JPH05235031A - Manufacture method of thin film transistor - Google Patents

Abstract

PURPOSE:To lessen the numbers of manufacturing steps while improving the crystal structure of polysilicon thin film. CONSTITUTION:An amorphous silicon thin film 3 is deposited on the surface of an insulating substrate 1. Next, impurities are implanted in the source.drain formation regions 3a of an amorphous silicon thin film 3 using a photoresist film 4 as a mask so as to form impurity implanted regions 5. Later, the photoresist film 4 is removed. Next, when the whole surface is irradiated with excimer laser, the amorphous silicon thin film 3 is polycrystallized simultaneously implanting impurities to activate the impurity implanted regions 5. Through these procedures, both polycrystallization and activation can be performed by only one time excimer laser irradiating step thereby enabling the crystal structure of a polysilicon thin film to be improved.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art In a method of manufacturing a thin film transistor, an amorphous silicon thin film is deposited on an upper surface of an insulating substrate such as a glass substrate and CW is applied to the amorphous silicon thin film.
The amorphous silicon thin film is polycrystallized by irradiating a laser to form a polysilicon thin film, and impurities such as boron ions are implanted into the source / drain formation region of this polysilicon thin film to form an impurity implantation region. There is a method of manufacturing a thin film transistor by irradiating a CW laser again to activate a region and then performing a predetermined process.

[0003]

However, in the conventional method for manufacturing such a thin film transistor, there are two methods of CW laser irradiation for polycrystallizing the amorphous silicon thin film and CW laser irradiation for activating the impurity implantation region. Since the CW laser irradiation is performed once, there is a problem that the number of manufacturing steps increases. In addition, since polycrystallization by CW laser irradiation is solid phase growth, the crystal structure of the polysilicon thin film is poor, and therefore the mobility is 10 cm ² / V.
There was a problem that it was relatively small at about sec. An object of the present invention is to provide a method of manufacturing a thin film transistor which can reduce the number of manufacturing steps and can improve the crystal structure of a polysilicon thin film.

[0004]

According to the present invention, an amorphous silicon thin film is deposited on an insulating substrate, impurities are injected into a source / drain formation region of the amorphous silicon thin film to form an impurity injection region, and then an excimer laser is formed. Is applied to polycrystallize the amorphous silicon thin film and simultaneously activate the impurity implantation region.

[0005]

According to the present invention, an impurity is injected into the source / drain formation region of the amorphous silicon thin film to form the impurity injection region, and then the excimer laser is irradiated to polycrystallize the amorphous silicon thin film and at the same time the impurity is injected. Since the region is activated, polycrystallization and activation can be performed at the same time by one excimer laser irradiation, so that the number of manufacturing steps can be reduced. In addition, since polycrystallization by excimer laser irradiation is liquid phase growth, the crystal structure of the polysilicon thin film can be improved.

[0006]

1 to 7 show respective steps of manufacturing a thin film transistor according to an embodiment of the present invention. Therefore, a method of manufacturing a thin film transistor will be described with reference to these drawings in order.

First, as shown in FIG. 1, a hydrogenated amorphous silicon thin film 2 is deposited on the upper surface of an insulating substrate 1 made of a glass substrate or the like by plasma CVD using a mixed gas of SiH ₄ and H ₂ . In this case, increase the temperature of the insulating substrate 1
About 0 to 350 ° C, preferably about 250 ° C, 10
˜20 SCCM of SiH ₄ and 10 times H ₂ mixed gas is used, and the thickness of the hydrogenated amorphous silicon thin film 2 is about 400 to 1000 Å, preferably 500 Å
Try to be around. Then, the hydrogen content of the hydrogenated amorphous silicon thin film 2 is 10 to 20 atomic%.
It becomes a degree. Next, in a subsequent step, dehydrogenation treatment is performed in order to prevent hydrogen from bumping and causing defects when high energy is applied by excimer laser irradiation. In this case, N
Heat treatment is performed in a ₂ atmosphere at a temperature of about 450 ° C. for about 1 hour so that the hydrogen content is 3 atomic% or less, preferably 1 atomic% or less. This dehydrogenation treatment can be performed on several tens to several hundreds of insulating substrates 1 at once.

Next, as shown in FIG. 2, a photoresist film 4 is pattern-formed on the upper surface of the portion of the amorphous silicon thin film 3 after the dehydrogenation treatment other than the source / drain formation region 3a. Then, using the photoresist film 4 as a mask, impurities such as boron ions are implanted into the source / drain formation region 3a of the amorphous silicon thin film 3 to form an impurity implantation region 5. Then, the photoresist film 4 is removed.

Next, as shown in FIG. 3, the wavelength is 308 nm.
XeCl excimer laser with an energy density of 250-35
When the irradiation is performed with a pulse width of about 0 mJ / cm ² and a pulse width of about 50 nsec, the amorphous silicon thin film 3 is polycrystallized to become the polysilicon thin film 6 and at the same time the impurity implantation region 5 is activated. In this way, the amorphous silicon thin film 3
Since the impurity implantation region 5 is activated at the same time as polycrystallization, the polycrystallization and activation can be performed simultaneously by one excimer laser irradiation, and therefore the number of manufacturing steps can be reduced. In addition, since polycrystallization by excimer laser irradiation is liquid phase growth, the polysilicon thin film 6
The crystal structure of can be improved, and the mobility can be increased. In addition, XeC with a wavelength of 308 nm
l Excimer laser, KrF with wavelength of 248 nm,
193 nm wavelength ArF, 175 nm wavelength ArCl,
Of course, an excimer laser such as XeF having a wavelength of 353 nm may be used.

Next, as shown in FIG. 4, unnecessary parts of the polysilicon thin film 6 are removed by element isolation. In this state, the central portion of the polysilicon thin film 6 is a channel region 6a, and both sides thereof are source / drain regions 6b made of activated impurity regions. Next, as shown in FIG. 5, a gate insulating film 7 made of a silicon oxide film and a silicon nitride film is formed on the entire surface. That is, first, a silicon oxide film is deposited on the entire surface by sputtering, and then a silicon nitride film is deposited on the surface of this silicon oxide film by plasma CVD using a mixed gas of SiH ₄ , NH _3, and N ₂ . When depositing a silicon nitride film by plasma CVD, the temperature of the insulating substrate 1 is about 250 ° C., SiH ₄ is about ₃₀ SCCM, and NH ₃ is 60 SC.
CM, N ₂ about 390 SCCM, output 6
When the pressure is set to about 00 W and the pressure is set to about 0.5 Torr, the polysilicon thin film 6 is simultaneously hydrogenated and the dangling bond thereof is reduced. Next, the gate electrode 8 made of Cr is formed on the upper surface of the gate insulating film 7 corresponding to the channel region 6a.
To form a pattern.

Next, as shown in FIG. 6, an interlayer insulating film 9 made of silicon nitride or the like is formed on the entire surface. Next, contact holes 10 are formed in the interlayer insulating film 9 and the gate insulating film 7 in the portions corresponding to the source / drain regions 6b. Next, as shown in FIG. 7, source / drain electrodes 11 made of Al and connected to the source / drain regions 6 b through the contact holes 10 are patterned on the upper surface of the interlayer insulating film 9. The field-effect thin film transistor thus obtained had a mobility of 80 cm ² / V · sec or more, and it was confirmed that the crystal structure of the polysilicon thin film 6 was extremely good.

In the above embodiment, the dehydrogenation process is performed after the hydrogenated amorphous silicon thin film 2 is deposited by plasma CVD, but the invention is not limited to this. For example, amorphous silicon containing no hydrogen by LPCVD. A thin film may be deposited. In this case, the temperature of the insulating substrate 1 when the amorphous silicon thin film containing no hydrogen is deposited by LPCVD is set to 500 to
The temperature is set to about 600 ° C., and the energy density of the excimer laser for polycrystallization and activation is set to about 400 mJ / cm ² . Therefore, in this case, it is not necessary to perform the dehydrogenation process, but since the temperature of the insulating substrate 1 is set to a relatively high temperature of about 500 to 600 ° C., it takes an extra time to raise the substrate temperature. become.

Further, in the above embodiment, the case where the present invention is applied to the thin film transistor having the normal MOS structure has been described. However, compared with the thin film transistor having the normal MOS structure, the breakdown voltage is improved and the reliability is improved. It can also be applied to a thin film transistor having an LDD structure. For example, in the thin film transistor having the LDD structure shown in FIG. 8 in which the same names are given to the parts having the same names as those of FIG. The region 6b is formed, and the source / drain regions 6c having a high impurity concentration are formed on both sides thereof. When manufacturing the thin film transistor having the LDD structure, for example, in a state as shown in FIG. 2, a low concentration is formed in a portion where the source / drain region 6b having a low impurity concentration and the source / drain region 5c having a high impurity concentration are to be formed. Impurities are implanted, then the photoresist film 4 is removed, and then another photoresist film is formed on the upper surface of the portion other than the portion where the source / drain regions 6c having a high impurity concentration are to be formed. With the mask as a mask, a high-concentration impurity may be implanted into a portion where the source / drain region 6c having a high impurity concentration should be formed.

Further, in the above embodiment, the case where the present invention is applied to the top gate type coplanar structure thin film transistor is explained, but it is also applicable to the stagger structure or back gate type coplanar or stagger structure thin film transistor. Of course. In the case of the back gate type, the gate electrode and the gate insulating film are formed on the upper surface of the insulating substrate, and the amorphous silicon thin film is deposited on the gate electrode and the gate insulating film.
This amorphous silicon thin film is polycrystallized to form a polysilicon thin film. When the polysilicon thin film is hydrogenated, it can be performed at the same time when the passivation film is deposited by plasma CVD.

[0015]

As described above, according to the present invention, after the impurities are implanted into the source / drain formation regions of the amorphous silicon thin film to form the impurity implantation regions,
Since the amorphous silicon thin film is polycrystallized by irradiating the excimer laser and the impurity implantation region is activated at the same time, polycrystallization and activation can be simultaneously performed by one excimer laser irradiation, thus reducing the number of manufacturing steps. Can be reduced. Further, since polycrystallization by the excimer laser irradiation is liquid phase growth, the crystal structure of the polysilicon thin film can be improved, and the mobility can be increased accordingly.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a state in which a hydrogenated amorphous silicon thin film is deposited on an upper surface of an insulating substrate when manufacturing a thin film transistor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a state where impurities are implanted into a source / drain formation region of an amorphous silicon thin film after dehydrogenation, in manufacturing the same thin film transistor.

FIG. 3 is a cross-sectional view showing a state in which an amorphous silicon thin film is polycrystallized and at the same time an impurity implantation region is activated by irradiating an excimer laser in manufacturing the same thin film transistor.

FIG. 4 is a cross-sectional view showing a state in which an unnecessary portion of the polysilicon thin film is removed by element isolation in manufacturing the same thin film transistor.

FIG. 5 is a cross-sectional view of a state in which a gate insulating film and a gate electrode are formed in manufacturing the same thin film transistor.

FIG. 6 is a cross-sectional view showing a state in which an interlayer insulating film and a contact hole are formed in manufacturing the same thin film transistor.

FIG. 7 is a cross-sectional view showing a state where source / drain electrodes are formed in manufacturing the same thin film transistor.

8 is a sectional view similar to FIG. 7 when the present invention is applied to a thin film transistor having an LDD structure.

[Explanation of symbols]

 1 Insulating Substrate 3 Amorphous Silicon Thin Film 3a Source / Drain Formation Region 4 Photoresist Film 5 Impurity Injection Region

[Procedure amendment]

[Submission date] December 17, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art In a method of manufacturing a thin film transistor, an amorphous silicon thin film is deposited on an upper surface of an insulating substrate such as a glass substrate and CW is applied to the amorphous silicon thin film.
The amorphous silicon thin film is polycrystallized by laser irradiation to form a polysilicon thin film, and impurities such as phosphorus ions and boron ions are injected into the source / drain formation regions of the polysilicon thin film to form impurity injection regions. There is a method of irradiating a CW laser again to activate the impurity-implanted region, and then manufacturing a thin film transistor through a predetermined process.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

Next, as shown in FIG. 2, a photoresist film 4 is pattern-formed on the upper surface of the portion of the amorphous silicon thin film 3 after the dehydrogenation treatment other than the source / drain formation region 3a. Next, using the photoresist film 4 as a mask, impurities such as phosphorus ions and boron ions are implanted into the source / drain formation regions 3a of the amorphous silicon thin film 3 to form impurity implantation regions 5. Then, the photoresist film 4 is removed.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 21/208 M 7353-4M 21/265 21/268 Z 8617-4M

Claims (3)

[Claims] 1. An amorphous silicon thin film is deposited on an insulating substrate, impurities are injected into a source / drain formation region of the amorphous silicon thin film to form an impurity injection region, and then an excimer laser is irradiated to the amorphous silicon thin film. A method of manufacturing a thin film transistor, comprising polycrystallizing a silicon thin film and activating the impurity implantation region at the same time. 2. The method of manufacturing a thin film transistor according to claim 1, wherein the thickness of the amorphous silicon thin film is about 400 to 1000 Å. 3. The energy density of the excimer laser is 2
The method of manufacturing a thin film transistor according to claim ^{2, wherein the} thickness is about 50 to 350 mJ / cm ² .