JP4884047B2 - Plasma processing method - Google Patents

Description

  The present invention relates to a plasma processing method, and more particularly to a plasma processing method for performing plasma processing such as etching on an object to be processed such as a semiconductor wafer in the course of manufacturing various semiconductor devices.

  In the manufacturing process of a semiconductor device, for example, a plasma etching process is repeatedly performed for the purpose of forming a fine circuit pattern on a target object such as a semiconductor wafer. In the plasma etching process, for example, in a chamber of a plasma etching apparatus configured to be evacuated under reduced pressure, a semiconductor is mounted on a mounting table by generating a plasma by applying a high-frequency voltage between opposed electrodes. Etching is performed by applying plasma to the wafer. In such a plasma etching process, etching is performed by providing a focus ring having an action of concentrating an etchant, which is an active species of plasma, on the surface of the semiconductor wafer on the outer periphery of the semiconductor wafer on the mounting table. .

  As prior art related to plasma processing using a focus ring, an abnormal discharge (arcing) is prevented from occurring between the surface of the semiconductor wafer and the focus ring due to a potential difference generated between the semiconductor wafer and the focus ring during etching. For this reason, a plasma processing apparatus has been proposed that is configured to be able to control the potential of the focus ring by applying a DC voltage to the lower electrode (for example, Patent Document 1).

  By the way, the focus ring is a consumable item, and while the plasma etching process is repeated, the focus ring is gradually scraped from the surface by the action of plasma, and its shape changes. When the focus ring is consumed and its thickness is reduced, there is a problem in that the etching shape on the periphery of the semiconductor wafer is adversely affected. Specifically, for example, when holes are formed by etching, holes are formed obliquely at the periphery of the semiconductor wafer, making it difficult to control the etching shape. Then, a difference occurs in the etching shape between the central portion and the peripheral portion of the wafer W, and the uniformity of the etching shape in the semiconductor wafer surface cannot be ensured. In order to prevent this non-uniform etching shape, the focus ring had to be replaced before the etching shape was greatly affected. For this reason, the replacement cycle of the focus ring is accelerated, which is a cause of shortening the component life.

As a method for predicting the wear level of the focus ring, a method has been proposed in which a plurality of electrical data that changes in accordance with the wear level of the focus ring is measured over time, and the measurement data is subjected to multivariate analysis ( For example, Patent Document 2). However, the method of Patent Document 2 only predicts the degree of wear, and no attention is paid to extending the life of the parts of the focus ring itself.
WO03 / 009363 Publication (Claims etc.) JP 2002-25982 A (claims, etc.)

  As a result of investigating the cause of the change in the etching shape due to the consumption of the focus ring, when the focus ring is consumed and its thickness is reduced, the state of the plasma sheath changes above the focus ring, and this causes the ions on the semiconductor wafer to change. It has been found that changing the incident angle affects the etching shape at the periphery of the semiconductor wafer. As a countermeasure, it is possible to previously set the thickness of the focus ring to be thick within a range that does not affect the etching shape. However, this method cannot inevitably change the etching shape little by little as the focus ring is consumed, and thus cannot be a fundamental solution.

  An object of the present invention is to provide a plasma processing method capable of reducing adverse effects on a processing result such as an etching shape caused by consumption of a focus ring as much as possible and extending a use period of the focus ring. .

In order to solve the above-mentioned problems, a first aspect of the present invention is that a mounting table for mounting a processing object is disposed in a processing container, a focus ring is disposed around the mounting table, and the processing object is placed on the mounting table. Is a plasma processing method for generating plasma in the processing container and performing plasma processing on the object to be processed,
When the focus ring is consumed by repeating the plasma treatment, a direct current voltage is applied to the focus ring according to the degree of consumption, thereby changing the electric field on the focus ring to change the plasma on the focus ring. A plasma processing method is provided in which the thickness of the sheath is adjusted to reduce the plasma sheath distortion corresponding to the degree of wear of the focus ring, and the plasma processing is made uniform.

In the first aspect, the exhaustion degree of the focus ring is preferably estimated based on the cumulative usage time of the focus ring.
Further, the DC voltage applied to the focus ring is preferably one said predetermined based on a corresponding relationship between the consumption degree of the focus ring and change of the upper field of the focus ring.

  In the first aspect, it is preferable that the DC voltage to the focus ring is determined based on a result of plasma processing that has already been performed.

  Furthermore, in the first aspect, it is preferable to perform a plasma treatment by detecting a change in the electric field above the focus ring and applying a predetermined DC voltage to the focus ring based on the detection result.

Furthermore, in the first aspect, by applying a DC voltage to said focus ring, than the plasma sheath thickness of the upper workpiece, it is preferable to increase the plasma sheath thickness of above the focus ring.
Further, the plasma treatment is dry etching, by a DC voltage applied to the focus ring, not preferable to suppress the difference in the object to be processed with the etching shape of the central portion and the etching shape of the peripheral portion .

Furthermore, in the first aspect, it is not preferable to control the DC voltage applied to the focus ring in a range of 10～500V.

According to a second aspect of the present invention , there is provided a control program for controlling a plasma processing apparatus operating on a computer, and the plasma processing method according to the first aspect is performed on a computer so that the plasma processing method of the first aspect is performed at the time of execution. Provided is a control program for controlling a processing device .

A third aspect of the present invention is a computer-readable storage medium that operates on a computer and stores a control program for controlling a plasma processing apparatus ,
The control program provides a computer-readable storage medium that, when executed, causes a computer to control the plasma processing apparatus so that the plasma processing method of the first aspect is performed.

According to the present invention, a DC voltage is applied to the focus ring according to its wear level, thereby changing the electric field on the focus ring to adjust the thickness of the plasma sheath on the focus ring, thereby reducing the wear level of the focus ring. Therefore, the uniformity of the plasma processing, such as the in-plane uniformity of the etching shape, can be improved. Therefore, the plasma processing method of the present invention can be advantageously used for improving the yield and reliability of the semiconductor device, and can cope with the miniaturization of the semiconductor device.

  In addition, even if the wear of the outer peripheral member progresses to some extent, by applying a voltage, the adverse effect on the plasma processing result can be reduced as much as possible, so that it is possible to effectively extend the component life of the outer peripheral member. Therefore, it is possible to reduce the downtime of the apparatus accompanying the replacement of parts and the cost of parts, and to improve the plasma processing efficiency.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a configuration example of a plasma etching apparatus that can be suitably used for carrying out the method of the present invention. The plasma etching apparatus 1 is configured as a capacitively coupled parallel plate etching apparatus in which electrode plates are opposed in parallel in the vertical direction, and a high frequency power source is connected to both.

  The plasma etching apparatus 1 has a chamber 2 formed into a cylindrical shape made of aluminum, for example, whose surface is anodized (anodized), and the chamber 2 is grounded. A substantially cylindrical susceptor support 4 for placing an object to be processed, for example, a semiconductor wafer (hereinafter referred to as “wafer”) W, is provided at the bottom of the chamber 2 via an insulating plate 3 such as ceramic. Further, a susceptor 5 constituting a lower electrode is provided on the susceptor support 4. A high pass filter (HPF) 6 is connected to the susceptor 5.

  A temperature control medium chamber 7 is provided inside the susceptor support 4, and the temperature control medium is introduced into the temperature control medium chamber 7 through the introduction pipe 8 and circulated so that the susceptor 5 can be controlled to a desired temperature. It is like that.

  The upper center portion of the susceptor 5 is formed into a convex disk shape, and an electrostatic chuck 11 having substantially the same shape as the wafer W is provided thereon. The electrostatic chuck 11 has a configuration in which an electrode 12 is interposed between insulating materials. When a DC voltage of, for example, 1.5 kV is applied from a DC power source 13 connected to the electrode 12, the electrostatic chuck 11 has a Coulomb force. The wafer W is electrostatically adsorbed.

  The insulating plate 3, the susceptor support 4, the susceptor 5, and the electrostatic chuck 11 are heated to a predetermined pressure (back pressure) with a heat transfer medium, for example, He gas, on the back surface of the wafer W that is a target object. A gas passage 14 is formed for supply, and heat transfer is performed between the susceptor 5 and the wafer W via the heat transfer medium so that the wafer W is maintained at a predetermined temperature. .

An annular focus ring 15, which is an outer peripheral member, is disposed on the upper peripheral edge of the susceptor 5 so as to surround the wafer W placed on the electrostatic chuck 11. The focus ring 15 is made of an insulating material such as ceramics or quartz, and acts to improve etching uniformity. Further, a DC power supply 16 is connected to the focus ring 15 so that a DC voltage of 10 to 500 V, for example, can be applied to the focus ring 15.
Further, instead of connecting the DC power supply 16, the focus ring 15 may be grounded to be at the ground potential.

  An upper electrode 21 is provided above the susceptor 5 so as to face the susceptor 5 in parallel. The upper electrode 21 is supported on the upper portion of the chamber 2 via an insulating material 22, constitutes a surface facing the susceptor 5, and has a large number of discharge holes 23, for example, an electrode plate 24 made of quartz, A conductive material that supports the electrode 24, for example, an electrode support 25 made of aluminum having an anodized aluminum surface is used. The interval between the susceptor 5 and the upper electrode 21 can be adjusted.

A gas introduction port 26 is provided at the center of the electrode support 25 in the upper electrode 21, and a gas supply pipe 27 is connected to the gas introduction port 26. Further, a valve is connected to the gas supply pipe 27. 28 and a mass flow controller 29 are connected to a processing gas supply source 30, and an etching gas for plasma etching is supplied from the processing gas supply source 30. In FIG. 3, only one processing gas supply source 30 is representatively illustrated. However, a plurality of processing gas supply sources 30 are provided, for example, halogens such as CF ₄ , CHF ₃ , Cl ₂ , and HBr. A system etching gas, a gas such as O ₂ , or a rare gas can be independently controlled in flow rate and supplied into the chamber 2.

  An exhaust pipe 31 is connected to the bottom of the chamber 2, and an exhaust device 35 is connected to the exhaust pipe 31. The exhaust device 35 includes a vacuum pump such as a turbo molecular pump, and is configured so that the inside of the chamber 2 can be evacuated to a predetermined reduced pressure atmosphere, for example, a predetermined pressure of 1 Pa or less. Further, a gate valve 32 is provided on the side wall of the chamber 2 so that the wafer W is transferred to and from an adjacent load lock chamber (not shown) with the gate valve 32 opened. It has become.

  A first high frequency power supply 40 is connected to the upper electrode 21, and a matching unit 41 is provided on the feeder line. Further, a low pass filter (LPF) 42 is connected to the upper electrode 21. The first high-frequency power supply 40 has a frequency in the range of 50 to 150 MHz, and forms a high-density plasma in a preferable dissociated state in the chamber 2 by applying such a high frequency. And plasma processing under low-pressure conditions is possible. The frequency of the first high frequency power supply 40 is preferably 50 to 80 MHz, and typically 60 MHz or a condition in the vicinity thereof is adopted as shown in FIG.

  A second high frequency power supply 43 is connected to the susceptor 5 as the lower electrode, and a matching unit 44 is provided on the power supply line. The second high frequency power supply 43 has a frequency in the range of several hundred kHz to several tens of MHz, and the wafer W is not damaged by applying power in such a frequency range. Appropriate ion action can be provided. As the frequency of the second high-frequency power source 43, for example, a condition such as 2 MHz is adopted as shown in FIG.

  A transmission window 2 a is formed on the side wall of the chamber 2 at a position substantially corresponding to the height at which the plasma sheath is formed by the plasma formed in the chamber 2. In addition, a monitor 50 serving as a sheath state detecting unit is disposed outside the transmission window 2a. The monitor 50 is equipped with a CCD camera, for example, and is configured so that the state of the plasma sheath can be observed through the transmission window 2a during the etching process in the plasma etching apparatus 1.

  Each component of the plasma etching apparatus 1 is connected to and controlled by a process controller 60 having a CPU. The process controller 60 includes a user interface 61 including a keyboard that allows a process manager to input commands to manage the plasma etching apparatus 1, a display that visualizes and displays the operating status of the plasma etching apparatus 1, and the like. It is connected.

  The process controller 60 stores a recipe in which a control program (software) for realizing various processes executed by the plasma etching apparatus 1 under the control of the process controller 60 and processing condition data are recorded. A storage unit 62 is connected.

  Then, if desired, an arbitrary recipe is called from the storage unit 62 by an instruction from the user interface 61 and is executed by the process controller 60, so that a desired one in the plasma etching apparatus 1 is controlled under the control of the process controller 60. Is performed. For example, as will be described later, the process controller 60 determines the DC voltage applied to the focus ring 15 based on the degree of wear of the focus ring 15 or the change in the plasma sheath above the focus ring 15 detected by the monitor 50. . In addition, recipes such as the control program and processing condition data may be stored in a computer-readable storage medium such as a CD-ROM, a hard disk, a flexible disk, a flash memory, or other recipes. It is also possible to transmit the data from the device at any time via, for example, a dedicated line and use it online.

Next, an outline of a process of etching the wafer W made of a silicon single crystal by the plasma etching apparatus 1 configured as described above will be described.
First, a wafer W on which a predetermined film (not shown) is formed is loaded into the chamber 2 from a load lock chamber (not shown) by opening the gate valve 32 and placed on the electrostatic chuck 11. The wafer W is electrostatically adsorbed on the electrostatic chuck 11 by applying a DC voltage from the DC power source 13.

  Next, the gate valve 32 is closed, and the inside of the chamber 2 is evacuated to a predetermined vacuum level by the exhaust device 35. Thereafter, the valve 28 is opened, and a processing gas supply pipe 27, a gas introduction port 26, an upper electrode are adjusted from the processing gas supply source 30 while adjusting a predetermined processing gas according to the etching purpose to a predetermined flow rate by the mass flow controller 29. 21 is introduced into the hollow portion 21 and uniformly discharged onto the wafer W through the discharge holes 23 of the electrode plate 24 as indicated by arrows in FIG.

  In this plasma processing, the inside of the chamber 2 is maintained at a predetermined pressure, and the susceptor 5 is adjusted to a predetermined temperature, so that the first high frequency power supply 40 is connected to the upper electrode 21 and the second high frequency power supply 43 is connected to the lower electrode. Each of the susceptors 5 is supplied with a predetermined high-frequency power, and the processing gas is turned into plasma to etch the wafer W. At this time, as will be described later, based on the degree of wear of the focus ring 15, the detection result of the electric field change above the focus ring 15, or the plasma processing result (for example, etching shape) that has already been performed, Is applied to correct the displacement of the plasma sheath due to the plasma generated in the chamber 2 and uniformly control the incidence of ions on the wafer W. This makes it possible to make the etching shape uniform in the plane of the wafer W.

  When the etching is completed, the supply of the high frequency power from the first high frequency power supply 40 and the second high frequency power supply 43, the application of the voltage from the DC power supply 16, and the supply of the processing gas from the processing gas supply source 30 are stopped. Thereafter, the gate valve 32 is opened, and the processed wafer W is unloaded from the chamber 2. In this way, the plasma etching process for one wafer W is completed.

Next, the principle of the plasma processing method of the present invention will be described.
First, FIGS. 2 to 4 are main part cross-sectional views showing a state in the vicinity of the focus ring 15 in a state where the plasma P is excited in the chamber 2. First, FIG. 2 shows the state of the plasma sheath Ps when the focus ring 15 is not consumed (for example, a new article immediately after replacement). In this state, the wafer W and the surface of the focus ring 15 are substantially flush with each other.
Here, the thicknesses t ₁ and t ₂ of the plasma sheath Ps, that is, the distance between the plasma P and the surface of the adjacent solid (wafer W, focus ring 15) is expressed by the following equation. In the following expression, t ₁ and t ₂ are collectively referred to as t.

t ∝ (1 / Ne) ^1/2 × V ^3/4
[Ne means plasma density and V means voltage of the susceptor 5 shown by the following formula]
V ∝ (P) ^1/2 / S
[Where P is the RF power supplied to the susceptor 5, and S is the surface area of the wafer W and the focus ring 15]

Then, the thickness t ₁ of the plasma sheath Ps on the wafer W obtained by the above formula is substantially equal to the thickness t ₂ of the plasma sheath Ps on the focus ring 15. In this state, as shown in FIG. 2, an etchant such as ions that are active species in the plasma (shown here as a plus sign; the same applies in FIGS. 3 and 4) is applied to the surface of the wafer W and the focus ring 15. As a result of being incident at a substantially right angle with respect to the surface of the wafer W, a process such as etching is performed substantially uniformly within the surface of the wafer W.

Next, FIG. 3 shows a state after the focus ring 15 is consumed due to use for a certain period. As shown in FIG. 3, the focus ring 15 is shaved and thinned by etching, and the surface position thereof is lowered from the surface of the wafer W. Accordingly, the end portion of the plasma P is lowered above the focus ring 15 as compared with the center position indicated by the broken line. That is, the thickness t ₁ of the plasma sheath Ps above the wafer W and the thickness t ₂ of the plasma sheath Ps above the focus ring 15 are the same, but the plasma sheath Ps is formed obliquely between these two regions. Distortion has occurred. In FIG. 3, the surface position of the focus ring 15 before consumption is represented by a broken line for the purpose of reference (the same applies in FIG. 4).

  When the distortion as shown in FIG. 3 occurs in the plasma sheath Ps, the incident angle of the etchant changes at the portion where the distortion occurs, and the etchant that should have been directed to the focus ring 15 originally is around the wafer W. Incidently toward the part. It is considered that the change in the incident angle of the etchant accompanying the change in the shape of the plasma sheath Ps becomes apparent as the change in the etching shape in the peripheral portion of the wafer W.

FIG. 4 shows a state in which a predetermined voltage (for example, 100 V) is applied from the DC power supply 16 to the focus ring 15 that has been consumed and thinned as shown in FIG. By applying a voltage to the thus focus ring 15, to change the electric field on the focus ring 15, the thickness of the plasma sheath Ps can be extended from t ₂ to t _3. Thereby, the distortion of the plasma sheath Ps is corrected, and the lower end of the plasma P can be formed substantially flush with the wafer W and the focus ring 15. Then, as shown in FIG. 4, an etchant such as an ion which is an active species in the plasma P can be incident substantially perpendicularly to the surface of the wafer W, and the etching shape disorder at the peripheral portion of the wafer W is improved. can do. In this case, the voltage applied from the DC power supply 16 to the focus ring 15 is preferably controlled in the range of 10 to 500V, for example. In addition, in order to change the electric field on the focus ring 15 and correct the distortion of the plasma sheath Ps, the focus ring 15 may be grounded to be a ground potential.

  Thus, by applying a predetermined voltage to the focus ring 15, it becomes possible to adjust the thickness of the plasma sheath Ps thereabove, so that the accuracy of the etching shape is improved and the surface of the wafer W is improved. The uniformity of the etching shape inside can be improved. Further, even if the consumption of the focus ring 15 progresses to some extent, the use can be continued without affecting the etching shape, so that the life of the part of the focus ring 15 is effectively prolonged, and the plasma etching apparatus 1 for replacement of parts is down. Time and parts costs can be reduced.

  Next, FIG. 5 is a flowchart showing an example of a processing procedure performed when a voltage is applied to the focus ring 15 in the plasma processing method according to the first embodiment of the present invention. In the present embodiment, the degree of wear of the focus ring 15 is estimated, and a procedure for determining whether or not to apply a voltage from the DC power supply 16 to the focus ring 15 according to the degree of wear and the amount of voltage in the case of application is shown. ing. The processing procedure of FIG. 5 can be implemented by being appropriately incorporated in the series of steps performed in the plasma etching apparatus 1.

  As shown in FIG. 5, first, in step S <b> 11, the component information of the focus ring 15 stored in the storage unit 62 is read by the process controller 60. The component information of the focus ring 15 may be directly input by the process manager via the user interface 61. This component information includes, for example, the date and time when the focus ring 15 was replaced and the cumulative operating time of the plasma etching apparatus 1 after that date and time. Based on the read component information, the wear level of the focus ring 15 is estimated in step S12.

  The degree of wear of the focus ring 15 has a proportional relationship with the usage time of the focus ring 15, and can be easily grasped from the usage time empirically. Therefore, for example, a table (not shown) in which the wear level of the focus ring 15 is associated with the usage time is prepared, and the wear level of the focus ring 15 can be easily checked by the process controller 60 comparing the component information with the table. Can be estimated. In addition, it is also possible to directly measure and grasp the degree of wear of the focus ring 15 without using estimation based on component information. In this case, the process of step S11 and step S12 can be omitted.

  Next, in step S13, it is determined whether or not it is necessary to apply a DC voltage from the DC power supply 16 to the focus ring 15 based on the degree of wear of the focus ring 15 obtained in step S12. If the focus ring 15 is depleted, it is determined that the voltage needs to be applied (Yes). If the focus ring 15 is almost depleted (for example, new), it is not necessary to apply the voltage (No). to decide.

If it is determined in step S13 that voltage application is necessary (Yes), the voltage amount to be applied is determined in step S14. In this case, for example, as illustrated in FIG. 6, a table 200 in which the degree of wear of the focus ring 15 and the amount of voltage to be applied from the DC power supply 16 are related can be used. The table 200 is created in advance by investigating the influence on the plasma sheath Ps by experimentally applying a voltage to the focus ring 15 having various wear levels, and is stored in the storage unit 62. The table 200 is read from the storage unit 62 by the process controller 60 and collated with the degree of wear (for example, a _l [mm]) of the focus ring 15 obtained in step S12 to thereby determine the amount of voltage applied to the focus ring 15 (this In this case, A ₁ [V]) is uniquely determined. In step S15, the determined predetermined DC voltage is applied from the DC power supply 16 to the focus ring 15.

  On the other hand, if it is determined in step S13 that voltage application is unnecessary (No), the plasma etching process is performed without applying the voltage from the DC power source 16 to the focus ring 15, and therefore the processes in steps S14 and S15 are performed. Is omitted.

  The processing procedure shown in FIG. 5 is preferably executed when, for example, the first wafer W belonging to a certain lot is processed. In this case, the second and subsequent wafers W of the same lot are repeatedly subjected to plasma etching without applying a voltage based on the determination in step S13 or by applying the predetermined voltage determined in step S14. Can be performed. At that time, the DC power supply 16 is turned on / off by the process controller 60 in conjunction with, for example, on / off (high frequency supply and stop) of the first high frequency power supply 40 and the second high frequency power supply 43 in the plasma etching apparatus 1. Can be done. Note that the processing procedure shown in FIG. 5 can be executed every time one wafer W is processed.

As shown in steps S11 to S15 in FIG. 5, the wear level is estimated from the usage time of the focus ring 15, and the voltage applied to the focus ring 15 is determined according to the wear level. the thickness _{t 2} of the plasma sheath Ps can be adjusted. Thereby, the disorder of the incident angle of ions at the peripheral edge of the wafer W accompanying the displacement of the plasma sheath Ps is corrected, thereby improving the uniformity of the etching shape in the wafer surface and improving the yield of the semiconductor device. It becomes possible. Further, even if the consumption of the focus ring 15 progresses to some extent, the use can be continued without affecting the etching shape as a result of the plasma processing by adjusting the amount of voltage applied thereto, so the frequency of replacement of the focus ring 15 is reduced. It is possible to reduce the downtime and parts cost of the plasma etching apparatus 1 associated with the replacement.

  In the table 200 of FIG. 6, the degree of wear of the focus ring 15 and the DC voltage applied thereto are related, but the usage time of the focus ring 15 and the amount of DC voltage to be applied are directly related. It is also possible to use a table. In this case, step S12 for estimating the wear level of the focus ring 15 is not necessary, but whether or not to apply a DC voltage to the focus ring 15 and the applied voltage are related to the wear level of the focus ring 15. Since it can be derived experimentally, it is assumed that the degree of wear of the focus ring 15 is known.

  FIG. 7 is a flowchart showing an example of a processing procedure performed when a voltage is applied to the focus ring 15 in the plasma processing method according to the second embodiment of the present invention. In the first embodiment, the applied voltage is determined based on the degree of wear of the focus ring 15 based on the knowledge that when the focus ring 15 is consumed, the plasma sheath Ps is displaced. On the other hand, in the present embodiment, the displacement of the plasma sheath Ps of the plasma P is more directly detected, and a voltage is applied to the focus ring 15 according to the amount of displacement (degree of displacement). The processing procedure of FIG. 7 can be implemented by being appropriately incorporated during the series of steps performed in the plasma etching apparatus 1.

  As shown in FIG. 7, first, in step S21, the state of the plasma sheath Ps in the plasma P generated in the chamber 2 is detected by the monitor 50. From the viewpoint of ensuring the uniformity of the plasma processing, the fluctuation of the plasma sheath Ps above the focus ring 15 (that is, the end portion of the plasma sheath Ps) becomes a problem, so the monitor 50 can observe the end portion of the plasma P. If it is.

  In the present embodiment, the monitor 50 images the plasma sheath Ps at the end of the plasma P, and the image data is sent to the process controller 60. In the process controller 60, image analysis is performed based on the image data from the monitor 50, and a change in the position of the end portion of the plasma sheath Ps is digitized and displayed on the display of the user interface 61 in real time. In step S22, the process controller 60 determines whether or not the end of the plasma sheath Ps is displaced based on the result of the image analysis.

If it is determined in step S22 that the end of the plasma sheath Ps is displaced (Yes), the process controller 60 refers to a table 201 as shown in FIG. Then, a voltage amount (B ₃ [V] in this case) applied from the DC power supply 16 to the focus ring 15 is determined based on the displacement amount (for example, b ₃ [mm]) of the plasma sheath Ps (step S23). The table 201 used at this time shows the correspondence between the amount of displacement of the end portion of the plasma sheath Ps and the applied voltage necessary to correct it, and is determined experimentally in advance. .

Based on the determination in step S23, a predetermined voltage (for example, B ₃ [V]) is applied from the DC power supply 16 to the focus ring 15 in the subsequent step S24. By applying this manner the voltage to the focus ring 15, for example, adjusting the thickness t ₂ of the plasma sheath Ps on the focus ring 15 to a suitable thickness. As a result, it is possible to correct the disturbance of the incident angle of ions at the peripheral edge of the wafer W due to the shape change of the plasma sheath Ps, improve the uniformity of the etching shape in the wafer surface, and improve the yield of the semiconductor device. become. Further, even if the consumption of the focus ring 15 progresses to some extent, the use can be continued without affecting the etching shape by adjusting the amount of voltage applied thereto, so that the frequency of replacement of the focus ring 15 can be reduced. Thus, it is possible to reduce the downtime and parts cost of the plasma etching apparatus 1 associated with the replacement.

  Next, in step S25, the process controller 60 determines whether or not the plasma processing has been completed. For example, when the first high frequency power supply 40 and the second high frequency power supply 43 are “ON” (ON), it is determined that the plasma processing is not ended (No), and when “OFF” (OFF), the plasma processing is performed. It is determined that the process is finished (Yes). If it is determined in step S25 that the plasma processing is completed (Yes), the DC power supply 16 is turned off in step S26.

  On the other hand, if it is determined in step S22 that the plasma sheath Ps is not displaced (No), the process returns to step S21, and the position of the end of the plasma sheath Ps is detected again.

  Also, if it is determined in step S25 that the plasma processing is not terminated (No), the process returns to step S21, and the position of the end of the plasma sheath Ps is detected again. As described above, while the plasma processing is performed in the plasma etching apparatus 1 (that is, while the plasma P is excited), the processing procedure shown in FIG. 7 is repeatedly performed, and the displacement of the plasma sheath Ps is performed during that time. If it occurs, an appropriate amount of voltage is applied from the DC power source 16 to the focus ring 15 to adjust the shape of the plasma sheath Ps, and control is performed so as not to adversely affect the etching shape.

Next, FIG. 9 is a flowchart showing an example of a processing procedure in the plasma processing method according to the third embodiment of the present invention. In the present embodiment, a voltage is applied to the focus ring 15 as necessary based on the etching shape that is the processing result in the plasma etching process.
First, a plasma etching process is performed on the first wafer W using the plasma etching apparatus 1 according to the above-described process. Thereafter, the etching shape (for example, the side wall angle of the hole) is measured for the first wafer W. As described above, when the focus sheath 15 is consumed and the plasma sheath Ps is distorted and the incident angle of an etchant such as ions is changed (see FIG. 3), for example, holes are obliquely formed at the peripheral edge of the wafer W. It is formed. Therefore, for example, by measuring the angle of the hole side wall with respect to the direction perpendicular to the surface of the wafer W based on an electron micrograph or the like, the existence (displacement) of the plasma sheath Ps can be estimated.

  When it is estimated that the plasma sheath Ps is displaced based on the etching shape, as shown in FIG. 9, the voltage applied to the focus ring 15 is determined according to the degree of the shape. At this time, the relationship between the change in the etching shape such as a hole and the voltage applied to the focus ring 15 in order to improve it can be experimentally associated in advance.

  Then, after determining the applied voltage, the determined voltage is applied to the focus ring 15 to perform a plasma etching process on the second wafer W. As described above, in the plasma etching process on the second wafer W, the voltage based on the processing result of the plasma etching process on the first wafer W is applied to the focus ring 15, thereby distorting the plasma sheath Ps. Since the correction is made, the in-plane uniformity of the etched wafer W can be improved. Needless to say, voltage application to the focus ring 15 is unnecessary if there is no problem in the etching shape of the first wafer W.

  In this way, when the plasma etching process is sequentially performed on the second, third,..., N-1 and nth wafers W, the plasma etching process preceding that is performed. The result is fed back to determine the amount of voltage applied to the focus ring 15. Then, by applying a predetermined voltage to the focus ring 15 in a subsequent process, a plasma etching process that ensures in-plane uniformity of the etching shape can be performed. Here, the measurement of the result (etching shape) of the plasma etching process and the determination of the applied voltage may be performed every time one wafer W is processed, or may be performed every predetermined number of wafers. For example, in FIG. 9, the plasma etching process for the second wafer W and the plasma etching process for the nth wafer W are performed by applying a voltage to the focus ring 15, and the n−1th sheet. The plasma etching process on the wafer W is performed without applying a voltage to the focus ring 15.

  Thus, in the third embodiment, ions are incident on the peripheral portion of the wafer W accompanying the shape change of the plasma sheath Ps by determining the voltage to be applied to the focus ring 15 in the subsequent etching based on the etching result. Corrects the angular disturbance. As a result, the uniformity of the etching shape in the wafer surface can be improved, and the yield of the semiconductor device can be improved. In addition, even if the consumption of the focus ring 15 progresses to some extent, the influence on the etching shape can be avoided by adjusting the amount of voltage applied thereto, so that the replacement frequency of the focus ring 15 can be reduced. The downtime of the plasma etching apparatus 1 and the part cost can be reduced.

As mentioned above, although embodiment of this invention was described, this invention is not restrict | limited to the said embodiment, A various deformation | transformation is possible.
For example, in the above embodiment, the capacitively coupled parallel plate type plasma etching apparatus that applies high frequency power to the upper electrode 21 and the susceptor 5 as the lower electrode, respectively, is used. For example, plasma etching that applies high frequency power only to the lower electrode An apparatus may be used. Furthermore, the type of plasma etching apparatus is not limited, and various types of plasma etching apparatuses such as an inductively coupled type and a microwave type can be used.

  In the above-described embodiment, the case where the uniformity of the etched shape in the wafer W plane is improved in the plasma etching process is described as an example. However, the processing content is not limited to the etching, and the outer peripheral member (around the wafer W) ( Any process that can improve the processing result by applying a voltage to, for example, a clamp ring can be applied to other plasma processing such as a film forming process.

BRIEF DESCRIPTION OF THE DRAWINGS Drawing which shows the outline | summary of the plasma etching apparatus suitable for implementation of the method of this invention. The figure which shows typically the state of the plasma sheath at the time of using the focus ring which is not consumed. The figure which shows typically the state of the plasma sheath at the time of using the exhausted focus ring. The figure which shows typically the state of the plasma sheath at the time of applying a voltage to the worn focus ring. The flowchart which shows an example of the voltage application procedure in the plasma processing of 1st Embodiment. The drawing which shows the table used for the plasma processing of 1st Embodiment. The flowchart which shows an example of the voltage application procedure in the plasma processing of 2nd Embodiment. Drawing which shows the table used for the plasma processing of 2nd Embodiment. The figure explaining the outline | summary of the plasma processing of 3rd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Plasma etching apparatus 2; Chamber 3; Insulating plate 4; Susceptor support stand 4
5; Susceptor 11; Electrostatic chuck 12; Electrode 15; Focus ring 16; DC power supply 50; Monitor 60; Process controller 61; User interface 62;

Claims (10)

  A placing table for placing the object to be treated is disposed in the processing container, a focus ring is disposed around the work table, and plasma is generated in the processing container with the object to be treated being placed on the placing table. A plasma processing method for performing plasma processing on an object to be processed,
  When the focus ring is consumed by repeating the plasma treatment, a direct current voltage is applied to the focus ring according to the degree of consumption, thereby changing the electric field on the focus ring to change the plasma on the focus ring. A plasma processing method in which the thickness of the sheath is adjusted and the plasma sheath is made uniform by reducing distortion of the plasma sheath that occurs in accordance with the degree of wear of the focus ring. The degree of wear of the focus ring to estimate based on the cumulative usage time of the focus ring, the plasma processing method according to claim 1. DC voltage applied to the focus ring is one said predetermined based on a corresponding relationship between the consumption degree of the focus ring and change of the upper field of the focus ring, according to claim 1 or claim 2 Plasma processing method.   The plasma processing method according to claim 1, wherein the DC voltage to the focus ring is determined based on a result of plasma processing already performed.   The plasma processing method according to claim 1, wherein a change in electric field above the focus ring is detected, and plasma processing is performed by applying a predetermined DC voltage to the focus ring based on the detection result. By applying a DC voltage to said focus ring, than the plasma sheath thickness of the upper workpiece, increasing the plasma sheath thickness of above the focus ring, claimed in any one of claims 5 Plasma processing method. The plasma processing is dry etching, and a DC voltage applied to the focus ring suppresses a difference between an etching shape at a central portion and an etching shape at a peripheral portion of the object to be processed. 7. The plasma processing method according to any one of 6 above. The plasma processing method according to any one of claims 1 to 7 , wherein a DC voltage applied to the focus ring is controlled in a range of 10 to 500V. A control program for controlling a plasma processing apparatus operating on a computer, wherein the computer executes the plasma processing method according to any one of claims 1 to 8 at the time of execution. A control program for controlling a plasma processing apparatus . A computer-readable storage medium that operates on a computer and stores a control program for controlling the plasma processing apparatus ,
A computer-readable storage medium for causing the computer to control the plasma processing apparatus so that the plasma processing method according to any one of claims 1 to 8 is performed when the control program is executed.

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