JP2015064404A - Phase shift mask and production method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase shift mask which gives high-contrast exposure patterns without increase of exposure of light from an exposure apparatus and its production method.SOLUTION: On a photomask substrate, there is provided a phase shift film 13 which reverses the phases of a translucent part 11, a light shielding part 12 and transmitted light, and the phase shift film 13 is arranged in a pattern boundary part composed of the light shielding part 12. The phase shift mask can reduce the exposure of the pattern boundary part exclusively without reduction of the exposure of a pattern part, enabling high-contrast patterning without increase of the entire exposure.

Description

  The present invention relates to a phase shift mask and a manufacturing method thereof.

  When a pattern is to be exposed by a photolithography process, the difference in exposure intensity decreases as the pattern becomes finer, and the contrast (intensity difference) decreases, making it impossible to obtain a pattern as designed. Therefore, a “phase shift mask (PSM)” has been known for a long time by providing a “phase shift film” (phase shifter) that reverses the phase of exposure light by 180 ° in the pattern to suppress a local contrast decrease. Yes.

  FIG. 6A shows an example of a pattern of a conventional phase shift mask 100. As shown in this figure, a phase shift film 103 is provided at a mask pattern boundary portion (hereinafter simply referred to as “pattern boundary portion”) between the light transmitting portion 101 and the light shielding portion 102 where the transparent substrate is exposed. When this pattern is exposed, the phase shift film 103 is not resolved, and the phase shift film 103 causes a difference in the exposure intensity between the light transmitting portion 101 and the light shielding portion 102 and increases the contrast, resulting in a pattern having a steep taper. can get.

FIG. 6B shows the intensity distribution of light incident from the exposure apparatus as coordinates on the horizontal axis and incident intensity (arbitrary unit) on the vertical axis, and the transmitted light I ₀ and diffracted light I ₁ interfere at the pattern boundary. The situation is shown schematically. As is clear from this figure, the role of the phase shift film 103 is to reduce the intensity of light that has passed from the pattern boundary portion of the light transmitting portion 101 to the light shielding portion side, thereby reducing the pattern boundary portion between the light transmitting portion 101 and the light shielding portion 102. The difference in exposure intensity is increased to increase the contrast. That is, the phase of the exposure light that has passed through the phase shift film 103 is shifted by 180 °, so that the contrast at the pattern boundary is enhanced by interfering with the light that has passed through the light transmitting part 101 at the pattern boundary.

  As described above, the “phase shift film” in the conventional phase shift mask is provided adjacent to the light shielding portion at the pattern boundary portion, more specifically at both ends of the pattern of the light transmitting portion.

JP 07-261367 A

  However, when the diffracted light transmitted through the phase shift film reaches the entire pattern portion, there is a problem that the total exposure amount decreases. For this reason, in the conventional phase shift mask, the exposure amount has to be increased as compared with a normal photomask at the time of exposure, which has been a main cause of increasing the exposure time.

  The present invention has been made in view of the above, and an object of the present invention is to provide a phase shift mask capable of obtaining an exposure pattern with high contrast without increasing the exposure amount from the exposure apparatus, and a method for manufacturing the same.

  In the phase shift mask according to the present invention, a light transmitting part, a light shielding part, and a phase shift film for inverting the phase of the transmitted light are provided on a photomask substrate, and the phase shift film includes a pattern boundary formed by the light shielding part. It is provided in the light-shielding part inside the part.

  With such a configuration, the opposite phase diffracted light transmitted through the phase shift film, which has been a problem with the conventional phase shift mask provided with the phase shift film at the pattern boundary, does not reach the central part of the pattern, and the adjacent light shielding The diffracted light can be prevented from reaching the part side. That is, interference between the diffracted light of the exposure pattern and the light transmitted through the phase shift film can be avoided, and an exposure pattern with high contrast can be obtained without increasing the exposure amount. In this specification, the term “diffracted light” simply means “diffracted light of light transmitted through the phase shift film” unless otherwise specified.

  In this case, the inner side of the mask pattern boundary portion where the phase shift film pattern is to be formed will be described in detail in an embodiment described later. As an example, a line and space with an exposure pattern of 3 μm is used. In this case, a 1 μm phase shift film can be provided at the center of the light shielding part pattern. Assuming that the transmittance of the phase shift film is 10%, in such a pattern, the diffracted light occupies about 59%. Therefore, by arranging a phase shift film having a width of about 3.0 μm or less with an interval of about 1.5 μm or less from the pattern boundary portion, the exposure amount of the pattern boundary portion is reduced without reducing the overall exposure amount. Thus, a high contrast exposure pattern can be obtained. The larger the width of the light-transmitting part with respect to the width of the adjacent light-shielding part, the more difficult it is to obtain the effect of “not reducing the exposure while maintaining a steep taper”, but conversely the light-transmitting part is narrow and the light-shielding part is wide The pattern is very effective. For example, when the present invention is applied to a hole pattern having a line width of about 2 μm or 3 μm, a very large effect is achieved.

  For patterns such as line and space, a light shielding film is provided adjacent to the light shielding portions on both sides of the light transmitting portion. In such a pattern, the phase shift film may be disposed so that the phase shift film is provided at a position symmetrical to the center of the light transmitting part.

In the first manufacturing method of the phase shift mask according to the present invention, after the pattern of the light shielding part is formed, the phase shift film is formed, and the pattern formation of the phase shift film formed on the pattern of the light shielding part by alignment drawing is performed. When doing
Patterning is performed so that the formation position of the phase shift film pattern is provided adjacent to the inner side of the pattern boundary portion formed of the light shielding portion.

In the second manufacturing method of the phase shift mask according to the present invention, the phase shift film is first formed and patterned, and then the light shielding portion is formed and patterned.
Patterning is performed so that the formation position of the phase shift film pattern is provided adjacent to the inner side of the pattern boundary portion formed of the light shielding portion.

  The phase shift mask according to the present invention can be manufactured by any of the above methods.

  According to the phase shift mask of the present invention, it is possible to reduce only the exposure amount at the pattern boundary without reducing the exposure amount of the pattern portion, and patterning with high contrast can be performed without increasing the overall exposure amount. It becomes.

(A) Pattern of phase shift mask 10 of the first embodiment (B) Intensity distribution I _{0 of} incident light that has passed through the slit-like light transmitting portion, intensity I _{1 of} diffracted light that has passed through the phase shift film, and Cross-sectional view of the light intensity distribution I ₂ obtained by combining these and the phase shift mask 10 Simulation results of light intensity under each condition Process sectional drawing which shows the manufacturing method of the phase shift mask of 2nd Embodiment Process sectional drawing which shows the manufacturing method of the phase shift mask of 3rd Embodiment Example of applying this embodiment to an isolated tohole pattern (A) An example of a conventional phase shift mask 100 is shown. (B) A diagram schematically showing the intensity distribution of light incident from the exposure apparatus as coordinates on the horizontal axis and incident intensity (arbitrary unit) on the vertical axis, and the state where transmitted light and diffracted light interfere at the pattern boundary.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings. In addition, the same code | symbol is used for the same member even if it is a different use aspect.

(First embodiment)
FIG. 1A shows a pattern of the phase shift mask 10 of the present embodiment. In this phase shift mask 10, a slit-like pattern composed of a light transmitting part 11 with a transparent substrate exposed and a linear pattern composed of a light shielding part 12 and a phase shift film 13 are alternately arranged. This is a “line and space” pattern.

FIG. 1B is obtained by combining the intensity distribution I _{0 of} incident light that has passed through the slit-shaped pattern made of the light transmitting portion 11, the intensity I _{1 of} diffracted light that has passed through the phase shift film 13, and these. The resulting light intensity distribution I ₁ is shown together with a sectional view of the phase shift mask 10. In addition, since the phase of the diffracted light I ₁ is shifted by 180 ° with respect to the incident light I ₀ , the incident intensity I ₂ obtained by combining both decreases.

  From FIG. 1A and FIG. 1B, the phase shift film 13 is not in the pattern boundary part between the light transmitting part 11 and the light shielding part 12 adjacent thereto, but in the light shielding part inside and adjacent thereto. It can be seen that the light transmissive portions are provided symmetrically in the light shielding portions on both sides of the pattern center.

  In the case of a “line and space” pattern in which a large number of line patterns are continuous as shown in FIG. 1, “being provided symmetrically in the light shielding portions on both sides of the pattern center of the adjacent light transmitting portions” This is effective in that a sharp taper with high contrast can be obtained at each edge (near the boundary between the line pattern and space pattern) without reducing the amount, but depending on the pattern, it is provided only on one side. Also good. For example, it is needless to say that the present invention can be applied to an isolated contact hole pattern as shown in FIG.

  As described above, since the phase shift film is provided on the inner side of the pattern boundary portion, the reverse phase diffracted light transmitted through the phase shift film 13 does not reach the center portion of the pattern, and the entire exposure pattern (that is, the opening portion). The diffracted light can be prevented from reaching. As a result, the total exposure amount is not reduced, and the contrast at the pattern boundary is increased.

FIG. 2 shows the result of the light intensity obtained by simulation under the following conditions for the above phase shift mask. The light shielding part was a chromium film, and the phase shift film was a film having a transmittance of 10% and a phase shift of 180 °. The horizontal axis of the graph represents coordinates with the central portion of the slit-like light transmitting portion as the origin, and the vertical axis represents the light intensity normalized in an arbitrary unit.
The width of the line and space (D1 / D2) and the width of the light shielding part and the semi-transparent film (a / b / c) in the line pattern,
D1 = 3 [μm],
D2 = 3 [μm],
a = 1 [μm]
b = 1 [μm]
c = 1 [μm]
The exposure amount at the peak position P and the exposure amount at the bottom position B were examined. For comparison, a binary mask without a phase shift film and a conventional phase shift mask (FIG. 6A) are shown superimposed.

All graphs have a Gaussian distribution. Table 1 shows the results obtained for the intensities at the peak position P and the bottom position P.
(Table 1)

  The exposure amount at the bottom position is not different from that of the conventional phase shift mask, and the exposure amount at the peak position is greatly increased as compared with the conventional case, which is almost the same as that of the binary mask. This indicates that the influence of the interference of the diffracted light that has passed through the phase shift film is eliminated. Quantitatively, the exposure amount at the same level as the conventional binary increases the exposure amount at the center part of the space pattern part by about 10% compared to the conventional halftone mask, while the conventional phase shift at the pattern boundary part. It was found that the exposure amount can be reduced to the same extent as that of the mask, and as a result, a higher contrast can be obtained than the conventional phase shift mask.

  However, since the position E of the pattern boundary is closer to the origin side than the bottom position B, the intensity difference during actual exposure is considered to be slightly smaller than this. For reference, the position E of the pattern boundary is shown on the graph. However, this point can be appropriately optimized by design. According to various experiments, it has been found that the effect of the present embodiment can be easily obtained when the width of the “line part” or “space part” in “line and space” is about 2 μm to 6 μm. ing.

  As an example, when the above-described 1 μm phase shift film is provided at the center of the line pattern, diffracted light accounts for 59% in calculation. At this time, by disposing a phase shift film having a width of about 3.0 μm or less with an interval of about 1.5 μm or less from the pattern boundary portion, the exposure amount of the pattern boundary portion is reduced without reducing the exposure amount. And a high-contrast pattern can be obtained. The simplest example satisfying such a condition is the above-described experimental example, that is, an example in which 1 μm−1 μm−1 μm is set for each line pattern width of 3 μm. However, as to how far the phase shift film is provided from the pattern boundary, whether the diffracted light reaches the central portion of the space pattern (mostly on the central axis of the opening) in this way. It is not essential to provide the light shielding portions and the phase shift films at equal intervals in the line pattern. For example, it may be 1.1 μm−0.9 μm−1.1 μm, and more specifically, the arrangement position of the phase shift film need not be provided symmetrically in the center of the light shielding film. However, the positions of the phase shift films provided in the light shielding portions on both sides of the space pattern are preferably provided so that the light intensity distribution is symmetric with respect to the center of the space pattern.

  As described above, according to the phase shift mask of this embodiment, a high-contrast resolution pattern can be obtained without increasing the exposure amount of the exposure apparatus.

(Second Embodiment)
FIG. 3A to FIG. 3E show process cross-sectional views illustrating the method of manufacturing the phase shift mask of the first embodiment. First, a light shielding part pattern 32 is formed on a transparent substrate 31 such as quartz glass by a known photolithography process or the like (FIG. 3A). In this step, an opening pattern is formed at a position where a phase shift film to be formed later is to be formed. Next, a phase shift film 33 is formed so as to cover the entire surface of the transparent substrate 31 including the light shielding portion pattern 32 (FIG. 3B).

  Next, after forming a photoresist film on the phase shift film 33, drawing / development is performed, and a photoresist film pattern 34 is formed at a location that later becomes a light transmitting portion (FIG. 3C). At this time, patterning is performed so that the phase shift film pattern is formed symmetrically in the light shielding portions on both sides of the pattern center of the adjacent light transmitting portions, and on the inner side of the pattern boundary portion composed of the light shielding portions.

Next, the phase shift film 33 and the light shielding portion 32 are collectively etched using the photoresist film pattern 34 as a mask, thereby simultaneously forming the light shielding portion pattern 32a and the phase shift film pattern 33a (FIG. 3 ( D)). In order to enable collective etching, it is preferable that the light shielding portion and the phase shift film contain the same metal. For example, when the light shielding portion is a Cr film or a silicide film containing Cr, a combination of, for example, chromium oxide (CrO ₂ ) or the like can be considered as the phase shift film. However, different metals may be used as long as collective etching is possible.

  In addition, materials that can be used as the light-shielding portion include metal compounds containing chromium, tantalum (Ta), chromium (Cr), or silicide containing tantalum. On the other hand, examples of materials that can be used as the phase shift film include oxide films or nitride films (MoSiN, MoSiON, SiON) mainly composed of silicide such as molybdenum silicide MoSi, tantalum, tantalum carbide (TaC), and hafnium tantalum (TaHf). And so on.

  Finally, the photoresist film pattern 34 is removed to complete the phase shift mask 30 (FIG. 3E).

  In addition, depending on the pattern, “being provided symmetrically in the light shielding portions on both sides of the pattern center of the adjacent light transmitting portions” is not essential, and the phase shift film of the configuration of the present embodiment may be applied only to one side. . In this case, the contrast on the side where the phase shift film is provided is improved.

(Third embodiment)
FIG. 4A to FIG. 4E show process cross-sectional views showing another method showing the method of manufacturing the phase shift mask of the first embodiment. First, a phase shift film pattern 43a is formed on the transparent substrate 41 by a known photolithography process or the like, for example, using an oxide film mainly made of MoSi (FIG. 4A). Specifically, for example, blanks on which a phase shifter film is formed are prepared, and after resist coating, drawing, and development, patterning is performed by dry etching. As the etching gas, a known fluorine-based or chlorine-based gas and oxygen mixed gas is used. At this time, the phase shift film pattern is formed symmetrically in the light shielding portions on both sides of the pattern center of the adjacent light-transmitting portion and inside the pattern boundary portion formed of the light shielding portion to be formed later. Pattern as possible.

  Next, the light shielding portion 42 is formed so as to cover the entire surface of the transparent substrate 41 including the phase shift film pattern 43a (FIG. 4B). The light shielding part 42 is preferably a light shielding part such as a metal compound having etching resistance different from that of the phase shift film, such as chromium. This is to prevent the phase shift film from being etched when the light shielding portion is etched.

  Next, after a photoresist film is formed on the light shielding portion 42, alignment is performed using a known alignment technique or the like to form a photoresist film pattern 44 (FIG. 4C). In this step, the positional relationship between the pattern 43a of the phase shift film and the pattern of the light shielding portion and the light transmitting portion is determined.

  Next, the light-shielding portion 42 is etched using the photoresist film pattern 44 as a mask to simultaneously form the light-transmitting portion pattern 41a and the light-shielding portion pattern 42a (FIG. 4D). In this step, a pattern of the light shielding part and the light transmitting part is formed. For patterning, a known photolithographic technique may be used to form the substrate by wet etching with a high selectivity. At this time, in consideration of drawing misalignment, the phase shift film pattern is designed to overlap the light shielding part pattern side between the light shielding part pattern and the phase shift film pattern. The overlap dimension is preferably in the range of 0.3 to 0.6 μm. A nitric acid-based etchant can be used for wet etching.

  Finally, the photoresist film pattern 44 is removed to complete the phase shift mask 40 (FIG. 4E).

  It should be noted that “being provided symmetrically in the light shielding portions on both sides of the pattern center of the adjacent light transmitting portion” is not essential, and the phase shift film of the configuration of the present embodiment may be applied only to one side depending on the pattern. . In this case, the contrast on the side where the phase shift film is provided is improved.

10, 30, 40 Phase shift mask 11, 31, 41 Transparent substrate (translucent portion)
12, 32, 42 Light-shielding part 32a, 42a Light-shielding part pattern 13, 33, 43 Phase-shift film 33a, 43a Phase-shift film pattern 34, 44 Photoresist film 100 Conventional phase-shift mask 101 Transparent substrate (translucent part)
102 light shielding part 103 phase shift film

Claims (7)

  A light transmitting portion, a light shielding portion, and a phase shift film for inverting the phase of the transmitted light are provided on the photomask substrate, and the phase shift film is disposed in the light shielding portion inside the pattern boundary portion including the light shielding portion. A phase shift mask provided.   2. The phase shift mask according to claim 1, wherein the mask pattern is a line-and-space pattern. 2. The phase shift mask according to claim 1, wherein the mask pattern is a line-and-space pattern, and the phase shift film is provided at the center of the pattern of the line portion.   4. The phase shift mask according to claim 3, wherein the phase shift film is separated from the boundary part of the light shielding part pattern by 1.5 μm or less and the width of the phase shift film is 3.0 μm or less.   2. The phase shift mask according to claim 1, wherein the mask pattern is a contact hole pattern. Forming a light-shielding portion pattern on the transparent substrate;
Forming a phase shift film so as to cover the entire surface of the transparent substrate including the pattern of the light shielding portion;
After forming a photoresist film on the phase shift film, a step of forming a pattern of the photoresist film at a location that later becomes a translucent portion;
Etching the phase shift film and the light shielding part together using the photoresist film pattern as a mask to simultaneously form the light shielding part pattern and the phase shift film pattern; and A method for manufacturing a phase shift mask according to claim 1, comprising a step of removing.   Forming a phase shift film pattern on the transparent substrate; forming a light shielding portion so as to cover the entire surface of the transparent substrate including the phase shift film pattern; and forming a photoresist film on the light shielding portion. Then, alignment is performed using a known alignment technique or the like to form a photoresist film pattern, and the light-shielding portion pattern is etched using the photoresist film pattern as a mask. 6. The method of manufacturing a phase shift mask according to claim 1, comprising a step of simultaneously forming a pattern of the light-shielding portion and a step of removing the pattern of the photoresist film.

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