JP2721586B2 - X-ray mask structure manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor manufacturing apparatus, and more particularly to a method for manufacturing an X-ray mask structure used in an exposure apparatus for performing X-ray exposure.

(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.

Due to the further integration of large-capacity memory elements (for example, 4MDRAM), devices having a capacity of 16 Mbit 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 line width that can be transferred is 0.
A high performance of 5 μm or less is beginning to be required. Therefore, an X-ray exposure apparatus (stepper) using light in the X-ray region (4 to 14 °) as an exposure light source wavelength is being developed.

An X-ray mask structure used in these X-ray exposure apparatuses is, for example, an X-ray mask made of an X-ray transmitting material as shown in FIG.
The X-ray transparent film 21 includes a holding frame 22 for holding the X-ray transparent film 21 on which an X-ray absorber 23 arranged with an alignment mark and a desired geometric arrangement is formed. I have.

The method of forming the X-ray transmission film 21 is roughly classified according to whether the material used is an organic thin film or an inorganic thin film. For the former, a material that has a high X-ray transmittance and is transparent to visible light is selected, and films such as polyimide, polyamide, and mylar are preferred because of their Young's modulus, thermal expansion coefficient, surface roughness, and the like. Used. These X-ray permeable films 21 are held in tension by a holding frame 22 with an adhesive, and these X-ray permeable films 21 are fixed in a form having a sufficient flatness.

On the other hand, when an inorganic material is used as the X-ray transmission film,
As shown in FIG. 3, a film 31 of a silicon compound of about 2 μm, in particular, silicon nitride or silicon carbide is formed on the substrate 32 ′ by a chemical vapor deposition method or the like so as to have a slight tensile stress. Next, the substrate 32 'on which the film 31 has been deposited is moved from the rear surface to a required region (X
When only the region for transmitting the line is removed by etching, a mask blank in which the inorganic thin film 31 is kept in tension on the substrate 32 'is obtained. However, in this state, since the substrate 32 'is thin, the strength is small and it is inconvenient for handling and practical use. Therefore, it is usual to use the reinforcing member 32 with an adhesive.

Incidentally, the X-ray absorber 23 or 33 shown in FIGS.
Has a minimum width of 0.5 μm or less, while an area exposed by a single exposure may be 10 mm □ or more. On the other hand, in a semiconductor process, the same wafer is often repeatedly exposed several times, and in order to guarantee the superposition, the position of the X-ray absorber must be shifted over the entire exposure area. 1/10 of the minimum line width, that is, only a deviation of 0.05 μm or less is acceptable as an integration of the deviation of the position generated by the entire process of manufacturing the X-ray mask structure. The displacement also occurs due to elongation of the X-ray transparent support film due to a rise in the temperature of the mask during exposure.

Therefore, at present, when the X-ray permeable support film is an organic film, the support film has a thermal expansion coefficient of 0.25 μm (256 M−
X-ray exposure of an absorber pattern having a line width of less than (DRAM) is difficult. Also, from 0.35 μm (64M-DRAM compatible) to 0.5
As an X-ray mask having an absorber pattern with a minimum line width of μm, an X-ray mask having an organic film as a support film is also possible. Has become.

(Problems to be Solved by the Invention) However, when an inorganic film is used as the X-ray permeable support film, a step of back-etching the substrate when preparing the inorganic X-ray permeable film is conventionally required, The displacement of the absorber pattern that occurs at this time is the largest displacement in the whole process, making the production of the X-ray mask structure extremely difficult.

The cause of this displacement is that the absorber pattern was set at a desired position before the back etching of the substrate, but the adhesion of the inorganic film to the substrate was lost by the back etching of the substrate. This is because the tensile stress in the film is released and the inorganic film is deformed.

On the other hand, as shown in the report of the Japan Society of Applied Physics 2P-2-3 in the spring of '86, the substrate was back-etched in advance, and the tensile stress in the inorganic film was balanced so that the deformation on the inorganic film was no longer caused. After forming a resist pattern, an absorber pattern is formed.

However, in this case, 2
An inorganic film that is a very thin X-ray permeable support film of about μm is put in a vacuum chamber to make a resist pattern by electron beam drawing, or put in a vacuum chamber to perform dry etching, Further, in order to perform the plating process, the substrate is immersed in a fluid plating solution, and these steps cause destruction of the inorganic film, resulting in a problem that the yield is extremely poor. Further, in order to avoid the destruction of the inorganic film, it is necessary to pay close attention to the process, and there is also a problem that the working efficiency is reduced.

On the other hand, as a technique similar to the present invention, an example in which an inorganic film and an organic film are formed into a multilayer structure and used as an X-ray permeable support film is disclosed in Japanese Unexamined Patent Publication (Kokai).
No. 50-57778.

However, in this invention, in order not to lower the transmittance of X-rays, both the inorganic film and the organic film cannot be thicker than a predetermined thickness (when the inorganic film is thickened by the same thickness as the inorganic film of the present invention, X-ray transmittance decreases by the amount of the organic film),
There is also a problem that the X-ray permeable support film is bent due to the difference in thermal expansion coefficient between the inorganic film and the organic film.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to reduce the displacement of the X-ray absorber having a desired pattern by the minimum line width.
An object of the present invention is to provide a method for manufacturing an X-ray mask, which can be suppressed to 1/10 or less and improve the yield of the process of forming an X-ray absorber.

(Means for Solving the Problems) The above object is achieved by the present invention described below.

That is, the present invention provides a method for manufacturing an X-ray mask structure in which a support film having X-ray permeability is held in a holding frame and a desired pattern made of an X-ray absorber is provided at a desired position on the support film. A step of forming a support film on the substrate, a step of applying an organic film on the support film, a step of back etching the substrate on which the support film is formed, and an annealing temperature of 100 to 500 ° C. after the back etching step. A method for producing an X-ray mask structure, comprising a step of performing annealing, a step of forming an X-ray absorber pattern after the annealing step, and a step of removing the organic film after forming the pattern. It is.

(Function) By forming an organic film, the process resistance of an inorganic film, which is an extremely thin X-ray permeable support film, is improved.
After performing back etching of the substrate, by performing annealing at 100 ° C to 500 ° C, more preferably at 200 ° C to 400 ° C,
Release of the tensile stress of the inorganic film as the support film is promoted,
The displacement of the X-ray absorber having a desired pattern shape from the desired position is suppressed to 1/10 or less of the minimum line width, and the yield of the X-ray absorber forming process is improved.

(Example) Hereinafter, an example of the present invention is described using a drawing.

Embodiment 1 FIG. 1 is a view showing a first embodiment of the present invention, and FIG.
Is a substrate, 12 is an inorganic film serving as an X-ray permeable support film, 13 is an organic film, 14 is a film formed by continuous vapor deposition of Cr / Au serving as a base for electrolytic plating, and 15 is a resist for electron beam lithography. , 16 are X-ray absorbers having a desired pattern shape set at a desired position.

First, a silicon nitride film 12 having a thickness of 2 μm was formed on a 3 mm thick silicon wafer 11 as a substrate by a CVD method. afterwards,
PMMA, which is originally used as an electron beam resist
In this embodiment, an organic film 13 is formed on the silicon nitride film 12 as an organic film 13 as shown in FIG. It was applied by a spin coating method in a thickness.

Next, as shown in FIG. 1 (b), after the silicon wafer 11 is back-etched by electrolytic etching, the Cr / Au film 14 of Cr 10 nm and Au 50 nm is exposed to the surface of the silicon nitride by resistance heating evaporation. The film was continuously formed on the side, that is, on the side on which the substrate was back-etched.

Further, after a Cr / Au film 14 was continuously formed, PMMA was formed to a thickness of 0.8 μm as a resist 15 for electron beam lithography by a spin coating method, and then, as shown in FIG. A desired pattern was set at a desired position by electron beam drawing.

Next, as shown in FIG. 1 (d), after forming an absorber pattern 16 having a thickness of 0.7 μm by Au electroplating, an electron beam lithography resist 15 located between the absorption patterns with methyl ethyl ketone. PMMA was removed (Fig. 1 (e)
Illustrated). At this time, the organic film 13 formed to improve the process resistance of the silicon nitride film 12 was also removed at the same time because PMMA was used in this embodiment.

When the organic film 13 cannot be removed with the same stripping agent as the electron beam drawing resist 15, a step of removing the organic film 13 may be further performed.

In this example, after the organic film 13 was formed by spray coating, the silicon wafer 11 as the substrate was back-etched, and then the organic film 13 was baked at 170 ° C. This baking simultaneously anneals the silicon nitride film 12, which is the X-ray permeable support film, to remove the residual stress of the X-ray permeable support film.

Note that this annealing may be performed independently before the baking of the organic film 13.

In the process of the present embodiment, a vacuum process or a process of immersing in a fluid after back etching the silicon wafer 11 includes a process of continuously forming the Cr / Au film 14 by resistance heating, and a resist pattern by electron beam lithography. Fifteen
There is a step of forming, a step of electroplating Au, and a step of removing the resist 15 and the organic film 13, but in all of these steps except the step of removing the resist 15 and the organic film 13, the organic film is used. The presence of 13 improved the process resistance of the silicon nitride film 12, which is an X-ray permeable support film, and significantly improved the yield per process.

Embodiment 2 FIG. 4 is a view showing a second embodiment of the present invention.
Denotes a substrate, 42 denotes an inorganic film serving as an X-ray permeable support film, 43 denotes X
Reference numeral 43 'denotes an X-ray absorber having a desired pattern shape set at a desired position, reference numeral 43' denotes an organic film, and reference numeral 45 denotes an electron beam drawing resist pattern.

First, R was placed on a 3 mm-thick silicon wafer 41 as a substrate.
Silicon carbide was formed to a thickness of 2 μm as an X-ray permeable support film 42 by the F sputtering method. A tantalum (Ta) 43, which is an X-ray absorber, was formed thereon to a thickness of 0.8 μm (see FIG. 4 (a)).

Next, as shown in FIG. 4 (b), the silicon wafer 41 is back-etched by electrolytic etching, and
Annealing was performed at 250 ° C. for 1 hour.

Further, a novolak-based resist 44 is placed on the side on which the silicon wafer 41 is back-etched as shown in FIG.
It was spin-coated to a thickness of 10 μm.

Next, as shown in FIG. 4 (d), the same novolak-based resist 45 was spin-coated on the Ta film 43 to a thickness of 0.5 μm and then drawn by an electron beam. Thereafter, the Ta film 43 is dry-etched under the conditions of CBrF ₃ 20 SCCM and 2 Pa to form a desired pattern shape 43 ′ as shown in FIG. 4E, and the remaining novolak-based resist 45 is reacted with oxygen. It was removed by reactive ion etching.

Finally, as shown in FIG. 4 (f), the organic film 44 was removed by oxygen reactive ion etching.

In the process of the present embodiment, as a vacuum process performed after back-etching the silicon wafer 41, a step of forming a resist pattern 45 by electron beam drawing, and a pattern formation of the Ta film 43 by reactive ion etching of CBrF ₃ There is a process, a process of removing the resist 45 by reactive ion etching of oxygen, and a process of removing the organic film 44 on the back surface.The organic film 44 is all of these except for the process of removing the organic film 44 on the back surface. In this step, the process resistance of the silicon carbide film 42, which is the X-ray permeable support film, was improved, and the yield per step was significantly improved.

In each of the first and second embodiments, electron beam lithography is used for forming a resist pattern. However, it is a matter of course that the pattern may be formed by X-ray exposure or ultraviolet exposure.

(Effects) As described above, according to the present invention, in the production of an X-ray mask structure, an organic film is formed, and after the substrate is back-etched, annealing at 100 ° C. to 500 ° C. is performed. By forming, the X-ray absorber having a desired pattern shape can be formed on the X-ray transparent support film with the positional deviation from the desired position being suppressed to 1/10 or less of the minimum line width. In addition, the yield in the process of forming the X-ray absorber can be improved, and the working efficiency can be improved.

In particular, when the substrate is back-etched, the tensile stress of the inorganic film, which is an X-ray permeable support film, is released, but partly remains, and is further released one after another by a process after the electron beam drawing of the resist. In contrast to the occurrence of misalignment with the pattern, in the present invention, annealing after back etching promotes the release of tensile stress, and the misalignment of the pattern due to the process after electron beam drawing can be reduced. The yield can be improved by improving the overall overlay accuracy when an element is created using the created X-ray mask structure.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating an embodiment of the present invention.
FIG. 4 is a diagram schematically illustrating another embodiment of the present invention. FIG. 2 is a view showing a typical example of an X-ray mask structure when an organic film is used as an X-ray transparent support film.
The figure shows the X-ray when an inorganic membrane is used as the X-ray permeable support membrane.
It is a figure showing a typical example of a line mask structure. 11, 32 ', 41: Substrate 12, 21, 31, 42: X-ray permeable support film 13, 44: Organic film 43: Film with X-ray absorbing material 14: Cr / Au continuous deposition film 15, 45: Resist Pattern 16, 23, 33, 43 ': Absorber pattern 22: Holding frame 32: Reinforcement

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Hideo Kato, Inventor 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yoshiaki Fukuda 3- 30-2, Shimomaruko, Ota-ku, Tokyo Within Canon Inc. (56) References JP-A-63-289931 (JP, A)

Claims (3)

(57) [Claims] In a method for manufacturing an X-ray mask structure, an X-ray permeable support film is held by a holding frame, and a desired pattern made of an X-ray absorber is provided at a desired position on the support film. A step of forming a support film thereon, a step of applying an organic film on the support film, a step of back etching the substrate on which the support film is formed, and annealing at an annealing temperature of 100 to 500 ° C. after the back etching step Performing an X-ray absorber pattern after the annealing step; and removing the organic film after forming the X-ray absorber pattern. 2. The method of manufacturing an X-ray mask structure according to claim 1, wherein the back etching of the substrate is performed after the step of applying the organic film. 3. The method according to claim 1, wherein the step of forming the X-ray absorber pattern includes a step of applying a resist, and a step of forming a resist pattern by a process including electron drawing, X-ray exposure, or ultraviolet exposure. The method for producing an X-ray mask structure according to the above.