JPH05267128A - Manufacture of x-ray mask - Google Patents

Abstract

PURPOSE:To obtain a method, in which the transfer of an extra-micro defect such as a pinhole, a pin dot, etc., can be prevented when a copy mask is manu factured from the master mask of an X-ray mask. CONSTITUTION:A master mask 16 prepared through an electron lithographic method is brought near and arranged onto a laminated substrate 10, in which a membrane 12, an X-ray absorber 13 and a resist 14 are laminated onto a substrate, X-rays 15 are inclined only by theta from a normal 25 and applied, and an X-ray absorber pattern 19 on the master mask 16 is transferred onto the resist 14. Since X-rays 15 are transmitted obliquely through the X-ray absorber pattern 19 at that time, effective transmission-film thickness of the X-ray absorber varies thus preventing transfer of micro defect onto the resist. The circuit pattern of the X-ray absorber is formed onto the membrane 12 through development and etching, the resist 14 is removed, and a window is shaped to the substrate 11 through an etchback.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing process of semiconductor devices, superconducting elements, surface acoustic wave elements, quantum effect elements and the like, and more particularly to a method of manufacturing an X-ray mask used in X-ray lithography.

[0002]

2. Description of the Related Art Semiconductor integrated circuits (hereinafter referred to as LSI)
The progress of miniaturization and high integration is remarkable, and the line width of the circuit pattern is finally moving to the ultrafine region of 0.2 μm. However, the conventional reduction projection exposure using light has a limit in resolution due to the diffraction phenomenon of light and cannot be applied to mass production of so-called ULSI having a line width of 0.2 μm. Therefore, X-ray lithography using soft X-rays having a wavelength of about 1 nm is used to create such an ultrafine pattern. This X-ray lithography technique is also used for manufacturing a macro machine, a Josephson device, a quantum effect device, or the like.

Mass production by this method requires an X-ray mask, which is an original plate of a circuit pattern. This requires sufficient performance and accuracy, and it is also necessary to be able to produce efficiently. .. For this reason, first, an X-ray mask as a master (hereinafter simply referred to as a master mask) is created by electron beam drawing or the like, and then a plurality of copy masks are created based on the master mask. ..

A conventional method for manufacturing an X-ray mask will be described below. The X-ray mask is an absorber that shields X-rays, X
The minimal components are the line-permeable membranes and the supports that support them. This master mask is generally prepared by laminating a membrane and an absorber material on a substrate, forming a desired absorber pattern using an electron beam drawing method and an etching technique, and hollowing out a part of the substrate. A method of manufacturing such an X-ray mask is disclosed in, for example, Japanese Patent Laid-Open No. 3-2980.
-110563, JP-A-3-110820, and JP-A-4-10616.

Next, a method of manufacturing a copy mask based on the master mask will be described with reference to FIG.

(A) Membrane 12, X-ray absorber 13, and resist 14 are sequentially laminated on a substrate 11 made of silicon single crystal (Si) and having a thickness of about 1 mm, and laminated plate 1
Form 0. Here, as the membrane 12, boron nitride (BN) or silicon nitride (Si) having good X-ray transparency is used.
N) or silicon carbide (SiC) is used,
It is formed to a thickness of about 2 μm. In addition, the X-ray absorber 13
For this, tantalum (Ta), gold (Au), tungsten (W), or the like is used, and is formed to a thickness of about 0.6 to 0.8 μm. As the resist 14, P
An organic resist such as MMA (polymethylmethacrylate) is used.

(B) The master mask 16 is fixed in parallel above the laminated plate prepared in (A) with a gap g (= about 10 μm) in parallel, and the X-ray 15 is perpendicular to the master mask 16 from above. The X-ray absorber pattern 19 on the membrane 18 supported by the support frame 17 is transferred to the resist 14 of the laminated plate.

(C) Next, the laminated plate having the pattern transferred in (B) is developed and etched, and X is used as a copy mask.
The line absorber pattern 21 is formed.

(D) Finally, back etching is performed to form a window 22 in the substrate 11. For this etching, an etching solution obtained by heating an alkaline aqueous solution such as potassium hydroxide is used.

[0010]

However, in the above-mentioned method, since the X-ray irradiation is performed perpendicularly to the master mask, the master mask has extremely small pins (for example, about 0.05 μm) of a line width size or less. If there is a defect such as a hole or pin dot, the resolution of the X-ray is too good, and these are also directly transferred to the copy mask. Therefore, when a semiconductor device is manufactured using the copy mask thus created, these defects are also transferred onto the wafer, resulting in device failure.

Therefore, conventionally, it is necessary to find and repair such an ultrafine defect. Such mask defect inspection includes, for example, Applied Physics No. 58.
Vol. 12, No. 12 (1989), P79 to P88, and as a modification of the mask, J. Vac.
Sci. Technol. B8 (6), 1557-15
64 (1990).

However, it is technically difficult to inspect and repair such ultrafine defects, and it is extremely inefficient in terms of time and cost.

The present invention has been made to solve the above problems, and an X-ray mask capable of eliminating very small defects such as pinholes and pin dots when a copy mask is manufactured from a master mask. The purpose is to obtain a manufacturing method.

[0014]

According to a first aspect of the present invention, there is provided a method of manufacturing an X-ray mask, which comprises forming a laminated substrate by laminating at least a membrane, an X-ray absorber and a resist on a wafer, A step of arranging a master X-ray mask created by a predetermined method in close proximity on this laminated substrate and transferring the circuit pattern of this master X-ray mask onto a resist by X-ray irradiation, and after transferring the pattern to the resist of the laminated substrate. A method for manufacturing an X-ray mask, comprising: a step of developing and etching to form a circuit pattern of an X-ray absorber on a membrane; and a step of back-etching a laminated substrate to form a window on a wafer. Upon irradiation, the incident optical axis of X-rays is tilted with respect to the normal line of the master X-ray mask.

A method for manufacturing an X-ray mask according to a second aspect of the present invention is the method for manufacturing an X-ray mask according to the first aspect, in which the master X-ray mask and the laminated substrate are integrated during X-ray irradiation. The master X-ray mask is rotated about the normal line thereof.

[0016]

In the method of manufacturing an X-ray mask according to the first aspect of the present invention, since the X-rays obliquely pass through the X-ray absorber forming the circuit pattern of the master X-ray mask, this X-ray absorber is effective. The transmission film thickness changes, and minute defects are not transferred onto the resist.

In the method of manufacturing an X-ray mask according to the second aspect of the present invention, the equivalent rotation of the X-ray incident direction causes the shadow of the minute defect on the master X-ray mask to move on the resist without overlapping. Therefore, the X-ray intensity on the resist is dispersed, and the minute defects are not transferred.

[0018]

The present invention will be described in detail based on the following examples.

First Embodiment FIG. 1 shows a method of manufacturing an X-ray mask according to a first embodiment of the present invention. In this figure, the conventional example (see FIG.
The same parts as those in (B) are designated by the same reference numerals, and description thereof will be omitted as appropriate.

In the present embodiment, the X-ray irradiation is not performed perpendicularly to the master mask, but is performed at a predetermined angle. That is, the same laminated plate 1 as that described in the conventional example (FIG. 8A).
After forming 0, a gap g is formed above the laminated plate 10.
The master mask 16 is fixed in parallel in parallel with the X-ray absorber pattern 19 on the laminated plate 1 by irradiating the X-ray 15 with the incident angle θ with respect to the normal 25 of the master mask 16 from above.
0 is transferred onto the resist 14. Thereby, as will be described later, the regular pattern of the X-ray absorber (minimum 0.2 μm
While a fine defect (about 0.05 μm) such as a pinhole or a pin dot is not transferred, an extremely high quality copy mask can be obtained. Note that, in this example, the steps other than the transfer step are the same as those in the conventional example, and thus the description thereof is omitted.

FIG. 2 shows how the regular circuit pattern on the master mask is transferred onto the resist. In FIG. 2A, the minimum value of the line width of the circuit pattern including the X-ray absorber pattern 19 and the minimum design value of the distance between the line widths are both x, and the thickness of the X-ray absorber pattern 19 is d. To do. In addition, the maximum value of the X-ray intensity to be irradiated is I
The resist 14 is exposed only to X-ray irradiation with a maximum value of max and a constant threshold value Ith smaller than this value.

As is clear from the figure, the X-ray 15 is the normal 2
Since it makes an angle θ with 5, the distance of transmission through the X-ray absorber pattern 19 is not constant, and the transmitted X-ray intensity I changes according to this transmission distance d ′. Therefore, the above threshold I
Assuming that the transmission distance corresponding to th is dth, I <Ith in a region where d ′> dth, and the resist 14 is not exposed to light.
In the region where d ′ <dth, I> Ith and the resist 1
4 is exposed.

That is, X on the resist 14 in this case
The line intensity distribution is as shown in FIG. 7B, and the resist pattern formed by this is as shown in FIG. As shown in these figures, both the minimum line width of the transferred circuit pattern and the distance between the minimum line widths are almost x, and the pattern of the master mask 16 is faithfully transferred. It should be noted that, in FIG. 7C, a negative type resist in which a portion exposed to X-rays remains as the resist 14 and an unexposed portion is removed in the developing step is shown, but a positive type resist can also be used.

Although FIG. 2 shows a state where the incident angle θ is maximum, as is clear from FIG. 4A, θ must satisfy the following expression (1). ..

Θ <arctan (x / d) (1) When the angle is larger than this angle, the resist pattern corresponding to the minimum line width and the minimum distance between line widths becomes x or less, and faithful transfer cannot be performed.

FIG. 3 shows a state of transfer onto the resist when minute defects are present in the X-ray absorber pattern of the master mask. In FIG. 7A, the sizes of the pinhole 27 and the pin dot 28 are both y, and the transmission distance in the X-ray absorber when the X-ray crosses the pinhole 27 diagonally is d1 and X-ray. Is a pin dot 28
Let d2 be the transmission distance in the X-ray absorber when it crosses diagonally.

In this case, d1>
In the area corresponding to the pinhole 27, I <
It becomes Ith and the resist 14 is not exposed. On the other hand, d2 <
Since it is dth, in the area corresponding to the pin dot 28, I>
It becomes Ith and the resist 14 is exposed.

That is, X on the resist 14 in this case.
The line intensity distribution is as shown in FIG. 7B, and the resist pattern formed by this is as shown in FIG. As shown in these drawings, the pinholes 27 and the pin dots 28 on the master mask 16 are not transferred to the resist 14, and only the regular circuit pattern is faithfully transferred.

Here, the minimum value of the incident angle θ is shown in FIG.
As is clear from the above, it must satisfy the following expression (2).

Θ> arcsin (2y / d) (2) However, in this case, dth = d / 2. At this time,
As is clear from FIG. 7C, d ′ = d / cos θ−d / 2> d−d / 2 = d / 2, and thus d ′> d / 2, and the condition for not transferring the pinhole 27. Meets

When the angle θ does not satisfy the expression (2), the pinhole 27 and the pin dot 28 are transferred onto the resist.

From the expressions (1) and (2), the incident angle θ of the X-ray is restricted by the following expression (3).

Arcsin (2y / d) <θ <arctan (x / d) (3) For example, d = 0.75 μm, x = 0.2 μm, y = 0.
Assuming that the thickness is 05 μm, the incident angle θ needs to satisfy the following expression (4) from the expression (3).

7.7 ° <θ <14.9 ° (4) In this embodiment, the predetermined gap g is provided between the master mask and the resist, but it is necessary to make them closely adhere to each other. You can

In this embodiment, defects such as pinholes and pin dots have been described. However, when there is a linear defect, the incident angle direction is set to be orthogonal to the longitudinal direction of the defect. As a result, the same effect as above can be obtained.

Furthermore, the longitudinal directions of the linear defects do not match,
For example, when they are orthogonal to each other, X-ray irradiation may be performed by sequentially changing the direction of the incident angle so as to be orthogonal to the longitudinal direction of each defect. However, in this case, it is necessary to take measures such as reducing the X-ray irradiation time or the X-ray intensity.

Second Embodiment Next, a second embodiment of the present invention will be described. In this embodiment, the master mask 16 and the laminated plate 10 shown in FIG.
While rotating around the normal line 25 as an axis, X-ray irradiation is performed on the normal line 25 at an incident angle θ. Hereinafter, this method will be described with reference to FIG. As shown in (A) of this figure, the X-rays irradiated from above the master mask 16 pass through the regular X-ray absorber pattern 19 and the pin dots 28, and the X-ray intensity distribution on the resist is shown in FIG. As shown in B).

As shown in this figure, in the regular X-ray absorber pattern 19, the incident direction of the X-rays is equivalently rotationally changed, so that a shadow region is superimposed, and the X-ray intensity is equal to or lower than the threshold value Ith. Will be secured. On the other hand, pin dot 2
With respect to No. 8, the X-ray intensity does not become equal to or lower than the threshold value Ith because no overlapping shadow region is generated.

Therefore, the transfer pattern on the resist is
It becomes like (C) and (D) of the same figure. In (D), the thick line 29 indicates the boundary of the area where the transfer is actually performed, and the broken lines 31 and 32 indicate the boundary where the transfer has not been reached. As indicated by a thick line 29, when the pattern has a rectangular shape, the edge of the transfer pattern lacks the radius r, but the incident angle is adjusted to be within the allowable range (r <x / 4). Is possible.

When the pattern and the defect are circular, the incident angle θ needs to satisfy the following expression (5) by calculation.

Arctan (0.5y / g) <θ <arctan (0.45x / g) (5) When the incident angle θ is larger than the above range, FIG. 6 (A),
As shown in (B), if the diameter of the circular pattern or the line width of the linear pattern is 90% or less of the design dimension x, and if the incident angle θ is smaller than the above range, pinholes or pin dots Will be transcribed.

Further, when the pattern and the defect are rectangular, the incident angle θ needs to satisfy the following expression (6) by calculation.

Arctan (0.55y / g) <θ <arctan (0.25x / g) (6) When the incident angle θ is larger than the above range, FIG.
As shown in (B), while the edges of the rectangular pattern or the straight line pattern are chipped such that r> x / 4, when the incident angle θ is smaller than the above range, a pinhole or a pin dot is transferred. Will be done.

For example, g = 10 μm, x = 0.2 μm,
When y = 0.05 μm, the incident angle θ needs to satisfy the following expression (7) from the expression (6).

0.16 ° <θ <0.29 ° (4)

[0046]

As described above, according to the first aspect of the invention, since the X-ray irradiation is performed with an inclination with respect to the normal line of the master X-ray mask, the X-ray on the master X-ray mask is
The effective transmission film thickness of the line absorber changes, and minute defects are not transferred onto the resist. Therefore, there is an effect that a high-quality X-ray mask can be manufactured very easily without the trouble of inspecting and correcting minute defects.

According to the second aspect of the present invention, when the X-ray irradiation is performed, the incident optical axis is inclined with respect to the normal line of the master X-ray mask, and the master X-ray mask and the laminated substrate are integrated to form the master X-ray. Since the normal line of the line mask is rotated as an axis, the incident direction of X-rays changes sequentially. As a result, the shadow caused by the minute defects on the master X-ray mask moves on the resist without overlapping, so that the X-ray intensity on the resist is dispersed and the minute defects are not transferred. Therefore, similarly to the above, there is an effect that a high quality X-ray mask can be manufactured very easily.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a method of manufacturing an X-ray mask according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing how a regular circuit pattern on a master mask is transferred onto a resist by the method in the first embodiment.

FIG. 3 is an explanatory diagram showing a state of transfer onto a resist when a minute defect exists in an X-ray absorber pattern on a master mask in the method according to the first embodiment.

FIG. 4 is an explanatory diagram for obtaining a maximum value and a minimum value of an X-ray incident angle in the method according to the first example.

FIG. 5 is an explanatory diagram showing a method of manufacturing an X-ray mask according to a second embodiment of the present invention.

FIG. 6 is an explanatory diagram showing an example of a resist pattern transferred by the method in the second embodiment.

FIG. 7 is an explanatory diagram showing another example of a resist pattern transferred by the method in the second embodiment.

FIG. 8 is an explanatory diagram showing a conventional method for manufacturing an X-ray mask.

[Explanation of symbols]

 11 substrate 12 membrane 13 X-ray absorber 14 resist 15 X-ray 16 master mask 19 X-ray absorber pattern 27 pinhole 28 pin dot

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiko Tanaka 3-31-1 Yushima, Bunkyo-ku, Tokyo Within Soltec Co., Ltd. (72) Inventor Mitsuaki Morikami 3-31-1 Yushima, Bunkyo-ku, Tokyo Stock company in Soltec

Claims (2)

[Claims] 1. A step of laminating at least a membrane, an X-ray absorber, and a resist on a wafer to form a laminated substrate, and an X-ray mask as a master prepared by a predetermined method is brought close to the laminated substrate. The step of arranging and transferring the circuit pattern of the X-ray mask onto the resist by X-ray irradiation, and developing and etching the laminated substrate after transferring the pattern to the resist of the laminated substrate to absorb X-rays on the membrane. A method of manufacturing an X-ray mask, comprising: a step of forming a circuit pattern of a body; and a step of back-etching the laminated substrate to form a window on the wafer. An X-ray mask manufacturing method, wherein an axis is inclined with respect to a normal line of the X-ray mask as the master. 2. The X as the master during X-ray irradiation.
2. The method for producing an X-ray mask according to claim 1, wherein the line mask and the laminated substrate are integrally rotated with the normal line of the X-ray mask as the master as an axis.