Page 1 of 28
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`Samsung Exhibit 1016
`Samsung Electronics Co., Ltd. v. Daniel L. Flamm
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`EP 0 601 788 A2
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`Page 2 of 28
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`EP 0 601 788 A2
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`The present invention relates to an electrostatic
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`chuck ("E-chuck") for high density plasma processing
`of articles such as semiconductor wafers. The E-
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`chuck overcomes the difficulties present with prior
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`art mechanical and electrostatic chucks in high den-
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`sity plasma processing applications and is particular-
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`Iy well suited to processes in which the article may be
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`RF biased for enhanced process performance in a
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`high density plasma process, such as that used in
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`SiO2 etching. The E-chuck addresses the require-
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`ments of uniform coupling of electrical and thermal
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`energy in a hostile electrical, thermal and chemical
`environment.
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`In the plasma processing of articles such as sem-
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`iconductorwafers, a common problem is the coupling
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`of electrical energy to the article being processed.
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`Typically, electromagnetic coupling of RF energy into
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`the "source" region of a plasma chamber is employed
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`to generate and maintain a high electron density plas-
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`ma having a low particle energy.
`In addition, RF
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`"bias" energy is usually capacitively coupled in the
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`plasma via the article being processed to increase
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`and control the energy of ions impinging on the arti-
`cle.
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`In a typical high density plasma reactor, the driv-
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`ing point RF "bias" impedance presented by the plas-
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`ma is very low. To achieve uniform ion energy and
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`flux to the article being processed (typically essential
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`for etching or other plasma processes), uniform cou-
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`pling of RF "bias" energy through the article being
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`processed to the plasma is required. The article being
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`processed typically is held against some kind of
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`chuck and RF bias energy is applied to the chuck.
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`What is desired is a constant plasma sheath voltage
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`across the surface of the article being processed.
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`The degree to which such a uniform plasma
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`sheath voltage can be achieved is a function not only
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`ofthe plasma density uniformity as generated by the
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`plasma source, but is also a function of the impe-
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`dance per unit area of the plasma sheath adjacent to
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`the article, the impedance per unit area ofthe article,
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`the impedance per unit area of any gap between the
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`article and the chuck and the impedance per unit
`area of the chuck.
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`Besides electrical coupling, the chuck should be
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`tightly thermally coupled tothe article being process-
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`ed. Typically the temperature of the article is a proc-
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`ess parameter to be controlled and this normally
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`means removing heat from or adding heat to the ar-
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`ticle during processing. Heat transfer in a low pres-
`sure or vacuum environment such as that used for
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`plasma processing is generally poor. Some means of
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`providing for adequate heat transfer between the ar-
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`ticle being processed and adjacent surfaces is usu-
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`ally necessary.
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`Typical prior art chucks mechanically clamp an
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`article to the chuck with a clamp ring applying a hold-
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`ing force at the periphery ofthe article. The thermal
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`contact between article and chuck is generally insuf-
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`ficient to accommodate the heat load imposed by the
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`plasma on the article. Without some means of im-
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`proved thermal contact between article and chuck,
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`the temperature of the article may rise out of accept-
`able limits.
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`Gas is typically introduced between the article
`and chuck to enhance thermal contact and heat
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`transfer from the article to the chuck. The gas pres-
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`sure required is a function of the heat load imposed
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`by the plasma, the desired maximum article temper-
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`ature, the temperature at which the chuck can be
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`maintained (such as with liquid cooling), the choice of
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`cooling gas and the article/gas and gas/chuck ac-
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`commodation coefficients (measures of how effec-
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`tively heat is transferred between a gas and a sur-
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`face). For biased high density plasma applications,
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`helium gas is used as the cooling gas and the gas
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`pressure required is typically in the 5 to 30 torr range.
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`For "low pressure" plasma processes (those op-
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`erating in millitorr pressure range), some means must
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`be provided to allow a significantly higher pressure in
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`the region between the article and chuck with respect
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`to the ambient pressure in the process chamber. In
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`addition, a leak of cooling gas into the process envir-
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`onment may produce undesirable results. Typically
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`some kind of seal, usually an elastomer, is used to al-
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`low maintenance of the pressure difference between
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`the two regions.
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`If the article to be processed is simply mechani-
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`cally clamped at its periphery to the chuck, and gas
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`introduced between article and chuck, the article will
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`bow away from the chuck due to the pressure differ-
`ence across the article. If a flat chuck is used on a
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`disk shaped article, a large gap results between the
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`article and the chuck with a peak gap at the center.
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`Under such conditions, thermal and electrical cou-
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`pling between the article and the chuck are non-u ni-
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`form. Mechanically clamped chucks typically pre-
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`compensate such article—bowing by attempting to
`match the chuck’s surface to the curvature of the ar-
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`ticle under stress. Theoretically, this can be done for
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`simply shaped articles (such as disks), but the pres-
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`ence of discontinuities or complex shapes make ana-
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`lytical precompensation impossible, and trial-and-er-
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`ror is required. Mismatches in curvatures between
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`the article and the chuck result in a variable gap be-
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`tween such surfaces, resulting in non uniform elec-
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`trical and thermal coupling.
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`Electrostatic chucks have been proposed to
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`overcome the non—uniform coupling associated with
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`mechanical chucks. Electrostatic chucks employ the
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`attractive coulomb force between oppositely charged
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`surfaces to clamp together an article and a chuck. In
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`principle, with an electrostatic chuck, the force be-
`tween article and chuck is uniform for a flat article
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`and flat chuck. The electrostatic force between the
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`article and the chuck is proportional to the square of
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`Page 3 of 28
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`

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`EP 0 601 788 A2
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`the voltage between them, proportional to the rela-
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`tive permittivity of the dielectric medium separating
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`them (assuming conductivity is negligible) and in-
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`versely proportional with the square of the distance
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`between them. Typically for biased-article high den-
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`sity plasma processing applications (such as SiO2
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`etching) a cooling gas is required to improve the heat
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`transfer between article and chuck to acceptable lev-
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`els. Introduction of gas cooling between article and
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`chuck, while required to achieve adequate heat trans-
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`fer, causes problems with prior art electrostatic
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`chucks when used in biased-article high density plas-
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`ma applications.
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`In particular, the requirement of introducing cool-
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`ing gas in the region between article and chuck re-
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`quires that some discontinuity be introduced in the
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`chuck surface, typically some type of ho|e(s) through
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`the chuck to a gas passage behind the surface. The
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`introduction of any discontinuity in the chuck surface
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`distorts the electric field in the vicinity of the discon-
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`tinuity, making arc breakdown and glow discharge
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`breakdown of the cooling gas more probable. With
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`DC bias applied between an article and a chuck, and
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`RF bias applied to the chuck, gas breakdown be-
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`comes probable with prior art electrostatic chucks
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`such as described in U.S. Patents 4,565,601 and
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`4,771,730.
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`In the ‘601 patent, a plurality of radial cooling gas
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`dispersion grooves in an upper surface of a plate
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`electrode connect to and extend outwardly from the
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`relatively large upperend ofa cooling gas supply pipe
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`extending vertically to the upper surface of the plate
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`electrode. Cooling gas from the supply pipe travels
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`outwardly in the radial grooves and into a plurality cir-
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`cular gas dispersion grooves also formed in the upper
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`surface of the plate electrode coaxial with the gas
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`supply pipe. The upper surface of the plate electrode
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`with the radial and circular patterns of grooves is cov-
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`ered with a thin insulating film upon which the article
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`to be process is placed. The upper open end of the
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`gas supply pipe forms a relatively large discontinuity
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`in the upper surface of plate electrode. The radial and
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`circular grooves are relatively wide and deep, slightly
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`less than the diameter of the gas supply pipe, and
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`form additional relatively wide and deep discontinui-
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`ties in the upper surface of the plate electrode and
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`relatively deep separation gaps between the plate
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`electrode and the article to be processed. Further, ir-
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`regularities in the coated surfaces of the grooves pro-
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`duce non-uniformities in gas flow and in the spacing
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`of the article and the plate electrode. Undesired arc
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`and glow discharge breakdowns of the cooling gas
`would occur if such an electrostatic chuck were em-
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`ployed in a high RF power, high density plasma reac-
`tor.
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`The same problems are particularly inherent in
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`the electrostatic chuck of the ’730 patent which in-
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`cludes a central and/or plurality of relatively large gas
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`feeding tubes to the upper surface of a plate elec-
`trode.
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`What is desired is an electrostatic chuck that can
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`accommodate cooling gas between the workpiece
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`and the chuck and which is designed to avoid gas
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`breakdown even when the chuck is used in a plasma
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`reactor environment including high RF bias power
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`and high density plasma.
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`The E-chuck of the present invention is particu-
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`Iarly useful in electrostatically holding an article to be
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`processed, such as a semiconductor wafer, in a plas-
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`ma reaction chamber while distributing a cooling gas
`between the face ofthe E-chuck and the underside
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`of the article, without contributing to arc or glow dis-
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`charge breakdown of the cooling gas.
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`The E-chuck comprises a metal pedestal having
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`a smooth upper surface for electrostatically attract-
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`ing and supporting the article. Asmooth layer ofa di-
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`electric material is bonded to the upper surface of the
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`pedestal.
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`One aspect of the present invention is that one
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`or more conduits are formed inside the metal pedes-
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`tal to permit cooling gas to be transported to one or
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`more cavities just below the dielectric. A plurality of
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`perforations which are much smaller in diameterthan
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`the conduits extend from the upper surface ofthe di-
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`electric down to the cavities. These perforations pro-
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`vide a path for the cooling gas to flow from the cavi-
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`ties in the pedestal to the region between the dielec-
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`tric layer and the semiconductor wafer or other work-
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`piece. The invention permits the use of perforations
`which are much smaller in diameterthan the smallest
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`conduit that could be fabricated in the body of the
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`metal pedestal. The use of such small perforations as
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`the outlets for the cooling gas greatly increases the
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`amount of RF bias power and plasma density to which
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`the E-chuck can be exposed without causing break-
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`down ofthe cooling gas.
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`A second, independent aspect of the invention is
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`that a cooling gas distribution channel is formed by
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`one or more grooves in the upper surface of the di-
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`electric Iayer for distributing a cooling gas between
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`the upper surface of the dielectric layer and the un-
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`derside of the article supported on the pedestal. Ac-
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`cording to this aspect of the invention, the depth of
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`the grooves is small enough to maintain a low product
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`of cooling gas pressure and groove depth so as to
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`avoid glow discharge breakdown of the cooling gas,
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`and the dielectric layer beneath the grooves is thick
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`enough to prevent dielectric breakdown. In contrast
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`with conventional E—chucks, the present invention lo-
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`cates the gas distribution channels in the layer of di-
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`electric material rather than in the metal pedestal,
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`thereby minimizing discontinuities in the electric field
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`adjacent the pedestal which could contribute to arc or
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`glow discharge breakdown of the cooling gas.
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`In general, in another aspect the invention is an
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`electrostatic chuck for holding a wafer in a plasma
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`Page 4 of 28
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`EP 0 601 788 A2
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`electrostatic chuck; striking a plasma in the plasma
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`chamber; running that plasma for a preselected per-
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`iod of time; terminating the plasma at the end ofthe
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`preselected period; and placing the next wafer on the
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`electrostatic chuck for plasma processing.
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`In general, in another aspect, the invention is a
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`method of forming passages in an electrostatic chuck
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`that connect an internal manifold to the top surface
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`of the dielectric. The method includes the steps of
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`drilling a first plurality of holes into the pedestal ex-
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`tending from the top surface ofthe pedestal into the
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`manifold; forming a dielectric layer on the surface of
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`the pedestal, the dielectric layer being sufficiently
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`thick to bridge over the holes of the first plurality of
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`holes; and drilling a second plurality of holes in the di-
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`electric layer, each hole of the second plurality of
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`holes aligned with a different one ofthe holes of the
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`first plurality of holes.
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`In general, in still another aspect, the invention
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`is a method for dechucking a wafer from a electrostat-
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`ic chuck following a plasma process. The method in-
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`cludes the steps of: at the completion of the plasma
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`process and while the RF source power is still on,
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`turning off the cooling gas; changing a DC potential
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`ofthe electrostatic chuck; slightly separating the wa-
`fer from the electrostatic chuck while the RF source
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`plasma is still present; after slightly separating the
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`wafer from the electrostatic chuck, turning offthe RF
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`source; after turning off the RF source power, sepa-
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`rating the wafer furtherfrom the electrostatic chuck;
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`and removing the wafer from the plasma chamber.
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`The following is a description ofa number of pre-
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`ferred embodiments of the invention, reference being
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`made to the accompanying drawings in which:-
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`Figure 1
`is a schematic view of an "OMEGA"
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`biased high density plasma reaction chamber of
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`Applied Materials, Inc., Santa Clara, California il-
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`lustrating the electrical circuitry therefor and in-
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`cluding the E-chuck of the present invention to
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`hold a semiconductor wafer on a pedestal of the
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`E-chuck. The "OMEGA" reaction chamber (with-
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`out a chuck) is described and illustrated in EP-A-
`O552491. Reference should be made to that
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`specification for a complete description of the
`"OMEGA" reaction chamber in which the E-
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`chuck ofthe present invention is particularly use-
`ful.
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`Figure 2 is top view of a pedestal included in the
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`E-chuck of the present invention and illustrates
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`a gas distribution system formed in the upper
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`surface of a layer of dielectric material bonded to
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`the upper surface of the pedestal to distribute
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`cooling gas over the surface of the layer from
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`cooling gas receiving holes extending upwardly
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`from an underside of the pedestal to upper ends
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`adjacent the upper surface of the pedestal under
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`the layer of dielectric material.
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`Figure 2a is an enlarged showing of Fig. 2.
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`processing chamber. The electrostatic chuck sup-
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`plies a cooling gas to the backside of the wafer
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`through a plurality of holes in the chuck that are dis-
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`tributed near the regions of highest leakage of the
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`cooling gas,
`i.e., the holes are distributed so as to
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`"feed the leaks'' while also supplying gas to the back-
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`side of the wafer. The chuck includes a pedestal hav-
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`ing a top surface, an internal manifold for carrying a
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`cooling gas, and a first plurality of holes leading from
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`the internal manifold toward the top surface. It also
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`includes a dielectric layer on the top surface of the
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`pedestal. The dielectric layer has a top side and sec-
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`ond plurality of holes, each ofwhich is aligned with a
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`different one ofthe holes ofthe first plurality of holes.
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`The first and second holes forming a plurality of pas-
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`sages extending from the internal manifold to the top
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`side ofthe dielectric layerand through which the cool-
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`ing gas is supplied to an interface formed bythe back-
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`side of the wafer and the top side ofthe dielectric lay-
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`er. Each ofthe first holes and the second hole aligned
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`therewith form a different one of the plurality of pas-
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`sages. The passages are concentrated in regions of
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`said dielectric layer that are in proximity to regions of
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`higher leakage of cooling gas when the wafer is held
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`against the electrostatic chuck by an electrostatic
`force.
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`In general, in yet another aspect the invention is
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`an electrostatic chuck in which an internal gas distrib-
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`ution manifold is formed by welding an insert into a
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`groove in the top ofthe chuck. In particular, the elec-
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`trostatic chuck includes a pedestal having a top sur-
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`face, an internal manifold for carrying a cooling gas,
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`and a first plurality of holes connecting the internal
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`manifold to the top surface; and it includes a dielectric
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`layer on top of the pedestal. The dielectric layer has
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`a second plurality of holes, each of which is aligned
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`with a different one of the holes of the first plurality
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`of holes. The first and second holes form a plurality
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`of passages extending from the internal manifold to
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`the top of the dielectric layer and through which the
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`cooling gas is supplied to a wafer backside. Each of
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`the first holes and the second hole aligned therewith
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`form a different one of the plurality of passages. The
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`pedestal includes a groove formed in its top surface
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`and there is an insert in the groove. The insert has a
`channel formed in its underside and the channel in
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`combination with the groove form a cavity that is part
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`of the internal manifold. At least some of the passag-
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`es pass through the insert into that channel.
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`In general, in still another aspect, the invention
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`is a computer—implemented method for preparing an
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`electrostatic chuck within a plasma chamber to re-
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`ceive a next wafer for plasma processing after a pre-
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`vious wafer has completed plasma processing. The
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`method includes the steps of removing the previous
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`wafer from the electrostatic chuck in the plasma
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`chamber;
`introducing a non-process gas into the
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`plasma chamber without any wafer present on the
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`Page 5 of 28
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`

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`EP 0 601 788 A2
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`Figure 14 shows a closeup of the groove network
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`on the surface of the dielectric layer,
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`Figure 15 shows a closeup ofanother portion of
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`the groove network on the surface of the dielec-
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`tric layer;
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`Figure 16 shows a closeup of yet another portion
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`of the groove network on the surface of the di-
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`electric layer;
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`Figure 17 shows a cross-sectional view of an al-
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`ternative perforation design for carrying cooling
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`gas to the underside of the wafer;
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`Figure 18 is a flow chart ofthe sequence for pro-
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`ducing the perforation shown in Fig. 17;
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`Figure 19 is an enlarged cross-sectional partial
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`view of the pedestal with a collar and a cover ring
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`in place;
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`Figure 20 is a closeup view of the gap and the
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`overlap formed between the underside of the
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`wafer and the collar shown in Fig. 19; and
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`Figures 21A-C present a flow chart of the wafer
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`chucking and dechucking procedure and the post
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`process procedure for reducing residual charge
`on the E-chuck.
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`As shown in Figures 1 and 2, the E-chuck 10 of
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`the present invention is adapted to support and elec-
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`trostatically hold an article or workpiece 12 to be
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`processed, such as a semiconductor wafer, on a ped-
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`estal 14 within a high density plasma reaction cham-
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`ber 16. Through gas distribution groove network 18,
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`the E-chuck 10 affects a cooling of the pedestal 14
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`and the wafer 12 supported thereon.
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`The plasma reaction chamber 16 further in-
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`cludes a cover ring 20 which is supported by four
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`rods, not shown. The purpose of the cover ring is to
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`prevent the plasma in the chamber above the work-
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`piece from contacting, and thereby corroding, part of
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`the E-chuck. Accordingly, the four rods position the
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`cover ring within 0.01 inch of the edges ofthe work-
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`piece and the E-chuck, a gap too small for the plasma
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`to penetrate. The rods lift the cover away from the
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`wafer and E-chuck when the wafer is being transport-
`ed to or from the E-chuck.
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`For a more detailed understanding of the plasma
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`reaction chamber 16 and its operation in processing
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`the wafer 12, the reader should refer to the drawings
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`and detailed description contained in EP-A-0552491
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`As shown in Figure 1, the electrical circuit for the
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`plasma reaction chamber 16 is conventional.
`It
`in-
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`cludes a conventional DC voltage source 24 which
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`supplies the clamping voltage which is coupled to the
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`E-chuck 10 through a low pass filter 26 which isolates
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`the DC voltage source 24 from the RF power supply
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`27. RF source power and RF bias power are each
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`coupled from the conventional RF power supply 27
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`through a matching network 28, with the source pow-
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`er being coupled to an inductive antenna 30 and the
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`bias power being coupled to the pedestal 14. Aground
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`reference for both the RF bias power and DC voltage
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`Figure 3 is sectional side view along the lines 3-
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`3 in Figure 2 showing the internal construction of
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`the pedestal and layer of dielectric material on
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`the upper surface thereofwith the cooling gas re-
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`ceiving holes extending vertically from an under-
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`side of the pedestal and a lift pin receiving hole
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`for use in mechanically positioning and lifting the
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`article being processed within the reaction
`chamber.
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`Figure 3a is an enlarged version of Figure 3.
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`Figure 4 is an enlarged illustration ofthe portion
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`of the pedestal and layer of dielectric material
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`within the circle 4 of Figure 2 and shows the
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`grooves defining the gas distribution system in
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`the layer of dielectric material with gas distribu-
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`tion holes through intersections of the grooves
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`and metal ofthe pedestal overthe upper ends of
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`the cooling gas receiving holes to define a cluster
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`of gas distribution holes over each cooling gas re-
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`ceiving hole.
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`Figure 5 is an enlarged version ofa portion ofthe
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`pedestal within the circle 5 of Figure 2 more
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`clearly illustrating the intersecting nature ofthe
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`grooves forming the gas distribution system, a
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`lift pin hole having an annulus there around free
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`of intersecting gas distributing grooves and a
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`portion of an outer annulus bounding a central
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`portion of the pedestal also free of intersecting
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`gas distributing grooves.
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`Figure 6 is an enlarged version of the portion of
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`the pedestal within the circle 6 in Figure 2 more
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`clearly illustrating the intersecting nature ofthe
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`grooves and gas distribution holes formed at the
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`intersection of such grooves ove