shown in FIG. FIG. 7C showing a cross-section CC ′ of FIG. 7A shows an example in which the width of the alignment groove after etching is widened. With such an alignment mark pattern that leaves a scan mark, it is difficult to maintain the relative positional accuracy between each layer pattern in the case of mask manufacturing that requires a plurality of exposure steps in order to use a multilayer film.

  The upper layer film patterning is performed by electron beam exposure so as to selectively remove an upper layer film defect region such as a light shielding film in which a scan mark for photomask alignment remains using a multilayer mask such as tritone. As a result, the alignment groove pattern provided in the lower layer film such as the halftone film can be stored without causing pattern deformation due to the electron beam scan trace.

  The present invention has been made on the basis of recognition of such a problem, and its purpose is to provide an electronic device that requires a plurality of exposure processes using a multilayer film such as a tritone mask in a photomask pattern manufacturing process. An object of the present invention is to provide a photomask alignment mark and a photomask manufacturing method using the alignment mark, in which a beam scan trace does not remain as a defect.

In order to achieve the above object, according to one embodiment of the present invention, there is provided a photomask in which a halftone film having a first pattern and a light-shielding film having a second pattern are stacked over a substrate. And
An alignment mark for forming the second pattern of the light shielding film;
The alignment mark has an alignment pattern provided by selectively removing a part of the halftone film exposed by selectively removing the light shielding film. Is provided.

According to another aspect of the present invention, there is provided a photomask in which a halftone film having a first pattern and a light-shielding film having a second pattern are stacked on a substrate,
An alignment mark for forming the second pattern of the light shielding film;
The alignment mark selectively selects a part of the first alignment pattern formed by selectively removing the light shielding film and the halftone film exposed inside the first alignment pattern. And a second alignment pattern formed by removing the photomask.

  Here, the first alignment pattern may include a range in which an electron beam is scanned to form the second alignment pattern on the halftone film.

On the other hand, according to another aspect of the present invention, there is provided a photomask manufacturing method in which a halftone film having a first pattern and a light-shielding film having a second pattern are stacked on a substrate. ,
A mask having openings corresponding to the first pattern and the alignment pattern is formed on the halftone film and the light shielding film stacked on the substrate, and the light shielding film and the halftone are formed through the openings. Removing the film;
Removing the mask;
Forming a resist layer on the light shielding film;
After obtaining information on the position with reference to the alignment pattern, exposing a region corresponding to the second pattern of the resist layer and a region including the alignment pattern;
A method of manufacturing a photomask is provided.

  Here, the region including the alignment pattern may include a region around the alignment pattern that is exposed when information on a position is acquired with reference to the alignment pattern.

  According to the present invention, after the alignment groove patterned on the halftone film using the photomask alignment mark is scanned with the electron beam, the light shielding film is patterned using the electron beam exposure so as to remove the scan trace. Thus, it becomes possible to form a phase shift mask.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view illustrating the planar structure of a semiconductor device according to an embodiment of the invention. That is, it shows a planar structure of a photomask in which alignment marks for photomasks according to an embodiment of the present invention are arranged. As shown in the figure,
Four photomask alignment marks 1 are arranged at four corners in the mask 10, and stepper alignment marks 2 are arranged along the inner periphery of the mask 10. Further, a stepper exposure region 3 is provided at the center of the mask 10. In the stepper exposure area 3, a plurality of main patterns 5 are equally arranged vertically and horizontally, and each main pattern 5 is partitioned by a scribe line 4. Photomask alignment marks 1 are arranged on the outer squares of the respective main patterns 5 on the scribe line 4.

  FIG. 2 is an enlarged schematic view illustrating the peripheral portion of the photomask alignment mark according to the embodiment of the present invention. FIG. 2A is a schematic diagram illustrating an enlarged planar structure of the peripheral portion of the photomask alignment mark, and FIG. 2B is a cross-sectional structure taken along the line AA ′ of FIG. It is a schematic diagram which illustrates this. As shown in the figure, a rectangular glass 7 is formed on the scribe line 4, and a patterned halftone film 6 such as MoSi is formed thereon. The halftone film 6 has a groove formed by etching away the photomask alignment mark region. On the halftone film 6, a light shielding film 8 such as patterned Cr is formed.

  The cross-sectional structure of the mask is basically the same in the main pattern 7 portion and the mask alignment mark 1 portion.

  However, in order to form a pattern of the light-shielding film 8 on the patterned halftone film 6 with high accuracy, the groove pattern (the cross mark shown in FIG. 2A) of the photomask alignment mark 1 is scanned with an electron beam. As described above, the scan trace remains on the nearby resist and the scan trace also remains on the light shielding film pattern.

In the photomask according to the embodiment of the present invention, in order to avoid this phenomenon, at the time of electron beam exposure to the light shielding film 8, the opening is made wider than the groove pattern for alignment, and the light shielding film region where the above-described scan trace remains is removed. It is.
As a result, a multilayer mask having a desired positional accuracy is realized.

Next, a method for manufacturing a photomask according to an embodiment of the present invention will be described.
FIG. 3 is a process cross-sectional view illustrating a photomask manufacturing method according to an embodiment of the present invention. As shown in FIG. 3A, first, a halftone film 6 such as MoSi and a light shielding film 8 such as Cr are laminated on the glass substrate 7.

Next, as shown in FIG. 3B, a photoresist 9 is applied on the light shielding film 8 and electron beam exposure 11 is performed.
Subsequently, as shown in FIGS. 3C and 3D, development, dry etching of the light shielding film 8 and etching of the halftone film 6 are sequentially performed.

Subsequently, as shown in FIGS. 3E and 3F, a photoresist is applied again, alignment by electron beam alignment mark scanning, and electron beam exposure (pattern for removing resist in the vicinity of the alignment mark scan region). I do.
Then, as shown in FIGS. 3G and 3H, after development, the light shielding film 8 is dry-etched.

  In this way, a phase shift mask is formed which has a photomask alignment mark having no defect and a main pattern in which the light shielding film for suppressing side lobes maintains a desired positional accuracy with respect to the halftone film. It is clear.

The embodiments of the present invention have been described above with reference to specific examples.
However, the present invention is not limited to these specific examples. For example, even if those skilled in the art have changed the design of the elements constituting the semiconductor device manufactured using the manufacturing method of the present invention, the scope of the present invention is within the scope of the present invention as long as it has the gist of the present invention. Is included.

It is a schematic diagram which illustrates the planar structure of the semiconductor device concerning embodiment of this invention. It is a schematic diagram which expands and illustrates the peripheral part of the alignment mark for photomasks concerning embodiment of this invention. It is process sectional drawing showing the manufacturing method of the photomask concerning embodiment of this invention. The structure of a conventional halftone type phase shift mask and its light intensity are shown. The structure of a conventional tritone mask type phase shift mask and its light intensity are shown. It is a schematic diagram which illustrates the planar structure of the photomask in which the alignment mark for conventional photomasks is arrange | positioned. It is the schematic diagram which expands and illustrates the structure around the alignment mark of the conventional photomask.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mask alignment mark 2 Alignment mark for steppers 3 Stepper exposure area 4 Scribe line 5 Main pattern 6 Halftone film 7 Quartz glass 8 Light shielding film 9 Side lobe 10 Mask 11 Photo mask alignment mark 12 Electron beam 13 Scanning trajectory 20 For stepper Alignment mark 30 Stepper exposure area 40 Scribe line 50 Main pattern 60 Halftone film 70 Quartz glass 80 Shading film

Claims (5)

A photomask in which a halftone film having a first pattern and a light-shielding film having a second pattern are stacked on a substrate,
An alignment mark for forming the second pattern of the light shielding film;
The alignment mark has an alignment pattern provided by selectively removing a part of the halftone film exposed by selectively removing the light shielding film. . A photomask in which a halftone film having a first pattern and a light-shielding film having a second pattern are stacked on a substrate,
An alignment mark for forming the second pattern of the light shielding film;
The alignment mark selectively selects a part of the first alignment pattern formed by selectively removing the light shielding film and the halftone film exposed inside the first alignment pattern. And a second alignment pattern formed by removing the photomask.   The photomask according to claim 2, wherein the first alignment pattern includes a range in which an electron beam is scanned to form the second alignment pattern on the halftone film. A method of manufacturing a photomask in which a halftone film having a first pattern and a light-shielding film having a second pattern are stacked on a substrate,
A mask having openings corresponding to the first pattern and the alignment pattern is formed on the halftone film and the light shielding film stacked on the substrate, and the light shielding film and the halftone are formed through the openings. Removing the film;
Removing the mask;
Forming a resist layer on the light shielding film;
After obtaining information on the position with reference to the alignment pattern, exposing a region corresponding to the second pattern of the resist layer and a region including the alignment pattern;
A method for manufacturing a photomask, comprising: 5. The photomask manufacturing method according to claim 4, wherein the region including the alignment pattern includes a region around the alignment pattern that is exposed when information on a position is acquired with reference to the alignment pattern. Method.

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