METHOD FOR MANUFACTURING STRUCTURE, AND STRUCTURE
There is provided a method for manufacturing a structure, including: forming a recess portion by performing a first etching to a surface of a member composed of Group III nitride; and flattening a bottom of the recess portion by performing a second etching to the bottom, wherein in forming the recess portion, a flat portion and a protruding portion are formed on the bottom of the recess portion, the protruding portion being raised with respect to the flat portion because it is less likely to be etched by the first etching than the flat portion, and in flattening the bottom, by etching the protruding portion by the second etching, the protruding portion is lowered.
1 . A method for manufacturing a structure, comprising:
forming a recess portion by performing a first etching to a surface of a member composed of Group III nitride; and
flattening a bottom of the recess portion by performing a second etching to the bottom,
wherein in forming the recess portion, a flat portion and a protruding portion are formed on the bottom of the recess portion, the protruding portion being raised with respect to the flat portion because it is less likely to be etched by the first etching than the flat portion, and
in flattening the bottom, by etching the protruding portion by the second etching, the protruding portion is lowered.
2 . The method for manufacturing a structure according to claim 1 , wherein the protruding portion is formed at a position corresponding to a dislocation of the Group III nitride constituting the member.
3 . The method for manufacturing a structure according to claim 1 , wherein the surface is composed of a c-plane of the Group III nitride, and the Group III nitride is etched from a direction perpendicular to the surface in the first etching, and the protruding portion is etched from a direction that is not perpendicular to the c-plane in the second etching.
4 . The method for manufacturing a structure according to claim 3 , wherein the first etching is photoelectrochemical etching.
5 . The method for manufacturing a structure according to claim 3 , wherein the second etching is wet etching using an acidic or alkaline etching solution.
6 . The method for manufacturing a structure according to claim 1 , wherein the Group III nitride is etched from a direction perpendicular to the surface in the first etching, and the protruding portion is mechanically removed in the second etching.
7 . The method for manufacturing a structure according to claim 6 , wherein the first etching is photoelectrochemical etching.
8 . The method for manufacturing a structure according to claim 6 , wherein the second etching is bubbling cleaning.
9 . The method for manufacturing a structure according to claim 6 , wherein the second etching is scrubbing.
10 . The method for manufacturing a structure according to claim 1 , wherein a maximum height of the protruding portion is 1/10 or less of a depth of the recess portion, which is measured by observing a 1000 nm square region of the bottom using an AFM after flattening the bottom.
11 - 12 . (canceled)
13 . The method for manufacturing a structure according to claim 1 , wherein the protruding portion is selectively etched with respect to the flat portion in the second etching in flattening the bottom.
14 . (canceled)
15 . The method for manufacturing a structure according to claim 1 ,
wherein the structure is used as a high electron mobility transistor, the method including:
forming a gate electrode of the high electron mobility transistor on the bottom, after flattening the bottom.
16 - 17 . (canceled)
18 . The method for manufacturing a structure according to claim 1 ,
wherein the first etching is photoelectrochemical etching,
the photoelectrochemical etching is performed in forming the recess portion, with a mask and a conductive member arranged on the surface,
the mask is made of a non-conductive material, defining an edge of the recess portion, and
the conductive member is arranged at a position away from the edge of the recess portion, and at least a part of the conductive member is arranged so as to be in contact with an etching solution of the photoelectrochemical etching; and
wherein the structure is used as a high electron mobility transistor, the recess portion is used as a recess in which a gate electrode of the high electron mobility transistor is arranged, and the conductive member is used as at least one of a source electrode and a drain electrode of the high electron mobility transistor.
19 . The method for manufacturing a structure according to claim 1 , wherein forming the recess portion and flattening the bottom is repeated alternately.
20 . A structure having a member, which is composed of Group III nitride and has a recess portion,
in which a maximum height at a position corresponding to a dislocation of the Group III nitride constituting the member is 2 nm or less, which is measured by observing a 1000 nm square region at a bottom of the recess portion using AFM, and
an arithmetic mean roughness (Ra) of the bottom measured by observing using the AFM is 0.4 nm or less.
21 . The structure according to claim 20 , used as a high electron mobility transistor, wherein the recess portion is used as a recess in which a gate electrode of the high electron mobility transistor is arranged.
22 . A method for manufacturing a structure, comprising:
performing photoelectrochemical etching to a region to be etched of a member composed of Group III nitride and used as a high electron mobility transistor; and
forming an element separation region of the high electron mobility transistor in the member,
wherein in performing the photoelectrochemical etching, the photoelectrochemical etching is performed to the region to be etched, using a conductive member that is arranged outside of a region where the element separation region should be formed and conducts with the region to be etched via a two-dimensional electron gas, and
the formation of the element separation region is performed after performing the photoelectrochemical etching.
23 . The method for manufacturing a structure according to claim 22 ,
wherein the region to be etched is a region where a recess portion is formed in which a gate electrode of the high electron mobility transistor is arranged.
24 . The method for manufacturing a structure according to claim 22 , wherein in performing the photoelectrochemical etching, the photoelectrochemical etching is performed using a mask made of a non-conductive material and having an opening in the region to be etched and an opening for exposing the conductive member.
25 . The method for manufacturing a structure according to claim 22 , wherein after performing the photoelectrochemical etching, the conductive member is removed, and a source electrode and a drain electrode of the high electron mobility transistor are formed.