JPH03129736A - Manufacture of oxide film - Google Patents

Abstract

PURPOSE:To add a halogen element such as chlorine into a silicon oxide film formed on the surface of a substrate semiconductor at a temperature lower than that in conventional cases by a method wherein a reactive gas is activated or decomposed chemically by using a high-frequency or microwave energy. CONSTITUTION:A sufficiently cleaned substrate 1 is loaded into a reaction furnace 3 at a temperature of 500 to 700 deg.C; a whole system is evacuated to produce a vacuum of 0.01 to 0.0001Torr. After that, HF at a concentration of 1 to 10%, especially 4%, from a valve 11 is mixed with oxygen from a valve 12. This mixed gas is introduced into a reaction system. Before this operation, a high-frequency energy 6 at, e.g. 135MHz is applied. In addition, when a pressure inside the reaction furnace is set to, e.g. 30Torr, the surface of the substrate is oxidized on the basis of an oxygen partial pressure recognized by the pressure. An oxidation temperature at this time is set to 1050 deg.C or lower, e.g. 900 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an active amount or decomposition of a reactive gas including a fluorine-based reactive gas and oxygen or other oxidizing gas by induction energy in a reaction system whose pressure is reduced to 1 atmosphere or less. By doing so, the temperature is below 1050"C, preferably 500"C.
The present invention relates to a method for producing an oxide film containing elemental fluorine by oxidizing a silicon semiconductor in an atmosphere maintained at a temperature of ~1050°C.

The present invention uses high frequency or microwave energy to chemically activate or decompose the reactive gas, thereby forming a silicon oxide film on the surface of the substrate semiconductor at a temperature 50 to 500'C lower than previously. The present invention relates to a method for producing an oxide film to which a halogen element such as chlorine is added.

Conventionally, in ICs, LSIs, and VLSIs in which semiconductors are left alone, especially insulated gate field-effect semiconductors (hereinafter referred to as MOS and FET), or these are integrated on the same substrate, the gate insulating film has been made thinner than before (100 mm). ~10
00 people, especially 100 to 500 people. Moreover, the silicon oxide film, which is the most important of the gate insulating films, is expected to have very little interfacial charge at the interface with the substrate semiconductor, especially silicon. For this reason, in the past, in order to reduce the interfacial charge to 10"cm-" or less, particularly 5 x 10'cm-" or less, this silicon oxide film was heated to a temperature of 1ioo"C or more, especially 1200°C, and the substrate semiconductor was exposed to oxygen. It is known that it is extremely effective to make it by heating and oxidizing it in hydrogen chloride (IIcI).

However, MOS and IC are VLSI (Very Lar
ge 5cale Int-egraHor+), the silicon wafers used are subjected to high-temperature heat treatment, which causes warping due to thermal strain caused by 50 to 200 slices being taken in and out of the reactor, resulting in the formation of so-called potato chips. It has become unavoidable.

Therefore, the thickness of the insulating film such as this gate oxide film is 600 to 800
It is required to be made at a low temperature of 'C. However, it has been found that at such temperatures, especially below 1100° C., the halides are not chemically activated, and as a result, even if such halides are added in the oxidation step, they do not diffuse into the film and have no effect at all.

In this conventional method, the present invention can be used for low-temperature oxidation of 1050'C or less, and the gate film thickness is 100 to 10%.
Even thin films for non-volatile memory with a gate film thickness of 0.000 μm or 10 to 100 μm thickness contain uniformly and chemically active fluorine elements, i.e., the interfacial charge of silicon unpaired. The aim was to create a silicon oxide film that could neutralize bonds and mobile ions such as sodium.

Further, in order to carry out such a method, the present invention aims to chemically activate a fluoride by applying high frequency energy or microwave energy to the fluoride and further converting the reactant into plasma. For this reason, the reaction system is
Atmospheric pressure or less, and this reduced pressure state of 1 atm or less, especially 0.1 to
At 100 torr, typically from 5 to 50 torr, the partial pressure of oxygen, which is an oxidizing gas, is also lower than at 75 Qtorr, and the oxidation rate can be relatively slowed down. The present invention also makes it possible to adjust the time required to form a predetermined film thickness on a silicon substrate so that it is not too short, such as 1 to 5 minutes, even during idle operation, and to make it within the range of 15 to 60 minutes. It is a characteristic of

The features of the present invention will be described below according to examples.

Example 1 FIG. 1 shows one embodiment of the invention.

In the drawing, a substrate (1) is loaded into a quartz port (2) and placed in a reactor (oxidation furnace) (3). In order to improve the mixing of the reactive gases in this reactor, a homogenizer (4) is provided on the gas inlet (5) side, and the substrate (1
) The boat (2) is loaded and unloaded from the discharge port (8) side. Substrate (herein, the term "substrate" is a general term for semiconductor substrates that have already gone through several processes, especially silicon single crystal semiconductor substrates, or substrates with a semiconductor film formed on a part of the surface of the substrate, such as SOS) (1) In the present invention, which performs a solid phase-vapor phase reaction, at least a portion of the surface must be a silicon semiconductor.

As shown in Figure 1, the fluorine-based reactive gas at a position away from the substrate is more likely to be an oxidizing gas (12) than (11).
will be introduced. Further, inert gas is introduced from (13) for purging and dilution, and hydrogen and lte are introduced from (18) for high frequency induction annealing. A high frequency induction furnace (6) is provided for chemically activating or decomposing these with high frequency energy. Furthermore, a resistance heating furnace (7) is provided to heat the substrate, and the reacted fluorine element and oxidizing gas are heated through valves (16) and (9).
It is then discharged from a decompression system using a vacuum pump.

The valve (9) is a needle valve and is for adjusting the pressure inside the reactor. A reactive gas containing elemental fluorine is introduced from (11) through a needle valve. Hydrogen fluoride (IIF) is a typical example of this reactive gas.

Typical oxidizing gases include oxygen (0□), ozone (03), water ()1,0), and nitrous oxide (NO2), but in this example, 02 was used. .

The reaction is carried out using 50 to 200 sufficiently cleaned substrates and 500 to 200 sheets.
Loaded into a reactor at a temperature of 700″C, the entire system was heated to 0.01
A vacuum was drawn to ~0,001 torr. After this 11F
was mixed in oxygen at a concentration of 1-10%, especially 4%. This mixed gas is transferred from the purge line (17) to the valve (15).
Then, the valve (16) was opened and the reactor was replaced with the reaction system. Prior to this, high frequency energy (6) was applied for 1 to 20 MI.
Iz, for example, 13.5 Hz RF was applied. Special Nico's induction energy is 100% to cause voltage excitation.
Turn on ~300W of power. Glow electricity in a plasma state was experimentally confirmed when the pressure inside the reactor was 0.001 to 1 torr.

Furthermore, the pressure inside the reactor is 1 to 100 torr, for example 30
torr, the substrate surface was oxidized based on the oxygen partial pressure observed due to this pressure. The oxidation temperature at this time was 800-1000''C1, especially 900''C. The film thickness was set to 100 to 1000 people, especially 100 to 300 people. To make the film thickness 500 to 1000, the oxidation temperature should be 1000.
It is preferable to set the temperature to 1050°C.

However, on the other hand, in order to increase the film thickness to 10 to 100 people, 600 to 8
It was preferable to set the temperature to 00°C.

Also, if you want to stop the oxidation, reduce the oxygen pressure in the reaction system to 0. It would have been better to immediately evacuate the inside of the reactor so that the pressure was below ITorr. After the oxidation for a predetermined period of time is completed, the pressure of the reaction system is forcibly reduced to 0.01 torr using a vacuum exhaust system to stop the oxidation reaction, and then the reaction system is filled with an inert gas to flow, and the reaction is stopped. After lowering the temperature of the system by 100 to 300"C below the oxidation temperature, the silicon oxide film was left to stand, the system was brought to normal pressure, and the substrate (1) was taken out.

In order to evaluate the silicon oxide film, an aluminum or silicon semiconductor (phosphorus-doped) electrode is provided on the film, and the C-VI characteristics (gate capacity it - gate voltage characteristics) are measured.
I asked for As a result, below 1050'C, e.g. 800°C
The silicon oxide film formed at a temperature of 200°C for 130 minutes (
±BT (bias-temperature treatment) with electric field strength I x 10'V 7 cm) was performed. The results showed that the drift of V was 0.1 V or less in the hydrochloric acid oxidation method using high frequency excitation of the present invention.

However, in the case of the conventional method that does not use high frequency excitation, the
There was a drift of 0.8V. In addition, this is roughly the same as the drift amount of the oxide film when oxidized without adding a halogen element, and not only a halogen element is added, but also a chemically activated or decomposed halogen element is added to the silicon oxide. It was found that it is important to add It has been found that the process of the invention, in which hydrogen chloride decomposes and generates chemically active chlorine and hydrogen, particularly at temperatures below 900'C, e.g. 700-800C, is of great importance in semiconductor electronics.

Also, the initial interfacial charge is 5X109~10I
01010 was obtained in the process of the invention, which was chemically activated and decomposed by radiofrequency energy.

In this example, high frequency induction energy was applied after mixing the oxygen and hydrogen chloride. However, high frequency energy is applied only to the halogen element through the valve (1) of the inlet (12).
It may be added near 8). At this time, chemical activation or decomposition of hydrogen chloride takes place, but chemical activation or decomposition of oxidizing gases such as oxygen does not take place. As a result, although the oxidation rate was not particularly fast at the same temperature, the effect of activated chlorine and hydrogen reduced the interfacial charge and B-
The T treatment had a significant stabilizing effect.

Furthermore, even when a halogen element in an active state, such as chlorine, was added to the film together with hydrogen after the oxide film had been formed, the effect of reducing the interfacial charge was observed.

The oxidation rate increases by 1.5 to 4 times depending on the presence or absence of high-frequency induction energy, and this is because not only the halides are chemically activated, but also oxygen, which is an oxidizing gas, is activated, and nascent oxygen or ozonized oxygen is activated. was found to accelerate the oxidation rate.

Example 2 FIG. 2 shows another embodiment of the invention.

Figure 2 shows a substrate (1) similar to that in Example 1 and a quartz boat (2
) is installed in the reactor (3). This loading was carried out in an atmosphere in which the reaction system was continuously purged with an inert gas or oxygen.

This reactor has a homogenizer (4) to facilitate mixing.
is provided on the inlet (5) side. Attach the boat (
2) is loaded and taken out from the exhaust port (8).

In FIG. 2, an exciter (20) is provided for chemically activating or decomposing the reactive gas by means of electrical energy, particularly microwave energy, at a location remote from the substrate. In addition, an induction excitation system (23), which is an oscillation source of high-frequency energy, is provided on the inner furnace core (3) side of the resistance heating furnace (7). The microwave has a frequency of 1 to 4 G It z, and chemically activates or decomposes the same halogen elements such as hydrogen fluoride (HF) and oxidizing gases such as oxygen (0□) as in Example 1, so-called It has a physically excited state, a chemically active state, or a nascent state.

For the reaction, a sufficiently clean substrate (3 to 5 inches) is
200 sheets are introduced into the reactor, and O2 and HF (gas mixture ratio is 4%), which have been adjusted in advance to a concentration of 1 to 10%, for example, 4%, are passed through the purge line (17) through the valves (15) (16).
was opened and closed and introduced into the reactor.

The other procedures for handling the reactor were the same as in Example 1.

The opening and closing of pulps (11) to (16) was controlled by a microcomputer in a temporally sequential manner. FIG. 3 shows the relationship between the growth rate and temperature of a halogen-doped silicon oxide film.

FIG. 3(A) shows the relationship between the temperature of the substrate in the reactor and the growth rate of the film. As is clear from the drawings, the higher the reaction temperature, the faster the film growth rate. Furthermore, when microwave energy (20) or high frequency energy (23) is not used, the growth rate is low as shown by curve (30). However, when microwave energy (20) was used to place HF and oxygen at a position away from the inside of the reactor loaded with the substrate, this growth rate increased and became curve (31). Further, when the energy power was increased, a certain increase in the growth rate was observed, but a tendency towards saturation was observed at 30 W or more.

In addition, a high frequency induction furnace (23) installed inside the resistance heating furnace
The electric field was placed in a direction perpendicular to the heating furnace (7), and the high frequency energy was devised so that it would not be absorbed by the resistance heating furnace. This induced energy was used as voltage excitation to cause chemical activation or decomposition of reactive gases on or near the substrate, rather than current excitation, where the energy was used to heat the substrate. Of course HF, 0. (not just the atmosphere at that time) le and H2 are activated or decomposed at the same time. As a result, the excited or nascent reactive gas immediately reacted with the substrate, oxidized, and bonded to the dangling bonds of silicon without transitioning to a stable state. In this case, it is activated even at a pressure of 100 to 760 torr.
That is, it had the effect of lowering Qss.

As is clear from FIG. 3(A), the oxidation rate became faster, and since high-frequency induction energy was used in this case, it was possible to easily generate high power of 100 to 300 W or more.

FIG. 3(B) shows the relationship between the pressure inside the reactor and the film growth rate when high frequency induction energy is used.

When microwave and radio frequency energy is added, the curve (31”
). The substrate temperature in this case was 800''C.

Of course, it is also possible to vary the substrate temperature or to use these two energies together.

When the silicon oxide film doped with a halogen element obtained in this example was used as a gate insulator of a MOS and FET attached to a DET electrode, Nss was 10' to 1010.
cm-2, and the effect of adding a halogen element to the B-T treatment was remarkable as in Example 1. Also M
The gm (mutual conductance) as an OS and FET is high, and the dielectric breakdown strength is homogeneous with very few pinholes! 8-10 x 10'V for quality
/cm was obtained with a gate film thickness of 200 to 300 mm, and extremely favorable characteristics were obtained.

As explained above, in order to obtain a homogeneous pinhole-free film quality at a low substrate temperature, the present invention has been developed over 110 times.
Fluorine, an active halogen element, which was previously possible only at temperatures above 0°C, can now be produced at temperatures of 600 to 1000'C, making it possible to produce thin gate insulators, which are important for the development of VLSIs. It is extremely important industrially that wafers can be heat treated without causing them to warp into a potato chip state.

Although the present invention is characterized by a pressure of 1 atm or less, some effects were seen even at a pressure of 1 atm, and this was particularly noticeable when high frequency energy was applied near the substrate in FIG. 2. Therefore, the induced energy (23) in FIG. 2 was effective in increasing the oxidation rate under normal pressure or pressurized conditions. For this reason, it was effective to apply the method of the present invention to cases where feed insulators were made from 1 to 2μ and used as LOGOS.

The present invention also provides an NMO5 structure MIS or FET in which a barrier layer such as a silicon nitride film is provided on the upper side of the gate insulating film.
It is also possible to apply it to a nonvolatile memory provided with a floating gate.

The method of the present invention includes a gate electrode made of impurity-doped silicon on the upper side, a silicide metal such as WSi, and a Mo-3t
Needless to say, this does not negate the use of a metal-semiconductor multilayer electrode.

[Brief explanation of the drawing]

FIGS. 1 and 2 are an example of the fabrication of a semiconductor of the present invention for carrying out the method of the present invention. FIG. 3 is a characteristic diagram of the growth rate and the growth rate obtained by leaving the material shown in FIG. 2 undisturbed. W-- Funeral map magic power (Torr)

Claims (1)

[Scope of Claims] 1. A silicon oxide film containing fluorine is formed by leaving a silicon semiconductor in an atmosphere at a temperature of 1050°C or less in which a reactive gas containing fluorine and an oxidizing gas are mixed by induction energy to oxidize it. A method for producing an oxide film, the method comprising: producing an oxide film on the semiconductor. 2. The method for producing an oxide film according to claim 1, characterized in that the reactive gas containing elemental fluorine is added at a mixing ratio of 10% or less to the oxide gas.