JPH04341571A - Process device adopting electron excitation - Google Patents

Abstract

PURPOSE:To provide a process device in which the internal pressure of a reaction vessel can freely be set and a large amt. of electrons can be injected into the reaction vessel at low acceleration voltage by isolating a glass vessel acting as an electron source with a diaphragm from the reaction vessel in which a prescribed process is carried out with plasma excited by electron beams generated from the electron source. CONSTITUTION:A glass vessel 1 is isolated from a reaction vessel 7 with a diaphragm 8 made of a thin polyester film 8a of 0.5-1.5mum thickness, a metal mesh 9 is fitted to the glass vessel side of the diaphragm 8 and the pressure difference between the vessels 1, 7 is maintained. At least the reaction vessel side of the polyester film 8a is coated with an electric conductive film 8b and this film 8b and the mesh 9 are grounded to prevent dielectric breakdown due to the accumulation of electric charges on the diaphragm 8.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a device that executes a predetermined process using electron excitation, and in particular, a device that generates plasma by excitation with an electron beam, and is widely used in the manufacture of semiconductor integrated circuits, the creation of thin films, surface treatment, etc. Plasma CV that has been
The present invention relates to a plasma processing device that can be used as a D device, a plasma etching device, or the like.

0002

[Prior Art] As mentioned above, plasma processing equipment is widely used in various technical fields, but with the aim of using it in even more fields, we are developing new plasma sources, improving its diagnostic technology, and improving its controllability. Various improvements have been made.

[0003] Electron beam-excited plasma processing equipment provides a plasma source useful for low-damage etching of semiconductors and for synthesizing organic thin films by exciting monomer gas with electron beams because it can obtain plasma with a low ion temperature. is expected to do so. Among them, an electron beam excited plasma source using a diaphragm made of a polymer has the electron beam source and the plasma reaction tank separated by the diaphragm, thus realizing a plasma processing device in which the reaction tank can be freely controlled from the outside. is possible.

0004

[Problems to be Solved by the Invention] As mentioned above, the electron beam excited plasma processing device using a diaphragm has been known as a carbon dioxide laser excitation method. There is generally a difference in pressure with the space that acts as a reaction tank. In other words, it is necessary to create a high vacuum at the source of the electron beam in order to lengthen the mean free path of the electrons and prevent energy loss before reaching the plasma reaction tank.On the other hand, in the plasma reaction tank where monomers are injected, From the viewpoint of membrane efficiency, etc., it is preferable not to use a vacuum as high as that of an electron beam source. In order to maintain the gas pressure difference between the electron beam source and the plasma reaction tank and maintain stable discharge, the thickness of the polymer diaphragm is generally several tens of tens of meters thick.
Because the thickness is as large as μm, and the electron accelerating voltage is therefore high, at several hundred thousand volts or more, the acceleration power source becomes large and countermeasures against penetrating X-rays are required, resulting in a large-scale device, and the plasma process equipment. The disadvantage is that it is not practical to use as a

[0005] Therefore, a method of maintaining the gas pressure difference between the electron beam source container and the plasma reaction container without using a diaphragm by differential pumping, and a method of exciting the reaction gas jet with an electron beam have been proposed. A reduction in electron beam acceleration voltage has been achieved. However, these conventional solutions have the disadvantage that it is difficult to obtain process uniformity over the substrate to be processed and that there are significant constraints on reaction control.

An object of the present invention is to alleviate the above-mentioned conventional drawbacks, reduce the electron beam accelerating voltage by using a thin diaphragm, realize miniaturization of the device, and, moreover, work as an electron beam source. A process device using electron beams that can completely separate the space where the plasma state is excited by the electron beam and the space where the plasma state is generated by being excited by the electron beam, ensuring uniformity of the process and having fewer restrictions on reaction control. This is what we are trying to provide.

[0007]

[Means for Solving the Problems] The electron beam processing apparatus of the present invention includes a first space in which electrons are generated, and a first space in which electrons are generated.
a second space in which a predetermined process is performed by excitation by electrons generated in the space; a diaphragm separating the first and second spaces; and a diaphragm on the first space side of the diaphragm. The device is characterized by comprising a mesh-like differential pressure support member that is arranged to support the pressure difference between the first and second spaces and that transmits electrons. Such a diaphragm has a thickness of 0.5 to 1.5μ, for example.
It can be formed using a polyester film of m. Further, it is preferable that at least the surface of the diaphragm on the second space side is coated with a conductive film, and that the mesh formed of metal and the conductive film are both grounded. Of course, in this case, the positive electrode side of the acceleration power source is grounded, the negative electrode side is connected to the cathode, and the anode is grounded.

The process device using electronic excitation of the present invention has the following features:
Furthermore, a first container defining a first space that generates electrons and is maintained in a high vacuum, and a second space that performs a predetermined process by excitation by the electrons generated in the first space. a second container that defines the space, and a first and second space defined by the first and second containers, and is arranged to isolate the first space and the second space, and supports the differential pressure between the first space and the second space. It is characterized by having a diaphragm that has high mechanical strength, is electrically conductive, and is highly permeable to electrons. Such a diaphragm can be made, for example, by implanting impurity ions such as boron into a silicon substrate and then selectively back-etching it so that it is supported by a silicon mesh with high mechanical strength. It can be formed by spin-coating a polyimide film or depositing a boron, carbon, and nitrogen compound film, and then selectively back-etching the silicon substrate.

[0009]

[Operation] In the above-mentioned electronic processing device of the present invention, a diaphragm having an extremely thin thickness and high electron permeability is used to separate the first space, which is an electron generation source, from the first space, which is used as a plasma reaction tank, for example. Since it is isolated from the second space where it acts, a sufficient current density can be obtained with a low accelerating voltage of 2000 to 5000 V. Therefore, a small accelerating power source can be used, and a transparent X Since no wires are generated, there is no need to protect them, and the entire device can be made smaller.

[0010] Furthermore, when a metal mesh is arranged adjacent to the first space side of the diaphragm to support differential pressure, the pressure in the second space is higher than the pressure in the first space. Even if this occurs, the thin diaphragm will not be damaged. Furthermore, by coating one or both sides of the diaphragm facing the second space with a conductive film and connecting this conductive film and the metal mesh to the same potential point, it is effective to prevent dielectric breakdown of the diaphragm due to electron charging. can be prevented.

[0011] Furthermore, when the first and second spaces are separated by a diaphragm having high electron permeability and conductivity and high mechanical strength, the same effect as described above will be exhibited. .

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagrammatic sectional view showing the structure of an embodiment of an electron beam processing apparatus according to the present invention, and in this embodiment, the apparatus is constructed as a plasma CVD apparatus. A glass container 1 defining a first space that acts as an electron source
is connected to a vacuum device, and its interior is heated to 10-5
A high vacuum of around Torr is maintained to lengthen the mean free path of electrons. Inside the glass container 1, a tungsten heater 2 that functions as an electron radiation source and a mesh-shaped anode 3 that accelerates electrons emitted from the tungsten heater are arranged. In this example, the tungsten heater 2 is connected to the negative electrode of the acceleration power source 4, and its positive electrode is grounded. Further, the anode 3 is also grounded.

The tungsten heater 1 is connected to a slider 6 via an isolation transformer 5, and this slider is connected to a
Connect to C100V commercial power supply. The current flowing through the dungsten heater 1 is adjusted by the slider 6 to heat it to a predetermined temperature and emit thermoelectrons.

A reaction tank 7 defining a second space in which plasma is generated by being excited by electrons emitted from the glass container 1 is connected to the glass container via a diaphragm 8. The diaphragm 8 includes aluminum conductive films 8 with a thickness of about 0.1 μm or less on both sides of a polyester film 8a with a thickness of 1.5 μm.
b and 8c were formed by vapor deposition. Further, a metal mesh 9 for supporting differential pressure is arranged on the electron beam source side of the diaphragm 8. In this example, the metal mesh 9 is composed of a copper mesh having 60 lines/inch to 100 lines/inch. The electron beam transmission area ratios of the copper mesh of 60 lines/inch to 100 lines/inch are 75% and 50%, respectively. Further, as shown in FIG. 1, conductive films 8b and 8c and metal mesh 9 are grounded.

A substrate 11 is attached to the reaction tank 7 via a substrate holding flange 10. In this example, styrene gas is circulated as a reaction gas through a reaction tank 7 to form a thin film of styrene on a substrate 11, and the substrate is made of KBr. In addition, the pressure of styrene vapor is 0.3 to 0.
．． Adjust within the range of 5 Torr.

Thermionic electrons emitted from the tungsten heater 2 are accelerated by the action of the acceleration power source 4, pass through the mesh anode 3, the metal mesh 9 for supporting differential pressure, and the diaphragm 8, and are injected into the reaction tank 7. A styrene film can be generated on the surface of the substrate 11 by exciting the styrene gas circulating in the reaction tank to generate plasma.

As mentioned above, the first space defined by the glass container 1 which acts as an electron source and the reaction tank 7
The second space defined by The diaphragm 8 will not be destroyed even if the first space is set to a high vacuum and the second space is set to a higher pressure to generate a pressure difference. Therefore, the thickness of the polymer film 8a constituting the diaphragm 8 can be made extremely thin, so that even if the voltage of the accelerating power source 3 is as low as 2,000 to 5,000 V, an electron beam with extremely high current density is injected into the reaction tank 7. can do. Therefore, the accelerating power source 4 can be made small-scale, and since highly transparent and harmful X-rays are not generated, the safety of the device is also high.

Furthermore, the polyester film 8 of the diaphragm 8
Since the conductive films 8b and 8c coated on both sides of the polyester film are grounded together with the metal mesh 9, it is possible to effectively prevent dielectric breakdown due to electric charge on the polyester film.

FIG. 2 is a diagrammatic cross-sectional view showing the configuration of an experimental apparatus for confirming the operation of the plasma processing apparatus according to the present invention. In this example, the same parts as in the previous example are given the same reference numerals as in the previous example, and the explanation thereof will be omitted.

In this example, a cylindrical anode 21 is placed in the glass container 1 instead of the mesh anode 3, an electrode 22 is placed in the reaction tank 7 instead of the substrate 11, and this electrode is connected to an ammeter. 23 to the ground, and was configured so that the current injected into the reaction tank could be measured. 10 inside of glass container 1
A high vacuum of about -5 Torr or less was maintained, and the pressure inside the reaction tank 7 was reduced to approximately 0.2 Torr.

A DC power supply 24 was provided to heat the tungsten heater 2, and the power supply to the tungsten heater was adjusted by a variable resistor 25. Further, the configuration is such that the current flowing through the tungsten heater 2 can be measured with an ammeter 26.

The accelerating voltage for accelerating the thermoelectrons emitted from the tungsten heater 2 was created by rectifying the voltage obtained on the secondary side of the insulating transformer 5 with a rectifier 27. Further, the configuration was such that the value of the accelerating voltage could be measured with a voltmeter 28.

The glass container 1 and the reaction tank 7 are separated by a diaphragm 8, and two types of diaphragms 8 were used in this experimental example. That is, the first diaphragm is composed of only the polyester film 8a with a thickness of 0.5 μm, and the second diaphragm is composed of a polyester film 8a with a thickness of 1 μm.
．． It was constructed by coating the surface of a 5 μm polyester film 8a on the reaction tank side with an aluminum conductive film 8b having a thickness of 0.1 μm or less.

Two types of metal meshes 9 for supporting the diaphragm 8 were also used. That is, 60 lines/inch and 100 lines/inch copper meshes were used. In either case, the metal mesh 9 was grounded. Also, 1.
A conductive film 8b coated on one side of a 5 μm polyester film 8a was also grounded.

[0025] With the configuration as described above, the acceleration voltage is set to 200
The graphs in FIGS. 3 and 4 show the results of measuring the current due to the electron beam flux injected into the electrode 22 placed in the reaction tank 7 using the ammeter 23 when changing the voltage from 0V to 6500V. FIG. 3 shows the case where the diaphragm 8 is composed of only a polyester film 8a with a thickness of 0.5 μm, and FIG. 4 shows the result of using a diaphragm 8 in which one side of the polyester film 8a with a thickness of 1.5 μm is coated with a conductive film 8b. In both graphs, curve A shows the case where 60 lines/inch metal mesh 9 is used, and curve B shows the case where 100 lines/inch metal mesh 9 is used.

As shown in FIG. 3, when a diaphragm 8 of 0.5 μm and a metal mesh 9 of 60 lines/inch are used,
When the accelerating voltage was increased to 2000 V or more, a current suddenly began to flow through the electrode 22, and when the current reached 120 μA at about 5000 V, the diaphragm 8 was damaged and the pressure on the electron beam source side suddenly increased. The diameter of the electron beam in this case was about 3 mm, so the current density reached 1.7 mA. This value is approximately equal to the current density of normal glow discharge.

As is clear from the above experimental results, in the plasma processing apparatus of the present invention, the
It was confirmed that an electron beam flux having a current density of 1 mA/cm2 or more at a low accelerating voltage of 00V was injected from the glass container 1 through the diaphragm 8 into the reaction tank 7, and the electron beam excited the reaction gas, It can be seen that excitation and processing of the substrate surface are sufficiently possible.

FIG. 5 shows a process for manufacturing another embodiment of a diaphragm used in a plasma processing apparatus according to the present invention. First, as shown in FIG. 5A, a silicon substrate 31 having a thickness of about 500 μm is prepared, and boron is implanted into one surface of the substrate at a concentration of about 10 −15 to 10 −19 atoms/cm 3 . Next, a resist 32 is coated on the back surface of the silicon substrate 31, and the resist 32 is coated at intervals of 100 to 300 μm.
A positive pattern of 00 to 300 μm square is formed. The pattern on the resist 32 is developed to form a window 33 (see FIG. 5B), and the silicon substrate 31 is back-etched through this window. At this time, since there is a difference in the etching rate between the bulk silicon substrate 31 to which boron has not been implanted and the surface portion to which boron has been implanted, only the surface portion to which boron has been implanted remains without being back-etched, resulting in a thickness A diaphragm 34 of about 2 μm can be obtained. Here, back etching is performed through the window 33, so that the bulk part of the silicon substrate that is not implanted with boron is not completely etched, and as shown in FIG. 5B, a part of the bulk remains and is implanted with boron. A mesh structure 35 will be formed which mechanically supports the surface portion. The last remaining resist is removed using a stripper.

The diaphragm 32 formed in this way has high mechanical strength because it is based on silicon, and is therefore supported by a silicon mesh structure 35 instead of the metal mesh for supporting differential pressure as in the previous example. Therefore, it can withstand the differential pressure between the electron beam source container and the reaction tank. Furthermore, since boron is implanted into silicon, it has electrical conductivity, and since no high electric field is generated inside, it has extremely good transmission characteristics for electron beams.

The present invention is not limited only to the embodiments described above, but can be modified and modified in many ways. For example, in the above example, a tungsten heater was used as an electron emission source, and the thermionic electrons emitted from the tungsten heater were utilized. All types of electrons can be used, including field emission electrons, secondary electrons due to collisions of electrons and ions, and electrons due to discharge. It can be selected depending on the characteristics such as.

Furthermore, if the density of electrons injected into the reaction tank is high, a large space charge may be generated in the diaphragm and it may be damaged. It is also possible to arrange electrodes such as In this case, in order to prevent organic substances from being deposited on this electrode, it is desirable to construct the electrode with a tungsten heater and heat it to a temperature of 1000° C. or higher. Furthermore, the probability of excitation of the reaction gas by electrons can be increased by applying a magnetic field to the reaction tank from the outside.

In addition, as a modification of the embodiment shown in FIG. 5, a highly heat-resistant polyimide film was spin-coated on the surface of the silicon substrate, or a boron, carbon, and nitrogen compound film (BCN film) was deposited. Thereafter, selective back etching may be performed through the resist in the same manner as in the above-mentioned embodiments to form a diaphragm supported by a mesh structure made of silicon. Even in such a diaphragm, the mechanical strength of the mesh-like structure made of silicon is high, so the diaphragm alone can support the differential pressure without using a separate mesh for supporting the differential pressure.

In the above embodiment, the plasma processing apparatus of the present invention was used as a plasma CVD apparatus to produce a styrene film, but other polymer films can also be produced, and electrons can be applied to a solid surface. Various surface treatments such as etching or processing can also be performed by irradiation. Further, electrons do not necessarily need to be irradiated continuously, but can also be irradiated intermittently.

[0034]

Effects of the Invention As described above, in the process apparatus using electron excitation of the present invention, the first space that acts as an electron source and the second space that acts as a reaction tank for carrying out a plasma process, for example, are separated by electron transmission. Since the second space is isolated by an extremely thin diaphragm having high properties, the pressure in the second space can be set independently of the pressure in the first space, and therefore there are no restrictions on process control. In addition, since the accelerating voltage can be lowered, the accelerating power source can be made smaller, and since no penetrating X-rays are generated, there is no need to protect against them, so the entire device can be made smaller. can do.

Furthermore, in a configuration in which a metal mesh is arranged adjacent to the electron source side of the diaphragm to support differential pressure,
Since the diaphragm can be made of a polymer membrane that is extremely thin with a thickness of 0.5 to 1.5 μm and has high electron permeability, an electron flow with a large current density can be transmitted from the electron source side to the diaphragm at a low accelerating voltage. can be injected into the reaction tank.

Furthermore, by coating at least the surface of the diaphragm on the reaction tank side with a conductive film and grounding the conductive film and the metal mesh, it is possible to effectively prevent dielectric breakdown of the diaphragm due to electric charge charged on the diaphragm. can do.

[Brief explanation of drawings]

FIG. 1 is a diagrammatic cross-sectional view showing the configuration of an embodiment of a plasma processing apparatus according to the present invention.

FIG. 2 is a diagrammatic cross-sectional view showing the configuration of an experimental apparatus for confirming the operation of the plasma processing apparatus according to the present invention.

FIG. 3 is a graph showing the relationship between acceleration voltage and electron beam current in the experimental apparatus shown in FIG. 2;

FIG. 4 is a graph showing the relationship between acceleration voltage and electron beam current in the experimental apparatus shown in FIG. 2;

FIG. 5 is a cross-sectional view showing a manufacturing process of a diaphragm used in a plasma processing apparatus according to the present invention.

[Explanation of symbols]

1 Glass container 2 Tungsten heater 3 Mesh anode 4 Acceleration power supply 5 Isolation transformer 6 Sly Duck 7 Reaction tank 8 Diaphragm 8a Polyester film 8b, 8c Conductive film 9 Metal mesh for differential pressure support 10　Flange for holding the board 11 Board 21 Cylindrical anode 22 Electrode 23 Ammeter 24 Heating DC power supply 31 Silicon substrate 32 Resist 33 Window 34 Diaphragm

Claims (7)

[Claims] 1. A first container defining a first space that generates electrons and is maintained in a high vacuum; a second container defining two spaces, a diaphragm separating the first and second spaces defined by the first and second containers, and a diaphragm on the first space side of the diaphragm, A process device using electronic excitation, comprising a mesh-like differential pressure supporting member arranged to support the diaphragm, supporting the differential pressure between the first space and the second space, and transmitting electrons. . 2. The differential pressure support member is made of a metal mesh, a diaphragm separating the first and second spaces is coated with a conductive film on at least a surface on the second space side, and the metal 2. A process device using electronic excitation according to claim 1, wherein the mesh and the conductive film are grounded. 3. The thickness of the diaphragm is 0.5 to 1.5μ.
2. A process device using electronic excitation according to claim 1, characterized in that m is defined as m. 4. The method according to claim 1, wherein a reaction gas is circulated in the second space and excited by an electron beam from the first space to generate plasma. Process equipment. 5. A first container defining a first space that generates electrons and is maintained in a high vacuum; and a first container that performs a predetermined process by excitation by the electrons generated in the first space. a second container defining a second space; and a first space and a second space defined by the first and second containers; A process device using electronic excitation, comprising a diaphragm that has mechanical strength capable of supporting differential pressure, is electrically conductive, and is highly permeable to electrons. 6. The electron beam processing apparatus according to claim 5, wherein the diaphragm is formed of silicon into which impurity ions are implanted. 7. A process device using electronic excitation according to claim 5, wherein the diaphragm is formed by coating a surface of a silicon substrate with a polyimide film or a compound film of boron, carbon, and nitrogen.