JPH0945882A - Semiconductor substrate and method of manufacturing the same - Google Patents

Abstract

(57) [Summary] [Object] To provide a semiconductor substrate and a method for manufacturing the same capable of significantly reducing warpage occurring in an SOI wafer. [Structure] The thickness of the oxide film formed on each of the two silicon wafers forming the SOI wafer is different. In order to further reduce the warpage, an oxide film of a silicon wafer which is subjected to polishing to form a semiconductor element and serves as an active layer is formed thicker than the other. On the contrary, the oxide film of the silicon wafer which is not polished may be formed thick. With this configuration, warpage that occurs in the SOI wafer can be significantly reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor substrate and a method for manufacturing the same, and more particularly, to SOI (Silicon On I).
and a method for manufacturing a wafer.

[0002]

2. Description of the Related Art Among semiconductor substrates used for semiconductor devices, there is a substrate called an SOI wafer. SOI
A wafer is a silicon film formed by forming a thin film of silicon on an insulating film in order to reduce the parasitic capacitance between the semiconductor element region and the substrate, which is an obstacle to speeding up MOS transistors and the like. SO with integrated circuit inside
It is a semiconductor substrate manufactured by the I technique.

There are several types of SOI wafer structures depending on the application. One of them has a silicon oxide film formed as an insulating film on one or both surfaces of two silicon substrates. There is one in which these are bonded by a direct bonding method and then one surface is polished to form an element forming region.

FIG. 3A is a schematic sectional view showing the structure of the SOI wafer. An oxide insulating film 30 is formed of silicon oxide on a support base side wafer 10 formed of silicon and serving as a support base, and an active layer 20 serving as an element formation region is further formed of silicon on the oxide insulating film 30. The film thickness of the silicon oxide film on the SOI wafer varies depending on the type of element to be formed and its application, but is usually 1 to 3 μm.
About m is required.

The conventional method for manufacturing an SOI wafer includes a method of forming an oxide insulating film on one of a support base side wafer and an active layer side wafer and then joining them, and a support base side wafer and There is a method in which an oxide insulating film having the same thickness is formed on both of the active layer side wafers and then these are bonded. Hereinafter, the above-mentioned SOI will be described with reference to the drawings.
A method of manufacturing a wafer will be described with reference to the drawings.

FIG. 4 is an explanatory view of a first conventional method for manufacturing an SOI wafer. Here, as the support base side wafer 1 and the active layer side wafer 2, 6 inches,
P type, plane orientation (100), specific resistance 5Ω · cm, thickness 62
A 5 μm silicon wafer is used.

In the first manufacturing method, the silicon oxide insulating film 11 is formed only on the active layer side wafer 2 by the combustion oxidation of oxygen / hydrogen under the temperature condition of about 1100 ° C. (FIG. 4A). . When the silicon oxide insulating film 11 is formed only on one wafer, the silicon oxide insulating film 11 is
The thickness is the same as that required for the finally completed SOI wafer. The silicon oxide insulating film 11 is formed to have a predetermined thickness in the range of 1 to 3 μm as described above.

Next, the support base side wafer 1 and the active layer side wafer 2 on which the silicon oxide insulating film 11 is formed are bonded by a direct bonding method (FIG. 4 (b)).

Finally, the silicon oxide insulating film 11 and the active layer side wafer 2 are polished to form an active layer 12 having a thickness of about 10 μm to complete the SOI wafer (FIG. 4).
(C)).

FIG. 5 is an explanatory view of a second conventional method for manufacturing an SOI wafer. Also here, as in the case of the first manufacturing method of FIG. 4, the support base side wafer 1 and the active layer side wafer 2 have a diameter of 6 inches, a P type, a plane orientation (100), a specific resistance of 5 Ω · cm, and a thickness. A silicon wafer having a size of 625 μm is used.

In the second manufacturing method, both the support base side wafer 1 and the active layer side wafer 2 have a thickness of about 1100.
The silicon oxide insulating films 13 and 14 are formed by oxygen / hydrogen combustion oxidation under the temperature condition of ° C (Fig. 5A). When the silicon oxide insulating films 13 and 14 are formed on both wafers, the silicon oxide insulating films 13 and 14 are each formed to have a thickness half that required for the finally completed SOI wafer. Therefore, the silicon oxide insulating film 13,
14 are each formed to a predetermined thickness in the range of 0.5 to 1.5 μm, and the silicon oxide insulating film 13 and
14 has the same thickness.

Next, the silicon oxide insulating film 13 on the support base side wafer 1 and the silicon oxide insulating film 14 on the active layer side wafer 2 are bonded by a direct bonding method, and the support base side wafer 1 and the active base side wafer 1 are activated. A silicon oxide insulating film 15 is formed between the layer side wafer 2. (FIG. 5 (b)).

Finally, the silicon oxide insulating film 14 and the active layer side wafer 2 are polished to form an active layer 16 having a thickness of about 10 μm to complete the SOI wafer (FIG. 5).
(C)).

As described above, according to the conventional method for manufacturing an SOI wafer, a predetermined amount is given to only one of the support base side wafer and the active layer side wafer because of the ease of forming an oxide film and other processing. A method of forming an oxide insulating film having a thickness and then joining them together, and a method of forming an oxide insulating film having the same thickness on both the support base side wafer and the active layer side wafer and then joining them together. It was limited to street patterns.

[0015]

However, the SOI wafer according to the conventional manufacturing method has a problem of warpage, which is caused by the difference in the coefficient of thermal expansion between silicon and the silicon oxide insulating film. It is considered that this is due to the imbalance between the tensile stress acting on the side wafer 10 and the active layer 20 and the compressive stress acting on the silicon oxide insulating film 30.

The warp generated in this SOI wafer is almost always a convex warp as shown in FIG. 3 (b).

The warp is measured by removing the oxide film on the back surface of the wafer 10 on the support base side using dilute hydrofluoric acid, and then measuring the warp by a capacitance method manufactured by ADE (ADE-7200).
It measured using E).

The graph L2 of FIG. 2 and the left column of Table 1 show the measurement results of the warp of the SOI wafer according to the conventional manufacturing method. In the first column of Table 1, "SiO2 of SOI wafer
“Film thickness (μm)” is the thickness of the silicon oxide insulating film of the completed SOI wafer, and “SiO2 of the active layer wafer” in the second row.
“Film thickness (μm)” is the thickness of the silicon oxide insulating film formed on the active layer side wafer, “SiO of the base wafer” in the third row.
2 “Film thickness (μm)” is the thickness of the silicon oxide insulating film formed on the support base side wafer, and “Warp (μm)” in the fourth row is
The measurement results of the warp generated in the completed SOI wafer are shown. The warp increases substantially in proportion to the film thickness of the silicon oxide insulating film, and is 50 to 80 μm when the film thickness is 1 μm.
m, the film thickness is 2 μm, the film thickness is 90 to 120 μm, and the film thickness is 3 μm, the film thickness is 180 to 220 μm.

The occurrence of warpage in the SOI wafer causes various defects in the device manufacturing process, resulting in a decrease in yield.

The present invention has been made in view of the above problems, and an object thereof is to provide a method for manufacturing an SOI wafer which can reduce the occurrence of warpage.

[0021]

According to the method of manufacturing a semiconductor substrate of the present invention, an oxide film having a first thickness is formed on at least one surface of a first silicon wafer, and at least one surface of a second silicon wafer is formed. An oxide film forming step of forming an oxide film having a second thickness different from the first thickness on one surface, and a first silicon wafer having the oxide film having the first thickness and a second thickness. And a second silicon wafer on which an oxide film having a thickness of 1 μm is formed by a direct adhesion method through an oxide film having a first thickness and an oxide film having a second thickness; And a polishing step of polishing a silicon wafer to a predetermined thickness.

The oxide film having the first thickness may be thicker than the oxide film having the second thickness.

Alternatively, the oxide film of the second thickness may be an oxide film thicker than the oxide film of the first thickness.

A silicon oxide film having a first thickness is formed on at least one surface of the first silicon wafer on which a semiconductor element is formed and which serves as an active layer, and a second silicon wafer which serves as a base for holding the first silicon wafer. A silicon oxide film forming step of forming a silicon oxide film having a second thickness different from the first thickness on at least one surface of the first silicon wafer,
The silicon oxide film of the first thickness formed on the silicon wafer of No. 1 and the silicon oxide film of the second thickness formed on the second silicon wafer are bonded together by a direct bonding method, An insulating separation film forming step of forming an insulating silicon oxide film for insulatingly separating a silicon wafer and a second silicon wafer, and an active layer constituting an SOI wafer by polishing the first silicon wafer to a predetermined thickness. And a polishing step for forming.

The silicon oxide film having the first thickness may be thicker than the silicon oxide film having the second thickness.

Alternatively, the silicon oxide film having the second thickness may be a silicon oxide film thicker than the silicon oxide film having the first thickness.

According to the semiconductor substrate of the present invention, the interface between the first silicon wafer, the second silicon wafer adhered to one surface of the first silicon wafer, and the first and second silicon wafers. And an oxide film of a first thickness provided on the first silicon wafer side, and an oxide film of a second thickness provided on the second silicon wafer side. And the thicknesses of the oxide films having the first and second thicknesses are different.

[0028]

DETAILED DESCRIPTION OF THE INVENTION A semiconductor substrate and a method of manufacturing the same according to the present invention will be described below with reference to the drawings and tables.

FIG. 1 is an explanatory view of a method for manufacturing a semiconductor substrate according to the present invention, which is composed of schematic sectional views of a silicon wafer or the like in the main manufacturing steps. As in the case of the conventional example, the silicon wafer to be used is 6 inches of P as the support base side wafer 1 and the active layer side wafer 2 and P.
Mold, plane orientation (100), specific resistance 5Ω · cm, thickness 625
A μm silicon wafer is used.

In the method for manufacturing an SOI wafer according to the present invention, the silicon oxide insulating film 3 is formed on the support base side wafer 1 and the active layer side by the combustion oxidation of oxygen / hydrogen under the temperature condition of about 1100 ° C. A silicon oxide insulating film 4 is formed on each wafer 2 (FIG. 1A). On this occasion,
The silicon oxide insulating film 4 is formed thicker than the silicon oxide insulating film 3, and the total film thickness of the silicon oxide insulating films 3 and 4 insulates the support base side wafer 1 and the active layer side wafer 2 from each other. The insulating film has a predetermined thickness.

Next, the silicon oxide insulating film 3 on the support base side wafer 1 and the silicon oxide insulating film 4 on the active layer side wafer 2 are bonded by a direct bonding method, and the support base side wafer 1 and the active base side wafer 1 are activated. A silicon oxide insulating film 5 is formed between the layer side wafer 2. (FIG. 1 (b)).

Finally, the silicon oxide insulating film 4 and the active layer side wafer 2 are polished to form an active layer 6 having a thickness of about 10 μm.
Are formed to complete the SOI wafer. (Figure 1
(C)).

FIG. 2 and Table 1 show the measurement results of the amount of warpage generated in the SOI wafers respectively manufactured by the semiconductor substrate manufacturing method according to the present invention and the conventional manufacturing method. The graph L1 of FIG. 2 and the right column of Table 1 show the SOI wafer manufactured by the method for manufacturing a semiconductor substrate according to the present invention, and the graph L2 of FIG. 2 and the left column of Table 1 show the warp of the SOI wafer according to the conventional manufacturing method. The measurement results are shown. In the left and right columns of Table 1, "SiO2 film thickness (μm) of SOI wafer" in the first column is the thickness of the silicon oxide insulating film of the completed SOI wafer, and "SiO2 film thickness of the active layer wafer" in the second column. (Μm) ”is the thickness of the silicon oxide insulating film formed on the active layer side wafer, and“ SiO2 of the base wafer ”in the third row.
“Film thickness (μm)” is the thickness of the silicon oxide insulating film formed on the support base side wafer, and “Warp (μm)” in the fourth row shows the measurement results of the warp that occurred in the completed SOI wafer. There is.

[Table 1]

From this measurement result, the warp is about 40 to 70 μm.
It is also understood that m is also reduced, and therefore, the warp is significantly reduced to about 30 to 45%. The reason why the warp is reduced is not necessarily clear, but it is considered that the tensile stress acting on the support base side wafer and the active layer side wafer and the compressive stress acting on the silicon oxide insulating film come close to the equilibrium state. To be That is, the adhesive interface is closer to the support base side wafer than the center of the silicon oxide insulating film, and the tensile stress acting on the active layer side wafer is relaxed by separating from the active layer side wafer, and the silicon oxide insulating film. For the reason that the compressive stress acting on the silicon oxide insulating film is relaxed by the interaction between the stress layer generated at the bonding interface due to the mutual adhesion and the thick silicon layer forming the supporting base side wafer, It is considered that the warp of the SOI wafer is reduced.

From the analysis result of the measurement result by the inventor, when the silicon oxide insulating film 4 in FIG. 1 is formed to be 0.5 μm or more thicker than the silicon oxide insulating film 3,
In particular, it has been found that the effect of reducing the warp of the SOI wafer is great.

In the above description, the case where the silicon oxide insulating film 4 is formed thicker than the silicon oxide insulating film 3 has been described. Conversely, when the silicon oxide insulating film 3 is formed thicker than the silicon oxide insulating film 4. Also, the warp of the SOI wafer can be reduced as compared with the conventional one.

[0037]

As described above, according to the semiconductor substrate manufacturing method of the present invention, the thickness of the oxide film formed on the two silicon wafers constituting the SOI wafer is different. It is possible to significantly reduce the warpage of the SOI wafer.

Of the two silicon wafers, the oxide film formed on the silicon wafer to be polished is formed thicker than the oxide film formed on the other silicon wafer, so that the warpage occurring in the SOI wafer can be further reduced. You can

On the contrary, of the two silicon wafers, the oxide film formed on the silicon wafer to be polished is formed thinner than the oxide film formed on the other silicon wafer, so that the warpage generated in the SOI wafer is reduced. can do.

Of the two silicon wafers that make up the SOI wafer, the thickness of the silicon oxide insulating film formed on the active layer side wafer that is polished to form the semiconductor element and becomes the active layer, and the base that holds the active layer. Since the thickness of the supporting base side wafer is different from that of the supporting base side wafer, the warpage of the SOI wafer can be significantly reduced.

Since the silicon oxide insulating film formed on the active layer side wafer is formed thicker than the silicon oxide insulating film formed on the support base side wafer, the warp generated on the SOI wafer can be further reduced.

On the contrary, since the silicon oxide insulating film formed on the active layer side wafer is formed thinner than the silicon oxide insulating film formed on the support base side wafer, the warp generated on the SOI wafer can be further reduced.

According to the semiconductor substrate of the present invention, the SOI
Since the thicknesses of the oxide films formed on the two silicon wafers forming the wafer are different, the warp generated on the SOI wafer can be significantly reduced.

[Brief description of drawings]

FIG. 1 is an explanatory view of a method for manufacturing a semiconductor substrate according to the present invention.

FIG. 2 is a graph showing the measurement results of the warp generated in the SOI wafer according to the present invention and the conventional manufacturing method.

FIG. 3 is a schematic cross-sectional view showing the structure of an SOI wafer.

FIG. 4 is an explanatory view of a first conventional method for manufacturing an SOI wafer.

FIG. 5 is an explanatory diagram of a second conventional method for manufacturing an SOI wafer.

[Explanation of symbols]

1, 10 Support base side wafer 2 Active layer side wafer 3, 4, 5, 11, 13, 14, 15, 30 Silicon oxide insulating film 6, 12, 16, 30 Active layer

Claims (7)

[Claims] 1. An oxide film having a first thickness on at least one surface of a first silicon wafer, and a second thickness different from the first thickness on at least one surface of a second silicon wafer. An oxide film forming step of forming an oxide film, respectively, the first silicon wafer having the oxide film of the first thickness formed thereon, and the second silicon having the oxide film of the second thickness formed thereon. A bonding step of bonding the wafer to the wafer by a direct bonding method through the oxide film having the first thickness and the oxide film having the second thickness, and polishing the first silicon wafer to a predetermined thickness. A method for manufacturing a semiconductor substrate, comprising a polishing step of processing. 2. The semiconductor substrate manufacturing method according to claim 1, wherein the oxide film having the first thickness is an oxide film thicker than the oxide film having the second thickness. Substrate manufacturing method. 3. The semiconductor substrate manufacturing method according to claim 1, wherein the oxide film having the second thickness is an oxide film thicker than the oxide film having the first thickness. Substrate manufacturing method. 4. A silicon oxide film of a first thickness is formed on at least one surface of a first silicon wafer on which a semiconductor element is formed and becomes an active layer, and a silicon oxide film having a first thickness is used as a base for holding the first silicon wafer. A silicon oxide film forming step of forming a silicon oxide film having a second thickness different from the first thickness on at least one surface of the second silicon wafer, and forming the silicon oxide film on the first silicon wafer. The silicon oxide film having the first thickness and the silicon oxide film having the second thickness formed on the second silicon wafer are pasted together by a direct bonding method to form the first silicon wafer. An insulating separation film forming step of forming an insulating silicon oxide film that insulates and separates the second silicon wafer, and an SOI wafer by polishing the first silicon wafer to a predetermined thickness. The method of manufacturing a semiconductor substrate, characterized in that a polishing process step of forming the active layer constituting the wafer. 5. The method for manufacturing a semiconductor substrate according to claim 4, wherein the silicon oxide film having the first thickness is the second silicon oxide film.
And a silicon oxide film thicker than the silicon oxide film having the thickness of 1. 6. The method for manufacturing a semiconductor substrate according to claim 4, wherein the silicon oxide film having the second thickness is the first silicon oxide film.
And a silicon oxide film thicker than the silicon oxide film having the thickness of 1. 7. A first silicon wafer, a second silicon wafer adhered to one surface of the first silicon wafer, and an oxide film provided at an interface between the first and second silicon wafers. The oxide film has an oxide film of a first thickness provided on the first silicon wafer side and an oxide film of a second thickness provided on the second silicon wafer side. A semiconductor substrate having different thicknesses of the oxide films having the first and second thicknesses.