JPH11126904A - Thin film transistor device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent ultraviolet rays from reaching an LDD area by providing an island-shaped light shielding layer, which is formed on an interlayer insulating film layer on a region equivalent to the upper region of a low impurity concentration region to cover the entire low impurity concentration region. SOLUTION: On a transparent insulating board 11, a channel region 12a, LDD regions 12b and 12c whereupon low-dose phosphorus ions are to be doped, a source region 12d whereupon a high dose phosphorus ions are to be doped and a semiconductor layer 12 having a drain region 12e are pattern-formed. Island-shaped light shielding layers 21 and 22 covering the upper parts of the LDD regions 12b and 12c are formed of the same material as a drain wiring 17 and a source wiring 18 in the region equivalent to the upper regions of the LDD regions 12b and 12c on the interlayer insulating film 16. Since the LDD regions 12b and 12c are covered with the light shielding layers 21 and 22, ultraviolet rays are prevented from reaching the LDD regions 12b and 12c even when a ultraviolet ray irradiation process is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a thin film transistor device having a semiconductor layer made of polysilicon and used for a drive circuit of a liquid crystal display device or the like, and a method of manufacturing the thin film transistor device.

[0002]

2. Description of the Related Art A thin film transistor device (hereinafter abbreviated as TFT) used for a driving circuit of a liquid crystal display device has a high mobility and good semiconductor characteristics. Polysilicon TFTs having different semiconductor layers have been developed. This polysilicon TFT generally suppresses the electric field intensity near the end of the source / drain region and reduces the leak current to improve the performance and reliability of the TFT and obtain good characteristics. Source with impurities
A low impurity concentration region (hereinafter abbreviated as an LDD region) whose impurity concentration is lower than that of the source / drain region is formed between the drain region and the drain region. However, in the LDD region, precise resistance value control is required in order to obtain good semiconductor characteristics with a polysilicon TFT.

On the other hand, in the case of a polysilicon TFT, hydrogen (H) plasma processing is performed on the polysilicon layer to terminate the crystal grain boundaries in the polysilicon layer and the dangling bonds of the polysilicon in the crystal grains with hydrogen. By doing so, the semiconductor performance is improved.

[0004]

However, in the above-described conventional polysilicon TFT, when the dangling bonds of the polysilicon in the polysilicon layer are terminated with hydrogen, the silicon-hydrogen (Si-H) bond is formed by ultraviolet rays. It is well known that it is destroyed by the irradiation of the stirrer Bronski effect.

In the process of manufacturing a liquid crystal display device and the like using a polysilicon TFT, a pixel electrode is used for forming various wirings or for developing, peeling, and cleaning steps for assembling a liquid crystal cell. , There are many steps of irradiating the polysilicon TFT with ultraviolet rays.

For this reason, in a polysilicon TFT, a silicon-hydrogen (Si-H) bond in a source / drain region or a low impurity concentration region is destroyed by ultraviolet irradiation during manufacture of a liquid crystal display element or the like. The resistance value of the source / drain region or the low impurity concentration region increases, and the resistance value of the LDD region fluctuates and the characteristics of the polysilicon TFT are degraded despite the necessity of precise control of the resistance value. Had the problem of saying.

In view of the above, the present invention has been made to solve the above-described problem. After terminating dangling bonds of polysilicon by hydrogen plasma treatment, the silicon TFT is irradiated with ultraviolet rays to the polysilicon TFT even though the polysilicon TFT is irradiated with ultraviolet rays. -Hydrogen (S
iH) A thin film transistor device and a thin film transistor device capable of preventing a resistance value in an LDD region from being increased in a manufacturing process of a liquid crystal display element or the like without breaking a bond and maintaining good semiconductor characteristics. It is intended to provide a manufacturing method.

[0008]

In order to solve the above-mentioned problems, the present invention provides an insulating substrate, a channel region formed on the insulating substrate and made of polysilicon, and a low-profile polysilicon film sandwiching the channel region. A semiconductor layer comprising a source / drain region formed into a resistance, a low impurity concentration region interposed between the channel region and the source / drain region on both sides of the channel region, and the channel region via a gate insulating film layer A gate electrode layer formed above, an interlayer insulating film layer covering the insulating substrate above the gate electrode layer, and an opening formed in the gate insulating film layer and the interlayer insulating film layer; Source·
A source / drain wiring layer connected to the drain region,
An island-shaped light-shielding layer formed in a region above the low impurity concentration region on the interlayer insulating film layer and covering the entire low impurity concentration region.

According to another aspect of the present invention, an island-shaped polysilicon layer is formed on an insulating substrate, and a gate insulating film layer is formed on the insulating substrate above the polysilicon layer. Forming a film, forming a gate electrode layer above the polysilicon layer through the gate insulating film layer, and forming a low impurity concentration region by ion-doping the polysilicon layer using the gate electrode layer as a mask. Forming a source / drain region by ion-doping the polysilicon layer via a mask covering above the low impurity concentration region; and terminating the low impurity concentration region and the source / drain region with hydrogen. A step of forming an interlayer insulating film layer on the insulating substrate after the hydrogen termination step, and the step of forming the gate insulating film layer and the Forming an opening in the interlayer insulating film layer, forming a source / drain wiring material on the interlayer insulating film layer, and etching the source / drain wiring material to form the source through the opening. Simultaneously forming a source / drain wiring layer connected to the drain region and an island-shaped light-shielding layer covering the entire upper portion of the low impurity concentration region.

With the above structure, in a polysilicon TFT in which dangling bonds of polysilicon are terminated with hydrogen by hydrogen plasma treatment, even if an ultraviolet irradiation step is performed in manufacturing a liquid crystal display element or the like, even if an LDD process is performed, By preventing the region from being irradiated with ultraviolet light, it is possible to prevent the resistance value of the LDD region from increasing during manufacturing, and to prevent the polysilicon TFT from being increased.
Higher performance polysilicon TFT by maintaining resistance in LDD region precisely controlled during manufacturing
Is what you get.

[0011]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described with reference to FIG. Reference numeral 10 denotes a polysilicon TFT used as a driving circuit of a liquid crystal display device (not shown). On a transparent insulating substrate 11 made of glass or quartz, a channel region 12a made of polysilicon and a low-dose phosphorus are provided. (P ⁺⁾ LDD region 12b which ions are doped, 12c, the high-dose phosphorus (P ⁺⁾ source region 12d which ions are doped,
A semiconductor layer 12 having a drain region 12e is patterned. A gate electrode 14 made of a molybdenum-tungsten alloy (hereinafter abbreviated as MoW) or the like is formed on the semiconductor layer 12 via a gate insulating film 13 made of a silicon oxide film (SiO ₂ ). It is covered with an interlayer insulating film 16 made of ₂ ).

A drain region 12e and a signal line (not shown) are formed on the interlayer insulating film 16 through a contact hole 20a, 20b, which has a three-layer structure of molybdenum-aluminum-molybdenum (Mo-Al-Mo). A source line 18 connecting the drain line 17, the source region 12d, and the pixel electrode (not shown) is formed. A region corresponding to the upper part of the LDD regions 12b and 12c on the interlayer insulating film 16 is made of the same material as that of the drain wiring 17 and the source wiring 18, and the LDD regions 12b and 12c
Island-shaped light-shielding layers 21 and 22 that cover the upper part are formed.

Next, a method of manufacturing the polysilicon TFT 10 will be described.

First, as shown in FIG.
After a polysilicon film is formed thereon, the film is etched to pattern the semiconductor layer 12 in a matrix.

As shown in FIG. 2B, a gate insulating film 13 is formed by a plasma CVD method.

As shown in FIG. 2C, a gate electrode 14 is formed. Using the gate electrode 14 as a mask, the semiconductor layer 12 is doped with phosphorus (P.sup. ⁺ ) Ions at a low dose, and the LDD region 12b, 12c is formed.

As shown in FIG. 2D, a mask 23 is formed, and the semiconductor layer 12 is doped with phosphorus (P.sup. ⁺ ) Ions at a high dose to form a source region 12d and a drain region 12e.
To form

As shown in FIG. 2 (e), the mask 23 is removed, heated and activated, and then exposed to hydrogen plasma to bond unbonded silicon (Si) bonds in polysilicon with hydrogen (H) and terminate. After forming the interlayer insulating film 16, contact holes 20 a and 20 a are formed.

As shown in FIG. 2F, a three-layer structure of molybdenum-aluminum-molybdenum (Mo-Al-Mo) is coated and then etched to form a drain wiring 17, a source wiring 18, and light shielding layers 21 and 22. Simultaneously, the polysilicon TFT 10 is completed.

The polysilicon TFT 1 thus constructed
When 0 was used to form a liquid crystal display element, good driving characteristics of the polysilicon TFT 10 were obtained.

Since the light-shielding layers 21 and 22 are island-shaped and do not contact the source wiring 18 and the drain wiring 17,
Between the gate and the source and between the gate and the source by the light shielding layers 21 and 22
An increase in capacitance coupling between the drains can also be suppressed.

With this configuration, silicon-hydrogen (S
iD) LDD regions 12b and 12c having a bond are covered with light-shielding layers 21 and 22, and the polysilicon TFT 10
Even if an ultraviolet irradiation step is performed in the liquid crystal display element forming step or the like after the formation, the ultraviolet light does not reach the LDD regions 12b and 12c, and the silicon-hydrogen (Si-H) bond in the LDD regions 12b and 12c is There is no destruction by. Therefore, during the formation of the liquid crystal display element and the like, the LDD region 1
The polysilicon TFT 10 can maintain good semiconductor characteristics without increasing the resistance values of 2b and 12c, and can be applied to a higher-performance liquid crystal display device and the like. Further, in the present embodiment, the light shielding layers 21 and 22
Are formed of the same material and in the same process as the source wiring 18 and the drain wiring 17, so that the manufacturing time and the manufacturing cost can be reduced.

The present invention is not limited to the above embodiment, but can be modified without departing from the spirit of the invention. The material of the light-shielding layer and the manufacturing method thereof are not limited. -A material different from the drain wiring layer may be used and formed in another manufacturing process.

[0024]

As described above, according to the present invention, the upper portion of the LDD layer of a polysilicon semiconductor terminated by dangling silicon-hydrogen (Si-H) bonds by dangling silicon (Si) by hydrogen plasma treatment. By covering with a light-shielding layer, even if ultraviolet rays are irradiated when manufacturing a liquid crystal display element or the like using a polysilicon TFT, the ultraviolet rays can be prevented from reaching the LDD layer, and silicon-hydrogen (LD) in the LDD layer can be prevented. Si-H)
Breakage of the bond is prevented. Therefore, the resistance value of the LDD layer of the polysilicon TFT does not increase during the manufacture of the liquid crystal display element and the like, and the resistance value of the LDD layer is maintained in a state controlled with high precision, and the semiconductor characteristics of the polysilicon TFT are maintained. Can be held satisfactorily, and as a result, display quality is high, high definition,
It can be applied to high-performance liquid crystal display devices and the like.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a polysilicon TFT according to an embodiment of the present invention.

FIGS. 2A and 2B show a method of manufacturing a polysilicon TFT according to an embodiment of the present invention. FIG. 2A shows the patterning of the semiconductor layer, FIG. 2B shows the formation of the gate insulating film, and FIG. (D) schematically shows the formation of the source and drain regions, (e) shows the formation of the contact holes after termination of the polysilicon, and (f) shows the formation of the source wiring, drain wiring and light-shielding layer. FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Polysilicon TFT 11 ... Insulating substrate 12 ... Semiconductor layer 12a ... Channel region 12b, 12c ... LDD region 12d ... Source region 12e ... Drain region 13 ... Gate insulating film 14 ... Gate electrode 16 ... Interlayer insulating film 17 ... Drain wiring 18 ... Source wiring 21, 22 ... Light shielding layer

Claims (3)

[Claims] 1. An insulating substrate, a channel region formed on the insulating substrate and made of polysilicon, a source / drain region formed by lowering the polysilicon with the channel region interposed therebetween, and both sides of the channel region. A semiconductor layer comprising a low impurity concentration region interposed between the channel region and the source / drain region; a gate electrode layer formed above the channel region via a gate insulating film layer; An interlayer insulating film layer covering the insulating substrate above, and a source / drain wiring layer connected to the source / drain region through an opening formed in the gate insulating film layer and the interlayer insulating film layer. An island-shaped light-shielding layer formed in a region above the low impurity concentration region on the interlayer insulating film layer and covering the entire low impurity concentration region. A thin film transistor device comprising: 2. An insulative substrate, a channel region formed on the insulative substrate and made of polysilicon, a source / drain region formed by lowering the polysilicon with the channel region interposed therebetween, and both sides of the channel region. A semiconductor layer comprising a low impurity concentration region interposed between the channel region and the source / drain region; a gate electrode layer formed above the channel region via a gate insulating film layer; An interlayer insulating film layer covering the insulating substrate above, and a source / drain wiring layer connected to the source / drain region through an opening formed in the gate insulating film layer and the interlayer insulating film layer. Forming the source / drain wiring layer on the interlayer insulating film layer in a region corresponding to a region above the low impurity concentration region; A thin film transistor device comprising: an island-shaped light-shielding layer covering the entire impurity concentration region. 3. A step of forming an island-shaped polysilicon layer on an insulating substrate; a step of forming a gate insulating film layer on the insulating substrate above the polysilicon layer; Forming a gate electrode layer above the polysilicon layer via a layer, ion-doping the polysilicon layer using the gate electrode layer as a mask to form a low impurity concentration region, Forming a source / drain region by ion-doping the polysilicon layer through a covering mask; hydrogen terminating the low impurity concentration region and the source / drain region; Forming an interlayer insulating film layer on a conductive substrate, and forming openings in the gate insulating film layer and the interlayer insulating film layer in the source / drain regions And a source material on the interlayer insulating film layer.
Forming a drain wiring material, and etching the source / drain wiring material to cover the entire source / drain wiring layer connected to the source / drain region through the opening and the upper portion of the low impurity concentration region; Forming a light-shielding layer in the form of an island at the same time.