JPH10242050A - Semiconductor thin film, semiconductor device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a semiconductor thin film excellent in uniformity of quality on the whole surface of a substrate, and reduce surface roughness, by setting the sequential scanning interval of a laser beam, to be a value less than or equal to the width of a rising region in the scanning progress direction side of a beam intensity profile in the scanning direction of a pulse laser beam. SOLUTION: The width R135 of a rising region higher than or equal to the crystallization threshold intensity in a laser intensity profile 131 is calculated. That is, the maximum intensity width 134 in a flat region corresponding to a laser intensity profile peak top is subtracted from the crystallization width 133 of an a-Si film 103, and the obtained value is divided by 2. When the maximum intensity width 134 of the peak flat region is, e.g. 0.7mm, the width of the rising region which is higher than or equal to the crystallization threshold intensity is 0.075mm. In the practical laser beam scanning irradiation, the scanning interval of the pulse laser is set to be lower than or equal to the value 0.0075mm of the width R135 of the rising region higher than or equal to the crystallization threshold intensity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystalline semiconductor thin film used for an active region of a thin film semiconductor device, and more particularly to a crystalline semiconductor thin film crystallized by pulsed laser beam sequential scanning irradiation. In addition, the present invention relates to a semiconductor device using the semiconductor thin film as an active region and a method of manufacturing the same, and particularly to an active matrix substrate for a liquid crystal display device, a thin film integrated circuit, an image sensor, a three-dimensional IC, and the like.

[0002]

2. Description of the Related Art In recent years, large and high-resolution liquid crystal display devices, monolithic liquid crystal display devices in which driver circuits are formed on the same substrate for cost reduction, high-speed and high-resolution contact type image sensors, three-dimensional For the realization of ICs and the like, attempts have been made to form high-performance semiconductor elements on insulating substrates such as glass or on insulating films. In general, a thin film silicon semiconductor is used for a semiconductor element used in these devices. Thin-film silicon semiconductors are roughly classified into two types: those made of an amorphous silicon semiconductor (a-Si) and those made of a crystalline silicon semiconductor.

[0003] Amorphous silicon semiconductors are most commonly used because they have a low production temperature, can be produced relatively easily by a gas phase method, and have high mass productivity. Since it is inferior to a crystalline silicon semiconductor, a method for manufacturing a semiconductor device made of a crystalline silicon semiconductor is strongly demanded in order to obtain higher-speed characteristics in the future. In addition, as a silicon semiconductor having crystallinity,
Polycrystalline silicon, microcrystalline silicon, amorphous silicon containing a crystalline component, and the like are known.

[0004] The following three methods are mainly known as methods for obtaining these crystalline silicon semiconductors in the form of thin films.

(1) A film having crystallinity is directly formed at the time of film formation.

(2) An amorphous semiconductor film is formed,
Crystallinity is imparted by applying heat energy.

(3) An amorphous semiconductor film is formed in advance,
Crystallinity is imparted by the energy of laser light.

However, in the above method (1), crystallization proceeds simultaneously with the film formation step, so that it is difficult to obtain crystalline silicon having a large grain size, and it is essential to increase the thickness of the silicon film. . However, even though the film thickness is increased, the crystal grain size is basically the same as the film thickness, and it is impossible in principle to produce a silicon film with good crystallinity by this method. It is. Further, since the film formation temperature is as high as 600 ° C. or higher, there is a problem of cost that an inexpensive glass substrate cannot be used.

The method (2) is used for crystallization of 600
Since heat treatment for several tens of hours is required at a high temperature of not less than ℃, productivity is very poor. Also, in order to utilize the solid-phase crystallization phenomenon, the crystal grains spread in parallel to the substrate surface and are several μm
However, since the grown crystal grains collide with each other to form a grain boundary, the grain boundary acts as a trap level for carriers, and the mobility of the thin film transistor (hereinafter, referred to as TFT) is reduced. It is a major cause of lowering. Further, each crystal grain has a twin structure, and a large number of crystal defects called so-called twin defects exist in one crystal grain.

For this reason, the method (3) is mainly used at present. In the above method (3), the crystallization is carried out by utilizing the melt-solidification process, so that the crystallinity within each crystal grain is very good. In addition, by selecting the wavelength of the irradiation light, only the silicon film to be annealed can be efficiently heated to prevent thermal damage to the underlying glass substrate, and the method of the above (2) can be used. There is an advantage that processing for a long time is not required. A high-output excimer laser annealing apparatus and the like have also been developed in terms of equipment, and are now being able to cope with large-area substrates. A method of manufacturing a semiconductor device using the method (3) is disclosed in Japanese Patent Application Laid-Open No. 8-51074.
And JP-A-8-201846.

In Japanese Patent Application Laid-Open No. 8-51074, the profiles (energy intensity distribution) of the pulse laser beam in the major axis direction and the minor axis direction are optimized, and the amorphous silicon film is crystallized at least in the minor axis direction. In this case, scanning is performed at a feed pitch at which overlapping regions can overlap. In JP-A-8-201846, a pulse laser beam is shifted so that a part thereof is overlapped with a driver TFT of a driver monolithic active matrix substrate for a liquid crystal display device, and an edge portion of the beam is always activated. The silicon film in the region is irradiated. It has also been proposed that the width of the semiconductor thin film with respect to the shifting direction of the pulsed laser beam is set to be equal to or larger than the shifting amount or an integral multiple of the shifting amount. Both are aimed at improving the film quality (crystallinity) uniformity of the silicon film crystallized by laser scanning.

[0012]

The method of the above (3) is as follows.
As described above, the method for crystallizing a silicon film on an insulating film is the most excellent, but has a large problem in uniformity. That is, as a laser oscillator serving as a light source, (300 to 500 mm) × (400 to 500 mm)
Has not been developed yet that has an output sufficient to collectively irradiate a large-area substrate.
Only those having a beam area of about 0 to ²⁰⁰ mm ² are available. Therefore, as proposed in JP-A-8-51074 and JP-A-8-201846, a laser beam having a small area is sequentially scanned with respect to a substrate (silicon film) while being shifted by a fixed amount. Yes, it is.

At this time, the non-uniformity of crystallinity caused by the sequential scanning becomes a serious problem.
No. 074 and Japanese Patent Application Laid-Open No. Hei 8-201846, a method of irradiating a pulsed laser beam so as to be shifted so that a part thereof is overlapped, or a method of scanning at a feed pitch at which a region to be crystallized can overlap. The method is commonly used.

In such a method of irradiating a pulsed laser beam so as to be shifted so that a part thereof is overlapped, a plurality of laser irradiations are performed at an arbitrary point on the target silicon film, that is, a plurality of times. Is repeated to crystallize the silicon film. At this time, the laser irradiation that most affects the crystallinity of the finally formed crystalline silicon film is the laser irradiation performed first on any point, and the crystal formed by the first melting and solidification is performed. Regarding the property, even if the laser irradiation of the same energy is repeated and then melted and solidified, the information is not completely reset. That is, in the crystallization step by the sequential scanning of the pulse laser, the variation in the crystallinity caused by the first irradiation at an arbitrary point on the silicon film finally becomes apparent as the variation in the crystallinity of the entire film.

Therefore, according to the techniques disclosed in the above-mentioned JP-A-8-51074 and JP-A-8-201846, it is possible to obtain a crystalline silicon film having high film quality uniformity over the entire surface of the substrate, which is the object of the present invention. Can not. Needless to say, when a semiconductor device is formed using the crystalline silicon film as an active region, the variation in crystallinity of the crystalline silicon film is directly reflected in the device characteristics, and causes a variation in characteristics between the devices. In particular, in the case of active matrix substrates for liquid crystal display devices, etc., which are actually sensory evaluated by human eyes, non-uniformity of element characteristics appears as display (contrast) unevenness, and extremely high uniformity of element characteristics. Is required. Therefore, the silicon film forming the active region is required to have extremely strict uniformity such that fine variations in film quality are not allowed.

Further, the crystalline silicon film crystallized in the process of melting and solidifying by laser irradiation has a crystallization mechanism.
A relatively large surface roughness results. That is, the amorphous silicon film has a melting point of 1 due to the energy of the laser.
It is instantaneously heated to 414 ° C. or more, and several tens of nsec. It is cooled to around room temperature in about a cooling time and solidified. At this time, since the solidification rate is too high, the silicon film is in a supercooled state and solidified instantaneously. In other words, the crystal grain boundary rises in a mountain shape. This phenomenon is particularly remarkable at the three poles where three crystal grains collide. FIG. 8 shows a sketch depicting an atomic force microscope (AFM) image of the surface state of the crystalline silicon film actually crystallized by intense light irradiation. In FIG. 8, the full scale in the XY direction is 1 μm, and the full scale in the Z direction is 50 nm.

The size of the surface roughness depends on the crystal grain size. Generally, as the crystal grain size increases, the local surface roughness also increases. That is, if the crystallinity of the silicon film is non-uniform, the local surface roughness also becomes non-uniform. Actually, as described above, in the crystalline silicon film crystallized by the sequential scanning of the pulse laser, since the film quality (crystallinity) varies within the substrate, the surface roughness of the silicon film is also affected by the variation. It is uneven. In the active matrix substrate for the liquid crystal display device described above, an auxiliary capacitance is generally provided in parallel with the liquid crystal capacitance. When the crystalline silicon film is used as an electrode of the auxiliary capacitance component together with the channel portion of the pixel TFT, the capacitance size deviates from a design value due to a change in the surface area ratio due to the surface roughness. In addition to the characteristic variation between the elements, it causes display defects such as display unevenness and flicker.

The present invention solves the above-mentioned problems and provides a crystalline silicon film crystallized in a melting and solidifying process by pulsed laser scanning irradiation, which has high film quality uniformity over the entire surface of the substrate and low surface roughness. It is an object to establish a thin film, a semiconductor device using the same, and a method for manufacturing the same.

[0019]

SUMMARY OF THE INVENTION The present invention is to realize a crystalline silicon film having high quality, high uniformity of film quality over the entire surface of the substrate, and having no surface roughness. Furthermore, by using this crystalline silicon film as an element material of a thin film semiconductor element, in a semiconductor device such as an active matrix substrate having a plurality of semiconductor elements, uniformity is improved by a simple process that can reduce cost. A semiconductor device can be realized. Specifically, the present invention has the following features.

(1) A crystalline semiconductor thin film formed on a substrate having an insulating surface, wherein the semiconductor thin film is formed by sequentially scanning and irradiating a silicon film formed on the substrate with a pulse laser beam. A crystalline silicon film that has been crystallized, and the crystalline silicon film has a beam intensity profile in the scanning direction of the pulsed laser light, the width of the rising region on the scanning direction side (R) or less, and It is characterized by being crystallized by a pulsed laser beam having a set scanning interval (P).

(2) The width (R) of the rising region is characterized by a strength range for crystallizing the silicon film.

(3) The beam intensity profile in the scanning direction of the laser beam is a laser beam having a substantially trapezoidal shape.

Here, the pulse laser beam has a wavelength of 400
It is preferably an excimer laser beam of nm or less.

(4) The pulse laser beam is designed so that its beam shape is elongated on the irradiation surface (the surface of the silicon film), and is sequentially arranged in the direction perpendicular to the elongated direction of the beam shape. It is characterized by being crystallized by scanning.

(5) In a semiconductor device having a plurality of thin film transistors formed on a substrate having an insulating surface, the silicon thin film formed on the substrate is scanned with a laser beam in a sequential scanning interval (P) of a pulse laser beam. The crystalline silicon film is crystallized by a pulsed laser beam set to a value equal to or less than the width (R) of the rising region on the traveling direction side of the beam intensity profile in the scanning direction, and the active regions of a plurality of thin film transistors are formed on the crystalline silicon film. It is characterized by the following.

Here, the plurality of thin film transistors are:
In an active matrix substrate having pixel electrodes, it is preferably used as a pixel switching thin film connected to each pixel electrode.

The plurality of thin film transistors are preferably used as thin film transistors constituting a driver circuit on a driver monolithic active matrix substrate in which an active matrix portion and a driver circuit are simultaneously formed on the same substrate.

(6) A plurality of pixel electrodes and thin film transistors for driving the respective pixel electrodes are provided on a substrate having an insulating surface, and each of the thin film transistors is connected to another capacitance component in parallel with the liquid crystal capacitance by the pixel electrodes. In the semiconductor device, the silicon thin film on the substrate is scanned such that a laser beam sequential scanning interval (P) is equal to or less than a width (R) of a rising region on a traveling direction side of a beam intensity profile in a scanning direction of a pulsed laser beam. Crystallized by a pulsed laser beam set to a value, a channel region of the thin film transistor and one electrode of the capacitance component connected to the thin film transistor are formed in the crystalline silicon film.

(7) a step of forming an amorphous silicon film on a substrate having an insulating surface;
When crystallizing by sequentially scanning and irradiating the pulsed laser light, the sequential scanning interval (P) of the pulsed laser light is set to be equal to or less than the width (R) of the rising region on the scanning traveling direction side of the beam intensity profile in the scanning direction of the laser light ( P <R), and irradiating with a laser beam; and patterning and forming the silicon film obtained in the above step on the element regions of the plurality of thin film transistors to form a thin film transistor. It is characterized by the following.

(8) A step of forming an amorphous silicon film on a substrate having an insulating surface and crystallizing it in a solid phase by heating, and sequentially irradiating the silicon film with a pulsed laser beam. When recrystallizing, the sequential scanning interval (P) of the pulsed laser beam is set to the rising region on the scanning advancing direction side in the intensity range where the silicon film is recrystallized in the beam intensity profile in the scanning direction of the laser beam. Of width (R) or less (P <R),
The method includes a step of irradiating a laser beam, and a step of forming a thin film transistor by patterning and forming the silicon film obtained in the above step so as to be element regions of a plurality of thin film transistors.

(9) Setting of the laser beam sequential scanning interval (P) is performed by irradiating the amorphous silicon film with a laser beam before scanning with the laser beam, and setting the area where the silicon film is crystallized in the laser scanning direction. The width (R) of the rising region is determined from the length and the beam profile of the laser light,
Scanning interval (P) below the width (R) of the rising area
Is set.

Preferably, the step of heating the amorphous silicon film to crystallize it in a solid phase state is performed after introducing a catalytic element which promotes the crystallization into the amorphous silicon film.

Further, the step of heating the amorphous silicon film to crystallize in a solid phase state includes the step of selectively introducing a catalyst element for promoting the crystallization into the amorphous silicon film, Thus, the step of patterning and forming the silicon film into element regions of a plurality of thin film transistors is performed by laterally growing crystals from a region where the catalytic element is selectively introduced to a peripheral portion thereof. A step of forming at least a channel region in an element region by using a silicon film in a region where crystals are laterally grown from a region where the catalyst element is selectively introduced to a peripheral portion thereof. preferable.

It is preferable to use Ni as the catalyst element.

The inventors of the present invention have determined that, in a high-quality crystalline silicon film crystallized by pulsed laser sequential scanning, the remaining problem is that high quality uniformity cannot be improved over the entire surface of the substrate with high quality and that surface roughness is not improved. The day-and-night experiment was over to see if it was possible to reduce this, and to somehow eliminate display defects caused by laser beam scanning irradiation during crystallization of the TFT active region in the liquid crystal display device. As a result, in the crystallization process of the silicon film, it was found that the energy distribution of the laser pulse initially irradiated at an arbitrary point on the silicon film is one of the factors that cause the film quality (crystallinity) of the silicon film to vary, It has been found that the above method can solve the problem.

An outline of the present invention is constituted on an insulating substrate,
In a silicon film having crystallinity crystallized by sequential scanning irradiation of a pulsed laser beam, in a beam intensity profile in a scanning direction of the pulsed laser beam, a rising region on a scanning traveling direction side in an intensity range where the silicon film is crystallized. The crystallization step is performed by setting the sequential scanning interval (P) of the laser beam to a value equal to or less than the width (R). With this configuration, at any one point of the silicon film, no matter what point is taken, it is first melted and crystallized by the weak laser energy, and then by the next stronger laser energy It will be recrystallized. In other words, the intensity distribution of the first laser energy that hits an arbitrary point on the silicon film is kept as small as possible, and the laser light of higher energy is irradiated in the second and subsequent irradiations to further reduce the variation.

As a result, the problems in the above-mentioned JP-A-8-51074 and JP-A-8-201846 when the laser beam is irradiated with the laser beam shifted are solved. Then, when the film quality of the crystalline silicon film thus obtained was actually evaluated by Raman spectroscopy, it was found that the film had excellent film quality uniformity as compared with the conventional film.

More specifically, the outline of the present invention will be described in comparison with JP-A-8-51074 and JP-A-8-201846. In JP-A-8-51074,
It discloses that a region preceding the laser scanning direction has an energy intensity distribution portion smaller than the energy required for crystallization of the target silicon film. However, the relationship between the width of the energy distribution smaller than the energy required for the crystallization of the silicon film and the scanning pitch of the laser pulse is described only within a range where crystallization can overlap. Further, it is stated that the energy is smaller than the energy required for crystallization, and the point of view is fundamentally different from the present invention.

That is, in Japanese Patent Application Laid-Open No. 8-51074, a laser is irradiated with a small energy to form a region which does not change in an amorphous silicon state, and then is crystallized by a high-energy laser irradiation to be uniform. However, the actual irradiation time of the laser pulse is extremely short, several tens of nanoseconds, and has a significant effect on the amorphous silicon film unless it is melted (that is, unless it is crystallized). Do not give. Therefore, performing laser irradiation at a low energy that does not cause crystallization of the amorphous silicon film has no special significance.
The technical advantage of the publication No. 1074 lies in the sequential scanning in which the crystallization regions which are generally performed are overlapped and laser irradiation is repeatedly performed.

In Japanese Patent Application Laid-Open No. Hei 8-201846, an edge portion of a pulsed laser beam is always irradiated onto a target silicon film. At first glance, it is similar to the present invention, but the point of the present invention is clarified by clarifying the difference. Therefore, the description will be made with reference to FIG. 7A shows an intensity profile 700 in the scanning direction 701 of the laser beam, and FIG. 7B shows a cross-sectional view of the silicon film when irradiated with the laser beam. The profile width generally referred to indicates a beam width (ie, full width at half maximum) 702 at half the maximum intensity value in the profile 700. JP-A-8-2
Beam edge (rising) referred to in JP 01846
The portion is generally a region indicated by a width (first edge width) 703 from the starting point of the rising of the beam to the maximum intensity. Alternatively, it is a region represented by a width (second edge width) 704 from the maximum intensity to half the intensity of the maximum intensity. That is, in Japanese Patent Application Laid-Open No. Hei 8-201846, the scanning direction 70 of the intensity profile 700 of the pulse laser is
1 means that scanning is performed at a scanning pitch equal to or less than the first edge width 703 or the second edge width 704.

However, assuming that the melting threshold of the target silicon film is 705 in the intensity profile 700 of FIG. 7A, the beam width (melting width) 706 at the melting threshold 705 actually contributes to crystallization. The region width of the crystallized silicon film is the same as the beam width (melt width) 706 in FIG. Here, reference numeral 712 denotes a crystallized silicon film, and 713 denotes an amorphous silicon film. The melting width 711 of the silicon film based on the beam width (melting width) 706 based on the melting threshold 705 of the pulsed laser beam at this time is determined by the laser intensity 707 to be set, the film quality and thickness of the target silicon film, It changes greatly depending on the material (heat capacity) of the base film and the coating film.

As described in Japanese Patent Application Laid-Open No. Hei 8-201846, a laser beam having a profile as described above is used at a scanning pitch indicated by the first edge width 703 or the second edge width 704 in the scanning direction 701. When scanning 700, a part of the amorphous silicon film 713 on the scanning direction 701 side is crystallized by the beam width (maximum intensity width) 708 indicated by the peak intensity region of the profile 700. The silicon film crystallized in this peak intensity region does not receive any higher energy by the subsequent laser irradiation,
The crystallinity is maintained, and is greatly different from the crystallinity crystallized at the edge portion, which causes nonuniformity of the film quality in the substrate. That is, even in Japanese Patent Application Laid-Open No. Hei 8-201846, by irradiating the amorphous silicon film with a laser beam with a small energy, fine nuclei can be formed even in the amorphous silicon state, which affects the subsequent crystallization. Although it is considered from the viewpoint of the possibility, in practice, no significant state change occurs in the amorphous silicon film unless it is melted as described above. Therefore, the first edge width 703 or the second edge width 704 of the laser beam 700 needs to be crystallized at the edge portion instead of irradiating the silicon film. For this purpose, the width of the edge region (width of the rising region) 709 is set with respect to the beam width (fusion width) 706 at the melting threshold 705, and the width of the rising region 7
The scanning pitch is set to a value less than or equal to 09 and the laser beam 7
00 must be scanned sequentially. This is the point of the present invention.

As the beam intensity profile in the scanning direction of the laser beam, it is desirable to use a laser beam having a substantially trapezoidal shape as shown in FIG. With a laser beam having such a shape, any point on the silicon film is first crystallized in the rising (edge) region of the laser beam, and then is irradiated with higher energy uniformly several times, and then rises. The non-uniformity associated with the intensity distribution in the region is reduced, and the tolerance for the output variation of the laser transmitter as the light source is increased.

As the pulsed laser light, if the wavelength of the laser light is 400 nm or less, since the silicon film has a large absorption coefficient in the wavelength range, the energy is efficiently given to the silicon film, A good crystalline silicon film can be obtained, and thermal damage to the underlying glass substrate and the like can be extremely small. Further, among these laser beams having a wavelength of 400 nm or less, in particular, the wavelength 308
Since the XeCl excimer laser beam of nm has a high oscillation output and high stability, its beam size can be expanded to some extent, and is most suitable as a means for annealing a silicon film on a large-area substrate.

The pulse laser beam is designed so that its beam shape is elongated on the irradiation surface, and is sequentially scanned in a direction perpendicular to the elongated direction of the beam shape. It is desirable to crystallize the silicon film. Because, in the scanning irradiation, the uniformity in the direction perpendicular to the scanning direction is relatively good, so by expanding the beam size in that direction, more uniform processing can be performed on a large substrate or the like, This is because the processing efficiency of the process also increases.

As described above, the crystalline silicon thin film of the present invention has excellent film quality uniformity over the entire surface of the substrate, and a plurality of TFTs formed on a substrate having an insulating surface.
This is particularly effective in the case where uniformity of characteristics is required, such as in an active region. The best example is an active matrix substrate for a liquid crystal display device, which is a field that is actually judged by human eyes. Therefore, the pixel TFT is required to have extremely high uniformity of element characteristics. By using the present invention for a pixel TFT of an active matrix substrate for a liquid crystal display device, display defects such as contrast unevenness caused by laser beam scanning can be completely eliminated, and a liquid crystal display device with extremely high display quality can be realized. become.

The pixels TF arranged in a matrix
In a driver monolithic active matrix semiconductor device having a driver circuit for driving the pixel TFT on the same substrate in addition to the TFT, in addition to the pixel TFT, a plurality of TFTs constituting the driver circuit are particularly required for the shift register circuit. For example, very high uniformity of characteristics is required. When these TFT characteristics vary,
The drive waveform for each line is different, and also in this case, uneven stripe display appears on the screen. As described above, human eyes are very severe and have the ability to discriminate subtle display unevenness. By applying the present invention to these TFTs, the channel regions of the plurality of TFTs constituting the driver circuit are
Regardless of crystallinity variation caused by laser scanning,
Since all have the same crystallinity, excellent characteristic uniformity can be obtained over the entire TFT element. As a result, the characteristics of the driver circuit for driving the pixel TFT are stabilized, and defects such as display unevenness due to variations in the driver circuit characteristics in the liquid crystal display device can be reduced.

Since the crystalline silicon film according to the present invention has good film quality uniformity over the entire surface of the substrate, local variations in the surface roughness of the silicon film due to laser crystallization can also be suppressed. In an active matrix substrate for liquid crystal display, one electrode portion of an auxiliary capacitance (Cs) connected in parallel with a liquid crystal pixel capacitance is formed in the same layer as the active region of the pixel TFT, and the capacitance is formed by a gate insulating film. The method of forming is often used. That is, the auxiliary capacitance (Cs) is provided in parallel with the liquid crystal pixel capacitance in order to alleviate the voltage drop phenomenon in the pixel electrode portion that occurs when the gate pulse signal is turned off. Variations in the screen in ()) cause display unevenness such as flicker on the screen. When an electrode of the auxiliary capacitance (Cs) is manufactured using the crystalline silicon film obtained by the conventional intense light irradiation, the surface roughness locally varies, and as a result, the capacitance value of the auxiliary capacitance (Cs) varies. It was difficult to obtain a liquid crystal display device having good display quality. In contrast, when the present invention is used, since the surface roughness of the silicon film is reduced, C
A variation in s capacitance can be suppressed, and a high-quality liquid crystal display device without display unevenness can be obtained.

As a method of manufacturing a semiconductor device of the present invention,
When an amorphous silicon film is formed on a substrate and then crystallized by sequentially scanning and irradiating the silicon film with a pulsed laser beam, the scanning interval (P) of the pulsed laser beam is set to the scanning interval of the laser beam. In the beam intensity profile in the direction, the laser beam is sequentially scanned so that the value is not more than the width (R) (P <R) of the rising region in the scanning direction in the intensity range where the silicon film can be melted and crystallized. Then, the silicon film is crystallized. Then, the obtained silicon film is patterned and formed so as to be element regions of a plurality of TFTs, thereby manufacturing a TFT. By using such a manufacturing method, a high-performance TFT having good uniformity between elements over the entire surface of the substrate can be obtained by a particularly simple method.

Here, the width (R) of the rising region
Varies as described above depending on the actually set laser energy intensity, the film quality and thickness of the target silicon film, and the underlying film and the coating film. Therefore, in order to maximize the effect of the present invention, first, the target amorphous silicon film is irradiated only once with the laser intensity at which the irradiation is actually performed, and the width melted (crystallized) at that time. (The film color can be confirmed differently when crystallized), and the beam profile of the laser beam is checked using a measuring device such as a profiler, and the width (R) of the rising region is calculated from the both, and this rising is calculated. It is desirable to set the scanning interval (P) below the width (R) of the region. Once the setting is made in this way, the above confirmation is not particularly necessary when processing is continued without changing the conditions after the second time.

As a start film for laser irradiation, in addition to the above-mentioned amorphous silicon film, the number of steps is increased.
It is also an effective means to use a crystalline silicon film crystallized by solid phase crystallization. A crystalline silicon film obtained by solid-phase crystallization of an amorphous silicon film by heat treatment has poor crystallinity.
Although it is not suitable as an FT channel region, it is effective in terms of producing a seed crystal at the time of laser crystallization because of its good uniformity. When the crystalline silicon film is irradiated with a laser beam, the crystalline silicon film is recrystallized with some crystal information left. Crystalline silicon by solid-phase crystallization,
Since it has good uniformity, the uniformity is reflected to some extent even after recrystallization by laser irradiation. Therefore, in the method of manufacturing a semiconductor device according to the present invention, the crystalline silicon film formed by solid-phase crystallization is sequentially scanned with a laser and recrystallized, thereby achieving the uniformity of the element characteristics aimed at by the present invention. It can be further improved.

In the solid phase crystallization step, after introducing a catalytic element for promoting crystallization into the amorphous silicon film,
It is desirable that this be done. According to this method, the heating temperature can be reduced, the processing time can be reduced, and the crystallinity can be improved. Specifically, by introducing a trace amount of a metal element such as nickel or palladium onto the surface of the amorphous silicon film and then heating, the crystallization is completed in about 550 ° C. for about 4 hours. In contrast, heat treatment at 600 ° C. or more for several tens of hours is required for ordinary solid-phase crystallization without using a catalyst element. In addition, the crystalline silicon film crystallized by the catalytic element has a twin structure in one grain of the crystalline silicon film crystallized by the ordinary solid phase growth method. Each of the columnar crystals is substantially in a single crystal state.

The crystalline silicon film crystallized by this catalytic element is very compatible with the recrystallization step by laser irradiation. In the recrystallization step by laser irradiation, the initial crystallinity is reflected to some extent, and a crystalline silicon film formed by ordinary solid-phase crystallization becomes a crystalline silicon film having many crystal defects, reflecting the twin structure. In contrast, in the case of a solid-phase crystallized silicon film using a catalytic element, each columnar crystal is bonded by recrystallization by laser irradiation, and a crystalline silicon film with very good crystallinity over a wide range is obtained. .

Further, by selectively introducing a catalytic element into a part of the amorphous silicon film and heating, only the region into which the catalytic element is selectively introduced is first crystallized, and then the region is laterally moved from the introduced region. Crystal growth can be performed in a direction (a direction parallel to the substrate). Inside this lateral crystal growth region, columnar crystals whose growth directions are almost aligned in one direction are tied together, and the crystallinity is better than the region where the catalyst element is directly introduced and crystal nuclei are generated randomly. Area. Therefore, by using the crystalline silicon film in the lateral crystal growth region for the channel region of the TFT,
The performance of the semiconductor device can be further improved. At this time, if the crystal growth direction in the lateral direction in the silicon film and the moving direction of the carrier in the TFT are configured to be substantially parallel, there is in principle no crystal grain boundary in the moving direction of the carrier. Since the probability of carrier scattering is reduced, a TFT having higher mobility can be realized.

The types of catalyst elements that can be used in the present invention include Ni, Co, Pd, Pt, Cu, Ag, Au, and I.
n, Sn, Al, and Sb can be used. One or a plurality of elements selected from these elements have an effect of promoting crystallization in a trace amount, and among them, Ni
The most remarkable effect can be obtained when is used. For this reason, we consider the following model. The catalyst element does not act alone, but acts on crystal growth by bonding to the silicon film to form silicide. This is a model in which the crystal structure at that time acts like a kind of template when the amorphous silicon film is crystallized, and promotes the crystallization of the amorphous silicon film. Ni forms silicide of _two Si and NiSi2. NiSi ₂ exhibits a fluorite-type crystal structure, which is very similar to the diamond structure of single crystal silicon. Moreover, NiSi ₂ has a lattice constant of 5.406 °, which is very close to the lattice constant of 5.430 ° in the crystalline silicon diamond structure. Therefore, NiSi ₂ is most suitable as a template for crystallizing an amorphous silicon film, and it is most preferable to use Ni as the catalyst element in the present invention.

[0056]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) A first embodiment using the present invention will be described. In the present embodiment, the present invention is utilized, in a process for producing a high-quality crystalline silicon film on a glass substrate,
Give an explanation.

FIG. 1 shows an outline of the present embodiment. FIG. 1A shows an intensity profile in the scanning direction of a laser beam used in the present embodiment, and FIG. 1 (C) is a plan view seen from above the substrate.

First, as shown in FIG. 1B, a glass substrate 101 having a thickness of 30
A base film 102 of about 0 nm made of silicon oxide is formed. This silicon oxide film is provided to prevent diffusion of impurities from the glass substrate. Next, an amorphous silicon (a-Si) film 103 having a thickness of 20 to 100 nm, for example, 30 nm is formed by a low pressure CVD method, a plasma CVD method, or the like. The a-Si film 103 is formed by a plasma CVD method.
When a film is formed, a large amount of hydrogen is contained in the film,
Since this may cause peeling of the film during the subsequent laser irradiation, it is necessary to perform a heat treatment at a temperature of about 450 ° C. for several hours to release hydrogen in the film.

Next, the laser beam 107 is scanned, and a-S
The i-film 103 is crystallized. At this time, a XeCl excimer laser (wavelength 308 nm, pulse width 40 nsec) was used as the laser light. The irradiation conditions of the laser beam 107 are as follows.
Heat to 00 ° C, energy density 200-350mJ /
cm ² , for example, 300 mJ / cm ² . Laser light 1
07 means that the beam size on the substrate surface is 150 mm ×
The beam is shaped by a homogenizer so as to have a long rectangular shape of 1 mm, and the beam is sequentially scanned in a direction perpendicular to a longitudinal direction of the beam, that is, in a short side direction.

First, a-Si film 1 on glass substrate 101
03 is irradiated once with laser light. The a-Si film 103 is crystallized by a laser beam having a trapezoidal intensity profile 131 with respect to the scanning direction 130 in FIG. 1A, and becomes a crystalline silicon film 103a. At this time, FIG.
In (A), assuming that the intensity of the melting threshold of the a-Si film 103 is a line 132, the beam width at that intensity value is a range that actually contributes to crystallization, and the intensity of the crystallized silicon film 103a is The width becomes the crystallization width 133. At this time, the crystallization width 133 of the a-Si film 103 with respect to the scanning direction 130 is actually measured. In this example, the crystallization width 133 was 0.85 mm. When this state is viewed from above the substrate, although the exact actual value is different, as shown in FIG. 1C, the a-Si film is crystallized to reflect the long rectangular beam size, and the crystalline silicon It is a film 103a.

Here, laser light intensity profile 1
31 is measured in advance by a measuring device such as a profiler, and the maximum intensity width 134 of the flat region corresponding to the peak top is determined in advance. If such a measurement device is not available, the intensity of the laser beam is reduced to the lowest energy at which crystallization is performed, and the width of the silicon film crystallized at that time is examined, so that the approximate flat region can be obtained. The maximum intensity width 134 can be known. That is, at such energy, the crystallization width 133 of the silicon film and the maximum intensity width 134 of the flat region at the top of the beam profile become substantially the same. The trapezoidal intensity profile 131 has a shape symmetrical with respect to the scanning direction 130.

Then, the width (R) 135 of the rising region above the crystallization threshold intensity in the laser intensity profile 131, which is the point of the present invention, is calculated. In other words, the value is obtained by subtracting the maximum intensity width 134 of the flat region corresponding to the peak of the laser intensity profile from the crystallization width 133 of the a-Si film 103, and dividing the value by two. In the present embodiment, since the maximum intensity width 134 of the peak flat region is 0.7 mm, the width (R) 13 of the rising region at the crystallization threshold intensity or more is 13 mm or more.
The value of 5 is 0.075 mm.

Next, a laser beam is actually scanned and irradiated to form a target crystalline silicon film. At this time, the scanning interval (P) 136 of the pulse laser is set to a value higher than the crystallization threshold intensity. Region width (R) 135
Is set to be 0.075 mm or less. In this embodiment, the scanning interval (P) 136 is set to 0.05 mm.

Next, laser light is sequentially scanned in the direction indicated by the scanning direction 130 in FIG. 1 to sequentially crystallize the a-Si film 103. By doing so, the width (R) 135 of the rising region can be seen at any one point of the silicon film.
The laser beam having the intensity distribution within the range is applied first, and the laser beam having higher energy is applied about 20 times after the second time. That is, a large distribution of crystallinity does not occur at the stage of first crystallization, and the overall crystallinity can be improved by laser irradiation of even higher energy.As a result, the obtained crystalline silicon film is It has excellent film quality uniformity. Actually, the phonon peak of crystalline Si was arbitrarily measured at 100 points in the substrate by Raman spectroscopy, and the uniformity was evaluated. As a result, the full width at half maximum of the peak was 4.6 to 4.8 cm ^-1.
And showed very good uniformity. On the other hand, in the case of the conventional film, the full width at half maximum of the peak is about 4.6 to 5.1 cm ^{-1 in} the same measurement.

In the present embodiment, the width (R) 135 of the rising region above the crystallization threshold intensity in the laser intensity profile is measured in advance, and the laser scanning interval (P) 136 is set based on the measured value. However, the width (R) 135 of the rising region greatly changes depending on the laser intensity used and the film quality and thickness of the target silicon film. Therefore, as long as the conditions such as the laser intensity and the film quality and thickness of the silicon film are not changed, the continuous processing may be performed using the value once set as the value of the width (R) 135 of the rising region. When the condition is changed, it is necessary to measure the width (R) 135 of the rising area again and reset the scanning interval (P) 136.

(Embodiment 2) A second embodiment using the present invention will be described. Example 1 In this example, steps of manufacturing an active matrix substrate for a liquid crystal display device over a glass substrate by using the present invention will be described. In this active matrix substrate, an N-type TFT is formed as an element for switching each pixel electrode.

In an actual active matrix substrate, hundreds of thousands or more of pixel electrodes and TFTs are arranged. In this embodiment, for simplification of description, description will be made focusing on an arbitrary pixel TFT. Hereinafter, FIG. 2 is a cross-sectional view illustrating a manufacturing process of an arbitrary pixel TFT of the active matrix substrate of the present embodiment, and the manufacturing process sequentially proceeds in the order of (A) → (E). FIG. 2E shows a completed view of the pixel TFT 221.

First, as shown in FIG. 2A, a glass substrate 201 having a thickness of 30
A base film 202 of about 0 nm made of silicon oxide is formed. This silicon oxide film is provided to prevent diffusion of impurities from the glass substrate. Next, an amorphous silicon (a-Si) film 203 having a thickness of 20 to 100 nm, for example, 30 nm is formed by a low pressure CVD method, a plasma CVD method, or the like. A-Si film 203 by plasma CVD
When a film is formed, a large amount of hydrogen is contained in the film,
Since this may cause peeling of the film during the subsequent laser irradiation, it is necessary to perform a heat treatment at a temperature of about 450 ° C. for several hours to release hydrogen in the film.

Next, as shown in FIG. 2B, an a-Si film 203 is formed by using the same method as described in the first embodiment.
XeCl excimer laser (wavelength 308 nm, pulse width 40 nsec) light 207 is sequentially scanned and irradiated to the a-Si
The film 203 is crystallized. By this step, the silicon film is melted and solidified, and becomes a crystalline silicon film 203a having excellent film quality uniformity over the entire surface of the substrate.

Next, by removing the portion of the crystalline silicon film 203a where the pixel TFT is to be formed and removing the other portion, isolation between the elements as shown in FIG.
After that, an island-shaped silicon film 208 constituting active regions (source region, drain region, channel region) of the TFT is formed.

Subsequently, as shown in FIG. 2D, a silicon oxide film having a thickness of 20 to 150 nm, here 100 nm, is formed as the gate insulating film 209 so as to cover the island-shaped silicon film 208 serving as the active region. Form a film. Here, TEOS (Tetra Etho) is used for forming the silicon oxide film.
xy Ortho Silicate) and a substrate temperature of 150 to 600 ° C., preferably 30 ° C., together with oxygen.
Decomposition and deposition were performed at 0 to 450 ° C. by an RF plasma CVD method. Alternatively, the substrate may be formed at a substrate temperature of 350 to 600 ° C., preferably 400 to 550 ° C. by a low pressure CVD method or a normal pressure CVD method using TEOS as a raw material together with an ozone gas.

Subsequently, by the sputtering method,
An aluminum film having a thickness of 300 to 600 nm, for example, 400 nm is formed. Then, the gate electrode 210 is formed by patterning the aluminum film. Gate electrode 21
0 is connected to a gate bus line formed in the same layer, from which a gate signal is input. Further, the surface of the aluminum electrode is anodized to form an oxide layer 211 on the surface. This state corresponds to FIG. The anodization is performed in an ethylene glycol solution containing tartaric acid at 1 to 5%, and the voltage is first increased to 220 V at a constant current, and the state is maintained for 1 hour to complete the process. The thickness of the oxide layer 211 thus obtained is 200 nm
It is. Note that since the oxide layer 211 has a thickness for forming an offset gate region in a later ion doping process, the length of the offset gate region can be determined in the anodic oxidation process. The offset gate region is provided for the purpose of reducing a leakage current at the time of TFT off operation.

Next, as shown in FIG. 2D, impurity ions (phosphorus) 212 are implanted into the active region by ion doping using the gate electrode 210 and the surrounding oxide layer 211 as a mask. Phosphine (PH ₃ ) is used as a doping gas, and the accelerating voltage is 60 to 90 k.
V, for example, 80 kV, and the dose amount is 1 × 10 ¹⁵ to 8 × 10
^{It is 15} cm ^-2 , for example, 2 × 10 ¹⁵ cm ^-2 . By this step, the region into which the impurities are implanted becomes the source region 214 and the drain region 215 of the TFT later, and the gate electrode 21
The region which is masked by the oxide layer 211 and the surrounding oxide layer 211 and into which impurities are not implanted is formed later by the channel region 21 of the TFT.
Form 3

After that, annealing is performed by laser light irradiation to activate the ion-implanted impurities, and at the same time, to improve the crystallinity of the portion where the crystallinity has deteriorated in the above-described impurity introducing step. At this time, a XeCl excimer laser (wavelength: 308 nm, pulse width: 40 nsec) was used as a laser, and the energy density was 150 to 400.
mJ / cm ^2, preferably irradiation was performed at 200~250mJ / cm ^2. The source region 214 and the drain region 2 into which the N-type impurity ions (phosphorus) thus formed are implanted.
The sheet resistance of No. 15 was 200 to 800 Ω / □.

Then, as shown in FIG.
A silicon oxide film of about 00 nm is formed as the interlayer insulating film 216. If this silicon oxide film is formed using TEOS as a raw material by a plasma CVD method with oxygen and a reduced pressure CVD method or a normal pressure CVD method with ozone, a good interlayer insulating film having excellent step coverage can be obtained. Can be

Next, a contact hole is formed in the interlayer insulating film 216, and a source electrode 217 and a pixel electrode 220 are formed. The source electrode 217 is formed of a metal material, for example, a two-layer film of titanium nitride and aluminum. The titanium nitride film is provided as a barrier film for preventing aluminum from diffusing into the semiconductor layer. Further, a source bus line is formed in the same layer as the source electrode 217, and a video signal is input to the source electrode 217 through the bus line. The pixel electrode 220 is formed of a transparent conductive film such as ITO.

Finally, in a hydrogen atmosphere of 1 atm.
Annealing is performed at 0 ° C. for about one hour to complete the N-type pixel TFT 221 shown in FIG. This annealing process has the effect of supplying hydrogen atoms to the interface between the active region of the pixel TFT 221 and the gate insulating film, thereby reducing dangling bonds that degrade the TFT characteristics. Note that the pixel TF
For the purpose of protecting T221, only necessary portions may be covered with a silicon nitride film formed by a plasma CVD method using SiH ₄ and NH ₃ as source gases.

Each TF manufactured according to the above embodiment
T is 60 to 80 in field effect mobility in all panels.
Good characteristics such as cm ² / Vs and a threshold voltage of 1.5 to ² V were exhibited. In addition, the uniformity of the TFTs in the panel was as good as about ± 8% in field effect mobility and about ± 0.2 V in threshold voltage. As a result, a liquid crystal display panel was manufactured using the active matrix substrate manufactured in this example, and the entire display was performed. As a result, display unevenness due to non-uniformity of TFT characteristics was greatly reduced, and high display quality was obtained. A liquid crystal display device was realized.

(Embodiment 3) A third embodiment using the present invention will be described. In this embodiment, steps of manufacturing an active matrix substrate for a liquid crystal display device on a glass substrate using the present invention will be described. In this active matrix substrate, an N-type TFT is formed as an element for switching each pixel electrode, and an auxiliary capacitance C is provided on the drain region side in parallel with the pixel liquid crystal capacitance.
s is provided.

FIG. 3 is a plan view showing the structure of an arbitrary pixel portion on the active matrix substrate described in this embodiment. FIG. 4 is a cross-sectional view taken along the line AA ′ of FIG. 3, and the process sequentially proceeds in the order of (A) → (E). FIG. 3 and FIG. 4E are completed diagrams of the pixel TFT and the auxiliary capacitance (Cs) portion manufactured in the present embodiment, and show an N-type pixel TFT 321 for pixel switching and an auxiliary capacitance (Cs) 324. .

First, as shown in FIG. 4A, a glass substrate 301 having a thickness of 300 nm is formed by a plasma CVD method.
A base film 302 made of a silicon oxide film is formed.
Then, an intrinsic (I-type) amorphous silicon film (a-Si film) 303 having a thickness of about 30 nm is formed on the base film 302 by a low pressure CVD method or a plasma CVD method. When the a-Si film 303 is formed by a plasma CVD method, a large amount of hydrogen is contained in the film, which causes peeling of the film during laser irradiation later. It is necessary to perform a heat treatment for several hours to release hydrogen in the film.

Next, using a method similar to the method described in the first embodiment, a XeCl excimer laser (wavelength 308 nm, pulse width 40 nsec) light 307 is applied to the a-Si film 303.
Are sequentially scanned and irradiated to crystallize the a-Si film 303.
By this step, the silicon film is melted and solidified, and the crystalline silicon film 303a having good film quality uniformity over the entire surface of the substrate.
become. Here, when the average surface roughness Ra of the surface of the crystalline silicon film 303a was measured by an atomic force microscope (AFM), it was a value of about 5 to 6 nm, and almost the same value was shown in the entire substrate. The average surface roughness Ra of the surface of the crystalline silicon film formed by the conventional method is almost the same as the absolute value (average value) in this embodiment, but is particularly in the range of 5 to 9 nm. Varies greatly in the direction in which The main variation is a local variation, and in the present invention, the variation due to such local singularity / abnormality is greatly reduced.

Next, by leaving a portion of the crystalline silicon film 303a where a pixel TFT and an auxiliary capacitor (Cs) are formed and removing other portions, isolation between elements as shown in FIG. After that, the island-shaped crystalline silicon film 3 constituting the active region (source region, drain region, channel region) of the pixel TFT and the lower electrode of the storage capacitor (Cs) later
08 is formed. When this state is viewed from above the substrate, the island-shaped silicon film 308 has a shape as shown in FIG.
Are formed.

Next, as shown in FIG. 4C, a photoresist is applied on the island-shaped crystalline silicon film 308,
Exposure and development are performed to form a mask 304. That is, the mask 304 is in a state where only a portion which will be a channel region of the TFT later is covered. Then, impurity ions (phosphorus) 312 are implanted by ion doping using the photoresist mask 304 as a mask. Phosphine (PH ₃ ) is used as a doping gas, the acceleration voltage is 5 to 30 kV, for example, 15 kV, and the dose is 1
× 10 ¹⁵ to 8 × 10 ¹⁵ cm ⁻² , for example, 2 × 10 ¹⁵ cm ⁻²
And By this step, the region into which the impurity ions have been implanted becomes the source region 314 of the pixel TFT 321 later.
Further, the drain region 315a of the pixel TFT 321 and the lower electrode 315b of the storage capacitor (Cs) 324 are formed. The region which is masked by the photoresist mask 304 and into which the impurity ions are not implanted is formed later by the pixel TFT 32 as described above.
One channel region 313 is obtained.

Next, as shown in FIG. 4D, the photoresist mask 304 is removed, and the thickness is 20 to 150 nm, here 1 nm, so as to cover the island-shaped crystalline silicon film 308.
A 00 nm silicon oxide film is formed as the gate insulating film 309. Here, TEOS is used for forming the silicon oxide film.
(Tetra Ethoxy Ortho Silic
ate) as a raw material and a substrate temperature of 150 to 6 together with oxygen.
Decomposition and deposition were performed at 00 ° C., preferably 300 to 400 ° C., by RF plasma CVD. After the film formation, the gate insulating film 30
Annealing was performed at 400 to 600 ° C. for several hours in an inert gas atmosphere in order to improve the bulk characteristics of the sample 9 itself and the interface characteristics between the crystalline silicon film and the gate insulating film. At the same time, the impurities doped in the source region 314, the drain region 315a, and the lower electrode 315b are activated by the annealing, and the resistance of the source region 314, the drain region 315a, and the lower electrode 315b is reduced. Was 800 to 1000 Ω / □.

Subsequently, by the sputtering method,
An aluminum film having a thickness of 300 to 500 nm, for example, 400 nm is formed. Then, the aluminum film is patterned to form a gate electrode 310a and a storage capacitor (Cs) 324.
Of the upper electrode 310b is formed. Here, the gate electrode 3
When viewed in a plan view, 10a constitutes the n-th gate bus line as shown in FIG. 3, and the storage capacitor (Cs)
Upper electrode 310b constitutes the (n + 1) th gate bus line.

Then, as shown in FIG.
A silicon oxide film of about 00 nm is formed as the interlayer insulating film 316. If this silicon oxide film is formed using TEOS as a raw material by a plasma CVD method with oxygen and a reduced pressure CVD method or a normal pressure CVD method with ozone, a good interlayer insulating film having excellent step coverage can be obtained. Can be

Next, a contact hole is formed in the interlayer insulating film 316, and a source electrode 317 and a pixel electrode 320 are formed. The source electrode 317 is formed of a metal material, for example, a two-layer film of titanium nitride and aluminum. The titanium nitride film is provided as a barrier film for preventing aluminum from diffusing into the semiconductor layer. Pixel electrode 32
0 is formed of a transparent conductive film such as ITO. When the state at this time is viewed from above the substrate, as shown in FIG. 3, the source electrode 317 forms a source bus line for transmitting a video signal to the TFT 321, and the pixel electrode 320 is arranged between the bus lines. I have.

Finally, in a hydrogen atmosphere of 1 atm.
Annealing is performed at 0 ° C. for about 1 hour to complete the pixel TFT 321 and the storage capacitor (Cs) 324 shown in FIG. By this annealing, hydrogen atoms are supplied to the interface between the active region of the pixel TFT 321 and the gate insulating film.
This has the effect of reducing dangling bonds that degrade FT characteristics. In order to further protect the pixel TFT 321,
Only necessary portions may be covered with a silicon nitride film formed by a plasma CVD method.

The TFT manufactured according to the above embodiment
Shows good characteristics similar to those of the second embodiment,
The channel region 313 and its storage capacitance (Cs) 324
Lower electrode 315b has a surface average roughness Ra
Are all suppressed within the range of about 5 to 6 nm, there is almost no leakage current through the gate insulating film 309, and the non-uniformity of each capacitance is also suppressed to a small value. as a result,
A liquid crystal display panel was manufactured using the active matrix substrate manufactured in this example, and the entire display was performed.
A liquid crystal display device with high reliability and high display quality without display unevenness was realized.

(Embodiment 4) A fourth embodiment using the present invention will be described. In this embodiment, a C-type TFT in which an N-type TFT and a P-type TFT are formed in a complementary manner,
A case of manufacturing a circuit having a MOS structure will be described.

FIG. 5 is a plan view showing the outline of the process of manufacturing the CMOS circuit (N-type TFT 422 and P-type TFT 423) described in this embodiment. Actually, tens of thousands of elements are simultaneously formed on a substrate, but in the present embodiment, description will be given focusing on an arbitrary CMOS circuit. FIG. 6 is a cross-sectional view showing the manufacturing process of the CMOS circuit taken along the line BB 'in FIG. 5, and the process proceeds sequentially in the order of (A) → (F). FIG. 6F is a completed view of an arbitrary CMOS circuit according to the present embodiment, and shows an N-type TFT.
422 and a P-type TFT 423.

First, as shown in FIG. 6A, a glass substrate 401 having a thickness of 30
A base film 402 of about 0 nm made of silicon oxide is formed. This silicon oxide film is provided to prevent diffusion of impurities from the glass substrate. Next, by a low pressure CVD method or a plasma CVD method,
For example, a 50 nm intrinsic (I-type) amorphous silicon film (a-
(Si film) 403 is formed.

Next, a photosensitive resin (photoresist) is applied on the a-Si film 403, and is exposed and developed to form a mask 4
04. At this time, the through hole of the photoresist mask 404 exposes the a-Si film 403 in the region 400 in a slit shape. That is, when the state of FIG. 6A is viewed from above, as shown in FIG.
The i film 403 is exposed, and the other portions are masked by the photoresist.

Next, as shown in FIG. 6A, a nickel thin film is deposited on the surface of the glass substrate 401 to form a nickel thin film 405. In this embodiment, the thickness of the nickel thin film 405 is controlled to be about 1 nm or less by increasing the distance between the deposition source and the substrate to a value larger than usual and reducing the deposition rate. At this time, the surface density of nickel on the a-Si film 403 was actually measured to be 1 × 10
It was about ¹³ atoms / cm ² . Then, by removing the photoresist mask 404, the nickel thin film 405 on the mask 404 is lifted off, which means that a small amount of nickel 405 is selectively added to the a-Si film 403 in the region 400. Then, this is annealed in an inert atmosphere, for example, at a heating temperature of 550 ° C. for 16 hours to be crystallized.

At this time, as shown in FIG.
In 00, crystallization of the silicon film 403 occurs in a direction perpendicular to the glass substrate 401 with nickel added to the surface of the a-Si film 403 as a nucleus, and the crystalline silicon film 40
3b is formed. In the peripheral region of the region 400, as shown by an arrow 406 in FIGS. 5 and 6B, crystal growth is performed in a lateral direction (a direction parallel to the substrate) from the region 400, and the lateral crystal growth is performed. A crystalline silicon film 403c is formed. The other region remains as the amorphous silicon film region 403 as it is. In the above crystal growth, the distance of crystal growth in the direction parallel to the substrate indicated by arrow 406 was about 80 μm.

After that, as shown in FIG. 6C, laser light 407 is irradiated to recrystallize the silicon film 403. At this time, a XeCl excimer laser (wavelength 308 nm, pulse width 40 nsec) was used as the laser light. The irradiation condition of the laser beam 407 at this time was such that the substrate was heated to 200 to 500 ° C., for example, 400 ° C. at the time of irradiation, and the energy density was 200 to 350 mJ / cm ² , for example, 280 mJ / cm ² . The laser beam 407 has a beam size of 100 mm × 1.3 mm on the substrate surface.
Is molded by a homogenizer so as to have a long rectangular shape, and has a trapezoidal intensity profile symmetrical with respect to the short side direction (scanning direction).

Here, in order to apply the present invention, as in the first embodiment, a single laser irradiation is performed on the silicon film in the amorphous region 403 to measure the actual crystallization width. . The crystallization width measured under the conditions of this example is 1.1 mm
It was width. Further, the flat region width of the peak top in the intensity profile of the laser beam 407 examined in advance by the beam profiler was 0.9 mm.
That is, in the present embodiment, the width of the rising region above the crystallization threshold intensity in the laser intensity profile is 0.1 mm, and from this value, the laser scanning pitch in the present embodiment is 0.08 mm (80 μm).
Was set. By the above steps, the crystalline silicon region 403
b and 403c recombine in part as seed crystals, resulting in better crystalline silicon regions 403b ′ and 403c ′
Becomes Further, the a-Si region 403 is crystallized into a crystalline silicon film 403a.

Next, as shown in FIG. 5 and FIG. 6D, a portion where a later N-type TFT 422 and a P-type TFT 423 are to be formed is left in a region of the high-quality crystalline silicon film 403c ′, and other portions are left. Isolation between elements is performed so that the island-shaped crystalline silicon films 408n and 408p constituting active regions (a source region, a drain region, and a channel region) of the TFT after etching are formed. At this time, when the glass substrate 401 is viewed from above, as shown in FIG. 5, island-shaped crystalline silicon films 408 serving as active regions of the respective TFTs are arranged. In FIG. 5, a source region 4 to be formed later in an island-shaped crystalline silicon film 408 to be an active region of each TFT.
14n, 414p and drain regions 415n, 415
p represents channel regions 413n and 413p. As can be seen from FIG. 5, in the present embodiment, the crystal growth direction of nickel indicated by the arrow 406 and the channel direction (carrier moving direction; horizontal direction on the paper) are arranged so as to be substantially parallel. With such an arrangement, the field-effect mobility of the TFT is improved, and the TFT having a higher driving capability is provided.
FT is obtained.

Next, as shown in FIG. 6E, island-shaped crystalline silicon films 408n and 408n serving as the active regions are formed.
A 100-nm-thick silicon oxide film is formed as the gate insulating film 409 so as to cover 8p. For the formation of the silicon oxide film, TEOS is used as a raw material here and is decomposed by RF plasma CVD at a substrate temperature of 300 to 400 ° C. together with oxygen.
Deposited. After the film formation, in order to improve the bulk characteristics of the gate insulating film 409 itself and the interface characteristics between the crystalline silicon film and the gate insulating film, 400 to 600 ° C. in an inert gas atmosphere.
For several hours.

Subsequently, as shown in FIG. 6E, aluminum (containing 0.1 to 2% of silicon) having a thickness of 400 to 800 nm, for example, 500 nm is formed by a sputtering method. By patterning, gate electrodes 410n and 410p are formed.

Next, the gate electrodes 410n and 410n are formed in the active regions 408n and 408p by ion doping.
Impurity ions (phosphorus and boron) using p as a mask
412 is injected. Phosphine (PH ₃ ) and diborane (B ₂ H ₆ ) are used as the doping gas. In the former case, the acceleration voltage is 60 to 90 kV, for example, 80 kV,
In the latter case, 40 kV to 80 kV, for example, 65 kV, the dose is 1 × 10 ¹⁵ to 8 × 10 ¹⁵ cm ⁻² , for example, phosphorus is 2 × 10 ¹⁵ cm ⁻² , and boron is 5 × 10 ¹⁵ cm ⁻² . I do. By this step, a region which is masked by the gate electrodes 410n and 410p and into which impurity ions are not implanted is later formed by T
FT channel regions 413n and 413p are obtained. At the time of doping, each element is selectively doped by covering a region not requiring doping with a photoresist. As a result, the source region 414n and the drain region 415n into which the N-type impurity has been implanted, and the source region 414p and the drain region 4 into which the P-type impurity has been implanted.
15P are formed, and as shown in FIGS. 6E and 6F, an N-channel TFT 422 and a P-channel TFT 4 are formed.
23 can be formed.

Thereafter, annealing is performed by laser light irradiation to activate the ion-implanted impurities. XeCl excimer laser (wavelength 30)
8 nm and a pulse width of 40 nsec), and the irradiation condition of the laser light was an energy density of 250 mJ / cm ^2.
Irradiated 4 shots per location.

Subsequently, as shown in FIG.
A silicon oxide film having a thickness of
Formed by a plasma CVD method using EOS as a raw material,
A contact hole is formed in this, and a TFT is formed by a metal material, for example, a two-layer film of titanium nitride and aluminum.
Of electrodes / wirings 417, 418, and 419 are formed. Finally, annealing is performed at 350 ° C. for about one hour in a hydrogen atmosphere at 1 atm to form an N-type TF constituting a CMOS circuit.
T422 and P-type TFT 423 are completed.

The CMO fabricated according to the above embodiment
In the S structure circuit, the field-effect mobility of each TFT is 150 to 180 cm ² / Vs for an N-type TFT, and
The FT is as high as 80 to 100 cm ² / Vs, and the threshold voltage is N
0.5 to 1 V for P-type TFT, -2.5 to -3 for P-type TFT
V and very good characteristics. Also, the TFT in the substrate
The uniformity of both the N-type TFT and the P-type TFT was very good with a field effect mobility of about ± 10% and a threshold voltage of ± 0.2 V or less.

Although the fourth embodiment according to the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible. is there.

For example, in the above-described four examples, a trapezoidal shape having a symmetrical shape as the intensity profile in the laser sequential scanning direction was used. However, the present invention can be applied to a laser beam having any beam profile as long as the profile has an intensity gradient on the side of the laser traveling direction, and the effect can be obtained.

In the above four embodiments, X
Using an eCl excimer laser, the a-Si film was crystallized or the solid-phase crystal growth silicon film was recrystallized. The present invention has the same effect, of course, when crystallized by irradiation with various other pulsed laser beams.
The same applies to the case where a 48 nm KrF excimer laser or the like is used.

In the fourth embodiment, the solid-phase crystal growth method employs a method in which a catalyst element is selectively used and crystal growth is performed in the lateral direction. Similar effects can be obtained by using the phase crystal growth method. Also, without selectively introducing the catalytic element, introducing the entire surface of the silicon film,
A method of growing a crystal as it is may be used. In this case, an excellent effect by the catalytic element can be obtained, and an extra process such as mask formation is not required.

As a method for introducing nickel as a catalyst element, various methods other than the vapor deposition method described in the fourth embodiment can be used. For example, a method of applying an aqueous solution in which a nickel salt is dissolved, or an SOG (spin-on-glass) material in which a nickel salt is dissolved is used.
A method of diffusing from an iO ₂ film is also effective, a method of forming a thin film by a sputtering method or a plating method, a method of directly introducing a film by an ion doping method, and the like can also be used. Further, as impurity metal elements that promote crystallization, in addition to nickel, cobalt, palladium, platinum, copper,
The effect can be obtained by using silver, gold, indium, tin, aluminum or antimony.

Further, as an application of the present invention, in addition to an active matrix type substrate for liquid crystal display, for example, a contact type image sensor, a driver built-in thermal head, a driver built-in type using an organic EL as a light emitting element, etc. An optical writing element, a display element, a three-dimensional IC, and the like can be considered. By using the present invention, high performance such as high speed and high resolution of these elements is realized. Further, the present invention is not limited to the MOS transistors described in the above embodiments,
It can be widely applied to all semiconductor processes including a bipolar transistor and an electrostatic induction transistor using a crystalline semiconductor as an element material.

[0112]

According to the present invention, the uniformity of the quality of a high-quality crystalline silicon film crystallized by a pulsed laser beam can be particularly improved. In addition, in a general semiconductor device using the semiconductor thin film as an element material, a thin film semiconductor having high performance, high reliability and high stability can be achieved without being governed by crystallization non-uniformity, stabilizing characteristics among a plurality of elements. The device can be realized. In particular, in the liquid crystal display device, the characteristics of the individual TFTs can be made uniform within the panel, and a liquid crystal display device having a high display level without display defects caused by laser sequential scanning can be obtained by a simple manufacturing process. Furthermore, high performance, high integration, and uniformity of characteristics required for the TFT constituting the peripheral drive circuit section can be achieved, and a full driver monolithic active matrix constituting the active matrix section and the peripheral drive circuit section on the same substrate. A substrate can be realized, and the module can be made compact, high-performance, and low in cost.

[Brief description of the drawings]

FIG. 1 shows an outline of a first embodiment.

FIG. 2 shows a manufacturing process of a second embodiment.

FIG. 3 shows an outline of a third embodiment.

FIG. 4 shows a manufacturing process of a third embodiment.

FIG. 5 shows an outline of a fourth embodiment.

FIG. 6 shows a manufacturing process of a fourth embodiment.

FIG. 7 shows an outline of the present invention.

FIG. 8: Atomic force microscope (AFM) on a silicon film surface
An image is shown.

[Explanation of symbols]

101, 201, 301, 401 Glass substrate 102, 202, 302, 402 Underlayer 103, 203, 303, 403 Amorphous silicon (a-Si) film 304, 404 Mask 405 Nickel thin film 406 Arrows 107, 207, 307, 407 Laser light 208, 308, 408 Island crystalline silicon film 209, 309, 409 Gate insulating film 210, 310, 410 Gate electrode 211 Oxide layer 212, 312, 412 Impurity ion 213, 313, 413 Channel region 214, 314, 414 Source region 215, 315, 415 Drain region 216, 316, 416 Interlayer insulating film 217, 317 Source electrode 417, 418, 419 Electrode / wiring 220, 320 Pixel electrode 221, 321 Pixel TFT 422 N-type TFT 423 P-type T FT 324 Auxiliary capacity (Cs)

Claims (9)

[Claims] 1. A semiconductor thin film having crystallinity formed on a substrate having an insulating surface, wherein the semiconductor thin film is formed by sequentially scanning and irradiating a silicon laser formed on the substrate with a pulsed laser beam. The crystalline silicon film is sequentially scanned with the laser light to a value not more than the width (R) of the rising region on the scanning direction side of the beam intensity profile in the scanning direction of the pulsed laser light. A semiconductor thin film characterized by being crystallized by a pulsed laser beam having an interval (P) set. 2. The semiconductor thin film according to claim 1, wherein the width (R) of the rising region is within a range of strength for crystallizing the silicon film. 3. The semiconductor thin film according to claim 1, wherein a beam intensity profile of the laser light in a scanning direction is a substantially trapezoidal laser light. 4. The pulse laser beam is designed such that its beam shape is elongated on an irradiation surface (silicon film surface), and is sequentially scanned in a direction perpendicular to the elongated direction of the beam shape. The semiconductor thin film according to claim 1, wherein the semiconductor thin film is crystallized. 5. A semiconductor device having a plurality of thin film transistors formed on a substrate having an insulating surface, wherein a silicon thin film formed on the substrate is scanned by a pulse laser beam with a laser beam sequential scanning interval (P). Crystallized by a pulsed laser beam having a value equal to or smaller than the width (R) of a rising region on the side of the traveling direction of the beam intensity profile in the direction, and the crystalline silicon film has active regions of a plurality of thin film transistors. A semiconductor device characterized by the above-mentioned. 6. A plurality of pixel electrodes and thin film transistors for driving the respective pixel electrodes are provided on a substrate having an insulating surface, and each of the thin film transistors is connected to another capacitance component in parallel with a liquid crystal capacitance by the pixel electrodes. In the semiconductor device, the silicon thin film formed on the substrate may be formed such that a laser beam sequential scanning interval (P) is equal to or less than a width (R) of a rising region on a traveling direction side of a beam intensity profile in a scanning direction of a pulse laser beam. Wherein the crystalline silicon film is crystallized by a pulsed laser beam, and a channel region of the thin film transistor and one electrode of a capacitance component connected to the thin film transistor are formed in the crystalline silicon film. 7. A step of forming an amorphous silicon film on a substrate having an insulating surface, and sequentially scanning and irradiating the amorphous silicon film with a pulsed laser beam to crystallize the amorphous silicon film. A step of setting the scanning interval (P) to a value less than or equal to (P <R) the width (R) of the rising region on the scanning progress direction side of the beam intensity profile in the scanning direction of the laser light, and irradiating the laser light. And a step of patterning and forming the silicon film obtained in the above step on element regions of a plurality of thin film transistors to produce a thin film transistor. 8. A step of forming an amorphous silicon film on a substrate having an insulating surface and crystallizing it in a solid state by heating, and sequentially scanning and irradiating the silicon film with a pulsed laser beam. When recrystallizing, the sequential scanning interval (P) of the pulsed laser light is determined by setting the rising area on the scanning advancing direction side in the intensity range where the silicon film is recrystallized in the beam intensity profile in the scanning direction of the laser light. A step of irradiating with a laser beam by setting the width to (R) or less (P <R), and forming the silicon film obtained in the above step in an element region of a plurality of thin film transistors by patterning. And a method of manufacturing a semiconductor device. 9. The setting of the sequential scanning interval (P) of the laser light is performed by irradiating the amorphous silicon film with a laser light before scanning with the laser light, and setting a region where the silicon film is crystallized in the laser scanning direction. The width (R) of the rising region is determined from the length and the beam profile of the laser light,
Scanning interval (P) below the width (R) of the rising area
9. The method for manufacturing a semiconductor device according to claim 7, wherein: