JPH1041241A - Manufacturing method of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce inter-lattice oxygen in an SOI layer by heat treating or plasma treating at a temp. higher than that causing a reductive reaction of this oxygen in a surface Si layer with H and lower than that causing a reductive reaction of oxygen in a buried oxide layer with hydrogen. SOLUTION: After forming an oxygen film 1 by oxidizing a Si substrate 1, oxygen ions are implanted. It is heat-treated in an Ar atmosphere to form a buried oxygen film 4 and recovers crystal defects in a surface Si layer 5, and annealed in an oxygen atmosphere. The oxide film 2 on the substrate is removed by an HF etchant, heat-treated in an H atmosphere at 950 deg. for 30 minutes to reduce the inter-lattice oxygen in the Si layer 5, using a diffusion furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to an SOI (Silicon On).
The present invention relates to a method for reducing interstitial oxygen, which is a nucleus of generation of process-induced defects in a surface silicon layer of an insulator substrate.

[0002]

2. Description of the Related Art At present, an SOI substrate is receiving attention as a future ULSI substrate. This SOI substrate manufacturing method includes a method of bonding silicon substrates together via an insulating film, a method of depositing a silicon thin film on an insulating substrate or a substrate having an insulating thin film on its surface, SIMOX (Sepox).
aration by Implanted Oxge
n) method. The SIMOX method is one of the methods of embedding an insulating layer in a silicon substrate. Specifically, after implanting high-concentration oxygen ions into the silicon substrate, the silicon substrate is annealed at a high temperature, In this method, a buried silicon oxide film is formed at a predetermined depth from the surface, and a silicon layer (SOI layer) on the surface side is used as an active region.

Conventionally, in this method, a silicon wafer is implanted with oxygen ions at a high concentration of about 0.4 to 15 × 10 ¹⁸ / cm ^{2 and then} heat-treated at 1000 to 1400 ° C. for several hours. Due to this heat treatment, the implanted oxygen reacts with silicon to form a silicon oxide film, and the damage of the silicon crystal due to the implantation is recovered, but the atmosphere gas has various other effects on the silicon wafer.

Japanese Patent Application Laid-Open No. 64-72533 discloses that after oxygen ion implantation, heat treatment is performed at 1050 ° C. in a hydrogen atmosphere to remove unnecessary implanted oxygen and change the implanted region to an insulating layer. ing. Also, JP-A-8-4616
According to Japanese Patent Publication No. 1 (1993), since a defect of surface silicon tends to disappear with a mixed gas of argon and oxygen, a protective film is formed on the surface and a heat treatment of hydrogen is performed at a high temperature of 1350 ° C. Also, when particles are attached to the surface during oxygen ion implantation, oxygen ions are not implanted or the amount of implantation is insufficient to improve the electrical insulation of the buried oxide film. In the publication No. 263538, 13
After heat treatment at 50 ° C. with a mixed gas of argon and oxygen, heat treatment is performed in an oxygen atmosphere to increase the thickness of the buried oxide film and improve its electrical insulation. Since the heat treatment of oxygen increases the thickness of the buried oxide film, the amount of implanted oxygen ions can be reduced.
There is also an advantage of improving the flatness of the interface between the I layer and the buried oxide film.

[0005] A technique for improving the crystal quality of a surface layer by heat-treating a silicon wafer in a hydrogen atmosphere has been disclosed in Y. Yamamoto. S
ato et al., "Ext. Abst. 18th I.
nt. Conf. Solid State Device
es and Materials, Jpn. Soc.
Appl. Phys. , Tokyo (1986) p52
9 ". According to this technique, by annealing a silicon wafer with hydrogen at a high temperature, interstitial oxygen serving as a nucleus of induced defects is diffused outward, the oxygen concentration is reduced, and a gettering site is formed inside silicon. In addition, micro defects and impurity metals distributed in the surface layer are trapped inside to improve the crystal quality.

However, there is a problem in applying this technique to a silicon wafer having an SOI structure. That is, the hydrogen diffused by the high-temperature treatment reduces the oxide film under the surface silicon layer, and the interface characteristics between the surface silicon layer and the oxide film deteriorate.

[0007]

However, if heat treatment is performed with argon after oxygen ion implantation, the ion implanted region becomes an oxide film, and a part of the implanted oxygen diffuses outward, but the SOI layer has an oxide film. Part of the injected oxygen remains between the lattices, particularly near the interface of the buried film. This oxygen causes defects in the subsequent heat treatment in the manufacturing process of the semiconductor device. Further, in the case of oxygen, Japanese Patent Application Laid-Open No. 7-26353
As shown in Japanese Patent Publication No. 8 (1993), if particles are attached to the surface at the time of oxygen ion implantation, oxygen may not be implanted or the implantation amount may be insufficient, and the electrical insulation of the buried oxide film may be deteriorated. , An increase in the thickness of the buried oxide film is observed.

On the other hand, a heat treatment in a hydrogen atmosphere is effective in terminating dangling bonds and reducing oxygen between lattices to improve crystallinity. However, when hydrogen annealing is performed after oxygen ion implantation, ion implantation is performed. In the SOI layer that has become amorphous due to the above, a crystal defect (OSF) caused by H ₂ O generated by being reduced by hydrogen at the time of recovery of an implantation defect.
Occurs, and since the inside of the buried oxide film region is not a complete silicon oxide film, a large number of Si-OH groups are present, and there is a fear that the dielectric breakdown voltage of the buried oxide film is reduced.

Further, the heat treatment in a hydrogen atmosphere at about 1000 ° C. is not sufficient for recovering crystallinity and improving the quality of the buried oxide film because the temperature is low. On the other hand, when performed at a high temperature, as described above, in addition to the reduction and removal of interstitial oxygen in the SOI layer, the oxide film at the interface of the buried oxide film is reduced and removed, and the characteristics of the buried oxide film deteriorate.

On the other hand, even in the method of performing heat treatment in an oxygen atmosphere after performing heat treatment in a mixed gas atmosphere of argon and oxygen, oxygen remains between lattices and defects (mainly, OSF ( Oxidation-i
nduced Stacking Faults).

[0011]

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, wherein oxygen is ion-implanted into a silicon substrate.
A first step of forming a buried oxide film and a surface silicon layer on the buried oxide film by performing a heat treatment at a predetermined temperature in an inert gas atmosphere; and a heat treatment in a hydrogen atmosphere after the first step. Atmosphere temperature, or the substrate temperature in the hydrogen plasma treatment is higher than the temperature at which the interstitial oxygen of the surface silicon layer causes a reduction reaction with hydrogen, and the temperature at which the oxygen of the buried oxide film causes a reduction reaction with hydrogen. And a second step of performing the heat treatment or the plasma treatment at a low temperature.

The method of manufacturing a semiconductor device according to claim 2 is characterized in that a heat treatment in an oxygen atmosphere is performed between the first step and the second step. Is the way.

Further, in the method of manufacturing a semiconductor device according to claim 3, in the second step, the heat treatment or the plasma treatment is performed by a heat treatment using a mixed gas of hydrogen and an inert gas or a mixed gas of hydrogen and an inert gas. 3. The method of manufacturing a semiconductor device according to claim 1, wherein the plasma processing is performed.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments.

FIG. 1 is a view showing a manufacturing process of a semiconductor device according to an embodiment of the present invention. FIG. 2 is a graph for explaining the effects of the present invention. SIMS (Secondary Ion Mass
(Spectrometry: secondary ion mass spectrometry)
It is a figure which shows the data evaluated by. In FIG. 1, 1 is a silicon substrate, 2 is a thermal oxide film, 3 is implanted oxygen ions, 4 is a buried oxide film, 5 is a surface silicon layer (SOI
Layer).

According to the present invention, as means for reducing the interstitial oxygen of the surface silicon layer of the SOI substrate and improving the characteristics of the buried oxide film, first, a high temperature (an atmosphere temperature of 1300 to 140
By performing a heat treatment in an atmosphere of an inert gas such as argon at 0 ° C.), the oxygen implanted region becomes a buried oxide film and the crystallinity of the surface silicon layer is recovered. Next, heat treatment in an oxygen atmosphere is performed at a similar high temperature (atmospheric temperature of 1300 to 1400 ° C.) to improve the interface and film quality of the buried oxide film.

After that, a heat treatment in a hydrogen atmosphere is performed at an atmosphere temperature (800 to 1000 ° C.) lower than the above heat treatment temperature, and the crystallinity of the surface silicon layer is recovered, and the silicon layer remains in the surface silicon layer. The interstitial oxygen that forms a solid solution is diffused by this thermal energy, undergoes reduction by hydrogen on the surface silicon layer surface, becomes H ₂ O, and is released into the atmosphere.

At this time, a loop in which a concentration gradient of interstitial oxygen is generated in the surface silicon layer, diffusion of interstitial oxygen to the surface silicon layer surface is accelerated, reduced and removed, and the concentration gradient is further increased is repeated. Wake up and the interstitial oxygen will decrease. Here, since the diffusion of interstitial oxygen and the reduction of the insulating film at the interface of the buried oxide film by the hydrogen diffused into the surface silicon layer occur simultaneously, there is a problem in the high-temperature heat treatment of hydrogen to suppress the reduction of the buried oxide film. Atmosphere temperature at the time of heat treatment in a hydrogen atmosphere is 800
~ 1000 ° C is appropriate. That is, at 800 ° C. or less, sufficient reduction of interstitial oxygen is not performed, and at 1000 ° C. or more, reduction of the buried oxide film occurs.

The same effect can be obtained by performing a hydrogen plasma treatment. In this case, the temperature of the SOI substrate is set to 700 to 1000 ° C. because the temperature of the SOI layer rises due to exposure to hydrogen plasma. The reason is the same as the above-mentioned reason for limiting the ambient temperature.

Next, a manufacturing process of the semiconductor device according to the first embodiment of the present invention will be described with reference to FIG.

First, the silicon substrate 1 is oxidized to 50 nm
After the oxide film 2 is formed, oxygen ions ( ¹⁶ O ⁺ ) are implanted at an implantation energy of 140 keV and a dose of 4 × 10 ¹⁷ cm ⁻² (FIG. 1A). At this time, the average range Rp of oxygen ions is 295 nm from the surface in the silicon substrate.
Part.

Next, a heat treatment is performed in an argon atmosphere at an atmosphere temperature of 1350 ° C. for 4 hours to react implanted oxygen to form a buried oxide film 4 and to recover crystal defects of the surface silicon layer 5. . As a result, an SOI substrate by the SIMOX method in which the thickness of the buried oxide film 4 is 70 nm and the thickness of the surface silicon layer 5 is 260 nm is formed. (FIG. 1 (b)).

Next, in an oxygen atmosphere, the atmosphere temperature is set to 13
Oxidation annealing was continued at 50 ° C. for 4 hours to improve the characteristics of the buried oxide film 4. That is, in the heat treatment step using oxygen, the interstitial oxygen decreased in the heat treatment step using argon increases to the order of 10 ¹⁸ cm ⁻³ , but the thickness of the buried oxide film 4 slightly increases to 105 nm, The electrical characteristics and the interface state of are improved. The thickness of the oxide film 2 on the surface becomes 310 nm, and the thickness of the surface silicon layer 5 becomes 130 nm (FIG. 1C).

Next, the oxide film 2 on the surface of the silicon substrate 1 is removed with an HF-based etchant, and a heat treatment is performed in a hydrogen atmosphere at a temperature of 950 ° C. for 30 minutes using a diffusion furnace. The interstitial oxygen of the layer 5 was reduced and removed (FIG. 1D).

In the above heat treatment step, the heat treatment with hydrogen is performed last.
Oxygen implantation and oxygen annealing increase interstitial oxygen again, which is not preferable.

In the heat treatment in the oxygen atmosphere in the above embodiment, the surface silicon layer 5 is reduced. However, if the characteristics of the buried oxide film need not be perfect, the heat treatment in the oxygen atmosphere is not required. Good.

[0027] By this process, as shown in FIG. 2, it could be reduced interstitial oxygen concentration of the surface silicon layer to 10 ²⁰ cm ^-3 from the order of approximately two orders of magnitude smaller 10 ¹⁸ cm ^-3 order.

Next, a second embodiment of the present invention will be described.

In this embodiment, the heat treatment in the hydrogen atmosphere in the first embodiment is performed by plasma processing. That is, the SOI substrate on which the buried oxide film is formed is loaded into a plasma processing apparatus, and hydrogen gas (flow rate 10 to 30) is supplied.
The pressure was evacuated while the pressure was 10 Torr while flowing (sccm). Subsequently, the substrate is heated at 900 ° C. (700 to 10
Applicable in the range of 00 ° C. ), And after holding for 1 minute, exposing the SOI substrate to a hydrogen plasma excited by a microwave having a frequency of 2.45 GHz and a power of about 1 kW for about 2 minutes, stopping the plasma generation, and stopping the temperature. The gas was replaced with argon and kept for 5 minutes. In this heat treatment with argon, damage due to H ₂ plasma is annealed, and the surface silicon layer (（300
The crystallinity of (ii) will be restored.

By this treatment, the interstitial oxygen concentration in the surface silicon layer is reduced to 10 ²⁰ , almost in the same manner as in the first embodiment.
It could be reduced from cm ^-3 orders approximately 2 orders of magnitude less 10 ¹⁸ cm ^-3 order.

The heat treatment in the hydrogen atmosphere in the first embodiment is replaced with the heat treatment in a mixed gas atmosphere of hydrogen and an inert gas, or the hydrogen plasma treatment in the second embodiment is replaced with the hydrogen plasma treatment in the second embodiment. The partial pressure of hydrogen is reduced by replacing the plasma treatment with a mixed gas of hydrogen and an inert gas (specifically, the partial pressure is (H ₂ / inert gas) = 0.
01 to 0.5 is appropriate. This is effective for further suppressing the reduction in the thickness of the buried oxide film. When the thickness of the buried oxide film is small, there is an effect even if the amount of reduction in the film thickness is small.

[0032]

As described above, by using the present invention, interstitial oxygen in the SOI layer, which cannot be achieved by the conventional high-temperature hydrogen annealing, can be reduced. Specifically, as shown in FIG.
Although it was distributed like a broken line in the MS profile, 9
By the hydrogen reduction treatment at 50 ° C., the interstitial oxygen concentration of the surface silicon layer as the device active region could be reduced by two digits or more.

A defect network such as a gettering site generated by the conventional hydrogen annealing method does not occur inside the SOI layer, and is processed at a relatively low temperature in a short time. The interface with the SOI layer is not reduced.

Therefore, by using the present invention, the interstitial oxygen concentration in the SOI layer can be reduced.
Occurrence of oxygen-induced defects induced by thermal stress or stress stress such as a CVD film in a transistor manufacturing process or a portion where the stress is concentrated is reduced, and as a result, induced defects are reduced. In addition, the margin for defects increases, and the process can be stabilized.

The characteristics of the buried oxide film are further improved by using the present invention. Furthermore,
By using the present invention, it is possible to further suppress the reduction of the buried oxide film.

As described above, the junction leak current can be reduced, the lifetime can be increased, the reliability of the gate oxide film can be improved, and the power consumption of the device can be reduced, the operation speed can be increased, and the yield can be increased.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a diagram provided for describing effects of the present invention.

[Explanation of symbols]

 Reference Signs List 1 silicon substrate 2 thermal oxide film 3 implanted oxygen ions 4 buried oxide film 5 surface silicon layer

Claims (3)

[Claims] A first step of forming a buried oxide film and a surface silicon layer on the buried oxide film by ion-implanting oxygen into a silicon substrate and performing a heat treatment at a predetermined temperature in an inert gas atmosphere; After the first step, the temperature of the atmosphere in the heat treatment in the hydrogen atmosphere or the temperature of the substrate in the hydrogen plasma treatment is equal to or higher than the temperature at which the interstitial oxygen of the surface silicon layer causes a reduction reaction with hydrogen, and A second step of performing the heat treatment or the plasma treatment at a temperature lower than a temperature at which oxygen of the buried oxide film causes a reduction reaction with hydrogen. 2. The method for manufacturing a semiconductor device according to claim 1, wherein a heat treatment in an oxygen atmosphere is performed between the first step and the second step. 3. The heat treatment or the plasma treatment in the second step is a heat treatment with a mixed gas of hydrogen and an inert gas or a plasma treatment of a mixed gas of hydrogen and an inert gas. 3. The method for manufacturing a semiconductor device according to claim 1 or 2.