JPH02248046A - Formation of sio2 film - Google Patents

Abstract

PURPOSE:To obtain a good superthin film having a small roughness in the interface between an Si substrate and an SiO2 film by a method wherein the Si substrate having a specified orientation is heated in order at a prescribed temperature respectively in an oxidizing atmosphere and in a non-oxidizing atmosphere. CONSTITUTION:A face (110) Si substrate 10 having an orientation of (110) or an orientation between (110) and less than 5 degrees is subjected to thermal oxidation in an atmosphere containing oxygen and the mixture of oxygen and hydrogen at 800 to 1200 deg.C to form an SiO2. Then, the substrate is subjected to high-temperature heat treatment at 1000 to 1400 deg.C in a non-oxidizing atmosphere (in a vacuum, argon and nitrogen atmosphere). Thereby, a good SiO2 superthin film 20 having a small roughness in the interface between the Si substrate and the SiO2 film is obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for forming a SiO2 film.

[Prior Art] The most common method for forming a Si02 film is described, for example, in the proceedings of the 49th Annual Conference of the Japan Society of Applied Physics.

800-120 in an oxidizing atmosphere, as disclosed in Volume 2, page 641 (lecture number 5p-N-1).
This is a thermal oxidation method that oxidizes the 3i surface at a high temperature of 0°C.

The SiO2 film formed by this method has a uniform composition,
It has the advantage that it is easy to obtain a clean 3 i /S i 02 interface.

[Problem to be solved by the invention] However, in recent years, as ultra-thin SiOz films of about 10 nm have become required, minute irregularities at the atomic level at the Si02/3i interface, which had not been viewed as a problem until now, have become increasingly necessary. has become a problem. In other words, in such an ultra-thin film, there is an unevenness at the interface that reflects the unevenness of the 3i surface before oxidation, which causes fluctuations in the SiO2 film thickness and deterioration of the electrical characteristics, which in turn reduces the high integration of the 3i ultra-high integrated circuit. This impedes improvements in temperature, performance, and yield.

The present invention was made to solve the conventional problems as described above, and S! An object of the present invention is to provide a method for forming a good ultra-thin SiO2 film with small irregularities at the /SiO2 interface.

[Means for Solving the Problems] The present invention provides an 800 to 12 substrate having a plane orientation of (iio) or within 5 degrees from (iio) in an oxidizing atmosphere.
This method of forming an SiO2 film is characterized by comprising a step of heating to 00°C, and a subsequent step of heating to 1000 to 1400°C in a non-oxidizing atmosphere.

[Function] The following describes the function of the present invention that allows the formation of an ultra-thin SiO2 film with small irregularities at the 3i/SiO2 interface.

When the present inventors investigated the Si/SiO2 interface of 5I02 formed by various methods, it was found that
It was found that a reaction occurs at the Si/SiO2 interface at higher temperatures, and that the (110) Si/SiO2 interface is energetically more stable than Si/SiO2 interfaces with other higher-order plane orientations. did.

Therefore, when a 3i substrate with a plane orientation of (110) or close to (110) is thermally oxidized, irregularities will be seen at the 3i/S i 02 interface, reflecting the irregularities on the Si substrate surface. By adding Si/SiO
The reaction occurs at the two interfaces and is energetically favorable (110)
A S i /S i 02 interface appears.

Since the (110) Si surface is very flat at the atomic level, the resulting Si/SiO2 interface is also a flat interface with very little unevenness. Further, by performing the high temperature heat treatment in a non-oxidizing atmosphere, an increase in the thickness of the SiO2 film obtained by thermal oxidation can be avoided. In this manner, by forming an ultra-thin SiO2 film by thermal oxidation and subsequent high-temperature heat treatment, it is possible to form a good ultra-thin SiO2 film with small irregularities at the Si/SiO2 interface.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

1 and 2 are partial cross-sectional views of a substrate for explaining the present invention in detail. In this example, a (110)3i substrate 10 having a (110) plane orientation is used, and for comparison, a (110)3i substrate 10 having a plane orientation tilted by 15 degrees from (tio)
A 15 degree off 3i substrate 110 was used (Fig. 1(a),
Figure 2(a)).

(110) 3i substrate 10 and (110) 15 degree off 3i substrate 110 at 900 to 1200°C for 10 to 120 degrees
Si is thermally oxidized in oxygen and oxygen/hydrogen mixed atmosphere for
02 films 20 and 120 were formed (FIG. 1(b)).

Figure 2(b)). After that, a part of each board was heated for 100 minutes using a lamp annealing device using an infrared lamp as a heat source.
High-temperature heat treatment was performed at 0 to 1400°C for 10 seconds to 30 minutes in a vacuum, argon, and nitrogen atmosphere (Figure 1 (C), Figure 2
Figure (C)). S of the sample immediately after thermal oxidation and after high temperature heat treatment
The state of the unevenness of the i/S i 02 interface was evaluated by high-resolution cross-sectional observation using a transmission electron microscope.

As a result, immediately after thermal oxidation, the unevenness of the Si/SiO2 interface was the same at 1 to 2 stops, regardless of whether a (110) 3 i substrate 10° (110) 15° off Si substrate 110 was used ( Fig. 1(b), Fig. 2(b)). However, after high-temperature heat treatment, when the (110) 3i substrate 10 is not used, the unevenness of the 3i/SiO2 interface is extremely flattened to 0.5 nm in all cases, and is flat at the atomic level ( 110) S i /SiO2 interface was obtained (Fig. 1(C)), whereas (110) 15
degree off S: When substrate 110 is used, the (110) plane is greatly tilted from the original Si / Si 02 interface, so the (IIO) plane and planes with other orientations appear alternately. “A sawtooth-shaped interface was obtained (Figure 2 (C)).

In this example, the effect of high-temperature heat treatment was explained using a (110) Si substrate, but similar effects were confirmed using a substrate tilted within 5 degrees from (110).

Further, although the thermal oxidation was performed in an oxygen and oxygen/hydrogen mixed atmosphere, other oxidizing atmospheres may be used, such as an atmosphere to which hydrogen chloride is added. Generally speaking, a lamp annealing device was used for the high-temperature heat treatment, but there is no problem in using other heat sources as well.

[Effects of the Invention] As explained above, according to the present invention, Si/Si
Provided is a method for forming an SiO2 film that can form an ultra-thin SiO2 film with a very flat 02 interface, and can increase the degree of integration, performance, and yield of a 3i ultra-high integrated circuit.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a substrate showing an example of the present invention in the order of steps, and FIG. 2 is a partial sectional view of a substrate for explaining a comparative example. 10... (110) Si substrate 20, 120... SiO2 film

Claims (1)

[Claims] (1) A Si substrate with a plane orientation of (110) or within 5 degrees from (110) is heated at 800 to 1200 in an oxidizing atmosphere.
A method for forming an SiO_2 film, comprising the steps of heating to 1000 to 1400°C in a non-oxidizing atmosphere.