JPH03250621A - Manufacture of semiconductor film - Google Patents

Abstract

PURPOSE:To form a polycrystalline semiconductor film having large and uniform grain size or to realize a hetero epitaxial growth at a low temperature by so ion implanting from the surface of an amorphous semiconductor film containing crystal formed on a substrate as to make the projecting distance of the implanted ions longer than the thickness of the amorphous film. CONSTITUTION:An amorphous semiconductor film 2 containing a crystal phase 3 is formed on a substrate 1. For example, the nuclei of the phase 2 is partly formed on the film 2 deposited on the substrate 1 by a plasma CVD, a thermal CVD, etc., by ion implanting. The accelerating energy of the ions to be implanted from the surface of the film 2 is so set that the projecting stroke of the element to be implanted is larger than the thickness of the semiconductor film and the effect of converting to amorphous state due to cascade collision of the implanted ions to the atoms of the semiconductor film and a defect density in a region crystallized in the semiconductor film are reduced. The power density of the ion beam is desirably 0.5-1W/cm<2>. If the power density of the beam is low, the crystal growing speed can be increased by heating the substrate 1(at 50-800 deg.C) when it is ion implanted.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for crystallizing a semiconductor film having an amorphous phase, and in particular to a method for growing a crystalline phase using an ion beam to produce uniform and controlled grains. The present invention relates to a method for forming a polycrystalline semiconductor film having a diameter.

[Prior Art] Conventionally, regarding crystal growth using an ion beam, there is an example in which amorphous silicon formed on a silicon substrate is grown in a solid phase by arsenic ion implantation (Jpn, J.
Appl, Phys, 21 (1982)S
uppl, 21-1. p211) and an example of combining xenon ion implantation and substrate heating during implantation (Nucl
ear Instrument, Meth.

ds Res, B 1, 9/20 (1987) I
)457). Regarding semiconductor films and ion implantation on glass substrates, we also have an example in which ions are implanted into a polycrystalline germanium film or silicon film deposited on quartz glass while heating germanium or silicon to increase the grain size ( Appl, phys, 64 (1,988
) p2337).

These examples using ion beams can perform solid phase growth at lower temperatures than other methods, and are expected to be applied to lower temperature semiconductor processes and three-dimensional integrated circuits.

[Problem to be solved by the invention] However, in the conventional crystal growth method using an ion beam, the projected range of implanted ions is set at the center of the film, so amorphization and crystallization are not balanced. The temperature reached is high, and it was necessary to raise the substrate temperature during ion implantation in order to grow crystal grains.

For example, for polycrystalline silicon films, at least 800°C
It is necessary to heat the substrate during the above-mentioned implantation, and if a material that cannot withstand this temperature is used as a substrate for a semiconductor film, serious problems such as deformation of the substrate shape and diffusion of substrate constituent elements into the semiconductor film may occur. there were.

Further, in the known method of forming crystal nuclei in a solid phase by heat treatment, a high temperature of at least 600° C. or higher is required for, for example, an amorphous silicon film.

[Means for Solving the Problems] The present invention includes a step of forming an amorphous semiconductor film containing crystals on a substrate, and a step of forming an amorphous semiconductor film containing crystals on a substrate, and
This is a method for manufacturing a polycrystalline semiconductor film on a substrate, including a crystal growth step of implanting ions so that the projected range of the implanted ions is larger than the film thickness of the amorphous semiconductor film.

Formation of an amorphous semiconductor film containing a crystalline phase can be achieved by depositing a semiconductor film containing crystal nuclei on a substrate by, for example, known plasma CVD or thermal CVD, or by applying ions to an amorphous semiconductor film deposited on a substrate. This can be achieved by partially nucleating a crystalline phase through injection.

In order to partially nucleate the crystal phase by the ion implantation described above, the acceleration energy of the implanted ions is set so that the projected range of the implanted ions is greater than the thickness of the semiconductor film. This reduces the amorphous effect caused by cascade collisions between the implanted ions and the constituent atoms of the semiconductor film, reduces the defect density in the crystallized region of the semiconductor film, and provides crystal nuclei of good quality. If the acceleration energy is smaller than the above film thickness, the formation density of crystal nuclei will be high in regions where energy devotion is large (although the crystallinity of the crystal nuclei will be inferior to the above conditions). No crystal nuclei are formed in the ion beam.The power density of the ion beam is preferably IW/crr+2 or more.If the power density is low, crystal nuclei can be formed by implanting ions while heating the substrate (50 to 800°C). It is also possible to form a nucleus.

The boundary value of the power density that requires substrate heating (the power density at which the rate of crystal nucleation changes significantly) depends on the type of semiconductor film and substrate,
It varies greatly depending on the ion species. The ion species used is not particularly limited, and is preferably a semiconductor constituent element to be crystallized, a substrate constituent element, or a rare gas element. In addition, even under the desirable conditions of the current density of the ion beam for nucleating the crystalline phase described above, it is possible to grow the crystalline phase while continuing the nucleation of the crystalline phase. The difference in grain size between the crystal grain size due to the crystal nucleus formed in the final stage and the grain size of the crystal formed at the final stage becomes large.

The ion acceleration energy in the step of ion implantation from the surface of the amorphous semiconductor film according to the present invention is set so that the projected range of the implanted element is larger than the film thickness of the semiconductor film, and the implanted ions and the semiconductor film are It is set so that the effect of amorphization due to cascade collisions of atoms is reduced and the defect density in the crystallized region of the semiconductor film is reduced. If the projected range of the implanted element is smaller than the film thickness, there will be parts in the semiconductor film where the ions cannot reach, and crystal phase growth will be difficult to occur in those parts. The power density of the ion beam is preferably 0.5 to IW/cm2. If the power density exceeds the above-mentioned power density, formation of crystal nuclei occurs, and controllability of crystal grain size deteriorates. The power density is 0゜5W・'c
If m 2 or more, crystal growth can be performed without particularly heating the substrate. In addition, if the power density of the ion beam is low, heating (50 to 80
0° C.), it is possible to increase the crystal growth rate. The boundary value of the power density required to heat the substrate changes depending on the type of semiconductor film and substrate, etc. If the semiconductor film is a silicon film, heating the substrate is not necessary if the temperature of the silicon film reaches 200 to 250° C. due to the heating effect of the ion beam. At a temperature below this temperature, growth of an amorphous phase is more likely to occur than growth of a crystalline phase, so it is important for the growth of a crystalline phase to heat the substrate with an external heater to a temperature above this temperature. The type of ion to be implanted is not particularly limited, but it is preferably a semiconductor constituent element to be crystallized, a substrate constituent element, or a rare gas element.

In the present invention, a control step can be provided between the step of forming the semiconductor film containing the crystal described above and the crystal growth step of implanting ions from the surface of the formed amorphous semiconductor film. The control step involves controlling the size or density of the crystals or their spatial arrangement in the film prior to subsequent crystal growth by amorphizing a portion of the crystals included in the semiconductor film containing the crystals. Ion implantation is performed on a portion of the semiconductor film so as to form a polycrystalline semiconductor film with larger and more uniform crystal grain sizes. Implanting ion current density: 0.3 to 0.7W
The acceleration energy of the ions is preferably set so that the projected range of the implanted element is about the same as or larger than the thickness of the semiconductor film.

If the projected range of the implanted element is smaller than the film thickness, it is not desirable because amorphization will not occur at a depth within the semiconductor film that the ions cannot reach. When the power density is higher than the above, the temperature of the semiconductor film becomes 200° C. or higher due to the heating effect caused by ion implantation, and crystal phase growth tends to occur.

The type of ions to be implanted is not particularly limited, but preferably a semiconductor constituent element, a substrate constituent element, or a rare gas element that crystallizes.

As a method of implanting ions into a portion of the surface of the semiconductor film, a method of irradiating the surface of the semiconductor film with a focused ion beam of a predetermined diameter can be used. The crystals in the hollow region into which the ion beam was implanted lose small crystals and become amorphous, and the grain size of relatively large crystals becomes smaller. Conditions such as the acceleration voltage, diameter, ion beam irradiation interval, and time of the focused ion beam may vary depending on the size, density, and spatial distribution of the crystals contained in the amorphous semiconductor film, and may vary depending on the subsequent crystal growth process. , are set so as to obtain a uniform polycrystalline film. In addition, a masking film such as a 5j02 film to be implanted is coated on the amorphous semiconductor film to a predetermined size, and ions are implanted into the exposed parts of the amorphous semiconductor film that are not covered with the masking film. A method can be used. Further, the ion implantation may be performed while heating the amorphous semiconductor film.

Furthermore, if optical absorption occurs due to implanted ions that reach the substrate, two or more types of ions may be implanted to cause these to react (for example, if optical absorption occurs due to silicon implantation, oxygen, nitrogen, etc. are ion-implanted). Light absorption can be suppressed by forming a transparent compound (S]o2 or 5i3Nn in the above example) in the substrate.

[Operations] According to the present invention, accelerated ions are implanted into a semiconductor film, and in the process of decelerating while losing energy, they directly (elastic collision between incident atoms and semiconductor atoms) or indirectly (elastic collision between incident atoms and semiconductor atoms) strike the lattice system. Inelastic collision between incident atoms and semiconductor electron system)
Energy is applied to locally heat the semiconductor film to high temperatures at the atomic level.

The temperature rise caused by this ion beam is short and local, so the average temperature rise of the substrate is much smaller than this, and furthermore, defects caused by ion implantation prevent the movement of semiconductor atoms. By accelerating the crystal growth of the semiconductor film, it is possible to realize crystal growth of the semiconductor film at a low temperature.

In addition, during the formation of crystal nuclei and crystal growth, the acceleration energy setting determined so that the projected range of the implanted ions is larger than the thickness of the semiconductor film is important because it prevents collisions caused by cascading between the implanted atoms and the semiconductor film constituent atoms. Suppressing the effect of crystallization and reducing the defect density within the crystallized region in the semiconductor film,
It works to obtain high quality crystal grains at low temperatures.

[Examples] The present invention will be described below based on Examples. Figures 1 and 2
FIG. 3, and FIG. 4 respectively show Example 1 of the present invention.
2. 3. 4 is a process explanatory diagram. 5 and 6 are diagrams showing the concentration distribution of implanted ions in Example 1,
FIG. 7 is a diagram showing the concentration distribution of implanted ions in Example 4.

Example 1 Plasma CV using silane gas as a raw material was applied on two types of glass substrates: quartz glass and alkaline earth/alumina borosilicate glass (trade name 7059 glass manufactured by Hooning).
An amorphous silicon film containing crystal nuclei was deposited to a thickness of 150 nm by method D (FIG. 1(a)). Next, we would like to implant silicon ions without heating the substrate at an acceleration energy of 180 keV, a dose of 5 x IO 16 cm2, and a beam current density of 6 μA/cm2 (Fig. 1(b)). The result of calculating the situation (using LSS theory) is shown in the fifth
As shown in the figure. These samples were compared before and after ion implantation by transmission electron microscopy and transmission electron diffraction. It was confirmed that the silicon film, which was amorphous including crystal grains of about 50 nm before ion implantation, had grown into a polycrystalline silicon film with crystal grains of about 600 nm. When the current density of the ion beam was changed, it was 3 μA /' cm 2
1 below! It has become clear that the growth of grains is extremely reduced when the flow density is increased. Further, the final grain size of the crystal grains was determined by the density of crystal nuclei, and the grain size of the crystal grains did not increase even if the dose amount was increased. Therefore, crystal growth ended when the entire area of the amorphous silicon layer changed to polycrystal.

On the other hand, the current density of the ion beam was reduced to 2 μA/c.
When the substrate was heated to about 300° C. and ions were implanted, a polycrystalline silicon film having the same grain size as in the case where the substrate was not heated was obtained on both glass substrates.

Furthermore, in order to oxidize the silicon implanted into the substrate, oxygen was accelerated with an energy of +10 keV, Dozu! 1x10+7
Figure 1 C).

The implantation depth of oxygen was made to match that of silicon, and the implantation amount was twice that of silicon. The oxygen concentration distribution calculated under these conditions is shown in FIG. After forming a pattern on the polycrystalline silicon film and examining the light absorption of the silicon-etched area, it was found that the light absorption was significantly suppressed compared to the case where oxygen was not implanted.

Example 2 Plasma CVD was performed on the same two types of glass substrates as in Example 1.
An amorphous silicon film containing crystal nuclei was deposited to a thickness of 150 nm by the method. On top of this, silicon oxide was deposited to a thickness of 200 nm by a sputtering method, and square masks each having a side of 500 nm were provided every 3 μm on the oxide film through a photophosphorographic process (FIG. 2(a)). Next, the silicon was accelerated with an energy of 100 keV, a dose of 1X10" pieces/cm2,
Beam current density 1μA.・I want to implant ions using Cm2 without heating the substrate and make the part without 77 amorphous amorphous (Fig. 2(b)). After that, the silicon oxide film is removed, and the silicon is further accelerated with an energy of 180 keV and a dose of It5xl□.
+a pieces/cm2, beam current density 2μA,/cm2
2. Ion implantation is performed under the condition of heating the substrate to 300° C. (Figure 2 (C)). When this sample was evaluated by transmission electron microscopy and transmission electron beam diffraction, it was found that a polycrystalline silicon film with a relatively uniform grain size of about 3 μm was formed on each glass substrate.

Example 3 Plasma CVD was performed on the same two types of glass substrates as in Example 1.
An amorphous silicon film with a thickness of 150 nm was deposited by the method (
Figure 3(a)). Next, accelerate the silicon with an energy of 180
Ion implantation was performed under the following conditions: k e V, dose: 3×10''/cm 2 , beam current density: 10 μA/cm 2 , and without heating the substrate to form a crystalline phase (FIG. 3(b)).

After this, in order to reduce the density of the crystal phase, the silicon is accelerated with an energy of 18Q ke V and a dose of jllx+
0+s pieces, /Cm2, Beam current density: 1μA/cm
”, ions were implanted under the conditions of heating the substrate to 200°C, and the crystalline phase with small grain size was made amorphous (Figure 3 (C)).Furthermore, the remaining crystalline phase was grown to crystallize the entire film. In order to
Accelerate silicon with energy 180keV and dose 5X10
16 pieces, 'C1n2, beam current density 2μA/Cm2,
Iono-implantation was carried out under the condition of substrate heating at 300°C (Fig. 3(d)
)). When this sample was evaluated by transmission electron microscopy and transmission electron beam diffraction, it was found that a polycrystalline silicon film with a grain size of about 3 μm was formed. In addition, the sample processed up to Figure 3 (C) was heated to 600°C in a nitrogen atmosphere.
When a similar evaluation was performed with time heat treatment, 3 μm
It was found that a polycrystalline silicon film with a grain size of about 100 mL was formed on each substrate. Note that crystal growth by heat treatment was also possible using a laser or a lamp.

Example 4 An amorphous silicon film with a thickness of 150 nm was deposited on a single crystal gallium arsenide substrate by sputtering (Fig. 4(a)).
. Next, add argon to the acceleration energy of 280 k e
Ion implantation was performed under the following conditions: V, dose: 115xl□+a, /Crr: 12, beam current density: 2 μA, 'Cm2, substrate heating: 250° C. (Fig. 4(b)). FIG. 7 shows the distribution of the injected argon. These samples were compared before and after ion implantation by transmission electron microscopy and transmission electron diffraction. It was observed that the silicon film, which was amorphous before ion implantation, had grown into a bubble-like single crystal silicon film.

Note that defects in the gallium arsenide substrate caused by argon implantation could be recovered by heat treatment.

[Effects of the Invention] According to the present invention, the formation or heteroepitaxial growth of a polycrystalline semiconductor film with a large grain size and uniform grain size, which was previously impossible, can be realized at a low temperature. According to the present invention, substrates that could not be used for semiconductor binding due to thermal deformation or diffusion of substrate constituent elements in conventional heating-based high-temperature processes can be used.

[Brief explanation of drawings]

FIG. 1, FIG. 2, FIG. 3, and FIG. 4 are diagrams for explaining a method of manufacturing a polycrystalline semiconductor film according to the present invention. Fifth
6 and 7 are diagrams for explaining the 1 degree distribution of ions implanted in Examples 1 to 3 of the present invention. 3 crystal phase 2ax, *Silicon film Si” Si” Si” Si”11111i1 459 Yashoj Moon Seal★ Fig. Amorphous silicon film +liN 甚１( +++1+++ Sl" +++++++++1 Figure Ar◆ Ar4- Ar+ Ar◆+l1itf
l1 8 Single crystal silicon film Figure 5 Depth/nm Figure 6 Figure 7 Procedure amendment September 29, 1990

Claims (1)

[Scope of Claims] 1) A step of forming an amorphous semiconductor containing crystals on a substrate, and determining that the projected range of implanted ions from the surface of the formed amorphous semiconductor film is A method for manufacturing a polycrystalline semiconductor film on a substrate, including a crystal growth step of implanting ions so that the film becomes larger than the film thickness. 2) The crystal part included in the amorphous semiconductor film,
Prior to the crystal growth step, a control step of adjusting the density and/or position of the crystal by making it amorphous,
3) The method according to claim 1, characterized in that the controlling step comprises implanting ions by irradiating the surface of the amorphous semiconductor film with a focused ion beam at intervals. The method according to claim 2. 4) The controlling step comprises masking the surface of the amorphous semiconductor film into a predetermined shape, and then implanting ions from the exposed surface of the amorphous semiconductor film that is not masked. the method of. 5) The crystal growth step is a heteroepitaxial growth step in which the substrate is a single crystal semiconductor or a single crystal insulator, and the amorphous semiconductor film has a composition different from that of the substrate. The method described in any of Section 4.