JP3837938B2 - Method for manufacturing thin film semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a thin film semiconductor device typified by a thin film transistor (TFT), a silicon on insulator (SOI), or the like. More specifically, the present invention relates to a method of manufacturing a high-performance and reliable thin film semiconductor device at a relatively low temperature of about 425 ° C. or less.
[0002]
[Prior art]
In the case of manufacturing a thin film semiconductor device represented by a polycrystalline silicon thin film transistor (p-Si TFT) at a low temperature of about 425 ° C. or lower where a general-purpose glass substrate can be used, the following manufacturing method has been conventionally employed. 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 to be a gate insulating film is applied to a chemical vapor deposition method (CVD method) or a physical vapor deposition method (PVD method). Form. Next, a gate electrode is made of tantalum or the like, and a field effect transistor (MOS-FET) composed of metal (gate electrode) -oxide film (gate insulating film) -semiconductor (polycrystalline silicon film) is formed. Next, an interlayer insulating film is deposited, contact holes are opened, and wiring is performed using a metal thin film. In order to improve the electrical characteristics as necessary, a plasma irradiation treatment consisting of 100% hydrogen is finally performed for about 2 hours, thereby completing the thin film semiconductor device.
[0003]
[Problems to be solved by the invention]
However, in these conventional methods of manufacturing a thin film semiconductor device, even if hydrogen plasma irradiation is performed to improve the semiconductor characteristics, the semiconductor characteristics are only slightly improved. Moreover, because the processing time is too long, the semiconductor film, the silicon oxide film, and the plasma processing apparatus itself are damaged by plasma, and many expensive plasma processing apparatuses must be purchased. I had many problems. In accordance with these facts, if a semiconductor device such as p-Si TFT is manufactured by a conventional manufacturing method, the manufacturing price increases, and the completed semiconductor device not only has excellent electrical characteristics but also is in use. There was also a problem in reliability such as deterioration over time.
[0004]
In view of the above-described circumstances, the present invention is intended to provide a method for manufacturing an excellent thin film semiconductor device in a low temperature process of about 425 ° C. or lower.
[0005]
[Means for Solving the Problems]
The method for manufacturing a thin film semiconductor device according to the present invention includes a first step of forming a semiconductor film containing a semiconductor substance containing silicon alone or a silicon substance on a substrate containing an insulating substance, and silicon oxide on the semiconductor film. A second step of forming an insulating film; and a third step of irradiating the insulating film with a nitrogen atom active species and nitriding the insulating film and the semiconductor film while keeping the temperature of the substrate at 425 ° C. or lower. The nitrogen atom active species is generated by a plasma composed of a mixed gas of a rare gas and a nitrogen-containing gas, the plasma source of the plasma is a radio wave, and the proportion of the nitrogen-containing gas in the mixed gas is 1% It is characterized by being 6% or less.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
First, in the present invention, as a first step, a semiconductor film typified by polycrystalline silicon (p-Si) is formed on an edge substance such as a glass substrate or an interlayer insulating film of a three-dimensional semiconductor device. The semiconductor film may be in a single crystal state, in a polycrystalline state, or in an amorphous state. However, the present invention is particularly effective when it is in a polycrystalline state. Indicates. 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 the trap level (grain boundary level) located between the crystal grains. This is also because of the reduction. Needless to say, the interface state always exists at the junction interface between the semiconductor film and the insulating film regardless of the crystalline state. Since this interface state is reduced, the present invention is effective regardless of the state of the semiconductor film. On the other hand, in addition to this effect for the polycrystalline film, an effect of reducing the grain boundary level is also recognized. The semiconductor film may be any semiconductor material such as silicon (Si) or silicon germanium (Si _x Ge _1-x : 0 <x <1), but from the viewpoint of easily forming a good MOS interface. Semiconductor materials having silicon as a main constituent element (silicon atom constituent ratio of about 80% or more) are excellent. The semiconductor film is formed by a vapor deposition method such as a physical vapor deposition method (PVD method) or a chemical vapor deposition method (CVD method). As the PVD method, a sputtering method, a vapor deposition method, or the like can be considered. As the CVD method, an atmospheric pressure chemical vapor deposition method (APCVD method), a low pressure chemical vapor deposition method (LPCVD method), a plasma chemical vapor deposition method (PECVD method), or the like can be used. A semiconductor film formed by vapor deposition is usually in a polycrystalline state, an amorphous state, or a mixed state 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 crystal film, respectively. Polycrystalline films obtained immediately after deposition may be used as active parts of semiconductor devices (source / drain regions and channel forming regions of field effect transistors and emitter / base / collector regions of bipolar transistors). It is possible. In contrast to this, an amorphous film or a mixed crystal film is crystallized, or a polycrystalline film is recrystallized to obtain a new polycrystalline film, which is then used as an active part. Things are also possible. Laser irradiation or rapid heat treatment is used to easily perform crystallization and recrystallization.
[0007]
Next, as a second step, an insulating film is formed on the semiconductor film using a plasma chemical vapor deposition apparatus (PECVD apparatus) or the like. In addition to the PECVD method, the insulating film is formed by other CVD methods such as a PVD method such as sputtering or vapor deposition, an atmospheric pressure chemical vapor deposition method (APCVD method), or a low pressure chemical vapor deposition method (LPCVD method). You may depend on. The PECVD method is most suitable from the standpoint that the nitrogen active species irradiation in the third step is performed continuously following the formation of the insulating film in the second step. In this case, the active species of nitrogen can be irradiated before impurities such as moisture in the air are mixed into the insulating film or the interface when the substrate touches the air or the like. This is because defects such as paired bonds can be efficiently terminated. Furthermore, productivity is improved by making it a continuous process. The temperature during the formation of the insulating film is at most about 425 ° C., usually about 400 ° C. or less. This is based on the premise that the semiconductor device targeted by the present application is manufactured on a general-purpose glass substrate on which an amorphous silicon thin film semiconductor device (a-Si TFT) is manufactured or a substrate having poor heat resistance such as a plastic substrate. It is from. As will be described later, the temperature of the third step is preferably about 400 ° C. or less, and it depends on the fact that the second step and the third step are preferably continuous. The insulating film is formed by irradiating the semiconductor film with plasma of an oxidizing gas containing oxygen or the like to grow an ultrathin silicon oxide film having a thickness of about 3 nm to 10 nm on the surface layer of the semiconductor film. In the case where an insulating film having a thickness of about 10 nm or more is required, a silicon oxide film or a silicon nitride film is deposited on the ultrathin silicon oxide film by a CVD method to form a laminated structure. In this case, after forming the first plasma oxide film on the surface layer of the semiconductor film, the second insulating film is continuously deposited without breaking the vacuum. In order to avoid problems such as inadvertent level formation in the gate insulating film and contamination of impurities into the gate insulating film, immediately after the plasma oxidation is completed, the second insulating film is formed within about 5 minutes at the latest. Start deposition. From the end of plasma oxidation to the start of insulating film deposition, the plasma processing chamber is set to the same conditions as those for insulating film deposition except that plasma is generated. In order to execute such a process, the substrate temperature in the plasma oxidation and the substrate temperature in the insulating film deposition must be substantially equal. That is, the temperature difference between the two is at most less than about 30 ° C. As a result, the substrate temperature reaches equilibrium even within the short time period, and a uniform insulating film can be stably deposited.
[0008]
When silicon oxide is used as the deposited insulating film, the raw material gas is a silane gas such as monosilane (SiH ₄ ), disilane (Si ₂ H ₆ ), dichlorosilane (Si ₂ H ₂ Cl ₂ ), or TEOS (Si (0C). ₂ H ₅ ) ₄ ) or the like, and an oxidizing gas such as oxygen (O ₂ ) or nitrous oxide (N ₂ O) are used. When silicon nitride is used, the silane gas described above and a nitriding gas such as ammonia (NH ₃ ) or nitrogen (N ₂ ) are used.
[0009]
The insulating film thus obtained is used as a gate insulating film of a MOS-FET. However, these insulating films contain a large amount of insulating film trapping levels and fixed charges in the film as compared with silicon thermal oxide films formed at temperatures of about 1100 ° C. or higher, and the interface levels are much higher. Is normal. Therefore, in the present invention, the following steps are used to improve the gate insulating film and the interface, and at the same time, the crystal grain boundary of the semiconductor film.
[0010]
After the second step is completed, as a third step, nitriding treatment is performed in which hydrogen or nitrogen is bonded to an insulating film such as a semiconductor film or silicon oxide, and an unpaired pair at the interface between the semiconductor film and the silicon oxide film. In this third step, the unpaired bond pair existing in the semiconductor film or at the interface is terminated with hydrogen, nitrogen, amino group or imino group (in this application, such treatment is widely referred to as nitriding treatment) This is because the trap level (deep states) near the center (near the intrinsic Fermi level) is reduced. At the same time, unpaired bond pairs existing in the oxide film or the insulating film are also terminated by these functional groups, and the charge in the insulating film such as the fixed charge of the oxide film is reduced. The main cause of deep states is an unpaired bond pair existing at the interface or grain boundary of the semiconductor film. These are easily deactivated by nitriding, and the trap level decreases if deactivated. In addition, the fixed charge in the insulating film causes a fluctuation in the flat band potential, or facilitates injection of the charge into the insulating film, thereby reducing the operation reliability of the semiconductor device. Therefore, by performing the nitriding process in the third step, it is possible to bring the flat band potential of the semiconductor device close to the ideal value, reduce deep states, and further increase the reliability of the semiconductor device.
[0011]
The most effective nitriding treatment is to irradiate the substrate on which the semiconductor film and the insulating film are formed with nitrogen active species. The nitrogen active species is generated by plasma composed of a mixed gas of a rare gas such as helium and a nitrogen-containing gas such as ammonia or nitrogen. Therefore, the nitriding process in the present invention is performed by a plasma processing apparatus such as a plasma enhanced chemical vapor deposition apparatus (PECVD apparatus). When the substrate temperature during nitriding is too low (less than about 100 ° C.), the reaction does not proceed. Conversely, when the substrate temperature is too high (about 425 ° C. or higher), the reverse reaction such as nitrogen or hydrogen desorption occurs. Since it becomes faster, it is performed at a substrate temperature between about 100 ° C. and 425 ° C. Ideally, the temperature is between about 250 ° C. and about 400 ° C. From the viewpoint of increasing productivity, it is preferable that the second process and the third process are continuously processed in the same PECVD apparatus. In this case, if the processing temperature in the second step and the processing temperature in the third step are greatly different, it takes a long time for the substrate to reach thermal equilibrium. In order to achieve thermal equilibrium within a short time of about 5 minutes, the temperature difference between the second step and the third step must be about 30 ° C. or less.
[0012]
Nitrogen active species irradiation is performed with noble gases such as helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe), nitrogen (N ₂ ), and nitrous oxide (N ₂ O). Atomic active species such as nitrogen are generated by a plasma consisting of a mixed gas with a nitrogen-containing gas such as ammonia (NH ₃ ) and nitric acid (HNO ₃ ), and the plasma containing this nitrogen atomic active species is converted into a semiconductor film or This is done by irradiating the insulating film. By such plasma irradiation, the unpaired bond pair existing in the semiconductor film surface layer part, the grain boundary part of the polycrystalline semiconductor film, and the insulating film is terminated by the functional group described above, and these defects are eliminated. Yes, because it is inactivated.
[0013]
As a plasma source of a plasma composed of a mixed gas of a rare gas and a nitrogen-containing gas, a radio wave (rf wave: 13.56 MHz or an integer multiple of 27.12 MHz or the like) or a super-high frequency (VHF wave: about 100 MHz) An electromagnetic wave having a frequency of several hundred MHz) or a microwave (an electromagnetic wave having a frequency in the GHz band such as 2.45 GHz or 8.3 GHz) is used. If ultra-high frequency or microwave is used, the plasma density increases, so that the nitriding process proceeds rapidly. However, from the viewpoint that a general-purpose PECVD apparatus corresponding to a large substrate such as 550 mm × 650 mm can be used, use of a radio wave represented by 13.56 MHz is optimal. When performing the mixed plasma irradiation, the ratio of the nitrogen-containing gas in the mixed gas of the rare gas and the nitrogen-containing gas is set to about 1% or more and about 10% or less. In particular, when a PECVD apparatus using a radio wave as a plasma source is used, the ratio of the nitrogen-containing gas must be about 1% or more and less than about 6% in accordance with a decrease in plasma density. This is because the present invention generates a large amount of excited states of a rare gas, and with the energy transition from this excited state, the nitrogen-containing gaseous atomic active species (hydrogen atom active species H ^* , nitro group active species NO ₂ ^* , nitrosyl) Group active species NO ^* , amino group active species NH ₂ ^* , imino group active species NH ^* , nitrogen atom active species N ^* ), and these functional groups are bonded to an unpaired bond pair. Because it is. In the conventional hydrogenation, for example, hydrogenation of the surface of the polycrystalline silicon film is performed using pure hydrogen plasma. In this case, almost all active species generated in the plasma are active species of hydrogen molecules (H ₂ ^* ). When effectively nitriding the surface of a semiconductor material such as silicon or the grain boundary portion of a polycrystalline semiconductor film at a low temperature of less than about 425 ° C. as in the present application, each unpaired bond pair in which nitrogen atoms are present randomly Must be joined one by one. Molecular active species require molecules to dissociate into atoms, and much of this dissociation energy is thermally supplied from the substrate. Therefore, at low temperatures where the substrate temperature is less than about 425 ° C., the progress of hydrogenation and nitridation is remarkably suppressed. In contrast, in the present application, a large amount of rare gas active species is generated in the plasma. The active species of the rare gas has a high excitation energy of about 20 eV. On the other hand, for example, the total energy that a nitrogen molecule dissociates into two nitrogen atoms and one of the nitrogen atoms reaches the first excited state is about 20 eV. Therefore, when the nitrogen molecule receives energy from the excited species of the rare gas, the first excited species of the nitrogen atom, that is, the nitrogen atom active species is easily generated. The nitrogen atom active species thus generated is chemically active and is an unpaired bond pair on the surface of the semiconductor film or at the grain boundary even at a low temperature of about 425 ° C. or less than about 400 ° C. Thus, the defect repair of the semiconductor film at a low temperature proceeds. In this case, when the ratio of nitrogen-containing gas is less than about 1%, the number of atomic active species of nitrogen-containing gas in the plasma is small, and conversely, when it is about 10% or more, the number of active species of rare gas decreases. Since the number of molecular active species of nitrogen-containing gas increases, the number of atomic active species of nitrogen-containing gas decreases and ends up. In particular, in plasma using radio waves with low plasma density, it is necessary to increase the number of atomic active species of nitrogen-containing gas, and the ratio of nitrogen-containing gas in the mixed gas should be about 1% or more and less than about 6%. I have to. In this case, even if it is rf plasma, a high quality interface and grain boundary having a low trapping level can be formed in a relatively short time. The maximum temperature excluding the second step or the third step in the manufacturing process of the semiconductor device of the present invention is about 425 ° C. when the semiconductor film is deposited. In order to carry out the third step at a temperature lower than the maximum temperature in the semiconductor device manufacturing process or the temperature at which the semiconductor film is deposited, that is, about 425 ° C. or less, the decrease in the nitriding reaction rate due to the lower temperature is compensated. Therefore, it is necessary to maximize the number of atomically active species of nitrogen-containing gas, and therefore the ratio of nitrogen-containing gas in the mixed gas must be about 1.5% or more and less than about 4.5%. . Furthermore, in the case of a polycrystalline semiconductor film in which crystal grain boundaries exist, it is necessary to release disordered bonds at the grain boundaries and newly bond hydrogen and nitrogen to these, so that an excellent semiconductor device can be obtained. The ratio of the nitrogen-containing gas in the mixed gas is preferably about 2% or more and less than about 4%. In order to promote the plasma nitriding reaction at a low temperature, the substrate is immersed in a dilute hydrofluoric acid solution or the like immediately before the plasma irradiation, and the semiconductor film surface and the grain boundary portion are terminated with hydrogen. In this case, the surface of the semiconductor film and the like is in an orderly state, and it is not necessary to break the disordered bond, so that the nitriding process proceeds easily.
[0014]
Conventional hydrogenation treatment has been performed for 2 to 6 hours. In contrast, the nitriding time in the third step of the present invention is about 10 seconds to 10 minutes. This is because in the conventional method, hydrogenation treatment was performed after the gate electrode (thickness of about 500 nm or more), the interlayer insulating film (thickness of about 500 nm or more), the metal wiring (thickness of about 500 nm or more), etc. were completed. It is. In order to efficiently perform hydrogenation, it is necessary to generate active species of hydrogen by plasma or the like. However, since these are chemically unstable, their lifetime is short, and gate electrodes, interlayer insulating films, metal wirings, etc. Etc., it is difficult to reach the gate insulating film and the active layer semiconductor film. Therefore, conventionally, the hydrogen plasma treatment time has to be lengthened, and thus, the semiconductor device suffers a lot of plasma damage at the same time as the hydrogenation treatment, and the plasma treatment device also has its life to the plasma generated by itself. It was because it was short. In contrast, in the present invention, nitriding is performed immediately after the gate insulating film is formed. This is because the nitriding process is performed directly under the condition that there is no gate electrode, interlayer insulating film, or metal wiring. However, in the semiconductor device of the present invention, since the gate insulating film is as thin as about 5 nm to about 120 nm, atomic active species such as hydrogen, nitrogen, and ammonia easily reach the semiconductor film. This is the reason why the nitriding time can be greatly shortened from 1/10 to 1/100 in the present invention. As the plasma irradiation time is shortened, the plasma damage to the thin film semiconductor device is reduced from 1/10 to 1/100, and the number of processing within the lifetime of the plasma processing apparatus is increased from 10 times to 100 times. Yes. If the nitriding time is less than about 10 seconds, the effect of nitriding does not appear, and if it is longer than about 10 minutes, the oxide film or the semiconductor film may be damaged so that it cannot be repaired later. Ideally, it is about 30 seconds to 120 seconds.
[0015]
In this way, a large amount of atomic active species of nitrogen-containing gas generated by plasma of a mixed gas of gas and nitrogen-containing gas is irradiated to the interface between the semiconductor film and the insulating film, and the like, Since the defects in the insulating film, the grain boundary portions of the polycrystalline semiconductor film, and the surface of the semiconductor film are terminated efficiently, the number of unpaired pairs at such sites is significantly reduced. In particular, the grain boundary termination of the polycrystalline semiconductor film reduces the number of trap levels in the forbidden band of the semiconductor film, thereby reducing the subthreshold characteristics and threshold voltage of the thin film semiconductor device, and at the same time The mobility is improved by reducing the number of inelastic scattering of a single charged substance at the boundary. Further, since defects in the oxide film near the interface are reduced and the quality of the gate insulating film is improved, a thin film semiconductor device with high operational reliability and a long life can be obtained.
[0016]
Example 1
1A to 1D are cross-sectional views showing a manufacturing process of a thin film semiconductor device for forming a MOS field effect transistor. In Example 1, general-purpose non-alkali glass having a strain point of about 650 ° C. was used as the substrate 101. First, a silicon oxide film having a thickness of about 200 nm was deposited on the substrate 101 by the ECR-PECVD method to form a base protective film 102. The deposition conditions of the silicon oxide film by the ECR-PECVD method are as follows.
[0017]
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
Deposition time: 40 seconds An intrinsic amorphous silicon film as a semiconductor film was deposited on the undercoat protective film to a thickness of about 50 nm by LPCVD. The LPCVD apparatus has a hot wall type and a volume of 184.5 l. The total reaction area after the substrate is inserted is about 44000 cm ² . The deposition temperature was 425 ° C., disilane (Si ₂ H ₆ ) having a purity of 99.99% or more was used as a source gas, and the resulting gas was supplied to a 200 sccm reactor. The deposition pressure was approximately 1.1 Torr. Under these conditions, the deposition rate of the silicon film was 0.77 nm / min. The amorphous semiconductor film thus obtained was irradiated with a xenon chlorine (XeCl) excimer laser to promote crystallization of the semiconductor film. In the irradiation laser energy density is 425mJ · cm ^-2, the semiconductor film is there at 10 mJ · cm ^-2 lower energy density than the energy density micro-crystallization occurs completely melted throughout the thickness direction. The thickness of the polycrystalline silicon thin film after laser crystallization was 61.8 nm. After the crystalline semiconductor film (polycrystalline silicon film) was formed in this way (first step), this crystalline semiconductor film was processed into an island shape to form a semiconductor film island 103 that later became the active layer of the semiconductor device. . (Fig. 1-a)
Next, a silicon oxide film 104 was formed by PECVD so as to cover the island 103 of the patterned semiconductor film (second process). This silicon oxide film functions as a gate insulating film of the semiconductor device. Prior to forming the gate insulating film, the substrate was cleaned by the following procedure.
[0018]
(1) Isopropyl alcohol cleaning by ultrasonic irradiation (27 ° C, 5 minutes)
(2) Nitrogen bubbled pure water cleaning (27 ° C., 5 minutes)
(3) Ammonia overwater cleaning (80 ° C., 5 minutes)
(4) Cleaning with pure water with nitrogen bubbling (27 ° C, 5 minutes)
(5) Sulfuric acid overwater cleaning (97 ° C, 5 minutes)
(6) Nitrogen bubbled pure water cleaning (27 ° C., 5 minutes)
(7) Diluted hydrofluoric acid aqueous solution (hydrofluoric acid concentration 1.67%) cleaning (27 ° C., 20 seconds)
(8) Pure water cleaning with nitrogen bubbling (27 ° C., 5 minutes)
The time from the completion of the eighth pure water cleaning until the substrate was placed in the plasma processing chamber of the PECVD apparatus was about 15 minutes.
[0019]
The PECVD apparatus is a single-wafer capacitively coupled type, and plasma is generated between parallel plate electrodes using a radio high frequency power source with an industrial frequency (13.56 MHz). The plasma processing chamber is isolated from the outside air by the reaction vessel, and is in a reduced pressure state of about 0.1 Torr to 10 Torr during the plasma processing. A lower plate electrode and an upper plate electrode are installed in parallel in the reaction vessel, and these two electrodes form a parallel plate electrode. A space between the parallel plate electrodes is a plasma processing chamber. The PECVD apparatus used in the present invention has parallel plate electrodes of 470 mm × 560 mm, and the distance between these parallel plate electrodes can be freely set between 18.0 mm and 37.0 mm depending on the position of the lower plate electrode. Can be set. Accordingly, the volume of the plasma processing chamber changes from 4738 cm ³ to 9738 cm ³ . When the distance between the electrodes is set to a predetermined value, the deviation of the distance between the electrodes within the flat electrode surface of 470 mm × 560 mm is only 0.5 mm. Accordingly, the deviation of the electric field strength generated between the electrodes is about 2% or less within the plane electrode surface, and a homogeneous plasma is generated in the plasma processing chamber. A silicon substrate on which an oxide film is to be formed is placed on the lower plate electrode. A heater is provided inside the lower plate electrode, and the temperature of the lower plate electrode can be arbitrarily adjusted between 250 ° C and 400 ° C. The temperature distribution in the lower plate electrode excluding the periphery of 2 mm is within ± 5 ° C with respect to the set temperature, and the substrate temperature deviation is kept within ± 2 ° C even if a large substrate of 360 mm x 465 mm is used. I can do it. The raw material gas used for the plasma processing is introduced into the upper plate electrode through the pipe, and further passes through the gas diffusion plate provided in the upper plate electrode, and flows out from the entire surface of the upper plate electrode to the plasma processing chamber with a substantially uniform pressure. If the process is in progress, a part of the mixed gas is ionized when it exits from the upper plate electrode, and plasma is generated between the parallel plate electrodes. Part or all of the source gas is involved in oxide film growth and nitrogen active species irradiation, and the residual mixed gas that was not involved in growth and irradiation and the product gas generated as a result of chemical reactions such as oxide film formation are exhaust gas and Then, it is exhausted through an exhaust hole provided in the upper periphery of the reaction vessel. The conductance of the exhaust hole is sufficiently larger than the conductance between the parallel plate electrodes, and the value is preferably 100 times or more the conductance between the parallel plate electrodes. Furthermore, the conductance between the parallel plate electrodes is sufficiently larger than the conductance of the gas diffusion plate, and the value is preferably 100 times or more the conductance of the gas diffusion plate. Due to such a configuration, the reaction gas is introduced into the plasma processing chamber from the entire surface of the large upper plate electrode of 470 mm × 560 mm with a substantially uniform pressure, and at the same time, the exhaust gas is exhausted from the plasma processing chamber at a uniform flow rate in all directions. So there. The flow rates of the various reaction gases are adjusted to predetermined values by the mass flow controller before being introduced into the pipe. The pressure in the plasma processing chamber is adjusted to a desired value by a conductance valve provided at the outlet of the exhaust hole. A vacuum exhaust device such as a turbo molecular pump is provided on the exhaust side of the conductance valve. In the present invention the dry pump of the oil-free is used as part of the vacuum exhaust system, there background vacuum degree in the reaction vessel of a plasma processing chamber such as 10 ^{@ 5} Torr stand. The reaction vessel and the lower plate electrode are at ground potential, and these and the upper plate electrode are electrically insulated by the insulating ring. At the time of plasma generation, a radio frequency of 13.56 MHz output from the high frequency oscillation source is applied to the upper plate electrode via the impedance matching circuit.
[0020]
The PECVD apparatus used in the present invention has become a thin film forming apparatus that can handle a large substrate of 360 mm × 465 mm because it has given up elaborate electrode control and homogeneous gas flow as described above. However, as long as these basic concepts are followed, it is possible to easily cope with the further increase in the size of the substrate, and it is possible to realize an apparatus that can actually handle a larger substrate of 550 mm × 650 mm. In the present invention, the most versatile high frequency of 13.56 MHz is used. Alternatively, a high frequency that is an integral multiple of this high frequency may be used. For example, double 27.12 MHz, triple 40.68 MHz, quadruple 54.24 MHz, etc. are also effective. Furthermore, a VHF wave of about 100 MHz to 1 GHz may be used. If the frequency is from an rf wave of about 10 MHz to a VHF wave of about several hundred MHz, it is possible to generate plasma between parallel plate electrodes. Therefore, plasma can be easily generated using a high frequency of a desired frequency by exchanging the impedance matching circuit with the high frequency oscillation source of the PECVD apparatus used in the present invention.
[0021]
In the first embodiment, the substrate is installed in a plasma processing chamber in which the temperature of the lower plate electrode is maintained at 375 ° C. The substrate surface temperature after the installation substrate is in equilibrium with the plasma processing chamber is 350 ° C. First, an oxygen film having a thickness of about 3 nm is formed on the surface of the semiconductor film by irradiating oxygen plasma. Oxidation conditions are oxygen flow of 5000 SCCM and the pressure in the plasma processing chamber is maintained at 1.5 Torr. The distance between the parallel plate electrodes is 21.6 mm, and the radio high frequency output is 500 W (0.19 W / cm ² ). The oxygen plasma irradiation time is 300 seconds. After the oxygen plasma irradiation, the plasma processing chamber is the same as the oxide film deposition condition except that plasma is generated. The processing chamber conditions before the oxide film deposition are as follows.
[0022]
Oxygen flow rate: O ₂ = 1200 SCCM
Argon flow rate: Ar = 4700 SCCM
TEOS flow rate: TEOS = 100SCCM
Radio high-frequency output: RF = 0W (No plasma can be generated)
Pressure: P = 1.5 Torr
Distance between electrodes: S = 20.9mm
Lower plate electrode temperature: Tsus = 375 ° C.
Glass substrate surface temperature: Tsub = 350 ° C.
Stabilization time: t = 20 seconds Continuously in this state, radio high frequency is applied to the upper plate electrode to generate plasma, and an oxide film is deposited on the surface of the semiconductor film. The high frequency output is 1000W. That is, an insulating film is deposited under the following conditions.
[0023]
Oxygen flow rate: O ₂ = 1200 SCCM
Argon flow rate: Ar = 4700 SCCM
TEOS flow rate: TEOS = 100SCCM
Radio high frequency output: RF = 1000 W (0.38 W / cm ² )
Pressure: P = 1.5 Torr
Distance between electrodes: S = 20.9mm
Lower plate electrode temperature: Tsus = 375 ° C.
Glass substrate surface temperature: Tsub = 350 ° C.
Deposition time: t = 33 seconds In this way, after forming a silicon oxide film in the second step, the plasma processing chamber is evacuated, and a mixed gas of helium and ammonia is continuously applied to the semiconductor film and the oxide film. Plasma was irradiated (third step). The plasma processing conditions are as follows.
[0024]
Helium flow rate: He = 4900SCCM
Ammonia flow rate: NH ₃ = 100 SCCM
Radio high frequency output: RF = 400 W (0.152 W / cm ² )
Pressure: P = 1.0 Torr
Distance between electrodes: S = 25mm
Lower plate electrode temperature: Tsus = 375 ° C.
Glass substrate surface temperature: Tsub = 350 ° C.
Plasma treatment time: t = 90 seconds Next, a first heat treatment was performed in an oxidizing atmosphere as a fourth step. Heat treatment was performed in hydrochloric acid steam air containing a 16% concentration hydrochloric acid aqueous solution in air with 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 heat treatment using hydrochloric acid was completed, the heat treatment was continued for 1 hour for the purpose of removing the halogen element from the oxide film. This heat treatment atmosphere is performed in steam-containing air having a dew point of 96 ° C., and the atmosphere does not contain hydrochloric acid. The heat treatment temperature is 345 ° C. and the pressure is 1 atm.
[0025]
Thus, after the fourth step was completed, the second heat treatment of the fifth step was performed, and the oxide film was dried. The second heat treatment was performed at 1 atm and 350 ° C. for 2 hours in a non-oxidizing atmosphere containing 3% hydrogen in argon. When the thickness of the gate insulating film was measured after completion of the fifth step, the thickness was 93 nm. In this way, the gate insulating film formation and the modification of the interface with the semiconductor film and the oxide film were completed. (Fig. 1-b)
Subsequently, a gate electrode 105 is formed by sputtering using a metal thin film. The substrate temperature during sputtering was 150 ° C. In Example 1, a gate electrode was made of tantalum (Ta) having a thickness of 750 nm, and the sheet resistance of the gate electrode was 2.44Ω / □. Next, impurity ions 106 serving as donors or acceptors are implanted using the gate electrode as a mask, and source / drain regions 107 and a channel formation region 108 are formed in a self-aligned manner with respect to the gate electrode. In Example 1, a CMOS semiconductor device was produced. When fabricating an NMOS transistor, the PMOS transistor portion is covered with an aluminum (Al) thin film, and phosphine (PH ₃ ) diluted in hydrogen at a concentration of 5% is selected as an impurity element, and the acceleration voltage is 70 kV. Total ions containing hydrogen were implanted into the source / drain regions of the NMOS transistor at a concentration of 5 × 10 ¹⁵ cm ⁻² . Conversely, when fabricating a PMOS transistor, the NMOS transistor part is covered with an aluminum (Al) thin film, and diborane (B ₂ H ₆ ) diluted in hydrogen at a concentration of 5% is selected as an impurity element to accelerate. implanted into the source and drain regions of the PMOS transistor at a concentration of 4 × 10 ¹⁵ cm ^-2 to total ion containing hydrogen at a voltage 70 kV. (FIG. 1-c) The substrate temperature at the time of ion implantation is 300 ° C.
[0026]
Next, an interlayer insulating film 109 was deposited by a PECVD method using TEOS (Si— (OCH ₂ CH ₃ ) ₄ ) and oxygen as source gases at a substrate temperature of 300 ° C. The interlayer insulating film was made of a silicon dioxide film, and the film thickness was about 500 nm. After the interlayer insulating film was deposited, heat treatment was performed at 350 ° C. for 2 hours in a nitrogen atmosphere to serve as both the baking of the interlayer insulating film and the activation of 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 sputtering, and a wiring 110 was formed to complete a thin film semiconductor device. (Fig. 1-d)
The transfer characteristics of the thin film semiconductor device thus prepared were measured. The measured channel formation region of the semiconductor device had a length of 10 μm and a width of 10 μm. The transfer characteristics were measured at room temperature. The mobility obtained from the saturation region at Vds = 8V of the NMOS transistor is 104 cm ² · V ⁻¹ · s ⁻¹ , the threshold voltage is 3.083 V, and the subthreshold swing is 0.301 V. It was. The mobility obtained from the saturation region of the PMOS transistor at Vds = −8V is 81 cm ² · V ⁻¹ · s ⁻¹ , the threshold voltage is −2.082 V, and the sub-threshold hold swing is 0. It was 373V. On the other hand, in the comparative example (corresponding to the prior art, the third, fourth, and fifth steps in this embodiment are not performed) in which hydrogen plasma irradiation is performed with 100% hydrogen for 2 hours after the completion of the thin film semiconductor device, The mobility was 55 cm ² · V ⁻¹ · s ⁻¹ , the threshold voltage was 3.685 V, and the subthreshold swing was 0.336 V. Further, the mobility of the PMOS of the comparative example was 77 cm ² · V ⁻¹ · s ⁻¹ , the threshold voltage was −2.639 V, and the sub-threshold swing was 0.486 V. As shown in this example, according to the present invention, both N-type and P-type semiconductor devices have high mobility, and can stably manufacture excellent thin film semiconductor devices exhibiting steep subthreshold characteristics. Made. However, because the oxide film quality in the interface transition region is high, the oxide film has high reliability, and it has become possible to easily and easily create a long-life thin-film semiconductor device in a low-temperature process that can use a general-purpose glass substrate. . Furthermore, the nitriding time could be reduced from over two hours of the conventional hydrogenation time to several minutes.
[0027]
【The invention's effect】
As described in detail above, the hydrogenation treatment, which has been effective for a long time while having a long time, can be effectively performed in a short time by the invention of the main building. Accordingly, it is recognized that the semiconductor device typified by the thin film transistor promotes high-speed operation, energy saving, and cost reduction, and at the same time, increases the operational stability of the semiconductor device.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a manufacturing process according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Substrate 102 ... Underlayer protection film 103 ... Semiconductor film island 104 ... Silicon oxide film 105 ... Gate electrode 106 ... Impurity ion 107 ... Source / drain region 108 ... Channel forming region 109 ... interlayer insulating film 110 ... wiring

Claims (5)

Forming a semiconductor film containing a silicon substance or a semiconductor substance mainly containing silicon on a substrate containing an insulating substance;
A second step of forming an insulating film containing silicon oxide on the semiconductor film;
Irradiating the insulating film with nitrogen atom active species, and nitriding the insulating film and the semiconductor film while keeping the temperature of the substrate at 425 ° C. or lower,
The nitrogen atom active species is generated by a plasma composed of a mixed gas of a rare gas and a nitrogen-containing gas, the plasma source of the plasma is a radio wave, and the proportion of the nitrogen-containing gas in the mixed gas is 1% or more A manufacturing method of a thin film semiconductor device, characterized by being 6% or less. In the manufacturing method of the semiconductor device according to claim 1,
A method of manufacturing a thin film semiconductor device, wherein the semiconductor film is a polycrystalline film. In the manufacturing method of the semiconductor device according to claim 1 or 2,
The method of manufacturing a thin film semiconductor device, wherein a difference between the temperature of the substrate in the third step and the temperature of the substrate in the second step is 30 ° C. or less. In the manufacturing method of the semiconductor device according to claim 1,
A method for manufacturing a thin film semiconductor device, wherein a ratio of the nitrogen-containing gas in the mixed gas in the third step is 1.5% to 4.5%. In the manufacturing method of the semiconductor device according to claim 1,
The method for manufacturing a thin film semiconductor device, wherein a ratio of the nitrogen-containing gas in the mixed gas in the third step is 2% or more and 4% or less.

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