JP2003188362A - Soi substrate and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make it possible to finely adjust the performance of an SOI (Silicon On Insulator) transistor. <P>SOLUTION: An SOI substrate 10, on which a handle wafer 11 composed of Si, a BOX 12 composed of SiO2, and a device wafer 13 composed of Si are stacked, is provided with a nitride layer 12a whose nitrogen peak concentration exists in the vicinity of the boundary face of the BOX 12 with the device wafer 13. Because the nitride layer 12a is provided in the vicinity of the Si boundary face of SiO2 of the BOX 12, it is possible to suppress the boron atoms implanted into the body by heat treatment from moving into the BOX when the SOI transistor is manufactured using the SOI substrate 10. As the concentration of boron to be implanted into the body can be low, a fine adjustment of the SOI transistor performance is possible. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an SOI (sili)
The present invention relates to an SOI substrate used for manufacturing a con on insulator transistor and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventional SOI substrates include a handle wafer (Si substrate) 11 and a BOX (SiO 2) as shown in FIG.
It has a three-layer structure of two films) 12 and a device wafer (Si layer) 13. SO created using the SOI substrate 10
As shown in FIG. 5B, the I-transistor is formed by introducing impurities into the device wafer 13 of the SOI substrate 10 to form the source 3
1, the drain 32 and the body portion 33 are provided, and the body portion 3
3, a gate 35 is provided on top of the gate insulating film 34 via the gate insulating film 34. In addition, the outer portion of the element region (31 to 33) of the device wafer 13 is oxidized to form the element isolation region 3
6 is set.

[0003]

[Problems to be Solved by the Invention] SOI transistor 1
In the case of 0, when introducing boron (boron) as an impurity into the body portion 33, for example, the same effect as that of the bulk transistor cannot be obtained unless a higher concentration of boron is implanted as compared with the bulk transistor. This can be thought of as follows.

Boron atoms implanted in the body part move into the BOX due to the heat treatment for transistor formation, and the boron concentration in the body part becomes thin. For this reason, although it is possible to finely adjust the transistor performance by implanting low-concentration boron ions in the bulk transistor, it is difficult in the SOI transistor.

The present invention has been made in view of the above problems, and the boron atom introduced into the body does not move into the BOX due to the heat treatment for transistor formation.
It is an object to provide an OI substrate and a method for making the same.

[0006]

The present invention relates to a P transistor used in a dual gate structure SOI transistor.
+ Uses technology that suppresses the phenomenon that boron in the gate penetrates the gate oxide film and diffuses into the channel. Usually, this phenomenon of boron penetration can be suppressed by nitriding the gate oxide film. The present invention suppresses the phenomenon of boron penetration from the channel portion to the BOX by applying this technique and nitriding the BOX. The BOX (SiO2) is nitrided so that the peak of nitrogen concentration is near the interface of the Si layer in SiO2. The nitriding amount at this time is approximately 0.5 to 10 atm%.
Adjust the peak concentration to about the same level.

The present invention has been made to solve the above problems, and the invention according to claim 1 relating to an SOI substrate comprises a BOX made of a silicon oxide film and silicon on a handle wafer made of silicon. In an SOI substrate in which a device wafer is laminated, a nitriding part having a nitrogen concentration peak is provided in the vicinity of the interface of the device wafer of the BOX.

The invention according to claim 2 relating to the method for producing an SOI substrate is formed on the device wafer by a device wafer oxidation step of oxidizing the upper surface of the device wafer to form a BOX of a predetermined thickness on the device wafer. BO
BOX nitriding step for nitriding X so that the peak concentration of nitrogen is located near the silicon interface of silicon oxide in the BOX, and wafer bonding for bonding the BOX surface of the device wafer having the nitrided BOX to the handle wafer And a device wafer grinding / polishing step of grinding / polishing the bonded device wafer to complete the SOI substrate.

According to a third aspect of the present invention relating to a method of forming an SOI substrate, a device wafer oxidizing step of oxidizing the upper surface of a device wafer to form a BOX which is sufficiently thinner than the BOX of the SOI substrate, and a thin upper surface of the device wafer. B
A BOX nitriding step of nitriding the OX so that the peak concentration of nitrogen is located near the silicon interface of the silicon oxide in the BOX, and an upper surface of the handle wafer is oxidized to overlap with a thin BOX of the device wafer to obtain a predetermined thickness. Thickness B
A step of oxidizing a handle wafer for forming an OX, a step of attaching a nitrided thin BOX surface of the device wafer to a BOX surface formed on the handle wafer, and a step of attaching the attached device wafer member to each other in a predetermined manner. A device wafer member grinding / polishing process for finishing the SOI substrate by grinding / polishing to a thickness.

The invention according to claim 4 is the same as the invention according to claim 2 or 3, wherein nitriding of the BOX is performed by
It is characterized in that nitrogen ions are implanted from the X surface by ion implantation for nitriding.

The invention according to claim 5 is characterized in that, in the invention according to claim 2 or 3, the BOX is nitrided by annealing in an atmosphere containing high temperature nitrogen.

When annealing and nitriding in a gas atmosphere containing high temperature nitrogen, for example, the following method is used. 1) Nitrogen SiO2 in an NH3 atmosphere. 2) Nitriding SiO2 in N2O atmosphere. 2) Nitriding SiO2 in NO atmosphere.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

Embodiment 1 FIG. 1 shows a sectional structure of an SOI substrate according to the present invention. The SOI substrate 10A is a handle wafer 11 made of Si.
And a BOX 12 made of a SiO 2 film and having a nitrided portion 12 a near the interface with the device wafer 13, and a device wafer 13 made of Si.

The S according to the first embodiment will be described below with reference to FIG.
A method of making the OI substrate 10A will be described.

First, as shown in FIG. 2A, the upper surface of a device wafer 13A made of Si is oxidized to form a device wafer 13A having a B0X12 made of a SiO2 film with a thickness of about 100 nm formed on the upper surface. (This B0X1
The device wafer 13A on which 2 is formed may be a ready-made product. ) Then, as shown in FIG.
Nitrogen ions are implanted into 2 by ion implantation, and the BOX 12 is nitrided so that the peak concentration of nitrogen is located near the Si interface of SiO 2 in the BOX 12 to form the nitrided portion 12a. Nitriding amount is approximately 0.5 to 10 atm
Adjust the peak concentration to about%. The condition (one example) of ion implantation at this time is energy = 4
5 keV, Dose = 2.5E20-5E21
atom / cm3.

Next, the BOX 1 having the nitride layer 12a
2 is turned upside down on the device wafer 13A formed on the upper surface, and the BOX is formed on the upper surface of the handle wafer 11 shown in FIG.
12 surfaces are pasted together. This bonding is performed using a known SO
This is performed by using the substrate bonding technique for the I wafer. As a result of this bonding, as shown in FIG. 2D, the handle wafer 11
A wafer 21 is obtained in which the BOX 12 having the nitrided portion 12a on the upper surface thereof and the device wafer member 13A are laminated. The nitrogen atom implanted by the ion implantation must be annealed and activated, but the nitrogen atom added at the time of bonding (1100 ° C.) is activated. Then, by grinding and polishing the device wafer 13A in the stacked wafers 21 so as to have a predetermined thickness, the nitride layer 12a having a nitrogen concentration peak near the Si interface of the BOX 12 is formed as shown in FIG. 2 (e). SO to have
The I substrate 10A can be obtained.

When an SOI transistor shown in FIG. 5B is produced using this SOI substrate 10A, even if the boron atoms are implanted in the body portion 33 and then heat treatment is performed, the boron implanted in the body portion 33 moves to the BOX 12 side. Is BOX1
This is suppressed by the nitride layer 12a provided in the vicinity of the Si interface of 2. Therefore, the boron concentration to be implanted in the body portion 33 can be made low, and the transistor performance can be finely adjusted.

Embodiment 2 A method of manufacturing an SOI substrate 10A according to Embodiment 2 will be described with reference to FIG.

First, as shown in FIG. 3A, the upper surface of the device wafer 13A made of Si is oxidized to form SiO2.
A device wafer 13A on which a thin B0X12A film is formed is formed. The film thickness of B0X12A is set to about 20 nm (may be about several nm to several tens of nm) so that the peak concentration of nitrogen is easily located near the desired Si interface when nitrided. Then, as shown in FIG. 3B, nitrogen ions are implanted into the BOX 12A from above by ion implantation so that the peak concentration of nitrogen is located near the Si interface of SiO 2 in the BOX 12A.
A is nitrided to form a nitrided portion 12a. The nitriding amount is set to a peak concentration of about 0.5 to 10 atm%. The method for producing the SOI substrate is based on the condition of ion implantation when the thickness is about 20 nm (example)
, Energy = 10 keV, dose (Dose) = 2.
It is 5E20-5E21 atom / cm3. The variation in the depth direction of nitrogen atoms at this time is due to nitriding B0X12.
By making A thin, it is reduced to about 1/3 of that of the first embodiment.

Further, as shown in FIG. 3C, the upper surface of the handle wafer 11 is oxidized to form the handle wafer 11 having B0X12B formed on the upper surface. The thickness of this B0X12B is the thin B0X1 formed on the device wafer 13A.
It is formed to a thickness of about 80 nm so as to have a predetermined thickness (for example, 100 nm) when overlapped with 2A.

Next, the device wafer 13A on which the BOX 12A having the nitrided portion 12a of FIG. 3B is formed is turned over, and the BOX 12A surface is attached to the BOX 12B surface formed on the handle wafer 11 as shown in FIG. 3C. To match. This bonding is performed by using a known SOI wafer substrate bonding technique.

By this bonding, as shown in FIG. 2D, the nitride layer 1 is formed on the handle wafer 11 near the Si interface.
BOX 12 having 2a formed thereon and a thick device wafer 13
A wafer 22 in which A is sequentially overlapped is obtained. The nitrogen atoms implanted by the ion implantation must be annealed and activated, but they are activated by the annealing (1100 ° C.) applied during bonding. Then,
The device wafer 13A on this wafer 25 is shown in FIG.
As shown in (d), the SOI substrate 10A having the nitride layer 12a in the vicinity of the Si interface of the BOX 12 can be obtained by grinding and polishing the device wafer 13 having a predetermined thickness.

Embodiment 3 In Embodiment 1 described above, B on the upper surface of the device wafer 13A
Nitriding of OX12 is performed by ion implantation of nitrogen ions (FIG. 2 (b)). In the third embodiment, instead of the ion implantation of nitrogen ions, as shown in FIG.
The BOX 12 on the upper surface of the device wafer 13A in FIG.
As shown in (b), it is annealed and nitrided in a NO atmosphere at 900 ° C. The nitriding is performed by surface treatment so that the device wafer 13A is not nitrided in the NO atmosphere. Due to the nitriding, nitrogen segregates at the device wafer / BOX interface with many dang bonds as shown in FIG. 4B. This nitrided BOX
A device wafer 13A having
The device wafer 13A is attached to the hand-wafer 11 and the device wafer 13A is ground and polished to form the SOI substrate 10A.

Although nitriding is performed in a NO atmosphere at 900 ° C. in the above, it can be performed in an N 2 O atmosphere at 950 ° C. Further, the nitriding performed in the atmosphere containing N is
It can also be applied to nitriding the BOX 12A of the second embodiment.

[0026]

As described above, the SOI substrate according to the present invention is
Since the nitriding portion is provided in the vicinity of the i interface, it is possible to suppress the movement of boron atoms implanted in the body portion into the BOX due to the heat treatment when forming the S0I transistor. Therefore, the concentration of boron to be implanted in the body portion can be made low, so that the S0I transistor performance can be finely adjusted.

Further, according to the SOI substrate producing method of the present invention, an SOI substrate having a nitride layer provided near the Si interface of the BOX can be easily produced.

[Brief description of drawings]

FIG. 1 is an explanatory view of a sectional structure of an SOI substrate according to the present invention.

FIG. 2 is an explanatory diagram of an SOI substrate making procedure according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of an SOI substrate manufacturing procedure according to the second embodiment of the present invention.

FIG. 4 is an explanatory diagram of an SOI substrate creation procedure according to the third embodiment of the present invention.

5A and 5B are a conventional SOI substrate and SO.
FIG. 3 is a cross-sectional structure explanatory diagram of an I transistor.

[Explanation of symbols]

10 ... SOI substrate 11 ... Silicon substrate, handle wafer 12, 12A, 12B ... BOX, silicon oxide film 12a ... Nitriding layer 13, 13A ... Silicon layer, device wafer

Claims (5)

[Claims] 1. An SOI substrate in which a BOX made of a silicon oxide film and a device wafer made of silicon are stacked on a handle wafer made of silicon, and a nitriding part having a nitrogen concentration peak near the interface of the BOX device wafer. An SOI substrate characterized by being provided with. 2. A device wafer oxidizing step of oxidizing a top surface of a device wafer to form a BOX having a predetermined thickness on the device wafer, and the BOX formed on the device wafer is filled with nitrogen in the vicinity of a silicon interface of silicon oxide in the BOX. BOX nitriding step of nitriding so that the peak concentration of the BOX is located, and BOX of the device wafer having the nitrided BOX
Wafer bonding step of bonding the surface to the handle wafer, and device wafer grinding for grinding and polishing the device wafer of the bonded wafer to complete the SOI substrate
A method of manufacturing an SOI substrate, comprising: a polishing step. 3. The upper surface of a device wafer is oxidized to form the S
A device wafer oxidation step for making a BOX sufficiently thinner than the BOX of the OI substrate, and a BOX nitriding step for nitriding the thin BOX on the upper surface of the device wafer so that the peak concentration of nitrogen is located near the silicon interface of the silicon oxide in the BOX, A handle wafer oxidation step of oxidizing the upper surface of the handle wafer to form a BOX having a predetermined thickness when superposed on the thin BOX of the device wafer, and a BOX surface formed on the handle wafer, A wafer bonding step for bonding the thin nitrided BOX surfaces, and a device wafer member grinding / polishing step for grinding and polishing the bonded device wafer member to a predetermined thickness to complete the SOI substrate. Characterized by S
How to make an OI substrate. 4. The method for producing an SOI substrate according to claim 2, wherein the BOX is nitrided by nitriding nitrogen ions from the surface of the BOX by ion implantation. 5. The method of manufacturing an SOI substrate according to claim 2, wherein the BOX is nitrided by annealing in a high temperature nitrogen-containing atmosphere.