JPS62130510A - Manufacture of semiconductor substrate - Google Patents

Abstract

PURPOSE:To enable stable crystal growth to be accomplished in a minute island by using the laser recrystallization process two times in forming a monocrystalline SOI (Silicon On Insulator) Si island. CONSTITUTION:A polycrystalline Si island 3 which is surrounded by SiO2 so as to be insulated and isolated is formed on an Si substrate 1. Then, a laser beam is applied to the island 3 to fuse and set it, and recrystallize it. Next, a recrystallized Si island 3' is selectively removed, leaving a portion thereof. Then, an amorphous Si island 4 is formed so as to cover the partially left island 3'. Next, the island 4 is recrystallized by irradiation with a laser beam. As a result, a recrystallized Si island 4' of good quality is obtained. Since a portion of the first recrystallized Si becomes a seed crystal and becomes a definite nucleus of crystal growth, stable crystal growth is accomplished, and thus the SiO recrystallized Si island 4 formed by the above manufacturing method becomes a nearly perfect monocrystalline Si island.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to 30 I (Sem1 conductor
0nInsulator) relates to a method for manufacturing a semiconductor substrate for forming a structural element.

Conventional technology SOI structural elements are expected to be devices that realize low power consumption and high-speed processing, and in particular, SOI structural elements are expected to realize low power consumption and high-speed processing.
Research on O-technical crystal formation technology is being actively conducted. Particularly active research and development is being carried out on a technique for melting and recrystallizing a polycrystalline or amorphous silicon layer formed on an insulating substrate such as 8102 by irradiating it with an energy beam such as a laser or an electron beam. [B, R, App
Leton & G, Cellar Edition Laser
Ant Electron Beam Interacunlan with Solid (La5er and Relectron-
Beam interaction with 5oli
ds), North-Holland, New York
rk.

(1982)) Various attempts have been made to obtain recrystallized layers with good crystal quality.

In the bridging epitaxy method and lateral seed beam annealing method, which are crystallization methods using a seed crystal, crystal growth occurs from the opening of the semiconductor substrate serving as the seed crystal, so in principle, the crystal orientation is However, in reality, due to the difficulty of the lateral nature of heat flow, single crystal growth from a seed crystal is at most several Qμm, and single crystallization over a large area is difficult. Have difficulty.

On the other hand, the crystallization method that does not use a seed crystal is advantageous for the formation of laminated SO etching. Although the crystal is of good quality, since there is no seed crystal, there is no nucleus for stable crystal growth, and grain boundaries still exist.

Problems to be Solved by the Invention However, in a SOR element formed in a recrystallized layer where grain boundaries exist, characteristic deterioration such as generation of leakage current and decrease in mobility occurs. Therefore, in order to realize SO devices as LSIs, especially next-generation VLSIs, it is required to form a single-crystal SOI substrate free of grain boundaries in the active region of the device.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention uses two laser recrystallization steps in a recrystallization method by laser irradiation of SO-processed microsilicon islands. Using a part of the recrystallized silicon island formed in the first time as a seed crystal, the silicon island formed again with amorphous silicon is irradiated with a second laser to provide a single crystal SO silicon island without grain boundaries. It is something.

In the second laser irradiation, a part of the single crystal silicon formed in the first recrystallization becomes a seed crystal in order to recrystallize under the conditions that the amorphous silicon melts but the single crystal silicon does not melt. This becomes a nucleus for stable crystal growth, and stable crystal growth is realized within the micro-island, forming a single-crystal SOI silicon island.

Example Below, an implementation sequence of the present invention is shown according to FIG.

FIG. 1 shows the process steps of the present invention; ' + ' + g in FIG. 1 is a sectional view, and b, c, d, and f are plan views. A polycrystalline silicon island 3 with a thickness of 0.5 μm surrounded by 5i022 and insulated and isolated on a silicon substrate 1
is formed by a commonly used IC manufacturing process such as the LPCVD method.

(a in FIG. 1) Next, as shown in b in FIG. 1, the polycrystalline silicon island 3 is irradiated with a laser beam Bi to melt and solidify and recrystallize. At this time, as the laser beam B, for example, a CWAr laser of 2 to 16 W and a scanning speed of 10 tyyt/see was used. After recrystallization, the silicon island A becomes a crystal of relatively good quality, but as shown in C in FIG. 1, some crystal grain boundaries cannot be avoided.

Next, the recrystallized silicon island 3' is selectively removed using photolithography and etching techniques used in the normal IC manufacturing process, and a portion of it is removed as shown in d of FIG. ,leave. Subsequently, as shown in Fig. 1e, amorphous silicon islands 4 formed by low temperature CVD or plasma-enhanced deposition at temperatures below 00°C are made to partially cover the remaining recrystallized silicon 3'. including,
Form again.

Next, as shown at f in FIG. 1, the islands 4 of sheamorphous silicon are recrystallized by irradiation with the laser beam B, similar to the first laser irradiation recrystallization.

The laser irradiation conditions at this time are such that the amorphous silicon 4 is melted but the crystalline silicon 3' is not melted, for example, about 1
It is desirable that the irradiation be performed at a power that is approximately 0% to 30% lower. That is, it is utilized that the amorphous silicon 4 has a laser beam absorption coefficient that is about 1 to 2 orders of magnitude larger than that of crystalline silicon &'t'J. [Nikkei Electronics, Tokuyama Delicatessen, research on racer-fin annealing technology that is rapidly expanding.

June 11, 1979 issue, P120. (1979)) As a result, a recrystallized silicon island 4' of good quality having the cross-sectional structure shown in g in FIG. 1 is obtained.

Diagram M2 is a process explanatory diagram of another row of a method for leaving a part of the recrystallized silicon island after the first recrystallization.

In FIG. 2, a is a plan view, and b, c, and d are sectional views.

When the polycrystalline silicon island 3' is recrystallized by laser beam B irradiation (2L in FIG. 2), as shown in FIG. A protuberance i) C of recrystallized silicon with a height of about 1 to 1.5 μm occurs at the portion. In this state, the recrystallized silicon island 3' is etched using an etching solution containing a mixture of HF and HNO3 for an appropriate time, for example, a time that is sufficient to etch silicon having a thickness of about 0.5 to 0.8 .mu.m. As a result,
As shown in FIG. 2C, most of the recrystallized silicon islands 3' are removed and only a portion of the raised thick portion C remains at the end of the island trace. In this state, an amorphous silicon island 4 is formed in the same manner as in the step 6 in FIG. The laser scan may be performed such that the end of the island where the recrystallized silicon 3' remains becomes the starting point of the laser scan. (D in Figure 2) If the method shown in Figure 1 is used once and some grain boundaries still occur in the recrystallized silicon islands, it is possible to use this method multiple times. Needless to say.

Despite the so-called seedless recrystallization method, the SOI recrystallized silicon formed by a method that exceeds the effects of the invention, Kong Island, is caused by a part of the first recrystallized silicon becoming a seed crystal. , since it becomes a clear nucleus for crystal growth, stable crystal growth is achieved, resulting in a near-perfect single-crystal silicon island. Therefore, the present invention provides single crystal S at the LSI or VLSI level.
This invention can be said to bring about a dramatic advance in realizing OI structures or three-dimensional stacked devices.

[Brief explanation of drawings]

FIG. 1 shows a process flow chart of one embodiment of the present invention.
r' r g is a cross-sectional view, c, d, f are plan views,
FIG. 2 shows a process flow chart of some other embodiments of the present invention, in which a is a plan view and FIGS. 2, c, and d are cross-sectional views. 1... Silicon substrate, 2... Si 0
2.301010. Polycrystalline silicon island, 4...-
Amorphous silicon island, 3/, 4/... Recrystallized silicon island, Mu... Grain boundary, B...
...Laser beam. Patent applicant: Director of the Agency of Industrial Science and Technology Tatsu Todoroki Figure 2

Claims (1)

[Claims] a step of forming a completely insulated non-single crystal semiconductor island on an insulating substrate, a step of recrystallizing the non-single crystal semiconductor island by irradiating the non-single crystal semiconductor island with an energy beam, and a step of recrystallizing the recrystallized semiconductor island. a step of etching away leaving a part of the recrystallized semiconductor, a step of re-forming the semiconductor island with an amorphous semiconductor including the remaining recrystallized semiconductor, and a step of melting the amorphous semiconductor into the re-formed semiconductor island to form a single crystal. A method for manufacturing a semiconductor substrate, comprising the step of recrystallizing the semiconductor islands again by irradiating the semiconductor with an energy beam under conditions that do not melt the semiconductor.