JP2016114820A - Pellicle for reflection type mask and manufacturing method of pellicle for reflection type mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pellicle for a reflection type mask, the pellicle capable of easily controlling the in-plane homogeneity of optical density in a wafer, in a method using an EUV lithography.SOLUTION: A pellicle 10 for a reflection type mask reflects with a multilayer reflective layer. The pellicle is provided in a reflection type mask, to control the in-plane homogeneity of optical density in a wafer. As a pellicle film 21 forms the distribution of transmittance, the thickness of the pellicle film 21 is made to have a given distribution or internal transmittance thereof is made to have a given distribution.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a mask pellicle used when a semiconductor device or the like is manufactured by a lithography technique, and an applicable reflective mask pellicle.

  Semiconductor integrated circuits are being miniaturized and highly integrated in order to improve performance and productivity, and lithography technology for forming circuit patterns is also a technology for forming finer patterns with high accuracy. Development is underway.

  Along with this, the wavelength of the light source of the exposure apparatus used for pattern formation has been shortened, and extreme ultraviolet light (Extreme Ultraviolet; hereinafter referred to as “EUV”) having a wavelength of 13.5 nanometers (nm) is used. A pattern transfer process has been developed.

  In lithography using EUV, unlike the conventional case of using deep ultraviolet light such as 193 nm, since the refractive index of all materials is a value close to 1, and the absorption coefficient is large, a transmission optical system using refraction is used. Unable to expose. Therefore, an exposure apparatus of a reflective optical system using a multilayer mirror (specifically, a multilayer mirror of molybdenum and silicon) in which materials having a large refractive index difference are alternately laminated is used.

  Similarly, for the mask, a multilayer film of molybdenum and silicon is formed on the substrate, and an exposure pattern is formed of a material that absorbs EUV with high efficiency. For example, as the material of the absorption pattern, a material mainly composed of tantalum is used, and a material in which a protective film containing ruthenium or the like is formed on the uppermost layer of the multilayer film is also used.

  However, the production of a reflective mask for EUV exposure has technical problems that must be solved. A reflective mask for forming a semiconductor device having a fine pattern is required to have a high precision along with a fine pattern line width as an original, and important pattern dimensions such as a gate pattern line width are strictly CD (Critical Dimension). Therefore, the target allowable value of the pattern is set in advance. The target allowable value of the mask CD in-plane uniformity that affects the wafer CD in-plane uniformity is becoming stricter, and control of the mask in-CD uniformity is an important issue.

  FIG. 10 shows a configuration of a conventional EUV pellicle, in which a pellicle film 2 is stretched on an outer frame portion 1 and a beam portion 3 is provided for reinforcement, and an antioxidant film is formed on both sides of the pellicle film. The pellicle frame 6 is bonded to the lower portion of the outer frame portion 1.

  FIG. 11 shows a simplified configuration in which the beam portion 3 for reinforcement is not provided. The pellicle film alone is weak in mechanical strength and may be easily broken due to vibration during conveyance. However, in EUV lithography, pattern transfer accuracy causes serious problems such as loss of EUV light amount, unevenness of light intensity, and generation of foreign matter, and a pellicle having a membrane portion without a beam structure is also employed. .

  As a method for correcting the CD in-plane uniformity of the mask, a method using a drawing apparatus or a process apparatus is representative.

On the other hand, a method for correcting the in-plane uniformity of a wafer onto which a mask pattern is transferred has also been proposed. In this method, a mask glass substrate is irradiated with a laser to create a transmittance distribution, whereby the exposure amount when the exposure apparatus transfers to the wafer is locally adjusted, and the CD in-plane uniformity of the wafer is controlled. (Non-Patent Document 1).

  However, this method cannot be used because EUV lithography uses a reflective mask in which EUV light is reflected by a multilayer reflective layer formed on a substrate.

Proc. Of SPIE Vol. 8166619-1

  The present invention has been made in view of the above problems, and provides a reflective mask pellicle capable of easily controlling the in-plane uniformity of the optical density of a wafer in a method using EUV lithography. Is.

As means for solving the above-mentioned problems, the invention according to claim 1 is a reflective mask pellicle reflected by a multilayer reflective layer using EUV lithography,
In order to control the optical density in-plane uniformity of a wafer, the pellicle for a reflective mask is provided on a reflective mask, and the pellicle film has a transmittance distribution.

  According to a second aspect of the present invention, there is provided a pellicle for a reflective mask according to the first aspect, wherein the pellicle film has a distribution in film thickness.

  According to a third aspect of the present invention, in the film thickness distribution of the pellicle film, the film thickness in the central part of the mask is made larger than that in the outer peripheral part of the mask. This is a reflective mask pellicle.

  According to a fourth aspect of the present invention, in the film thickness distribution of the pellicle film, the film thickness of the mask central portion is made thinner than that of the outer peripheral portion of the mask. This is a reflective mask pellicle.

  The invention according to claim 5 is characterized in that the film thickness distribution of the pellicle film is a film thickness distribution inclined from the left side to the right side or from the right side to the left side of the mask. A pellicle for a reflective mask as described in 1. above.

  The invention according to claim 6 is characterized in that the film thickness distribution of the pellicle film is a film thickness distribution inclined from the upper side to the lower side or from the lower side to the upper side of the mask. Item 3. A reflective mask pellicle according to Item 2.

  The invention according to claim 7 is the reflective mask pellicle according to claim 1 or 2, wherein the film thickness distribution of the pellicle film is an arbitrary film thickness distribution.

  The invention according to claim 8 is characterized in that the internal material transmittance of the pellicle film is changed to give a distribution in the internal transmittance of the pellicle film. Pellicle.

The invention described in claim 9 is a method for manufacturing a reflective mask pellicle according to any one of claims 1 to 7,
Coating and forming a resist film on the pellicle film;
Irradiating the resist film with a laser beam modulated in intensity, and drawing;
Developing the drawn resist film by developing a film thickness distribution of the resist film;
And a step of forming a film thickness distribution on the pellicle film by etching.

The invention described in claim 10 is a method for manufacturing a pellicle for a reflective mask according to claim 1 or 8, wherein
A method for producing a pellicle for a reflective mask, comprising a step of irradiating a pellicle film with a laser to change a material characteristic inside the pellicle film to change an internal transmittance.

  According to the present invention, it is possible to provide a reflective mask pellicle that enables control of uniformity within a CD surface of a wafer, which has been difficult in the conventional method using EUV lithography.

It is a conceptual sectional view showing one structure of an EUV mask pellicle of the present invention. It is a conceptual sectional view showing one structure of an EUV mask pellicle of the present invention. It is a conceptual sectional view showing one structure of an EUV mask pellicle of the present invention. It is a conceptual sectional view showing one structure of an EUV mask pellicle of the present invention. It is a conceptual sectional view showing one structure of an EUV mask pellicle of the present invention. It is a conceptual sectional view showing one structure of an EUV mask pellicle of the present invention. It is the conceptual diagram which showed the relationship between OD (optical density) and the transmittance | permeability. It is the result which showed the CD in-plane uniformity of an EUV mask. It is the simulation result which showed the CD in-plane uniformity of the wafer by the presence or absence of a pellicle. It is a conceptual sectional view showing the structure of a conventional EUV mask pellicle. It is a conceptual sectional view showing the structure of a conventional EUV mask pellicle.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. FIG. 1 shows a pellicle for a reflective mask according to the present invention, which is composed of an outer frame part 1, a pellicle film, and a pellicle frame 6. A film having a thicker film at the center of the mask than at the outer periphery of the mask. 2 shows a reflective mask pellicle provided with a pellicle film 21 having a thickness distribution.

  FIG. 2 shows a reflective mask pellicle having a pellicle film 22 having a film thickness distribution that is thinner at the center of the mask than at the outer periphery of the mask. ing.

  FIG. 3 shows a reflective mask pellicle provided with a pellicle film 23 having a film thickness distribution in which the pellicle film thickness distribution is inclined to the left or right or up and down of the mask. .

  FIG. 4 shows a reflective mask pellicle provided with a pellicle film 24 having an arbitrary film thickness distribution among the reflective mask pellicles of the present invention.

  FIG. 5 shows a reflective mask having a pellicle film 25 having a transmittance distribution in the central portion and the outer peripheral portion of the mask that is different in the magnitude distribution of the transmittance in the pellicle film of the reflective mask pellicle of the present invention. A pellicle for use is shown.

  FIG. 6 shows a pellicle for a reflective mask having a pellicle film 26 in which the distribution of the transmissivity in the pellicle film has different transmittance distributions on the left and right or top and bottom of the mask. Is shown.

  The pellicle film of the EUV pellicle of the present invention may be either single crystal silicon or polycrystalline silicon. However, since the polycrystalline film has a problem that the absorption rate (absorption coefficient) of light in the EUV wavelength band is high, Crystalline silicon is preferred.

The in-plane uniformity of the wafer CD is controlled by giving the pellicle a distribution of transmittance with respect to EUV light and controlling the exposure amount of the exposure machine. In order to determine how much the transmittance is changed, the relationship between the optical density (OD value: Optical Density) and the transmittance, and the OD value and the film thickness are in a proportional relationship. It is known that the relationship between the OD value and the transmittance is expressed by OD = −Log ₁₀ T, where T means the absolute transmittance.

  FIG. 7 shows the relationship between the OD value and the transmittance T. That is, since there is a proportional relationship between the OD value and the film thickness, it can be seen that the transmittance can be controlled by changing the film thickness. Therefore, if the pellicle film thickness distribution is formed, the transmittance is locally changed, and as a result, the CD in-plane uniformity of the wafer can be controlled.

  As a method of manufacturing a pellicle having a film thickness distribution according to the present invention, a silicon thin film layer that is manufactured in advance by manufacturing a structure including a pellicle film and an outer frame portion in the same manufacturing process as an stencil mask on an SOI substrate. Or a method of manufacturing a structure including a pellicle film and an outer frame in a manufacturing process similar to that for a stencil mask after first etching the surface of a silicon thin film layer. is there.

  As a method for forming irregularities in the silicon thin film layer, a resist film thickness distribution can be created after resist development by performing drawing with a laser beam whose intensity is modulated after applying the resist to the silicon thin film layer. By performing etching thereafter, irregularities can be formed in the silicon thin film layer.

  As a method of forming a region having changed transmittance in the silicon thin film layer to be a pellicle film, the transmittance can be changed by laser irradiation to the inside of the silicon thin film layer. Examples of the laser irradiation means include a femtosecond laser, an attosecond laser, a zeptosecond laser, or a yoctosecond laser.

  With the EUV pellicle of the present invention, it is possible to control the CD in-plane uniformity of a wafer in lithography using EUV light.

  Hereinafter, the details of the examples will be described by taking the manufacturing process of the EUV pellicle using the SOI substrate as an example. First, an SOI substrate having a diameter of 200 mm (8 inches) was prepared. In this SOI substrate, the silicon thin film layer, the BOX layer, and the supporting substrate layer are 100 nm, 1 μm, and 725 μm in thickness, respectively.

  Next, a chromium nitride layer was formed on the support substrate layer by sputtering, and the chromium nitride layer in the pattern effective region (region corresponding to the exposure region) was removed by photolithography and RIE dry etching using chlorine-based gas.

Subsequently, the support substrate layer was etched with an ICP plasma etching apparatus using a fluorine-based gas. The exposure of the BOX layer serving as an etching stopper was detected from the change in the light reflectance of the etched surface. Since the region to which the chromium nitride layer was previously applied (the portion other than the pattern effective region) was not etched by the fluorine-based gas, it sufficiently functioned as an etching mask and remained after the etching process.

  Next, the BOX layer was removed by etching with a hydrofluoric acid aqueous solution and rinsed with ultrapure water so that a clean silicon thin film layer was exposed. Thus, a structure in which the effective pattern area was a silicon thin film layer (membrane) was obtained.

  Next, after applying a resist to the surface of the silicon thin film layer, the intensity of the laser is modulated, and laser drawing is performed so that the intensity increases from the center of the silicon thin film layer to the outer periphery. Thereafter, resist development was performed, and it was confirmed that the resist film thickness distribution was convex. Then, when dry etching was performed using a fluorine-based gas, a silicon thin film layer having a convex film thickness distribution could be formed.

  When the thickness of the silicon thin film layer was measured at the center and the outer periphery, the film thickness at the center was 57 nm, the outer periphery was 77.1 nm, and the transmittance of the EUV light was measured. It was confirmed that the distribution was 84% and the outer peripheral portion had a distribution of 79%, and it was possible to form a convex film thickness distribution and a silicon thin film layer having a high transmittance at the central portion.

  FIG. 8 shows the CD in-plane uniformity of the EUV mask. It is a mask having a so-called concentric tendency in which CD of Line 100 nm is measured at 25 locations in the plane, and the CD in the central portion is about 4 nm smaller than the outer peripheral portion.

  Next, by using lithography simulation, the wafer CD result was simulated in consideration of the influence on the wafer CD of the wafer CD without the pellicle and the change in transmittance at the center and the outer periphery of the silicon thin film layer with the pellicle.

  FIG. 9 shows the result. When the pellicle was used, it was confirmed that the CD in-plane uniformity of the wafer was improved by 55%.

  Another form of this invention is shown. Similar to the first embodiment, the process until the pattern effective region is formed of the silicon thin film layer based on the SOI substrate is the same.

  By performing laser irradiation on the silicon thin film layer using a femtosecond laser, a region where the transmittance was changed was formed, and a transmittance distribution was created. Since the EUV mask used in the evaluation is the same mask as in Example 1 in which the CD at the center of the mask has a concentric tendency smaller than that of the outer periphery, the transmittance distribution of the silicon thin film layer is 84% at the center and 79% at the outer periphery. As a result, the pellicle thin film layer having such a transmittance distribution was actually formed.

  By implementing the present invention, in lithography using EUV light, the uniformity of the mask in the CD plane is controlled by forming the film thickness distribution on the pellicle film, thereby controlling the uniformity of the wafer in the CD plane. can do. Further, by performing laser irradiation on the pellicle film, and forming a region where the transmittance has changed in the pellicle film, it is possible to control the transmittance and to control the CD in-plane uniformity of the wafer.

DESCRIPTION OF SYMBOLS 1 ... Outer frame part 2 ... Pellicle film 3 ... Beam structure part 4 ... Antioxidation film 5 ... Insulator layer 6 ... Pellicle frame 10 ... Reflective mask 21 ... -Pellicle film 22 having a thicker film thickness distribution at the mask central part than the mask outer peripheral part ... The film thickness distribution at the mask central part is thinner than the mask outer peripheral part. The pellicle film 23 has a pellicle film 24 whose pellicle film thickness distribution is inclined to the left or right or up and down of the mask. The pellicle film 25 has a pellicle film thickness distribution having an arbitrary film thickness distribution. ..Pellicle film 26 in which the distribution of transmittance in the pellicle film has different transmittance distributions in the central portion and the outer periphery of the mask. The distribution of transmittance in the pellicle membrane is on the left and right or top and bottom of the mask. Peri with different transmittance distribution Le film

Claims (10)

A pellicle for a reflective mask reflected by a multilayer reflective layer using EUV lithography,
A pellicle for a reflective mask, which is provided on a reflective mask for controlling the optical density in-plane uniformity of a wafer, and the pellicle film has a transmittance distribution.   2. The reflective mask pellicle according to claim 1, wherein the thickness of the pellicle film is distributed.   3. The pellicle for a reflective mask according to claim 1, wherein the film thickness distribution of the pellicle film is such that the film thickness at the center of the mask is thicker than at the outer periphery of the mask.   3. The reflective mask pellicle according to claim 1, wherein the film thickness distribution of the pellicle film is such that the film thickness at the center of the mask is made thinner than at the outer periphery of the mask.   3. The reflective mask pellicle according to claim 1, wherein the film thickness distribution of the pellicle film is a film thickness distribution inclined from the left side to the right side of the mask or from the right side to the left side.   3. The reflective mask pellicle according to claim 1, wherein the film thickness distribution of the pellicle film is a film thickness distribution inclined from the upper side to the lower side of the mask or from the lower side to the upper side.   3. The reflective mask pellicle according to claim 1, wherein the film thickness distribution of the pellicle film is an arbitrary film thickness distribution.   2. The pellicle for a reflective mask according to claim 1, wherein a material characteristic inside the pellicle film is changed to have a distribution in the internal transmittance of the pellicle film. A method for manufacturing a pellicle for a reflective mask according to any one of claims 1 to 7,
Coating and forming a resist film on the pellicle film;
Irradiating the resist film with a laser beam whose intensity is modulated, and drawing,
Forming a resist film thickness distribution by developing the drawn resist film; and
A method of manufacturing a pellicle for a reflective mask, comprising: forming a film thickness distribution on the pellicle film by etching. A method for manufacturing a pellicle for a reflective mask according to claim 1 or 8,
A method for manufacturing a pellicle for a reflective mask, comprising a step of irradiating a pellicle film with a laser to change a material characteristic inside the pellicle film to change an internal transmittance.