JP2000077672A - Method for manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize the damage to a substrate carrying a semiconductor film and an oxide film caused by a plasma and, in addition, to repair the damage by performing a nitriding treatment on the substrate and performing a first heat treatment on the substrate in an oxidizing atmosphere, and then, a second heat treatment on the substrate. SOLUTION: After a silicon oxide film is formed, the film is subjected to a nitrogen plasma treatment. Then the substrate 101 on which the oxide film is formed is introduced to a parallel plate capacitively coupled plasma chemical vapor deposition(PECVD) device and irradiated with the light emitted from ammonia plasma. Thereafter, a first heat treatment is performed on the substrate 101 in an oxidizing atmosphere. After the first heat treatment, the oxide film is dried through a second heat treatment. Then a gate electrode 105 is formed of a metallic thin film, and source and drain areas 107 and a channel forming area 108 are formed in a self-aligning way against the gate electrode 105 by implanting impurity ions which become a donor or an acceptor. Thereafter, the manufacturing of a semiconductor device is completed by depositing an interlayer insulating film 109 and forming wiring 110.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device typified by a thin film transistor (TFT) and the like. More specifically, the present invention relates to a method for manufacturing a semiconductor device having high performance and high reliability at a relatively low temperature of about 600 ° C. or lower.

[0002]

2. Description of the Related Art Polycrystalline silicon thin film transistors (p-Si
When manufacturing a semiconductor device typified by TFT) at a low temperature of about 600 ° C. or less, which can use a general-purpose glass substrate,
Conventionally, the following manufacturing method has been adopted. First, a polycrystalline silicon film (p-Si film) is formed by an excimer laser irradiation method or the like, and then a silicon oxide film serving as a gate insulating film is formed by chemical vapor deposition (CVD) or physical vapor deposition (PVD). Formed. Next, a gate electrode is formed of tantalum or the like, and a field effect transistor (MOS) composed of a metal (gate electrode) -oxide film (gate insulating film) -semiconductor (polycrystalline silicon film) is formed.
FET). Next, an interlayer insulating film is deposited, a contact hole is opened, and wiring is formed using a metal thin film. In order to improve the electric characteristics as needed, a hydrogen plasma treatment is finally performed for about 2 hours to complete the semiconductor device.

[0003]

However, in the conventional method of manufacturing a semiconductor device, if hydrogen plasma irradiation is performed to improve the semiconductor characteristics, the processing time is too long, so that the semiconductor film, silicon oxide film, Further, the plasma processing apparatus itself suffers from many problems such as damage due to plasma, and the necessity of purchasing many expensive plasma processing apparatuses. In accordance with such a fact, if a semiconductor device such as a p-Si TFT is manufactured by a conventional manufacturing method, the manufacturing cost rises, and the completed semiconductor device not only has poor electrical characteristics but also has a problem in use. There was also a problem in reliability such as deterioration over time.

The present invention has been made in view of the above circumstances, and has as its object to provide a method of manufacturing an excellent semiconductor device in a low-temperature process at about 600 ° C. or less.

[0005]

According to the present invention, there is provided a semiconductor film formed on an insulating material provided on a substrate and an insulating film typified by silicon oxide formed on the semiconductor film. The method for manufacturing a semiconductor device whose main component is described above is characterized by at least the following five steps. That is, a first step of forming a semiconductor film on an insulating material provided on a substrate, a second step of depositing an oxide film on the semiconductor film by a vapor deposition method, A third step of subjecting the substrate having an oxide film to a nitriding treatment, a fourth step of subjecting the substrate to a first heat treatment under an oxidizing atmosphere, and a fifth step of further subjecting the substrate to a second heat treatment. Process.

First, in the present invention, as a first step, a semiconductor film typified by polycrystalline silicon (p-Si) is formed on an edge material such as an interlayer insulating film of a three-dimensional semiconductor device formed on a glass substrate or a semiconductor substrate. To form The semiconductor film may be in a crystalline state or an amorphous state, but when it is in a polycrystalline state, the present invention exhibits its effects. This is because the present invention reduces the trap level (interface level) existing at the interface between the semiconductor film and the insulating film, and reduces the trap level (grain boundary level) located between crystal grains. Is also reduced. Needless to say, the interface state always exists at the bonding interface between the semiconductor film and the insulating film regardless of the crystal state. Since this interface state is reduced, the present invention is effective regardless of the state of the semiconductor film. On the other hand, for a polycrystalline film, in addition to this effect, an effect of reducing the grain boundary level is also recognized. The semiconductor film is made of silicon (Si) or silicon germanium (S
_{i x Ge 1-x: 0} <x <1) or the like but may be there in any semiconductor material, conveniently good from the perspective of configuring the MOS interface, the main constituent element of silicon simple substance and silicon ( Semiconductor materials having a silicon atom composition ratio of about 80% or more) are excellent. Semiconductor films are deposited by physical vapor deposition (PVD).
) Or a vapor phase deposition method such as a chemical vapor deposition method (CVD method). As the PVD method, a sputtering method, an evaporation method, or the like can be considered. Atmospheric pressure chemical vapor deposition (APC)
VD), low pressure chemical vapor deposition (LPCVD), plasma chemical vapor deposition (PECVD), and the like. A semiconductor film formed by a vapor deposition method is usually in a polycrystalline state, an amorphous state, or a mixed state thereof immediately after deposition. A thin film in a polycrystalline state is called a polycrystalline film, and a thin film in an amorphous state or a mixed state is called an amorphous film or a mixed crystalline film, respectively. Active part of semiconductor device (source / drain region and channel formation region of field effect transistor,
Emitter and base of bipolar transistors
As the collector region, the polycrystalline film obtained immediately after the deposition can be used as it is. In contrast to this, a new polycrystalline film is obtained by crystallizing an amorphous film or mixed crystal film or recrystallizing a polycrystalline film, and then using this as an active part. It is also possible to do. Laser irradiation or rapid heat treatment is used for crystallization or recrystallization.

Next, as a second step, an oxide film is deposited on the semiconductor film by a vapor deposition method. Oxide deposition at most 60
It is performed at a temperature of about 0 ° C. or less, usually at a temperature of about 400 ° C. or less. This is because it is assumed that the semiconductor device to which the present invention is applied is manufactured on a substrate having poor heat resistance, such as a general-purpose glass substrate or a plastic substrate. This oxide film is used as a gate insulating film of a MOS-FET.
In order to easily obtain a good interface between the semiconductor film and the insulating film, the main constituent material of the oxide film is silicon oxide (SiO _x : 0 <x ≦ 2).
It is desirable that it is. Oxide film is deposited by physical vapor deposition (PVD).
) Or a vapor phase deposition method such as a chemical vapor deposition method (CVD method). As the PVD method, a sputtering method, an evaporation method, or the like can be considered. Atmospheric pressure chemical vapor deposition (APCV)
D), low pressure chemical vapor deposition (LPCVD), plasma chemical vapor deposition (PECVD), and the like.
The oxide film thus obtained contains a larger amount of oxide film trapping levels and fixed charges in the oxide film than the thermal oxide film formed at a temperature of about 1100 ° C. or higher, and further has a much higher interface state. It is usually high. Therefore, in the present invention, the following three steps (third, fourth, and fifth steps) are performed to reform the oxide film, the interface, and the crystal grain boundaries.

After the second step is completed, as a third step, the substrate on which the semiconductor film and the silicon oxide film are formed is subjected to a nitriding treatment including hydrogenation. In this method, hydrogen (—H), amino group (—NH ₂ ), imino group (= NH), nitrogen (≡N), etc. are bonded to an unpaired bond pair at the interface between the semiconductor film and the semiconductor film and the silicon oxide film. This reduces the trap states (deep states) near the center of the forbidden zone (near the intrinsic Fermi level). At the same time, unpaired bonding pairs existing in the oxide film are also terminated with these functional groups, thereby reducing the oxide film fixed charge. The main cause of deep states is an unpaired pair existing at the interface or grain boundary of the semiconductor film. These are easily made inert by the nitriding treatment, and if they are inactivated, the trap level decreases. In addition, the fixed charge in the oxide film causes a change in the flat band potential and facilitates injection of the charge into the oxide film, thereby lowering the operation reliability of the semiconductor device. Therefore, by performing the nitriding treatment in the third step, the flat band potential of the semiconductor device is made closer to the ideal value, the deep states are reduced, and the reliability of the semiconductor device is further increased. The easiest way to perform the nitriding treatment is to irradiate the substrate with ammonia (NH ₃ ) plasma or nitrogen (N ₂ ) plasma. In ammonia plasma irradiation, hydrogen (-H) or amino group (-NH)
₂ ) A chemical reaction for bonding an imino group (= NH) or the like proceeds easily, and the unpaired electron pair is efficiently terminated. In addition, in the case of ammonia plasma, rf waves (13.56 MHz or higher harmonics thereof) that can be easily enlarged can be used. On the other hand, if microwaves (2.45 GHz or the like) are used, nitriding by nitrogen plasma becomes extremely difficult and the safety and durability of the plasma processing apparatus are increased. In the nitriding treatment, if the substrate temperature is too low (less than about 100 ° C.), the reaction does not proceed,
If the substrate temperature is too high (about 450 ° C. or more), the progress of the reverse reaction such as hydrogen elimination is accelerated.
This is performed at a substrate temperature of about 0 ° C. Ideally, the temperature is between about 250 ° C. and about 400 ° C. By this nitriding treatment, an extremely thin silicon nitride oxide film (SiON) of about 0.3 nm to about 5 nm is formed at the interface. This means that charge injection from the semiconductor film into the gate insulating film is less likely to occur and the operation reliability of the semiconductor device is increased.

[0009] Conventional hydrogenation treatment has been performed for 2 to 6 hours. On the other hand, the nitriding time including hydrogenation in the third step of the present invention is about 10 seconds to about 10 minutes. This is a conventional method using a gate electrode (thickness 500).
This is because the hydrogenation treatment was performed after the formation of the interlayer insulating film (about 500 nm or more), the metal wiring (about 500 nm or more), and the like. In order to perform hydrogenation efficiently, it is necessary to generate hydrogen radicals by plasma or the like, but these are chemically active and react quickly, so their life is short, and gate electrodes, interlayer insulating films, metal wiring, etc. Does not readily reach the gate insulating film or the active layer semiconductor film. Therefore, conventionally, the hydrogen plasma processing time has to be extended, and thus, a large amount of plasma damage is caused to the semiconductor device at the same time as the hydrogenation processing, and the plasma processing apparatus also extends its life to the plasma generated by itself. It was so short. On the other hand, in the present invention, immediately after the gate insulating film is formed, the above-described treatment for bonding the functional groups is performed.
The hydrogenation, amination, iminoization, or nitridation treatment is performed directly in a state where no gate insulating film, interlayer insulating film, and metal wiring exist. Of course, in the semiconductor device of the present invention, since the gate insulating film is as thin as about 5 nm to about 120 nm, radicals such as hydrogen, nitrogen, ammonia, amino groups, and imino groups easily reach the semiconductor film. This is because the nitriding time of the present invention is one tenth of that of the conventional hydrogenation.
This is the reason why it could be greatly reduced from 1 to 100 times. When the ammonia plasma irradiation is used for the nitriding treatment, the plasma damage is reduced from 1/10 to 1/100 as the plasma irradiation time is shortened, and the number of processed wafers within the life of the plasma processing apparatus is increased from 10 times to 100 times. Yes, because it doubles. If the processing time of the third step is less than about 10 seconds, the effect of hydrogenation or nitridation does not appear, and if the processing time is about 10 minutes or more, plasma damage to the oxide film or semiconductor film may not be repaired after the fourth step. Yes. Ideally, it is about 30 seconds to about 120 seconds.

[0010] Plasma damage is caused by irradiating high-energy photons (ultraviolet rays) or ions generated from plasma to an oxide film or a semiconductor film to cut a chemical bond of a substance such as an oxide film or a semiconductor film. As a result, an unpaired pair or a fixed charge is generated inside the semiconductor film or the oxide film. This plasma damage is particularly remarkable for a silicon oxide film. This is because the silicon oxide film is exposed to the plasma as a gate insulating film, so that it is directly exposed to ion irradiation, and the oxide film is amorphous and has a large distribution in the bond angle and interatomic distance of Si-O-Si. It is because it has. In the present invention, although the plasma irradiation time in the third step is as short as less than about 10 minutes at the longest, slight plasma damage still enters the oxide film and the interface. Also, since the oxide film is formed at a low temperature of about 600 ° C. or less, the fixed oxide and the trapping level inherent in the low-temperature formed oxide film are more abundant than a high-quality thermal oxide film. Further, with the above-described nitriding treatment, unpaired bond pairs derived from nitrogen atoms also appear in the insulating film, at the interface, and at the grain boundaries of the polycrystalline semiconductor film. Therefore, in the fourth step, low-quality low-temperature-formed oxide films, plasma damage, defects derived from nitriding, and the like are modified by the first heat treatment.

In a fourth step, the oxide film is subjected to a first heat treatment at a temperature of about 200 ° C. to 450 ° C. in an oxidizing atmosphere. The oxidizing atmosphere is hydrochloric acid (HCl) or nitric acid (HNO
₃ ) an acid such as hydrofluoric acid (HF) or water (H ₂ O) that can chemically break the bond of the oxide film, oxygen (O ₂ ), nitrous oxide (N ₂₀ ), It is composed of a gas containing at least an oxygen-containing gas such as carbon dioxide (CO ₂ ). The substance capable of chemically breaking the bond of the oxide film is also an oxidation promoting substance of the semiconductor film and the nitride film. Of course, this atmosphere may be made of a substance capable of chemically breaking the bond of the oxide film, an oxygen-containing gas, and an inert gas. One of the simplest examples is air with water vapor. In this case, water vapor is a substance capable of breaking the bond of the oxide film, and oxygen in the air is an oxygen-containing gas. The former substance capable of breaking a bond of an oxide film has a property of preferentially breaking a distorted bond or a weak bond between elements (silicon and oxygen) constituting an oxide film such as a silicon oxide film. On the other hand, the latter supplies oxygen to an oxide film or an interface having an oxygen deficiency, and forms an incomplete oxide film (for example, SiO _x : 0 <x <2) or an interface having many oxygen deficiencies to a complete oxide film ( For example, it is improved to an interface having few SiO ₂ ) or oxygen vacancies. Further, a nitrogen atom having an unpaired bond pair is oxidized to form a nitrided oxide film. Due to this first heat treatment, the distorted bonds and weak bonds constituting the oxide film are repeatedly cut and recombined, and finally the oxide film has a normal and strong bond composed of S
The idea of the stitch of the i-O-Si bond is taken. In addition, in the case of an insulating film simply subjected to a simple nitridation treatment, those which are impractical due to a large number of fixed electrification and oxide film trapping levels are greatly reduced by the first heat treatment. This significantly improves the quality of the nitrided oxide film. Thus, trap levels, fixed charges, and interface levels in the insulating film composed of the oxide film and the nitrided oxide film are significantly reduced. From the standpoint of a semiconductor device, this implies that the flat band potential approaches the ideal value (the difference between the work function of the metal forming the gate electrode and the work function of the semiconductor), reduces the threshold voltage, and further improves the reliability of the semiconductor device. It means that we are increasing. The higher the processing temperature of the fourth step, the shorter the processing time. A temperature of at least about 200 ° C. is required to complete the processing in a common sense processing time (at most about 24 hours). On the other hand, in the present invention, in the third step, defects in the semiconductor film and the oxide film are repaired with hydrogen, nitrogen or the like. If the temperature of the heat treatment in the fourth step is too high, hydrogen and amino groups terminating the defects in the crystalline semiconductor film and the oxide film may be released, and the number of defects may increase. In order to prevent elimination of hydrogen and amino groups and to minimize defects in the polycrystalline semiconductor film and the oxide film, the processing temperature in the fourth step is preferably about 400 ° C. or less.

After the fourth step, a second heat treatment is performed in a non-oxidizing atmosphere as a fifth step. The non-oxidizing atmosphere is performed under an inert atmosphere such as nitrogen (N ₂ ) or argon (Ar), an atmosphere containing hydrogen in the inert atmosphere, or an atmosphere consisting of hydrogen alone. In the second heat treatment of the fifth step, substances such as acid and water diffused into the oxide film during the first heat treatment are removed. When these substances remain in the oxide film, they become potential oxide film levels or interface states, which lowers the reliability of the semiconductor device. Therefore, performing the second heat treatment in the fifth step significantly increases the reliability of the semiconductor device. In order to remove the acid and water diffused in the oxide film, the effect can be recognized by performing a heat treatment in an atmosphere containing no acid or water. However, if this second heat treatment is performed in an oxidizing atmosphere containing oxygen or the like, a new imperfect interface is formed with the progress of oxidation, and the second heat treatment is performed, and the effect of reducing the interface state is weakened. Therefore, the second heat treatment is performed in an inert atmosphere or a weak reducing atmosphere. The pressure is preferably as low as less than about 1 Torr. In this case, the interface state is kept low, and an excellent semiconductor device can be obtained. In order to further reduce the interface state, the second heat treatment is preferably performed in a hydrogen-containing atmosphere. In this case, the heat treatment may be performed in an atmosphere of hydrogen alone, but in consideration of safety, hydrogen is diluted with an inert gas such as nitrogen or argon to a concentration less than about 4%, which is lower than the lower explosion limit, and heat treated. It is desirable to do. The heat treatment temperature in the fifth step is substantially the same as the heat treatment temperature in the fourth step, or is set higher than the heat treatment temperature in the third step. This is because the temperature of the second heat treatment is preferably higher in order to quickly and effectively remove unnecessary substances from the oxide film and to further improve the stitch structure of the oxide film.
In this sense, it is most preferable that the heat treatment temperature in the fifth step be the highest temperature in all the steps after the second step until the semiconductor device is completed. The higher the temperature in the fourth and fifth steps, the greater the effect of reforming the oxide film and interface and the effect of repairing plasma damage.However, high-temperature processing does not repair the unpaired pair in the semiconductor film. It promotes the elimination of the terminating functional group such as hydrogen, and as a result, increases the deep state of the semiconductor. As described above, in the present invention, the heat treatment temperature in the fifth step is the maximum temperature until the semiconductor device is completed after the second step. Therefore, unless these groups are eliminated in the fifth step, hydrogen, amino groups, and the like are not thermally eliminated from the semiconductor device thereafter. In order to prevent hydrogen or the like terminating the dangling bond pair from being released in the third step by the time the semiconductor device is completed, it is preferable to set the substrate temperature in the fifth step to about 400 ° C. or lower where hydrogen desorption does not occur. The relationship between the temperature of the first heat treatment and the temperature of the second heat treatment is preferably that the second heat treatment temperature is higher than the first heat treatment temperature by about 25 ° C. to about 75 ° C. For example, the first heat treatment is performed from about 300 ° C. to 350
℃, the second heat treatment from about 350 ℃ to 400 ℃
It would be ideal to do it on the order. With this temperature relationship, the effect of repairing the knitted structure of the oxide film in the first heat treatment and the effect of removing unnecessary substances in the second heat treatment can be reliably achieved even if the temperature fluctuation of the heat treatment furnace is taken into consideration, and the desorption of hydrogen from the semiconductor film is also reduced. This is because it can be kept to a minimum.

After all, the effects of the third to fifth steps are discussed from the viewpoint of the semiconductor characteristics. In the third step, the flat band potential is brought close to an ideal value, the oxide film fixed charge is reduced, and the semiconductor film and the interface are reduced. In the fourth step, trap levels, fixed charges, and interface trap levels in the insulating film are reduced by reducing deep states and repairing plasma damage and defects in the insulating film in the fourth step. This leads to an increase in the reliability of the semiconductor device, such as a reduction in leakage current and trap levels in the insulating film. Capture levels (tail states and deep
When the number of states is reduced, not only the number of charge carriers contributing to electric conduction increases, but also the scattering of the charge carriers due to trapped charges is reduced, so that the mobility is increased. In addition, the sub-threshold swing and the threshold voltage are reduced, and a good semiconductor device showing a steep switching performance can be obtained.

The formation of the oxide film in the second step and the nitridation in the third step are performed in order to efficiently perform nitriding and hydrogenation in a short time.
Although it must be performed continuously, it is not always necessary to be continuous between the third step and the fourth step or between the fourth step and the fifth step. For example, another step of forming a gate electrode between the fourth step and the fifth step may be included. However,
From the standpoint of speeding up the diffusion of the substance capable of breaking the bond of the oxide film or the oxygen-containing gas into the oxide film in the fourth step, or quickly removing these substances from the gate insulating film in the fifth step It is desirable that these steps be continuous.

[0015]

(Embodiment 1) FIGS. 1 (a) to 1 (d)
FIG. 2 is a cross-sectional view showing a manufacturing process of a thin film semiconductor device for forming a MOS field effect transistor. In the first embodiment, a general-purpose non-alkali glass having a strain point of about 650 ° C. was used as the substrate 101. First, ECR-PEC is placed on the substrate 101.
A silicon oxide film was deposited to a thickness of about 200 nm by the VD method to form a base protective film 102. The conditions for depositing the silicon oxide film by the ECR-PECVD method are as follows.

Monosilane (SiH ₄ ) flow rate: 60 sccm Oxygen (O ₂ ) flow rate: 100 sccm Pressure: 2.40 mTorr Microwave (2.45 GHz) output: 2250 W Applied magnetic field: 875 Gauss Substrate temperature ... 100 ° C. Film formation time... 40 seconds An intrinsic amorphous silicon film was deposited as a semiconductor film to a thickness of about 50 nm on the underlying protective film by LPCVD. LP
The CVD equipment is a hot wall type with a volume of 184.5 l
The total reaction area after inserting the substrate is about 44000 cm ² . The deposition temperature is 425 ° C. and the purity is 99.9 as a source gas.
200 sc using disilane (Si ₂ H ₆ ) of 9% or more
cm reactor. Deposition pressure is about 1.1 Torr
Under these conditions, the deposition rate of the silicon film is 0.77 nm.
/ Min. The amorphous semiconductor film thus obtained was irradiated with a krypton fluorine (KrF) excimer laser to promote crystallization of the semiconductor film. The irradiation laser energy density was 245 mJ · cm ^−2, which was 15 mJ · cm ⁻² lower than the energy density at which the semiconductor film was completely melted over the entire thickness direction and microcrystallization was caused. After the crystalline semiconductor film (polycrystalline silicon film) is thus formed (first step), the crystalline semiconductor film is processed into an island shape, and the island 103 of the semiconductor film which will later become the active layer of the semiconductor device
Was formed. (FIG. 1A) Next, a silicon oxide film 104 was formed by ECR-PECVD so as to cover the island 103 of the semiconductor film subjected to the patterning process (second step). This silicon oxide film functions as a gate insulating film of the semiconductor device. The conditions for depositing the silicon oxide film as the gate insulating film are the same as the conditions for depositing the silicon oxide film as the base protective film, except that the deposition time is reduced to 24 seconds.
However, immediately before the deposition of the silicon oxide film, the substrate was irradiated with oxygen plasma in an ECR-PECVD apparatus to form a low-temperature plasma oxide film on the surface of the semiconductor. The plasma oxidation conditions are as follows.

Oxygen (O ₂ ) flow rate: 100 sccm Pressure: 1.85 mTorr Microwave (2.45 GHz) output: 2000 W Applicable magnetic field: 875 Gauss Substrate temperature: 100 ° C. Processing time: An oxide film of about 3.5 nm is formed on the semiconductor surface by plasma oxidation for 24 seconds. After the oxygen plasma irradiation ends,
An oxide film was deposited continuously while maintaining the vacuum. Therefore, the silicon oxide film serving as the gate insulating film was composed of a plasma oxide film and a vapor deposition film, and had a thickness of 115 nm.

After forming the silicon oxide film in the second step, a nitrogen plasma treatment was performed as a third step. The substrate on which the oxide film was formed was introduced into a parallel plate capacitively coupled PECVD apparatus, and the substrate was irradiated with ammonia plasma (third step). Ammonia plasma conditions are as follows.

Ammonia (NH ₃ ) flow rate: 1000 sccm Argon (Ar) flow rate: 1000 sccm Pressure: 1 Torr rf wave (13.56 MHz) output: 200 W Distance between electrodes: 25 mm Substrate temperature 370 ° C. Processing time: 90 seconds Next, as a fourth step, a first heat treatment was performed in an oxidizing atmosphere. The heat treatment was performed in hydrochloric acid steam air containing a hydrochloric acid aqueous solution having a concentration of 16% in air at a dew point of 96 ° C.
The processing temperature was 345 ° C., the processing time was 2 hours, and the processing chamber pressure was 1 atm. After the completion of the heat treatment with hydrochloric acid, one step is to remove halogen elements in the oxide film.
The heat treatment was continued for hours. This heat treatment atmosphere has a dew point of 96.
The test is carried out in air containing water vapor at ℃, and the atmosphere does not contain hydrochloric acid. The heat treatment temperature is 345 ° C. and the pressure is 1 atm. As shown in this example, when an acid is used for the first heat treatment, the heat treatment is performed in an atmosphere mainly composed of steam and oxygen, or steam, oxygen, and an inert gas, in the latter half of the first heat treatment. preferable.

After the completion of the fourth step, the second heat treatment of the fifth step was performed to dry the oxide film. The second heat treatment was performed in a non-oxidizing atmosphere containing 3% of hydrogen in argon at 1 atm and 400 ° C. for 2 hours. Thus, the deposition of the gate insulating film and the modification of the oxide film and the interface are completed. (Figure 1
b) Subsequently, a gate electrode 105 is formed by a sputtering method using a metal thin film. The substrate temperature during sputter is 150 ° C
It was. In the first embodiment, α having a thickness of 750 nm
A gate electrode was formed from tantalum (Ta) having a structure, and the sheet resistance of the gate electrode was 0.8Ω / □. Next, using the gate electrode as a mask, an impurity ion 106 serving as a donor or an acceptor is implanted, and a source / drain region 107 and a channel formation region 108 are formed in a self-aligned manner with respect to the gate electrode. In the first embodiment, the CMOS
A semiconductor device was manufactured. When fabricating an NMOS transistor, the PMOS transistor portion is made of aluminum (A
l) After covering with a thin film, 5%
Phosphine (PH ₃ ) diluted at a concentration of 7 × 10 3
^At a concentration of ¹⁵ cm ^-2 , the source of the NMOS transistor
Driven into the drain region. Conversely, when fabricating a PMOS transistor, after covering the NMOS transistor portion with an aluminum (Al) thin film, diborane (B ₂ H ₆ ) diluted in hydrogen at a concentration of 5% is selected as an impurity element and accelerated. 5x total ions containing hydrogen at a voltage of 80 kV
It was implanted into the source / drain region of the PMOS transistor at a concentration of 10 ¹⁵ cm ^-2 . (FIG. 1-c) The substrate temperature at the time of ion implantation is 300 ° C.

Next, TEOS (Si- (O
Using CH ₂ CH ₃ ) ₄ ) and oxygen as source gases, an interlayer insulating film 109 was deposited at a substrate temperature of 300 ° C. The interlayer insulating film was made of a silicon dioxide film, and its thickness was about 500 nm. After the deposition of the interlayer insulating film, a heat treatment was performed at 350 ° C. for 2 hours in a nitrogen atmosphere to bake the interlayer insulating film and activate the impurity element added to the source / drain regions. Finally, a contact hole was opened, aluminum was deposited at a substrate temperature of 180 ° C. by a sputtering method, and a wiring 110 was formed to complete a thin film semiconductor device. (Figure 1
-D) The transfer characteristics of the thin film semiconductor device thus prepared were measured. The length and width of the channel formation region of the semiconductor device measured were 10 μm each, and the measurement was performed at room temperature. N
The mobility of the MOS transistor obtained from the saturation region at Vds = 8 V is 93.4 cm ² · V ⁻¹ · s ⁻¹ , the threshold voltage is 3.21 V, and the
The swing was 0.477V. The mobility of the PMOS transistor obtained from the saturation region at Vds = −8 V is 45.2 cm ² · V ⁻¹ · s ⁻¹ , the threshold voltage is −3.71 V, and the sub slash hold swing is It was 0.504V. On the other hand, in the comparative example in which the third to fifth steps are deleted from the first embodiment, the mobility of the NMOS transistor is 74.2 cm ² · V ⁻¹ · s ⁻¹ ,
The threshold voltage is 4.34 V, the subthreshold hold swing is 0.651 V, the mobility of the PMOS transistor is 32.6 cm ² · V ⁻¹ · s ⁻¹ , and the threshold voltage is −7.
00V, sub-leash hold swing 0.63
It was 3V. According to the present invention, both N-type and P-type semiconductor devices have a high mobility, a low threshold voltage, and a good thin-film semiconductor device showing a steep sub-threshold hold characteristic has been stably manufactured. In addition, the CMOS circuit (ring oscillator) produced by the present invention exhibited better operation stability than the comparative example. As shown in these examples, according to the present invention, a thin film semiconductor device having excellent characteristics and a highly reliable oxide film can be easily and easily formed in a low-temperature process in which a general-purpose glass substrate can be used. I can do it.

[0022]

As described in detail above, the present invention minimizes plasma damage and makes it possible to repair the thin-film semiconductor device, which has conventionally suffered enormous plasma damage and was expensive to manufacture. . At the same time, the effect of remarkably improving the electrical characteristics of the semiconductor device, improving the operation stability thereof, and further reducing the cost is recognized.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a manufacturing process of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 ... Substrate 102 ... Underlying protective film 103 ... Semiconductor film island 104 ... Silicon oxide film 105 ... Gate electrode 106 ... Impurity ions 107 ... Source / drain region 108 ...・ Channel forming region 109 ・ ・ ・ Interlayer insulating film 110 ・ ・ ・ Wiring

Claims (14)

[Claims] In a method of manufacturing a semiconductor device having at least a semiconductor film formed on a substrate and an insulating film formed on the semiconductor film as a constituent feature, a first method for forming a semiconductor film on a substrate is provided. Step, a second step of depositing an oxide film by a vapor deposition method, a third step of performing a nitriding treatment on the substrate, and a fourth step of performing a first heat treatment on the substrate in an oxidizing atmosphere, A fifth step of subjecting the substrate to a second heat treatment. 2. The method according to claim 1, wherein the semiconductor film is a polycrystalline film. 3. The method of manufacturing a semiconductor device according to claim 1, wherein said semiconductor film is mainly composed of silicon (Si). 4. The method according to claim 1, wherein the oxide film is made of silicon oxide (SiO _x : 0 <
4. The method for manufacturing a semiconductor device according to claim 1, wherein x ≦ 2 is mainly used. 5. The method for manufacturing a semiconductor device according to claim 1, wherein said third step is irradiation with plasma containing ammonia (NH ₃ ). 6. The method for manufacturing a semiconductor device according to claim 1, wherein said fourth step is performed in an atmosphere containing a substance capable of breaking a bond of said oxide film. 7. The method according to claim 6, wherein the substance capable of breaking the bond of the oxide film is water. 8. The method for manufacturing a semiconductor device according to claim 6, wherein the substance capable of breaking the bond of the oxide film contains a halogen atom. 9. The method according to claim 1, wherein the fifth step is performed in a non-oxidizing atmosphere. 10. The method according to claim 1, wherein the fifth step is performed in an inert atmosphere. 11. The method according to claim 1, wherein the fifth step is performed in a hydrogen-containing atmosphere. 12. The method according to claim 1, wherein the heat treatment temperature in the fifth step is substantially the same as the heat treatment temperature in the third step. 13. The method of manufacturing a semiconductor device according to claim 1, wherein the heat treatment temperature in the fifth step is higher than the heat treatment temperature in the third step. 14. The manufacturing of a semiconductor device according to claim 12, wherein the heat treatment temperature in the fifth step is the highest temperature in all the steps from the second step to the completion of the semiconductor device. Method.