JP2001015762A - Thin-film semiconductor device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable high density integration by providing a second thin-film transistor having a gate electrode formed of a silicon film containing impurities, and a first thin-film transistor whose source or drain region is directly connected to the gate electrode of the second thin-film transistor. SOLUTION: A semiconductor layer 111 which is to become a first thin-film transistor and a semiconductor layer 121 to be a second thin-film transistor are formed on a substrate 100. Next, a gate insulated film 112 is formed. Then, an opening 113 is provided on the gate insulated film 112, to expose a part of the source/drain region of the first thin-film transistor. Next, a gate electrode 114 of the first thin-film transistor, and a gate electrode 124 of the second thin-film transistor are formed simultaneously by a doped polysilicon film. The gate electrode 124 of the second thin-film is extended to the opening 113 and is directly connected electrically to the source/drain region of the first transistor, so that degree of integration can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film semiconductor device used for a liquid crystal display device and the like and a method of manufacturing the same.

[0002]

2. Description of the Related Art A thin film transistor formed on an insulating substrate or an insulating film is a MOS transistor formed on a silicon wafer.
It is characterized in that the manufacturing method is simpler than that of the field-effect transistor, and that it can be manufactured at low cost using a large-sized substrate. Utilizing the characteristics, the thin film transistor has been mainly applied to a liquid crystal display device and developed. In particular, a thin film transistor in which an active layer is formed of a polycrystalline silicon film has high mobility, and thus has been used for a display device with a built-in drive circuit. However, in order to meet demands for larger and higher definition liquid crystal display devices, higher performance has always been required for thin film transistors used in display devices. In addition, thin film transistors are desired to be applied not only to display devices and photoelectric conversion, but also to a wider variety of functional elements including the field of LSI. For this purpose, high performance and high integration of thin film transistors are required.

[0003] The performance of a thin film transistor is improved by improving the mobility and miniaturization. However, in order to improve the performance, it is necessary to form a thin film transistor on a large glass substrate at low cost when applied to a display device or the like. In addition, there is a demand for a reduction in manufacturing cost along with a demand for a larger glass substrate size, but it is difficult to draw a fine pattern on a large glass substrate at a high speed, which is a high cost in terms of manufacturing a thin film transistor. The emphasis was on cost reduction over performance improvement. Therefore, the performance improvement of the conventional thin film transistor is naturally limited and insufficient.

FIG. 5 shows a conventional example of a thin film transistor.
In FIG. 5, 111 is an island-shaped semiconductor region serving as a first thin film transistor, 114 is a gate electrode of the first thin film transistor, 121 is an island-shaped semiconductor region serving as a second thin film transistor, and 124 is a gate electrode of a second thin film transistor. is there. Gate electrode 124 of second thin film transistor
Is the wiring 11 connecting the two contact holes 116
It is connected to a source / drain region (not shown) of the first thin film transistor via 7 '.

FIG. 6 is a sectional view taken along the line XX 'of FIG. Each part such as a thin film which is a component of the thin film transistor is denoted by a common number in FIGS. FIG.
In FIG. 7, a semiconductor layer 111 to be a first thin film transistor and a semiconductor layer 121 to be a second thin film transistor are formed over a substrate 100, and a gate insulating film 112 is formed so as to cover the semiconductor layers 111 and 121. Also in FIG. 6, the gate electrode 124 of the second thin film transistor is a wiring 117 ′ connecting the two contact holes 116.
Via a source (not shown) of the first thin film transistor
Connected to the drain region. In addition, 125 is a protective film.

[0006]

In thin-film semiconductor devices such as thin-film transistors, their applications are expanding not only to conventional application fields such as display devices but also to various applications. Further improvement in the degree of integration is required. For this purpose, for example, as described above, for example, in the case of a thin film transistor, improvement of the mobility, miniaturization of a processing pattern and improvement of accuracy, development of a process technology for high integration, and the like have been performed. Due to the bias toward display devices, development for high integration was not always sufficient. Therefore, an object of the present invention is to provide a thin-film semiconductor device that can achieve higher integration, particularly in a thin-film transistor.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a second thin film transistor having a gate electrode formed of a silicon film containing an impurity, and a gate electrode of the second thin film transistor. A first thin film transistor directly connected to the source or drain region.

Further, the present invention provides a step of forming a semiconductor film on an insulating substrate or an insulating film, a step of crystallizing the semiconductor film, and a step of patterning the crystallized semiconductor film to form a first thin film transistor and Forming a region to be a second thin film transistor; forming a gate insulating film over the entire surface of the insulating substrate or the insulating film; and forming an opening in the gate insulating film over a region to be a source or drain region of the first thin film transistor. Forming a first thin film transistor and a second thin film transistor by using a silicon film containing impurities.
Forming a gate electrode of the thin film transistor, and removing the gate insulating film using the gate electrode as a mask to expose a semiconductor layer serving as source / drain regions of the first thin film transistor and the second thin film transistor; A second step of forming a contact hole in the impurity-containing insulating film on the source / drain region in the impurity-containing insulating film, and a step of forming an electrode; A gate electrode of the thin film transistor is directly electrically connected to a source or drain region of the first thin film transistor.

Further, the gate electrode is formed of a silicon film containing impurities formed from a liquid material, and the method of forming the silicon film includes a step of applying a liquid material containing silicon atoms and boron or phosphorus to a substrate. And a step of heat-treating the coating film.

The liquid material containing a silicon atom and boron or phosphorus has a general formula of Si _a X _b Y _c (where X represents a hydrogen atom and / or a halogen atom, and Y represents a boron atom or a phosphorus atom. A and c each represent an integer of 3 or more, and b represents an integer of 2 or more and a or less than 2a + c + 2) and a solvent.

Further, the above general formula Si _a X _b Y _c (where,
X represents a hydrogen atom and / or a halogen atom, Y represents a boron atom or a phosphorus atom, a and c each represent an integer of 3 or more, and b represents an integer of 2a + c + 2 or less. The compound is characterized in that the value of a + c is 5 or 6.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to embodiments.
FIG. 1 is a diagram showing a layout of a thin film semiconductor device according to the present invention. In FIG. 1, 111 is an island-shaped semiconductor region serving as a first thin-film transistor, 114 is a gate electrode of the first thin-film transistor, 121 is an island-shaped semiconductor region serving as a second thin-film transistor, and 124 is a gate of the second thin-film transistor Electrodes. The gate electrode of the second thin film transistor is formed of a doped silicon film containing impurities, and is directly connected to the source / drain region of the first thin film transistor via an opening 113 opened in the gate insulating film. . When a thin film transistor is connected in the structure of the present invention, a contact hole can be omitted, so that the degree of integration can be improved. Further, at the time when the step of forming the gate electrode is completed, part of the wiring between the gate electrode and the source / drain region is completed, so that the resistance to static electricity is improved.

Next, a method of manufacturing the thin film semiconductor device of the above embodiment will be described. 2 to 4 are views showing the manufacturing process of the above embodiment, and correspond to the cross-sectional views along AA 'in FIG. In FIG. 1 to FIG. 4, common portions are denoted by common numbers for respective portions such as a thin film which is a component of the thin film transistor. In FIG. 2, a semiconductor layer 111 to be a first thin film transistor and a semiconductor layer 121 to be a second thin film transistor are formed over a substrate 100. The semiconductor layers 111 and 121 are first formed as amorphous silicon films having a thickness of about 500 angstroms by a low-pressure CVD method, and then the amorphous silicon films are converted into polycrystalline silicon films by crystallization treatment such as laser annealing. After that, it is processed into a desired pattern. Next, a gate insulating film 112 is formed. The gate insulating film 112 may be formed by thermal oxidation as long as the substrate 100 has heat resistance.
It is formed at a low temperature such as a PECVD (plasma CVD) method. The film thickness is several tens to several hundreds of angstroms. Next, an opening 113 is provided in the gate insulating film 112 to expose a part of a source / drain region (not shown) of the first thin film transistor. Next, the gate electrode 114 of the first thin film transistor and the gate electrode 124 of the second thin film transistor are simultaneously formed by the doped polysilicon film. The gate electrode 124 of the second thin film transistor extends to the opening 113 and is electrically connected to a source / drain region (not shown) of the first thin film transistor.

As the liquid material containing silicon atoms and boron or phosphorus used in the formation of the doped silicon film, a modified silane compound is used. The modified silane compound may be used alone or as a mixture with an unmodified silane compound. The unmodified silane compound is cyclopentasilane, cyclohexasilane, or the like, and the modified silane compound is a compound obtained by modifying the unmodified silane compound with a dopant atom such as phosphorus or boron. In forming a doped silicon film, first, a coating film is formed using a solution in which the modified silane compound is dissolved in a hydrocarbon-based solvent such as n-pentane or benzene and the viscosity or the like is adjusted. As a method of forming the coating film, spin coating, roll coating, curtain coating, dip coating,
A spray method, an ink-jet method, or a combination thereof can be used. Next, heat treatment at 100 ° C. to 200 ° C. is performed to remove the solvent from the coating film.
Next, the coating film is converted into an amorphous silicon film by heat treatment at 300 ° C. to 550 ° C. Next, the amorphous silicon film is converted into a polycrystalline doped silicon film by laser annealing.

FIG. 2 shows a state after the doped silicon film formed as described above is patterned. The laser annealing is performed before the patterning.
At the same time as the doped silicon film is polycrystallized by the laser annealing, impurity atoms such as phosphorus or boron diffuse from the doped silicon film into the underlying silicon film 111 in the opening 113 shown in FIGS. Ohmic connection is made between the doped silicon film and the underlying silicon film. After the laser annealing, the doped silicon film is patterned to form gate electrodes 114 to 12 as shown in FIG.
4 is processed.

Next, as shown in FIG.
The gate insulating film 112 is removed using
The silicon layer which becomes the drain regions (111S and 111D) is exposed.

Next, as shown in FIG. 4, an impurity-doped insulating film (PSG film or BSG film) 115 is formed. The insulating film can be formed as a SOG film by a spin coating method or the like. Next, heat treatment such as laser annealing or lamp annealing is performed to diffuse impurities in the insulating film into the silicon layer 111S or 111D in contact with the insulating film, thereby forming source / drain regions 111S and 11D. Although not shown below, a contact hole is opened and an electrode is formed to complete a thin film transistor.

[0018]

According to the thin film semiconductor device of the present invention, the gate electrode of the thin film transistor is formed of a silicon film containing impurities, and the source / drain of the first thin film transistor is formed through the opening formed in the gate insulating film. Since the thin film transistors are directly connected to the region, the thin film transistors can be integrated at a high density.

[Brief description of the drawings]

FIG. 1 is a diagram showing a layout of a thin film transistor according to the present invention.

FIG. 2 is a cross-sectional view taken along the line AA ′ of FIG. 1, illustrating a manufacturing process of the thin film transistor according to the present invention.

FIG. 3 is a view showing a manufacturing process of the thin film transistor according to the present invention, and is a cross-sectional view along AA ′ of FIG. 1;

FIG. 4 is a diagram illustrating a manufacturing process of the thin film transistor according to the present invention, and is a cross-sectional view taken along the line AA ′ of FIG. 1;

FIG. 5 is a diagram showing a layout of a thin film transistor according to the related art.

FIG. 6 is a sectional view taken along line AA ′ of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 100 Substrate 111, 121 Semiconductor film 112 Gate insulating film 114, 124 Gate electrode 116 Contact hole 117 Electrode wiring

Claims (5)

[Claims] 1. A second thin film transistor having a gate electrode formed of a silicon film containing an impurity, and a first thin film transistor in which a gate electrode of the second thin film transistor is directly connected to a source or drain region. A thin-film semiconductor device, comprising: 2. A step of forming a semiconductor film on an insulating substrate or an insulating film; a step of crystallizing the semiconductor film; and a first thin film transistor and a second thin film transistor by patterning the crystallized semiconductor film. Forming a region to be formed, forming a gate insulating film over the entire surface of the insulating substrate or the insulating film, and forming an opening in the gate insulating film over a region to be a source or drain region of the first thin film transistor. A step of forming gate electrodes of the first thin film transistor and the second thin film transistor from the silicon film containing impurities, and removing the gate insulating film using the gate electrode as a mask to remove the first thin film transistor and the second thin film transistor. Exposing a semiconductor layer to be a source / drain region of the thin film transistor of FIG. A step of forming a contact hole in the impurity-containing insulating film on the drain region; and a step of forming an electrode, wherein the gate electrode of the second thin film transistor formed of the silicon film containing the impurity has a first electrode. A method for manufacturing a thin film semiconductor device, wherein the method is electrically connected directly to a source or drain region of a thin film transistor. 3. The method according to claim 1, wherein the gate electrode is formed of a silicon film containing impurities formed from a liquid material, and the method of forming the silicon film includes applying a liquid material containing silicon atoms and boron or phosphorus to a substrate. 3. A method for manufacturing a thin film semiconductor device according to claim 2, comprising the steps of: heat-treating said coating film. 4. The liquid material containing a silicon atom and boron or phosphorus has a general formula of Si _a X _b Y _c (where X represents a hydrogen atom and / or a halogen atom, and Y represents a boron atom or a phosphorus atom. Wherein a and c each represent an integer of 3 or more, and b represents an integer of 2 or more and a or less than 2a + c + 2), and a solvent. Production method. 5. The general formula Si _a X _b Y _c (where X represents a hydrogen atom and / or a halogen atom, Y represents a boron atom or a phosphorus atom, and a and c each represent an integer of 3 or more. 5. The method for manufacturing a thin film semiconductor device according to claim 4, wherein the modified silane compound represented by (b is an integer not less than a and not more than 2a + c + 2) has a value of a + c of 5 or 6. 6.