Plasma processing apparatus

Abstract

A plasma processing apparatus according to the present invention is characterized by comprising a processing chamber (104), a sample stage (103) which is provided in the processing chamber (104) and on which a wafer (150) to be processed is placed, a conveyance chamber (201) which is connected to the processing chamber (104), and a process valve (301) which is provided between the processing chamber (104) and the conveyance chamber (201), is driven vertically in a vertical direction, and has an opening / closing mechanism, wherein: during wafer conveyance between the processing chamber (104) and the conveyance chamber (201), pressure adjustment (801, 804, 808, 810) is performed in the two stages of the processing chamber (104) and the conveyance chamber (201) before and after opening (802, 809) of the process valve (301).

Description

Plasma processing equipment

[0001] The present invention relates to a plasma processing apparatus.

[0002] Semiconductor devices installed in electronic devices such as smartphones and PCs are becoming increasingly miniaturized and three-dimensional in order to meet the demands of lower power consumption, larger capacity, and higher performance. In the manufacturing process of these three-dimensional semiconductor devices, processing of high aspect ratio structures and three-dimensional structures is essential, and in addition to the conventional "anisotropic etching" that etches perpendicular to the wafer surface, "isotropic etching" technology and equipment that can etch laterally to the wafer surface are required.

[0003] A known plasma processing apparatus that performs isotropic etching with high precision is the plasma processing apparatus described in Patent Document 1, which is a conventional technique. Patent Document 1 describes a plasma processing apparatus and its operating method that controls the amount of etching to a level of several nanometers or less by forming a reaction layer through radical adsorption and desorbing the reaction layer through heating in order to achieve fine processing by isotropic etching.

[0004] The process involves transporting a wafer, the workpiece, into a processing chamber in a vacuum vessel using a transport mechanism and placing it on a sample stage equipped with an electrostatic adsorption function. Plasma is then generated in a discharge unit, and a gas supply plate equipped with a circularly arranged ion-shielding mechanism (ion-shielding plate) reduces ions and electrons, supplying only radicals to the wafer. Supplying only radicals to the wafer generates relatively highly reactive gas particles, such as neutral particles and radicals, which adsorb onto the surface of the film layer to be etched on the wafer, forming a reaction layer on the surface through a chemical reaction (adsorption process). Next, heat and kinetic energy are applied to the reaction layer, desorbing and removing it from the wafer surface (desorption process). This plasma processing system selectively etches the desired film by alternately repeating the adsorption and desorption processes at a predetermined cycle.

[0005] Wafers to be processed by plasma processing are transferred into or out of a processing chamber via a transfer chamber. To prevent foreign matter from adhering to the wafers and to prevent corrosion inside the transfer chamber, an inert gas or non-flammable N2 gas is introduced into the transfer chamber and processing chamber, and the pressure is adjusted to a desired level. For example, a pressure adjustment sequence described in Patent Document 2 is known, which adjusts the pressure in the transfer chamber and processing chamber.

[0006] In Patent Document 2, in order to prevent the process gas from flowing from the processing chamber to the transfer chamber, a non-flammable N ２ Gas is introduced and the pressure in the transfer chamber is adjusted to be equal to or higher than the pressure in the processing chamber. Next, the process valve (PV) is opened and the wafer is loaded onto the sample stage in the processing chamber. Finally, the process valve (PV) is closed and the dry etching process begins. This pressure adjustment sequence prevents corrosive gases remaining in the processing chamber as process gases from flowing into the transfer chamber.

[0007] JP 2015-185594 A JP 2007-27339 A

[0008] In the prior art of Patent Document 2, pressure adjustment during wafer transfer is performed using non-flammable N ２ This is done in one step before opening the process valve (PV) so that the pressure in the transfer chamber is equal to or higher than the pressure in the processing chamber using gas. Because a pressure difference occurs between the transfer chamber and the processing chamber, non-flammable N2 gas is introduced from the transfer chamber to the processing chamber when the process valve (PV) is open. ２ When the gas is large, the N ２ The gas may collide with the periphery of the process valve (PV) or the side wall of the processing chamber, scattering foreign matter into the processing chamber. Therefore, the pressure in the processing chamber is adjusted to a value equal to or slightly lower than the pressure in the transfer chamber.

[0009] N2 flows in from the transfer chamber due to the pressure difference between the transfer chamber and the processing chamber. ２ The gas flows from the process valve (PV) horizontally to the sample stage, and N ２ The gas is introduced into the processing chamber from above in a direction perpendicular to the sample stage and is exhausted from an exhaust hole below the sample stage.

[0010] First, reaction products are generated during etching and adhere to and accumulate on the inner walls of the processing chamber, including the area around the process valve (PV). Next, when the process valve (PV) is opened, N ２ The gas collides with the reaction products, which peel off from the walls of the processing chamber and become foreign matter floating in the processing chamber. Finally, the floating foreign matter that is not evacuated, especially the floating foreign matter generated near the process valve (PV), is removed by the N gas for adjusting the pressure of the processing chamber that flows vertically to the sample stage. ２ Collisions with gases and horizontal flow of N from the transfer chamber ２ There is a risk that the particles may collide with the gas and be scattered in the direction of the sample stage.

[0011] In particular, when the pressure in the processing chamber is equal to or slightly lower than the pressure in the transfer chamber, it is assumed that the scattered foreign matter is likely to float or accumulate in the processing chamber without being exhausted, and the N ２ There is a risk that the amount of foreign matter that collides with the gas and scatters toward the sample stage will increase. In other words, if the pressure adjustment for the processing chamber during wafer transfer is performed in one step, there is a risk that the amount of foreign matter will increase.

[0012] Foreign matter on the wafer can cause defects not only during dry etching but also in the processed shape, resulting in defects in semiconductor devices and lowering yields.

[0013] An object of the present invention is to reduce foreign particles on a wafer by adjusting the pressure in the processing chamber during wafer transfer in a plasma processing apparatus.

[0014] A plasma processing apparatus according to one embodiment of the present invention comprises a processing chamber, a sample stage provided within the processing chamber on which a wafer to be processed is placed, a transfer chamber connected to the processing chamber, and a process valve provided between the processing chamber and the transfer chamber and having an opening / closing mechanism that moves up and down in the vertical direction, and is characterized in that, when a wafer is transferred between the processing chamber and the transfer chamber, two-stage pressure adjustment is performed in the processing chamber and the transfer chamber before and after the process valve is opened.

[0015] By adjusting the pressure in two stages, the processing chamber and the transfer chamber, before and after the process valve (PV) is opened, the N ２Even if the gas collides with the periphery of the process valve (PV) or the side wall of the processing chamber, foreign matter is not scattered inside the processing chamber, and furthermore, accumulation of foreign matter inside the processing chamber is suppressed, thereby reducing the number of foreign matters on the wafer that are generated when the wafer is transported in the plasma device.

[0016] FIG. 1 is a longitudinal sectional view showing an outline of the configuration of a plasma processing apparatus according to an embodiment of the present invention. FIG. 2 is a plan view showing an outline of the configuration of a gas dispersion plate of the plasma processing apparatus according to an embodiment of the present invention. FIG. 3 is a schematic sectional view showing a flow of pressure adjustment gas when PVs of the transfer chamber and processing chamber of the plasma processing apparatus according to an embodiment of the present invention are closed. FIG. 4 is a schematic sectional view showing a flow of pressure adjustment gas when PVs of the transfer chamber and processing chamber of the plasma processing apparatus according to an embodiment of the present invention are open. FIG. 5 is a schematic sectional view showing a flow of pressure adjustment gas and foreign matter when PVs of the transfer chamber and processing chamber of the plasma processing apparatus according to an embodiment of the present invention are opened and closed. FIG. 6 is a flowchart showing one-stage pressure adjustment for wafer transfer in the plasma processing apparatus according to an embodiment of the present invention. ２ 1 is a flow chart showing a gas and wafer transfer sequence in a case where two-stage pressure adjustment is performed for wafer transfer in the plasma processing apparatus according to the embodiment of the present invention; 2 is a flow chart showing pressures in the transfer chamber and the processing chamber, opening and closing of the process valve (PV), and introduction of N into the processing chamber in a case where two-stage pressure adjustment is performed for wafer transfer in the plasma processing apparatus according to the embodiment of the present invention; ２ 1 is a diagram showing a gas and wafer transfer sequence; FIG. 2 is a cross-sectional view showing a schematic diagram of the amount of pressure adjustment gas introduced into the transfer chamber and processing chamber, the flow of the pressure adjustment gas introduced into and flowing into the processing chamber, and foreign matter in two-stage pressure adjustment during wafer transfer in the plasma processing apparatus according to an embodiment of the present invention; and FIG. 3 is a correlation diagram showing the pressure of the processing chamber, the amount of pressure adjustment gas introduced into the transfer chamber and processing chamber, and the number of foreign matter on the wafer in the second-stage pressure adjustment during wafer transfer in the plasma processing apparatus according to an embodiment of the present invention.

[0017] The configuration of a plasma processing apparatus 100 according to an embodiment of the present invention is shown in Fig. 1. Fig. 1 is a vertical cross-sectional view showing a schematic diagram of the plasma processing apparatus 100. The plasma processing apparatus 100 includes a vacuum vessel 101 and an exhaust opening at its bottom for reducing the pressure inside the vacuum vessel 101. The opening is connected to a vacuum pump 1121 through an exhaust pipe. A variable valve 1122 is disposed on the path between the opening and the vacuum pump 1121, and adjusts the flow rate or speed of the exhaust by increasing or decreasing the cross-sectional area of ​​the path or the opening.

[0018] The interior of the vacuum vessel 101 is broadly divided into a discharge section 102 at the top of the vacuum vessel and a processing chamber 104 at the bottom. The discharge section 102 and the processing chamber 104 are both cylindrical spaces, and their respective central axes are coaxial or located at a position that can be regarded as such. Between them is a circular gas dispersion plate 106, which is also located at a position that can be regarded as such and whose central axes coincide with each other. This separates the discharge section 102 and the processing chamber 104, and they communicate with each other through a plurality of through holes provided in the gas dispersion plate 106.

[0019] A cylindrical discharge tube 107 is installed around the outer periphery of the discharge unit 102. An ICP coil 108 is installed outside the discharge tube 107. The ICP coil 108 is connected to a high frequency power supply 110 via a matching box 109, and generates plasma 1011 by an ICP discharge method. The frequency of the high frequency power from the high frequency power supply 110 is assumed to be in the frequency band of several tens of megahertz, such as 13.56 MHz.

[0020] A top plate 1012 is installed above the discharge part 102. A gas dispersion plate is installed below the top plate 1012, and the process gas 1110 is introduced into the vacuum vessel 101 through the gas dispersion plate. A seal member such as an O-ring is sandwiched between the lower surface of the top plate 1012 and the upper surface of the upper end of the discharge tube 107. This provides an airtight seal between the inside of the discharge part 102 and the outside of the vacuum vessel 101.

[0021] The supply flow rate of the processing gas 1110 is adjusted by a mass flow controller 1114 installed for each gas type. As the processing gas 1110, a combustible gas, a combustion-supporting gas, a mixed gas thereof, or a mixed gas thereof diluted with an inert gas is used.

[0022] A sample stage 103 for placing a wafer thereon is disposed in a processing chamber 104 at the bottom of the vacuum vessel 101, at a position that coincides with or is considered to be close to the central axis of the discharge section 102 and the processing chamber 104. The processing gas 1110 passes through an exhaust hole 111 and is exhausted by a vacuum pump 1121.

[0023] An IR lamp unit 105 for heating the wafer and the inside of the processing chamber 104 is installed on the outer periphery between the sample stage 103 and the discharge part 102. The IR lamp unit 105 mainly comprises an IR lamp 1017, a reflector 1018 for reflecting IR light, and an IR light transmitting window 1019.

[0024] A circular lamp is used as the IR lamp 1017. The IR lamp 1017 emits light (herein referred to as IR light) mainly ranging from visible light to infrared light. The IR lamp 1017 is connected to a lamp power supply 1020 that supplies power, and a high frequency cut filter 1021 is disposed between the two to prevent noise from the high frequency power applied to the ICP coil 108 from entering the lamp power supply 1020.

[0025] The multiple IR lamps 1017 (three in the figure) located at each radius on a concentric circle are configured so that the amount of power supplied to each arc-shaped portion can be adjusted independently, allowing the radial distribution of the heating amount of the wafer to be adjusted.

[0026] A reflector 1018 is installed above the IR lamp 1017 to reflect the radially emitted IR light downward (toward the wafer placement direction). In addition, a quartz IR light transmission window 1019 is arranged to allow the IR light to pass from the bottom surface of the IR lamp unit 105 to the inner peripheral wall surface.

[0027] The space inside the inner periphery of the IR lamp unit 105 is a flow path through which plasma 1011 formed in the discharge part 102 arranged above flows, and a dielectric gas dispersion plate 106 is installed in this flow path. Here, the gas dispersion plate 106 will be described with reference to FIG. 2.

[0028] 2 is a plan view schematically illustrating the configuration of the gas dispersion plate 106. As shown in FIG. 2, the gas dispersion plate 106 has a plurality of through-holes arranged concentrically around the outer periphery of its surface. The gas dispersion plate 106 reduces ions and electrons generated by the plasma 1011 of the ICP discharge method and allows neutral particles and radicals of the gas to pass through the through-holes. The arrangement of the through-holes determines the distribution of radicals introduced into the processing chamber 104, thereby adjusting the distribution within the wafer surface to be processed.

[0029] Returning to FIG. 1 , in this embodiment, the gas dispersion plate 106 is also made of a transparent material such as quartz, and most of the IR light emitted from its outer periphery passes through the gas dispersion plate 106 without being blocked by it, and reaches the inside of the processing chamber 104.

[0030] The transfer chamber 201 has a structure including a process valve (PV) 301 that is movable up and down in the vertical direction and has an opening and closing mechanism between the transfer chamber 201 and the processing chamber 104. Gas is supplied to the transfer chamber 201 from a pressure adjusting valve 2110 for purging, and is exhausted to a vacuum pump 2121 of the transfer chamber 201.

[0031] N for adjusting the pressure in each chamber in accordance with the opening and closing operation of the process valves (PV) in the processing chamber 104 and the transfer chamber 201 during wafer transfer. ２ The gas flow is as follows. FIG. 3 shows the pressure adjusting gas (N ２ In the PV closed state 450, the process valve (PV) 301 provided between the processing chamber 104 and the transfer chamber 201 is closed, and the N ２ There is no gas conduction.

[0032] When the PV is closed 450, N in the processing gas 1110 ２The gas is introduced into the discharge unit 102 by controlling the flow rate with a mass flow controller 1114. ２ The gas is supplied to the processing chamber 104 through the through holes in the gas distribution plate 106. N ２ The gas passes through the exhaust hole 111 via the variable valve 1122 and the vacuum pump 1121 before being discharged.

[0033] The pressure inside the processing chamber 104 is adjusted by fully opening the variable valve 1122 and adjusting the pressure with N ２ The gas supply amount to the processing chamber 104 by the mass flow controller 1114 and the exhaust amount from the processing chamber 104 by the vacuum pump 1121 are adjusted.

[0034] On the other hand, the pressure inside the transfer chamber 201 is adjusted by N ２ The pressure is adjusted by adjusting the amount of gas introduced into the transfer chamber 201 through the gas pressure adjusting valve 2110 and the amount of gas discharged through the vacuum pump 2121 .

[0035] In FIG. 3, 411 is N introduced into the processing chamber 104. ２ The gas 412 is N exhausted from the processing chamber 104. ２ The gas 420 is N introduced into the transfer chamber 201. ２ The gas 422 is N exhausted from the transfer chamber 201. ２ gases, respectively.

[0036] In addition, the pressure in each chamber can be set to the desired pressure by controlling the mass flow controller 1114, variable valve 1122, vacuum pump 1121, pressure regulating valve 2110, and vacuum pump 2121 using a control device not shown, and the pressure in the processing chamber 104 is set to a value slightly lower than the pressure in the transfer chamber 201.

[0037] FIG. 4 shows the pressure adjusting gas (N) in the processing chamber 104 and the transfer chamber 201 when the PV is open 460 during wafer transfer. ２ 3. When the PV is opened 460, the N in the processing gas 1110 is ２ The gas is introduced into the discharge unit 102 by controlling the flow rate with a mass flow controller 1114. ２The gas is supplied to the processing chamber 104 through the through holes in the gas distribution plate 106. N ２ The gas passes through the exhaust hole 111 , the variable valve 1122 , and the vacuum pump 1121 to be exhausted.

[0038] When the PV is open 460, the variable valve 1122 is fully opened as in the case of the PV is closed 450, and the flow rate of the mass flow controller 1114 is set to the flow rate set in the case of the PV is closed 450.

[0039] On the other hand, pressure-regulating N introduced into the transfer chamber 201 from the pressure regulation valve 2110 ２ Since the process valve (PV) 301 provided between the processing chamber 104 and the transfer chamber 201 is open, a part of the gas flows from the transfer chamber 201, which has a higher pressure, to the processing chamber 104, which has a lower pressure. In FIG. 4, 421 indicates N 2 flowing from the transfer chamber 201 to the processing chamber 104. ２ The gas flowing in is shown. ２ The gas 421 passes through the exhaust hole 111 in the processing chamber 104 via the variable valve 1122 and the vacuum pump 1121 and is then exhausted.

[0040] 5A and 5B are schematic diagrams showing the behavior of reaction products generated after dry etching near the process valve (PV) when the PV is opened and closed. FIG. 5A is a schematic diagram showing the state in which the process valve (PV) 301 is closed after dry etching. After dry etching, the process valve (PV) 301 is closed, and reaction products 490 are generated on the processing chamber 104 side. N introduced into the processing chamber 104 ２ Gas 411 and N introduced into the transfer chamber 201 ２ The gas 420 is exhausted to the exhaust side of each chamber, and the direction of the flow is perpendicular to the sample stage 103 .

[0041] 5B is a schematic diagram showing a state in which the process valve (PV) 301 is opened to transfer the wafer 150 from the sample stage 103 to the transfer chamber 201 after the dry etching is completed. Before the process valve (PV) 301 is opened, the pressure in the transfer chamber 201 is adjusted to be higher than the pressure in the processing chamber 104. When the process valve (PV) 301 is opened, the N２ A part of the gas 420 flows from the transfer chamber 201 into the processing chamber 104, which has a low pressure, and is exhausted to the exhaust side of the processing chamber 104. ２ The flow direction of the gas 421 is horizontal to the sample stage 103, and collides with the reaction product 490 near the process valve (PV) 301, generating floating foreign matter 400. ２ The flow direction of the gas 411 remains perpendicular to the sample stage 103 and is exhausted to the exhaust side of the processing chamber 104 .

[0042] FIG. 5C shows the pressure adjusting N 2 gas in the state where the process valve (PV) 301 is opened after the dry etching is completed. ２ 1 shows a schematic diagram of the gas flow direction. ２ The flow of the gas 411 is perpendicular to the sample stage 103, and the N ２ The flow of the gas 421 is horizontal to the sample stage 103. When the process valve (PV) 301 is opened, the N ２ The gas 421 collides with and separates from reaction products 490 adhering to the inner wall of the processing chamber 104 , and these products float within the processing chamber 104 as foreign matter 400 .

[0043] In particular, the foreign matter 400 floating near the process valve (PV) 301 is caused by N ２ The foreign matter 400 collides with the gas 421 and is scattered in the direction of the sample stage 103 in the processing chamber 104. The foreign matter 400 scattered in the direction of the sample stage 103 is irradiated with N ２ N flowing in from the horizontal direction to the gas 411 and the sample stage 103 ２ The gas collides with the gas 421, scattering onto the sample stage 103 and adhering to the wafer 150. In this embodiment, the wafer is transferred from the transfer chamber to the processing chamber, subjected to the dry etching process, and the pressure is adjusted in one step during the wafer transfer from the processing chamber to the transfer chamber. ２The gas and wafer transfer sequences are shown in FIG.

[0044] 6 and 7, the wafer 150 is transferred from the transfer chamber 201 to the sample stage 103 of the processing chamber 104 (step 603), and after the dry etching process (step 606), the wafer 150 is transferred from the sample stage 103 to the transfer chamber 201 (step 609). The pressures in the transfer chamber 201 and the processing chamber 104 are adjusted (steps 601 and 607) before the wafer transfer (steps 603 and 609) and before the PV is opened (steps 602 and 608).

[0045] First, in step 601, N ２ The flow rate of the gas 420 is set to 0.18 L / min, and the pressure inside the transfer chamber 201 is adjusted to 50 Pa. ２ The flow rate of the gas 411 is set to 4.36 L / min, and the pressure inside the processing chamber 104 is adjusted to 49 Pa. In the pressure adjustment in step 601, it is desirable to adjust the pressure inside the processing chamber 104 to a value equal to or slightly lower than the pressure inside the transfer chamber 201.

[0046] Next, in step 602, the process valve (PV) 301 is opened, and then in step 603, the wafer 150 is loaded from the transfer chamber 201 onto the sample stage 103 of the processing chamber 104. After the loading of the wafer 150 is completed, in step 604, the process valve (PV) 301 is closed. Thereafter, in step 605, N introduced into the processing chamber 104 is ２ The introduction amount of the gas 411 was set to 0 L / min, and the N ２ After venting the gases and reducing the pressure, wafer 150 is subjected to a dry etching process in step 606 .

[0047] After the dry etching process of the wafer 150 is completed, in step 607, N ２ The flow rate of the gas 420 is set to 0.2 L / min, and the pressure inside the transfer chamber 201 is adjusted to 50 Pa. ２The flow rate of the gas 411 is set to 4.36 L / min, and the pressure inside the processing chamber 104 is adjusted to 49 Pa. In the pressure adjustment in step 607, it is desirable to adjust the pressure inside the processing chamber 104 to a value equal to or slightly lower than the pressure inside the transfer chamber 201.

[0048] Next, in step 608, the process valve (PV) 301 is opened, and then in step 609, the wafer 150 is transferred from the sample stage 103 of the processing chamber 104 to the transfer chamber 201. After the wafer 150 has been transferred out, in step 610, the process valve (PV) 301 is closed. Thereafter, in step 611, N introduced into the processing chamber 104 is ２ The introduction amount of the gas 411 was set to 0 L / min, and the N ２ The gas is evacuated to reduce pressure.

[0049] In this embodiment, when a wafer is transferred from the transfer chamber to the processing chamber, subjected to a dry etching process, and a single stage of pressure adjustment is performed during transfer from the processing chamber to the transfer chamber, the number of foreign particles on the wafer is measured. As a result, the number of foreign particles is 84, which is a large number of foreign particles on the wafer.

[0050] Next, a flow chart of the case where the pressure in the processing chamber is adjusted in two stages during wafer transfer in this embodiment is shown in FIG. 8. The flow chart shows the pressures in the transfer chamber and the processing chamber, the opening and closing of the process valve (PV), and the pressure in the processing chamber. ２ The gas and wafer transfer sequences are shown in FIG.

[0051] 8 and 9, similarly to Figures 6 and 7, the wafer 150 is transferred from the transfer chamber 201 to the sample stage 103 of the processing chamber 104 (step 803), and after the dry etching process (step 807), the wafer 150 is transferred from the sample stage 103 to the transfer chamber 201. In Figures 6 and 7, the pressure adjustment of the transfer chamber 201 and the processing chamber 104 (steps 601 and 607) is a one-stage pressure adjustment performed only before the PV is opened (steps 602 and 608), but in Figures 8 and 9, the pressure adjustment is a two-stage pressure adjustment performed in which the pressure adjustment (1) (steps 801 and 808) of the transfer chamber 201 and the processing chamber 104 is performed before the PV is opened (steps 802 and 809) and also the pressure adjustment (2) (steps 804 and 810) of the transfer chamber 201 and the processing chamber 104 is performed after the PV is opened (steps 802 and 809).

[0052] First, in the first stage of pressure adjustment (550) of the transfer chamber 201 and the processing chamber 104 in step 801, N ２ The flow rate of the gas 420 is set to 0.18 L / min, and the pressure inside the transfer chamber 201 is adjusted to 50 Pa. ２ The flow rate of the gas 411 is set to 4.36 L / min, and the pressure inside the processing chamber 104 is adjusted to 49 Pa. In this first stage of pressure adjustment (550) in step 801, it is desirable to adjust the pressure inside the processing chamber 104 to a value equal to or slightly lower than the pressure inside the transfer chamber 201.

[0053] Next, in step 802 , the process valve (PV) 301 is opened, and then in step 803 , the wafer 150 is carried from the transfer chamber 201 onto the sample stage 103 in the processing chamber 104 .

[0054] After the wafer 150 has been loaded, a second stage of pressure adjustment (560) is performed in step 804. In this second stage of pressure adjustment (560), the N 2 introduced into the processing chamber 104 is ２ The flow rate (x L / min) of the gas 411 is set to be less than the flow rate (4.36 L / min) in the first stage, and the pressure inside the processing chamber 104 is adjusted to less than 49 Pa (x Pa), which is lower than in the first stage.

[0055] After the second stage pressure adjustment is performed and maintained for 5 seconds or more, the process valve (PV) is closed in step 805. Then, in step 806, N ２ The introduction amount of the gas 411 was set to 0 L / min, and the N ２ After venting the gases and reducing the pressure, wafer 150 is subjected to a dry etching process in step 807 .

[0056] After the dry etching process of the wafer 150 is completed, in the first stage of pressure adjustment (550) of step 808, N introduced into the transfer chamber 201 ２ The flow rate of the gas 420 is set to 0.2 L / min, and the pressure inside the transfer chamber 201 is adjusted to 50 Pa. ２The flow rate of the gas 411 is set to 4.36 L / min, and the pressure inside the processing chamber 104 is adjusted to 49 Pa. In this first stage of pressure adjustment (550) in step 808, it is desirable to adjust the pressure inside the processing chamber 104 to a value equal to or slightly lower than the pressure inside the transfer chamber 201.

[0057] Next, in step 809, the process valve (PV) 301 is opened, and then, in step 810, the second stage of pressure adjustment (560) is performed. In this second stage of pressure adjustment (560), the N 2 introduced into the processing chamber 104 is ２ The flow rate (x L / min) of the gas 411 is set to be less than the flow rate (4.36 L / min) in the first stage, and the pressure inside the processing chamber 104 is adjusted to less than 49 Pa (x Pa), which is lower than in the first stage.

[0058] After the second stage pressure adjustment is performed and maintained for 5 seconds or more, in step 811, the wafer 150 is transferred from the sample stage 103 of the processing chamber 104 to the transfer chamber 201. After the wafer 150 has been transferred out, in step 812, the process valve (PV) 301 is closed 404. Thereafter, in step 813, N introduced into the processing chamber 104 is ２ The introduction amount of the gas 411 was set to 0 L / min, and the N ２ The gas is evacuated to reduce pressure.

[0059] A mechanism for reducing foreign matter generated during wafer transfer in a two-stage pressure adjustment sequence in the plasma etching apparatus of the present invention will be described. In the first stage of pressure adjustment before the PV is opened (steps 802 and 809) in the two-stage pressure adjustment sequence during wafer transfer, the pressure in the transfer chamber 201 is 50 Pa and the pressure in the processing chamber 104 is 49 Pa, as shown in Figures 8 and 9. N introduced into the transfer chamber 201 at the timing when the process valve (PV) 301 is opened is ２ A portion of the gas 420 flows from the transfer chamber 201 into the processing chamber 104 .

[0060] When the process valve (PV) 301 is opened, the pressure in the processing chamber 104 is 49 Pa. ２ The number of molecules increases and the molecular density is high. ２ Gas 421 or N introduced into the processing chamber 104 ２The distance until the collision with the molecules of the gas 411 or particles of foreign matter or the like is shortened, and the mean free path λ can be shortened.

[0061] The mean free path λ is expressed as λ = v × t (λ: mean free path [m], v: gas flow velocity [m / s], t: mean free time [s]). ２ The kinetic energy K when the gas and foreign matter collide is K = (m × v ２ ) / 2 (K: kinetic energy [J], m: mass [kg], v: gas flow velocity [m / s]).

[0062] The flow velocity v increases in proportion to the mean free path λ. In the first stage of pressure adjustment before the PV opening (steps 802 and 809), the pressure in the transfer chamber 201 is set to 50 Pa and the pressure in the processing chamber 104 is set to 49 Pa. ２ Gas N ２ When the process valve (PV) 301 is opened, the reaction product 490 near the process valve (PV) 301 flows from the transfer chamber 201 to the processing chamber 104 in a direction horizontal to the sample stage 103. ２ When the N ions collide with the gas 421, the mean free path λ becomes shorter. ２ The kinetic energy K of the floating foreign matter 400 that collides with the gas 421 is reduced, and the foreign matter 400 can be prevented from scattering toward the sample stage 103 when the PV is opened (steps 802 and 809).

[0063] As shown in FIGS. 8 and 9, in the second stage of pressure adjustment after the PV is opened (steps 802 and 809) in the two-stage pressure adjustment sequence during wafer transfer, N ２ The amount of gas 411 introduced (x L / min) is set to be less than the amount introduced in the first stage (4.36 L / min), and the pressure in the processing chamber 104 is adjusted to less than 49 Pa (x Pa), which is lower than the amount introduced in the first stage. By adjusting the pressure in the second stage, the pressure in the processing chamber 104 is reduced to less than 49 Pa (x Pa), which generates a pressure difference between the first and second stages.

[0064] When the PV is opened (steps 802 and 809), the foreign matter 400 floating in the processing chamber 104 is removed by N ２ In the second stage of pressure adjustment after the PV is opened (steps 802 and 809), the N ２ The pressure in the processing chamber 104 is adjusted to less than 49 Pa by reducing the amount of gas 411 introduced. ２ The number of molecules is reduced and the molecular density is low. ２ Gas 411 N ２ The distance until the collision with molecules or particles such as foreign matter becomes longer, and the mean free path λ becomes longer. ２ The kinetic energy K of the floating foreign matter 400 that collides with the gas 411 increases, and the floating foreign matter 400 that is floating when the PV is opened (steps 802 and 809) is discharged in the exhaust direction before adhering to the wafer 150, thereby reducing the amount of foreign matter 400 on the wafer 150.

[0065] Next, an outline of the amount of pressure adjusting gas (N2 gas) introduced during the second stage of wafer transfer having a sequence for adjusting the pressure inside the processing chamber in two stages and a method for reducing foreign matter will be described. Figure 10 shows the amount of pressure adjusting gas (420, 411) introduced into the transfer chamber 201 and the processing chamber 104 during the two-stage pressure adjustment during wafer transfer, and the amount of pressure adjusting gas (N2 gas) introduced and flowing into the processing chamber 104 during the second stage pressure adjustment. ２ The foreign matter 400 was scattered when the PV was opened (steps 802 and 809), and was introduced into the processing chamber 104. ２ The flow of the gas 411 is perpendicular to the sample stage 103, and the N ２ The flow of the gas 421 is horizontal to the sample stage 103 .

[0066] In FIG. 10, 420-1 is the N introduced into the transfer chamber 201 by the first stage pressure adjustment. ２ The amount of gas introduced is N 411-1, which is introduced into the processing chamber 104 by the first stage pressure adjustment. ２ The amount of gas introduced is controlled by the second stage pressure adjustment.２ The amount of gas introduced is controlled by the second stage pressure adjustment. ２ The amount of gas introduced is 411-2 / 420-2, which is N introduced into the transfer chamber 201 at the second stage of pressure adjustment. ２ N introduced into the processing chamber 104 for gas 420-2 ２ The ratio of the amount of gas 411-1 introduced to the amount of gas 411-2 introduced is also shown.

[0067] Condition (A) in FIG. 10 indicates the amount of N introduced into the transfer chamber 201 at the first stage of pressure adjustment. ２ N introduced into the processing chamber 104 for gas 420-1 ２ The ratio of the amount of gas 411-1 introduced is set to 411-1 / 420-1≧24, and N ２ N introduced into the processing chamber 104 for gas 420-2 ２ The ratio of the amount of gas 411-2 introduced is set to 411-2 / 420-2<3.5, and the pressure in the processing chamber 104 is in the region of p<18 Pa. The foreign matter 400 floating when the PV is opened (steps 802 and 809) is generated by the large pressure difference between the first and second processing chambers 104 and the N introduced into the processing chamber 104. ２ The amount of gas 411-2 introduced is also reduced, so that the amount of N 2 flowing from the transfer chamber 201 into the processing chamber 104 is reduced. ２ The particles collide with the gas 421 and are scattered in the direction of the sample stage 103 and are adsorbed onto the wafer 150, increasing the amount of foreign matter 400 on the wafer 150.

[0068] Condition (B) in FIG. 10 is the N introduced into the transfer chamber 201 at the first stage of pressure adjustment. ２ N introduced into the processing chamber 104 for gas 420-1 ２ The ratio of the amount of gas 411-1 introduced is set to 411-1 / 420-1≧24, and N ２ N introduced into the processing chamber 104 for gas 420-2 ２ The ratio of the amount of gas 411-2 introduced is set to 3.5≦411-2 / 420-2≦11.5, and the pressure p of the processing chamber 104 is in the range of 18 Pa to 33 Pa. The foreign matter 400 floating when the PV is opened (steps 802 and 809) is introduced into the processing chamber 104 due to the pressure difference between the first and second stages. ２The gas collides with the gas 411-2 and is discharged in the exhaust direction from the sample stage 103.

[0069] Condition (C) in FIG. 10 is the N introduced into the transfer chamber 201 in the first stage of pressure adjustment. ２ N introduced into the processing chamber 104 for gas 420-1 ２ The ratio of the amount of gas 411-1 introduced is set to 411-1 / 420-1≧24, and N ２ N introduced into the processing chamber 104 for gas 420-2 ２ The ratio of the amount of gas 411-2 introduced is set to 411-2 / 420-2>11.5, and the pressure in the processing chamber 104 is in the region of p>33 Pa. When the PV is opened (steps 802 and 809), the floating foreign matter 400 is not exhausted because the pressure difference in the processing chamber 104 between the first and second stages is small. ２ The particles collide with the gas 411-2, are scattered in the direction of the sample stage 103, and are adsorbed onto the wafer 150, increasing the amount of foreign matter 400 on the wafer 150.

[0070] 11 shows the measurement results of the number of foreign particles on a wafer in the second stage pressure adjustment during wafer transfer in the plasma processing apparatus of the present invention described in FIG. 10. A graph 600 shown in FIG. 11 shows the number of foreign particles on a wafer in the first stage pressure adjustment. ２ N introduced into the processing chamber 104 for gas 420-1 ２ The introduction rate ratio of the gas 411-1 is set to 411-1 / 420-1≧24, and the pressure of the processing chamber 104 in the second stage pressure adjustment and the N ２ The amount of gas introduced and the number of foreign particles 400 on the wafer 150 are shown.

[0071] Under the condition (A) of FIG. 11, the floating foreign matter 400 when the PV is opened (steps 802 and 809) is generated due to the large pressure difference between the first and second processing chambers 104 and the N introduced into the processing chamber 104. ２ The amount of gas 411-2 introduced also decreases, causing it to collide with the N2 gas 421 flowing from the transfer chamber 201 into the processing chamber 104, scattering in the direction of the sample stage 103 and adsorbing to the wafer 150, increasing the number of foreign particles on the wafer 150.

[0072] Under the condition (B) of FIG. 11, N introduced into the transfer chamber 201 under the first stage pressure adjustment ２ N introduced into the processing chamber 104 for gas 420-1 ２ The ratio of the amount of gas 411-1 introduced is set to 411-1 / 420-1≧24, and N ２ N introduced into the processing chamber 104 for gas 420-2 ２ The ratio of the amount of gas 411-2 introduced is set to 3.5≦411-2 / 420-2≦11.5, and the pressure p of the processing chamber 104 is in the range of 18 Pa to 33 Pa. Under this condition (B), the floating foreign matter 400 collides with the processing chamber N2i 411, and a pressure difference occurs in the processing chamber 104 between the first stage and the second stage. ２ The gas 411-2 collides with the gas 411-2 and is discharged in the exhaust direction from the sample stage 103, and the number of foreign particles on the wafer 150 becomes 20 or less.

[0073] Under the condition (C) of FIG. 11, N introduced into the transfer chamber 201 under the first stage pressure adjustment ２ N introduced into the processing chamber 104 for gas 420-1 ２ The ratio of the amount of gas 411-1 introduced is set to 411-1 / 420-1≧24, and N ２ N introduced into the processing chamber 104 for gas 420-2 ２ The ratio of the amount of gas 411-2 introduced is 411-2 / 420-2>11.5, and the pressure in the processing chamber 104 is in the region of p>33 Pa. Under this condition (C), the floating foreign matter 400 is not discharged in the exhaust direction because the pressure difference between the first and second processing chambers 104 is small, and is introduced into the processing chamber 104 by N ２ The particles collide with the gas 411-2, are scattered in the direction of the sample stage 103, and are adsorbed onto the wafer 150, increasing the number of particles on the wafer 150.

[0074] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those 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, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is also possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0075] 100... plasma processing apparatus, 101... vacuum vessel, 102... discharge unit, 103... sample stage, 104... processing chamber, 105... IR lamp unit, 106... gas dispersion plate, 107... discharge tube, 108... ICP coil, 109... matching box, 110... high frequency power supply, 111... exhaust hole, 150... wafer, 201... transfer chamber, 301... process valve (PV), 1011... plasma, 1012... top plate, 1017... IR lamp, 1018... reflector, 1019... IR light transmission window, 1020... lamp power supply, 1021... high frequency cut filter, 1110... processing gas, 1114... mass flow controller, 1121... vacuum pump, 1122... variable valve, 2110... pressure adjustment valve, 2121... vacuum pump, 400... foreign matter, 411, 412, 420, 421, 422...N ２ Gas, 450...when PV is closed, 460...when PV is open, 490...reaction products.

Claims

1. A plasma processing apparatus having a processing chamber, a sample stage provided within the processing chamber on which a wafer to be processed is placed, a transfer chamber connected to the processing chamber, and a process valve provided between the processing chamber and the transfer chamber and having an opening and closing mechanism that moves up and down in the vertical direction, wherein, when a wafer is transferred between the processing chamber and the transfer chamber, the pressure in the processing chamber and the transfer chamber is adjusted in two stages before and after the process valve is opened.

2. The plasma processing apparatus according to claim 1, characterized in that in a first stage of pressure adjustment before the process valve is opened, the transfer chamber is set to a first pressure and the processing chamber pressure is set to a second pressure lower than the first pressure, and in a second stage of pressure adjustment after the process valve is opened, the processing chamber pressure is set to a third pressure lower than the second pressure set in the first stage of pressure adjustment.

3. The plasma processing apparatus according to claim 2, wherein the amount of pressure adjusting gas introduced into the processing chamber during the second stage pressure adjustment is made smaller than the amount introduced during the first stage pressure adjustment.

4. The plasma processing apparatus according to claim 3, characterized in that, when a wafer is transferred from the transfer chamber to the processing chamber, the first stage pressure adjustment is performed, then the process valve is opened, the wafer is transferred from the transfer chamber onto the sample stage, then the second stage pressure adjustment is performed, and the process valve is closed after waiting for 5 seconds or more.

5. The plasma processing apparatus of claim 3, characterized in that, when transferring a wafer from the processing chamber to the transfer chamber, the process valve is opened after the first stage pressure adjustment, the second stage pressure adjustment is performed, and the wafer is transferred from the sample stage to the transfer chamber after waiting for 5 seconds or more, and then the process valve is closed.

6. A plasma processing apparatus as described in claim 3, characterized in that the ratio of the amount of pressure adjustment gas introduced into the processing chamber to the amount of pressure adjustment gas introduced into the transfer chamber is 24 or more during the first stage pressure adjustment, and 3.5 or more and 11.5 or less during the second stage pressure adjustment, and the third pressure in the processing chamber during the second stage pressure adjustment is in the range of 18 Pa to 33 Pa.

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