JPH11261101A - Manufacture of photosensor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photosensor equipped with a double gate thin-film transistor, wherein a source electrode and a drain electrode are protected against disconnections, and the phorosensor is prevented from deteriorating in characteristics, even if a top gate insulating film is enlarged in thickness. SOLUTION: A top gate insulating film is of two-layered structure composed of a first top gate insulating film 25, which serves also as a blocking layer and a second top gate insulating film 30. Therefore, when the first top gate insulating film 25 which serves as a blocking layer is lessened in thickness as much as possible, the edge of the insulating film 25 becomes low in height, so that a source electrode 27 and a drain electrode 28 can be prevented from being disconnected at the edge of the insulating film 25. As shown in figure (c), after the source electrode 27 and the drain electrode 28 have been formed, the exposed surface of the first top gate insulating film 25 that serves as a block layer is subjected to a contaminate removal treatment, whereby a photosensor of this constitution can be prevented from deteriorating in characteristics.

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 photo sensor element having a double gate type thin film transistor.

[0002]

2. Description of the Related Art FIG. 3 is a cross-sectional view of a part of an example of a photosensor element having a conventional double gate type thin film transistor (see, for example, Japanese Patent Application Laid-Open No. 6-342929). This photosensor element has a transparent substrate 1. A bottom gate electrode 2 is provided at a predetermined position on the upper surface of the transparent substrate 1, and a bottom gate insulating film 3 is provided on the entire upper surface. A semiconductor layer 4 made of amorphous silicon is provided on a portion corresponding to the bottom gate electrode 2 on the upper surface of the bottom gate insulating film 3.
A blocking layer / top gate insulating film 5 is provided at the center of the upper surface of the semiconductor layer 4. N ⁺ silicon layers 6 and 7 are provided on both sides of the upper surface of the blocking layer / top gate insulating film 5 and both sides of the upper surface of the semiconductor layer 4. A source electrode 8 and a drain electrode 9 are provided on the upper surfaces of the n ⁺ silicon layers 6 and 7 and the upper surface of the bottom gate insulating film 3. At the center of the upper surface of the blocking layer / top gate insulating film 5, a top gate electrode 10 is formed and formed at the same time as the formation of the source electrode 8 and the drain electrode 9.

[0003]

By the way, in such a conventional photosensor device, since the top gate electrode 10 is provided on the semiconductor layer 4 via the blocking layer and the top gate insulating film 5, the blocking layer and the top gate electrode 10 are provided. In order to prevent interlayer defects due to defects in the top gate insulating film 5, the thickness of the blocking layer and the top gate insulating film 5 needs to be as large as possible, for example, about 2000 to 3000 °. However, when the thickness of the blocking layer / top gate insulating film 5 is increased, the height of the end portion of the blocking layer / top gate insulating film 5 is increased, and the n ⁺ silicon layer 6 overlapping the end portion is provided. , 7, the source electrode 8 and the drain electrode 9 may be disconnected at the end portions. Also,
When the thickness of the blocking layer and the top gate insulating film 5 is increased, the etching time (over-etching time) when the film is etched with an etching solution (BHF) becomes longer. There is a problem that the damage given to the bottom gate insulating film 3 through the hole defect becomes large. Further, for example, there is a problem that organic contaminants generated when the n ⁺ silicon layers 6 and 7 are formed by the photolithography method remain on the surface of the blocking layer and top gate insulating film 5 to deteriorate device characteristics. there were. An object of the present invention is to prevent a conventional problem caused by the thickness of the top gate insulating film from occurring even if the thickness of the top gate insulating film is increased, and to perform a predetermined manufacturing process. The purpose is to prevent the generated contaminants from remaining.

[0004]

According to the first aspect of the present invention,
A substrate, a bottom gate electrode provided on the substrate,
A bottom gate insulating film provided on the bottom gate electrode; a semiconductor layer provided on the bottom gate insulating film; and a blocking layer and a first top gate insulating film provided at a central portion on the semiconductor layer. And two n ⁺ silicon layers provided on both sides of the blocking layer and the first top gate insulating film and on both sides of the semiconductor layer.
A source electrode and a drain electrode provided on two n ⁺ silicon layers, and a second top gate insulating film provided on the source electrode, the drain electrode, and the blocking layer and the first top gate insulating film therebetween. And this second
And a top gate electrode provided on the top gate insulating film, wherein after the source electrode and the drain electrode are formed, the blocking layer and the first top gate insulating film are formed. Is subjected to a contaminant removal treatment, and thereafter, the second top gate insulating film is formed. The invention according to claim 2 provides a substrate, a bottom gate electrode provided on the substrate, a bottom gate insulating film provided on the bottom gate electrode, and a semiconductor layer provided on the bottom gate insulating film. And two n ⁺ silicon layers continuously provided on the semiconductor layer on the bottom gate insulating film on both sides of the semiconductor layer; and a blocking layer and a first top gate insulating film provided on the semiconductor layer. A film, a source electrode and a drain electrode provided on both sides of the blocking layer and the first top gate insulating film and on the two n ⁺ silicon layers, and the source electrode, the drain electrode, and the blocking layer therebetween. A second top gate insulating film provided on the first top gate insulating film; and a top gate electrode provided on the second top gate insulating film. A method of manufacturing a photosensor element, comprising: after forming the source electrode and the drain electrode, performing a contaminant removal process on a surface of the blocking layer and the first top gate insulating film; The second top gate insulating film is formed. According to the present invention, the top gate insulating film has a two-layer structure of the blocking layer and the first top gate insulating film and the second top gate insulating film. And the thickness of the second top gate insulating film can be made as large as possible. Therefore, even if the overall thickness of the top gate insulating film is made large, the blocking layer and the first top gate insulating film can be formed. The conventional problem caused by the film thickness can be prevented. Further, according to the present invention, the contaminant removal treatment is performed on the surface of the blocking layer and the first top gate insulating film after forming the source electrode and the drain electrode.
It is possible to prevent contaminants generated in a predetermined manufacturing process from remaining.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIGS.
(D) shows each manufacturing process of the photosensor element in the first embodiment of the present invention. Therefore, a method for manufacturing a photosensor element in this embodiment will be described with reference to these drawings in order. First,
As shown in FIG. 1A, a bottom gate electrode 22 made of a light-shielding material such as chromium or aluminum is pattern-formed at a predetermined position on an upper surface of a transparent substrate 21 made of an acrylic resin, glass, or the like. A bottom gate insulating film 23 made of silicon nitride is formed, a semiconductor layer 24 made of amorphous silicon is formed on the entire upper surface thereof, and a blocking layer made of silicon nitride and a first top gate insulating film are formed on a predetermined portion of the upper surface. The film 25 is patterned. Next, the natural oxide film (not shown) formed on the surface of the semiconductor layer 24 is removed by etching with an NH ₄ F solution. This is because an n ⁺ silicon layer 26 described later (FIG. 1B)
This is for improving the contact between the semiconductor layer 24 and the semiconductor layer 24. Also, at this time, the surface of the blocking layer and the first top gate insulating film 25 is also slightly etched, so that organic contaminants remaining at this stage on the surface of the blocking layer and the first top gate insulating film 25 are removed. You.

Next, as shown in FIG. 1B, an n ⁺ silicon layer 26 is formed on the entire upper surface. Next, as shown in FIG. 1C, the n ⁺ silicon layer 26 and the semiconductor layer 24 are patterned. In this case, the n ⁺ silicon layer 26
And the semiconductor layers 24 on both sides of the upper surface of the blocking layer / first top gate insulating film 25 and on both sides thereof
Is formed on the upper surface of the substrate. Next, a source electrode 27 and a drain electrode 28 made of a light-shielding material such as chromium or aluminum are pattern-formed on the upper surfaces of the two n ⁺ silicon layers 26 and the bottom gate insulating film 23. Next, organic contaminants (not shown) remaining on the exposed surface of the blocking layer and the first top gate insulating film 25 are removed by etching with an NH ₄ F solution. Next, as shown in FIG. 1 (D), a second top gate insulating film 29 made of silicon nitride is formed on the entire upper surface, and I
A top gate electrode 30 made of a transparent material such as TO is patterned. In this case, the top gate electrode 30
A pattern is formed so as to cover the blocking layer and the first top gate insulating film 25 and the source electrode 27 and the drain electrode 28 on both sides thereof. Thus, the photo sensor element in this embodiment is manufactured.

As described above, in this method of manufacturing a photosensor element, the top gate insulating film is used as the blocking layer and the first layer.
Of the first gate insulating film 25 and the second top gate insulating film 29.
The thickness of the top gate insulating film 25 can be made as small as possible, and the thickness of the second top gate insulating film 29 can be made as large as possible. For example, the thickness of the blocking layer and the first top gate insulating film 25 is set to 1000
And the thickness of the second top gate insulating film 29 is 1
When the thickness is about 2,000 to 2,000 (for example, about 1,500), the thickness of the top gate insulating film as a whole can be about 2,000 to 3,000 as in the conventional case. Therefore, if the overall thickness of the top gate insulating film is increased to about 2000 to 3000 degrees as in the conventional case, it is possible to prevent interlayer defects due to defects in the overall top gate insulating film. Further, the thickness of the blocking layer and the first top gate insulating film 25 is set to 1
If the thickness is reduced to about 000 °, the height of the end portion of the blocking layer / first top gate insulating film 25 is reduced, and the n ⁺ silicon layer 2 overlapping the end portion is reduced.
6. The source electrode 27 and the drain electrode 28 can be prevented from being disconnected at the end portions. Furthermore, when the thickness of the blocking layer and the first top gate insulating film 5 is reduced to about 1000 °, the etching time (over-etching time) when etching the film with an etching solution (BHF) is shortened. The damage that the etchant gives to the bottom gate insulating film 23 through the pinhole defect of the semiconductor layer 24 can be reduced.

In this method of manufacturing a photosensor element, after forming the source electrode 27 and the drain electrode 28, the surface of the blocking layer and the first top gate insulating film 25 is organically etched by NH ₄ F solution. Since the contaminant removal processing is performed, organic contaminants generated in a predetermined manufacturing process can be prevented from remaining, and therefore, deterioration of device characteristics due to such residual organic contaminants can be prevented. .

(Second Embodiment) FIGS. 2A to 2D show respective manufacturing steps of a photosensor element according to a second embodiment of the present invention. Therefore, a method for manufacturing a photosensor element in this embodiment will be described with reference to these drawings in order. First, as shown in FIG. 2A, a bottom gate electrode 22 is pattern-formed at a predetermined position on an upper surface of a transparent substrate 21, a bottom gate insulating film 23 is formed on the entire upper surface, and a semiconductor is formed on the entire upper surface. A layer 24 is formed, and a blocking layer and a first top gate insulating film 25 are pattern-formed at a predetermined location on the upper surface.
Next, the natural oxide film (not shown) formed on the surface of the semiconductor layer 24 is removed by etching with an NH ₄ F solution.
Next, as shown in FIG.
Is doped with n-type dopant ions using the top gate insulating film 25 as a mask, and the semiconductor layer 24 in a region other than under the blocking layer and the first top gate insulating film 25 is also used.
Is an n ⁺ silicon layer 26.

Next, as shown in FIG. 2C, the n ⁺ silicon layer 26 is patterned. In this case, the n ⁺ silicon layer 26 is formed on the upper surface of the bottom gate insulating film 23 on both sides of the semiconductor layer 24 so as to be continuous with the semiconductor layer 24. Next, a source electrode 27 is formed on both sides of the upper surface of the blocking layer / first top gate insulating film 25, the upper surface of the two n ⁺ silicon layers 26, and the upper surface of the bottom gate insulating film 23.
And the drain electrode 28 is patterned. Next, organic contaminants (not shown) remaining on the exposed surface of the blocking layer and the first top gate insulating film 25 are removed by etching with an NH ₄ F solution. Next, as shown in FIG. 2D, a second top gate insulating film 29 is formed on the entire upper surface, and a top gate electrode 30 is formed at a predetermined position on the upper surface.
Is patterned. Also in this case, the top gate electrode 3
0 is a blocking layer / first top gate insulating film 25
And the source electrode 27 and the drain electrode 28 on both sides thereof are patterned. Thus, the photo sensor element in this embodiment is manufactured.

As described above, also in this method for manufacturing a photosensor element, the top gate insulating film serves as the blocking layer and the first layer.
Since the two-layer structure of the top gate insulating film 25 and the second top gate insulating film 29 is used, the same effect as in the first embodiment can be obtained. However, in this case, the bottom gate insulating film 2 on both sides of the semiconductor layer 24
3 the upper surface to the n ⁺ silicon layer 26 since provided is continuously in the semiconductor layer 24 does not occur at all disconnection due to the end portions of the blocking layer and the n ⁺ silicon layer 26 first top gate insulating film 26 You can do so.

Also in this method of manufacturing the photosensor element, after the source electrode 27 and the drain electrode 28 are formed, the surface of the blocking layer and the first top gate insulating film 25 is organically etched by NH ₄ F solution. Since the contaminant removal processing is performed, organic contaminants generated in a predetermined manufacturing process can be prevented from remaining, and therefore, deterioration of device characteristics due to such residual organic contaminants can be prevented. . However, in this case, FIG.
In the step shown in (B), the surface of the blocking layer and the first top gate insulating film 25 is also doped with n-type dopant ions, but the blocking layer and the first top gate are etched by the NH ₄ F solution. Since the n-type dopant ion contaminated layer on the surface of the insulating film 25 is also removed, deterioration of device characteristics due to the n-type dopant ion contaminated layer can be prevented. When a resist used for patterning the blocking layer and the first top gate insulating film 25 is used as an ion doping mask, the blocking layer and the first top gate insulating film 2 are used.
No n-type dopant ion-contaminated layer is formed on the surface of No. 5.

Further, in this method for manufacturing a photosensor element, the blocking layer and the first top gate insulating film 25 are also used.
The doping of the n-type ions to a mask, so to form a n ⁺ silicon layer 26, n ⁺ silicon layer 26
The manufacturing process can be simplified as compared with the case of forming by forming a film.

In the above embodiment, the case where the organic contaminants are removed by the etching process using the NH ₄ F solution has been described, but the present invention is not limited to this. For example, ashing by ultraviolet irradiation or ashing by oxygen plasma may be used. Further, after performing an ashing process by ultraviolet irradiation or an ashing process by oxygen plasma, an etching process by an NH ₄ F solution may be performed. Further, an ion etching process may be used. In the case of the ion etching treatment, the subsequent washing step and drying step are not required as compared with the other treatments described above, so that no contaminant residue due to moisture adhesion or poor drying does not occur, and Because of the physical etching, the surface of the blocking layer and the first top gate insulating film 25 can be shaved to expose a new surface. In addition, the ion etching process may be performed after performing any one of an etching process using an NH ₄ F solution, an ashing process using ultraviolet irradiation, and an ashing process using oxygen plasma. Further, an ashing process by ultraviolet irradiation or an ashing process by oxygen plasma may be performed, then an etching process by an NH ₄ F solution may be performed, and then an ion etching process may be performed.

The apparatus used for the ion etching process may be a dry etching apparatus, but a plasma CVD apparatus is more preferable. That is, in the case of a plasma CVD apparatus, ion etching is performed by introducing an etching gas such as Ar, He, and H ₂ , and thereafter, when the introduced gas is switched to a silicon nitride film forming gas, the film is continuously formed in a vacuum. This is because the second top gate insulating film 29 can be formed.

In the above embodiment, for example, FIG.
As shown in (D), the case where the top gate electrode 30 is formed so as to cover the blocking layer and the first top gate insulating film 25 and each part of the source electrode 27 and the drain electrode 28 on both sides thereof will be described. However, the present invention is not limited to this. For example, although not shown, FIG.
Explaining with reference to (D), the top gate electrode 30
May be formed so as to cover the left half (or right half) of the blocking layer / first top gate insulating film 25 and part of the source electrode 27 (or drain electrode 28) on the left (or right) side thereof. Good. Further, the top gate electrode 30 is formed so as to cover the central portion of the blocking layer and the first top gate insulating film 25, and light is transmitted from between the top gate electrode 30 and the source electrode 27 and the drain electrode 28 to the semiconductor layer. 24 may be directly incident on the surface.

[0017]

As described above, according to the present invention, the top gate insulating film has a two-layer structure of the blocking layer and the first top gate insulating film and the second top gate insulating film. In addition, the thickness of the first top gate insulating film can be reduced as much as possible, and the thickness of the second top gate insulating film can be increased as much as possible. Also, it is possible to prevent the conventional problem caused by the thickness of the blocking layer and the first top gate insulating film from occurring. According to the invention,
After the source electrode and the drain electrode are formed, the surface of the blocking layer and the first top gate insulating film is subjected to the contaminant removal treatment, so that contaminants generated in a predetermined manufacturing process do not remain. Therefore, it is possible to prevent the element characteristics from deteriorating due to such residual contaminants.

[Brief description of the drawings]

FIGS. 1A to 1D are cross-sectional views showing respective manufacturing steps of a photosensor element according to a first embodiment of the present invention.

FIGS. 2A to 2D are cross-sectional views illustrating respective manufacturing steps of the photosensor element according to the first embodiment of the present invention.

FIG. 3 is a partial cross-sectional view of an example of a conventional photosensor element.

[Explanation of symbols]

Reference Signs List 21 transparent substrate 22 bottom gate electrode 23 bottom gate insulating film 24 semiconductor layer 25 blocking layer and first top gate insulating film 26 n ⁺ silicon layer 27 source electrode 28 drain electrode 29 second top gate insulating film 30 top gate electrode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 29/78 622

Claims (8)

[Claims] A substrate, a bottom gate electrode provided on the substrate, a bottom gate insulating film provided on the bottom gate electrode; a semiconductor layer provided on the bottom gate insulating film; A blocking layer and a first top gate insulating film provided at a central portion on the semiconductor layer; and two n layers provided on both sides of the blocking layer and the first top gate insulating film and on both sides of the semiconductor layer ^{A +} silicon layer, a source electrode and a drain electrode provided on the two n ⁺ silicon layers, and the source electrode, the drain electrode, and the blocking layer between them provided on the first top gate insulating film. A method for manufacturing a photosensor element comprising: a second top gate insulating film; and a top gate electrode provided on the second top gate insulating film. After the formation of the drain electrode and the drain electrode, the surface of the blocking layer and the first top gate insulating film is subjected to a contaminant removal treatment, and then the second top gate insulating film is formed. A method for manufacturing a photosensor element. A substrate; a bottom gate electrode provided on the substrate; a bottom gate insulating film provided on the bottom gate electrode; a semiconductor layer provided on the bottom gate insulating film; Two n ⁺ silicon layers provided continuously on the semiconductor layer on the bottom gate insulating film on both sides of the semiconductor layer; a blocking layer and a first top gate insulating film provided on the semiconductor layer; A source electrode and a drain electrode provided on both sides of the blocking layer and the first top gate insulating film and on the two n ⁺ silicon layers, the source electrode, the drain electrode, and the blocking layer and the first electrode therebetween; A second top gate insulating film provided on the top gate insulating film of
A method of manufacturing a photosensor element comprising a top gate electrode provided on the second top gate insulating film, wherein after forming the source electrode and the drain electrode, the blocking layer and the first top electrode are formed. A contaminant removal process is performed on the surface of the gate insulating film.
A method of manufacturing a photosensor element, comprising forming a top gate insulating film according to any one of the preceding claims. 3. The method according to claim 1, wherein
The method for manufacturing a photosensor element, wherein the contaminant removal processing is any one of an etching processing using an NH ₄ F solution, an ashing processing using ultraviolet irradiation, and an ashing processing using oxygen plasma. 4. The invention according to claim 1 or 2,
The method for manufacturing a photosensor element, wherein the contaminant removal treatment is performed by performing an ashing treatment with ultraviolet irradiation or an ashing treatment with oxygen plasma and then performing an etching treatment with an NH ₄ F solution. 5. The method according to claim 1, wherein
The method for manufacturing a photosensor element, wherein the contaminant removing process is an ion etching process. 6. The invention according to claim 1 or 2,
The method of manufacturing a photosensor element, wherein the contaminant removal processing is performed by performing any one of an etching processing using an NH ₄ F solution, an ashing processing using ultraviolet irradiation, and an ashing processing using oxygen plasma, and then performing an ion etching processing. Method. 7. The method according to claim 1, wherein
The method of manufacturing a photosensor element, wherein the contaminant removal processing is performed by performing an ashing processing using ultraviolet irradiation or an ashing processing using oxygen plasma, then performing an etching processing using an NH ₄ F solution, and then performing an ion etching processing. Method. 8. The invention according to claim 5, wherein the ion etching is performed using a plasma CVD apparatus, and thereafter, the second top gate insulating film is formed using the plasma CVD apparatus. A method for manufacturing a photosensor element, comprising forming a film.