JPH02192719A - Formation of single crystal semiconductor thin film - Google Patents

Abstract

PURPOSE:To enlarge a solid phase growth distance as well as to expand an effective area for forming a device by a method wherein a second amorphous Si film is single-crystallized using as a seed a highly doped single crystal Si film remained on a groove and a stripelike part parallel to the groove. CONSTITUTION:A groove 3 to reach an Si substrate 1 is provided in an SiO2 film 2 on the substrate 1 and a first amorphous Si film is formed on the whole surface of the film 2. Then, after an impurity is doped to the amorphous film in a high concentration, the amorphous film is single-crystallized to form a single crystal Si film 5. Then, the film 5 is removed by etching leaving the upper part of the groove 3 and a stripelike part parallel to the groove 3 and a non-doped second amorphous Si film is formed on the film 2 and the remained film 5. Moreover, after this Si film is single-crystallized to form a single crystal Si film 6, a flattening is performed and the films 5 and 6 are formed on the film 2 to form a SOI film 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming a single crystal semiconductor thin film on an insulator 11Q.

[Conventional technology]

Generally, an insulating film is formed on a single-crystal semiconductor substrate, a groove in which the substrate is exposed is formed in the insulating film, an amorphous semiconductor thin film is formed on the insulating film and the groove, and the substrate exposed in the groove is seeded. There is a method in which this thin film is successively single-crystalized from the groove in a solid phase by heat treatment, which is called the lever recrystallization method.
I (5ilicon 0nlnsmoe altOr)
It is a useful technique in technology and is attracting attention.

By the way, in the case of forming a single crystal semiconductor thin film by such solid phase growth, taking 8i as an example, the amorphous S1 thin film undergoes a phase transition to a single crystal from the contact part with the substrate in the groove, and first the upper surface of the substrate Single crystallization progresses in a direction perpendicular to (vertical) direction, and then single crystallization progresses in a direction parallel to the top surface of the substrate (lateral direction), resulting in amorphous S1.
The thin film becomes single crystal over the entire area.

However, the solid phase growth distance differs greatly depending on whether the amorphous S1 thin film contains impurities or not, and the solid phase growth distance is small in the case of non-doped, which does not contain impurities.
Conventional practice has been to provide a region with high impurity concentration and use this region as a seed to expand the solid phase growth distance.
For example, Japanese Patent Application Laid-Open No. 63-60517 (HOIL 2
There is a method described in 1/20).

This is a non-doped amorphous semiconductor thin film formed on an insulating film and a trench, with multiple high-concentration regions of impurities arranged in parallel in a direction perpendicular to the trench, and non-doped using the substrate in the trench and these high-concentration regions as seeds. This method converts an amorphous semiconductor thin film into a single crystal.

[Problem to be solved by the invention]

In the method described in the above publication, single crystallization progresses in a figure-7 shape in the non-doped region surrounded by the two high concentration regions and the groove, so that the final crystal subgrains form in a complex diamond-shaped pattern. Boundaries are formed, and it is necessary to form a device channel while avoiding these subgrain boundaries due to the characteristics of the device, which poses a problem in that the area in which a device can be effectively formed is limited.

The present invention has been made with the above points in mind, and an object of the present invention is to extend the solid phase growth distance of a non-doped amorphous semiconductor region, thereby increasing the effective area in which a device can be formed.

[Failure to solve the problem]

In order to achieve the above object, in the method for forming a single crystal semiconductor thin film of the present invention, an insulating film is formed on a single crystal semiconductor substrate, an iM in which the substrate is exposed is formed on the insulating film, and an iM is formed on the insulating film. and forming a first amorphous semiconductor thin film on the groove, doping the first amorphous semiconductor thin film with impurities at a high concentration, and then monocrystallizing the first amorphous semiconductor thin film to form a single crystal. 4 crystalline semiconductor films were formed, and the mI single crystal semiconductor thin film 1 was removed by etching leaving a strip parallel to the trench and the nIS trench, and the remaining i
The method is characterized in that a non-doped second amorphous semiconductor thin film is formed on the "single crystal semiconductor thin film" (f), and the second amorphous semiconductor thin film is made into a single crystal.

[Effect]

With the above structure, when the flattened second amorphous semiconductor thin film is single-crystalized, the single-crystal high-concentration region of the single-crystalized impurity on the groove and in the band is used as a seed for single-crystalization. As the growth progresses, the solid phase growth distance is expanded, and moreover, it is located approximately midway between the groove and the band.

Crystal subgrain boundaries are formed parallel to the grooves, and the crystal subgrain boundaries do not form a complicated pattern as in the conventional method, thereby expanding the effective area for device formation.

〔Example〕

Examples will be described with reference to the drawings.

First, the process of forming a single crystal Si thin film will be explained with reference to FIGS. 1 and 2. In addition, FIG. 1 is a perspective view of the state in which the single crystal Si thin film is finally formed, FIG. 2(a),
(t)) is a perspective view in the middle of formation.

Now, as shown in FIG. 2(a), a single crystal St substrate (1
), a Si02 film (2) is formed as an insulator 11ss, a groove (3) in which the substrate (1) is exposed is formed in the 5102 film (21), and a groove (3) is formed on the 8i021 pattern (2) and the groove (3). A first amorphous Si thin film (hereinafter referred to as a first ab+ film) (4) is formed.

Then, by ion implantation, the first a-8i film (4)
After doping with phosphorus [P] to a high concentration of 3 to 5XIO (cm2), it was heated at 600°C21 in a nitrogen atmosphere.
Heat treatment is performed for 6 hours to single-crystallize the first a-8i film (4), thereby forming a first single-crystal S+ thin film C51.

Here, since the first a-8i film (4) is highly doped, the solid phase growth distance changes as shown by the solid line in FIG. 3 depending on the heat treatment time, and from FIG. , the heat treatment time at which the growth distance is the longest is set at 16 hours, and the solid phase growth distance at this time is approximately 39) tm. In addition, the third
The saturated region is a polycrystalline region.

Next, as shown in Section 2(3)(1)), the Si thin film (5) is removed by etching, leaving the Si thin film (5) on the groove +31 and in the band-shaped portion parallel to the groove (3). then the first
As shown in the figure, a non-doped second amorphous S
i thin film (hereinafter referred to as the second a-8i film) 2, and the second a-8i film was heated for 60 minutes in a nitrogen atmosphere.
Heat treatment was performed at 0° C. for 8 hours to single-crystallize the second a-8i film to form a second single-crystal Si thin film (6), and then planarize this Si thin film [6]. second single crystal S
i-thin @f51, f6) is formed on the Sio2 film (2) to form the S01 film (7).

By the way, when the non-doped second a-8i film is made into a single crystal, the high-tope single crystal S on the groove (3) and the band-like portion is
i thin 1f9% (because single crystallization progresses for all 5 films, the solid phase growth distance changes as shown by the dashed line in the third layer depending on the heat treatment time, the maximum growth distance is 600 ° C, After 8 hours of heat treatment, it becomes about 8 μm, which is almost twice as large as the conventional 4-5) rrn.

At this time, the Si thin film C5) on the groove (3) and the 8i
As the single crystallization of the second a-8i film progresses from both sides parallel to the thin film (5), the groove (
A crystal sub-grain boundary C8) is formed in a straight line parallel to the groove (3) at a position approximately midway between the groove (3) and the belt-shaped portion, and the sub-grain boundary (8) does not form a complicated pattern as in the conventional case.

Then, a gate (G) and a drain (DJ) are formed when a MOS transistor is formed on the obtained 80I film (7).

The arrangement of the source (8) is, for example, as shown in FIG. A p-MOS transistor 00 is formed parallel to the groove in the vicinity of the first single crystal S1 thinning r5) on the groove (3). It is sufficient to form a channel by avoiding the crystal subgrain boundary [8] in the middle of the region, and by such /jc!INK, the device forming region of SOIg(n) can be effectively utilized.

In this case, the source contact region (Cs) of the n-MOS transistor (9) is
is formed on a single-crystal Si thin film (5) to reduce source contact resistance.

Therefore, according to the embodiment, the non-doped second a-
When monocrystalizing the 8i film, the high-tope first single-crystal Si thin film (5) on the groove (3) and in the band was used as a seed, so the solid phase growth distance of the second a-8i film was changed from the conventional method. The crystal subgrain boundaries do not form a complicated pattern as in the conventional case, and the effective area for device formation can be expanded.

In addition, although the case of forming a single-crystal S1 thin film was explained in the embodiment described in mJ, the present invention is not limited to this.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

In order to single-crystallize the second amorphous semiconductor thin film using the high-tope single-crystal semiconductor thin film remaining on the grooves and in the strips, the solid-phase growth distance of the non-doped second amorphous semiconductor thin film is made longer than before. Moreover, the crystal subgrain boundaries are formed in a straight line parallel to the grooves at approximately the midpoint between the grooves and the strips, and the crystal subgrain boundaries are not as complex as in the past. This is very advantageous in obtaining an S 01 film with a large effective surface area for devices, since the effective area for device formation can be expanded without forming a pattern.

[Brief explanation of the drawing]

The drawings show an embodiment of the method for forming a single crystal semiconductor thin film according to the present invention, and FIG. 1 is a perspective view of a formed single crystal semiconductor thin film, and FIGS. FIG. 3 is a diagram showing the relationship between heat treatment time and solid phase growth distance, and FIG. 4 is a plan view showing the device arrangement pattern. (1)...Single crystal 81 substrate, (2)...S i02
Membrane, (3)...Groove, (5). (6)... 1st. Second single crystal Si thin film.

Claims (1)

[Claims] (1) forming an insulating film on a single crystal semiconductor substrate; forming a groove in the insulating film in which the substrate is exposed; forming a first amorphous semiconductor thin film on the insulating film and on the groove; 1st
After doping the first amorphous semiconductor thin film with impurities at a high concentration, the first amorphous semiconductor thin film is single-crystallized to form a single-crystal semiconductor thin film, and by etching, strips are formed on the groove and parallel to the groove. The single crystal semiconductor thin film is removed leaving behind the single crystal semiconductor thin film, a non-doped second amorphous semiconductor thin film is formed on the insulating film and the remaining single crystal semiconductor thin film, and the second amorphous semiconductor thin film is removed. A method for forming a single-crystal semiconductor thin film characterized by forming a single crystal.