JP2007208302A - Plasma processing method and plasma processing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma processing method which can prevent the occurrence of surface arching on the substrate to be processed and can improve productivity more than ever before. <P>SOLUTION: Ar gas is fed into a vacuum chamber 1 and under this state, relatively low high frequency power such as 300 W is supplied first from high frequency power supply 11 to a mounting stage 2 (a lower electrode) to generate weak plasma and adjust the conditions of charge accumulated inside a semiconductor wafer W by having the plasma act on a semiconductor wafer W. At this time, direct voltage (HV) to an electrostatic chuck 4 is not applied so that the charges can be easily moved. After that, direct voltage to the electrostatic chuck 4 starts to be applied. Thereafter, high frequency voltage for regular treatment such as 2,000 W is supplied to generate strong plasma for regular plasma treatment. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a plasma processing method and a plasma processing apparatus, and more particularly to a plasma processing method and a plasma processing apparatus for performing a plasma etching process or the like on a target substrate such as a semiconductor wafer or an LCD substrate.

  2. Description of the Related Art Conventionally, a plasma processing method for processing a substrate to be processed such as a semiconductor wafer or an LCD substrate with plasma has been widely used. For example, in a manufacturing process of a semiconductor device, as a technique for forming a fine electric circuit on a substrate to be processed, for example, a semiconductor wafer, a thin film formed on the semiconductor wafer is removed by etching using plasma. A plasma etching process is frequently used.

  In an etching apparatus that performs such plasma etching processing, for example, plasma is generated in a processing chamber (etching chamber) configured to be hermetically closed. Then, the semiconductor wafer is placed on a susceptor provided in the etching chamber and etching is performed.

  Various types of means for generating the plasma are known. Among them, in a type of apparatus that generates plasma by supplying high-frequency power to a pair of parallel plate electrodes provided so as to face each other vertically, one of the parallel plate electrodes, for example, the lower electrode also serves as a susceptor. . Then, a semiconductor wafer is disposed on the lower electrode, a high frequency voltage is applied between the parallel plate electrodes, plasma is generated, and etching is performed.

  However, in such an etching apparatus, so-called surface arcing that causes lightning-like abnormal discharge may occur on the surface of the semiconductor wafer during etching.

  For example, when the insulator layer is formed on the conductor layer and the insulator layer is etched, the surface arcing is performed by etching the insulator layer made of a silicon oxide film, for example, from the lower metal layer. In many cases, such as when a contact hole leading to a conductive layer is formed, the silicon oxide film whose thickness is reduced by etching is destroyed.

  When such an abnormal discharge occurs, many parts of the silicon oxide film in the semiconductor wafer are destroyed, so that most elements of the semiconductor wafer become defective. At the same time, metal contamination occurs in the etching chamber, so that the etching process cannot be performed continuously, and the etching chamber needs to be cleaned. For this reason, there has been a problem in that productivity is significantly reduced.

  The present invention has been made in response to such a conventional situation, and a plasma processing method and a plasma processing which can prevent the occurrence of surface arcing occurring in a substrate to be processed and can improve the productivity as compared with the prior art. The device is to be provided.

The invention of claim 1 is a plasma processing method for performing plasma processing by applying plasma to a substrate to be processed, and after the substrate to be processed is carried into a processing chamber for performing the plasma processing, the plasma processing is performed. Before performing a step of applying a low power high frequency power to the lower electrode on which the substrate to be processed is placed, a step of applying a low power high frequency power to the upper electrode provided facing the lower electrode, Applying a DC voltage to an electrostatic chuck for adsorbing and holding the substrate to be processed; applying a high power high frequency power to the lower electrode;
And a step of applying plasma processing to the substrate to be processed by applying high-frequency high-frequency power to the upper electrode in the order described above.

  Invention of Claim 2 is the plasma processing method of Claim 1, Comprising: Between the process of applying the high frequency electric power of the low power to the said upper electrode, and the process of applying a DC voltage to the said electrostatic chuck, The method includes a step of stopping application of low-power high-frequency power to the lower electrode and a step of stopping application of low-power high-frequency power to the upper electrode.

A third aspect of the present invention is the plasma processing method according to the first or second aspect, wherein in the step of applying high-frequency power of low power to the upper electrode, a plasma weaker than the plasma used for the plasma processing is applied. The weak plasma is a plasma formed by Ar gas, O ₂ gas, CF ₄ gas, or N ₂ gas.

Invention of Claim 4 is the plasma processing method of any one of Claims 1-3, Comprising: It is weaker than the plasma used for the said plasma processing in the process of applying the high frequency electric power of the low power to the said upper electrode Plasma is applied to the substrate to be processed, and the weak plasma is formed by high frequency power of 0.15 to 1.0 W / cm ² .

  Invention of Claim 5 is the plasma processing method of any one of Claims 1-4, Comprising: In the process of applying the high frequency electric power of the low power to the said upper electrode, it is weaker than the plasma used for the said plasma processing Plasma is applied to the substrate to be processed, and the weak plasma is applied to the substrate to be processed for 5 to 20 seconds.

  The invention of claim 6 is a plasma processing apparatus having a processing chamber capable of being evacuated and performing plasma processing on the substrate to be processed in the processing chamber, wherein the substrate to be processed is disposed in the processing chamber. A lower electrode, a top electrode provided opposite to the lower electrode, a first high-frequency power source for applying high-frequency power to the lower electrode, and for applying high-frequency power to the upper electrode A second high frequency power source, an electrostatic chuck for attracting and holding the substrate to be processed, a direct current power source for supplying a direct current voltage to the electrostatic chuck, and a gas supply system for supplying a gas for generating plasma And a control unit that controls the first high-frequency power source, the second high-frequency power source, the DC power source, and the gas supply system, and the control unit is disposed in the processing chamber in the processing target. A step of applying low power high frequency power from the first high frequency power source to the lower electrode after loading the plate and before performing the plasma treatment; and the upper electrode from the second high frequency power source. Applying low power high frequency power, applying a DC voltage from the DC power source to the electrostatic chuck, and applying high power high frequency power from the first high frequency power source to the lower electrode. And a step of applying high-frequency high-frequency power from the second high-frequency power source to the upper electrode and performing plasma processing on the substrate to be processed is controlled in the order described above. To do.

  A seventh aspect of the present invention is the plasma processing apparatus according to the sixth aspect, wherein the control unit applies a low-frequency high-frequency power to the upper electrode and applies a DC voltage to the electrostatic chuck. Between the step of stopping the application of the low-power high-frequency power to the lower electrode and the step of stopping the application of the low-power high-frequency power to the upper electrode. Features.

Invention of Claim 8 is the plasma processing apparatus of Claim 6 or 7, Comprising: In the process of applying the high frequency electric power of low power to the said upper electrode, the said control part is more than the plasma used for the said plasma processing. Control is performed so that weak plasma acts on the substrate to be processed, and the weak plasma is plasma formed by Ar gas, O ₂ gas, CF ₄ gas, or N ₂ gas.

A ninth aspect of the present invention is the plasma processing apparatus according to any one of the sixth to eighth aspects, wherein the control unit is used for the plasma processing in a step of applying high-frequency power of low power to the upper electrode. Control is performed so that a plasma weaker than the plasma to be applied acts on the substrate to be processed, and the weak plasma is formed by a high frequency power of 0.15 to 1.0 W / cm ² .

  A tenth aspect of the present invention is the plasma processing apparatus according to any one of the sixth to ninth aspects, wherein the control unit is used for the plasma processing in a step of applying high-frequency power of low power to the upper electrode. Control is performed so that a plasma weaker than the plasma to be applied acts on the substrate to be processed, and the weak plasma is applied to the substrate to be processed for 5 to 20 seconds.

  According to the present invention, it is possible to prevent the occurrence of surface arcing that occurs in the substrate to be processed, and to improve the productivity as compared with the prior art.

  The details of the present invention will be described below with reference to the drawings.

  FIG. 1 schematically shows a schematic configuration of an entire plasma processing apparatus (etching apparatus) used in an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a material made of, for example, aluminum or the like. A cylindrical vacuum chamber which is configured to be hermetically closed and constitutes a processing chamber is shown.

  The vacuum chamber 1 is connected to a ground potential. Inside the vacuum chamber 1, a mounting table 2 made of a conductive material such as aluminum is formed in a block shape and also serves as a lower electrode.

  The mounting table 2 is supported in the vacuum chamber 1 via an insulating plate 3 such as ceramic, and an electrostatic chuck 4 is provided on the semiconductor wafer W mounting surface of the mounting table 2. The electrostatic chuck 4 is configured such that an electrostatic chuck electrode 4a is interposed in an insulating film 4b made of an insulating material, and a DC power source 5 is connected to the electrostatic chuck electrode 4a. . The electrostatic chuck electrode 4a is made of, for example, copper, and the insulating film 4b is made of polyimide or the like.

  Further, in the mounting table 2, a heat medium flow path 6 for circulating an insulating fluid as a heat medium for temperature control, and a temperature control gas such as helium gas are provided on the back surface of the semiconductor wafer W. A gas flow path 7 for supply is provided.

  Then, by circulating an insulating fluid controlled to a predetermined temperature in the heat medium flow path 6, the mounting table 2 is controlled to a predetermined temperature, and between the mounting table 2 and the back surface of the semiconductor wafer W. Gas for temperature control is supplied through the gas flow path 7 to promote heat exchange between them, and the semiconductor wafer W can be accurately and efficiently controlled to a predetermined temperature.

  In addition, a focus ring 8 made of a conductive material or an insulating material is provided on the outer periphery above the mounting table 2, and a power supply for supplying high-frequency power is provided almost at the center of the mounting table 2. An electric wire 9 is connected. A high frequency power source (RF power source) 11 is connected to the feeder line 9 via a matching unit 10, and high frequency power of a predetermined frequency is supplied from the high frequency power source 11.

  In addition, an exhaust ring 12 having an annular shape and formed with a large number of exhaust holes is provided outside the focus ring 8 described above, and the exhaust connected to the exhaust port 13 via the exhaust ring 12 is provided. The processing space in the vacuum chamber 1 is evacuated by a vacuum pump of the system 14 or the like.

  On the other hand, a shower head 15 is provided on the top wall portion of the vacuum chamber 1 above the mounting table 2 so as to face the mounting table 2 in parallel, and the shower head 15 is grounded. Therefore, the shower head 15 and the mounting table 2 function as a pair of electrodes (upper electrode and lower electrode).

  The shower head 15 is provided with a large number of gas discharge holes 16 on the lower surface thereof, and has a gas introduction portion 17 on the upper portion thereof. A gas diffusion space 18 is formed in the interior. A gas supply pipe 19 is connected to the gas introduction part 17, and a gas supply system 20 is connected to the other end of the gas supply pipe 19. The gas supply system 20 includes a mass flow controller (MFC) 21 for controlling a gas flow rate, a processing gas supply source 22 for supplying a processing gas for etching, for example, and an Ar for supplying Ar gas. It consists of a gas supply source 23 and the like.

  On the other hand, an annular magnetic field forming mechanism (ring magnet) 24 is arranged around the outside of the vacuum chamber 1 concentrically with the vacuum chamber 1, and a magnetic field is formed in the processing space between the mounting table 2 and the shower head 15. Is supposed to form. The entire magnetic field forming mechanism 24 can be rotated around the vacuum chamber 1 at a predetermined rotational speed by a rotating mechanism 25.

  The plasma processing mechanisms such as the DC power source 5, the high frequency power source 11, and the gas supply system 20 for performing plasma processing on the semiconductor wafer W are configured to be controlled by the control unit 40.

  Next, an etching process procedure performed by the etching apparatus configured as described above will be described.

  (First embodiment)

  First, a gate valve (not shown) provided in the vacuum chamber 1 is opened, and a semiconductor wafer W is transferred by a transfer mechanism (not shown) through a load lock chamber (not shown) arranged adjacent to the gate valve. Is loaded into the vacuum chamber 1 and placed on the mounting table 2. Then, after the transfer mechanism is retracted out of the vacuum chamber 1, the gate valve is closed. At this time, the application of the DC voltage (HV) from the DC power source 5 to the electrostatic chuck electrode 4a of the electrostatic chuck 4 is not performed.

  Thereafter, while exhausting the inside of the vacuum chamber 1 to a predetermined degree of vacuum through the exhaust port 13 by the vacuum pump of the exhaust system 14, first, Ar gas is supplied into the vacuum chamber 1 from the Ar gas supply source 23. Then, as shown in FIG. 2, first, a relatively low-frequency high-frequency power (for example, 13.56 MHz) such as 300 W is supplied from the high-frequency power source 11 to the mounting table 2 serving as the lower electrode to generate weak plasma. This weak plasma is caused to act on the semiconductor wafer W.

  The reason why the weak plasma acts on the semiconductor wafer W in this way is as follows.

  That is, the state of the semiconductor wafer W to be processed is not uniform depending on the processing state in the previous step (for example, a film forming step such as CVD), and for example, charges are accumulated inside the semiconductor wafer W. There is a case. In addition, when strong plasma is applied in a state where charges are accumulated inside the semiconductor wafer W in this way, there is a high possibility that surface arcing or the like will occur. Therefore, before applying such strong plasma, weak plasma is applied. This is for the purpose of uniformly adjusting (initializing) the state of charges accumulated in the semiconductor wafer W by the action.

  In adjusting the state of the charge accumulated inside the semiconductor wafer W, in order to facilitate the movement of the charge from the inside of the semiconductor wafer W, the electrostatic chuck 4 is applied to the electrostatic chuck electrode 4a. The semiconductor wafer is adjusted (initialized) with the weak plasma in a state where no DC voltage (HV) is applied.

The high frequency applied power for generating such weak plasma is about 0.15 W / cm ^{2 to} 1.0 W / cm ² , for example, about 100 to 500 W, and the weak plasma is applied to the semiconductor wafer W. The time is, for example, about 5 to 20 seconds.

In the above description, Ar gas is used and Ar gas plasma is applied. However, the gas type is not limited to this, and examples thereof include O ₂ gas, CF ₄ gas, and N ₂ gas. Gas can also be used. However, in selecting this gas type, a gas gas with a low degree of undesired effects such as etching on the semiconductor wafer W and the inner wall of the vacuum chamber 1 is selected. In addition, it is necessary to select a plasma that easily ignites. Furthermore, the optimum gas species may change depending on what kind of processing is performed on the semiconductor wafer W to be processed in the previous process, and it is preferable to select them appropriately in consideration of these.

  Then, after applying a weak plasma to the semiconductor wafer W as described above, a DC voltage (HV) is applied from the DC power source 5 to the electrostatic chuck electrode 4a as shown in FIG. After that, a predetermined processing gas (etching gas) is supplied from the processing gas supply source 22 into the vacuum chamber 1, and a normal processing power such as 2000 W is applied to the mounting table 2 as the lower electrode from the high frequency power source 11. A high-frequency power (frequency, for example, 13.56 MHz) is supplied to generate strong plasma, and normal plasma processing (etching processing) is performed. In FIG. 2, the horizontal axis represents time, and the vertical axis represents the voltage value in the case of the electrostatic chuck HV and the power value in the case of the RF output.

  At this time, a high frequency electric field is formed in the processing space between the shower head 15 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. Then, a magnetic field is formed by the magnetic field forming mechanism 24, and etching with plasma is performed in this state.

  Then, when a predetermined etching process is executed, the etching process is stopped by stopping the supply of high-frequency power from the high-frequency power source 11, and the semiconductor wafer W is removed from the vacuum chamber 1 by a procedure reverse to the above-described procedure. Take it out.

  As described above, first, a weak plasma is applied to the semiconductor wafer W, and then the semiconductor wafer W is etched. As a result, the rate at which surface arcing occurs in the semiconductor wafer W is substantially zero regardless of the lot. (1% or less). On the other hand, when the processing is started without applying the weak plasma as described above, the ratio of occurrence of surface arcing on the semiconductor wafer W may be about 80% depending on the lot. This is because the semiconductor wafer W has been charged in the process prior to the etching, and such surface arcing occurs particularly when the so-called low-K film is formed by CVD. The probability of doing was high.

  Therefore, it was confirmed that by causing weak plasma to act on the semiconductor wafer W as described above before starting normal processing, the rate at which surface arcing occurs in the semiconductor wafer W can be significantly reduced.

  In the above embodiment, as shown in FIG. 1, a case has been described in which an apparatus having a configuration in which high-frequency power is applied only to the mounting table 2 that is the lower electrode, but for example, as shown in FIG. 3. The so-called upper / lower application type plasma processing apparatus configured to apply the high frequency power from the high frequency power supply 31 via the matching device 30 to the shower head 15 as the upper electrode can also be applied.

  In this case, for example, as shown in FIG. 4, first, application of low-power high-frequency power to the mounting table 2 that is the lower electrode is started, and then low-frequency high-frequency power is applied to the shower head 15 that is the upper electrode. Application is started, and application of high-frequency power to the mounting table 2 serving as the lower electrode is once stopped. In this state, after weak plasma is applied to the semiconductor wafer W for a predetermined period, the application of the high frequency power to the shower head 15 as the upper electrode is also stopped, and the plasma is once extinguished.

  Thereafter, application of DC voltage (HV) to the electrostatic chuck electrode 4a of the electrostatic chuck 4, application of normal high-frequency power (high power high-frequency power) for processing to the mounting table 2 as the lower electrode, upper part Application of normal high-frequency power for processing (high-power high-frequency power) to the shower head 15 as an electrode is started in this order, and normal processing of the semiconductor wafer W is started.

  Thus, the present invention can also be applied to the upper and lower application type plasma processing apparatus.

  In addition to applying weak plasma as described above, or before starting the processing alone, it is also preferable to reduce the charge inside the semiconductor wafer W by applying, for example, an ionizer. . Generation of surface arcing can also be suppressed by the action of such an ionizer. The ionizer may be installed in the chamber or may be installed in another place outside the chamber.

  By the way, in the plasma processing method shown in FIG. 2, the electrostatic chuck 4 is not applied with the high frequency power after the weak plasma is generated by applying the weak high frequency power to the mounting table 2 as the lower electrode. Application of DC voltage (HV) to the electrostatic chuck electrode 4a is started. As described above, when application of the DC voltage (HV) to the chuck electrode 4a is started in a state where the RF power after applying the weak RF power and generating the weak plasma is not applied, the DC voltage ( When the application of (HV) is started, there is a possibility of generating a lightning-like discharge and damaging the substrate. In such a case, as shown in FIG. 5, the DC voltage (HV) to the electrostatic chuck electrode 4a in a state where high-frequency power is applied to the mounting table 2 (a state where weak plasma is generated). If the application of is started, the occurrence of discharge can be suppressed.

  In the first embodiment, the method of generating weak plasma using Ar gas before plasma processing such as etching and the timing of applying DC voltage to the electrostatic chuck electrode 4a at that time have been described.

  (Second embodiment)

  Next, a preferred example will be described regarding the relationship between the timing of applying high-frequency power when performing plasma processing such as etching processing and the timing of applying DC voltage to the electrostatic chuck electrode 4a.

  The electrostatic chuck 4 includes a bipolar type and a monopolar type, and these types include a Coulomb type and a Johnson Rabeck type, respectively. Among these, when the unipolar and coulomb electrostatic chuck 4 is used, it is preferable that the semiconductor wafer W be attracted by the following sequence. FIG. 6 shows the sequence. The horizontal axis represents time, the vertical axis represents the applied high-frequency power value (W) for the dotted line, and the applied DC voltage value (V) for the solid line.

  That is, after the semiconductor wafer W is mounted on the mounting table 2 (electrostatic chuck 4), introduction of gas into the vacuum chamber 1 is started. Then, as shown by a dotted line in FIG. 6, first, application of high-frequency power to the mounting table 2 is started to generate plasma, and thereafter, as shown by a solid line in FIG. DC voltage (HV) is applied to 4a.

  Note that the temperature of the semiconductor wafer W is not sufficiently controlled before the application of the DC voltage (HV) to the electrostatic chuck electrode 4a since the semiconductor wafer W is not attracted to the electrostatic chuck 4. For this reason, the high-frequency power applied to the mounting table 2 when the plasma is generated for the first time is a high-frequency power (for example, about 500 W) with a lower power than when performing the processing, and the temperature of the semiconductor wafer W is increased by the action of the plasma. It is preferable not to raise.

  When removing the semiconductor wafer W from the electrostatic chuck 4, as shown in the figure, after the plasma processing is completed, first, the applied high-frequency power value is set to a power value (0 W) with a lower power than when the processing is performed. Not). Thereafter, the application of the DC voltage (HV) to the electrostatic chuck electrode 4a is stopped, and then the application of the high frequency power is stopped to extinguish the plasma. When the application of the DC voltage (HV) to the electrostatic chuck electrode 4a is stopped, a voltage (for example, about -2000V) having a polarity opposite to that at the time of adsorption is applied to the electrostatic chuck electrode 4a. The charge is removed and the semiconductor wafer W is easily removed. The application of the reverse polarity voltage is performed as necessary. When the semiconductor wafer W can be easily removed from the electrostatic chuck 4 without applying the reverse polarity voltage, the reverse polarity voltage is applied. No voltage is applied.

  FIG. 7 illustrates a copper electrode portion (Cu) and a polyimide insulating film portion (PI) of the electrostatic chuck (ESC) in the sequence of the adsorption of the semiconductor wafer W by the electrostatic chuck 4 as described above. Back surface oxide film part (B.S.Ox) and silicon substrate part (Si sub) and oxide film part (Ox) of multilayer semiconductor wafer (Multi Layer Wafer), processing space part (Space) and upper electrode in vacuum chamber The change of the electric potential of each part of a part (Wall) is shown.

  As shown in the figure, first, when the wafer support pins provided on the mounting table 2 are lowered and the semiconductor wafer W is mounted on the mounting table 2, as shown by (1) in FIG. The potential is zero, and thereafter, when the introduction of gas into the vacuum chamber 1 is started, the potential of each part is zero as shown by (2) in the figure.

  Thereafter, when application of high-frequency power is started to generate plasma, as shown by (3) in the figure, the potential of the semiconductor wafer W becomes a potential of about minus several hundred volts determined by the plasma state.

  In this state, when application of the DC voltage (HV) to the electrostatic chuck electrode 4a is started, as shown by (4) in the figure, the potential of the electrostatic chuck electrode 4a becomes the applied DC voltage ( HV) potential (for example, about 1.5 KV), a potential difference occurs in the insulating film portion (PI), and the semiconductor wafer W is attracted.

  Thus, according to the sequence of adsorption of the semiconductor wafer W by the electrostatic chuck 4 as described above, accompanying the application of a DC voltage (HV) to the electrostatic chuck electrode 4a on the surface of the semiconductor wafer W. Since no high voltage is applied, it is possible to prevent undesired abnormal discharge from occurring on the surface of the semiconductor wafer W.

  In addition, there exists an effect which is demonstrated below about the sequence which applies a direct-current voltage after applying high frequency electric power demonstrated in the 2nd Example.

  A sequence as shown in FIG. 9, that is, after high frequency power is applied to the lower electrode (or upper electrode) after application of DC voltage to the electrostatic chuck electrode 4a at the start of plasma processing, and after high frequency power is turned off after the plasma processing is completed When the DC voltage is turned off, a large voltage is applied to the semiconductor wafer W as shown in FIG. As a result, the surface of the semiconductor wafer W may be damaged, specifically, a chip having a diameter of about several tens of μm may occur. Depending on the location where the chip occurs, arcing may occur during etching, resulting in a product defect. . Further, the chipped portion may become particles and adhere to the surface of the semiconductor wafer W.

  However, in the case of the sequence of RF ON → HV ON at the start of processing and HV OFF → RF OFF at the end of processing described in the present embodiment, no high voltage is applied to the semiconductor wafer W, so that the semiconductor wafer W is damaged. And particles on the surface of the semiconductor wafer W can be prevented.

  Further, even if the surface of the semiconductor wafer W is not damaged in the sequence as shown in FIG. 9, the semiconductor wafer W is charged by applying a DC voltage to the electrostatic chuck electrode 4a. There is a possibility that charged particles normally floating in the processing chamber due to force adhere to the semiconductor wafer W.

  However, in the sequence of RF ON → HV ON at the start of processing and HV OFF → RF OFF at the end of processing, since the high frequency discharge is maintained before the DC voltage is applied to the electrostatic chuck, it is floating. Charged particles are trapped in the ion sheath, and as a result, adhesion of particles to the surface of the semiconductor wafer W can be reduced. There is also such an effect.

  The results of verifying the effect of the trap in the ion sheath are shown below.

  FIG. 11 shows the result of examining the difference in the number of adhered particles due to the difference in the DC applied voltage of the electrostatic chuck for adsorbing the semiconductor wafer W.

  That is, first, a CF-based reactant serving as a particle generation source is attached to the processing chamber of the plasma processing apparatus (seasoning), and then the semiconductor wafer W is loaded into the processing chamber and placed on the electrostatic chuck. Then, the processing gas is circulated for a certain period of time, and after that, the semiconductor wafer W is neutralized and carried out of the processing chamber, and the number of particles adhering to the semiconductor wafer W is divided into three types. This is a count for each of the three sizes, and shows the results of investigation in each case where the DC voltage of the electrostatic chuck was 0 V, 1.5 kV, 2.0 kV, and 2.5 kV.

  As shown in the figure, it is understood that the number of particles adhering to the semiconductor wafer W increases when the DC applied voltage of the electrostatic chuck is increased. That is, it can be seen that application of a DC voltage to the electrostatic chuck affects the adhesion of particles to the semiconductor wafer W.

The processing conditions of the seasoning process are as follows: pressure: 6.65 Pa, high frequency power: 3500 W, gas used: C ₄ F ₈ / Ar / CH ₂ F ₂ = 13/600/5 sccm, wafer back pressure (center / periphery) : 1330/3990 Pa, temperature (ceiling / side wall / bottom): 60/60/60 ° C., high frequency application time: 3 minutes.

  In addition, the conditions for pressure, working gas, wafer back pressure, and temperature when the semiconductor wafer W is placed on the electrostatic chuck and gas is circulated are the same as described above, high-frequency power = 0, and gas flow time is 60. Seconds.

  Further, in the static elimination step, the static elimination of the semiconductor wafer W is performed by pressure: 26.6 Pa, applied voltage: -1.5 kV, voltage application time: 1 second, pressure: 53.2 Pa, N2: 1000 sccm, time: 15 The electrostatic chuck was neutralized with an applied voltage of -2.0 kV and a voltage application time of 1 second. It should be noted that the charge removal is performed in this way because if the semiconductor wafer W bounces when the semiconductor wafer W after the completion of the process is transported, there is a possibility that extra particles may be reattached. This is to prevent such a jump of the semiconductor wafer W from occurring.

Also, FIG. 12 shows that after the seasoning process, the semiconductor wafer W is placed in the processing chamber, and in this state, O ₂ dry cleaning is performed to generate a large number of particles from the reactants attached in the seasoning process. The number of particles adhering to the wafer W is determined by the sequence of RF ON → HV ON at the start of processing, HV OFF → RF OFF at the end of processing, and HV ON → RF ON at the start of processing, and RF OFF → HV OFF at the end of processing. It shows the measurement results for the case of the sequence. In this measurement, the seasoning process and the charge removal process are the same as described above, and the O ₂ dry cleaning process is performed under the following conditions: pressure: 13.3 Pa, high frequency power: 1000 W, gas used: O ₂ = 1000 sccm, wafer back pressure (Center / periphery): 1330/3990 Pa, temperature (ceiling / side wall / bottom): 60/60/60 ° C., high frequency application time: 30 seconds.

  As shown in the figure, by adopting the sequence of RF ON → HV ON at the start of the process and HV OFF → RF OFF at the end of the process, the number of attached particles can be greatly reduced.

  As shown in the sequence shown in FIG. 8, the DC voltage (HV) applied to the electrostatic chuck electrode 4a in a state in which the semiconductor wafer W is supported by the wafer support pins (support bars) provided on the mounting table 2. The application is started (2), and then the wafer supporting pins are lowered to place the semiconductor wafer W on the mounting table 2 (3, 4), and the semiconductor wafer W is attracted. The surface of the electrode does not become the potential of the applied DC voltage (HV). Therefore, even with such an adsorption sequence, it is possible to prevent undesired abnormal discharge from occurring on the surface of the semiconductor wafer W. However, such a sequence cannot be performed unless the wafer support pins are conductive and the semiconductor wafer W is supplied with electric charges from the pins.

  In addition, the abnormal discharge that occurs at the time of adsorption by the electrostatic chuck as described above can be prevented by using a bipolar electrostatic chuck even in the same coulomb electrostatic chuck.

  In the above example, the embodiment of the etching process using the parallel plate type etching apparatus has been described. However, the present invention is not limited to such an embodiment, and can of course be used for any plasma process. . In the above-described embodiment, the case where weak plasma is applied in the vacuum chamber of the etching apparatus that performs the etching process has been described. However, the weak plasma is applied in a place different from the apparatus that performs the process, and the semiconductor wafer W is formed. It can also be initialized.

The figure which shows typically schematic structure of the apparatus used for one Embodiment of this invention. The figure for demonstrating the plasma processing method which concerns on one Embodiment of this invention. The figure which shows typically schematic structure of the apparatus used for other embodiment of this invention. The figure for demonstrating the plasma processing method which concerns on other embodiment of this invention. The figure for demonstrating the plasma processing method which concerns on the modification of embodiment shown in FIG. The figure for demonstrating the chucking method by an electrostatic chuck. The figure for demonstrating the change of the electric potential of each part in the chucking method of FIG. The figure for demonstrating the change of the electric potential of each part in another chucking method. The figure for demonstrating the comparative example of the chucking method by an electrostatic chuck. The figure for demonstrating the change of the electric potential of each part in the chuck | zipper method of FIG. The figure which shows the relationship between the applied voltage of an electrostatic chuck, and the number of particles. The figure which shows the difference in the number of particles by the difference in a sequence.

Explanation of symbols

  W: Semiconductor wafer, 1 ... Vacuum chamber, 2 ... Mounting table (lower electrode), 4 ... Electrostatic chuck, 5 ... DC power supply, 11 ... High frequency power supply, 15 ... Shower head (upper electrode) .

Claims (10)

A plasma processing method for performing plasma processing by applying plasma to a substrate to be processed,
A step of applying high-frequency power of low power to a lower electrode on which the substrate to be processed is placed after the substrate to be processed is carried into a processing chamber for performing the plasma processing and before the plasma processing is performed;
Applying high-frequency power of low power to the upper electrode provided facing the lower electrode;
Applying a DC voltage to the electrostatic chuck for attracting and holding the substrate to be processed;
Applying high power high frequency power to the lower electrode;
Applying a high-frequency high-frequency power to the upper electrode to perform a plasma treatment on the substrate to be processed;
In the order described above. The plasma processing method according to claim 1,
Between the step of applying low power high frequency power to the upper electrode and the step of applying a DC voltage to the electrostatic chuck,
A plasma processing method comprising: a step of stopping application of low-power high-frequency power to the lower electrode; and a step of stopping application of low-power high-frequency power to the upper electrode. In the step of applying high-frequency power of low power to the upper electrode, a plasma weaker than the plasma used for the plasma processing is applied to the substrate to be processed, and the weak plasma is Ar gas, O ₂ gas, or CF 3. The plasma processing method according to claim 1, wherein the plasma processing method is a plasma formed by ₄ gas or N ₂ gas. In the step of applying low power high frequency power to the upper electrode, plasma weaker than the plasma used for the plasma treatment is applied to the substrate to be processed, and the weak plasma is 0.15 to 1.0 W / cm ^2. The plasma processing method according to claim 1, wherein the plasma processing method is formed by high-frequency power.   In the step of applying low-power high-frequency power to the upper electrode, a plasma weaker than the plasma used for the plasma processing is applied to the substrate to be processed, and the weak plasma is applied to the substrate to be processed for 5 to 20 seconds. The plasma processing method according to any one of claims 1 to 4, wherein the plasma processing method is performed. A plasma processing apparatus having a processing chamber capable of being evacuated and performing plasma processing on a substrate to be processed in the processing chamber,
A lower electrode disposed in the processing chamber for mounting the substrate to be processed;
An upper electrode provided to face the lower electrode;
A first high frequency power source for applying high frequency power to the lower electrode;
A second high frequency power source for applying high frequency power to the upper electrode;
An electrostatic chuck for adsorbing and holding the substrate to be processed;
A DC power supply for supplying a DC voltage to the electrostatic chuck;
A gas supply system for supplying a gas for generating plasma;
A controller that controls the first high-frequency power source, the second high-frequency power source, the DC power source, and the gas supply system;
The controller is
Applying low-frequency high-frequency power from the first high-frequency power source to the lower electrode after carrying the substrate into the processing chamber and before performing the plasma processing;
Applying low power high frequency power from the second high frequency power source to the upper electrode;
Applying a DC voltage from the DC power source to the electrostatic chuck;
Applying high power high frequency power from the first high frequency power source to the lower electrode;
Applying a high-power high-frequency power from the second high-frequency power source to the upper electrode to perform a plasma treatment on the substrate to be processed;
Is controlled to be performed in the above order. The plasma processing apparatus according to claim 6, wherein
The control unit, between the step of applying a low power high frequency power to the upper electrode and the step of applying a DC voltage to the electrostatic chuck,
Stopping application of low-power high-frequency power to the lower electrode; stopping application of low-power high-frequency power to the upper electrode;
The plasma processing apparatus is controlled so as to be performed. The control unit controls the plasma to be weaker than the plasma used for the plasma processing to act on the substrate to be processed in the step of applying low power high frequency power to the upper electrode,
The plasma processing apparatus according to claim 6 or 7, wherein the weak plasma is plasma formed by Ar gas, O ₂ gas, CF ₄ gas, or N ₂ gas. The control unit controls the plasma to be weaker than the plasma used for the plasma processing to act on the substrate to be processed in the step of applying low power high frequency power to the upper electrode,
9. The plasma processing apparatus according to claim 6, wherein the weak plasma is formed by a high frequency power of 0.15 to 1.0 W / cm < ² >. The control unit controls the plasma to be weaker than the plasma used for the plasma processing to act on the substrate to be processed in the step of applying low power high frequency power to the upper electrode,
The plasma processing apparatus according to claim 6, wherein the weak plasma is applied to the substrate to be processed for 5 to 20 seconds.

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