JPS6339554B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a method for manufacturing a single crystal layer for forming a single crystal layer on an insulating underlayer.

(Description of Prior Art) With the rapid development of semiconductor integrated circuit technology, attempts have been made to form large-scale integrated circuits on large-area substrates and to form three-dimensional circuits. To this end, it is desirable to form a single-crystal semiconductor thin film on an insulating layer, and if this so-called SOI (Semiconductor on Insulator) technology is skillfully performed, it will be possible to stack multiple semiconductor active layers. This also makes it possible to realize a three-dimensional IC.

FIG. 1 is a diagram for explaining a conventional method of forming a germanium (Ge) single crystal thin film on an insulating substrate as a base layer. According to this conventional method, a thin layer of Ge is grown on an insulating substrate 1 by any suitable deposition method. This grew
The Ge layer is amorphous or polycrystalline.
Therefore, this Ge layer is irradiated with a radiation beam such as a linear light beam or an electron beam and scanned to sequentially melt the irradiated portions to perform two-dimensional zone melting. Efforts are being made to make it into a single crystal. However, in this case, it is difficult to form a thin layer of Ge over the entire upper surface of the substrate 1 and to monocrystallize this layer. For this reason, as shown in FIG. 1, the Ge layer 2 is usually formed on the substrate 1 in a plurality of band-like or island-like regions. For example, in the case of a band-shaped Ge layer region, a linear radiation beam that spreads in a direction perpendicular to the longitudinal direction of the band-shaped region is irradiated, and this linear radiation beam is sequentially applied in the longitudinal direction of the band-shaped region. Zone melting is performed by scanning.

However, according to this conventional method, the temperature distribution inside the Ge layer irradiated with the radiation beam is
Since there is no absorption of radiation in the gap between adjacent band-shaped regions, the central part of the Ge layer in this region becomes high temperature, and the peripheral part of the region becomes low temperature, which causes nucleation for crystallization to occur in the band-shaped region. The process starts from the periphery of the Ge layer and then progresses to the center, but the disadvantage is that the single crystals in the center do not connect well and therefore a uniform single crystal cannot be obtained.

(Object of the Invention) An object of the present invention is to provide a single crystal manufacturing method for forming a uniform, high quality single crystal semiconductor thin layer on an insulating underlayer.

(Structure of the Invention) In order to achieve this object, according to the method for manufacturing a single crystal layer of the present invention, a semiconductor thin layer is formed before annealing the semiconductor thin layer by irradiating the semiconductor thin layer with a radiation beam such as a light or an electron beam. This is an improved method in which a first layer made of a material with high thermal conductivity is provided on an insulating base layer, and then a first layer made of a material with low thermal conductivity is placed on this first layer. A plurality of second layers are provided spaced apart from each other, and then the grooves between the adjacent second layers extend over a portion of the second layers, and through the grooves the aforementioned first layer is formed. The method is characterized in that a plurality of thin semiconductor layers in contact with the semiconductor layer are provided at a distance from each other, and then two-dimensional zone melting is performed on these thin semiconductor layers to form a single crystal.

(Description of Examples) Examples of the present invention will be described below with reference to the drawings.

FIGS. 2A to 2E are process diagrams showing the formation state at the main process steps as partial cross-sectional views for explaining the method for manufacturing a single crystal layer according to the present invention. Note that these figures are merely shown schematically to the extent that the configuration of the present invention can be understood.

First, as shown in FIG. 2A, an insulating base layer 1 is formed.
Prepare 1. As this base layer, an insulating substrate such as quartz itself may be used, or an insulating layer stacked directly or indirectly on any type of semiconductor substrate may be used. In this embodiment, this layer 11 will be described as an insulating substrate.

Next, as shown in FIG. 2B, a material (substance) having a high thermal conductivity, that is, a high thermal conductivity and a high melting point is applied over the entire surface of the substrate 11.
(For example, a metal with a high melting point such as W or Ta is suitable, but an insulator with high thermal conductivity such as BN or AlN may also be used.) A first layer 12 is formed.

Next, on this first layer 12, as shown in _FIG . Form. In this case, after this second layer 13 is once formed on the entire surface of the first layer 12,
Using a technique such as photolithography or photomasking, a plurality of fine grooves 14 extending in a direction perpendicular to the illustrated cross section are formed, preferably at equal pitches in the width direction perpendicular to the extending direction. The second layer 13 of the lever is separated into a plurality of strip-like regions.

Subsequently, a plurality of strip-shaped semiconductor thin layers 15 are separated from each other, preferably at equal pitches in the width direction, on the substrate 11 on which the strip-shaped second layer 13 is formed.
Moreover, it is formed to extend in the longitudinal direction along the fine groove 14. In this case, as shown in FIG.
It is provided so as to be centered on the fine groove 14 between them and to extend over a portion of both of the second layers 13. Therefore, this groove 14 is located at the center of each second layer 13 in the width direction. In this case, the semiconductor thin layer 15 filling the fine grooves 14 is brought into contact with the lower second layer 12 having a high thermal conductivity.

Next, as shown in FIG. 2E, the semiconductor thin layer 15
As is, or after providing a protective layer 16 made of an insulating material over the entire upper surface of the substrate 11 including the semiconductor thin layer 15, it may be exposed to light or electronic radiation. With radiation beam 17,
This semiconductor thin layer 15 is annealed. This radiation beam irradiation is preferably performed by scanning the strip-shaped semiconductor thin layers 15 in the longitudinal direction with a linear beam 17 that extends in the width direction of the semiconductor thin layers 15. In this case, this beam scanning may be performed for each individual band-shaped semiconductor thin layer 15, or may be performed for several strips or all at once.

In this way, a two-dimensional zone melting of the thin semiconductor layer 15 is effected by the radiation beam 17. In this case, if this semiconductor thin layer 15 is not in contact with the lower first layer 12, the temperature distribution of the portion of the semiconductor thin layer 15 that has been melted by radiation beam irradiation will be at the center of this melted portion. It is high in the area and low in the peripheral area in the width direction. However, in the case of the present invention, the central portion 18 of this thin semiconductor layer 15 is in direct contact with the lower first layer 12 with high thermal conductivity through the fine groove 14, and the remaining portion is in direct contact with the first layer 12 with high thermal conductivity. Since it is configured to be in direct contact with the small second layer 13, the heat in the central portion 18 of the melted portion of the semiconductor thin layer 15 by the zone melting method is transferred to the first layer 1.
As a result, the temperature distribution is such that the temperature in the central portion 18 is lower than that in the remaining melted portions, and gradually increases in temperature toward the periphery in the width direction. Therefore, the molten part that has been irradiated with the radiation beam is gradually cooled and solidified starting from the central part 18 where the temperature is lowest, a single crystal nucleus is generated in this part 18, and the solidification is further continued in order toward the periphery in the width direction. Proceed to form a single crystal. In this way, the entire region of the band-shaped semiconductor thin layer 15 can be made into a single crystal.

It is clear that the present invention is not limited only to the embodiments described above.

First, the dimensions of each layer to be formed on the insulating base layer,
Not only the shape and arrangement but also the material can be selected as required. For example, the first layer does not necessarily have to be provided on the entire surface of the substrate, but can be formed only on the lower portion of the area where the single crystal layer is to be formed. Further, although the second layer and the semiconductor thin layer are formed into band-like regions, they can also be formed into island-like regions. Also, Ge or any other suitable material can be used as the semiconductor thin layer.

Furthermore, the formation of the second layer and the semiconductor thin layer and the formation of the first layer can be formed using ordinary semiconductor technology, and the methods for forming the second layer and the semiconductor thin layer themselves are not particularly important. do not have.

Furthermore, if the present invention described above is applied to an insulating base layer formed on an IC wafer, it becomes possible to realize a three-dimensional IC in which two or more active layers are laminated. In this case, in particular, by using an electrically conductive layer such as W as the first layer having high thermal conductivity, this first layer enables electrical and electrical connections between the active layers provided above and below the first layer. Alternatively, magnetic shielding can be easily performed.

Furthermore, since an IC can be formed on a uniform, high-quality single-crystal semiconductor thin layer formed by the method of the present invention, it is also possible to fabricate a three-dimensional IC by laminating a large number of active layers with insulating layers in between. I can do it.

Furthermore, the term "layer" mentioned above shall be understood to also include the meaning of a so-called film.

(Effects of the Invention) As is clear from the embodiments described above, according to the present invention, a first layer having high thermal conductivity is provided on an insulating base layer, and a plurality of layers are formed on the upper side of the first layer, which are spaced apart from each other by grooves. A second layer having a low thermal conductivity is provided, and a plurality of thin semiconductor layers are formed at a distance from each other, centering on each groove, and extending not only within the groove but also over the upper portions of the two adjacent second layers. After that, a two-dimensional zone melting method is applied to this semiconductor thin layer to make it into a single crystal. Therefore, the temperature distribution of the semiconductor thin layer portion melted by zone melting is can be easily and reliably distributed such that the temperature in the center portion in the width direction of this portion is the lowest and gradually increases in temperature toward the peripheral portions. Therefore, according to the present invention, solidification and single crystallization start from the center of the molten part, and single crystallization progresses sequentially toward the periphery, eventually covering the entire area of the semiconductor thin layer. It completely becomes a single crystal. In this case, the direction in which this single crystallization progresses is not the direction in which they collide with each other from the periphery to the center as in the conventional case, but in the direction in which they become discrete from the center to the periphery, resulting in a uniform and high crystallization. A high-quality, large-sized single-crystal semiconductor thin layer can be easily and reliably obtained, and the manufacturing yield is also extremely high. Further, since this single crystal semiconductor thin layer can be easily manufactured using conventional semiconductor technology, the manufacturing cost is also low.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a part of the substrate as a cross section for explaining the conventional method of forming a single crystal on an insulating substrate, and FIGS. 2A to 2E are for explaining the method of manufacturing a single crystal according to the present invention. FIG. 3 is a manufacturing process diagram showing a state at a main manufacturing stage as a schematic cross-sectional view. 11... Insulating base layer, 12... First layer (made of a material with high thermal conductivity), 13... Second layer (made of a material with low thermal conductivity), 14... Fine groove, 15... ...Semiconductor thin layer, 16...Protective layer, 17
. . . Radiation beam, 18 . . . Central part of the melted part.

Claims (1)

[Claims] 1. A first layer made of a material with high thermal conductivity is provided on an insulating base layer, and then a plurality of second layers made of a material with low thermal conductivity are provided on the first layer. are spaced apart from each other, and then a plurality of semiconductor thin layers extend over a portion of the second layers around the grooves between the adjacent second layers and contact the first layer through the grooves. 1. A method for producing a single crystal, comprising: providing layers separated from each other; and then performing two-dimensional zone melting on the thin semiconductor layer to form a single crystal.