JPH11177098A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

(57) Abstract: After forming a recess in an insulating substrate 101,
An amorphous semiconductor film is deposited on the insulating substrate 101. The surface of the amorphous semiconductor film is heated and scanned with an excimer laser to form a polycrystalline semiconductor film 102. A first impurity region 103, a second impurity region 104, and an insulator film region 105 are provided in a polycrystalline semiconductor film 102. According to the present invention, a thin film transistor which can operate at high speed and is effective for a semiconductor device used for a liquid crystal display device or a display terminal can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention particularly relates to a semiconductor device having a high performance thin film transistor.

[0002]

2. Description of the Related Art A conventional semiconductor device and its manufacturing method will be described with reference to FIG.

[0003] As shown in FIG.
An amorphous silicon thin film 202 is deposited thereon. Next, FIG.
As shown in (b), when the surface of the amorphous silicon thin film is scanned in the direction of 203 by a linear excimer laser 204, the amorphous silicon thin film 202 is heated by the excimer laser 204, and Changes to a polycrystalline structure.
Excimer laser 2 covers the entire surface of the amorphous silicon film 202.
When scanning heating is performed at 04, a polycrystalline silicon thin film as shown in FIG. 2 (c) is formed. In FIG. 2C, the polycrystalline silicon thin film is composed of silicon crystal grains, and crystal grain boundaries 206 are formed between the crystal grains. The above process is called a laser heating process, and is used when manufacturing a high-quality polycrystalline silicon thin film for forming a thin film transistor on a substrate of a low melting point material such as glass. Regarding these, for example, "1996 Society for Inform
ation Display International Symposium Digest of Te
chnical Papers, pp.17-20 "and" IEEE Transactions on
Electron Devices, vol.43, no.9, 1996.pp.1454-145
8 "etc.

FIG. 2 (d) shows a transistor formed using the polycrystalline silicon thin film of FIG. 2 (c). A gate insulating film 208 such as a silicon oxide film is provided on the polycrystalline silicon thin film 205. Further, a source impurity implantation region 207 and a drain impurity implantation region 209 are provided. A gate electrode is provided over the source and drain regions and the gate insulating film, and a current between the source and the drain can be controlled by a voltage of the gate electrode.

FIG. 3 shows the dependence of the size of silicon crystal grains on the irradiation laser energy. When the laser energy density is less than 200 mJ / cm ² , silicon does not crystallize, but when it exceeds 200 mJ / cm ² , crystallization starts, and the size of crystal grains increases as the laser energy density increases. However, when the laser energy density exceeds 250 mJ / cm ² , silicon crystal grains become small. In order to fabricate a polycrystalline silicon thin film transistor having good characteristics, the silicon crystal grains may be enlarged, so that the laser energy density is set to 250 mJ / cm ² . The value of the laser energy density in the related art described above depends on the properties of the amorphous silicon film (for example, the growth method and the film thickness) and may be different. Regarding these, for example, "AppliedPhysics Letters, vol. 63, no. 14, 1993, pp. 1
969-1971 "etc.

[0006]

In the above prior art, the performance varies between transistors due to the variation in the position and size of crystal grains existing in the silicon channel region below the gate electrode. .

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to provide a semiconductor device having a convex or concave portion provided on a surface of an insulating substrate. The problem can be solved by controlling the position of generation of crystal grain nuclei and the size of crystal grains.

Specifically, a polycrystalline semiconductor film formed on and in contact with the present insulating substrate, first and second conductive regions for passing a current through the polycrystalline semiconductor film, Semiconductor device having an insulating film formed on and in contact with a film, and a control electrode for controlling a current flowing between first and second conductive regions formed on and in contact with the insulating film In the above, the problem can be solved by a semiconductor device or the like in which the average value of the volume of the crystal grains of the polycrystalline semiconductor film in the region below the control electrode is larger than the average value of the volume of the crystal grains of the polycrystalline semiconductor film in the region other than the region below the control electrode. .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an outline of the present invention will be described with reference to FIG. After the concave portions are formed in the insulating substrate 101, an amorphous semiconductor film is deposited on the insulating substrate 101. The surface of the amorphous semiconductor film is heated and scanned with an excimer laser to form a polycrystalline semiconductor film 102. A first impurity region 103, a second impurity region 104, and an insulator film region 105 are provided in a polycrystalline semiconductor film 102.

Hereinafter, a polycrystalline thin film transistor according to an embodiment of the present invention will be described with reference to FIGS.

FIG. 4 shows a process of forming a polycrystalline semiconductor film according to the present invention. First, the insulating substrate 402 (for example, glass,
On the fused quartz, sapphire, etc.), a groove having a downward convex shape is processed by machining, laser, etching process or the like. Next, a semiconductor thin film 401 (for example, S
i, Ge, SiGe, etc.) are deposited using a chemical vapor deposition method, a sputtering method, or the like. The thickness of the semiconductor film 401 is desirably 50 nm or less. Next, the surface of the semiconductor thin film 401 is scanned in the direction 403 by an excimer laser 404 (KrF, XeCl, or the like). The energy of the excimer laser 404 depends on the manufacturing method and thickness of the semiconductor film 401. Check the optimal value in advance. It is preferable that the optimum value of the irradiation energy of the excimer laser be +100 mJ / cm ² or less from the energy value at which the semiconductor film enters a microcrystalline state. Further, the shape of the excimer laser beam may be a point or a line.
When the scanning by the excimer laser is completed, the semiconductor film becomes 405
And a polycrystalline region of 406. Here, the polycrystalline region includes a single crystal region. Note that the crystal grain boundaries are omitted in the figure. Further, the polycrystalline region is formed on the groove of the insulating substrate 402. Forming a first impurity region for a source electrode and a second impurity region for a drain electrode in the microcrystalline region 405;
When an insulating film for a gate electrode is provided in a polycrystalline region and metal electrodes are provided on a source, a drain, and a gate, a thin film transistor 806 of (d) is obtained. In (d), the microcrystalline region 804 of the adjacent transistor 807 is etched to perform element isolation.
In 02, the shape of the groove may be a dotted shape like 501 in FIG. 5 or a linear shape like 601 in FIG. In the case of a linear shape, the shape of the groove is desirably parallel to the width of the gate electrode 803, that is, perpendicular to the channel current, in order to make the channel current uniform.

Further, source and drain regions are provided in a direction perpendicular to the direction of the linear groove, and a polycrystalline semiconductor region is formed on the linear groove with respect to the first, second,. With this arrangement, a high-performance gate array is formed.

In the insulating substrate 402, the shape of the groove may be a wedge-shaped V-shaped groove as shown at 701 in FIG. 7, a semicircular groove as at 702, or a rectangular groove. A semicircle has the advantage that foreign matter is less likely to adhere during manufacturing, and a rectangle can be processed by anisotropic etching.

In addition, the surface of the insulating substrate 402 may be an upwardly projecting protrusion such as 703 and 704 in addition to the downwardly convex groove.

[0015]

According to the present invention, a thin film transistor which can operate at high speed and is effective for a semiconductor device used for a liquid crystal display device, a display terminal or the like can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional structural view of a polycrystalline thin film transistor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a manufacturing process of a conventional polycrystalline thin film transistor.

FIG. 3 is a diagram illustrating the relationship between the size of crystal grains of a polycrystalline semiconductor film and laser energy density in a laser crystallization method.

FIG. 4 is a cross-sectional view illustrating a manufacturing process of a polycrystalline thin film transistor according to an embodiment of the present invention.

5A is a plan view of an insulating substrate, and FIG. 5B is a cross-sectional view thereof, according to another embodiment of the present invention.

6A is a plan view of an insulating substrate according to another embodiment of the present invention, and FIG. 6B is a cross-sectional view thereof.

FIGS. 7A, 7B, and 7C are cross-sectional views of an insulating substrate according to another embodiment of the present invention.

[Explanation of symbols]

101: insulating substrate, 102: polycrystalline semiconductor, 103: drain impurity region, 104: source impurity region, 105
... gate insulator region, 201 ... insulating substrate, 202 ... amorphous silicon film, 203 ... excimer laser scanning direction, 20
4: excimer laser, 205: polycrystalline silicon film, 20
6 ... Grain boundary, 207 ... Source impurity region, 208 ... Gate insulator region, 209 ... Drain impurity region, 301
... Dependence of crystal grain size on laser energy density, 401
... Amorphous semiconductor film, 402 ... Insulating substrate, 403 ... Excimer laser scanning direction, 404 ... Excimer laser, 405 ...
Microcrystalline region, 406: polycrystalline region, 501: groove, 502
... top surface of insulating substrate, 503 ... side surface of insulating substrate, 601 ...
Groove, 602: Upper surface of insulating substrate, 603: Side surface of insulating substrate, 701: V-shaped groove, 702: Semicircular groove, 703: Wedge-shaped projection 704: Circular projection, 801: Insulating substrate, 802: Source impurity region, 803 ... Gate insulating film region, 804, drain impurity region, 805, polycrystalline channel region, 806
... Transistor 1, 807 ... Transistor 2.

Claims (18)

[Claims] A polycrystalline semiconductor film formed on and in contact with an insulating substrate; first and second conductive regions for flowing a current through the polycrystalline semiconductor film; In a semiconductor device having an insulating film formed in contact therewith, and a control electrode for controlling a current flowing between the first and second conductive regions formed in contact with the insulating film, The average value of the volume of the crystal grains of the polycrystalline semiconductor film in the region under the control electrode is larger than the average value of the volume of the crystal grains of the polycrystalline semiconductor film in the region other than the region under the control electrode. Semiconductor device. 2. A polycrystalline semiconductor film formed on and in contact with an insulating substrate, first and second conductive regions for flowing a current through the polycrystalline semiconductor film, and In a semiconductor device having an insulating film formed in contact therewith, and a control electrode for controlling a current flowing between the first and second conductive regions formed in contact with the insulating film, The surface of the insulating substrate in contact with the polycrystalline semiconductor film in the region under the control electrode has at least a portion having a convex or concave portion, and the crystal grains of the polycrystalline semiconductor film in the region under the control electrode The average value of the volume is
A semiconductor device characterized by being larger than the average value of the volume of crystal grains of the polycrystalline semiconductor film in a region other than below the control electrode. 3. A polycrystalline semiconductor film formed on and in contact with an insulating substrate; first and second conductive regions for flowing a current through the polycrystalline semiconductor film; In a semiconductor device having an insulating film formed in contact therewith and a control electrode formed in contact with the insulating film to control a current flowing between the first and second conductive regions, A semiconductor device, characterized in that a surface of the insulating substrate in contact with the polycrystalline semiconductor film in a region under the control electrode has a projection or a depression at least in part. 4. A height difference of a surface of the insulating substrate in a region under the control electrode including the protrusion or the recess is a height difference of a surface of the insulating substrate in contact with the polycrystalline semiconductor film in a region other than under the control electrode. 4. The semiconductor device according to claim 3, wherein the value is larger than the value. 5. The semiconductor device according to claim 1, wherein the protrusion or the recess in the region below the control electrode has an island shape. 6. The semiconductor device according to claim 1, wherein said projection or recess in a region below said control electrode is linear. 7. The semiconductor device according to claim 5, wherein said convex or concave portion in a region below said control electrode has a wedge-shaped cross section in at least one direction. 8. The semiconductor device according to claim 5, wherein said convex or concave portion in a region below said control electrode has a semicircular cross section in at least one direction. 9. The semiconductor device according to claim 5, wherein said convex or concave portion in a region below said control electrode has a rectangular cross section in at least one direction. 10. The semiconductor device according to claim 6, wherein a linear direction of said convex or concave portion is perpendicular to a direction of a current flowing between said first and second conductive regions. 11. The semiconductor device according to claim 10, wherein a plurality of said polycrystalline semiconductor films serving as said current paths are formed. 12. A step of forming a convex or concave portion on an insulating substrate, a step of forming a semiconductor film in contact with the insulating substrate including the convex or concave portion, and irradiating a laser to the semiconductor film to form a polycrystalline semiconductor film. Forming an insulating film in contact with the polycrystalline semiconductor film, and introducing a conductive impurity into the polycrystalline semiconductor film to form first and second conductive regions. Forming a control electrode for controlling a current flowing through the polycrystalline semiconductor film between the first and second conductive regions in contact with the insulating film. 13. The method of manufacturing a semiconductor device according to claim 12, wherein said convex or concave portions are formed in an island shape. 14. The method of manufacturing a semiconductor device according to claim 12, wherein said convex or concave portion is formed in a straight line. 15. The manufacturing method of a semiconductor device according to claim 12, wherein said first and second conductive regions are formed in a region other than a region in which said convex or concave portions are formed. Method. 16. The method of manufacturing a semiconductor device according to claim 12, wherein said convex or concave portion has a wedge-shaped cross section in at least one direction. 17. The method of manufacturing a semiconductor device according to claim 12, wherein said convex or concave portion has a semicircular cross section in at least one direction. 18. The method of manufacturing a semiconductor device according to claim 12, wherein the convex or concave portion has a rectangular cross section in at least one direction.