JP2621642B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a structure of a semiconductor device and a method of manufacturing the same.

[Conventional technology]

A device transfer method is known as one of the methods for obtaining an SOI (Silicon-On-Inlulator) device (Tsuneo Hamaguchi, Nobuhiro Endo, Applied Physics Vol. 56, No. 11 (1987) pp.
1480-1484).

5 (a) to 5 (d) show SOI structure n-channel MOSFEs.
FIG. 9 is a process cross-sectional view for describing a process for obtaining T.

First, on the surface of a silicon substrate 407, an n-channel MOSFET including a polysilicon gate 403, a source 405, and a drain 406, which are element-isolated by a field oxide film 404, is formed. [FIG. 5 (a)]. After bonding the support substrate 409 to the surface of the silicon substrate 407 using the first epoxy adhesive 408, selective polishing is performed using a processing liquid that selectively dissolves only silicon from the back surface of the silicon substrate. In the selective polishing, since the processing speed becomes extremely slow when reaching the back surface of the field oxide film 404 of the n-channel MOSFET, a thin-film n-channel MOSFET can be easily obtained [FIG. 5 (b)]. Further, after bonding to the semiconductor substrate 411 using the second epoxy adhesive 410 on the back surface of the obtained thin-film n-channel MOSFET [FIG. 5 (c)], the supporting substrate 4
By removing the first adhesive 09 and the first adhesive 408, the second epoxy adhesive in which the thin film n-channel MOSFET is an insulator is formed.
A structure adhered to the semiconductor substrate 411 via 410 can be obtained [FIG. 5 (d)].

[Problems to be solved by the invention]

By such means, it is possible to obtain a structure in which an n-channel MOSFET having a thin film structure is formed on the second epoxy adhesive 410 which is an insulator, that is, a thin-film n-channel MOSFET having an SOI structure. n-channel MOSF
The back surface 412 of the active layer of the ET is in direct contact with the second epoxy adhesive 410. Since about 40 ppm of sodium ions are contained in the epoxy adhesive, an inversion layer is formed on the back surface 412 of the active layer of the thin-film n-channel MOSFET due to the presence of possible ions (positive charges) in the adhesive. However, there is a problem that a leak current flows between the source and the drain via the gate. (Soji Takahashi, Yoshihiro Hayashi, Shigenobu Wada, Takemitsu Gakuo, Spring 1990 1990 37th JSAP Related Lectures, Lecture Book pp642 (30p-ZC-10)).

An object of the present invention is to provide a structure of a semiconductor device for suppressing the formation of an inversion layer on the back surface of a thin-film MOSFET active layer adhered to a semiconductor substrate or an insulating substrate, and a method of manufacturing the same.

[Means for solving the problem]

In order to achieve the above object, in a semiconductor device according to the present invention, a MOSFET is formed on an inorganic insulating film, and the MOSF
A first wiring layer formed on the ET surface layer and a second wiring layer connected to the back gate of the MOSFET formed on the back surface of the inorganic insulating film are connected by a vertical wiring penetrating the element isolation oxide film layer. A thin film device having the structure described above is bonded to a semiconductor substrate or an insulating substrate on the side of the back gate.

Further, in order to obtain the structure of the semiconductor device described above, in the first method for manufacturing a semiconductor device according to the present invention, the MO which is element-isolated by the main surface of the field oxide film is used.
A step of applying a first adhesive to a surface of the silicon substrate on which the S-structure device is formed to bond the support substrate, and removing a silicon layer between the back surface of the silicon substrate and the field oxidation A step of forming an inorganic insulating film on the back surface of the silicon substrate; and a step of passing through the inorganic insulating film and the field oxide film from the back surface of the silicon substrate to a wiring layer formed on the surface of the MOS structure device. Forming a hole, forming a back gate pattern on the back surface of the MOS substrate using a conductive material on the back surface of the silicon substrate, and using a second adhesive on the back surface of the silicon substrate. The method is characterized by comprising a step of bonding a semiconductor substrate or an insulating substrate, and a step of removing the support substrate and the first adhesive.

Further, in the second method for manufacturing a semiconductor device according to the present invention, a silicon layer is formed on the inorganic insulating film.
Forming a MOS structure device on an SOI (Silicon-On-Insulator) substrate, applying a first adhesive to a device formation surface of the SOI substrate, and bonding a support substrate;
Removing the layer from the back side of the SOI substrate where the devices are not formed to the inorganic insulating film, and from the back side of the SOI substrate to the wiring layer formed on the surface of the MOS structure device through the inorganic insulating film. A step of forming a through-hole reaching the substrate, a step of forming a back gate pattern of the MOS structure using a conductive material on the back surface of the inorganic insulating film, and a semiconductor using a second adhesive on the back surface of the SOI substrate. The method is characterized by comprising a step of bonding a substrate or an insulating substrate, and a step of removing the support substrate and the first adhesive.

[Action]

In the structure of the semiconductor device according to the present invention, since the MOSFET formed on the inorganic insulating film is bonded to the semiconductor substrate or the insulating substrate by the adhesive, the adhesive directly contacts the silicon active layer on the back surface of the MOSFET. I will not do it.
As a result, mobile ions contained in the adhesive (for example,
Due to the presence of sodium ions, no inversion layer is formed on the back surface of the MOSFET, and no leakage current flows through the back surface inversion layer. Further, even when fixed charges exist at the interface between the inorganic insulating film and the MOSFET, the formation of the inversion layer is suppressed by applying a back bias through the back gate of the MOSFET formed on the back surface of the inorganic insulating film. Can be.

That is, in the manufacture of the semiconductor device according to the present invention, (1) there is no interface between the adhesive and the back surface of the MOSFET, which is the cause of the formation of the inversion layer on the back surface of the MOSFET active layer; Since the formation of the inversion layer on the back surface of the layer can be suppressed, no leak current flows on the back surface of the MOSFET.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a structure in which an n-channel MOSFET is bonded to a silicon substrate according to a first embodiment of the present invention. As shown in the figure, an n-channel MOSFET having a polysilicon gate 403 and the like on a silicon oxide film 102 which is an inorganic insulating film, an element is separated by a field oxide film 404, and an n-channel MOSFET is formed on the back surface of the silicon oxide film 102 M
The back gate of OSFET is formed by backside aluminum wiring 103,
The back aluminum wiring 103 is connected to the front aluminum wiring 401 of the n-channel MOSFET via the through-hole buried wiring 101.

A back bias can be applied to the n-channel MOSFET formed on the silicon oxide film 102 by the back aluminum wiring (back gate) 103. Therefore, even if a positive fixed charge exists at the interface 104 between the back surface of the n-channel MOSFET and the silicon oxide film, the formation of an inversion layer on the back surface of the n-channel MOSFET can be suppressed by applying a negative potential to the back gate. Can be.

Furthermore, the above-mentioned n-channel MOSFET is made of an epoxy adhesive.
Although bonded to the silicon substrate 411 by 410, since the silicon oxide film 102 is formed on the back surface 105 of the n-channel MOSFET, the back surface of the active layer of the n-channel MOSFET is not directly in contact with the epoxy adhesive. Therefore, an inversion layer is not formed on the back surface 104 of the n-channel MOSFET active layer by sodium ions (positive charges) contained in the epoxy adhesive layer.

2 (a) to 2 (d) show a method of manufacturing a semiconductor device having a structure according to the first embodiment of the present invention.

First, a support substrate 409 is bonded to a silicon substrate (see FIG. 5A) having an n-channel MOSFET formed on a silicon substrate by a normal LSI forming process using a first epoxy adhesive 408, and then is selectively polished. To obtain a thin film n-channel MOSFET [FIG. 2 (a)]. Thereafter, a silicon oxide film 102 is formed on the back surface of the thin-film n-channel MOSFET by CVD (Chemical Vapor Deposition) or sputtering [FIG. 2 (b)]. Note that the insulating film formed on the back surface may be silicon nitride or aluminum nitride. Thereafter, the thin film n-channel MOSF
A through-hole is formed from the back side of the ET through the silicon oxide film 102 and the field oxide film 404 to the aluminum wiring 401 on the front side, and a through-hole buried wiring 101 is formed.
Further, an aluminum film is formed on the back surface side, and the aluminum film is etched to form the back surface aluminum wiring (back gate) 103 of the thin film n-channel MOSFET [FIG. 2 (c)]. Finally, the silicon substrate 411 is adhered to the back surface of the thin-film n-channel MOSFET with the second epoxy adhesive 410, and the support substrate 409 and the first epoxy adhesive 408 are removed. A semiconductor device having a structure in which a thin film n-channel MOSFET with a back gate (103) is bonded is obtained (FIG. 2 (d)).

Although the embodiment shown in FIG. 2 shows the case where the thin film n-channel MOSFET is bonded to the silicon substrate 411, the third embodiment
As shown in FIG.
A silicon substrate 207 already formed as a device by forming a MOSFET interlayer insulating film 202, an underlying MOSFET gate 203, an underlying field oxide film 204, an underlying MOSFET source 205, an underlying MOSFET drain 206, a passivation film 208, etc.
It is obvious that a thin-film n-channel MOSFET with a back gate can be bonded to the substrate. In the above-described embodiment, the case where the thin film n-channel MOSFET with the back gate is bonded is shown. However, it is obvious that the thin film p-channel MOSFET with the back gate or the thin film CMOS device with the back gate can be bonded to the semiconductor substrate. Further, since the back gate wiring formed of this metal material has high thermal conductivity, it is obvious that the back gate wiring also serves as a heat sink for a semiconductor element.

Next, a second embodiment of the present invention will be described with reference to FIGS.

In the method of manufacturing a semiconductor device described in the first embodiment of the present invention, the embodiment in which the n-channel MOSFET is formed on the silicon substrate 407 has been described.
This embodiment corresponds to the case of forming on an (ilicon-On-Insulator) substrate 301.

FIG. 4A is a cross-sectional view showing the structure of the SOI substrate. S
On the OI substrate, the single crystal silicon layer 3 is formed on the silicon oxide film 302.
03 is formed. Silicon single crystal layer 3 of the SOI substrate
In FIG. 3, a polysilicon gate 403, a source 405, a drain 406, an aluminum oxide 401 and the like are formed by a normal process to form an n-channel MOSFET [FIG. 4 (b)]. Next, after bonding the support substrate 409 using the first epoxy adhesive 408 [FIG. 4 (c)], the SOI substrate 301 is selectively polished.
Is thinned. At this time, the stopper for the selective polishing is the silicon oxide film 302 of the SOI substrate. Furthermore, a silicon oxide film is formed on the back surface of the obtained thin film n-channel MOSFET.
A through-hole is formed through the 302 to the front side aluminum wiring 401, and the through-hole buried wiring 101 is formed. Then, the rear side aluminum wiring (back gate) 103 is formed [4th.
Figure (d)]. Finally, after bonding the silicon substrate 411 with the second epoxy adhesive 410, the support substrate 409 and the adhesive 408 are removed [FIG. 4 (e)].

In the structure of the semiconductor device obtained by the above-described manufacturing method, the presence of the silicon oxide film 302 formed on the back surface of the thin-film n-channel MOSFET
The back surface of the active layer of the FET does not directly contact the adhesive 410.
In addition, as is clear from FIG.
By the back gate 103 formed on the back surface of the SFET,
A back bias can be applied.

In the manufacturing method shown in the first embodiment of the present invention, a step of forming a silicon oxide film on the back surface side by a CVD method or a sputtering method after thinning (FIG. 2B) was required. However, the manufacturing method described in this embodiment using an SOI substrate is characterized in that a back surface silicon oxide film forming step is not required.

〔The invention's effect〕

As described above, if the present invention is applied, a thin film MOSF
Even if ET is bonded to the semiconductor substrate with an adhesive,
The back surface of the active layer of the MOSFET does not directly contact the adhesive.
Therefore, no inversion layer is formed on the back surface of the active layer due to the influence of ions contained in the adhesive, and no leak current flows between the source and the drain via the back surface of the active layer. This is because the inorganic insulating film exists on the back surface of the thin-film MOSFET active layer. Further, according to the present invention, since the back gate of the thin film MOSFET is formed on the back surface of the inorganic insulating film, it is possible to apply a back bias to the thin film MOSFET. This back bias application can also suppress the formation of the backside inversion layer.

[Brief description of the drawings]

FIGS. 1 and 2 (a) to 2 (d) are a sectional view showing a structure of a semiconductor device according to a first embodiment of the present invention and a sectional view showing a manufacturing process thereof. FIG. 4 is a cross-sectional view of a semiconductor device having a structure in which an oxide film is formed and a device in which a back gate is formed on the back surface of the silicon oxide film is bonded to a silicon substrate by an adhesive, and a method of manufacturing the same. FIG. 3 shows a thin film n-channel MOSFET on a silicon substrate on which devices are formed.
FIG. 9 is a cross-sectional view for explaining another application example of the first embodiment of the present invention when the first embodiment is bonded. FIG. 4 (a) to (e)
FIG. 9 is a manufacturing process diagram for explaining a second embodiment of the present invention when an SOI substrate is used. Fig. 5 (a)-
FIG. 4D is a process sectional view for explaining the conventional semiconductor device and the manufacturing method thereof. 101 ... through-hole buried wiring, 102 ... silicon oxide film, 103 ... backside aluminum wiring (back gate), 104 ...
Back surface of device active layer, 201: Aluminum wiring on the underside of the underlying MOSFET, 202: Interlayer insulating film of the underlying MOSFET, 203: Underlying MOSF
ET gate, 204: underlying field oxide film, 205: source of underlying MOSFET, 206: drain of underlying MOSFET, 207
…… Silicon substrate, 208 …… Passivation film, 301…
... SOI substrate, 302 ... Silicon oxide film, 303 ... Silicon, 401 ... Aluminum wiring on the device surface side, 402 ... Interlayer insulating film, 403 ... Polysilicon gate, 404 ... Field oxide film, 405 ... Source , 406 drain, 407 silicon substrate, 408 first adhesive (epoxy resin), 4
09: Support substrate, 410: Second adhesive (epoxy resin), 411: Silicon substrate, 412: Back surface of device active layer.

Claims (3)

(57) [Claims] A MOSFET formed on an inorganic insulating film;
A first wiring layer formed on the SFET surface layer and a second wiring layer connected to the back gate of the MOSFET formed on the back surface of the inorganic insulating film are connected by a vertical wiring penetrating the element isolation oxide film layer. A thin film device having the structure described above is adhered to a semiconductor substrate or an insulating substrate on the side of the back gate. 2. A step of applying a first adhesive to a surface of a silicon substrate on which a MOS structure device whose element is separated by a field oxide film on one main surface is formed, and adhering a support substrate; Removing the silicon layer between the back surface of the substrate and the field oxide film, and forming an inorganic insulating film on the back surface of the silicon substrate,
Forming a through hole from the back surface of the silicon substrate to the wiring layer formed on the surface of the MOS structure device through the inorganic insulating film and the field oxide film; and forming the silicon substrate on the back surface of the MOS structure device. Forming a back gate pattern using a conductive material on the back surface side, bonding a semiconductor substrate or an insulating substrate to the back surface of the silicon substrate using a second adhesive; Removing the first adhesive. 3. A step of forming a MOS structure device on the front side of an SOI substrate having a silicon layer formed on an inorganic insulating film, and applying and supporting a first adhesive on a device forming surface of the SOI substrate. A step of bonding a substrate, a step of removing a layer from the back side of the SOI substrate to the inorganic insulating film, and a step of penetrating the inorganic insulating film from the back side of the SOI substrate and forming the SOI substrate on the surface of the MOS structure device. Forming a through-hole to a wiring layer, forming a back gate pattern of the MOS structure device using a conductive material on the back surface of the inorganic insulating film, and forming a second adhesive on the back surface of the SOI substrate A method of bonding a semiconductor substrate or an insulating substrate by using the method, and a step of removing the support substrate and the first adhesive.