JP5205840B2 - Manufacturing method of semiconductor substrate - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor substrate having a semiconductor single crystal layer on an oxide film, such as an SOI (Silicon On Insulator) substrate.

  As one of semiconductor device substrates, there is an SOI (Silicon On Insulator) substrate in which a silicon layer (hereinafter also referred to as an SOI layer) is formed on a silicon oxide film that is an insulating film. This SOI substrate has a small parasitic capacitance and high radiation resistance because the SOI layer on the surface layer of the substrate, which is a device manufacturing region, is electrically separated from the inside of the substrate by a buried oxide film layer (BOX layer). Has characteristics. Therefore, effects such as high-speed and low-power consumption operation and prevention of soft errors are expected, and it is promising as a substrate for high-performance semiconductor elements.

Typical methods for manufacturing this SOI substrate include a wafer bonding method and a SIMOX method. In the wafer bonding method, for example, after forming a thermal oxide film on one surface of two single crystal silicon substrates (silicon wafers), the two wafers are brought into close contact with each other through the formed thermal oxide film, This is a method for producing an SOI substrate by increasing the bonding force by performing a bonding heat treatment, and then thinning one of the wafers (a wafer for forming an SOI layer (hereinafter referred to as a bond wafer)) by mirror polishing or the like. As this thinning method, a bond wafer is ground and polished to a desired thickness, or at least one of hydrogen ions or rare gas ions is implanted into the bond wafer to form an ion implantation layer, There is a method called an ion implantation separation method in which the bond wafer is separated from the ion implantation layer after bonding.
On the other hand, in the SIMOX method, oxygen is ion-implanted into a single crystal silicon substrate, and then a high temperature heat treatment (oxide film formation heat treatment) is performed to react the implanted oxygen and silicon to form a BOX layer. A method for manufacturing a substrate.

  In recent years, in CMOS-LSI, which is the main application of SOI substrates, the trend toward miniaturization and high integration of devices has become more and more significant, and what was called an ultra-thin film about 100 nm until several years ago. But now it is no longer surprising. At present, the average film thickness required for an ultra-thin SOI layer is much less than 100 nm and is several tens of nm. At the same time, the demand for thinning the BOX layer is also increasing. Around 2015, it is expected that a 10 nm SOI layer and a 10 nm BOX layer will be required, and the film thickness uniformity at that time is ± 0.1 nm. A level is required.

  In consideration of the quality of the SOI layer and the BOX layer to be formed, the degree of freedom and uniformity of the film thickness, the ion implantation delamination method is the most promising among the above-described current SOI substrate manufacturing methods, but a 10 nm SOI In order to obtain a layer, it is necessary to adjust the film thickness by performing sacrificial oxidation after forming a thicker SOI layer, so the process becomes complicated and the cost is unavoidable. Even if it is used, the film thickness uniformity of the SOI layer is limited to ± 0.6 nm level (standard deviation σ = 0.2 nm) at present as described in Patent Document 1.

International Publication No. WO03 / 009386 Pamphlet

  The present invention has been made in view of such a problem. A semiconductor substrate in which an oxide film having a high film thickness uniformity and a semiconductor single crystal layer are formed on the surface of a semiconductor single crystal substrate is manufactured at low cost. It aims at providing the method of manufacturing by.

In order to achieve the above object, the present invention is a method of manufacturing a semiconductor substrate having a semiconductor single crystal layer on an oxide film by sequentially forming an oxide film and a semiconductor single crystal layer on the surface of the semiconductor single crystal substrate. Forming an oxide film having an epitaxial relationship with the semiconductor single crystal substrate on the surface of the semiconductor single crystal substrate by contacting at least an oxidizing solution or a gas thereof with the semiconductor single crystal substrate; that provides a method of manufacturing a semiconductor substrate, characterized by a step of epitaxially growing a semiconductor single crystal layer on the oxide film.

In this manner, first, an oxide film that maintains an epitaxial relationship with the semiconductor single crystal substrate is formed on the surface of the semiconductor single crystal substrate by bringing the oxidizing solution or the gas into contact with the semiconductor single crystal substrate. If such an oxide film having an epitaxial relationship with the semiconductor single crystal substrate is formed, a semiconductor single crystal layer having the same orientation as the underlying semiconductor single crystal substrate can be epitaxially grown on the oxide film. it can. As a result, a semiconductor substrate having a semiconductor single crystal layer on an oxide film can be manufactured.
In this specification, “an oxide film having an epitaxial relationship with a semiconductor single crystal substrate” means that a semiconductor single crystal layer having the same crystal structure as that of the semiconductor single crystal substrate can be epitaxially grown on the oxide film. It means an oxide film having a structure.
In addition, a semiconductor substrate manufacturing method having such a process does not require any other special process such as ion implantation or bonding of two substrates, and an ultra-thin film, a high A semiconductor substrate having a uniform semiconductor single crystal layer can be manufactured at low cost.

In this case, the oxidizing solution or gas, have preferably be azeotropic concentration.
In this way, if the oxidizing solution or its gas is of an azeotropic concentration, there is no change in the concentration of the solution or gas due to evaporation or condensation. An oxide film with excellent properties can be obtained.

In this case, before the step of bringing the oxidative solution having the azeotropic concentration or the gas into contact with the semiconductor single crystal substrate, the oxidizing solution having the azeotropic concentration or the gas is brought into contact with the semiconductor single crystal substrate. further comprising the step is not preferable.
As described above, the step of bringing the semiconductor single crystal substrate into contact with the oxidizing solution having the azeotropic concentration or the gas before the step of bringing the semiconductor single crystal substrate into contact with the oxidizing solution or the gas having the azeotropic concentration is provided. Then, a relatively thick oxide film having a thickness of about 10 nm or more can be formed.

Moreover, the method of manufacturing a semiconductor substrate according to the present invention, the semiconductor single crystal substrate, has the preferable be a Si single crystal substrate.
Thus, if the semiconductor single crystal substrate is a Si single crystal substrate, a semiconductor single crystal substrate having a large diameter of 300 mm or more and excellent crystallinity can be obtained relatively easily. It is suitable for epitaxial growth of the retained oxide film or semiconductor single crystal layer.

Further, the semiconductor single crystal layer, Si layer, SiGe layer, it is not preferable that either of the Ge layer.
These semiconductor layers have high versatility of source gases, are well known for physical properties as a semiconductor single crystal layer, and have a wide range of applications to electronic devices.

Further, the oxidizing solution or gas, have preferably be a nitric acid solution or a gas.
Thus, if a nitric acid aqueous solution or its gas is used as the oxidizing solution or its gas, a higher quality chemical oxide film can be formed by its strong oxidizing power.

  According to the present invention, a semiconductor single crystal layer (SOI layer) having a very thin ultrathin film whose thickness is about 10 nm or less and high film thickness uniformity such as ± 0.1 nm level, for example. Etc.) can be obtained by a simple process on the oxide film (BOX layer). As a result, a semiconductor substrate capable of manufacturing a next-generation high-performance device can be provided at an extremely low cost.

Hereinafter, the present invention will be described in detail.
As described above, the demand for thinning the SOI layer and the BOX layer in the SOI substrate becomes more and more serious, and in the near future, an ultra-thin SOI structure such as a 10 nm SOI layer and a 10 nm BOX layer, ± 0.1 nm level It is expected that an SOI layer having a uniform film thickness will be required. However, in the current method for manufacturing an SOI substrate, in order to obtain the above ultra-thin SOI structure, the cost is inevitably high. The film thickness uniformity did not reach a level that satisfies the requirements.

The inventor forms an oxide film (chemical oxide film) by bringing a Si single crystal substrate into contact with an oxidizing solution or its gas, compared with a case where an oxide film (thermal oxide film) is formed by thermal oxidation. It was noted that a dense oxide film is formed at a much lower temperature. For example, when a Si single crystal substrate is immersed in an azeotropic nitric acid aqueous solution, it is oxidized at about 120 ° C. due to the strong oxidizing power of nitric acid, and an oxide film of about 1.3 nm is formed in about 1 hour. The reason why oxidation is performed at such a low temperature is that O ₂ molecules diffuse in silicon in thermal oxidation that requires high temperature, whereas in the oxidation with nitric acid aqueous solution, O ⁻ ions act as an oxidizing agent, so the temperature is low. This is considered to be because diffusion is possible and reactivity to silicon bonds is high.
If oxidation is performed by such a low-temperature reaction, there is no thermal stress due to a large difference in thermal expansion coefficient between the silicon single crystal substrate and the oxide film. The present invention has been completed by conceiving that silicon can be epitaxially grown on this oxide film.

Hereinafter, the present invention will be described in more detail with reference to the drawings, but the present invention is not limited thereto.
1A to 1C are flowcharts showing an example of a method for manufacturing a semiconductor substrate according to the present invention.

First, as shown in FIG. 1A, a semiconductor single crystal substrate 11 for sequentially forming an oxide film and a semiconductor single crystal layer on the surface is prepared.
As the semiconductor single crystal substrate 11, a Si single crystal substrate is preferably used, but a semiconductor single crystal substrate such as Ge or a compound semiconductor can also be used.

Next, the oxidizing solution or its gas is brought into contact with the semiconductor single crystal substrate 11 prepared above.
For example, the semiconductor single crystal substrate 11 is put into a treatment tank filled with an oxidizing solution for forming an oxide film or its gas, and held at a predetermined temperature for a predetermined time, thereby forming the oxide film 12 on the surface. (FIG. 1 (b)).
At this time, if an oxidizing solution is used, the configuration of the treatment tank can be made simpler, but a method of exposing to an oxidizing solution gas (oxidizing solution vapor) can also be adopted.

As this oxidizing solution or its gas, it is preferable to use an aqueous nitric acid solution because a high-quality chemical oxide film can be formed by its strong oxidizing power. However, it is not limited to this, for example, sulfuric acid, ozone-dissolved water, hydrogen peroxide solution, a mixed solution of hydrochloric acid and hydrogen peroxide solution, a mixed solution of sulfuric acid and hydrogen peroxide solution, sulfuric acid and nitric acid A mixed solution of the above, aqua regia and the like or a mixture thereof may be used.
When an oxidizing gas is used, the vapor of these oxidizing solutions is used.

  The oxide film (chemical oxide film) 12 thus formed maintains an epitaxial relationship with the semiconductor single crystal substrate 11. Therefore, it is possible to epitaxially grow a semiconductor single crystal layer on this oxide film 12.

  Moreover, it is preferable that the oxidizing solution or the gas thereof has an azeotropic concentration that forms an azeotropic state. The azeotropic state refers to a state where, when a liquid mixture having a certain composition is heated to boiling, the boiling point becomes maximum or minimum at a specific concentration, and the composition of the solution and the composition of the vapor coincide. In the azeotropic state, there is no change in the concentration of the solution (or vapor) due to evaporation or condensation. Therefore, when the semiconductor single crystal substrate is oxidized using an azeotropic oxidizing solution or its gas, the film thickness uniformity and the film thickness reproducibility of the formed oxide film are good.

  In the case of forming a relatively thick oxide film having a thickness of about 10 nm or more, an oxidizing solution having a concentration lower than the azeotropic concentration or a gas thereof (the concentration of the component having oxidizing power is the azeotropic concentration). It is preferable to perform a step of contacting an azeotropic oxidizing solution or a gas thereof, as described above, after performing the step of contacting the lower one). With such a process, a relatively thick oxide film as described above is formed in a shorter time than when an oxide film is formed only by allowing an azeotropic oxidizing solution or its gas to act. be able to. The reason for this is not necessarily completely elucidated, but is thought to be due to a slight difference in the quality (atomic density, etc.) of the oxide film formed depending on the concentration of the oxidizing solution.

  At this time, not only two stages but also multiple stages may be sequentially switched from low concentration (less than azeotropic concentration) to high concentration (azeotropic concentration). Further, the concentration of the oxidizing solution may be continuously increased from less than the azeotropic concentration to the azeotropic concentration. That is, a solution having an azeotropic concentration may be continuously obtained by concentrating a solution having an azeotropic concentration.

As described above, by causing the oxidizing solution or the gas to act on the semiconductor single crystal substrate 11, the oxide film 12 is formed to have a desired film thickness, for example, about 1 to 10 nm or more. be able to. In addition, the oxide film 12 having high film thickness uniformity can be obtained.
The oxide film 12 formed here becomes a buried oxide film (BOX layer) of a semiconductor substrate to be finally manufactured, and the film thickness is also reflected.

Next, the semiconductor single crystal substrate 11 on which the oxide film 12 is formed is washed with pure water and then dried by spin drying or the like, and then an epitaxial growth apparatus for forming the semiconductor single crystal layer 13 on the oxide film 12 And epitaxial growth is performed (FIG. 1C).
For example, in the case where the semiconductor single crystal layer 13 is an Si layer, the Si layer is intended by holding it at a temperature of 600 to 900 ° C. for a predetermined time while supplying a silane-based gas such as monosilane gas as a source gas. The film can be grown with good film thickness uniformity.

  The semiconductor single crystal layer 13 can be a semiconductor single crystal layer such as a SiGe layer or a Ge layer in addition to the Si layer. When these various semiconductor single crystal layers are grown, a gas for growing a semiconductor single crystal layer corresponding to each is appropriately selected and used.

Then, the semiconductor substrate 20 in which the oxide film (buried oxide film) 12 is formed on the semiconductor single crystal substrate 11 and the semiconductor single crystal layer 13 is formed on the oxide film 12 is manufactured through the above-described steps. can do.
The semiconductor single crystal layer 13 of the semiconductor substrate 20 according to the present invention has a very thin film thickness (for example, 10 nm level or less) and a high film thickness uniformity such as ± 0.1 nm level. it can. Further, the buried oxide film 12 has a film thickness of, for example, about 1 to 10 nm, and a film with high film thickness uniformity can be obtained.

  In addition, a semiconductor substrate manufacturing method having such a process does not require a special process such as ion implantation or bonding of two substrates, and an ultra-thin film and high film thickness uniformity can be achieved by a simple process. A semiconductor substrate 20 having the semiconductor single crystal layer 13 on the oxide film 12 can be manufactured. Therefore, the semiconductor substrate 20 as described above can be manufactured at an extremely low cost as compared with the prior art.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples of the present invention, but the present invention is not limited thereto.

Example 1
A Si single crystal substrate having a diameter of 200 mm was prepared as the semiconductor single crystal substrate 11 (see FIG. 1A). In order to form a chemical oxide film on the surface of the Si single crystal substrate 11, the surface is immersed in a treatment tank filled with an azeotropic nitric acid aqueous solution having a nitric acid concentration of 68 wt% and kept at the boiling point (121 ° C.) for 1 hour. Then, an oxide film 12 having a thickness of 1.4 nm was formed (see FIG. 1B). Thereafter, rinsing with pure water and spin drying were performed, and the resultant was put into a single wafer epitaxial growth apparatus.

  The epitaxial growth apparatus in which the Si single crystal substrate 11 was introduced was heated to 870 ° C. in a hydrogen atmosphere and then monosilane gas was introduced to form an epitaxial Si layer 13 having a thickness of about 10 nm on the oxide film 12. Thereby, the semiconductor substrate (SOI substrate) 20 in which the oxide film 12 and the single crystal Si layer 13 were sequentially formed on the entire surface of one main surface of the Si single crystal substrate 11 could be manufactured (FIG. 1 ( c)).

  The SOI layer (single crystal Si layer) 13 of the manufactured SOI substrate 20 is evaluated by using an X-ray diffraction method and a transmission electron microscope, and a single crystal is formed. Was confirmed to be within ± 0.1 nm.

(Example 2)
A Si single crystal substrate having a diameter of 200 mm was prepared as the semiconductor single crystal substrate 11 (see FIG. 1A). In order to form a chemical oxide film having a thickness of 10 nm on the surface of the Si single crystal substrate 11, first, it was immersed for 10 minutes in a treatment tank filled with a nitric acid aqueous solution having a nitric acid concentration of 40 wt%, and then azeotropic with a nitric acid concentration of 68 wt%. It was immersed in another treatment tank filled with an aqueous nitric acid solution and kept at the boiling point (121 ° C.) for 10 hours to form a 10 nm oxide film 12 on the surface (see FIG. 1B). Thereafter, rinsing with pure water and spin drying were performed, and the resultant was put into a single wafer epitaxial growth apparatus.

  The epitaxial growth apparatus in which the Si single crystal substrate 11 was introduced was heated to 870 ° C. in a hydrogen atmosphere and then monosilane gas was introduced to form an epitaxial Si layer 13 having a thickness of about 10 nm on the oxide film 12. Thereby, the semiconductor substrate (SOI substrate) 20 in which the oxide film 12 and the single crystal Si layer 13 were sequentially formed on the entire surface of one main surface of the Si single crystal substrate 11 could be manufactured (FIG. 1 ( c)).

  The SOI layer (single crystal Si layer) 13 of the manufactured SOI substrate 20 is evaluated by using an X-ray diffraction method and a transmission electron microscope, and a single crystal is formed. Was confirmed to be within ± 0.1 nm.

  The present invention is not limited to the above embodiment. The above embodiment is merely an example, and the present invention has the same configuration as that of the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

It is a flowchart which shows an example of the manufacturing method of the semiconductor substrate which concerns on this invention.

Explanation of symbols

11 ... Semiconductor single crystal substrate, 12 ... Oxide film, 13 ... Semiconductor single crystal layer,
20: Semiconductor substrate.

Claims (5)

A method of manufacturing a semiconductor substrate having a semiconductor single crystal layer on an oxide film by sequentially forming an oxide film and a semiconductor single crystal layer on a surface of the semiconductor single crystal substrate, comprising:
Forming an oxide film having an epitaxial relationship with the semiconductor single crystal substrate on the surface of the semiconductor single crystal substrate by contacting the semiconductor single crystal substrate with an azeotropic oxidizing solution or a gas thereof;
And a step of epitaxially growing a semiconductor single crystal layer on the oxide film. Before contacting the semiconductor single crystal substrate with the azeotropic oxidizing solution or the gas thereof, contacting the semiconductor single crystal substrate with the oxidizing solution or the gas having an azeotropic concentration lower than the semiconductor single crystal substrate. The method for manufacturing a semiconductor substrate according to claim 1 , wherein: 3. The method of manufacturing a semiconductor substrate according to claim 1, wherein the semiconductor single crystal substrate is an Si single crystal substrate. It said semiconductor single crystal layer, Si layer, SiGe layer, a semiconductor substrate manufacturing method according to any one of claims 1 to 3, characterized in that either a Ge layer. The oxidizing solution or a gas, an aqueous nitric acid solution or the method of manufacturing a semiconductor substrate according to any one of claims 1 to 4, characterized in that its gas.

Images