JP4353352B2 - Semiconductor device and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device and a manufacturing method thereof, 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 manufacturing method thereof. In particular, the present invention is effective for a semiconductor device provided with a thin film transistor (TFT) provided over a substrate having an insulating surface, and is applied to an active matrix liquid crystal display device, a contact image sensor, a three-dimensional IC, and the like. It is possible.
[0002]
[Prior art]
In recent years, in order to realize high-resolution liquid crystal display devices, high-speed, high-resolution contact image sensors, three-dimensional ICs, etc., attempts have been made to form high-performance semiconductor elements on insulating substrates such as glass and insulating films. Has been made. As such a semiconductor element, it is common to use a thin-film silicon semiconductor. Thin film silicon semiconductors are roughly classified into two types: amorphous silicon semiconductors (a-Si) and crystalline silicon semiconductors.
[0003]
Amorphous silicon semiconductors are most commonly used because they are low in manufacturing temperature and can be manufactured relatively easily by a vapor phase method, and thus are excellent in mass productivity. However, since amorphous silicon semiconductors are inferior in physical properties such as dielectric properties compared to crystalline silicon semiconductors, a simple method for producing crystalline silicon semiconductors that can achieve further high-speed characteristics in the future. Establishment is strongly demanded.
[0004]
As a method for producing a crystalline silicon semiconductor, the following methods (1) and (2) are known.
(1) After forming an amorphous silicon semiconductor film, the amorphous silicon semiconductor film is irradiated with an energy beam such as a laser beam, and the amorphous silicon semiconductor film is crystallized by the light energy to be crystalline. A silicon semiconductor film having
(2) After an amorphous silicon semiconductor film is formed, the amorphous silicon semiconductor film is crystallized by heating and crystallizing the amorphous silicon semiconductor film by the thermal energy.
[0005]
Generally, the above method (1) is used. In this method, since the crystallization phenomenon in the melting and solidifying process is used, the crystal grains are small, but there are few crystal defects in the crystal grains, and a relatively high quality crystalline silicon semiconductor film can be obtained. However, in the crystalline silicon semiconductor film manufactured by the method (1), the defect density at the grain boundary portion increases, so that the defect at the grain boundary portion functions as a large trap with respect to carriers, and the semiconductor device As a result, sufficient performance cannot be obtained. Also, for example, when using the excimer laser that is currently most commonly used as a laser light source, the stability of the laser light is not sufficient, so it is easy to perform uniform processing over the entire surface of the substrate. In addition, it is not possible to form a plurality of crystalline silicon semiconductor films having uniform characteristics on the same substrate, which may cause variations in characteristics between semiconductor elements.
[0006]
The method (2) is superior in uniformity and stability in the substrate as compared with the method (1), but it requires a heat treatment for about 30 hours under a high temperature condition of 600 ° C. or higher. There is a problem that the processing time becomes long and the throughput cannot be improved. Further, in the method (2), since the crystal structure to be crystallized is a twin crystal structure, relatively large crystal grains of about several μm can be obtained, but a large number of twin defects are included in the crystal grains. Furthermore, the crystallinity is inferior to the crystallinity of the silicon semiconductor film produced by the method (1).
[0007]
On the other hand, a method for improving the methods (1) and (2) and obtaining a high-quality crystalline silicon film has been developed.
[0008]
First, as an improvement method of the method (1), the exposed region formed by the mask is irradiated with a pulse laser beam, and the silicon film in the exposed region irradiated with the pulsed laser beam is melted, and the melted silicon film However, there is a crystallization treatment method in which the crystal growth direction is controlled by utilizing the phenomenon that crystallization proceeds with directionality by sequentially solidifying from a region close to the surrounding non-irradiation region (non-melting region), It is disclosed in Japanese translations of PCT publication No. 2000-505241.
[0009]
In this crystallization treatment method, the amorphous silicon film is controlled to grow in the direction along the scanning direction by reducing the scanning pitch of the pulse laser irradiated while scanning. Further, by adjusting the shape of the mask and the island shape of the silicon film irradiated with the laser, a crystal region close to a single crystal having a relatively small area but no crystal grain boundary is manufactured.
[0010]
As an improvement method of the method (2), there is a method for reducing the heating temperature, shortening the processing time, and improving the crystallinity by introducing a catalytic element that promotes crystallization of the amorphous silicon film. Attention has been paid.
[0011]
Specifically, a crystalline silicon film is obtained by introducing a trace amount of a metal element such as nickel into the surface of the amorphous silicon film and then performing heat treatment.
[0012]
In such a method using a catalytic element, a crystal nucleus with an introduced metal element as a nucleus is generated early in an amorphous silicon film, and then crystallization progresses rapidly around this crystal nucleus. To do.
[0013]
This method can reduce the heating temperature and the processing time by early generation of crystal nuclei by introduction of a catalytic element, and a crystalline silicon film that has been crystallized can be produced by a conventional solid phase growth method (described above). Unlike the case where the crystalline silicon film grown by the method (2) has a twin structure in which crystal defects are increased, a plurality of columnar crystals (networks) are connected. Although it is small, the inside is close to a single crystal.
[0014]
In Japanese Patent Laid-Open No. 11-2607823, a catalytic element is introduced into a partial region of an amorphous silicon film and heat treatment is performed, so that a lateral direction extends from the introduction region into which the catalytic element is introduced to its peripheral region. A crystal growth method for growing crystals is disclosed.
[0015]
In particular, in the crystal growth method described in this publication, the introduction pattern of the region into which the catalyst element is introduced is formed in a stripe (line and space) shape, and the width of the introduction pattern and the interval between the introduction patterns are defined. This stabilizes the lateral crystal growth.
[0016]
Further, as a crystal growth method combining the method (1) and the method (2), the crystallinity of the crystalline silicon film obtained by solid phase crystallization by introducing a catalytic element and heat-treating is further improved. For this purpose, Japanese Patent Application Laid-Open No. 7-161634 discloses a crystal growth method that further includes a step of irradiating intense light such as laser light after heat treatment. By performing such a light irradiation process in addition, the crystallinity of the crystalline silicon film crystallized by performing the heat treatment in the presence of the catalytic element can be further enhanced, and the speed of the semiconductor device can be further increased. ing.
[0017]
[Problems to be solved by the invention]
In the crystalline silicon film obtained in the above Japanese translation of PCT publication No. 2000-505241, the silicon film in the region melted by the laser light irradiation is successively settled from the region close to the surrounding non-irradiated region (non-melted region). Since the directionality is controlled and crystallization is performed, the crystal is formed of columnar crystal grains (grains) whose growth direction is controlled. FIG. 11 is a cross-sectional view schematically showing the state of the crystal grains. Here, X01 represents the crystal growth direction, and X02 represents the crystal grain boundary.
[0018]
However, as shown in FIG. 11, the crystal grains grown by this method are grown in substantially the same direction to form a plurality of columnar crystals having the same growth direction. None of these are relevant. Therefore, crystal defects and dangling bonds are frequently generated in each crystal grain boundary, and the trap barrier against carrier movement of the semiconductor element is increased. As a result, the number of crystal grain boundaries crossed by the carriers is large when the carrier movement direction and the crystal growth direction are parallel to the active region of the semiconductor element. When the number of crystal grain boundaries crossed by carriers increases, the characteristics are remarkably lowered, and the variation in characteristics between elements increases.
[0019]
Specifically, when a TFT is manufactured by using the above method so that the carrier moving direction is parallel or perpendicular to the crystal growth direction, the carrier moving direction is parallel or perpendicular to the TFT. Between these, a large characteristic difference of about 5 times occurs, and the restriction given to the element design layout becomes large.
[0020]
Even when the semiconductor element is manufactured so that the growth direction is along the carrier movement direction of the semiconductor element, as shown in FIG. 11, there is a limit to the length of crystal grains along the crystal growth direction. Yes, a plurality of crystal grains are connected in the semiconductor element. For this reason, depending on the crystal state in the active region of each semiconductor element and the state in which the columnar crystals are connected, the characteristics of the semiconductor element are influenced and there is a possibility that a large variation occurs.
[0021]
FIG. 12 shows the result of crystallization of a silicon film with a mask for forming an exposure region irradiated with a laser beam as a shape including a bent shape in the crystallization treatment method described in JP-T-2000-505241. FIG. X01 indicates the crystal growth direction, and X02 indicates the crystal grain boundary.
[0022]
By including a bent shape in the mask shape in this way, even in the crystallization treatment method described in JP-T-2000-505241, a part of the mask shape, such as the region indicated by X03 surrounded by the crystal grain boundary, is used. A region close to a single crystal can be formed. However, this region cannot be grown as large as forming the active region of the semiconductor element by this region alone. In addition, it is necessary to align the active region of the semiconductor element with high precision with respect to the single crystal region X03, and there is a problem that the process becomes complicated.
[0023]
Further, as shown in FIG. 13, the crystalline silicon film obtained by the method of Japanese Patent Laid-Open No. 11-260723 has a uniform crystal growth state when viewed macroscopically, and has a crystal plane orientation in a relatively large region. Are evenly aligned. Here, Y01 represents the crystal growth direction, Y02 represents the crystal grain boundary, and Y03 represents the catalyst element introduction region.
[0024]
The crystal grain boundary of the crystalline silicon semiconductor film obtained by this method is larger than the crystal grain boundary shown in FIG. 10, as shown by the region surrounded by Y02 in FIG. It is also possible to form the active region of the semiconductor element in one crystal grain.
[0025]
However, the crystalline silicon film obtained by this method has a problem that crystal defects appearing in crystal grains increase. A crystalline silicon film crystallized by introducing a catalyst element and heating it forms crystal grains in a state where a network in which columnar crystals having a width of 800 to 1000Å are connected to each other is formed. Although the inside of each columnar crystal is in a single crystal state, a large number of crystal defects such as transitions are generated in the crystal grains due to bending, branching, etc. of each columnar crystal. Therefore, in the crystalline silicon semiconductor film obtained by this method, even if the active region of the semiconductor element is formed by one region having a single plane orientation, due to crystal defects existing in the crystal grains. It is not possible to obtain sufficient performance. For example, TFT field effect mobility, at most 100 cm ² / Vs.
[0026]
Moreover, in practice, it is very difficult to form an active region of a semiconductor element in accordance with one region having a single plane orientation, and even if the direction of crystal growth is adjusted to the carrier movement direction, The crystal grain boundary Y02 is necessarily included in the active region. For this reason, the crystalline silicon semiconductor obtained by this method cannot reduce variation in characteristics of the semiconductor device.
[0027]
In the method described in JP-A-7-161634, a step of irradiating intense light such as laser light in order to eliminate a large amount of crystal defects in crystal grains appearing in a crystalline silicon film crystallized by a catalytic element. Has been added. However, if the laser power of the laser beam is too low, the effect of irradiating the laser beam will not appear, and the original crystal state will be almost maintained. If the laser power of the laser beam is too high, the original crystal state will be lost. Since the crystal state is the same as when the crystal is reset and crystallized only by laser light, it is not easy to properly irradiate strong light such as laser light, and there is almost no margin of laser power.
[0028]
In addition, when the laser power of the irradiated laser beam is optimum, crystal defects in the crystal grains can be reduced while maintaining the crystallinity in the crystallization process by the catalytic element, while the laser beam is regenerated by the laser beam. A new crystal grain boundary is generated by the crystallization process. The new crystal grain boundaries generated by such laser light irradiation have a higher trap density and higher energy for semiconductor carriers than the crystal grain boundaries seen in the solid-phase crystallization state by the catalytic element. .
[0029]
In a semiconductor device using a crystalline silicon semiconductor film obtained by this method, since it recrystallizes taking over the high uniformity of the crystalline silicon film solid-phase crystallized by the catalytic element, Compared with the method in which the silicon film is directly crystallized by laser, the crystal uniformity is remarkably increased. In addition, since the new crystal grain boundary generated by laser light irradiation has less influence than the crystal grain boundary generated when solid-phase crystal growth is caused by introduction of the catalytic element, by adding a laser light irradiation process, In total, the characteristics of the semiconductor device can be improved.
[0030]
However, the generation of new crystal grain boundaries due to laser light irradiation occurs at random, and the influence causes variations in the characteristics of the semiconductor device. As a result, compared to a semiconductor device manufactured only by solid-phase crystallization using a catalytic element, the characteristics become unstable and the characteristics vary greatly. With a crystalline silicon semiconductor film obtained by this method, a high-speed In order to realize a high-speed performance semiconductor device having current drive capability, sufficient characteristics have not been obtained.
[0031]
The present invention has been made to solve the above problems, and provides a semiconductor device having a high-speed performance having a high-speed current drive capability and a reduced variation in performance, and a method for manufacturing the same. Objective.
[0032]
[Means for Solving the Problems]
In order to solve the above problems, a semiconductor device of the present invention is a semiconductor device in which an active region is formed of a crystalline silicon film on a substrate having an insulating surface, and the active region is an amorphous silicon film. A region that is solid-phase-grown along one direction from a region where a trace amount of the catalyst element that promotes crystallization is introduced as a seed crystal, and the solid-phase-grown region is crystallized in approximately one direction by melting and solidifying the region. It is characterized by being formed by a grown silicon film having crystallinity.
[0033]
In the semiconductor device of the present invention, the crystal growth direction of the silicon film having crystallinity grown by melting and solidifying is substantially perpendicular to the crystal growth direction of the solid phase grown region. Preferably there is.
[0034]
In the semiconductor device of the present invention, the active region is formed by a group of crystal grains arranged in a line along a crystal growth direction of a region that has been crystal-grown by melting and solidifying. The deviation of the plane orientation between the line-shaped crystal grain groups is within 5 °. It is preferable.
[0036]
In the semiconductor device of the present invention, the active region is formed by a group of crystal grains arranged in a line along a crystal growth direction of a region where the crystal is grown by melting and solidifying each line. It is preferable that at least 80% or more of silicon atoms are connected in a lattice form at an atomic level in the crystal grain boundary of the crystal group.
[0037]
In the semiconductor device of the present invention, the active region is formed by a group of crystal grains arranged in a line along a crystal growth direction of a region where the crystal is grown by melting and solidifying each line. It is preferable that a low-angle grain boundary is formed between the crystal grain boundaries.
[0038]
In the semiconductor device of the present invention, it is preferable that the low-inclination grain boundary has a planar orientation rotation angle between crystal grains within 5 °.
[0039]
In the semiconductor device of the present invention, it is preferable that the position of the crystal grain boundary is defined by etching by a seco etching method.
[0040]
In the semiconductor device of the present invention, the plane orientation of the crystal grain group and the tilt angle of the crystal orientation at the crystal grain boundary are preferably measured by an EBSP method.
[0041]
In the semiconductor device of the present invention, the active region extends along the crystal growth direction of the region grown by melting and solidifying the moving direction of carriers moving through the active region and the line-like crystal grain boundaries. It is preferably formed so as to be substantially parallel to the direction.
[0042]
In the semiconductor device of the present invention, the active region formed in the active region contains 1 × 10 5 of nickel element as a catalytic element. ¹⁶ ~ 5x10 ¹⁷ atoms / cm ^Three It is preferable to contain in the density | concentration.
[0043]
In the method for manufacturing a semiconductor device of the present invention, a catalytic element that promotes crystallization of an amorphous silicon film is selectively introduced into a part of an amorphous silicon film formed on a substrate having an insulating surface. And heat-treating the amorphous silicon film, so that the catalyst element is selectively introduced from a portion adjacent to the region. Solid phase growth along a certain direction forms a solid phase growth region Steps, and Using the solid phase growth region of the amorphous silicon film as a seed crystal, Heating while scanning in the direction, By melting and solidifying Sequential recrystallization step, and The amorphous silicon film Recrystallized crystallinity Area with And a step of forming an active region.
[0044]
In the semiconductor device manufacturing method of the present invention, the crystalline silicon film crystallized by the introduction of the catalytic element is heated by scanning the laser beam along a direction orthogonal to the crystallization direction. It is preferable.
[0045]
In the method for manufacturing a semiconductor device according to the present invention, the catalyst element is introduced into a region formed in a line shape or a stripe shape on an amorphous silicon film formed on a substrate having the insulating surface, and the laser The light is preferably scanned along a direction in which the region formed in the line shape or stripe shape extends.
[0046]
In the method for manufacturing a semiconductor device of the present invention, it is preferable that the width of each of the regions formed in the line shape or the stripe shape is formed in a range of 1 to 15 μm.
[0047]
In the method of manufacturing a semiconductor device of the present invention, the step of heating the crystalline silicon film crystallized by introducing the catalytic element in a predetermined direction and sequentially recrystallizing the crystalline silicon film By scanning the substrate or pulsed laser beam in one direction while irradiating it with pulsed laser light, it is possible to recrystallize sequentially by reflecting the crystallinity of the region recrystallized by the pulsed laser light of the previous stage. Are preferred.
[0048]
In the method for manufacturing a semiconductor device according to the present invention, at least a first-stage pulse laser beam of the pulse laser beam irradiated while scanning the crystalline silicon film in a certain direction is crystallized by introducing the catalyst element. The second-stage pulse laser light after the irradiated region is irradiated with the pulse laser beam is irradiated to the region where the crystal growth due to the introduction of the catalytic element is not performed. It is preferable.
[0049]
In the semiconductor device manufacturing method of the present invention, the scanning pitch of the pulsed laser light is such that the crystalline silicon film region that melts when irradiated with the pulsed laser light is crystalline in the adjacent non-melted crystalline silicon film. It is preferable to set the length to be shorter than the length that can be recrystallized.
[0050]
In the method for manufacturing a semiconductor device of the present invention, it is preferable that a scanning pitch of the pulse laser beam is 0.1 μm to 1.5 μm.
[0051]
In the semiconductor device manufacturing method of the present invention, it is preferable that the pulse laser beam is elongated along a direction perpendicular to a scanning direction.
[0052]
In the method of manufacturing a semiconductor device according to the present invention, the intensity profile of the beam intensity of the pulse laser beam is such that the intensity profile on the opposite side of the pulse laser beam in the scanning direction suddenly decreases from a constant intensity to 0 intensity. Is preferred.
[0053]
In the semiconductor device manufacturing method of the present invention, the pulsed laser light is preferably irradiated using a laser irradiation means having a shielding means for mechanically masking a part on the opposite side to the scanning direction.
[0054]
In the method for manufacturing a semiconductor device of the present invention, the shielding means of the laser irradiation means has a range in which the intensity of the pulsed laser light continuously decreases from at least the intensity necessary for melting the crystalline silicon film. It is preferable to shield.
[0055]
In the semiconductor device manufacturing method of the present invention, it is preferable that the pulsed laser light is irradiated with an intensity at which the crystalline silicon film melts over the entire film.
[0056]
In the semiconductor device manufacturing method of the present invention, an excimer laser having a wavelength of 400 nm or less is used as the pulse laser beam, and an energy density with respect to the surface of the crystalline silicon film is 200 to 600 mJ / cm. ² It is preferable to irradiate in the range which becomes.
[0057]
In the method of manufacturing a semiconductor device according to the present invention, the step of heating the crystalline silicon film crystallized by introducing the catalytic element while scanning in a predetermined direction and sequentially recrystallizing the crystalline silicon film is performed on the crystalline silicon film. By sequentially scanning the substrate or continuous wave laser beam in one direction while irradiating the continuous wave laser beam, the crystallized area is recrystallized in order to reflect the crystallinity of the region previously recrystallized by the continuous wave laser beam. Is preferably carried out by
[0058]
In the method of manufacturing a semiconductor device of the present invention, the step of irradiating the crystalline silicon film with a continuous wave laser beam is performed by scanning the continuous wave laser beam by melting the silicon film in the irradiated region by the continuous wave laser beam. Accordingly, it is preferable that recrystallization is sequentially performed while moving the interface between the solid state and the liquid state in the silicon film.
[0059]
In the semiconductor device manufacturing method of the present invention, it is preferable that a solid-state laser is used as the continuous wave laser beam.
[0060]
In the semiconductor device manufacturing method of the present invention, the active region is preferably formed along the scanning direction of the laser beam.
[0061]
In the method for manufacturing a semiconductor device of the present invention, the catalyst element that promotes crystallization of the amorphous silicon film is at least one element selected from Ni, Co, Fe, Pd, Pt, Cu, and Au. It is preferable.
[0062]
In the semiconductor device manufacturing method of the present invention, after performing the step of sequentially recrystallizing the crystalline silicon film by scanning the laser beam, the crystallinity other than at least becoming an active region by a subsequent step By introducing the element selected from Group 5 B into the region of the silicon film, and performing the second heat treatment on the crystalline silicon film, the element selected from Group 5 B is introduced. It is preferable to further perform a step of moving the catalyst element to the region, and reducing the amount of the catalyst element contained in the region of the crystalline silicon film that becomes an active region in a later step.
[0063]
In the semiconductor device manufacturing method of the present invention, it is preferable that the moving direction of the catalytic element moved by the second heat treatment is substantially parallel to the scanning direction of the laser beam.
[0064]
In the semiconductor device manufacturing method of the present invention, the element selected from Group 5 B is preferably at least one element selected from P, N, As, Sb, and Bi.
[0065]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a semiconductor device manufacturing method of the present invention and a semiconductor device manufactured by the manufacturing method will be described with reference to the drawings.
[0066]
FIG. 1A to FIG. 1D are plan views of a semiconductor device for explaining the outline in each step of the semiconductor device manufacturing method according to the present invention.
[0067]
In FIG. 1A, a silicon film is grown in one direction with respect to the stripe-shaped introduction region 1 by introducing the catalyst element into the stripe-shaped introduction region 1 and performing heat treatment. Indicates the state. Thus, by forming the catalyst element introduction region 1 in a stripe shape, the silicon film is crystallized approximately linearly in the direction of the arrow A perpendicular to the stripe-like introduction region 1, and as a result. A crystal domain 4 having a substantially single plane orientation surrounded by a domain boundary 3 substantially parallel to the arrow A is formed. In addition, since the crystallization speed from each catalytic element introduction region 1 in the direction of arrow A is substantially equal, each crystal domain 4 grown from each catalytic element introduction region 1 collides with an intermediate portion of each catalytic element introduction region 1. Therefore, a growth boundary 5 is formed at a substantially middle portion of each catalytic element introduction region 1.
[0068]
Next, the silicon film crystallized by the introduction of the catalytic element is irradiated with pulsed laser light, and the region irradiated with the pulsed laser light is melted and solidified.
[0069]
FIG. 1B shows a single pulse laser beam along a direction perpendicular to the striped catalyst element introduction region 1 on the crystalline silicon film in the state of FIG. The state which irradiated is shown. Thus, by irradiating the pulse laser beam, the silicon film in the region 6 irradiated with the pulse laser beam is instantaneously melted and recrystallized immediately thereafter. In this case, reflecting the crystallinity of the non-irradiated region, crystal growth proceeds sequentially along the direction of the arrow B from both ends near the non-irradiated region that is not irradiated with the pulse laser beam in the region 6, and in this direction A region 8 that is crystallized in the lateral direction is formed. Further, in the central portion of the region 6, the melted silicon film is supercooled and crystal nuclei are randomly generated. Therefore, in this portion, the region 9 in which crystallization without directivity has progressed is formed.
[0070]
Next, the second pulse laser beam is irradiated along the region 6 so as to partially overlap the region 6 irradiated with the first pulse laser beam.
[0071]
FIG. 1C shows a state after irradiation with the second pulse laser beam. By irradiation with the pulse laser beam, the silicon film in the region 10 irradiated with the pulse laser beam is melted, and then the solidified crystallization of the melted silicon film proceeds. In this case, crystallization proceeds sequentially from both side edges of the region 10 reflecting the crystallinity of the adjacent non-irradiated region as in the case of the first pulse laser light irradiation. Accordingly, in the region irradiated with the laser beam for the second time, the crystal grows so as to take over the crystal growth of the region 8 crystallized by the first pulse laser beam irradiation. As a result, the newly grown region 11 forms a region 12 in a substantially single crystal state extending from the region 8 crystallized by the first pulse laser light irradiation.
[0072]
By sequentially scanning such pulse laser light in the direction indicated by arrow C in FIG. 1D, a single crystal state region can be formed over a large area indicated by the region 14 in FIG. it can. When the single crystal region 14 is formed in this manner, the semiconductor 15 is continuously formed in the single crystal region 14 while avoiding the region 15 and the growth boundary portion 16 where the catalytic element introduction region 1 was formed. The active region 17 of the device is formed.
[0073]
Thus, a crystalline silicon film that has been crystallized laterally by a catalytic element has a single plane orientation region (domain) with a relatively large area along the growth direction, and the orientation between each domain is The deviations are small and the trap level for carriers is also low. Using a region having such characteristics as a seed crystal, the silicon semiconductor film recrystallized by melting and solidifying by pulsed laser light irradiation has a good microscopic crystal component property of the silicon film by lateral crystallization by a catalytic element. Since the crystal is grown by taking over the uniformity of the plane orientation, a crystalline silicon film almost in the state of a single crystal having almost no crystal defects and having a large plane orientation is aligned in the range of several tens μm to several hundreds μm. Can be formed over size. Therefore, by forming the active region of each semiconductor element in such a region having excellent crystallinity, a semiconductor device having high performance and small variation in characteristics can be manufactured. This is particularly effective when forming an active region of a TFT having a large channel width that requires a large current.
[0074]
As a method for manufacturing a semiconductor device of the present invention, continuous wave laser light can be applied in addition to pulsed laser light. By irradiating a continuous-wave laser beam onto a crystalline silicon film crystallized with a catalytic element and continuously scanning it, the scanning direction reflects the crystallinity of the crystalline silicon film crystallized with the catalytic element. The crystal growth proceeds, the crystal grain group is arranged in one direction, and the plane orientation between the adjacent crystal grains can be made substantially the same.
[0075]
FIG. 14 is a cross-sectional view schematically showing a change in state of the silicon film when the continuous wave laser beam and the silicon film are irradiated. ₂ The case where the crystalline silicon film 302 formed through the film 301 is irradiated with continuous wave laser light while scanning in the direction of an arrow 303 is shown.
[0076]
When the continuous wave laser beam is used in this way, unlike the pulse laser beam, the region irradiated with the laser beam is always in a molten state due to the high temperature of the crystalline silicon film. Further, the portion after being irradiated with the continuous wave laser beam is recrystallized after melting. Therefore, on the silicon film 302 irradiated with the continuous wave laser beam, the liquid region 302a which has been irradiated with the laser beam to be in a liquid state, and the solid region which has been recrystallized after being irradiated with the laser beam. 302b exists.
[0077]
When the continuous wave laser beam is scanned in the direction of the arrow 305 shown in FIG. 14, an interface portion between the solid region 302b and the liquid region 302a indicated by 304 in the drawing is shown by the arrow 306 along the scanning direction of the continuous wave laser beam. The recrystallization of the crystalline silicon film proceeds sequentially along the arrow 305 direction.
[0078]
When using continuous wave laser light, unlike the case of using pulsed laser light in this way, the silicon film always has an interface between a solid part and a liquid part and is irradiated to the silicon film. Crystallinity is controlled by the intensity and scanning speed of the continuous wave laser beam. Therefore, if the scanning speed of the continuous wave laser beam is too slow, the crystalline silicon film is heated more than necessary, and the crystallinity information of the original silicon film crystallized by the catalytic action of the catalytic element is reset. It will be. The same problem occurs when the intensity of the continuous wave laser beam is too strong. For this reason, when continuous wave laser light is used, there are optimum values of the intensity and scanning speed of the laser light.
[0079]
As such a continuous wave laser beam, a solid laser is preferable and excellent in stability. Further, unlike the case of using the above-described pulse laser beam, the wavelength of the laser beam to be irradiated can be sufficiently used if it is 600 nm or less.
[0080]
In the method for manufacturing a semiconductor device described above, in the region where the crystal is grown in the lateral direction by introduction of the catalytic element, a crystal domain having a uniform plane orientation is formed along the growth direction, and the direction in which the crystal growth proceeds A laser beam (pulse laser beam, continuous wave laser beam, hereinafter simply referred to as “laser beam” indicates pulse laser beam and continuous wave laser beam) in a direction perpendicular to the above. Scanning is proceeding with crystallization by melt-solidification. For this reason, since one crystal domain can be grown as a seed crystal, there are almost no crystal defects, and a crystallized region having almost a single crystal state with excellent crystallinity with a wide range of plane orientations can be obtained. . Therefore, it is desirable that the direction of crystal growth by introduction of the catalyst element and the direction of crystal growth by melt solidification by laser irradiation are substantially perpendicular.
[0081]
Further, the active region of the semiconductor device manufactured by the above method is constituted by a group of crystal grains arranged in a line along the crystal growth direction in melt-solidification crystallization by laser light irradiation, and the line The crystal grains arranged in a line have substantially the same plane orientation as the adjacent line-shaped crystal grains. Therefore, the influence of the crystal grain boundary can be reduced, the trap density with respect to the semiconductor carrier at the crystal grain boundary can be reduced, and the energy of the trap level can be reduced. As a result, a semiconductor device having such an active region has very high performance and high current drive capability, and further has small variations between semiconductor elements and excellent stability. .
[0082]
In FIG. 1, the crystal grain boundary is shown as a position etched by the secco etching method, and the crystal grain is shown as a region surrounded by the crystal grain boundary. Furthermore, the plane orientation between the crystal grains and the tilt angle of the crystal orientation at the crystal grain boundary show values measured by the EBSP method.
[0083]
Also by the method of Japanese translation of PCT publication No. 2000-505241, it is possible to obtain a group of crystal grains arranged in line along the same direction. However, in the semiconductor film obtained by this method, there is no relation to the plane orientation between adjacent crystal grains, and since each is independent, the trap density of the crystal grain boundary with respect to the carrier becomes very large, When there is a semiconductor element in which carriers move beyond the line-shaped crystal grains, the characteristics are remarkably deteriorated and the variation between elements becomes large.
[0084]
Actually, when there is no correlation between the plane orientations of adjacent line-shaped crystal grains, the field effect between the TFT in which the carrier movement direction is parallel to the line direction and the TFT in the vertical direction The difference in mobility is as large as about 5 times. On the other hand, in the semiconductor device of the present invention, a difference is similarly observed in the field effect mobility, but the difference in the field effect mobility is about 1.5 times, and the difference is reduced as compared with the above TFT. ing. Further, in the semiconductor device of the present invention, the electric field transfer effect is improved as compared with the conventional semiconductor device, so that the design layout between elements is not greatly restricted as compared with the conventional semiconductor device.
[0085]
Further, in the semiconductor device of the present invention manufactured as described above, the deviation of the plane orientation between adjacent line-shaped crystal grains is within 5 °. For this reason, the continuity at the crystal grain boundary is maintained, and the trap density and trap level energy at the crystal grain boundary with respect to the semiconductor carrier can be reduced to such an extent that the characteristics of the semiconductor element are not significantly deteriorated. it can.
[0086]
In the semiconductor device of the present invention manufactured as described above, the crystal grain boundaries of the line-shaped crystal grains constituting the active region of the semiconductor device are continuously connected at the atomic level. . For this reason, the trap density and energy level of carriers at the crystal grain boundary can be minimized. In the present invention, it is further known that 80% or more of silicon atoms are continuously connected at the atomic level in the crystal grain boundary, and as a result, variation in characteristics (field effect mobility) is ± 5%. The field-effect mobility can be suppressed to a difference of 2 times or less even when the direction of melt solidification and crystallization of the silicon film by laser irradiation is 90 ° different from the direction of movement of the semiconductor carrier. I know it.
[0087]
Further, the fact that the lattices are continuously connected at the atomic level between the crystal grains means that the adjacent line-like crystal grain boundaries constitute a small-angle tilt grain boundary. In a small-angle grain boundary, the crystal orientation shift occurs in a plane when viewed from a plane, and the alignment of the lattice itself rotates at a small angle (refracted). However, the lattices of adjacent crystal grains at the crystal grain boundary are connected to each other. In this state, the carrier trap density and energy level at the crystal grain boundary can be minimized, and as a result, the high-speed characteristics of the semiconductor device can be maximized, Variation in characteristics between elements can be minimized. Furthermore, the rotation angle of the small-angle crystal grain boundary between adjacent line-shaped crystal grains at this time is within 5 °. For this reason, the trap density and trap level energy at the crystal grain boundary portion with respect to the semiconductor carrier can be reduced to such an extent that the characteristics of the semiconductor device are not significantly deteriorated.
[0088]
Further, in the semiconductor device of the present invention, the carrier moving direction in the active region and the line direction of the line-shaped crystal grains arranged along approximately one direction in the crystalline silicon film constituting the active region are roughly It is desirable to configure the semiconductor device so as to be parallel. If a semiconductor device is manufactured in this way, the influence of crystal grain boundaries on carriers can be eliminated as much as possible for elements that require particularly high carrier mobility. However, in the semiconductor device of the present invention, even when the line direction and the carrier moving direction are not parallel as described above, a very high mobility can be obtained as compared with the conventional semiconductor device. Therefore, the semiconductor device of the present invention can increase the degree of freedom in design layout.
[0089]
Further, in the semiconductor device of the present invention, a catalytic element that promotes crystallization is introduced into the amorphous silicon film in order to control the plane orientation of adjacent line-shaped crystal grains. As a catalytic element for promoting such crystallization, one or more of Ni, Co, Fe, Pd, Pt, Cu, Au, etc. can be used. Crystallization of a high quality silicon film can be promoted.
[0090]
However, since the catalyst element promotes crystal growth by silicidation in the amorphous silicon film, it is preferable that the lattice constant of the silicide compound of the catalyst element approximates the lattice constant of single crystal silicon. Ni is diatomic Si and NiSi which is a silicide compound ₂ Form. NiSi ₂ Has a fluorite-type crystal structure, which is very similar to the diamond structure of single crystal silicon. Furthermore, NiSi has a crystal structure with a diamond structure having a lattice constant of 5.430Å. ₂ Has a lattice constant of 5.406 Å, which is closest to the lattice constant of silicon. Therefore, NiSi ₂ Is the most excellent template for crystallization of an amorphous silicon film, and crystallization of the amorphous silicon film is most promoted, so Ni is suitable as a catalyst element.
[0091]
When manufacturing the semiconductor device of the present invention, first, a step of solid-phase crystallization of the amorphous silicon film in the lateral direction with the catalytic element is performed, so that the active (channel) region in the active region of the semiconductor device includes: A catalytic element will be contained. The concentration of nickel contained in the active region of the semiconductor device is 5 × 10 ¹⁷ atom / cm ^Three If it exceeds, the number of regions present in the active region as nickel silicide increases, which adversely affects the characteristics of the semiconductor device. The nickel concentration is 1 × 10 ¹⁶ atom / cm ^Three If it is less, the catalytic effect due to the introduction of nickel cannot be sufficiently obtained, and the plane orientation of the crystal grains cannot be sufficiently controlled. Therefore, nickel is 1 × 10 ¹⁶ ~ 5x10 ¹⁷ atom / cm ^Three It is desirable to introduce so that it may become the density | concentration of.
[0092]
In addition, when the width of the catalyst element introduction region for introducing the catalyst element formed in a line shape or stripe shape is less than 1 μm, the catalyst element having a concentration necessary for lateral crystal growth should be introduced. On the contrary, when the thickness exceeds 15 μm, the introduced catalytic element does not act efficiently on the lateral crystal growth, and some remains in the introduction region. Various problems occur, such as auto-doping in later laser scanning, etching damage to the underlying film, and influence on TFT characteristics. Therefore, the width of the catalyst element introduction region is preferably set to 1 to 15 μm.
[0093]
In the case of manufacturing the semiconductor device of the present invention, at least the first-stage pulsed laser beam irradiation is applied to the crystalline silicon film laterally grown by the catalytic element. It is effective to form the region to be a region using a region crystallized by irradiating laser light from a crystallization region by a catalytic element.
[0094]
The catalytic element is a metal element mainly composed of a transition metal such as nickel, and the presence of such a catalytic element in the semiconductor film hinders the reliability and electrical stability of the semiconductor device, It is not preferable. In particular, when these catalytic elements are present as silicide, the TFT causes a serious problem of an increase in leakage current during off operation. Therefore, by manufacturing the semiconductor device by the above-described method, the catalytic element is efficiently used only when growing a crystal to be a seed crystal. In the active region of the actual semiconductor device, the crystal by the catalytic element is used. By using a region that does not correspond to the formation region (region grown by reflecting the crystallinity of the seed crystal with pulsed laser light), the amount of catalytic element remaining in the active region of the semiconductor device can be reduced as much as possible. The reliability of the apparatus can be improved.
[0095]
Further, when the semiconductor device of the present invention is manufactured, a laser beam is irradiated in a pulsed or continuous manner on a crystalline silicon film grown in a solid phase in the lateral direction by selectively introducing a catalytic element. However, by scanning the substrate in one direction with the laser beam, it is possible to manufacture high-performance semiconductor elements by sequentially recrystallizing the crystallized area of the region crystallized by the previous pulse irradiation. This process is the most important process. Especially when the scanning pitch of the pulse laser beam is longer than the length that can be recrystallized reflecting the crystallinity of the adjacent non-melting region when the pulse laser beam is irradiated. The region of random crystal nuclei seen by normal laser light irradiation is formed, and normal grain-like crystal grains are formed, so the scanning pitch of pulse laser light is melted when irradiated with pulse laser light It is necessary to make the length of the region adjacent to the region to be recrystallized to reflect the crystallinity of the adjacent non-melted region. With such a length, the crystal grains are formed in a line along the growth direction.
[0096]
FIG. 2 is a schematic view showing a laser annealing apparatus used in the process of melting and solidifying a silicon film by laser light irradiation when manufacturing the semiconductor device of the present invention.
[0097]
This laser annealing apparatus has a laser oscillator 21 that oscillates a laser beam D having a predetermined intensity. The laser beam D oscillated laterally from the laser oscillator 21 is reflected by a mirror 22 and guided to a homogenizer 23 installed above the substrate. Then, the homogenizer 23 forms a long laser beam E along one direction. A shielding mask 24 is provided between the homogenizer 23 and the substrate so that the long laser beam E has a desired intensity profile. The shielding mask 24 has an opening 24a that transmits only a portion near the top in the intensity profile of the laser light E, and the substrate is irradiated with laser light F that transmits the opening 24a of the shielding mask 24.
[0098]
In the present invention, when recrystallized with pulsed laser light, the silicon film is sequentially recrystallized to reflect the crystallinity of the region recrystallized by pulse irradiation in the previous stage. If it has a profile that gradually decreases like a general Gaussian shape, the laser energy gradually rises from the region crystallized from the previous pulse laser irradiation. The required energy cannot be obtained near the crystal in the region crystallized by the preceding pulse. Therefore, in such an intensity profile, there is always a power region lower than that required for recrystallization, so the crystallinity of the region crystallized by the previous pulse irradiation cannot be taken over, and the crystallinity is poor. It remains as a region, and sufficient characteristics cannot be obtained. For this reason, the beam intensity of the pulse laser beam irradiated onto the crystalline silicon film is such that the intensity file at least on the opposite side to the direction in which the pulse laser beam is scanned decreases rapidly from a certain intensity to zero. It is desirable to have a short rectangular shape.
[0099]
In the above laser annealing apparatus, in order to realize such a beam intensity profile of the pulsed laser beam, at least a part on the opposite side to the scanning direction of the pulsed laser beam is mechanically masked by the shielding mask 24. Thus, the intensity file of the pulse laser beam on the opposite side is suddenly lowered from a certain intensity to zero. For this reason, a desired intensity profile can be easily realized without significantly changing the optical system of the laser annealing apparatus. Moreover, it becomes easy to adjust the irradiation region of the pulse laser beam by the shielding mask.
[0100]
FIG. 3 is an explanatory diagram showing the intensity profile of the pulse laser beam E irradiated from the homogenizer 24 and the intensity profile of the pulse laser beam F transmitted through the opening 24a of the shielding mask 24 and irradiated onto the substrate.
[0101]
As shown in FIG. 3, the pulse laser beam E shaped into a long shape by the homogenizer 24 has a Gaussian shape as shown in FIG. 3, but the pulse laser beam F transmitted through the shielding mask 24 24, only the high energy portion near the top passes through the opening 24a, and the bottom portion where the energy is low is cut by the shielding mask 24, and the strength of the top hat shape where the strength suddenly rises from 0 to the top. A profile 32 is obtained. In addition, the shielding mask 24 may be installed in another position, and the shape may be changed and used. In FIG. 3, both end portions of the intensity profile are profiles with a steep intensity gradient, but it is sufficient that the intensity profile rises rapidly on the opposite side with respect to the scanning direction.
[0102]
It has been found that if the scanning pitch of the pulse laser beam when irradiating the pulse laser beam is 1.5 μm or less, it can be recrystallized reflecting the crystallinity of the adjacent non-molten region. In addition, if the irradiation width of the pulse laser beam is 0.1 μm or more, no major limitation is imposed on the laser irradiation conditions. Therefore, it is desirable that the scanning pitch of the pulse laser beam is in the range of 0.1 to 1.5 μm. However, considering the throughput (processing capacity per hour) in the step of irradiating the pulsed laser beam, it is more preferable to set a larger value within the above range.
[0103]
In this case, the beam shape of the pulsed laser light irradiated on the surface of the crystalline silicon film suffices if the scanning method has a length equal to or longer than the scanning pitch. If the length in the vertical direction is increased, crystallization can be performed over a wide area by scanning with the pulse laser beam once. Therefore, as shown in FIGS. It is desirable to form a substantially long rectangular shape that is long in a direction perpendicular to the scanning direction. In this way, the total power of the laser beam for irradiating the pulsed laser can be reduced, and a wide range of crystallization can be performed by irradiating the pulsed laser once, greatly reducing the processing time in this process. be able to.
[0104]
If the intensity of the pulse laser beam is small, the silicon film is not sufficiently melted, and crystal defects existing after solid-phase crystallization with a catalytic element cannot be sufficiently improved. In the present invention, since the silicon film is crystallized reflecting the crystalline state of the adjacent non-melting region, the strength range is set so that at least the entire region of the crystalline silicon film irradiated with the pulse laser beam is melted. Irradiation is necessary. Specifically, excimer laser light with a wavelength of 400 nm or less is most suitable. If an excimer laser that irradiates a pulsed laser with a wavelength of 400 nm or less is used, the absorption coefficient for the silicon film is extremely high, and the glass substrate is not thermally damaged, and only the silicon film is heated instantaneously. can do. Excimer laser light has a large oscillation output and is suitable for processing a large area substrate. Among such excimer lasers, in particular, XeCl excimer laser light with a wavelength of 308 nm has a large output, so that the beam size at the time of light irradiation to the substrate can be increased, it can be easily applied to a large area substrate, and the output is further increased. Since it is relatively stable, it is most desirable for mass production of crystalline silicon films.
[0105]
Furthermore, when this laser beam is used, the surface energy density of the laser beam is 200 mJ / cm with respect to the silicon film surface. ^Three When it becomes smaller, the crystalline silicon film is not sufficiently melted over the entire film, and crystal defects existing after solidification crystallization by the catalytic element cannot be sufficiently improved. 600mJ / cm ^Three If it exceeds, ablation (vaporization) of the silicon film occurs, and there is a possibility that the silicon film jumps. For this reason, the surface energy density of the laser beam with respect to the silicon film surface is 200 to 600 mJ / cm. ^Three It is preferable to irradiate with pulsed laser light.
[0106]
FIG. 4 is a schematic view showing another laser annealing apparatus for irradiating a substrate with laser light. In this laser annealing apparatus, when a shielding mask 41 having a plurality of line-shaped openings 41a is provided between the substrate 101 and a homogenizer (not shown in FIG. 4) and irradiated with pulsed laser light, one pulse is emitted. At the time of laser light irradiation, a plurality of regions are simultaneously crystallized. If a plurality of openings 41a are formed in such a shielding mask 41, the pulse laser light G irradiated from the homogenizer 41 is formed into a plurality of elongated pulse laser lights H through the shielding mask 41, and the substrate Are irradiated with a pulse laser beam I.
[0107]
If the semiconductor device is manufactured so that the carrier flow direction (channel direction) of the semiconductor device and the scanning direction of the laser beam are substantially parallel, the carrier moving direction and the active region in the active region of the semiconductor device are obtained. Since the line direction of the line-shaped crystal grains of the crystalline silicon film is substantially parallel, the influence of the crystal grain boundaries on the carriers can be eliminated as much as possible. Therefore, if an active region used in a semiconductor device is designed in this way, a semiconductor element having excellent current driving capability can be obtained.
[0108]
Moreover, when manufacturing the semiconductor device of this invention, the process which introduce | transduces a catalyst element and crystallizes an amorphous silicon film to a horizontal direction is included. As described above, the catalytic elements that promote crystallization mainly consist of metals, and the presence of such elements in a large amount in the semiconductor means that the reliability and electrical stability of the device using the semiconductor element are increased. Is not preferable. Therefore, after the catalytic element is used for crystallization of the amorphous silicon film, most of the catalytic element remaining in the silicon film is moved to a region other than the semiconductor element region, thereby reducing the remaining catalytic element. Is planned. Specifically, a method is effective in which an element selected from Group 5 B is introduced into a region of the silicon film other than a region which will later become an active (channel) region of the semiconductor device and a heat treatment is performed. As a result, the catalyst element that promotes crystal growth moves to a region where an element selected from Group 5 B is introduced, and as a result, the remaining amount of the catalyst element in the active (channel) region of the semiconductor device is greatly reduced. can do. This method is particularly effective for a catalyst element in a silicide state that adversely affects semiconductor characteristics. If the final semiconductor element region is formed by removing the region where the group 5 B element is introduced and the catalyst element is introduced, a high concentration region of the catalyst element does not remain on the substrate.
[0109]
In this case, in the semiconductor device of the present invention, the line-shaped crystal grains arranged in substantially one direction along the scanning direction of the laser light are formed, and the catalyst element is moved rather than moving between different crystal grains. Because the efficiency of moving the catalytic element is better when the catalytic element is moved into the same crystal grain, the catalytic element is moved along the direction of the line-shaped crystal grains aligned along the scanning direction of the laser beam. Therefore, it is desirable that the moving direction in which the catalytic element is moved to the region where the element selected from Group 5 B is introduced is approximately parallel to the scanning direction when irradiating the laser beam. In this way, as a result, the residual amount of the catalytic element in the active (channel) region of the semiconductor device can be greatly reduced.
[0110]
Here, as an element selected from Group 5 B, at least one element of P, N, As, Sb, and Bi can be used. If one or more elements selected from these are used, the catalyst elements contained in the semiconductor film can be efficiently moved. Although no detailed knowledge has been obtained yet regarding the mechanism for moving such a catalyst element, it has been found that P is the most effective among the above elements.
[0111]
FIG. 15 is a photograph-substituting photograph showing the fine structure of the semiconductor device of the present invention, and an arrow 400 indicates the scanning direction of the laser light. As described above, in the semiconductor device of the present invention, the crystal grains 401 are long and linear in the laser beam scanning direction, and the crystal grain boundaries 402 formed therebetween are formed along the laser scanning direction. Yes. The crystal grain boundaries 402 between the crystal grains 401 are grain boundaries that are manifested by Secco etching, and the plane orientations between adjacent crystal grains 401 are substantially the same despite the crystal grain boundaries 402 being seen. It has become.
[0112]
Hereinafter, specific examples using the method for manufacturing a semiconductor device of the present invention will be described.
[0113]
(Example 1)
In the first embodiment, a circuit having a CMOS structure in which an N-channel TFT and a P-channel TFT are complementarily configured, which is used in a peripheral drive circuit of an active matrix liquid crystal display device, a general thin film integrated circuit, or the like, is made of glass A process for manufacturing on a substrate will be described.
[0114]
FIGS. 5A to 5D are plan views of a semiconductor device for explaining, for each process, a process for manufacturing a CMOS structure in which the N-type TFT and the P-type TFT of Example 1 are complementarily configured. is there.
[0115]
6 (a) to 6 (c) respectively explain the process of manufacturing the structure of FIG. 5 (a) for each process, and show cross-sectional views along the line AA ′ of FIG. 5 (a). ing. FIGS. 7A to 7G illustrate the steps of manufacturing the structure shown in FIGS. 5B to 5D for each step, and B in FIGS. 5B to 5D. Sectional drawing which follows the -B 'line is shown.
[0116]
When manufacturing the CMOS structure of the first embodiment, first, as shown in FIG. 6A, in order to prevent impurities from diffusing from the glass substrate in a later step, on the glass substrate 101, for example, Then, a base film 102 made of silicon oxide having a film thickness of about 300 to 500 nm is formed by sputtering or plasma CVD. Next, an intrinsic (I-type) amorphous silicon film (a-Si film) 103 is formed to a thickness of 20 to 80 nm, for example, 50 nm by plasma CVD. In Example 1, a parallel plate type plasma CVD apparatus was used, and the material gas was SiH. _Four Gas and H ₂ Gas was used. And the power density of RF power is 10 to 200 mW / cm. ² For example, 80 mW · cm ² As a plasma was generated. At this time, the heating temperature of the substrate is desirably 400 ° C. or lower, and in this embodiment, it is set to 300 ° C.
[0117]
Next, after depositing an insulating thin film such as a silicon oxide film or a silicon nitride film over the entire surface of the a-Si film 103, a mask 104 is formed by patterning. In this example, a silicon oxide film was deposited on the a-Si film 103 by using TEOS (Tetra Ethoxy Ortho Silicate) as a raw material and decomposing and depositing by RF plasma CVD in the presence of oxygen. In this case, the film thickness of the silicon oxide film is desirably in the range of 100 to 400 nm. In this example, the film thickness of the silicon oxide film was 150 nm. As shown in FIG. 2A, the region 100 where the a-Si film 103 is exposed is formed in a slit shape by the through holes formed in the mask 104, and portions other than the region 100 are formed by the mask 104 in the a-Si region. The film 103 is not exposed. In this case, the line width L of each region 100 exposed by the a-Si film 103 is preferably set in a range of 1 to 15 μm. In the first embodiment, the line width L of the region 100 is set to 10 μm. It was.
[0118]
Next, a small amount of nickel 105 is added to the surfaces of the a-Si film 103 and the mask 104. As nickel 105 to be added, nickel was added by a DC sputtering method using a target of pure nickel (99.0% or more). Specifically, the sputtering process was performed with the DC power set to an extremely low power of about 50 W and the substrate rotated at a high speed of 2000 mm / min. In this example, argon was used as the gas used in this sputtering process, and nickel was sputtered under extremely low concentration conditions under a high pressure condition of 10 Pa or higher during sputtering. In FIG. 6A, the sputtered nickel 105 is shown as a thin film in order to make the drawing easy to see, but actually, it is formed in a state of about a monoatomic layer or less. When sputtering was actually performed under the conditions of DC power of 60 W and argon gas pressure of 18 Pa, the nickel concentration on the a-Si film 103 exposed in the region 100 was 6 × 10 6. ¹³ atoms / cm ² It became a grade (TRIXRF measured value).
[0119]
Next, as shown in FIG. 6B, in a state where nickel is sputtered at a low concentration, the heating temperature is 530 to 600 ° C., for example, 580 ° C. in an inert gas atmosphere, for example, a nitrogen gas atmosphere. And anneal for 11 hours.
[0120]
At this time, in the region 100 in which nickel is added on the surface of the a-Si film 103, silicidation of the nickel 105 existing on the surface of the a-Si film 103 occurs, and in this region 100, the crystal grows using silicide as a nucleus. Region 103a is formed. Subsequently, in the peripheral region of the region 103a, as indicated by an arrow J in each of FIGS. 5A and 6B, crystals grow from the region 103a in the lateral direction (direction parallel to the substrate). Thus, a region 103b in which crystals are grown in the lateral direction is formed.
[0121]
Thus, the region 103b of the crystalline silicon film grown in the lateral direction collides with the region 103b of the crystalline silicon film grown from the other adjacent region 103a to finish the crystal growth, and the crystal grown from both directions A crystal boundary 103c is formed at a portion where the conductive silicon films collide with each other.
[0122]
In the region 103b in which the crystal is grown in the lateral direction, as shown in FIG. 5 (a), a domain 103d having a plane orientation aligned along the crystal growth direction is formed. A dotted line 103e in FIG. 5A shows a domain boundary forming each domain 103d, and a region surrounded by the domain boundary 103e is one domain. In this case, since the nickel 105 sputtered on the mask 104 is masked by the mask 104, it does not reach the lower a-Si film 103, and the a-Si film 103 is crystallized in the region 100. Only the nickel 105 added on the exposed a-Si film 103 is involved. The nickel concentration in the crystalline silicon film grown in the lateral direction is 5 × 10 5. ¹⁷ ~ 1x10 ¹⁸ atom / cm ^Three The nickel concentration in the region 103a in which crystal is directly grown by adding nickel is 1 × 10 ¹⁹ atoms / cm ^Three It was about. In the above crystal growth, the length of crystal growth in the direction parallel to the substrate indicated by the arrow J was about 130 μm at the longest portion.
[0123]
Next, as shown in FIG. 6C, the mask 104 is removed by etching. In Example 1, as the etchant, the mask 104 was removed by wet etching using 1:10 buffered hydrofluoric acid (BHF) which has sufficient etching selectivity with the underlying silicon film 103.
[0124]
Next, the line-shaped region 107 shown in FIGS. 5B and 7A is irradiated with the pulsed laser light K to bring the crystalline silicon film in the region 107 into a molten state. The molten silicon film is recrystallized immediately thereafter.
[0125]
In this example 1, a XeCl excimer laser (wavelength: 308 nm, pulse width: 40 nsec) is used as the laser light at this time, and the substrate is heated to 200 to 459 ° C., for example, 400 ° C. during irradiation, and the energy density is 200 to 600 mJ / cm. ^Three For example, 400 mJ / cm ^Three The irradiation conditions were as follows.
[0126]
After the silicon film in the irradiated region 107 is instantaneously melted when irradiated with the pulse laser beam, the direction indicated by the arrow M in FIG. Recrystallize. At this time, the silicon crystal in the adjacent non-irradiated region 103b becomes a seed crystal, and the crystalline silicon films 103f and 103h grown in the lateral direction indicated by the arrow M are formed from both ends of the region 107, reflecting the crystallinity. Is done. The central portion 103g is a region where the crystal nuclei are randomly generated and crystallized in a supercooled state before crystal growth in the arrow M direction starts. In this example, the crystal growth distance in the horizontal direction indicated by the arrow M was about 1.5 μm.
[0127]
Here, in Example 1, pulse laser light was irradiated using the laser annealing apparatus shown in FIG. The opening formed in the shielding mask at this time was 10 μm × 5 mm. Therefore, the region 107 of the laser beam K irradiated onto the region 103b on the glass substrate 101 also has a long rectangular shape of 10 μm × 5 mm.
[0128]
5 and 7, the case has been described where the silicon film is solidified by the pulsed laser light emitted from one of the openings 41 a formed in the shielding mask 41.
[0129]
Then, as shown in FIG. 4, the glass substrate 101 is moved at a constant speed in the direction of C ′ in a state where the pulse laser beam K is irradiated, thereby scanning the glass substrate 101 with the pulse laser beam K. It is. At this time, the moving distance of the glass substrate 101 becomes the scanning pitch P in the pulse time during which the pulse laser beam is not irradiated. In this embodiment, the scanning pitch P is defined by the moving speed of the glass substrate 101 in the C ′ direction and the oscillation frequency of the pulsed laser light K. In the laser annealing apparatus shown in FIG. 4, since the glass substrate 101 is moved, when viewed from the glass substrate 101, the scanning direction of the pulsed laser light K and the moving direction C of the glass substrate 101 are opposite.
[0130]
FIG. 5C shows the state of the glass substrate 101 when the second pulse laser beam is irradiated. The region 107 ′ irradiated with the second pulse laser beam is scanned by the scanning pitch P in the direction of arrow C from the first pulse laser beam K irradiation, as shown in FIG. The pulse laser beam K is irradiated to a region 107 ′ shifted downward from the irradiation region by a scanning pitch P.
[0131]
Then, after the region 107 ′ irradiated with the pulse laser beam K is melted, it is recrystallized along the direction of the arrow M ′ reflecting the crystallinity of the adjacent non-irradiated region. As a result, a pair of regions 103f ′ and 103h ′ recrystallized in the lateral direction and a region 103g ′ crystallized by random nucleation at the center are formed. At this time, the region 103f ′ on the side opposite to the scanning direction C is crystallized so as to take over the crystal of the region 103f crystallized by the first pulse laser beam irradiation. A substantially single-crystal region 103 i in which the crystal growth is extended in the scanning direction C is formed.
[0132]
In this way, if the irradiation of the pulse laser beam K is sequentially scanned at the scanning pitch P in the direction indicated by the arrow C in the figure, as shown in FIGS. 5 (d) and 7 (b), a substantially single crystal is obtained. The region 103i in the state is further extended to form a single crystal region over a wide range.
[0133]
In Example 1, the oscillation frequency of the pulse laser beam was 200 Hz, and the time interval between the first pulse laser beam irradiation and the second pulse laser beam irradiation was 5 msec. Further, the scanning pitch P of the pulse laser beam is set to 0.5 μm, for example, in the range of 0.1 to 1.5 μm. At this time, assuming that the width of the laser beam in the scanning direction of the pulse laser beam is 10 μm, a total of 20 pulse laser irradiations are performed at an arbitrary point in the region 103b. However, in this case, since the crystal state of the region 103i is defined reflecting the crystal state when crystallized at the time of the last pulse laser light irradiation, the last pulse laser light irradiation is the most important. Become.
[0134]
The region 103i formed in this way is a line-like crystal indicated by N in FIGS. 5D and 7B along the scanning direction C when the pulse laser beam is irradiated when viewed microscopically. Consists of grains. According to the observation of the two-dimensional crystal plane orientation using the EBSP method, the crystal grains are not independent of each other, but are in a substantially single crystal state in which they are arranged in parallel with substantially the same plane orientation. In addition, at the grain boundary portion of the line-shaped crystal grain, a small-angle tilt boundary within 5 ° is formed. Moreover, the continuity of the lattice is almost maintained, and 80% or more of atoms are connected in each grain boundary portion.
[0135]
Next, as shown in FIG. 7F, element isolation is performed by removing an unnecessary portion of the silicon film using a region 103i crystallized in a substantially single crystal state. A crystalline silicon film 111n to be an active region and a crystalline silicon film 111p having a desired island shape to be an active region of a P-type TFT later are formed. In this example 1, the crystalline silicon films 111n and 111p were formed so that the carrier moving direction of the later TFT and the crystal growth direction by laser light scanning were approximately parallel.
[0136]
Next, as shown in FIG. 7D, the gate insulating film has a thickness of 20 to 150 nm, for example, a thickness of 100 nm, so as to cover the crystalline silicon films 111n and 111p serving as the active regions. A silicon oxide film 112 is formed. In the first embodiment, the silicon oxide film 112 is formed by using TEOS as a raw material and heating the substrate at 150 to 600 ° C., preferably 300 to 450 ° C. in the presence of oxygen, by RF plasma CVD. Deposited by. Subsequently, a high melting point metal is deposited on the silicon oxide film 112 by sputtering, and this is patterned to form a gate electrode 113 located at a predetermined portion on the crystalline silicon film 103. As the refractory metal used for forming the gate electrode 113, tantalum (Ta) and tungsten (W) are desirable. In the first embodiment, a gate electrode 113 is formed using a two-layer structure in which a small amount of nitrogen added Ta and pure Ta are stacked, so that the combined thickness of the two layers is 300 to 600 nm, for example, 450 nm. did.
[0137]
Subsequently, phosphorus (P) 115 is implanted by ion doping. In this case, the gate electrode 113 serves as a mask, and phosphorus 115 is not implanted into the crystalline silicon films 111n and 111p below the gate electrode 113. In the first embodiment, phosphine (PH) is used as a doping gas for doping phosphorus 115. _Three As the doping conditions, the acceleration voltage is 60 to 90 kV, for example 80 kV, and the dose is 2 × 10 ¹⁵ ~ 8x10 ¹⁵ cm ^-2 For example, 5 × 10 ¹⁵ cm ^-2 It was.
[0138]
By this step, the regions of the crystalline silicon films 111n and 111p that are masked by the gate electrode 113 and are not implanted with phosphorus 115 become the channel regions 118n and 118p of the TFT through a subsequent step. The regions of the crystalline silicon films 111n and 111p into which phosphorus 115 is implanted without being masked by the gate electrode 113 become TFT source regions 119n and 119p and drain regions 120n and 120p through a subsequent process. In this step, phosphorus 115 is implanted to form an N-type impurity region in the N-channel TFT. That is, in this step, phosphorus 115 is implanted into the source / drain regions also in the P-channel TFTs that are complementarily installed in the N-channel TFTs to form N-type impurity regions 119n ′ and 120n ′. Yes.
[0139]
Next, as shown in FIG. 7E, a photoresist 121 covering the gate insulating film 112 and the gate electrode 113n on the crystalline silicon film 111n to be an N-type channel TFT is provided by a photolithography process to form P-type. As a mask for selective doping to prevent the impurities from being implanted.
[0140]
In this state, boron 116 is implanted by ion doping. In the first embodiment, diborane (B) is used as a doping gas for implanting boron 116. ₂ H ₆ 1 × 10 ¹⁶ ~ 5x10 ¹⁶ cm ^-2 For example 2 × 10 ¹⁶ cm ^-2 The doping was performed by applying an acceleration voltage of 40 to 80 kV, for example, 65 kV, at a high dose.
[0141]
In this step, boron 116 is not implanted into the crystalline silicon film 111p below the gate electrode 113p because the gate electrode 113p serves as a mask. Further, boron 116 is doped through the gate insulating film 112 into the crystalline silicon film 111p in the region where the gate electrode 113p is not formed. As a result, the source region 119n ′ and the drain region 120n ′ in which the N-type impurity phosphorus is implanted in the previous step is implanted into the source region 119n ′ and the drain region 120n ′ by so-called counter-doping. As a result, the characteristics are inverted and P-type impurity regions 119p and 120p are obtained. In this way, an N-channel TFT and a P-channel TFT can be formed on the same substrate.
[0142]
Next, as shown in FIG. 7F, after removing the photoresist 121 provided as a mask for selective doping, a temperature of 500 to 600 ° C. in an inert atmosphere, for example, in a nitrogen atmosphere. As a condition, by performing heat treatment for several hours to several tens of hours, nickel contained in this region is trapped by phosphorus contained in the source / drain regions of the N-type and P-type TFTs. Then, as shown by an arrow 122q in FIG. 7F, nickel existing in the channel region is moved to the adjacent source regions 119n and 119p and drain regions 120n and 120p, respectively. As a result, the concentration of nickel existing in the channel region can be greatly reduced.
[0143]
Here, each TFT was arranged in the direction shown in FIG. That is, the scanning direction C of the pulse laser beam when irradiating the pulse laser beam and the direction Q in which nickel is moved are made substantially parallel. By arranging the TFTs in this way, the direction N of the crystal grains of the line crystals in the channel region and the movement direction Q of nickel are the same, and the movement of nickel into the source region and the drain region is different. It is performed without exceeding the grain boundary. As a result, the nickel transfer efficiency is improved, and the remaining amount of nickel in the channel region can be greatly reduced.
[0144]
When the concentration of nickel remaining in the channel region at this time is measured by secondary ion mass spectrometry (SIMS), 5 × 10 5 before performing this step. ¹⁷ ~ 1x10 ¹⁸ atoms / cm ^Three The concentration of nickel in the channel region was about 5 × 10 ¹⁶ atoms / cm ^Three Reduced to a degree.
[0145]
On the other hand, activation of the source region and the drain region is simultaneously performed by this heat treatment. The sheet resistance value of the N-type impurity region manufactured by this process was 0.5 to 1 kΩ / □, and the sheet resistance values of the P-type impurity regions 119p and 120p were 1 to 2 kΩ / □. Furthermore, by this heat treatment process, the gate insulating film is fired at the same time, and the bulk characteristics of the gate insulating film itself and the interface characteristics between the crystalline silicon film and the gate insulating film are improved.
[0146]
Next, as shown in FIG. 7G, a 900 nm-thickness silicon oxide film is formed as the interlayer insulating film 123 by plasma CVD. Then, contact holes 121 are formed in portions corresponding to the source regions 119n and 119p and the drain regions 120n and 120p on the crystalline silicon film of each TFT of the interlayer insulating film 123, respectively. In the contact hole 121 formed in the interlayer insulating film 123, an electrode / wiring 124 that is electrically connected to the source / drain region of the TFT is formed by a metal film, for example, a two-layer film of titanium nitride and aluminum. . Thereafter, annealing is performed for 1 hour under a temperature condition of 350 ° C. in a hydrogen atmosphere of 1 atm. Thus, the N-channel TFT 125 and the P-channel TFT 126 are completed. Furthermore, in order to protect the N-type and P-type TFTs 125 and 126 as necessary, a protective film made of a silicon nitride film or the like may be provided thereon.
[0147]
In the CMOS structure circuit obtained through the steps described above, the field effect mobility of each TFT is 450 to 500 cm for the N-type TFT 125. ² / Vs, 150-200cm with P-type TFT126 ² A high value of / Vs was obtained, and the threshold voltage was about 1.0 V for the N-type TFT 125 and about -1.5 V for the P-type TFT 126, and very good characteristics were obtained. In addition, the variation in characteristics, which is a problem in the semiconductor device obtained by the conventional crystallization method, can be suppressed to about ± 10% in field effect mobility and about ± 0.2 V in threshold voltage. Note that the above characteristics were obtained by measuring 30 points on a 400 mm × 320 mm substrate.
[0148]
In addition, the increase and variation in leakage current in the TFT off region, where the remaining catalytic element is particularly problematic, can be reduced to the same level as when no catalytic element is used without any abnormal point. did it. For this reason, the manufacturing yield can be greatly improved. Furthermore, even after repeated measurements and durability tests due to bias and temperature stress, there was almost no deterioration in characteristics, and the reliability was high and the electrical characteristics were stable compared to TFTs obtained by conventional crystallization methods. A circuit was obtained.
[0149]
(Example 2)
In Embodiment 2, a process of manufacturing an N-channel TFT used for a driver circuit, a pixel portion, and a thin film integrated circuit of an active matrix liquid crystal display device over a glass substrate will be described.
[0150]
FIG. 8 is a plan view of the semiconductor device for explaining a process for manufacturing the N-type TFT according to the second embodiment.
[0151]
FIGS. 9A to 9C each illustrate a process of manufacturing the N-type TFT according to the second embodiment for each process, and show cross-sectional views taken along the line AA ′ of FIG. . FIGS. 10A to 10D each illustrate a process of manufacturing the N-type TFT of the second embodiment for each process, and show cross-sectional views taken along the line BB ′ of FIG. ing.
[0152]
To manufacture the N-type TFT of Example 2, first, as shown in FIG. 9A, in order to prevent impurities from diffusing from the glass substrate 201 in a later step, For example, the base film 202 made of silicon oxide having a thickness of about 300 to 500 nm is formed by sputtering or plasma CVD. Next, an intrinsic (I-type) amorphous silicon film (a-Si film) 203 having a thickness of 20 to 80 nm, for example, 40 nm is formed by plasma CVD.
[0153]
Next, a mask 204 in which an insulating thin film such as a silicon oxide film or a silicon nitride film is deposited over the entire surface of the a-Si film 203 is formed. In Example 2, a silicon oxide film was deposited on the a-Si film 203 by using TEOS (Tetra Ethoxy Ortho Silicate) as a raw material and using an RF plasma CVD method in the presence of oxygen. In this case, the film thickness of the silicon oxide film is preferably in the range of 100 to 400 nm. In Example 2, the film thickness of the silicon oxide film was 150 nm. The mask 204 has slit-like through holes, and the a-Si film 203 is exposed in the region 200 where the through holes are formed. Due to the through holes formed in the mask 204, as shown in FIG. 8, the region 200 where the a-Si film 203 is exposed has a slit shape. The portion other than the region 200 is in a state where the a-Si film 203 is not exposed by the mask 204. In this case, the line width L of each region where the a-Si film 203 is exposed is desirably set in a range of 1 to 15 μm, and in this example 2, it is set to 8 μm.
[0154]
Next, a small amount of nickel 205 is added on the surfaces of the a-Si film 203 and the mask 204. The nickel 205 was added by holding the solution in which the nickel 205 was dissolved on the a-Si film 203 and the mask 204, extending the nickel solution onto the substrate with a spinner, and drying it. In Example 2, nickel acetate was used as the solute, ethanol was used as the solvent, and the nickel concentration in the solution was adjusted to 10 ppm. The concentration of the added nickel 205 is 5 × 10 5 by measurement using a total reflection X-ray fluorescence analysis (TRXRF) method. ¹³ atoms / cm ² It was about.
[0155]
Next, as shown in FIG. 9B, in this state, annealing is performed for 11 hours under an inert gas atmosphere, for example, in a nitrogen atmosphere, at a heating temperature of 530 to 600 ° C., for example, 580 ° C.
[0156]
At this time, in a region where nickel 205 is added on the surface of the a-Si film 203, silicidation of the nickel 205 existing on the surface of the a-Si film 203 occurs, and the a-Si film 203 is formed using this silicide as a nucleus. Crystallizes, and in this region 200, a region 203a of a crystalline silicon film is formed. Subsequently, in the peripheral region of the region 200, as indicated by an arrow R, a crystalline silicon film region 203b in which crystals grow laterally (in a direction parallel to the substrate) from the region 200 is formed. Further, the region 203d is left outside the region 203b where the amorphous silicon film remains.
[0157]
As the crystallization proceeds from each region 200 in the lateral direction, a boundary 203c where crystals grown in the lateral direction from each region collide with each other is formed at a substantially central portion of each region 200.
[0158]
Nickel 205 attached to the mask does not reach the underlying a-Si film 203 because it is masked by the mask 204 and does not participate in the crystallization of the a-Si film 203. The nickel concentration in the region 203b of the crystalline silicon film grown in the lateral direction is 5 × 10 ¹⁷ ~ 1x10 ¹⁸ atoms / cm ^Three The nickel concentration in the region 203a of the crystalline silicon film directly grown by adding nickel 205 is 1 × 10 ¹⁹ atoms / cm ^Three It was about. In the above crystal growth, the length of crystal growth in the direction parallel to the glass substrate 201 indicated by the arrow R was about 130 μm at the longest portion.
[0159]
Next, as shown in FIG. 9C, the mask 204 is removed by etching. In Example 2, as the etchant, the mask 204 was removed by wet etching using 1:10 buffered hydrofluoric acid (BHF) which has sufficient etching selectivity with the underlying silicon film 203.
[0160]
Next, as shown in FIG. 10D, pulse laser light is irradiated in a line shape in a direction orthogonal to the region 200, the region irradiated with the pulse laser light is melted, and then recrystallized. Thus, a crystalline silicon film is formed.
[0161]
In this example 2, a XeCl excimer laser (wavelength: 308 nm, pulse width: 40 nsec) is used as the pulse laser beam at this time, and the substrate is heated to 200 to 450 ° C., for example, 400 ° C. during the irradiation with the pulse laser beam. 200 to 600 mJ / cm ² For example, 400 mJ / cm ² The irradiation conditions were as follows.
[0162]
In the second embodiment, similarly to the first embodiment, the long-shaped pulse laser beam S is sequentially scanned in the direction of the arrow U in FIG. The region 203j that inherits the crystallinity is grown.
[0163]
The difference from Example 1 is that crystallization by irradiation with the pulsed laser light S is performed on the amorphous silicon film region 203d outside the region 203b laterally grown by the nickel 205 and also on the outer side. It is a point. Also in this case, since the silicon film is melted and solidified by the first irradiation with the pulsed laser light S to the region 203b, the crystallinity at that time is taken over and the silicon film is irradiated by the subsequent irradiation with the pulsed laser light S. Since melting and solidification proceeds, a high-quality crystalline silicon film 203j is formed also in the region 203c that is an amorphous silicon film.
[0164]
In the second embodiment, the scanning pitch width P of the pulse laser beam S is set to 0.1 to 1.5 μm, for example, 0.5 μm. Further, the width of the laser beam S with respect to the scanning direction of the pulse laser beam S was set to 10 μm. In this case, a total of 20 irradiations of the pulsed laser beam S are performed at any one point on the silicon film. However, in actuality, among the irradiations of the pulsed laser light S irradiated a plurality of times to each position on the silicon film, by the final irradiation of the pulsed laser light S, the irradiation of the preceding pulsed laser light S Since it is crystallized reflecting the crystallinity of the crystallized adjacent region, the last irradiation with the pulsed laser beam S is most important in defining the crystallinity of the crystalline silicon film.
[0165]
The region 203j formed by sequentially scanning such pulsed laser light S is composed of line-shaped crystal grains along the scanning direction of the pulsed laser light. According to the observation of the two-dimensional crystal plane orientation using the EBSP method, each crystal grain has almost the same plane orientation across the crystal grain boundary. In the grain boundary portion of the line-shaped crystal grain, a small-angle grain boundary within 5 ° is formed.
[0166]
Next, as shown in FIG. 10 (c), a region 203j formed from a region 203b grown by nickel 205 is used to form a region 203j in a substantially single crystal state. In addition, by removing other unnecessary portions of the silicon film, element isolation is performed, and a crystalline silicon film 211 formed in a desired island shape is formed.
[0167]
Next, as shown in FIG. 10C, a silicon oxide film which is a gate insulating film having a thickness of 20 to 150 nm, for example, a thickness of 100 nm so as to cover the crystalline silicon film 211 serving as an active region. 212 is formed. In the second embodiment, the silicon oxide film 212 is formed by using TFOS as a raw material and heating the substrate at 150 to 600 ° C., preferably 300 to 450 ° C. in the presence of oxygen, by an RF plasma CVD method. Decomposed and deposited by Alternatively, the silicon oxide film 212 may be formed by a low pressure CVD method or an atmospheric pressure CVD method using TEOS as a raw material and heating the substrate temperature to 350 to 600 ° C., preferably 400 to 550 ° C. in the presence of ozone gas. Good. After the formation of the silicon oxide film 212, in order to improve the bulk characteristics of the silicon oxide film 212 itself and the interface characteristics between the crystalline silicon film 211 and the silicon oxide film 212, the temperature is set to 400 to 600 ° C. in an inert gas atmosphere. Heat treatment was performed for 1 to 4 hours under temperature conditions. Subsequently, aluminum is formed to a thickness of 400 to 800 nm, for example, 600 nm by sputtering, and this is patterned to form a gate electrode 213 located at a predetermined portion on the crystalline silicon film 212. Form. Next, the surface of the gate electrode 213 made of aluminum is anodized to form an oxide layer 214 on the surface. This anodic oxidation is obtained by first raising a voltage up to 220 V and holding it in that state for 1 hour in an ethylene glycol solution containing 1 to 5% tartaric acid. The thickness of the obtained oxide layer 214 was 200 nm. Note that since the oxide layer 214 has a thickness for forming an offset gate electrode in a subsequent ion doping step, the length of the offset gate region can be determined by the anodic oxidation step.
[0168]
Subsequently, phosphorus, which is an impurity, is implanted using an ion doping method. In this case, the gate electrode 213 and the oxide layer 214 formed on the silicon oxide film 212 serve as a mask, and phosphorus is not implanted into the crystalline silicon film 211 corresponding to a portion under the gate electrode 213. In Example 2, phosphine (PH) is used as a doping gas for doping phosphorus. _Three As the doping conditions, the acceleration voltage is 60 to 90 kV, for example, 80 kV, and the dose is 1 × 10 ¹⁵ ~ 8x10 ¹⁵ cm ^-2 For example 2 × 10 ¹⁵ cm ^-2 It was.
[0169]
By this step, the region of the crystalline silicon film 211 that is masked by the gate electrode 213 and is not implanted with phosphorus becomes a channel region of the TFT later. In addition, regions of the crystalline silicon film 211 into which phosphorus is implanted without being masked by the gate electrode 213 later become a source region 219 and a drain region 220 of the TFT. In this step, phosphorus is implanted to form an N-type impurity region in the N-channel TFT.
[0170]
At this time, by arranging the TFTs as shown in FIG. 8, the carrier flow direction (the direction of the source region 219 → the drain region 220) and the line-shaped crystal constituting the channel region 218 with respect to the operation of the TFT. Since the grain line direction (growth direction T) is parallel, a TFT having higher mobility can be obtained.
[0171]
Next, as shown in FIG. 10C, annealing is performed by irradiating laser light V, thereby activating the ion-implanted impurity and at the same time, the portion of the crystallinity deteriorated by the impurity introduction step. Improve crystallinity.
[0172]
At this time, as the laser light V, a XeCl excimer laser (wavelength 308 nm, pulse width 40 nsec) is used, and the energy density is 150 to 400 mJ / cm. ² , Preferably 200 to 250 mJ / cm ² It was. The sheet resistance of the N-type impurity region thus formed was 200 to 500Ω / □.
[0173]
Next, as shown in FIG. 10D, a silicon oxide film or a silicon nitride film having a thickness of about 600 nm is formed to form an interlayer insulating film 223. In the case where a silicon oxide film is formed as the interlayer insulating film 223, TEOS is used as a raw material, and a plasma CVD method in the presence of oxygen or a low pressure CVD method in the presence of ozone is used. A silicon oxide film is formed. When a silicon nitride film is formed as the interlayer insulating film 223, SiH _Four And NH _Three A silicon nitride film is formed by using a plasma CVD method using as a source gas. This silicon nitride film can reduce unpaired bonds that degrade TFT characteristics by supplying hydrogen atoms to the interface between the active region and the gate insulating film.
[0174]
Next, contact holes 223 a reaching these regions are formed in portions corresponding to the source region 219 and the drain region 220 on the crystalline silicon film 211 of the TFT of the interlayer insulating film 223. In the contact hole 223a formed in the interlayer insulating film 223, an electrode / wiring 224 that is electrically connected to the source region 219 and the drain region 220 of the TFT by a metal material, for example, a two-layer film of titanium nitride and aluminum. Form. The titanium nitride film is provided as a barrier film for preventing aluminum from diffusing into the semiconductor layer. When this TFT is used for pixel switching of a liquid crystal display device or the like, the drain electrode 220 may be a pixel electrode made of a transparent conductive film such as ITO. Further, when this TFT 225 is used for a thin film integrated circuit or the like, a contact hole may be formed also on the gate electrode 213 and wiring necessary for this contact hole may be provided.
[0175]
Finally, annealing is performed for 1 hour under a temperature condition of 350 ° C. in a water vapor atmosphere of 1 atm to complete a desired TFT 225. In order to protect the TFT 225, a protective film such as a silicon nitride film may be further provided.
[0176]
The TFT 225 manufactured through the processes described above has a field effect mobility of 450 cm. ² / Vs and the threshold voltage were about 1.0 V, and the performance was remarkably improved. Furthermore, the field effect mobility could be suppressed to about ± 10% and the threshold voltage to about ± 0.2V. Note that the above characteristics were obtained by measuring 30 points on a 400 mm × 320 mm substrate.
[0177]
The above characteristics were obtained for a TFT designed so that the carrier movement direction of the TFT and the crystal growth direction by the scanning of the pulse laser beam irradiation are parallel to each other. Even in a TFT designed so that the direction of movement of crystal and the direction of crystal growth are perpendicular to each other, the field effect mobility is 350 cm. ² / Vs and a threshold voltage of about 1.2 V, sufficiently high performance compared with a TFT obtained by a conventional method, and variation in characteristics within the substrate could be suppressed to a small level.
[0178]
In addition, the TFT of Example 2 has high reliability with little deterioration in characteristics even after repeated measurement, durability test by bias or temperature stress. In addition, the increase and variation in the leakage current in the TFT off region, where the remaining catalytic element is particularly problematic, should be reduced to a level of about several pA, which is equivalent to the case where no catalytic element is used, with no abnormal point. I was able to. For this reason, the manufacturing yield can be greatly improved.
[0179]
Furthermore, if a liquid crystal panel is manufactured using the TFT of the second embodiment, display unevenness is small and pixel defects due to TFT leakage are extremely small as compared with a liquid crystal panel using a TFT manufactured by a conventional manufacturing method. A liquid crystal panel having a high contrast ratio and a high display quality can be manufactured.
[0180]
(Example 3)
In the third embodiment, a case where continuous wave laser light is used as laser light applied to the silicon film will be described. The third embodiment is substantially the same as the first and second embodiments except that a continuous wave laser beam is used. Therefore, the illustration is omitted with reference to the drawings used in the first and second embodiments. .
[0181]
First, as in Examples 1 and 2, a base insulating film made of a silicon oxide film or the like is formed on a glass substrate, and an amorphous silicon film (a-Si film) is formed on the base insulating film. To do.
[0182]
Next, after depositing an insulating thin film such as a silicon oxide film or a silicon nitride film over the entire surface of the amorphous silicon film, patterning is performed to form a mask having openings at predetermined portions. Then, a catalytic element is selectively introduced onto the amorphous silicon film on which the mask is formed using the opening of the mask (the state of the glass substrate on which the amorphous silicon film is formed at this time) FIG. 6 (a) is referred to, and the description in Example 1 is referred to for the method of introducing the catalyst element).
[0183]
Next, in this state, in an inert gas atmosphere, for example, in a nitrogen gas atmosphere, the heating temperature is set to 530 to 600 deg. Crystal growth. 6C and 9C are referred to for the state at this time. In addition, FIG. 1 (a) and FIG. 5 (a) are referred to in plan view.
[0184]
Next, the crystalline silicon film in this state is scanned while continuously irradiating continuous wave laser light. Thereby, this crystalline silicon film is crystallized along the scanning direction of the laser beam. The scanning direction of this laser beam is the same as that of the pulse laser beam scanning method of the first and second embodiments. As a continuous wave laser beam irradiated to the crystalline silicon film, a diode-pumped continuous wave YAG laser beam was used. The wavelength was 532 nm and the power fluctuation was 1% or less. Furthermore, the output of the continuous wave YAG laser was 10 W, and the scanning speed was 50 to 200 cm / sec, for example, 100 cm / sec with respect to the substrate. In the crystalline silicon film, the part irradiated by the continuous wave laser light irradiation melts, and an interface between the silicon in the solid state and the silicon in the liquid state occurs at the boundary between the laser light irradiation region and the non-irradiation region, The interface continuously moves as the laser beam scans, so that a crystal grain boundary along one direction grows reflecting the crystallinity of the original crystalline silicon film.
[0185]
Thereafter, unnecessary portions of the crystalline silicon film are removed, element isolation is performed, and patterning is performed in an island shape that later becomes an active region (source and drain regions, channel region) of the TFT. In the following steps, the TFT is completed through the same steps as in the first and second embodiments.
[0186]
In Example 3, the crystalline silicon film is recrystallized in the lateral direction (laser beam scanning direction) using the continuous wave laser beam as described above. In this Example 3, it became clear that higher TFT characteristics can be obtained as compared with Examples 1 and 2 using pulsed laser light. Specifically, N channel type TF is 600 cm. ² A field effect mobility of more than / Vs was obtained.
[0187]
The semiconductor device according to the present invention has been specifically described above based on the three embodiments. However, the present invention is not limited to the above three embodiments, and various types based on the technical idea of the present invention. Can be modified.
[0188]
For example, in the above three embodiments, a method of applying an aqueous solution of nickel salt to the surface of the amorphous silicon film and a low-power DC sputtering method are adopted, but before the amorphous silicon film is formed, In addition, by selectively introducing nickel into the surface of the base film, the upper amorphous silicon film can be crystallized. That is, the catalytic element that promotes crystallization of amorphous silicon may be introduced from the upper side of the amorphous silicon film and grown from the surface side of the amorphous silicon film, or may be introduced to the lower side. The crystal may be grown from the back side of the amorphous silicon film.
[0189]
As a method for introducing nickel, various methods can be used in addition to the method of the above embodiment. For example, as a solvent for dissolving nickel salt, SOG (spin on glass) material is used, and SiO ₂ A method of diffusing from a film, a method of directly introducing by an ion doping method, a method of forming a thin film by a plating method, or the like can be used.
[0190]
In addition to nickel, cobalt, iron, palladium, platinum, copper, and gold can be used as the catalyst element.
[0191]
In Examples 1 and 2, the pulsed laser light for melting and solidifying the crystalline silicon film crystallized by the catalytic element is not limited to the XeCl excimer laser having the wavelength of 308 nm used in Examples 1 and 2, but the wavelength. A 248 nm KrF excimer laser, an ArF excimer laser with a wavelength of 198 nm, or the like may be used. Moreover, although it becomes a wavelength of a visible region, it is also possible to use a YAG laser. Further, the same effect can be obtained with respect to the irradiation shape of the pulsed laser light to be irradiated even if the shape is other than the above-described long rectangular shape.
[0192]
In addition to the active matrix substrate for liquid crystal display, the device to which the semiconductor device of the present invention is applied includes, for example, a contact image sensor, a driver built-in thermal head, a driver using an organic EL or the like as a light emitting element. Even when applied to a built-in optical writing element or display element, a three-dimensional IC, etc., these elements can achieve high speed and high resolution.
[0193]
Furthermore, the semiconductor device of the present invention is not limited to the MOS transistor described in the first embodiment, but can be applied to a wide range of semiconductor processes such as a bipolar transistor and an electrostatic induction transistor using a crystalline semiconductor as an element material. Can do.
[0194]
【The invention's effect】
The semiconductor device and the manufacturing method thereof according to the present invention are obtained by using, as a seed crystal, a region in which a small amount of a catalytic element that promotes crystallization of an amorphous silicon film is introduced and solid-phase grown in a direction transverse to the substrate. The active region is the region that has been crystal-grown in approximately one direction by the melt-solidification process by irradiating light to the phase-grown region, so that a semiconductor device with high performance and stable characteristics can be realized. Therefore, a high-performance semiconductor device with a high degree of integration can be manufactured by a simple manufacturing process.
[0195]
Furthermore, in the manufacturing process using the manufacturing method of the present invention, the yield rate can be greatly improved, and the cost of the product can be reduced. In particular, liquid crystal display devices that require improved switching characteristics of the pixel switching TFTs on the active matrix substrate and higher performance and higher integration of the TFTs constituting the peripheral drive circuit section satisfy these improvements at the same time. A driver monolithic active matrix substrate that constitutes the active matrix portion and the peripheral drive circuit portion on the same substrate can be realized, and the module can be made compact, high-performance, and low in cost.
[Brief description of the drawings]
FIGS. 1A to 1D are plan views for explaining a method of manufacturing a semiconductor device according to the present invention for each step.
FIG. 2 is a schematic view showing a laser annealing apparatus used in the process of melting and solidifying a silicon film by irradiation with pulsed laser light when manufacturing a semiconductor device of the present invention.
FIG. 3 is an explanatory diagram showing an intensity profile of pulsed laser light that passes through a shielding mask and is irradiated onto a substrate.
FIG. 4 is a schematic view showing another laser annealing apparatus used in the process of melting and solidifying a silicon film by irradiation with pulsed laser light when manufacturing the semiconductor device of the present invention.
FIGS. 5A to 5D are plan views for explaining a process for manufacturing a CMOS structure in which an N-type TFT and a P-type TFT of Example 1 are complementarily configured;
FIGS. 6A to 6C each illustrate a process for manufacturing the structure of FIG. 5A for each process, and are cross-sectional views taken along line AA ′ of FIG. Is shown.
FIGS. 7A to 7G illustrate the steps of manufacturing the structure shown in FIGS. 5B to 5D for each step, and FIGS. Sectional drawing which follows the BB 'line of is shown.
8 is a plan view for explaining a process for manufacturing the N-type TFT according to Embodiment 2. FIG.
FIGS. 9A to 9C each illustrate a process of manufacturing the N-type TFT shown in FIG. 8 for each process, and show cross-sectional views along the line AA ′ of FIG. Yes.
FIGS. 10A to 10D each illustrate a process of manufacturing the N-type TFT of Example 2, and show a cross-sectional view along the line BB ′ in FIG. Yes.
FIG. 11 is a cross-sectional view schematically showing the state of crystal grains of a crystalline silicon film obtained by the method of JP-T-2000-505241.
FIG. 12 shows a crystallization treatment method described in JP 2000-505241 A, and results of crystallization as a shape including a bent shape in the shape of a mask for forming an exposure region irradiated with laser light. FIG.
FIG. 13 is a plan view showing a crystalline silicon film obtained by the method of Japanese Patent Application Laid-Open No. 11-260723.
FIG. 14 is a cross-sectional view schematically showing a change in state of a silicon film when the silicon film is irradiated with a continuous wave laser beam.
FIG. 15 is a schematic view for substituting a photograph showing a fine structure of a semiconductor device of the present invention.
[Explanation of symbols]
1 Catalyst element introduction area
3 Domain boundary
4 Crystal domain
6 areas
8 areas
9 areas
10 areas
11 areas
12 areas
14 areas
15 areas
16 Growth boundary
17 Active region
100 areas
101 glass substrate
102 Base film
103 Amorphous silicon film
104 mask
105 nickel
107 areas
107 'area
111n, 111p crystalline silicon film
118n, 118p channel region
119n, 119p source region
120n, 120p drain region
125 N-channel TFT
126 P-channel TFT
200 areas
201 glass substrate
202 Base film
203 Amorphous silicon film
204 mask
205 nickel
211 crystalline silicon film
213 Gate electrode
214 Oxide layer
218 channel region
219 Source region
220 Drain region
223 interlayer insulation film
224 Electrodes and wiring
225 TFT

Claims (32)

A semiconductor device in which an active region is formed of a crystalline silicon film on a substrate having an insulating surface,
The active region is a region that is solid-phase-grown using a region that is solid-phase-grown along one direction from a region where a small amount of catalytic element that promotes crystallization of an amorphous silicon film is introduced as a seed crystal. A semiconductor device characterized by being formed of a silicon film having crystallinity that has been crystallized in approximately one direction by melting and solidifying.   The crystal growth direction of the silicon film having crystallinity grown by melting and solidifying is a direction substantially orthogonal to the crystal growth direction of the solid phase grown region. Semiconductor device. The active region is formed by a group of line-shaped crystal grains arranged in approximately one direction along a crystal growth direction of a region grown by melting and solidifying.
The semiconductor device according to claim 1, wherein a deviation of a plane orientation between the line-shaped crystal grain groups is within 5 ° . The active region is formed by a group of line-shaped crystal grains arranged in approximately one direction along a crystal growth direction of a region grown by melting and solidifying.
2. The semiconductor device according to claim 1, wherein at least 80% or more of silicon atoms are connected in a lattice form at an atomic level in a crystal grain boundary of each line-shaped crystal grain group. The active region is formed by a group of line-shaped crystal grains arranged in approximately one direction along a crystal growth direction of a region grown by melting and solidifying.
2. The semiconductor device according to claim 1, wherein a small-angle grain boundary is formed between the line-like crystal grain boundaries. 6. The semiconductor device according to claim 5 , wherein a rotation angle of a planar orientation between crystal grains is within 5 ° in the small-angle grain boundary. The grain boundary, the position is defined by etching with Secco etching method, a semiconductor device according to any one of claims 3-6. The inclination of crystal orientation at the grain group of plane orientation and crystal grain boundary is a surface measured by EBSP method, the semiconductor device according to any one of claims 3-6. The active region is substantially parallel to the crystal growth direction of the region grown by melting and solidifying the moving direction of carriers moving through the active region and the direction along each of the line-shaped crystal grain boundaries. It is formed to the semiconductor device according to any one of claims 1-6. Active regions formed in the active region, the nickel element is a catalytic element is contained in a concentration of ^{1 × 10 16 ~5 × 10 17} atoms / cm 3, according to any one of claims 1-9 Semiconductor device. Selectively introducing a catalytic element for promoting crystallization of the amorphous silicon film into a part of the amorphous silicon film formed on the substrate having an insulating surface;
Heat-treating the amorphous silicon film to form a solid-phase growth region by solid-phase growth along a certain direction from a portion adjacent to the region where the catalytic element is selectively introduced;
The solid phase growth region of the amorphous silicon film as a seed crystal, a step of heating while scanning in a predetermined direction with respect to solid phase growth direction, sequentially recrystallized from melting and solidification,
Of the amorphous silicon film, the region having the recrystallized crystalline, forming an active region,
A method for manufacturing a semiconductor device, comprising: The semiconductor device according to claim 11 , wherein the crystalline silicon film crystallized by the introduction of the catalytic element is heated by scanning a laser beam along a direction orthogonal to the crystallization direction. Method. The catalytic element is introduced into a region formed in a line shape or a stripe shape on the amorphous silicon film formed on the substrate having the insulating surface,
The method of manufacturing a semiconductor device according to claim 12 , wherein the laser light is scanned along a direction in which the region formed in the line shape or the stripe shape extends. 14. The method of manufacturing a semiconductor device according to claim 13 , wherein each of the regions formed in the line shape or the stripe shape has a width in a range of 1 to 15 μm. The step of heating the crystalline silicon film crystallized by the introduction of the catalytic element while scanning in a predetermined direction and sequentially recrystallizing is performed by irradiating the crystalline silicon film with a pulse laser beam, by scanning the pulsed laser beam in one direction, is carried out by sequentially recrystallized reflecting the crystallinity of the recrystallized region by preceding pulse laser beam, to any one of claims 11 to 14 The manufacturing method of the semiconductor device of description. Of the pulsed laser light that is irradiated while scanning the crystalline silicon film in a certain direction, at least the first-stage pulsed laser light is irradiated to a region crystallized by introduction of the catalytic element, and this region is irradiated with this laser beam. The semiconductor laser device manufacturing method according to claim 15 , wherein the second-stage pulse laser beam after the pulse laser beam irradiation is applied to a region where crystal growth by introduction of the catalytic element is not performed. Method. The scanning pitch of the pulse laser beam is not longer than a length that allows the region of the crystalline silicon film that melts when irradiated with the pulse laser beam to be recrystallized reflecting the crystallinity of the crystalline silicon film in the adjacent non-melting region. The method of manufacturing a semiconductor device according to claim 15 or 16 , wherein The method for manufacturing a semiconductor device according to claim 17 , wherein a scanning pitch of the pulsed laser light is 0.1 μm to 1.5 μm. The method of manufacturing a semiconductor device according to claim 15 , wherein the pulsed laser light is elongated along a direction perpendicular to a scanning direction. Intensity profile of the beam intensity of the pulsed laser beam is opposite intensity profile of at least the scanning direction of said pulsed laser light, it decreases to rapidly 0 intensity from a constant intensity, according to any one of claims 15 to 19 A method for manufacturing a semiconductor device. 21. The method of manufacturing a semiconductor device according to claim 20 , wherein the pulsed laser light is irradiated using a laser irradiation unit having a shielding unit that mechanically masks a part of the side opposite to the scanning direction. The semiconductor device according to claim 21 , wherein the shielding means of the laser irradiation means shields the irradiated pulsed laser light at least in a range where the intensity continuously decreases from the intensity required for melting the crystalline silicon film. Manufacturing method. 23. The method of manufacturing a semiconductor device according to claim 15 , wherein the pulsed laser light is irradiated with an intensity at which the crystalline silicon film melts over the entire film. 24. The semiconductor device according to claim 23 , wherein an excimer laser having a wavelength of 400 nm or less is used as the pulsed laser light, and irradiation is performed in an energy density range of 200 to 600 mJ / cm ² with respect to the surface of the crystalline silicon film. Production method. The step of heating the crystalline silicon film crystallized by the introduction of the catalytic element while scanning in a predetermined direction and sequentially recrystallizing is performed by irradiating the crystalline silicon film with a continuous wave laser beam, by scanning the continuous wave laser beam in one direction, is carried out by sequentially recrystallized reflecting the crystallinity of previously recrystallized by the continuous wave laser beam area, more of claims 11 to 14 A method for manufacturing the semiconductor device according to claim 1. The step of irradiating the crystalline silicon film with the continuous wave laser light is performed by melting the silicon film in the irradiated region by the continuous wave laser light, and the solid state and the liquid state of the silicon film in accordance with the scanning of the continuous wave laser light. 26. The method of manufacturing a semiconductor device according to claim 25 , wherein recrystallization is sequentially performed while moving the interface. 26. The method of manufacturing a semiconductor device according to claim 25 , wherein a solid-state laser is used as the continuous wave laser beam. 28. The method of manufacturing a semiconductor device according to claim 12 , wherein the active region is formed along a scanning direction of the laser beam. Catalytic element which promotes crystallization of the amorphous silicon film, Ni, Co, at least one element selected Fe, Pd, Pt, Cu, from Au, according to any one of claims 11 to 28 Semiconductor device manufacturing method. After performing the step of sequentially recrystallizing the crystalline silicon film by scanning the laser beam,
At least a step of introducing an element selected from Group 5 B into a region of the crystalline silicon film other than an active region by a later step;
By performing a second heat treatment on the crystalline silicon film, the catalyst element is moved to a region where an element selected from Group 5 B is introduced, and a crystal that becomes an active region in a later step Reducing the amount of the catalytic element contained in the region of the porous silicon film;
The method for manufacturing a semiconductor device according to claim 12 , further comprising: 31. The method of manufacturing a semiconductor device according to claim 30 , wherein a moving direction of the catalytic element moved by the second heat treatment is substantially parallel to a scanning direction of the laser light. 32. The method of manufacturing a semiconductor device according to claim 30 , wherein the element selected from Group 5 B is at least one element selected from P, N, As, Sb, and Bi.

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