JPS5855119B2 - Vapor phase growth method and equipment for magnesia spinel - Google Patents

Description

[Detailed description of the invention] The chemical formula is n Mg'OHAz2o s-However, n
refers to the manufacturing method of magnesia spinel, which is represented by - which refers to the number of moles of MgO.
The present invention relates to a method of vapor-phase growth of magnesia spinel instead of sapphire in semiconductor devices, which is generally referred to as .

The present invention further relates to an apparatus for performing this vapor phase growth.

SO8 has various attractive features and is attracting attention as the ace of high-speed logic elements, but on the other hand, it has various problems and has not become mainstream in the current semiconductor industry.

The problems are as follows.

(1) Higher cost than homosilicon epitaxial growth.

The reasons for this are (a) that the sapphire substrate itself is expensive, and (0) that surface treatments such as polishing techniques and chemical surface treatment techniques are difficult for sapphire.

(2) The crystallinity of the silicon active layer is poor compared to homosilicon epitaxial growth.

The reason for this is considered to be (a) unstable At atoms mixed into the silicon epitaxial active layer as P-type impurities due to the poor crystallinity of the sapphire substrate.

Next, <o) Due to the lattice mismatch between the silicon layer, which is several microns thick, grown on the sapphire substrate with a thickness of 2oo to 300 microns, the silicon layer is likely to be strained, resulting in poor crystallinity. .

Furthermore, strain caused by the difference in thermal expansion between sapphire and silicon of the substrate is also considered.

In order to eliminate these drawbacks of SO8, 200 to 3
The present inventors have developed a semiconductor device with a new structure (hereinafter referred to as improved SO8) in which a sapphire single crystal film of 2 to 5 μm is formed on a 00 μm silicon substrate, and a silicon epitaxial active layer is formed on this sapphire single crystal. has already proposed.

When a thin sapphire layer is formed on such a thick silicon substrate, the crystal structure of the latter is regulated by the former and becomes similar to the latter.

Therefore, the silicon epitaxial layer on the sapphire layer is cured and has good crystallinity in a state similar to when it is grown on a silicon substrate.

However, as a result of research conducted by the present inventors, it has been found that the following problems remain unsolved with the improved SO8.

First, lattice mismatch due to the difference between the crystal structure of silicon (cubic crystal) and the crystal structure of sapphire (trigonal crystal) inevitably deteriorates the crystallinity of the silicon epitaxial layer.

Next, the coefficient of thermal expansion of silicon crystal (3,59x 10
'(1771/'C) and the coefficient of thermal expansion of the sapphire crystal (
Due to the difference of 8,40×10″″6crrL/C), the crystallinity of the silicon active layer deteriorates in the manufacturing process of the improved SO8.

Thirdly, cracks are likely to occur due to the difference in hardness 7 of silicon crystal and hardness 9 of sapphire crystal.

Due to the above-mentioned drawbacks, carrier mobility in this silicon epitaxial layer is low, reaching only 60 to 70% compared to bulk silicon.

Therefore, it was found that the device characteristics of the improved SO8 were not fully satisfactory, and there remained problems that required further improvement.

It is known to use magnesia spinel crystal (nMgO.At203), which is an insulating material having the same crystal structure as silicon, in place of sapphire in a general SO8 device.

This magnesia spinel crystal (lattice constant a=8.080
There is a mismatch in lattice constant between the silicon crystal (lattice constant a=5,430).

However, in each (100 planes), the lattice spacing twice that of a spinel crystal and the lattice opening three times that of a silicon crystal are almost equal, so there is no lattice mismatch between the two crystals, and good silicon It is said that epitaxial crystals can be obtained.

Further, since the dielectric constant of magnesia spinel is 8 compared to 10 of sapphire crystal, in the case of a thin film layer, parasitic capacitance can be reduced by using magnesia spinel.

Although it is desirable to use magnesia spinel as described above in both general SO8 and improved SO8, the problem lies in its production and removal.

Conventionally, magnesia spinel has been prepared by pulling a single crystal from a melt of a predetermined composition.

However, since the melting point of At203 exceeds 2000° C., the temperature of the melt increases, leading to evaporation of Mg.

As a result, it is extremely difficult to control the composition of the melt.

Therefore, it is an object of the present invention to solve the above problem by making magnesia spinel predominant in a gas phase rather than in a liquid phase.

The method according to the present invention (the chemical formula is n Mg 0-A40
3, where n is the number of moles of MgO. In order to grow magnesia spinel in a vapor phase, H flowing through the first channel
A step of contacting Ct gas with liquid or solid At to obtain a first reaction gas; HCt gas and solid M flowing through the second flow path so as not to be mixed with the HCt gas flowing through the first flow path;
g to obtain a second reaction gas; mixing the first reaction gas, the second reaction gas, and CO2 gas to obtain a third reaction gas; and the third reaction gas and the single crystal substrate. The method comprises the step of contacting the.

This method has many advantages when used to replace modified SO8 sapphire with magnesia spinel.

However, this method can also be used to replace conventional SO8 sapphire with magnesia spinel.

The step of obtaining the first reaction gas consists in using liquid or solid aluminum and hydrogen chloride gases as starting materials.

As aluminum, pure aluminum (purity 99.99
9% or more) is used.

Aluminum is in a solid or liquid state and its temperature is convenient for reaction with hydrogen chloride, generally 500 -
The temperature is 700°C, preferably within the range of 500 to 600°C.

Hydrogen chloride gas is generally kept at room temperature and comes into contact with heated aluminum.

Due to this contact, the following formula: % formula % (1) It is thought that the following reaction will occur.

By using metal kt as one of the starting materials,
"Deliquescence of starting material that occurs when AtCt3 is used"
problems caused by this will be prevented.

Furthermore, some water present in HCt reacts with At to generate At203.

Therefore, the introduction of HCt does not oxidize the Si substrate and prevent the growth of the At203 single crystal.

The first reaction gas generated in the above steps - AtCt3
and N2? R and -, which is considered to be a combined gas, are transported to the region of the Si substrate.

In the step of obtaining the second reaction gas, liquid or solid Mg
(l!: Contact with HCt gas.

This HCt gas needs to flow through a different flow path from the HCt gas that contacts At.

That is, magnesium and aluminum are placed in different channels, and their contact reactions are carried out without being influenced by each other.

) One feature of the present invention is that the reaction conditions with ICt gas are controlled differently for Mg and At to grow good magnesia spinel crystals.

As the magnesium, pure magnesium with a purity of 99.999% or more is used.

The heating temperature for magnesium is preferably 500 to 640°C.

This is inconvenient since magnesium is heated above its melting point and its vapor is intensely generated.

Hydrogen chloride gas is generally kept at room temperature and has the following formula: % formula % (2) It is thought that it reacts with Mg.

Therefore, it is considered that the second reaction gas consists of MgCl2 and N2.

N2 gas or Ar, N2, or a mixture thereof can be used to transport the first and second reactant gases toward the substrate.

In the next mixing step, the first and second reactant gases and CO2 gas are mixed and the mixed gas is brought into contact with the substrate.

The substrate is a single crystal of magnesia spinel in the case of the SO8 device and a single crystal of silicon in the case of the improved SO8 device.

In this contact, the silicon substrate is heated between 950°C and 13°C.
It is heated to a temperature of 50°C, generally 1000°C to 1270°C.

In addition, the magnesia spinel substrate has a temperature of 1000'C to 130'C.
It is heated to 0°C.

In both cases, if the heating temperature falls below the lower limit, the epitaxial growth rate of the magnesia spinel will be low, while if it exceeds the upper limit, undesirable reactions will occur between the gas mixture and the substrate.

The oxidation reaction of the first and second reaction gases by CO2 is expressed by the following equation: %formula% (3) It is thought that.

In the current mixing stage, the mixing of the three gas components does not necessarily have to occur simultaneously.

If CO2 and other components are mixed too slowly, the first reaction gas (
AtCt3+H2) and the second reaction gas (MgCt2+11
2), and if the temperature of these gases is lowered, there is a risk of decomposition of 1 g into metal At or metal depending on the case.

From the viewpoint of growing the generated n\1go-At203 on the substrate, it is better to mix CO2 and other components slowly.

The flow rate of the various gases mentioned above is 1 (in contact with At) - (Ct is 1
X 10-3~I X 10-1rnOZ/life*
HC, a in contact with M g is lx 10-3 to lx 1
0-'mo, 4/xi.

It is desirable that CO2 be two to three times the total flow rate of the HCt gas.

Magnesia spinel is most stable when the 1 value is between 0.1 and 3.5.

In order to obtain magnesia spinel with such n value,
The flow rate of HCl in contact with At is 0.1 to I L/rri
The flow rate of HCl in contact with yt, Mg is 0.5~
177M, and the flow rate of CO2 is 2 of the total flow rate of HCl.
Preferably, it is twice to three times as large.

When the diameter of the reaction tube is 7Qgm, the flow rate of the carrier gas for conveying the first and second reaction gases is 10t/sequential to 3
0t/seki is desirable.

The magnesia spinel vapor phase growth apparatus of the present invention includes (a)
a reaction tube equipped with one or more HCt gas inlets; (c) a first hollow body having one end connected to any of the HCt gas inlets and the other end opening into the reaction tube; At retainer disposed inside the hollow body mouth, one end of which is attached to the HCt
A second hollow body connected to either of the gas inlet ports and having the other end opened into the reaction tube A, (e) an Mg retainer disposed inside the second hollow body A, (F), and U heating. (g) Mg heating means; (7) a substrate support stand disposed in the reaction tube (a) facing the respective openings of the first hollow body and the second hollow body (2); ('J) the second hollow body; a CO2 introduction pipe that opens into the reaction tube A at any part from the opening of the hollow body 1 and the opening of the second hollow body 2 to the substrate support 6;
2) The material gas generation region is heated by an electric furnace, and the growth substrate region is heated by high frequency.

The Mg retainer is At when viewed in the flow direction of the HCt gas.
It is preferable that the retainer C is disposed in front or behind the retainer C.

There are usually two HC inlet ports in the above-mentioned device, each of which is connected to the At8\ holding hollow body and the Mg holding hollow body.

Further, in some cases, the inlet of one HC may be connected to the two hollow bodies.

The two hollow bodies mentioned above can be constructed in various ways.

For example, two tubes may be placed in parallel within the reaction tube,
The interior of one tube may be divided along its long axis, or two large and small tubes may be arranged coaxially.

The two hollow bodies may be constructed in any manner as long as the respective gases flowing inside the hollow bodies mix with each other when exiting the above-mentioned open end.

Preferably, the At and Mg retainers are offset in the direction of the HCt gas flow and are provided with mutually independent heating means.

For this purpose, kt and Mg are heated to different optimal reaction temperatures.

Hereinafter, a specific example of the vapor phase epitaxial growth apparatus of the present invention will be described based on the drawings.

The drawing is a sectional view showing a horizontal vapor phase growth apparatus, in which a small tube 2 is fixed in a quartz reaction tube 1.

The small tube 2 is doubled by a partition wall 2a, and an upper hollow body 2b and a lower hollow body 2C are formed by the partition wall 2a.

Each hollow body 2b, 2c has a semicircular cross section.

One end of the small tube 2 communicates with a hydrogen chloride tube 4 passing through the quartz reaction tube 1, and the other end is open into the reaction tube 1.

The partition 2a extends into the HCt gas introduction pipe 4, and the partition wall 2a extends into the HCt gas introduction pipe 4.
The interior is divided into two flow paths.

He. A carrier gas consisting of one or more gases of A r l N2 and H2 gas can be flowed into the tube 4 together with HCl.

The flow rates and gas types of the two divided flow paths can be made different from each other.

In the illustrated embodiment, an approximately double concentric tubular structure is formed between the reaction tube 1 and the region in which the small tube 2 is arranged.

However, it is not necessarily necessary to adopt a double concentric tube structure.

Inside each hollow body 2b, 2c is a plate 5b.

5c is placed.

The plate 5b is located in front of the plate 5c when viewed in the flow direction of the HCt gas.

Magnesium 6b and aluminum 6c are received in the plates 5b and 5c, respectively.

Known heating means 7b, 7c connected to mutually independent energy supplies (not shown) are provided around the reaction tube 1 to surround Mg and At.

A carrier gas port 8 is provided at one end of the reaction tube 1 .

The carrier gas flowing from the inlet 8 initially passes through the hollow bodies 5b and 5.
c, and then flows in the direction of the substrate 10 together with the Mg and At reaction gases.

In a part of the space of the reaction tube 1, a support 9 made of SiC coated carbon, Mo, Nb, etc. is fixed on a base 15 made of quartz.

Three disc-shaped substrates 10 are supported on the support stand 9.

Known high-frequency heating means 12 are provided in the area of the substrate.

Furthermore, a fitting cap 13 is provided on the outlet 11 side of the reaction tube.

Although the disc-shaped substrate 10 is supported by the stand 9 by its flat surface, it may be supported by its periphery.

A CO2 introduction pipe 14 passes through the wall of the reaction tube 1 and connects to the substrate 10.
and midway between the outlet end of the hollow body and for this spacing d
=% ~ 3AD approaches the former and opens.

Introducing CO2 at such an opening position
This is preferable from the viewpoint of controlling the timing of the start of oxidation of MgCl2 and AtC23 by CO2.

The flat surfaces of the substrate 10 are the (111) plane, the (110) plane, and the (1
00) plane, preferably (100) plane.

When the substrate 10 is silicon, 1000 to 1
It is heated to 270°C.

A single crystal of magnesia spinel can be epitaxially grown on the substrate 10 using the apparatus as described above.

If a magnesia spinel single crystal is vapor-phase grown in the above-mentioned apparatus and then a silicon active layer is epitaxially grown in the same apparatus, the productivity of improved SO8 can be increased.

Furthermore, since silicon is grown on a fresh magnesia spinel single crystal, this method is advantageous in terms of the crystallinity of silicon.

In this method, first, the supply of HCt gas from the inlet 4 is stopped.

To this end, the HCt gas is replaced by I]2 gas or one or more carrier gases He, Ar, N2.

Also, stop introducing CO2 from the CO2 inlet 14,
H2 gas or one or more carrier gases such as He, Ar, and N2 are fed from 14.

A mixed gas of H2 gas and one or more of He+Ar+N2 may be introduced through the inlets 4 and 14.

Then, heating by the heating means 7 is stopped to prevent evaporation of Mg and A7.

On the other hand, the Si substrate is heated to 1000 to 110% by heating means.
Heat to 0°C.

After continuing to purge HCt, AtCt31MgCt2, etc. with the carrier gas for about 5 to 15 minutes, 5IH from inlet 8
By introducing 4 or S r C1<, Si single crystal can be epitaxially grown on magnesia spinel.

In the above description, a horizontal device has been described in conjunction with the drawings, but exactly the same effects can be achieved in a vertical device.

Further, although the present invention has been described with respect to a method for manufacturing improved SO8, the present invention is not limited to improved SO8.
This method involves epitaxially growing a magnesia spinel single crystal film on a substrate and can be applied to various fields.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 A magnesia spinel single crystal was epitaxially grown using an apparatus as shown in the drawings.

Growth conditions are shown in Table 1.

Growth was continued for 10 minutes under the above conditions to obtain a grown layer with a thickness of 3 microns.

It was confirmed by X-ray diffraction and compositional analysis by IMA that this layer was a magnesia spinel single crystal with an n value of -0.2 and a growth plane of (111).

Subsequently, silicon was grown on the magnesia spinel single crystal under the conditions shown in Table 2.

Growth was continued for 2 minutes under the conditions described above to obtain a grown layer with a thickness of 4 microns.

It was confirmed by X-ray diffraction that this layer was single-crystal epitaxial silicon having a (111) plane.

[Brief explanation of the drawing]

The drawing is a sectional view showing a specific example of a vapor phase growth apparatus according to the present invention. 1...Reaction tube, 2...Tube, 2b, 2c
...Hollow part, 4...HC1 introduction pipe, 5
...Plate, 6...Aluminum, 7...
... Heating means, 8 ... Carrier gas inlet, 9.
... Board support stand, 10 ... Board, 11.
...Outlet, 12...Heating means, 13...
...Grinning cap, 14...C02
Introductory tube.

Claims (1)

[Claims] 1. The chemical formula is n Mg 0-At20.3, where n is M
a step of contacting the IIct gas flowing through the first flow path with the limbs or solids σ) At to obtain a first reaction gas in order to make the magnesia spinel, represented by the number of moles of gO, into a gas phase family; a step of contacting the HCt gas flowing through the flow path with solid Ag and the HCt gas flowing through the second flow path so as not to be placed on a stand, to obtain a second reaction gas; the first reaction gas;
A method for vapor phase growth of magnesia spinel, comprising the steps of: mixing a second reaction gas and CO2 gas to obtain a third reaction gas; and bringing the third reaction gas into contact with a single crystal substrate. The n value in the chemical formula 2111 is 0.1 to 3.50
) In order to grow magnesia spinel, heat A4 for 7IO to 400'C to 700°C, set the flow rate of the HCt gas flowing through the first flow path to 100cc/min to 1000cc/min, and set the Mg to 300cc/min to 1000cc/min. ℃ to 700'C and flowing through the second flow path.
A method for vapor phase growth of magnesia spinel according to claim 1, characterized in that the flow of gas is set at 50 cc/min to 1000 cc/min. 3. The following elements: (a) One or more HCt gases. Reaction tube equipped with an inlet (
b) A first hollow body whose one end is connected to any of the HCt gas inlets and whose other end opens into the reaction tube A; (c) Holding of kt disposed inside the first hollow body inlet. (b) a second hollow body whose one end is connected to either of the HCt gas inlet ports and whose other end opens into the reaction tube (e) a Mg gas inlet disposed inside the second hollow body (2); a holder, (f) heating means for the A7, (g) a heating means for the Mg, (7) facing the respective openings of the first hollow body mouth and the second hollow body 2 in the reaction tube A; (a) a CO2 introduction pipe that opens into the reaction tube A at any part from the openings of the first hollow body mouth and the second hollow body 2 to the substrate support base; -) A monocrystalline magnesia spinel family leader device, characterized in that the material gas generation region is heated by an electric furnace and the family leader substrate region is heated by high frequency; A patent claim characterized in that the CO2 introduction pipe is disposed in front or behind the At retainer C when viewed in the gas flow direction and opens between the material gas generation region and the chief substrate region. The single crystal magnesia spinel patriarch device according to item 3.