JP4489820B2 - Phase shift mask blank manufacturing method and phase shift mask blank manufacturing apparatus - Google Patents

Description

The present invention relates to a method and apparatus for manufacturing a phase shift mask blank particularly suitable for ArF excimer laser and F ₂ excimer laser.

  In recent years, there is a contradictory relationship between the two important characteristics required for photolithography, high resolution and ensuring the depth of focus, and the practical resolution cannot be improved only by increasing the NA of the exposure apparatus lens and shortening the wavelength. (Monthly Semiconductor World 1990.12, Applied Physics, Volume 60, November (1991), etc.).

Under such circumstances, phase shift lithography is attracting attention as a next-generation photolithography technique, and a part of it has been put into practical use. Phase shift lithography is a method that improves the resolution of optical lithography by changing only the mask without changing the optical system. By providing a phase difference between the exposure light that passes through the photomask, interference between the transmitted light and each other is achieved. The resolution can be improved dramatically by using.
The phase shift mask is a mask having both light intensity information and phase information, and various types such as a Levenson type, an auxiliary pattern type, and a self-alignment type (edge enhancement type) are known. These phase shift masks have a complicated structure and require advanced techniques for manufacturing as compared with conventional photomasks having only light intensity information.

As one of the phase shift masks, a phase shift mask called a so-called halftone phase shift mask has been recently developed.
In this halftone type phase shift mask, the light semi-transmissive portion has two functions of a light shielding function for substantially blocking exposure light and a phase shift function for shifting (usually inverting) the light phase. Therefore, it is not necessary to separately form the light shielding film pattern and the phase shift film pattern, and the structure is simple and the manufacturing is easy.
In the halftone phase shift mask, the mask pattern is processed by the dry etching process. However, in the method of realizing the light shielding function and the phase shift function in separate layers, the layer having the light shielding function and the layer having the phase shift function are separated. Both require a high degree of control to obtain a good pattern shape. On the other hand, since a single etching process can be used by configuring a single-layer light semi-transmissive part having both a light shielding function and a phase shift function, the mask manufacturing process can be simplified and easily improved. It is possible to obtain a pattern shape.

  As shown in FIG. 10, the halftone phase shift mask has a light transmission part (transparent substrate exposed part) 200 that transmits light having a strength that substantially contributes to exposure through a mask pattern formed on the transparent substrate 100. And a light semi-transmissive part (light-shielding part / phase shifter part) 300 that transmits light of an intensity that does not substantially contribute to exposure (FIG. 5A) and transmits through this light semi-transmissive part. By shifting the phase of the light so that the phase of the light transmitted through the light semi-transmissive portion is substantially inverted with respect to the phase of the light transmitted through the light transmissive portion ((b) in the figure). ), The light passing through the vicinity of the boundary between the light semi-transmission part and the light transmission part and entering each other's area by the diffraction phenomenon cancels each other, and the light intensity at the boundary part becomes almost zero, and the contrast of the boundary part I.e. improve resolution Those (FIG. (C)).

  By the way, the above-described halftone phase shift mask and the light semi-transmissive portion and the light semi-transmissive film (phase shift layer) in the blank have optimum values required for both the light transmittance and the phase shift amount. Need to be. Specifically, (1) the transmittance can be adjusted in the range of 3 to 20% at the exposure wavelength of i-line, KrF excimer laser, ArF excimer laser, etc. (2) The exposure wavelength is usually 180 °. The phase angle can be adjusted to a nearby value, and (3) the inspection wavelength is 257 nm, 266 nm, 364 nm, 488 nm, etc., and usually has an inspectable transmittance of 65% or less. is necessary.

However, as the wavelength of the laser used for exposure is shortened from i-line (365 nm) or KrF excimer laser (248 nm) to ArF excimer laser (193 nm), the above-described conventional halftone phase shift mask and its manufacture are described. The following problems have arisen in the method.
That is, when mass-producing phase shift mask blanks, if there are variations in the phase angle and transmittance between the blanks and in the plane, the yield is poor, especially in mask blanks for short wavelengths such as ArF and F ₂ excimer lasers. In the conventional mask blanks for i-line and KrF excimer lasers, there is a problem that the variation in the phase angle and transmittance between the blanks and in the plane is large and the yield is poor, so that it cannot be applied as it is.
Monthly Semiconductor World 1990.12 Applied Physics Vol. 60, November (1991)

The present invention has been made under the background described above, and it is a first object to provide a manufacturing method of a phase shift mask blank having a high yield, which can reduce variations in phase angle and transmittance between blanks as much as possible. .
Another object of the present invention is to provide a method of manufacturing a phase shift mask blank having a high yield, which can reduce variations in phase angle and transmittance in the plane of the blank as much as possible.
Furthermore, a third object is to provide a phase shift mask blank manufacturing apparatus and the like that can reduce variations in phase angle and transmittance between blanks as much as possible and can manufacture with good yield.
It is a fourth object of the present invention to provide a phase shift mask blank manufacturing apparatus and the like that can reduce variations in phase angle and transmittance in the plane of the blank as much as possible and can manufacture with good yield.

  In order to achieve the above object, the present invention has the following configuration.

(Configuration 1) In a method of continuously producing a plurality of phase shift mask blanks having at least a phase shift film on a transparent substrate,
The method includes a step of continuously forming a phase shift film on a transparent substrate using a sputtering method,
The method of manufacturing a phase shift mask blank, wherein a variation in phase angle of the phase shift film between the plurality of blanks is within ± 2 °.

(Configuration 2) In a method for continuously producing a plurality of halftone phase shift mask blanks having at least a light semi-transmissive film on a transparent substrate,
The method includes a step of continuously forming a light semi-transmissive film on a transparent substrate using a sputtering method,
The halftone phase shift mask characterized in that variations in phase angle and transmittance of the light semi-transmissive film between the plurality of halftone phase shift mask blanks are within ± 2 ° and ± 4%, respectively. Blank manufacturing method.

(Configuration 3) In a method of continuously producing a plurality of photomask blanks having a thin film for forming a pattern on a transparent substrate,
The method includes a step of continuously forming the thin film on the transparent substrate using a sputtering method,
In the step of continuously forming the thin film on the transparent substrate using a sputtering method, the transparent substrate is carried into a sputtering chamber, and a thin film for forming a pattern is formed in the sputtering chamber. A series of processes in which a transparent substrate after film formation is carried out is sequentially performed on a plurality of substrates, and the film formation time is reduced by carrying in and carrying out the transparent substrate at substantially constant intervals. Including the step of making it constant between blanks,
And the photomask blank manufacturing method characterized by excluding the first to at least fifth film formation from the photomask blank obtained in the step.

(Structure 4) The manufacturing method according to Structure 3, wherein the thin film for forming the pattern is a phase shift film, and the photomask blank is a phase shift mask blank.

(Structure 5) The manufacturing method according to Structure 3, wherein the thin film for forming the pattern is a light translucent phase shift film, and the photomask blank is a halftone phase shift mask blank. Method.

(Configuration 6) In a method for producing a photomask blank having a thin film for forming at least a pattern on a transparent substrate,
A method for producing a photomask blank, wherein the thin film is formed by sputtering a target facing a position shifted from the central axis of the substrate while rotating the substrate.

(Structure 7) The manufacturing method according to Structure 6, wherein the target and the substrate are arranged so that surfaces of the substrate and the target facing each other have a predetermined angle.

(Structure 8) The manufacturing method according to Structure 6 or 7, wherein the film is formed by rotating the transparent substrate an integer number of times between the start of film formation and the end of film formation.

(Structure 9) The manufacturing method according to any one of structures 6 to 8, wherein the thin film for forming the pattern is a phase shift film, and the photomask blank is a phase shift mask blank.

(Configuration 10) The manufacturing method according to Configuration 9, wherein the in-plane variation of the phase angle of the phase shift film is within ± 2 °.

(Structure 11) The thin film for forming the pattern is a light semi-transmissive phase shift film, and the photomask blank is a halftone phase shift mask blank. The manufacturing method of crab.

(Configuration 12) The configuration 11 is characterized in that an in-plane variation in phase angle of the light semi-transmissive phase shift film is within ± 2 ° and an in-plane variation in transmittance is within ± 4%. Manufacturing method.

(Structure 13) The light translucent phase shift film is a film containing metal, silicon, and nitrogen as main components formed by sputtering a target made of metal and silicon in an atmosphere containing nitrogen. 13. The manufacturing method according to Configuration 11 or 12, wherein the light translucent phase shift film is formed so that a content of nitrogen is larger than that of silicon.

(Configuration 14) A photomask manufactured by patterning a thin film in the photomask blank according to any one of Configurations 1 to 13.

(Structure 15) A pattern transfer method, wherein pattern transfer is performed using the photomask according to Structure 14.

(Configuration 16) A load lock mechanism that introduces substrates one by one, a substrate transfer mechanism that introduces substrates from the load lock chamber to the sputtering chamber one by one at regular intervals, a sputtering chamber that forms a film on the substrate, An apparatus for manufacturing a photomask blank, comprising at least an unload lock mechanism for discharging substrates one by one from a sputtering chamber.

(Structure 17) An apparatus for manufacturing a photomask blank, comprising: a substrate mounting table having a rotation mechanism; and a target facing a position where the central axis is shifted from the central axis of the substrate.

(Structure 18) The manufacturing apparatus according to Structure 17, wherein the target and the substrate are arranged such that surfaces of the substrate and the target facing each other have a predetermined angle.

(Configuration 19) Means for detecting the rotation position of the substrate, and when the substrate comes to the same rotation angle position as when the substrate is rotated an integer number of times from when the discharge is turned on (deposition start) and when the discharge is turned on The apparatus for producing a halftone phase shift mask blank according to any one of Structures 16 to 18, further comprising means for turning off the discharge (end of film formation).

[Action]
According to the above configurations 1 and 2, the phase angle variation of the phase shift film between the phase shift mask blanks is ± 2 °, or the phase angle of the light semi-transmissive film and the transmittance are varied between the halftone phase shift mask blanks. Since they are within ± 2 ° and ± 4%, respectively, mass production and practical use of manufacturing a phase shift mask for short wavelengths such as ArF and F ₂ excimer lasers can be realized. Beyond this range, it is difficult to put the mass-production practical use of manufacturing a phase shift mask for short wavelengths such as ArF and F ₂ excimer lasers.
In the case of a KrF excimer laser, although it is practically possible at present, it is preferable that the variation in the phase angle and transmittance of the light semi-transmissive film between mask blanks is small. Is also applicable to a phase shift mask blank for KrF excimer laser.

  According to the above configurations 3 to 5, variations in film characteristics (transmittance (OD), film thickness, etc.) in the photomask blank can be suppressed, and in particular, the phase angle of the phase shift film between the phase shift mask blanks. Can produce a phase shift mask with a variation of ± 2 ° or a variation in phase angle and transmittance of the light semi-transmissive film between the halftone phase shift mask blanks within ± 2 ° and ± 4%, respectively. .

According to the configurations 6 to 12 above, in-plane variation in film characteristics (transmittance (OD), film thickness, etc.) in the photomask blank can be suppressed, and in particular, the phase shift film in the plane of the phase shift mask blank. Phase shift mask blank with a variation in phase angle of ± 2 ° or a variation of the phase angle and transmittance of the light semi-transmissive film within the plane of the halftone phase shift mask blank within ± 2 ° and ± 4%, respectively. Therefore, the practical use of a phase shift mask for a short wavelength such as ArF or F ₂ excimer laser can be realized. Beyond this range, it is difficult to put into practical use a phase shift mask for short wavelengths such as ArF and F ₂ excimer lasers.
In the case of a KrF excimer laser, although it is practically possible at present, it is preferable that the variation in the phase angle and transmittance of the light semi-transmissive film in the mask blank plane is small. The present invention can also be applied to a phase shift mask blank for a KrF excimer laser.

  According to the configuration 13, it is possible to further suppress the variation in the phase angle.

  According to the configuration 14, it is possible to obtain a photomask in which variations between masks or in a mask surface are suppressed.

  According to the above configuration 15, excellent fine pattern processing is possible.

  According to the apparatuses of the above configurations 16 to 19, it is possible to suppress variations in film characteristics (transmittance (OD), film thickness, etc.) between the blanks or in the plane in the photomask blank. Variation of phase angle of the phase shift film within the phase shift mask blank within ± 2 °, and variation of the phase angle and transmittance of the light semi-transmissive film between the halftone phase shift mask blanks or in the plane, respectively A phase shift mask blank that is within ± 2 ° and within ± 4% can be manufactured.

  The present invention will be described in detail below.

As a result of conducting research to achieve the above-mentioned objectives, the following was found.
In the halftone phase shift mask, it is functionally important that the phase angle and transmittance of the light semi-transmissive portion are adjusted to desired values. The error ranges of the phase angle and the transmittance are required to be about ± 2 ° and ± 4 °, respectively, for both blank variation (blank blank variation) and blank distribution (in-plane variation). Factors that change the phase angle and transmittance include (1) the procedure for forming a light semi-transmissive film, (2) the performance of a sputtering apparatus for forming the light semi-transmissive film, and (3) the material of the light semi-transmissive film. It is done.

(1) A film forming procedure for forming a light semi-transmissive film will be described in detail.
When the film formation time of the light semi-transmissive film is determined by the start and end of sputtering, the interval between the end of sputtering and the start of the next sputtering should be constant. Variation in phase angle and transmittance between blanks (variation between blanks) Is effective within ± 2 ° and ± 4 ° respectively (improvement of reproducibility). The sputtering phenomenon changes the temperature and surface state of the target and shield, and at the same time changes the degree of vacuum in the vacuum chamber. When intermittent sputtering is performed in which the interval from the end of sputtering to the start of the next sputtering is not constant as in the prior art, the state of the target and the shield changes every moment. As in the present invention, if the interval from the end of sputtering to the start of the next sputtering, the sputtering time, and the sputtering conditions are always constant, the fluctuations in the phase angle and transmittance are reduced after the number of manufactured sheets is 5 to 10. That is, by continuously forming a light semi-transmissive film at regular intervals and excluding the 5th to 10th sheets from the start, halftone phase shift mask blanks with little variation in phase angle and transmittance can be stably obtained. It is possible to manufacture. Specifically, it is possible to stably manufacture halftone phase shift mask blanks in which variations in phase angle and transmittance between blanks are within ± 2 ° and ± 4 °, respectively.

In order to realize this process, as shown in FIG. 1, a load lock mechanism capable of constantly maintaining a vacuum chamber (sputter chamber) for performing sputtering in a high vacuum state is provided, and the substrate is introduced from the load lock chamber to the sputter chamber. It is necessary to have a device configuration that can be continuously performed at regular intervals. For this purpose, a load lock mechanism for introducing substrates one by one is provided, and the volume of the load lock chamber can be continuously introduced from the load lock chamber to the sputtering chamber at regular intervals. Need to design to volume.
In the conventional halftone phase shift mask blank manufacturing apparatus, from the viewpoint of throughput, about 10 substrates are set in the load lock chamber (or in-line method). In this method, the volume of the load lock chamber is small. Since it is large, it takes time to make the load lock chamber have a predetermined degree of vacuum. During this time, film formation is not performed in the sputtering chamber, so that all film formation is completed and the next cassette is set in the load lock chamber. When the film is formed, the substrate is not continuously introduced into the sputtering chamber at regular intervals. In this case, a further problem is that if the substrate is not continuously introduced into the sputtering chamber at regular intervals, the film formation in the sputtering chamber will not be stable, and the first 5 to 10 blanks will have a phase angle or transmittance. There is a large variation in the interval and the yield is poor.

In FIG. 1, a load lock chamber 11 is provided with a valve 12 that isolates the load lock chamber 11 from the atmosphere, and a valve 14 that isolates the load lock chamber 11 and the sputter chamber 13. The load lock chamber 11 is a single-wafer type that can continuously introduce the substrate into the sputtering chamber described above at a predetermined interval and is designed to have a predetermined volume. The sputtering chamber 13 has a function equivalent to a vacuum chamber for performing sputtering as shown in FIG. When the substrate is introduced into the sputtering chamber 13 by a robot arm, a feeding chamber 15 may be provided between the sputtering chamber 13 and the load lock chamber 11. The robot arm 19 can move the hand 19b in the B direction in the figure by opening and closing the arm 19a in the A direction in the figure, the robot arm 19 can rotate in the C direction in the figure, and the robot arm 19 can move in the vertical direction with respect to the paper surface. It can be configured. Furthermore, an unload lock chamber 16 having the same configuration as that of the load lock chamber 11 may be added in order to improve the deposition throughput. An example of the process of forming a light semi-transmissive film on a transparent substrate will be described with reference to FIG.
1) After the valve 14 is closed, venting is performed to bring the inside of the load lock chamber 11 to atmospheric pressure.
2) Open the valve 12 and introduce a single transparent substrate into the load lock chamber 11.
3) The valve 12 is closed and the load lock chamber 11 is exhausted.
4) After the load lock chamber 11 reaches a predetermined degree of vacuum, the valve 14 is opened to move the transparent substrate to the sputtering chamber 13.
5) In the sputtering chamber 13, a light semi-transmissive film is formed using the configuration shown in FIG.
6) After the formation of the light semi-transmissive film, the valve 17 is opened and the substrate is moved to the unload lock chamber 16. At this time, the unload lock chamber 16 needs to be evacuated to a predetermined degree of vacuum.
7) After the valve 17 is closed, venting is performed to bring the unload lock chamber to atmospheric pressure.
8) Open the valve 18 and take out the substrate.
The steps 1) to 4) are completed during the period from the completion of the formation of the light semi-transmissive film in the sputtering chamber 13 to the movement of the substrate from the sputtering chamber 13 to the unload lock chamber 16, and the load lock. The next substrate is made to wait in the chamber 11. When the previous film formation is completed and the substrate is moved from the sputter chamber 13 to the unload lock chamber 6, the standby transparent substrate is moved to the sputter chamber 13, and the light semi-transmissive film is subsequently formed.
By such a process, it is possible to form a light semi-transmissive film continuously (continuously) at regular intervals except during maintenance of the apparatus.

(2) Next, the performance of the sputtering apparatus for forming the light semi-transmissive film will be described in detail. Gas pressure during sputtering to form a light semi-transmissive film, output of DC power supply for sputtering, and sputtering time directly affect the transmittance and phase angle, thus improving the accuracy of gas flow controller, DC power supply and other equipment. It is necessary to improve the accuracy of the setting signal transmitted from the controller. Since the gas pressure during sputtering is also affected by the exhaust conductance of the apparatus, a mechanism capable of accurately determining the opening of the exhaust valve and the position of the shield is also required. Specific control accuracy will be described later.
In addition, in the film containing silicon nitride, gas such as moisture generated from the inner wall of the vacuum chamber has a great influence on the optical characteristics of the film, so a pump that can exhaust the vacuum chamber sufficiently is installed and the inner wall of the vacuum chamber is baked. It is necessary to provide a mechanism that can. The degree of vacuum in the vacuum chamber is generally 2 × 10 ⁻⁵ pa or less when the film formation rate is 10 nm / min, and 1 × 10 ⁻⁵ pa or less when the film formation rate is 5 nm / min. is there.
Furthermore, in order to keep the distribution of the phase angle and transmittance in the blanks (in-plane variation) within ± 2 ° and ± 4 °, respectively, the film is formed while the transparent substrate is rotated and the film is formed from the start of the film formation. It is necessary to perform film formation by rotating the transparent substrate an integer number of times until the film is completed. For this purpose, for example, a sensor that detects the rotation angle position of the substrate detects the substrate rotation angle position when the discharge is turned on (deposition start), and the sensor rotates the substrate an integer number of times to discharge. It is necessary to provide a mechanism for turning off the discharge (end of film formation) when the substrate comes to the same rotation angle position as when turning on.

The in-plane distribution of the phase angle and transmittance also varies depending on the positional relationship between the substrate and the target. The positional relationship between the target and the substrate will be described with reference to FIG.
The offset distance (the distance between the central axis of the substrate and the straight line passing through the center of the target and parallel to the central axis of the substrate) is adjusted by the area where the distribution of the phase angle and the transmittance should be ensured. Generally, when the area where the distribution should be secured is large, the necessary offset distance becomes large. As in this embodiment, in order to realize a phase angle distribution within ± 2 ° and a transmittance distribution within ± 4 ° within a 152 mm square substrate, the offset distance needs to be about 200 mm to 350 mm, and the preferred offset distance is 240 mm to 280 mm.
The optimum range of the target-substrate vertical distance (T / S) varies depending on the offset distance, but in order to achieve a phase angle distribution within ± 2 ° and a transmittance distribution within ± 4 ° within a 152 mm square substrate, The target-substrate vertical distance (T / S) needs to be about 200 mm to 380 mm, and the preferable T / S is 210 mm to 300 mm.
The target inclination angle affects the film formation speed. In order to obtain a large film formation speed, the target inclination angle is suitably from 0 ° to 45 °, and the preferred target inclination angle is from 10 ° to 30 °.
FIG. 9 shows the upper limit of T / S and the lower limit of T / S that can realize a phase angle distribution within ± 2 ° and a transmittance distribution within ± 4 ° in a 152 mm square substrate when the offset distance is changed.

(3) Next, the influence of the material of the light semi-transmissive film on the phase angle and the transmittance will be described in detail. The phase angle and transmittance of the light semi-transmissive film vary depending on the deposition rate and the degree of nitridation. The deposition rate and the degree of nitridation are affected by the nitrogen partial pressure during sputtering. However, when the light semi-transmissive film is completely nitrided, the influence of the nitrogen partial pressure during sputtering is small. In the nitrided metal silicide film, by adjusting the flow rate of nitrogen introduced during sputtering so that the nitrogen content measured by ESCA is greater than that of silicon, the influence of fluctuations in nitrogen partial pressure on optical characteristics is reduced. It is possible. If this method is used, the in-plane distribution of the phase angle and the transmittance can be reduced at the same time. Note that when oxygen is added simultaneously with nitrogen during sputtering, the phase angle and transmittance are greatly affected by fluctuations in the flow rate of oxygen. Can be reduced.

Note that the photomask blank in the configuration of the present invention refers to, for example, a light shielding film (chromium or chromium compound containing oxygen, nitrogen, carbon, etc. in chromium, other chromium compounds, etc.) and a phase shift in a phase shift mask blank in the photomask. Includes membranes.
Further, in the phase shift mask blank in the configuration of the present invention, not only the halftone phase shift mask blank but also the variation in phase angle is within ± 2 °, for example, Levenson type, auxiliary pattern type, self-alignment The present invention can also be applied to blanks for manufacturing other phase shift masks such as a mold (edge enhancement type).

(Example)
Hereinafter, examples of the present invention will be described in more detail.
Using the DC magnetron sputtering apparatus described with reference to FIG. 1, 200 halftone phase shift mask blanks for ArF excimer laser (193 nm) were successively formed at regular intervals.
Specifically, using a mixed target of molybdenum (Mo) and silicon (Si) (Mo: Si = 8: 92 mol%), a mixed gas atmosphere (Ar: N) of argon (Ar) and nitrogen (N ₂ ). ₂ = 10%: 90%, pressure: 0.1 Pa) A thin film of molybdenum and silicon (MoSiN) (film thickness of about 670 Å) is formed on the transparent substrate by reactive sputtering (DC sputtering). Thus, a phase shift mask blank (film composition: Mo: Si: N = 7: 45: 48) for ArF excimer laser (wavelength 193 nm) was obtained.

Here, the sputtering chamber 3 in the DC magnetron sputtering apparatus shown in FIG. 1 has a vacuum chamber 1 as shown in FIG. 2, and a magnetron cathode 2 and a substrate holder 3 are arranged inside the vacuum chamber 1. ing. A sputtering target 5 bonded to a backing plate 4 is attached to the magnetron cathode 2. In the embodiment, oxygen-free steel is used for the backing plate 4, and indium is used for bonding the sputtering target 5 and the backing plate 4. The backing plate 4 is cooled directly or indirectly by a water cooling mechanism. The magnetron cathode 2, the backing plate 4, and the sputtering target 5 are electrically coupled. A transparent substrate 6 is attached to the substrate holder 3.
In the present embodiment, the target and the substrate are arranged so that the sputtering target 5 and the substrate 6 in FIG. 2 have a predetermined angle between the opposing surfaces of the substrate and the target, as shown in FIG. The device of the configuration was used. In this case, the offset distance between the sputtering target and the substrate was 340 mm, the target-substrate vertical distance (T / S) was 380 mm, and the target tilt angle was 15 °.
The vacuum chamber 1 is exhausted by a vacuum pump through an exhaust port 7. After reaching a degree of vacuum that does not affect the characteristics of the film formed by the atmosphere in the vacuum chamber, a mixed gas containing nitrogen is introduced from the gas inlet 8 and a negative voltage is applied to the magnetron cathode 2 using the DC power source 9. Sputtering is performed. The DC power source 9 has an arc detection function and can monitor the discharge state during sputtering. The pressure inside the vacuum chamber 1 is measured by a pressure gauge 10.
The transmittance of the light semi-transmissive film formed on the transparent substrate is adjusted by the type and mixing ratio of the gas introduced from the gas inlet 8. If the mixed gas is argon and nitrogen, the transmittance increases by increasing the ratio of nitrogen. If a desired transmittance cannot be obtained simply by adjusting the ratio of nitrogen, the transmittance can be further increased by adding oxygen to a mixed gas containing nitrogen.
The phase angle of the light semitransmissive film was adjusted by the sputtering time, and the phase angle at the exposure wavelength was adjusted to about 180 °.

Evaluation of variation between blanks About 200 phase shift mask blanks (size: 15.2 cm square) obtained above, the variation between blanks in the phase angle and transmittance was examined. The result is shown in FIG.
From FIG. 3, it can be seen that halftone phase shift mask blanks with phase angle and transmittance variations between blanks within ± 2 ° and within ± 4 ° can be stably manufactured in the third and subsequent sheets. In addition, it was confirmed that the variation between the blanks of the phase angle and the transmittance was within ± 2 ° and ± 4 °, respectively, from the 11th sheet to the 200th sheet. In this case, the yield is 100% with respect to the phase angle and the transmittance.

In Example 1, 200 blanks were produced in the same manner as in Example 1 except that the sputtering chamber was opened for maintenance in the middle (190th sheet), and the phase angle and transmittance variation among the blanks were examined. . The result is shown in FIG.
From FIG. 4, when the apparatus of the present invention is used, the variation between the blanks of the phase angle and the transmittance is within ± 2 ° and within ± 4 °, respectively, except for the first few and five immediately after opening the sputtering chamber. It can be seen that halftone phase shift mask blanks can be manufactured stably and the yield is 100% with respect to phase angle and transmittance.

  In addition, halftone phase shift mask blanks were manufactured using a method of setting about 10 substrates in a conventional load lock chamber and an in-line manufacturing apparatus. In either case, the blanks of phase angle and transmittance were used. It was difficult to keep the variations within ± 2 ° and ± 4 °, respectively, and the yield was also poor.

In Example 1, the film was formed while rotating the transparent substrate, and the film was formed by rotating the transparent substrate an integer number of times between the start of film formation and the end of film formation. The in-plane variation was investigated.
As a result, it was confirmed that halftone phase shift mask blanks having in-plane variations in phase angle and transmittance within ± 2 ° and ± 4 °, respectively, could be manufactured stably.

Furthermore, in the said Example, the following thing was understood.
As shown in FIG. 5, in order to suppress the variation in the phase angle within the range of about 180 ° to about 172 °, the power of the DC power source is set to about 1.77 kW to about 1.825 kW (the variation in the phase angle is reduced). It can be seen that it is necessary to control in the range of about 1.82 kW to about 1.81 kW) in order to keep it in the range of about 180 ° to about 178 °. Therefore, it is necessary to suppress the fluctuation of the power of the DC power source to the center value ± 0.5%.
Similarly, in order to suppress variations in phase angle and transmittance from FIG. 6, the film formation time is about 560 seconds to about 615 seconds (preferably in order to suppress phase angle variations in the range of about 180 ° to about 178 °. It can be seen that it is necessary to control within the range of about 600 seconds to about 594 seconds. Therefore, it is necessary to suppress the fluctuation of the film formation time to the center value ± 0.5%.
Similarly, in order to suppress the variation in phase angle from FIG. 7 and to adjust the nitrogen flow rate introduced during sputtering so that the nitrogen content measured by ESCA in the nitrided metal silicide film is larger than that of silicon. Therefore, in order to reduce the influence of the fluctuation of the nitrogen partial pressure on the optical characteristics, the nitrogen flow rate is about 35 sccm or more (preferably about 35 sccm to about 178 ° in order to suppress the variation in the phase angle within the range of about 180 ° to about 178 °. It can be seen that it is necessary to control within the range of 35.5 sccm).
Note that the nitrogen flow rate that can reduce the influence of the fluctuation of the nitrogen partial pressure on the optical characteristics varies depending on the exhaust performance of the apparatus and the DC power.

Evaluation of in-plane variation For one of the phase shift mask blanks obtained above, the in-plane phase angle and transmittance variation were examined.
As a result, the variation in the phase angle was within ± 0.8 ° (average value 179.5 °, range 178.8 ° to 180.3 °) in the 132 mm square range excluding the substrate peripheral portion 10 mm. Further, the variation in transmittance was within ± 1.3% (average value 6.16%, range 6.08% to 6.23%).
For comparison, when film formation is performed at an offset distance of 340 mm, a target-substrate vertical distance (T / S) of 400 mm, and a target tilt angle of 15 °, the phase angle variation is ± 3.5 ° (average value 178). .8 °, range 175.3 ° to 181.7 °). Further, the transmittance variation was ± 8% (average value 6.07%, range 5.83% to 6.56%).
Furthermore, for comparison, when the target is disposed at a position facing the substrate (offset distance 0 mm, target tilt angle 0 °), the phase angle variation is ± 2.7 ° at a target diameter of 16 inches φ ( The average value was 179.8 °, and the range was 177.1 ° to 182.0 °. Further, the transmittance variation was ± 4.2% (average value 6.19%, range 6.00% to 6.45%).
The larger the offset distance, the easier it is to reduce the in-plane variation. However, if the offset distance is too large, the capacity of the vacuum chamber increases, so that the performance of evacuation deteriorates and the film formation rate also decreases.
The in-plane variation was evaluated based on whether both the highest point (plus part) and the lowest point (minus part) with respect to the average value (center value) were within the specified range.

Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the above embodiments.
For example, although molybdenum is used as a metal constituting the light semi-transmissive film, the present invention is not limited to this, and zirconium, titanium, vanadium, niobium, tantalum, tungsten, nickel, palladium, or the like can be used.
Further, although a target made of molybdenum and silicon is used as a target containing metal and silicon, the present invention is not limited to this. In the target containing metal and silicon, molybdenum has high controllability of transmittance and high get density in the evening when using a sputtering target containing metal and silicon, and reduces particles in the film. It is excellent in that it can. Titanium, vanadium, and niobium have excellent durability against alkaline solutions, but are slightly inferior to molybdenum in target density. Tantalum is superior in durability to alkaline solutions and target density, but slightly inferior to molybdenum in controllability of transmittance. Tungsten has similar properties to molybdenum, but is slightly inferior to molybdenum in the discharge characteristics during sputtering. Nickel and palladium are excellent in terms of optical properties and durability against alkaline solutions, but are somewhat difficult to dry etch. Zirconium is excellent in durability against an alkaline solution, but is inferior to molybdenum in target density, and dry etching is somewhat difficult. Taking these into account, molybdenum is currently most preferred. The nitrided molybdenum and silicon (MoSiN) thin film (light semi-transmissive film) is preferably molybdenum from the viewpoint of excellent chemical resistance such as acid resistance and alkali resistance.

In addition, in order to obtain a thin film having a composition that satisfies various characteristics as a phase shift mass while ensuring discharge stability during film formation, a target containing 70 to 95 mol% of silicon and a metal is included. It is preferable to form a light semi-transmissive film containing nitrogen, metal, and silicon by performing DC magnetron sputtering in an atmosphere.
This is because when the silicon content in the target is more than 95 mol%, in DC sputtering, it becomes difficult to apply a voltage on the target surface (erosion part) (it becomes difficult for electricity to pass), so that the discharge becomes unstable. This is because if it is less than 70 mol%, a film constituting the light semi-transmissive portion having a high light transmittance cannot be obtained.
In addition, the discharge stability is further improved by the combination of nitrogen gas and DC sputtering.
The discharge stability during film formation also affects the film quality. If the discharge stability is excellent, a light semi-transmissive film with good film quality can be obtained.

(The invention's effect)
As described above, according to the present invention, a variation in phase angle and transmittance between blanks can be reduced as much as possible, and a method for manufacturing a phase shift mask blank with a high yield can be provided.
In addition, it is possible to provide a method of manufacturing a phase shift mask blank with a high yield, which can reduce variations in phase angle and transmittance in the plane of the blank as much as possible.
Furthermore, it is possible to provide a phase shift mask blank manufacturing apparatus that can reduce variations in phase angle and transmittance between blanks as much as possible, and can manufacture with good yield.
In addition, it is possible to provide a phase shift mask blank manufacturing apparatus that can reduce variations in the phase angle and transmittance in the plane of the blank as much as possible, and can manufacture with good yield.

It is a figure for demonstrating the transfer principle of a halftone type phase shift mask. It is a schematic diagram of the sputtering chamber in the DC magnetron sputtering apparatus used in the examples. It is a figure which shows the dispersion | variation in the phase angle between the blanks in an Example, and the transmittance | permeability. It is a figure which shows the dispersion | variation in the phase angle between the blanks in another Example, and the transmittance | permeability. It is a figure which shows the relationship between DC electric power and a phase angle. It is a figure which shows the relationship between film-forming time, a phase angle, and the transmittance | permeability. It is a figure which shows the relationship between a nitrogen flow rate and a phase angle. It is a schematic diagram for demonstrating the positional relationship of a target and a board | substrate. It is a figure which shows the upper limit of T / S and the lower limit of T / S which can implement | achieve a phase angle distribution within +/- 2 degree and transmittance | permeability distribution within +/- 4 degree, when changing an offset distance. It is a schematic diagram for demonstrating the sputtering device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Magnetron cathode 3 Substrate holder 4 Backing plate 5 Sputtering target 6 Transparent substrate 6a The part holding a transparent substrate 7 Exhaust port 8 Gas introduction port 9 DC power supply 10 Pressure gauge 10
DESCRIPTION OF SYMBOLS 11 Load lock chamber 12 Valve 13 Spatter chamber 14 Valve 15 Feeding chamber 16 Unload lock chamber 17 Valve 18 Valve 19 Robot arm 100 Transparent substrate 200 Light transmission part 300 Light semi-transmission part

Claims (11)

In a manufacturing method by a DC magnetron sputtering method of a photomask blank having at least a thin film for forming a pattern on a transparent substrate,
Rotate the film-forming surface consisting of the plane of the substrate upward on a horizontal plane,
The thin film is deposited by sputtering a single target that is inclined and opposed to the deposition surface, and the transparent substrate is rotated an integer number of times between the start of discharge and the stop of discharge. A method for producing a photomask blank, comprising performing film formation. By detecting the rotation angle position of the substrate at the time of starting discharge and starting film formation, and stopping the discharge when the substrate is at the same rotation angle position after the substrate is rotated, The manufacturing method according to claim 1, wherein the rotation of the substrate from the start to the end is an integer number of times. The manufacturing method according to claim 1, wherein the target has an inclination angle of 45 degrees or less. The manufacturing method according to claim 1, wherein the target is located at a position where a straight line passing through the center of the substrate and parallel to the central axis of the substrate is shifted. . The manufacturing method according to claim 1, wherein a central axis of the substrate is at a position not passing through the target. The thin film for forming the pattern is a light semi-transmissive phase shift film, the photomask blank is a halftone phase shift mask blank,
The manufacturing method according to claim 1, wherein the single target includes 70 to 95 mol% of silicon and a metal. The thin film for forming the pattern is a light semi-transmissive phase shift film, the photomask blank is a halftone phase shift mask blank,
The light semi-transmissive phase shift film is a film containing metal, silicon, and nitrogen as main components formed by sputtering a target made of metal and silicon in an atmosphere containing nitrogen, and the light semi-transmissive The method according to claim 1, wherein the nitrogen content in the phase shift film is greater than that of silicon. The manufacturing method according to claim 1, wherein the substrate rotates on a horizontal plane with the substrate center as an axis. In a method for continuously manufacturing a plurality of photomask blanks having a thin film for forming a pattern on a transparent substrate, the method includes: forming the thin film on the transparent substrate one by one using a sputtering method. Including a step of continuously forming a film, wherein the thin film is continuously formed on the transparent substrate using a sputtering method, wherein the transparent substrate is carried into a sputtering chamber and a pattern is formed in the sputtering chamber. A series of processes in which a thin film is formed and a transparent substrate after film formation is carried out from the sputtering chamber is sequentially performed on a plurality of substrates, and the loading and unloading of the transparent substrate are performed at substantially constant intervals. The manufacturing method according to claim 1, further comprising a step of making the film formation time constant between a plurality of blanks.   The manufacturing method according to claim 9, wherein an interval from the end of sputtering to the start of sputtering for the next transparent substrate is made constant. A pattern transfer method using a photomask manufactured by the method for manufacturing a photomask blank according to claim 1 .

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