JP3405500B2 - X-ray exposure method - Google Patents

Description

BACKGROUND OF THE INVENTION [0001] [Technical Field of the Invention The present invention relates to an X-ray exposure method Ru used in a semiconductor device fabrication. 2. Description of the Related Art In recent years, there has been a remarkable increase in the degree of integration of semiconductor integrated circuits, but this is supported by the progress of exposure technology for transferring circuit patterns onto wafers. Conventionally,
Optical lithography using ultraviolet light as a light source has been used for the exposure. However, as the pattern to be transferred has become smaller, the problem of resolution degradation due to the influence of light diffraction has become more serious. On the other hand, an X-ray exposure technique using soft X-rays as a light source has an advantage that a high resolution, which is difficult with exposure using ultraviolet light, can be obtained because of its short wavelength. For this reason, X-ray exposure technology is expected as an exposure technology for the next generation, and research and development are being actively conducted. An X-ray exposure technique that has been mainly developed so far is to dispose an X-ray mask and a wafer close to each other with a gap of about several tens of μm and irradiate the X-ray mask with X-rays to pattern the wafer. This is a proximity exposure technology for exposing to light. In principle, this is an equal-size exposure in which the X-ray mask pattern is directly transferred onto the wafer. One of the important issues for putting this exposure technique into practical use is the development of a defect-free mask and a defect-free pattern transfer technique. In order to realize the defect-free mask, a mask defect inspection device using an electron beam and a mask defect correction device using an ion beam have been developed. By using these, at present, pattern defects of the X-ray mask are almost completely removed, and it is possible to provide a defect-free X-ray mask. [0004] However, even if the defect of the X-ray mask is eliminated, when the pattern is actually formed by exposure, it is caused by a defect existing in the X-ray irradiation system (beam line). Defects appear on the transferred pattern. In particular, if the X-ray extraction window has a defect such as a foreign substance attached or scratched, the defect is transferred onto the wafer and becomes a pattern defect, which has been a problem. Usually, the X-ray extraction window also serves as a partition for changing the X-ray optical path atmosphere from a vacuum to an atmosphere or a replacement gas atmosphere such as helium gas, and suppresses the attenuation of the X-rays due to air or gas. Therefore, they are often arranged near the X-ray mask. For this reason, the penumbra of the projected image of the defect of the X-ray extraction window on the wafer becomes relatively small, and a considerably small defect is transferred to the wafer. The penumbra becomes more blurred when it gets bigger,
It will not be transferred. For example, if the distance between the X-ray extraction window and the X-ray mask is 2 mm and the width of the X-ray emission angle is 1 mrad, the penumbra of a defect on the X-ray extraction window is 2 μm. Therefore, if a defect of 2 μm or more is present at a position corresponding to the X-ray transmitting region of the X-ray mask of the X-ray extraction window, the X-ray is attenuated and becomes a defect of the transfer pattern, resulting in disconnection or short circuit of the integrated circuit. Cause. Further, even a defect smaller than 2 μm causes unevenness of X-ray intensity and causes a problem such as a change in dimension of a transfer pattern. In order to avoid this problem, a method of swinging the X-ray extraction window during exposure has been proposed. In this method, the influence of the defect is made lower than the threshold value in the development of the X-ray resist by averaging, in other words, blurring the attenuation region of the X-ray due to the defect in the X-ray extraction window. Therefore, in this method, the effect is greater when the X-ray extraction window is sufficiently far from the X-ray mask, that is, the penumbra is large and the X-ray attenuation due to the defect is small. However, when the X-ray extraction window is close to the X-ray mask, the defect size is large to some extent, and the X-ray attenuation due to the defect is large, the defect of the X-ray extraction window can be reduced even by using the above-described method. Influence on the transfer pattern cannot be eliminated. SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has been made to prevent the defect from affecting the transfer pattern even if the defect exists in the X-ray extraction window. Aim. [0009] [Means for Solving the Problems] X-ray exposure light how the invention, the projected image onto the X-ray mask of the defects present on the X-ray extraction window is on the pattern of the X-ray mask To be located
Exposure is performed after the relative positions of the X-ray extraction window and the X-ray mask are arranged. For this reason, the projected image of the defect existing on the X-ray extraction window does not arrive before the X-ray mask. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a configuration of an X-ray exposure apparatus according to an embodiment of the present invention. In the figure, first, 1 is an absorber layer for absorbing X-rays formed of a tantalum film having a thickness of 0.65 μm, 2 is an X-ray permeable membrane serving as a base for forming the absorber layer 1, and 3 is A silicon substrate 4 for holding the membrane 2 is a holding mount for the same, and these constitute an X-ray mask 5. In the absorber layer 1, punch patterns 6a, 6b, 6c and remaining patterns 7a, 7b are formed. The X-ray mask 5 is mounted on an X-ray mask stage 8 of an X-ray exposure apparatus. On the back side of the X-ray mask 5, 1 mm
An X-ray extraction window 11 made of a window material 10 made of silicon nitride having a thickness of 1 μm supported by a thick silicon member 9 and an X-ray beam line 14 are arranged via a movable body 13 made of an elastic plate. . The movable body 13 is moved by a motor 15 to move the X-ray extraction window 11 in the plane direction of the X-ray mask 5. The motor 15 is controlled and driven by a control mechanism 16 using a stepping motor. Further, a wafer 17 is arranged so as to face the surface of the X-ray mask 5. A negative resist SAL is provided on the surface of the wafer 17.
601 (manufactured by Shipley Fur East Co., Ltd.) is applied and formed. Also, the wafer 17
Are mounted on the wafer stage 19 of the X-ray exposure apparatus. Although not shown, a soft X-ray 20 having a center wavelength of 0.8 nm generated from a synchrotron electron storage ring (X-ray generation source) is led to the X-ray beam line 14. The X-ray mask 5 is irradiated through the X-ray extraction window 11 with a line 20. Then, this X-ray mask 5
Is passed through the extraction patterns 6a, 6b, 6c formed in the absorber layer 1 and reaches the resist 18 on the wafer 17. As a result, the pattern formed by the absorber 1 on the X-ray mask 5 is projected on the resist 18. With the above configuration, first, the distance L between the X-ray extraction window 11 and the X-ray mask 5 is set to 2 mm, the gap between the X-ray mask 5 and the wafer 17 is controlled to 30 μm.
Exposure was performed at an X-ray irradiation dose at which a 2 μm pattern was formed.
As a result of this exposure, the transfer patterns 21, 22, and 23 are formed on the resist 18 so that those portions remain after being developed. Here, as shown in FIG. When the window defect 12 due to the attachment of foreign matter is present, the defect 22 in which the pattern is missing in the remaining transfer pattern 22
a occurs. First, the position of the window defect 12 is measured as described below. First, as described above, the X-ray mask 5 and the wafer 17 are exposed in a predetermined positional relationship in the plane direction to form a pattern. Next, X
The position of the line mask 5 and the position of the wafer are moved by the same amount in the plane direction, and exposure is performed on another different wafer to form a pattern in the same manner as described above. Then, the coordinates of the defect 22a on these two wafers on which the pattern is formed are measured. The measurement of the defect position was carried out using a defect inspection apparatus SEM-Spec (manufactured by KLA Instruments Corporation) using an electron beam. Defects appearing at different positions by the defect inspection on the two wafers are the defects 22a. That is, since the pattern or defect transferred on the X-ray mask 5 moves together with the X-ray mask 5, the pattern is formed as described above.
It will be at the same position on one wafer. However, the X-ray extraction window 11 has not moved in the exposure of the two wafers, that is, the relative position between the X-ray mask 5 and the wafer 17 has been changed. For this reason, the defect 22a to which the window defect 12 of the X-ray extraction window 11 has been transferred appears at different positions on the two wafers. When the position of the window defect 12 of the X-ray extraction window 11 is measured as described above, this is the point of the present invention. It should be located on the patterns 7a and 7b. In this embodiment, the above-described operation is performed by driving the motor 14 under the control of the control mechanism 16 to move the X-ray extraction window 11 and changing the relative position with respect to the X-ray mask 5 in the plane direction. . FIG. 2 is substantially the same as FIG. 1 except that the position of the window defect 12 is left due to a change in the relative position between the X-ray extraction window 11 and the X-ray mask 5.
The state in which it is located above is shown. As shown in FIG. 2, if the projected image of the window defect 12 on the X-ray mask 5 is located on the remaining pattern 7 b on the X-ray mask 5 having a larger area, the window defect 12 The image is no longer projected onto the wafer 17, and a defect-free transfer pattern 22 can be formed. In particular, when the pattern to be transferred has a small exposure area like a contact hole and the area of the remaining pattern on the X-ray mask is large, the defect on the X-ray extraction window is expressed by Formula 1
Even if there were 0, all of them could be located behind the remaining pattern. During the exposure, X
X also applies to dust defects newly attached to the line extraction window.
It was possible to deal without replacing the wire extraction window and transfer a defect-free pattern. In the above description, the X-ray extraction window 11 is moved. However, the present invention is not limited to this, and the X-ray mask 5 may be moved.
Needless to say, both may be moved. As described above, according to the present invention , X
After arranging the relative positions of the X-ray extraction window and the X-ray mask so that the projected image of the defect existing on the X-ray mask on the X-ray mask is located on the pattern of the X-ray mask. Exposure was performed. Therefore, according to the present invention,
Since the projected image of the defect existing on the X-ray extraction window does not reach ahead of the X-ray mask, even if a defect exists in the X-ray extraction window, the defect does not affect the transfer pattern. . The X-ray transmission area of a normal X-ray mask is at most about 50% of its effective area. On the other hand, almost 100% of the effective area of the X-ray extraction window is the X-ray transmission area. For this reason, conditions on the X-ray extraction window are much more severe than those on the X-ray mask. Further, the defect of the X-ray mask is a defect specific to the mask, while the defect of the X-ray mask is
Defects in the line extraction window will affect all exposures. Therefore, defects in the X-ray extraction window greatly affect the yield of the entire lithography process. As described above, since the defect of the X-ray extraction window does not affect the transfer pattern, the production yield of the integrated circuit is greatly improved. Naturally, the manufacturing yield of the X-ray extraction window itself is greatly improved because the requirements for defects are relaxed. And the economic ripple effect of them is very large.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing a configuration of an X-ray exposure apparatus according to an embodiment of the present invention. FIG. 2 is a configuration diagram showing a configuration of the X-ray exposure apparatus according to the embodiment of the present invention, showing a state in which the relative position between the X-ray extraction window 11 and the X-ray mask 5 has been changed from FIG. [Description of Signs] 1 ... absorber layer, 2 ... membrane, 3 ... silicon substrate, 4
... holding mount, 5 ... X-ray mask, 6a, 6b, 6c ...
Extraction pattern, 7a, 7b: Remaining pattern, 8: X-ray mask stage, 9: Silicon member, 10: Window material, 11: X-ray extraction window, 12: Window defect, 13: Movable body, 14: Beam line, 15 ... Motor, 16 ... Control mechanism, 17 ... Wafer, 18 ... Resist, 19 ... Wafer stage, 20 ... Soft X-ray, 21, 22, 23 ... Remaining transfer pattern, 22a ... Defect.

Continuation of the front page (72) Inventor Misao Sekimoto 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Takashi Okubo 1-3-1 Gotenyama, Musashino City, Tokyo (56) References JP-A-3-212927 (JP, A) JP-A-58-116731 (JP, A) JP-A-61-65434 (JP, A) Hei 4-100049 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 7/20 503 G21K 5/02

Claims (1)

(57) [Claim 1] A beam line evacuated to a high vacuum through which X-rays emitted from an X-ray source pass, and the X-rays are sent from the beam line to the atmosphere or a replacement gas. An X-ray extraction window to be taken out into the atmosphere; and a pattern arranged opposite to the X-ray extraction window, irradiated with X-rays emitted from the extraction window, and absorbing the X-rays, formed on the X-ray permeable film. An X-ray mask , wherein the X-ray mask for a defect existing on the X-ray extraction window is provided.
The projected image is positioned on the pattern of the X-ray mask.
So that the relative position between the X-ray extraction window and the X-ray mask
X is characterized in that exposure is performed after the
Line exposure method .