JP3397760B2 - Method for manufacturing thin film transistor - 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 of manufacturing a semiconductor device using a semiconductor layer manufactured by a highly mass-producible forming method.

[0002]

2. Description of the Related Art Conventionally, a polycrystalline semiconductor device has been manufactured by forming a polycrystalline semiconductor film by forming it in the temperature range of 550 ° C. to 900 ° C. by low pressure CVD and using the polycrystalline semiconductor film.

Recently, large-area liquid crystal displays and the like have been developed, and it has become necessary to form a polycrystalline semiconductor device on a large-area substrate. Forming a polycrystalline semiconductor layer directly on a large-area substrate by the low pressure CVD method has many difficulties due to the problem of reaction temperature, and usually, after a non-single crystal semiconductor film is formed, crystallization treatment is performed, A polycrystalline semiconductor layer is formed on a large area substrate. When a non-single crystal semiconductor film is obtained by the low pressure CVD method, it is difficult to form a uniform film on a large area substrate.

Further, when a non-single crystal semiconductor film is obtained by the plasma CVD method, there is a problem that the film forming process takes time and it is difficult to obtain uniform film thickness on a large area substrate.

As a means for solving such a problem, there is a method using a sputtering method. In particular, in the magnetron-type sputtering method, a) electrons are confined in the vicinity of the target by the magnetic field, and damage to the substrate surface by high-energy electrons is suppressed. B) High-speed film formation over a large area at low temperature. C) It is highly safe and industrial because it does not use dangerous gases. There are advantages such as.

However, it is known that the semiconductor film obtained by the sputtering method has a microstructure, that is, the presence of silicon atoms is biased, and thermal crystallization is difficult.

[0007]

The present invention solves such problems and provides a method for more effectively producing a semiconductor device using a semiconductor film which can be thermally crystallized at a lower temperature. is there.

[0008]

According to the present invention, there is provided a step of forming a semiconductor film on a substrate by a sputtering method in a hydrogen atmosphere or an inert gas atmosphere containing hydrogen, and a method for forming a semiconductor film obtained by the sputtering method. The method is characterized in that a silicon oxide film is formed by a sputtering method in an atmosphere of oxygen or an inert gas containing oxygen before or after, and each film is formed in a dedicated reaction chamber, and the order of forming these films is set. It is characterized in that it can be formed continuously in the same device arbitrarily without specifying.

By forming each of these films in a dedicated reaction chamber, the amount of oxygen in the semiconductor film is adjusted to 7 × 10 ¹⁹ cm ^-3.
The following is most preferable, and the feature is that it is 1 × 10 ¹⁹ cm ^-3 or less.

As an example of a method of forming a part of the semiconductor film as a channel formation region, an amorphous material obtained by sputtering in an atmosphere of hydrogen or an inert gas containing hydrogen (amorphous or extremely thin state) (Close) semiconductor film (hereinafter referred to as Si film) 450 ℃ ~ 700 ℃ typically 60
By applying a temperature of 0 ° C. to the semiconductor film to crystallize at least the channel formation region, the active layer for an insulated gate semiconductor device of the present invention can be obtained.

Conventionally, there is known an example of manufacturing a thin film transistor using an a-Si (amorphous silicon) film obtained by a hydrogen-added sputtering method, but it is known that its electrical characteristics are low. . Therefore, generally, an a-Si film is obtained by a sputtering method without adding hydrogen.

However, the present inventor can prevent formation of a microstructure in the formed a-Si film by adding hydrogen in the sputtering method. It was found that thermal crystallization can be performed at a low temperature of 700 ° C or 600 ° C or lower.

The semiconductor film after the crystallization has an average crystal grain size of about 5 to 400Å, and the hydrogen content in the semiconductor film is 5 atom% or less. Further, this crystalline semiconductor film has a lattice distortion, and microscopically, the interfaces of the respective crystal grains are strongly in close contact with each other, which has the effect of eliminating the barrier against carriers at the crystal grain boundaries. Therefore, impurity atoms such as oxygen segregate at the grain boundaries of polycrystals without lattice distortion to form a barrier, which hinders carrier movement. When formed in the reaction chamber, the amount of oxygen present in the film is 7 × 10 ¹⁹ c
m ^-3, which can be reduced to a very small amount, preferably 1 × 10 ¹⁹ cm ^-3 or less, and the formed semiconductor film has lattice strain so that a barrier is not formed or its existence is neglected. The electron mobility was 50 to 300 cm ² / V · S, which was a very good characteristic because the electron mobility was as high as possible.

The semiconductor film obtained by the plasma CVD method has a large proportion of amorphous components, and the amorphous component portions are naturally oxidized to form an oxide film inside, while the sputtered film is dense and naturally oxidized. Does not proceed to the inside of the semiconductor film and is oxidized only in the vicinity of the surface.Due to this denseness, crystal grains with lattice distortion push each other strongly, and the energy barrier for carriers near the crystal grain interface is increased. It has the feature that is not formed.

The present invention provides a method for manufacturing an insulated gate type semiconductor device by positively utilizing the excellent characteristics of a semiconductor film formed by such a sputtering method.
Therefore, individual films are produced in a dedicated sputtering reaction chamber.

The silicon oxide film formed by this sputtering method can be used as an insulating film or a gate insulating film on a substrate, and the semiconductor film can be used as an active layer or an impurity layer and a gate electrode.

As described above, according to the method of the present invention, the minimum required portion of the insulated gate semiconductor device can be formed by the sputtering method. Therefore, in the insulated gate semiconductor device as shown in FIG. 1 (D), the lower side (18) of the active layer, that is, the contact portion with the base insulating film is partially oxidized to be in the state of SiOx. The electrical characteristics are slightly worse. As a result, a back channel cannot be generated in this portion, and the reverse leakage current can be reduced. This is very effective when this semiconductor device is used as a CMOS and shows a significant effect in reducing the off current.

Furthermore, since it is a semiconductor film formed by a sputtering method, its grain size is 5-40 after thermal crystallization.
0Å is typically 50 to 200Å, and since the grain size is small as described above, the reverse leakage at this portion can be reduced by the N ⁺ -I (P ⁺ -I) junction.

When the semiconductor film is continuously formed in a state of being sandwiched by the silicon oxide film, and then the semiconductor film is thermally crystallized, the upper and lower silicon oxide films suppress the grain size of silicon 5 to 30.
It can be set to 0Å, preferably 50 to 200Å.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, as embodiments of the present invention,
The present invention will be described with reference to examples.

[0021]

[Embodiment] [Embodiment 1] This embodiment is a multi-chamber magnetron type whose outline is shown in FIG.
This is an example in which a Si semiconductor film produced by an RF sputtering apparatus is thermally crystallized to obtain a crystalline silicon semiconductor layer, and a thin film transistor is produced using this silicon semiconductor layer.

In this multi-chamber type sputtering apparatus, as shown in FIG. 2, a preliminary chamber (1), a reaction chamber (3) for silicon oxide, and a reaction chamber (4) for semiconductor film are a second oxidation reaction chamber (5). Further, it is partitioned and connected to the substrate take-out chamber (6) and the gate valve (7), and each chamber is a system capable of completely independent exhaust and introduction of gas.

The exhaust system includes a reaction and low vacuum exhaust system in which a rotary pump and a turbo molecular pump are connected in series, and a high vacuum exhaust system in which a cryopump is further connected.
Equipped with a system, it can exhaust up to 1 × 10 ^-7 Pa as back pressure.

When loading the substrate into each chamber, the gate valve for partitioning the chamber is opened and closed. The pressure difference between the chambers is reduced and the pressure difference between the chambers is reduced. Perform after the atmospheric gas is prepared. As a result, it is possible to reduce unnecessary mixing of impurities and the like as much as possible.

The strength of the magnetic field supply means provided near the sputtering target can be varied by external control (for example, the amount of applied power or the distance to the target can be varied).

The substrate take-out chamber (6) of this sputtering apparatus is provided with a heating means and an atmosphere gas supply means so that the semiconductor film can be heat-treated, and the thermal crystallization of the semiconductor film can be carried out without taking the substrate out of the apparatus. Is possible.

FIG. 1 shows a process of manufacturing a thin film transistor manufactured in this embodiment.

First, 10 glass substrates (11) / cassette were set in the preliminary chamber (1) through the gate valve (7), and one of them was loaded into the silicon oxide film forming reaction chamber (3). A SiO ₂ film (12) was formed on the glass substrate (11) to a thickness of 200 nm by the magnetron type RF sputtering method under the following conditions. O ₂ 100% atmosphere Film formation temperature 150 ℃ RF 813.56NHz) Output 400W Pressure 0.5Pa Single crystal silicon is used as the target

It was also effective to add a halogen element to the underlying silicon oxide film to enhance the effect of preventing the alkali metal element from coming out of the substrate.

After evacuating the reaction chamber after formation of this film to a high vacuum, the gate valve is opened and closed to transfer the substrate to the reaction chamber for semiconductor film (4), and then the Si film (13) to be a channel formation region is formed. Form a film with a thickness of 100 nm.

At this time, the back pressure was set to 1 × 10 ^-7 Pa or less, and a turbo molecular pump and a cryopump were used for exhaust. The amount of gas supplied had a purity of 5N (99.999%) or higher, and the additive gas was 4N or higher of argon used as necessary. Target single crystal silicon is also 5 × 10 ¹⁸ cm
The oxygen concentration was ^-3 or less, for example, 1 × 10 ¹⁸ cm ^-3 , and oxygen as an impurity in the formed film was extremely reduced.

The film forming conditions are H ₂ / (H ₂ + Ar) = 80% (partial pressure ratio) in an atmosphere of argon and hydrogen which are inert gases. Film forming temperature 150 ° C. RF (13.56 MHz) Output 400 W Total pressure The target was 0.5 Pa, and the target was a single crystal Si target.

Next, the substrate was moved to a reaction chamber (5) dedicated to silicon oxide, and a gate oxide film (SiO ₂ ) (15) was formed to a thickness of 100 nm by the magnetron type RF sputtering method under the following conditions. Before forming the gate insulating film, a bias was applied to the substrate side in a 100% hydrogen atmosphere to clean the surface of the semiconductor (13) with plasma hydrogen.

The gate insulating film was formed under the following conditions. Oxygen 95% by volume NF ₃ 5% by volume Pressure 0.5pa Film forming temperature 100 ℃ RF (13.56MHz) Output 400W

When forming this gate oxide film, if the ratio of oxygen to the inert gas is large and sputtering is most preferably 100% oxygen, the interface state density of the gate insulating film can be reduced and the characteristics are very good. A transistor can be realized.

Further, in this embodiment, since NF ₃ was added as a part of the reaction gas during the reaction, fluorine was added to the gate insulating film. As a result, it was possible to neutralize the dangling bonds of silicon in the film and remove the cause of generation of fixed charges in the film.

After that, the substrate (11) is moved to the substrate take-out chamber (6) where it is heated in a temperature range of 450 ° C. to 700 ° C., particularly 600 ° C. for 10 hours in hydrogen or an inert gas, and In the examples, the Si film (13) was thermally crystallized in an atmosphere of 100% nitrogen to produce a silicon semiconductor film (semi-amorphous or semi-crystal) with high crystallinity.

Impurity purity in the amorphous silicon film formed by such a method and in the film after crystallization by heat treatment was examined by SIMS (secondary ion equivalent analysis) method. Then, of the impurity concentrations during film formation, oxygen was 8 × 10 ¹⁸ cm ⁻³ and carbon was 3 × 10 ¹⁶ cm ⁻³ . Further, hydrogen had a concentration of 4 × 10 ²⁰ cm ^-3 , and when the density of silicon was 4 × 10 ²² cm ^-3 , the amount was equivalent to 1 atomic%. These were investigated with reference to the oxygen concentration of 1 × 10 ¹⁸ cm ⁻³ of the target single crystal silicon. In this SIMS analysis, the distribution in the depth direction (depth profile) of the film after film formation was examined, and the minimum value was used as a reference. This is because the surface has silicon oxide that is naturally oxidized with the atmosphere.
These values did not change significantly even after the crystallization treatment, and the oxygen impurity concentration was 8 × 10 ¹⁸ cm ⁻³ .

In this example, oxygen was added just in case.
Palm, for example N₂Add O at 0.1cc / sec and 1cc / sec
It was Then the oxygen concentration after crystallization is 1 × 10²⁰cm^-34 x 10
²⁰cm ^-3And many. However, when using such a coating,
Sometimes the temperature required for crystallization should be above 700 ° C, or
By increasing the crystallization time by at least 5 times
For the first time, crystallization was possible. That is, industrially the substrate glass
Considering the softening temperature of, 700 ℃ or less, preferably 600 ℃
The following treatments are important and when more crystallization is needed
It is also important to reduce the time interval. However, such as oxygen concentration
No matter how small the amount of impurities is, heat will be generated below 450 ° C.
Crystallization of a-Si semiconductor by Neil is not possible experimentally
there were.

Further, in the present invention, if such a high quality sputtering apparatus is used, the oxygen concentration during film formation becomes 1 × 10 ²⁰ cm ^-3 or higher due to leaks from the apparatus. In such a case, the characteristics of the present invention cannot be expected.

Thus, it was determined that the oxygen concentration was 7 × 10 ¹⁹ cm ^-3 or less and the heat treatment temperature was 450 to 700 ° C.

As can be seen from the data of laser Raman analysis shown in FIG. 6, in this semiconductor film, the position of the peak indicating the presence of crystals is shifted to the lower wave number side than the position of the peak of ordinary single crystal silicon. And was able to avoid the existence of lattice distortion.

Further, although the present invention has been described by using the silicon semiconductor in the present embodiment, it is also possible to use a germanium semiconductor or a semiconductor in which silicon and germanium are mixed, and in that case, heat It was possible to reduce the temperature applied during crystallization by about 100 ° C.

Next, the substrate is taken out of this apparatus, and the thermally crystallized silicon semiconductor film is subjected to device isolation patterning to obtain the shape shown in FIG. 1A. A part of this semiconductor film is used as an insulated gate semiconductor. It was configured as a channel forming region of the device.

Further, patterning was performed once more to form contact holes for impurity region electrodes to form a structure as shown in FIG. 1 (B).

Then, a semiconductor layer containing phosphorus is formed on the entire surface of the substrate by the low pressure CVD method. Then, photolithography was performed using a predetermined mask pattern to form the phosphor-mixed semiconductor film as the gate electrode (20) and the impurity region electrodes (16) and (16 ′). (Fig. 1 (C))

By forming this electrode by the low pressure CVD method, good characteristics can be obtained without damaging the underlying gate insulating film.

The gate electrode is not limited to a doped semiconductor layer and other materials can be used.
Further, a structure in which an electrode made of metal or the like is laminated on the semiconductor material electrode may be used.

Next, this gate electrode (20) or gate electrode
Using the resist pattern and the like used when etching (20) as a mask, the impurity regions (14) and (1
4 ') was formed using the ion implantation technique. Figure 1 (D)
After that, thermal annealing was performed for 15 minutes at 400 ° C. in a hydrogen atmosphere to activate.

As a result, the semiconductor layer below the gate electrode (20) was formed as the channel region of the insulated gate semiconductor device.

Next, an insulating film (17) covering the upper surfaces of all of these is formed.
Was formed to obtain the state of FIG. 1E, and the insulated gate semiconductor device was completed.

In the case of the present embodiment, the semiconductor layer forming the channel region and the semiconductor layers of the source and the drain are made of the same material, which simplifies the process. Further, since the same semiconductor layer is used, the source and drain semiconductor layers also have crystallinity and carrier mobility is high, so that an insulated gate semiconductor device having better electrical characteristics can be realized.

The above is a method for manufacturing a thin film transistor using the thermocrystalline silicon semiconductor layer manufactured in this embodiment. For comparison, the Si layer of FIG. 1A, which is a channel formation region, is used.
Four reference examples in which the hydrogen concentration, which is the condition for forming the film of (13) by the magnetron type RF sputtering method, is changed, are shown below.

Reference Example 1 In this reference example, the partial pressure ratio of the atmosphere during sputtering when producing (13) of FIG. 1 (A), which becomes the channel formation region in the production method of Example 1, is H ₂ / ( H ₂ + Ar) = 0% (partial pressure ratio), and other conditions were the same as in Example 1. The oxygen concentration at this time was 2 × 10 ²⁰ cm ⁻³ .

Reference Example 2 In this reference example, the partial pressure ratio of the atmosphere during sputtering when producing (13) of FIG. 1 (A), which becomes the channel forming region in the production method of Example 1, is H ₂ / ( H ₂ + Ar) = 20% (partial pressure ratio), and the others were manufactured by the same method as in Example 1. The oxygen concentration at this time was 7 × 10 ¹⁹ cm ⁻³ .

Reference Example 3 In this example, the partial pressure ratio of the atmosphere during sputtering when producing (13) of FIG. 1 (A), which becomes the channel formation region in the production method of Example 1, is H ₂ / (H ₂ + Ar) = 50% (partial pressure ratio), and the others were manufactured by the same method as in Example 1. The oxygen concentration at this time was 3 × 10 ¹⁹ cm ⁻³ .

Reference Example 4 In this reference example, the partial pressure ratio of the atmosphere during sputtering when producing (13) of FIG. 1 (A), which becomes the channel forming region in the production method of Example 1, is H ₂ / ( H ₂ + Ar) = 70% (partial pressure ratio), and other conditions were the same as in Example 1. The oxygen concentration at this time was 1 × 10 ¹⁹ cm ⁻³ .

The results of comparing the electrical characteristics of the above described examples are shown below.

FIG. 4 shows the completed Example 1 and Reference Example 1
Carrier mobility μ (FIELD M
OBILITY) and hydrogen partial pressure ratio during sputtering (P _H / P _TOTAL =
It is a graph of the relationship of H ₂ / (H ₂ + Ar)). Figure 4
Table 1 shows the correspondence between the plotted points in and the above examples.

[0060]

[Table 1]

It can be seen from FIG. 4 that a remarkably high mobility μ (FIELD MOBILITY) is obtained at a hydrogen partial pressure of 20% or more.

FIG. 5 is a graph showing the relationship between the threshold voltage and the hydrogen partial pressure ratio (P _H / P _TOTAL = H ₂ / (H ₂ + Ar)) during sputtering. Hydrogen partial pressure ratio (P _H / P _TOTAL = H ₂ / (H ₂ + Ar))
And the corresponding relationship between the above example numbers are the same as in Table 1.

Considering that the lower the threshold voltage is, the lower the operating voltage for operating the thin film transistor, that is, the gate voltage, and good characteristics as a device can be obtained, the result of FIG. By the sputtering method under a high condition, a normally off state with a threshold voltage of 8 V or less can be obtained. That is,
A device using a crystalline semiconductor layer obtained by obtaining the Si film shown in (13) of FIG. 1 (A), which will be the channel formation region, and thermally crystallizing this Si film has good electrical properties. It can be seen that the characteristics are exhibited.

Further, FIG. 5 shows that the higher the hydrogen partial pressure ratio, the lower the threshold voltage. From this, it is understood that, when the a-Si film which becomes the channel formation region in each of the above-described examples is produced by the sputtering method, the electrical characteristics of the device tend to be improved if the partial pressure ratio of hydrogen is increased.

The mechanism of the semi-amorphous or semi-crystalline semiconductor used in the present invention will be briefly described.

That is, in the sputtering method, when a single crystal silicon semiconductor is used as a target and sputtering is performed with a mixed gas of hydrogen and argon, atomic silicon is separated from the target due to the sputtering (impact) of heavy atoms of argon, and the formation is performed. It flies on a substrate having a surface, but at the same time, a lump in which several tens to several hundreds of thousands of atoms are solidified separates from the target as a cluster and flies to the formation surface.

During this flight, hydrogen bonds with the dangling bonds of silicon around the periphery of this cluster, and is formed as a relatively highly ordered region on the surface to be formed.

That is, a mixture of clusters having high ordering on the film-forming surface and having Si—H bonds in the periphery and pure amorphous silicon is used. By heat-treating this in a non-oxidizing gas at 450 ℃ ~ 700 ℃,
Si-H bonds react with other Si-H bonds to form Si-Si bonds.

However, at the same time this bond pulls on each other, the highly ordered clusters tend to shift their phase to a more highly ordered state, ie crystallization. However, between adjacent clusters, Si-Si bound to each other pulls each other. The results show that the crystal has lattice distortion and the laser Raman crystal peak is 520 cm ^{- 1 of a} single crystal.
The measurement is shifted to the lower wave number side.

Since the Si-Si bond between the clusters anchors (connects) each other's clusters, the energy bands in each cluster can be electrically connected to each other via the anchoring points. Therefore, it is possible to obtain carrier mobility of 10 to ²⁰⁰ cm ² / V Sec, which is fundamentally different from that of polycrystalline silicon in which the grain boundaries act as a carrier barrier.

That is, as in the present invention, a semi-amorphous or semi-crystal based on such a definition has an apparent crystallinity, but it can be electrically predicted to have substantially no grain boundaries.

Of course, the annealing temperature is not the medium temperature annealing of 450 ° C. to 700 ° C. in the case of the silicon semiconductor, but 10
When crystallizing with crystal growth of 00 ° C. or higher, oxygen and the like in the film are broken out to the grain boundaries by the crystal growth and form a barrier. This is a material with the same crystals and grain boundaries as a single crystal.

When the degree of anchoring between clusters in this semiconductor is increased, the carrier mobility becomes higher. For this purpose, the amount of oxygen in this film is adjusted to 7 × 10 ¹⁹ cm ^-3 instead of 2 × 10 ¹⁹ cm ^-3 as in the above-mentioned embodiment.
When it is preferably 1 × 10 ¹⁹ cm ⁻³ or less, crystallization can be performed at a temperature lower than 600 ° C., and high carrier mobility can be obtained.

FIG. 6 shows the reference examples 1, 2, 3, 4 of the present invention.
The crystallinity obtained by thermally crystallizing the a-Si film when the partial pressure ratio of hydrogen at the time of sputtering when forming the Si film (13) to be the channel formation region of 3 shows a Raman spectrum of a silicon semiconductor layer having a. Table 2 shows the relationship between the display symbols shown in FIG. 6, the example numbers, and the hydrogen partial pressure ratio during sputtering.

[0075]

[Table 2]

Looking at FIG. 6, in comparison with the curve (61), the curve (6
2) That is, comparing the case where the partial pressure ratio of hydrogen at the time of sputtering when forming the Si semiconductor layer to be the channel formation region is 0% and the case where it is 20%, the hydrogen content at the time of sputtering when thermally crystallized is compared. The Raman spectrum when the pressure ratio is 20% shows that the crystallinity of the semiconductor silicon is remarkably exhibited.

Further, the average crystal grain size is 5 to 5 from the half width.
400Å Typically 50-300Å. The peak position of the Raman spectrum was shifted to the lower wave number side than the peak position of 520 cm ⁻¹ of the single crystal silicon, and it clearly had lattice strain. This clearly shows the feature of the present invention. That is, by the sputtering method with hydrogen added
The effect of producing a Si film is that it appears only after the Si film is thermally crystallized.

As described above, when the lattice strain is present, each of the fine crystal grains is in a state of being forcibly contracted with each other, so that the close contact between the crystal grain boundaries becomes strong and the crystal grain boundary portions are increased. There is no energy barrier for carriers in
In addition, segregation of impurities such as oxygen is less likely to occur, and as a result, high carrier mobility can be realized.

The grain size as referred to in the present invention is shown by using the numerical value calculated by the Raman spectrum obtained when the produced semiconductor film is subjected to the laser Raman spectroscopic analysis. It is unclear whether or not exists, and rather, as described above, it is expected that grain boundaries do not exist.

As a method of varying the crystal grain size of the semiconductor film, a method of varying the RF power to be applied during the sputtering film formation can be considered.

As another method, the strength of the magnetic field of the magnetic field supplying means installed near the target may be changed. For example, when the magnetic field supplying means is an electromagnet, the grain size of the semiconductor film formed on the substrate can be increased by increasing the current flowing through the coil to increase the magnetic field. The reverse is also possible.

Table 3 below shows data showing the effects of the present invention.

[0083]

[Table 3]

In Table 3, the hydrogen partial pressure ratio means the Si film (see FIG. 1A) which becomes the channel forming region in this embodiment.
(13)) is a condition for producing by the magnetron type RF sputtering method.

The S value means the value of [d (ID) / d (VG)] ^-1 at the rising portion of the curve in the graph showing the relationship between the gate voltage (VG) and the drain current (ID) showing the characteristics of the device. It is the minimum value, and the smaller this value is, the sharper the slope of the curve showing the (VG-ID) characteristic is, and the higher the electrical characteristic of the device is. VT represents a threshold voltage. μ represents the mobility of carriers, and the unit is (cm ² / V · s). The on / off characteristic is the logarithmic value of the ratio between the ID value and the minimum ID value at VG = 30 volts in the curve showing the (VG-ID) characteristic.

From Table 3, it can be seen that in order to obtain a semiconductor device having a higher overall performance by the method of the present invention, it is appropriate to adopt the condition that the hydrogen partial pressure ratio is 80% or more.

In this embodiment, the underlying silicon oxide film and the semiconductor film are continuously formed in a dedicated reaction chamber, but the invention is not particularly limited to this case, and the structure of the semiconductor device to be manufactured is also not limited thereto. However, it is apparent that it is within the scope of the technical idea of the present invention to continuously form the semiconductor film, the gate insulating film, the gate electrode and the like in a dedicated reaction chamber. [Embodiment 2] In this embodiment, an insulated gate semiconductor device having the structure shown in FIG. 3 is shown. Although coating an insulating substrate with a silicon oxide film is the same as that in Embodiment 1, this embodiment shows a manufacturing method in which formation of a gate insulating film is finished before formation of a semiconductor layer forming a channel region. ing. Metallic molybdenum was formed on the insulating film (12) by a sputtering method to have a thickness of 3000 liters and subjected to predetermined patterning to form a gate electrode (20).

Next, a gate oxide film (SiO ₂ ) (15) having a thickness of 100 nm was formed by the magnetron type RF sputtering method under the following conditions by using the multi-chamber type sputtering apparatus of FIG. 2 (B). Oxidizing atmosphere 100% Pressure 0.5pa Film forming temperature 100 ℃ RF (13.56MHz) Output 400W

A silicon target or a synthetic quartz target was used. When forming this oxide film, it is possible to reduce the interface state density of the gate insulating film by sputtering with a large ratio of oxygen to the inert gas, most preferably 100% oxygen, and realize a transistor with excellent characteristics. it can.

Next, the substrate is moved to the reaction chamber (4) dedicated to the semiconductor film to form a channel formation region on the silicon oxide film.
An a-Si film (13) is formed to a thickness of 100 nm.

The film forming conditions are H ₂ / (H ₂ + Ar) = 80% (partial pressure ratio) in an atmosphere of argon and hydrogen which are inert gases. Film forming temperature 150 ° C. RF (13.56 MHz) Output 400 W Total pressure The target was 0.5 Pa, and the target was a Si target.

Thereafter, the substrate on which the semiconductor film has been formed is taken out from the reaction chamber, and the substrate is not taken out of the apparatus, but is passed through the substrate passage chamber.
In the temperature range of 450 ° C to 700 ° C in (2), especially in the temperature of 600 ° C for 10 hours in hydrogen or an inert gas, in this example, 100% nitrogen atmosphere in the a-Si film (13) Was thermally crystallized to produce a silicon semiconductor layer having high crystallinity. At this time, at the same time, the substrate was newly moved from the preliminary chamber to the reaction chamber (3) dedicated to the silicon oxide film, and the gate insulating film was formed under the above conditions.

The amount of oxygen impurities existing in the semiconductor film formed by such a method is 1 × by SIMS analysis.
The carbon content was 10 ¹⁹ cm ^-3 , the carbon content was 4 x 10 ¹⁸ cm ^-3 , and the hydrogen content was 5% or less. As a result, the channel region (22) could be formed on the gate electrode (20). During this heat treatment, the substrate introduced into the reaction chamber for silicon oxide afterwards for the purpose of forming the gate insulating film is moved to the semiconductor film reaction chamber (4) through the substrate passage chamber, and the semiconductor film is moved under the same conditions. Well formed.

Next, the heat-treated substrate is removed from the passage chamber by N
After moving to the reaction chamber (9) for forming a semiconductor film, the n ⁺ a-Si film (1
4) was formed into a film with a thickness of 50 nm by the magnetron type RF sputtering method under the following conditions. At the same time, the substrate on which the semiconductor film had been formed was heat-treated in the substrate passage chamber, a new substrate was simultaneously introduced into the reaction chamber for the gate insulating film, and thereafter, a plurality of treatments were similarly performed at the same time.

The film-forming conditions are as follows: the hydrogen partial pressure ratio is 10 to 99% or more (80% in this embodiment), and the argon partial pressure ratio is 10 to 99% (19% in this embodiment). RF (13.56MHz) output 400W, total pressure 0.5Pa, and phosphorus-doped single crystal silicon was used as the target.

Next, an aluminum film for the source and drain electrodes is formed on the semiconductor layer (14) and patterned to form the source and drain impurity regions (14) (1
4 ') and source and drain electrodes (16) and (16') were formed to complete the semiconductor device.

In this embodiment, since the gate insulating film is formed before forming the semiconductor film in the channel forming region,
During the thermal crystallization process, the vicinity of the interface between the gate insulating film and the channel region is appropriately thermally annealed, and the interface state density can be reduced. Further, since the back pressure is set to 1 × 10 ⁻⁶ Pa or less and the exhaust gauge is combined with the turbo molecular pump and the cryopump during the formation of each film, the film formation can be performed in a state in which there are few oil-free impurities. The oxygen impurity amount in the active layer (13) in this example was 1 × 10 ¹⁹ cm ⁻³ , and its mobility μ was 40.8.

Although the a-Si film is used as the semiconductor layer to be thermally crystallized in this example and the like, the present invention is also effective when thermally crystallizing another non-single crystal semiconductor. There is no end.

Although Ar was used as the inert gas during the above-mentioned sputtering, a halogen gas such as He or a reactive gas such as SiH ₄ and Si ₂ H ₆ which was made into plasma was used as the other gas. May be. Further, in the deposition of the a-Si film by the magnetron type RF sputtering method of the present embodiment, the hydrogen concentration is 5 to 100%, the deposition temperature is in the range of 50 to 500 ° C., the RF output is in the range of 500 Hz to 100 GHz, 1W-10MW
Can be arbitrarily selected within the range, and may be combined with a pulse energy source.

By using more intense light irradiation (wavelength of 1000 nm or less) energy and electron cyclotron resonance (ECR) conditions, hydrogen may be made to have a higher plasma for sputtering.

This is a microstructure in a film formed by sputtering by making light atoms such as hydrogen more plasma and efficiently generating positive ions necessary for sputtering, in the case of the present embodiment, an a-Si film. This is to prevent the formation of microstructures inside. Further, the other reactive gas may be applied to the above means.

In this embodiment, an amorphous semiconductor film is simply a-Si.
Described as a membrane. It usually represents a silicon semiconductor, but it may also be germanium or a mixture of silicon and germanium Si _x Ge _{1 -X} (0 <X <1).

Needless to say, the structure of the present invention can be applied to a staggered type, a coplanar type, an inverted staggered type, and an inverted coplanar type insulated gate field effect transistor.

[0104]

EFFECT OF THE INVENTION With the structure of the present invention, thermal crystal becomes a problem in the step of obtaining a crystalline semiconductor by thermally crystallizing a non-single crystal semiconductor obtained by an industrially useful sputtering method. It was possible to solve the problem of difficulty in conversion, and it was possible to fabricate a high-performance thin film transistor by using this crystalline semiconductor layer.

Further, according to the method of the present invention, the minimum required portion of the insulated gate semiconductor device can be formed by the sputtering method. Therefore, in the insulated gate semiconductor device as shown in FIG. 1D, the lower side of the active layer (18)
That is, a part of contact with the base insulating film is partially oxidized and has a semi-insulating property, and the electrical characteristics in this part are slightly deteriorated. As a result, a back channel cannot be generated in this portion, and the reverse leakage current can be reduced. This is very effective when this semiconductor device is used as a CMOS and shows a significant effect in reducing the off current.

Further, it is possible to reduce the concentration of oxygen impurities existing in the semiconductor film, it is difficult to form a barrier against carriers near the crystal grain boundaries, and an insulated gate semiconductor device having a very high mobility is realized. We were able to.

Furthermore, since a plurality of different processes can be performed in the same device, continuous processes can be performed without being affected by the outside. In addition, productivity can be improved because a plurality of processes can be performed at the same time. Further, since the semiconductor film and the gate insulating film that influence the characteristics of the insulated gate semiconductor device can be continuously formed, the characteristics are not affected by external factors and constant electric characteristics can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process of the first embodiment.

FIG. 2 is a schematic view of a multi-chamber sputtering apparatus for the present invention.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a diagram showing the relationship between the partial pressure ratio of hydrogen and the mobility of carriers.

FIG. 5 is a diagram showing a relationship between a hydrogen partial pressure ratio and a threshold value.

FIG. 6 is a Raman spectrum of the crystalline semiconductor film of the present invention.

[Explanation of symbols]

(1) ... spare room (2) ・ ・ ・ Substrate passage chamber (3) (4) ... Sputtering chamber (5) (6) (7) (8) ・ ・ ・ Gate valve

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI H01L 21/336 H01L 29/78 627B 627G (56) Reference JP-A-1-103825 (JP, A) JP-A-2-224255 (JP, A) JP 60-254661 (JP, A) JP 59-124163 (JP, A) JP 63-168021 (JP, A) JP 57-104260 (JP, A) (JP 58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 29/786 H01L 21/20 H01L 21/31 H01L 21/336

Claims (3)

(57) [Claims] 1. A first silicon oxide film is formed above a substrate by a sputtering method, and the non-single-crystal semiconductor film is formed by the sputtering method without exposing the first silicon oxide film to the atmosphere. A second silicon oxide film formed on the non-single-crystal semiconductor film by a sputtering method without exposing the non-single-crystal semiconductor film to the air. A method of manufacturing a thin film transistor in which the non-single-crystal semiconductor film is crystallized without being exposed, wherein the crystallized semiconductor film has a channel formation region, and the channel formation region is the second silicon oxide film. A method for manufacturing a thin film transistor, which is covered and the non-single-crystal semiconductor film is a non-single-crystal semiconductor film in which silicon and germanium are mixed. 2. A first silicon oxide film is formed above a substrate by a sputtering method, and the non-single-crystal semiconductor film is formed by the sputtering method without exposing the first silicon oxide film to the atmosphere. A second silicon oxide film formed on the non-single-crystal semiconductor film by a sputtering method without exposing the non-single-crystal semiconductor film to the air. A method of manufacturing a thin film transistor in which the non-single-crystal semiconductor film is crystallized without being exposed, wherein the crystallized semiconductor film has a channel formation region, and the channel formation region is the second silicon oxide film. And the formation of the first silicon oxide film, the non-single-crystal semiconductor film, and the second silicon oxide film and the crystallization of the non-single-crystal semiconductor film are performed in the same apparatus. The non-single crystal semiconductor film is made of silicon and germanium. The method for manufacturing a thin film transistor, wherein the presence and is a non-single crystal semiconductor film mixed. 3. The method of manufacturing a thin film transistor according to claim 1, wherein the crystallization is performed by heating.