KR100219570B1 - Half-tone phase shift mask and manufacturing method of the same - Google Patents

Abstract

A halftone phase shift mask having a high transmittance and easy to manufacture is disclosed. The present invention provides a halftone phase shift mask comprising a substrate transparent to exposure light, a phase shifter pattern formed on the transparent substrate, and a phase shift groove formed by etching the transparent substrate. In addition, the present invention provides a manufacturing method suitable for manufacturing the halftone phase shift mask.

The halftone phase shift mask according to the present invention has a higher transmittance and a uniform surface of the phase shift groove as compared with the conventional halftone phase shift mask. Therefore, a short wavelength can be used to form a fine pattern with excellent contrast.

Description

Halftone phase shift mask and manufacturing method of the same

The present invention relates to a phase inversion mask and a method of manufacturing the same, and more particularly, to a phase inversion mask suitable for forming a fine pattern and easy to manufacture.

As semiconductor devices have recently been highly integrated and their patterns become finer, it is difficult to form patterns having a line width below a predetermined limit with a conventional photo mask. Therefore, the research on the phase shift mask (PSM), which has a very high resolution of the implemented pattern and a smaller critical dimension (CD), is being actively conducted.

The phase shift mask includes a phase shifter that is not present in the conventional photo mask. In the method of forming a pattern using a phase shift mask, a phase shifter defining a pattern to be transferred onto a semiconductor substrate and an exposure light transmitted through a portion of the substrate on which the phase shifter is not formed are different from each other by 180 °. Therefore, they interfere with each other at the edges of the pattern to improve the contrast of the pattern.

Among phase shift masks, in particular, half tone phase shift masks are phase shifters using phase shift materials that are translucent at 30% or less for exposure to light and are capable of inverting the phase by 180 °. ). The reason why the phase shifter should be translucent with respect to the exposure light is that the pattern cannot be formed if the light transmitted through the phase shifter has an intensity enough to expose the photosensitive film. Representative examples of such halftone phase shift materials include MoSiON and Cr oxide. The halftone phase shift mask is easy to manufacture and can be effectively applied to the formation of contact holes having a pattern in which line-space is dense at high density and openings having a small size.

FIG. 1 shows a conventional halftone phase shifter mask with a MoSiON phase shifter 3 of thickness d1 on a transparent substrate 1.

The phase difference between the exposure light transmitted through the substrate 1 and the exposure light transmitted through the MoSiON halftone phase shifter 3 in the halftone phase shifter mask is expressed by Equation 1 below with respect to the MoSiON halftone phase shifter 3. The transmittance of the exposed light is determined by the following equation.

Φ = 2π (n-1) d1 / λ

T = exp (-4πkd1 / λ)

Where ΔΦ is the phase difference, n is the refractive index of the phase shifter, λ is the wavelength of the exposure light, d1 is the thickness of the MoSiON halftone phase shifter, and k is the attenuation constant of the exposure light.

However, when using 248 nm short wavelength ultraviolet light (DUV) or 193 nm ArF aximmer laser as the exposure light in a photolithography using a molybdenum halftone phase shift mask, the MoSiON half of which ΔΦ in Equation 1 becomes 180 ° At the thickness d1 of the tone phase shifter 3, it cannot have a k value that can transmit light 5% or more. The reason is that n and k values vary depending on the wavelength of light for each material, and the shorter the wavelength, the larger the value of k and the lower the transmittance. Therefore, the MoSiON halftone phase shift mask is half the effect of the phase shift when using a short wavelength light source.

In order to solve the problem of the decrease in transmittance, a modified halftone phase shift mask as shown in FIG. 2 is proposed.

Referring to FIG. 2, a chromium film pattern 13 for adjusting transmittance is formed on a transparent substrate 11. In addition, a phase shift groove 15 is formed by etching the substrate 11 to a depth D1 using the chromium film pattern 13 as an etching mask.

In the MoSiON halftone phase shift mask shown in Fig. 1, since the MoSiON halftone phase shifter has n and k values that can cause phase inversion while appropriately adjusting the transmittance, the halftone phase shift with the MoSiON halftone phase shifter layer alone. A mask can be formed. However, since the chromium film does not have n and k values that can cause the transmittance control and phase inversion together, the phase shift groove 15 formed by etching only the substrate 11 by controlling only the transmittance with the chromium film pattern 13. To reverse the phase. That is, the thickness of the chromium film pattern 13 is made as thin as possible to increase the transmittance, and the value of the phase inversion is maintained at 180 ° by adjusting the depth D1 of the phase shift groove 15. In this case, the substrate etching depth D1 can be easily obtained by inserting π into ΔΦ of Equation 1 by the etching depth D1 = λ / 2 (N-1) (where N is the refractive index of the substrate 11. )

For example, when a light source having a wavelength of 248 nm is used as the exposure light and the substrate 11 is formed of quartz, since the N value of the quartz is about 1.5, the etching depth D1 of the substrate is 2480 kV.

However, the halftone phase shift mask shown in Fig. 2 is advantageous for controlling transmittance. However, when the transparent substrate is etched to cause phase reversal, the etching depth is deep and the etching cannot be performed uniformly. Therefore, there is a problem that the surface of the phase shift groove 15 becomes uneven and the phase of transmitted light is unevenly reversed.

Accordingly, an object of the present invention is to provide a phase inversion mask that is suitable for fine pattern formation and easy to manufacture in order to solve the problems of the prior art described above.

Another object of the present invention is to provide a manufacturing method suitable for manufacturing the phase inversion mask.

In order to achieve the above object, the present invention is a substrate transparent to the exposure light;

A phase shifter pattern formed on the transparent substrate; And a phase shift groove formed by etching the transparent substrate.

In the present invention, the phase shifter pattern is formed to have a thickness d to have a transmittance T of 5 to 30% with respect to the exposed light, and the thickness d is determined by the following equation.

d = -λlnT / 4πk

(Where k is the attenuation constant of the exposure light by the phase shifter pattern, and λ is the wavelength of the exposure light).

The phase shifter pattern is preferably formed of any one selected from MoSiON, SiN _x , amorphous C, and CrF.

The phase shift groove is formed by etching to a depth D such that the phase difference ΔΦ between the exposure light passing through the phase shift groove and the exposure light passing through the phase shifter pattern is 180 °. (D) is determined by the following formula.

D = ｛λ / 2 (N-1)｝-｛2 (n-1) d / 2 (N-1)｝

Where N is the refractive index of the substrate, n is the refractive index of the phase shifter pattern, λ is the wavelength of the exposure light, and d is the thickness of the phase shifter pattern.

The light shielding film pattern may further include a light shielding film pattern on a predetermined region of the phase shifter pattern. The light shielding film pattern may have a transmittance of 5 to 30% with respect to the exposure light, and may be formed of any one selected from Cr, Al, and MoSi. desirable.

In order to achieve the above another object, the present invention comprises the steps of forming a phase shifter pattern on a substrate transparent to the exposure light; And etching the substrate to form a groove for phase shift by using the phase shifter pattern as an etch mask.

In order to achieve the above another object, the present invention also provides a method of forming a phase shifter film and a material film having a light blocking function on a substrate transparent to exposure light; Etching the material film and the phase shifter film to form a material film pattern and a phase shifter pattern;

Etching the substrate using the material layer pattern and the phase shifter pattern as an etch mask to form a phase shift groove; And patterning a material film pattern formed on the phase shifter pattern to form a light shielding film pattern.

In the method of manufacturing the halftone phase shift mask, the phase shifter pattern is formed of any one selected from MoSiON, SiN _x , amorphous C, and CrF, and has a transmittance T of 5 to 30% with respect to the exposed light. It is preferable that the thickness d be formed, and the thickness d is determined by the following equation.

d = -λlnT / 4πk

Where k is the attenuation constant of the exposed light and λ is the wavelength of the exposed light.

The phase shift groove is formed by etching to a depth D such that the phase difference ΔΦ between the exposure light passing through the phase shift groove and the exposure light passing through the phase shifter pattern is 180 °. D is determined by the following formula.

D = ｛λ / 2 (N-1)｝-｛2 (n-1) d / 2 (N-1)｝

Where N is the refractive index of the substrate, n is the refractive index of the phase shifter pattern, λ is the wavelength of the exposure light, and d is the thickness of the phase shifter pattern.

In addition, the light blocking material layer is preferably formed of any one selected from Cr, Al, and MoSi.

The phase inversion mask by this invention can fully transmittance | permeability compared with the conventional phase inversion mask. In addition, since the depth of the phase shift groove formed by etching the transparent substrate is not large, a groove having a uniform surface may be formed. Therefore, a short wavelength light source can be used to form a fine pattern with improved contrast.

1 is a cross-sectional view showing a conventional halftone phase shift mask in which a MoSiON halftone phase shifter is formed.

Fig. 2 is a sectional view showing a conventional halftone phase shift mask in which a chrome film pattern and a phase shift groove are formed.

3 is a cross-sectional view showing a halftone phase shift mask according to the first embodiment of the present invention.

4 is a cross-sectional view showing a halftone phase shift mask according to a second embodiment of the present invention.

5 to 7 are cross-sectional views illustrating a method of manufacturing the halftone phase shift mask shown in FIG.

8 to 12 are cross-sectional views illustrating a method of manufacturing the halftone phase shift mask shown in FIG.

Hereinafter, a halftone phase shift mask and a method of manufacturing the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Halftone phase shift mask

First embodiment

3 shows a halftone phase shift mask according to the first embodiment of the present invention. Referring to FIG. 3, a phase shifter 23A having a thickness d2 is formed on the transparent substrate 21. In addition, a phase shift groove 25 formed by etching the substrate 21 to a depth D2 is formed.

In the above halftone phase shift mask, the transmittance is adjusted by adjusting the thickness d2 of the phase shifter 23A, and the value of the phase inversion is adjusted to 90 ° to 270 ° by adjusting the depth D2 of the phase shift groove 25. More preferably, the value of the phase inversion is adjusted to 180 degrees.

In the present invention, the phase shifter 23A is preferably formed of any one selected from MoSiON, SiN _x , amorphous C, and CrF. The light transmittance of the phase shifter 23A is preferably 5 to 30%, more preferably 5 to 15%.

The values of the thickness d2 of the phase shifter 23A and the depth D2 of the phase shift groove 25 suitable for the present invention can be obtained as follows.

First, since the transmittance T1 and the thickness d1 of the conventional halftone phase shift mask phase shifter (3 in FIG. 1) are already known, the attenuation constant k of the light of the phase shifter is as follows.

k =-λlnT1 / 4πd1

The k value thus obtained and the transmittance T2 (T2 > T1) desired in the present invention are substituted into Equation 2 again to obtain the thickness d2 of the phase shifter 23A of the present invention as follows.

d2 = d1lnT2 / lnT1

Substituting d2 into Equation 1 shows the degree of phase inversion ΔΦ 1 caused by the phase shifter 23A.

ΔΦ1 = 2π (n-1) d2 / λ = 2π (n-1) d1lnT2 / lnT1λ

Since the transmittance was increased from T1 to T2, the thickness d2 of the phase shifter is reduced compared to the thickness d1 of the phase shifter which caused the phase inversion of the conventional 180 °. Therefore, the value ΔΦ 1 of phase inversion also decreases from 180 °. The substrate is etched to the etching depth D2 in order to adjust the value of this reduced phase inversion to 180 °. The etching depth D2 of the substrate is calculated by substituting the refractive index N of the substrate into Equation 1 as follows.

ΔΦ2 = (π-ΔΦ1) = 2π (N-1) D2 / λ

---> D2 = ｛λ / 2 (N-1)｝-｛2 (n-1) d2 / 2 (N-1)｝

The substrate etch depth D2 thus obtained is smaller by 2 (n-1) d2 / 2 (N-1) than the depth D1 (= λ / 2 (N-1)) etched in the conventional halftone phase inversion mask.

That is, if only the attenuation constant k or thickness d1 of light of the conventional phase shifter pattern made of the same material and the transmittance T1 for the exposed light are known, the halftone phase shift pattern having the desired transmittance T2 according to the present invention ( The thickness d2 of 23A) can be easily determined from Equation 3 below and the etching depth D2 of the substrate from Equation 4 below.

d2 = -λlnT2 / 4πk = d1lnT2 / lnT1

D2 = ｛λ / 2 (N-1)｝-｛2 (n-1) d2 / 2 (N-1)｝

Where d1 is the thickness of the conventional phase shifter pattern, d2 is the thickness of the phase shifter pattern of the present invention, T1 is the transmittance of the conventional phase shifter pattern, T2 is the transmittance of the phase shifter pattern of the present invention, and n is the phase of the present invention. The refractive index of the shifter pattern, N, is the refractive index of the substrate of the present invention, λ represents the wavelength of the exposure light.)

For example, in the half-tone phase shift mask for DUV currently used, the thickness of the MoSiON phase shifter pattern showing 5% transmittance is 1350 Hz. Therefore, if the thickness of the MoSiON phase shifter pattern suitable for forming a halftone phase shift mask having a transmittance of 8% and the etching depth of the substrate are calculated by Equations 3 and 4, the thickness of the phase shifter pattern is 1138 1, and the etching depth of the substrate is It is about 390Å.

The halftone phase shift mask formed through the above process has a high transmittance even for short wavelength exposure light such as a DUV light source of 248 nm. In addition, since the etching depth of the substrate is also lower than that of the conventional halftone phase inversion mask, the groove surface for phase shift can be uniformly formed. Therefore, when the photolithography process is performed using the halftone phase shift mask according to the present invention, the phase difference between the light passing through the shifter pattern and the light passing through the substrate on which the shifter pattern is not formed is uniformly 180 °. Offset interference may occur at the edge of the pattern to form a fine pattern with improved contrast.

Second embodiment

4 shows a halftone phase shift mask according to a second embodiment of the present invention. The same reference numerals as in Fig. 3 denote the same members, and reference numeral 27A denotes a light shielding film pattern.

The halftone phase shift mask according to the second embodiment further includes a light shielding film pattern 27A on a predetermined region of the phase shifter 23A and the halftone phase shift mask of the first embodiment shown in FIG. There is a difference. The reason why the light shielding film pattern 27A is further formed is as follows.

If only the phase shifter 23A is formed as shown in FIG. 3, a small amount of light passes through the phase shifter 23A. Therefore, when the photoresist corresponding to this portion has a step, irregular reflection occurs at that portion, and light may be focused on a specific portion of the photoresist, thereby causing the portion to be undesirably exposed.

In addition, when the halftone phase shift mask is relatively displaced with respect to the wafer to form a repeating pattern on the wafer, photoresist portions corresponding to edge portions of the halftone phase shift mask may overlap. Therefore, since the light transmitted through the edge portion of the halftone phase shift mask is repeatedly irradiated to the photoresist, there is a problem in that the photoresist that should not be exposed is exposed.

Therefore, the light shielding film pattern 27A is formed on the predetermined region on the phase shifter 23A to prevent the photoresist from being unnecessarily exposed.

The light shielding film pattern 27A may be formed of any one selected from chromium, aluminum, and MoSi so as to have a transmittance of 0 to 30% with respect to the light source.

The reason why the light shielding film pattern 27A does not need to be completely opaque is that only a small amount of light source passes through the phase shifter pattern 23A, and then passes through the light shielding film pattern 27A again, even though the light shielding film pattern 27A is not opaque. This is because light does not finally reach the photoresist.

Method for manufacturing halftone phase shift mask

5 to 7 are cross-sectional views illustrating a method of manufacturing the halftone phase shift mask shown in FIG.

Referring to FIG. 5, the phase shifter film 23 is formed on the transparent substrate 21 so as to have a thickness d2, and a photoresist pattern 24 is formed on the phase shifter film 23 to subsequently form a phase shifter pattern. Form.

The phase shifter layer 23 is preferably formed of any one selected from MoSiON, SiN _x , amorphous C, and CrF. In the thickness d2 of the phase shifter 23, the light transmittance is preferably 5 to 30%, more preferably 5 to 15%.

Next, as illustrated in FIG. 6, the phase shifter layer 23 is etched using the photoresist pattern 24 as an etching mask to form a phase shifter pattern 23A. Subsequently, the transparent substrate 21 is etched to a depth D2 using the photoresist pattern 24 and the phase shifter pattern 23A as an etch mask to form a phase shift groove 25.

Finally, as shown in FIG. 7, the photoresist pattern 24 is removed to complete a halftone phase shift mask with improved transmittance and uniformity of the exposure light.

8 to 12 are cross-sectional views illustrating a method of manufacturing the halftone phase shift mask shown in FIG. The same reference numerals as in Figs. 5 to 7 denote the same members.

Referring to FIG. 8, the phase shifter film 23 and the material film 27 are sequentially formed on the transparent substrate 21. Subsequently, a first photoresist pattern 29 is formed on the material layer 27.

The phase shifter layer 23 is preferably formed of any one selected from MoSiON, SiN _x , amorphous C, and CrF. The thickness d2 of the phase shifter film 23 is such that the light transmittance is 5 to 30%, more preferably 5 to 15%.

In addition, the material layer 27 is formed of any one selected from chromium, aluminum, and MoSi, and preferably has a transmittance of 0 to 30% with respect to the exposure light.

Referring to FIG. 9, the material layer 27 is patterned using the first photoresist pattern 29 as an etching mask to form a material layer pattern 27A, and then the first photoresist pattern 29 is formed. Remove it.

Next, as shown in FIG. 10, the phase shifter layer 23 is patterned by using the material layer pattern 27A as an etching mask to form a phase shifter pattern 23A. Then, the transparent substrate 21 is continuously formed. The depth D2 is etched to form the phase shift groove 25.

Subsequently, as shown in FIG. 11, a second photoresist pattern 31 defining a light shielding film pattern is formed on the material film pattern 27A.

Finally, using the second photoresist pattern 31 as an etching mask, the material layer pattern 27A is etched to form a light shielding pattern 27B having a light shielding function, and then the second photoresist pattern 31. Is removed to complete the halftone phase shift mask.

The present invention has been described above in detail by way of examples, but the present invention is not limited to the above embodiments, and it is apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention. .

The halftone phase shift mask formed by the present invention can easily adjust the thickness of the shifter to increase the transmittance of light passing through the shifter and form a phase shift groove having a uniform surface because the etching depth of the substrate is reduced. have. Therefore, when the halftone phase shift mask formed by the present invention is used, it is possible to perform a photolithography process using a short wavelength light source. In addition, accurate phase reversal effect can be achieved to form fine patterns with improved contrast.

Claims (16)

A substrate transparent to exposure light; A phase shifter pattern formed on the transparent substrate and having a thickness d to have a transmittance T of 5 to 30% with respect to the exposed light; And A phase shift groove formed by etching a substrate between the translucent phase shifter patterns so that a phase difference ΔΦ between the exposure light passing through the phase shift groove and the exposure light passing through the phase shifter pattern is 180 °. And a phase shift groove formed by etching to a depth (D). The halftone phase reversal mask according to claim 1, wherein the thickness d is determined by the following equation. d = -λlnT / 4πk (Where k is the attenuation constant of the exposure light by the phase shifter pattern, and λ is the wavelength of the exposure light). The halftone phase inversion mask of claim 1, wherein the phase shifter pattern is formed of any one selected from MoSiON, SiN _x , amorphous C, and CrF. The halftone phase inversion mask according to claim 1, wherein the depth (D) is determined by the following equation. D = ｛λ / 2 (N-1)｝-｛2 (n-1) d / 2 (N-1)｝ Where N is the refractive index of the substrate, n is the refractive index of the phase shifter pattern, λ is the wavelength of the exposure light, and d is the thickness of the phase shifter pattern. The halftone phase inversion mask of claim 1, further comprising a light shielding film pattern on a predetermined region of the phase shifter pattern. The halftone phase reversal mask of claim 5, wherein the light blocking film pattern has a transmittance of 5 to 30% with respect to the exposed light. The halftone phase reversal mask of claim 5, wherein the light shielding pattern is formed of any one selected from Cr, Al, and MoSi. Forming a phase shifter pattern on a substrate transparent to exposure light with a thickness (d) to have a transmittance (T) of 5-30% with respect to the exposure light; And Forming a phase shift groove by etching the substrate between the phase shifter patterns using the phase shifter pattern as an etch mask, the exposure light passing through the phase shift groove and the exposure light passing through the phase shifter pattern. And forming a phase shift groove by etching at a depth D such that the phase difference ΔΦ is 180 °. 10. The method of claim 8, wherein the thickness d is determined by the following formula. d = -λlnT / 4πk Where k is the attenuation constant of the exposed light and λ is the wavelength of the exposed light. The method of claim 8, wherein the phase shifter pattern is formed of any one selected from MoSiON, SiN _x , amorphous C, and CrF. 10. The method of claim 8, wherein the depth D is determined by the following equation. D = ｛λ / 2 (N-1)｝-｛2 (n-1) d / 2 (N-1)｝ Where N is the refractive index of the substrate, n is the refractive index of the phase shifter pattern, λ is the wavelength of the exposure light, and d is the thickness of the phase shifter pattern. Forming a phase shifter film on a substrate transparent to the exposure light with a thickness d having a transmittance T of 5 to 30% with respect to the exposure light; Forming a material film having a light blocking function on the phase shifter film; Etching the material film and the phase shifter film to form a material film pattern and a phase shifter pattern; Forming a phase shift groove by etching the substrate by using the material film pattern and the phase shifter pattern as an etch mask, and a phase difference between the exposure light passing through the phase shift groove and the exposure light passing through the phase shifter pattern ( Etching to a depth D such that ΔΦ is 180 ° to form a phase shift groove; And And patterning the material film pattern formed on the phase shifter pattern to form a light shielding film pattern. The method of claim 12, wherein the phase shifter layer is formed of any one selected from MoSiON, SiN _x , amorphous C, and CrF. The method of claim 12, wherein the light blocking material layer is formed of any one selected from Cr, Al, and MoSi. 13. The method of claim 12, wherein the thickness d is determined by the following equation. d = -λlnT / 4πk Where k is the attenuation constant of the exposed light and λ is the wavelength of the exposed light. The method of manufacturing a halftone phase inversion mask according to claim 12, wherein the depth D is determined by the following equation. D = ｛λ / 2 (N-1)｝-｛2 (n-1) d / 2 (N-1)｝ Where N is the refractive index of the substrate, n is the refractive index of the phase shifter pattern, λ is the wavelength of the exposure light, and d is the thickness of the phase shifter pattern.