JP3322284B2 - Phase shift mask and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask having a pattern used in a projection exposure apparatus, and more particularly, to a phase shift mask capable of transferring a high-resolution pattern by giving a phase difference to exposure light passing through the pattern. And its manufacturing method.

[0002]

2. Description of the Related Art As a conventional phase shift mask, FIG.
There is a lower shifter type Levenson type phase shift mask as shown in FIG. The phase shift mask 40 is formed by sequentially laminating an etching stopper layer 42, a shifter layer 43, and a light shielding layer 44 on a transparent substrate 41. The symbol S indicates a light-shielding portion, the symbol Tn indicates a light-transmitting portion having no shifter, and the symbol Ta indicates a light-transmitting portion having a shifter.

The lower shifter type Levenson type phase shift mask 40 is superior in characteristics to the upper shifter type because there is no problem such as step coverage.
However, since the shifter layer 43 is much thicker than the light-shielding layer 44, it is not sufficient to handle only a planar mask pattern, and the three-dimensional mask shape taking the thickness of the shifter layer 43 into consideration is not enough. Affect.

That is, as shown in FIG. 14, when the inner diameter difference between the light-shielding layer edge 44a and the shifter side wall 43a is small (in the case of the drawing, there is almost no inner diameter difference), the light enters obliquely. Through the shifter layer 43,
The light transmitting portion T having no shifter from the shifter layer side wall 43a
n, the irradiation light L2 and L3 canceling out the irradiation light L1, the Si light corresponding to the light transmitting portion Tn having no shifter.
The light intensity distribution P1 on the wafer 45 is smaller than the dimension W1 on the mask 40. On the other hand, the light intensity distribution on the wafer 45 corresponding to the translucent portion Ta having the shifter (FIG. 13) is the same as the dimension W1 on the mask 40. In the drawing, reference numeral 46 indicates a resist layer.

As shown in FIG. 15, the side wall 53a of the shifter layer 53 is recessed from the edge 54a of the light shielding layer 54 in order to prevent the occurrence of a dimensional error of the exposure light on the wafer. Is being studied. In the figure, reference numeral 51 denotes a transparent substrate, 52 denotes an etching stopper layer, and S, Tn and Ta denote FIG.
It shows the same part as.

In the present phase shift mask 50, FIG.
As shown in FIG. 6, irradiation light L2 and L3 obliquely incident
Does not pass through the shifter layer 53, so that its phase does not reverse and does not cancel out the irradiation light L1. Therefore, the light intensity distribution P2 on the wafer 45 corresponding to the light transmitting portion Tn having no shifter is Is the same as the dimension W1 in this case, and thus an error in the exposure width dimension on the wafer 45 can be avoided. However, the edge 54a of the light shielding layer 54
Since the protrusions protrude like eaves, there is a problem in physical resistance, and the eaves-like parts are chipped off and become foreign matter, which may contaminate the photomask.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems relating to the conventional phase shift mask, and has been made in consideration of the fact that pattern exposure is performed on an object to be exposed, for example, a wafer. It is an object of the present invention to prevent a dimensional error from occurring between the size of the irradiation light and the size of the exposure light on the object to be exposed, and not to reduce the mechanical strength of the mask even in such a case.

[0008]

In order to achieve the above object, a phase shift mask according to the present invention is provided on a transparent substrate.
A lower shifter-type Levenson-type phase shift mask formed by sequentially forming a shifter layer and a light-shielding layer, wherein a light-shielding portion, a light-transmitting portion having no shifter, and a light-transmitting portion having a shifter are alternately arranged in a plane. The phase shift mask at the boundary between the light-shielding part and the light-transmitting part without shifter.
The shifter layer exists under the light-shielding layer edge, and an etching stopper layer is provided between the shifter layer and the transparent substrate, however, the etching stopper layer is not provided on the light-transmitting portion having no shifter. I have.

Further, the method for manufacturing a phase shift mask according to the present invention comprises the following steps: (a)
Forming a film for forming an etching stopper layer, a film for forming a shifter layer, a film for forming a light shielding layer, and a film for forming a first resist layer in this order; (b) forming a film for forming a first resist layer; Forming a light-shielding layer resist pattern by drawing, (c) etching a light-shielding layer forming film exposed from the light-shielding layer resist pattern to form a light-shielding layer, and (d) forming a light-shielding layer resist pattern. (E) a step of forming a second resist layer forming film, (f) a step of drawing a second resist layer forming film to form a shifter layer resist pattern, (g) a shifter layer resist Forming a shifter layer by etching the shifter layer forming film exposed from the pattern,
(H) a step of exposing the transparent substrate by etching the film for forming an etching stopper layer exposed from the shifter layer to form an etching stopper layer;
(I) a step of removing the resist pattern for the shifter layer.

The step (h) and the step (i)
Regarding the steps described in the section, the order can be changed.

[0011]

When the light is applied to the phase shift mask according to the first aspect, the light applied to the light shielding layer is prevented from traveling, and the light applied to the light transmitting portion having the shifter has a phase inverted. The light applied to the exposure target, for example, the wafer, and the light emitted to the light-transmitting portion having no shifter are directly directed to the exposure target without reversing the phase. Since the etching stopper layer does not exist in the light-transmitting portion having no shifter, the energy loss that would be consumed if the etching stopper layer was present for the irradiation light perpendicularly incident on the light-transmitting portion. Disappears. Therefore, the amplitude distribution of the light irradiated perpendicularly to the exposure target object becomes higher as a whole. Therefore, even if the above-mentioned vertical irradiation light is canceled by the irradiation light which is obliquely incident on the phase shift mask, transmits through the shifter layer, and further escapes from the side wall of the shifter layer into the light-transmitting portion having no shifter, the vertical irradiation The distribution width of light on the object to be exposed does not become narrow. As a result, the width dimension of the light intensity distribution on the exposure target can be kept the same as the width dimension of the light intensity distribution on the mask. As described above, by preventing an error from occurring in the irradiation light distribution width on the exposure target, the resolution performance of the mask can be improved.

Moreover, in the phase shift mask of the present invention, the shifter layer can be present under the edge of the light-shielding layer, and the edge of the light-shielding layer does not have an eaves shape. Nor.

[0013]

EXAMPLES (Example of a phase shift mask) First, an example of a phase shift mask according to the present invention shown in FIG. The phase shift mask 10 includes a transparent substrate 11, an etching stopper layer 12 formed on the transparent substrate 11 for stopping the progress of the etching process, and a phase shift mask formed on the etching stopper layer 12 for inverting the phase of the exposure light. And a light-shielding layer 14 formed on the shifter layer 13 to block the progress of exposure light.

The portion where the light-shielding layer 14 is formed constitutes a light-shielding portion S that does not allow exposure light to pass therethrough.
3 does not have a shifter and constitutes a light-transmitting portion Tn, and the light-shielding layer 14 does not exist but the shifter layer 1 does not exist.
The portion where 3 exists constitutes a light transmitting portion Ta having a shifter. In order to achieve the main function of the phase shift mask that the light transmitted through the light transmitting portions adjacent to each other cancel each other out, the light transmitting portion Tn having no shifter and the light transmitting portion Ta having the shifter are as follows. They are arranged alternately in the plane. The etching stopper layer 12 does not exist in the light transmitting portion Tn having no shifter.

Now, as shown in FIG.
Consider a case where the wafer 15 on which the wafers 6 are stacked is used as an exposure target and the wafer 15 is irradiated with exposure light through the phase shift mask 10. As the exposure light, a normal incident light L1 vertically incident on the light transmitting part Tn having no shifter and oblique incident lights L2 and L3 incident on the light transmitting part Tn from an oblique direction are considered. The light amplitude distribution of the vertically incident light L1 incident on the wafer 15 has a positive convex curve shape as indicated by Q1. On the other hand, the light amplitude distributions of the obliquely incident lights L2 and L3 have curves inverting phases as shown by Q2 and Q3, respectively, due to the transmission of the light through the shifter layer 13, and have negatively convex curves. Become.

Since the actual light intensity distribution on the wafer 15 is obtained by combining the above-mentioned Q1, Q2, and Q3, the distribution is in a state where both tails are canceled out as indicated by PO. However, in the present embodiment, since the etching stopper layer 12 does not exist in the translucent portion Tn having no shifter, the amplitude distribution Q1 of the normal incident light L1 transmitted therethrough does not exist.
Are generally higher as indicated by the symbol R. Although it depends on the material and thickness of the etching stopper layer 12, it is usually about 10 to 20% higher. As a result, even if the oblique incident light L2, L3 cancels out,
The upper light intensity distribution is always kept the same as the size of the exposure light width W1 on the mask 10. Therefore, the resolution performance of the pattern image formed on the wafer 15 can be maintained with high accuracy.

Further, in the shift mask 10 shown in FIG. 1, the shifter layer 13 exists under the light-shielding layer edge 14a, and the light-shielding layer edge 14a does not have an eaves shape. There is no contamination of the photomask 10.

(First Embodiment of Manufacturing Method of Phase Shift Mask) (1) As shown in FIG. 3, a coating 22 for forming an etching stopper layer, a coating 23 for forming a shifter layer, and a light shielding A layer forming film 24 and a first resist layer forming film 25 are sequentially and uniformly formed. As a specific method of forming each layer, a known thin film forming method can be applied. Each layer can be composed of, for example, the following materials.

Light shielding layer forming film 24: Cr (chromium) shifter layer forming film 23: SiO ₂ etching stopper layer forming film 22: Tantalum, alumina (Al ₂ O ₃ )

(2) Thereafter, the first resist layer forming film 25 is drawn, that is, subjected to pattern exposure to form a light-shielding layer resist pattern 25 '(FIG. 4). Then, the light-shielding layer forming film 24 exposed from the light-shielding layer resist pattern 25 'is etched to form a light-shielding layer 24' (FIG. 5). As the etching treatment in this case, for example, wet etching using a mixed solution of ceric ammonium nitrate and perchloric acid can be applied.

(3) Thereafter, the light-shielding layer resist pattern 25 'is peeled off (FIG. 6), and the second resist layer forming film 2 is removed.
6 (FIG. 7), and a second resist layer forming film 26 is drawn to form a resist pattern 2 for the shifter layer.
6 ′ is formed (FIG. 8). Then, the shifter layer forming film 2 exposed from the shifter layer resist pattern 26 '
3 is etched to form a shifter layer 23 '(FIG. 9). As the etching treatment in this case, so-called dry etching in which glow discharge is caused in a reduced-pressure atmosphere in which a reactive gas such as CF ₄ or C ₂ F ₆ is present and etching is performed by active radicals generated in plasma can be applied. .

(4) Thereafter, the etching stopper layer forming film 22 exposed from the shifter layer 23 'is etched to form an etching stopper layer 22', thereby exposing the transparent substrate 21 (FIG. 10). Finally, the resist pattern 26 'for the shifter layer is peeled off (FIG. 11). Thus, the target phase shift mask 10 is manufactured. The etching of the etching stopper layer forming film 22 is performed by using KOH or NaOH.
Wet etching with an aqueous solution of

(Second embodiment of manufacturing method of phase shift mask )
Example) The steps (1) to (3) in the first embodiment, that is, the series of steps shown in FIGS. 3 to 9 are performed to form the shifter layer 23 '(FIG. 9). Then, instead of the above-mentioned step (4), ie, the step of first etching the film 22 and then peeling off the resist pattern 26 ', the resist pattern 26' for the shifter layer is peeled off first (see FIG. 12), then shifter layer 2
Film 2 for forming etching stopper layer exposed from 3 '
2 to form an etching stopper layer 22 '.
To expose the transparent substrate 21 (FIG. 1).
1) Thus, a target phase shift mask 10 is manufactured.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to those embodiments and can be variously modified within the technical scope described in the claims.

[0025]

According to the phase shift mask of the present invention, since the etching stopper layer is not disposed in the light transmitting portion having no shifter, the amplitude distribution of the vertical irradiation light transmitted through the light transmitting portion is not provided. The overall level of becomes higher, even if there is oblique irradiation light that penetrates the shifter layer and enters the light-transmitting part, canceling both tails of vertical irradiation light,
The light intensity distribution on the exposure object is always kept the same as the size of the irradiation light width (W1) on the phase shift mask. As a result, the resolution performance of the pattern image formed on the exposure target can be maintained with high accuracy.

Moreover, in the phase shift mask shown in FIG. 1, since the shifter layer exists under the light-shielding layer edge and the light-shielding layer edge does not become eaves-like, the light-shielding layer is chipped off and contaminates the photomask. Nor.

According to the method for manufacturing a phase shift mask according to the second and third aspects, it is possible to reliably and easily manufacture a phase shift mask in which an etching stopper layer does not exist in a light-transmitting portion having no shifter. it can.

[0028]

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a main part of an embodiment of a phase shift mask according to the present invention.

FIG. 2 is a diagram schematically showing an operation state of the phase shift mask.

FIG. 3 is a cross-sectional view showing one step in an example of a method for manufacturing the phase shift mask, particularly a state in which respective layers are uniformly laminated.

FIG. 4 is a cross-sectional view showing a step in an example of a method for manufacturing the same phase shift mask, in particular, a state where a light-shielding layer resist pattern is formed.

FIG. 5 is a cross-sectional view showing a step in an example of a method for manufacturing the phase shift mask, in particular, a state in which a light shielding layer is formed by etching.

FIG. 6 is a cross-sectional view showing one step in an example of the method for manufacturing the phase shift mask, in particular, a state in which a resist pattern for a light-shielding layer is removed.

FIG. 7 is a cross-sectional view showing one step in an example of a method for manufacturing the phase shift mask, particularly a state in which a second resist layer forming film is formed.

FIG. 8 is a cross-sectional view showing one step in an example of a method for manufacturing the phase shift mask, particularly a state in which a resist pattern for a shifter layer is formed.

FIG. 9 is a cross-sectional view showing a step in an example of a method for manufacturing the phase shift mask, particularly a state in which a shifter layer is formed by etching.

FIG. 10 is a cross-sectional view showing a step in an example of the method for manufacturing the phase shift mask, particularly a state in which an etching stopper layer is formed by etching.

FIG. 11 is a cross-sectional view showing a main part of the completed phase shift mask.

FIG. 12 is a cross-sectional view showing a main part step in another example of the method for manufacturing a phase shift mask, in particular, a state in which a resist pattern for a shifter layer is peeled off.

FIG. 13 is a cross-sectional view showing a main part of an example of a conventional phase shift mask.

FIG. 14 is a diagram schematically showing an operation state of the conventional phase shift mask.

FIG. 15 is a cross-sectional view showing a main part of another example of the conventional phase shift mask.

FIG. 16 is a diagram schematically showing an operation state of the conventional phase shift mask.

[Explanation of symbols]

 Reference Signs List 10 phase shift mask 11 transparent substrate 12 etching stopper layer 13 shifter layer 13a sidewall of shifter layer 14 light-shielding layer 14a edge of light-shielding layer 15 wafer 16 photoresist

Claims (3)

(57) [Claims] 1. A lower shifter-type Levenson-type phase shift mask in which a shifter layer and a light-shielding layer are sequentially formed on a transparent substrate, wherein the lower shifter-type phase-shift mask has a light-shielding part, a light-transmitting part without a shifter, and a shifter. In a phase shift mask in which light transmitting portions are alternately arranged in a plane, a light shielding portion and a shifter are used.
Below the light-shielding layer edge at the boundary with the light-transmitting part without
A phase shift mask, wherein a shifter layer is present, and an etching stopper layer is provided between the shifter layer and the transparent substrate, and the etching stopper layer is not provided in a light-transmitting portion having no shifter. (A) A film for forming an etching stopper layer, a film for forming a shifter layer, a film for forming a light-shielding layer, and a film for forming a first resist layer are sequentially and uniformly formed on a transparent substrate. (B) drawing a first resist layer forming film to form a light-shielding layer resist pattern; (c)
(D) forming a light-shielding layer by etching the light-shielding layer forming film exposed from the light-shielding layer resist pattern;
Removing the resist pattern for the light shielding layer, (e) second step
A step of forming a resist layer forming film, (f) drawing a second resist layer forming film to form a shifter layer resist pattern, and (g) a shifter layer forming film exposed from the shifter layer resist pattern. (H) etching a coating film for forming an etching stopper layer exposed from the shifter layer to form an etching stopper layer, thereby exposing the transparent substrate, and (i) exposing the transparent substrate. 2. The method for manufacturing a phase shift mask according to claim 1, further comprising the step of sequentially removing the layer resist pattern. (A) A film for forming an etching stopper layer, a film for forming a shifter layer, a film for forming a light-shielding layer, and a film for forming a first resist layer are sequentially and uniformly formed on a transparent substrate. (B) drawing a first resist layer forming film to form a light-shielding layer resist pattern; (c)
(D) forming a light-shielding layer by etching the light-shielding layer forming film exposed from the light-shielding layer resist pattern;
Removing the resist pattern for the light shielding layer, (e) second step
A step of forming a resist layer forming film, (f) drawing a second resist layer forming film to form a shifter layer resist pattern, and (g) a shifter layer forming film exposed from the shifter layer resist pattern. To form a shifter layer by etching, (h) removing the resist pattern for the shifter layer, and (i) etching the film for forming an etching stopper layer exposed from the shifter layer to form an etching stopper layer. 2. The method according to claim 1, further comprising the step of exposing the transparent substrate.