JP4307968B2 - Pellicle manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a pellicle used in an exposure process, and more particularly to a method for manufacturing a pellicle used in an exposure process using exposure light corresponding to the manufacture of a highly integrated circuit as a light source.

  Photolithographic techniques used in the manufacturing process of semiconductor devices such as LSI require a step of forming a resist film by applying a resist composition to the surface of a substrate to be processed, a step of forming a resist pattern latent image by exposure, and the like. Accordingly, there are included a step of performing a heat treatment, a step of developing this to form a desired fine pattern, and a step of processing the substrate to be processed using this fine pattern as a mask.

  In the step of forming the resist pattern latent image, the resist film is irradiated with exposure light through a mask on which a predetermined resist pattern is formed. At this time, if there is dust or scratches on the surface of the mask, these are also transferred to the resist film, and a desired resist pattern latent image cannot be formed. Therefore, conventionally, a pellicle is attached to the mask. The pellicle has a structure in which a material having a high transmittance with respect to exposure light is bonded to the pellicle frame. When such a pellicle is used, the dust adheres to the pellicle instead of the mask, so that it is possible to form a resist pattern latent image without transferring the dust attached to the pellicle to the resist film.

  By the way, in recent years, with the increase in the degree of integration of semiconductor devices, the dimensions of individual elements have been reduced, and the widths of patterns such as wirings and gates constituting each element have also been reduced. Along with this, as one means for reducing the size of the pattern, the wavelength of the exposure light used when forming the resist pattern latent image is being shortened.

Conventionally, a technique using a KrF (krypton fluoride) excimer laser (wavelength: 248 nm) as an exposure light source has been used for manufacturing a semiconductor device having a pattern size of 250 nm to 180 nm. In recent years, the practical use of an ArF (argon fluoride) excimer laser (wavelength: 193 nm) has been studied in the manufacture of semiconductor devices having pattern dimensions of 130 nm to 100 nm. Furthermore, in manufacturing a semiconductor device having a pattern size of 70 nm to 50 nm, it is considered to use an F ₂ (fluorine) laser (wavelength: 157 nm) having a shorter wavelength as an exposure light source.

By the way, when such short-wavelength light is used as an exposure light source, a pellicle having excellent transparency and light resistance to exposure light is required. Conventionally, for a KrF excimer laser or an ArF excimer laser, a pellicle film made of a fluorine-based organic polymer film having a thickness of about several μm is bonded to a pellicle frame. On the other hand, the F ₂ laser has a problem that the fluorine-based organic polymer is inferior in light resistance. In view of this, use of a pellicle plate made of a glass substrate instead of the fluorine-based organic polymer film has been studied.

  An inorganic pellicle using a glass substrate is superior in exposure light transmittance and light resistance compared to an organic pellicle using a fluorine-based organic polymer film. However, since the thickness of the glass substrate is usually about several hundred μm, there is a problem that the glass substrate is bent by its own weight and a desired resist pattern latent image cannot be obtained.

  Therefore, a method has been proposed in which the glass substrate is fixed to the pellicle frame and tensile stress is applied to the glass substrate in this state to eliminate the bending of the glass substrate. Specifically, there is a method of applying a tensile stress to a glass substrate by using a pellicle frame having a small coefficient of thermal expansion with respect to the glass substrate, bonding the glass substrate to the glass substrate at a high temperature, and lowering the temperature to room temperature (for example, , See Patent Document 1). There is also a method of applying a tensile stress to a glass substrate by using a pellicle frame having a higher thermal expansion coefficient than that of the glass substrate, and bonding the glass substrate to the glass substrate at a low temperature and then keeping the glass substrate at room temperature (see, for example, Patent Document 2). .)

JP 2002-40628 A JP 2002-40629 A

  However, according to the above-described conventional method, the pellicle frame must be configured using materials having different thermal expansion coefficients with respect to the glass substrate. For this reason, there has been a problem that the degree of freedom in selecting the material of the Pellkle frame is reduced.

  In addition, the work of bonding the glass substrate to the pellicle frame must be performed in a clean environment in order to prevent the entry of foreign substances. However, according to the conventional method, this can be achieved at a high or low temperature. There must be. For this reason, there is a problem that the manufacturing equipment becomes large and leads to an increase in cost.

  The present invention has been made in view of such problems. That is, an object of the present invention is to provide a method for manufacturing a pellicle having a pellicle plate without bending.

  It is another object of the present invention to provide a method for manufacturing a pellicle that can increase the degree of freedom in selecting a material for the pellicle frame.

  Furthermore, an object of the present invention is to provide a method for manufacturing a pellicle that does not require a large-scale manufacturing facility and can reduce costs.

  Other objects and advantages of the present invention will become apparent from the following description.

  In the method for producing a pellicle of the present invention, a heat absorption film is formed on one surface of a pellicle plate made of a glass substrate, and then the other surface of the pellicle plate is placed at room temperature while the pellicle plate is heated from the side of the heat absorption film. The pellicle frame is bonded to the pellicle frame maintained through the adhesive layer, the heating to the pellicle plate is stopped after the adhesive layer is cured, and the heat absorption film is removed after the temperature of the pellicle plate is lowered to room temperature. To do.

  In the present invention, the means for heating the pellicle plate can be an infrared lamp.

  In the present invention, the means for heating the pellicle plate may be an infrared laser. In this case, a predetermined temperature distribution can be created on the pellicle plate by changing the scanning speed of the infrared laser.

  In the present invention, the heat absorption film can be a metal film. In this case, the heat absorption film can be any one film selected from the group consisting of a chromium film, a molybdenum film, and a tantalum film.

  As described above, in the present invention, after the heat absorption film is formed on one surface of the pellicle plate made of the glass substrate, the other surface of the pellicle plate is placed at room temperature while the pellicle plate is heated from the heat absorption film side. The pellicle frame is adhered to the pellicle frame that is maintained at the same temperature, and after the adhesive layer is cured, heating to the pellicle plate is stopped, and the heat absorption film is removed after the temperature of the pellicle plate is lowered to room temperature. A tensile stress can be generated in the pellicle plate regardless of the value of the coefficient of thermal expansion. Therefore, it is possible to prevent the pellicle plate from being bent and to increase the degree of freedom in selecting the material of the pellicle frame.

  Further, according to the present invention, it is only necessary to heat the pellicle plate, so there is no need to make the entire work environment high or low while maintaining the cleanliness. Therefore, a large-scale manufacturing facility such as a constant temperature bath can be eliminated, and the cost can be reduced.

  FIG. 1 is an example of a perspective view of a pellicle bonded to a mask in the present embodiment. As shown in the figure, a pellicle 1 according to the present embodiment includes a pellicle plate 2 and a pellicle frame 3 that supports the pellicle plate 2. The size of the pellicle frame 3 can be, for example, an outer shape of 150 mm × 120 mm and a height of 4 mm. The pellicle plate 2 can have the same outer dimensions as the pellicle frame 3 and a thickness of about several hundred μm.

The pellicle plate 2 is made of a transparent material having a high transmittance with respect to exposure light, particularly F ₂ laser light having a wavelength of 157 nm. For example, a quartz glass substrate doped with fluorine can be used. Here, the thickness of the quartz glass substrate can be set to, for example, about 800 μm.

  On the other hand, the pellicle frame 3 can be formed using, for example, an aluminum alloy, stainless steel, polyethylene, polycarbonate, or quartz glass that has been subjected to black alumite treatment. In the present embodiment, the material constituting the pellicle frame 3 may have any thermal expansion coefficient with respect to the material constituting the pellicle plate 2. That is, the pellicle frame 3 may be made of a material having a larger thermal expansion coefficient than the pellicle plate 2 or may be made of a material having a small thermal expansion coefficient. Further, it may be made of a material having a thermal expansion coefficient comparable to that of the pellicle plate 2.

  As shown in FIG. 1, the pellicle 1 is affixed to a mask 4 via an adhesive layer (not shown). At this time, the surface to which the pellicle 1 is bonded coincides with the mask surface on which the pattern 5 is formed, and the pellicle 1 is placed so as to surround the pattern 5. Here, the pattern 5 is a predetermined pattern transferred to a resist film (not shown) when irradiated with exposure light, and is formed of, for example, a chromium (Cr) film having a thickness of about 100 nm to 150 nm. ing. As the adhesive layer, for example, a silicone adhesive, an acrylic adhesive, an epoxy adhesive, or the like can be used.

  Next, a method for manufacturing a pellicle according to the present embodiment will be described with reference to FIGS. In these drawings, the same reference numerals as those in FIG. 1 indicate the same parts.

  In the present embodiment, first, a metal film 6 as a heat absorption film is formed on one surface of the pellicle film 2 (FIG. 2A). The metal film 6 can be formed by a sputtering method or the like. In the present embodiment, for example, a chromium (Cr) film, a molybdenum (Mo) film, a tantalum (Ta) film, or the like can be used as the metal film 6. Moreover, the film thickness of the metal film 6 can be about 10 nm, for example.

In the present embodiment, an inorganic film or an organic film other than the metal film can be used as the heat absorption film. Examples of the inorganic film include a silicon nitride (Si _x N _y ) film. Examples of the organic film include a carbon (C) film and a silicon carbide (SiC) film. These films can be formed by a CVD (Chemical Vapor Deposition) method or the like.

  Next, with the pellicle plate 2 heated from the metal film 6 side, the pellicle frame 3 maintained at room temperature (about 25 ° C.) is bonded to the surface of the pellicle plate 2 where the metal film 6 is not formed (FIG. 2 (b)). For example, the pellicle plate 2 can be attached to the pellicle frame 3 via an adhesive layer 7 made of silicone resin, acrylic resin, epoxy resin, or the like. The surface temperature of the pellicle plate 2 can be set to about 200 ° C., for example.

  As a means for heating the pellicle plate 2, for example, an infrared lamp can be used. In the present embodiment, since the metal film 6 is provided on the pellicle plate 2, heat is absorbed by the metal film 6 when an infrared lamp is irradiated from the metal film 6 side. Thereby, radiation of heat from the pellicle plate 2 to the pellicle frame 3 can be suppressed. Accordingly, the pellicle plate 2 heated to a high temperature and the pellicle frame 3 at room temperature are bonded together in a state where there is a temperature difference.

  In the present embodiment, the pellicle plate 2 may be heated using an infrared laser. By controlling the scanning speed of the infrared laser light, the irradiation time at each point on the pellicle plate 2 can be changed, so that a desired temperature distribution can be created on the pellicle plate 2.

  For example, in FIG. 2B, the infrared laser light is scanned from the left end to the right end in the figure. At this time, since the irradiation time becomes longer as the scanning speed becomes slower, the irradiation energy on the corresponding pellicle plate 2 becomes larger and the temperature rises. For example, when the irradiation energy has a distribution indicated by a dotted line in FIG. 3, the temperature distribution at each point is indicated by a solid line in the figure. In FIG. 3, the horizontal axis represents the coordinate x on the pellicle plate, and the vertical axis represents the intensity distribution I (x).

  When the temperature at each point on the pellicle plate changes, the stress applied to the corresponding point also changes, so that a desired stress distribution can be created on the pellicle plate. Therefore, for example, when the pellicle plate has a rectangular shape, the mechanical strength of the pellicle can be improved by reducing the stress at the corner portion where stress tends to concentrate. Further, by controlling the stress distribution, it is possible to prevent local bending of the glass substrate.

  Note that the temperature distribution may be created on the pellicle plate by a method other than changing the scanning speed of the infrared laser beam. For example, after irradiating the entire surface of the pellicle plate with an infrared laser to raise the temperature as a whole, the infrared laser is irradiated locally on a portion where the temperature is to be increased. This method can also create a temperature distribution on the pellicle plate.

  The heating of the pellicle plate 2 is continued until the adhesive layer 7 is cured. After the adhesive layer 7 is cured, heating is stopped and the pellicle plate 2 is allowed to stand until the temperature drops to room temperature. At this time, the pellicle plate 2 expanded by heating contracts in the process of returning to room temperature. On the other hand, since the pellicle frame 3 remains at room temperature from the beginning, it does not shrink like the pellicle plate 2. Therefore, the pellicle plate 2 contracts while the periphery is pulled by the pellicle frame 3. Thereby, since the tensile stress always acts on the pellicle plate 2, it is possible to prevent the pellicle plate 2 from being bent by its own weight. Further, even when mechanical vibration is applied to the pellicle during exposure, the deformation of the pellicle can be suppressed.

  After the pellicle plate 2 returns to room temperature, the metal film 6 that has become unnecessary is removed. For example, the metal film 6 can be removed by performing wet etching or dry etching on the metal film 6.

  When an organic film is used as the heat absorption film, the organic film can be removed by plasma treatment using oxygen, for example. However, even when the heat absorption film is made of any material, it is not necessary to remove the light when transmitting light in the wavelength region used in the exposure process.

  Through the above steps, the pellicle 1 shown in FIG. 2C can be manufactured. 2C corresponds to a cross-sectional view of the pellicle 1 in FIG. However, the adhesive layer 7 is omitted in FIG.

  According to the present embodiment, since the pellicle plate is returned to the normal temperature after bonding the high temperature pellicle plate and the normal temperature pellicle frame, tensile stress is generated on the pellicle plate regardless of the value of the thermal expansion coefficient of the pellicle frame. Can do. Therefore, it is possible to increase the degree of freedom in selecting the material for the pellicle frame.

  In addition, according to the present embodiment, since only the pellicle plate has to be heated, there is no need to make the entire working environment high or low while maintaining the cleanliness. Therefore, a large-scale manufacturing facility such as a high-temperature or low-temperature thermostatic chamber can be dispensed with, and the cost can be reduced.

  Furthermore, according to the present embodiment, since the heating to the pellicle plate is non-contact heating by an infrared lamp or the like, it is possible to suppress the adhesion of foreign matter to the pellicle. In addition, since the metal film is removed after the pellicle plate is bonded to the pellicle frame, the foreign substance can be removed together with the metal film even when the foreign substance adheres to the surface. Therefore, a pellicle with few foreign matters can be manufactured.

It is an example of the perspective view of the pellicle concerning this invention. (A)-(c) is an example of sectional drawing which shows the manufacturing method of the pellicle concerning this invention. In this invention, it is an example of the figure which shows the relationship between the irradiation energy distribution of infrared rays on a pellicle board, and temperature distribution.

Explanation of symbols

1 Pellicle 2 Pellicle plate 3 Pellicle frame 4 Mask 5 Pattern 6 Metal film 7 Adhesive layer

Claims (5)

  After a heat absorption film is formed on one side of a pellicle plate made of a glass substrate, it is bonded to a pellicle frame in which the other side of the pellicle plate is maintained at room temperature while the pellicle plate is heated from the side of the heat absorption film Manufacturing the pellicle, wherein the heat absorption film is removed after the temperature of the pellicle plate is lowered to room temperature after the adhesion layer is cured and the heating to the pellicle plate is stopped Method.   The method for manufacturing a pellicle according to claim 1, wherein the means for heating the pellicle plate is an infrared lamp.   The method for manufacturing a pellicle according to claim 1, wherein the means for heating the pellicle plate is an infrared laser, and a predetermined temperature distribution is created on the pellicle plate by changing a scanning speed of the infrared laser.   The method for manufacturing a pellicle according to any one of claims 1 to 3, wherein the heat absorption film is a metal film.   The method of manufacturing a pellicle according to claim 4, wherein the heat absorption film is any one film selected from the group consisting of a chromium film, a molybdenum film, and a tantalum film.

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