JPH0794748A - Method of fabricating semiconductor film - Google Patents

Abstract

PURPOSE:To fabricate a uniform large area semiconductor film with higher field effect mobility in a low temperature process with high productivity by accelerating group IV element ions and hydrogen from a plasma source including the ions and implanting the ions into a microcrystal semiconductor film comprising a group IV element formed on a substrate. CONSTITUTION:Ions 21 from a plasma source including IV group element ion, e.g. silicon ions and hydrogen ions are accelerated using an ion implanting apparatus, and the silicon ions and the hydrogen ions are simultaneously implanted into a microcrystal semiconductor film 14 made of a IV element, e.g. silicon formed on a substrate 13. The implantation conditions are as follows. 5% SiH4 gas diluted with hydrogen for example is introduced from a gas introduction inlet with RF power of 200W for plasma formation, the acceleration voltage of the ions 21 in the plasma is 100KV, the ion current density is 10 muA/cm<2>, and the substrate temperature upon the implantation is 350 deg.C. Thus, the degree of crystallization of a semiconductor film is sharply improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor film used for thin film transistors and the like.

[0002]

2. Description of the Related Art In recent years, there is an increasing need to fabricate a thin film transistor on a transparent insulating substrate in order to fabricate an externally mounted drive circuit such as a liquid crystal display or an image sensor on the same substrate as a display or an image sensor. At that time, in order to use a glass substrate which is easy to have a large area and is inexpensive as the transparent insulating substrate, it is necessary to lower the manufacturing process temperature. For example, Corning's # 7059 glass has a strain point temperature of 593 ° C. and a usable process temperature of at least 600 ° C. or lower, preferably 450 ° C. or lower. In order to use a cheaper glass substrate or plastic substrate, a lower process temperature is preferable.

On the other hand, in a large area display, a long image sensor, etc., in order to drive a large load or drive at high speed, the semiconductor film formed for a thin film transistor must have a large field effect mobility. The semiconductor film of a thin film transistor is divided into a channel portion where no impurity is injected and a source and drain portion where impurity is injected to make a P-type or N-type semiconductor. Excellent transistor characteristics can be obtained.

For the above reasons, it can be manufactured at a low temperature,
In addition, for the purpose of manufacturing a semiconductor film having a high field effect mobility, research on an amorphous silicon film, a polycrystalline silicon film and the like has been extensively conducted.

The amorphous silicon film has a temperature of about 200 to 300 ° C. by the plasma CVD method, and a temperature of 400 to 300 ° C. by the LPCVD method.
Although it can be manufactured at a low temperature of about 500 ° C., the field effect mobility is generally as small as about 0.6 cm ² / V · s, which is insufficient for driving a large load or forming a high-speed driving circuit.

On the other hand, a polycrystalline silicon film having a large field effect mobility of about 30 to 150 cm ² / V · s has been obtained. However, since the thin film manufacturing temperature is as high as 600 ° C. or higher, a quartz substrate or high An expensive substrate such as strain point glass must be used, and it is difficult to use an inexpensive glass substrate.

Therefore, a method for improving the semiconductor characteristics such as field effect mobility by studying a method of forming an amorphous silicon film at a low temperature and then performing a crystallization treatment at a low temperature to convert the film into a polycrystalline silicon film. Has been done. Examples of this crystallization treatment method include methods such as furnace annealing, laser annealing, and lamp annealing.

[0008]

The method of furnace annealing is as follows.
Even if the annealing temperature is about 550 to 600 ° C., the annealing time is about 4 to 24 hours, and if the temperature is lowered, annealing for a longer time is required, and as a result, the influence on the glass substrate becomes large, resulting in heat shrinkage or heat shrinkage. Warpage due to heat becomes a problem. There is also a problem that the processing time is long and the productivity is poor.

In the laser annealing method, it is possible to use a short-wavelength laser to absorb the amorphous silicon film as much as possible so as not to damage the glass substrate, but it is difficult to irradiate a large area. Therefore, there is a problem in the uniformity of the boundary area of laser irradiation.

The lamp annealing method is a method in which the amorphous silicon film on the substrate is irradiated with lamp light to anneal the film. Although it is possible to irradiate a large area to some extent,
Since it contains long-wavelength light, there is a problem that it penetrates the amorphous silicon film and damages the glass substrate.

As a method of solving such a problem, in Japanese Patent Application No. 4-307350, an ion shower doping method is used to implant silicon ions together with a large amount of hydrogen ions into an amorphous silicon film. It is disclosed that the amorphous silicon film can be crystallized and converted into a polycrystalline silicon film by the assist effect of hydrogen ions even without it. Also here, apart from crystallization,
Periodic table III with a large amount of hydrogen ions in polycrystalline films
It is disclosed that implantation of group or group V element ions has a self-activating effect in which impurity ions are activated simultaneously with implantation even without annealing. By this method, it became possible to crystallize an amorphous silicon film into a polycrystalline silicon film by a low temperature process and to implant impurities into the polycrystalline silicon film by a low temperature process.

However, in order to crystallize the amorphous silicon film, a very large amount of ion implantation is required, and there is a problem that productivity is very poor under normal implantation conditions and it is not practical.

An object of the present invention is to solve the above problems and to provide a method for uniformly manufacturing a semiconductor film having a high crystallization and a high field effect mobility in a low temperature process with high productivity and in a large area. To do.

[0014]

According to the manufacturing method of the present invention, ions from a plasma source containing group IV element ions and hydrogen ions of the periodic table are accelerated to form the above-mentioned ions together with hydrogen ions.
It is characterized in that group IV element ions are implanted into a microcrystalline semiconductor film made of a group IV element of the periodic table formed on a substrate.

Further, in the method for producing a P-type semiconductor film of the present invention, ions from a plasma source containing Group IV element ions and Group III element ions of the Periodic Table and hydrogen ions are accelerated, and the ions together with the hydrogen ions are added. It is characterized in that the group IV element ion and the group III element ion are implanted into a microcrystalline semiconductor film made of a group IV element of the periodic table formed on a substrate.

Further, in the method for producing an N-type semiconductor film of the present invention, the ions from the plasma source containing the group IV element ions and the group V element ions of the periodic table and hydrogen ions are accelerated, and the ions are added together with the hydrogen ions. Group IV element ions and the group V element ions are formed on a substrate in a periodic table.
It is characterized in that it is implanted into a microcrystalline semiconductor film made of a group IV element.

In the present invention, the structure of the semiconductor film to which the ion implantation is applied is preferably a microcrystalline film. The microcrystalline film referred to here is a fine particle having crystal particles contained in an amorphous film and having a crystal particle diameter of 50 nm or less, and the ratio of the area occupied by the crystal particles on the film surface, that is, It refers to a film having a crystallization rate of 0.05 or more and 0.5 or less.

As a measuring method of the crystallization rate, a UV reflected light intensity measuring method utilizing an absorption band peculiar to a crystalline film which is not present in an amorphous film, or a transmission electron microscope observing method can be used.

In the present invention, as the group IV element ions to be implanted, it is preferable to use the same element ions as in the semiconductor film.

[0020]

[Function] When accelerating and implanting Group IV element ions and hydrogen ions into the amorphous semiconductor film, crystallization does not proceed unless a very large amount of ions are implanted. In the case of a film, crystallization easily proceeds with a relatively small amount of ion implantation. The reason for this is that fine particles of crystals exist in the microcrystalline film, and crystallization using these as nuclei is likely to proceed. This is because the As a result, the implantation time for crystallization is significantly shortened, and the crystallization rate of the obtained semiconductor film is increased, so that the field effect mobility is also increased.

In the microcrystalline semiconductor film, at the same time as the periodic table group IV element ion and hydrogen ion, the periodic table group III
By accelerating and implanting group I or group V element ions, the crystallization rate is increased to improve the field effect mobility of the semiconductor film as described above, and at the same time, a P-type or N-type impurity element is added. And the impurity element can be activated at the same time as the implantation by the action of self activation. As a result, a P-type or N-type semiconductor film having a high field effect mobility can be manufactured by a low temperature process without an annealing step.

[0022]

EXAMPLES Example 1 The present invention will be specifically described below with reference to the drawings showing the examples.

FIG. 1 shows a schematic sectional view of an ion implantation apparatus used in the present invention. 1 is a gas inlet, 2 is a chamber forming a plasma chamber for forming a plasma source, 3 is a high frequency power source for exciting the plasma source, 4 is a high frequency electrode for supplying high frequency power to the plasma source, and 5 is ionization It is a magnet for increasing efficiency and adjusting the plasma shape, and these form a plasma source. 6 is a first-stage ion acceleration power source for extracting ions from the plasma source,
7 is a second-stage ion acceleration power source for additionally accelerating the extracted ions, 8 is a deceleration power source for suppressing secondary electrons, 9 is a mesh-shaped electrode plate, and 10 is for insulating each electrode plate. Of insulators, and these form the ion accelerator. Reference numeral 11 denotes a substrate holder on which a substrate 12 to be injected is mounted, and has a rotating mechanism here for improving uniformity.

A hydrogen-diluted raw material gas (for example, hydrogen-diluted SiH ₄ ) is introduced from the gas inlet 1 and high-frequency power is applied to the high-frequency electrode 4 to form a plasma source excited to form a space between the acceleration electrode plates 9. After accelerating with, the substrate holder 11
Ions are implanted into the substrate 12 mounted on the substrate. With the above structure, it is possible to implant ions into a large-area substrate without mechanically scanning the sample substrate and electrically scanning the ion beam. By using such a device, a semiconductor film formed on a substrate is provided with a periodic table group III, group IV, group I
A step of accelerating ions from a plasma source containing group II element ions, hydrogen ions, etc. and implanting these ions can be performed.

Next, taking a silicon semiconductor film as an example, a method for producing a silicon semiconductor film having a high crystallization rate by implanting ions into the microcrystalline silicon film by using the above ion implantation apparatus will be described.

First, a SiH ₄ / H ₂ gas ratio of 1 was formed on a Corning # 7059 substrate by plasma CVD.
A mixed gas of / 30 is introduced to form a microcrystalline silicon film with a film thickness of 100 nm at a substrate temperature of 300 ° C. and an RF power of 400 W. This microcrystalline silicon film is irradiated with UV light having a wavelength of 280 nm.
When measured by the intensity of reflected light, the crystallization rate was 0.20. The measuring method is as follows.

When ultraviolet rays emitted from a deuterium lamp were made incident on a silicon film at an incident angle of 5 ° and the intensity of reflected light was measured by a spectroscope, the E ₂ band (band gap 4.31 eV) peculiar to crystalline silicon was absorbed. Thus, a peak of reflected light is observed at a wavelength of 280 nm. Since the height of this peak is proportional to the ratio of the area occupied by crystal grains on the surface of the silicon film, that is, the crystallization rate, it can be compared with the peak height of a polycrystalline silicon film having a crystallization rate of 1.0 measured in advance. The crystallization rate of the film can be calculated.

The crystallization rate obtained as described above substantially matches the area ratio of crystal grains existing in the amorphous silicon film obtained by observation with a transmission electron microscope. Also,
According to X-ray diffraction, the microcrystalline semiconductor film has a peak intensity in an orientation indicating a crystal, but the intensity is weaker than that of a polycrystalline film. Further, according to Raman spectroscopy, a peak is seen near the Raman shift of 520 cm ^-1 , which is different from the case of the amorphous state near 490 cm ^-1 .

Next, as shown in FIG. 2, ions 21 from a plasma source containing silicon ions and hydrogen ions are applied to the microcrystalline silicon film 14 formed on the substrate 13 by using the ion implantation apparatus of FIG. Is accelerated to simultaneously implant silicon ions and hydrogen ions. The injection conditions are as follows: 5% SiH ₄ gas diluted with hydrogen is introduced from the gas inlet 1, the RF power for plasma formation is 200 W, the acceleration voltage of the ions 21 in the plasma is 100 kV, and the ion current density is 10 μA / cm. ^2. The substrate temperature at the time of implantation was 350 ° C. When implanted for 13 minutes under these conditions, the total ion implantation amount of silicon ions and hydrogen ions is about 5 × 10 ¹⁶ / c
m ² .

FIG. 3 shows the result of measuring the crystallization rate of the silicon semiconductor film in which the total ion implantation amount was changed by changing the implantation time. The horizontal axis represents the total ion implantation amount, and the vertical axis represents the crystallization rate. The crystallization rate was measured in the same manner as the measurement before ion implantation.

In addition, FIG. 3 also shows the results of measuring the crystallization rate of a silicon semiconductor film prepared by forming an amorphous silicon film instead of the microcrystalline silicon film and implanting ions in the same manner. Indicated. It should be noted that the amorphous silicon film is produced by a plasma CVD method at a SiH ₄ / H ₂ ratio of 2 /.
3 gas, substrate temperature 250 ℃, RF power 50W
I went there.

From FIG. 3, in the case of an amorphous silicon film,
It can be seen that a very large amount of ion implantation is necessary for crystallization, but in the case of a microcrystalline silicon film, crystallization proceeds with a small amount. For example, in order to obtain the crystallization rate of 0.5, in the case of an amorphous silicon film, the total ion implantation amount must be at least 3.2 × 10 ¹⁷ ions / cm ² or more. In order to perform such a large amount of implantation, an ion current density of 10 μA / cm ² (6.25 × 10 ¹³ pieces / c) which is a normal implantation condition is used.
m ² · sec), it takes about 85 minutes. On the other hand, in the case of a microcrystalline silicon film, 3.2 × 10 ¹⁶ pieces /
A crystallization rate of 0.5 can be obtained with an ion implantation amount of cm ² , and the implantation time can be shortened to about 8 minutes and 30 seconds.

Example 2 Next, as another example of the present invention, a method of manufacturing a thin film transistor using the above ion implantation apparatus will be described.

First, as shown in FIG. 2, a film thickness of 10 is formed on a # 7059 glass substrate 13 manufactured by Corning Co., Ltd. by an RF power of 400 W and a substrate temperature of 250 ° C. by a plasma CVD method.
A 0 nm microcrystalline silicon film is formed.

Next, using the ion implanter of FIG.
Introduce 5% SiH ₄ gas diluted with hydrogen, and set the RF power to 20
Ions from plasma formed at 0 W are accelerated at a voltage of 80 k
It was accelerated by V and implanted with an ion implantation current of 10 μA / cm ² for 13 minutes. The total ion implantation amount at this time is 5 × 10 ¹⁶ ions / cm ² . The substrate temperature at the time of implantation was 350 ° C.

Next, as shown in FIG. 4, the semiconductor film is patterned into an island shape to form a silicon film 14 'which forms the channel of the transistor. The gate insulating film 17 has a film thickness of 1 so as to cover the silicon film 14 ′ from above.
00nm SiO _{2 is applied} to AP (Atomospheric Pressure)
It is formed at a substrate temperature of 430 ° C. by the CVD method. The gate insulating film 17 can be formed at 450 ° C. or lower by the LPCVD method, the plasma CVD method, the sputtering method, or the like.

A gate electrode 18 of a transistor is formed on the gate insulating film 17 with Al having a film thickness of 300 nm. In particular, as the gate electrode 18, Al, AlS
i, bilayer Ti / AlSi, bilayer TiN / Al, bilayer Ti
It is preferable to use a metal film containing aluminum such as N / AlSi because the resistance can be lowered.

Next, using the ion implantation apparatus shown in FIG. 1, the source and drain are formed in a self-aligned manner. The implantation conditions were that B ₂ H ₆ gas having a hydrogen concentration of 95% was introduced, the ion acceleration voltage was 80 kV, and the implantation dose of impurity ions was 1 × 10 ¹⁶ / cm ² . As shown in FIG. 4, by accelerating ions 22 from a plasma source containing boron ions and hydrogen ions, and implanting boron ions that are Group III elements together with hydrogen ions, the source and drain parts of a P-type thin film transistor are formed. 15 and 16 were formed. At this time, if the hydrogen concentration is 80% or more, the implantation dose of impurity ions is set to 5 × 10 ^{14 to} 5 × 10 ¹⁶ ions / cm ² so that annealing for activation is sufficient. Can be self-activated.

In the case of producing an N-type thin film transistor, similarly, ions 22 from a plasma source formed by introducing hydrogen-diluted PH ₃ gas are accelerated to generate hydrogen ions and phosphorus ions which are Group V elements. By injecting, the source and drain parts of the N-type thin film transistor can be formed by self-alignment. Alternatively, arsenic ions may be implanted by introducing AsH ₃ gas diluted with hydrogen.

Next, a SiO ₂ film having a film thickness of 500 nm is formed by A
A film is formed at a substrate temperature of 430 ° C. by the PCVD method to form an interlayer insulating film 19. After forming the contact holes in the source and drain portions, the extraction electrode 20 is formed by the sputtering method and ohmic contact is made to obtain a thin film transistor. A schematic sectional view of the final structure is shown in FIG.

As described above, according to the above embodiment, all process temperatures can be performed at 450 ° C. or lower, and a silicon semiconductor film having a high crystallization rate can be easily obtained. Further, by using this semiconductor film, a thin film transistor having high driving ability and operating at high speed can be obtained.

The microcrystalline silicon film can be formed under the conditions other than the above, such as plasma CVD using SiH ₄
/ H ₂ gas ratio in the range of 1/30 to 1/100,
The substrate temperature is preferably in the range of 150 to 400 ° C.

As the material of the microcrystalline semiconductor film in the present invention, silicon germanium (SiGe) or the like can be used in addition to silicon (Si).

In the present invention, germanium ions other than silicon ions can be used as the group IV element ions to be implanted. In this case, as the introduced gas,
GeH ₄ gas diluted with hydrogen is used.

In the ion implantation for forming the source and drain in the second embodiment, only the impurity implantation is performed and the silicon ion implantation is not performed because the crystallization by the silicon ion implantation has already been completed. When the P-type semiconductor film or the N-type semiconductor film is produced by one-time implantation, the following may be done. In the case of a P-type semiconductor film, B ₂ H ₆ gas diluted with hydrogen and SiH ₄ gas diluted with hydrogen are mixed and introduced into an ion implantation apparatus, and boron ions and silicon ions may be simultaneously implanted together with hydrogen ions. In the case of an N-type semiconductor film, hydrogen diluted P
H ₃ gas and SiH ₄ gas diluted with hydrogen may be mixed and introduced, and phosphorus ions and silicon ions may be simultaneously injected together with hydrogen ions.

[0046]

According to the present invention, the crystallization rate of a semiconductor film can be significantly improved, so that a semiconductor film having a high field effect mobility can be uniformly formed in a large area in a low temperature process with high productivity. It can be manufactured.

Further, according to the present invention, the implanted impurity element is self-activated without performing annealing for activation, so that P-type or N-type having a large field effect mobility is obtained.
Type semiconductor film can be uniformly manufactured in a large area by a low temperature process with high productivity.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an ion implantation apparatus used in an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing an ion implantation step which is an embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a total ion implantation amount and a crystallization rate.

FIG. 4 is a schematic cross-sectional view showing another embodiment of the present invention, which is an ion implantation process for forming a source and a drain when manufacturing a thin film transistor.

FIG. 5 is a schematic cross-sectional view showing a thin film transistor manufactured according to an example of the present invention.

[Explanation of symbols]

1; Gas inlet 2; Chamber 3; High frequency power supply 4; High frequency electrode 5; Magnet 6; First stage ion acceleration power supply 7; Second stage ion acceleration power supply 8; Deceleration power supply 9; Electrode plate 10; Insulator 11 Substrate holder 12; substrate 13; insulating substrate 14; microcrystalline silicon film 14 '; channel silicon film 15; source silicon film 16; drain silicon film 17; gate insulating film 18; gate conductive film 19; Interlayer insulating film 20; Extraction electrodes 21, 22; Ions from plasma source

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 21/76 21/84 H01L 21/265 Z 9169-4M 21/76 R 8122-4M 21/84

Claims (3)

[Claims] 1. An ion from a plasma source containing a group IV element ion and a hydrogen ion of the periodic table is accelerated to form the group IV element ion together with the hydrogen ion on the substrate. A method for manufacturing a semiconductor film, which comprises implanting into a microcrystalline semiconductor film made of a group element. 2. Ion of group IV element and group III of the periodic table
Ions from a plasma source containing group element ions and hydrogen ions are accelerated to generate the group IV element ions and the group III element ions together with hydrogen ions from the group IN element of the periodic table formed on the substrate. A method for manufacturing a P-type semiconductor film, which comprises injecting the microcrystalline semiconductor film into the microcrystalline semiconductor film. 3. The group IV element ion and the group V element ion together with the hydrogen ion are accelerated by accelerating the ions from the plasma source containing the group IV element ion and the group V element ion and the hydrogen ion of the periodic table. Is injected into a microcrystalline semiconductor film made of a Group IV element of the periodic table formed on a substrate.