JPH0712022B2 - Semiconductor manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of manufacturing a semiconductor used for a semiconductor device having an extremely small size.

[Conventional Technology and Its Problems] The addition of impurity atoms into a semiconductor is an essential technology for controlling the type and density of carriers in the semiconductor.
A method of adding during semiconductor growth and a method of adding after growth by ion implantation have been used. However, in any of these methods, the addition of impurity atoms is limited to the technology for controlling the density of impurity atoms, and it has not been possible to specify the position where impurity atoms are added in the semiconductor. Therefore, the positions of impurity atoms in the semiconductor were random. On the other hand, the positions of the constituent elements of the semiconductor are strictly determined not only in the element semiconductor but also in the compound semiconductor,
It has been considered that the structure of a semiconductor can be strictly controlled if a technique for precisely determining the shape occupied by the semiconductor has a probability.
In recent years, the growth of semiconductors can be controlled at the atomic layer level by the molecular beam epitaxy growth method, and fine line-shaped semiconductor structures have been formed due to the progress of fine processing technology.

However, even if the semiconductor shape control technology is established, the position occupied by impurity atoms in the semiconductor must be controlled,
The structure of semiconductors cannot be said to be strictly controlled. In particular, when the device size is reduced, the uneven distribution of local impurity atoms becomes a problem. For two-dimensional and one-dimensional semiconductors, Journal of the Physical Society of Japan, Vol. 40, p. 489 (198
As pointed out by Nagaoka in 5 years), it is very difficult to control the conduction properties of electrons because the Anderson localization of electrons becomes remarkable due to a slight nonuniformity. It is well known that even in a three-dimensional object, the irregularity of the impurity arrangement gives fluctuations to the potential felt by the electron and deforms the band structure. Therefore, unless the arrangement of impurity atoms in the semiconductor is strictly controlled,
It is considered difficult to realize a semiconductor device having an extremely fine size.

The present invention has been made based on the above conventional circumstances, and an object thereof is to provide a method for manufacturing a semiconductor in which the positions of impurity atoms are regularly controlled.

[Means for Solving the Problems] In order to achieve the above object, the present invention makes a semiconductor surface further adsorb a molecule containing an impurity atom, and then a tunnel emitted from a tunnel electron emission source having a sharp tip. By using electrons to scan the tunnel electron emission source or the semiconductor to excite and decompose the adsorbed molecules, only impurity atoms are separated in the vicinity of the semiconductor surface and at an integer multiple of the interatomic spacing of the semiconductor. It has a regularity in the lattice positions or interstitial positions of semiconductor atoms and is sequentially replaced or arranged.

[Operation] Impurity atoms in the semiconductor of the present invention are regularly arranged at intervals that are integer multiples of the atomic intervals of the semiconductor. Therefore, the potential felt by the electrons is completely regular, localization does not occur due to fluctuations, and a semiconductor device having an ultrafine structure can operate. Such addition of impurities is performed by scanning the semiconductor or tunnel electron emission source using a tunnel electron emission source that can arrange impurity atoms one by one at the semiconductor surface or at a specific position immediately below the semiconductor surface.

EXAMPLES Next, the present invention will be described with reference to examples.

Example 1 FIG. 2 is a schematic view of a semiconductor 1 obtained in an example according to the present invention. Impurity atoms are added only on the atomic layers 2 separated by n atomic layers as shown in FIG.
Here, n is an integer. FIG. 2B shows the arrangement of the impurity atoms 3 on the atomic layer 2 to which the impurity atoms are added. In this case, the positions occupied by the constituent elements are the intersections of the longitude and latitude lines. Impurity atoms occupy substitution positions that are separated by m atom intervals in both the meridian direction and the latitude direction. Immediately above and directly below each impurity atom, impurities are arranged with an n-atom layer apart. Therefore, the positions of the impurity atoms in the semiconductor of FIG. 2 are quite regular with respect to the positions of the constituent atoms, and the electrons in the semiconductor move by feeling the regular impurity potential in addition to the potential of the regular constituent elements. Therefore, the energy dispersion relation of electrons, that is, the band structure is strictly determined uniquely, and the electrons are not localized. If such a semiconductor is used for a transistor having an ultrafine structure, desired characteristics can be obtained. In FIG. 2, the position of the impurity atom occupies the substitution position with respect to the semiconductor atom, but it is possible to create a regular impurity atom potential in the same manner by selecting a specific interstitial position.

Next, a method of manufacturing the semiconductor configured as described above will be described.

FIG. 1 schematically shows a sample cross section in the step of arranging impurity atoms in the manufacturing process. FIG. 1 (a) shows a replacement position in which a molecule 5 containing an impurity atom is further adsorbed on the surface of a clean semiconductor layer 4 and a tungsten tip having a sharp tip, which is a tunnel electron emission source 6, is arranged to place an impurity. It is shown just above. This arrangement is very similar to that of a so-called scanning tunneling microscope. A scanning tunneling microscope directly observes the atomic arrangement of a solid surface, as described in the article by Gerd Winig and Heinlippi Roller, page 50, August 1985, Scientific American. It is an excellent way to By choosing a low voltage between the chip and the semiconductor, it is possible to observe an adsorption structure in which molecules are regularly adsorbed on the semiconductor surface. This observation is performed by detecting the local intensity of the tunnel current flowing between the chip and the semiconductor surface. The movement of the place is performed by using a movement mechanism that uses the piezo effect for the chip or the semiconductor. If the chip is positively biased with respect to the semiconductor and the voltage value is selected so that the energy of the tunnel electrons is sufficient to decompose the adsorbed molecules, the emitted tunnel electrons 7 will cause only the adsorbed molecules directly below the chip to be absorbed. It is possible to disassemble.

FIG. 1 (b) shows that the adsorbed molecules are decomposed in this way, and the impurity atom 3 is arranged only at a predetermined substitution position on the semiconductor surface. FIG. 1 shows that undecomposed adsorbed molecules are desorbed by raising the sample temperature or irradiating light, and only the impurity atoms 3 regularly arranged on the semiconductor surface are left. (C).

After that, a semiconductor having a constant atomic layer thickness is grown by the atomic layer epitaxy method or the molecular beam epitaxy method using the monolayer adsorption, and the impurity atoms are arranged again by using the method shown in FIG. For example, a semiconductor having the structure shown in FIG. 2 can be obtained. When gallium arsenide is used as the material of the semiconductor layer in FIG. 1, silicon can be added as an impurity atom by using trimethyl silicon, silicon fluoride, silicon chloride, or silane as the adsorbing molecule.

Example 2 FIG. 3 (a) shows that the impurity atom 13 in the substitution position of the impurity atom-added atom line 9 on the center line in the semiconductor thin wire 8 having a thickness corresponding to 9 atomic layers on each side of the cross section. As shown in FIG. 3 (b), the semiconductor thin wires 8 are arranged so that the ratios of the respective position intervals form the Fibonacci sequence. Here, the Fibonacci sequence is a _n = a _n-1 × a _{n-2 in the} sequence {a _n }.
Means a sequence of integers satisfying, and the unit of the integer is the atomic spacing on the center line.

Since the electrons in the semiconductor thin wire 8 move by feeling the impurity potential forming the Fibonacci sequence, the energy dispersion relation of the electrons is uniquely determined as in the first embodiment, and the electrons are not localized.

The problem with the semiconductors shown in Examples 1 and 2 is the change in the position of the impurity atom due to the diffusion of the impurity atom. If such a change occurs, the regularity of arrangement will be lost. The diffusion coefficient is generally determined by the type of semiconductor and the type of impurity atom, and the degree of its size is determined by the self-diffusion coefficient of the semiconductor. Growth temperature of 700 ℃ for heterojunction structure of gallium arsenide and aluminum gallium arsenide
However, a flat interface was obtained at the atomic layer level, so at the molecular beam epitaxy growth temperature (up to 500 ℃), the impurity diffusion is almost negligible. That is, it is not necessary to consider the impurity diffusion of the molecular beam of the semiconductor at the epitaxy growth temperature, and it can be completely ignored at the lower temperature.

[Effects of the Invention] As described above, according to the present invention, a semiconductor in which impurity atoms are regularly arranged is obtained, and a semiconductor device having an ultrafine structure can operate without being affected by fluctuations in the impurity potential.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an embodiment of the present invention, FIG. 2 is a schematic diagram showing the structure of a semiconductor obtained by the method,
FIG. 3 is a schematic view showing the structure of a semiconductor obtained according to another embodiment of the present invention. 1 ... semiconductor 2 ... impurity atom-added atomic layer 3,13 ... impurity atom, 4 ... semiconductor layer 5 ... adsorption molecule, 6 ... tunnel electron emission source 7 ... tunnel electron, 8 ... semiconductor wire 9 ...... Atomic beam with added impurity atoms

Claims (1)

[Claims] 1. A molecule containing an impurity atom is further adsorbed on a semiconductor surface, and then tunnel electrons emitted from a tunnel electron emission source having a sharp tip are used to scan the tunnel electron emission source or the semiconductor to carry out the adsorption. By exciting and decomposing molecules, only the impurity atoms are ordered in the vicinity of the semiconductor surface and at regular intervals at the lattice positions or interstitial positions of the semiconductor atoms with a distance that is an integer multiple of the interatomic spacing of the semiconductor. A method for manufacturing a semiconductor, which comprises replacing or arranging.