JP2728971B2 - X-ray exposure apparatus and X-ray exposure method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an X-ray exposure apparatus and an X-ray exposure method using an X-ray mask structure suitable for semiconductor production.

[Conventional technology]

In recent years, with the increase in density and speed of semiconductor integrated circuits,
The pattern line width of integrated circuits tends to be reduced to 70% in about three years.

With the further integration of large-capacity memory elements (for example, 4MDRAM), devices with a 16-Mbit capacity and the like have been designed with a 0.5 μm rule. For this reason, even higher performance is required for printing equipment, and the minimum transferable line width is 0.5μ.
The high performance of less than m is beginning to be required. For this reason, a stepper using light in the X-ray region (4 to 20 °) as the exposure light source wavelength is being developed.

The X-ray mask support used for the X-ray exposure is, for example, as shown in FIGS. 9 (a) and 9 (b), an X-ray transmission film 2 made of an X-ray transmission material, and a tension-holding film. As shown in FIGS. 10 (a) and (b), the X-ray mask support comprises a holding frame 1.
An X-ray absorber 3 having a desired pattern is formed on a radiation transmitting film 2.

An X-ray exposure apparatus using the X-ray mask structure as described above comprises an X-ray source, a chamber for partitioning an X-ray exposure area, a wafer chuck for fixing a member to be exposed such as a silicon wafer at a predetermined position, and the X-ray exposure apparatus. A mask holding means for superposing a mask structure on a predetermined position on a member to be exposed is formed as a main part.

[Problems to be solved by the invention]

X-ray exposure is performed using the X-ray mask structure and the X-ray exposure apparatus as described above. However, such a conventional X-ray exposure method has the following problems. That is,
Since an X-ray exposure apparatus uses X-rays having higher energy than conventional light as a light source, photoelectrons and Auger electrons are generated from a mask, and a helium atmosphere is used in an X-ray exposure apparatus so that the X-ray intensity does not decrease. When X-ray exposure is performed in this dry atmosphere, static electricity is also generated due to friction between the mask and gas. Originally, at the time of X-ray exposure, the gap between the mask surface and the exposed member was 10 μm to several
Despite the necessity to maintain a constant value of 10 μm, the mask surface is charged due to the photoelectrons, Auger electrons, and static electricity, and the mask surface and the member to be exposed come into contact and are discharged, and the mask surface is damaged. In some cases, the resist on the member to be exposed is overexposed due to the influence of emitted photoelectrons and secondary electrons, and the dimensional accuracy and the like may be deviated when a fine pattern is formed.

Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an X-ray exposure apparatus and an X-ray exposure method which are particularly excellent in antistatic properties and dimensional accuracy.

[Means for solving the problem]

 The above object is achieved by the present invention described below.

That is, the X-ray exposure apparatus of the present invention comprises an X-ray generation unit,
An X-ray exposure apparatus having means for fixing a member to be exposed at a predetermined position and holding means for fixing an X-ray mask structure at a predetermined position, wherein the X-ray mask structure has a conductive X-ray transmitting film. And a holding frame having a conductive coating electrically connected to the X-ray transmitting film, and an X-ray absorber held on the X-ray transmitting film, wherein the gripping means comprises the X-ray mask. It is characterized by comprising means for electrical conduction with the conductive coating of the structure.

Further, the X-ray exposure method of the present invention is an X-ray exposure method for exposing a member to be exposed to X-rays through an X-ray mask structure, wherein the X-ray mask structure has conductivity. And a holding frame having a conductive coating electrically connected to the X-ray transmitting film; and an X-ray absorber held on the X-ray transmitting film. The X-ray exposure is carried out in a state where the X-ray exposure is carried out in a state where the X-ray mask structure is fixed to a holding means provided with a means for electrically connecting the conductive film to the conductive film.

 Hereinafter, the present invention will be described in detail.

First, in the X-ray mask support and the X-ray mask structure of the present invention, the X-ray transmitting film has conductivity. In the present invention, as a method of imparting conductivity to the X-ray permeable film, for example, a method of forming the X-ray permeable film itself with a conductive material can be mentioned, and in the present invention, B or P doped S
i, C, etc. are preferably used. Further, a method of coating the surface of the X-ray permeable film with a conductive film to impart conductivity to the X-ray permeable film may be used. Among the above methods, in the present invention, a method of imparting conductivity to the X-ray permeable film by coating the surface of the X-ray permeable film with a conductive film is particularly preferably used. That is, even when the X-ray transmission film itself is formed of a conductive material such as Si, it is necessary to further cover the surface of the Si film with a conductive film, for example, when manufacturing an X-ray mask structure. In the process, it is preferable in order to prevent poor conductivity due to oxidation of the surface of the Si film, and as a material for forming the X-ray transmission film, it is particularly excellent in transmittance of alignment light and X-ray such as SiC and SiN. Since an insulating material can also be used, a wide range of material can be selected as desired.

In the present invention, the X-ray permeable membrane is specifically as described above.
It is formed of an inorganic film such as Si, C, SiC, SiN, BN, or AlN or a composite film of the inorganic film and an organic film such as polyimide, and has X-ray resistance, visible light transmittance, X-ray transmittance, and intensity. It is preferable to use SiC and SiN, which are excellent in average in all respects, etc.
m or less. In addition, the conductive film covering the surface of the X-ray transmission film is, specifically, carbon, A
It is made of a stable conductive material such as u, Pt, AiPd, etc., and it is particularly preferable to use carbon from the viewpoint of X-ray transparency and the like, and it is preferable to form it with a thickness of 10-100 mm. In particular, when the thickness of the conductive film is extremely small, poor conductivity occurs. On the other hand, when the thickness is too large, the transmittance of alignment light and X-rays is reduced.

Further, in the X-ray mask support and the X-ray mask structure of the present invention, the holding frame has a conductive coating electrically connected to the X-ray transmitting film. As the material for forming the conductive film, similar to the conductive film coated on the surface of the X-ray transparent film described above, carbon, Au, Pt, AuPd, Cu, Zn, etc. It is preferable to use Au, Pt, or AuPd because of the low surface oxidation.
When the conductive film is formed integrally with the conductive film, the thickness of the conductive film is preferably 10 to 100 ° in view of the conductivity, the transmittance of alignment light and X-rays. Alternatively, when the conductive film is formed independently of the conductive film, the conductive film is formed to be thicker than the conductive film provided on the X-ray transmission film, so that a separation preventing effect at the time of contact with an electrical conduction means described later is provided. You.
The thickness is usually at most about 1 mm.

In the present invention, the holding frame is for holding the X-ray permeable membrane in tension, and when a reinforcing frame is provided below the holding frame, this reinforcing frame is also included. The holding frame is, specifically,
It is formed using a material such as quartz glass, borosilicate glass (pyrex), ceramics, Si, and Ti.

Further, in the present invention, the X-ray absorber held on the X-ray transmitting film is formed to a thickness of 0.5 μm to 1.0 μm by using a material having a large X-ray absorption such as Au, Ta, W or the like. Preferably.

The X-ray mask structure of the present invention described in detail above has, for example, the structure shown in FIG. 1, FIG. 2, and FIG.
First, in the embodiment shown in FIG. 1, the X-ray transmitting film 2 itself is formed of a conductive material, and the holding frame 1 has a conductive coating 4a electrically connected to the X-ray transmitting film 2. It is a line mask structure. In the figure, reference numeral 3 denotes an X-ray absorber.
Next, the embodiment shown in FIG.
Is an X-ray mask structure on which a conductive continuous film 4 continuously covering the X-ray mask is formed. Forming the conductive film as a continuous film in this manner is preferable in that the number of processes for manufacturing the X-ray mask structure can be reduced.

The embodiment shown in FIG. 3 is a particularly preferred example of the X-ray mask structure of the present invention. That is, the X-ray mask structure has the X-ray transmission film 2 having the conductive film 4b and the holding frame 1 having the conductive film 4a electrically connected to the conductive film 4b. In FIG. 2, reference numeral 3 denotes an X-ray absorber. This aspect is X
Conductive film 4b on the line permeable film and conductive film 4a on the holding frame
Are provided independently of each other, so that the film thicknesses of the conductive film 4b and the conductive film 4a can be set independently of each other. That is, as described above, the conductive film 4b on the X-ray transmission film has an X-ray transmittance,
From the viewpoint of the alignment light transmittance, it is preferably about 10 to 100 °, but the conductive film 4a on the holding frame may be subjected to a mechanical force due to contact with the electrical conduction means and attachment / detachment to / from the mask check. It is preferable that the film is formed thicker than that.

Next, an X-ray exposure apparatus of the present invention used for X-ray exposure using the above-described X-ray mask structure will be described in detail. FIG. 4 shows a schematic configuration diagram of the apparatus of the present invention. The apparatus of the present invention includes X-ray generating means (not shown), means 13 for fixing the X-ray exposed member 12 at a predetermined position, and gripping means 15 for fixing the X-ray mask structure 14 at a predetermined position. FIG. 4 shows the arrangement relationship of the above-mentioned respective means. The fixing means 13 for the X-ray exposed member and the fixing means 15 for the X-ray mask structure are relatively positioned so as to have a desired interval (gap) therebetween. The X-ray generating means is arranged so that X-rays (arrows) are irradiated to the X-ray exposure member 12 through the X-ray mask structure 14. The chamber 11 can be used from a vacuum to an atmospheric pressure, but is preferably a helium atmosphere at a pressure of about 100 torr in consideration of X-ray attenuation and heat conduction. The basic configuration described above may be in accordance with a conventionally known X-ray exposure apparatus, and may have a known additional unit as necessary.
A feature of the apparatus of the present invention is that the gripping means 15 includes means for electrically connecting to the X-ray mask structure 14. The conduction means will be described in detail with reference to FIGS. 5 to 7 are enlarged views of the X-ray mask structure 14 and the holding means 15 shown in FIG. First,
In FIGS. 5 and 6, reference numerals 25 and 35 denote mask checks, and reference numerals 26 and 36 denote V blocks which constitute a part of the mask check and serve as a reference when positioning the X-ray mask structure. Further, earth springs 27 and 37 are provided on the V blocks 26 and 36, and are in contact with the conductive coatings 24 and 34 of the holding frames 21 and 31, respectively. With this configuration, photoelectrons and Auger electrons generated from the X-ray absorbers 23 and 33 during X-ray exposure are absorbed by the conductive films 24 and 34 formed on the X-ray transmission films 22 and 32. Furthermore, such electrons are in holding frame 2.
Ground springs 27 and 37 and gripping means (V blocks 26 and 36 and mask checks 25 and 35) flow to the conductive coatings 24 and 34 of 1, 31 to the chamber, thereby preventing the X-ray mask structure from being charged.

The earth springs 27 and 37 used here are preferably made of phosphor bronze, stainless steel, or the like and covered with a noble metal such as Au, Pt, or Pd from the viewpoint of preventing surface corrosion.
Also, the shape of the contact end is curved so that the part in contact with the X-ray mask does not damage the surface of the X-ray mask. Not as long.

Although 27 and 37 are called earth springs, pins or the like having no spring property may be used.

According to FIG. 5, the shape of the holding frame 21 (21b) has a slope, but as shown in FIG. 6, the ground spring 37 does not become higher than the holding frame 31, and the gap between the mask wafers must be affected. It is not necessary to have a slope.

When the mask checks 25 and 35 or the V-blocks 26 and 36 are formed of a conductive material such as stainless steel or Al, it is sufficient that electrons can flow without the ground springs 27 and 37 in particular.

Further, as shown in FIG. 7, the holding means for the X-ray mask structure does not have a V-block, and the earth spring 47 has a mask chuck 45.
May be provided directly.

 Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 An X-ray mask structure 28 of the present invention shown in FIG. 5 was produced as follows. The Si wafer to be the holding frame 21a is set in a chamber for plasma CVD (chemical vapor synthesis).

After reducing the back pressure to 2 × 10 ^-6 Torr, 10 sccm of silane gas and 10 sccm of methane gas diluted to 10% with hydrogen were supplied, the temperature of the Si wafer was heated to 350 ° C., and the pressure of 5 × 10 ^-6 was obtained.
^A silicon carbide film was formed by applying a high-frequency power of 50 W at ^-3 Torr to form an X-ray transmission film 22. An electron beam resist PMMA (OEBR-1000, trade name: manufactured by Tokyo Ohka Co.) is applied on the X-ray transparent film 22 by continuously depositing Cr and Au serving as plating electrodes by EB evaporation on the X-ray transparent film 22. To form a desired pattern. Next, a sulfurous acid plating solution (Neutronex 30
9, trade name: manufactured by EEJA) at 50 ° C. and 1 mA / cm ² . After that, the resist is stripped with a special stripper, and the plating electrode is removed using an RIE (reactive ion etching) device.
r Exfoliated by plasma to obtain X-ray absorber 23. Further, the SiN film on the back surface of the Si wafer 21a was etched to a desired window size, and the Si wafer was back-etched with 30 wt% KOH to form a holding frame 21a. A reinforcing material 21b made of pyrex glass was further adhered to a lower portion of the holding frame 21a with an epoxy adhesive.

Finally, the X-ray mask structure was set in a resistance heating evaporator to reduce the back pressure to 2 × 10 ⁻⁶ Torr, and then carbon was evaporated at a rate of 2 ° / sec to form a conductive film 24.

Example 2 An X-ray mask structure 48 of the present invention shown in FIG. 7 was produced as follows. First, the Si wafer serving as the holding frame 41a is set in an EB evaporator together with an evaporation mask. Back pressure 2 × 10 ^-6 To
While pulling and rotating to rr, Cr 2Å / sec, Au 10Å / sec
The partial deposition is performed at the above speed to form the conductive film 44a. further,
The Si wafer is set in a chamber for plasma CVD (chemical vapor synthesis).

First, after the back pressure was reduced to 2 × 10 ⁻⁶ Torr, 10 sccm of silane gas and 10 sccm of methane gas diluted to 10% with hydrogen were supplied. The temperature of the Si wafer was heated to 650 ° C. and the pressure was 5 × 10
^A high frequency power of 50 W was applied at ^-3 Torr to form a silicon carbide film, which was used as an X-ray transmission film.

Next, this was set on a high frequency sputter device, and the back pressure was set at 2
After pulling to × 10 ^-6 Torr, Ar gas is 5sccm and pressure is 1.0 × 10
Applying high frequency power of 200 W at ^-2 Torr on the X-ray transmitting film 42
A Ta film was formed. Furthermore, by the spattering method on it
An SiO ₂ film was formed, then an electron beam resist PMMA was applied, and formed into a desired pattern by an electron beam lithography apparatus. Then PI
An X-ray absorber 43 was obtained by patterning SiO ₂ using CF ₄ with Ta and using CBrF ₃ gas with an E (reactive ion etching) apparatus. Further, the SiC film on the back surface of the Si wafer 41a is etched to a desired window size, and the Si wafer is subjected to 30 wt% KO.
Backing was performed with H, and then the SiC film on the side surface and the back surface was peeled off to obtain a shape as shown in FIG.

After that, this was set in the EB vapor deposition machine and the back pressure was set to 2 × 10 ^-6 Torr
Then, Au is deposited at a rate of 1Å / sec to form a conductive film 44b. The reinforcing member 41b, which is a part of the holding frame 41, is made of quartz glass. The reinforcing member 41b is processed so as to have a slope, and is set in an EB vapor deposition machine. After reducing the back pressure to 2 × 10 ⁻⁶ Torr, Pt was deposited at a rate of 5 ° / sec while rotating to form a conductive film 44a. Finally, the reinforcing member 41b was bonded to 41a to complete the X-ray mask structure.

Example 3 An X-ray mask structure 58 of the present invention shown in FIG. 8 was produced as follows.

The Si wafer serving as the holding frame 51a is placed in a thermal diffusion furnace and heated at a temperature of 1100 ° C. in a BH ₄ gas to adjust the surface B concentration to 10 ²⁰ cm ⁻³ .

After setting the Si wafer after the above processing in a high frequency sputter device and reducing the back pressure to 2 × 10 ⁻⁶ Torr, the pressure is 10 × 10 ⁻² Torr with 10 sccm of Ar gas, the substrate temperature is 150 ° C., and the high frequency power is 500
W was applied to form a W film on the surface of the Si wafer. On top of this, PIQ (trade name: Hitachi Chemical), the lower layer of the three-layer resist, and Si-containing electron beam resist SNR (trade name, the upper layer)
Toyo Soda) was applied, and a desired pattern was formed using an electron beam lithography apparatus. Thereafter, the lower layer PIQ of the two-layer resist was patterned using an O ₂ gas using an RIE (reactive ion etching) apparatus, and W was etched using an SF ₆ gas to form an X-ray absorber 53.

Further, the surface having a high concentration of B of the Si wafer 51a is etched to a desired window size, and the Si wafer is subjected to EDP (46.4 mol% of etherylenediamine, 4 mol% of pyrocatechol, 49.6 mol of H ₂ O).
%) Etching was performed at 118 ° C, and the holding frame 5 was used as shown in Fig. 8.
Formed 1a.

Next, the mask was set in an EB evaporation apparatus together with the evaporation mask, the back pressure was reduced to 5 × 10 ⁻⁷ Torr, and Pt was evaporated at a rate of 10 ° / sec to form a conductive film.

Finally, a reinforcing member 51b (made of pyrex glass) was bonded to the holding frame 51a, thereby completing the X-ray mask structure of the present invention.

Embodiment 4 In the X-ray exposure apparatus shown in FIG.
5 to 8, a device provided with an earth spring as shown in FIGS.
Each of the line mask structures was set as shown in FIGS. 5, 7, and 8, and subjected to X-ray exposure.

The minimum line width of the X-ray mask is 0.25 μm. As a member to be exposed, Al is deposited on a Si wafer, and an X-ray resist RAY-PN (trade name: manufactured by Hoechst) is applied thereon. Was used. In addition, these masks and the members to be exposed are provided with alignment marks.

The mask is set on a mask cassette (not shown), and the member to be exposed is set on a wafer cassette (not shown), carried by a transfer system (not shown), and arranged to face each other. The mask and the wafer are controlled by the alignment mark so that the proximity gap is 50 μm and the positional accuracy is 0.03 μm or less. The mask is fixed to the mask holding means 15 and the wafer is fixed to the means 13 for fixing the member to be exposed.

The X-rays generated from the SOR are converted into X-rays having a wavelength of approximately 7 to 14 ° by being reflected by a mirror and passing through a Be window. When the setting of the mask and the wafer is completed with these X-rays, a shutter (not shown) is opened, and exposure is performed for one second. In the case of step exposure, the wafer is stepped and the steps from alignment to exposure are repeated.

Regarding the exposure result, after the exposure was completed, the resist was developed and the increase in the patterned resist was evaluated by an EB length measuring machine.
As a result of the evaluation, in each of the X-ray mask structures of Examples 1 to 3, there was no excessive exposure, and the line width accuracy was controlled to ± 0.03 μm at the minimum line width, and the overlay accuracy was controlled to ± 0.1 μm, and printing was possible.

〔effect〕

As described above, according to the present invention, the holding frame of the X-ray mask structure has a conductive coating, and a conductive portion is formed on at least a part of the means for gripping the conductive coating. Such connection prevents charge during exposure and effectively removes photoelectrons, Auger electrons, and the like generated during exposure, thereby realizing X-ray exposure with proper and excellent dimensional accuracy.

[Brief description of the drawings]

1, 2, and 3 are cross-sectional views of the X-ray mask structure of the present invention. FIG. 4 is a diagram schematically illustrating a cross section of the X-ray exposure apparatus according to the present invention. FIGS. 5, 6, 7, and 8 are diagrams schematically illustrating the positional relationship between the X-ray mask structure of the present invention and the gripping means for the X-ray mask structure. 9 (a) and 9 (b) are diagrams schematically illustrating a conventional X-ray mask support, and FIG. 9 (b) is a cross-sectional view taken along line AA 'of FIG. 9 (a). 10 (a) and 10 (b) are diagrams schematically illustrating a conventional X-ray mask structure, and FIG. 10 (b) is a cross-sectional view taken along the line BB 'of FIG. 10 (a). 1,21,31,41,51 ... holding frame 2,22,32,42,52 ... X-ray permeable film 3,23,33,43,53 ... X-ray absorber 4,4a, 24,34 , 44a, 54 ... conductive film 4b, 44b ... conductive film 11 ... chamber 12 ... X-ray exposed member 13 ... fixing means 14 ... X-ray mask structure 15 ... gripping means 16 ... conductive Means 25,35,45,55 ... Mask check 26,36,56 ... V block 27,37,47,57 ... Earth spring

Continued on the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI Technical display location H01L 21/30 531E

Claims (4)

(57) [Claims] 1. An X-ray exposure apparatus comprising: an X-ray generating means; a means for fixing an X-ray exposed member at a predetermined position; and a gripping means for fixing an X-ray mask structure at a predetermined position.
An X-ray transmission film having a conductive line mask structure, a holding frame having a conductive coating electrically connected to the X-ray transmission film, and an X-ray absorber held on the X-ray transmission film And
An X-ray exposure apparatus, wherein said holding means comprises means for electrically connecting said conductive film of said X-ray mask structure. 2. An X-ray exposure apparatus according to claim 1, wherein said electric conduction means is said holding means made of a conductive material. 3. An X-ray exposure apparatus according to claim 1, wherein said electric conduction means is a conductive portion attached to said holding means. 4. An X-ray exposure method for exposing a member to be exposed to X-rays through an X-ray mask structure, wherein the X-ray mask structure has a conductive X-ray transmitting film; A holding frame having a conductive coating electrically connected to the permeable membrane;
An X-ray absorber held on a X-ray transparent film, and the X-ray mask structure is fixed to a gripping means provided with means for electrically connecting the X-ray mask structure to a conductive film of the X-ray mask structure. , The X
An X-ray exposure method comprising performing line exposure.