Patent Application
20070044916
The present invention relates to a system for processing samples supplied as substrate-like processing objects, such as semiconductor wafers in the vacuum state. More particularly, the present invention relates to a vacuum processing system that performs continuous processing of samples in a vacuum vessel or chamber by using plasma.
In recent years, with demands for enhanced accuracy and density of semiconductor devices, processing with enhanced fineness and accuracy is required for a circuit pattern that is formed on a semiconductor wafer. Anisotropy should be realized to obtain fine and high accuracy processing.
For example, according to a general practice, when performing etching a wafer by using plasma (plasma etching), the bias voltage is applied to the wafer, and ions are accelerated by the electric field to be drawn along the vertical direction, whereby the anisotropy is realized. In this event, the wafer has heat input occurring by the bias voltage being applied, so that the wafer temperature increases.
A close relationship exists between the wafer temperature and the deposition efficiency of reaction products being deposited on sidewalls during etching. The linewidth (CD (critical dimension)) of the circuit pattern of a finally obtainable wafer is significantly influenced by reaction products deposited on sidewalls during etching. Consequently, unless appropriate control of the wafer temperature can be performed, there occurs a nonuniform processed profile not having reproducibility. The distribution of reaction products has a tendency that the density thereof is lower than that in the vicinity of the center of the wafer. As such, in order to obtain a uniform processed profile in the plane of the wafer, positive control should be performed for the temperature distribution of the wafer. In addition, the density distribution of the reaction products in the wafer is variant with a variation in etching conditions. As such, in a case where the etching conditions vary during a process as in the case that an anti-reflective coating and polysilicon are continuously processed, the temperature distribution should be shifted to an optimal temperature distribution in coordination with conditions.
However, according to general conventional methods, in order to control an average temperature distribution of a wafer, the temperature of an electrostatic attraction device, which is used as a wafer stage, is regulated to a constant temperature by using a coolant discharged from a circulator. In this case, a heat transfer gas, such as helium, is supplied to a portion between the wafer and the electrostatic attraction device to secure heat transfer characteristics. These methods are advantageous in that since the heat capacity of coolant is large, even when the amount of heat gain from the plasma is large, the wafer temperature does not sharply increase and hence the temperature is relatively stable. However, the methods are not suitable for varying the wafer temperature with good response characteristics in coordination with conditions as described above.
For example, methods have been proposed that reduces a CD shift amount by controlling the increase of the wafer temperature while a plurality of wafers are being continuously processed. According to an example of such methods, the flow rate of coolant being circulated inside an electrode on which wafers are stacked is regulated in unit of the wafer (see Japanese Patent Laid-Open No. 2003-203905, for example).
According to the conventional technique described above, it is not considered that the temperature distribution in the plane of the wafer should be appropriately regulated. As such, problems remain pending resolution, particularly, in a case where etching conditions vary in such an event where an anti-reflective coating and polysilicon are continuously processed during a single process. That is, problems occur in such a case where an optimal temperature distribution in the plane of the wafer should be realized.
More particularly, sufficient consideration is not taken into a configuration necessary to quickly shift the temperature distribution in the plane of the wafer to an appropriate one in coordination with an appropriate etching condition(s) with respect to a respective film layer. Further, sufficient consideration is not taken regarding a configuration for being formed by accurately and appropriately shifting the temperature distribution, consequently leading to a loss of the efficiency for wafer processing.
Objects of the present invention are, but not limited to, as follows:
(1) First object of the invention is to provide an electrostatic attraction device at a low cost, wherein a temperature distribution in a plane of the electrostatic attraction device can be shifted with good response characteristics in coordination with a respective etching condition, thereby to enable a uniform bias voltage can be applied to an wafer;
(2) Second object of the invention is to provide an electrostatic attraction device, wherein a temperature distribution in a plane of the electrostatic attraction device can be finely regulated in coordination with a respective etching condition; and
(3) Third object is to provide an electrostatic attraction device wherein power consumption of heating systems can be restrained, and a thermal load imposed on a circulator discharging coolant to the electrostatic attraction device can be reduced.
The first object is achieved by a structure formed in the manner that a ceramic film is formed by a spray method on a base material of the electrostatic attraction device. Electrode films for electrostatic attraction are formed by a spray method on a surface of the ceramic film, a ringular heater film is formed in a spray method between the electrode films in a radial direction of the electrode films, and a ceramic film is formed by a spray method on upper surfaces of the electrode films and the heater film.
The second object is achieved by a structure wherein a plurality of heater films are each provided in an inner portion and an outer portion in the radial direction on the electrostatic attraction device.
The third object is achieved by a structure wherein a vacuum insulation layer is formed in a base material of the electrostatic attraction device, and heater films are provided in an inner portion and an outer portion in the radial direction of the vacuum insulation layer.
According to the present invention, the electrostatic attraction device containing the heater(s) buried therein in a spray method can be provided, so that manufacturing costs can be reduced in comparison to the case of a sintered ceramics. Further, according to the present invention, a temperature distribution in a plane of a wafer can be controlled with good response characteristics by control of the heater(s) buried in the vicinity of the wafer. Further, the temperature distribution in the plane of the wafer can be varied in coordination with a respective etching condition. Furthermore, according to the present invention, power consumption of the heater(s) can be restrained, thereby enabling a thermal load on a circulator to be reduced.
The above-mentioned and other objects, features, and advantages of this invention will become more apparent by reference to the following detailed description of the invention taken in conjunction with accompanying drawings, wherein:
FIGS. 1 to 3 shows a first embodiment of the present invention by way of an example wherein the embodiment is adapted in an effective magnetic field microwave plasma processor.
To begin with, the configuration of the first embodiment will be described by reference to
First, processing gases are introduced into a vacuum processing chamber 1 through a processing gas introduction pipe 13. The processing gases are converted into plasma 7 by interaction between a microwave 5 and a magnetic field. The microwave 5 is generated by a microwave oscillator 19 and is introduced through a waveguide 4, and the magnetic field is generated by the coil 6 wound around a vacuum chamber unit 3. The process (etching process in the present case) is performed in the manner that the wafer 9 is exposed to the plasma. Particularly, a high frequency power source 10 connected through a capacitor 18 controls incidence of ions to thereby control the etching state. DC power sources 11 each apply voltage to the electrostatic attraction device 8. In the drawing, numeral 17 denotes a coil that prevents entrance of high frequency components. Numeral 12 denotes a vacuum pump 12. The pressure in the processing chamber is maintained constant by adjustment of the opening of a valve 15. A heater power source 28 is connected to a heater film in the electrostatic attraction device 8 through a coil 27.
The high frequency power source 10, the DC power sources 11, the vacuum pump 12, the coil 6, a microwave oscillator 19, and a shut-off valve 13′ provided to a processing gas supplying pipe 13 are connected to a controller unit 110. The heater power source 28 is also connected with the controller unit 110. Thereby, the connected devices are monitored by the controller unit 110 for their operation states and their signals are received thereby, and instructions for their operation are issued to the devices. That is, the controller unit 110 regulates operations of respective portions of vacuum processing system according to the present embodiment.
The electrostatic attraction device 8 being used in the embodiment will be described in details with reference to
The electrostatic attraction device 8 is a sample table that allows the wafer 9, which is a sample representing a processing object, to be mounted and held on its upper surface. The material of a base material 2, which is an essential component of the electrostatic attraction device 8, is a metal having electro-conductivity. In a base material 2, there are provided coolant channels 31 and 32, insides of which allows flowing of coolants serving as heat exchange mediums, in a center side portion and outer periphery side portion, respectively, of the base material 2. The coolants having the temperatures different from one another circulate the insides of the respective coolant channels 31 and 32. Thereby, temperature of the base material 2 or the electrostatic attraction device 8 (sample table) is regulated to be appropriate in the center side and outer periphery side thereof.
The respective coolants circulated through the coolant channels 31 and 32 travel through a coolant temperature regulator 201, whereby the coolants are regulated to predetermined temperatures and then recirculated to return to coolant channels 31 and 32. Similarly as for example, the high frequency power source 10, electrostatic-attraction dedicated DC power sources 11A and 11B, a heater power source 28, also the coolant temperature regulator 201 is connected with the controller unit 110. Thereby, the operation of the coolant temperature regulator 201 is monitored and regulated in accordance with instructions received.
In the vacuum processing chamber unit 3 of the vacuum processing system thus configured, the density of reaction products formed corresponding to processing is different in the near-center portion and near-outer periphery portion of the wafer 9. More specifically, in the present embodiment, cases can take place where the density in near-outer periphery portion tends to become relatively low. As such, when the temperature distribution in the plane of the wafer 9 is homogenized, the CD (critical dimension) in a near-outer periphery portion tends to be reduced. To overcome this problem, in the present embodiment, the temperature of coolant in the coolant channel 32 on the outer periphery side is set lower than the coolant temperatures of the coolant channel 31 on the inner periphery side.
On the surface of the base material 2, a high resistance alumina film 20 for proving electrical insulation is disposed by being splayed. On the surface of the high resistance alumina film 20, electrostatic attraction electrode films 33 and 34 of an electro-conductive material, such as tungsten or nickel, are disposed by being sprayed with an appropriate mask to predetermined shapes.
A heater film 22 of an electro-conductive material, such as tungsten or nickel, is sprayed between the electrostatic attraction electrode films 34 along the radial direction thereof. The electrostatic attraction films 34 each have a substantially ringular shape, and the electrostatic attraction film 33 on the center side has a substantially circular shape. The heater film 22, which is provided on the inner side of electrostatic attraction film 34 on the outer periphery side with respect to the radial direction of the electrostatic attraction device 8, has a substantially ringular shape. An inner periphery side and outer periphery side of the heater film 22 are sandwiched by the electrostatic attraction films 34.
Further, a high resistance ceramic film 21 to be used as an electrostatic attraction film is disposed by being sprayed in such a manner as to cover the surfaces of the base material 2, the high resistance alumina film 20, the heater film 22, and the electrostatic attraction electrode films 33 and 34. A wafer mounting surface on which the wafer 9 is to be mounted is formed on the high resistance ceramic film 21. In the state where the wafer 9 is placed on the high resistance ceramic film 21, power is supplied to the electrostatic attraction films 33 and 34, and electrostatic attraction forces with static electricity are generated by static in the high resistance ceramic film 21 sandwiched by the wafer 9 and the underlying film layer. Thereby, the wafer 9 is held.
The heater film 22 is thus provided on the inner side between the electrostatic attraction electrode films 34 in such a manner as to be surrounded thereby. As such, an outer peripheral portion of the wafer 9 is compressed by attraction forces caused by the electrostatic attraction electrode films 34 along the direction of the electrostatic attraction device 8, whereby leak of helium gases can be restrained. Further, response characteristics with respect to temperature variations can be improved since the heater film 22 is disposed closer to the wafer 9.
In the electrostatic attraction according to the present embodiment, the signs different from one another are imparted to the respective electrostatic attraction electrode films 33 and 34. Thereby, electric charges of the different signs are induced to the electrostatic attraction film, whereby electrostatic attraction forces are generated to effect the attraction. Thereby, the wafer 9 can be cooled in coordination with the temperature distribution formed in the base material 2.
However, since the pressure in the processing chamber is reduced to a level of several Pa's, heat transfer is insufficient as in that state. To overcome this problem, a through-hole 30 is provided in the base material 2 to introduce a heat transfer gas, such as helium gas, whereby the heat transfer between the wafer and the electrostatic attraction film is secured. Although not described in detail in the present embodiment, the through-hole 30 is provided so that pressure loss of the heat transfer gas is minimized and the gas is transferred to the entirety of the reverse side of the wafer 9, whereby a groove pattern is formed on the surface of the electrostatic attraction film.
In addition, for power supply to the electrostatic attraction films 33 and 34, the electrostatic attraction films 33 and 34 are, respectively, connected to coils 17A and 17B and further to the DC power sources 11A and 11B via conductive materials passed through insides of holes formed in the base material 2 and the high resistance alumina film 20. Similarly, the heater film 22 is connected to a coil 27 and the heater power source 28 via a conductive material passed through the inside of a hole formed in the base material 2 and the high resistance alumina film 20, whereby power is supplied to the heater film 22.
As shown in
As a comparative example for the use of describing effects of the present embodiment,
Generally, films such as those are etched in the following manner. A BARC is etched by using a gas mixture of chlorine and oxygen, and a polysilicon film is etched by using a gas mixture of chlorine, oxygen, and oxygen bromide. The drawings are each a schematic view showing the film structure in the center. The lefthand portion of the view shows a CD shift amount in a case where etching according to the conventional technique was performed without the heater being not operated. The righthand portion of the view shows a CD shift amount in a case where etching according to the present embodiment was performed.
It can be known that, as shown in
From these shown results, it was verified that the total of the CD shift amounts after etching of the BARC and the polysilicon is relatively small in the near-outer periphery portion, that is, the CD in the near-outer periphery portion is large.
Then, according to the present embodiment, as shown in
Thus, according to the present embodiment, all the components constituting the electrostatic attraction device, i.e., the base material, the heater, the insulation material between the electrostatic attraction electrodes, the heater, the electrostatic attraction electrodes, and the electrostatic attraction film, are manufactured by the low-cost spraying technique. Consequently, the low cost heater-containing electrostatic attraction device can be provided. In addition, the heater film is disposed between the electrostatic attraction electrodes along the radial direction thereof. Consequently, the heating system can be provided in the vicinity of the wafer, so that the in-plane temperature distribution can be expected to vary with good response characteristics. The bias voltage in the plane of the wafer can be expected to be homogenized by thinning of the sprayed film between the base material and the wafer and by homogenizing the impedance.
Further, when the power for the heater buried in the outer periphery of the wafer is regulated in association with alteration of the etching conditions during the process, the density distribution, the deposition efficiency, and the like of reaction products under the respective etching condition can be controlled. Consequently, the electrostatic attraction device that obtains homogenized CD distribution in the plane of the wafer can be provided.
A second embodiment of the present invention will be described hereinbelow with reference to
Effects of the present embodiment will be described herein below.
As can be seen from the results shown in
As described above, with the two heating systems (two heaters) being provided, it was verified that the temperature distribution in the plane of the wafer can be finely regulated with good response characteristics. However, since increase in the power supply for the heater should be considered, results in the case where the double heating systems and the vacuum insulation layer are provided will be described. In practice, etching is continuously performed on the BARC and then on the polysilicon film. As such, in the present embodiment, the temperature of the base material 2 is set slightly lower than the ideal temperature of the polysilicon. Then, as shown in
Flow of the process of the wafer 9 in the vacuum processing system according to any one of the above-described embodiments will be described with reference to
With reference to
In this state, information, such as a recipe suited for the process of the BARC and conditions such as the temperatures of the coolants in the electrostatic attraction device 8, and helium gas pressure and bias power for the interior of the processing chamber, are read from the data contained in the database 916, and operation of the vacuum processing system is regulated by the controller unit 110 in coordination with the respective conditions (step 903). For example, the heater film 22 is energized with the set amount of power and is heated to provide an appropriate temperature distribution in the wafer 9.
Subsequently, processing gases are supplied into the vacuum processing chamber 1 (step 904). Then, the processing gases are excited by using electric fields and magnetic fields of the microwave oscillator 19, coil 6, and the like shown in
Subsequently, information such as a recipe suited for the process of the polysilicon film, which is a lower layer, and operation conditions for the interior of the processing chamber are read from the data contained in the database 916, are received by the controller unit 110, and operation conditions for the vacuum processing system are set to be suitable for the process of the polysilicon film (step 909). In this event, similarly as in the above-described first embodiment, the amount of power to be supplied to the heater film 22 and the like is regulated, and the temperature distribution in the wafer 9 is altered and set. For example, power supply to the heater film 22 is stopped, and the temperature distribution in the electrostatic attraction device 8 or the temperature distribution in the wafer 9 is abruptly altered to the initial state, whereby setting is performed in a short time.
In this state, gases are supplied into the vacuum processing chamber 1 (step 910), plasma is formed (step 911), and the etching process of the polysilicon film is started (step 912). Similarly as in step 907, also in the case of the polysilicon film, arrival at the termination point is monitored by the termination-point determination device (step 913). If it is determined that the process has arrived at the termination point, the process is returned to step 912 and is thereby continued until it is determined that the process has arrived at the termination point. If it is determined that the process has arrived at the termination point of the polysilicon film, at step 914 the etching process is stopped. In this event, cancellation of attraction forces of the electrostatic attraction films 33 and 34 and charge neutralization are effected. Thereby, the wafer 9 is separated from the electrostatic attraction device 8, and is then carried outside the chamber (step 915). After the wafer 9 is thus carried away, in an event that the process of another wafer is performed, then the process returns to the beginning (“START”). In another event, the process enters a standby state.
As described above, in the event of continuously processing a layered structure having a plurality of vertically disposed film layers, regulation is performed for the power being supplied to the heater film disposed in the dielectric film constituting the sample-mounting surface, particularly, to the heater film disposed and surrounded between the electrostatic attraction film. In accordance with the regulation, the temperature distribution can be altered in a short time with high accuracy, and the efficiency in the event of processing a plurality of films can be improved. Consequently, the operating efficiency of the vacuum processing system can be significantly improved.
Although the present invention have been described in detail with reference to the embodiments, it should be understood that various changes, substitutions, and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
