JPS58200543A - Thermal oxidizing method - Google Patents

Abstract

PURPOSE:To prevent the exfoliation of a spinel epitaxial film by thermally oxidizing the whole in dried oxygen in the thermal oxidizing method forming silicon dioxide SiO2 to a boundary between the spinel epitaxial film and a silicon single crystalline substrate. CONSTITUTION:When magnesia spinel is grown onto the silicon single crystalline substrate of a (100) crystal face orientation in an epitaxial manner and thermally oxidized for five hr by dried oxygen at one atmosphere at 1,200 deg.C, exfoliation is not generated at all even through quenching after thermal oxidation through the temperature of thermal oxidation is higher than oxidation in steam. The diffraction intensity of a (400) diffraction peak increases by approximately one and a half times as large as that before thermal oxidation, and single crystallinity is, on the contrary, improved.

Description

[Detailed Description of the Invention] The present invention is Spinel! ! ! ! The present invention relates to a method for thermally oxidizing a silicon single crystal substrate on which an oxide has been grown.

Due to the increasing speed and density of semiconductor integrated circuits (ζ), methods of separating elements with insulators are being investigated.

For example, 808 (8i1icon t'* '5aph
ire) It is known as the representative method. Especially in recent years, there has been an upsurge in the research and development of ``3-layer integrated circuits'' in which semiconductors and active layers are multilayered. Technology development for forming crystalline films is actively underway. Among them, magnesia spinel MgO on silicon-crystalline substrates is being developed.
・The method of growing a silicon semiconductor film and forming a semiconductor single-crystal film on it uses a low-cost, quality-guaranteed silicon single-crystal substrate. Single-crystal films are attracting attention because they can be easily and inexpensively formed on insulators. Epitaxial II/8i
Spinel epitaxial film / 8 double layer structure of single crystal substrate
10□/8i Disclosed the ability to create a three-layer structure of a single crystal substrate (41 Application No. 56-109367). Silicon dioxide, StO, is most widely used as an insulating layer for semiconductor devices, and is an extremely excellent insulator for semiconductor devices. In addition, its dielectric constant is smaller than that of sapphire or magnesia spinel, and therefore the parasitic capacitance between semiconductor elements formed in the semiconductor active layer can be reduced, which is advantageous in increasing the speed of element operation.

The present invention provides a thermal oxidation method for forming bi-inertial silicon 8iO at the boundary of a spinel epitaxial single crystal silicon single crystal substrate.Specifically, it specifically specifies its formation after thermal oxidation. be. The present inventor thermally oxidized silicon single crystal substrates on which magnesia spinel was epitaxially grown under various conditions. As a result, they discovered that silicon single crystal substrates could be thermally oxidized through a spinel epitaxial film under any conditions without any problem. The biggest problem is that the spinel epitaxial film peels off when the wafer is cooled due to thermal oxidation.As a result of various studies to solve this problem, we found that this peeling phenomenon is extremely dependent on the atmosphere. It was discovered that peeling is likely to occur when oxidized to 1lIII in an atmosphere containing water vapor, but peeling does not occur when thermal oxidation is carried out in dry acid violet. The present invention is based on this discovery and will be explained below by way of examples.

EXAMPLE Magnesia spinel was epitaxially grown to a thickness of about 0.4 μm on a silicon single crystal substrate with crystal plane orientation (100) by a vapor phase growth method. The silicon single crystal substrate used had a diameter of 1 Jhc) 15 +
*s X l 5 su++ chips were cut and thermally oxidized.

First, thermal oxidation was performed in water vapor at 1000°C and 1 atm for 1 hour, and then slowly cooled. Immediately after cooling, the magnesia spinel film was attached to the wafer, and its single crystallinity was evaluated by X1m diffraction. There was no difference. However, with the passage of time, the spinel film began to peel off, and the entire surface peeled off within several hours. After the peeling, the thickness of the silicon dioxide film formed on the surface of the silicon substrate was measured using an ellipsometer and was found to be 0.2 μm.

For thermal oxidation in steam such as s 1200'C%
1 atm drying a! 5. In the case of time thermal oxidation, the thermal oxidation temperature is higher than in the case of steam oxidation.
However, no peeling occurred even when formed after thermal oxidation.
Then, when the single crystallinity of the magnesia spinel film after thermal oxidation was evaluated by the symmetric reflection X* diffraction method as in the case of steam oxidation, the diffraction intensity of the (400) diffraction peak was 1.5% higher than that before thermal oxidation. It has increased by about twice as much, and rather the single crystallinity has been improved. Of course, no diffraction peaks other than (40G) diffraction were observed due to the zero order/l:l of acid and sulfuric acid.
The thickness of the silicon dioxide film formed on the silicon single crystal substrate was measured by etching only the magnesia spinel film with a mixed solution (phosphorus sulfuric acid) of about 0.3.
The result above was 0. The reason for this is that when a Si single crystal substrate is thermally oxidized through a magnesia spinel film, the oxidation mechanism is different between steam oxidation and oxygen oxidation, so MgO・mu120B/ 8102/8i multilayer structure MgO-me 120. It is interpreted that the bonding state of the interface between 8i02 and 8i02 is different, and that the bonding is weaker in the formation of water vapor folds, leading to the separation of the spinel film.

Therefore, the present invention aims to reduce water vapor in the thermal oxidation atmosphere as much as possible when thermally oxidizing a silicon single crystal substrate through an epitaxial film of spinel oxide, such as magnesia spinel, grown on a silicon single crystal substrate. It discloses that it is necessary to Silicon dioxide is a high-quality insulating layer and has a low dielectric constant, so it is extremely effective in achieving high integration through device isolation and speeding up operation, and the MgO 120&/8s01 layer can be epitaxially grown on the entire surface of the wafer as a semiconductor active layer. It is an extremely useful insulating layer, and the production of such an insulating layer is only possible with the present invention. Therefore, we believe that the present invention has great industrial value.

Claims (1)

[Claims] 1. An oxide single crystal layer with a spinel disc crystal structure is formed on single crystal silicon, and then the single crystal silicon is oxidized to form a silicon dioxide layer under the skeleton spinel oxide. A thermal oxidation method characterized in that no water vapor is included in the oxidizing atmosphere during the first stage of formation. 2 Spinel oxide is magnesia spinel Mg0-AI
20. The thermal oxidation method according to claim 1. 3. The thermal oxidation method according to claim 1, wherein the oxidizing atmosphere is a dry oxygen atmosphere.