JPH09319066A - Manufacture of halftone phase shift mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of a defect only by adding a comparatively simple process and to obtain a high-quality shift mask as the result by forming a second light shielding film pattern by etching a first light shielding film pattern. SOLUTION: A translucent film 32 and a light shielding film 33 are formed on a transparent substrate 31 in turn first. Besides, a resist pattern 34a is formed on the film 33. By etching the film 33 by using the pattern 34a as the mask, the light shielding film pattern 33a is formed. Thereafter, the pattern 34a is peeled and washed. By etching the film 32 by using the pattern 33a as the mask, a translucent film pattern 32a is formed. Thereafter, a resist pattern 35a is formed on the pattern 33a. By etching the pattern 33a by using the pattern 35a as the mask, the light shielding film pattern 33b of a final shape is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photomask used when a fine pattern such as an LSI is transferred by a projection exposure apparatus, and in particular, to a halftone phase in which resolution is improved by giving a phase difference between exposure lights. The present invention relates to a method for manufacturing a shift mask.

[0002]

2. Description of the Related Art In the manufacture of a semiconductor LSI, a phase shift mask is used as one of photomasks serving as a fine pattern transfer mask. This phase shift mask is designed to improve the resolution of a transfer pattern by giving a phase difference between exposure lights passing through the mask. As one of the phase shift masks, a phase shift mask described in JP-A-4-136854 is known as a mask particularly suitable for transferring an isolated hole or space pattern.

This phase shift mask is formed on a transparent substrate,
By forming a semi-transparent film that allows light of an intensity that does not substantially contribute to exposure to pass therethrough and at the same time shifts the phase of the light passing through, and partially removes this semi-transparent film, A mask pattern having a light-transmitting portion that transmits light having an intensity that contributes to exposure and a semi-light-transmitting portion that transmits light that does not substantially contribute to exposure is formed. This phase shift mask shifts the phase of light passing through the semi-transparent portion so that the phase of light passing through the semi-transparent portion is substantially inverted with respect to the phase of light passing through the transparent portion. By providing such a relationship, the light passing through the translucent portion and the semi-translucent portion in the vicinity of the boundary and wrapping around due to diffraction cancel each other out, and the contrast of the boundary portion can be well maintained. This is called a halftone phase shift mask.

In this phase shift mask, when the wavelength of the exposure light is λ and the refractive index of the semi-transparent film to the exposure light is n, the value of the thickness t of the semi-transparent film is generally t = λ / It is usually set to a value that satisfies {2 (n-1)}, and the transmittance of the semi-transparent film at the wavelength of the exposure light is set to about 1 to 50%.

As described above, the halftone phase shift mask has a semi-transparent portion that has both a phase shift function and a light shielding function. That is, this semi-translucent part is
The boundary portion of the pattern functions as a phase shift layer, and the other portions function as a light shielding layer.
Therefore, a small amount of leaked light also occurs in a portion where it is ideal to completely block the exposure light. Normally,
The total exposure amount is adjusted so that even if the leaked light is present, the exposure is not substantially achieved.

As described above, since the halftone phase shift mask also serves as the light shielding portion by the semi-transparent portion, it is necessary to provide a light shielding film like a conventional general phase shift mask in principle. There is no. However, in order to cover the drawbacks of this halftone phase shift mask, it has been proposed to provide a light shielding film on or below the semitransparent film forming the semitransparent portion. The halftone phase shift mask according to this proposal will be described below from the background of the proposal.

As is well known, a halftone phase shift mask is a mask (reticle) of a reduction projection exposure apparatus (stepper) which is an exposure apparatus usually used for semiconductor manufacturing.
Used as. The stepper reduces a projection image obtained by projecting a reticle with exposure light using a projection lens and forms an image on a semiconductor wafer that is a transfer target to perform reduction projection exposure. In this reduction projection exposure, usually, the same reticle pattern is repeatedly transferred and exposed at different positions on one semiconductor wafer, and a large number of semiconductor chips are obtained from one wafer. Therefore, when pattern transfer is performed using this stepper, the peripheral area is exposed by the covering member (aperture) provided in the stepper so that only the transfer area of the phase shift mask (reticle) is exposed. .

However, it is difficult in terms of mechanical precision to install the aperture with high accuracy (for example, accuracy of 1 μm or less) so that only the transfer area is exposed. In many cases, the exposed portion is a non-transfer area around the outer periphery of the transfer area. It will be visible in the area. Even if the aperture has a high precision and there is no protruding portion, the exposure light is diffracted and reaches the non-transfer area because of the distance between the aperture and the transfer target.

As described above, when the exposure light passes through a wider area than the original transfer area, the following problems have been found. That is, the halftone phase shift mask is usually formed with a semi-transmissive film that allows light having an intensity that does not substantially contribute to exposure to pass through in the non-transfer area.
For this reason, as described above, when the exposure light passes through a wider area than the original transfer area, the exposed portion is exposed with light having an intensity that does not substantially contribute to the exposure. Of course, even if there is this protruding part, 1
No problem occurs with one exposure.

However, there is a case where the exposed portion (exposed exposed portion) by the protrusion overlaps the transfer area or overlaps with the exposed portion when exposed in the next exposure. Even if the exposure amount does not substantially contribute to the exposure in one exposure, they may be added to reach the amount that contributes to the exposure. Therefore, this causes the same effect as the case where the area which should not be exposed originally is exposed, resulting in a defect. In addition, a pattern size (for example, a so-called i-line having a wavelength of 365 nm, about 0.3 to 0.5 is used) in which the original advantage of this halftone phase shift mask is exhibited.
In a pattern larger than (μm) (approximately several to several tens of times or more), the side lobe effect becomes remarkable in the vicinity of the pattern, and unnecessary reduction of the resist film may occur, resulting in a defect.

As a device capable of eliminating such a defect,
A halftone phase that is formed on the semi-transparent film formed in the non-transfer area and forms a light-shielding portion having a predetermined width or more in the non-transfer area adjacent to the boundary between the transfer area and the non-transfer area. A shift mask has been proposed as disclosed in Japanese Patent Laid-Open No. 6-282063.

FIG. 4 is a sectional view of a manufacturing process of the halftone phase shift mask according to the above proposal. In this method, first, as shown in FIG. 4A, a semi-transmissive light-shielding film 12 made of chromium is formed on a transparent substrate 11 by a sputtering method, and SOG is formed thereon by a spin coating method.
A phase shift film 13 made of (spin on glass) is formed. The semi-transmissive light-shielding film 12 and the phase shift film 13 made of SOG form a semi-transmissive film 14.
Next, the light-shielding film 1 made of chromium is formed on the semi-transparent film 14.
5 is formed by the sputtering method, and the light shielding film 1 is further formed.
A positive type electron beam resist 16 is formed on the surface 5 by spin coating.

Next, a resist pattern 16a is formed by electron beam drawing, the light-shielding film 15 is wet-etched using the resist pattern 16a as a mask, and then the phase-shifting film 13 is dry-etched to form the light-shielding film pattern 15a and the phase-shifting film pattern. 13a is formed. Next, after removing the resist pattern 16a, a negative electron beam resist 17 is formed by spin coating as shown in FIG. Next, a resist pattern 17a is formed by electron beam writing as shown in FIG. 4D, and the light shielding film pattern 15 is formed using this and the phase shift film pattern 13a as a mask.
By wet-etching a and the semi-transmissive light-shielding film 12, the final shape of the light-shielding film pattern 15b and the semi-transmissive light-shielding film pattern 12a are formed. Finally, FIG.
The desired halftone phase shift mask is completed by peeling the resist pattern 17a as shown in (e).

However, in the above-mentioned conventional example, the film structure formed on the transparent substrate 11 is a structure of chromium / SOG / chrome. In order to form a film having such a structure, a chrome film is formed in a vacuum device, then SOG film is taken out from the vacuum device, spin coated to apply SOG, and baked in a furnace to form a SOG film. However, after that, it is necessary to put it in the vacuum apparatus again to form a chromium film. That is, there is a problem in that the process is complicated, the manufacturing takes time, and the defect is likely to occur because the process is complicated. Further, since the SOG is processed and then the chromium is processed, the probability of occurrence of a defect is high also here. If you add more, SOG and chromium have a problem in adhesion,
There is a possibility that chromium will be peeled from SOG or SOG will be peeled from chromium.

Therefore, in order to solve the above-mentioned problems, for example, a MoSiON single layer film is used for the semi-translucent film and Cr is used for the light shielding film.
Is used in the literature (Proc. SPIE, Vol 2
621, 266-272 (1995)).

FIG. 5 is a sectional view of a manufacturing process of the halftone phase shift mask according to the above proposal. In this method, first, as shown in FIG.
A semi-transparent film 22 made of MoSiON is formed thereon by a sputtering method, and then a light-shielding film 23 made of chromium is formed on the semi-transparent film 22 by a sputtering method. The positive electron beam resist 24 is formed by spin coating.

Next, as shown in FIG. 5B, a resist pattern 24a is formed by electron beam drawing, the light-shielding film 23 is wet-etched using this as a mask, and then the semi-translucent film 22 is dry-etched. Thus, the light shielding film pattern 23a and the semi-transmissive film pattern 22a are formed. Next, after peeling off the resist pattern 24a, FIG.
As shown in (c), a negative electron beam resist 25 is formed by spin coating. Next, as shown in FIG. 5D, a resist pattern 25a is formed by electron beam drawing,
The light-shielding film pattern 23a having the final shape is wet-etched by using this as a mask.
3b is formed. Finally, the resist pattern 25a is peeled off as shown in FIG. 5E to obtain a desired halftone phase shift mask.

[0018]

In the second conventional example described above, since the semi-translucent film has a single layer, the number of steps for manufacturing blanks and masks is reduced as compared with the example using SOG. I have found that there are still the following problems. That is, in the mask manufacturing process, first, the resist pattern 24a is formed by electron beam drawing, the light shielding film 23 is wet-etched using this as a mask, and then the semi-transparent film 2 is formed.
2 is dry-etched to form the light-shielding film pattern 23a and the semi-light-transmitting film pattern 22a, but it has been found that this step has a large defect generation factor. That is, in the etching of the light-shielding film 23 made of chromium, for example, wet etching is performed for a predetermined time by using an etching solution made of ceric ammonium nitrate and perchloric acid, rinsed with pure water and dried. The etching liquid is not completely dropped and is crystallized and remains on the semi-translucent film 22 or the resist pattern 24a which is a base, or remains as a thin film due to insufficient drying of water. The same applies to dry etching using chlorine or carbon tetrachloride for etching chromium.
Reaction products accumulate and dust adheres. Therefore, if the semi-transmissive film 22 is dry-etched as it is in the next step, those portions act as a mask and the semi-transmissive film 22 is not etched.
Eventually, many semi-transmissive film patterns 22a become defects.

[0019]

Means for Solving the Problems The present invention (first present invention)
In order to solve the above problems, the following method of manufacturing a halftone phase shift mask is used. That is, first, a semi-transparent film and a light-shielding film are sequentially formed on a transparent substrate,
Further, a resist pattern is formed on the light shielding film. next,
The light shielding film is etched by using the resist pattern as a mask to form a light shielding film pattern. Then, the resist pattern is peeled off and washed. Then, the semi-transmissive film is etched using the light-shielding film pattern as a mask to form a semi-transmissive film pattern. Then, a resist pattern is formed on the light-shielding film pattern, and the light-shielding film pattern is etched using the resist pattern as a mask to form a light-shielding film pattern having a final shape.

In the second aspect of the present invention, the following halftone phase shift mask manufacturing method is used. First, a semi-transparent film and a light shielding film are sequentially formed on a transparent substrate, and a resist pattern is further formed on the light shielding film. Next, the light shielding film is etched by using the resist pattern as a mask to form a light shielding film pattern. Then, rinse treatment is performed with an organic solvent. Then, the semi-transmissive film is etched using the resist pattern and the light-shielding film pattern as a mask to form a semi-transmissive film pattern. Then, after the resist pattern is peeled off, a resist pattern is formed again on the light shielding film pattern. Then, the light shielding film pattern is etched by using the resist pattern as a mask to form a final shape of the light shielding film pattern.

Further, in the third aspect of the present invention, the following halftone phase shift mask manufacturing method is used. First, a semi-translucent film and a light-shielding film are sequentially formed on a transparent substrate, and a resist pattern is formed on the light-shielding film by coating, exposing and developing a resist. Next, the light shielding film is etched by using the resist pattern as a mask to form a light shielding film pattern. Then, the resist pattern is developed again. Then, rinse treatment is performed with an organic solvent. afterwards,
The semi-transmissive film is etched using the resist pattern and the light-shielding film pattern as a mask to form a semi-transmissive film pattern. Then, after peeling off the resist pattern,
A resist pattern is formed again on the light shielding film pattern. Then, the light shielding film pattern is etched by using the resist pattern as a mask to form a final shape of the light shielding film pattern.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a method of manufacturing a halftone phase shift mask according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a sectional view showing a first embodiment of the present invention. In this figure, the transparent substrate 31
Is a quartz glass substrate having a mirror-polished surface (size 6 inches square, thickness 0.25 inch), which has been subjected to predetermined cleaning. In the first embodiment, first, as shown in FIG. 1A, a semi-transparent film 32 made of molybdenum, silicon, oxygen, and nitrogen is formed on the transparent substrate 31 to a film thickness of 160 nm.
The film is formed by a sputtering method, and subsequently, a light shielding film 33 made of chromium is formed thereon to a film thickness of 100 nm. next,
A positive electron beam resist (EBR-9: manufactured by Toray) 34 is applied on the light-shielding film 33 by a spin coating method to a film thickness of 500 nm.

Next, a desired pattern is drawn on the resist 34 with an electron beam and developed to form a resist pattern 34a as shown in FIG. 1 (b). Next, using the resist pattern 34a as a mask, the light-shielding film 33 is etched using an etching solution composed of cerium ammonium nitrate and perchloric acid to form a first light-shielding film pattern 33a. Next, after removing the resist pattern 34a and performing a predetermined cleaning, the semi-transmissive film 32 is used as a mask for the semi-transmissive film 32 with a mixed gas of CF ₄ / O ₂ , a pressure of 0.4 Torr, and RF. By performing dry etching under the condition of a power of 100 W, a semi-transparent film pattern 32a is formed as shown in FIG.

Then, after performing predetermined cleaning, FIG.
As shown in (d), a positive electron beam resist (E
BR-9: manufactured by Toray Industries, Inc.) 35 is applied by a spin coating method to a film thickness of 500 nm and baked. Next, this resist 3
5 draw the desired pattern with electron beam, develop,
A resist pattern 35a shown in FIG. 1E is formed on the first light shielding film pattern 33a. Next, using the resist pattern 35a as a mask, the first light-shielding film pattern 33 is formed.
By etching a using an etchant composed of cerium ammonium nitrate and perchloric acid, as shown in FIG.
The second light-shielding film pattern 3 having the final shape as shown in (e)
3b is formed. Finally, as shown in FIG. 1F, the resist pattern 35a is peeled off and a predetermined cleaning is performed.

According to the first embodiment, the foreign matter attached in the etching process of chromium (light-shielding film 33) is removed by removing the resist pattern 34a and adding a cleaning process, and a clean chromium pattern (first The semi-translucent film 32 can be dry-etched by using the light-shielding film pattern 33a) as a mask, and the occurrence of defects can be prevented. Therefore, the halftone phase shift mask could be obtained with no defect and high quality. However, in this method, the surface of the chromium pattern is also slightly etched depending on the dry etching conditions, and the quality of the surface and the etched chromium particles adhere to the semi-translucent film 32 during etching to act as a mask, As a result, a film residue or surface roughness may occur, so it is necessary to set the optimum etching conditions.

FIG. 2 is a sectional view showing a second embodiment of the present invention. In this figure, the transparent substrate 31 is a quartz glass substrate (size 6 inch square, thickness 0.25 inch) whose surface is mirror-polished, which has been subjected to predetermined cleaning. In the second embodiment, first, as shown in FIG. 2A, a semi-translucent film 32 made of molybdenum, silicon, oxygen, and nitrogen is formed on the transparent substrate 31 by a sputtering method with a film thickness of 160 nm, and then continuously. Light-shielding film 3 made of chrome on it
3 is formed to a film thickness of 100 nm. Next, a positive electron beam resist (EBR-9: manufactured by Toray Industries, Inc.) 34 is applied on the light-shielding film 33 by a spin coating method to a film thickness of 500 nm.

Next, a desired pattern is drawn on the resist 34 with an electron beam and developed to form a resist pattern 34a as shown in FIG. 2B. Next, using the resist pattern 34a as a mask, the light-shielding film 33 is etched using an etching solution composed of cerium ammonium nitrate and perchloric acid to form a first light-shielding film pattern 33a. Next, after rinsing with IPA (isopropyl alcohol), as shown in FIG. 2C, the semi-transparent film 32 is CF ₄ / O ₂ with the resist pattern 34a and the first light-shielding film pattern 33a as a mask. The mixed gas, the pressure is 0.2 Torr, and the RF power is 100 W, and dry etching is performed to form the semi-transparent film pattern 32a. Subsequent steps are the same as those in the first embodiment, the resist pattern 34a is peeled off, and the resist 35 is applied again (see FIG.
(D)), which is used as a resist pattern 35a (see FIG. 2).
(E)) Etching is performed using this resist pattern 35a as a mask to form a second light-shielding film pattern 33b (FIG. 2 (e)), and the resist pattern 35a is removed (FIG. 2 (f)).

According to the second embodiment as described above, foreign matters attached on the resist (pattern 34a) and the semi-translucent film 32 in the etching process of chromium (light-shielding film 33) are washed away by a rinse treatment with an organic solvent. At the same time, the surface of the semi-transparent film 32 covered with water molecules is replaced with an organic substance, so that the surface is cleaned and the occurrence of defects can be prevented. Therefore, the halftone phase shift mask could be obtained with no defect and high quality. Further, in this method, unlike the first embodiment, since the chromium pattern (light-shielding film pattern 33a) is covered with the resist pattern 34a, the etching conditions can be freely selected.

Next, a third embodiment of the present invention will be described with reference to FIG. 2 used in the second embodiment. In the third embodiment, the same steps as in the second embodiment are performed until the first light-shielding film pattern 33a is formed (up to FIG. 2B). That is, the semi-translucent film 32, the light-shielding film 33, and the resist 34 are sequentially formed on the transparent substrate 31 (FIG. 2A),
Electron beam drawing and development are applied to the resist 34 to form a resist pattern 34a (FIG. 2B), and the resist pattern 34a is used as a mask for etching to form a first light-shielding film pattern 33a.

In the third embodiment, next, the developer MIB
The resist pattern 34a is again developed with K (methyl isobutyl ketone). Then IPA
Rinse with (isopropyl alcohol).
After that, the semi-transmissive film 32 is dry-etched under the conditions of a mixed gas of CF ₄ / O ₂ , a pressure of 0.2 Torr, and an RF power of 100 W by using the resist pattern 34a and the first light-shielding film pattern 33a as a mask. As shown in (c), a semi-transparent film pattern 32a is formed.

Thereafter, the same steps as those in the second embodiment are performed again. First, the resist pattern 34a is peeled off, the resist 35 is applied again (FIG. 2D), and this is used as the resist pattern 35a (FIG. 2E). ), This resist pattern 3
The second light-shielding film pattern 33b is formed by etching using 5a as a mask (FIG. 2E), and the resist pattern 3 is formed.
5a is peeled off.

According to the third embodiment as described above, the foreign matter adhered on the resist pattern 34a and the semi-transparent film 32 in the chromium (light-shielding film 33) etching process is subjected to redevelopment and rinsing with an organic solvent. Since the surface of the semi-transparent film 32 that has been washed away and simultaneously covered with water molecules is replaced with an organic substance, it can be cleaned and the occurrence of defects can be prevented. In addition, by side etching of the first light-shielding film pattern 33a when the first light-shielding film pattern 33a is formed, as shown in FIG.
As shown in FIG. 3A, the state in which the edge of the resist pattern 34a is slightly protruding is improved as shown in FIG. 3B by adding a redevelopment process, and the damage of the edge of the resist pattern due to the next dry etching is prevented. It is possible to obtain an ideal mask state. Further, due to the film reduction of the resist pattern 34a, stubborn stains, foreign matters and the like which cannot be removed only by the rinse treatment can be removed. From these, in the third embodiment, the halftone phase shift mask could be obtained with no defect and high quality.

In the above embodiment, the second shape of the final shape is used.
The light-shielding film pattern 33b is provided on the semi-transmissive film pattern 32a in at least a part of one or both of the inside and the outside of the transfer region.

In the above embodiment, the transparent substrate 31
Although quartz glass is used as the glass, other glass such as soda lime glass, aluminoborosilicate glass, or borosilicate glass can be used.

Further, the resist patterns 34a, 35a
When forming, is not limited to the method using electron beam drawing exposure, and may be light exposure. In that case, it is needless to say that a resist corresponding to the exposure conditions and a corresponding developing solution and rinsing solution are used.

[0036]

As described above, according to the method of manufacturing a halftone phase shift mask of the present invention, the occurrence of defects is suppressed only by adding a relatively simple process, and as a result, a high quality halftone phase shift mask is obtained. Obtainable.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of a method for manufacturing a halftone phase shift mask according to the present invention.

FIG. 2 is a sectional view showing a second embodiment of a method of manufacturing a halftone phase shift mask according to the present invention.

FIG. 3 is a cross-sectional view showing an effect of a redevelopment process in a third embodiment of the invention.

FIG. 4 is a cross-sectional view showing a manufacturing process of a conventional halftone phase shift mask.

FIG. 5 is a cross-sectional view showing another example of the manufacturing process of the conventional halftone phase shift mask.

[Explanation of symbols]

 31 transparent substrate 32 semi-transparent film 32a semi-transparent film pattern 33 light-shielding film 33a first light-shielding film pattern 33b second light-shielding film pattern 34 resist 34a resist pattern 35 resist 35a resist pattern

Claims (3)

[Claims] 1. A step of forming a semi-translucent film and a light-shielding film in order on a transparent substrate, and further forming a resist pattern on the light-shielding film; and a step of etching the light-shielding film using the resist pattern as a mask to form the light-shielding film pattern. And a step of removing the resist pattern and washing, and a step of etching the semitransparent film by using the light shielding film pattern as a mask to form a semitransparent film pattern, and Forming a resist pattern on the light-shielding film pattern, and etching the light-shielding film pattern using the resist pattern as a mask to form a light-shielding film pattern in a final shape. Method of manufacturing tone phase shift mask. 2. A step of sequentially forming a semi-translucent film and a light-shielding film on a transparent substrate, and further forming a resist pattern on the light-shielding film; and a step of etching the light-shielding film using the resist pattern as a mask to form the light-shielding film pattern. And a step of rinsing with an organic solvent, and then a step of etching the semitransparent film using the resist pattern and the light shielding film pattern as a mask to form a semitransparent film pattern, Then, after removing the resist pattern, a step of forming a resist pattern again on the light-shielding film pattern, and then by etching the light-shielding film pattern using the resist pattern as a mask, the light-shielding film pattern of the final shape And a step of forming a halftone phase shift mask. 3. A step of sequentially forming a semi-transparent film and a light-shielding film on a transparent substrate, and further forming a resist pattern on the light-shielding film by applying, exposing, and developing a resist, and using the resist pattern as a mask, A step of etching the light-shielding film to form a light-shielding film pattern, a step of developing the resist pattern again, a step of rinsing with an organic solvent, and a mask of the resist pattern and the light-shielding film pattern. And a step of forming a semi-transparent film pattern by etching the semi-transparent film, and then peeling the resist pattern, forming a resist pattern again on the light-shielding film pattern, and then the resist pattern By etching the light-shielding film pattern using the mask as a mask, the light-shielding film pattern of the final shape is formed. And a step of forming the halftone phase shift mask.