JP2011099956A - Method and apparatus for baking resist - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for baking a resist, for reducing the time required for baking and enhancing the process ability while preventing coating defects such as coating irregularity and foaming, in baking (PAB: post applied bake) after application of a resist in the manufacture of a photomask. <P>SOLUTION: When heating and drying a resist film 2 after applying the resist on a photomask substrate 1, heating is carried out by a hot plate 10 to the lower face of the substrate and by near IR rays K2 to a light-shielding layer or a halftone layer 1b on the upper face of the substrate. The apparatus includes a hot plate that mounts a substrate and heats the lower face of the photomask, and a near IR source unit 20 that heats the upper face of the substrate from the upside of the substrate. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to coating film baking in photomask manufacturing, and in particular, resist baking that can reduce the time required for baking and improve process capability without causing coating defects such as coating unevenness and foaming. The present invention relates to a method and a baking apparatus.

  In the manufacture of photomasks and semiconductor devices, hot-air circulating ovens have been used as post-applied baking (PAB) to heat and dry the coating film after applying an electron beam resist or photoresist. Many have been used. Heat drying using this oven is performed in a batch mode (simultaneous processing of a plurality of sheets) because it takes 30 to 60 minutes for the substrate temperature to rise to a desired temperature.

  In the batch system using an oven, there are many defects due to cross contamination, and there are many variations in quality between substrates. In recent years, hot plates for heating a substrate from the back side have been used, and many of the above problems have been solved.

When this hot plate is used, in order to heat the substrate placed on the hot plate from the back surface, if the substrate has a large heat capacity or / and the substrate has a low thermal conductivity, the surface of the substrate It takes a certain amount of time to heat the resist in (1).
In particular, when the substrate is a silicon wafer for manufacturing a semiconductor device, the thickness of the substrate is 0.5 to 0.8 mm. For example, a 200 mm wafer has a heat capacity of about 40 J / K and is relatively small. I can say that. The thermal conductivity is about 168 W / mK, which can be said to be relatively high. Therefore, the corresponding time until the resist on the surface of the substrate is heated is 30 seconds or less, which is not a problem.

  On the other hand, when the substrate is a quartz substrate manufactured by a photomask, for example, a 6-inch substrate has a thickness of about 6.35 mm, a length of 15.2 cm, and a width of about 15.2 cm. Therefore, the heat capacity is about 320 J / K. There are relatively large ones. That is, the heat capacity of the quartz substrate is about 8 times the heat capacity of the silicon wafer.

Further, the thermal conductivity of the quartz substrate is about 1.5 W / mK, which can be said to be relatively low. That is, the thermal conductivity of the quartz substrate is about 1/100 times that of the silicon wafer.
Therefore, the corresponding time until the resist applied on the surface of the substrate is heated is about 5 to 10 minutes.

For this reason, in the process of forming the resist coating film on the substrate, the time required for baking after coating limits the process time for forming the coating film, and the process capability of forming the coating film decreases. There is.
The problem that the process capability is lowered is the same in post-exposure baking (PEB: Post Exposure Bake) in which the resist after exposure to the resist is heated.

  As a method of shortening the time required for baking and improving the process capability when using this hot plate, for example, an upper heater is provided above the hot plate on which the substrate is placed, and the atmosphere in the chamber (nitrogen or air) There has been proposed a method of heating the substrate or heating it to flow on the substrate surface. Certainly, according to this method, the process capability is improved by, for example, about 10%.

  However, in the method of providing the upper heater, the outermost surface of the resist is directly heated, so that the outermost surface is dried while the volatilization of the solvent inside the resist is insufficient, and coating defects such as coating unevenness and foaming may occur. In addition, since the solvent remains in the resist after baking, there is a problem in that development failure and dry etching resistance decrease are caused in a later process.

Japanese Patent Publication No. 61-53632

  The present invention has been made to solve the above-described problems. In photomask manufacturing using a quartz substrate, the coating film after coating a resist is heated and dried by baking after coating (PAB). An object of the present invention is to provide a resist baking method and a baking apparatus capable of reducing the time required for baking and improving the process capability without causing coating defects such as coating unevenness and foaming.

  The present invention provides a lower surface of the photomask substrate by a hot plate on which the photomask substrate is placed in drying of the coating film in which a resist is coated on a photomask substrate provided with a light shielding layer or a halftone layer on a transparent substrate. And baking with a near infrared ray from the upper surface of the photomask substrate.

  Further, the present invention is a resist baking method according to the above invention, wherein the light shielding layer or the halftone layer is a metal, an alloy, or a main component containing any one of Cr, Si, Mo, Ta, Zr, Al, and Hf. A resist baking method characterized by being a metal oxide or a metal nitride.

  Further, the present invention provides a hot plate for placing the photomask substrate and heating the lower surface of the photomask substrate, and heating the lower surface of the photomask substrate in the heat drying of the coating film after applying a resist on the photomask substrate. A resist baking apparatus comprising a near-infrared light source unit for heating a resist coating film on a photomask substrate from above.

  The present invention provides a method for heating and drying a coating film after applying a resist on a photomask substrate, heating the lower surface of the photomask substrate with a hot plate, and a photomask substrate from above the hot plate on which the photomask substrate is placed. Since the light-shielding layer or halftone layer provided on the upper surface is heated by near infrared rays, the baking time is shortened without causing coating defects such as coating unevenness and foaming in baking after coating (PAB). Thus, the resist baking method can improve the process capability.

  Further, according to the present invention, the light shielding layer or the halftone layer is a metal, an alloy, a metal oxide, or a metal nitride containing Cr, Si, Mo, Ta, Zr, Al, or Hf as a main component. Therefore, it is possible to cope with various photomask substrates.

Further, the present invention provides a hot plate for placing the photomask substrate and heating the lower surface of the photomask substrate, and heating the lower surface of the photomask substrate in the heat drying of the coating film after applying a resist on the photomask substrate. Since it is a resist baking apparatus provided with a near-infrared light source unit that heats the upper surface of the photomask substrate from above, in baking after coating (PAB),
The resist baking apparatus can reduce the time required for baking and improve the process capability without causing coating defects such as coating unevenness and foaming.

It is sectional drawing which shows the outline of an example of the baking apparatus of the resist by this invention. It is the elements on larger scale of the photomask substrate and resist coating film which are shown in FIG. It is sectional drawing explaining the baking method of the resist by this invention. It is explanatory drawing of the specific example showing the relationship between a heating time and a substrate temperature at the time of using the conventional resist baking method. It is explanatory drawing of the specific example showing the relationship between heating time and a substrate temperature in the baking method of the resist by this invention. This shows the uniformity of temperature distribution on the quartz substrate when a conventional resist baking method is used. 4 shows the uniformity of temperature distribution on a quartz substrate in the resist baking method according to the present invention.

Embodiments of the present invention will be described below.
FIG. 1 is a sectional view schematically showing an example of a resist baking apparatus according to the present invention. As shown in FIG. 1, the resist baking apparatus includes a hot plate (10) for placing a photomask substrate and heating the lower surface of the photomask substrate, and a photomask substrate provided above the hot plate. A near-infrared light source unit (20) that heats the upper surface from above, a bake chamber (30) that houses the hot plate and the near-infrared light source unit, and an intake port (40) and an exhaust port (50) provided on the upper surface of the bake chamber It is configured.

FIG. 1 shows a state in which the photomask substrate (1) is placed on the hot plate (10). A resist coating film (2) is provided on the upper surface of the photomask substrate (1). The near-infrared light source unit (20) includes an infrared lamp (21), a wavelength selection filter (22) that transmits near-infrared light, and a housing (23). The near-infrared light source unit (20) irradiates the upper surface of the photomask substrate (1) with only the near-infrared light out of the light emitted from the infrared lamp (21) through the wavelength selection filter (22) and heats it.
An intake port (40) and an exhaust port (50) are provided on the upper surface of the bake chamber (30) to ventilate the atmosphere (nitrogen or air) in the chamber.

  FIG. 2 is a partially enlarged view of the photomask substrate (1) and the resist coating film (2) shown in FIG. As shown in FIG. 2, the photomask substrate (1) has a light shielding layer or a halftone layer (1b) provided on the upper surface of a quartz substrate (1a). A resist coating film (2) is provided on the upper surface of the photomask substrate (1).

  FIG. 3 is a cross-sectional view for explaining a resist baking method according to the present invention. Since the resist coating film (2) shown in FIG. 3 is a coating film immediately after the resist is applied and the solvent is not volatilized, by heating the resist coating film (2), the coating film is heated and dried. That is, baking (PAB) after application is performed.

  As shown in FIG. 3, the photomask substrate (1) is heated by heating (K1) on the lower surface of the photomask substrate (quartz substrate (1a)) with the hot plate (10) and above the hot plate (10). Heating (K2) by near infrared rays irradiated from the near infrared light source unit (20) is performed. Heating (K1) by the hot plate (10) is conducted by heat conduction (D2) of the quartz substrate (1a) to the resist coating film (2) through the light shielding layer or halftone layer (1b) (D2). The resist coating film (2) is heated.

  Also, heating (K2) by near infrared rays directly heats the light shielding layer or halftone layer (1b), and the heat generated by the heated light shielding layer or halftone layer (1b) is applied to the resist coating film (2). The resist coating film (2) is heated by heat conduction (D3).

  Thus, the heating of the resist coating film (2) is performed by heating (K1) by the hot plate (10) and heating by the near infrared ray (K2) through the light shielding layer or the halftone layer (1b). Since the process is performed from the lower surface of (2), the time required for baking the resist coating film can be shortened and the process capability can be improved without causing coating defects such as coating unevenness and foaming.

  As a material used for the light shielding layer or the halftone layer (1b) provided on the upper surface of the quartz substrate (1a), a metal mainly containing any one of Cr, Si, Mo, Ta, Zr, Al, and Hf An alloy, a metal oxide, or a metal nitride is preferable, and is selected in accordance with a light shielding characteristic and a transmission characteristic.

  FIG. 2 illustrates a conventional resist baking method, that is, a case where only a hot plate (10) is used. Since the heat capacity of the quartz substrate is relatively large as about 320 J / K and the thermal conductivity is relatively low as about 1.5 W / mK, the time until the resist on the surface of the substrate is heated is as described above. It will be about 5-10 minutes.

  FIG. 4 is an explanatory diagram of a specific conventional case. FIG. 4 shows the time and substrate temperature when using the method shown in the above proposal, in which an upper heater is provided above the hot plate on which the substrate is placed, and the atmosphere in the chamber is heated to flow over the substrate surface. This represents the relationship. As shown in FIG. 4, the temperature of the quartz substrate reaches 210 ° C. in about 5 minutes.

  On the other hand, FIG. 5 shows the relationship between the time and the substrate temperature in the resist baking method according to the present invention. As shown in FIG. 5, the temperature of the quartz substrate reaches 210 ° C. in about 2.5 minutes. That is, according to the resist baking method of the present invention, the time until the temperature of the quartz substrate reaches 125 ° C. is remarkably shortened.

  FIG. 6 is an explanatory diagram of other specific characteristic values. FIG. 6 shows a quartz substrate when using the method shown in the above proposal, in which an upper heater is provided above the hot plate on which the substrate is placed, and the atmosphere in the chamber is heated to flow over the substrate surface. It represents the uniformity of the temperature distribution. In FIG. 6, the uniformity of the temperature distribution on the quartz substrate is indicated by an isotherm, and the temperature range (reference characters P to U) is about 1.2 ° C.

  On the other hand, FIG. 7 shows the uniformity of the temperature distribution on the quartz substrate in the resist baking method according to the present invention. As shown in FIG. 7, the temperature range (reference characters P to Q) on the quartz substrate is about 0.2 ° C., and the uniformity of the temperature distribution on the quartz substrate is very good.

DESCRIPTION OF SYMBOLS 1 ... Photomask substrate 1a ... Quartz substrate 1b ... Light shielding layer or halftone layer 2 ... Resist coating film 10 ... Hot plate 20 ... Near infrared light source unit 21 ... Infrared ray Lamp 22 ... Wavelength selection filter 23 ... Case 30 ... Bake chamber 40 ... Intake port 50 ... Exhaust port D1 ... Heat conduction D2 of quartz substrate ... Light shielding layer or halftone Heat conduction D3 of the light-shielding layer or halftone layer heated by near infrared rays K1 Heating by a hot plate K2 Heating by near infrared rays PQ, PU U Quartz Isotherm on substrate

Claims (3)

  In drying the coating film obtained by coating a resist on a photomask substrate on which a light-shielding layer or a halftone layer is provided on a transparent substrate, heating the lower surface of the photomask substrate with a hot plate on which the photomask substrate is placed A resist baking method comprising heating near infrared rays from the upper surface of a photomask substrate.   The light shielding layer or the halftone layer is a metal, an alloy, a metal oxide, or a metal nitride containing Cr, Si, Mo, Ta, Zr, Al, or Hf as a main component. The resist baking method according to claim 1.   In heating and drying the coating film after applying a resist on the photomask substrate, a hot plate for placing the photomask substrate and heating the lower surface of the photomask substrate, and applying the resist on the photomask substrate above the hot plate A resist baking apparatus comprising a near infrared light source unit for heating a film from above.

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