JP2002353140A - Semiconductor device and its fabricating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a high performance semiconductor element in which the characteristics are stabilized by suppressing variation, and to fabricate a high integration high performance semiconductor device by a convenient high yield fabrication process. SOLUTION: The semiconductor device has a silicon film including a crystal region wherein the crystal region of the silicon film includes an active region 109 in which migration of carriers is controlled. The active region 109 comprises a group of linear grains arranged substantially in one direction (Y axis) and contains catalyst element Ni for accelerating crystallization of an amorphous silicon film. The lattices of individual grains belonging to the group of linear grains are continuous, in atomic level, to the lattices of adjacent grains through a small inclination angle grain boundary GB located between.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device and a method of manufacturing the same, and more particularly, to a semiconductor device having a crystalline silicon film obtained by crystallizing an amorphous silicon film as an active region, and a method of manufacturing the same. In particular, the present invention relates to a thin film transistor (TF) provided on a substrate having an insulating surface.
This is effective for a semiconductor device using T), and can be used for an active matrix liquid crystal display device, a contact 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 have been developed.
High-speed, high-resolution contact image sensor, 3D IC
In order to realize such a technique, attempts have been made to form a high-performance semiconductor element on an insulating substrate such as glass or an insulating film. In general, a thin film silicon semiconductor is used for a semiconductor element used in these devices. As the thin film silicon semiconductor, an amorphous silicon semiconductor (a-Si)
And those composed of crystalline silicon semiconductors.

[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 has been strongly demanded in order to obtain higher-speed characteristics in the future.

As a method for obtaining a silicon semiconductor in the form of a thin film having crystallinity, a method in which an amorphous semiconductor film is formed and crystallinity is imparted by the energy of laser light is generally used. I have. In this method, the crystallization phenomenon in the melt-solidification process is utilized, so that the grain boundaries are favorably processed in spite of the small grain size, and a relatively high-quality crystalline silicon film is obtained. Taking an excimer laser as an example, a laser having sufficient stability has not yet been obtained, and the performance of a semiconductor device is not sufficient. In particular, when the irradiation power of the laser is increased, the crystallinity is generally improved, but there is a problem that the dispersion is increased.

As another useful method, there is a method utilizing a catalytic element which promotes crystallization of an amorphous silicon film. Specifically, a small amount of a metal element such as nickel or palladium is introduced on the surface of the amorphous silicon film, and then heating is performed, thereby lowering the heating temperature, shortening the processing time, and improving the crystallinity. It is intended.

When a semiconductor device is manufactured using the crystalline silicon film obtained by such a method, a semiconductor device having higher performance than before can be obtained, but its performance is still insufficient. Therefore, in Japanese Patent Application Laid-Open No. Hei 7-161634, in order to further enhance the crystallinity of a crystalline silicon film that has been solid-phase crystallized by introducing a catalytic element, the intensity of laser light or the like is further increased after the crystallization step using the catalytic element. A step of irradiating light is added. That is, in this step, the crystallinity of the crystalline silicon film crystallized by the heat treatment using the catalytic element is further enhanced, and as a result, the speed of the semiconductor device is increased.

[0007]

The silicon film crystallized using the catalyst element has good crystallinity, but has many defects in each crystal grain. Therefore, as a silicon film used for an active layer of a high-performance semiconductor device aimed at by the present invention, a high-quality crystalline silicon film with further reduced crystal defects is desired. To further improve the crystallinity, refer to
There is a method of irradiating a laser beam after crystal growth by a catalytic element as described in 161634.

However, when a crystalline silicon film crystallized by a catalytic element is actually irradiated with a laser, there is almost no effect at a low laser power, and the state is not improved because the original crystalline state is almost maintained. Conversely, when the laser power is high, the original crystal state is reset, and a state similar to that obtained by crystallization using only the laser is obtained. In such a case, a problem of crystallinity variation occurs as in the conventional laser crystallization method.

The present invention has been made in view of the above circumstances, and a main object of the present invention is to realize a high-performance semiconductor element having stable characteristics with little characteristic variation and to easily provide a high-performance semiconductor device with a high degree of integration. And a high-yield manufacturing process.

[0010]

According to the present invention, there is provided a semiconductor device having a silicon film including a crystal region, wherein the crystal region of the silicon film includes an active region in which carrier movement is controlled, The active region is composed of a group of linear crystal grains arranged substantially in one direction, and contains a catalytic element that promotes crystallization of the amorphous silicon film.

[0011] In a preferred embodiment, the silicon film is supported on a substrate having an insulating surface.

In a preferred embodiment, the group of linear crystal grains extends from one end to the other end of the active region.

In a preferred embodiment, a plurality of the active regions are arranged on the substrate.

In a preferred embodiment, the lattice of the individual grains belonging to the group of the linear crystal grains and the lattice of the adjacent grains are continuous at an atomic level via a grain boundary located therebetween. are doing.

In a preferred embodiment, a small-angle crystal grain boundary is formed between each crystal grain belonging to the group of linear crystal grains and an adjacent crystal grain.

The inclination of the crystal orientation at the crystal grain boundary is:
It is preferable that the angle is 10 ° or less in a plane parallel to the surface of the silicon film.

The crystal grain boundary is located at a portion of the silicon film to be etched by the Secco etching method, and the crystal grain is defined by a region surrounded by the crystal grain boundary. The inclination of the crystal orientation is EBSP.
It is specified by the measured value by the method.

In a preferred embodiment, the layout is defined so that the direction of movement of carriers in the active region and the direction in which the linear crystal grains constituting the active region extend are substantially parallel. I have.

In a preferred embodiment, the channel region formed in the active region includes nickel element of 1 ×.
It is contained at a concentration of 10 ^{16 to} 5 × 10 ¹⁷ atoms / cm ³ .

The method for manufacturing a semiconductor device according to the present invention comprises the steps of: preparing a silicon film containing a catalytic element for promoting crystallization of amorphous silicon; and irradiating the silicon film with a laser beam. A crystallization step of causing the support member and / or the laser beam to scan in one direction, thereby sequentially forming a crystal region reflecting the crystallinity of the region crystallized by the irradiation of the laser beam in the scanning direction. Including.

The method of manufacturing a semiconductor device according to the present invention comprises the steps of: preparing a silicon film containing a catalytic element for promoting crystallization of amorphous silicon; and irradiating the silicon film with a pulse laser beam. A crystallization step of scanning the support member and / or the laser beam in one direction, thereby sequentially forming a crystal region reflecting the crystallinity of the region crystallized by irradiation of the pre-pulse laser beam along the scanning direction; including.

A semiconductor device according to the present invention comprises a step of preparing a silicon film containing a catalytic element for promoting crystallization of amorphous silicon, and a step of irradiating the silicon film with a continuous oscillation laser beam while irradiating the silicon film with a continuous wave laser beam. A crystallization step of scanning the member and / or the laser beam in one direction, thereby sequentially forming a crystal region reflecting the crystallinity of the region crystallized by the irradiation of the continuous wave laser beam along the scanning direction. including.

In a preferred embodiment, the step of preparing the silicon film includes a step of depositing a silicon film on a member having an insulating surface, and a step of introducing the catalytic element into the silicon film. .

In a preferred embodiment, the scanning pitch of the pulse laser beam in the crystallization step is such that a region melted by the irradiation of the pulse laser beam is recrystallized by reflecting the crystallinity of the crystallized region. It is set to be able to.

The scanning pitch of the pulse laser beam is set to 0.1.
It is preferably in the range of 1 μm to 1 μm.

In a preferred embodiment, a beam cross-sectional shape of the pulse laser light on the surface of the amorphous silicon film is substantially long and rectangular, and a scanning direction of the pulse laser light is long. Set perpendicular to the direction.

In a preferred embodiment, in the crystallization step, an intensity profile of the pulse laser beam measured along a scanning direction of the pulse laser beam changes sharply in a region located behind the scanning direction. It has a rectangular wave shape.

In a preferred embodiment, the intensity profile of the pulsed laser light is obtained by cutting off an end portion of the pulsed laser light emitted from a light source located rearward in the scanning direction. It is.

In a preferred embodiment, a portion where the pulse laser beam emitted from the light source is cut off has a level of the intensity profile lower than a level required for crystallization of the amorphous silicon film. Part.

[0030] In a preferred embodiment, the intensity of the pulsed laser beam in the crystallization step is at a level at which the amorphous silicon film is melted in the entire thickness direction.

The pulse laser beam has a wavelength of 400 n.
It is preferable to set the irradiation conditions so that the energy density on the surface of the silicon film is 250 mJ / cm ² or more using excimer laser light of m or less.

In a preferred embodiment, the step of irradiating the silicon film with a continuous wave laser beam includes melting the silicon film in an irradiation area with the continuous wave laser beam, and scanning the solid film with the continuous wave laser beam. Crystallization is performed sequentially while moving the interface.

[0033] In a preferred embodiment, the intensity of the continuous wave laser beam in the crystallization step is at a level at which the silicon film melts over the entire thickness direction.

In a preferred embodiment, a solid-state laser is used as the continuous wave laser light.

In a preferred embodiment, the layout is defined so that the direction in which carriers flow in the active region is substantially parallel to the scanning direction of the laser light with respect to the scanning direction of the laser light. .

A method for manufacturing a semiconductor device according to the present invention comprises the steps of: preparing an amorphous silicon film containing a catalytic element for promoting crystallization of amorphous silicon; While irradiating the light, the support member and / or the laser light is scanned in one direction, whereby the crystal regions reflecting the crystallinity of the regions crystallized by the irradiation of the pre-pulse laser light are sequentially arranged along the scanning direction. Crystallization step.

[0037] In a preferred embodiment, the step of preparing the amorphous silicon film includes the steps of: depositing an amorphous silicon film on a member having an insulating surface; Introducing a catalytic element.

[0038] In a preferred embodiment, the scanning pitch of the pulse laser beam in the crystallization step is such that a region melted by the irradiation of the pulse laser beam is recrystallized by reflecting the crystallinity of the crystallized region. It is set to be able to.

The scanning pitch of the pulse laser beam is set to 0.1.
It is preferably in the range of 1 μm to 1 μm.

In a preferred embodiment, a beam cross section of the pulse laser beam on the surface of the amorphous silicon film is substantially long and rectangular, and a scanning direction of the pulse laser beam is long. Set perpendicular to the direction.

In a preferred embodiment, in the crystallization step, an intensity profile of the pulse laser light measured along a scanning direction of the pulse laser light changes sharply in a region located behind the scanning direction. It has a rectangular wave shape.

In one preferred embodiment, the intensity profile of the pulsed laser light is obtained by cutting off an end portion of the pulsed laser light emitted from the light source located rearward in the scanning direction. It is.

In a preferred embodiment, a portion where the pulse laser beam emitted from the light source is cut off has a level of the intensity profile lower than a level required for crystallization of the amorphous silicon film. Part.

The intensity of the pulse laser beam in the crystallization step is at a level at which the amorphous silicon film is melted over the entire thickness direction.

In a preferred embodiment, an excimer laser beam having a wavelength of 400 nm or less is used as the pulse laser beam, and irradiation conditions are set so that the energy density on the surface of the silicon film is 250 mJ / cm ² or more. I do.

In a preferred embodiment, the layout is defined such that the direction in which carriers flow in the active region is substantially perpendicular to the scanning direction of the pulsed laser beam with respect to the scanning direction of the pulsed laser beam. I have.

In one preferred embodiment, at least one element selected from the group consisting of Ni, Co, Fe, Pd, Pt, Cu, and Au is used as the catalyst element.

In a preferred embodiment, after the crystallization step, a step of introducing an element selected from Group V B into a region of the silicon film other than a region finally functioning as a channel region. And heat treatment, group V B
Transferring the catalytic element to the region where the element selected from the above is introduced, thereby relatively reducing the concentration of the catalytic element in the channel region.

[0049] In a preferred embodiment, a direction of movement of the catalyst element by the heat treatment is substantially parallel to a scanning direction of the pulse laser beam.

As the element selected from Group V B, P,
It is preferable to use at least one element selected from the group consisting of N, As, Sb, and Bi.

[0051]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A high-quality crystalline silicon film is indispensable for realizing a high-performance semiconductor device aimed at by the present invention. The active region of the semiconductor device according to the present invention is composed of a group of linear (line-shaped) crystal grains arranged substantially in one direction, and the active region has a predetermined amount for promoting crystallization of the amorphous silicon film. Of the catalyst element.

According to the present invention, the influence of the crystal grain boundary can be suppressed to a small value, the trap density of semiconductor carriers at the crystal grain boundary can be reduced, and the energy of the trap level can be suppressed to be shallower. As a result, it is possible not only to realize a semiconductor device having a high current driving capability, but also to reduce variation in characteristics between semiconductor devices and exhibit stable characteristics.

In the present invention, the crystal grain boundaries located between the above-mentioned groups of linear crystal grains are in a state where lattices are continuously connected at the atomic level. In this state, the carrier trap density and the energy level at the crystal grain boundaries are minimized. Further, that the lattice is continuously connected between the crystal grains means that the crystal grain boundaries of adjacent linear crystal grains constitute a so-called “small tilt grain boundary”. In such a small-angle grain boundary, a shift in crystal orientation occurs at a small rotation angle. In other words, at the crystal grain boundaries, the arrangement of the lattice itself is rotated (refracted) by a small angle.
However, the lattices of adjacent crystal grains are continuous. In such a case, the carrier trap density and the energy level at the crystal grain boundary are minimized, so that the operation speed of the semiconductor device is improved and the characteristic variation between elements is reduced.

It is desirable that the rotation angle of the crystal orientation at the small-angle crystal grain boundary is within 10 °. Rotation angle is 1
If the angle is within 0 °, the continuity of the lattice at the grain boundary portion is substantially maintained, and the trap density and the energy of the trap level with respect to the semiconductor carrier can be greatly reduced.

Conventionally, there has been known a method of irradiating a laser beam to an amorphous silicon film under special conditions to obtain a group of linear crystal grains arranged substantially in one direction. In the obtained crystal, the plane orientation between adjacent crystal grains was not relevant, and each crystal grain had an independent plane orientation. In such a case, compared to the present invention, the trapping property of the crystal grain boundaries for the carrier is large,
When there is a semiconductor element in which carriers have to move beyond the crystal grains, the characteristics of the semiconductor element are remarkably deteriorated, and there is a problem that the characteristic variation between the elements is increased. In this case, when TFTs are manufactured such that the carrier movement direction is parallel or perpendicular to the line direction, the field-effect mobility (hereinafter, referred to as “the field effect mobility”) of each TFT.
(Referred to simply as "mobility") showed a large difference of about 5 times.

On the other hand, in the present invention, in the above arrangement, the TF
When T was manufactured, the difference in mobility depending on the direction of the current was 1.
It is about 5 to 2 times. Further, according to the present invention, since the average value of the mobility is improved as compared with the conventional example, the degree of freedom of the element design layout is improved.

In the present specification, the “crystal grain boundary” is a portion of the crystal that is etched by the Secco etching method, and the “crystal grain” is a crystal region surrounded by the crystal grain boundary. . Further, the “plane orientation of the crystal grain group” and “the tilt angle of the crystal orientation at the crystal grain boundary” in the present specification are:
This is a value measured by the EBSP method.

In the semiconductor device of the present invention, it is preferable that the layout is designed so that the major axis direction of the linear crystal grains constituting the active region is substantially parallel to the carrier moving direction in the active region. As described above, according to the present invention, although the trapping property for carriers at the crystal grain boundaries adjacent to the line-shaped crystal grains is sufficiently smaller than that of the conventional example, the influence of the crystal grain boundary portions on the carrier mobility is reduced. Is not nothing. For this reason, in an element requiring particularly high carrier mobility, it is possible to minimize the influence of the grain boundary on carriers by making the carrier movement direction in the active region substantially parallel to the major axis direction of the crystal grains. preferable. However, according to the present invention, even in an element that does not have such an arrangement, higher mobility than that of the conventional example can be achieved.

In the semiconductor device according to the present invention, a catalyst element for promoting crystallization of amorphous silicon is introduced into the amorphous silicon film in order to control the plane orientation of adjacent linear crystal grains. As such a catalyst element, it is preferable to use nickel most suitable for controlling the plane orientation.

According to the present invention, the catalytic element introduced for crystallization ultimately remains in a region functioning as a channel region of the active region. When nickel is used as the catalyst element, the concentration of nickel contained in the channel region is desirably 1 × 10 ^{16 to} 5 × 10 ¹⁷ atoms / cm ³ . Nickel concentration of 5 × 10 ¹⁷ atoms
If it exceeds / cm ³ , nickel silicide will be formed at many locations in the active region, and the characteristics of the semiconductor element will be degraded. If the nickel concentration is 5 × 10 ¹⁷ atoms / cm ³ or less, nickel is dissolved in the silicon film and does not precipitate as silicide, and no adverse effect on the semiconductor device is observed. Conversely, when the nickel concentration in the active region is 1 × 10 ¹⁶ at
If it is less than oms / cm ³ , the catalytic effect of nickel cannot be sufficiently obtained, and the plane orientation of crystal grains cannot be sufficiently controlled.

When a crystal is grown by introducing an amount of nickel which is expected to have a sufficient effect as a catalyst, even if a known process for reducing the amount of nickel in the active region is performed after the crystal growth, Nickel concentration of 1 × 10 ¹⁶ atoms
It cannot be reduced below s / cm ³ .

Next, a method of manufacturing a semiconductor device according to the present invention will be described.

First, after introducing a catalytic element for promoting crystallization into an amorphous silicon film formed on a substrate having an insulating surface, the crystalline silicon film is irradiated with a laser beam. The substrate and / or the laser beam is scanned in one direction. By doing so, the crystallization proceeds sequentially reflecting the crystallinity of the region crystallized by the previous irradiation with the laser light. Note that a pulsed laser or a continuous wave laser can be used as a laser to be used.

In the method disclosed in Japanese Patent Application Laid-Open No. 7-161634, after a catalyst element is introduced and solid phase crystal growth is performed by heat treatment, recrystallization is performed by laser beam irradiation. In this method, the scanning by the pulse laser is performed so that the influence of the region crystallized by the heat treatment is not inherited by the adjacent region. In this pulse laser scanning process, new crystal grain boundaries are randomly generated,
The effect of crystallization by the catalytic element is reduced. For this reason,
The crystal state obtained by the conventional laser scanning method is substantially equal to the crystal state obtained by performing laser crystallization without adding a catalytic element.

On the other hand, in the present invention, after the catalytic element is introduced into the amorphous silicon film, crystallization by laser irradiation is performed without performing a heat treatment step using a furnace or the like. Specifically, by scanning the substrate or the laser beam in one direction, the crystallization proceeds sequentially reflecting the crystallinity of the region crystallized by the preceding pulse. As a result, crystal grains arranged along the scanning direction are formed. If the beam cross section of the pulsed laser light is elongated in a direction perpendicular to the scanning direction, linear crystal grains can be arranged in the scanning direction. The angle between the major axis of the crystal grain and the scanning direction is typically set to be parallel. Since the crystal grains extending in a line shape are regularly arranged in the scanning direction, the position and direction of the crystal grain boundary can be controlled.

The effect obtained by the addition of the catalytic element appears in the crystal grain boundaries and in the crystal grains. In the crystal grain boundary portion, dangling bonds of silicon are reduced, and a low-angle grain boundary substantially atomically continuous is formed. This is a phenomenon that is not observed unless a catalytic element is introduced. On the other hand, in the crystal grains, the defect density is reduced as compared with the case where no catalytic element is introduced. In addition to these phenomena, in the present invention, as a result of controlling the crystal grain boundaries generated in the laser irradiation step with good reproducibility, characteristic variations due to laser irradiation, which has been a problem in the conventional method, are reduced.

In the present invention, the substrate and / or the laser beam is scanned in one direction while irradiating the laser beam onto the amorphous silicon film into which the catalytic element has been introduced. The crystallization proceeds sequentially while reflecting the crystallinity of the crystallized region.

This crystallization step is the most important for obtaining the effects of the present invention, and sufficient effects cannot be obtained if the conditions of the result formation step are inappropriate. In particular, when pulsed laser light is used, the scanning pitch of the pulsed laser light is an important parameter, and the scanning pitch is such that the region that is melted when irradiating the pulsed laser reflects the crystallinity of the adjacent unmelted region. It is adjusted to be less than the maximum length that can be achieved. By doing so, the crystal grains are formed in a line along the growth direction. If the scanning pitch at this time is equal to or longer than the above-mentioned length, a region formed by random crystal nuclei seen in a normal laser irradiation step is formed, and normal grain-like crystal grains are formed.

The area to be melted during pulsed laser irradiation is
The maximum length that can be crystallized by reflecting the crystallinity of the adjacent non-molten region is 1 μm. For this reason, the scanning pitch is required to be 1 μm or less. Scan pitch is 1
If the size exceeds μm, the region cannot be crystallized (random nucleation region) due to the crystallinity of the region crystallized by the preceding pulse.

On the other hand, in order to increase the throughput (processing capacity per time) of the pulse laser irradiation step, the larger the scanning pitch, the more preferable. When the scanning pitch is 0.1 μm or more, the effects of the present invention can be sufficiently obtained without greatly restricting the laser irradiation conditions. Also, by making the scanning pitch smaller than 0.1 μm,
There is no particular advantage.

As described above, when pulse laser light is used, it is desirable to set the scanning pitch in a range of 0.1 μm or more and 1 μm or less.

Hereinafter, the present invention will be described in the case of using pulsed laser light. However, with respect to the beam diameter and the intensity profile, the items described for the pulsed laser light also hold true for the continuous wave laser light.

The cross section of the beam formed by the pulsed laser beam on the surface of the amorphous silicon film is preferably long and substantially rectangular. It is desirable that the scanning by the pulse laser is performed along a direction (short axis direction) perpendicular to the longitudinal direction of the beam cross section.

The size of the beam cross section measured along the scanning direction may be any size as long as it is equal to or larger than the scanning pitch. Since the power of the laser pulse output from the laser oscillator is limited, it is preferable to reduce the beam cross-sectional size in the direction parallel to the scanning direction and increase the beam cross-sectional size in the direction perpendicular to the scanning direction. .

By making the cross section of the beam into such a long rectangular shape, crystallization can be efficiently advanced over a wide area, and the processing time of this step can be shortened.

Next, the beam intensity profile of the pulse laser beam suitably used in the present invention will be described in detail.

It is desirable that the profile of the beam intensity in the scanning direction of the laser beam has a rectangular wave shape such that the intensity on the rear side in the scanning direction rapidly decreases from a certain level to a zero level.

In one embodiment of the present invention, as described above,
While irradiating the amorphous silicon film with the catalytic element in a pulsed manner with laser light, the substrate or the laser light is scanned in one direction to reflect the crystallinity of the region crystallized by the previous pulse. The crystallization proceeds sequentially. The size (irradiation length) of the beam section measured along the scanning direction of the laser beam has a length equal to or longer than the scanning pitch. For this reason, crystal growth occurs in a lateral direction from a region irradiated with the rear end portion of the beam in the scanning direction (a region crystallized by the former pulse). Therefore, to achieve proper crystallization,
The beam intensity profile of the portion located on the rear side in the scanning direction is important. If the beam intensity profile of this portion has a gentle curve like a Gaussian shape, the laser energy gradually increases in the scanning direction from the region crystallized by the preceding pulse. In that case, the energy of the laser to be irradiated becomes insufficient near the region crystallized by the preceding pulse. Therefore, in the laser having such a profile in which the intensity changes gently, a region in which the power is given lower than the level required for crystallization occurs, and the crystallinity of the region crystallized by the preceding pulse is appropriately inherited. The part which cannot do it appears. Such a portion is not preferable because it remains as a region having poor crystallinity.

In order to optimize the beam intensity profile of the laser light, it is preferable to use a laser irradiation device having a mechanism for blocking a portion located on the rear side in the scanning direction of the pulse laser light. According to such a mechanism, a necessary beam intensity profile can be easily obtained without largely changing the optical system of the laser irradiation apparatus and without making optically difficult adjustments.

In order to easily obtain an optimum beam intensity profile for the present invention, a region of the laser beam having an intensity lower than the intensity required for crystallization of the amorphous silicon film into which the catalytic element has been introduced is used. It is sufficient to cut the area and set the intensity of the area to substantially zero. Specifically, a shielding plate having an opening may be inserted on the optical axis of the laser beam, and a portion of the laser beam having a required intensity may be aligned with the position of the opening.

Next, the intensity of the laser beam irradiation step will be described.

When the laser beam intensity is low, the silicon film is not sufficiently melted, cannot sufficiently crystallize the adjacent region crystallized by the preceding pulse, and cannot be crystallized. Can not be obtained. Therefore, the intensity of the laser beam is set to an intensity such that the amorphous silicon film in which the catalytic element is introduced is melted over the entire film and the crystallinity of the preceding crystallization region can be sufficiently inherited and crystallized. It is necessary that the strength is such that the amorphous silicon film into which the catalytic element is introduced is melted over the entire film.

The laser beam used in the present invention has a wavelength of 4
Excimer laser light of 00 nm or less is most suitable. When the wavelength is 400 nm or less, the absorption coefficient for the silicon film is extremely high, and only the silicon film can be instantaneously heated without thermally damaging the glass substrate. Excimer laser light has a large oscillation output and is suitable for processing a large-area substrate. Especially, X of wavelength 308 nm
Since the output of the eC excimer laser beam is large, the beam size at the time of irradiating the substrate can be increased, it is easy to cope with a large-area substrate, and the output is relatively stable.

The surface energy density of the laser beam is preferably at least 250 mJ / cm ² on the silicon film. If the energy density is 250 mJ / cm ² or more, the above-mentioned amorphous silicon into which the catalytic element has been introduced can be melted over the entire film. The crystallization can be advanced in the lateral direction.

Next, the relationship between the scanning direction of the laser beam and the direction of the semiconductor element will be described.

It is desirable to design the element layout of the semiconductor device such that the carrier movement direction (channel direction) during element operation is substantially parallel to the scanning direction of the laser beam. By adopting the layout in this manner, the moving direction of the carriers in the active region of the semiconductor device is substantially parallel to the line direction (long-axis direction) of the linear crystal grains constituting the active region. The influence of the field can be eliminated as much as possible, and an element having a very high current driving capability can be obtained.

As a catalyst element for promoting crystallization, N
i, Co, Fe, Pd, Pt, Cu, and / or A
u can be used. These catalyst elements have an effect of promoting crystallization in a very small amount. Among these, the most remarkable effect is obtained particularly when Ni is used.

Since all of the above-mentioned catalyst elements are metal elements, if they are present in a large amount in a semiconductor, the reliability and electrical stability of the semiconductor element may be impaired. In particular,
If these catalytic elements are precipitated as silicide in the channel region, the leakage current of the TFT during the off operation increases.

In the present invention, a catalytic element is intentionally introduced into the silicon film for crystallization, and the catalytic element remains in the active region of the final semiconductor device. It is important to reduce it. In the present invention,
After using the catalytic element for the crystallization treatment of the amorphous silicon film,
This problem has been solved by moving most of the catalyst element remaining in the silicon film to a region other than the semiconductor element formation region. Specifically, an element (getter) selected from Group V B is introduced into at least a region other than a region that functions as a channel region of the semiconductor device in the silicon film, and heat treatment is performed. As a result, the catalyst element moves (diffuses) to the region where the getter element is introduced,
The amount of the catalytic element in the channel region can be reduced.

This method is effective in reducing the amount of a silicide-state catalytic element that has a large adverse effect on semiconductor characteristics. If a region where the catalytic element is collected is etched and a semiconductor element is formed using the other semiconductor region, the catalytic element high concentration region does not remain on the substrate.

It is desirable that the direction of movement of the catalyst element in the above-mentioned gettering step be substantially parallel to the scanning direction of the laser beam on the amorphous silicon film. Although the transfer efficiency of the catalyst element is high within the crystal grain, the efficiency is low for the movement across the crystal grain boundary. Therefore, by making the moving direction of the catalytic element coincide with the scanning direction of the laser beam (the line direction of the crystal grain), the catalytic element can move within the crystal grain without crossing the crystal grain boundary, so that the moving efficiency is increased and the channel is improved. The residual amount of the catalyst element in the region can be greatly reduced.

As the group V element B, P, N, As, S
At least one element selected from the group consisting of b and Bi can be used. One or more of these elements can efficiently move the catalyst element. The details of the mechanism by which these elements move the catalytic element are unknown, but experiments show that the effect of P is the highest.

[0093]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a schematic configuration of a laser irradiation apparatus used in the present embodiment will be described with reference to FIG. In the illustrated laser irradiation apparatus, after a pulse laser beam 506 emitted from a laser oscillator 501 is reflected by a mirror 502,
It is led to the homogenizer 503. Homogenizer 50
Reference numeral 3 denotes an apparatus for shaping the beam shape of the laser beam 506, and a plane (X) perpendicular to the beam axis (optical axis) of the laser beam 506.
The shape in (−Y plane) is changed to a long shape 507 that extends long in the X-axis direction.

In the case of performing conventional laser irradiation, the laser beam 506 is irradiated onto the surface of the substrate 101 while being formed by the homogenizer 503.
The intensity profile of the laser beam 506 is adjusted using the shielding plate 504 having a slit-shaped opening. Shield plate 504
Is arranged between the homogenizer 503 and the substrate 101 so as to vertically cross the optical axis of the laser beam 507, and blocks a part of the laser beam 507.

In the present embodiment, the laser beam 50 on the substrate 101 is assumed to be in a state where the shielding plate 504 is not inserted.
The optical system is set so that the beam size of 7 becomes 10 mm × 0.2 mm. Actually, since the shielding plate 504 is inserted at an appropriate position, the end of the beam cross section (long shape) of the laser beam 507 is cut by the shielding plate 504. Here, the interval between the shielding plate 504 and the substrate 101 is set to about several mm.

In this embodiment, as shown in FIG. 1, both ends of a strip extending in the major axis direction (Y-axis direction) of the beam cross section are cut by the shielding plates 50. For this reason, the beam of the laser beam 508 on the substrate 101 has a reduced size (width) in the X-axis direction, and is 300 mm × 0.05 mm (50 μm).
m) is molded so as to have a cross-sectional shape having a size of m).

FIG. 2 shows the intensity profile of the laser beam before and after such molding.

As can be seen from FIG. 2, the homogenizer 5
The cross-sectional intensity profile of the laser beam 507 formed into a long shape by the use of Gaussian 03 has a Gaussian shape.
When the laser light 507 passes through the opening (slit) of the shielding plate 504, light having only a region near the top of the intensity distribution (high energy portion) is selectively irradiated to the substrate. That is, the footing region (the portion having a relatively low intensity) in which the intensity changes gradually is cut, whereby the laser beam 508 having a top hat-shaped intensity profile shown in the lower half of FIG.
1 will be irradiated.

Referring back to FIG.

In this embodiment, the substrate 101 is scanned with the pulse laser beam by moving the substrate 101 in the direction 505 of the arrow pointing in the positive direction of the X-axis. The substrate 101 is driven at a speed of, for example, 2 to 18 mm / min. The substrate 101 is irradiated with a pulsed laser beam while moving the substrate 101. In this case, n
The substrate 10 is irradiated (for example, 0.003 to 0.01 seconds) between the irradiation of the first pulse (the former pulse: n is an arbitrary natural number) and the irradiation of the (n + 1) th pulse (the latter pulse).
The distance traveled by 1 defines the scanning pitch P. The scanning pitch P is controlled by adjusting the moving speed of the substrate in the direction of arrow 505, and the scanning pitch P in this embodiment is adjusted.
Is set to 0.1 to 1 μm, for example, 0.5 μm.
The scanning direction of the laser beam with respect to the substrate 101 is a direction opposite to the direction 505 of the arrow (negative direction of the X axis).

Next, reference will be made to FIG. FIG. 3 (a)
1 schematically shows the substrate surface when pulsed laser light is irradiated using a laser irradiation device. FIG.
In (a), the arrow S indicates the laser scanning direction,
This direction is opposite to the substrate moving direction 505 in FIG. 1 (negative direction of the X axis).

As shown in FIG. 3A, a pulse laser having a width (size measured along the scanning direction S) L and a beam cross section extending in one direction is applied to the silicon film at a scanning pitch P. As the irradiation is sequentially performed, crystal grains grow along the scanning direction S, and linear crystal grains parallel to the scanning direction S are formed. In FIG. 3A, the scanning direction S
Grain boundaries (not shown in FIG. 3A) are formed in a direction parallel to.

In this embodiment, the width L of the laser beam measured along the scanning direction S is set to 50 μm. As a result, a total of 100 times (= 0.5 /
(50 times) pulse laser irradiation.

Amorphous; Of a plurality of pulsed lasers that are continuously superimposed on an arbitrary position on the surface of the silicon film, the last pulse has the most important effect on the crystallinity at that position. give. With this last pulse,
Lateral crystal growth that reflects the crystallinity of the adjacent region (previous region) crystallized by the pre-pulse proceeds.

The above-described crystal structure of the present invention can be obtained by such laser irradiation. That is, the crystal grain boundaries located between the adjacent line-shaped crystal grain groups are continuously connected at the atomic level in a lattice, so that a crystalline silicon film constituting a “small tilt grain boundary” can be obtained.

[Embodiment 1] Next, referring to FIGS. 3B to 3C and FIGS. 4A to 4G, the first embodiment of the present invention will be described.
An embodiment will be described. 3B to 3C show N-type TFTs.
FIGS. 4A to 4G are views showing a planar layout of FIG.
FIG. 6 is a process sectional view of the TFT shown in FIG. 3B or 3C.

In this embodiment, an N-type TFT is formed on a glass substrate.
Has been produced. This TFT is used not only for a driver circuit and a pixel portion of an active matrix type liquid crystal display device, but also for an element constituting a thin film integrated circuit.

First, as shown in FIG. 4A, a glass substrate 101 having a thickness of 30
Underlayer 102 made of silicon oxide having a thickness of about 0 to 500 nm
Was deposited. This silicon oxide film is provided to prevent diffusion of impurities from the glass substrate 101.

Next, a thickness of 2
After forming an intrinsic (I-type) amorphous silicon film (a-Si film) 103 of 0 to 60 nm, for example, 40 nm, a small amount of nickel 104 was added on the surface of the amorphous silicon film 103. The addition of a small amount of nickel 104 can be performed by holding a solution in which nickel is dissolved on the amorphous silicon film 103, uniformly spreading the solution on the substrate 101 with a spinner, and drying. In this example, nickel acetate was used as a solute and water was used as a solvent, so that the nickel concentration in the solution was 10 ppm. The concentration of nickel added in this manner on the surface of the amorphous silicon film 103 was measured by total reflection X-ray fluorescence spectroscopy (TRXRF) and found to be about 5 × 10 ¹² atoms / cm ² .

Next, as shown in FIG. 4B, the amorphous silicon film 103 was crystallized by irradiating a pulsed laser beam 105 to obtain a crystalline silicon film 103a. As a laser beam, a XeCl excimer laser (wavelength 308 nm,
A pulse width of 40 nsec) was used. The irradiation conditions of the laser beam are as follows: the substrate is irradiated at 200 to 450 ° C., for example,
And the energy density is 200-450 mJ / cm
² , for example, 350 mJ / cm ² .

In this embodiment, since the pulse scanning pitch P, the beam shape and the beam shape in the crystallization step are important parameters, the laser irradiation apparatus shown in FIG. Irradiated with pulsed laser. As a result, a crystalline silicon film shown in FIGS. 3B and 3C was obtained. The grain boundaries GB shown in FIGS. 3B and 3C (portions shown by “broken lines” in the drawings) cannot be visually observed. Grain boundary GB
Can be observed by performing secco etching on the silicon film. After performing the Secco etching, two-dimensional observation of the crystal plane orientation by the EBSP method reveals that adjacent linear crystal grains sandwiching the crystal grain boundary GB have a correlation with the plane orientation. It was found that a small-angle grain boundary of 10 ° or less was formed in the crystal grain boundary GB portion. Such a crystal structure is represented by Ni
This was obtained by performing the above-described pulse laser beam irradiation after adding a catalyst element such as silicon to silicon, and was not observed when Ni was not added.

Next, as shown in FIG. 4C, an insulating thin film such as a silicon oxide film or a silicon nitride film is deposited on the crystalline silicon film 103a, and the insulating thin film is patterned to form a mask. 106 was formed. In this embodiment, the mask 106 is formed from a silicon oxide film. The silicon oxide film is made of, for example, TEOS (Tetra Ethox).
y Ortho Silicate) is used as a raw material, and is decomposed together with oxygen by an RF plasma CVD method to be deposited on the crystalline silicon film 103a. The thickness of the mask 106 is preferably 100 nm to 400 nm,
In this embodiment, the thickness is set to 150 nm.

Next, as shown in FIG.
Phosphorus 107 was doped from above the entire surface of the silicon film 103a. The phosphorus ion doping conditions include an acceleration voltage of 5 to 10 kV and a dose of 5 × 10 ¹⁵ to 1 × 10 ^16.
cm ^-2 . By this ion doping step, phosphorus is implanted into a region of the crystalline silicon film 103a that is not covered with the mask 106, and a phosphorus-doped crystalline silicon region 103b is formed. The crystalline silicon film 103a in the region covered by the mask 106 is not doped with phosphorus.

As shown in FIGS. 3B and 3C, the crystalline silicon film 103 at the end of the phosphorus doping has a region 103a covered with a mask 106 and a region 103b into which phosphorus has been implanted. Are classified. Note that FIG.
(B) and (c) show a TFT active region 109 formed in a later step. This TFT active region 10
9 shows a mask 10 at the stage when the phosphorus doping is completed.
6 are completely covered.

Next, an inert atmosphere (for example, a nitrogen atmosphere)
580 to 650 with respect to the silicon film 103
Heat treatment is performed at a temperature of ° C. for several hours to several tens of hours. In this embodiment, the treatment was performed at 600 ° C. for 12 hours.

By this heat treatment, the phosphorus in the region 103b draws the nickel 104 diffused in the crystalline silicon film 103a in the entire peripheral direction as shown by the arrow 108. As a result of the gettering performed on nickel in this manner, the nickel concentration in the region 103a is significantly reduced.

The gettering direction (diffusion direction) 108 of the nickel 104 is performed in four directions from the region 103a toward the periphery. However, as in the present embodiment, the region 103a
However, when it is composed of linear crystal grains along a certain direction, the gettering efficiency differs depending on the relationship between the moving direction of nickel and the direction in which the crystal grains extend. This is because nickel 104 does not easily move beyond the crystal grain boundary GB and easily moves within the crystal grain. As a result, gettering efficiency is increased in a direction parallel to the direction in which the crystal grains extend (line direction). FIG. 3 (b) and (c)
In the layout shown in FIG. 5, the nickel 104 moves mainly in the direction of the solid arrow 108 and hardly moves in the direction 108 shown by the dotted arrow. In this embodiment, TF
Gettering region 1 surrounding T active region 109
Since 03b is provided, gettering can be efficiently performed in the line direction of crystal grains.

In terms of gettering efficiency, FIG.
The arrangement example shown in FIG. 3C is more preferable than the arrangement example of the TFT shown in FIG. This is because, when nickel moves along the battle arrow 108 from within the area 103a to the gettering area 103b, the movement distance in the arrangement example shown in FIG.

The nickel concentration in the region 103a is
5 × 10 ¹⁷~ 1 × 10¹⁸at
oms / cm^ThreeBut after the gettering process
5 × 10¹⁶atoms / cm^ThreeReduced to a degree
Was. Nickel concentration was measured by secondary ion mass spectrometry (SIM
S).

Next, the silicon oxide film 1 used as a mask was
06 is removed by etching. As an etchant, a sufficiently large selective etching is performed between the silicon oxide film 106 and the silicon film 103 located below. In this embodiment, wet etching with 1:10 buffered hydrofluoric acid (BHF) was performed.

Thereafter, as shown in FIG. 4E, isolation between elements is performed by selectively removing unnecessary portions of the silicon film 103. By this step, FIG.
Alternatively, the region 103b shown in FIG.
The island-shaped crystalline silicon film 109 is patterned from the region 103a where the nickel concentration is reduced. The size of the patterned crystalline silicon film 109 is, for example, 30 μm × 20 μm. The crystalline silicon film 109 functions as an active region of a semiconductor device.

Next, a silicon oxide film having a thickness of 20 to 150 nm, here 100 nm, is formed as the gate insulating film 110 so as to cover the crystalline silicon film 109. The silicon oxide film was formed by using TEOS as a raw material and decomposing and depositing it together with oxygen by an RF plasma CVD method.
The substrate temperature during the deposition is 150 to 600 ° C., preferably 30
0 to 450 ° C. The formation of this silicon oxide film is based on TE
It may be performed by a low pressure CVD method or a normal pressure CVD method using OS as a raw material together with ozone gas. In that case, the substrate temperature is set to 350 to 600 ° C., preferably 400 to 550.
It is preferably set to ° C.

After the deposition of the silicon oxide film, in order to improve the bulk characteristics of the gate insulating film and the interfacial characteristics between the crystalline silicon film and the gate insulating film, the silicon oxide film is heated at 400 to 600 ° C. in an inert gas atmosphere. Annealing was performed for 4 hours.

Next, a thickness of 4
After depositing an aluminum film having a thickness of 00 to 800 nm, for example, 600 nm, the aluminum film was patterned to form a gate electrode 111.

The surface of this aluminum film is oxidized by an anodic oxidation method, and as shown in FIG.
An oxide layer 112 was formed on the surface of No. 11. Anodizing is
The test was carried out in an ethylene glycol solution containing tartaric acid at 1 to 5%. At first, the voltage was increased to 220 V at a constant current, and the state was maintained for 1 hour, and then terminated. The thickness of the obtained oxide layer 112 was 200 nm. Oxide layer 112
Defines the size of the offset gate region in a later ion doping step. Therefore, the oxide layer 1
By adjusting the thickness of the substrate 12, the size of the offset gate region can be controlled to a desired size.

Next, impurities (phosphorus) were implanted into the basin of the active region 109 which was not covered by the gate electrode 111 and the oxide layer 112 by an ion doping method. Phosphine (PH ₃ ) is used as the doping gas, the acceleration voltage is 60 to 90 kV, for example, 80 kV, and the dose is 1 × 10 ¹⁵ to 8 × 10 ¹⁵ c.
m ⁻² , for example, 2 × 10 ¹⁵ cm ⁻² . By this step, the regions 114 and 115 into which the impurities are implanted later function as source / drain regions of the TFT. The region 113 which is masked by the gate electrode 111 and the oxide layer 112 and in which the impurity is not implanted functions as a channel region of the TFT.

When the layout of the TFT is laid out as shown in FIG. 3B, the direction in which carriers flow during the operation of the TFT (the direction from the region 114 to the region 115) and the line-shaped crystal grains forming the channel region 113 are shown. Is parallel to the line direction. In this case, as compared with the TFT having the arrangement shown in FIG.
And a TFT having higher mobility can be obtained.

Next, as shown in FIG. 4F, annealing is performed by irradiation with a laser beam 116 to activate the implanted impurities and, at the same time, recover the crystallinity deteriorated in the impurity introducing step. . In this embodiment, the laser light 1
XeCl excimer laser (wavelength 308 n)
m, pulse width 40 nsec) and energy density 1
50 to 400 mJ / cm ² , preferably 200 to 250
Irradiation was performed under the condition of mJ / cm ² . N-type impurity (phosphorus) regions 114 and 115 thus activated
Had a sheet resistance of 200 to 800 Ω / □.

Next, a silicon oxide film or a silicon nitride film having a thickness of about 600 nm was formed as the interlayer insulating film 120. If a silicon oxide film is formed by a plasma CVD method using TEOS and oxygen, or a low-pressure CVD method or a normal pressure CVD method using TEOS and ozone,
An interlayer insulating film having excellent step coverage can be obtained. When a silicon nitride film deposited by a plasma CVD method using SiH ₄ and NH ₃ as a source gas is used as an interlayer insulating film, hydrogen contained in the silicon nitride film is supplied to an interface between the active region and the gate insulating film. ,
Unpaired bonds (dangling bonds) in the active region can be vacated with hydrogen atoms. Since the dangling bonds in the active region deteriorate the transistor characteristics, the transistor characteristics can be improved if the number of dangling bonds is reduced.

Next, after forming a contact hole in the interlayer insulating film 120, a metal material, for example, a two-layer film of titanium nitride (lower layer) and aluminum (upper layer) is deposited. The lower titanium nitride film functions as a barrier layer for preventing the upper aluminum from diffusing into the semiconductor layer. By patterning this two-layer film, the source / drain electrodes / wirings 121 of the TFT are formed.

When the TFT 122 is used as a pixel switching TFT in a liquid crystal display device or the like, the drain electrode can be formed integrally with a pixel electrode made of a transparent conductive film such as ITO. In the case where the TFT 122 is used for a thin film integrated circuit or the like, after forming a contact hole also on the gate electrode 111, a low-resistance backing wire is provided on the interlayer insulating film 120 and electrically connected to the gate electrode 111. Thereby, it is preferable to improve the signal transmission speed.

Next, annealing is performed at 350 ° C. for 1 hour in a hydrogen atmosphere at normal pressure (1 atm) to obtain a TFT 12.
2 is completed. If necessary, a protective film made of a silicon nitride film or the like may be provided on the TFT 122 for the purpose of protecting the TFT 122.

The TFT 122 manufactured as described above
Means that in the case of the layout shown in FIG.
Despite the high performance of about 0 cm ² / Vs and the threshold voltage of about 1.0 V, the characteristic variation in the substrate is about ± 10% in mobility and about ± 0.2 V in threshold voltage. Very good. This variation is 400 ×
This is a result obtained by measuring 30 TFTs in a substrate having a size of 320 mm. On the other hand, in the case of the layout shown in FIG. 3C, the mobility is 300 cm ² / Vs
And the threshold voltage was about 1.5 V, which was sufficiently higher than the conventional method. In addition, variation in characteristics within the substrate was similarly reduced.

Further, even after repeated measurements and durability tests by bias and temperature stress, almost no characteristic deterioration was observed, and high reliability was confirmed.

The increase and the variation of the leakage current in the off region of the TFT, in which the catalytic element is particularly problematic, can be reduced to about several pA (pico-ampere) which is the same as when no catalytic element is used without any abnormal point. The production yield was greatly improved.

The active matrix substrate for liquid crystal display was actually evaluated for lighting using the TFT of this example. As a result, a liquid crystal panel having excellent display quality and high contrast ratio was obtained, with less display unevenness and extremely less pixel defects due to TFT leak as compared with those produced by the conventional method.

Embodiment 2 Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. 5 (a) to 5 (c) and FIGS. 6 (a) to 6 (g).
An embodiment will be described.

In this embodiment, an N-channel TFT and a P-channel TFT forming a peripheral driving circuit of an active matrix type liquid crystal display device and a general thin film integrated circuit are used.
Are formed on a glass substrate in a complementary manner.

FIG. 5A is a plan view showing the scanning direction of the pulse laser beam. FIGS. 5B to 5C are plan views for explaining the fabrication of the N-channel TFT and the P-channel TFT according to the present embodiment, respectively.
(A)-(g) is sectional drawing of the process.

First, as shown in FIG. 6A, a thickness of 300 to 50 is formed on a glass substrate 201 by, for example, a CVD method.
A base film 202 of about 0 nm made of silicon oxide is formed. Next, a thickness of 20 to 60 is applied by a plasma CVD method.
An intrinsic (I-type) amorphous silicon film (a-Si film) 203 having a thickness of, for example, 30 nm is formed. The substrate heating temperature at this time is desirably about 400 ° C., and was set to 400 ° C. in this embodiment.

A parallel plate type apparatus was adopted as a plasma CVD apparatus, and SiH ₄ gas and H ₂ gas were used as source gases. The RF power has a power density of 10 to 1
00mW / cm ^2, it was set lower as for example a 80 mW / cm ^2. The deposition rate of the amorphous silicon film 203 in this embodiment was about 50 nm / min.

The thus obtained a-Si film 203
Was about 2%.

Next, a slight amount of nickel 204 was added on the surface of the amorphous silicon film 203. The addition of a small amount of nickel 204 was performed by holding the solution in which nickel was dissolved on the a-Si film 203, spreading the solution uniformly on the substrate 201 by a spinner, and drying the solution. In this example, nickel acetate was used as the solute, water was used as the solvent, and the nickel concentration in the solution was adjusted to 5 ppm. The concentration of nickel on the surface of the a-Si film 203 was determined by TRXR.
When measured by the F method, 3 × 10 ¹² atoms / cm ²
It was about.

Next, as shown in FIG. 6B, the amorphous silicon film 203 was crystallized by irradiating a pulsed laser beam 205 to obtain a crystalline silicon film 203a. XeCl excimer laser (wavelength 308 nm, pulse width 40 nsec) was used as the laser light. 200 to 450 substrates
° C., while heating for example to 400 ° C., the energy density 200~450mJ / cm ^2, for example, 350 mJ / cm ²
Was irradiated.

Also in this embodiment, the crystallization step was performed in the same manner as in the first embodiment, using the laser irradiation apparatus shown in FIG. Specifically, a shielding plate 504 was provided on the substrate 201, and an unnecessary beam end of the laser light 507 was shielded by the shielding plate 504. As a result, the size of the laser light irradiated on the substrate 201 is 10 mm × 0.05 mm (50 mm).
μm). After the crystallization step, as shown in FIG. 6 (c), unnecessary portions of the silicon film 203a were removed, and element isolation was performed. Thus, island-shaped crystalline silicon films 209n and 209p functioning as active regions (source / drain regions, channel regions) of the TFT were formed.

Next, the crystalline silicon films 209n, 209p
20 to 150 nm, here 100 n to cover
A silicon oxide film having a thickness of m is formed as the gate insulating film 210. In this embodiment, the formation of the silicon oxide film is performed using TEO.
By the RF plasma CVD method using S and oxygen,
The substrate temperature is 150 to 600 ° C., preferably 300 to 45
This was performed at 0 ° C.

Next, as shown in FIG. 6D, after a high-melting-point metal film was deposited by a sputtering method, the high-melting-point metal film was patterned to form gate electrodes 211n and 211p. The refractory metal film is desirably formed from tantalum (Ta) or tungsten (W). This embodiment has a two-layer structure of a Ta film to which a small amount of nitrogen is added and a pure Ta film, and has a total thickness of 300.
A high melting point metal film having a thickness of up to 600 nm, for example, 450 nm was used.

Next, the ion doping method is used to activate
The gate electrodes 211n and 21n are provided in the regions 209n and 209p.
Using 1p as a mask, phosphorus 217 was implanted. Dopin
Phosphine as PH (PH_Three) Using dopin
The acceleration conditions are as follows: the acceleration voltage is 60 to 90 kV, for example, 8
0 kV, and the dose amount is 2 × 10¹⁵~ 8 × 10¹⁵c
m ^-2, For example, 5 × 10¹⁵cm^-2And By this process
Masked by the gate electrodes 211n and 211p.
Phosphorous is not implanted into the region
Function as channel regions 213n and 213p of
become.

Further, by the above doping step, the N-type impurity regions 214n and 214n in the N-channel type TFT are formed.
15n are formed. At this stage, the regions that become the source / drain regions 214n 'and 215n' of the P-channel TFT become N-type impurity regions as a result of the phosphorus doping.

Next, as shown in FIG. 6E, a mask 219 for selective doping is formed of a photoresist by photolithography so as to completely cover the N-type TFT. Of the active region 209p of the P-type TFT not covered by the mask 219, the gate electrode 211p
Boron 218 is implanted into the region not masked by the ion doping method. here,
Using diborane (B ₂ H ₆ ) as a doping gas,
1 × 1 at an accelerating voltage of 0 kV to 80 kV, for example, 65 kV
A high dose implantation of 0 ^{16 to} 5 × 10 ¹⁶ cm ⁻² , for example, 2 × 10 ¹⁶ cm ⁻² was performed. Boron 218 is deposited on the gate insulating film 2
10 is implanted into the active region 209p so as to pass therethrough. In this doping step, a region that will function as the channel region 213p of the P-type TFT later is masked by the gate electrode 211p, so that boron is not implanted into this region.

Since the P-type impurity concentration of the high-dose boron 218-doped regions 214n 'and 215n' is higher than the concentration of the previously doped N-type impurity phosphorus, the P-type impurity And 215p (counter doping). Thus, N
A channel TFT and a P-channel TFT are formed on the same substrate.

Next, a mask for selective doping is used.
After removing the used photoresist, it is placed in an inert atmosphere.
Temperature of 500-600 ° C under ambient atmosphere, for example, in a nitrogen atmosphere
For several hours to several tens of hours. In this embodiment
Was treated at 550 ° C. for 6 hours as an example. This
Heat treatment in the TFT active area of the driver
The source / drain regions 214n, 215n,
Phosphorus doped at 14p and 215p is
First, nickel existing in the region is trapped. And figure
As shown in FIG. 6 (f), the channel regions 213n, 213
The nickel present in p is represented by arrow 208
Direction, that is, adjacent source / drain regions 214
n, 215n, 214p, and 215p. So
As a result, nickel in the channel regions 213n and 213p
The concentration is greatly reduced. The arrangement of the TFTs at this time is shown in the figure.
5 (b) and 5 (c)
Was. That is, the laser scanning direction S during recrystallization is
Kel's moving direction 208 is set to be approximately parallel
Was. With such an arrangement, the channel region 2
13n, 213p and the direction in which the linear crystal grains extend.
The direction of movement of the socket is the same as that of the
Transfer of nickel to the region exceeds the grain boundary GB
Done without. As a result, nickel transfer efficiency is improved
However, the amount of residue in the channel was significantly reduced. This and
Of nickel in channel regions 213n and 213p of
Was measured by SIMS.¹⁶ato
ms / cm ^ThreeTo a degree. Before this process
Nickel concentration in crystalline silicon film is 5 × 10¹⁷atom
s / cm^ThreeIt was about.

By the above-mentioned heat treatment, the activation of the source / drain regions 214n, 215n, 214p and 215p is simultaneously performed. The sheet resistance of the N-type impurity regions 214n and 215n obtained by this heat treatment is 0.5
１1 kΩ / □, and the P-type impurity regions 214p, 215
The sheet resistance value of p was 2-3 kΩ / □.

By the above heat treatment, the gate insulating film 210
Is performed at the same time, thereby improving the bulk characteristics of the gate insulating film and the interface characteristics between the crystalline silicon film and the gate insulating film.

Next, as shown in FIG.
After a 0 nm silicon oxide film was formed as an interlayer insulating film 220 by a plasma CVD method, a contact hole was formed in the interlayer insulating film. After depositing a two-layered film of a metal material, for example, titanium nitride and aluminum, the two-layered film is patterned to form a TFT electrode / wiring 22.
Form one.

Thereafter, in a hydrogen atmosphere at 1 atm.
Annealed at 50 ° C for 1 hour, N-channel TFT
223 and a P-channel TFT 224 are completed. If necessary, a protective film made of a silicon nitride film or the like may be provided on the TFT for the purpose of protecting the TFTs 223 and 224.

According to the CMOS structure circuit of this embodiment, T
FT mobility of 400 to 450c with N-channel TFT
m ² / Vs, 150 to ²⁰⁰ cm ^{2 for} P-channel TFT
/ Vs. The threshold voltage is about 1.0 V for an N-channel TFT, and -1.V for a P-channel TFT.
It was as good as about 5V. Further, in the present embodiment, the characteristic variation, which has conventionally been a problem when a catalytic element is used, is about ± 10% in mobility and ± 0.2 V in threshold voltage.
It was able to be suppressed to the extent. The characteristic fluctuation is 4
Using a substrate having a size of 00 mm × 320 mm, it was determined by measuring 30 points in the substrate.

Even after repeated measurements and durability tests with bias and temperature stress, almost no deterioration in characteristics was observed, and very high reliability and stable circuit characteristics were obtained as compared with the conventional one.

[Embodiment 3] Hereinafter, a third embodiment of the present invention will be described. In this embodiment, continuous wave laser light is used instead of pulsed laser light.

First, as in the first and second embodiments,
A base insulating film made of silicon oxide with a thickness of about 300 to 500 nm is formed over a glass substrate. This base film is provided to prevent diffusion of impurities from the glass substrate.
In order to further enhance the impurity diffusion effect, the base film may have a two-layer structure with the silicon nitride film. Next, a film thickness of 20 to
60 nm intrinsic (I-type) amorphous silicon film (a-Si
Film) is deposited on the underlying film.

Thereafter, a catalytic element is added to the silicon film. In the present embodiment, for example, 10 ppm of a catalytic element (in this embodiment, nickel) in terms of weight with respect to the a-Si film.
Is applied by spin coating to form a catalyst element-containing layer. Since the amount of the catalyst element to be added is extremely small, the concentration of the catalyst element on the surface of the silicon film is controlled by total reflection X-ray fluorescence (TRXRF). The concentration of the catalyst element in this embodiment is 7 ×
It is about 10 ¹² cm ^-2 .

In this embodiment, a method in which nickel is added by a spin coating method is used. However, a thin film of a catalytic element (such as a nickel film) is formed on a silicon film by another method, for example, a vapor deposition method or a sputtering method. May be formed.

Next, the silicon film is irradiated with a continuous wave laser beam and continuously scanned, so that the silicon film is crystallized in the laser scanning direction. At this time, the continuous oscillation laser light is diode-excited continuous oscillation YAG.
A laser was used. The wavelength was 532 nm and the power fluctuation was 1% or less. The output of the continuous wave YAG laser is 1
0 W, 50-200 cm / sec with respect to the substrate
The laser beam was scanned at a scanning speed (for example, 100 cm / sec). As a result, the silicon film in the portion irradiated with the laser beam melted, and a solid-liquid interface was generated at the boundary between the laser beam irradiated region and the non-irradiated region. As the solid-liquid interface moves with the scanning of the continuous wave laser light, a crystal group along one direction grows, reflecting the crystallinity of the previously crystallized region.

In the case where the continuous wave laser beam is used, unlike the pulse laser beam, the silicon film in the region irradiated with the laser beam is partially heated to a temperature higher than the melting point. Some are always in a molten state. As a result, the boundary between the irradiation / non-irradiation region of the continuous wave laser beam always exists in the silicon film, and this boundary forms a solid / liquid interface. Therefore, as shown in FIG. 7, when the solid-liquid interface is moved by scanning with a laser beam, crystallization of the silicon film can be appropriately performed.

When a continuous wave laser is used, unlike a pulse laser beam, a solid / liquid interface is always maintained during scanning, so that crystal growth is performed in the direction of movement of the solid / liquid interface. The crystallinity can be controlled by adjusting the laser power and the scanning speed at this time. If the scanning speed is too fast, the solid-liquid interface cannot sufficiently take over the crystallinity of the solid region to grow crystals, and if the scanning speed is too slow, the silicon film is heated more than necessary,
The crystallinity information by the catalytic element is reset.
Therefore, it is necessary to set the scanning speed of the laser beam in an appropriate range while considering the laser power.

After the above-described crystallization step, unnecessary portions of the crystalline silicon film are removed to perform element isolation, and island-like crystallinity which will later become an active region (source / drain region, channel region) of the TFT. A silicon film was formed. After that, using the same method as that shown in the first and second embodiments, the TF
T was completed.

In the case where the silicon film is recrystallized in the lateral direction (laser scanning direction) using the continuous wave laser, more excellent TFT characteristics can be obtained as compared with the recrystallization using the pulse laser. Can be Specifically, N-channel type T
Field effect mobility of 600 cm ² / Vs or more can be obtained by FT.

As described above, by irradiating a continuous oscillation laser beam onto a silicon film containing a catalytic element and continuously scanning the same, crystal growth can be performed along the scanning direction by the effect of the catalytic element. Can be. As a result, it is possible to form a texture structure in which the crystal grain groups are arranged in one direction and the crystal grains are continuous at the atomic level (in other words, a small tilt grain boundary having a tilt angle of 10 ° or less).

As the continuous wave laser, a solid-state laser is preferable and stability is high. As a wavelength, unlike a pulse laser, a wavelength of 600 nm or less can be used sufficiently.

The crystal grains obtained by the embodiment of the present invention are arranged along the laser scanning direction as shown in FIG. The grain boundaries between the crystal grains here are grain boundaries that are revealed by seco etching, and despite the crystal grain boundaries being observed, the plane orientation between adjacent crystal grains is substantially the same as the plane orientation. Has become.

Although the present invention has been specifically described with reference to the three embodiments, the present invention is not limited to the above embodiments, and various modifications based on the technical concept of the present invention are possible. is there. For example, in the above-described embodiment, as a method for introducing nickel, a method in which an aqueous solution in which a nickel salt is dissolved is applied to the surface of the amorphous silicon film is employed. Alternatively, even if nickel is introduced into the surface of 202, the same effect can be obtained. That is, the catalyst element that promotes crystallization of the amorphous silicon film is
It may be introduced from above or below the amorphous silicon film.

Further, the method of introducing nickel is not limited to the coating method, and various other methods can be used. For example, a method of direct introduction by ion doping or a method of forming an extremely thin film by vapor deposition or plating, which is difficult to control, can be used.

As the impurity metal element that promotes crystallization, cobalt, iron, palladium, platinum, copper, and / or gold may be used instead of or together with nickel.

In the first and second embodiments,
As a means for crystallizing an amorphous silicon film into which a catalytic element has been introduced by laser beam irradiation, XeC having a wavelength of 308 nm is used.
Although an excimer laser is used, the present invention is not limited to this as described in the third embodiment. The pulse laser is not limited to the above example.
m KrF excimer laser or ArF with a wavelength of 198 nm
An excimer laser may be used.

As a semiconductor device to which the present invention is applied,
In addition to the active matrix type substrate for liquid crystal display, for example, a contact type image sensor, a thermal head with a built-in driver, an optical writing element and a display element with a built-in driver using an organic EL as a light emitting element, a three-dimensional IC, etc. Conceivable. By applying the present invention, high performance such as high speed and high resolution of these elements is realized.

The elements constituting the semiconductor device according to the present invention are not limited to MOS transistors. INDUSTRIAL APPLICABILITY The present invention can be widely applied to the manufacture of a wide range of semiconductor devices including a bipolar transistor using a crystalline semiconductor and an electrostatic induction transistor.

[0177]

According to the present invention, a crystal structure substantially functioning as a single crystal in a certain direction is realized, and trap levels at crystal grain boundaries are reduced. As a result, a crystal film in which carrier mobility is stably improved can be obtained, and a high-performance semiconductor element with less variation can be formed. Further, according to the present invention, the production yield of the semiconductor device can be improved, and the product price can be kept low.

Further, when a liquid crystal display device is manufactured according to the present invention, the switching characteristics of the pixel switching TFT required for the active matrix substrate are improved, and the high performance and high performance required for the TFT constituting the peripheral drive circuit are required. Integration can be achieved. Therefore, it is possible to realize a driver monolithic active matrix substrate which forms an active matrix portion and a peripheral drive circuit portion on the same substrate,
The module is compact, high performance, and low cost.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a configuration of a laser irradiation apparatus that can be suitably used in a method for manufacturing a semiconductor device of the present invention.

FIG. 2 is a graph showing a beam intensity profile of laser light in the laser irradiation apparatus of FIG.

FIG. 3A is a plan view for explaining a first embodiment of the present invention, and FIGS. 3B and 3C are each a plan view showing a linear crystal grain of a crystalline silicon film, a thin film transistor, It is a top view which shows the arrangement relationship of.

FIG. 4 is a process sectional view showing a manufacturing process of the first embodiment of the present invention.

FIG. 5A is a plan view showing a scanning direction of a pulse laser beam. (B)-(c) are plan views for explaining the fabrication of the TFT according to the second embodiment of the present invention.

FIG. 6 is a process sectional view showing the manufacturing process of the second embodiment of the present invention.

FIG. 7 is a diagram showing a recrystallization step using continuous wave laser light.

FIG. 8 is a diagram showing an example of a line-shaped crystal grain according to the present invention.

[Explanation of symbols]

101, 201 Glass substrate or quartz substrate 102, 202 Base film 103, 203 Silicon film 104, 204 Nickel 105, 205 Laser beam 106 Mask film 107 Phosphorus 108, 208 Movement (gettering) direction of nickel 109, 209 TFT active region ( Element region) 110, 210 Gate insulating film 111, 211 Gate electrode 112 Anodized layer 113, 213 Channel region 114, 214 Source region 115, 215 Drain region 116 Laser light 217 Phosphorus 218 Boron 219 Doping mask 120, 220 Interlayer insulating film 121 , 221 electrode / wiring 122 N-channel TFT 223 N-channel TFT 224 P-channel TFT

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 21/322 H01L 21/322 R 21/336 29/78 627G 29/786 627Z 618Z F term (reference) 2H092 GA11 GA60 JA24 JA28 KA02 KA03 MA17 MA28 MA30 NA05 NA13 NA21 NA24 NA27 PA06 5F045 AA08 AB03 AB04 CA15 HA18 5F052 AA02 BA04 BA18 BB02 BB04 BB07 CA07 DA02 DB03 EA12 EA16 FA06 FA19 HA01 JA01 JA04 5F110 AA01BB02 DD02 DD17 EE03 EE04 EE14 EE34 EE44 FF02 FF29 FF30 FF32.

Claims (31)

[Claims] 1. A semiconductor device provided with a silicon film including a crystal region, wherein the crystal region of the silicon film includes an active region in which carrier movement is controlled, and the active region extends substantially along one direction. A semiconductor device comprising a group of line-shaped crystal grains arranged side by side and containing a catalytic element for promoting crystallization of an amorphous silicon film. 2. The semiconductor device according to claim 1, wherein said silicon film is supported on a substrate having an insulating surface. 3. The semiconductor device according to claim 2, wherein the group of linear crystal grains extends from one end to the other end of the active region. 4. The semiconductor device according to claim 2, wherein a plurality of said active regions are arranged on said substrate. 5. The lattice of individual crystal grains belonging to the group of linear crystal grains and the lattice of adjacent crystal grains are continuous at an atomic level via a grain boundary located therebetween. Item 2. The semiconductor device according to item 1. 6. The semiconductor device according to claim 1, wherein a small-angle crystal grain boundary is formed between each crystal grain belonging to the group of linear crystal grains and an adjacent crystal grain. 7. The semiconductor device according to claim 6, wherein a tilt angle of a crystal orientation at the crystal grain boundary is 10 ° or less in a plane parallel to a surface of the silicon film. 8. The crystal grain boundary of the silicon film,
The semiconductor device according to claim 5, wherein the crystal grain is located at a portion to be etched by a secco etching method, and the crystal grain is defined by a region surrounded by the crystal grain boundary. 9. The semiconductor device according to claim 7, wherein the tilt angle of the crystal orientation is defined by a value measured by an EBSP method. 10. The layout is defined such that a direction in which carriers move in the active region and a direction in which linear crystal grains forming the active region extend are substantially parallel to each other. 10. The semiconductor device according to any one of items 1 to 9. 11. The channel region formed in the active region includes nickel element of 1 × 10 ^{16 to} 5 × 10 ¹⁷ atoms.
The semiconductor device according to claim 1, wherein the semiconductor device is contained at a concentration of s / cm ³ . 12. A step of preparing a silicon film containing a catalytic element for promoting crystallization of amorphous silicon, and irradiating the silicon film with a laser beam while irradiating the support member and / or the laser beam. A method of scanning in one direction, thereby sequentially forming a crystal region reflecting the crystallinity of a region crystallized by irradiation of a laser beam in order along a scanning direction. 13. A step of preparing a silicon film containing a catalytic element for promoting crystallization of amorphous silicon, and irradiating the silicon film with a pulsed laser beam.
A crystallization step of scanning the support member and / or the laser beam in one direction, thereby sequentially forming a crystal region reflecting the crystallinity of the region crystallized by irradiation of the pre-pulse laser beam along the scanning direction; A method for manufacturing a semiconductor device, comprising: 14. A step of preparing a silicon film containing a catalytic element for promoting crystallization of amorphous silicon, and irradiating the silicon film with a continuous oscillation laser beam while irradiating the supporting member and / or the laser. A crystallization step of sequentially forming, in the scanning direction, crystal regions that reflect the crystallinity of the regions crystallized by irradiation with the continuous wave laser light in one direction, thereby scanning the light in one direction. Manufacturing method. 15. The method according to claim 12, wherein the step of preparing the silicon film includes: a step of depositing a silicon film on a member having an insulating surface; and a step of introducing the catalytic element into the silicon film. 15. The method for manufacturing a semiconductor device according to any one of 14. 16. The scanning pitch of the pulse laser beam in the crystallization step is set so that a region melted by the irradiation of the pulse laser beam can be recrystallized by reflecting the crystallinity of the crystallized region. Claim 13
13. The method for manufacturing a semiconductor device according to item 5. 17. The scanning pitch of the pulse laser beam is as follows:
17. The method for manufacturing a semiconductor device according to claim 16, wherein the thickness is in a range of 0.1 μm to 1 μm. 18. A beam cross-sectional shape of the pulsed laser beam on the surface of the amorphous silicon film is substantially a rectangular shape, and a scanning direction of the pulsed laser beam is perpendicular to a long-side direction of the beam cross-sectional shape. 19. The method for manufacturing a semiconductor device according to claim 13, which is set. 19. In the crystallization step, the intensity profile of the pulsed laser beam measured along the scanning direction of the pulsed laser beam has a rectangular wave shape that changes sharply in a region located behind the scanning direction. The method of manufacturing a semiconductor device according to claim 13, further comprising: 20. The pulse laser light intensity profile is obtained by blocking an end portion of the pulse laser light emitted from a light source, which is located rearward in the scanning direction. 20. The method for manufacturing a semiconductor device according to item 19. 21. A portion where the pulsed laser light emitted from the light source is blocked out of the intensity profile.
21. The method according to claim 20, wherein the portion has a level lower than a level required for crystallization of the amorphous silicon film. 22. The intensity of the pulse laser beam in the crystallization step is at a level at which the amorphous silicon film is melted over the entire thickness direction.
22. The method for manufacturing a semiconductor device according to any one of 6 to 21. 23. The pulse laser beam having a wavelength of 40
Using excimer laser light of 0 nm or less, the silicon film
The energy density on the surface is 250 mJ / cm ^TwoAnd above
23. The semiconductor device according to claim 22, wherein the irradiation conditions are set so that
Manufacturing method of body device. 24. The method of manufacturing a semiconductor device according to claim 14, wherein the step of irradiating the silicon film with a continuous oscillation laser beam includes melting the silicon film in an irradiation area with the continuous oscillation laser beam, A method of manufacturing a semiconductor device in which crystallization is performed sequentially while moving a solid / liquid interface with scanning of an oscillating laser beam. 25. The method of manufacturing a semiconductor device according to claim 14, wherein the intensity of the continuous wave laser beam in the crystallization step is at a level at which the silicon film melts in the entire thickness direction. A method for manufacturing a semiconductor device, comprising: 26. The method of manufacturing a semiconductor device according to claim 14, wherein a solid-state laser is used as the continuous wave laser light. 27. The layout is defined such that a carrier flowing direction in the active region is substantially parallel to a scanning direction of the laser light with respect to a scanning direction of the laser light. The method for manufacturing a semiconductor device according to any one of the above. 28. Ni, Co, F as the catalyst element
3. The method according to claim 1, wherein at least one element selected from the group consisting of e, Pd, Pt, Cu, and Au is used.
8. The method for manufacturing a semiconductor device according to any one of items 7. 29. After the crystallization step, a step of introducing an element selected from Group V B into a region of the silicon film other than a region finally functioning as a channel region; Treating the catalyst element to a region into which an element selected from Group V B has been introduced, thereby relatively reducing the concentration of the catalyst element in the channel region. 27. The method of manufacturing a semiconductor device according to any one of 12 to 26. 30. The method according to claim 29, wherein a direction of movement of the catalyst element by the heat treatment is substantially parallel to a scanning direction of the laser beam. 31. The element selected from Group V B:
30. At least one element selected from the group consisting of P, N, As, Sb, and Bi is used.
0. A method for manufacturing a semiconductor device according to item 0.