JP2003031480A - Reticle for electron beam exposure, reticle blank for electron beam reduction exposure, and method of manufacturing the same - Google Patents

Abstract

[PROBLEMS] To provide a reticle for electron beam exposure, a reticle blank for electron beam reduction exposure, and a method of manufacturing the reticle, which have extremely small warpage and can reduce the occurrence of positional distortion of the blank due to resist stress. A method of manufacturing a reticle blank for electron beam reduction exposure according to the present invention is a method of manufacturing a reticle blank for electron beam exposure, comprising a Pyrex (registered trademark) glass substrate 12 having a silicon membrane and a support for supporting the silicon membrane. A step of providing pillars on the Pyrex (registered trademark) glass substrate 12, a step of preparing an SOI wafer composed of the thin film silicon layer 15, the silicon oxide layer and the silicon support substrate, and a step of preparing a thin film of the SOI wafer. The method includes a step of bonding the surface of the silicon layer 15 to the Pyrex (registered trademark) glass substrate 12, a step of removing the silicon support substrate, and a step of removing the silicon oxide layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reticle for electron beam exposure, a reticle blank for electron beam reduction exposure, and a method for manufacturing the same, which can reduce the occurrence of positional distortion of the blank due to resist stress.

[0002]

2. Description of the Related Art In recent years, with the high integration of semiconductor integrated circuits, a charged particle beam such as an electron beam or an ion beam has replaced the photolithography technique using light, which has been the main means for forming fine patterns for many years. Alternatively, a new exposure method using X-rays has been studied and put into practical use. Of these, electron beam exposure that uses electron beams to form patterns is
Since the electron beam itself can be narrowed down to a few nm,
A major feature is that fine patterns of 0.1 μm or less can be produced.

However, the conventional electron beam exposure method is
Since the method is a one-stroke writing method, the finer the pattern, the more the electron beam must be drawn, so that the drawing time becomes longer and the throughput is greatly affected.

Therefore, a method has been proposed in which a reticle is used to collectively expose several hundred μm squares on a wafer. FIG. 6A is a sectional view showing the reticle.
FIG. 6B is a perspective view of the reticle shown in FIG.

As shown in FIG. 6A, in this reticle, an electron beam transmitting portion opening (not shown) is formed in a membrane-shaped electron beam scattering portion (silicon membrane portion) 1 having a thickness of about 2 μm. It is a stencil type. At this time, the area that can be exposed by a single electron beam is 25 on the wafer.
It is about 0 μm square (about 1 mm square on the reticle). Therefore, in order to bake the entire semiconductor chip, it has a structure in which a membrane of about 1 mm square is spread, and this is supported by silicon 2 having lattice-like columns.

The reticle is generally manufactured by the following method. First, the Si wafer 2 is wet-etched with a potassium hydroxide aqueous solution from the back surface of the (100) plane Si wafer 2 in which boron is doped. Parts other than the wet-etched area are protected by silicon nitride or the like. Further, by doping boron with a concentration of 1 × 10 ²⁰ atom / cm ³ to a desired thickness, the wet etching rate can be slowed by the doped boron, so that the membrane can be easily manufactured. Then, a resist or the like was applied on the membrane, the resist pattern was exposed on the membrane using an electron beam drawing device, etc., and the pattern was transferred to a silicon membrane to produce a stencil pattern.

However, in the case of the above method, since the wet etching has the crystal plane anisotropy, the pillars 2 between the membranes 2
Has an angle of 54.74 °. For this reason, there is a problem that the reticle for one chip becomes very large, and in order to make the pillars 2 between the membranes as thin as possible and more vertical, a method using dry etching for etching the silicon pillars has been proposed. .

One is a method which also uses a boron-doped silicon wafer. This method is shown in FIG.
It is shown in (c). First, as shown in FIG. 7A, the surface of the silicon wafer 4 is doped with boron to form a boron-doped layer 3.

After that, as shown in FIG. 7B, vertical pillars are formed by digging from the back surface of the silicon wafer 4 to a point of several tens μm of a predetermined thickness by dry etching. Next, as shown in FIG. 7C, only the final wet etching is used to stop the etching with the membrane having a predetermined thickness. The silicon oxide layer 5 is protected except for the etching location. Next, the silicon oxide layer 5 is removed.

SO is a further simplification of this method.
This is a method using an I (Silicon On Insulator) wafer. FIG. 8 is a sectional view showing an SOI wafer. SOI
As shown in FIG. 8, the wafer has a structure in which a silicon oxide layer 7 is formed on a silicon supporting substrate (supporting wafer) 8 and a thin film silicon layer 6 is further formed thereon. Therefore, the intermediate silicon oxide layer 7 can be used as an etching stop layer for dry etching. By dry-etching a predetermined part of the silicon support substrate 8, a reticle blank having vertical columns of several hundred μm width can be obtained. It was possible to make.

FIGS. 9A to 9C are sectional views showing a method of manufacturing a reticle blank using an SOI wafer.

First, as shown in FIG. 9A, an SOI wafer including a thin film silicon layer 6, a silicon oxide layer 7 and a silicon supporting substrate 8 is prepared. Next, as shown in FIG. 9B, a resist or a silicon oxide layer 9 is formed on the silicon supporting substrate 8.

Thereafter, as shown in FIG. 9C, the resist or the silicon oxide layer 9 is patterned to protect the resist or the silicon oxide layer, leaving only the pattern of the pillars 8a to 8c. To do. Next, the silicon supporting substrate 8 is dry-etched using this pattern as a mask and the silicon oxide layer 7 as an etching stopper.
Next, the silicon oxide layer 7 is removed by wet etching. After that, the pattern is removed. As a result, a reticle blank having vertical stanchions 8a to 8c having a width of several hundred μm is manufactured.

In any of the above methods, etching must be performed to a depth corresponding to the thickness of the silicon wafer. For example, 300 μm or more when using a 3-inch wafer and 700 μm when using an 8-inch wafer
It is necessary to vertically etch the above depth.

In order to etch this depth, etching utilizing side wall protection is often used. this is,
In order to suppress the lateral etching of the groove to be etched, by adding a gas that forms a polymer for etching protection of the resist surface to the etching gas, it was possible to perform etching with good verticality.

When an electron beam reduction exposure reticle blank is manufactured using an 8-inch wafer, the structure is as shown in FIG. That is, the wafer 10 is 132 mm ×
Two structural processed portions (membrane regions) 11 having columns with a size of 55 mm are formed side by side.

[0017]

However, the reticle blank for electron beam reduction exposure produced from the SOI wafer having the above-mentioned conventional silicon supporting substrate has the following problems. First, since the silicon support substrate 8 has a significantly larger warp than a normal glass reticle, columns (lattice silicon) 8a to 8c made of the silicon support substrate are formed.
When the wafer is chucked by the exposure apparatus, a large distortion occurs.

Secondly, a resist film must be coated on the silicon supporting substrate in order to form a pillar on the silicon supporting substrate, and an opening pattern is formed in the thin film silicon layer 6. Since a resist film must be applied on the thin silicon layer, resist stress causes positional distortion in the entire blank.

The present invention has been made in consideration of the above circumstances, and an object thereof is an electron beam exposure reticle and an electron beam exposure reticle which have a very small warp and can reduce the occurrence of blank positional distortion due to resist stress. A reticle blank for line reduction exposure and a method for manufacturing the same.

[0020]

In order to solve the above problems, it was decided to use a glass substrate having a small warp and a very flat surface as a supporting substrate for a reticle blank for electron beam reduction exposure. . It is known that warpage remains in single crystal silicon even if the thickness is increased to several mm. Therefore, it can be said that glass is overwhelmingly advantageous over silicon when flatness is required.

It is not difficult to manufacture an SOI wafer by using a glass supporting substrate instead of the silicon supporting substrate. However, it is very difficult to form the lattice-like pillars on the glass supporting substrate in such a state and leave only the thin film silicon layer on the glass supporting substrate having the pillars. Further, if the glass supporting substrate is made thin to facilitate processing, the glass supporting substrate will be deformed when the resist is applied. Therefore, it was decided to first form the columns on the glass supporting substrate having a thickness of several mm or more and then add the membrane.

An electron beam exposure reticle blank according to the present invention is an electron beam exposure reticle blank comprising a membrane and a supporting substrate having columns for supporting the membrane, wherein the supporting substrate is made of glass. To do.

According to the reticle blank for electron beam reduction exposure, since glass is used as the material of the substrate that supports the membrane, the warp can be made much smaller than that of the conventional silicon supporting substrate. As a result, it is possible to suppress the distortion caused by chucking the reticle to the exposure apparatus and the positional distortion caused by the resist stress.

In addition, in the reticle blank for electron beam reduction exposure according to the present invention, it is preferable that impurities are introduced into the membrane to adjust stress.

The electron beam reduction exposure reticle according to the present invention is a reticle used when exposing with an electron beam, and supports a membrane, an opening formed in the membrane for transmitting the electron beam, and the membrane. And a glass support substrate having columns.

According to the electron beam reduction exposure reticle,
Since the glass substrate is used as the substrate for supporting the membrane, the warp can be significantly reduced as compared with the conventional silicon supporting substrate. As a result, it is possible to suppress the distortion caused by chucking the reticle to the exposure apparatus and the positional distortion caused by the resist stress.

Further, in the electron beam reduction exposure reticle according to the present invention, it is preferable that impurities for stress adjustment are introduced into the membrane.

A method for producing a reticle blank for electron beam reduction exposure according to the present invention is a method for producing a reticle blank for electron beam exposure, which comprises a glass substrate having a silicon membrane and a supporting column for supporting the same. A step of preparing and performing a process of providing a pillar on the glass substrate; a step of preparing an SOI wafer composed of a thin film silicon layer, a silicon oxide layer and a silicon supporting substrate;
The method is characterized by further comprising a step of bonding the surface of the thin film silicon layer of the wafer to a glass substrate having a support, a step of removing the silicon supporting substrate, and a step of removing the silicon oxide layer.

Further, in the method of manufacturing a reticle blank for electron beam reduction exposure according to the present invention, after the step of removing the silicon oxide layer, a step of introducing impurities for stress adjustment into the thin film silicon layer is performed. It is also possible to include further.

Further, in the method of manufacturing a reticle blank for electron beam reduction exposure according to the present invention, the SOI wafer is provided between the step of preparing an SOI wafer and the step of laminating.
It is possible to further include a step of introducing impurities for adjusting stress into the thin film silicon layer of the wafer.

A method of manufacturing a reticle blank for electron beam reduction exposure according to the present invention is a method of manufacturing a reticle blank for electron beam exposure, which comprises a glass substrate having a silicon membrane and a support for supporting the silicon membrane. And a step of forming a support on the glass substrate on which the conductive film is formed.

[0032]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a plan view showing a reticle blank for electron beam reduction exposure according to an embodiment of the present invention, and FIG. 1B is a plan view 1b-shown in FIG.
It is sectional drawing which followed the 1b line.

As shown in FIG. 1A, the Pyrex (registered trademark) glass substrate 12 has a size of 6 inches × 6.
It is a substrate having a flat flatness and a flatness with a thickness of 6.25 mm and a square inch plane. The Pyrex (registered trademark) glass substrate 12 is formed with structural processing portions 12a and 12b having two columns, and the plane of the structural processing portion having each column is 132 mm × 55 mm.
It has a rectangular shape of the size.

As shown in FIG. 1B, a Pyrex (registered trademark) glass substrate 1 processed into a structure having columns.
A thin-film silicon layer (active layer) 15 having a thickness of about 2 μm, which serves as a membrane, is attached on top of 2. Impurities for adjusting stress are introduced into the active layer 15. In other words, since the area that can be exposed by a single electron beam is about 250 μm square on the wafer (about 1 mm square on the reticle), 1 mm is needed to burn the entire semiconductor chip.
It has a structure in which a membrane of about a corner is spread, and this is supported by a glass substrate 12 having lattice-like columns.

2 to 5 are views showing a method for manufacturing the electron beam reduction exposure reticle blank shown in FIG.

First, as shown in FIG. 2, a Pyrex (registered trademark) glass substrate 12 having a size of 6 inches × 6 inches, a thickness of 6.25 mm, and a flatness of 1 μm or less is prepared.

Next, as shown in FIG. 3A, this Pyrex (registered trademark) glass substrate 12 is processed into a structure having lattice-like columns by ultrasonic processing. Next, the Pyrex (registered trademark) glass substrate 12 is washed. Next, the SOI wafer 16 shown in FIG. 3B is prepared.
The SOI wafer 16 includes a silicon support substrate 13 and a BOX layer (silicon oxide layer) formed on the support substrate 13.
14 and a thin film silicon layer (active layer) 15 formed on the BOX layer 14 and having a thickness of about 2 μm.

Next, as shown in FIG. 4, a Pyrex (registered trademark) glass substrate 1 processed into a structure having columns.
SOI wafer 16 so as to have the same shape as the planar shape of 2
Is processed into a flat rectangular shape. Next, after bonding the surface of the thin film silicon layer 15 of the SOI wafer 16 and the Pyrex (registered trademark) glass substrate 12 at room temperature, the bonded substrate is heat-treated (baked) at 1100 ° C.
As a result, the SOI wafer 16 and the Pyrex (registered trademark) glass substrate 12 are chemically bonded and directly bonded.

Thereafter, as shown in FIG. 5, the silicon supporting substrate 13 of the SOI wafer on the bonded substrates is
It is removed by wet etching using potassium hydroxide. Then, the BOX layer 14 of the SOI wafer is removed by wet etching using a mixed solution of hydrofluoric acid and ammonium fluoride. At this time, the etching solution is BO
Since the X layer 14 and the active layer 15 have a sufficient etching selection ratio (a sufficient difference in etching rate), the active layer 15 serving as a membrane is not etched at all.

Next, in order to adjust the stress of the membrane-formed active layer, the active layer 15 is doped with phosphorus as an impurity by thermal diffusion using a thermal diffusion device. The phosphorus concentration at this time is about 1 × 10 ¹⁸ atoms / cm ³ . In this way, the reticle blank for electron beam reduction exposure shown in FIG. 1 is manufactured.

An electron beam reduction exposure reticle can be manufactured by opening an opening (not shown) of an electron beam transmission portion in the membrane (active layer 15) of this electron beam reduction exposure reticle blank. Photolithography technology is used to open the openings.

According to the above-mentioned embodiment, since the glass substrate 12 is used as the substrate for supporting the membrane, the warp can be remarkably reduced as compared with the conventional silicon supporting substrate. As a result, it is possible to suppress the distortion caused by chucking the reticle to the exposure apparatus and the positional distortion caused by the resist stress.

Further, in the above-mentioned embodiment, since the reticle blank for electron beam reduction exposure is manufactured using the glass substrate having a quadrangular plane, the reticle manufactured by this reticle blank also has a quadrangular plane. . Therefore, there is also an advantage that the reticle blank for electron beam reduction exposure can be used without making a large change in specifications of the reticle manufacturing apparatus, the inspection apparatus, the reticle holder, etc. which are currently used.

Next, a method of manufacturing a reticle blank for electron beam reduction exposure according to a modification of the above embodiment will be described. The description of the same parts as those in the above embodiment will be omitted.

First, a Pyrex (registered trademark) glass substrate is prepared, and a conductive film made of a conductive material is formed to a thickness of about 2 μm on the entire surface of this Pyrex (registered trademark) glass substrate. Then, this Pyrex (registered trademark) glass substrate is processed into a structure having columns by ultrasonic processing,
To wash. In this way, a reticle blank for electron beam reduction exposure is manufactured.

Also in the above modification, the same effect as in the above embodiment can be obtained.

The present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the gist of the present invention. For example, although the Pyrex (registered trademark) glass substrate is used in the above-described embodiment, if the glass material has a small warpage and can be flattened,
It is also possible to use another glass substrate, for example, a substrate made of low thermal expansion glass manufactured by Zerodur.

In the above embodiment, the thickness is 6.25.
Although a Pyrex (registered trademark) glass substrate having a thickness of mm is used, a glass substrate having another thickness can be used as long as it has a thickness of several mm or more.

Further, in the above embodiment, the glass substrate 1
Although ultrasonic processing is used when processing 2 into a structure having columns, it is not limited to this, and other processing methods can be used.

In the above embodiment, the SOI wafer 16 and the Pyrex (registered trademark) glass substrate 12 are directly bonded to each other, but the SOI wafer and the Pyrex (registered trademark) glass substrate are bonded to each other by anodic bonding. It is also possible.

Further, in the above-mentioned embodiment, the silicon supporting substrate 13 and the BOX layer 14 of the SOI wafer in the bonded substrates are removed by wet etching, but the removing method is not limited to this and other methods may be used. A removing method can be used, and for example, the silicon supporting substrate 13 and the BOX layer 14 can be removed by grinding / polishing or dry etching.

In the above embodiment, the active layer 15 is doped with phosphorus, which is an impurity, by thermal diffusion using a thermal diffusion device. However, impurity ions are introduced into the active layer 15 by ion implantation. It is also possible to do so.

In the above embodiment, the active layer 15 is doped with phosphorus, but other impurities can be introduced as long as the stress of the active layer can be adjusted.

Further, in the above-mentioned embodiment, the impurities for stress adjustment are introduced after the SOI wafer 16 and the Pyrex (registered trademark) glass substrate 12 are bonded together. It is also possible to introduce it.

[0055]

As described above, according to the present invention, glass is used as the material of the substrate having the columns for supporting the membrane. Therefore, it is possible to provide an electron beam exposure reticle, an electron beam reduction exposure reticle blank, and a method for manufacturing the same, which have extremely small warpage and can reduce occurrence of positional distortion of the blank due to resist stress.

[Brief description of drawings]

FIG. 1A is a plan view showing an electron beam reduction exposure reticle blank according to an embodiment of the present invention, and FIG.
FIG. 3B is a sectional view taken along line 1b-1b shown in FIG.

FIG. 2 is a plan view showing a Pyrex (registered trademark) glass substrate.

3 (a) is a sectional view of the Pyrex (registered trademark) glass substrate shown in FIG. 2 processed into a structure having lattice-like columns, and FIG. 3 (b) is a sectional view showing an SOI wafer.

FIG. 4 is an SOI shown in FIG. 3B on a Pyrex (registered trademark) glass substrate having a structure having pillars shown in FIG.
It is sectional drawing which shows the board | substrate which stuck together the wafer.

5 is a SOI wafer supporting substrate and BOX shown in FIG. 4;
It is sectional drawing which shows the board | substrate which removed the layer (silicon oxide layer).

FIG. 6A is a cross-sectional view showing a reticle,
(B) is a perspective view of the reticle shown in (a).

7A to 7C are cross-sectional views showing a method of manufacturing a conventional electron beam exposure reticle blank.

FIG. 8 is a cross-sectional view showing an SOI wafer.

9A to 9C are cross-sectional views showing a method of manufacturing a reticle blank using an SOI wafer.

FIG. 10 is a plan view showing a reticle using an 8-inch wafer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electron beam scattering part (silicon membrane part) 2 ... Silicon having lattice-like pillars 3 ... Boron-doped layer 4 ... Silicon wafer 5 ... Silicon oxide layer 6, 15 ... Thin film silicon layer (active layer) 7, 14 ... Silicon oxide Layer (BOX layer) 8, 13 ... Silicon support substrate 8a to 8c ... Support 9 ... Resist or silicon oxide layer 10 ... 8 inch reticle blank 11 ... Membrane region 12 ... Pyrex (registered trademark) glass substrate 12a, 12b ... Structure processing unit 16 ... SOI substrate

Claims (8)

[Claims] 1. A reticle blank for electron beam exposure, comprising a support substrate having a membrane and columns for supporting the membrane, wherein the support substrate is made of glass. 2. The reticle blank for electron beam reduction exposure according to claim 1, wherein impurities for adjusting stress are introduced into the membrane. 3. A reticle used when exposing with an electron beam, comprising: a membrane; an opening formed in the membrane for transmitting an electron beam; and a glass support substrate having a column for supporting the membrane. A reticle for electron beam reduction exposure, which is characterized by: 4. The reticle for electron beam reduction exposure according to claim 3, wherein impurities for adjusting stress are introduced into the membrane. 5. A method for manufacturing a reticle blank for electron beam exposure, which comprises a glass substrate having a silicon membrane and a support for supporting the silicon membrane, the step of preparing a glass substrate and performing a process of providing the support on the glass substrate. And a step of preparing an SOI wafer composed of a thin film silicon layer, a silicon oxide layer and a silicon supporting substrate, a step of bonding a surface of the thin film silicon layer of the SOI wafer and a glass substrate having columns, and the above silicon supporting substrate And a step of removing the silicon oxide layer, the method for producing a reticle blank for electron beam exposure. 6. After the step of removing the silicon oxide layer,
The method of manufacturing a reticle blank for electron beam reduction exposure according to claim 5, further comprising the step of introducing an impurity for adjusting the stress into the thin film silicon layer. 7. The method further comprising the step of introducing an impurity for stress adjustment into the thin film silicon layer of the SOI wafer between the step of preparing an SOI wafer and the step of laminating. 5. The method for producing a reticle blank for electron beam reduction exposure according to item 5. 8. A method of manufacturing a reticle blank for electron beam exposure, which comprises a glass substrate having a silicon membrane and columns supporting the silicon membrane, the method comprising: forming a conductive film on the glass substrate; And a step of forming a support on the glass substrate on which the film has been formed, the method for producing a reticle blank for electron beam reduction exposure.