JP3611143B2 - Bonded wafer and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bonded wafer and a manufacturing method thereof, and more particularly, to a bonded wafer having a polysilicon layer interposed and a manufacturing method thereof.
[0002]
[Prior art]
In SOI (silicon on insulator) with a conventional bonded wafer structure, an insulating layer formed on the back surface of the silicon wafer on the active layer side is laminated and bonded to the surface of the silicon wafer on the substrate side. In this case, as shown in FIG. 7, since the bonding surface is a bond between silicon and oxygen, it is considered that water adsorbed on silicon is involved in this bond. When the bonded surfaces are completely dry, the bonding is impossible.
[0003]
[Problems to be solved by the invention]
As described above, in the conventional bonded SOI, since one side of the bonded surface is an oxide film and the other side is silicon having an OH group, it is important to control the adsorbed water of the silicon. That is, there is a problem that poor bonding is likely to occur in this bonding.
[0004]
Accordingly, an object of the present invention is to obtain a bonded wafer that can be easily bonded. Moreover, it aims at providing the manufacturing method of the bonded wafer.
[0005]
[Means for Solving the Problems]
[0006]
The invention described in claim 1 is a bonded wafer having a silicon substrate layer, a polysilicon layer laminated on the silicon substrate layer, and a silicon active layer laminated on the polysilicon layer.
[0007]
The invention according to claim 2 has a silicon substrate layer, a silicon active layer laminated on the silicon substrate layer, and an insulating layer interposed between the silicon substrate layer and the silicon active layer. The bonded wafer is a bonded wafer in which a polysilicon layer is interposed between the insulating layer and the silicon substrate layer or between the insulating layer and the silicon active layer.
[0008]
The invention according to claim 3 is a silicon substrate layer, a polysilicon layer laminated on the silicon substrate layer, laminated on the polysilicon layer, and a silicon portion and an insulating portion are mixed on the polysilicon layer side. A laminated wafer having a silicon active layer.
[0009]
A fourth aspect of the present invention is the bonded wafer according to the first or third aspect , wherein the polysilicon layer is doped with a dopant for forming the same conductivity type as the silicon active layer.
[0010]
請Motomeko 5 to the described invention, the step of superimposing the back surface of the silicon wafer for active layer on the surface of the silicon wafer for the substrate, a step of heat-treating the silicon wafer superimposed, a manufacturing method of the laminated wafer including The method for producing a bonded wafer in which a polysilicon layer is deposited on the back surface of the active layer wafer.
[0011]
The invention described in請Motomeko 6, the flatness of the polysilicon layer surface is the preparation method of the laminated wafer according to請Motomeko 5 is 0.5nm or less in Ra value.
[0012]
The invention according to claim 7 is the production of the bonded wafer according to claim 5 or 6 , wherein the polysilicon layer is doped with a dopant for forming the same conductivity type as the silicon wafer for the active layer. Is the method.
[0013]
In the invention according to claim 8 , the back surface of the silicon wafer for active layer to which the polysilicon layer is deposited is composed of silicon, silicon dioxide, silicon and silicon dioxide mixed surface, silicon and polysilicon mixed surface, and dioxide. the claims 5 to 7 Neu Zureka 1 wherein is constituted by any one of the blending surface of the silicon and the metal wiring is a method for producing a laminated wafer according.
[0014]
[Action]
In the bonded wafer according to the present invention, at the time of bonding, peeling at the bonding interface and defects such as generation of voids are eliminated. In addition, when applied to an SOI structure, the continuity of the crystal lattice with silicon dioxide is improved. Bonding defects can be reduced. In addition, even when the silicon surface and the silicon surface are bonded together, their conduction can be ensured by diffusing the dopant into the polysilicon layer. Furthermore, the bonding force between the two silicon wafers can be made constant over the entire surface by depositing and bonding the polysilicon layer on the mixed surface of silicon and silicon dioxide.
[0015]
Here, the bonding force of the bonding surface between the silicon dioxide film and the silicon layer is larger than the bonding force between the silicon dioxide films by bonding, and further, that of the bonding surface between the silicon layers is larger than this. . Further, when polysilicon is laminated on the silicon dioxide film by CVD, the bonding force between these silicon dioxide film and polysilicon film is sufficiently strong. Therefore, after laminating the polysilicon layer on the silicon dioxide film, bonding the polysilicon layer to the surface of the silicon wafer results in a larger bonding force than when bonding the silicon wafer and the silicon dioxide film.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a bonded wafer according to one embodiment of the present invention. As shown in this figure, in the bonded wafer according to this embodiment, a polysilicon layer 12 having a predetermined thickness is laminated on a silicon substrate layer 11, and a silicon active layer 13 is laminated on the polysilicon layer 12. This is the structure. A predetermined device is formed in the silicon active layer 13.
[0017]
As a bonded wafer having such a structure, two silicon wafers (polished wafer: PW) are prepared, and a polysilicon layer is deposited on one of the wafer surfaces by CVD. Then, the surface of the polysilicon layer is formed with a surface roughness of about 5 mm in terms of Ra value, for example. Here, the surface of the polysilicon layer was superimposed on the mirror surface of the other polished wafer at room temperature, and a predetermined bonding heat treatment (heated to 850 ° C. for 2 hours in a dry O ₂ atmosphere) was performed. FIG. 6 is a graph showing the relationship between the Ra value on the surface of the polysilicon layer and the bonding force. As shown in this figure, by setting the Ra value to 0.5 nm (5 angstroms) or less, the bonding force after bonding can be increased.
[0018]
FIG. 2 is a sectional view showing a bonded wafer according to another embodiment of the present invention. In this embodiment, a silicon dioxide layer 22 is laminated on a silicon substrate layer 21, and a polysilicon layer 23 is further laminated thereon. A silicon active layer 24 is laminated on the polysilicon layer 23. In this case, the bonding surface is formed between the polysilicon layer 23 and the silicon active layer 24. Therefore, after a silicon dioxide layer is grown on the surface of one silicon wafer (substrate side) and a polysilicon layer is grown on the surface by CVD, the polysilicon layer is superimposed on the mirror surface of the other silicon wafer (active layer side). Thus, bonding is performed under the same conditions as in the above embodiment.
[0019]
FIG. 3 is a cross-sectional view showing a bonded wafer according to still another embodiment of the present invention. In this embodiment, a polysilicon layer 32 is laminated on a silicon substrate layer 31, a silicon dioxide layer 33 is laminated thereon, and a silicon active layer 34 is further laminated thereon. The bonding surface is formed between the silicon substrate layer 31 and the polysilicon layer 32.
[0020]
FIG. 4 is a sectional view showing another embodiment of the present invention. In this embodiment, the polysilicon layer 42 is laminated on the silicon substrate layer 41 in the same manner as in the above embodiment. However, the polysilicon layer 42 is composed of the silicon dioxide layer 44 of the silicon active layer 43 and silicon. It is laminated on the surface mixed with the surface. This silicon dioxide layer 44 functions as a buried insulating layer.
[0021]
FIG. 5 is a sectional view showing still another embodiment of the present invention. As shown in this figure, when a thick silicon dioxide film is formed, silicon dioxide films 51A and 52A are deposited on two silicon wafers 51 and 52, respectively, and the silicon dioxide films 51A and 52A are further formed. The polysilicon films 51B and 52B are laminated on each other by CVD. These polysilicon films 51B and 52B are overlapped and bonded together. As a result, it is possible to obtain a silicon dioxide film having a thickness twice as large as the thickness (about 2 μm) of the silicon dioxide film formed by oxidation in a normal wet O ₂ atmosphere. Moreover, since the polysilicon layers are bonded together, the bonding force can be further increased.
[0022]
【The invention's effect】
According to the present invention, it is possible to eliminate the bonding failure of the bonded wafers. Further, the dopant can be easily and uniformly diffused in the polysilicon layer. Therefore, the polysilicon layer can be made conductive. Moreover, even if it exists in the surface which has an unevenness | corrugation, it can stick together reliably by depositing a polysilicon layer. Further, boron contamination can also be prevented by bonding the silicon surface to the silicon surface.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a bonded wafer according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a bonded wafer according to another embodiment of the present invention.
FIG. 3 is a cross-sectional view showing a bonded wafer according to still another embodiment of the present invention.
FIG. 4 is a cross-sectional view showing a bonded wafer according to another embodiment of the present invention.
FIG. 5 is a cross-sectional view showing a bonding process according to still another embodiment of the present invention.
FIG. 6 is a graph showing the relationship between the Ra value of the polysilicon surface and the bonding force of the bonded wafer according to one embodiment of the present invention.
FIG. 7 is a schematic view showing a conventional bonded interface between SiO ₂ and Si.
[Explanation of symbols]
11 Silicon substrate layer ,
12 polysilicon layer,
13 silicon active layer,
22 Silicon dioxide layer.

Claims (8)

A silicon substrate layer;
A polysilicon layer laminated on the silicon substrate layer;
A bonded wafer having a silicon active layer laminated on the polysilicon layer. A silicon substrate layer;
A silicon active layer laminated on the silicon substrate layer;
In a bonded wafer having an insulating layer interposed between the silicon substrate layer and the silicon active layer,
A bonded wafer in which a polysilicon layer is interposed between the insulating layer and the silicon substrate layer or between the insulating layer and the silicon active layer. A silicon substrate layer;
A polysilicon layer laminated on the silicon substrate layer;
A bonded wafer having a silicon active layer laminated on the polysilicon layer and having a silicon portion and an insulating portion mixed on the polysilicon layer side. The bonded wafer according to claim 1 or 3, wherein the polysilicon layer is doped with a dopant for forming the same conductivity type as that of the silicon active layer. Superimposing the back surface of the silicon wafer for the active layer on the surface of the silicon wafer for the substrate;
In a method for manufacturing a bonded wafer, including a step of heat-treating the stacked silicon wafers,
A method for producing a bonded wafer in which a polysilicon layer is deposited on the back surface of the active layer wafer. The method for producing a bonded wafer according to claim 5, wherein the flatness of the surface of the polysilicon layer is 0.5 nm or less in terms of Ra value. The method for producing a bonded wafer according to claim 5 or 6 , wherein the polysilicon layer is doped with a dopant for forming the same conductivity type as that of the silicon wafer for the active layer. The back surface of the active layer silicon wafer to which the polysilicon layer is deposited is any of silicon, silicon dioxide, a mixed surface of silicon and silicon dioxide, a mixed surface of silicon and polysilicon, and a mixed surface of silicon dioxide and metal wiring. The method for producing a bonded wafer according to any one of claims 5 to 7, wherein the method comprises:

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