JPH0722500U - Microwave plasma CVD device - Google Patents

Abstract

(57) [Summary] [Object] To provide a microwave plasma CVD apparatus capable of preventing microwave leakage when a metal is used for a substrate holder and adjusting the substrate temperature. The substrate holder 1 is made of metal and has a thickness of about 1/4 of the wavelength of the microwave in the waveguide, and heating and / or cooling means for the substrate 3 is provided inside the substrate holder 1.
One or two or more metal plates 9 are arranged below the substrate holder 1 so as to be separated from the substrate holder 1, and each of the metal plates 9 is configured to be movable along the longitudinal direction of the reaction tube 4.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a microwave plasma CVD apparatus, and more particularly to a microwave plasma CVD apparatus capable of preventing microwave leakage when a metal is used for a substrate holder and adjusting the substrate temperature.

[0002]

[Prior art]

 An example of a conventional microwave plasma CVD apparatus is shown in FIG. In the figure, 21 is a quartz substrate holder, 22 is a quartz substrate supporting rod for supporting the substrate placed on the substrate holder 21, 3 is a substrate such as a silicon wafer, 4 is a reaction tube, 5 is a micro Variable short-circuit plate for wave matching, 6a is a rectangular waveguide, 6b is a sleeve provided so that microwaves do not leak from the gap between the waveguide 6a and the reaction tube 4, 7 is an O-ring, 8 Indicates a stainless steel chamber.

In the waveguide 6a, the longitudinal direction of the reaction tube 4 becomes parallel to the electric field direction of the microwave M injected therein, and moreover, the waveguide 6a and the reaction tube 4 are fitted so as to be orthogonal to each other. There is a circular hole in it. A reaction tube 4 is inserted through the hole, and a sleeve 6b is arranged around the hole. The reaction tube 4 is made of a ceramic such as quartz or aluminum, which has a small dielectric loss due to microwaves, and has a circular cross section. A chamber 8 is arranged below the reaction tube 4, and an inlet / outlet (not shown) and an exhaust port for the substrate 3 are provided in the chamber 8 and is connected to a high vacuum exhaust system or a large flow exhaust system (not shown). is doing. The substrate holder 21 is supplied with rotational power from a substrate support rod 22 connected to a rotational driving source such as a motor (not shown). The substrate support rod 22 is inserted into a through hole formed in the center of the bottom surface of the chamber 8. The O-ring 7 is used to close the space formed by the reaction tube 4 and the chamber 8. The substrate holder 21, the substrate support rod 22, and the rotation driving source can be raised and lowered by an elevator (not shown).

Conventionally, for forming a film on the substrate 3, the reaction gas is introduced into the reaction tube 4 at a pressure of about 40 Torr, microwaves are input, and plasma P is generated, whereby the reaction gas is decomposed and the substrate is separated. The heating was done at the same time.

[0005]

[Problems to be solved by the device]

 As described above, in the conventional apparatus, the reaction gas is decomposed by plasma and the substrate is heated at the same time. Therefore, the microwave input power is kept constant and the substrate temperature is controlled. It was not possible to control the temperature of the substrate by changing it.

Therefore, a method of controlling the temperature of the substrate holder so that the temperature of the substrate can be controlled regardless of the state of the microwave input power can be considered. For that purpose, a heater is embedded in the substrate holder. Therefore, it is difficult to perform such complicated processing on the conventional substrate holder made of a dielectric material such as quartz or ceramic.

Furthermore, when a relatively easy-to-process metal such as copper, aluminum, or stainless steel is used for the substrate holder, the substrate holder itself serves as an antenna, and microwaves pass through the lower part of the sleeve and leak to the outside, which may cause electromagnetic interference. There was a problem of causing it or adversely affecting the human body.

[0008]

[Means for Solving the Problems]

 In order to solve the above problems, in the microwave plasma CVD apparatus according to the present invention, the substrate holder is made of metal, and the thickness of the substrate holder is an abbreviation for the wavelength in the waveguide of the microwave (hereinafter referred to as λg). Molded into 1/4, one or more metal plates are provided below the substrate holder, spaced apart from the substrate holder, and each of the metal plates is movable along the longitudinal direction of the reaction tube. It is configured to be Further, the above substrate holder is provided with a heater and / or a flow path through which a cooling liquid circulates.

[0009]

[Action]

 With the above configuration, the metal substrate holder and the metal plate or the gap between the metal plates can be arranged in a dimension having a predetermined electrical meaning, and the thickness of the metal substrate holder is λg / 4 electrically. In addition to setting various dimensions, the metal board holder and metal plate are arranged in a choke structure.

Further, since the substrate temperature is controlled by the heating and / or cooling means inside the substrate holder, it is not affected by the plasma temperature, that is, the state of the microwave input power, and the microwave input power is kept constant and the substrate temperature is kept constant. It is possible to control the temperature and control the temperature of the substrate to be constant by changing the microwave input power.

In the microwave plasma CVD apparatus of the present invention, in order to prevent external leakage of microwaves when a metal is used for the substrate holder, a metal plate having a thickness of about λg / 4 is attached to the lower portion of the metal substrate holder by λg. A choke structure can be formed by arranging one or more sheets at / 4 intervals. However, at this time, due to the relative permittivity εr and the thickness of the reaction tube, the propagation velocity of the microwave is shorter than λg when the microwave passes through the reaction tube, that is, the wavelength becomes shorter. No longer serves as a short-circuit board. Since the metal plate can be moved in the microwave plasma CVD apparatus of the present invention, the distance between the metal substrate holder and the metal plate or the metal plates is always kept at the microwave wavelength in the reaction tube even when plasma is formed. It can be adjusted to 1/4 of the above, and can always have an effective choke structure regardless of the properties of the reaction tube. The same applies to changes in wavelength depending on the type of reaction gas.

[0012]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a main part of a microwave plasma CVD apparatus according to the present invention, and the same reference numerals as those in FIG. 4 denote the same or corresponding parts. Reference numeral 1 denotes a metal substrate holder having a thickness t of λg / 4. To control the temperature of the substrate, cavities 11a and 11b are provided so that a heater 12 can be installed and water W can be filled. It communicates with the hollow portion of the substrate support rod 2 formed of a cylindrical cylinder. A through hole is formed in the center of the partition wall between the cavities 11a and 11b of the substrate holder 1, and a thin tube 14 is fitted into this through hole to connect the cavity 11a and the hollow portion of the thin tube 14 to each other. The conducting wire is passed through the thin tube 14, the conducting wire is drawn out to the outside without being immersed in the water W, and is connected to a power source (not shown). The drain pipe 15 is inserted into the hollow portion of the substrate support rod 2 so that the thin pipe 14 is inserted therein, and the water W poured into the gap between the substrate support rod 2 and the drain pipe 15 by a pump (not shown). Is used for draining water. The drained water is sent to a heat sink (not shown), cooled by heat exchange, passed through the pump, and again poured into the gap between the substrate support rod 2 and the drain pipe 15.

The heater 12 is a well-known Nichrome wire wound or a sintered body of SiC, and has a through hole for inserting the conductor wire of the heater 12 so as not to come into contact with the inner wall of the cavity 11 a of the substrate holder 1 to prevent a short circuit. It is housed in the cavity 11a together with the vacant insulator 13 having a concave cross section.

With such a structure, the metal substrate holder 1 is heated by the heater 12 when the temperature of the substrate 3 does not reach the optimum temperature at the time of film formation, and conversely, when the temperature exceeds the optimum temperature, the metal W is heated by the water W. By cooling the substrate holder 1, the temperature of the substrate 3 can be optimally maintained. This series of controls can be realized by, for example, a thermocouple and a temperature controller.

Also in this embodiment, the substrate holder 1 can be rotated and moved up and down as in the conventional case, and the film thickness on the substrate 3 can be made uniform and the position of the substrate holder 1 can be adjusted.

The metal plate 9 is formed into a ring shape by punching, cutting, etc., and is inserted into the reaction tube 4 with the substrate supporting rod 2 inserted through the central through hole, and the chamber 8 is inserted with the rod 16 having a small diameter. It is connected to a ring-shaped knob 10 arranged outside. Therefore, when the knob 10 is moved up and down, the metal plate 9 is also moved up and down in association with each other, and the gap g 1 between the substrate holder 1 and the metal plate 9 can be set to a predetermined size. The position of the knob 10 may be set manually, but if the knob 10 is connected to a linear movement mechanism using a ball screw, a manipulator, or the like and controlled by a microcomputer or the like, more accurate position setting is possible. The outer shape of the metal plate 9 is preferably as close as possible to the inner diameter of the reaction tube 4.

The rod 16 is inserted into a through hole formed in the bottom surface of the chamber 8, and the O-ring 7 is connected to the chamber 8 to prevent outside air from entering the space formed by the reaction tube 4 and the chamber 8. It is loaded in the gap.

When the embodiment of FIG. 1 having the above-described structure is used for actual work, the upper surface of the substrate holder 1 (the surface on which the substrate 3 is placed) is substantially the same as the lower E surface of the waveguide 6a. It is desirable to position it. This is because the effective length of the substantially constricted region of the microwave waveguide due to the outer diameter of the substrate holder 1 is set to approximately λg / 4. However, since the microwave wavelength is shortened as described above, it is possible to adjust the position of the substrate holder 1 in accordance with the properties of the reaction tube and the reaction gas in order to set the effective length of the constriction region appropriately in consideration of the experiment and the like. I don't want it. In addition, it is important that the gap g between the substrate holder 1 and the metal plate 9 is similarly set appropriately so that the microwave leakage is reduced.

FIG. 2 is a view showing an example of a metal plate moving mechanism when a plurality of metal plates are arranged below the substrate holder 1. The metal plates 9a and 9b are connected to the knobs 10a and 10b, respectively, through small-diameter rods 16a and 16b penetrating the chamber 8. The rod 16a is connected to the through hole 17 of the metal plate 9b and the rod 16b is connected to the knob 10a. The through holes 18 are respectively inserted. In this case as well, as described in the embodiment of FIG. 1, O-rings (not shown) fill the gaps between the rods 16a and 16b and the chamber 8. Reference numeral 2 is a substrate support rod, but the outer shape is omitted as a two-dot chain line for understanding of the drawing, and the chamber 8 is also shown as a partial cross section in the same meaning. Other configurations are omitted in the drawing.

Since the example of FIG. 2 has the above-described structure, the metal plate 9a or 9b can be independently moved by moving the knob 10a or the knob 10b.

FIG. 3 is a graph showing the result of measuring the amount of microwave leakage from the lower portion S of the sleeve 6b when a diamond is synthesized on the substrate using the embodiment of FIG. 1 by a microwave leakage detector. is there. As is apparent from this figure, by appropriately adjusting the position of the metal plate 9, microwave leakage is effectively reduced. When the thickness of the wall of the reaction tube 4 is 2 mm and 4 mm, as a result of adjusting the position of the metal plate 9, the microwave leakage amounts are 1.5 mW / cm ² and 1.2 mW / cm ² , respectively. The safety standard value is 5 mW / cm ² or less, and it is clear that this example does not adversely affect the surrounding environment. By the way, the microwave leakage amount when the metal plate 9 was removed was 20 mW / cm ² , and it can be seen that the metal plate 9 is useful for preventing microwave leakage.

Next, a series of procedures and conditions for synthesizing the diamond will be described in detail. The substrate holder 1, the substrate support rod 2 and the metal plate 9 are made of stainless steel, the upper surface of the substrate holder 1 is set to the same height as the lower E surface of the waveguide 6a, the diameter of the metal plate 9 is 42 mm, and the thickness is 42 mm. Was 10 mm. The reaction tube 4 was made of quartz. The diameter of the sleeve 6b was 54 mm in both the upper and lower sides. As a procedure, first, the substrate 3 is placed on the substrate holder 1, the exhaust system connected to the chamber 8 is switched to the high vacuum exhaust system, and the inside of the reaction tube 4 is changed to 10 ^-3 After evacuating to about Torr, the exhaust system was switched to a large flow rate exhaust system, a reaction gas consisting of a mixed gas of methane and hydrogen was introduced at 100 cc / min and a methane concentration of 1%, and the inside of the reaction tube 4 at 40 Torr. Hold at pressure. Next, a microwave M having an oscillation frequency of 2 450 MHz with a constant input power of 1 kw was applied to generate plasma P, and the temperature of the substrate 3 was set to 850 ° C. by adjusting the flow rate of water in the substrate holder 1.

At this time, the diameter of the reaction tube 4 is 46.5 mm, the thickness of the tube wall is 2 mm, the gap g between the metal ring 9 and the substrate holder 10 is changed in the vicinity of λg / 4, and the sleeve 6 b is moved from the lower part. The microwave leakage amount was measured, and the measured value was plotted on a graph with the microwave leakage amount on the vertical axis and the gap g on the horizontal axis. Further, the diameter of the reaction tube 4 was 42.5 mm, the thickness of the tube wall was 4 mm, and the measured values were plotted in the above graph by the same method. FIG. 3 is obtained under such conditions and procedures.

Since the diamond film obtained by the above diamond synthesis can optimally adjust the substrate temperature at a higher plasma temperature than the conventional one, the film forming rate is about 2% as compared with the case where the conventional substrate holder is used. It is about twice as fast as 0.4 μm per hour.

Further, as described above, the larger the number of metal rings 9, the higher the microwave leakage prevention effect is, and the leakage amount is 0. It was 1 mW / cm ² .

Although the embodiment has been described above, the present invention is not limited to this, and various modifications can be made. For example, although the metal plate and the knob are connected by two rods in the above embodiment, more or one rod may be used. Although the cooling liquid for cooling the substrate is water, other liquids such as oil may be used.

[0027]

[Effect of device]

 As described above, by providing one or more movable metal plates under the temperature-controllable metal substrate holder and changing the position of the metal plates in a predetermined manner in response to the change in the wavelength of the microwave, the sleeve It is possible to minimize the leakage of microwaves from the. Furthermore, regardless of the plasma temperature, the substrate temperature can be adjusted to be the most suitable for diamond growth, so that the film formation rate is faster than that of the conventional microwave plasma CVD apparatus, and diamond with excellent crystallinity can be obtained. .

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is a view showing an example of using a plurality of metal plates in the present invention.

FIG. 3 is a graph showing changes in the amount of microwave leakage with respect to changes in the gap between the substrate holder and the metal plate during diamond synthesis in the apparatus according to the present invention.

FIG. 4 is an explanatory diagram showing a conventional example.

[Explanation of sign]

 1 Substrate holder 2 Substrate support rod 3 Substrate 4 Reaction tube 5 Variable short-circuit plate 6a Waveguide 6b Sleeve 7 O-ring 8 Chamber 9 Metal ring 10, 10a, 10b Knob 11a, 11b Cavity 12 Heater 13 Insulator 14 Capillary tube 15 Drain pipe 16 , 16a, 16b sticks

Claims (2)

[Scope of utility model registration request] 1. A substrate holder is provided in which a waveguide is installed orthogonal to a reaction tube, a sleeve surrounding the reaction tube is projectingly provided on upper and lower surfaces of the waveguide, and a substrate is placed in the reaction tube. , Plasma C for depositing and etching a film on the substrate
In the VD apparatus, the substrate holder is made of metal, and the thickness of the metal holder is formed to be about ¼ of the wavelength of the microwave in the waveguide, and the substrate holder is separated from the substrate holder below the substrate holder. One or two or more metal plates are provided, and each of the metal plates is movable along the longitudinal direction of the reaction tube. 2. The microwave plasma CV according to claim 1, wherein a heater is embedded in the substrate holder and / or a flow path through which a cooling liquid circulates is installed in the substrate holder.
D device.