Substrate holding device and method of manufacturing the same
A substrate holding device includes a base body that has a flat plate-like shape and that includes gas passages that open in an upper surface of the base body, and a plurality of protrusions that protrude from the upper surface of the base body. At least an upper part of each of the protrusions has a conical frustum shape having a base angle of 70° or more and 85° or less.
1. A device for holding a substrate comprising:
a base body having a flat plate-like shape and including an upper surface and a plurality of protrusions including a first protrusion and a second protrusion, the plurality of protrusions protruding from the upper surface, the base body defining a gas passage that opens in the upper surface;
wherein at least an upper part of the first protrusion has a conical frustum shape with a base angle between 70° and 85°;
wherein the second protrusion is located around the gas passage;
wherein the base angle of the second protrusion is smaller than the base angle of the first protrusion; and
wherein a cross-sectional area of a base end portion of the second protrusion is larger than a cross-sectional area of a base end portion of the first protrusion.
2. The device according to claim 1 , each of the plurality of protrusions including a top surface for contacting the substrate,
wherein a ratio of a height of each of the protrusions to a maximum width of the top surface is 1 or more, a ratio of a total contact area between the substrate and the plurality of protrusions to an area of the substrate is 0.30% or less, and center-to-center distances between adjacent protrusions are 3.0 mm or less.
3. A device for holding a substrate comprising:
a base body having a flat plate-like shape and including an upper surface and a plurality of protrusions including a first protrusion and a second protrusion, the plurality of protrusions protruding from the upper surface, the base body defining a gas passage that opens in the upper surface;
wherein at least an upper part of the first protrusion has a conical frustum shape with a base angle between 70° and 85°;
wherein the second protrusion is located around the gas passage;
wherein the base angle of the second protrusion is smaller than the base angle of the first protrusion;
wherein a cross-sectional area of a base end portion of the second protrusion is larger than a cross-sectional area of a base end portion of the first protrusion; and
wherein the first protrusion is formed by laser processing.