JP6335229B2 - Substrate temperature control method and plasma processing apparatus - Google Patents

Description

  The present invention relates to a substrate temperature control method and a plasma processing apparatus.

  Conventionally, in a semiconductor device manufacturing process, plasma processing is used in which plasma is applied to a substrate (for example, a semiconductor wafer) disposed in a vacuum processing chamber to perform etching processing or film formation processing.

  In such a plasma processing apparatus, a temperature control mechanism is provided on a mounting table on which a substrate is mounted to heat or cool the helium (He) gas or the like between the substrate mounting surface of the mounting table and the back surface of the substrate. A heat transfer gas (so-called backside gas) serving as a heat medium is supplied to promote heat exchange between the mounting table and the substrate.

  In such a plasma processing apparatus, a technique is known in which the flow rates of gases having different thermal conductivities, such as helium (He) gas and argon (Ar) gas, are individually controlled and supplied as backside gas. (For example, patent document 1).

  Moreover, the technique which adjusts the flow volume of heat transfer gas intermittently and controls the pressure of heat transfer gas is known (for example, refer patent document 2).

JP 2002-327275 A JP 2000-232098

  Among the plasma processing apparatuses described above, in a plasma processing apparatus having a structure in which high-frequency power is applied to the mounting table, there is a possibility that electric discharge occurs in a heat transfer gas supply line such as helium (He) gas. For this reason, the conductance and electric field strength are lowered by covering the heat transfer gas supply line with an insulator and reducing the distance of the heat transfer gas supply line long or by inserting a baffle plate. . As a result of reducing the conductance in this way, it becomes difficult to supply a heat transfer gas such as helium (He) gas, and particularly in a region where the pressure of the heat transfer gas is low, for example, a region of 1330 Pa (10 Torr) or less, It becomes difficult to accurately control the pressure, and the temperature control of the substrate in such a low pressure region of the heat transfer gas cannot be accurately performed, and there is a problem that the temperature control range is substantially limited. .

  The present invention has been made in response to such a conventional situation, can accurately control the temperature of the substrate in a low pressure region of the heat transfer gas, and expands the temperature control range to increase the process margin. It is an object of the present invention to provide a substrate temperature control method and a plasma processing apparatus that can perform the same.

In one aspect of the substrate temperature control method of the present invention, a substrate is placed on a substrate placement surface of a placement table that is installed in a vacuum processing chamber and is cooled or heated, and the back surface of the substrate and the mounting table are A heat transfer gas is supplied between the substrate mounting surface and the pressure of the heat transfer gas is detected, and the detected pressure value is compared with a set pressure value, and the detected pressure value is the pressure value. A substrate temperature control method for controlling the supply of the heat transfer gas so as to be a set value and controlling the temperature of the substrate, wherein the pressure of the heat transfer gas is a lower limit value that enables stable pressure control. When the temperature of the substrate is controlled by suppressing the heat exchange between the substrate and the mounting table, the pressure set value is set during the plasma processing. A first period that is a first pressure set value equal to or greater than a lower limit pressure value, and a first period that is lower than the low pressure value Just repeat alternately and the second period of the pressure set value, the first pressure set value is in the range of 13300Pa from 1330 Pa, the second pressure set value is equal to or in the range of 665Pa from 0Pa .

One aspect of the plasma processing apparatus of the present invention is a substrate placed on a substrate placement surface of a placement table that is installed in a vacuum processing chamber and is cooled or heated, and the back surface of the substrate and the substrate of the placement table described above A plasma processing apparatus for performing plasma processing by applying plasma to the substrate while supplying a heat transfer gas between the mounting surface and controlling the temperature of the substrate, wherein a supply flow for supplying the heat transfer gas A bent portion that is provided in the middle of the path and reduces the electric field strength and conductance by bending the supply flow path; and the supply flow path on the substrate mounting surface side from the bent portion, and the heat transfer gas The pressure detection mechanism for detecting the pressure of the pressure sensor and the pressure detection value detected by the pressure detection mechanism and the pressure set value are compared, and the heat transfer gas is supplied so that the pressure detection value becomes the pressure set value. Heat transfer gas supply system to be controlled The heat transfer gas supply control mechanism sets the pressure of the heat transfer gas to a low pressure value lower than a lower limit pressure value, which is a lower limit value of pressure capable of stable pressure control, When performing temperature control of the substrate while suppressing heat exchange with the mounting table, during the plasma processing, a first period in which the pressure set value is set to a first pressure set value equal to or higher than the lower limit pressure value; The second period of time set as the second pressure set value lower than the low pressure value is alternately repeated.

  According to the present invention, the temperature control of the substrate in the low pressure region of the heat transfer gas can be performed with high accuracy, and the process control can be expanded by extending the temperature control range.

The figure which shows typically schematic structure of the plasma etching apparatus used for one Embodiment of this invention. The figure which shows typically the principal part schematic structure of the plasma etching apparatus of FIG. The graph for demonstrating the substrate temperature control method which concerns on one Embodiment. The graph for demonstrating the substrate temperature control method which concerns on one Embodiment. The graph for demonstrating the substrate temperature control method which concerns on a modification. The figure which shows typically the principal part schematic structure of the plasma etching apparatus which concerns on a modification. The figure which shows typically the principal part schematic structure of the plasma etching apparatus which concerns on a modification. The figure which shows typically the principal part schematic structure of the plasma etching apparatus which concerns on a modification. The figure which shows typically the principal part schematic structure of the plasma etching apparatus which concerns on a modification. The figure which shows typically the principal part schematic structure of the plasma etching apparatus which concerns on a modification. The figure which shows typically the principal part schematic structure of the plasma etching apparatus which concerns on a modification. The figure which shows typically the principal part schematic structure of the plasma etching apparatus which concerns on a modification.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of a plasma etching apparatus used in this embodiment. First, the configuration of the plasma etching apparatus will be described.

  The plasma etching apparatus has a vacuum processing chamber 1 that is hermetically configured and is electrically grounded. The vacuum processing chamber 1 has a cylindrical shape, and is made of, for example, aluminum having an anodized film formed on the surface thereof. In the vacuum processing chamber 1, a mounting table 2 that horizontally supports a semiconductor wafer W that is a substrate to be processed is provided.

  The mounting table 2 has a base 2a made of a conductive metal, such as aluminum, and has a function as a lower electrode. The mounting table 2 is supported by an insulating support 4 via an insulating plate 3. A focus ring 5 made of, for example, single crystal silicon is provided on the outer periphery above the mounting table 2. Further, a cylindrical inner wall member 3 a made of, for example, quartz is provided so as to surround the periphery of the mounting table 2 and the support table 4.

  A first high frequency power source 10a is connected to the base material 2a of the mounting table 2 via a first matching unit 11a, and a second high frequency power source 10b is connected via a second matching unit 11b. Yes. The first high frequency power supply 10a is for generating plasma, and high frequency power of a predetermined frequency (27 MHz or more, for example, 40 MHz) is supplied from the first high frequency power supply 10a to the base material 2a of the mounting table 2. It has become. The second high-frequency power source 10b is for ion attraction (bias), and the second high-frequency power source 10b has a predetermined frequency (13.56 MHz or less, for example, 3.5 MHz or lower) than that of the first high-frequency power source 10a. 2 MHz) is supplied to the base material 2 a of the mounting table 2. On the other hand, a shower head 16 having a function as an upper electrode is provided above the mounting table 2 so as to face the mounting table 2 in parallel. The shower head 16 and the mounting table 2 have a pair of electrodes ( Upper electrode and lower electrode).

  An electrostatic chuck 6 for electrostatically attracting the semiconductor wafer W is provided on the upper surface of the mounting table 2. The electrostatic chuck 6 is configured by interposing an electrode 6a between insulators 6b, and a DC power source 12 is connected to the electrode 6a. When the DC voltage is applied from the DC power source 12 to the electrode 6a, the semiconductor wafer W is attracted by the Coulomb force.

  A refrigerant channel 2b is formed inside the mounting table 2, and a refrigerant inlet pipe 2c and a refrigerant outlet pipe 2d are connected to the refrigerant channel 2b. The mounting table 2 can be controlled to a predetermined temperature by circulating an appropriate refrigerant such as cooling water in the refrigerant flow path 2b.

  Further, a backside gas supply pipe 30 for supplying a heat transfer gas (backside gas) such as helium gas is provided on the back side of the semiconductor wafer W so as to penetrate the mounting table 2 and the like. As shown in FIG. 2 in an enlarged manner, the backside gas supply pipe 30 has a bent portion 30a bent in the base 4 made of an insulator, and the bent portion 30a reduces the electric field strength and conductance. As a result, the occurrence of discharge in the backside gas supply pipe 30 can be suppressed.

  The backside gas supply pipe 30 is connected to the backside gas supply source 300. Further, a pressure control valve 301 is inserted in the backside gas supply pipe 30, and an exhaust pipe 302 that branches from the downstream side of the pressure control valve 301 is connected. An exhaust control valve 303 is inserted in the exhaust pipe 302, and an exhaust device (not shown) is connected to the end of the exhaust pipe 302. Further, the backside gas supply pipe 30 is provided with a pressure gauge 304 for detecting the pressure of the backside gas.

  Then, the pressure control unit 310 compares the pressure detection value by the pressure gauge 304 with the pressure setting value preset in the pressure control unit 310, and the pressure control is performed so that the pressure detection value and the pressure setting value match. The opening degree of the valve 301 and the exhaust control valve 303 is adjusted, and control is performed so that the pressure of the backside gas becomes a predetermined pressure (pressure set value). That is, the backside gas supply source 300, the pressure control valve 301, the exhaust pipe 302, the exhaust control valve 303, the pressure gauge 304, the pressure control unit 310, and the like constitute a heat transfer gas (backside gas) supply control mechanism. ing.

  By the refrigerant circulation mechanism such as the refrigerant flow path 2b, the refrigerant inlet pipe 2c, and the refrigerant outlet pipe 2d, and the above-described heat transfer gas (backside gas) supply control mechanism, the upper surface of the mounting table 2 is adsorbed by the electrostatic chuck 6 The held semiconductor wafer W can be controlled to a predetermined temperature.

  The shower head 16 described above is provided on the top wall portion of the vacuum processing chamber 1. The shower head 16 includes a main body 16 a and an upper top plate 16 b that forms an electrode plate, and is supported on the upper portion of the vacuum processing chamber 1 via an insulating member 45. The main body portion 16a is made of a conductive material, for example, aluminum whose surface is anodized, and is configured such that the upper top plate 16b can be detachably supported at the lower portion thereof.

  Gas diffusion chambers 16c and 16d are provided inside the main body portion 16a, and a large number of gas flow holes 16e are formed at the bottom of the main body portion 16a so as to be positioned below the gas diffusion chambers 16c and 16d. Has been. The gas diffusion chambers 16c and 16d are divided into two parts: a gas diffusion chamber 16c provided in the central portion and a gas diffusion chamber 16d provided in the peripheral portion. The supply status can be changed.

  The upper top plate 16b is provided with a gas introduction hole 16f so as to penetrate the upper top plate 16b in the thickness direction so as to overlap the gas flow hole 16e. With such a configuration, the processing gas supplied to the gas diffusion chambers 16c and 16d is dispersed and supplied into the vacuum processing chamber 1 through the gas flow holes 16e and the gas introduction holes 16f. It has become. The main body 16a and the like are provided with a pipe (not shown) for circulating the refrigerant so that the shower head 16 can be cooled to a desired temperature during the plasma etching process.

  In the main body 16a, two gas inlets 16g and 16h for introducing the processing gas into the gas diffusion chambers 16c and 16d are formed. Gas supply pipes 15a and 15b are connected to the gas inlets 16g and 16h, and a processing gas supply source 15 for supplying a processing gas for etching is connected to the other ends of the gas supply pipes 15a and 15b. Has been. The gas supply pipe 15a is provided with a mass flow controller (MFC) 15c and an on-off valve V1 in order from the upstream side. The gas supply pipe 15b is provided with a mass flow controller (MFC) 15d and an on-off valve V2 in order from the upstream side.

  Then, a processing gas for plasma etching is supplied from the processing gas supply source 15 to the gas diffusion chambers 16c and 16d via the gas supply pipes 15a and 15b, and the gas flow holes 16e are supplied from the gas diffusion chambers 16c and 16d. In addition, they are dispersed and supplied in the form of a shower into the vacuum processing chamber 1 through the gas introduction holes 16f.

  A variable DC power source 52 is electrically connected to the shower head 16 as the upper electrode through a low-pass filter (LPF) 51. The variable DC power supply 52 can be turned on / off by an on / off switch 53. The current / voltage of the variable DC power supply 52 and the on / off of the on / off switch 53 are controlled by a control unit 60 described later. As will be described later, when a high frequency is applied from the first high frequency power supply 10a and the second high frequency power supply 10b to the mounting table 2 to generate plasma in the processing space, the control unit 60 turns on as necessary. The off switch 53 is turned on, and a predetermined DC voltage is applied to the shower head 16 as the upper electrode.

  A cylindrical grounding conductor 1 a is provided so as to extend from the side wall of the vacuum processing chamber 1 above the height position of the shower head 16. The cylindrical ground conductor 1a has a top wall at the top.

  An exhaust port 71 is formed at the bottom of the vacuum processing chamber 1, and an exhaust device 73 is connected to the exhaust port 71 via an exhaust pipe 72. The exhaust device 73 has a vacuum pump, and by operating this vacuum pump, the inside of the vacuum processing chamber 1 can be depressurized to a predetermined degree of vacuum. On the other hand, a loading / unloading port 74 for the semiconductor wafer W is provided on the side wall of the vacuum processing chamber 1, and a gate valve 75 for opening and closing the loading / unloading port 74 is provided at the loading / unloading port 74.

  In the figure, reference numerals 76 and 77 denote depot shields that are detachable. The deposition shield 76 is provided along the inner wall surface of the vacuum processing chamber 1 and has a role of preventing etching by-products (depots) from adhering to the vacuum processing chamber 1. A conductive member (GND block) 79 connected to the ground in a DC manner is provided at substantially the same height as the semiconductor wafer W of the deposition shield 76, thereby preventing abnormal discharge.

  The operation of the plasma etching apparatus having the above configuration is comprehensively controlled by the control unit 60. The control unit 60 includes a process controller 61 that includes a CPU and controls each unit of the plasma etching apparatus, a user interface 62, and a storage unit 63. 2 is also controlled by the control unit 60.

  The user interface 62 includes a keyboard that allows a process manager to input commands in order to manage the plasma etching apparatus, a display that visualizes and displays the operating status of the plasma etching apparatus, and the like.

  The storage unit 63 stores a recipe in which a control program (software) for realizing various processes executed by the plasma etching apparatus under the control of the process controller 61 and processing condition data are stored. Then, if necessary, an arbitrary recipe is called from the storage unit 63 by an instruction from the user interface 62 and executed by the process controller 61, so that a desired process in the plasma etching apparatus is performed under the control of the process controller 61. Processing is performed. In addition, recipes such as control programs and processing condition data may be stored in a computer-readable computer storage medium (eg, hard disk, CD, flexible disk, semiconductor memory, etc.), or It is also possible to transmit the data from other devices as needed via a dedicated line and use it online.

  Next, a method for controlling the temperature of the semiconductor wafer W in the plasma etching apparatus having the above configuration will be described. As described above, the mounting table 2 is temperature adjusted to a predetermined temperature by the refrigerant circulating in the refrigerant flow path 2b. In many cases, the mounting table 2 is cooled because the plasma P acts on the semiconductor wafer W mounted and fixed on the mounting table 2 to increase its temperature. Then, a backside gas such as helium gas is supplied between the wafer mounting surface of the mounting table 2 and the back surface of the semiconductor wafer W through the backside gas supply pipe 30, and a backside gas having a constant pressure is supplied between them. By being present, heat exchange between the semiconductor wafer W and the mounting table 2 is promoted, and as a result, the temperature of the semiconductor wafer during plasma processing is maintained at a predetermined temperature.

  Therefore, if the pressure of the backside gas is high, the temperature of the semiconductor wafer W becomes closer to the temperature of the mounting table 2, while if the pressure of the backside gas is low, the heat between the semiconductor wafer W and the mounting table 2 is increased. The exchange amount decreases, and a difference occurs between the temperature of the semiconductor wafer W and the temperature of the mounting table 2. For example, when the mounting table 2 is cooled to a predetermined temperature, the higher the backside gas pressure, the lower the temperature of the semiconductor wafer W, and the lower the backside gas pressure, the higher the temperature of the semiconductor wafer W.

  A straight line A shown in the graph of FIG. 3 with the vertical axis representing temperature and the horizontal axis representing backside gas pressure represents the relationship between the temperature of the semiconductor wafer W and the backside gas pressure. The pressure control unit 310 adjusts the pressure of the backside gas based on the pressure of the backside gas determined based on the required temperature of the semiconductor wafer W as shown by the straight line A shown in the graph of FIG. The temperature of the semiconductor wafer W is controlled. Such control is performed when the pressure is equal to or higher than a predetermined lower limit pressure value (1330 Pa (10 Torr in the case of the graph of FIG. 3), in other words, when the set temperature is equal to or lower than the upper limit temperature shown in the graph of FIG.

  On the other hand, when the pressure of the backside gas has to be less than a predetermined lower limit pressure value (1330 Pa (10 Torr in the case of the graph of FIG. 3)), in other words, a set temperature equal to or higher than the upper limit temperature shown in the graph of FIG. In this case, the temperature control of the semiconductor wafer W is performed by the following pressure control of the backside gas.

  The pressure of the backside gas is set to a low pressure value lower than the lower limit pressure value, for example, 665 Pa (5 Torr), and the temperature of the semiconductor wafer W needs to be controlled to a certain level by suppressing heat exchange between the semiconductor wafer W and the mounting table 2. In the first period, the pressure setting value in the gas pressure control unit 310 is set to a first pressure setting value that is higher than the low pressure value (665 Pa (5 Torr)) and equal to or higher than the lower limit pressure value (1330 Pa (10 Torr)). And a second period in which the second pressure set value is lower than the low pressure value (665 Pa (5 Torr)) are alternately repeated.

  The graph of FIG. 4 with the vertical axis representing pressure and the horizontal axis representing time shows an example where the first pressure set value is 1330 Pa (10 Torr) and the second pressure set value is 0 Pa. The first period to be the pressure set value and the second period to be the second pressure set value are, for example, a short period of about 0.01 to 10 seconds, more preferably about 0.1 to 10 seconds, Control for repeating these periods alternately a plurality of times is performed.

  This is due to the following reason. That is, as described above, the backside gas supply pipe 30 is set to have a low conductance to prevent discharge due to the high frequency power applied to the mounting table 2, and the backside gas has a low pressure set value. If it is attempted to control the pressure, it becomes difficult to perform stable pressure control. In general, the backside gas pressure capable of performing stable pressure control is about 1330 Pa (10 Torr), and stable pressure control cannot be performed at a pressure lower than this pressure. For this reason, by repeating the first period, which is a set pressure at which stable pressure control can be performed, and the second period, where the pressure is lower than the target pressure, alternately, an average temperature is allowed while allowing some temperature fluctuations. The pressure of the backside gas is controlled so that becomes a desired temperature.

  As a result, the temperature of the semiconductor wafer W can be set to a temperature in a high temperature region that could not be set because the temperature control with high accuracy is difficult in the past, and the semiconductor in a pressure region where the heat transfer gas is low. The temperature control of the wafer W can be performed with high accuracy. Further, the process margin can be expanded by extending the temperature control range.

  It is conceivable that such temperature control of the semiconductor wafer W is performed by changing the temperature of the refrigerant flowing through the refrigerant flow path 2b of the mounting table 2, but the temperature of the mounting table 2 is changed by changing the temperature of the refrigerant. Changing it takes time and cannot be done in a short time. For this reason, when performing several types of plasma processing continuously in the vacuum processing chamber 1, it cannot be applied to the case where the set temperature of the semiconductor wafer W is changed by the processing.

The graph of FIG. 5 with the vertical axis representing pressure and the horizontal axis representing time shows a modification using two types of heat transfer gas, for example, helium gas and argon gas. As shown in the graph of FIG. 5, during the second period (second set pressure value 0 Pa) of helium gas as the heat transfer gas shown in FIG. You may make it supply hot gas, for example, argon gas. As the heat transfer gas, nitrogen (N ₂ ) gas, oxygen (O ₂ ) gas, or the like may be used in addition to helium gas and argon gas.

  Further, a third period is provided in which the third pressure set value is lower than the first pressure set value and higher than the second pressure set value, and the first to third periods are defined as the first period, the second period, and the third period. Alternatively, the first period, the third period, the second period, or the like may be sequentially repeated. In this case, as the heat transfer gas, three kinds of gases having different work functions of heat transfer may be used, and different heat transfer gases may be allowed to flow for each of the first to third periods.

  6 to 12 show the configuration of another embodiment of the pressure gauge 304. As described above, since high-frequency power is applied to the mounting table 2, it is difficult to detect the pressure of the backside gas in the vicinity of the mounting table 2. However, if the pressure of the backside gas is detected at a portion closer to the mounting surface of the semiconductor wafer W of the mounting table 2, the backside gas pressure is detected more accurately and the backside gas pressure is controlled more accurately. can do.

  A pressure gauge 304a shown in FIG. 6 is provided with a diaphragm 601 that is physically deformed by the pressure of the backside gas in a part of the backside gas supply pipe 30 of the mounting table 2, and the displacement of the diaphragm 601 is measured by laser light. A laser displacement meter to be read at 602 is provided.

  The pressure gauge 304b shown in FIG. 7 is provided with a diaphragm 601 that is physically deformed by the pressure of the backside gas in a part of the backside gas supply pipe 30 of the mounting table 2, and a sound wave or The electromagnetic wave 603 is applied and the displacement of the diaphragm 601 is read by the resonance frequency.

  A pressure gauge 304 c shown in FIG. 8 is provided with a diaphragm 601 that is physically deformed by the pressure of the backside gas in a part of the backside gas supply pipe 30 of the mounting table 2, and light 604 is applied to the diaphragm 601. , And the CCD 605 detects the position where the light 604 is reflected and returned from the diaphragm 601, thereby reading the displacement of the diaphragm 601.

  A pressure gauge 304d shown in FIG. 9 is provided with a diaphragm 601 that is physically deformed by the pressure of the backside gas and a reference surface 606 on a part of the backside gas supply pipe 30 of the mounting table 2. The distance difference between 601 and the reference surface 606 is measured with a laser interferometer or electromagnetic wave interferometer using a laser or electromagnetic wave 607, and the displacement of the diaphragm 601 is read.

  A pressure gauge 304e shown in FIG. 10 is provided with a diaphragm 601 that is physically deformed by the pressure of the backside gas in a part of the backside gas supply pipe 30 of the mounting table 2, and the displacement of the diaphragm 601 is determined by the diaphragm 601. In this configuration, reading is performed above and below the liquid level of the liquid 608 in the conduit 609 connected to the portion 601.

  A pressure gauge 304f shown in FIG. 11 is provided with a diaphragm 601 that is physically deformed by the pressure of the backside gas in a part of the backside gas supply pipe 30 in the stage 2 and measures the displacement of the diaphragm 601. The measurement is performed by the circuit 610. The measurement circuit 610 includes a solar cell 611, and the solar cell 611 is irradiated with light from a light source 612 provided outside to obtain a power source. The measurement signal is led out to the outside by an optical fiber 613. Thus, the structure is difficult to be affected by the high frequency power applied to the mounting table 2.

  A pressure gauge 304g shown in FIG. 12 is obtained by replacing the solar cell 611 of the pressure gauge 304f shown in FIG. 11 with a Peltier element 620 and applying heat to the Peltier element 620 to obtain a power source. Other parts are the same as those of the pressure gauge 304f, and thus redundant description is omitted.

  Like the above pressure gauges 304a to 304g, a diaphragm 601 that is physically deformed by the pressure of the backside gas is provided in a part of the backside gas supply pipe 30 of the mounting table 2, and the displacement of the diaphragm 601 is changed. By reading, the pressure of the backside gas can be detected with high accuracy, and the pressure of the backside gas can be controlled with high accuracy.

  Next, a procedure for plasma etching the thin film formed on the semiconductor wafer W by the plasma etching apparatus having the above configuration will be described. First, the gate valve 75 is opened, and the semiconductor wafer W is loaded into the vacuum processing chamber 1 from the loading / unloading port 74 via a load lock chamber (not shown) by a transfer robot (not shown) and mounted on the mounting table 2. . Thereafter, the transfer robot is retracted out of the vacuum processing chamber 1 and the gate valve 75 is closed. Then, the inside of the vacuum processing chamber 1 is exhausted through the exhaust port 71 by the vacuum pump of the exhaust device 73.

  After the inside of the vacuum processing chamber 1 reaches a predetermined degree of vacuum, a predetermined processing gas (etching gas) is introduced from the processing gas supply source 15 into the vacuum processing chamber 1, and the inside of the vacuum processing chamber 1 is set to a predetermined pressure. Retained. At this time, the supply state of the processing gas from the processing gas supply source 15 can be made different between the central portion and the peripheral portion, and the supply amount from the central portion and the peripheral portion of the entire processing gas supply amount. The ratio with the supply amount from the section can be controlled to a desired value.

  In this state, high-frequency power having a frequency of 40 MHz, for example, is supplied from the first high-frequency power supply 10 a to the mounting table 2. Further, from the second high frequency power supply 10b, high frequency power (for bias) having a frequency of, for example, 3.2 MHz is supplied to the base material 2a of the mounting table 2 for ion attraction. At this time, a predetermined DC voltage is applied from the DC power source 12 to the electrode 6a of the electrostatic chuck 6, and the semiconductor wafer W is attracted to the electrostatic chuck 6 by Coulomb force.

  As described above, an electric field is formed between the shower head 16 as the upper electrode and the mounting table 2 as the lower electrode by applying high-frequency power to the mounting table 2 as the lower electrode. Due to this electric field, a discharge occurs in the processing space where the semiconductor wafer W exists, and the thin film formed on the semiconductor wafer W is etched by the plasma of the processing gas formed thereby. During this etching process, in the present embodiment, the temperature of the semiconductor wafer W can be set to a temperature in a high temperature region that could not be set because the accurate temperature control is difficult in the past, and The temperature control of the semiconductor wafer W in the low pressure region of the heat transfer gas can be accurately performed. In addition, the process margin can be expanded by extending the temperature control range.

  Further, as described above, a direct current voltage can be applied to the shower head 16 during the plasma processing, and therefore the following effects are obtained. That is, depending on the process, a plasma having a high electron density and low ion energy may be required. If a DC voltage is used in such a case, the ion energy injected into the semiconductor wafer W is suppressed and the plasma electron density is increased, thereby increasing the etching rate of the thin film to be etched of the semiconductor wafer W. The sputter rate to the thin film serving as a mask provided on the upper part of the etching target is lowered, and the selectivity is improved.

  When the etching process described above is completed, the supply of high-frequency power, the supply of DC voltage, and the supply of processing gas are stopped, and the semiconductor wafer W is unloaded from the vacuum processing chamber 1 by a procedure reverse to the procedure described above. The

  As described above, according to this embodiment, the substrate temperature can be accurately controlled in the low pressure region of the heat transfer gas, and the temperature control range can be expanded to increase the process margin. A control method and a plasma processing apparatus can be provided. In addition, this invention is not limited to said embodiment, Various deformation | transformation are possible.

  W ... Semiconductor wafer, 1 ... Vacuum processing chamber, 2 ... Mounting table, 30 ... Backside gas supply pipe, 300 ... Backside gas supply source, 301 ... Pressure control valve, 302 ... Exhaust pipe, 303... Exhaust control valve, 304... Pressure gauge, 310.

Claims (10)

A substrate is placed on a substrate placement surface of a placement table that is installed in a vacuum processing chamber and is cooled or heated, and a heat transfer gas is introduced between the back surface of the substrate and the substrate placement surface of the placement table. Supply and detecting the pressure of the heat transfer gas, comparing the detected pressure detection value with a pressure setting value, and supplying the heat transfer gas so that the pressure detection value becomes the pressure setting value. A substrate temperature control method for controlling the temperature of the substrate,
The pressure of the heat transfer gas is set to a low pressure value lower than a lower limit pressure value, which is a lower limit value of pressure capable of stable pressure control, and temperature control of the substrate is performed by suppressing heat exchange between the substrate and the mounting table. When doing
During the plasma processing, a first period in which the pressure set value is a first pressure set value that is equal to or greater than the lower limit pressure value and a second period in which a second pressure set value that is lower than the low pressure value are alternated. it repeatedly in the first pressure set value is in the range of 13300Pa from 1330 Pa, the substrate temperature control method of the second pressure set value is equal to or in the range of 665Pa from 0 Pa. The substrate temperature control method according to claim 1,
The substrate temperature control method , wherein the first period is shorter than the second period . The substrate temperature control method according to claim 1 or 2,
The substrate temperature control method, wherein the first period and the second period are in a range of 0.01 seconds to 10 seconds. A substrate temperature control method according to any one of claims 1 to 3,
The substrate temperature control method, wherein the heat transfer gas is one of helium gas, argon gas, nitrogen gas, and oxygen gas. A substrate temperature control method according to any one of claims 1 to 3,
The heat transfer gas is any one of helium gas, argon gas, nitrogen gas, and oxygen gas, and the two types of gas are alternately supplied in the first period and the second period. And a substrate temperature control method. A substrate temperature control method according to any one of claims 1 to 5,
The pressure of the heat transfer gas is detected by a pressure gauge that is provided on the mounting table and deforms according to the pressure of the heat transfer gas, and a detection mechanism that detects a deformation amount of the diaphragm. Substrate temperature control method. A substrate temperature control method according to any one of claims 1 to 6,
When the pressure of the heat transfer gas is set to a low pressure value less than a predetermined lower limit pressure value, and the temperature of the substrate is controlled by suppressing heat exchange between the substrate and the mounting table,
The substrate temperature control characterized by sequentially repeating the first period, the second period, and a third period in which the third pressure set value is lower than the first pressure set value and higher than the second pressure set value. Method. The substrate temperature control method according to claim 7, comprising:
The heat transfer gas is any one of three gases of helium gas, argon gas, nitrogen gas, and oxygen gas, and the three types of gas in the first period, the second period, and the third period. Substrate temperature control method. A substrate is placed on a substrate placement surface of a placement table that is installed in a vacuum processing chamber and is cooled or heated, and a heat transfer gas is introduced between the back surface of the substrate and the substrate placement surface of the placement table. A plasma processing apparatus for controlling plasma by supplying plasma to the substrate while controlling the temperature of the substrate,
A bent portion that is provided in the middle of the supply flow path for supplying the heat transfer gas, and reduces the electric field strength and conductance by bending the supply flow path;
A pressure detection mechanism that is provided in the supply flow channel on the substrate mounting surface side from the bent portion and detects the pressure of the heat transfer gas;
A heat transfer gas supply control mechanism that compares the pressure detection value detected by the pressure detection mechanism with a pressure setting value and controls the supply of the heat transfer gas so that the pressure detection value becomes the pressure setting value; Comprising the heat transfer gas supply control mechanism,
The pressure of the heat transfer gas is set to a low pressure value lower than a lower limit pressure value, which is a lower limit value of pressure capable of stable pressure control, and temperature control of the substrate is performed by suppressing heat exchange between the substrate and the mounting table. When doing
During the plasma processing, a first period in which the pressure set value is a first pressure set value that is equal to or greater than the lower limit pressure value and a second period in which a second pressure set value that is lower than the low pressure value are alternated. The plasma processing apparatus is characterized by being repeated. The plasma processing apparatus according to claim 9, wherein
The pressure detection mechanism is
A diaphragm that is provided on the mounting table and deforms according to the pressure of the heat transfer gas;
A plasma processing apparatus comprising: a detection mechanism that detects a deformation amount of the diaphragm.

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