JP2007288032A - Surface treating device for semiconductor substrate, manufacturing method therefor, and generation source of sulfur - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for semiconductor device which easily performs a surface treatment for reducing a defect on a top surface of a semiconductor substrate and a dangling bond at an end by bonding them to sulfur, and to provide a generation source of sulfur. <P>SOLUTION: A surface treating device for semiconductor substrate is a surface treating device for semiconductor substrate that performs termination processing for a surface of a substrate with supplied gas containing supplied in a chamber adjusted to predetermined pressure. The device includes a sulfur gas generation source where a layer containing sulfur is formed, a stage where the substrate whose surface is to be surface-treated is fixed, a heater which heats the inside of the chamber to temperature at which the gas is produced by the sulfur gas generation source, and an exhausting device which controls the inside of the chamber to fixed pressure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductor substrate surface treatment apparatus and method for terminating dangling bonds on a semiconductor surface with sulfur, and a sulfur source.

Conventionally, when an electrode is formed on a semiconductor substrate, the management of the interface between the semiconductor substrate and the device affects the performance of the device. Therefore, it is important to treat the surface of the semiconductor substrate before forming the electrode on the surface of the semiconductor substrate. ing.
That is, a dangling bond in which an atomic covalent bond is broken (dangling bond) is performed on the outermost surface of a semiconductor substrate made of a compound semiconductor substrate in which a silicon substrate, gallium arsenide, nitride compound semiconductor, or the like is stacked. There is a bond with no opponent.

  When an electrode is formed on the outermost surface of a semiconductor substrate where a dangling bond exists in this way, a new potential barrier is generated at the interface between the semiconductor substrate and the electrode due to the dangling bond, and the operating voltage of the semiconductor device (MOS transistor) The threshold voltage of the diode, the forward voltage of the diode, etc.) will increase.

In order to suppress the increase in the operating voltage described above, it is necessary to reduce dangling bonds on the surface of the semiconductor substrate. As this method, surface treatment of the semiconductor substrate is known.
For example, as a typical method, contact etching is performed by etching a silicon oxide film on the surface of a semiconductor substrate with photolithography, and a molecular beam epitaxy (MBE) apparatus is used for the surface of the semiconductor substrate exposed at the opening. A surface treatment for reducing dangling bonds in a semiconductor substrate by depositing a Se (selenium) layer having a thickness of a monoatomic layer and covalently bonding the bonds of Se atoms and bonds in a dangling bond state. The method is well known.

However, most of the methods using the MBE apparatus are expensive and the diameter of a wafer that can be processed by a commercially available MBE apparatus is small (relative to a small-diameter wafer). It cannot cope with the processing of large diameter wafers.
Further, since the MBE apparatus is a single wafer type and is compatible with a single wafer, the throughput is poor, and the productivity is very poor for use in a process of simply reducing dangling bonds.
Furthermore, there is a problem that Se used for bonding with dangling bonds is highly toxic, and handling is required in the surface treatment process.

For this reason, as a process that is relatively easy to process and has a high throughput, a method is known in which a semiconductor substrate having dangling bonds is immersed in a yellow ammonium sulfide solution to perform a termination process on the surface of the semiconductor substrate.
That is, in order to terminate dangling bonds on the surface of the semiconductor substrate, the semiconductor substrate is immersed in an aqueous solution of yellow ammonium sulfide, and a sulfur (S) layer having a monoatomic thickness is deposited on the surface of the semiconductor substrate. There is a method of sulfurating by bonding with dangling bonds, and removing excess sulfur not bonded (for example, see Patent Document 1).
Japanese Patent Laid-Open No. 02-187029

As described above, in the surface treatment method disclosed in Patent Document 1, a monoatomic sulfur atomic layer (sulfur layer) is formed on the surface of a semiconductor substrate by immersion in an aqueous ammonium sulfide solution.
However, since the aqueous ammonium sulfide solution easily reacts with oxygen and hydrogen, when the semiconductor substrate is taken out from the aqueous ammonium sulfide solution, the ammonium sulfide on the surface of the semiconductor substrate comes into contact with the outside air, resulting in polysulfide, polythion hydrochloride / ammonium hydrogen sulfide, etc. The reactants adhere to the surface of the semiconductor substrate so as to cover the sulfur layer.
Therefore, it is necessary to remove the reactant attached to the surface of the semiconductor substrate, and it is necessary to add a step of sublimating and removing the reactant by vacuum heating the semiconductor substrate after performing the surface treatment.

However, even if a vacuum heating treatment for sublimation removal of the reactant is added, the reactant may not be completely removed, resulting in a residue of the reactant, and forming an electrode above the residue of the reactant. The resistance between the semiconductor substrate and the electrode increases due to the influence of the residual of the reactant, and the operating voltage of the semiconductor device (the threshold voltage of the MOS transistor, the forward voltage of the diode, etc.) increases. The effect of reducing the bond will not be obtained much.
SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and a semiconductor device manufacturing method and a sulfur source that easily perform surface treatment to reduce dangling bonds on the surface of a semiconductor substrate by combining with sulfur. The purpose is to provide.

  A surface treatment apparatus for a semiconductor substrate according to the present invention is a surface treatment apparatus for a semiconductor substrate that performs termination treatment of the surface of the semiconductor substrate with a gas containing sulfur supplied in a chamber adjusted to a predetermined pressure. A sulfur gas generation source in which a layer containing a gas is formed, a stage for fixing a semiconductor substrate on which surface termination is performed, a heater for heating the inside of the chamber to a temperature at which the gas is generated from the sulfur gas generation source, And an exhaust device (pump) for controlling the pressure in the chamber to a certain level (decreasing the pressure to a desired pressure suitable for processing).

  The surface treatment apparatus for a semiconductor substrate according to the present invention is characterized in that the heater controls the temperature to a value that gives thermal energy for breaking a bond between sulfur and atoms forming the surface of the substrate.

  The surface treatment apparatus for a semiconductor substrate according to the present invention is characterized in that the sulfur gas generation source and a stage are provided to face each other.

  The surface treatment apparatus for a semiconductor substrate according to the present invention further includes a revolving mechanism for revolving the stage and the sulfur gas generation source around a rotation axis existing between the stage and the sulfur gas.

  The semiconductor substrate surface treatment apparatus of the present invention further includes a rotation mechanism for rotating the stage and / or the sulfur gas generation source.

  The surface treatment apparatus for a semiconductor substrate according to the present invention is characterized in that the sulfur gas generation source includes a substrate and a layer containing sulfur formed on the substrate.

  The surface treatment method for a semiconductor substrate of the present invention is a semiconductor manufacturing method for performing a termination treatment on the surface of a semiconductor substrate with a gas containing sulfur supplied in a chamber adjusted to a predetermined pressure. A sulfur gas generation source formed on the substrate and a stage for fixing the semiconductor substrate on which the surface termination process is performed, a step of heating with a heater, a step of generating gas from the sulfur gas generation source, and the generated gas to generate sulfur. A step of attaching to the surface of the semiconductor substrate and performing a termination treatment on the surface of the semiconductor substrate.

  The surface treatment method for a semiconductor substrate according to the present invention further includes a step of controlling the temperature from 50 ° C. to 300 ° C., preferably from 100 ° C. to 200 ° C. within the range of the termination treatment temperature.

  The surface treatment method for a semiconductor substrate according to the present invention further comprises a step of revolving the stage and the sulfur gas generation source by a revolution mechanism around a rotation axis existing between the stage and the sulfur gas. To do.

  The semiconductor substrate surface treatment method of the present invention further includes a step of rotating the stage and / or the sulfur gas generation source by a rotation mechanism.

  The surface treatment method for a semiconductor substrate of the present invention is characterized in that the sulfur gas generation source is composed of a substrate and a layer containing sulfur formed on the substrate.

  The sulfur-containing gas generation source of the present invention is a sulfur gas generation source that generates sulfur-containing gas for terminating the surface of the semiconductor substrate, and a substrate, and a sulfur-containing material layer formed on the substrate, It is characterized by having.

As described above, according to the present invention, it is possible to batch-process large-diameter wafers compared to the case of using an MBE apparatus, and greatly improve the throughput in the surface treatment process of a semiconductor substrate. be able to.
Further, according to the present invention, since selenium is not used for the surface treatment of the semiconductor substrate, it is possible to prevent selenium from being taken into the body more than necessary, and the safety in the process can be improved.

The present invention is an apparatus for performing a surface treatment of a semiconductor substrate with a gas containing sulfur supplied in a chamber adjusted to a predetermined pressure, and a sulfur gas generation source having a sulfur-containing layer formed on a surface thereof. A stage for fixing the semiconductor substrate to be subjected to surface termination, a heater for heating the inside of the chamber to a temperature at which gas is generated from a sulfur gas generation source, and an exhaust device for keeping the pressure in the chamber constant (vacuum) Pump).
That is, in the present invention, a sulfur gas generation source is provided in the same chamber (same stage) as the semiconductor substrate to be subjected to surface termination treatment, and sulfur (sulfur atoms and sulfur molecules, sulfur molecules, A gas containing a compound containing a sulfur atom as a constituent element is generated, and sulfur is covalently bonded to dangling bonds on the surface of the semiconductor substrate by this gas to perform surface treatment of the semiconductor substrate.

  In addition, the present invention removes an insulator such as an oxide film formed on the surface of a semiconductor substrate by lithography to deposit an electrode, opens a contact hole, and removes sulfur from the surface of the semiconductor substrate. Then, a surface treatment of the semiconductor substrate is performed to suppress a dangling bond at the terminal.

A semiconductor device according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of the first embodiment.
In this figure, the surface treatment apparatus 1 for a semiconductor substrate, as described above, treats dangling bonds existing on the surface and defects of the semiconductor substrate with sulfur. Have. Although not shown in the figure, the surface treatment environment in the chamber 4 is timely exhausted from the exhaust port, and the inside of the chamber 4 during the surface treatment has a predetermined pressure (for example, 2 × 10 ⁻⁴ Pa). : as a range, is controlled to ^{5 × 10 5 Pa~1 × 10 -5} Pa), as almost 130 ° C. vicinity (range temperature in the chamber 4 by the heater 3 is controlled to 50 ° C. to 300 ° C.).
Hereinafter, a method for producing a sulfur gas generation source (range: 50 ° C. to 300 ° C.) will be described, and an apparatus and a method using termination treatment using the sulfur gas generation source will be sequentially described.

<Sulfur gas source>
As the sulfur gas generation source, for example, a substrate in which a material layer containing sulfur as a constituent element is formed on the surface by dipping in a chemical solution containing sulfur as a constituent element, such as an ammonium sulfide aqueous solution, that is, a sulfur gas generation source (hereinafter referred to as a sulfur gas generation source). A gas generating wafer 5) is prepared. Sulfur is known as an element that is easily sublimated, and what is attached to the substrate can be easily separated from the gas generating wafer 5 by heating treatment.
Here, the substrate used as the base of the gas generating wafer 5 may be a compound semiconductor substrate made of silicon, gallium arsenide, nitride, or the like, a metal plate, or the like.
If possible, the substrate of the gas generating wafer 5 is preferably formed of a material that does not react with the aqueous ammonium sulfide solution.

The substrate is immersed in a sulfide solution (a solution containing sulfide), for example, an aqueous solution of ammonium sulfide (25 ° C.) for about 30 minutes, that is, chemical treatment is performed, and sulfur adheres to the substrate surface.
Next, the substrate is taken out from the aqueous ammonium sulfide solution, and the ammonium sulfide solution adhering excessively on the substrate is removed by blowing nitrogen, and the substrate is dried.

At this time, as a result of the drying treatment, a reaction generated by contacting an aqueous solution of ammonium sulfide such as polysulfide, polythionate, and ammonium hydrogen sulfide on the upper part of the material layer containing dried sulfur. Objects are deposited and adhered by several μm to several tens of μm. In order to remove the reactant, for example, a vacuum heat treatment is performed for about 1 hour in an environment of a pressure of 2000 Pa (15 Torr) and a temperature of 200 ° C., and a sulfur-containing material layer (a part of the reactant is formed). May be formed).
Through the above-described steps, a material layer containing sulfur with a thickness of several atoms is formed on the substrate, and the gas generating wafer 5 is obtained.

By this treatment, a material layer containing sulfur, that is, a sulfur gas generation source is formed on the substrate surface, and the gas generation wafer 5 is obtained. Then, by gasifying the material layer in the chamber 4, a sulfur-containing layer for terminating treatment is formed on the surface of the semiconductor substrate to be processed (hereinafter, semiconductor substrate 6) by sulfur contained in the generated gas. Then, it is covalently bonded to a dangling bond on the surface of the semiconductor substrate 6.
Here, in order to make the generation of sulfur gas efficient, the termination of the gas generation wafer 5 is not performed, that is, the density of dangling bonds on the surface of the substrate that is covalently bonded to sulfur in the chemical treatment process. It is desirable to use less material.

Thereby, sulfur which is not covalently bonded to the dangling bond of the substrate can be easily separated by sublimating from the gas generating wafer 5 at a temperature lower than the bonded sulfur.
Further, when a substrate having a high dangling bond density is used as the gas generating wafer 5, this dangling bond is preliminarily treated with some atoms (which may also contain sulfur), a shield layer is formed, and then The material layer may be formed on the shield layer by being immersed in an aqueous ammonium sulfide solution.

In addition, the material layer is not formed by immersing in an aqueous ammonium sulfide solution, but a dampling bond on the substrate surface is reduced by forming a shield layer in advance on the substrate surface with a gas containing sulfur using a plasma apparatus. Then, the material layer may be formed on the shield layer by immersing in an aqueous ammonium sulfide solution.
In addition, the material layer may be formed in a dry state using a gas containing sulfur, instead of being formed by immersing the material layer in an aqueous ammonium sulfide solution. By forming the material layer in a dry state, no reactant is generated on the substrate, so there is no step of removing the reactant by vacuum heat treatment, and the gas generating wafer 5 can be created in a short time.

  Further, it is desirable that the substrate used for the gas generating wafer 5 has less irregularities on the surface and is flatter. Here, when the surface has many irregularities, the surface area of the substrate increases, that is, the surface area of the material layer on the gas generating wafer 5 increases, but it is difficult for sulfur to be sublimated from the substrate by being attracted to or colliding with the surface irregularities. As a result, the efficiency of gas generation is reduced.

<First Embodiment of Surface Treatment of Semiconductor Substrate>
A first embodiment of a surface treatment apparatus 1 for a semiconductor substrate will be described with reference to FIG. As shown in FIG. 1, a quartz boat 2 is disposed in a chamber 4. A gas generation wafer 5 and a surface (substrate) that terminates a surface facing the surface of the gas generation wafer 5 are disposed on the quartz boat 2. The semiconductor substrate 6 is fixed so as to be the surface 6A).
As described above, the pressure (degree of vacuum) in the chamber 4 is controlled to about 2 × 10 ⁻⁴ Pa and the temperature is controlled to about 130 ° C. by the heater 3. Thereby, the temperature of each of the gas generating wafer 5 and the semiconductor substrate 6 is also controlled to about 130 ° C.

Here, the gas generation wafer 5 used as a gas generation source is produced by the process already described. Further, in the semiconductor substrate 6, an oxide film or the like is formed on the surface 6A, and the region to be terminated is contact-opened by lithography and etching, so that the surface of the semiconductor substrate 6 is exposed.
As described above, the degree of vacuum (pressure) in the chamber 4 is controlled by the exhaust port and the exhaust device (not shown) that exhausts the gas in the chamber 4 from the exhaust port.

Next, referring to FIG. 1, a semiconductor manufacturing method in which termination treatment for dangling bonds on the surface 6 </ b> A of the semiconductor substrate 6 is performed with sulfur by the surface treatment apparatus 1 for a semiconductor substrate according to the first embodiment will be described.
The semiconductor substrate 6 and the gas generating wafer 5 are fixed by inserting a part of each substrate into a groove provided in the quartz board 2.
Then, after the degree of vacuum in the chamber 4 is set to 2 × 10 ⁻⁴ Pa by the exhaust device, the chamber 4 is heated by the heater 3 (vacuum heating), and is controlled to a predetermined temperature by a temperature control device (not shown). .

Here, the inside of the chamber 4, that is, the gas generating wafer 5 and the semiconductor substrate 6 are set to a predetermined temperature, for example, about 130 ° C. By the vacuum heat treatment, sulfur that has been warmed up and separated (sublimated) from the material layer of the gas generating wafer 5 is generated, and the chamber 4 is filled with sulfur at the degree of vacuum.
Further, the predetermined temperature is equal to or lower than the temperature at which the surface dangling bond on the surface 6A of the semiconductor substrate 6 is separated from the covalent bond between the sulfur dangling bonds contained in the gas and the gas generating wafer. It is important to control from the state of sulfur adhering to the substrate surface 5 to a temperature at which sulfur adhering to the substrate surface sublimates from the substrate.

  That is, in the material layer formed on the gas generating wafer 6 by being immersed in the ammonium sulfide aqueous solution, it adheres not only to the surface of the substrate or the dangling bond at the end of the defect but also to the surface of the substrate. But only sulfur that is not covalently bonded. Since the covalently bonded sulfur is not broken unless heat (heat energy) of 300 ° C. or higher is applied, the covalently bonded sulfur sublimates before the covalently bonded sulfur in the material layer. Then, it diffuses into the chamber 4 as gas.

As a result, a gas containing sulfur sublimated from the material layer of the gas diffusing wafer 5 diffuses in the chamber 4, and a part thereof is covalently bonded to the surface dangling bond on the surface 6 </ b> A of the semiconductor substrate 6.
At this time, when the chamber 4 is heated to 130 ° C., the sulfur covalently bonded to the dangling bond on the surface 6A is stably broken down on the surface 6A as the covalent bond is not sublimated and sublimated. Will remain.

As described above, the temperature in the chamber 4, that is, the surface temperature of the gas generating wafer 5 and the semiconductor substrate 6 is less than the temperature at which the covalent bond between the atoms and the sulfur on the surface 6A of the semiconductor substrate 6 to be terminated is broken. It is set in a temperature range (hereinafter referred to as a termination processing temperature range) that is equal to or higher than the temperature at which sulfur that is not covalently bonded to the substrate surface of the gas generating wafer 5 sublimates from the substrate surface. (Sulfur is known as an element that is easily sublimated.)
Thereby, the inside of the chamber 4 can be almost filled with sulfur. Further, the sulfur sublimated from the gas generating wafer 5 effectively forms a covalent bond with a dangling bond which is an unbonded hand of the atom on the surface 6A. Unnecessary excess sulfur sublimates from the surface 6A, thereby forming a minimum necessary sulfur layer for reducing dangling bonds and improving the bonding characteristics at the interface between the electrode and the semiconductor substrate. .

The surface treatment apparatus for a semiconductor substrate according to the present invention performs the termination treatment at a lower temperature within the above termination treatment temperature range, thereby controlling the temperatures of the chamber 4, the gas generating wafer 5 and the semiconductor substrate 6. The time for raising the temperature and the time required for cooling can be reduced.
Thereby, according to the surface treatment apparatus for a semiconductor substrate of the present invention, temperature control itself is easy compared with a high temperature, the overall surface treatment time of the semiconductor substrate 6 can be reduced, and more surface treatment can be performed. Throughput can be improved.
Further, according to the surface treatment apparatus for a semiconductor substrate of the present invention, if the gas generating wafer 5 is prepared in advance as in the prior art, the surface of the semiconductor substrate 6 is subjected to termination treatment by covalently bonding sulfur to the semiconductor substrate 6. In order to sublimate the above reactants, it is not necessary to heat in a vacuum, and the surface treatment of the semiconductor substrate 6 is satisfactorily performed, so that the characteristics (contact resistance) at the interface with the electrode formed thereon can be reduced. it can.

<Second Embodiment of Surface Treatment of Semiconductor Substrate>
A second embodiment of the surface treatment apparatus 1 ′ for a semiconductor substrate will be described with reference to FIG. As shown in FIG. 2, in the second embodiment, a heater 3, a revolution stage 10, a revolution mechanism 11 of the revolution stage 10, a substrate stage 12, a rotation mechanism 13 of the substrate stage 12, and a substrate stage 12 are provided in the chamber 4. Mounting jig 14, gas generating wafer stage 15, rotation mechanism 16 of gas generating wafer stage 15, and mounting jig 17 for gas generating wafer 15 are provided. Control of the degree of vacuum in the chamber 4 is the same as that in the first embodiment of the surface treatment of the semiconductor substrate already described.

The revolution stage 10 is, for example, a circular metal plate, and is connected to a revolution mechanism 11 that rotates the revolution stage 10 via a rotation shaft 11a provided at the center of the metal plate. The revolution mechanism 11 is provided on the bottom plate 1 a of the chamber 4. This rotating shaft 11a is connected perpendicularly to the surfaces of the revolution stage 10 and the bottom surface 1a.
The revolution mechanism 11 rotates the rotation shaft 11 a at a predetermined rotation speed (for example, 5 to 12 rpm), that is, the revolution stage 10 is rotated so that the rotation surface is parallel to the surface of the revolution stage 10.

The substrate stage 12 is, for example, a circular metal plate, and the semiconductor substrate 6 to be processed in the termination process is fixed with the surface 6A, which is the processing surface, facing upward (exposed) with respect to the substrate stage 12. Mount. The substrate stage 12 is connected to a rotation mechanism 13 provided at the center of the metal plate via a rotation shaft 13 a of the rotation mechanism 13. The rotating shaft 13a is connected perpendicularly to the 12 surfaces of the substrate stage.
The rotation mechanism 13 rotates the rotation axis 13a at a predetermined rotation speed (for example, 32-78 rpm), that is, rotates the substrate stage 12 so that the rotation surface is parallel to the surface of the substrate stage 12 on which the semiconductor substrate 6 is fixed. Let The rotation mechanism 13 is connected to the revolution stage 10 by a mounting jig 14 so as to be substantially perpendicular to the revolution stage 10, and the surface of the substrate stage 12 on which the semiconductor substrate 6 is fixed is the rotation stage 10. The rotation mechanism 13 (the rotation shaft 13a) and the mounting jig 14 are provided with a predetermined angle so as not to be parallel to the surface on which the mounting jig 14 is provided.

The gas generation wafer stage 15 is, for example, a circular metal plate, and the gas generation wafer 5 that generates sulfur used for termination processing is fixed upward (exposed) with respect to the gas generation wafer stage 15. And mount. The gas generating wafer stage 15 is connected to a rotation mechanism 16 provided at the center of the metal plate via a rotation shaft 16 a of the rotation mechanism 16. The rotating shaft 16a is connected perpendicularly to the surface 15 of the gas generating wafer stage.
The rotation mechanism 16 rotates the rotation shaft 16a at a predetermined rotation speed (for example, 32-78 rpm), that is, generates gas so that the rotation surface is parallel to the surface of the gas generation wafer stage 15 on which the gas generation wafer 5 is fixed. The wafer stage 15 is rotated. The rotation mechanism 16 is connected to the revolution shaft 10 by a mounting jig 17 so as to be substantially perpendicular to the revolution shaft 10, and the surface of the gas generation wafer stage 15 to which the gas generation wafer 5 is fixed is revolved. The rotation mechanism 16 (of the rotation shaft 16) is provided with a predetermined angle so as not to be parallel to the surface of the stage 10 (so as not to be parallel).

The rotation of the substrate stage 12 and the gas generating wafer stage 15 is rotated by the rotation mechanisms 13 and 16 operating. The revolution stage 10 is rotated by operating the revolution mechanism 11, and the substrate stage 12 and the gas generating wafer stage 15 are connected to the revolution stage via the mounting jig 17. The substrate stage 12 and the gas generation wafer stage 15 also revolve according to the rotation. The rotation and revolution system is not limited to the revolution mechanism 11 and the rotation mechanisms 13 and 16 described above, and any rotation mechanism may be used.
Further, without providing the rotation mechanism 13 and the rotation shaft 13a, the substrate stage 12 may be directly fixed to the mounting jig 14 so that only the revolution is performed, and only the gas generation wafer stage 15 may be rotated and revolved together.
The substrate stage 12 and the gas generation wafer stage 15 are arranged with the predetermined angle adjusted in an angle range in which the surface 6A of the semiconductor substrate 6 and the material layer of the gas generation wafer 5 face each other.

  With the above-described configuration, in addition to the effects of the first embodiment, centrifugal force is generated by the revolution of the revolution stage 10 and the rotation of the gas generation wafer stage 5, and sulfur is more easily generated from the gas generation wafer 5 into the chamber 4. Will be sublimated. Further, the gas containing sulfur sublimated from the gas generating wafer 5 is uniformly diffused into the chamber 4. For this reason, the surface treatment apparatus 1 ′ for the semiconductor substrate according to the second embodiment can uniformly supply sulfur into the surface 6 </ b> A of the semiconductor substrate 6, and can effectively perform termination treatment for dangling bonds.

  Further, the substrate stage 12 also rotates, and the semiconductor substrate 6 rotates within the stage surface, so that sulfur is more uniformly connected to the surface 6A of the surface 6A of the semiconductor substrate 6 by a tangling bond. Further, even if excessive sulfur adheres to a limited portion of the semiconductor substrate 6, it can be removed by centrifugal force generated by the revolution of the revolution stage 10 and the rotation of the substrate stage 12. As a result, a sulfur layer is formed almost uniformly in the surface 6A, and the termination process is performed to uniformly reduce the number of dangling bonds exposed by opening the contact of the semiconductor substrate 6 (dangling). The bond density can be reduced).

As described above, according to the semiconductor substrate surface treatment apparatuses 1 and 1 ′ of the first and second embodiments, the dangling bonds on the outermost surface exposed by opening the contact of the semiconductor substrate 6 are exposed. By terminating sulfur by covalent bonding, the density of dangling bonds can be reduced, and the potential barrier at the interface between the electrode formed thereon and the semiconductor substrate 6 can be lowered. By reducing the potential barrier, it is possible to improve the characteristics of the semiconductor device, such as lowering the forward voltage in the case of a diode and reducing the variation in threshold voltage in the case of a MOS transistor.
The semiconductor substrate 6 to be subjected to termination processing may be any of a silicon substrate, a silicon substrate, a ceramic substrate, and a substrate in which a compound semiconductor such as GaAs or GaN is stacked on a SiC substrate.

Further, when an electrode is formed on the layer made of sulfur covalently bonded to the surface dangling bond exposed by opening the contact of the semiconductor substrate 6, this electrode has a Schottky characteristic with respect to the semiconductor substrate 6. It may have either (rectifying characteristics) or ohmic characteristics (low resistance).
Further, it is considered that the controllability is improved by preventing the supply of sulfur to the semiconductor substrate 6 after the layer in which sulfur is covalently bonded to the dangling bond is formed on the surface 6A of the semiconductor substrate 6. For this reason, a protective wall may be provided to prevent the gas containing sulfur from being supplied to the semiconductor substrate 6 fixed to the substrate stage 12.
The above-mentioned “sulfur” is a constituent material used for the termination treatment existing in the chamber 4, and is a kind of termination treatment using sulfur molecules, sulfur atoms, and further sulfur molecules and sulfur atoms as constituent elements. And a compound used as a part.

<Application Examples of Embodiments of the Present Invention>
As an example of the semiconductor substrate 6, when forming an SBD having a low voltage loss between the Schottky electrode and the semiconductor substrate as an SBD (Schottky barrier diode) having a low forward voltage shown in FIG. The result of having measured the characteristic is described below.
-Device creation Diffusion layer forming the semiconductor substrate 100 is an N-type silicon substrate, doped N-type impurities have been N ^- formed on one main surface of the semiconductor layer N ^{- -} semiconductor layer and the N impurity than the semiconductor layer is large N ⁺ And a semiconductor layer.
By heating the semiconductor substrate 100 in an oxygen atmosphere in an oxidation chamber, the other main surface of the semiconductor substrate 100 is oxidized to form an oxide film.

Then, a resist is applied on the oxide film, photolithography is performed on the resist, and a resist mask pattern is formed in order to form the diffusion layer 102.
Using the resist mask pattern as a mask, the oxide film is etched to expose the surface of the semiconductor substrate 100 to form an opening for forming the P ⁺ semiconductor layer 102.
Then, boron atoms are diffused into the semiconductor substrate 100 from the opening, and the P ⁺ semiconductor layer 102 exposed on the other main surface of the semiconductor substrate 100 is formed in an island shape. Then, the resist is removed by chemical treatment. Then, an oxide film is formed on the surface of the semiconductor substrate 100.

B. Surface Treatment As shown in FIG. 3, the oxide film 101 is formed by etching the oxide film in a region for forming an electrode, which will be described later, to open a contact. For this reason, after applying the resist, a resist pattern is formed by photolithography so that the resist is removed only in the region where the electrode is to be formed.
Then, the oxide film 101 is etched to remove the oxide film 101, and then the resist is removed.
Next, the natural oxide film formed on the exposed surface of the semiconductor substrate 100 is removed by dilute hydrofluoric acid, so that the semiconductor substrate 6 is obtained. Next, termination processing is performed by the surface treatment apparatus 1 ′ for the semiconductor substrate in the second embodiment, and the sulfur layer 103 covalently bonded to the dangling bond is formed.

C. Formation of Schottky Electrode Then, a barrier metal 104 constituted by stacking Mo (molybdenum) / V (vanadium) with a thickness of 100 nm is formed by sputtering or vapor deposition.

Next, after cleaning the surface of the barrier metal 104 with buffered hydrofluoric acid, an electrode material made of Al (aluminum) is deposited to a thickness of 5 μm by vapor deposition or sputtering. The Al is a bonding metal for bonding by Al wire bonding or the like.
Then, a resist is applied to the surface of the electrode material made of Al, and a resist pattern that leaves only the portion of FIG. 3 is formed by lithography. Using this resist pattern as a mask, the exposed metal (Al / Mo / V) Are sequentially etched.
Then, after the etching of the exposed portion is completed, the resist pattern used as a mask is removed.

D. Next, a resist is applied to the surface on which the above-described electrodes are formed, and the entire surface is masked.
Then, a blasting process (for example, sandblasting) is performed on the back surface (the surface on which the electrode is not formed), a metal attached to the back surface is removed, and a pretreatment for forming a back electrode is performed.
Then, after removing the resist on the front surface, cleaning with buffered hydrofluoric acid is performed to form a back electrode 106 on the back surface. The back electrode 106 is formed as an ohmic (low resistance) electrode on the back surface of the semiconductor substrate 100.
The back electrode 106 is formed by stacking Ti (titanium) / Ni (nickel) / Pd (palladium) / Ag (silver) at a thickness of 100 nm / 500 nm / 50 nm / 100 nm by sputtering or vapor deposition. As the back electrode 106, Ti—Ni—Au, Cr—Ni—Au, or the like may be used.

FIG. 4 shows Vf (forward voltage) characteristics of the SBD formed by the above-described process and the SBD not subjected to the surface treatment. In FIG. 4, the horizontal axis is the voltage (V) applied in the forward direction, and the vertical axis is the forward current (A) flowing corresponding to this voltage.
As can be seen from FIG. 4, it can be seen that the SBD subjected to the surface treatment with sulfur by the semiconductor device 1 of the present invention has a lower forward voltage value than the SBD not subjected to the surface treatment. .

It is the conceptual diagram which opened the side of the apparatus which shows the example of an internal structure of the surface treatment apparatus 1 of the semiconductor substrate by the 1st Embodiment of this invention. It is the conceptual diagram which opened the side of the apparatus which shows the example of an internal structure of the surface treatment apparatus 1 'of the semiconductor substrate by the 2nd Embodiment of this invention. It is a conceptual diagram which shows the cross-sectional structure of the Schottky diode formed by application. 4 is a graph showing Vf characteristics of the Schottky diode of FIG. 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1 '... Semiconductor substrate surface treatment apparatus 2 ... Quartz boat 3 ... Heater 4 ... Chamber 5 ... Gas generating wafer 6,100 ... Semiconductor substrate 10 ... Revolution stage 11 ... Revolution mechanism 11a, 13a, 16a ... Rotating shaft 12 ... Substrate stages 13 and 16 Rotating mechanisms 14 and 17 Mounting jig 15 Gas generating wafer stage

Claims (12)

In the chamber adjusted to a predetermined pressure, a semiconductor substrate surface treatment apparatus that performs a termination treatment of the surface of the semiconductor substrate with a gas containing sulfur supplied.
A sulfur gas generation source in which a layer containing sulfur is formed;
A stage for fixing a semiconductor substrate on which surface termination is performed;
A heater for heating the inside of the chamber to a temperature at which the gas is generated from the sulfur gas generation source;
A surface treatment apparatus for a semiconductor substrate, comprising: an exhaust device (pump) for controlling the pressure in the chamber at a constant level.   2. The surface treatment apparatus for a semiconductor substrate according to claim 1, wherein the temperature is controlled to 50 to 300 [deg.] C., preferably 100 to 200 [deg.] C.   The surface treatment apparatus for a semiconductor substrate according to claim 1, wherein the sulfur gas generation source and the stage are provided to face each other.   The revolving mechanism which revolves the said stage and sulfur gas generation source centering on the rotating shaft which exists between this stage and sulfur gas is characterized by the above-mentioned. Semiconductor substrate surface treatment equipment.   5. The surface treatment apparatus for a semiconductor substrate according to claim 1, further comprising a rotation mechanism for rotating the stage and / or the sulfur gas generation source. The sulfur gas generation source is a substrate,
6. The surface treatment apparatus for a semiconductor substrate according to claim 1, comprising: a layer containing sulfur formed on the substrate. In the chamber adjusted to a predetermined pressure, a semiconductor substrate surface treatment method for terminating the surface of the semiconductor substrate with a gas containing sulfur supplied,
A step of heating with a heater a stage for fixing a semiconductor substrate on which a sulfur gas generation source in which a layer containing sulfur is formed and a surface termination treatment is performed;
A step of generating gas from a sulfur gas source;
A surface treatment method for a semiconductor substrate, comprising: attaching sulfur to the surface of the semiconductor substrate by the generated gas, and performing a termination treatment on the surface of the semiconductor substrate.   8. The surface treatment method for a semiconductor substrate according to claim 7, further comprising a step of controlling the temperature within a range of the termination treatment temperature from 50 [deg.] C. to 300 [deg.] C., preferably from 100 [deg.] C. to 200 [deg.].   9. The method according to claim 7, further comprising a step of causing the stage and the sulfur gas generation source to revolve by a revolution mechanism around a rotation axis existing between the stage and the sulfur gas. A method for surface treatment of a semiconductor substrate.   The semiconductor substrate surface treatment method according to claim 7, further comprising a step of rotating the stage and / or the sulfur gas generation source by a rotation mechanism. The sulfur gas generation source is a substrate,
The method for treating a surface of a semiconductor substrate according to any one of claims 7 to 10, wherein the surface treatment method comprises a layer containing sulfur formed on the substrate. It is a sulfur gas generation source that generates a gas containing sulfur for terminating the semiconductor substrate surface,
A substrate,
A sulfur-containing gas generation source comprising a sulfur-containing material layer formed on the substrate.

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