JPH0795529B2 - Vertical diffusion CVD system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical diffusion CVD apparatus which is one of semiconductor manufacturing apparatuses, and more particularly to improvement of atmospheric gas control in a load lock chamber.

[0002]

2. Description of the Related Art In a vertical diffusion CVD apparatus, an airtight reaction chamber composed of a vertically arranged quartz tube, a heater surrounding the reaction chamber, and a heater provided below the reaction chamber. An airtight load lock chamber provided, and a wafer loading mechanism, a wafer transfer mechanism, provided inside the load lock chamber,
The boat is mounted on the wafer loading mechanism and is loaded with wafers in multiple stages.

The wafers are processed by loading the wafers loaded into the load lock chamber into the boat by the wafer transfer mechanism, loading the boat into the reaction chamber by the wafer loading mechanism, and then in a high-temperature reaction gas atmosphere. When the wafer is processed, the boat is pulled out to the load lock chamber by the wafer loading mechanism, and the wafer is taken out from the boat by the wafer transfer mechanism.

In the above-described series of wafer processing, the load lock chamber needs to be in an inert gas atmosphere having a predetermined oxygen concentration in order to prevent oxidation of the wafer. Further, since unprocessed wafers are carried into the load lock chamber from the atmosphere and processed wafers are carried out from the load lock chamber, the load lock chamber is opened every time the wafer is carried in and out. Therefore, after opening the load-lock chamber, the gas control to make the inside of the chamber as desired as possible in an inert gas atmosphere is very important in terms of equipment mobility, inert gas consumption, or product quality assurance. This is one of the factors.

Conventionally, an inert gas, N
A supply pipe for supplying ₂ gases and a discharge pipe are provided, and an inert gas, N ₂ gas is supplied to the load lock chamber from the supply pipe and discharged from the discharge pipe to thereby inactivate the inside of the load lock chamber. It was replaced with N ₂ gas.

[0006]

However, since only one discharge pipe is conventionally provided, if the diameter of the discharge pipe is increased in order to increase the replacement speed, the reverse flow (back diffusion) from the discharge pipe is caused. Occurs, and there is a problem that a predetermined oxygen concentration cannot be obtained, and if the diameter of the discharge pipe is reduced in order to prevent backflow from the discharge pipe, there is a problem that the replacement time becomes long.

In view of the above situation, the present invention is a vertical diffusion CV capable of obtaining a predetermined oxygen concentration while the replacement time is short.
It is intended to provide a D device.

[0008]

According to the present invention, in a vertical diffusion CVD apparatus in which a load lock chamber is airtightly connected under a reaction chamber, the exhaust gas from the load lock chamber is passed through a plurality of exhaust pipes. It is characterized in that an oxygen concentration meter for detecting the oxygen concentration in the load lock chamber is provided and the exhaust pipe for exhausting the filling gas is selected according to the oxygen concentration in the load lock chamber. It is a thing.

[0009]

When the oxygen concentration is high, the exhaust pipe is selected so that the exhaust flow rate is large, and when the oxygen concentration is less than the predetermined value, the exhaust pipe is selected so that the exhaust flow rate is small.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a reaction chamber, 2 is a heater, 3 is a load lock chamber which is airtightly connected to the reaction chamber 1, 4 is a boat for holding wafers in multiple stages, and the boat 4 is a wafer. It is moved up and down by the charging mechanism 5, and is charged into and discharged from the reaction chamber 1. The wafer transfer mechanism 6 has a wafer handling unit 7 that moves up and down, and loads and unloads wafers to and from each stage of the boat.

A supply source (not shown) of an inert gas or N ₂ gas (hereinafter referred to as a filling gas) is connected to the load lock chamber 3 via a mass flow controller 8 and a large-diameter exhaust pipe. 9 is connected, and the pressure inside the load lock chamber 3 is detected by a pressure sensor 14, and the pressure signal of the pressure sensor 14 is input to the mass flow controller 8.

The exhaust pipe 9 is provided with a first solenoid valve 10, and further a small-diameter bypass pipe 11 connecting the upstream side and the downstream side of the solenoid valve 10. The bypass pipe 11 has a second
A solenoid valve 12 is provided. The opening and closing of the first electromagnetic valve 10 and the second electromagnetic valve 12 are controlled by a controller 13. An oxygen concentration meter 16 is provided upstream of the bypass pipe 11 of the exhaust pipe 9 via an electromagnetic valve 15. The oxygen concentration meter 16 detects the oxygen concentration in the exhaust gas, and the detection result is described above. The controller 13 is input.
Reference numeral 17 is a supply / stop solenoid valve for supplying and stopping the filling gas.

The operation will be described below.

Before the wafer processed in the reaction chamber 1 is drawn into the load lock chamber 3, the inside of the load lock chamber 3 is filled with a filling gas atmosphere having a predetermined oxygen concentration or less.

The stop solenoid valve 17, the first solenoid valve 1
When 0 is opened and the second solenoid valve 12 is closed, the filling gas whose flow rate is set by the mass flow controller 8 is supplied to the load lock chamber 3 and further exhausted from the exhaust pipe 9. The oxygen concentration of the filling gas in the exhaust gas is detected by the oxygen concentration meter 16 and monitored by the controller 13. Thus, when the oxygen concentration reaches a set value, for example, 1% or less, the controller 13 sets the first electromagnetic valve 10 in the closed state and the second electromagnetic valve 12 in the open state to fill gas. Is exhausted through the bypass pipe 11.

At the initial stage of filling the filling gas having a high oxygen concentration, the large-diameter exhaust pipe 9 exhausts the gas, and when the oxygen concentration becomes lower than the set value, the small-diameter bypass pipe 11 exhausts the gas. It is possible to fill the filling gas in a short time, prevent backflow from the exhaust pipe side, and reliably reach the desired oxygen concentration.

After the desired oxygen concentration is reached, the filling gas is further supplied and circulated to maintain the oxygen concentration.

The mass flow controller 8 controls the flow rate of the filling gas based on a signal from the pressure sensor 14 so that the pressure inside the load lock chamber 3 does not exceed a set value.

In the above embodiment, it is assumed that the filling gas is filled by the gas purging method, the load lock chamber 3 has a volume of 500 l, a flow rate of 200 l / min, an exhaust pipe inner diameter of 20 mm,
When the inner diameter of the bypass pipe is 11 mm, the replacement time is about 60 minutes, and the flow rate for maintaining the oxygen concentration of 1 ppm or less is about 80 l / min. Therefore, it is possible to shorten the time by about 35 minutes compared with the case of replacing only with the exhaust pipe inner diameter of 9.5 mm.
Exhaust pipe inner diameter (please enter the specific value of the conventional example) mm
The flow rate of the filling gas to be maintained may be 120 l / min less than the case where the replacement is performed only with the gas.

In the above embodiment, the small-diameter exhaust pipe is provided as a bypass pipe, but it may be connected to the load lock chamber independently of the large-diameter exhaust pipe. In addition, a plurality of exhaust pipes may be provided and the diameters of the exhaust pipes may be selected to be different from each other.

[0022]

As described above, according to the present invention, the oxygen concentration of the filling gas to be filled in the load lock chamber can be kept below a predetermined value in a short time, and the backflow from the exhaust system can be prevented.
The filling can be performed reliably.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an embodiment of the present invention.

[Explanation of symbols]

 1 Reaction Chamber 3 Load Lock Chamber 9 Exhaust Pipe 10 First Solenoid Valve 11 Bypass Pipe 12 Second Solenoid Valve 16 Oxygen Analyzer

Claims (1)

[Claims] 1. In a vertical diffusion CVD apparatus in which a load lock chamber is hermetically connected below a reaction chamber, the filling gas from the load lock chamber is exhausted through a plurality of exhaust pipes and the load lock chamber is also provided. A vertical diffusion CVD apparatus characterized in that an oxygen concentration meter for detecting the oxygen concentration inside is provided, and an exhaust pipe for exhausting a filling gas is selected according to the oxygen concentration inside the load lock chamber.