JP2002093738A - Manufacturing device for polycrystalline semiconductor film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser anneal device for manufacturing a polycrystalline semiconductor film, whereby a highly reliable transistor free of characteristic variations can be obtained by preventing inclusion of impurities to a polycrystalline semiconductor film and reducing projection of a grain part of polycrystalline silicon, when a polycrystalline semiconductor film is formed by laser annealing method. SOLUTION: The manufacturing apparatus of a polycrystalline semiconductor film for crystallizing an amorphous semiconductor film formed on an insulated substrate by means of a beam anneal method has a local shield which can control the atmosphere of the surface of a substrate, which is subjected to beam irradiation in the periphery of laser beam, when laser beam is directed to an amorphous semiconductor film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for producing a polycrystalline semiconductor film by irradiating an amorphous semiconductor film formed on an insulating substrate with a laser to produce a polycrystalline semiconductor film.

[0002]

2. Description of the Related Art A liquid crystal display (LCD) having a thin film transistor (TFT) integrated with a driving circuit in which peripheral circuits are formed on the same substrate together with a high definition liquid crystal display.
Various techniques for forming a polycrystalline silicon film on an insulating substrate made of glass, quartz, or the like have been studied for the purpose of manufacturing.

The driving circuit and the thin film transistor (TFT) are formed using the polycrystalline silicon film.
In particular, a laser annealing method for irradiating the amorphous silicon semiconductor film formed on a glass insulating substrate with a laser beam having a uniform intensity from the front side of the amorphous silicon semiconductor film to melt and recrystallize silicon. It has been known. This laser annealing method uses a thin and long beam pulse whose scanning direction is the short axis direction, so that instantaneous heating and cooling of silicon is performed and the thermal effect on the glass substrate is small, so that inexpensive glass can be used, It has an advantage that a thin film transistor having high mobility can be formed, and has been actively studied.

In the laser annealing method, a linear laser beam 12 is formed as shown in FIG. 5, and the laser beam 12 is applied to an amorphous silicon thin film 13 formed on a glass substrate in the short axis direction. By irradiating the amorphous silicon thin film 13 in the direction indicated by the arrow in FIG.
Can be crystallized in a short time to form polycrystalline silicon.

[0005]

However, polycrystalline silicon formed by this method is very sensitive to surface contamination of the amorphous silicon semiconductor film. Also, when laser annealing is performed in the atmosphere, oxygen in the atmosphere dissolves into silicon and segregates at the grain boundaries of the polycrystalline silicon, which causes volume expansion due to oxidation of the silicon, thereby increasing the surface of the polycrystalline silicon. The height (surface roughness) of the projections is increased. When the height of the protrusion increases, the coverage of the gate insulating film deteriorates, and an electric field concentrates on the tip of the protrusion, which causes a decrease in the reliability of the gate insulating film. In order to prevent this, a polycrystalline semiconductor film manufacturing apparatus that performs laser annealing in a vacuum has been devised and used. However, this conventional manufacturing apparatus requires a chamber to be provided, resulting in a very high apparatus cost. There is a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a polycrystalline semiconductor film manufacturing apparatus capable of manufacturing a good polycrystalline semiconductor film as inexpensively as possible. With the goal.

[0007]

According to the present invention, there is provided an apparatus for manufacturing a polycrystalline semiconductor film for crystallizing an amorphous semiconductor film formed on an insulating substrate by a beam annealing method. When the amorphous semiconductor film is irradiated with the laser beam, a local shield portion which can control an atmosphere of a surface of the substrate to be irradiated with the laser beam is provided.

The local shield portion is made of a material that transmits the laser beam, has an upper surface provided with an inlet through which the laser beam can be received and an inert gas can be introduced, and has a lower surface provided with the inlet. An exhaust port for exhausting the active gas may be provided.

In addition, a forced exhaust port provided on a side surface of the local shield portion for forcibly discharging the inert gas on the substrate surface, and the laser beam provided outside the forced exhaust port is irradiated with the laser beam. And an air curtain section for shielding the substrate region to be protected from the atmosphere with the inert gas.

It is preferable that the exhaust port of the local shield has a width wider than a width of the laser beam and a length longer than a length of the laser beam.

According to the apparatus for manufacturing a polycrystalline semiconductor film of the present invention thus configured, since the atmosphere on the substrate surface can be controlled with an inexpensive apparatus, impurity contamination during laser annealing can be prevented and oxygen content can be reduced. Pressure to a predetermined value (for example, 0.1 Pa
By controlling to (1) below, oxygen segregation at the grain boundary portion can be prevented, the height of surface protrusions of the polycrystalline semiconductor film can be reduced, and a favorable polycrystalline semiconductor film can be obtained.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a polycrystalline semiconductor film manufacturing apparatus according to the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 shows a first embodiment of an apparatus for manufacturing a polycrystalline semiconductor film according to the present invention. The manufacturing apparatus of this embodiment includes an excimer laser light source 6, an optical lens 7, a local shield 9, and a mirror 15. The excimer laser light 8 generated from the excimer laser light source 6 is reflected by a mirror 15 and then sent to a local shield 9 via a laser optical lens 7. The laser light incident on the local shield part 9 is a rectangular light beam having a thin and long cross section. The local shield 9 is shown in FIG.
As shown in FIG. 3, a hollow box is formed of a material that transmits laser light, and an inlet 10 for introducing a processing gas containing nitrogen gas or a predetermined concentration of oxygen containing nitrogen gas as a main component is provided on a side surface. And an exhaust port 9a for exhausting the processing gas is provided on the bottom surface.
The exhaust port 9 a has an elongated rectangular shape, and the length of the rectangle is longer than the length of the beam of the laser beam incident on the local shield 9 and the width of the beam of the laser beam incident on the local shield 9. It is configured to be wider than the width of. The flow rate of the processing gas introduced into the local shield unit 9 through the inlet 10 can be adjusted by a flow rate adjusting unit (not shown).

Next, the operation of the manufacturing apparatus of this embodiment will be described.
The case of manufacturing a polycrystalline silicon film will be described as an example. FIG. 3 is a sectional view of a semiconductor substrate on which an amorphous silicon film is formed. First, in FIG. 3, an SiN film 2 and a SiOx film 3 are sequentially formed as an undercoat layer by an plasma CVD method on an insulating substrate 1 made of, for example, alkali-free glass, and an amorphous silicon film 4 is formed as an active layer. I do. Thereafter, the entire substrate on which the amorphous silicon film 4 is formed is annealed for 1 hour in an N2 atmosphere at 500 ° C. to reduce the hydrogen concentration inside the amorphous silicon film 4 to a predetermined concentration.

Next, this substrate is set in the manufacturing apparatus of this embodiment shown in FIG. A nitrogen gas is introduced into the local shield part 9 from the inlet 10 to control the atmosphere on the surface of the substrate 1. From the experimental results, it is necessary to adjust the flow rate of the nitrogen gas so that the oxygen partial pressure can be controlled to 0.1 Pa or less when the purpose is to reduce the surface protrusion of the polycrystalline silicon. Excimer laser light 8 emitted from the excimer laser light source 6 is incident on the upper surface of the local shield 9 via the mirror 15 and the laser optical lens 7.
Then, the laser light 8 incident on the upper surface of the local shield portion 9
Irradiates the amorphous silicon film 4 through the local shield part 9 and through an outlet provided on the bottom surface.

In this embodiment, an elongated laser beam 8 is formed using an excimer laser having a wavelength of 308 nm and a pulse width of 25 nsec.
The amorphous silicon film 4 was laser-annealed while scanning the substrate 1 so as to be irradiated with a pulse to form a polycrystalline silicon film. Laser annealing increases the irradiation energy density to 280
It was set to mJ / cm2. Alternatively, the laser light may be irradiated while heating the glass substrate 1 which is an insulating substrate. In addition,
The scanning direction is the short axis direction of the laser beam 8 as in the case of the related art.

As shown in FIG. 1, since the manufacturing apparatus of the present embodiment includes the local shield 9, it is necessary to control the atmosphere on the surface of the amorphous silicon film 4 to be irradiated with the laser beam to a desired atmosphere. This makes it possible to prevent impurity contamination during laser annealing. Further, by controlling the partial pressure of oxygen contained in the nitrogen gas to 0.1 Pa or less, it becomes possible to prevent oxygen from dissolving into the polycrystalline silicon film 4,
Oxygen segregation at the grain boundary can be prevented and the height of the surface protrusions of polycrystalline silicon can be reduced, so that a highly reliable transistor can be obtained.

Further, since the local shield 9 is a hollow box, the manufacturing cost is not high, and an apparatus for manufacturing a polycrystalline semiconductor film which is as inexpensive as possible can be obtained.

As described above, the manufacturing apparatus of the present embodiment can obtain a polycrystalline semiconductor film which is as inexpensive as possible and has good characteristics without local characteristic fluctuation due to impurities.

In the present embodiment, the local shield 9
Although nitrogen gas or a gas containing nitrogen gas as a main component is introduced as a processing gas from the inlet port 10, another inert gas other than nitrogen gas may be used. Further, in the present embodiment, the inlet 10 is provided on the side surface of the local shield part 9, but may be provided on the upper surface.

(Second Embodiment) Next, FIG. 4 shows the configuration of an apparatus for manufacturing a polycrystalline semiconductor film according to the present invention. The manufacturing apparatus according to this embodiment has a configuration in which forced exhaust ports 21 and 22 and air curtain sections 23 and 24 are provided in the manufacturing apparatus according to the first embodiment. Each of the forced exhaust ports 21 and 22 is a hollow box inside a rectangular parallelepiped provided on the side surface of the local shield section 9, and the entire bottom surface is a processing gas (nitrogen gas or gas mainly containing nitrogen gas). And an exhaust port for exhausting the processing gas is provided on the upper surface.

The air curtain sections 23 and 24 are provided on the side faces of the forced exhaust ports 21 and 22 opposite to the side face on which the local shield section 9 is provided. An inlet (not shown) for introducing the processing gas is provided on the side surface or the upper surface, and an exhaust port for exhausting the processing gas is provided on the bottom surface. I have. For this reason, the periphery of the region of the amorphous silicon film irradiated with the laser beam via the local shield part 9 can be shielded from the atmosphere by the processing gas.

The manufacturing apparatus according to the second embodiment has forced exhaust ports 21 and 22 for forcibly exhausting a processing gas near the substrate surface, and air curtains 23 and 24. Therefore, the airflow control inside the local shield part 9 becomes easier than in the first embodiment, and the oxygen partial pressure on the substrate surface can be easily lowered. In the present embodiment, nitrogen gas is introduced into the inside of the local shield 9 and the exhaust amount is adjusted so that the oxygen partial pressure on the substrate surface becomes 0.1 Pa or less. Further, in the present embodiment, nitrogen gas is used, but another inert gas may be used.

As described above, by using the manufacturing apparatus of the present embodiment, a better polycrystalline semiconductor film can be obtained than in the case of the first embodiment. Further, as in the case of the first embodiment, the manufacturing apparatus can be made as inexpensive as possible.

[0025]

As described above, according to the present invention, a favorable polycrystalline semiconductor film can be manufactured as inexpensively as possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of a polycrystalline semiconductor film according to the present invention.

FIG. 2 is an exemplary perspective view showing the configuration of a local shield unit according to the first embodiment;

FIG. 3 is a cross-sectional view of a substrate on which an amorphous silicon film is formed.

FIG. 4 is a diagram showing a configuration of a second embodiment of the polycrystalline semiconductor film according to the present invention.

FIG. 5 is a diagram showing a beam scanning method when forming a polycrystalline semiconductor film from an amorphous semiconductor film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass substrate 2 SiN film 3 SiOx film 4 Amorphous silicon film 6 Excimer laser light source 7 Laser optical lens 8 Laser beam 9 Local shield part 9a Exhaust port 10 Inlet 12 Linear laser beam 13 Amorphous silicon thin film 15 Mirror 21 , 22 forced exhaust port 23,24 air curtain

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor: Takashi Fujimura 1-9-2, Hara-cho, Fukaya-shi, Saitama F-term in the Toshiba Fukaya factory (reference) 5F052 AA02 BA07 BB07 CA04 CA08 DA02 DB03 EA15 JA01 5F072 AA06 JJ09 KK05 KK30 RR05 SS06 YY08 5F110 AA30 BB01 DD02 DD03 DD13 DD14 GG02 GG13 PP03 PP04 PP05 PP06 PP10 PP35

Claims (4)

[Claims] In an apparatus for manufacturing a polycrystalline semiconductor film for crystallizing an amorphous semiconductor film formed on an insulating substrate by a beam annealing method, a laser beam is applied to the amorphous semiconductor film when the amorphous semiconductor film is irradiated with the laser beam. An apparatus for manufacturing a polycrystalline semiconductor film, comprising: a local shield portion capable of controlling an atmosphere on a surface of a substrate irradiated with light. 2. The local shield section is made of a material that transmits the laser beam. The local shield section has an inlet on an upper surface through which the laser beam is received and through which an inert gas can be introduced. 2. The apparatus for manufacturing a polycrystalline semiconductor film according to claim 1, wherein an exhaust port for exhausting the active gas is provided. 3. The method according to claim 1, wherein the local shield is provided on a side surface of the local shield.
A forced exhaust port for forcibly discharging the inert gas on the substrate surface, and an air curtain provided outside the forced exhaust port to shield a substrate region irradiated with the laser beam from the atmosphere with the inert gas. 3. The apparatus for producing a polycrystalline semiconductor film according to claim 1, further comprising: 4. The laser device according to claim 1, wherein the outlet of the local shield has a width greater than a width of the laser beam and a length longer than a length of the laser beam. 3. The apparatus for manufacturing a polycrystalline semiconductor film according to any one of 3.