JP3451431B2 - X-ray exposure mask and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask for X-ray exposure and a method for manufacturing the same, and more particularly to a mask caused by stress caused by sidewall oxidation of the X-ray absorber pattern after the X-ray absorber pattern is formed. The present invention relates to an X-ray exposure mask having a characteristic structure for reducing distortion and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the miniaturization of semiconductor devices in recent years, X-ray exposure using X-rays as light having a shorter wavelength has been developed instead of UV exposure, and X-ray masks used for such X-ray exposure. A heavy metal film of Ta, W or the like is used as the absorber, and as a manufacturing method, various methods such as a back etching subsequent type and a back etching preceding type have been tried.

Of these, the back etching preceding type, in which the absorber is patterned after the back etching step, is less affected by the stress of the membrane and the distortion due to the adhesion of the mask frame, and the positional accuracy is improved, as compared with the back etching subsequent type. Therefore, a conventional X-ray exposure mask will be described with reference to FIG.

See FIG. 7A. FIG. 7A is a schematic sectional view of a conventional X-ray exposure mask. First, dichlorosilane is formed on both surfaces of a silicon wafer 31 having a thickness of, for example, 2 μm. After depositing the SiC films 32 and 33 by a CVD method using acetylene as a source gas, a resist pattern (not shown) having a window pattern corresponding to the membrane region 35 is formed on the backside SiC film 33 by a photolithography process. Is formed, and dry etching is performed using this resist pattern as a mask to form an opening in a region corresponding to the membrane region 35 of the SiC film 33. In this case, the upper SiC film 32 becomes a membrane film.

Then, a Ta film, which will be an X-ray absorber film, is deposited to a thickness of 0.4 μm, for example, on the surface-side SiC film 32, which will be a membrane film, by using a sputtering method. By annealing at a temperature of ℃, the stress of the Ta film to be the X-ray absorber film is corrected, and then the Ta film is attached to the SiC mask frame 34 with an adhesive (not shown), For example, adhesion is performed by applying a weight of about 5 kg and performing heat treatment at 200 ° C. for 5 minutes.

Then, the silicon wafer 31 is etched from the back side using KOH as an etching solution to expose the SiC film 32, and the exposed portion of the SiC film 32 is used as a membrane region 35. Then, a photolithography process is performed to form the SiC film 32. A resist pattern (not shown) for forming the X-ray absorber pattern 37 is formed in the exposure pattern region 36 on the surface side of the film 32, and dry etching is performed using this resist pattern as a mask to etch the Ta film. X-ray absorber pattern 3
By forming 7, the basic structure of the X-ray exposure mask is obtained. Note that the Ta film remaining around becomes the X-ray blocker 38.

See FIG. 7B. FIG. 7B shows the exposure pattern region 36 and the membrane region 3 in the X-ray exposure mask manufactured as described above.
5 is a diagram showing the positional relationship between the X-ray blocker 38 and the X-ray blocker 38, and a rectangular exposure pattern region 36 is formed inside a rectangular membrane region 35. Although the X-ray blocker 38 is illustrated as being located outside the rectangular membrane region 35, it is actually located in contact with the rectangular exposure pattern region 36 as shown in FIG. 7A. There is something.

Since such a mask for X-ray exposure is a mask of the same size, as the device pattern is miniaturized, higher position accuracy is required. The most important factor that deteriorates the pattern position accuracy is the occurrence of mask distortion due to the stress of the X-ray absorber film (Ta film in the case of FIG. 7) itself. That is, if the formed X-ray absorber film has stress, the stress is released when the X-ray absorber is processed by dry etching or the like to form the X-ray absorber pattern in the exposure pattern region. Then, mask distortion will occur.

Therefore, it is necessary to control the stress of the X-ray absorber film with high precision, but this stress control is not difficult in the process. For example, as described above, the stress control of the X-ray absorber film is not possible. By performing annealing treatment after the film, X
The stress of the line absorber film can be controlled.

[0010]

However, with the miniaturization of the device pattern, even if the stress of the X-ray absorber film is set to 0 in the process, a compressive stress is generated after the formation of the X-ray absorber pattern. Since there is a problem of causing mask distortion, this situation will be described with reference to FIG.

See FIG. 8. FIG. 8 shows the maximum mask distortion L & S (line-and-space) when the size of the membrane area is 34 mm □ and the size of the exposure pattern area is 30 nm □.
It is explanatory drawing of pattern dependence, and as shown in the figure, L & S
It is understood that the mask maximum distortion amount rapidly increases as the pattern becomes smaller.

It is considered that this is because the sidewall surface of the X-ray absorber pattern is oxidized by about several nm after the pattern is formed, and the compressive stress is generated in the film due to the oxidation. As the pattern becomes finer, the total side wall area increases, so the mask distortion becomes remarkable, and it is considered that the L & S pattern dependence shown in FIG. 8 can be obtained.

The mask distortion due to the side wall oxidation hinders the production of a highly accurate mask, but such side wall oxidation cannot be controlled under the film forming conditions during film formation. Therefore, the change in the maximum mask distortion amount when the size of the membrane region was changed while the size of the exposure pattern region was fixed to 30 mm □ was investigated.
The result is shown in FIG.

See FIG. 9. FIG. 9 is an explanatory diagram of the membrane area size dependence of the maximum mask distortion amount when the size of the exposure pattern area is fixed to 30 mm □, and the pattern dimension rule of the L & S pattern is as follows. , 0.1 μm and 1.0 μm. As is clear from the figure, when the pattern size rule of the L & S pattern is large, the membrane region size dependency can be seen, but since the original strain amount is small, it does not cause much problem.

On the other hand, when the pattern size rule of the L & S pattern is small, the membrane region size dependency becomes remarkable, but the closer the size of the membrane region to the size of the exposure pattern region, the smaller the maximum mask distortion amount, When the membrane area and the exposure pattern area coincide with each other, the distortion is eliminated in principle. This is because when the same pattern is formed on the entire surface of the membrane region, mask distortion due to sidewall oxidation occurs evenly in the membrane film, and mask position distortion does not appear.

However, in practice, it is very difficult to match the membrane area and the exposure pattern area. That is, since the membrane area is formed from the back surface as described above, while the exposure pattern area is formed from the front surface, the problem of front and back alignment, the problem of misalignment when bonding the wafer and the mask frame, or the silicon back surface. This is because it is difficult to accurately match the two due to problems such as side etching during etching.

Further, in the dry etching process of the X-ray absorber film, the temperature and the way of applying the substrate bias are different near the boundary between the membrane film and the silicon substrate, so that the processed shape is different from the central portion of the membrane. There is also.

A method for reducing mask distortion due to stress caused by an X-ray blocker has been proposed (if necessary, see Japanese Patent Laid-Open No. 2-56921). This will be described with reference to FIG. 10A is a schematic sectional view of a conventional improved X-ray exposure mask, and FIG. 10B is an arrangement of an exposure pattern region, a rectangular strip blocker, and an X-ray blocker. It is a figure which shows a relationship, Furthermore, it is X of FIG.10 (c).
It is a figure which shows the shape of the absorber pattern provided in the line blocker.

10 (a) and 10 (b), this improved X-ray exposure mask is provided with a strip-shaped rectangular blocker 47 made of a solid pattern around a rectangular exposure pattern region 45 provided with an absorber pattern 46. , The X-ray blocker 48 located outside the absorber pattern 49
Is provided.

At this time, refer to FIG. 10C. The absorber pattern 4 provided on the X-ray blocker 48.
As shown in the figure, the shape of 9 may be a simple grid pattern, and the pattern density may be the same as the pattern density of the absorber pattern 46 formed in the exposure pattern area 45. In addition to reducing the stress caused by the blocker 48, the strip-shaped rectangular blocker 47
Is intended to absorb the penumbra blurring caused by the mechanical aperture.

However, even in such an improved X-ray exposure mask, the influence of sidewall oxidation is not taken into consideration, and a solid pattern strip-shaped rectangular blocker 47 is provided in the membrane region 44. Therefore, it is essentially impossible to match the membrane region 44 and the exposure pattern region 45.

Therefore, it is an object of the present invention to suppress the occurrence of mask distortion due to sidewall oxidation of the X-ray absorber pattern without making the membrane region and the exposure pattern region coincide with each other.

[0023]

FIG. 1 is a block diagram showing the principle of the present invention. Means for solving the problems in the present invention will be described with reference to FIG. Note that FIG. 1 is a schematic sectional view of the X-ray exposure mask. See FIG. 1 (1) In the present invention, in the X-ray exposure mask, the dummy pattern 4 is arranged on the membrane film 1 other than the exposure region 7, and the pattern rule and the pattern density of the dummy pattern 4 are set in the exposure region 7. It is characterized in that the pattern rule and the pattern density of the X-ray absorber pattern 3 provided on the membrane film 1 are effectively made equal.

As described above, by providing the dummy pattern 4 having the pattern rule and the pattern density which are effectively equal to the pattern rule and the pattern density of the X-ray absorber pattern 3 on the membrane film 1 other than the exposed area 7, It is possible to form almost the same pattern on the entire surface of the region 8 and thereby, the influence of the sidewall oxidation becomes uniform on the entire surface of the membrane region 8.
It is possible to suppress the occurrence of mask distortion without matching the exposure area 7 with the exposure area 7. In the present specification,
The term "effectively equal" does not mean that they are equal in terms of mathematical rigor, but does not mean that the strain caused by sidewall oxidation is within the allowable range of mask strain at each moment. It is meant.

(2) Further, according to the present invention, in the method for manufacturing an X-ray exposure mask, the silicon wafer 5 supporting the membrane film 1 provided with the X-ray absorber film is back-etched to form the membrane region 8. After that, the X-ray absorber pattern 3 is formed on the membrane film 1 in the exposed area 7, and the pattern rule and the pattern density of the X-ray absorber pattern 3 are also effectively equal on the membrane film 1 other than the exposed area 7. It is characterized in that a dummy pattern 4 having a pattern rule and a pattern density is formed.

The formation of such a dummy pattern 4 is suitable for the manufacturing process of the back etching precedent type, and since the restriction of the stress control of the X-ray absorber film is relaxed, a certain low stress can be obtained. This simplifies the manufacturing process because it is not necessary to measure stress.

(3) Further, according to the present invention, in the method for manufacturing an X-ray exposure mask, the silicon wafer 5 supporting the membrane film 1 is back-etched to form the membrane region 8, and then the X film is formed on the membrane film 1. A line absorber film is deposited, and then an X-ray absorber pattern 3 is formed on the membrane film 1 in the exposure region 7, and the pattern rule of the X-ray absorber pattern 3 is also formed on the membrane film 1 other than the exposure region 7. And the dummy pattern 4 having a pattern rule and a pattern density that are effectively equal to the pattern density.

Since the provision of the dummy pattern 4 relaxes the restriction on the stress control of the X-ray absorber film as described above, the X-ray absorption is performed after the back surface etching of the silicon wafer 5, that is, after the bonding with the mask frame 4. It is possible to form a body film, which eliminates the deterioration of the X-ray absorber film due to the temperature at the time of bonding with the mask frame 4, so that strong bonding can be performed by a high-temperature bonding process.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will now be described with reference to FIGS. 2 to 4. First, referring to FIGS. 2 and 3, the first embodiment of the present invention will be described. The manufacturing process of the first embodiment will be described. Referring to FIG. 2A, first, a SiC film 12 having a thickness of, for example, 2.0 μm is formed on both surfaces of a silicon wafer 11 having a thickness of, for example, 2 μm by a CVD method using dichlorosilane and acetylene as source gases. Deposit 13. In this case, the upper S
The iC film 12 becomes a membrane film.

Next, referring to FIG. 2B, a resist pattern (not shown) having a window pattern to be a membrane region is formed on the SiC film 13 on the back surface side by a photolithography process, and this resist pattern is used as a mask for dry etching. By performing etching, opening 14 is provided in a region of SiC film 13 corresponding to the membrane region.

Next, referring to FIG. 2C, a Ta film 1 to be an X-ray absorber film is formed on the SiC film 12 on the surface side to be a membrane film by using a sputtering method.
X is deposited to a thickness of 0.4 μm and then annealed at a temperature of, for example, 300 ° C.
The stress of the Ta film 15, which is the line absorber film, is corrected.

Referring to FIG. 2D, the mask wafer for X-ray exposure and the thickness are, for example,
After bonding with a 4 mm SiC mask frame 16 using an adhesive (not shown), for example, by applying a weight of about 5 kg, heat treatment is performed at 200 ° C. for 5 minutes. Adhere.

Next, referring to FIG. 3 (e), the silicon wafer 11 is etched from the back side by using KOH as an etching solution to form Si.
The C film 12 is exposed, and the exposed portion of the SiC film 12 is used as the membrane region 17.

Next, referring to FIG. 3G, a resist pattern (not shown) for forming an X-ray absorber pattern and a dummy pattern is formed on the surface side of the SiC film 12 by an electron beam exposure method, and this resist is used. The Ta film 15 is etched by dry etching using the pattern as a mask, and the X-ray absorber pattern 18 and the dummy pattern 19 are formed to obtain the basic structure of the X-ray exposure mask. The Ta film 15 remaining in the periphery without being etched in this etching step becomes the X-ray blocker 20.

In this case, the dummy pattern 19 is X
It is formed almost continuously from the exposure pattern area where the line absorber pattern 18 is formed, and the pattern dimension rule and the pattern density of the dummy pattern 19 are X.
The pattern size rule and the pattern density of the linear absorber pattern 18 are effectively made equal.

As described above, according to the first embodiment of the present invention, the pattern dimension rule of the X-ray absorber pattern 18 and the pattern dimension rule effectively equal to the pattern density are provided around the X-ray absorber pattern 18. Since the dummy pattern 19 having the pattern density is provided, it is possible to effectively suppress the occurrence of mask distortion due to sidewall oxidation.

Further, since the stress control of the Ta film 15, that is, the X-ray absorber film is relaxed, if a certain low stress is obtained, it is not necessary to measure the stress, and the process is simplified. , The throughput is improved.

Next, with reference to FIG. 3, an exposure method using the X-ray exposure mask of the first embodiment of the present invention will be described. As shown in FIG. 3, an X-ray exposure mask is arranged on an X-ray resist 23 provided on a silicon wafer 21 so that the X-ray absorber patterns 18 closely oppose each other, and an X-ray having a mechanical aperture 23 is provided. X-ray beam 24 by stepper
Exposure is performed by irradiating with. In this case, the mechanical aperture 23 needs to have a shape that masks the peripheral area including the dummy pattern 19 so that only the X-ray absorber pattern 18 is transferred.

Next, the manufacturing process of the second embodiment of the present invention will be described with reference to FIGS. Referring to FIG. 5A, first, similarly to the first embodiment, the thickness is, for example, 2 μm on both sides of the silicon wafer 11 by the CVD method using dichlorosilane and acetylene as source gases. Is, for example, 2.0 μm SiC films 12 and 13
Deposit. In this case, the upper SiC film 12 becomes the membrane film.

Next, as shown in FIG. 5B, a resist pattern (not shown) having a window pattern to be a membrane region is formed on the backside SiC film 13 by a photolithography process, and this resist pattern is used as a mask for dry etching. By performing etching, opening 14 is provided in a region of SiC film 13 corresponding to the membrane region.

Next, referring to FIG. 5C, the silicon wafer 1 provided with the SiC films 12 and 13 is provided.
1 and a mask frame 16 made of SiC having a thickness of 4 mm, for example, face each other so that the sides on which the openings 14 are provided face each other, and are bonded using an alloy bonding method.

Next, as shown in FIG. 5 (d), the silicon wafer 11 is etched from the back side using KOH as an etching solution to form Si.
The C film 12 is exposed, and the exposed portion of the SiC film 12 is used as the membrane region 17.

Next, referring to FIG. 6 (e), a Ta film 1 to be an X-ray absorber film is formed on the SiC film 12 on the surface side to be a membrane film by using a sputtering method.
5 is deposited to a thickness of 0.4 μm, for example. In this case, since the bonding process with the mask frame 16 has already been completed, the stress control of the Ta film 15 is not necessary.

Next, referring to FIG. 6G, a resist pattern (not shown) for forming an X-ray absorber pattern and a dummy pattern is formed on the surface side of the SiC film 12 by an electron beam exposure method, and this resist is used. The Ta film 15 is etched by dry etching using the pattern as a mask, and the X-ray absorber pattern 18 and the dummy pattern 19 are formed to obtain the basic structure of the X-ray exposure mask. The Ta film which is not etched in this etching step and remains in the periphery becomes the X-ray blocker 20.

Also in this case, the dummy pattern 19 is formed almost continuously from the exposure pattern region in which the X-ray absorber pattern 18 is formed, and the pattern dimension rule and the pattern density of the dummy pattern 19 are the same. ,
The pattern size rule and the pattern density of the X-ray absorber pattern 18 are effectively made equal.

As described above, in the second embodiment of the present invention, since the Ta film is formed after the step of adhering to the mask frame 16, in the step of adhering to the mask frame 16, a high temperature of 500 ° C. or higher is used. It is possible to use an alloy joining method that requires the above, whereby it becomes possible to more firmly and more reliably bond the X-ray exposure mask wafer and the mask frame 16. The dummy pattern 19
The effect of providing is similar to that of the first embodiment.

Although the respective embodiments of the present invention have been described above, the present invention is not limited to the configurations and conditions described in the above respective embodiments, and various modifications can be made.
For example, in each of the above embodiments, KOH is used as the etching solution in the silicon back surface etching step, but the etching solution is not limited to KOH, and hydrofluoric nitric acid or the like may be used.

Further, in each of the above-mentioned embodiments, the Ta film is used as the X-ray absorber film for the sake of simplification of description, but the Ta film is not necessarily limited to the Ta film, and the S film is not limited to the Ta film.
i-containing amorphous film, Ge-containing amorphous Ta film,
Alternatively, a W film or the like may be used, and in particular, an Si-containing amorphous Ta film or G which is an amorphous film.
When the e-containing amorphous Ta film is used, since there is no crystal grain boundary, oxidation at the crystal grain boundary is eliminated,
Thereby, the effect of sidewall oxidation will be further mitigated.

In each of the above embodiments, the SiC film is used as the membrane film, but the S film is not always used.
The material is not limited to the iC film, and a SiN film, a diamond film, or the like may be used.

Further, in the above-mentioned second embodiment, the bonding with the mask frame is carried out by the alloy joining method, but as in the above-mentioned first embodiment, the heat of the epoxy resin or the like is used. Adhesion may be performed using a plastic resin or an ultraviolet curable resin.

As a modification of the second embodiment, a silicon wafer is adhered to a mask frame, first an X-ray absorber film is deposited, then back etching is performed, and then X-ray absorption is performed. The line absorber pattern and the dummy pattern may be formed. In this case as well, since the temperature of the bonding step does not contribute to the alteration of the X-ray absorber film, the alloy joining method can be applied.

In each of the above embodiments, a SiC mask frame is used as the mask frame, but it does not necessarily have to be made of SiC, and a glass mask frame may be used. , Especially Na
When glass containing is used, the anodic bonding method can be applied.

[0053]

According to the present invention, the pattern dimension rule and the pattern density of the X-ray absorber pattern are effectively the same as the pattern dimension rule and the pattern density of the X-ray absorber pattern around the exposure pattern region. Since the dummy pattern is provided, it is possible to suppress the generation of mask distortion due to the sidewall oxidation of the X-ray absorber pattern, which contributes to the improvement of the reliability of the X-ray exposure mask or the cost reduction. large.

When the X-ray absorber film is formed after adhering to the mask frame, the adhering step with the mask frame can be performed at a high temperature, whereby the X-ray exposure mask wafer and The adhesion to the mask frame can be strengthened, and it greatly contributes to the improvement of the reliability of the X-ray exposure mask.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a principle configuration of the present invention.

FIG. 2 is an explanatory diagram of a manufacturing process up to the middle of the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of the manufacturing process after FIG. 2 of the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of an exposure method using the X-ray exposure mask according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram of a manufacturing process up to the middle of the second embodiment of the present invention.

FIG. 6 is an explanatory diagram of the manufacturing process after FIG. 5 of the second embodiment of the present invention.

FIG. 7 is an explanatory diagram of a conventional X-ray exposure mask.

FIG. 8 is an explanatory diagram of L & S pattern dependence of the maximum mask distortion amount.

FIG. 9 is an explanatory diagram of the membrane area size dependency of the maximum mask distortion amount.

FIG. 10 is an explanatory diagram of a conventional improved X-ray exposure mask.

[Explanation of symbols]

1 Membrane film 2 Dummy pattern 3 X-ray absorber pattern 4 mask frame 5 Silicon wafer 6 Silicon etching mask 7 exposure area 8 Membrane area 11 Silicon wafer 12 SiC film 13 SiC film 14 openings 15 Ta film 16 mask frame 17 Membrane area 18 X-ray absorber pattern 19 dummy patterns 20 X-ray blocker 21 Silicon wafer 22 X-ray resist 23 Mechanical aperture 24 X-ray beam 31 Silicon wafer 32 SiC film 33 SiC film 34 mask frame 35 Membrane area 36 exposure pattern area 37 X-ray absorber pattern 38 X-ray blocker 41 Silicon wafer 42 Membrane membrane 43 mask frame 44 Membrane area 45 exposure pattern area 46 Absorber pattern 47 Belt-shaped rectangular blocker 48 X-ray blocker 49 Absorber pattern

Claims (3)

(57) [Claims] 1. A dummy pattern is arranged on a membrane film other than the exposed region, and a pattern rule and a pattern density of the dummy pattern are provided on the membrane film in the exposed region. An X-ray exposure mask characterized by having a density substantially equal to that of the mask. 2. A silicon wafer supporting a membrane film provided with an X-ray absorber film is back-etched to form a membrane region, and then an X-ray absorber pattern is formed on the membrane film in the exposure region. A method of manufacturing an X-ray exposure mask, characterized in that a dummy pattern having a pattern rule and a pattern density that are effectively equal to the pattern rule and the pattern density of the X-ray absorber pattern is also formed on the membrane film other than the exposure region. . 3. A silicon wafer supporting a membrane film is back-etched to form a membrane region,
An X-ray absorber film is deposited on the membrane film, and then an X-ray absorber pattern is formed on the membrane film in the exposed region, and the X-ray absorber pattern is also formed on the membrane film other than the exposed region. A method of manufacturing an X-ray exposure mask, comprising forming a dummy pattern having a pattern rule and a pattern density that are effectively equal to the pattern rule and the pattern density.