JPH1098007A - Heating-type laser treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the efficiency of heat treatment and laser irradiation of a substrate and to also improve the throughput. SOLUTION: A heating-type laser treatment device is provided with a load- lock chamber 1, a heating chamber 2, at least one irradiation chamber 3, a laser optical system for irradiating with a laser beam 4 and a transporting mechanism 5. The load-lock chamber 1 receives a substrate 0 to be treated from the atmosphere and stores it once. The heating chamber 2 stores the substrate 0 transported from the load lock chamber 1 and heats it to a predetermined temperature. The irradiating chamber 3 is provided with a transparent window 3a. It stores the substrate 0 which has been transported from the heating chamber 2. The laser optical system irradiates the substrate 0, stored in the irradiation chamber 3 with the laser beam 4 through the transparent window 3a to carry out a desired treatment. The transporting mechanism 5 transports the substrate 0, in accordance with the predetermined sequence among the load-lock chamber 1, the heating chamber 2 and the irradiation chamber 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heating type laser processing apparatus. More specifically, the present invention relates to a heating type laser processing apparatus used for recrystallization of a semiconductor thin film formed on a substrate and irradiating laser light while heating the substrate.

[0002]

2. Description of the Related Art A thin film semiconductor device is suitable for a driving substrate of an active matrix type liquid crystal display, and is being actively developed. Active matrix liquid crystal displays are building up a large market for small portable TVs and car navigation displays, beginning with displays for notebook computers. Furthermore, in the multimedia age, various types of displays are required as machine interfaces. It is necessary for further development of the active matrix type liquid crystal display to commercialize a display that meets the needs of the market. Technically speaking, thin film semiconductor devices with integrated amorphous silicon thin film transistors have been improved with the development of the liquid crystal display market. Performance is insufficient. It is considered that an ideal form is to form a peripheral drive circuit, an image signal processing circuit, and the like, which are called a system-on-chip technology, on the same glass substrate by the same process. This is considered to be realized by a thin film semiconductor device in which polycrystalline silicon thin film transistors are formed by a low-temperature process. In order to integrally form a driving circuit and a signal processing circuit using a thin film transistor, it is most important to form a high-performance semiconductor thin film on a glass substrate. The only way to obtain an electron mobility of 100 cm ² / v · s or more is to use polycrystalline silicon. At present, a liquid crystal display integrated with a peripheral driving circuit in which a polycrystalline silicon thin film transistor using a high-temperature process is formed integrally is realized. However, in the high-temperature process, heat treatment at 1000 ° C. or more is required for solid-phase growth of a semiconductor thin film, and expensive quartz glass is used as a substrate. Quartz glass becomes very expensive for large substrates. In order to manufacture a polycrystalline silicon thin film transistor using an inexpensive glass substrate, the process temperature must be set to 400 ° C. or less.

[0003]

Laser annealing using laser light has been developed as one of the methods for making the manufacturing process of a thin film semiconductor device a low-temperature process. This involves irradiating a laser beam to a non-single-crystal semiconductor thin film such as amorphous silicon or polycrystalline silicon formed on an insulating substrate and locally heating and melting the semiconductor thin film. It becomes something. Using the crystallized semiconductor thin film as an active layer (channel region), a thin film transistor is integrated and formed. The crystallized semiconductor thin film has high carrier mobility, so that the thin film transistor can have high performance. As shown in FIG. 6, in this laser annealing, the vertical direction (Y
Insulating substrate 0 is intermittently irradiated with a pulse of laser light 4 formed in a belt shape along direction (direction). At the same time, the laser light 4 is moved in the lateral direction (X direction) relative to the insulating substrate 0 while partially overlapping the irradiation areas. In the illustrated example, the insulating substrate 0 is step-moved in the −X direction with respect to the irradiation area of the fixed laser beam 4. As described above, by overlapping the laser beams 4, crystallization of the semiconductor thin film can be performed relatively uniformly. At present, excimer lasers are widely used as laser light sources.
However, this excimer laser cannot make the cross-sectional area of the laser light extremely large due to the relation of output power. For this reason, the laser light is shaped into a band, and scanning (scanning) is performed while overlapping the laser light, thereby irradiating the transparent insulating substrate made of large glass or the like. However, at the time of this scanning, the crystal grain size and the like become non-uniform due to the influence of the energy distribution of the laser beam 4. As a result, the operating characteristics of the thin film transistor integrated in the thin film semiconductor device become uneven, so that it is difficult to perform a uniform display when used in a display or the like. In particular, when the overlap irradiation is performed, the portion annealed at the edge of the laser beam has a different crystallinity from other portions, and is generally in a bad state. In addition, when a thin film transistor having a bottom gate structure is formed, heat accumulation differs between the gate electrode and the glass substrate, so that a difference occurs in the optimum energy of laser light applied to the semiconductor thin film.

One of the methods for solving the above problem is a substrate heating method. When the laser light is irradiated while heating the substrate, the time from melting to solidification of the semiconductor thin film is delayed because the laser energy is small, and the influence of the variation in the energy distribution of the laser light is reduced. Therefore, variation in characteristics of the thin film transistor is reduced. However, in the conventional heating type laser processing apparatus, due to its configuration, the substrate is taken out of the cassette, mounted on a stage, heated, irradiated with laser light, cooled, and then stored in the cassette again. With such an apparatus configuration, heating and cooling take several hours, which is not productive. Therefore, a laser irradiation apparatus capable of efficiently heating and cooling the substrate is required.

[0005]

The following means have been taken in order to solve the above-mentioned problems of the prior art. That is, the heating type laser processing apparatus according to the present invention includes a load lock chamber, a heating chamber, an irradiation chamber, a laser optical system, and a transport mechanism as a basic configuration. The load lock chamber receives a substrate to be processed from the atmosphere and temporarily stores the substrate. The heating chamber stores the substrate transferred from the load lock chamber and heats the substrate to a predetermined temperature. There is at least one irradiation chamber,
It has a transparent window and stores the substrate transferred from the heating chamber. The laser optical system performs predetermined processing by irradiating the substrate stored in the irradiation chamber with laser light through the window.
The transfer mechanism transfers the substrate according to a predetermined sequence between the load lock chamber, the heating chamber, and the irradiation chamber.

Preferably, a cooling unload lock chamber is provided separately from the load lock chamber, and the processed substrate transferred from the irradiation chamber via the transfer mechanism is temporarily stored and cooled, and then is cooled to the atmosphere. Discharge. The heating chamber is of a batch type capable of storing a plurality of substrates at the same time. A plurality of the irradiation chambers are provided, and the laser optical system switches the optical path of one laser beam and sequentially distributes the laser light to the plurality of irradiation chambers. In some cases, a non-single-crystal semiconductor thin film is formed on the surface of the substrate taken in through the load lock chamber, which includes a film formation chamber, while the irradiation chamber stores the film-formed substrate. A recrystallization process for converting the semiconductor thin film from non-single crystalline to polycrystalline by irradiation with laser light is realized.

In the heating type laser processing apparatus according to the present invention, a substrate is fed from a cassette to a vacuum load lock chamber. Thereafter, the substrate is fed to a heating chamber (preheat chamber). After being heated here, it enters the irradiation chamber and is irradiated with laser light. Thereafter, the sheet is fed to the unload lock chamber and cooled, and then returns to the original cassette. By setting the load lock chamber and the heating chamber in a batch system, and adjusting the laser light irradiation time and timing, it is possible to heat the substrate and irradiate the laser light with high throughput without time loss. The efficiency is further improved by providing a plurality of irradiation chambers. For example, when a substrate is being conveyed in one irradiation chamber, laser light irradiation of the substrate can be performed in another irradiation chamber simply by switching the optical path of the laser light.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic block diagram showing a basic configuration of a heating type laser processing apparatus according to the present invention. The heating type laser processing apparatus includes a load lock chamber 1, a heating chamber 2, at least one irradiation chamber 3, a laser optical system for irradiating a laser beam 4, and a transport mechanism 5. The load lock chamber 1 receives the substrate 0 to be processed from the atmosphere and temporarily stores it. The heating chamber 2 stores the substrates 0 sequentially transported from the load lock chamber 1 and heats them to a predetermined temperature. The irradiation chamber 3 has a transparent window 3 a and stores the substrate 0 transferred from the heating chamber 2. A laser optical system (not shown) irradiates a substrate 0 stored in the irradiation chamber 3 with a laser beam 4 through a window 3a to perform a predetermined process. The transport mechanism 5 transports the substrate 0 among the load lock chamber 1, the heating chamber 2, and the irradiation chamber 3 according to a predetermined sequence. In the present embodiment, the load lock chamber 1, the heating chamber 2, the irradiation chamber 3, and the like are arranged radially. The transport mechanism 5 is arranged at the center of these. The transfer mechanism 5 includes a robot unit 5a, and is individually connected to each of the peripheral chambers via a gate valve 7. The robot unit 5a transports the substrate 0 to each of the peripheral chambers according to a predetermined process order.

In some cases, the load lock chamber 1
Separately, a cooling unload lock chamber may be provided. The processed substrate 0 transported from the irradiation chamber 3 via the transport mechanism 5 is temporarily stored, cooled, and then discharged to the atmosphere. The heating chamber 2 is of a batch type capable of storing a plurality of substrates 0 at the same time. Usually, a plurality of irradiation chambers 3 are provided, and the laser optical system switches the optical path of one laser beam 4 to sequentially distribute the laser beams to the plurality of irradiation chambers 3. In addition, the present embodiment includes the film forming chamber 6, and forms a non-single-crystal semiconductor thin film on the surface of the substrate 0 taken in through the load lock chamber 1. The film forming chamber 6 is composed of, for example, a CVD device. The irradiation chamber 3 stores the substrate 0 on which the film has been formed, receives the irradiation of the laser beam 4, and performs a recrystallization process for converting the semiconductor thin film from non-monocrystalline to polycrystalline.

FIG. 2 is a schematic block diagram showing an example of a laser optical system included in the heating type laser processing apparatus shown in FIG. For example, when performing a recrystallization process, XY
An insulating substrate 0 made of low-melting glass or the like is put into the irradiation chamber 3 in which the stage 3b is incorporated. On the surface of the insulating substrate 0, a non-single-crystal semiconductor thin film 10 is previously formed. As the semiconductor thin film 10, for example, P-CVD
Amorphous silicon is formed by the method. In the irradiation chamber 3, for example, the insulating substrate 0 is irradiated with a laser beam 4 emitted from an excimer laser light source 43. Amorphous silicon is once melted and crystallized in a cooling process to be converted into polycrystalline silicon. As a result, the carrier mobility of the semiconductor thin film 10 increases, and the electrical characteristics of the thin film transistor can be improved. A beam former (homogenizer) 45 is inserted in order to shape the cross section of the laser beam 4 into a band shape (line shape) and to keep the energy cross section intensity uniform. The band-shaped laser light 4 that has passed through the beam former 45 is reflected by the reflecting mirror 4.
After being reflected at 6, the light is irradiated to the insulating substrate 0 housed in the irradiation chamber 3 through the window 3a. When the pulse of the laser beam 4 is intermittently irradiated, the XY stage 3b is step-moved in the −X direction in synchronization with the intermittent irradiation. Thereby, the laser light 4
The laser beam 4 is moved in the X direction (lateral direction) relative to the substrate 0 while partially overlapping the irradiation areas of FIG.

FIG. 3 is a schematic perspective view showing a specific configuration example of a heating type laser processing apparatus according to the present invention. This heating type laser processing apparatus is roughly divided into a main body, a laser optical system, a film forming system, and a substrate feeding section. The main body includes a load lock chamber 1, an unload lock chamber 8, three irradiation chambers 31 to 33, a heating chamber 2, and a film forming chamber 6. The laser optical system includes an excimer laser light source (laser oscillation tube) 43, a reflecting mirror 46, a beam former (homogenizer) 45, and a switching mirror 47. This laser optical system has three irradiation chambers 3 in the main body.
Optically connected to 1 to 33. The film forming system includes a gas supply system 61, a main body control rack 62, a remote heat exchanger module 63, a main body pump module 6
4. The process pump module 65 and the like are included. This film forming system is connected to a film forming chamber 6 of the main body.
Perform processing required for CVD. Finally, the substrate feeding system includes an automatic cassette loading station 12 for handling the substrate cassette 11, and is connected to the load lock chamber 1 and the unload lock chamber 8 of the main body. The chambers constituting the main body 5 are arranged in a star shape, and a transport mechanism 5 composed of a transport robot is provided at the center thereof.
Is located. The transfer mechanism 5 is connected to each of the peripheral chambers via a gate valve.

The substrates stored in the substrate cassette 11 are sequentially stored from the automatic cassette loading station 12 into the load lock chamber 1 of the main body. These substrates are sequentially sent to the film forming chamber 6 by the transport mechanism 5. here,
After the semiconductor thin film is formed on the surface of the substrate, it is sent to the heating chamber 2 via the transfer mechanism 5. After heating to a predetermined temperature (for example, 400 ° C.) in the heating chamber 2, the substrate is sequentially sent to one of the three irradiation chambers 31 to 33 via the transfer mechanism 5. Here, the semiconductor thin film formed on the substrate after being irradiated with the laser beam 4 from the laser optical system is subjected to a recrystallization process. At this time, since the substrate is previously heated to a desired temperature in the heating chamber 2, the quality of the recrystallized semiconductor thin film is improved. After the laser irradiation processing, the substrate is fed to the unload lock chamber 8 via the transfer mechanism 5, where it is cooled and then returns to the original cassette 11. In this embodiment, the load lock chamber 1 and the heating chamber 2 are of a batch type. By matching the timing with the laser irradiation time, the substrate can be heated and the laser irradiation can be performed at high throughput without time loss. The main body is provided with three irradiation chambers 31 to 33. By properly using the three irradiation chambers, the processing flow of the substrate is facilitated. For example, when a substrate is being transferred in a certain irradiation chamber, the laser light 4
Is switched by the switching mirror 47, the laser beam 4 can be distributed to another irradiation chamber.

FIG. 4 is a process chart showing a method of manufacturing a thin film semiconductor device by partially utilizing a heating type laser processing apparatus according to the present invention. Here, a thin film transistor having a bottom gate structure is integrated over a substrate 70. First, as shown in (A), a metal is deposited by sputtering on a substrate 70 made of non-alkali glass having an area of 300 mm × 350 mm. Here, Mo.Ta was deposited.
The metal deposited by photolithography and etching is patterned and processed into a gate electrode 71. Thereafter, the surface of each gate electrode 71 is anodized to form a Ta oxide film 7.
Form 2

In step (B), the substrate 70 is loaded into the heating type laser processing apparatus according to the present invention. First, the wafer is sent to a film forming chamber,
N and SiO ₂ are deposited to form a two-layer gate insulating film 73a, 73
3b is provided. A semiconductor thin film 74 is provided thereon by depositing amorphous silicon. Here, it is important to continuously grow the gate insulating films 73a and 73b and the semiconductor thin film 74 without breaking the vacuum in the same film forming chamber. Thereafter, the substrate is transferred to the heating chamber. Here, the substrate 70 is heated to, for example, a temperature of 400 ° C. The amorphous silicon semiconductor thin film 74 formed by the PE-CVD method contains about 10% of hydrogen, and this hydrogen is desorbed by the heat treatment at 400 ° C. After performing this heat treatment, the substrate 70 is transferred from the heating chamber to the irradiation chamber. Where the wavelength is 308 nm
XeCl excimer laser light 75 is applied to recrystallize the semiconductor thin film 74. The amorphous silicon is melted by the energy of the laser light and becomes polycrystalline when it hardens. Crystallinity (mainly grain size) is determined by the time at which the solidification occurs. By heating the substrate, the energy of the laser beam can be reduced, and the speed from melting to solidification is reduced, and the influence of the variation in the energy of the laser beam is reduced. Therefore, the characteristic variation of the recrystallized semiconductor thin film is reduced. In this example, it is possible to process one substrate in about two minutes simply by irradiating a laser beam shaped into a line of 150 mm × 0.4 mm and scanning left and right.
After the recrystallization processing is completed, the substrate 70 is taken out of the heating type laser processing apparatus and proceeds to a subsequent step.

As shown in FIG. 1C, SiO ₂ is deposited on the semiconductor thin film 74 by a PE-CVD method. Here, the SiO ₂ is patterned using the backside exposure technique,
Process into That is, by performing backside exposure using the gate electrode 71 as a mask, the stopper 76 aligned with the gate electrode 71 can be obtained by self-alignment. Here, the semiconductor thin film 74 is doped with a low concentration of phosphorus 77 by an ion doping method.

Proceeding to the step (D), a high-concentration phosphorus 78 is formed in a region of the semiconductor thin film to be an N-channel thin film transistor.
Doping. Further, a region of the semiconductor thin film to be a P-channel transistor is doped with high concentration boron. A resist 79 is used to separate phosphorus and boron into regions. Usually, impurity ions are implanted in a polycrystalline silicon thin film transistor of a high temperature process by using an ion implantation method. It has a mass separation function and can implant only specific impurity ions. However, in this method, since the ion beam is scanned, a long processing time is required to implant high-concentration impurity ions in a large area, resulting in poor productivity. Therefore, in this embodiment, the impurities are implanted by using the ion doping method. In the ion doping method, ions in a plasma state are accelerated by an electric field at a stretch to dope a substrate.
Can be processed in a short time. On the other hand, since there is no mass separation, unnecessary atoms may be doped. In addition, the exact number of atoms is not known, which causes variation. Recently, a large-sized ion implantation apparatus that eliminates both disadvantages has been developed, so that improvement in performance is expected.

Proceeding to step (E), a laser beam is again irradiated to activate the doped atoms. This is the same method as recrystallization, but weak energy is sufficient because it is not necessary to enlarge the crystal. In general, heat may be applied to activate the glass, but simple heat treatment cannot be used because glass shrinks at 400 ° C. or higher. A method of applying heat only to the semiconductor thin film, such as RTA or laser irradiation, is used. still,
300 ° C if hydrogen is implanted simultaneously during ion doping
There are reports that impurities are activated at about the temperature. Thereafter, SiO ₂ is deposited for insulation between wirings to form an interlayer insulating film 80.

In step (F), after a contact hole is opened in the interlayer insulating film 80, metal aluminum is deposited by sputtering, patterned into a predetermined shape, and processed into a wiring 81.

Finally, proceeding to step (G), SiN is deposited to form a passivation film 82. This passivation film 82 prevents impurities from entering from outside. As described above, the present manufacturing process is designed to be implemented by adding a heating type laser processing apparatus and an ion doping apparatus to a normal amorphous silicon thin film transistor manufacturing line.
It is also conceivable to adopt a top gate structure as in the case of the polycrystalline silicon thin film transistor of the high temperature process. Although the top gate structure is suitable for obtaining high mobility, it is considered that it is difficult to stably form a gate insulating film and to form a source / drain.

Finally, with reference to FIG. 5, an example of an active matrix display device in which a thin film semiconductor device manufactured by using a heating type laser processing apparatus is assembled as a driving substrate will be briefly described. This display device includes a driving substrate 101, a counter substrate 102, and an electro-optical material 103 held between the two.
And a panel structure comprising: As the electro-optical material 103, a liquid crystal material or the like is widely used. Drive board 10
1 can be made of glass which can have a large area and is relatively inexpensive. The pixel array unit 104 and the drive circuit unit are integrated on the drive substrate 101, and a monolithic structure can be adopted. That is, the pixel array unit 104
In addition, a peripheral driving circuit unit can be integrally built. The drive circuit section includes a vertical drive circuit 105 and a horizontal drive circuit 1
06. Further, a terminal portion 107 for external connection is formed at an upper end of a peripheral portion of the drive substrate 101. The terminal portion 107 is connected to a vertical drive circuit 105 and a horizontal drive circuit 106 via a wiring 108. On the other hand, a counter electrode (not shown) is formed entirely on the inner surface of the counter substrate 102. A row-shaped gate line 109 and a column-shaped signal line 110 are formed in the pixel array unit 104. The gate line 109 is connected to the vertical drive circuit 105, and the signal line 110 is connected to the horizontal drive circuit 106. At the intersection of the two lines, a pixel electrode 111 and a thin film transistor 112 for driving the pixel electrode 111 are integrally formed.
Further, thin film transistors are also integratedly formed in the vertical drive circuit 105 and the horizontal drive circuit 106.

[0021]

As described above, according to the present invention,
By providing a batch-type load lock chamber and a heating chamber, heat treatment and laser irradiation of the substrate can be performed efficiently, and processing of the substrate can be performed at a high throughput with little time loss.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing a basic configuration of a heating type laser processing apparatus according to the present invention.

FIG. 2 is a block diagram showing an example of a laser optical system incorporated in the heating type laser processing apparatus shown in FIG.

FIG. 3 is a perspective view showing a specific configuration example of a heating type laser processing apparatus according to the present invention.

FIG. 4 is a process chart showing a method for manufacturing a thin-film semiconductor device using a heating type laser processing apparatus according to the present invention.

FIG. 5 is a perspective view showing an example of an active matrix display device in which a thin film semiconductor device manufactured by the manufacturing method shown in FIG. 4 is assembled as a drive substrate.

FIG. 6 is a schematic view showing an example of a conventional laser irradiation method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Load lock chamber, 2 ... Heating chamber, 3 ... Irradiation chamber, 4 ... Laser light, 5 ... Transport mechanism, 6 ... Film formation chamber

Claims (5)

[Claims] A load lock chamber for receiving a substrate to be processed from the atmosphere and temporarily storing the substrate; a heating chamber for storing the substrate transported from the load lock chamber and heating the substrate to a predetermined temperature; At least one irradiation chamber that has a window and stores a substrate transferred from the heating chamber, and a laser optical system that performs predetermined processing by irradiating the substrate stored in the irradiation chamber with laser light through the window. A heating laser processing apparatus comprising: a transfer mechanism that transfers a substrate according to a predetermined sequence among the load lock chamber, the heating chamber, and the irradiation chamber. 2. An unload lock chamber for cooling is provided separately from the load lock chamber. The processed substrate transferred from the irradiation chamber via the transfer mechanism is temporarily stored, cooled, and then discharged to the atmosphere. The heating type laser processing apparatus according to claim 1. 3. The heating laser processing apparatus according to claim 1, wherein the heating chamber is of a batch type capable of storing a plurality of substrates at the same time. 4. The apparatus according to claim 1, wherein a plurality of irradiation chambers are provided.
2. The heating laser processing apparatus according to claim 1, wherein the laser optical system switches an optical path of one laser beam and sequentially distributes the laser beam to the plurality of irradiation chambers. 5. A non-single-crystal semiconductor thin film is formed on a surface of a substrate taken in through the load lock chamber, the irradiation chamber containing a film-formed substrate. 2. The heating type laser processing apparatus according to claim 1, wherein said heating type laser processing apparatus realizes a recrystallization process for converting said semiconductor thin film from non-single crystalline to polycrystalline by receiving laser beam irradiation.