JPH04294522A - Formation of single crystal semiconductor film - Google Patents

Abstract

PURPOSE:To obtain a high-quality single crystal semiconductor film. CONSTITUTION:This single crystal semiconductor film forming method contains a process for forming an insulating film 21 of silicon dioxide having a plurality of openings 27 at intervals which are five or more times longer than the film thickness of the first silicon dioxide film 17 from the plurality of openings 25 of the film 17 on a single crystal silicon film 19 formed on the film 17 having the openings 25, process for forming a polycrystalline silicon film on the second silicon dioxide film, and process for transforming the polycrystalline silicon into single crystals by irradiating the polycrystalline silicon film with an energy beam.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for forming a single crystal semiconductor film, and in particular to a method for forming a single crystal semiconductor film, in which a single crystal silicon film is formed by melting and recrystallizing non-single crystal silicon using an energy beam. This invention relates to improvements in film formation methods.

0002

[Prior Art] Conventionally, as a method for forming a single crystal silicon film, an energy beam is applied to a polycrystalline silicon film deposited through a silicon dioxide film, which serves as an insulating film, with an opening provided on a silicon substrate. A method is used in which a single crystal silicon film is formed by irradiating, melting, recrystallizing, and performing lateral epitaxial crystal growth using a silicon substrate as a seed crystal.

By the way, the amount of heat released from the surface of the polycrystalline silicon film due to convection is very small compared to the amount of heat flowing from the polycrystalline silicon film to the silicon substrate. Particularly when an electron beam is used as the energy beam, the polycrystalline silicon film is heated in a vacuum, and no heat flows out due to convection.

Furthermore, since the thermal conductivity of silicon is about an order of magnitude higher than that of silicon dioxide, the amount of heat that flows into the silicon substrate through the opening in the silicon dioxide film is far greater than the amount of heat that flows into the silicon substrate through the silicon dioxide film. big. As a result, the temperature of the opening becomes lower than the temperature of the surrounding area, making it difficult to uniformly heat and melt the polycrystalline silicon film.

Therefore, as shown in FIG. 1, in order to ensure uniformity in the amount of heat loss in the polycrystalline silicon film, the thickness of the silicon dioxide film 3 is gradually thinned to form a tapered opening. In addition to making it easier to supply heat to the interface between the polycrystalline silicon film 5 and the silicon substrate 1, the area of the contact portion between the polycrystalline silicon film 5 and the silicon substrate 1 is reduced to reduce the amount of heat flowing out from the seed crystal part 2. (T. Hamasa
ki et al. , J. Appl. Phys. 62(
1987) p. 126) has been reported.

However, in order to obtain the silicon dioxide film 3 having such a complicated opening, it is necessary to use at least three masks, which causes problems in terms of the number of steps, manufacturing time, and cost.

[0007] Furthermore, since the opening is wider than the one described above, there is also the problem that the element forming area becomes narrower.

Furthermore, the area of the opening can be determined by lithography.
Since it cannot be made smaller beyond the limits of technology, it is possible to make the area of the opening an optimal size for melting the seed crystal part 2, but the area of the opening cannot be made smaller than the limits of lithography technology. Therefore, the area of the opening cannot be reduced so that other parts of the polycrystalline silicon film 5 are not heated more than necessary. As a result, when the polycrystalline silicon film 5 is melted, impurities such as oxygen from the silicon dioxide film 3 are mixed into the polycrystalline silicon film 5, causing crystal defects and deteriorating the film quality. In addition, in order to ensure uniformity of heat loss, the contact between the polycrystalline silicon film and the underlying single-crystalline silicon film is made as small as possible, and the area of the opening is reduced, which causes the problem that the polycrystalline silicon film does not melt. There is also.

Furthermore, in order to form a multilayer single crystal silicon film using such a method, as shown in FIG. 6, a silicon dioxide film 7 and a polycrystalline silicon film 9 are formed on this single crystal silicon film 6 in the same manner as in FIG.
form. In this case as well, heat flows out to the silicon substrate 1 through the seed crystal part 10, and the amount of heat is adjusted by the contact area between the polycrystalline silicon film 9 and the single crystal silicon film 6 and the shape of the opening. Similar problems arise as in the case of monocrystalline silicon films.

0010

SUMMARY OF THE INVENTION As described above, in the conventional method of forming a single crystal silicon film, it is difficult to dissipate heat from a molten polycrystalline silicon film in a predetermined manner. As a result, there is a problem in that the polycrystalline silicon film is not melted or is heated more than necessary, making it impossible to obtain a high-quality single-crystalline silicon film.

The present invention has been made in consideration of the above circumstances, and its object is to provide a method for forming a single crystal semiconductor film that can obtain a high quality single crystal film.

0012

[Means for Solving the Problems] In order to achieve the above object, the method for forming a single crystal semiconductor film of the present invention includes a single crystal semiconductor film formed on a first insulating film having a plurality of openings. forming a second insulating film having a plurality of openings whose distance from the plurality of openings of the first insulating film is five times or more the thickness of the first insulating film; A step of forming a non-single crystal semiconductor film on the second insulating film, and an energy
The method is characterized by comprising a step of irradiating the non-single crystal semiconductor film with a beam to single crystallize the non-single crystal semiconductor film.

Another method of forming a single crystal semiconductor film according to the present invention includes the steps of forming an insulating film on the single crystal semiconductor film;
forming a plurality of openings in the insulating film at intervals of 1 to 20 times the thickness of the insulating film;
The method is characterized by comprising a step of forming a non-single crystal semiconductor film on the insulating film, and a step of irradiating the non-single crystal semiconductor film with an energy beam to make the non-single crystal semiconductor film into a single crystal.

[0014]

In the method for forming a single crystal semiconductor film of the present invention, the non-single crystal semiconductor film melted by the energy beam releases heat through the opening provided on the second insulating film. The amount of heat flowing out of the non-single crystal semiconductor film through its opening depends on the distance between the opening in the first insulating film and the opening in the second insulating film. That is, the narrower the interval, the more heat will flow out, and the wider the interval, the less heat will flow out. At this time, if the distance between the opening in the first insulating film and the opening in the second insulating film is five times or more the thickness of the second insulating film, the opening in the second insulating film is It is possible to prevent heat from flowing out more than necessary through the film, and it is possible to easily melt the non-single crystal semiconductor film.

[0015] The seed crystal portion is formed by depositing an insulating film,
Since the simple steps of drilling a hole and depositing a non-single crystal semiconductor film are sufficient, one layer of single crystal semiconductor films can be stacked using a single mask, simplifying the formation process.

Furthermore, if the interval between the openings of the second insulating film is made less than one time the thickness of the second insulating film, the adjacent openings will function as one opening, and the area around the opening will be The temperature decreases, and melting of the non-single crystal semiconductor film stops progressing. Furthermore, if the interval between the openings is made larger than 20 times the thickness of the second insulating film, it becomes difficult for heat to escape, and the non-single crystal semiconductor film is heated more than necessary, resulting in crystal defects.

[0017] Therefore, by setting the interval between the openings of the second insulating film to 1 to 20 times the thickness of the second insulating film, a high-quality single crystal semiconductor film can be obtained.

[0018]

Embodiments Hereinafter, embodiments will be described with reference to the drawings.

FIG. 3 is a diagram showing a method for forming a single crystal silicon film according to an embodiment of the present invention. To explain this according to the formation process, first, a CVD method is used on a (100) oriented single crystal silicon substrate 11 to form an insulating film with a thickness of about 2.5 mm.
A 0 μm silicon dioxide film 13 is deposited. Next, a tapered opening 13a is provided at a desired position in the silicon dioxide film 13 to form a seed crystal portion.

Next, silane (S) is applied on the silicon dioxide film 13.
The thickness is about 0.0mm by CVD method using thermal decomposition of iH4).
After a polycrystalline silicon film of 8 .mu.m is deposited to fill the opening 13a, the polycrystalline silicon film is melted and recrystallized using an energy beam to form a single crystal silicon film 15.

Next, a silicon dioxide film 17 having a thickness of about 2.0 μm is deposited on the single crystal silicon film 15 using the CVD method, and then a photoresist pattern is formed on this silicon dioxide film 17. Using RIE (reactive ion etching) as a mask, a cylindrical opening 25 with a diameter of 1 μm and a depth of 2 μm is formed at a position 10 μm away from the seed crystal portion 12.

Next, a polycrystalline silicon film having a thickness of about 0.8 μm is deposited on the silicon dioxide film 17 provided with the opening 25 using the CVD method so as to fill the opening 25, and then this polycrystalline silicon film is deposited using the CVD method so as to fill the opening 25. A single crystal silicon film 19 is formed by irradiating the film with an energy beam.

Next, a film with a thickness of 2.0 mm is deposited on the single crystal silicon film 19.
After depositing the silicon dioxide film 21 with a thickness of μm, the opening 25
The distance L2 between the silicon dioxide films 17 and 2 is 10 μm.
An opening 27 having a thickness 5 times the film thickness t of 1 is formed. Note that the interval L1 between the openings on the same silicon dioxide film is 15 μm for both the openings 25 and 27 (silicon dioxide film 17
, 21). Next, the silicon dioxide film 21 provided with this opening 27 is
A polycrystalline silicon film with a thickness of about 0.8 μm is placed on top of the opening 27.
A single crystal silicon film 23 is formed by irradiating this polycrystalline silicon film with an energy beam.

If the distance between the openings 25 and 27 is made five times the film thickness t of the silicon dioxide films 17 and 21 as described above, more heat than necessary is transferred from the openings 25 and 27 to the polycrystalline silicon films 15 and 27. It can prevent you from running away from 23. Furthermore, by making the spacing between the openings on the same silicon dioxide film 7.5 times the film thickness of the silicon dioxide film, the heat flow between the openings and the upper and lower silicon films can be adjusted appropriately. Because of this relationship, temperature control could be performed well and a high quality single crystal silicon film could be obtained. That is, heat could be made to flow only along each opening.

[0025] Thereafter, by repeating the same steps, the required number of single crystal silicon films can be obtained.

FIG. 4 is a diagram showing a method of forming a single crystal silicon film according to another embodiment of the present invention. Also, Figure 5 is Figure 4
This is a top view of the sample substrate shown in .

First, a source/drain 3 is formed in an element formation region divided by an element isolation insulating film 31 on a semiconductor substrate 29.
3, a gate electrode 35 and a gate insulating film 37 having a thickness of about 0.5 μm are formed. Furthermore, an interlayer insulating film 38 is formed.

Next, after forming a cylindrical opening with a diameter of 1 .mu.m in the interlayer insulating film 38, a cylindrical opening with a thickness of about 0.0 mm is formed on the interlayer insulating film 38.
A polycrystalline silicon film of 8 μm is deposited to fill the opening and etched into a predetermined shape. Note that the interval L1 between the openings of the interlayer insulating film 38 was set to be 1 to 20 times the thickness of the interlayer insulating film 38. Next, using a scanning method to be described later, an electron beam is irradiated only to the area around the opening of the interlayer insulating film 38, as indicated by 43 in the figure, to melt and recrystallize the polycrystalline silicon film. A single crystal silicon film 39 is then formed.

Next, an insulating film 40 with a thickness of about 1.5 μm is deposited on the interlayer insulating film 38 on which the single crystal silicon film 39 has been formed, and then a cylindrical opening with a diameter of 1 μm is formed in this insulating film 40. do. Note that the distance between the openings of the insulating film 40 is set to be between 1 and 20 times the thickness of the insulating film 40, and the distance L2 between the openings of the interlayer insulating film 38 is set so that the distance between the openings of the insulating film 40
The film thickness was set to be five times or more than the film thickness of .

Next, a polycrystalline silicon film with a thickness of about 0.8 μm is formed on the insulating film 40 so as to fill the opening, and then electrons are deposited in the region where the element will be formed, as shown by 45 in the figure. A single crystal silicon film 41 is formed by scanning the beam.

[0031] Thereafter, by repeating the same steps, the required number of single crystal silicon films can be obtained.

Next, the electron beam scanning method in this embodiment will be explained using FIG.

This is T. Hamasaki et
al. , J. Appl. Phys. 59 (1986) 2
971. This is a method that controls the irradiation area by deflecting a spot-shaped electron beam at high speed.

Half width 150 emitted from beam light source 47
A spot beam 49 of .mu.m is deflected in the X direction by a deflection plate 53 whose plate-to-plate voltage is controlled by an oscillator 51 to generate a linearized electron beam 55. At this time, as shown in FIG. 7, the sine wave 59 with a frequency of 36 MHz is
The plate-to-plate voltage is amplitude-modulated with a Hz modulated wave 61 and is applied to the deflection plate 5.
3. Also, the length of the electron beam in the X direction is approximately 5
It was controlled as much as possible.

Next, under the conditions of a beam acceleration voltage of 10 kV and a beam current of 32 mA, the electron beam 55 is accelerated at a speed of 1 by a magnetic field generated by a magnetic field generator (not shown) comprising, for example, a coil.
The sample substrate 57 is heated by scanning in the Y direction (direction perpendicular to the X direction) at 00 mm/s to perform recrystallization.

FIG. 8 shows a graph showing the flow from the seed crystal portion (opening in the insulating film) when the upper polycrystalline silicon film, which becomes the single crystal silicon film 41 shown in FIG. 4, is recrystallized using the method of this embodiment. 3 is a diagram showing the relationship between the distance, the maximum temperature of the thermal history of the upper polycrystalline silicon film, and the maximum temperature of the thermal history of the single crystal silicon film 39. FIG. In the figure, a solid line 63 represents the maximum temperature of the single crystal silicon film 39, and a solid line 67 represents the maximum temperature of the upper polycrystalline silicon film.

For comparison, we also investigated the maximum temperature of the thermal history of the silicon film when the upper polycrystalline silicon film, which will become the single crystal silicon film 9, was recrystallized using the conventional method shown in FIG. Ta. In FIG. 8, a broken line 65 indicates the maximum temperature of the single crystal silicon film 6, and a broken line 69 indicates the maximum temperature of the upper polycrystalline silicon film.

As can be seen from this figure, in the conventional method, the upper polycrystalline silicon film that is made into a single crystal loses heat to the lower film etc. at the seed crystal part, so the maximum temperature there is equal to the melting point temperature of silicon ( 1414 DEG C.), and areas away from the seed crystal part are overheated because they are preheated by beam energy during single crystallization. Further, since the heat of the upper polycrystalline silicon film flows into the single crystal silicon film 6 through the seed crystal portion, the maximum temperature at the seed crystal portion exceeds the melting point of silicon. This causes deterioration of film quality.

On the other hand, in the case of this embodiment, since the opening is formed in the above-mentioned relationship, even if the seed crystal part is irradiated with an electron beam having an optimum irradiation energy density for melting, the upper The maximum temperature of the upper polycrystalline silicon film is approximately 100% because the seed crystal part of the polycrystalline silicon film does not lose heat to the lower film, etc., and the region where the element is formed does not overheat. becomes constant. For the same reason, single crystal silicon film 39
The temperature is also kept below 1000℃.

FIG. 9 shows measurement results showing the relationship between the oxygen concentration in the single crystal silicon film formed by the method described above and the temperature of the molten silicon film. In addition, the oxygen concentration is SIM
The temperature was measured using a photothermometer.

[0041] The reason why oxygen got mixed into the single-crystal silicon film is thought to be because oxygen diffused into the silicon dioxide film, which is an insulating film formed therebelow.

As can be seen from this figure, when the temperature of the silicon film exceeds the melting point of silicon (1414.degree. C.) by only about 150.degree. C., the amount of oxygen mixed in increases four times. Therefore, if overheating is prevented using the method of this embodiment, a single crystal silicon film with a sufficiently small amount of oxygen mixed in can be obtained.

[0043] Furthermore, when an n-type MOS transistor was formed using the upper single crystal silicon film obtained in this way and its mobility was investigated, the value was 550 cm2.
/V·s, and a good result was obtained. On the other hand, the mobility value of an n-type MOS transistor formed using the conventional method is 320 cm2 /V・s due to the influence of oxygen contamination.
It was only a moderate amount.

Furthermore, when an element is formed on the lower single-crystal silicon film obtained by the conventional method as shown in FIG.
Although deterioration of characteristics such as a change in threshold value was observed, such deterioration of characteristics was not observed when the lower single crystal silicon film obtained in this example was used.

Note that the present invention is not limited to the embodiments described above. In the above embodiment, the case of using a polycrystalline silicon film has been described, but similar effects can be obtained even if an amorphous silicon film is used instead of the polycrystalline silicon film.

Furthermore, although the shape of the opening is cylindrical, similar effects can be obtained by using other shapes, such as polygons. In addition, various modifications can be made without departing from the gist of the present invention.

[0047]

As described above, according to the method for forming a single crystal semiconductor film of the present invention, an appropriate amount of heat can be released from a non-single crystal film through the opening, so that a high quality single crystal film can be formed. Obtainable.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining a conventional method for forming a single-layer single-crystal silicon film.

FIG. 2 is a diagram for explaining a conventional method for forming a multilayer single crystal silicon film.

FIG. 3 is a diagram for explaining a method for forming a single crystal silicon film according to an embodiment of the present invention.

FIG. 4 is a diagram for explaining a method for forming a single crystal silicon film according to another embodiment of the present invention.

FIG. 5 is a top view of the sample substrate shown in FIG. 4;

FIG. 6 is a diagram showing an example of an electron beam scanning method.

FIG. 7 is a diagram showing a modulated wave used for deflecting an electron beam.

FIG. 8 is a diagram showing the relationship between the distance from the seed crystal portion and the maximum temperature of the thermal history of each silicon film when recrystallizing the upper polycrystalline silicon film.

FIG. 9 is a diagram showing the relationship between the oxygen concentration in a single crystal silicon film and the temperature of the melted silicon film.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1...Silicon substrate, 2...Seed crystal part, 3...Silicon dioxide film, 5...Polycrystalline silicon film, 6...Single crystal silicon film, 7
... silicon dioxide film, 9 ... polycrystalline silicon film, 10 ... seed crystal part, 11 ... silicon substrate, 13 ... silicon dioxide film, 15 ... single crystal silicon film, 17 ... silicon dioxide film,
19... Single crystal silicon film, 21... Silicon dioxide film, 2
3... Single crystal silicon film, 25, 27... Opening, 29... Semiconductor substrate, 31... Insulating film for element isolation, 33... Source/drain, 35... Gate electrode, 37... Gate insulating film, 38
...Interlayer insulating film, 39... Single crystal silicon film, 41... Single crystal silicon film, 43, 45... Scanning direction of electron beam, 47
...beam light source, 49...spot beam, 51...oscillator,
53... Deflection plate, 55... Electron beam, 57... Sample substrate, 5
9...Sine wave, 61...Modulated wave, 63, 65, 67, 69...
temperature curve.

Claims (2)

[Claims] 1. A single crystal semiconductor film formed on a first insulating film having a plurality of openings, the first insulating film having a distance from the plurality of openings in the first insulating film. A step of forming a second insulating film having a plurality of openings having a thickness of five times or more the film thickness, a step of forming a non-single crystal semiconductor film on the second insulating film, and an energy beam A method for manufacturing a semiconductor single crystal film, comprising the step of single crystallizing the non-single crystal semiconductor film by irradiation. 2. A step of forming an insulating film on a single-crystal semiconductor film, wherein the distance between openings in the insulating film is 1 of the thickness of the insulating film.
a step of forming a plurality of openings whose size is greater than or equal to 20 times, and a step of forming a non-single crystal semiconductor film on the insulating film;
A method for manufacturing a semiconductor single crystal film, comprising the step of irradiating the non-single crystal semiconductor film with an energy beam to single crystallize the non-single crystal semiconductor film.