JPH03155647A - Holder for semiconductor wafer - Google Patents

Abstract

PURPOSE:To enable delivery at a stable attitude without positional displacement to a wafer tray on the opposite side by linking and operating a gas blow means and a knockout mechanism after the stoppage of the application of voltage of an electrostatic chuck. CONSTITUTION:A blow gas pushed in and introduced while being communicated with a blow-gas introducing path 9 is flowed in a fine clearance between the chuck surface of an electrostatic chuck 6 and a wafer 5, and flowed so a to slowly leak into a process treating chamber 1 from the peripheral end of the clearance, and static pressure resisting electrostatic attraction is generated all over the attracting surface in the process. A plurality of knockout pins 12 dispersed and disposed to the electrostatic chuck 6 are driven collectively to a lower section against the force of a return spring 15 by the pressing force of a driving gas introduced to a gas introducing path 17 at the same time, and the noses of pin shafts are projected from the chuck surface of the electrostatic chuck 6 and the plate surface of the wafer 5 is pushed downward. Accordingly, the wafer 5 attracted and held by the electrostatic chuck 6 through residual charges up to that time receives the concurrent action of the static pressure of the blow gas and the projecting operation of the knockout pins, is removed forcibly from the chuck surface against electrostatic attraction, and is delivered to a tray 4 standing by in a lower section.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is equipped in a processing chamber of a semiconductor wafer processing apparatus, and uses electrostatic force to attract and fix a semiconductor wafer brought in from outside to a predetermined position. The present invention relates to a semiconductor wafer holding device that applies external force to a fixed wafer to separate it from a suction surface after processing.

[Conventional technology]

In the above-mentioned semiconductor wafer processing equipment that performs processes such as etching, CVD, and ashing on semiconductor wafers, the processing chamber is maintained at a vacuum pressure, and wafer holding equipment used under this reduced pressure has traditionally been commonly used. An electrostatic chuck is used.

As is well known, this electrostatic chuck has a structure that incorporates insulated divided electrodes inside the chuck body facing the chuck surface, and the Coulomb force of the electric charge generated by applying a voltage between these electrodes is used to hold the semiconductor wafer ( The wafer (hereinafter referred to as ``wafer'') is suctioned and held on the chuck surface, and the wafer is transferred to and from a wafer transport mechanism located outside the process chamber.

By the way, when the wafer held on the electrostatic chuck is transferred to the tray of the wafer transport mechanism after wafer processing, the voltage application to the electrodes is stopped to release the wafer from adsorption. In this case, simply stopping the voltage application to the electrodes will not allow the wafer to be instantly removed due to the adsorption force caused by the charges remaining in the insulating layer of the electrostatic chuck, and the residual charges will naturally disappear. If the wafer is removed after the wafer is removed, the waiting time until the wafer is removed becomes longer, and the throughput of the transfer process to the wafer transport mechanism is reduced.

As a countermeasure for this, conventionally, as a means to forcibly remove the wafer that is attracted to the electrostatic chuck after stopping the voltage application, the wafer is removed from the electrostatic chuck using the following gas blow release method or by operating a knockout pin. A mechanical separation method is known in which the material is mechanically forcibly removed from the surface.

Here, in the gas blow detachment method, after the voltage application to the electrostatic chuck is stopped, an inert gas such as nitrogen is blown from the outside toward the surface of the wafer through a gas blowing hole that penetrates the chuck surface of the electrostatic chuck. This method uses the gas dynamic pressure to force the wafer MP$4 from the chuck surface. On the other hand, in the mechanical detachment method, a knockout pin is built into the electrostatic chuck side, and after the voltage application is stopped, the knockout pin is operated to protrude to forcibly detach the wafer from the chuck surface.

[Problem to be solved by the invention]

By the way, the above-described conventional wafer detachment method using gas blow or mechanical means alone has the following problems.

That is, immediately after the voltage application to the electrostatic chuck is stopped, a considerable amount of adsorption force remains due to the residual charge. Therefore, in order to forcibly separate the wafer from the chuck surface of the electrostatic chuck using a gas blow method against the adsorption force of this residual charge, it is necessary to blow a large amount of blow gas toward the wafer from the outside, and The blow gas directly flows into the process chamber and diffuses. Moreover,
The process chamber must always be maintained in a high vacuum state from the perspective of wafer processing, and therefore the pressure fluctuations within the chamber due to gas blowing must be minimized (if possible, the internal volume of the process chamber must be increased in advance (or It is necessary to install a vacuum pump with a large exhaust capacity, which is disadvantageous in terms of cost.Moreover, if there is a slight deviation between the center of the sea urchin and the position where the blow gas is sprayed, the gas flow will cause it to become static. The posture of the wafer detached from the electric chuck is tilted, and the transfer to the tray of the wafer transport mechanism becomes unstable.

On the other hand, in the method described above in which the wafer is forcibly separated from the electrostatic chuck using the mechanical separation mechanism, gas does not diffuse into the processing chamber unlike in the gas blow type.
In addition, by increasing the number of distributed knockout pins, the transfer posture of the wafer can be stabilized when receiving the wafer to the tray on the other side. Excessive stress may be generated on the surface, causing damage to patterns, thin films, etc. formed on the surface.

The present invention has been made in consideration of the above points, and when a wafer that is being held by an electrostatic chuck is forcibly removed from the chuck surface, a large amount of blow gas introduced from the outside is used in the process, unlike the conventional method. The wafer can be safely removed from the electrostatic chuck without spreading it into the room and without damaging the pattern or thin film formed on the wafer surface, which is a problem with the mechanical removal method mentioned above! The object of the present invention is to provide a semiconductor wafer holding device which can be forcibly removed and transferred to the other party's wafer transfer tray with high accuracy.

[Means to solve the problem]

In order to solve the above problems, the present invention supplies an inert gas from the outside between the chuck surface and the wafer after the voltage application to the electrostatic chuck is stopped. Gas blowing means for pushing and supplying;
The knockout mechanism is configured to include a knockout mechanism that mechanically forcibly detaches the wafer from the chuck surface by operating almost simultaneously with the gas blow.

Here, the knockout mechanism is composed of various means such as kick-starting. That is, (1) Penetrating the chuck surface of the electrostatic chuck and dispersing kk! on its circumferential surface. It consists of a plurality of knockout pins provided therein, and a knockout pin driving means that collectively pushes out each knockout pin from the chuck surface toward the wafer by applying gas pressure from behind.

(2) Multiple knockout pins penetrate the chuck surface of the electrostatic chuck and are distributed on the circumferential surface, and each knockout pin is pushed out from the chuck surface toward the wafer at once by gas pressurization from behind. It consists of a knockout pin driving means.

(3) The wafer is placed side by side on the outer periphery of the electrostatic chuck with its lower end facing the upper peripheral edge of the wafer held by the electrostatic chuck, and the wafer is removed from the chuck surface by upward movement of the electrostatic chuck. Constructed as a cylindrical ring.

(Function) With this configuration, in order to forcibly detach the wafer held by the electrostatic chuck from the electrostatic chuck after the process, the gas blowing means and the knockout mechanism are activated after the voltage application to the electrostatic chuck is stopped. almost at the same time,
In reality, the knockout mechanism is activated with a slight delay after the gas blow.

Then, by forcing a small amount of gas supplied from outside the process chamber using gas blowing means between the chuck surface of the electrostatic chuck and the wafer plate surface (the wafer plate surface has a microscopically uneven surface), The gas spreads and flows through the tiny gap between the chuck surface of the electrostatic chuck and the wafer plate surface, and slowly leaks into the processing chamber from the outer periphery.

During this process, the differential pressure between the blow gas pressure and the vacuum pressure in the processing chamber is applied to the entire surface of the wafer as static pressure, and this static pressure resists the residual charge of the electrostatic chuck and pulls the wafer away from the chuck surface. act. This allows the wafer to float slightly off the chuck surface.

On the other hand, due to the operation of the knockout mechanism which operates with a slight delay in the gas blow, the wafer 1 is subjected to a mechanical protruding force in the detachment direction. As a result, a mechanical ejecting action is applied to the wafer in addition to the detachment force caused by the gas blow, and as a result, 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 during the wafer detachment process is extremely small compared to the conventional gas blow detachment method in which the wafer is detached using gas blow alone, and has almost no effect on pressure fluctuations in the process chamber. In addition, the mechanical operating force applied to the wafer plate surface via the knockout mechanism is much smaller than the conventional mechanical detachment method that detaches the wafer by operating the knockout pin alone. The stress applied to the plate surface is very small, and there is no fear that the conductor pattern, insulating thin film, etc. formed on the wafer surface will be damaged by this stress.

In addition, the knockout mechanism (1), (2) mentioned in the previous section
.

Regarding (3), by disposing the knockout pin in the chuck surface area of the electrostatic chuck as in (1) and <2), the knockout pin is not exposed inside the processing chamber during the wafer processing process, and the CVD Even in the case of processing, there is no risk of problems with the knockout mechanism due to deposits of deposits. In this case, the knockout pin should be hermetically sealed against the process chamber and isolated from the gas pressurization side. This can prevent the driving gas applied when protruding and operating the knockout pin from diffusing into the process chamber.

In addition, instead of the knockout pin penetrating the chuck surface of the electrostatic chuck, the knockout mechanism is a fixedly installed cylindrical ring juxtaposed to the electrostatic chuck as shown in (3),
According to a configuration in which the periphery of the wafer is brought into contact with the end face of the cylindrical ring and forcibly removed by lifting the electrostatic chuck,
There is no need for a complicated knockout pin or its driving means, and when removing a wafer, simply move the electrostatic chuck upward while holding the wafer, and the wafer will relatively hit the lower end surface of the cylindrical ring and be forced out of the electrostatic chuck. Will be left.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

Embodiment 1: In Figures 1 to 3, ■ indicates a process treatment chamber;
．． 3 is a high vacuum exhaust pump connected to the process chamber l;
4 is a rough evacuation pump; 4 is a wafer transfer mechanism that transports wafers 5 into and out of the process chamber l through a vacuum valve (not shown) by operating a handling mechanism (not shown); 6 is a transfer tray; electrostatic chuck,
6a is an electrode of the electrostatic chuck 6, and 6b is a power source that applies voltage to the electrode 6a. In addition, the electrostatic chuck 6 is fixed to the tip of a chuck holder 7 downward with a bolt, and the chuck holder 7 is vertically movably supported via a bellows 8, and the shaft is pulled out to the outside. The lower part is connected to a lifting drive mechanism (not shown).

On the other hand, a blow gas introduction passage 9 is bored in the center of the electrostatic chuck and the chuck holder 7, and the tip thereof opens to the chuck surface of the electrostatic chuck 6. Solenoid valve outside the process chamber,
Gas source 1 via gas flow regulator 10 combined with a throttle valve
1, and these constitute a gas blowing means.

In addition to the gas blowing means, an electrostatic chuck 6
is equipped with a knockout mechanism that mechanically removes the wafer. That is, knockout pins 12 are disposed vertically through the electrostatic chuck 6 at a plurality of locations such that the tips of the pin shafts are retractable from the chuck surface of the electrostatic chuck. Knockout pin 12, as clearly shown in the structural details of the figure.
The rear end protrudes into an annular groove 13 formed on the side of the chuck holder 7, and a pressure receiving flange 14. Together with the return spring 15, it is isolated from the process chamber 1 via a bellows 16 and hermetically sealed. Further, the annular groove 13 is connected to the gas source 11 shown in FIG. 1 through a driving gas introduction passage 17 bored in the chuck holder 7, and the gas piping path is connected to a gas supply solenoid valve 18° and an atmospheric gas supply passage 17. An exhaust gas electromagnetic valve 19 communicating with the side is connected, and these constitute a gas pressurization type drive means for protruding and operating the knockout pin 12 from behind.

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

Next, the operation of the wafer holding device having the above configuration will be explained. First, in the loading step in which the wafer 5 carried in from outside the processing chamber 1 is attracted and held by the electrostatic chuck 6, and in the wafer processing step, the solenoid valve of the gas flow rate regulator 10 is closed and the gas blowing means is inactive. Furthermore, on the knockout mechanism side, the solenoid valve 19 is opened to the atmosphere, and the knockout pin 12 is moved back inward of the electrostatic chuck 6 by the force of the return spring 15.

In this state, when transferring the wafer 5 carried into the processing chamber 1 from the outside to the electrostatic chuck 6, first move the tray 4 carrying the wafer 5 to a position directly below the electrostatic chuck 6. , the electrostatic chuck 6 is lowered together with the chuck holder 7 by an elevating drive mechanism (not shown), and the chuck surface of the electrostatic chuck 6 touches the wafer 5.
When the wafer 5 comes into contact with the chuck surface, a voltage is applied to the electrode 6a of the electrostatic chuck 6 to attract the wafer 5 to the chuck surface. Further, after the wafer has been attracted, the electrostatic chuck 6 is raised and returned to its normal position, and the tray 4 is retreated to the outside by operating the handling mechanism. Then, predetermined wafer processing is performed while the wafer 5 is held on the electrostatic chuck 6. Note that during this wafer processing process, the process chamber 1 is maintained in a high-turbine state.

On the other hand, (in the unloading step of transporting the wafer 5 outside the room after processing, the tray 4 was first moved to a position facing the electrostatic chuck 6, and then the electrostatic chuck G was lowered to the wafer transfer position. After that, the voltage application to the 74 poles is stopped. Immediately after the voltage application to the electrostatic chuck 6 is stopped, the fine flow rate is reduced to a constant flow rate from the gas source 11 to the gas blowing means by the flow rate regulator 10. gas is supplied, and the gas is forced into the minute gap between the chuck surface of the electrostatic chuck 6 and the wafer 5 through the blow gas introduction passage 9.Furthermore, for the knockout mechanism, the operation of the gas blow means is In conjunction, the solenoid valve 18 is opened,
The electromagnetic valve 19 is switched to close, and driving gas is introduced from the gas source 11 through the gas introduction passage 17 before and after the knockout pin 12.

As a result of the above operation, as shown in FIG. From process chamber 1
During this process, static pressure (corresponding to the differential pressure between the vacuum pressure in the processing chamber and the blow gas) that resists the electrostatic adsorption force is generated on the entire adsorption surface. At the same time, the plurality of knockout pins 12 distributed in the electrostatic chuck 6 are collectively driven downward against the return spring 15 by the pressurizing force of the driving gas introduced into the gas introduction passage 17, and the tip of the bottle shaft is The wafer 5 protrudes from the chuck surface of the electric chuck 6 and pushes the plate surface of the wafer 5 downward. As a result, the wafer 5, which had been held by the electrostatic chuck 6 due to the residual charge, is now affected by the static pressure of the blow gas and the knockout pin. Simultaneously with the ejection operation, the receiver is forcibly separated from the chuck surface in the direction of arrow P in the figure against the electrostatic attraction force, and is delivered to the tray 4 waiting below. Further, once the transfer of the wafer 5 is completed, the gas supply to the gas blowing means and the knockout mechanism is stopped and the wafer receiver returns to its initial state, thereby completing the series of transfer operations of the wafer receiver.

In the above, by always maintaining constant conditions the protrusion stroke and moving speed of the knockout pin 12, and the distance between the electrostatic chuck 6 and the tray 4, which is placed in standby at a lower position opposite to the electrostatic chuck 6, the displacement of the wafer 5 can be prevented. Transfers can be carried out reliably with high precision without causing any problems.

Embodiment 2; Figures 4 to 6 show an embodiment of the present invention that is different from Embodiment 1. That is, in Embodiment 1, the knockout pins are driven to protrude from the chuck surface all at once by gas pressurization. On the other hand, in this embodiment, the knockout pins are moved in and out of the chuck surface all at once using a drive mechanism that combines a feed screw and a transmission gear mechanism.

In the figure, the knockout pins 12 penetrating the electrostatic chuck 6 and distributed at four locations are each guided and supported by the chuck holder 7 so as to be movable in the vertical direction.
As clearly shown in FIG. 6, each knockout pin 12 is threadedly connected to a feeding gear 20. In addition, 12a shows a feed screw cut on the shaft of the knockout pin 12, and 21 shows a slide bearing of the knockout pin 12.When the gear 20 is rotated here, the gear 20 is sent to the knockout pin 12 as a nut of the feed screw. This causes the knockout pin 12 to protrude and retract from the chuck surface of the electrostatic chuck 6. On the other hand, knockout pin 1
As shown in FIG. 5, the gears 20 arranged in four locations along with 2 are interconnected via a large-diameter ring gear 22,
One of the gears 20 is transmission-coupled to a drive shaft 25 via spur gears 23 and 24, and the drive shaft 25 is further pulled out from the chuck holder 7 and connected to a drive motor 26.

With this configuration, when the wafer 5 is forcibly removed from the electrostatic chuck 6, the drive motor 26 is activated in conjunction with the gas blow.
By starting, the four knockout pins 12 are interlocked via the transmission gear mechanism and the feed screw mechanism described above to protrude from the chuck surface of the electrostatic chuck 6, and the wafer 15 is forcibly removed. .

By the way, as in this embodiment, a feed screw and a transmission gear mechanism are used as driving means for the knockout pin 12.

In a configuration that uses a drive mechanism that combines a drive motor,
By controlling the rotational speed of the drive motor 26, the ejection stroke and ejection speed of the knockout pin 12 at the time of wafer removal can be freely adjusted to set optimal conditions corresponding to the size of the semiconductor wafer 5, etc. Moreover, if a servo motor is adopted as the drive motor 26, the knockout pin 1
2 ejection speed.

The stroke amount can be controlled even more easily, and the impact on the wafer 5 caused by the protrusion of the knockout pins 12 can be minimized, thereby safely avoiding damage to the wiring pattern and thin film of the wafer.

Embodiment 3: FIGS. 7 and 8 show a further different embodiment of the present invention. The difference between this embodiment and the above-mentioned embodiments 1 and 2 is that in the knockout mechanism, instead of providing a knockout pin that penetrates the electrostatic chuck and is provided, it is arranged side by side on the outer circumferential side so as to surround the electrostatic chuck 6. A cylindrical ring designated by the reference numeral 27 is provided inside the process chamber 1, and the other components including the gas blowing means are basically the same as those of the previously described embodiment. Here, the cylindrical ring 27
is attached to the case of the processing chamber 1, and is positioned such that its lower end face faces the upper peripheral edge of the wafer 5 held by the electrostatic chuck 6.

Then, in the wafer unloading process, immediately after the voltage application to the electrostatic chuck 6 is stopped, Example! Similar to the embodiment described in FIGS. 1 to 3, blow gas is introduced into the gap between the chuck surface of the electrostatic chuck 6 and the wafer 5 to counteract the electrostatic attraction force due to the residual charge. While generating pressure, the electrostatic chuck 6 is moved along with the chuck holder 7 from the position shown in FIG. 7 to the position shown in FIG. Move upward in the Q direction. As a result, the wafer 5 moves relative to the cylindrical ring 27, and the peripheral edge of the wafer 5 hits the lower end surface of the ring, and together with the static pressure of the blow gas, it is forced from the chuck surface in the direction of arrow P in the figure. The tray is separated and passed to the tray 4 waiting below.

In this embodiment, the knockout mechanism has a simpler structure than the previously described embodiments 1.2. Note that the wafer release position (
In order to shorten the wafer transfer distance between the electrostatic chuck 6 and the tray 4 (when the electrostatic chuck 6 moves upward), it is recommended to configure the tray 4 of the wafer transfer mechanism as a system configuration that can move up and down. good.

〔Effect of the invention〕

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

In other words, after stopping the voltage application to the electrostatic chuck, a gas blowing means presses and supplies an inert gas from the outside between the chuck surface and the wafer, and the gas blowing means supplies the wafer attracted to the chuck surface of the electrostatic chuck. With a configuration equipped with a knockout l1tl that operates simultaneously to mechanically forcibly remove the wafer from the chuck surface, (1) In the wafer unloading process, the gas blowing means and the knockout mechanism are By operating in tandem, the synergistic effect of both forces allows the wafer to be forcibly removed from the electrostatic chuck safely and reliably, and the wafer can be transferred to the other party's wafer tray in a stable posture without shifting its position, improving throughput. can be achieved.

(2) In this case, the amount of blowing gas applied to the gas blowing means and the ejecting force of the knockout mechanism may be changed as in the conventional method by performing either gas blowing or mechanical ejecting operation alone to forcibly remove the wafer. Therefore, the amount of blow gas that slowly leaks and diffuses into the processing chamber is small and has almost no effect on the vacuum pressure inside the processing chamber, and the stress generated on the wafer surface due to the knockout mechanism's ejection operation is reduced. Since the thickness is also very small, there is no risk of damaging the thin film, conductor pattern, etc. formed on the surface, and high reliability can be obtained.

(3) As a knockout mechanism, it is also possible to incorporate the knockout pin inside the electrostatic chuck so that it is not exposed to the outside when the wafer is attracted, or to install a cylindrical ring without a movable mechanism on the outer circumference of the electrostatic chuck. By providing this, there is no fear of trouble occurring in the knockout mechanism due to deposition of film even in the case of CVD processing.

[Brief explanation of the drawing]

Figures 1 to 3, Figures 4 to 6, and Figure 7
8 and 8 respectively show the configuration and operation of different embodiments of the present invention, FIGS. 1, 4, and 7 are wafer suction state diagrams, and FIGS. FIG. 3 is a detailed structural diagram of the main parts in FIG. 1, and FIGS. 5 and 6 are a plan view of the transmission gear mechanism in FIG. 4 and the connection between the knockout pin and the feed gear, respectively. FIG. In the figure, l: process chamber, 5: wafer, 6: electrostatic chuck,
9 Nibro gas introduction passage, 11: gas source, 12: knockout pin, 12a: feed screw, 17: pressurized gas introduction passage, 20.22.23.24: gear of transmission gear mechanism, 2
5: Drive shaft, 26: Drive motor, 27: Cylindrical shaft Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1) A semiconductor wafer holding device for holding a semiconductor wafer carried into a processing chamber in a predetermined position;
In the case where the electrostatic chuck is installed with the chuck surface facing downward in the processing chamber, the chuck surface and the wafer are separated from each other after the voltage application to the electrostatic chuck is stopped. A semiconductor wafer holding device comprising: a gas blowing means for forcing and supplying an inert gas from the outside between the gaps; and a knockout mechanism that mechanically forcibly removes the wafer from the chuck surface by operating almost simultaneously with the gas blowing. 2) In the semiconductor wafer holding device according to claim 1,
The knockout mechanism uses multiple knockout pins that penetrate the chuck surface of the electrostatic chuck and are distributed on the circumferential surface of the electrostatic chuck, and each knockout pin is collectively directed from the chuck surface toward the wafer by applying gas pressure from behind. A semiconductor wafer holding device comprising a knockout pin driving means that protrudes. 3) In the semiconductor wafer holding device according to claim 1,
The knockout mechanism penetrates the chuck surface of the electrostatic chuck and interlocks multiple knockout pins distributed on the circumferential surface of the electrostatic chuck with a feed screw and a transmission gear mechanism to operate the knockout pins to protrude and retract from the chuck surface. A semiconductor wafer holding device comprising a knockout pin driving means. 4) In the semiconductor wafer holding device according to claim 1,
A knockout mechanism is arranged in parallel on the outer circumferential side of the electrostatic chuck with its lower end facing the upper peripheral edge of the wafer held by the electrostatic chuck, and the wafer is removed from the chuck surface by upward movement of the electrostatic chuck. A semiconductor wafer holding device characterized by being a cylindrical ring.