1. Field of the Invention
The present invention relates to a substrate dechucking device and substrate dechucking method for dechucking from the substrate holder a substrate held in a substrate holder in a plasma processing apparatus, which is used in a thin film formation process, or a patterning process in the manufacture of a semiconductor device, liquid crystal display panel, or photovoltaic cell.
2. Description of the Related Art
Efforts have been vigorously undertaken in recent years to realize plasma processing apparatus that are more precise, faster, capable of handling larger surface areas, produce less damage, and are highly reliable, in order to produce devices with higher functionality, while lowering the processing costs thereof. Uniform, accurate control of the temperature of a substrate on the inner surface of this substrate is required in particular for achieving film uniformity on a substrate in the process of forming a film on a substrate, and for ensuring dimensional accuracy in a dry etching process, which is used in pattern transfer. Consequently, as means for controlling substrate temperature, plasma processing apparatus, which make use of either mechanical suctions, or electrostatic suction electrodes, are coming into use.
A conventional plasma processing apparatus, which utilizes an electrostatic suction electrode, will be described hereinbelow. Examples of conventional plasma processing apparatus are disclosed in Japanese Patent Application Laid-open Nos. 63-72877, 2-7520, 3-102820, 4-100257, and 10-189544.
FIG. 2 is a cross-sectional view of the reaction chamber of a plasma processing apparatus shown in the above-mentioned Japanese Patent Application Laid-open No. 4-100257. This conventional plasma processing apparatus 30 will be explained hereinbelow.
In FIG. 2, 31 is a vacuum chamber, this vacuum chamber 31 has a gas inlet 31a, which is connected to an etching gas injecting device 32, and an exhaust opening 31b connected to an evacuation device 33. Inside the vacuum chamber 31 there is provided an electrostatic suction electrode 35, which has a surface that is an insulating layer, and has a pair of internal electrodes (not shown in the figure) on the inside, and which electrostatically sucks a to-be-processed substrate (hereafter referred to simply as substrate) 34. To the electrostatic suction electrode 35 are connected a direct current power supply 36 for electrostatically sucking a substrate 34, and a high frequency power supplying device 37. Furthermore, the direct current power supply 36 has a switching mechanism 38 for inversion.
Further, in the vacuum chamber 31, a quartz glass plate 39 is provided opposite the electrostatic suction electrode 35, and on the outside of the vacuum chamber 31, an ultraviolet light source 40, such as a mercury lamp, for example, is provided opposite the quartz glass plate 39. There is also a lifting mechanism (not shown in the figure), which raises and lowers a substrate 34 for placing and removing a substrate 34 on/from the electrostatic suction electrode 35. This lifting mechanism utilizes a sliding seal, such as a bellows.
The operation of a conventional plasma processing apparatus 30 constituted in this manner will be explained. First, a substrate 34 placed on top of the electrostatic suction electrode 35 by the lifting mechanism is secured to the surface of the electrostatic suction electrode 35 by applying +voltage and xe2x88x92voltage, respectively, from the direct current supply 36 to a pair of internal electrodes inside the electrostatic suction electrode 35. And then, in this state, ordinary plasma processing is performed on the substrate 34.
When plasma processing is complete, a residual electric charge remains in the insulating layer of the surface of the electrostatic suction electrode 35 even after the direct current supply 36 has been shut off, and the substrate 34 is maintained in the state of being sucked to the electrostatic suction electrode 35. Consequently, if a substrate 34 is lifted by the lifting mechanism in this state as-is, there are cases in which this substrate 34 is damaged.
To prevent this kind of trouble, and to stably lift a substrate 34 from an electrostatic suction electrode 35 without causing damage thereto, the following method for dechucking a substrate 34 from an electrostatic suction electrode 35 is being used.
That is, once plasma processing is complete, after negating the residual electric charge in a substrate 34 by applying a direct current voltage, which inverts polarity, to the internal electrodes of the electrostatic suction electrode. 35 in accordance with the switching mechanism 38, the lifting mechanism is operated, and the substrate 34 is removed from the electrostatic suction electrode 35. Further, thereafter, ultraviolet light of the ultraviolet light source 40 is irradiated onto the insulating layer surface of the electrostatic suction electrode 35 via the quartz glass plate 39 in an attempt to extinguish the residual electric charge of the surface of the electrostatic suction electrode 35.
However, the above-mentioned residual electric charge cannot be completely removed by simply applying a polarity-inversing direct current voltage to the internal electrodes of an electrostatic suction electrode 35 as described above. Further, when the application duration of the above-mentioned direct current voltage is too long, conversely, there are cases in which an electrostatic suction electrode 35 will suck a substrate 34. As a result thereof, there are cases in which the substrate 34 cannot be safely removed in accordance with the lifting mechanism, giving rise to trouble when the substrate 34 is to be transferred to the next process.
Further, because the above-mentioned lifting mechanism makes use of a sliding seal, such as a bellows, there is a limit to the endurance of a vacuum seal, and due to the deterioration over time of the spring force of the bellows, the balance between the residual suction force and the lifting force can break down. Thus, there is the above-mentioned problem of reliability with a conventional plasma processing apparatus 30.
Further, as another conventional example, there is a method, which utilizes an electricity-removing plasma, and which reduces residual electric charge by, for example, gradually lowering the power being applied. But the problem is that since the residual suction force is not directly monitored, in view of the temporal risk, there is a tendency to lengthen the plasma discharge duration, thereby lowering throughput.
The present invention is constituted to solve for problems such as these, and has as an object the provision of a substrate dechucking device and a substrate dechucking method, which enable a substrate held in a substrate holder to be safely dechucked from the substrate holder.
To solve for the above-mentioned problems, the present invention presents a substrate dechucking device which is provided with a substrate holder for holding a substrate in a state where the backside of the substrate makes contact with the holder, and which dechucks from the substrate holder a substrate being held in the substrate holder in a state where the substrate is electrically charged and has a residual suction force, this substrate dechucking device comprising a lifter for lifting a substrate, the lifter being capable of protruding and retracting from the substrate holder, a drive source for generating a driving force to cause the lifter to protrude and retract, and a pair of magnetic coupling portions disposed to face to each other, one of the magnetic coupling portions being mounted to a movable member which is driven to move by the drive source, the other of the magnetic coupling portions being mounted to the lifter side, thereby transmitting the driving force of the drive source to the lifter via the magnetic coupling portions.
According to this constitution, trouble can be prevented in the transfer process, and reliability can be enhanced by enabling a substrate held in a substrate holder to be safely dechucked from the substrate holder while canceling residual suction force of the substrate.
A substrate dechucking device of a first aspect of the present invention provides a substrate holder for holding a substrate in a state where contact is made with the backside of the substrate and which dechucks from the substrate holder a substrate being held in the substrate holder in a state where the substrate is electrically charged and has a residual suction force. This device comprises a lifter for lifting a substrate, said lifter being capable of protruding and retracting from the substrate holder, a drive source for generating a driving force to cause the lifter to protrude and retract, and a pair of magnetic coupling portions disposed to face to each other, one of the magnetic coupling portions being mounted to a movable member which is driven to move by the drive source, the other of the magnetic coupling portions being mounted to the lifter side, thereby transmitting the driving force of the drive source to the lifter via the magnetic coupling portions.
According to this constitution, by moving one of the magnetic coupling portions with the driving force of the drive source, a force resulting from the magnetic force generated between the magnetic coupling portions is applied to the other of the magnetic coupling portions, and the lifter connected to the side of this other of the magnetic coupling portions receives the driving force of the drive source, and a substrate being sucked to a substrate holder is biased in the lifting direction. In this case, because it is possible to perform a lifting operation by adjusting the acting force of the lifter on the substrate while adjusting the amount of travel for which the one of the magnetic coupling portions travels, the substrate can be safely dechucked from the substrate holder. In other words, since the positional difference between the one magnetic coupling portion and the other magnetic coupling portion enables generation of a linear functional lifting force which is substantially proportional to the difference in distance of movement therebetween, it is possible to achieve stable dechucking without forcibly bending the substrate.
A substrate dechucking device of a second aspect of the present invention is such that a substrate holder for holding a substrate in a state where contact is made with the backside of the substrate is disposed inside of a sealable vacuum chamber, and that a substrate being held in the substrate holder in a state wherein the substrate is electrically charged and has a residual suction force is dechucked from the substrate holder. This device comprises a lifter for lifting a substrate, said lifter being capable of protruding and retracting from the substrate holder and disposed inside of the chamber, a drive source for generating a driving power to cause the lifter to protrude and retract, said drive source being disposed outside the chamber, and magnetic coupling portions disposed outside and inside of the chamber respectively so as to face to each other through a portion constituting the vacuum chamber, the magnetic coupling portion disposed outside the chamber being mounted to a movable member which is moved by the drive source, the magnetic coupling portion disposed inside the chamber being mounted to the lifter side, thereby transmitting the driving force of the drive source to the lifter via the magnetic coupling portions.
According to this constitution, when one of the magnetic coupling portions is made as outside-the-chamber magnetic coupling portion, and the other of the magnetic coupling portions is made as inside-the-chamber magnetic coupling portion, the operational effect is the same as in the operational effect of the substrate dechucking device of the first aspect, and because the drive portion is also provided outside of the chamber, it is possible to do away with product defects resulting from the dust generated by the drive portion.
Further, the substrate dechucking device can comprise controlling means by providing a measuring device for measuring the difference in distance of movement between the magnetic coupling portion inside the chamber and the magnetic coupling portion outside the chamber in the lifting direction, so that the residual suction force between a substrate and the substrate holder is determined based on the difference in distance measured, thereby controlling the lifting operation. According to this constitution, because it is possible to determine (by way of pseudo-measurement) the residual suction force between a substrate and the substrate holder, so as to carry out a lifting operation while adjusting the force exerted on the substrate by the lifter, the substrate can be safely dechucked from the substrate holder.
Further, this controlling means is capable of performing control so that when the difference in distance of movement between the magnetic coupling portion inside the chamber and the magnetic coupling portion outside the chamber reaches a prescribed upper limit value during a lifting operation, the above-mentioned lifting operation is stopped for some time. According to this constitution, because a lifting operation can be performed while adjusting the force exerted on a substrate by the lifter so as not to become excessive, it is possible to prevent the substrate from breaking.
Further, this controlling means is capable of performing control so that, when the difference in distance of movement between the magnetic coupling portion inside the chamber and the magnetic coupling portion outside the chamber becomes not to exceed a prescribed lower limit value during a lifting operation for reducing suction force in order to reduce the residual suction force between a substrate and the substrate holder, the above-mentioned lifting operation for reducing the suction force is stopped, and a lifting operation for the next process transfer operation is performed. According to this constitution, a substrate can be safely dechucked from the substrate holder by gradually reducing the residual suction force between a substrate and the substrate holder.
Further, the chamber comprises a plasma generating device which generates plasma to cause electrical charging to the substrate. Also, the substrate holder has an electrode for electrostatic suction, and electrical charging to the substrate is caused by this electrostatic suction of a substrate to the substrate holder.
Furthermore, the measuring device may be a transmission-type displacement gauge which can be fixedly provided on the magnetic coupling portion disposed outside the chamber, that is in the ambient air space outside of the chamber. According to this constitution, too, a substrate can be safely dechucked from the substrate holder inside of the vacuum chamber.
A substrate dechucking method of a first aspect of the present invention is a substrate dechucking method for dechucking from a substrate holder a substrate being held in a state where there exists a residual suction force after cancellation of static electricity, the substrate dechucking method comprising: moving a first movable body which includes one magnetic coupling portion by a drive source; moving a second movable body which includes the other magnetic coupling portion by the magnetic force generated between the magnetic coupling portions, the other magnetic coupling portion being disposed to oppose the one magnetic coupling; and dechucking a substrate by means of a lifter provided on the second movable body. In this method, by moving the magnetic coupling portion of the first movable body, a substrate is dechucked from the substrate holder by the lifter moved by the second movable body via the magnetic force alone.
According to this method, by moving the magnetic coupling portion of the first movable body by a driving device, a force is applied to the other magnetic coupling portion by the magnetic force of the former magnetic coupling portion and locomotive movement is transmitted to a second movable body coupled to the other side of the latter magnetic coupling portion, and a substrate sucked to the substrate holder is urged in the lifting direction. In this case, it is possible to perform a lifting operation while adjusting the force exerted on a substrate by the lifting device by adjusting the amount of movement of the one magnetic coupling to be moved, so that a substrate can be safely dechucked from the substrate holder. In other words, the positional difference between the one magnetic coupling portion and the other magnetic coupling portion generates a linear functional lifting force which is substantially proportional to the difference in distance of movement therebetween, so that it possible to achieve stable dechucking without forcibly bending a substrate.
A substrate dechucking method of a second aspect of the present invention is a substrate dechucking method for dechucking from a substrate holder, in a sealable vacuum chamber, a substrate being held in a state where there exists a residual suction force after cancellation of static electricity, the substrate dechucking method comprising: moving a first movable body including one magnetic coupling portion and disposed outside of the vacuum chamber by a drive source; moving a second movable body including the other magnetic coupling portion in the lifting direction by the magnetic force of the magnetic coupling, the other magnetic coupling portion being disposed inside of the vacuum chamber and located to oppose the one magnetic coupling portion; and dechucking a substrate by means of a lifter provided on the second movable body.
In this method, a pair of magnetic coupling portions are provided respectively inside of the chamber and outside of the chamber such that they are opposed to each other through a portion constituting the chamber. By moving the magnetic coupling portion of a first movable body provided outside of the chamber, a force is applied to the magnetic coupling portion inside the chamber by the magnetic force of the magnetic coupling portion outside the chamber, and the lifter of the second movable body connected to the magnetic coupling portion inside the chamber is urged in the substrate lifting direction, thereby dechucking a substrate from the substrate holder.
According to this constitution, when the one of the magnetic coupling portions is made as outside-the-chamber magnetic coupling portion and the other as inside-the-chamber magnetic coupling portion, the same operational effect can be obtained as that of the substrate dechucking method of the first aspect.
Further, the difference in distance of movement between the magnetic coupling portion inside the chamber and the magnetic coupling portion outside the chamber in the lifting direction can be measured during a lifting operation, and the lifting operation can be performed in accordance with the difference in distance measured. According to this method, it is possible while adjusting the force exerted on the substrate by the lifter, to determine (by way of pseudo-measurement) residual suction force between a substrate and the substrate holder and to carry out a lifting operation, so that the substrate can be safely dechucked from the substrate holder.
Further, when the difference in distance of movement between the magnetic coupling portion inside the chamber and the magnetic coupling portion outside the chamber reaches a prescribed upper limit value during a lifting operation, the above-mentioned lifting operation is stopped for some time to return the magnetic coupling portion outside the chamber to the original position, and thereafter the above-mentioned lifting operation is repeated, so that the suction force between a substrate and the substrate holder can be reduced. According to this method, a lifting operation is performed while adjusting the force exerted on a substrate by the lifter so as not to become excessive, so that the substrate can be prevented from breaking.
Further, during a suction force reducing lifting operation in order for reducing the residual suction force between a substrate and the substrate holder, the above-mentioned lifting operation is repeated until the difference in distance of movement between the magnetic coupling portion inside the chamber and the magnetic coupling portion outside the chamber becomes not to exceed a prescribed lower limit value, and when the difference in distance becomes not to exceed a prescribed lower limit value, the above-mentioned lifting operation is stopped to perform a lifting operation for the next process transfer operation, thereby dechucking a substrate from the substrate holder. According to this method, a substrate can be safely dechucked from the substrate holder by gradually reducing the residual suction force between a substrate and the substrate holder.
Furthermore, the present invention is a plasma processing apparatus for performing dry etching of a substrate using plasma, comprising a sealable vacuum chamber (1) for accommodating therein a substrate which is to be subjected to plasma processing, a vacuum evacuation device (1b) for evacuating an internal gas from the chamber to create a vacuum state therein, a reaction gas supply device (1a) for introducing a reaction gas inside the chamber, a substrate holder (3) equipped with electrostatic suction electrodes (6) in which a substrate is placed and sucked to be held, a plasma gas-generating high-frequency power source device (11) which is connected to the electrostatic suction electrodes, direct current power source devices (8, 9) which are connected to the electrostatic suction electrodes for electrostatic suction of a substrate, and a substrate dechucking device for dechucking a processed substrate from a substrate holder, characterized in that this substrate dechucking device is actuated by the above-mentioned magnetic couplings.
Further, the present invention is a plasma processing method, wherein a substrate is transferred inside of a sealable vacuum chamber, a reaction gas is injected into the chamber after evacuating internal gas from the chamber to create a vacuum state therein, a plasma is generated in accordance with a high-frequency power source, and dry etching is performed on a substrate which is electrostatically sucked to the substrate holder, characterized in that the method for dechucking a substrate from the substrate holder in a state where there exists residual suction force after the etching process is completed is a method carried out using the magnetic force of the above-mentioned magnetic coupling.
According to this method, in order for dechucking a substrate from a substrate holder after the completion of the etching, a movable body outside of the chamber is moved, and a second movable body inside of the chamber which is linked to the former movable body only by a magnetic force is moved in the lifting direction, thereby dechucking the substrate. Thus, there is no need to provide any member which passes through the chamber to transmit a locomotive movement from outside of the chamber, so that the integrity of the vacuum chamber seal can be maintained.