JP2723582B2 - X-ray mask - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor manufacturing apparatus, and more particularly to an X-ray mask structure having excellent mask surface flatness.

(Prior Art) 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. Therefore, an X-ray exposure apparatus using light in the X-ray region (7 to 14 °) as an exposure light source wavelength is being developed.

The X-ray exposure apparatus has an X-ray source (X
-Ray), an exposure chamber 20, a wafer chuck 26 for fixing an exposure target material 25 such as a silicon wafer at a predetermined position, an X-ray mask 24 for fixing at a predetermined position, a mask chuck 22, an alignment light source, an alignment detector 23, and the like. It is configured as an element.

As a mask structure used in these X-ray exposure apparatuses, for example, as shown in FIG. 11, a silicon compound of about 2 μm, particularly silicon nitride, silicon carbide or the like is formed on a silicon wafer 1 by a chemical vapor deposition method or the like. The film 2 is formed to have a slight tensile stress (FIG. 11a). Next, an absorber pattern 3 is formed on the surface of the film 2 using a material such as gold that absorbs X-rays well (FIG. 11b). Then, the silicon wafer 1 is made to pass through a required area (X-rays) from the back surface. When only the inorganic thin film 2 is removed by etching, a mask in which the inorganic thin film 2 is held in tension on the silicon wafer 1 is obtained. However, in this state, since the silicon wear 1 is thin, the strength is small and it is inconvenient for handling and practical use.
As shown in FIG. 11d, it is common to use the reinforcing member 4 bonded with an adhesive 5.

(Problems to be Solved by the Invention) As an X-ray transmitting film for holding the absorber of the X-ray mask as described above, silicon carbide has a promising thermal expansion coefficient close to that of a silicon substrate serving as a holding frame. ing. From the viewpoint of X-ray transmittance, the thinner the better these X-ray transmitting films are, the better the thickness is. Considering both of these performances, silicon carbide having a thickness of about 2 μm is conventionally used in many cases.

These silicon carbide films 2 are formed on the silicon substrate 1, and it is required to set a print gap with a silicon wafer to be exposed to 10 to several tens μm at the time of exposure. Very high flatness is required on the entire surface.

Therefore, in the case of the mask of the prior art as shown in FIG. 11, since the mask surface is entirely flat, a high flatness is required even in the peripheral portion where X-rays are not actually transmitted, and there is a difficulty in processing. there were.

In addition, when the silicon carbide film is irradiated with a semiconductor laser (for example, 830 nm) at an angle of, for example, 17.5 ° prior to the X-ray exposure and the alignment of the mask is performed, the film thickness of 2.0 μm is about 54%. There is a problem that there is reflection, the S / N ratio of the alignment light is lowered, and the alignment efficiency is poor.
Also, depending on the arrangement of the alignment detecting section, the detection may be hindered by the reflected light.

Further, as shown in FIG. 3, the silicon carbide film has a problem that the reproducibility of the alignment is poor because the reflectance greatly changes due to a slight difference in the film thickness.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide an X-ray mask structure excellent in flatness and alignment.

(Means for Solving the Problems) The above object is achieved by the present invention described below. That is,
The present invention relates to an X-ray mask structure having an X-ray absorber having a desired pattern, an X-ray transmission film holding the absorber, and a holding frame holding the X-ray transmission film, wherein the X-ray transmission film is A single-layer thin film that transmits X-rays and alignment light used for alignment of the X-ray mask structure, and has a thickness such that the thin film has a reflectance close to a minimum with respect to the alignment light. An X-ray mask structure.

(Function) In the X-ray mask structure, the periphery of the holding frame is formed as an inclined surface, and the X-ray transmitting film is fixed on the inner flat surface, whereby a mask structure having excellent flatness can be obtained. Further, when the mask is used in an X-ray exposure apparatus, the X-ray mask has an extremely small reflectivity to alignment light, so that an X-ray mask having excellent alignment properties, proper and excellent dimensional accuracy can be obtained. Exposure is achieved.

(Examples) The present invention will be described in more detail below with reference to examples shown in the drawings.

Example 1 FIG. 1 is a sectional view of an X-ray mask manufacturing process of the present invention, and FIG. 2 is a view showing an apparatus for manufacturing a silicon carbide film as a mask membrane in the mask.

1 in FIG. 1 (a) is a silicon substrate which has been polished on both sides, and a portion where a silicon carbide film does not need to be formed is cut off obliquely. The angle θ of the inclined surface is arbitrary, but is generally preferably 5 to 45 °.

In FIG. 2, reference numeral 14 denotes a chamber for plasma CVD (chemical vapor synthesis), and the silicon substrate 1
A vapor deposition cover 13 having a hole equal to the film formation area of the film 2 is set on the sample holder 7 which can be heated up to 800 ° C. in the CVD chamber 14.

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 from a hole formed in the lower electrode 8. Substrate 1 temperature 650
C., and a high frequency power of 50 W was applied at a pressure of 5.times.10.sup.- ³ Torr to form a silicon carbide film.

The reflectance of the formed silicon carbide film was monitored by using a semiconductor laser (830 nm) 9, a mirror 10, and a detector 11, and measuring the reflectance by irradiating the laser at an angle of 127.5 °. The mirror 10 and the detector 11 are protective members.
Protected by 12.

The film formation was stopped when the film thickness was about 2.1 μm and the reflectivity was 32.7% (point a in FIG. 4), and the silicon carbide film 2 was formed as shown in FIG. 1 (b).

FIG. 4 is a graph showing the relationship between the thickness (horizontal axis) of a silicon carbide film formed on a silicon substrate and the reflectance (vertical axis) of 830 nm laser light at an incident angle of 17.5 °.

Next, as shown in FIG. 1 (c), SiO ₂ 4
Was sputter-deposited, and only the back-etched surface on the back surface of the substrate 1 was patterned and removed with a mixed solution of hydrofluoric acid and ammonium fluoride to form a protective film 4.

Next, as shown in FIG. 1 (d), the silicon substrate 1 was back-etched with a solution of pyrocatechol: ethylenediamine: water = 4: 46.4: 49.6. The reflectance of the film 2 thus manufactured was measured at 830 nm with light having an incident angle of 17.5 °. As a result, the reflectance was almost 0 as shown at point a in FIG.

FIG. 3 is a graph showing the relationship between the film thickness (horizontal axis) of the silicon carbide film after use as an X-ray mask and the reflectivity (vertical axis) of 830 nm laser light at an incident angle of 17.5 °. As can be seen by comparing FIGS. 3 and 4, when silicon having a higher refractive index than the silicon carbide film 2 is used as the substrate, when the reflectance is maximized on the substrate, after the substrate is etched. Shows the minimum reflectance of

Next, the absorber 3 was formed by a gold plating process as shown in FIG.

In the above method, a particularly good film thickness distribution can be selected and the polished area becomes narrower than the method of forming the film 2 on the entire surface of the substrate 1 (FIG. 11). 2
When the film was formed, a flatness of only 0.5 μm could be obtained by the same film forming method and polishing method as the conventional method shown in FIG.

FIG. 6 is a simplified diagram of an X-ray exposure apparatus using the X-ray mask structure of the present invention, and 20 is an exposure chamber. 21 is
The Be window port, 30 is an exhaust port, the exposure chamber 20 is shut off from the X-ray generation source by Be, and the exposure inside the chamber can be performed in any state such as the atmosphere, vacuum, and He atmosphere.

Reference numeral 22 denotes a mask stage, 23 denotes an alignment detection unit, 24 denotes a mask, 25 denotes a wafer, 26 denotes a wafer chuck, 27 denotes a wafer stage, 28 denotes an X-axis stage drive motor, and 29 denotes a Y-axis guide.

When the mask 24 is attracted to the mask stage 22, it is mechanically set using a positioning pin, an orientation flat, or the like in a predetermined direction. The wafer 25 is similarly set on the wafer chuck 26, and then the mask 24
Alignment detection unit 23
And then exposed by X-rays.

The mask 24 prepared above was set in the exposure chamber 20 as shown in FIG. 6, and a semiconductor laser (830 nm) having an incident angle of 17.5 ° was used.
m) The alignment of the mask 24 and the wafer 25 was performed using the alignment light. However, the reflection from the mask surface was almost 0, and the alignment could be performed very accurately.
Alignment could be performed with an accuracy of 025 μm. SOR
Using the light as an X-ray source, the pattern of the absorber 3 on the mask 24 was printed on the wafer.

Example 2 FIG. 7 is a view showing an apparatus for manufacturing a silicon carbide film as a mask membrane of an X-ray mask according to the present invention.

In FIG. 7, 15 is a magnetron sputtering chamber, 16 is a sample holder, and 17 is a shutter.

The SiO ₂ (glass) substrate 1 which has been polished on both sides and the portion where the mask membrane is not formed is slanted off is set on the sample holder 16 and the evaporation cover 13 is set. After reducing the back pressure to 2 × 10 ^-6 Torr, argon gas was flowed at 30 sccm to 5 × 10 ^-3 Torr, and the high frequency power was 10
0 W was applied to the silicon carbide target 18. After the discharge was sufficiently stabilized, the shutter 17 was opened to start film formation. While measuring the reflectance of the silicon carbide film in the same manner as in the first embodiment, it was found that the film thickness was about 2.1 μm and the reflectance was 3.4% (b in FIG. 5).
(Point), the shutter was closed, and a silicon carbide film 2 was formed as shown in FIG.

FIG. 5 shows the relationship between the thickness (horizontal axis) of the silicon carbide film formed on the SiO ₂ (glass) substrate and the reflectivity (vertical axis) of 830 nm laser light at an incident angle of 17.5 °. It is.

Next, as shown in FIG. 1C, the protective film 4 is coated with a negative resist (OM
R-83, manufactured by Tokyo Ohkasha).

Next, as shown in FIG. 1 (d), the SiO ₂ substrate 1 was etched with a 1: 1 solution of hydrofluoric acid: ammonium iodide.

Next, the absorber 3 is formed on the film 2 by dry etching of Ta as shown in FIG.
A 0.7 μm mask was obtained. Further, as shown in FIG. 3B, the reflectivity of the film 2 became almost zero. As can be seen by comparing FIGS. 3 and 5, when SiO ₂ (glass) having a lower refractive index than the silicon carbide film 2 is used, when the reflectance becomes extremely small on the substrate, It shows a very small reflectance even after etching.

The mask 24 was set in the exposure chamber 20 as shown in FIG. 6, and alignment of the mask 24 and the wafer 25 was performed using a semiconductor laser (830 nm) alignment light having an incident angle of 17.5 °. The value was almost 0, alignment could be performed very accurately, and alignment could be performed with an accuracy of 0.03 μm. Using the SOR light as an X-ray source, the pattern of the absorber 3 was printed on the wafer.

Embodiment 3 FIG. 8 is a sectional view of an X-ray mask of the present invention.

The silicon substrate 1 which has been polished on both sides and the portion where a film is not formed is obliquely scraped off is placed on a rotatable sample holder 16 of a magnetron sputtering chamber 15 as shown in FIG.
After reducing the back pressure to 2 × 10 ^-6 Torr, flowing argon gas at 20 sccm to 2 × 10 ^-6 Torr,
75 W was applied to a double target 18 of silicon and carbon. After the discharge is sufficiently stabilized, rotate the sample holder 16,
The shutter 17 was opened to start film formation. While measuring the reflectance of the formed silicon carbide film, a film thickness of about 1.9 μm and a reflectance of 3
At 2.7% (point c in FIG. 4), the shutter was closed, and a silicon carbide film 2 was formed as shown in FIG. 1 (b).

Further, SiO ₂ was sputter-deposited on both surfaces, and only the center of the back surface was etched with a mixed solution of ammonium fluoride and hydrofluoric acid to form a first layer.
A protective film 4 as shown in FIG.

Then pyrocatechol: ethylenediamine: water = 4: 4
The silicon substrate 1 was back-etched with a liquid of 6.4: 49.6 to form a shape as shown in FIG. 1 (d). Absorber 3 was formed on substrate 1 by dry-etching W. Finally, as shown in FIG. 8, a reinforcing member 6 was bonded with an adhesive 5 to form a mask 24. The membrane 2 thus obtained
Is that the reflectance is almost 0 as shown at point c in FIG.
The flatness was 0.3 μm.

The mask 24 is set in an exposure chamber 20 as shown in FIG. 6, and a semiconductor laser (830 nm) having an incident angle of 17.5 ° is used.
The alignment of the mask 24 and the wafer 25 was performed using the alignment light, but the reflection from the mask surface was almost 0,
Very accurate alignment, 0.025
The alignment was performed with an accuracy of μm. Using the SOR light as an X-ray source, the pattern of the absorber 3 was printed on the wafer.

Embodiment 4 An exposure apparatus using alignment by a He-Ne laser (632.8 nm) will be described as a fourth embodiment.

In FIG. 7, 15 is a magnetron sputtering chamber, 16 is a sample holder, and 17 is a shutter.

The silicon substrate 1 which has been polished on both sides and the portion where a film is not formed is slanted off is set on the sample holder 16 and the evaporation cover 13 is further set. Back pressure 2 × 10
After drawing to ^-6 Torr, argon gas was flowed at 30 sccm and 5 ×
10 ^-3 Torr, high frequency power 100W silicon carbide target
18 was applied. After the discharge was sufficiently stabilized, the shutter 17 was opened to start film formation. The reflectance was monitored while measuring the reflectance by using a He-Ne laser (632.8 nm) 9, a mirror 10, and a detector 11 to make the laser incident at an angle of 15 °. The mirror 10 and the detector 11 are protective members.
Protected by 12. While measuring the reflectivity of the formed silicon carbide film, the film formation was stopped when the film thickness became about 2.05 μm and the reflectivity reached 35% (point d in FIG. 10), as shown in FIG. 1 (b). Then, a silicon carbide film 2 was formed.

Then, as in FIG. 1 (c), SiO ₂ on both surfaces of the silicon substrate
Was sputter-deposited, and only the back side of the substrate 1 was patterned and removed with a mixed solution of hydrofluoric acid and ammonium fluoride to form a protective film 4. As shown in FIG. 1 (d), the silicon substrate 1 was back-etched with a solution of pyrocatechol: ethylenediamine: water = 4: 46.4: 49.6.

Next, as shown in FIG. 1 (e), the absorber 3 was formed by a gold plating process, and a mask having a flatness of 0.5 μm was obtained.
Further, as shown in the point d in FIG. 9, a film 2 having a reflectance of almost 0 was obtained.

FIG. 9 shows the film thickness (horizontal axis) when only the silicon carbide film was used.
It is a figure which shows the relationship with the reflectance (longitudinal ratio) of 6328 degrees of He-Ne laser light of the incident angle of 15 degrees. FIG. 10 shows the case of a silicon carbide film on a silicon substrate.

The mask 24 was set in an exposure chamber 20 as shown in FIG. 6, and a He-Ne laser (632.8 nm) having an incident angle of 15 ° was used.
The alignment of the mask 24 and the wafer 25 was performed using the alignment light, but the reflection from the mask surface was almost 0,
Very accurate alignment, 0.025
The alignment was performed with an accuracy of μm. Using the SOR light as an X-ray source, a pattern having a minimum line width of 0.25 μm was printed on the wafer.

The reflectance in the above description is a value defined by the following equation.

Although the present invention has been described with reference to the preferred embodiments,
The present invention is not limited to these embodiments. The periphery of the holding frame of the X-ray mask is formed as an inclined surface, the X-ray transmitting film is held on the inner flat surface, and the X-ray mask is It is apparent that other configurations are the same as those of the prior art, and include many modified embodiments other than the above embodiments, as long as the relationship has a minimum reflectance.

(Effects) As described above, according to the present invention, in the X-ray mask structure, the periphery of the holding frame is formed as an inclined surface, and the X-ray transmitting film is fixed on the inner flat surface, so that the flatness is improved. An excellent mask structure can be obtained, and when the mask is used in an X-ray exposure apparatus, the X-ray mask has a minimum reflectance to alignment light, thereby improving alignment properties. X-ray exposure which is excellent, appropriate and excellent in dimensional accuracy is realized.

[Brief description of the drawings]

FIG. 1 is a sectional view of an X-ray mask manufacturing process of the present invention. 1: Silicon substrate 2: Silicon carbide film 3: Absorber 4: Protective film 24: Mask FIG. 2 shows a device for manufacturing a silicon carbide film which is an X-ray transmission film (mask membrane) of the X-ray mask of the present invention. It is. 1: Silicon substrate 7: Sample holder 8: Lower electrode 9: Semiconductor laser (830nm) 10: Mirror 11: Detector 12: Protective member 13: Evaporation cover 14: Plasma CVD chamber FIGS. 3, 4 and 5 The figure shows the thickness of silicon carbide film (horizontal axis)
FIG. 9 is a diagram showing a relationship between the reflectance of a laser beam of 830 nm at an incident angle of 17.5 ° (vertical axis). FIG. 3 shows only the silicon carbide film, FIG. 4 shows the silicon substrate, and FIG.
₂ (glass) Value on the substrate. FIG. 6 is a simplified diagram of an X-ray exposure apparatus. 20: Exposure chamber 21: Be window port 22: Mask stage 23: Alignment detector 24: Mask 25: Wafer 26: Wafer chuck 27: Wafer stage 28: X axis stage drive motor 29: Y axis guide 30: Exhaust port 7 The figure shows an apparatus for manufacturing a silicon carbide film as a mask membrane of an X-ray mask according to the present invention. 1: Silicon substrate 9: He-Ne laser 10: Mirror 11: Detector 12: Protection member 13: Deposition cover 15: Chamber for magnetron sputtering 16: Sample holder 17: Shutter 18: Silicon carbide target FIG. 8 shows the present invention. It is sectional drawing of an X-ray mask. 5: Adhesive 6: Reinforcement 23: Mask FIGS. 9 and 10 show the thickness of silicon carbide film (horizontal axis) and reflectivity of 632.8 nm He-Ne laser beam at an incident angle of 15 ° (vertical axis). )
FIG. FIG. 9 shows the values on the silicon substrate only, and FIG. 10 shows the values on the silicon substrate. FIG. 11 is a sectional view showing a manufacturing process of a conventional X-ray mask structure. 1: Silicon substrate 2: Silicon carbide film 3: Absorber 4: Reinforcer 5: Adhesive 24: Mask

Claims (4)

(57) [Claims] 1. An X-ray mask structure comprising an X-ray absorber having a desired pattern, an X-ray transmission film for holding the absorber, and a holding frame for holding the X-ray transmission film. Is X
A single-layer thin film that transmits the alignment light used for aligning the line and the X-ray mask structure, and has such a film thickness that the thin film has a reflectance close to a minimum with respect to the alignment light. An X-ray mask structure, characterized in that: 2. The X-ray permeable film according to claim 1, wherein a periphery of said holding frame is formed as an inclined surface, said X-ray permeable film is fixed on an inner flat surface, and said X-ray permeable film is not fixed on said inclined surface. X-ray mask structure. 3. The X-ray permeable film is made of silicon carbide.
Or the X-ray mask structure according to 2. 4. The X-ray mask structure according to claim 2, wherein said alignment light is visible light or near-infrared light.