JP2929151B2 - 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.
A technique for diffusing an electron beam using a deflection electrode is disclosed. Japanese Patent Application Laid-Open No. 1-105540 discloses a technique in which an electron beam plasma apparatus is provided with a magnetic field canceling means to diffuse an electron beam. Japanese Patent Application Laid-Open No. 63-190299 discloses a technique for fixing an electrode pair via a spacer in an electron beam plasma apparatus. Also,
Japanese Unexamined Patent Publication No. 64-53422 discloses a technique relating to 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, since only a sheet-like plasma with a beam-shaped component at the center of the axis remaining can be generated, not only a high-density uniform plasma region cannot be obtained, but also a wide It is not possible to obtain a uniform sheet-like plasma over a range, for example a semiconductor wafer or L
It is not suitable for processing an object having a large area, such as a CD substrate, and is difficult to realize. This problem is a similar problem in plasma devices such as a CVD device and a sputtering device other than the plasma etching device.

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 for processing the object to be processed by the plasma, the electron acceleration means for drawing electrons into the processing chamber, and the electrons drawn by the electron acceleration means are branched and compressed into a flat shape. And a magnetic field forming means for transferring.

In the present invention, the structure of the electron accelerating means is not limited as long as it can draw electrons into the processing chamber, but it is necessary to provide at least an annular coil for forming a magnetic field.

The magnetic field forming means may have any structure as long as it branches and compresses and transports the electrons drawn into the processing chamber in a flat shape. Preferably, the electron drawn from the magnetic field forming means is used. And a solenoid coil for transferring flattened electrons along a flat surface. In this case, a pair of permanent magnets that split electrons and compress them in a flat shape can be formed by rectangular permanent magnets whose opposing surfaces have the same pole (N pole). It is also possible. Although a single solenoid coil may be used, it is preferable to provide a plurality of coils in parallel in the electron transfer direction because electrons can be transferred over a long distance.

[0012]

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 branched while maintaining the electron beam component and compressed in a flat shape, it is excited in a reactive gas supplied in the processing chamber by being transferred along the plane of the magnetic field formed by the solenoid coil along the plane of the magnetic field. To generate a sheet-like plasma.

[0013]

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 and a magnetic field forming means of the present invention, and FIG. 3 is a side view of FIG. Arrow G in the drawing indicates the direction of the magnetic field.

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 the plasma processing means 23 which converts the reactive gas into plasma by the irradiation of the electrons and performs the plasma processing.

In this case, the plasma generation means 21 supplies a discharge gas for plasma generation such as argon (Ar) to one end of a closed vessel 1 which is a cylindrical body made of, for example, stainless steel or the like. 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.
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 vacuum pump (not shown) is connected to an exhaust hole 19 provided in the lower part of the acceleration space 8 via an opening / closing valve 19a. Is maintained at a predetermined vacuum pressure. The anode electrode 7 and the acceleration electrode 22a
A region between them is an electron acceleration region 11.

On the other hand, the plasma processing means 23 activates the reaction gas by introducing the 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 that holds the electron beam horizontally, a magnetic field forming device 25 that is disposed on the electron acceleration device side, branches the electrons drawn from the electron acceleration device 22, compresses the electrons into a flat shape, and transfers the electrons.
It comprises a magnetic field forming means 25 and a magnetic field focusing means 26 arranged on the side of the processing chamber wall facing the magnetic field forming means 25.

In this case, the magnetic field forming means 25 comprises a pair of rectangular cross-sections which vertically separate the columnar electron beam drawn in from the electron accelerating means 22 so that the N poles are opposed to each other and compressed so as to be compressed. Permanent magnets 25a, 25b,
It comprises a plurality (two shown in the drawing) of solenoid coils 25c for transferring plasma having flattened electrons along a flat plane. In addition, 25d is a cylindrical chamber. The magnetic field converging means 26 has a pole (N) on the surface of the magnetic field forming means 25 opposite to the permanent magnets 25a and 25b.
The pole (S pole) opposite to the pole (pole) is formed of a rod-shaped permanent magnet having a rectangular cross section and disposed toward the inside of the processing chamber. In this case, the permanent magnets 25a and 25b have a length of 40 mm, the surface magnetic field is set to about 2 KG, the magnetic field focusing permanent magnet 26 is set to a length of 260 mm, the surface magnetic field is set to 2 KG, and the solenoid coil 25 c The length is set to about 30 cm, and the magnetic field near the semiconductor wafer W is set to about 50G. The space between the magnetic field forming means 25 and the magnetic field focusing permanent magnet 26 is the plasma processing region 12.

Therefore, 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
Since the magnetic field configuration formed by the magnetic field lines of No. 6 is formed as shown in FIGS. 2 and 3, the electrons drawn into the processing chamber by the accelerating electrode 22a and the annular coil 22b of the electron accelerating means 22 generate the magnetic field. After the axial components of the electron beam are pushed back by the magnetic lines of force of the pair of permanent magnets 25a and 25b of the means 25 and are branched to the left and right and compressed flat, the electron beams are flattened along the magnetic lines of force formed by the solenoid coil 25c. It is conveyed in the direction along and is focused by the magnetic field focusing permanent magnet 26 to form a sheet-like plasma region at a position above and above the susceptor 24 (see FIG. 4).

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.

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 lines of force formed by the annular coil 22b, and accelerated. It is transferred inside. The electrons drawn into the processing chamber 3 are branched right and left by the pair of permanent magnets 25a and 25b of the magnetic field forming means 25 while keeping the electron beam components, and are compressed flat, and then formed by the solenoid coil 25c. The magnetic flux is transferred along the deflected plane by the magnetic field lines, and the end is focused by the focusing permanent magnet 26. In this state, the reaction gas Cl or Ar supplied into the processing chamber 3 is excited and turned into plasma, and the sheet-like plasma is converted into a susceptor 24.
And at a position near and above the semiconductor wafer W.

Then, a reactive species, that is, reactive gas, ions and electrons are extracted from the sheet-like plasma region by the high frequency voltage applied to the susceptor 24, and the reactive species are accelerated in a plasma sheath on the surface of the semiconductor wafer W,
The semiconductor wafer W is etched by collision with accelerated ions.

In the above embodiment, the case where the magnetic field forming means 25 is formed by one set of the permanent magnets 25a and 25b has been described. However, the magnetic field forming means 25 does not necessarily have to be only one set of the permanent magnets 25a and 25b. However, one or more sets of permanent magnets 25a, 25b can be arranged downstream of the set of permanent magnets 25a, 25b, that is, on the side of the magnetic field converging means. The magnetic field configuration can be formed, and the uniformity of the sheet-like plasma can be improved.

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.

[0028]

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 branched by the magnetic field forming means and compressed and transferred in a flat shape.
A sheet-like plasma having a high density and a uniform distribution in the radial direction of the object to be processed can be generated, and the processing accuracy can be improved.

2) According to the second aspect of the present invention, the magnetic field forming means is flattened with a pair of permanent magnets facing each other to branch and compress the electrons drawn by the electron accelerating means. Since it is composed of a solenoid coil that transports electrons along an uneven plane, it is possible to generate a sheet-like plasma having a high density in the radial direction of the object to be processed and a uniform density over a large area, and Plasma treatment of the processing object can be performed.

[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 means and a magnetic field forming means in 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

Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI H05H 1/24 H01L 21/302 B (72) Inventor Motosuke Miyoshi 72 Horikawacho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Horikawacho Plant ( 72) Inventor Haruo Okano 1 Toshiba-cho, Komukai, Koyuki-ku, Kawasaki-shi, Kanagawa Prefecture (72) Inventor Katsuya Okumura 1-kotoshiba-cho, Komukai-shi, Kawasaki-shi, Kanagawa Toshiba Tamagawa Plant ( 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) ) Surveyed field (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. A plasma apparatus comprising: electron acceleration means for drawing electrons into a processing chamber; and magnetic field forming means for branching, flattening and transferring electrons drawn by the electron acceleration means. 2. A pair of permanent magnets for splitting electrons drawn by an electron accelerating means and compressing them in a flat shape, and a solenoid coil for transferring the flattened electrons along a flat surface. 2. The plasma apparatus according to claim 1, wherein the plasma apparatus comprises: