WO1999000837A1

WO1999000837A1 - Vacuum processing chamber workpiece lifter

Info

Publication number: WO1999000837A1
Application number: PCT/US1998/013127
Authority: WO
Inventors: Gregory S. Sexton; Vernon W. H. Wong; Richard Beer; John Patrick Holland
Original assignee: Lam Research Corporation
Priority date: 1997-06-30
Filing date: 1998-06-29
Publication date: 1999-01-07

Abstract

A dielectric or semiconductor workpiece having a flat back face is processed in a vacuum plasma processing chamber. An r.f. electrostatic chuck electrode holds the workpiece in situ in the chamber while the workpiece is being processed. The chuck electrode has a flat face (68) on which the workpiece flat face bears while the workpiece is being processed. A mechanism (50) lifts and lowers the workpiece relative to the chuck. The mechanism includes plural spring biased metal pins (56) extending through openings (58) in the chuck. The pins are so close to the electrode that the pins and electrodes are at the same r.f. potential and temperature. Each pin is biased so an upper pin face contacts the workpiece face while (1) the workpiece is clamped to the electrode and (2) moved by the pins relative to the electrode. Since no gaps are between the pins and electrode, all portions of the workpiece back face are at the same r.f. voltage and temperature and plasma is uniformly supplied to the workpiece exposed front face.

Description

VACUUM PROCESSING CHAMBER WORKPIECE LIFTER

Field of Invention

The present invention relates generally to apparatus for plasma processing workpieces in a vacuum chamber and more particularly to a mechanical mechanism for lifting and lowering such workpieces relative to a workpiece holder while preventing gaps between the workpiece and the mechanism while the workpiece is on the holder and is being processed by a plasma.

Background Art When dielectric, semiconductor and metal workpieces are plasma processed in vacuum processing chambers the chamber is supplied with an ionizable gas that is excited by an electric or electromagnetic field to a plasma state. The plasma etches the workpiece or deposits material onto the workpiece while the workpiece is in place on a workpiece holder, frequently a metal electrostatic chuck.

The workpieces are moved through such processing chambers by various mechanical mechanisms . The semiconductor and dielectric workpieces usually are respectively of wafer or panel form, having a flat face abutting and mating with a corresponding flat face of the electrostatic chuck during plasma processing. The chuck develops an electrostatic force to clamp the workpiece to the chuck. A preferred electrostatic chuck for dielectric workpieces is disclosed in the co-pending commonly assigned application of Paul K. Shufflebotham et al., Serial No. 08/542,959, filed October 13, 1995.

Prior art mechanisms for lowering such workpieces onto and lifting them from electrostatic chucks have included a lifter platform in which is embedded several fixed metal pins extending through openings in the chuck. The pins are raised upwardly in the chuck openings to receive the workpieces. After the workpieces have been transferred to the pins, the pins are lowered, i . e . , retracted, so that top faces of the pins are lower than the planar face of the electrostatic chuck. We have realized that virtually perfect alignment between the top faces of the fixed pins and of the electrostatic chuck is necessary to achieve proper wafer processing, particularly by a plasma. However, the top faces of the fixed or embedded prior art pins cannot usually be perfectly aligned with the electrode top face. We have discovered that the misalignment between the top faces of the pins and the electrostatic chuck top face prevents proper workpiece processing at workpiece areas in the region directly above the pins. The misalignment of the top pin faces and the electrostatic chuck planar face causes gaps between the pins and the workpiece bottom face. These gaps cause a larger reactive (i.e. capacitive) impedance between the bottom workpiece face and the top faces of the nonaligned metal pins than the capacitive impedance between the metal pins abutting the bottom workpiece face. The gap capacitance causes reduced attraction of the plasma charge carriers to the semiconductor or dielectric workpiece portions exposed to the plasma in the region directly above the gaps relative to the exposed workpiece portions aligned with the workpiece back face portion contacting the electrode or fixed metal pins. In consequence, plasma charge carriers which perform the etching and deposition functions, act differently against the exposed workpiece portions that are above the gaps compared to the way the plasma etches and deposits material on the exposed workpiece portions above the workpiece bottom face portions contacting the electrode or fixed metal pins. In addition, the gaps cause a temperature differential in the exposed portions of the workpiece that are vertically aligned with the gaps compared to the portions of the workpiece which are not vertically aligned with the gaps but which contact the chuck upper face. The fixed metal pins contacting the workpiece and the chuck portion contacting the workpiece have substantially the same heat transfer properties to the workpiece . The vacuum in a gap between a pin and the workpiece has virtually no heat conductance capability. Consequently, the temperature of the workpiece portions vertically aligned with the gaps is somewhat different from the workpiece portions above the regions without gaps . The temperature difference is sufficient to cause chemical species in the plasma to react differently with the portions of the workpiece above the gaps than the workpiece portions which are not above the gaps.

The temperature and capacitance effects associated with the gaps may be noticeable to a lesser degree with semiconductor or other conductive workpieces, but are quite pronounced with dielectric workpieces. Semiconductor workpieces have considerably lower electrical conductivity than metals and usually have substantially lower thermal conductivity than metals. Dielectric workpieces have much lower electrical conductivity than semiconductors and usually have substantially lower thermal conductivity than metals. As a result of the low electrical conductivities of the workpieces, charge carriers do not migrate readily in the semiconductor workpieces and have virtually no migration in the dielectric workpieces, whereby the high electric impedance of the gaps substantially reduces the directed flux of the plasma processing charge carriers on the portion of the workpiece surface above the gaps exposed to the plasma to decrease the plasma etching and deposition effects . The high thermal impedance of the gaps and the low thermal conductivity of the semiconductor and dielectric workpieces reduce the temperature of the exposed surface of the workpiece portions aligned with the gaps. The reduced temperatures of these exposed workpiece portions cause a further reduction in mobility of the plasma charge carriers above the gaps. If the pins extend above the electrode, the pins contact the dielectric panel and cause a gap between the electrode and the panel, causing a lower flux of charged carriers and a lower heat transfer in the gap between the electrode and panel .

There are important mechanical reasons for the top edges of all the pins to abut the workpiece lower planar face. Many workpieces have substantial area; for example, dielectric, glass workpieces processed to form flat panel displays. It is important to minimize deflection of such workpieces during processing and while the workpieces are lowered onto and lifted from the workpiece holder. To maintain the planar characteristics of such large workpieces the top faces of the pins must be within +000/-001mm of alignment with the workpiece holder planar top surface.

We_ have found such an alignment to be virtually impossible to achieve with lifter mechanisms having fixed or embedded pins acting on dielectric workpieces having the stated dimensions. Lifter mechanisms with fixed or embedded pins are difficult to adjust during installation, service and/or maintenance. Pins of fixed pin lifters have been usually adjusted manually in the past. To obtain the correct adjustment, many trial and error iterations are necessary to place the pins to within acceptable tolerances of the workpiece holder surface. If the pins need adjusting after initial installation, e . g. due to wear under processing conditions, the chamber vacuum must be broken, causing significant processor down time. It is accordingly an object of the present invention to provide a new and improved mechanism for lifting and lowering workpieces relative to workpiece holders in vacuum processing chambers.

Another object of the invention is to provide a new and improved mechanism for lifting and lowering relatively large area, thin workpieces in vacuum processing chambers wherein the workpieces are maintained in a planar condition while being lifted and lowered and while in si tu on a workpiece holder. An additional object of the invention is to provide a new and improved mechanism for lowering and lifting dielectric and semiconductor workpieces relative to a chuck having an r.f. bias applied to it in a vacuum plasma processing chamber, wherein the lifting mechanism is arranged so virtually all of the workpiece surface area exposed to the plasma is maintained at substantially the same charge and temperature conditions so there is uniform application of plasma to the exposed surface.

An additional object of the invention is to provide a new and improved mechanism for lowering and lifting dielectric and semiconductor workpieces relative to a chuck having an r.f. bias applied to it in a vacuum plasma processing chamber, wherein the lifting mechanism is arranged so virtually all of the workpiece surface area exposed to the plasma is maintained at substantially the same r.f. potential.

An additional object of the invention is to provide a new and improved mechanism for lowering and lifting dielectric and semiconductor workpieces relative to a chuck having an r.f. bias applied to it in a vacuum plasma processing chamber, wherein the lifting mechanism is arranged so virtually all of the workpiece surface area exposed to the plasma is maintained at substantially the same temperature .

Still a further object of the invention is to provide a new and improved mechanism for lowering and lifting workpieces relative to a chuck of a vacuum processing chamber, wherein individual pins of the mechanism are automatically adjusted to bear against the workpiece .

Disclosure of the Invention

In accordance with one aspect of the invention a dielectric or semiconductor workpiece processed in a vacuum plasma processing chamber is selectively lifted from and lowered onto a face of an electrode by a mechanical mechanism that maintains portions of the workpiece contacting the mechanical mechanism at substantially the same r.f. potential and temperature as the workpiece portions engaging the electrode.

Preferably the mechanical mechanism includes pins having end faces that are co-planar with a face of the electrode against which a back face of the workpiece bears when the workpiece is on the electrode. A spring bias arrangement urges the pins against the workpiece back face while the workpiece is on the electrode to provide the co-planar relationship of the electrode face and the. pin end faces . The spring biased metal pins extend through openings in the electrode and are arranged to be at the same r.f. potential and temperature as the chuck. The pins fit so snugly in the openings that the r.f. coupling and radiant heat transfer between the electrode and pins cause the pins and electrode to be at substantially the same r.f. potential and temperature. Each pin is preferably biased by a separate spring.

In accordance with another aspect of the invention, a workpiece processed in a vacuum plasma processing chamber is selectively lifted from and lowered onto a face of a workpiece holder by a mechanical mechanism including spring biased pins having an upper face contacting a back face of the workpiece that mates with a face of the holder. The spring bias is such that the upper pin faces and holder face are co-planar while the workpiece is on the holder. The pins maintain the workpiece back face in substantially the same plane when the pins lift and lower the workpiece relative to the holder.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of a specific embodiment thereof, especially when taken in conjunction with the accompanying drawings.

Brief Description of Drawing

Fig. 1 is an overall view of a vacuum plasma processing chamber of the type utilizing the present invention; Fig. 2 is an enlarged view of a preferred embodiment of a portion of the chamber illustrated in Fig. 1; and

Figs. 3A-3D are schematic diagrams helpful in describing the operation of the mechanism illustrated in Figs . 1 and 2.

Description of the Preferred Embodiment

Reference is now made to Fig. 1 of the drawing, wherein plasma processor 8 that can be used for processing a dielectric or semiconductor workpiece 9, e.g. by (1) etching a glass flat panel used in a flat panel display or a semiconductor wafer and/or (2) depositing films on such a panel or wafer, is illustrated as including vacuum chamber 10, preferably configured as a right parallelepiped having electrically grounded, sealed exterior surfaces formed by rectangular metal, preferably anodized aluminum, sidewalls 12. Vacuum chamber 10 also includes rectangular metal, preferably anodized aluminum, bottom end plate 16 and rectangular top end plate structure 18, including dielectric window structure 19. Sealing of these exterior surfaces of chamber 10 is provided by conventional gaskets (not shown) .

A suitable gas that can be excited to a plasma is supplied to the interior of chamber 10 from gas source 14 via port 20 in sidewall 12. The interior of chamber 10 is maintained in a vacuum condition, at a pressure typically in the range of 0.5-100 milliTorr, by vacuum pump 15 connected to port 22 in sidewall 12. The gas in vacuum chamber 10 is excited to a plasma by a suitable electric source, such as coil 24, mounted immediately above window 19 and excited by r.f. source 26 via matching network 28 that is resonant to the frequency of source 26; it is to be understood however that any suitable method of plasma generation can be employed. Metal electrostatic chuck 30 is fixedly mounted in chamber 10 on a support structure including grounded metal base 27 that is electrically decoupled from the chuck by electrical insulating sheets 29; base 27 is fixed to side wall 12. In a preferred embodiment chuck 30 is of the type described in the co-pending commonly assigned application of Paul K. Shufflebotham et al., Serial No. 08/542,959, filed October 13, 1995. Such a chuck is particularly designed to selectively hold a non- plastic dielectric workpiece, particularly a flat glass substrate sheet of a flat panel display.

In one embodiment, the temperature of workpiece 9 is controlled to be between 25°-400°C by supplying (1) helium gas from source 33 via conduit 34 and groove 35 to the workpiece 9 back face, i.e., to the face of the workpiece not exposed to the ions in processing chamber 10, and (2) a recirculating coolant liquid, e.g., a mixture of water and ethylene glycol , from temperature control unit 39 to chuck 30 via conduits 37. Groove 35 extends about the periphery of chuck 30, outside the portion of the workpiece 9 exposed face to be processed by the plasma. Liquid from unit 39 flows into cavity 41 in electrostatic chuck 30; cavity 41 is below interior portions of workpiece 9. Typically, the pressure of the helium gas applied to the back face of workpiece 9 is in the 5-15 Torr range and the helium flow rate through conduit 34 is in the 5-70 seem range. The helium flows from source 33 through a flow controller (not shown) and a pressure transducer (not shown) into conduit 34 and groove 35 via a stem and one arm of a "T" connection, the other arm of which is connected through an orifice having a controlled opening to a pump .

Chuck 30 is constructed so the planar back face of workpiece 9 abuts flat planar face 68 of the chuck, except in portions of the chuck face where groove 35 is located and except where lifting pins 56 are located. Chuck 30 applies an electrostatic force to the workpiece so the exposed surface of the workpiece is flat and lies in a plane substantially parallel to the chuck flat planar face. This result is achieved even though workpiece 9 may be warped or wavy when put onto the chuck and despite the tendency of the helium gas flowing through groove 35 to bow the workpiece upwardly into chamber.10 away from the flat planar face of chuck 30. Chuck 30 is also constructed so a high thermal conductivity path is provided through the chuck to workpiece 9 from the cooling liquid flowing into cavity 41.

In the preferred embodiment, electrostatic chuck 30 is a monopolar device having only one electrode, metal plate 36, connected to a high voltage output of DC source 38, including low pass r.f. rejection filter 139. Typically the high voltage output of source 38 is negative with respect to ground terminal 42 to attract relatively low mobility positive ions of the plasma to the exposed face of workpiece 9.

A radio frequency (e.g. 4.0 mHz) bias voltage is supplied to chuck 30 for ion energy control on the exposed face of workpiece 9. To this end, r.f. source 44 is connected via matching network 46 to chuck 30. The plasma formed in chamber 10 acting on the exposed face of workpiece 9 is usually at a voltage close to ground. The r.f. voltage applied by source 44 to chuck 30 is coupled to the back face of workpiece 9, i . e . , the face of the workpiece opposite from the workpiece front face exposed to the plasma in chamber 10. A portion of the r.f. voltage applied to the back face of workpiece 9 is capacitively coupled by dielectric workpieces to the workpiece front face. For semiconductor workpieces, a portion of the r.f. voltage applied to the workpiece back face is transferred by the charge carriers of the semiconductor to the workpiece exposed face . In any event, a portion of the r.f. voltage at the back face of the workpiece has a tendency to be coupled through the thickness of the workpiece to corresponding portions of the workpiece exposed surface. If the r.f. voltage on one portion of the workpiece back face differs from the r.f. voltage on another portion of the workpiece back face, there are corresponding differences in r.f. voltage and charge on corresponding different portions of the workpiece exposed face. These differences in r.f. voltage and charge on different portions of the workpiece front face have a tendency to differentially affect the action of plasma on the different regions of the exposed face. In a similar manner, the thermal conductivity of the dielectric and semiconductor workpieces is such that differences in temperature on different regions of the workpiece back face are transferred as temperature differences to the corresponding regions of the workpiece exposed face. The resulting temperature differences at different regions of the workpiece exposed face affect the mobility of charge carriers in the plasma acting on the exposed face. Consequently, the combined effects of r.f. voltage and temperature differences on different regions of the dielectric and semiconductor back face affect the way the plasma acts on corresponding regions of the workpiece exposed face .

Workpiece 9 is lowered onto and lifted from the upper face of electrode 30 by a mechanical lifting mechanism including lifting platform 50 driven vertically in chamber 51 in electrostatic chuck 30 by drive 52 via vertically extending shaft 54. Platform 50 carries vertically extending metal pins 56 which have a small clearance in vertically extending bores 58 of chuck 30. Bores 58 extend from chamber 51 through chuck 30 to the top planar face of the chuck. In one preferred embodiment, eight pins 56 are included (only four are illustrated) and are arranged to be equally spaced about the circumference of a circle having its center aligned with the axis of shaft 54, at the center of chuck 30.

Pins 56 are arranged so that the top faces thereof engage the back face of workpiece 9 while the workpiece flat back face abuts the top flat face of electrode 36. The arrangement is such that there is no gap between the top faces of pins 56 and the back face of workpiece 9 while the workpiece is clamped to the top face of electrostatic chuck 30. Because of the close proximity of the walls of metal pins 56 to the metal walls of bores 58 in chuck 30 through which the pins extend, the top faces of the pins are at virtually the same r.f. voltage and temperature as the top face of chuck 30. Thereby, the portions of the bottom or back face of workpiece 9 contacting the top faces of pins 56 are at the same r.f. voltage and temperature as the r.f. voltage and temperature of the workpiece back face portions abutting the top face of electrode 36. As a result, there is uniform application of plasma to the exposed face of workpiece 9 for the portions of the workpiece vertically aligned with the workpiece back face abutting the chuck 30 top face and for the portions of the workpiece exposed face aligned vertically aligned with the top faces of pins 56.

Chuck 30 and pins 56 are at virtually the same r.f. voltage and temperature because the metal pin walls and metal walls of bores 58 through which the pins extend are in such close proximity to each other. The pins are so close to the chuck bore walls that the pins are guided by bores 58 as the pins are raised and lowered by platform 50; in one preferred embodiment the spacing between the walls of pins 56 and the walls of bores 58 is in the range of about 0.025 to 0.125 mm. As a result, there is very high reactive coupling of the chuck r.f. voltage to the metal pins. The capacitance between pins 56 and the chuck bore walls is so great that the pins are at virtually the same r.f. voltage as the chuck. Similarly, the thermal radiant coupling between the metal walls of bores 58 and metal pins 56 is so great that the pins and chuck 30 are at virtually the same temperature. The same temperature exists at the pins and chuck even though there is virtually no thermal conduction medium between pins 56 and chuck 30 which are in the very low pressure atmosphere of chamber 10.

To enable the top faces of pins 56 to be co-planar with the top face of chuck 30 so the back face of workpiece 9 abuts the top faces of the pins and the top face of the chuck while the workpiece is electrostatically clamped to the chuck, the individual pins, in one preferred embodiment, are spring-biased upwardly, as illustrated in greater detail in Fig. 2. In particular, each of pins 56 includes a vertically extending shaft 60 having a circular cross section. Shaft 60 includes upper segment 62 and lower segment 64, such that the upper segment has a slightly larger diameter than the lower segment to form shoulder 65 that extends outwardly from the lower segment to the upper segment . The upper part of segment 62 extends through bore 58 in chuck 30 and is arranged so that when no load is applied to pin 56, top face 66 of pin 56 extends slightly above top face 68 of chuck 30; typically, top pin face 66 is about 0.75 mm above top chuck face 68 when no load is applied to pin 56. The lower part of bore 58 is tapered outwardly to form frustoconical section 70 and facilitate insertion of pin 56 into bore 58.

Pin 56 is biased upwardly to the position illustrated in Fig. 2 by compression spring 72, having a top end bearing against shoulder 65 and a bottom end captured by the top face of flat washer 74, having a bottom face bearing against lifter plate or platform 50. Spring 72 encircles the top portion of lower shaft segment 64. The lower portion of shaft segment 64, extending into cavity 76 of lifter plate 50, is held in place by C-ring clamp 78, having a top face bearing against the ceiling of cavity 76. Cavity 76 has an enlarged segment extending to the wall of lifter platform 50 to enable installation of C-ring clamp 78. The spring constant and length of spring 72 are such that spring 72 is only partially compressed when the top face 66 of pin 56 bears workpiece 9 as a load.

Reference is now made to Figs. 3A-3D to assist in providing a better understanding of how spring biased pins 56 and lifter plate 50 function to raise and lower a relatively large area workpiece 9 that is subject to substantial deflection and to maintain such a workpiece in a relatively planar condition.

In Fig. 3A, drive mechanism 52 has translated shaft 54 and lifter plate 50 vertically, so that top faces 66 of pins 56 are substantially above the top face 68 of chuck 30, while the top faces of the pins are compressed to a certain extent by workpiece 9 bearing on them. As illustrated in Fig. 3A, the top face of lifter platform 50 is in close proximity to ceiling 82 of cavity 51 traversed by lifter plate 50. Spring 72 is compressed a substantial amount when lifter plate 50 is at the top of its throw in proximity to ceiling 82 and the workpiece bears on the pin upper face, as illustrated in Fig. 3A. In particular, spring 72 is compressed by in excess of 1.25 mm, i.e., by an amount greater than the amount that upper pin face 66 extends above chuck face 68 when there is no load on the pins and the pins and lifter plate 50 are in the fully retracted position illustrated in Fig. 2. When workpiece 9 is clamped by electrostatic chuck

30 including electrode 36 so that the bottom face of the workpiece bears and is held against the upper face of chuck 30, as illustrated in Fig. 3B, upper face 66 of pin 56 is compressed so that the upper pin face is aligned with upper chuck face 68. This occurs because of the spring constant and length of spring 72 and the distance between washer 74 and shoulder 65 when the workpiece is clamped into place on the electrostatic chuck.

After workpiece 9 has been removed (as illustrated in Fig. 3C) from pins 56 by a transfer mechanism (not shown) in chamber 10, spring 72 forces the top face 66 of pin 56 upwardly, above the position that the upper pin face occupies when the pin is loaded by workpiece 9; in this regard, the position of upper face 66 of pin 56 in Fig. 3C is farther from lifter plate 50 and the upper face 68 of chuck 30 than in Fig. 3A. Platform 50 is illustrated in Fig. 3C as being driven to the same upward position that the platform occupies in Fig. 3A.

When platform 50 is retracted, i.e., driven downwardly, with no load on pin 56, the upper pin face 66 extends slightly above chuck upper face 68, as illustrated in Figs. 2 and 3D.

Because of the use of spring biased pins 56, the bottom face of workpiece 9 is maintained relatively planar while the workpiece is lowered onto and lifted from chuck 30 and the back face of the workpiece conforms with top planar face 68 of chuck 30, which is coincident with the top faces 66 of pins 56. Because of the co- planar arrangement of the top face 68 of chuck 30 and the top faces 66 of pins 56 while the workpiece is chucked, there are no substantial temperature variations on the exposed face of workpiece 9 and virtually all areas of the workpiece are acted on in the same manner by the plasma, except the portions of the workpiece outside the inner edge of groove 35.

While there has been described and illustrated one specific embodiment of the invention, it will be clear that variations in the details of the embodiment specifically illustrated and described may be made without departing from the true spirit and scope of the invention as defined in the appended claims. For example, compression springs 56 can be replaced by belleville or leaf springs. Also the illustrated individually mounted spring arrangement can be replaced with a cartridge containing an assembly of springs. Another alternative is to spring bias lifter plate 50 and to fixedly mount metal pins 56 on such a plate so the pins bear collectively on the workpiece back face. However, the individually spring biased pins of the illustrated preferred embodiment are advantageous because such pins (1) result in a self leveling and self adjusting structure while the workpiece is clamped to chuck 30 and (2) eliminate fine tune mechanical adjustments to compensate for small differences from assembly to assembly. Also the individually spring biased pins 56 are self centered in bores 58 as plate 50 is raised and lowered because the pins are not rigidly held on plate 50.

WHAT IS CLAIMED:

1. Apparatus for processing a dielectric or semiconductor workpiece having a face, comprising a vacuum processing chamber, an electrode for holding the workpiece in the chamber while the workpiece is being processed in the chamber, the electrode having a face mating with the workpiece face while the workpiece is being processed, an r.f. source connected to supply r.f. voltage to the electrode, and a mechanical mechanism for mechanically lifting the workpiece away from and lowering the workpiece onto the electrode face, the mechanical mechanism being arranged to maintain portions of the workpiece face contacting the mechanical mechanism at substantially the same r.f. potential as the workpiece face portions contacting the electrode while the workpiece is on the electrode.

2. The apparatus of claim 1 wherein the mechanical mechanism is arranged to maintain portions of the workpiece face contacting the mechanical mechanism at substantially the same temperature as the workpiece face portions contacting the electrode while the workpiece is on the electrode.

3. The apparatus of claim 2 wherein the mechanism includes a plurality of metal pins extending through openings in the electrode, the pins being arranged to be at substantially the same r.f. potential and temperature as the electrode while the workpiece is on the electrode, each pin having an upper face contacting the workpiece face while the workpiece is on the electrode and lifted by the pins away from the electrode face .

4. The apparatus of claim 3 wherein the pins fit so snugly in the openings that the r.f. coupling and radiant heat transfer between the electrode and the pins cause the pins and electrodes to be at substantially the same r.f. potential and temperature.

5. The apparatus of claim 4 wherein the mechanism spring biases the metal pins so the upper face of each pin is spring biased against the workpiece face while the workpiece is on the electrode.

6. The apparatus of claim 5 wherein each pin is biased by a separate spring.

7. The apparatus of claim 3 wherein the mechanism spring biases the metal pins so the upper face of each pin is spring biased against the workpiece face while the workpiece is on the electrode.

8. The apparatus of claim 7 wherein each pin is biased by a separate spring.

9. The apparatus of claim 1 wherein the mechanism includes a plurality of metal pins extending through openings in the electrode, the pins being arranged to be at the same r.f. potential and temperature as the electrode while the workpiece is on the electrode, each pin having an upper face contacting the workpiece face while the workpiece is on the electrode and lifted by the pins away from the electrode face.

10. The apparatus of claim 9 wherein the clearance between the pins and the bores in the electrode is such that the r.f. coupling between the electrode and the pins causes the pins and electrodes to be at substantially the same r.f. potential. 11. The apparatus of claim 10 wherein the mechanism spring biases the metal pins so the upper face of each pin is spring biased against the workpiece face while the workpiece is on the electrode.

12. The apparatus of claim 11 wherein each pin is biased by a separate spring.

13. The apparatus of claim 10 wherein the mechanism spring biases the metal pins so the upper face of each pin is spring biased against the workpiece face while the workpiece is on the electrode.

14. The apparatus of claim 1 wherein the electrode is included in an electrostatic chuck.

15. The apparatus of claim 1 wherein the electrode face includes a peripheral groove adapted to be connected to a supply of cooling gas, the groove being arranged so the periphery of the workpiece face is contacted by the cooling gas.

16. Apparatus for processing a dielectric or semiconductor workpiece having a face, comprising a vacuum processing chamber, a holder for holding the workpiece in the chamber while the workpiece is being processed in the chamber, the holder having a face mating with the workpiece face while the workpiece is being processed, and a mechanical mechanism for mechanically lifting the workpiece away from and lowering the workpiece onto the electrode face, the mechanical mechanism being arranged to maintain portions of the workpiece face contacting the mechanical mechanism at substantially the same temperature as the workpiece face portions contacting the holder while the workpiece is on the holder. 17. The apparatus of claim 16 wherein the mechanism includes a plurality of metal pins extending through openings in the electrode, the pins being arranged to be at substantially the same temperature as the holder while the workpiece is on the holder, each pin having an upper face contacting the workpiece face while the workpiece is on the holder and lifted by the pins away from the holder face.

18. The apparatus of claim 16 wherein the clearance between the pins and the bores in the electrode is such that the pins and holder are at substantially the same temperature .

19. The apparatus of claim 18 wherein the mechanism spring biases the metal pins so the upper face of each pin is spring biased against the workpiece face while the workpiece is on the holder.

20. The apparatus of claim 19 wherein each pin is biased by a separate spring.

21. Apparatus for processing a workpiece having a face, comprising a vacuum processing chamber, a holder for holding the workpiece in the chamber while the workpiece is being processed in the chamber, the holder having a face mating with the workpiece face while the workpiece is being processed, and a mechanical mechanism for mechanically lifting the workpiece away from and lowering the workpiece onto the holder face, the mechanism including plural spring biased pins extending through openings in the holder, each pin having an upper face spring biased to contact the workpiece face while the workpiece is on the holder. 22. The apparatus of claim 21 wherein each pin is biased by a separate spring.

Claims

AMENDED CLAIMS[received by the International Bureau on 11 December 1998 (11.12.98); original claims 1-22 replaced by new claims 1-23 (11 pages)]

1. Apparatus for processing a dielectric or semiconductor workpiece having a back face, comprising a vacuum processing chamber, a chuck for holding the workpiece in the chamber while the workpiece is being processed in the chamber, the chuck having an upper face mating with a substantial segment of the workpiece back face while the workpiece is being processed, an r.f. source connected to supply r.f. voltage to an electrode of the chuck, and a mechanical mechanism for mechanically lifting the workpiece away from and lowering the workpiece onto the chuck upper face, the chuck being arranged so that at least one opening in the chuck through which the mechanical mechanism extends has a tendency to cause portions of the workpiece back face above the at least one opening to be at an r.f . potential different from the r.f. potential of said segment of the workpiece contacting the chuck upper face, characterized by the mechanical mechanism extending through the at least one opening in the chuck and being urged into contact with portions of the workpiece back face while the workpiece is being processed, the mechanical mechanism, the chuck and the electrode being arranged to maintain said portions of the workpiece back face contacting the mechanical mechanism at substantially the same r.f. potential as the workpiece back face segments contacting the chuck segments while the workpiece is on the chuck face and being processed to thereby overcome said tendency.

2. Apparatus for processing a dielectric or semiconductor workpiece having a back face and a front face exposed to reactant materials during processing, comprising a vacuum processing chamber, a holder for holding the workpiece in the chamber while the workpiece is being processed in the chamber, the holder having an upper face for mating with and contacting the workpiece back face while the workpiece is being processed, and a mechanical mechanism for mechanically lifting the workpiece away from and lowering the workpiece onto the holder upper face, the mechanical mechanism including plural metal pins extending through openings in the holder, the pins being arranged so all of the pins are at substantially the same temperature as the holder while the workpiece is on the holder and being processed in the chamber, characterized by each pin having an upper face arranged to be urged into contact with the workpiece back face while the workpiece (a) back face is on the holder upper face during workpiece processing and (b) is lifted by the pins away from the holder upper face, the holder^" and the mechanism being arranged so the temperature of the workpiece portions abutting the pins and abutting the holder during processing is substantially the same such that the reactant materials incident on the workpiece exposed face directly above the workpiece portions contacting the pins react substantially the same as the reactant materials incident on the workpiece exposed face directly above the workpiece portions contacting the holder upper face .

3. Apparatus for processing a workpiece having a back face and an exposed front face that is processed, comprising a vacuum processing chamber, a holder for holding the workpiece in the chamber while the workpiece is being processed in the chamber, the holder having an upper face for mating with the workpiece back face while the workpiece is being processed, and a mechanical mechanism for mechanically lifting the workpiece away from and lowering the workpiece onto the holder face, the mechanism including plural spring biased metal pins extending through openings in the holder, characterized by each pin of the mechanism having an upper face spring biased for contacting the workpiece back face while the workpiece is on the holder and the exposed face is being processed in the chamber.

4. The apparatus of claim 1 or 3 wherein t e- mechanical mechanism and chuck are arranged to maintain the workpiece back face portions contacting the mechanical mechanism at substantially the same temperature as the workpiece back face segment contacting the chuck segment while the workpiece is on the chuck and being processed.

5. The apparatus of claim 3 wherein the pins are arranged to cause the upper faces thereof to be at substantially the same r.f. potential and temperature as the chuck upper face segment while the workpiece is on the chuck and being processed.

6. The apparatus of claim 1, 2 or 4 , as dependent on claim 1, wherein the mechanism includes a plurality of metal pins extending through plural openings in the chuck, each pin having an upper face for contacting the chuck back face while the workpiece is (a) being processed and is on the chuck and (b) lifted by the pins away from the chuck face, the pins being arranged to cause the upper faces thereof to be at substantially the same r.f. potential and temperature as the chuck upper face segment while the workpiece is on the chuck and being processed.

7. The apparatus of claim 3 or 6 wherein the pins are arranged to fit so snugly in the openings that r.f .- coupling and radiant heat transfer between the chuck and the pins cause the upper faces of the pins and chuck to be at substantially the same r.f. potential and temperature as the chuck upper face segment while the workpiece is on the chuck and being processed.

8. The apparatus of claim 6 or 7 wherein the mechanism spring biases the metal pins so the upper face of each pin of the mechanical mechanism is spring biased against the workpiece back face while the workpiece is on the chuck and being processed.

9. The apparatus of claim 4 wherein each pin is biased by a separate spring.

10. The apparatus of claim 1 or 3 wherein the mechanism includes a plurality of metal pins extending through plural openings in the chuck, each pin having an upper face for contacting the chuck back face while the workpiece is (a) being processed and is on the chuck and

(b) lifted by the pins away from the chuck face, the pins being arranged to cause the upper faces thereof to be at substantially the same r.f. potential as the chuck upper face segment while the workpiece is on the chuck and being processed.

11. The apparatus of claim 10 wherein clearance between the pins, electrode and openings in the chuck through which the pins extend is small enough to cause the r.f. coupling between the electrode and the pins to be such that the pins and chuck upper face are at substantially the same r.f. potential.

12. The apparatus of claim 11 wherein the mechanism spring biases the metal pins so the upper face of each pin in the mechanical mechanism is spring biased against the workpiece face while the workpiece is on the electrode .

13. The apparatus of claim 12 wherein each pin is biased by a separate spring.

14. The apparatus of any of the preceding claims wherein the chuck is an electrostatic chuck.

15. The apparatus of any of the preceding claims wherein the chuck upper face includes a peripheral groove adapted to be connected to a supply of cooling gas, the groove being arranged so the periphery of the workpiece face is contacted by the cooling gas, the chuck upper face portion including the peripheral groove being arranged so it is at an r.f. potential different from the r.f. potential of the substantial segment of the chuck- upper face .

16. The apparatus of any of claims 3 and 6-13 wherein the plural metal pins are located toward a center portion of the workpiece while the workpiece is being processed and is on the holder.

17. The apparatus of claim 3 further including a source of heat exchange fluid, a conduit for coupling the fluid between the fluid source and the holder, the holder and the fluid coupled to the holder being arranged so that the upper face of the holder mating with the workpiece bottom face is at substantially the same temperature, the plural pins being arranged to be spring biased against the back face while the workpiece is being processed, the pins being radiantly coupled with the holder and thermally coupled via conduction with the back face of the workpiece while the workpiece is being processed and the pins are urged against the workpiece back face so that the upper face of each pin, while in contact with the workpiece back face during processing is at substantially the same temperature as the portion of the holder upper face mating with the workpiece back face, the heat coupled between the pins and the workpiece back face portions abutting the pins and the holder upper face mating with the workpiece back face being such that there is uniform temperature of the workpiece exposed- face to cause reactive materials in the vacuum processing chamber incident on the exposed face of the workpiece to react the same regardless of whether the reactive materials are incident on portions of the exposed face directly above the holder face mating with the workpiece face or directly above the openings through which the plural spring biased pins extend.

18. A method of processing a dielectric or semiconductor workpiece with charge particles in a vacuum processing chamber, the chamber including a chuck having an electrode and an upper face, and a mechanical mechanism for lifting the workpiece away from and lowering a back face of the workpiece onto the upper face, the chuck including openings through which portions of the mechanical mechanism extend, the openings extending through portions of the upper face, the method comprising applying an r.f. voltage to the electrode, characterized by while the back face of the workpiece is on the chuck upper face and the workpiece is in the vacuum of the vacuum chamber and being processed by charge particles and the r.f. voltage is applied to the chuck and the mechanical mechanism is being urged against the workpiece back face, coupling from the electrode via (1) the chuck (a) substantially the same r.f. voltage to a substantial segment of the bottom face^~- differing from portions of the bottom face abutting the openings and (b) an r.f. voltage that differs materially from said substantially the same voltage to portions of the back face abutting said openings, and (2) the mechanical mechanism an r.f. voltage to the workpiece back face portions abutting said openings, the r.f. voltages coupled during processing to the bottom face portions and the substantial segment of the bottom face being substantially the same such that during processing there is substantially uniform charge and r.f. potential applied by the chuck to the workpiece portions exposed to the plasma directly above (1) said substantial segment and (2) the lower face portions abutting said openings.

19. A method of processing a dielectric or semiconductor workpiece with charge particles in a vacuum processing chamber, the chamber including a chuck having an electrode and an upper face, and a mechanical mechanism for lifting the workpiece away from and lowering a back face of the workpiece onto the upper face, the chuck including openings through which portions of the mechanical mechanism extend, the openings extending through portions of the upper face, the method comprising while a bottom face of the workpiece is on the chuck upper face and the workpiece is in the vacuum of the vacuum chamber and being processed by charge particles- and the mechanical mechanism is being urged against the workpiece back face coupling heat directly by conduction between the chuck and a substantial segment of the back face differing from portions of the back face abutting the openings so all of the substantial segment is at substantially the same temperature, and radiantly coupling heat via the openings between the chuck and portions of the back face abutting the openings to cause the portions of the back face abutting the openings to be at a temperature different from the substantial segment of the bottom face, radiantly coupling heat via the openings between the chuck and segments of the mechanical mechanism in the openings, characterized by coupling heat directly by conduction between the segments of the mechanical mechanism in the openings and the portions of the bottom' face abutting the openings, the heat coupled to the bottom face portions and the substantial segment of the bottom face being such that there is a substantially uniform temperature applied by the chuck to the workpiece region portions exposed to the plasma directly above (1) said substantial segment and (2) the bottom face portions abutting said openings.

20. The method of claim 18 or 19 wherein the mechanical mechanism includes metal pins extending through the openings, and spring biasing the pins against the back face while the workpiece is being processed.

21. The method of claim 18 or 19 wherein the mechanical mechanism includes metal pins extending through the openings, and individually spring biasing each of the pins against the back face while the workpiece is being processed.

22. The method of any of claims 18, 19, 20 or 21 further including transferring heat between the chuck and the substantial segment by conduction, radiantly transferring heat between the chuck and the mechanism, and transferring heat by conduction between the mechanism and the back face portions abutting said openings, the heat transfers occurring while the back face of the workpiece is on the chuck upper face and the workpiece is in the vacuum of the vacuum chamber and being processed by charge particles and the r.f. voltage is applied to the chuck and the mechanical mechanism is being urged against the workpiece back face, the heat transfer being such that the workpiece portions exposed to the plasma directly above (1) said substantial segment and (2) the back face portions abutting said openings are at substantially the same temperature.

23. The method of any of claims 18, 19, 20, 21 or 22 wherein the workpiece is a dielectric.