JP3488590B2 - Manufacturing method of metal thin film and thin film transistor, and semiconductor device using metal thin film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal thin film used as an electrode or wiring in various semiconductor devices such as thin film transistors.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal display (LCD) device, a TFT LCD that uses a thin film transistor (TFT) for driving and controlling liquid crystal has been widely used.

In some TFT LCDs, a bottom gate type TFT is used in which a gate electrode made of a metal thin film is formed on a transparent substrate such as glass and an active layer of the transistor is formed above the gate electrode. In this bottom gate type TFT, a material having a low melting point such as aluminum (Al) cannot be used for the material of the gate electrode and the gate wiring, and tantalum (Ta) or chromium (Cr) is usually used. There is.

[0004]

However, the resistance value of such Ta or Cr gate electrode and its wiring increases due to an electromigration phenomenon or the like during use under high temperature conditions. There is a tendency. And
If the resistance of this gate electrode or its wiring becomes high,
There is a problem that the operating characteristics of the TFT are deteriorated and the display characteristics of the LCD are deteriorated.

The present invention has been made to solve the above problems, and a method of manufacturing a metal thin film capable of preventing the resistance of a metal thin film such as a gate electrode from increasing and a semiconductor using the same. The purpose is to provide a device.

[0006]

The method for producing a metal thin film according to the present invention is characterized in that after forming a metal thin film of Cr , the metal thin film is annealed by using a laser. Thus, when annealed by the laser, the crystal structure of the metal thin film changes. In the Cr thin film,
The {110} orientation, which is the closest packed surface, grows preferentially. Therefore, this metal thin film has a homogeneous structure in which the grain size is relatively oriented to {110} and has a relatively large grain size, and electromigration is less likely to occur when a current is passed through, which is suitable for an electrode material or the like.

Further, the method of manufacturing a thin film transistor according to the present invention comprises a transparent substrate made of Cr to be a gate electrode.
That the metal thin film is formed and annealed with against laser light to the metallic thin film, the close-packed metal crystal of the metal thin film
The {110} plane, which is a dense plane, is oriented, and then the metal
The thin film pattern is formed, the gate electrode is formed, and
The active region of the thin film transistor is formed above the gate electrode . In a liquid crystal display device, a thin film transistor is formed on a transparent substrate. A gate electrode is formed below the active region of the thin film transistor in order to apply a desired electric field to the active region. By using a laser-annealed metal thin film for this gate electrode, the operating characteristics of the thin film transistor can be maintained stable for a long period of time, and a high-quality liquid crystal display device can be obtained.

Further, the present invention is a semiconductor device using a metal thin film made of Cr , wherein the metal thin film is a densest close-packed surface of metal crystals by an annealing treatment using a laser beam after film formation. It is characterized in that the orientation of the 110} plane is strengthened. In a semiconductor device using such a metal thin film having a strong orientation, it is possible to suppress an increase in resistance due to the use of the metal thin film, and maintain good operating characteristics for a long time.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

[Manufacturing Method] FIG. 1 is a diagram for explaining a manufacturing method of a semiconductor device according to the present invention. In addition, in the drawing, it is a schematic explanatory view partially showing a transistor corresponding to one pixel of the liquid crystal display device.

First, a glass substrate 10 is prepared, and a Cr thin film is formed on the entire surface thereof. And in this state, Cr
The thin film is irradiated with excimer laser to perform excimer laser annealing (ELA). By such an excimer laser annealing, the crystal state of Cr changes, and most of Cr becomes {110} oriented.

Next, a predetermined portion is removed from the obtained Cr thin film by using a normal patterning technique to form a pattern of the gate electrode 12 (FIG. 1 (a)).

When the gate electrode 12 is thus formed, the gate insulating layer 14 made of a laminated body of the SiO ₂ film and the SiN film is formed thereon (FIG. 1).
(B)). Then, an amorphous Si layer (a-
(Si) is laminated and annealed to form a poly-Si layer (Poly-Si) 24 (FIG. 1C).

Next, the injection stopper 30 is attached to the gate electrode 12.
Then, impurities are implanted from above to form the channel region on the gate electrode 12 and the source and drain regions on both sides thereof in the poly-Si layer 24. Furthermore, an insulating layer 50 of SiO ₂ is formed on the insulating layer 50, and the upper part of the source region of the insulating layer 50 is removed by etching, and Al
To form a source electrode 70 (FIG. 1 (d),
(E)).

Next, a flattening film 52 is used to cover the upper surface to flatten the surface, form a contact hole above the drain region, connect the drain region, and locate the pixel portion on the surface of the flattening film 52. The transparent electrode 60 is formed (FIG. 1 (f)). The flattening film 52 is formed of acrylic resin, and the transparent electrode 60 is formed by stacking a transparent conductive material such as ITO and then patterning.

As described above, the TFT and the pixel electrode are formed on the substrate 10. These configurations are 1 of LCD
In a TFT LCD, TFTs and pixel electrodes corresponding to the number of pixels are formed on a matrix in a matrix corresponding to one pixel. Since the common electrode is formed on the liquid crystal layer via the liquid crystal layer, the potential of the pixel electrode is controlled by the TFT to control the voltage application of each pixel to the liquid crystal for display.

In the use of such a liquid crystal display device, a current flows through the gate electrode 12 because the TFT is turned on and off. The gate electrode 12 operates at a considerably high temperature due to heat generation when the current flows, irradiation of the backlight, and various other factors. The gate electrode 12 is formed of a thin film. Therefore, when the gate electrode 12 is used, electromigration is likely to occur, and the resistance value is likely to increase with continued use.

However, the gate electrode 12 of this embodiment is
At the stage of its formation, excimer laser annealing is performed using an excimer laser. When such excimer laser annealing is performed, the laser is efficiently absorbed by the Cr thin film, and the temperature becomes extremely high. Then, the atmosphere does not become too high and the cooling rate is fast. By such annealing, the crystal structure of Cr is changed, and almost all of the crystals have a {110} orientation.

That is, the Cr thin film simply laminated on the glass substrate 10 has a crystal structure of {11
The 0}, {200}, and {211} orientations are mixed, and the ratio γ of the {110} orientation is about 0.5 to 0.6. Here, γ is I {110} for the X-ray diffraction intensity from the {110} plane, I {200} for the X-ray diffraction intensity from the {200} plane, and I for the X-ray diffraction intensity from the {211} plane.
When {211} is set, γ = I {110} / [I {110} + I {200} + I
{211}] is calculated.

Then, for the Cr thin films formed in layers,
When the excimer laser annealing is performed, the ratio γ of {110} orientation becomes 0.7 to 1.0, and the ratio γ of {110} orientation becomes very large. And like this, {11
In a thin film in which almost all the 0} orientation is {11
The crystal diameter of the 0} orientation preferentially grows to a sufficient size, and electromigration that tends to occur at the boundary of the crystal diameter can be suppressed. Therefore, it is possible to effectively prevent the resistance value of the thin film from increasing even when a current is applied at a high temperature.

As a result, it is possible to prevent the resistance of the gate electrode of the transistor (TFT) for pixel drive control from increasing due to continuous use. Therefore, it is possible to prevent the operating characteristics of the transistor from deteriorating with continued use, and it is possible to obtain a high-quality LCD device. Such a high-quality display is particularly suitable for, for example, a display for a vehicle-mounted navigation device having a severe operating temperature environment.

Since the metal thin film is used as the gate wiring of the LCD and also as the gate electrode of the driver portion when the driver is built in the LCD panel, it is possible to prevent the resistance increase even with this gate electrode.

FIG. 2 shows a change in resistance value with continued use. As described above, in the gate electrode 12 not subjected to the laser annealing, the resistance value increased after being used for about 200 hours, and after being used for 1500 hours, the resistance value was increased to 4
The resistance value is increasing. On the other hand, in the gate electrode of this embodiment, the resistance value does not increase even after being used for 2000 hours. From this, it is understood that the gate electrode of the present embodiment suppresses an increase in resistance value due to continuous use. This data is 3 μm wide and 10 c long.
This is done for a Cr thin film having a thickness of m and a thickness of 100 nm. In addition, this excimer laser annealing is performed by E-met.
The er value was 1.8 mJ.

Further, FIG. 3 shows the result of the X-ray diffraction test for the sample of the metal thin film which was subjected to the excimer laser annealing. Thus, the Bragg angle in the figure is 44 °
There is a large peak of {110} plane in the vicinity. The intensity of reflection on each orientation surface in this sample is as follows: I {110} = 690, I {200} = 48, I {21
1} = 51.

Further, FIG. 4 shows the result of the X-ray diffraction test for the metal thin film sample before the excimer laser annealing. In this case, the reflection intensity on each orientation plane is I {110} = 324, I {200} = 70, I {21
1} = 67.

From this, it is understood that a Cr thin film having a strong {110} orientation can be obtained by excimer laser annealing.

[Others] In the above embodiments, only Cr has been described as a material for forming the metal thin film . However , other metals (for example, Ta) also tend to have the same orientation due to annealing, and the same treatment as in the present embodiment should be performed.
Is also suitable . Further, it can be suitably applied to metal wirings such as semiconductor integrated circuits other than liquid crystal display devices.

[0028]

As described above, according to the present invention,
Laser annealing the metal thin film. Therefore, it is possible to suppress the occurrence of electromigration due to the current flow in the metal thin film, and it is possible to suppress the increase in resistance.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a method of manufacturing a metal thin film according to an embodiment.

FIG. 2 is a diagram showing a change with time of a resistance change rate.

FIG. 3 is a diagram showing a result of an X-ray diffraction test on a sample of a metal thin film that has been subjected to excimer laser annealing.

FIG. 4 is a diagram showing a result of an X-ray diffraction test on a metal thin film sample before performing excimer laser annealing.

[Explanation of symbols]

10 glass substrate, 12 gate electrode, 14 gate insulating layer, 24 poly-Si layer, 30 injection stopper, 50
Insulating layer, 52 flattening film, 60 transparent electrode, 70 source electrode.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-2-39536 (JP, A) JP-A-1-225136 (JP, A) JP-A-4-369229 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 29/786 H01L 21/28 H01L 21/3205 H01L 21/336

Claims (6)

(57) [Claims] 1. After forming a metal thin film of Cr , the metal thin film is annealed using a laser to orient the {110} plane which is the closest packed surface of the metal crystals of the metal thin film. And a method for producing a metal thin film. 2. The X-ray diffraction intensity from the {110} plane is I
The X-ray diffraction intensities from the {110} and {200} planes are I {2
X-ray diffraction intensity from the {00} and {211} planes is I {21
1}, γ = I {110} / [I {110}
+ I {200} + I {211}]
The orientation ratio γ of the {110} plane in the film is 0.7 to 1.
It is 0, The manufacturing method of the metal thin film of Claim 1 characterized by the above-mentioned . 3. A metal thin film made of Cr to be a gate electrode is formed on a transparent substrate, and the metal thin film is annealed by using a laser beam to obtain a densest dense surface of metal crystals of the metal thin film. {110} plane orientation, and then the gold
A method of manufacturing a thin film transistor , which comprises patterning a metal thin film, forming a gate electrode, and forming an active region of the thin film transistor above the gate electrode . 4. The X-ray diffraction intensity from the {110} plane is I
The X-ray diffraction intensities from the {110} and {200} planes are I {2
X-ray diffraction intensity from the {00} and {211} planes is I {21
1}, γ = I {110} / [I {110}
+ I {200} + I {211}], the orientation ratio γ of the {110} plane in the metal thin film is 0.7 to 1.
4. The thin film transistor according to claim 3, which is 0.
Method of manufacturing the transistor . 5. A semiconductor device using a metal thin film made of Cr.
And the metal thin film is annealed using laser light after the film formation.
By reason, the orientation of the {110} plane, which is the densest dense surface of the metal crystal,
A semiconductor device using a metal thin film, which is characterized by having enhanced directivity . 6. The X-ray diffraction intensity from the {110} plane is I
The X-ray diffraction intensities from the {110} and {200} planes are I {2
X-ray diffraction intensity from the {00} and {211} planes is I {21
1}, γ = I {110} / [I {110}
+ I {200} + I {211}]
The orientation ratio γ of the {110} plane in the film is 0.7 to 1.
It is 0, The metal thin film of Claim 5 characterized by the above-mentioned.
Used semiconductor device.