JP2011129698A - Photomask manufacturing method and charged particle beam lithography system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photomask manufacturing method and a charged particle beam lithography system, which suppress a reduction in pattern dimensional accuracy by absorption of an amine compound of a resist film in blanks. <P>SOLUTION: After a chemically amplified resist film is formed on a substrate to perform a first pre-baking process, drawing is performed with charged particle beams without exposing to the atmosphere or in a state that all the amine compound absorbed into the chemically amplified resist film is substantially desorbed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a photomask used for charged particle beam writing and a charged particle beam writing apparatus.

  A charged particle beam drawing apparatus having excellent resolution is used to form a photomask for forming a circuit pattern. With such a charged particle beam drawing apparatus, a pattern drawing is performed by irradiating a charged particle beam such as an electron beam, for example, to a blank in which a Cr film (light shielding film) and a resist film are sequentially formed on a quartz glass substrate. Then, by performing development and etching, a mask pattern having a Cr light-shielding pattern is formed.

  As a resist used for forming such a photomask, a chemically amplified resist (hereinafter referred to as CAR) capable of obtaining high sensitivity with a small exposure amount is used. CAR is a resist containing, for example, an alkali-soluble resin, an acid generator, and the like. When irradiated with an electron beam or the like, the acid generator is decomposed to generate an acid, and the acid is decomposed or the crosslinking is progressed by the acid. The pattern can be formed by alkali development.

  At this time, since a very small amount of a basic substance such as an amine compound in the atmosphere is adsorbed to the resist film, the acid generated by the electron beam irradiated thereafter is deactivated, and the sensitivity of the resist film is reduced. Problems arise. Usually, a plurality of blanks formed at the same time in order to improve the coating uniformity of the resist are sequentially used for pattern drawing. Therefore, since a difference occurs in storage time, the adsorption amount varies depending on the storage time, and a PCD (Post Coating Delay) phenomenon occurs in which the sensitivity varies. As a result, the pattern dimension varies.

  Thus, for example, Patent Document 1 describes that baking is performed again within 3 hours before drawing to restore sensitivity.

Japanese Patent Laid-Open No. 11-30868

  In recent years, with the high integration of semiconductor devices, improvement in dimensional accuracy of photomask patterns is required. For example, if the pattern has a line width of 20 nm or less, even a fluctuation of 1 nm cannot be allowed. Therefore, it is necessary to further suppress the adsorption of the amine compound and further improve the dimensional accuracy.

  Therefore, an object of the present invention is to provide a photomask manufacturing method and a charged particle beam drawing apparatus capable of suppressing a decrease in pattern dimensional accuracy due to adsorption of amine compounds of a CAR film in a blank.

  The method for manufacturing a photomask of one embodiment of the present invention is characterized in that a chemically amplified resist film is formed over a substrate, prebaked, and then drawn with a charged particle beam without being exposed to the atmosphere.

  In addition, in the method for manufacturing a photomask of one embodiment of the present invention, the chemically amplified resist film is formed over the substrate, the first heat treatment is performed, and then the amine compound adsorbed on the chemically amplified resist film is removed. Drawing is performed with a charged particle beam in a state where substantially all of the desorption is performed and substantially all of the amine compound is desorbed.

In the photomask manufacturing method of one embodiment of the present invention, the amine compound is desorbed by holding the substrate in a vacuum atmosphere of 1.33 × 10 ⁻⁴ Pa or less from 5 hours or more before drawing. Can do.

  In the photomask manufacturing method of one embodiment of the present invention, the amine compound can be desorbed by performing the second heat treatment on the substrate before drawing.

  A charged particle beam lithography apparatus according to one embodiment of the present invention includes a load lock chamber for loading and unloading a substrate having a chemically amplified resist film, and an amine compound that is loaded into the substrate and adsorbed on the chemically amplified resist film. Desorption chamber for desorbing substantially all, transport chamber for transporting a substrate from which all amine compounds are substantially desorbed under vacuum, and irradiation of a charged particle beam to the substrate transported from the transport chamber And a drawing chamber for drawing.

  According to the photomask manufacturing method and the charged particle beam drawing apparatus of one embodiment of the present invention, it is possible to suppress a decrease in pattern dimensional accuracy of the photomask due to adsorption of amine compounds in the CAR film in the blank.

FIG. 10 is a cross-sectional view illustrating a manufacturing process of a photomask of one embodiment of the present invention. FIG. 10 is a cross-sectional view illustrating a manufacturing process of a photomask of one embodiment of the present invention. 6 is a flowchart illustrating a manufacturing process of a photomask of one embodiment of the present invention. FIG. 10 is a cross-sectional view illustrating a manufacturing process of a photomask of one embodiment of the present invention. FIG. 10 is a cross-sectional view illustrating a manufacturing process of a photomask of one embodiment of the present invention. 6 is a flowchart illustrating a manufacturing process of a photomask of one embodiment of the present invention. FIG. 10 is a cross-sectional view illustrating a manufacturing process of a photomask of one embodiment of the present invention. 6 is a flowchart illustrating a manufacturing process of a photomask of one embodiment of the present invention. It is a figure which shows the charged particle beam drawing apparatus of 1 aspect of this invention. It is a figure which shows the charged particle beam drawing apparatus of 1 aspect of this invention. It is a figure which shows the charged particle beam drawing apparatus of 1 aspect of this invention.

  In the photomask manufacturing method of this embodiment, after forming a CAR film on a substrate and performing a pre-bake treatment, the amine compound adsorbed on the CAR film is substantially completely desorbed without being exposed to the atmosphere. Drawing is performed with a charged particle beam in a state where substantially all of the amine compound is desorbed.

  Here, as the substrate, a substrate in which a Cr film or the like as a light shielding film is formed on quartz glass or the like normally used for a photomask is used.

  A commonly used CAR material is dissolved in a solvent (organic solvent) on such a substrate to obtain a predetermined viscosity, and then a known apparatus such as a spin coater, applicator, bar coater, spinner, curtain flow coater is used. By applying, a CAR film is formed.

  The CAR material used here is a resin that is solubilized / insolubilized in a developer by an acid, an acid generator that generates an acid by irradiation of a charged particle beam, and the generated acid is excessively diffused in the CAR film. There is no particular limitation as long as a quencher that prevents the profile from being deteriorated is included.

  As a resin that is solubilized in a developer by an acid and used as a positive resist, a phenol resin such as a novolak resin capable of alkali development or a substituted polystyrene can be used. In addition, PMMA (polymethyl methacrylate) developed with a mixed solvent of methyl isobutyl ketone and isopropyl alcohol can also be used.

  Resins that are insolubilized in acid developer and used as negative resists include alkali-developable alkyl etherified melamine resins, alkyl etherified benzoguanamine resins, alkyl etherified urea resins, alkyl ether group-containing phenolic compounds, etc. Can be used.

  Acid generators that generate acid upon irradiation with a charged particle beam include bissulfoniudiazomethanes, nitrobenzyl derivatives, polyhydroxy compounds and aliphatic or aromatic sulfonates, onium salts, sulfonylcarbonylalkanes, sulfonylcarbonyl Compounds such as diazomethanes, halogen-containing triazine compounds, oxime sulfonate compounds, and phenylsulfonyloxyphthalimides can be used.

  Quenchers that prevent the generated acid from excessively diffusing in the CAR film and degrading the pattern profile include tertiary amines, benzyl carbamates, benzoin carbamates, o-carbamoylhydroxyamines, o -Carbamoyl oximes, dithiocarbamate quaternary ammonium salts and the like can be used.

  A pre-bake process (first pre-bake process) is performed on the CAR film thus formed on the substrate. This pre-baking process is performed to remove volatile components such as a solvent in the CAR film. The pre-bake treatment conditions may be any conditions that do not affect the structure of the CAR film itself. For example, the pre-bake treatment conditions may be 10 to 20 minutes at 80 to 150 ° C. in the air or an inert gas atmosphere.

  In this way, blanks having a CAR film are formed on the substrate. A plurality of such blanks are usually formed at the same time, stored in the atmosphere, and then used for drawing. Accordingly, the drawing time differs and the storage time varies depending on the blanks. Therefore, the amine compound contained in a very small amount in the storage atmosphere (in the atmosphere) is adsorbed on the CAR film, and the amount of adsorption varies depending on the storage time. . Therefore, it is stored without being exposed to the atmosphere until drawing, or substantially all of the amine compound adsorbed on the CAR film before drawing is desorbed.

  Here, the amine compound is a compound having an amino group, and examples thereof include ammonia, primary amines, secondary amines, tertiary amines, and nitrogen-containing heterocyclic compounds.

As a method of storing without exposing to the atmosphere until drawing, blanks are placed in a storage chamber or the like that can be evacuated, for example, 1.33 × 10 ⁻⁴ Pa or less directly from the pre-baking apparatus (first pre-baking process). The method of introducing and storing in a vacuum is mentioned. The pre-bake treatment is preferably performed in a vacuum atmosphere. However, when the pre-bake treatment is performed in the air or in an inert gas atmosphere, it is necessary to evacuate immediately after introduction into a storage chamber or the like. In this way, the blank can be stored without adsorbing the amine compound.

  As a method for desorbing substantially all of the amine compound adsorbed on the CAR membrane, specifically, using a desorption chamber or by controlling the conditions in an existing apparatus under vacuum. Holding, and performing a pre-bake process (second pre-bake process). Note that the adsorption force of the amine compound after the pre-bake treatment (first pre-bake treatment) to the CAR film is relatively weak and can be easily desorbed.

Examples of the method for holding in vacuum include a method in which a blank pump is provided in a desorption chamber that is equipped with a vacuum pump or the like and can be evacuated to 1.33 × 10 ⁻⁴ Pa or less, and is held in vacuum. Even when exposed to the atmosphere for a long time (for example, 1 week to 1 month), desorption of amine compounds can be achieved by holding the blank in vacuum for 5 hours or more, preferably 12 hours or more for drawing. It becomes possible. In addition, after the pre-baking process (first pre-baking process), for example, when the exposure to the atmosphere is short, such as exposure to the atmosphere (atmosphere in which the amine-based compound exists) only during transportation, the vacuum holding time May be shorter.

  As a method for performing the pre-bake process (second pre-bake process), blanks are introduced into a desorption chamber equipped with a heating mechanism such as a hot plate and a heater, and an exhaust mechanism for exhausting the desorbed amine compound, and heated under predetermined conditions. A method is mentioned. At this time, the amine compound can be desorbed by heating at 80 to 150 ° C. for 10 to 20 minutes in a vacuum or a high purity inert gas atmosphere. Here, the high purity inert gas atmosphere refers to an inert gas atmosphere in which at least an amine compound does not exist. Note that it is not always necessary to provide a desorption chamber provided with a heating mechanism, and it is also possible to perform a heat treatment by providing a heating mechanism and a desorption mechanism in an existing apparatus.

  In this way, the desorption state of the amine compound to be desorbed can be monitored by providing an amine compound detection mechanism in the desorption chamber or the like. For example, the pH and pressure (total pressure or partial pressure of the amine compound) are monitored, and the point at which the fluctuation disappears can be regarded as a state in which substantially all of the amine compound has been desorbed. Alternatively, drawing is performed with a charged particle beam on blanks from which an amine-based compound has been desorbed under predetermined conditions, and a condition for eliminating pattern dimension variation is found experimentally. The state where the desorption treatment is performed under the conditions may be a state where substantially all of the amine compound is desorbed.

  In this manner, the amine compound is not adsorbed on the blanks, or substantially all of the amine compound adsorbed on the blanks is desorbed, and while maintaining this state, the charged particle beam is applied to the mask pattern. Draw.

  In order to maintain the state in which the amine compound is not adsorbed or the amine compound is desorbed, it is necessary to carry the blank into the drawing apparatus (drawing chamber) without exposing it to the atmosphere. However, even when the atmosphere is exposed to the atmosphere for a short time at the time of carrying in, the amine compound can be desorbed by holding the vacuum for a predetermined time before introducing the drawing apparatus (for example, in a load lock chamber).

  And after irradiating a blank with a charged particle beam and drawing a mask pattern, a photomask is formed by performing a post-baking process, development, etc.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
1A to 1C are cross-sectional views showing the photomask manufacturing process according to this embodiment, and FIG. 2 is a flowchart thereof.

  As shown in FIG. 1a, first, for example, a quartz glass substrate sub. After the Cr film 11 is formed thereon, a CAR film 12 in which an acid generator and a quencher are dispersed in a resin is applied, and prebaking treatment is performed, for example, at 130 ° C. for 10 minutes in an Ar flow by a prebaking apparatus (not shown). (Step 1-1). Blanks 10 from which volatile components such as organic solvents in the CAR film have been removed are formed by the pre-bake treatment.

After the pre-baking process, the storage chamber 22 is provided with an exhaust mechanism 21 including an exhaust pump (not shown), a pressure gauge (not shown), etc., as shown in FIG. 1B, without exposing the blank 10 to the atmosphere. (Step 1-2), and the inside of the storage chamber 22 is evacuated to 1.33 × 10 ⁻⁴ Pa or less by the exhaust mechanism 21. And the blanks 10 are stored in this state (Step 1-3). At this time, the amine compound 13 present in a very small amount in the atmosphere is not present in the storage chamber 22 and therefore is not adsorbed by the CAR film of the blank 10.

  Next, the blanks 10 stored in vacuum are introduced into a charged particle beam drawing apparatus without being exposed to the atmosphere, and drawing is performed by irradiating the charged particle beam (Step 1-4). Furthermore, a photomask is formed by performing post-baking treatment, development, and the like.

In this manner, after the pre-bake treatment, the blanks are stored without adsorbing the amine compound and used for drawing, so that it is possible to suppress a reduction in pattern dimensional accuracy of the photomask. Specifically, when stored in the air, the sensitivity variation is 1 μC / cm ² or more and the line width variation of the pattern is 1 nm or more. However, when stored in a vacuum for 1 month, the sensitivity variation is less than 1 μC / cm ^2. The variation in the line width dimension of the pattern becomes less than 1 nm, and the influence of PCD can be sufficiently suppressed. Therefore, good pattern dimensional accuracy can be obtained without managing and controlling the storage time of the substrate after applying the CAR film.

(Embodiment 2)
3A and 3B are sectional views showing the photomask manufacturing process according to this embodiment, and FIG. 4 is a flowchart thereof.

  As in the first embodiment, the blank 10 that has been pre-baked (Step 2-1) is stored in the storage case 31 as shown in FIG. 3a (Step 2-2). At this time, the atmosphere in the storage case 31 is not particularly limited, but is preferably a clean atmosphere purged with an inert gas or the like in order to prevent adhesion of dust and the like.

  The CAR film of the blank 10 stored in this way adsorbs a small amount of amine compound 13 in the atmosphere. Therefore, the amine compound is desorbed from the CAR film.

First, as shown in FIG. 3b, the blanks 10 are carried into a desorption chamber 35 having an exhaust mechanism 34 having an exhaust pump 32, a pressure gauge 33, and the like (Step 2-3). Next, the inside of the desorption chamber 35 is evacuated to 1.33 × 10 ⁻⁴ Pa or less by the exhaust mechanism 34 (Step 2-4), and the blanks 10 are held until the amine compound 13 is substantially completely desorbed (Step 2). -5).

  At this time, by monitoring the pressure gauge 33, the time when the amine compound and the like are not volatilized and the pressure fluctuation is eliminated can be set to a state in which the amine compound is substantially completely desorbed. In addition, you may monitor pH and the partial pressure of an amine compound.

  Further, the holding time may be obtained experimentally in advance. For example, drawing is performed with a charged particle beam on a blank held in vacuum for a predetermined time, and the pattern dimension is measured. Then, a holding time at which there is no variation in pattern dimensions can be obtained and used as the holding time. The holding time is preferably 5 hours or longer under normal storage conditions (for example, 1 week to 1 month in the air). More preferably, it is 12 hours or more.

  Next, the blanks 10 from which substantially all the amine compound has been desorbed is introduced into a charged particle beam drawing apparatus without being exposed to the atmosphere, and drawing is performed by irradiating the charged particle beam (Step 2-6). Furthermore, a photomask is formed by performing post-baking treatment, development, and the like.

  In this manner, after the pre-bake treatment, the amine compound adsorbed on the blanks is desorbed and used for drawing, and similarly to the first embodiment, it is possible to suppress a reduction in pattern dimensional accuracy of the photomask.

(Embodiment 3)
FIG. 5 is a sectional view showing a photomask manufacturing process according to this embodiment, and FIG. 6 is a flowchart thereof.

  As in the first embodiment, the blanks 10 subjected to the first pre-bake process (Step 3-1) are stored in the storage case 31 as in the second embodiment (Step 3-2).

  Then, in order to desorb the amine compound from the CAR film 12, first, as shown in FIG. 5, the blank 10 is provided with an exhaust mechanism 44 having an exhaust pump 42, a pressure gauge 43, and a heating mechanism 45 such as a hot plate. It is carried into the desorption chamber 46 provided (Step 3-3).

Next, the inside of the desorption chamber 46 is evacuated to 1.33 × 10 ⁻⁴ Pa or less by the exhaust mechanism 44 (Step 3-4). At this time, a vacuum is not necessarily required, and a high purity inert gas atmosphere may be used.

  Then, the blanks are heated, for example, at 130 ° C. for 10 minutes by the heating mechanism 45, and the second pre-baking process is performed (Step 3-5). In this state, the blank 10 is heated until substantially all of the amine compound is desorbed (Step 3-6).

  At this time, the pressure gauge 43 can be monitored, and the time when the amine compound does not volatilize and the pressure fluctuation disappears can be set to a state in which the amine compound is substantially completely desorbed. In addition, you may monitor pH and the partial pressure of an amine compound.

  Further, the holding time may be obtained experimentally. For example, drawing is performed with a charged particle beam on a blank heated for a predetermined time, and the pattern dimension is measured. Then, the heating time at which the pattern dimension does not fluctuate can be obtained and used as the heating time. The second pre-baking time is preferably 10 minutes or longer under normal storage conditions (for example, 1 week to 1 month in the air).

  Next, the blanks 10 from which substantially all the amine compound has been desorbed is introduced into a charged particle beam drawing apparatus without being exposed to the atmosphere, and drawing is performed by irradiating the charged particle beam (Step 3-7). Furthermore, a photomask is formed by performing post-baking treatment, development, and the like.

  In this manner, after the pre-bake treatment, the amine compound adsorbed on the blanks is desorbed and used for drawing, and similarly to the first embodiment, it is possible to suppress a reduction in pattern dimensional accuracy of the photomask.

  In these first to third embodiments, blanks are transferred from the storage chamber and the desorption chamber to the charged particle beam drawing apparatus. At this time, these chambers may be connected to the charged particle beam drawing apparatus and transferred. Specifically, as shown in FIG. 7, a load lock chamber 51 that can be evacuated for carrying in and out blanks, and a transfer chamber 52 including a transfer arm 52 a for transferring the blanks 10 in a vacuum, In a charged particle beam drawing apparatus provided with an alignment chamber 53 for performing alignment and a charged particle beam drawing chamber 54 for performing drawing on blanks, these chambers (storage chamber, By connecting the gate 57 of the desorption chamber 56 and opening the gates 55, 57, the blanks 10 can be carried into the charged particle beam drawing apparatus without being exposed to the atmosphere.

(Embodiment 4)
The present embodiment is different from the third embodiment in that a photomask is formed according to the same flow as in the third embodiment, but a charged particle beam drawing apparatus provided with a desorption chamber is used.

  As shown in FIG. 8, the charged particle beam drawing apparatus of the present embodiment includes a load lock chamber 61 that can be evacuated to carry in and out blanks, and a transport arm 62 a for transporting the blanks 10 in a vacuum. A transfer chamber 62, an alignment chamber 63 for performing alignment, and a charged particle beam drawing chamber 64 for performing drawing on blanks are provided, and an exhaust mechanism 65a and a heating mechanism are provided between the load lock chamber 61 and the transfer chamber 62. The desorption chamber 65 provided with 65b is connected.

  Using such a charged particle beam drawing apparatus, the blanks 10 are first carried into the load lock chamber 61 and conveyed to the desorption chamber 65. Next, as in the third embodiment, a pre-bake process (second pre-bake process) is performed in a vacuum or in a high-purity inert gas atmosphere. Then, the blanks 10 are transferred to the alignment chamber 63 and the charged particle beam drawing chamber 64 through the transfer chamber 62 in a state where substantially all of the amine-based compound is desorbed, and similarly drawn by irradiating the charged particle beam. I do.

  In this manner, after the pre-bake treatment, the amine compound adsorbed on the blanks is desorbed and used for drawing, and similarly to the first embodiment, it is possible to suppress a reduction in pattern dimensional accuracy of the photomask.

  As shown in FIG. 9, a heating mechanism 74 such as a hot plate may be provided in the load lock chamber 71 without newly providing a desorption chamber, and the load lock chamber 71 may have a function of the desorption chamber.

  Similarly to the present embodiment, the charged particle beam drawing apparatus may have a structure in which the storage chamber of the first embodiment and the desorption chamber of the second embodiment are installed.

  In addition, this invention is not limited to embodiment mentioned above. Various other modifications can be made without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 10 ... Blanks 11 ... Cr film 12 ... CAR film 13 ... Amine compound 21, 34, 44, 65a ... Exhaust mechanism 22 ... Storage chamber 31 ... Storage case 32, 42 ... Exhaust pump 33, 43 ... Pressure gauge 35, 46, 65 ... Desorption chamber 45, 65b, 74 ... Heating mechanism 51, 61, 71 ... Load lock chamber 52, 62 ... Transfer chamber 52a, 62a ... Transfer arm 53, 63 ... Alignment chamber 54, 64 ... Charged particle beam drawing chamber 55, 57 ... Gate 56 ... Chamber

Claims (5)

  A method for forming a photomask, comprising: forming a chemically amplified resist film on a substrate; performing a pre-bake treatment; and performing drawing with a charged particle beam without exposing to the atmosphere. After forming a chemically amplified resist film on the substrate and performing the first pre-bake treatment,
Substantially desorbing the amine compound adsorbed on the chemically amplified resist film;
2. A photomask forming method comprising performing drawing with a charged particle beam in a state where substantially all of the amine compound is desorbed. The amine compound is desorbed by holding the substrate in a vacuum atmosphere of 1.33 × 10 ⁻⁴ Pa or less from 5 hours or more before the drawing. A method for forming a photomask.   3. The method of forming a photomask according to claim 2, wherein the amine compound is desorbed by performing a second pre-bake treatment on the substrate before the drawing. A load lock chamber for loading and unloading a substrate having a chemically amplified resist film;
A desorption chamber for carrying in the substrate and desorbing substantially all of the amine compound adsorbed on the chemically amplified resist film;
A transport chamber for transporting the substrate from which substantially all of the amine compound has been desorbed, under vacuum;
A drawing chamber for performing drawing by irradiating the substrate transported from the transport chamber with a charged particle beam;
A charged particle beam drawing apparatus comprising:

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