JPS6320011B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing semiconductor integrated circuits, particularly high-density, high-performance semiconductor integrated circuits. and its manufacturing method. The formation of completely isolated single-crystal semiconductor islands is an important technology that dramatically improves the electrical characteristics of devices built into the single-crystal semiconductor islands, leading to the realization of high-speed, low-power consumption devices. . It can also be said to be a particularly important technology for realizing tertiary elements with a stacked structure, which is being considered with the aim of achieving high integration.

Conventional structure and its problems It is well known that there is an SOS structure as an island of isolated semiconductor crystals. SOS
The structure consists of a silicon (Si) single crystal formed on a saphire (single crystal alumina Al ₂ O ₃ ) substrate, and a single crystal Al ₂ O ₃ with a lattice constant similar to that of Si is used as the insulator substrate. A single crystal Si layer is formed on an Al ₂ O ₃ substrate by phase epitaxial growth. However, the Si single crystal thus obtained has Al 2 O 3 from the Al ₂ O ₃ substrate during vapor phase epitaxial growth.
It is unavoidable that defects will occur due to diffusion of Al 2 O ₃ and the slight difference in lattice constant between Al ₂ O 3 and Si. Therefore, when an element is fabricated in a silicon single crystal with an SOS structure, it is difficult to obtain the expected improvement in characteristics. Furthermore, the realization of, for example, a tertiary element is far from being realized due to the high temperature process of about 1000° C. during epitaxial growth and the difficulty of further forming Al ₂ O ₃ on the active element.

Under these circumstances, a method has recently been developed in which non-single crystal Si is deposited on an amorphous insulator such as SiO ₂ or Si ₃ N ₄ and then irradiated with an energy beam such as a laser or an electron beam to form a single crystal. Attempts have been made and various structures have been proposed.

For controlling single crystallization, for example, there is a graph-o-epitaxial method in which a grating is provided on an insulating substrate. As shown in the cross-sectional view of FIG. 1, it is said that a desired orientation of the single crystal Si layer 2 can be obtained by grating on the insulating substrate 1 formed in advance. However, with the above method, it is difficult to control the grating structure and energy beam irradiation conditions, etc., and it is difficult to obtain a single crystal Si layer with a desired orientation, which increases the number of grating processes that are difficult to control. There are many problems such as becoming

Furthermore, a method called a lateral epitaxial method, a cross-sectional view of which is shown in FIG. 2, has been proposed.
In this method, a part of the insulating film, for example, SiO ₂ 11, is opened to expose a part of the single crystal Si 10 of the base substrate, and then non-single crystal Si, such as polycrystalline Si 12, is deposited, and then irradiated with, for example, a laser beam. polycrystalline
When recrystallizing Si 12, single crystal Si substrate 10
The single crystal Si 12A is grown laterally using the exposed portion 10A of the SiO 2 as a seed and is formed on the SiO ₂ 11. However, in the method shown in FIG. 2, there is a limit to the area of the single crystal Si 12A that extends laterally from the exposed portion 10A of the single crystal Si substrate 10 as a seed, and to a certain extent from the exposed portion 10A of the single crystal Si substrate 10. Even during recrystallization, the grown single crystal Si 12A does not extend to the distant polycrystalline Si 12B, making it difficult to obtain a large single crystal. For this reason, it has been considered to form a large number of exposed portions 10A that serve as seeds at small intervals, but in this case,
Grain boundaries occur where single crystals that have grown from each seed come into contact, making it difficult to obtain large single crystals and requiring many openings in the underlying single crystal. Therefore, it is difficult to obtain islands of single crystal semiconductor that are completely insulated.

Next, we will discuss a reported example using a silicon island 22 having a pentagonal planar shape as shown in FIG. 3a. Third
Figure b is a cross-sectional view of this, in which
SiO ₂ 21 is formed, and silicon islands 22 are further formed. This report was published in the Materials Research Society Symposia Proceedings.
Proceedings) vol.1 “Laser and Electron−
Beam Solid Interactions and Materials
These are shown on P493 and P498 of "Processing". P493 shows that nucleation and growth occur from the sharp tip 22A during recrystallization using a laser beam.
Crystal growth is insufficient. Especially in the case of a large island, it is rare for the energy beam to first enter the pointed tip 22A. For example, if you try to cover the entire area with five beam scans, the beam will hit the tip with a probability of 1/5. However, since the other four do not touch the tip, the tip 22A cannot serve as a nucleation source. P498 also shows that nucleation occurs from the center of the island rather than the edges, indicating that there is no tip effect. Even looking at these examples, there is no established theory about the effect of such a tip, and there are many unknown points.

Purpose of the Invention In view of such conventional problems, the present invention forms a single crystal semiconductor island completely insulated and isolated on an amorphous insulator substrate by considering the planar shape of the island. It is an object of the present invention to obtain a semiconductor device which enables the formation of high-speed, low-consumption electronic elements by building elements into islands, and which is also suitable for realizing so-called tertiary element elements in which active elements are laminated.

Composition of the Invention The present invention, when forming a high-quality semiconductor island pattern by recrystallization, forms a semiconductor film into an island pattern in which the entire side on the start side of energy beam scanning has minute irregularities in a planar shape. death,
This is a method of recrystallizing the island pattern by scanning and irradiating an energy beam such as a laser or an electron beam starting from this fine uneven portion. In the present invention, by recrystallizing the beam so as to cover the unevenness provided at the end of the island during all beam scanning, all of the semiconductor islands can be made into single crystals or crystal grains with extremely large grain size can be formed. This makes it possible to obtain a single crystal group. That is, in the present invention, after forming a non-single-crystal semiconductor layer on an insulating substrate, an island-like pattern having the above-mentioned unevenness is formed by a process such as photolithography, selective oxidation, or insulator embedding. By recrystallizing the pattern with an energy beam, it is possible to form single crystal semiconductor islands with good controllability and high quality.

DESCRIPTION OF EMBODIMENTS FIG. 4 shows the structure of a completely insulated semiconductor single crystal island in a first embodiment of the present invention,
4A is, for example, a sectional view taken along the line -' in FIG. 4B, and FIG. 4B is an example of a plan view. 30 is a single crystal silicon substrate on which a semiconductor element (not shown) is built; 31 and 31' are substrates 30;
The SiO _{2 layer} 32 formed above is a silicon island which is completely insulated and made into a single crystal, and 32A is a fine rectangular or sawtooth pattern formed at the end of the silicon island 32. As can be seen from FIG. 4, the fine pattern 32A having unevenness in the planar shape formed on the entire side of the island 32 where energy beam scanning is started is smaller than the overall shape of the island, and its shape is various. It is a choice. FIG. 4b shows four examples of islands 32 with various fine patterns 32A.

FIG. 5 illustrates the manufacturing process of this embodiment using cross-sectional views. As shown in FIG. 5a, for example, a silicon substrate 30 is oxidized in a water vapor atmosphere to form SiO ₂ 31 with a thickness of 1.0 μm, and then polycrystalline silicon 4 is deposited at 600° C. by, for example, reduced pressure vapor phase epitaxy.
2 to grow 0.5 μm. Next, as shown in b in the same figure,
A protective oxide film 50 and a silicon nitride film 51 are sequentially grown, and selectively formed in FIG. 4b by ordinary photolithography.
The protective oxide film 50 and silicon nitride film 51 having the same pattern as the island 32 shown in FIG. Further, as shown in c of the same figure, polycrystalline silicon 42 other than the lower part of silicon nitride film 51 is completely oxidized by oxidation in a water vapor atmosphere to form a selective oxide film ₃₁ '. ，
A polycrystalline silicon island having the shape shown in FIG. 4b is formed, which is completely insulated by 31' and has a fine pattern 32A formed thereon. After that, for example, the continuous wave argon laser 52 is
The polycrystalline silicon islands 42 are recrystallized by scanning at a power of 18 watt/cm ² and a speed of 1 mm/sec to 10 cm/sec to form monocrystalline silicon islands 32 as shown in FIG. .

FIG. 5d shows a plan view of the process of recrystallizing a silicon island by laser irradiation. A laser beam 53 is scanned in the direction of an arrow 531 from the fine pattern portion 32A of the polycrystalline silicon island 42.

According to the above embodiment, when recrystallizing a polycrystalline silicon island by laser irradiation, in the fine pattern portion 32A at the end of the silicon island, it is difficult for many grain boundaries to enter because the pattern is fine, and the solidification of silicon is prevented. In this case, the generation of nuclei for crystal growth that matches the pattern shape is likely to occur. Since nucleation is difficult to occur at the interface between Si and SiO ₂ where there is no fine pattern 32A, the crystal nuclei generated at the fine pattern portion 32A serve as seeds when the entire polycrystalline silicon island 42 is melted and recrystallized. . Therefore, in forming the polycrystalline silicon island 42, by forming a concavo-convex pattern with a fine planar shape on one side where the energetic scanning of the island is started, the formation of nuclei for crystal growth can be performed with good controllability, and the process It is possible to easily form a high-quality single crystal silicon island 32 that is completely insulated and isolated.

Note that the laser beam is directed toward the polycrystalline silicon island 42 from the direction of the fine pattern portion 32A in the direction of arrow 5.
When scanning as shown in Figure 31, even if the beam spot diameter is small relative to the width of the island, there will be 1.5% within the beam diameter.
If a pattern of more than 100 concavities and convexities is included, that is, if the size of the beam spot 54 is as shown by the broken line in d in FIG. One pattern will be included, and nucleation can occur in either scan. Therefore, no matter how wide the island is, the entire island can easily be made into large crystal grains, and does not have the drawbacks of the conventional example described above.

Next, a second embodiment of the present invention will be described based on the drawings. FIG. 6 is a conceptual diagram of the second embodiment when viewed from a plane. FIG. 6a shows an irradiation method using, for example, a continuous wave laser beam when the size of the polycrystalline silicon island 42 is sufficiently larger than the size of the beam spot 53 in the scanning direction. 42 is
It is a polycrystalline silicon island that is insulated and isolated, and is shown as a fine pattern on the left side of the drawing, for example.
A rectangular repeating pattern 32A having a width of 0.1 to 10 .mu.m and a length of, for example, several .mu.m is formed, and the scanning direction of the laser beam spot 53 is from left to right in the drawing. b in Figure 6 is
This figure shows a state in the middle of irradiation when the polycrystalline silicon island 42 is larger in width and length in the beam scanning direction than the spot diameter of the laser beam. That is, the laser beam is scanned with the end of the silicon island where the fine pattern 32A is cut out as the entrance side, and after the first scan 651, a second scan is performed at a width where the diameters of the laser beam spots 53 overlap, for example. 652 is a conceptual diagram of the state of recrystallization during the process, 42 is polycrystalline silicon that has not been irradiated with the laser beam, and 651A is the first scan 651, which is controlled by the fine pattern 32A at the end. This is the area where single crystals are growing.
651B is the end of the laser beam on the polycrystalline silicon side, and a large number of small single crystal groups are formed along the scanning end of the laser beam using the polycrystalline silicon as a seed. 652A is a portion made into a single crystal by the second laser beam scan,
In this case, by selecting the second scanning position so that the spot diameters appropriately overlap with those of the first scanning, the small single crystal group 651B formed during the first scanning is remelted to form a single crystal.
Completely continuous single crystal silicon is obtained at the boundary between the first and second laser beam scans.

As described above, according to this embodiment, by scanning the continuous wave energy beam from the side of the silicon island where the fine pattern is formed, it first follows the crystal nuclei controlled in the fine pattern forming area at the end. Thus, single crystal silicon can be grown as the beam scans. In addition, by using a periodic rectangular or sawtooth pattern as the above-mentioned fine pattern, exactly the same crystal nucleus can be formed even in the case of a wide island even by overlapping several scans, which further improves single crystal growth. Improves controllability.

Note that in the first embodiment, a continuous wave laser beam is used as the energy beam, but
It goes without saying that continuous wave electron beams, pulsed lasers, pulsed electron beams, or high energy density heaters may be used for scanning. Furthermore, it goes without saying that an amorphous semiconductor layer other than polycrystalline may be used as the non-single crystal semiconductor layer before energy beam irradiation.

Furthermore, as a method for insulating and isolating the semiconductor islands, in addition to selective oxidation, for example, an insulating isolation method explained using the process diagram shown in FIG. 7 can be used. Figure 7a
30 is a silicon substrate, 71 is SiO ₂ formed by vapor phase growth, and 42 is non-single crystal silicon grown by vapor phase growth. FIG. 7b shows a state in which non-single crystal silicon 42 is selectively left by photolithography, and as shown in FIG. 7c, SiO ₂ 71' is then formed by vapor phase growth. Further, as shown in FIG. 7D, the SiO ₂ 71' is selectively removed again using photolithography to form islands 42 of non-single crystal silicon. Needless to say, at this time, a pattern including fine irregularities is repeatedly formed on a part of the end portion of the silicon island 42. Using this method, compared to forming SiO ₂ by thermal oxidation of silicon,
All processes can be performed at low temperatures of about 600°C or less, which is particularly effective for creating tertiary elements.

Effects of the Invention As described above, the present invention provides, on an insulating substrate, a semiconductor island pattern having fine irregularities such as a rectangular or sawtooth shape in plan view on one side where scanning of an energy beam starts. By irradiating the energy beam while scanning the fine uneven pattern portion as a starting point, when recrystallizing the semiconductor island, it is possible to form a single crystal with good controllability. By building elements into the isolated high-quality single-crystal islands thus formed, high-performance elements can be realized, and three
This will greatly contribute to the realization of next-dimensional elements.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the graph-o-epitaxial method, Figure 2 is a cross-sectional view of the lateral epitaxial method, Figures 3 a and b are pattern plan views and cross-sectional views of reported examples showing shape effects, and Figure 4 a is a sectional view of the single crystal island of the first embodiment of the present invention, FIG. 4b is a plan view of the single crystal island pattern of the first embodiment of the present invention,
FIGS. 5a, b, and c are cross-sectional views of the process of forming a semiconductor island according to the present invention, FIG. 5d is a plan view showing the positional relationship between the laser spot and the pattern, and FIGS. Conceptual diagram of the laser beam irradiation method of the example,
FIGS. 7a to 7d are process cross-sectional views of another embodiment of the semiconductor island forming method. 30...Silicon substrate, 31, 31', 50...
...Silicon thermal oxide film, 42...Non-single crystal silicon layer, 32, 651A, 652A...Recrystallized single crystal, 32A...Fine pattern part of island end,
51...Silicon nitride film, 52...Laser beam, 53...Laser beam spot, 531,5
32, 533, 534, 651, 652... Laser beam scanning direction, 71, 71'... SiO ₂ formed by vapor phase growth.

Claims (1)

[Claims] 1. A step of forming a semiconductor film on an amorphous insulating substrate, a step of forming the semiconductor film into an island-like pattern in which the entire side on the start side of energy beam scanning has minute irregularities in a planar shape, and Recrystallizing the semiconductor island pattern by irradiating the semiconductor island pattern with the energy beam while scanning the semiconductor island pattern starting from a side having fine irregularities of the semiconductor island pattern. A method for manufacturing a semiconductor device, characterized in that: