JP2016136553A - Plasma processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing apparatus that is enhanced in yield.SOLUTION: A plasma processing apparatus comprises a processing chamber which is disposed in a vacuum container and reduced in internal pressure, a plate member formed of dielectric material which constitutes an upper portion of the vacuum container and transmits therethrough electric field to be supplied into the processing chamber, a sample table which is disposed at a lower portion in the processing chamber and on which a wafer as a processing target is mounted, a shower plate formed of a dielectric material which is disposed below the plate member and above the upper surface of the sample table so as to confront the sample table, constitutes a ceiling face of the processing chamber and has a through-hole for introducing processing gas used for plasma formation to process the wafer into the processing chamber, and a gas supply line for supplying rare gas into the gap between the shower plate and the plate member to heat at least one of the shower plate and the plate member.SELECTED DRAWING: Figure 1

Description

The present invention relates to a plasma processing apparatus, and more particularly to a plasma processing apparatus suitable for performing surface treatment of a semiconductor substrate or the like using plasma and a surface treatment of a semiconductor substrate or the like using the plasma processing apparatus. The present invention relates to a plasma processing method.

Due to miniaturization of recent semiconductor elements, higher accuracy in dimensional accuracy, that is, CD (Critical Dimension) accuracy is required for an etching process for transferring a mask formed by lithography to a lower layer film. In mass production sites, in addition to high CD controllability, ensuring CD reproducibility is an important issue.

In general, factors that cause the CD to fluctuate in the etching process include reaction products generated from the material to be processed on the inner wall of the etching process, consumption of the etching process chamber member due to long-term use, temperature of the etching process chamber member, and the like. And the like, the adhesion probability of radicals to the inner wall of the processing chamber changes, and the plasma state that affects the etching performance changes.

As a technique for suppressing the temperature fluctuation of the etching processing chamber member, a technique disclosed in Japanese Patent Laid-Open No. 2012-49393 (Patent Document 1) has been known. In this prior art, hot air (air) is blown on the top surface of the dielectric window (quartz plate) to heat the dielectric window, and the temperature of the dielectric window is kept constant. A plasma processing apparatus capable of suppressing temperature fluctuations of a flowing process gas is disclosed.

JP 2012-49393 A

In the above-described conventional technique, problems have arisen because the following points are not sufficiently considered. That is, it is effective to suppress the temperature fluctuation of both the quartz plate and the shower plate in order to suppress the temperature fluctuation of the process gas.

However, in the case of Patent Document 1, since the dielectric window and the shower plate are insulated from each other by vacuum, there is a problem that even if only the dielectric window is heated, the heat is not easily transmitted to the shower plate. Further, since there is no means for directly heating the shower plate, the problem that the temperature of the process gas fluctuates due to the fluctuation of the temperature of the shower plate has been insufficiently considered.

In a plasma processing apparatus such as that disclosed in Patent Document 1, generally, ceramics such as quartz and alumina are used as the material of the dielectric window constituting the upper surface of the etching chamber from the viewpoint of plasma resistance and dielectric constant. However, since such a material has low thermal conductivity, the dielectric window member alone tends to have non-uniform temperature. For example, a distribution in which the temperature at the center of the dielectric window is high and the temperature at the outer periphery is low is likely to occur. It is known.

According to the study by the present inventors, in an inductively coupled plasma etching apparatus having a structure in which the outer periphery of an alumina dielectric window 130 as shown in FIG. The phenomenon that the dielectric window 130 is damaged when etching is performed under high etching conditions has been confirmed. In order to clarify this phenomenon, the temperature of the dielectric window 130 when there is plasma heat input was examined.

FIG. 5 shows a temperature distribution generated in the plane of the dielectric window 130 when plasma heat input equivalent to 500 W is applied to the dielectric window 130 made of alumina. Here, the horizontal axis in the figure indicates the radius of the dielectric window 130, and the vertical axis indicates the temperature of the dielectric window 130. Note that 0 mm on the horizontal axis indicates the center of the dielectric window 130, and 200 mm indicates the outermost periphery of the dielectric window 130.

According to the above result, when high-power plasma heat input is applied to the dielectric window 130, the temperature at the center of the dielectric window 130 is high, and the temperature gradually decreases as it approaches the outer periphery of the dielectric window 130. It has been found that such a temperature distribution has occurred in the dielectric window 130.

In this case, the dielectric window made of alumina is used in the above result, but in Patent Document 1, quartz is used as the material of the dielectric window. For this reason, quartz has a lower thermal conductivity than alumina (thermal conductivity quartz: 1.5 W / m · k, alumina: 24.0 W / m · k). It can be expected that the temperature distribution tends to occur more easily by itself.

Furthermore, in the recent semiconductor industry, the development of plasma processing equipment compatible with 450 mm wafers has been started from the viewpoint of productivity improvement and cost reduction, and the main parts constituting the plasma processing chamber as the wafer diameter increases. The large diameter is inevitable. For this reason, in the 450 mm wafer compatible plasma apparatus, due to the increase in the diameter of the dielectric window and the shower plate, the temperature non-uniformity in the direction of the surface or the direction of the surface of the substrate-like sample such as a semiconductor wafer and the influence thereof are affected. It is expected that the problem of the processing and the resulting processed shape will be increased, and the yield of the processing will be impaired.

Accordingly, an object of the present invention is to provide a plasma processing apparatus capable of improving the yield.

The object is to provide a processing chamber disposed inside the vacuum vessel, the inside of which is decompressed, a dielectric plate member that constitutes the upper portion of the vacuum vessel and transmits an electric field supplied to the processing chamber, and the processing chamber A sample stage placed under the substrate and on which a wafer to be processed is placed, and a dielectric shower which is arranged below the plate member and above the upper surface of the sample stage to face the sample stage and constitutes the ceiling surface of the processing chamber A shower plate having a through hole through which a processing gas used to form plasma for processing the wafer is introduced into the processing chamber, and a gap between the shower plate and the plate member. This is achieved by a plasma processing apparatus provided with a gas supply line for supplying a rare gas for heating at least one of them.

The present invention suppresses temperature fluctuations of the dielectric window and the shower plate alone and suppresses temperature fluctuations of the process gas, thereby suppressing CD fluctuations and enabling more stable and stable plasma processing. An apparatus can be provided.

It is a longitudinal cross-sectional view which shows the outline of the lecturer of the plasma processing apparatus which concerns on the Example of this invention typically. It is a figure which expands and shows typically the structure of the part which introduce | transduces process gas into a process chamber in the plasma processing apparatus which concerns on the Example shown in FIG. It is a figure which expands and shows typically the structure of the part which introduce | transduces process gas into a process chamber in the plasma processing apparatus which concerns on the modification of the Example shown in FIG. It is a figure which expands and shows typically the structure of the part which introduce | transduces process gas into a process chamber in the plasma processing apparatus which concerns on another modification of the Example shown in FIG. It is a graph which shows the example of the temperature distribution which generate | occur | produces in the surface of a dielectric material window when the plasma heat input is given to the dielectric material window.

Embodiments of the present invention will be described with reference to the drawings.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view schematically showing an outline of an instructor of a plasma processing apparatus according to an embodiment of the present invention. In particular, in this embodiment, an ECR type microwave plasma etching apparatus will be described.

In the plasma processing apparatus of this example, a dielectric window 106 made of a member capable of transmitting a microwave electric field such as quartz having a disk shape is formed on the upper part of a vacuum vessel 101 whose cylindrical upper part is opened. The inside and outside are hermetically sealed by a seal member such as an O-ring that is placed and sandwiched between the lower surface of the outer peripheral edge portion and the upper end surface of the cylindrical portion of the vacuum vessel 101. Below the dielectric window 101 is a circular shape having a ceiling surface of the processing chamber 107 in the vacuum vessel 101 and having a plurality of through holes arranged in the center for introducing processing gas into the processing chamber 107. The provided shower plate 105 is arranged with a gap between it and the dielectric window 106.

A processing gas is supplied to the gap between the shower plate 105 and the dielectric window 106 via the valves 118 and 119 from a gas supply device 108 disposed outside the vacuum vessel 101 and connected by a gas pipe line. The processing gas diffused in the gap is introduced into the processing chamber 107 from above through a plurality of through holes. Further, a vacuum exhaust port is disposed on the bottom surface of the processing chamber 107, and is connected to a vacuum exhaust device 109 having a vacuum pump such as a turbo molecular pump disposed below the vacuum vessel 101 in communication with the vacuum exhaust port. .

Since the plasma processing apparatus of this example generates plasma by exciting the processing gas introduced into the processing chamber 107, a microwave electric field is supplied to the processing chamber 107. In order to transmit this electric field, a waveguide 110 through which the electric field propagates is disposed above the dielectric window 106. The waveguide 110 of the present example is a cylindrical waveguide having a circular cross section extending in the vertical direction above the dielectric window 110 and a rectangular cross section in which one end side of the cylindrical waveguide is connected at the upper end. And a rectangular waveguide.

The electric field supplied to the inside of the waveguide 110 is oscillated from the first high-frequency power source 103 under the control of the first DC power source 104. Further, since the first DC power supply 104 includes a pulse oscillator, it can oscillate intermittently modulated high frequency or continuous high frequency.

The frequency of the high frequency is not particularly limited, but in this embodiment, a 2.45 GHz microwave (high frequency for plasma generation) is used. A magnetic field generating coil 111 that forms a magnetic field is provided on the outer periphery of the processing chamber 107, and the electric power oscillated from the first high-frequency power source 103 is generated in the processing chamber 107 due to interaction with the formed magnetic field. High density plasma is generated. The magnetic field generating coil 111 is covered with a coil case 112 which is a yoke.

In the processing chamber 107, a sample stage 102 is disposed below the shower plate 105. The upper surface of the sample stage 102 is covered with a dielectric film (not shown) made of ceramics or the like formed by a method such as thermal spraying, and a metal film electrode placed inside the sample stage 102 irradiates the high frequency filter 116. A second DC power source 117 is connected via the terminal. Due to the direct current supplied from the second direct current power source 117 to the film-like electrode, an adsorbing force due to electrostatic force is formed between the film 113 and the wafer 113 placed on the dielectric film.

Further, a metal disk-like electrode disposed inside the sample stage 102 is connected to a second high-frequency power source 115 as a bias high-frequency power source via a matching circuit 114, and plasma is formed in the processing chamber 107. In this state, high-frequency power is supplied, and a bias potential is formed above the upper surface of the wafer 113 placed on the sample stage 102 in accordance with the plasma potential. Note that, inside the electrode, a temperature-controlled refrigerant connected to a temperature controller (not shown) and adjusting the temperature of the sample stage 102 and the wafer 113 placed on the sample table 102 flows through the inside to exchange heat. A refrigerant flow path is disposed.

The vacuum vessel 101 is another vacuum vessel (not shown) and is placed on a transfer means such as a robot arm arranged inside, and a vacuum transfer vessel provided with a transfer chamber in which the wafer 113 is transferred, and a gate valve is provided between them. It is connected by sandwiching. When the wafer 113, which is a sample transported into the processing chamber 107 by the robot arm, is transferred onto the sample stage 102 and placed on the dielectric film, the wafer is transferred from the second DC power source 117 into the film. It is attracted to and held on the upper surface of the coating on the sample stage 102 by an electrostatic force formed by a DC voltage applied to the arranged film-like electrode.

In this state, a processing gas adjusted to a predetermined type and composition is supplied into the processing chamber 107 through the through hole of the shower plate 105 by the gas supply device 108, and then exhausted by the operation of the vacuum exhaust device 109. After the pressure in the processing chamber 107 is set to a predetermined vacuum level due to the balance between the amount and the supply amount of the processing gas, the microwave electric field propagated through the waveguide 110 is subjected to the dielectric window 106 and the shower plate 105. And is introduced into the processing chamber 107, and the processing gas is excited by the interaction generated by the magnetic field supplied from the magnetic field generating coil 111 into the processing chamber 107 to generate plasma.

In this state, high frequency power is supplied from the second high frequency power supply 115 to the disk-shaped electrode in the sample stage 102 to form a bias potential above the wafer 113, and charged particles in the plasma are transferred to the wafer 113 based on the potential difference. Etching of a film to be processed having a film structure composed of a plurality of film layers including a mask formed in advance on the upper surface of the wafer 113 is attracted to the surface and collided. In addition, since the second high-frequency power source 115 includes a pulse oscillator, it is modulated on the sample stage 102 so as to repeat on / off or high output (large amplitude) and low output (small amplitude) in a predetermined cycle. Intermittent high frequency power or continuous waveform high frequency power is applied.

In the plasma processing apparatus of this example, the processing gas supplied from the gas supply apparatus 109 is branched into two gas lines via a valve 118 and a valve 119, and the dielectric window 106 and between this and the shower plate 105 are separated. Supplied in gaps. The processing gas flowing in the gas line on the valve 118 side passes through a gas groove formed in the dielectric window 106 and is a gap between the dielectric window 106 and the shower plate 105 and in the center of the shower plate 105. It is supplied into a disk or cylindrical space arranged separately from the surrounding ring-shaped space, and is introduced from above into the processing chamber 107 through a through-hole disposed in the center of the shower plate 105. The

Further, the processing gas flowing in the gas line on the valve 119 side is a ring-shaped gas in the gas introduction ring 127 that is sandwiched between the dielectric window 106 and the upper end surface of the cylindrical portion of the vacuum vessel 101. Through the path, it flows into the ring-shaped space on the outer peripheral side, which is a gap between the dielectric window 106 and the shower plate 105. After the processing gas from the gas line on the valve 119 side diffuses inside the ring-shaped space, a plurality of through holes arranged in a ring shape on the lower surface on the outer peripheral side of the shower plate 105 communicating with the ring-shaped space And introduced into the processing chamber 107 from above.

Further, a gas supply device 126 for supplying a rare gas (for example, nitrogen) is connected to each of the two branched gas lines via heaters 120 and 125, valves 120 and 121, 122 and 123, which can be temperature-controlled. ing. At this time, a high-temperature inert gas heated by the heater 120 and the heater 125 is independently supplied to each of these gas lines by adjusting the opening and closing of the valves 120 and 122. For this reason, in these gas lines, since piping may become hot, it is desirable to wind a heat insulating material around piping.

Since the plasma processing apparatus of the present embodiment has the above-described configuration, the space between the dielectric window 106 and the shower plate 105 is adjusted to a desired temperature by a heater on each of the central side and the outer peripheral side. Further, the inert gas is supplied, and the temperatures of the dielectric window 106 and the shower plate 105 can be set to values within a desired range, and fluctuations in these temperatures are suppressed. Furthermore, by individually controlling the temperature on the center side and the outer peripheral side with the above configuration, the temperature of the dielectric window 106 and the shower plate 105 can be more accurately controlled.

Next, the aspect of gas supply will be described below. FIG. 2 is a diagram schematically showing an enlarged configuration of a portion for introducing the processing gas into the processing chamber in the plasma processing apparatus according to the embodiment shown in FIG. In particular, the valve opening / closing state when an inert gas is supplied to the space between the dielectric window 106 and the shower plate 105 is shown.

In general, in a plasma processing apparatus that etches a film layer on the surface of a wafer 113, in order to generate stable plasma so that CD fluctuation can be suppressed, the inner surface of the processing chamber 107 is heated in advance before the processing is started. A value close to the temperature during processing is performed. By starting the process with the temperature close to the one being processed in advance, the change in the temperature of the inner surface of the processing chamber 107 during the process is reduced and the processing shape is prevented from deviating from the intended one. To do. For example, it is conceivable that the temperature of the dielectric window during plasma processing is 80 ° C. to 100 ° C.

Also in this embodiment, by supplying a high-temperature inert gas to the space between the dielectric window 106 and the shower plate 105 before the start of processing, the dielectric window 106 and the shower plate 105 are processed before the plasma processing. Can be heated to a desired temperature range. As shown in FIG. 2, with the valves 118, 119 on the side of the gas supply device 108 for supplying the processing gas closed, the valves 120, 121, 120 on the gas line connected to the inert gas supply device 126 are provided. By opening 122 and 123, an inert gas is supplied through two gas lines.

Supplying such a rare gas at a predetermined temperature is performed before forming a plasma and starting a process of an arbitrary step, and after completing the process step and before starting the process of the next step. To do. By heating the dielectric window 106 and the shower plate 105 that constitute the inner wall of the processing chamber 107 before and after the plasma treatment, the temperature variation of the dielectric window 106 and the shower plate 105 can be suppressed, and By suppressing the temperature fluctuation of the process gas, it is possible to provide a plasma processing apparatus that realizes processing with high reproducibility and reliability.

Next, in the embodiment of FIG. 1, a mode of supplying a high-temperature inert gas during the plasma processing will be described below with reference to the drawings.

FIG. 3 shows a detailed view of a plasma processing apparatus having a function of adjusting the temperature of the central portion and the outer peripheral portion of the dielectric window 106 and the shower plate 105 during the plasma processing. FIG. 3 is a diagram schematically showing an enlarged configuration of a portion for introducing a processing gas into a processing chamber in a plasma processing apparatus according to a modification of the embodiment shown in FIG. In addition, since the thing of the same code | symbol as Example 1 has the structure and function similar to Example 1, description is abbreviate | omitted.

As shown in FIG. 3, the valve 118 on the two branched gas lines connected to the gas supply device 108 for supplying the processing gas is opened, the valve 119 is closed, and the gas supply device 126 for supplying the rare gas is connected. The two gas lines connected to the gas line for the processing gas in which the valve 118 is arranged, and the valves 120 and 121 arranged on one gas line are opened, and the gas for the processing gas in which the valve 119 is arranged The valve 122 and the valve 123 arranged on the other gas line connected to the other gas line are closed. By this opening / closing control, the processing gas for plasma processing is placed in the ring-shaped region on the outer peripheral side in the region partitioned from the periphery of the central portion of the gap between the dielectric window 106 and the shower plate 105. Is supplied with a hot noble gas.

Such supply of the processing gas and the rare gas is performed in a state where plasma is formed in the processing chamber 107. As a result, plasma processing that can suppress fluctuations in the temperature of the dielectric window 106 and the shower plate 105 while performing plasma processing, can suppress fluctuations in the temperature of the processing gas, and has improved reliability and reproducibility. Can be realized.

Furthermore, since the temperature of the shower plate 105 and the dielectric window 106 above the plasma is formed during the processing of the wafer 113 by forming the plasma, the temperature is adjusted before and after the plasma forming process. In this case, it is not necessary to heat the dielectric window 106 and the shower plate 105 in this case, the throughput of the entire apparatus is improved, and a plasma processing apparatus with higher productivity can be provided.

In the case of this modification, since the high temperature inert gas is supplied into the processing chamber 107 simultaneously with the processing gas during the plasma processing, the plasma state changes due to the influence of the high temperature inert gas, so that something is wrong with the plasma processing. There is concern about the potential for adverse effects. Accordingly, an example will be described in which the temperature of the dielectric window 106 and the shower plate 105 can be controlled during plasma processing without supplying a high-temperature inert gas into the processing chamber 107.

FIG. 4 shows a detailed view of a plasma processing apparatus having a function of adjusting the temperature of the central portion and the outer peripheral portion of the dielectric window 106 and the shower plate 105 during the plasma processing. FIG. 4 is a diagram schematically showing an enlarged configuration of a portion for introducing a processing gas into a processing chamber in a plasma processing apparatus according to another modification of the embodiment shown in FIG. 1 to 3 have the same configuration and functions as those shown in FIG.

As shown in FIG. 4, the valve 118 on the gas supply device 108 side for supplying the processing gas is opened, the valve 119 is closed, the valves 120 and 121 on the inert gas side are opened, and the valves 122 and 123 are closed. As a result, the process gas for plasma processing was set in the central region of the gap between the dielectric window 106 and the shower plate 105, and the temperature at the outer peripheral side was set higher than the temperature during processing in the processing chamber 107. A rare gas is supplied. The high-temperature noble gas introduced from one location of the gas introduction ring 128 to the outer peripheral region is discharged from another location into the gas introduction ring 128 without being supplied into the processing chamber 107 as shown in the figure. It flows out of the vacuum vessel 101.

With the configuration in which the processing gas and the rare gas are supplied during the plasma processing, the temperature variation of the dielectric window 106 and the shower plate 105 is suppressed while the plasma processing is performed, and the temperature variation of the processing gas is suppressed. By doing so, a plasma processing apparatus capable of realizing processing with high reproducibility and reliability can be provided. Further, the high-temperature rare gas is not supplied into the processing chamber 107 in a state where plasma is formed, and fluctuations in conditions in the processing chamber 107 can be suppressed during the processing of the wafer 113, so that more stable plasma is generated and yield is improved. An improved plasma processing apparatus can be provided.

DESCRIPTION OF SYMBOLS 101 ... Vacuum vessel 102 ... Sample stage 103 ... 1st high frequency power supply 104 ... 1st DC power supply 105 ... Shower plate 106 ... Dielectric window 107 ... Processing chamber 108 ... Gas supply apparatus 109 ... Vacuum exhaust apparatus 110 ... Waveguide 111 ... Magnetic field generating coil 112 ... Coil case 113 ... Wafer 114 ... Matching circuit 115 ... Second high frequency power source 116 ... High frequency filter 117 ... Second DC power source 118 ... Valve 119 ... Valve 120 ... Valve 121 ... Valve 122 ... Valve 123 ... Valve 124 ... Heater 125 ... Heater 126 ... Inert gas supply device 127 ... Gas introduction ring 128 ... Gas introduction ring 129 ... Vacuum vessel 130 ... Dielectric window.

Claims (4)

A processing chamber disposed inside the vacuum vessel and depressurized inside, a dielectric plate member that constitutes an upper portion of the vacuum vessel and transmits an electric field supplied to the processing chamber, and a lower portion of the processing chamber A sample table on which a wafer to be processed is placed, and a dielectric shower plate which is disposed below and above the plate member and above the upper surface of the sample table to face the sample table and constitutes the ceiling surface of the processing chamber. A shower plate having a through hole through which a processing gas used to form plasma for processing the wafer is introduced into the processing chamber, and at least one of these is heated between the shower plate and the plate member A plasma processing apparatus having a gas supply line for supplying a rare gas.
The plasma processing apparatus according to claim 1, comprising a function of supplying the rare gas before or after formation of plasma for processing the wafer.
2. The plasma processing apparatus according to claim 1, wherein the shower plate and the plate are supplied while the processing gas is supplied into the processing chamber from the through-hole disposed in a central portion of the shower plate during processing of the wafer. The plasma processing apparatus provided with the function to supply the said rare gas to the area | region of the outer peripheral side of the said center part between the gaps between members.
  4. The plasma processing apparatus according to claim 3, wherein the rare gas is supplied to the region on the outer peripheral side and then discharged outside the vacuum chamber without being introduced into the processing chamber. 5.

Images