JPH03268317A - Forming method of x-ray mask - Google Patents

Abstract

PURPOSE:To obtain a highly precise X-ray mask with superior reproducibility by forming an X-ray absorber pattern of the X-ray mask by a selective CVD method. CONSTITUTION:An X-ray absorber pattern 31 of an X-ray mask is formed by a selective CVD method. That is, an absorber deposition blocking film 27a is formed on the region except the absorber pattern forming region of a membrane 23, and absorber is deposited on the region exposed from the film 27a of the membrane 23 by the selective CVD method. Tungsten is preferably used for absorber material, and the absorber deposition blocking film 27a is preferable to be constituted of an insulating film. Thereby an X-ray mask having a highly precise absorber pattern can be obtained with superior reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing an X-ray mask for X-ray imaging used in manufacturing semiconductor devices, electronic devices, optical devices, and the like.

(Prior Art) In manufacturing highly integrated semiconductor devices such as 16 Mbit DC dynamic (RAM), a technology that can form extremely fine patterns is required. Therefore, X-ray phosphorography, which can form fine patterns of less than 1/4 micron (1/4 um) in size, has become the main focus.

In the field of X-ray phosphorography, an SOR (Synchronized rotor) is used as an X-ray source.
1 Radiation), and development of commercial-grade technology is progressing.

However, since a lens optical system such as that used in optical lithography cannot be used, only a mask of the same size can be used, and the mask dimensional accuracy must be much higher than that of a mask for optical lithography that uses a reduction optical system. For this reason, establishing techniques for producing X-ray masks is an important issue.

As an example of a conventional method for manufacturing an X-ray mask, for example, see the document
Process Conference), 19
89. There was one disclosed in p. 84). Fourth
Figures (A) to (D) are process diagrams for explaining the process,
FIG. 3 is a cross-sectional view showing the state of the X-ray mask in the main steps in the process.

In this conventional manufacturing method, first, a silicon substrate 1
S i Nt 113 serving as a membrane is formed on the surface of the substrate 1 to a thickness of approximately Ium by a known film forming method. Roughly speaking, a SiN film 15, which serves as a mask when back-etching the silicon substrate 11, is formed on the back surface of the silicon substrate 11 by a known film forming technique and buttering technique (FIG. 4(A)).
.

Next, a tungsten thin film 17 of 0.8μ, for example, is deposited on the membrane 13 as an absorber material by high frequency sputtering.
It is formed to have a film thickness of approximately 100 m. Next, a resist pattern 9 having a predetermined shape is formed on this tungsten thin film 17 by a known method (FIG. 4(B)).

Next, anisotropic ECR (ElectronCyclo
tron Re5onance) - tungsten thin film 1 by plasma reactive ion etching technology
The absorber pattern 17a is formed by removing the exposed portion of the resist pattern 19 of No. 7 (FIG. 4(C)).

Document (2) reports that a 0.25 um tungsten pattern was obtained by a special etching technique in which the ECR plasma of SFs gas was used and the substrate temperature was cooled to about -20°C.

Next, a back-etching mask 15 is applied to the silicon substrate 110.
The exposed portions are etched by a suitable method to obtain the desired X-ray mask (FIG. 4(D)).

In addition, in order to obtain a better pattern, for example, reference ■ (Microelectronic Engineering (Micr
oelectronic En9inee r ri
ng) 9 (1989) p, 127-130), an X! ! Masks are suggested. Note that FIG. 5 is a cross-sectional view of the X-ray mask taken at the same position as FIG. 4(D).

The absorber is rectangular ×! ! In the case of a mask (an x!! mask like the one shown in Figure 4 (D)), X-rays reach the resist that faces the absorber, which is not originally exposed to x1s, due to Fresnel diffraction, deteriorating the pattern shape, but the absorption of the tapered shape body 1
In the X-ray mask having 7b, Fresnel diffraction can be reduced and the pattern shape can be improved accordingly.

(Problem to be Solved by the Invention) However, in the conventional method for manufacturing an X-ray mask disclosed in the above-mentioned document ①, in order to obtain an absorber pattern, an absorber material such as a ringsten thin film is tri-etched. was. Absorber material breaks W (tungsten), T
Metals such as a (tantalum), AuC and gold generally have the problem of exhibiting characteristics such as difficulty in achieving a selectivity with an etching mask and difficulty in anisotropic etching. For this reason, it has been difficult to obtain highly accurate absorber patterns required for X-ray masks with good reproducibility.

Furthermore, when producing an X-ray mask with a tapered shape as disclosed in Document ① by dry etching, in addition to being difficult to process, a rather complicated processing process is required to obtain the tapered shape. . For this reason,
'It is becoming increasingly difficult to obtain highly accurate absorber patterns with good reproducibility.

The present invention has been made in view of these points, and therefore, an object of the present invention is to provide a method for manufacturing an X-ray mask having a desired absorber pattern without modifying the absorber. be.

In order to achieve this object, according to the first invention of this application, when producing an X-ray mask, the Xi absorber pattern of the X-ray mask is selected using the CVD method. It is characterized by being formed by.

Incidentally, in applying the first invention, the above-mentioned absorber pattern is formed by forming an absorber deposition prevention film on a region of the membrane other than the region where the absorber pattern is planned to be formed, and the above-mentioned absorber deposition of the aforementioned membrane is performed. It is preferable to deposit an absorber by selective CVD in a region opposite to W on the blocking film.

In addition, when applying the first invention, if the membrane is made of a material unsuitable for selectively depositing the absorber, an absorber deposition base II is formed on the membrane in advance, and the absorber is deposited on the membrane in advance. , 11! of this absorber deposition base film other than the area where the absorber pattern is planned to be formed! Preferably, an absorber deposition prevention film is formed over the area.

Further, in applying the first invention, when the absorber pattern is made into a tapered shape, the above-mentioned absorber deposition prevention film is applied to the thickness of the core layer at the boundary with the region where the absorber pattern is planned to be formed. If the cross-sectional shape in the transverse direction is formed to be tapered, an absorbent body having a tapered shape can be obtained in the area where the absorber pattern is to be formed.

In addition, in the method for producing an X-ray mask of the first invention,
It is preferable to use tungsten as the material for the absorber. Further, it is preferable that the absorber deposition prevention lIN be formed of an insulating film, and more preferably a silicon oxide film. Further, it is preferable to use polysilicon as the base film for absorber deposition.

Further, the second invention of this application is characterized in that the absorber pattern having a tapered shape is formed in a process including the following steps ① to ②.

■...A mask material is placed above the WI region other than the area where the absorber pattern is planned to be formed on the membrane, and the cross-sectional shape of the mask material in the thickness direction at the boundary with the area where the absorber pattern is planned to be formed is tapered. The process of forming it so that it becomes .

(2) A step of forming an absorber on the above-mentioned mask material and above the above-mentioned membrane.

(2) A process of removing the above-mentioned absorber by an etch-back method until the above-mentioned mask material is exposed.

In carrying out the second invention, it is preferable to use tungsten as the material for the absorber. Furthermore, it is preferable to use silicon oxide silicon as the mask material.6 (Function) According to the structure of this invention, the absorber pattern of the membrane (this base film in the case of the structure using the absorber deposition base lI!8) The absorber forming material is selected by CVD on the area to be formed.
Since the desired absorber pattern is formed by deposition by a method, the desired absorber pattern can be obtained without etching the absorber itself.

In general, in this invention, absorber deposition prevention III
v! In the structure used, the absorber deposition prevention film can be made of a silicon oxide film, etc., but this can be patterned with high reproducibility and high precision using conventionally known photolithography technology, electron beam (EB) phosphorography technology, and etching technology. I can do it. Therefore, if the absorber is deposited by selective CVD on the region of the membrane (or this base film in the case of a configuration using a base film for absorber deposition) that is exposed from the absorber deposition prevention film, the desired absorber pattern can be obtained with high reproducibility. Can be formed well.

Roughly speaking, in the case of a structure in which an absorber deposition prevention film is formed so that the cross-sectional shape in the thickness direction of the core layer at the boundary with the region where the absorber pattern is planned to be formed is tapered, the absorber Tapering of the deposition prevention film is performed using conventionally known techniques (for example, Reference ■: Proceedings of the Japan Society of Applied Physics Fall 1988, p.
567, lecture number 7p-14), it is possible to easily form a tapered absorber pattern in the region where the absorber pattern is to be formed, and it is also possible to easily form an absorber pattern with a tapered shape that can reduce Fresnel diffraction. can get.

The use of the absorber deposition substrate III also allows the method of the invention to be applied even when the membrane is constructed of a material unsuitable as a selective CvD substrate.

Further, according to the configuration of the second invention, an absorber pattern having a tapered shape can be formed without using selective CvD.

(Example) Hereinafter, with reference to the drawings,
Examples of methods for manufacturing line masks will be described. It should be noted that each figure used in the explanation schematically shows the dimensions, shapes, and arrangement relationships of each component to the extent that this invention can be understood.

First, an absorber pattern is formed by selective CVD method.XII
An embodiment of the first invention for producing a mask will be described.

<Sash 1! ii! Example> First, an example will be described in which an X-ray mask (corresponding to the X-ray mask in FIG. 4(D)) having a rectangular absorber pattern is manufactured by the method of the first invention. FIGS. 1(A) to 1(F) are process diagrams showing the state of the X-ray mask in the main steps in the X-ray mask manufacturing process of this first embodiment using cross-sectional views.

First, in this embodiment, a silicon substrate 2 of 5 inches (1 inch is approximately 2.54 cm) is prepared as a substrate.

Next, the flow rate of S I H4 is 703 CCM, NH3 (D
Flow rate @ 140 S CCM, N2 (07M, m'
8800 SCCM, substrate temperature 1Fr400″C, RF
In this example, 5iNt123 is formed as a membrane on a silicon substrate 21 to a thickness of 2.0 μm by CVD under conditions of a power of 400 W and a pressure of 0.2 Torr (FIG. 1(A)).

Next, an absorber pattern is formed on this membrane 23. In this embodiment, tungsten is used as the absorber and this pattern is formed by selective CVD as described below.

First, tungsten (
In this example, a polysilicon film is used as a film 25 (this film is referred to as a base film 25 for absorber deposition) that enables the deposition of an absorber) on Si Ni 123, and in this example, a polysilicon film with a thickness of 0.1 um is used. The polysilicon film 25 is formed with a film thickness of
i-600°C1 pressure! C under the condition of 1.5 Torr
This is done using the VD method.

Next, in order to prevent the absorber from being deposited in areas other than the area where the absorber pattern is planned to be formed in this polysilicon film 25 in the selective CVD process performed, the absorber is prevented from being deposited in this area. A film (this film is referred to as an absorber deposition prevention film) is formed as described below. In this embodiment, the absorber deposition prevention film is made of a silicon oxide film.

First, set the argon pressure to 5 mTorr, and set the RF power to
A silicon oxide film 27 as a thin film for forming an absorber deposition prevention film is formed on the entire surface of the polysilicon film 25 with a thickness of 0.5 um in this example by sputtering at 600 W. Figure (C)).

Next, silicon oxide 112 was coated using the subi coating method.
7 (ZT SM RV 3 Shi"; resist manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied to a film thickness of 1.0 um, and then this sample was prebaked for 60 seconds at a temperature of t 90 "C. Next, this resist film was exposed using a 115 reduction projection exposure system N, and then developed using a developer (NMD-W 2.38%) manufactured by Tokyo Ohka Kogyo Co., Ltd. to form a resist pattern 29vi- form (Figure 1 (
D)) This resist pattern 29 has a shape in which the area where the absorber pattern is to be formed is exposed, and its cross section is approximately rectangular.

Next, using this resist pattern 29 as an etching mask, a cathode-type parallel plate type RIE (reactive ion etching) device of fl 1% was used, the flow rate of CHF3 was 953CCM, the flow rate of 02 was 5SCCM, and the pressure was 37.
The exposed portion of the silicon oxide film 27 from the resist pattern 29 is etched under conditions of 5 mTorr and RF power of OOW.Next, the resist pattern 29 is removed using a mixed solution of sulfuric acid and hydrogen peroxide. As a result, an absorber deposition prevention film 27a made of a silicon oxide film is formed on a region of the polysilicon (base film for absorber deposition) 25 other than the area where the absorber pattern is planned to be formed (FIG. 1(E)).
The cross-sectional shape of the core layer 27a in the thickness direction at the boundary between the absorber deposition prevention film 27a and the area where the absorber pattern is to be formed is approximately rectangular.

Next, absorber deposition prevention film 27a of polysilicon 1!25
Tungsten is deposited on the exposed region by selective CVD to form a desired rectangular absorber pattern 31 (FIG. 1(F)).

In this example, H2 flow rate %500SCCM, W F
s flow jl 'M 5 S CCM, substrate temperature Iv40
By CVD method with 0"C1 pressure of 0.2 Torr,
Selective deposition of tungsten is performed.

Thereafter, as in the conventional method, back etching is performed (not shown) from the back surface of the silicon substrate 21 until the back surface of the membrane 23 is exposed, thereby forming the X-ray mask of the first embodiment (not shown).

By the way, the absorber deposition prevention film 27a can be left as is, or it can be removed. If removed, it is silicon oxidation! From 27 to absorber deposition prevention film 2
It can be removed under the same etching conditions as those for patterning 7a. Alternatively, it can be removed by using a 5% hydrofluoric acid (HF) aqueous solution.

<M22 Fushi> Next, by the method of the first invention, an X-ray mask having an absorber pattern having a tapered shape (corresponding to the x!! mask in Fig. 5, however, the taper of the embodiment is reversed) (It becomes a taper.) 8 An example of manufacturing will be explained. l! Figure 2 (A
) to (E) are process diagrams for explaining the process, and show the state of the X-ray mask in the main steps in the X-ray mask manufacturing process of the second embodiment using one absorber pattern 31 in FIG. It is a process diagram shown with a sectional view of the main part focusing on the peripheral part.

It should be understood that in Fig. 2, the film thickness ratio of each film is different from that in Fig. 1 in order to emphasize the collecting body stacking stop 1127 and the like.

First, S as a membrane is placed on a silicon substrate 2].
An iN film 23, a polysilicon film 25 as a base film for absorber deposition, and a silicon oxide film 1127 as a thin film for forming an absorber deposition prevention film are sequentially formed under the same conditions as in the first example (see FIG. 2(A)). )).

Next, the silicon oxide film 27 is processed in the following manner so that the cross-sectional shape in the thickness direction of the core layer 27 at the boundary with the region where the absorber pattern is to be formed is tapered.

First, in this second embodiment, LMR-UV resist (Fuji Pharmaceutical Co., Ltd. type resist) is coated on the silicon oxide film 27 to a film thickness of 1.0 m by the sand coating method.
Next, exposure is performed using a 115 reduction projection exposure apparatus, and then development is performed.

The LM UV resist easily forms a resist pattern 33 with an overhang shape (FIG. 2(B)).

Next, using this resist pattern 33 as an etching mask and using a hexode-type R etching tool W, the flow rate of CHF2 was reduced to 1.
The exposed portion of the silicon oxide film 27 from the resist pattern 33 was etched under the conditions of 00 S CCM, 02 flow rate of 143 CCM, pressure of 70 mTorr, and RF power of 1.5 KW. The resist pattern 33 is removed using the mixed solution. As a result, an absorber deposition prevention film 27b made of a silicon oxide film is formed on a region of the polysilicon (base film for absorber deposition) 25 other than the region where an absorber pattern is planned to be formed.
1! An absorber deposition prevention film 27b (hereinafter abbreviated as tapered absorber deposition prevention film 27b) having a taper angle θ of 75° at the boundary with the region is obtained (see FIG. 2(C)).
)), the above-mentioned taper processing is described in the literature ■ (1988
Proceedings of the Japan Society of Applied Physics Autumn 2018, page 567, lecture number 7
The technique disclosed in p-ni-14) is used.

Next, tungsten is deposited by selective CVD on the region exposed from the tapered absorber deposition prevention film 27b of the polysilicon 1125 under the same conditions as in the first example, thereby forming an absorber pattern 35 having an inversely tapered shape. (Fig. 2(D)).

After that, as in the first embodiment, back etching is performed from the back surface of the silicon substrate 21 until the back surface of the membrane 23 is exposed (not shown).
A mask can be formed (not shown). i
! In the case of the embodiment as well, the absorber deposition prevention 1127a may be left as is or may be removed.

Absorber pattern 3 obtained by the manufacturing method of this second example
The taper No. 5 is a reverse taper, but in terms of the objective of reducing Fresnel diffraction, the same effect as that of a forward taper (X-ray mask in diagram N5) can be obtained.

Next, select absorbent pattern 35 having a tapered shape C
A second embodiment of the method for producing an X-ray mask according to the second invention, which is formed without using the VD method, will be described. Figure 3 (A) and (B)
2 is a diagram for explaining the process, and is a process diagram of the main parts shown in a cross-sectional view at a depth similar to FIG. 2.

A membrane 23 and a base film 25 for absorber deposition are sequentially formed on a silicon substrate 21 in the same manner as in the embodiment of the first invention.Next, the base film for absorber deposition is formed! In this case, a silicon oxide film V is used as the mask material 4 in the region other than the region where the absorber pattern is to be formed in No. 25, and the thickness direction of the mask material 4] at the boundary with the region where the absorber pattern is to be formed in the mask material 41. is formed so that the cross-sectional shape is tapered (third
(A), such a mask material 41 (hereinafter referred to as tapered mask material 41) can be formed by a procedure completely similar to the procedure for producing the tapered absorber deposition prevention film 27b of the first invention.

Next, a tungsten film 43 as an absorber material is deposited on the entire surface of this sample by a known CVD method (see Fig. 3).
A)).

Next, a resist (not shown) is applied on this tungsten film 43 to flatten the sample surface, and then SF,
The resist and tungsten film 41 are removed by an etch-back method using gas until the surface of the tapered mask material 41 is exposed. As a result, an absorbent pattern 35 having an inverted tapered shape is obtained (FIG. 3(B)).

In the above, each embodiment of the method for manufacturing an X-ray mask according to the first and second inventions has been described, but these inventions are not limited to the above-mentioned embodiments, and various modifications as described below are possible. can be added.

For example, the substrate, membrane,
The constituent materials of the absorber, the base film for absorber deposition, the absorber deposition prevention film, and the mask material are merely examples within the scope of the present invention, and any of them can be changed to other suitable materials.

In addition, the film-forming methods and numerical conditions for the membrane, base film for absorber deposition, absorber deposition prevention film, and mask material, as well as the tapered absorber deposition prevention film and tapered The method and numerical conditions for forming the mask material can also be changed to other suitable methods and conditions.

In addition, the taper angle of the absorber deposition prevention film with a chill bar,
The taper angle of the tapered mask material can be changed depending on the design of the X-ray mask.

It should also be understood that the selective CVD deposition conditions for tungsten are just one example.

In addition, in the above embodiment, the membrane was a SiN film that was unsuitable for depositing the absorber, so a polysilicon film was formed on the membrane as a base film for absorber deposition.
If the membrane is constructed of a material on which absorbent can be deposited, no such procedure is necessary.

(Effects of the Invention) As is clear from the above description, according to the method for producing an X-ray mask of the second invention of this application, the desired X-ray mask can be produced.
A line mask can be formed without etching the absorber. Therefore, problems that occur when etching the absorber are eliminated, and a highly accurate X-ray mask can be obtained with good reproducibility.

In addition, a highly accurate X-ray mask having a tapered absorber pattern that can reduce Fresnel diffraction can also be easily obtained.

In addition, in the method for manufacturing the XII mask of the first invention, the absorber is deposited after patterning the absorber deposition prevention film, and in the method for manufacturing the X-ray mask of the second invention, after patterning the mask material. Deposit the absorber. Therefore, when an electron beam resist is used for patterning the absorber deposition prevention film or patterning the mask material, the underlying layer of the electron beam resist is not a metal but a silicon oxide film or the like. Therefore, according to Tsuta and the second invention, during electron beam lithography, the influence of backscattering is smaller than when the resist is made of metal (absorber), and from this point of view as well, a highly accurate X-ray mask is required. can get.

[Brief explanation of drawings]

FIGS. 1(A) to (F) are process diagrams showing the first embodiment of the X-ray mask manufacturing method of the first invention, and FIGS. 2(A) to (D) are the X-ray mask manufacturing method of the first invention. 3A and 3B are main part process diagrams for explaining the second embodiment of the method for producing a mask, and FIGS. 3A and 3B are main parts for explaining the third embodiment of the method for producing an X-ray mask according to the second invention. The process diagram and FIGS. 4(A) to 4(D) are diagrams for explaining the prior art, and FIG. 5 is a diagram for explaining another prior art. 2] Substrate (silicon substrate) 23 Membrane (SiN film) 25 Base film for absorber deposition (polysilicon film) 27
--- Thin film for forming absorber deposition prevention film (silicon oxide film) 29 --- Resist pattern 27 a --- Absorber deposition prevention film 27 b --- Tapered absorber deposition prevention film 31 ---
...Absorber pattern 33--Overhang-shaped resist pattern 35-
- Absorber pattern 1 having a reverse tapered shape... Tapered mask material (A) 43... Tungsten film. (B) Patent applicant Oki Electric Industry Co., Ltd. (Polysilicon film) ((3) 7. Thin film (silicon oxide film) for forming absorber deposition prevention film - First embodiment of the invention's method for producing an X-ray mask Figure 3 Overhang-shaped resist pattern Process diagram of main parts for explaining the second embodiment of the X-ray mask production method of the first invention First embodiment of the X-ray mask production method of the first invention Figure 1 - Main steps for explaining the second embodiment of the X-ray mask manufacturing method of the invention Figure 15 Diagram for explaining the prior art Figure 4 X-ray mask of the invention Figure 4 shows the main steps for explaining an example of the manufacturing method.

Claims (10)

[Claims] (1) A method for producing an X-ray mask, characterized in that, in producing the X-ray mask, an X-ray absorber pattern of the X-ray mask is formed by a selective CVD method. (2) In the method for manufacturing an X-ray mask according to claim 1, the formation of the absorber pattern is performed by forming an absorber deposition prevention film on a region of the membrane other than the region where the absorber pattern is planned to be formed; A method for producing an X-ray mask, characterized in that an absorber is deposited in a region exposed from the absorber deposition prevention film by a selective CVD method. (3) In the method for producing an X-ray mask according to claim 1, the formation of the absorber pattern comprises forming a base film for absorber deposition on a membrane, and forming an absorber pattern on the base film for absorber deposition. An absorber deposition prevention film is formed on a region other than the planned region, and selective CVD is applied to a region of the base film for absorber deposition that is exposed from the absorber deposition prevention film.
1. A method for producing an X-ray mask, characterized by depositing an absorber by a method. (4) In the method for producing an X-ray mask according to claim 2 or 3, the absorber deposition prevention film has a cross-sectional shape in the thickness direction of the film at a boundary with a region where an absorber pattern is to be formed. 1. A method for manufacturing an X-ray mask, characterized in that the mask is formed to have a tapered shape. (5) When producing an X-ray mask, the X-ray absorber pattern of the X-ray mask is formed by placing a mask material above the region of the membrane other than the area where the absorber pattern is planned to be formed, and then forming the absorber pattern of the mask material. The mask material is formed so that the cross-sectional shape in the thickness direction at the boundary with the formation area is tapered, an absorber is formed on the mask material and above the membrane, and the absorber is formed by an etch-back method. A method for producing an X-ray mask, characterized in that the method is performed by removing the mask material until it is exposed. (6) The method for manufacturing an X-ray mask according to any one of claims 1 to 5, characterized in that tungsten is used as a material for the absorber. (7) The method for manufacturing an X-ray mask according to any one of claims 2 to 4, wherein the absorber deposition prevention film is composed of an insulating film. (8) The method for manufacturing an X-ray mask according to claim 7, wherein a silicon oxide film is used as the insulating film. (9) The method for manufacturing an X-ray mask according to claim 3 or 6, wherein polysilicon is used as the base film for depositing the absorber. (10) The method for manufacturing an X-ray mask according to claim 5, wherein a silicon oxide film is used as the mask material.