JP3229750B2 - Polycrystalline semiconductor film, semiconductor device and solar cell using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polycrystalline semiconductor film, a solar cell using the polycrystalline semiconductor film as a photoelectric conversion layer, and a thin film transistor using the polycrystalline semiconductor film as a channel layer.

[0002]

2. Description of the Related Art In recent years, thin film transistors have been widely used as driving elements for liquid crystal displays, contact image sensors, and the like. In this thin film transistor, a thin film semiconductor is used as an active layer for controlling a carrier traveling path.

[0003] Unlike a conventional single-crystal semiconductor, this thin-film semiconductor has a feature that it can be formed on an insulating substrate such as glass or quartz, and can be formed on a relatively large-area substrate. However, it has been possible to apply to devices that are difficult with conventional single crystal semiconductors.

Conventionally, an amorphous semiconductor typified by an amorphous silicon film has been mainly used as such a thin-film semiconductor. However, an amorphous semiconductor film has a problem in terms of physical properties. Because of its low carrier mobility, its application range was limited.

[0005] This mobility problem cannot be solved by, for example, a conventional thin film transistor made of an amorphous semiconductor film, and an integrated circuit (IC) for a driving element is mounted on the support substrate on a chip. A step of connecting the IC and an element formed on the substrate by wire bonding has been required.

Accordingly, a polycrystalline semiconductor film has recently been receiving attention and being studied as a material that can replace the amorphous semiconductor. There are various types of polycrystalline semiconductor films depending on the formation method. In particular, research on a method of forming a polycrystalline semiconductor film capable of forming a large area at a low temperature has been actively conducted.

This polycrystalline semiconductor film has a carrier mobility three orders of magnitude higher than that of the above-mentioned amorphous semiconductor film, so that it is not necessary to adopt the above-described steps, and it is possible to incorporate all elements on a supporting substrate. This makes it possible to reduce manufacturing costs and the like.

On the other hand, in the field of solar cells, a solar cell using a thin-film polycrystalline semiconductor is expected to be able to increase photoelectric conversion efficiency at low cost. In a solar cell made of this polycrystalline semiconductor film, it is an essential condition for increasing the crystal grain size in the polycrystalline semiconductor film and improving the carrier mobility in the film.

As a specific method of manufacturing a polycrystalline semiconductor film, a method of directly forming a polycrystalline semiconductor film by chemical vapor deposition (CVD), or a method using an amorphous semiconductor film as a starting material, A so-called solid phase growth method in which a polycrystalline semiconductor film is formed by performing a heat treatment for several tens of hours at a temperature range of about 600 ° C. to form a polycrystalline semiconductor film, and further, a laser or the like is applied to the amorphous semiconductor film as a starting material. By irradiating the energy beam,
A laser recrystallization method or the like in which a polycrystalline semiconductor film is locally melted to obtain a polycrystalline semiconductor film has been proposed.

Generally, the crystal grain boundaries are ones that greatly affect the electrical characteristics of the polycrystalline semiconductor film. A polycrystalline semiconductor film usually consists of a set of a large number of crystal grains surrounded by the crystal grain boundaries, and the crystal grain boundaries act to hinder carrier traveling in the semiconductor film. I do. Therefore, it is important to form a polycrystalline semiconductor film so as to suppress generation of such crystal grain boundaries.

In this respect, among the above-mentioned various manufacturing methods, a polycrystalline semiconductor film formed by a solid phase growth method or a laser recrystallization method usually has a large crystal grain of several μm, and thus the result is large. As a result, the number of crystal grain boundaries can be reduced, and a favorable polycrystalline semiconductor film can be formed. For example, as disclosed in U.S. Pat. No. 5,221,365, an amorphous semiconductor film formed on a substrate having fine irregularities on its surface is subjected to a heat treatment so that a large-sized amorphous semiconductor film is formed. There is a method for forming a crystalline semiconductor film.

[0012]

However, according to the above-described method for forming a polycrystalline semiconductor film, although relatively large crystal grains can be obtained, the position of the crystal grain boundary in the film plane of the polycrystalline semiconductor film is determined. There is no control. That is, the crystal grain boundaries in the film plane in the formed polycrystalline semiconductor film are the heat efficiency and heat conduction in the polycrystallized film, or the surface state of the substrate used, the nucleation position, the crystal growth rate, etc. The position is determined by various factors, and it is not possible to control the position of the crystal grain boundary and the size of the crystal grain which is to be concomitantly determined.

For this reason, for example, if a crystal grain boundary exists in the polycrystalline semiconductor film serving as a channel region of the thin film transistor, the traveling of carriers is hindered, and good switching characteristics cannot be obtained. turn into.

[0014] Also in the solar cell, the generation efficiency per unit area is reduced due to the random existence of crystal grain boundaries that do not contribute to power generation. Further, there is a problem that the photocarriers are recombined at the crystal grain boundaries and adversely affect the photoelectric conversion characteristics.

Accordingly, the present invention has been made to solve the above-mentioned problems, and a first object of the present invention is to provide a polycrystalline semiconductor film in which the position of a crystal grain boundary in a film plane is controlled, and It is to provide a manufacturing method thereof.

A second object of the present invention is to provide a thin film transistor having a large grain size and having good switching characteristics without the presence of crystal grain boundaries in a polycrystalline semiconductor film serving as a channel region. .

A third object of the present invention is to provide a solar cell using a polycrystalline semiconductor film having a large grain size and controlling a grain boundary that does not contribute to power generation to improve current collection efficiency.

[0018]

A polycrystalline semiconductor film according to the present invention is provided with a plurality of bumps having minute planes on a surface thereof, so that the surface is uneven due to a step between adjacent regions. A polycrystalline semiconductor film formed thereon, wherein a crystal grain boundary in a film plane of the polycrystalline semiconductor film is provided on a step of the substrate, and a height difference due to the step is reduced. , 30 ° or more and 500 ° or less.

[0019]

The solar cell according to the present invention has a first electrode provided with a large number of regions having a fine flat surface with a large number of irregularities on the surface, and a step for controlling a grain boundary between adjacent regions. As a substrate, a polycrystalline semiconductor film of one conductivity type including a crystal grain boundary whose position is controlled by reflecting the uneven shape of the substrate surface on the substrate, and a polycrystalline semiconductor film of another conductivity type formed on the polycrystalline semiconductor film. A semiconductor layer, and a transparent electrode formed on the semiconductor layer, wherein a crystal grain boundary in the polycrystalline semiconductor film is provided on a step of the substrate, and a transparent crystal positioned at the crystal grain boundary is provided. A collecting electrode is provided on the electrode.

The thin film transistor according to the present invention comprises a plurality of regions having a fine flat surface provided with a plurality of irregularities on the surface,
A substrate provided with a step for controlling a grain boundary between adjacent regions, a polycrystalline semiconductor film including a grain boundary whose position is controlled on the substrate by reflecting the uneven shape of the substrate surface; the region between the grain boundaries as a channel region, a source formed across the channel region, a drain region, Tona is, the crystal grain boundary in the film of the polycrystalline semiconductor film
Are provided on the step of the substrate .

[0022]

According to the polycrystalline semiconductor film of the present invention, the orientation of the crystal in a specific direction in a crystal grain surrounded by a crystal grain boundary provided on a step between adjacent regions having minute planes is adjusted. It is also possible to make them uniform, so that the electrical characteristics in the semiconductor film can be made uniform.

According to the solar cell of the present invention, the collector electrode for collecting photocarriers is generally provided on the surface of the polycrystalline semiconductor film portion where the crystal grain boundary whose position is specified by the step of the substrate exists. A collecting electrode is provided in the vicinity of the crystal grain boundary that recombines the photocarriers and adversely affects the photoelectric conversion characteristics, so that occurrence of such recombination can be suppressed.

When the polycrystalline semiconductor film of the present invention is used as a channel region of a thin film transistor, a state where no crystal grain boundary exists in the polycrystalline semiconductor film portion of the channel region can be formed. An element having good switching characteristics can be obtained without obstruction of carrier traveling due to a large grain boundary.

[0025]

1A to 1D are cross-sectional views of an element structure showing a method of manufacturing a polycrystalline semiconductor film according to the present invention for each step. In the first step shown in FIG.
Substrate 1 made of glass or quartz on which _X or SiO ₂ is formed
In order to form a large number of regions having minute planes of an arbitrary shape on the surface of the substrate, a resist 2 is formed by patterning using conventionally known photolithography.

Next, in a second step shown in FIG. 1B, the surface of the substrate on which the resist 2 is formed is etched by reactive ion etching, and then the resist 2 is removed. Thereby, a large number of regions 3 having minute planes are formed,
Asperities are formed on the substrate surface.

For patterning with the resist 2, for example, a resist pattern as shown in FIG. 2A is used so that a step 4 is formed between the regions 3 by the etching. FIG. 2A is a vertical view of the substrate 1 from the surface side of the substrate 1 shown in FIG. 1A, and a resist 2 formed on the substrate 1 is patterned in a line shape.

In such a case, since the portion (corresponding to 2) that is not etched by the protection of the resist and the portion 2 'to be etched are divided into a line shape, the regions 3, 3 are etched. A step 4 is formed between them. (See FIG. 1B). Particularly, in the case of polycrystallization by an energy beam, it is preferable that the step is clear. For example, the surface shape of the uneven portion due to the step is preferably as close to 90 ° as viewed in cross section.

In this embodiment, the size of the region is 0.1 μm to 100 μm between each line as the short side direction of the line.
m, and the reactive gas for the reactive ion etching is CHF ₃ gas, CH ₄ , H ₂ and N ₂ when the substrate material is quartz or a glass substrate on which a SiO ₂ film is formed. ₂ mixed gas etc. can be used.

Particularly, in the present invention, the selection of the size of the region is important, but in addition, the setting of the size (depth) of the step is also an important factor.

The size of the step depends on the degree (depth) of the etching by the reactive ion etching in the second step.
In general, in order to obtain the effect of the present invention, the depth is preferably set to 30 ° to 500 °, and more preferably, set to a range of 50 ° to 300 °. In particular, when the angle is 30 ° or less, no crystal grain boundary is generated in such a stepped portion. On the other hand, when the angle is 500 ° or more, crystal grains in a minute region are largely separated at the stepped portion, and a continuous polycrystalline semiconductor film cannot be formed. This is because it occurs. These have all been clarified by the results of observation with an electron microscope.

In this embodiment, the shape of the minute region is a line shape as shown in FIG. 2A. However, the present invention is not limited to this. What is necessary is just to determine the shape, specifically, a rectangular shape,
Any shape such as a lattice shape, a rhombus shape, and a circular shape may be used.

Further, the size of the steps due to the adjacent minute regions does not need to be all the same as in the present embodiment.
Irregularities may be used as long as the depths fall within the above range.

Next, in a third step shown in FIG. 1C, an amorphous semiconductor film 5 made of amorphous silicon is formed on the surface of the substrate 1 on which the minute regions have been formed. The film thickness is 300
The thickness is set to {1200} so as to cover the four steps. The amorphous semiconductor film 5 is formed by, for example, a plasma CVD method, and the film forming condition is silane (Si).
H ₄₎ gas flow 30~80sccm (Standar
d Cubic Centimeters per M
inute), substrate temperature 100-600 ° C, pressure 1
3.3 to 266 Pa, power is 13.56 MHz, 3 to
100W.

Then, in the fourth step shown in FIG.
By irradiating the energy beam 6 to the amorphous semiconductor film 5 and polycrystallizing the irradiated area, a polycrystalline semiconductor film 7 made of polycrystalline silicon can be obtained.

FIG. 2B is a schematic view of the polycrystalline semiconductor film obtained by such a process. This figure is also a view seen from a direction perpendicular to the surface of the substrate, as in FIG. 2A. According to this figure, the crystal grain boundaries 8 are formed so as to be aligned with the linear stepped portions 4. It can be seen that the crystal growth in the lateral direction has stopped at the step.

As can be seen from FIG. 2B, since no step was formed in advance in the longitudinal direction of the line, the crystal growth was stopped by various conventional factors, and the shape of the crystal grain boundary and the The positions are random.

As the amorphous semiconductor film irradiated with the energy beam, a film formed by the CVD method in this embodiment is used, but the present invention is not limited to such a manufacturing method. In addition, a film formed by a vapor deposition method, a sputtering method, or the like may be used, and a semiconductor film to be irradiated with an energy beam may be a polycrystalline film. In this case, by irradiating the initially poor polycrystalline semiconductor with an energy beam, it becomes possible to modify a high-quality polycrystalline semiconductor film in which the position control of the crystal grain boundary, which is an effect of the present invention, is performed.

A specific example of the poor polycrystalline semiconductor film is a polycrystalline silicon film formed at a low temperature such as a normal temperature. It has a very large number of grain boundaries and an extremely small carrier mobility. However, regardless of whether the film is an amorphous semiconductor film or a polycrystalline semiconductor film to which an energy beam is irradiated, impurities in the semiconductor film, specifically, Oxygen,
It is preferable that the concentration of hydrogen, nitrogen, carbon and the like be as low as possible. The reason is that any of the impurities acts to inhibit crystal growth during polycrystallization, and therefore, in order to remove these impurities, for example, the ultimate vacuum degree of a semiconductor film forming apparatus is reduced. It is preferable that the concentration of impurities in the semiconductor film be reduced by increasing the temperature or performing a process of releasing impurities in the film by performing a heat treatment after the formation of the semiconductor film.

The energy beam used is as follows:
Short wavelength pulse laser, copper vapor laser, ruby laser, Y
An AG laser or the like, specifically, ArF excimer laser, F ₂ excimer laser, KrF excimer laser, XeCl
An excimer laser, a XeF excimer laser, or the like can be used, and irradiation conditions are as shown in Table 1.

[0041]

[Table 1]

In particular, when irradiating a laser, it is preferable that one irradiation region is irradiated with 10 pulses or more to be polycrystallized. More preferably, the substrate on which the semiconductor film to be irradiated is formed is 100 ° C. to 600 ° C. Irradiation with a laser beam while heating in the following temperature range is suitable for polycrystallization of a film. In particular, the temperature is preferably 200 ° C. or more and 500 ° C. or less in the temperature range,
In this embodiment, the temperature was set to about 400 ° C. to perform polycrystallization.

According to such irradiation, the polycrystallization grows in a lateral direction parallel to the film surface while having an orientation in which the surface free energy of the semiconductor is minimized, that is, an orientation direction.
In particular, when the surface is a silicon film having a free surface, it is oriented to the (111) plane.

Although not used in this embodiment, a cap film made of an oxide film such as SiOx or a nitrogen oxide film such as SiNx is previously formed on the amorphous semiconductor film or the polycrystalline semiconductor film to be irradiated. It is also possible to control the orientation direction to [100] or [110] by irradiating an energy beam through such a cap film.

In such a driving force for crystal growth in the lateral direction, the value of the surface free energy at the position of the step provided in advance on the surface of the substrate serving as an underlayer is due to the different direction of the surface free energy. Will change,
As a result, the lateral crystal growth stops.

Therefore, by controlling the size and position of the region having the minute plane, it is possible to generate a crystal grain boundary at a desired position, and to control the size of the crystal grain by the distance between adjacent steps. The size can be set to a desired value.

According to the present inventors, depending on the setting of the interval between adjacent steps, a crystal grain boundary may be generated in the crystal grains in the region. Since all of the crystal grains that have been decomposed by the crystal grain boundaries are aligned on the (111) plane as described above, even if such crystal grain boundaries are generated in the minute region, However, it has been confirmed that the influence of this hardly affects the electrical characteristics of the polycrystalline semiconductor film.

Therefore, when the polycrystalline semiconductor film of the present invention is used, for example, as a channel region of a thin film transistor, a state where no crystal grain boundary exists in the polycrystalline semiconductor film portion of the channel region can be formed. According to this, the carrier traveling is not hindered by the grain boundary as in the related art, and an element having good switching characteristics can be obtained.

Further, in the polycrystalline semiconductor film of the present invention,
As for the crystallinity in the crystal grains surrounded by the crystal grain boundaries, the defect density in the grains is high quality as compared with a film formed by the solid phase growth method.

Further, the polycrystalline semiconductor film according to the present invention may be used as a semiconductor material for photoelectric conversion in a solar cell. In this case, there is a crystal grain boundary whose position is specified by a step. It is preferable to provide a collecting electrode for collecting photocarriers on the surface of the polycrystalline semiconductor film portion. According to this, since the crystal grain boundary portion that does not contribute to power generation is located below the collector electrode that hinders light irradiation, a decrease in efficiency per unit area can be prevented. Further, by providing a collecting electrode near the crystal grain boundary which generally recombines photocarriers and adversely affects photoelectric conversion characteristics, it is possible to suppress the occurrence of such recombination.

Further, according to the polycrystalline semiconductor film of the present invention, since the position of a crystal grain boundary which causes a phenomenon of a decrease in mechanical strength as a conventional semiconductor can be controlled, the mechanical strength as a semiconductor can be controlled. Thus, for example, it can be used as a polycrystalline semiconductor material for a micromachine.

[0052]

Although only the polycrystalline silicon film has been described in the embodiments, the polycrystalline semiconductor film according to the present invention is not limited to these, and the same applies to a semiconductor film made of germanium or gallium.

Next, the polycrystalline semiconductor film according to the present invention is
Embodiments used as a semiconductor material for photoelectric conversion in an n-junction solar cell will be described with reference to FIGS. 3A to 4E.

First, as shown in FIG. 3A, a large number of small planes having an arbitrary shape are formed in the same manner as in the steps shown in FIGS. 1A and 1B of the above-described embodiment. For this purpose, the resist is patterned and etched by reactive ion etching using the resist as a mask to form irregularities on the surface of the substrate 10. Due to the unevenness, a large number of these regions 12, 12 having minute planes are formed. A step 11 is formed between these regions. In this embodiment, a high melting point metal such as tantalum (Ta) or tungsten (W) is used as a substrate, and this substrate 10 is used as one electrode. The height of the step 11 is 100 to 500 °, and the width between the steps, that is, the width of the minute regions 12 is 200 μm.
２2 cm.

Next, in the step shown in FIG. 3B, an n-type amorphous silicon film 13 doped with phosphorus is formed on the surface of the substrate 10 on which the minute regions 12 and 12 are formed by 500 to 20 nm.
A film is formed by a plasma CVD method to a thickness of 00 Å. The film forming conditions are such that the SiH ₄ gas flow rate is 30 to 8
0 sccm, phosphine (PH ₃ ) gas flow rate is 10 to ₃
0 sccm, substrate temperature 400-600 ° C, pressure 1
3.3-266 Pa, power 13.56 MHz, 30
１００100W.

Next, in the step shown in FIG. 3C, the n-type amorphous silicon film 12 is irradiated with the excimer laser 6 and the irradiated region is polycrystallized, so that the film is made of polycrystalline silicon. An n-type polycrystalline semiconductor film 14 is obtained. The laser energy density at this time was 200 to 500 mJ / cm ² ,
The number of shots was 100 to 1000 shots, and the substrate temperature during laser irradiation was 300 to 500 ° C. At this time, the formed n-type polycrystalline semiconductor film 14 is formed such that the crystal grain boundaries 15 are aligned with the step 11 of the substrate 10.

Subsequently, a step of forming an n-type amorphous silicon film on the n-type polycrystalline semiconductor film 14 in the same manner as the step shown in FIG. 3B, and a step shown in FIG. The polycrystallization by the excimer laser 6 is repeated in the same manner as
An n-type polycrystalline film 14 of about 0 to 50 μm is formed. The film formation of the amorphous silicon and the polycrystallization thereof are repeated as described above because the film thickness of 2 is obtained by the polycrystallization using the excimer laser.
Since the film thickness of about 000 ° is the limit at which a film with good film quality can be obtained, a good film is laminated in multiple layers to obtain a desired film thickness. In addition, when a multilayer is stacked, a polycrystalline semiconductor film stacked thereover inherits above a crystal grain boundary of a base polycrystalline semiconductor film, and a crystal grain boundary is formed at a similar position. That is, the crystal grain boundary 1 is formed at the step 11 portion of the substrate 10.
5 are formed.

Next, in the step shown in FIG. 4D, boron or the like is diffused into the surface of the polycrystalline semiconductor film 14 by thermal diffusion to form a p-type polycrystalline semiconductor layer 16. The bonding depth at this time is 0.
It was 1 μm.

In the step shown in FIG. 4E, a transparent electrode 17 made of ITO or the like is formed on the surface of the p-type polycrystalline semiconductor layer 16 by sputtering at a thickness of 500 to 2,000 ° in the step shown in FIG. (Al) on the step 11 of the polycrystalline semiconductor film 14, that is, on the grain boundary 15 of the polycrystalline semiconductor film 14 whose position is controlled.
Is formed.

As described above, by providing the collecting electrode for collecting photocarriers on the surface of the polycrystalline semiconductor film portion where the crystal grain boundary whose position is specified by the step is present, the photocarriers are generally recombined and the photoelectric conversion is performed. A collecting electrode is provided in the vicinity of the crystal grain boundary, which adversely affects the conversion characteristics, and the occurrence of such recombination can be suppressed.

Next, the polycrystalline semiconductor film according to the present invention is
A second embodiment used as a semiconductor material for photoelectric conversion in an n-junction solar cell will be described with reference to FIGS. 5 (A) to 5 (D).

As in the steps shown in FIGS. 3A to 3C of the first embodiment, the surface 11 of the Ta, W high melting point metal substrate 10 has a step 11 of 100 to 500.degree. Are formed so as to be 200 μm to 2 cm, and a large number of minute regions 12 are formed. Then, an n-type amorphous silicon film 13 doped with phosphorus is formed to a thickness of 500 to 2000 ° by a plasma CVD method. Then, the amorphous silicon film 13 is polycrystallized using the excimer laser 6 to form an n-type polycrystalline semiconductor film 14 having a crystal grain boundary 13 at the step portion 11 of the substrate 10.

Next, in the step shown in FIG. 5A, the amorphous silicon film 2 doped with phosphorus is
0 is formed by a plasma CVD method in a film thickness of 10 to 50 μm. The film forming conditions are such that the flow rate of the SiH ₄ gas is 30 to 80.
sccm, PH ₃ gas flow rate is 10-30 sccm, substrate temperature is 400-600 ° C., pressure is 13.3-266P
a, The power is 13.56 MHz, 30 to 100 W.

Subsequently, in the step shown in FIG. 5B, the amorphous silicon film 20 is polycrystallized by a solid phase growth method in which the amorphous silicon film 20 is crystallized at 500 to 700 ° C. for 20 hours. To form At this time, as shown in FIG. 5B, the formed polycrystalline silicon film 21 inherits information of the crystal grain boundary 15 of the underlying polycrystalline silicon film 14, and the grain boundary 15 is formed at a similar position.

Next, in the step shown in FIG. 5C, boron or the like is diffused into the surface of the polycrystalline semiconductor film 21 by thermal diffusion to form a p-type polycrystalline semiconductor layer 22.

Then, in the step shown in FIG. 5D, a transparent electrode 17 made of ITO or the like is formed on the surface of the polycrystalline semiconductor layer 22, and is formed on the step 11 of the substrate 10, that is, on the polycrystalline semiconductor film 2.
A collector electrode 18 made of Al is formed on the crystal grain boundary 15 whose position is controlled.

As described above, by providing the collecting electrode for collecting the photocarriers on the surface of the polycrystalline semiconductor film portion where the crystal grain boundary whose position is specified by the step is provided, the photocarriers are generally recombined and the photoelectric conversion is performed. A collecting electrode is provided in the vicinity of the crystal grain boundary, which adversely affects the conversion characteristics, and the occurrence of such recombination can be suppressed.

Next, a third example in which the polycrystalline semiconductor film according to the present invention was used as a semiconductor material for photoelectric conversion in a solar cell.
An embodiment will be described with reference to FIG. This embodiment uses pn
This is one in which an i-type amorphous silicon layer is interposed at a pn junction interface of a junction type solar cell.

Similar to the steps shown in FIGS. 3A to 3C of the first embodiment, the surface of the Ta, W high melting point metal substrate 10 has a step 11 of 100 to 500.degree. Are formed so as to be 200 μm to 2 cm, and a large number of minute regions 12 are formed. Then, an n-type amorphous silicon film doped with phosphorus is formed to a thickness of 500 to 2000 ° by a plasma CVD method. Then, the amorphous silicon film 4 is polycrystallized using the excimer laser 6 to form an n-type polycrystalline semiconductor film having a crystal grain boundary at the step portion 11 of the substrate 10. Then, similarly to the step shown in FIG. 3C, the polycrystallization by the excimer laser 6 is repeated to form the n-type polycrystalline film 13 having a thickness of about 10 to 50 μm.
Alternatively, as shown in FIG. 4A, an amorphous silicon film doped with phosphorus is formed on a polycrystalline film semiconductor by a plasma CVD method of 10 to 50 μm.
The polycrystalline semiconductor film 21 is formed by forming a polycrystalline silicon film by polycrystallization by a solid phase growth method of crystallizing at 00 to 700 ° C. for 20 hours (FIG. 6A).
reference).

In the step shown in FIG. 6B, i-type amorphous silicon 23 is formed on polycrystalline semiconductor film 21 to a thickness of 20 to 350 ° by a plasma CVD method. The film formation conditions are as follows: SiH ₄ gas flow rate is 30 to 80 sccm, substrate temperature is 400 to 600 ° C., pressure is 13.3 to 266 Pa, power is 13.56 MHz, and 30 to 100 W.

Subsequently, in a step shown in FIG. 6C, a p-type amorphous silicon film 24 is formed on the i-type amorphous silicon film 23 with a thickness of 50 to 100 ° by a plasma CVD method. The film forming conditions are such that the SiH ₄ gas flow rate is 30 to 80 sc
cm, diborane (B ₂ H ₆ ) gas flow rate is 30 sccm, substrate temperature is 400 to 600 ° C., pressure is 13.3 to 266P.
a, The power is 13.56 MHz, 30 to 100 W.

Then, in the step shown in FIG. 6D, a transparent electrode 17 is formed on the surface of the p-type amorphous silicon 24, and the position of the polycrystalline semiconductor film 21 is controlled on the step 11 of the substrate 10, that is. An Al collector electrode 18 is formed on the crystal grain boundary 15.

In this step, an excimer laser is used for forming the underlying polycrystalline semiconductor film, but another laser such as a YAG laser can be used.

As the polycrystallization method, in addition to the above-described energy beam method, a solid phase growth method, a polycrystalline film or an amorphous film formed on a substrate in a vacuum or an inert gas atmosphere may be used. A capping film is formed on SiO ₂ on a polycrystalline film or an amorphous film formed on a substrate by so-called RTA method of rapidly heating and crystallizing with a halogen lamp, and the whole is heated to 1350 ° C. Then, an area of 1 mm in width and 50 to 125 mm in length is defined as 1
Heated and melted to 450 ° C, and this melted area is 1-2 mm / s
A recrystallization method such as a so-called ZMR method in which the whole is crystallized by operating with ec, or a method of heating and melting using a high frequency or an alternating magnetic field can be used.

In each of the above-described embodiments, the collector electrode is provided on the crystal grain boundary whose position is controlled in the polycrystalline semiconductor film. However, the collector electrode is further provided at the center of the crystal grain boundary. May be configured. As described above, by providing the collecting electrode for collecting the photocarriers on the surface of the intermediate portion of the polycrystalline semiconductor film portion where the crystal grain boundaries whose positions are specified by the steps are provided, the occurrence of the recombination of the photocarriers can be further reduced. Can be suppressed, and a decrease in photoelectric conversion efficiency can be suppressed.

Next, an embodiment of a thin film transistor (TFT) using a polycrystalline semiconductor film for a channel portion according to the present invention will be described with reference to FIGS. FIG. 7A is a sectional view of the TFT of this embodiment, and FIG. 7B is a plan view of FIG. 7A viewed from above with the metal wiring removed. In this embodiment, a channel portion of a TFT is formed on a polycrystalline silicon film in which a crystal grain boundary obtained by providing a projection on a substrate is controlled.

As shown in FIG. 7A, on a transparent insulating substrate 30 made of glass or the like, a convex portion 31 having a step of 100 to 500 ° is formed in a portion to be a channel portion of the TFT. On this substrate 30, the above-described polycrystalline semiconductor film 32 of the present invention is provided. P This substrate 30 ^- (or n ^-) type or i-type amorphous silicon film of plasma CV
A film having a thickness of 500 to 1000 ° is formed by the D method or the like, and is polycrystallized by irradiation with an excimer laser, whereby a polycrystalline semiconductor film 32 is obtained. A gate electrode 34 is provided on convex portion 31 of polycrystalline semiconductor film 32 via gate insulating film 33, and n is formed by self-alignment using gate electrode 34 as a mask.
(Or p) type source and drain regions 35 and 36 are provided. Source / drain electrodes 37 and 38 are provided in ohmic contact with the source / drain regions 35 and 36 through the protective film 39 of the gate electrode 34 and the contact holes, respectively. The TFT of this embodiment is
As shown in FIG. 7 (B), the crystal grain boundary 15 that is perpendicular to the channel, i.e., Y-axis direction is a position control so as to be positioned in the stepped portion, the channel portion parallel to the X-axis direction in the crystal grain boundaries 15 runs. Accordingly, a structure in which a current flowing between the source and drain regions does not cross a crystal grain boundary is possible, and a high-speed operation TFT can be manufactured.

Next, the steps of the TFT of this embodiment will be described with reference to FIG.
This will be described with reference to FIGS. In the step shown in FIG. 8A, a p ⁻ -type amorphous silicon film is formed on a transparent insulating substrate 30 such as glass provided with a projection 31 with a step of 100 to 500 ° by, for example, a plasma CVD method.
It is formed with a thickness of 0 to 1000 °. This film formation condition is Si
H ₄ gas flow rate 30~80sccm, B ₂ H ₆ gas flow rate 0～30Sccm, the substrate temperature is 400 to 600 ° C., a pressure 13.3～266Pa, power 13.56 MHz,
30 to 100W. Next, the amorphous silicon film is polycrystallized by irradiating the excimer laser 6 to form a p ⁻ type polycrystalline semiconductor film 32. At this time, the laser energy density is 15
0 to 350 mJ / cm ² , and the substrate temperature is 20 to 400 ° C. By this polycrystallization, the polycrystalline semiconductor film 32 is controlled so that the crystal grain boundary 15 is located at the step.

Subsequently, in a step shown in FIG. 8B, after patterning the polycrystalline semiconductor film 32, a gate insulating film 33 made of SiO _{2 is} formed on the polycrystalline semiconductor film 32.
Substrate temperature of 200 to 600 using a CVD method and a sputtering method.
The film is formed at a temperature of 1000C to a thickness of 1000 to 2000C. Polycrystalline silicon is formed on the gate insulating film 33 by a CVD method or the like at a substrate temperature of 200 to 500 ° C. to a temperature of 500 to 2000 °, and a gate electrode 34 is formed through a photolithography process.

In this state, using the gate electrode 34 as a mask,
By ion implantation to form source and drain regions, P
(Phosphorus) ions are implanted at an energy of 10 to 100 KeV and a dose of 2 × 10 ¹⁵ to 10 ¹⁶ cm ⁻² . Thereafter, activation of the source and drain regions 35 and 36 and recovery of the crystallinity of the gate electrode 34 are simultaneously performed by excimer laser, thermal annealing or the like. Note that activation may not be performed depending on ion implantation conditions and the like.

Next, in the step shown in FIG. 8C, the protective insulating film 39 is formed by a CVD method, a sputtering method or the like to a thickness of 500 to 1000 °.
Form a film. Then, a contact hole penetrating the protective insulating film 39 is formed in a square of 1 to 2 μm on the source and drain regions 35 and 36 by a photolithography process, and a metal film 800 of Al, Cr or the like is formed by a vacuum deposition method, a sputtering method, or the like.
0-15000Å is formed. This metal film is patterned by a photolithography process, and source and drain electrodes 37 and 38 are formed, whereby a thin film transistor can be manufactured. In this step, ion implantation is performed at P
Although ions were used, of course, there is no problem with As (arsenic) ions or the like. Alternatively, the channel region may be formed of an n ⁻ -type or i-type polycrystalline semiconductor film, and B (boron) may be ion-implanted into the source and drain regions.

Next, a second embodiment of a thin film transistor (TFT) using a polycrystalline semiconductor film according to the present invention for a channel portion will be described with reference to FIGS. FIG. 9 is a sectional view of the TFT of this embodiment. In this embodiment, the crystal grain boundary of the polycrystalline semiconductor is controlled by the step of the gate electrode provided on the substrate, and the channel portion of the TFT is formed on the polycrystalline silicon film. As shown in FIG. 9, a transparent insulating substrate 40 made of glass or the like is
A gate electrode 41 made of Mo, Ta, or the like is formed. Due to the gate electrode 41, 〜50 is formed on the substrate 40.
A step of 0 ° will be formed. This gate electrode 4
An insulating film 42 having a thickness of 1000 to 2000 Å is provided on the substrate 40 including the substrate 1 by a CVD method or the like. This insulating film 4
2 is provided with the above-described polycrystalline semiconductor film 43 of the present invention. The polycrystalline semiconductor film 43 is formed by forming an amorphous silicon film on the insulating film 42 by 500 to 1000 by a plasma CVD method or the like.
Å Obtained by forming and polycrystallizing by irradiation with excimer laser. After forming a 500-1000 ° P-doped n-type amorphous silicon or polycrystalline silicon film doped with phosphorus on the polycrystalline semiconductor film 43 by a plasma CVD method or the like, source and drain regions 45 and 46 are formed by patterning. You. Source and drain regions 4
Source and drain electrodes 47, 48 on
Is provided, and the TFT of this embodiment is obtained. In the TFT of this embodiment, similarly to the above-described embodiment, the position of the crystal grain boundary orthogonal to the channel is controlled so as to be located at the step, and the crystal grain boundary runs parallel to the channel portion. Accordingly, a structure in which a current flowing between the source and drain regions does not cross a crystal grain boundary is possible, and a high-speed operation TFT can be manufactured.

Next, a method of manufacturing the thin film transistor according to the second embodiment will be described with reference to FIGS. 10 (A) to 10 (C).

First, the gate electrode 4 is formed on the transparent insulating substrate 40.
A metal layer of Cr, Mo, Ta or the like to be 1 is formed to a thickness of about 500 ° by vapor deposition, sputtering or the like, and this metal layer is patterned to form a gate electrode 41. After that, the insulating film 42
Is formed at a temperature of 200 to 600 ° C. with a thickness of 1000 to 2000 ° by using a CVD method, a sputtering method or the like. And
An amorphous silicon film is formed on the insulating film 42 by PECVD, L
The substrate is formed at a temperature of 100 to 500 ° C. by 500 to 1000 ° by PCVD, sputtering, vapor deposition or the like. Next, the amorphous silicon film is irradiated with an excimer laser 6 to be polycrystallized.
A polycrystalline semiconductor film 43 is formed. The laser energy density at this time is 150 to 350 mJ / cm ² , and the substrate temperature is 2
0 to 400 ° C. By this polycrystallization, the polycrystallized semiconductor film 43 is controlled so that the crystal grain boundary 15 is located at the step (FIG. 10A).

Next, in the step shown in FIG. 10B, an n-type amorphous silicon film or a polycrystalline silicon film doped with P (phosphorus) is
Substrate temperature of 100 to 500 ° C by sputtering, sputtering, evaporation, etc.
500 to 1000 °. The P-doped semiconductor film is patterned through a photolithography process to form source and drain regions 45 and 46.

Subsequently, in a step shown in FIG. 10C, a metal film of Al, Cr, or the like is formed on the source and drain regions 45 and 46 by a vacuum evaporation method or a sputtering method in the range of 8000 to 1500.
0 ° is formed. Then, the metal film is patterned by a photoresist process to form source and drain electrodes 47 and 48.

These TFTs can be used, for example, in a liquid crystal display (LCD). LCDs are divided into a peripheral drive unit that requires high speed and a pixel unit that does not require much speed. Therefore, the TFT used for the peripheral driving circuit may be configured to be manufactured by a conventional manufacturing method in consideration of the yield and the like by increasing the speed with the TFT manufactured in this patent and having a controlled crystal grain boundary.

[0088]

According to the polycrystalline semiconductor film of the present invention, a connection formed on a step between adjacent regions having minute planes is formed.
Crystal grain surrounded by the crystal grains by boundaries, it becomes possible to align the orientation of the crystal in a specific direction, so that the electrical characteristics of the semiconductor film can be made uniform.

According to the solar cell of the present invention, the collector electrode for collecting photocarriers is generally provided on the surface of the polycrystalline semiconductor film portion where the crystal grain boundary whose position is specified by the step of the substrate exists. A collecting electrode is provided in the vicinity of the crystal grain boundary that recombines the photocarriers and adversely affects the photoelectric conversion characteristics, so that occurrence of such recombination can be suppressed.

When the polycrystalline semiconductor film of the present invention is used as a channel region of a thin film transistor, a state in which no crystal grain boundary exists in the polycrystalline semiconductor film portion of the channel region can be formed. An element having good switching characteristics can be obtained without obstruction of carrier traveling due to a large grain boundary.

[Brief description of the drawings]

FIGS. 1A to 1D are cross-sectional views of an element structure showing a method of manufacturing a polycrystalline semiconductor film according to the present invention for each step.

FIGS. 2A and 2B are plan views of a polycrystalline semiconductor of the present invention.

FIGS. 3A to 3C are cross-sectional views illustrating an example in which a polycrystalline semiconductor film of the present invention is used for a pn junction type solar cell in each step.

4 (D) and 4 (E) are cross-sectional views showing the above-described embodiment in each step.

FIGS. 5A to 5D are cross-sectional views showing a second embodiment in which the polycrystalline semiconductor film of the present invention is used for a pn junction type solar cell, in each step.

FIGS. 6A to 6D are cross-sectional views showing a third embodiment in which the polycrystalline semiconductor film of the present invention is used for a pn junction type solar cell, according to each process.

7A and 7B show a thin film transistor using a polycrystalline semiconductor film of the present invention for a channel region, FIG. 7A is a cross-sectional view, and FIG. 7B is a plan view.

FIGS. 8A to 8C are cross-sectional views showing a thin film transistor using a polycrystalline semiconductor film of the present invention for a channel region in each step.

FIG. 9 is a cross-sectional view illustrating a thin film transistor using the polycrystalline semiconductor film of the present invention for a channel region.

FIGS. 10A to 10C are cross-sectional views illustrating a thin film transistor using a polycrystalline semiconductor film of the present invention for a channel region in each step.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 resist 3 minute region 4 step 5 amorphous semiconductor film 8 crystal grain boundary

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoichiro Aya 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP 5-275333 (JP, A) JP Hei 5-275451 (JP, A) JP-A 1-239094 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/18 H01L 21/20 H01L 21/34 H01L 21 / 36 H01L 21/84

Claims (10)

(57) [Claims] 1. A substrate having a large number of irregularities on its surface, a large number of regions having minute planes, and a step for controlling a grain boundary between adjacent regions, and a substrate on the substrate. and a polycrystalline semiconductor film which is formed with a position-controlled crystal grain boundaries inside film reflecting the uneven shape of the surface consists of the upper
The crystal grain boundary in the polycrystalline semiconductor film is
A polycrystalline semiconductor film, which is provided on a step . 2. The height difference caused by the step is 30 ° or more and 5 ° or more.
2. The polycrystalline semiconductor film according to claim 1, wherein the thickness is not more than 00 ° . 3. The surface shape of the uneven portion due to the step is cut off.
3. The method according to claim 2, wherein the plane is formed at an angle of about 90 degrees.
Polycrystalline semiconductor film. 4. A fine plane by providing a large number of irregularities on the surface.
A large number of provided regions, and a grain boundary between the adjacent regions.
A board provided with a step for control, and a board
Includes grain boundaries whose position is controlled to reflect the surface irregularities
A polycrystalline semiconductor film having a semiconductor junction inside;
The crystal grain boundary in the polycrystalline semiconductor film is
A semiconductor provided on a step of the substrate.
Body device . 5. A minute plane by providing a large number of irregularities on the surface.
A large number of provided regions, and a grain boundary between the adjacent regions.
A substrate as a first electrode provided with a step for control;
Position is controlled on the substrate by reflecting the unevenness of the substrate surface.
A polycrystalline semiconductor film of one conductivity type including a crystal grain boundary,
A semiconductor layer of another conductivity type formed on the crystalline semiconductor film;
A transparent electrode formed on a semiconductor layer.
The crystal grain boundaries in the single crystal semiconductor film are
On the transparent electrode located at the crystal grain boundary.
A solar cell comprising an electrode. 6. On a transparent electrode located between steps of the substrate.
6. The device according to claim 5, further comprising a collector electrode.
Solar cell. 7. A substrate provided with a large number of regions having minute planes by providing a large number of irregularities on the surface, and a step for controlling a grain boundary between adjacent regions, and a substrate provided on the substrate. reflecting the uneven surface position-controlled grain boundary of including
A polycrystalline semiconductor film of one conductivity type, and
Intrinsic amorphous semiconductor layer formed and on the intrinsic semiconductor layer
Consisting of an amorphous semiconductor of another conductivity type formed in
The crystal grain boundaries in the polycrystalline semiconductor film are
A semiconductor device provided on a step . 8. A fine plane by providing a large number of irregularities on the surface.
A large number of provided regions, and a grain boundary between the adjacent regions.
A substrate as a first electrode provided with a step for control;
Position is controlled on the substrate by reflecting the unevenness of the substrate surface.
A polycrystalline semiconductor film of one conductivity type including a crystal grain boundary,
An intrinsic amorphous semiconductor layer formed on the crystalline semiconductor film;
Of other conductivity type formed on intrinsic amorphous semiconductor layer
A semiconductor layer and a transparent electrode formed on the amorphous semiconductor layer;
And a crystal in the polycrystalline semiconductor film.
A grain boundary is provided on the step of the substrate and located at the crystal grain boundary.
The collector electrode is provided on the transparent electrode to be placed.
Solar cells. 9. On a transparent electrode located between steps of the substrate.
9. The device according to claim 8, further comprising a collector electrode.
Solar cells. 10. A substrate provided with a plurality of regions provided with a plurality of irregularities on the surface and having a minute plane, and a step for controlling a grain boundary provided between adjacent regions, and a substrate provided on the substrate. A polycrystalline semiconductor film including a crystal grain boundary whose position is controlled by reflecting the unevenness of the surface, and a region sandwiched by the crystal grain boundary are checked.
Channel region and the channel region
A source and drain region, wherein the polycrystalline semiconductor is
A crystal grain boundary in the film is provided on the step of the substrate.
A semiconductor device characterized in that: