JPS6357939B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma vapor phase growth apparatus used for manufacturing semiconductor substrates and substrates as materials for solar cells. More specifically, silicon nitride (SiN), silicate glass (SiO ₂ ), or phosphosilicate glass (PSG) are used as interlayer insulating films and final protective films for semiconductor substrates, and amorphous silicon and other materials are used as solar cell materials. When growing a thin film such as amorphous silicon carbide (Si _x C _1-x ) on a substrate, the desired thin film is recently often grown by plasma vapor phase epitaxy.

Generally, in the chemical vapor phase production method using glow discharge, gas molecules are activated by high-energy particles, so thin films can be produced on the substrate at low temperatures ranging from room temperature to several hundred degrees Celsius.

Conventionally, a plasma vapor phase growth apparatus used in such a process generally has a configuration as shown in FIG. In the figure, 1 is a heater, and 2 is a reaction tube, which is generally made of quartz. One end is wide open as an inlet/outlet for the contents, and the other end is constricted and has an exhaust hole 2-1. Reference numeral 3 denotes a boat made of heat-resistant insulator such as quartz, the bottom surface of which forms a flat or cylindrical surface to match the lower side of the reaction tube, and the substrate holding electrode 4 on the upper surface aligned with the tube axis of the reaction tube. A plurality of sheets are held so as to form vertical surfaces and at substantially equal intervals. Reference numeral 5 denotes a lid provided at the entrance/exit of the contents of the reaction tube, and on its inner surface are a connecting rod 5-1 that connects to the boat, and two rods that pass through the lid and supply high-frequency power to the substrate holding electrode. A terminal 14 is provided. The substrate holding electrodes are connected alternately to every other substrate using lead wires 13 from inside these terminals to form groups of substrate holding electrodes facing each other. Reference numeral 6 denotes a reaction gas introduction ring provided between the contents inlet/outlet of the reaction tube and the lid, and a reaction gas introduction pipe 6-1 provided with a valve is provided. 7 is an exhaust pump that exhausts the reaction tube from the exhaust hole 2-1.

When plasma vapor phase growth is performed using such an apparatus, glow discharge occurs between multiple substrate holding electrodes,
A thin film of a type depending on the reaction gas is generated on the substrate 11 held by the electrodes, but the glow discharge leaks to the outside between the electrodes, and a thin film is also generated on the reaction tube and boat. In order to take the substrate in and out before and after thin film formation, the boat is slid on the inside of the reaction tube, so the grown film attached to the reaction tube etc. may peel off in powder form, or the quartz board or the reaction tube itself may be damaged. Quartz powder is generated from the surface. These powders may be blown up when creating a vacuum before forming a thin film, and some of them may adhere to the substrate.
If film growth is performed under such conditions, a thin film will be formed even in the areas where the powder has adhered, resulting in abnormal projections (flakes). This portion has a small electrical insulating effect, and external moisture easily passes through this portion, leading to defects in semiconductor devices and lowering product yields.

The present invention has been made to solve these problems and provides a plasma vapor phase growth apparatus in which powder generation, which is a major cause of reduced product yield, does not occur at least in the reaction chamber. This will be explained in detail below with reference to the drawings.

Figure 2 is a vertical cross-sectional view along the tube axis of the reaction tube.
15 is an external reaction tube, 12 is a lid provided with an inlet/outlet for the contents of the external reaction tube, and between 15 and 12 is a reaction gas introduction tube 6-1 with a valve similar to that shown in FIG. An introduction ring 6 is provided. 1
Reference numeral 6 denotes an internal reaction tube, which is fixed to the lid 12 so that its axis substantially coincides with the axis of the external reaction tube, and a gas inlet 16 is provided at the upper end of the portion in contact with the lid.
-1 is open. Furthermore, a gas flow stopper flange 16-2 is attached to the end opposite to the gas inlet cover.
is provided around the entire circumference of the inner reaction tube and close to the inner surface of the outer reaction tube, and a heat-resistant insulator such as quartz is provided at the bottom of the inner surface of the inner reaction tube at approximately the center in the tube axis direction. A boat 16-3 made of aluminum is fixed, and a plurality of substrate holding electrodes 17 are provided on this boat at substantially equal intervals in a plane perpendicular to the tube axis. Every other electrode is electrically connected to form a set, forming a group of electrodes facing each other, and a lead wire is connected between each electrode group and two terminals 14 for supplying high-frequency power provided on the lid 12. It is connected by 13. Further, the upper tube wall of the electrode group in the internal reaction tube is largely opened, and is closed by a canopy 18 except when the substrate 11 is taken in and taken out. Furthermore, the end of the internal reaction tube opposite to the lid 12 is a narrow exhaust hole 16-4 with a reduced diameter, and legs 16-5 are provided on the lower side of the outer periphery to be inscribed in and held in the external reaction tube. It is being Furthermore, this leg 1
Instead of a 6-5 fixed leg, a vehicle such as a roller may also be used.

Note that the reaction gas introduction pipe 6-1 may be attached directly to the lid 12. In this case, the reaction gas introduction ring 6, the gas inlet 16-1, and the gas stop flange 16-2 are unnecessary. Alternatively, the reaction gas introduction tube may be directly attached to the external reaction tube.

In the plasma vapor phase growth apparatus configured as described above, when attaching or detaching the substrate to or from the substrate holding electrode, the locking mechanism (not shown) of the lid 12 is removed, and the lid and the internal reaction tube fixed thereto are connected to the external reaction tube. Pull out more. Next, the canopy 18 is removed, and the substrate is attached to and detached from the substrate holding electrode 17. Once the attachment and detachment of the substrates is completed, the above operations may be performed in the reverse order to accommodate the inner reaction tube in the outer reaction tube.

During this operation, the lower inner surface of the outer reaction tube and the leg 16-5 of the inner reaction tube slide against each other, so fine quartz powder is generated. Regardless of the flow path, it is extremely rare for this fine powder to enter the interior of the internal reaction tube. In addition, there is no sliding part inside the internal reaction tube, and there is a possibility that the thin film attached to this part will come off when the canopy 18 is attached or removed, but since the canopy is not slid, fine powder will be generated. It won't be.

As a result, when plasma vapor phase growth was performed using the apparatus of the present invention, the number of abnormal protrusions was clearly reduced compared to when using the conventional apparatus. In addition, if you prepare a spare canopy, you can always use a cleaned canopy, which can almost prevent the thin film from detaching from the canopy, which actually reduces the product yield caused by abnormal protrusions. The decrease can be ignored, and the practical effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a conventional plasma vapor phase growth apparatus. FIG. 2 is a longitudinal sectional view showing the structure of the reaction tube portion of the plasma vapor phase growth apparatus of the present invention, and FIG. 3 is an external view of the internal reaction tube portion. In the figure, 15 is an external reaction tube, 16 is an internal reaction tube, 16-3 is a boat, 17 is a substrate holding electrode,
18 is a canopy.

Claims (1)

[Claims] 1. In a plasma vapor phase growth apparatus for producing a thin film of a semiconductor compound on the surface of a semiconductor substrate, an external reaction tube having one end opened as an inlet/outlet for contents and the other end connected to an exhaust pump as an exhaust port. and an inner reaction tube that is fixed to the lid of the contents inlet and outlet of the outer reaction tube and inserted into the outer reaction tube substantially coaxially with the outer reaction tube, and the inner reaction tube has an inner bottom surface. having vertical surfaces at substantially equal intervals on a boat fixed to the boat, and electrically connecting every other terminal separately by lead wires from two terminals provided through the lid. A plurality of substrate holding electrodes configured into two groups and an opening with a lid formed above the plurality of substrate holding electrodes are provided, and a gas inlet and a gas inlet and an opening with a lid are provided in close contact with the lid of the content inlet and outlet. A gas flow prevention flange is provided on the outer periphery of the gas flow prevention flange in close proximity to the gas inlet and opposite to the lid of the content inlet/outlet, and a reactive gas introducing means is provided at an intermediate position between the lid of the content inlet and outlet and the gas flow prevention flange. A reaction tube for a plasma vapor phase growth apparatus featuring: 2. The reaction tube of the plasma vapor phase growth apparatus according to claim 1, with a reaction gas introduction tube sandwiched between the content inlet/outlet and the lid of the content inlet/outlet of the external reaction tube as a reactant gas introduction means. A reaction tube of the plasma vapor phase epitaxy apparatus, characterized in that the reaction gas introduction ring is a reaction gas introduction ring. 3. In the reaction tube of the plasma vapor phase growth apparatus according to claim 1, the reaction gas introduction tube is directly attached to the wall of the outer reaction tube close to the content inlet/outlet of the outer reaction tube as the reaction gas introduction means. A reaction tube of the plasma vapor phase growth apparatus characterized by: 4. In a plasma vapor phase growth apparatus that generates a thin film of a semiconductor compound on the surface of a semiconductor substrate, an external reaction tube having one end opened as an inlet/outlet for contents and the other end connected to an exhaust pump as an exhaust port, and this external reaction tube an inner reaction tube fixed to the lid of the contents inlet/outlet and inserted into the outer reaction tube substantially coaxially with the outer reaction tube; A boat, and two sets of terminals each having a vertical surface substantially equally spaced therefrom and separately electrically connected to each other by lead wires from two terminals provided through the lid. A plurality of substrate holding electrodes arranged in a group and an opening with a lid formed above the plurality of substrate holding electrodes are provided,
The reaction tube of the plasma vapor phase growth apparatus, characterized in that a gas introduction tube is provided passing through the lid of the content inlet/outlet.