JPS60157017A - Flow rate detector of reaction gas for organic metal growth in gas phase - Google Patents

Abstract

PURPOSE:To measure accurately the flow rate of a reaction gas for a MOCVD by providing a means for irradiating a vacuum ultraviolet light to a flow passage of the reaction gas for the organic metal growth in gas phase (MOCVD) and a means for impressing a voltage vertically to the optical passage. CONSTITUTION:A vacuum ultraviolet light discharging tube 3 such as Ar, H2, Kr, Xe discharging tube is attached in an ionizing chamber 1 communicating to a reaction gas supplying passage to the MOCVD apparatus (figure is omitted) through a gas introducing hole 2, and attached with an optical trap (figure is omitted) at the position opposed to the tube 3. An electrode 7 for impressing the voltage vertically to the optical passage of the ultraviolet light from the tube 3 is provided, an ion collector 9 is arranged opposingly to the electrode 7, and the collector 9 is connected to an ammeter 10 for fine current. In this way, since precise characteristic control of film is performed, the flow rate of the reaction gas for the MOCVD can be measured accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flow rate detector for a reaction gas for organometallic vapor phase growth.

The metal organic chemical vapor deposition method (MOCVD method), which grows compound semiconductor crystals by thermally decomposing organic gold, is easy to obtain uniform growth over a large area and has good steepness, so it has recently been used to create short wavelength lasers, etc. By the way, the MOCVD method is rapidly becoming used for
All of the component elements and thorns of the compound crystal to be grown can be introduced into the reaction tank in a gaseous state. Therefore,
The properties of the grown layer, such as the composition of the grown layer, the growth rate, or the thickness of the grown film, can be controlled by flow clauses, i.e., the properties of the grown layer strongly depend on the amount of reactant gas supplied. ing. The amount of reactant gas supplied is smaller than that of carrier gas (hydrogen), and typical examples include A and H.
In the case of No. 3, a dilution of 10 is used, and in the case of organometallic gas, bubbling with hydrogen is performed.

However, although the characteristics of the grown layer can be controlled by adjusting the flow rate, it is not known to what extent the organometallic gas is mixed into the carrier gas (hydrogen) and transported during bubbling. In reality, the carrier gas flow rate and bubbler temperature are only controlled by trial and error, and in order to better control the characteristics of the growth layer, it is necessary to know the exact value of how much gas is actually flowing. 〇An object of the present invention is to provide a method for detecting the flow rate of a reaction gas for organic metal vapor phase growth, which accurately measures the flow rate of a reaction gas for MOCVD in order to precisely control the characteristics of a film.

In order to achieve this first objective, the flow rate detector according to the present invention includes means for irradiating vacuum ultraviolet light onto the flow path of a reaction gas for organometallic vapor phase growth, and a means for applying a voltage perpendicular to the optical path of the vacuum ultraviolet light. A micro-ammeter is provided to ionize only the reactive gas using vacuum ultraviolet light and detect the ion current value, and the flow rate of the reactive gas is measured from the ion current value detected by the micro-ammeter. Hereinafter, the present invention will be described with reference to actual examples with reference to the accompanying drawings.

FIG. 1.2 schematically shows an embodiment of the gas flow rate detector, and 1 is an ionization chamber that communicates with a reaction gas supply passage to an MOCVD apparatus (not shown) through a gas inlet 2;
A vacuum ultraviolet light discharge tube 6 such as an A', H2°Kr, A trap 5 is attached, and this optical trap 5 is provided with an anode 6.

An electrode 7 is provided for applying a voltage perpendicular to the optical path of the ultraviolet light from the zero discharge tube 3, which acts to absorb secondary electrons emitted by ultraviolet light, and this electrode 7 is connected to a power source 8. On the other hand, an ion collector 9 is arranged opposite to the electrode 7, and this ion collector 9 is connected to a microammeter 10. In FIG. Parts corresponding to those shown in Fig. 2 are indicated by the same reference numerals.In Fig. 3, 11 is a filter, 12.
13 is a bypass flow rate variable pulp.

The ionization potential of the reaction gas used in Fl(oCVD) is lower than the ionization potential of hydrogen used as a carrier gas, as illustrated in the table below.

Therefore, the Ar resonance line (11,6 eV, 11.8 e
V), Kr resonance line (to, 03 eV, 10.6
4 eV) and It2 life alpha rays (10.2ev)
By emitting vacuum ultraviolet light into the ionization chamber 1, only the reaction gas can be ionized.

In fact, when the reactive gas and carrier gas from the gas inlet 2 pass through the ionization chamber 1 and flow to the exhaust gas treatment system, only the reactive gas is ionized by the vacuum ultraviolet light irradiation trap from the radiation tube 3, and the carrier gas is ionized. Gaseous hydrogen is not ionized.

The ion current at this time is detected by a microcurrent meter 10 connected to the ion collector 9. In this way, the microammeter 10
The concentration of the reactant gas is measured based on the value of the ionic current detected in the step. FIG. 4 shows the relationship between the ion current and the gas flow rate measured in this way.

Figure 5 shows the gas flow rate detector of the present invention in an actual MOCvD.
An example of use applied to the device is shown below. 14 to 16 are gas flow rate detectors configured to detect the flow rates of each of the three reaction gas components; Al-A3.81 to B3 are pulp; 1
7 is the reaction monk of the phantom CVD device.

Each element is connected as shown. When measuring the gas flow rate in the apparatus configured as described above, first, the pulps A1 to A3i are closed, the pulps 81 to B3 are opened, and the detectors 14 and 1 are connected to each reactant gas component.
Send it to 5.16. In this way, each detector measures the concentration of the reactant gas. Then, after performing precise flow control of the reaction gas based on the measurement results, valves B1 to B
At the same time as closing 3, valves A1 to A3 'f: open M
Supplying Reactant Gas to Reaction '417 of OCvD Device As explained above, according to the present invention, it is possible to precisely control the organometallic gas in MOCVD, which has been insufficiently controlled in the past. The composition distribution and impurity distribution of the Si-grown layer can be made steep, and a uniform film can be obtained with good reproducibility. Therefore, the detector of the present invention is of great help in making compound semiconductors hostile in the MOCVD method.

[Brief Description of the Drawings] Fig. 1.2 is a schematic plan view and cross-sectional view showing the configuration of the gas flow rate detector of the present invention, and Fig. 3 shows a reaction gas flow path system for the device shown in Fig. 1.2. Diagram - Figure 4 is a graph showing the relationship between ion current and gas flow rate, and Figure 5 is a schematic diagram showing an example of applying the detector of the present invention to an MOCVD device.@In the figure, 1: Ionization chamber , 6: discharge tube, 5: optical trap, 7: electrode, 9: ion collector, 102 microcurrent meter. Fig. 1 Fig. 2 Fig. 3 Sword λ helmet amount (SCCm) February 24, 1980 Mr. Commissioner of the Japan Patent Office 1 Indication of the case 1983 Patent Application No. 12064 2 Name of the invention Organometallic gas Reaction gas for phase growth V) Detector 3, relation to the case of the person who makes corrections to the flow Patent applicant address 2500 Hagizono, Chigasaki City, Kamarayo Prefecture Name Japan Vacuum Technology Co., Ltd. 4, agent address 105 Address Tokyo Bussan Building Annex, 1-1-15 Nishi-Shinbashi, Minato-ku Tel: (591) 02616, Contents of the amendment Attached drawing 9 Figure 3, ``Kirisu'' general purpose correction.

Claims (1)

[Claims] A means for irradiating a flow path of a reaction gas for organometallic vapor phase growth with vacuum ultraviolet light and a means for applying a voltage perpendicular to the optical path of the vacuum ultraviolet light are provided, and only the reaction gas is ionized by the vacuum ultraviolet light, Flow rate detection of a reaction gas for organometallic vapor phase growth, characterized in that a microammeter is provided to detect the ion current value, and the flow rate of the reaction gas is measured from the ion current value detected by the microammeter. vessel.