JP2013115268A - Plasma processing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a temperature of a dielectric window installed above a shower plate to suppress a variation in temperature of the shower plate to enable seasoning using plasma heating for a fixed time.SOLUTION: Plasma processing equipment includes: a vacuum vessel to which a processing gas is supplied through a gap formed between a shower plate and a dielectric window, and through the open holes; a plasma generation device for supplying high frequency energy to the vacuum vessel to generate plasma by interaction with a magnetic field; and a control device for controlling the inside of the vacuum vessel to a target temperature range. The control device, when plasma processing is started in a processing stop period, performs control for generating the plasma for a fixed time shorter than a time required to increase a temperature of the shower plate from a center Tb to an upper limit Td in a control region, to heat the dielectric window and the shower plate to the target temperature control range set by the control device.

Description

  The present invention relates to a plasma processing apparatus, and more particularly, to a plasma processing apparatus provided with a shower plate that distributes and supplies a processing gas.

In the plasma processing apparatus, in order to stabilize the processing performance of the sample, so-called seasoning (aging process) is performed in which a gas such as Ar is supplied into the processing chamber and plasma is generated for a predetermined time before the processing of the sample. In this processing, the wall surface of the processing chamber is heated by plasma, and the temperature of the inner wall of the processing chamber is set to a predetermined value.
The seasoning process is preferably terminated when the inner wall temperature reaches a predetermined value. For this reason, it has been conventionally considered to detect and set the end timing. For example, in Patent Document 1, in the case of an apparatus that does not have a means for directly measuring the temperature of the processing chamber inner wall, the inner wall temperature of the apparatus is estimated by using a plasma emission spectrum having a high correlation with the inner wall temperature of the apparatus. It is shown that the end point of seasoning is detected based on temperature.

JP 2010-219198 A

  Of the processing chamber walls, the temperature of the shower plate provided with a number of holes for supplying gas into the processing chamber is difficult to measure accurately because the shower plate is placed in a vacuum.

  Further, the above prior art assumes that Si is used for the inner wall of the processing chamber, and uses the fact that the reaction between F in the plasma and Si of the inner wall of the processing chamber depends on the temperature of the inner wall. The inner wall temperature is estimated on the basis of the emission spectrum amount of SiF. However, when the inner wall of the apparatus is heated using plasma, a light emission amount having a high correlation with the inner wall temperature of the apparatus is not always stably obtained.

  For example, when the shower plate is made of yttria, the emission spectrum cannot be obtained. For this reason, the end point of seasoning cannot be detected. Even if the light emission is obtained, the light emission amount changes with time. For this reason, it is difficult to correctly estimate the end point of seasoning.

  The present invention has been made in view of these problems, and provides a plasma processing apparatus capable of stably adjusting the temperature of a shower plate at the start of wafer processing after the end of seasoning.

  In order to solve the above problems, the present invention employs the following means.

A vacuum container having a dielectric plate and a shower plate in which a plurality of through holes are formed, a gap formed between the shower plate and the dielectric window, and a processing gas supplied through the through holes, and the vacuum A mounting electrode for mounting and holding a sample in the container; a high-frequency bias power source for supplying a high-frequency bias voltage to the mounting electrode; an exhaust device for exhausting the vacuum processing container; and the vacuum processing container An electromagnetic coil for forming a magnetic field; a plasma generator for supplying high-frequency energy to the vacuum processing vessel to generate plasma by interaction with the magnetic field; and a control device for controlling the inside of the vacuum vessel to a target temperature range ,
When the plasma processing is started during the processing stop period, the control device continues the predetermined shower plate from the central temperature Tb of the temperature control range that is a temperature realized by intermittent plasma processing for each wafer. A target temperature control range by the control device by generating plasma and fixing the dielectric window and the shower plate for a fixed time shorter than the time required to raise the temperature to the upper limit temperature Td of the temperature control range, which is a temperature realized by plasma processing. Until heated.

  Since the present invention has the above-described configuration, it is possible to stably adjust the temperature of the shower plate at the start of wafer processing after the end of seasoning.

It is a longitudinal cross-sectional view which shows the outline of a structure of the plasma apparatus which concerns on embodiment of this invention. It is a figure which shows the temperature change of the shower plate at the time of seasoning of the plasma processing apparatus shown in FIG. FIG. 6 is a characteristic diagram showing how t1 / t2 changes with respect to a difference ΔT = Tb−Ta between Ta and Tb. It is a figure explaining a plasma etching processing method.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a longitudinal sectional view showing an outline of a configuration of a plasma apparatus according to an embodiment of the present invention. As shown in the figure, a shower plate 102 (for example, made of quartz or yttria) for introducing an etching gas into the vacuum container 101, a dielectric window 103 (for example, for example) The processing chamber 104 is formed by installing and sealing (made of quartz).

  A heater 122 is installed outside the vacuum vessel 101, and the heater is connected to a heater controller 123. A temperature sensor 124 is installed in the vacuum vessel 101, and a signal from the sensor 124 is transmitted to the heater controller 123. The controller 123 controls the heater 122 so that the inner wall of the vacuum vessel 101 reaches an arbitrary temperature.

  A gas supply device 105 for flowing an etching gas is connected to the shower plate 102. In addition, a vacuum exhaust device (not shown) is connected to the vacuum vessel 101 via a vacuum exhaust port 106.

  In order to radiate electric power for generating plasma into the processing chamber 104, a waveguide 107 (or an antenna) is provided above the dielectric window 103. The waveguide 107 is supplied with an electromagnetic wave generated by an electromagnetic wave generating power source 109.

  The frequency of the electromagnetic wave is not particularly limited, but in the present embodiment, a microwave of 2.45 GHz is used. A magnetic field generating coil 110 that forms a magnetic field is provided on the outer periphery of the processing chamber 104, and the electric power generated by the electromagnetic wave generation power source 109 is generated in the processing chamber 104 due to the interaction with the formed magnetic field. Generate plasma.

  In addition, a wafer mounting electrode 111 is provided below the vacuum vessel 101 so as to face the shower plate 102. The wafer mounting electrode 111 has an electrode surface covered with a sprayed film (not shown), and a DC power supply 116 is connected through a high frequency filter 115. Further, a high frequency power supply 114 is connected to the wafer mounting power supply 111 via a matching circuit 113. The wafer mounting electrode 111 has a coolant channel 117, and the coolant channel is connected to a temperature controller 118. The wafer mounting electrode has a heater 119, and the heater is connected to the heater controller 120. Further, a temperature sensor 121 is installed on the wafer mounting electrode 111, and the signal is transmitted to the heater controller 120 to control the temperature of the wafer 112 to a desired temperature. The temperature control is performed by controlling the set temperature of the temperature adjuster 118 that controls the output of the heater 119 and the temperature of the refrigerant.

  The wafer 112 transferred into the processing chamber 104 is adsorbed onto the wafer mounting electrode 111 by the electrostatic force generated by the DC voltage applied from the DC power supply 116 and the temperature is adjusted. After supplying a desired etching gas by the gas supply device 105, the inside of the vacuum chamber 101 is set to a predetermined pressure, and plasma is generated in the processing chamber 104. By applying high frequency power from a high frequency power supply 114 connected to the wafer mounting electrode 111 in this state, ions in the plasma can be drawn into the wafer and the wafer 112 can be etched.

  In addition, in order to control the temperature of the dielectric window 103, a gas line (not shown) for introducing dry air at room temperature is provided in the waveguide 107 above the dielectric window 103, and the temperature for heating the dry air is also provided. A temperature monitor for monitoring the temperature of the wind heater 126 and the dielectric window 103 is provided.

  The warm air heater 126 is connected to the warm air heater controller 127, and the dry air heated by the warm air heater 126 is introduced into the waveguide through the gas introduction hole 134. The heated dry air comes into contact with the dielectric window 103 and heats the dielectric window 103. Note that the dielectric window 103 can be cooled by introducing dry air at room temperature without being heated by the hot air heater 126. For this reason, the dielectric window 103 can be heated or cooled by turning the hot air heater 126 on and off. In order to discharge the introduced dry air, a conductive pipe 125 is disposed in the waveguide in front of the electromagnetic wave generating power supply 109, and the dielectric plate 133 is disposed so that the dry air does not enter immediately before the electromagnetic wave generating power supply 109. Install. Thereby, the introduced dry air can be discharged out of the waveguide through the pipe 125.

  Regarding the temperature in the etching chamber, the inner wall of the vacuum vessel 101 is controlled by a heater 124, and the wafer mounting electrode 111 is controlled by a heater 119 and a temperature controller 118. However, for the shower plate 102, which occupies another area as the surface area in the etching chamber, active temperature control is not performed, and the temperature is strongly influenced by heat input from plasma.

  The shower plate 102 is a parallel disk concentrically disposed directly below the dielectric window 103, and the gap between the shower plate 102 and the dielectric window 103 allows process gas to flow without causing abnormal discharge. 1 mm or less. For this reason, since the form factor becomes as large as 0.81, when there is actually heat input from plasma, heat exchange of about several hundred W is performed by heat transfer by radiation. For this reason, the temperature of the dielectric window 103 is strongly influenced by the temperature of the shower plate 102.

  In the case of a plasma etching processing apparatus for processing a wafer having a diameter of 300 mm, the area where the shower plate is in contact with other parts is 1% or less of the total surface area. It is strongly affected by the temperature.

  The temperatures of the shower plate 102 and the dielectric window 103 during the etching process reach a certain saturation temperature due to heat input from the plasma. When the temperature of the dielectric window 103 is not controlled, since the dielectric window 103 is exposed to the atmosphere, the temperature of the dielectric window 103 decreases from the saturation temperature to about room temperature during the processing stop period. . The temperature of the shower plate 102 during the processing stop period is also the same (the heat transfer with the dielectric window 103 that has decreased to about room temperature causes the shower plate to decrease to the same extent as the dielectric window 103).

  When the temperature of the dielectric window 103 is controlled to a temperature that is 50 ° C. higher than the lowest temperature during the processing stop period, for example, the temperature of the shower plate 102 during the processing stop period is also adjusted to a temperature that is about 50 ° C. higher. .

  Next, it will be described with reference to FIG. 2 what plasma heating time can be used to control the shower plate within a predetermined temperature range even if the heating time is fixed without measuring the temperature of the shower plate 102. .

  FIG. 2 is a diagram showing the time change of the temperature of the shower plate 102 when the plasma processing apparatus shown in FIG. 1 is continuously generated and heated. The temperature of the shower plate 102 at the start of plasma heating is Ta due to the long-term processing stop. This temperature Ta is the lowest temperature (this temperature is maintained by a hot air heater or the like) taken by the shower plate 102 during a process stop period without plasma heating by the etching process.

  In addition, the maximum temperature during the processing stop period reaches each time when the etching process is continuously performed (when the wafer processing of each single wafer (or lot) is completed when the wafer is continuously processed). This is a temperature (saturation temperature) Tb specific to the etching process. Therefore, the temperature of the shower plate 102 during the processing stop period is the minimum Ta or the saturation temperature Tb. During the etching process, the temperature of the shower plate 102 fluctuates for each etching process (for each recipe) with the heating from the plasma, but is adjusted to be within the range of the lower limit Tc and the upper limit Td around Tb. ing.

  When plasma heating (continuous heating) for aging is performed from the stopped state, the temperature of the shower plate 102 increases from Ta to Tc. The plasma heating time t1 required to increase from Ta to Tc is the time required to reach the lower limit of the temperature control range from the lowest possible temperature during the processing stop period, and the current temperature of the shower plate 102 (Ta The above is the time that must be heated when the temperature is controlled by plasma heating in a state where it is not known). That is, t1 is the lower limit of the heating time by plasma heating during the aging process.

  In this state, if the plasma heating is continued (continuous heating), the temperature of the shower plate 102 passes Tb and finally exceeds Td. The plasma heating time t2 required to reach Td from Tb is the time required to reach the upper limit of the temperature control range from the highest temperature that can be taken during the processing stop period. That is, when the temperature of the shower plate 102 is not known, when plasma heating (continuous heating) is performed, it is a time during which heating should not be continued any more. For this reason, t2 is the upper limit of the heating time in plasma heating.

  Therefore, in order to fix the plasma heating time, t2> t1, that is, 1> t1 / t2 must be satisfied. If this condition is satisfied, when the temperature of the shower plate 102 is in the range of Ta to Tb, the plasma heating is performed for the fixed time t1, so that it is higher than the lower limit of the temperature control range. The temperature can be set lower than the upper limit. That is, the temperature of the shower plate 102 can be set within the temperature control range.

  When the present invention is applied to an etching processing apparatus, a dummy process is performed by previously attaching a thermometer to the shower plate, and at that time, the temperature change of the shower plate 102 is measured to obtain t1, and this is calculated. It is preferable to set a fixed time for plasma heating.

  Next, under what conditions, the condition of 1> t1 / t2 will be described with reference to FIG.

  FIG. 3 is a characteristic diagram obtained by numerical simulation to show how t1 / t2 changes with respect to the difference ΔT = Tb−Ta between Ta and Tb. Since Tb varies depending on the thermal output (recipe) of plasma used for the etching process, it is necessary to determine whether plasma heating is possible up to a predetermined temperature at a fixed time t1 when Tb varies.

The numerical simulation assumes an etching apparatus that processes a wafer having a diameter of 300 mm, the thickness of the dielectric window 103 is 30 to 50 mm capable of withstanding atmospheric pressure, the thickness of the shower plate 102 is 10 mm, and the shower plate and the dielectric The windows are made of quartz having a diameter of 450 mm and a thermal diffusivity of 7.42 × 10 ⁻⁷ m ² / s when the temperature is 100 ° C., and Ar gas plasma is used for plasma heating. During heating, Ar gas is filled in a 1.0 mm space between the shower plate 102 and the dielectric window 103 at 1000 Pa, and the heat flux to the plasma side surface of the shower plate 102 by plasma heating is 1600 W / m ² , The dielectric window 103 is controlled at a constant 80 ° C., and the temperature control range is calculated under the condition of ± 5 ° C. centering on Tb. did.

The heat flux 1600 W / m ² from the plasma to the shower plate 102 assumed in the numerical simulation was obtained as follows. That is, plasma heating occurs when ion flux or electron flux enters the shower plate 102 from the plasma through the ion sheath and carries energy from the plasma. The incident flux is called the Bohm flux Γi [m ⁻² s ⁻¹ ], and the electron density is n [m ⁻³ ] and the electron charge is e [C] as described in “Plasma Electronics” Ohm, edited by Hideo Sakurai. ], The electron temperature is Te [eV], and the ion mass is mi [kg], which is calculated by the following equation (1).

The energy P [W / m ² ] carried by the bomb flux is energy εi [J] due to acceleration of ions by the ion sheath, and average energy 2eTe [J] lost due to electrons passing through the ion sheath and colliding with the wall. The following equation (2) is obtained by multiplying the three sums of energy εc [J] necessary for maintaining one electron / ion pair by Baume flux.

In the case of a dielectric such as the shower plate 102, the accelerating voltage to ions in the ion sheath is a floating potential φF [V], and the electron mass is me [kg]. The

At this floating potential, the energy εi due to acceleration of ions by the ion sheath is εi = eφF.

The pressure at the time of discharge in the etching process using general electron cyclotron resonance plasma or inductively coupled plasma is 0.05 to 1 Pa. At that time, plasma, electron temperature is about ³ to 5 eV, and electron density is about 10 ¹⁶ to 10 ¹⁸ m ⁻³ .

  In the case of Ar gas, the energy required to maintain one electron / ion pair is known to be about 25 to 40 eV when the electron temperature is 3 to 5 eV.

As a typical case, when the electron temperature is 3 eV, the electron density is 10 ¹⁷ m ^−3, and the energy P carried from the plasma to the shower plate 102 by the Baume flux is calculated in the case of Ar gas, it is 1600 W / m ⁻² . Become. A numerical simulation was performed assuming this value as heat flux.

  From FIG. 3, it can be seen that 1> t1 / t2 when ΔT is 30 ° C. or less, and that the temperature of the shower plate 102 can be kept within the temperature control range by seasoning using plasma heating for a fixed time. In the experimental machine simulating the conditions used in the numerical simulation, the hot air heater controller 127 was set so that the average ΔT was 25 ° C. for the temperature of the dielectric window.

  When ΔT is larger than 30 ° C., the temperature drop of the shower plate 102 during the processing stop period is suppressed by increasing the control temperature of the dielectric window 103. Alternatively, the shower plate 102 may be made of a material having a higher thermal diffusivity, for example, yttria, and ΔT may be reduced.

  In the numerical simulation, the temperature control range is the same temperature range above and below Tb, but it is not always necessary to have the same width. For example, when a cleaning process using plasma is performed after seasoning by plasma heating, and an etching process is started after the cleaning process, an increase or decrease in the temperature of the shower plate 102 due to the cleaning process is also taken into consideration. It is better to set the temperature control range.

  Next, the plasma etching method of the present invention will be described with reference to FIG.

  FIG. 4 is a diagram showing the temperature of the dielectric window 103 and the temperature change of the shower plate 102 when the continuous etching process is performed in lot units after the process is stopped. Further, FIG. 4 shows a case where the plasma heating is always performed before the continuous etching process of each lot.

  The dielectric window 103 is controlled within a predetermined temperature range. The temperature of the shower plate 102 falls outside the temperature control range during the processing pause 201. Next, the temperature of the shower plate 102 can be set within the temperature control range by performing the plasma heating 202 for the set fixed time and heating the shower plate 102.

  For this reason, the etching continuous process 203 of the first lot can be started in a state where the temperature of the shower plate 102 is within the temperature control range. Next, the temperature of the shower plate 102 becomes the saturation temperature specific to each etching process by the etching continuous process 203 of the first lot.

  Even if the plasma heating 204 is performed for the set fixed time after completion of the etching continuous process 203 of the first lot, the temperature of the shower plate 102 is within the temperature control range. For this reason, the etching process 205 of the second lot can be started in a state where the temperature of the shower plate 102 is within the temperature control range.

  In FIG. 4, plasma heating is always performed before each lot. However, in order to improve the throughput of the etching processing apparatus, when it is considered that there is no processing stop period between lots, plasma heating between lots is performed. It is not necessary to do.

  As described above, according to the present embodiment, by controlling the temperature of the dielectric window installed on the upper portion of the shower plate, the temperature fluctuation of the shower plate is suppressed, and the temperature of the shower plate is further reduced before the etching process. By suppressing the fluctuation, seasoning by plasma heating in a fixed time can be performed. This makes it possible to obtain an optimal shower plate temperature at the start of wafer processing.

  Further, since the temperature fluctuation of the shower plate is suppressed, the interaction between the shower plate and the plasma, which fluctuates depending on the shower plate temperature, is stabilized, and the plasma processing performance is stabilized.

DESCRIPTION OF SYMBOLS 101 Vacuum container 102 Shower plate 103 Dielectric window 104 Processing chamber 105 Gas supply apparatus 106 Vacuum exhaust port 107 Waveguide 108 Cavity resonator 109 Electromagnetic wave generation power source 110 Magnetic field generation coil 111 Wafer mounting electrode 112 Wafer 113 Matching circuit 114 High-frequency power supply 115 Filter 116 DC power supply for electrostatic adsorption 117 Flow path for refrigerant 118 Temperature controller 119 Heater 120 Heater controller 121 Temperature sensor 122 Heater 123 Heater controller 124 Temperature sensor 125 Pipe 126 Hot air heater 127 Hot air heater controller 128 Infrared Measurement Type Temperature Monitor 129 Dielectric Plate

Claims (2)

A vacuum container having a dielectric plate and a shower plate in which a plurality of through holes are formed, a gap formed between the shower plate and the dielectric window, and a processing gas supplied through the through holes, and the vacuum A mounting electrode for mounting and holding a sample in the container; a high-frequency bias power source for supplying a high-frequency bias voltage to the mounting electrode; an exhaust device for exhausting the vacuum processing container; and the vacuum processing container An electromagnetic coil for forming a magnetic field; a plasma generator for supplying high-frequency energy to the vacuum processing vessel to generate plasma by interaction with the magnetic field; and a control device for controlling the inside of the vacuum vessel to a target temperature range ,
When the plasma processing is started during the processing stop period, the control device continues the predetermined shower plate from the central temperature Tb of the temperature control range that is a temperature realized by intermittent plasma processing for each wafer. A target temperature control range by the control device by generating plasma and fixing the dielectric window and shower plate for a fixed time shorter than the time required to raise the temperature to the upper limit temperature Td of the temperature control range, which is a temperature realized by plasma processing. A plasma processing apparatus characterized by heating to a temperature. A vacuum container having a dielectric plate and a shower plate in which a plurality of through holes are formed, a gap formed between the shower plate and the dielectric window, and a processing gas supplied through the through holes, and the vacuum A mounting electrode for mounting and holding a sample in the container; a high-frequency bias power source for supplying a high-frequency bias voltage to the mounting electrode; an exhaust device for exhausting the vacuum processing container; and the vacuum processing container An electromagnetic coil for forming a magnetic field; a plasma generator for supplying high-frequency energy to the vacuum processing vessel to generate plasma by interaction with the magnetic field; and a control device for controlling the inside of the vacuum vessel to a target temperature range ,
The control device is realized by plasma by a time t1 required to raise the temperature of the shower plate from the lowest temperature Ta to the lower limit Tc of the temperature control range during the processing stop period, and the plasma processing of the shower plate intermittently for each wafer. When the time t2 required to raise the temperature from the central temperature Tb of the temperature control range, which is a temperature, to the upper limit temperature Td of the temperature control range, which is a temperature realized by continuous plasma processing, is set so that t2> t1. After setting temperatures Ta and Tb, plasma is generated to heat the dielectric window and shower plate to a target temperature control range by the control device.

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