JP2010180469A - Ion plating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To neutralize negative charge charged on a substrate. <P>SOLUTION: The ion plating apparatus includes a vacuum chamber 1, a substrate holder 4 attached via an insulating member in the vacuum chamber, an evaporation source having an electron gun 9 for heating an evaporation material in the vacuum chamber, a deposition-preventive plate 20 attached to the side wall of the vacuum chamber via an insulator 21 along the side wall and the bottom wall of the vacuum chamber, and a plasma source 11 which generates electron beams for ionizing evaporation particles evaporated from the evaporation source in the vacuum chamber. The plasma source 11 includes a case 12 in which a hot cathode 15 and an electron emission electrode 17 are arranged, and a discharge power supply for applying discharge voltage between a hot cathode 15 and an electron extraction electrode 17. The electron in the plasma P1 formed in the case 12 is extracted in the vacuum chamber 1 based on the discharge voltage. The ion plating apparatus further includes a direct-current voltmeter 22 for measuring the electric potential between the substrate holder 4 and the wall of the vacuum chamber 1, and a control unit 23 for controlling the discharge voltage so that the electric potential becomes a reference value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ion plating apparatus provided with a plasma generation source.

  Examples of apparatuses for forming a film on a substrate include a vacuum deposition apparatus, a sputtering apparatus, and an ion plating apparatus. In particular, the ion plating apparatus has excellent film adhesion to the substrate and can provide a high-quality film. Therefore, in recent years, it has been used for various thin film formations such as coating of optical lenses.

  FIG. 1 shows a schematic example of an ion plating apparatus.

  In the figure, reference numeral 1 denotes a vacuum chamber which is evacuated by a vacuum pump (not shown) through an exhaust passage 2.

  A substrate holder 4 on which a substrate 3 (3a, 3b, 3c,...) Is set is attached to a central portion of the upper wall of the vacuum chamber via a holder support shaft 5. Note that an intermediate portion of the holder support shaft is formed of an insulating member.

In a base 6 provided on the bottom wall of the vacuum chamber 1, a crucible 8 in which an evaporating material 7 is accommodated is installed.
Further, an electron gun 9 is provided in the base 6 adjacent to the crucible 8, and an electron beam EB from the electron gun is deflected by, for example, 270 ° by a deflector (not shown). The evaporating material 7 accommodated in the crucible is impacted. A scanning coil (not shown) is provided between the electron gun 9 and the crucible 8 and is generated from the electron gun and deflected 270 ° by the deflector (not shown). An electron beam EB is scanned over the evaporating material 7.

  In addition, in the base 6, a rotating shaft B integrated with a shutter S that shields scattered particles from the crucible 8 in the direction of the substrate holder 4 has a drive mechanism (not shown) comprising a motor or the like. ) Is rotatably mounted.

  A reactive gas supply pipe 10 is provided on the side of the vacuum chamber 1.

In the figure, reference numeral 11 denotes a plasma generation source, and an electron beam from the plasma generation source is irradiated between the substrate holder 4 and the crucible 8.
In the plasma generation source, reference numeral 12 denotes a cylindrical case, and a cylindrical shield cylinder 13 having an orifice formed at the tip is attached to the tip, and an argon gas supply pipe 14 is provided on the side. It has been.
A hot cathode 15 made of, for example, tungsten is provided on the inner bottom wall portion of the case 12, and a heating power source 16 is connected to the hot cathode.
In the plasma generation source 11, reference numeral 17 denotes an electron extraction electrode disposed around the tip of the shield tube 13, and a DC power supply (discharge power supply) 18 is connected to the electron extraction electrode via a resistor (not shown). Has been. Reference numeral 19 denotes an annular DC coil disposed around the tip of the shield tube 13, which is composed of an electromagnet that forms a magnetic field parallel to the direction in which electrons are drawn through the shield tube 13, and is generated in the case 12. The plasma is focused in the direction of the central axis of the case. The hot cathode 16, the electron extraction electrode 17, the case 12, the heating power supply 16 and the DC power supply (discharge power supply) 18 constitute a discharge circuit, and the discharge circuit is connected to the vacuum via a resistor (not shown). Connected to chamber 1.

In the figure, reference numeral 20 denotes a deposition plate which is attached to the grounded inner wall of the vacuum chamber 1 via an insulator 21 so as to surround the plasma generation region in the vacuum chamber 1 with the substrate holder 4. This is to prevent the evaporated particles from the material 7 from adhering to the inner wall of the vacuum chamber.
It should be noted that the evaporated particles from the evaporation material can go to the plasma region in the direction of the substrate 3 so that the evaporation material 7 in the crucible 8 is irradiated with the electron beam EB from the electron gun 9. Further, the inside of the vacuum chamber 1 can be efficiently exhausted by a vacuum pump (not shown) through the exhaust passage 2 so that the reactive gas from the reactive gas supply pipe 10 can go to the plasma generation region. Similarly, an opening is provided at an appropriate location of the deposition preventing plate 20.

In the ion plating apparatus having such a configuration, first, the inside of the vacuum chamber 1 is evacuated by a vacuum pump (not shown).
When the inside of the vacuum chamber reaches a predetermined degree of vacuum, the electron beam EB from the electron gun 9 is irradiated to the evaporation material in the crucible 8.
By this irradiation, the evaporating material 7 is heated and eventually evaporates. At this time, the shutter S is in a shielding position (position between the crucible 8 and the substrate holder 4).
When evaporation of the evaporation material starts, argon gas is introduced into the case 12 from the argon gas supply pipe 14 in the plasma generation source 11.
At the same time, by supplying a current from the heating power source 18 to the hot cathode 15, the hot cathode is heated to a temperature at which thermionic electrons can be emitted.

  Next, a predetermined current is passed through the coil 19 to generate a magnetic field necessary for plasma ignition and stable plasma.

  In this state, when a predetermined positive voltage is applied between the electron extraction electrode 17 and the hot cathode 15 from the DC power supply (discharge power supply) 18, a positive electric field is formed above the orifice of the shield tube 13, and the electric field Thus, the thermal electrons from the hot cathode 15 begin to accelerate in the direction of the electron extraction electrode 17. Due to the acceleration of the thermoelectrons, the thermoelectrons and the introduced argon gas repeatedly collide, and plasma P1 is generated in the case 12.

  The electrons in the plasma P1 generated in this way are drawn into the vacuum chamber 1 by the electric field while being focused in the central axis direction of the case 12 by the magnetic field formed by the coil 19.

  On the other hand, in the vacuum chamber 1, when the evaporation of the evaporating material 7 is stabilized, the shutter S is rotationally moved to a position greatly deviated from the position between the crucible 8 and the substrate holder 4.

  Then, the electrons from the plasma generation source 11 drawn into the vacuum chamber 1 collide with the evaporated particles and excite and ionize the particles, so that plasma P2 is formed in the vacuum chamber.

  At this time, since a reactive gas (for example, oxygen gas) is introduced into the vacuum chamber from the reactive gas supply pipe 10, the reactive gas also contains electrons from the plasma generation source 11. Ionized by collision.

  The ionized evaporated particles and the reactive gas in the plasma P2 are attracted to and attached to the substrate 3, and a film of a reaction product of the evaporated particles and the reactive gas is formed on the substrate.

  In such film formation, (1) electrons extracted into the vacuum chamber 1 and electrons in the plasma P2 flow into the extraction electrode 17.

  (2) Negative charges due to electrons are accumulated on the surface of the substrate 3, the substrate holder 4 and the deposition preventing plate 20 exposed to the plasma P2, and a negative voltage is applied to the surface of the substrate or the like. (That is, it is in a floating state with respect to the vacuum chamber 1 at the ground potential). On the other hand, since the plasma P2 has a ground or positive potential, a difference between the potential of the plasma P2 and the potential of the substrate 3 or the like occurs near the surface of the substrate 3 or the like. The ions (positive ions) in the plasma are accelerated toward the substrate and the like, and the phenomenon of irradiating (striking) the substrate occurs. As a result, the charged charge (negative charge) on the surface of the substrate 3 or the like is neutralized (this neutralization is referred to as neutralization by the plasma self-bias potential).

  Due to the phenomena (1) and (2), the plasma P2 formed in the vacuum chamber 1 is stably maintained.

JP-A-9-256148

  Now, when the evaporating material 7 is irradiated with electrons from the electron gun 9, secondary electrons and reflected electrons are generated from the evaporating material along with the generation of evaporating particles. These electrons reach the substrate 3, the substrate holder 4, and the deposition plate 20 regardless of the position of the shutter S, and negative charges accumulate on the surface of the substrate and the like, but the neutralizing action by the self-bias potential of the plasma. Neutralized by

  However, when the plasma P2 is not generated in the vacuum chamber 1, the neutralization action due to the self-bias potential of the plasma does not occur. Further, in the initial stage of the generation of the plasma P2 (when the plasma P2 is not yet stable), the neutralizing action is performed only slightly. As a result, negative charges due to the electrons accumulate on the surface of the substrate or the like, causing an unexpected situation in forming a film on the substrate 3. For example, when the substrate is made of calcium fluoride, the substrate is discolored, and when the substrate is made of plastic, the adhesion of the coating substance to the substrate is reduced.

  Further, the potential of the plasma P2 generated in the vacuum chamber 1 is uniquely determined once each parameter of the plasma generation source 11 is set. On the other hand, the charged state of the substrate 3 and the like varies depending on the pressure in the vacuum chamber 1 and the type of coating material. Therefore, even if the stable plasma P2 is generated in the vacuum chamber 1, it is not always sufficiently neutralized by the neutralizing action of the plasma P2 by the self-bias potential. Further, the charged state of the substrate 3 or the like cannot be controlled by the self-bias potential of the plasma P2.

  It is an object of the present invention to provide a novel ion plating apparatus that solves such problems.

  An ion plating apparatus according to the present invention includes a vacuum chamber, a substrate holder attached to an upper wall in the vacuum chamber via an insulating member, and an evaporation having an electron gun for heating a vapor deposition material provided at a lower portion of the vacuum chamber. A source, an adhesion preventing plate attached to the side wall of the vacuum chamber via an insulating member along the side wall and the bottom wall in the vacuum chamber, and for ionizing the evaporated particles evaporated from the evaporation source in the vacuum chamber A plasma generation source for generating an electron beam is provided, and the plasma generation source applies a discharge voltage between a discharge chamber in which a hot cathode and an electron extraction electrode are disposed, and the hot cathode and the electron extraction electrode. And a means for supplying a discharge gas into the discharge chamber, and electrons in the first plasma formed in the discharge chamber are converted into the chit based on the discharge voltage. In the ion plating apparatus configured to be pulled out into the chamber, the potential between the substrate holder or the adhesion preventing plate and the ground is detected, and the discharge voltage is controlled so that the potential becomes a reference value. It is characterized by.

  According to the present invention, in the vacuum chamber, the plasma P2 formed immediately after the evaporation of the evaporation material is always in a state having a self-bias potential such that the charge due to charging of the substrate is sufficiently neutralized. Therefore, it does not cause an unexpected situation in the film formation on the substrate, and even if the charged state of the substrate or the like changes depending on the pressure in the vacuum chamber or the kind of the coating material, the charged charge on the substrate or the like is sufficient. Neutralized.

  Further, the charged state of the substrate or the like during film formation is maintained in a state having a self-bias potential of plasma P2 suitable for the evaporation material.

1 shows a schematic example of a conventional ion plating apparatus. 1 shows a schematic example of an ion plating apparatus of the present invention.

First, the principle of the present invention will be described.
In order to sufficiently neutralize the negative charges due to the charging of the substrate 3 and the like described in the problem to be solved by the invention by the neutralizing action by the self-bias potential of the plasma P2, the electron irradiation to the evaporation material 7 is performed. At the same time or earlier, the plasma generation source 11 is operated to generate plasma P2 in the vacuum chamber 1 by extracting electrons from the plasma generation source, and the self-bias potential of the plasma P2 is the substrate 3 What is necessary is just to make it controllable so that the electric charge by this charge may be fully neutralized, even if it is in any state of charge.

  The charged state of the substrate 3 or the like can be known from, for example, the floating potential value of the substrate holder 4. It can be controlled by a positive voltage applied between the cathodes 15.

Therefore, for example, the floating potential value of the substrate holder 4 is constantly monitored, and the voltage applied between the electron extraction electrode 17 and the hot cathode 15 from the DC power source (discharge power source) 18 based on the floating potential value is always determined. If appropriately controlled, the charge due to the charging of the substrate 3 and the like described in the problem to be solved by the invention should be sufficiently neutralized by the neutralizing action by the self-bias potential of the plasma P2.
FIG. 2 shows a schematic example of the ion plating apparatus of the present invention made based on such a principle. In the figure, the same reference numerals as those used in FIG. 1 denote the same components.

  The ion plating apparatus shown in FIG. 2 differs from the ion plating apparatus shown in FIG. 1 in that a DC voltmeter 22 for measuring the floating potential between the substrate holder 4 at a floating potential and the vacuum chamber 1 at a ground potential. And a control device 23 for controlling the DC power supply (discharge power supply) 18 based on a floating potential from the DC voltmeter is newly provided.

In the ion plating apparatus having such a configuration, first, the inside of the vacuum chamber 1 is evacuated by a vacuum pump (not shown).
When the inside of the vacuum chamber reaches a predetermined degree of vacuum, the electron beam EB from the electron gun 9 is irradiated to the evaporation material in the crucible 8. At this time, a reactive gas is introduced into the vacuum chamber from the reactive gas supply pipe 10.
By this irradiation, the evaporating material 7 is heated and starts to evaporate. Initially, the shutter S is in the shielding position (position between the crucible 8 and the substrate holder 4), but is immediately rotated to a position greatly deviating from the shielding position.
At the same time, the plasma generation source 11 introduces argon gas from the argon gas supply pipe 14 into the case 12 and supplies current from the heating power source 18 to the hot cathode 15 to cause the hot cathode to flow. Heat to a temperature at which thermionic emission is possible. At the same time, a predetermined current is supplied to the coil 19 to generate a magnetic field necessary for plasma ignition and stable plasma.
In this state, when a predetermined positive voltage is applied between the electron extraction electrode 17 and the hot cathode 15 from the DC power supply (discharge power supply) 18, a positive electric field is formed above the orifice of the shield tube 13, and the electric field Thus, the thermal electrons from the hot cathode 15 begin to accelerate in the direction of the electron extraction electrode 17. Due to the acceleration of the thermoelectrons, the thermoelectrons and the introduced argon gas repeatedly collide, and plasma P1 is generated in the case 12.
Electrons in the plasma P1 generated in this way are drawn into the vacuum chamber 1 by the electric field while being focused in the direction of the central axis of the case 12 by the magnetic field formed by the coil 19, and the evaporated particles and the reaction. Since it collides with the reactive gas and the particles and the reactive gas are excited and ionized, the plasma P2 is formed in the vacuum chamber. Therefore, in this example, the plasma P2 is formed at a relatively early stage (when the apparatus is operating, that is, at the start of film formation).
The ionized evaporated particles and the reactive gas in the plasma P2 are attracted to and attached to the substrate 3, and a film of a reaction product of the evaporated particles and the reactive gas is formed on the substrate.
In such an ion plating apparatus, a plurality of floating elements corresponding to the formation of a high quality film and a state in which the charged state of the substrate 3 or the like does not cause any problem for the film formation on the substrate by experiments or the like in advance. A potential value is measured as a reference potential value and set in the control device 23, and the DC voltmeter 22 always measures the potential (floating potential) of the substrate holder 4 from the time of operation of the device (at the start of film formation). Yes.
Accordingly, the control device 23 always compares the floating potential value from the DC voltmeter 22 with the reference potential value from the time of operation of the device (at the start of film formation), and the difference between the floating potential value and the reference potential value is zero. Is sent to the DC power supply 18, and the DC power supply applies a positive DC voltage based on such a control signal between the electron extraction electrode 17 and the hot cathode 15. become.
As a result, the plasma P2 formed in the initial stage immediately after the evaporation of the evaporating material 7 has a self-bias potential so that the charge due to charging of the substrate 3 and the like is always sufficiently neutralized. In the subsequent film formation process, a self-bias potential suitable for the evaporation material is obtained.

  In the above example, the floating potential is obtained by measuring the voltage between the substrate holder 4 and the vacuum chamber 1, but the voltage between the deposition preventing plate 20 and the portion at the ground potential is measured. You may make it ask.

  In the above example, the ion plating apparatus in which the plasma generation source 11 is provided in the vacuum chamber 1 is shown, but the present invention is also applied to an ion plating apparatus in which the plasma generation source is connected to the outside of the vacuum chamber 1. It goes without saying that the invention can be implemented.

DESCRIPTION OF SYMBOLS 1 ... Vacuum chamber 2 ... Exhaust passage 3 ... Substrate 4 ... Substrate holder 5 ... Holder support shaft 6 ... Base 7 ... Evaporating material 8 ... Crucible 9 ... Electron gun 10 ... Reactive gas supply pipe 11 ... Plasma generation source 12 ... Case DESCRIPTION OF SYMBOLS 13 ... Shield cylinder 14 ... Argon gas supply pipe 15 ... Hot cathode 16 ... Heating power source 17 ... Electron extraction electrode 18 ... DC power source (discharge power source)
DESCRIPTION OF SYMBOLS 19 ... Annular DC coil 20 ... Depositing plate 21 ... Insulator 22 ... DC voltmeter 23 ... Control device S ... Shutter B ... Rotating shaft EB ... Electron beam P1, P2 ... Plasma

Claims (2)

  A vacuum chamber, a substrate holder attached to an upper wall in the vacuum chamber via an insulating member, an evaporation source provided at a lower portion of the vacuum chamber and having an electron gun for heating a deposition material, a side wall in the vacuum chamber, and A deposition plate attached to the side wall of the vacuum chamber via an insulating member along the bottom wall, and a plasma generation source for generating an electron beam for ionizing evaporated particles evaporated from the evaporation source in the vacuum chamber The plasma generation source includes a discharge chamber in which a hot cathode and an electron extraction electrode are disposed, a discharge power source for applying a discharge voltage between the hot cathode and the electron extraction electrode, and the discharge A means for supplying a discharge gas into the chamber is provided, and electrons in the first plasma formed in the discharge chamber are drawn into the vacuum chamber based on the discharge voltage. In ion plating apparatus, the detecting a potential between the substrate holder or deposition preventing plate and the ground, said potential ion plating apparatus forms so as to control the discharge voltage so as to become the reference value.   2. The ion plating apparatus according to claim 1, wherein a potential between the substrate holder or the deposition preventing plate and a vacuum chamber is detected.

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