JPS59185772A - Control device for flow rate of evaporating gas in high melting metallic compound - Google Patents

Abstract

PURPOSE:To perform control with high accuracy by providing a measuring part for the concn. of carrier gas and metallic evaporating gas in a thermostatic oven, and controlling the flow rate of the carrier gas and the amt. of the metallic evaporating gas to be generated. CONSTITUTION:A thermostatic oven 1, a source tank 2 which is provided therein and contains a high melting metallic compd. 3 to be evaporated, a feed pipe 5 which is connected thereto and feeds the carrier gas from a supplying source 4 to the tank 2, a delivery pipe 6 which delivers the gaseous mixture composed of the evaporating gas of the compd. 3 generated in the tank 2 and the carrier gas to the outside of the oven 1, a sensor 10 for measuring the concn. of the carrier gas and a sensor 12 for measuring the concn. of the gaseous mixture which are attached respectively in the pipe 5 and the pipe 6 and measure the concn. of the carrier gas and the gaseous mixture flowing in the respective pipes, and a control device 19 which controls the flow rate of the carrier gas and the evaporating rate of the compd. 3 in accordance with the concn. measuring signal therefrom are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flow rate control device that is capable of controlling the flow rate of a high melting point metal compound with high accuracy when the compound is vaporized and transported.

For example, in the production of VLSIs, a high melting point metal compound used as a gate material with low resistivity is heated and evaporated, and the resulting evaporated gas is deposited on a semiconductor wafer through a gas phase reaction in a reactor. In this case, it is very important to accurately control the flow rate of evaporated gas in order to obtain high-quality products.

When performing this type of flow rate control, a carrier gas control method is generally employed. This method maintains the vapor pressure constant by keeping the heating temperature of the material constant, and also obtains a constant amount of evaporated gas by controlling the flow rate of the carrier gas for transporting the evaporated gas. , in this method, although it is possible to estimate the flow rate of evaporated gas as a function of heating temperature and carrier gas flow rate, it is impossible to directly measure it; It is not possible to manage or control changes in the amount of evaporation due to changes in temperature or changes in temperature associated with evaporation.

An object of the present invention is to provide a flow rate control device that can control the flow rate of evaporative gas with high precision.

In order to achieve the above object, the flow rate control device of the present invention includes a constant temperature bath whose internal temperature can be set to an arbitrary high temperature, and a source installed in the constant temperature bath to accommodate a high melting point metal compound to be evaporated. a tank, and connected to the source tank;
A feed pipe that sends a carrier gas from a supply source to the source tank, and a mixed gas of the carrier gas and the evaporated gas of the high melting point metal compound evaporated in the source tank from the source tank to the outside of the constant temperature chamber. A thermal dynamic sensor for measuring the carrier gas concentration and a mixed gas concentration measurement sensor that is attached to the above-mentioned inlet pipe and the outlet pipe respectively in a thermostatic chamber and measures the concentration of the carrier gas and mixed gas flowing in each pipe. A control device that controls the flow rate of the carrier gas or the amount of evaporation of the high melting point metal compound based on the concentration measurement signal from the sensor.

Embodiments of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, 1 is a constant temperature bath, and the constant temperature bath 1 is
The internal temperature can be set to any desired high temperature.

A closed source tank 2 containing a high melting point metal compound 3 to be evaporated is disposed inside the constant temperature bath 1, and a carrier gas from a supply source 4 is fed into the source tank 2. The feed pipe 5 is connected to the feed pipe 6 for supplying the mixed gas of the high melting point metal compound 3 evaporated in the source tank 2 and the carrier gas to the reactor 7. The inlet pipe 5 is provided with a valve 8 and a carrier gas flow rate sensor 9 in a portion located outside the constant temperature chamber 1, and a thermal sensor 11 for measuring the concentration of carrier gas in a portion located inside the constant temperature chamber 1. On the other hand, the delivery pipe 6 is provided with a thermal sensor for measuring the concentration of the mixed gas in the part located inside the thermostatic oven 1, and a thermodynamic sensor for preventing condensation of evaporated gas is provided in the part located outside the thermostatic oven 1. A heater 13 is attached.

The thermal sensors 11 and 12 utilize the fact that the thermal conductivity of gas differs depending on its components, and detect the change as a change in resistance value.

For example, in the case of a reduced pressure type vapor phase growth apparatus for film growth, a reducing gas supply source 14 for reducing evaporated gas in the mixed gas is connected to the reactor 7 via a flow rate regulator 15. Furthermore, a vacuum pump 16 is connected to keep the inside of the reactor 7 in a reduced pressure state. In addition, 17 in the figure
18 is a vacuum gauge, and 18 is a reactor heater for vapor phase growth of evaporated matter using reducing gas.

Further, the control device 19 to which the thermal sensors 11 and 12 are connected is connected to a bridge circuit for determining the concentration ratio of the carrier gas and the mixed gas by bridge-coupling the thermal sensors 11 and 12, and the bridge circuit an arithmetic circuit 21 that calculates the flow rate of evaporated gas based on the concentration ratio signal from the carrier gas flow rate sensor 9 and a flow rate signal from the carrier gas flow rate sensor 9, a display unit that displays the calculated evaporative gas flow rate, and the arithmetic circuit m The control circuit B compares the evaporative gas flow rate signal of the carrier gas with the set value in the setting device U, opens and closes the valve 8 according to the difference therebetween, and controls the flow rate of the carrier gas.

Next, the operation of the flow rate control device having the above configuration will be explained.

In its use, a high-purity ultrafine powdered high-melting metal compound (for example, molybdenum pentachloride, tungsten hexachloride, etc.) is stored in the source tank 2, and the temperature of the constant temperature bath 1 is set so that the above-mentioned metal evaporates. Raise the temperature to a level where it is sufficiently generated.

In this state, when an inert carrier gas such as argon or helium is fed into the source tank 2 from the supply source 4 through the feed pipe 5, the evaporated gas generated in the source tank 2 mixes with this carrier gas. , and transported to the reactor 7 through the delivery pipe 6. In this case, the constant temperature chamber 1 is
The low-temperature carrier gas that has flowed into the chamber is heated to the chamber temperature in the thermostatic chamber 1, and its concentration is measured by a thermal sensor 11 before flowing into the source tank 2. The concentration of the mixed gas flowing through the interior is measured by thermal sensors 11 and 12.
The concentration measurement signal from the carrier gas flow rate sensor 9 is converted into a concentration ratio signal by the bridge circuit, and is input to the calculation circuit 21 together with the flow rate signal from the carrier gas flow rate sensor 9 to calculate the flow rate of the evaporated gas. The calculated flow rate signal is then input to display n and control circuit B, where it is displayed as an evaporated gas flow rate, and in the control circuit, the evaporated gas flow rate is compared with the set value in the setter row. At the same time, the flow rate of the carrier gas is adjusted by controlling the pulp 8 so that the difference between them becomes zero, and thereby the flow rate of the vaporized gas in the delivery pipe 6 is maintained at the set value. At this time, in order to keep the O reference point of the gas concentration ratio signal constant, it is desirable that the gas humidity in the inlet pipe 5 and the outlet pipe 6 be equal. It is necessary to make the mixed gas temperature in the tube 6 higher than that in the source tank. Therefore, a temperature sensor is attached to the inlet pipe 5 side, and a heater is provided to the outlet pipe 6 side, and the temperature of the carrier gas on the inlet pipe 5 side is determined based on the temperature of the carrier gas.
It may be configured to control the temperature of the mixed gas at °C.

The mixed gas that has been kept warm by the heater 13 and has flowed into the reactor 7 is heated by the heater 18 together with a reducing gas such as hydrogen that is supplied into the reactor 7 via the flow rate regulator 15.
Here, a gas phase reaction occurs and the material is deposited on the surface of a semiconductor wafer or the like. At this time, the inside of the reactor 7 is generally kept under reduced pressure by a vacuum pump in order to improve the gas phase reaction.

Note that the unreacted mixed gas that has passed through the reactor 7 is exhausted through the vacuum pump 16.

In the above embodiment, the flow rate of the evaporated gas is controlled by AT control of the carrier gas by opening and closing the pulp 8, but the flow rate of the evaporated gas is controlled by controlling the heating temperature of the source tank 2 via the control circuit η. The amount of evaporation may be controlled.

According to the flow rate control device of the present invention described above, there are remarkable effects as listed below.

(1) The flow rate of evaporated gas is controlled by directly measuring the concentration of the mixed gas sent out from the source tank, so the amount of evaporation changes due to changes in the surface of the harmful substance over time, temperature changes accompanying evaporation, etc. Nevertheless, the flow rate of evaporated gas can be controlled with high precision.

(2) The concentration detection part for generating evaporated gas and controlling its flow rate is installed in a thermostatic chamber, and the evaporated gas controlled at a predetermined flow rate is sent to the next process, resulting in high quality with good reproducibility. film growth can be performed.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a flow rate control device according to the present invention. 1... Constant temperature bath, 2... Source tank, 3...
...Low pressure vapor substance, 4... Supply source, 5... Feed pipe,
6... Delivery pipe, 11. , 12... Thermal sensor, 19... Control device. Patent applicant Nippon Tailan Co., Ltd.

Claims (1)

[Claims] 1. A Sos tank for accommodating a constant-temperature bath compound whose internal temperature can be set to an arbitrary high temperature, and a SoS tank connected to the source tank and supplying a carrier gas from a supply source to the source tank. a delivery pipe for delivering a mixed gas of the vaporized gas of the high melting point metal compound evaporated in the source tank and a carrier gas from the source tank to the outside of the thermostatic chamber; A thermal dynamic sensor for measuring carrier gas concentration and a thermal dynamic sensor for measuring mixed gas concentration, which are attached to the pipe and the delivery pipe, respectively, and measure the concentration of the carrier gas and mixed gas flowing in each pipe, and based on the concentration measurement signal in the sensor. A control device for controlling the flow rate of a carrier gas or the amount of evaporation of a high melting point metal compound using a high melting point metal compound.