JP2675044B2 - Method of manufacturing mask for X-ray exposure - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing an X-ray exposure mask applicable to an X-ray exposure apparatus that transfers a fine pattern with high accuracy.

[Conventional technology]

In recent years, X-ray transfer technology has come to be used for transferring fine patterns. As a defect repairing method for manufacturing a defect-free X-ray exposure mask, a method similar to the defect repairing method that occurs in a light-shielding pattern in the conventional photomask manufacturing process has been attempted.

In this repair method, defects in the X-ray absorber pattern of the mask for X-ray exposure are inspected in the step of forming the pattern, and then the detected pattern defects are repaired by a method using a focused ion beam or a laser beam. To do. In this case, the pattern defects include a pattern missing part (hereinafter referred to as a white defect) and a pattern unnecessary part (hereinafter referred to as a black defect).

For the black defect of the pattern, for example, a method of applying an ion beam to the black defect to remove it by sputtering or a method of applying a laser beam to the black defect to remove it by evaporation is used.

For white defects in the pattern, for example, by using an ion beam or a laser beam, a gas containing a heavy metal element having a large X-ray absorption coefficient, such as W (CO) ₆ ,
A heavy metal element, in the above example, a method of depositing W on a white defect portion to form a necessary portion (hereinafter, referred to as an ion beam induced chemical deposition method and a laser beam induced chemical deposition method) is performed. Further, a method of directly irradiating an ion beam containing a heavy metal element having a large X-ray absorption coefficient onto the X-ray transparent film to form a required pattern (hereinafter, referred to as an ion beam direct deposition method) is also conceivable. .

Hereinafter, these correction methods will be described with reference to the drawings.

FIG. 3 is a diagram for explaining a conventional method for manufacturing an X-ray exposure mask including a black defect correcting step. In the figure, 1 is a mask layer pattern, 11 is a normal pattern, 12 is a black defect, 2 is an X-ray absorber layer, 21 is a normal X-ray absorber pattern, 22 is an X-ray absorber pattern black defect, and 3 is an X-ray. The transparent film, 5 is a mask support frame, 6 is an ion beam or laser beam, and 8 is damage.

It is assumed that another unnecessary black defect 12 of the normal pattern 11 is detected in the step of forming the mask layer pattern 1 (FIG. 3A). Using this pattern as a mask, the X-ray absorber layer 2 is removed by, for example, reactive ion etching (3rd
Next, the black defect portion is irradiated with the ion beam or the laser beam 6 and removed by sputtering or evaporation (FIG. 3 (c), (d)). The removal of this black defect causes damage 8 to the X-ray transparent film 3.
Then, the mask supporting frame 5 is removed by etching so that a part thereof remains, so that an X-ray exposure mask with few pattern defects can be obtained.

FIG. 4 is a diagram for explaining a conventional method for manufacturing an X-ray exposure mask including a white defect correction step. In the figure, the same numbers as those in FIG. 3 indicate the same contents. In addition, 13 is a white defect, 23 is a white defect of the X-ray absorber pattern, and 24 is a corrected X-ray absorber pattern.

It is assumed that a white defect 13 in which a necessary pattern does not exist is detected in the mask layer pattern 1 forming step (FIG. 4A). Similar to the case of repairing the black defect in FIG. 3, the X-ray absorber layer 2 is removed by, for example, reactive ion etching (FIG. 4 (b)), and then the above-mentioned ion beam induced chemical deposition method, A modified X-ray absorber pattern 24 is formed by a laser beam induced chemical deposition method, an ion beam direct deposition method or the like (FIGS. 4C and 4D). After that, the mask supporting frame 5 is removed by etching while leaving a part thereof, whereby an X-ray exposure mask with few pattern defects can be obtained.

[Problems to be solved by the invention]

However, since there is a great difference in the structure between the X-ray exposure mask and the photomask, some problems occur in such a correction method. The difference in the configuration between the X-ray exposure mask and the photomask is as follows.

The structure of the X-ray exposure mask comprises an X-ray transmissive film 3, an X-ray absorber pattern 21 formed thereon, and a mask support 5 which supports the X-ray transmissive film.

The X-ray transmission film 3 is made of a material having a small absorption coefficient for X-rays having an exposure wavelength, such as an inorganic material (SiN, SiN: H, BN: H, BN).
C, C, SiC, Ti), organic materials (polyimide, parylene) or composite films thereof are known, and the thickness thereof is 0.3 μm to 6 μm.

On the other hand, as the X-ray absorber 2, a material having a large absorption coefficient for X-rays having an exposure wavelength, for example, a heavy metal and alloys thereof (Ta, W, W: Ti, WN, Au) are used. Its thickness is
It is from 0.3 μm to 1.0 μm.

Since the X-ray exposure mask is used for transferring a fine pattern that constitutes a large-scale integrated circuit, the minimum line width of the pattern is considered to be 0.2 μm to 0.5 μm. In the X-ray exposure mask and photomask, the aspect ratio of the pattern is H / W as shown in FIG. 5 (W is the pattern width of the X-ray absorber or the light-shielding pattern as shown in FIG. 5, H
Is the thickness (height) of the pattern), the pattern aspect ratio of the X-ray exposure mask used for fine pattern transfer is usually larger than 1. For example, W = 0.2μ
H / W = 1.6〜 when m〜0.5μm, H ＝ 0.8μm ～ 1μm
It becomes 5.

On the other hand, the photomask consists of a substrate that is transparent to ultraviolet light and visible light and a light-shielding pattern formed on it, and the material of the light-shielding pattern is Cr, MoSi, etc., and its thickness H is 0.07 μm to 0.1 μm,
Since the pattern line width W is 0.3 μm or more, the aspect ratio H / W is
It is less than 0.3. Further, glass or quartz is used for the substrate, and the thickness thereof is 1 mm or more.

As described above, it can be seen that the X-ray exposure mask is characterized by having a pattern with a large aspect ratio on a very thin film as compared with the photomask.

Therefore, in the conventional defect correction method as described above, X
The following problems arise due to the circumstances peculiar to the line exposure mask.

First, when the pattern black defect on the mask for X-ray exposure is repaired by the conventional technique, that is, when the unnecessary X-ray absorber pattern is removed by the ion beam or the laser beam, the ion beam or the laser beam is used. There is a problem that the X-ray transparent film around or under the pattern is also partially removed. For example, in the method of evaporating and removing pattern black defects by thermal work such as a laser beam, the material of the X-ray absorber usually has a higher melting point than the material of the X-ray transmissive film and has a high resistance to the laser beam. For this reason, when the laser beam applied to the X-ray absorber bulges out of the absorber pattern and irradiates the X-ray transparent film in the peripheral portion, or when the X-ray under the X-ray absorber is removed immediately after the X-ray absorber is removed.
When the X-ray transparent film is irradiated, the X-ray transparent film is partially removed. Since the X-ray transmission film originally transmits X-rays, even if damage occurs, X-ray transmission will not be hindered. However, even if a part of the film is damaged, the mechanical strength will decrease and it will easily break. There is a problem that stress concentration occurs locally and expansion and contraction occur, resulting in poor exposure accuracy.

A problem similar to this occurs also in the photomask, but in the case of the X-ray exposure mask, the pattern absorber has a large aspect ratio, and thus it is necessary to irradiate the laser beam for a long time to remove the pattern absorber. However, the fact that the X-ray transparent film is thin and the influence of the damage is great overlaps with each other, which is a serious problem.

Second, when the pattern white defect on the X-ray exposure mask is repaired by the conventional technique, the ion beam direct deposition method,
The ion beam induced chemical deposition method and the laser induced chemical deposition method have a problem that it is difficult to form an X-ray absorber pattern having an aspect ratio of 1 or more with high shape accuracy.

The present invention is intended to solve the above-mentioned problems, and shortens the beam irradiation time to shorten the working time, the damage to the base is small, and the X-ray absorber pattern can be accurately formed. An object is to provide a method for manufacturing an exposure mask.

[Means for solving the problem]

As a result of various researches for solving the above problems, instead of modifying the X-ray absorber pattern, the mask layer pattern existing on the X-ray absorber layer is modified to form the X-ray absorber pattern. By completing the present invention by finding that it is possible to avoid the occurrence of the above problems,
The present invention is a method for manufacturing an X-ray exposure mask, which comprises the step of forming a pattern on an X-ray absorber layer existing therebelow using a mask layer formed in a pattern, wherein the pattern of the mask layer is defective. It is characterized in that it comprises an inspecting step, a step of correcting a pattern defect of the detected mask layer, and a step of forming a mask pattern on the X-ray absorber layer by the mask layer in which the pattern defect is corrected.

[Action]

According to the method of manufacturing an X-ray exposure mask of the present invention, the mask layer pattern is inspected for defects, and the black defect and the white defect detected at that time are corrected by respective suitable methods to make a mask layer pattern of the defect. After that, an X-ray absorber pattern is formed to manufacture an X-ray exposure mask with few defects, thereby shortening the beam irradiation time and the working time, and the damage to the base is reduced, and The absorber pattern can be formed with high shape accuracy.

〔Example〕

 Hereinafter, embodiments will be described with reference to the drawings.

[Example 1] [Example 1] will be described with reference to FIG.

The X-ray transparent film 3 is formed on one surface of the Si wafer forming the mask support frame 5 by a low pressure chemical vapor deposition method to a thickness of 0.5.
After forming a SiN film with a thickness of μm to 2 μm and forming an X-ray absorber layer 2 made of a tantalum film with a thickness of 0.3 μm to 1 μm on the film surface by a sputtering method, using an electron cyclotron resonance (ECR) plasma deposition method. Thickness 0.1 μm to 0.
A 3 μm SiO ₂ film was formed on the X-ray absorber layer 2 as a mask layer. Further, thereafter, a resist layer pattern forming a circuit pattern is formed on the mask layer by an electron beam plate making method, and the mask layer is dry-etched and removed by using the resist layer pattern as a mask, as shown in FIG. A mask layer pattern 1 forming a circuit pattern was formed (step I).

When the defect of the mask layer pattern is inspected,
It is assumed that the black defect 12 as shown in FIG. 4A is detected (step IIa).

Next, a focused ion beam 6 as shown in FIG. 1B is applied to the SiO ₂ layer pattern 12 which is a black defect to remove it by spattering, and a modified mask layer pattern 11 as shown in FIG. Was obtained (step IIIa). More specifically, for a square isolated black defect having a thickness of 0.25 μm and a side of 1 μm, which consists of a SiO ₂ layer, a beam acceleration voltage of 30 kV and a beam current of 110 pA G
By irradiating a ⁺ focused ion beam for about 1 second,
The isolated black defect could be removed by sputter etching. In the step of removing the SiO ₂ film, by detecting the secondary ions or secondary electrons generated by the focused ion beam irradiation, it is detected that the SiO ₂ film is removed and the tantalum film is exposed, and the beam irradiation is performed. If stopped, the extent of removing the X-ray absorber layer 2 by sputter etching can be extremely reduced.

Next, the underlying tantalum layer is CB using the pattern layer as a mask.
Removal by reactive ion etching using rF ₃ gas made it possible to obtain an X-ray absorber pattern 21 having no pattern defects as shown in FIG. 1 (d) (step IVa).

After that, while protecting the pattern portion with a jig so as not to come into contact with the etching solution, the silicon under the pattern portion is heated to a liquid temperature of 80 from the side opposite to the side having the X-ray absorber pattern.
The mask for X-ray exposure with few pattern defects was obtained by etching away with a 20% by weight potassium hydroxide aqueous solution at 0 ° C. (step V).

By the way, the etching rate of tantalum, which is the X-ray absorber material, by the Ga ⁺ focused ion beam is approximately the same as the etching rate of the SiO ₂ layer, which is the mask layer material. Therefore, when repairing an isolated black defect, the ion beam protrudes from the SiO ₂ layer pattern portion and irradiates the tantalum layer around the black defect, so that the tantalum layer is partially removed and the depth of 0.3 μm is reduced.
Even if a dent around m is formed, in the next step IVa, the X-ray transparent film SiN in the reactive ion etching is formed.
Since the etching rate of is less than 1/3 of the etching rate of tantalum, the depression of about 0.3 μm depth in the tantalum film is only the depression of about 0.1 μm depth in the SiN film. There is no practical problem. Further, if the beam irradiation is stopped by detecting the secondary ions and the secondary electrons as described above, the damage of the X-ray transmission film can be almost eliminated.

[Example 2] In the example described in Example 1, the following step was performed instead of step IIIa as a method of removing the black defect in the mask layer pattern.

That is, by irradiating the black defect 12 of the mask layer pattern with a rectangular shaped laser beam, SiO ₂ forming a black defect is formed.
The layer was removed by evaporation to obtain a modified mask layer pattern as shown in FIG. 1C (step IIIb). Since the underlying layer of the mask layer is a tantalum layer which is a refractory metal, the amount of the tantalum layer evaporated and removed was small.

Thereafter, Step IVa and Step V described in Example 1
Was used to obtain an X-ray exposure mask with few pattern defects.

Example 3 A mask layer pattern was formed by the method of the steps described in Example 1. Next, when the mask layer pattern is inspected for defects, a white defect portion 13 as shown in FIG. 2A is detected (step IIc).

Next, as shown in FIG. 2 (b), while spraying pyrene gas onto the tantalum film surface of the white defect portion, the Ga ⁺ focused ion beam is irradiated to the white defect portion based on the ion beam induced chemical deposition method. A pattern of carbon having a predetermined shape with a thickness of 0.3 μm is formed (step IIIc).

Thus, a modified mask layer pattern 14 as shown in FIG. 2C was obtained. More specifically, the beam acceleration voltage is 30 kV for a square isolated white defect with a side of 1 μm,
By irradiating the tantalum layer in the white defect portion with a Ga ⁺ integrated ion beam having a beam current of 130 pA for 4 seconds, a carbon layer pattern having a thickness of about 0.3 μm and a side of 1 μm could be formed. Then, using the normal mask layer pattern 11 made of SiO ₂ layer and the modified mask layer pattern 14 made of carbon as a mask as in Example 1, the tantalum layer 2 is formed by reactive etching using CBrF ₃ gas. After removal, a corrected X-ray absorber pattern as shown in FIG. 2 (d) was obtained (step IVc). Then, using the process V described in Example 1, an X-ray exposure mask with few X-ray absorber pattern defects was obtained.

As another example of white defect repair, a repair pattern may be formed by an ion beam direct deposition method.

Further, in the above-mentioned Examples 1 to 3, tantalum was selected as the X-ray absorber material and SiO ₂ was selected as the mask layer material, but the method of the present invention is not limited to these materials.

By the way, the present invention can be applied even if the mask layer material is an organic resist layer. However, in many cases, the inspection and correction for the organic film pattern are more difficult than the inspection and correction for the inorganic layer pattern described in this embodiment.

Further, although the isolated defects have been described in the above-mentioned first to third embodiments, as shown in FIG. 6, for example, as shown in FIG. 6, the defect may be any defect such as a part of the pattern or a continuous pattern in addition to the isolated defect. Good. In FIG. 6, A is a cut, B is a bridge, C is a depression, D is a protrusion, E is a defect consisting of white dots (pinholes), and F is a defect consisting of black dots, and these defect locations are raster-scanned and vector-scanned. It may be corrected by scanning and irradiating the beam by an appropriate method such as.

〔The invention's effect〕

As described above, according to the present invention, the following effects can be obtained.

In the correction of the white defect of the pattern, the pattern can be easily formed because a pattern having a small aspect ratio can be formed as compared with the conventional technique, and this is remarkable as the pattern line width W becomes smaller. For example, when W = 0.2 μm, the aspect ratio H / W in the prior art is 4 (H = 0.8 μm), but the aspect ratio H / W in the present invention is 1.3 (H = 0.25 μm). Yes, pattern formation becomes easier.

In the correction of the black defect of the pattern, since the aspect ratio of the pattern is smaller in the present invention, the beam irradiation time is shorter and the damage to the base is slight.

The working time can be shortened in both cases of white defects and black defects.

In the same repair device using a focused ion beam or a laser beam, it is possible to repair both black defects and white defects in the mask layer pattern depending on whether or not the chemical deposition gas is sprayed.

That is, by directly irradiating the beam without blowing gas, etching is performed to correct the black defect, and
By irradiating the beam while spraying gas, X
The gas adsorbed on the surface of the linear absorber layer can be ionized and deposited to form a repair pattern, and repair can be performed very easily.

Further, irradiation with a focused ion beam or laser beam makes it possible to obtain a pattern with good shape accuracy.

In the correction of the pattern white defect according to the present invention, the material of the pattern to be formed is not limited to the X-ray absorber material, for example, a heavy metal, and various materials can be selected as long as the material has etching resistance to the reaction gas. For example, C, SiO ₂ , Si
N, SiC, etc. are known.

Since the defect correction of the present invention is the correction of the mask layer, the re-correction is easy even after the correction once.

[Brief description of the drawings]

FIG. 1 is a view for explaining a method for manufacturing an X-ray exposure mask including a mask layer pattern black defect repairing step according to the present invention, and FIG. 2 is a mask layer pattern white defect repairing step X according to the present invention. FIG. 3 is a diagram for explaining a method for manufacturing a mask for X-ray exposure, and FIG. 3 shows a conventional method for manufacturing a mask for X-ray exposure, which includes a step of correcting a black defect in an X-ray absorber caused by a black defect in a mask layer pattern. 4 and 5 are views showing a conventional method for manufacturing a mask for X-ray exposure, which includes a step of correcting white defects in an X-ray absorber caused by white defects in a mask layer pattern, and FIG. 5 is an explanation of an aspect ratio of the pattern. FIG. 6 and FIG. 6 are diagrams for explaining the types of defects. 1 ... Mask layer pattern, 2 ... X-ray absorber layer, 3 ...
X-ray transparent film, 5 ... Mask support frame, 6 ... Ion beam or laser beam, 11 ... Normal pattern, 12 ... Black defect of mask layer pattern, 13 ... White defect of mask layer pattern, 14 ... Corrected mask layer pattern, 21 ... Normal X-ray absorber pattern, 22 ... Black defect of X-ray absorber pattern, 23 ... White defect of X-ray absorber pattern, 24 ... Corrected X-ray Absorber pattern.

Claims (4)

(57) [Claims] 1. A method of manufacturing an X-ray exposure mask, comprising the step of forming a pattern on an X-ray absorber layer existing therebelow using a mask layer formed in a pattern, wherein the mask layer pattern is provided. A method for manufacturing an X-ray exposure mask, comprising the steps of: defect inspection, the step of correcting a detected pattern defect in the mask layer, and the step of forming a mask pattern on the X-ray absorber layer by the mask layer in which the pattern defect has been corrected. 2. The mask layer pattern is a black defect, and secondary ions generated at the time of removing the black defect by ion beam sputtering,
Alternatively, the method for manufacturing an X-ray exposure mask according to claim 1, wherein the beam irradiation is stopped at the same time as the exposure of the X-ray absorber layer by detecting secondary electrons. 3. The method for manufacturing an X-ray exposure mask according to claim 1, wherein the mask layer pattern is a black defect, and the black defect is removed by irradiation with a shaped laser beam. 4. The X-ray according to claim 1, wherein the mask layer pattern is a white defect, and the white defect is corrected by a laser beam induced chemical deposition method, an ion beam induced chemical deposition method, or an ion beam direct deposition method. Method for manufacturing exposure mask.