JP2001118914A - Electrostatic chuck provided with a wafer contact electrode and wafer chucking method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic chuck which supplies a current leakage from a wafer. SOLUTION: A device and a method in which a nonconductive wafer is electrostatically chucked. For example, a wafer contact electrode which can electrically contact with silicon substrate material to be able to supply a proper electric drain of primary beam which is infused into the wafer by SEM and to equally transfer a voltage impressed from the outside through the wafer silicon, is provided. Because of a comparatively large contact area of the wafer contact electrode with the rear side of the wafer a silicon substrate voltage can be effectively controlled. Such normal merit of electrostatic chuck as avoiding particle contamination caused by a mandatory flatenning of the wafer or by mechanically contacting with the wafer, can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic chuck for gripping a non-conductive wafer, and more particularly, to an electrostatic chuck having at least one wafer contact electrode. Things.

[0002]

BACKGROUND OF THE INVENTION To hold silicon wafers and other substrates in place during steps associated with various inspections and processes of a manufacturing flow performed in a vacuum environment where vacuum chucks cannot be used. Generally, electrostatic and mechanical chuck mechanisms are used. Such a process,
Without limitation, ion implantation, plasma etching, charged particle beam (SEM (scanning electron microscope), FIB (focused ion beam)), X-rays and charged species are implanted into the substrate or It may include other processes for extracting charged particles from the material. Such a process may intentionally or unconsciously generate a surface potential or electric field near the surface of the substrate. For example, it is generally necessary to be able to control the electric field around the surface of the wafer or substrate to produce some desired effect on the substrate due to high electric fields or to prevent unwanted damage. It is.

[0003] Mechanical chucks, such as chucks with mechanical fingers to grip the edges of the wear or substrate, are electrically connected to the back of the wafer and over a large area to provide a current leakage path. It has the advantage of being in contact. However, mechanical chucks
It has the disadvantage that it tends to distort the shape of the wafer and tends to cause unwanted particle contamination by mechanical gripping action.

[0004] Electrostatic chucks tend to flatten the wafer when the electrostatic gripping force pulls the wafer against the chucking surface and are less desirable than mechanical chucks because they are cleaner. Has the advantage that the possibility of particle contamination is reduced. The design of the electrostatic chuck essentially requires a dielectric rather than a conductive surface in contact with the wafer. Reliable electrical contact to some substrates has proven to be very difficult. The wafer is typically non-conductive,
Alternatively, the semiconductor device may have a non-conductive layer (eg, an oxide layer) on the rear side. The formation of cracks in such non-conductive layers to establish electrical contact is not acceptable from a processing point of view. For example, this may result in particle contamination or may have to be compromised in subsequent manufacturing processing steps. Thus, the electrostatic chuck has the disadvantage that it does not provide a meaningful current leakage path from the wafer.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide an improved electrostatic chuck for gripping a non-conductive wafer. An object of the present invention is to provide a wafer chucking method. It is another object of the present invention to provide an electrostatic chuck device having at least one wafer contact electrode.

[0006]

SUMMARY OF THE INVENTION In accordance with the present invention, an electrical contact is made to an otherwise electrically isolated substrate while maintaining the advantages of an electrostatic chuck. In accordance with one aspect of the present invention, there is provided an electrostatic chuck apparatus, which includes a chucking surface for receiving a non-conductive wafer, and a gripper for gripping the wafer against the chucking surface when biased. A chucking electrode for generating an electrostatic force, and at least one wafer contact electrode having a conductive surface that contacts the wafer when the wafer is gripped to provide a current path to the wafer. are doing.

[0007] Various embodiments of the present invention can have one or more additional beneficial features. For example, the chucking surface and at least one surface contact electrode preferably contact the back surface of the wafer.
The at least one wafer contact electrode preferably has a contact area of at least 15 cm ² . The chucking surface can have a substantially flat, circular surface made of a dielectric material, and the at least one wafer contact electrode at least partially surrounds the chucking surface. It is possible to have at least one annular segment. The chucking surface can have a substantially flat and circular surface made of a dielectric material, and the at least one wafer contact electrode has an annular ring substantially surrounding the chucking surface. It is possible to have

The at least one wafer contact electrode is capable of protruding above the chucking surface;
It can be mounted on a spring (or otherwise elastically biased) so that the wafer is held firmly against the back of the wafer when gripped on the chuck. is there. The at least one
The wear contact electrodes may have an “L” shaped cross-section, where the upper portion of the cross-section contacts the backside of the wafer when the wafer is gripped on the chuck, and The lower portion of the cross section can be used to move the wear contact electrode away from the wafer during placement of the wafer on the chucking surface.

A first set of chucking electrodes may be provided to apply a gripping force to a wafer in a first region of the chucking surface when the first set of chucking electrodes is energized. And providing a second set of chucking electrodes to impart a gripping force to a wafer in a second region of the chucking surface when the second set of chucking electrodes is energized. It is possible. The first area of the chucking surface can have a substantially centrally located circular area on the chucking surface, and the second area of the chucking surface captures the first area. It is possible to have a substantially annular area surrounding it. The conductive surface of the at least one wafer contact electrode can be located between a first area of the chucking surface and a second area of the chucking surface.

[0010] The chucking surface can be comprised of a dielectric material, and the at least one wafer contact electrode can be embedded in the dielectric material. The at least one wafer contact electrode may be formed by a process comprising one of sputtering, plating, vacuum deposition, or placing a section of metal or other conductive material within the dielectric material. Attached on body material.

In accordance with another aspect of the present invention, a method is provided for chucking a non-conductive wafer while establishing a current path to the wafer. According to the method, a wafer is placed on a chucking surface, a chucking electrode is energized to generate an electrostatic force that grips the wafer against the chucking surface, and a current path to the wafer is provided. For this purpose, at least one wear contact electrode having a conductive surface that contacts the wafer when the wafer is gripped is brought into contact with the rear side of the wafer.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention has an electrode structure that allows electrical contact with a non-conductive wafer. By obtaining sufficient contact area on the back side of the wafer (eg, a silicon wafer), all the advantages of an electrostatic chuck, such as cleanliness and flatness, are maintained, along with the advantages of a mechanical chuck with a large electrical contact area. ,
In addition, it is possible to avoid the drawbacks of mechanical chucks, which make the shape of the wafer non-uniform and generally cause particle contamination. Another embodiment of the present invention has an electrode that can be added to an existing electrostatic chuck, which allows for providing electrical contact to an electrically isolated substrate.

Experiments have shown that in order to achieve a reliable contact, especially for a non-conductive wafer, a substantial area of the wafer is required. Either contact must be made or the non-conductive material must be removed locally and a contact made at that location.

FIG. 1 is a schematic perspective view of an electrostatic chuck device 100 having a conductive ring wafer contact electrode 105 according to the present invention. Apparatus 100 includes an electrostatic chuck 110 having a chucking surface 115 of a dielectric material and an internal electrode 120 embedded in the dielectric material. FIG. 1 is cut away to show the hidden electrodes. The conductive ring electrode 105 is connected to the spring 12
5,130 or other resilient biasing element, which is resiliently biased upwards, so that when the wafer is gripped against chucking surface 115, the rear side of the wafer ( (Not shown in FIG. 1).
Springs 125, 130 can also be used to provide electrical contact to wafer contact electrode 105. The electrodes have a substantial contact area to produce the desired electrical contact. In the embodiment of FIG. 1, the wafer contact electrode 105 is a coaxial annular ring held against the backside of the wafer, but the shape and orientation of the wafer contact electrode do not depart from the scope of the present invention. It is possible to correct it. Since the wafer contact electrode 105 surrounds the chucking surface, it is conventional to provide a consistent and reliable electrical connection to a wafer having an isolation layer on the backside of a dielectric material. It can be added to an electrostatic chuck.

The electrostatic chuck itself typically has an electrode embedded in a dielectric material. Quartz, glass or sapphire is commonly used as the dielectric material. The electrode material is selected from a list of common materials used in the semiconductor processing industry as known to those skilled in the art. Such materials include, for example, stainless steel and aluminum. Gold, brass and copper are not commonly used due to the detrimental effects these materials have on common semiconductor materials. The chucking electrodes can be laid out as a semi-circular plate in the dielectric within the same plane and facing each other horizontally, as shown schematically at 120 in FIG. The positive and negative chucking electrodes can also be concentric rings with equal surface area.

Another embodiment has a chucking electrode layout having a configuration incorporating various interlocked finger structures. These chucking electrodes are electrically biased during the gripping period and a voltage is applied from an external power supply. The gripping voltage is typically between 500 V and 4 V, depending on the dielectric material, its thickness and the desired gripping force.
000V. The power supply is DC and has very low voltage ripple, on the order of a few mV. Larger gripping electrode bias ripples appear as fields above the surface of the wafer and provide a source of noise in, for example, SEM images of the wafer gripped on a chuck.

A preferred wafer contact electrode configuration for a single size wafer chuck has an annular ring independently suspended around the outside of the electrostatic chuck, such as the ring electrode 105 of FIG. This ring is electrically isolated from ground and is suspended from several springs in the form of isolation posts. These springs are manufactured from a non-magnetic material such as, for example, a beryllium copper alloy, in order to avoid magnetic field distortion of the SEM image of the wafer held in a chuck shape. The upper side of the annular ring projects slightly above the surface of the chuck, so that when a gripped wafer is present on the chuck, it is held firmly against the backside of the wafer. The ring may have an "L" shaped cross-section, with the upper portion of the "L" contacting the wafer and the lower horizontal portion of the "L" during the period of robotic placement of the wafer on the chuck. Used to move the ring away from the wafer during operation. The robot that carries the wafer has a "U" shaped end effector (acting body), which carries the wafer at a predetermined position on the wafer chuck. The inside dimensions of the end effector are such that its inside end is further away from the diameter of the chuck. When the wafer is placed on the chuck, the end effector is moved down, during this movement the wafer is first placed on the ring and the end effector continues to move down And ultimately press down on the horizontal portion of the "L" section of the ring. At this point, the wafer is placed on the ring. This is because when the ring is pushed down, the wafer will eventually sit on the dielectric surface of the chuck. When the wafer is seated on the chuck, a wafer grip voltage is applied and the wafer is held in place by the electrostatic gripping force. The robot end effector is dimensioned such that its thickness is significantly less than the height of the vertical "L" cross section of the ring. Thus, it is possible to move the end effector to a position where the ring is held against the backside of the wafer and is no longer in contact with any part of the end effector, this position being either the wafer or the ring. It allows the end effector to be withdrawn horizontally without contacting the heel, which does not have the potential to generate particles.

FIG. 2 shows an electrostatic chuck 2 with an integrated wafer contact electrode 205 according to another embodiment of the present invention.
FIG. The gripping electrodes 210, 215 are embedded in a body made of a dielectric material 220 having a chucking surface 225. The wafer contact electrode 205 in this embodiment is buried in the main body made of the dielectric substance 220 of the electrostatic chuck, and
Chucking surface 225 when 0,215 is energized
Is exposed at the chucking surface 225 to make surface contact with the back side of the wafer being gripped against. An electrical conductor 230 extending from the wafer contact electrode 205 is also shown in FIG.

FIG. 3 is a cross-sectional perspective view of another electrostatic chuck embodiment with integrated electrodes according to the present invention. As shown in FIG. 3, the electrostatic chuck device 300 is configured by depositing a conductive material such as a conductive film on a surface on a dielectric chuck main body by plating, injection, vacuum deposition, sputtering, or other modes. Chucking surface 3
Wafer contact electrode 30 formed as a conductive region on
Five. For example, a thin layer of metal or conductive metal oxide can be deposited on different areas of the electrostatic chuck by sputtering or vacuum deposition. An extension 315 of the wafer contact electrode 305 extends to the end of the chuck body to establish an electrical connection with a suitable supply or discharge. Gripping electrode 320,
325 is embedded in the dielectric body of the chuck.

In each of these embodiments, the area of the electrode is critical to achieve the required conductivity,
Typically a value of 35 cm ² . 15cm in width of 1cm
A surface as small as the length was still effective. The shape and number of wafer contact electrodes were not particularly important. In particular, the wafer contact electrode need not be in the form of an annular ring. It is important that the conductive material does not extend above the buried electrode that produces the electrostatic gripping effect, but some overlap is acceptable without unduly affecting the gripping force Things.

[0021] Wafers of different diameters, such as 200 mm and 300 mm, can be received using a single electrostatic chuck, and 300 mm wafers can be overhanged from the ends of the chuck. As another example, if needed for a particular application, additional areas of the electrostatic chuck can be provided outside the ring to provide additional grip and planarization of the 300 mm wafer. is there.

FIG. 4 is a perspective view of a conventional mechanical chuck 400 on which a wafer 405 is mounted. The chuck has mechanical clamps or clips 410, 415 and a mechanical arm 420 that cooperates to keep the wafer on the conductive plate 425. A mechanical chuck with a conductive surface also produces the desired effect due to the large conductive contact area with the back side of the wafer and the point contact of the conductive clamping element with the front side of the wafer, but the wafer is not placed on the chuck. It has significant disadvantages in that the wafer is not physically flat when held at a low temperature and particle contamination.

FIG. 5A is a perspective view of a conventional mechanical chuck 500 modified to illustrate the principles in accordance with the present invention.
FIG. 5B is a partial cross-sectional view of the modified mechanical chuck of FIG. 5A. The chuck 500 is a conductive base plate 52
5 having a non-conductive tape 530 on its upper surface.
It is covered with. Wafer 535 is maintained on the chuck by strips 540 and 545 of non-conductive tape, so that electrical contact between wafer 535 and chuck 505 has not been established. As shown, the wafer 535 has a core of silicon 550 surrounded by a silicon oxide coating 555.

FIG. 6A is a perspective view of a chuck modified to illustrate the principles in accordance with the present invention. FIG. 6B is a partial cross-sectional view of the modified chuck of FIG. 6A with the wafer taped to the chuck. 6A and 6B,
The configuration of FIGS. 5A and 5B includes a source (supply) through a conductive bias and drain (discharge) contact 610.
This has been modified by adding an annular ring 600 of copper tape in electrical contact with 605. The chuck is typically 20-30 cm in diameter. The annular ring 600 has a radial width of about 1 cm.

FIG. 7A is a cross-sectional perspective view of an electrostatic chuck 700 having a wafer contact electrode 705 according to the present invention before mounting the wafer. The ring-shaped wafer contact electrode 705 has an “L” shaped cross-section and is elastically biased upward, for example, by springs 710, 715, so that the upper surface of the wafer contact electrode 705 is It projects above the chucking surface 720.

FIG. 7B is a cross-sectional perspective view of the electrostatic chuck 700 of FIG. 7A when a wafer 725 is mounted using a robot end effector having support arms 730 and 735. When the wafer is positioned on the chucking surface, the robot end effector is lowered to the position shown in FIG. 7B, so that the wafer contact electrode is retracted away from the wafer and the wafer is moved to the chucking surface 72.
Put on 0. The gripping electrodes (not shown) are then energized so that the wafer is gripped against the chucking surface as shown in FIG. 7B. FIG. 7C is a cross-sectional view of the chuck of FIGS. 7A and 7B showing the wafer 725 gripped on the chuck and the robot end effector positioned for withdrawal. The arms 730 and 735 of the robot end effector are positioned high enough not to contact the wafer contact ring 705, thus allowing the upper surface of the wafer contact ring 705 to contact the back side of the wafer 725. .
Instead of using a robot end effector to move the ring, it is also possible to provide a separate actuator for this purpose. It is desirable to move the ring downward so that the wafer contacts the chucking surface and allows for an initial gripping action. Spring 7
The resilience of 10,715 is preferably sufficiently light that the gripping force of the chuck is sufficient to overcome the resilience of the spring. On the other hand, the upward elastic force applied to the wafer contact electrode is smaller than the downward gravity applied to the wafer, so that the wafer can be gripped by the chuck without having to retract the wafer contact electrode. .

FIG. 8 is a partial cross-sectional view of a conventional mechanical chuck 800 that uses point contacts, such as point contacts 805, to establish electrical contact with wafer 810. Wafer 810 has a silicon oxide coating 820
Has a core 815 made of silicon surrounded by. The chuck body 825 is covered with an electrically insulating tape 830. Some areas of the silicon oxide coating 820 have been removed at 835,
Electrical and physical contact between the point contact 805 and the silicon 815 is ensured.

FIG. 9A is a cross-sectional view showing a conventional chuck arrangement 900 that uses point contacts 905, 910 for drilling through a non-conductive layer of a wafer 915. In this case, a point contact is attached to the vibrator 920 to perform perforation during loading of the wafer onto the chuck. FIG.
B shows a portion of wafer 915 showing prior art using point contacts 905, 910 to pierce or create a cut through non-conductive layer 925 to make contact with silicon region 930 of wafer 915. It is sectional drawing. This technique has proven to be ineffective for most wafers and has the disadvantage of producing undesirable particle contamination.

Electrical measurements with point contacts as in FIGS. 4, 8, 9A, 9B show contact resistances in excess of 30 to 40 megaohms, and often depend on the non-conductive coating on the wafer. 10
The resistance was as high as about e7 and 10e11 ohms.

For example, about 1 as in FIGS. 6A and 6B.
The use of a large area with a width of a few centimeters and a length of a few centimeters allows the SEM primary beam to generate sufficient conductivity to the silicon of the wafer to form sufficient surface contact and obtain sufficient leakage current. And the electric field above the wafer can be controlled. The silicon acts as a conductive electrode over the area of the wafer. A typical value for the contact area of the wafer contact electrode with the back side of the wafer is 35 cm ² in the preferred embodiment. 1
Surfaces as small as 15 cm long with a width of cm may still be effective.

FIG. 10 is a perspective view of an electrostatic chuck 1000 according to the present invention having the capability for 8 inch and 12 inch wafers. If the system is to accept 8 inch and 12 inch wafers on the same chuck, the preferred configuration is to have four or more embedded gripping electrodes, one set as described above. And an extra set of electrodes are disposed coaxially about the inner set, thereby extending the face of the chuck beyond the 8 inch chuck. When used with 8 inch wafers, only the inner set of electrodes is energized; when using 12 inch wafers, the outer set of electrodes is additionally energized. The robot end effector described above allows the robot end effector to pass beyond the end of the 12 inch chuck and also supports the 8 inch wafer without scratching along the bottom of the wafer or along the surface of the chuck. Slots or grooves may be provided on the surface of the chuck to allow removal of the partial effector. The groove of the end effector can be of the order of a few mm deep,
It is thicker than the dielectric covering the gripping electrodes. If such grooves are provided, the electrode pattern must be configured so that the electrodes do not extend into the area of the grooves. Instead of providing a groove in the chuck,
A wafer lift device can be provided to lift the wafer from the chucking surface such that an end effector can be inserted between the wafer and the chucking surface to pick up or place the wafer. is there. The wafer lift device moves up and down, for example, to lift the wafer to protrude and remove through a chuck or to hold the wafer upward so that the end effector can be removed during the loading period. It is possible to take the form of three or more lift pins that can be adjusted. Any other suitable configuration for placing and removing wafers can be used. Preferably, a configuration is used that avoids complicating the configuration of the ring and avoids reducing the chucking area.

Referring to FIG. 10, the chuck body 100
5 is made of a dielectric material and has buried gripping electrodes 1010, 1015 for 8 inch wafers and additional buried gripping electrodes 1020, 1025 for 12 inch wafers. . When gripping an 8-inch wafer, only the electrodes 1010 and 1015 are energized. When gripping a 12-inch wafer, all the electrodes 1010, 1015, 1020, and 1025 are energized. In this configuration, it is possible to implement the wafer contact electrode as a suspended ring in two gripping areas, but the wafer contact electrode may be implemented as a gripping electrode pattern, such as an embedded wafer contact electrode 1035. It is more practical to incorporate into a chucking surface 1030 consisting of a dielectric medium between. Wafer contact electrode 1035
Are formed by depositing a conductive material directly on the surface of the dielectric, for example, by a sputtering or plating process that places a thin section of metal in a predetermined area of the dielectric material. Grooves 1040, 1045 are provided to allow the arm of the robot end effector to place the wafer on the chucking surface 1030 and to withdraw the end effector. The outer diameter of the chucking surface 1030 is, for example, 1
The outer diameter of the wafer contact electrode is 2 inches (ie, 300 mm) and 8 inches (ie, 200 mm).

FIGS. 11 and 12 show an electrostatic chuck device similar to that of FIG. 1 according to the present invention in more detail.
FIG. 11 shows a conductive ring wafer contact electrode 1 according to the present invention.
FIG. 10 is a perspective view of an electrostatic chuck device 1100 including
The state in which the mm wafer 1110 is positioned is shown. FIG. 12 is a sectional view of the chuck 1100 of FIG. In this embodiment, the chuck device 1100 has an aluminum mounting base 1120,
An electrostatic chuck unit 1125 is mounted thereon.
The electrostatic chuck unit 1125 can be, for example, a conventional unit having a dielectric chuck body made of aluminum nitride, alumina or sapphire available from Kyocera Corporation Fine Ceramics Group. Wafer contact electrode 1105 can be, for example, a ring machined from aluminum. The upper surface of the wafer contact electrode 1105, which contacts the back side of the wafer held on the chuck, can be chrome plated for wear resistance and to minimize particle contamination. The wafer contact electrode 1105 can be elastically biased upward by a suitable element such as a spring. One such spring is shown as 1125. These springs may be manufactured from beryllium copper alloy to provide an electrical connection to the wafer contact ring 1105 without introducing unwanted electromagnetic fields that may disrupt SEM imaging or other charged particle beam operations Is possible. For example, an insulator 1130 made of an appropriate material such as PEEK (polyetheretherketone)
And an insulator such as the base 11 for mounting the spring.
20 may be provided for electrical isolation from the mounting base 1120.
Electrically isolated from For example, a holding screw such as a holding screw 1140 acts to limit upward movement of the wafer contact electrode 1105 when a wafer does not exist on the chuck, and wears when a wafer does not exist on the chuck. It acts to ground the contact electrode 1105. If used in connection with simple electrical circuits, the screws 114
The presence of the wafer on the chuck can be detected using the contact of the wafer contact electrode 1105 to the head of the
In step 05, the wafer is displaced downward, the contact state is cut off, and a signal indicating that a wafer is present on the chuck is generated. As shown in FIGS. 11 and 12, the wafer contact ring 110
5 has an “L” -shaped cross-section, as shown in FIGS.
When the wafer 1110 is placed on the chucking surface 1135 as shown in the sequence of FIG.
105 can be retracted. One arm 1145 of the robot end effector 1115 is shown in FIG.

FIG. 13 is a plan view of an electrostatic chuck 1300 according to the present invention having the capability for 8 inch and 12 inch wafers. FIG. 14 is a sectional view of a part of the chuck device 1300 of FIG. The chuck 1300 has a dielectric chuck main body 1305 having an embedded gripping electrode (not shown). The chucking surface of chuck body 1305 is divided into a central circular area 1310 and an annular outer area 1315. Area 131
0 and 1315 are separated by an annular groove 1320. The outer diameter of the annular groove 1320 is, for example, 8 inches (20
0 mm) and the outer diameter of region 1315 is 12 inches (300 mm). 8 electrostatic gripping electrodes (not shown)
An area 1315 is buried below the surface of the area 1310 for gripping an inch wafer, and is further provided with an area 1315 to assist a gripping electrode buried below the area 1310 for gripping a 12-inch wafer. Another electrostatic gripping electrode (not shown) is buried under the surface. Channels 1325 and 1330 are provided for the power cable to pass through the chuck body to the gripping electrodes.

FIG. 15 is a perspective view of the chuck 1300 of FIGS. 13 and 14 with the addition of a wafer contact ring 1335 mounted within an annular groove 1320. Wafer contact ring 133
5 is machined from, for example, aluminum and has a hard chrome coating for wear resistance and to minimize particle generation. Wafer contact ring 13
35 is resiliently biased upward, so that its upper surface can be, for example, insulators 1355, 1360,
Beryllium copper alloy springs 1340,1 electrically separated from chuck body 1350 by 1365
Region 1 by being supported on 345, 1350
It protrudes above the chucking surface on the plane defined by 310 and 1315. Holding screw 1370,
1375 and 1380 act to limit upward movement of wafer contact ring 1335 and act to indicate wafer presence detection as described above with reference to retaining screw 1140 of FIG. FIG. 15 further illustrates holes 1505,
1510 and 1515 through which pins 1520 (not visible), 152 of the wafer list device are shown.
5, 1430 to move the wafer up and down relative to the chucking surface 1350 during the wafer transfer period, which allows the wafer to be moved between the wafer and the chucking surface without the need to provide a slot in the chucking surface. It allows the robot end effector to pass.

FIG. 16 shows a flowchart of a method 1600 for chucking a non-conductive wafer while establishing a current path for the wafer in accordance with the present invention. In step 1605, a wafer is placed on the chucking surface. In step 1610, a chucking electrode is energized to generate an electrostatic force that grips the wafer against the chucking surface. Step 1615
Contacting at least one wafer contact electrode, which has a conductive surface that contacts the wafer when the wafer is gripped, with the backside of the wafer to provide a current path for the wafer.

For example, if the wafer contact electrode is retracted during the period of placing and gripping the wafer on the electrode, the order of these steps can be as shown in FIG. is there. On the other hand, the order of these steps is, for example, before energizing the chucking electrode to generate an electrostatic force that grips the wafer against the gripping surface.
It is possible to modify the wafer to be contacted by the wafer contact electrode as the wafer is moved toward the chucking surface.

Embodiments of the apparatus and method according to the present invention provide good electrical drainage or ejection of a primary beam injected into a sample wafer by, for example, a SEM, and that an externally applied voltage is applied to the silicon of the wafer. Electrical contact to the silicon substrate material that can be uniformly transmitted to the substrate. Effective control of the silicon substrate voltage is achieved through the relatively large contact area of the bias electrode, which is very difficult to achieve using point contacts to the side or back of the wafer. The area of the bias electrode often causes mechanical damage to the wafer, avoiding problems associated with point contacts and clips that generate particle contamination and often cause mechanical distortion to the wafer. Embodiments in accordance with the present invention maintain the advantages of conventional electrostatic chucks, mainly due to forced planarization of the wafer and avoiding particle generation due to mechanical contact with the wafer.

Although the specific embodiments of the present invention have been described in detail above, the present invention is not limited to these specific examples, and various modifications can be made without departing from the technical scope of the present invention. Of course is possible.

[Brief description of the drawings]

FIG. 1 is a schematic cutaway perspective view showing an electrostatic chuck having a conductive ring electrode according to the present invention.

FIG. 2 is a schematic sectional perspective view showing an electrostatic chuck having an integrated electrode according to the present invention.

FIG. 3 is a schematic sectional perspective view showing another electrostatic chuck provided with an integrated electrode according to the present invention.

FIG. 4 is a schematic perspective view showing a conventional mechanical chuck on which a wafer is mounted.

FIG. 5A is a schematic perspective view in which a conventional mechanical chuck is modified to illustrate the principle according to the present invention, and FIG.
2A is a schematic partial cross-sectional view of the modified mechanical chuck of FIG.

FIG. 6A is a schematic perspective view of a modified chuck for illustrating the principle according to the present invention, and FIG. 6B is a schematic partial cross-sectional view of the modified chuck of FIG.

FIG. 7A is a schematic cross-sectional perspective view of an electrostatic chuck provided with a contact electrode according to the present invention before mounting a wafer, and FIG. 7B is a case where the wafer is mounted using a robot effector; A) a schematic sectional view of the chuck of FIG.
(C) is a schematic cross-sectional view of the chuck of (A) and (B), showing a state where the wafer is held on the chuck and the robot effector is positioned for extraction.

FIG. 8 is a schematic partial cross-sectional view of a conventional mechanical chuck that uses point contacts to establish electrical contact with a wafer.

FIG. 9A is a schematic diagram showing a conventional chuck configuration using point contacts to drill holes through the non-conductive layer of the wafer, and FIG. FIG. 1 is a schematic partial cross-sectional view of a wafer showing prior art using point contacts to drill holes through.

FIG. 10 is a schematic perspective view showing an electrostatic chuck according to the present invention having the capability for 8 inch and 12 inch wafers.

FIG. 11 is a schematic perspective view of an electrostatic chuck including a conductive ring electrode according to the present invention, showing a state where a wafer is positioned by a robot end effector.

FIG. 12 is a schematic sectional view of the chuck shown in FIG. 11;

FIG. 13 is a schematic plan view showing an electrostatic chuck according to the present invention having the capability for 8 inch and 12 inch wafers.

FIG. 14 is a schematic cross-sectional view of the chuck of FIG.

FIG. 15 is a schematic perspective view of the chuck of FIGS. 13 and 14 with the addition of a wafer contact ring according to the present invention.

FIG. 16 is a flowchart showing the flow of a method according to the present invention.

[Explanation of symbols]

 Reference Signs List 100 electrostatic chuck device 105 wafer contact electrode 110 electrostatic chuck 115 chucking surface 120 internal electrode 125, 130 spring

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor James Henry Brown United States of America, California 95123, San Jose, Los Pinos Way 392 (72) Inventor Daniel Nicholas Buoy United States of America, California 94552, Castro Valley, Mount Lassen Drive 19592

Claims (15)

[Claims] 1. An electrostatic chuck device comprising: (a) a chucking surface for receiving a non-conductive wafer; and (b) generating an electrostatic force for gripping the wafer against the chucking surface when energized. (C) at least one wafer contact electrode having a conductive surface that contacts the wafer when the wafer is gripped to provide a current path to the wafer; An electrostatic chuck device characterized in that: 2. The electrostatic chuck device according to claim 1, wherein the chucking surface and the at least one wafer contact electrode are in contact with a rear surface of the wafer. 3. The electrostatic chuck device according to claim 1, wherein the at least one wafer contact electrode has a contact area of at least 15 cm ² . 4. The method of claim 1, wherein said chucking surface has a substantially flat and circular surface made of a dielectric material, and wherein said at least one wafer contact electrode is at least partially formed by said at least one wafer contact electrode. An electrostatic chuck device having at least one annular segment surrounding a chucking surface. 5. The chuck of claim 1, wherein the chucking surface has a substantially flat and circular surface made of a dielectric material, and wherein the at least one wafer contact electrode is substantially the chucking surface. An electrostatic chuck device having an annular ring surrounding a king surface. 6. The method of claim 1, wherein the at least one wafer contact electrode protrudes above the chucking surface and is held securely behind the wafer when the wafer is gripped on the chuck. An electrostatic chuck device mounted on a spring. 7. The method according to claim 1, wherein the at least one wafer contact electrode has an L-shaped cross section, and an upper portion of the cross section corresponds to a rear side of the wafer when the wafer is gripped on the chuck. Contacting, and the lower portion of the cross-section can be used to move the wafer contact electrode in a direction away from the wafer during the time of placing the wafer on the chucking surface. Electrostatic chuck device. 8. The first set of chucking electrodes of claim 1, wherein the first set of chucking electrodes is energized to apply a gripping force to a wafer in a first region of the chucking surface. And a second set of chucking electrodes is provided to apply a gripping force to a wafer in a second region of the chucking surface when the second set of chucking electrodes is energized. An electrostatic chuck device characterized in that: 9. The chucking surface of claim 8, wherein the first area of the chucking surface has a substantially centrally located circular area on the chucking surface, and the second area of the chucking surface. An electrostatic chuck device, wherein the region has a substantially annular region surrounding the first region. 10. The method of claim 9, wherein the at least one
An electrostatic chuck device, wherein the conductive surface of a wafer contact electrode is located between a first area of the chucking surface and a second area of the chucking surface. 11. The electrostatic capacitor according to claim 1, wherein said chucking surface is comprised of a dielectric material and said at least one wafer contact electrode is embedded in said dielectric material. Chuck device. 12. The method according to claim 11, wherein the at least
The dielectric material is formed by a process in which one wafer contact electrode comprises one of sputtering, plating, vacuum deposition, or placing a section of metal or other conductive material within the dielectric material. An electrostatic chuck device attached to an upper surface. 13. The electrostatic chuck device according to claim 1, further comprising a wafer presence indicator. 14. The apparatus of claim 13, wherein the wafer presence indicator is in a first condition when a wafer is present on the electrostatic chuck device and is in a second condition when the wafer is not present in the electrostatic chuck device. An electrostatic chuck device comprising the electrical contact according to claim 1. 15. A method of chucking a non-conductive wafer while establishing a current path to the wafer, comprising: (a) placing the wafer on a chucking surface; and (b) placing the wafer on the chucking surface. (C) energizing the chucking electrode to generate an electrostatic force that grips the wafer; and (c) providing a conductive path that contacts the wafer when the wafer is gripped to provide a current path to the wafer. Contacting the back side of the wafer with at least one wafer contact electrode having the same.