JP6674809B2 - Phase shift mask blank cleaning apparatus and phase shift mask blank manufacturing method - Google Patents

Description

  The present invention relates to a phase shift mask blank cleaning apparatus capable of forming a fine and highly accurate exposure pattern, and a technique suitable for use in a phase shift mask blank manufacturing method using the same.

  Generally, in a manufacturing process of a semiconductor device, a fine pattern is formed using a photolithography method. To form this fine pattern, a number of substrates, which are usually called transfer masks, are used. This transfer mask generally has a fine thin film pattern made of a metal thin film or the like provided on a translucent glass substrate. A photolithography method is also used in manufacturing the transfer mask.

  2. Description of the Related Art In recent years, as the degree of integration of semiconductor devices has been remarkably improved, there has been an increasing demand for finer patterns in transfer masks. Binary masks and phase shift masks are known as transfer masks. The binary mask is a mask having a light-shielding film pattern made of, for example, a chromium-based material on a light-transmitting substrate. The phase shift mask is a mask in which a phase shift layer that causes a predetermined phase difference with respect to exposure light is formed on a translucent substrate.

  The phase shift photomask is characterized by transmitting a small amount of light even in a light-shielded portion of the pattern. Since the phase of the transmitted light and the light of the main pattern are reversed, the reversed light is transmitted at the boundary of the pattern. The light intensity decreases due to interference between the light and the main pattern light, and this phenomenon can obtain the effect of improving the resolution in order to prevent the spread of the light intensity distribution from spreading, and has been conventionally used in various fields.

  In manufacturing a phase shift mask blank for forming such a phase shift mask, a heat treatment is performed to enhance the chemical resistance of the phase shift mask blank. However, in such a heating step, there is a problem that a large amount of particles are generated inside the heating furnace. Since such particles have a relatively high heating temperature, they adhere when adhered to the phase shift mask blanks, and it is difficult to remove the adhered particles in a subsequent cleaning step.

  For this reason, there is a method of removing particles by using a chemical solution having a high cleaning effect. However, there is a problem that a chemical solution having a high cleaning effect changes the optical characteristics of the phase shift layer.

JP-A-8-272071 JP 2006-078953 A JP 2007-271720 A

  The present invention has been made in view of the above circumstances, and provides a phase shift mask blank cleaning apparatus capable of effectively removing particles and suppressing a change in optical characteristics of a phase shift layer, and a phase shift mask. An object of the present invention is to provide a method for manufacturing a shift mask blank.

That is, the apparatus for cleaning phase shift mask blanks of the present invention has the following configuration.
An apparatus for cleaning a phase shift mask blank, comprising: a transparent substrate; and a phase shift layer formed on a surface of the transparent substrate, a rotating unit configured to rotate the phase shift mask blank, and a surface of the phase shift mask blank. And an injection nozzle for injecting high-concentration ozone water having an ozone concentration of 40 ppm or more at a predetermined interval, and supplying the high-concentration ozone water having a liquid temperature in a range of 40 ° C to 60 ° C to the injection nozzle. And ozone water heating means .

  According to the phase shift mask blank cleaning apparatus having such a configuration, the high-concentration ozone water is sprayed onto the surface of the phase shift mask blank, so that even if the phase shift mask blank is heat-treated, it is present on the surface. Particles are reliably removed with strong oxidizing power. In addition, since such high-concentration ozone water hardly changes the optical characteristics of the phase shift layer as compared with other oxidizing agents, for example, high-concentration acid, the phase shift layer does not deteriorate the optical characteristics. Particles fixed on the surface of the shift mask blank can be removed.

The spray nozzle is characterized by comprising ozone water supply means for supplying the high-concentration ozone water having an ozone concentration of 79 ppm or more and 150 ppm or less.

  A nozzle moving means for scanning the spray nozzle in parallel with the surface of the phase shift mask blank is provided.

  The distance between the tip of the spray nozzle and the surface of the phase shift mask blank is set in a range of 5 mm or more and 20 mm or less.

  The phase shift layer is characterized by being composed of any of molybdenum silicide oxide, nitride, carbide, oxynitride, carbonitride and oxycarbonitride.

The method for manufacturing a phase shift mask blank of the present invention has the following configuration.
A transparent substrate, a phase shift layer formed on the surface of the transparent substrate, a method for manufacturing a phase shift mask blanks, comprising a phase shift layer forming step of forming the phase shift layer on the transparent substrate, A heating step of heating the phase shift mask blanks, and while rotating the phase shift mask blanks, an ozone concentration of 40 ppm or more and a liquid temperature of 40 ° C. or more and 60 ° C. or less with respect to the surface of the phase shift mask blanks . A cleaning step of injecting high-concentration ozone water to clean the phase shift layer.

  According to the method for manufacturing a phase shift mask blank having such a configuration, even if the phase shift mask blank has been heat-treated, the high concentration ozone water is sprayed onto the surface of the phase shift mask blank. Particles can be reliably removed with strong oxidizing power. In addition, since such high-concentration ozone water hardly changes the optical characteristics of the phase shift layer as compared with other oxidizing agents, for example, high-concentration acid, the phase shift layer does not deteriorate the optical characteristics. Particles fixed on the surface of the shift mask blank can be removed.

  According to the phase shift mask blank cleaning apparatus and the phase shift mask blank manufacturing method of the present invention, a phase shift mask capable of effectively removing particles and suppressing a change in optical characteristics of a phase shift layer. It is possible to provide a blank cleaning apparatus and a method of manufacturing a phase shift mask blank.

It is sectional drawing which shows an example of a phase shift mask blank. FIG. 3 is a cross-sectional view illustrating an example of a phase shift mask. It is a schematic diagram showing the cleaning equipment of the phase shift mask blanks of the present invention. FIG. 4 is an enlarged plan view of a main part showing the vicinity of an injection nozzle in FIG. 3. 3 is a flowchart showing a method of manufacturing a phase shift mask blank of the present invention step by step.

  Hereinafter, a phase shift mask blank cleaning apparatus and a phase shift mask blank manufacturing method according to an embodiment of the present invention will be described with reference to the drawings. The embodiments described below are specifically described for better understanding of the gist of the invention, and do not limit the invention unless otherwise specified. Also, in the drawings used in the following description, for the sake of simplicity, features of the present invention may be enlarged for convenience, for convenience, and the dimensional ratio of each component is the same as the actual size. Is not always the case.

<Phase shift mask blank cleaning equipment>
First, FIG. 1 illustrates a phase shift mask blank which is an object to be cleaned by the phase shift mask blank cleaning apparatus of the present invention.
FIG. 1 is a cross-sectional view illustrating an example of a phase shift mask blank.
The phase shift mask blank MB includes a transparent substrate 10, a phase shift layer 11 formed on one surface of the transparent substrate 10, and a light shielding layer 13 formed on the phase shift layer 11.

  As the transparent substrate 10, a material having excellent transparency and optical isotropy is used, and for example, a quartz glass substrate can be used. The size of the transparent substrate 10 is not particularly limited, and is appropriately selected according to a substrate (for example, a semiconductor substrate) to be exposed using the mask. As an example, it can be applied to a substrate having a diameter of about 100 mm, a rectangular substrate having a side of about 50 to 100 mm, and a side of 300 mm or more, and a quartz substrate having a length of 450 mm, a width of 550 mm, a thickness of 8 mm, and a maximum side dimension of 1000 mm or more. Thus, a substrate having a thickness of 10 mm or more can also be used.

  Further, the flatness of the transparent substrate 10 may be reduced by polishing the surface of the transparent substrate 10. The flatness of the transparent substrate 10 can be, for example, 20 μm or less. As a result, the depth of focus of the mask is increased, and it is possible to greatly contribute to fine and highly accurate pattern formation. Further, the smaller the flatness is 10 μm or less, the better.

  The phase shift layer 11 is mainly composed of a transition metal (for example, the transition metal is molybdenum) and silicon. Specifically, the phase shift layer 11 is an oxide, a nitride, a carbide, an oxynitride, a carbonitride, and a molybdenum silicide. It can be composed of one selected from oxycarbonitrides, and can also be composed by laminating two or more selected from these.

  The phase shift layer 11 has, for example, a thickness (for example, 60) that can give a phase difference of approximately 180 ° to any light (for example, i-line having a wavelength of 365 nm) in a wavelength region of 300 nm or more and 500 nm or less. １７０170 nm). The light-shielding layer 13 is formed with a thickness (for example, 40 nm to 200 nm) at which predetermined optical characteristics can be obtained.

  FIG. 2 is a sectional view showing a phase shift mask using the phase shift mask blanks of FIG. The phase shift mask M is obtained by forming a phase shift pattern 11A in a predetermined exposure pattern on the phase shift layer 11 described above. Such a phase shift mask M is formed by forming a resist film (not shown) on the phase shift layer 11 and exposing light including, for example, krypton-fluorine laser light (wavelength 248 nm), argon-fluorine laser light (wavelength 193 nm) and the like. Can be used to form a fine pattern using a photolithography method. Note that the exposure light may be light having an arbitrary wavelength, and is not limited.

FIG. 3 is a schematic view showing a phase shift mask blank cleaning apparatus of the present invention.
FIG. 4 is an enlarged plan view of a main part showing the vicinity of the injection nozzle of FIG.
The phase shift mask blank MB cleaning apparatus 20 (hereinafter, may be simply referred to as a cleaning apparatus) includes a housing 21, a holding mechanism 22 housed in the housing 21, an injection nozzle 23, and an injection nozzle 23. , An ozone water supply mechanism 24 for supplying high-concentration ozone water W to the injection nozzle 23, and a control unit 25 for controlling these components.

The housing 21 is, for example, a substantially cylindrical container entirely formed of stainless steel, and houses a holding mechanism 22 therein.
The holding mechanism 22 includes, for example, a stage 31 on which a rectangular phase shift mask blank MB is mounted, and rotating means 32 for rotating the stage 31, for example, a motor.

  The jet nozzle 23 jets the high-concentration ozone water W while maintaining a predetermined interval Δt (see FIG. 4) at the tip 23a of the jet nozzle 23 with respect to the surface of the phase shift mask blank MB. The predetermined interval Δt is set to, for example, 5 mm or more and 20 mm or less, and in this embodiment, 10 mm. By setting such an interval range, volatilization of dissolved ozone from the high-concentration ozone water W is suppressed, and scattering of the high-concentration ozone water W on the surface of the phase shift mask blank MB is prevented.

  A concentration meter 33 for detecting the ozone concentration is connected to the injection nozzle 23. The concentration meter 33 continuously measures the ozone concentration of the high-concentration ozone water W to be ejected, and outputs the concentration signal as a concentration signal to the control unit 25. Is output to

  The nozzle moving means 26 scans at least the tip portion of the injection nozzle 23 in parallel with the surface of the phase shift mask blank MB. Thereby, the high-concentration ozone water W is uniformly sprayed on the entire surface of the phase shift mask blank MB while maintaining a predetermined interval between the tip portion 23a of the spray nozzle 23 and the surface of the phase shift mask blank MB.

The ozone water supply mechanism 24 includes an ozone water generator 36 that generates high-concentration ozone water W, and an ozone water heater 37 that heats the generated high-concentration ozone water W.
The ozone water generator 36 generates, for example, ozone by performing a silent discharge (dielectric barrier discharge) on oxygen gas as a raw material gas, and dissolves the generated ozone to a high concentration in water to form a high-concentration ozone. Water W is generated. The method of generating ozone is not only silent discharge to oxygen gas, but also ultraviolet irradiation of short wavelength such as a mercury lamp, electrolysis of dilute sulfuric acid using a graphite electrode and a platinum electrode, or a platinum cathode and a lead dioxide anode. Various ozone generation methods can be used, such as forming a solid polymer electrolyte membrane between them and electrolyzing water.

  The high-concentration ozone water W generated by such an ozone water generator 36 has an ozone concentration in a range of 30 ppm to 150 ppm, in this embodiment, 90 ppm. Conventionally, the ozone concentration of cleaning ozone water for a phase shift mask blank, which is generated by a general ozone water generator, is about 20 ppm. However, in the present invention, ozone water having an ozone concentration higher than that of the conventional general ozone water in a range of 30 ppm to 150 ppm is used. The high-concentration ozone water in the present invention refers to ozone water having an ozone concentration of 30 ppm or more and 150 ppm or less.

The ozone water heater 37 includes, for example, a liquid tank that stores the high-concentration ozone water W generated by the ozone water generator 36, and a heating unit that heats the inside of the liquid tank. The ozone water heater 37 heats the high-concentration ozone water W generated by the ozone water generator 36 so that the liquid temperature is in a range of 40 ° C. or more and 60 ° C. or less, and in this embodiment, 50 ° C. Thereby, for example, high-concentration ozone water W (heating) having an ozone concentration of 90 ppm and a liquid temperature of 50 ° C. is formed.
The heated high-concentration ozone water W formed by the ozone water supply mechanism 24 as described above is pressure-fed to the injection nozzle 23 via a supply pump, piping, and the like.

  The control unit 25 controls the rotating unit 32 of the holding mechanism 22 and each unit of the ozone water supply mechanism 24, and includes, for example, a CPU and an interface. The controller 25 continuously monitors the ozone concentration of the high-concentration ozone water W output from the concentration meter 33 during the cleaning operation, and generates ozone water so that the ozone concentration of the high-concentration ozone water W is within a set range. The control unit 36 is controlled. It is also preferable that a temperature sensor is further added to the injection nozzle 23 to control the ozone water heater 37 so that the liquid temperature of the high-concentration ozone water W falls within a set range.

The operation and effect of the cleaning device 20 for the phase shift mask blank MB having the above configuration will be described.
The phase shift mask blank MB cleaning apparatus 20 of the present invention mounts the phase shift mask blank MB (uncleaned) to be cleaned on the stage 31 and rotates the stage 31 by the rotating means 32. Then, the ozone water supply mechanism 24 jets high-concentration ozone water W heated to 50 ° C. and having an ozone concentration of 90 ppm onto the surface of the phase shift mask blank MB. The injection flow rate of the high-concentration ozone water W may be, for example, in the range of 500 ml / min to 4000 ml / min. Further, by the scanning operation of the nozzle moving means 26, the heated high-concentration ozone water W spreads evenly over the entire surface of the phase shift mask blank MB.

  The heated high-concentration ozone water W removes particles existing on the surface of the phase shift mask blank MB that has been heat-treated in the previous process with a strong oxidizing power. By using the heated high-concentration ozone water W as a cleaning liquid, for example, even particles fixed to the surface of the phase shift mask blank MB in the heating step can be reliably removed. The heated high-concentration ozone water W hardly changes the optical characteristics of the phase shift layer 11 as compared with other oxidizing agents, for example, high-concentration acids. Particles fixed on the surface of the phase shift mask blank MB can be removed without deteriorating.

  In the above-described embodiment, the high-concentration ozone water W is heated by the ozone water heater 37 so as to be higher than the water temperature of the raw water. It may be configured to spray on the surface of the MB.

<Method of manufacturing phase shift mask blanks>
A method for manufacturing a phase shift mask blank according to the present invention will be described with reference to FIGS. FIG. 5 is a flowchart showing step by step the method for manufacturing a phase shift mask blank of the present invention.
When manufacturing a phase shift mask blank by the method for manufacturing a phase shift mask blank of the present invention, first, the phase shift layer 11 is formed on one surface of the transparent substrate 10 (phase shift layer forming step: S1).

  The phase shift layer 11 can be formed by, for example, sputtering or thin film bonding. As the transparent substrate 10, for example, a quartz glass substrate can be used. The phase shift layer 11 is mainly composed of a transition metal (for example, molybdenum is a transition metal) and silicon. Specifically, the phase shift layer 11 is an oxide, nitride, carbide, oxynitride, or carbonitride of molybdenum silicide. And one selected from oxycarbonitrides.

Next, a heat treatment is performed on the phase shift mask blank MB having the phase shift layer 11 formed on one surface of the transparent substrate 10 (heating step: S2). The heat treatment of the phase shift mask blank MB is performed, for example, in an annealing furnace in the atmosphere or in an atmosphere containing oxygen so that the phase shift mask blank MB is maintained at a temperature of 250 ° C. to 600 ° C. for 60 minutes or more. Heating may be performed. By such heating step S 2, the chemical resistance of the phase shift mask blank MB is enhanced.

  Next, the phase shift mask blank MB after the heat treatment is washed with high-concentration ozone water W (washing step: S3). In the cleaning step S3, the phase shift mask blanks MB are rotated on the stage 31 using the cleaning apparatus 20 shown in FIG. High-concentration ozone water W is sprayed over the entire surface of the MB. As the high-concentration ozone water W, for example, high-concentration ozone water heated to 50 ° C. and having an ozone concentration of 90 ppm is used.

  The particles fixed to the surface of the phase shift mask blank MB are reliably removed by washing the surface of the phase shift mask blank MB that has undergone the heating process by the injection of the high-concentration ozone water W. Then, a clean phase shift mask blank MB having no particles on its surface can be obtained.

  Next, a light-shielding layer 13 is formed on the phase-shift layer 11 of the phase-shift mask blank MB that has been cleaned by spraying the high-concentration ozone water W (light-shielding layer forming step: S4). Obtain mask blanks MB. The light shielding layer 13 can be formed by, for example, sputtering or thin film bonding. The light-shielding layer 13 may be made of Cr alone, Cr oxide, nitride, carbide, oxynitride, carbonitride, oxycarbonitride, or the like.

  After that, when the phase shift mask M is formed using the phase shift mask blank MB on which the light shielding layer 13 is formed, a desired exposure pattern is formed on the phase shift mask blank MB by the photolithography step S5. The formed phase shift pattern 11A is formed. This makes it possible to obtain a high-precision phase shift mask M from which particles have been removed and on which a desired exposure pattern has been accurately reflected.

  As described above, the embodiments of the present invention have been described with reference to the drawings. However, each of these embodiments is presented as an example, and is not intended to limit the scope of the invention. These embodiments can be implemented in other various forms, and various omissions, replacements, additions, or changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention as well as in the inventions described in the claims and their equivalents.

The effect of the present invention was verified.
In the verification, 14 heat-treated phase shift mask blanks MB (samples) formed under the same conditions as shown in FIG. 1 were prepared. Then, these samples were taken as a set of two sheets to be Examples 1 to 6 of the present invention and Comparative Example 1, and the ozone concentration and the liquid temperature of the ozone water were set as shown in “Ozone water conditions” in Table 1, and The sample was washed with ozone water under the following conditions.
Table 1 shows “transmittance and phase difference before washing”, “transmittance and phase difference after washing”, “changes in transmittance and phase difference before and after washing” and “one set of samples” in each sample. The average and the detergency of the amount of change for each sample are shown. In addition, the washability was evaluated in four grades: excellent, good, acceptable, and unacceptable.

According to the results shown in Table 1, a sample concentration of ozone in this invention Examples 1 to 6 were washed had use of high concentration ozone water 40ppm~124ppm, it was confirmed that high cleaning property. In particular, it was confirmed that Example 1 of the present invention in which the ozone concentration was set to 124 ppm and Examples 4 and 5 of the present invention in which the liquid temperature was 50 ° C. had a particularly high particle cleaning effect. On the other hand, in the sample shown in Comparative Example 1 which was washed using low-concentration ozone water having an ozone concentration of 20 ppm, the cleaning property was low and particles were not sufficiently removed.
According to the method for manufacturing a phase shift mask blank of the present invention, it was confirmed that a phase shift mask blank having few particles and little change in transmittance and phase difference can be obtained.

DESCRIPTION OF SYMBOLS 10 Transparent substrate 11 Phase shift layer 13 Light shielding layer 20 Cleaning device 21 Housing 22 Holding mechanism 23 Injection nozzle 24 Ozone water supply mechanism 25 Control part 26 Nozzle moving means 33 Densitometer MB Phase shift mask blanks W High concentration ozone water

Claims (6)

A transparent substrate, a phase shift layer formed on the surface of the transparent substrate, a phase shift mask blank cleaning apparatus having a,
A rotating means for rotating the phase shift mask blank, an injection nozzle for injecting high-concentration ozone water having an ozone concentration of 40 ppm or more while maintaining a predetermined interval with respect to the surface of the phase shift mask blank, and the injection nozzle, An ozone water heating means for supplying the high-concentration ozone water having a liquid temperature in the range of 40 ° C. or more and 60 ° C. or less, and an apparatus for cleaning phase shift mask blanks. 2. The apparatus for cleaning phase shift mask blanks according to claim 1, wherein said spray nozzle is provided with an ozone water supply means for supplying said high concentration ozone water having an ozone concentration of 79 ppm or more and 150 ppm or less. Cleaning device of the phase shift mask blank of claim 1 or 2, wherein one item, characterized in that a nozzle moving means for parallel scanning the jet nozzle to the surface of the phase shift mask blank. The space between the tip of the injection nozzle and the surface of the phase shift mask blank is set in a range of 5 mm or more and 20 mm or less, The phase shift mask blank according to any one of claims 1 to 3 , wherein Cleaning equipment. Wherein the phase shift layer is an oxide of molybdenum silicide, nitride, carbide, oxynitride, claims 1, characterized in that it is composed of one of carbon nitride and oxide carbide nitride 3 any one The apparatus for cleaning a phase shift mask blank according to any one of the preceding claims. A transparent substrate, a phase shift layer formed on the surface of the transparent substrate, a method for manufacturing a phase shift mask blanks, comprising:
A phase shift layer forming step of forming the phase shift layer on the transparent substrate,
A heating step of heating the phase shift mask blanks,
While rotating the phase shift mask blank , high-concentration ozone water having an ozone concentration of 40 ppm or more and a liquid temperature of 40 ° C. or more and 60 ° C. or less is jetted to the surface of the phase shift mask blank, And a cleaning step of cleaning the phase shift mask blanks.

Images