JP3327991B2 - Penning discharge type etching / deposition method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Penning discharge type etching / deposition method and apparatus which can be used, for example, for manufacturing a quartz oscillator.

[0002]

2. Description of the Related Art OA devices such as word processors and personal computers include:
Microcomputers are built in, and a crystal oscillator is used for generating a clock in order to determine the standard of operation of those microcomputers. The oscillation frequency of the crystal unit used in this type of microcomputer is required to have an accuracy on the order of PPM. Adjustment of the oscillation frequency of the crystal unit is usually performed by adjusting the amount of metal adhered to the electrodes on both sides of the crystal unit. That is, in order to accurately adjust the oscillation frequency of the crystal oscillator to the specified frequency, a substance is additionally added on the oscillator while measuring the frequency of the crystal oscillator by vapor deposition, and from the relational expression Δf = kΔM, When a predetermined frequency is reached, a method of stopping vapor deposition is adopted. In the above equation, Δf is a change in frequency due to the addition of the mass ΔM, and k is a proportional constant.
In this conventional adjustment method, a metal film is first thinned on the electrode part of the crystal unit for safety, and the adhesion of the metal film is repeated while measuring the oscillation frequency with a frequency counter. However, there is a drawback that not only is it necessary to carry out a process, but also it takes time and effort, but also there are too many metal films, and when it is deposited by vapor deposition, it does not fit well with the base and there is a lot of secular change in oscillation frequency.

In order to improve such disadvantages, a film thickness is set so as to obtain a required frequency when forming a base electrode of a crystal unit, and an insufficient substrate is additionally subjected to a vapor deposition process. A method of adjusting the frequency of an excessive substrate by removing an excess amount by an etching process has been proposed. As an example, an aperture having a diameter of about 6 mm is opened in one of the cathodes of the small Penning discharge device, a quartz crystal as a workpiece is placed in the aperture, and the anode is positioned directly below the aperture and in a position deviated from the aperture. Between the electrodes and close to the aperture of the discharge chamber.At the position directly below the aperture, argon ions, which have an etching effect, are directly guided to the crystal unit via the aperture, and etching is performed, while the anode is removed from the position directly below the aperture. When moved to a different position, argon ions are prevented from impinging on the crystal unit through the aperture, and instead, the material of the opposite cathode is sputtered and deposited on the crystal unit.
63-9585).

[0004]

By the way, in the conventional proposal in which the frequency is adjusted by selectively performing both etching and vapor deposition using Penning discharge, the etching is performed by mechanically moving the anode. 10 to 20 minutes to move the anode to switch between process and deposition process
It takes about seconds and the setting of the position is delicate. As a result, the frequency adjustment process takes too much time and the reproducibility is poor. Therefore, this method is not practical for an in-line system in which the frequency adjustment step is usually performed for 2 to 3 seconds, and there is a problem in terms of productivity such that the discharge chamber and the crystal unit must be brought into close contact.

Accordingly, the present invention solves the problems of the prior art, and switches between etching and deposition at a very high speed to adjust the thickness of the metal thin film of the crystal unit, thereby quickly mounting the crystal unit. It is an object of the present invention to provide a Penning discharge type etching / deposition method and apparatus which can be set at a predetermined position.

[0006]

In order to achieve the above object, a penning discharge type etching / deposition method according to a first aspect of the present invention is directed to a method in which a cylindrical anode disposed in a yoke member is opposed. A pair of cathodes are provided, and a permanent magnet is attached to the inner surface of the yoke member that forms a closed magnetic circuit outside each cathode.Apertures for extracting molecules and atoms of cathode material and ions of carrier gas from a Penning discharge unit are attached. The control electrode is arranged coaxially along the axis, and the discharge chamber of the Penning discharge unit and the portion provided with the control electrode are differentially evacuated or discharged from the aperture while introducing a carrier gas into the discharge chamber of the Penning discharge unit. The location where the control electrode is provided is set to a higher vacuum than the discharge chamber of the Penning discharge unit, and the potential generated at the control electrode Set the voltage to be applied to the control electrode so that it is sufficiently higher than the potential, perform the devouring process, and control so that the potential generated at the control electrode is sufficiently lower than the plasma potential of the Penning discharge part. An etching process using carrier gas ions is performed by setting a voltage to be applied to the electrode. The penning discharge type etching / deposition apparatus according to the second aspect of the present invention is provided with a cylindrical anode in a yoke member forming a vacuum vessel wall, a cathode on one side of the anode, and a cathode on the other side. A cathode with an aperture is arranged, a permanent magnet is provided inside a yoke member forming a closed magnetic circuit outside the cathode on one side of the anode, and an opening portion of the yoke member outside the cathode with an aperture on the other side of the anode. A permanent magnet with an aperture is provided around the inside to form a magnetic circuit passing through the yoke member, and a control electrode with an aperture and a ground electrode with an aperture are provided outside the discharge chamber adjacent to the opening of the yoke member. Arranged sequentially,
By controlling the voltage applied to the control electrode with an aperture, etching and deposition processing is performed on an object to be processed located outside the earth electrode with the aperture.

[0007]

In the penning discharge type etching / deposition method and apparatus according to the present invention, a permanent magnet is provided inside the yoke member to form a magnetic circuit passing through the yoke member. The internal axial magnetic field can be greater than 400 Gauss, while the magnetic field at the location of the control electrode outside the discharge chamber can be less than 10 Gauss, so that the control electrode outside the discharge chamber becomes the anode. The second Penning discharge can be prevented from occurring in this portion. Also, since a portion surrounding the control electrode outside the discharge chamber is differentially evacuated to a higher vacuum than the discharge chamber, a discharge can be prevented from occurring in this portion in combination with a low magnetic field. Become. In addition, etching with carrier gas ions,
Deposition by cathode material molecules sputtered from the opposing cathode and passing through the aperture will occur at the same time, but no deposition is observed since the etching rate is one or more digits higher. Therefore, in the present invention, at the time of deposition, the voltage applied to the control electrode is controlled such that a potential sufficiently higher than the plasma potential of the Penning discharge device is generated at the aperture of the control electrode. As a result, the plasma potential is several tens of volts lower than the anode potential, the potential at the starting point of the carrier gas ions is the same as the plasma potential, and the initial velocity is several eV. Although it does not enter the vibrator, the cathode material molecules or atoms sputtered from the opposing cathode have no charge, so they can pass through the aperture of the control electrode and reach the crystal oscillation, and thus the deposition is performed. Become. For example, when the potential of the cylindrical anode is set to 1500 volts, the deposition can be performed by setting the potential of the control electrode to 2100 volts, and by setting the potential of the control electrode to -1000 volts, carrier gas ions can be removed. It can be pulled out and etched. As described above, the switching between the deposition and the etching is performed simply by setting the potential of the control electrode with respect to the potential of the cylindrical anode, so that the switching can be performed in a time of the order of microseconds. The frequency adjustment can be performed accurately and at high speed.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an embodiment of a penning discharge type etching / deposition apparatus according to the present invention. Reference numeral 1 denotes a yoke member, a pure iron bobbin type portion 1a having both ends opened and defining a cylindrical space therein. And an end plate portion 1b made of pure iron that closes one end, that is, one open end of the bobbin mold portion 1a, and a pure iron flange portion 1c that is superimposed on the other open end of the bobbin mold portion 1a. And a part of the vacuum vessel wall. Although not shown, the body of the bobbin-shaped portion 1a of the yoke member 1 is provided with a port for preliminary exhaust and introduction of a carrier gas such as argon gas. A cylindrical anode 2 made of SUS is coaxially supported and arranged in an insulating support member 3 in the winding frame type portion 1a, and the cylindrical anode 2 is connected to a power supply via a connector (not shown). ing. Also, silver disk-shaped cathodes 4 and 5 are provided opposite to the openings at both ends of the reel-shaped portion 1a with the cylindrical anode 2 interposed therebetween so as to cover these openings. 5 has an aperture in the center. Each cathode 4, 5 has an aluminum foil (not shown) sandwiched therebetween to ensure good thermal contact with the yoke member 1.
Outside the cathodes 4 and 5, disk-shaped permanent magnets 6 and 7 are provided between the end plates 1 b and the flanges 1 c of the yoke member 1 between the cathodes 4 and 5 for vacuum thermal insulation. And the upper permanent magnet 7 has an aperture in the center. Both magnets are preferably made of SmCo and are provided axially symmetric. Accordingly, a magnetic circuit is formed that passes through the bobbin-shaped portion 1a, the end plate portion 1b, and the flange portion 1c of the yoke member 1. The axial magnetic field inside the cylindrical anode 2 and the opposing cathodes 4 and 5 becomes 400 gauss or more, and is defined by the aperture of the cathode 5 at the upper part of the discharge chamber, the aperture of the magnet 7 above and the inner peripheral part of the flange part 1c. The magnetic field outside the opening 10 is configured to be 10 Gauss or less. Above the opening 10, an annular control electrode 11 having a central aperture is attached by an insulating support member 12 coaxially with the axis of the opening 10.
Reference numeral 11 is connected to a control power supply (not shown) so that the potential can be switched between a high potential and a low potential with respect to the potential of the cylindrical anode 2. Ground electrode above control electrode 11
The ground electrode 13 has an aperture coaxial with the axis of the opening 10 and is supported on the flange portion 1c of the yoke member 1 via a support 14 made of SUS. The thus constructed assembly is hermetically mounted on the wall 15 of the vacuum device. In FIG. 1, reference numeral 16 denotes a carrier of the crystal unit 17 whose frequency is to be adjusted.

Next, the operation of the illustrated apparatus configured as described above will be described. By forming the magnetic circuit as described above, the magnetic field in the Penning discharge chamber formed by the yoke member 1 is made to be 400 gauss or more, and several gauss outside the discharge chamber which constitutes a portion for transporting A ⁺ (argon ions) or silver atoms. In the Penning discharge chamber, a discharge of several tens of mA occurs at about 2 × 10 ⁻³ Torr, and no Penning discharge occurs in the vicinity of the extraction portion, that is, in the vicinity of the control electrode 11. (1) In the case of the etching mode, a voltage of 1500 V is applied to the cylindrical anode 2 and the control electrode 11 is applied.
Is −1000 V, and the crystal unit 17 to be processed is located at a position 60 mm from the cathode 4 below.
Now, a 0.5 mA argon ion beam is extracted, and the beam radius R of the 0.5 mA argon ion beam is defined as R = 0.63 cm,
When the cross-sectional area and 1.23Cm ^2, the current density of argon ions is 406 × 10 ^-6 A / cm ^2, and the number of ions argon ions ^{406 × 10 -6 A / cm 2} /1.6022+10 -19 C = 3.8 × Ten
¹⁵ A ⁺ ions / cm ² · sec, and argon ions (1500
The sputtering rate of silver by eV) is 〜5. Accordingly, the number of silver atoms sputtered by the argon ion beam is 3.8 × 10 ¹⁵ × 5 = 1.9 × 10 ¹⁶ Ag atoms / cm ² · sec. On the other hand, the density of silver is 10.492 g / cm ³ ,
The molecular weight is 107.870 and the Avogadro number is 6.022 × 10 ²³
/ Mol, the number of silver atoms in 1 cm ³ is (10.492 / 107.870) × 6.022 × 10 ²³ = 5.867 × 10 ²² . Therefore, the number of silver atoms sputtered by an argon ion beam, 1.9 × 10 ¹⁶ / cm ² · sec, is 1.9 × 10 ¹⁶ /5.867×10 ²² = 3.3 × 10 ^-7 cm / sec, and the etching rate is 33 Å / cm. sec
Becomes Regarding the consumption of the cathode, the discharge current for one cathode is 0.5 mA × [(0.7) ² × π] / [(0.3) ² × π] = 2.7 mA 2.7 mA / [(0.7) ² × π] = 1.767 × 10 ⁻³ A / cm ² [1.767 × 10 ⁻³ A / cm ² ] /1.6022+10 ⁻¹⁹ C = 1.103 ×
10 ¹⁶ / cm ² · sec, and the silver sputtering rate is up to 5, the number of sputtered silver atoms is 1.103 × 10 ¹⁶ / cm ² · sec. Since the sputtering rate of silver is ５5, the number of silver atoms to be bonded is 1.103 × 10 ¹⁶ × 5 / cm ² · sec 9.4 × 10 ^-7 cm / sec = 94
Angstrom / sec. Therefore, the time for a silver plate having a thickness of 2 mm to be sputtered to 1.5 mm is 0.15 / 94 × 10 ⁻⁸ = 1.596 × 10 ⁵ seconds = 44.3 hours. On the other hand, the total charge entering the anode is 2.7 mA × 2 × 1.6 × 10 ⁵ = 864 coulombs.

(2) In the deposition mode, when the voltage applied to the cylindrical anode 2 is 1500 V, the voltage applied to the control electrode 11 is set to 2100 V or more. Assuming that the angle dependency of the differential sputtering rate obeys the cosine law, and as shown in FIG. 2, the number of silver atoms sputtered at a normal solid angle dω for one vertically incident argon ion is a
dω, the total sputtering rate η is Therefore, a diameter of 0.6 cm at the center of the silver cathode 4
Of the silver atoms sputtered from the region S1 of the formula (1), n1 = adω × S1 cosθ × incident argon ions / cm ² . Further, the area S1
Is deposited from the annular region S2 having a width of 0.4 cm outside the area of n2 = adω ′ × S2 cosθ × incident argon ion / cm ² . All discharge current and 50 mA, as one 25mA, the area S1 of 0.6 φ n1 = (η / π ) · [(π · 0.3 2) / (π · 6 2)] · 0.3
² π × [(25 × 10 ^-3 ) / (1.602 × 10 ^-19 )] / 0.7 ² · π = 3.58 × 10 ¹⁴ silver atoms / 0.3 ² × πcm ² , while the area outside it is: When the dω' the ~ 0.1dω, n2 = n1 × 0.1 × (0.7 2 - 0.3 2) / 0.3 2 = 1.59 × 10
¹⁴ silver atoms / 0.3 ² × πcm ² is deposited, in whole, n1 + n2 = 5.2 × 10 14 silver atoms ^{/ 0.3 2 × πcm 2 = 1.83} × 10
¹⁵ silver atoms / cm ² · sec = 3.1 angstroms / second, and the consumption of the cathode takes 4.8 hours to consume a depth of 1.5 mm.

FIG. 3 shows equipotential lines representing a magnetic field distribution formed by two permanent magnet bodies 6 and 7 provided axially symmetrically. In the discharge chamber, the strength of the magnetic field is 445 Oersteds. It is 13 to 3 Oe near the drawer outside the discharge chamber. FIG. 4 shows the magnetic field distribution on the central axis, the vertical axis represents the strength of the magnetic field, and the horizontal axis represents the position along the central axis. From this graph, 900 Gauss in the anode,
It can be seen that at a position corresponding to the control electrode, it is about -1 to -3 Gauss. FIG. 5 shows the electric field distribution in the etching mode, and FIG. 6 shows the electric field distribution in the deposition mode.

As described above, the potential of the cylindrical anode 2 is
When the voltage is 1500 V, the potential of the control electrode 11 is controlled to 2100 V so that silver as a cathode material is placed on the crystal unit 17.
Deposition can be performed at a rate of Å / sec, and by switching the potential of the control electrode 11 to −1000 V, etching with carrier gas ions, that is, argon gas ions in the illustrated example, can be performed at a rate of 30 Å / sec. . Moreover, since the switching of the potential of the control electrode 11 can be performed by voltage control, this switching can be performed at a very high speed of 1 msec.

In the illustrated embodiment, an example in which the present invention is applied to the frequency adjustment of a quartz oscillator has been described. However, the present invention can be naturally applied to the processing of other articles which require fine adjustment and include thin film formation and etching. . Although the illustrated apparatus is configured in a cylindrical shape, it is not necessarily limited to a cylindrical shape, and may be configured in an arbitrary shape according to an application object. The material of the cathode is not limited to silver, but can be arbitrarily selected according to the material of the thin film to be formed.

[0014]

As described above, according to the present invention, in the etching and devotion using Penning discharge, a lead-out part extending from the Penning discharge chamber to the outside is provided, and a control electrode is arranged in this lead-out part. By forming a magnetic circuit so that the magnetic field is substantially limited to the Penning discharge chamber, and by differentially evacuating the control electrode part to a higher vacuum than the Penning discharge chamber, the discharge at the control electrode part is prevented. It is possible to switch between etching and deposition at a very high speed (on the order of microseconds) by controlling the potential applied to the control electrode with respect to the potential of the cylindrical anode in the Penning discharge chamber. Become like As a result, when the present invention is applied to frequency adjustment of a crystal unit, a very small amount of deposition and etching can be repeatedly performed at high speed for frequency adjustment, and frequency adjustment can be performed at high speed and with high accuracy. And can be easily incorporated into inline systems.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a Penning discharge type etching / deposition apparatus according to the present invention.

FIG. 2 is an operation explanatory diagram of the apparatus shown in FIG. 1 in a deposition operation mode.

FIG. 3 is a diagram showing equipotential lines representing a distribution of a magnetic field formed by a magnetic circuit.

FIG. 4 is a graph showing the strength of a magnetic field on the central axis of the device shown in FIG.

FIG. 5 is a schematic diagram showing an electric field distribution in an etching mode.

FIG. 6 is a schematic diagram showing an electric field distribution in a deposition mode.

[Explanation of symbols]

 1: Yoke member 2: Cylindrical anode 3: Insulating support member 4: Cathode 5: Aperture ... Cathode with aperture 6: Permanent magnet 7: Permanent magnet with aperture 8: Gap for vacuum thermal insulation 9: Vacuum thermal insulation Gap 10: Opening 11: Control electrode 12: Insulating support member 13: Earth electrode 14: Support 15: Vacuum device wall 16: Carrier 17: Quartz resonator

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-97671 (JP, A) JP-A-5-251406 (JP, A) JP-A-60-94728 (JP, A) JP-A-2-97 214119 (JP, A) JP-B 63-9855 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23F 4/04 C23C 14/35

Claims (2)

(57) [Claims] 1. A Penning discharge in which a pair of cathodes are provided so as to face each other across a cylindrical anode disposed in a yoke member, and a permanent magnet is attached to the inner surface of the yoke member forming a closed magnetic circuit outside each cathode. A control electrode is disposed outside the discharge chamber of the Penning discharge unit coaxially along the axis of the aperture for taking out the molecules and atoms of the cathode material and ions of the carrier gas from the unit, and providing the discharge chamber and the control electrode of the Penning discharge unit Differentially evacuating the part or the carrier gas into the discharge chamber of the Penning discharge part and flowing out of the aperture through the aperture to evacuate the part provided with the control electrode. Set to
The voltage applied to the control electrode is set so that the potential generated at the control electrode is sufficiently higher than the plasma potential of the Penning discharge part, and the devotion process using the cathode material is performed. An etching / deposition method using Penning discharge, characterized in that a voltage applied to a control electrode is set so as to be sufficiently lower than a plasma potential of a Penning discharge part to perform an etching treatment with carrier gas ions. 2. A cylindrical anode is provided in a yoke member forming a vacuum vessel wall, a cathode is disposed on one side of the anode, and a cathode with an aperture is disposed on the other side thereof. A permanent magnet is provided inside the yoke member forming a closed magnetic circuit outside the cathode, and a permanent magnet with an aperture is provided around the inside of the opening of the yoke member outside the cathode with the other aperture on the anode, A magnetic circuit passing through the yoke member is formed, and a control electrode with an aperture and a ground electrode with an aperture are sequentially arranged outside the discharge chamber adjacent to the opening of the yoke member, and a voltage applied to the control electrode with the aperture is provided. By controlling the
A penning discharge type etching / deposition apparatus characterized in that an object to be processed located outside an earth electrode with an aperture is subjected to etching and deposition processing.