JP2003249450A - Preparing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for preparing a semiconductor device having satisfactory characteristics. <P>SOLUTION: In the preparing method for a semiconductor device, a first amorphous semiconductor film where the concentration of oxygen is set to 7×10<SP>19</SP>cm<SP>-3</SP>or less is formed on an insulating board, the first amorphous semiconductor film is crystallized by heat treatment, and a second amorphous semiconductor film is formed by a magnetron type RF sputtering method using a single crystal silicon as a target under an atmosphere containing argon. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device using a semiconductor having a microcrystal structure having lattice strain.

SUMMARY OF THE INVENTION According to the present invention, a semiconductor target having an impurity concentration of 5 × 10 ¹⁸ cm ⁻³ or less in an atmosphere of hydrogen or hydrogen as a main component gas (the rest is an inert gas such as argon) is sputtered. Thus, by thermally crystallizing an amorphous semiconductor having an oxygen concentration of 7 × 10 ¹⁹ cm ^-3 or less, preferably 1 × 10 ¹⁹ cm ^-3 or less, a lattice strain of an oxygen concentration of 7 × 10 ¹⁹ cm ^-3 or less can be obtained. The present invention relates to a semiconductor device using a semiconductor having a microcrystal structure.

[0003]

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

It is also known to form microcrystals by the plasma CVD method.

[0005]

[Problems of the prior art] When a non-single crystal semiconductor film is obtained by a low pressure CVD method, it is difficult to form a uniform film on a large-area substrate.

Further, when the microcrystal is formed by the plasma CVD method, there is a problem that the film forming process takes time. Further, if left in the atmosphere, there is a problem that natural oxidation occurs and the film itself is not dense.

[0007]

An object of the present invention is to obtain a microcrystalline semiconductor having a lattice strain by thermally crystallizing a dense non-single-crystal semiconductor which does not undergo spontaneous oxidation and which is obtained by a sputtering method which is industrially produced in a good quantity. For the purpose of the invention. Then, it is intended to use it in the active region of the insulating gate type field effect semiconductor device, particularly in the channel forming region.

[0008]

The present invention has an average crystal grain size of 5 to 400 Å
And the hydrogen content therein is 5 atomic% or less. In particular, oxygen as an impurity is characterized by being 7 × 10 ¹⁹ cm ^-3 or less, preferably 1 × 10 ¹⁹ cm ^-3 or less. And by giving each microcrystal a lattice strain, the crystal interfaces of the micro are closely contacted to each other,
It tries to eliminate the barrier for carriers at the grain boundaries.

Therefore, in a polycrystalline grain boundary having no lattice strain, oxygen segregates there and the barrier inhibits carrier movement. However, in the present invention, such a lattice strain causes a barrier. Since it has no or negligible level, it has an electron mobility of 5 to 300 cm ² / Vsec, which is an order of magnitude superior.

The present invention relates to an amorphous (amorphous or very close to) semiconductor film (hereinafter a-Si) formed on a substrate by sputtering in an atmosphere containing hydrogen or hydrogen and an inert gas as main components. And a step of crystallizing the amorphous semiconductor film obtained by the sputtering method at a temperature of 450 to 700 ° C., typically 600 ° C.

[0011]

【Example】

(Embodiment 1) This embodiment is a magnetron type
The a-Si film produced by the RF (radio frequency) sputtering device is thermally crystallized to have a lattice strain, and its average crystal grain size is as small as 5 to 400 Å, and the amount of contained hydrogen is 5
Oxygen as an impurity is less than or equal to 7% 10 ¹⁹
A polycrystal silicon semiconductor layer of cm ³ or less, preferably 1 × 10 ¹⁹ cm ^-3 or less, which was a crystal (also referred to as semi-amorphous Quasi-crystal or Semi-amrphas) was formed. A thin film transistor was manufactured using this microcrystalline silicon semiconductor layer.

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

First, a silicon oxide film (12) is formed on a glass substrate (11).
Was formed to a thickness of 200 nm by a magnetron type RF sputtering method under the following conditions. O ₂ 100% atmosphere Film formation temperature 150 ℃ RF (13.56MHz) Output 400W Pressure 0.5 Pa Single crystal silicon is used as a target

Furthermore, a high-purity magnetron type RF
The a-Si film (1
3) is deposited to a thickness of 100 nm.

In this sputtering method, 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. The single crystal silicon of the target was also made to have an oxygen concentration of 5 × 10 ¹⁸ cm ^-3 or less, for example, 1 × 10 ¹⁸ cm ^-3 , so that oxygen as an impurity in the formed film was extremely reduced.

The film forming conditions were a hydrogen content ratio of 20 to 100% and an argon content ratio of 80 to 0%, for example, a hydrogen content of 100%. In such an atmosphere, H ₂ / (H ₂ + Ar) = 100% (partial pressure ratio), film formation temperature 150 ° C. RF (13.56 MHz) output 400 W, total pressure 0.5 Pa, and a high-purity Si target was used.

After that, the temperature of 450 to 700 ° C., for example 600 ° C., is applied for 10 hours, and the a-Si film (1) is formed in hydrogen or an inert gas, in this embodiment, 100% hydrogen atmosphere.
Thermal crystallization of 3) was performed. It was so-called microcrystal (or semi-amorphous).

The 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 is added just in case, for example N ₂ O.
Was added as 0.1cc / sec and 10cc / sec. Then, the oxygen concentration after crystallization increased to 1 × 10 ²⁰ cm ^-3 and 4 × 10 ²⁰ cm ^-3 . However, when such a coating was used, at the same time, the temperature required for crystallization was 700 ° C. or more, or the crystallization time was at least 5 times or more, whereby crystallization could be achieved. That is, considering industrially the softening temperature of the glass of the substrate, the treatment at 700 ° C. or lower, preferably 600 ° C. or lower is important, and it is also important to further reduce the time required for crystallization. However, no matter how the impurities such as oxygen concentration were reduced, it was experimentally impossible to crystallize the a-Si semiconductor by thermal annealing below 450 ° C.

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 a leak 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. Of course, in germanium, or in the case of a compound semiconductor of silicon and germanium, the anneal temperature could be lowered by about 100 ° C.

This microcrystalline semiconductor had a lattice distortion and was shifted to the low wave number side as compared with single crystal silicon, as is apparent from the laser Raman analysis data shown in FIG.

A method of manufacturing an insulating gate type field effect transistor which is a semiconductor device of the present invention will be described below. That is, the device isolation patterning is performed on the thermally crystallized microcrystalline silicon semiconductor obtained by the method of the present invention, and FIG.
The shape of (a) was obtained.

Next, an n ⁺ a-Si film (14) was formed in a thickness of 50 nm by a magnetron type RF sputtering method under the following conditions. The film forming conditions are as follows: hydrogen partial pressure ratio of 20 to 99% or more (80% in this embodiment), argon partial pressure ratio of 80 to 0% (in this embodiment).
19%), PH ₃ partial pressure ratio of 0.1% to 10% (1% in the example), film formation temperature 150 ° C RF (13.56MHz) output 400W total pressure 0.5Pa, single crystal (oxygen) as a target. Concentration 1 × 10 ¹⁸ cm
^-3 ) Si was used as the target.

In order to manufacture the semiconductor layer having one conductivity type, the PCVD method may be used. Further, after forming the active layer, impurities (for example, B (boron), P (phosphorus), As (arsenic)) may be added by an ion implantation method in order to form a source and a drain. After that, gate region patterning was performed to obtain the shape shown in FIG.

Next, a gate silicon oxide film (15) was formed to a thickness of 100 nm by a magnetron type RF sputtering method under the following conditions to obtain the shape shown in FIG. 1 (c). Oxygen atmosphere 100% pressure 0.5pa, film formation temperature 100 ℃ RF (13.56MHz) Output 400W Single crystal silicon target or synthetic quartz target was used.

Next, contact hole opening patterning was performed to obtain the shape shown in FIG. 1 (d). Finally, an aluminum electrode (16) was formed to a thickness of 300 nm by vacuum evaporation and patterned to obtain the shape shown in FIG. 1 (e). Then, a hydrogen thermal anneal was performed at 375 ° C. in a 100% hydrogen atmosphere. The thin film transistor was completed by carrying out the heating for 30 minutes. This hydrogen thermal anneal is for reducing the interface level between the polycrystalline silicon semiconductor and the silicon oxide insulating film and improving the device characteristics.

In the thin film transistor shown in FIG. 1 (e), S is a source electrode, G is a gate electrode, and D is a drain electrode. In addition, the size of the channel part (17) of the thin film transistor shown in FIG.
The size is × 100 μm.

The above is the method of manufacturing a thin film transistor using the polycrystalline silicon semiconductor layer manufactured in this embodiment. In order to show the effect of the present invention, the a-Si layer of FIG. 1 (a) which is a channel forming region is formed. Five examples were prepared in which the concentration of hydrogen and the concentration of oxygen mixed involuntarily as conditions for forming the film of (13) by the magnetron type RF sputtering method were changed.

(Embodiment 2) In this embodiment, the partial pressure ratio of the atmosphere at the time of sputtering is H ₂ / (when forming (13) of FIG. 1 (a), which becomes the channel forming region in the manufacturing method of Embodiment 1. H ₂ + Ar) = 0% (partial pressure ratio), and other conditions were the same as in Example 1. The oxygen concentration was 2 × 10 ²⁰ cm ^-3 .

(Embodiment 3) In this embodiment, the partial pressure ratio of the atmosphere at the time of sputtering is H ₂ / (when forming (13) of FIG. 1 (a), which becomes the channel forming region in the manufacturing method of Embodiment 1. H ₂ + Ar) = 20% (partial pressure ratio), and the others were manufactured by the same method as in Example 1. The oxygen concentration during film formation was 7 × 10 ¹⁹ cm ^-3 .

(Embodiment 4) In this embodiment, the partial pressure ratio of the atmosphere at the time of sputtering when manufacturing (13) of FIG. 1 (a), which becomes the channel forming region in the manufacturing method of Embodiment 1, is H ₂ / ( H ₂ + Ar) = 50% (partial pressure ratio), and other conditions were the same as in Example 1. The oxygen concentration during film formation was 3 × 10 ¹⁹ cm ⁻³ .

(Embodiment 5) In this embodiment, the partial pressure ratio of the atmosphere at the time of sputtering when manufacturing (13) of FIG. 1 (a), which becomes the channel formation region in the manufacturing method of Embodiment 1, is H ₂ / ( H ₂ + Ar) = 80% (partial pressure ratio), and others were manufactured by the same method as in Example 1. The oxygen concentration during the film formation was 1 × 10 ¹⁹ cm ⁻³ .

The results of comparing the electrical characteristics of the above examples will be shown below. FIG. 2 shows the completed channel portions of the first to fifth embodiments (carrier mobility μ (FIELD in (17) of FIG. 6e).
MOBILITY) hydrogen partial pressure ratio during sputtering (P _H / P
It is a graph of the relationship of _TOTA = H ₂ / (H ₂ + Ar)).
Table 1 below shows the correspondence between the plot points in FIG. 2 and the examples.

[0035]

[Table 1]

According to FIG. 2, when the hydrogen partial pressure is 0%, the oxygen concentration is
Is 2 × 10²⁰cm^-3There is also 3 × 10 ^-1cm²V / sec and bull
On the other hand, as in the present invention, the oxygen concentration is 20% or more.
7 × 10¹⁹cm^-3Remarkably high mobility of 2 cm below²/ Vs
Is it clear that μ (FIELD MOBILITY) is obtained above ec?
It

It is presumed that this is because, when hydrogen was added, oxygen in the chamber in the sputter was turned into water and could be removed positively by the cryopump. Figure 3 shows the threshold voltage and the hydrogen partial pressure ratio (P _H / P _TOTAL = H ₂ / (H ₂ +
It is a graph of the relationship of Ar)).

The correspondence between the hydrogen partial pressure ratio (P _H / P _TOTAL = H ₂ / (H ₂ + Ar)) and the example number is 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 lower the gate voltage is, and good characteristics as a device can be obtained, the result of FIG. A threshold voltage of 8 V or less can be obtained by a sputtering method under conditions of high 20% or more.
You can get the state of Marioff. That is, a device using a microcrystalline silicon semiconductor layer obtained by obtaining an a-Si film shown in (13) of FIG. 1A to be a channel formation region and recrystallizing the a-Si film. It can be seen that (the thin film transistor in this example) exhibits good electrical characteristics.

The laser Raman spectrum of the polycrystalline silicon semiconductor layer obtained by thermally crystallizing the a-Si film is shown. Figure 4
Table 2 shows the relationship between the display symbol shown in, the example number, and the hydrogen partial pressure ratio during sputtering.

[0040]

[Table 2]

As shown in FIG. 4, the curve (4
3) In other words, comparing the case where the hydrogen partial pressure ratio during sputtering is 0% and 100% when the a-Si semiconductor layer that becomes the channel formation region ((17) in FIG. 1 (e)) is produced, ,
When crystallized by thermal annealing, the Raman spectrum when the partial pressure ratio of hydrogen at the time of sputtering is 100% has a remarkable crystallinity, and the average crystal grain size is 5 to more than the half width. 400 Å Typically 50 to 300 Å. Then, the peak value of 520 cm ^{-1 of the} single crystal silicon is shifted to the lower wave number side, and the lattice strain is obviously present. This clearly shows the feature of the present invention. That is, the effect of producing an a-Si film by the hydrogen-added sputtering method appears only when the a-Si film is thermally crystallized.

With such a lattice strain, since the fine crystal grains are forcibly contracted with each other, the close contact between the crystal grain boundaries becomes strong, and the energy barrier for carriers at the crystal grain boundaries also increases. Segregation of impurities such as oxygen is also unlikely to occur. As a result, high carrier mobility can be expected.

Generally, when the drain voltage VD is low in a thin film transistor which is a field effect transistor, the relationship between the drain current ID and the drain voltage VD is expressed by the following equation. ID = (W / L) μC (VG-VT) VD (Solid.State electronics.Vol.24.No.11.pp.1059.198
1.Printed in Britain) In the above formula, W is the channel width, L is the channel length, μ
Is the carrier mobility, C is the capacitance of the gate oxide film, VG
Is a gate voltage and VT is a threshold voltage.

Ar was used as the inert gas during the above-mentioned sputtering, but other inert gas such as He or a reactive gas such as SiH ₄ and Si ₂ H ₆ which is made into plasma is an atmosphere gas. You may add and use it for some. In forming the a-Si film by the magnetron type RF sputtering method of this embodiment, the hydrogen concentration is 5 to 100%, and the film forming temperature is room temperature to 500%.
In the range of ° C, the RF output is in the range of 500 Hz to 100 GHz, the output can be arbitrarily selected in the range of 100 W to 10 MW, and may be combined with a pulse energy source. Photo-sputtering may be performed by applying more intense light irradiation (wavelength 100 to 500 nm or less) energy.

This is because light atoms such as hydrogen are made to be more plasma, positive ions necessary for sputtering are efficiently generated, and hydrogen or hydrogen atoms are uniformly added to the film formed by sputtering. As a result, This is for forming a semiconductor film in which the mixing of oxygen is suppressed to 7 × 10 ¹⁹ cm ^-3 or less, preferably 1 × 10 ¹⁹ cm ^-3 or less.

In the present invention, an amorphous semiconductor film is simply referred to as an a-Si film in the specification. However, although this mainly uses silicon semiconductors, germanium, SixGe _1-x
It may be (0 <x <1). This may be a P or N type semiconductor as well as an intrinsic semiconductor.

Further, the other reactive gas may be applied to the above means.

[0048]

With the structure of the present invention, in the process of thermally crystallizing a non-single-crystal semiconductor obtained by an industrially useful sputtering method to obtain a polycrystalline semiconductor, it is difficult to thermally crystallize. It was possible to solve the problem and to fabricate a high-performance thin film transistor using this polycrystalline semiconductor layer.

[Brief description of drawings]

FIG. 1 shows a manufacturing process of Examples 1 to 6.

FIG. 2 shows a relationship between a partial pressure ratio of hydrogen added at the time of manufacturing an a-Si film to be a channel formation region and a carrier mobility in a thin film transistor manufactured in this example in a manufacturing process of a thin film transistor manufactured in this example. Is shown.

3A and 3B show a partial pressure ratio of hydrogen added at the time of manufacturing an a-Si film to be a channel formation region and a threshold value in a thin film transistor manufactured in this example in a manufacturing process of a thin film transistor manufactured in this example. It shows the relationship.

FIG. 4 shows a Raman spectrum of a polycrystalline silicon semiconductor manufactured in this example.

[Explanation of symbols]

11 ... Glass substrate 12 ... Silicon oxide film 13 ... Microcrystalline semiconductor active layer 14 ... N ⁺ a-Si film 15 ... Gate oxide film 16 ... Aluminum electrode 17 ... Channel formation region S ... Source electrode G ... Gate electrode D ... Drain electrode

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 29/786 H01L 29/78 618A F term (reference) 4K029 BA35 BB10 BD01 DC39 EA00 EA05 GA01 5F052 AA17 DA02 DA03 DB07 JA01 5F103 AA08 BB22 DD16 GG03 HH04 LL13 PP15 RR05 RR06 5F110 AA01 CC01 DD02 DD13 EE03 EE43 FF02 FF28 GG01 GG02 GG03 GG14 GG16 GG25 GG33 GG34 GG43 GG60 HK03 QP25 HK03 QP25 HK03 HK32 HK32 HK32 HK32 HK32 HK32 HK32 HK32 HK32 HK32

Claims (5)

[Claims] 1. An amorphous semiconductor film having an oxygen concentration of 7 × 10 ¹⁹ cm ⁻³ or less formed on an insulating substrate by a magnetron RF sputtering method using a semiconductor target in an atmosphere containing argon. A method for manufacturing a semiconductor device, comprising: 2. A magnetron type RF sputtering method using silicon as a target in an atmosphere containing argon,
A method for manufacturing a semiconductor device, which comprises forming an amorphous semiconductor film having an oxygen concentration of 7 × 10 ¹⁹ cm ⁻³ or less on an insulating substrate. 3. An amorphous semiconductor film having an oxygen concentration of 7 × 10 ¹⁹ cm ⁻³ or less is formed on an insulating substrate by a magnetron RF sputtering method using a single crystal silicon as a target in an atmosphere containing argon. A method for manufacturing a semiconductor device, which comprises forming the semiconductor device. 4. The oxygen concentration on the insulating substrate is 7 × 10 ¹⁹ cm.
^-3 or less, a first amorphous semiconductor film is formed, the first amorphous semiconductor film is crystallized by a heat treatment, and a single crystal silicon is used as a target in an atmosphere containing argon. A method for manufacturing a semiconductor device, which comprises forming a second amorphous semiconductor film by an RF sputtering method. 5. The method for manufacturing a semiconductor device according to claim 1, wherein the oxygen concentration is 1 × 10 ¹⁹ cm ⁻³ or less.