JP2594051B2 - Plasma processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a plasma processing method.

(Prior Art) For example, in a conventional plasma CVD apparatus, dozens of disk-shaped electrode plates are installed on an electrode support rod provided below along an axial direction, and a wafer is placed along each of the electrode plates. Is provided to form a CVD film on a wafer to be processed.

(Problems to be Solved by the Invention) However, in the related art, it takes much longer time to raise the temperature of the loaded wafer and the electrode plate to a predetermined temperature than the time for forming the CVD film. Was.

Because, as is well known, heat is transmitted by convection, radiation, and conduction. However, the inside of a reaction tube in this type of plasma processing apparatus is reduced in pressure to an atmosphere with a high degree of vacuum. Therefore, the temperature of the object to be processed such as a wafer must be increased only by radiation from the heater. On the other hand, this type of electrode plate generally has about 10 times the heat capacity of the wafer.

As a result, it takes time to raise the temperature of a workpiece such as a wafer to a predetermined processing temperature, and as a result, the CVD
It takes a long time to form a film, and the throughput cannot be improved, which is a problem.

The present invention has been made in view of the aspects of the present invention, and aims to improve the processing efficiency by shortening the time for elevating an object to be processed such as a wafer to a predetermined temperature, and to enable accurate film formation processing. It is an object of the present invention to provide a plasma processing method.

[Means for Solving the Problems] According to the present invention, a gas supply unit for introducing a gas and a gas discharge unit for discharging the introduced gas are provided. A plurality of objects to be processed housed in a reaction chamber having a heater and a process of forming a predetermined film on the objects in a plasma atmosphere of a reaction gas for film formation. Loading a plurality of objects to be processed into the reaction chamber; and, after the loading, setting the reaction chamber to a non-reactive gas atmosphere; and heating the reaction chamber with a heater under the non-reactive gas atmosphere. Heating to a predetermined temperature, and after reaching the predetermined temperature, introducing a reaction gas for film formation into the reaction chamber, further generating plasma in the reaction chamber, and forming a predetermined film on each of the objects to be processed. And the process of The plasma processing method is provided. In this case, for example, an argon gas can be used as the non-reactive gas.

(Function and Effect) According to the present invention, the reaction chamber is first set to a non-reactive gas, for example, an argon gas atmosphere, so that the reaction chamber is kept at a predetermined temperature. Therefore, not only radiation from the heater but also convection of the non-reaction gas Can also transfer heat to the object to be processed and heat it. Accordingly, the object to be processed can be heated to the predetermined temperature faster than before.

In addition, since the reaction gas is introduced into the reaction chamber after the temperature in the reaction chamber reaches a predetermined temperature as described above, a film having uniform film quality can be formed. That is, if the reaction chamber is heated while introducing the reaction gas into the reaction chamber, the reaction proceeds even before the temperature reaches a predetermined temperature, and a film is formed. Then, a film having a different film quality from the expected film quality after the predetermined temperature is formed in the lower layer, and the yield of the device may be reduced depending on the film quality of the lower layer.

In this regard, in the present invention, the reaction chamber is set to a non-reactive gas atmosphere, and after the reaction chamber is heated to reach a predetermined temperature, the reaction gas is introduced into the reaction chamber. Since it is after the intended predetermined temperature, a uniform film can be formed.

(Example) Next, an example in which the plasma processing method of the present invention is performed in a horizontal furnace using a parallel plate electrode type plasma CVD apparatus will be described.

This plasma CVD apparatus supplies a gas into a reaction tube set at a certain pressure, for example, a quartz reaction tube, and applies a high-frequency voltage between coaxially arranged electrodes at predetermined intervals inside the reaction tube. Then, a reaction gas flowing between the electrodes is excited to generate plasma energy, and the energy is used to grow a thin film on a wafer in a gas phase. The specific configuration is as follows.

A lid (3) for loading / unloading a semiconductor wafer (2) is provided at one end of a cylindrical container, for example, a quartz reaction tube (1), which is hermetically sealed to a diameter of, for example, 220 mm and a length of, for example, 2500 mm. A gas supply pipe (4) for flowing a gas, for example, a reaction gas, is connected to (3). A gas discharge pipe (5) for discharging the inflowing reaction gas is connected to the other end of the quartz reaction tube (1). For example, a heater (6) is provided in a cylindrical shape so as to surround the quartz reaction tube (1).

The wafers (2) carried into the lime reaction tube (1) are arranged, for example, as follows.

That is, a disk-like graphite plate (7A), (7B) having a diameter of, for example, 170 mm and a thickness of, for example, 8 mm made of a plasma electrode, for example, a heat-resistant material at regular intervals of 10 mm, for example
Are arranged, for example, 50 sheets. In this arrangement, the graphite plates (7A) and (7B) are coaxially arranged such that the centers thereof are substantially on one straight line. This arrangement is supported, for example, on a quartz glass board (8) on the graphite plate (7A),
Grooves (not shown) for fitting (7B) are provided at equal intervals of 10 mm.

It is not always necessary to set this groove, and of course, this interval may be changed sequentially as needed. For example, the distance may be changed as the distance increases in the gas flow direction.
This may be provided so that the back side compensates for a change in the inter-electrode gas concentration.

In order to commonly connect the rows of such graphite plates (7A) and (7B) every other sheet, the graphite plates (7A) and (7B) serving as electrode plates are provided with through holes (9). The connecting rods (10A) and (10B) for connecting the graphite plates (7A) and (7B) are provided in the holes (9). For example, when the quartz glass board (8) supporting the graphite plates (7A) and (7B) is directed downward, the through-hole (9) is formed at a middle position as the height of the graphite plates (7A) and (7B). Two locations are provided on each of the left and right sides of the peripheral edge.

By installing the connecting rods (10A) and (10B) in the through holes (9), respectively, there is an effect of electrical connection and mechanical holding. At this time, among these connecting rods (10A) and (10B), the upper left and lower right of the through holes (9) of the graphite plates (7A) and (7B) are the connecting rods (10A) for the anode, and the lower left and upper right Is a connecting rod (10B) for the cathode.

This connecting rod for anode (10A) and connecting rod for cathode (10B)
Are graphite plates (7A), (7
B) is in contact with The state of this contact is shown in FIG.
The connecting rod (10A) for the anode and the connecting rod (10B) for the cathode are made of a graphite plate (7A) with an insulating conductor (11) made of, for example, quartz or ceramic for the purpose of electrical insulation. Covers the part except for the contact part with (7B).

That is, the connecting rod (10A) for the anode is in contact with the graphite plate (7A) for the anode, and the nut (13) is used to wash the nut (13) using the thread (12) cut on the connecting rod (10A) for the anode. (1
4) Tighten through. This allows the connecting rod (1
The graphite plate (7A) is fixed to 0A). It is desirable that the nut (13) and the washer (14) are electrically conductive and heat-resistant, emit little impurities and do not react with the reaction gas. The connecting rod for the cathode (10B)
It is fixed to the graphite plate (7B) for the cathode in the same way as for the anode.

Further, the connecting rod (10A) for the anode and the graphite plate (7B) for the cathode are electrically insulated. This is because the connecting rod (10A) for the anode is covered with the sleeve (11) in the through hole (9). Similarly, the connecting rod (10B) for the cathode and the graphite plate (7A) for the anode are also electrically insulated. Connecting rods for these two anodes (10
A) is a connecting plate (1) before and after the group of graphite plates (7).
5) Connected. The same applies to the connecting rod (10B) for the cathode.

This makes it possible to provide at least two equipotential supply points for each of the graphite plates (7A) and (7B). The connecting rods (10A) and (10B) are connected to the terminals of the plasma excitation power supply. Dispersing the connecting rods (10A) and (10B) at a plurality of locations contributes to mechanical retention and electrical uniformity, but hinders the flow of gas and reduces the wafer (2). It may hinder set / reset, so it is necessary to set the optimal number. In addition, connecting rod (10A) (1
By providing the thread (12) in 0B), the electrode interval can be set and changed arbitrarily.

 Next, the operation of this device will be described.

Open the lid (3) of the quartz reaction tube (1), install the graphite plates (7A) and (7B) in each groove of the quartz board (8), and fix them with the connecting rods (10A) and (10B). . The graphite plate (7A), (7B) is loaded into the quartz reaction tube (1) with the wafer (2) supported on both sides. After loading, the lid (3) is closed.

Next, an argon gas, for example, is introduced as a purge gas into the quartz reaction tube (1), and the inside of the quartz reaction tube (1) is replaced with argon gas to form a purge gas atmosphere, and the inside of the quartz reaction tube (1) is maintained at 300 ° C. . Thereafter, a reaction gas such as silane gas 200 SCCM (Standard Cubic Cm / Mi
nutes) and 1600 SCCM of ammonia gas flowing through
Hold at 2 Torr. When this reaction gas flows into the graphite plate (7A) and (7B), a high frequency power, for example, 450 KHz, 400W power is applied between the graphite plates (7A) and (7B), and the atmosphere between the graphite plates (7A) and (7B) is applied. A plasma of the reaction gas is generated therein, and is excited to a high energy, and a plasma CVD film is uniformly formed on the surface of the wafer (2) supported by the graphite plates (7A) and (7B).

Such a reaction flows from the pipe (4) and is discharged to the pipe (5), and in the reaction of the reaction gas set to a predetermined gas pressure state, the connecting rods (10A), (10B), the graphite plate (7A) , (7B), the voltage distribution of each graphite plate (7A), (7B) is kept constant,
The effective plasma state is determined for each graphite plate (7A), (7B)
It is possible to generate a predetermined film pressure on the wafer (2) in the meantime.

Prior to the treatment with the reaction gas, the inside of the quartz reaction tube (1) is replaced with argon gas to make a purge gas atmosphere so that the inside of the quartz reaction tube (1) is maintained at 300 ° C. (2) and the heat transfer to the graphite plates (7A) and (7B) is performed not only by the radiation of the heater (6) but also by convection by argon gas. The temperature can be raised to a predetermined processing temperature. Therefore, processing efficiency is improved.

Next, another embodiment will be described. As shown in FIG. 4, in this embodiment, at least two pairs of connecting rods (21) are used. In this case, the electrode plate (22) does not need to be provided with a through hole. The electrode plate (22) is provided with at least two equipotential supply points per sheet. or,
The connecting rods (21) of each pair are connected to each other at at least one of the front, rear and middle of the group of electrode plates (22) or simultaneously with the connecting body (23).

The connecting body (23) is preferably made of a material that has heat resistance and does not react with the reaction gas, and may be electrically a conductor or a semiconductor. Further, the connecting rods (21) are alternately connected to the electrode plate (22) and the anode and the cathode alternately.
By providing at least two pairs of connecting rods (21) in this manner, the voltage distribution is constant, the electrode plate (22) can be reliably supported, and a constant interval between the electrode plates (22) can be maintained.

In this other embodiment, the pair of electrode rods (21) need not necessarily be used for power supply, and may be used only for supporting the electrode plate (22).

[Brief description of the drawings]

FIG. 1 is an explanatory view of a plasma CVD apparatus configured to carry out an embodiment of the present invention, and FIGS.
FIG. 4 is an explanatory view of an electrode in the figure, and FIG. 4 is an explanatory view of another embodiment. 1 ... quartz reaction tube 2 ... wafer 7A, 7B ... graphite plate 9 ... through-hole 10A, 10B ... connecting rod 15 ... connecting plate

Claims (2)

(57) [Claims] 1. A plurality of workpieces housed in a reaction chamber having a gas supply section for introducing a gas and a gas discharge section for discharging the introduced gas are heated by a heater, and further formed into a film. A plasma processing method for performing a process of forming a predetermined film on the object to be processed in a plasma atmosphere of a reaction gas for use, a step of loading a plurality of objects to be processed into the reaction chamber, after the loading, the reaction chamber To a non-reactive gas atmosphere; heating the reaction chamber to a predetermined temperature by heating with a heater under the non-reactive gas atmosphere; Introducing a plasma into the reaction chamber and generating plasma in the reaction chamber to form a predetermined film on each of the objects to be processed. 2. The plasma processing method according to claim 1, wherein the non-reactive gas is an argon gas.