JP3143967B2 - 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 In a method of manufacturing a thin film transistor, an amorphous silicon film is formed on an upper surface of an insulating substrate such as a glass substrate, and the amorphous silicon film is irradiated with an excimer laser to convert the amorphous silicon film into polysilicon. A polysilicon film is formed, and an impurity implanted region serving as a source / drain region is formed by implanting impurities such as phosphorus ions into a portion of the polysilicon film other than a channel formation region, and an excimer laser is again applied to activate the impurity implanted region. There is a method of manufacturing a thin film transistor by irradiating and then performing a predetermined process.

[0003]

However, in such a conventional method of manufacturing a thin film transistor, two times of laser irradiation for turning the amorphous silicon film into polysilicon and laser irradiation for activating the impurity implantation region are used. Since laser irradiation is performed, there is a problem that the number of manufacturing steps is large. An object of the present invention is to provide a method for manufacturing a thin film transistor which can reduce the number of manufacturing steps.

[0004]

SUMMARY OF THE INVENTION The present invention, silicon in a portion except for the channel formation region of the amorphous silicon film
Impurities are implanted through an oxide film to form an impurity-implanted region, and thermal annealing is performed to convert the amorphous silicon film channel formation region into polysilicon and activate the impurity-implanted region. A gate insulating film is formed thereon.

[0005]

According to the present invention, after forming an impurity-implanted region by impurity implantation in a portion except for a channel-forming region of an amorphous silicon film, a thermal annealing process is performed to convert the amorphous silicon film's channel-forming region into polysilicon. At the same time, since the impurity implantation region is activated,
Polysiliconization and activation can be performed simultaneously by a single thermal annealing process, so that the number of manufacturing steps can be reduced.

[0006]

1 to 3 show the steps of manufacturing a thin film transistor according to an embodiment of the present invention. Therefore, a method for manufacturing a thin film transistor will be described with reference to these drawings in order.

First, as shown in FIG. 1, an underlying silicon oxide film 2 is formed on an upper surface of an insulating substrate 1 made of a glass substrate or the like. Next, an amorphous silicon film 3 is formed on the upper surface of the underlying silicon oxide film 2. Next, a surface protection silicon oxide film 4 is formed on the upper surface of the amorphous silicon film 3. Next, a photoresist film 6 is pattern-formed on the upper surface of the surface protection silicon oxide film 4 at a portion corresponding to the channel formation region 5 of the amorphous silicon film 3. next,
Using the photoresist film 6 as a mask, impurity implantation regions 7 serving as source / drain regions are formed on both sides of the channel formation region 5 of the amorphous silicon film 3 by implanting impurities such as phosphorus ions.

Next, the photoresist film 6 and the surface protection silicon oxide film 4 are removed by etching (see FIG. 2). Next, when a thermal annealing process is performed at a temperature of about 600 ° C. for 24 hours to 72 hours, the channel forming region 5 of the amorphous silicon film 3 is converted into polysilicon, and simultaneously the impurity implantation region 7 is activated. In this manner, since the channel formation region 5 of the amorphous silicon film 3 is converted to polysilicon and the impurity implantation region 7 is activated at the same time, the conversion to polysilicon and activation can be performed simultaneously by a single thermal annealing process. Therefore, the number of manufacturing steps can be reduced.

Next, as shown in FIG. 3, a gate insulating film 8 made of silicon oxide, silicon nitride or the like is formed on the entire surface. Next, a contact hole 9 is formed in the gate insulating film 8 in a portion corresponding to the impurity implantation region 7. Next, a gate electrode 10 made of aluminum or the like is pattern-formed on the upper surface of the gate insulating film 8 in a portion corresponding to the channel formation region 5, and at the same time, the source / drain connected to the impurity implantation region 7 via the contact hole 9 is formed. Electrode 11
Is formed on the upper surface of the gate insulating film 8 by patterning. Thus, a thin film transistor is manufactured.

When impurities such as phosphorus ions are implanted into the amorphous silicon film 3 using the photoresist film 6 as a mask, the impurities are expanded in the lateral direction due to the annealing treatment. Therefore, as shown in FIG. 4, the dimension of the photoresist film 6 is increased by the extent of this spread, and
As shown in (2), the channel length of the channel forming region 5 is set to a predetermined length after the annealing process.

[0011]

As described above, according to the present invention, after an impurity implantation region is formed in a portion of an amorphous silicon film excluding a channel formation region by impurity implantation,
Since the thermal annealing process is performed to convert the amorphous silicon film channel formation region to polysilicon and activate the impurity implantation region at the same time, the polysilicon formation and activation can be performed simultaneously by a single thermal annealing process. Therefore, the number of manufacturing steps can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a state in which an impurity implanted region is formed by implanting an impurity into a portion excluding a channel formation region of an amorphous silicon film formed on an insulating substrate in manufacturing a thin film transistor according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state in which a channel forming region of an amorphous silicon film is converted into polysilicon and an impurity implantation region is activated by performing thermal annealing in manufacturing the thin film transistor.

FIG. 3 is a cross-sectional view showing a state where a gate electrode and a source / drain electrode are formed in manufacturing the thin film transistor.

FIG. 4 is a sectional view similar to FIG. 1 when the thin film transistor is actually manufactured.

FIG. 5 is a sectional view of a state similar to FIG. 2 when the thin film transistor is actually manufactured.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 3 Amorphous silicon film 5 Channel formation region 7 Impurity implantation region

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 29/786 H01L 21/265 H01L 21/336

Claims (1)

(57) [Claims] An impurity is implanted into a portion of the amorphous silicon film excluding a channel formation region through a silicon oxide film to form an impurity implantation region, and a thermal annealing process is performed to thereby form a channel formation region of the amorphous silicon film. Forming a gate insulating film thereon after activating the impurity-implanted region at the same time as turning the polysilicon into polysilicon.