JP2000196047A - Soi substrate and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a laminated SOI wafer equipped with an SOI layer and a high- concentration impurity layer which are both excellent in thickness uniformity, by a method wherein impurity ions and hydrogen ions are implanted into the same wafer from above the same surface changing in the depth of implantation, and the wafer is separated at a region where hydrogen ions are implanted. SOLUTION: Impurity ions are implanted into the surface of a bonded wafer 1 for the formation of a high-concentration impurity layer 3, and then hydrogen ions are implanted into the impurity ion-implanted surface. Moreover, hydrogen ions are implanted as deep as a certain point beyond the high-concentration impurity layer 3. By this setup, a fine air bubble layer 5 is formed in parallel with the surface of the wafer 1 and brought into close contact with a base wafer 2 where an oxide film 4 is formed. The laminate composed of the wafers 1 and 2 are thermally treated in an inert gas atmosphere, and a separated wafer 6 and a laminated SOI wafer A are separated from one another by rearrangement of crystal and condensation of air bubbles. By this setup, a laminated SOI wafer which is possessed of a high- concentration impurity layer 3 as thick as 0.1 to 0.2 μm and as high in impurity concentration peak as 1×1018 atmos/cm3 or above can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an SOI substrate and a method of manufacturing the same, and more particularly, to a SOI substrate for a BiCMOS device.
The present invention relates to a bonded SOI wafer for a MOS device and a method for manufacturing the bonded SOI wafer.

[0002]

2. Description of the Related Art An SOI (silicon on insulator) wafer has a silicon layer (SOI layer) on a buried oxide film (hereinafter referred to as a BOX film). However, two silicon wafers (a base wafer and a bond wafer) are used. )
Is bonded via a silicon oxide film, the so-called bonded SOI wafer has excellent crystallinity of the SOI layer, and therefore has excellent device characteristics to be formed on the SOI layer and is very useful. When a bipolar transistor is formed on this SOI layer, at least 1 × 1
A buried layer containing an impurity (dopant) of 0 ¹⁷ atoms / cm ³ (hereinafter, referred to as a high-concentration impurity layer or simply a high-concentration layer) must be formed, and a bonded SOI wafer having this high-concentration layer is required. As a manufacturing method, for example, there is the following method.

(1) Impurities are diffused or ion-implanted into the surface of a device forming wafer to form a high-concentration layer, which is bonded to a supporting wafer having an oxide film formed on the surface, and then the element forming wafer is thinned. how to. (Japanese Patent Laid-Open No. 5
(No. 136108) (2) A bonded SOI wafer is prepared in advance by a bonding method, impurities are gas-diffused or ion-implanted into the SOI layer to modify the SOI layer into a high-concentration layer, and then the SOI layer is formed on the high-concentration layer. A method of growing an epitaxial layer. (Prior arts of JP-A-1-196169 and JP-A-8-139180 (FIG. 7)) (3) A bonded SOI wafer is prepared in advance by a bonding method, and a high-concentration layer is formed only directly above the BOX layer through the SOI layer surface. A method of ion-implanting impurities by adjusting the implantation energy so that it is formed. (JP-A-4-23915)
No. 3)

By the way, as a device using a bonded SOI wafer, not only a bipolar device but also a so-called high performance BiCMOS device combining bipolar and CMOS has recently been manufactured. The bonded SOI wafer for producing this high-performance BiCMOS device also requires a high-concentration layer as in the case of the bipolar device. However, due to its characteristics, the thickness of the SOI layer is reduced to about 1 to 2 μm. A film thickness uniformity of ± 0.1 μm is required.

When a bonded SOI wafer is used for a CMOS device for low power consumption and low voltage driving, a high concentration layer is not necessarily required, but at least the SOI layer has a thickness of 0.3 μm. The following ultra-thin films are required. In addition, if a high concentration layer of about 0.1 to 0.2 μm (peak concentration of 1 × 10 ¹⁸ atoms / cm ³ or more) can be formed, it is very useful in device design and device characteristics. However, conventionally, a bonded SOI wafer having such a structure cannot be manufactured.

[0006]

SUMMARY OF THE INVENTION Such a BiCMO
When a bonded SOI wafer having a high-concentration layer is manufactured by the conventional manufacturing method described in the above (1) to (3) to be used for S and CMOS, there are the following problems. In case (1), the SOI layer is thinned by grinding and polishing.
The film thickness uniformity of the I layer can be obtained only at most about the target value ± 0.3 μm. In the case of (2) Since the SOI layer thinned by grinding and polishing becomes a high-concentration layer, the uniformity of the thickness of the high-concentration layer is ±± as in (1).
Only about 0.3 μm can be obtained. In addition, since the epitaxial growth is performed, the number of steps is increased and the cost is increased. In the case of (3), since impurities are implanted with high energy, the crystallinity of the SOI layer on the high concentration layer is deteriorated, and the characteristics of the BOX film are also deteriorated because they are partially implanted into the BOX film.

Further attention is focused on the formation of a high concentration layer (peak concentration of 1 × 10 ¹⁸ atoms / cm ³ or more) of about 0.1 to 0.2 μm.
Of course, it is impossible because it becomes 0.3 μm,
In the case of (1), after forming the high-concentration layer, the bonding heat treatment is performed at 1000 ° C. or more for a long time.
The condition of × 10 ¹⁸ atoms / cm ³ or more cannot be satisfied. In the case of (3), in order to recover the crystallinity of the SOI layer deteriorated by the ion implantation, a high temperature
Since a long-time heat treatment is required, the conditions of about 0.1 to 0.2 μm and 1 × 10 ¹⁸ atoms / cm ³ or more cannot be satisfied as in (1). The peak impurity concentration means an impurity concentration in a region where the impurity concentration is highest in the high concentration layer.

[0008] The present invention has been made in view of the above-mentioned problems of the prior art.
An object of the present invention is to provide a bonded SOI wafer having an SOI layer and a high-concentration impurity layer having a uniform thickness and a method of manufacturing the bonded wafer.

[0009]

In order to achieve the above object, a bonded SOI wafer according to claim 1 of the present invention is a bonded SOI wafer having a high concentration impurity layer on a buried oxide film, The high-concentration impurity layer has a thickness of 0.1 to 0.2 μm and a peak impurity concentration of 1 × 10 ¹⁸ atoms / cm ³ or more.

According to a second aspect of the present invention, there is provided a method for manufacturing a bonded SOI wafer, comprising bonding two silicon wafers through a silicon oxide film to form a high-concentration impurity on the buried oxide film. In the method for manufacturing a bonded SOI wafer having a layer, after implanting impurity ions from the surface of the first silicon wafer and implanting hydrogen ions or rare gas ions deeper than the impurity ions, the first silicon wafer The surface on which the ion implantation is performed and the surface of the second silicon wafer are brought into close contact with each other with a silicon oxide film interposed therebetween, and the first wafer is separated and bonded in the region where the hydrogen ions or the rare gas ions are implanted. After fabrication, the bonded SOI wafer is heat-treated.
As described above, the implantation of impurity ions and the implantation of hydrogen ions or rare gas ions from the same surface side of the same wafer at different depths are performed, and the film is peeled off in the region where the hydrogen ions or rare gas ions have been implanted. Bonded SOI having SOI layer excellent in thickness uniformity and high concentration impurity layer
Wafers can be made.

According to a third aspect of the present invention, there is provided a bonded SOI wafer having a high-concentration impurity layer on a buried oxide film by bonding two silicon wafers via a silicon oxide film. In the manufacturing method, after forming a silicon oxide film on the surface of the first silicon wafer, implantation of impurity ions through the oxide film and implantation of hydrogen ions or rare gas ions deeper than the impurity ions are performed from the same surface side. The surface of the first silicon wafer where the ion implantation is performed and the surface of the second silicon wafer are brought into close contact with each other via a silicon oxide film,
The method is characterized in that a bonded SOI wafer is manufactured by peeling the first wafer in the hydrogen ion or rare gas ion implanted region to produce a bonded SOI wafer. In this way, by implanting impurity ions and implanting hydrogen ions or rare gas ions from the same surface side via the oxide film, implantation damage to the silicon wafer can be reduced, and the oxide film is once removed. If the bonding is performed via a newly formed oxide film after the removal, the impurity ions implanted into the oxide film by ion implantation can be removed, so that the characteristics of the buried oxide film can be improved.

Further, in the invention described in claim 4 of the present invention, the peeling heat treatment temperature is set to 400 to 800 ° C., and the heat treatment applied to the bonded SOI wafer after peeling is performed by using a rapid heating / cooling device. The heat treatment is performed at a temperature higher than the heat treatment temperature. By setting such a peeling heat treatment temperature and a heat treatment condition after the peeling, the diffusion of the high-concentration impurity layer can be suppressed and the bonding strength can be made sufficient.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flow chart showing an example of a manufacturing process of a bonded SOI wafer according to claim 2 of the present invention. Step (a) is a step of preparing a bond wafer 1 serving as an SOI layer and a base wafer 2 serving as a support substrate. As the bond wafer 1, for example, a wafer having an n-type conductivity and a relatively high resistivity (low impurity concentration) of about 1 to 100 Ω · cm is selected. Base wafer 2
May be substantially the same shape (diameter, orientation flat, etc.) as the bond wafer 1 described above.
The conductivity type, the resistivity, and the like are not particularly limited, and an insulating substrate such as quartz, sapphire, silicon carbide, or aluminum nitride may be used depending on the application.

In the step (b), impurity ions are implanted into the surface of the bond wafer 1 to form the high-concentration impurity layer 3, for example, antimony (Sb) ions are implanted. In addition to antimony (Sb) ions, arsenic (As) or phosphorus (P) may be used as n-type impurity ions. Also,
As the p-type impurity, boron (B) ions are mainly used. The conductivity type of the bond wafer 1, the impurity concentration, and the type of impurity ions to be implanted are not particularly limited.
It can be appropriately selected according to the purpose. Further, implantation conditions such as implantation energy and dose amount are appropriately set depending on the concentration and thickness of the target high-concentration impurity layer.

Step (c) is a step of implanting at least one of hydrogen ions and rare gas ions, here hydrogen ions, into the surface of the bond wafer 1 on which antimony (Sb) ions have been implanted. The implantation of the hydrogen ions is performed at least in the case of antimony (S
b) To a depth exceeding the high concentration impurity layer 3 formed by ion implantation. This implantation of hydrogen ions is a step for causing separation in a region where hydrogen ions have been implanted by a hydrogen ion separation method (also called a smart cut method) described in Japanese Patent Application Laid-Open No. 5-211128.
Hydrogen ions are implanted to form a microbubble layer (encapsulation layer) 5 parallel to the surface at the average penetration depth of ions inside the bond wafer 1, which is brought into close contact with the base wafer 2 on which the oxide film 4 is formed, and then heat-treated (separated) When heat treatment is added, one of the wafers can be peeled into a thin film with the microbubble layer as a peeling surface as shown in steps (d) and (e). In recent years, a technique of performing low-temperature heat treatment at 400 ° C. or lower or peeling without applying heat treatment, depending on the conditions at the time of ion implantation, has also been reported.

As the peeling heat treatment in the step (e), for example, if a heat treatment is applied at a temperature of about 400 ° C. or more in an inert gas atmosphere, the SOI wafer bonded to the peeled wafer 6 by rearrangement of crystals and aggregation of bubbles. (SOI layer (microbubble layer) 5 + high-concentration impurity layer 3 + buried oxide film 4 + base wafer 2) A. Since the uniformity of the thickness of the separated bonded SOI wafer A depends on the uniformity of the hydrogen ion implantation depth, the target thickness is ± 0.01 μm.
The following uniformity is sufficiently obtained. If the temperature of the peeling heat treatment is set to 800 ° C. or lower (400 ° C. or higher), it is possible to prevent a phenomenon that the high concentration layer 3 into which antimony (Sb) ions are implanted spreads by diffusion or lowers the peak concentration. .

Incidentally, the steps (b) and (c) are interchanged,
Although antimony (Sb) ions can be implanted after hydrogen ions have been implanted, in this case, the temperature at the time of implantation of antimony (Sb) ions is set to prevent separation during implantation of antimony (Sb) ions. It is necessary to set the temperature to 400 ° C. or lower.

In the step (f), the bonding heat treatment is performed at a temperature exceeding the peeling heat treatment temperature in order to improve the bonding strength of the bonded SOI wafer A formed by the peeling heat treatment to a level that can withstand the device manufacturing step. When the bonding heat treatment temperature is set to 1000 ° C. or more, sufficient bonding strength can be obtained, and the separation heat treatment can be performed. In addition, if the bonding heat treatment is performed using a rapid heating / cooling device, the temperature can be raised and lowered almost in a short time, and a high-temperature heat treatment can be performed in a short time. It is possible to prevent phenomena such as the diffusion of the impurity layer by diffusion and the reduction of the peak concentration. Here, a rapid heating / cooling device, such as a lamp heating device using heat radiation, requires only a few seconds to several tens of seconds to raise the temperature to a target heat treatment temperature and to lower the temperature from that temperature. Devices, which are not particularly complex and expensive. In the embodiments of the present invention described later, lamp heating called SHS-2800 manufactured by STEACH MICROTECH INTERNATIONAL CO., LTD. Is used.

By the above steps (a) to (f),
(G), a bonded SOI wafer A having the high-concentration impurity layer 3 excellent in the uniformity of the thickness of the SOI layer 8 can be manufactured. In particular, the peeling heat treatment temperature is 400
To 800 ° C., and the thickness of the high-concentration impurity layer is reduced to 0.1 to
0.2 μm and the impurity peak concentration is 1 × 10
A bonded SOI wafer having a structure of ¹⁸ atoms / cm ³ or more, which has not been obtained conventionally, can be obtained.

Further, if a bonded SOI wafer is manufactured by using such a manufacturing method, an ultrathin film having a SOI layer thickness of 0.3 μm or less required for a CMOS device can be obtained. Since it is possible to form a high concentration layer of about 1 to 0.2 μm (at a concentration of 1 × 10 ¹⁸ atoms / cm ³ or more), the degree of freedom in device design is increased, and gettering of harmful impurities by the high concentration layer is achieved. Since an effect can be expected, it is very useful for device characteristics.

FIG. 2 is a flow chart showing an example of the manufacturing process of the bonded SOI wafer according to the third aspect of the present invention. The difference from the first embodiment shown in FIG.
In this case, the oxide film 7 is formed in advance on the bond wafer 1 ′, and the oxide film 7 is removed in the step (d ′) after implantation of antimony (Sb) ions and hydrogen ions. That is, by forming the oxide film 7 on the bond wafer 1 'in advance, the bond wafer 1'
Damage due to ion implantation introduced into the semiconductor device can be reduced. However, since antimony (Sb) ions are implanted into the oxide film 7 due to the implantation of antimony (Sb) ions, the oxide film 7 is once removed and another oxidation is performed as in the step (d ′). By bonding to the base wafer 2 'via the film 4', it is possible to prevent the quality of the buried oxide film of the SOI wafer from being deteriorated. If the quality of the buried oxide film does not matter much depending on the use of the SOI wafer, the bonding can be performed without removing the oxide film. Steps (e ′) to (h ′) are the same as steps (d) to (g) in the first embodiment shown in FIG.

(Examples 1, 2, and 3) A bonded SOI wafer having a diameter of 6 inches was manufactured according to the steps shown in FIGS. Table 1 shows detailed production conditions and measurements.

[0023]

[Table 1] However, regarding the data of the Sb ⁺ implantation amount and the n ⁺ layer in Examples 2 and 3 in Table 1, (a) shows the data of Example 2 and (b) shows the data of Example 3; Example 2 and Example 3 have the same data.

(Comparative Examples 1, 2, 3) Using the same wafer as in Examples 1, 2 (3), an SOI wafer having a diameter of 6 inches was manufactured by the above-mentioned conventional manufacturing method (1). Table 2 shows detailed production conditions and measurements.

[0025]

[Table 2] However, the data of the Sb ⁺ implantation amount and the n ⁺ layer in Comparative Examples 2 and 3 in Table 2 are (a) the data of Comparative Example 2, (b) the data of Comparative Example 3, and the other items are not shown. The same data is used in Comparative Example 2 and Comparative Example 3.

[0026]

As described above, according to the present invention, the SOI layer and the high-concentration impurity layer of the bonded SOI wafer are formed by a method using ion implantation. In addition to obtaining a bonded SOI wafer excellent in quality, the manufacturing process can be greatly simplified, and it can be manufactured at a relatively low cost. Further, it becomes possible to manufacture a bonded SOI wafer having a high-concentration impurity layer having a structure that cannot be obtained by the conventional method,
Use of such an SOI wafer is very useful in device design and device characteristics.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an example of a manufacturing process of a bonded SOI wafer according to the present invention.

FIG. 2 is a flowchart showing another example of the manufacturing process of the bonded SOI wafer according to the present invention.

[Explanation of symbols]

1, 1 '... bond wafer 2, 2' ... base wafer 3, 3 '... high concentration impurity layer 4, 4' ... oxide film 5, 5 '... microbubble layer 8, 8' ... SOI layer A ... bonded SOI Wafer

Claims (4)

[Claims] 1. A bonded SOI wafer having a high-concentration impurity layer on a buried oxide film, wherein the high-concentration impurity layer has a thickness of 0.1 to 0.2 μm and a peak impurity concentration of 1 A bonded SOI wafer having a density of × 10 ¹⁸ atoms / cm ³ or more. 2. A method for manufacturing a bonded SOI wafer having a high-concentration impurity layer on a buried oxide film by bonding two silicon wafers through a silicon oxide film. After the implantation of impurity ions and the implantation of hydrogen ions or rare gas ions deeper than the impurity ions, the surface of the first silicon wafer where the ions are implanted and the surface of the second silicon wafer are combined with a silicon oxide film. A bonded SOI wafer is prepared by peeling the first wafer in the hydrogen ion or rare gas ion implanted region to form a bonded SOI wafer, and then heat-treating the bonded SOI wafer. Wafer manufacturing method. 3. A method for manufacturing a bonded SOI wafer having a high-concentration impurity layer on a buried oxide film by bonding two silicon wafers through a silicon oxide film. After forming a silicon oxide film, implanting impurity ions through the oxide film and implanting hydrogen ions or rare gas ions deeper than the impurity ions, and then performing ion implantation of the first silicon wafer And the surface of the second silicon wafer are adhered through a silicon oxide film,
A method for manufacturing a bonded SOI wafer, comprising: forming a bonded SOI wafer by peeling the first wafer in the hydrogen ion or rare gas ion implantation region; and heat-treating the bonded SOI wafer. 4. The method according to claim 1, wherein the first silicon wafer is separated by 4
The heat treatment to be applied to the bonded SOI wafer after the peeling is performed by rapid heating.
4. The method for manufacturing a bonded SOI wafer according to claim 2, wherein the temperature is higher than a peeling heat treatment temperature by using a rapid cooling device.