JP2929150B2 - Plasma equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma apparatus using an electron beam excited plasma.

[0002]

2. Description of the Related Art With the recent increase in performance and miniaturization of semiconductor devices, fine processing is required also in plasma processing of an object to be processed such as a semiconductor wafer, and the degree of vacuum in a vacuum processing chamber is further reduced. There is an increasing need to more efficiently convert the reaction gas into a plasma in the closed state. As one of the plasma processes, a predetermined reaction gas is turned into plasma by extracting electrons from the plasma, accelerating and irradiating them,
An electron beam excitation type plasma apparatus for processing an object to be processed by this plasma is known, and the applicants have already attempted to develop a plasma apparatus of this type.

[0003] That is, Japanese Unexamined Patent Publication No. 1-155555 discloses an electron beam plasma apparatus.
An example in which an electron beam is diffused using a deflection electrode is described. Japanese Patent Application Laid-Open No. 1-105540 discloses an example in which an electron beam plasma device is provided with a magnetic field canceling means to diffuse an electron beam. Japanese Patent Application Laid-Open No. 63-190299 describes an example in which an electrode pair is fixed via a spacer in an electron beam plasma apparatus. Also,
JP-A-64-53422 describes a second plasma means for converting an etching gas into a plasma by a first plasma in an electron beam plasma apparatus.

[0004] As shown in FIG.
For example, a cathode electrode 2 having an introduction hole 2a for ejecting a discharge gas for generating plasma such as argon (Ar) is provided at one end in a cylindrical container 1 formed of stainless steel or the like. A wafer holder 4 for holding a semiconductor wafer W to be processed is disposed at the end of the processing chamber 3 opposite to the cathode electrode 2. Further, between the cathode electrode 2 and the wafer holder 4, in order from the cathode electrode 2 side, first and second intermediate electrodes 5 and 6, each having a through hole coaxially at the center, and an anode electrode 7
, And an electron beam acceleration electrode 9 is provided between the anode electrode 7 and an acceleration space 8. In addition, annular coils 13 to 16 for forming a magnetic field are arranged outside the hermetically sealed container 1 outside the first and second intermediate electrodes 5 and 6, the anode electrode 7, and the electron beam accelerating electrode 9 respectively. I have. Further, the intermediate chamber 17 of the discharge region 10, the acceleration space 8
The processing chamber 3 is provided with exhaust holes 18, 19, and 20, respectively. A vacuum pump (not shown) is connected to each of the exhaust holes 18, 19, and 20, and the intermediate chamber 17, the acceleration space 8, and the processing chamber 3 are provided. The inside is maintained at a predetermined vacuum pressure.

[0005] With the above configuration, a discharge voltage V1 is applied between the anode electrode 7 and the cathode electrode 2 to cause a discharge, thereby generating plasma in the discharge region 10 accommodating the cathode electrode 2. Further, by applying an electron beam acceleration voltage V2 to the accelerating electrode 9, electrons are extracted from the plasma generated in the discharge region 10 and sent to the electron beam acceleration region 11, accelerated, and accelerated by the plasma processing region 12 (specifically, the processing). The reaction gas such as chlorine (Cl) or argon (Ar) introduced into the processing chamber 3 through the reaction gas introduction pipe 3a is activated to generate high-density plasma. The plasma processing of the semiconductor wafer W can be performed. At this time, the etching rate is improved by applying a DC voltage V3 to the wafer holder 4 or floating the wafer holder 4 to draw the reactive species in the plasma, that is, the reactive gas, ions and electrons into the semiconductor wafer W.

In this type of plasma apparatus, rectangular permanent magnets are arranged on both sides of an electron beam introduced into the processing chamber 3 in order to make the plasma density uniform, and plasma is generated by the lines of magnetic force of the permanent magnets. A method of compressing and expanding to make a flat shape, that is, a sheet shape, has also been developed (see JP-A-59-27499).

[0007]

However, in the conventional sheet-like plasma generation method, a certain thickness is obtained by compressing and expanding a cylindrical plasma generated by a discharge in a magnetic field with a pair of rectangular permanent magnets. Although it is possible to generate a sheet plasma having an area and an area, not only is it not possible to obtain a uniform sheet-like plasma over a wide range, but also the plasma density decreases contrary to the homogenization. It has been difficult to achieve high-precision processing of a processing target having a large area, such as an LCD or an LCD substrate. This problem is caused by C
A similar problem occurs in a plasma apparatus such as a VD apparatus and a sputtering apparatus.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and makes it possible to form an electron beam-excited plasma into a sheet over a wide range and to make the plasma density in the plane uniform so that highly accurate processing can be performed. It is an object to provide a plasma device.

[0009]

In order to achieve the above object, a plasma apparatus according to the present invention excites a predetermined reaction gas supplied into a processing chamber by extracting electrons from plasma and irradiating them with acceleration. Assuming a plasma apparatus that performs plasma processing and processes a target object with the plasma, an electron accelerating means for drawing electrons into the processing chamber, and a magnetic field for compressing and transferring the electrons drawn by the electron accelerating means into a flat shape. Forming means, and a magnetic field focusing means disposed on the processing chamber end side facing the magnetic field forming means,
The magnetic field focusing means is constituted by a magnetic field focusing magnet and an electron guiding electrode arranged on the magnetic field focusing surface side of the magnet.

In the present invention, the electron accelerating means may have any structure as long as it can draw electrons into the processing chamber, but at least an annular coil for forming a magnetic field for passing through the anode electrode and the electron beam accelerating electrode. Must be provided.

The magnetic field forming means may have any structure as long as the electrons drawn into the processing chamber are compressed and transferred in a flat shape, but preferably the electrons drawn by the magnetic field forming means are flattened. It is better to comprise a pair of permanent magnets facing each other so as to be compressed, and a solenoid coil that transports flattened electrons along a flat surface. In this case, a pair of permanent magnets that compress electrons in a flat shape have opposite surfaces of the same polarity (N
(Pole) can be formed of a rectangular permanent magnet. Also, the solenoid coil may be singular,
Providing a plurality of coils in parallel in the electron transfer direction is preferable in that electrons can be transferred over a long distance.

The magnetic field converging magnet of the magnetic field converging means may be disposed at the terminal end of the processing chamber so as to focus the terminal end of the plasma compressed flat by the magnetic field forming means in the processing chamber. Any magnet may be used, but it is preferable that the magnet is formed of a rectangular permanent magnet having a pole opposite to the pole on the surface facing the permanent magnet of the magnetic field forming means.

In addition, the potential of the electron guiding electrode is constant as long as the electrons drawn into the processing chamber by the electron accelerating means are efficiently taken into the flattened sheet-like plasma region. However, it is preferable to make the potential variable.

[0014]

According to the plasma apparatus of the present invention configured as described above, electrons are drawn into the processing chamber from the plasma by the electron acceleration means, and the drawn electrons are generated by the magnetic field of the pair of permanent magnets of the magnetic field forming means. After being compressed into a flat shape, it is transported in a direction along a flat surface along a magnetic field line formed by a solenoid coil, is focused by a magnet of a magnetic field focusing means, and is formed into a sheet by the potential of an electron guiding electrode. The amount of electrons in the reduced plasma region is increased, and a stable plasma region is formed.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. Here, a case where the plasma apparatus of the present invention is applied to a plasma etching apparatus will be described by assigning the same reference numerals to the same portions as those of the conventional plasma apparatus shown in FIG.

FIG. 1 is a schematic sectional view of an example of the plasma apparatus of the present invention, FIG. 2 is a schematic plan view of an electron accelerating means, a magnetic field forming means and a magnetic field focusing means in the present invention, and FIG. 3 is a side view of FIG. Have been.

The plasma apparatus according to the present invention has a plasma generating means 21 for converting a discharge gas into plasma, an electron accelerating means 22 for extracting electrons from the plasma and accelerating the extracted electrons, and an accelerating means for accelerating the electrons. The main part is constituted by plasma processing means 23 for performing plasma processing by turning the reaction gas into plasma by the irradiation of the electrons.

In this case, the plasma generating means 21 discharges a plasma-generating discharge gas such as argon (Ar) to one end of the closed vessel 1 which is a cylindrical body made of, for example, stainless steel. A cathode electrode 2 having a spouting inlet 2a; an anode electrode 7 disposed at an intermediate portion of the closed container 1; and first and second intermediate electrodes disposed between the anode electrode 7 and the cathode electrode 2. 5 and 6. Further, an intermediate chamber 17 is formed between the second intermediate electrode 6 and the anode electrode 7, and this intermediate chamber 17 is formed.
A vacuum pump (not shown) is connected to an exhaust hole 18 provided at a lower portion of the intermediate chamber 17 via an on-off valve 18a, and the inside of the intermediate chamber 17 is maintained at a predetermined degree of vacuum.

The area between the cathode electrode 2 and the anode electrode 7 is a discharge region 10. In addition, the first and second
Closed container 1 outside the intermediate electrodes 5 and 6 and the anode electrode 7
The coils 13 to 15 each formed in an annular shape for forming a magnetic field are arranged outside the.

The electron accelerating means 22 includes an acceleration space 8 for transferring electrons extracted from the plasma, and an acceleration space 8 for extracting electrons from the plasma in the discharge region 10 and extracting the electrons.
An electron beam accelerating electrode 22a (hereinafter referred to as an accelerating electrode) for accelerating the electrons inside and introducing the electron beam into the processing chamber 3 of the plasma processing means 23, and a ring for forming a magnetic field provided outside the accelerating electrode 22a. And a coil 22b.
In this case, the inner diameter of the annular coil 22b is set to about 50 mm, and a current of 8A to 15A is applied. A vacuum pump (not shown) is connected to an exhaust hole 19 provided below the acceleration space 8 via an on-off valve 19a, so that the interior of the acceleration space 8 is maintained at a predetermined vacuum pressure. In addition,
The region between the anode electrode 7 and the acceleration electrode 22a is an electron acceleration region 11.

On the other hand, the plasma processing means 23 activates the reaction gas by introducing electrons accelerated by the accelerating electrode 22a and the annular coil 22b of the electron acceleration means 22 and a reaction gas such as Cl gas or Ar gas. A processing chamber 3 and an object to be processed, such as a semiconductor wafer W, disposed in the processing chamber 3
A susceptor 24 for horizontally holding the magnetic field, a magnetic field forming means 25 disposed on the electron acceleration means side for compressing and transferring the electrons drawn from the electron acceleration means 22 into a flat shape, and a magnetic field forming means 2
Magnetic field focusing means 26 disposed on the processing chamber wall side opposite to 5
It is composed of

In this case, the magnetic field forming means 25 comprises a pair of permanent magnets 25a, 25b having a rectangular cross section which face each other with their N poles facing each other in order to compress the columnar electron beam drawn in from the electron accelerating means 22. And a plurality (two shown in the drawing) of solenoid coils 25c for transferring plasma having flattened electrons along a flat surface. In addition, 25d is a cylindrical chamber. The magnetic field focusing means 26 is provided by the permanent magnet 25 of the magnetic field forming means 25.
The poles (S) opposite to the poles (N poles) of the opposing surfaces of
Pole) is formed by a rod-shaped permanent magnet 26a having a rectangular cross section disposed toward the inside of the processing chamber, and a non-magnetic material such as stainless steel disposed to cover the magnetic field focusing surface side of the permanent magnet 26a. And a plate-like electrode for electron guidance 26b. In this case, the permanent magnets 25a and 25b of the magnetic field forming means 25 have a length of 160 mm and a surface magnetic field of about 1 mm.
~ 1.2KG, permanent magnet 26a for magnetic field focusing
Is set to 260 mm in length, the surface magnetic field is set to 1 to 1.2 KG, the length of the solenoid coil 25c is set to about 30 cm, and a current of 3 A (ampere) is supplied. A power supply 26c is connected to the electron guiding electrode 26b so that a potential of -100V to + 50V can be applied. The magnetic field forming means 25 and the magnetic field focusing permanent magnet 2
6 is a plasma processing region 12.

Accordingly, the annular coil 22b of the electron accelerating means 22 and the permanent magnets 25a, 25
b, solenoid coil 25c and permanent magnet 2 for focusing magnetic field
In the magnetic field configuration formed by each magnetic field line of No. 6, a magnetic field G as shown in FIGS. 2 and 3 is formed, so that the electrons drawn into the processing chamber by the accelerating electrode 22a and the annular coil 22b of the electron accelerating means 22 After being compressed flat by the pair of permanent magnets 25a and 25b of the magnetic field forming means 25,
The sheet is transferred in the direction along the deflected plane along the line of magnetic force formed by the solenoid coil 25c, is focused by the magnetic field focusing permanent magnet 26, and forms a sheet-like plasma region at a position above and above the susceptor 24 (FIG. 4). reference). At this time, by changing the potential of the electron guiding electrode 26b, the amount of electrons drawn into the plasma region is increased, and at the same time, outside the sheet-like plasma region, that is, outside the sheet-like plasma region, and the magnetic field focusing permanent magnet 26a Can be suppressed from flowing around the wall behind.

The susceptor 24 is connected to a high frequency power supply RF for drawing reactive species (reactive gas, ions and electrons) in the excited plasma to the semiconductor wafer W side. The bias voltage of this high-frequency power supply RF is several MHz to
Dozens of MHz (specifically, 2-3 MHz to 13.56 MH
z). Further, the susceptor 24 is provided with a clamp ring 24b for fixing and holding the semiconductor wafer W around the upper surface side of a susceptor body 24a made of, for example, stainless steel, and ethylene glycol and water are supplied to a refrigerant passage 24c provided in the susceptor body 24a. Is connected to a supply pipe 27a and a discharge pipe 27b of a refrigerant in which He gas or N2 gas is supplied / discharged to a backside gas reservoir (not shown) provided on the mounting surface side of the semiconductor wafer W. A tube 28 is connected.

Next, the operation of the plasma apparatus of the present invention configured as described above will be described. First, a discharge gas is introduced from the discharge gas introduction hole 2a, and the cathode electrode 2
In a state where the gas is evacuated so that the pressure between the first intermediate electrode 5 and the first intermediate electrode 5 becomes, for example, about 1.0 Torr, the pressure between the cathode electrode and the first and second intermediate electrodes 5 and 6 and the anode electrode 7 is increased. When a glow discharge is generated by applying a discharge voltage V1 to the electrode, plasma is generated in the discharge region 10. In this case, the first and second intermediate electrodes 5 and 6 are for facilitating glow discharge at a low voltage, and the glow discharge is first generated between the cathode electrode 2 and the first intermediate electrode 5. Thereafter, the process proceeds to the second intermediate electrode 6 and the anode electrode 7. After a stable glow discharge is formed between the cathode electrode 2 and the anode electrode 7, the switches S1 and S2 are turned off.

The electrons in the plasma generated as described above are drawn into the acceleration space 8 by application of the acceleration voltage V2 to the acceleration electrode 22a, accelerated by the magnetic force lines formed by the annular coil 22b, and accelerated. It is transferred inside. The electrons drawn into the processing chamber 3 are compressed in a flat shape by the pair of permanent magnets 25a and 25b of the magnetic field forming means 25, and are then transported along the flat surface by the lines of magnetic force formed by the solenoid coil 25c. The end is focused by the magnetic field focusing permanent magnet 26a. In this state, the electrons excite the reaction gas Cl or Ar supplied into the processing chamber 3 to be turned into plasma, and the sheet-like plasma is formed at a position above and above the susceptor 24 and the semiconductor wafer W. At this time, by changing the potential of the electron guiding electrode 26b, the amount of electrons drawn into the plasma region is increased, and outside the sheet-like plasma region, that is, outside the sheet-like plasma region, and the magnetic field focusing permanent magnet 2
The sneak of the plasma toward the wall behind 6a is suppressed, and the plasma density is increased. And susceptor 2
Reactive species, that is, reactive gases, ions and electrons are extracted from the sheet-like plasma region by the high-frequency voltage applied to 4, and the reactive species are accelerated in the plasma sheath on the surface of the semiconductor wafer W and collide as an ion beam. The semiconductor wafer W is etched.

In the plasma etching apparatus configured as described above, a comparison experiment was performed between the case where the electron guiding electrode 26b was floating (Comparative Example) and the case where a potential was applied to the electron guiding electrode 26b (Example). However, the following results were obtained.

Experimental conditions Semiconductor wafer W: poly Si Reaction gas: Ar Ring coil 22b: 8A Solenoid coil 25c: 3A Electrode inducing electrode of comparative example: floating Electrode inducing electrode 26b of embodiment: 0V (Grounded to the wall of the processing chamber 3) As a result of conducting an experiment under the above conditions, in the comparative example, the amount of electrons taken in was 3.8 A, the average etching rate was 13.2 Angstroms / min (min). However, in the example, the amount of electrons taken in was 5.3 to 5.5 A, and the average etching rate was 32.3 Angstroms / minute (min).
Thus, the amount of electrons taken in can be increased by about 1.4 times in the amount of electrons taken in, and the average etching rate can be increased by about 2.
A four-fold increase was achieved.

In the above embodiment, the case where the plasma apparatus of the present invention is applied to a plasma etching apparatus has been described.
Needless to say, the present invention can be applied to other electron beam excitation type plasma devices such as a device and a sputtering device. In the above embodiment, the case where the object to be processed is a semiconductor wafer has been described. However, the object to be processed is not limited to a semiconductor wafer. For example, an LCD substrate or the like can be similarly processed.

[0030]

As described above, according to the plasma apparatus of the present invention, since it is configured as described above, the following effects can be obtained.

1) According to the first aspect of the present invention, the electrons drawn by the electron accelerating means are compressed and transferred flat by the magnetic field forming means, and the ends of the electrons are focused by the magnetic field focusing means. At the same time, electrons can be effectively taken in by the potential of the electron guiding electrode, so that a uniform and high-density sheet-like plasma can be generated in the radial direction of the object to be processed, and the processing accuracy is improved. Can be.

According to the second aspect of the present invention, the magnetic field forming means includes a pair of permanent magnets facing each other to compress the electrons drawn by the electron accelerating means into a flat shape and a flattened electron. Since it is composed of a solenoid coil that moves along a plane, a sheet-like plasma having a uniform density in the radial direction of the object to be processed can be generated over a wide area, and plasma processing of a large object to be processed can be performed. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a plasma device of the present invention.

FIG. 2 is a schematic plan view showing an electron accelerating unit, a magnetic field forming unit, and a magnetic field focusing unit according to the present invention.

FIG. 3 is a side sectional view of FIG. 2;

FIG. 4 is a schematic perspective view showing a generation state of a sheet-like plasma region by the plasma device of the present invention.

FIG. 5 is a schematic sectional view showing a conventional plasma device.

[Explanation of symbols]

 Reference Signs List 22 electron accelerating means 22a electron beam accelerating electrode 22b annular coil 25 magnetic field forming means 25a, 25b permanent magnet 25c solenoid coil 26 magnetic field focusing means 26a magnetic field focusing permanent magnet 26b electron guiding electrode 26c power supply

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H05H 1/24 H01L 21/302 B (72) Inventor Motosuke Miyoshi 72 Horikawa-cho, Sai-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Horikawa-cho Co., Ltd. Inside the factory (72) Inventor Haruo Okano 1 Toshiba-cho, Komukai, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Within the Toshiba Research Institute Co., Ltd. In the factory (56) References JP-A-2-265150 (JP, A) JP-A-3-162581 (JP, A) JP-A-5-136067 (JP, A) JP-A-5-291189 (JP, A) (58) Fields surveyed (Int.Cl. ⁶ , DB name) H05H 1/24 H05H 1/46 C23C 14/35 C23F 4/00 H01L 21/205 H01L 21/3065

Claims (2)

(57) [Claims] 1. A plasma apparatus for extracting and accelerating and irradiating electrons from plasma to excite a predetermined reaction gas supplied into a processing chamber into plasma and performing processing of an object to be processed with the plasma. An electron accelerating means for drawing electrons into the processing chamber, a magnetic field forming means for compressing and transferring the electrons drawn by the electron accelerating means in a flat shape, and a magnetic field forming means disposed on the terminal side of the processing chamber opposite to the magnetic field forming means. A plasma apparatus, comprising: a magnetic field converging means, wherein the magnetic field converging means is constituted by a magnetic field converging magnet and an electron guiding electrode disposed on the magnetic field converging surface side of the magnet. 2. A magnetic field forming means comprising a pair of permanent magnets facing each other to compress the electrons drawn by the electron accelerating means into a flat shape, and a solenoid coil for transferring the flattened electrons along a flat surface. The plasma apparatus according to claim 1, wherein