JP2006078953A - Halftone phase shift mask and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a halftone phase shift mask having the high transmittance of over 6% (9 to 15%), suppressing side etching in a halftone film portion, and having the smooth horizontal plane of a quartz surface, and to provide a method for manufacturing the mask. <P>SOLUTION: The halftone phase shift mask is produced by forming a MoSi-based halftone phase shift film having a film thickness giving a phase difference of ≤135° on a quartz glass substrate and engraving the quartz glass substrate with high perpendicular property and in-plane uniformity by dry etching by magnetic neutral line discharge plasma. The method for manufacturing a halftone phase shift mask includes steps of forming the MoSi halftone phase shift film having a film thickness giving the phase difference of ≤135° on the quartz glass substrate by reactive sputtering and etching the quartz glass substrate using a chromium film as a mask by dry etching by magnetic neutral line discharge plasma with addition of a gas having an effect of protecting a side wall to the process gas. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a halftone phase shift mask used for manufacturing a semiconductor large scale integrated circuit (VLSI) by a lithography technique and a manufacturing method thereof.

  In advanced semiconductor lithography, various super-resolution techniques are used in order to exceed the resolution limit of the exposure wavelength caused by the light diffraction phenomenon. One of them is a method using a halftone phase shift mask. A halftone phase shift mask is a semi-transparent halftone film that is partially transmissive to projection exposure light on a transparent substrate, where the light intensity formed at the boundary of the phase pattern is zero. The pattern resolution is improved, and the layer structure is simple and the manufacturing process is easy.

  In general, as shown in FIG. 7 of the accompanying drawings, a halftone phase shift mask material (blanks) is formed by vacuum-forming a thin film (for example, MoSiON) B having a semi-transmission characteristic of light on a synthetic quartz glass substrate A. Is produced. This thin film B is formed by adjusting the film quality and the film thickness dB so as to satisfy both the light transmittance (approximately 6%) and the phase difference (approximately 180 °) suitable for semiconductor lithography by using a reactive sputtering method. . That is, the thickness dB of the thin film B is configured such that the phase difference between the optical path R1 passing only through the synthetic quartz glass substrate A and the optical path R2 passing through the thin film B and the synthetic quartz glass substrate A is 180 °.

  FIG. 8 shows an example of a conventional manufacturing method of a halftone phase shift mask composed of a two-layer film. FIG. 8A shows blanks made of a quartz glass substrate A, a halftone film B, a chromium film C, and a resist film D. A pattern of this blank is formed in a desired pattern on the resist film D in the exposure and development process shown in FIG. Next, as shown in FIG. 8C, the chromium film C and the halftone film B are etched with a desired pattern formed in the resist film D, and the resist film D is peeled off. Next, as shown in FIG. 8D, resist E is applied again, and as shown in FIG. 8E, a pattern is formed in a desired pattern on the resist film E in the exposure and development process. The chromium film C is etched along the pattern. Thereafter, the remaining resist E is peeled off to obtain a halftone phase shift mask as shown in FIG.

  As described above, the halftone phase shift mask blanks having a transmittance of approximately 6% or less can control the transmittance and the phase difference only with the film, so that the structure is simple and the dry etching process for pattern formation is also simple. Could be configured. However, about 6% of the half-tone phase shift mask material using ArF laser light with a short exposure wavelength (wavelength of 193 nm) has been achieved for the MoSi-based film standardized on the market, but it has high transmittance. (9-15%) and phase difference (180 °) are very difficult to achieve at the same time, and proposals on the market have changed the film material to SiON and have a complicated structure (Non-Patent Document 1). reference).

  By the way, in manufacturing technology of a semiconductor integrated circuit using this type of mask, finer pattern resolution is required year by year. Therefore, in order to realize a finer resolution, it is necessary to give the halftone film a high transmittance (9 to 15%) exceeding 6%.

In order to solve this problem, as a halftone phase shift mask blank made of a single layer film, the halftone film thickness is reduced to increase the transmittance, and the halftone film thickness is reduced. Has been proposed to ensure a phase difference of 180 ° (see Patent Document 1 and Patent Document 2). For example, if a halftone film portion having a phase difference of approximately 175 ° and a quartz portion having a slight depth of 5 ° are etched, the phase difference can be set to 180 °.
“Development of attenuating PSM shifter for F2 and high transmittion ArF lithography”; O. Nozawa, et al., SPIE Vol.5130, 39 (2003), Photomask and Next-Generation Lithography Mask Technology X) JP-A-7-152142 JP 2003-121988 A

  When the film composition or the film composition ratio is changed, various peripheral equipment changes and process conditions are required for pattern processing. If the MoSi-based halftone film standardized on the market can be used for high transmittance products, the mask process equipment can be used, and the process setting effort can be reduced.

  On the other hand, the dry etching process of the halftone phase shift mask has the following problems. In other words, in the conventional method of dry etching a mask having a structure, the pattern cross section should be finished vertically, but since the halftone film etching rate is larger than that of quartz, the side etching of the halftone film proceeds and the cross section There was a problem that a level difference would occur. Further, as shown in FIG. 9, a groove called a sub-trench is formed on the horizontal quartz surface, and further, there is a problem that surface roughness due to etching occurs on the quartz surface that should be the horizontal surface. For this reason, it is difficult to etch the quartz portion deeply.

  Therefore, in order to realize a finer resolution, the present invention has a high transmittance (9 to 15%) exceeding 6%, can suppress the side etching of the halftone film portion, and has a smooth quartz surface. It is an object of the present invention to provide a halftone phase shift mask capable of achieving the above and a manufacturing method thereof.

  In order to achieve the above object, a halftone phase shift mask according to the present invention is provided with a MoSi halftone phase shift film having a thickness such that the phase difference is 135 ° or less on a quartz glass substrate, The quartz glass substrate is dug with good perpendicularity and in-plane uniformity by dry etching using magnetic neutral discharge plasma, and the phase difference is 180 °.

  In the halftone phase shift mask according to the present invention, the halftone phase shift film may be made of MoSiON and have a refractive index of about 2.45, an extinction coefficient of about 0.58, and a thickness of about 46 nm.

  In one embodiment of the halftone phase shift mask according to the present invention, the halftone phase shift film has a film thickness such that the phase difference is 110 ° to 135 °. The halftone phase shift film has an ArF laser transmittance of 9 to 15%.

  In addition, the method for producing a halftone phase shift mask according to the present invention comprises forming a MoSi-based halftone phase shift film on a quartz glass substrate by a reactive sputtering method so that the phase difference is 135 ° or less. Then, using the chromium film as a mask, the quartz glass substrate is etched by adding a gas having a sidewall protecting effect to the process gas by dry etching using magnetic neutral discharge plasma.

  In one embodiment of the method of manufacturing a halftone phase shift mask according to the present invention, the process gas used for dry etching by magnetic neutral discharge plasma is mainly composed of CF4, CHF3, etc., and sidewalls added to the process gas Gases having a protective effect are C4F8, C3F8, C2F6, and the like.

  Preferably, the amount of the gas having a sidewall protecting effect added to the process gas is 20% or less, and the etching treatment of the quartz glass substrate can be performed in an atmosphere of 0.34 Pa or less.

  In the halftone phase shift mask according to the present invention, a halftone phase shift film made of MoSi having a film thickness such that the phase difference is 135 ° or less is provided on a quartz glass substrate, and a magnetic neutral line discharge plasma is used. Since the quartz glass substrate is dug with good perpendicularity and in-plane uniformity by dry etching, a halftone phase shift mask having a high transmittance of 9% or more can be provided. The fine pattern resolution requirement can be satisfied, and it can be advantageously used for manufacturing a semiconductor large-scale integrated circuit that requires super-resolution. In addition, a mask manufacturer that performs mask processing can process an existing facility simply by changing the conditions.

  In the method of manufacturing a halftone phase shift mask according to the present invention, a halftone phase shift film made of MoSi is formed on a quartz glass substrate by a reactive sputtering method so that the phase difference is 135 ° or less. Next, using a structure in which a quartz glass substrate is etched by adding a gas having a sidewall protecting effect to a process gas by dry etching with magnetic neutral discharge plasma using a chromium film as a mask. The half-tone phase shift film portion and the quartz glass substrate portion can be subjected to simple collective dry etching, and a vertical and smooth pattern cross section can be obtained. Further, by using dry etching with magnetic neutral discharge plasma, the in-plane uniformity of the quartz glass substrate can be improved by changing the current value of the magnetic field coil. Further, by using high-density plasma, it is possible to improve the roughness of the quartz etching surface and the sub-trench.

Embodiments of the present invention will be described below with reference to FIGS.

  FIG. 1 schematically shows the configuration of a halftone phase shift mask according to the present invention. In FIG. 1, 1 is a quartz glass substrate, 2 is a halftone phase shift film made of a MoSiON film formed on the quartz glass substrate 1, and 3 is a portion dug by etching of the quartz glass substrate 1. By matching the phase difference due to the thickness d1 of the halftone phase shift film 2 with the phase difference due to the depth d2 of the portion 3 in which the quartz glass substrate 1 is dug, the optical path R1 passing only through the quartz glass substrate A and the halftone The phase difference between the phase shift film 2 and the optical path R2 passing through the quartz glass substrate 1 is 180 °.

Next, a method for manufacturing a halftone phase shift mask according to an embodiment of the present invention will be described with reference to FIG.
FIG. 2A shows a blank 10 prepared for producing the halftone phase shift mask of the present invention. The illustrated blank 10 has a quartz glass substrate 11 and a refractive index of about 10 formed thereon. It consists of a halftone phase shift film 12 made of a MoSiON film having an extinction coefficient of about 0.58 and a thickness of about 46 nm, and a chromium film 13. A resist layer 14 is applied on the chromium film 13.

FIG. 2B shows an exposure / development process of the blanks 10, and in this process, a pattern is formed on the resist film D in a desired pattern.

  FIG. 2C shows an etching process for the chromium film 13, the halftone phase shift film 12, and the quartz glass substrate 11. In this etching process, a dry etching apparatus using magnetic neutral discharge plasma, which will be described later with reference to FIG. 3, is used. In this dry etching apparatus, by adding a gas having a sidewall protecting effect such as C4F8, C3F8, and C2F6 to a process gas mainly composed of CF4, CHF3, etc., the chromium film 13, the halftone phase shift film 12, and the quartz The glass substrate 11 can be collectively dry etched. Thus, a mask pattern is formed. The formed mask pattern can provide a vertical and smooth pattern cross section as schematically shown in FIG. In this case, the in-plane uniformity of the substrate can be improved by controlling the current value of the magnetic field coil in the dry etching apparatus using magnetic neutral line discharge plasma. Further, it is possible to improve the roughness of the etched surface of the quartz glass substrate 11 and the sub-trench. After the etching process is thus performed to form a mask pattern, the resist film 14 is peeled off.

  FIG. 2D shows a resist coating process. In this step, as shown, a resist film 15 is applied on the mask pattern formed in the previous step.

  FIG. 2E shows exposure and development and the etching process of the chromium film 13. First, by exposure and development, the resist film 15 is removed with a pattern larger than the mask pattern in the etching step shown in FIG. 2C, and the chromium film 13 is etched with the pattern of the obtained resist film 15.

  FIG. 2F shows a step of removing the resist film 15, and the resist film 15 is peeled off.

  As an example when the method shown in FIG. 2 is performed, for example, in the production of a halftone phase shift mask having a transmittance of 15%, the phase difference of the halftone phase shift film 12 is about 114 °, and the film thickness thereof is as follows. Is 46 nm, and the depth to be etched of the quartz glass substrate 11 is about 60 nm.

  Further, in the production of a halftone phase shift mask having a transmittance of 9%, the phase difference of the halftone phase shift film 12 is about 135 °, the film thickness thereof is 54 nm, and the quartz glass substrate 11 is etched. The depth to be is about 41 nm.

  FIG. 3 shows an example of a dry etching apparatus using a magnetic neutral discharge plasma used in the method of the present invention. In the illustrated etching apparatus, reference numeral 21 denotes a vacuum chamber, which includes an upper plasma generation part 21a and a substrate electrode part 21b. The substrate electrode portion 21 b is provided with an exhaust port 21 c and is connected to the turbo molecular pump 23 via the pressure adjustment valve 22.

  The plasma generator 21 a includes a cylindrical dielectric side wall 24, and three magnetic fields constituting magnetic field generating means for forming a magnetic neutral line 25 in the vacuum chamber 21 outside the dielectric side wall 24. Coils 26, 27, and 28 are provided, and these magnetic field coils form a magnetic neutral line 25 in the plasma generation unit 21 a at the top of the vacuum chamber 21. A substrate electrode 29 is provided below the vacuum chamber 21 via an insulator member 30, and the substrate electrode 29 is connected via a capacitor 31 to a high frequency power source 32 that applies an RF bias.

  Between the intermediate magnetic field coil 27 and the outside of the dielectric side wall 24, a double-winding high-frequency coil 33 for generating plasma is disposed. These high-frequency coils 33 are connected to a high-frequency power source 34, and three magnetic field coils 26 are provided. 27 and 28, an alternating electric field is applied along the magnetic neutral line 25 formed in the plasma generating part 21a at the upper part of the vacuum chamber 21 to generate discharge plasma on the magnetic neutral line.

  The top plate 35 of the plasma generation unit 21 a at the upper part of the vacuum chamber 21 is in contact with the upper flange of the dielectric side wall 24 through an O-ring.

  Further, a gas introduction port 36 for introducing a process gas, that is, an etching gas into the vacuum chamber 21 is provided in the plasma generation unit 21a above the vacuum chamber 21, and this gas introduction port 36 is a gas supply (not shown). An etching gas supply source is connected via a gas flow rate control device for controlling the flow rate of the passage and the etching gas.

  The structure of the halftone phase shift mask having high transmittance of the present invention uses MoSi-based film quality standardized on the market. However, by reducing the film thickness, the transmittance is increased, and the halftone film is responsible for it. The phase difference is approximately 110 ° to 135 °, and the remaining approximately 45 ° to 70 ° is achieved by carving a quartz glass substrate by dry etching.

  Further, in the halftone phase shift mask according to the present invention having this structure, the quartz glass substrate portion is deeply dry-etched. Therefore, the halftone phase shift film and the quartz glass substrate are etched by side etching of the halftone film portion in the pattern cross section. Steps are inevitably generated at the interface. To solve this problem, a process with CF4, CHF3, etc. as the main component in a dry etching system using magnetic neutral discharge plasma used in the dry etching process to form a mask pattern. By adding a gas such as C4F8, C3F8, or C2F6 to the gas that has a sidewall protecting effect, the halftone phase shift film and the quartz glass substrate can be easily and collectively dry etched, and a vertical and smooth pattern cross section can be obtained. .

  In the method according to the present invention, the halftone phase shift film can be made as close to 180 ° as possible within the range of 180 ° or less, since the depth of engraving on the quartz glass substrate can be reduced, so that the etching process is simplified. In order to satisfy the side-by-side requirement of high transmittance chemical resistance of 9 to 15% at a wavelength of 193 nm using the above-described MoSi system, the upper limit of the phase difference of the halftone phase shift film is 135 °.

  In the method according to the present invention, in the dry etching process, NLDE-9035 manufactured by ULVAC, Inc. is used as a mask dry etching apparatus, and the pressure is 0.68 Pa, the high frequency power supply 34 is 500 W, and the high frequency power supply 32 is 100 W, 0 to 7% of C4F8 was added as an additive gas to the process gas CF4. As the amount of C4F8 added increased, the side etching amount of the MoSi halftone phase shift film portion gradually decreased. Further, when 7 to 20% of C4F8 was added to the process gas CF4, side etching did not occur. Furthermore, when the amount of C4F8 added was increased to 20% or more, the etching rate in the depth direction of the film gradually decreased and etching was not performed. From this, in order to suppress the occurrence of side etching, when CF4 is used as the process gas and C4F8 is used as the additive gas, the additive gas C4F8 is preferably added in an amount of 7 to 20%.

  NLDE-9035 made by ULVAC, Inc. is used as a mask dry etching apparatus, CF4 is used as a process gas, 8.5% of C4F8 is added thereto, 500 W to the high frequency power supply 34, and 100 W to the high frequency power supply 32, respectively. The pressure was set to 0.1 to 0.7 Pa. The dry etching characteristics in that case are shown in FIG. As shown in FIG. 5, it can be seen that when the pressure is 0.34 Pa or less, the perpendicularity of the quartz glass substrate increases, and when the pressure is 0.34 Pa or more, the cross section of the quartz glass substrate has a tail. This shows that the pressure during dry etching is preferably 0.34 Pa or less in order to maintain the perpendicularity of the quartz glass substrate.

  FIG. 6 shows the spectral transmittance of the halftone phase shift film according to the present invention.

  In the illustrated embodiment, the NLD dry etching method is used. However, it is also possible to perform the etching process using an ICP or ECR method. In addition, the halftone phase shift film used in the present invention is not limited to the MoSiON film, and it is also possible to form a MoSiN, MoSiO, or MoSiHON film by changing the reactive gas species during sputtering film formation. .

The schematic sectional drawing which shows the structure of the halftone type phase shift mask by this invention. The schematic sectional drawing which shows the pattern formation process of the halftone type phase shift mask by the method of this invention. The schematic diagram which shows the dry etching apparatus which can be used with the method of this invention. The schematic diagram which shows the cross-sectional shape when a halftone type phase shift mask is pattern-formed by dry etching by the method of this invention. The figure which shows the dry etching characteristic when the pressure at the time of dry etching is changed. The graph which shows the spectral transmission factor of the halftone type phase shift mask by this invention. 1 is a schematic cross-sectional view showing the structure of a generally used halftone phase shift mask. The schematic sectional drawing which shows the pattern formation process of the conventional halftone type | mold phase shift mask. The schematic diagram which shows the cross-sectional shape when a halftone type phase shift mask is pattern-formed by dry etching based on the conventional method.

Explanation of symbols

1: Quartz glass substrate 2: Halftone phase shift film 3: Excavated portion of quartz glass substrate 1 10: Blanks 11: Quartz glass substrate 12: Halftone phase shift film 13: Chrome film 21: Vacuum chamber 22: Pressure adjustment Valve 23: turbo molecular pump 24: dielectric side wall 25: magnetic neutral wire 26: magnetic field coil 27: magnetic field coil 28: magnetic field coil 29: substrate electrode 30: insulator member 31: blocking capacitor 32: high frequency power supply 33: high frequency coil 34: High frequency power source 35: Top plate 36: Gas inlet

Claims (8)

  A MoSi-based halftone phase shift film having a thickness such that the phase difference is not more than 135 ° is provided on the quartz glass substrate, and the quartz glass substrate is surfaced with good verticality by dry etching using magnetic neutral discharge plasma. A halftone phase shift mask having a phase difference of 180 ° by digging with good uniformity.   2. The halftone phase shift mask according to claim 1, wherein the halftone phase shift film is a MoSiON film and has a refractive index of about 2.45, an extinction coefficient of about 0.58, and a thickness of about 46 nm.   2. The halftone phase shift mask according to claim 1, wherein the halftone phase shift film has a film thickness such that a phase difference is 110 ° to 135 °.   The halftone phase shift mask according to claim 1, wherein the halftone phase shift film has an ArF laser transmittance of 9 to 15%.   A MoSi-based halftone phase shift film is formed on a quartz glass substrate by a reactive sputtering method so that the phase difference is 135 ° or less, and then a magnetic neutral line discharge is performed using the chromium film as a mask. A method for producing a halftone phase shift mask, characterized in that a quartz glass substrate is etched by adding a gas having a sidewall protecting effect to a process gas by dry etching using plasma.   The process gas used for dry etching by magnetic neutral discharge plasma is mainly composed of CF4 or CHF3, and the gas with side wall protection effect added to the process gas is either C4F8, C3F8 or C2F6 The method for producing a halftone phase shift mask according to claim 5.   The method for producing a halftone phase shift mask according to claim 5 or 6, wherein the amount of the gas having a sidewall protecting effect added to the process gas is 20% or less.   6. The method for producing a halftone phase shift mask according to claim 5, wherein the etching treatment of the quartz glass substrate is performed in an atmosphere of 0.34 Pa or less.