JP2005181722A - Halftone phase shift mask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent film reduction of photoresist of a halftone phase shift mask, by suppressing the light intensity on the side of a hole pattern. <P>SOLUTION: The halftone phase shift mask is provided with a phase shift part 10, formed by using a halftone phase shift film 1 which inverts the phase of transmitted light by 180°, and the phase shift part 10 has a plurality of films 2, which are arranged at prescribed intervals and do not invert the phase of the transmitted light. The halftone phase shift film 1 has 4 to 20% for the light transmissivity and the film 2 has 0 to 50% for the light transmissivity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a halftone phase shift mask. In particular, the present invention relates to a structure of a halftone phase shift mask used in an optical lithography apparatus, a manufacturing method thereof, an exposure method, and an exposure apparatus.

  FIG. 7 is a diagram showing a cross-sectional structure of a conventional halftone phase shift mask.

  A conventional halftone phase shift mask has a structure in which a halftone phase shift film 1 is selectively formed on a transparent substrate 3 (see Patent Document 1).

  In photolithography, when exposure is performed by applying light having a wavelength of 157 nm or more, quartz glass is generally applied as a transparent substrate material, and the size is 6 inches square and the thickness is 0.25 inches. Further, as a material of the halftone phase shift film 1, molybdenum silicide (MoSi) having a higher dry etching rate than other materials is applied, it has optical characteristics of transmittance of 4 to 20%, and a phase difference of 180. The thickness is set to be °. The thickness D of the halftone phase shift film is expressed by the following equation where λ is the exposure wavelength and n is the refractive index of the halftone phase shift film.

D = λ / 2 (n−1)
When a conventional halftone phase shift mask is applied and transferred to the photoresist using an exposure device, the light that has passed through the halftone phase shift area and the diffracted light that has passed through the transmission area overlap each other, resulting in strong sidelobe light. It becomes. As a result, the film thickness of the photoresist is reduced.

  FIG. 8 is a simulation result when using an exposure light having a wavelength of 157 nm for an isolated hole pattern having a diameter of 100 nm formed of a halftone phase shift film having a transmittance of 5%. 8A and 8B are a sectional view and a plan view of a conventional halftone phase shift mask. FIG. 8C shows a light intensity distribution obtained by simulation. The light transmitted through the halftone phase shift film and the diffracted light from the transmission region formed by the halftone phase shift film overlap, and side lobes are generated beside the hole pattern.

FIG. 8D shows a photoresist shape when exposure light having a wavelength of 157 nm is used for an isolated hole pattern having a diameter of 100 nm formed of a halftone phase shift film having a transmittance of 5%, as described above. This is a result obtained by simulation. The side lobe on the side of the hole pattern in the light intensity distribution shown in FIG. 8C is transferred, and the film thickness of the photoresist is reduced.
JP-A-4-136854

  As described in the prior art, when a conventional halftone phase shift mask is applied and transferred to a photoresist using an exposure apparatus, the light passing through the halftone phase shift region and the diffracted light of the light passing through the transmission region Overlap, causing a reduction in photoresist film thickness.

  An object of the present invention is to prevent a film loss of a photoresist in a halftone phase shift mask.

The halftone phase shift mask according to the present invention includes a phase shift portion formed using a halftone phase shift film that reverses the phase of transmitted light by 180 °,
The phase shift unit includes a plurality of phase non-inversion units that are arranged at a predetermined interval with respect to the halftone phase shift film and that do not invert the phase of the transmitted light.

A transparent substrate;
A first halftone phase shift film formed in an annular shape on the transparent substrate and inverting the phase of transmitted light by 180 °;
A first phase non-inversion part that is formed adjacent to the outside of the first halftone phase shift film on the transparent substrate and does not invert the phase of transmitted light;
A second halftone phase shift film formed on the transparent substrate adjacent to the outside of the first non-phase-inverted portion and inverting the phase of transmitted light by 180 °;
And a second phase non-inversion portion which is formed adjacent to the outside of the second halftone phase shift film on the transparent substrate and does not invert the phase of transmitted light.

  At least one of the first phase non-inversion part, the second halftone phase shift film, and the second phase non-inversion part is formed in an annular shape so as to surround a film adjacent to the inside. Features.

The light transmittance of the first and second halftone phase shift films is 4 to 20%,
The light transmittance of the first and second phase non-inversion parts is 0 to 50%.

The first and second halftone phase shift films are formed with a width of 50 to 100 nm,
The first and second phase non-inversion parts are formed with a width of 50 to 100 nm.

  The first and second halftone phase shift films and the first and second phase non-inversion portions have light resistance to light in a short wavelength region of at least 250 nm or less.

  The first and second halftone phase shift films are made of tantalum silicide (TaSi), zircon silicide (ZrSi), molybdenum silicide (MoSi), chromium fluoride (CrF), and silicon oxide (SiO2). It contains at least one of them.

  The first and second phase non-inversion parts include at least one of tantalum silicide (TaSi), zircon silicide (ZrSi), molybdenum silicide (MoSi), chromium fluoride (CrF), and silicon oxide (SiO2) as a material. It is characterized by containing one.

The halftone phase shift mask further includes a third halftone phase shift film formed on the transparent substrate adjacent to the outside of the second phase non-inversion portion and for inverting the phase of transmitted light by 180 °. Prepared,
The first, second and third halftone phase shift masks are integrally formed so as to cover the first and second phase non-inversion parts.

  According to the present invention, the light transmitted through the halftone phase shift film having a phase of 180 ° and the light transmitted through the adjacent film having a phase of 0 ° are canceled out, and the light intensity on the side of the hole pattern can be suppressed. it can. Therefore, the film thickness reduction of the photoresist can be prevented, and the shape of the photoresist after exposure can be formed into a favorable shape.

  Further, the transmittance of the halftone phase shift film can be optimized without considering the reduction of the photoresist film, and the resolution can be improved.

Embodiment 1 FIG.
As described below, in the first embodiment, side lobes generated when exposure is performed using a halftone phase shift mask is suppressed, and the film thickness reduction of the photoresist due to the light intensity of the side lobes is significantly reduced. Improves contrast in intensity and significantly improves the resolution performance of the photoresist.

  FIG. 1 is a diagram showing a cross-sectional structure of the halftone phase shift mask in the first embodiment.

  In FIG. 1, the halftone phase shift mask 100 includes a transparent substrate 3 and a phase shift unit 10. The phase shift unit 10 includes a halftone phase shift film 1 and a film 2 (an example of a phase non-inversion unit).

  The halftone phase shift film 1 is formed in an annular shape on the transparent substrate 3, and the first halftone phase shift film 11 that reverses the phase of transmitted light by 180 °, and the first phase on the transparent substrate 3. A second halftone phase shift film 12 formed adjacent to the outer side of the film 21 as an example of a non-inversion portion and inverting the phase of transmitted light by 180 °, and the second phase non-inversion on the transparent substrate 3. And a third halftone phase shift film 12 that is formed adjacent to the outside of the film 22 as an example of the inversion part and inverts the phase of transmitted light by 180 °, and so on.

  The film 2 is composed of a plurality of films 21, 22,... (An example of a phase non-inversion portion) arranged at a predetermined interval with respect to the halftone phase shift film 1, and the phase of transmitted light is changed. It is a film that is not reversed. The film 2 is formed adjacent to the outside of the first halftone phase shift film 11 on the transparent substrate, and the first film 21 that does not reverse the phase of transmitted light, and the first film 21 on the transparent substrate 3. And a second film 22 which is formed adjacent to the outside of the two halftone phase shift films 12 and which does not invert the phase of the transmitted light, and so on. In other words, the halftone phase shift mask 100 is formed on the remaining pattern portion on the side of the hole pattern formed by the halftone phase shift film 1 that inverts the phase of transmitted light by 180 ° on the transparent substrate 3. The film 2 having a phase opposite to that of 1, that is, a phase of 0 °, is arranged in such a manner that the halftone phase shift film 1 and the film 2 are alternately arranged from the hole edge of the hole 40.

  Here, the halftone phase shift film 1 and the film 2 are made of a material having sufficient light resistance to light in a short wavelength region of at least 250 nm or less.

  FIG. 2 shows a hole pattern of a hole 40 of 100 nm square on one side formed by the halftone phase shift film 1 having a transmittance of 5%, a position of 50 nm from the hole pattern edge, and 150 nm, 250 nm, 350 nm,. The first, second, third,... Film 2 having a width of 50 nm and a transmittance of 15% is inserted at the position of..., That is, the halftone phase shift film 1 FIG. 6 is a diagram showing a simulation result in the case of using exposure light having a wavelength of 157 nm using a new halftone phase shift mask in which films and films 2 are alternately arranged.

  2A and 2B show a cross-sectional structure and a plan view of the new halftone phase shift mask. FIG. 2C shows a light intensity distribution obtained by simulation. The light transmitted through the halftone phase shift film 1 having a phase of 180 ° and the light transmitted through the film 2 having a phase of 0 ° cancel each other, and the light intensity of the side lobe beside the hole pattern is suppressed.

  FIG. 2 (d) shows the result of the simulation of the cross-sectional shape of the photoresist when a novel halftone phase shift mask is used and exposure light having a wavelength of 157 nm is used. In a hole pattern with a side of 100 nm square formed of a halftone phase shift film 1 having a transmittance of 5%, at a position of 50 nm from the hole pattern edge, and at a position of 150 nm, 250 nm, 350 nm,. By using a novel halftone phase shift mask in which the first, second, third,... Film 2 having a transmittance of 15% and having a phase of 0 ° is disposed, the light intensity of the side lobe can be suppressed. The film thickness of the photoresist does not occur, and a good shape is obtained.

  FIG. 3 is a diagram illustrating an example of a configuration when the halftone phase shift mask has a plurality of hole patterns.

  In FIG. 2, the first halftone phase shift film 11 and the film 21 as an example of the first phase non-inversion part, the second halftone phase shift film 12 and the film as an example of the second phase non-inversion part. 22 ... are all formed in an annular shape so as to surround the film adjacent to the inner side, but when the halftone phase shift mask has a hole pattern of a plurality of holes 40, each film has another hole pattern. By sharing the film to be formed, the first halftone phase shift film 11, the first film 21, and the second halftone phase shift film 12 are formed in an annular shape so as to surround the film adjacent to the inside. The subsequent films can also be formed so as not to surround the adjacent film inside. In other words, the first halftone phase shift film 11 surrounds the adjacent film on the inside, and the first film 21, the second halftone phase shift film 12, the second film 22, and so on. , At least one is formed in an annular shape so as to surround the membrane adjacent to the inside. In FIG. 3, the first halftone phase shift film 11, the first film 21, and the second halftone phase shift film 12 are formed in an annular shape so as to surround a film adjacent to the inner side. This membrane does not surround the membrane adjacent to the inside. In FIG. 3, the second halftone phase shift film 12 is formed in a lattice shape.

  FIG. 4 is a diagram showing a focus margin improvement effect and a sidelobe suppression effect when the halftone phase shift mask in the first embodiment is used.

  In FIG. 4, although it differs depending on the transmittance of the film 2 applied to the halftone phase shift mask in the first embodiment, the focus margin is improved by about 7% at the maximum as compared with the conventional halftone phase shift mask, and the side of the hole pattern. The light intensity of the side lobes can be suppressed up to about 67%. An effect can be obtained by setting the transmittance of the film 2 applied to the new halftone phase shift mask 100 to a range of 0 to 50%.

  As described above, exposure using the halftone phase shift mask 100 according to the first embodiment suppresses side lobes, reduces photoresist film loss due to side lobe effects, and increases light intensity contrast. The resolution of the photoresist can be improved.

  FIG. 5 is a diagram showing manufacturing steps of the halftone phase shift mask in the first embodiment.

  In FIG. 5, step (a) is a deposition step of depositing the halftone phase shift film 1 on the transparent substrate 3, step (b) is a deposition step of depositing the etch stop film 6, and step (c) is an electron. After applying the line resist 5, the exposure process by the electron beam 4, the process (d) is the development process, and the process (e) is the etching of the etch stop film 6 and the halftone phase shift film 1 using the electron beam resist 5 as a mask. Step, step (f) is a removal step for removing the electron beam resist 5, step (g) is a step for depositing the film 2, and step (h) is an exposure step using the electron beam 4 after applying the electron beam resist 5. Step (i) is a development step, Step (j) is an etching step of the film 2 using the electron beam resist 5 as a mask, Step (k) is a step of removing the electron beam resist 5, and Step (l) is Etch back process of film 2, process m) shows the etch stop film 6 etch-back process.

  A halftone phase shift film 1 is formed on the transparent substrate 3 by sputtering, vacuum deposition or the like (step (a)), and an etch stop film 6 is formed thereon (step (b)). The etch stop film 6 requires a film having a large etching selection ratio with the halftone phase shift film 1 and the film 2, and Poly-Si or the like is effective.

  Furthermore, the electron beam resist 5 is apply | coated on it (process (c)).

  The material of the transparent substrate 3 must have a high transmittance of 80% or more at the wavelength of the exposure light to be applied. For example, quartz glass having a transmittance of 85% or more at an exposure light wavelength of 157 nm or more is effective. As the material of the halftone phase shift film 1, tantalum silicide (TaSi), zircon silicide (ZrSi), molybdenum silicide (MoSi), chromium fluoride (CrF), and silicon oxide (SiO2) are effective. When the halftone phase shift film 1 is formed, the film thickness is such that a phase of 180 ° is obtained and the light transmittance is 4 to 20%.

  Next, the electron beam resist is patterned into a resist region and a non-resist region by drawing and developing processes using the electron beam 4.

  In the electron beam resist developing step, when a positive electron beam resist 5 is applied, the electron beam resist 5 is dissolved in the developer in the region irradiated with the electron beam, and the halftone phase shift film 1 is exposed. In the region where the electron beam is not irradiated, the electron beam resist 5 is not dissolved in the developer, so that the pattern of the electron beam resist remains (step (d)).

  Next, the etch stop film 6 is etched using the electron beam resist 5 as a mask, and then the halftone phase shift film 1 is etched using the etch stop film 6 as a hard mask (step (e)). At this time, the etching selectivity between the halftone phase shift film 1 and the transparent substrate 3 must be sufficient.

  Thereafter, the electron beam resist is peeled and removed (step (f)).

  The description so far is the same as the manufacturing process of the conventional halftone phase shift mask. However, in the case of the halftone phase shift mask according to the first embodiment, in the electron beam resist exposure step to the halftone phase shift film 1 etching step shown in steps (c) to (f), the remaining pattern portion beside the hole pattern. In addition, a space pattern for embedding the film 2 described below is formed. The optimum distance 7 from the hole edge to the space having a width of 8 is preferably about 50 to 100 nm, although the optimum value varies depending on the optical conditions. Also, the space width 8 is preferably about 50 to 100 nm, and the left and the left of the hole edge are alternately arranged. Hereinafter, for the new halftone phase shift mask, the steps after the film 2 are further formed are continued.

  As shown in the step (g), the film 2 is formed by sputtering, vacuum deposition or the like. As a material for the film 2, tantalum silicide (TaSi), zircon silicide (ZrSi), molybdenum silicide (MoSi), chromium fluoride (CrF), and silicon oxide (SiO2) are effective. At the time of film formation, the film thickness is made thicker than a film thickness that completely fills at least a space of width 8 and can obtain a phase of 0 °.

  Next, an electron beam resist 5 is applied and exposed with an electron beam (step (h)). The pattern formed by this exposure is accurately overlapped with the pattern formed up to the step (f) to form a remaining pattern having a width 9 larger than the width 8 of the space, and completely covering the space of width 8. At this time, the width 9 of the remaining pattern is preferably set to a width represented by the following formula (step (i)).

(Width 9) = ((distance 7) + (width 8)) / 2
Next, development (step (i)) is performed, and the film 2 is etched using the electron beam resist 5 as a mask. At this time, the etch stop film 6 functions as a hard mask, and the halftone phase shift film 1 remains without being etched (step (j)).

  Thereafter, the electron beam resist 5 is peeled and removed (step (k)).

  Next, the etch stop film 6 is used to etch back the entire surface, and the film 2 protruding above the etch stop film 6 is removed (step (l)). At this time, the etching selectivity between the film 2 and the transparent substrate 3 must be sufficient. Since the film thickness of the film 2 is the sum of the film thickness of the halftone phase shift film 1 and the film thickness of the etch stop film 6, the etch stop is performed in advance so that the film thickness becomes a film thickness that can obtain a phase of 0 °. When the film 6 is formed, the film thickness is set to a desired film thickness.

  Thereafter, the etch stop film 6 is removed by etching back the entire surface (step (m)), and the new halftone phase shift mask 100 according to the first embodiment is completed. At the time of etch back, the etching selection ratio between the etch stop film 6, the halftone phase shift film 1, the film 2 and the transparent substrate 3 must be sufficient.

  FIG. 6 is a diagram showing a cross-sectional structure of the halftone phase shift mask (light transmittance of the film 2 is 0%).

  FIG. 6A shows a case where the film 2 (transmittance 0%) is inserted between the halftone phase shift films 1. FIG. 6B shows a case where the film 2 (transmittance 0%) is arranged on the upper layer of the halftone phase shift film 1. FIG. 6C shows the case where the film 2 (transmittance 0%) is disposed below the halftone phase shift film 1. Since the light transmittance of the film 2 disposed in the remaining pattern portion on the side of the hole pattern may be 0 to 50%, when the light transmittance is set to 0%, the halftone phase shift film 1 is used as shown in FIG. It may be inserted in the center of the remaining pattern between the formed hole patterns (FIG. 6A), or may be arranged in the upper layer or the lower layer (FIGS. 6B and 6C). In other words, the first, second, and third halftone phase shift films 11, 12, and 13 may be integrally formed so as to place the first and second films 21 and 22 thereon. Alternatively, they may be integrally formed so as to cover the first and second films 21 and 22. Cr or the like is effective as a film material when the light intensity is set to 0%.

  As described above, when the conventional halftone phase shift mask is applied and transferred to the photoresist using the exposure apparatus, the light passing through the halftone phase shift region and the diffracted light of the light passing through the transmission region overlap each other. This causes film loss of the photoresist.

  However, when the halftone phase shift mask in the above embodiment is applied and transferred to the photoresist using the exposure apparatus, the light transmitted through the halftone phase shift film 1 having a phase of 180 ° forming the hole pattern and the hole pattern The light transmitted through the film 2 having a phase of 0 ° arranged at the center of the remaining pattern is canceled out, and the light intensity at the center of the remaining pattern between the hole patterns is suppressed. Therefore, the film thickness of the photoresist does not occur and a good shape is obtained. Conventionally, since the film thickness of the photoresist is reduced, a high transmittance halftone phase shift film capable of further improving the contrast cannot be applied. However, by applying the halftone phase shift mask in this embodiment, the photoresist This makes it possible to optimize the transmittance of the halftone phase shift film without considering the reduction of the film thickness, leading to further improvement in resolution.

FIG. 3 is a diagram showing a cross-sectional structure of a halftone phase shift mask in the first embodiment. It is a figure which shows the simulation result at the time of using the exposure light of wavelength 157nm using the new halftone phase shift mask which has arrange | positioned the halftone phase shift film | membrane 1 and the film | membrane 2 by turns. It is a figure which shows an example of a structure in case a halftone phase shift mask has a some hole pattern. It is the figure which showed the focus margin improvement effect and the sidelobe suppression effect at the time of using the halftone phase shift mask in Embodiment 1. FIG. 6 is a diagram showing a manufacturing process of the halftone phase shift mask in the first embodiment. FIG. It is a figure which shows the cross-sectional structure (The light transmittance of the film | membrane 2 is 0%) of a halftone phase shift mask. It is a figure which shows the cross-section of the conventional halftone phase shift mask. It is a simulation result at the time of using the exposure light of wavelength 157nm about the isolated hole pattern with a diameter of 100 nm formed of the halftone phase shift film | membrane which has a transmittance | permeability of 5%.

Explanation of symbols

  3 transparent substrate, 1 halftone phase shift film, 2 film, 4 electron beam, 5 electron beam resist, 6 etch stop film, 7 distance, 8 width, 10 phase shift part, 11, 12, 13 halftone phase shift film, 21 films, 22 films, 40 holes, 100 halftone phase shift mask.

Claims (9)

A phase shift portion formed using a halftone phase shift film that reverses the phase of transmitted light by 180 °,
The halftone phase shift mask, wherein the phase shift unit includes a plurality of phase non-inversion units that are arranged at a predetermined interval with respect to the halftone phase shift film and that do not invert the phase of the transmitted light. A transparent substrate;
A first halftone phase shift film formed in an annular shape on the transparent substrate and inverting the phase of transmitted light by 180 °;
A first non-phase-inversion portion formed on the transparent substrate adjacent to the outside of the first halftone phase shift film and not inverting the phase of transmitted light;
A second halftone phase shift film formed on the transparent substrate adjacent to the outside of the first non-phase-inverted portion and inverting the phase of transmitted light by 180 °;
A halftone phase shift comprising: a second phase non-inversion portion formed on the transparent substrate adjacent to the outside of the second halftone phase shift film and not inverting the phase of transmitted light. mask.   At least one of the first phase non-inversion part, the second halftone phase shift film, and the second phase non-inversion part is formed in an annular shape so as to surround a film adjacent to the inside. The halftone phase shift mask according to claim 2, wherein: The light transmittance of the first and second halftone phase shift films is 4 to 20%,
3. The halftone phase shift mask according to claim 2, wherein the light transmittance of the first and second phase non-inversion parts is 0 to 50%. The first and second halftone phase shift films are formed with a width of 50 to 100 nm,
3. The halftone phase shift mask according to claim 2, wherein the first and second phase non-inversion portions are formed with a width of 50 to 100 nm.   The first and second halftone phase shift films and the first and second phase non-inversion parts have light resistance to light in a short wavelength region of at least 250 nm or less. Halftone phase shift mask.   The first and second halftone phase shift films are made of tantalum silicide (TaSi), zircon silicide (ZrSi), molybdenum silicide (MoSi), chromium fluoride (CrF), and silicon oxide (SiO2). The halftone phase shift mask according to claim 2, wherein at least one of them is contained.   The first and second phase non-inversion parts include at least one of tantalum silicide (TaSi), zircon silicide (ZrSi), molybdenum silicide (MoSi), chromium fluoride (CrF), and silicon oxide (SiO2) as a material. The halftone phase shift mask according to claim 2, comprising one. The halftone phase shift mask further includes a third halftone phase shift film formed on the transparent substrate adjacent to the outside of the second phase non-inversion portion and for inverting the phase of transmitted light by 180 °. Prepared,
3. The halftone phase according to claim 2, wherein the first, second and third halftone phase shift masks are integrally formed so as to cover the first and second phase non-inversion parts. Shift mask.

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