This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2006-245281, filed on Sep. 11, 2006, the entire content of which is incorporated herein by reference.
The present invention relates to a method for forming a fine pattern on a substrate and more specifically to a manufacturing method of substrate having a fine pattern thereon.
In recent years, there are requests to form a fine pattern on various substrates in various fields. As such, forming much narrower, and finer patterns is necessary to meet the demand.
To form a fine pattern on a substrate, a glass mask where a required pattern is formed is used. Such a glass mask is set on a substrate coated with photosensitive resin, and the photosensitive resin on the substrate is exposed and developed through irradiation of the light beam from the upper side of the glass mask. As a result, a pattern identical to that formed on the glass mask is formed on the substrate.
However, in such a pattern forming method, only the pattern having a size the same as the mask size can be formed, because of a restriction on pattern formation. Moreover, in the pattern formation method using a glass mask, the pattern which may be formed on the substrate has been restricted in its minimum width to about 1 μm. However, in recent years, it is intensively expected to form patterns at the nanometer size and therefore it has been difficult to satisfy this requirement with the glass mask as explained above.
In addition, a method to form a fine pattern on a substrate by condensing and irradiating various energy beams such as a laser beam and an electron beam to a photosensitive resin coated on the substrate in order to scan such photosensitive resin is also widely known. In this pattern forming method, less restriction is applied to the pattern to be formed and the desired pattern can be formed because a glass mask on which a pattern is previously formed is not required.
After a desired pattern is depicted with the laser beam, the unhardened region of the photosensitive resin is removed by conducting a development process and thereby a desired fine pattern can be formed on the substrate.
The followings are several documents describing conventional pattern forming methods.
Japanese Laid-Open Patent Application (JP-A) Publication No. 2006-106277
Japanese Laid-Open Patent Application (JP-A) Publication No. 2002-160079
However, in the pattern forming method using the laser beam shown in
Moreover, to expose a photosensitive resin with the conventional pattern forming method, the photosensitive resin starts to be hardened from the surface region of the photosensitive resin layer on the laser beam incident side. Since a fine pattern has to be formed on the surface of the substrate, pattern formation must be conducted stably under the condition that the photosensitive resin is adhered to the surface of substrate. Therefore, the laser beam should irradiate sufficiently the photosensitive resin from its surface up to the boundary of the photosensitive resin and the surface of the substrate. However, if the photosensitive resin coated on the substrate is too thick, irradiation of laser beam becomes insufficient, and the boundary of the photosensitive resin and the substrate is likely irradiated insufficiently with the laser beam. Therefore, thickness of the photosensitive resin must be rigidly controlled.
Alternatively, forming a pattern of nanometer size is possible through exposure by an electron beam. However, the price of facilities utilizing an electron beam exposure apparatus required for nanometer pattern formation are so expensive, that this pattern forming method is cost prohibitive.
It is an object of the present invention to realize a low cost fine pattern forming method.
In order to solve the problems explained above, the present invention is characterized by the steps of forming a photosensitive member on a substrate, condensing an ultra-short pulse laser, and irradiating a condensed ultra-short pulse laser from the side of substrate by positioning the focal point of the same pulse laser at an interface between the substrate and the photosensitive member.
Moreover, the present invention is characterized by the steps of forming a photosensitive member on a surface of a substrate, positioning a pulse laser to a region of the substrate on which patterns are to be formed and positioning the focal point thereof to an interface between the substrate and the photosensitive member, irradiating said pulse laser toward the interface from the side of the substrate opposite to the side having the photosensitive resin so as to transmit the pulse laser through the substrate, and removing selectively any of the photosensitive member reacted with the pulse laser and the photosensitive member not reacted with the pulse laser.
Moreover, the present invention is characterized by a pattern forming apparatus comprising a setting part for setting the substrate on which a photosensitive member for formation of patterns is formed, an oscillator for oscillating an ultra-short pulse laser, a condensing means for condensing the ultra-short pulse laser oscillated from the oscillator, and a controller for controlling the oscillator and relatively moving the substrate and the ultra-short pulse laser, wherein the ultra-short pulse laser is irradiated toward the interface through the substrate so that the focal point of the same pulse laser is located at the interface between the photosensitive member and the substrate.
Moreover, the present invention is characterized by a manufacturing method of a recording medium, comprising the steps of forming a photosensitive member on a substrate, forming patterns on the substrate by irradiating a condensed ultra-short pulse laser from the side of the substrate by positioning the focal point of the same pulse laser to an interface between the substrate and the photosensitive member, removing selectively any of a region of the photosensitive member reacted with irradiation of the ultra-short pulse laser and a region of the photosensitive member not reacted with irradiation of the same pulse laser, forming a metal layer on the substrate from which the photosensitive member is removed, peeling the metal layer from the substrate, and forming a pattern on a recording medium using the metal layer as a die.
In addition, the present invention is characterized by a manufacturing method of a member on which patterns are formed, comprising the steps of coating a photosensitive material on the member, irradiating a pulse laser from the side of the member to an interface between the member and the photosensitive material so as to transmit the same pulse laser through the member, and removing selectively any of a region reacted with irradiation of the pulse laser or a non-reacted region thereof.
With the structure and methods explained above according to the present invention, a finer groove pattern or the like can be formed on a substrate at comparatively low cost.
An ultra-short pulse laser is a laser having a very short light emitting period, as short as femtosecond to picosecond, and pulse width. Thereby a very high intensity, as high as 1010 W/cm2 or more, is obtained. In the case where such an ultra-short pulse laser is used for processing a material, almost no thermal diffusion is detected from the region of the material where the ultra-short pulse laser is irradiated. Moreover, since the laser beam is absorbed only in the irradiated region of the material, no thermal influence is applied to a portion of the material peripheral to the irradiated region, and thereby high quality processes can be conducted.
Moreover, in the case where the ultra-short pulse laser is used, the laser beam is absorbed by all substances because the pulse laser is irradiated through a multiple-photon absorbing process with less dependence on the substance during the processes.
In addition, since the ultra-short pulse laser is irradiated to the substance without causing alterations to material due to an exchange of energy through plasma, it also provides an advantage that stable processing shapes can be attained.
The present embodiment utilizes the multiple-photon absorbing process among the characteristics explained above. In the multiple-photon absorbing process, the procedure can be selectively conducted only at the area near the focal point as shown in
In the present embodiment, a photosensitive resin that is transparent to a laser beam, such as a light-hardening resin, is preferably the material to be processed. Only a region of the photosensitive resin that is smaller than a spot size of the ultra-pulse laser is hardened, by setting a focal point of the ultra-short pulse laser to a portion within the photosensitive resin.
Moreover, the ultra-short pulse laser is condensed and irradiated in such a manner as to locate a focal point of the ultra-short pulse laser at an interface between the substrate and the photosensitive resin layer formed on the substrate. When an irradiation of the ultra-short pulse laser is completed, unhardened portion of the resin is removed from the substrate by conducting a cleaning process or development process. As a result, a nanometer-sized fine pattern is formed on a surface of the substrate.
A more tangible pattern forming sequence will be explained with reference to the accompanying drawings.
As shown in
Subsequently, the ultra-short pulse laser is irradiated to the photosensitive resin layer, by positioning the ultra-short pulse laser in a manner that the focal point of the ultra-short pulse laser is set at the interface between the substrate and the photosensitive resin layer, while the glass disk is rotated (c). The ultra-short pulse laser is relatively moved under the glass disk in the direction indicated by the arrow (1). The ultra-short pulse laser is irradiated to the desired location of the glass disk after positioning of the ultra-short pulse laser. Thereby, the photosensitive resin layer at the area irradiated with the ultra-short pulse laser is reacted and hardened.
In the present invention, the ultra-short pulse laser is preferably radiated through the glass disk, in other words, from the side of the glass disk where the photosensitive resin layer is not formed. Although the photosensitive resin layer is formed in a uniform thickness, there is a high possibility that a strict thickness of the photosensitive resin layer is not even and varies within a very narrow range. Therefore, when the ultra-short pulse laser is radiated from the side of the glass disk on which the photosensitive resin layer is formed, a certain area is likely insufficiently irradiated.
Meanwhile, uniform thickness of the glass disk is attainable at an accuracy higher than that of the photosensitive resin layer. Therefore, by radiating the ultra-short pulse laser through the glass disk, the photosensitive resin layer can be exposed sufficiently, without any influence in change of the focal point of the ultra-short pulse laser due to refraction generated by non-uniformity of the thickness of the photosensitive resin layer. Thereby, a size of the hardening pattern becomes more stable.
Moreover, since the ultra-short pulse laser is radiated through the glass disk in this embodiment, the photosensitive resin layer can be exposed from the side interfacing the glass disk. As a result, the photosensitive resin layer starts to be hardened from the side contacting the glass disk. Therefore, management of the thickness of the photosensitive resin layer requires less severity than that of the pattern forming method of the prior art.
The hardened area and non-hardened area are formed on the photosensitive resin layer, as shown in
The concentric grooves are formed on the glass disk in
a) shows a glass disk on which the grooves are formed with the process shown in
Subsequently, as shown in
Thereafter, grooves are formed on a substrate of the magnetic recording medium (d) by using the peeled nickel layer as a die or stamper. Then, the nickel layer is removed from the surface of the medium. In addition, the magnetic recording medium is produced by forming a magnetic layer and conducting various coating processes on the medium.
In the example explained above, matters related to the magnetic recording medium have been explained as an example of the recording medium. However, the recording medium is not limited to the magnetic recording medium. The method of producing recording medium explained with reference to
For instance, the method of the present embodiment can also be applied to manufacture a recording medium conducting optical recording steps.
In the example explained above, grooves are formed on the disk type substrate, but the object to form grooves according to the present invention is not limited to the rotating disk type substrate.
a) is a diagram showing a principle organization of a sequence for forming grooves on a substrate. In
b) is a diagram showing a structure of an apparatus for moving a work such as a glass substrate. In the example of
Meanwhile, the NC apparatus turns on a laser oscillator, in accordance with movement of the XY table, when a laser emitting port is located at the position of the glass substrate to form the pattern thereon, the ultra-short pulse laser radiates toward the desired part on the glass substrate. Moreover, when a part of the glass substrate not required to form the pattern is located at the laser emitting port, the NC apparatus turns off the laser oscillator. With the structure explained above, a desired pattern can be formed on the glass substrate.
Referring to
c) is a diagram showing an example of a structure of the apparatus for moving the laser beam in place of a work. In the example of
An example of forming the groove on the substrate using the light hardening resin has been explained in the above example. Apart from the above-explained example, formation of a fine pattern using the ultra-short pulse laser is also possible by using a material, such as photoresist used for manufacturing semiconductor devices, which is hardened by conducting a baking process after coated on the substrate, or a solid-state photosensitive material like a dry film.
The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the invention in the appended claims and their equivalents.