Patent Application
20240012331
The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2022-109497, filed Jul. 7, 2022, the contents of which are hereby incorporated herein by reference in their entirety.
The present invention relates to a method of manufacturing a patterned base member, a processing method, and a method of manufacturing a laser element.
Patterning of a resist by electron beam irradiation is expected to be applied to, for example, nano-scale micromachining. For example, Japanese Unexamined Patent Application Publication No. 2011-165980 discloses a method of manufacturing a nanoimprint mold using a combination of a positive resist and a negative resist as an etching mask exposed to an electron beam.
Japanese Unexamined Patent Application Publication No. 2011-165980 focuses on the disturbance of the pattern when the positive resist is formed, but the shape of the positive resist may be changed at the time of etching after the formation. As the pattern to be obtained becomes finer, the influence of the change in shape becomes larger, and in some cases, an intended pattern cannot be formed on a workpiece depending on the magnitude of the change.
A method of manufacturing a patterned base member of one embodiment of the present disclosure includes forming a resist layer including a positive resist on a base member, exposing a portion of the resist layer to an electron beam to form an exposed portion and an unexposed portion in the resist layer, developing the resist layer to remove the exposed portion and leave the unexposed portion to provide a patterned resist layer, irradiating an entirety of the patterned resist layer with an electron beam, and etching the base member using the patterned resist layer as an etching mask or using a patterned mask layer to which the pattern of the patterned resist layer is transferred, as an etching mask.
A processing method of one embodiment of the present disclosure includes providing the patterned base member manufactured by the above method, transferring the pattern of the patterned base member to a processing resist layer disposed on a workpiece to provide a patterned processing mask layer, and etching the workpiece using the patterned processing mask layer as an etching mask.
A method of manufacturing a laser element of one embodiment of the present disclosure includes forming a semiconductor layered body including a plurality of semiconductor layers and forming a diffraction grating in the semiconductor layered body by the above processing method.
In the method of manufacturing a laser element of one embodiment of the present disclosure, the base member is a nitride semiconductor substrate, and the method includes providing a patterned substrate as the patterned base member manufactured by the above method and layering a plurality of semiconductor layers on the patterned substrate.
A method of manufacturing a patterned base member of one embodiment of the present disclosure can improve the accuracy of the pattern of the resulting patterned base member. A processing method of one embodiment of the present disclosure can improve the processing accuracy. A method of manufacturing a laser element of one embodiment of the present disclosure can improve the accuracy of patterning on a laser element.
Amore complete appreciation of embodiments of the invention and many of the attendant advantages thereof will be readily obtained by reference to the following detailed description when considered in connection with the accompanying drawings.
Certain embodiments of the present invention will be described below with reference to the accompanying drawings as appropriate. The embodiments disclosed below are intended to give a concrete form to the technical idea of the present invention and are not intended to limit the present invention to the embodiments below unless specifically stated otherwise. Sizes or positional relationships of members illustrated in each drawing may be exaggerated in order to clarify the descriptions.
A method of manufacturing a patterned base member according to a first embodiment is described referring to
As shown in
A resist layer 2 is first formed on a base member 1 as shown in
A positive resist is a resist that becomes more soluble in a developing solution through electron beam irradiation. For example, a chemically amplified positive resist can be used as the positive resist. For the positive resist, for example, poly(methyl methacrylate) (PMMA) (such as a product manufactured by MicroChem Corporation in the U.S.), polymethylglutarimide (PMGI) (such as a product manufactured by MicroChem Corporation in the U.S.), or ZEP520 manufactured by Zeon Corporation can be used.
The base member 1 is a material to be processed in the etching step S105, which is a subsequent step. Examples of the material of the base member 1 include semiconductors such as silicon and nitride semiconductors and glass.
Subsequently, a portion of the resist layer 2 is exposed to an electron beam EB to form an exposed portion 2a and an unexposed portion 2b in the resist layer 2 as shown in
The exposed portion 2a can have a regular pattern made of a plurality of regions as shown in
The area of the exposed portion 2a is preferably smaller than the area of the unexposed portion 2b in a top view. The time taken by electron beam drawing can thus be shorter than otherwise. The ratio of the area of the exposed portion 2a to the area of the unexposed portion 2b is preferably less than 1, more preferably ½ or less, still more preferably ⅙ or less. For example, the shape and arrangement of the exposed portion 2a may be determined so that the exposed portion 2a does not reach the outer edges of the resist layer 2 in a top view as shown in
The depth of the exposed portion 2a may be equal to or smaller than the thickness of the resist layer 2. For example, the depth of the exposed portion 2a can be one half or more of the thickness of the resist layer 2. The depth of the exposed portion 2a may be adjusted by changing the intensity and the irradiation time of the electron beam applied.
Subsequently, the resist layer 2 is developed as shown in
The resist layer 2 can be developed by immersing a complex including the base member 1 and the resist layer 2 in a developing solution. Through immersion in the developing solution, the exposed portion 2a is dissolved in the developing solution, and the unexposed portion 2b remains. Examples of the developing solution used for the development include an alkaline aqueous solution in which at least one alkaline compound is dissolved. Examples of the alkaline compound include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, ammonia water, ethylamine, n-propylamine, diethylamine, di-n-propylamine, triethylamine, methyldiethylamine, ethyldimethylamine, triethanolamine, tetramethylammonium hydroxide (TMAH), pyrrole, piperidine, choline, 1,8-diazabicyclo-[5.4.0]-7-undecene, and 1,5-diazabicyclo-[4.3.0]-5-nonene. The developing solution may be an organic solvent such as hydrocarbon solvents, ether solvents, ester solvents, ketone solvents, and alcohol solvents or a solvent containing an organic solvent.
Before the immersion in the developing solution, the resist layer 2 may be heated to make a difference in solubility in the developing solution between the exposed portion 2a and the unexposed portion 2b. For example, the temperature for the heating can be 50° C. to 180° C. For example, the time for the heating can be 5 seconds to 600 seconds. After the immersion in the developing solution, washing with a rinse liquid such as water and/or alcohol and drying may be performed.
Subsequently, the patterned resist layer 3 is irradiated with the electron beam EB as shown in
The whole or a portion of the patterned resist layer 3 may be irradiated with the electron beam EB. The region irradiated with the electron beam EB preferably includes at least a boundary portion of the pattern of the patterned resist layer 3. The region irradiated with the electron beam EB preferably includes at least a whole patterned portion of the pattern of the patterned resist layer 3. The degree of the change in shape of the boundary portion of the pattern can thus be reduced in the etching step S105, which is a subsequent step, and the accuracy of the processing pattern formed in the base member 1 can be more certainly improved. For example, an entirety of patterned resist layer 3 is irradiated with the electron beam EB. For example, at least an entirety of a patterned portion of patterned resist layer 3 is irradiated with the electron beam EB.
The patterned resist layer 3 may be irradiated with the electron beam EB using a similar electron beam to the beam used in the step S102 of forming an exposed portion and an unexposed portion by electron beam drawing. In this case, the irradiation time can be shortened by irradiating only a portion of the patterned resist layer 3 with the electron beam EB. The beam size of the electron beam EB applied to the patterned resist layer 3 may be large enough to irradiate the whole patterned resist layer 3 at once. This constitution allows the whole patterned resist layer 3 to be irradiated with the electron beam EB in a shorter time than in the case of electron beam drawing. Examples of the method of irradiating the whole patterned resist layer 3 with the electron beam EB at once include a method disclosed in Japanese Translation of PCT International Application Publication No. JP-T-2003-502698.
Subsequently, the base member 1 is etched using the patterned resist layer 3 as an etching mask. A patterned base member 4 can thus be provided as shown in
For example, the etching is dry etching. By dry-etching the base member 1, a pattern closer to the pattern of the etching mask can be formed in the base member 1 than in the case of wet etching. In the case of dry etching, the shape of the patterned resist layer 3 may change due to local growth of the patterned resist layer 3 caused by a reaction with an etching gas. By performing the electron beam irradiation step S104, such a reaction of the patterned resist layer 3 with the etching gas may be suppressed. A gas that has a lower etching rate for the patterned resist layer 3 than the etching rate for a workpiece such as the base member 1 is selected as the etching gas. For example, a gas containing at least one of a chlorine-based gas and a fluorine-based gas can be used as the etching gas.
The etching step S105 may be performed until the patterned resist layer 3 is completely removed or may be stopped to leave the patterned resist layer 3. In the case where the patterned resist layer 3 is left after the etching step S105, a step of removing the patterned resist layer 3 may be performed after the etching step S105.
As a modification, the following describes an example in the case where the etching step S105 is performed using a patterned mask layer to which the pattern of the patterned resist layer 3 has been transferred as an etching mask.
A mask layer 5 is formed on the base member 1 as shown in
After the patterned resist layer 3 is provided as shown in
For example, the etching is dry etching. Dry-etching of the mask layer 5 allows a pattern closer to the pattern of the patterned resist layer 3 to be formed in the mask layer 5 than in the case of wet etching. By performing the electron beam irradiation step S104 earlier, the reaction of the patterned resist layer 3 with the etching gas may be suppressed. A gas that has a lower etching rate for the patterned resist layer 3 than the etching rate for the mask layer 5 is selected as the etching gas. For example, a gas containing at least one of a chlorine-based gas and a fluorine-based gas can be used as the etching gas.
The etching may be performed until the patterned resist layer 3 is completely removed or may be stopped to leave the patterned resist layer 3. In the case where the patterned resist layer 3 is left after the step S107 of providing a patterned mask layer, a step of removing the patterned resist layer 3 may be performed before the etching step S105, or the patterned resist layer 3 may remain.
The base member 1 is then etched using the patterned mask layer 6 as an etching mask in the etching step S105. In the case where the patterned resist layer 3 is left, the patterned resist layer 3 is also considered to be a portion of the etching mask. In the case where the etching rate for the patterned resist layer 3 is larger than the etching rate for the base member 1 in the etching step S105, the patterned mask layer 6 is preferably formed in this way. The base member 1 can thus be efficiently processed. The etching rate for the patterned mask layer 6 is preferably smaller than the etching rate for the base member 1 in the etching step S105. The base member 1 can thus be more efficiently processed. For example, the patterned mask layer 6 can be a silicon oxide film, and the base member 1 can be a nitride semiconductor substrate. The etching rate for the etching mask does not necessarily have to be smaller than the etching rate for the base member 1 in the etching step S105. In this case, the etching mask has such a thickness to prevent the etching mask from being completely removed during the etching step S105.
A processing method according to a second embodiment is described referring to
As shown in
The patterned base member 4 is provided by the method described for the first embodiment.
Subsequently, the pattern of the patterned base member 4 is transferred to a processing resist layer 13 disposed on a workpiece 12 to provide a patterned processing mask layer 14. The pattern of the patterned base member 4 may be directly transferred to the processing resist layer or may be transferred using a replica mold 11 as an intermediate as shown in
In the case of using the replica mold 11 as an intermediate, a step of forming the replica mold 11 using the patterned base member 4 as a mold is further included. The pattern of the replica mold 11 is then transferred to the processing resist layer 13 disposed on the workpiece 12 in the step S202 of providing a patterned processing mask layer 14 to provide the patterned processing mask layer 14. In the case of using the replica mold 11 as an intermediate, the replica mold 11 may be repeatedly used to form the patterned processing mask layer 14, and a new replica mold 11 may be produced using the patterned base member 4 again when the pattern of the replica mold 11 is worn. Accordingly, the processing accuracy of the pattern can be further improved.
As the materials of the replica mold 11 and the processing resist layer 13, materials used in a known imprinting technique can be employed. For example, a cured product provided by pressing the patterned base member 4 against a UV-curable resist and curing the resist by UV irradiation can be used as the replica mold 11. For example, a cured product provided by pressing the replica mold 11 against a UV-curable processing resist layer 13 and curing the layer by UV irradiation can be used as the patterned processing mask layer 14. The replica mold 11 may be constituted of a complex member of a substrate and a resist.
The workpiece 12 is etched using the patterned processing mask layer 14 as an etching mask as shown in
A method of manufacturing a laser element according to a third embodiment is described referring to
As shown in
A first semiconductor layered body 22 in which a plurality of semiconductor layers are layered is formed as shown in
Subsequently, a diffraction grating is formed in the first semiconductor layered body 22 as shown in
After the step S302 of forming a diffraction grating, a second semiconductor layered body 23 may be formed on the first semiconductor layered body 22 as shown in
A method of manufacturing a laser element according to a fourth embodiment is described referring to
As shown in
As shown in
Subsequently, a plurality of semiconductor layers are layered on the patterned substrate 26 as shown in
Examples of the semiconductor constituting the semiconductor layered body 27 include group III to V semiconductors. For example, the semiconductor constituting the semiconductor layered body 27 is a nitride semiconductor such as GaN, AlGaN, AlN, AlInGaN, and InGaN. For example, the peak wavelength of the laser beam emitted from the laser element 20A can be 200 nm or more and 600 nm or less and may be 200 nm or more and 500 nm or less. For example, the laser element 20B that emits a laser beam with such a wavelength can be formed by constituting the semiconductor layered body 27 using a nitride semiconductor.
The patterned base member 4 provided in the first embodiment may be used as a portion of the laser element 20B as described above without using the processing method described for the second embodiment. The patterned base member 4 is a substrate in the fourth embodiment, but a portion of the semiconductor layered body may be the patterned base member 4. The patterned substrate 26 may be provided by the processing method described for the second embodiment.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-109497 | Jul 2022 | JP | national |
