JP3019533B2 - Method for manufacturing thin film transistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thin film transistor.

[0002]

2. Description of the Related Art Thin film transistors are used to drive pixels in liquid crystal displays and the like. Conventionally, this is formed through processes such as batch film formation by thermal CVD or plasma CVD, patterning by photolithography, and etching. This method is a multi-step process, and the device itself is likely to be damaged through the steps of applying and removing the resist. Therefore, there is a concern that the yield may decrease significantly as the display area increases. Have been.

[0003] One of the methods for realizing the reduction in the number of processes is as follows.
Attempts to apply laser CVD, which enables the formation of a patterned thin film without using a resist process, to TFT formation have been made in the 51st Annual Meeting of the Japan Society of Applied Physics.
-Zf-10. In the case of this report, when forming an ohmic contact between the drain and source electrodes and the semiconductor, a semiconductor film to be an ohmic layer is formed on the electrode, and a dopant material is applied. Is diffused into a semiconductor to form an ohmic layer, so that another step is required for forming an ohmic contact.

[0004]

[Problems that the Invention is to Solve] of such a conventional follower
It is difficult to fabricate a display panel with a high yield by a method using photolithography , and a multi-step process is required to form an ohmic contact by a conventional direct film formation method using a laser. An object of the present invention is to provide a film forming method which solves such problems of the conventional method.

[0005]

According to the present invention, in order to solve the problems of the prior art, a first laser beam is partially irradiated to a substrate surface in a raw material gas atmosphere for forming a metal thin film. Drain by forming a metal thin film pattern
After configuring each of the source electrodes, a semiconductor film is formed by irradiating a second laser beam in a source gas atmosphere for forming a semiconductor thin film so as to cover both the drain electrode and the source electrode at once. Next, the second laser beam is irradiated in a source gas atmosphere for forming an insulating film to form a gate insulating film. Thereafter, the third laser beam is irradiated in a source gas atmosphere for forming a metal thin film.
A laser beam is irradiated between the drain electrode and the source electrode to form a gate electrode, and finally, by ion doping using the gate electrode as a mask, the drain electrode and the semiconductor film on the source electrode are formed. A measure was taken to partially modify the layer to a high concentration impurity layer.

[0006]

When a substrate is irradiated with a laser beam in an atmosphere of a source gas for forming a metal, an insulating film, and a semiconductor film, a decomposition reaction of the source gas occurs at an irradiated portion to form a thin film. By patterning the laser light relative to the substrate or transferring the laser light through a mask having a desired pattern shape, a patterned thin film of any shape can be obtained. Using this film forming method, the drain and source electrodes are formed on a glass substrate, then the amorphous silicon film and the gate insulating film are formed on these electrodes in order, and finally the gate electrode is formed via the amorphous silicon film and the gate insulating film. By forming the TFT above the drain and source electrodes, the structure of the TFT other than the ohmic contact layer can be obtained without photolithography. Also, by doping impurity ions from the outermost surface using the gate electrode as a mask, the amorphous silicon on the drain and source electrodes becomes n ⁺ silicon or p ⁺ silicon, and the drain and source electrodes and the amorphous silicon are in ohmic contact. Will come in contact.

In the present invention, since no resist is used for pattern formation, damage to the semiconductor is small. Further, since the ohmic contact layer is also obtained by ion implantation using the gate electrode as a mask, multiple steps such as application, annealing, and removal of a dopant are not required.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Amorphous silicon TF on a quartz substrate
An embodiment in which the method according to the present invention is applied to forming T will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing the apparatus of the present invention.
As shown in FIG. 1A, a quartz substrate 2 is fixed on a stage 3 in a chamber 1. W (CO) as source gas
_The laser beam W is condensed on the surface of the quartz substrate 2 by the optical lens 5 emitted from the second harmonic 4 of the YAG laser using the ₆ , and the stage 3 is driven to sweep the quartz substrate 2, thereby forming the laser direct writing W. Then, a drain electrode 6 and a source electrode 7 are formed. Subsequently, as shown in FIG.
Using i ₂ H ₆ , light emitted from an ArF laser 8 passes through a mask 9, a lens 10 and a drain electrode 6, a source electrode 7.
Irradiation so as to cover both the amorphous silicon film 1
Form one. Subsequently, without stopping the irradiation of the ArF laser , only the raw material was changed to SiH ₄ and N ₂ O, and a gate insulating film was formed on the amorphous silicon film 11 as a gate insulating film.
An iO ₂ film 12 is formed. Subsequently, as shown in FIG. 1 (c), using W (CO) ₆ as a source gas, the light emitted from the second harmonic 4 of the YAG laser is condensed on the surface of the quartz substrate 2 by the lens 5 and the stage 3 To drive the quartz substrate 2
Is formed to form a laser direct writing W, and the gate electrode 13 is formed. Subsequently, as shown in FIG. 1D, the ion implantation apparatus 14 uses the gate electrode 3 as a mask,
An ohmic contact line 15 is formed by doping P ions at an acceleration voltage of 100 to 150 keV.

The light source for forming the drain, source and gate electrodes does not necessarily have to be the second harmonic of the YAG laser. An Ar laser or a copper vapor laser may be used. The electrode material is not necessarily required to be W, but may be Cr. In this case, Cr is used as the source gas.
(CO) ₆ is used. The impurity to be implanted is not necessarily P
And B may be used.

In the present invention, since no resist is used, the number of steps is small, and the device is not damaged, so that a TFT can be formed with a high yield. Also, since the ohmic contact is formed by ion implantation,
The number of steps is much smaller than the method of applying a dopant and diffusing the dopant.

[0012]

As described above, according to the method of the present invention, a TFT can be formed with a small number of steps and a high yield.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment to which the present invention is applied.

[Explanation of symbols]

Reference Signs List 1 chamber 2 quartz substrate 3 stage 4 second harmonic of YAG laser 5 lens 6 drain electrode 7 source electrode 8 ArF laser 9 mask 10 lens 11 amorphous silicon film 12 SiO ₂ film 13 gate electrode 14 ion implantation device 15 ohmic contact layer

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 29/786 H01L 21/336 H01L 21/205 H01L 21/285 H01L 21/316

Claims (1)

(57) [Claims] 1. A drain and a source electrode are formed by forming a metal thin film pattern by partially irradiating a laser beam in a source gas atmosphere for forming a metal thin film to form a metal thin film pattern. In a source gas atmosphere, a laser beam is irradiated in a shape covering both the drain electrode and the source electrode at a time to form a semiconductor film, and then a laser beam is irradiated in a source gas atmosphere for forming an insulating film. Forming a gate insulating film, and thereafter, irradiating a laser beam between the drain electrode and the source electrode in a source gas atmosphere for forming a metal thin film to form a gate electrode, and finally using the gate electrode as a mask A method of manufacturing a thin film transistor, wherein a part of the semiconductor film above the drain electrode and the source electrode is modified into a high concentration impurity layer by ion doping. Law.