JPS6310516A - Recrystalization of thin film - Google Patents

Abstract

PURPOSE:To enable uniform and good crystallized film to be obtained, by controlling the position on which double-humped beams are radiated against an island. CONSTITUTION:Out of an insulating film 12, a heat sink layer (made of polycrystal Si, W, Mo, Cr, a silicide material of high-melting-point metal, or the like) 13, an insulating film 14, and a polycrystal Si layer 15 which are all piled in order on a substrate 11, the island of the polycrystal Si and the insulating film 4 is covered with a cap layer 16 such as SiN, and beams comprising CWAr laser, YAG laser in a pulse mode, or the like are radiated from above. Then, the beams are formed having a distribution of double-humped energy. Radiation method for the double-humped beams is that a beam-scanning process is done while the positioning relation of the energy distribution to the island polycrystal Si 15 being maintained. That is, the beam scanning is done in the direction X perpendicular to the direction of beam separation. Owing to this beam annealing, temperature(on radiation) at the edge part of the polycrystal Si 15, where heat easily stands, is not extremely increased, but is kept smaller than that at the position corresponding to the tops of the double-humped beams, and besides the temperature at the edge parts is kept proper enough to fuse them.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an SO constituting a TPT for driving a flat display.
Thin Il structure! ! The present invention relates to a method of recrystallizing (amorphous Si).

[Conventional technology]

In recent years, in order to drive display devices such as ELDs and LC ports and achieve high image quality, active matrix systems using SOI structure TPT have been studied. One TPT is provided for each display cell, but a driver is also required to drive it.

This driver is required to operate at a high speed of several MHz or more, and from the viewpoint of cost, it is desired that it be integrated into an IC on a glass substrate such as borosilicate glass.

A TP that is a component of a driver that satisfies these requirements
As a method for realizing T, a method has been proposed in which a polycrystalline Si (silicon) film having a heat sink structure as shown in FIG. 3 is laser annealed. In this method, as shown in FIG. 3, a first insulating film 12 and a heat sink layer (high thermal conductivity layer) 13 are sequentially laminated on a substrate 11, and a second insulating film 14 and an amorphous layer are deposited on the heat sink layer 13. sex 5i1
5 and a cap layer 16 made of a third insulating film covering this amorphous 5i15 are laminated in an island shape.
5 is recrystallized. According to this method, an island-shaped polycrystal 51 annealed with a Gaussian distributed beam 20
15 width (perpendicular to the scanning direction) is 10 to 20 tm
If it's a degree.

Although the heat distribution is well controlled (the temperature at the edge of the island is higher than the center) and a high-quality recrystallized film is obtained, this is not possible in an Ar laser annealing system with a beam diameter of at most 100-φ. When a film with a width larger than 7 times is annealed, the 1gL degree distribution is not well controlled, and the crystallinity of the entire film cannot be uniformly crystallized. In other words, the mobility is low and high-speed operation is not possible. There was a problem.

Such a wide film is a TPT with a long channel width.
(It is desirable to configure it with one Si island as much as possible for high integration).

An object of the present invention is to eliminate such conventional drawbacks and provide a thin film recrystallization method capable of obtaining a homogeneous and well-crystallized film by controlling the irradiation position of the bimodal beam on the islands.

[Means for solving problems]

In the present invention, a first insulating film and a heat sink layer are laminated on a substrate, and a second insulating film and an amorphous S
In the method of recrystallizing the amorphous Si by stacking i and a cap layer consisting of a third insulating film covering the amorphous Si layer in the form of an island, high energy with a bimodal energy distribution is obtained. The center of the beam is connected to the island-shaped amorphous Si.
Beam annealing is performed by irradiating the edge region of the beam, and beam annealing is performed sequentially for the portion other than the edge region so that one peak of the bimodal beam almost overlaps the other peak of the previously scanned bimodal beam. This thin film recrystallization method is characterized by the following.

[Principle/effect]

The insulating film/P8229 layer/insulating film/island-like amorphous Si are laminated on the substrate in this order, and the island-like amorphous S1 is covered with an insulating film as a cap layer such as 31Nx, and from above, a bimodal layer is formed. Scan with a high-energy beam (using an ArCW laser annealing device, etc.) perpendicular to the direction in which the peaks are lined up. In this case, when annealing the edge region of the island-like amorphous Si in the scanning direction, the center part of a high-energy beam having a bimodal energy distribution is irradiated onto the edge region of the island-like amorphous Si. scan. As a result, the temperature at the edge of the island-like amorphous Si where heat tends to accumulate does not become extremely high, and the temperature at the edge of the island-like amorphous Si
side) is maintained lower than the temperature at the corresponding location. Furthermore, since the overlapping portion of the beams, which has lower but not too small energy than the peak portion, hits, the temperature of this edge portion does not become too low. Therefore, crystallization progresses from the edge region where the temperature is low to the region corresponding to the peak, and the range from the edge region irradiated with the beam to the region corresponding to the peak is homogeneously recrystallized without producing grain boundaries. Ru. In this case, the scattering phenomenon of the film due to the accumulation of heat at the edge portion, which occurs when the peak of the beam is applied to the edge portion, does not occur.

Furthermore, for the inner region of the island-like amorphous Si, beam annealing is performed with one peak located near the portion corresponding to the peak of the previously scanned region. As a result, the region corresponding between the peaks of the bimodal beam is uniformly crystallized, so that only one grain boundary enters the boundary region each time it is scanned, and the entire film is almost uniformly crystallized. . That is, by performing a plurality of scans, a large-area island-shaped Si film with good crystallinity can be obtained throughout.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram for explaining a thin film recrystallization method according to an embodiment of the present invention. FIG. 2 is a plan view of the thin film being recrystallized. Here, a case will be described in which polycrystalline Si is used as the thin film to be annealed.

Insulating films 12 are sequentially laminated on a substrate 11 such as a glass substrate (borosilicate glass, soda glass, etc.). Heat sink layer (polycrystalline Si, VT No., Cr, or silicided high melting point metal, etc.) 13. Of the multilayer film of the insulating film 14 and the polycrystalline Si layer 15, the islands of polycrystalline Si and the insulating film 14 are covered with a cap layer 16 such as SiNx, and a beam (such as a JAr laser or a pulsed mode YAG laser) is applied from above. At this time, the beam shape is made to have a bimodal energy distribution as shown in the figure.To create such a bimodal beam, beams from two light sources are irradiated at the same time. There are two methods: one is to circularly polarize a single laser beam using a quarter-wave plate, and the other is to separate it into two bimodal beams using a quartz crystal multipolar plate. The irradiation method with such a bimodal beam is to scan while maintaining the energy distribution shown in FIG. Beam scanning is performed in the direction Since the energy at the peak is the superposition of the bases of the two beams, it decreases only to a slightly lower level than at the peak.
When annealing with a beam with such an energy distribution, the temperature at the edge of polycrystalline 5i15 where heat tends to accumulate (
(during irradiation) does not become extremely high and remains lower than the temperature at the position corresponding to the peak of the bimodal beam. Moreover.

The temperature at this edge is maintained at a value sufficient to cause melting. Therefore, crystallization progresses from the edge part where the temperature is low to the part corresponding to the peak, and the area A from the edge irradiated with the beam to the area corresponding to the peak is uniformly crystallized without grain boundaries. . In this case, since the peak of the beam does not hit the edge portion, heat will not accumulate abnormally at the edge portion, and the polycrystalline 5i15 will not be scattered.

In addition, for the area inside the edge of the polycrystal 5i15, 21-■
As shown in ~21-I■, beam annealing is performed with one peak of the beam almost aligned. As a result, the region corresponding to the peaks of the bimodal beam progresses from crystallization from the region corresponding to the beam valley (center of the beam) to the region corresponding to the peak (outside), resulting in an overall homogeneous state. A well crystallized film can be obtained.

If such beam annealing is performed by sequentially shifting the pitch, island-shaped polycrystalline S with a large width of several tens of pm or more can be formed.
With respect to the i-film, a substantially homogeneously crystallized Si film can be obtained with only one grain boundary occurring at the beam boundary for each scan.

In the embodiments of the present invention, polycrystalline Si was selected as the film to be beam-annealed, but it goes without saying that an amorphous Si layer may also be used. In addition, there is no phenomenon of scattering of the amorphous Si film during annealing.
In particular, if there are beam annealing conditions that do not cause problems in controlling heat distribution, a structure in which the cap layer 16 is not provided does not impair the spirit of the present invention. Furthermore, the substrate is not limited to glass (Si, quartz, sapphire, compound semiconductors such as GaAs, InP, etc., and the present invention can be applied to any other material,
It is valid.

〔Effect of the invention〕

As explained above, according to the present invention, island-shaped amorphous Si
The edge region of the island is annealed by controlling the irradiation position of the bimodal beam so that the heat distribution is such that crystallization progresses from the edge to the inside of the island. Since the regions to be crystallized are continuously connected in the lateral direction by overlapping, a film with good crystallinity can be obtained over a large area. That is, a transistor with a large channel width can be formed using only one island, which is very advantageous for high integration.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the present invention in detail, FIG. 2 is a plan view of a film to be recrystallized, and FIG. 3 is a diagram for explaining a conventional thin film recrystallization method.

Claims (1)

[Claims] (1) A first insulating film and a heat sink layer are laminated on a substrate, at least amorphous Si is laminated in an island shape on the heat sink layer via a second insulating film, and the amorphous Si is re-layered. In the crystallization method, beam annealing is performed by irradiating the center portion of a high-energy beam having a bimodal energy distribution onto the edge region of the island-shaped amorphous Si, and the portion excluding the edge region is A thin film recrystallization method characterized by successive beam annealing such that one peak of the bimodal beam substantially overlaps the other peak of the previously scanned bimodal beam.