JP3021250B2 - Method for manufacturing semiconductor film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor film used for a thin film transistor or the like.

[0002]

2. Description of the Related Art In recent years, there has been an increasing need to manufacture thin film transistors on a transparent insulating substrate in order to form an externally mounted driving circuit such as a liquid crystal display or an image sensor on the same substrate as a display or an image sensor. In that case, in order to use an inexpensive glass substrate that can be easily enlarged in area as the transparent insulating substrate, it is necessary to lower the temperature of the manufacturing process. For example, Corning # 7059 glass has a strain point temperature of 593 ° C. and a usable process temperature of at least 600 ° C. or less, preferably 450 ° C. or less. In order to use an inexpensive glass substrate or plastic substrate, a lower process temperature is preferable.

On the other hand, in a large-area display, a long image sensor, or the like, in order to drive a large load or drive at a high speed, the field effect mobility of a semiconductor film formed for a thin film transistor must be large. The semiconductor film of a thin film transistor is divided into a channel portion in which impurity implantation is not performed and a source and drain portion in which impurity implantation is performed to form a P-type or N-type semiconductor. Transistor characteristics can be obtained.

For the above reasons, it can be manufactured at a low temperature,
In addition, studies on amorphous silicon films, polycrystalline silicon films, and the like have been actively conducted for the purpose of manufacturing semiconductor films having high field-effect mobility.

An amorphous silicon film is formed at a temperature of about 200 to 300 ° C. by a plasma CVD 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 configuring a high-speed drive 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. An expensive substrate such as a strain point glass must be used, and it is difficult to use an inexpensive glass substrate.

For this purpose, 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 to a polycrystalline silicon film to improve semiconductor characteristics such as field effect mobility has been studied. Have been. Examples of the crystallization method include furnace annealing, laser annealing, and lamp annealing.

[0008]

The furnace annealing method 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, longer annealing is required, and as a result, the influence on the glass substrate becomes large, and heat shrinkage and 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 as much as possible in the amorphous silicon film 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 region of the laser irradiation.

The lamp annealing method is a method in which an amorphous silicon film on a substrate is irradiated with lamp light to anneal the film. Some large area irradiation is possible, but usually
Since it contains long-wavelength light, there is a problem in that the glass substrate is damaged by passing through the amorphous silicon film.

As a method for 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 the polycrystalline film
It is disclosed that when a group or group V element ion is implanted, the impurity ions are activated at the same time as the implantation even without annealing, which has a self-activating effect. According to this method, crystallization from an amorphous silicon film to a polycrystalline silicon film can be performed by a low-temperature process, and impurities can be implanted into the polycrystalline silicon film by a low-temperature process.

However, crystallization of an amorphous silicon film requires a very large amount of ions to be implanted. Under ordinary implantation conditions, the productivity is extremely poor and there is a problem that it is not practical.

An object of the present invention is to solve the above-mentioned problems and to provide a method for uniformly producing a semiconductor film having a high field-effect mobility with a high productivity and a large area by a low-temperature process. Is what you do.

[0014]

According to the present invention, there is provided a method for manufacturing a semiconductor device, comprising: accelerating ions from a plasma source containing group IV element ions and hydrogen ions;
Group IV element ions are implanted into a microcrystalline semiconductor film formed of a Group IV element of the periodic table formed on a substrate.

In the method of manufacturing a P-type semiconductor film according to the present invention, ions from a plasma source containing Group IV element ions, Group III element ions and hydrogen ions are accelerated together with hydrogen ions to form the P-type semiconductor film. The method is characterized in that the group IV element ions and the group III element ions are implanted into a microcrystalline semiconductor film formed of a group IV element of the periodic table formed on a substrate.

In the method of manufacturing an N-type semiconductor film according to the present invention, ions from a plasma source containing Group IV element ions, Group V element ions and hydrogen ions are accelerated together with hydrogen ions. Group IV element ions and the group V element ions are formed on a substrate of a periodic table formed on a substrate.
It is characterized by being implanted into a microcrystalline semiconductor film made of a group IV element.

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

As a method of measuring the crystallization ratio, 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 observation method can be used.

In the present invention, the group IV element ions to be implanted are preferably the same element ions as in the semiconductor film.

[0020]

In the case where ions of group IV elements and hydrogen ions of the periodic table are accelerated and implanted into an 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 crystal grains are present in the microcrystalline film, and crystallization is easily progressed using these as nuclei. Is significantly increased. Thereby, the implantation time for crystallization is significantly reduced, 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, a group IV element ion and a hydrogen ion of the periodic table are simultaneously added to the microcrystalline semiconductor film.
As described above, the crystallization rate is increased to improve the field-effect mobility of the semiconductor film by accelerating and implanting the group or group V element ions, and at the same time, the P-type or N-type impurity element is implanted. , And these impurity elements can be activated simultaneously with the injection by the action of self-activation. Thus, a P-type or N-type semiconductor film with high field-effect mobility can be manufactured by a low-temperature process without an annealing step.

[0022]

Embodiment 1 Hereinafter, the present invention will be described in detail with reference to the drawings showing an embodiment.

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

A hydrogen-diluted raw material gas (for example, hydrogen-diluted SiH ₄ ) is introduced from the gas inlet 1, and a high-frequency power is applied to the high-frequency electrode 4 to form an excited plasma source. After accelerating with the substrate holder 11
Is implanted into the substrate 12 mounted on the substrate. With the above configuration, ion implantation into a large-area substrate can be performed without mechanical scanning of the sample substrate and electrical scanning of the ion beam. By using such an apparatus, a semiconductor film formed on a substrate can be formed on a group III, IV, or I group of the periodic table.
A step of implanting these ions by accelerating ions from a plasma source containing group II element ions, hydrogen ions, and the like can be performed.

Next, a method for producing a silicon semiconductor film having a high crystallization rate by performing ion implantation on a microcrystalline silicon film by using the above-described ion implantation apparatus, taking a silicon semiconductor film as an example.

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, and a 100 nm-thick microcrystalline silicon film is formed 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.
The crystallization ratio was 0.20 as measured by reflected light intensity. The measuring method is as follows.

The ultraviolet light emitted from the deuterium lamp was incident on the silicon film at an incident angle of 5 °, and the intensity of the reflected light was measured by a spectroscope. The absorption of the E ₂ band (band gap 4.31 eV) peculiar to crystalline silicon was found. As a result, 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 the crystal grains on the silicon film surface, that is, the crystallization rate, the peak height is compared with the peak height of the previously measured polycrystal silicon film having a crystallization rate of 1.0. The crystallization ratio of the film can be determined.

The crystallization ratio obtained as described above substantially coincides with the area ratio of the crystal grains present 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 a direction indicating a crystal, but has a lower intensity than a polycrystalline film. Furthermore, according to Raman spectroscopy, peaks were observed around the Raman shift 520 cm ^-1, different from the vicinity of 490 cm ^-1 in the case of amorphous.

Next, as shown in FIG. 2, ions 21 from a plasma source containing silicon ions and hydrogen ions are deposited on a microcrystalline silicon film 14 formed on a substrate 13 by using the ion implantation apparatus shown in FIG. And silicon ions and hydrogen ions are implanted simultaneously. The implantation conditions are as follows: a 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 under these conditions for 13 minutes, 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 ratio of the silicon semiconductor film in which the total ion implantation amount was changed by changing the implantation time. The horizontal axis indicates the total ion implantation amount, and the vertical axis indicates the crystallization ratio. The measurement of the crystallization ratio was performed in the same manner as the measurement before ion implantation.

FIG. 3 also shows the results of measurement of the crystallization ratio of a silicon semiconductor film formed by forming an amorphous silicon film instead of the microcrystalline silicon film and then performing ion implantation in the same manner. Indicated. The amorphous silicon film was formed by a plasma CVD method with an SiH ₄ / H ₂ ratio of 2/2.
3 gas, substrate temperature 250 ° C, RF power 50W
I went in.

FIG. 3 shows that in the case of an amorphous silicon film,
Although a very large amount of ion implantation is required for crystallization, it can be seen that in the case of a microcrystalline silicon film, crystallization proceeds with a small amount. For example, in order to obtain a crystallization rate of 0.5, in the case of an amorphous silicon film, the total ion implantation amount is required to be at least 3.2 × 10 ¹⁷ / 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 / 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 /
A crystallization rate of 0.5 can be obtained with an ion implantation amount of cm ² , and the implantation time can be reduced to about 8 minutes and 30 seconds.

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

First, as shown in FIG. 2, on a # 7059 glass substrate 13 manufactured by Corning Incorporated, an RF power of 400 W, a substrate temperature of 250.degree.
A 0 nm microcrystalline silicon film is formed.

Next, using the ion implantation apparatus shown in FIG.
Hydrogen diluted 5% SiH ₄ gas was introduced, and RF power 20
Ion from plasma formed at 0 W is accelerated to 80 k
V was accelerated, and implantation was performed at an ion implantation current of 10 μA / cm ² for 13 minutes. At this time, the total ion implantation amount is 5 × 10 ¹⁶ / cm ² . The substrate temperature at the time of implantation was 350 ° C.

Next, as shown in FIG. 4, the semiconductor film is patterned in an island shape to form a silicon film 14 'for forming a channel of the transistor. A gate insulating film 17 having a thickness of 1 to cover the silicon film 14 'from above.
00nm SiO ₂ with AP (Atomospheric Pressure)
The substrate is formed at a substrate temperature of 430 ° C. by a CVD method. The gate insulating film 17 can also be formed at 450 ° C. or lower by an LPCVD method, a plasma CVD method, a sputtering method, or the like.

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

Next, a source and a drain are formed by self-alignment using the ion implantation apparatus shown in FIG. The implantation conditions were such that a 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 ions / cm ² . As shown in FIG. 4, ions 22 from a plasma source containing boron ions and hydrogen ions are accelerated, and boron ions as a group III element are implanted together with the hydrogen ions, so that the source and drain portions of the P-type thin film transistor are formed. Nos. 15 and 16 were formed. At this time, if the hydrogen concentration is 80% or more, the implantation dose of the impurity ions is set to 5 × 10 ^{14 to} 5 × 10 ¹⁶ / cm ² , so that the annealing for activation is sufficient. Can self-activate.

In the case of fabricating an N-type thin film transistor, ions 22 from a plasma source formed by introducing a hydrogen-diluted PH ₃ gas are similarly accelerated so that phosphorus ions, which are Group V elements, are accelerated together with hydrogen ions. By implanting, the source and drain portions of the N-type thin film transistor can be formed in a self-aligned manner. Alternatively, arsenic ions may be implanted by introducing AsH ₃ gas diluted with hydrogen.

Next, a 500 nm thick SiO ₂ film was
A film is formed at a substrate temperature of 430 ° C. by a PCVD method, and an interlayer insulating film 19 is formed. After forming the contact holes in the source and drain portions, the extraction electrode 20 is formed by a sputtering method, and an ohmic contact is made to obtain a thin film transistor. FIG. 5 shows a schematic sectional view of the final structure.

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

[0042] As a manufacturing method of a microcrystalline silicon film, can other than the above conditions, the plasma CVD method, SiH ₄
/ H ₂ gas ratio in the range of 1/30 to 1/100,
Preferably, the substrate temperature is in the range of 150 to 400 ° C.

As a material for 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 the drain in the second embodiment, since the crystallization has already been performed by the silicon ion implantation, only the impurity implantation is performed, and the silicon ion implantation is not performed. In the case of manufacturing a P-type semiconductor film or an N-type semiconductor film by a single implantation, the following may be performed. 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 implanted simultaneously with hydrogen ions. In the case of an N-type semiconductor film, hydrogen-diluted P
H ₃ gas and hydrogen-diluted SiH ₄ gas may be mixed and introduced, and phosphorus ions and silicon ions may be implanted together with hydrogen ions.

[0046]

According to the present invention, the crystallization ratio of a semiconductor film can be greatly improved. Therefore, a semiconductor film having a high field-effect mobility can be uniformly formed over a large area with a low temperature process. Can be manufactured.

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

[Brief description of the 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 sectional view showing an ion implantation step according to one embodiment of the present invention.

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

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

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

[Explanation of symbols]

DESCRIPTION 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; 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

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI H01L 29/78 627G (56) References JP-A-63-194326 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/265 H01L 21/263 H01L 21/336 H01L 29/786

Claims (3)

(57) [Claims] An ion from a plasma source containing a group IV element ion and a hydrogen ion is accelerated so that the group IV element ion is formed together with a hydrogen ion on a substrate of the periodic table formed on a substrate. A method for manufacturing a semiconductor film, wherein the semiconductor film is implanted into a microcrystalline semiconductor film made of a group III element. 2. Group IV element ions and Period III of the periodic table
Accelerate ions from a plasma source containing group element ions and hydrogen ions, and together with hydrogen ions, the group IV element ions and the group III element ions from the group IN elements of the periodic table formed on the substrate. A method for manufacturing a P-type semiconductor film, characterized by injecting into a microcrystalline semiconductor film. 3. An ion from a plasma source containing a group IV element ion, a group V element ion and a hydrogen ion in the periodic table, and the group IV element ion and the group V element ion together with hydrogen ions. Is implanted into a microcrystalline semiconductor film formed of a Group IV element of the periodic table formed on a substrate.