JP5067313B2 - Method for manufacturing halftone phase shift mask and method for manufacturing semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing a halftone phase shift mask and a method for manufacturing a semiconductor device. For example, when a large-scale semiconductor integrated circuit is patterned on a wafer by a step-and-repeat method, the light-shielding property is reduced by film reduction. The present invention relates to a configuration for preventing a dimensional variation in a main circuit region caused by multiple exposure caused by light transmitted through a metal thin film such as Cr.

  The demand for miniaturization of semiconductor devices is constantly evolving, and in recent years, a pitch pattern finer than the wavelength of an exposure light source used in the semiconductor device manufacturing process has been demanded. Accordingly, halftone phase shift masks are frequently used in the formation of fine patterns.

  In order to form a precise and controlled resist pattern dimension on a wafer, it is usual that the same degree of accuracy must be given on the reticle, and various implementations are required to achieve that accuracy on the reticle. Has been made. Manufacturing specifications related to reticle manufacturing required in such a miniaturized era are defined in the ITRS Roadmap lithography.

  In recent semiconductor device manufacturing processes, various super-resolution masks have been proposed to realize a fine pitch pattern. Typical examples include halftone phase shift masks and Levenson type phase shift masks, which have been used in actual semiconductor device manufacturing sites since the exposure light source was i-line (for example, Patent Document 1 and Patent Document 1). 2).

  In recent years, halftone phase shift masks have high linewidth uniformity and two-dimensional shape fidelity in the halftone phaseshift mask itself due to the demand for high linewidth uniformity required when manufacturing semiconductor devices. Is required. In order to realize this on the reticle, the light-shielding band Cr layer on the halftone film is used as a hard mask (see, for example, Patent Document 1 described above).

  It is desired to make the light-shielding band Cr film having a function as a hard mask as thin as possible. At present, a Cr film having a film thickness of about 40 to 50 nm is laminated and functions as a light-shielding band and hard mask. . Here, a manufacturing process of a conventional halftone phase shift mask will be described with reference to FIGS.

  First, as shown in FIG. 8A, a halftone film 32 such as MoSi having a phase shift effect and a Cr film 33 having a light shielding function are sequentially formed on a quartz substrate 31 by a sputtering method. A blank substrate (dry plate) is formed. Next, as shown in FIG. 8B, a negative electron beam resist 34 is applied on the Cr film 33.

  Next, as shown in FIG. 8C, the main circuit area 36 of the reticle is exposed with an electron beam drawing machine and then developed to form a predetermined circuit pattern in the main circuit area 36, and the light-shielding band area. A resist pattern 35 in which the electron beam resist 34 is left is formed on 37.

Next, the Cr film 33 is patterned by etching with a plasma gas containing Cl using the resist pattern 35 as a mask to form a hard mask 38. At this time, the Cr film 32 remaining in the light shielding band region 37 becomes the light shielding band light shielding film 39. Next, as shown in FIG. 8D, the resist pattern 35 is removed by ashing using O ₂ . At this time, the surface of the hard mask 38 made of Cr is slightly etched to reduce the film thickness.

Next, as shown in FIG. 9E, the halftone film pattern 40 is formed by etching the halftone film 32 using the hard mask 38 as a mask and a sulfur halide gas, for example, SF ₆ or the like as an etchant gas. Form. Next, as shown in FIG. 9F, a positive electron beam resist 41 is applied to the entire surface.

  Next, as shown in FIG. 9G, the electron beam resist 41 is exposed by an electron beam type drawing machine and then developed to form a resist pattern 42 having an opening that exposes the main circuit region 36. Next, the hard mask 38 made of Cr exposed in the main circuit region 36 is selectively removed using the resist pattern 42 as a mask.

Next, as shown in FIG. 9H, the resist pattern 42 is removed by ashing using O ₂ . At this time, the surface of the light shielding band light shielding film 39 made of Cr is etched to reduce the film thickness.
Thus, in the manufacturing process of the halftone phase shift mask, the light shielding band light shielding film provided in the light shielding band region made of the Cr film is used as a hard mask for etching the halftone film.
JP 2007-193036 A JP 09-050112 A

  However, when a large-scale semiconductor integrated circuit is manufactured using a step-and-repeat exposure apparatus, the pattern of the main circuit area existing in the four corner areas is reduced due to the reduction of the light-shielding band shading film made of Cr. Since there is a problem that the dimensional uniformity is remarkably deteriorated as compared with the central portion, this situation will be described with reference to FIGS.

  FIG. 10 is an explanatory diagram of the exposure relationship between adjacent exposure shots. Each side of each exposure shot area 51 becomes a double exposure area that is subjected to multiple exposure by two exposure shots 52, and the four corner areas have four exposures. A four-exposure area 54 that is multiple-exposed by the shot 52 is obtained.

  11A and 11B are explanatory diagrams of problems of the resist pattern due to the reduction of the light shielding band light shielding film. FIG. 11A shows the case where the light shielding band light shielding film is sufficiently thick, and FIG. 11B shows the light shielding band light shielding film. Shows the case where the film becomes thinner due to film reduction. In each figure, the left figure represents a halftone phase shift mask, and the right figure represents a resist pattern on a wafer.

  As shown in FIG. 11A, if the light-shielding band light-shielding film is sufficiently thick and sufficiently functions as the light-shielding film, a resist pattern faithful to the pattern on which the halftone phase shift mask is formed is formed on the wafer. The

  However, as shown in FIG. 11B, when the light-shielding band light-shielding film becomes thinner due to film reduction, light passes through the light-shielding band light-shielding film. In the region, the dimensional variation is significant. In such shot corners, the characteristics of the semiconductor device change due to line width fluctuations.

  In order to solve such a problem, it is conceivable to increase the thickness of the entire film in order to compensate for the reduced film thickness, but if the entire thickness is increased, the main circuit area is naturally increased in thickness, There arises a problem of affecting the etching accuracy of the halftone layer.

  In the Levenson-type phase shift reticle, it has been proposed that the light-shielding band Cr pattern has a film thickness distribution in order to achieve both pattern accuracy and light-shielding performance (see, for example, Patent Document 2 described above). However, in this proposal, after the patterning in the main circuit region is performed in a state where the Cr film is thick, the Cr film pattern in the main circuit region is thinned.

  As a result, since the Cr film is thick at the stage of patterning the Cr film, the patterning accuracy is lowered, and even if the technique is applied to the manufacturing process of the halftone phase shift mask, the halftone film The problem that the etching accuracy decreases cannot be solved.

  Therefore, an object of the present invention is to achieve both the patterning accuracy and the light shielding property when the hard mask and the light shielding band light shielding film are used together.

  From one aspect of the present invention, a step of sequentially forming a halftone film and a hard mask / light-shielding film on a transparent substrate, and a step of forming a film reduction compensation light-shielding film on the hard mask / light-shielding film, Selectively removing the light-shielding film for film decompensation on the circuit region; forming a hard mask / light-shielding film exposed in the main circuit region to form a hard mask; and Etching the halftone film as a mask to form a halftone film pattern, and leaving the film for compensating film depletion in a light shielding band area around the main circuit area when removing the hard mask A method of manufacturing a halftone phase shift mask is provided.

  Another aspect of the present invention provides a method for manufacturing a semiconductor device having an exposure process using a halftone phase shift mask manufactured by the above-described method for manufacturing a halftone phase shift mask.

  According to the disclosed method for manufacturing a halftone phase shift mask, it is possible to manufacture a reticle having a highly accurate halftone film pattern while maintaining the light blocking property of the light blocking thin film Cr. As a result, it is possible to greatly improve the dimensional uniformity in the exposure shot that occurs during the step-and-repeat exposure method, and it is possible to prevent the loss of process margins that are increasingly reduced with miniaturization. become.

  Here, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is an explanatory diagram of a manufacturing process of a halftone phase shift mask according to an embodiment of the present invention. First, as shown in FIG. 1A, a halftone film 2 having a phase shift effect, a hard mask / light-shielding film 3 such as Cr having a sufficient patterning accuracy, and a film decompensating light-shielding film 4 are provided. A blank substrate (dry plate) is formed by sequentially forming a film.

  As the halftone film 2 in this case, for example, MoSi, TaSi or the like is used. Further, the film decompensation light shielding film 4 may be the same Cr as the hard mask and light shielding film 3, may be the same MoSi as the halftone film 2, or polycrystalline silicon having a high etching resistance in the hard mask removing step. Alternatively, SiON may be used. When the same Cr as the hard mask / light-shielding film 3 is used as the film decompensation light-shielding film 4, it may be formed continuously with the hard mask / light-shielding film 3.

  Next, as shown in FIG. 1B, the film decompensation light shielding film 4 in the main circuit region 6 is removed to expose the hard mask / light shielding film 3, and the film decompensation light shielding film left in the light shielding zone region. Reference numeral 4 denotes a light-shielding band reduction compensation light-shielding film 5. Next, after applying an electron beam resist, exposing and developing with an electron beam drawing machine, as shown in FIG. 1 (c), the hard mask / light-shielding film 3 exposed in the main circuit region 6 is etched with Cl-containing etching gas. The hard mask 7 is formed by etching.

  Next, as shown in FIG. 1D, the halftone film pattern 8 is formed by etching the halftone film 2 using the hard mask 7 as a mask. Next, the basic structure of the halftone phase shift mask is completed by removing the exposed portion of the hard mask 7 by etching. At this time, the remaining portion of the hard mask 7 in the light shielding band becomes the light shielding band light shielding film 9.

  Thus, in the embodiment of the present invention, since the light shielding band film decompensating light shielding film 5 is provided in the light shielding band region in addition to the light shielding band light shielding film 9 also serving as the hard mask 7, the light shielding function is sufficiently provided. It is possible to prevent the deterioration of the dimensional uniformity of the exposure shot edge formed in the multiple exposure region of the step-and-repeat exposure method.

  Further, when the hard mask is formed, since the hard mask and light shielding film 3 has a thin film thickness that can sufficiently maintain the patterning accuracy, a halftone film pattern can be formed with high accuracy.

  When the same Cr as that of the hard mask / light-shielding film 3 is used as the film decompensation light-shielding film 4, the process of removing the electron beam resist is performed in the steps of FIGS. The film loss compensation of the light shielding film 4 in the light shielding zone region is caused, but if the film thickness is set in advance, the light shielding function can be sufficiently exhibited.

  Based on the above, the manufacturing process of the halftone phase shift mask according to the first embodiment of the present invention will be described next with reference to FIGS. First, as shown in FIG. 2A, a halftone film 12 made of MoSi having a thickness of 50 to 70 nm, for example, 60 nm, and a Cr having a thickness of 70 to 80 nm, for example, 80 nm, are formed on a quartz substrate 11. A film 13 is sequentially formed by a sputtering method to form a blank substrate (dry plate). Next, as shown in FIG. 2B, a positive electron beam resist 14 is applied on the Cr film 13.

Next, as shown in FIG. 2C, the main circuit region 16 of the reticle is exposed with an electron beam drawing machine, and then developed to form a resist pattern 15 having an opening that exposes the main circuit region 16. To do. Next, the Cr film 13 in the main circuit region 16 is etched to a thickness of 40 to 50 nm by etching with a plasma gas containing Cl using the resist pattern 15 as a mask, for example, a plasma gas composed of a Cl ₂ + O ₂ mixed gas. 50 nm.

Next, as shown in FIG. 2D, the resist pattern 15 is removed by ashing using O ₂ . At this time, the surface of the Cr film 13 is etched to reduce the film. Next, as shown in FIG. 3E, a negative electron beam resist 18 is applied to the entire surface.

Next, as shown in FIG. 3 (f), the main circuit region 16 of the reticle is exposed by an electron beam drawing machine and then developed to form a resist pattern 19 having a predetermined circuit pattern in the main circuit region 16. . Next, the Cr film 13 in the main circuit region 16 is patterned to form a hard mask 20 by performing etching with a plasma gas containing Cl, for example, a plasma gas composed of a Cl ₂ + O ₂ mixed gas, using the resist pattern 19 as a mask. At this time, the Cr film 13 in the light shielding band region becomes the light shielding band light shielding film 21.

Next, as shown in FIG. 3G, the resist pattern 19 is removed by ashing using O ₂ . At this time, the surfaces of the hard mask 20 and the light shielding band light shielding film 21 made of a Cr film are etched to reduce the film thickness.

Next, as shown in FIG. 3H, the halftone film pattern 22 is formed by etching the halftone film 12 using the hard mask 20 as a mask and a sulfur halide gas, for example, SF ₆ as an etchant gas. To do.

  Next, as shown in FIG. 4I, a positive electron beam resist 23 is applied to the entire surface. Next, as shown in FIG. 4 (j), the electron beam resist 23 is exposed by an electron beam drawing machine and then developed to form a resist pattern 24 having an opening that exposes the main circuit region 16. Next, the hard mask 20 made of Cr exposed in the main circuit region 16 is selectively removed using the resist pattern 24 as a mask.

Finally, as shown in FIG. 4 (k), by removing the resist pattern 24 by ashing using O ₂ , the basic configuration of the halftone phase shift mask of Example 1 of the present invention is completed. At this time, the surface of the light shielding band light shielding film 21 made of Cr is etched to reduce the film thickness.

  As described above, in Example 1 of the present invention, the surface of the Cr film in the shading zone region is etched and reduced in the steps of FIGS. 2D, 3G, and 4K. However, since the film thickness of the Cr film 13 is previously increased to about 70 to 80 nm in anticipation of the film thickness reduction, the final film thickness of the light shielding band light shielding film can be sufficiently increased.

  In addition, the Cr film thickness at the stage of forming the hard mask is 40 to 50 nm, which is the same as the conventional film thickness, so that the patterning accuracy can be sufficiently maintained, thereby the patterning accuracy of the halftone film. Will not be adversely affected.

  Next, with reference to FIGS. 5 to 7, a manufacturing process of the halftone phase shift mask according to the second embodiment of the present invention will be described. First, as shown in FIG. 5A, a halftone film 12 made of MoSi having a thickness of 50 to 70 nm, for example, 60 nm, and a Cr film 25 having a thickness of 40 to 50 nm, for example, 50 nm, are formed on a quartz substrate 11. Then, a MoSi film 26 having a thickness of 50 to 70 nm, for example, 60 nm, is sequentially formed as a film decompensation film by a sputtering method to form a blank substrate (dry plate). Next, a positive electron beam resist 14 is applied on the MoSi film 13 as shown in FIG.

Next, as shown in FIG. 5C, the main circuit region 16 of the reticle is exposed with an electron beam drawing machine and then developed to form a resist pattern 15 having an opening for exposing the main circuit region 16. To do. Next, the MoSi film 26 in the main circuit region 16 is removed by etching using a sulfur halide-based gas, for example, SF ₆ using an etchant gas with the resist pattern 15 as a mask, and the Cr film 25 is exposed.

Next, as shown in FIG. 5D, the resist pattern 15 is removed by ashing using O ₂ . At this time, the surface of the Cr film 25 is etched to reduce the film. Next, as shown in FIG. 6E, a negative electron beam resist 18 is applied to the entire surface.

Next, as shown in FIG. 6 (f), the main circuit region 16 of the reticle is exposed by an electron beam drawing machine and then developed to form a resist pattern 19 having a predetermined circuit pattern in the main circuit region 16. . Next, the Cr film 25 in the main circuit region 16 is patterned to form a hard mask 20 by performing etching with a plasma gas containing Cl, for example, a plasma gas composed of a Cl ₂ + O ₂ mixed gas, using the resist pattern 19 as a mask. At this time, the Cr film 25 in the light shielding band region becomes the light shielding band light shielding film 27.

Next, as shown in FIG. 6G, the resist pattern 19 is removed by ashing using O ₂ . At this time, the surface of the hard mask 20 made of a Cr film is etched to reduce the film. Next, as shown in FIG. 6H, the halftone film pattern 22 is formed by etching the halftone film 12 using the hard mask 20 as a mask and a sulfur halide gas, for example, SF ₆ as an etchant gas. To do.

  Next, as shown in FIG. 7I, a positive electron beam resist 23 is applied to the entire surface. Next, as shown in FIG. 7 (j), the electron beam resist 23 is exposed by an electron beam drawing machine and then developed to form a resist pattern 24 having an opening for exposing the main circuit region 16. Next, the hard mask 20 made of Cr exposed in the main circuit region 16 is selectively removed using the resist pattern 24 as a mask.

Finally, as shown in FIG. 7 (k), by removing the resist pattern 24 by ashing using O ₂ , the basic configuration of the halftone phase shift mask according to the second embodiment of the present invention is completed.

  As described above, in the second embodiment of the present invention, since the film reduction compensation light shielding film is provided in the light shielding band region, the light shielding band light shielding film is not reduced, and the light shielding function can be sufficiently exhibited. . The thickness of the Cr film forming the hard mask is 40 to 50 nm from the beginning, and the thickness is not affected by the etching process of FIG. 5C, so that the patterning accuracy can be sufficiently maintained with good reproducibility. Thus, the patterning accuracy of the halftone film is not adversely affected.

  As mentioned above, although each Example of this invention was described, this invention is not restricted to the conditions shown in each Example. For example, in Example 1 and Example 2 described above, a positive electron beam resist pattern is used in the hard mask removal step. However, the hard mask may be removed without using the electron beam resist pattern. . In the case of Example 1, it is necessary to form a film about 30 nm thicker than that of Example 1 in anticipation of film decrement of the light shielding band light shielding film accompanying the removal process of the hard mask.

In the second embodiment, the film decompensation film is made of the same MoSi as the halftone film, but may be made of polycrystalline silicon, SiON, or the like. In that case, a fluorine-based gas such as SF ₆ may be used as an etchant in the step of FIG.

Here, the following supplementary notes are disclosed regarding the embodiment of the present invention including Example 1 and Example 2.
(Supplementary Note 1) A step of sequentially forming a halftone film and a pattern formation light shielding film on a transparent substrate, a step of forming a film decompensation light shielding film on the pattern formation light shielding film, and a main circuit region Selectively removing the film decompensation light-shielding film; forming a pattern on the pattern-forming light-shielding film exposed in the main circuit region to form a mask pattern; and using the mask pattern as a mask, the half A half step comprising: etching a tone film to form a halftone film pattern; and leaving the film decompensation light-shielding film in a light-shielding band area around the main circuit area when the mask pattern is removed A method of manufacturing a tone phase shift mask.
(Additional remark 2) The manufacturing method of the halftone phase shift mask of Additional remark 1 whose said light-shielding film for film | membrane depletion compensation consists of the same material as the said light-shielding film for pattern formation.
(Supplementary note 3) The method of manufacturing a halftone phase shift mask according to supplementary note 1, wherein the film decompensation light-shielding film is made of a material having an etch rate smaller than that of the pattern-forming light-shielding film with respect to the etchant in removing the mask pattern. .
(Additional remark 4) The manufacturing method of the halftone phase shift mask of Additional remark 3 whose said light-shielding film for film | membrane reduction compensation consists of either polycrystalline silicon, SiON, or MoSi.
(Additional remark 5) The manufacturing method of the halftone phase shift mask of Additional remark 3 whose said film reduction compensation light shielding film consists of the same material as the said halftone film.
(Additional remark 6) The manufacturing method of the semiconductor device which has an exposure process using the halftone phase shift mask manufactured by the manufacturing method of the halftone phase shift mask of any one of Additional remark 1 thru | or Additional remark 5.

It is explanatory drawing of the manufacturing process of the halftone phase shift mask of embodiment of this invention. It is explanatory drawing of the manufacturing process to the middle of the halftone phase shift mask of Example 1 of this invention. It is explanatory drawing of the manufacturing process until the middle of FIG. 2 after the halftone phase shift mask of Example 1 of this invention. It is explanatory drawing of the manufacturing process after FIG. 3 of the halftone phase shift mask of Example 1 of this invention. It is explanatory drawing of the manufacturing process to the middle of the halftone phase shift mask of Example 2 of this invention. It is explanatory drawing of the manufacturing process to the middle after FIG. 5 of the halftone phase shift mask of Example 2 of this invention. It is explanatory drawing of the manufacturing process after FIG. 6 of the halftone phase shift mask of Example 1 of this invention. It is explanatory drawing of the manufacturing process to the middle of the conventional halftone phase shift mask. It is explanatory drawing of the manufacturing process after FIG. 8 of the conventional halftone phase shift mask. It is explanatory drawing of the exposure relationship of an adjacent exposure shot. It is explanatory drawing of the problem of the resist pattern by the film reduction of a light-shielding zone light-shielding film.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light transmissive substrate 2 Halftone film 3 Hard mask and light shielding film 4 Film decompensation light shielding film 5 Light shielding band film decompensation light shielding film 6 Main circuit area 7 Hard mask 8 Halftone film pattern 9 Light shielding band light shielding films 11 and 31 Quartz Substrate 12, 32 Halftone film 13, 25, 33 Cr film 14 Electron beam resist 15 Resist pattern 16, 36 Main circuit region 17, 37 Shading zone region 18, 34 Electron resist 19, 35 Resist pattern 20, 38 Hard mask 21 , 27, 39 Light-shielding band Light-shielding film 22, 40 Halftone film pattern 23, 41 Electron beam resist 24, 42 Resist pattern 26 MoSi film 51 Exposure shot area 52 Exposure shot 53 Double exposure area 54 Quadruple exposure area

Claims (5)

A step of sequentially forming a halftone film and a hard mask / light-shielding film on a transparent substrate, a step of forming a light-shielding film for film decompensation on the hard mask / light-shielding film, and the film decompensation on the main circuit region Selectively removing the light shielding film, forming a pattern on the hard mask and light shielding film exposed in the main circuit region to form a hard mask, and etching the halftone film using the hard mask as a mask A halftone phase shift mask having a step of forming a halftone film pattern and a step of leaving the light-shielding film for film decompensation in a light-shielding band region around the main circuit region when the hard mask is removed Manufacturing method. 2. The method of manufacturing a halftone phase shift mask according to claim 1, wherein the film decompensation light shielding film is made of the same material as the hard mask and light shielding film. 2. The method of manufacturing a halftone phase shift mask according to claim 1, wherein the film decompensation light-shielding film is made of a material having an etch rate smaller than that of the hard mask / light-shielding film with respect to an etchant at the time of removing the hard mask. 4. The method of manufacturing a halftone phase shift mask according to claim 3, wherein the light-shielding film for film decompensation is made of any one of polycrystalline silicon, SiON, and MoSi. A method for manufacturing a semiconductor device, comprising an exposure step using the halftone phase shift mask manufactured by the method for manufacturing a halftone phase shift mask according to any one of claims 1 to 4.

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