WO2012060024A1

WO2012060024A1 - Illumination shape optimization method, mask shape optimization method, and pattern formation method

Info

Publication number: WO2012060024A1
Application number: PCT/JP2011/002216
Authority: WO
Inventors: 清水但美; 三坂章夫; 笹子勝
Original assignee: パナソニック株式会社
Priority date: 2010-11-01
Filing date: 2011-04-14
Publication date: 2012-05-10
Also published as: JP2012099596A

Abstract

When exposure is performed using a photomask having at least a light-transmitting part that transmits exposure light, a partial-light-blocking part having a lower transmissivity for the exposure light than the light-transmitting part, and a phase-shift part that transmits the exposure light with a different phase than the light-transmitting part, the optical intensity distribution for the exposure light that has passed through the photomask is obtained for each of multiple divided points formed by dividing the pupil plane (100) of the projection optical system, and the illumination shape of the exposure light is set on the basis of the optical intensity distribution.

Description

Illumination shape optimization method, mask shape optimization method, and pattern formation method

The present invention relates to an illumination shape optimization method, a mask shape optimization method, and a pattern formation method.

In recent years, miniaturization of circuit patterns has become more and more necessary for high integration of large scale integrated circuit devices (hereinafter referred to as LSIs) realized using semiconductors. As a result, it has become very important to reduce the line pattern that composes the circuit, or to refine the contact hole pattern that connects multiple layers of wiring via an insulating layer. However, it is necessary to form a fine pattern. In order to solve this problem, a technique for optimizing the illumination shape of the exposure apparatus and the mask shape of the photomask to enlarge the process window has been proposed.

However, there is a problem that it takes a lot of calculation time because it is necessary to use many variables in the optimization of the conventional illumination shape and mask shape.

A method for obtaining an optimal illumination shape and mask shape for solving such problems is proposed in Patent Document 1.

Hereinafter, the method for optimizing the illumination shape and the mask shape disclosed in Patent Document 1 will be described with reference to FIG.

First, as shown in FIG. 20A, an image is formed by providing illumination from a single illumination source to a plurality of illumination points 1400 and a predetermined mask pattern, and by providing illumination to the predetermined mask pattern. Select the fragmentation point in the image plane. Here, Fig.20 (a) shows an Abbe image.

Next, determine the illumination intensity and image log slope at each fragmentation point, and at the same time change the illumination source brightness and shape and the mask diffraction order magnitude and phase to minimize the image log at the fragmentation point. An image is formed on the image plane so that the luminance at the fragmentation point falls within a predetermined range while maximizing the inclination.

20B and 20C show part of an image generated by illuminating the DRAM pattern on the mask shown in FIG. In FIGS. 20 (b) and (c), the bright areas represent image brightness that increases the normalized image log slope, and the illumination intensity is such that these normalized image log slopes are maximized for each pattern. The illumination shape and mask shape can be optimized by changing the brightness and shape and the magnitude and phase of the diffraction order of the mask.

JP 2004-312027 A

However, the most ideal photomask to be optimized in the method disclosed in Patent Document 1 is a CPL (Chromeless Phase Lithography) mask. In other words, the method disclosed in Patent Document 1 is applied to a photomask having a plurality of phase differences and a plurality of transmittances (for example, an enhancer mask (a photomask having a translucent part, a semi-shielding part, and a phase shift part)). Are not compatible, and it is impossible to optimize the illumination shape and mask shape for such a photomask.

In view of the above, an object of the present invention is to enable optimization of an illumination shape and a photomask shape, respectively, even when a photomask having a plurality of phase differences and a plurality of transmittances is used.

In order to achieve the above object, an illumination shape optimization method according to the present invention includes a translucent part that transmits exposure light, a semi-light-shielding part that has a lower transmittance of the exposure light than the translucent part, A method for optimizing the illumination shape of the exposure light in exposure using a photomask having at least a phase shift portion that transmits the exposure light in a phase different from that of the light transmitting portion, the pupil plane of the projection optical system being A light intensity distribution of the exposure light transmitted through the photomask is obtained at each of a plurality of divided points, and the illumination shape is set based on the light intensity distribution.

In order to achieve the above object, the mask shape optimization method according to the present invention includes a translucent part that transmits exposure light, and a semi-light-shielding part that has a lower transmittance of the exposure light than the translucent part. And a method for optimizing the mask shape of a photomask having at least a phase shift unit that transmits the exposure light at a phase different from that of the light transmitting unit, and a plurality of pupil planes of the projection optical system are divided. At each of the dividing points, the light intensity distribution of the exposure light transmitted through the photomask is obtained, and each of the light transmitting part, the semi-light-shielding part, and the phase shift part is provided so that the contrast of the light intensity distribution is improved. Set the shape.

According to the present invention, even when a photomask having a plurality of phase differences and a plurality of transmittances is used, the illumination shape and the mask shape can be optimized.

In addition, according to the present invention, even when a photomask having a plurality of phase differences and a plurality of transmittances is used, the illumination shape and the mask shape can be optimized, respectively, so that they are formed by exposure using a projection optical system. The resolution of the obtained pattern can be improved, and the process window for obtaining a desired pattern can be expanded by exposure using the projection optical system, thereby improving the yield.

FIG. 1 is a diagram showing a schematic configuration of an example of an exposure apparatus that is an application target of an illumination shape optimization method, a mask shape optimization method, and a pattern formation method according to an embodiment. FIG. 2 is a diagram illustrating a pupil plane of the projection lens divided in the illumination shape optimization method and the mask shape optimization method according to the embodiment. FIGS. 3A and 3B are diagrams showing the structure of an enhancer mask used in the illumination shape optimization method, mask shape optimization method, and pattern formation method according to one embodiment. ) Is a plan view, and FIG. 3B is a cross-sectional view taken along the line II ′ in FIG. 4 (a) to 4 (f) show exposure light beams transmitted through an enhancer mask at each source position on the pupil plane of the projection lens in the illumination shape optimization method and mask shape optimization method according to an embodiment. It is a figure which shows the result of having calculated | required intensity distribution. FIGS. 5A and 5B are diagrams illustrating illumination shapes optimized by the illumination shape optimization method according to the embodiment. FIGS. 6A and 6B show how the optical contrast of the light intensity distribution at each source position is improved by changing the mask shape in the mask shape optimization method according to one embodiment. FIG. FIG. 7 is a plan view of an enhancer mask having a mask shape optimized by a mask shape optimization method according to an embodiment. FIG. 8A is a diagram illustrating a target pattern to be formed by a photomask that is an application target of the mask shape optimization method according to the embodiment, and FIG. 8B is a diagram according to the embodiment. It is a figure which shows the mask pattern to which the mask shape was optimized by the mask shape optimization method, and the assist pattern was added. FIGS. 9A and 9B are diagrams showing the structure of an enhancer mask including a light-shielding portion used in the illumination shape optimization method, mask shape optimization method, and pattern formation method according to an embodiment. 9A is a plan view, and FIG. 9B is a cross-sectional view taken along line IV-IV ′ in FIG. 9A. FIGS. 10A to 10D are cross-sectional views showing respective steps of the pattern forming method according to the embodiment. FIG. 11A is a plan view of an enhancer mask used in the pattern forming method according to the embodiment, and FIG. 11B is a plan view of a resist pattern formed by the pattern forming method according to the embodiment. It is. FIG. 12A is a plan view showing one layer having a block made up of a logic part and a block made up of an SRAM part (static random access memory) to be formed by the pattern forming method according to the embodiment. 12B is a plan view of the target pattern of the logic part, FIG. 12C is a plan view of the target pattern of the SRAM part, and FIG. 12D is an optimization of the logic part. FIG. 12E is a plan view of the optimized mask shape of the SRAM unit. FIG. 13A is a plan view of a photomask corresponding to one block obtained by dividing the mask shape of the same layer in the pattern forming method according to one embodiment, and FIG. 13B is one embodiment. It is a top view of the photomask corresponding to the other block by which the mask shape of the same layer is divided | segmented in the pattern formation method which concerns on. FIG. 14A is a diagram illustrating a state in which exposure is performed using a photomask corresponding to one block obtained by dividing the mask shape of the same layer in the pattern forming method according to the embodiment. FIG. 14B is a diagram illustrating a state in which exposure is performed using a photomask corresponding to another block obtained by dividing the mask shape of the same layer in the pattern forming method according to the embodiment. FIG. 15 is a flowchart of a pattern forming method according to an embodiment. FIG. 16 is a flowchart illustrating an example of a procedure performed by combining an illumination shape optimization method and a mask shape optimization method according to an embodiment. FIG. 17 is a flowchart illustrating another example of a procedure performed by combining an illumination shape optimization method and a mask shape optimization method according to an embodiment. FIG. 18 is a flowchart illustrating another example of a procedure performed by combining an illumination shape optimization method and a mask shape optimization method according to an embodiment. FIG. 19 is a diagram showing a schematic configuration of an example of an EUV exposure apparatus to which the present invention is applied. FIGS. 20A to 20D are diagrams for explaining a conventional illumination shape and mask shape optimization method.

(Embodiment)
Hereinafter, an illumination shape optimization method, a mask shape optimization method, and a pattern formation method according to an embodiment will be described with reference to the drawings. The illumination shape optimization method and the mask shape optimization method according to the present embodiment are implemented as information processing by software on a computer, for example.

FIG. 1 shows a schematic configuration of an example of an exposure apparatus to which the present embodiment is applied. In the exposure apparatus shown in FIG. 1, the exposure light 17 emitted from the light source 10 sequentially passes through a stop 11 that adjusts the shape of the exposure light 17, an illumination lens 12, a photomask 13, and a projection lens 14, and is mounted on a stage 16. The placed wafer 15 is irradiated. In the exposure apparatus shown in FIG. 1, the illumination optical system 18 is configured by the diaphragm 11 and the illumination lens 12, and the projection optical system 19 is configured by the projection lens 14. However, the illumination optical system 18 and the projection optical system 19 are included. It goes without saying that the configuration (for example, the number of lenses, etc.) is not limited to this.

First, an illumination shape optimization method according to this embodiment will be described.

In the illumination shape optimization method according to this embodiment, first, as shown in FIG. 2, the pupil plane 100 of the projection lens is finely divided in a virtual XY coordinate system. Here, “101” is a source position obtained by subdividing the pupil plane 100, and “102” to “104” are specific source positions.

Next, at each source position 101 shown in FIG. 2, for example, the light intensity distribution of the exposure light transmitted through the photomask 200 shown in FIG. The photomask 200 used in the present embodiment is a photomask having a plurality of transmittances and a plurality of phase differences, specifically, an enhancer mask.

FIGS. 3A and 3B are views showing the structure of an enhancer mask used in the present embodiment, FIG. 3A is a plan view, and FIG. 3B is an I in FIG. 3A. FIG.

As shown in FIGS. 3A and 3B, the enhancer mask 200 includes a semi-light-shielding portion 202 having a light-shielding property for exposure light and a semi-light-shielding portion 202 on a transparent substrate 201 that transmits the exposure light. And an enclosed phase shift unit 203. A portion of the transparent substrate 201 where the semi-light-shielding portion 202 and the phase shift portion 203 are not formed is a translucent portion 204, and the transmittance of the semi-light-shielding portion 202 with respect to exposure light is smaller than that of the translucent portion 204. Moreover, the semi-light-shielding part 202 and the translucent part 204 transmit the exposure light in the same phase. The phase shift unit 203 transmits the exposure light in the opposite phase with the semi-light-shielding unit 202 and the translucent unit 204 as a reference. For example, as illustrated in FIG. 3B, the phase shift unit 203 may be formed by digging up the transparent substrate 201 so that a phase difference of 180 degrees is generated in the exposure light. Instead of digging down, a phase shift film may be formed.

4 (a) to 4 (f) show the results of obtaining the light intensity distribution of the exposure light transmitted through the enhancer mask 200 at each source position in FIG. 2 by simulation using a computer. Specifically, FIG. 4A shows the light intensity distribution of the exposure light transmitted through the II-II line including the point A in the enhancer mask 200 shown in FIG. FIG. 4B shows the light intensity distribution of the exposure light transmitted through the II-II ′ line including the point A in the enhancer mask 200 shown in FIG. 3A. 4 is a result obtained at the source position 103 (coordinate (0, 7)) of FIG. 2, and FIG. 4C is an exposure through which the II-II line including the point A in the enhancer mask 200 shown in FIG. It is the result of calculating | requiring the light intensity distribution of light in the source position 104 (coordinate (7, 0)) of FIG. FIG. 4D shows the light intensity distribution of the exposure light transmitted through the line III-III ′ including the point B in the enhancer mask 200 shown in FIG. 4 (e) shows the light intensity distribution of the exposure light transmitted through the III-III 'line including the point B in the enhancer mask 200 shown in FIG. 3 (a). FIG. 4F shows the result obtained at the source position 103 (coordinates (0, 7)). FIG. 4F shows the exposure light transmitted through the III-III ′ line including the point B in the enhancer mask 200 shown in FIG. The light intensity distribution is obtained at the source position 104 (coordinate (7, 0)) in FIG. 4A to 4F, the higher the peak 300 of the light intensity distribution, or the greater the difference between the peak 301 and the minimum light intensity 302 in the light intensity distribution, the higher the light contrast.

As shown in FIGS. 4A to 4C, the exposure light transmitted through the point A of the enhancer mask 200 has a high contrast at any of the source positions 102 to 104. On the other hand, as shown in FIGS. 4D to 4F, the exposure light transmitted through the point B of the enhancer mask 200 has a high contrast only at the source position 103. Therefore, in order to obtain a high contrast for both the points A and B of the enhancer mask 200, the source position 103 is selected from the source positions 102 to 104. Similarly, when a source position that provides high optical contrast is selected from source positions obtained by subdividing the pupil plane 100 of the projection lens, a photo having a plurality of transmittances and a plurality of phase differences is selected. For the mask, for example, an optimized illumination shape as shown in FIG. 5A can be obtained. In FIG. 5A, “400” is the pupil plane with the optimized illumination shape, “401” is the selected source position, and “402” is the unselected source position. It is. Further, FIG. 5A shows the illumination shape optimized for the first quadrant of the XY coordinate system, and therefore, considering the symmetry, the optimized illumination shape used for actual exposure is As shown in FIG. Such an optimized illumination shape can be realized, for example, by adjusting the diaphragm 11 in the exposure apparatus shown in FIG.

Subsequently, a mask shape optimization method according to the present embodiment will be described.

In the mask shape optimization method according to the present embodiment, for example, as shown in FIGS. 6A and 6B, the light contrast of the light intensity distribution obtained at each source position selected as described above is obtained. The mask shape of the photomask is changed so as to further improve (that is, the optical contrast is further increased). Here, FIG. 6A shows the light intensity distribution of the exposure light transmitted through the II-II ′ line including the point A in the enhancer mask 200 obtained at the source position 103 (coordinates (0, 7)) of FIG. FIG. 6B shows a state in which the optical contrast of the enhancer mask 200 obtained at the source position 103 (coordinates (0, 7) in FIG. 2 is included. 'Indicates how the optical contrast of the light intensity distribution of the exposure light transmitted through the line is improved. In FIGS. 6A and 6B, “500” indicates the light intensity distribution before the mask shape is changed, and “501” indicates the light intensity distribution after the mask shape is changed. Show. As shown in FIGS. 6A and 6B, the optical contrast is clearly improved after the mask shape is changed by the mask shape optimization method according to the present embodiment.

7 changes the mask shape of the enhancer mask 200 shown in FIG. 3A so that the optical contrast of the selected source position is improved by using the mask shape optimization method according to the present embodiment. The planar structure of the enhancer mask 600 obtained by this is shown. Here, “601” is a transparent substrate, “602” is a semi-light-shielding portion obtained by deforming the semi-light-shielding portion 202, and “603” is a phase shift portion obtained by modifying the phase-shifting portion 203. “604” is a translucent part formed by deforming the translucent part 204. In this way, by changing the shape of each part of the photomask (in this embodiment, the semi-light-shielding part, the phase shift part, and the light-transmitting part) so as to improve the light contrast of the selected source position, a plurality of parts can be obtained. An optimized mask shape of a photomask having transmittance and a plurality of phase differences can be obtained.

Here, it is most efficient to optimize the mask shape based on the shape of the phase shift portion that most affects the optical contrast, and then sequentially optimize the shape of the semi-light-shielding portion and the shape of the light-transmitting portion. However, it is also possible to optimize the shape of the portion other than the phase shift portion first.

Further, in the optimization of the mask shape, as described above, not only the shape of each part of the photomask is changed, but also from the phase shift unit 611 and the semi-light-shielding unit 612 as shown in FIG. 8B, for example. An assist pattern 613 that is not transferred by exposure may be added around the mask pattern. FIG. 8A shows a desired pattern (target pattern) to be formed by the mask pattern shown in FIG.

In the illumination shape optimization method and mask shape optimization method according to the present embodiment described above, the inter-line end space portion (for example, point A of the enhancer mask 200) and the line width center portion (for example, the enhancer). Although the light intensity distribution of the exposure light transmitted through each of the points B) of the mask 200 is obtained, in practice, the illumination shape and the mask shape may be optimized by further increasing the calculation target of the light intensity distribution.

Further, in the illumination shape optimization method and the mask shape optimization method according to the present embodiment, as a photomask having a plurality of transmittances and a plurality of phase differences, a semi-light-shielding portion, a phase shift portion, and a light-transmitting portion An enhancer mask having However, instead of this, in addition to the semi-light-shielding portion, the phase shift portion, and the light-transmitting portion, a photomask provided with a light-shielding portion that does not transmit exposure light on a transparent substrate may be used. 9 (a) and 9 (b) are diagrams showing the structure of such a photomask, FIG. 9 (a) is a plan view, and FIG. 9 (b) is an IV-IV in FIG. 9 (a). It is sectional drawing of a line.

As shown in FIGS. 9A and 9B, a photomask (enhancer mask) 620 includes a semi-light-shielding portion 622 having a light-shielding property with respect to exposure light on a transparent substrate 621 that transmits exposure light, and a half-mask. A phase shift unit 623 surrounded by the light shielding unit 622 and a light shielding unit 625 that does not transmit exposure light are provided. In the transparent substrate 621, a portion where the semi-light-shielding portion 622, the phase shift portion 623, and the light-shielding portion 625 are not formed is a light-transmitting portion 624. small. Moreover, the semi-light-shielding part 622 and the translucent part 624 transmit the exposure light in the same phase. The phase shift unit 623 transmits the exposure light in the opposite phase with the semi-shielding unit 622 and the translucent unit 624 as a reference. For example, as illustrated in FIG. 9B, the phase shift unit 623 may be formed by digging up the transparent substrate 621 so that the exposure light has a phase difference of 180 degrees. For example, as illustrated in FIG. 9B, the film that becomes the light-transmitting portion 624 may be formed on the film that becomes the semi-light-shielding portion 622.

When a photomask having a light-shielding portion is a target, a space portion between line ends (for example, point A of the photomask 620) and a center portion of the line width (for example, point B of the photomask 620) when optimizing the illumination shape and the mask shape. In addition, the light intensity distribution of the exposure light that has passed through the light shielding part line width (eg, point C of the photomask 620) may be obtained. Specifically, when optimizing the illumination shape, a source position that provides a high light contrast may be selected based on the thus obtained light intensity distribution. Further, when optimizing the mask shape, the mask shape may be changed so that the light contrast of the light intensity distribution obtained at each source position selected as described above is further improved. Also in this case, it is preferable to carry out the optimization of the shape of the phase shift portion.

In this embodiment, the illumination shape is optimized and then the mask shape is optimized. Instead, the mask shape is optimized and then the illumination shape is optimized. May be. Alternatively, only one of illumination shape optimization and mask shape optimization may be performed. Moreover, after optimizing the mask shape, known OPC (optical proximity correction) may be performed.

Subsequently, the pattern forming method according to the present embodiment, specifically, the pattern forming method using the illumination shape and the mask shape optimized as described above will be described with reference to the drawings.

10 (a) to 10 (d) are cross-sectional views showing respective steps of the pattern forming method according to the present embodiment.

First, as shown in FIG. 10A, a film to be processed 701 such as a metal film or an insulating film is formed on the substrate 700, and then, as shown in FIG. For example, a positive resist film 702 is formed. Furthermore, in this embodiment, the resist film 702 is coated by forming a top coat 703 on the resist film 702 on the premise of immersion exposure.

Next, as shown in FIG. 10C, for the enhancer mask 600 whose mask shape is optimized by the method of this embodiment, the illumination shape is changed by the method of this embodiment using, for example, an ArF excimer laser as a light source. The optimized exposure light 704 is irradiated.

FIG. 11 (a) shows a planar configuration of the enhancer mask 600 shown in FIG. 10 (c). As shown in FIGS. 10C and 11A, the enhancer mask 600 includes a semi-light-shielding portion 602 having a light-shielding property with respect to the exposure light 704, and a semi-light-shielding portion 602 on the transparent substrate 601 that transmits the exposure light 704. And a phase shift unit 603 surrounded by a light shielding unit 602. A portion where the semi-light-shielding portion 602 and the phase shift portion 603 are not formed in the transparent substrate 601 is a light-transmitting portion 604, and the transmittance of the semi-light-shielding portion 602 with respect to the exposure light 704 is smaller than that of the light-transmitting portion 604. Moreover, the semi-light-shielding part 602 and the translucent part 604 transmit the exposure light 704 in the same phase. The phase shift unit 603 transmits the exposure light 704 in the opposite phase with the semi-shielding unit 602 and the translucent unit 604 as a reference. The phase shift unit 603 may be formed by digging up the transparent substrate 601 so that the exposure light 704 has a phase difference of 180 degrees, or instead of digging up the transparent substrate 601, a phase shift film is formed. May be.

In the exposure shown in FIG. 10C, the resist film 702 is exposed to the exposure light 704 (transmitted light 706) transmitted through the light transmitting portion 604, and a latent image portion 702a is formed. Further, the exposure light 704 (transmitted light 705) transmitted through the semi-shielding portion 602 and the exposure light 704 transmitted through the phase shift portion 603 (transmitted light 707 (having the opposite phase of the transmitted light 705 and 706)) are resists. The film 702 is not exposed.

Next, the top coat 703 and the resist film 702 are developed to remove the latent image portion 702a, thereby forming a resist pattern 708 as shown in FIG.

FIG. 11B shows a planar configuration of the resist pattern 708 after the development shown in FIG. Here, the dimension of the space 800 between the opposing patterns in FIG. 11B is (k × λ / NA) or less (where k is a constant determined by a process technique such as mask resolution and illumination conditions, and λ is exposure light) Where NA is the numerical aperture of the reduction projection optical system of the exposure apparatus). For example, when an ArF excimer laser having a wavelength λ of 193 nm is used as a light source, the actual dimension to be transferred (the dimension of the space 800 between the opposing patterns) is 50 nm or less.

Up to this point, the case where one type of optimized illumination shape is applied to the photomask used for exposure has been described. Subsequently, each of a plurality of blocks obtained by dividing the mask shape of the same layer A case where the illumination shape optimization method according to this embodiment described above is applied to a pattern formation method using a plurality of photomasks corresponding to the above will be described with reference to the drawings. In general, a plurality of pattern layouts exist in an exposure area of a photomask corresponding to one layer. The inventors of the present application pay attention to the fact that there is an illumination shape suitable for each pattern layout, and separately produce a photomask for each pattern layout (block), and set the illumination shape for each of the photomasks. I came up with an optimization. As a result, the resolution of the pattern can be further improved.

Specifically, first, the mask shape of one layer shown in FIG. 12A is divided into, for example, a block 901 composed of a logic unit and a block 902 composed of an SRAM unit. FIGS. 13A and 13B show a planar configuration of two photomasks corresponding to each of the divided

blocks

901 and 902. In a photomask 910 shown in FIG. 13A, a block 901 including a logic portion is arranged on a transparent substrate 911. Further, in the photomask 920 shown in FIG. 13B, a block 902 including an SRAM portion is disposed on the transparent substrate 921. Here, the illumination shape in the exposure using the photomask 910 and the photomask 920 obtained by dividing the mask shape of the same layer is optimized by the method of this embodiment described above.

FIG. 12B shows a planar configuration of a desired pattern (target pattern) of the logic portion to be formed by the photomask 910, and FIG. 12C is to be formed by the photomask 920. The plane structure of the target pattern of the SRAM section is shown.

FIG. 12D shows a planar configuration of the optimized mask shape of the block (logic unit) 901 arranged on the photomask 910 shown in FIG. 13A. FIG. FIG. 13 shows a plan configuration of an optimized mask shape of a block (SRAM unit) 902 arranged on the photomask 920 shown in FIG. In FIGS. 12D and 12E, “903” is a semi-shielding portion, “904” is a phase shift portion, and “905” is a translucent portion.

Next, in the exposure using the photomask 910, the illumination shape is optimized by the method of the present embodiment, whereby the block (logic unit) 901 is transferred onto the wafer 1000 as shown in FIG. Subsequently, in the exposure using the photomask 920, the illumination shape is optimized by the method of the present embodiment, whereby the block (SRAM portion) 902 is transferred onto the wafer 1000 as shown in FIG. Thereby, a pattern of one layer composed of the block (logic unit) 901 and the block (SRAM unit) 902 can be formed.

As described above, in exposure using a plurality of photomasks corresponding to each of a plurality of blocks obtained by dividing the mask shape of the same layer, the illumination shape is optimized for each photomask and each photo By optimizing the mask shape of the mask, a finer pattern can be formed.

In the above description, both the illumination shape and the mask shape are optimized by the method of this embodiment. Instead, only one of the illumination shape and the mask shape is optimized by the method of this embodiment. May be used. In addition, the mask shape of the same layer was divided into two to produce two photomasks. Instead, the mask shape of the same layer was divided into three or more to produce three or more photomasks. May be. In addition, the mask shape of one layer is divided into a block composed of a logic part (that is, a logic circuit) and a block composed of an SRAM part (that is, a memory), but the type of block to be divided is appropriately set according to the layer. It goes without saying that it is done.

FIG. 15 is a flowchart of the above-described pattern forming method using a plurality of photomasks corresponding to each of a plurality of blocks obtained by dividing the mask shape of the same layer.

As shown in FIG. 15, first, in step S11, a photomask A (for example, photomask 910 shown in FIG. 13A) corresponding to one block obtained by dividing the mask shape of the same layer is set in the exposure apparatus. Is done. In parallel with step S11, in step S12, a wafer coated with a resist or the like is set in the exposure apparatus.

Next, in step S13, alignment and leveling between the photomask A and the wafer, focusing, and the like are performed, and then exposure using the photomask A is performed in step S14 (see FIG. 14A).

When the exposure using the photomask A is completed, in step S15, the photomask A is removed from the exposure apparatus, and subsequently, the photomask B corresponding to another block in which the mask shape of the same layer is divided (for example, FIG. A photomask 920) shown in 13 (b) is set in the exposure apparatus.

Next, in step S16, alignment and leveling between the photomask B and the wafer, focusing, and the like are performed, and then exposure using the photomask B is performed in step S17 (see FIG. 14B).

Finally, in step S18, the resist applied to the wafer is developed, thereby completing the pattern formation.

In the illumination shape optimization method, mask shape optimization method, and pattern formation method according to the present embodiment described above, a semi-light-shielding photomask having a plurality of transmittances and a plurality of phase differences is used. However, in addition to the semi-light-shielding portion, the phase-shifting portion, and the light-transmitting portion, a photomask having a light-shielding portion that does not transmit exposure light may be targeted. . It goes without saying that the illumination shape optimization method, mask shape optimization method, and pattern formation method according to this embodiment can be applied to a photomask different from the enhancer mask.

Hereinafter, a procedure performed by combining the illumination shape optimization method and the mask shape optimization method according to the present embodiment will be described with reference to the flowchart of FIG.

First, in step S21, the design (initial value) of the target pattern is determined. Next, in step S22, the light intensity distribution of the exposure light transmitted through the target photomask is obtained at each source position obtained by finely dividing the pupil plane of the projection optical system (for example, a projection lens). Next, in step S23, the illumination shape is optimized by selecting a source position having a relatively high light contrast in the light intensity distribution from each source position.

Next, in step S24, the light intensity distribution of the selected source position is changed by changing the shape of each of the constituent parts (for example, the light shielding part, the semi-light shielding part, the phase shift part, and the light transmitting part) of the photomask. Adjust the light contrast. Thus, in step S25, the mask shape is optimized so that the light contrast of the light intensity distribution at the selected source position is improved.

Next, in step S26, as a lithography performance evaluation, a process window such as a depth of focus or an exposure margin is enlarged or a mask error factor value is minimized, and the process window is enlarged and a mask error factor value is minimized. Evaluate whether or not the process window standard and the mask error factor value standard set in advance are satisfied. If the standard is satisfied (achievement of the standard), the illumination shape and the mask shape are determined to be the shapes optimized in steps S23 and S25 in step S27. That is, the optimization of the illumination shape and the mask shape is completed. On the other hand, when the standard is not satisfied (standard not achieved), the illumination shape and the mask shape are optimized again. In this case, it is not always necessary to optimize both the illumination shape and the mask shape. If the standard can be achieved by the performance evaluation in step S26, the optimization is performed again for only one of the illumination shape and the mask shape. May be. The flowchart of FIG. 17 shows a procedure for only optimizing the illumination shape when the standard cannot be achieved in the performance evaluation of step S26. Further, the flowchart of FIG. 18 shows a procedure for performing only mask shape optimization when the standard cannot be achieved in the performance evaluation in step S26.

16 to 18 show a case where the mask shape optimization method according to this embodiment is executed after the illumination shape optimization method according to this embodiment is executed. Instead, after the mask shape optimizing method according to the present embodiment is performed, the illumination shape optimizing method according to the present embodiment may be performed.

As described above, according to the illumination shape optimization method and the mask shape optimization method according to the present embodiment, even when a photomask having a plurality of phase differences and a plurality of transmittances is used, illumination is performed. Each shape and mask shape can be optimized. For this reason, the resolution of the pattern formed by exposure using the projection optical system can be improved, and the process window for obtaining a desired pattern by the exposure using the projection optical system is expanded, thereby improving the yield. Can be improved.

In the above description, it is assumed that an exposure apparatus having an optical system such as an illumination lens and a projection lens is used. Instead, an exposure apparatus (EUV (extreme ultraviolet) exposure, etc.) having a reflection mirror optical system is used. The present invention can also be applied. Specifically, in this embodiment, “transmittance” is “reflectance”, “translucent part” is “reflective part”, “semi-shielding part” is “semi-reflective part”, and “shielding part” By replacing each with “non-reflective portion”, the illumination shape and mask shape can be optimized even when a photomask having a plurality of phase differences and a plurality of reflectances is used.

FIG. 19 shows a schematic configuration of an example of an EUV exposure apparatus having a reflecting mirror optical system. In the exposure apparatus shown in FIG. 19, the EUV 26 exiting the EUV generation apparatus 20 is sequentially reflected on the reflection mirror 21A, the reflection mirror 21B, the reflection type photomask 22, the reflection mirror 23A, the reflection mirror 23B, the reflection mirror 23C, and the reflection mirror 23D. After that, the wafer 24 placed on the stage 25 is irradiated. In the exposure apparatus shown in FIG. 19, the illumination optical system 27 is configured by the reflection mirrors 21A and 21B, and the projection optical system 28 is configured by the reflection mirrors 23A, 23B, 23C, and 23D. Needless to say, the configuration of the projection optical system 28 (for example, the number of mirrors) is not limited to this.

Even when the exposure apparatus shown in FIG. 19 is used, the light intensity distribution of the EUV 26 that has passed through the reflective photomask 22 is obtained at each of a plurality of division points obtained by dividing the pupil plane of the projection optical system 28. Based on the light intensity distribution, the illumination shape can be optimized. In addition, the shape of each component (for example, a reflection portion, a semi-reflection portion, a non-reflection portion, and a phase shift portion) of the reflective photomask 22 can be optimized so that the contrast of the light intensity distribution is improved.

As described above, the present invention is useful for an illumination shape and mask shape optimization method in exposure performed in a semiconductor manufacturing process or the like.

DESCRIPTION OF SYMBOLS 10 Light source 11 Aperture 12 Illumination lens 13 Photomask 14

Projection lens

15, 24

Wafer

16, 25 Stage 17

Exposure light

18, 27 Illumination

optical system

19, 28 Projection optical system 19
20

EUV generator

21A, 21B, 23A, 23B, 23C, 23D Reflective mirror 22 Reflective photomask 100

Pupil plane

101, 102, 103, 104

Source position

200, 600, 620

Enhancer mask

201, 601, 621, 911, 921

Transparent substrate

202, 602, 612, 622, 903

Semi-shielding part

203, 603, 611, 623, 904

Phase shift part

204, 604, 624, 905

Translucent part

300, 301 Peak 302 Minimum light intensity 400 Optimum illumination shape Selected pupil surface 401 Selected source position 402 Unselected source position 500 Light intensity distribution before changing mask shape 501 Light intensity distribution after changing mask shape 613 Assist pattern 62 Light shielding portion 700 Semiconductor substrate 701 Work film 702 Resist film 702a Latent image portion 703 Top coat 704 Exposure light 705 Light transmitted through semi-light shielding portion 706 Light transmitted through light transmission portion 707 Light transmitted through phase shift portion 708 Resist pattern 800 Space between opposing patterns 901 Block made up of logic portion 902 Block made up of

SRAM portion

910, 920 Photomask 1000 Wafer

Claims

A translucent part that transmits exposure light; a semi-light-shielding part having a lower transmittance of the exposure light than the translucent part; and a phase shift part that transmits the exposure light in a phase different from that of the translucent part. A method of optimizing the illumination shape of the exposure light in exposure using a photomask,
Obtaining a light intensity distribution of the exposure light transmitted through the photomask at each of a plurality of dividing points obtained by dividing the pupil plane of the projection optical system, and setting the illumination shape based on the light intensity distribution Lighting shape optimization method characterized by
The method of optimizing an illumination shape according to claim 1,
The illumination shape optimization method, wherein the illumination shape is set by selecting a division point having a relatively large difference in light intensity in the light intensity distribution among the plurality of division points.
In the optimization method of the illumination shape of Claim 1 or 2,
The method of optimizing an illumination shape, wherein the pupil plane is a pupil plane of a projection lens.
The method for optimizing an illumination shape according to any one of claims 1 to 3,
The method for optimizing an illumination shape, wherein the photomask further includes a light shielding portion that does not substantially transmit the exposure light.
A translucent part that transmits exposure light; a semi-light-shielding part having a lower transmittance of the exposure light than the translucent part; and a phase shift part that transmits the exposure light in a phase different from that of the translucent part. A method for optimizing the mask shape of a photomask,
At each of a plurality of division points obtained by dividing the pupil plane of the projection optical system, a light intensity distribution of the exposure light transmitted through the photomask is obtained, and the light transmission is improved so that the contrast of the light intensity distribution is improved. A mask shape optimization method, wherein the shape of each of the first and second semi-shielding portions and the phase shift portion is set.
The method of optimizing a mask shape according to claim 5,
The transmission point is selected such that a division point having a relatively large difference in light intensity in the light intensity distribution is selected from the plurality of division points, and the contrast of the light intensity distribution at the selected division point is improved. A mask shape optimization method, wherein the shape of each of the first and second semi-shielding portions and the phase shift portion is set.
The method for optimizing a mask shape according to claim 5 or 6,
A method for optimizing a mask shape, comprising optimizing the shape of the semi-light-shielding portion after optimizing the shape of the phase shift portion, and then optimizing the shape of the translucent portion.
The method for optimizing a mask shape according to any one of claims 5 to 7,
The method for optimizing a mask shape, wherein the pupil plane is a pupil plane of a projection lens.
The method for optimizing a mask shape according to any one of claims 5 to 8,
The method of optimizing a mask shape, wherein the photomask further includes a light shielding portion that does not substantially transmit the exposure light.
A translucent part that transmits exposure light; a semi-light-shielding part having a lower transmittance of the exposure light than the translucent part; and a phase shift part that transmits the exposure light in a phase different from that of the translucent part. A pattern forming method using a photomask,
The illumination shape of the exposure light is set based on the light intensity distribution of the exposure light transmitted through the photomask obtained at each of a plurality of division points obtained by dividing the pupil plane of the projection optical system. In addition, the pattern forming method is characterized in that the shapes of the translucent part, the semi-light-shielding part and the phase shift part are set so that the contrast of the light intensity distribution is improved.
A pattern formation method using a plurality of photomasks corresponding to each of a plurality of blocks obtained by dividing a mask shape of the same layer,
At least one photomask of the plurality of photomasks includes a translucent part that transmits exposure light, a semi-shielding part having a lower transmittance of the exposure light than the translucent part, and the transmissive part of the exposure light. It has at least a phase shift part that transmits with a phase different from the optical part,
The illumination shape of the exposure light in the exposure using the at least one photomask passes through the at least one photomask obtained at each of a plurality of division points obtained by dividing the pupil plane of the projection optical system. The pattern forming method is set based on a light intensity distribution of the exposure light.
In the pattern formation method of Claim 11,
The shape of each of the said light transmission part, the said semi-light-shielding part, and the said phase shift part is set so that the contrast of the said light intensity distribution may improve, The pattern formation method characterized by the above-mentioned.
In the pattern formation method of Claim 11 or 12,
The pattern forming method, wherein the plurality of blocks include a memory block and a logic circuit block.