JP2000216393A - Manufacture of semiconductor device and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a semiconductor device which can be manufactured without damaging the thin-film element part and whose reliability is high, and to provide a liquid crystal display device. SOLUTION: In this manufacturing method, a structure in which a conductive light-shielding layer 2 is formed in the lower part of a thin-film element part 7 via an interlayer film 3, a contact hole 9 which comes into with the light- shielding layer 2 and a contact hole 10 which comes into contact with the source/drain of the thin-film element part 7 are formed simultaneously. At this time, etching operation is performed by wet treatment or wet treatment after a dry treatment. Thereby, it is possible to prevent the potential difference from being generated due to a plasma in the dry treatment between the thin-film element part 7 (an active layer 4) and the light-shielding layer 2, and the active layer 4 is protected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device suitable for manufacturing a thin film transistor (TFT) for a liquid crystal display device, and a liquid crystal display device.

[0002]

2. Description of the Related Art A liquid crystal display device has hundreds of thousands to millions of transparent pixel electrodes, and its driving method is roughly classified into a simple matrix method and an active matrix method. The active matrix method has a thin film transistor (TFT) as a pixel driving element or a switching element in each transparent pixel electrode, whereas the simple matrix method does not have a transistor. For this reason, the active matrix method requires a higher level of fabrication technology than the simple matrix method, but is superior in reproducing moving images,
Because of its good image quality, it has attracted attention.

In recent years, thin film transistors are mainly produced by forming and processing an amorphous or polycrystalline silicon film as an active layer. The details are disclosed in, for example, Japanese Patent Application Laid-Open No. 8-195495. From the viewpoint of the data signal transmission speed and the storage capacity, the pixel driving element is
A characteristic requiring a large ON / OFF current ratio (a large ON current and a small OFF current) is required. Also, as the structure of the entire pixel driving element including the thin film transistor, many examples have been developed and proposed according to the number of pixels, the application, and the like.

FIG. 5 shows one manufacturing process of one of the thin film transistors. A light-shielding layer 2 is formed on a transparent substrate 1, and a thin-film element portion (thin film transistor) including an active layer 4 made of a polycrystalline silicon film, a gate oxide film 5, and a gate electrode 6 via an interlayer film 3. 7 is formed. The thin film element part 7 is covered with an interlayer film 8. The light-shielding layer 2 is for preventing the characteristic deterioration of the thin film element portion 7 due to light irradiation, and is a conductor layer that is also used as a wiring layer according to design.

Therefore, when forming the contact holes 9 for connecting the light-shielding layer 2 and the conductive layer (wiring layer) above the light-shielding layer 2 in the interlayer films 3 and 8, this is conventionally performed by a dry etching technique using plasma. At the same time, the contact holes 10 for the source and the drain of the thin film element portion 7 are formed.

[0006]

However, just before the opening of the contact holes 9 and 10 by dry etching,
The active layer 4 and the light-shielding layer 2 are each exposed to plasma. However, since there is an electrical resistance difference between the thin-film element portion 7 and the light-shielding layer 2, a potential difference is generated between the two via the interlayer film 2, thereby causing an active state. Layer 4 will be damaged. In response,
The active layer 4 causes crystal defects and the like, resulting in insufficient on-current and reduced withstand voltage.

In addition, the damaged thin film element portion 7
In the liquid crystal display device using the pixel driving unit, a defective bright point due to insufficient ON current and a defective bright spot due to a decrease in withstand voltage occur, which greatly affects reliability.

The present invention has been made in view of the above problems, and has as its object to provide a highly reliable semiconductor device manufacturing method and a liquid crystal display device which can be manufactured without damaging the thin film element portion.

[0009]

In order to solve the above-mentioned problems, the invention according to claim 1 includes a step of forming a conductor layer above or below an active layer via an interlayer film. When a layer is formed or when the conductor layer is processed after formation, when a part of the active layer is electrically exposed directly or through a conductive material, a contact hole for contacting the conductor layer is formed. The formation is performed by a wet etching method.

Here, the conductor layer includes a layer for the purpose of light shielding and wiring, and "at the time of formation of the conductor layer" corresponds to a case where a contact hole for contacting a lower signal line or the like is formed. . Further, “when processing the conductor layer after forming it” corresponds to a case where a contact hole for contacting the conductor layer is formed in the interlayer film covering the conductor layer or a pattern is formed on the formed conductor layer. Further, "when a part of the active layer is electrically exposed directly or through a conductive material", when forming a contact hole contacting the active layer, or via a wiring material connected to the active layer. And electrically exposed to the outside. The same applies to claims 4, 5, and 6.

According to the first aspect of the present invention, in the above case, it is possible to avoid processing only by dry etching using plasma, and to switch to wet etching or wet etching after first performing dry etching. Thus, the active layer is prevented from being directly or indirectly exposed to the plasma, so that the active layer is not damaged.

[0012] The invention according to claim 4 includes a step of forming a conductor layer above or below the active layer via an interlayer film.
When a part of the active layer is electrically exposed directly or through a conductive material when forming the conductor layer or processing the conductor layer after the formation, the thickness of the interlayer film is reduced. By setting the thickness to at least 300 nm or more, even if the active layer and the conductive layer are exposed to plasma, the influence of the potential difference between the two is reduced to protect the active layer.

According to a fifth aspect of the present invention, there is provided a step of forming a conductor layer above or below the active layer via an interlayer film.
When a part of the active layer is electrically exposed directly or via a conductive material when processing the conductive layer after forming the conductive layer, the conductive layer is formed of the same material as the active layer. Thus, even if the active layer and the conductive layer are exposed to plasma, the generation of a potential difference between the two is reduced, and the active layer is protected.

According to the present invention, a step of forming an active layer above the conductor layer via the interlayer film, a step of forming a contact hole in the interlayer film to contact the conductor layer, Forming a wiring film for connecting the conductor layer to a predetermined potential via a contact hole, wherein the wiring film is formed of a semiconductor material at the same time as the step of forming the gate electrode of the active layer. I have. That is, according to the present method, the same operation and effect as those in claim 5 can be obtained, and the floating state of the conductive layer is avoided by lowering the conductive layer to some potential, thereby reducing the thickness of the thin film element portion. The desired characteristics are maintained.

Further, according to the invention of claim 7, by using the semiconductor device manufactured by each of the above methods as a pixel driving element of the liquid crystal display device, a liquid crystal display device with excellent reliability can be obtained.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. In each of the embodiments described below, a method of manufacturing a semiconductor device forming a pixel driving element of a liquid crystal display device will be described.

FIGS. 1 and 2 show a first embodiment of the present invention. Referring to FIG. 1, aluminum, titanium, and the like as a conductive layer on a transparent substrate 1 such as a glass substrate.
Tungsten, tungsten silicide, molybdenum,
After forming a light-shielding layer 2 made of a conductive material such as copper or chromium, a silicon oxide film (Si) is formed thereon as a first interlayer film 3.
O ₂ ), silicon nitride (Si ₃ N ₄ ), PSG (Phospho Si
license Glass), NSG (Non-doped Silicate Glas)
s), an insulating film such as a BPSG (Boron Phospho Silicate Glass) film is formed to a thickness of 300 nm or more. afterwards,
After forming a thin film element portion (thin film transistor) 7 including an active layer 4 made of polycrystalline silicon, a gate oxide (insulating) film 5 and a gate electrode 6 made of polycrystalline silicon, the thin film element portion 7 is formed as a first interlayer film 3. It is covered with a second interlayer film 8 made of a similar material. In the above-described film forming process of each layer, a known film forming technique such as a PVD method or a CVD method is used. or,
The gate oxide film 5 is formed by an oxidation method such as a high-temperature oxidation method, a low-temperature oxidation method, and an anodic oxidation method.

After the formation of the second interlayer film 8, contact holes 9 for contacting the source side and the drain side of the light-shielding layer 2 and the thin film element portion 7, respectively, are formed by lithography.
Form 10. Processing of the contact holes 9 and 10
It is desirable to perform wet etching by selective chemical corrosion using an etchant, but it is also possible to perform processing halfway by dry etching using plasma and then switch to wet etching. In the present embodiment,
After the contact hole 10 and the upper portion 9a of the contact hole 9 are opened by dry etching, the lower portion 9b of the contact hole 9 is processed by wet etching.

The present embodiment is designed to lower the light-shielding layer 2 to a wiring or a predetermined potential on the same layer as a wiring or an electrode formed on the source side and the drain side of the thin film element portion 7. If the thin film element portion 7 and the light shielding layer 2 are simultaneously exposed to the outside when the contact holes 9 and 10 are formed, processing by plasma is avoided, and processing is performed by switching to wet etching or switching to wet etching in the middle. To do.

Therefore, there is no potential difference between the thin film element portion 7 and the light shielding layer 2 during the processing, so that the thin film element portion 7 is not damaged, and the shortage of the ON current and the reduction of the breakdown voltage occur. There is no. When the light-shielding layer 2 is not used as a wiring, the potential is lowered to a predetermined potential to avoid a floating state, so that an adverse effect on image quality can be avoided.

Referring to FIG. 2, a wiring 11 is formed by forming and patterning a wiring film of aluminum, tungsten or the like in the opened contact holes 9 and 10. At the time of forming the pattern, in the dry etching method, a plasma potential acts on the thin film element portion 7 and the light shielding layer 2 via the wiring material 11, and the active layer 4 is damaged by a potential difference between the two. This is performed by a wet etching method. Next, a third interlayer film 12 is formed on the wiring 11.
And a light-shielding film 13 that covers the upper part of the thin-film element part 7 is connected to the source side of the thin-film element part 7. The light shielding film 13 is made of a conductive material, and is connected to an ITO (Indium Tin Oxide) film 15 which is a transparent pixel electrode via a flattening film 14. An organic film (light distribution film) 16 is formed on the ITO film 15. On one counter substrate 20, an ITO film 19, an organic film 18, and a color filter (not shown) are formed in a known manner, and the liquid crystal 17 is sealed between the substrates 1 and 20 to realize a liquid crystal display device. Be composed.

Therefore, if the thin film element section 7 manufactured according to the present embodiment is used as a pixel driving element, a liquid crystal display device having high reliability and excellent image quality can be obtained.

FIG. 3 shows a second embodiment of the present invention. In the present embodiment, a method for manufacturing a pixel driving element for a liquid crystal display device having a structure in which a light shielding layer is formed above the thin film element section 7 will be described.

On the transparent substrate 1, a thin film element portion 7 having the same structure as that of the first embodiment is formed, and a first interlayer film 21 is formed thereon. After forming contact holes 22 for contacting the source and drain regions of the thin film element section 7 with respect to the first interlayer film 21, a wiring film 23 is formed and patterned. The processing of the wiring film 23 may be performed by a dry etching method. In this case, however, the thickness of the first interlayer film 21 is set to at least 300 nm or more to avoid the influence of the plasma acting on the thin film element portion 7. That is,
The first interlayer film 21 is used as a protective film to protect the thin film element unit 7 from plasma. Further, with this configuration, it is possible to avoid a coupling phenomenon between the gate electrode 6 of the thin film element unit 7 and the signal line (drain wiring 22) when driving the liquid crystal display device.

Also in this embodiment, the light shielding layer is also used as a wiring layer, and a contact hole 25 is opened in the second interlayer film 24 so as to be connected to the wiring 23 connected to the source or drain of the thin film element portion 7. Later, it is formed. If this contact hole 25 is formed by dry etching, a plasma potential acts indirectly on the thin film element 7 via the wiring 23, and if the source and drain sides of the thin film element 7 have different potentials, A potential difference is generated between the two, and the thin film element portion 7 (active layer 4) is damaged. Therefore, the above problem is avoided by forming the contact hole 25 by a wet etching method or a combination of dry and wet, similarly to the method of forming the contact hole 9 in the above-described first embodiment.

According to the present embodiment, the same effects as those of the first embodiment can be obtained. If the thin film element section 7 formed as described above is used as a pixel driving element in a liquid crystal display device, A highly reliable product can be obtained.

FIG. 4 shows a third embodiment of the present invention. In the present embodiment, when forming the thin film element portion 7 above the light shielding layer 32 made of a conductive material formed on the transparent base material 1 via the interlayer film 33, the gate electrode 6 of the thin film element portion 7 is formed at the same time. Then, a wiring film 61 connected to the light shielding layer 32 is formed of the same material (polycrystalline silicon) as the gate electrode 6. That is, the present embodiment is an example of a configuration in which wiring is performed using a film of the same layer as the gate electrode 6 of the thin film element portion 7 for the purpose of lowering the light shielding layer 32 to some potential.

The formation of the contact hole 34 for contacting the light-shielding layer 32 in the interlayer film 33 can be performed by a wet etching method, a dry etching method, or a combination thereof. Since the active layer 4 and the gate oxide film 5 constituting the thin film element portion are previously covered with a photoresist (thickness: about 1.3 μm), the active layer 4 is greatly affected by plasma even in the dry etching method. There is no.

After the formation of the contact hole 34, a polycrystalline silicon film is formed, and is formed and processed as the gate electrode 6 of the thin film element portion 7 and the wiring film 61 connected to the light shielding layer 2. Although the wiring film 61 is formed of a high-resistance polycrystalline silicon film, it is not sufficient to function as a normal wiring. However, the light-shielding layer 32 is dropped to some potential in order to avoid floating of the light-shielding layer 32. This configuration is sufficient because a high electrical conductivity is not required when performing the function. Further, according to this configuration, the polycrystalline silicon film 6
Even if the dry etching method is used during the processing of 61, a plasma potential is applied to the active layer 4 and the light-shielding layer 32 via the same material, so that no large potential difference occurs between the active layer 4 and the light-shielding layer 32. No damage is taken.

Therefore, according to the present embodiment, the same effects as those of the above-described first embodiment can be obtained, and when the thin film element section 7 manufactured thereby is used as a pixel driving element for a liquid crystal display device. In addition, a highly reliable and high quality liquid crystal display device can be obtained.

Although the embodiments of the present invention have been described above, the present invention is, of course, not limited to these embodiments.
Various modifications are possible based on the technical idea of the present invention.

For example, in the first embodiment described above, the contact hole 9 is formed by wet etching or a combination of dry etching and wet etching so that the contact between the thin film element portion 7 and the light shielding layer 2 is made. Although no potential difference is generated between the thin film elements, the interlayer film 3 interposed between the thin film element portion 7 and the light shielding layer 2 may be formed to a thickness of at least 300 nm or more. Damage to the element portion can be reduced. Therefore, in this case, even if the contact hole 9 is formed by the dry etching method, no significant damage is given to the thin film element portion 7.

Instead of the above structure, the light shielding layer 2 is made of the same material (polycrystalline silicon,
Or amorphous silicon), it is possible to avoid the occurrence of a large potential difference between the two, so that even with this configuration, it is possible to avoid damage to the active layer 4 and obtain a highly reliable liquid crystal display device. Can be.

Further, in each of the above embodiments, a method of manufacturing a thin film transistor as a semiconductor device used as a pixel driving element for a liquid crystal display device has been described. Of course, other semiconductor devices such as a dynamic RAM (DRAM) memory cell may be used. The present invention is applicable to an apparatus.

[0035]

As described above, according to the present invention, the following effects can be obtained.

According to the method of manufacturing a semiconductor device of the first aspect, it is possible to avoid damage to the active layer due to a potential difference, thereby improving drive failure and breakdown voltage due to insufficient on-current and improving reliability. Can be.

According to the second aspect of the present invention, the active layer and the conductor layer are not simultaneously exposed to plasma, so that damage to the active layer can be avoided.

According to the third aspect of the present invention, the wiring layer to which the active layer and the conductor layer are connected is processed by the wet etching method, so that the active layer can be prevented from being damaged.

According to the method of manufacturing a semiconductor device of the fourth aspect, the thickness of the interlayer film interposed between the active layer and the conductor layer is set to 300 nm or more, so that the active layer and the conductor during dry etching can be formed. Damage to the active layer due to a potential difference between the active layer and the layer can be avoided.

According to the fifth aspect of the present invention, the potential difference between the active layer and the conductive layer during dry etching is reduced by forming the conductive layer with the same material as the active layer. Thus, damage to the active layer can be avoided.

According to the method of manufacturing a semiconductor device of the sixth aspect, the present invention is applied as a pixel drive element for a liquid crystal display device while avoiding the floating state of the conductor layer while obtaining the same effects as the fifth aspect of the invention. In some cases, good image quality is obtained.

According to the liquid crystal display device of the seventh aspect,
By using a semiconductor device manufactured by any of the above methods as a pixel driving element, a highly reliable liquid crystal display device can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one manufacturing step of a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view of a pixel portion of a liquid crystal display device using the same semiconductor device as a pixel driving element.

FIG. 3 is a schematic cross-sectional view showing one manufacturing step of a semiconductor device according to a second embodiment of the present invention.

FIG. 4 is a schematic sectional view showing one manufacturing step of a semiconductor device according to a third embodiment of the present invention.

FIG. 5 is a schematic cross-sectional view showing one manufacturing step of a semiconductor device according to a conventional method.

[Explanation of symbols]

2, 32: light shielding layer, 3, 8, 21, 24, 33: interlayer film, 4: active element, 6: gate electrode, 7: thin film element,
9, 25: contact hole, 61: wiring film.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/768 F term (Reference) 2H092 GA17 GA25 GA34 JA24 JA34 JA37 JA46 KA02 KA04 MA08 MA18 MA19 NA25 4M104 AA09 BB01 BB02 BB04 BB13 BB14 BB16 BB18 BB28 BB40 CC01 EE06 EE12 EE15 GG09 GG16 GG20 HH20 5F033 HH08 HH11 HH17 HH18 HH19 HH20 HH28 PP06 PP14 QQ08 QQ10 QQ11 QQ19 RR01 A11 RR04 RR04 A11 RR04 RR06 A11 RR04 RR06 A11 RR04 DD02 DD12 DD13 DD14 EE09 FF23 FF24 GG02 GG13 GG42 GG44 NN03 NN22 NN23 NN24 NN25 NN33 NN35 NN44 NN45 NN46 NN47 QQ03 QQ08

Claims (7)

[Claims] A step of forming a conductive layer above or below an active layer via an interlayer film, wherein the conductive layer is formed or processed after the conductive layer is formed. When a part of the active layer is electrically exposed directly or through a conductive material, a contact hole for contacting the conductive layer is formed by a wet etching method. 2. The method according to claim 1, wherein a contact hole for contacting the active layer is formed simultaneously with the formation of the contact hole for contacting the conductor layer. 3. The method of manufacturing a semiconductor device according to claim 2, wherein the processing of the wiring film filling each contact hole of the conductor layer and the active layer is performed by a wet etching method. 4. A step of forming a conductor layer above or below the active layer with an interlayer film interposed therebetween, wherein at the time of forming the conductor layer or processing the conductor layer after the formation, When a part of the active layer is electrically exposed directly or via a conductive material, the thickness of the interlayer film is at least 300 nm or more. 5. A step of forming a conductor layer above or below an active layer via an interlayer film, wherein when the conductor layer is formed and then processed, a part of the active layer is directly Alternatively, when the conductive layer is electrically exposed via a conductive material, the conductive layer is formed of the same material as the active layer. 6. A step of forming an active layer above a conductor layer through an interlayer film; a step of forming a contact hole in the interlayer film to contact the conductor layer; and forming the conductor layer through the contact hole. Forming a wiring film for connecting a layer to a predetermined potential, wherein the wiring film is formed of a semiconductor material simultaneously with the step of forming the gate electrode of the active layer. . 7. A liquid crystal display device using a semiconductor device manufactured by the method for manufacturing a semiconductor device according to claim 1 as a pixel driving element.