Process for the production of mutually electrically insulated mo

Details Process for the production of mutually electrically insulated mo Process for the production of mutually electrically insulated mo

1986-06-05

1988-02-16

Hearn, Brian E.

Fishing, trapping, and vermin destroying

437 68, 437 92, 437 69, 437247, 156628, 156643, 156657, 156644, 357 49, 357 56, H01L 21263, H01L 2176, H01L 2195

Patent

active

047255617

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to a process for the production of mutually electrically insulated monocrystalline silicon islands. It more particularly applies to the field of producing bipolar or MOS integrated circuits of the silicon on insulant type, in which components operating under "high voltage" must be electrically insulated from components operating under "low voltage".
The silicon on insulant technology used for producing mutually insulated monocrystalline silicon islands constitutes a significant improvement compared with the standard methods in which the active components of integrated circuits are directly produced on a solid silicon monocrystalline substrate. Thus, the use of an insulating material leads to a considerable decrease in the stray capacitances between the source and the substrate on the one hand and the drain and the substrate on the other of the active components of the integrated circuit and consequently to an increase in the operating speed of said circuit. It also leads to a significant simplification in the production processes, an increase in the integration density and a better behaviour of the circuit to high voltages.
One of the presently known methods for producing a monocrystalline silicon layer on an insulating support is diagrammatically shown in longitudinal sectional form in FIG. 1. This technology consists of forming on a type n or p monocrystalline silicon substrate 2, silicon oxide patterns 4 and then forming by gaseous phase deposition a thick polycrystalline silicon layer 6 surmounting said oxide patterns. On the complete polycrystalline silicon layer 6 is then deposited an insulating silicon oxide layer 8, more particularly by a chemical gaseous phase deposition process (LPCVD).
The following stage consists of recrystallizing the polycrystalline silicon layer 6 in monocrystalline form. This recrystallization consists of melting the silicon of layer 6 by heating it through the oxide layer 8 by means of a heating source. On cooling, the silicon layer 6 recrystallizes in monocrystalline form from the substrate 2, which then acts as a germ for growth. Mutually insulated monocrystalline silicon islands can then be produced in this monocrystalline silicon layer.
This process for obtaining a monocrystalline silicon layer on an oxide layer has in particular been described in an article in Materials research society symposia proceedings, vol 13, 1983 entitled "Lateral epitaxial growth of thick polysilicon films on oxidized three inch wafers" by G. K. Celler et al, pp 575 to 580.
This process suffers from a certain number of disadvantages. In particular, the surface of the recrystallized silicon layer 6 has an often significant roughness and the surface of the recrystallized zones on the oxide patterns 4 is not planar. These surface states impose a supplementary stage of polishing the surface of the recrystallized layer 6. Moreover, this process has a only a limited efficiency. Thus, the ratio of the zones recrystallized on insulant to the unused zones per silicon wafer is approximately 50%. Moreover, this process uses an epitaxy deposit of the silicon layer to be recrystallized, which generally takes a long time and is difficult to carry out. Finally, the alignment of the future resin masks for producing the components above the insulating patterns 4 is difficult to obtain by photolithography, because the recrystallized silicon of layer 6 is no longer transparent in the irradiation range generally used for the alignment of the masks.
The present invention relates to a process for the production of mutually electrically insulated monocrystalline silicon islands making it possible, inter alia, to obviate the aforementioned disadvantages.
According to the invention, the production process comprises the following successive stages: silicon substrate, embedding in the substrate the patterns of the first insulating material and for forming above said embedded or buried patterns a monocrystalline silicon layer, islands. silicon film.
The process of the invention more particu

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