JP5319731B2 - Parallel plate type dry etching apparatus and dry etching method - Google Patents

Description

  The present invention relates to a parallel plate type dry etching apparatus and a dry etching method.

  A parallel plate type dry etching apparatus is basically provided with a pair of plate-like electrodes facing each other in parallel in a vacuum processing container (chamber), one electrode is connected to the ground potential, and the other electrode is connected to the other electrode. A high-frequency voltage is supplied and a predetermined etching gas is flown to generate a plasma of the etching gas between both electrodes, and radicals, ions, or electrons in the plasma are used to place the plasma on one electrode. A workpiece (etching substance) on the surface of the processing substrate is etched.

  In general, in the anode-coupled arrangement type in which the substrate to be processed is arranged on the ground side electrode, chemical etching mainly by chemical reaction between radicals in the plasma and the substance to be etched is mainly used. On the other hand, in the cathode-coupled arrangement type in which the substrate to be processed is arranged on the electrode on the high frequency input side, physical and chemical etching in which ions in the plasma are pulled perpendicularly to the surface of the substrate to be processed and chemically react with the etching target material. (Reactive ion etching) is performed.

Japanese Patent Laid-Open No. 01-171224

  Conventionally, in this type of dry etching apparatus, the plasma density that affects the etching processing characteristics can be variably controlled by the pressure of the etching gas, high-frequency power, etc., but the plasma density on the substrate to be processed is spatial (particularly in the radial direction). B) Uniformity is an issue. In other words, the plasma density tends to be lower in the peripheral portion with respect to the central portion of the substrate to be processed, and there is a problem (points to be improved) that the etching processing characteristics become non-uniform on the substrate to be processed. .

  One solution to this problem is to increase the diameter of the electrode so that the peripheral portion of the electrode where the plasma density is reduced is farther radially outward than the peripheral portion of the substrate to be processed. However, recently, the size of the substrate to be processed has increased, and further increasing the electrode size has disadvantages (such as an increase in the size and complexity of the cooling mechanism and an increase in power consumption). It is too large to be an effective or practical solution.

  The present invention has been made in view of such conventional problems, and improves the distribution characteristics of the plasma density on the substrate to be processed, and further makes the plasma density uniform on the substrate to be processed without requiring an increase in electrode size. A parallel plate type dry etching apparatus and a dry etching method are provided.

In the parallel plate type dry etching apparatus of the present invention, first and second electrodes facing each other are provided in a vacuumable processing container, a high-frequency voltage is applied between the first and second electrodes, and an etching gas is introduced. A parallel plate type dry etching apparatus for generating a plasma of the etching gas and etching the substrate to be processed disposed on the second electrode by using the plasma in the radial direction of the substrate to be processed in order to control the distribution characteristic of plasma density, provided the electric field intensity correcting projections forming the step protrudes to the second electrode side with respect to the first electrode near the periphery of the first electrode the amount of projection of the electric field intensity correcting projections provided with a protrusion amount adjustment means for variably adjusting the electric field strength correction protrusion of the opening formed in the upper surface of the processing chamber And a flange portion extending radially outward from an upper end portion of the flange portion is fixed to the upper surface of the processing vessel around the opening, and the protrusion amount adjusting means includes: The cylindrical support is disposed inside the annular projecting member, the first electrode is attached to the lower surface of the annular projecting member, and a flange portion extending radially outward from an upper end thereof overlaps the flange portion of the annular projecting member. A member, one or more annular spacer plates inserted between the flange portion of the cylindrical support member and the flange portion of the annular projecting member, the flange portion of the cylindrical support member, and the annular spacer plate And a bolt for detachably fixing to the flange portion of the annular projecting member, and by changing the number of the annular spacer plates, the front with respect to the first electrode Adjusting the relative amount of projection of the annular projection member.

The parallel plate type dry etching method of the present invention generates a plasma of the etching gas by applying a high-frequency voltage between the first and second electrodes facing each other in a vacuumable processing vessel and flowing an etching gas. A parallel plate type dry etching method for etching a substrate to be processed disposed on the second electrode using the plasma, wherein the step protrudes toward the second electrode with respect to the first electrode. A field density correction protrusion for forming the first electrode is provided near the periphery of the first electrode, and the amount of protrusion of the field intensity correction protrusion is adjusted to distribute the plasma density in the radial direction of the substrate to be processed. It controls the adjustment of the field intensity correcting protrusion amount of projection is arranged annular projecting member hangs down vertically downward inside the top opening formed in the processing vessel, before A flange portion extending radially outward from the upper end portion of the annular projecting member is fixedly attached to the upper surface of the processing vessel around the opening, and a cylindrical support member is disposed inside the annular projecting member, and the cylindrical shape The first electrode is attached to the lower surface of the support member, and a flange portion extending radially outward from the upper end portion of the cylindrical support member is overlaid on the flange portion of the annular projecting member, and the cylindrical support member One or a plurality of annular spacer plates are inserted between the flange portion of the annular projecting member and the flange portion of the annular projecting member, and the flange portion of the cylindrical support member and the annular spacer plate are used as the flange portion of the annular projecting member. By removably fixing with bolts and changing the number of the annular spacer plates, by adjusting the relative protruding amount of the annular protruding member with respect to the first electrode Divide.

  In the parallel plate type dry etching apparatus or the dry etching method of the present invention, in the plasma ion sheath along the first electrode and the electric field intensity correcting protrusion, the horizontal electric field and the electrode parallel to the electrode are near the edge of the step. A large (reinforced) electric field is generated by adding the electric field in the direction perpendicular to the vector, and the kinetic energy of electrons in the plasma is strengthened by this reinforcing electric field, and the density of the plasma is increased. The reinforcing electric field acting on the plasma density increases as the protruding amount or level difference of the protruding portion increases. Therefore, by adjusting the protrusion amount of the electric field intensity correcting protrusion by the protrusion amount adjusting means, the degree of electric field reinforcement in the peripheral portion of the electrode is adjusted to control the distribution characteristics of the plasma density in the radial direction of the substrate to be processed. It is possible to make the plasma density uniform.

  According to the parallel plate type dry etching apparatus or dry etching method of the present invention, it is necessary to improve the plasma density distribution characteristics on the substrate to be processed and further increase the electrode size by the configuration and operation as described above. The plasma density on the substrate to be processed can be made uniform.

1 is a schematic longitudinal sectional view showing a configuration of a parallel plate type dry etching apparatus according to a first embodiment of the present invention. It is a figure for demonstrating the effect | action of the cyclic | annular protrusion member in the said dry etching apparatus. It is a schematic longitudinal cross-sectional view which shows the structure of the parallel plate type dry etching apparatus by 2nd Embodiment.

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

  FIG. 1 shows the configuration of a parallel plate type dry etching apparatus according to the first embodiment of the present invention.

  The processing container 10 of this dry etching apparatus is configured as a cylindrical vacuum chamber having both ends closed, for example, made of aluminum. A gate valve 12 that is opened when a substrate to be processed, for example, a semiconductor wafer W, is loaded into or unloaded from the container 10 is provided on the side wall of the processing container 10. A gas supply pipe 14 for introducing an etching gas is connected to the upper surface of the processing container 10, and an exhaust pipe 16 for vacuum exhaust is connected to the bottom of the container 10. The gas supply pipe 14 communicates with an etching gas supply source (not shown), and the exhaust pipe 16 communicates with a vacuum pump (not shown).

  In the processing chamber 10, the upper electrode 18 and the lower electrode 20 are arranged in parallel with each other at a certain interval in the center, and the semiconductor wafer W is arranged on the lower electrode 20. Both electrodes 18 and 20 are selected to have a size (diameter) somewhat larger than that of the semiconductor wafer W.

  The lower electrode 20 is a disk made of a conductive member such as aluminum, and is electrically connected to the ground potential, and is physically made of a member having high thermal conductivity, such as aluminum, installed at the center of the bottom of the container. It is being fixed on the cylindrical support stand 22 which becomes via an insulating material (not shown). An annular refrigerant passage 22 a extending in the circumferential direction, for example, is provided inside the support base 22. A refrigerant, for example, cooling water, having a predetermined temperature is supplied to the refrigerant passage 22a through a refrigerant supply pipe 24, 26 from a cooling device (not shown) provided outside the apparatus.

  A circular electrostatic chuck sheet 28 is crowned on the upper surface of the lower electrode 20, and the semiconductor wafer W is placed on the electrostatic chuck sheet 28. The electrostatic chuck sheet 28 is formed, for example, by laminating a pair of polyimide resin films and enclosing a thin conductive film 28a made of, for example, copper foil for adsorbing the semiconductor wafer W by electrostatic force. The conductive film (electrostatic chucking electrode) 28a is fed with a predetermined DC voltage for electrostatic chucking from a DC power source 32 through a lower electrode 20, a support base 22, and a power feeding rod 30 penetrating the bottom of the container. . The coil 34 and the capacitor 36 included in the DC voltage supply circuit constitute a filter for removing high frequency noise.

  The upper electrode 18 is a disk member made of a conductive member such as aluminum, and has a cylindrical support portion 40 extending downward from the upper surface of the processing vessel 10 and an outer peripheral side surface flush with a bolt or the like (see FIG. (Not shown) is fixedly attached horizontally. A high frequency voltage of, for example, 13.56 MHz is applied to the upper electrode 18 from the high frequency power source 42 with a predetermined power (electric power) via the capacitor 44. A number of vent holes 18a are formed in the upper electrode 18, and a gas introduction chamber 46 is formed thereon. The etching gas from the gas supply pipe 14 is introduced into the gas introduction chamber 46 and flows into the plasma discharge space between the electrodes 18 and 20 through the vent hole 18a of the upper electrode 18 at a uniform pressure and flow rate. ing.

  This dry etching apparatus is in close contact with or in contact with the outer peripheral side surfaces of the upper electrode 18 and the cylindrical support portion 40, and has an arbitrary step d within a predetermined range from the upper electrode 18 toward the outer peripheral end of the lower electrode 20. An annular projecting member 50 for correcting the electric field intensity configured to project is provided. The annular protruding member 50 may be made of a conductive material, but may be made of an insulating material. However, in this embodiment, since it is an anode coupling arrangement type that supplies a high frequency voltage to the upper electrode 18 side, reactive ions in the plasma are not only applied to the upper electrode 18 but also to the annular protruding member 50 due to the self-bias or sputtering effect. A material that can adapt to such a sputtering effect is preferable because it is incident with a considerable impact.

  A plurality of through holes 50a are formed in the annular projecting member 50 at predetermined intervals in the circumferential direction, and the bolts 52 are perpendicular to the through holes 50a with the heads facing the lower surface side of the annular projecting member 50. It penetrates. And the axial part of the volt | bolt 52 penetrates the ceiling surface of the container 10 so that raising / lowering is possible, and it is screwing together with the nut 54 outside the container 10 (upper surface). The washer member 56 attached to the nut 54 may have a sealing function. With this configuration, by rotating the nut 54, the annular projecting member 50 can be displaced in the vertical direction, and the projecting amount (step) d with respect to the upper electrode 18 can be adjusted.

In this dry etching apparatus, when the material to be etched on the surface of the semiconductor wafer W is, for example, a SiO2 film, a mixed gas of CF4 and Ar, for example, as an etching gas is supplied from the gas supply pipe 14 to the both electrodes 18 via the gas introduction chamber 46. , 20 into the plasma discharge space. Then, fluorine active species F * and reactive ions CF4 ⁺ and Ar ⁺ are generated from the etching gas (CF 4 / Ar) sent into the plasma atmosphere, and these active species and reactive ions are converted into a semiconductor on the lower electrode 20. By falling or entering the wafer W, the oxide film (SiO2) on the surface of the wafer W is etched.

  In this embodiment, the action of the annular projecting member 50 corrects or corrects the electric field from the upper electrode 18 side with respect to the plasma discharge space to a uniform intensity in the radial direction of the semiconductor wafer W, whereby the plasma density in the same direction or Since the concentration of the decomposition products in the plasma can be made uniform, uniform etching processing characteristics can be obtained on the semiconductor wafer W.

  The operation of the annular projecting member 50 will be described with reference to FIG. The plasma PR generated in the plasma discharge region between the electrodes 18 and 20 diffuses not only in the space between the electrodes 18 and 20 but also in the periphery (radially outside). An ion sheath SH is formed at the boundary between the plasma PR and a nearby object. Here, the ion sheath SH is an electric field space that exists because the velocity of electrons is much larger than the velocity of positive ions, and all voltage or potential changes between the plasma PR and the adjacent object occur in this sheath. . In the ion sheath SH along the upper electrode 18, an electric field Ey in the vertical direction (y direction) is generated from the plasma PR side toward the electrode 18.

  As described above, the plasma PR generated between the electrodes 18 and 20 diffuses to the periphery (radially outward), and therefore the plasma density tends to be lower in the electrode peripheral portion than in the electrode central portion. Therefore, in the ion sheath SH along the upper electrode 18, the strength of the electric field Ey is inevitably lowered as the distance from the center of the electrode is increased in the radial direction. However, in the dry etching apparatus of this embodiment, the electric field in the ion sheath SH is reinforced near the periphery of the upper electrode 18 by the action of the annular projecting member 50 as described below, and the in-plane (diameter on the semiconductor wafer W). (Direction) Uniform plasma density can be obtained.

  More specifically, the annular projecting member 50 protrudes toward the lower electrode 20 from the upper electrode 18 around the upper electrode 18 to form a step, so that the inside of the step or inside the ion sheath SH along the inner peripheral surface 50a. Thus, an electric field Ex in the lateral direction (x direction) parallel to the electrode 18 is generated. Then, in the ion sheath SH in the vicinity of the step edge portion 50c of the annular projecting member 50, the lateral electric field Ex on the step vertical surface 50a side orthogonal to the vertical electric field Ey on the step horizontal surface 50b side is added in vector. A large (reinforced) electric field Es is generated in the combined inward oblique direction (direction toward the wafer center). By this reinforcing electric field Es, in the vicinity of the step edge portion (corner portion) 50c of the annular projecting member 50, acceleration or kinetic energy given to electrons is reinforced, plasma excitation is strengthened, and plasma density is increased. The reinforcement of the electric field strength in the vicinity of the peripheral portion of the upper electrode 18 as described above and the enhancement of the plasma density can be variably adjusted by changing the protrusion amount d of the annular protrusion member 50.

  That is, as the protruding amount d is increased, the lateral electric field Ex generation region along the step vertical surface 50a is expanded and the reinforcing electric field Es is also increased, and the step edge portion 50c is the lower electrode 20 or the peripheral portion of the semiconductor wafer W. Since it approaches the side, the degree of enhancing the plasma density increases.

  Conversely, as the projection amount d is reduced, the lateral electric field Ex generation region along the step vertical surface 50a is reduced to reduce the reinforcing electric field Es, and the step edge portion 50c is formed around the lower electrode 20 or the semiconductor wafer W. Since it moves away from the part, the degree of enhancing the plasma density decreases. As a condition for obtaining a reinforcing electric field Es larger than the electric field Ey in the vertical direction at the periphery of the upper electrode 18 without the annular protruding member 50, the protruding amount d is at least the width (thickness) of the ion sheath SH along the upper electrode 18. It must be greater than f.

  As described above, in the dry etching apparatus of this embodiment, the annular projecting member 50 that can project toward the lower electrode 20 side is provided on the outer periphery of the upper electrode 18, and the projecting amount or step d of the annular projecting member 50 is variable. With the adjustable structure, the electric field strength in the vicinity of the periphery of the upper electrode 18 is moderately reinforced, and the density of the plasma PR generated between the electrodes 18 and 20 is made uniform in the radial direction of the semiconductor wafer W. In-plane uniform etching processing characteristics can be obtained.

  FIG. 3 shows a configuration of a parallel plate type dry etching apparatus according to the second embodiment.

  In the second embodiment, the annular projecting member 60 is fixedly attached to the processing container 10, the upper electrode 18 is retracted with respect to the annular projecting member 60, and the retracted amount or step g can be variably adjusted. .

  More specifically, a cylindrical annular projecting member 60 is disposed so as to hang vertically downward in a circular opening 10a formed in the ceiling surface of the processing container 10, and radially outward from the upper end of the annular projecting member 60. The extending flange portion 60 a is placed on the upper surface of the processing vessel 10 around the outer periphery of the circular opening 10 a via an O-ring 64 and fixedly attached with a bolt 66. Then, the upper electrode 18 is fixedly attached to the lower surface of the cylindrical support member 68 which is substantially the same shape as the annular projecting member 60 and is slightly smaller than the annular projecting member 60 by bolts or the like (not shown), and the flange portion 68a of the cylindrical support member 68 is attached to the annular projecting member. It is configured such that it is overlapped on one or more annular spacer plates or sheets 70 on the 60 flange portions 60a, and is detachably fixed with bolts 72. In such a configuration, the amount (step) g of the annular projecting member 60 projecting relative to the upper electrode 18 can be arbitrarily adjusted by changing the number of the annular spacer plates 70 stacked.

  Also in the configuration of the second embodiment, the electric field strength in the vicinity of the periphery of the upper electrode 18 is moderately reinforced, and the density of the plasma PR generated between the electrodes 18 and 20 is uniform in the radial direction of the semiconductor wafer W. As a result, in-plane uniform etching characteristics can be obtained on the semiconductor wafer W. However, when adjusting the protruding amount (step) g of the annular protruding member 60, the distance between the electrodes 18 and 20 may change, thereby changing the etching processing characteristics such as the etching rate. However, since this kind of change is uniform in the surface on the semiconductor wafer W, it is easy to adjust the gas pressure of the etching gas, the degree of vacuum in the processing vessel 10, the power supplied from the high-frequency power source 42, etc. It can be corrected.

  The substrate to be processed in the present invention is not limited to a semiconductor wafer, and may be, for example, an LCD (liquid crystal display) substrate or the like, and can be any substrate that can be a target of dry etching processing.

DESCRIPTION OF SYMBOLS 10 Processing container 14 Gas supply pipe 16 Exhaust pipe 18, 18 Upper electrode 20 Lower electrode 40 Support part 42 High frequency power supply 50 Annular protrusion member 52 Bolt 54 Nut 60 Annular protrusion member 68 Support member 70 Annular spacer board

Claims (3)

First and second electrodes opposite to each other are provided in a vacuumable processing container, a high frequency voltage is applied between the first and second electrodes, and an etching gas is flown to generate plasma of the etching gas, A parallel plate type dry etching apparatus for etching a substrate to be processed disposed on the second electrode using plasma,
Wherein in order to control the distribution characteristic of plasma density in the radial direction of the substrate, the electric field intensity correcting protrusions the first to form a step projecting to the second electrode side with respect to the first electrode the provided near the periphery of the electrode, the amount of projection of the electric field intensity correcting projections provided with a protrusion amount adjustment means for variably adjusting,
The electric field intensity correcting protrusion is arranged so as to hang vertically downward inside an opening formed on the upper surface of the processing container, and a flange portion extending radially outward from an upper end portion of the protrusion is formed around the opening. Having an annular protruding member fixedly attached to the upper surface of the container;
The projecting amount adjusting means is disposed inside the annular projecting member, the first electrode is attached to a lower surface thereof, and a flange portion extending radially outward from an upper end portion of the flange portion of the annular projecting member. An overlying cylindrical support member, one or more annular spacer plates inserted between the flange portion of the cylindrical support member and the flange portion of the annular projecting member, and the flange of the cylindrical support member And a bolt for removably fixing the annular spacer plate to the flange portion of the annular projecting member,
Adjusting the amount of protrusion of the annular protrusion member relative to the first electrode by changing the number of the annular spacer plates;
Parallel plate type dry etching equipment. To the first electrode, forming a large number of vent holes for pouring the etching gas to a plasma discharge space between the first electrode and the second electrode, a parallel plate of claim 1 Dry etching equipment. A high-frequency voltage is applied between the first and second electrodes facing each other in a vacuumable processing vessel, and an etching gas is flown to generate plasma of the etching gas, and the plasma is used to generate plasma on the second electrode. A parallel plate type dry etching method for etching a substrate to be processed disposed on a substrate,
Provided the electric field intensity correcting projections forming the step protrudes to the second electrode side with respect to the first electrode near the periphery of the first electrode, the amount of projection of the electric field intensity correcting projections To control the distribution characteristics of the plasma density in the radial direction of the substrate to be processed ,
The adjustment of the protrusion amount of the electric field intensity correction protrusion is as follows:
An annular projecting member is disposed so as to hang vertically downward inside an opening formed on the upper surface of the processing container, and a flange portion extending radially outward from an upper end portion of the annular projecting member is disposed around the opening. Fixedly attached to the top surface of the processing vessel
A cylindrical support member is disposed inside the annular projecting member, the first electrode is attached to the lower surface of the cylindrical support member, and a flange portion extending radially outward from the upper end of the cylindrical support member Over the flange portion of the annular projecting member,
Inserting one or more annular spacer plates between the flange portion of the cylindrical support member and the flange portion of the annular projecting member;
The flange portion of the cylindrical support member and the annular spacer plate are detachably fixed to the flange portion of the annular projecting member with a bolt,
By changing the number of the annular spacer plates, a relative protrusion amount of the annular protrusion member with respect to the first electrode is adjusted.
The dry etching method performed by this.

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