JPH02224320A - X-ray mask and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an X-ray mask used for transferring fine patterns by X-ray lithography.

(Prior Art) Conventionally, an X-ray mask as shown in FIG. 1 has been used to transfer a pattern by X-ray lithography. That is, an X-ray transparent thin film 2 was provided using the St substrate 1 as a frame, and an X-ray absorber pattern 3 was formed on the X-ray transparent thin film 2. The X-ray absorber pattern 3 was mainly manufactured using two methods.

One is to create a mask pattern for dry etching the X-ray absorber using a lithography method such as electron beam lithography, and use this dry etching mask pattern as a mask to process the X-ray absorber to absorb X-rays. This is a method of manufacturing body pattern 3. That is, for example, as disclosed in the June 1985 issue of Electronic Materials (P, 59-63), Ta is used as an X-ray absorber, a SiO□ film is formed on Ta, and the SiO□ film is A resist is applied on top, a pattern is drawn by electron beam lithography, Sin is dry-etched using the formed resist pattern as a mask, and Ta is dry-etched using the 5iOz pattern as a mask to form an X-ray absorber pattern. I was making 3.

The other method is to form a positive/negative reversal pattern of the required pattern on the X-ray transparent thin film 2 using an X-ray transparent material, and then apply the X-ray absorbing metal to the pattern using a selective plating method or the like. This is a method of filling the unformed parts. In this case, a pattern made in advance is made of a material such as a resist that can be easily removed by immersion in a solvent or oxygen plasma ashing, and the X-ray absorbing metal is filled between the patterns. , when removed, an X-ray absorber pattern 3 is formed and has the form shown in FIG.

(Problem to be Solved by the Invention) However, in any case, in the conventional X-ray mask, the X-ray absorber pattern 3 is produced based on phosphorography means such as electron beam lithography. Therefore, it was extremely difficult to make an extremely small X-ray absorber pattern 3 of 0.1- or less. To ensure the ability to block X-rays,
The X-ray absorber pattern 3 needs to be thicker than a predetermined thickness regardless of the size of the pattern. For this reason, whether the X-ray absorber is processed by dry etching or the thin gap between the positive and negative reversal patterns is filled with the X-ray absorber by plating or sputtering, the X-ray absorber pattern 3 of 0.1lIa+ or less It was extremely difficult to form the cross section with good shape and precision. Furthermore, even when it comes to forming patterns on the original resist, etc., it is extremely difficult to form patterns of 0.1- or less size based on lithographic means such as electron beam lithography. It was extremely difficult to form a pattern with such a high height and vertical side walls. Among them, in the case of electron beam lithography, there is a proximity effect, so there are
, 1- or less was extremely difficult to create.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide an easy-to-manufacture X-ray mask having an extremely fine X-ray absorber pattern, which has not been possible in the past, and a method for manufacturing the same.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention does not adopt the concept of forming an xvA absorber pattern on an X-ray transparent film, but instead creates a pattern of a cross-section of a film adhered to a substrate. It is characterized by using the thin lines drawn as a mask pattern.

(Function) In this way, by using the cross section of the deposited film to obtain a thin line pattern whose line width is the deposited film, an X-ray mask with extremely fine line patterns can be obtained, and the line width can be reduced. Enables precise control.

Furthermore, by alternately depositing films with high X-ray transmittance and films with low X-ray transmittance, it is possible to form very close line-and-space mask battens.

Furthermore, by stacking and bonding two masks orthogonally to each other, it is possible to realize an X-ray mask with very fine hole tabs or lattice tabs, or an X-ray mask with thin line tabs with a defined length.

(Example) FIG. 2 shows the X-ray mask of the present invention and its manufacturing method. First, a Ta (tantalum) film 5 as an X-ray absorber is sputter-deposited on a flat St (silicon) substrate 4 to a desired film thickness for the line width of the pattern [Fig.
)]. The Ta film 5 of the Si substrate 4 on which the Ta film 5 is attached
Another Si substrate 6 is bonded to the deposited layer using an adhesive 7 such as epoxy resin (FIG. 2 O)). The X-ray absorber Ta film 5 is sandwiched between the Si substrates 4 and 6 via the adhesive 7, and the whole is cut into thin pieces perpendicular to the surface of the Ta film 5 [FIG. 2(c)]. Both sides of the cut are polished to make them thinner and finished to the desired thickness. As shown in Figure 2 (d), the front surface can be thinned to the same thickness (although it may be thinned to the same thickness as shown in Figure 2 (e), one side is flat and the other side is concave and part of it is thinned to the specified thickness). Although not shown, both surfaces may be polished into concave surfaces.

Once the sample is thinned to a certain extent, by attaching a reinforcing frame 8 made of stainless steel or the like around one side and polishing the other side, the sample can be easily thinned to a thickness of 1 μm or less without breaking. Also, even if a similar reinforcing frame 8 is attached after polishing,
This is effective in preventing damage during subsequent handling [Figure 2(f)].

(season).

As a result, as shown in FIGS. 2(d), (e), and ((to)), a layer of adhesive 7 is formed on one side with a thin line equal to the thickness of the sputter-deposited Ta film 5 in the center. An X-ray mask of the present invention having a structure of Si substrates on both sides can be obtained.The X-ray transmittance of a substance depends on the atomic weight of the constituent elements,
The layer through which X-rays pass through most is the layer of adhesive 7 made of elements such as C, H, 0, etc., the next layer is the St substrate section 4.6, and the thin wire section of Ta film 5 is the X-ray absorbing layer through which X-rays are most difficult to pass through. Becomes a department. When the intensity of incident X-rays is 1°, the X-ray intensity I when transmitted through a thick material is I=1. It is expressed as e-'. μ is called the absorption coefficient, and is determined by the type of material and the wavelength of incident X-rays.

In the case of the above configuration, if the X-ray transmission intensity of the Ta thin line part is 10 and the transmission X-ray intensity of the Si part is Is=, then I
If sz/It- is approximately 3 or more so that a pattern can be created by X-ray lithography, it can be used as a mask.

The wavelength range of electron beam excitation type X-ray sources, plasma X-ray sources, X-rays from synchrotron radiation, etc. developed for X-ray lithography is about 3 Å to 30 nm. From the absorption coefficients of Ta and Si for several wavelengths in this range, and using the mask thickness t as a parameter, the mask contrast I si / I T- and Si4,6 part X-ray transmittance are calculated as shown in Figure 3. It becomes like this.

As shown in Figure 3, if the mask thickness is appropriately selected according to the wavelength, the transmittance of the Si4 and Si6 parts is quite high, and a large mask contrast I SiZ i Tm can be obtained, resulting in a very good X-ray mask. I understand that.

The width of the Ta thin wire 5 can be controlled in advance by controlling the thickness of the film deposited on the St substrate, so it can be controlled very accurately. With conventional filling methods such as dry etching, plating, and sputtering, it is extremely difficult to control the line width to about ±0.05 m, but with the mask of the present invention, the line width can be controlled to about ±0.005 m. It is relatively easy to create a codon roll with an accuracy of about .001-.

Further, since the width of the Ta thin wire 5 serving as the X-ray absorber and the mask thickness t are theoretically unrelated, sufficient mask contrast can be obtained regardless of the thinness of the Ta thin wire 5.

Unless a certain level of X-ray transmittance is ensured in the Si4.6 portion that becomes the X-ray transmitting portion, an enormous amount of exposure time will be required when using an X-ray mask, but the thicker the mask, the higher the mask contrast will be.

The higher the mask contrast is, the more advantageous it is to transfer a thin pattern, so the X-ray mask of the present invention has a very large effect compared to conventional X-ray masks where the thickness of the absorber is limited due to manufacturing considerations. bring.

Furthermore, in the X-ray mask of the present invention, the lines are smooth, there are no burrs or joints that occur when drawing with an electron beam, and both side walls of the absorber batten are vertical and parallel.

Although FIG. 2 shows an X-ray mask in which the X-ray absorber has only one ray bar, it is possible to make X-ray masks in various other forms.

FIG. 4 shows another embodiment of the present invention, in which a W (tungsten) film 10 as an X-ray absorber and a Be (beryllium) film 11 as an X-ray transmitter are alternately deposited on a Si substrate 12. This was then bonded to another Si substrate 13 using an adhesive 14, and produced in the same manner as in the case of FIG. 2. This is an X-ray mask having line and space buttons. 15 is a reinforcing frame. The broken line shows the state before the substrate is sliced and polished.

With conventional X-ray masks, it was particularly difficult to manufacture an X-ray mask with closely spaced fine tabs, but according to the present invention, it is easy to make 0. It is possible to obtain an X-ray mask having a line and space pattern up to O05Jrm or less.

In Figures 2 and 4, an isolated line or line-and-space pattern of the X-ray absorber is arranged near the center of the X-ray mask, and the peripheral part is made of Si, so that the X-ray A so-called absorber-remaining batan mask was obtained, in which the line absorber had a line flap.

FIG. 5 shows another embodiment of the invention. In this example,
Ta17 is deposited on the Si flat substrate 16 as an X-ray absorber to a thickness of about 2 or more, and Si0□18 is deposited thereon as an X-ray transmitter to a desired thickness for the baton line width. Furthermore, T a 19 is deposited again to a thickness of about 2 pm or more [FIG. 5(a)]. The entire film is sliced perpendicular to the film surface, both cut surfaces are polished, and the film is thinned to a predetermined thickness (FIG. 5(b)). To facilitate processing, it may be pasted onto another Si substrate and then sliced, as in the case of FIG. In addition, as shown in FIG. 2(e), it may be partially thinned by concave polishing.
Attach the part 9 to the X-ray shielding frame 20 [Fig. 5(c)]
]. The holes in the X-ray shielding frame 20 must be opened accurately within the width of the X-ray shielding parts of Ta17.19 on both sides outside the width of the central Si0□18 button, but the laser hole opening of the stainless steel plate It is possible to easily open the hole by machining or the like.

The X-ray shielding frame 20 can also serve as reinforcement for the thinned portion.

The X-ray mask shown in FIG. 5(c) is a so-called punch-out mask in which only the thin 5iOz18 line portion easily transmits X-rays, and the other portions do not transmit X-rays.

A similar X-ray mask can be obtained by preparing in advance a metal flat substrate that will serve as an X-ray absorber instead of a Si substrate, depositing an X-ray transmitter thereon, and then depositing an X-ray absorber metal thereon.

It goes without saying that even in the embodiments shown in FIGS. 2 and 4, an X-ray shielding frame for limiting the exposure area as shown in FIG. 5(c) may be provided.

Typical examples of the X-ray mask of the present invention are shown in FIG. 2, FIG. 4, and FIG. 5.
The gap between the X-ray absorbers and the deposited X-ray absorber can be adjusted by controlling the thickness of the X-ray transmitter.

Furthermore, various types of X-ray absorbers, X-ray transmitters, and substrates can be used. As the X-ray absorber, Ta, W
, Au (gold), pt (platinum), M.

Various heavy metals such as (molybdenum) and alloys containing these as main components can be used. In addition, with the present invention, masks can be made thicker using materials such as Fe (iron), Cu (copper), Co (balt), and Ni (nickel), which are difficult to use as absorbers in conventional X-ray masks due to their high transmittance. Can be used as an absorbent material.

X-ray transmitting materials include those having an X-ray transmittance comparable to or lower than that of Si, such as SiO□, Si, and Cy.
, St, Ny, 5ill Oy Nz + A
I' (aluminum).

AI! 0:I, BezO*, C (carbon), Be, etc. are used. In addition to Si, glass, ceramics such as 5iO1, AlzOi, Bet's, various metal plates, etc. can be used as the substrate on which the film is attached.

The film attachment of the X-ray absorber and X-ray transmitter is done by Metsuki.

Any method may be used, such as sputtering, CVD, spin code, etc.

Moreover, the type of adhesive for bonding the substrates together is not limited.

Furthermore, in an X-ray mask, if the thickness of the absorber button portion is constant, the thinner the transmitting button portion, the higher the contrast. Therefore, it is better to make the transparent button part as thin as the mechanical strength of the mask allows.

Figure 6 shows an X-ray mask of the present invention that takes this point into consideration.
As shown in the figure, press the X-ray absorber button 21 from one side of the mask.
The X-ray transmitting body portion 22 is selectively dry-etched and thinned, leaving . Dry etching may be performed from both sides. After reinforcing it with a frame like the one shown at 20 in FIG. 4, it may be completely removed. In this way, the X-ray transmittance of the X-ray absorber button 21 portion does not change, but the X-ray transmittance of the X-ray transmitter portion 22 increases, improving the contrast as an X-ray mask.
The amount of exposure required for transfer can also be reduced.

In addition, in FIG. 6, 23 is a substrate.

Also, when making the X-ray masks shown in Figures 2, 4, and 5,
Although we have shown that it is bonded to another Si substrate with an adhesive to facilitate slicing and polishing, it is not just a simple substrate, but a second Si substrate.
It should be noted that for the X-ray masks shown in Figures 4 and 5, it may be bonded to a Si substrate on which an X-ray absorber or an X-ray transmitter is deposited, or an X-ray absorber metal substrate, etc. Nor.

Furthermore, when two X-ray masks of the present invention are used by laminating them together, various effects other than those described above are produced.

7th. FIG. 8 shows an embodiment of the X-ray mask of the present invention in which two masks are laminated together. Second. 4th. The mask of the present invention shown in FIGS. 5 and 6 has a line pattern lined up in one direction or an isolated line pattern in one direction, and its length cannot be defined. On the other hand, FIG. 7 shows Ta24 and SiO
□5i26 with 25 line and space buttons
and another 5i27 are bonded with adhesive 28 to the same X-ray mask as in FIG. 4, and the same as in FIG. X-ray masks are stacked and pasted together at right angles. The length of the line and space button is 5iO-z
The width of the pattern 30 is limited, and a line-and-space pattern whose length is defined as a line segment is obtained.

FIG. 8 shows, as in FIG. 4, Ta32 and S on the Si substrate 31.
i-substrates 31 are deposited alternately, and another substrate 35 is bonded with adhesive 34.
Two X-ray masks having line-and-space patterns with various line widths and space widths are laminated and pasted together at right angles. In addition to thin wires with various shapes, masks with fine hole patterns and lattice patterns can be obtained.

In the above description, the case where the substrate on which the film is applied is flat is shown, but it is clear that the substrate does not need to be flat. For example, if a substrate with an arcuate curvature is used, a mask having an arcuate button can be formed, and if a film is applied to the surface of a cylindrical substrate, a ring-shaped button can be formed.

(Effect of the invention) As described above, according to the present invention, the side walls are vertical.

Parallel, smooth, and capable of high X-ray exposure contrast, with fine line patterns up to about 0.005-width.
Line masks can be easily produced.

In addition, since the thickness of the film determines the width of the thin line that forms the finished mask, controlling the film thickness makes it possible to accurately obtain a thin line with the desired line width. Furthermore, by alternately depositing films with low X-ray transmittance and films with high X-ray transmittance, a mask having closely spaced thin line patterns can be easily formed.

In addition, by stacking two masks and pasting them together, you can easily create line patterns with precisely defined lengths, holes and leftovers with precisely defined vertical and horizontal dimensions, and even lattice pattern masks. can do.

Therefore, by using the present X-ray mask, it is possible to easily and efficiently produce fine patterns of 0, 1- or less, which have been difficult to produce conventionally, by transfer. In addition to being useful as an evaluation X-ray mask for examining the limits of fine batten formation and the limits of resist resolution, it can also be applied to the production of high-performance diffraction gratings, Fresnel zone plates, etc.

[Brief explanation of the drawing]

1 and 2 are configuration diagrams of a conventional X-ray mask, FIG. 3 is a characteristic diagram showing a calculation example of the mask contrast X-ray transmittance of the X-ray mask of the present invention, and FIGS. 4 and 5. 6, 7, and 8 are cross-sectional views showing embodiments of the X-ray mask of the present invention. 1... Si substrate, 2... X-ray transparent thin film, 3...
X-ray absorber button, 4...Si flat substrate, 5...T
a (tantalum) film, 6... Si substrate, 7... adhesive, 8... reinforcing frame, 10... W (tungsten), 1
1...Be (beryllium), 12...Si substrate, 1
3... Si substrate, 14... Adhesive, 15... Reinforcement frame, 16... Si flat substrate, 1'7" T a ,
18... SiOx, 19... Ta, 20... X-ray shielding frame, 21... X-ray absorber button, 22... X-ray transmitting body portion, 23... Si substrate, 24...・・T a
, 25=SiO, ,26-S i , 27=S
i. 28...Adhesive, 29...Ta, 30...Sin
, batan, 31...Si substrate, 32- Ta,
33...SiO, 34...Adhesive, 35...S
i board. Patent applicant: Agent of Nippon Telegraph and Telephone Corporation

Claims (5)

[Claims] (1) A material with high or low X-ray transmittance is disposed on the substrate in one layer or in multiple layers alternately, and the cross section of the film layer appears as a thin line or line and space. The whole or part of both sides or one side is polished, and the X-ray transmittance ratio between the cross-sectional parts of any two of the base, the material with low X-ray transmittance, and the material with high X-ray transmittance. An X-ray mask characterized in that the ratio is 1:3 or more for any wavelength between 3 Å and 30 Å. (2) The X-ray mask according to claim 1, further comprising a frame for reinforcing the X-ray mask. (3) A material portion with high X-ray transmittance is selectively dry-etched from at least one surface of the X-ray mask, and the material portion with high X-ray transmittance is selected from the material portion with low X-ray transmittance of the X-ray mask. The X-ray mask according to claim 1, characterized in that the portion is formed thin. (4) A patent claim characterized in that a portion of a material with high X-ray transmittance that has been previously coated with a film to make a mask from at least one side of the X-ray mask is completely removed by selective dry etching. X-ray mask according to scope 1. (5) A step of forming a film made of a material with high X-ray transmittance or a film made of a material with low X-ray transmittance in one layer or in multiple layers alternately; (c) polishing both or one side of the sliced thin piece in which the cross section of the membrane appears A method for manufacturing an X-ray mask.