JPH11219905A - Thin film semiconductor device, method for manufacturing the same, method for manufacturing thin film transistor, thin film transistor, and liquid crystal display device - Google Patents

Abstract

(57) [Summary] (Modified) [PROBLEMS] To increase the crystal grain size of a crystalline semiconductor by a method that does not adversely affect other manufacturing steps when manufacturing a thin film semiconductor device. A surface of a semiconductor to be irradiated with a laser is processed into a shape in which a temperature gradient component parallel to a base substrate is generated in one direction during laser irradiation. During cooling, crystal growth occurs in a direction parallel to this temperature gradient, and the crystal grows parallel to the underlying substrate, and unlike the case where it grows in the vertical direction, the growth stops at the interface or surface with the underlying silicon oxide film 2 Therefore, high-quality polycrystalline silicon 5 having a large crystal grain size of 1 μm can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thin film semiconductor device and a method for manufacturing the same.

[0002]

2. Description of the Related Art With respect to a method of manufacturing a crystalline semiconductor by irradiating a semiconductor with an energy beam, a method of controlling the crystallinity is described in Japanese Patent Application Laid-Open No. 61-241909. There is a method of selectively forming a crystal having a specific plane orientation by forming a groove in an insulator underlying a semiconductor to be formed.

[0003]

In the above-mentioned prior art, the step of the groove of the underlying insulating film is 2,000.degree., And the crystalline semiconductor manufactured by this method is used for a thin film transistor for driving a pixel or a circuit of a liquid crystal display device. In the region where the semiconductor is removed, the metal wiring is likely to be cut due to the exposed step, and the manufacturing yield is reduced.

[0004]

In order to solve the above-mentioned problems, the feature of the present invention is that the surface of a semiconductor to be irradiated with a laser is processed without modifying the underlying insulating film so that the surface is parallel to the surface when the laser is irradiated. The purpose of the present invention is to provide a shape in which a component of a temperature gradient is generated in one direction.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1A, an underlying silicon oxide film 2 is formed on a glass substrate 1 by a plasma CVD method using tetraethylorthosilicate (TEOS) and oxygen gas as raw materials. A 70 nm-thick amorphous silicon film 3 is formed thereon by a low pressure CVD method using disilane as a source gas. Next, as shown in FIG. 1B, a photolithography method and anisotropic dry etching using methane tetrafluoride and oxygen gas are performed to a depth of 2
A groove having a thickness of 0 nm and a width of 1 μm is formed at a pitch of 1 μm.

When the XeCl excimer laser 4 having an energy density of 450 mJ / cm ² is irradiated on the amorphous silicon 3 as shown in FIG. Due to the difference in heat capacity resulting from the difference in film thickness, a temperature difference occurs during melting, and a temperature gradient parallel to the substrate occurs.

Since crystal growth occurs in the direction parallel to this temperature gradient during cooling, the crystal grows parallel to the underlying substrate as shown in FIG. The growth is not stopped at the interface or the surface of the high-quality polycrystalline silicon 5 having a large crystal grain size of 1 μm.

When the surface shape of the polycrystalline silicon 5 is examined with an atomic force microscope (AFM), as shown in FIG. 2, the step on the surface is reduced from 20 nm to 10 nm by laser irradiation. This step is much smaller than the unevenness of about 50 nm that occurs when the surface is not processed. It is probable that the step due to the processing was reduced because a slight surface tension acted when the silicon was melted and recrystallized. Also, unlike the conventional case, when the crystal grows in parallel with the underlying substrate, it is considered that the growth of large projections is suppressed.

As described above, according to the present invention, a high-quality crystalline semiconductor having a large crystal grain size can be manufactured. In the above embodiment, the surface shape of the amorphous silicon 3 is set to a depth of 20 n.
Although grooves having a width of 1 μm and a width of 1 μm are arranged at a pitch of 1 μm, the shape may be any shape that can generate a temperature gradient component parallel to a semiconductor base substrate in one direction when irradiated with an energy beam. Is not limited. In addition, the present invention is not limited to silicon, and may be any semiconductor material that can be melted and recrystallized by irradiation with an energy beam.

Next, a description will be given of a second embodiment in which the present invention is applied to the manufacture of an n-type thin film transistor having a coplanar structure. As described in the first embodiment, the base silicon oxide film 2 and the amorphous silicon film 3 are formed on the glass substrate 1 as shown in FIG.
After forming a groove having a width of 1 μm and a pitch of 1 μm, X
Irradiate with eCl excimer laser 4 to obtain polycrystalline silicon 5
Is prepared.

Then, as shown in FIG. 3A, the polycrystalline silicon 5 is patterned into an island shape by photolithography and dry etching. Next, a gate insulating film 6 made of 100 nm silicon oxide is formed by a plasma CVD method using TEOS and oxygen gas as raw materials. Next, a 100-nm niobium (Nb) 7 film is formed by a sputtering method.
Next, as shown in FIG. 3B, the gate electrode 8 is formed by etching the niobium 7 and the gate insulating film 6 by photolithography and dry etching. Next, as shown in FIG. 3C, after implanting impurity phosphorus (P) by a plasma doping method, it is activated by irradiation with a XeCl excimer laser 4,
A source region 9 and a drain region 10 are formed.

Next, as shown in FIG. 3D, a protective film 11 made of silicon oxide having a thickness of 300 nm is formed, and contact holes 12 are formed by photolithography and dry etching.
Open. Next, as shown in FIG.
After forming a film of chromium (Cr) with a thickness of nm, the thin film transistor is completed by forming a source electrode 13 and a drain electrode 14 by patterning by photolithography and wet etching.

As described above, by using high-quality polycrystalline silicon having a large crystal grain size according to the present invention for the active layer, a high-performance thin film transistor having a mobility of 300 cm ² / V · s or more can be manufactured. In the above embodiment, the structure of the thin film transistor is a coplanar type. However, the present invention does not limit the type of a transistor to be applied, such as a thin film transistor having a forward stagger structure or a reverse stagger structure.

Next, a description will be given of a third embodiment in which the thin film transistor according to the present invention is applied to a drive element of a display pixel of an active matrix type liquid crystal display device.

FIG. 4 shows the configuration of an active matrix type liquid crystal display device according to an embodiment of the present invention. In the figure,
A thin film transistor (TFT) is provided for each of a plurality of liquid crystal cells (LC) arranged in a matrix, and each liquid crystal cell is driven by a switching operation of the TFT. Here, a gate voltage is sequentially applied to the gate lines G1 to GM, which are electrodes commonly extracted from the gates of the TFTs arranged in the horizontal direction on the glass substrate 1, and the gate is turned on for each gate line. Go.

On the other hand, drain lines D1 to D1, which are electrodes commonly extracted from the respective drains of the TFTs arranged in the vertical direction,
The data voltage for each of the turned on gate lines is sequentially applied to DN, and is applied to each liquid crystal cell. FIG. 5 shows a planar structure of one pixel including one liquid crystal cell and a TFT. FIG. 6 shows a cross-sectional structure taken along a broken line XX 'in FIG.

A TFT formed near the intersection of the drain wiring D and the gate wiring G and a liquid crystal cell LC connected to the TFT via a source electrode 13 are arranged. The sectional structure of the TFT is almost the same as that of the second embodiment. This structure can be obtained by the manufacturing method described in the same embodiment, but only the points different from the above-described process are as follows. The gate wiring G was formed simultaneously with the gate electrode 8 by film formation and etching.

After forming the source and drain electrodes 13 and 14, an interlayer insulating film 15 made of SiN was formed. After processing this to form a contact hole to the source electrode 13, ITO was deposited and patterned to form the pixel electrode 16. Next, other portions such as liquid crystal other than the TFT will be described below.

The TN liquid crystal 17 is sealed between a glass substrate on which a TFT is formed and a glass substrate (opposite substrate) 18 facing the TFT. On the counter substrate, a black matrix 19 for blocking unnecessary light rays and a counter electrode 20 made of ITO are formed.

The liquid crystal is formed between the counter electrode 20 of the counter substrate 18 and the T.
It is driven by a voltage between the pixel electrodes 16 of the FT substrate, and displays an image on a pixel matrix by changing the brightness to be displayed for each pixel. A polarizing plate 21 for deflecting light is attached to each of the glass substrates 1 and 18. This 2
If the deflecting axes of the deflecting plates are arranged orthogonally or in parallel, the display modes are normally black and normally white, respectively.

Also, an alignment film 22 for aligning the liquid crystal.
However, it is applied to the surface of the interlayer insulating film 15 and the pixel electrode 16 on the surface in contact with the liquid crystal, that is, on the glass substrate 1 side, and on the surface of the counter electrode 20 on the counter substrate 18 side. The surface of the alignment film is treated by a rubbing method after coating to give anisotropy for aligning liquid crystal molecules.

When the TFT manufactured according to the present invention is used as a driving element for a pixel in a display section of an active matrix type liquid crystal display device, the thin film transistor can be reduced in size due to the high mobility of the active layer, and thus high definition and low resolution can be achieved. It is possible to manufacture a liquid crystal display device with low power consumption. Further, when a peripheral circuit is formed by the thin film transistor according to the present invention, the size of the liquid crystal display device can be reduced by reducing the frame area.

[0024]

According to the present invention, a high quality crystalline thin film semiconductor device having a large crystal grain size can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a crystallization method using a laser beam of a semiconductor according to the present invention.

FIG. 2 is a diagram showing a result of examining a surface shape of a crystalline semiconductor manufactured according to the present invention by AFM.

FIG. 3 is a diagram showing a manufacturing process of a thin film transistor to which the present invention is applied.

FIG. 4 is a diagram showing a configuration of an active matrix type liquid crystal display device in which a thin film transistor according to the present invention is applied to a pixel driving element.

FIG. 5 is a diagram showing a planar structure of one pixel of a liquid crystal display device in which a thin film transistor according to the present invention is applied to a pixel driving element.

FIG. 6 is a diagram showing a cross section of one pixel of a liquid crystal display device in which a thin film transistor according to the present invention is applied to a pixel driving element.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... Underlying silicon oxide film, 3 ... Amorphous silicon, 4 ... XeCl excimer laser, 5 ... Polycrystalline silicon, 6 ... Gate insulating film, 7 ... Niobium (Nb), 8 ... Gate electrode, 9 ... source region, 10 ... drain region, 11 ...
Protective film, 12: contact hole, 13: source electrode,
14 drain electrode, 15 interlayer insulating film, 16 pixel electrode, 17 liquid crystal, 18 counter substrate, 19 black matrix, 20 counter electrode, 21 polarizing plate, 22 alignment film.

Claims (10)

[Claims] In a method of manufacturing a thin film semiconductor device in which a semiconductor is irradiated with an energy beam and melt-crystallized to produce a crystalline semiconductor, a semiconductor surface shape before the energy beam irradiation is applied to a semiconductor base substrate during laser irradiation. A method of manufacturing a thin film semiconductor device, comprising processing a shape in which a component of a temperature gradient parallel to one direction occurs in one direction. 2. A method for manufacturing a thin film semiconductor device in which a semiconductor is irradiated with an energy beam and melt-crystallized to produce a crystalline semiconductor, wherein the semiconductor surface shape before the energy beam irradiation is higher than a certain reference position. A thin film semiconductor device, which is formed into a shape that alternately appears in one direction with a low region. 3. A method for manufacturing a thin film semiconductor device in which a semiconductor is irradiated with an energy beam and melt-crystallized to produce a crystalline semiconductor, wherein the shape of the semiconductor surface before the energy beam irradiation is higher than a certain reference position. A thin film semiconductor device, which is formed into a shape which alternately appears in one direction with a low surface. 4. A method for manufacturing a thin film semiconductor device in which a semiconductor is irradiated with an energy beam and melt-crystallized to produce a crystalline semiconductor, wherein the semiconductor surface shape before the energy beam irradiation is higher than a certain reference position. A thin film semiconductor device, which is formed into a shape that alternately appears in one direction with a low area having a low area. 5. A method for manufacturing a thin film semiconductor device in which a semiconductor is irradiated with an energy beam and melt-crystallized to produce a crystalline semiconductor, wherein the semiconductor surface shape before the energy beam irradiation is higher than a certain reference position. A thin film semiconductor device, which is formed so as to alternately appear in one direction with a low surface. 6. The method according to claim 1, wherein the semiconductor is silicon. 7. A gate electrode made of an electrically conductive material, a gate insulating film made of an insulator, an active layer made of a semiconductor, an ohmic contact layer formed by injecting impurities into a semiconductor, and an electrically conductive material on a supporting substrate. 7. The method for manufacturing a thin film transistor according to claim 1, wherein an active layer is manufactured in the method for manufacturing a thin film transistor including a source / drain electrode. 8. A gate electrode made of an electrically conductive material, a gate insulating film made of an insulator, an active layer made of a semiconductor, an ohmic contact layer formed by injecting impurities into a semiconductor, and an electrically conductive material on a supporting substrate. A thin film transistor comprising a source / drain electrode, wherein a shape of a surface of an active layer is higher and lower than a certain reference position at least in a certain direction alternately in one direction. 9. A gate electrode made of an electrically conductive material, a gate insulating film made of an insulator, an active layer made of a semiconductor, an ohmic contact layer formed by implanting impurities into a semiconductor, and an electrically conductive material on a supporting substrate. A thin film transistor comprising a source / drain electrode, wherein a shape of a surface of an active layer has a shape in which a high region and a low region with respect to a certain reference position alternately appear periodically in at least one direction. . 10. A liquid crystal display device using a thin film transistor for driving a pixel or driving a peripheral circuit, wherein the thin film transistor is used.
The liquid crystal display device according to the item.