JPH03256365A - Semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE:To arrange that the inclination of an electron energy band in the depth direction directly under a gate insulating film becomes gentle and that a channel current flows even in a deep part of a silicon film whose influence by scattering is small by a method wherein a patterned conductive film of Al or the like and an insulating film are formed sequentially on a transparent glass substrate and the silicon film is formed on the insulating film to form a transistor. CONSTITUTION:A P-type polysilicon film 4 doped with boron is formed directly above an Al film 2 via a first insulating film 3 by an SiO2 film which has been arranged and installed on the whole surface of a transparent glass substrate 1 including the Al film 2 which has been arranged and installed in an element formation region S of the substrate 1. A gate electrode 5 of polysilicon doped with phosphorus at about 1020cm-3 which can form a channel on the p-type polysilicon film by applying a voltage is formed, via a gate insulating film 47, on a part directly above the central part of the silicon film. An Al interconnection part 6 reaching both end parts of the polysilicon film 4 is formed by passing a second insulating film 7 as an interlayer insulating film which has been arranged and installed, so as to cover the gate electrode, on the whole surface of the first insulating film 3 including the p-type polysilicon film 4.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a semiconductor device and a method for manufacturing the same, and more specifically, it relates to a semiconductor layer on an insulating substrate such as a glass substrate used in the field of manufacturing semiconductor devices. The present invention relates to a WIllE transistor in which a polycrystalline silicon thin film is disposed, and a method for forming the same.

(b) Conventional technology Conventionally, after forming an amorphous or polycrystalline non-single crystal silicon thin film on an amorphous substrate such as a quartz or glass substrate, furnace annealing or the like is performed to form a polycrystalline or large crystal grain size film. Techniques for producing silicon thin films have been proposed.

Thin film transistors formed from this silicon thin film are required to have high performance when operating liquid crystal displays.
It is being actively researched.

Conventionally, an N-channel MOSFET (TPT
), the silicon film 2 is directly deposited on the transparent glass substrate 21.
2 has been proposed.

Note that 23 is an IQI? It is a polysilicon gate electrode doped with impurities of about Cm-",
24 is a metal wiring portion that penetrates the interlayer insulating film 25 and reaches the silicon film 22.

In this structure, the thickness of the silicon film 22 is
It is known that if it is formed thinly for the OO person, the power effect transfer (hereinafter referred to as the degree of movement) will increase compared to the thickness of several TOOO people, and a thin film transistor with good performance will be obtained. This is said to be because when the silicon film 22 is formed thin, the gradient of the energy band of electrons directly under the gate insulating film 26 becomes gentler, and the channel is formed deep into the silicon 1122, resulting in less surface scattering of charges. (Nikkei Microdevice, March 1988)
Month 1 No. 33 P. 35-37).

Figure 5 shows an N-channel MOSFET with the structure shown in Figure 3.
This diagram shows the electron energy in the depth direction directly under the gate insulating film, and shows the case where a channel is formed. It can be seen from FIG. 5 that the slopes of the energy bands Ec, EA, and Ev are steep. Therefore, charges flowing through the channel are susceptible to surface scattering.

FIG. 4 shows the structure of a MOSFET in which a gate electrode is also formed on the lower surface side (below) of the silicon film in order to further increase the mobility.

That is, in FIG. 4, the thin film transistor T has, for example, an upper gate electrode 33 and a lower gate electrode 34 formed on the upper and lower surfaces of a non-single crystal silicon film 32, respectively. The gradient of the electron energy band in the depth direction directly below is made gentler, thereby increasing the electron mobility of the thin film transistor.

(c) Problems to be Solved by the Invention However, what can be achieved with this method? Especially in the case of a low-temperature process, not only the gate insulating film 37 on the upper surface of the silicon film 32 but also the gate insulating film 37 on the lower surface Similarly to the gate insulating film 37 on the upper surface, pre-treatment and post-treatment must be performed on the upper gate insulating film 37 to make the insulation @ 36 denser and to control the interface unit density. The process becomes very complicated.

(D) Elaborate means for solving the problem 1f17-Depart This invention comprises a transparent glass substrate, a conductive film disposed in an element formation area on the transparent glass substrate, and an entire surface of the transparent glass substrate including the conductive film. a substantially thin silicon film formed directly above the conductive film via the first insulating film, and a gate insulating film disposed directly above the center of the silicon film. a gate electrode disposed on the silicon film and capable of forming a channel portion on the silicon film by applying a voltage; and a second insulating film disposed on the entire surface of the first insulating film including silicon to cover the gate electrode. , and a wiring portion that penetrates the second insulating film and reaches both ends of the silicon film.

That is, the present invention is a semiconductor device in which a gate electrode is disposed on the upper surface side of a silicon film, and a conductive film is disposed on the lower surface side of the silicon film via a first insulating film. The energy band of electrons in the depth direction of the silicon film side on the lower surface of the film causes bending, and when a voltage is applied from the gate electrode on the upper surface side and a channel is formed, the electrons in the depth direction of the silicon film directly under the gate insulating film The slope of the energy band becomes gentle, and the channel is formed not only on the surface of the silicon film directly under the gate insulating film, but also deep within the silicon film, so the charge flowing through the channel is easily scattered in the silicon film. It flows not only on the surface but also in the silicon film, which is not subject to much scattering.

For this purpose, for example, a non-single-crystal silicon film is formed on a transparent glass substrate such as quartz, and a MOSFET of a thin film transistor is formed.
When an ET is fabricated, high field effect mobility can be obtained and the performance of the transistor can be improved.

In addition, this invention: i As a method for forming the above semiconductor device,
A predetermined pattern of conductors is formed on the element formation area on the transparent glass substrate.
ll! A first insulating film is formed on the entire surface of the transparent glass substrate including the conductive film, a silicon film in a predetermined pattern is formed directly above the conductive film via the first insulating film, and a silicon film is formed in the center of the silicon film. A gate electrode of a predetermined pattern is formed directly above the gate insulating film, and then a t-th electrode including a silicon film is formed.
A second insulator is placed on the entire surface of the IIIiA edge to cover the gate electrode.
A method of manufacturing a semiconductor device is provided in which a film is formed and a wiring portion extending to both ends of the silicon film is formed by penetrating the second insulating film.

That is, this invention forms a silicon thin film above a transparent glass substrate such as quartz, and when forming a semiconductor device by forming a transistor on the silicon thin film, a thin first insulating film is placed under the silicon film. By forming a patterned conductive film, the electron energy band in the depth direction of the silicon film side on the lower surface of the silicon film bends, and when a channel is formed by applying an appropriate gate voltage, the depth directly below the gate insulating film Since the inclination of the electron energy band in the direction becomes gentle, a channel can be formed deep into the silicon film, and a MOSFET with high mobility can be formed.

As the transparent glass substrate in this invention, quartz or aluminosilicate glass (A l *0s-S i O *-Rl
O:R is a monovalent alkali) or borosilicate glass (
B*OsSiO*RtO (R is a monovalent alkali) is preferred.

Preferred examples of the conductive film in the present invention include metal films such as Al, Ti, or W, alloy films such as WSt, and nonmetallic conductive films such as polysilicon and germanium. And the film thickness is 0.2 to 1.0 μm
is preferable, and 0.5 μm is more preferable.

Preferred examples of the first insulating film in the present invention include a 5ins film, 5isN*II, and the like. The film thickness is preferably 0.05 to 1.0 gg+,
0.1 μ- is more preferable.

As the material for the silicon film in this invention, either non-monocrystalline or polycrystalline silicon may be used; in this case, the impurity doping material may be a known p-type or n-type impurity. , the doping amount is 10”~10”am
-3 is preferred.

In this invention, a substantially thin silicon film is defined as having a film thickness of 0. It means a thin film of O1 to 0.3μ, which can increase the mobility of electrons.

This silicon film is made by LPGVD (low pressure chemical vapor deposition)
A thin film can be formed on the first insulating film using a known method such as a plasma CVD method or a plasma CVD method.

Also, the above! The insulating film and the conductive film can also be formed using known techniques.

As the gate insulating film and the second insulating film in this invention, a Stow film, a 5isN+ film, etc. are preferably used.

As the gate electrode in this invention, for example, phosphorus can be used as I.
It is preferable to use a conductive material such as O''am-3 doped polysilicon, At or Tt.

Alternatively, WSi may be used.

(e) Examples The present invention will be described in detail below based on examples shown in the drawings. Note that this invention is not limited by this.

In FIG. 1, an N-channel lll0sFET consists of a quartz transparent glass substrate (hereinafter simply referred to as a substrate) l, an AI film 2 disposed in an element formation area S on the substrate, and an
The first 5ins film is disposed on the entire surface of the substrate 1 including one film.
Boron (B) is a thin film of 2000 mm thick formed directly on the All 12 through the insulating film 3 and the first insulating film.
A p-type polysilicon film 4 doped with approximately 10 am− and a gate insulating film 4 directly over the center of the silicon film.
A gate electrode 5 made of polysilicon doped with about 1 g of phosphorus, which can form a channel on the p-type polysilicon film by applying a voltage, and a p
A second insulating film 7 as a glabellar insulating film is disposed on the entire surface of the first insulating film 3 including the polysilicon film 4 so as to cover the gate electrode 5, and a polysilicon film is formed by penetrating the second insulating film. It mainly consists of the AI wiring tI56 reaching both ends of the film 4.

As described above, in this example, when forming a thin film transistor using a silicon film on a quartz substrate, a patterned AI metal layer was formed on the bottom surface of the silicon film through an insulating film. Explain the method.

substrate! An At film 2 with a predetermined pattern is formed in the upper element formation region S by sputtering, and a 5i film is deposited on the entire surface of the substrate including the At film.
ns first insulating film 3 is formed by the CVD method, a polysilicon film with a predetermined pattern is formed by the LPCVD method directly on the A1 film 2 via the first insulating film, and after doping with p-type impurities, the p-type impurity is doped. Forming a gate electrode 5 in a predetermined pattern directly above the center of the mold polysilicon film 4 with a gate insulating film 47 interposed therebetween,
Thereafter, a second insulating film 7 is formed on the entire surface of the first insulating film including the p-type polysilicon film 4 so as to cover the gate electrode 5, and the Al wiring portions 6 reaching both ends of the p-type polysilicon 114 are connected to the second insulating film 7 so as to cover the gate electrode 5. It is formed to penetrate through the insulating film 7.

Below, the operation will be explained using an energy band diagram (see Figure 2) in the depth direction directly under the gate insulating film. FIG. 3 is a diagram showing the electron energy band of , and shows the case where a channel is formed.

In the second WJ, 8 indicates the energy band of electrons in the gate insulating film 47, 9 indicates the energy band of electrons in the p-type polysilicon film 4, and IO indicates the energy band of electrons in the first insulating film 3 on the lower surface of the p-type polysilicon film. The electron energy band 11 indicates the electron energy band in the At film 2 on the lower surface of the first insulating film 3, respectively. Further, 12 is an electron in the channel portion.

On the other hand, FIG. 5 shows an N-channel MOS having the structure shown in FIG.
This is a diagram showing the energy of electrons in the depth direction directly under the gate insulating film of the FET, and shows the case where a channel is formed like in FIG. 2.

The polysilicon film 22 of the conventional example shown in FIG. 2 to FIG.
It can be seen that the iso-energy lines in the electron energy band in the depth direction directly below the channel in the p-type polysilicon film 4 have a gentler slope than the iso-energy lines in the middle electron energy band. As a result, the charges flowing through the channel are not easily affected by surface scattering, and the channel current can flow even deep in the p-type polysilicon I [4] where the influence of scattering is small, providing a MOSFET with high mobility. can.

That is, in the conventional example, polysilicon is used for the gate electrode 5, and the polysilicon film in the element part has a thickness of 2000 nm and a NA of 2,000.
In the case of an N-channel MOSFET, which is a p-type semiconductor with s = 10 "am-", even if sufficient impurity is added to the gate electrode 5, the thickness of the depletion layer directly under the gate insulating film is 1500 ~
Although the number of people is about 2,000, as in this embodiment shown in FIG.
When l1I2 is formed, the thickness of the depletion layer reliably reaches the bottom surface of the p-type polysilicon film in the element portion S, and the depth at which the channel is formed increases, thereby increasing the mobility.

In this embodiment, the polysilicon thin film 4 is formed on the quartz substrate l, and the gate electrode 5 is formed on the silicon thin film.
In a thin film transistor in which a thin film transistor is formed by disposing a thin film transistor, a step of forming a metal film 2 of Al on a substrate l, a step of forming a first insulating film 3 of Sing on the metal film, and a step of forming a first insulating film 3 of Sing on the metal film. By forming a polysilicon film 4 on the first insulating film 3 on the patterned AI metal film 2, electrons in the depth direction directly under the channel are formed. The slope of the energy band can be made gentler, the channel extends deep into the polysilicon film 4, and the charge flowing through the channel is less affected by scattering on the surface, and the current flow even deep in the polysilicon film 4. A MOSFET with high mobility can be obtained by allowing the current to flow.

(F) Effects of the Invention As described above, according to the present invention, a semiconductor device is formed by forming a silicon thin film on a transparent glass substrate such as quartz, and disposing a gate electrode on the silicon thin film to form a thin film transistor. In this method, a patterned conductive film and an insulating film such as A1 are sequentially formed on a transparent glass substrate, and a silicon film is formed on the insulating film to form a transistor. This has the effect of increasing the field effect mobility of the MOSFET by making the slope of the electron energy band warmer and allowing the channel current to flow deep into the silicon film where it is less affected by scattering.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the configuration showing one embodiment of the present invention, Fig. 2 is an energy band diagram in the depth direction directly under the gate insulating film in the above embodiment, and Fig. 3.4 is an explanatory diagram of the configuration of a conventional example. , FIG. 5 is an energy band diagram of the conventional example shown in FIG. l...Quartz transparent glass substrate, 2...
A11y (conductive film), 3...9i0* film (first insulating film), 4...
... p-type polysilicon pus, 5 ... gate electrode, 6 ... wiring part, 7
...S i O * Wi (second insulating film), first
Figure 2 Figure 15

Claims (1)

[Claims] 1. A transparent glass substrate, a conductive film disposed in an element formation region on the transparent glass substrate, and a first insulating film disposed on the entire surface of the transparent glass substrate including the conductive film. , a substantially thin silicon film formed directly above the conductive film via the first insulating film, and a substantially thin silicon film disposed directly above the central part of the silicon film via the gate insulating film, and the silicon film is formed by applying a voltage. A gate electrode on which a channel portion can be formed, a second insulating film disposed on the entire surface of the first insulating film including a silicon film so as to cover the gate electrode, and a silicon film passing through the second insulating film. A semiconductor device consisting of a wiring section that reaches both ends of a film. 2. Form a conductive film in a predetermined pattern in the element formation area on a transparent glass substrate, form a first insulating film on the entire surface of the transparent glass substrate including the conductive film, and directly above the conductive film via the first insulating film. A silicon film with a predetermined pattern is formed on the silicon film, a gate electrode with a predetermined pattern is formed directly over the center of the silicon film via a gate insulating film, and then a first silicon film containing the silicon film is formed.
A method for manufacturing a semiconductor device, in which a second insulating film is formed on the entire surface of the insulating film so as to cover a gate electrode, and a wiring portion extending to both ends of the silicon film is formed by penetrating the second insulating film.