JPH10123695A - Phase shift mask and its manufacture, manufacture of semiconductor device using this phase shift mask, and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently manufacture a multistage phase shift mask by forming a light shielding thin film pattern in a prescribed part of the boundary part between the non-phase shift area and phase shift area of a light permeable base, forming a transition part changed stepwise on the boundary part having no light shielding thin film pattern applied thereto by a plurality of etchings of different quantities. SOLUTION: In the first etching, an etching mask 11 is used, the width is set to once, with the step width of a transition part as unit, and the etching quantity is set to once with the height of one step as unit. In the second and third etchings, etching masks 12, 13 are used, respectively, the etching widths are set to 2 times and 4 times the unit width of the steps, and the etching quantities are also set to 2 times and 4 times the unit height of the steps. When such three etchings are repeated, a smooth stair-like transition part 4 having 8 steps (2<3> ). Namely, the etching mask can have 2<n> (n represents an integer exceeding 2) steps with the step width of the transition part as unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase shift mask which is a kind of photomask used as an original for forming a pattern in photolithography for transferring a fine circuit pattern in the manufacture of a semiconductor integrated circuit, and a method of manufacturing the same. is there. The present invention also relates to a method for manufacturing a semiconductor device in which a pattern is formed using a phase shift mask by optical lithography, and a semiconductor device manufactured by the method.

[0002]

2. Description of the Related Art In order to improve the functions and performance of semiconductor integrated circuits, high integration is being promoted. This high integration has been achieved by forming the same circuit in a smaller area by miniaturizing the pattern. In other words, it can be considered that the miniaturization of patterns has supported the semiconductor industry.

[0003] The formation of a fine pattern has been performed by a photolithography technique in which a photomask, which is an original of the pattern, is reduced in size or reduced in size and transferred to a semiconductor substrate in the process of forming an integrated circuit. Generally, the resolution dimension L of a pattern in photolithography is L = kl × λ /
It is known to be given in NA. Here, λ is the exposure wavelength, NA is the numerical aperture of the projection optical system, and kl is a constant determined by the process and usually takes a value of about 0.5. That is, to form a fine pattern, it is effective to reduce the exposure wavelength λ and increase the numerical aperture NA.

For this reason, in order to form a finer pattern by photolithography, the exposure wavelength has been shortened. At present, Kr having a wavelength of 248 nm is used.
Lithography technology using an F excimer laser as a light source is being put to practical use. On the other hand, DOF in the transfer
Is generally given by DOF = k2 × λ / NA ² , and the depth of focus DOF becomes smaller as the wavelength becomes shorter. As described above, in addition to the improvement of the resolution by shortening the wavelength, the resolution is further improved and the DOF is improved.
There is a demand for improved photolithography technology.

As a means for improving the performance of the photolithography technique, a so-called super-resolution technique is considered promising, and a modified illumination technique and a phase shift exposure technique are typical examples. Above all, an exposure technique using a so-called Levenson phase shift mask is considered to be the most promising, because it can significantly improve the resolution and the DOF. The Levenson phase shift mask is a photomask that modulates the phases of the transmitted lights of adjacent light-shielding film openings so that the phases are opposite to each other.

The improvement of characteristics in exposure by the Levenson phase shift mask will be described with reference to the drawings. First, formation of an image in transfer using a conventional mask will be described. FIG. 21 shows how illumination light is modulated by a conventional photomask. FIG. 21A shows a cross-sectional structure of a conventional photomask 200, in which 201 indicates a light-shielding film pattern, and 202 indicates a light-shielding film opening pattern. FIG.
1 (b) shows the electric field amplitude immediately after the light shielding film. As shown in these figures, the electric field immediately after the opening of one light shielding film of the photomask is modulated by the opening. The electric field is similarly modulated by the adjacent openings.

FIG. 22 shows an electric field of a projected image on a semiconductor wafer on which a transfer pattern of the photomask of FIG. 21 is formed. FIG. 22A shows the electric field amplitude on the wafer, 204 denotes the electric field due to each aperture, and 205 denotes the combined electric field. FIG. 22B shows the electric field strength on the wafer. Since the numerical aperture NA of the image forming system is less than 1, spatially minutely changing components are removed from the modulation information immediately after the photomask, and an electric field having a gradual change is formed.
The electric field modulated by adjacent openings also has a gradual fluctuation. The resulting electric field has considerable strength between adjacent openings, and the two openings are not separated.

FIG. 23 shows how illumination light is modulated by a Levenson phase shift mask. FIG.
3 (a) shows a cross-sectional structure of the Levenson phase shift mask 300, where 301 is a light-shielding film pattern, 302 is a light-shielding film opening pattern that has not undergone phase shift processing, and 303 is a light-shielding film opening pattern that has undergone phase shift processing. . FIG.
(B) shows the electric field amplitude immediately after the light shielding film. As shown in these figures, the modulation of the electric field by one light-shielding film opening is the same as that by the conventional mask, but the electric field modulated by the adjacent openings has a phase inverted by the action of the Levenson phase shift mask. Becomes

FIG. 24 shows an electric field of a projected image of the Levenson phase shift mask on a semiconductor wafer on which a transfer pattern is formed by the Levenson phase shift mask of FIG. FIG. 24A shows the electric field amplitude on the wafer, 304 denotes the electric field due to each aperture, and 305 denotes the combined electric field. Since the image of one light-shielding film aperture is formed by an optical system having the same numerical aperture NA as that of the conventional mask, the image has a gradual fluctuation similarly to that of the conventional mask. FIG.
(B) shows the electric field strength above the way. Unlike those of conventional masks, the phases of adjacent openings are inverted,
The electric fields between the openings cancel each other out, and the two openings are formed separately. That is, it is possible to form a high-resolution image as compared with an image formed by a conventional mask.

As described above, the exposure using the Levenson phase shift mask can improve the resolution,
An ordinary Levenson phase shift mask has the following disadvantages because it is configured to give one of two phases of 0 ° or 180 ° to the opening of the light shielding film.
That is, when forming a dark pattern including fine dark lines,
This dark pattern is always formed in an annular shape and cannot be formed as an open line. In other words, a dark pattern can only be formed as a multiple-connected region that always includes one or more short-connected bright regions.

This will be described with reference to the drawings. FIG. 25-
FIG. 28 is a view showing a conventional Levenson phase shift mask having two types of phases in which a phase shifter is formed by etching a quartz substrate, and FIGS. 29 to 31 are fine dark line patterns by the Levenson phase shift mask. FIG. FIG. 25 shows a conventional phase shift mask 40.
FIG. 26 is a plan view of the phase shift mask 400. FIG. 27 is a sectional view of the phase shift mask taken along line AA shown in FIG. FIG. 28 is a sectional view of the phase shift mask taken along line BB shown in FIG.

In forming the fine dark line pattern, the quartz substrate 4
The light-shielding film pattern 405 for forming a dark line formed in No. 01 is formed so as to be sandwiched between two light-shielding film opening patterns 402 and 403 in which the phases of transmitted light are opposite to each other. Required by principle. At this time, as long as the dark line does not connect two points on the boundary that defines the entire area where the mask is formed, that is, unless it is a line connecting the ends of the mask, the two light-shielding film opening patterns At least one of 402 and 403 needs to be a closed figure. The light-shielding film openings 403 subjected to the shifter processing in FIGS. 25 to 28 are formed as the closed figures. In FIG. 25, the light-shielding film opening 402 that has not been subjected to the shifter processing is formed so as to surround the light-shielding film opening 403 that has been subjected to the shifter processing. A light-shielding film pattern 405 corresponding to a required dark line is formed between the two types of light-shielding film opening patterns 402 and 403.

FIG. 29 and FIG. 30 show how the phase shift mask is transmitted when illumination light is applied vertically. FIG. 29A shows a cross section of a portion of the light-shielding film 405 for forming a dark line of the phase shift mask. The intensity of light passing through this cross-section is, as shown in FIG.
To produce dark lines. FIG. 30A shows a cross section at the boundary of the phase shift region of the phase shift mask. The intensity of light passing through this cross section results in a dark line portion as shown in FIG. 30B.

FIG. 31 shows a resist pattern formed on the positive resist on the wafer by the phase shift mask 400. A dark line image is formed in the portion corresponding to the light-shielding film pattern 405 by the light-shielding film pattern, and the positive resist is not dissolved by development, so that the resist pattern 406 is formed. The required pattern is this 40
6, even at the boundary between the light-shielding film opening pattern 402 and the light-shielding film opening pattern 403 where the light-shielding film pattern 405 does not exist, the phase of the transmitted light is inverted across the boundary. An image is formed, and a resist pattern 407 is formed on the wafer. That is,
An open linear pattern is not formed and unnecessary pattern 4
A closed pattern including the pattern 07 is formed.

For this reason, it is impossible to use a positive resist for forming a wiring pattern which generally needs to form an open line, and the resolution is generally inferior to that of a positive resist. However, it is necessary to use a negative resist, and there is an inconvenience that sufficient resolution cannot be obtained.

[0016]

As a method for compensating for such a disadvantage of the prior art, there is a method in which one light-shielding film opening is provided.
By changing the phase of the transmitted light substantially continuously, the phase difference of the transmitted light between the light-shielding film openings on both sides of the linear light-shielding film pattern is 180 °, and the linear light-shielding is performed. A method has been proposed in which the entire region surrounding the film pattern is a bright region. (An example of this method is Pro
c. SPIE 2440 p515. In this example, in order to change the phase of the transmitted light substantially continuously inside one light-shielding film opening, 0 °, 4 °
By forming a portion having a phase difference of 5 gradations of 5 °, 90 °, 135 °, and 180 ° in the same light-shielding film opening, a dark line image is generated due to the adjacency between the 0 ° portion and the 180 ° portion. Have been around. However, in this example, the resist pattern forming step and the etching step are performed four times each in order to form the substantially continuous phase change portion. In such a method, a mask having n + 1 phase gradation is required. Is
Each of them requires a resist pattern forming process and an etching process n times, requires many drawing and etching processes, and has a drawback that the production cost increases and the yield decreases.

The present invention has been made in order to solve such a conventional drawback, and the number of phase shift masks of multi-phase gradation in which the phase changes substantially continuously is dramatically reduced as compared with the conventional one. An object of the present invention is to provide a method of manufacturing a phase shift mask realized by the number of times of resist patterning and etching, and a multi-phase gradation phase shift mask manufactured by the manufacturing method.

[0018]

According to a method of manufacturing a phase shift mask of the present invention, light is shielded at a predetermined portion of a boundary between a non-phase shift area where a phase shift does not occur and a phase shift area where a phase shift occurs where a phase shift occurs. Forming a conductive thin film pattern and, at the boundary where the light-shielding thin film pattern is not applied, using a different etching mask pattern having an opening portion and a non-opening portion for n times (n is a predetermined number exceeding 2) (Integral) etching to form a transition portion in which the etching depth changes stepwise into 2 n -th power types.

In the method for manufacturing a phase shift mask according to the present invention, the light-shielding thin film formed on the light-transmitting substrate is patterned to form the light-shielding thin film pattern, and then the phase shift region and the transition portion are formed. It is characterized by having done.

In the method of manufacturing a phase shift mask according to the present invention, after forming the phase shift region and the transition portion,
The light shielding film pattern is formed.

According to a method of manufacturing a phase shift mask of the present invention, the etching mask is formed by using a material having a light-shielding property and a conductive property, and is coated with an electron beam resist and patterned by electron beam exposure. It is a feature.

In the method of manufacturing a phase shift mask according to the present invention, the light transmitting substrate is etched by wet etching, and the etching mask is formed of a material having corrosion resistance to a chemical used for the wet etching. It is assumed that.

In the method of manufacturing a phase shift mask according to the present invention, the etching mask in the wet etching is formed of an amorphous silicon thin film doped with phosphorus or boron, and a chemical containing at least hydrogen fluoride is used in the wet etching. It is characterized by the following.

The method of manufacturing a phase shift mask according to the present invention is characterized in that the etching mask pattern is formed of a resist for dry etching of a light transmitting substrate.

In the method for manufacturing a phase shift mask according to the present invention, the etching amount of the n-th etching may be any one of unit powers of 2 to the power of (m-1), where m is a natural number of n or less. It is characterized by being.

In the method of manufacturing a phase shift mask according to the present invention, the etching amount of the m-th etching of the n-th etching is unit power of 2 (m-1), where m is a natural number of n or less. It is characterized by the following.

In the method of manufacturing a phase shift mask according to the present invention, the mask pattern of the etching mask of the n-th etching includes an elongated rectangle, and the smaller width of the elongated rectangle is such that m is equal to or less than n. As a natural number of
It is one of the unit width and the power of 2 (m-1).

In the method of manufacturing a phase shift mask according to the present invention, the mask pattern of the etching mask of the m-th etching of the n-times etching includes a long rectangle, and the width of the small side of the long rectangle is m less than or equal to n or less. Is a unit width of 2 to the power of (m-1) as a natural number.

[0029] The phase shift mask of the present invention is characterized in that it is manufactured by the method of manufacturing each of the phase shift masks. Further, a method of manufacturing a semiconductor device according to the present invention is characterized in that a pattern is transferred to a photo resist film or the like using a phase shift mask manufactured by any one of the manufacturing methods described above. Further, a semiconductor device according to the present invention is manufactured by transferring a pattern to a photo resist film or the like using a phase shift mask formed by any one of the above manufacturing methods.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. 1 to 6 are views for explaining a phase shift mask manufactured according to the present invention as an embodiment of the present invention. FIG. 1 is a perspective view of a phase shift mask 100 manufactured according to the present invention, FIG. 2 is a plan view thereof, FIG. 3 is a sectional view thereof, and FIG.
FIG. 3B is a cross-sectional view taken along a line BB in FIG. 2. 4 and 5 are views for explaining the operation of the phase shift mask, and FIG. 6 is a view showing a modification of the phase shift mask.

1 to 3, reference numeral 1 denotes a quartz plate as a substrate of the phase shift mask 100, and 2 denotes a surface serving as a reference for a phase shift with respect to perpendicularly transmitted light. Face. This is a region that is not covered with the light-shielding film and has an opening in the light-shielding film. Reference numeral 3 denotes a phase shift surface or a phase shift region, which is formed as a concave portion so that transmitted light of this region causes a phase shift with respect to transmitted light of the reference surface 2. That is, the thickness in the transmission direction of the transmitted light is thin in this region. This region is also a region where no light-shielding film is formed and the light-shielding film is open. Reference numeral 4 denotes a transition region between a reference plane where no phase shift occurs and a phase shift plane 3 where two phase shifts occur. The transition area 4 is formed such that its thickness changes stepwise from the reference plane 2 to the phase shift plane 3. Have been. Reference numeral 5 denotes a light-shielding film pattern formed at a boundary between a reference plane (non-phase shift area) 2 where no phase shift occurs and a phase shift plane (phase shift area) 3 where a phase shift occurs. This light-shielding film pattern 5 is made of, for example, chrome (C
r) A film is formed. In this example, the shape of the light-shielding film pattern 5 is a line pattern for forming a fine dark line.

As described above, in forming a fine dark line pattern,
The light-shielding film pattern 5 for forming a dark line includes two light-shielding film opening patterns 2 in which the phases of transmitted light are opposite to each other.
3 are formed. The light-shielding film opening 3 subjected to the shifter processing is formed as a closed figure. The light-shielding film opening 2 that has not been subjected to the shifter processing is formed so as to surround the light-shielding film opening 3 that has been subjected to the shifter processing. The light-shielding film pattern 5 corresponding to the required dark line is 2
The light shielding film is formed between the opening patterns 2 and 3 of the light shielding film.

As described above, the phase shift of the transmitted light between the reference plane 2 and the phase shift plane 3 is formed so as to be the opposite phase, that is, 180 °. This is set according to the wavelength of the transmitted light. For example, when using the i-line (365 nm),
The phase shift surface 3 is formed at a depth of about 4,325 °.

The light-shielding mask 5 is used, for example, when forming a dark line of a level of 1 μm or less using this mask.
Its width is formed to about 1 μm. The width of the transition region between the reference plane 2 and the phase shift plane 3 is set so that the transmitted light on both sides does not interfere with each other.

FIG. 4 and FIG. 5 show how light is transmitted when illumination light is applied vertically to such a phase shift mask. FIG. 4A shows a cross section of a portion of the light-shielding film 5 for forming a dark line of the phase shift mask. The intensity of light passing through this cross-section is, as shown in FIG. Part. FIG. 5A shows a cross section of a transition region portion of the phase shift mask. The intensity of light passing through this cross section does not produce a dark line portion as shown in FIG. 5B.

FIG. 6 shows a pattern of transmitted light by the phase shift mask 100 shown in FIGS. Only the dark lines 6 formed by the light shielding mask 5 are formed. The broken line 7 indicates the position of an unnecessary dark line formed by the conventional phase shift mask, but is not formed by the phase shift mask of the present invention.

FIG. 7 shows a modification of the light shielding film 5. This is because the transition section 4 is located all around the boundary between the reference plane 2 and the phase shift plane 3.
Is formed, and a light shielding film 5 is formed on a part thereof. From the viewpoint of the light shielding function, the light shielding film 5 may be deformed in this way or another shape as long as the required planar shape is maintained.

Embodiment 2 8 to 12 show a manufacturing process of a phase shift mask for i-line exposure as another embodiment of the present invention. First, as shown in FIG. 8, chrome (C
r) A photomask blank 10 having a film 8 formed thereon and an electron beam (EB) resist film 9 formed thereon is prepared. Next, referring to FIG. 9, with respect to the photomask blank 10 of FIG. 8, a portion of the electron beam resist film 9 corresponding to the region A where the chrome film 8 is etched away is removed by an electron beam drawing technique. Next, the electron beam resist film is patterned. Next, using the pattern of the electron beam resist film 9 as a mask, the chrome film 8 is used.
Is etched, and thereafter, the electron beam resist film 9 is peeled off, and the pattern of the chrome film 8 is inspected and corrected.

Next, referring to FIG. 10, with respect to the intermediate mask body of FIG. 9 formed in this way, an electron beam resist film 9 is applied to the entire surface, and a region B to be etched by the first quartz substrate etching is applied. EB writing is performed so as to remove the portion of the electron beam resist film 9 corresponding to
The substrate quartz 1 is dry-etched by 270 ° by reactive ion etching (RIE) using HF ₃ / CO / Ar gas, and then the electron beam resist film 9 is peeled off.

Referring now to FIG. 11, an electron beam resist film 9 is applied to the entire surface of the intermediate mask shown in FIG. 10, and corresponds to the region C to be removed by the second quartz substrate etching. The pattern of the electron beam resist film 9 is formed by EB drawing, and the substrate quartz 1 is etched by 540 °. Further, as a third quartz substrate etching, a similar process is performed to etch the substrate quartz 1 by 1,081 °. Further, the same process is performed as the fourth quartz substrate etching, and the substrate quartz 1 is etched by 2,163 °. (According to the wavelength of the transmitted light, the amount of etching is slightly adjusted to make the maximum amount of etching 4325 °.)

For example, a portion etched by all four etchings is etched by about 4,325 °, and is irradiated with i-line (365 nm) with respect to light transmitted through a Cr opening where etching is not performed. Works as a shifter with a 180 ° phase difference.

By performing the resist patterning four times and etching the quartz substrate 1 as described above, the transition portion 4 including the unetched portion has a phase of 16 gradations (that is, 2 to the fourth power). It is possible to form a phase shift mask having a gradation. FIG. 12 shows a cross section of the phase shift mask thus formed. The chrome film 8 of FIG. 11 is left as the light shielding film pattern 5. A transition portion 4 between the non-phase shift region 2 and the phase shift region 3 is formed on that side, and operates so as to modulate the optical path length in the light transmission direction in multiple steps in a plane orthogonal to the light transmission direction. Are manufactured. Further, according to this manufacturing method, a phase shift mask 100 having a multi-stage structure, which is a characteristic when manufactured by this manufacturing method, can be obtained.

The method of manufacturing the phase shift mask according to this embodiment described above can be summarized as follows. That is, a photomask blank including a light transmitting substrate and a light shielding thin film formed on one main surface of the light transmitting substrate is prepared as a material. Next, the light-shielding thin film is etched to form a necessary light-shielding film pattern. next,
At least two steps of processing the light-transmitting substrate located in a predetermined region (phase shift region) of the opening (region from which the light-shielding thin film is removed) formed in the light-shielding thin film by etching.
N or more times. The etching mask pattern and the etching amount in each of the n etching steps are different from each other, and the light-transmitting substrate is formed so as to have a maximum of 2 n etching depths by the n etching steps. To process.

In the examples shown in FIGS. 8 to 12, the portion to be the light-shielding film pattern 5 in the completed phase shift mask 100 is formed by first patterning the chrome film 8. However, the light-shielding film pattern 5 may be formed as the last step after the etching of the quartz substrate 1 is completed. In FIG. 7, after forming the phase shift region 3 and the transition region 4 on the quartz substrate 1, a light shielding film pattern 5 is formed on a part of the transition region.

Embodiment 3 13 to 16 show a method of manufacturing a phase shift mask according to another embodiment of the present invention. First, as shown in FIG. 13, a chrome (Cr) film 8 used as an etching mask for the quartz substrate 1 is formed on the quartz substrate 1. As described above, a film having a light-shielding property and a conductive property is used as an etching mask in this manufacturing method. Next, an electron beam resist film 9 is formed thereon. Next, the electron beam (E
B) The electron beam resist film 9 is patterned by a drawing technique so as to remove a portion of the electron beam resist film 9 corresponding to the region A where the chrome film 8 is removed by etching. Next, the chrome film 8 is etched using the pattern of the electron beam resist film 9 as a mask. next,
The electron beam resist film 9 is removed, a defect inspection of the patterned chrome film 8 is performed, and a defect is corrected if necessary.

Next, referring to FIG.
The quartz substrate 1 is wet-etched to a predetermined depth by the above pattern. Thereafter, the chrome film 8 is removed.

Next, referring to FIG. 15, a chrome film 8 is formed again on the entire surface of the quartz substrate 1. Next, an electron beam resist film 9 is formed on the entire surface. Next, the electron beam resist film 9 is patterned by an electron beam drawing technique so as to remove a portion of the electron beam resist film 9 corresponding to the region B where the chromium film 8 is removed by etching. Next, the chrome film 8 is etched using the pattern of the electron beam resist film 9 as a mask. next,
The electron beam resist film 9 is removed, a defect inspection of the patterned chrome film 8 is performed, and a defect is corrected if necessary.

Next, referring to FIG. 16, the region B of the quartz substrate 1 is wet-etched to a predetermined depth by the pattern of the chrome film 8. Thereafter, the chrome film 8 is removed. By repeating the above etching process, a predetermined etching is performed on a predetermined region of the quartz substrate as in the second embodiment to form a phase shift mask.

The use of a material having conductivity and light-shielding properties as a mask for etching the quartz substrate 1 has already been described. The reason why the conductivity is necessary is to prevent the electron beam resist from being charged when the electron beam resist is patterned by electron beam exposure. The light-shielding property is required in order to inspect the patterned mask for defects such as pinholes by light irradiation. Materials satisfying such a need and suitable as an etching mask are:
There is silicon doped with impurities outside of chrome. In addition, wet etching is performed using hydrofluoric acid or the like.

The repetition steps are as follows. First, a chromium film 8 (a mask for etching quartz) is formed on the quartz substrate 1, and an electron beam resist film 9 is formed thereon. Is formed. Next, the chromium film 8 is formed by the pattern of the electron beam resist film 9.
Is patterned by etching. After that, the electron beam resist film 9 is removed, and the pattern inspection of the chrome film 8 is inspected and corrected. Thereafter, the quartz substrate 1 is etched using the pattern of the chrome film 8 as a mask. After that, the pattern of the chrome film 8 is removed. This step is repeated.

In this case, the light-shielding film pattern 5 in the phase shift mask 100 after the etching of the quartz substrate 1 is completed.
There are both a method in which the quartz substrate 1 is formed before the etching is started and a method in which the quartz substrate 1 is formed after the etching of the quartz substrate 1 is completed. In FIG. 7, after forming the phase shift region 3 and the transition region 4 on the quartz substrate 1, a light shielding film pattern 5 is formed on a part of the transition region.

The method of manufacturing the phase shift mask of this embodiment described above can be summarized as follows. That is, the step of processing the light-transmitting substrate by etching using the light-transmitting substrate as a material includes at least two steps.
N or more times. The etching mask pattern and the etching amount in each of the n etching steps are different from each other, and the light-transmitting substrate is formed so as to have a maximum of 2 n types of etching depths by the n etching steps. Process. Thereafter, a light-shielding thin film is formed on the light-transmitting substrate and is patterned.

Further, each of the n times of etching of the transparent substrate is performed by wet etching, and the etching mask of each of the n times of etching has corrosion resistance to a chemical solution used for wet etching. It is formed of a material having conductivity and light shielding properties.

Further, the etching mask in the above wet etching is formed of an amorphous silicon thin film doped with phosphorus or boron, and a chemical containing at least hydrogen fluoride is used for the wet etching.

Embodiment 4 17 and 18 are views for explaining a method of manufacturing a phase shift mask according to another embodiment of the present invention. These figures show the concept of the pattern arrangement of the etching mask pattern when a smooth transition is formed at the boundary between the phase shift region and the non-phase shift region in the phase shift mask, and the phase shift formed by this etching mask. It is the top view and sectional drawing which show the structure of the transition part of a shift mask. 17A is a plan view of the quartz substrate 1 and FIG.
Is a partial plan view of a plurality of etching masks 11 to 13. FIG. (C) is a diagram showing a relationship between the etching masks 11 to 13 and binary numbers. Also, in FIG.
(A) is a cross-sectional view of the quartz substrate 1, which shows an AA cross section in (A) of FIG. FIG. 18B is a cross-sectional view of the plurality of etching masks 11 to 13 and corresponds to the etching mask of FIG. (C) is a diagram showing a relationship between the etching masks 11 to 13 and binary numbers.

Referring to FIGS. 17 and 18, the etching process will be described. First, the etching mask 11 in FIGS. 17 and 18 is used for the first etching of the quartz substrate 1 serving as a phase shift mask. In this mask, the opening 11a and the non-opening 11b are alternately, that is, striped in a width that is one time (that is, 2 to the power of 0) in units of the width of the step at the transition part of the phase shift mask. Are arranged. The first etching amount using this mask is set to one time (that is, 2 to the power of 0) in units of the height (step) of one step of the phase shift mask.

Next, the second etching of the quartz substrate 1 is performed by using the etching mask 12 shown in FIGS.
Is used. In this mask, the etching opening portions 12a and the non-opening portions 12b are alternately arranged in a width twice (ie, a power of 2) twice a unit of the width of the step of the transition portion of the phase shift mask. . The amount of the second etching using this mask is set to twice (that is, 2 to the power of 2) a unit of the height (step) of one step of the phase shift mask.

Next, the third etching of the quartz substrate 1 is performed by using the etching mask 13 shown in FIGS.
Is used. In this mask, the etching openings 13a and the non-openings 13b are alternately arranged in a width of four times (ie, twice the square of two) a unit of the width of the step of the transition portion of the phase shift mask. . The third etching amount using this mask is one step of the transition part of the phase shift mask.
The height of the step (step) as a unit, four times that (ie,
2 times the power of 2).

When etching of the quartz substrate 1 is repeated three times in this manner, the result of the etching is as shown in FIG.
As shown in the cross-sectional view of FIG.
A step-like transition portion 4 of (2 to the third power stage) is obtained. That is, a multi-stage phase shift mask is formed in which the optical path length in the light transmission direction has multiple modulation gradations in a plane orthogonal to the light transmission direction.

The above is generalized as follows. That is, the etching mask has a width (W × 2) times (n−1) times the unit of the step width of the transition portion of the completed phase shift mask (the width is defined as W).
^n-1 ) The openings and non-openings are arranged in stripes. Here, n is an integer starting from 1, and an etching mask is formed for each integer. Where n is stopped depends on the number of steps of the completed phase shift mask. The number of steps can be as high as 2 n.

Next, considering the etching amount,
The etching amount is defined as the unit of the step of the transition portion of the completed phase shift mask (the step is defined as H), and the depth (H × 2) times (n × 1) times of each etching.
^2n-1 ) is removed by etching. Here, it is assumed that the integer as n matches the integer as n in the above etching mask. In this manner, a multi-stage phase shift mask having a transition portion having a phase gradation of 2 ⁿ (2 ⁿ ) can be manufactured by n times of etching. For example, in the case of a phase shift mask having a phase of eight gradations, seven etchings are required in the conventional method, but three etchings are possible in the present method.

The order of the use of the etching mask, that is, the order of the magnitude of the etching amount is such that the integer n is 1
It is effective to start from and increase sequentially.
However, this order is not so limited, and even if etching is performed in a different order, the same phase shift mask can theoretically be formed as a result. However, the position of the mask needs to be aligned at the ends.

Next, the above description will be described with reference to the binary numbers shown in FIGS. 17C and 18C. The binary numbers in FIGS. 17C and 18C are
Each step width of the transition section 4 of the phase shift mask corresponds to a step having a small etching amount and a step having a large etching amount. This binary number corresponds to the etching amount of the stairs in units of one step of the stairs. Also, the stairs in which the numeral 1 stands in the first digit of the binary number indicates that the etching is performed in the first etching. Also, the stairs where the number 1 stands in the second digit of this binary number,
This indicates that etching is performed in the second etching. Similarly, the step in which the number 1 stands in the third digit of the binary number indicates that the step is etched by the third etching.

In other words, for each step width of the transition portion of the phase shift mask to be completed, a binary number that monotonically increases from the shallower etching to the deeper etching is set, and the number 1 is set at the nth digit. In this case, an etching mask having an opening in the portion is used, and the depth of the power of 2 (n-1) is removed by etching in steps of steps. If the same operation is performed for each digit of the placed binary number, a phase shift mask in which the etching depth is gradually increased can be formed. The width of the step and the size of the step of the phase shift mask are determined by the wavelength of the light beam to be used and the pattern of the line to be formed using the phase mask.

The phase shift mask shown in FIGS. 1 to 3 described earlier is a diagram showing a multi-stage phase shift mask obtained by the manufacturing method described above. According to such a manufacturing method, as shown in FIGS. 1 to 3, a phase shift mask in which a transition portion transitioning from a 0 ° transmission portion to a 180 ° transmission portion is formed in a fine step shape is obtained. For this reason,
For example, there is no abrupt change from 0 ° to 180 ° when a normal two-phase mask is formed, and as a result of such a change, there is no dark pattern formed in the transfer pattern, and isolated wiring is positive. It can be formed with a resist.

This will be described with reference to the drawings. When a thin wiring pattern is formed using the phase shift mask of the present invention as shown in FIGS. 1 to 3, only a necessary line pattern 6 is formed as shown in FIG. In addition, the unnecessary line pattern 7 which has occurred in the past is eliminated, and there is no practically problematic influence. In order to realize this, seven etchings were required in the conventional method to manufacture a phase shift mask having eight gradations, but in the present method, three etchings were required.
Substantial process shortening is possible.

The method of manufacturing the phase shift mask according to this embodiment described above can be summarized as follows. That is, in the present invention, the step of processing the light-transmitting substrate by etching is provided at least n times, that is, at least two times, and the etching mask pattern and the etching amount in each of the n etching steps are different from each other. Yes, up to 2 with n etching steps
The light transmissive substrate is processed so as to have an etching depth of n-th power. As described above, in this embodiment, the etching amount of the n-th arbitrary etching is a unit amount of 2 to the power of (m-1), where m is a natural number of n or less. To be one of

Further, the etching amount of the m-th etching of the n-th etching is set to 2 (m-1) to the unit amount, where m is a natural number of n or less.

Also, in this embodiment, the mask pattern of the etching mask of the n-th arbitrary etching includes an elongated rectangle, and the smaller width of the elongated rectangle is such that m is n or less. As a natural number, the unit width is set to any one of 2 to the power of (m-1).

Further, in this embodiment, the mask pattern of the etching mask of the m-th etching of the n-th etching includes a long rectangle, and the width of the small side of the long rectangle is smaller than or equal to n or less. As a natural number, the unit width is set to 2 (m−1) power.

Embodiment 5 FIG. Next, a method for manufacturing a semiconductor device using the phase shift mask of the present invention will be described. The phase shift mask of the present invention is used at various stages in a semiconductor device manufacturing process using an optical lithography technique. For example, in general, in a photolithography process, a photo resist film is formed on a semiconductor substrate, and thereby a base film such as a conductive film or an insulating film is etched to form a pattern.

FIG. 19 is a view showing a method of exposing a mask pattern on a resist film on a semiconductor wafer using the phase shift mask of the present invention. Referring to FIG.
The exposure by the photolithography technique will be described. The light emitted from the light source 501 is transmitted to the condenser lens 50.
2, the light is irradiated onto a mask 503 such as the phase shift mask of the present invention. The light that has passed through the mask 503 passes through a reduction projection lens system 504. The pattern of the mask 504 is projected onto the photo resist film on the semiconductor wafer 506 at a predetermined reduction magnification. The resist film used in this method can use any resist agent such as a positive or negative resist agent used in a conventional method for manufacturing a semiconductor device.

FIG. 20 shows a main process of a method for manufacturing a semiconductor device using the phase shift mask of the present invention. As shown in FIG. 20, first, in step 1, a device and a mask are designed. Next, in step 2, various masks are prepared. A phase shift mask according to the present invention is also provided. Meanwhile, in step 3, a semiconductor wafer is prepared. Next, in step 4, the designed structure is formed on the wafer by processes such as film formation, pattern formation, and impurity doping. In this process, a pattern is formed on the resist film on the wafer by photolithography using the phase shift mask of the present invention and another photomask. Subsequently, the wafer is etched. A semiconductor chip obtained by such a process is assembled to produce a semiconductor device.

As described above, for example, a method of manufacturing a semiconductor device according to one of the embodiments of the present invention includes a phase shift region, a non-phase shift region, and a step-like transition region between both regions. A step of forming a phase shift mask in which a pattern of a light shielding film is formed at a predetermined position between the phase shift area and the non-phase shift area, a step of forming a photo resist film on the semiconductor substrate, and a photo lithography technique. Transferring a pattern from the phase shift mask to the resist film. The above is
Although some embodiments and modified examples of the present invention have been described, the present invention is not limited to these, and can be used and modified in other combinations or situations.

[0075]

As described above, according to the present invention, a multi-stage phase shift mask can be efficiently manufactured with a small number of etchings. Further, a phase shift mask having multi-stage side walls manufactured by such a manufacturing method can be obtained. Further, a method for manufacturing a semiconductor device using the phase shift mask thus obtained can be obtained, and a semiconductor device manufactured by the manufacturing method can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a phase shift mask according to a first embodiment manufactured by a manufacturing method of the present invention.

FIG. 2 is a plan view showing the phase shift mask of the first embodiment manufactured by the manufacturing method of the present invention.

FIG. 3 is a diagram showing a phase shift mask according to the first embodiment manufactured by the manufacturing method of the present invention.

FIG. 4 is a cross-sectional view showing the phase shift mask according to the first embodiment manufactured by the manufacturing method of the present invention.

FIG. 5 is a diagram for explaining the operation of the phase shift mask according to the first embodiment manufactured by the manufacturing method of the present invention.

FIG. 6 is a diagram for explaining the operation of the phase shift mask of the first embodiment manufactured by the manufacturing method of the present invention.

FIG. 7 is a diagram showing the phase shift mask of the first embodiment manufactured by the manufacturing method of the present invention.

FIG. 8 is a diagram showing a manufacturing process of the phase shift mask according to the second embodiment of the present invention.

FIG. 9 is a diagram showing a manufacturing process of the phase shift mask according to the second embodiment of the present invention.

FIG. 10 is a diagram showing a manufacturing process of the phase shift mask according to the second embodiment of the present invention.

FIG. 11 is a diagram showing a manufacturing process of the phase shift mask according to the second embodiment of the present invention.

FIG. 12 is a diagram showing a manufacturing process of the phase shift mask according to the third embodiment of the present invention.

FIG. 13 is a diagram showing a manufacturing process of the phase shift mask according to the third embodiment of the present invention.

FIG. 14 is a diagram showing a manufacturing process of the phase shift mask according to the third embodiment of the present invention.

FIG. 15 is a diagram showing a manufacturing step of the phase shift mask according to the third embodiment of the present invention.

FIG. 16 is a diagram showing a manufacturing process of the phase shift mask according to the third embodiment of the present invention.

FIG. 17 is a view illustrating a step of manufacturing the phase shift mask according to the fourth embodiment of the present invention, and is a plan view showing the arrangement of the etching mask.

FIG. 18 is a view for explaining a manufacturing step of the phase shift mask according to Embodiment 4 of the present invention, and is a cross-sectional view showing the arrangement of the etching mask.

FIG. 19 is a view showing a method of exposing a resist pattern on a semiconductor wafer to a mask pattern according to the fifth embodiment of the present invention.

FIG. 20 is a diagram showing a manufacturing process of the semiconductor device in the fifth embodiment of the present invention.

FIG. 21 is a view for explaining the structure and operation of a conventional phase shift mask.

FIG. 22 is a view for explaining the operation of a conventional phase shift mask.

FIG. 23 is a view for explaining the structure and operation of a conventional levelson phase shift mask.

FIG. 24 is a view for explaining the operation of a conventional Resonson phase shift mask.

FIG. 25 is a perspective view showing a conventional levelson phase shift mask.

FIG. 26 is a plan view showing a conventional levelson phase shift mask.

FIG. 27 is a cross-sectional view showing a conventional Resonson phase shift mask.

FIG. 28 is a sectional view showing a conventional Resonson phase shift mask.

FIG. 29 is a view for explaining the operation of the conventional Reverson phase shift mask.

FIG. 30 is a diagram for explaining the operation of a conventional Resonson phase shift mask.

FIG. 31 is a diagram for explaining the operation of a conventional Resonson phase shift mask.

[Explanation of symbols]

Reference Signs List 1 light-transmitting substrate (quartz substrate), 2 non-phase shift region (reference plane), 3 phase shift region, 4 transition region, 5 light shielding film pattern, 8 chrome film (etching mask), 9 electron beam resist film.

Claims (14)

[Claims] A step of forming a light-shielding thin film pattern at a predetermined portion of a boundary between a non-phase-shift region of the light-transmitting substrate that does not cause a phase shift and a phase-shift region that causes a phase shift; At the boundary where the etching is not performed, n times (n is a constant integer exceeding 2) of different etching amounts are performed with different etching mask patterns having openings and non-openings, so that the etching depth is 2 times. forming a transition portion that changes stepwise in the n-th power type. 2. The light-shielding thin film formed on a light-transmitting substrate is patterned to form the light-shielding thin film pattern, and then the phase shift region and the transition portion are formed. 3. The method for manufacturing a phase shift mask according to item 1. 3. The method according to claim 1, wherein the light-shielding film pattern is formed after forming the phase shift region and the transition portion. 4. The method according to claim 1, wherein the etching mask is formed using a material having a light-shielding property and a conductive property, and an electron beam resist is applied and patterned by electron beam exposure. 2. A method for manufacturing a phase shift mask according to any one of the above items. 5. The method according to claim 1, wherein the etching of the light-transmitting substrate is performed by wet etching, and the etching mask is formed of a material having corrosion resistance to a chemical used for the wet etching. 2. The method for manufacturing a phase shift mask according to claim 1. 6. The method according to claim 5, wherein an etching mask for the wet etching is formed of an amorphous silicon thin film doped with phosphorus or boron, and a chemical containing at least hydrogen fluoride is used for the wet etching. Method of manufacturing phase shift mask 7. The method for manufacturing a phase shift mask according to claim 1, wherein said etching mask pattern is formed by a resist for dry etching of a light transmitting substrate. 8. The etching amount of an arbitrary etching of the n times of etching is any one of unit power of 2 (m−1), where m is a natural number of n or less. 8. The method for manufacturing a phase shift mask according to any one of 1 to 7. 9. The method according to claim 8, wherein the etching amount of the m-th etching of the n-th etching is unit power of 2 (m−1), where m is a natural number of n or less. A manufacturing method of the phase shift mask described in the above. 10. The mask pattern of an etching mask of an arbitrary etching of the n-th etching includes a long rectangle, and a smaller width of the long rectangle is defined as a unit width of 2 of m, where m is a natural number of n or less. The method for manufacturing a phase shift mask according to any one of claims 1 to 7, wherein the method is any of (m-1) th power. 11. A mask pattern of an etching mask of an m-th etching of the n-th etching includes a long rectangle, and a width of a small side of the long rectangle is defined as a unit width of 2 with m being a natural number of n or less. The method for manufacturing a phase shift mask according to claim 10, wherein the power is (m-1). 12. The method according to claim 1, wherein
A phase shift mask manufactured by the method for manufacturing a phase shift mask described in the paragraph. 13. A method for manufacturing a semiconductor device, wherein a pattern is transferred using a phase shift mask manufactured by the manufacturing method according to claim 1. 14. A semiconductor device manufactured by transferring a pattern using a phase shift mask formed by the manufacturing method according to claim 1.