JP3495035B2 - Silicon film fabrication method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high quality semiconductor film applicable to a thin film device by a low temperature process.

[0002]

2. Description of the Related Art A sputtering method is known as a method of obtaining a semiconductor film by a low temperature process, but a semiconductor film having electric characteristics that can be practically used cannot be obtained. For example, when an I-type semiconductor is produced and used, a known III-valent compound that imparts oxygen or a P- or N-type conductivity type to a target,
Since a large amount of V-valent impurities are present, a good quality I-type semiconductor film cannot be obtained by the sputtering method.

Further, P or N is conventionally formed by the sputtering method.
As a method of obtaining a single-conductivity-type semiconductor film, for example, if a single-conductivity-type silicon film is to be obtained, a target obtained by adding an impurity imparting one-conductivity-type to single-crystal silicon is used, and an argon-only atmosphere Or sputtering in an argon atmosphere to which a reaction gas (for example, Phoshin) containing an element imparting one conductivity type is added using a single crystal silicon target to which an impurity imparting P or N type is not added. It is believed that this is a known method. But in the traditional way
It was not possible to obtain a P-type or N-type semiconductor film that is a semiconductor of one conductivity type having a conductivity of 10 ⁻⁵ (Ωcm) ⁻¹ or more. This is because the impurities imparting the P or N type conductivity do not substitute in the semiconductor to serve as donors or acceptors.

[0004]

DISCLOSURE OF THE INVENTION The present invention uses a sputtering method which can form a film at a low temperature and is excellent in productivity, such as a good quality semiconductor film, for example, an I type semiconductor and a semiconductor having one conductivity type having a high conductivity. It is an object of the invention to manufacture a film.

[0005]

The present invention is a method for forming a semiconductor film by sputtering in an atmosphere in which the partial pressure ratio of hydrogen in an inert atmosphere such as argon containing hydrogen is preferably 30% or more. And a method for making the substrate in an insulating state, that is, a floating state, and a method for producing a semiconductor film by producing a semiconductor film by sputtering with a distance between the substrate and the target being 90 mm or more. The reason why the substrate is made floating is to prevent ion bombardment against the substrate that occurs when the substrate is set to the ground potential. 90mm distance between substrate and target
The semiconductor film obtained by sputtering in an inert atmosphere containing hydrogen is separated from the above, and in an atmosphere in which a large amount of hydrogen is present at the time of sputtering, the atomic clusters that pop out from the target and form the target are hydrogen. This is because it is easy for the dangling bonds of the cluster to be neutralized by hydrogen while flying in the plasma.
This cluster reaches the substrate and bonds with other clusters via hydrogen. Therefore, when a cluster in which the dangling bonds are neutralized by hydrogen reaches the substrate from the target and the partial pressure ratio of hydrogen during film formation is large, the cluster frequently collides with hydrogen atoms, so that the silicon cluster is unpaired. The number of bonds is reduced, and the bonds of silicon clusters through hydrogen are more dense, so that a dense semiconductor film (for example, a silicon film) can be obtained.

However, when the hydrogen partial pressure ratio in an inert gas such as argon is increased to 80% or more, the film forming rate becomes extremely poor, and the good productivity characteristic of the sputtering method cannot be utilized. Further, when the hydrogen partial pressure ratio was set to about 30%, a practical film formation rate was obtained and a certain degree of film characteristics were obtained. This can be seen from the graph of FIG. 2 showing the relationship between the hydrogen partial pressure during sputtering and the Raman spectrum of the formed intrinsic silicon semiconductor film. It can be seen that when the hydrogen partial pressure is 30% or more, a sharp peak showing crystallinity appears. From this figure, a peak shifted to the low frequency side from the peak 521 cm ^-1 of single crystal silicon is observed. The peak shifted to the low frequency side from 521 cm ^-1 shows a crystalline state having a weak lattice strain. Also, the apparent grain size is 50 to 500 Å when calculated from the full width at half maximum, and it looks like a microcrystal. However, in reality, there are many regions with high crystallinity and they have a cluster structure. It can be seen that a film having a semi-amorphous structure in which silicon is bonded to each other (anchoring) is formed. The semiconductor film having the Raman spectrum shown in FIG. 2 has a substrate temperature of 150 ° C., a film forming pressure of 0.5 pa, and a distance between the substrate and the target of 80 mm using a single crystal silicon target. The film forming atmosphere is a mixed atmosphere of argon and hydrogen, and the RF output is 400 W.

If the hydrogen partial pressure at the time of film formation is 30% or more, it can be used as a semiconductor film for the time being. However, the semiconductor film formed under the condition that the hydrogen partial pressure is high is a channel of the insulating gate type field effect transistor. When used in the formation region, the carrier mobility has a hydrogen partial pressure ratio (P _H /
It has been found that the use of a semiconductor film having a high P _TOTAL ) is higher. The semiconductor film used in the channel formation region of the insulated gate field effect transistor shown in FIG. 3 is a silicon semiconductor whose Raman spectrum is shown in FIG.

Therefore, in the present invention, the distance between the target and the substrate is set to 90 mm or more in order to increase the collision between hydrogen atoms and the clusters forming the sputtered target, so that the hydrogen partial pressure is as low as about 30%. Even so, it is intended to obtain a film quality equivalent to that obtained at a high hydrogen partial pressure.

With the structure of the present invention, the kinetic energy of the clusters of the elements forming the target on the substrate surface can be reduced, so that the clusters can be prevented from being sputtered on the substrate and the substrate can be electrically connected. This is effective in obtaining a high-quality semiconductor film that is not damaged by the impact of sputtering, together with the floating. In order to prevent the substrate from being damaged by the sputtering of ions, there is a method of reducing the input RF power in addition to the method of increasing the distance between the substrate and the target. In this case, the distance between the substrate and the target cannot be secured. Therefore, since the hydrogen partial pressure must be increased, the film formation rate is further reduced due to the synergistic effect of the small RF power and the high hydrogen partial pressure, which is a practical problem.

If a semiconductor layer having a P or N type conductivity type is to be obtained, a III-valent or V-valent element which is an element imparting a P or N type conductivity type is preferably 1 × 1.
A single crystal or polycrystalline semiconductor target added with 0 ¹⁷ cm ⁻³ or more can be used. At the time of this film formation, by setting the temperature of the substrate to 200 ° C. or lower, a semiconductor film having one conductivity type of P or N type having low conductivity and high crystallinity can be manufactured.

With the structure of the present invention, at a film forming temperature (substrate temperature) of 300 ° C. or less, the conductivity of a single crystal or polycrystal silicon target is 100 (Ωcm) ⁻¹ to
A film was formed by sputtering in an atmosphere containing hydrogen, using a target to which an element having a valence of III or V, which is an impurity imparting one conductivity type, was added so as to be 0.1 (Ωcm) ⁻¹ , and By setting the substrate temperature at 200 ° C. or lower, preferably 150 ° C. or lower during this sputtering, P having a conductivity of 10 ⁻² (Ωcm) ⁻¹ or higher is obtained.
Alternatively, an N-type semiconductor layer can be obtained.

It goes without saying that the structure of the present invention can be applied not only to the silicon semiconductor but also to other semiconductors. For example, an impurity imparting one conductivity type (for example, boron or phosphorus III
A semiconductor film of Si _x Ge _1-x (0 ≦ X ≦ 1) having one conductivity type can be obtained by simultaneously using silicon (silicon) added with valence and V valence elements and a germanium target. it can. In this case, there is another feature that the composition ratio of the semiconductor film can be changed by changing the area of each target. According to this idea, a semiconductor film having a more complicated composition ratio can be obtained by using a plurality of targets at the same time.

[0013]

[Embodiment 1] This embodiment is a magnetron type R shown in FIG.
An N-type silicon semiconductor film is formed on a glass substrate using an F sputtering apparatus to form a silicon oxide film with a thickness of 1000Å, and then 300
A semiconductor film is manufactured under film forming conditions of ℃ or less.

The magnetron type RF sputtering apparatus shown in FIG. 1 will be described below. In FIG. 1, (12) is a substrate,
(13) is a holder that can be rotated if necessary and is in an electrically floating state, (14) is a heater for heating the substrate, (15) is a gas introduction system, and (17) is a gas introduction system valve. Reference numeral (18) is a gas supply system, for example, a cylinder filled with hydrogen. Although only one type of gas supply system is shown in FIG. 1, other gas supply systems such as argon, Foshin, diborane, and nitrogen may be provided if necessary, in which case a plurality of gas introduction systems are provided. At the same time, gas may be introduced into the reaction chamber. Further, (19) is a high frequency power supply (13.56 MHz), (20) is a high frequency matching device, and (21) is a magnetron portion in which a permanent magnet (22) rotating as necessary is provided in a circular shape. .

Further, (23) is a shutter for preventing sputtered particles (sputtered atoms, clusters, ions, etc.) from reaching the substrate. The shutter (23) prevents impurities from becoming sputtered particles and reaching the substrate immediately after the start of sputtering, but it can be used so that the sputtered particles do not reach the formation surface if necessary. (24) is the target. As the target, a thin film doped with impurities can be formed by mixing impurity elements such as phosphorus, boron, fluorine and other halogen elements as necessary. (25) is a gas exhaust system, (26) is a turbo molecular pump, and (27) is an oil rotary pump. Also, (28) and (29) are exhaust system valves. Further, (34) is provided with an exhaust system (34) equipped with a cryopump 31 and a rotary pump (33) for exhausting a higher vacuum state and specific impurities. Note that (30) and (33) are valves of this exhaust system (34).

Of these, the exhaust system (34) provided with a cryopump is mainly used for high vacuum exhaust before film formation.
The inside of the reaction vessel can be evacuated to about 0 ^-10 Torr, and the gas or molecules adsorbed in the reaction vessel can be evacuated. In particular, high vacuum evacuation before film formation is effective for reducing the amount of impurities such as oxygen, carbon and nitrogen contained in the film.

In this embodiment, the substrate (12) was heated by the heater (14), but it may be heated by an infrared lamp.

In this embodiment, the target used is a molten silicon target having a resistivity ρ = 0.60 Ωcm to which antimony, which is an impurity imparting one conductivity type, is added, but an impurity imparting another conductivity type is used. For example, if it is N-type, it is II, if it is a known P, As, Sb, P-type which is a V-valent
It goes without saying that a known B which is an I-valent element can be used. Further, it is effective to increase the conductivity of the target as much as possible by a method such as thermal annealing. Further, impurities other than those contributing to the conductivity type in the target, such as carbon, oxygen, and nitrogen, are preferably 2 × 10 ¹⁸ / cm ³ or less.
The film forming conditions are as follows: in a mixed atmosphere of hydrogen and argon,
Using the hydrogen partial pressure as a parameter, the film forming temperature is 150 ° C., the pressure is 0.5 pa, the RF power is 400 W, and the distance between the substrate and the target is 100 mm. The substrate was electrically floating. The silicon semiconductor film was formed on a glass substrate to a thickness of 2000Å.

FIG. 4A shows the N obtained in this embodiment.
The relationship between the conductivity σ (Ωcm) ^{−1 of the} type semiconductor film and the partial pressure ratio% of hydrogen in the atmosphere during film formation is shown. It can be seen from this figure that a value of σ = 10 ^-2 (Ωcm) ^-1 or more is obtained when the hydrogen partial pressure during sputtering is 30% or more. This figure also shows that the hydrogen partial pressure should be as high as possible.

FIG. 5 shows a Raman spectrum obtained in this example due to the difference in hydrogen partial pressure ratio during film formation.
This figure also shows the spectrum of extremely crystalline single crystal silicon with a hydrogen partial pressure ratio (P _H / P _T ) of 30% or more.
It can be seen that a sharp peak appears at a position lower than the wave number of 1 cm ^-1 . Thus, it is a great feature of the present invention that a semiconductor film having high crystallinity as shown in FIG. 5 can be obtained at a film forming temperature (substrate temperature) as low as 150 ° C. This is obvious in consideration of the fact that an inexpensive large-area glass substrate can be generally used if the process is performed at 200 ° C. or lower.

Generally, if a value of σ = 10 ^-1 (Ωcm) ^-1 or more can be obtained, it can be practically used as the source and drain regions of an insulating gate type field effect transistor. Considering this, a silicon film having one conductivity type (N-type silicon film in this case) obtained by sputtering in an inert atmosphere to which hydrogen is added can be formed in a large area. It can be said that the semiconductor film has one conductivity type, which is more economical and at the same time excellent in electrical characteristics as compared with the impurity ion doping.

The conductivity of the film obtained by this sputtering is 1/100 to 1/3 of the conductivity of the target, that is, P-type or N-type having a conductivity of 0.1 (Ωcm) ⁻¹ or more. It is useful to be able to obtain a semiconductor.

In the structure of the present invention, the substrate (generally a glass substrate, a silicon substrate or the like is used) is electrically floated in order to reduce the influence of ion sputtering on the substrate. In this embodiment, the substrate holder (13) is floating. Here, when the substrate is set to the ground potential, that is, when the substrate holder (13) is set to the ground potential, the semiconductor film to be formed is hit by the sputtering effect of the ions, so that the XRD intensity varies widely depending on the sample, and this semiconductor film is used The reproducibility of the device is extremely poor.

When the distance between the substrate and the target is half that of this embodiment, only low conductivity was obtained as shown in FIG. 4 (B). That is, the distance between the substrate and the target is 100m
It becomes desirable that it is m or more.

That is, in the present invention, when a semiconductor film is formed by sputtering in an inert atmosphere containing hydrogen, it is intended to obtain the same film quality as in the case of high hydrogen partial pressure by sputtering at low hydrogen partial pressure. In this case, the distance between the target and the substrate when sputtering is performed at a low hydrogen partial pressure may be made longer than the distance between the substrate and the target when the hydrogen partial pressure is high.

In this example, an N-type silicon semiconductor film was formed on a substrate by using a target to which antimony was added, but the target used for sputtering film formation has an impurity imparting an N-type conductivity type. Then, phosphorus (P)
V, such as arsenic, arsenic (As), and antimony (Sb), and boron (B) and aluminum if they are impurities that impart a P-type conductor.
A single crystal or polycrystalline silicon target to which a trivalent element such as (Al) is added can be used. As the single crystal or polycrystal semiconductor target, not only silicon, that is, silicon, but also a semiconductor film to be formed may be Ge, Se, or a compound semiconductor such as gallium arsenide or gallium antimony.

In the structure of the present invention, the semiconductor film having one conductivity type after film formation may be subjected to thermal annealing at a temperature of 700 ° C. or lower.

Conventionally, a conductivity of 10 ⁻² (Ωcm) ⁻¹ or more, which has been obtained by thermally annealing a semiconductor film having one conductivity type obtained by a sputtering method or a CVD method, is obtained at a low temperature (1
It is a great feature of the present invention that it can be obtained by sputtering at 50 ° C. or lower. This is clear from the Raman spectrum of the N-type semiconductor film obtained by the method of the present invention which is not annealed immediately after the film formation shown in FIG. Looking at FIG. 5, the partial pressure of hydrogen is 50%.
The Raman spectrum of the N-type semiconductor film obtained by sputtering in the atmosphere described above shows single crystal silicon (c-Si).
It can be seen that a peak exhibiting crystallinity appears at a wave number lower than the peak of 521 cm ⁻¹ .

In this embodiment, a specific impurity such as oxygen, carbon or nitrogen is selected by using a cryopump provided in the exhaust system (34) shown in the magnetron type RF sputtering apparatus shown in FIG. Evacuation is effective in improving the quality of the semiconductor film formed by sputtering. For example, when impurities such as oxygen, carbon, and nitrogen are present in the film of a P or N type semiconductor film to which an impurity imparting one conductivity type is added, in addition to the impurities contributing as an acceptor or a donor, a device is formed using the semiconductor film. It adversely affects the performance of the device when it was manufactured. For example, if oxygen element is mixed in a semiconductor layer that constitutes a solar cell, conversion efficiency and durability may be deteriorated.
Therefore, by efficiently exhausting the impurities such as oxygen, carbon, and nitrogen, it is possible to prevent adverse effects on the semiconductor film.

By using a cryopump, which is an adsorption pump provided in the sputtering apparatus shown in FIG. 1 used in this embodiment, molecules composed of impurities such as oxygen, carbon and nitrogen can be efficiently exhausted. . For example, in this example, when film formation was performed using only an exhaust system (25) equipped with a turbo molecular pump, the oxygen concentration contained in the formed film was determined by SIMS (secondary ion mass spectrometry) method. According to the ^results, it was about 3 × 10 ¹⁹ cm ⁻³ , but an exhaust system equipped with a cryopump at the same film forming pressure (34)
The oxygen concentration contained in the film formed by the combined use of the above was able to be 6 × 10 ¹⁸ cm ⁻³ . The carbon concentration in the formed coating film can be 3 × 10 ¹⁶ cm ⁻³ , the hydrogen content is 4 × 10 ²⁰ cm ⁻³ , and the silicon content is 4 × 10 4.
It was 1 atom% when compared with ²² cm ^-3 .

In the structure of the present invention, it has been obtained as data that a relatively high film forming pressure of about 2.5 pa is good (FIG. 6), and it is unsuitable to form a film in an ultrahigh vacuum state. Is. Therefore, as described above, the use of a cryopump capable of exhausting oxygen, carbon, and nitrogen as adsorbed molecules has a remarkable effect. Furthermore, in the present invention, since the film is formed by sputtering in a mixed atmosphere of an inert gas such as argon and hydrogen, oxygen, which is the most problematic impurity, is bonded to hydrogen and becomes a molecule to be present in the reaction space. To do. Therefore, when the cryopump is used as described above, the molecules of oxygen and hydrogen can be efficiently exhausted. Further, as in the configuration of the present invention, P
-Type or N-type conductivity-type impurities (such as phosphorus,
In the case of forming a semiconductor film that must contain (antimony), in a vapor phase growth method such as a CVD method using a reaction gas, it is necessary to add an impurity that contributes to the conductivity type into the vapor phase. There is a problem that unnecessary impurities are mixed in. As a method of solving such a problem, there is a method of using a special reaction furnace by using a reaction gas having an extremely high purity, but there are problems of cost and poor productivity.

From the above, as in the present embodiment, a turbo molecular pump and a cryopump are used in combination, and a semiconductor film, particularly one conductivity type, is imparted by sputtering in an inert atmosphere containing hydrogen without using a reaction gas. III
A method for manufacturing a semiconductor film containing a valent or V-valent element is performed by using oxygen, carbon, which are unnecessary impurities in the formed semiconductor film,
It can be said that this method is capable of efficiently exhausting nitrogen, and has a low cost and excellent productivity.

In the structure of the present invention, the N-type semiconductor film after film formation may be subjected to thermal annealing at a temperature of 700 ° C. or lower.

In the present invention, a single crystal or polycrystal semiconductor target is used as a target, and an impurity which imparts a P-type or N-type conductivity type to the target II
100% ionized I or V valence impurities,
That is, since the III-valent or V-valent impurity is completely substituted as an acceptor or a donor, by sputtering this target in an atmosphere containing hydrogen, a cluster in which the impurity is substituted as an acceptor or a donor is provided. Fly toward the substrate and reach the substrate while neutralizing dangling bonds by hydrogen plasma, so that the III- or V-valent impurities in the semiconductor film formed by sputtering have a high ionization rate. It was possible to increase the ionization rate by substituting these impurities as acceptors or donors.

It goes without saying that the structure of the present invention can be applied not only to the silicon semiconductor but also to other semiconductors. For example, silicon to which an impurity imparting one conductivity type is added
A Si _x Ge _{1 -x} semiconductor film having one conductivity type can be obtained by simultaneously using a target of and germanium. In this case, the composition ratio of the semiconductor film can be changed by changing the area of each target.
According to this idea, a semiconductor film having a more complicated composition ratio can be obtained by using a plurality of targets at the same time.

At the time of sputtering, a halogen element is added to the atmosphere, and NF ₃ or the like is added in an amount of about 0.1 to 10% in order to neutralize dangling bonds of clusters of sputtered atoms like hydrogen. May be.

[0037]

[Embodiment 2] This embodiment is a magnetron type R shown in FIG.
A P-type Si _x Ge _1-x semiconductor film added with boron (B) was obtained by using an F sputtering apparatus. In this embodiment, a magnetron type RF sputter device is used, pressure is 2.5 pa, RF power is 200 W, and substrate temperature is 100.
℃, the distance between the substrate and the target is 90mm, sputtering was performed in a mixed atmosphere of hydrogen and argon with a hydrogen partial pressure ratio of 80%, and then thermal annealing was performed at 600 ℃ for 72 hours. N-type Si _x Ge _1-x It is a semiconductor film. In addition, the single crystal target of silicon and germanium has phosphorus of 1 × 10.
^{Of the} N-type Si _x Ge _1-x semiconductor film formed on the substrate by arranging a plurality of molten substrates containing ¹⁷ cm ^-3 or more dispersed in the same area and further rotating the substrate side by planetary rotation. Increased uniformity.

Also in this embodiment, since boron in the single crystal target of silicon and germanium is substituted as the acceptor, it has a conductivity of 1/100 to 1/3 of the conductivity of the target which is a feature of the present invention. A P-type semiconductor can be manufactured.

The reason why the reaction pressure is increased to 2.5 pa is based on the experimental result shown in FIG. 6 (A) conducted by the present inventor. FIG. 6 shows the pressure and XRD at the time of forming the N-type silicon semiconductor film which was annealed at 600 ° C. for 72 hours after the film formation.
It shows the relationship with the strength (INTENSITY). The film formation conditions for which the data in FIG. 6 were obtained were those in which phosphorus was added to a single crystal or polycrystal silicon target so that the target resistivity was 2 to 3 KΩcm, and the film formation temperature was 150 ° C. The RF power is 400 W, and the atmosphere is a mixed atmosphere of hydrogen and argon with a hydrogen partial pressure ratio (P _H / P _T ) of 30%. The distance between the substrate and the target is 120 mm, and the target is in an electrically floating state.

After the film formation, 60 in an inert atmosphere
The thermal annealing was performed at 0 ° C. for 72 hours. Figure 6
From (A), it can be seen that the reaction pressure of about 2.5 pa exhibits higher crystallinity. However, when the distance between the substrate and the target was 60 mm, the crystallinity of the film became low as shown in (B). This is because the clusters consisting of the atoms that make up the target reach the substrate and form the film, and at the same time the sputter effect also occurs, resulting in damage to the clusters that should become semiconductor films on the substrate and the quality of the resulting thin film. This is because it had a bad influence. Furthermore, the substrate holder (13) was electrically floating, ie insulated from the surroundings.

The RF power of 200 W is based on the experimental results shown in FIG. The data shown in FIG. 7 shows the relationship between the input power during film formation and the XRD intensity (INTENSITY) when the film forming pressure was 0.5 pa under the same manufacturing conditions as shown in FIG. It was done. It can be seen from FIG. 7 that the crystallinity of the semiconductor film is higher when the input power during sputtering is a relatively low value of about 200 W. This result also shows that when the input power is increased, the sputtering effect on the substrate occurs and the sputtered film is adversely affected. Even if the distance between the substrate and the target is 120 mm, the semiconductor film formed by the ion sputtering effect may be damaged even when the substrate holder is electrically floating, that is, the substrate is not floating.

In the present embodiment, the substrate temperature is set to 100 ° C., which shows the effect of improving the film quality by forming the film at the substrate temperature of 200 ° C. or less which is the constitution of the present invention.
It is based on the experimental results shown in. The data shown in FIG. 8 shows the relationship between the substrate temperature and the XRD intensity of the obtained film under the same manufacturing conditions as the case shown in FIG. 6 (A). As shown in FIG. 8, when the film formation temperature (the substrate temperature in this case) is 100 ° C. or higher, the crystallinity of the film after thermal annealing is low, whereas when the film formation temperature is 100 ° C. or lower, the heat treatment is It can be seen that the crystallinity of the film after annealing is high. The trend shown in FIG. 8 can be explained by the following model. Since the silicon film obtained by sputtering in this example is sputtered in an atmosphere in which a large amount of hydrogen is present at the time of sputtering, the elements composing the target are clusters of tens to hundreds of thousands of atoms. While the clusters fly out of the target and fly in the hydrogen plasma, the dangling bonds of the clusters are neutralized by hydrogen, and the clusters reach the substrate. At this time, in the target, the impurity imparting the P-type or N-type conductivity acts as an acceptor or a donor, so that the impurity is an acceptor or a donor even in the cluster flying toward the substrate. . Therefore, when the cluster reaches the substrate and forms a silicon film, the impurity imparting the P-type or N-type conductivity acts as an acceptor or a donor in the film formed by sputtering.

When the cluster in which the dangling bond is neutralized by the hydrogen reaches the substrate from the target, the hydrogen neutralizing the dangling bond of the silicon cluster separates when the temperature during film formation is high. On the substrate, the clusters cannot bond with each other and cannot form order. Therefore, when a silicon film formed in an atmosphere of 200 ° C. or higher is annealed by heat, it is impossible to attain a more highly ordered state, and as a result, the XRD intensity is low. On the other hand, when the temperature at the time of film formation is low, the clusters of silicon, which are the sputtered particles, bond on the substrate via hydrogen. As a result, a relatively high order state is realized. This membrane from 450 degrees to 700
By thermal annealing at a temperature of 100 degrees, the silicon clusters bonded via hydrogen become bonds between silicon atoms,
The silicon comrades pull each other because they move to a higher ordered system and the existing silicon bonds to each other. When measured by laser Raman spectroscopy as a crystal,
As shown in FIG. 2, a peak shifted from the single-crystal silicon peak 521 cm ^-1 to the low frequency side is observed. This 521 cm ^-1
The peak shifted to the lower frequency side shows a crystalline state with weak lattice distortion. The apparent grain size is 50 to 500 Å, which is similar to that of microcrystals, when calculated from the half-width, but in reality, there are many regions with high crystallinity, which have a cluster structure. Can form a film having a semi-amorphous structure in which silicon is bonded to each other (anchoring).
Therefore, the film formation temperature is low (at 150 ° C or lower)
Although the order of the silicon film obtained by sputtering of Si is further promoted by thermal annealing, the film formed at a high substrate temperature has no order and is thermally annealed from the beginning as described above. However, it is not possible to form a semi-amorphous structure film in which the respective clusters are mutually bonded (anchoring) to each other by silicon, and there is almost no XRD peak.

From the above, when a semiconductor film having one conductivity type is produced by sputtering in an atmosphere of an inert gas containing hydrogen, for example, sputtering using a target to which an impurity imparting one conductivity type is added. The substrate temperature during sputtering is 200 ℃ or less, preferably 150
It can be concluded that the temperature should be below ℃.

As described above, when the film is formed at a low temperature, the sputtered silicon clusters are bonded by hydrogen in the atmosphere, and the silicon clusters are bonded by thermal annealing. This is because its crystallinity is preserved and promoted.

Also in this embodiment, the conductivity of the sputtered film can be increased by increasing the conductivity of the target. This is because the impurities that have become acceptors or donors in the target exist at a high ionization rate in the film formed by sputtering in an atmosphere containing hydrogen and are replaced as acceptors or donors as described above. , Target conductivity of 1
P or N with high conductivity of / 100 to 1/3
This is because a semiconductor film having a shape can be obtained.

[0047]

Example 3 In this example, an N-type semiconductor film mixed with Si _x C _{1 -X} and (0 ≦ X ≦ 1) phosphorus was obtained under the same conditions as in Example 2. In the present embodiment, the targets of silicon and carbon are finely dispersed and arranged, and the stoichiometric ratio can be changed by changing the amounts thereof. In this case, the target or substrate was rotated to increase the uniformity of the film produced.

In the examples in the present specification, a target to which an element imparting one conductivity type to a semiconductor, such as antimony, phosphorus, or boron, was added was used, but Si to which these impurities are not added is used. , Ge, Si _x Ge
_1-X , Si _x C _1-X , (0 ≦ X ≦ 1) and other targets are used to produce non-doped true semiconductor I-type semiconductors Si, Ge,
It goes without saying that a semiconductor film of Si _x Ge _1-X , Si _x C _1-X , (0 ≦ X ≦ 1) or the like may be formed.

[0049]

[Embodiment 4] This embodiment relates to a method for manufacturing a semiconductor film by sputtering in an inert atmosphere containing hydrogen, in which a substrate is placed in a floating state insulated from the surroundings, and further carbon and nitrogen in a film forming atmosphere are used. The oxygen concentration is 1 × 10 ¹⁹ cm ⁻³ or less by using the cryopump and the turbo molecular pump as described in Example 1, and the concentration of the impurity imparting the P or N conductivity type is 1 ×. An I-type semiconductor is obtained using a single crystal or polycrystalline target having a concentration of 10 ¹⁷ cm ^-3 or less and an oxygen concentration of 1 × 10 ¹⁷ cm ^-3 or less.

In this embodiment, the partial pressure of hydrogen is set to 30% and the film forming pressure is set to be 0.
Sputtering was performed using the RF sputtering apparatus shown in FIG. 1 under the film forming conditions of 5 pa, RF power of 250 W, and substrate temperature of 150 ° C.

The I-type silicon semiconductor film produced in this example exhibits a Raman spectrum similar to that shown in FIG. 5, and is a characteristic of the present invention that is a high-quality semi-amorphous or microcrystalline semiconductor at low temperature (300 ° C. or lower). I was able to get it. A mobility of 40.1 cm ² / V could be obtained when an N channel type insulated gate type field effect transistor was manufactured using this I type silicon semiconductor.

[0052]

According to the structure of the present invention, a high quality semiconductor film can be obtained by electrically floating the substrate, and a high quality semiconductor film can be obtained by separating the substrate from the target by 90 mm or more. A semiconductor film could be obtained.

[Brief description of drawings]

FIG. 1 shows a sputtering apparatus used for realizing the method of the present invention.

FIG. 2 shows a Raman spectrum of a semiconductor film manufactured in an example.

FIG. 3 shows the relationship between the mobility (μ) of the insulating gate type field effect transistor using the semiconductor film manufactured in the example and the hydrogen partial pressure ratio at the time of forming the semiconductor film.

FIG. 4 shows a relationship between conductivity of a semiconductor film manufactured in an example and hydrogen partial pressure at the time of forming the semiconductor film.

FIG. 5 shows a Raman spectrum of a semiconductor film manufactured by the method of the present invention.

FIG. 6 shows the relationship between the film forming pressure of the semiconductor film manufactured in the example and the XRD intensity of the film.

FIG. 7 shows the relationship between the applied power and the XRD intensity of the film when forming the semiconductor film manufactured in the example.

FIG. 8 shows the relationship between the substrate temperature (deposition temperature) and the XRD intensity of the film during the film formation of the semiconductor film manufactured in the example.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-59-35015 (JP, A) JP-A-2-109378 (JP, A) JP-A-2-109379 (JP, A) JP-A-60- 43482 (JP, A) JP-A-63-312962 (JP, A) JP-A-61-573 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/203 C23C 14 / 34-14/46

Claims (7)

(57) [Claims] 1. A method for producing a silicon film using a sputtering method using an RF magnetron sputtering apparatus, comprising: a substrate and a single crystal doped with an impurity imparting one conductivity type;
A polycrystalline silicon target is provided oppositely, and using the silicon target, 0.1-10% NF
₃ is added to form the silicon film in an atmosphere containing hydrogen
And the conductivity of the silicon target is 100 (Ωcm) ^-1
Is 0.1 (Ωcm) ⁻¹ , and the distance between the substrate and the silicon target is 90.
not less than mm, a manufacturing method of the silicon film, wherein the film formation pressure of said silicon film is at least 2.5 Pa. 2. A method for producing a silicon film using a sputtering method using an RF magnetron sputtering apparatus, comprising a single crystal containing a substrate and a valence III element or a valence V element.
A polycrystalline silicon target is provided oppositely, and using the silicon target, 0.1-10% NF
Sputtering in an atmosphere containing ₃ and hydrogen
Therefore, the silicon film is formed, and the conductivity of the silicon target is 100 (Ωcm) ^−1.
Is 0.1 (Ωcm) ⁻¹ , and the distance between the substrate and the silicon target is 90.
not less than mm, a manufacturing method of the silicon film, wherein the film formation pressure of said silicon film is at least 2.5 Pa. 3. The silicon according to claim 1 or 2, wherein the substrate is insulated from the surroundings.
Membrane fabrication method. 4. The atmosphere according to any one of claims 1 to 3, wherein the atmosphere contains argon or nitrogen.
A method for manufacturing a silicon film. 5. The method according to any one of claims 1 to 4.
There are, carbon in the silicon target, oxygen, concentration of nitrogen
Silicone characterized by being 2 × 10 ¹⁸ / cm ^-3 or less
A method for forming a membrane. Te 6. any claim smell of claims 1 to 5 <br/>, making the silicon film above the RF magnetron sputtering apparatus, characterized in that the turbo-molecular pump and a cryopump is provided Method. Te smell <br/> 7. claims 1 to any one of claims 6, wherein the silicon film is deposited in an inert atmosphere containing hydrogen, the partial pressure of the hydrogen is 30% or more sheet, characterized in that
Method for producing recon film .