JPS60236211A - Beam annealing method - Google Patents

Abstract

PURPOSE:To reduce crystal line grain boundary generated in an island region by single-cyrstallizing the island non-single-crystal semiconductor region formed on an insulator through irradiation of energy beam from the side of island region so that single-crystallization progresses toward the periphery from the center of island region. CONSTITUTION:An island region 1 and periphery thereof are single-crystallized like the conventional case and the beams B are irradiated within a short period of time toward the side portions of island region 1 from the areas elevated a little from the sides of four corners. The energy of beam B heats and fuses islant region 1 within a short period of time without absorption by insulation layer 3 and cap layer 4. Since the energy is absorbed at the side more than other area in the island region 1, temperature distribution of at the center of island region 1 becomes higher than the side portions. Therefore, in the cooling process after irradiation of beam B, an initial crystal 6 is produced at the center, this initial crystal 6 grows up to the entire part of island region 1, thereby completing the single-crystallization. Since the single-crystallization is carried out as explained above, crystalline grain boundary is little generated in the single-crystallized island region 1.

Description

[Detailed description of the invention] tal fl:4 Jk@ノ? "lf [The present invention relates to a beam annealing method, and in particular, the present invention relates to a beam annealing method, in particular,
The present invention relates to a method for converting a non-single crystal silicon layer into a single crystal using silicon on indulator technology.

Background of the fbl technology Sol technology is a technology that forms a silicon single crystal on an insulator on the surface of a substrate and forms elements on the single crystal. It is expected that this will become possible. The single crystallization technology according to the present invention is one of the most important single crystal formation technologies in the Sol technology, and the success or failure of this single crystal formation greatly influences the characteristics of the semiconductor device i6.

For the single crystallization, polycrystalline silicon or amorphous silicon formed on the insulator -■- by a heating method, for example, a chemical vapor deposition method (CVD method) is generally used.
For example, a method of single crystallization by irradiation heating (annealing) with an energy beam such as a laser beam, the so-called beam annealing method, is used, but the current single crystallization technology is still in an immature state.

(C) Prior Art and Problems FIG. 1 shows, in side view, a typical conventional beam annealing method for converting island-like regions of polycrystalline silicon into single crystals. The island region 1 is a region in which a semiconductor element is formed and is made of polycrystalline silicon and is in the form of an island, and is located on a base 2 whose surface is made of silicon dioxide. The island region l is surrounded by an insulating layer 3 made of silicon dioxide, and its surface is covered with a cap layer 4 made of silicon dioxide or the like provided to prevent the surface from becoming rough. Single crystallization is performed by irradiating the island-like region 1 from above with an energy beam B such as a laser beam while sweeping it in the direction of arrow a, and heating and melting the island-like region l.

FIG. 2 is a plan view showing the state of the crystal obtained by single crystallization using the above method, and a large number of grain boundaries 5 are generated in the island-like region 1. The existence of this crystal grain boundary 5 is a drawback that hinders the formation of a high quality semiconductor element in the island region 1.

This situation is the same even if the material of the island region is a non-single crystal semiconductor other than polycrystalline silicon.

+d) Purpose of the Invention In view of the above-mentioned conventional drawbacks, an object of the present invention is to provide a beam annealing method for reducing grain boundaries generated in an island region of a non-single crystal semiconductor when the island region is made into a single crystal. There is something to do.

tel Structure of the Invention The above object is to provide an island-like non-single-crystal semiconductor region formed on an insulator so that single crystallization progresses from the center of the island-like region toward the periphery. This is achieved by a beam annealing method characterized in that the island-like region is made into a single crystal by irradiating the region with an energy beam from the side.

According to the present invention, the energy ray beam may be irradiated simultaneously from all sides of the island-like region, or the energy ray beam may be irradiated from three opposite directions with the island-like region in between. The energy ray beam may be moved relative to the island region in a direction substantially perpendicular to the direction.

According to this method, unlike the conventional method, the temperature distribution of the island-like region melted by the irradiation is higher on the sides and lower in the center, so that single crystallization starts from the center and is the first to be formed. Since the initial crystal grows toward the sides, the island region becomes a crystal with almost no grain boundaries, making it possible to form a high-quality semiconductor device.

(f) Embodiments of the Invention Examples of the present invention will be described below with reference to the drawings. The same reference numerals indicate the same objects throughout the figures.

FIG. 3 is a diagram showing one embodiment of the beam annealing method according to the present invention in side view (al and figure 4 shown in plan view).
The figure is a plan view showing the temperature distribution of the island-like region during single crystallization using the method, and FIG. 5 is a side view showing another embodiment of the beam annealing method according to the present invention (Al and The figure shown in FIG. 6 is a plan view showing the temperature distribution of the island-like region during single crystallization using the method.

In the method shown in FIG.
The beam B and its surroundings are the same as shown in FIG. 1, and the beam B is simultaneously irradiated for a short period of time toward the sides of the island-like region 1 from all four sides and slightly diagonally above.

The reason why the irradiation direction is set slightly upward is to prevent the beam B from being obstructed by other island-like regions in the vicinity of the island-like region 1. The energy of the beam B is transmitted through the insulating layer 3,
The island-shaped region 1 is heated and melted in a short time without being absorbed by the cap layer 4. At this time, since absorption of the energy in the island-like region 1 is large at the side portion, the island-like region 1
The temperature distribution of the side part is higher than the center part, as shown in the isodotted line in FIG. This growth extends over the entire island-like region 1, resulting in single crystallization. Since the single crystallization process is as described above, there are almost no grain boundaries in the single crystallized island region 1.

Furthermore, since this method does not heat anything other than a portion of the island-like region, other semiconductor elements formed within the base body 2 are less likely to deteriorate.

The inventor of the present application has a thickness of approximately 1 μm and a size of approximately 80×50 μm.
By irradiating a continuous wave argon laser beam onto a polycrystalline silicon island-like region having a rectangular shape of m, it was possible to obtain a crystal without grain boundaries. The irradiation conditions at this time are: a beam diameter of approximately 50XlOμ which irradiates the side part with a length of 80 μm (the 50 μm side is aligned with the elongated direction of the irradiation side), and a beam that irradiates the side part with a length of 50 p+s. Diameter is approximately 30x10μ
Approximately elliptical shape of steel (30μm side aligned with the longitudinal direction of the irradiation side), power of each beam is approximately 5W, angle between the irradiation direction of each beam and the island surface is approximately 30 degrees, and irradiation time is approximately In ILL, silicon dioxide with a thickness of about 0.5 μm was used for the camping layer.

Note that the argon laser beam is a continuous wave, but
In this method, a pulsed laser beam can also be used, and the number of irradiation pulses in this case may be one pulse or multiple pulses.

In addition, in the method shown in FIG. 5, the island-like region 1 to be single-crystalized and its surroundings are the same as those shown in FIG. The light is continuously irradiated from slightly diagonally above on three opposing sides with the beam in a sweeping motion in the direction of the arrow a in FIG.

The reason why the irradiation direction is made slightly obliquely upward is the same as the case shown in FIG. The energy of the beam B is hardly absorbed by the insulating layer 3 and the cap layer 4, and heats and melts the island region 1 during the sweep passage.

At this time, the absorption of the energy in the island-like region l is large at the side part, so the temperature distribution in the island-like region 1 is slightly different from that shown in FIG. As shown in the isodotted line in Figure 6, an initial crystal 6 is generated in the center during the cooling process after irradiation with beam B.
Initial crystal 6 grows, and this growth extends over the entire island region 1 to form a single crystal. Since the single crystallization process is as described above, there are almost no grain boundaries in the single crystallized island region 1.

Furthermore, this method has the feature that a plurality of island-like regions 1, which are lined up in a row in the sweep direction as shown in FIG.

The inventor of the present application has a thickness of approximately 1 μm and a size of approximately 80×50 μm.
The length of the polycrystalline silicon island region forming the rectangle of a crane is 80 μm
By irradiating one side with a continuous wave argon laser beam,
A crystal without grain boundaries could be obtained. The irradiation conditions at this time were: the beam diameter was approximately 20μφ, the power of each beam was approximately 7W, the angle between the irradiation direction of each beam and the surface of the island area was approximately 30 degrees, and the sweep speed was approximately 501/sec. For the camp layer, silicon dioxide having a thickness of approximately 0°5 μm was used.

In the methods shown in FIGS. 3 and 5, the beam B is not limited to a laser beam, but may be any other energy beam as long as it forms a predetermined beam. In addition, if the temperature increase in the island-like region 1 due to the irradiation of the beam B is insufficient, it is effective to uniformly raise the temperature of the island-like region 1 at the time of irradiating the beam B or to raise it uniformly in advance. For this purpose, a method such as irradiating the island region l with another energy beam from above or below may be added.

Further, in the above embodiment, the material of the island region is polycrystalline silicon, but the present invention is also applicable to other non-single crystal semiconductors such as amorphous silicon.

fgl Effects of the Invention As explained above, according to the configuration of the present invention, when an island-like region of a non-single-crystal semiconductor is made into a single crystal, a beam annealing method for reducing grain boundaries generated in the island-like region is provided. This has the effect of making it possible to form high-quality semiconductor elements in island-like regions.

[Brief explanation of the drawing]

Figure 1 is a side view of a typical conventional beam annealing method for single-crystallizing island-like regions of polycrystalline silicon, and Figure 2 is a plan view showing the state of crystals resulting from single-crystallization using that method. , FIG. 3 is a side view of one embodiment of the beam annealing method according to the present invention + al and a plan view (b).
1, FIG. 4 is a plan view showing the temperature distribution of the island-like region during single crystallization using the method, and FIG. 5 is a side view showing another embodiment of the beam annealing method according to the present invention. FIG. 6 is a plan view showing the temperature distribution of the island region during single crystallization using the method. In the drawings, 1 is an island region, 2 is a base, 3 is an insulating layer,
4 is a cap layer, 5 is a grain boundary, 6 is an initial crystal, B is a beam, a is an arrow, and b is an isodotted line. l～・v-s cabinet

Claims (3)

[Claims] (1) For an island-shaped non-single-crystal semiconductor region formed on an insulator, from the sides of the island-shaped region so that single crystallization progresses from the center of the island-shaped region toward the peripheral edge. A beam annealing method characterized by irradiating the island-like region with an energy beam to form a single crystal. (2) Claim (1) characterized in that the energy ray beam is irradiated from all sides of the island-like region simultaneously.
Beam annealing method described in section. (3) While irradiating the energy ray beam from three opposing directions with the island-like region in between, move the energy ray beam relative to the island-like region in a direction approximately perpendicular to the opposing directions. A beam annealing method according to claim (1), characterized in that: