Sample separation method and plasma processing device

Abstract

This plasma processing device suppresses the adhesion of foreign matter to a sample when the sample is separated.　The plasma processing device comprises: a processing chamber which is disposed inside a vacuum container and in which plasma for processing a sample is formed; and a sample table which is disposed inside the processing chamber and on a top surface of which the sample is placed and held. The following steps are executed: a first step in which, after the processing of the sample has been completed, plasma is formed using gas supplied into the processing chamber, and in that state the sample is raised to a position spaced apart from the top surface of the sample table in the upward direction and then placed on the top surface again; a second step in which, after the sample has been placed on the top surface of the sample table again, power is supplied to an electrode inside the sample table and the sample is charged to a positive potential, and in that state the plasma is extinguished; and a third step in which, after the supply of power to the electrode has been stopped, the sample is moved to a position spaced apart from the top surface of the sample table in the upward direction.

Description

Sample removal method and plasma processing apparatus

[0001] The present invention relates to a sample detachment method and a plasma processing apparatus.

[0002] Semiconductor manufacturing processes include plasma processing processes in which a semiconductor wafer (hereinafter simply referred to as a wafer) is processed using plasma. In this plasma processing process, the wafer is placed on a sample stage installed in a processing chamber of a plasma processing device, and plasma is generated in the processing chamber, exposing the wafer surface to the plasma. Wafers are processed appropriately by appropriately setting conditions such as the gas species supplied into the processing chamber, the pressure inside the processing chamber, the energy applied to the plasma generation source, and the high-frequency power applied to the wafer.

[0003] In the plasma processing process described above, it is necessary to reduce the defect rate in order to maximize the number of semiconductor devices that can be obtained from each wafer and reduce manufacturing costs. Factors that reduce the yield of semiconductor devices include non-uniformity of the plasma processing and the unexpected adhesion of foreign matter to the wafer surface.

[0004] Normally, during plasma discharge, foreign particles become negatively charged due to the influx of electrons. Furthermore, during plasma discharge, an ion sheath (a thin layer of positive charge) is formed on the wafer surface. Therefore, negatively charged foreign particles are subjected to a repulsive force due to the potential difference between the wafer surface and the plasma, and the foreign particles do not adhere to the wafer surface. However, it has been pointed out that when the wafer is removed from the sample stage after plasma processing, the repulsive force no longer acts between the foreign particles and the wafer, causing the foreign particles in the processing chamber to adhere to the wafer.

[0005] To address this problem, a technique for reducing adhesion of foreign matter to a sample in a plasma processing apparatus is described in, for example, the following document.

[0006] Patent Document 1 describes that foreign matter inside the processing chamber of a plasma processing apparatus is positively charged, and that a particle removal electrode to which a negative voltage is applied is placed inside the processing chamber, and the positively charged foreign matter is attracted to the particle removal electrode, thereby suppressing adhesion of foreign matter to the sample being processed.

[0007] Patent Document 2 describes a case in which both positively and negatively charged foreign matter are present in the processing chamber of a plasma processing apparatus, and describes controlling the potential of the sample so that no potential difference occurs between the sample and the inner wall of the processing chamber while the plasma discharge is interrupted.

[0008] JP 2003-100720 A JP 2019-153814 A

[0009] In the technology described in Patent Document 1, a negative potential is applied to an electrode to attract positive foreign matter to the electrode surface by an electric field, but at this time, the electric field accelerates ions, and high-energy ions are incident on the electrode surface, raising concerns about an increase in foreign matter due to sputtering. Furthermore, since there is no description of a method for positively charging foreign matter, if negatively charged foreign matter is present, a sufficient effect of preventing foreign matter from adhering to the sample cannot be obtained.

[0010] Furthermore, while the technology described in Patent Document 2 can suppress adhesion of foreign matter to the sample due to Coulomb force, conversely, the repulsive force due to Coulomb force does not work, so there is a risk that foreign matter may easily adhere to the sample surface due to other forces such as the gravity of the foreign matter itself, thermophoretic force, and frictional force with the gas.

[0011] An object of the present invention is to provide a technique capable of suppressing adhesion of foreign matter to a sample when the sample is released in a plasma processing apparatus.

[0012] In order to solve the above-mentioned problems, for example, the configurations described in the claims are adopted. The present application includes a plurality of means for solving the above-mentioned problems, and one example thereof is a sample detachment method for a plasma processing apparatus including a processing chamber arranged inside a vacuum vessel in which plasma for processing a sample is generated, and a sample stage arranged inside the processing chamber and on whose upper surface the sample is placed and held, the sample detachment method comprising: a first step of, after sample processing is completed, lifting the sample to a position spaced above the upper surface of the sample stage and placing it again on the upper surface in a state in which the plasma is generated using a gas supplied into the processing chamber; a second step of, after the sample is placed again on the upper surface of the sample stage, supplying power to an electrode inside the sample stage to charge the sample to a positive potential, thereby extinguishing the plasma; and a third step of, after stopping the supply of power to the electrode, moving the sample to a position spaced above the upper surface of the sample stage.

[0013] Another example includes a processing chamber arranged inside a vacuum vessel in which plasma for processing a sample is generated, a sample stage arranged inside the processing chamber and on whose top surface the sample is placed and held, an electrode arranged inside the sample stage, a plurality of pins each configured to be movable in the up and down direction of the sample stage through a through-hole formed on the top surface of the sample stage, the plurality of pins moving upward to move the sample to a position separated from the top surface of the sample stage and moving downward to be housed inside the sample stage, and a control device for controlling the supply of gas into the processing chamber, the supply of power to the electrode, and the operation of the plurality of pins. and a control device for controlling the control of the sample so that, after the processing of the sample is completed, the sample is lifted to a position spaced above the upper surface of the sample stage and placed again on the upper surface while the plasma is formed using a gas supplied into the processing chamber; a second step for supplying power to an electrode inside the sample stage after the sample has been placed again on the upper surface of the sample stage to charge the sample to a positive potential and extinguish the plasma; and a third step for stopping the supply of power to the electrode and moving the sample to a position spaced above the upper surface of the sample stage, wherein the control device controls the control of the sample so that the following steps are performed: a first step for lifting the sample to a position spaced above the upper surface of the sample stage and placing it again on the upper surface while the plasma is formed using a gas supplied into the processing chamber after the processing of the sample is completed; a second step for supplying power to an electrode inside the sample stage after the sample has been placed again on the upper surface of the sample stage to charge the sample to a positive potential and extinguish the plasma; and a third step for stopping the supply of power to the electrode and moving the sample to a position spaced above the upper surface of the sample stage.

[0014] According to the present invention, in a plasma processing apparatus, it is possible to suppress adhesion of foreign matter to a sample when the sample is released. Other problems, configurations, and effects will become clear in the following description of the embodiments.

[0015] FIG. 1 is a diagram showing an example of a change in foreign substance charge amount over time during discharge and afterglow in the presence of negative ions; FIG. 2 is a diagram showing an example of a foreign substance charge amount distribution after plasma is turned off in the presence of negative ions; FIG. 3 is a diagram showing an example of a change in foreign substance charge amount over time during discharge and afterglow in a rare gas; FIG. 4 is a diagram showing an example of a foreign substance charge amount distribution after plasma is turned off in a rare gas; FIG. 5 is a diagram showing an example of a configuration of a plasma processing apparatus to which the sample desorption method according to embodiment 1 is applied; FIG. 6 is a diagram showing an example of a flowchart for the sample desorption method according to embodiment 1; FIG. 7 is a diagram showing changes in the state around the sample due to the sample desorption method according to embodiment 1; FIG. 8 is a diagram showing an example of a time chart for the sample desorption method according to embodiment 1; FIG. 9 is a diagram showing an example of a configuration of a plasma processing apparatus according to embodiment 2; FIG. 10 is a diagram showing an example of a configuration of a control mechanism according to embodiment 2.

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the description of the embodiments, and various changes and modifications can be made by those skilled in the art within the scope of the technical ideas disclosed in this specification. Furthermore, in all drawings used to explain the present invention, components having the same functions are given the same reference numerals, and repeated explanations thereof may be omitted.

[0017] (Background of the Study) Generally, in a plasma processing apparatus, when a sample such as a semiconductor wafer is subjected to plasma processing in a processing chamber, an electrostatic adsorption electrode adsorbs the sample by Coulomb force.

[0018] When the plasma-treated sample is removed from the sample stage, the pusher pin is raised in the plasma to perform dechucking, which releases the electrostatic adhesion between the sample and the electrode.The plasma is then turned off, and the sample is transported outside the processing chamber.

[0019] However, when a sample that has been subjected to plasma processing is dechucked and then the plasma is turned off, there is a concern that foreign matter in the processing chamber may adhere to the sample. The reason for this is explained below.

[0020] When plasma is generated in the processing chamber, the difference in diffusion speed between electrons and ions causes more electrons than ions to be lost to the sample surface. As a result, a region where the density of positive ions is greater than the density of electrons is formed near the sample surface. This region is called the ion sheath. This ion sheath causes the sample to have a lower potential than the plasma, generating an electric field from the plasma to the sample.

[0021] Foreign matter can be generated inside the processing chamber. Foreign matter mainly originates from the inner wall of the processing chamber. In plasma, electrons, which have a high diffusion rate, are more likely to be incident on foreign matter than ions, causing the foreign matter to become negatively charged. As a result, negatively charged foreign matter is subjected to a repulsive force by the electric field of the sheath formed on the sample surface, and does not adhere to the sample.

[0022] On the other hand, when the plasma is turned off, i.e., extinguished, the sheath disappears. As a result, the force of the sheath electric field no longer acts on the charged foreign particles. The foreign particles, for example, fall under their own weight and easily adhere to the sample.

[0023] Therefore, in order to suppress adhesion of foreign matter to the sample after the plasma is turned off, it is effective to intentionally apply a potential to the sample to generate a repulsive force against the charged foreign matter.

[0024] However, when the plasma is turned off, the charge on the particles also changes. The way in which the charge on the particles changes depends on whether or not negative ions are present in the plasma. In particular, when negative ions are present, three types of particles ultimately exist: positively charged particles, negatively charged particles, and uncharged particles. This makes it difficult to prevent particles from adhering due to electrostatic forces from the sample.

[0025] Here, the manner in which the charge amount of foreign matter changes when negative ions are present will be described with reference to the drawings.

[0026] FIG. 1 shows an example of the change in charge amount of a foreign object over time during discharge and afterglow in the presence of negative ions. As shown in FIG. 1, during discharge, i.e., during plasma generation, the inflow of electrons is dominant as described above, so the foreign object 100 is negatively charged (see first state 101). When the plasma is turned off, the afterglow phase begins. In second state 102, which is the initial stage of the afterglow, the electron temperature drops, and the absolute value of the negative charge decreases. After a certain time has passed, the electron temperature drops to about the ion temperature and stabilizes (see third state 103). At this time, there is no significant change in the charge amount of the foreign object 100.

[0027] After that, the electron and ion densities decrease further, and when the Debye length and the size of the processing chamber reach the same order of magnitude, most of the electrons are absorbed and lost by the inner walls of the processing chamber, and positive and negative ions become dominant (see fourth state 104). At this time, the positive and negative ions have similar masses and similar diffusion rates, so that approximately the same amounts of positive and negative ions are incident on the foreign object 100. As a result, the charge on the foreign object 100 approaches zero. After the end of the afterglow, ions no longer enter the foreign object 100, and the charge on the foreign object 100 reaches a steady state (see fifth state 105).

[0028] Figure 2 shows an example of the charge distribution of foreign particles after plasma is turned off in the presence of negative ions. In the distribution diagram shown in Figure 2, the horizontal axis represents the charge amount, and the vertical axis represents the number of foreign particles with that charge amount. The final charge amount of the foreign particles depends on the ratio of incident positive ions to negative ions. Therefore, as shown in Figure 2, the distribution of the charge amount of the foreign particles has a shape that spreads out on both the positive and negative sides around 0.

[0029] Next, how the charge amount of foreign matter changes when there are no negative ions will be described with reference to the drawings.

[0030] Fig. 3 is a diagram showing an example of the change over time in the charge amount of a foreign substance during discharge and afterglow in a rare gas (when negative ions are not present). In Fig. 3, a first state 101, a second state 102, and a third state 103 are similar to the first state 101, the second state 102, and the third state 103 in Fig. 1. Also, in Fig. 3, a sixth state 106 and a seventh state 107 are states that replace the fourth state 104 and the fifth state 105 in Fig. 1.

[0031] In the first state 101 during discharge, the second state 102 during afterglow, and the third state 103, the charge amount of the foreign object changes in the same way as when negative ions are present. When the Debye length and the processing chamber size are approximately the same, there is a time period in which only positive ions are incident on the surface of the foreign object 100 because there are no negative ions (see the sixth state 106). As a result, in the time period in the seventh state 107 when the charge amount of the foreign object 100 reaches a steady state, the charge amount of the foreign object becomes all positive.

[0032] 4 is a diagram showing an example of the charge distribution of foreign matter after plasma is turned off in a rare gas (when negative ions are not present). The charge distribution of foreign matter after plasma is turned off in a rare gas is, for example, all positive, as shown in FIG.

[0033] As described above, when a foreign particle has a positive charge, applying a positive potential to the surface of the sample causes an electrostatic force to act on the foreign particle in a direction away from the sample, so that the foreign particle no longer adheres to the sample.

[0034] (Outline of the embodiment) Before describing specific embodiments of the present invention, the outline of the embodiment of the present invention will be summarized as follows.

[0035] One representative plasma processing apparatus of the present invention is as follows. The plasma processing apparatus includes a processing chamber, a gas composition measurement mechanism, a radio frequency power supply, an electrode, a pusher pin, a transfer arm, a DC voltage, and a DC power supply. The processing chamber processes a sample using plasma. The gas supply mechanism supplies gas into the processing chamber. The gas composition measurement mechanism measures the gas composition in the processing chamber. The radio frequency power supply supplies radio frequency power for generating the plasma. The sample stage holds a sample in the processing chamber. The electrode electrostatically attracts the sample to the sample stage. The pusher pin dechucks the electrostatically attracted sample from the sample stage. The transfer arm transports the sample from the processing chamber to the outside. The DC power supply applies a DC voltage to the electrode.

[0036] In the plasma processing apparatus, the electrodes are composed of a first electrode to which a positive DC voltage is applied and a second electrode to which a negative DC voltage is applied. The plasma processing apparatus also includes a first power supply that supplies a DC voltage to the first electrode and a second power supply that supplies a DC voltage to the second electrode. The following sample (e.g., semiconductor wafer) desorption method is performed in the plasma processing apparatus.

[0037] In the above-described plasma processing apparatus, after plasma processing of the sample is completed, the supply of a rare gas is started by the gas supply mechanism without turning off the plasma. Next, the DC voltages supplied to the first and second electrodes from the first and second power sources are set to zero, and the electrostatically adsorbed sample is dechucked from the sample stage by raising the pusher pins. The pusher pins are then lowered to place the sample back on the sample stage. Next, in the gas composition measurement mechanism, a DC voltage is applied to the first and second electrodes so that the sample surface becomes a positive voltage when the gas that generates negative ions used during plasma processing of the sample is replaced with the rare gas. Next, the high-frequency power supplied from the high-frequency power source is set to zero to turn off the plasma. Next, after waiting for a certain period of time, the pusher pins are raised to lift the sample from the sample stage, and the sample is transported out of the processing chamber by the transport arm.

[0038] (Embodiment 1) A sample desorption method according to embodiment 1 of the present invention will be described with reference to the drawings.

[0039] FIG. 5 is a diagram showing an example of the configuration of a plasma processing apparatus to which the sample desorption method according to the first embodiment is applied. FIG. 5 shows a cross-sectional view of a main part of the plasma processing apparatus. The plasma processing apparatus 1 shown in FIG. 5 is an electron cyclotron resonance (ECR) type plasma processing apparatus. Hereinafter, electron cyclotron resonance may be simply referred to as "ECR." The present invention is also applicable to other types of plasma processing apparatuses other than ECR type plasma processing apparatuses.

[0040] In the plasma processing apparatus 1, an electromagnetic wave is supplied from a magnetron 501, which is a high-frequency power source, through a waveguide 502 and a dielectric window 503 to a processing chamber 504. Plasma is generated by resonance between the electromagnetic wave and electrons undergoing cyclotron motion due to a static magnetic field generated by a solenoid coil 505. For example, when a microwave with a frequency of 2.45 GHz (gigahertz) is used as the plasma source, an electron cyclotron resonance phenomenon occurs by generating a static magnetic field of 0.0875 T (tesla) in the processing chamber 504 using the solenoid coil 505, thereby efficiently generating plasma.

[0041] A sample stage 507 is provided in the processing chamber 504, on which a sample wafer 506 is placed. A high-frequency power supply 508 for supplying bias power to the wafer 506 is connected to the sample stage 507 via a matching box 509. The sample stage 507 also includes a first electrode 510 and a second electrode 511 for electrostatically chucking the wafer 506. Variable DC power supplies 512 and 513 for supplying DC voltages to the first electrode 510 and the second electrode 511 are connected to the first electrode 510 and the second electrode 511, respectively. A dielectric layer 514 is provided between the first electrode 510 and the wafer 506, and between the second electrode 511 and the wafer 506.

[0042] Here, a mechanism for electrostatically chucking the wafer 506 using two electrodes, the first electrode 510 and the second electrode 511, as described above, is called a hyperbolic type. In hyperbolic electrodes, potentials of opposite polarities are applied to each electrode to chuck the wafer 506. In this case, the potential of the wafer 506 is often designed to be the average value of the DC voltages applied to the first electrode 510 and the second electrode 511. For example, if a DC voltage of +500 V is applied to one of the first electrode 510 and the second electrode 511 and a voltage of −500 V is applied to the other electrode, the voltage of the wafer 506 will be 0 V. If a DC voltage of +700 V is applied to one electrode and a DC voltage of −300 V is applied to the other electrode, the voltage of the wafer 506 will be 200 V.

[0043] Additionally, a plurality of pusher pins 515 are provided inside the sample stage 507 for lifting the wafer 506 when dechucking the wafer 506. The plurality of pusher pins 515 are an example of the "plurality of pins" in the present application. The plurality of pusher pins 515 are configured so that each pin passes through a through-hole formed in the upper surface of the sample stage 507 and can move in the up and down directions of the sample stage 507. The plurality of pusher pins 515 move the sample wafer 506 to a position separated from the upper surface of the sample stage 507 by moving upward, and move downward to be housed inside the sample stage 507, thereby placing the sample wafer 506 on the upper surface of the sample stage 507.

[0044] Three or more pusher pins 515 are provided in the electrode, and while the wafer 506 is electrostatically chucked to the sample stage 507 and undergoing plasma processing, the pusher pins 515 are housed in the sample stage 507. When dechucking the wafer 506 from the sample stage 507, the pusher pins 515 rise and protrude by a certain length from the sample stage 507, thereby lifting the wafer 506 and detaching it from the sample stage 507.

[0045] The plasma processing apparatus 1 is provided with a transfer arm 516 for transferring the wafer 506 out of the processing chamber 504. During plasma processing, the transfer arm 516 is isolated outside the processing chamber 504 by a lid 517. When transferring the wafer 506 out of the processing chamber 504, the lid 517 is opened and the wafer 506 in the processing chamber 504 is transferred by the transfer arm 516.

[0046] Gas is supplied to the inside of the processing chamber 504 by a gas supply mechanism 518. A pump 520 is connected to the inside of the processing chamber 504 via a valve 519, and the gas inside the processing chamber 504 is exhausted. The pressure inside the processing chamber 504 can be adjusted to a constant value by controlling the gas exhaust speed by adjusting the opening of the valve 519.

[0047] The inner wall material of the processing chamber 504 includes a conductive region. This conductive region is grounded (earthed) via a conductor 521. The conductive region may be the entire inner wall or a part of the inner wall. Furthermore, this conductive region may be exposed to plasma, or its surface may be covered with a thin insulating film whose potential changes to approximately 0 V immediately after the plasma is turned off.

[0048] The plasma processing apparatus 1 further includes a measurement mechanism 522 having time resolution for measuring the gas composition in the processing chamber 504. The measurement mechanism 522 may be, for example, a spectrometer for measuring plasma emission spectrum, a mass analyzer, or the like. The gas composition measurement mechanism of the plasma processing apparatus 1 according to this embodiment is not limited to the above, and other mechanisms may also be used.

[0049] In the plasma processing apparatus 1, after the plasma processing is performed, the wafer 506 is detached in the following detachment procedure.

[0050] Fig. 6 is a diagram showing an example of a flowchart for the sample desorption method according to the first embodiment. Fig. 7 is a diagram showing changes in the state around the sample due to the sample desorption method according to the first embodiment. As shown in Fig. 6, the sample desorption method according to the first embodiment is a sample desorption method in a plasma processing apparatus including a processing chamber disposed inside a vacuum vessel in which plasma for processing the sample is generated, and a sample stage disposed inside the processing chamber and on whose upper surface the sample is placed and held. The sample desorption method according to the first embodiment includes first step S101 to third step S103, which will be described below. The sample desorption method according to the first embodiment may further include a fourth step S104.

[0051] In the first step S101, after processing of the sample wafer 506 is completed, the sample wafer 506 is lifted to a position spaced above the upper surface of the sample stage 507 (FIG. 7, state 111) and placed again on the upper surface while plasma is being generated using a gas (e.g., a rare gas) supplied into the processing chamber 504. The first step S101 reduces the charge on the sample. Note that in the first step S101, after it is detected that the amount of negative ions in the plasma has become smaller than a predetermined value, the sample wafer 506 may be lifted to a position spaced above the upper surface of the sample stage 507 while plasma is being generated, and placed again on the upper surface.

[0052] In the second step S102, after the sample wafer 506 is placed on the upper surface of the sample stage 507 again, power is supplied to the electrode inside the sample stage 507 (FIG. 7, state 112), and once purging with a gas such as a rare gas is completed (FIG. 7, state 113), the plasma is extinguished with the sample wafer 506 charged to a positive potential (FIG. 7, state 114). Note that in the second step S102, a positive DC voltage, or high-frequency power or square-wave power may be supplied to the electrode inside the sample stage 507 so that the average voltage or the self-bias value formed in the sample wafer 506 becomes positive.

[0053] The third step S103 is a step of moving the wafer 506, which is the sample, to a position spaced above the upper surface of the sample stage 507 after the supply of power to the electrodes has been stopped.

[0054] The fourth step S104 is a step of discharging the wafer 506, which is the sample, to the outside of the processing chamber 504 (FIG. 7, state 115).

[0055] Fig. 8 is a diagram showing an example of a time chart for the sample detachment method according to the first embodiment. Fig. 8 shows a time chart of each physical quantity and mechanism operation in the sample detachment method according to the first embodiment. For convenience, the time chart in Fig. 8 is shown in association with three process steps. The three process steps are a processing process, a dechucking process, and a sample transfer process.

[0056] The processing process refers to the steps in which plasma processing is performed by exposing the sample (here, wafer 506) to plasma. The dechucking process refers to the steps from detaching the sample after (having been subjected to) plasma processing from the sample stage 507 to immediately before transferring the sample. The sample transfer process refers to the steps in which the sample is transferred to the outside of the processing chamber 504 by the transfer arm 516.

[0057] In the time chart shown in Figure 8, (a) is the "sample surface voltage" and indicates the voltage of the surface of the sample wafer 506 exposed to the processing chamber 504. (b) is the "rare gas flow rate ratio" and indicates the ratio of the rare gas to the total gas flow rate supplied from the gas supply mechanism 518 into the processing chamber 504. (c) is the "rare gas filling level" and indicates the ratio of the rare gas to the total gas inside the processing chamber 504. (d) is the "microwave incident power" and indicates the supplied power of the electromagnetic waves for generating plasma. (e) is the "push-up pin operation" and indicates the operation of the pusher pin 515.

[0058] As shown in Figure 8, the time when the processing process ends and the dechucking process begins is defined as time 0. First, at time t1, the type of gas supplied from the gas supply mechanism 518 is limited to a rare gas. At time t2, the pusher pins are raised to dechuck the sample wafer 506 from the sample stage 507. Thereafter, at time t3, the pusher pins 515 are lowered, and the sample wafer 506 is placed back on the sample stage 507. The time when the measurement mechanism 522 confirms that the composition ratio of the rare gas in the processing chamber 504 is sufficient is defined as time t4, and the microwave power is set to 0 at time t6 (> t4). Here, at time t5, when t3 < t5 < t6 is satisfied, the variable DC power supplies 512 and 513 are controlled so that the potential of the surface of the sample wafer 506 becomes positive. At time t7 (>t6), the voltage application from the variable DC power supplies 512 and 513 is turned off, and at time t8 (>t7), the pusher pin 515 is raised again to move to the sample transport process.

[0059] In the time chart shown in FIG. 8, the time conditions to be met are as follows:

[0060] t1<t4<t6 (Formula 1) t2<t3<t5<t6 (Formula 2) t6<t7<t8 (Formula 3)

[0061] In the dechucking process, the procedure may differ from that shown in the time chart of FIG. 7 as long as the following three conditions are satisfied: the plasma is turned off only after the processing chamber 504 is sufficiently filled with the noble gas; a positive DC voltage is applied to the wafer 506 after the pusher pins 515 are lowered, and the plasma is turned off while the potential of the wafer 506 is controlled to be positive; and after the plasma is turned off, the DC voltage applied to the wafer 506 is turned off, and then the pusher pins 515 are raised again, and the wafer 506 is transported out of the processing chamber 504.

[0062] By adopting the above-described sample desorption method, the plasma is turned off when the processing chamber is filled with a rare gas, i.e., when no gas that generates negative ions is present in the processing chamber, and the charge of the foreign particles can be controlled to a positive value by the mechanism already described in Figure 3. Furthermore, because the potential of the sample wafer is controlled to a positive value, an electric field is generated from the wafer to the grounded conductor portion of the processing chamber wall. This electric field exerts an electrostatic force on the positively charged foreign particles in a direction away from the wafer, thereby suppressing their adhesion to the wafer.

[0063] This will be examined in more detail below. During the dechucking process, a positive DC potential is applied to the wafer before the plasma is turned off, i.e., when the foreign particle charge is negative. However, if there is an area in the processing chamber with a higher potential than the ground potential due to the nature of the plasma, a sheath is formed with that high-potential area as the reference potential. Therefore, negatively charged foreign particles are repelled by the wafer due to the sheath potential, and are not attracted to the wafer potential and do not adhere to the wafer.

[0064] Immediately after the plasma is turned off, negatively charged particles are exposed to a positive potential, but the sign of the charge reverses to positive before the particles adhere to the wafer, and the repulsive force of the electric field generated by the wafer prevents the particles from adhering to the wafer. The time from plasma turning off to the end of the afterglow can be estimated by the ion decay time. The ion decay time is expressed by the following formula:

[0065]

[0066] where L is the size of the processing chamber (m), μ ｉ＋ is the mobility of the ion (m ２ V －１ s －１ ), E ＤＣ is the electric field (V / m). The length of the treatment chamber is 0.1 m, μ ｉ＋ to 0.5 (m ２ V －１ s －１ ), E ＤＣ If τ is 100V / m, ｄｒ，ｉ＋ ~2 －３ It becomes s.

[0067] On the other hand, if we consider a quartz particle with a diameter of 200 nm and a charge of -10, and assume two forces, an electric field of 100 V / m and gravity, the particle will move in 2 －３ It moves by 0.054 mm during s.

[0068] For example, in a process such as etching a wafer with plasma, the size of the sheath is on the order of several mm to several cm, so charged particles in the plasma are also present at a height of several mm or more away from the wafer. Therefore, even if such particles are subjected to an electric field of 100 V / m during the afterglow, they will not adhere to the wafer by the time the afterglow ends. Furthermore, as described above, the charge of the particles changes from negative to positive during the afterglow, so the EDC assumed above acts as a repulsive force on the particles at least by the time the afterglow ends. Therefore, the method of this embodiment can prevent charged particles from adhering to the wafer.

[0069] At time t5 in Fig. 8, a positive DC voltage was applied to the wafer using a DC power supply for the electrostatic chuck. However, a different power supply may be used instead. Furthermore, the applied voltage may be other than DC as long as the time average is positive. For example, the applied voltage may be a sine wave to which a positive bias voltage is applied, or a square wave whose duty ratio is controlled so that the time average is positive.

[0070] According to the first embodiment, after wafer processing, while a gas such as an inert gas (rare gas) is supplied into the processing chamber to generate plasma, the wafer is raised to a position spaced above the upper surface of the sample stage, and then lowered and placed back on the upper surface of the sample stage. A predetermined power is then supplied to the sample stage or the electrode to generate a positive potential on the wafer, and the plasma is then extinguished. During the afterglow after the plasma is extinguished, the charge of foreign particles in the plasma changes from negative to positive, thereby suppressing adhesion of foreign particles to the wafer.

[0071] Second Embodiment A plasma processing apparatus according to a second embodiment of the present invention will be described. Note that, in this embodiment, the configurations different from those of the plasma processing apparatus shown in the first embodiment will be described.

[0072] Fig. 9 is a diagram showing an example of the configuration of a plasma processing apparatus according to embodiment 2. Fig. 9 shows a cross section of a main part of the plasma processing apparatus according to embodiment 2. The plasma processing apparatus 1A according to embodiment 2 is an ECR type plasma processing apparatus, as in embodiment 1, but may be a plasma processing apparatus other than an ECR type.

[0073] As shown in FIG. 9 , the plasma processing apparatus 1A according to the second embodiment further includes a control mechanism 530 in addition to the components of the plasma processing apparatus 1 described in the first embodiment. The control mechanism 530 is an example of a "control device" in the present application. The control mechanism 530 controls the magnetron 501, variable DC power supplies 512 and 513, the pusher pin 515, the gas supply mechanism 518, the valve 519, and the like, in response to a user's operation or in a fully or semi-automatic manner. For example, the control mechanism 530 controls the variable DC power supplies 512 and 513 and the magnetron 501 based on the measurement results of the measurement mechanism 522, and automatically executes the time chart shown in FIG. 8 . The measurement mechanism 522 is an example of a "detector" in the present application.

[0074] That is, the control mechanism 530 controls each part so that, after processing of the sample wafer 506 is completed, a first step is performed in which the sample wafer 506 is lifted to a position spaced above the upper surface of the sample stage 507 and re-mounted on the upper surface while plasma is being formed using the gas supplied into the processing chamber 504. The measurement mechanism 522 detects the amount of negative ions in the plasma formed in the processing chamber 504. After detecting in the first step S101 that the amount of negative ions in the plasma has become smaller than a predetermined value, the control mechanism 530 may control each part so that, while plasma is being formed, the sample wafer 506 is lifted to a position spaced above the upper surface of the sample stage 507 and re-mounted on the upper surface.

[0075] Furthermore, the control mechanism 530 controls each part so that a second step is performed in which, after the sample wafer 506 is placed on the upper surface of the sample stage 507 again, power is supplied to the electrodes inside the sample stage 507, i.e., the first electrode 510 and the second electrode 511, to charge the sample wafer 506 to a positive potential and then extinguish the plasma. Note that in the second step S102, the control mechanism 530 may control each part so that a positive DC voltage, or high-frequency power or square-wave power is supplied to the electrodes inside the sample stage 507 so that the average value of the voltage or the self-bias value formed in the sample wafer 506 becomes positive.

[0076] Furthermore, the control mechanism 530 controls each part so that a third step is performed in which the sample wafer 506 is moved to a position spaced above the upper surface of the sample stage 507 after the supply of power to the electrodes, i.e., the first electrode 510 and the second electrode 511, is stopped.

[0077] Furthermore, the control mechanism 530 controls each part, particularly the transfer arm 516 and the lid 517 , so that the wafer 506 is discharged out of the processing chamber 504 .

[0078] FIG. 10 is a diagram illustrating an example of the configuration of a control mechanism according to the second embodiment.

[0079] The control mechanism 530 is configured, for example, by a computer. As shown in Fig. 10 , the control mechanism 530 has a configuration in which, for example, a processor (CPU, MPU, etc.) 5301, a memory (ROM, RAM, etc.) 5302, a storage (HDD, SSD, etc.) 5303, an interface 5304, etc. are connected to each other so as to be able to communicate with each other via a communication bus 5305. The control mechanism 530 realizes various controls by, for example, executing a predetermined program PR stored in the storage 5303 or the memory 5302. In other words, the processor 5301 constituting the control mechanism 530 functions as a control unit that controls each unit by reading the stored program PR, expanding it in the memory 5302, and executing it.

[0080] When the plasma processing apparatus of the second embodiment is realized by using a system other than the ECR type plasma source, the control target of the control mechanism 530 is changed from the magnetron 501 to various plasma energy supply sources.

[0081] According to the plasma processing apparatus 1A of the second embodiment, similarly to the first embodiment, adhesion of foreign matter to the sample when the sample is released can be suppressed in the plasma processing apparatus.

[0082] According to these embodiments, in the plasma processing apparatus, when the sample is released, the charge amount of the foreign matter is controlled to be positive, and the Coulomb force caused by the positive DC voltage applied to the sample surface can prevent the foreign matter from adhering to the sample.

[0083] In addition, a program for causing one or more processors constituting a control mechanism in the plasma processing apparatus according to the embodiment to execute each process so that a sample detachment method based on the process flow performed in the plasma processing apparatus according to the embodiment is also an embodiment of the present invention. Furthermore, a tangible, non-transitory recording medium on which the program is recorded is also an embodiment of the present invention.

[0084] Various embodiments have been described above in detail. However, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments are detailed descriptions of the entire system in order to clearly explain the present invention, and the present invention is not necessarily limited to a system including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0085] 1, 1A... plasma processing apparatus, 501... magnetron, 502... waveguide, 503... dielectric window, 504... processing chamber, 505... solenoid coil, 506... wafer, 507... sample stage, 508... high frequency power supply, 509... matching box, 510... first electrode, 511... second electrode, 512, 513... variable DC power supply, 514... dielectric layer, 515... pusher pin, 516... transfer arm, 517... lid, 518... gas supply mechanism, 519... valve, 520... pump, 521... conducting wire, 522... measurement mechanism, 530... control mechanism

Claims

1. A sample detachment method for a plasma processing apparatus equipped with a processing chamber, disposed inside a vacuum vessel, in which plasma for processing a sample is generated, and a sample stage, disposed inside the processing chamber, on whose upper surface the sample is placed and held, comprising: a first step of, after processing of the sample is completed, lifting the sample to a position spaced above the upper surface of the sample stage and placing it again on the upper surface, with the plasma being formed using gas supplied into the processing chamber; a second step of, after the sample has been placed again on the upper surface of the sample stage, supplying power to an electrode inside the sample stage to charge the sample to a positive potential, and extinguishing the plasma; and a third step of, after stopping the supply of power to the electrode, moving the sample to a position spaced above the upper surface of the sample stage.

2. A sample detachment method according to claim 1, further comprising the step of discharging the sample to the outside of the processing chamber after the third step.

3. A sample detachment method according to claim 1 or 2, wherein the charge on the sample is reduced by the first step.

4. A sample desorption method according to claim 1 or 2, wherein the gas is a rare gas.

5. A sample detachment method as defined in claim 1 or claim 2, wherein, after it is detected in the first step that the amount of negative ions in the plasma has become smaller than a predetermined value, the sample is lifted to a position spaced above the upper surface of the sample stage and placed on the upper surface again while the plasma is still being formed.

6. A sample detachment method according to claim 1 or 2, wherein in the second step, a positive DC voltage, or high frequency power or square wave power is supplied to the electrode inside the sample stage so that the average value of the voltage or the self-bias value formed in the sample becomes positive.

7. A system comprising: a processing chamber disposed within a vacuum vessel in which plasma for processing a sample is generated; a sample stage disposed within the processing chamber and on whose upper surface the sample is placed and held; an electrode disposed within the sample stage; a plurality of pins, each of which is configured to be movable in the vertical direction of the sample stage through a through-hole formed in the upper surface of the sample stage, and which moves upward to move the sample to a position spaced apart from the upper surface of the sample stage and moves downward to be stored within the sample stage, thereby placing the sample on the upper surface of the sample stage; and a control device that controls the supply of gas into the processing chamber, the supply of power to the electrode, and the operation of the plurality of pins, wherein the control device performs a first step of, after the processing of the sample is completed, lifting the sample to a position spaced apart from the upper surface of the sample stage and placing it again on the upper surface, with the plasma formed using the gas supplied into the processing chamber; and a second step of, after the sample has been placed on the upper surface of the sample stage, supplying power to the electrode within the sample stage to extinguish the plasma in a state in which the sample is positively charged. and a third step of moving the sample to a position spaced above the upper surface of the sample stage after stopping the supply of power to the electrode.

8. The plasma processing apparatus according to claim 7, wherein the sample is discharged to the outside of the processing chamber after the third step.

9. A plasma processing apparatus according to claim 7 or 8, wherein the first step reduces the charge on the sample.

10. A plasma processing apparatus according to claim 7 or 8, wherein after the processing of the sample is completed, a rare gas is supplied into the processing chamber to form the plasma, and the first step is carried out in which the sample is lifted upward from the upper surface of the sample stage, separated from the upper surface, and placed on the upper surface again.

11. A plasma processing apparatus as defined in claim 7 or claim 8, further comprising a detector for detecting the amount of negative ions in the plasma formed in the processing chamber, wherein after detecting in the first step that the amount of negative ions in the plasma has become smaller than a predetermined value, the control device lifts the sample to a position spaced above the upper surface of the sample stage and places it again on the upper surface while the plasma is being formed.

12. A plasma processing apparatus according to claim 7 or 8, comprising a power supply that supplies a positive DC voltage, or high frequency power or square wave power to the electrode inside the sample stage in the second step so that the average voltage or the self-bias value formed in the sample becomes positive.

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