JP3911787B2 - Sample processing apparatus and sample processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrostatic chuck and a sample processing method and apparatus using the electrostatic chuck, and more particularly to a sample holding using a static force, which is used for processing a thin plate sample such as a semiconductor substrate or a liquid crystal substrate or a sample holding during transportation. And a sample processing method and apparatus using the same.
[0002]
[Prior art]
Conventionally, as a bipolar type electrostatic chuck using a pair of electrodes having different polarities, for example, as described in JP-A-57-64950, a pair of semicircular or concentric planar electrodes has been provided. An electrostatic adsorption device is known. In this publication, the ratio of the electrode area of the pair of planar electrodes to the area of the electrostatic adsorption device is increased, an object is placed on the pair of planar electrodes via an insulator having a thickness of 50 to 200 μm, and Can be applied to both conductive objects and conductive objects whose surfaces are covered with a thin insulating film, with stronger adsorption, and more It is described that the structure can be made simple, and that the adsorption force becomes maximum when the positive and negative electrode areas are made equal. In addition, as for a bipolar type electrostatic chuck, JP-A-6-120329 can be cited.
[0003]
Such a method of holding a sample, for example, a wafer, using an electrostatic chuck has the following advantages. (1) Since there is no mechanical contact with the processing surface of the wafer, there is no contamination of the wafer with abrasion powder or the like. (2) Since the wafer is fixed by suction on the entire back surface of the wafer, the warpage of the wafer can be corrected, the contact with the suction surface becomes more reliable during fine processing such as etching, and the thermal conductivity is improved to control the temperature of the wafer. Becomes easier. For these reasons, it is currently widely applied to sample stands (or called “electrodes”) of plasma processing apparatuses such as dry etching apparatuses and CVD apparatuses.
[0004]
As a bipolar type electrostatic chuck used in a plasma processing apparatus, for example, an electrostatic adsorption apparatus as described in Japanese Patent Publication No. 57-44747 is known. In this publication, by making the electrode area to which a positive voltage is applied larger than the negative electrode, it is possible to obtain a larger adsorption force during plasma discharge, and the adsorption force in the absence of plasma is the area of both electrodes. It is described that the maximum is 1 when the ratio is 1.
[0005]
Usually, in order to remove the processed wafer from the electrode, a rod-like support (generally called “pusher” or “lift pin”) is lifted from the inside of the electrode to push up the wafer and remove it. For example, US Pat. No. 4,565,601 and Japanese Patent Laid-Open No. 6-252253 can be cited as examples of this. However, when the wafer has a residual suction force, if the wafer is forcibly peeled against the residual suction force, there arises a problem that the wafer is cracked or an abnormal discharge occurs and the device is destroyed.
[0006]
In order to cope with the harmful effects caused by such residual adsorption force, various static elimination methods have been proposed. For example, as described in US Pat. No. 5,117,121, as a method for removing static electricity from the electrostatic chuck when the sample is detached from the electrostatic chuck, a residual adsorption having a polarity opposite to the adsorption voltage and a current higher than the adsorption voltage. A method of applying a force extinction voltage is known. Further, as disclosed in Japanese Patent Application Laid-Open No. 58-185773, there is known a method of turning off a DC voltage for an electrostatic chuck and then turning off a high frequency power for generating a plasma. In addition, JP-A 1-112745, JP-A 4-247476, and the like can be cited as methods relating to sample detachment in an electrostatic chuck.
[0007]
[Problems to be solved by the invention]
The conventional electrostatic chucks described in JP-A-57-64950 and JP-B-57-44747 do not give consideration to the residual attracting force.
[0008]
That is, in a case where it is necessary to control the wafer temperature to a predetermined temperature during the processing of a sample like a plasma processing apparatus, a heat transfer gas is supplied between the wafer back surface and the electrostatic chuck. For this reason, a structure in which a dispersion groove (or “gas groove”) is provided on the wafer placement surface of the electrostatic chuck to uniformly supply the heat transfer gas is employed. In addition, in a wafer to be plasma-treated, a depression is formed on the wafer placement surface of the electrostatic chuck so as to reduce the contact area between the wafer placement surface of the electrostatic chuck and the wafer so as to reduce the adhesion of foreign matter to the wafer. (For example, JP-A-7-86382). From such a technical point of view, various patterns of dispersion grooves and depressions have been developed. In this way, when the wafer placement surface of the electrostatic chuck has grooves and depressions, the adsorption area on the positive electrode and negative electrode sides varies depending on the size and shape of the dispersion grooves and depressions, which causes residual adsorption force. End up.
Even when an electrostatic chuck is used in plasma, the amount of charge stored on the attracting surfaces on the positive and negative sides differs depending on the generation of self-bias voltage due to plasma or the application of a high-frequency bias. Adsorption force will occur.
[0009]
For this reason, even in the bipolar type electrostatic chuck, there has been a problem that a static elimination step for removing the residual attracting force is required and the throughput in wafer conveyance is reduced. In addition, since charges remain on the dielectric film of the electrostatic chuck, which is the attracting surface, the foreign matter is easily attracted, and there is a problem that the foreign matter adheres to the back surface of the newly attracted and held sample. In particular, there is a high possibility of a problem when a deposit having a charge is generated as in a CVD apparatus.
[0010]
Further, for those that perform residual adsorption force removal as described in US Pat. No. 5,117,121, a static elimination step such as newly applying a reverse voltage is required. For this reason, there exists a problem of reducing the throughput in sample conveyance. In addition, when a reverse voltage is excessively applied, there is a problem that an electrostatic attracting force is generated again and a residual attracting force is generated. On the other hand, in the case of removing the residual adsorption force as described in JP-A-58-185773, the supply of high-frequency power for plasma generation is stopped after the supply of the DC voltage for electrostatic adsorption is stopped. Therefore, further static elimination time is required. For this reason, there exists a problem of reducing the throughput in sample conveyance. In addition, when the heat transfer gas supply to the back of the sample is used together with the electrostatic adsorption, the supply of the heat transfer gas is usually stopped when the supply of the DC voltage for electrostatic adsorption is stopped. As a result, the sample temperature rises and the sample processing proceeds, which has a problem of adversely affecting the sample that has been processed.
[0011]
Further, in general, in a plasma processing apparatus, a high frequency voltage is applied to a sample stage and the incident energy of ions in the plasma to the sample is controlled by a bias voltage generated on the sample stage. When using a chuck, due to the electrode structure of the electrostatic chuck, it is difficult to apply a bias voltage to the sample evenly compared to the monopole type electrostatic chuck, which may affect the uniform processing of the sample. There was a problem of having sex.
[0012]
  The purpose of the present invention is toTrialCan reduce the waiting time for withdrawal and improve throughputA sample processing apparatus and a sample processing method are provided.
[0013]
[Means for Solving the Problems]
  The above purpose isA sample processing apparatus for processing a sample disposed in a vacuum container using plasma generated above the sample in the vacuum container, the plurality of electrodes having different polarities disposed in the vacuum container and A sample stage having a dielectric film disposed on these electrodes, on which the sample is placed, and a DC power supply for supplying a DC voltage for giving the electrodes different polarities A high-frequency power source for supplying a high-frequency power for generating a bias voltage in the sample stage, and means for supplying a heat transfer gas between the dielectric film and the sample during the processing of the sample. This is achieved by stopping the supply of the high-frequency power at the end of the processing and extinguishing the plasma above the sample after a predetermined time.
[0014]
  And a means for adjusting the temperature of the sample stage, and after the supply of the high frequency power is stopped at the end of the processing of the sample, the supply of the DC voltage and at least the predetermined timeBetween the sample and the dielectric film.This is achieved by supplying the heat transfer gas. Furthermore, it is achieved by equalizing the area of the adsorption surface of the sample of the electrode located below the dielectric film for each polarity. Furthermore, the electrode of the electrode positioned below the dielectric film is provided with a recess for supplying the heat transfer gas between the sample and the sample placed on the dielectric film. This is achieved by equalizing the area of the adsorption surface of the sample for each polarity, excluding the recessed portion. Furthermore, a lift pin disposed inside the sample stage is provided to push up the sample above the sample stage, and after stopping the supply of the DC voltage for the predetermined time, the sample is detached from the dielectric film by the lift pin. To achieve this.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
First, the cause of the residual adsorption force and the effect of the present invention will be described with reference to FIGS. In FIG. 22, the area ratio of the actual adsorbed portion on two electrodes (assumed to be electrodes A and B) is, for example, electrode A: electrode B = 2.8 (152.5 cm).²): 1 (54cm²) Shows a simplified equivalent circuit of the electrostatic chuck. As shown here, when the equivalent circuit of the electrostatic chuck during wafer adsorption is simply described, the parallel circuit of the capacitance Ca of the electrode A and the resistance Ra of the dielectric film on the electrode A, and the electrode B Considering that the capacitance Cb and the parallel circuit of the resistor Rb of the dielectric film on the electrode B are replaced with those connected in series via the resistance Rw of the wafer (which is sufficiently smaller than Ra and Rb). it can.
[0016]
When, for example, a voltage of 400 V is applied between the electrodes A and B in this state, assuming that the potential difference finally generated between each electrode and the wafer is Va and Vb, the following equation is established and the stable state is obtained.
Va + Vb = 400 (1)
Ra: Rb = Va: Vb (2)
However, when ceramics are used as the dielectric film, the volume resistivity changes as shown in FIG. 23 depending on the applied voltage. From this, the volume resistivity of the dielectric film of the electrostatic chuck used in this description can be expressed by the following equation when the applied voltage is V.
Volume resistivity = 1 × 10^{(11.953-0.000764V)}... (3)
Given the volume resistivity, the resistance of the actual attracting portion on each electrode can be calculated, so the potential difference between each electrode and the wafer can be found by solving equations (1)-(3). In the case of this example, the potential pressure Va to the wafer is 126V, and Vb is 274V. Next, since the electrostatic capacitance of the dielectric is a value obtained by dividing the product of the dielectric constant and the area by the thickness, the electrostatic capacitance is calculated assuming that the relative dielectric constant of the ceramic is assumed to be 5. The amount of charge stored on the dielectric film can be calculated from the capacitance and the potential difference on the dielectric film obtained from the above-described equations (1) to (3). However, in actual adsorption, a space represented by surface roughness exists between the wafer and the dielectric film. The space is considered to be almost the same as the vacuum space even if heat transfer gas is interposed in the vacuum vessel. This spatial distance is assumed to be about 3 μm in this example, and if the thickness of the dielectric film is 300 μm, the space is 1 / 100th of that of the dielectric film when compared in size. For this reason, even if the dielectric constant is 1/5 of the dielectric film, as a result, it has a capacity of about 20 times. Therefore, it calculated with the electrostatic capacitance in space here. . Summarizing the above results, the electrode A has an area of 152.5 cm.², Capacitance: 46 nF, potential pressure with wafer: 126 V, charge amount: 5.8 × 10^-6Coulomb [C], electrode B area: 54 cm², Capacitance: 16 nF, potential pressure with wafer: 274 V, charge amount: 4.4 × 10^-6Coulomb [C]. From this result, it can be seen that there is a difference in the amount of charge stored in the actual adsorption portion on the electrode A and the electrode B.
[0017]
FIGS. 24A to 24C are schematic diagrams showing changes in the amount of charge stored in each capacitance component when the DC power supply is turned off from the adsorption state. During the adsorption, as shown in FIG. 24A, the dielectric film on the electrode stores a larger amount of charge and is in an unbalanced state. Thereafter, when the application of the DC voltage is stopped, the electric charge corresponding to the electric charge amount on the electrode B is quickly eliminated through the circuits 1 and 2 because the resistance of the wafer is sufficiently smaller than the resistance value of the dielectric film. (FIG. 24B). However, the charge remaining in the dielectric film on the electrode A is discharged (FIG. 24 (c)) through the circuit 3 or 4, but since the values of the resistors Ra and Rb are large, the discharge time constant is large. The static elimination time becomes longer. This residual electric charge causes the residual adsorption force.
[0018]
On the other hand, when the area ratio of the actual attracting portions on the two electrodes is 1: 1 as in the embodiment of the present invention, the resistance value on each electrode is the same and the potential difference from the wafer is the same. The amount of charge stored is the same. Therefore, when the application of the DC voltage is stopped, the charge removal is performed only by the circuits 1 and 2 shown in FIG. 24A, so the charge removal time is short and no residual adsorption power remains.
FIG. 25 shows the state of occurrence of the residual adsorption force when the area ratio of the actual adsorption portion on the electrode is actually changed. The horizontal axis indicates the time after the DC power is turned off, and the vertical axis indicates the residual adsorption force. From this result, it can be seen that when the area ratio of the adsorption portion on each electrode is 1: 1, no residual adsorption force is generated, but as the area ratio increases, the generated residual adsorption force increases.
Therefore, in the electrostatic chuck configured such that the area ratio of the portion that adsorbs the wafer in the dielectric film on the two electrodes as in this example is 1: 1, there is almost no generation of residual adsorption force, An electrostatic chuck having a short static elimination time can be provided. In the sample processing apparatus provided with the electrostatic chuck of the present invention, the throughput of the apparatus is improved. Further, there is no possibility that the wafer is damaged when the wafer is pushed up by lift pins or the like after the processing is completed.
[0019]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows an example of a sample processing apparatus using an electrostatic chuck according to an embodiment of the present invention. Examples of the sample processing apparatus include a processing apparatus using plasma such as an etching apparatus and a film forming apparatus, and a vacuum processing apparatus such as an ion implantation apparatus that does not use plasma. In this case, a plasma processing apparatus will be described as an example.
[0020]
A gas supply device 2 and a vacuum exhaust device 3 are connected to the vacuum container 1. The vacuum vessel 1 is provided with a plasma generator 4 for generating plasma 5 inside. In the vacuum vessel 1, a sample stage on which a sample to be processed by the plasma 5, for example, a substrate 9 such as a wafer as a semiconductor element substrate or a liquid crystal substrate is disposed. The sample stage is configured using an electrostatic chuck 10.
[0021]
In this case, the electrostatic chuck 10 includes an electrode (inner electrode) 11, an electrode (ring electrode) 12, an insulating film 13 and an insulating film (dielectric film) 14 for electrostatic attraction. The electrode 11 has a coolant channel 21 formed therein and a ring-shaped recess for forming the electrode 12 on the upper surface. The electrode 12 is formed in a ring shape. The electrode 11 is made of a conductive material such as an aluminum alloy. An electrode 12 is provided in a recess on the upper surface of the electrode 11 via an insulating film 13 formed of a sprayed film (in this case, alumina). The electrode 12 is formed of a tungsten sprayed film. The insulating film 13 is between the electrode 11 and the electrode 12 and insulates both of them in a DC manner. On the surfaces of the electrode 11 and the electrode 12, an insulating film 14 for electrostatic adsorption made of a sprayed film (in this case, alumina) is formed. The insulating film 13 is made of a material having a higher resistance value than that of the insulating film 14 for electrostatic adsorption. This is because an electric circuit for electrostatic attraction is formed through the insulating film 14.
[0022]
The inner electrode 11 is connected to a lead wire 18 for applying a voltage. A voltage application lead wire 16 is connected to the ring electrode 12. The lead wire 16 is connected to the ring electrode 12 through a through hole formed by an insulating tube 15 provided in the inner electrode 11. The lead wire 16 and the inner electrode 11 are electrically insulated by the insulating tube 15. Lead wires 16 and 18 are connected to power sources 8a and 8b for electrostatic attraction via low-pass filters 19a and 19b, respectively. A negative voltage DC power supply 8a is applied to the ring electrode 12, and a positive voltage DC power supply 8b having the same absolute value as the voltage applied to the ring electrode 12 is applied to the inner electrode 11. Each electrode can also be grounded by switching the connection from the terminal 82a, 82b side to the terminal 83a, 83b side by switching operation of the switches 84a, 84b. Since the inner electrode 11 and the ring electrode 12 are electrically insulated from the substrate 9 by the insulating film 14 for electrostatic adsorption, positive and negative voltages are applied to the inner electrode 11 and the ring electrode 12 by the electrostatic adsorption power supplies 8a and 8b. By applying the voltage, a DC circuit is formed through the substrate 9 and charges are charged, so that the substrate 9 can be electrostatically adsorbed on the upper surfaces of the electrodes 11 and 12.
[0023]
In addition, as shown in FIG. 3, the lead wire 16 is connected to the ring electrode 12 by providing a flange on the upper portion of the insulating tube 15, an electrode core 161 in the upper space of the flange, and an electrode core in the lower space of the flange. 161 and a socket 162 fixed to the flange by screwing are provided. A lead wire 16 is inserted into the socket 162 for connection. The ring electrode 12 is formed by thermal spraying with the electrode core 161 fixed. Thereby, the electrode core 161 can be easily connected to the ring electrode 12. In this case, the material of the electrode core 161 is tungsten and the same material as that of the ring electrode 12 is used, so that the connection with the ring electrode 12 is ensured. Although the detailed illustration of the connection between the inner electrode 11 and the lead wire 18 is omitted, a female screw is formed on the inner electrode 11 and a male screw is formed on the tip of the lead wire 18 so that the inner electrode 11 and the lead wire 18 are connected. This can be easily performed by bolting the wire 18.
[0024]
A through hole 20 in which an insulating tube is installed is provided in the center of the inner electrode 11. The through-hole 20 is used when introducing a heat transfer gas to the electrostatically attracted substrate back surface. In this case, the insulating film 14 for electrostatic attraction is formed by thermal spraying, and finally is polished and processed into a flat and predetermined film thickness state. If the insulating film 14 by thermal spraying is used, a recess (not shown) is formed in advance on the electrode surface to easily form grooves on the surface of the inner electrode 11 or the ring electrode 12 after the formation of the insulating film 14. Can be formed. This facilitates electrode design in which gas dispersion grooves are provided on the electrode surface.
[0025]
The gas distribution groove (or gas groove) on the electrode surface is used to supply heat transfer gas (for example, helium gas) to the back surface of the substrate for temperature control of the substrate to be processed and to make the substrate temperature distribution uniform. Provided to adjust heat transfer characteristics. In this case, the gas dispersion grooves are circumferentially provided as shown in FIG. 2 and are partially connected in the circumferential direction. In this case, the depth of the gas dispersion groove is 0.3 mm.
[0026]
Further, the suction surface of the insulating film 14 in direct contact with the substrate 9 where no gas dispersion grooves are formed is the suction surfaces A1 to A4, the suction surfaces B1 to B4, the suction surface D corresponding to the inner electrode 11, and the ring electrode. And the total area of the suction surfaces C1 to C4 and the total area of the suction surfaces A1 to A4, the suction surfaces B1 to B4, and the suction surface D are equal to each other. It is set to be.
[0027]
In this case, the insulating film 13 is thermally sprayed with a thickness of 0.3 mm, the ring electrode 12 with a thickness of 0.1 mm, and the insulating film 14 with a thickness of 0.4 mm. The contact surface of the insulating film 14 with the substrate 9 is processed to 0.3 mm by polishing. The sprayed film on the inner electrode 11 formed in this way is 0.8 mm even at the thickest part of the film. That is, the film formed on the inner electrode 11 is thicker at the ring electrode 12 portion than the other portions, but the thickness is very thin at 0.8 mm. Therefore, when a high-frequency voltage is applied to the inner electrode 11, the method of applying the high-frequency voltage applied to the entire inner electrode 11 is such that it can be ignored even if there is an insulating film. Will not be affected.
[0028]
Attachment of the electrostatic chuck 10 to the lower surface of the vacuum vessel 1 is performed by a ground plate 24. The inner electrode 11 is attached to the ground plate 24 via an insulating plate 23. When supplying the heat transfer gas to the gas supply through hole 20 provided in the center, the contact portion of each component is sealed so that the heat transfer gas does not leak through the through hole 20 portion. The electrode 11, the insulating plate 23, and the ground plate 24 are fastened and fixed with bolts (not shown).
[0029]
A cover 22 is installed around the outside of the inner electrode 11. The cover 22 is smoothly inclined toward the outer peripheral portion. Therefore, there is no part which becomes a shadow when receiving ion irradiation in plasma from above. Therefore, even if a reaction product generated when processing such as plasma etching is deposited on the cover 22, it can be easily removed by exposure to cleaning plasma. Therefore, foreign matter reduction can be easily performed.
[0030]
Furthermore, a high frequency power supply 7 for applying a bias voltage is connected to the inner electrode 11 together with an electrostatic attraction power supply 8b. The high frequency power supply 7 generates a high frequency bias voltage at the inner electrode 11. However, in order to prevent abnormal discharge between the inner electrode 11 and the ground plate 24, the diameters of the inner electrode 11, the insulating plate 23, and the ground plate 24 are changed greatly in order so that both the inner electrode 11 and the ground plate 24 They are not directly facing each other. Accordingly, it is not necessary to provide another insulating member on the outer peripheral portion of the inner electrode 11, and the cover 22 can also be used.
[0031]
Note that the temperature control of the substrate 9 shown in FIG. 1 is controlled based on the temperature of the refrigerant flowing through the refrigerant flow path 21 provided in the inner electrode 11. That is, the temperature of the inner electrode 11 is controlled by the temperature of the refrigerant, and the temperature of the substrate 9 is controlled via the insulating film 14 and the heat transfer gas. In this case, although the coolant channel 21 is provided only in the inner electrode 11, the temperature of the ring electrode 12 is also controlled by heat conduction through the thin insulating film 13. Therefore, the refrigerant need not be supplied to the ring electrode 12. As a result, it is sufficient to provide the refrigerant flow path 21 to the inner electrode 11, and the mechanism can be simplified.
[0032]
According to the plasma processing apparatus configured in this way, in this case, as a method of applying a DC voltage to the two electrodes, a negative voltage is applied to the ring electrode 12 and an application to the ring electrode 12 is applied to the inner electrode 11. Is configured to apply a positive voltage having a reverse polarity and the same absolute value. According to this, the electrode potential is as shown in FIG.
[0033]
FIG. 4 shows the potentials of the substrate and each electrode when the substrate being electrostatically attracted is exposed to plasma. The plasma in this case is generated by a power supply means different from the voltage applied to the electrode of the electrostatic chuck. As an example, FIG. 4 shows the potential states of the substrate 9, the ring electrode 12, and the inner electrode 11 during adsorption when a voltage of −250 V is applied to the ring electrode 12 and +250 V is applied to the inner electrode 11. In such an electrostatic chuck connected to a DC power source, the potential of the wafer being attracted is 0V. Therefore, even when the potential of the wafer is changed to about −20 V by generating plasma, the change in potential difference between the wafer and each electrode is small. Therefore, the change in the amount of charge stored between the wafer and each electrode is also small.
[0034]
In the electrostatic chuck in which the electrostatic adsorption power source is connected so as to apply the DC voltage having the same absolute value with different polarities to the respective electrodes as in this embodiment, only the plasma is generated. The residual adsorption force in this state is extremely small. For this reason, when the wafer is detached from the electrostatic chuck, there is almost no influence of the residual attracting force. Further, if the application of the DC voltage by the electrostatic attraction power source is continued even after the plasma is extinguished, it returns to the initial state where no plasma is generated. This eliminates the potential difference between the wafer and each electrode. As a result, the same principle as described in the description of FIGS. 22 to 25 described above, that is, by making the adsorption area equal, the charge amount becomes equal, and the charge remaining on either electrode when the DC power supply is turned off. Will disappear. In other words, there is an effect that the generation of the residual adsorption force can be eliminated.
[0035]
In addition, there is a case where a high frequency voltage is applied to the sample stage for the purpose of promoting the processing of the substrate to generate a bias potential (usually about −300 V or less). In this case, as shown in FIG. 4, the potential difference between the substrate and each electrode changes, and a large difference occurs in the amount of stored charge. However, even in that case, after the plasma is extinguished, the residual adsorption force can be prevented from being reduced by applying a DC voltage to the electrode for a certain period of time. Furthermore, by stopping the application of the high-frequency voltage during plasma generation and maintaining the plasma generation for a certain period of time, the same state as when the above-mentioned plasma is generated, that is, a range that does not cause a problem of about −20V. The potential difference can be reduced. That is, the attractive force at a potential difference of about −20 V is extremely small, and even if it is pushed up with the lift pin as it is, the substrate does not crack. Therefore, in the removal of the residual adsorption force when using high frequency voltage application, the time from the supply stop of these high frequency voltages to the stop of plasma generation and the time from the plasma stop to the supply stop of the DC voltage for electrostatic adsorption are adjusted. As a result, it is possible to remove the residual adsorption force more efficiently.
[0036]
In addition, when a high frequency voltage is applied as shown in FIG. 4, the potential between the wafer and the inner electrode becomes large on the positive voltage electrode side. Conversely, on the negative voltage electrode side, the potential between the wafer and the ring electrode decreases. In the case of the electrode configuration of the present embodiment, the inner electrode having the adsorbing portions at the outer peripheral portion and the central portion is on the positive voltage side. By utilizing this phenomenon, the central portion and the outer peripheral portion of the wafer are made stronger. Can be retained. Thereby, it is possible to further suppress the leakage of heat transfer gas from the outer peripheral portion of the wafer during the plasma processing. Further, when it is desired to further cool the wafer center portion, it is effective because the suction force of the wafer center portion is large. Conversely, if it is not desired to cool the wafer central portion too much, the area of the gas groove in the wafer central portion is increased and the gas groove depth is increased to reduce the heat transfer efficiency in the gas groove portion. You can do that. In this case, in the portion corresponding to the ring electrode 12, the adsorption area is reduced in accordance with the portion corresponding to the inner electrode 11, and the depth of the gas groove is kept shallow.
[0037]
Next, FIG. 5 shows a time chart when processing is performed in the order of substrate adsorption, plasma processing start, plasma processing end, and static elimination in the substrate, and the procedure will be described. First, the substrate is carried into the vacuum container by a transfer device (not shown). After the substrate is placed on the electrostatic chuck 10, first, a DC voltage is applied between the positive and negative electrodes 11 and 12 in order to attract the substrate. Next, a heat transfer gas is introduced into a gas groove provided on the surface of the insulating film 14 (dielectric film). At this time, a processing gas for processing the substrate has already been introduced into the vacuum vessel 1 by the gas supply device 2 and maintained at a desired pressure. Thereafter, energy for plasma generation (for example, a microwave electric field, a high frequency electric field, etc.) is introduced into the vacuum chamber 1 by the plasma generator 4. Thereby, plasma is generated in the vacuum container 1. Next, a high-frequency voltage for generating a bias potential is applied to the substrate (Note that the necessity of applying the high-frequency voltage depends on the process. However, when applying a high-frequency voltage, in order to achieve impedance matching Application and stop are performed while the plasma is stably generated). Simultaneously with the completion of the wafer processing by the plasma, the introduction of energy for generating the plasma is stopped and the plasma is extinguished. The high frequency voltage is stopped before the plasma disappears. In this case, the plasma disappears in 4 seconds after the high frequency voltage is stopped. As a result, as described above, the imbalance of the amount of charge stored in the insulating film (dielectric film) on each electrode generated during the plasma processing is almost eliminated. After the processing of the substrate is completed, the heat transfer gas is no longer needed and is stopped. Although not shown in the figure, the heat transfer gas accumulated in the dispersion grooves and the gas supply path is exhausted. Subsequently, the wafer is transferred for removing the substrate from the electrostatic chuck, but before that, since many processing gases usually used for plasma processing are harmful, they are exhausted sufficiently. In this embodiment, the time is about 10 seconds. In this embodiment, the electrostatic chuck static elimination (residual adsorption force removal) is completed within the exhaust time of the processing gas. More specifically, the introduction of the heat transfer gas and the processing gas is stopped 1 sec after the plasma disappears, and the heat transfer gas remaining in the dispersion groove is exhausted (0.5 sec). Thereafter, the application of the DC voltage for electrostatic attraction is finished 3 seconds after the plasma disappears. Within 3 seconds after the plasma disappears, the amount of charge stored in the insulating film (dielectric film) on each remaining electrode excluding the amount of charge unbalance eliminated by maintaining the plasma generation after the high-frequency voltage is stopped. The balance is canceled as described above. Therefore, since the amount of charge on both electrodes is balanced, after the DC voltage is stopped, the charge polarized on both electrodes quickly disappears (about 2 to 3 seconds). Then, the substrate can be transferred immediately after the exhaust of the processing gas. After the substrate is unloaded from the vacuum vessel, if there is a new substrate processing, the substrate is similarly loaded and the processing is repeated. If there is no new substrate processing, the processing ends.
[0038]
As described above, since the final static elimination of the electrostatic chuck can be completed within the exhaust time of the processing gas, it is not necessary to separately provide a static elimination time for the electrostatic chuck. This improves the operating rate of the apparatus.
[0039]
Here, according to the time chart shown in FIG. 5, the time from the stop of the high-frequency voltage to the stop of the plasma generation is set to 4 seconds, but this time is the removal of the residual adsorptive force after the plasma is stopped (resolving the imbalance of the charge amount). ) Set as appropriate in consideration of time. FIG. 6 shows the relationship between the time from the high frequency voltage supply stop to the plasma generation stop and the residual adsorption force. According to FIG. 6, in this case, the residual attractive force is not reduced so much until about 3 sec after the high-frequency voltage supply is stopped. When the plasma is extinguished about 4 seconds after the high-frequency voltage supply is stopped, the residual adsorption force is reduced to about half. Further, when the plasma is extinguished about 5 seconds or more after the high-frequency voltage supply is stopped, the residual adsorption force is reduced to a substantially constant low value. This low residual adsorption force is due to a potential difference that occurs when only plasma is generated without applying a high-frequency voltage. Therefore, as described above, there is no particular problem even if the substrate is detached while the low residual adsorption force remains.
[0040]
Next, a method for detaching the substrate from the electrostatic chuck will be described with reference to FIGS. The inner electrode 11 is provided with insulating tubes 34 at a plurality of locations. In the hole of the insulating tube 34, a lift pin 30 is provided so as to penetrate the substrate 9 from the mounting surface of the electrostatic chuck. A stepping motor 32 is attached to the lower part of the lift pin 30 via a load cell 31. A signal from the load cell 31 is input to the control device 33. The control device 33 outputs a signal so as to control the stepping motor 32. In a state where the substrate 9 is disposed on the insulating film 14 of the electrostatic chuck, a cover 22 is provided so as to surround the outer peripheral portion of the electrode 11 and the outer peripheral portion of the substrate. In this case, the gap between the outer peripheral end face of the substrate 9 and the cover 22 is set within about 1 mm. When the substrate 9 is detached from the electrostatic chuck by the lift pins 30, even if the substrate 9 is displaced on the lift pins 30, the tolerance is within a range that does not cause a problem when the substrate is delivered to a transfer device (not shown). It is set within the movement range.
[0041]
Therefore, if the sample stage is configured as described above, the lift pin 30 can forcefully remove the substrate even if some residual adsorption force remains. That is, when the lift pin 30 is raised and a force greater than the residual adsorption force acts on the substrate and the substrate jumps, the position of the substrate is maintained by the cover 22. Thereby, even when the residual adsorption force does not completely disappear, the substrate can be safely detached.
[0042]
When the substrate is detached, when the lift pin 30 is raised as shown in FIG. 8, the load of the load cell 31 is increased by a constant size as in the case where a spring load is applied by a component such as a bellows. Here, when the lift pins 30 are in contact with the back surface of the substrate 9 and there is a residual adsorption force on the substrate, the load cell 31 detects by further applying a load due to the residual adsorption force, as shown in FIG. Projecting load appears. Here, an allowable push-up force is set so that the residual adsorption force remains and the substrate is not cracked or abnormally jumped when forcibly pushed-up by the lift pins. The allowable pushing force is stored in the control device, and the lift pin 30 is raised by the stepping motor 32. When the lift pin 30 comes into contact with the substrate and the lift pin 30 further rises and the load detected by the load cell 31 exceeds the allowable push-up force, the controller 33 slows or raises the lift speed of the lift pin by the stepping motor 32. Stop. Thereby, damage of a board | substrate and a conveyance mistake of a board | substrate can be prevented.
[0043]
Therefore, by performing such substrate removal control, it is possible to start the substrate removal operation after the plasma is stopped, and to perform the substrate removal immediately after the application of the DC voltage for electrostatic adsorption is stopped, thereby further improving the throughput. Can be achieved.
[0044]
As described above, according to the present embodiment, in the bipolar type electrostatic chuck having the gas groove on the sample arrangement surface, the charges of the respective adsorption portions corresponding to the positive and negative electrodes immediately before the supply of the DC voltage for electrostatic adsorption is stopped. Since the amounts are equal, when the supply of the DC voltage is stopped, an equal amount of the charge of both electrodes disappears, and no residual charge is generated on both electrodes. Therefore, there is an effect that it is possible to eliminate the charge eliminating work after the supply of the DC voltage is stopped. Thereby, the throughput in sample conveyance can be improved.
[0045]
In addition, according to the present embodiment, the same insulating film for electrostatic adsorption is provided on the upper surfaces of the inner electrode and the ring electrode, and the areas of the respective adsorption surfaces corresponding to both the positive and negative electrodes are equal except for the gas groove portion. Therefore, the amount of charge charged on each of the adsorption surfaces corresponding to the positive and negative electrodes immediately before the supply of the DC voltage for electrostatic adsorption is stopped becomes equal, so when the supply of DC voltage is stopped, Does not generate residual charge. Therefore, it is not necessary to eliminate static electricity after the supply of DC voltage is stopped, and the throughput in sample transportation can be improved.
[0046]
As described above, according to this embodiment, the electrostatic chuck is configured so that the area ratio of the portion of the dielectric film that has two electrodes and sucks the wafer becomes 1: 1. It is possible to provide an electrostatic chuck that generates almost no force and has a short static elimination time. Therefore, in the sample processing apparatus equipped with this electrostatic chuck, since the static elimination time is short, the throughput of the apparatus is improved, and there is almost no generation of residual attracting force. There is no such thing as damaging the wafer.
[0047]
In addition, since the inner electrode and the ring electrode constitute a pair of concentric electrodes, the entire substrate is conditionally uniform with the center of the substrate being point-symmetrical, so that the substrate processing can be made uniform.
Furthermore, since the residual attractive force disappears after the supply of DC power is stopped, even when the substrate is removed and the substrate is no longer on the electrostatic chuck, the substrate placement surface has a foreign object having a charge compared to when the residual attractive force is present. Since it becomes difficult to adhere, foreign matter does not adhere to the back surface of a new substrate.
[0048]
In the first embodiment, voltages of the same potential, which are positive and negative, are applied to the inner electrode 11 and the ring electrode 12. However, during the plasma processing, the adsorption voltage of both electrodes is equal to the bias voltage. As such, the respective voltages may be varied by the DC power supplies 81a and 81b. In this way, since the electrostatic adsorption area is equal, the electrostatic adsorption force becomes equal even during the plasma processing, and extreme in-plane temperature distribution can be prevented from being uneven.
[0049]
Further, in the arrangement of the pair of electrodes, the present embodiment has been described by taking as an example the case where the electrode 12 is arranged slightly inside from the outer peripheral portion of the electrode 11 shown in FIG. 9A, but shown in FIG. 9B. Thus, the electrode 12 may be provided on the outer periphery of the electrode 11. Further, as shown in FIG. 9C, the electrode 12 may be provided at the center of the electrode 11.
According to the configuration of FIG. 9B, the processing of the recess for providing the ring electrode 12a is facilitated, which can contribute to cost reduction. In addition, since one end of the ring electrode 12a is opened in stress, damage such as cracking does not occur when subjected to a thermal cycle. According to the configuration of FIG. 9C, when the gas groove is formed, processing outside the electrode 12b is facilitated. Further, it is difficult to control the temperature of the outer peripheral portion in a normal plasma processing apparatus. However, since the degree of freedom in designing the gas groove at the outer periphery of the electrode 12b is high, it becomes easier to control the temperature of the outer periphery.
[0050]
In this embodiment, the DC power source is connected to the inner electrode 11 so as to apply a positive potential and the ring electrode 12 is applied with a negative potential. You may connect as shown. FIG. 10 shows a configuration in which an electrostatic adsorption power supply 8a is connected so that a ground potential is applied to the inner electrode 11 and a negative potential is applied to the ring electrode 12 as a method of applying a DC voltage to the two electrodes. . FIG. 11 shows the potential between the wafer and each electrode when the wafer being attracted and held by the electrostatic chuck shown in FIG. 10 is exposed to the plasma generated by the plasma generator. As an example, when considering the case where −500 V is applied to the ring electrode 12, the potential of the wafer during adsorption is −250 V, and the inner electrode is 0 V. Therefore, the potential difference between each electrode and the wafer is equal to 250 V, and the attractive force is also equal. Thereafter, when the wafer is exposed to plasma, a bias potential of about −20 V is generated in the wafer, and the potential difference between each electrode and the wafer changes. In this case, the potential difference between the inner electrode 11 and the wafer changes from 250V to 20V. The potential difference between the ring electrode 12 and the wafer changes from 250V to 480V. As a result, the adsorption force is reduced at the inner electrode portion. However, the ring electrode portion is in a state where the attractive force is further increased. Therefore, the cooling gas that has flowed to the back surface of the wafer is sufficiently sealed in the vicinity of the outer periphery of the wafer, and there is no leakage of heat transfer gas, which is convenient. In the case of plasma processing, the temperature outside the wafer tends to rise, and cooling is required. In the case of the present embodiment, the adsorptive power at the ring electrode 12 is increased, which is also effective in making the temperature distribution uniform during plasma processing.
[0051]
In FIG. 12, the ring electrode 12 and the inner electrode 11 are floated with respect to the ground potential, and the electrostatic attraction power supply 8 a is connected. A voltage having a lower potential than the inner electrode 11 is applied to the ring electrode 12. Moreover, each electrode can also be made into the same electric potential by switching operation of the switch 84a. As an example, FIG. 13 shows the state of the potential of the wafer, the ring electrode, and the inner electrode that are attracted and held by the electrostatic chuck when a potential difference of 500 V is generated between the ring electrode 12 and the inner electrode 11. In the electrostatic chuck configured as described above, the potential of the wafer being attracted is an intermediate potential between the ring electrode 12 and the inner electrode 11, and the potential difference between the ring electrode 12 and the inner electrode 11 is the same. In this state, even when the wafer is exposed to plasma and a high frequency voltage is further applied to the wafer to generate a bias potential, the voltage applied to the ring electrode 12 and the inner electrode 11 is floating with respect to the ground potential. Therefore, the bias potential changes together with the wafer potential, and as a result, the potential difference between the wafer and each electrode does not change. Therefore, there is no change in the amount of charge stored in the dielectric film of each electrode-like actual attracting portion, so there is no change in the adsorption force distribution. That is, since the adsorptive force does not change, an effect that almost no residual adsorptive force is generated can be expected. In this embodiment, an example in which a voltage having a lower potential than that of the inner electrode 11 is applied to the ring electrode 12 is not necessarily required, and the same effect can be obtained by connecting in reverse.
[0052]
In addition, even when the connections are made as shown in FIGS. 10 and 12, there is a case where a high-frequency voltage is applied to the wafer to generate a bias potential (usually about −300 V or less) for the purpose of promoting the wafer processing. In this case, however, the potential difference between the wafer and the electrode changes, and a difference occurs in the amount of stored charge. In that case, the plasma is maintained for a certain time after the supply of the high-frequency voltage is stopped as described above. Moreover, after the plasma is extinguished, the residual adsorption force (unbalance in the amount of charge between the electrodes) can be reduced by applying a DC voltage for a certain period of time.
[0053]
Also in the electrostatic chuck to which a DC power source is connected as shown in FIGS. 10 and 12, the amount of charge stored in the dielectric film in the portion that actually attracts the object to be attracted on the positive and negative electrodes is made substantially the same. As a result, the charge removal (residual charge removal) is performed smoothly, and the generation of residual adsorption force hardly occurs. However, when a very large attractive force is required, it is necessary to apply a large DC voltage between the positive and negative electrodes. In this case, the amount of electric charge stored in the dielectric film is also natural. The time required for static elimination may increase from several seconds to several tens of seconds. In such a case, the charge removal time can be shortened by applying a voltage having the opposite polarity to that during the adsorption between the positive and negative electrodes. In this way, it is possible to provide an electrostatic chuck and a sample processing apparatus that have a shorter static elimination time.
[0054]
Next, a second embodiment of the present invention will be described with reference to FIGS.
FIG. 14 shows the basic structure of this electrostatic chuck. A dielectric film 35 is fixed on the aluminum block 34 via an adhesive 36. The dielectric film 35 is made of an alumina sintered body. Two electrodes, that is, a ring electrode 31 and an inner electrode 32 are concentrically embedded in the dielectric film 35. The two electrodes 31 and 32 have a thickness of about 50 to 100 microns and are made of tungsten. Application of a DC voltage to these two electrodes is performed through a conductive wire 38 that is completely sealed with an insulating resin 43. The conducting wire 38 and each electrode are brazed 37. In this embodiment, a ground voltage is applied to the inner electrode 32, and a DC power source 40 is connected to the ring electrode 31 via a switch 39. By the switching operation of the switch 39, the negative potential of the DC power source 40 and the ground 41 are switched and connected. When a negative voltage is applied to the ring electrode 31 by the switch 39 in a state where the wafer is loaded on the surface 44 of the dielectric film 35, a potential difference is generated between the wafer and each electrode. As a result, the wafer can be electrostatically attracted and fixed to the contact surface 44. Further, if the switch 39 is switched in reverse and the ring electrode 31 is grounded, the charge stored between the wafer and each electrode can be removed.
[0055]
In this case, the thickness of the dielectric film 35 is 1 mm as a whole, but the thickness of the dielectric film on the electrodes 31 and 32 is processed to 300 μm and the surface roughness is 3 μm. A gas groove 46 is provided on the surface 44 of the dielectric film as shown in the figure at a depth of about 20 microns in this case. The gas groove 46 is formed so that a heat transfer gas for promoting cooling of the wafer being processed spreads efficiently over the entire back surface of the wafer. Heat transfer gas is introduced into the gas groove 46 from the heat transfer gas inlet 45 via an external pipe (not shown). The gas groove pattern is set so that the temperature distribution of the wafer being processed has a desired value. In this embodiment, the area of the portion that actually attracts the wafer on the ring electrode and the area of the portion that actually attracts the wafer on the inner electrode are 1: 1. . Further, the area of the gas groove portion on the ring electrode and the area of the gas groove portion on the inner electrode are set to 1: 1. In the electrostatic chuck, four lift pins 47 are provided concentrically. The lift pin 47 is provided in the inside thereof by being insulated from the electrodes 31 and 32 and the aluminum block 34 by an insulating tube 48. The lift pins 47 can be driven up and down by an up-and-down mechanism (not shown) such as an external motor, and are used for transporting the wafer after completion of processing.
[0056]
According to the electrostatic chuck configured as described above, the depth of the gas groove is about 1/10 or less than the thickness of the dielectric film on the electrode, and the static chuck of the portion that actually attracts the wafer is used. Although different from the electroadhesive force, an electrostatic attractive force is similarly generated. FIG. 16 shows the relationship of electrostatic attraction force depending on the distance between the wafer and the dielectric film. In this case, as shown in FIG. 16A, a spacer was provided on the electrostatic chuck to examine the wafer attracting force. The case where a mirror wafer is used as the wafer is shown in (b), and the case where a wafer with an SiO 2 film is used is shown in (c). According to this, it can be seen that almost no adsorption force is generated at 30 μm or more. Therefore, in the case of a gas groove shallower than 30 μm, it is necessary to take into account the electrostatic adsorption force in the gas groove. In particular, the electrostatic attraction force is surely generated when the thickness is 20 μm or less.
[0057]
In the present embodiment, the area of the portion that actually attracts the wafer and the area of the gas groove portion in the inner electrode and ring electrode shape during electrostatic attraction are the same in the actual adsorption surface and the gas groove portion, respectively. Since the area is set, the amount of charge during electrostatic attraction is equal, and the residual attraction force is hardly generated after the supply of the DC voltage is stopped as in the first embodiment.
[0058]
In the electrostatic chuck of the second embodiment, an alumina sintered body is used. Usually, a ceramic material is often used for the dielectric film of the electrostatic chuck. However, the ceramic material has a characteristic that the resistivity depends not only on the applied voltage but also on the temperature as described above. FIG. 17 shows measured values of resistivity when the applied voltage of the dielectric film used in the electrostatic chuck of this example is 200V. From this figure, it can be seen that the resistivity changes about 30 times between the case where the temperature of the dielectric film is 20 degrees and the case where it is minus 50 degrees. If the resistivity of the dielectric film is too low, no charge is stored between the dielectric film surface and the wafer back surface, and no attractive force is generated. On the other hand, if the resistivity is too high, the discharge time constant of the charge accumulated between the dielectric film surface and the wafer back surface becomes large, and the static elimination time becomes long. For this reason, there arises a problem that the residual adsorption force remains.
[0059]
In processes that require fine processing with high reproducibility, the temperature of the electrostatic chuck is controlled in order to manage the temperature of the wafer being processed. However, when the temperature of use varies widely depending on the process, there is a possibility that it cannot be used for a process at a certain temperature. For example, in an etching apparatus, it is necessary to control the wafer temperature from a low temperature of about minus 60 ° C. to a temperature of about 100 ° C. In a film forming apparatus using CVD or sputtering, the temperature may reach a high temperature of about 100 ° C. to 700 ° C. In such a case, the resistivity of the dielectric film is controlled by adding an impurity such as a metal oxide to the basic material of the dielectric film. In this way, an appropriate value may be set within the temperature range to be used.
[0060]
By using the electrostatic chuck having the dielectric film configured as described above, it is possible to quickly remove static electricity while ensuring a sufficient adsorption force over the entire operating temperature range. Moreover, in the sample processing apparatus provided with such an electrostatic chuck, since the processing in the entire temperature range can be performed with one processing apparatus, the apparatus can be operated with a high operating rate.
In addition, when an electrostatic chuck is used for processes with different operating temperatures, the attractive force changes because the resistivity of the dielectric film differs depending on the operating temperature. If the adsorption force changes, the thermal conductivity of the adsorption part changes and the process may change. In such a case, a voltage that generates the same attractive force may be applied based on the result of a preliminary check according to the temperature to be used.
In the processing apparatus including the electrostatic chuck configured as described above, it is possible to always provide a processing apparatus with good reproducibility.
[0061]
In the first and second embodiments described above, positive and negative charges accumulated in the electrostatic adsorption film (insulating film 14 and dielectric film 35) immediately before the application of the DC voltage for electrostatic adsorption is stopped. In order to make the amount the same, the actual adsorption area corresponding to the positive and negative electrodes is made equal, but if the adsorption area cannot be made the same, the following may be performed.
[0062]
For example, in FIG. 14, the area of the actual adsorption portion on the inner electrode 32 is 54 cm.²In contrast, the area of the actual adsorption portion on the ring electrode 31 is 152.5 cm.²Then, the adsorption part area on the ring electrode 31 side is 2.8 times as large as the adsorption part area on the inner electrode 32 side. Therefore, in order to make the amount of electric charge stored between the wafer and the dielectric film on each electrode during adsorption substantially the same when the applied voltage is 400 V, which is the use condition, the description has been made with reference to FIGS. Based on the same concept, the surface roughness is 3 μm on the surface of the dielectric film on the inner electrode 32 and 3.9 μm on the surface of the dielectric film on the ring electrode 31. At this time, when the potential difference generated between each electrode and the wafer is obtained from the above-described equation, it is 274 V between the inner electrode and the wafer and 126 V between the ring electrode and the wafer. The capacitance of the dielectric film on the inner electrode is 16 nF, and the capacitance of the dielectric film on the ring electrode is 35 nF. From these conditions, the amount of charge stored in the dielectric film on each electrode is calculated to be 4.4 × 10 4 for the dielectric film on the inner electrode.^-6Coulomb [C], 4.4 × 10 4 for the dielectric film on the ring electrode^-6Coulomb [C]. Therefore, it can be seen that the charge amount stored in the dielectric film is the same on both electrode sides. Therefore, when the application of the voltage from the DC power supply is stopped from this state, the generation of the residual adsorption force is suppressed by the same principle as described in the description of FIGS. 22 to 25 described above, and the static elimination time is shortened.
[0063]
That is, the product of the ratio of the capacitance of the dielectric film of the actual attracting portion on each electrode and the ratio of the resistance of the dielectric film of the actual attracting portion on each electrode is approximately 1, that is, If the electrostatic chuck is designed so that Ca · Ra = Cb · Rb based on the relationship of Ca · Va = Cb · Vb, the amount of charge stored in the actual adsorption portion on each electrode during adsorption is the same. Become. Thereby, generation | occurrence | production of residual adsorption | suction force can be suppressed.
[0064]
In the above description, the adsorption area on the side of the inner electrode 32 has been described as being small. However, reducing the adsorption area on the side of the ring electrode 31 may be considered depending on the processing conditions. When the relationship between the electrostatic attraction force when the gas was supplied to the back surface of the wafer and the wafer temperature was examined by experiments, the electrostatic attraction force was better and the cooling was better. On the other hand, when the electrostatic capacity (Q = C · V) in each electrode part is equal, the adsorption force per unit area becomes larger when the electrostatic adsorption area is reduced. Based on these, considering the temperature distribution in the sample surface during sample processing, when it is necessary to further cool or heat the outside of the sample, a cooling gas is supplied to the back side of the sample and the outside of the sample is strongly adsorbed and By holding, the temperature distribution can be improved. Therefore, when the adsorption areas are different, there is an effect that the in-plane temperature distribution of the sample can be adjusted by appropriately setting the adsorption area of each electrode.
[0065]
Next, a third embodiment using the electrostatic chuck of the present invention will be described with reference to FIG. In this embodiment, a new dummy wafer 50 is loaded on the dielectric film 53 and is attracted by applying a voltage higher than the voltage applied during actual processing by the DC power supply 54. As a result, the foreign matter adhering to the surface of the dielectric film, for example, a foreign matter having a negative charge, is normally not repelled by a charge larger than the charge during the normal wafer adsorption (a negative charge in this portion). The foreign matter adhering to the surface of the dielectric film is repelled and transferred to the back surface of the wafer. Thus, if the dummy wafer is taken out by a method similar to that for carrying a normal wafer, foreign matter on the dielectric film can be removed. In this figure, only the negatively charged foreign matter is shown, but there is also a positively charged foreign matter.
In an electrostatic chuck that periodically performs this operation, the number of foreign substances adhering to the back surface of the processing wafer can be reduced, and a clean process can always be performed. Therefore, in the processing apparatus provided with the electrostatic chuck of this embodiment, the product yield can be improved. Moreover, since the frequency | count of the decomposition | disassembly operation | work of the apparatus performed in order to clean the foreign material accumulate | stored in the apparatus can be reduced, an apparatus with a high operation rate can be provided.
[0066]
In the third embodiment, the removal of foreign matter having either positive or negative charge has been described. However, an example in which both positive and negative foreign matter can be removed will be described with reference to FIG. In this case, instead of the DC power supply of FIG. 18, the polarity of the applied voltage is changed to a DC power supply that can be switched between positive and negative, and a new dummy wafer 50 is loaded on the surface of the dielectric film 53, and FIG. As shown, a DC alternating voltage having an absolute value larger than the voltage applied to attract the wafer during normal processing is applied. By performing such an operation, foreign matter that cannot be removed only by the operation shown in the example of FIG. 18, that is, in this case, foreign matter that is positively charged and adsorbed by the dielectric film and electrostatic force is transferred to the dummy wafer. And can be removed. Therefore, according to the present embodiment, the dielectric film can be more effectively cleaned.
In this embodiment, a new dummy wafer is used to remove foreign matter on the dielectric film. However, the present invention is not limited to this, and any member made of a clean conductive or semiconductive material may be used. good. However, it is preferable to avoid materials containing substances that cause heavy metal contamination.
In this embodiment, a DC alternating voltage is applied. However, the present invention is not limited to this, and a similar effect can be expected even when an AC voltage is applied.
[0067]
A fourth embodiment using the electrostatic chuck of the present invention will be described with reference to FIGS. FIG. 20 shows a configuration of a sample processing apparatus using an electrostatic chuck. In this case, the sample processing apparatus includes an atmospheric loader unit and a vacuum processing unit. The atmospheric loader unit has a cassette installation position where a plurality of cassettes 61 can be arranged. In addition, the atmospheric loader unit includes an atmospheric transfer robot 62 for transferring a wafer stored in the cassette 61 to the vacuum processing unit or a wafer processed by the vacuum processing unit into the cassette. The vacuum processing unit is configured by connecting a load lock chamber 63, an unload lock chamber 64, a processing chamber A 70, a processing chamber B 71, a processing chamber C 72, and a processing chamber D 73 around the vacuum transfer chamber 65. The load lock chamber 63 and the unload lock chamber 64 are located on the atmospheric loader 60 side. A vacuum transfer robot 66 is provided in the vacuum transfer chamber 65. The vacuum transfer robot 66 has an arm 67 and a hand 68 at the tip of the arm 67. The vacuum transfer robot 66 operates so that the hand 69 can be inserted into each chamber 63, 64, 70, 71, 72, 73. The hand 68 has wafer mounting surfaces at both ends. An electrostatic chuck as shown in FIG. 21 is formed on the wafer mounting surface at the tip of the hand 68. The electrostatic chuck includes an outer electrode 681, an insulating film 682, an inner electrode 683, and an insulating film 684 for electrostatic adsorption. For example, three convex portions are formed on the outer electrode 681 at the tip of the hand 68, and a concave portion for forming the inner electrode 683 is formed in a part of the convex portion. An insulating tube 685 is attached to the concave portion of the outer electrode 681 so as to penetrate the electrode, and an electrode core 686 is attached in the insulating tube 685. An insulating film 682 made of a sprayed film is formed in the recess, and an inner electrode 683 made of a sprayed film is formed on the insulating film 682. The inner electrode 683 is easily connected to the electrode core 686 by thermal spraying of the inner electrode 683. An insulating film 684 made of a sprayed film is formed on the upper surfaces of the outer electrode 681 and the inner electrode 683. A lead wire 689 is connected to the electrode core 686, and a lead wire 688 is connected to the outer electrode 681. The lead wire 688 and the lead wire 689 are connected to an electrostatic attraction power source (not shown). An insulating cover 687 is provided on the lower surface of the outer electrode 681. In this case, the convex portion on which the electrostatic adsorption surface is formed has the smallest possible contact area with the wafer in order to reduce the adhesion of foreign matter. Further, the areas of the attracting surfaces corresponding to the outer electrode 681 and the inner electrode 683 on the electrostatic attracting surface are the same.
[0068]
According to the sample processing apparatus configured as described above, the atmospheric transfer robot 62 takes out the wafer from the cassette 61 and carries the wafer into the load lock chamber 63. The wafer transferred to the load lock chamber is transferred to a processing chamber (for example, processing chamber 71) designated by the vacuum transfer robot 66. At this time, first, a wafer already processed in the processing chamber 71 is received by one hand 68. Next, the direction of the hand 68 is changed, and an unprocessed wafer is carried into the processing chamber 71. The processed wafer held on one side of the hand 68 is transferred to the next processing chamber (for example, the processing chamber 70) by the vacuum transfer robot 66. On the other hand, a wafer to be processed in another processing chamber (for example, the processing chamber 72) is transferred by the same movement of the atmospheric transfer robot 62 and the vacuum transfer robot 69 described above.
[0069]
Here, when the vacuum transfer robot 66 receives a wafer in the load lock chamber 63 and each processing chamber, DC voltages having different positive and negative polarities and equal absolute values are applied to the outer electrode 681 and the inner electrode 683. As a result, charges having the same charge amount are stored in the insulating film on the surface corresponding to each electrode of the electrostatic attraction surface. Further, when the vacuum transfer robot 66 delivers the wafer in the unload lock chamber 64 and each processing chamber, the supply of the DC voltage applied to the outer electrode 681 and the inner electrode 683 is stopped. Thereby, the electric charge stored in the insulating film on the surface corresponding to each electrode of the electrostatic attraction surface disappears with a good balance. As a result, the wafer is easily detached from the electrostatic attraction surface without any residual attraction force remaining on the electrostatic attraction surface. The wafer is detached from the electrostatic attraction surface of the hand 68 by using the lift pins as shown in FIGS. When the wafer is detached from the hand 68, the application of the DC voltage for electrostatic adsorption is stopped when the wafer on the hand 69 arrives at a predetermined position and stops by the vacuum transfer robot 66. At the same time, when the wafer arrives at a predetermined position and stops, the lift pins are started to rise. Even if the charge of the electrostatic chuck has not completely disappeared when the lift pin contacts the wafer, the movement of the stepping motor is controlled while detecting the pressing force of the lift pin by the load cell as shown in FIGS. By using this method together, the lifting force of the lift pins is controlled, so that the wafer is not damaged. As a result, the application of the DC voltage for electrostatic attraction is stopped, and after a few seconds (about 2 to 3 seconds) until the electric charges polarized on both the positive and negative electrodes disappear, the lift pins are raised and the wafer is detached. You don't have to. Therefore, it is possible to improve the throughput during wafer transfer. If the time of several seconds until the electric charge disappears does not affect the throughput of the entire wafer processing, it is not particularly necessary to control the lifting force of the lift pins using the load cell.
[0070]
In addition, since the positive and negative charge amounts stored in the insulating film on the electrostatic adsorption surface are equalized immediately before the supply of DC voltage is stopped, it is ensured that the residual amount can be ensured only by stopping the application of the DC voltage for electrostatic adsorption. The adsorption power can be extinguished. Therefore, even if this electrostatic chuck is used for the wafer holding portion of the atmospheric transfer robot 62, the wafer can be moved to the cassette storing stage without any problem when the wafer is stored in the cassette.
[0071]
As described above, according to the present embodiment, by using the electrostatic chuck for the wafer holding portion of the transfer robot, the wafer can be securely held on the arm, so that the sample processing with improved wafer transfer reliability can be achieved. It can be a device.
In addition, since the wafer can be securely held on the arm, the transfer speed of the transfer robot can be increased, and the throughput can be improved. Further, by adopting this electrostatic chuck in a transfer robot provided with a hand having two wafer holding units on the arm, when replacing a processed wafer and an unprocessed wafer in one processing chamber, Even if the direction of the hand is changed from one to the other by the transfer robot, that is, the rotation speed when the arm is rotated (or the hand is rotated) is increased, the wafer is not detached by the centrifugal force. Therefore, wafer replacement in the processing chamber can be performed quickly, and loss time in wafer processing can be reduced.
In this embodiment, the electrostatic chuck is also used for the atmospheric transfer robot. However, the atmospheric transfer robot may be another holding means such as a vacuum chuck.
[0072]
The present invention has been described above by taking the electrostatic chuck and the sample processing apparatus of the first to fourth embodiments as examples, but the most important point is the electrostatic chuck and the sample transport apparatus applied to the processing chamber. In the applied electrostatic chuck, the amount of charge stored in the dielectric film immediately before stopping the DC voltage applied between the positive and negative electrodes is made the same. By doing so, it is possible to provide an electrostatic chuck in which static elimination is smooth and almost no residual attracting force is generated. In addition, when applied to a sample processing apparatus such as a plasma processing apparatus or a vacuum processing apparatus, the sample is securely held during the sample processing and the sample transport, and the sample is transferred during the next processing. Therefore, it is possible to provide a sample processing apparatus with a high operating rate.
[0073]
  As described above, according to the above embodiment,Since the amount of charge stored in the insulating film for electrostatic adsorption corresponding to each electrode is equalized immediately before the DC voltage applied to the positive and negative electrodes is stopped, another charge eliminating step is provided after the DC voltage application is stopped. Without charge, the charge stored in the insulating film for electrostatic adsorption can be quickly extinguished. Thereby, an electrostatic chuck with little residual attracting force and a short static elimination time can be provided.
[0074]
  Also,UpAs described above, when considering the operation time of the lift pins and the like, there is no particular loss time, but if further necessary, it is shorter if a voltage having a polarity opposite to that during adsorption is applied after the applied voltage is stopped. Over time, the charge stored in the dielectric film can be extinguished.
[0075]
  Also,According to the above embodiment,The amount of charge generated during the plasma processing of the plasma processing in which the application of the high-frequency voltage for generating the bias voltage is performed simultaneously by maintaining the plasma generation for a predetermined time after the application of the high-frequency voltage is stopped. Can be eliminated. In addition, after the plasma generation is stopped, a DC voltage for electrostatic adsorption is applied for a predetermined time, so that an imbalance of the charge amount during plasma generation can be eliminated. Furthermore, the elimination of the charge accumulated in the insulating film for electrostatic attraction after stopping the application of the DC voltage for electrostatic attraction is completed within the exhaust time of the processing gas. A plasma processing apparatus that is not reduced can be provided.
[0076]
  Also,According to the above exampleSince the residual adsorption power disappears after the supply of DC power is stopped, it is difficult for foreign objects with charges to adhere to the substrate placement surface compared to when there is residual adsorption force, and foreign substances adhere to the back side of a new substrate. There is an effect that there is no.
[0077]
  Also,DifferentIf an object is attached, either by applying a voltage higher than the normal applied voltage to the electrode for electrostatic adsorption or by applying an alternating voltage having an absolute value larger than the normal applied voltage, Foreign matter adhering to the dielectric film (insulating film for electrostatic adsorption) can be transferred to the dummy wafer and removed, so that the foreign matter on the back surface of the product wafer can be reduced by performing this periodically. .
[0078]
  further,Like the above exampleWhen applied to all locations of the wafer holder of the sample processing apparatus, no residual adsorption force is generated in the wafer holder, so that the wafer can be easily and reliably delivered. Therefore, it is possible to provide a highly reliable sample processing apparatus.If a power failure occurs during the processing of the wafer held by the electrostatic chuck, the adsorption force of the wafer is reduced, and the wafer is not lifted by the pressure of the heat transfer gas remaining on the back surface of the wafer. In this case, the pressure of the heat transfer gas may be lowered while the adsorption force of the wafer is maintained. That is, when a sudden stop of the DC voltage to the electrostatic chuck occurs, an auxiliary battery is provided in the DC power source that supplies the voltage to the inner electrode and the ring electrode, and the adsorption force is held by the auxiliary battery for a certain period of time. The heat transfer gas may be exhausted. As an example of the simplest method of exhausting the heat transfer gas, when the supply voltage is off, the heat transfer gas supply line connected to the wafer back surface is connected to the processing chamber where the wafer is arranged. There is a method of connecting through a valve that opens the supply line. In this way, when the supply of voltage is turned off, the heat transfer gas flows into the processing chamber, and the pressure between the wafer back surface and the processing chamber is balanced, so that the wafer does not shift.
[0079]
【The invention's effect】
  According to the present invention, it is possible to provide a sample processing apparatus and a sample processing method capable of reducing the waiting time for sample detachment and improving the throughput.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an example of a sample processing apparatus using an electrostatic chuck according to an embodiment of the present invention.
FIG. 2 is a plan view of the electrostatic chuck when FIG. 1 is viewed from II-II.
FIG. 3 is a diagram showing details of a part III in FIG. 1;
4 is a diagram showing each electrode potential in the electrostatic chuck of FIG. 1. FIG.
5 is a diagram showing a time chart up to electrostatic chuck adsorption / processing / static elimination in the apparatus of FIG. 1; FIG.
6 is a diagram showing a residual adsorption force in a required time from a supply stop of high-frequency voltage to a plasma generation stop time in the apparatus of FIG. 1;
7 is a longitudinal sectional view showing the electrostatic chuck portion of FIG. 1;
8 is a diagram illustrating a load applied to a wafer when the wafer is detached from the electrostatic chuck of FIG. 7;
9 is a longitudinal sectional view showing another example of electrode arrangement of the electrostatic chuck of FIG. 1. FIG.
10 is a longitudinal sectional view showing another example of connection of the electrostatic chuck DC power supply of FIG. 1; FIG.
11 is a diagram showing each electrode potential in the electrostatic chuck of FIG.
12 is a longitudinal sectional view showing still another example of connection of the electrostatic chuck DC power supply of FIG. 1; FIG.
13 is a diagram showing each electrode potential in the electrostatic chuck of FIG. 12. FIG.
FIG. 14 is a perspective view showing an electrostatic chuck according to a second embodiment of the present invention.
15 is a plan view of the electrostatic chuck of FIG.
FIG. 16 is a diagram illustrating a relationship between a gap and electrostatic attraction during electrostatic attraction.
FIG. 17 is a diagram showing the temperature dependence of the resistivity of the dielectric film of the electrostatic chuck of FIG.
FIG. 18 is a third embodiment using the electrostatic chuck of the present invention, and is a schematic diagram in the case where foreign matters on a dielectric film are transferred to a dummy wafer and removed.
19 is another example of foreign matter removal in FIG. 18, and is a diagram showing a DC alternating voltage applied to the electrostatic chuck.
FIG. 20 is a diagram showing a fourth embodiment using the electrostatic chuck of the present invention, and showing an example in which the wafer holding portion of the sample processing apparatus is entirely constituted by an electrostatic chuck.
21 is a cross-sectional view showing details of a wafer holding unit of a transfer robot in the apparatus of FIG.
FIG. 22 is a diagram showing an equivalent circuit of the electrostatic chuck.
FIG. 23 is a diagram showing the relationship between the volume resistivity of ceramics and the applied voltage.
24 is a diagram showing an adsorption and static elimination operation in the equivalent circuit of FIG. 22;
FIG. 25 is a diagram showing the relationship between the residual adsorption force and the discharge time when the adsorption area ratio changes.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Vacuum container, 2 ... Gas supply apparatus, 3 ... Vacuum exhaust apparatus, 4 ... Plasma generator, 5 ... Plasma, 6 ... Heat transfer gas supply apparatus, 7 ... High frequency power supply, 8a, 8b ... Power supply for electrostatic adsorption, DESCRIPTION OF SYMBOLS 9 ... Board | substrate, 10 ... Electrostatic chuck, 11 ... Inner electrode, 12 ... Ring electrode, 13 ... Insulating film, 14 ... Insulating film, 15 ... Insulating tube, 16 ... Lead wire, 17 ... Insulating tube, 18 ... Lead wire, 19a, 19b ... low pass filter, 20 ... through hole, 21 ... refrigerant flow path, 22 ... cover, 23 ... insulating plate, 24 ... ground plate, 81a, 81b ... DC power supply, 82a, 82b, 83a, 83b ... terminal, 84a , 84b... Switch.

Claims (10)

A sample processing apparatus for processing a sample disposed in a vacuum vessel using plasma generated above the sample in the vacuum vessel,
A sample stage disposed in the vacuum vessel, having a plurality of electrodes of different polarities and a dielectric film disposed on the electrodes, and the sample is placed on the dielectric film; and A DC power source for supplying a DC voltage for providing the different polarities; a RF power source for supplying a high frequency power for generating a bias voltage on the sample stage; and between the dielectric film and the sample during processing of the sample. Means for supplying heat transfer gas to
A sample processing apparatus for stopping the supply of the high-frequency power at the end of the processing of the sample and extinguishing the plasma above the sample after a predetermined time. The sample processing apparatus according to claim 1,
Means for adjusting the temperature of the sample stage, and after the supply of the high-frequency power is stopped at the end of the processing of the sample, the supply of the DC voltage and the sample and the dielectric for at least the predetermined time A sample processing apparatus for supplying the heat transfer gas to a body membrane . The sample processing apparatus according to claim 1 or 2,
The sample processing apparatus with the same area for every said polarity of the adsorption surface of the said sample of the said electrode located under the said dielectric film. The sample processing apparatus according to claim 1,
Adhesion of the sample of the electrode located below the dielectric film, having a recess to be supplied with the heat transfer gas between the sample and the sample placed on the dielectric film A sample processing apparatus having the same area of the surface for each polarity and excluding the recessed portion. The sample processing apparatus according to claim 4,
Means for adjusting the temperature of the sample stage, and after the supply of the high-frequency power is stopped at the end of the processing of the sample, supply of the DC voltage and the depression to the depression for at least the predetermined time Sample processing device that supplies heat transfer gas. The sample processing apparatus according to any one of claims 1 to 5,
Sample processing is provided with a lift pin that is arranged inside the sample table and pushes up the sample above the sample table, and after stopping the supply of the DC voltage for the predetermined time, the sample is detached from the dielectric film by the lift pin. apparatus. A sample is arranged on a sample stage having a plurality of electrodes having different polarities and a dielectric film arranged on these electrodes, and the sample is placed on the dielectric film. Supplying a DC voltage to the electrodes to give the different polarities to adsorb the sample onto the dielectric film, supplying a heat transfer gas between the sample and the dielectric film, and the sample A sample processing method for processing a sample by generating a plasma above the sample in the vacuum vessel while generating a bias voltage by supplying high-frequency power to a table,
A sample processing method in which the supply of the high-frequency power is stopped at the end of the processing of the sample and the plasma above the sample is extinguished after a predetermined time. The sample processing method according to claim 7, comprising:
Processing the sample while adjusting the temperature of the sample stage, and stopping the supply of the high frequency power at the end of the processing of the sample, and then supplying the DC voltage and at least the predetermined time A sample processing method for supplying a heat transfer gas between a sample and the dielectric film. The sample processing method according to claim 8, comprising:
The sample stage is provided with a depression on the dielectric film in which a heat transfer gas is supplied between the sample stage and the sample.
Means for adjusting the temperature of the sample stage, and after the supply of the high frequency power is stopped at the end of the processing of the sample, the heat transfer gas is supplied to the depression for at least the predetermined time. Sample processing method to be performed. The sample processing apparatus according to any one of claims 7 to 9,
A sample processing apparatus, wherein after stopping the supply of the DC voltage for the predetermined time, the sample is detached from the dielectric film by a lift pin that is arranged inside the sample table and pushes up the sample above the sample table.

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