JPH0786591A - Manufacture of thin-film transistor - Google Patents

Abstract

PURPOSE:To increase the manufacturing yield rate of 7 TFTs and to improve throughput by forming the blocking layers of all TFTs formed on the same insulated substrate of a metal thin film, which has undergone sufficent anode oxidation uniformly to a bulk. CONSTITUTION:A semiconductor layer 104 is formed on a gate electrode 102 at the upper surface of a glass substrate 101 through a gate insulating film. A transistor forming part 107a having the shape corresponding to a channel region and a power supplying wiring part 107b for supplying the current into the forming part 107a are provided on the upper surface of the layer 104. Thus, the aluminum interconnection having these parts is formed. The upper surface of the power supplying wiring part 107 is covered with resist (oxidation preventing film) 108. The device is dipped into oxidizing liquid, and the current is made to flow from the power supplying wiring part 107b. Only the transistor forming part 107a undergoes anode oxidation. Thereafter, the resist 108 and the power supplying wiring part 107b are removed. The oxidized forming part 107a is made to remain, and the blocking layer is obtained. The layer is used as the etching stopper in the formation of the electrode.

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, and more particularly, to a method of manufacturing a thin film transistor in which a blocking layer for protecting the channel region of a semiconductor layer is formed on the upper surface of the channel region.

[0002]

2. Description of the Related Art As a so-called "reverse stagger type" thin film transistor (hereinafter abbreviated as "TFT" as appropriate), a conductive layer 2 for a gate electrode is formed on an upper surface of an insulating substrate 1 such as a glass plate as shown in FIG. Then, a gate insulating film (for example, a silicon nitride film) 3, a semiconductor layer (non-doped amorphous silicon) 4, a contact layer (n ⁺ -silicon layer) 5 are formed on top of this.
Source electrode 6A made of aluminum or the like
It is known that the drain electrode 6B is formed. In this "inverted stagger type" TFT, a blocking layer 7A made of an insulating film such as silicon nitride is formed as an etching stopper in order to protect the channel region 4a of the semiconductor layer 4 from etching during processing of the source / drain electrodes. ing.

The blocking layer 7A is formed by depositing a semiconductor layer 4 on the gate insulating film 3 and then forming a silicon nitride film 7 on the entire surface thereof. The silicon nitride film 7 is wet-etched using a resist 8 (hydrofluoric acid-based). It is patterned by etching with an etching solution (FIGS. 11 and 1).
2).

[0004]

However, when the blocking layer is formed according to the above process,
If a pinhole is formed in the semiconductor layer 4 or if the step coverage of the step portion 3a of the gate insulating film 3 is poor, the etching solution (hydrofluoric acid-based etching solution such as HF) may be removed when the silicon nitride film 7 is etched. It reaches the gate insulating film 3 on the lower layer side of the semiconductor layer 4 and invades the gate insulating film 3, resulting in deterioration of the gate breakdown voltage of the transistor.

As one method for solving this problem, it has been considered to form the blocking layer with an anodized metal film. In this proposal, in order to form the blocking layer of the TFT, a metal thin film (aluminum) 17 deposited on a semiconductor layer is formed into a transistor forming portion 17a having a shape corresponding to a channel region as shown in FIG.
.. and power supply wiring portions 17b, 17b, ... for supplying current to the forming portions 17a, 17a, .. A current is passed to anodize the metal wiring layer 17, and then etching is performed to supply the power supply wiring portion 17
b is removed, and the oxidized transistor forming portion 17a is left as a blocking layer.

However, when the anodic oxidation is performed by the above-mentioned method, the transistor forming portion 1 is supplied with the current.
7a, 17a, ... Not only the power supply wiring section 17
Since the oxidation of b, 17b, ... Also progresses at the same time, the power supply ability of the power supply wiring portions 17b, 17b, .. is deteriorated, and in particular, the current supply to the transistor forming portions 17a, 17a ,. It becomes sufficient, and it becomes difficult to uniformly anodize all of the transistor formation portions 17a, 17a, ... (Oxidation to bulk). As a result, the blocking layer 17A is not sufficiently insulated, and an interlayer short circuit is likely to occur in the transistor.
The manufacturing yield and the throughput were decreased. The present invention has been made in view of the above circumstances, and the blocking layers of all TFTs formed on the same insulating substrate are formed of a metal thin film that is sufficiently and uniformly anodized up to the bulk. It is an object of the present invention to provide a method for manufacturing a thin film transistor, which increases the manufacturing yield of TFTs and improves throughput.

[0007]

In order to achieve the above object, in the manufacturing method of the present invention, when the metal thin film forming the blocking layer is anodized, the upper surface of the power supply wiring portion of the metal thin film is preliminarily coated with a resist or the like. A metal thin film covered with an anti-oxidation film and anodized in this state, and thereafter, the anti-oxidation film and the unoxidized power supply wiring part thereunder are removed, and only the transistor formation part is oxidized. I left it.

[0008]

Since the surface of the power supply wiring portion of the metal thin film is covered with the anti-oxidation film, the power supply wiring portion is not oxidized during the anodic oxidation, and therefore the transistor forming portion is sufficiently anodized. During the oxidation, the current is stably supplied from the power supply wiring portion to the transistor forming portion.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a plan view showing a layout of a TFT array provided with a plurality of thin film transistors 100 formed by the manufacturing method of this embodiment, and FIG.
It is a longitudinal cross-sectional view taken along line II-II. The thin film transistor (TFT) 100 of this embodiment is a so-called “inverse stagger type” transistor, and the gate electrode 102 extending in the left-right direction in FIG. 1 of the transistor 100 is an insulating substrate (glass plate).
101 is provided in plurality. Above the gate electrode 102, a plurality of drain wirings 116 are formed so as to extend in the vertical direction in FIG. 1 via a gate insulating film 103 and the like (FIGS. 1 and 2). Further, the drain electrode of the TFT 100 is conductively connected to the drain wiring 116, and the source electrode is the pixel electrode (ITO) 10A on the pixel regions 10, 10 ,.
Conductively connected to 10A, ... (FIG. 2).

A blocking layer 107A is formed on the upper surface of the channel region 104a of the semiconductor layer 104 of the TFT 100. The blocking layer 107A is provided to protect the channel region 104a of the semiconductor layer from etching during patterning of the source / drain electrodes. In the present embodiment, the anodized aluminum thin film (Al
₂ O ₃ ).

Next, a method of forming the blocking layer 107A of the TFT 100 will be described with reference to FIGS. FIG. 3 shows the shape of the gate electrode 102 formed on the upper surface of the glass substrate (insulating substrate) 101. The gate electrode 102 is formed by depositing a conductive layer made of, for example, Cr by, for example, a sputtering method, and patterning the deposited conductive layer. When the gate electrode 102 is formed in this way, a gate insulating film (for example, Si ₃ N ₄ ) 103 is formed thereon by a plasma CVD method or the like, and a semiconductor layer 104 made of non-doped silicon is formed thereon by a sputtering method or the like. And an aluminum thin film (metal thin film) 117 for forming the blocking layer 107A are sequentially deposited thereon by a sputtering method or the like (FIG. 4).

Next, the aluminum thin film (metal thin film) 117 on the semiconductor layer (i-Si) 104 is patterned, for example, according to the shape of the gate electrode 102 formed thereunder, and as shown in FIG. Convex area (transistor formation portion) 107a and linear area (power supply wiring portion)
Aluminum wiring (metal wiring) 107 including 107b is obtained. This sectional structure is shown in FIG. Then, the power supply wiring portion 107 of the patterned aluminum wiring 107.
A resist (antioxidant film) 108 is formed on the surface of b (hatched portion in FIG. 7).

When this is inserted into a known anodizing device (not shown) filled with an anodizing solution and a current is passed through the aluminum wiring 107, the resist 108 of the aluminum wiring 107 is inserted.
Part not covered with (transistor formation part 107
a) is oxidized (Fig. 8). At this time, the resist 108
The power supply wiring portions 107b, 107b, ... Covered with are not anodized, and a desired current is applied to the substrate 1 during anodization.
All transistor formation portions 107a, 107 on 01
a, ...

When the anodic oxidation process is completed, the resist (antioxidation film) 108 is removed by, for example, an oxidizing solvent, and the unoxidized aluminum layer (power supply wiring portion 107b) is replaced with a non-hydrofluoric acid-based etching solution. Then, the shape shown in FIG. 9, that is, the oxidized aluminum is left only on the transistor formation portion, and is left on the semiconductor layer 104 to form the blocking layer 107A.

A contact layer (n ⁺ -Si layer) in which n-type impurities are introduced on the blocking layer 107A.
105 is deposited by a sputtering method or the like, and a conductive layer (for example, an aluminum thin film) 106 for forming a source electrode / drain electrode is further deposited thereon by a sputtering method so that the electrode patterns shown in FIGS. Further, the patterning method using plasma etching with high processing accuracy is used for processing. In this case, the source electrode 106B and the drain electrode 1
06A and a semiconductor layer (i-Si layer) 10 below the electrode
Since the blocking layer 107A made of aluminum oxide (Al ₂ O ₃ ) is formed between the channel region 104a and the semiconductor layer 4, the channel region 104a of the semiconductor layer is protected.

As described above, according to the method of manufacturing a thin film transistor of this embodiment, the blocking layer is formed by anodizing the metal thin film,
Unlike the case where the blocking layer is formed of silicon nitride, it is not necessary to use a hydrofluoric acid-based etching solution at the time of patterning, and the gate insulating film is not attacked by the etching solution. Further, since the power supply wiring portion 107b of the aluminum wiring 107 is anodized while being covered with an antioxidant film such as a resist, the wiring portion 107b is not oxidized during anodization to increase resistance. Therefore, sufficient current is supplied to the transistor forming portion 107a, regardless of the distance from the power source.
All the transistor forming portions 107a are completely and uniformly oxidized up to the bulk.

In this embodiment, the power supply wiring portion 107b is used.
Was covered with a resist, but if it is not anodized and does not require a hydrofluoric acid-based etching solution for its removal, the wiring part 107b is formed by a film made of another material.
May be covered.

Further, the thin film transistor 100 of this embodiment.
Forms a contact layer (n ⁺ -Si layer) 105 between the source / drain electrodes 106A and 106B and the drain wiring 116 / pixel electrode 10A. The source / drain electrodes are directly connected to the drain wiring / pixel. It may be configured to be connected to the electrodes. Also, although an example in which an aluminum thin film is used as the metal thin film to be anodized is shown, a thin film of another metal, such as Ta, may be used.

[0019]

According to the present invention, since the blocking layer of the thin film transistor forms the metal wiring patterned in a predetermined shape by selective anodic oxidation, the etching solution may attack the gate insulating film during the pattern formation. Therefore, the gate breakdown voltage is prevented from lowering. Further, when the metal wiring is anodized, the power supply wiring portion is covered by the function of the antioxidant film to prevent oxidation, so that sufficient current is supplied to all transistor formation portions on the insulating substrate,
Oxidation of the formation portion is sufficiently and uniformly performed, so that the yield in manufacturing the thin film transistor can be improved.

[Brief description of drawings]

FIG. 1 is a plan view showing a layout of a TFT array provided with a plurality of thin film transistors formed by the manufacturing method of this embodiment.

FIG. 2 is a vertical cross-sectional view of the thin film transistor taken along the line II-II of FIG.

FIG. 3 is a plan view showing a step of forming a gate electrode on the upper surface of the glass substrate.

FIG. 4 is a cross-sectional view showing a step of depositing a gate insulating film, a semiconductor layer, and an aluminum thin film on the gate electrode.

FIG. 5 is a plan view showing a process of forming aluminum wiring in a predetermined shape on the upper surface of a semiconductor layer deposited on a gate electrode via an insulating film.

6 is a sectional view taken along line VI-VI of FIG.

FIG. 7 is a plan view showing a process of forming a resist on the upper surface of a transistor forming portion of aluminum wiring.

FIG. 8 is a plan view showing a process in which a transistor forming portion is anodized by passing a current through aluminum wiring.

FIG. 9 is a plan view showing a process of removing a resist and a power supply wiring section and leaving an oxidized transistor forming section.

FIG. 10 is a cross-sectional view of a conventional thin film transistor in which a blocking layer is formed of a silicon nitride film.

FIG. 11 is a cross-sectional view showing a step of patterning a silicon nitride film using a resist in the conventional step of forming a blocking layer.

FIG. 12 is a cross-sectional view showing a process in which a conventional blocking layer is formed by patterning a silicon nitride film.

FIG. 13 is a plan view for explaining a method of forming a blocking layer by anodic oxidation of metal wiring.

[Explanation of symbols]

 100 thin film transistor (TFT) 101 glass substrate (insulating substrate) 102 gate electrode 103 gate insulating film (silicon nitride film) 104 semiconductor layer 104a channel region 106A drain electrode 106B source electrode 107 aluminum wiring (metal wiring) 107a transistor forming portion 107b for power supply Wiring part 107A Blocking layer 108 Resist (oxidation prevention film)

Claims (3)

[Claims] 1. A semiconductor layer is formed on a gate electrode formed on an insulating substrate via a gate insulating film, and a source electrode and a drain electrode are formed on the semiconductor layer so as to face the gate electrode. In the method of manufacturing a thin film transistor in which a blocking layer serving as a stopper at the time of patterning the source / drain electrodes is formed on the upper surface of the channel region of the semiconductor layer, the channel is formed on the upper surface of the semiconductor layer in forming the blocking layer. A metal wiring having a transistor formation portion having a shape corresponding to the region and a power supply wiring portion for supplying a current to the formation portion is formed, and an antioxidant film covering the upper surface of the power supply wiring portion is formed. After immersing this in an oxidizing solution and flowing an electric current from the power supply wiring part to anodize the transistor forming part, A method of manufacturing a thin film transistor, characterized in that the power supply wiring portion is removed. 2. The method of manufacturing a thin film transistor according to claim 1, wherein the metal wiring is made of aluminum. 3. The removal of the power supply wiring portion is performed by using a non-hydrofluoric acid-based etching solution.
Or the method for manufacturing the thin film transistor according to 2.