JPH05109737A - Manufacture of thin film transistor - Google Patents

Abstract

PURPOSE:To eliminate crystal defect, impurities, etc., from an element activation region, at the time of manufacturing a thin film transistor. CONSTITUTION:On an insulative substrate 1, an amorphous silicon film 4 is deposited, thereon an oxide film 5 is formed, a photo resist mask 6 which is patterned and formed on the film 5 is us as a mask, and ions are implanted. Thereby only the amorphous silicon film 4 at the part corresponding to a region 3 where an element is not formed is turned into a high impurity region to forin a gettering layer 7. By laser annealing after the photo resist film 6 is eliminated, the amorphous silicon film 4 is crystallized to form a polycrystalline silicon film. At the same time, crystal defect, impurities, etc., in the amorphous silicon film 4 of the part corresponding to an element formation region 2 are made to be absorbed in a high impurity region 7 around the defect and impurities. After that, the oxide film 5 is eliminated, and the polycrystalline silicon film (the gettering layer 7) in unnecessary parts is eliminated by element isolation. In this state, the polycrystalline silicon film is formed only in the element formation region 2 on the insulative substrate 1.

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 transistor manufacturing technique using a silicon wafer, a gettering technique is used to remove crystal defects, impurities and the like from an element active region to obtain good element characteristics. On the other hand, in the thin film transistor manufacturing technology, since a semiconductor thin film made of amorphous silicon, polysilicon, or the like is deposited on an insulating substrate made of glass or the like and then elements are separated, the semiconductor thin film is patterned in the element formation region. The gettering technology used in the transistor manufacturing technology using a wafer cannot be used.

[0003]

As described above, in the conventional thin film transistor manufacturing technology, the gettering technology used in the transistor manufacturing technology using the silicon wafer cannot be utilized, so that crystal defects, impurities, etc. are eliminated. There is a problem in that it may not be possible to remove from the element active region, and eventually good element characteristics may not be obtained. An object of the present invention is to provide a method of manufacturing a thin film transistor capable of removing crystal defects, impurities and the like from an element active region.

[0004]

According to the present invention, a semiconductor thin film is deposited in a device forming region and a non-device forming region around the device forming region, and then only a portion of the semiconductor thin film corresponding to the non-device forming region is made into a high impurity region. A gettering layer is formed and then annealed so that crystal defects, impurities, etc. in the semiconductor thin film in the portion corresponding to the element formation region are absorbed in the surrounding gettering layer, and then the gettering layer is removed. is there.

[0005]

According to the present invention, only the semiconductor thin film in the portion corresponding to the non-element formation region is made into a high impurity region to form a gettering layer and then annealed to crystallize the semiconductor thin film in the portion corresponding to the element formation region. Defects, impurities, etc. are absorbed by the gettering layer around them, and the gettering layer is removed thereafter. Therefore, crystal defects, impurities, etc. can be removed from the element active region.

[0006]

1 to 4 show the 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, an amorphous silicon film 4 is deposited on a device forming region 2 on the upper surface of an insulating substrate 1 made of glass or the like and a non-device forming region 3 around the device forming region 2. Next, an oxide film 5 is formed on the upper surface of the amorphous silicon film 4 by thermal oxidation. Next, a photoresist film 6 is patterned on the upper surface of the oxide film 5 in the portion corresponding to the element formation region 2. Then, using the photoresist film 6 as a mask, ions of gettering such as phosphorus, boron, argon, oxygen, and carbon are implanted into the amorphous silicon film 4 in a portion corresponding to the non-element formation region 3 by an ion implantation device, Only the portion of the amorphous silicon film 4 corresponding to the non-element formation region 3 is made into a high impurity region and the gettering layer 7 is formed.
And After that, the photoresist film 6 is removed.

Next, as shown in FIG. 2, laser annealing is performed to crystallize the amorphous silicon film 4 to form a polysilicon film 8 and to crystallize the amorphous silicon film 4 in a portion corresponding to the element formation region 2. Defects and impurities are absorbed by the gettering layer 7 around the defects. After that, the oxide film 5 is removed, and then the unnecessary polysilicon film 8, that is, the gettering layer 7 in the portion corresponding to the non-element formation region 3 is removed by element isolation. Therefore, in this state, the element formation region 2 on the upper surface of the insulating substrate 1 is formed.
The polysilicon film 8 is formed only on the above.

Next, as shown in FIG. 3, a gate insulating film 9 made of silicon oxide, silicon nitride or the like is formed on the entire surface. Next, a gate electrode 11 made of aluminum is patterned on the upper surface of the gate insulating film 9 in a portion of the polysilicon film 8 corresponding to the channel region 10. Next, with the gate electrode 11 as a mask, source / drain forming ions such as phosphorus and boron are implanted by an ion implanter to form source / drain regions 12 in the polysilicon film 8 on both sides of the gate electrode 11.

Next, as shown in FIG. 4, an interlayer insulating film 13 made of silicon oxide, silicon nitride or the like is formed on the entire surface. Next, contact holes 14 are formed in the interlayer insulating film 13 and the gate insulating film 9 in the portions corresponding to the source / drain regions 12. Next, the source / drain electrode 15 made of aluminum and connected to the source / drain region 12 through the contact hole 14 is formed on the interlayer insulating film 13.
Pattern on the upper surface of the. Thus, the thin film transistor is manufactured.

In the thin film transistor manufactured as described above, only the amorphous silicon film 4 in the portion corresponding to the non-element formation region 3 is made into a high impurity region to form the gettering layer 7 and then annealed to obtain the element formation region 2
The crystal defects and impurities in the portion of the amorphous silicon film 4 corresponding to are absorbed in the gettering layer 7 around the crystal defects, and the gettering layer 7 is removed thereafter. It can be removed, and good device characteristics can be obtained. Further, the amorphous silicon film 4 is crystallized into the polysilicon film 8 by one annealing step, and at the same time, crystal defects, impurities, etc. in the amorphous silicon film 4 in the portion corresponding to the element formation region 2 are gettered around the amorphous silicon film 4. Can be absorbed in the layer 7, and due to element isolation,
Since the unnecessary polysilicon film 8 in the portion corresponding to the non-element formation region 4, that is, the gettering layer 7, is removed, the number of steps can be prevented from increasing as much as possible. Further, if the same ions as the source / drain forming ions are used as the gettering ions, the gettering ions can be implanted by the source / drain forming ion implantation apparatus.

In the above embodiment, the amorphous silicon film 4 deposited on the upper surface of the insulating substrate 1 is crystallized to form the polysilicon film 8. However, the present invention is not limited to this, and the polysilicon film is directly deposited on the upper surface of the insulating substrate. You may do so. Further, a thermal diffusion method may be used instead of the ion implantation apparatus, and high temperature heat treatment may be performed instead of laser annealing. Further, the invention can be applied not only to the coplanar type thin film transistor but also to a stagger type thin film transistor.

[0013]

As described above, according to the present invention, only the semiconductor thin film in the portion corresponding to the non-element formation region is made into a high impurity region to form a gettering layer and then annealed to form the element formation region. Since crystal defects, impurities, etc. in the corresponding portion of the semiconductor thin film are absorbed by the gettering layer around it and the gettering layer is removed thereafter, crystal defects, impurities, etc. can be removed from the element active region. As a result, good device characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a method of manufacturing a thin film transistor according to an embodiment of the present invention, in which an amorphous silicon film and an oxide film are formed on an upper surface of an insulating substrate, and a patterned photoresist film is used as a mask to generate ions for gettering. Sectional drawing of the state which inject | poured and formed the gettering layer.

FIG. 2 is a view showing a crystal defect in a portion of the amorphous silicon film corresponding to an element formation region, which is obtained by crystallizing the amorphous silicon film into a polysilicon film by laser annealing after removing the photoresist film in manufacturing the same thin film transistor. FIG. 6 is a cross-sectional view showing a state in which impurities such as impurities are absorbed by a gettering layer around the impurities.

FIG. 3 is a view showing an ion for forming a source / drain when a gate insulating film and a gate electrode are formed after removing an oxide film and an unnecessary polysilicon film (gettering layer) in manufacturing the same thin-film transistor. FIG. 4 is a cross-sectional view showing a state where source / drain regions are formed by implanting silicon.

FIG. 4 is a cross-sectional view showing a state in which an interlayer insulating film, contact holes, and source / drain electrodes are formed in manufacturing the same thin film transistor.

[Explanation of symbols]

 1 Insulating Substrate 2 Element Forming Area 3 Non-Element Forming Area 4 Amorphous Silicon Film 5 Oxide Film 7 Gettering Layer 8 Polysilicon Film

Claims (1)

[Claims] 1. A semiconductor thin film is deposited on an element formation region and a non-element formation region around the element formation region, and then only a portion of the semiconductor thin film corresponding to the non-element formation region is made into a high impurity region to form a gettering layer. By annealing, a crystal defect, an impurity, or the like in the semiconductor thin film in a portion corresponding to the element forming region is absorbed in the gettering layer around it, and then the gettering layer is removed. Production method.