JPH04360580A - Field-effect transistor and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce the number of manufacturing steps, and to efficiently form a micro-offset gate region by providing an anodized film at least on the side face of a gate electrode, and making the side of the film correspond to the boundary face between a channel region of a semiconductor layer and a source/ drain region. CONSTITUTION:With an aluminum film 4 formed on a gate insulating film 3 of a part of a semiconductor layer 2, corresponding to a channel region 2a as a mask an ion implantation is conducted to form a source/drain region 2b. A surface of the film 4 is anodized to form an aluminum oxide film 5, and a gate electrode 6 is formed of the film 4 which is not anodized. Thus, the side of the film 5 corresponding to a boundary between the region 2a of the layer 2 and the region 2b, the thickness of the film 5 becomes a length L of an offset gate region 2c, and the region 2c can be efficiently formed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field effect transistor and a method of manufacturing the same.

0002

2. Description of the Related Art Among field effect transistors, there is a type called an offset gate structure as an element designed to reduce leakage current. In such a field effect transistor, the length of the gate electrode is made smaller than the channel length of a semiconductor layer made of polysilicon or the like, so that the channel regions on both sides of the gate electrode are made into offset gate regions. . When manufacturing such a conventional field effect transistor, first a polysilicon layer is patterned on the top surface of an insulating substrate made of ceramic, glass, etc., this polysilicon layer is covered with a gate insulating film, and then a polysilicon layer is formed. A photoresist film is patterned on the upper surface of the gate insulating film in a portion corresponding to the channel region, and ions are implanted using this photoresist film as a mask to form source/drain regions in the polysilicon layer on both sides of the photoresist film. After that, the photoresist film is removed and activated to diffuse ions, and then a layer narrower than the channel region is formed on the upper surface of the gate insulating film in a portion of the polysilicon layer corresponding to the center of the channel region. The gate electrode is patterned so that the channel regions on both sides of the gate electrode are offset gate regions.

0003

[Problems to be Solved by the Invention] However, in the conventional manufacturing method of such a field effect transistor, compared to manufacturing a normal field effect transistor, it is difficult to mask the gate electrode made of, for example, polysilicon. Compared to the case where ion implantation is performed as an ion implantation method, there is a problem that the number of manufacturing steps is increased due to the step of patterning a photoresist film for an ion implantation mask and the step of removing it, resulting in higher costs. Furthermore, if the length of the offset gate region (L; see Figure 3) is large, the on-current of the field effect transistor will decrease, so it is desirable that the length of the offset gate region be as small as 1μ or less. Since the resist film forming process and the gate electrode forming process are separate, it is not possible to form the offset gate region efficiently, and therefore high processing accuracy is required.
There was a problem that the cost became even higher. An object of the present invention is to provide a field effect transistor and a method for manufacturing the same, which can reduce the number of manufacturing steps and efficiently form a minute offset gate region.

0004

[Means for solving the problem] The invention according to claim 1 includes:
In a field effect transistor in which the length of the gate electrode is smaller than the channel length of the semiconductor layer, an anodic oxide film is provided on at least the longitudinal side of the gate electrode, and the side of the anodic oxide film is formed on the side of the semiconductor layer. This corresponds to the interface between the channel region and the source/drain region. The invention according to claim 4 provides a method of forming a gate insulating film on a semiconductor layer, forming an aluminum film on the gate insulating film in a portion corresponding to a channel region of the semiconductor layer, and performing ion implantation using the aluminum film as a mask. By performing this step, source/drain regions are formed in the semiconductor layer on both sides of the aluminum film, and by anodizing the surface of the aluminum film, an aluminum oxide film is formed on the surface of the aluminum film, and an anode is formed on the surface of the aluminum film. The gate electrode is formed of the aluminum film that is not oxidized.

[0005]

[Operation] According to the present invention, an anodic oxide film is provided on at least the side surface of the gate electrode, and the side surface of the anodic oxide film is made to correspond to the interface between the channel region and the source/drain region of the semiconductor layer. Therefore, it is sufficient to provide an anodic oxide film on at least the side surfaces of the gate electrode, and the number of manufacturing steps can be reduced compared to the conventional case where a photoresist film for an ion implantation mask is patterned and then removed. Furthermore, the thickness of the anodic oxide film can be used as it is for the offset gate region, and by controlling the thickness of the anodic oxide film, the offset gate region can be efficiently formed.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, FIG. 4 shows the structure of a field effect transistor according to an embodiment of the present invention. In this field effect transistor, a polysilicon layer (semiconductor layer) is formed on the top surface of an insulating substrate 1 made of ceramic, glass, etc.
A gate insulating film 3 made of silicon oxide or the like is provided on the upper surface of the polysilicon layer 2, and a gate insulating film 3 made of silicon oxide or the like is provided on the upper surface of the polysilicon layer 2. ) A gate electrode 6 made of aluminum is provided on the upper surface of the gate insulating film 3 in a portion corresponding to 1.), an aluminum oxide film (anodized film) 5 is provided on the surface of the gate electrode 6, and Source/drain regions 2b are formed in the polysilicon layer 2, channel regions 2a on both sides of the gate electrode 6 are used as offset gate regions 2c, and an interlayer insulating film 7, a contact hole 8, and a source/drain electrode 9 are provided. It has a structure.

Next, to explain the case of manufacturing a field effect transistor having such a structure, first, as shown in FIG. 1, an insulating substrate 1 made of ceramic, glass, etc.
A polysilicon layer 2 is patterned on the top surface. next,
As shown in FIG. 2, a gate insulating film 3 made of silicon oxide or the like is formed on the entire surface, and the polysilicon layer 2 is covered with this gate insulating film 3. Next, an aluminum film 4 for forming a gate electrode and the like is patterned on the upper surface of the gate insulating film 3 in a portion of the polysilicon layer 2 corresponding to the channel region 2a. Next, by performing ion implantation using the aluminum film 4 as a mask, source/drain regions 2b are formed in the polysilicon layer 2 on both sides of the aluminum film 4, and then activation is performed by excimer laser irradiation or the like to implant ions. Spread.

Next, as shown in FIG. 3, the surface of the aluminum film 4 is anodic oxidized.
An aluminum oxide film 5 is formed on the surface of the aluminum film 4, and a gate electrode 6 is formed from the aluminum film 4 which is not anodized. In this case, the aluminum oxide film 5 may be porous or non-porous depending on the selection of the anodic oxidation solution, but it is preferable that it be dense and non-porous with no surface roughness. Further, by selecting the anodic oxidation conditions such as the applied voltage, it is possible to set the thickness of the aluminum oxide film 5 to about 0.1 μm. In this way, a gate electrode 6 narrower than the channel region 2a is formed on the upper surface of the gate insulating film 3 in a portion of the polysilicon layer 2 corresponding to the center of the channel region 2a, and the channel regions on both sides of the gate electrode 6 are formed. 2a becomes an offset gate region 2c.

Next, as shown in FIG. 4, an interlayer insulating film 7 made of silicon nitride or the like is formed on the entire surface. in this case,
The aluminum oxide film 5 forms an interlayer insulating film together with the interlayer insulating film 7. Next, the interlayer insulating film 7 and the gate insulating film 3 are etched to form the source/drain regions 2b.
A contact hole 8 is formed in a portion corresponding to . Next, the source/drain region 2 is connected through the contact hole 8.
A source/drain electrode 9 made of aluminum and connected to b is formed on the upper surface of the interlayer insulating film 7. In this way, a field effect transistor with an offset gate structure is manufactured.

In the field effect transistor manufactured in this manner, ions are implanted using the aluminum film 4 for forming the gate electrode 6 etc. as a mask. The number of manufacturing steps can be reduced compared to the case where the film is patterned and then removed. In addition, by anodizing the surface of the aluminum film 4, the aluminum film 4
Since the aluminum oxide film 5 is formed on the surface of the polysilicon layer 2 and the gate electrode 6 is formed by the aluminum film 4 which is not anodized, the side surfaces of the aluminum oxide film 5 are connected to the channel region 2a and the source/drain region 2b of the polysilicon layer 2. The length L of the offset gate region 2c corresponds to the boundary surface with the aluminum oxide film 5, and the thickness of the aluminum oxide film 5 remains unchanged (however, the amount of diffusion due to annealing is not taken into consideration).
becomes. Therefore, the offset gate region 2c can be formed efficiently, and if the amount of diffusion after ion implantation is considered, the length L of the offset gate region 2c can be automatically adjusted by controlling the thickness of the aluminum oxide film 5. It is also possible to control the Furthermore, since the aluminum oxide film 5 forms an interlayer insulating film together with the interlayer insulating film 7, there are two interlayer insulating films, which can contribute to reducing interlayer short circuits.

[0011] In the above embodiment, the present invention is applied to a TFT (thin film transistor) using a semiconductor thin film, but the present invention is not limited to this, and can be applied to a field effect transistor star using a single crystal semiconductor substrate. It can also be applied. Moreover, it can be applied not only to the coplanar type but also to the staggered type. In this case, ion implantation and diffusion may be performed after the gate electrode is anodized.

0012

As explained above, according to the present invention, an anodic oxide film is provided on at least the side surface of the gate electrode, and the side surface of the anodic oxide film is used as the boundary between the channel region and the source/drain region of the semiconductor layer. Since it is made to correspond to the surface, it is only necessary to provide an anodic oxide film on at least the side surfaces of the gate electrode, compared to the conventional case where a photoresist film for an ion implantation mask is patterned and then removed. The number of manufacturing steps can be reduced, and the thickness of the anodic oxide film can be used as is for the offset gate region, and by controlling the thickness of the anodic oxide film, the offset gate region can be efficiently formed. This can lead to cost reductions.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a state in which a polysilicon layer is formed on the upper surface of an insulating substrate during manufacturing of a field effect transistor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a state in which ions are implanted using the aluminum film as a mask after forming a gate insulating film and an aluminum film in manufacturing the same field effect transistor.

FIG. 3 is a cross-sectional view of an aluminum oxide film and a gate electrode formed by anodic oxidation during manufacture of the same field-effect transistor.

FIG. 4 is a cross-sectional view of a state in which an interlayer insulating film, contact holes, and source/drain regions are formed during manufacturing of the same field-effect transistor.

[Explanation of symbols]

1 Insulating substrate 2 Polysilicon layer (semiconductor layer) 2a Channel region 2b Source/drain region 2c Offset gate region 3 Gate insulating film 4 Aluminum film 5 Aluminum oxide film (anodized oxide film) 6 Gate electrode

Claims (4)

[Claims] 1. In a field effect transistor in which the length of the gate electrode is smaller than the channel length of the semiconductor layer, an anodic oxide film is provided on at least the side surfaces of the gate electrode in the length direction, and the side surfaces of the anodic oxide film are provided with an anodic oxide film. A field effect transistor characterized in that: corresponds to an interface between a channel region and a source/drain region of the semiconductor layer. 2. The field effect transistor according to claim 1, which has a TFT structure. 3. The field effect transistor according to claim 1, wherein the gate electrode is made of aluminum, and the anodic oxide film is made of aluminum oxide. 4. Forming a gate insulating film on the semiconductor layer,
An aluminum film is formed on the gate insulating film in a portion corresponding to the channel region of the semiconductor layer, and ions are implanted using the aluminum film as a mask, thereby injecting a source into the semiconductor layer on both sides of the aluminum film.
An electric field characterized in that an aluminum oxide film is formed on the surface of the aluminum film by forming a drain region and anodizing the surface of the aluminum film, and a gate electrode is formed by the aluminum film that is not anodized. A method of manufacturing an effect type transistor.