Source: http://www.google.com/patents/US7724493?dq=U.S.+patent+number+7,325,728
Timestamp: 2016-08-26 13:42:24
Document Index: 18702284

Matched Legal Cases: ['art 21', 'art 21', 'art 21', 'art 121', 'art 121', 'art 121']

Patent US7724493 - Electrostatic chuck device - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsAn electrostatic chuck device provided with a dielectric plate with a surface embossed to give it a plurality of projections, an electrode, and an external power source, wherein substrate supporting surfaces of the plurality of projections are covered by conductor wiring and the conductor wiring electrically...http://www.google.com/patents/US7724493?utm_source=gb-gplus-sharePatent US7724493 - Electrostatic chuck deviceAdvanced Patent SearchPublication numberUS7724493 B2Publication typeGrantApplication numberUS 12/289,207Publication dateMay 25, 2010Filing dateOct 22, 2008Priority dateJun 18, 2002Fee statusPaidAlso published asUS7623334, US7791857, US7848077, US20040040665, US20060158823, US20090059462, US20090122459, US20100046134Publication number12289207, 289207, US 7724493 B2, US 7724493B2, US-B2-7724493, US7724493 B2, US7724493B2InventorsShigeru Mizuno, Masahito Ishihara, Sunil Wickramanayaka, Naoki MiyazakiOriginal AssigneeCanon Anelva CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (42), Non-Patent Citations (2), Referenced by (1), Classifications (12), Legal Events (1) External Links: USPTO, USPTO Assignment, EspacenetElectrostatic chuck device
US 7724493 B2Abstract
On the other hand, at projections 21 b of the embossed part 21 where the substrate 17 and the dielectric plate 22 come into direct contact, as shown in FIG. 25, fine clearances 30 (distance δ of clearances) are generated due to the fine projections and recesses on the surface of the substrate 17 or dielectric plate 22. The distance δ of the clearances 30 is extremely small or about 0.1 μm, so the force generated across the clearances 30 becomes extremely large. This is called the “Johnsen-Rahbek effect” (“JR effect”).
As shown in FIG. 25, the substrate 17 and the top surfaces of the projections 21 b of the embossed part 21 at the dielectric plate 22 come into contact at several points. These contact points form clearances 30 between the substrate 17 and the projections 21 b. The clearance 30 is in a vacuum state or filled with an inert gas. Therefore, in calculating the electrostatic force, a large clamping force is generated by the distance of “δ” shown in FIG. 25. This means that the substrate is basically fixed on the electrostatic chuck device 18 by the force generated on the embossed part. That is, at the back of the substrate 17, an extremely large pressure is present on a smaller surface area. As a result, the substrate 17 and the dielectric plate 22 are abraded by friction and fine particles are generated. Part of these particles directly sticks on the back of the substrate, while the remainder falls into the depressions (or clearances 21 a) of the embossed part 21 and is deposited there. With repeated processing of a substrate 17, the number of particles deposited in the depressions increases and the particles start to stick on the back of the substrate. The particles stick on the back of the substrate for two reasons. The first reason is the electrostatic force generated between the substrate and the particles. The second reason is that the particles start floating freely due to the rapid flow of the inert gas through the clearances 21 a between the substrate and the dielectric plate. These free-floating particles can stick on the back of the substrate.
The embossed part 121 on the surface of the dielectric plate 122 is comprised of a plurality of projections 121 b, depressions 121 c, and an outer peripheral projection 121 d. The projections 121 b form columnar shapes. The outer peripheral projection 121 d has a ring shape. The outer peripheral projection 121 d is included in the “projections” in concept. The embossed part 121 of the dielectric plate 122 forms clearances 121 a at the back of the substrate 17. At the embossed part 121 of the dielectric plate 122, all of top surfaces (substrate supporting surfaces) of the plurality of projections 121 b are provided with conductor layers 142. As the material of the dielectric plate 122, AlN (aluminum nitride) having good heat conductivity is used.
In FIG. 13 and FIG. 14, to facilitate the explanation, the configuration of a bipolar electrostatic chuck device illustrated enlarged in the thickness direction is shown. FIG. 13 is an enlarged longitudinal sectional view of an electrostatic chuck device 40, while FIG. 14 is a longitudinal sectional view of the location “A” in FIG. 13. The electrostatic chuck device 40 is comprised of metal electrodes 201 and 202, thin dielectric layers 203, and a thick insulating case 204. The metal electrodes 201 and 202 are formed on their top surfaces with a plurality of embossed projections 205. Normally, the embossed projections 205 are circular in shape in a horizontal cross section. However, the embossed projections 205 are not limited to this shape. When the horizontal sectional shape of the embossed projections 5 is circular, the diameter is in the range of 1 to 5 mm. The size of the diameter is not important, but a smaller diameter is more preferable to control the generation of particles. The height (h) of the embossed projections 205 is about 10 μm or larger. The height can also be increased to several mm. The top surfaces of the embossed projections 205 are covered by the thin dielectric layers 203. The thickness of the dielectric layers 203 is preferably made smaller than 1 μm. The reduction of the thickness increases the efficiency of declamping of the substrate. The electrical resistance of the dielectric layers 203 is not important. However, a dielectric material doped with a required impurity is more advantageous.
Next, the operation of the bipolar electrostatic chuck device will be explained. When giving two different bias voltages to the metal electrodes 201 and 202, as shown in FIG. 15, charges are generated on the surfaces of the metal electrodes 201 and 202 and the substrate 213. Two electrostatic forces (F1, F2) are generated based on the distribution of the charges. The force F1 is generated between the substrate 213 and the surface of the metal electrode called the “depressions 216”. The force F2 is generated between the substrate 213 and the top surfaces of the metal embossed projections 205. The height (h) of the embossed projections 205 is larger than 10 μm and the thickness (t) of the dielectric layers 203 is smaller than 1 μm. Therefore, the force F1 is smaller by about four orders than the force F2. Therefore, the substrate 213 is inherently fixed on the electrostatic chuck device 40 by the force F2.
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