JPH04199608A - Manufacture of soi wafer - Google Patents

Abstract

PURPOSE:To prevent the instable state of a laminated interface by a method wherein the Si semiconductor supporting substrate, which is covered by an insulating film having an excess-oxygen layer on the surface, and another Si semiconductor substrate are opposingly positioned and they are closely fixed. CONSTITUTION:An Si semiconductor supporting substrate 13 and an Si semiconductor substrate 11, which is covered by an insulating film 14 and having an excess-oxygen layer 14A, whereon excessive oxygen is introduced on the surface, are closely fixed in an opposing manner. An oxide film 11A is grown by diffusing oxygen on the semiconductor substrate by conducting a heat treatment, and the Si semiconductor substrate and the Si semiconductor substrate are laminated. Then, an Si semiconductor active layer is formed by thinning off the Si semiconductor substrate 11. Accordingly, the interface which works as the interface of the semiconductor active layer and the base oxide film is the oxide layer, which is grown by diffusing excessive oxygen generated in the oxide film when the heat treatment for lamination is conducted, and the remaining semiconductor active layer. As a result, the instable state of the interface can be substantially removed completely.

Description

[Detailed Description of the Invention] [Summary] A semiconductor wafer having a semiconductor layer on an insulating layer, that is, an SOI
Regarding the improvement of the method of manufacturing wafers, by adopting a simple method, the interface between the Si semiconductor substrate and the underlying oxide film is created at a different position from the actual bonding interface, that is, within the Si semiconductor substrate. In order to avoid the instability of the state at the bonding interface and the adverse effects of impurities such as heavy metals on semiconductor devices, the semiconductor device is covered with an insulating film with an oxygen-rich layer on the surface into which excess oxygen is introduced. The Si semiconductor support substrate and the Si semiconductor substrate are placed in close contact with each other facing each other, and heat treatment is performed to diffuse the oxygen into the Si semiconductor substrate to generate an oxide film, and the Si semiconductor support substrate and the Si semiconductor substrate are bonded together. Combine, then
The method is configured to include a step of thinning the Si semiconductor substrate to form a Si semiconductor active layer.

[Industrial Application Field] The present invention relates to a semiconductor device in which a semiconductor layer is on an insulating layer.
, that is, SOI (silicon on 1n
The present invention relates to an improvement in a method of manufacturing a sulator wafer.

Semiconductor devices using an SOI structure can improve device characteristics because the junction capacitance and wiring capacitance are reduced, and also improve noise resistance by forming an isolation region that reaches from the surface to the insulating layer. be able to.

Among these SOI structures, bonded SOI wafers are attracting attention because of the crystallinity of the active layer in which elements are built, and their compatibility with conventional semiconductor device manufacturing processes. , there are still problems that need to be solved.

[Conventional technology]

Figures 5 to 8 are cross-sectional side views of essential parts of an SOI wafer at important points in the process to explain a conventional technique for creating an SOI wafer suitable for manufacturing high-speed bipolar semiconductor devices. This will be explained below with reference to these figures. In the case of SO wafers, basically the Si semiconductor substrate and the Si semiconductor support substrate are bonded together, but before the bonding, the Si semiconductor substrate and the Si semiconductor support substrate are separately bonded. It is up to you which substrate to perform the processing or processing on first.
Moreover, it goes without saying that they may be performed at the same time.

Referring to FIG. 5, by applying the ion implantation method, dopant ions such as As are implanted into the Si semiconductor substrate 1 to form an impurity-introduced layer 2.

By applying the thermal oxidation method (see FIG. 6), the Si semiconductor support substrate 3
An insulating film 4 made of Sin is then formed.

Refer to FIG. 7. A Si semiconductor substrate 1 having an impurity-introduced layer 2 and a Si semiconductor support substrate 3 having an insulating wA4 are bonded together so that the impurity-introduced layer 2 and the insulating film 4 face each other.

Referring to FIG. 8, by grinding and polishing the Si semiconductor substrate 1, a thin Si semiconductor active layer 1' is obtained.

[Problem to be solved by the invention]

Generally, the insulating film 4 is often formed on the Si conductor substrate 1 side which is the base of the Si semiconductor active layer 1', or on both the Si semiconductor substrate 1 and the Si semiconductor supporting substrate 3.

If it is formed on only three Si semiconductor supporting substrates, the bonding interface will be the interface itself between the Si semiconductor active layer 1' and the insulating wA4, as seen in the explanation of the conventional technology, and the Si semiconductor When a semiconductor device is fabricated in the active Ill', the bonding interface enters into the semiconductor device.

Since the bonded interface is literally a surface where two separate objects are bonded together, it goes without saying that there is an extremely high risk of contamination, such as the presence of impurities such as heavy metals, at the interface.

Therefore, generally, the insulating film 4 is formed by thermally oxidizing at least the side of the Si semiconductor active layer 1' in which a semiconductor device is to be fabricated. In this case, the interface between the Si semiconductor active layer 1' and the insulating film 4 is clean, and all contaminants and the like come out to the surface of the insulating film 4.

However, depending on the type of semiconductor device to be fabricated on the SOI wafer, S, which is the base material of the Si semiconductor active layer 1', may be
i It is not always possible to thermally oxidize the semiconductor substrate 1 side.

The conventional technique exemplified above is also one in which the insulating film 4 cannot be formed on the Si semiconductor substrate 1 side.

In other words, since the S0I wafer needed there is for incorporating a bipolar semiconductor device, it requires a buried layer to draw out the collector, but ion implantation is performed to form this buried layer. from,
That is, if thermal oxidation is performed after forming the impurity-introduced layer 2, the impurity will be thermally diffused, and its control is not easy, but rather difficult. Note that there are many other cases, not only the above case, in which the insulating film 4 cannot be formed on the Si semiconductor substrate 1 side.

For the reasons mentioned above, in the conventional technique explained in FIGS. 5 to 8G, the insulating film 4 is formed on the Si semiconductor support substrate 3 side. Since the interface between the Si semiconductor active layer 1' and the insulating film 4 is the bonding interface itself, the state of the interface is unstable and impurities such as heavy metals are likely to accumulate. There is a possibility that the characteristics of the device will be directly affected.

The present invention employs simple means to create an interface between the Si semiconductor active layer and the underlying oxide film at a position different from the actual bonding interface, that is, within the Si semiconductor active layer, and bond the Si semiconductor active layer to the underlying oxide film. An attempt is made to avoid unstable conditions at the interface and impurities such as heavy metals from adversely affecting semiconductor devices.

(Means for Solving the Problems) In the method for manufacturing a 301 wafer according to the present invention, (1) an oxygen-excess layer into which excess oxygen is introduced (11 wafers);
A Si semiconductor support substrate (e.g., Si semiconductor support substrate 13) and a Si semiconductor substrate (e.g., Si semiconductor substrate 11) covered with an insulating film (e.g., insulating film 14) having 14A) on the surface thereof are placed in close contact with each other facing each other, and heat-treated. The oxygen is diffused into the Si semiconductor substrate to form an oxide film (for example, the oxide film 11A), and the Si semiconductor support substrate and S
i Paste together the semiconductor substrate and proceed as follows 1. In step z, the Si semiconductor substrate is thinned to form a Si semiconductor active layer (for example, S
(2) In step (1) above, oxygen ions are implanted into the surface of the insulating film covering the Si semiconductor support substrate to form an oxygen-excess layer. (3) In the above (1), an impurity layer (for example, n A type impurity layer 12) is formed.

[Function] In the SOI wafer created by adopting the above method, it is not the actual interface between the Si semiconductor active layer and the oxide film that acts as the interface between the Si semiconductor active layer and the underlying oxide film. During the heat treatment for bonding, excess oxygen in the oxygen ion implantation layer in the oxide film diffuses into the Si semiconductor substrate that becomes the Si semiconductor active layer, forming an oxide layer and preventing such oxygen from entering. In other words, the interface is newly generated within the Si semiconductor substrate. Therefore, there is virtually no instability in the state at the interface, and there is a considerable risk that impurities such as heavy metals may accumulate, so when semiconductor devices are manufactured, their characteristics are less likely to be adversely affected. .

〔Example〕

1 to 4 are cross-sectional side views of essential parts of an SOI wafer at key points in the process for explaining one embodiment of the present invention, and detailed explanation will be given below with reference to these figures.

As ions are implanted into the Si semiconductor substrate 11 by applying the ion implantation method shown in FIG. to add n-type impurity fi
form 12. Note that this n-type impurity layer 12 is formed as needed and is not essential, and the impurity ions are also selected as needed and are not limited to As. Further, it goes without saying that the implanted As is activated during the heat treatment.

By applying the thermal oxidation method (see FIG. 2), the Si semiconductor support substrate 1
An insulating film 14 made of SiO2 and having a thickness of, for example, 1 [μm] is formed on the substrate 3.

By applying the ion implantation method, the Si semiconductor substrate 1 is implanted at a dose of, for example, l x l Q I5 (am-2) and an acceleration energy of, for example, 20 (KeV).
Oxygen ions are implanted into the insulating film 14 on the side to be bonded to the insulating film 14 to form an oxygen-excess layer 14A having a thickness of, for example, 50 (nm).

Refer to FIG. 3. The n-type impurity N12 of the Si semiconductor substrate 11 and the oxygen-excess layer 14A of the Si semiconductor support substrate 13 are placed facing each other at a temperature of 7.
00V], and then the temperature was increased to 100V.
The Si semiconductor substrate 11 and the Si semiconductor support substrate 1 are heated by heat treatment for 30 (minutes) in a nitrogen atmosphere set to 0 ("C).
Paste 3 together.

During the heat treatment in this bonding, the oxygen-excess layer 1
Since oxygen is diffused from 4A into the Si semiconductor substrate 11, an oxide film 11A is generated in the Si semiconductor substrate 11. In FIG. 3, the newly generated interface is indicated by symbol 15A, and the actual bonded interface is indicated by symbol 15B.

Referring to FIG. 4, the Si semiconductor substrate 11 is ground using a diamond grindstone to a thickness of, for example, about 10 [μm].

A slight amount of colloidal silica is mixed into an aqueous solution of amine as an abrasive, and a polishing cloth made of non-woven fabric is used to polish Si.
The ground surface of the semiconductor substrate 11 is polished to a thickness of, for example, 3 μm.
] as the Si semiconductor active layer ii'.

As is clear from the above, the created SOI
In the wafer, the substantial interface between the Si semiconductor active layer 11i11' and the oxide film, which is involved in the operation of the semiconductor device, is S
An interface 15A that is not newly generated in the i-semiconductor active layer 11'
Therefore, it is located at a different position from the bonding interface 15B, and the bonding interface 15B does not become a component in the semiconductor device.

〔Effect of the invention〕

In the method for manufacturing an SOI wafer according to the present invention, a Si semiconductor support substrate covered with an insulating film having an oxygen-rich layer on the surface and a Si semiconductor substrate are placed in close contact with each other, and heat treatment is performed to remove oxygen. It is diffused into the Si semiconductor substrate to form an oxide film, the Si semiconductor support substrate and the Si semiconductor substrate are bonded together, and the Si semiconductor substrate is ground and polished to form a thin Si semiconductor active layer.

In the SOI wafer created by adopting the above configuration, what acts as the interface between the 31 semiconductor active layer and the underlying oxide film is not the actual interface between the Si semiconductor active layer and the oxide film, but the bonded interface. During the heat treatment for bonding, excess oxygen in the oxygen ion implantation layer in the oxide film diffuses into the Si semiconductor substrate, which becomes the Si semiconductor active layer, resulting in an oxide layer and an oxide layer where such oxygen does not enter and remains. It becomes an interface with the semiconductor active layer; in other words, the interface is newly generated within the Si semiconductor substrate. Therefore, there is virtually no instability in the state at the interface, and there is a considerable risk that impurities such as heavy metals may accumulate, so when semiconductor devices are manufactured, their characteristics are less likely to be adversely affected. .

[Brief explanation of the drawing]

Figures 1 to 4 are cutaway side views of essential parts of an S○■ wafer at key points in the process for explaining one embodiment of the present invention, and Figures 5 to 8 are side views for explaining a conventional example. SO at key points in the process
2A and 2B each represent a cutaway side view of a main part of an I wafer. In the figure, 11 is a Si semiconductor substrate, IIA is an oxide film, 12 is an n-type impurity layer, 13 is 31 semiconductor support substrate, 1
4 is an insulating film, 14A is an oxygen-rich layer, and 15A and 15B are interfaces, respectively. Patent Applicant Fujitsu Ltd. Representative Patent Attorney Shoji Aiya Representative Patent Attorney Hiroshi Watanabe - 11/31 Semiconductor substrate Figure 1 Figure 2 Figure 11': Si semiconductor active layer Figure 4 Figure 5 Figure 6 figure

Claims (3)

[Claims] (1) A Si semiconductor support substrate covered with an insulating film having an oxygen-excess layer on the surface into which excess oxygen has been introduced and a Si semiconductor substrate are placed in close contact with each other facing each other, and heat treatment is performed to transfer the oxygen to the Si semiconductor substrate. It is characterized by including the steps of: diffusing to form an oxide film, bonding a Si semiconductor support substrate and a Si semiconductor substrate, and then thinning the Si semiconductor substrate to form a Si semiconductor active layer. A method for manufacturing an SOI wafer. (2) The method for manufacturing an SOI wafer according to claim 1, characterized in that oxygen ions are implanted into the surface of the insulating film covering the Si semiconductor support substrate to generate an oxygen-excess layer. (3) S on the side to be bonded to the Si semiconductor support substrate
2. The method of manufacturing an SOI wafer according to claim 1, further comprising forming an impurity layer imparting conductivity on the surface of the semiconductor substrate.