JPH0745836A - Thin film transistor and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a TFT and a method for manufacturing the same in which number of manufacturing steps can be reduced as compared with that of prior arts, a throughput and an yield can be improved and a manufacturing cost is low. CONSTITUTION:A source electrode 5a and a drain electrode 5b are provided at a predetermined gap on an insulating board 1, a source region 6a and a drain region 6b are respectively provided on the electrodes 5a and 5b, a functional layer 2a is provided at least in a gap between the region 6a and the region 6b, and a gate electrode 4a is provided on the layer 2a through an insulating film 3a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor (hereinafter referred to as T
FT) and its manufacturing method. More specifically, the present invention relates to a TFT capable of simplifying the manufacturing process and reducing the manufacturing cost, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In an active matrix type liquid crystal display device or the like, a TFT is used as a switching element for turning on and off each pixel. Since the TFT is provided on the liquid crystal layer side of the insulating substrate that holds the liquid crystal layer of the liquid crystal display device, for example, it is necessary to provide the TFT in a narrow range of 3 to 10 μm and on the insulating substrate. Therefore, unlike a normal semiconductor device, amorphous silicon, polysilicon, or the like is used as the functional layer.

An example of the structure of a conventional TFT is shown in FIG.
In FIG. 5, the source region is formed on the insulating substrate 21 such as glass.
A semiconductor layer 22 having a drain region 22a, a drain region 22b, and a channel region 22c is provided. A gate electrode 24 is provided on the channel region 22c via a gate insulating film 23,
An insulating film that covers the source region 22a and the drain region 22b
Contact holes 26 and 27 are provided in 25, and a source electrode 28 and a drain electrode 29 are formed. The drain electrode 29 is connected to the pixel electrode (not shown) and is made of the same material as the pixel electrode (for example, ITO). Further, 30 is a wiring metal.

Next, a conventional method for manufacturing a TFT will be described with reference to FIGS.

First, as shown in FIG. 6A, a semiconductor layer made of polysilicon, amorphous silicon, or the like is deposited on an insulating substrate 21 such as glass, and then a photoresist film is applied and exposed to light to form a mask. The semiconductor layer 22 that functions as an active region of the TFT is formed by forming the pattern, and then performing etching and patterning (hereinafter referred to as a photolithography process).

Next, as shown in FIG. 6B, an insulating film made of, for example, silicon nitride and an electrode film made of aluminum are sequentially provided on the semiconductor layer 22, and then the insulating film and the electrode film are formed. A gate insulating film 23 and a gate electrode 24 are formed by performing a photolithography process on the. Further, by using the gate electrode 24 as a mask, impurities are ion-implanted into the semiconductor layer 22 to make it a p ^{+ type} or n ^{+ type} conductivity type, thereby forming a source region 22a and a drain region 22b.

Next, as shown in FIG. 6C, the semiconductor layer
A contact hole 26 for the source electrode and the drain electrode is formed by depositing an insulating film 25 made of, for example, silicon nitride on the entire surface of the insulating substrate 21 provided with the gate electrode 24 and the gate electrode 24 and then performing a photolithography process. , 27 are formed.

Next, as shown in FIG. 6 (d), an insulating substrate
A drain electrode 29 is formed with a pixel electrode (not shown) of the liquid crystal display device by forming a transparent electrode film made of, for example, ITO on the entire surface of 21 and then performing a photolithography process.

Finally, as shown in FIG. 5, a source electrode 28 and a wiring metal 30 are formed by forming an electrode film made of, for example, aluminum on the entire surface of the insulating substrate 21 and then performing a photolithography process.

As described above, the conventional TFT is formed on the insulating substrate 21 by the film forming process 6 times and the photolithography process 5 times.

[0011]

In the conventional TFT, the semiconductor layer is provided on the insulating substrate, and the electrode film is provided thereon. Therefore, as described above, the film forming step is performed six times and the film forming step is performed five times. A photolithography process is required. Therefore, so-called throughput decreases, and as the number of processes increases,
Dust and the like tend to enter and defects in the circuit pattern are likely to occur, which lowers the yield. As a result, there is a problem that the manufacturing cost increases.

The present invention has been made in order to solve such a problem, and it is an object of the present invention to provide a TFT and a manufacturing method thereof which can simplify the structure and reduce the number of manufacturing steps, particularly the number of photolithography steps. To aim.

[0013]

The TFT of the present invention is
(A) A source electrode and a drain electrode provided on an insulating substrate with a constant gap, (b) a source region and a drain region formed of a high-concentration impurity semiconductor layer provided on the source electrode and the drain electrode, respectively ( c) A functional layer provided at least in the gap between the source region and the drain region, and (d) a gate electrode provided on the functional layer with a gate insulating film interposed therebetween.

Further, it is preferable that the source electrode and the drain electrode have a two-layer structure of a transparent electrode film and a metal electrode film in order to reduce the wiring resistance.

The manufacturing method of the TFT according to the present invention is (e)
A conductive film and a high-concentration impurity semiconductor layer are sequentially laminated on an insulating substrate, and (f) the high-concentration impurity semiconductor layer and the conductive film are sequentially patterned to form a source region and a drain region and a source electrode and a drain, each having a constant gap. An electrode, (g) a semiconductor layer, an insulating film, and an electrode film are sequentially provided on the insulating substrate provided with the source region and the drain region, and (h) at least a constant gap between the source region and the drain region, The semiconductor layer, the insulating film, and the electrode film are patterned so that the functional layer, the gate insulating film, and the gate electrode are formed above them.

Further, the liquid crystal display device according to the present invention is an active matrix type liquid crystal display device in which pixels are formed in a matrix and each pixel has a switching element, and the TFT is used as the switching element. is there.

[0017]

According to the TFT of the present invention, since the source electrode and the drain electrode are provided on the insulating substrate and the functional layer is provided thereon, the patterning of the semiconductor layer by the photolithography process is performed. This can be performed simultaneously with the patterning of the electrodes, and it is not necessary to pattern and form the contact holes for the source electrode and the drain electrode. As a result, the TFT can be formed by only two or three photolithography steps.

[0018]

The present invention will be described below with reference to the drawings. FIG. 1 is a sectional explanatory view showing an embodiment of the TFT of the present invention, FIG. 2 is a sectional explanatory view showing another embodiment of the TFT of the present invention, and FIG. 3 is a process of an embodiment of the manufacturing method of the TFT of the present invention. FIG. 4 is a sectional explanatory view showing an active matrix type liquid crystal display device in which the TFT of the present invention is used as a switching element.

First, the TFT of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the TFT of the present invention is provided on an insulating substrate 1 made of, for example, glass or plastics, which holds a liquid crystal material of a liquid crystal display device. The source electrode 5a and the drain electrode 5b are formed on the insulating substrate 1 with a constant gap, for example, IT.
It is provided by O, tin oxide, or the like. If the source electrode 5a and the drain electrode 5b are formed of an ITO film, a tin oxide film, or the like, they can be formed simultaneously with the pixel electrodes of a liquid crystal display device or the like, and the number of film forming steps can be reduced, which is preferable. However, it may be formed of an aluminum film, a chromium film, a tantalum film, a molybdenum film, or the like. A high-concentration impurity semiconductor layer is deposited on the upper surfaces of both electrodes 5a and 5b, and a source region 6a and a drain region 6b are provided, respectively. The functional layer 2a, the gate insulating film 3a, and the gate electrode 4 are formed on the gap between the source region 6a and the drain region 6b and on the surfaces of these regions 6a and 6b.
a is sequentially stacked.

For the above-mentioned functional layer 2a, a polysilicon film, an amorphous silicon film or the like having a thickness of about 0.1 to 1.0 μm is used for ease of film formation, and for the gate insulating film 3a,
A silicon nitride film having a thickness of about 0.05 to 1.0 μm, SiO ₂ ,
SiON or the like is used, and for the gate electrode 4a, an aluminum film, a chromium film, a tantalum film, a molybdenum film or the like having a thickness of about 0.1 to 0.4 μm is used. Further, for the high-concentration impurity semiconductor layer forming the source region 6a and the drain region 6b, amorphous silicon or polysilicon having an impurity concentration of about 10 ¹⁹ to 10 ²¹ / cm ³ is usually used.
An impurity such as PH ₃ or As is formed into an n ^{+ type} conductivity type, or an impurity such as B is formed into a p ^{+ type} conductivity type,
The source region 6a and the drain region 6b are n ⁺
Shape or p ^{+ type,} the same conductivity type is formed.

FIG. 2 shows the structure of another embodiment of the TFT of the present invention. In FIG. 2, 9a and 9b are metal electrode films provided on the transparent electrode films 8a and 8b made of ITO or the like, and the source electrode 5a and the drain electrode 5a are respectively formed by the two-layer structure of the transparent electrode film and the metal electrode film. 5b is formed. The other reference numerals indicate the same parts as in FIG. In this embodiment, by providing the metal electrode films 9a and 9b on the transparent electrode films 8a and 8b and the wiring film (not shown), the electric resistance of each electrode and wiring is reduced, and a high voltage characteristic is obtained. It is designed so that it can be obtained. The transparent electrode films 8a and 8b have the same IT as the conventional one.
O, tin oxide, indium oxide, or the like is used, and molybdenum, tantalum, tungsten, aluminum, or the like is used as the metal electrode films 9a and 9b, which are attached to the insulating substrate 1 by a vacuum deposition method, a sputtering method, or the like, respectively. It can be provided by etching.
Since the metal electrode films 9a and 9b block light, they cannot be provided on the pixel electrode (not shown).
Therefore, a photolithography process for removing the metal electrode film on the pixel electrode is required before patterning the gate electrode (consisting of the metal electrode film), which increases the photolithography process by one process compared with the structure shown in FIG. However, the characteristics can be improved with a smaller number of steps than the conventional method. In this case, the source electrode 5a, the drain electrode 5b, and the wiring portion may be directly formed with only the metal electrode films 9a and 9b without providing the transparent electrode films 8a and 8b such as an ITO film. A TFT such as a display device requires a transparent electrode film as a pixel electrode, and therefore the source electrode 5a
In order to remove the transparent electrode film from the above, a patterning process of the transparent electrode film is further required, and the photolithography process is increased, which is not preferable. Therefore, the TF of this embodiment is
In T, the source electrode and the drain electrode have a two-layer structure of a transparent electrode film and a metal electrode film.

Next, a method of manufacturing the TFT of the present invention will be described. 3 (a) to 3 (c) are manufacturing process explanatory diagrams showing an embodiment of the manufacturing method of the TFT element of the present invention.

First, as shown in FIG. 3A, a conductive film 5 made of ITO, tin oxide or the like, a high-concentration impurity semiconductor layer 6 made of amorphous silicon or polysilicon is formed on an insulating substrate 1 made of glass, plastics or the like. Are sequentially provided by a vapor deposition method, a P-CVD method, an LP-CVD method, or the like. The conductive film 5 is formed of ITO together with the pixel electrode of the liquid crystal display device.
May be provided by a single layer of a transparent electrode film such as, or may be provided by sequentially laminating a transparent electrode film such as ITO and a metal electrode film such as aluminum. As a specific example, in order to form a TFT element for a liquid crystal display device, after cleaning the insulating substrate 1 made of glass, a conductive film 5 made of ITO having a thickness of about 0.05 to 0.2 μm is formed on the insulating substrate by vacuum deposition. 1 was deposited. After that, PH ₃ gas mixed with N ⁺ impurities was applied to the conductive film 5 at 150 to 800 ° C.
The n ^{+ -type} amorphous silicon layer has a thickness of about 0.02 ~
It was deposited to about 0.3 μm.

Next, as shown in FIG. 3 (b), a photolithography process by ordinary exposure and etching is performed,
Source electrode 5a, drain electrode 5b and pixel electrode (not shown) having a constant gap, and the electrode 5
source region 6a and drain region 6 on a and 5b, respectively.
b is formed. As the etching method, a dry etching method such as a reactive ion etching (RIE) method or a CDE method, or a wet etching method using a hydrofluoric acid (HF) or nitric acid (HNO ₃ ) solution can be used. As a specific example, after applying a photoresist film, the TFT
After exposing a wiring pattern such as a pixel electrode and a pixel electrode by projection, developing the mask to form a mask, and then performing an etching process by the RIE method, the source region 6a and the drain region 6b, the source electrode 5a and the drain electrode 5b, and the pixel electrode Was formed.

Next, as shown in FIG. 3C, the semiconductor layer 2, the insulating film 3, and the electrode film 4 are formed on the entire surface of the insulating substrate 1 by C.
The layers are sequentially formed by the VD method, the LP-CVD method or the like. To deposit the semiconductor layer 2 by the CVD method, SiH ₄ gas, H ₂
Gas or N ₂ gas with carrier gas
By reacting at 200 to 400 ° C. for 10 to 60 minutes, a semiconductor layer such as polysilicon or amorphous silicon can be formed. To deposit the insulating film by the CVD method, Si
An insulating film made of silicon nitride, silicon oxide, SiON or the like can be formed by introducing H ₄ gas, NH ₃ gas and the like together with N ₂ gas as a carrier gas and reacting at 200 to 400 ° C. for 10 to 60 minutes. Further, the electrode film is formed by vacuum vapor deposition of chromium, molybdenum, aluminum, tantalum, etc.,
It is deposited by a sputtering method or the like. As a specific example, first, SiH ₄ gas and N ₂ gas are introduced, and the temperature is about 30 at 650 to 900 ° C.
After reacting for 1 minute to deposit a semiconductor layer 2 made of polysilicon having a thickness of about 0.05 to 0.4 μm, an annealing process was performed by raising the temperature from ambient temperature to 800 to 1100 ° C. by a laser annealing device. After that, the surface is further H
After cleaning with F, SiH ₄ gas and NH ₃ gas are introduced and reacted at 600 to 900 ° C. for about 60 minutes to deposit an insulating film 3 made of a silicon nitride film having a thickness of about 0.2 to 0.4 μm. Let After further cleaning with pure water, chromium is sputtered to a thickness of about 0.2-0.5 μm.
A film was formed so that the electrode film 4 was provided.

Finally, the semiconductor layer 2, the insulating film 3, and the electrode film 4 are simultaneously subjected to a photolithography process, whereby the functional layer 2a of the TFT, the gate insulating film 3a, and the gate insulating film 3a, respectively.
The gate electrode 4a is formed to have a structure as shown in FIG. The etching method is the same as that shown in FIG. As a specific example, a functional layer 2a of the TFT, a gate insulating film 3a, and a gate electrode 4a were formed by forming a mask and then performing etching by the RIE method in the same manner as in the case of FIG. 3B.

The above-mentioned embodiment is merely an example, and the materials and thicknesses of the insulating film and the electrodes, and the forming method are not limited to the above-mentioned embodiment, and other known materials and methods can be used.

Next, a liquid crystal display device using the above-mentioned TFT as a pixel switching element will be described.

FIG. 4 is a partial sectional explanatory view of an active matrix type liquid crystal display device in which the TFT of the present invention is used as a switching element. The liquid crystal display device is the same as a normal liquid crystal display device, and two transparent substrates 11 and 12 made of glass or the like are arranged in parallel, and a transparent pixel electrode 13 made of ITO or the like is provided on each of the opposing surfaces. 14
Further, the alignment films 15 and 16 are provided, and the gap between the insulating substrates 11 and 12 is filled with the liquid crystal material 17. The TFT 18 is provided on one insulating substrate 11 with the above-described structure, and is covered with a protective film 19 to be insulated. The drain electrode 5b of the TFT 18 is
The pixel electrodes 13 are integrally formed of the same material and are connected to each other. The source electrode 5a and the gate electrode 4a of the TFT 18 are respectively connected to wirings (not shown) provided between pixels so that the TFT 18 of each pixel can be individually driven from the outside. In the liquid crystal display device of the present invention, the TFT 18 is provided with the above-described simplified structure, and the source electrode 5a and the drain electrode 5b of the TFT 18 are provided.
Since the pixel electrode 13 and the pixel electrode 13 are made of the same material,
These can be simultaneously formed in the same photolithography process. As a result, the pixel electrode 13 is formed on the insulating substrate 11.
Also, the TFT 18 can be easily formed in a small number of steps, and one insulating substrate 11 can be formed only by providing an alignment film 15 made of polyimide or the like thereon by printing or the like, and an active matrix type liquid crystal display device can be obtained with a small number of steps. You can Moreover, since the number of steps is small, the yield is improved.

[0031]

According to the TFT of the present invention, a source electrode and a drain electrode are provided on an insulating substrate, and a functional layer, a gate insulating film, and a gate electrode are provided thereon, so that a photolithography process can be performed. Only two or three steps are required, so that the throughput can be improved and the yield can be increased as the number of steps is reduced. Also, since the total man-hours can be reduced,
It greatly contributes to cost reduction.

Furthermore, by using the TFT of the present invention in an active matrix type liquid crystal display device, the cost of the liquid crystal display device and the throughput can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing an embodiment of a TFT of the present invention.

FIG. 2 is a cross-sectional explanatory view showing another embodiment of the TFT of the present invention.

FIG. 3 is a cross-sectional explanatory view showing a manufacturing process of an embodiment of the method for manufacturing a TFT of the present invention.

FIG. 4 is a cross-sectional explanatory view showing an active matrix type liquid crystal display device in which the TFT of the present invention is used as a switching element.

FIG. 5 is a cross-sectional explanatory view showing an example of a conventional TFT.

FIG. 6 is a cross-sectional explanatory view showing a manufacturing process of an example of a conventional TFT manufacturing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Semiconductor layer 2a Functional layer 3 Insulating film 3a Gate insulating film 4 Electrode film 4a Gate electrode 5 Conductive film 5a Source electrode 5b Drain electrode 6 High concentration impurity semiconductor layer 6a Source region 6b Drain region 8a Transparent electrode film 8b Transparent electrode Film 9a Metal electrode film 9b Metal electrode film 11 Transparent substrate 12 Transparent substrate 18 TFT

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Makoto Takamura, 21 Mizozaki-cho, Saiin, Ukyo-ku, Kyoto ROHM Co., Ltd.

Claims (4)

[Claims] 1. A source region and a drain electrode provided on an insulating substrate with a constant gap, and (b) a source region made of a high-concentration impurity semiconductor layer provided on the source electrode and the drain electrode, respectively. And a drain region, (c) a functional layer provided at least in a gap between the source region and the drain region, and (d) a gate electrode provided on the functional layer via a gate insulating film. 2. The thin film transistor according to claim 1, wherein the source electrode and the drain electrode have a two-layer structure of a transparent electrode film and a metal electrode film. 3. A source region having a constant gap by (e) sequentially laminating a conductive film and a high-concentration impurity semiconductor layer on an insulating substrate, and (f) successively patterning the high-concentration impurity semiconductor layer and the conductive film. And (d) a semiconductor layer, an insulating film, and an electrode film are sequentially provided on the insulating substrate provided with the source region and the drain region, and (h) at least the source region. A method of manufacturing a thin film transistor, characterized in that the semiconductor layer, the insulating film and the electrode film are patterned so that a functional layer, a gate insulating film and a gate electrode are respectively formed on and above a certain gap between the drain region and the drain region. 4. An active matrix liquid crystal display device in which pixels are formed in a matrix and a switching element is provided for each pixel, wherein the switching element is the thin film transistor according to claim 1.