JP2001110716A - Mask for x-ray exposure and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce generation of mask distortions due to side wall oxidization of an X-ray absorber pattern, without making a membrane region coincide with an exposure pattern region. SOLUTION: Dummy patterns 4 are arranged on a membrane film 1 except an exposure region 7, and the pattern rule and pattern density of the dummy patterns 4 is practically made equal to the pattern rule and pattern density of an X-ray absorber pattern 3 which is provided on the membrane film 1 in the exposure region 7.

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 of manufacturing the same, and more particularly, to a mask resulting from stress accompanying oxidation of a sidewall of an X-ray absorber pattern after formation of the X-ray absorber pattern. The present invention relates to an X-ray exposure mask characterized by a configuration for reducing distortion and a method for manufacturing the same.

[0002]

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

[0003] Among them, the back-etching 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 type. Therefore, a conventional X-ray exposure mask will be described with reference to FIG.

FIG. 7A is a schematic cross-sectional view of a conventional X-ray exposure mask. First, dichlorosilane is applied to both sides of a silicon wafer 31 having a thickness of, for example, 2 μm. After depositing 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 membrane region 35 on SiC film 33 on the back side 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 of the SiC film 33 corresponding to the membrane region 35. In this case, the upper SiC film 32 becomes a membrane film.

Then, a Ta film serving as an X-ray absorber film is deposited to a thickness of, for example, 0.4 μm on the SiC film 32 on the surface side serving as the membrane film by sputtering, and then, for example, 300 μm thick. By annealing at a temperature of ° C., the stress of the Ta film serving as the X-ray absorber film is corrected, and then the film is attached to an SiC mask frame 34 using an adhesive (not shown). For example, bonding is performed by performing a heat treatment at 200 ° C. for 5 minutes under a load of about 5 kg weight.

Next, the SiC film 32 is exposed by etching the silicon wafer 31 from the back side using KOH as an etchant, and the exposed portion of the SiC film 32 is made a membrane region 35. A resist pattern (not shown) for forming an X-ray absorber pattern 37 is formed in the exposure pattern area 36 on the surface side of the film 32, and the Ta film is etched by performing dry etching using the resist pattern as a mask. And X-ray absorber pattern 3
By forming 7, the basic structure of the X-ray exposure mask can be obtained. Note that the Ta film remaining around becomes an X-ray blocker 38.

FIG. 7B shows an exposure pattern area 36 and a membrane area 3 of the X-ray exposure mask manufactured as described above.
FIG. 5 is a diagram showing an arrangement relationship of an X-ray blocker 38 and a rectangular exposure pattern area 36 inside a rectangular membrane area 35. Although the X-ray blocker 38 is shown to be located outside the rectangular membrane area 35, it is actually located in contact with the rectangular exposure pattern area 36 as shown in FIG. Is what it is.

Since such an X-ray exposure mask is an equal-size mask, higher positional accuracy is required as the device pattern becomes finer. The primary factor that degrades the pattern position accuracy is the occurrence of mask distortion due to the stress of the X-ray absorber film (Ta film in FIG. 7) itself. That is, when the formed X-ray absorber film has a stress, the stress is released when the X-ray absorber is processed by dry etching or the like and an X-ray absorber pattern is formed in an exposure pattern region. This causes mask distortion.

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

[0010]

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

FIG. 8 shows L & S (line-and-space) of the maximum mask distortion when the size of the membrane region is 34 mm square and the size of the exposure pattern region is 30 nm square.
FIG. 9 is an explanatory diagram of pattern dependency, and shows L & S as shown in the figure.
It is understood that the maximum distortion amount of the mask increases rapidly as the pattern becomes smaller.

This is considered to be because the X-ray absorber pattern has a sidewall surface oxidized by about several nm after the pattern is formed, and the oxidation generates a compressive stress in the film. It is considered that the total of the side wall areas increases as the pattern becomes finer, so that the mask distortion becomes remarkable and the L & S pattern dependency shown in FIG. 8 can be obtained.

Although the mask distortion due to the sidewall oxidation hinders the fabrication of a high-precision mask, such sidewall oxidation cannot be controlled by the film forming conditions at the time of film formation. Therefore, with the size of the exposure pattern area fixed at a size of 30 mm square, the change in the maximum mask distortion when the size of the membrane area was changed was examined.
FIG. 9 shows the result.

FIG. 9 is an explanatory diagram of the dependence of the maximum distortion amount of the mask on the size of the membrane area when the size of the exposure pattern area is fixed to 30 mm square. , 0.1 μm and 1.0 μm. As is clear from the figure, when the pattern dimension rule of the L & S pattern is large, there is little problem because the original distortion amount is small, though the membrane region size dependence is observed.

On the other hand, when the pattern dimension rule of the L & S pattern is small, the dependence on the size of the membrane region becomes remarkable, but as the size of the membrane region approaches the size of the exposure pattern region, the maximum mask distortion becomes smaller. When the membrane region and the exposure pattern region match, distortion is eliminated in principle. This is because, when substantially 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, so that mask position distortion does not appear.

However, it is actually very difficult to make the membrane region coincide with the exposure pattern region. That is, the formation of the membrane region is performed from the back surface as described above, while the formation of the exposure pattern region is performed from the front surface. This is because it is difficult to accurately match the two due to a problem of side etching at the time of etching.

Further, in the dry etching step of the X-ray absorber film, the temperature and the way of applying a 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 JP-A-2-56921). This will be described with reference to FIG. FIG. 10A is a schematic cross-sectional view of a conventional improved X-ray exposure mask, and FIG. 10B is an arrangement of an exposure pattern area, a rectangular strip blocker, and an X-ray blocker. FIG. 11 is a diagram showing the relationship, and further, X in FIG.
It is a figure which shows the shape of the absorber pattern provided in the line blocker.

Referring to FIGS. 10A and 10B, this improved X-ray exposure mask is provided with a band-shaped rectangular blocker 47 made of a solid pattern around a rectangular exposure pattern area 45 provided with an absorber pattern 46. The X-ray blocker 48 located outside the absorber pattern 49
Is provided.

At this time, the absorber pattern 4 provided on the X-ray blocker 48 at this time is shown in FIG.
As shown in the figure, the shape of the pattern 9 may be a simple lattice pattern, as long as the pattern density is the same as the pattern density of the absorber pattern 46 formed in the exposure pattern area 45. The stress caused by the blockers 48 is reduced, and the band-shaped rectangular blockers 47 are formed.
Is to absorb penumbra blur caused by the mechanical aperture.

However, even in such an improved X-ray exposure mask, the influence of side wall oxidation is not considered at all, and a band-shaped rectangular blocker 47 having a solid pattern is provided in the membrane region 44. Therefore, it is essentially impossible to match the membrane region 44 with the exposure pattern region 45.

Accordingly, an object of the present invention is to suppress the occurrence of mask distortion due to oxidation of the side wall 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, and means for solving the problems in the present invention will be described with reference to FIG. FIG. 1 is a schematic sectional view of an 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 area 7 and the pattern rule and pattern density of the dummy pattern 4 are changed. The pattern rule and pattern density of the X-ray absorber pattern 3 provided on the membrane film 1 are effectively equalized.

As described above, the dummy pattern 4 having a pattern rule and a pattern density which are substantially equal to the pattern rule and the pattern density of the X-ray absorber pattern 3 is provided also on the membrane film 1 other than the exposure region 7. Almost the same pattern can be formed on the entire surface of the region 8, whereby the influence of the side wall oxidation is uniform on the entire surface of the membrane region 8.
It is possible to suppress the occurrence of mask distortion without making the exposure area 7 coincide with the exposure area 7. In the present specification,
“Effectively equal” does not mean that they are equal with mathematical rigor, but is equivalent to the extent that the distortion caused by sidewall oxidation falls within the allowable range of the mask distortion at that time. Is what it means.

(2) Further, according to the present invention, in the method of manufacturing a mask for X-ray exposure, a silicon wafer 5 supporting a membrane film 1 provided with an X-ray absorber film is etched on the back surface to form a membrane region 8. After that, the X-ray absorber pattern 3 is formed on the membrane film 1 in the exposure region 7, and the pattern rule and the pattern density of the X-ray absorber pattern 3 on the membrane film 1 other than the exposure region 7 are also effectively equal. 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 a manufacturing process of a type in which the back surface etching is advanced, whereby the restriction on the stress control of the X-ray absorber film is relaxed, so that a certain low stress can be obtained. This eliminates the need to measure stress, thereby simplifying the manufacturing process.

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

As described above, the provision of the dummy pattern 4 alleviates the restriction on the stress control of the X-ray absorber film, so that the X-ray absorption after the back surface etching of the silicon wafer 5, that is, after the bonding with the mask frame 4. Since the body film can be formed, the X-ray absorber film is not deteriorated due to the temperature at the time of bonding with the mask frame 4, so that a strong bonding by a high-temperature bonding process can be performed.

[0029]

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

Referring to FIG. 2B, a resist pattern (not shown) having a window pattern serving as a membrane region is formed on the backside SiC film 13 by a photolithography process. An opening 14 is provided in a region corresponding to the membrane region of the SiC film 13 by performing etching.

Referring to FIG. 2C, a Ta film 1 serving as an X-ray absorber film is formed on the surface side SiC film 12 serving as a membrane film by sputtering.
5 is deposited to a thickness of, for example, 0.4 μm, and then annealed at a temperature of, for example, 300 ° C. to obtain X.
The stress correction of the Ta film 15 serving as the line absorber film is performed.

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

Next, as shown in FIG. 3 (e), the silicon wafer 11 is etched from the back side using
The C film 12 is exposed, and the exposed portion of the SiC film 12 is used as a membrane region 17.

Next, 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. The Ta film 15 is etched by performing 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 around without being etched in this etching step becomes the X-ray blocker 20.

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

As described above, in the first embodiment of the present invention, the pattern size rule and the pattern size rule that are substantially equal to the pattern size rule and the pattern density of the X-ray absorber pattern 18 around the X-ray absorber pattern 18 are provided. 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.

In addition, since the restriction on the stress control of the Ta film 15, ie, the X-ray absorber film, is relaxed, if a certain low stress is obtained, it is not necessary to measure the stress, so that the process is simplified. , Improving the throughput.

Next, an exposure method using an X-ray exposure mask according to the first embodiment of the present invention will be described with reference to FIG. Referring to FIG. 3, 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 pattern 18 is closely opposed to the X-ray resist. X-ray beam 24 by stepper
Exposure is performed by irradiating. In this case, the mechanical aperture 23 needs to have a shape that masks the peripheral region including the dummy pattern 19 so that only the X-ray absorber pattern 18 is transferred.

Next, a manufacturing process according to 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 silicon wafer 11 having a thickness of, for example, 2 μm is formed on both surfaces of the silicon wafer 11 by a CVD method using dichlorosilane and acetylene as source gases. Are, for example, 2.0 μm SiC films 12 and 13.
Is deposited. In this case, the upper SiC film 12 becomes a membrane film.

Referring to FIG. 5B, a resist pattern (not shown) having a window pattern serving as a membrane region is formed on the backside SiC film 13 by a photolithography process. An opening 14 is provided in a region corresponding to the membrane region of the SiC film 13 by performing etching.

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

Next, as shown in FIG. 5D, the silicon wafer 11 is etched from the back side using KOH as an etchant, thereby
The C film 12 is exposed, and the exposed portion of the SiC film 12 is used as a membrane region 17.

Referring to FIG. 6E, a Ta film 1 serving as an X-ray absorber film is formed on the SiC film 12 on the surface side serving as a membrane film by sputtering.
5 is deposited to a thickness of, for example, 0.4 μm. In this case, since the bonding step with the mask frame 16 has already been completed, it is not necessary to control the stress of the Ta film 15.

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 of the SiC film 12 by electron beam exposure. The Ta film 15 is etched by performing 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 remaining around without being etched in this etching step becomes the X-ray blocker 20.

In this case as well, the dummy pattern 19 is formed almost continuously from the exposure pattern area in which the X-ray absorber pattern 18 is formed, and the pattern size rule and pattern density of the dummy pattern 19 are ,
The pattern density 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 bonding with the mask frame 16, the high temperature of 500 ° C. or more is required in the step of bonding with the mask frame 16. Can be used, whereby the bonding between the mask wafer for X-ray exposure and the mask frame 16 can be performed more firmly and more reliably. The dummy pattern 19
The effect provided by is the same as in the case of the first embodiment.

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

In each of the above embodiments, a Ta film is used as the X-ray absorber film for simplicity of explanation, but is not necessarily limited to the Ta film.
i-containing amorphous film, Ge-containing amorphous Ta film,
Alternatively, a W film or the like may be used. In particular, an amorphous Si-containing amorphous Ta film or a G film may be used.
When an e-containing amorphous Ta film is used, since there is no crystal grain boundary, oxidation at the crystal grain boundary disappears,
Thereby, the influence of the sidewall oxidation is further reduced.

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

Further, in the second embodiment, the bonding with the mask frame is performed by using the alloy bonding method. However, as in the first embodiment, the heat of epoxy resin or the like is used. The bonding may be performed using a plastic resin or an ultraviolet curable resin.

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

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

[0053]

According to the present invention, the pattern size rule and the pattern density of the X-ray absorber pattern are substantially the same as the pattern size rule and the pattern density of the X-ray absorber pattern around the exposure pattern area. Since the dummy pattern is provided, it is possible to suppress the occurrence of mask distortion due to the oxidation of the side wall of the X-ray absorber pattern, thereby contributing to improvement in reliability or cost reduction of the X-ray exposure mask. large.

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

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram of a manufacturing process partway through the first embodiment of the present invention.

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

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

FIG. 5 is an explanatory diagram of a manufacturing process partway through a second embodiment of the present invention.

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

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

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

FIG. 9 is an explanatory diagram of the dependence of the maximum distortion amount of the mask on the size of the membrane region.

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

[Explanation of symbols]

 DESCRIPTION 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 Opening 15 Ta film 16 Mask frame 17 Membrane area Reference Signs List 18 X-ray absorber pattern 19 Dummy pattern 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 absorption Body pattern 38 X-ray blocker 41 Silicon wafer 42 Membrane film 43 Mask frame 44 Membrane area 45 Exposure pattern area 46 Absorber pattern 47 Strip shape Rectangular blocker 48 X-ray blocker 49 Absorber pattern

Claims (3)

[Claims] 1. A pattern rule and a pattern density of an X-ray absorber pattern provided on a membrane film of an exposure area, wherein a dummy pattern is arranged on a membrane film other than an exposure area. An X-ray exposure mask having a density substantially equal to the density. 2. A silicon wafer supporting a membrane film provided with an X-ray absorber film is back-etched to form a membrane region. Then, an X-ray absorber pattern is formed on the membrane film in an exposure region. A method of manufacturing a mask for X-ray exposure, comprising: forming a dummy pattern having a pattern rule and a pattern density that are substantially equal to the pattern rule and the pattern density of the X-ray absorber pattern on a membrane film other than the exposure region. . 3. After a silicon wafer supporting the membrane film is etched on the back surface to form a membrane region,
Depositing an X-ray absorber film on the membrane film, and then forming an X-ray absorber pattern on the membrane film in the exposed area, and also forming the X-ray absorber pattern on the membrane film in areas other than the exposed area; A method of manufacturing a mask for X-ray exposure, 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.