JPH0787178B2 - Method for forming single crystal semiconductor thin film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for forming a single crystal semiconductor thin film in which a single crystal semiconductor thin film is formed on an insulating film formed on a single crystal semiconductor substrate.

[Conventional technology]

In general, an insulating film such as a silicon oxide film is formed on a single crystal silicon substrate as a single crystal semiconductor substrate, and a single crystal silicon film as a single crystal semiconductor thin film is epitaxially grown on this insulating film. The [insulator] film has been attracting attention as an element material for achieving higher integration, higher speed, and lower power consumption of integrated circuits.

And conventionally, as a method of forming a single crystal silicon film as a single crystal semiconductor thin film that constitutes such an SOI film,
The recrystallization method using laser light and the full-face epitaxial growth method are well known. One of them is to partially remove the insulating film on the silicon substrate to expose the silicon substrate and expose the exposed silicon. A solid-phase epitaxial growth method (hereinafter referred to as SPE) in which an amorphous silicon film is formed on a substrate and an insulating film, and the exposed silicon substrate is used as a seed to single crystallize the amorphous silicon film in the upward and horizontal directions. Method), the substrate temperature for single crystallization can be as low as about 600 ° C, and the flatness of the grown single crystal silicon film is good. Is preferred.

However, in the case of the normal SPE method as described above, random nuclei are generated in the amorphous silicon film during the single crystallization, and the nuclei hinder the growth of the single crystal silicon in the horizontal direction. The growth distance of the single crystal silicon film in the horizontal direction is limited, and is only about 5 μm.

So, for example, Second International Workplace Electronics, Electronics Devices SOI Technology and 3D Integration-March 19-21,1985, pp63-68 [2nd Internat
ional Workshop on Future Electron Devices-SOI Tec
hnology and 3D Integration-March 19-21,1985, pp63
−68] 's “IMPURITY EFFECTS IN LATERAL SOLLD PHASE
EPITAXY "(H.ISHIWARA et al.), The amorphous silicon film described above is doped with phosphorus [P] or boron [B] at a high concentration to increase the growth distance of the single crystal silicon film in the horizontal direction. It has been reported that can be extended to 24 μm.

[Problems to be solved by the invention]

However, since it is difficult to fabricate a device in a single crystal silicon film in which P or B is highly doped, a semiconductor three-dimensional circuit element is fabricated using an SOI film made of such a highly concentrated single crystal silicon film. There is a problem that you cannot do it.

Therefore, in the present invention, without doping impurities,
A technical problem is to increase the growth distance of a single crystal semiconductor thin film in the horizontal direction so that a single crystal semiconductor thin film having good film quality and capable of device fabrication can be obtained.

[Means for solving problems]

The present invention has been made in view of such technical problems, in which an insulating film is formed on a single crystal semiconductor substrate, and the insulating film is partially removed to partially remove the substrate surface. Exposing, forming an amorphous semiconductor thin film of the same material as the substrate on the insulating film including the partially exposed substrate surface,
While the substrate is heated and held, silicon ions are implanted into the entire surface of the amorphous semiconductor thin film, and the amorphous semiconductor thin film is single-crystallized by solid phase epitaxial growth in the upward and horizontal directions. In the method for forming a crystalline semiconductor thin film, the amorphous semiconductor thin film on the exposed substrate is single-crystallized only by heating the substrate, and then the amorphous semiconductor thin film is held while the substrate is heated and held. In order to allow the implanted ions to reach the entire region in the thickness direction, the conditions are changed sequentially such that the ratio of the implantation energy of silicon ions and the dose amount is changed. Characterized by repeated injections.

[Action]

Therefore, according to the present invention, the amorphous semiconductor thin film is formed on the single crystal semiconductor substrate and the insulating film which are exposed by partially removing the insulating film. Single crystal is formed by a solid-phase epitaxial growth method in the direction to form a single crystal semiconductor thin film.

At this time, as described in the above-mentioned literature, the generation rate of random nuclei generated in the amorphous semiconductor thin film is n.
[Cm ⁻² s ⁻¹ ], and the horizontal epitaxial growth rate is V [cm / s], the maximum horizontal growth distance L of the single crystal semiconductor thin film is (V / n) ^1/3. It is known that when an amorphous semiconductor thin film is single-crystallized, ion implantation is performed on the entire surface of the amorphous semiconductor thin film while the substrate is heated and held at a predetermined temperature. Irradiation damage is uniformly applied to the thin film semiconductor thin film, but even if the crystallinity is disturbed by irradiation damage in the portion that has already become a single crystal, the crystallinity is immediately restored by annealing out and the deterioration of crystallinity is prevented. In the non-single-crystal amorphous portion, random nuclei generated by heating return to amorphous again due to irradiation damage, so that the nucleation rate n is reduced while keeping the growth rate V constant. It is possible to conduct single crystal semiconductors without high-concentration doping of impurities. Increase in maximum growth distance in the horizontal direction of the thin film Hakare, film quality is good, the single-crystal semiconductor thin film device fabrication is obtained.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings showing one embodiment thereof.

First, as shown in FIG. 2 (a), the surface of a single crystal silicon substrate (1) as a single crystal semiconductor substrate having a plane orientation of (100) is further cleaned with an acid after RCA cleaning, that is, organic cleaning. As shown in FIG. 2 (b), the surface of the substrate (1) is thermally oxidized to form an insulating film (2) made of a silicon oxide film having a film thickness of about 500 Å, and then, shown in FIG.
As shown in Fig. 3, a part of the insulating film (2) is etched in parallel with the <001> axis by a normal lithographic technique, and the insulating film (2) is partially removed to form a window (3). The substrate (1) is exposed.

Next, the surfaces of the substrate (1) and the insulating film (2) are cleaned by RCA again to reduce the pressure for forming amorphous silicon as shown in FIG.
The substrate (1) is set on the susceptor (Sc) of the CVD device, and as shown in FIG. 2 (d), a non-crystalline semiconductor thin film is formed on the exposed substrate (1) and insulating film (2). A crystalline silicon thin film (4) is formed.

By the way, in FIG. 3, (Tu) is a quartz reaction tube, and (Su)
h) is a holder for holding the susceptor (Sc) in the reaction tube (Tu), (P) is a rotary pump for exhausting the reaction tube (Tu),
(G) is a vacuum gauge, (B) is a DC power supply that supplies a DC bias between the electrode (E) provided in the reaction tube (Tu) and the susceptor (Sc) via the tungsten wire (W),
(T) is a temperature control means for measuring the temperature of the susceptor (Sc) via the thermocouple (t) and controlling the energization of the infrared lamp (Lm) to control the temperature of the substrate (1). A high-frequency power supply that applies high-frequency waves to a high-frequency heating coil (C) wound around a reaction tube (Tu) to generate plasma of introduced gas, (G
S) is Si in the reaction tube (Tu) through the gas introduction part (g).
It is a reaction gas supply means that supplies each gas of H ₄ , PH ₃ , and Ar.

Then, using such a low pressure CVD apparatus, while maintaining the temperature of the substrate (1) at 550 ° C., the surfaces of the substrate (1) and the insulating film (2) are cleaned by Ar ⁺ plasma to thermally decompose SiH ₄ . After forming an amorphous silicon thin film (4) with a film thickness of about 2000 Å by the above, the substrate (1) is transferred into the reaction chamber of the ion implantation apparatus as shown in FIG. The substrate (1) is set on (H), and the substrate (1) is heated and held at about 600 ° C. by the heater (h), and the ion generating / accelerating means (Ia) is formed on the entire surface of the amorphous silicon thin film (4).
Si ⁺ is injected and the amorphous silicon thin film (4) is single-crystallized by the solid phase epitaxial growth method.

That is, without performing ion implantation at first, the heater (h)
If the substrate (1) is kept at about 600 ° C by heating the
As shown in FIG. 6E, using the substrate (1) of the window (3) as a seed, the amorphous silicon thin film (4) is single-crystallized by upward solid phase epitaxial growth, and the silicon thin film (4) is formed in about 60 minutes. 4) reaches the upper surface and a single crystal silicon layer (5) grows on the upper side of the window (3).

Next, continuing to maintain the temperature of the substrate (1) to about 600 ° C., Si ⁺
The energy [KeV] and dose [× 10 ¹⁵ cm ^-2 ] ratio of 160 / 1.0, 80 / 0.36, 40 / 0.18 were sequentially switched, and Si ⁺ implantation was repeated under each condition. , As shown in FIG. 1, by solid phase epitaxial growth in the horizontal direction,
A single crystal silicon thin film (6) as a single crystal semiconductor thin film is formed.

By repeating the ion implantation conditions on the entire surface of the silicon thin film (4) in this manner, the ions do not reach only a limited region in the thickness direction of the silicon thin film (4), but The implanted ions can reach the entire region of the thin film (4) in the thickness direction. By repeatedly performing ion implantation on the entire surface of the silicon thin film (4) by changing the conditions as described above, irradiation damage is uniformly given to the silicon thin film (4). , Even if the crystallinity is disturbed by irradiation damage, the crystallinity is immediately recovered by annealing out and the deterioration of the crystallinity is prevented. In the non-single-crystallized amorphous part, random nuclei generated by heating ( 7)
To return to an amorphous state again by irradiation damage, reduce the generation rate of nuclei (7) while keeping the epitaxial growth rate constant, and increase the maximum growth distance L of the single crystal silicon thin film (6) in the horizontal direction. The maximum growth distance L of about 8 μm was achieved in the process of about 10 hours.

By the way, as a literature on ion implantation into silicon substrates at high temperature, the Journal of Applied
Physics Volium 40, Number 2 Fueburari 1969 P.
842〜854 (JOURNAL OF APPLIED PHYSICS VOLUME40, NUMB
ER2FEBRUARY 1969 P.842 ~ 854].

〔The invention's effect〕

As is apparent from the above description, the present invention forms an insulating film on a single crystal semiconductor substrate, partially removes the insulating film to partially expose the substrate surface, and then partially exposes the substrate surface. An amorphous semiconductor thin film of the same material as the substrate is formed on the insulating film including the substrate surface, and while the substrate is heated and held, ion implantation of silicon ions is performed on the entire surface of the amorphous semiconductor thin film, A method for forming a single crystal semiconductor thin film, wherein the amorphous semiconductor thin film is single-crystallized by solid-phase epitaxial growth in an upward direction and a horizontal direction, wherein the amorphous semiconductor thin film on the exposed substrate is heated only by heating the substrate. After the single crystal is crystallized, the implantation energy and dose of silicon ions are adjusted so that the implanted ions reach the entire region in the thickness direction of the amorphous semiconductor thin film while heating and holding the substrate. Of the single crystal semiconductor thin film in the horizontal direction without impurity doping because the ion implantation is repeatedly performed on the entire surface of the amorphous semiconductor thin film under each condition. It is possible to obtain a single crystal semiconductor thin film capable of increasing the phase epitaxial growth distance, preventing deterioration of crystallinity, having a good film quality, and capable of producing a device, which is extremely effective for producing a semiconductor three-dimensional circuit element.

[Brief description of drawings]

The drawings show one embodiment of the method for forming a single crystal semiconductor thin film of the present invention. FIG. 1 is a sectional view of the final step of forming the single crystal semiconductor thin film, and FIGS. Sectional views during formation of the crystalline semiconductor thin film, FIG. 3 and FIG.
The figure shows the depressurized CV used for forming single crystal semiconductor thin films.
It is a schematic block diagram of a D apparatus and an ion implantation apparatus. (1) …… Single crystal silicon substrate, (2) …… Insulating film,
(4) …… Amorphous silicon thin film, (6) …… Single crystal silicon thin film.

Claims (1)

[Claims] 1. An insulating film is formed on a single crystal semiconductor substrate, the insulating film is partially removed to partially expose the substrate surface, and the partially exposed substrate surface is also included in the insulating film. An amorphous semiconductor thin film of the same material as that of the substrate is formed on the substrate, and while the substrate is heated and held, ion implantation of silicon ions is performed on the entire surface of the amorphous semiconductor thin film to form the amorphous semiconductor thin film. In a method for forming a single crystal semiconductor thin film which is single crystallized by solid phase epitaxial growth in the upward and horizontal directions, the amorphous semiconductor thin film on the exposed substrate is single crystallized only by heating the substrate. Then, while the substrate is heated and held, the ratio of the implantation energy and the dose amount of silicon ions is changed so that the implanted ions reach the entire region in the thickness direction of the amorphous semiconductor thin film. A method for forming a single crystal semiconductor thin film, which is characterized by sequentially switching and repeatedly performing ion implantation on the entire surface of the amorphous semiconductor thin film under each condition.