Manufacturing method of ceramic electrostatic chuck

The present invention provides a method for manufacturing a ceramic electrostatic chuck which enables high purity and minimum thickness variation of a dielectric layer formed of ceramics or composite ceramics. The method includes: forming grooves for electrode pattern formation in a dielectric layer formed of ceramics or composite ceramics and having a density of 95% or greater; forming an electrode pattern by filling the grooves with a metal; forming an activated bonding layer configured for joining on the dielectric layer; and joining an insulator layer, which is formed of ceramics or composite ceramics and has a density of 95% or greater, with the dielectric layer.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent application JP 2018-100819 filed on May 25, 2018, entitled “MANUFACTURING METHOD OF CERAMIC ELECTROSTATIC CHUCK”, the contents of which is hereby incorporated by reference in its entirety for all purposes.

BACKGROUND OF THE INVENTION

Technical Field

The present invention involves a manufacturing method of a ceramic electrostatic chuck, and particularly involves a manufacturing method of a ceramic electrostatic chucks used in fabrication of semiconductor or liquid crystal display (LCD) panels.

Description of the Prior Art

Conventional methods for manufacturing ceramic electrostatic chucks generally includes: laminating and sintering green sheets as well as green sheets printed with high-melting metal (e.g., tungsten or molybdenum) paste for electrode formation; and sintering (such as hot-pressing) high-melting metal (e.g., tungsten or molybdenum) plates for electrode formation as well as ceramic powder surrounding the plates.

Prior Art Documents

However, in the abovementioned methods employing high temperature sintering, there may be variations in the thickness of the formed dielectric layer due to the shrinkage of ceramics. Furthermore, in the methods employing laminated green sheets, it is necessary to add auxiliary agents for body forming and diffusion components for obtaining adhesion with high-melting metals. Accordingly, it is difficult to obtain ceramics having a high purity. Moreover, in the methods employing hot-pressing, one restriction is that the electrode needs to be mesh-shaped, since voids easily occur at the interface between the ceramics and the high-melting metal plates used as electrodes.

SUMMARY OF THE INVENTION

In view of the problems set forth above, the present invention provides a method for manufacturing a ceramic electrostatic chuck which enables high purity and minimum thickness variation of a dielectric layer. The method comprises: forming grooves for electrode pattern formation in a dielectric layer formed of ceramics or composite ceramics and having a density of 95% or greater; forming an electrode pattern by filling the grooves with a metal; forming an activated bonding layer configured for joining on the dielectric layer; and joining an insulator layer, which is formed of ceramics or composite ceramics and has a density of 95% or greater, with the dielectric layer.

In the present invention, additives used in conventional methods for promoting sinterability are not required. Further, even if additives for adjustment of resistance values are added to composite ceramics used in the present invention, no other additives are contained in such composite ceramics.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a cross-sectional view of an electrostatic chuck manufactured according to an embodiment of the present invention.

As shown inFIG. 1, an electrostatic chuck1includes: a dielectric layer2, an electrode pattern3-a,a bonding layer4-aon dielectric layer side, a bonding layer4-bon first insulator layer side, and a first insulator layer5-a.

The dielectric layer2is a dielectric formed of a sintered body of a ceramic material or a composite ceramic material, which has a density of 95% and more. The ceramic material may be, for example, Al2O3, sapphire, Y2O3, AlN, Si3N4, etc. With regard to volume resistivity for the ceramic material or composite ceramic material of the sintered body, the dielectric layer and the insulator layers may have a volume resistivity of 1.0E+8(Ωcm) or greater. Further, composite materials, into which SiC, TiO2, TiN, etc. are added for adjustment of resistance values, may be used for the dielectric layer and the insulator layers.

The electrode pattern3-ais an electrode formed of a material, such as metals, embedded in grooves formed into a pattern in the dielectric layer2. In the case that metals or their alloys are employed, for example, metals within the range from group IVB to group IB of the periodic table are used.

The bonding layer4-aon dielectric layer side and the bonding layer4-bon first insulator layer side are configured to join the dielectric layer2and the first insulator layer5-atogether. The bonding layer4-aon dielectric layer side and the bonding layer4-bon first insulator layer side are respectively formed of surface-activated ceramics. The thicknesses of the bonding layers are not specifically limited, but the total thickness of the bonding layers after being joined are preferably 50 μm or less.

The insulator layer5-ais an insulator formed of a sintered body of a ceramic material or a composite ceramic material, which has a density of 95% and more.

Next, referring toFIG. 2, a method of manufacturing a ceramic electrostatic chuck is described.

A ceramic material or composite ceramic material with a high purity is sintered for preparing a dielectric having a density of 95% or greater in advance.

As shown in (A) ofFIG. 2, the sintered ceramic or composite ceramic dielectric having a density of 95% or greater is processed to have a flatness of 0.05 mm or less, and then processed to form a desired electrode pattern thereon, thereby forming the dielectric layer2.

Further, as shown in (B) ofFIG. 2, a metal layer3-bfunctioned as an electrode is formed on a surface of the dielectric layer2on which the abovementioned grooves are formed. The metal layer3-bmay be formed using metallization methods such as plating, thermal spraying, chemical vapor deposition (CVD), or physical vapor deposition (PVD). The metal layer3-bis preferably formed to have a thickness greater than the depth of the grooves. Next, as shown in (C) ofFIG. 2, by grinding and polishing the surface on which the metal layer3-bis formed, the remaining metal in the grooves is exposed to be the electrode pattern3-a.

As shown in (D) ofFIG. 2, the bonding layer4-aon dielectric layer side, which is configured for attachment to the first insulator layer5-a,is formed on a surface of the dielectric layer2on which the electrode pattern3-ais formed. The bonding layer4-aon dielectric layer side may be formed using film forming approaches such as CVD or PVD. The bonding layer4-aon dielectric layer side is formed to have a film thickness greater than the surface roughness Rz of the surface on which the electrode pattern is formed.

Further, the first insulator layer5-ato be bonded to the dielectric layer2is prepared in advance. Similar to the dielectric layer2, the first insulator5-ahas the bonding layer4-bon first insulator layer side formed thereon.

The bonding layer4-aon dielectric layer side and the bonding layer4-bon first insulator layer side are polished for adjusting the surface roughness thereof, such that there is no gap between the joined bonding layers4-aand4-b.The surface roughness is preferably 0.1 μm or less.

After the adjustment of surface roughness has been performed, the bonding layer4-aon dielectric layer side and the bonding layer4-bon first insulator layer side are activated via plasma, etc. Such activating technique can be found in, for example, JP 2006-073780, the content of which is hereby incorporated by reference in its entirety for all purposes.

As a final stage, the surface-activated bonding layers are stacked and joined together at a low temperature and under a low load, thereby obtaining the electrostatic chuck1provided with the electrode pattern3therein, as shown in (E) ofFIG. 2. Since sintered ceramics or composite ceramics can be joined at a low temperature and under a low load, and electrostatic chuck having a high purity and suppressed variation in thickness of the dielectric layer can be manufactured.

As further shown inFIG. 3, in the method of the present invention, in addition to the electrode disposed in the electrostatic chuck, a metallic component functioned as a heater may also be disposed in the electrostatic chuck. In the example shown inFIG. 3, a heater pattern6is first formed in the first insulator layer5-a,followed by joining the first insulator layer5-awith a second insulator layer5-b.In such case,4-cdenotes a bonding layer on heater side, and4-ddenotes a bonding layer on second insulator layer side.

Further, as can be seen inFIG. 4, grooves are provided in the electrostatic chuck for introducing cooling gases, for example, to an absorbed surface of an absorbed object to be cooled. In the example shown inFIG. 4, introduction grooves7are formed in the first insulator layer5-a,followed by joining the first insulator5-awith the second insulator layer5-b.In such case,4-edenotes a bonding layer on introduction groove side, and4-fdenotes a bonding layer on second insulator layer side.

Although the present invention has been described in detail with reference to the preferred embodiments and drawings, those with ordinary skill in the art would understand that various modifications, changes, and equivalents can be made without departing from the spirit and scope of the present invention. However, these modifications, changes, and equivalents should also be included in the scope of the present invention.