JP2007201306A - Reflective reticle and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflective reticle for an EUV exposing device excellent in a line width controlability and capable of decreasing its manufacturing cost. <P>SOLUTION: The reflective reticle 2 with a first absorber 8 formed in pattern shape on the surface of a multilayer film mirror 6 for reflecting an extreme ultraviolet light comprises a reflectance factor adjustment means 10 for adjusting the reflectance factor of the extreme ultraviolet light at a part of the surface of the reticle. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reflective reticle used in an ultra-short ultraviolet projection exposure apparatus and a method for manufacturing the reflective reticle.

  In recent years, with the progress of miniaturization of semiconductor integrated circuits, in order to improve the resolving power of an optical system limited by the light diffraction limit, a wavelength shorter than this (for example, about 11 to 14 nm) is used instead of conventional ultraviolet rays. An extreme ultraviolet projection exposure apparatus using extreme ultraviolet rays has been developed (see Patent Document 1).

Japanese Patent Laid-Open No. 2003-14893

  The above-mentioned ultra-short ultraviolet projection exposure apparatus (hereinafter referred to as EUV exposure apparatus) includes an illumination optical system that irradiates a reticle on which a desired circuit pattern is formed with ultra-short ultraviolet (EUV light), a reticle stage that holds the reticle, A projection optical system that reduces and transfers an image of a circuit pattern onto a wafer and a wafer stage that holds the wafer are provided. Here, for example, a ring field optical system composed of six aspherical mirrors is used as the projection optical system. In the ring field optical system, since a chip of about 30 mm square cannot be exposed at once, the reticle and wafer are scanned synchronously. The reticle used in the EUV exposure apparatus is a reflection type and has a configuration as shown in FIG. That is, a multilayer film 102 for reflecting EUV light is formed on the surface of a substrate 100 such as glass, and the circuit pattern is formed by providing the absorber 104 in a pattern on the surface of the multilayer film 102. For the absorber 104, a combination of material and thickness is selected so that the reflectance of EUV light is substantially close to zero. For example, when EUV light having a wavelength of 13.5 nm is used, a metal such as Ta having a thickness of about 200 nm is used for the absorber.

  One important performance of the EUV exposure apparatus is the line width controllability of the exposed circuit pattern. This is because if the line width deviates from a desired value, the electrical characteristics of the manufactured device deteriorate. Although the line width changes due to various factors, it is particularly strongly influenced by the imaging performance of the projection optical system. For example, flare is often recognized in the projection optical system of an EUV exposure apparatus. There is a problem that the line width of the pattern formed by the flare changes. FIG. 8 shows the light intensity distribution of the transfer image of the resist pattern. When flare is present, the light intensity of the transferred image on the wafer increases overall. As a result, the resist line width increases. The flare is caused by the shape waviness of the mirror constituting the projection optical system, but the flare amount on the wafer further depends on the pattern distribution of the reticle. For example, in the case of a reticle having almost no reflection pattern, flare hardly occurs. On the other hand, when a reticle having a large area ratio of the reflection pattern is used, a lot of flare is generated. In general, there are many places where a reflection pattern rate is large and a place where the reflection pattern ratio is small in the plane of the reticle. Therefore, there are areas with a lot of flare and areas with a small flare in the exposure field plane. As a result, the amount of change in the line width of the pattern varies in the exposure field plane.

  As a method for correcting such a line width change, a means for correcting the pattern line width of the reticle can be considered. For example, a line width correction amount is calculated in advance from the flare characteristic of the exposure apparatus and the pattern distribution of the reticle, and the circuit design drawing is corrected when the reticle is manufactured. However, this method has a problem that the calculation amount is enormous and it is difficult to realize high-precision calculation. Further, instead of obtaining the correction amount by calculation, a method is also conceivable in which a reticle is created and exposed in advance, and the correction amount is obtained from the measured line width of the resist pattern. However, in this case, it is necessary to make a new reticle, which is problematic in terms of manufacturing cost, and it is difficult to correct the reticle pattern line width by an additional process.

  An object of the present invention is to provide a reflective reticle for an EUV exposure apparatus that has excellent line width controllability and can reduce manufacturing costs, and a method for manufacturing the reflective reticle.

  The reflective reticle of the present invention is a reflective reticle (2) in which a first absorber (8) is formed in a pattern on the surface of a multilayer mirror (6) that reflects extreme ultraviolet light. The part is provided with a reflectance adjusting means (10) for adjusting the reflectance of the extreme ultraviolet light.

  The reflective reticle manufacturing method of the present invention includes a step (S10) of forming a reflective reticle in which a multilayer film and a first absorber pattern are formed on a substrate, and an EUV exposure apparatus using the reflective reticle. The step of forming a resist pattern on the wafer (S11), the step of measuring the line width of the resist pattern (S12), and the step of calculating the difference between the measured line width and the designed circuit line width (S13) And a step (S14) of calculating a film thickness of the second absorber formed to correct the calculated difference, and a step (S15) of forming the second absorber with the calculated film thickness. It is characterized by that.

  The reflective reticle manufacturing method of the present invention includes a step (S20) of forming a reflective reticle in which a multilayer film and an absorber pattern are formed on a substrate, and a wafer in an EUV exposure apparatus using the reflective reticle. Forming a resist pattern thereon (S21), measuring a line width of the resist pattern (S22), calculating a difference between the measured line width and the designed circuit line width (S23); Calculating a film thickness for etching a part of the absorber to correct the calculated difference (S24), and etching a part of the absorber with the calculated film thickness (S25). It is characterized by including.

  According to the reflective reticle of the present invention, line width control can be reliably performed even in the case where there are a lot of flare and a little flare in the exposure field plane. Also, the manufacturing cost can be reduced.

  Further, according to the reflective reticle manufacturing method of the present invention, the line width control can be reliably performed even when there are a lot of flares and a few flares in the exposure field plane, thereby reducing the manufacturing cost. A reflection type reticle can be manufactured.

  Hereinafter, the reflective reticle 2 used in the EUV exposure apparatus according to the first embodiment will be described with reference to the drawings. The reflective reticle 2 includes a multilayer mirror 6 formed on a substrate 4 and a first absorber 8 formed in a pattern on the surface of the multilayer mirror 6, and further includes a reflective surface on the surface. A part of the second absorber 10 is provided as a reflectance attenuation layer that functions as a reflectance adjusting means for adjusting the reflectance of extreme ultraviolet light.

  The formation position and film thickness distribution of the second absorber 10 are determined based on the flare characteristics of the EUV exposure apparatus and the pattern arrangement of the reticle. That is, the second absorber 10 is formed in a portion where the area ratio of the reflecting portion is large when the area of the reflecting portion on the surface of the reticle is compared with the area of the non-reflecting portion, and the thickness is increased according to the ratio. Is determined. As a result, the line width of the resist pattern formed on the wafer can be set to a desired value.

Note that the second absorber is formed of a substance having a smaller absorption rate than the first absorber. For example, when using exposure light having a wavelength of around 13 nm, Ta, Ta compounds are used as the first absorber 8, and Si, B, C and these compounds (for example, B ₄ ) are used as the second absorber 10. C, SiC) or the like is used.

  Next, the principle of line width correction of the reflective reticle according to this embodiment will be described with reference to FIG. When the line width changes as shown in FIG. 8 due to the flare characteristics of the EUV exposure apparatus, the light intensity distribution is corrected as shown in FIG. 2 by the reflective reticle according to the present embodiment.

  By providing the second absorber in the reflection part on the reflection type reticle, the reflectance of that part is lowered. Since the non-reflecting part where the absorber exists originally does not reflect the EUV light, even if the second absorber is formed, the non-reflecting state is unchanged. As a result, the light intensity distribution is corrected, and the line width of the resist can be corrected. The resist line width is determined by the thickness of the second absorber. As the film thickness increases, the reflectivity of the reflecting portion decreases. Therefore, the line width of the resist can be controlled to a desired value by setting an appropriate film thickness.

  The line width change due to the flare is determined depending on the flare characteristics of the exposure apparatus itself (the amount of flare and its distribution in the field) and the pattern distribution of the reticle. Therefore, it is preferable that the film thickness of the second absorber has an appropriate in-plane distribution so that the line width due to flare is corrected to a desired value. Qualitatively, the second absorber may be provided in a region where the flare amount is large, and the film thickness may be set larger as the flare amount is larger.

  Next, a manufacturing method of the reflective reticle according to the first embodiment will be described. First, a reflective reticle in which the pattern of the multilayer film 6 and the absorber 8 is formed on the substrate 4 is created (step S10). Next, a resist pattern is formed on the wafer by the EUV exposure apparatus using the reflective reticle (step S11). Next, the line width of the resist pattern is measured, and the difference between this measured value and the designed circuit line width is calculated (step S12). Next, the thickness of the second absorber 10 that corrects this difference is calculated (step S14). Next, the second absorber 10 is formed on the reflective reticle based on the calculation result (step S15).

  According to the manufacturing method of the reflective reticle, the line width can be reliably controlled even in the case where there are a lot of flares and a region with little flares in the exposure field plane, and the reflection type reduces the manufacturing cost. A reticle can be manufactured.

  The second absorber 10 is formed so as to give an arbitrary film thickness distribution at an arbitrary position on the reflection surface of the reflective reticle based on the difference calculated in step S12. Techniques such as vapor deposition, sputtering, and CVD can be applied as the means for forming the second absorber. Further, when the second absorber 10 is formed, a film thickness distribution is formed by, for example, arranging a mask having an opening between the material source and the reticle and moving the mask during the film formation. be able to. The second absorber is preferably made of a material having a low absorption rate for EUV light. If the absorptance is small, the controllability of the film thickness can be made relatively loose and the manufacture can be performed easily.

  Next, a reflective reticle used in an EUV exposure apparatus according to the second embodiment will be described with reference to the drawings. The reflective reticle 20 includes a multilayer mirror 24 formed on a substrate 22, and a first absorber 26 formed in a pattern on the surface of the multilayer mirror 24, and further includes a reflective surface on the surface. A part 26a in which the thickness of the first absorber 26 as a reflectance adjusting means for adjusting the reflectance of extreme ultraviolet light is partially reduced is provided.

  The portion 26a in which the thickness of the first absorber 26 is reduced has its formation position and film thickness distribution determined based on the flare characteristics of the EUV exposure apparatus and the pattern arrangement of the reticle. That is, the portion 26a in which the thickness of the first absorber 26 is reduced is formed in a portion where the area ratio of the non-reflecting portion is large when the area of the reflecting portion on the surface of the reticle is compared with the area of the non-reflecting portion. The thickness of the first absorber 26 is determined according to the size of the ratio. As a result, the line width of the resist pattern formed on the wafer can be set to a desired value.

  Next, the principle of line width correction of the reflective reticle according to this embodiment will be described with reference to FIG. When the line width changes as shown in FIG. 8 due to the flare of the EUV exposure apparatus, the light intensity distribution is corrected as shown in FIG. 5 by the reflective reticle according to the present embodiment. That is, by reducing the thickness of the first absorber on the reflective reticle, the reflectance of that portion increases. The reflectance of the reflecting portion where the first absorber is not present is unchanged. As a result, the light intensity distribution is corrected, and the line width of the resist can be corrected. The line width is determined by the thickness of the absorber. Since the reflectance of the non-reflective portion increases as the film thickness decreases, the line width of the resist can be controlled to a desired value by setting an appropriate film thickness. The reflective reticle according to the present embodiment improves the uniformity of the line width by correcting the line width of the region with a small flare amount so as to match the line width of the region with a large flare amount.

  The line width change due to the flare is determined depending on the flare amount determined by the performance of the exposure apparatus itself, its distribution in the field, and the pattern distribution of the reticle. Therefore, the film thickness of the first absorber preferably has an appropriate in-plane distribution so that the line width due to flare is corrected to a desired value. Qualitatively, the first absorber in the region where the flare amount is small may be thinned, and the film thickness may be reduced as the flare amount is smaller.

  Next, a method for manufacturing a reflective reticle according to the second embodiment will be described. First, a reflective reticle in which a pattern of the multilayer film 24 and the absorber 26 is formed on the substrate 22 is created (step S20). Next, a resist pattern is formed on the wafer by the EUV exposure apparatus using the reflective reticle (step S21). Next, the line width of the resist pattern is measured (step S22), and the difference between the measured value and the designed circuit line width is calculated (step S23). Next, the thickness of the first absorber 26 that corrects this difference is calculated (step S24). Next, the first absorber 26 of the reflective reticle is etched based on the calculation result (step S25).

  In addition, according to the manufacturing method of the reflection type reticle, the line width control can be reliably performed even in the case where there are a lot of flares and a little flares in the exposure field plane, thereby reducing the manufacturing cost. A reflective reticle can be manufactured.

  Note that techniques such as ion etching and laser ablation can be applied as processing means for the absorber. At the time of ion etching, a film thickness distribution can be formed by irradiating a part of the reticle surface with ions in a beam shape and moving the irradiation position.

1 is a cross-sectional view of a reflective reticle according to a first embodiment. It is a figure for demonstrating the principle of the line | wire width correction | amendment by the reflection type reticle concerning 1st Embodiment. It is a figure for demonstrating the manufacturing method of the reflection type reticle concerning 1st Embodiment. It is sectional drawing of the reflection type reticle concerning 2nd Embodiment. It is a figure for demonstrating the principle of the line | wire width correction | amendment by the reflection type reticle concerning 2nd Embodiment. It is a figure for demonstrating the manufacturing method of the reflection type reticle concerning 2nd Embodiment. It is sectional drawing of a multilayer film reflective mirror. It is a figure which shows the light intensity distribution of the transfer image of a resist pattern in the case where flare exists and when it does not exist.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2,20 ... Reflective type reticle, 4,22 ... Substrate, 6,24 ... Multilayer film, 8, 26 ... First absorber, 10 ... Second absorber.

Claims (11)

In a reflective reticle in which a first absorber is formed in a pattern on the surface of a multilayer mirror that reflects extreme ultraviolet light,
A reflective reticle comprising a reflectance adjusting means for adjusting the reflectance of the extreme ultraviolet light on a part of the surface of the reticle.   2. The reflective reticle according to claim 1, wherein the reflectivity adjusting means is a reflectivity attenuating layer disposed on a reflective surface of the reticle.   The reflective reticle according to claim 2, wherein the reflectance attenuation layer is a second absorber.   2. The reflective reticle according to claim 1, wherein the second absorber is formed in a portion where the area ratio of the reflective portion on the surface of the reticle is large.   5. The reflective reticle according to claim 1, wherein the second absorber is made of a material having a smaller absorption rate than the first absorber. 6.   2. The reflective reticle according to claim 1, wherein the reflectivity adjusting means is configured such that a film thickness of a part of the first absorber formed on the surface of the reticle is thinner than that of other parts. .   The reflective reticle according to claim 6, wherein the part of the first absorber is the part of the first absorber having a small area ratio of the reflection part. Forming a reflective reticle having a multilayer film and a first absorber pattern formed on a substrate;
Forming a resist pattern on a wafer with an EUV exposure apparatus using the reflective reticle;
Measuring the line width of the resist pattern;
Calculating a difference between the measured line width and the design circuit line width;
Calculating the film thickness of the second absorber to be formed to correct the calculated difference;
Forming the second absorber having the calculated thickness, and a method of manufacturing a reflective reticle.   9. The method of manufacturing a reflective reticle according to claim 8, wherein the second absorber is formed in a portion where the area ratio of the reflective portion is large. Forming a reflective reticle having a multilayer film and a first absorber pattern formed on a substrate;
Forming a resist pattern on a wafer with an EUV exposure apparatus using the reflective reticle;
Measuring the line width of the resist pattern;
Calculating a difference between the measured line width and the design circuit line width;
Calculating a film thickness for etching a part of the first absorber to correct the calculated difference;
And a step of etching the part of the first absorber with the calculated film thickness.   11. The method of manufacturing a reflective reticle according to claim 10, wherein the part of the first absorbers is the part of the first absorber having a small area ratio of the reflection part.

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