JP2584117B2 - Method for manufacturing thin film transistor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thin film transistor used for an active matrix array of a liquid crystal display device, an image sensor, a three-dimensional integrated circuit, a semiconductor memory, and the like.

2. Description of the Related Art A method of manufacturing an active matrix array for a liquid crystal display in which thin film transistors are integrated in a matrix will be described as an example.

For the active layer of the thin film transistor used for the active matrix array, amorphous silicon that can be formed on a large-area substrate at a relatively low temperature of around 300 ° C. has been mainly used. Since a thin film transistor has low mobility, it is difficult to form a driver circuit over the same substrate. Therefore, in recent years, research on a thin film transistor using polycrystalline silicon as an active layer, which can form a driver circuit with higher mobility than amorphous silicon on the same substrate, is being actively conducted.

FIG. 3 illustrates a method of manufacturing a staggered n-channel polycrystalline silicon thin film transistor as an example.

As shown in FIG. 3 (a), a metal thin film 2 such as a Cr thin film is formed on a light transmitting substrate 1 such as a glass substrate, and an amorphous silicon thin film 3 doped with phosphorus (P) is formed on the metal thin film 2. To form As shown in FIG. 3 (b), the P-doped amorphous silicon thin film 3 and metal thin film 2 are selectively removed into the shape of source / drain electrodes by using photolithography technology. Next, as shown in FIG. 3C, an undoped amorphous silicon thin film 4a is formed so as to cover the source / drain electrodes. As shown in FIG. 3D, the amorphous silicon thin film 4 is irradiated with a laser beam to crystallize the amorphous silicon thin film, thereby obtaining a silicon thin film (4b). Next, as shown in FIG. 3 (e), after the crystallized silicon thin film 4 is etched and removed in an island shape, a gate insulating film 5 made of a SiNx film or the like is formed on the entire surface. Finally, a gate electrode 6 is formed as shown in FIG. 3 (f), and a thin film transistor is completed.

Regarding the above technology, for example, IEE Transactions on Electron Devices [IEEE Trans.on Electron Devices, Vol.36 No.12 pp.2
868-2872 December 1989].

Problems to be Solved by the Invention In such a conventional method of manufacturing a thin film transistor,
It is necessary to separately produce two types of thin films, an undoped amorphous silicon thin film 4a and an amorphous silicon thin film 3 doped with impurities.

When a liquid crystal display device is manufactured using a polycrystalline silicon thin film transistor, it is important to form a driver circuit of the liquid crystal display device on the same substrate. For that purpose, a C-MOS structure (a structure in which an n-channel thin film transistor and a p-channel thin film transistor are integrated) that can reduce power consumption is required. However, according to the conventional manufacturing method shown in FIG. 3, in order to form two types of n-channel and p-channel thin film transistors on the same substrate, two types including a donor and an acceptor in addition to an undoped amorphous silicon thin film are used. Therefore, it is necessary to prepare three types of amorphous silicon thin films in total, and there is a problem that the forming process becomes very complicated.

An object of the present invention is to provide a method of manufacturing a thin film transistor in which the manufacturing process is simple and a C-MOS structure can be easily manufactured even on the same substrate.

Means for Solving the Problems In order to achieve the above object, the present invention provides a semiconductor thin film used for an active layer on a light-transmitting substrate, a metal in which an impurity serving as a donor or an acceptor is introduced, a metal silicide in which an impurity is introduced. Alternatively, a step of selectively forming a source / drain electrode made of a conductive metal oxide doped with an impurity, and forming a semiconductor thin film serving as an active layer so as to cover the source / drain electrode; Irradiating an energy beam to crystallize the semiconductor thin film, forming an insulating film on the crystallized semiconductor thin film, and forming a gate electrode on the insulating film; It has a configuration in which source / drain electrodes doped with impurities of the opposite type for a MOS structure are added.

Function The present invention can form a metal thin film such as a Cr thin film and a metal silicide thin film doped with impurities continuously by the same apparatus such as a sputtering method by the above-described configuration, and apply an energy beam to the semiconductor thin film. The semiconductor thin film is crystallized by performing the irradiation, and at the same time, the impurities contained in the source / drain electrodes composed of the metal silicide thin film diffuse into the semiconductor thin film and are electrically activated, thereby forming an impurity-doped region. Is done.

Further, two types of source / drain electrodes made of metal, metal silicide or conductive metal oxide, each containing an impurity serving as a donor and an acceptor for a semiconductor thin film serving as an active layer on the same light-transmitting substrate, are selectively used. In this case, n-channel and p-channel thin film transistors can be easily formed on the same light-transmitting substrate.

Embodiment An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a process chart showing a method for manufacturing a thin film transistor according to a first embodiment of the present invention.

First, as shown in FIG. 1A, a metal thin film 12 such as a Cr thin film is formed on a light transmitting substrate 11 such as a glass substrate. Up to this point, a MoSixx thin film (hereinafter abbreviated as MoSix: P) 13 doped with phosphorus (P) is formed on the Cr thin film 12 in the same manner as in the conventional example. The Cr thin film 12 and the MoSix: P thin film 13 are continuously formed by the same apparatus by a sputtering method. Next, as shown in FIG.
The MoSix: P thin film 13 and the Cr thin film 12 are removed by etching.
As shown in FIG. 1C, an undoped amorphous silicon thin film 14a is formed in the same manner as in the conventional example so as to cover the metal of the source / drain electrodes. For forming the amorphous silicon thin film 14a, a plasma vapor deposition method (PECVD method) is used as in the related art. Next, as shown in FIG. 1D, the amorphous silicon thin film 14a is irradiated with an energy beam.
In FIG. 1, a XeCl excimer laser (wavelength: 308 nm) is used as an energy beam, and the amorphous silicon thin film 14a is crystallized into a silicon thin film 14b by irradiation with the energy beam, and is simultaneously contained in the source / drain electrodes. The impurity (P) is taken into the semiconductor thin film and is electrically activated. After the crystallized silicon thin film 14b is etched into an island shape as shown in FIG. 1 (e), a gate insulating film 15 made of a SiNx film or the like is formed by PECVD as in the conventional example, and further, FIG. As shown in FIG. 7, a gate electrode 16 is formed in the same manner as in the conventional example to complete a thin film transistor.

In such a method of manufacturing a thin film transistor, an amorphous silicon thin film 3 containing an impurity (P) is formed as in a conventional example.
Since MoSix: P can be continuously deposited together with Cr by sputtering without the need to form by PECVD, the fabrication process is simplified, throughput is increased, and cost is reduced.

Although the P-doped MoSix thin film was used as a metal electrode to form the n-channel thin film transistor of FIG. 1, for example, a p-channel thin film transistor was formed by using a boron (B) -doped MoSix thin film as a source / drain electrode. realizable.

In the present embodiment, the case where the MoSix thin film 13, that is, the metal silicide is used as the source / drain electrodes containing impurities is shown, but a metal or a conductive metal oxide may be used.

FIG. 2 is a process chart of a method for manufacturing a thin film transistor according to a second embodiment of the present invention.

As shown in FIG. 2 (a), a translucent substrate such as a glass substrate
A MoSix film 23 a doped with phosphorus (P) is formed on 21. As shown in FIG. 2 (b), after the MoSix: P film 23a is etched in the shape of the first source / drain electrode 23a, the entire surface is doped with B to form a WSix thin film (hereinafter abbreviated as WSix: B).
Form 23b. Then, as shown in FIG.
WSix: B film with different shape from source / drain electrode
23b is etched to form a second source / drain electrode 23b. The MoSix: P thin film 23a and the WSix: B thin film 23b are formed by a sputtering method. As shown in FIG. 2D, an undoped amorphous silicon thin film 24 is formed so as to cover the first and second source / drain electrodes 23a and 23b.
The amorphous silicon thin film 24a is formed by a plasma vapor deposition method (PECVD method). Next, as shown in FIG. 2 (e), the amorphous silicon thin film 24a is irradiated with an energy beam. In FIG. 2 (e), similarly to FIG. 1 (d), an XeCl excimer laser (wavelength
308 nm), and the amorphous silicon thin film 24a is crystallized into a silicon thin film 24b by irradiation with an energy beam, and at the same time, impurities (P and B) contained in the first and second source / drain electrodes. Is silicon thin film 24
It is taken into b and is electrically activated. After the crystallized silicon thin film 24b is etched into an island shape as shown in FIG. 2 (f), a gate insulating film 25 made of a SiNx film or the like is formed by PECVD.
The gate electrode is formed by a method as shown in FIG.
26 is formed, and the thin film transistor is completed.

When a thin film transistor was manufactured by using the manufacturing method of the present invention, n-channel and p-channel thin film transistors could be easily formed on the same substrate, and the manufacturing process could be simplified.

In the method of manufacturing a thin film transistor shown in FIG. 2, the first source / drain electrode (MoSix: P thin film 23a)
Even if the order of forming the second source / drain electrodes (WSix: B thin film 23b) is reversed, the same effect as that of FIG. 2 can be obtained. Therefore, the order in which the electrodes are formed can be selected according to the etching characteristics of the first and second source / drain electrode materials, and the degree of freedom in the fabrication process is increased.

In this embodiment, a general sputtering method was used to form an electrode into which impurities were introduced, but other methods can be used, for example, by using a multi-source sputtering method, a vapor phase growth method, or ion implantation. Has the same effect. Further, when a silicon semiconductor is used for the active layer, the electrode material for introducing the impurity is preferably a silicide (silicide) or a metal that forms a silicide (silicide) by irradiation with an energy beam.

Effects of the Invention As is apparent from the above embodiments, according to the present invention, since the source / drain electrodes composed of the metal silicide thin film doped with impurities are used, the conventional plasma CV
There is no need to create a semiconductor thin film doped with impurities, which was created by D. This simplifies the manufacturing process, and allows easy creation of p-channel and n-channel transistors by selecting the impurities to be introduced into the source / drain electrodes. A C-MOS structure in which an n-channel thin-film transistor and a p-channel thin-film transistor are integrated on the same substrate can be easily formed, and a thin-film transistor capable of reducing manufacturing cost can be provided.

[Brief description of the drawings]

1 (a) to 1 (f) are process cross-sectional views showing a method for manufacturing a thin film transistor according to a first embodiment of the present invention, and FIG. 2 (a).
3 (g) to 3 (g) are process sectional views showing a method for manufacturing a thin film transistor according to a second embodiment of the present invention, and FIGS. 3 (a) to 3 (f) are process sectional views showing a method for manufacturing a conventional thin film transistor. 11: translucent substrate; 13: P-doped MoSix thin film (source / drain electrode made of metal, metal silicide, conductive metal oxide, etc. doped with impurities); 14a: undoped amorphous silicon thin film ( Semiconductor thin film), 14b ……
Silicon thin film (semiconductor thin film), 15 ... gate insulating film, 6
... Gate electrode.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location H01L 29/40 H01L 27/14 C (72) Inventor Yutaka Miyata 1006 Kazuma Kazuma, Kadoma City, Osaka Matsushita Inside Electric Industry Co., Ltd. (72) Inventor Tatsuo Yoshioka 1006 Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-1-225363 (JP, A) JP-A-2-10742 (JP, A) JP-A-61-184882 (JP, A)

Claims (5)

(57) [Claims] A step of selectively forming a source / drain electrode made of any one of a metal doped with an impurity, a metal silicide, and a conductive metal oxide on a light transmitting substrate; Forming a semiconductor thin film to be an active layer so as to cover the drain electrode, and irradiating the semiconductor thin film with an energy beam to crystallize and remove impurities contained in the source / drain electrodes in the semiconductor thin film; Electrically activating the semiconductor thin film by diffusing the semiconductor thin film, forming a pattern on the semiconductor thin film, and forming a gate insulating film on the translucent substrate including the patterned semiconductor thin film. Process and
Forming a gate electrode on the insulating film. 2. A first source / drain electrode made of any one of a metal doped with a first impurity, a metal silicide, and a conductive metal oxide is selectively formed on a light transmitting substrate. And doping a second impurity on the light-transmitting substrate different from the first source / drain electrode and made of any one of metal, metal silicide, and conductive metal oxide A step of selectively forming a second source / drain electrode; a step of forming a semiconductor thin film serving as an active layer so as to cover the first and second source / drain electrodes; An energy beam is irradiated for crystallization, and the first and second impurities contained in the first and second source / drain electrodes are removed from the first and second source / drain electrodes in the semiconductor thin film. A step of electrically activating the semiconductor thin film by diffusing the semiconductor thin film, a step of patterning the semiconductor thin film, and a step of forming a gate on the translucent substrate including the patterned semiconductor thin film. A method for manufacturing a thin film transistor, comprising at least a step of forming an insulating film and a step of forming a gate electrode over the insulating film. 3. The method of manufacturing a thin film transistor according to claim 2, wherein a step of selectively forming the first source / drain electrode and a step of selectively forming the second source / drain electrode are interchanged. . 4. The method for manufacturing a thin film transistor according to claim 1, wherein a semiconductor thin film containing silicon is used as the semiconductor thin film to be an active layer. 5. The method of manufacturing a thin film transistor according to claim 1, wherein a laser beam is used as an energy beam.