JP6368000B1 - Photomask, photomask blank, and photomask manufacturing method - Google Patents

Abstract

A halftone mask capable of achieving both a fine pattern and multiple gradations is provided.
[Solution]
On a transparent substrate, a laminated region of a phase shift film and a semi-transmissive film, and a semi-transmissive region made of a semi-transmissive film having a higher light transmittance of exposure light than the laminated region, the laminated region is the semi-transmissive region And / or a boundary portion in contact with the transparent region where the transparent substrate is exposed, the phase shift film shifts the phase of the exposure light, and the light transmittance of the laminated region with respect to the exposure light is 1 to 8%. is there. At the boundary, the intensity distribution of exposure light changes sharply, and the cross-sectional shape of the exposed photoresist pattern can be improved.
[Selection] Figure 3

Description

  The present invention relates to a photomask having a function of a multi-tone halftone mask used for a flat panel display or the like, a photomask blank, and a photomask manufacturing method.

In a technical field such as a flat panel display, a multi-tone photomask called a halftone mask having a function of limiting an exposure amount by the light transmittance of a semi-transmissive film is used.
The halftone mask can realize a multi-tone photomask having three or more gradations by using a transparent substrate, a light-shielding film, and a semi-transmissive film having an intermediate light transmittance.

  In Patent Document 1, a photomask blank having a light-shielding film formed on a transparent substrate is processed, a pattern of the light-shielding film is formed, a semi-transmissive film is formed, and the light-shielding film and the semi-transmissive film are patterned. A method for forming a tone mask is disclosed.

  In such a halftone mask, for example, in a flat panel display manufacturing process, photoresist patterns having different film thicknesses are formed in a single exposure process in a TFT (thin film transistor) channel region and a source / drain electrode formation region. This may be used to reduce the lithography process.

  On the other hand, in order to improve the image quality of flat panel displays, there is an increasing demand for finer wiring patterns. Japanese Patent Application Laid-Open No. 2004-228688 discloses a phase shift mask provided with a phase shifter that inverts the phase at the edge portion of the light shielding region in order to secure an exposure margin when a projection exposure machine tries to expose a pattern close to the resolution limit. ing.

JP 2005-257712 A JP2011-13283A

  In the halftone mask, the change in exposure light intensity at the boundary between the semi-transmissive film and the light-shielding film is relatively gradual, and the photoresist exposed using the halftone mask has a cross section at such a boundary. The shape shows a gentle inclination, and the process margin is lowered. As a result, it is difficult to form a fine pattern.

  By using a phase shift mask, the resolution can be improved and the pattern can be further miniaturized. However, it is impossible to reduce the lithography process like a halftone mask. Therefore, when it is used for manufacturing a flat panel display, it cannot contribute to a reduction in manufacturing cost.

  The fine pattern type gray-tone mask, which is different from the half-tone mask, can obtain a relatively steep exposure light intensity distribution between the light-shielding part and the semi-transmissive part, but has a problem that the depth of focus becomes shallow. is there.

  Thus, with the conventional photomask, it has been impossible to achieve both a reduction in manufacturing cost of a flat panel display or the like and a resolution problem.

  In view of the above-described problems, an object of the present invention is to provide a photomask and a method for manufacturing the same that can achieve both reduction of the lithography process and further miniaturization of the pattern.

The photomask according to the present invention is
A semi-transmissive region composed of a semi-transmissive film on a transparent substrate, a phase shift film for reversing the phase of exposure light in order from the transparent substrate side, a laminated region of the semi-transmissive film, and a transparent region where the transparent substrate is exposed. Prepared,
The laminated region has a boundary portion in contact with the semi-transmissive region, or a boundary portion in contact with the transparent region, or a boundary portion in contact with the semi-transmissive region and a boundary portion in contact with the transparent region,
The light transmittance of the semi-transmissive region with respect to the exposure light is greater than the light transmittance of the laminated region with respect to the exposure light, and is smaller than the light transmittance with respect to the exposure light of the transparent substrate.

The photomask according to the present invention is
The light transmittance of the laminated region with respect to exposure light is 1% to 8%.

  By adopting such a photomask configuration, the intensity of exposure light that changes sharply at the boundary between a semi-transmissive region made of a semi-transmissive film and a region where the semi-transmissive film and the phase shift film are laminated (laminated region). Distribution can be obtained. As a result, the photoresist obtained by one-time exposure using the photomask can simultaneously form photoresists having different film thicknesses corresponding to the respective regions having different light transmittances, and the photomasks having different film thicknesses. At the boundary portion of the resist, the film thickness changes sharply, and the rectangular shape of the cross-sectional shape is improved.

The photomask according to the present invention is
The phase shift angle of the semi-transmissive film is 0.1 degrees or more and 20 degrees or less.

  By adopting such a photomask structure, the phase difference of the exposure light between the laminated region and the transparent region becomes approximately 180 degrees, and the cross-sectional shape of the photoresist obtained by the exposure using the photomask is laminated. In a portion corresponding to the boundary portion between the region and the transparent region, it changes sharply and a good rectangularity can be obtained.

The photomask according to the present invention is
At the boundary where the laminated region is in contact with the transparent region, at least a part of the side wall of the phase shift film in the laminated region is covered with the semi-transmissive film.

  With such a photomask structure, when patterning the stacked region, side etching can prevent the end of the semi-transmissive film from retreating from the end of the phase shift film in the stacked region. . As a result, desired optical characteristics can be obtained at the boundary where the laminated region is in contact with the transparent region, and a favorable cross-sectional shape of the photoresist can be realized.

A photomask manufacturing method according to the present invention includes:
Forming a phase shift film on the transparent substrate;
Forming a first photoresist on the phase shift film;
Forming a first photoresist pattern by exposing and patterning the first photoresist with a drawing apparatus; and
Etching the phase shift film using the first photoresist pattern as a mask to expose the transparent substrate to form a pattern of the phase shift film;
Removing the first photoresist;
Forming a semipermeable membrane;
Forming a second photoresist on the semi-transmissive film;
Exposing the second photoresist with a drawing apparatus and patterning to form a second photoresist pattern;
Etching the semi-transmissive film and the phase shift film using the second photoresist pattern as a mask to expose the transparent substrate, the pattern of the semi-transmissive film, and the phase shift film and the semi-transmissive film Forming a laminated pattern; and
Removing the second photoresist.
The end portion of the second photoresist pattern has a predetermined distance from the end portion of the pattern of the phase shift film to the side that becomes the laminated region in a region where the portion that becomes the laminated region and the portion that becomes the transparent region are adjacent to each other. It is characterized by receding by a distance.

In addition, the photomask manufacturing method according to the present invention includes:
The predetermined distance is greater than or equal to an overlay error of a drawing apparatus that exposes the second photoresist.

By such a photomask manufacturing method, a laminated pattern of a phase shift film and a semi-transmissive film and a semi-transmissive film pattern are formed, and a pattern in which the laminated pattern and the pattern made of the semi-transmissive film are in contact with each other at a boundary portion is formed. It can be formed easily.
In addition, at the end of the laminated pattern on the transparent region (region where the transparent substrate is exposed) side, the position of the end of the phase shift film and the end of the semi-transmissive film can be matched. For this reason, the laminated pattern maintains the structure in which the phase shift film and the semi-transmissive film are laminated even at the end in contact with the transparent region, and has optical characteristics as a laminated film.

A photomask manufacturing method according to the present invention includes:
Forming a phase shift film on the transparent substrate;
Forming a third photoresist on the phase shift film;
Forming a third photoresist pattern by exposing and patterning the third photoresist with a drawing apparatus; and
Etching the phase shift film using the third photoresist pattern as a mask to expose the transparent substrate to form a pattern of the phase shift film;
Removing the third photoresist;
Forming a semipermeable membrane;
Forming a fourth photoresist on the semi-transmissive film;
Forming a fourth photoresist pattern by exposing and patterning the fourth photoresist with a drawing apparatus; and
Etching the semi-transmissive film and the phase shift film using the fourth photoresist pattern as a mask to expose the transparent substrate, the pattern of the semi-transmissive film, and the phase shift film and the semi-transmissive film Forming a laminated pattern; and
Removing the fourth photoresist;
The third photoresist pattern has an opening in a region where the pattern of the semi-transmissive film is formed.

  By such a photomask manufacturing method, the restrictions on the design of the third photoresist pattern for forming a pattern in which the laminated pattern and the semi-transmissive film pattern are in contact with each other at the boundary are alleviated, and the photomask is manufactured. Becomes easier.

In addition, the photomask manufacturing method according to the present invention includes:
Forming a phase shift film on the transparent substrate;
Forming a first photoresist on the phase shift film;
Forming a first photoresist pattern by exposing and patterning the first photoresist with a drawing apparatus; and
Etching the phase shift film using the first photoresist pattern as a mask to expose the transparent substrate to form a pattern of the phase shift film;
Removing the first photoresist;
Forming a semipermeable membrane;
Forming a second photoresist on the semi-transmissive film;
Exposing the second photoresist with a drawing apparatus and patterning to form a second photoresist pattern;
Etching the semi-transmissive film using the second photoresist pattern as a mask to form a transparent region exposing the transparent substrate, a pattern of the semi-transmissive film, and a laminated pattern of the phase shift film and the semi-transmissive film And a process of
Removing the second photoresist.
The end portion of the second photoresist pattern is a predetermined region from the end portion of the pattern of the phase shift film to the side that becomes the transparent region in a region where the portion that becomes the laminated region and the portion that becomes the transparent region are adjacent to each other. It is characterized by protruding by a distance.

In addition, the photomask manufacturing method according to the present invention includes:
The predetermined distance is larger than both the side etching amount of the semi-transmissive film and the overlay error of the drawing apparatus that exposes the second photoresist.

  Even when the transflective film is etched by isotropic etching such as wet etching, the end of the transflective film is at the end of the laminated region with respect to the end of the phase shift film. Can be prevented from retreating.

The photomask blanks according to the present invention are
A phase shift film having a characteristic of inverting the phase of exposure light is formed on a transparent substrate.

  By using a photomask blank provided with a phase shift film having a characteristic of reversing the phase of exposure light on a transparent substrate in advance, it is possible to reduce the production time and cost of the photomask.

  According to the present invention, a photomask capable of achieving both a halftone effect and a phase shift effect can be realized, which can contribute to pattern miniaturization and reduction in the number of lithography processes.

Sectional drawing which shows the main manufacturing processes of the photomask by Embodiment 1 of this invention. Sectional drawing which shows the main manufacturing processes of the photomask by Embodiment 1 of this invention. Sectional drawing which shows the main manufacturing processes of the photomask by Embodiment 1 of this invention. Sectional drawing which shows the main manufacturing processes of the photomask by Embodiment 2 of this invention. Sectional drawing which shows the main manufacturing processes of the photomask by Embodiment 2 of this invention. Sectional drawing which shows the main manufacturing processes of the photomask by Embodiment 3 of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, none of the following embodiments gives a limited interpretation in the recognition of the gist of the present invention. The same or similar members are denoted by the same reference numerals, and the description thereof may be omitted.

(Embodiment 1)
Hereinafter, main manufacturing steps of the first embodiment of the photomask according to the present invention will be described.

As shown in FIG. 1A, a phase shift film 12, for example, a chromium (Cr) oxide film having a film thickness of 120 nm is formed on a transparent substrate 11 such as synthetic quartz glass by vapor deposition, sputtering, CVD, or the like. The formed photomask blanks 10 are prepared.
Note that the photomask manufacturing period can be shortened by preparing the photomask blanks 10 in advance.

  The phase shift film 12 has a function of shifting the phase of the exposure light, and has a property that the phase of the exposure light is inverted by a single film (that is, the phase shift angle is approximately 180 degrees). The light transmittance of the phase shift film 12 has such an optical characteristic that the light transmittance with respect to the exposure light in the laminated region with the semi-transmissive film 14 to be described later is 1 to 8%, more preferably 4 to 7%. Is good.

  On the other hand, the light transmittance of the semi-transmissive film is determined by the residual after development in the portion where the semi-transmissive area pattern is transferred when the projection exposure apparatus is used to transfer and expose the photoresist film on the FPD panel using this photomask. The film thickness is set to a desired value. Specifically, the light transmittance of the semi-transmissive film is often set within a range of 20 to 60%. Therefore, for example, when the light transmittance of the semi-transmissive film is about 50%, the light transmittance as the phase shift film alone film is set to about 7 to 15%, for example. By doing so, the light transmittance of the laminated region can be in the range of 1 to 8% (preferably 4 to 7%).

  The main reason for setting the light transmittance of the laminated region in the above range is to transmit the exposure light that has passed through the phase shift portion and other portions adjacent to the phase shift portion (that is, a semi-transmissive region or a transparent region). The effect of improving the rectangularity of the resist shape at the boundary by fully exhibiting the phase shift effect that is the interaction with the exposure light, and the portion that is not adjacent to the phase shift portion (that is, N and N in FIG. 3) This is to reduce the amount of exposure light transmitted through the central portion of L and K), and to ensure the film thickness of a resist film after development and to withstand the etching process. If the light transmittance is too low, the phase shift effect is not sufficiently exhibited. Conversely, if the light transmittance is too high, the amount of exposure light cannot be suppressed, and the film thickness of the resist film after development cannot be secured.

  For example, the phase shift film 12 having predetermined optical characteristics can be obtained by using a chromium oxide film and adjusting the composition and film thickness. When a chromium oxide film is used as the phase shift film, the range in which the light transmittance can be adjusted under the condition that the phase of the exposure light is reversed is limited. As described above, when the light transmittance of the semi-transmissive film is about 20%, it is necessary to set the light transmittance of the phase shift film to about 20 to 40%. However, it is not possible to realize this with the chromium oxide film. Realistic.

  In such a case, a film having a higher light transmittance than the chromium oxide film can be used as the phase shift film. Examples thereof include silicon dioxide, magnesium fluoride, alumina (aluminum oxide), titania (titanium oxide), zirconia (zirconia oxide), and tantalum oxide. These have high durability in addition to high light transmittance, and are often used for antireflection films. Typical transparent conductive film materials include tin-doped indium oxide (ITO), aluminum-doped zinc oxide (AZO), antimony-doped tin oxide (ATI), and niobium-doped titanium oxide (NTO).

  Other possibilities for the phase shift film include a chromic oxynitride film, a film whose composition changes in the film thickness direction, and a film in which films having different compositions are laminated, but is not limited thereto. Absent.

  The exposure light that determines the values of light transmittance and phase shift angle means exposure light for exposing a photoresist using a photomask in a lithography process for manufacturing a product.

  Thereafter, as shown in FIG. 1B, a first photoresist 13 is formed on the phase shift film 12 by a coating method or the like.

  Thereafter, as shown in FIG. 1C, the first photoresist 13 is exposed by, for example, a photomask drawing apparatus, and then developed to be patterned to form first photoresist patterns 13a, 13b, and 13c. To do.

Thereafter, as shown in FIG. 1D, the phase shift film 12 is etched using the first photoresist patterns 13a, 13b, and 13c as masks to form phase shift film patterns 12a, 12b, and 12c. The first photoresist patterns 13a, 13b and 13c are removed by ashing or the like.
The etching method of the phase shift film 12 may be a wet etching method or a dry etching method, but the wet etching method can be suitably used from the viewpoint of manufacturing cost.
When a chromium-based film such as a chromium oxide film is used as the phase shift film 12, a cerium-based etching solution, for example, a ceric ammonium nitrate aqueous solution can be preferably used, but is not limited thereto.

Thereafter, as shown in FIG. 2A, a semi-transmissive film 14 is formed by vapor deposition, sputtering, CVD, or the like, and a second photoresist 15 is formed on the semi-transmissive film 14 by coating or the like. To do.
The light transmittance of the semi-transmissive film 14 is set to be 10 to 70% with respect to the exposure light. Further, the phase shift angle of the semi-transmissive film 14 is, for example, 0.1 to 80 degrees, but is preferably set to a sufficiently small value, for example, 0.1 to 20 degrees compared to 180 degrees.

As the semi-transmissive film 14, for example, a Cr (chromium) film having a film thickness of 4 nm can be used to obtain a light transmittance of 50% and a phase shift angle as small as 1.5 degrees. In this case, the change of the light transmittance with respect to the exposure light can be kept within 2% with respect to the exposure light of g-line, h-line, and i-line. That is, since the wavelength dependence of exposure light can be reduced, even when a photomask obtained in this embodiment is used and a mixed wavelength of g-line, h-line, and i-line is used as exposure light, it is stable. A wide range of exposure conditions can be obtained.
Further, since the phase shift angle is very small compared to 180 degrees, the phase shift angle of the region where the phase shift film 12 and the semi-transmissive film 14 described later are laminated is substantially the phase shift angle of only the phase shift film 12. Determined by As a result, the material and film thickness of the phase shift film 12 can be easily set without considering the phase shift angle of the semi-transmissive film 14.

Thus, by adopting a Cr thin film (film thickness of 0.5 to 50 nm) as the semi-transmissive film 14, the change of the light transmittance with respect to the exposure light can be changed with respect to the exposure light of g-line, h-line, and i-line. Therefore, the phase shift angle can be set to a very small value of 0.1 to 20 degrees, so that it can be suitably used as the semi-transmissive film 14 in particular.
In addition, since the influence of the phase shift angle of the semi-transmissive film 14 is small, a photomask blank in which the phase shift film 12 is formed on the transparent substrate 11 is prepared in advance, and the semi-transmissive film according to the customer's request. A light transmittance of 14 can be set. Therefore, it is possible to contribute to shortening the delivery time of the photomask and reducing the manufacturing cost.

  Further, a Cr oxide film (film thickness: 1 to 15 nm) can be adopted as the semi-transmissive film 14. At this time, although the difference in light transmittance is about 4 to 8% with respect to the g, h and i lines, the phase shift angle can be kept in the range of 1 to 20 degrees. When a Cr oxide film is used as the semi-transmissive film 14, the composition is close to that of the phase shift film 12. Therefore, when the semi-transmissive film 14 and the phase shift film 12 are etched in the same process, both etching rates can be easily adjusted. There is.

The light transmittance can be adjusted by the film thickness of the semi-transmissive film 14, and a film thickness that provides a desired light transmittance may be selected.
Moreover, although the chromium film can employ | adopt suitably as the material of the semipermeable membrane 14, it will not be limited to this, Other materials may be used if the said optical characteristic is acquired.

Thereafter, as shown in FIG. 2B, the second photoresist 15 is exposed by, for example, a photomask drawing apparatus, and then developed to be patterned to form second photoresist patterns 15a and 15b.
At this time, as shown in FIG. 2B, the end position of the second photoresist pattern 15a is phase-shifted by a predetermined distance d with respect to the end positions of the phase shift film patterns 12b and 12c. It moves to the pattern 12b, 12c side of the film, that is, in the direction opposite to the area where the transparent substrate is exposed (hereinafter referred to as the transparent area). Similarly, the end position of the second photoresist pattern 15b moves with respect to the end position of the phase shift film pattern 12a by the distance d toward the phase shift film pattern 12a, that is, in the direction opposite to the transparent region. ing.

  In such an arrangement of the first and second photoresist patterns, the region where the first photoresist patterns 13a, 13b and 13c are formed overlaps with the region where the second photoresist patterns 15a and 15b are formed. In the region (laminated region of the phase shift film and the semi-transmissive film described later), the end portions of the first photoresist patterns 13a, 13b, and 13c are more transparent than the end portions of the second photoresist patterns 15a and 15b. This can be achieved by adjusting the pattern widths of the first photoresist patterns 13a, 13b, and 13c so that the first photoresist patterns 13a, 13b, and 13c protrude.

Here, the value of the distance d is set to a value equal to or greater than the overlay error of the photomask drawing apparatus for forming the second photoresist patterns 15a and 15b.
As a result, when the second photoresist 15 is exposed, even if the overlay shift with respect to the phase shift film patterns 12a, 12b, 12c by the photomask drawing apparatus occurs, the second photoresist patterns 15a, 15b The end portion does not protrude from the phase shift film patterns 12a, 12b, and 12c toward the transparent region.

  When the phase shift film 12 is etched by isotropic etching such as a wet etching method, if the side etching amount of the phase shift film 12 is a magnitude that cannot be ignored with respect to the overlay error, the value of the distance d is The value can be set to a value obtained by adding the side etching amount of the phase shift film 12 to the overlay error of the photomask lithography apparatus. However, by adjusting the etching rates of the phase shift film 12 and the semi-transmissive film 14, it is not necessary to correct the side etch amount. For example, as a method of adjusting the etching rate, there is a method of adjusting the film forming conditions so that the etching rate of the surface layer is slow in the film thickness direction, and the etching rate is increased toward the lower layer.

Next, as shown in FIG. 3, the semi-transmissive film 14 and the phase shift film patterns 12a, 12b, and 12c are etched by dry etching or wet etching using the second photoresist patterns 15a and 15b as masks. Transmission film patterns 14a and 14b and phase shift film patterns 12d, 12e and 12f are formed.
The semi-transmissive film 14 and the phase shift film patterns 12a, 12b, and 12c may be etched in the same process or in different processes.
Thereafter, the second photoresist patterns 15a and 15b are removed by an ashing method or the like.

Thus, the semi-transmissive film 14 and the phase shift film patterns 12a, 12b, and 12c are etched by the same second photoresist pattern 15a and 15b. For this reason, the position of the end of the phase shift film 12 and the position of the end of the semi-transmissive film 14 coincide with each other at the boundary where the region where the phase shift film 12 and the semi-transmissive film 14 are laminated (laminated region) is in contact with the transparent region. To do.
Therefore, even at such an end portion, the structure in which the phase shift film and the semi-transmissive film are stacked is maintained, and the optical characteristics of the stacked films are obtained.

The etching method of the semi-transmissive film 14 may be a wet etching method or a dry etching method, but the wet etching method can be preferably used from the viewpoint of manufacturing cost.
When a chromium film is used as the semipermeable membrane 14, a cerium-based etching solution, for example, a ceric ammonium nitrate aqueous solution can be preferably used, but the invention is not limited thereto.
However, when the wet etching method is used, the wet etching amount increases in the upper layer portion in the stacked region. Therefore, strictly speaking, the cross section of the pattern of the laminated region has a tapered shape with a narrow upper layer, and the end of the semi-transmissive film 14 tends to recede toward the side of the laminated region with respect to the end of the phase shift film 12. . Therefore, the dry etching method has an advantage that a finer pattern can be formed although the manufacturing cost increases.

Further, when the etching of the semi-transmissive film 14 and the etching of the phase shift film patterns 12a, 12b, and 12c are performed with the same etching solution or etching gas, the etching process can be performed in the same process, thereby reducing the manufacturing cost and the work period. Shortening becomes possible. For example, the semi-transmissive film 14 and the phase shift film are made of a chromium-based film, and an aqueous ceric ammonium nitrate solution or the like is used as an etching solution, so that etching can be performed in the same etching process.
It should be noted that the etching rate of the semi-transmissive film 14 and the phase shift film can be adjusted by adjusting the additive, the etching temperature, etc., and a commercially available etching solution can be used.

Due to the optical characteristics of the phase shift film 12 described above, the phase difference between the semi-transmissive film 14 and the film in which the phase shift film 12 is laminated and the single film of the semi-transmissive film 14 is approximately 180 degrees due to the optical characteristics of the phase shift film 12. It becomes.
Furthermore, when the phase shift angle of the semi-transmissive film 14 is a small value of, for example, 20 degrees or less (relative to 180 degrees), the phase shift angle of the film in which the semi-transmissive film 14 and the phase shift film 12 are stacked is It is substantially determined by the phase shift angle of the phase shift film 12. Therefore, the phase difference between the laminated region of the semi-transmissive film 14 and the phase shift film 12 and the transparent region can also be set to about 180 degrees. That is, the phase difference between the laminated region of the semi-transmissive film 14 and the phase shift film 12 and the region of the semi-transmissive film 14 alone film and the phase difference between the laminated region of the semi-transmissive film 14 and the phase shift film 12 and the transparent region, Both can be set to approximately 180 degrees. At this time, the phase shift angle of the phase shift film 12 may be finely adjusted according to the film thickness or the like as necessary in order to set the above-described two phase differences to about 180 degrees.
In the present specification, “approximately 180 degrees” means 180 ± 20 degrees, and means a phase difference of exposure light that can sufficiently obtain an interference effect of exposure light.

In FIG. 3, the laminated region of the semi-transmissive film 14 and the phase shift film 12 includes the laminated region (region K) of the phase shift film pattern 12d and the semi-transmissive film pattern 14b, the phase shift film pattern 12e, and the semi-transmissive film. This is indicated by the laminated region (region L) of the pattern 14a and the laminated region (region N) of the phase shift film pattern 12f and the semi-transmissive film pattern 14a.
When the light transmittance of the exposure light in the portion where the transparent substrate is exposed is 100%, the light transmittance of the exposure light in each of the laminated regions is 1 to 8%, and the exposure light in the region formed of the semi-transmissive film 14 Since the light transmittance of 10 to 70% and the light transmittance of the exposure light of the transparent substrate 11 is 100%, a three-tone photomask can be obtained.

  When exposing the photoresist using the photomask of this embodiment, the film thickness of the photoresist is relative to each other in one exposure process corresponding to the laminated region, the region made of a semi-transmissive film, and the transparent region. Thick regions, thin regions and regions without photoresist can be formed.

When the photoresist is exposed using the photomask manufactured according to the present embodiment, the boundary between the region L and the region of the semi-transmissive film 14a (indicated by the region M and referred to as a semi-transmissive region), and the region N And the region M are in contact with each other, the phase difference of the exposure light is approximately 180 degrees.
Since the region L and the region N have a light transmittance greater than zero, part of the exposure light passes through the region L and the region N. The phase difference between the exposure light transmitted through the region L and the region N and the exposure light transmitted through the region M is approximately 180 degrees, and the exposure light intensity changes sharply at the boundary portion due to the light interference effect.

  If the phase shift angle of the semi-transmissive film 14 is sufficiently small, for example, the laminated region (region K) of the phase shift film pattern 12d and the semi-transmissive film pattern 14b is in contact with the transparent region (region P, region Q). The phase difference of the exposure light is approximately 180 degrees at the boundary portion, the boundary portion where the region N and the transparent region (region R) are in contact, and the boundary portion where the region L and the transparent region (region Q) are in contact. For this reason, the intensity of the exposure light at this boundary portion changes steeply, the film thickness of the photoresist corresponding to the boundary portion changes sharply, and the rectangularity is improved. Further, since the light transmittance of the region K is set to 1 to 8%, the central portion of the N, L, K region where the phase shift effect cannot be obtained (other than the boundary portion with the transparent region or the semi-transmissive film region) In this part), the exposure of the photoresist is suppressed, and the film thickness of the photoresist after development can be sufficiently secured.

For example, when the photomask according to the present embodiment is applied to a photoresist exposure process for processing a TFT of a flat panel display, a photoresist pattern of a channel region is formed by the region M by one exposure. The photoresist pattern of the source / drain electrode formation region can be formed by the region L and the region N. In this case, the thickness of the photoresist pattern in the source / drain electrode formation region can be increased compared with the photoresist pattern in the channel region.
Furthermore, since the cross-sectional shape of the photoresist at the boundary between the channel region and the source / drain electrode formation region is steep, the channel length can be accurately controlled, and further, the source / drain electrode formation region can be accurately controlled. Compared with a photomask using a film and a semi-transmissive film, a fine TFT can be manufactured.

(Embodiment 2)
Hereinafter, a photomask manufacturing method according to another embodiment will be described with reference to FIGS.
In the present embodiment, in the phase shift film pattern, it is not necessary to enlarge the pattern in consideration of the overlay error of the photomask drawing apparatus. As a result, there are effects that the restrictions on the pattern design are relaxed and the design effort is reduced.

As shown in FIG. 4A, a photomask blank 10 is prepared by forming a phase shift film 12 on a transparent substrate 11 by vapor deposition, sputtering, CVD, or the like.
Thereafter, a third photoresist 16 is formed on the phase shift film 12 by a coating method or the like.
Note that the same phase shift film as in the first embodiment can be used as the phase shift film 12 in the second embodiment.

Thereafter, as shown in FIG. 4B, the third photoresist 17 is applied to, for example, a photomask drawing apparatus so as to have an opening in a region (region M) where a pattern made of a single semi-transmissive film is formed. Then, patterning is performed by developing, and third photoresist patterns 16a and 16b are formed.
In the step shown in FIG. 1C of the first embodiment, a transparent region (in FIG. 3) sandwiched between laminated regions (region L and region K in FIG. 3) of adjacent phase shift film 12 and semi-transmissive film 14. In the region where the region Q) is to be formed, an opening is provided in the first photoresist 13. However, in the third photoresist 17 in FIG. 4B, it is not necessary to open the region Q ′ (see FIG. 5C) corresponding to the region Q.

In addition, in the opening of the third photoresist 17, not only the case where a semi-transmissive region as shown by the region M ′ in FIG. 5C is formed, for example, a plurality of semi-transmissive regions are adjacent, As in the case where a transparent region exists between these regions (such as a line-and-space (L / S) pattern made up of a single semi-permeable membrane) or a transparent region exists between the semi-transmissive region and the laminated region A pattern in which a semi-transmissive region and a transparent region exist may be formed.
Further, for the special purpose such as, for example, the formation of a monitor portion for film thickness inspection after etching and the adjustment of the opening area in order to control the etching rate of dry etching, It does not prevent the opening from being provided in the region to be the transparent region.

Thereafter, as shown in FIG. 4C, the phase shift film 12 is etched by the dry etching method or the wet etching method using the third photoresist patterns 17a and 17b as a mask, and the phase shift film patterns 12g and 12h are obtained. Form.
Thereafter, the third photoresist patterns 16a and 16b are removed by an ashing method or the like.

Thereafter, as shown in FIG. 5A, a semi-transmissive film 14 is formed by vapor deposition, sputtering, CVD, or the like, and a fourth photoresist 17 is formed on the semi-transmissive film 14 by coating or the like. To do.
The semi-permeable membrane 14 of the second embodiment can use the same semi-permeable membrane as that of the first embodiment.

Thereafter, as shown in FIG. 5B, the fourth photoresist 17 is exposed by, for example, a photomask drawing apparatus, and then developed to be patterned to form fourth photoresist patterns 17a and 17b.
In this case, the fourth photoresist patterns 17a and 17b can use the same pattern as the second photoresist patterns 15a and 15b.

Thereafter, as shown in FIG. 5C, the patterns 12g and 12h of the semi-transmissive film 14 and the phase shift film are etched by a dry etching method or a wet etching method using the fourth photoresist patterns 17a and 17b as a mask, Semi-transmissive film patterns 14a and 14b and phase shift film patterns 12i, 12j and 12k are formed.
The etching of the semi-transmissive film 14 and the phase shift film patterns 12g and 12h may be performed in the same process or in different processes.
Thereafter, the fourth photoresist patterns 17a and 17b are removed by an ashing method or the like.
In FIG. 5C, when the semi-transmissive film 14 and the phase shift film 12 can be etched by the same wet etching solution or etching gas, the etching can be performed in the same process, and the manufacturing process can be reduced.

  When the photoresist is exposed using the photomask of the second embodiment, a photoresist pattern having a steep cross-sectional shape can be obtained as in the first embodiment.

  In the second embodiment, the third photoresist patterns 16a and 16b formed on the phase shift film 12 do not need to be enlarged in consideration of the overlay error of the photomask drawing apparatus, and the third photoresist pattern The design constraints are eased, and the third photoresist pattern design is facilitated.

Furthermore, in the first embodiment, the space between the first photoresist pattern 13a and the first photoresist pattern 13b is twice the predetermined distance d (2d), so that the second photoresist pattern 15a and the second photoresist pattern 15b. It becomes narrower than the photoresist pattern 15b.
Therefore, if the first photoresist patterns 13a, 13b, and 13c formed on the phase shift film 12 with high integration of electronic circuits are densely arranged, the first photoresist pattern 13a and the first photoresist pattern The space between 13b is rate-limited by the resolution limit of a photomask drawing apparatus.
In the second embodiment, since the restriction on the pattern design due to the resolution limit is released, the pattern can be miniaturized. In particular, when the laminated pattern of the phase shift film 12 and the semi-transmissive film 14 are adjacent to each other and, for example, a line-and-space pattern is arranged at a gorge pitch for high integration, the laminated pattern of the phase-shift film 12 and the semi-transmissive film 14 When the space between them is narrow, there is no need to provide an opening in a portion that becomes a transparent region (space portion) sandwiched between these laminated patterns, and the effect of contributing to miniaturization is great.

(Embodiment 3)
Hereinafter, a photomask manufacturing method according to another embodiment will be described with reference to FIG.
In this embodiment, the semi-transmissive film 14 can be prevented from retreating due to side etching when the phase shift film 12 and the semi-transmissive film 14 are isotropically etched like wet etching.

  For example, when a Cr thin film is used as the semi-transmissive film 14 and a Cr oxide film is used as the phase shift film 12, the semi-transmissive film 14 is on the phase shift film 12. When etching isotropically, the side etching amount of the Cr thin film becomes large. In particular, when the film thickness of the semi-transmissive film 14 is smaller than the film thickness of the phase shift film 12, this side etching amount becomes significant.

Such side etching has a problem of hindering pattern miniaturization.
Although this problem is solved by the dry etching method, the wet etching method is advantageous from the viewpoint of manufacturing cost. Hereinafter, a method for preventing the above-described side etching problem even when wet etching is used will be described.

In the step of FIG. 2B, the positions of the end portions of the second photoresist patterns 15a and 15b are opposite to the end positions of the phase shift film patterns 12b, 12c and 12a in the direction opposite to the transparent region. Has moved.
On the other hand, in the present embodiment, after the step of FIG. 2A, exposure is performed by, for example, a photomask drawing apparatus, followed by development to perform patterning, and the second photo as shown in FIG. 6A. Resist patterns 15c and 15d are formed.

The positions of the end portions of the second photoresist patterns 15c and 15d shown in FIG. 6A are moved by a distance e in the transparent region side direction with respect to the end positions of the phase shift film patterns 12b, 12c and 12a. doing.
The value of e is set to a distance larger than both the side etching amount and the overlay error of the drawing apparatus that exposes the second photoresist. The value of e depends on the wet etching processing time and the drawing apparatus, but specifically becomes a value of 0.1 to 0.9 [μm], for example.

  In the first embodiment, the first photo resist pattern 13a, 13b, 13c has the first photo pattern so that the end of the first photo resist pattern 13a, 13b, 13c protrudes from the end of the second photo resist pattern 15a, 15b to the transparent region side. The pattern widths of the resist patterns 13a, 13b, and 13c were adjusted. However, in this embodiment, there is no need to make adjustments such as increasing the pattern width of the first photoresist patterns 13a, 13b, and 13c.

  Next, as shown in FIG. 6B, the semi-transmissive film 14 is etched by wet etching using the second photoresist patterns 15c and 15d as a mask to form semi-transmissive film patterns 14c and 14d. The second photoresist patterns 15c and 15d are removed by ashing or the like.

  The etching process time is set to a time during which the maximum film thickness can be etched in consideration of the film thickness variation of the semi-transmissive film 14. Since the etching processing time is set to the time for etching only the semi-transmissive film 14, the wet etching time is shortened as compared with the case where the phase shift film 12 and the semi-transmissive film 14 are etched. As a result, the amount of overetching with respect to the semipermeable membrane 14 is reduced.

  At this time, it is preferable to use an etching solution in which the etching rate of the phase shift films 12b, 12c, and 12a is sufficiently low (for example, 1/10 or less) with respect to the etching rate of the semi-transmissive film 14. Such an etchant uses a ceric ammonium nitrate aqueous solution and can be adjusted by adjusting additives, etching temperature, etc., and commercially available etchants can be used.

6B, the side wall surfaces of the phase shift film patterns 12b, 12c, and 12a are covered with the semi-transmissive film 14 in the vicinity of the boundary with the semi-transmissive film 14, and the phase shift film is formed on the transparent substrate 11 side. The patterns 12b, 12c, and 12a are exposed.
Even in this case, since the etching rate of the phase shift films 12b, 12c, and 12a is sufficiently low, side etching of the exposed side wall portions of the patterns 12b, 12c, and 12a of the phase shift film can be suppressed.

  As described above, it is possible to prevent the side etching of the semi-transmissive film patterns 14c and 14d from proceeding on the phase shift film patterns 12b, 12c, and 12a.

  In FIG. 6 (b), the semi-transmissive film patterns 14c and 14d have a shape partially protruding from the phase shift film patterns 12b, 12c and 12a, but the semi-transmissive film 14 is a thin chrome film. Yes, the amount protruding to the transparent region side is about the film thickness or less. Further, since the side coverage of the vapor deposition or sputtered film is generally low, the protruding amount is smaller than that of the semi-transmissive film 14 to be formed. Therefore, the protruding portions of the semi-transmissive film patterns 14c and 14d do not adversely affect the exposure of the photoresist using this mask.

  ADVANTAGE OF THE INVENTION According to this invention, the photomask which can implement | achieve reduction of the photolithographic process at the time of product manufacture and pattern miniaturization can be provided, and industrial applicability is very large.

10 Photomask blanks 11 Transparent substrate 12 Phase shift films 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, 12j, 12k Phase shift film pattern 13 First photoresist 13a, 13b, 13c First Photoresist pattern 14 Semi-transmissive film 14a, 14b, 14c, 14d Semi-permeable film pattern 15 Second photoresist 15a, 15b, 15c, 15d Second photoresist pattern 16 Third photoresist 16a, 16b Third Photoresist pattern 17 Fourth photoresist 17a, 17b Fourth photoresist pattern

Claims (8)

A semi-transmissive region composed of a semi-transmissive film on a transparent substrate, a phase shift film for reversing the phase of exposure light in order from the transparent substrate side, a laminated region of the semi-transmissive film, and a transparent region where the transparent substrate is exposed. Prepared,
The laminated region has a boundary portion in contact with the semi-transmissive region, or a boundary portion in contact with the transparent region, or a boundary portion in contact with the semi-transmissive region and a boundary portion in contact with the transparent region,
The light transmittance of exposure light of the semi-transmissive region is rather smaller than the light transmittance for exposure light of large the transparent substrate than the light transmittance for exposure light of said deposition area,
The photomask according to claim 1, wherein a phase shift angle of the semi-transmissive film is not less than 0.1 degrees and not more than 20 degrees . 2. The photomask according to claim 1, wherein the light transmittance of the laminated region with respect to the exposure light is 1% to 8% when the light transmittance with respect to the exposure light of the transparent substrate is 100%. 3. The photo according to claim 1, wherein at the boundary portion where the laminated region is in contact with the transparent region, at least a part of a side wall of the phase shift film in the laminated region is covered with the semi-transmissive film. mask. Forming a phase shift film for inverting the phase of exposure light on a transparent substrate;
Forming a first photoresist on the phase shift film;
Forming a first photoresist pattern by exposing and patterning the first photoresist with a drawing apparatus; and
A first etching step of forming a pattern of the first photoresist pattern by etching the phase shift film as a mask, the phase shift film to expose the transparent substrate,
Removing the first photoresist;
Forming a semi-transmissive film so as to cover the pattern of the phase shift film ;
Forming a second photoresist on the semi-transmissive film;
Exposing the second photoresist with a drawing apparatus and patterning to form a second photoresist pattern;
Etching the semi-transmissive film and the phase shift film using the second photoresist pattern as a mask to expose the transparent substrate, the pattern of the semi-transmissive film, and the phase shift film and the semi-transmissive film A second etching step for forming a laminated pattern;
Removing the second photoresist.
The phase shift angle of the semipermeable membrane is not less than 0.1 degrees and not more than 20 degrees,
In the region where the layered portion where the semi-transmissive film is formed on the phase shift film and the portion where the semi-transmissive film is directly formed on the transparent substrate and then becomes the transparent region are adjacent,
An end portion of the second photoresist pattern is set back by a predetermined distance from an end portion of the pattern of the phase shift film before the second etching step toward the side of the stacked region. Photomask manufacturing method.   5. The method of manufacturing a photomask according to claim 4, wherein the predetermined distance is equal to or greater than an overlay error of a drawing apparatus that exposes the second photoresist. Forming a phase shift film for inverting the phase of exposure light on a transparent substrate;
Forming a third photoresist on the phase shift film;
Forming a third photoresist pattern by exposing and patterning the third photoresist with a drawing apparatus; and
Etching the phase shift film using the third photoresist pattern as a mask to expose the transparent substrate to form a pattern of the phase shift film;
Removing the third photoresist;
Forming a semi-transmissive film so as to cover the pattern of the phase shift film ;
Forming a fourth photoresist on the semi-transmissive film;
Forming a fourth photoresist pattern by exposing and patterning the fourth photoresist with a drawing apparatus; and
Etching the semi-transmissive film and the phase shift film using the fourth photoresist pattern as a mask to expose the transparent substrate, the pattern of the semi-transmissive film, and the phase shift film and the semi-transmissive film Forming a laminated pattern; and
Removing the fourth photoresist;
The phase shift angle of the semipermeable membrane is not less than 0.1 degrees and not more than 20 degrees,
The method of manufacturing a photomask, wherein the third photoresist pattern has an opening in a region where the pattern of the semi-transmissive film is formed. Forming a phase shift film for inverting the phase of exposure light on a transparent substrate;
Forming a first photoresist on the phase shift film;
Forming a first photoresist pattern by exposing and patterning the first photoresist with a drawing apparatus; and
Etching the phase shift film using the first photoresist pattern as a mask to expose the transparent substrate to form a pattern of the phase shift film;
Removing the first photoresist;
Forming a semi-transmissive film so as to cover the pattern of the phase shift film ;
Forming a second photoresist on the semi-transmissive film;
Exposing the second photoresist with a drawing apparatus and patterning to form a second photoresist pattern;
Etching the semi-transmissive film using the second photoresist pattern as a mask to form a transparent region exposing the transparent substrate, a pattern of the semi-transmissive film, and a laminated pattern of the phase shift film and the semi-transmissive film And a process of
Removing the second photoresist.
The phase shift angle of the semipermeable membrane is not less than 0.1 degrees and not more than 20 degrees,
In the region where the layered portion where the semi-transmissive film is formed on the phase shift film and the portion where the semi-transmissive film is directly formed on the transparent substrate and then becomes the transparent region are adjacent,
An end of the second photoresist pattern protrudes from the end of the phase shift film pattern by a predetermined distance toward the transparent region. 8. The photo according to claim 7, wherein the predetermined distance is larger than any of a side etching amount of the semi-transmissive film and an overlay error of a drawing apparatus that exposes the second photoresist in the laminated pattern. Mask manufacturing method.

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