JPS6347256B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a lateral epitaxial growth method, and in particular to a coating material for irradiating a non-single crystal silicon layer with an electron beam.

(b) Background of the Technology In recent years, lateral epitaxial growth has attracted attention as a technology for realizing multilayer integrated circuits or three-dimensional integrated circuits.

In this method, for example, an amorphous silicon layer is deposited on a silicon dioxide layer, and recrystallization starts from one point and is applied to the entire area.Since single crystallization progresses in the horizontal direction, it is called lateral epitaxial. It's called growth. Since the non-single crystal silicon layer gradually becomes molten, albeit partially, it is covered with a film of silicon dioxide or the like so that the surface shape does not change. This covering layer is called a cap.

As a heating means for single crystallizing a non-single crystal silicon layer, scanning irradiation with laser light, electron beam, etc. is generally used, but a rod-shaped infrared heater is sometimes used.

Lateral epitaxial growth may also be performed on single crystal silicon substrates with selectively deposited insulators, as shown in FIG. 1a. In this case, the newly formed single crystal layer inherits the crystal orientation of the substrate crystal on the single crystal silicon 1, and inherits the crystal orientation of the single crystal layer grown up to that point on the insulator 2. The purpose of this lateral epitaxial growth is to obtain an integrated circuit substrate having the structure shown in FIG. 1b, and the insulator 2 is usually silicon dioxide.

(c) Prior art and problems When laser light is used for the single crystallization, there is almost no absorption in the silicon dioxide layer, so even if a silicon dioxide layer is used for the cap, the cap itself will not be softened and deformed. However, when an electron beam is used, the energy of the electron beam is also absorbed by the silicon dioxide layer, which causes softening of the silicon dioxide layer, and the purpose of maintaining the substrate surface shape is not achieved.

Regarding the single crystallization temperature of the non-single-crystal silicon layer, if the temperature of the non-single-crystal silicon layer is raised to the extent that single crystallization progresses sufficiently on the silicon substrate, the temperature rises on the silicon dioxide layer with low thermal conductivity. If the temperature rises too much, "peeling" occurs, and if an attempt is made to lower the temperature to avoid this "peeling", the temperature rise on the silicon substrate will not be sufficient, and a situation will occur in which non-single crystal silicon will not become single crystal.

(d) Purpose of the Invention The purpose of the present invention is to provide a cap suitable for maintaining the surface shape of a substrate in single crystallization of non-single crystal silicon by electron beam irradiation, and to provide a cap suitable for maintaining the surface shape of a substrate. It is an object of the present invention to provide a method for reducing the difference in temperature rise of a non-single crystal silicon layer on a silicon dioxide layer and sufficiently promoting single crystallization while avoiding "peeling".

(e) Structure of the invention In the lateral epitaxial growth method of the present invention,
A non-single-crystal silicon layer is formed on a single-crystal silicon substrate on which a first insulating layer is selectively formed in the surface region.
After sequentially depositing a second insulating layer and a high melting point metal layer, the first insulating layer controls the amount of electron beam irradiation to the surface of the high melting point metal layer above the first insulating layer. The non-single-crystal silicon layer is made into a single crystal by reducing the amount of electron beam irradiation to the surface of the refractory metal layer above the single-crystal silicon substrate, which is not irradiated with the electron beam.

(f) Embodiment of the invention FIG. 2 shows an embodiment of the invention. As in the case of FIG. 1, a silicon dioxide layer 2 is selectively formed on the surface of a silicon substrate 1, and a polycrystalline silicon layer 3 (400 nm thick) is deposited to cover it. In the present invention, a 50 nm thick silicon nitride layer 4 and a 40 nm thick tungsten layer 5 are further deposited thereon. Note that 3 may be amorphous silicon, and the silicon nitride layer 4 may be a silicon dioxide layer. Furthermore, 5 may be other high melting point metals, such as molybdenum, platinum, etc. The deposition of these layers can be performed using conventional techniques.

The tungsten layer 5 is for preventing the surface shape from changing when the polycrystalline silicon layer becomes partially molten in a later process, and the silicon nitride layer 4 is for preventing the polycrystalline silicon layer from changing in this situation. This is to prevent the silicon layer 3 and tungsten layer 5 from reacting.
Since the layer 4 is thin and depends on the tungsten layer to maintain the surface shape, a material that softens easily such as silicon dioxide can also be used. The tungsten layer also serves to prevent the substrate surface from being charged during the subsequent electron beam irradiation process.

Next, as shown in FIG. 2b, a second silicon nitride layer 6 (thickness
50 nm) is selectively deposited. The silicon nitride layer 6 is for attenuating the amount of electron beam irradiation on the polycrystalline silicon on the silicon dioxide layer 2, and it is also within the technical scope of the present invention to achieve this purpose by other means. . The surface of the substrate subjected to such processing is irradiated with an electron beam 7 in a scanning manner. 8 is an electron gun. The accelerating voltage of the electron beam is set so that most of the energy is transmitted through the silicon nitride layer 4 and tungsten layer 5 and absorbed by the polycrystalline silicon layer.

The irradiation intensity of the electron beam is controlled so that the temperature of the polycrystalline silicon layer on the single crystal silicon is just above the melting point. As mentioned above, the polycrystalline silicon layer on the silicon dioxide layer becomes hotter under the same irradiation conditions, but when electron beam irradiation is moderately weakened by the silicon nitride layer 6 as in this example, The difference between the two is small. Therefore, even under conditions in which the polycrystalline silicon layer sufficiently progresses to single crystallization on single-crystal silicon, the temperature of the polycrystalline silicon layer on the silicon dioxide layer does not rise transiently, and "peel-off" occurs.
never happens.

Although the embodiments described above attenuated the electron beam irradiation by a silicon nitride layer, the attenuating material used for this purpose need not be deposited on the substrate surface, but can be used with a suitable mask. The electron beam may be selectively attenuated. Furthermore, if information regarding the pattern of the silicon dioxide layer 2 can be used as an electrical signal, the current value of the electron beam can be controlled by the electrical signal to achieve a desired irradiation amount.

(g) Effects of the Invention As explained above, according to the present invention, a cap that does not soften and deform even when irradiated with an electron beam is used, so the flatness of the substrate surface is ensured, and furthermore, the silicon dioxide layer Lateral epitaxial growth using an electron beam can be performed without causing "peeling" on the surface.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the shape of a silicon substrate on which lateral epitaxial growth is performed, and FIG. 2 is a diagram explaining the present invention, in which 1 is a silicon substrate, 2 is a silicon dioxide layer, and 3 is a silicon substrate. 4 is a silicon nitride layer, 5 is a tungsten layer, and 6 is a second silicon nitride layer.

Claims (1)

[Claims] 1. A non-single crystal silicon layer, a second insulating layer, and a high melting point metal layer are sequentially coated on a single crystal silicon substrate on which a first insulating layer is selectively formed in the surface region. After depositing, the amount of electron beam irradiation on the surface of the high melting point metal layer above the first insulating layer is changed to the amount of irradiation of the electron beam on the surface of the high melting point metal layer above the single crystal silicon substrate on which the first insulating layer is not formed. A lateral epitaxial growth method characterized in that the non-single crystal silicon layer is made into a single crystal by reducing the amount of electron beam irradiation to the non-single crystal silicon layer. 2. By depositing a third insulating layer on the surface of the high melting point metal layer on the first insulating layer,
The lateral epitaxial growth method according to claim 1, characterized in that the amount of electron beam irradiation to the non-single crystal silicon layer in the region is reduced.