JPS63291418A - Manufacture of mask for x-ray exposure - Google Patents

Abstract

PURPOSE:To form a mask for X-ray exposure use which is finely made with high accuracy and is free from defects by incorporating a correcting process of a mask absorber pattern for X-ray exposure use in a formation process of a mask absorber and by correcting pattern defects in the form of an interlayer pattern as an absorber etching mask use before etching such an absorber having a thick thickness. CONSTITUTION:Membranes 2 are formed as X-ray transmission materials at the side of the main plane and the opposite side of a X-ray mask supporting substrate 1 and an etching protective film 4 consisting of silicon oxide, silicon nitride and the like is formed after depositing an absorber film 3. Then, an interlayer 30 for a pattern correction use consisting of metallic materials or compounds having the metallic materials as a main constituent is deposited. Subsequently, after coating an ultraviolet resist of PMMA and the like or resists of electron beams and X-rays, patterns are created with an exposure technique to form themselves into resist patterns 5 and the interlayer 30 for pattern correction use is treated by using the resist patterns 5 as masks. And then, an interlayer pattern 30' for pattern correction use in which the resist patterns 5 are faithfully reflected is formed. Then, the interlayer pattern 30'' is formed by correcting some existing faults and defects 14 or defective residues 13.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to X-ray exposure technology, which is a technology for forming fine patterns used for semiconductor integrated circuit manufacturing. , relates to the production of an X-ray exposure mask with few defects.

(Prior Art) As the performance of semiconductor integrated circuits increases, there is an X-ray exposure technique that uses soft X-rays with a wavelength of about 4 to 20 A as a radiation source as a technique for forming fine patterns in the submicron region. An essential component of this technology is an x-ray exposure mask. X-ray masks block (absorb) soft X-rays well.
The mask substrate (membrane) supports the absorber bat and is highly transparent to soft X-rays. Inorganic materials such as silicon nitride (SixNy) manufactured by low pressure CVD (LP-CVD) and organic polymer materials such as polyimide are used as X-ray mask substrates. As the body material, high-melting point, high-density metal materials such as Ta, W, MO, etc. are used from the viewpoint of X-ray blocking ability and microfabricability.

In FIG. 3, a conventional method of manufacturing an X-ray exposure mask will be explained.

Here, 1 is an X-ray mask support substrate, 2 is a mask substrate (membrane material), 4 is an etching protection film (etching mask layer), 3 is a mask absorber film, 5 is a resist batten, and 4' is an etching pattern. The formed mask button layer, 3' is a mask absorber button, 10 is a membrane region (
window part).

On the X-ray mask support substrate 1, 0, 1 to 5 p.p.
5txN for a thickness of m (x and y are integers).

Inorganic materials such as BN, SiC films, etc.
A membrane 2 made of an organic material (polymer film) such as imide or mylar is formed (3A). Next, Ta is deposited on the surface of the membrane 2 as an absorber film 3.

A film of a high-density material (heavy metal) with a large atomic number, such as W, Re, Mo, Au, Pt, etc., is formed by a film forming technique such as a sputtering method, a plasma CVD method, a vacuum evaporation method, or a plating method. Furthermore, an etching mask (etching protective film) 4 made of an inorganic film such as silicon oxide or silicon nitride or a polymer film such as polyimide is placed on the absorber film 3 by sputtering or plasma CV.
The film is formed to a desired thickness using a film forming technique such as the D method or the spin code method (3B). Subsequently, the surface of the etching mask 4 is coated with an ultraviolet resist such as %PMMA or an electron beam resist to a desired thickness, and then a resist pattern is formed by forming a desired pattern using ultraviolet rays, electron beams, X-rays, etc. Form 5 (3C).

Furthermore, using the resist pattern 5 as a mask, the etching mask 4 is processed using fine processing techniques such as sputter etching and reactive sputter etching, such as ion etching, to form an etching mask pattern that faithfully reflects the resist pattern 5. 4' is formed. Furthermore, using the etching mask button 4' as a mask, microfabrication techniques such as reactive sputter etching are used to
The absorbent film 3 is processed to form an absorbent batten 3' having a desired pattern (3D). Next, after removing the etching mask batten 4' remaining on the absorber batten 3' by sputter etching or reactive sputter etching, a window portion is formed on the back side of the X-ray mask support substrate 1. Formed by sputter etching method, reactive sputter etching method, etc. (3E
). Finally, by selectively etching the window pattern as a mask from the back side of the X-ray mask support substrate 1 as shown in the figure, and providing a membrane region (window portion) 10 on the X-ray mask support substrate 1, a mask for X-ray exposure is formed. is completed to obtain the desired mask (3F).

Here, an important issue in X-ray exposure technology is improving the quality of X-ray exposure masks in order to improve device yield and reliability. As a means to achieve this, automatic mask defect inspection technology and mask pattern correction technology are being developed and put into practical use.

Generally, X uses resist work or etching process.
In the line mask manufacturing process, bump defects occur due to causes such as contamination within the equipment used in each step and various problems during sample handling. Defects that occur on masks are broadly divided into defective defects such as white spots (pinholes), dents, cuts, poor cutting, and missing parts, and residual defects such as black spots, dust, protrusions, contamination, and bridges. . Therefore, from the viewpoint of improving the quality of X-ray masks, it is necessary to eliminate the defects that occur in these absorber battens.

Generally, there is a relationship between mask quality and device yield.
It is known that the following relationship holds true.

y=(1/(1+DA)) Here, Y is the device yield (%), D is the mask defect density (pieces/d), A is the chip area CCd), and N is the number of device steps.

This relational expression means that unless the number of defects is reduced by the increase in device chip size, the yield of devices will decrease, and it also means that good devices can be produced even if there are some mask defects. It also appears. However, in X-ray exposure technology that uses a diverging X-ray source, the step-and-repeat method (stepper method) has been adopted due to problems such as bump blur and runout errors caused by the resolution of the bumps and the geometry of the equipment. Adopted. In this stepper method, one original mask is used to repeatedly expose the entire silicon wafer in steps, so if a defective original mask is used, all chips will have defects. Therefore, a defect-free X-ray exposure mask is required for stepper type xai light.

Mask modification, which has been proposed to improve the quality of X-ray exposure masks, is done after the completion of the mask process as shown in Figure 3.
This has been done using focused ion beam (FIB) technology, which has the ability to focus to diameters below 0.1 μm (high resolution) and very high focused current densities. The slam correction technique will be explained in FIG.

Here, 11 is a finely focused ion beam, 12 is a scattering of residual defect material, 13 is a residual defect, 14 is a missing defect, 1
5 is a gas molecule as a raw material for an opaque film, 16 is a deposited 9 opaque film, 17 is a nozzle for supplying gas molecules as a raw material for an opaque film, and 3' is a mask absorber button.

First, (a) correction of the residual defect shown in the figure will be explained.

A focused ion beam (FIB) is created using a liquid metal ion source. Gallium is generally considered to be an ideal material for focused ion beam generation due to its low corrosivity and low vapor pressure.

Gallium is heated in a tank and allowed to flow along a tungsten needle toward an extraction electrode. When 4-10 KV is applied between the tungsten needle and the extraction electrode, gallium ions are generated from the tungsten needle.

The gallium ions are focused through a series of Einzern lenses and accelerated by an extraction voltage of 10-100 KV. The gallium ions 11 that have been focused and accelerated in this way are transported to the precisely positioned residual defect 1.
By precisely controlling the sputtering effect of the focused and accelerated gallium ions 11 at the position 3, the residual defects 13 existing on the absorber batt 3' are etched away.

On the other hand, the repair of the missing defect shown in Figure (B) basically involves depositing amorphous carbon or the like in the missing defect area. That is, by selectively depositing an opaque film of amorphous carbon using a combination of the chemical effect associated with the excitation of an ion beam and a nozzle supplying gas molecules as a raw material for the opaque film, defects on the absorber baton can be selectively deposited. Correct. The opaque film of amorphous carbon is formed by the collision of focused and accelerated beam-shaped excited gallium particles 11 and carbon gas particles 14 injected from a nozzle 16 for supplying gas molecules as raw material for the opaque film. . The opaque carbon film is selectively deposited on the areas swept by the gallium beam, and while forming the deposited film 15, it gradually fills in and corrects the defects present on the absorber.

Here, since the carbon film has a low stopping power against soft X-rays having a wavelength of about 4 to 20 A, it cannot be used as a material for repairing defects in the X-ray mask absorber batten. Therefore, as a material for repairing defects in the X-ray mask absorber batten, it is necessary to deposit heavy metals similar to the absorber material.

The X-ray exposure mask absorber batten repair technique using FIB technology is for repairing residual defects and missing defects present on the mask batten based on the principle described above.

For detailed slam correction methods, see the literature Microelectronic Manufacturing and Testing, 1986, No. 2 (Micr
oelectronic manufacturing
andTesting).

(Problems to be Solved by the Invention) The conventional Xa exposure mask manufacturing process and the mask absorber batten modification process are performed independently.・In the method of manufacturing a defect-free X-ray exposure mask by modifying the mask absorber pattern made of a material (high melting point), (1) the mask manufacturing process and the defect correction process are independent; (i) In the manufacturing process of X Wp 111 optical masks, most of the defects and residual defects occur in the process of forming the resist batten. After forming residual defects and missing defects on the absorber batten using a resist batten with residual defects and missing defects,
It was inefficient and lacking in productivity to repair residual defects and missing defects on the absorber batten. (i) The absorber batten, which acts as a mask for ), so it is usually 0.4
It becomes a thick film of ~0.8 ptra. Therefore, it takes a very long time to repair such a thick film of high-density, high-melting-point material using a focused ion beam.

(lv) o, The absorber batten, which is relatively thick at 4 to 0.8 pm, is placed on a relatively thin membrane of approximately 0.1 to 4 μm. When carrying out the modification, damage to the membrane by the ion beam was unavoidable, (v)
In order to correct defects, the carbon film used in the prior art cannot be used, and there are essential problems such as the need to deposit a heavy metal film that has a high blocking ability against soft X-rays.

(Object of the invention) The present invention has been proposed in view of the above points, and
The process of modifying the mask absorber button for X-ray exposure is incorporated into the mask absorber forming process as a step in the mask absorber forming process, and the process for modifying the absorber's etching mask is incorporated into the mask absorber forming process as a step in the mask absorber forming process. By correcting the batten defects in the form of an interlayer batten, and by performing absorber processing using a defect-free etching mask, the aim is to realize a highly precise and defect-free X-ray exposure mask. shall be.

(Means for Solving the Problems) In order to solve the problems of the prior art, the present invention provides a bump correction method between the resist film (resist baton) and the etching protection film (etching mask baton) of the absorber film. A thin film made of metal, a metal compound, an inorganic compound, or an organic polymer is placed as an interlayer film, and the bumps of the batten correction interlayer film that reflect the shape of the resist pattern are corrected using conventional batten correction technology. Then, a defect-free X-ray exposure mask is manufactured by using this batten-corrected defect-free interlayer pattern made of any of metal, metal compound, inorganic compound, or organic polymer as an etching mask for the absorber film. It is something.

(Function) In order to configure the mask absorber batten manufacturing process with the process of correcting the mask absorber pattern as one step of the mask absorbent batten manufacturing process, the etching protective film (etching mask) of the resist film (resist batten) and absorber film is formed.
Metals, metal compounds,
A thin film made of either an inorganic compound or an organic polymer is arranged, and the flaps of the intermediate film for batten correction, which reflect the shape of the resist pattern, are modified using conventional batten modification technology. defective metals, metal compounds,
By using an interlayer batten made of either an inorganic compound or an organic polymer as an etching mask for the absorber film, (a) batten defects (residual defects and missing defects), most of which occur during the resist batten formation process, can be eliminated. can be corrected at the stage of the etching mask of the absorber film, and (b) the interlayer film used for baton correction is very thin and can be made of metal, metal compound, inorganic compound, or organic polymer with low density. Therefore, it is possible to significantly shorten the repair time when repairing residual defects and missing defects using FIB technology. To be used as an etching mask for
Carbon films can be used to repair missing defects using conventional FIB technology, and the resistance of carbon films, which has been a problem in the past, does not pose a problem.

(Example) Next, examples of the present invention will be described.

It should be noted that the embodiments are merely illustrative, and it goes without saying that various changes and improvements may be made without departing from the spirit of the present invention.

(First Example) FIG. 1 is a mask manufacturing process for explaining the present invention in detail.

1 is an X-ray mask support substrate, 2 is a mask substrate (membrane), 3 is a mask absorber film, 3' is a mask absorber button,
4 is an etching protective film (etching mask), 4' is an etching mask button, 5 is a resist pattern, 10 is a membrane region (window part), 30 is an intermediate film for patch correction, 30' is an intermediate film button for patch correction, 30 “ is the intermediate film baton after the batan correction.

L P on the surface opposite to the flat surface side of the X-ray mask support substrate 1
-CV D (Low Pressure-Chemi
5ixN, BN, S to a thickness of 0.1 to 5 μm using film forming techniques such as Cally VaporDeposited) method, GUTSUFFCVD method, or spin code method.
A membrane 2 is formed as an X-ray transparent material made of an inorganic material such as iC or an organic polymer film such as polyimide or Mylar (IA). Next, as an absorber film 3 on the surface of the membrane 20, 'pa, W
A film of a heavy metal with a large atomic weight (mass) or density, such as Re@Mo, Au t pt, etc., or a film made of a compound whose main component is the above-mentioned material can be prepared by sputtering, plasma CVD, vacuum evaporation, or plating. After depositing a film to a desired thickness using a film forming technique such as a method or an ion blating method, a film of an inorganic material such as silicon oxide or silicon nitride or an organic material such as polyimide is deposited on the surface of the absorber film 30. The etching protective film (etching mask) 4 of the absorber film made of a polymer film is formed by sputtering and plasma C.
The etching protective film 4 is formed to a desired thickness using a dry film forming technique such as a VD method or an ion blating method or a wet film forming technique such as a spin code method. Further, on the upper surface of the etching protection film 4, 3i, Ti, V,
Low-density metal materials such as Cr and Ni and Ta
, W, Mo, or other high-density metal material similar to the absorber material, or a compound containing the above-mentioned metal material as a main component, is formed by sputtering or plasma CVD.
The film is deposited to a desired thickness using a film forming technique typified by the method (IB). Subsequently, after coating the surface of the above-described interlayer film 30 for batten correction with an ultraviolet resist such as PMMA or an electron beam/X-ray resist to a desired thickness, the batten is removed using an exposure technique such as ultraviolet rays, electron beams, or X-rays. A resist pattern 5 is created by forming a desired pattern (IC).

Furthermore, using the resist pattern 5 as a mask, the batten correction intermediate film 30 is processed using a microfabrication technique such as sputter etching, reactive sputter etching, or ion etching to form a batten that faithfully reflects the resist pattern 5. A correction intermediate film batten 30' is formed (ID).

Next, the missing defects 14 and residual defects 13 existing on the batten repairing intermediate film batten 30' are repaired by using a well-known mask batten repair technique using laser light or FIB to repair the absorber film. An intermediate film batten 30' made of the above-mentioned material after batten modification is formed on the etching mask 4 (IE). Next, using the defect-free intermediate film batten 30' after batten repair as a mask, the etching mask is etched by microfabrication technology such as sputter etching, reactive sputter etching, or ion etching. 4 to form an etching mask batten 4' that faithfully reflects the defect-free batten repair intermediate film batten 30' after batten repair. Furthermore, using the etching mask button 4' as a mask, the absorber M3 is processed by a microfabrication technique capable of selective etching such as reactive sputter etching to form an absorber button 3' having a desired shape. IF). Next, after removing the etching mask batten 4' remaining on the absorber batten 3' by sputter etching or reactive sputter etching, a window portion is formed on the back side of the X-ray mask support substrate 1. is formed using processing techniques such as sputter etching or reactive sputter etching (
IG). Finally, by selectively etching the back surface of the X-ray mask support substrate 1 using the window batten as a mask as shown in the figure, and providing a membrane region (window portion) 10 on the X-ray mask support substrate 1, defect-free X-ray exposure is performed. Complete the mask to obtain the desired mask (IH).

It is clear that in the step (IG) in FIG. 3, even if the etching mask batten 4' remaining on the absorber batten 3' is not removed, there will be no problem in the characteristics of the X-ray mask. It is.

(Second Embodiment) FIG. 2 describes an X-ray mask manufacturing method when an inorganic material or an organic polymer film is used as the batten correction intermediate film.

An X-ray transparent material 2 is formed to a desired thickness on the surface opposite to the permanent surface of the X-ray mask support substrate 1 (2A).

Next, after depositing the absorber film 3 to a desired thickness on the flat surface of the X-ray mask support substrate l, the absorber film 3
On the surface of the absorber film, an etching protective film 4 (an etching mask, an etching mask for the absorber film, which also serves as an interlayer film for patch correction, which has a slower etching speed than that of the absorber film during reactive sputter etching of the absorber film) is applied. An inorganic material or organic polymer film is formed to a desired thickness (2B). Subsequently, a resist film is formed on the batten correction intermediate film/etching mask material 4, and then a desired batten is formed by a batten creation technique to form a resist batten 5 (2C). next,
Using the resist pattern 5 as an etching mask, the interlayer film 4, which serves as a batten correction interlayer film and etching protection material, is processed to form a batten repair interlayer film and etching mask batten 4' that faithfully reflects the resist pattern (2D
). Subsequently, the missing defects and residual defects present on the batten repair intermediate film/etching mask batten 4' are corrected by batten repair technique, and the etching mask batten 4' after batten repair is formed on the absorber film 3. (2E). Next, the absorber film 3 is processed using a microfabrication technique that allows selective etching using the defect-free etching mask batten 4'' that has been subjected to batten correction as a mask to obtain an absorber batten 3' having a desired shape. (2F) After that, back etching is performed in the same manner as in the first embodiment to obtain a defect-free mask for X-ray exposure.

(Effects of the Invention) As explained above, according to the present invention, a metal, a metal compound, or A thin film made of either an inorganic compound or an organic polymer is arranged, and the flap of the above-mentioned batten-correcting interlayer film that reflects the shape of the resist pattern is modified, and the batten of the batten-modified interlayer film is made of a metal, a metal compound, an inorganic compound, or an organic polymer. A method for manufacturing an X-ray exposure mask that uses a defect-free interlayer film made of any polymer as an etching mask for the absorber film, thereby realizing a defect-free X-ray exposure mask, is as follows: effective.

(1) Batten defects that occur in the resist batten manufacturing process (
(1) The interlayer film used for batten repair is very thin and has a low density metal film, mainly consisting of the above metals. In addition to being able to use either a compound, an inorganic compound, or an organic polymer as a component, it is also possible to significantly shorten the batten repair time. Since it is used as an etching mask, an opaque film such as carbon can be used to repair defects, and the resistance of the opaque film is not a problem. In addition, since it is carried out on the absorber membrane, there is no damage such as thermal effects to the extremely thin membrane.

[Brief explanation of the drawing]

FIG. 1 shows the first method of manufacturing an X-ray exposure mask of the present invention.
Embodiment FIG. 2 shows a second embodiment of the present invention, FIG. 3 shows a conventional method for manufacturing an X-ray exposure mask, and FIG. 4 shows a bump correction method using FIB technology. 1... X-ray mask support substrate, 2... Mask substrate (membrane), 3... Mask absorber film, 3'*aa mask absorber button, 4... Etching mask protective film (etching mask) , 4'...Etching mask bang, 4"...Etching mask after bang correction, 5-...
Resist baton, 10... Membrane region (window part), 11... Narrowly focused ion beam, 12.
...Residual defects Scattering objects of constituent materials, 13...Residual defects,
14... Loss defect, 15... Gas molecules as raw material for opaque film, 16... Deposited opaque film, 17...
・Nozzle for supplying gas molecules as raw material for opaque film, 3
0...Intermediate film for slam correction, 30'--Intermediate film for slam correction, 30''...Intermediate film for correction of slam after correction. Fig. 2 Fig. 3

Claims (2)

[Claims] (1) A first step of depositing a metal film mainly composed of a high-density material on an X-ray mask substrate, and a second step of depositing a first intermediate film made of an inorganic material on the metal film. , a third step of depositing a thin film made of a metal, a metal compound, an inorganic compound, or an organic polymer as a second intermediate film on the first intermediate film; metal,
A fourth step of forming a resist pattern on a thin film made of a metal compound, an inorganic compound, or an organic polymer; and a metal, a metal compound, or an inorganic compound as the second intermediate film using the resist pattern as an etching mask. , a fifth step of etching a thin film made of any one of organic polymers, and an etching mask for etching the etching pattern of the thin film made of any one of metal, metal compound, inorganic compound, and organic polymer as the second intermediate film. a sixth step of etching the intermediate film made of the first inorganic material using the first inorganic material as an etching mask; and etching the metal film mainly composed of the high-density material using the etching pattern of the first intermediate film as an etching mask. A method for manufacturing an X-ray exposure mask, comprising a seventh step. (2) Residual defects or missing defects in the thin film pattern formed in the fifth step made of metal, metal compound, inorganic compound, or organic polymer as a second intermediate film that reflects the shape of the resist pattern, etc. 2. The method of manufacturing an X-ray exposure mask according to claim 1, further comprising the step of modifying the X-ray exposure mask.