JP6243660B2 - Mask blank manufacturing method and transfer mask manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a mask blank that is an original of a transfer mask used for manufacturing a semiconductor device and the like, and a method for manufacturing a transfer mask.

 In general, in a manufacturing process of a semiconductor device, a fine pattern is formed using a photolithography method. Also, a number of transfer masks (usually called photomasks) are usually used for forming this fine pattern. This transfer mask is generally provided with a light-shielding fine pattern made of a metal thin film or the like on a translucent glass substrate, and the photolithographic method is also used in the production of this transfer mask.

  As the degree of integration of semiconductor circuits is improved, the size of the pattern is reduced, and the transfer mask is required to have higher accuracy. Particularly, due to the recent increase in density and accuracy of VLSI devices, the requirements for transfer masks are becoming stricter year by year. In order to increase the accuracy of the transfer mask, it is necessary to improve the quality of the mask blank, which is an original when the transfer mask is manufactured, and stabilization of the quality of the mask blank is also an important issue. .

By the way, although the said mask blank forms the thin film used as a transfer pattern on board | substrates, such as a glass substrate, the reactive sputtering method is mentioned as one of the formation methods of such a thin film. The reactive sputtering method is a method of forming a thin film by reacting sputtered particles flying from a sputtering target and a reactive gas introduced into a film formation chamber and depositing the reaction product on a substrate.
In the reactive sputtering method, the composition of the thin film, which is a reaction product, varies depending on the flying amount of the sputtered particles and the reactive gas concentration in the film forming chamber, so that the optical properties and the like of the thin film can be adjusted.

  However, the surface resistance value of the sputtering target fluctuates with a decrease in the target material or a change in the shape of the target surface. For this reason, even if reactive sputtering is repeatedly performed under the same conditions, the composition and optical properties of the formed thin film may vary. In order to manage such fluctuations, for example, the following thin film forming methods of Patent Documents 1 to 3 have been proposed.

In Patent Document 1, the plasma emission spectrum is measured at the time of plasma emission of sputtering, and the film formation rate predicted from the composition of the film formed from the spectrum and the intensity of the spectrum is predicted. Techniques for managing the properties of thin films are disclosed.
In Patent Document 2 and Patent Document 3, an optical film thickness meter is provided in a vacuum vessel of a sputtering apparatus to measure the film thickness and refractive index of an optical thin film during film formation at the same time. A method of managing is disclosed.

JP 2007-224322 A JP-A-4-176866 JP 2005-345826 A

A thin film (for example, a light-shielding film or a light semi-transmissive film) formed on the substrate of the mask blank for producing the transfer mask usually has a low transmittance and an optical density of about 3.0 or more is required.
The method of measuring the plasma emission spectrum disclosed in Patent Document 1 is not suitable for the management related to the thin film formation of the mask blank for manufacturing the transfer mask. Since the thin film of the mask blank is a thin film having a high extinction coefficient, the sputtered particles adhere to the measurement window and become noise when measuring the spectrum of the plasma light. For this reason, since the spectral intensity of plasma light cannot be measured, the flying amount of sputtering particles cannot be measured accurately. In the case of a thin film formed by reactive sputtering, the optical intensity of the thin film changes depending on the reactive gas concentration (partial pressure) in addition to the amount of particles flying from the sputtering target. Indirect management by is not sufficient.

  Further, the management method using an optical film thickness meter disclosed in Patent Document 2 and Patent Document 3 is also a method suitable for forming a thin film having a composition whose extinction coefficient is close to 0. It is not suitable for management of thin film formation of a mask blank for manufacturing a high transfer mask. If the extinction coefficient is close to 0 as in the thin film managed by the methods of Patent Documents 2 and 3, it is possible to ignore the change in the absorptance due to the thickness of the thin film, but the above mask blank having a high extinction coefficient. This is because the thin film cannot be ignored. The thin film formed on the mask blank substrate has a high extinction coefficient. For example, the extinction coefficient is 2 or more in the light-shielding film and the extinction coefficient is 0.5 or more in the light semi-transmissive film. Such factors must be taken into account. For this reason, accurate management is difficult with the methods disclosed in Patent Document 2 and Patent Document 3.

  Therefore, the present invention has been made in view of such a conventional problem, and the object of the present invention is to first accurately manage the state of a thin film formed by sputtering to stabilize the quality. It is to provide a method for manufacturing a mask blank from which a mask blank can be obtained, and secondly, to provide a method for manufacturing a transfer mask using a mask blank having a stable quality.

As a result of intensive studies to solve the above-mentioned problems, the present inventor can accurately manage the state of the formed thin film by measuring the optical characteristics and the like of the thin film immediately after the sputtering film formation in the sputtering apparatus. The present inventors have found that it is possible to quickly detect even if the optical characteristics of the formed thin film vary. The present invention has been completed as a result of intensive studies based on the obtained knowledge.
That is, in order to solve the above problems, the present invention has the following configuration.

(Configuration 1)
A method of manufacturing a mask blank having a thin film for forming a transfer pattern on a substrate, wherein the thin film is formed by a sputtering method using a single wafer sputtering apparatus, and the film is formed on the substrate in the sputtering apparatus. After forming a thin film, the optical characteristic value and substrate temperature of the thin film immediately after film formation are measured in the sputtering apparatus, and the optical characteristic of the formed thin film is evaluated based on the measurement result. A method for manufacturing a mask blank.

As in Configuration 1, by performing the evaluation of the thin film formed by sputtering immediately after the film formation, not only the evaluation of the thin film but also the environment in the film formation chamber (for example, the remaining amount of the target, the temperature, etc.) is also evaluated. be able to. The sputtering film formation is performed under film formation conditions that can obtain a predetermined optical characteristic value in advance. If the optical property value of the thin film immediately after film formation is out of the specified range, it means that the remaining amount of the target, temperature in the film formation chamber, voltage, reaction gas flow rate, etc. are out of the predetermined range. , It is possible to detect abnormality when the film is continuously formed under the same conditions. Further, when the temperature of the substrate after the sputtering film formation is abnormal, it is possible to detect an abnormality such as an overheated state in the sputtering chamber or excessive energy of the sputtering particles.
Moreover, it can suppress that a foreign material adheres to a thin film by evaluating a thin film within a sputtering device with few dust generation risks.
According to invention of the structure 1, the state of the thin film formed by sputtering method can be managed correctly, and the mask blank with stable quality can be supplied continuously.

(Configuration 2)
The sputtering apparatus includes a film formation chamber for forming the thin film on a substrate, a measurement chamber for measuring an optical characteristic value and a substrate temperature of the formed thin film, and a space between the film formation chamber and the measurement chamber. The film formation chamber, the measurement chamber, and the transfer path can all be maintained in a vacuum state, and the thin film is formed on the substrate in the film formation chamber. After film formation, the substrate is transferred from the film formation chamber to the measurement chamber through the transfer path, and the optical property value and substrate temperature of the thin film immediately after film formation are measured in the measurement chamber. A method for manufacturing a mask blank according to Configuration 1.
As in Configuration 2, after a thin film is deposited on the substrate in the vacuum deposition chamber, the substrate is transported from the deposition chamber to the measurement chamber that is also in a vacuum through a vacuum transport path. By measuring the optical characteristic value of the thin film immediately after film formation and the substrate temperature in the measurement chamber, the effect of the above configuration 1 is preferably obtained.

(Configuration 3)
The optical characteristic of the thin film formed immediately after film formation is evaluated by compensating for the variation in the optical characteristic value due to temperature to evaluate the optical characteristic of the thin film formed. Mask blank manufacturing method.
Since the temperature of the substrate immediately after film formation is increased, the optical characteristic value measured at that temperature is different from the optical characteristic value at room temperature. According to the third aspect of the invention, the data measured in the clean state immediately after the film formation is compensated for the variation factor due to temperature (the variation in the optical characteristic value due to the temperature), thereby reducing the thickness of the thin film obtained by the sputtering film formation. It becomes possible to judge the state accurately.

(Configuration 4)
4. The method of manufacturing a mask blank according to any one of configurations 1 to 3, wherein the optical characteristic value is a transmittance of a substrate on which the thin film is formed.
The thin film of the mask blank needs to have a predetermined optical density that has been set. As in Configuration 4, by measuring the transmittance of the thin film (substrate with a thin film) immediately after film formation, the optical density of the formed thin film can be managed. In addition, since the film is formed under the film forming conditions (cathode voltage, reaction gas flow rate) for forming a predetermined thin film (composition, film thickness, transmittance), the state in the film forming chamber is changed by the change in transmittance. Changes can be detected quickly.

(Configuration 5)
4. The method of manufacturing a mask blank according to any one of configurations 1 to 3, wherein the optical characteristic value is a reflectance of the thin film.
As in Configuration 5, by measuring the reflectance (front surface, back surface) of the formed thin film, the quality of the thin film can be managed from its reflection characteristics. In addition, the reflectance of a thin film formed by reactive sputtering varies depending on the composition ratio of atoms forming the thin film. By measuring the reflectance immediately after film formation, the composition of the formed thin film can be determined more accurately. In addition, film formation conditions can be adjusted based on composition information obtained from reflectance measurement.

(Configuration 6)
6. The method for manufacturing a mask blank according to any one of configurations 1 to 5, wherein film formation conditions for a subsequent thin film are controlled based on an evaluation result of optical characteristics of the thin film previously formed.
The thin film formed by the single-wafer sputtering apparatus inevitably changes its optical properties due to changes in the remaining amount of the target, the environment in the film forming chamber, etc. while the film formation is repeated. Since the film formation conditions of the subsequent thin film are controlled based on the evaluation results of the optical characteristics of the thin film previously formed, a mask blank that suppresses variations in optical characteristics even when sputtering film formation is repeated. Can be manufactured. For example, the n-th film forming condition is calculated based on the evaluation result of the m-th film (n ≧ 2, n> m, m ≧ 1) on which the thin film has been formed first, and n based on the condition The first film can be formed.

(Configuration 7)
A method for producing a transfer mask, comprising patterning the thin film of the mask blank produced by the method for producing a mask blank according to any one of Structures 1 to 6.
By producing a transfer mask using a mask blank having a stable quality obtained by the present invention, a highly accurate transfer mask can be obtained.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the mask blank which can manage the state of the thin film formed by sputtering method correctly and can obtain the mask blank with the stable quality can be provided.
In addition, according to the present invention, it is possible to provide a method for manufacturing a transfer mask that can provide a highly accurate transfer mask using a mask blank having a stable quality.

It is a schematic block diagram of the whole single wafer type sputtering apparatus. It is a block diagram of the film-forming chamber in the said sputtering apparatus. It is a block diagram of the measurement chamber in the said sputtering device. It is a graph which shows the result of the experiment example for demonstrating this invention, and shows the transmittance | permeability immediately after film-forming of a mask blank sample, and after annealing cooling. It is a graph which shows the result of the experiment example for demonstrating this invention, the transmittance | permeability immediately after film-forming of a mask blank sample and after annealing cooling, and the calculated transmittance | permeability which performed temperature compensation.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings as appropriate.
The method for manufacturing a mask blank according to the present invention is a method for manufacturing a mask blank having a thin film for forming a transfer pattern on a substrate as in the configuration 1, wherein the thin film is formed by single-wafer sputtering. After forming the thin film on the substrate in the sputtering apparatus using the apparatus, the optical property value and the substrate temperature of the thin film immediately after the film formation are measured in the sputtering apparatus, and the measurement is performed. Based on the results, the optical characteristics of the formed thin film are evaluated.

In the mask blank manufacturing method according to the present invention, a single wafer sputtering apparatus used for forming a thin film has a structure as shown in FIG.
FIG. 1 is a schematic configuration diagram of an entire single wafer sputtering apparatus. FIG. 2 is a configuration diagram of a film forming chamber in the sputtering apparatus, and FIG. 3 is a configuration diagram of a measurement chamber in the sputtering apparatus.
Note that the configuration of the sputtering apparatus shown in FIGS. 1 to 3 is merely an example, and the sputtering apparatus used in the present invention is not limited to this.

  As shown in FIG. 1, the sputtering apparatus used in the present invention has four chambers, a load lock chamber 1, a film formation chamber 2, a measurement chamber 3, and an unload lock chamber 4, radially around the transfer chamber 5. It is composed of a formed vacuum chamber. Inside the transfer chamber 5, a robot arm 12 capable of loading and unloading a substrate from each chamber to the chamber via the transfer chamber 5 is installed. The robot arm 12 is configured to be able to expand and contract around a rotation axis, and the substrate can be carried into and out of each chamber by holding the substrate in its hand.

Further, a load lock mechanism capable of always maintaining a high vacuum state in the film formation chamber 2 for performing the sputtering film formation is provided, and the substrate introduction from the load lock chamber 1 through the transfer chamber 5 to the film formation chamber 2 is performed at a constant interval. Therefore, the device configuration can be continuously performed.
The load lock chamber 1 is provided with a gate 13 that separates the load lock chamber 1 from the outside of the apparatus (atmosphere) and a gate 51 that separates the load lock chamber 1 and the transfer chamber 5. Similarly, a gate 52 for isolating the film formation chamber 2 and the transfer chamber 5 and a gate 53 for isolating the measurement chamber 3 and the transfer chamber 5 are provided. Further, the unload lock chamber 4 is provided with a gate 41 for isolating the outside of the apparatus (atmosphere) from the unload lock chamber 4 and a gate 54 for isolating the unload lock chamber 4 and the transfer chamber 5. .

  A reactive gas 8 and an inert gas 9 mixed with the reactive gas as needed are supplied into the film forming chamber 2. The supply amounts of the reactive gas 8 and the inert gas 9 are controlled by adjusting the valves 10 and 11 by the flow controller 7.

  The measurement chamber 3 includes an optical monitor 31 and a temperature monitor 32. The data of the optical monitor 31 and the temperature monitor 32 are stored in the control unit 6. The control unit 6 evaluates the state of the formed thin film (such as optical characteristics) based on the data of the optical monitor 31 and the temperature monitor 32. Based on this evaluation result, when necessary (when the quality of the formed thin film is out of a predetermined allowable range), the film forming conditions are changed with respect to the cathode power source 21 and the flow controller 7 in the film forming chamber 2. Control for.

In the sputtering apparatus configured as described above, film formation and measurement after film formation are performed as follows.
The gate 13 of the load lock chamber is opened, and the substrate is carried into the load lock chamber 1 in the atmospheric state by a robot arm (not shown) (same configuration as the robot arm 12). After the substrate is loaded, the gate 13 is closed, and the inside of the load lock chamber 1 is deaerated until a predetermined vacuum state is reached.

  When the inside of the load lock chamber 1 is in a predetermined vacuum state, the gate 51 to the transfer chamber 5 is opened, and the substrate is carried from the load lock chamber 1 into the transfer chamber 5 by the robot arm 12. The The inside of the transfer chamber 5 is in a predetermined vacuum state. Subsequently, the gate 52 between the transfer chamber 5 and the film forming chamber 2 is opened, and the substrate is carried into the film forming chamber 2 from the transfer chamber 5 by the robot arm 12. After the gate 52 is closed and the film formation chamber 2 is in a high vacuum state, sputtering film formation is performed on the substrate.

  When the film formation is completed, the gate 52 is opened, and the substrate (substrate with a thin film) is carried into the transfer chamber 5 from the film formation chamber 2 by the robot arm 12. Subsequently, the gate 53 between the transfer chamber 5 and the measurement chamber 3 is opened, and the substrate is carried into the measurement chamber 3 from the transfer chamber 5 by the robot arm 12. In the measurement chamber 3 in which the gate 53 is closed and is in a predetermined vacuum state, the optical characteristic value and the substrate temperature of the thin film immediately after film formation are measured.

  When the measurement after the film formation is completed, the gate 53 is opened, and the substrate is carried into the transfer chamber 5 from the measurement chamber 3 by the robot arm 12. Subsequently, the gate 54 between the transfer chamber 5 and the unload lock chamber 4 is opened, and the substrate is carried into the unload lock chamber 4 from the transfer chamber 5 by the robot arm 12. After the gate 54 is closed, the gate 41 to the outside is opened, and the inside of the unload lock chamber 4 is in the atmospheric state. Then, the substrate is carried out of the apparatus by a robot arm (not shown) (same configuration as the robot arm 12).

  The detailed structure of the film forming chamber 2 is shown in FIG. As shown in FIG. 2, the film forming chamber 2 has a cathode 22 and a substrate holder 25 disposed therein. A sputtering target 23 bonded to a backing plate 24 is attached to the cathode 22. The backing plate 24 is cooled directly or indirectly by a water cooling mechanism. The cathode 22, the backing plate 24, and the sputtering target 23 are electrically coupled. The substrate holder 25 is mounted with a substrate 100 for film formation.

  The film forming chamber 2 (vacuum tank) is evacuated by a vacuum pump through an exhaust port 28. After reaching the degree of vacuum that does not affect the characteristics of the film formed by the atmosphere in the film formation chamber 2, a reactive gas (sputtering gas) is introduced from the gas inlet 27, and a negative voltage is applied to the cathode 22 using the power source 21. In addition, sputtering film formation is performed. The power source 21 has an arc detection function and can monitor the discharge state during sputtering. The pressure inside the film forming chamber 2 is measured by a pressure gauge 26.

The detailed structure of the measurement chamber 3 is shown in FIG. The measurement chamber 3 includes therein a substrate holder 37, an optical property measurement unit that can measure the optical property of a thin film formed on the substrate, and a temperature measurement unit that can measure the temperature of the substrate. FIG. 3 shows a transmittance measuring means as an example of the optical characteristic measuring means.
Specifically, the transmittance measuring means is disposed at a position where the light projecting element 34 and the light receiving element 35 face each other with the substrate holder 37 interposed therebetween, and the light projecting element 34 is connected to the light source 33. With respect to the substrate with a thin film (not shown) placed on the substrate holder 37, the data of the transmittance of the thin film obtained by the light receiving element 35 is sent to the optical monitor 31, and further the control unit (control means) 6 Stored in

  Here, the case where the transmittance measuring means is provided as the optical characteristic measuring means has been shown, but for example, the embodiment may be provided with a reflectance measuring means, and both the transmittance measuring means and the reflectance measuring means may be provided. It may be a form provided. It is preferable that the reflectance measuring means can measure both the front and back surfaces of the thin film.

  Further, the temperature measuring means is specifically provided with a thermometer 36 in the vicinity of the substrate holder 37. The thermometer 36 is a non-contact type radiation thermometer, for example, and measures the temperature of the substrate surface (thin film side). The measured substrate temperature data is sent to the temperature monitor 32 and further stored in the control unit 6 in synchronization with the thin film transmittance data.

  Also, the control unit 6 shown in FIGS. 1 to 3 evaluates the state (optical characteristics and the like) of the formed thin film based on the data of the optical monitor 31 and the temperature monitor 32. For example, the optical characteristics of the thin film obtained by sputtering deposition can be accurately evaluated by compensating for the variation factor due to temperature (the variation of the optical characteristic value due to temperature) to the stored transmittance data. To do. Based on this evaluation result, when the quality of the thin film deviates from a predetermined allowable range, for example, the film formation of the next substrate is stopped and the sputtering film formation is performed on the cathode power supply 21 and the flow controller 7 in the film formation chamber 2. Processes such as changing conditions (resetting) and replacing targets are performed.

  According to the first aspect of the invention, the thin film formed by sputtering is evaluated immediately after the film formation, so that not only the evaluation of the thin film but also the environment in the film forming chamber (for example, the remaining amount of the target, the temperature, etc.) Evaluation can also be performed. The sputtering film formation is performed under film formation conditions that can obtain a predetermined optical characteristic value in advance. If the optical property value of the thin film immediately after film formation is out of the specified range, it means that the remaining amount of the target, temperature in the film formation chamber, voltage, reaction gas flow rate, etc. are out of the predetermined range. , It is possible to detect abnormality when the film is continuously formed under the same conditions. Further, when the temperature of the substrate after the sputtering film formation is abnormal, it is possible to detect an abnormality such as an overheated state in the sputtering chamber or excessive energy of the sputtering particles.

Moreover, it can suppress that a foreign material adheres to a thin film by evaluating a thin film in the same sputtering apparatus with few dust generation risks after film-forming.
As described above, according to the invention of Configuration 1, the state of the thin film formed by the sputtering method can be accurately managed, and a mask blank having a stable quality can be continuously supplied.

Further, in the present invention, as shown in FIG. 1 and the like, a sputtering apparatus used for sputtering film formation includes a film formation chamber 2 for forming a thin film on a substrate, an optical characteristic value of the formed thin film, and a substrate temperature. And a transfer chamber 5 serving as a transfer path for transferring a substrate between the film formation chamber 2 and the measurement chamber 3, and the film formation chamber 2, the measurement chamber 3, and Any of the transfer chambers 5 can be maintained in a vacuum state.
As described above, with this configuration, after a thin film is formed on the substrate in the vacuum deposition chamber 2, the substrate is also in a vacuum state from the deposition chamber 2 via the vacuum transfer chamber 5. Since it is transported to the measurement chamber 3 and the optical property value and substrate temperature of the thin film immediately after film formation can be measured in this measurement chamber 3, the effect of the invention of the above-described configuration 1 is preferably obtained.

Further, in the present invention, the optical characteristics at the room temperature of the formed thin film can be evaluated by compensating the variation of the optical characteristic value due to the temperature to the measured optical characteristic value of the thin film immediately after the film formation. .
That is, since the temperature of the substrate immediately after film formation is increased, the optical property value measured at that temperature is different from the optical property value at room temperature, but the data measured in a clean state immediately after film formation is By compensating for the variation factor due to temperature (the variation in the optical characteristic value due to temperature), it becomes possible to accurately determine the state of the thin film obtained by sputtering film formation (particularly at room temperature).

  In the present invention, any of a contact-type measurement method and a non-contact-type measurement method can be applied as the substrate temperature measurement method. When measuring the substrate temperature using a contact-type temperature measuring device, it is preferable that the measurement attachment is brought into contact with the back surface in order to prevent the substrate from being contaminated or damaged. When using a non-contact type measuring machine such as a radiation infrared thermometer, it is preferable to measure the temperature on the thin film side. In the present invention, it is more preferable to use a non-contact type measuring device in consideration of the fact that the actual thin film temperature can be measured.

As for the compensation method of the variation factor due to temperature, a coefficient (hereinafter referred to as “temperature compensation coefficient”) is derived from the change amount of the optical measurement value with respect to the temperature change amount of the standard thin film to be formed. A method of deriving the optical characteristic value of the thin film formed in a standard state (for example, normal temperature (room temperature) 23 ° C.) based on the coefficient is preferable.
As for temperature correction, a correction value may be set in advance according to the composition of the thin film to be formed. Optical characteristic values are measured several times at different temperatures, and dK / dT (K is an optical characteristic). The correction value may be calculated from the value (T is temperature).

  The optical characteristic value is, for example, the transmittance of the substrate on which a thin film is formed. The thin film on the mask blank needs to be formed to have a predetermined optical density that has been set. Therefore, the optical density of the formed thin film can be managed by measuring the transmittance of the thin film (substrate with thin film) immediately after the film formation. In addition, since the film is formed under the film forming conditions (cathode voltage, reaction gas flow rate) for forming a predetermined thin film (composition, film thickness, transmittance), the state in the film forming chamber is changed by the change in transmittance. It is also possible to quickly detect changes in

  The acquisition of the optical characteristic value by the transmittance is not limited to the case where the thin film on the mask blank is a single layer, but can also be applied to the case of a laminated structure. By measuring the transmittance to the previous layer in the stacking order, the transmittance of the layer can also be approximately derived. When the reflectance is measured simultaneously, correction may be performed in consideration of interface reflection with the previous layer, front surface reflection, back surface reflection, and the like in the stacking order.

Moreover, it is also preferable that the above optical characteristic value is, for example, the reflectance of a thin film. By measuring the reflectance of the deposited thin film, the quality of the thin film can be managed from its reflection characteristics. In addition, since the reflectivity of a thin film formed by reactive sputtering varies depending on the composition ratio of atoms forming the thin film, the composition of the formed thin film can be determined by measuring the reflectivity immediately after film formation. Can be determined more accurately. In addition, film formation conditions can be adjusted based on composition information obtained from reflectance measurement.
The acquisition of the optical property value based on the reflectance can be performed both when the thin film on the mask blank is a single layer and when it is a laminated structure.

  The measurement wavelength of the optical characteristic values such as transmittance and reflectance described above may be a single wavelength or a plurality of wavelengths. Further, a method of scanning a specific wavelength range may be used. The light source used for optical measurement is not particularly limited, and a light source having a specific wavelength such as a laser light source may be used, and has a specific wavelength range such as a deuterium lamp (D2 lamp). There may be. Preferably, in the present invention, a light source including a wavelength (for example, an ArF excimer laser wavelength of 193 nm and a KrF excimer laser wavelength of 254 nm) used as exposure light when performing pattern transfer onto a semiconductor substrate using a transfer mask is used. It is to measure using.

  As described above, in the present invention, the subsequent film formation conditions can be controlled based on the evaluation results of the optical characteristics of the previously formed thin film. It is inevitable that the optical characteristics of the thin film formed by the single-wafer sputtering apparatus gradually change due to changes in the remaining amount of the target, the environment in the film formation chamber, and the like while the film formation is repeated. The thin film to be formed is a reaction product of reactive gas and particles flying from the target. The optical properties such as transmittance and reflectance of the formed thin film are determined by the amount of reactive gas during the sputtering (reaction Varies depending on the flow rate of the reactive gas. For example, when oxygen or nitrogen is a reactive gas, the silicon or metal compound layer has a higher transmittance as the proportion of oxygen or nitrogen contained in the reaction product in the thin film increases, and the proportion of oxygen or nitrogen as lower. The transmittance is lowered. Therefore, the transmittance of the substrate on which the thin film has been previously formed is measured. If the transmittance is higher than the design reference value, the reactive gas flow rate is reduced when the sputtering is performed next. Increase the reactive gas flow rate during sputtering. The reactive gas flow rate can be controlled by PID control or PI control. In addition to controlling the reactive gas flow rate, it may be necessary to adjust the voltage of the cathode power supply in the film forming chamber.

  According to the present invention, since the film formation conditions of the subsequent thin film can be controlled based on the evaluation results of the optical characteristics of the thin film previously formed, even if the sputtering film formation is repeated, variations in the optical characteristics are prevented. A suppressed mask blank can be manufactured. For example, the n-th film forming condition is calculated based on the evaluation result of the m-th film (n ≧ 2, n> m, m ≧ 1) on which the thin film has been formed first, and n based on the condition The first film can be formed.

  If the optical measurement value is abnormal or the measured temperature deviates from the standard temperature after film formation at the stage of measuring the optical characteristic value of reflectance or transmittance, temperature compensation Needless to say, it is understood that the formed thin film is abnormal. If such an abnormality is confirmed, sputtering film formation on the next substrate may be stopped, and operations such as target replacement and resetting of conditions may be performed.

  The present invention can be applied to a mask blank having a thin film formed by a reactive sputtering method on a substrate such as a glass substrate, and is not particularly limited to the type of mask blank and transfer mask or the type of thin film. For example, it is preferably applied to a binary mask blank in which a light shielding film is formed on a mask blank substrate, or a phase shift type mask blank in which a phase shift film or a phase shift film and a light shielding film are formed on a mask blank substrate. Is done. As for the type of the thin film, it can be applied to the light-shielding film, light semi-transmissive film (phase shift film), hard mask layer, etching stopper layer, and the like formed by reactive sputtering.

  The mask blank substrate is not particularly limited as long as it is a substrate used for a transfer mask for manufacturing a semiconductor device. For example, when used for a mask blank for a binary mask or a mask blank for a phase shift type mask, it is not particularly limited as long as it has transparency with respect to the exposure wavelength to be used. A glass substrate (for example, soda lime glass, aluminosilicate glass, etc.) is used. Among these, a synthetic quartz substrate is particularly preferably used because it is highly transparent in an ArF excimer laser (wavelength 193 nm) effective for fine pattern formation or in a shorter wavelength region.

  The light shielding film may be a single layer or a plurality of layers (for example, a laminated structure of a light shielding layer and an antireflection layer). Further, when the light shielding film has a laminated structure of a light shielding layer and an antireflection layer, the light shielding layer may be composed of a plurality of layers. Further, the light semi-transmissive film (phase shift film) may be a single layer or a plurality of layers.

  As such a mask blank, for example, a binary mask blank including a light shielding film formed of a material containing chromium (Cr), or a light shielding film formed of a material containing transition metal and silicon (Si). Binary mask blank provided, binary mask blank provided with light shielding film formed of material containing tantalum (Ta), material containing silicon (Si), or material containing transition metal and silicon (Si) And a phase shift mask blank provided with the phase shift film.

Examples of the material containing chromium (Cr) include chromium alone and chromium-based materials (CrO, CrN, CrC, CrON, CrCN, CrOC, CrOCN, etc.).
As the material containing tantalum (Ta), in addition to tantalum alone, a compound of tantalum and another metal element (for example, Hf, Zr, etc.), at least one of nitrogen, oxygen, carbon, and boron in addition to tantalum A material containing two elements, specifically, a material containing TaN, TaO, TaC, TaB, TaON, TaCN, TaBN, TaCO, TaBO, TaBC, TaCON, TaBON, TaBCN, TaBCON, and the like.

  As the material containing silicon (Si), a material further containing at least one element of nitrogen, oxygen, and carbon, specifically, a silicon nitride, an oxide, a carbide, an oxynitride ( A material containing oxynitride), carbonate (carbide oxide), or carbonitride (carbonitride) is preferable.

  Moreover, as the material containing the transition metal and silicon (Si), in addition to the material containing the transition metal and silicon, the material further contains at least one element of nitrogen, oxygen and carbon in addition to the transition metal and silicon. Is mentioned. Specifically, a transition metal silicide or a material containing a transition metal silicide nitride, oxide, carbide, oxynitride, carbonate, or carbonitride is preferable. As the transition metal, molybdenum, tantalum, tungsten, titanium, chromium, hafnium, nickel, vanadium, zirconium, ruthenium, rhodium, niobium, and the like are applicable. Of these, molybdenum is particularly preferred.

The present invention also provides a method for manufacturing a transfer mask.
That is, the transfer mask manufacturing method is characterized by patterning the thin film of the mask blank manufactured by the above-described mask blank manufacturing method.
As a patterning method for the thin film on the mask blank, a photolithography method is most preferable because highly accurate patterning can be performed.
By producing a transfer mask using a mask blank having a stable quality obtained by the present invention, a highly accurate transfer mask can be obtained.

Hereinafter, the present invention will be specifically described by way of examples.
In this example, after a predetermined thin film was formed on a substrate by a sputtering method using a single wafer sputtering apparatus, the transmittance and substrate temperature of the thin film immediately after film formation were measured in the sputtering apparatus. Based on the measurement results, it is shown that the optical characteristics of the thin film formed can be evaluated by compensating the fluctuation of the optical characteristic value due to temperature to the optical characteristic value of the thin film immediately after the film formation.

A light shielding film made of CrOCN was formed on the surface of the glass substrate as follows, and a binary mask blank was produced.
A synthetic quartz substrate (size: about 152 mm × 152 mm × thickness 6.35 mm) was prepared as a glass substrate.

Next, the synthetic quartz substrate was placed in a film forming chamber in a single-wafer DC sputtering apparatus having the same configuration as that shown in FIG. 1, and the light shielding film was formed by sputtering. That is, using a Cr target, a mixed gas of argon (Ar), carbon dioxide (CO ₂ ), nitrogen (N ₂ ) and helium (He) (flow rate ratio Ar: CO ₂ : N ₂ : He = 22: 39: 6:33, pressure = 0.2 Pa), a light shielding film made of CrOCN was formed to a thickness of 45 nm. The film forming conditions for the light shielding film were set so that the optical density at a wavelength of 193 nm was about 1.9.

In this way, after forming the light shielding film, the substrate having the light shielding film was transported to the measurement chamber in the sputtering apparatus, and the transmittance for light having a wavelength of 193 nm and the substrate temperature at the time of measuring the transmittance were measured.
Next, the substrate was taken out from the sputtering apparatus, annealed at 250 ° C. and then slowly cooled to room temperature (23 ° C.), and then the transmittance of the light shielding film was measured again in a vacuum environment.

In order to derive the temperature compensation coefficient, binary mask blank samples 1 to 10 were manufactured under the same conditions as described above.
For each sample, the temperature (t ₁₎ and the transmittance of the substrate immediately after the film formation (T _1), and, after having been subjected to the annealing at room temperature 23 ℃ (t ₂₎ until the transmittance of cooled mask blank (T ₂ ), The amount of change (temperature coefficient) in transmittance per 1 ° C. of the substrate on which the thin film was formed was calculated, and the average value was taken as the temperature compensation coefficient. Table 1 shows the results of Samples 1 to 10, and FIG. 4 shows the transmittance immediately after the film formation of Samples 1 to 10 and after annealing cooling.

  As shown in Table 1 and FIG. 4, it was found that the transmittance of the light-shielding film varies with temperature.

Next, mask blank samples 11 to 15 in which a CrOCN light-shielding film was formed on a glass substrate were manufactured under the same conditions as in samples 1 to 10 above. Then, the transmittance immediately after the film formation is compensated with the temperature compensation coefficient derived above (the average value of the temperature coefficient in Table 1 (0.00173% / ° C.)), and the actual transmittance after annealing cooling. The measurement results were compared. The results are shown in Table 2 and FIG.
The transmittance after compensation of the temperature compensation coefficient was calculated by the following formula (I).
Formula (I) T ₁ − (t ₁ −23) × 0.00173

As shown in Table 2, when the calculated transmittance obtained by performing temperature compensation by predicting the room temperature as described above was compared with the transmittance measured at the room temperature after annealing cooling, the error was ± 0.004. % Range. It was confirmed that the optical measurement value measured at a high substrate temperature immediately after the film formation can be approximated to the optical property value when the room temperature is cooled after annealing by performing temperature compensation.
Therefore, the transmittance and substrate temperature of the thin film immediately after film formation are measured in the sputtering apparatus, and based on the results, the variation of the optical characteristic value due to temperature is compensated for the optical characteristic value of the thin film immediately after film formation. Thus, it is possible to accurately evaluate the optical characteristics of the deposited thin film at room temperature.

DESCRIPTION OF SYMBOLS 1 Load lock chamber 2 Deposition chamber 3 Measurement chamber 4 Unload lock chamber 5 Transfer chamber 6 Control unit 7 Flow controller 12 Robot arm 21 Cathode power source 22 Cathode 23 Sputtering target 25 Substrate holder 26 Pressure gauge 31 Optical monitor 32 Temperature monitor 33 Light source 34 Light projecting element 35 Light receiving element 36 Thermometer 100 Substrate

Claims (6)

A method of manufacturing a mask blank having a thin film for forming a transfer pattern on a substrate,
The thin film is formed by a sputtering method using a single wafer sputtering apparatus,
The single wafer sputtering apparatus includes a film formation chamber for forming the thin film on a substrate, a measurement chamber for measuring an optical characteristic value and a substrate temperature of the formed thin film, the film formation chamber, and the measurement chamber. The film forming chamber, the measurement chamber, and the transfer path can all be maintained in a vacuum state.
After depositing the thin film on the substrate in the deposition chamber , the substrate is transported from the deposition chamber to the measurement chamber through the transport path, and the optical characteristics of the thin film immediately after deposition in the measurement chamber A method of manufacturing a mask blank, comprising measuring a value and a substrate temperature, and evaluating optical characteristics of a thin film formed based on the measurement result. 2. The mask according to claim 1 , wherein the optical characteristic value of the thin film immediately after film formation is evaluated by compensating for the variation in the optical characteristic value due to temperature to evaluate the optical characteristic value of the thin film formed. Blank manufacturing method. The optical characteristic value, mask blank manufacturing method according to claim 1 or 2, wherein said thin film is a transmittance of the substrate which is formed. The optical characteristic value, mask blank manufacturing method according to claim 1 or 2, characterized in that the reflectivity of the thin film. Based on the evaluation result of the optical properties of a thin film formed above, a manufacturing method of a mask blank according to any one of claims 1 to 4, characterized in that controlling the film formation conditions of the subsequent films. Method for producing a transfer mask, which comprises patterning the thin film of the mask blank manufactured by the manufacturing method of the mask blank according to any one of claims 1 to 5.

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