JP3171322B2 - SOI substrate and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an SOI (Silicon On I / O) having a silicon active layer on a supporting substrate.
nsulator) substrate structure.

[0002]

2. Description of the Related Art A typical SOI substrate has a structure in which a silicon active layer 803 is laminated on a silicon dioxide film 802 formed on a silicon substrate 801 as shown in FIG. In the SOI structure, since each transistor and the like formed in the silicon active layer can be completely separated by the insulating film, many problems caused by the pn junction separation can be solved. That is, the structure is advantageous for suppressing soft errors due to radiation, reducing power consumption, increasing speed, and the like.

However, there is a disadvantage that the presence of a thick oxide film under the silicon active layer is susceptible to metal contamination during the manufacturing process.

When a semiconductor device is manufactured using a normal silicon substrate, a method of forming a polycrystalline silicon layer or a silicon nitride layer on the back surface of the wafer or forming a crystal defect layer in the silicon substrate is used. A method is employed in which a strained layer is formed in advance, and metal contamination generated during the manufacturing process is captured (gettered) by the strained layer to protect the surface active layer forming the semiconductor element from metal contamination.

In general, metal diffusion is much slower in an insulating film than in silicon. Therefore, in the case of the SOI structure in which a thick insulating film exists under the silicon active layer, there is a problem that the surface active layer cannot be sufficiently protected from metal contamination.

For the purpose of improving such disadvantages, Japanese Patent Application Laid-Open No. Hei 4-199632 discloses a structure as shown in FIG.

That is, the semiconductor device has a structure in which a semiconductor active layer 901, a first insulating film 902, a sink layer 903, a second insulating film 904, and a semiconductor supporting substrate 905 are sequentially stacked. This structure has a structure in which a first oxide film is formed on a silicon substrate by thermal oxidation, a second insulating film is formed on a support substrate, and a polycrystalline Si film, an amorphous Si film, or an amorphous silicon nitride film is further formed thereon. Is tightly adhered to the
It is manufactured by a method of bonding by heating at a temperature of 00 ° C.

However, for example, in the case where a polycrystalline silicon film is deposited on the back surface of a silicon substrate and heavy metals are gettered, it is known that the heavy metal gettering action is lost in the polycrystalline silicon films when heated to 1000 ° C. or more. Have been. This is because in the manufacturing process of the SOI substrate,
This is because the crystal grain size of the polycrystalline silicon layer which should have the gettering ability of the heavy metal becomes large and the gettering ability cannot be maintained. JP-A-4-1996 mentioned above
32, the polycrystalline S in the insulating film of the SOI
The method of forming an i-film has almost no gettering effect on heavy metals. Further, even if an amorphous Si film is used, it is polycrystallized by a very short heat treatment at 1000 ° C. (in the order of minutes), so there is no difference from a polycrystalline silicon film.

Therefore, the conventional technology (Japanese Patent Laid-Open No. 4-1996)
32) In the structure obtained by the manufacturing method shown in
There is a problem that a sufficient gettering action cannot be obtained.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide an SOI substrate which maintains a high gettering ability even after a high-temperature heat treatment in an SOI manufacturing process or a semiconductor device manufacturing process.

[0011]

According to the present invention, there is provided an SOI substrate in which a support substrate, an insulating layer and a silicon active layer are sequentially laminated, wherein the insulating layer is selected from the group consisting of boron, carbon, oxygen and nitrogen. 10 at least one impurity
^It has a polycrystalline silicon region containing a concentration of ¹⁷ cm ^-3 or more.
And the polycrystalline silicon region has an island shape, a plurality of films or
The present invention relates to an SOI substrate which exists as a patterned discrete film . The present invention also provides an SOI device in which a support substrate, an insulating layer, and a silicon active layer are sequentially stacked.
In the substrate, polycrystalline silicon containing, in the insulating layer, (a) boron and (b) at least one impurity selected from the group consisting of carbon, oxygen, and nitrogen at a concentration of 10 ¹⁷ cm ⁻³ or more in total The present invention relates to an SOI substrate having a region. The present invention provides a SOI substrate supporting substrate and the insulating layer and the silicon active layer are sequentially stacked, the insulating layer, have a polycrystalline silicon region grain size is 20nm or less, the polycrystalline silicon region
But discrete islands, multiple films or patterned
The present invention relates to an SOI substrate which is present as a film .

Here, the polycrystalline silicon region containing impurities can exist in the insulating layer in various forms. For example, a polycrystalline silicon film sandwiched between insulating films from both sides, an insulating film, Examples include a form in which the film is discontinuously present in an island shape. From the viewpoint of manufacturing, it is easy and preferable to form a film. In this case, the number of layers may be one or more, and may be a plurality of layers. In addition, they need not be continuous in the film plane, but may be discretely provided by patterning.

As described above, when impurities are contained in the polycrystalline silicon region provided in the insulating layer, it is possible to prevent silicon from becoming large particles even at a high temperature. Therefore, since the number of gettering sites does not decrease, the gettering action is maintained.

Further, according to the present invention, in an SOI substrate in which a support substrate, an insulating layer and a silicon active layer are sequentially laminated, at least one polycrystalline silicon film and one silicon nitride film are provided in the insulating layer. SO characterized by
It relates to an I substrate.

Further, the present invention relates to an SOI substrate in which a supporting substrate, an insulating layer and a silicon active layer are sequentially laminated, wherein the insulating layer has at least one silicon germanium film in the insulating layer. .

When a polycrystalline silicon film and a silicon nitride film are present in the insulating layer, the strain increases, and the gettering effect is further increased. It is preferable that the polycrystalline silicon film and the silicon nitride film are particularly stacked in contact with each other.

Since silicon germanium, which is a mixed crystal of silicon and germanium, also has a large gettering effect, a silicon germanium film can be provided in the insulating layer as a gettering layer.

In the case where a polycrystalline silicon film and a silicon nitride film are present in the insulating layer, or even when silicon germanium is present, impurities of 10 ¹⁷ cm ^-3 or more are contained in the polycrystalline silicon film and the silicon germanium film. By including it, a gettering effect can be further expected.

In the present invention, by using the above structure, the gettering action of the polycrystalline silicon region formed in the insulating layer is not impaired even at a high temperature treatment of 1000 ° C. or more. It can sufficiently capture the heavy metals coming in, and protect the silicon active layer from heavy metal contamination.

[0020]

Next, an embodiment of the present invention will be described in detail with reference to the drawings.

[Embodiment 1] FIG. 1 is a sectional view for explaining a first embodiment of the present invention. Silicon substrate 1
01, a first insulating film 102 is formed, and
There is a silicon (polycrystalline) film 103 doped with an impurity of about × 10 ¹⁷ cm ⁻³ or more, and the second insulating film 1
04, a silicon active layer 105 is formed thereon.

[0022] As the impurity, boron, carbon, oxygen, nitrogen, and the like are suitable, such impurities 1 × 10 ¹⁷ cm
^The polycrystalline silicon film containing about ⁻³ or more does not increase in crystal grain size even after a long-time heat treatment at a temperature of 1000 ° C. or more. Therefore, a high gettering ability with respect to heavy metals can be maintained even in a bonding SOI substrate forming step described later and a heat treatment step of forming a semiconductor element.

When boron is selected as an impurity, if the silicon film 103 is thick, the whole insulating layer including the first insulating film 102, the silicon film 103, and the second insulating film 104 may work as a conductive layer. Can be But,
For example, even if it contains impurities of about 1 × 10 ²⁰ cm ⁻³ ,
When the film thickness is limited to about 5 nm or less, the insulating properties of the three-layer insulating layer can be maintained, and the influence on the characteristics of the semiconductor element can be avoided. That is, the upper limit of the doping amount of the impurity can be appropriately adjusted in consideration of the film thickness.

Also, by doping not only boron alone but also carbon, oxygen, nitrogen, etc. of the same degree, the crystal grain size can be kept small even after high temperature treatment, so that the boron doping amount is reduced. Therefore, even if the thickness of the silicon film 103 is about 20 to 30 nm, the insulating properties of the entire insulating layer can be maintained.

On the other hand, boron has a property that it has a large adverse effect on semiconductor elements such as iron and at the same time forms a chemically stable compound with impurities having a small diffusion coefficient in an oxide film.
By including the gettering layer, the influence on the semiconductor element can be reduced, so that a more effective gettering layer can be formed.

[Manufacturing Example 1] Next, an example of a method of forming the structure shown in FIG. 1 will be described with reference to FIG.

First, as shown in FIG.
First, a first silicon dioxide film 202 is formed, and an amorphous silicon film 203 doped with impurities such as oxygen is deposited thereon. The silicon dioxide film 202 may be formed by thermal oxidation or CVD (Chemical Vapor).
Deposition) method may be used. Here, the silicon film is deposited in an amorphous state because the surface has good flatness, and this flatness is very effective for surely performing later bonding.

Next, as shown in FIG. 2B, the substrate formed in FIG. 2A is bonded to a silicon substrate 205 having a silicon dioxide film 206 formed on both surfaces by thermal oxidation.
Lamination is performed by heat treatment at a temperature of about 1000 to 1100 ° C. for about 1 hour. By this heat treatment, the two substrates are bonded, and at the same time, the amorphous silicon film 203 is changed to a polycrystalline silicon film 204. Despite such a heat treatment, impurities such as boron, carbon, oxygen, nitrogen, etc.
Since it is contained at about 0 ¹⁷ cm ^-3 or more, the crystal grain size can be kept small. For example, by containing the impurity at 10 ¹⁸ cm ⁻³ , the crystal grain size can be kept at about 20 nm or less, and a layer having a sufficient gettering site (total surface area of crystal grains) can be formed. it can. The thickness of the thermal oxide film formed on both surfaces of the silicon substrate 205 is 20 to
About 50 nm is desirable from the viewpoint of gettering.

Next, as shown in FIG.
05 is thinned by mechanical polishing, and a silicon active layer 20 is formed on the surface.
Leave 7. The thickness of the silicon active layer 207 is selected depending on the uniformity of polishing and the type of a semiconductor device to be manufactured.

The bonded SOI manufactured by the above method
For the purpose of confirming the heavy metal gettering effect of the substrate, the SOI substrate which was forcibly contaminated was heat-treated, and the distribution of heavy metal impurities after the heat treatment was examined.

The substrate used is 200 silicon on a silicon substrate.
thermal oxide film of 10 nm, polycrystalline silicon film of 10 nm (doped with boron and oxygen to a concentration of 10 ¹⁸ cm ⁻³ ), 50 nm
This is an SOI substrate on which a second thermal oxide film having a thickness of 50 nm and a silicon active layer having a thickness of about 50 nm are formed. For comparison, an SOI sandwiching a polycrystalline silicon film not doped with an impurity was manufactured.

A typical contaminant heavy metal, iron or copper, is forcibly contaminated on the substrate by about 10 ¹² cm ⁻² ,
After heat treatment at 0 ° C. for 1 hour, the impurity concentration of each layer was evaluated. When iron is contaminated, about 85% of the contaminated amount is added to the polycrystalline silicon layer by about 10% in the SOI substrate structure of the present invention.
% Was detected in the surface silicon active layer and the rest in the silicon dioxide film. On the other hand, in the conventional SOI substrate structure, about 40% of the contamination amount remains in the surface silicon layer, and it was confirmed that the SOI structure of the present invention can effectively reduce the contamination amount of the silicon active layer.

When copper is contaminated, about 60% of the contaminated amount is added to the polycrystalline silicon layer by about 3% in the SOI substrate structure of the present invention.
% Was detected in the surface silicon thin film layer, and 30% or more was detected in the substrate silicon (near the interface with the oxide film). On the other hand, in the conventional SOI substrate structure, about 20% of the amount of contamination was detected in the surface silicon layer and about 40% was detected in the polycrystalline silicon layer, confirming the effectiveness of the present invention.

Second Embodiment Next, a second embodiment of the present invention will be described in detail with reference to the drawings. FIG.
FIG. 6 is a sectional view for explaining a second embodiment of the present invention. A first insulating film 302 on a silicon substrate 301;
Is formed thereon, and a first silicon (polycrystalline) film 303 doped with an impurity of about 1 × 10 ¹⁷ cm ⁻³ or more is provided thereon, and a second insulating film 304 and a second silicon A (polycrystalline) film 305, a third insulating film 306,
A silicon active layer 307 is formed thereon.

As impurities in the first silicon film 303, boron, carbon, oxygen, nitrogen and the like are suitable, and a polycrystalline silicon film containing such impurities in an amount of about 1 × 10 ¹⁷ cm ⁻³ or more is 1000 The crystal grain size does not increase even after a long-time heat treatment at a temperature of not less than ° C. The gettering effect can be expected even if the second silicon film 305 does or does not include an impurity, but by including an impurity different from that in the first silicon film, the first silicon layer can have a gettering effect. A gettering effect of impurities that are difficult to getter can be expected.

In the case where the high-temperature heat treatment is performed for a long time in the manufacturing process of the semiconductor device, there is no possibility that impurities such as boron that change the conductivity of the semiconductor diffuse into the silicon active layer on the surface. In such a case, by selecting oxygen as an impurity in the second silicon film 305 near the surface and selecting boron as an impurity in the first silicon film 303, the diffusion of boron can be reduced while maintaining the overall gettering effect. The effect of stopping at one silicon film 303 can also be provided.

Since the gettering effect is relatively large at the silicon / insulating film interface and the like, the gettering effect is about twice as large as that of the first embodiment by doubling the silicon film. You can have.

[Production Example 2] Next, an example of a method of forming the structure shown in FIG. 3 will be described with reference to FIG.

First, as shown in FIG.
First, a first silicon dioxide film 402 is formed, and an amorphous silicon film 403 doped with impurities such as oxygen is deposited thereon. The silicon dioxide film 402 can be formed by thermal oxidation or CVD (Chemical Vapor).
Deposition) method may be used. Here, the silicon film is deposited in an amorphous form because the surface has good flatness.

Next, as shown in FIG. 4B, thermal oxidation is performed following FIG. 4A to form a second silicon dioxide film 4 on the surface.
05, and a second amorphous silicon film 406 is formed thereon.
To form The amorphous silicon film 403 becomes a polycrystalline silicon film 404 during thermal oxidation. The second amorphous silicon film is doped with, for example, boron.

Next, as shown in FIG. 4C, the substrate formed in FIG. 4B is bonded to a silicon substrate 408 formed on both sides with a silicon dioxide film 409 formed by thermal oxidation. Lamination is performed by heat treatment at a temperature of about 1000 to 1100 ° C. for about 1 hour. By this heat treatment, the two substrates are bonded and at the same time, the second amorphous silicon film 406 is changed to a polycrystalline silicon film 407.

Next, as shown in FIG.
08 is thinned by mechanical polishing, and a silicon active layer 41 is formed on the surface.
Leave 0. Thus, the structure shown in FIG. 3 can be formed.

[Third Embodiment] Next, a third embodiment of the present invention will be described in detail with reference to the drawings. FIG.
FIG. 9 is a cross-sectional view for explaining a third embodiment of the present invention. An insulating film 502 is formed on a silicon substrate 501, and a silicon active layer 503 is formed thereon.
The insulating film 502 includes a silicon film 5 doped with impurities.
04. The silicon film 504 is formed discretely instead of continuously. Such a structure is advantageous in the case where a film having a certain degree of conductivity is used by doping impurities such as boron at a high concentration, or in the case where a contact between the upper layer and the silicon substrate 501 is required in the element structure. In addition, higher gettering efficiency can be expected as the concentration of boron is higher, which is advantageous.

[Manufacturing Example 3] Next, an example of a method of forming the structure shown in FIG. 5 will be described with reference to FIG.

First, as shown in FIG. 6A, a silicon dioxide film 602 is formed on a silicon substrate 601, and an amorphous silicon film 603 doped with impurities is formed thereon.
The amorphous silicon film 603 is patterned.

Next, as shown in FIG. 6B, following FIG. 6A, a silicon dioxide film 605 is formed on the surface, and the surface is flattened. This planarization is as follows: 1) A silicon dioxide film is formed on the whole, planarized by mechanical polishing using the silicon film as a stopper, and a silicon dioxide film is deposited on the surface. 2) A silicon dioxide film is formed on the whole and flattened by mechanical polishing. 3) A method in which a silicon dioxide film is formed over the entire surface, flattened by mechanical polishing using the silicon film as a stopper, and a silicon film is formed on the surface, followed by thermal oxidation. And the like. At this stage, if a temperature of about 700 ° C. or more is applied, the silicon film 604 becomes polycrystalline,
Otherwise, it remains amorphous.

Next, as shown in FIG. 6C, a silicon substrate 606 having a silicon dioxide film
It is bonded to the surface of the substrate formed in (b).

Thereafter, the silicon dioxide film 607 and most of the silicon substrate 606 are mechanically polished to form a silicon active layer 6 on the surface as shown in FIG.
08 is formed.

Embodiment 4 Next, a fourth embodiment of the present invention will be described in detail with reference to the drawings. FIG.
FIG. 9 is a cross-sectional view for explaining a fourth embodiment of the present invention. An insulating film 702 is formed on a silicon substrate 701, and a multilayer film 703 is formed thereon.

As the multilayer film, a film including at least one of a polycrystalline silicon film or an amorphous silicon film and a silicon nitride film, or a mixed crystal of silicon and germanium, ie, a silicon germanium film Is preferable. Since large strain is accumulated at the interface between the silicon film and the silicon nitride film, there is a remarkable gettering effect on the silicon side of the interface.

[0051]

The SOI substrate of the present invention maintains a high gettering ability even after high-temperature heat treatment in an SOI manufacturing process or a semiconductor device manufacturing process. The surface silicon active layer can be protected from problematic heavy metal contamination.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a method of manufacturing the SOI structure shown in FIG.

FIG. 3 is a sectional view showing a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a method of manufacturing the SOI structure shown in FIG.

FIG. 5 is a sectional view showing a third embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a method of manufacturing the SOI structure shown in FIG.

FIG. 7 is a sectional view showing a fourth embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating a conventional SOI structure.

FIG. 9 is a cross-sectional view showing a gettering structure in a conventional SOI.

[Explanation of symbols]

101, 201, 205, 301, 401, 408, 5
01, 601, 606, 701, 801 Silicon substrate 102, 302, 702, 902 First insulating film 103 Silicon film 104, 304, 904 doped with impurities Second insulating film 105 Silicon active layer 202, 402 First Silicon dioxide films 203, 403, 406, 603 Amorphous silicon films 204, 604 Silicon films 206, 409, 602, 605, 607, 802
Silicon dioxide films 207, 410, 503, 608, 705, 803
Silicon active layer 303 First silicon film doped with impurities 305 Second silicon film 306 Third insulating film 404, 407 Polycrystalline silicon film 405 Second silicon dioxide film 502 Insulating film 504 Silicon doped with impurities Film 703 multilayer film 704 second insulating film 901 semiconductor active layer 903 sink layer 905 semiconductor support substrate

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-199632 (JP, A) JP-A-59-186331 (JP, A) JP-A-55-15286 (JP, A) JP-A 8- 116038 (JP, A) JP-A-7-29911 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/322

Claims (16)

(57) [Claims] 1. A supporting substrate and the insulating layer and the silicon active layer is an SOI substrate, which are sequentially stacked, the insulating layer, have a polycrystalline silicon region grain size is 20nm or less, the polycrystalline silicon region But an island
Or S present as a plurality of films
OI substrate. 2. An SOI substrate in which a support substrate, an insulating layer and a silicon active layer are sequentially stacked, wherein at least one selected from the group consisting of (a) boron and (b) carbon, oxygen and nitrogen is provided in the insulating layer. An SOI substrate having a polycrystalline silicon region containing a single impurity in a concentration of 10 ¹⁷ cm ⁻³ or more. 3. The SOI substrate according to claim 2 , wherein the polycrystalline silicon region exists in an island shape. 4. The SOI substrate according to claim 2 , wherein said polycrystalline silicon region exists as a plurality of films. 5. The SOI substrate according to claim 2 , wherein the polycrystalline silicon region exists as a patterned discrete film. 6. An SOI substrate in which a support substrate, an insulating layer, and a silicon active layer are sequentially laminated, wherein the insulating layer has two polycrystalline silicon films as polycrystalline silicon regions, The polycrystalline silicon film farther from the silicon active layer in the silicon film contains one type of impurity selected from the group consisting of boron, carbon, oxygen and nitrogen.
A polycrystalline silicon film containing a concentration of 0 ¹⁷ cm ⁻³ or more, wherein the polycrystalline silicon film near the silicon active layer is selected from the group consisting of boron, carbon, oxygen, and nitrogen; One type of impurity different from the impurity contained in the far-side polycrystalline silicon film is set to 10 ¹⁷ cm
An SOI substrate, which is a polycrystalline silicon film containing a concentration of ⁻³ or more or a polycrystalline silicon film containing no impurities. 7. The polycrystalline silicon film farther from the silicon active layer is a polycrystalline silicon film containing boron as an impurity, and the polycrystalline silicon film closer to the silicon active layer contains oxygen as an impurity. 7. The SOI substrate according to claim 6, wherein the SOI substrate is a polycrystalline silicon film. 8. An insulating layer existing between the polycrystalline silicon region and the silicon active layer has a thickness of 20 to 50 n.
The SOI substrate according to claim 2 , wherein m is equal to or less than m. 9. An SOI substrate in which a supporting substrate, an insulating layer, and a silicon active layer are sequentially stacked, wherein the insulating layer has at least one polycrystalline silicon film and one silicon nitride film. SOI substrate. 10. An SOI substrate in which a supporting substrate, an insulating layer, and a silicon active layer are sequentially stacked, wherein at least one silicon germanium film is provided in the insulating layer. 11. An SOI substrate in which a support substrate, an insulating layer, and a silicon active layer are sequentially stacked, wherein at least one impurity selected from the group consisting of boron, carbon, oxygen, and nitrogen is contained in the insulating layer by 10 ^17. c
An SOI substrate having a polycrystalline silicon region containing a concentration of m ⁻³ or more, wherein the polycrystalline silicon region exists in an island shape. 12. An SOI substrate in which a supporting substrate, an insulating layer, and a silicon active layer are sequentially stacked, wherein at least one impurity selected from the group consisting of boron, carbon, oxygen, and nitrogen is contained in the insulating layer by 10 ^17. c
An SOI substrate having a polycrystalline silicon region containing a concentration of m ⁻³ or more, wherein the polycrystalline silicon region exists as a plurality of films. 13. An SOI substrate in which a support substrate, an insulating layer, and a silicon active layer are sequentially stacked, wherein at least one impurity selected from the group consisting of boron, carbon, oxygen, and nitrogen is contained in the insulating layer by 10 ^17. c
An SOI substrate having a polycrystalline silicon region containing a concentration of m ⁻³ or more, wherein the polycrystalline silicon region exists as a patterned discrete film. 14. supporting substrate and the insulating layer and the silicon active layer is an SOI substrate, which are sequentially stacked, the insulating layer, have a polycrystalline silicon region grain size is 20nm or less, the polycrystalline silicon region But puta
An SOI substrate characterized by being present as a thinned discrete film . 15. An insulating film is formed on a supporting substrate and an amorphous silicon film containing at least one impurity selected from the group consisting of boron, carbon, oxygen and nitrogen at a concentration of 10 ¹⁷ cm ⁻³ or more. And a step of repeating at least once in order, a step of superposing and bonding a silicon substrate having an insulating film formed on both sides to a surface of the substrate on which the amorphous silicon film is formed, Polishing the silicon substrate from the side to form a silicon active layer. 16. The method for manufacturing an SOI substrate according to claim 15, wherein said amorphous silicon film is formed by patterning after forming an amorphous silicon film on the entire surface.