JP2645663B2 - Thin film semiconductor device and method of manufacturing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high performance thin film semiconductor device which can be realized by using a semiconductor thin film, and a method for manufacturing the same.

(2) Conventional technology and its problems In recent years, thin film semiconductor devices have attracted attention as a component of a three-dimensional integrated circuit or a switching element for a flat display, and have been actively studied.
lhi et al. published IEEE Trans.Electron Devices ED.
−32 (1985), pp. 258-281. Semiconductor thin films used for such applications include those in an amorphous state, a polycrystalline state, and a single crystalline state. However,
A semiconductor device using a thin film in an amorphous state has a problem that performance is inferior to those of the other two. As a high-performance thin film semiconductor device, a device using a semiconductor thin film in a polycrystalline state or a single crystal state has been most widely studied at present.
These thin film semiconductor devices use either an n-channel thin film transistor using electrons as carriers or a p-channel thin film transistor using holes. Such a thin-film semiconductor device consumes a large amount of power during operation, and its use is significantly restricted.
Therefore, in order to reduce this power consumption, a complementary thin film semiconductor device having a structure in which an n-channel thin film transistor and a p-channel thin film transistor are formed on the same substrate and these thin film transistors are connected has been attempted.

This type of complementary thin film semiconductor device is conventionally manufactured by the steps shown in FIG. On a substrate 11 made of a semiconductor or an insulating material such as silicon, patterns 12 and 12 ′ of a semiconductor thin film in a polycrystalline state or a single crystal state were formed at desired positions, and gate insulating films 13 and 13 ′ were formed. [FIG. 1 (a)], and thereafter, gate electrodes 14, 14 'are formed via this [FIG. 1 (b)]. Thereafter, the pattern 12 of the semiconductor thin film and the gate electrode 11 are exposed, while the pattern 12 ′ of the semiconductor thin film and the gate electrode 14 ′ are covered with a resist 15 or the like. Arsenic is ion-implanted to form source / drain electrodes 16. [FIG. 11 (c)]. Next, while the ion-implanted pattern 12 of the semiconductor thin film is covered with a resist 17 or the like, boron showing p-type conductivity is ion-implanted into the pattern 12 ′ of the semiconductor thin film to form a source / drain electrode 16. '(FIG. 1 (d)). Thereafter, formation of an interlayer insulating film 18 and opening of a through hole are performed [FIG. 1 (e)]. Next, by forming the wiring 19, the drain electrodes of the p-channel thin-film transistor and the n-channel thin-film transistor are connected to each other, thereby completing the manufacture of the complementary thin-film semiconductor device [first.
(F) of FIG.

When a control voltage is applied to the gate electrodes 14 and 14 'in the thin film semiconductor device having the above structure, electrons or holes are formed near the interface between the gate insulating films 13 and 13' and the semiconductor thin films 12 and 12 '. Carriers are induced to form a channel. In this state, the source electrode / drain electrode
When a voltage is applied between the electrodes 16 and 16 ', a current flows between the two electrodes along the channel, and the device operates as a complementary thin film semiconductor device.

However, the conventional semiconductor device shown in FIG. 1 has a characteristic defect due to its structure. That is, since the channel is as long as several μm to several tens μm, it is difficult to obtain a sufficiently large drain current. In order to solve this problem, a method of further shortening the channel length has been adopted. However, in this method, the channel length cannot be made shorter than the limit value of the processing technology, and there is a limit in performance improvement. Further, when the channel length is shortened, the variation in the processing, that is, the variation in the performance of the semiconductor device becomes relatively large, and there is a disadvantage that the manufacturing yield of the device is reduced.

Further, as a semiconductor thin film in the complementary thin film semiconductor device shown in FIG. 1, a semiconductor thin film in a polycrystalline state or a single crystal state is widely used. In a thin film semiconductor device having a polycrystalline semiconductor thin film, compared to a single crystal semiconductor device,
At present, only extremely inferior characteristics can be obtained. The reason is that boundaries between crystal grains (usually referred to as crystal grain boundaries) hinder the flow of carriers between the source electrode and the drain electrode, and reduce the mobility of carriers. .

For the purpose of removing the drawbacks of the semiconductor device made of the semiconductor thin film, a method has been proposed in which the number of crystal grain boundaries that hinder the flow of carriers in the channel is reduced or eliminated. The former method of reducing the grain boundaries in the channel is to perform a long heat treatment,
It enlarges the crystal grains. This method has a drawback that requires an extremely long heat treatment of several tens of hours. Furthermore, the performance of the device by this method is not sufficient.

On the other hand, in order to eliminate the crystal grain boundaries from within the channel and improve the performance of the semiconductor device, the semiconductor thin film on the polycrystal or amorphous is irradiated with a laser beam or an electron beam, once melted, and turned into a single crystal state. Methods are also widely used. However, in this method, although the performance of the semiconductor device is excellent, it is difficult to use an inexpensive substrate such as glass which is inferior in heat resistance because the semiconductor thin film is melted.

As described above, the conventional thin film semiconductor device has a drawback that excellent performance cannot be obtained, an inexpensive substrate cannot be used, and a manufacturing yield is reduced.

(3) Object of the Invention It is an object of the present invention to provide a thin-film semiconductor device which solves the above-mentioned problems in a conventional complementary thin-film semiconductor device so that a high-performance device can be formed on an inexpensive substrate. It is to provide for the manufacturing method.

(4) Constitution of the Invention The channel of the thin film semiconductor device of the present invention is formed on the side wall of the pattern of the semiconductor thin film, and unlike the conventional one formed on the surface of the semiconductor thin film, extremely excellent performance is obtained. Is obtained. Hereinafter, the thin film semiconductor device of the present invention and the method of manufacturing the same will be described in detail with reference to examples.

FIG. 2 is a sectional view for explaining an embodiment of the present invention. A first conductive layer 22 is formed on a substrate 21 made of a semiconductor or insulating material such as silicon, and then,
A first semiconductor thin film 23, a second conductive layer 24, a second semiconductor thin film 25, and a third conductive layer 26 for forming a channel of the first conductivity type are formed (FIG. 2A). . Thereafter, starting with the first conductive layer 22, the first semiconductor thin film 23, the second conductive layer 24,
The second semiconductor thin film 25 and the third conductive layer 26 for forming a channel of a second conductivity type different from the first conductivity type are etched to deposit a gate insulating film 27 [FIG. b)). A gate electrode 28 is formed so as to cover the sidewalls of the processed semiconductor thin films 23 and 25. Next, the first semiconductor thin film 2 is so exposed that a part of the first conductive layer 22 and a part of the second conductive layer 24 are exposed.
3, the second conductive layer 24, the second semiconductor thin film 25, the third conductive layer 26
Then, the gate insulating film 27 is etched (FIG. 2C). Thereafter, deposition of an interlayer insulating film 29 and opening of a through hole are performed [FIG. 2 (d)], and a wiring 30 is formed, thereby completing the manufacture of the semiconductor device [FIG. 2 (e)].

The channel of the thin film transistor in the complementary thin film semiconductor device manufactured as described above is the first semiconductor thin film.
23, and the side wall of the pattern of the second semiconductor thin film 25. Therefore, when a control voltage is applied to the gate electrode 28, carriers are induced on the side walls of the patterns of the first semiconductor thin film 23 and the second semiconductor thin film 25, and a channel is formed. In this state, when a voltage is applied between the first conductive layer 22 and the third conductive layer 26, the device operates as a complementary thin film semiconductor device, and a predetermined output appears on the second conductive layer 24.

As the first semiconductor thin film 23 and the second semiconductor thin film 25 shown in FIG. 2, a single crystal or a polycrystal is deposited by a vapor phase growth method or a vacuum evaporation method, or A thin film in an amorphous state is deposited by a sputtering method, and the thin film is manufactured by irradiating the thin film with a laser beam or an electron beam or by annealing in a furnace to change the thin film into a single crystal or a polycrystalline state. With such a structure, for the reasons described below, even if the semiconductor thin film is in a polycrystalline state, its performance can be significantly improved as compared with the conventional semiconductor device shown in FIG. it can.

The reason is that, in the device of the present invention, the channel length is determined solely by the thickness of the semiconductor thin film, and the channel length of the conventional semiconductor device is several μm to several hundred μm without paying special attention to the processing accuracy. This is because a large drain current value can be obtained because the thickness can be reduced from 0.05 μm to 5 μm, which is equal to the thickness of the semiconductor thin film.

Further, even if the first and second semiconductor thin films used in the present invention are not single crystals, but are polycrystalline, the characteristics of the crystal grains in the polycrystalline semiconductor thin film are controlled. Performance can be further improved. That is, after depositing amorphous silicon or germanium or a semiconductor thin film mixed with these by a sputtering method, a laser beam or an electron beam is applied to polycrystallize the semiconductor thin film to form a columnar crystal grain perpendicular to the substrate surface. It becomes a thin film. The crystal grain boundary of the semiconductor thin film is perpendicular to the substrate surface and substantially parallel to the direction of the channel, and does not hinder carrier transport. For this reason, the performance of the semiconductor device can be further improved.

The thickness of the semiconductor thin film in the present invention described above is 0.05
The range from μm to 5 μm is most suitable. If the thickness is less than 0.05 μm, a uniform polycrystalline semiconductor thin film cannot be obtained, resulting in a semiconductor device having poor performance.
On the other hand, when the thickness is more than 5 μm, there arises a problem that the thin film is peeled off from the substrate or that processing of the thin film becomes difficult.

Now, as the semiconductor thin film of the present invention, in addition to silicon, germanium, or a mixture thereof, GaAs or InSb
And the like are also effective. However, a simple substance of silicon or germanium or a mixture thereof is most suitable for the present invention because it is easy to form a thin film and control characteristics.

In the embodiment of the present invention described in FIG. 2, the channel uses only a part of the end of the pattern of the semiconductor thin film, that is, a part of the outer periphery of the pattern. However, according to the present invention, the entire periphery of the pattern can be used as a channel by essentially the same manufacturing method as shown in FIG. FIG. 3 shows another embodiment of the present invention. Gate insulating film 37 and gate electrode
38 is formed over the entire peripheral portion of the pattern of the first semiconductor thin film 33 and the second semiconductor thin film 35, and the entire peripheral portion serves as a channel. 31 indicates a substrate, 3
Reference numerals 2, 34 and 36 denote a first conductive film, a second conductive film, and a third conductive film serving as source / drain electrodes.
By doing so, the channel width of the semiconductor device can be significantly increased, and the drain current can be increased in proportion thereto.

In the complementary thin film semiconductor device shown in FIGS. 2 and 3, the upper and lower thin film transistors are represented by p.
Whether to use the channel type or the n-channel type can be determined by the material forming the source electrode and the drain electrode of these thin film transistors. For example, in FIGS. 2 and 3, an n-channel thin film transistor is provided at the end of the pattern of the first semiconductor thin films 23 and 33, while a p-channel thin film transistor is provided at the end of the pattern of the second semiconductor thin films 25 and 35. To manufacture, the first conductive layers 22 and 32 are semiconductor thin films containing n-type impurities such as P and As, while the third conductive layer
Reference numerals 26 and 36 denote semiconductor thin films containing p-type impurities such as B. Further, as the second conductive layers 24 and 34, semiconductors containing n-type impurities on the sides in contact with the first semiconductor thin films 23 and 33 On the other hand, a semiconductor thin film containing a p-type impurity is disposed on the side in contact with the second semiconductor thin films 25 and 35, and a conductive layer having a three-layer structure in which a metal film is sandwiched between these semiconductor thin films is used. good. Contrary to the above, p-channel thin film transistors are provided on the first semiconductor thin films 23 and 33, while second semiconductor thin films 25 and 3 are provided.
In the case of a complementary thin-film semiconductor device having an n-channel thin film transistor, the type of impurities in the semiconductor thin film in the first, second, and third conductive layers may be replaced. In addition, the first conductive layers 22 and 32 and the third conductive layers 26 and 36 are formed of a composite film of a semiconductor thin film containing impurities and a metal film, so that the resistance of the conductive layers is reduced. The device can be made even more sophisticated.

In the present invention described above, the semiconductor thin film can be manufactured at a low temperature because the crystalline state of the semiconductor thin film only needs to be polycrystalline. For this reason, a high-performance semiconductor device can be formed on an inexpensive substrate such as glass.

(5) Effects of the Invention As described above, in the present invention, a channel is formed on the side wall of the pattern of the semiconductor thin film, so that the thin film semiconductor device has a short channel. Further, when the present semiconductor thin film is in a polycrystalline state, a crystal grain boundary which hinders carrier transport can be made substantially parallel to the channel direction.
For these reasons, the present invention provides a high-performance complementary thin-film semiconductor device.

Further, in the present invention, since a complementary thin film semiconductor device can be manufactured at a low temperature, there is an advantage that an inexpensive substrate such as glass can be used.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a conventional method for manufacturing a thin-film semiconductor device, FIG. 2 is a cross-sectional view for explaining a method for manufacturing a thin-film semiconductor device according to the present invention, and FIG. It is sectional drawing which shows the other Example of a thin film type semiconductor device. 11,21,31 …… Substrate, 12,12 ′ …… Semiconductor thin film pattern, 23,
33 ... first semiconductor thin film, 25,35 ... second semiconductor thin film, 22,32 ... first conductive layer, 24,34 ... second conductive layer,
26,36 ... third conductive layer, 13, 13 ', 27, 37 ... gate insulating film, 14, 14', 28, 38 ... gate electrode, 16, 16 '... source electrode / drain electrode, 18,29,39 …… Interlayer insulating film, 19,30,
40 ... Wiring.

Claims (2)

(57) [Claims] 1. A p-channel type thin film transistor and n
A thin film semiconductor device comprising a channel type thin film transistor, wherein the p channel type thin film transistor and n
A stacked body of semiconductor thin films constituting a channel type thin film transistor is composed of a first semiconductor thin film and a second semiconductor thin film stacked with a conductive layer interposed therebetween, and further, a sidewall portion of the pattern of the first semiconductor thin film and A thin film semiconductor device, wherein a gate electrode is formed via a gate insulating film so as to cover a side wall of the pattern of the second semiconductor thin film. 2. A step of forming a first conductive layer on a substrate;
A step of forming a first semiconductor thin film for forming a channel of the first conductivity type on the first conductive layer, and a step of forming a second conductive layer on the first semiconductor thin film, Forming a second semiconductor thin film on the second conductive layer for forming a channel of a second conductivity type different from the first conductivity type, and forming a third conductive layer on the second conductive layer; Forming on a semiconductor thin film, processing the first conductive layer, processing the first semiconductor thin film, processing the second conductive layer, and forming the second semiconductor A step of processing the thin film, a step of processing the third conductive layer, and further covering the side wall of the pattern of the processed first semiconductor thin film and the second semiconductor thin film, forming a gate electrode. Forming a thin film semiconductor device via a gate insulating film. Production method.