JPS59127644A - Apparatus for controlling generation of stock gas - Google Patents

Abstract

PURPOSE:To precisely control the flow amount of generated stock gas even in a small flow amount, by a method wherein a gaseous mixture is branched into two streams at the outlet of an output arranged pipe and a second gas flow controller is provided to one of branched arranged pipes while a gas resistance means is provided to the other branched arranged pipe. CONSTITUTION:The outlet of carrier gas is branched by a branching device 20 and second flow controller 21 similar to a first flow controller 11 is provided to one of branched pipes while a gas resistance means 23 for imparting resistance to a gas flow amount is provided to the other branched pipe and taken out from an outlet 22. Stock gas of which the flow amount is regulated by the second gas flow amount controller 21 is sent out from the outlet 22 and the residue in the stock gas which is generated in a bubbler 12 and issued from the outlet 22 is taken out from an outlet 24 through the gas resistance means 23.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a raw material gas generation control device that precisely controls the flow rate of gas generated by a bubbler.

In general, as a method for generating and supplying raw material gas in crystal growth equipment 1 or chemical synthesis equipment, a certain gas such as nitrogen or hydrogen (hereinafter referred to as carrier gas) is placed in a sealed container i (hereinafter referred to as ba, plastic). There is a method in which the gas is passed through a raw material liquid stored in a tank, the raw material liquid vapor is included in the gas, and the gas is sent to the reaction section. At this time, the carrier gas contains vapor of the raw material liquid at a concentration corresponding to the saturated vapor pressure of the raw material liquid.

FIG. 1 shows a configuration diagram of a conventional device for generating raw material gas and controlling its flow rate. This configuration is based on the assumption that a raw material liquid 13 is stored in a bubbler 12 and a carrier gas is passed through it in the direction of an arrow 16. At that time, the carrier gas contains the saturated vapor of the raw material liquid 13.The carrier gas containing the raw material vapor is taken out from the bubble 212 in the direction of the arrow 17 and sent to the primary reaction section. This bubbler 12 is housed in a container 19 storing a liquid 18 (water, ethylene glycol, etc. is used) whose temperature is precisely controlled to keep the bubbler 12 at a constant set temperature. The vapor pressure is determined by this set temperature.

The flow rate of this carrier gas is controlled by a gas flow rate regulator 11, which is a combination of a flow meter and a flow rate control valve, or a mass 70-controller.

By the way, the net flow rate f of the raw material gas sent to the reaction section is
is determined by a linear equation.

V9=(fo+fs)×−・・・・・・・・・(1)I)T Here, sfo is the flow rate of the carrier gas, and the pressure of the carrier gas containing the raw material vapor is I)T, the saturated vapor of the raw material liquid Set the pressure to 9. Since normally fan > fs, (1)
The equation can be approximated as shown in equation (2).

fs=fox Color...---(2)T As can be seen from this equation (1), the flow rate control of the raw material gas is
Carrier gas flow rate f. This is done by controlling the saturated vapor pressure of the raw material. Furthermore, this is done by controlling the vapor pressure. Further, the vapor pressure λ is controlled by controlling the temperature of the bubbler 12.

In this raw material gas control device, #, when the amount is large to some extent (lcc/m1n (lscc/m1n in standard state)
) and above) the flow rate is well controlled. However, in a region where the flow rate is small, the number of bubbles generated in the bubbler decreases, so the gas flow at the outlet of the source gas generation control device pulsates, making it difficult to maintain a constant flow rate. In the vapor phase growth method of semiconductors using organometallic raw materials (hereinafter referred to as No-VPg), the organometallic raw materials are fed into a reaction part by a raw material gas control device using hydrogen as a carrier gas. For example, Ga doped with zinc at a low concentration (p(1018c77L-3))
Let us consider the case where dithyl zinc (DgZn), which is used as a dopant raw material, is fed into the first reaction section of the present raw material gas generation control device when growing a thin film of As. At this time DEZ
When n is stored in the bubbler 12 and the bubbler temperature is 0'O, the flow rate of the carrier gas (hydrogen) is 0.1c under standard conditions.
c/min (0.1 scc/min) or less. This corresponds to the generation of about 24 bubbles per minute even if the diameter of the bubbles generated in the bubbler is 1 mm. When crystal growth is performed under these conditions, the flow rate of the dopant gas DEZn changes over time as shown in the graph in Figure 2 (a), and as a result, the hole concentration in the grown semiconductor layer changes as shown in Figure 2 (a) in the direction of the growth layer. (It fluctuates like the BLO graph.

An object of the present invention is to overcome these conventional drawbacks and provide a source gas generation control device that can precisely and stably control the flow rate of source gas generated from a bubbler even at a small flow rate.

The configuration of the present invention provides a raw material gas generation control device that includes a first gas flow rate regulator in the middle of a pipe that introduces a carrier gas into a liquid raw material stored in a bubbler. The mixed gas with the raw material gas is branched into two at the outlet of the output pipe, and each of these branched output pipes is equipped with a second gas flow rate regulator, and the other branch pipe is equipped with a gas resistor that provides resistance to the gas flow rate. It is characterized by having a means.

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

The block diagram of the embodiment of the present invention shown in FIG. 3 is shown. Number 1 in the diagram
The configurations 1 to 19 are the same as the conventional configuration shown in FIG. In this embodiment, the outlet of the carrier gas having a conventional configuration is branched into two branches by a bifurcater 20, and a second gas flow regulator 21 similar to the first gas flow regulator 11 is connected to the outlet.
The gas is discharged from the outlet 22 by providing a gas resistance means 23 for providing resistance to the gas flow rate at the other end of the branch. As the gas resistance means 23, it is possible to use pulp whose gas flow rate can be adjusted or a material made of thin pipes to provide resistance. The raw material gas whose flow rate is adjusted by the second gas flow rate regulator 21 is sent out through the outlet 22. On the other hand, out of the raw material gas generated by the bubbler 12, the remainder of what is sent out from the outlet 22 is transferred to the gas resistance means 2.
3 through exits 24 and 9. In this way, the flow rate of the carrier gas supplied to the bubbler 12 and the flow rate of the carrier gas containing the raw material gas can be independently controlled.

There are two uses when using this embodiment of the configuration.

The first usage is to take the raw material gas delivered from the outlet 22 into the next reaction section.

The device of this example is used for DE to introduce zinc as a dopant in the growth of GaAs by the MO-VPE method.
It is used as a Zn vapor generation process control system, IJBZni is used as the raw material liquid 13, and hydrogen is used as the carrier gas. The carrier gas containing DgZn is sent to the next crystal growth furnace through the outlet 22.

For example, when doping with a hole concentration of IQ"(m" or less), the bubbler temperature of DEZn is set to 0 as described above.
℃, and the flow rate of the carrier gas containing DgZn is approximately Q, l.
It must be less than or equal to SCC/lTl1n. In this case, if the flow rate of the carrier gas hydrogen is set to 1 sec/min in the first flow rate regulator 11 located upstream of the bubbler 12, at this level of flow rate, no pulsating flow is observed at the outlet of the bubbler 12 and a constant flow rate of gas is generated. can occur. Further, the flow rate of the carrier gas containing DEZn in the second flow rate regulator 21 is controlled to a predetermined flow rate of 0.1 scc/min or less, and is sent to the outlet 22, and the remaining gas is released to the outside from the outlet 24. be done.

The flow rate of the carrier gas containing DEZn obtained in this example is shown in FIG.
The hole concentration distribution in the growth layer direction of the s-crystal is shown in the graph of FIG. 4 (bl).

Next, the second usage is to send the second flow Jij: the gas on the outlet 24 side, which does not pass through the regulator 21, to the reaction section through the gas resistance means 23. Second flow regulator 21
The gas whose flow rate has been adjusted is passed through the entire outlet 22 and discarded to the outside.
The remaining gas is sent to the reaction section through the outlet 24. In this way, the difference in the flow rate between the gas flow rate generated from the bubbler 12 set by the first flow rate regulator 11 and the gas flow rate discarded from the outlet 22 is sent to the reaction section.

The mass flow controller used as the flow rate regulator 11.21 usually controls the flow rate using a combination of a heater and a thermocouple. When a gas containing triethyl indium (TEIn) or triethyl gallium (TEGa) is supplied to this mass flow controller as a raw material gas, the digas may be thermally decomposed by the heater. This second
By using this method, this problem can be avoided because the raw material gas used for the reaction does not pass through the flow controller. In this case, DEZn is used as the raw material liquid, and the gas outlet 24 that does not pass through the second flow rate regulator 21 is used.
The flow rate of the carrier gas containing DEZn that is rapidly discharged is set to 0.1 sec/m I n (i.e., 0.9 cc/m I from the second flow rate regulator 21).
As a result of doping GaAs with zinc in the same way as in the first method, almost the same results were obtained in the second method.

The present invention has been described above in the case where it is applied to an apparatus for doping zinc during growth of GaAs by MO-VPE, but it can also be applied to an apparatus for growing other semiconductor materials or an apparatus for synthesizing other chemicals. It goes without saying that it can be done.

As described above in detail, by applying the present invention, it is possible to realize a device that precisely and safely controls the flow rate of the raw material gas generated from the hubbler even at a small flow rate.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a conventional raw material gas generation control device, and Figure 2 (al, (bl) is the DE sent out from the device in Figure 1.
A graph showing changes in Zn flow rate over time, a distribution diagram of the hole concentration in the growth layer direction of GaAs grown using DEZn as a dopant, and Figure 3 is a cross-sectional view of an example of the present invention.
FIGS. 4(a) and 4(1) are graphs and distribution charts similar to FIGS. 2(a) and 2(b) obtained in accordance with the examples of the present invention. In the figure, 11.21...Flow rate regulator, 12...
Bubbler, 13... Raw material liquid, 14...
Carrier gas bubbles, 15... Carrier gas outlet, 16.17... Gas flow direction arrow, 1
8...liquid, 19...liquid container, 2
0...Bifurcater, 22.24...Outlet, 23...Gas resistance means. Agent Patent Attorney Susumu Uchihara

Claims (1)

[Claims] In a raw material gas generation control device equipped with a first gas flow rate regulator in the middle of a pipe that introduces a carrier gas into a liquid raw material stored in a bubbler, a mixed gas of a carrier gas and a raw material gas generated by the bubbler is produced. is branched into two at the outlet of the output pipe, 10,000 of these branched pipes are equipped with a second gas flow rate regulator, and 10,000 of the branched pipes are equipped with gas resistance means for providing resistance to the gas flow rate. A raw material gas generation control device characterized by: