JP3380953B2 - Heating laser processing equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD 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 drive substrate of an active matrix type liquid crystal display and is under active development. The active matrix liquid crystal display is building a large market for small portable TVs and car navigation displays, led by laptop computers. Further, in the multimedia age, various types of displays are required as machine interfaces. It is necessary to commercialize a display that meets the needs of the market for further development of the active matrix type liquid crystal display. From a technical point of view, thin-film semiconductor devices with integrated amorphous silicon thin film transistors have been improved with the development of the liquid crystal display market, but in order to realize an ideal display as an active matrix system, it should be used as a transistor. Performance is insufficient. It is considered that it is ideal that the peripheral drive circuit, the image signal processing circuit, and the like, which are called system-on-chip technology, are formed on the same glass substrate in the same process. It is considered that this is realized by a thin film semiconductor device in which polycrystalline silicon thin film transistors are integratedly 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. To obtain an electron mobility of 100 cm ² / v · s or more, there is no choice but to use polycrystalline silicon. Currently, a liquid crystal display with a peripheral drive circuit integrated with a polycrystalline silicon thin film transistor formed by a high temperature process is realized. However, since the semiconductor thin film is solid-phase grown in the high temperature process, heat treatment at 1000 ° C. or higher is required, and expensive quartz glass is used as the 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 400 ° C. or lower.

[0003]

Laser annealing using a laser beam has been developed as a part of a method for reducing the manufacturing process of a thin film semiconductor device to a low temperature process. This is because a non-single crystalline semiconductor thin film such as amorphous silicon or polycrystalline silicon formed on an insulating substrate is irradiated with laser light to locally heat and melt, and then the semiconductor thin film is crystallized in the cooling process. It will be transformed. A thin film transistor is integrally formed by using this crystallized semiconductor thin film as an active layer (channel region). Since the crystallized semiconductor thin film has high carrier mobility, the thin film transistor can have high performance. As shown in FIG. 6, in this laser annealing, the vertical direction of the insulating substrate 0 (Y
The insulating substrate 0 is intermittently irradiated with a pulse of laser light 4 formed in a strip shape along the (direction). At this time, at the same time, the laser beam 4 is moved laterally (X direction) relative to the insulating substrate 0 while partially overlapping the irradiation region. In the illustrated example, the insulating substrate 0 is step-moved in the −X direction with respect to the fixed irradiation region of the laser light 4. Thus, by overlapping the laser beams 4, the semiconductor thin film can be crystallized relatively uniformly. At present, an excimer laser is widely used as a light source of laser light.
However, this excimer laser cannot extremely increase the cross-sectional area of the laser light due to the output power. Therefore, the transparent insulating substrate made of a large glass or the like is irradiated by shaping the laser beam into a band shape and scanning (scanning) it while overlapping it. However, during this scanning, the grain size of the crystal becomes non-uniform due to the influence of the energy distribution of the laser light 4. As a result, the operating characteristics of the thin film transistors that are integrated and formed in the thin film semiconductor device vary, so that it is difficult to perform uniform display when used in a display or the like. In particular, when overlapping irradiation is performed, the crystallinity of the annealed portion at the edge of the laser beam differs from that of the other portions, and the state is generally poor. Further, when forming a thin film transistor having a bottom gate structure, since heat accumulation differs between the gate electrode and the glass substrate, a difference occurs in the optimum energy of the laser light with which the semiconductor thin film is irradiated.

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

[0005]

Means for Solving the Problems The following means have been taken in order to solve the above-mentioned problems of the conventional technology. That is, the heating type laser processing apparatus according to the present invention has, as a basic configuration, a load lock chamber, a heating chamber, an irradiation chamber, a laser optical system, and a transfer mechanism. The load lock chamber receives a substrate to be processed from the atmosphere and temporarily stores it. The heating chamber stores the substrate transferred from the load lock chamber and heats it to a predetermined temperature. Irradiation chamber is provided a plurality pieces, and stores the substrate transferred from the heating chamber has a transparent window.
The laser optical system switches the optical path of one laser beam to
A plurality of irradiation chambers are sequentially distributed, and a substrate stored in each irradiation chamber is irradiated with laser light through the window to perform a predetermined process. The transfer mechanism transfers the substrate among the load lock chamber, the heating chamber, and the irradiation chamber according to a predetermined sequence.

[0006] Preferably, in addition to the load lock chamber, an unload lock chamber for cooling is included, and the processed substrate transferred from the irradiation chamber via the transfer mechanism is temporarily stored and cooled before being exposed to the atmosphere. Discharge. Further, the heating chamber is a batch type capable of storing a plurality of substrates at the same time . In some cases, while forming a non-monocrystalline semiconductor thin film on a surface of the substrate captured via the load lock chamber includes a deposition chamber, the irradiation chamber contains a film-forming processed substrate Then, a recrystallization treatment for converting the semiconductor thin film from non-single crystallinity to polycrystallinity upon irradiation with laser light is realized.

In the heating type laser processing apparatus according to the present invention, the substrate is sent from the cassette to the vacuum load lock chamber. After that, the substrate is fed to the heating chamber (preheat chamber). After being heated here, it enters the irradiation chamber and is irradiated with laser light. After that, it is fed to the unload lock chamber and cooled, and then it returns to the original cassette. The load lock chamber and the heating chamber are batch type and the irradiation time and the timing of the laser light are matched to each other, so that the substrate can be heated and the laser light can be irradiated with high throughput without time loss. Here, efficiency is improved by Rukoto provided a plurality of irradiation chambers. That is, when the substrate is being transported in one irradiation chamber, the laser beam can be irradiated onto the substrate in another irradiation chamber simply by switching the optical path of the laser light.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic block diagram showing the basic configuration of a heating type laser processing apparatus according to the present invention. This 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 transfer 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 transferred from the load lock chamber 1 and heats them to a predetermined temperature. The irradiation chamber 3 has a transparent window 3a and stores the substrate 0 transferred from the heating chamber 2. A laser optical system (not shown) irradiates the substrate 0 stored in the irradiation chamber 3 with the laser light 4 through the 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 this embodiment, the load lock chamber 1, the heating chamber 2, the irradiation chamber 3 and the like are radially arranged. 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 conveys the substrate 0 to the peripheral chambers according to a predetermined process order.

In some cases, the load lock chamber 1
In addition to this, an unload lock chamber for cooling may be provided, and the processed substrate 0 transferred from the irradiation chamber 3 via the transfer mechanism 5 is temporarily stored, cooled, and then discharged into the atmosphere. Further, the heating chamber 2 is a batch type capable of storing a plurality of substrates 0 at the same time. Normally, 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 a film forming chamber 6, and forms a non-single crystalline 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 film-formed substrate 0 and receives a laser beam 4 to perform a recrystallization process for converting the semiconductor thin film from non-single crystalline 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 recrystallization processing, XY
The insulating substrate 0 made of low melting point glass or the like is put into the irradiation chamber 3 in which the stage 3b is incorporated. A non-single-crystal semiconductor thin film 10 is previously formed on the surface of the insulating substrate 0. As the semiconductor thin film 10, for example, P-CVD
Amorphous silicon is formed by the method. In the irradiation chamber 3, the insulating substrate 0 is irradiated with the laser light 4 emitted from, for example, an excimer laser light source 43. Amorphous silicon is once melted, crystallized in the cooling process, and converted into polycrystalline silicon. As a result, the carrier mobility of the semiconductor thin film 10 is increased 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-sectional shape of the laser beam 4 into a band shape (line shape) and maintain the uniformity of energy cross-section strength. 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 insulating substrate 0 housed in the irradiation chamber 3 is irradiated through the window 3a. When the pulse of the laser beam 4 is emitted intermittently, the XY stage 3b is stepwise moved in the −X direction in synchronization with this. This allows 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 region of.

FIG. 3 is a schematic perspective view showing a specific structural example of the heating type laser processing apparatus according to the present invention. The heating laser processing apparatus is roughly divided into a main body section, a laser optical system, a film forming system, and a substrate feeding section. The main body portion 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 consists of three irradiation chambers 3 in the main body.
It is 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, and a main body pump module 6.
4. The process pump module 65 and the like are included. This film forming system is connected to the film forming chamber 6 of the main body,
Perform the processing required for CVD. Finally, the substrate feeding system includes an automatic cassette load station 12 that handles a substrate cassette 11, and is connected to the load lock chamber 1 and the unload lock chamber 8 of the main body. Each chamber constituting the main body 5 is arranged in a star shape, and the transfer mechanism 5 including a transfer robot is provided in the center thereof.
Has been placed. 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 load station 12 into the load lock chamber 1 of the main body. These substrates are sequentially transferred to the film forming chamber 6 by the transfer 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 any of the three irradiation chambers 31 to 33 via the transfer mechanism 5. Here, the semiconductor thin film formed on the substrate by being irradiated with the laser beam 4 from the laser optical system is recrystallized. At this time, since the substrate is heated in advance 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, cooled there, and then returned to the original cassette 11. In this embodiment, the load lock chamber 1 and the heating chamber 2 are of a batch type, and by adjusting the laser irradiation time and timing, it is possible to heat the substrate and perform laser irradiation with high throughput without time loss. The main body part is provided with three irradiation chambers 31 to 33, and the process flow of the substrate is made smooth by properly using these. For example, when the substrate is being transported in a certain irradiation chamber, the laser light 4
The laser beam 4 can be distributed to other irradiation chambers only by switching with the switching mirror 47.

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

Proceeding to step (B), the substrate 70 is put into the heating type laser processing apparatus according to the present invention. First, the film is sent to the film forming chamber, and Si is formed by plasma CVD (PE-CVD).
N and SiO ₂ are deposited to form a two-layer gate insulating film 73a, 7
3b is provided. Amorphous silicon is deposited thereon to form a semiconductor thin film 74. Here, it is important to continuously grow the gate insulating films 73a and 73b and the semiconductor thin film 74 in the same film forming chamber without breaking the vacuum. After this, the substrate is transferred to the heating chamber. Here, the substrate 70 is heated to a temperature of 400 ° C., for example. The amorphous silicon semiconductor thin film 74 formed by the PE-CVD method contains about 10% of hydrogen, and this hydrogen is desorbed by heat treatment at 400 ° C. After performing this heat treatment, the substrate 70 is transferred from the heating chamber to the irradiation chamber. Wavelength 308nm
The XeCl excimer laser beam 75 is irradiated to recrystallize the semiconductor thin film 74. Amorphous silicon is melted by the energy of laser light and becomes polycrystalline silicon when it is solidified. The crystallinity (mainly grain size) is determined by the time for this hardening. By heating the substrate, the energy of the laser light can be small, and the speed from melting to solidifying is slowed, and the influence of the variation in the energy of the laser light 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 2 minutes simply by irradiating a laser beam shaped into a line of 150 mm × 0.4 mm and scanning to the left and right.
After the recrystallization process is completed, the substrate 70 is taken out of the heating type laser processing apparatus and the subsequent process is performed.

As shown in (C), SiO ₂ is deposited on the semiconductor thin film 74 by PE-CVD. Here, SiO ₂ is patterned by using the backside exposure technique and the stopper 76
To process. That is, by performing the back surface 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 step (D), high-concentration phosphorus 78 is formed in the region of the semiconductor thin film which will be an N-channel type thin film transistor.
Dope. In addition, high-concentration boron is doped in the region of the semiconductor thin film that becomes the P-channel type transistor. A resist 79 is used to separate phosphorus and boron into regions. Usually, in a high temperature process polycrystalline silicon thin film transistor, impurity ions are implanted by using an ion implantation method. This has a mass separation function and can implant only specific impurity ions. However, in this method, since the ion beam is scanned, it takes a long processing time to implant high-concentration impurity ions in a large area, resulting in poor productivity. Therefore, in this embodiment, impurities are implanted by using the ion doping method. The ion doping method is to dope an electric field of plasma ions at once to dope the substrate.
It can be processed in a short time. On the other hand, since no mass separation is performed, unnecessary atoms may be doped. Moreover, since the exact number of atoms is not known, it causes variations. Recently, a large-sized ion implantation system has been developed that eliminates the drawbacks of both types, and therefore performance improvement is expected.

In step (E), laser light is irradiated again to activate the doped atoms. It is the same method as recrystallization, but weak energy is sufficient because it is not necessary to make the crystal large. Generally, heat may be applied to activate the glass, but glass cannot be subjected to a simple heat treatment because it 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 ℃ if hydrogen is simultaneously injected during ion doping
There is also a report that impurities are activated at a moderate temperature. After that, SiO ₂ is deposited for insulation between the wirings to form an interlayer insulating film 80.

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

Finally, in step (G), SiN is deposited to form a passivation film 82. The passivation film 82 prevents impurities from entering from the outside. As described above, this manufacturing process is designed so that it can be carried out by adding a heating type laser processing device and an ion doping device to a normal amorphous silicon thin film transistor manufacturing line.
It is also possible to adopt a top gate structure like the polycrystalline silicon thin film transistor of the high temperature process. However, although the top gate structure is suitable for obtaining high mobility, it is considered difficult to stably form the gate insulating film and form the source / drain.

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

[0021]

As described above, according to the present invention,
By providing the batch type load lock chamber and the heating chamber, it becomes possible to efficiently perform the substrate heating process and the laser irradiation process, and it is possible to process the substrate with a small time loss and a high throughput.
In particular, providing multiple irradiation chambers improves efficiency.
It That is, the substrate is carried in a certain irradiation chamber.
When switching the laser light path, simply change the irradiation path.
The substrate can be irradiated with laser light.

[Brief description of 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 laser processing apparatus according to the present invention.

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

5 is a perspective view showing an example of an active matrix type 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 ... Transfer mechanism, 6 ... Film forming chamber

Claims (4)

(57) [Claims] 1. A load lock chamber that receives a substrate to be processed from the atmosphere and temporarily stores it, a heating chamber that stores the substrate transferred from the load lock chamber and heats it to a predetermined temperature, and a transparent chamber. a plurality pieces of irradiation chamber for storing the substrate transferred from the heating chamber includes a window, one of the laser light of the optical path switching by the plurality several irradiation tea
A laser optical system for performing predetermined processing by irradiating a substrate stored in each irradiation chamber with laser light through the window, and a predetermined distance between the load lock chamber, the heating chamber, and the irradiation chamber. A heating type laser processing apparatus comprising a transfer mechanism for transferring a substrate according to a sequence. 2. A unload lock chamber for cooling is provided separately from the load lock chamber, and the processed substrate transferred from the irradiation chamber via the transfer mechanism is temporarily stored, cooled, and then discharged into the atmosphere. The heating type laser processing apparatus according to claim 1. 3. The heating type laser processing apparatus according to claim 1, wherein the heating chamber is a batch type capable of simultaneously storing a plurality of substrates. 4. A non-single crystalline semiconductor thin film is formed on the surface of the substrate, which includes a film forming chamber and is taken in through the load lock chamber, while the irradiation chamber stores the formed substrate. 2. The heating laser processing apparatus according to claim 1, which realizes a recrystallization treatment for converting the semiconductor thin film from non-single crystalline to polycrystalline by receiving laser light irradiation.