KR102009369B1 - Plasma processing apparatus - Google Patents

Abstract

On the high frequency transmission path near the upper electrode configured to be movable in the vertical direction, it is possible to effectively prevent the occurrence of unwanted resonance phenomenon without causing particles. In this cathode coupling type capacitively coupled plasma processing apparatus, an upper electrode 44 configured to be movable in the vertical direction is coaxially opposed to the susceptor (lower electrode) 14 in the upper portion of the chamber 10. Is installed. The upper electrode 44 includes an electrode body 46 facing the susceptor 14, a conductive back plate 48 facing the ceiling wall (top cover) 10b of the chamber 10, and an electrode body. It has a ring-shaped dielectric 52 which joins the periphery of the electrode main body 46 and the periphery of the back board 48 so that the space | gap 50 is formed between the 46 and the back board 48. As shown in FIG. The back plate 48 of the upper electrode 44 is physically and electrically connected to the chamber 10 which is a ground potential member via the bellows 72.

Description

Plasma Processing Equipment {PLASMA PROCESSING APPARATUS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitively coupled plasma processing apparatus of a cathode coupling type, and more particularly, to an upper electrode that is movable up and down.

In general, a capacitively coupled plasma processing apparatus arranges an upper electrode and a lower electrode in parallel in a processing container configured as a vacuum chamber, and mounts a substrate to be processed (semiconductor wafer, glass substrate, etc.) on the lower electrode. And high frequency power is applied to either one of both electrodes. The electrons are accelerated by the electric field formed between the two electrodes by this high frequency electric power, the plasma is generated by the collision ionization of the electrons and the processing gas, and the desired surface treatment or processing is performed on the substrate surface by the radicals or ions in the plasma. Here, the distance between the upper electrode and the lower electrode (hereinafter referred to as 'gap between electrodes') determines the application efficiency or stability of high frequency power, plasma density distribution, and the like, in relation to other process conditions such as pressure. Thus, it has become an important process condition on hardware that influences the characteristics or results of the plasma process.

In recent years, in such a cathode coupling type capacitively coupled plasma processing apparatus, in order to be able to adjust the gap between electrodes, the lower electrode on the cathode side on which the substrate is placed is fixed, and the upper electrode serving as the counter electrode is moved upward and downward. The apparatus structure which made it possible to draw attention is attracted (patent document 1). Such an upper electrode movable plasma processing apparatus has an upper electrode support mechanism for movably supporting the upper electrode in a vertical direction at a distance from the side wall of the chamber in the decompression space of the chamber (processing vessel), and further, the lower electrode. As seen from the side, an elastic bellows is provided for hermetically connecting the backside region of the upper electrode and the chamber ceiling wall. Since the bellows is made of a metal having high strength and durability, for example, stainless steel, the upper electrode is electrically connected to the chamber via the bellows and grounded. Even in the upper electrode movable type, the upper electrode is generally configured as a shower head having a plurality of gas injection holes for supplying a processing gas to a plasma generating space or a processing space between both electrodes.

When a processing gas is supplied from a shower head (upper electrode) in a chamber depressurized to a predetermined pressure, and a high frequency power of a frequency suitable for generating plasma from a high frequency power source is applied to the lower electrode, a high frequency discharge between the lower electrode and the upper electrode is applied. As a result, plasma of the processing gas is generated. The generated plasma diffuses into the processing space, and the high frequency power flows through the upper electrode into the chamber at the ground potential. At this time, an electrical resonance phenomenon may occur on a high frequency transmission path (hereinafter, referred to as a "high frequency transmission path near the upper electrode") from the processing space to the chamber at the ground potential via the upper electrode. The occurrence of such a resonance phenomenon is undesirable because it prevents the stable generation of plasma.

There are a plurality of paths in the high frequency transmission path near the upper electrode. In particular, the resonance phenomenon on the high frequency transmission path (hereinafter referred to as 'high electrode back side high frequency transmission path') from the processing space to the chamber of the ground potential via the upper electrode and the bellows is the high frequency power applied to the plasma space. In addition to the loss of and the loss of the bellows, abnormal discharge in the depressurized space (ceiling space) between the rear surface area of the upper electrode and the chamber ceiling wall when viewed from the lower electrode side is caused, so that the active resonance suppression is required.

For this purpose, it is necessary to ensure that the intrinsic resonance frequency in the high frequency transmission path near the upper electrode does not overlap with the frequency of the high frequency power applied at the time of plasma generation. By the way, in the upper electrode movable type, since the gap between electrodes is adjusted so as to be an optimal process condition, fluctuations in the inductance component of the high frequency transmission path on the back side of the upper electrode accompanying the expansion and contraction of the bellows occur. Therefore, the frequency-impedance characteristics of the high frequency transmission path near the upper electrode also change depending on the process conditions. That is, the resonance frequency inherent in the high frequency transmission path is changed.

More specifically, the smaller the inter-electrode gap, the longer the bellows, the larger the inductance, and the lower the natural resonance frequency. On the contrary, the larger the gap between the electrodes, the shorter the bellows contract and the smaller the inductance, so the higher the natural resonance frequency. For example, if the movement range of the upper electrode (i.e., the stretching range of the bellows) is 70 mm, the continuous series resonant frequency is from about 40 MHz to about 60 MHz when the gap between the electrodes is continuously changed from the minimum value to the maximum value. It changes continuously (FIG. 4 of patent document 1). Therefore, when a frequency of 40 MHz to 60 MHz is used for the high frequency for plasma generation, the intrinsic series resonant frequency of the high frequency transmission path near the upper electrode overlaps with the frequency of the high frequency for plasma generation by adjusting the gap between the electrodes. When the series resonance occurs.

The method of the said patent document 1 is equipped with the electroconductive bypass member in the pressure reduction space (ceiling space) between an upper electrode and a chamber ceiling wall in order to cope with this problem. The bypass member is typically configured to be bendable by bending a rectangular aluminum sheet, and connects the upper electrode and the chamber ceiling wall in parallel with the bellows. By providing this bypass member, the resonance point of the frequency-impedance characteristic on a high frequency transmission path near an upper electrode can be made into the higher frequency domain side, for example, 70 MHz or more (FIG. 6 of patent document 1). Therefore, when the inter-electrode gap is changed from the minimum value to the maximum value, even if the inter-electrode gap is arbitrarily adjusted by using a high frequency for plasma generation of 40 MHz to 60 MHz, it overlaps with the intrinsic series resonance frequency on the high frequency transmission line near the upper electrode. Therefore, no resonance phenomenon occurs that impairs the stability of the plasma.

Japanese Patent Laid-Open No. 2011-204764

However, the bypass member as described above may be a particle generation source due to its physical structure and elasticity. Particles generated from the bypass member in the ceiling space enter the processing space through a gap between the upper electrode and the side wall of the chamber, and have an undesirable effect on the plasma process such as generating an abnormal discharge. Further, even when the bypass member is used, there is a limit in moving the resonance point of the frequency-impedance characteristic on the high frequency transmission path near the upper electrode toward the higher frequency region, and it is not perfect as a countermeasure for resonance.

Because the plasma is usually a nonlinear load, in the chamber of the capacitively coupled plasma processing apparatus, harmonics having an integer multiple of the fundamental waves, or fundamental waves or IMDs having the sum or difference of fundamental waves and harmonics Intermodulation distortion) inevitably occurs. The most influential among these harmonics or IMD, i.e., having a large high frequency power, is the second harmonic. For this reason, when using the high frequency for plasma generation of 40 MHz, for example, it is necessary to prevent the generation of the resonance phenomenon not only in the fundamental wave of 40 MHz but also in the 2nd harmonic of 80 MHz. Therefore, even when the fluctuation range of the series resonance frequency is set to a frequency higher than 70 MHz by providing the bypass member as described above, the series resonance frequency of the high frequency transmission path near the upper electrode is secondary by adjusting the gap between the electrodes. When overlapping with the harmonic frequency (80 MHz), series resonance occurs. The series resonance caused by the second harmonic not only causes the problem of power loss or component loss, but also affects the plasma process as in the case of series resonance in the fundamental wave.

The present invention solves the problems of the prior art as described above, and does not cause particle generation on the high frequency transmission path near the upper electrode in the cathode coupling method of configuring the upper electrode, which is the opposite electrode, to be movable in the vertical direction. Provided is a capacitively coupled plasma processing apparatus capable of effectively preventing the occurrence of unwanted resonance.

The present invention also provides a capacitively coupled plasma processing apparatus for improving the function of moving the resonance point of the frequency-impedance characteristic on the high frequency transmission path near the upper electrode to the higher frequency region side.

A plasma processing apparatus in accordance with the first aspect of the present invention is a high frequency discharge of a processing gas in a processing space between an upper electrode and a lower electrode provided to face each other in a vacuum-ventable tubular processing container that accommodates a substrate to be processed. A plasma processing apparatus for generating a plasma by the substrate and performing a desired treatment on the substrate held on the lower electrode under the plasma, wherein the upper electrode is moved in a vertical direction at intervals from a sidewall of the processing container. An upper electrode support mechanism for supporting the movable electrode; and a flexible conductive partition wall connecting the upper electrode and the ceiling wall of the processing container from the rear surface side of the upper electrode when viewed from the lower electrode side; An electrode body facing the lower electrode and a ceiling wall of the processing container; Back plate (背板) of opposite conductivity, and so that the air gap formed between the electrode body and the back plate has the dielectric material of a ring shape to join the perimeter of the peripheral portion and the back plate of the electrode body.

In the above device configuration, when the height position of the upper electrode is changed to adjust the gap between the electrodes, the conductive partition wall expands and contracts, and its inductance changes, and further, the intrinsic resonance frequency on the high frequency transmission path near the upper electrode changes. In particular, the series resonant frequency on the high frequency transmission path (high frequency transmission path on the back side of the upper electrode) from the processing space to the processing container at ground potential via the upper electrode and the conductive partition wall is changed.

On the other hand, in the above apparatus configuration, a capacitor is formed between the electrode main body and the back plate of the upper electrode, and the capacitance thereof is determined by the permittivity, area, and thickness of the voids. Therefore, by inserting a capacitor with a very low capacitance on the high frequency backside of the upper electrode, the variation range of the series resonance frequency on the high frequency backside of the upper electrode with the gap adjustment between the electrodes is greatly increased toward the high frequency region. It becomes possible to move, and it is easy to move to the frequency range higher than the frequency of the high frequency to be used, and higher than the frequency of the 2nd harmonic.

In the plasma processing apparatus according to the second aspect of the present invention, a high frequency discharge of a processing gas is performed in a processing space between an upper electrode and a lower electrode provided to face each other in a vacuum-ventable tubular processing container that accommodates a substrate to be processed. A plasma processing apparatus for generating a plasma by the substrate and performing a desired treatment on the substrate held on the lower electrode under the plasma, wherein the upper electrode is movably supported in a vertical direction at intervals from a side wall of the processing container. And an expandable conductive partition wall connecting the upper electrode and the ceiling wall of the processing container from the rear surface side of the upper electrode when viewed from the lower electrode side, wherein the upper electrode is the lower electrode. An electrode body facing the electrode, and a ceiling wall of the processing container A conductive back plate and which, has a dielectric that is interposed in a sandwich between the electrode body and the back plate.

In the above device configuration, when the height position of the upper electrode is changed to adjust the gap between the electrodes, the conductive partition wall expands and contracts, and its inductance changes, and further, the intrinsic resonance frequency on the high frequency transmission path near the upper electrode changes. In particular, the series resonant frequency on the high frequency transmission path (high frequency transmission path on the back side of the upper electrode) from the processing space to the processing container at ground potential via the upper electrode and the conductive partition wall is changed.

On the other hand, in the above-described device configuration, a capacitor is formed between the electrode body and the back plate of the upper electrode, and its capacitance is determined by the dielectric constant, area, and thickness of the dielectric. Therefore, a capacitor with a low capacitance is inserted on the high frequency backside of the upper electrode, thereby shifting the fluctuating range of the series resonance frequency on the high frequency backside of the upper electrode with the gap adjustment between the electrodes toward the high frequency region. It becomes possible to make it possible, and can move to the frequency range higher than the frequency of the high frequency used at least.

According to the plasma processing apparatus of the present invention, by having the configuration as described above, particles are not generated on the high frequency transmission path near the upper electrode in the cathode coupling method of configuring the upper electrode, which is the opposite electrode, to be movable in the vertical direction. It is possible to effectively prevent the occurrence of unwanted resonance phenomenon. Further, the function of moving the resonance point of the frequency-impedance characteristic on the high frequency transmission path near the upper electrode to the higher frequency region side can be improved.

1 is a cross-sectional view showing the configuration of a plasma processing apparatus in one embodiment of the present invention.
2 is a partially enlarged cross-sectional view showing the main configuration of the vicinity of the upper electrode in the plasma processing apparatus.
3 is a circuit diagram showing an equivalent circuit of a high frequency transmission path near the upper electrode in the plasma processing apparatus.
4 is a partially enlarged cross-sectional view showing the configuration of the vicinity of the upper electrode in the comparative example.
5 is a circuit diagram showing an equivalent circuit of the high frequency transmission path near the upper electrode in the comparative example.
6 is a diagram showing frequency-impedance characteristics of the high frequency transmission path near the upper electrode in the comparative example.
7 is a diagram showing a frequency-impedance characteristic (partly estimated value) of the high frequency transmission path near the upper electrode in the experimental example.
8 is a cross-sectional view showing the configuration of the plasma processing apparatus in the second embodiment.
9 is a partially enlarged cross-sectional view showing a modification of the configuration near the upper electrode.
10 is a partially enlarged cross-sectional view showing another modification of the configuration of the vicinity of the upper electrode.
11 is a partially enlarged cross-sectional view showing another modification of the configuration of the vicinity of the upper electrode.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

<Example 1>

Fig. 1 shows the configuration of a plasma processing apparatus in one embodiment of the present invention. This plasma processing apparatus is constituted as a capacitive coupling type (parallel flat type) plasma etching apparatus of a cathode coupling method, and is formed by, for example, a cylindrical vacuum chamber whose surface is made of anodized aluminum (anode oxidation treatment). Container (10). The chamber 10 has a cylindrical side wall 10a, a disc top cover 10b which hermetically covers an upper end of the side wall 10a, and a bottom wall connected to the lower end of the side wall 10a. (Not shown) and grounded.

In the center of the bottom of the chamber 10, a susceptor support 12 electrically insulated from the chamber 10 is provided, and on the susceptor support 12 a thick disc-shaped book made of aluminum, for example. The acceptor 14 is fixedly arranged coaxially with the chamber 10. The susceptor 14 constitutes a lower electrode, on which the semiconductor wafer W is placed, for example, as a substrate to be processed.

The electrostatic chuck 16 for holding the semiconductor wafer W is mounted on the upper surface of the susceptor 14. The electrostatic chuck 16 interposes an electrode 18 made of a conductive film between a pair of insulating layers or insulating sheets, and the DC power source 22 is electrically connected to the electrode 18 via a switch 20. Is connected. By the DC voltage from the DC power supply 22, the semiconductor wafer W can be held by the electrostatic chucking force by the electrostatic chuck 16. Although not shown, the susceptor support 12 is cooled to a predetermined temperature by a coolant, for example, coolant, and the heat transfer gas, for example, He gas, is transferred to the upper surface of the electrostatic chuck 16 and the semiconductor wafer W through a gas supply line. There is also a wafer temperature control mechanism for supplying the back surface of the wafer).

Around the susceptor 14, a cylindrical inner wall member 26 made of, for example, aluminum with anodized surface is provided via a ring-shaped insulator 24, and the inner wall member 26 and the chamber ( An annular exhaust space 27 extending to the bottom of the chamber 10 is formed between the side walls 10a of 10. The focus ring 30 is mounted on the ring insulator 24 and the inner wall member 26 via an annular dielectric 28 made of, for example, quartz. The focus ring 30 is for improving the uniformity of etching, and is made of silicon, for example, and is disposed on the electrostatic chuck 16 so as to cover the periphery of the semiconductor wafer W.

An exhaust port (not shown) of the chamber 10 is formed at the bottom of the exhaust space 27. An exhaust device 34 is connected to the exhaust port via an exhaust pipe 32. The exhaust device 34 has a vacuum pump such as a turbo molecular pump, so that the interior of the chamber 10 can be decompressed to a desired degree of vacuum. An APC valve (not shown) for controlling the pressure in the chamber 10 is provided in the middle of the exhaust pipe 32. The side wall 10a of the chamber 10 is equipped with a gate valve (not shown) which opens and closes the inlet / outlet (not shown) of the semiconductor wafer W. As shown in FIG.

Two susceptor feeders are electrically connected to the susceptor 14. The high frequency power supply unit of the first system includes a high frequency power source 36 for outputting a high frequency RF ₁ of a constant frequency (for example, 40.68 MHz) suitable for generation of plasma, and an impedance of the high frequency power source 36 to the load side. It has a matcher 38 for matching impedance. The high frequency power supply unit of the second system is a high frequency power supply 40 for outputting a high frequency RF ₂ of a constant frequency (for example, 3.2 MHz) suitable for the introduction of ions from the plasma to the semiconductor wafer W on the susceptor 14. ) And a matching unit 42 for matching the impedance of the load side with the impedance of the high frequency power supply 40.

The configuration of the vicinity of the upper electrode as the counter electrode is as follows. In the upper portion of the chamber 10, an upper electrode 44 configured to face in parallel with the susceptor 14 and move in the vertical direction is provided coaxially with the susceptor 14. The upper electrode 44 includes an electrode body 46 facing the susceptor 14, a conductive back plate 48 facing the ceiling wall (top cover) 10b of the chamber 10, and an electrode body. It has a ring-shaped dielectric 52 which joins the periphery of the electrode main body 46 and the periphery of the back board 48 so that the space | gap 50 is formed between 46 and the back board 48. As shown in FIG.

The electrode main body 46 of the upper electrode 44 is a thick disk-shaped conductor made of, for example, anodized aluminum, and has a gas buffer chamber 54 therein, and a plurality of gases on its lower surface. It has a ventilation hole 46a, and has the gas inlet 46b in the upper surface. In this experimental example, in order to etch silicon on the main surface of the semiconductor wafer W, a disk-shaped top plate 56 made of quartz having high etching resistance on the surface (lower surface) of the electrode main body 46. Is attached. The quartz top plate 56 is provided with a plurality of gas ventilation holes (through holes) 56a communicating with the gas ventilation holes 46a of the electrode main body 46. The electrode body 46 and the quartz top plate 56 are integrated to form a shower head.

The back plate 48 of the upper electrode 44 is a circular plate body made of, for example, anodized aluminum, and has a cylindrical shaft (upper electrode support member) 58 extending in a direction perpendicular to the center thereof. An opening 48a for passing therethrough is formed. The back board 48 is fixed to the outer peripheral surface of the lower end of the shaft 58. Since the electrode main body 46 is fixed to the back board 48 via the ring-shaped dielectric 52 as mentioned later, it may be directly fixed to the lower end of the shaft 58, and the other member may be interposed.

The ring-shaped dielectric 52 is made of, for example, alumina, and the upper surface of the periphery thereof is larger than the upper surface of the electrode body 46 so that the void 50 is formed between the electrode body 46 and the back plate 48. The electrode main body 46 is mounted and supported by the flange part 52a which is in close contact with the lower surface of the peripheral part of the back board 48 at the position as high as the gap size of 50, and protrudes radially inward from the inner peripheral surface. In this experimental example, a ring-shaped top plate 60 made of quartz is also attached to the lower surface of the ring-shaped dielectric 52 for silicon etching. A small gap 61 of several mm or less is formed between the outer circumferential surface of the back plate 48, the ring dielectric 52, and the ring top plate 60 and the side wall 10a of the chamber 10.

The shaft 58 is made of stainless steel, for example, and is an insulating guide member, for example a collar 62, which is mounted in the central opening of the ceiling wall (top cover) 10b of the chamber 10. It is installed to be movable in the vertical direction along the. In addition, the upper end of the shaft 58 is coupled to a lift mechanism (not shown) above the chamber 10, and the upper electrode 44 can move upward and downward like a piston by a lift driving force of the lift mechanism. In addition, it is possible to stop and fix at any height position within a movable range (for example, 70 mm).

The inner side of the shaft 58 is hollow, and the process gas supply pipe 66 from the process gas supply unit 64 disposed outside the chamber 10 passes through the space inside the shaft 58 to form the electrode main body 46. Is connected to the gas inlet port 46b. The process gas supply pipe 66 in the illustrated configuration includes a rigid downstream gas pipe 68 that moves up and down with the upper electrode 44 by the driving force of the lift mechanism, the process gas supply part 64 and the downstream gas pipe ( It consists of the flexible upstream gas pipe 70 which connects the inlet port 68a of 68. As shown in FIG.

Adjacent to the outer side of the shaft 58, a bellows 72 for hermetically connecting the upper electrode 44 and the ceiling wall (top cover) 10b of the chamber 10 is mounted. The bellows 72 is made of, for example, stainless steel and functions as a flexible partition wall that blocks pressure. The bellows 72 forms a ceiling space CS between the upper electrode 44 and the ceiling wall 10b of the chamber 10. The ceiling space CS communicates with the plasma generation space or the processing space PS between the electrodes 14 and 44 via the gap 61 at the edge of the side wall 10a of the chamber 10 and is a decompression space. .

The bellows 72 has an upper end coupled to the ceiling wall 10b of the chamber 10, and a lower end coupled to the back plate 48 of the upper electrode 44. As a result, the back plate 48 of the upper electrode 44 is electrically connected to the chamber 10 serving as the ground potential member via the bellows 72.

The control unit 74 includes one or a plurality of microcomputers, and according to software (program) and recipe information stored in an external memory or an internal memory, each part in the apparatus, in particular, a high frequency power source 36, 40, a matching device. Each of the operations 38 and 42, the exhaust device 34, and the lift mechanism is controlled, and the operation (sequence) of the entire device is controlled.

The control unit 74 also stores an operation panel (not shown) for a man machine interface including various input devices such as a keyboard or a display device such as a liquid crystal display, and various data such as various programs or recipes and setting values. Or an external storage device (not shown) that accumulates. In this embodiment, the control unit 74 is shown as one control unit, but a plurality of control units may take the form of sharing the functions of the control unit 74 in parallel or hierarchically.

The basic operation of sheet type dry etching in this capacitively coupled plasma etching apparatus is performed as follows. First, the semiconductor wafer W to be processed is loaded into the chamber 10 with the gate valve open, and placed on the electrostatic chuck 16. Then, the processing gas, for example Cl-based etching gas, is introduced from the processing gas supply unit 64 into the chamber 10 at a predetermined flow rate and flow rate ratio, and the vacuum exhaust path by the exhaust device 34 is introduced into the chamber 10. Set the pressure to the set value. In addition, the high frequency RF ₁ (40.68 MHz) from the high frequency power supply 36 and the high frequency RF ₂ (3.2 MHz) from the high frequency power supply 40 are superimposed (or alone) and applied to the susceptor 14. . In addition, a DC voltage is applied from the DC power supply 22 to the electrode 18 of the electrostatic chuck 16 to fix the semiconductor wafer W on the electrostatic chuck 16. The etching gas discharged from the shower head (upper electrode) 44 is discharged under a high frequency electric field between both electrodes 44 and 14, and plasma is generated in the processing space PS. The workpieces (silicon in this experimental example) of the main surface of the semiconductor wafer W are etched by radicals or ions contained in the plasma.

In this plasma etching apparatus, the gap between the electrodes, which is one of the process conditions, can be arbitrarily adjusted by moving the upper electrode 44 up and down and changing its height position, whereby pressure, gas flow rate, RF power, etc. The margin of use of other process conditions is also expanded.

On the other hand, harmonics having a frequency of an integral multiple of each fundamental wave, or IMD (intermodulation distortion) having frequencies of sums or differences of fundamental waves or fundamental waves and harmonics are generated from the plasma generated in the chamber 10. These harmonics or IMDs not only cause power loss or component loss, but also affect the plasma process. These undesirable phenomena in the cathode coupling type capacitively coupled plasma etching apparatus include a high frequency transmission path from the processing space to the chamber 10 at ground potential via the upper electrode 44, that is, the upper electrode. On the near high frequency transmission path 75, in particular, the high frequency transmission path from the processing space to the chamber 10 at the ground potential via the upper electrode 44 and the bellows 72, that is, the high frequency transmission path on the back side of the upper electrode ( On 76), it appears prominent when series resonance occurs for either harmonic or IMD. Of course, even when series resonance occurs with respect to any fundamental wave on the high frequency transmission path 75 near the upper electrode, there is a risk of damaging the components on the high frequency transmission path 75, which is not preferable.

Therefore, it is necessary to devise such that no series resonance occurs on the high frequency transmission line 75 near the upper electrode for any one of fundamental waves, harmonics, and IMD. In addition, the most influential among the harmonics or the IMD, that is, having a large high frequency power is the second harmonic, and it is practically sufficient to prevent series resonance in the fundamental wave and the second harmonic. As in this experimental example, when high frequency (RF ₁ ) of 40.68 MHz is used for plasma generation, series resonance may be prevented at 40.68 MHz of the fundamental wave frequency and 81.36 MHz of the second harmonic frequency.

It goes without saying that it is also necessary to prevent the series resonance for the high frequency RF ₂ (3.2 MHz) and the second harmonic (6.4 MHz) for ion insertion. However, in this type of upper electrode movable plasma processing apparatus, even if the inter-electrode gap is minimized, the inherent series resonance frequency of the high frequency transmission path 75 near the upper electrode does not become several 10 MHz or less. Therefore, series resonance does not become a problem for high frequency RF ₂ (3.2 MHz) and its second harmonic (6.4 MHz).

In this embodiment, instead of providing a bypass member as disclosed in Patent Document 1, by special designing on the configuration of the upper electrode 44 itself, generation of particles on the high frequency transmission path near the upper electrode is caused. Instead, the generation of series resonance at the high frequency RF ₁ for plasma generation is reliably prevented, and also the series resonance at the second harmonic is surely prevented.

As shown in an enlarged view of the main part in FIG. 2, the upper electrode 44 in this embodiment includes an electrode main body 46 facing the susceptor 14 via the processing space PS, and a ceiling space ( The conductive body plate 48 facing the ceiling wall 10b of the chamber 10 and the air gap 50 are formed between the electrode body 46 and the plate plate 48 in the CS 10. It consists of a ring-shaped dielectric 52 which couples the periphery and the periphery of the back plate 48. In addition, in FIG. 2 (and FIGS. 4, 9-11), the inner peripheral surface of at least one of the ring-shaped dielectric 52 and the ring-shaped top plate 60 is simplified to a flat surface for ease of illustration and understanding. Doing.

3 shows an equivalent circuit of the high frequency transmission path 75 near the upper electrode. In this equivalent circuit, the capacitors C ₅₆ , C ₅₀ , the coil L ₇₂ and the resistor R ₇₂ form a series circuit between the interface 44S and the ground potential, and the high frequency transmission path 76 on the backside of the upper electrode. It corresponds to.

The capacitor C ₅₆ is allocated by the quartz top plate 56 attached to the lower surface of the electrode main body 46, and its capacitance is determined by the dielectric constant, area, and thickness of the quartz top plate 56. The capacitor C ₅₀ is formed between the electrode body 46 and the back plate 48 of the upper electrode 44, and its capacitance is mainly determined by the dielectric constant, area and thickness of the void 50. The coil L ₇₂ is assigned to the inductor portion of the bellows 72, and its inductance depends on the material, shape and size of the bellows 72, but varies with the length of the bellows 72. That is, the shorter the bellows 72 shrinks, the smaller the inductance becomes, and the longer the bellows 72 extends, the larger the inductance becomes. The resistor R ₇₂ is assigned to the resistance of the bellows 72, and the resistance value is determined by the material, shape and size of the bellows 72, and does not depend on the length of the bellows 72. The capacitor C ₆₁ is present in the high frequency transmission path from the boundary surface 44S described above in parallel with the high frequency transmission path 76 on the upper electrode back side to the side wall 10a of the chamber 10 through the gap 61. It is a capacitor, which is mainly determined according to the dielectric constant and dimensions of the gap 61, and does not depend on the height position of the upper electrode 44.

Here, as a comparative example, as shown in FIG. 4, the structure which omitted each element of the back board 48, the space | gap 50, and the ring-shaped dielectric 52 from the upper electrode 44 is considered. In this comparative example, the lower end of the bellows 72 is coupled to the upper surface (back side) of the electrode main body 46.

Fig. 5 shows an equivalent circuit of the high frequency transmission path 75 'near the upper electrode in this comparative example. Capacitor in the equivalent circuit (C _56, C _50), a coil (L ₇₂₎ and a resistor (R _72), the experiment example equivalent circuit (Fig. 3), the capacitor (C _56, C ₅₀₎ in the coil (L ₇₂ ) And resistance (R ₇₂ ), respectively. In other words, if the capacitor C ₅₀ is omitted from the equivalent circuit (FIG. 3) of the experimental example, the equivalent circuit (FIG. 5) of the comparative example is obtained. From the opposite viewpoint, when the capacitor C ₅₀ is added to the equivalent circuit of FIG. 5 (FIG. 5), it becomes the equivalent circuit (FIG. 3) of an experiment example.

By the way, the structure of the upper electrode vicinity in a comparative example is substantially the same as the structure of the upper electrode vicinity except the bypass member in the said patent document 1. Therefore, when the material, shape, and size of the chamber, the upper electrode, the bellows, the susceptor, and the like are the same as the upper electrode near the patent document 1, the frequency-impedance characteristics of the high frequency transmission path 75 'near the upper electrode are shown in FIG. It becomes as shown in 6 (this FIG. 6 corresponds to FIG. 4 of patent document 1).

In Fig. 6, the 'gap minimum time' is when the gap between the electrodes is minimized, that is, when the bellows 72 is longest, and the inductance thereof becomes the maximum value L _72max . The inherent series resonance frequency f _S1 and the parallel resonance frequency f _P1 in the high frequency transmission path 75 'near the upper electrode at this time are theoretically represented by the following equation (1), ( Appears as 2).

f _S1 = 1 / _2π√ (L _{72maxC 56} )

_{f P1 = 1 / 2π√ {(} L 72max · C 56 · C 61 / (C 56 + C 61)} ···· (2)

However, C ₅₆ and C ₆₁ are capacitances of the capacitors C ₅₆ and C ₆₁ .

In FIG. 6, the series resonant frequency f _S1 is about 38 MHz, and the parallel resonant frequency f _P1 is about 45 MHz.

In addition, when the field, the inter-electrode gap, maximum gap when 'have the maximum, that is, becomes a bellows 72 is the shortest, and when the inductance is to be the minimum value (L _72min). The inherent series resonance frequency f _S2 and the parallel resonance frequency f _P2 in the high frequency transmission path 75 'near the upper electrode at this time are theoretically represented by the following equation (3), ( 4) appears.

f _S2 = 1 / 2π√ (L _{72minC 56} )

_{f P2 = 1 / 2π√ {(} L 72min · C 56 · C 61 / (C 56 + C 61)} ···· (4)

In FIG. 6, the series resonance frequency f _S2 is about 64 MHz and the parallel resonance frequency f _P2 is about 75 MHz.

As described above, the upper electrode 44 of the experimental example has a configuration including a back plate 48, a cavity 50, and a ring-shaped dielectric 52 in addition to the electrode body 46 and the quartz top plate 56. As for the equivalent circuit, the capacitor C ₅₀ is included on the high frequency transmission path 76 on the back side of the upper electrode. In this case, the capacitor C ₅₀ is connected in series with the capacitor C ₅₆ , and the combined capacitance C _S is represented by the following equation (5).

_{C S = C 50 · C 56} / (C 50 + C 56) ···· (5)

However, C ₅₀ and C ₅₆ are capacitances of the capacitors C ₅₀ and C ₅₆ .

Here, the capacitance of the capacitor C ₅₀ is expressed by the following equation (6) when the permittivity of the cavity 50 is ε ₅₀ , the area is S ₅₀ , and the thickness is d ₅₀ .

_{C 50 = ε 50 · S 50} / d 50 ···· (6)

On the other hand, the capacitance of the capacitor C ₅₆ is expressed by the following equation (7) when the permittivity of the quartz top plate 56 is ε ₅₆ , the area is S ₅₆ , and the thickness is d ₅₆ .

_{C 56 = ε 56 · S 56} / d 56 ···· (7)

The dielectric constant ε ₅₀ of the void 50 is 1, and is about one fourth of the dielectric constant ε ₅₆ of the quartz top plate 56. Further, the area S ₅₀ of the void 50 is smaller than the area S ₅₆ of the quartz top plate 56 (approximately as small as the area of the central opening 48a of the back plate 48), for example, 0.8 It is a ship. Thus, for example, if the thickness d ₅₀ of the pore 50 is equal to the thickness d ₅₆ of the quartz top plate 56, C ₅₀ = 0.2 C ₅₆ from equations (6) and (7), From (5), C _S ≒ 0.17 C ₅₆ .

As described above, according to the experimental example, the capacitor C ₅₀ formed by the back plate 48 of the upper electrode 44, the gap 50, and the ring-shaped dielectric 52 is connected to the high frequency transmission path 76 on the back side of the upper electrode. By virtue of the configuration provided on the upper side), the synthesized capacitance C _S on the high frequency transmission path 76 on the back side of the upper electrode can be significantly reduced. Thereby, the resonance point of the frequency-impedance characteristic of the high frequency transmission path 75 near the upper electrode in the experiment example is higher than the resonance point of the frequency-impedance characteristic of the upper electrode near the upper electrode in the comparative example. It can be moved to the area side greatly. In other words, if C _S ≒ KC ₅₆ (K is a coefficient smaller than 1), the frequency-impedance characteristic (particularly each resonance point) can be set to a high frequency as a whole by about 1 / √K times.

In addition, the natural series resonant frequency f _S1 and the parallel resonant frequency f _{P1 of the} high frequency transmission path 75 near the upper electrode at the 'gap minimum time' are theoretically expressed from the equivalent circuit of FIG. , (9).

f _S1 = 1 / _2π√ (L _{72maxC S} ) (8)

_{f P1 = 1 / 2π√ {(} L 72max · C S · C 61 / (C S + C 61)} ···· (9)

However, C _S and C ₆₁ are capacitances of the capacitors C _S and C ₆₁ .

In addition, the natural series resonance frequency f _S2 and the parallel resonance frequency f _{P2 of the} high frequency transmission path 75 near the upper electrode at the 'gap maximum time' are theoretically expressed from the equivalent circuit of FIG. ), (11).

f _S2 = 1 / 2π√ (L _72min C _S ) 10

f _P2 = 1 / 2π√ {(L _72min C _S C ₆₁ / (C _S + C ₆₁ )} ...

As described above, when the thickness d ₅₀ of the gap 50 is the same as the thickness d ₅₆ of the quartz top plate 56 to be C _S ≒ 0.17 C ₅₆ , the high frequency transmission path 75 near the upper electrode is provided. The frequency-impedance characteristic of is as shown in FIG. Here, the natural series resonance frequency f _S1 of the 'gap minimum time' is about 93 MHz (38 × 1 / √0.17), and the natural series resonance frequency f _S2 of the 'gap maximum time' is about 156 MHz (64). × 1 / √0.17). The natural series resonant frequency f _S when the gap between the electrodes is halfway between the minimum and maximum is about halfway between about 93 MHz and about 156 MHz.

In addition, since the values of the intrinsic parallel resonance frequencies f _P1 and f _P2 at the 'gap minimum time' and 'gap maximum time' according to the experimental example also depend on the capacitance of the capacitor C ₆₁ , the intrinsic parallelism in the comparative example It cannot be calculated from the value of the resonant frequencies f _P1 and f _P2 (conventional) and the value of K in the relational equation of C _S ≒ KC ₅₆ (conventional). However, since K is a coefficient smaller than 1, the intrinsic parallel resonant frequencies f _P1 and f _P2 in the experimental example move toward the frequency region higher than the intrinsic parallel resonant frequencies f _P1 and f _P2 in the comparative example, Moreover, it exists in the frequency range higher than the intrinsic series resonant frequencies f _S1 and f _S2 in an experiment example from the relationship of Formula (8), (10), Formula (9), (11). Therefore, the parallel resonance point shown in FIG. 7 is estimation and was not calculated by calculation.

Thus, in the plasma etching apparatus of this embodiment, even if the gap between the electrodes is adjusted by changing the height position of the upper electrode 44 by the lift mechanism, the high frequency for plasma generation on the high frequency transmission path 75 near the upper electrode ( Not only can the series resonance at RF ₁ ) (40.68 MHz) be completely avoided, but also the series resonance at its second harmonic (81.36 MHz) can be completely avoided.

 <Other embodiments or modifications>

8 shows a configuration of a plasma processing apparatus in a second embodiment of the present invention. What is different from the first embodiment described above in this second embodiment is that the DC power supply unit 80, the switch 82, and the filter circuit 84 apply a DC voltage to the electrode main body 46 of the upper electrode 44. ), And all others are the same as in the first embodiment.

The DC power supply unit 80 is made of, for example, a variable DC power supply, and is configured to output a DC voltage (V _DC ) of -2000 to + 1000V. Alternatively, the DC power supply unit 80 may have a plurality of DC power supplies for outputting different DC voltages as another embodiment, and may selectively output one of the plurality of DC voltages. The polarity and absolute value of the output (voltage, current) of the DC power supply unit 80 and the on / off switching of the switch 82 are controlled by the controller 74.

In the chamber 10, a DC grounding component (not shown) made of a conductive material such as Si, SiC, or the like is attached to a suitable location in contact with the processing space PS. This DC ground component is always grounded via a ground line (not shown).

The filter circuit 84 applies the DC voltage V _DC from the DC power supply unit 80 to the electrode main body 46 of the upper electrode 44, while the processing space PS and the susceptor 14 are applied. It is comprised so that the high frequency electric current which flowed in through the upper electrode 44 may flow to a ground line, and not to a DC power supply unit 80 side. Although not shown, the filter circuit 84 is made of, for example, an LC ladder circuit, and has a ground potential from the processing space PS via the electrode body 46 of the upper electrode 44 and the filter circuit 84. The inductance of the coil in the LC ladder circuit and the capacitance of the capacitor are selected so that resonance does not occur on the high frequency transmission path (hereinafter referred to as 'upper electrode DC applied system high frequency transmission path') 86 up to. These coils and capacitors are commercial electronic components, and these inductances and capacitances can be selected without any limitation on hardware. In addition, the upper electrode DC applying system high frequency transmission path 86 has an electrical parallel relationship with the high frequency transmission path 75 near the upper electrode to the high frequency transmission path 76 near the upper electrode as viewed from the plasma side, and has a series resonance. Regarding, they are independent of each other.

In the structure provided with such an upper DC bias mechanism, the photoresist film (especially used for the mask of a plasma etching) is applied to the electrode main body 46 of the upper electrode 44, for example by applying negative DC voltage (V _DC ). , ArF resistor film) can be enhanced.

In addition, when the plasma is generated in the chamber 10, an ion sheath (hereinafter referred to as an “upper electrode sheath”) is formed between the plasma and the upper electrode 44. This upper electrode sheath acts as a capacitor for high frequency power. Therefore, the high frequency transmission path from the plasma to the ground potential via the electrode body 46 of the upper electrode sheath and the upper electrode 44 is the high frequency transmission path 75 near the upper electrode or the upper electrode DC applied system high frequency transmission. It corresponds to the addition of the capacitor | condenser of an upper electrode sheath in the inlet of the furnace 86 in series. Here, the capacitor of the upper electrode sheath changes its thickness (advanced capacitance) according to process conditions (pressure, RF power, gas type, etc.) or DC voltage (V _DC ), and the larger the sheath thickness, the smaller the capacitance. The smaller the sheath thickness, the larger the capacitance. Therefore, the presence of the upper electrode sheath causes the series resonant frequency to move slightly toward the higher frequency region side, and as the sheath thickness increases, the amount of movement increases.

9-11, the modification of the upper electrode in this invention is shown. In the modification of FIG. 9, the space of the void 50 in the upper electrode 44 is filled with the dielectric 88 to have an electrode structure without the void 50. In this case, the capacitance of the capacitor C ₈₈ formed between the electrode main body 46 and the back plate 48 of the upper electrode 44 is mainly determined by the dielectric constant, area, and thickness of the dielectric 88. Therefore, the material of the dielectric 88 is preferably low in dielectric constant. For example, when quartz is used for the dielectric ₈₈ , the capacitance of the capacitor C ₈₈ is approximately four times the capacitance of the capacitor C ₅₀ when the void 50 is formed. However, the composite capacitance C _S with the capacitor C ₅₆ of the quartz top plate 56 is C _S ≒ 0.5 C ₅₆ from the above equation (5), and the frequency-impedance characteristic of the high frequency transmission path 75 near the upper electrode. The series resonant frequency at can be shifted right by about 1 / √0.5 times on the frequency axis. In other words, the series resonance frequency of the 'minimum gap' can be moved to about 54 MHz. In this case, therefore, series resonance can be prevented at least for the fundamental frequency 40.68 MHz of the high frequency RF ₁ for plasma generation.

In the modification of FIG. 10, the periphery of the back plate 48 is extended downward to surround the outer peripheral surface of the dielectric 88. Basically, it is based on the modification of FIG.

In the modification of FIG. 11, a conductor, for example, an electrode plate 90 of silicon is attached to the lower surface of the electrode main body 46. For example, when etching the silicon oxide film on the main surface of the semiconductor wafer W, such a silicon electrode plate 90 is used as the top plate. In this case, in the high frequency transmission path 75 near the upper electrode, the capacitor C ₅₆ disappears, and only the capacitor C ₅₀ is the capacitor on the back electrode high frequency transmission path 76. However, the capacitance of the capacitor C ₅₀ is very small as described above, for example, C _{50 50} 0.2 C ₅₆ when the thickness of the void 50 is equal to the thickness of the quartz top plate ₅₆ . Therefore, in this case, the series resonance frequency in the frequency-impedance characteristic of the high frequency transmission path 75 near the upper electrode can be shifted to the right by about 1 / √0.2 times. In other words, the series resonance frequency of the 'gap minimum time' can be moved to about 84 MHz. In this case, therefore, series resonance at the fundamental wave frequency 40.68 MHz of the high frequency RF ₁ for plasma generation can be prevented, and series resonance at 81.36 MHz of the second harmonic can also be prevented.

Of course, it is possible to further increase the effect to move by increasing the thickness (d ₅₀₎ of the cavity (50). For example, when d ₅₀ is doubled, C ₅₀ ≒ 0.1 C ₅₆ . Therefore, in this case, the series resonant frequency in the frequency-impedance characteristic of the high frequency transmission line 75 near the upper electrode can be moved to the right by about 1 / √0.1 times on the frequency axis. That is, the series resonant frequency of the 'gap minimum time' can be moved to about 118 MHz.

As such, by forming the air gap ₅₀ that imparts a small capacitor C ₅₀ inside the upper electrode 44, the series resonance frequency in the frequency-impedance characteristics of the high frequency transmission path 75 near the upper electrode is greatly increased. It can be moved to the right side (higher frequency region side), whereby the series resonance at the high frequency RF ₁ for plasma generation and the series resonance at the second harmonic can be reliably prevented.

Moreover, the structure which forms the space | gap 50 inside the upper electrode 44 is compared with the structure which fills the space | gap 50 with the dielectric 88 (FIG. 9, FIG. 10), The whole upper electrode 44 There is also an advantage that the volume, weight and cost are significantly lower.

In addition, it is also possible to use together the upper electrode structure which concerns on this invention, and the bypass member of patent document 1 together. In particular, in the present invention, when the upper electrode 44 has an electrode structure having no voids 50, the use with the bypass member may be practical. In such a case, the bypass member has a light burden on the effect of shifting the resonance point of the frequency-impedance characteristic toward the higher frequency region side, so that the optimum configuration can be obtained from other viewpoints such as prevention of particle generation, cost reduction, or ease of mounting. Can be.

The present invention is not limited to the plasma etching apparatus as in the above embodiment, but is applied to the capacitively coupled plasma processing apparatus of the cathode coupling method that performs any plasma process such as plasma CVD, plasma ALD, plasma oxidation, plasma nitridation, sputtering, and the like. It is possible. The substrate to be processed in the present invention is not limited to a semiconductor wafer, and various substrates or photomasks, CD substrates, printed boards, and the like for flat panel displays, organic ELs, and solar cells can also be used.

10: chamber
10a: sidewall of the chamber
10b: ceiling wall (top cover)
14: susceptor (lower electrode)
34: exhaust device
36, 40: high frequency power supply
38, 42: matcher
44: upper electrode (shower head)
46: electrode body
50: void
52: ring-shaped dielectric
64: processing gas supply unit
74: control unit
75: high frequency transmission line near the upper electrode
76: high frequency transmission path on the back of the upper electrode
80: DC power supply unit
84: filter circuit

Claims (10)

A plasma generated by a high frequency discharge of a processing gas is generated in a processing space between an upper electrode and a lower electrode disposed to face each other in a vacuum-ventable tubular processing container that accommodates a substrate to be processed in and out, and under the plasma, the lower electrode A plasma processing apparatus for performing a desired process on the substrate held on an image,
An upper electrode support mechanism for movably supporting the upper electrode in a vertical direction at intervals from a side wall of the processing container;
A stretchable conductive partition wall connecting the upper electrode and the ceiling wall of the processing vessel from the rear surface side of the upper electrode when viewed from the lower electrode side;
A first high frequency power source for applying a first high frequency wave for generating plasma to the lower electrode,
The upper electrode includes an electrode body facing the lower electrode, a conductive back plate facing the ceiling wall of the processing container, and a periphery of the electrode body and the back plate such that voids are formed between the electrode body and the back plate. Has a ring-shaped dielectric to join the periphery,
At the height position of the upper electrode which minimizes the distance between the upper electrode and the lower electrode by the upper electrode supporting mechanism, from the interface between the processing space and the upper electrode to the ground potential via the upper electrode. And a series resonant frequency present in a frequency-impedance characteristic on a high frequency transmission line of the second harmonic of the first high frequency. delete The method of claim 1,
And a second high frequency power source for applying a second high frequency power for introducing ions from the plasma to the substrate on the lower electrode to the lower electrode. delete delete A plasma generated by a high frequency discharge of a processing gas is generated in a processing space between an upper electrode and a lower electrode disposed to face each other in a vacuum-ventable tubular processing container that accommodates a substrate to be processed in and out, and under the plasma, the lower electrode A plasma processing apparatus for performing a desired process on the substrate held on an image,
An upper electrode support mechanism for movably supporting the upper electrode in a vertical direction at intervals from a side wall of the processing container;
A stretchable conductive partition wall connecting the upper electrode and the ceiling wall of the processing vessel from the rear surface side of the upper electrode when viewed from the lower electrode side;
A first high frequency power source for applying a first high frequency wave for generating plasma to the lower electrode,
The upper electrode has an electrode body facing the lower electrode, a conductive back plate facing the ceiling wall of the processing container, and a dielectric sandwiched between the electrode body and the back plate;
At a height position of the upper electrode where the distance between the upper electrode and the lower electrode is minimized, a frequency on a high frequency transmission path from the interface between the processing space and the upper electrode to the ground potential via the upper electrode; The series resonant frequency present in the impedance characteristic is higher than the frequency of the second harmonic of the first high frequency. delete The method of claim 6,
And a second high frequency power source for applying a second high frequency power for introducing ions from the plasma to the substrate on the lower electrode to the lower electrode. delete The method according to claim 1 or 6,
And a direct current power source for applying a direct current voltage through a filter circuit to the electrode body of the upper electrode.

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