TWI447804B - A plasma processing method and a plasma processing apparatus - Google Patents

Description

Plasma processing method and plasma processing device

The present invention relates to a technique for applying a plasma treatment to a substrate to be processed, and more particularly to a capacitive coupling type plasma processing apparatus and a plasma processing method.

Plasma, etching, deposition, oxidation, sputtering, and the like in a process of a semiconductor device or an FPD (Flat Panel Display) are used to plasma the process gas at a relatively low temperature. Previously, in a monolithic plasma processing apparatus, particularly a plasma etching apparatus, a capacitive coupling type plasma processing apparatus was in the mainstream.

In general, in a capacitively coupled plasma processing apparatus, an upper electrode and a lower electrode are arranged in parallel in a processing container configured as a vacuum processing chamber, and a substrate to be processed (a semiconductor wafer, a glass substrate, or the like) is placed on the lower electrode. A high frequency voltage is applied to either side of the two electrodes. The electrons are accelerated by the electric field generated by the high-frequency voltage at the two electrodes, and the plasma is generated by the collision of electrons with the processing gas to generate plasma, and the desired fine processing is applied to the surface of the substrate by free radicals or ions in the plasma ( For example, etching processing). Here, the electrode to which the high frequency side is applied is connected to the high frequency power source via a blocking capacitor in the matching device, and thus operates as a cathode.

A cathode coupling method in which a high frequency is applied to a lower electrode of a support substrate as a cathode, and the self-bias voltage generated by the lower electrode is used to pull the ions in the plasma to the substrate nearly vertically, and the anisotropic etching can be performed. . More In the cathode coupling method, in the treatment in which the upper electrode is likely to adhere to deposits such as polymers (hereinafter referred to as deposits), the impact of ions incident on the upper electrode is also sputtering, and the deposited film can be removed (if any) The advantage of attaching the oxide film together).

In the conventional capacitive coupling type plasma processing apparatus using the cathode coupling method, it is presumed that the upper electrode on the anode side to which no high frequency is applied is DC-grounded. Generally, the processing container is made of metal such as aluminum or stainless steel and has a safety grounding, so that the upper electrode can be grounded through the processing container; therefore, an integral assembly structure in which the upper electrode is directly mounted on the ceiling of the processing container is adopted. Or the ceiling of the processing container is used as it is for the structure of the upper electrode.

However, in recent years, in the semiconductor manufacturing process, with the miniaturization of design rules, high-density plasma under low pressure is required, and the high-frequency frequency of the capacitive-coupled plasma processing device is also becoming higher and higher. Currently, the standard is 40MHz. The above frequency. However, if the frequency becomes high, the high-frequency current is concentrated in the center portion of the electrode, so that the plasma density generated in the processing space between the electrodes is also higher on the center side of the electrode than on the edge portion side of the electrode, so that the processing surface The problem of reduced internal average is more pronounced.

The present invention has been made in view of the above problems of the prior art, and a first object thereof is to provide a plasma processing method and a plasma processing apparatus, which are directed to a cathode coupling method in which a deposition film is adhered to an electrode on an anode side, and it is strongly prevented. It will affect the processing of future projects and significantly improve the average of processing.

Further, a second object of the present invention is to provide a plasma processing method and a plasma processing apparatus which can stably maintain the average of processing even if the number of times of plasma treatment is accumulated so that the processing environment in the processing container is temporally changed.

In order to achieve the above first object, a first plasma processing method according to the present invention is a plasma processing method in which a first electrode and a second electrode are arranged in parallel in a processing chamber which can be vacuumed and grounded at a predetermined interval. The electrode supports the substrate to be opposed to the first electrode by the second electrode, and then evacuates the inside of the processing container to a specific pressure between the first electrode and the second electrode and the sidewall of the processing container. Supplying a desired processing gas in the processing space while applying a high frequency to the second electrode, and applying a desired plasma treatment to the substrate under the plasma generated in the processing space; characterized in that the first electrode is The capacitor is electrically connected to the ground potential via an electrostatic capacitance variable portion of the electrostatic capacitor, and is electrically connected to the ground potential via an electrostatic capacitor variable space, and then the electrostatic capacitance variable portion is switched in accordance with processing conditions of plasma treatment applied to the substrate. Electrostatic capacitance.

Further, a first plasma processing apparatus according to the present invention includes a processing container that can be evacuated and grounded, a first electrode that is attached to the processing container via an insulator or a space, and an electrical connection to the first electrode. electrode a capacitance variable portion having a variable capacitance between the ground potential and a first portion of the processing container disposed at a predetermined interval from the first electrode, and supporting the substrate to be processed facing the first electrode a second electrode; and a processing gas supply unit that supplies a desired processing gas in a processing space between the first electrode and the second electrode and the side wall of the processing container; and a power for generating the processing gas in the processing space a first high-frequency power supply unit that applies a first high frequency to the second electrode; and a capacitance control that switches the capacitance of the capacitance variable unit in accordance with processing conditions for plasma treatment applied to the substrate unit.

In the capacitive coupling type used in the present invention, when a high frequency from a high-frequency power source is applied to the second electrode, high-frequency discharge between the second electrode and the first electrode, and the second electrode and the processing container side wall ( The high-frequency discharge between the inner walls) generates a plasma of the processing gas in the processing space, and then the generated plasma will diffuse to the square, especially upward and radially outward, and the electron current in the plasma passes through. The first electrode or the side wall of the processing container flows to the ground.

Here, the electrostatic capacitance of the capacitance variable portion is switched in accordance with the processing conditions of the plasma treatment, whereby the capacitance or the ground capacitance around the first electrode can be arbitrarily switched from a high capacitance (low resistance) to a low capacitance (high resistance). In particular, the high-capacitance (low-resistance) grounding mode increases the ratio of the flow between the first electrode and the second electrode in the electron current of the plasma, and enhances the sputtering effect of the ions on the first electrode, thereby facilitating the polymer. The deposition film is likely to adhere to the second electrode. Moreover, the low-capacitance (high-resistance) grounding mode increases the flow between the first electrode and the sidewall of the processing vessel in the electron current of the plasma. Since the ratio of the movement spreads the spatial distribution of the plasma density to the outside in the radial direction, it is suitable for the treatment of the average treatment, or the treatment of the deposited film on the second electrode (for example, the treatment of the last project).

Further, a second high frequency having a lower frequency than the first high frequency may be applied to the second electrode, or a desired direct current voltage may be applied to the first electrode.

In order to achieve the above second object, the second plasma processing method according to the present invention is to arrange the first electrode and the second electrode in parallel in a processing chamber which can be vacuumed and grounded, and to arrange the substrate to be processed in parallel at a predetermined interval. The second electrode is supported to face the first electrode, and then the inside of the processing container is evacuated to a specific pressure, and a supply space is required in a processing space between the first electrode and the second electrode and the side wall of the processing container. Applying a high frequency to the second electrode while applying a high frequency to the substrate, applying a desired plasma treatment to the substrate in the plasma generated in the processing space; and the first electrode is mounted on the substrate via an insulator or a space The processing container is electrically connected to the ground potential via the capacitance variable portion of the electrostatic capacitance, and the electrostatic capacitance of the capacitance variable portion is switched in accordance with the number of processed substrates of the substrate to be subjected to plasma treatment.

Further, a second plasma processing apparatus according to the present invention is characterized in that it has a processing container that can be evacuated and grounded, and a first electrode that is attached to the processing container via an insulator or a space; and is electrically connected to the above a capacitance variable portion having a variable capacitance between the electrode and the ground potential; and a parallel arrangement of the first electrode at a predetermined interval in the processing container, and supporting the substrate to be processed facing the first electrode a second electrode; and the first electrode and the second electrode and the sidewall of the processing container a processing gas supply unit that supplies a desired processing gas in the processing space; and a first high-frequency power supply that applies the first high frequency to the second electrode in order to generate the plasma of the processing gas in the processing space. And a capacitance control unit that switches the electrostatic capacitance of the capacitance variable portion in accordance with the number of processed substrates of the substrate to be subjected to plasma treatment.

In the second method or apparatus described above, the electrostatic capacitance of the capacitance variable portion is switched in accordance with the number of processed substrates of the substrate to be subjected to the plasma treatment, whereby the spatial division characteristics of the plasma density can be controlled to be processed. In-plane segmentation characteristics, the results can be maintained to maintain the average of processing.

According to an ideal aspect of the present invention, the electrostatic capacitance value of the variable capacitance portion is increased in advance, and then the electrostatic capacitance value is decreased as the number of processed sheets is increased.

According to the plasma processing method and the plasma processing apparatus of the present invention, by the above-described structure and action, a deposition film is adhered to the electrode on the anode side for the cathode coupling method, and it is possible to prevent the influence of the subsequent processing of the project as much as possible. And significantly improve the average of the treatment. Further, even if the number of times of plasma treatment is accumulated so that the processing environment in the processing container is temporally changed, the average of the processing can be kept stable.

Preferred embodiments of the present invention are described below with reference to the accompanying drawings.

Figure 1 is a view showing a plasma etching apparatus in an embodiment of the present invention. structure. The plasma processing apparatus is a capacitively coupled (parallel plate type) plasma etching apparatus configured as a cathode coupling, and has a cylindrical vacuum processing chamber having a surface such as aluminum coated with alumina (anodized). Container) 10. The processing chamber 10 is safely grounded.

At the bottom of the processing chamber 10, a cylindrical susceptor support 14 is disposed via an insulating plate 12 such as ceramics, and a susceptor 16 made of, for example, aluminum is provided on the support table 14. The susceptor 16 constitutes a lower electrode on which, for example, a semiconductor wafer W as a substrate to be processed is placed.

Above the susceptor 16, an electrostatic chuck 18 for holding the semiconductor wafer W by electrostatic attraction is provided. The electrostatic chuck 18 is formed by sandwiching an electrode 20 made of a conductive film between a pair of insulating layers or insulating sheets; and the electrode 20 is electrically connected to the DC power source 22. The semiconductor wafer W can be adsorbed and held by the electrostatic chuck 18 by Coulomb force by the voltage from the DC power source 22. Around the electrostatic chuck 18 and above the susceptor 16, in order to improve the averaging of etching, a focus ring 24 composed of, for example, 矽 is disposed. On the side of the susceptor 16 and the susceptor support 14, for example, a cylindrical inner wall member 25 made of quartz is adhered.

The inside of the susceptor support table 14 is provided with, for example, a refrigerant chamber 26 extending in the circumferential direction. The refrigerant chamber 26 is circulated and supplied with a refrigerant having a specific temperature, such as cooling water, through the pipes 27a and 27b by an external cooling unit (not shown). The temperature of the semiconductor wafer W on the susceptor 16 can be controlled by the temperature of the refrigerant. Further, a heat transfer gas such as helium gas from a heat transfer gas supply means (not shown) is supplied between the upper surface of the electrostatic chuck 18 and the back surface of the semiconductor wafer W via the gas supply line 28. .

The susceptor 16 is connected to the high-frequency power source 30 for plasma generation via the matching unit 32 and the power supply rod 33. This high-frequency power source 30 applies a specific high frequency, for example, a high frequency of 40 MHz, to the susceptor 16 when plasma processing is performed in the processing chamber 10.

Above the susceptor 16, an upper electrode 34 is disposed in parallel with the susceptor. The upper electrode 34 is an electrode plate 36 having a plurality of gas ejection holes 36a and composed of a semiconductor material such as tantalum or tantalum carbide, and detachably supporting the electrode plate 36, and is composed of a conductive material, for example, The surface is formed of an electrode support 38 made of anodized aluminum, and is attached to the processing chamber 10 via an annular insulator 35 in an electrically suspended state. The upper electrode 34 and the susceptor 16 and the side wall of the processing chamber 10 form a plasma generating space or a processing space PS.

The annular insulator 35 is made of, for example, alumina (Al ₂ O ₃ ), and the outer peripheral surface of the upper electrode 34 and the side wall of the processing chamber 10 are hermetically sealed to physically support the upper electrode 34 and constitute the upper electrode. A portion of the electrostatic capacitance between the 34 and the processing chamber 10.

The electrode support body 38 has a gas buffer chamber 40 therein, and has a plurality of gas vent holes 38a connected to the gas discharge holes 36a of the channel electrode plates 36 from the gas buffer chamber 40. The gas buffer chamber 40 is connected to the processing gas supply unit 44 via a gas supply pipe 42. When a specific processing gas is introduced into the gas buffer chamber 40 from the processing gas supply unit 44, the processing gas is ejected toward the processing space PS by the gas ejection hole 36a of the electrode plate 36 toward the semiconductor wafer W on the susceptor 16. . So, on The portion electrode 34 also serves as a shower head for supplying a processing gas to the processing space PS.

Further, a passage (not shown) for flowing a refrigerant such as cooling water is also provided inside the electrode support body 38, and the entire upper electrode 34, particularly the electrode plate 36, is adjusted to a specific temperature by an external cooling means via a refrigerant. Further, in order to further stabilize the temperature control of the upper electrode 34, it may be a structure in which a heater (not shown) including a resistance heating element is mounted inside or on the electrode support 38.

Between the upper surface of the upper electrode 34 and the ceiling of the processing chamber 10, a space having an appropriate size is provided, and a space 50 is formed there. The space 50 may be an atmospheric space, ideally forming a vacuum space, not only thermally isolating the upper electrode 34 from the processing chamber 10 or the ambient temperature, but also preventing the upper electrode 34 from interposing between the upper electrode 34 and the processing chamber 10 by gas exclusion. The function of discharge. When the space 50 is thus vacuumed, it is exhausted separately from the processing space PS, and the vacuum state is maintained by the airtight structure. In this embodiment, in order to further improve the discharge preventing function, all or a part of the inner wall of the space 50 (the above example is only the upper surface) is covered with a sheet-shaped insulator 52. As the insulator 52, a polyimide-based resin excellent in heat resistance can be suitably used, and Teflon (registered trademark) or quartz can be used.

The annular space formed between the susceptor 16 and the susceptor support table 14 and the side wall of the processing chamber 10 is an exhaust space, and an exhaust port 54 of the processing chamber 10 is disposed at the bottom of the venting space. This exhaust port 54 is connected to the exhaust device 58 via an exhaust pipe 56. The exhaust unit 58 has a vacuum pump such as a turbo molecular pump, and the inside of the processing chamber 10, particularly the treatment space PS, can be depressurized to a specific degree of vacuum. Moreover, a switch is installed on the side wall of the processing chamber 10 The gate valve 62 of the semiconductor wafer W is carried in and out of the outlet 60.

In the plasma etching apparatus, a variable capacitor 86 having a variable capacitance is provided in the space 50, and the capacitance of the capacitor 86 is variable by being provided outside the processing chamber 10, for example, the capacitance control unit 85 provided thereon.

Here, a configuration example of the variable capacitor 86 is shown in FIGS. 2 and 3 . The variable capacitor 86 has a conductor plate 88 that is movable between a first position that contacts or approaches the upper surface of the upper electrode 34 and a second position that is separated upward from the upper electrode 34; and The conductor plate 88 is operated by an upper and lower movement or displacement, such as the operating rod 90. Here, a capacitor is formed between the conductor plate 88 and the upper electrode 34. The larger the area of the conductor plate 88, the greater the sensitivity or range of the variable capacitance. The operating mechanism 90 of FIG. 2 is made of a conductive material, a material having a conductive property at a high frequency, or a material having a low-frequency property with high frequency, and is grounded directly or via the processing chamber 10. The operating mechanism 90 of Fig. 3 can also be an insulating material. The capacitance control unit 85 has, for example, a stepping motor that can arbitrarily control the amount of rotation, and a motion conversion mechanism (for example, a ball) that converts the rotation of the rotary drive shaft of the stepping motor into a straight-forward (elevating) motion of the operating mechanism 90. The screw mechanism) or the like; the capacitance of the variable capacitor 86 can be continuously changed by the variable control of the height position of the conductor plate 88. The closer the conductor plate 88 is to the ceiling surface of the processing chamber 10, the more the grounding capacitance of the upper electrode 34 can be reduced. Conversely, the closer the conductor plate 88 is to the upper surface of the upper electrode 34, the more the grounding capacitance of the upper electrode 34 can be increased. Extremely, the conductor plate 88 is brought into contact with the upper electrode 34 to ground the upper electrode 34, so that the grounding capacitance can be made infinite.

Fig. 4 shows the configuration of the capacitance variable portion 85 of the other embodiment. In this embodiment, an annular liquid containing chamber 94 is formed in the annular insulator 35 disposed between the upper electrode 34 and the processing chamber 10, and can be introduced and exported from the outside of the processing chamber 10 via the piping 92. The structure of a liquid (for example, an organic solvent such as Galden (registered trademark)) Q. The electrostatic capacitance of the entire annular insulator 35 or the grounding capacitance of the upper electrode 34 can be changed by changing the type (dielectric ratio) or the amount of the dielectric liquid Q.

Further, the capacitance control unit 85 is provided with a control signal for instructing the capacitance (target value) of the variable capacitor 86 by the controller 96 that controls the operation of each part in the plasma processing apparatus and the entire apparatus.

In the plasma etching apparatus, in order to perform etching, the gate valve 62 is first opened, and the semiconductor wafer W to be processed is carried into the processing chamber 10 and placed on the electrostatic chuck 10. Then, the processing gas supply unit 44 introduces a processing gas, that is, an etching gas (generally a mixed gas) into the processing chamber 10 at a specific flow rate and a flow ratio, and the pressure in the processing chamber 10 is made by vacuum evacuation of the exhaust unit 58 as Set value. Further, a high frequency (40 MHz) is applied to the susceptor 16 by the high frequency power source 30 with a specific power. Further, a DC voltage is applied to the electrode 20 of the electrostatic chuck 18 by the DC power source 22 to fix the semiconductor wafer W to the electrostatic chuck 18. The etching gas discharged from the shower head of the upper electrode 34 is plasma-treated in the processing space PS by high-frequency discharge, and the film on the main surface of the semiconductor wafer W is etched by radicals or ions generated by the plasma.

The capacitive coupling type plasma etching device is a pair of susceptors (lower electrode 16 applies a high frequency of 40 MHz or more, whereby the plasma is densified in an ideal dissociation state, and a high-density plasma can be formed even under a lower pressure condition. Further, in the cathode coupling mode, the anisotropic etching is performed by pulling the ions in the plasma almost vertically to the wafer W by the self-bias voltage generated in the susceptor 16.

Further, a first frequency suitable for generating a higher frequency of the plasma (for example, 40 MHz) and a second frequency suitable for pulling a lower frequency of the ion (for example, 2 MHz) may be superposed on the lower electrode to serve as a lower portion. 2 frequency overlap application method. In the device configuration for this case, for example, as shown in Fig. 5, a high frequency power source 64 for supplying the second high frequency to the susceptor 16, a matching unit 66, and a power supply rod 68 may be added. In the lower two-frequency overlapping application method, the plasma density generated in the processing space PS is optimized by the first frequency (for example, 40 MHz), and the second frequency (for example, 2 MHz) will occur in the susceptor 16. The self-bias voltage or ion sheath is optimized to achieve a more selective anisotropic etch.

Next, the action of the variable capacitor (capacitor variable portion) 86 in the plasma etching apparatus will be described. In FIGS. 6 and 7, the upper electrode 34 is electrically connected to the processing chamber 10 (ground) of the ground potential via the variable capacitor 36 and the fixed capacitor or capacitors 70 and 72. Here, the capacitance between the capacitor 70 and the side wall of the upper electrode 34 and the processing chamber 10 is mainly imparted by the annular insulator 35. On the other hand, the capacitor 72 is connected in parallel with the variable capacitor 86 and has a capacitance (fixed capacitance) between the upper electrode 34 and the ceiling of the processing chamber 10. The capacitance or grounding capacitance around the upper electrode 34 is the sum of the capacitance of the variable capacitor 86 and the capacitance of the capacitors 70 and 72. Assigned to a synthetic capacitor.

First, the capacitance of the variable capacitor 86 is increased, and the grounding capacitance (composite capacitance) of the upper electrode 34 is selected to be 2000 pF or more (extremely, the conductor plate 88 is in contact with the upper electrode 34 as an infinite capacitance value). The role of the situation). At this time, as shown in FIG. 6, when the high frequency power source 30 is applied to the susceptor 16, the high frequency discharge between the susceptor 16 and the upper electrode 34, and the susceptor 16 and the side wall of the processing chamber 10 are shown. Between the high-frequency discharge, a plasma of the processing gas is generated in the processing space PS, and then the generated plasma is diffused to the square, especially upward and radially outward, and the electron current in the plasma is transmitted through the upper electrode 34. Or the side wall of the processing chamber 10 or the like flows to the ground. Here, the higher the high frequency of the susceptor 16, the more the high frequency current concentrates on the central portion of the susceptor due to the surface effect, and the upper opposite electrode 34 is grounded via a high capacitance, that is, a low resistance. The proportion of electron current in the plasma flowing to the side wall of the processing chamber 10 will be low, and most of it will flow to the upper electrode 34, especially at its center. As a result, the spatial division characteristic of the plasma density is likely to be the highest in the center of the electrode, and the lower the peripheral portion going to the outer side in the radial direction is the lower the mountain profile. On the other hand, by flowing a large amount of high-frequency current or electron current to the upper electrode 34, the amount of ion incidence caused by the self-bias voltage in the upper electrode 34 is also increased, and the effect of enhancing the splash is enhanced.

In contrast, when the capacitance of the variable capacitor 86 is lowered and the ground capacitance (composite capacitance) of the upper electrode 34 is selected to be 250 pF or less, as shown in FIG. 7, the plasma distribution in the processing space PS will be Expand outward in the radial direction. In this case, when the high frequency power supply 30 is used When the high frequency is applied by the device 16, the high frequency discharge between the susceptor 16 and the upper electrode 34, and the high frequency discharge between the susceptor 16 and the side wall of the processing chamber 10 generate a plasma of the processing gas in the processing space PS. Then, the generated plasma is diffused upward and radially outward, and the electron current in the plasma flows to the ground through the upper electrode 34 or the side wall of the processing chamber 10. Then, the high-frequency current in the susceptor 16 is concentrated at the center of the susceptor, as in the case of Fig. 6. However, since the grounding capacitance or the electric resistance of the upper electrode 34 is low, even if the high-frequency current is concentrated in the central portion of the susceptor 16, it is difficult to flow to the upper electrode 34 directly opposite. Therefore, the ratio of the electron current flowing in the plasma to the side wall of the processing chamber 10 is not so low, and can be arbitrarily adjusted to flow to the susceptor 16 and the upper electrode 34 according to the grounding capacitance value, that is, according to the capacitance value of the variable capacitor 86. Between, and the ratio of electron current between the susceptor 16 and the sidewall of the processing chamber 10. On the other hand, if the high-frequency current or the electron current flowing through the upper electrode 34 is small, the amount of incident light in the upper electrode 34 may be reduced as the sputtering effect is lowered.

The plasma etching apparatus of this embodiment has a structure in which the capacitance of the capacitance variable portion 86 can be changed as described above, and the grounding capacitance of the upper electrode 34 is appropriately switched in accordance with the processing conditions, in particular, high capacitance grounding (low resistance) is selected. In either mode or low-capacitance ground (high-resistance) mode, the prevention or reduction of the memory effect described later is balanced with the processing average, or the trade-off is optimized to improve the processability of the entire process.

Next, an example of a specific plasma etching process in the plasma etching apparatus of this embodiment will be described. This etching process forms a connection hole (through hole) for the organic low-k film which is an interlayer insulating film, and uses the lower 2 frequency The rate overlaps the application method (Fig. 5).

Fig. 8 is a view showing a detailed configuration example of the processing gas supply unit 44 in this embodiment. The main gas supply pipe 42 is connected to a supply source of various raw material gases as a process gas supply system via dedicated or branched gas supply pipes. In this embodiment, as a raw material gas for the mixed gas for etching, as described later, six types of CF ₄ , CHF ₃ , CH ₃ F, C ₄ F ₈ , Ar, and N ₂ are used, so that six kinds of these are prepared. The gas supply sources 100 to 110 of the material gases. The individual dedicated gas supply pipes are provided with flow controllers (MFC) 100a to 110a and switching valves 100b to 110b that can be independently controlled by the controller 96.

As shown in Fig. 9(a), the main surface of the semiconductor wafer W to be etched is a lower layer wiring layer 112, a barrier layer 114, and an organic low in the multilayer wiring structure. a -k film (interlayer insulating film) 116 and a mask 118. The wiring layer 112 is, for example, a copper wiring layer, and is formed, for example, by dual damascene processing. The barrier layer 114 is, for example, a tantalum nitride (SiN) film having a film thickness of 1000 Å (0.1 μm), which is formed, for example, by a CVD (Chemical Vapor Deposition Chemical Vapor Deposition) method. The organic low-k film 116 is, for example, a SiOC-based low-k film having a film thickness of 1 μm, and is formed, for example, by a CVD method. The mask 118 is a resist film formed by a general photolithography method, and has an opening 118a at the opening position of the through hole.

In this embodiment, the semiconductor wafer W of the object to be processed is subjected to a three-step etching process. First, as the first step, etching is performed by stacking. The main etching conditions in this first step are as follows.

Process gas: CF ₄ /CH ₃ F/N ₂ = flow rate 50/5/100sccm

Processing chamber pressure: 20mTorr

High frequency power: 40MHz/2MHz=1000/0W

In the first step, the etching gas system uses a perfluorocarbon-based CH ₃ F. As a result, the H molecule decomposed by the plasma in CH ₃ F immediately reacts with F, becomes HF, and is exhausted, thereby leaving only C. As a result, a large amount of carbon-based deposits are generated and adhere to the opening portion 118a of the resist mask 118 and the vicinity thereof, which will become a protective film for improving the mask selection ratio in the subsequent process. However, since a large amount of polymer is generated and the second high frequency (2 MHz) is not applied to the susceptor 16, that is, the ion incidence to the upper electrode 34 is weak, the upper electrode 34 easily adheres to the deposit.

Therefore, regarding the ground capacitance of the upper electrode 34, the capacitance of the variable capacitor 86 is increased as shown in FIG. 5 to switch to the high capacitance ground (low resistance) mode, and the ground can be short-circuited at the extreme. Thereby, the ion incidence efficiency to the upper electrode 34 is increased, and ion splashing is promoted, so that the deposited film does not adhere.

This first step, as shown in Fig. 9(b), is formed at the bottom of the hole 116a of the organic low-k film 116, and ends when it reaches a certain depth, for example, around 1000 Å. At the end of the first step, the supply of the mixed gas of CF ₄ /CH ₃ F/N ₂ is stopped, that is, the switching valves 100b, 104b, and 110b are closed, and the output of the high-frequency power source 30 is turned off. However, the action of the exhaust device 58 continues.

Next, as the second step, the main etching is performed. In step 2 The main etching conditions are as follows.

Processing gas: CHF ₃ /CF ₄ /Ar/N ₂ = flow rate 40/30/1000/150sccm

Processing room pressure: 30mTorr

High frequency power: 40MHz/2MHz=1000/1000W

In the second step, plasma-assisted etching by chemical reaction is performed, and ion-assisted etching by ion irradiation is superimposed to perform high-speed anisotropic etching. At this time, since the processing of the second step is started in a state where the deposited film generated in the previous first step is not attached to the upper electrode 34, the processing in the first step is not affected.

In fact, even in the second step, a large amount of polymer is generated from the perfluorocarbon-based CHF ₃ , and although it is not comparable to the case of the first step, the deposit easily adheres to the upper electrode 34, and because The processing time is long and the accumulation of accumulated film is likely to increase significantly.

In view of this, in the second step, the ground capacitance of the upper electrode 34 is also made into the high capacitance ground (low resistance) mode as shown in FIG. 5, and the ground can be short-circuited at the extreme. Thereby, the ion incidence efficiency to the upper electrode 34 is increased, and ion splashing is promoted, so that the deposited film does not adhere.

The second step is as shown in Fig. 9(c), and is formed at the bottom of the hole 116a of the organic low-k film 116, and ends when it reaches a certain depth, for example, around 8000 Å. When the first step is completed, the on-off valves 102b, 100b, 108b, and 110b are turned off, and the supply of the mixed gas of CHF ₃ /CF ₄ /Ar/N ₂ is stopped, and the two high-frequency power sources 30 and 64 are temporarily cut off. Output.

Secondly, as the last third step, etching is performed. This step 3 The main etching conditions in the step are as follows.

Process gas: C ₄ F ₈ /Ar/N ₂ = flow rate 6/1000/150 sccm

Processing chamber pressure: 50mTorr

High frequency power: 40MHz/2MHz=1000/1000W

This third step is also to maintain the anisotropy (vertical state) of the hole 116a, and the organic low-k film 116 is continuously etched before reaching the base film (tantalum nitride) 62. In this case, also in the state where the upper electrode 34 does not adhere to the deposited film produced in the previous second step, the processing of the third step is started, so that it is not affected by the processing of the second step.

The C ₄ F ₈ /Ar/N ₂ mixed gas used as the etching gas in the third step has a higher characteristic than the base film (tantalum nitride) 62, although a perfluorocarbon-based polymerization is produced. Things, but the amount is small, and there is no subsequent processing after this third step. In other words, even in the third step, even if the deposited film is adhered to the upper electrode 34, it is not necessary to consider the effect (memory effect) of the next process being affected by the previous process due to the deposited film. Further, the deposited film attached to the upper electrode 34 or the side wall of the processing chamber 10 may be additionally removed by, for example, plasma cleaning.

In view of this, in the third step, the ground capacitance of the upper electrode 34 is taken as the low capacitance ground (high resistance) mode as shown in FIG. Thereby, the electron current flowing between the susceptor 16 and the upper electrode 34 is relatively reduced, and the electron current flowing between the susceptor 16 and the side wall of the processing chamber 10 is relatively increased, so that the electricity generated in the processing space PS is generated. The pulp density can be expanded outward in the radial direction.

At this time, the etching rate on the semiconductor wafer W can be made spatial (especially in the radial direction), but the edge portion etching rate is preferably higher than the central portion. In the first step and the second step, the grounding capacitance of the upper electrode 34 is set to be higher as described above, so that the plasma density is higher and the peripheral portion is higher. Therefore, the etching rate of the through-hole formation is also likely to be relatively high in the center portion and low in the peripheral portion. As a result, at the point of the end of the second step, the depth of the bottom of the hole 116a is spatially inconsistent (especially in the radial direction), the center portion is relatively deep, and the edge portion is relatively shallow.

Therefore, in the last third step, the plasma density is relatively low at the center portion and relatively high at the peripheral portion, so that the etching rate on the semiconductor wafer W is relatively low at the center portion and relatively high at the peripheral portion. The inconsistency of the previous etching depth can be offset to some extent. Thereby, the in-plane average of the etching rate of the entire first to third steps can be improved.

As described above, according to this embodiment, the grounding capacitance of the upper electrode 34 is configured to be variable, and then, in accordance with the processing conditions, for example, in the continuous processing, the current processing is a process in which the deposited film is likely to adhere to the upper electrode 34. In this process, the ground capacitance of the upper electrode 34 is switched to the high capacitance ground (low resistance) mode, so that the deposited film is difficult to adhere to the upper electrode 34, and the influence or memory effect on the next process can be prevented or even reduced. . Further, when the deposition film is less likely to adhere to the upper electrode 34, the ground capacitance of the upper electrode 34 is switched to the low capacitance ground (high resistance) mode in this process, and the density of the plasma generated in the processing space PS is made. Spreading outward in the radial direction, thereby improving the processing average .

The through-hole etching of the organic low-k film in the above embodiment is only an example, and the present invention can be applied to any multi-step processing, and is of course applicable to a single-step process. Further, a DC power source (not shown) may be electrically connected to the upper electrode 34 as a structure or a mode in which an arbitrary DC voltage is applied to the upper electrode 34. At this time, the upper electrode 34 is in a state of being electrically suspended from the potential of the processing chamber 10, that is, the ground potential, and functions as a direct current.

Further, as another embodiment, the electrostatic capacitance value may be changed in accordance with the number of processed wafers. Generally, as the temperature of the parts inside the processing chamber rises due to the plasma, the etching rate at the edge portion of the wafer tends to decrease. Therefore, especially in the initial stage of etching, the etching rate of the wafer center is increased to match the etching rate of the edge portion of the wafer to maintain the average value; and as the number of processing sheets increases, if the etching rate of the edge portion of the wafer is decreased, the etching rate is decreased. The capacitance value of the capacitance variable portion reduces the etching rate reduction at the edge portion of the wafer.

The high frequency frequency used in the above embodiment is just an example, and any frequency can be used in conjunction with the processing. Moreover, various portions of the structure within the device can be modified. In particular, the configuration of the capacitance variable portion 86 in the above embodiment is merely an example, and any capacitance configuration in which the capacitance or the ground capacitance around the upper electrode 34 can be changed within a desired range can be employed. The above embodiments are related to a plasma etching apparatus and a plasma etching method, but the present invention is also applicable to other plasma processing apparatuses and processing methods such as plasma CVD, plasma oxidation, plasma nitriding, and sputtering. Further, the substrate to be processed in the present invention is not limited to a semiconductor wafer, and may be various substrates for a flat panel display, a photomask, a CD substrate, a printed substrate, or the like.

10‧‧‧Processing room (processing container)

16‧‧‧Receptor (lower electrode)

30‧‧‧High frequency power supply

34‧‧‧Upper electrode

35‧‧‧Circular insulator

36‧‧‧Electrode plate

36a‧‧‧ gas ejection holes

38‧‧‧Electrode support

40‧‧‧ gas buffer room

42‧‧‧ gas supply pipe

44‧‧‧Process Gas Supply Department

50‧‧‧ space

52‧‧‧Insulator

64‧‧‧High frequency power supply

70, 72‧‧‧ capacitor

85‧‧‧Electrostatic capacitance control department

86‧‧‧Variable capacitor (capacitor variable part)

[Fig. 1] is a longitudinal sectional view showing the structure of a plasma etching apparatus in an embodiment of the present invention

[Fig. 2] A diagram showing a configuration example of a variable capacitor in a plasma etching apparatus according to an embodiment.

[Fig. 3] A diagram showing another configuration example of a variable capacitor in a plasma etching apparatus according to an embodiment.

[Fig. 4] A longitudinal sectional view showing the structure of the plasma etching apparatus in a modification of the embodiment

[Fig. 5] A longitudinal sectional view showing the structure of the plasma etching apparatus in a modification of the embodiment

[Fig. 6] A diagram schematically showing a high-frequency discharge situation in a processing chamber when the plasma etching apparatus of the embodiment is switched to a high-capacitance (low-resistance) grounding mode

[Fig. 7] A diagram schematically showing a high-frequency discharge situation in a processing chamber when the plasma etching apparatus of the embodiment is switched to a low-capacitance (high-resistance) grounding mode

[Fig. 8] is a longitudinal sectional view showing the structure of a plasma etching apparatus used in the etching method of the embodiment

[Fig. 9] In the etching method of the embodiment, a schematic sectional view showing the state of each step of the multiple steps

10‧‧‧Processing room (processing container)

12‧‧‧Insulation board

14‧‧‧Resistor support table

16‧‧‧Receptor (lower electrode)

18‧‧‧Electrostatic suction cup

20‧‧‧ electrodes

22‧‧‧DC power supply

24‧‧‧ Focus ring

25‧‧‧ Inner wall components

26‧‧‧The refrigerant room

27a‧‧‧Pipe

27b‧‧‧Pipe

28‧‧‧ gas supply line

30‧‧‧High frequency power supply

32‧‧‧matcher

33‧‧‧Power rod

34‧‧‧Upper electrode

35‧‧‧Circular insulator

36‧‧‧Electrode plate

36a‧‧‧ gas ejection holes

38‧‧‧Electrode support

38a‧‧‧ gas vents

40‧‧‧ gas buffer room

42‧‧‧ gas supply pipe

44‧‧‧Process Gas Supply Department

50‧‧‧ space

52‧‧‧Insulator

54‧‧‧Exhaust port

56‧‧‧Exhaust pipe

58‧‧‧Exhaust device

60‧‧‧ moving into and out

62‧‧‧ gate valve

85‧‧‧Electrostatic capacitance control department

86‧‧‧Variable capacitor (capacitor variable part)

96‧‧‧ Controller

Claims (16)

A plasma processing method in which a first electrode and a second electrode are arranged in parallel at a predetermined interval in a processing chamber which can be vacuumed and grounded, and the substrate to be processed is supported by the second electrode so as to be opposed to the first electrode Then, the inside of the processing container is evacuated to a specific pressure, and a desired processing gas is supplied into a processing space between the first electrode and the second electrode and the side wall of the processing container, and only the first electrode and the first electrode are A high frequency is applied to the second electrode of the second electrode, and a desired plasma treatment is applied to the substrate under the plasma generated in the processing space; and the first electrode is mounted via an insulator or a space. At the same time, the processing container is electrically connected to the ground potential via the capacitance variable portion of the electrostatic capacitance, and then the first high frequency is applied to the second electrode, and the processing conditions of the plasma treatment applied to the substrate are applied to the deposited film. When the treatment is easy to adhere to the first electrode, the capacitance of the capacitance variable portion is switched to be high, and the deposited film is less likely to adhere to the first electrode. When the process, the electrostatic capacitance of the variable portion of the electrostatic capacitance switch is low. The plasma processing method according to claim 1, wherein in the processing of the plurality of steps, the electrostatic capacitance of the capacitance variable portion is switched to be higher during the processing of each step other than the last step; At the time of the last step, the electrostatic capacitance of the capacitance variable portion is switched to be low. The plasma processing method according to claim 1, wherein a variable capacitor is used in the capacitance variable portion. The plasma processing method according to claim 1, wherein a second high frequency having a lower frequency than the first high frequency is applied to the second electrode. The plasma processing method according to any one of claims 1 to 4, wherein a desired DC voltage is applied to the first electrode. A plasma processing apparatus characterized by having a processing container capable of vacuum evacuation and being grounded; and a first electrode mounted to the processing container via an insulator or a space; and electrically connected between the first electrode and a ground potential a capacitance variable portion having a variable capacitance; and a second electrode that is disposed in parallel with the first electrode at a predetermined interval in the processing container, and then supports the substrate to be processed facing the first electrode; and a processing gas supply unit that supplies a desired processing gas in a processing space between the first electrode and the second electrode and the side wall of the processing container; and a plasma for generating the processing gas in the processing space, but only a first high-frequency power supply unit that applies a first high frequency to the second electrode of the first electrode and the second electrode; and a processing condition of a plasma treatment applied to the substrate, wherein the electrostatic capacitance is variable And a capacitance control unit that switches the ground capacitance of the first electrode. In the plasma processing apparatus according to the sixth aspect of the invention, the capacitance control unit switches the capacitance of the capacitance variable portion to a state in which the deposition film is likely to adhere to the first electrode. When the deposition film is hard to adhere to the first electrode, the capacitance of the capacitance variable portion is switched to be low. The plasma processing apparatus according to the sixth aspect of the invention, wherein the capacitance control unit electrostatically changes the capacitance variable portion in the processing of each step other than the last step in the multi-step processing The capacitance is switched to be higher; in the processing of the last step, the capacitance of the capacitance variable portion is switched to be lower. The plasma processing apparatus according to claim 6, wherein the capacitance variable portion has a variable capacitor. The plasma processing apparatus according to claim 6, further comprising a second high-frequency power supply unit that applies a second high frequency having a lower frequency than the first high frequency to the second electrode. The plasma processing apparatus according to any one of claims 6 to 10, further comprising a DC power source that applies a desired DC voltage to the first electrode. A plasma processing method in which a first electrode and a second electrode are arranged in parallel at a predetermined interval in a processing chamber which can be vacuumed and grounded, and the substrate to be processed is supported by the second electrode so as to be opposed to the first electrode Then, the inside of the processing container is evacuated to a specific pressure, and a desired processing gas is supplied into a processing space between the first electrode and the second electrode and the side wall of the processing container, and the second electrode is applied to the second electrode. 1 High-frequency, and applying a desired plasma treatment to the substrate under the plasma generated in the processing space; characterized in that the first electrode is mounted on the processing container via an insulator or a space, and the electrostatic capacitance is passed through the electrostatic capacitor. The variable portion is electrically connected to the ground potential, and then the electrostatic capacitance of the capacitance variable portion is switched in accordance with the number of processed substrates of the substrate to which the plasma treatment is to be applied. The plasma processing method according to claim 12, wherein the electrostatic capacitance value of the capacitance variable portion is increased in advance, and the electrostatic capacitance value is decreased as the number of processed sheets is increased. A plasma processing apparatus characterized by having a processing container capable of vacuum evacuation and being grounded; and a first electrode mounted to the processing container via an insulator or a space; and electrically connected to the first electrode and a ground potential a capacitance variable portion having a variable capacitance; and a second electrode that is disposed in parallel with the first electrode at a predetermined interval in the processing container, and then supports the substrate to be processed facing the first electrode; and a processing gas supply unit that supplies a desired processing gas in a processing space between the first electrode and the second electrode and the side wall of the processing container; and a plasma for generating the processing gas in the processing space The second high-frequency power supply unit that applies the first high frequency to the second electrode; and the number of processed chips of the substrate to which the plasma treatment is applied is cut The capacitance control unit that replaces the capacitance of the capacitance variable portion. The plasma processing apparatus according to claim 14, wherein the capacitance control unit increases the electrostatic capacitance value of the capacitance variable portion in advance, and then reduces the static electricity as the number of processed sheets increases. Capacitance value. A plasma processing apparatus characterized by comprising: a processing container capable of vacuum evacuation and being grounded; a first electrode mounted to the processing container via an insulator or a space; electrically connected between the first electrode and a ground potential; An annular liquid storage chamber is formed in the annular insulator provided between the first electrode and the side wall of the processing container, and a specific dielectric constant is added to the liquid storage chamber from the processing container through the pipe. a liquid or a capacitance variable portion that derives a capacitance having a specific dielectric ratio from the liquid storage chamber to the processing container to change a capacitance; and a predetermined interval from the first electrode in the processing container And a second electrode that supports the substrate to be processed facing the first electrode, and a process for supplying a desired processing gas in a processing space between the first electrode and the second electrode and the sidewall of the processing container. a gas supply unit that applies a first high frequency to the second electrode in order to generate a plasma of the processing gas in the processing space Power supply unit; and processed according to the processing conditions of sheet plasma processing of the substrate to be plasma treated or the embodiment of the substrate, the capacitance of the variable switching unit Electrostatic capacitance control unit for electrostatic capacitance.