JPH09153623A - Thin film semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable prevention of voids and hillocks and hence prevention of disconnection without increasing wiring resistance, by providing a multilayer structure of wiring in which an aluminum metal film and a refractory metal film are stacked. SOLUTION: A wiring 7 has a multilayer structure in which an aluminum metal film 11 and a refractory metal film are stacked. In the drawing, the refractory metal film is made of a titanium metal film 10. Also, other refractory metal films, such as, a tungsten metal film, a molybdenum metal film and a chromium metal film, may be used in place of the titanium metal film. The titanium metal film 10 functions as a barrier layer so that the aluminum metal film 11 does not directly contact a semiconductor thin film 4, thereby preventing generation of voids. In this double structure, mechanical strength of the wiring is secured by the titanium metal film 10. On the contrary, if the upper titanium metal film 10 is stacked on the lower aluminum metal film 11, the upper titanium 10 prevents migration of aluminum atoms even when stress is applied to the aluminum metal film 11.

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 in which bottom gate type thin film transistors and the like are integrated and formed. More specifically, the present invention relates to a film structure of wiring that connects individual thin film transistors.

[0002]

2. Description of the Related Art A thin film semiconductor device is suitable for a drive substrate of an active matrix type liquid crystal display panel and has been actively developed in recent years. In particular, a thin film semiconductor device formed by assembling bottom gate type thin film transistors is suitable for low-temperature processes, and the cost and size of an insulating substrate can be reduced, and therefore has attracted attention. A conventional thin-film semiconductor device is basically a gate electrode patterned on an insulating substrate, a gate insulating film covering the gate electrode, a semiconductor thin film formed on the gate insulating film, which is an active layer of a bottom-gate thin film transistor, and And an interconnection formed on the interlayer insulation film and connected to the thin film transistor through a contact hole. In addition, when applied to a drive substrate of an active matrix type display panel, pixel electrodes are also formed.

[0003]

A single-layer aluminum metal film has been conventionally used as a wiring for connecting thin film transistors. Since aluminum has a relatively high conductivity, it is possible to reduce the resistance of the wiring. However, when a single-layer aluminum metal film is used as the wiring material, there is a problem that disconnection failures occur frequently due to the occurrence of so-called "voids" and "hillocks". The voids result from the progress of alloying at the contact interface between the aluminum semiconductor film and the impurity semiconductor thin film forming the source region and the drain region of the thin film transistor. Since aluminum on the wiring side migrates to the semiconductor thin film side, contact failure occurs, which causes disconnection. Further, hillocks are generated as a result of migration of aluminum atoms due to stress applied to the aluminum metal film, which causes disconnection and the like. In order to prevent these voids and hillocks, it is necessary to increase the thickness of the metal aluminum film, which causes a step difference with other wiring layers. Since stress concentrates on this step, it causes a disconnection, and further, when applied to an active matrix display panel, adversely affects the alignment state of the liquid crystal in contact with the substrate surface. It has been proposed to use, for example, a titanium metal film as a wiring material instead of the aluminum metal film that causes such voids and hillocks. If the aluminum metal film is replaced with a titanium metal film, it is possible to prevent the disconnection due to the above-mentioned voids, hillocks and the like. However, since the titanium metal film has a lower conductivity than the aluminum metal film, the wiring resistance increases and becomes a problem in driving the circuit.

[0004]

The following means have been taken in order to solve the above-mentioned problems of the prior art. That is, the thin film semiconductor device according to the present invention has, as a basic configuration, a gate electrode formed by patterning on an insulating substrate, a gate insulating film covering the gate electrode, and an active layer of a bottom gate type thin film transistor formed thereon. The semiconductor thin film, the interlayer insulating film that covers the semiconductor thin film, and the wiring that is formed thereon and is connected to the thin film transistor through the contact hole. Characteristically, the wiring has a multilayer structure in which an aluminum metal film and a refractory metal film are stacked. As the refractory metal film, for example, a titanium metal film can be used. In one aspect of the present invention, the multi-layer structure is a two-layer structure in which an upper aluminum metal film and a lower refractory metal film are stacked. In another aspect, the multilayer structure is a two-layer structure in which a refractory metal film on the upper layer side and an aluminum metal film on the lower layer are stacked. In another aspect, the multi-layer structure is a three-layer structure in which an upper refractory metal film, an intermediate aluminum metal film, and a lower refractory metal film are stacked. When the thin film semiconductor device having such a structure is applied to a driving substrate of an active matrix type display panel, pixel electrodes that are patterned and connected to thin film transistors are integratedly formed on the interlayer insulating film.

According to the present invention, bottom gate type thin film transistors are integratedly formed on an insulating substrate. As a wiring for electrically connecting the thin film transistors, for example, a multilayer structure of a titanium metal film and an aluminum metal film is adopted. This enables thinning and prevention of disconnection without increasing wiring resistance. For example, it is possible to prevent the generation of hillocks by stacking an aluminum metal film on the lower layer side and a titanium metal film on the upper layer side. That is, even if stress is applied to the aluminum metal film, migration of aluminum atoms can be suppressed by the titanium metal film on the upper layer side. On the contrary, if a titanium metal film is used on the lower layer side and an aluminum metal film is formed thereon, the occurrence of voids can be prevented. That is, in this multilayer structure, the titanium metal film is interposed between the impurity semiconductor thin film and the aluminum metal film in the contact hole. This titanium metal film functions as a barrier layer and can prevent the alloying of silicon and aluminum forming the semiconductor thin film. The titanium metal film itself does not react with the semiconductor thin film. Furthermore, by adopting a three-layer structure of a titanium metal film / aluminum metal film / titanium metal film as wiring, both hillocks and voids can be prevented.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a process diagram showing a first embodiment of a thin film semiconductor device according to the present invention. First, the structure of the thin film semiconductor device will be described in detail with reference to FIG. As illustrated, the gate electrode 2 is patterned on the insulating substrate 1. A gate insulating film 3 is formed so as to cover the gate electrode 2. A semiconductor thin film 4 is formed on the gate insulating film 3. This semiconductor thin film 4 becomes an active layer of the bottom gate type thin film transistor 5, and is patterned in an island shape in accordance with its element region. This semiconductor thin film 4
An impurity is highly selectively implanted into the region 5 to form a source region S and a drain region D of the thin film transistor 5. Between the source region S and the drain region D, a channel region Ch in which impurities are not implanted is left. The bottom gate type thin film transistor 5 having such a configuration is covered with an interlayer insulating film 6. This interlayer insulating film 6
A wiring 7 is formed on the upper surface of the thin film transistor 5, and is electrically connected to the source region S of the thin film transistor 5 through a contact hole. The wiring 7 is covered with a passivation film 8, and a pixel electrode 9 is patterned on the wiring 7. The pixel electrode 9 is electrically connected to the drain region D of the thin film transistor 5 through a contact hole opened in the passivation film 8 and the interlayer insulating film 6. In this example, the thin film transistor 5 serving as a switching element for driving the pixel electrode 9 is shown. However, in addition to this switching element, a peripheral drive circuit portion can be integrated on the insulating substrate 1. This drive circuit unit can also be composed of a bottom gate type thin film transistor. In this case, the wiring is connected to both the source region S and the drain region D of the thin film transistor.

As a feature of the present invention, the wiring 7 has a multi-layer structure in which an aluminum metal film 11 and a refractory metal film are stacked. In this example, this refractory metal film is the titanium metal film 1
Consists of zero. Instead of the titanium metal film, another refractory metal film such as a tungsten metal film, a molybdenum metal film, or a chromium metal film may be used. These refractory metal films have relatively high resistance, but are characterized in that they are chemically stable. In addition, it has sufficient mechanical strength and does not easily break. As shown in (E), the multilayer structure of the wiring 7 is a two-layer structure in which the aluminum metal film 11 on the upper layer side and the titanium metal film 10 on the lower layer side are stacked. The titanium metal film 10 is interposed between the aluminum metal film 11 and the source region S in the contact hole. Titanium metal film 1
0 functions as a barrier layer, and since the aluminum metal film 11 and the semiconductor thin film 4 are not in direct contact with each other, no void is generated. In this two-layer structure, the titanium metal film 10 secures the mechanical strength of the wiring, while the aluminum metal film 11 secures the desired conductivity. Further, by interposing the titanium metal film 10, a void that causes a disconnection failure is prevented.

The method of manufacturing the thin film semiconductor device according to the present invention will be described in detail with reference to FIG. First (A)
As shown in, a metal film made of Mo / Ta or the like is formed on the transparent insulating substrate 1 made of glass or the like. This metal film is patterned into a predetermined shape to form the gate electrode 2.
Next, as shown in (B), a gate insulating film 3 is formed so as to cover the gate electrode 2. The gate insulating film 3 is formed by, for example, LP-CVD method, plasma CVD method or AP-CV method.
It is composed of a SiO ₂ film or a SiN _x film formed by the D method. In this example, in order to obtain a sufficient gate breakdown voltage, SiO ₂ / SiN _x /
A gate insulating film 3 having a three-layer structure of SiO ₂ was formed by a plasma CVD method. Next, as shown in (C), the semiconductor thin film 4 to be the active layer of the thin film transistor 5 is formed by LP-CV.
The film is formed by the D method or the plasma CVD method. In this example, non-single-crystal silicon was deposited to a thickness of 50 nm by the plasma CVD method. Then, an excimer laser beam was irradiated to improve the crystallinity. Further, a photoresist 20 was applied on the semiconductor thin film 4, and the back surface was exposed by self-alignment using the gate electrode 2 as a mask. As a result, the photoresist 20 is patterned into a shape that matches the gate electrode 2. Using the patterned photoresist 20 as a mask, impurities are region-selectively implanted by, for example, ion doping or the like to form a source region S and a drain region D in the semiconductor thin film 4. When forming an N-channel type transistor, for example, phosphorus is implanted as an impurity. Further, when a P-channel type transistor is produced, for example, boron is implanted as an impurity. Further, in order to activate the impurities implanted in the semiconductor thin film 4, for example, an excimer laser beam is irradiated to reduce the resistance of the source region S and the drain region D. After this, the semiconductor thin film 4
Are separated for each element region of each thin film transistor. That is, the semiconductor thin film 4 is etched and patterned in an island shape. In addition, used photoresist 2
0s are removed. Next, as shown in (D), an interlayer insulating film 6 is deposited so as to cover the thin film transistor 5. A SiO ₂ film or a SiN _x film can be used as the interlayer insulating film. In this example, the interlayer insulating film 6 was formed by depositing SiO ₂ by the AP-CVD method. A contact hole is opened in this interlayer insulating film 6 to expose a part of the source region S. For example, a titanium metal film 10 is formed on the interlayer insulating film 6.
Is formed to a thickness of 100 nm. Further, the aluminum metal film 11 is formed to have a thickness of 300 nm, for example. This multilayer structure is etched to form the wiring 7. Finally, as shown in (E), a passivation film 8 is formed so as to cover the wiring 7. As the passivation film 8, for example, an inorganic film of SiO ₂ or SiN _x can be used.
Alternatively, an organic film such as acrylic resin may be applied thickly to form the passivation film 8 so as to absorb the level difference of the wiring 7. The passivation film 8 and the interlayer insulating film 6 are selectively etched to remove the drain region D of the thin film transistor 5.
Open a contact hole communicating with. A transparent conductive film such as ITO is formed on the passivation film 8 and patterned into a predetermined shape to form the pixel electrode 9. Pixel electrode 9
Is electrically connected to the drain region D through the contact hole.

FIG. 2 is a schematic partial sectional view showing a second embodiment of the thin film semiconductor device according to the present invention. The basic configuration is the same as that of the first embodiment shown in FIG. 1E, and corresponding parts are designated by corresponding reference numerals to facilitate understanding. The difference is that the wiring 7 has a two-layer structure in which an upper titanium metal film 10 and a lower aluminum metal film 11 are stacked. That is, as compared with the first embodiment shown in FIG. 1, the laminated relationship of the aluminum metal film 11 and the titanium metal film 10 is reversed. In this embodiment, since the aluminum metal film 11 is covered with the titanium metal film 10, generation of hillocks can be suppressed. That is, even if stress is applied to the aluminum metal film 11, the titanium metal film 10
Since is located on the upper part, migration of aluminum atoms can be suppressed, and as a result, hillocks can be suppressed. By adding, for example, silicon atoms reaching the solid solution limit to the aluminum metal film 11, alloying at the interface between the aluminum metal film 11 and the semiconductor thin film 4 made of silicon or the like can be suppressed, and voids can be prevented to some extent.

FIG. 3 is a schematic partial sectional view showing a third embodiment of the thin film semiconductor device according to the present invention. Basically, it is the same as the first embodiment shown in FIG. 1E, and corresponding parts are designated by corresponding reference numerals to facilitate understanding. The difference is that the wiring 7 has a three-layer structure in which an upper titanium metal film 10, an intermediate aluminum metal film 11 and a lower titanium metal film 10 are stacked.
By sandwiching the intermediate aluminum metal film 11 between the upper and lower titanium metal films 10 in this manner, it is possible to effectively suppress both voids and hillocks, which have conventionally been problems.

Finally, an example of an active matrix type display panel assembled by using the thin film semiconductor device according to the present invention as a driving substrate is shown in FIG. 4 for reference. As shown in the figure, the display panel is composed of a drive substrate 101 made of glass or the like, a counter substrate 102 made of glass or the like, and a liquid crystal 103 held between the two. On the drive substrate 101, a pixel array unit 104 and a drive circuit unit are integrally formed. The drive circuit section includes a vertical drive circuit 105 and a horizontal drive circuit 1
06. Further, a terminal portion 107 for external connection is formed at an upper end of a peripheral portion of the drive substrate 101. The terminal portion 107 is connected to a vertical drive circuit 105 and a horizontal drive circuit 106 via a wiring 108. Pixel array section 1
Reference numeral 04 denotes a gate wiring 109 and a signal wiring 11 which intersect each other.
0 is provided. A pixel electrode 111 and a thin film transistor 112 that drives the pixel electrode 111 are provided at the intersections of the wirings 109 and 110.
And are formed in an integrated manner. On the other hand, on the inner surface of the counter substrate 102, although not shown, a counter electrode and a color filter as needed are formed.

[0012]

As described above, according to the present invention, the wiring connecting the thin film transistors has a multilayer structure in which an aluminum metal film and a refractory metal film such as a titanium metal film are stacked. With this configuration, voids and hillocks can be suppressed without increasing the resistance of the wiring, and disconnection can be prevented.
Further, by combining a titanium metal film having a relatively high resistance but a large mechanical strength with an aluminum metal film having a relatively weak mechanical strength but a small electric resistance, it is possible to reduce the thickness of the entire wiring. The step appearing on the surface of the insulating substrate becomes inconspicuous. Therefore, it is possible to prevent the disconnection failure of the wiring due to the step, and also to prevent the disconnection or crack of the other wiring intersecting with this. Furthermore, when applied to a drive substrate of an active matrix type liquid crystal display panel, it is possible to prevent defective alignment of liquid crystal.

[Brief description of the drawings]

FIG. 1 is a process drawing showing a first embodiment of a thin film semiconductor device according to the present invention.

FIG. 2 is a schematic sectional view showing a second embodiment of a thin film semiconductor device according to the present invention.

FIG. 3 is a schematic cross-sectional view showing a third embodiment of a thin film semiconductor device according to the present invention.

FIG. 4 is a schematic perspective view showing an example of an active matrix type display panel in which the thin film semiconductor device according to the present invention is assembled as a drive substrate.

[Explanation of symbols]

 1 Insulating Substrate 2 Gate Electrode 3 Gate Insulating Film 4 Semiconductor Thin Film 5 Thin Film Transistor 6 Interlayer Insulating Film 7 Wiring 8 Passivation Film 9 Pixel Electrode 10 Titanium Metal Film 11 Aluminum Metal Film

Claims (6)

[Claims] 1. A gate electrode patterned on an insulating substrate, a gate insulating film covering the gate electrode, a semiconductor thin film formed on the gate electrode to be an active layer of a bottom gate type thin film transistor, and an interlayer insulating film covering the semiconductor thin film. A thin film semiconductor device comprising a film and a wiring formed on the film and connected to a thin film transistor through a contact hole, wherein the wiring has a multilayer structure in which an aluminum metal film and a refractory metal film are stacked. Characteristic thin film semiconductor device. 2. The thin film semiconductor device according to claim 1, wherein the refractory metal film is a titanium metal film. 3. The thin film semiconductor device according to claim 1, wherein the multi-layer structure is a two-layer structure in which an upper aluminum metal film and a lower refractory metal film are stacked. 4. The thin film semiconductor device according to claim 1, wherein the multilayer structure is a two-layer structure in which a refractory metal film on an upper layer side and an aluminum metal film on a lower layer side are stacked. 5. The multi-layer structure according to claim 1, which is a three-layer structure in which an upper refractory metal film, an intermediate aluminum metal film, and a lower refractory metal film are stacked. Thin film semiconductor device. 6. The thin film semiconductor device according to claim 1, further comprising a pixel electrode formed on the interlayer insulating film by patterning and connected to the thin film transistor.