JP5317992B2 - Plasma processing apparatus and electrode plate for plasma processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma processing apparatus capable of effectively attaining uniformity in plasma density. <P>SOLUTION: A dielectric material 90 disposed on the main surface of an electrode 38 has a flat first portion formed in the center of the electrode 38 so as to be in concentric configuration with a substrate in a processing vessel, with a first diameter larger than or equal to 1/10 of the gauge of the substrate and a first constant thickness, and a flat second portion formed in the side more outside than the first portion, with a second diameter larger than or equal to the first diameter and a second constant thickness thinner than the first constant thickness. The dielectric material has a thickness profile assimilated to an ideal thickness profile to perform a uniform processing operation to the workpiece. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a technique for performing plasma processing on a substrate to be processed, and more particularly to a high-frequency discharge plasma processing apparatus that generates a plasma by applying a high frequency to an electrode and an electrode plate for the plasma processing apparatus.

  In processes such as etching, deposition, oxidation, sputtering and the like in the manufacturing process of semiconductor devices and FPDs (Flat Panel Displays), plasma is often used in order to allow a process gas to react well at a relatively low temperature. In general, plasma processing apparatuses are broadly classified into methods that use glow discharge or high-frequency discharge and methods that use microwaves as methods for generating plasma.

  In a high-frequency discharge type plasma processing apparatus, an upper electrode and a lower electrode are arranged in parallel in a processing vessel or a reaction chamber, a substrate to be processed (semiconductor wafer, glass substrate, etc.) is placed on the lower electrode, and an upper electrode is placed. Alternatively, a high frequency voltage for plasma generation is applied to the lower electrode through a matching device. Electrons are accelerated by the high-frequency electric field generated by the high-frequency voltage, and plasma is generated by impact ionization between the electrons and the processing gas.

  Recently, with the miniaturization of design rules in the manufacturing process, high-density plasma under low pressure is required for plasma processing, and the above-described high-frequency discharge type plasma processing apparatus is much more than conventional (generally 27 MHz or less). A frequency in a high high frequency region (50 MHz or more) has been used. However, when the frequency of the high-frequency discharge increases, the high-frequency power applied from the high-frequency power source through the power supply rod to the back surface of the electrode propagates through the electrode surface by the skin effect and is centered from the edge portion of the electrode main surface (surface facing the plasma). It flows toward the part. When high-frequency current flows from the edge to the center on a uniform electrode main surface, the electric field strength at the center of the electrode main surface is higher than the electric field strength at the edge, and the density of the generated plasma is also high. The electrode center side is higher than the electrode edge side. The plasma resistivity is low at the center of the electrode where the plasma density is high, and current also concentrates at the center of the electrode even at the opposing electrode, further increasing the non-uniformity of the plasma density.

  In order to solve this problem, a structure in which the central portion of the main surface of the high-frequency electrode is formed of a high resistance member is known (for example, Patent Document 1). In this technique, the central portion of the main surface (plasma contact surface) of the electrode on the side connected to the high frequency power source is configured with a high resistance member, and more high frequency power is consumed as Joule heat there. The electric field strength at the surface is relatively lowered at the center of the electrode rather than at the outer periphery of the electrode, and the above-described plasma density non-uniformity is corrected.

JP 2000-323456 A

  However, in the high-frequency discharge type plasma processing apparatus as described above, if the central portion of the main surface of the high-frequency electrode is made of a high-resistance member, the consumption of high-frequency power (energy loss) due to Joule heat may increase. There is.

  The present invention has been made in view of such problems of the prior art, and provides a high-frequency discharge plasma processing apparatus and an electrode plate for the plasma processing apparatus that can efficiently achieve uniform plasma density on a substrate to be processed. provide.

The plasma processing apparatus of the present invention is a plasma processing apparatus that performs a plasma process on a substrate to be processed having a predetermined diameter, and is disposed in the processing container that can be depressurized to store the substrate to be processed. A first electrode, a gas supply unit for supplying a processing gas into the processing vessel, a high-frequency electric field forming unit for forming a high-frequency electric field in the processing vessel to generate plasma of the processing gas, and the first A dielectric provided on a main surface of one electrode, and the dielectric is formed at the center of the dielectric so as to be concentric with the substrate disposed in the processing container. a flat first portion having a first diameter and a first predetermined thickness of at least 1/10 of the diameter, is formed in the radially outer side than the first portion is greater than said first diameter A second diameter and the first constant thickness A flat second portion having a remote smaller second predetermined thickness is formed on the radially outer side than the second portion, the central portion thickness toward the edge portion from that of the first electrode And a third portion that is linearly and tapered, and has a film thickness profile that simulates an ideal film thickness profile for obtaining uniform processing on the substrate to be processed.

In the plasma processing apparatus of the present invention, the dielectric provided on the main surface of the first electrode is a flat first having a first diameter of 1/10 or more of the aperture of the substrate and a first constant thickness. and portions, formed on the radially outer side than the first portion, a second portion flat having a second diameter and smaller second predetermined thickness than the first predetermined thickness greater than the first diameter And a third portion formed radially outward from the second portion and having a thickness that decreases linearly and tapered from the center portion of the first electrode toward the edge portion, The impedance on the electrode center side is relatively high with respect to the plasma space side, and the impedance on the electrode edge side is lowered to strengthen the high-frequency electric field on the electrode edge side while weakening the high-frequency electric field on the electrode center side. By the electric field strength on the substrate To improve the uniformity of the plasma density.

The ideal film thickness profile of the dielectric for obtaining a uniform plasma treatment on the substrate to be processed is such that the thickness of the dielectric decreases in an arch shape from the center to the edge of the electrode. It is difficult to form the main surface of the electrode into a curved concave surface. The invention, together with a stepwise decreasing the thickness of the dielectric towards the edge portion from the center portion of the first electrode from said first portion to said second portion, the electrode in the third portion By reducing the length of the first electrode linearly and taperingly toward the electrode edge portion, a film thickness profile simulating the ideal film thickness profile is realized while facilitating the processing of the main surface of the first electrode.

In the above configuration, the area size of the dielectric may be arbitrarily set according to the size of the substrate to be processed, but typically may be set to substantially the same size. That is, the position of the edge portion where the thickness of the dielectric is minimized may be set near the position facing the edge portion of the substrate to be processed. In addition, since there is a certain correlation between the dielectric constant of the dielectric that gives good in-plane uniformity and the thickness of the dielectric at the center of the electrode, the center of the electrode can be matched to the dielectric constant of the dielectric used. What is necessary is just to set the thickness of the dielectric in a part.

  As a preferred embodiment of the present invention, a conductive shield member may be provided on the main surface of the first electrode so as to cover a part of the dielectric, for example, the vicinity of the edge portion. According to such a configuration, it is possible to weaken the effect of reducing the electric field strength of the dielectric in the region covered with the shield member, and to adjust the electric field strength distribution by changing the shape and / or size of the opening of the shield member. Can do. This shield member is preferably attached detachably, that is, replaceable.

  Further, as a preferred aspect, on the main surface of the first electrode, the outer electrode portion from a position separated by a desired distance radially outward from the outer peripheral edge of the dielectric is moved toward the plasma generation space. It can also be set as the structure which protrudes only the protrusion amount. In such an electrode structure, by providing a protruding portion on the outer side in the radial direction of the dielectric, the electric field strength distribution characteristics can be controlled or adjusted in a direction in which the electric field strength is increased in the region near the edge portion of the substrate to be processed. The electric field intensity distribution control by the overhanging portion can be adjusted or varied depending on the overhanging amount of the overhanging portion and the position of the overhanging step portion.

  Further, as another preferred embodiment, a configuration in which the dielectric protrudes toward the plasma generation space by a desired protrusion amount on the main surface of the first electrode is also possible. In such an electrode structure, the electric field strength distribution characteristics can be controlled or adjusted in such a direction as to increase the electric field strength by the amount of the dielectric projecting at each position in the plasma generation space facing the dielectric.

  According to still another preferred embodiment, a cavity is provided inside the dielectric on the main surface of the first electrode, and a fluid dielectric material (preferably an organic solvent) is placed in the cavity. In this configuration, the dielectric constant and impedance of the entire dielectric can be arbitrarily adjusted by appropriately selecting or setting the amount of the dielectric material to be put into the cavity and the shape of the occupied space. Such a cavity can also be formed in a solid dielectric, wherein at least the front surface of the main surface of the first electrode is made of a solid dielectric, and the inner wall surface or recess is formed as an electrode base material. (Conductor) can also be used.

  In the plasma processing apparatus of the present invention, an electrostatic chuck for attracting and holding the substrate to be processed by the Coulomb force may be provided on the main surface of the first electrode on the high frequency power source side, or the counter electrode, that is, the first electrode. You may provide in the main surface of 2 electrodes. When the electrostatic chuck is provided on the main surface of the first electrode, the second electrode may be connected to the ground potential through the processing container, and the high-frequency current in the plasma may be passed to the ground through the processing container. .

An electrode plate for a plasma processing apparatus according to the present invention is an electrode plate provided in a processing vessel of a plasma processing apparatus that performs plasma processing on a substrate to be processed having a predetermined diameter, and has a dielectric on the main surface facing the plasma. And the dielectric is formed at the center of the dielectric so as to be concentric with the substrate disposed in the processing container, and has a first diameter of 1/10 or more of the aperture of the substrate and the first a first portion flat with a constant thickness of 1, than said first portion is formed radially outwardly, than the first second diameter and said first predetermined thickness greater than the diameter A flat second portion having a small second constant thickness and a radially outer side than the second portion, and the thickness is linear and tapered from the electrode center portion toward the electrode edge portion. A third portion that decreases, and the substrate to be processed includes It has a thickness profile Gishi ideal thickness profile to obtain a uniform process of. The electrode plate having such a configuration can exhibit the same operation as the first electrode provided with the dielectric in the plasma processing apparatus.

  According to the plasma processing apparatus or the electrode plate for a plasma processing apparatus of the present invention, uniform plasma density on the substrate to be processed can be efficiently achieved by the configuration and operation as described above.

It is a longitudinal cross-sectional view which shows the structure of the plasma etching apparatus in one Embodiment of this invention. It is a top view which shows the principal part of the susceptor structure by one structural example. FIG. 2 is a partially enlarged longitudinal sectional view showing a main part of the susceptor structure of FIG. 1. It is a figure which shows an example of the convex part number density distribution characteristic in the susceptor structure of FIG. It is a figure which shows typically the mechanism of the high frequency discharge in a plasma etching apparatus. It is a top view which shows the directivity of the high frequency current which flows through the main surface of a high frequency electrode. It is a substantially longitudinal cross-sectional view which shows the flow of the high frequency current in the susceptor structure of the said structural example, and the radiation | emission of high frequency electric power (electric field). It is a characteristic view which shows the attenuation | damping characteristic in the depth direction of the electromagnetic waves (high frequency current) which flow through a conductor. It is a figure which shows the electric field strength distribution characteristic in an electrode radial direction when the ratio of the convex part number density of an electrode center part and an edge part is made into a parameter in the said structural example. It is a fragmentary longitudinal cross-section which shows the structure which provides an electrostatic chuck integrally with the susceptor by the said structural example. It is a figure which shows the impedance ratio characteristic of the convex part and bottom face part in the susceptor structure with an electrostatic chuck of FIG. It is a figure which shows the manufacturing method of the susceptor structure with an electrostatic chuck of FIG. 10 in order of a process. It is a figure which shows the modification of the susceptor structure by the said structural example. It is a longitudinal cross-sectional view which shows the structural example which applied the electrode convex part structure by the said structural example to an upper electrode. It is a top view which shows the electrode structure by the 2nd structural example. FIG. 16 is a partially enlarged longitudinal sectional view showing a main part of the electrode structure of FIG. 15. It is a figure which shows an example of the number distribution characteristic of the recessed part in the electrode structure of FIG. It is a figure which shows the manufacturing method of the structure which provides an electrostatic chuck integrally in the electrode structure by the said 2nd structural example in order of a process. It is a top view which shows the lower electrode structure in one Embodiment of this invention. It is a top view which shows the upper electrode structure by the said embodiment. It is a figure which shows an example of the parallel plate electrode structure in the said embodiment. It is a figure which shows the electric field strength distribution of the radial direction between electrodes which uses the film thickness of the center part of an upper electrode as a parameter in the parallel plate electrode structure of FIG. It is a figure which shows the more concrete Example of the film thickness profile regarding the dielectric film of the upper electrode in the said embodiment. It is a figure which shows the electric field strength distribution characteristic of the radial direction between the electrodes obtained by the Example and ideal profile of FIG. 23, respectively. It is a figure which shows another more concrete Example of the film thickness profile regarding the dielectric film of the upper electrode in the said embodiment. It is a figure which shows the electric field strength distribution characteristic of the radial direction between the electrodes obtained by the Example of FIG. It is a figure which shows another more concrete Example of the film thickness regarding the dielectric film of the upper electrode in the said embodiment, and a film quality profile. It is a figure which shows the electric field strength distribution characteristic of the radial direction between the electrodes obtained by the Example of FIG. FIG. 29 is a diagram showing the correlation between the dielectric constant of a dielectric film created from the data points in FIG. 28 and giving practically sufficient in-plane uniformity and the film thickness at the center of the electrode. It is a figure which compares and compares the 3rd Example (upper electrode) and a comparative example about the etching rate distribution characteristic of organic film etching. It is a figure which shows the lower electrode structure by the said embodiment in contrast with a comparative example. It is a figure which compares embodiment (lower electrode) and the comparative example about the etching rate distribution characteristic of organic film etching. It is a fragmentary sectional view which shows the principal part of the upper electrode structure in one Example. It is a figure which shows the electric field strength distribution characteristic of the radial direction between the electrodes obtained by the Example of FIG. It is a fragmentary sectional view which shows the principal part of the upper electrode structure by one Example as contrasted with a comparative example and a reference example. It is a figure which shows the electric field strength distribution characteristic of the radial direction between the electrodes obtained by the Example of FIG. 35, a comparative example, and a reference example, respectively. It is a fragmentary sectional view which shows the principal part of the upper electrode structure by one Example as contrasted with a comparative example. It is a figure which shows the distribution characteristic of the normalized etching rate obtained by the Example and comparative example of FIG. It is a fragmentary sectional view which shows the principal part of the upper electrode structure by one Example as contrasted with a comparative example and a reference example. It is a figure which shows the electric field strength distribution characteristic of the radial direction between the electrodes each obtained by the Example of FIG. 39, a comparative example, and a reference example. It is a fragmentary sectional view showing the important section of the upper electrode structure by one example. It is a fragmentary sectional view showing the important section of the upper electrode structure by one example. It is a fragmentary sectional view which shows the specific example in the Example of FIG. It is a figure which shows the electric field strength distribution characteristic of the radial direction between the electrodes obtained by the Example of FIG. It is a fragmentary sectional view which shows the modification in the Example of FIG.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows the configuration of a plasma processing apparatus according to an embodiment of the present invention. This plasma processing apparatus is configured as an RIE type plasma etching apparatus, and has a cylindrical chamber (processing vessel) 10 made of metal such as aluminum or stainless steel. The chamber 10 is grounded for safety.

  In the chamber 10, for example, a disk-like lower electrode or susceptor 12 on which a semiconductor wafer W is placed is provided as a substrate to be processed. The susceptor 12 is made of, for example, aluminum, and is supported by a cylindrical support portion 16 that extends vertically upward from the bottom of the chamber 10 via an insulating cylindrical holding portion 14. On the upper surface of the cylindrical holding part 14, a focus ring 18 made of quartz, for example, surrounding the upper surface of the susceptor 12 in an annular shape is disposed.

  An exhaust passage 20 is formed between the side wall of the chamber 10 and the cylindrical support portion 16, and an annular baffle plate 22 is attached to the entrance or midway of the exhaust passage 20 and an exhaust port 24 is provided at the bottom. . An exhaust device 28 is connected to the exhaust port 24 via an exhaust pipe 26. The exhaust device 28 includes a vacuum pump, and can reduce the processing space in the chamber 10 to a predetermined degree of vacuum. A gate valve 30 that opens and closes the loading / unloading port of the semiconductor wafer W is attached to the side wall of the chamber 10.

  A high frequency power supply 32 for generating plasma is electrically connected to the susceptor 12 via a matching unit 34 and a power feed rod 36. The high frequency power source 32 applies high frequency power of a predetermined high frequency, for example, 60 MHz, to the lower electrode, that is, the susceptor 12. A shower head 38, which will be described later, is provided on the ceiling portion of the chamber 10 as an upper electrode having a ground potential. Accordingly, the high frequency voltage from the high frequency power supply 32 is capacitively applied between the susceptor 12 and the shower head 38.

  An electrostatic chuck 40 is provided on the upper surface of the susceptor 12 to hold the semiconductor wafer W with an electrostatic attraction force. The electrostatic chuck 40 has an electrode 40a made of a conductive film sandwiched between a pair of insulating films 40b and 40c, and a DC power source 42 is electrically connected to the electrode 40a via a switch 43. The semiconductor wafer W can be adsorbed and held on the chuck by a Coulomb force by a DC voltage from the DC power source 42.

  Inside the susceptor 12, for example, a refrigerant chamber 44 extending in the circumferential direction is provided. A coolant having a predetermined temperature, for example, cooling water is circulated and supplied to the coolant chamber 44 from the chiller unit 46 through the pipes 48 and 50. The processing temperature of the semiconductor wafer W on the electrostatic chuck 40 can be controlled by the temperature of the coolant. Further, a heat transfer gas such as He gas from the heat transfer gas supply unit 52 is supplied between the upper surface of the electrostatic chuck 40 and the back surface of the semiconductor wafer W via the gas supply line 54.

  The shower head 38 at the ceiling includes an electrode plate 56 on the lower surface having a large number of gas vent holes 56a, and an electrode support 58 that detachably supports the electrode plate 56. A buffer chamber 60 is provided inside the electrode support 58, and a gas supply pipe 64 from the processing gas supply unit 62 is connected to a gas inlet 60 a of the buffer chamber 60.

  A magnet 66 extending annularly or concentrically is disposed around the chamber 10. In the chamber 10, an RF electric field in the vertical direction is formed by the high frequency power supply 32 in the space between the shower head 38 and the susceptor 12. A high-density plasma can be generated near the surface of the susceptor 12 by high-frequency discharge.

  The control unit 68 controls the operation of each unit in the plasma etching apparatus, such as the exhaust device 28, the high frequency power supply 32, the electrostatic chuck switch 43, the chiller unit 46, the heat transfer gas supply unit 52, and the processing gas supply unit 62. It is also connected to a host computer (not shown).

  In order to perform etching in this plasma etching apparatus, first, the gate valve 30 is opened, and the semiconductor wafer W to be processed is loaded into the chamber 10 and placed on the electrostatic chuck 40. Then, an etching gas (generally a mixed gas) is introduced into the chamber 10 from the processing gas supply unit 62 at a predetermined flow rate and flow rate ratio, and the pressure in the chamber 10 is set to a set value by the exhaust device 28. Further, high frequency power is supplied from the high frequency power supply 32 to the susceptor 12 with a predetermined power. Further, a DC voltage is applied from the DC power source 42 to the electrode 40 a of the electrostatic chuck 40 to fix the semiconductor wafer W on the electrostatic chuck 40. The etching gas discharged from the shower head 38 is turned into plasma by high-frequency discharge between the electrodes 12 and 38, and the main surface of the semiconductor wafer W is etched by radicals and ions generated by the plasma.

  In this plasma etching apparatus, by applying a high frequency in a frequency region (50 MHz or higher) much higher than the conventional (generally 27 MHz or lower) to the susceptor (lower electrode) 12, the plasma is densified in a preferable dissociated state, High density plasma can be formed even under lower pressure conditions.

  Next, features of the present invention in this plasma etching apparatus will be described in detail.

  2 and 3 show the configuration of the main part of the susceptor 12 as an example of the electrode structure according to the first configuration example. 2 is a plan view, and FIG. 3 is a partially enlarged longitudinal sectional view. As shown in the figure, the main surface of the susceptor 12 (in this configuration example, the upper surface of the susceptor 12, that is, the surface on the plasma generation space side) has a large number of discrete cylindrical convex portions 70 made of a conductor or a semiconductor in a discrete manner. Is provided. Each of these convex portions 70 constitutes a small electrode for applying high-frequency power or a high-frequency electric field to plasma, and preferably gradually increases from the electrode center portion toward the electrode edge portion as shown in FIG. It is arranged on the main surface of the susceptor 12 with such number density distribution or area density distribution.

  The operation of the susceptor 12 according to this embodiment will be described with reference to FIGS. As shown in FIG. 5, when high frequency power from a high frequency power supply 32 is supplied to the susceptor 12, the plasma PZ of the etching gas is generated near the semiconductor wafer W by high frequency discharge between the susceptor (lower electrode) 12 and the upper electrode 38. The generated plasma PZ diffuses in all directions, particularly upward and radially outward, and the electron current or ion current in the plasma PZ flows to the ground through the upper electrode 38 and the chamber side wall. Here, in the susceptor 12, the high frequency power applied from the high frequency power supply 32 to the back surface or the back surface of the susceptor through the power supply rod 36 propagates through the electrode surface layer due to the skin effect, and as shown in FIG. On the surface, the high-frequency current i flows in a reverse radial shape from the edge portion toward the center portion.

As shown in FIG. 7, in this embodiment, the high-frequency current i flows on the surface layer of the convex portion 70 on the main surface of the susceptor 12. Since the convex portion 70 protrudes toward the upper electrode 38 side, that is, the plasma PZ side, it is electrically coupled to the plasma PZ with a lower impedance than the bottom surface portion 12a of the main surface. For this reason, the high frequency power carried by the high frequency current i flowing through the surface layer of the main surface of the susceptor 12 is mainly emitted from the top surface of the convex portion 70 toward the plasma PZ. In order to increase the impedance ratio Z _12a / Z ₇₀ between the convex portion 70 and the bottom surface portion 12a on the main surface of the susceptor 12, that is, the ratio of the high frequency wave power or the power supply rate applied to the plasma PZ through the convex portion 70 is set. In order to increase the thickness, a configuration in which a dielectric 72 is provided around the convex portion 70 (on the bottom surface portion 12a) as shown in FIG.

  As described above, in this configuration example, a large number of convex portions 70 provided discretely on the main surface of the susceptor 12 function as small electrodes for supplying high-frequency power to the plasma PZ. By selecting the attributes (shape, size, spacing, density, etc.) of the convex portions 70, the high frequency power supply characteristics of the susceptor 12 that is an assembly of small electrodes can be set to desired characteristics.

  For example, as shown in FIG. 4, the distribution density is such that the number density of the protrusions 70 gradually increases from the center of the electrode toward the electrode edge as shown in FIG. The uniformity of the high-frequency power or the high-frequency electric field applied to the PZ (particularly the uniformity in the electrode radial direction) can be improved. In the example of FIG. 9, the radius of the susceptor 12 is 150 mm, and the ratio Ne / Nc between the number density Nc of the protrusions 70 at the center of the electrode and the number density Ne of the protrusions 70 at the electrode edge is 1 (times), 2 The electric field intensity distribution in the radial direction on the susceptor 12 when (double), 4 (double), 6 (double), or 8 (double) is selected is shown. It can be seen that as the ratio Ne / Nc is increased, the uniformity of the electric field strength is improved, and thus the uniformity of the plasma density is improved.

Of the other attributes of the convex portion 70, the size is particularly important. If the height of the convex portion 70 is too small, or more precisely, smaller than the skin depth δ, a part or most of the high-frequency current i is below the convex portion 70 on the main surface of the susceptor 12. The high-frequency electric field supplied from the projection 70 to the plasma PZ is weakened. Here, skin depth δ is a factor that the amplitude of the high-frequency current flowing through the surface layer of the conductor attenuates to 1 / e at the depth δ, and is given by the following equation (1).
δ = (2 / ωσμ) ^1/2 (1)
Where ω = 2πf (f: frequency), σ: conductivity, μ: permeability.

  As shown in FIG. 8, the amplitude of the electromagnetic wave (high-frequency current) flowing through the surface layer of the conductor is attenuated in the depth direction of the conductor due to the skin effect, and is attenuated to about 5% at a depth three times the skin depth δ. . Therefore, by setting the height of the convex portion 70 to be three times or more of the skin depth δ, most of the high-frequency current i (about 95% or more) is caused to flow into the convex portion 70, and plasma is generated from the convex portion 70. High frequency power can be efficiently discharged to the PZ. For example, when the material of the susceptor 12 and the convex portion 70 is aluminum and the frequency of the high frequency power supply 32 is 100 MHz, the skin depth δ is 8 μm. Therefore, the height of the convex portion 70 may be set to 24 μm or more.

  In addition, the width size of the convex portion 70, particularly the width size in the electrode radial direction is also important, and the larger the width size in the electrode radial direction is, the better it is to flow the high-frequency current i to the top surface of the convex portion 70. It may be set within a range of 30 μm to 500 μm at 3 times or more of δ, preferably at a frequency of 100 MHz.

The distance interval between the convex portions 70 also may be selected to such a value as to optimize the impedance ratio Z _12a / Z ₇₀ between the protrusions 70 and the bottom portion 12a, for example in the range of 100μm~1mm the 100MHz Preferably it is set.

  FIG. 10 shows a configuration example in which an electrostatic chuck 40 is integrally provided on the susceptor 12 in this plasma etching apparatus. As shown in the figure, the lower insulating film 40b of the electrostatic chuck 40 is formed on the main surface of the susceptor 12 and more precisely on the convex portion 70 and the dielectric 72, and the electrode film 40a is formed on the lower insulating film 40b. The upper insulating film 40c is formed on the electrode film 40a.

In this laminated structure, the film thickness D1 of the lower insulating film 40b of the electrostatic chuck 40 is important, and it is preferable to make the film thickness D1 relatively small as long as other conditions allow. That is, the ratio D2 / D1 (the parameter on the vertical axis in FIG. 11) between the distance (D1) from the top surface of the convex portion 70 to the electrode film 40a and the distance (D2) from the susceptor bottom surface portion 12a to the electrode film 40a is increased. As shown in FIG. 11, the ratio Z _12a / Z ₇₀ (function value in FIG. 11) of the impedance Z ₇₀ of the convex portion 70 on the main surface of the susceptor 12 and the impedance Z _12a of the bottom surface portion 12a is increased. be able to. From FIG. 11, this ratio D2 / D1 is preferably selected to be 2 (times) or more.

11, parameters S _12a / S ₇₀ on the horizontal axis the ratio of the total area S _12a of the total area S ₇₀ and the bottom portion 12a of the protrusion 70 (precisely, the convex portion top surface) on the main surface of the susceptor 12 It is. The impedance ratio Z _12a / Z ₇₀ (function value in FIG. 11) can also be increased by reducing the ratio S _12a / S ₇₀ , that is, by increasing the occupied area ratio of the convex portion 70. As described above, the higher the impedance ratio Z _12a / Z ₇₀ , the higher the high-frequency power supply rate from the projection 70 to the plasma PZ. From FIG. 11, the ratio S _12a / S ₇₀ is preferably selected to be 4 (times) or less.

  FIG. 12 shows a manufacturing method of the susceptor structure with an electrostatic chuck (FIG. 10) in the order of steps.

  First, as shown in FIG. 12A, for example, a resin mask 74 having an opening 74a corresponding to the convex portion 70 is placed on the main surface of a susceptor body (electrode substrate) 12 made of, for example, aluminum. In this mask 74, the planar shape and planar size of the opening 74a define the planar shape and planar size of the convex portion 70, and the depth of the opening 74a is the height size of the convex portion 70 (D2-D1: for example, 150 μm). Is specified.

  Next, as shown in FIG. 12B, the material of the convex portion 70, such as aluminum (Al), is sprayed on the entire main surface of the susceptor body 12 from above the mask 74, and the aluminum is put into the opening 74 a of the mask 74. Fill to the height of the top surface of the mask.

  Next, when the mask 74 is dissolved and removed from the main surface of the susceptor body 12 with, for example, a chemical solution, a large number of protrusions 70 of a predetermined size are formed on the main surface of the susceptor body 12 as shown in FIG. It remains discrete with a distribution pattern.

Next, as shown in FIG. 12 (d), a dielectric material such as alumina (Al ₂ O ₃ ) is sprayed on the entire main surface of the susceptor body 12, and a predetermined height (above the top surface of the convex portion 70 ( The dielectric film (72, 40b) is formed to a film thickness that reaches D1 (for example, 50 μm).

  Next, as shown in FIG. 12E, the material of the electrode film 40a of the electrostatic chuck 40 such as tungsten (W) is sprayed on the dielectric film 40b over the entire main surface of the susceptor body 12 to obtain a predetermined film thickness. An electrode film 40a (D3: for example, 50 μm) is formed.

  Next, as shown in FIG. 12 (f), a dielectric material such as alumina is sprayed on the electrode film 40 a over the entire main surface of the susceptor body 12, so that the upper insulating film 40 c of the electrostatic chuck 40 has a predetermined film thickness. (D4: 200 μm, for example).

  In this configuration example, a dielectric 72 for filling the periphery of the convex portion 70 (covering the bottom surface portion 12a) on the main surface of the susceptor body 12 and a lower insulating film 40b constituting a part of the electrostatic chuck 40 are 1 It can be integrally formed at the same time by a single thermal spraying process.

  Although the susceptor 12 of the above configuration example is provided with the columnar convex portion 70 on the main surface, any shape can be given to the convex portion 70. For example, as shown in FIG. A configuration in which the convex portions 70 are provided concentrically is also possible. That is, also in the susceptor structure of FIG. 13, when a high-frequency current flows from the electrode edge portion toward the center portion, high-frequency power is efficiently emitted from the convex portion 70 having a lower impedance than the bottom surface portion 12a to the plasma PZ side. Therefore, the distribution characteristic is such that the area density of the convex portion 70 gradually increases from the electrode center portion toward the electrode edge portion, thereby improving the uniformity of the electric field strength in the radial direction of the electrode, and thus making the plasma density uniform. Can be achieved.

  The configuration in which a large number of convex portions 70 functioning as small electrodes are discretely provided on the main surface of the electrode as described above can also be applied to the counter electrode, that is, the upper electrode 38 as shown in FIG. In the configuration example of FIG. 14, a convex portion 70 is provided on the main surface (lower surface, that is, the surface on the plasma generation space side) of the electrode plate 56 of the shower head 38, and a dielectric is formed around the convex portion 70 (on the bottom surface portion 56b). 72 is provided. The gas vent hole 56a may be provided so as to penetrate the convex portion 70 in the vertical direction. According to such a configuration, the upper electrode 38 receives the high-frequency current from the plasma PZ mainly through the convex portion 70. Therefore, by appropriately selecting the attribute of the convex portion 70 also in the upper electrode 38, for example, the distribution density is set such that the area density of the convex portion 70 gradually increases from the electrode center portion toward the electrode edge portion. The density uniformity can be further improved.

15 and 16 show the configuration of the main part of the susceptor 12 as an example of the electrode structure according to the second configuration example. 15 is a plan view, and FIG. 16 is a partially enlarged longitudinal sectional view. As shown in the drawing, in this configuration example, a large number of discrete cylindrical recesses 80 of a certain size are provided on the main surface of the susceptor 12 in a discrete manner. Since these concave portions 80 are recessed facing the counter electrode side, that is, the plasma PZ side, they are electrically coupled to the plasma PZ with a higher impedance than the top surface portion 12a of the main surface. For this reason, the high frequency power carried by the high frequency current i flowing through the surface layer of the main surface of the susceptor 12 is mainly emitted from the top surface portion 12a toward the plasma PZ. To increase the impedance ratio Z ₈₀ / Z _12a of the recess 80 and the top wall 12a on the main surface of the susceptor 12, i.e. to increase the proportion of high-frequency wave power given from top wall 12a to the plasma PZ, 16 As shown, a dielectric 82 may preferably be provided in the recess 80.

  As described above, in the second configuration example, a large number of concave portions 80 provided discretely on the main surface of the susceptor 12 function as electrode mask portions that suppress the supply of high-frequency power to the plasma PZ. By appropriately selecting the attributes (shape, size, spacing, density, etc.) of the recess 80, the high-frequency power supply characteristics of the susceptor 12 can be controlled to desired characteristics. For example, as shown in FIG. 17, by setting the distribution density so that the number density of the recesses 80 gradually decreases from the center of the electrode toward the electrode edge, the high frequency power or high frequency electric field applied to the plasma PZ from the susceptor 12 is increased. Uniformity (especially radial uniformity) can be improved, and thus plasma density uniformity can be improved. Other attributes of the recess 80 may be handled basically in the same manner as the protrusion 70 in the above-described embodiment. For example, the depth size and width size of the recess 80 may be set to a value that is three times or more the skin depth δ. .

  FIG. 18 shows a manufacturing method of a structure in which an electrostatic chuck is integrally provided on the susceptor 12 of this configuration example in the order of steps.

  First, as shown in FIG. 18A, for example, a resin mask 84 having an opening 84a corresponding to the recess 80 is placed on the main surface of a susceptor body (electrode substrate) 12 made of, for example, aluminum. In the mask 84, the planar shape and planar size of the opening 84 a define the planar shape and planar size of the recess 80.

  Next, as shown in FIG. 18B, solid particles (for example, dry ice pellets) or fluid (high-pressure jet water) are sprayed on the entire main surface of the susceptor body 12 from above the mask 84 by the blast method. The member (aluminum) in the opening 84a of 84 is physically removed, and the recess 80 having a desired depth is formed therein.

  Next, when the mask 84 is removed from the main surface of the susceptor body 12, as shown in FIG. 18C, a large number of recesses 80 of a predetermined size are discretely distributed in a predetermined distribution pattern on the main surface of the susceptor body 12. Remain in.

Next, as shown in FIG. 18D, a dielectric material such as alumina (Al ₂ O ₃ ) is sprayed on the entire main surface of the susceptor body 12 to reach a predetermined height from the susceptor top surface portion 12a. A dielectric film (82, 40b) is formed on the substrate.

  Next, as shown in FIG. 18 (e), an electrode material for electrostatic chuck, for example, tungsten (W), is sprayed on the dielectric film 40b over the entire main surface of the susceptor body 12, and an electrode film having a predetermined thickness is formed. 40a is formed.

  Next, as shown in FIG. 18 (f), a dielectric material such as alumina is sprayed on the electrode film 40 a over the entire main surface of the susceptor body 12 to form the upper insulating film 40 c with a predetermined film thickness.

  Also in the second configuration example, the dielectric 82 for filling the concave portion 80 on the main surface of the susceptor body 12 and the lower insulating film 40b constituting a part of the electrostatic chuck 40 are integrated together in one spraying process. Can be formed.

  Also in this second configuration example, a configuration in which a large number of concave portions 80 functioning as electrode mask portions on the main surface of the electrode are discretely omitted is omitted from illustration, but may be applied to the counter electrode, that is, the upper electrode 38. Is possible. Therefore, a configuration in which the convex portion 70 is provided on the susceptor 12 side and the concave portion 80 is provided on the upper electrode 38 side, or a configuration in which the concave portion 80 is provided on the susceptor 12 side and the convex portion 70 is provided on the upper electrode 38 side is possible.

FIG. 19 and FIG. 20 show one configuration example of the electrode in one embodiment of the present invention. FIG. 19 shows a configuration example applied to the susceptor 12, and FIG. 20 shows a configuration example applied to the upper electrode 38 (more precisely, the electrode plate 56). In this embodiment, a dielectric film or dielectric layer 90 is provided on the main surface of the electrode, that is, the surface on the plasma generation space side (the lower surface in the case of the upper electrode 38, the upper surface in the case of the susceptor 12), and the dielectric at the center of the electrode The thickness of the film 90 is configured to be larger than the thickness of the dielectric film 90 at the electrode edge portion. The front surface (surface on the plasma generation space side) of the dielectric film 90 is substantially flush. The dielectric film or dielectric layer 90 may be formed, for example, by spraying a ceramic made of alumina (Al ₂ O ₃ ) on an electrode substrate made of aluminum, for example.

  According to such an electrode structure, since the impedance at the electrode center portion side is relatively large with respect to the plasma PZ side and the impedance at the electrode edge portion side is low, the high frequency electric field at the electrode edge portion side is enhanced while the electrode center portion side is The high frequency electric field is weakened, and the uniformity of the electric field strength or plasma density is improved. In particular, in the configuration example of FIG. 19, when a current that has turned from the back surface side of the electrode 12 to the main surface side due to the skin effect flows into the dielectric film 90, a portion having a small film thickness (a thin portion of the dielectric layer) starts from the plasma side. Since it is easy to penetrate, it is possible to enhance the discharge of high-frequency power and the plasma density on the electrode edge side.

One of the important parameters in the film thickness distribution characteristic of the dielectric film 90 is the film thickness at the center of the electrode. In the parallel plate electrode structure in which a disk-shaped dielectric film 90 to the upper electrode 38 as shown in FIG. 21, the simulation of the electric field intensity distribution in the radial direction between electrodes and the thickness D _c of the upper electrode central portion to the parameter As a result, electric field strength distribution characteristics as shown in FIG. 22 were obtained. This simulation assumes a 300 mm diameter semiconductor wafer as the substrate to be processed, using aluminum for the upper electrode 38, alumina (Al ₂ O ₃ ) for the dielectric film 90, and aluminum for the lower electrode 12. Yes. FIG. 22 shows that within the range of 0.5 mm to 10 mm, the in-plane uniformity of the electric field strength is improved as the film thickness at the center of the electrode is increased, and the film thickness of 8 mm to 10 mm is particularly preferable. Note that the position of “0” on the horizontal axis in FIG. 22 represents the position of the electrode center point.

  In addition, a profile in which the film thickness of the dielectric film 90 changes in a decreasing manner from the electrode center to the electrode edge is also important. 23 and 24 show an example of a film thickness profile for the dielectric film 90 of the upper electrode 38. FIG.

  In the embodiment [1] shown in FIG. 23A, the thickness D of the dielectric film 90 is D = 9 mm (flat or constant) when φ (diameter) is 0 to 30 mm, and D is 8 mm (flat) when φ is 30 to 160 mm. ), Φ = 160 to 254 mm, and D = 8 to 3 mm (taper).

  In Example [2] shown in FIG. 23B, φ = 30 mm and D = 9 mm (flat), φ30 to 80 mm, D = 8 mm (flat), and φ80 to 160 mm, D = 8 to 3 mm (taper). To do.

  In Example [3] shown in FIG. 23 (C), D = 9 mm (flat) at φ0-30 mm, D = 8 mm (flat) at φ30-160 mm, and D = 8-3 mm (taper) at φ160-330 mm. To do.

  FIG. 23D clearly shows the profiles of the above-described embodiments [1], [2], and [3] with curves. In addition, although the cross-sectional shape is not shown, the profile of Example [4] in which D is set to 0.5 mm (flat) at φ0 to 150 mm is shown, and an ideal profile is also shown. Here, an ideal profile is set to D = 9 to 0 mm (arch type) at φ0 to 300 mm.

  FIG. 24 shows electric field intensity distribution characteristics in the radial direction between the electrodes obtained by Examples [1], [2], [3], [4] and ideal profiles, respectively. From FIG. 24, the electric field strength distribution characteristic by the ideal profile is the most excellent in in-plane uniformity, and the examples [1], [2], [3], and [4] are examples close to the ideal profile [1] It can be seen that the in-plane uniformity of [3] and [3] is excellent.

Note that, as shown in FIGS. 23A, 23B, and 23C, the upper electrode 38 (electrode plate 56) receives a high-frequency current from the diffused plasma PZ. Alternatively, the edge may be extended radially outward by increasing the diameter. Here, a sprayed coating 92 having a film thickness of, for example, 20 μm may be formed on the main surface of the upper electrode 38 around the dielectric film 90 or on a radially outer portion. Although not shown, a similar sprayed coating 92 can be formed on the inner wall surface of the chamber 10. As the spray coating 92, for example, Al ₂ O ₃ , Y ₂ O _3, or the like can be used. Further, the front surfaces of the dielectric film 90 and the sprayed coating 92, that is, the surfaces exposed to the plasma are substantially flush.

  25 and 26 show another example of the film thickness profile for the dielectric film 90. FIG. In the embodiment [5] shown in FIG. 25A, the thickness D of the dielectric film 90 is set to φ = 250 mm and D = 5 mm (flat). In the embodiment [6] in FIG. 25B, φ = 30 mm and D = 9 mm (flat), and φ = 30 to 250 mm, D = 8 to 3 mm (taper). In the embodiment [7] of FIG. 25 (C), D = 9 mm (flat) when φ0 to 30 mm, and D = 5 to 3 mm (taper) when φ30 to 250 mm. FIG. 23D clearly shows the profiles of Examples [5], [6], and [7] with curves.

  FIG. 26 shows the electric field intensity distribution characteristics in the radial direction between the electrodes obtained by Examples [5], [6], and [7], respectively. From FIG. 26, among these Examples [5], [6], and [7], Example [6] that is closest to the ideal profile is the most excellent in in-plane uniformity, and Example [5] It can be seen that there is sufficient practicality. That is, even in a profile in which the film thickness D of the dielectric film 90 decreases in a substantially linear or tapered manner from the electrode center to the electrode edge as in the embodiment [6], the surface is close to the arch-type ideal profile. Internal uniformity is obtained. Further, even in the case where the film thickness D of the dielectric film 90 is substantially constant (flat) from the center of the electrode to the electrode edge as in the embodiment [5], practical in-plane uniformity can be obtained.

  27 and 28 show another example of the film thickness and film quality profile for the dielectric film 90. FIG. In the embodiment [8] shown in FIG. 27A, the thickness D of the dielectric film 90 is set such that D = 9 mm (flat) when φ0 to 30 mm, and D = 8 to 3 mm (taper) when φ30 to 250 mm. . In the embodiment [9] in FIG. 27B, φ = 30 mm and D = 5 mm (flat), and φ30 to 250 mm, D = 5 to 3 mm (taper). FIG. 27C clearly shows the profiles of the embodiments [8] and [9] with curves.

Here, with the dielectric constant ε as a parameter, the embodiment [8] is an embodiment [8] -A in which the material of the dielectric film 90 is alumina (Al ₂ O ₃ ) having a dielectric constant ε = 8.5, It is divided into Example [8] -B which is silicon oxide (SiO ₂ ) with ε = 3.5. In addition, Example [9] is also Example [9] -A which is alumina (Al ₂ O ₃ ) with ε = 8.5, and Example [9] -A which is silicon oxide (SiO ₂ ) with ε = 3.5. 9] -B.

FIG. 28 shows the electric field strength distribution characteristics in the radial direction between the electrodes obtained by Examples [8] -A, [8] -B, [9] -A, and [9] -B, respectively. From FIG. 28, between [8] -A and [9] -A in the case of ε = 8.5, [8] -A where the film thickness D _{c at} the center of the electrode is larger than [9] -A. Is excellent in the in-plane uniformity of the electric field strength E, and [9] − in which the film thickness D _{c at} the center of the electrode is small between Examples [8] −B and [9] −B where ε = 3.5. It can be seen that B has better in-plane uniformity of the electric field strength E than [8] -B.

The graph of FIG. 29 shows the correlation between the dielectric constant ε of the dielectric film 90 that gives practically sufficient in-plane uniformity and the film thickness D _c at the center based on the data of FIG. From this graph, it can be seen that the film thickness D _c at the center should be set in correspondence with the dielectric constant ε of the dielectric film 90.

30 shows an etching rate distribution characteristic (X direction, Y direction) of organic film etching using the plasma etching apparatus (FIG. 1) according to the embodiment. Example (A) ) And a comparative example (B) in which the upper electrode 38 is not provided with the dielectric film 90 according to the present invention. Example (A) corresponds to Example [1] above. The main etching conditions are as follows.
Wafer diameter: 300 mm
Etching gas: NH ₃
Gas flow rate: 245sccm
Gas pressure: 30mTorr
RF power: Bottom = 2.4kW
Wafer back pressure (center / edge): 20/30 Torr (He gas)
Temperature (chamber side wall / upper electrode / lower electrode) = 60/60/20 ° C

  As is clear from FIG. 30, the example (A) is much superior to the comparative example (B) in the in-plane uniformity of the etching rate in correspondence with the electric field strength distribution characteristics.

FIG. 31 shows an example (A) in which a dielectric film 90 according to the present invention is provided on a susceptor (lower electrode) 12 in comparison with a comparative example (B). For example, in the case of corresponding to a semiconductor wafer W having a diameter of 300 mm, in the embodiment (A), the film thickness D of the dielectric film 90 in the susceptor 12 is 4 mm at the center of the electrode and 200 μm at the electrode edge, and in the comparative example (B). A dielectric film 94 having a uniform thickness of 0.5 mm is provided on the upper surface of the susceptor 12. The material of the dielectric films 90 and 94 may be alumina (Al ₂ O ₃ ).

  FIG. 32 shows the etching rate distribution characteristics (X direction, Y direction) of organic film etching using the plasma etching apparatus of the embodiment (FIG. 1), with the examples (A) and 31 (B) of FIG. Comparative example (B) is shown in comparison. Etching conditions are the same as those in FIG. Also in the case of the susceptor (lower electrode) 12, it can be seen that the in-plane uniformity of the etching rate is significantly superior in the example (A) than in the comparative example (B). It can also be seen that the etching rate itself is about 10% greater in Example (A) than in Comparative Example (B). In Example (A), the film thickness D of the dielectric film 90 at the center of the electrode is set to 4 mm. However, the same effect can be obtained even if the film thickness is increased to about 9 mm.

  33 and 34, a further embodiment of the invention will be described. This embodiment is particularly suitable for application to a configuration in which the dielectric film 90 is provided on the upper electrode 38. As shown in FIGS. 33A and 33B, in this embodiment, a conductive shield plate 100 that covers a part of the dielectric film 90 (usually around the edge portion) is formed on the main surface of the upper electrode 38. Provide. The shield plate 100 is preferably made of, for example, an aluminum plate whose surface is anodized (92), and is preferably detachably attached to the upper electrode 38 with a screw 102. At the center of the shield plate 100, an opening 100a having a desired diameter θ is formed so as to be coaxial with the dielectric film 90 and expose at least the center of the dielectric film 90. The thickness of the shield plate 100 may be selected to be about 5 mm, for example.

  As a specific example, θ is set to 200 mm in the embodiment (A) shown in FIG. 33A, and θ is set to 150 mm in the embodiment (B) shown in FIG. In both examples (A) and (B), the dielectric film 90 is formed in a disk shape having a diameter of 250 mm, and the film thickness profile is D = 8 mm (flat) at φ0 to 160 mm, and D at φ160 to 250 mm. = 8 to 3 mm (taper).

  FIG. 34 shows the electric field strength distribution characteristics in the radial direction between the electrodes obtained by the embodiments (A) and (B) of FIG. FIG. 34 shows that by covering a part of the dielectric film 90 with the conductive shield plate 100, the action of the dielectric film 90 in the covered region, that is, the electric field strength reducing effect can be significantly reduced or canceled. Therefore, the electric field strength distribution characteristics between the electrodes 12 and 38 can be adjusted by changing the aperture θ of the opening 100a of the shield plate 100 (by exchanging parts of the shield plate 100).

A further embodiment of the present invention is shown in FIGS. This embodiment is also particularly suitable for application to a configuration in which the dielectric film 90 is provided on the upper electrode 38. As shown in FIG. 35A, in this embodiment, on the main surface of the upper electrode 38, the outer electrode portion 38f from the position in the radial direction larger than the dielectric film 90 (position of the aperture ω) as the inter-electrode gap G _f is small in the electrode portion 38f than the inter-electrode gap G ₀ in the membrane 90, causing the desired amount of projection toward the susceptor 12 side or the plasma generating space side (bulging amount) h just overhang .

As a specific example, in the embodiment (A) shown in FIG. 35A, the dielectric film 90 has a diameter of 80 mm, a film thickness profile of φ0-60 mm, D = 3 mm (flat), and φ60-80 mm, D = 3. in the configuration which is 1 mm (tapered), omega = set to 260 mm, the inter-electrode gap G _o in the dielectric film 90 relative to the G _o = 40 mm, set h = 10 mm, the electrodes in the outer electrode protruding portion 38f between gap G _f is in G _f = 30mm. Note that the protruding step portion of the outer electrode protruding portion 38f is inclined by about 60 °. This inclination angle can be selected arbitrarily.

FIG. 35B shows a configuration in which the dielectric film 90 having the same diameter size and the same film thickness profile as that of the embodiment (A) is provided without providing the overhanging portion 38f on the upper electrode 38 as a comparative example. FIG. 35C shows a configuration in which neither the overhanging portion 38 f nor the dielectric film 90 is provided on the upper electrode 38 as a reference example. Figure 35 (B), it is constant in both the inter-electrode gap radial (C), a G _o = 40 mm.

  FIG. 36 shows the radial electric field strength distribution characteristics between the electrodes obtained in the example (A) of FIG. 35 in comparison with the comparative example (B) and the reference example (C). As shown in FIG. 36, by providing an overhanging portion 38f on the outer side in the radial direction of the dielectric film 90 as in the embodiment (A), a region in the vicinity of the edge portion of the semiconductor wafer W (in the illustrated example, the radius from the center is about The electric field strength distribution characteristics can be controlled or adjusted in the direction of increasing the electric field strength E in the region of 90 mm to 150 mm. The amount of electric field intensity distribution control by the overhanging portion 38f can be adjusted by the overhanging amount h, and preferably h = 10 mm or more.

Moreover, as shown in FIG. 37, the position (value of aperture ω) of the protruding step portion of the outer electrode protruding portion 38f can be arbitrarily selected. Specifically, in the embodiment of FIG. 37A, ω = 350 mm is set, and in the embodiment of FIG. 37B, ω = 400 mm. In both examples (A) and (B), the dielectric film 90 has a film thickness profile of φ0 to 80 mm and D = 8 mm (flat), and φ80 to 160 mm and D = 8 to 3 mm (taper). , the inter-electrode gap G _o in the dielectric film 90 is set to bulging amount h = 10 mm with respect to G _o = 30 mm, and the electrode gap G _f in the outer electrode protruding portion 38f to G _f = 20 mm. Further, the protruding step portion of the outer electrode protruding portion 38f is inclined by about 60 °.

In FIG. 37C, as a reference example, the dielectric film 90 having the same diameter size and the same film thickness profile as those of the embodiments (A) and (B) is provided without providing the overhanging portion 38f on the upper electrode 38. Indicates. The gap between the electrodes is constant in the radial direction, and G _o = 30 mm.

FIG. 38 shows the etching rate (normalized value) distribution characteristics of the oxide film etching obtained in the examples (A) and (B) of FIG. 37 in comparison with the reference example (C). As main etching conditions, the wafer diameter was 300 mm, the pressure was 15 mTorr, and C ₄ F ₆ / Ar / O ₂ / CO was used as the processing gas. 38, in the configuration in which the protruding step portion of the outer electrode protruding portion 38f is provided radially outside the edge of the semiconductor wafer W on the main surface of the upper electrode 38, the protruding step portion position is closer to the wafer edge ( It can be seen that the smaller the ω is, the greater the effect of increasing the etching rate (that is, the electric field strength or plasma electron density) in the region near the wafer edge (in the example shown, the region having a radius of about 70 mm to 150 mm from the center).

In the embodiment of FIGS. 35 to 38, as described above, the electrode portion radially outward from the dielectric film 90 on the main surface of the upper electrode 38 is projected toward the plasma generation space. On the other hand, as shown in FIG. 39A, a configuration in which the dielectric film 90 projects over the main surface of the upper electrode 38 by a desired amount of projection (projection amount) k toward the plasma generation space is also possible. is there. As a specific example, in the embodiment of FIG. 39A, the dielectric film 90 has a diameter of 250 mm and a film thickness profile of φ0 to 160 mm, D = 8 mm (flat), and φ160 to 250 mm, D = 8 to 3 mm (taper). in) the configuration, the tapered surface 90a set k = 5 mm toward the susceptor 12 side, and the inter-electrode gap G _m in the dielectric film 90 and G _m = 35 mm. The electrode portion radially outward from the dielectric film 90 is a flat surface, and the inter-electrode gap _Go is _Go = 40 mm.

In FIG. 39B, as a comparative example, the dielectric film 90 having the same film thickness profile as that of the embodiment (A) is not projected on the upper electrode 38 in the reverse direction (with the taper 90a facing the back side). The provided structure is shown. FIG. 39C shows a configuration in which the dielectric film 90 is not provided on the upper electrode 38 as a reference example. Figure 39 (B), it is constant in both the inter-electrode gap radial (C), a G _o = 40 mm.

  FIG. 40 shows the electric field intensity distribution characteristics in the radial direction between the electrodes obtained in the example (A) of FIG. 39 in comparison with the reference example (B) and the comparative example (C). From FIG. 40, as shown in the embodiment (A), by extending the dielectric film 90, the electric field strength distribution characteristics in the direction of increasing the electric field strength E at each position in the radial direction as compared with the case (B) where the dielectric film 90 is not formed. Can be controlled or adjusted. The amount of electric field intensity distribution control by the overhanging portion 38 can be adjusted by the overhanging amount k, and preferably k = 5 mm or more.

  FIG. 41 shows a modification of the configuration in which the overhanging portion 38 f is provided on the main surface of the upper electrode 38 on the radially outer side of the dielectric film 90. As shown in the figure, the edge portion of the dielectric film 90 may be continuous with the outer electrode protruding portion 38f, or the edge portion of the dielectric film 90 may be extended together with the outer electrode protruding portion 38f. is there.

  42 to 45 show still another embodiment of the present invention. In this embodiment, as shown in FIG. 42, a dielectric film 90 provided on the main surface of the upper electrode 38 is formed of a hollow dielectric having a cavity 104 therein, for example, a hollow ceramic. Also in this embodiment, a profile that makes the thickness of the hollow dielectric 90 on the radial center side larger than the thickness on the edge side is preferable.

  A desired amount of fluid dielectric material NZ is placed in the cavity 104 of the hollow dielectric 90. The dielectric fluid NZ in the cavity 104 forms part of the dielectric 90 according to its occupied volume. Such a dielectric fluid NZ may be a powder or the like, but an organic solvent (for example, Galden) is particularly preferable. For example, a plurality of pipes 106 and 108 may be connected to different locations (for example, the center portion and the edge portion) of the cavity 104 from the back side of the electrode 38 as a port for taking the dielectric fluid NZ into and out of the cavity 104. When the dielectric fluid NZ is inserted into the cavity 104 of the hollow dielectric 90, as shown in FIG. 42B, the dielectric fluid NZ is introduced from one pipe 106 while the cavity 104 is introduced from the other pipe 106. Remove the air inside. When the amount of the dielectric fluid NZ in the cavity 104 is reduced, as shown in FIG. 42C, while the air is sent from one pipe 106, the dielectric fluid NZ in the cavity 104 is sent from the other pipe 106. Just exit.

  FIG. 43 shows a specific example in this embodiment. The entire hollow dielectric 90 is formed in a disk having a diameter of 210 mm, the thickness is φ0 to 60 mm and D = 6 mm (flat), and φ60 to 210 mm is D = 6 to 3 mm (taper). The cavity 104 of the hollow dielectric 90 has a thickness α of 2 mm and a diameter β of 180 mm.

  FIG. 44 shows the electric field strength distribution characteristics in the radial direction between the electrodes obtained in the specific example of FIG. In the figure, the distribution characteristic A with ε = 1 is obtained in the state of FIG. 42A, that is, in the state where the cavity 104 of the hollow dielectric 90 is completely emptied and filled with air. Further, the distribution characteristic B of ε = 2.5 is obtained in the state shown in FIG. 42C, that is, in the state where the cavity 104 of the hollow dielectric 90 is fully filled with Galden. By adjusting the amount of Galden put into the cavity 104, an arbitrary characteristic between the two characteristics A and B can be obtained.

  Thus, in this embodiment, the dielectric constant or dielectric impedance of the entire dielectric 90 can be variably controlled by changing the type and amount of the flowable dielectric material NZ to be inserted into the cavity 104 of the hollow dielectric 90. Can do.

  FIG. 45 shows various modifications of this embodiment. In the modification of FIG. 45A, the front surface of the dielectric 90 is formed by the ceramic plate 91, and the wall surface facing the ceramic plate 91 in the inner cavity 104 is formed by the base material (aluminum) of the upper electrode 38. To do. That is, the concave portion 38 c corresponding to the shape of the dielectric 90 is formed on the main surface of the upper electrode 38, and the concave portion 38 c is covered with the ceramic plate 91. In order to seal the outer periphery of the ceramic plate 91, for example, a seal member 110 such as an O-ring is preferably provided. In this case, the shape of the recess 38c or the cavity 104 is important, and a shape in which the thickness on the center side is larger than the thickness on the edge side is preferable.

  45 (B) and 45 (C) limit or localize the space or cavity 104 allocated to the dielectric fluid NZ within the hollow dielectric 90 to a specific region. For example, as shown in FIG. 45B, the space of the cavity 104 is localized in the central region of the dielectric 90, or the thickness of the ceramic plate 91 is changed in the radial direction as shown in FIG. In this case, a configuration in which the space of the cavity 104 is relatively localized in the peripheral region of the dielectric 90 is possible (by gradually decreasing from the center toward the edge). Thus, by defining the space of the cavity 104 in a desired region or shape in the hollow dielectric 90, various variations can be provided in the dielectric constant adjustment function by the dielectric fluid NZ.

  In the configuration example of FIG. 45D, the cavity 104 in the hollow dielectric 90 is divided into a plurality of chambers, and the loading and unloading of the dielectric fluid NZ and the filling amount are controlled independently for each chamber. is there. For example, as shown in the figure, the cavity 104 can be divided into two chambers 104 </ b> A on the center side and chamber 104 </ b> B on the peripheral side by an annular partition plate 91 a formed integrally with the ceramic plate 91.

  The preferred embodiments of the present invention have been described above, but it is also possible to combine the electrode structures in the above embodiments and the above configuration examples. For example, the electrode structure having the dielectric 90 according to the above embodiment and the electrode structure having the convex portion 70 according to the first configuration example or the electrode structure having the concave portion 80 according to the second configuration example can be combined. That is, the electrode structure according to the above embodiment is applied to the susceptor 12 as shown in FIG. 19, for example, and the upper electrode 38 has the electrode structure according to the first structure example (FIGS. 2 and 3) or the second structure example. The application of the electrode structure (FIGS. 15 and 16) or the electrode structure according to the above embodiment is applied to the upper electrode 38 as shown in FIG. 20, and the susceptor 12 has the electrode structure according to the first configuration example (FIG. 2). , FIG. 3) or an application to which the electrode structure (FIGS. 15 and 16) according to the second configuration example is applied. Of course, an application in which the electrode structure according to the embodiment or the first or second configuration example is applied to both the upper electrode and the lower electrode, or the electrode structure according to the embodiment or the first or second configuration example is an upper portion. An application using a conventional general electrode for the other electrode is also possible.

  Further, the plasma etching apparatus (FIG. 1) in the above embodiment is a system in which one high frequency power for plasma generation is applied to the susceptor 12. However, although not shown in the drawings, the present invention applies a method of applying high-frequency power for plasma generation to the upper electrode 38 side, and applies first and second high-frequency powers having different frequencies to the upper electrode 38 and the susceptor 12, respectively. It can also be applied to a method (upper and lower high-frequency application type) and a method of applying first and second high-frequency powers having different frequencies to the susceptor 12 (lower two-frequency superimposed application type). The present invention is applicable to a plasma processing apparatus having at least one electrode in a possible processing container. Furthermore, the present invention can also be applied to other plasma processing apparatuses such as plasma CVD, plasma oxidation, plasma nitridation, and sputtering. Further, the substrate to be processed in the present invention is not limited to a semiconductor wafer, and various substrates for flat panel displays, photomasks, CD substrates, printed substrates, and the like are also possible.

Claims (17)

A plasma processing apparatus for performing plasma processing on a substrate to be processed having a predetermined aperture,
A depressurizable processing container for storing the substrate to be processed;
A first electrode disposed in the processing container;
A gas supply unit for supplying a processing gas into the processing container;
A high-frequency electric field forming part for forming a high-frequency electric field in the processing container in order to generate plasma of the processing gas;
A dielectric provided on the main surface of the first electrode;
The dielectric is formed at the center of the dielectric so as to be concentric with the substrate disposed in the processing container, and has a first diameter equal to or more than 1/10 of the diameter of the substrate and a first constant. a first portion flat having a thickness, said first portion is formed radially outward from the first second larger than the diameter of the diameter and the second is smaller than the first predetermined thickness A flat second portion having a constant thickness and a radially outer side than the second portion, and the thickness is linear and tapered from the center portion of the first electrode toward the edge portion. A plasma processing apparatus having a film thickness profile simulating an ideal film thickness profile for obtaining uniform processing on the substrate to be processed.   2. The plasma processing apparatus according to claim 1, wherein high-frequency power for generating the plasma is supplied from a back surface opposite to the main surface of the first electrode.   A high frequency for generating the plasma from a back surface opposite to the main surface of the second electrode, the second electrode being disposed in the processing container so as to face the first electrode in parallel. The plasma processing apparatus of Claim 1 which supplies electric power. Wherein the third portion of the dielectric is formed on the outer side than the second portion in the radial direction, the plasma processing apparatus according to any one of claims 1 to 3.   5. The plasma processing apparatus according to claim 1, wherein a thickness of the dielectric in the first electrode is minimized near a position facing an edge portion of the substrate to be processed. Setting the thickness of the first portion of the dielectric in the first electrode to a value corresponding to the dielectric constant of the dielectric, the plasma processing apparatus according to any one of claims 1 to 5.   The plasma processing apparatus according to claim 1, wherein a conductive shield member that covers a part of the dielectric is provided on a main surface of the first electrode.   The plasma processing apparatus according to claim 7, wherein the shield member has an opening having a desired diameter that exposes at least a central portion of the dielectric.   The plasma processing apparatus according to claim 1, wherein a thickness of the first portion of the dielectric is 8 mm to 10 mm.   On the main surface of the first electrode, a desired protrusion of the outer electrode portion from a position separated by a desired distance radially outward from the outer peripheral edge of the dielectric toward the space where the plasma is generated. The plasma processing apparatus according to any one of claims 1 to 6, wherein the plasma processing apparatus is projected by an amount.   The plasma processing apparatus according to any one of claims 1 to 6, wherein the dielectric is protruded by a desired protrusion amount toward a space where the plasma is generated on a main surface of the first electrode. .   The plasma processing apparatus according to claim 1, wherein a cavity is provided inside the dielectric on the main surface of the first electrode, and a fluid dielectric material is placed in the cavity.   The plasma processing apparatus according to claim 12, wherein at least two ports are provided on the first electrode for taking in and out the dielectric substance into the cavity.   The plasma processing apparatus according to claim 12, wherein the dielectric substance is an organic solvent.   The plasma processing apparatus according to any one of claims 12 to 14, wherein at least a front surface of the dielectric is made of a solid in the main surface of the first electrode. An electrode plate provided in a processing vessel of a plasma processing apparatus for performing plasma processing on a substrate to be processed having a predetermined diameter,
A dielectric is provided on the main surface facing the plasma,
The dielectric is formed at the center of the dielectric so as to be concentric with the substrate disposed in the processing container, and has a first diameter that is 1/10 or more of the aperture of the substrate and a first constant. a first portion flat having a thickness, said first portion is formed radially outward from the first second larger than the diameter of the diameter and the second is smaller than the first predetermined thickness A flat second portion having a constant thickness, and a second portion that is formed radially outward from the second portion and has a thickness that decreases linearly and tapered from the electrode center portion toward the electrode edge portion. 3 parts,
An electrode plate having a film thickness profile imitating an ideal film thickness profile for obtaining uniform processing on the substrate to be processed. The electrode plate according to claim 16 , wherein a thickness of the first portion of the dielectric is 8 mm to 10 mm.

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