JP2692323B2 - Semiconductor wafer holding device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is provided in a process processing chamber of a semiconductor wafer processing apparatus and electrostatically attracts and fixes a semiconductor wafer carried in from outside to a predetermined position for processing. After that, the present invention relates to a semiconductor wafer holding device for applying an external force to a fixed wafer to separate it from the suction surface.

[Conventional technology]

In the above-mentioned semiconductor wafer processing apparatus that performs process processing such as etching, CVD, and ashing on a semiconductor wafer, the process processing chamber is held at a vacuum pressure. An electrostatic chuck is used.

As is well known, this electrostatic chuck has a structure in which insulated divided electrodes are incorporated in the chuck body so as to face the chuck surface, and the semiconductor wafer () is formed by the Coulomb force of charges generated by applying a voltage between the electrodes. (Hereinafter referred to as "wafer") is suction-held on the chuck surface, and the wafer is transferred between the wafer transfer mechanism arranged outside the process processing chamber.

By the way, when transferring the wafer held on the electrostatic chuck to the tray of the wafer transfer mechanism after the wafer processing, the voltage application to the electrodes is stopped to release the suction of the wafer. Even if the voltage application to the electrodes is stopped, the attraction force due to the electric charges remaining in the insulating layer of the electrostatic chuck cannot act to instantly separate the wafer, and the wafer must wait for the residual charges to spontaneously disappear. If the wafer is detached, the waiting time until the wafer is detached becomes long, and the throughput of the transfer process to the wafer transfer mechanism is reduced.

As a measure against this, as a means for forcibly releasing the wafer that has been conventionally attracted to the electrostatic chuck after the voltage application is stopped, the following method of gas blow detachment or the operation of a knockout pin is used to chuck the wafer of the electrostatic chuck. A mechanical separation method is known in which the surface is mechanically forcibly separated.

Here, the gas blow separation method blows an inert gas such as nitrogen toward the plate surface of the wafer from the outside through a gas blowing hole penetrating the chuck surface of the electrostatic chuck after the voltage application to the electrostatic chuck is stopped. This is a method of forcibly separating the wafer from the chuck surface by the gas dynamic pressure. On the other hand, in the mechanical detachment method, a knockout pin is incorporated on the electrostatic chuck side, and after the voltage application is stopped, the knockout pin is projected and operated to mechanically detach the wafer from the chuck surface.

[Problems to be solved by the invention]

By the way, the above-mentioned conventional gas blow or the wafer detachment method in which the mechanical means is independently operated has the following problems.

That is, immediately after the voltage application to the electrostatic chuck is stopped, a considerable amount of the attraction force due to the residual charges remains. Therefore, in order to forcibly separate the wafer by the gas blow method from the chuck surface of the electrostatic chuck against the attraction force of the residual charges, it is necessary to blow a large amount of blow gas toward the wafer from the outside, and The blow gas flows into the process chamber as it is and diffuses. In addition, the process chamber must be kept in a high vacuum state from the viewpoint of wafer processing. Therefore, in order to reduce the pressure fluctuation in the chamber due to gas blow, the internal volume of the process chamber must be increased in advance, or It is necessary to install a vacuum pump having a large exhaust capacity, which is disadvantageous in cost in any case. Moreover, if there is a slight misalignment between the center of the wafer and the position where the blow gas is blown, the attitude of the wafer separated from the electrostatic chuck due to the gas flow is inclined and the transfer of the wafer to the tray of the wafer transfer mechanism becomes unstable.

On the other hand, in the method in which the wafer is forcibly released from the electrostatic chuck by the mechanical release mechanism described above, the gas does not diffuse into the process chamber unlike the gas blow method, and the number of knockout pins dispersed is increased. This stabilizes the wafer delivery posture to the tray on the other side, but since a large knockout pin is locally applied to the plate surface of the wafer, excessive stress is generated on the surface such as bending of the wafer. May damage the pattern or thin film formed on the surface.

The present invention has been made in view of the above points, and when a wafer held by an electrostatic chuck is forcibly released from the chuck surface, a large amount of blow gas introduced from the outside as in the conventional method is used in the process chamber. Without damaging the pattern and thin film formed on the surface of the wafer, which would be a problem in the mechanical separation method described above, without causing any damage to the electrostatic chuck, and forcibly and securely forcibly separating the wafer from the electrostatic chuck, An object of the present invention is to provide a semiconductor wafer holding device that can be transferred to a wafer transfer tray with high accuracy.

[Means for solving the problem]

In order to solve the above-mentioned problems, the present invention applies an inert gas from the outside between the chuck surface and the wafer after the voltage application to the electrostatic chuck is stopped with respect to the wafer adsorbed on the chuck surface of the electrostatic chuck. It is configured to include a gas blow means for pushing and supplying and a knockout mechanism for mechanically forcibly detaching the wafer from the chuck surface by operating almost simultaneously with the gas blow.

Here, the knockout mechanism is configured by the following means. That is, a cylinder which is arranged side by side on the outer peripheral side of the electrostatic chuck with the lower end surface facing the peripheral edge of the upper surface of the wafer attracted and held by the electrostatic chuck, and which separates the wafer from the chuck surface by the upward movement operation of the electrostatic chuck. Configure as a ring.

[Action]

With such a configuration, in order to forcibly release the wafer sucked and held by the electrostatic chuck from the electrostatic chuck after the processing, in order to forcibly release the voltage to the electrostatic chuck, the gas blowing means and the knockout mechanism are operated at substantially the same timing, Actually, the knockout mechanism is activated with a slight delay after the gas blow.

Then, by injecting a small amount of gas supplied from outside the process chamber by the gas blowing means between the chuck surface of the electrostatic chuck and the wafer plate surface (the plate surface of the wafer has a microscopic uneven surface), The gas spreads and flows in a minute gap between the chuck surface of the electrostatic chuck and the wafer plate surface, and slowly leaks from the outer periphery into the process processing chamber. In this process, the differential pressure between the blow gas pressure and the vacuum pressure in the process chamber is applied as static pressure to the entire surface of the wafer, and this static pressure resists the residual charge of the electrostatic chuck and separates the wafer from the chuck surface. To work. This causes the wafer to slightly float above the chuck surface.

On the other hand, the operation of the knockout mechanism that operates a little later than the gas blow causes the wafer to be mechanically ejected in the detaching direction. As a result, the wafer is not only detached by the gas blow but also mechanically ejected, so that the wafer is easily detached from the chuck surface of the electrostatic chuck.

In this case, the amount of blow gas introduced from the outside in the process of separating the wafer is very small compared to the conventional gas blow separation method in which the wafer is separated by gas blow alone, and it almost affects the pressure fluctuation in the process chamber. Absent. In addition, the mechanical operating force applied to the plate surface of the wafer via the knockout mechanism is smaller than that of the conventional mechanical detachment method in which the wafer is detached only by operating the knockout pin alone. The stress exerted on the wafer is extremely small, and there is no fear that this stress will damage the conductor pattern, the insulating thin film, etc. formed on the wafer surface.

In addition, as described in the previous section, the knockout mechanism is a fixedly installed cylindrical ring arranged in parallel with the electrostatic chuck, and the rising edge of the electrostatic chuck abuts the peripheral edge of the wafer against the end surface of the cylindrical ring to forcibly release it. According to this, a complicated knockout pin and its driving means are unnecessary,
When the wafer is detached, only by moving the electrostatic chuck upward while holding the wafer, the wafer relatively abuts the lower end surface of the cylindrical ring and is forcibly detached from the electrostatic chuck.

〔Example〕

Hereinafter, a reference example which is a basis of the present invention and an embodiment of the present invention will be described with reference to the drawings.

Reference Example 1: In FIGS. 1 to 3, 1 is a process chamber,
2 and 3 are high vacuum exhaust pumps connected to the process chamber 1,
A rough evacuation pump 4 is a wafer transfer tray of a wafer transfer mechanism for loading / unloading the wafer 5 into / from the chamber through a vacuum valve (not shown) of the process chamber 1 by operating a handling mechanism (not shown), and 6 is a static tray. Electric chuck,
6a is an electrode of the electrostatic chuck 6, and 6b is a power source for applying a voltage to the electrode 6a. Further, the electrostatic chuck 6 is fixed to the tip of the chuck holder 7 downwardly through a bolt,
In addition, the chuck holder 7 is supported by a bellows 8 so as to be movable up and down, and a shaft portion pulled out to the outside is connected to a lift drive mechanism (not shown).

On the other hand, a blow gas introduction passage 9 is formed in the center of the electrostatic chuck 6 and the chuck holder 7 and has a tip opening to the chuck surface of the electrostatic chuck 6, and the gas introduction passage 9 is formed. Is a solenoid valve outside the process chamber,
It is connected to a gas source 11 by a pipe through a gas flow rate controller 10 in which a throttle valve is combined, and these constitute a gas blow means.

In addition to the gas blowing means, the electrostatic chuck 6 is provided with a knockout mechanism having the following structure for mechanically separating the wafer. That is, the electrostatic chuck 6
Knockout pins 12 are dispersedly arranged at a plurality of positions penetrating vertically through the shaft so that the tips of the pin shafts can be projected and retracted from the chuck surface of the electrostatic chuck 6. Here, as clearly shown in the structural detail view of FIG. 3, the rear end of the knockout pin 12 projects into the annular groove 13 formed on the chuck holder 7 side, and in the groove, the pressure receiving flange 14 and the return spring. Along with the bellows 15, the bellows 16 is isolated from the process processing chamber 1 and hermetically sealed. Further, the annular groove 13 is provided in the chuck holder 7
1 is connected to the gas source 11 shown in FIG. 1 through a driving gas introduction passage 17 that is drilled in the gas supply solenoid valve, and a gas supply solenoid valve 18 and an exhaust gas solenoid valve 19 communicating with the atmosphere side are connected to the gas pipeline. And, these constitute a gas pressurizing drive means for operating the knockout pin 12 by projecting it from the rear.

In FIG. 3, the chuck surface of the electrostatic chuck 6 is provided with shallow concave grooves carved in a lattice shape, for example, as indicated by reference numeral 6c.

Next, the operation of the wafer holding device having the above structure will be described. First, in the loading step of adsorbing and holding the wafer 5 carried in from the outside of the process processing chamber 1 on the electrostatic chuck 6 and the process processing of the wafer, the electromagnetic valve of the gas flow rate controller 10 is closed to deactivate the gas blowing means. Further, on the knockout mechanism side, the solenoid valve 19 is opened to the atmosphere side, and the knockout pin 12 is retracted inward of the electrostatic chuck 6 by the biasing of the return spring 15.

In this state, when the wafer 5 loaded into the process chamber 1 from the outside is transferred to the electrostatic chuck 6, first, when the tray 4 on which the wafer 5 is mounted moves to a position directly below the electrostatic chuck 6 and faces the electrostatic chuck 6, The electrostatic chuck 6 is moved downward together with the chuck holder 7 by an elevator drive mechanism (not shown), and when the chuck surface of the electrostatic chuck 6 contacts the wafer 5, a voltage is applied to the electrode 6a of the electrostatic chuck 6. The wafer 5 is attracted to the chuck surface. Further, after the wafer is adsorbed, the electrostatic chuck 6 is returned to the home position and the tray 4 is retracted to the outside by the operation of the handling mechanism. Then, a predetermined wafer process is performed with the wafer 5 held on the electrostatic chuck 6. In this wafer processing process, the process processing chamber 1 is kept in a high vacuum state.

On the other hand, in the unloading process in which the wafer 5 is carried out of the room after the process, the tray 4 is first moved to a position facing the electrostatic chuck 6, and then the electrostatic chuck 6 is lowered to the wafer transfer position and then to the electrode. The voltage application of is stopped. Immediately after the voltage application to the electrostatic chuck 6 is stopped, a small amount of gas that is regulated to a constant flow rate by the flow rate controller 10 from the gas source 11 is supplied to the gas blowing means,
Gas is pushed into the minute gap between the chuck surface of the electrostatic chuck 6 and the wafer 5 through the blow gas introduction passage 9 and carried in. Further, for the knockout mechanism, the solenoid valve 18 is opened and the solenoid valve 19 is linked to the operation of the gas blow means.
Is closed and driving gas is introduced from the gas source 11 to the back of the knockout pin 12 through the gas introduction passage 17.

By the above operation, as shown in FIG. 2, on the one hand, the blow gas pushed in through the blow gas introduction passage 9 flows through the minute gap between the chuck surface of the electrostatic chuck 6 and the wafer 5, and from the peripheral end thereof. It flows so as to slowly leak into the process processing chamber 1, and in this process, a static pressure (corresponding to the differential pressure between the vacuum pressure and the blow gas in the process processing chamber) that opposes the electrostatic adsorption force is generated on the entire adsorption surface.
At the same time, the plurality of knockout pins 12 dispersedly arranged on the electrostatic chuck 6 are collectively driven downward against the return spring 15 by the pressing force of the driving gas introduced into the gas introduction passage 17.
The tip of the pin shaft projects from the chuck surface of the electrostatic chuck 6 and pushes the plate surface of the wafer 5 downward. As a result, the wafer 5 which has been attracted and held on the electrostatic chuck 6 by the residual charge is subjected to the simultaneous action of the above-mentioned static pressure of the blow gas and the operation of projecting the knockout pin, and resists the electrostatic attraction force to the chuck surface. Is forcibly withdrawn as indicated by an arrow P in the figure, and is delivered to the tray 4 waiting below. Also,
When the delivery of the wafer 5 is completed, the gas supply to the gas blowing means and the knockout mechanism is stopped and the initial state is returned to again, whereby the series of wafer delivery operations are completed.

In addition, in the above description, the displacement of the wafer 5 is always maintained by keeping the protruding stroke and the moving speed of the knockout pin 12 and the distance between the electrostatic chuck 6 and the tray 4 which is opposed to the knockout pin 12 and which is in the lower standby position. The transfer can be performed with high accuracy without causing any trouble.

Reference Example 2: FIGS. 4 to 6 show a reference example which is the basis of the present invention and is different from the reference example 1. That is, in Reference Example 1, the knockout pins are collectively driven by the gas pressurizing operation so as to project from the chuck surface, whereas in this Reference Example, the knockout pins are collectively driven by the drive mechanism combining the feed screw and the transmission gear mechanism. Then, it is operated so as to appear and disappear from the chuck surface.

In the figure, the knockout pins 12 penetrating the electrostatic chuck 6 and distributed at four locations on the circumference are guided and supported by the chuck holder 7 so as to be vertically movable,
And each knockout pin as clearly shown in FIG.
Each 12 is screwed to the feed gear 20. In addition,
12a is a lead screw, 21 cut on the axis of the knockout pin 12,
Shows a slide bearing of the knockout pin 12. When the gear 20 is rotated here, the gear 20 is fed to the knockout pin 12 as a nut of the feed screw, and the knockout pin 12 appears and disappears from the chuck surface of the electrostatic chuck 6. On the other hand, the gears 20 lined up at four locations on the circumference together with the knockout pins 12 are large-diameter ring gears as shown in FIG.
One of the gears 20 is connected to each other via 22 and is a spur gear 2
It is transmission-coupled to the drive shaft 25 via 3, 24, and the drive shaft 25 is further pulled out from the chuck holder 7 and connected to the drive motor 26.

With this configuration, when the wafer 5 is forcibly released from the electrostatic chuck 6, the drive motor 26 is linked to the gas blow.
4 knockout pins 12 are interlocked with each other via the transmission gear mechanism and the feed screw mechanism described above to project from the chuck surface of the electrostatic chuck 6 and the wafer 5
Will be forcibly withdrawn.

By the way, as in this reference example, when the drive mechanism that combines the feed screw, the transmission gear mechanism, and the drive motor is adopted as the drive means for the knockout pin 12, the drive motor is
By controlling the rotation speed of 26, the protruding stroke and the protruding speed of the knockout pin 12 at the time of detaching the wafer can be freely adjusted to set the optimum condition according to the size of the semiconductor wafer 5. If a servomotor is used as the drive motor 26, the protrusion speed and stroke amount of the knockout pin 12 can be controlled more easily, and the impact exerted on the wafer 5 by the protrusion of the knockout pin 12 can be minimized. It is possible to safely avoid damage to the wiring pattern and thin film.

Embodiment 1: FIGS. 7 and 8 show an embodiment of the present invention.
The difference between this embodiment and the reference examples 1 and 2 is that the knockout mechanism is arranged side by side on the outer peripheral side so as to surround the electrostatic chuck 6 instead of providing a knockout pin that penetrates through the electrostatic chuck. As a result, a cylindrical ring 27 is provided inside the process chamber 1, and the rest is basically the same as the above embodiment including the gas blowing means. Here, the cylindrical ring 27 is attached to the case of the process processing chamber 1, and the lower end surface thereof is the electrostatic chuck 6
The wafer 5 is attracted and held on the upper surface of the wafer 5 at a position facing the peripheral portion of the upper surface.

Then, in the wafer unloading process, immediately after the voltage application to the electrostatic chuck 6 is stopped, the reference example 1 (see FIG. 1 to FIG.
As in the case of FIG. 3), blow gas is pushed into the gap between the chuck surface of the electrostatic chuck 6 and the wafer 5 to generate a static pressure that opposes the electrostatic adsorption force due to the residual charge, and the wafer 5 is The electrostatic chuck 6 together with the chuck holder 7 is moved upward from the position shown in FIG. 7 to the position shown in FIG. As a result, the wafer 5 moves relative to the cylindrical ring 27, the peripheral edge of the wafer 5 abuts against the lower end surface of the ring, and in combination with the static pressure of the blow gas, the wafer 5 is forcibly forced from the chuck surface as shown by an arrow P in the drawing. It leaves and is delivered to the tray 4 waiting below it.

In this embodiment, the knockout mechanism has a simpler structure as compared with the reference examples 1 and 2 described above. In order to shorten the wafer transfer distance between the electrostatic chuck 6 and the tray 4 at the wafer separation position (the electrostatic chuck 6 moves upward), the tray 4 of the wafer transfer mechanism can be moved up and down. It is better to configure as.

〔The invention's effect〕

Since the wafer holding device according to the present invention is configured as described above, it has the following effects.

That is, a gas blowing means for supplying an inert gas from the outside between the chuck surface and the wafer by supplying an inert gas to the wafer adsorbed on the chuck surface of the electrostatic chuck after stopping the voltage application to the electrostatic chuck, and gas blowing With a configuration that includes a knockout mechanism that mechanically forcibly releases the wafer from the chuck surface by simultaneous operation, (1) In the wafer unloading process, the gas blow process and the knockout mechanism are linked after the voltage application to the electrostatic chuck is stopped. By doing so, the wafers can be safely and reliably forcibly released from the electrostatic chuck due to the synergistic action of both, and can be handed over to the wafer tray of the other side in a stable posture without displacement, thereby improving the throughput. .

(2) In addition, in this case, the blow gas amount given to the gas blowing means and the projecting operation force of the knockout mechanism are
Compared with the conventional method in which either the gas blow or the mechanical ejection operation is independently performed to forcibly release the wafer, the amount is smaller. Therefore, a small amount of blow gas that slowly leaks and diffuses into the process chamber has little effect on the vacuum pressure in the process chamber, and the stress generated on the surface of the wafer by the knock-out mechanism's protruding operation is extremely small. High reliability is obtained without fear of damaging the formed thin film or conductor pattern.

Further, as a knockout mechanism, by providing a cylindrical ring having no movable mechanism on the outer peripheral side of the electrostatic chuck, there is no fear of occurrence of trouble in the knockout mechanism due to deposition and deposition of a film even in the case of CVD processing.

[Brief description of the drawings]

FIGS. 1 to 3 and 4 to 6 show the configurations and operations of different reference examples which are the basis of the present invention, and FIGS. 7 and 8 show the embodiment of the present invention. FIG. 1, FIG. 4, and FIG. 7 are diagrams showing a wafer suction state, FIGS. 2 and 8 are diagrams showing a forced wafer detachment state, and FIG. Detailed structure diagram of essential parts, No. 5
FIG. 6 and FIG. 6 are a plan view of the transmission gear mechanism in FIG. 4 and a perspective structural view showing the connection between the knockout pin and the feed gear, respectively. In the figure, 1: process chamber, 5: wafer, 6: electrostatic chuck, 9: blow gas introduction passage, 11: gas source, 12: knockout pin, 12
a: lead screw, 17: pressurized gas introduction passage, 20, 22, 23, 24: gears of transmission gear mechanism, 25: drive shaft, 26: drive motor, 27: cylindrical ring.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-59-151426 (JP, A) JP-A-61-59831 (JP, A) JP-A-61-156814 (JP, A) JP-A-62- 120931 (JP, A) JP 62-120932 (JP, A) JP 53-41983 (JP, A) JP 62-227235 (JP, A)

Claims (1)

(57) [Claims] 1. A semiconductor wafer holding device for holding a semiconductor wafer carried into a process processing chamber at a predetermined position, wherein an electrostatic chuck is installed in the process processing chamber with its chuck surface facing downward. The gas blow means that pushes an inert gas from the outside between the chuck surface and the wafer after the voltage application to the electrostatic chuck to the wafer attracted to the chuck surface of the electrostatic chuck is stopped. A knockout mechanism for mechanically forcibly detaching the wafer from the chuck surface by operating the knockout mechanism so that the lower end surface faces the peripheral edge of the upper surface of the wafer attracted to and held by the electrostatic chuck. It is a cylindrical ring that is placed side by side and separates the wafer from the chuck surface by the upward movement operation of the electrostatic chuck. Semiconductor wafer holding apparatus.