JPH0521764A - Manufacturing for semiconductor device - Google Patents

Abstract

PURPOSE:To make it easy to form an ultrathin SOI layer uniformly, by controlling with high accuracy the depth of a thermal oxide layer and a buried insulating layer in ion implantation. CONSTITUTION:A mask layer 13 with an opening part 12 is formed on a Si substrate 11. Through the opening part 12, an oxigen-ion implantation is carried out for a separation region between devices in the Si substrate 11. A mask layer 13 is removed, and then on the surface of the Si substrate 11, a thermal oxide film 15 is formed so that the lower face thereof is located at about 0.5mum in depth with respect to an original surface of the Si substrate 11. In this case, an oxigen-ion-implantation region 114 is changed into a buried oxide silicon layer 14. After the silicon substrate 11 is put on a supporting substrate 16, heating is carried out and the silicon substrate 11 is bonded through the thermal oxide film 15 to the supporting substrate 16. Since the thermal oxide film 15 with uniform thickness is formed all over the silicon substrate 11, the silicon substrate 11 can be bonded through all the face thereof to the supporting substrate 16. Consequently, an SOI substrate having an ultrathin SOI layer can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor substrate,
In particular, SOI (Silicon on Insu) having a very thin silicon layer
lator) substrate manufacturing method.

In recent years, for the purpose of reducing parasitic capacitance and improving radiation resistance, an S film provided with an insulating film on the bottom of a semiconductor element is used.
Attention has been paid to a semiconductor IC having an OI structure. Several manufacturing methods are known for forming an SOI substrate used when forming a semiconductor IC having this SOI structure. However, an SOI substrate having the highest silicon crystallinity has a silicon substrate with an insulating film. It is obtained by a wafer laminating method in which laminating and polishing is performed on a supporting substrate via a via. Since the defect-free single crystal silicon substrate is used in the SOI substrate formed by this wafer bonding method, there is no problem in crystal quality, but variations in the film thickness in the process of polishing and thinning the silicon substrate cause variations in the element region. Is directly connected to the variation in the thickness of the active layer, and particularly when the MOS transistor with the ultra-thin SOI layer is manufactured, the variation in the film thickness causes the variation in the characteristics. Control is extremely important.

[0003]

2. Description of the Related Art Initially, a wafer bonding type SOI
When manufacturing a substrate, a thermal oxide film having a uniform thickness is formed on the entire surface of the silicon substrate, the silicon substrate is heat-bonded onto the supporting substrate through the thermal oxide film, and the silicon substrate is placed on the back surface. Was polished to a predetermined thickness to form an SOI layer.

However, in this method, since the control of the thickness of the SOI layer depends only on the precision of the polishing apparatus, the ultrathin S
When forming the OI layer, there arises a problem that sufficient accuracy and uniformity of thickness cannot be obtained.

Therefore, conventionally, as a method of manufacturing an SOI substrate having an ultrathin SOI layer with high accuracy and excellent uniformity, a method shown below with reference to FIG. 4 has been proposed. Figure 4
(a) Reference, that is, the method is, for example, 0.2 μm on the entire surface of the silicon substrate 51.
After forming a thermal oxide film 55 having a thickness of about m, an oxidation resistant film pattern 53 having an opening 52 in a portion corresponding to, for example, an element isolation region is formed on the thermal oxidation film, and the oxidation resistant film pattern is formed. The surface of the silicon substrate 51 is selectively oxidized using 53 as a mask,
A selective oxide film 54 having a thickness of about 0.6 μm is formed in the opening 52 of the oxidation resistant film pattern 53.

Referring to FIG. 4B, after removing the oxidation resistant film pattern 53, the silicon substrate 51 is inverted and heated on the support substrate 56 made of, for example, silicon through the upper surface of the selective oxide film 54. Stick it. (57 is a cavity) See FIG. 4 (c). Then, from the rear side of the Si substrate 51, the selective oxide film 54 is formed.
Is polished by using the bottom surface of the Si substrate 51 as a stopper, and the SOI layer 51S is made of the Si substrate 51 and has a thin film thickness of, for example, about 0.2 μm, which corresponds to the height difference between the selective oxide film 54 and the thermal oxide film 55.
A method for forming an SOI substrate having

[0007]

According to the above-mentioned conventional method, the thickness of the SOI layer 51S can be strictly controlled by the thicknesses of the thermal oxide film 55 and the selective oxide film 54, so that an extremely thin uniform film is obtained. It is possible to form an SOI layer having a thickness. However, in this conventional method, the silicon substrate 51 is not adhered to the support substrate 56 over the entire surface, but is partially adhered through the selective oxide film 54 selectively formed on the surface of the silicon substrate 51. Therefore, the adhesive force of the silicon substrate 51 to the support substrate 56 is partially weakened, and during the polishing or the SO
When the I substrate is divided into chips, etc., the selective oxide film 55
In the peripheral portion of the SOI layer 51S, peeling or damage of the SOI layer 51S from the support substrate 56 occurs, and a semiconductor IC or the like having an SOI structure is of high quality.
There is a problem that it becomes difficult to manufacture with a high yield.

Therefore, the present invention makes it possible to manufacture an SOI substrate having a uniform film thickness and stably obtaining an ultra-thin SOI layer that is uniformly adhered to a supporting substrate at a high yield.
An object is to provide a method for manufacturing an OI substrate.

[0009]

FIG. 1 is a process sectional view for explaining the principle of the present invention. As shown in FIG. 1 (a), the above-mentioned problem is that a substance that combines with silicon to form an insulator, such as oxygen (O ⁺ ), is applied to a partial region in the silicon substrate 1 at a predetermined depth from the main surface side. Ion implantation to a depth d ₁ (2 is an opening, 3 is a mask layer, 104 is an O ⁺ implantation region), and then FIG.
As shown in (b), a thermal oxide film 5 having a bottom surface is formed on the main surface of the silicon substrate 1 at a depth d ₂ shallower than the bottom surface of the ion implantation region, and at the same time, in the O ⁺ implantation region 104, for example. Step of forming a buried insulator layer 4 made of silicon oxide (SiO ₂ ), and then, as shown in FIG. 1 (c), the silicon substrate 1 is heat-bonded onto the supporting substrate 6 via the thermal oxide film 5. Step, and then, as shown in FIG. 1D, the silicon substrate 1 is polished from the back side using the embedded insulator layer 4 as a stopper, and the semiconductor substrate 1 is formed on the support substrate 6 with the thermal oxide film 5 interposed therebetween. A method for manufacturing a semiconductor substrate according to the present invention, which has a step of forming an SOI substrate having a thin layer, that is, a thin SOI layer 1S attached thereto, or a step of forming an insulating film on the main surface of a silicon substrate, and combining it with silicon. The material forming the insulator is the silicon substrate. A step of implanting ions deeper than the bottom surface of the insulating film through the insulating film from the main surface side, heating the silicon substrate to a support substrate through the insulating film, and at the same time, embedding the insulator in the ion implantation region. A step of forming a layer, wherein the silicon substrate is polished from the back side using the embedded insulator layer as a stopper, and a thin layer of the silicon substrate is attached onto a supporting substrate through the insulating film.
This is solved by the method for manufacturing a semiconductor substrate according to the present invention, which includes the step of forming an I substrate.

[0010]

That is, in the method of the present invention, as shown in FIG. 1, the buried insulating layer 4 formed inside the silicon substrate 1 by selectively ion-implanting oxygen or nitrogen is polished to the silicon substrate 1. Since the silicon substrate 1 is used as a polishing stop layer when it is thinned, the silicon substrate 1 is adhered onto the support substrate 6 by using a thermal oxide film 3 formed on the entire surface of the silicon substrate 1 to have a uniform thickness. It can be performed through the entire surface without impairing the flatness of No. 1. Therefore, the support substrate 6 of the SOI layer 1S formed by polishing the silicon substrate 1 on the back surface
Since the adhesion failure to the top is eliminated, the warp and peeling of the SOI layer 1S are avoided, and the yield of semiconductor ICs and the like formed on the SOI layer 1S is improved.

In the method of the present invention, the SOI layer
The thickness of 1S is the depth d of the embedded insulator layer 4 that serves as a stopper.
_It is defined by the difference between ₁ and the depth d ₂ of the thermal oxide film 5, and the depth d ₁ of the buried insulating layer 4 by the ion implantation and the depth of the thermal oxide film 5 at the time of thermal oxidation are highly controlled. Therefore, it becomes easy to form an SOI layer having an extremely thin uniform thickness.

As described above, according to the present invention, an SOI substrate having an ultrathin SOI layer having a uniform film thickness can be manufactured with good yield and stability.

[0013]

EXAMPLES The present invention will be described in detail below with reference to illustrated examples. FIG. 2 is a process sectional view of one embodiment of the method of the present invention,
FIG. 3 is a process sectional view of another embodiment of the method of the present invention.
The same object is denoted by the same reference numeral throughout the drawings.

Referring to FIG. 2 (a), when a SOI substrate having an SOI layer having a thickness of, for example, about 0.1 to 0.2 μm is formed by the first method according to the present invention, it is generally used for manufacturing a semiconductor device. Si substrate with high quality equivalent to 11
A mask layer 13 made of an organic or inorganic material having a film thickness of about 1 to 2 μm and having, for example, an opening 12 that exposes a portion corresponding to an element isolation region is formed on the upper surface of the mask layer 13. At a portion corresponding to the element isolation region of the Si substrate 11, at an acceleration energy of, for example, 300 to 400 KeV, 1 × 10
Oxygen (O ⁺ ) is ion-implanted at a dose of about ¹⁷ to 1 × 10 ¹⁸ cm ^-2 . In this embodiment, this ion implantation forms an O ⁺ implantation region 114 having a peak concentration at a depth of about 0.6 to 0.7 μm, for example.

Referring to FIG. 2 (b), after the mask film 13 is removed, the surface of the silicon substrate 11 is wet-oxidized at a normal temperature of about 1000.degree. A thermal oxide film 15 having a bottom surface is formed at a depth of about 0.5 μm from the surface, and at the same time, the thermal oxide film 15 is formed.
^The implantation region 114 is changed to the buried silicon oxide (SiO ₂ ) layer 14. At this time, the bottom surface of the embedded SiO ₂ layer 14 is formed so as to project downward by about 0.1 to 0.2 μm (d ₃ ) from the bottom surface of the thermal oxide film 15.

Referring to FIG. 2 (c), the silicon substrate 11 is then used.
Is inverted and placed on a support substrate 16 made of, for example, silicon and heated to about 1000 ° C. to form a thermal oxide film 15 on the substrate surface.
It is stuck on the support substrate 16 via. Since the thermal oxide film 15 is formed on the entire surface of the silicon substrate 11 with a uniform thickness,
The silicon substrate 11 is stuck on the support substrate 16 over the entire surface while maintaining the flatness.

Referring to FIG. 2 (d), the silicon substrate 11 is embedded from the back side by a well-known mechanochemical polishing means using an alkaline etching solution, and the bottom surface of the SiO ₂ layer 14 is polished as a stopper to heat the support substrate 16. An ultrathin SOI layer 11 having a thickness (t) of 0.1 to 0.2 μm, which is attached through an oxide film 15 and divided into a plurality of regions by a buried SiO ₂ layer 14.
The SOI substrate 17 having S is completed.

Referring to FIG. 3 (a), when forming an SOI substrate having an SOI layer having a thickness of about 0.1 to 0.2 μm by the second method according to the present invention, first, a method such as wet oxidation is used. An insulating film, for example, a thermal oxide film 15 having a thickness of about 0.5 to 2 μm is formed on the surface of the Si substrate 11 similar to the above embodiment.

Next, referring to FIG. 3B, a mask layer 13 having an opening 12 for exposing a portion corresponding to an element isolation region is formed on the thermal oxide film 15, and the opening of the mask layer 13 is formed. Oxygen (O ⁺ ) with the same dose amount as that in the above-mentioned embodiment is ion-implanted through the thermal oxide film 15 through the thermal oxide film 15 through 0.1 to 0.2 to 0.2 from the bottom surface of the thermal oxide film into the silicon substrate 11. An O ⁺ implantation region 114 having a depth of about μm is formed.

Referring to FIG. 3 (c), the silicon substrate 11
Is inverted and placed on a support substrate 16 made of, for example, silicon and heated to about 1000 ° C. to form a thermal oxide film 15 on the substrate surface.
It is stuck on the support substrate 16 via. At this time, the O ⁺ implantation region 114 changes into the buried SiO ₂ layer 14.

Note that the silicon substrate 11 is stuck on the support substrate 16 over the entire surface while maintaining the flatness, as in the above-described embodiment. Then, as shown in FIG. 3 (d), the silicon substrate 11 is buried from the back side in the same manner as in the above-mentioned embodiment by a SiO ₂ layer.
The bottom surface of 14 is polished as a stopper, and is adhered on the support substrate 16 via the thermal oxide film 15, and is divided into a plurality of regions by the embedded SiO ₂ layer 14 and has a thickness (t) of about 0.1 to 0.2 μm. Thin S
The SOI substrate 17 having the OI layer 11S is completed.

In the above-mentioned embodiment, the embedded Si layer formed by implanting oxygen (O ⁺ ) ions into the embedded insulator layer.
Although the O ₂ layer 14 is used, a buried silicon nitride (S) formed by nitrogen (N ⁺ ) ion implantation and heat treatment similar to the embodiment is used.
An i ₃ N ₄ ) layer may be used.

[0023]

As described above, according to the present invention, the SO
The adhesion of the I layer to the surface of the supporting substrate is performed on the entire surface without impairing the flatness, and the thickness of the SOI layer is the depth of the buried insulating layer formed by ion implantation with high depth control accuracy. And the depth of the thermal oxide film formed on the surface with good thickness controllability.

Therefore, according to the present invention, an extremely thin SOI layer of about 0.1 μm can be stably formed with a uniform thickness, and peeling of the SOI layer is prevented.
The quality and manufacturing yield of the SOI substrate having the I layer can be improved.

[Brief description of drawings]

FIG. 1 is a process sectional view for explaining the principle of the present invention.

FIG. 2 is a process sectional view of an embodiment of the method of the present invention.

FIG. 3 is a process sectional view of another embodiment of the method of the present invention.

FIG. 4 is a process sectional view of a conventional method.

[Explanation of symbols]

1 Silicon substrate 2 openings 3 Mask layer 4 Embedded insulator layer 5 Thermal oxide film 6 Support substrate

Claims (5)

[Claims] 1. A step of ion-implanting a substance that combines with silicon to form an insulator into a partial region in a silicon substrate from a main surface side to a predetermined depth, wherein the main surface of the silicon substrate is Forming a thermal oxide film having a bottom surface shallower than the bottom surface of the ion-implanted region and simultaneously forming a buried insulating layer in the ion-implanted region, the silicon substrate being heat-bonded onto the supporting substrate via the thermal oxide film. And a step of polishing the silicon substrate from the back side using the embedded insulator layer as a stopper to form an SOI substrate in which a thin layer of the silicon substrate is adhered on a supporting substrate via the thermal oxide film. Manufacturing method of semiconductor substrate. 2. A step of forming an insulating film on a main surface of a silicon substrate, a substance which combines with silicon to form an insulator is passed through the insulating film from the main surface side of the silicon substrate, and a bottom surface of the insulating film. A step of implanting ions deeper, a step of heat-bonding the silicon substrate on a support substrate via the insulating film, and a step of forming an embedded insulator layer in the ion-implanted region, and a step of implanting the silicon substrate from the back side. A method for manufacturing a semiconductor substrate, which comprises a step of polishing an insulator layer as a stopper and forming an SOI substrate in which a thin layer of the silicon substrate is adhered on a supporting substrate via the insulating film. 3. The method of manufacturing a semiconductor substrate according to claim 1, wherein the substance that combines with the silicon to form an insulator is oxygen, and the buried insulator layer is a silicon oxide layer. . 4. The method of manufacturing a semiconductor substrate according to claim 1, wherein the substance that combines with the silicon to form an insulator is nitrogen, and the buried insulator layer is a silicon nitride layer. . 5. The injection region of a substance that combines with the silicon to form an insulating layer is defined so that the buried insulating layer serves as an element isolation region. Of manufacturing a semiconductor substrate.