JPS6380534A - Plasma processing apparatus - Google Patents

Abstract

PURPOSE:To enable ion doping or etching of impurities without using differential exhaust or the like and to prevent wafers from being contaminated with the impurities, by providing a high-frequency electrode and a magnetic field creating section on the outside of an insulating cylindrical tube and providing a first conducting bias section and a second conducting bias section opposed thereto within said cylindrical tube. CONSTITUTION:A high-frequency electrode 22 which causes highfrequency glow discharge in an insulating cylindrical tube 21 is provided on the outside of the insulating cylindrical tube 21. An electromagnet 24 arranged on the outside of the high-frequency electrode 22 generates a magnetic field, by which electrons are excited to move spirally. By utilizing high-frequency power effectively in this manner, polasma can be created stably in the insulating cylindrical tube 21 with a relatively low vacuum (10<-3>-10<-4> torr). Bias electrodes 29-a and 29-b are connected to DC high-voltage power supplies 33-a and 33-b, respectively. By applying a desired voltage to the bias electrodes, they are caused to eject charged particles from a discharge chamber A to a substrate chamber B and to accelerate them. In this manner, there is no need of producing impurities by sputtering the highfrequency electrode. The impurities can be implanted uniformly in a wafer having a large area without using differential exhaust or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a plasma processing apparatus used in the manufacture of semiconductor elements in the semiconductor industry, and in particular to an ion doping apparatus and an ion doping apparatus used for implanting impurities into semiconductor elements, semiconductor thin films, etc. , relates to a plasma processing apparatus used for etching semiconductor thin films and the like.

Conventional Technology Methods for implanting impurities in the form of ions to a desired amount and depth into a semiconductor thin film, etc. include (1) an ion source, an ion accelerator, a mass separation unit, and a substrate chamber, such as those currently available on the market; (2) A simple ion implantation device that uses a direct current glow discharge as an ion source and implants ions through an ion acceleration section that has a mass separation section [Figure 4 J, C, Muller, at, al: (
Proc, European Photovoltaic
5olar Energy Conf, ) (Promeding European Photoportic Solar
Energy Conference) (Luxembourg)
) Sept, 1977, P897-909), a plasma CV method in which a capacitively coupled high-frequency electrode is provided in the substrate chamber and a chemical vapor phase reaction is caused by high-frequency glow discharge.
Method of applying DC voltage to the high frequency electrode of D device (fifth method)
Figure).

In FIGS. 4 and 5, 1 is a discharge chamber, 2 is an anode electrode for DC glow discharge, 3 is a DC power source for discharge, 4 is an electrode for acceleration, 5 is a DC power source for acceleration, 6 is a gas introduction tube, and 7 is a DC glow discharge anode electrode. is an insulator, 8 is a gas exhaust pipe, 9 is a substrate stand, 11 is a vacuum protrusion, 1
2 is a substrate stand, 13 is a high frequency electrode, 14.15 is an insulator,
16 is a matching box, 17 is a high frequency oscillator, 18
19 is a gas introduction pipe, and 20 is a gas discharge pipe. In addition, in etching, the plasma CVD
There was a method of etching by introducing a reactive gas such as CF4 into the apparatus.

Problems to be Solved by the Invention In the conventional technique of implanting impurities in the form of ions into semiconductor elements, etc., the method (1) using a commercially available ion implantation device has a mass separation section, etc. The device configuration is complicated and difficult to maintain or modify, and in order to implant impurities into a large sample area, it is necessary to add a mechanism such as electrically scanning the ion beam or mechanically scanning the sample. In addition, the overall structure of the device was complicated, making maintenance and modification difficult. In a simple ion implantation device using direct current glow discharge (2), a differential In addition, if the discharge electrode is enlarged to inject impurities into a large sample area, the discharge may become uneven and unstable due to creeping discharge of the electrode, and furthermore, the discharge electrode may become the ion source. Since the electrode is located internally, there are problems such as impurity contamination caused by sputtering of the electrode by ions accelerated by the ion sheath. The method of applying impurities is a simple method that can be used to implant impurities into a large area sample, but since the pressure used is in the range of 1 to 10-3 Torr where high-frequency glow discharge occurs, it is difficult to apply Since the ion acceleration voltage is 100 to 1 Kv, which does not cause abnormal discharge, compared to methods (1) and (2), impurities are injected at a high concentration into the extreme surface layer of the semiconductor material. There were problems such as impurity contamination caused by sputtering defects and damaged electrodes.

Further, in etching, a method in which reactive gas is introduced into a plasma CVD apparatus using capacitively coupled high-frequency glow discharge has problems such as impurity contamination caused by sputtering of the high-frequency electrode.

Means for Solving the Problems In order to solve the problems above, the plasma processing apparatus of the present invention includes an insulating cylindrical tube connected to a gas introduction tube, and an insulating cylindrical tube provided outside the insulating cylindrical tube. a discharge chamber consisting of a high-frequency electrode and a magnetic field generation source; a substrate chamber consisting of a high vacuum chamber at ground potential connected to a gas exhaust pipe; and a substrate stand at ground potential provided inside the high vacuum chamber; and the substrate chamber. and a first conductive bias section that is insulated from the discharge chamber and connected to a first DC power source between the substrate stand and the discharge chamber, and the first conductive bias section that is located within the discharge chamber. A second conductive bias section is provided at a position facing the first DC power supply or the second DC power supply and connected to the first DC power supply or the second DC power supply.

That is, the present invention uses as an ion source an insulating cylindrical tube with a high-frequency electrode and a magnetic field generator arranged outside, and a first ion source that draws charged particles into the insulating cylindrical tube and accelerates them to a desired energy. A conductive bias section and a second conductive bias section for pushing charged particles toward the first bias section are provided at a position facing the first conductive bias section.

Function: By providing a high-frequency electrode outside the insulating cylindrical tube, ions generated by high-frequency discharge inside the insulating cylindrical tube are accelerated by the ion sheath and sputter the high-frequency electrode to generate impurity movements ( Cyclotron motion:
When electrons with an average kinetic energy of thermal motion similar to that at room temperature rotate at the same frequency as the 13.56 MHz radio frequency, the radius of gyration is approximately 0.140), and the energy supplied by the radio frequency is effectively utilized. For example, 10
Stable and uniform discharge is possible even at a gas pressure of -3 to 10 Torr. This 10-5 to 10-
The average confession path of ions under a pressure of 4 Torr varies depending on the ion type, but it is about the same (several tens of meters) or longer than the distance from the discharge chamber to the substrate stand, so it is possible to discharge without using differential pumping etc. Pushing out and accelerating charged particles with a simple structure of first and second conductive bias parts arranged in a chamber, transporting the charged particles to a sample such as a semiconductor substrate on a substrate table, and irradiating the sample. becomes possible. Furthermore, since the degree of vacuum inside the device is 10 to 10 Torr and the high frequency electrode for discharge and the conductive bias part for acceleration are separated, creepage due to low degree of vacuum or high snow pressure may occur. Charged particles can be accelerated to 11c6v or more without causing abnormal discharge such as discharge or avalanche discharge, and without instability of discharge due to coincidence of the discharge electrode and accelerating electrode. Additionally, due to the type of discharge, by using an insulating cylindrical tube with a large diameter as the discharge chamber, impurities can be easily uniformly injected into a large area sample set on a substrate table. becomes.

EXAMPLES The present invention will be explained in more detail below based on the drawings.

FIG. 1 shows a schematic diagram of a first embodiment of a plasma processing apparatus according to the present invention. The insulating cylindrical tube 21 of the discharge chamber A is made of ceramics, quartz glass, etc., and the high-frequency electrode 22 that generates a capacitively coupled high-frequency glow discharge in the insulating cylindrical tube 21 is made of copper, nickel, etc. with good conductivity. It is provided on the outside of the insulating cylindrical tube 21. One side of the high-frequency electrode 22 is connected to the high-frequency oscillator 24 via a matching box 23, and the other side is grounded to the insulating cylindrical tube 2.
High frequency power is supplied within 1. Furthermore, high frequency electrode 2
By exciting the swirling movement (cyclotron movement) of electrons by the magnetic field generated by the electromagnet 26 placed outside the 2, and by effectively using high-frequency power, a relatively high degree of vacuum (1
Plasma is stably generated inside the insulating cylindrical tube 1 at a pressure of 0-3-10-4 Torr. Material gas is supplied to the discharge chamber A from a gas cylinder 26 to a pulp 27 and a flow scenery control device 28.
Then, it is conducted through the through hole 3Q of the second conductive bias portion electrode 29-a inside the insulating cylindrical tube 21 through the insulating tube 31 made of quartz glass, ceramics, Teflon, etc.

Further, the grain 1 facing the second conductive bias section connects the first bias section electrode 29-b to an insulating flange 32 made of ceramics, quartz glass, vinyl chloride, acrylic, etc.
It is provided between the discharge chamber A and the substrate chamber B via. The bias portion electrodes 29-a and 29-b are connected to a DC high voltage power source 32-a.
and 32-b, and by applying a desired voltage, the charged particles in the discharge chamber A are pushed out to the substrate chamber B and accelerated. The substrate chamber B is connected to a gas exhaust pipe 35 leading to a vacuum exhaust system 34, and has a pressure of 10-5-1O-6 Torr.
maintained at a pressure of A board stand 38 fixed inside the board chamber B by a board support rod 36 and an insulating flange 37 made of quartz, ceramics, acrylic, vinyl chloride, etc. is made of metal such as stainless steel brass and aluminum. The sample is placed on 38. By connecting the substrate stand 18 to the DC power supply 39, the first bias section 2
The accelerated charged particles are given an additional speed through the through hole 9-b. First bias section electrode 29-b and substrate stand 3
The charged particle beam, which has obtained a kinetic energy corresponding to the potential difference with respect to the charged particle beam 8, is irradiated onto a sample 40 such as a semiconductor substrate on the substrate table 38, and a desired amount of impurities is implanted or etched into the sample.

FIG. 2 shows the current flowing through the substrate table 38 when the current flowing through the electromagnet 26 (the strength of the magnetic field in the discharge chamber A) is changed in the first embodiment of the plasma processing apparatus according to the present invention. (slightly larger than the amount of electricity of ions irradiated to the substrate stage). In this case, the inner diameter of the insulating cylindrical tube is 130
i11'll, the diameter of the substrate stand is 1QQ711ff, the distance between the substrate stand and the first conductive bias section is 15 Qff,
The gas is nitrogen gas, and the frequency of the high frequency supplied is 13.5o.
MHz/power is esoW.

The potential difference of the substrate stand 38 with respect to the first conductive bias section 29-b is -a, sKV, and the magnetic flux density on the central axis of the insulating cylindrical tube 21 when the current flowing through the electromagnet 25 is 1 A when there is no discharge. is approximately tstsG.

In this embodiment, the pressure inside the substrate chamber is 3. ○×1O-4T
If the current does not flow through the electromagnet below orr, discharge chamber B
No discharge occurred, confirming that the discharge excitation effect by the magnetic field is highly effective.

FIG. 3 shows a schematic diagram of a second embodiment of the plasma processing apparatus according to the present invention. The insulating cylindrical tube 41 of the discharge chamber C is made of ceramics, quartz glass, etc., and the high frequency electrode 42 for inductively coupled glass high frequency glow discharge is made of a highly conductive metal such as copper or nickel. Provided outside of 41.

This high-frequency electrode 42 is connected to a high-frequency oscillator 44 via a matching box 43 to supply high-frequency power into the insulating cylindrical tube 41, and electromagnets 45-a and AS- are placed outside the high-frequency electrode 42. By exciting the swirling movement of electrons (cyclotron movement) by the magnetic field generated by b, and further confining the plasma generated by the discharge, and by effectively using high-frequency power for the discharge, a relatively high degree of vacuum (1o-
3 to 1 O-4 Torr), plasma is stably generated inside the insulating cylindrical tube 41.

Material gas is supplied to the tube 41 from a gas cylinder 46 through a pulp 47, a flow rate control device 48, an insulating tube 49 made of quartz, ceramics, Teflon, etc. This is done through the through hole 51 of the conductive flange 50-a. A partition wall 52 made of quartz, ceramics, etc. is provided on the side of the conductive flange 50-a exposed to discharge plasma, and the material gas that has passed through the through hole 51 is transferred to the high frequency electrode 42 of the discharge chamber C through the through hole 53 of the partition wall 52. introduced between. Furthermore, a second conductive flange 50-a
a first conductive flange 50 provided at a position facing the
-b is provided on the substrate chamber via an insulating flange 54 made of ceramics, quartz, vinyl chloride, acrylic, etc.,
A protective coating 55 made of quartz, ceramics, or the like is provided on the surface of the conductive flange 50-b that is exposed to charged particles generated by discharge. By connecting the conductive flanges 50-a and 5o-b to DC high voltage sources 56-a and 56-b and applying a desired potential, charged particles in the discharge chamber C are pushed out to the substrate chamber, Perform full acceleration. The substrate chamber is connected to a gas exhaust pipe 58 leading to a vacuum exhaust system 57,
A pressure of 10-3-10-6 Torr is maintained. Also,
A board stand 61 fixed inside the board chamber by an insulating flange 59 made of quartz, ceramics, acrylic, vinyl chloride, etc. and a board support rod 60 is made of metal such as stainless steel, copper, aluminum, etc. A sample 62 is placed on top. Furthermore, by connecting the substrate pedestal 61 to a DC power source 63 and applying a potential, the charged particles accelerated through the conductive flanges 5o-b are accelerated or decelerated. The charged particles, which have obtained kinetic energy according to the potential difference between the conductive flange 50-b and the substrate pedestal 61, are irradiated onto the sample 62 on the substrate pedestal 61, thereby implanting or etching a desired amount of impurities.

Effects of the Invention The present invention generates 1o- This enables stable generation at a relatively low pressure of 6 to 10-4 Torr, and because the pressure is low, the mean free path of the charged particles is equal to or longer than the distance from the discharge chamber to the white of the substrate. Therefore, with a simple structure of a first conductive bias section and an opposing second conductive bias section, charged particles can be accelerated to an energy of 1 key or more without requiring differential pumping, etc. By irradiating a sample such as a semiconductor above, it becomes possible to perform ion doping and etching of impurities. Further, by providing the high frequency electrode outside the discharge chamber, it is possible to prevent the sample from being contaminated by impurities generated by sputtering or etching of the discharge electrode. Furthermore, due to the type of discharge, by using a discharge chamber with the same structure and large diameter, it is possible to uniformly irradiate a large area of the sample with charged particles. The same effect can be obtained by applying a gas, connecting the gas inlet tube to the substrate chamber, connecting the gas exhaust tube to the discharge chamber, and providing a protective coating or partition on the conductive bias section. The plasma processing apparatus according to the present invention is extremely simple and highly useful as an apparatus for ion doping and etching of impurities into semiconductors and the like.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a first embodiment of a plasma processing apparatus according to the present invention, and FIG.
8, the pressure inside the substrate chamber B is 3.5X.
10. 3.0X10. The graph shown in FIG. 3 for the case of 2.5×10 Torr is a schematic diagram of the second embodiment of the plasma processing apparatus according to the present invention. Figure 4 shows a simple ion implantation device using DC glow discharge among conventional techniques (Reference 1)
FIG. 5 is a schematic diagram of a method of performing ion doping with a plasma CVD apparatus using high-frequency glow discharge among conventional techniques. A...discharge chamber, B...substrate chamber, 21.
...Insulating cylindrical tube, 22...High frequency electrode,
31... Insulating tube, 32.37... Insulating flange, 40-... Sample. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure 3: Laseki current (A) Figure 3: Figure 4

Claims (5)

[Claims] (1) A discharge chamber consisting of an insulating cylindrical pipe connected to the gas introduction pipe, a high frequency electrode and a magnetic field generation source provided outside the insulating cylindrical pipe, and a ground connected to the gas exhaust pipe. A substrate chamber consisting of a high-potential vacuum chamber and a ground potential substrate stand provided therein; a first DC power source that is insulated from the substrate chamber and the discharge chamber and provided between the substrate stand and the discharge chamber; a first conductive bias section connected to the first conductive bias section, and a first conductive bias section connected to the first DC power supply or the second DC power supply provided in the discharge chamber at a position facing the first conductive bias section. 1. A plasma processing apparatus comprising two conductive bias sections. (2) The plasma processing apparatus according to claim 1, wherein the substrate table is connected to a DC power source independent of the first and second DC power sources while maintaining insulation from the high vacuum chamber. (3) The plasma processing apparatus according to claim 1 or 2, wherein a gas introduction pipe is connected to the substrate chamber. (4) The plasma processing apparatus according to claim 1, 2, or 3, characterized in that a gas exhaust pipe is connected to the discharge chamber. (5) A partition wall or a surface coating is provided on the sides of the first conductive bias section and the second conductive bias section that are exposed to charged particles generated by discharge, or The plasma processing apparatus according to item 2, 3, or 4.