JP6392061B2 - Electronic device, manufacturing method thereof, and manufacturing apparatus thereof - Google Patents

Description

  The present invention relates to an electronic device using an oxide semiconductor for a channel, a manufacturing method thereof, and a manufacturing apparatus thereof.

  In recent years, in order to realize high definition, large size, and high-speed response in liquid crystal displays, high mobility thin transistors (TFTs) are required. In addition, the use of organic EL (Electrouminescence) elements is progressing in order to realize higher-brightness and high-contrast displays, thinned mobile terminals, and flexible displays. The organic EL element is a current-driven element driven by a TFT, and in order to exhibit sufficient light emission performance, an element that realizes high mobility is also required in the TFT that drives the organic EL element. However, the electron mobility of amorphous silicon, which has been mainly used as a constituent material of TFT channels in the past, is not so high, and it is difficult for the organic EL element to realize sufficient light emission performance.

Therefore, a TFT using a metal oxide (oxide semiconductor) that can provide high electron mobility for a channel has been proposed. As a metal oxide used in such a TFT, an oxide semiconductor, for example, IGZO made of an oxide of indium (In), gallium (Ga), and zinc (Zn) is known (for example, non-patent literature). 1). Since IGZO has a relatively high electron mobility (for example, 10 cm ² / (V · s) or more) even in an amorphous state, a metal oxide such as IGZO is expected to be used for a TFT channel.

  By the way, the TFT includes a passivation film made of, for example, a silicon nitride (SiN) film in order to surely protect the channel from external moisture or gas such as the atmosphere. In the case where a passivation film made of a silicon nitride film is formed by plasma CVD (Chemical Vapor Deposition), hydrogen radicals or hydrogen ions may be included as hydrogen atoms in the passivation film depending on the processing gas used for the plasma processing. Hydrogen atoms contained in the passivation film diffuse into the channel, and oxygen atoms in the IGZO are desorbed to change the characteristics of the IGZO, for example, the threshold voltage (Vth). Therefore, a processing gas containing no hydrogen atoms is used. It has been proposed to form a passivation film by plasma CVD (see, for example, Patent Document 1).

Japanese Patent Application No. 2014-049797

"Oxide semiconductor TFT for realizing light and thin sheet display", Kentaro Miura et al., Toshiba Review Vol. 67 No. 1 (2012)

  However, in plasma CVD, oxygen atoms may be lost in a channel made of IGZO due to the influence of sputtering, heat, etc., and dangling bonds may be generated in the channel. Since the dangling bonds trap carriers (electrons and holes), there is a problem that the electron mobility of the channel is lowered and the performance and reliability of the TFT are lowered.

  An object of the present invention is to provide an electronic device, a manufacturing method thereof, and a manufacturing apparatus thereof that can prevent deterioration in performance of an oxide semiconductor and at the same time improve reliability.

In order to achieve the above object, an electronic device of the present invention includes a metal oxide film forming an oxide semiconductor, a first film adjacent to the metal oxide film, and the metal sandwiching the first film. an electronic device and a second layer opposite the oxide film, before Symbol second film is a fluorine-containing film, the concentration of fluorine atoms at the boundary of the first film and the metal oxide film, The concentration of fluorine atoms in the portion other than the boundary of the metal oxide film is higher than the concentration of fluorine atoms in the portion other than the boundary and lower than the concentration of fluorine atoms in the second film. The density distribution has a density gradient that decreases toward the boundary.

In order to achieve the above object, a method of manufacturing an electronic device according to the present invention includes a metal oxide film that forms an oxide semiconductor, a first film adjacent to the metal oxide film, and the first film interposed therebetween. in a method of manufacturing an electronic device and a second layer facing the metal oxide film, before Symbol the second film constituted by fluorine-containing film, the metal oxide fluorine atoms from該弗-containing film It is diffused into the object layer, the concentration of the fluorine atoms at the boundary of the first film and the metal oxide film is high and the first than the concentration of the fluorine atoms in the portion other than the boundary of the metal oxide film It is characterized by being lower than the concentration of fluorine atoms in the second film .

In order to achieve the above object, a method of manufacturing an electronic device according to the present invention includes an electronic device including a metal oxide film forming an oxide semiconductor and a fluorine-containing film adjacent to the metal oxide film with another film interposed therebetween. In the method of manufacturing a device, a channel is formed in the metal oxide film, the other film and the fluorine-containing film are insulating films, and at least one of a fluoride gas, an oxygen atom, and a nitrogen atom The fluorine-containing film is formed by CVD using a gas containing hydrogen, and fluorine atoms are diffused from the fluorine-containing film, whereby the concentration distribution of fluorine atoms in the other film is determined by the metal in the other film. A concentration gradient that decreases toward the boundary and increases at the boundary in a portion other than the boundary with the oxide film, and the concentration of the fluorine atom increased at the boundary is the fluorine source in the fluorine-containing film. And wherein the lower than the concentration of.

In order to achieve the above object, an electronic device manufacturing apparatus of the present invention includes a metal oxide film forming an oxide semiconductor and a fluorine-containing film adjacent to the metal oxide film with another film interposed therebetween. An electronic device manufacturing apparatus comprising: a channel is formed in the metal oxide film; the other film and the fluorine-containing film are insulating films; and a fluoride gas, at least oxygen atoms and nitrogen atoms The fluorine-containing film is formed by CVD using a gas containing any of the above, and by diffusing fluorine atoms from the fluorine-containing film, the concentration distribution of fluorine atoms in the other film is A concentration gradient that decreases toward the boundary and increases at the boundary in a portion other than the boundary with the metal oxide film, and the concentration of fluorine atoms increased at the boundary is in the fluorine-containing film. And wherein the lower than the concentration of atom.

  According to the present invention, the concentration of fluorine atoms at the boundary between the first film and the metal oxide film is higher than the concentration of fluorine atoms at a portion other than the boundary between the metal oxide films, and at least other than the boundary between the first films. The concentration distribution of fluorine atoms in the portion has a concentration gradient that decreases toward the boundary. There are many dangling bonds that occur due to the loss of oxygen atoms from the metal oxide, but the concentration of fluorine atoms at the boundary between the first film and the metal oxide film is metal. Since the concentration of fluorine atoms in the portion other than the boundary of the oxide film is higher than that of the oxide film, many fluorine atoms exist at the boundary, and many dangling bonds are terminated by many fluorine atoms. Accordingly, generation of defects due to dangling bonds can be suppressed, so that deterioration in performance of the oxide semiconductor can be prevented and reliability can be improved at the same time.

  Further, according to the present invention, the fluorine-containing film adjacent to the metal oxide film directly or with another film interposed between the metal oxide film uses a fluoride gas and a gas containing at least one of oxygen atoms and nitrogen atoms. Since it is formed by CVD, the fluorine-containing film surely contains fluorine atoms. Accordingly, fluorine atoms diffuse from the fluorine-containing film to the metal oxide film, and dangling bonds existing in the metal oxide film can be terminated by the fluorine atoms. As a result, generation of defects due to dangling bonds can be suppressed, so that deterioration in performance of the oxide semiconductor can be prevented and reliability can be improved.

It is a fragmentary sectional view showing roughly the composition of bottom gate type oxide TFT as a general electronic device. FIG. 2A is a graph showing how the initial characteristic values of the silicon oxide film TFT and the fluorine-containing silicon nitride film TFT change with respect to the energy of the irradiated light. FIG. 2A shows how the S value changes. 2 (B) shows how the threshold voltage change amount changes, and FIG. 2 (C) shows how the hysteresis voltage change amount changes. FIG. 3A is a graph showing changes in characteristic values when a PBTS (Positive Bias Temperature Instability) test is performed after heat treatment of the silicon oxide film and the fluorine-containing silicon nitride film TFT. FIG. 3B shows a temporal change in the relationship between the gate voltage and the drain current in the fluorine-containing silicon nitride film TFT, and FIG. 3C shows a silicon oxide film. FIG. 3D shows the degree of change in the threshold voltage change amount with respect to the load time in the fluorine-containing silicon nitride film TFT. It is a fragmentary sectional view which shows the mode of the diffusion of the fluorine atom from the passivation film in a TFT to a channel. It is sectional drawing of the sample for analysis which has a structure imitating TFT shown in FIG. It is a graph which shows the measurement result by SIMS of the distribution of the fluorine atom after the heat processing of the sample for analysis shown in FIG. It is a fragmentary sectional view showing roughly the composition of bottom gate type TFT as an electronic device concerning an embodiment of the invention. It is sectional drawing which shows schematically the structure of the plasma CVD film-forming apparatus as an electronic device manufacturing apparatus which concerns on embodiment of this invention. It is process drawing which shows a part of manufacturing method of TFT in FIG. 10 is a graph schematically showing a state of fluorine atom distribution in a TFT manufactured by the TFT manufacturing method of FIG. 9; FIG. 8 is a partial cross-sectional view schematically showing a configuration of a first modification of the TFT of FIG. 7. FIG. 8 is a partial cross-sectional view schematically showing a configuration of a second modification of the TFT in FIG. 7. FIG. 8 is a partial cross-sectional view schematically showing a configuration of a third modification of the TFT in FIG. 7. FIG. 10 is a partial cross-sectional view schematically showing a configuration of a fourth modification of the TFT in FIG. 7. FIG. 10 is a partial cross-sectional view schematically showing a configuration of a fifth modification of the TFT in FIG. 7. FIG. 10 is a partial cross-sectional view schematically showing a configuration of a sixth modification of the TFT in FIG. 7.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a partial cross-sectional view schematically showing a configuration of a bottom-gate oxide thin transistor (TFT) as a general electronic device.

  In FIG. 1, a TFT 10 formed on a substrate 11 includes a gate electrode 12 formed on the substrate 11, a gate insulating film 13 covering the gate electrode 12, and an oxide formed on the gate insulating film 13 and made of IGZO. The semiconductor layer 15, the channel 14 formed in a part of the oxide semiconductor layer 15, the etch stop film 17 covering the channel 14, the source electrode 18, the drain electrode 19, the etch stop film 17, and the source electrode 18. And a passivation film 20 covering the drain electrode 19.

By the way, prior to the present invention, in order to confirm the influence on the initial characteristic value of TFT when using a passivation film not containing hydrogen atoms, the inventors have used hydrogen-containing silicon nitride as a passivation film containing a large amount of hydrogen atoms. (SiN: H) film, silicon oxide (SiO ₂ ) film as a passivation film containing a small amount of hydrogen atoms, and fluorine-containing silicon nitride (SiN: F) containing very few hydrogen atoms and substantially no hydrogen atoms ) The initial characteristic value of the TFT using the film was measured. The channels of these TFTs consisted of IGZO, and the measured initial characteristic values are shown in Table 1 below.

As shown in Table 1, since the TFT using the hydrogen-containing silicon nitride film did not operate, any initial characteristic value could not be measured. This was thought to be because a large amount of hydrogen atoms contained in the hydrogen-containing silicon nitride film diffused into the channel, and oxygen atoms in IGZO constituting the channel were desorbed. On the other hand, a TFT using a silicon oxide film as a passivation film (hereinafter referred to as “silicon oxide film TFT”) and a TFT using a fluorine-containing silicon nitride film as a passivation film (hereinafter referred to as “fluorine-containing silicon nitride film TFT”). Each of the initial characteristic values could be measured because, for example, the electron mobility was higher in the fluorine-containing silicon nitride film TFT than in the silicon oxide film TFT, and the S value indicating the switching performance was The fluorine-containing silicon nitride film TFT is smaller than the silicon oxide film TFT, and the hysteresis voltage change amount (ΔV _H ) is smaller in the fluorine-containing silicon nitride film TFT than in the silicon oxide film TFT. That is, each initial characteristic value of the fluorine-containing silicon nitride film TFT was better than each initial characteristic value of the silicon oxide film TFT. Further, the absolute value of the threshold voltage change amount (ΔV _th ) is smaller in the fluorine-containing silicon nitride film TFT than in the silicon oxide film TFT. In other words, the reliability of the fluorine-containing silicon nitride film TFT was improved over the reliability of the silicon oxide film TFT.

In addition, the change of each initial characteristic value of the TFT with respect to the light energy when the TFT is driven by irradiating light to each of the silicon oxide film TFT and the fluorine-containing silicon nitride film TFT is confirmed. Are shown in FIGS. 2 (A) to 2 (C). In FIGS. 2A to 2C, the silicon oxide film TFT and the fluorine-containing silicon nitride film TFT are indicated by “SiO ₂ ” and “SiN: F”, respectively.

When the energy of the irradiated light changes, the hysteresis voltage changes as shown in FIG. 2A regarding the change of the S value and as shown in FIG. 2B regarding the amount of change in the threshold voltage (ΔV _th ). As for the amount (Δ (ΔV _H )), as shown in FIG. 2C, the fluorine-containing silicon nitride film TFT is more preferable than the silicon oxide film TFT in the region of 2.7 eV or more for any initial characteristic value. It was confirmed that the change in the characteristic value was small. That is, it was confirmed that the fluorine-containing silicon nitride film TFT was superior to the silicon oxide film TFT with respect to the initial characteristics. The band gap of IGZO is 3 to 3.2 eV, while the fluorine-containing silicon nitride film TFT has a small change in characteristic value even at 3 to 3.2 eV. As a result, it was inferred that the reliability of the fluorine-containing silicon nitride film TFT was improved.

  Further, after the formation of the silicon oxide film (passivation film), the silicon oxide film TFT was subjected to a heat treatment at 350 ° C., and after the formation of the fluorine-containing silicon nitride film (passivation film), the fluorine-containing silicon nitride film TFT was subjected to a heat treatment at 350 ° C. Thereafter, the characteristic values of each TFT were measured to confirm the reliability of each TFT, and the confirmation results are shown in FIGS. 3 (A) to 3 (D).

  FIG. 3 shows the result of the PBTS test after the silicon oxide film and the fluorine-containing silicon nitride film TFT are heat treated (hereinafter referred to as “after heat treatment”), and FIG. 3A shows the silicon oxide film after the heat treatment. FIG. 3B shows temporal changes in the relationship between the gate voltage and the drain current in the fluorine-containing silicon nitride film TFT after the heat treatment. In each figure, each symbol indicates a measured value of gate voltage and drain current at each elapsed time. Specifically, a solid line without a symbol indicates a measured value in an initial state, “◇” indicates a measured value after 100 seconds, “◯” indicates a measured value after 1000 seconds, and “Δ” indicates A measured value after 5000 seconds has elapsed, and a broken line without a symbol indicates a measured value after 10,000 seconds have elapsed. 3A and 3B, as the load time elapses, the relationship between the gate voltage and the drain current moves in the direction of the arrow in each drawing. 3A and 3B, the fluorine-containing silicon nitride film TFT after the heat treatment has a smaller temporal change in the relationship between the gate voltage and the drain current than the silicon oxide film TFT after the heat treatment. It was found that the current flowed stably.

  FIG. 3C shows the degree of change in the threshold voltage change amount with respect to the load time in the silicon oxide film TFT after the heat treatment, and FIG. 3D shows the threshold voltage change with respect to the load time in the fluorine-containing silicon nitride film TFT after the heat treatment. Indicates the degree of change in quantity. In each figure, each symbol indicates a temperature at the time of measurement, “◇” is room temperature, “◯” is 50 ° C., “Δ” is 75 ° C., and “□” is 100 ° C. 3C and 3D, the fluorine-containing silicon nitride film TFT after the heat treatment has a smaller change in the threshold voltage with respect to the load time and the threshold voltage is more stable than the silicon oxide film TFT after the heat treatment. I found out that That is, it has been confirmed that the fluorine-containing silicon nitride film TFT is superior to the silicon oxide film TFT in terms of reliability.

  The reason why the fluorine-containing silicon nitride film TFT is superior to the silicon oxide film TFT in terms of initial characteristics and reliability is that the present inventors present the presence of fluorine atoms contained in the passivation film of the fluorine-containing silicon nitride film TFT. The following mechanism was inferred.

  In the TFT 10, when an etch stop film 17 made of, for example, silicon oxide is formed on the IGZO film constituting the channel 14 by plasma CVD, the IGZO film is sputtered by positive ions or the like, or from the IGZO film due to the influence of heat. Oxygen atoms are released and dangling bonds such as zinc atoms are generated mainly near the surface of the IGZO film, that is, near the boundary between the etch stop film 17 and the channel 14. The dangling bonds trap carriers in the channel 14 during the operation of the TFT, and deteriorate the initial characteristics and reliability of the TFT 10.

  On the other hand, when the passivation film 20 contains fluorine atoms (indicated by “F” in FIG. 4), after the TFT 10 is formed, the fluorine atoms contained in the passivation film 20 are etched off as shown in FIG. It diffuses into the channel 14 through the film 17 and terminates dangling bonds generated near the boundary between the etch stop film 17 and the channel 14. This suppresses carrier traps in the channel 14 and improves the initial characteristics of the TFT 10. In addition, since the bond energy of zinc atom and fluorine atom is higher than that of zinc atom and oxygen atom (the former is 364 kJ / mol, the latter is 284 kJ / mol), the dangling bonds terminated by fluorine atoms are stable. The fluorine atom is not released again and does not return to the dangling bond. As a result, the reliability of the channel 14 is improved, and hence the reliability of the TFT 10 is improved.

  Further, the present inventors prepared an analytical sample (FIG. 5) having a structure simulating a TFT shown in FIG. 4, and actively diffuses fluorine atoms contained in the passivation film 20 into the channel 14. Then, after the formation of the analytical sample in which the passivation film 20 is composed of a fluorine-containing silicon nitride film, the analytical sample is subjected to heat treatment, and then the distribution of fluorine atoms in the analytical sample is analyzed by secondary ion mass spectrometry (SIMS). Ion Mass Spectrometry).

  FIG. 6 is a graph showing the results of SIMS measurement of the distribution of fluorine atoms after the heat treatment of the analytical sample shown in FIG. In FIG. 6, the distribution of fluorine atoms in the TFT when the heat treatment is performed for 1 hour is indicated by a broken line, and the distribution of fluorine atoms in the TFT when the heat treatment is performed for 3 hours is indicated by a solid line.

  In FIG. 6, the number (concentration) of fluorine atoms diffused from the passivation film 20 decreases from the etch stop film 17 toward the channel 14, but once exhibits an extreme value at the boundary between the etch stop film 17 and the channel 14. To increase. This result confirms that the above-described mechanism, that is, the dangling bond generated in the vicinity of the boundary between the etch stop film 17 and the channel 14 is terminated by the fluorine atom, and that the inferred mechanism is correct.

Further, the longer the heat treatment time, the larger the number of fluorine atoms diffusing from the passivation film 20. However, as shown in FIG. 6, the longer the heat treatment time, the more fluorine atoms at the boundary between the etch stop film 17 and the channel 14. since the greater the number of extreme values of fluorine atoms for terminating the dangling bonds near the boundary of the etch stop film 17, and channel 14 is considered to be fluorine atoms diffused from the passivation film 20.

  That is, the present inventors have found that a fluorine-containing film can be terminated by fluorine atoms diffused from a fluorine-containing layer by performing a heat treatment by providing a fluorine-containing film in the vicinity of a channel where a dangling bond exists. Obtained. The present invention is based on the knowledge described above.

  Next, the electronic device according to the present embodiment will be described.

  FIG. 7 is a partial cross-sectional view schematically showing a configuration of a bottom gate type TFT as an electronic device according to the present embodiment. The configuration of the TFT 21 in FIG. 7 is almost the same as the configuration of the TFT 10 in FIG.

  In FIG. 7, a TFT 21 includes a gate electrode 12 formed on a substrate 11, a gate insulating film 13, an oxide semiconductor layer 15, and a channel 14 (metal oxide film) formed in part of the oxide semiconductor layer. ), An etch stop film 22 (first film) covering the oxide semiconductor layer 15 including the channel 14 and partially exposing the oxide semiconductor layer 15 other than the channel 14, a source electrode 18, and a drain electrode 19 and a passivation film 23 (second film) covering the etch stop film 22, the source electrode 18 and the drain electrode 19. In the TFT 21, the gate insulating film 13 and the etch stop film 22 are made of a silicon oxide film containing a small amount of hydrogen atoms, and the passivation film 23 is made of a fluorine-containing silicon nitride film. Note that a small amount of hydrogen atoms contained in the gate insulating film 13 and the etch stop film 22 are inevitably mixed in the manufacturing process, and do not greatly affect the effect of the present invention. Is preferably not included.

  FIG. 8 is a cross-sectional view schematically showing a configuration of a plasma CVD film forming apparatus as an electronic device manufacturing apparatus according to the present embodiment. This plasma CVD film forming apparatus is preferably used when forming the passivation film 23 in the TFT 21.

  In FIG. 8, the plasma CVD film forming apparatus 24 has, for example, a substantially casing-shaped chamber 25 that accommodates the substrate 11 on which the TFT 21 is formed, and is placed on the bottom of the chamber 25 to place the substrate 11 on the upper surface. The mounting table 26, an ICP (Inductively Coupled Plasma) antenna 27 disposed outside the chamber 25 so as to face the mounting table 26 inside the chamber 25, and a ceiling portion of the chamber 25 are configured, and the mounting table 26 and the ICP And a window member 28 interposed between the antennas 27. A constant gap is maintained between the ICP antenna 27 and the window member 28 by a spacer (not shown).

  The chamber 25 has an exhaust device (not shown). The exhaust device evacuates the chamber 25 to decompress the inside of the chamber 25. The window member 28 of the chamber 25 is made of a dielectric and partitions the inside and the outside of the chamber 25.

  The window member 28 is supported on the side wall of the chamber 25 via an insulating member (not shown), and the window member 28 and the chamber 25 are not in direct contact and are not electrically connected. The window member 28 has a size capable of covering at least the entire surface of the substrate 11 placed on the placement table 26. The window member 28 may be composed of a plurality of divided pieces.

  Three gas introduction ports 29, 30, 31 are provided on the side wall of the chamber 25, and the gas introduction port 29 is connected to a silicon halide gas supply unit 33 disposed outside the chamber 25 through a gas introduction pipe 32. The gas introduction port 30 is connected to a nitrogen-containing gas supply unit 35 disposed outside the chamber 25 via a gas introduction tube 34, and the gas introduction port 31 is disposed outside the chamber 25 via a gas introduction tube 36. The noble gas supply unit 37 is connected.

The silicon halide gas supply unit 33 supplies a silicon halide gas containing no hydrogen atom, for example, silicon tetrafluoride (SiF ₄ ) gas, to the inside of the chamber 25 through the gas inlet 29, and supplies a nitrogen-containing gas. The unit 35 supplies a nitrogen-containing gas not containing hydrogen atoms, for example, nitrogen (N ₂ ) gas, into the chamber 25 through the gas inlet 30, and the rare gas supply unit 37 passes through the gas inlet 31. A rare gas such as argon gas is supplied into the chamber 25. That is, the processing gas not containing hydrogen is supplied into the chamber 25 by mixing silicon tetrafluoride gas and nitrogen gas. Note that the processing gas may contain a gas not containing hydrogen in addition to the silicon tetrafluoride gas or the nitrogen gas. Each gas introduction pipe 32, 34, 36 has a mass flow controller and a valve (both not shown), and adjusts the flow rate of each gas supplied from the gas introduction ports 29, 30, 31.

  The ICP antenna 27 is formed of an annular conductor or a conductor plate disposed along the upper surface of the window member 28, and is connected to a high frequency power supply 39 through a matching unit 38. The high frequency current from the high frequency power supply 39 flows through the ICP antenna 27, and the high frequency current causes the ICP antenna 27 to generate a magnetic field inside the chamber 25 through the window member 28. Since the magnetic field is generated due to the high-frequency current, it changes in time (periodic), but the time-changed magnetic field generates an induced electric field, and electrons accelerated by the induced electric field enter the chamber 25. Inductively coupled plasma is generated by colliding with the introduced gas molecules and atoms.

  In the plasma CVD film forming apparatus 24, plasma is generated from silicon tetrafluoride gas or nitrogen gas supplied into the chamber 25 by inductively coupled plasma, and a fluorine-containing silicon nitride film is formed by CVD, whereby the passivation film 23 is formed. Form. At this time, since neither silicon tetrafluoride gas nor nitrogen gas contains hydrogen atoms, the fluorine-containing silicon nitride film forming the passivation film 23 does not contain hydrogen atoms resulting from the processing gas.

  It should be noted that moisture due to environmental factors other than the processing gas, such as a minute amount of moisture adsorbed on the substrate 11 when the substrate 11 is transported or moisture that has not been sufficiently removed by the exhaust device, is present in the chamber 25. Hydrogen atoms resulting from the moisture may be contained in a very small amount in the fluorine-containing silicon nitride film that forms the passivation film 23. That is, although the amount of hydrogen atoms contained in the passivation film 23 can be suppressed as much as possible by using a processing gas that does not contain hydrogen atoms (the presence of hydrogen atoms is suppressed), the amount of the passivation film 23 is still extremely small. Of hydrogen atoms. At this time, the main component of the fluorine-containing silicon nitride film to be formed is silicon nitride, and fluorine atoms generated by the decomposition of silicon tetrafluoride gas are dispersed and contained in the silicon nitride. In this case, the present invention can be realized by making the concentration of fluorine atoms higher than the concentration of hydrogen atoms. Further, in this embodiment, for example, carbon tetrafluoride gas may be introduced as an additive gas when forming the passivation film 23 or as another process before and after the formation of the passivation film 23. In some cases, a trace amount of carbon atoms generated from the carbon tetrafluoride gas converted into plasma in 25 is contained in the passivation film 23 to partially constitute silicon carbonitride. However, since such a small amount of silicon carbonitride does not hinder the effects of the present invention, it can be said that the passivation film 23 substantially corresponds to a fluorine-containing silicon nitride film as a whole. That is, the fluorine-containing silicon nitride film according to the present embodiment does not exclude such a fluorine-containing silicon nitride film containing a trace amount of impurities including carbon and the like. The concept regarding such a fluorine-containing silicon nitride film is similarly applied when a passivation film described later corresponds to a fluorine-containing silicon oxide film, a fluorine-containing silicon oxynitride film, or other materials.

  Bonding of silicon atoms and fluorine atoms in silicon tetrafluoride gas and bonding between nitrogen atoms in nitrogen gas has high binding energy (the former is 595 kJ / mol, the latter is 945 kJ / mol), so it is not easy to make it into plasma. Since the inductively coupled plasma generated using the ICP antenna 27 has a very high density, plasma can be generated from silicon tetrafluoride gas or nitrogen gas having a bond with high binding energy.

  The rare gas such as argon gas supplied by the rare gas supply unit 37 is not a material gas directly constituting the silicon nitride film, but moderately includes a silicon tetrafluoride gas and a nitrogen gas which are material gases directly constituting the silicon nitride film. In addition, it plays an auxiliary role in CVD, such as adjusting the concentration to a high level and facilitating discharge for generating inductively coupled plasma.

  Further, the plasma CVD film forming apparatus 24 further includes a controller 40, and the controller 40 controls the operation of each component of the plasma CVD film forming apparatus 24.

Note that the silicon halide gas not containing hydrogen atoms supplied by the silicon halide gas supply unit 33 is not limited to silicon tetrafluoride gas, but other silicon halide gas, for example, silicon chloride (SiCl ₄ ). Alternatively, the nitrogen-containing gas supplied by the nitrogen-containing gas supply unit 35 is not limited to nitrogen gas, and may be other nitrogen-containing gas.

  Next, a manufacturing method of the TFT 21 as a manufacturing method of the electronic device according to the present embodiment will be described.

  FIG. 9 is a process diagram showing a part of the manufacturing method of the TFT in FIG.

  First, metal (for example, copper (Cu) / molybdenum (Mo), titanium (Ti) / aluminum (Al) / titanium or molybdenum (Mo) / aluminum / molybdenum) PVD (Physical Vapor Deposition), photoresist A gate electrode 12 having a predetermined width is formed on the substrate 11 through photolithography for developing the substrate into a predetermined pattern, etching using the developed photoresist, and stripping of the photoresist.

  Next, a gate insulating film 13 made of a silicon oxide film is formed so as to cover the gate electrode 12 by CVD, and an IGZO film constituting the channel 14 is further formed by PVD. Thereafter, an etch stop film 22 made of a silicon oxide film is formed so as to cover the IGZO film by plasma CVD. At this time, oxygen atoms are released from the IGZO film by sputtering of cations and the like, and dangling bonds such as zinc atoms are generated mainly near the boundary between the etch stop film 22 and the IGZO film (channel 14).

  Further, the etch stop film 22 is partially removed to partially expose the IGZO film.

  Next, the source electrode 18 and the drain electrode 19 that are in contact with the exposed portions of the IGZO film are formed by PVD (FIG. 9A), and thereafter, in the plasma CVD film forming apparatus 24, silicon tetrafluoride gas, nitrogen gas Then, a passivation film 23 made of a fluorine-containing silicon nitride film is formed by CVD using argon gas (FIG. 9B).

  Next, the TFT 21 is subjected to a heat treatment, for example, a heat treatment in which the substrate 11 is continuously heated to 350 ° C. for 3 hours. At this time, thermal energy is applied to the fluorine atoms contained in the passivation film 23, and the fluorine atoms (indicated by “F” in the figure) diffuse into the channel 14 through the etch stop film 22 (FIG. 9C )). The fluorine atom diffused into the channel 14 terminates a dangling bond existing in the channel 14. Thereafter, this process is terminated. In some cases, fluorine atoms are introduced into the etch stop film 22 when the passivation film 23 is formed, and the fluorine atoms introduced into the etch stop film 22 may diffuse into the channel 14 by heat treatment. Even when fluorine atoms diffuse into the channel 14 via 22, or when fluorine atoms diffuse directly from the etch stop film 22 into the channel 14, the effect of the present invention is not changed.

  FIG. 10 is a graph schematically showing the distribution of fluorine atoms in the TFT manufactured by the TFT manufacturing method of FIG. Normally, the distribution state of fluorine atoms shown in FIG. 10 can be confirmed by SIMS.

  As shown in FIG. 10, the concentration of fluorine atoms slightly decreases toward the channel 14 in the passivation film 23, but is substantially constant, but clearly decreases in the etch stop film 22 from the passivation film 23 toward the channel 14. After increasing so as to exhibit an extreme value at the boundary between the etch stop film 22 and the channel 14 (hereinafter referred to as “channel boundary”), it becomes substantially constant at a portion other than the boundary of the channel 14. Here, the concentration of the fluorine atom at the channel boundary is higher than the portion other than the channel boundary in the channel 14 because the fluorine atom terminates the dangling bond generated in the vicinity of the boundary. Further, the fluorine atoms diffuse from the passivation film 23 into the channel 14, and the concentration of the fluorine atoms in the passivation film 23 is based on the concentration of the fluorine atoms in the channel 14, particularly the concentration of the fluorine atoms in the channel 14 other than the channel boundary. Is also expensive. In the present embodiment, the “channel boundary” does not mean an ideal “boundary” having no thickness but a boundary as a layer having a thickness within a certain depth from the boundary surface. The range of the constant depth can be defined by, for example, the depth at which the number of existences decreases rapidly in the distribution of the number of unbonded hands. In the positional comparison of “other than channel boundary”, the range of a certain depth is clearly distinguished, and therefore the positions indicated by “channel boundary” and “other than channel boundary” are not obscured in this embodiment.

  According to the present embodiment, fluorine atoms diffuse into the channel 14 from the passivation film 23 made of a fluorine-containing silicon nitride film, and the concentration of fluorine atoms at the channel boundary in the channel 14 is greater than the concentration of fluorine atoms at portions other than the channel boundary. Therefore, many fluorine atoms exist at the channel boundary, and many dangling bonds generated near the channel boundary are terminated by many fluorine atoms. As a result, a decrease in electron mobility in the channel 14 can be suppressed, thereby preventing a decrease in the performance of the TFT 21 and at the same time improving reliability.

  In the above-described embodiment, the passivation film 23 is formed by CVD using silicon tetrafluoride gas or nitrogen gas, so that the passivation film 23 surely contains fluorine atoms. Thereby, the dangling bonds existing in the channel 14 can be reliably terminated by the fluorine atoms from the passivation film 23.

  In the present embodiment described above, any gas (silicon tetrafluoride gas, nitrogen gas, or argon gas) used for CVD does not contain hydrogen atoms when forming the passivation film 23. There is no diffusion of atoms, so that the desorption of oxygen atoms from the channel 14 can be prevented, and the degradation of the performance of the TFT 21 can be reliably prevented.

  In the present embodiment described above, the passivation film 23 is not directly adjacent to the channel 14 but is opposed to the channel 14 via the etch stop film 22. At this time, the etch stop film 22 is transferred from the passivation film 23 to the channel 14. Thus, it is possible to prevent the fluorine atoms from being unevenly distributed at the channel boundary of the channel 14 and to terminate each dangling bond evenly. Further, since the number of fluorine atoms that pass through the etch stop film 22 per time is limited, for example, by adjusting the time of the heat treatment, the number of fluorine atoms that pass through the etch stop film 22 can be controlled to control the channel. The degree of termination of the unbonded hand at 14 can be controlled.

  Although the present invention has been described above by using the embodiment, the present invention is not limited to the above-described embodiment.

For example, in the TFT 21 described above, the passivation film 23 is composed of a fluorine-containing silicon nitride film, but the passivation film 23 is composed of a fluorine-containing silicon oxide (SiO: F) film or a fluorine-containing silicon oxynitride (SiON: F) film. May be. When forming the former in the plasma CVD film forming apparatus 24, at least one of silicon tetrafluoride gas, oxygen (O ₂ ) gas and nitrous oxide (N ₂ O) gas, and rare gas such as argon gas is used in CVD. When the latter is formed, at least one of silicon tetrafluoride gas, nitrogen gas, oxygen gas and nitrous oxide gas, and a rare gas such as argon gas are used in CVD. A rare gas such as argon facilitates the start of discharge and brings about an effect of adjusting the gas concentration, but it is not always necessary to obtain the effect of the present invention.

  In the TFT 21 described above, fluorine atoms are diffused only from the passivation film 23. However, the etch stop film 22 and the gate insulating film 13 are composed of, for example, a fluorine-containing silicon oxide film or a fluorine-containing silicon nitride film, and only from the passivation film 23. Alternatively, fluorine atoms may diffuse from the etch stop film 22 or the gate insulating film 13 toward the channel 14.

  In the TFT 21 described above, the channel 14 is made of IGZO, but the element constituting the channel 14 is not limited to IGZO. For example, an oxide semiconductor containing at least zinc oxide as a constituent element such as ITZO, ZnO, IZO, and AZO. Alternatively, other metal oxides such as IGO may be used.

  The configuration of the TFT to which the present invention is applied is not limited to the configuration of the TFT 21 in FIG. For example, as shown in FIG. 11, the etch stop film 22 is omitted as compared with the TFT 21 of FIG. 7, and the present invention is applied to a TFT 43 having two layers of passivation films 41 and 42 instead of the one layer of passivation film 23. May be. In this case, at least one of the two layers of passivation films 41 and 42 is composed of a fluorine-containing silicon nitride film, a fluorine-containing silicon oxide film, or a fluorine-containing silicon oxynitride, and a channel is formed from at least one of the two layers of the passivation films 41 and 42. Fluorine atoms diffuse into 14.

  Further, as shown in FIG. 12, the passivation film 23 is omitted as compared with the TFT 21 of FIG. 7, and the present invention is applied to a TFT 46 having two layers of etch stop films 44 and 45 instead of the one layer of etch stop film 22. You may apply. In this case, at least one of the two layers of etch stop films 44 and 45 is composed of a fluorine-containing silicon nitride film, a fluorine-containing silicon oxide film, or a fluorine-containing silicon oxynitride, and at least one of the two layers of etch stop films 44 and 45 Fluorine atoms diffuse from the As a result of the diffusion, the concentration distribution of fluorine atoms in the fluorine-containing film exhibits a concentration gradient such that the concentration decreases toward the IGZO film.

  Furthermore, as shown in FIG. 13, the gate electrode 12 formed on the substrate 11, the gate insulating film 13, the oxide semiconductor layer 15 including the channel 14, the etch stop film 47 covering only the channel 14, and the etch The present invention is applied to a TFT 50 including a passivation film 23 that covers the stop film 47, the channel 14, and the oxide semiconductor layer 15, and a source electrode 48 and a drain electrode 49 that pass through the passivation film 23 and are in contact with the oxide semiconductor layer 15. May be. Also in this case, at least one of the etch stop film 47 and the passivation film 23 is made of a fluorine-containing silicon nitride film, a fluorine-containing silicon oxide film, or a fluorine-containing silicon oxynitride. Fluorine atoms diffuse into the channel 14.

  Further, as shown in FIG. 14, the present invention may be applied to a TFT 53 having two layers of etch stop films 51 and 52 instead of the one layer of etch stop film 47 as compared with the TFT 50 of FIG. In this case, at least one of the two layers of etch stop films 51 and 52 is composed of a fluorine-containing silicon nitride film, a fluorine-containing silicon oxide film, or a fluorine-containing silicon oxynitride, and at least one of the two layers of etch stop films 51 and 52. Fluorine atoms diffuse from the As a result of the diffusion, the concentration distribution of fluorine atoms in the fluorine-containing film exhibits a concentration gradient such that the concentration decreases toward the IGZO film.

  Further, as shown in FIG. 15, an oxide semiconductor layer 55 including a channel 54 formed of an IGZO film directly formed on the substrate 11, a gate insulating film 57 covering the channel 54, and the gate insulating film 57 A TFT 62 including a gate electrode 58 to be formed, a passivation film 59 that covers the gate electrode 58 and the oxide semiconductor layer 55, and a source electrode 60 and a drain electrode 61 that pass through the passivation film 59 and are in contact with the oxide semiconductor layer 55. The present invention may be applied to. In this case, at least one of the gate insulating film 57 and the passivation film 59 is composed of a fluorine-containing silicon nitride film, a fluorine-containing silicon oxide film, or a fluorine-containing silicon oxynitride, and a channel is formed from at least one of the gate insulating film 57 and the passivation film 59. Fluorine atoms diffuse into 54. As a result of the diffusion, the concentration distribution of fluorine atoms in the fluorine-containing film exhibits a concentration gradient such that the concentration decreases toward the IGZO film.

  In addition, as shown in FIG. 16, the present invention may be applied to a TFT 65 including two layers of gate insulating films 63 and 64 instead of the one layer of gate insulating film 57 as compared with the TFT 62 of FIG. In this case, at least one of the two layers of gate insulating films 63 and 64 is composed of a fluorine-containing silicon nitride film, a fluorine-containing silicon oxide film, or a fluorine-containing silicon oxynitride, and at least one of the two layers of gate insulating films 63 and 64. Fluorine atoms diffuse from the As a result of the diffusion, the concentration distribution of fluorine atoms in the fluorine-containing film exhibits a concentration gradient such that the concentration decreases toward the IGZO film.

  In the above-described embodiment, the case where the window member is made of a dielectric in the plasma CVD film forming apparatus has been described. I can't. For example, the electronic device manufacturing apparatus may use a single or a plurality of metal members as the window member (for example, JP 2012-227427 A), or a solenoid coil as the antenna. As long as the device can generate high-density plasma, such as a microwave plasma device, it is not limited thereto.

  In addition, an object of the present invention is to supply a computer, for example, the controller 40, with a storage medium storing software program codes for realizing the functions of the above-described embodiments, and the CPU of the controller 40 is stored in the storage medium. It is also achieved by reading and executing the program code.

  In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the program code and the storage medium storing the program code constitute the present invention.

  Examples of the storage medium for supplying the program code include RAM, NV-RAM, floppy (registered trademark) disk, hard disk, magneto-optical disk, CD-ROM, CD-R, CD-RW, DVD (DVD). -ROM, DVD-RAM, DVD-RW, DVD + RW) and other optical disks, magnetic tapes, non-volatile memory cards, other ROMs, etc., as long as they can store the program code. Alternatively, the program code may be supplied to the controller 40 by downloading from another computer or database (not shown) connected to the Internet, a commercial network, a local area network, or the like.

  Further, by executing the program code read by the controller 40, not only the functions of the above-described embodiments are realized, but also an OS (operating system) running on the CPU based on the instruction of the program code. Includes a case where the functions of the above-described embodiment are realized by performing part or all of the actual processing.

  Further, after the program code read from the storage medium is written to the memory provided in the function expansion board inserted into the controller 40 or the function expansion unit connected to the controller 40, the program code is read based on the instruction of the program code. A case where the CPU of the function expansion board or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing is also included.

  The form of the program code may include an object code, a program code executed by an interpreter, script data supplied to the OS, and the like.

11 Substrate 13, 57, 63, 64 Gate insulating film 14 Channel 15 Oxide semiconductor layer 21, 43, 46 TFT
22, 44, 45, 47, 51, 52 Etch stop film 23, 41, 42, 59 Passivation film 24 Plasma CVD film forming apparatus

Claims (14)

An electronic device comprising a metal oxide film forming an oxide semiconductor, a first film adjacent to the metal oxide film, and a second film facing the metal oxide film with the first film interposed therebetween in,
Before Symbol second film is made of a fluorine-containing film,
The concentration of fluorine atoms at the boundary between the first film and the metal oxide film is higher than the concentration of fluorine atoms at a portion other than the boundary of the metal oxide film, and the concentration of fluorine atoms in the second film. lower than, at least the concentration distribution of fluorine atoms in the portion other than the boundary of the first film, the electronic device characterized by having a concentration gradient that decreases toward the boundary.   2. The electronic device according to claim 1, wherein the concentration of the fluorine atoms in the fluorine-containing film is higher than the concentration of the fluorine atoms in a portion other than the boundary of the metal oxide film.   The fluorine-containing film is any one of a fluorine-containing silicon nitride (SiN: F) film, a fluorine-containing silicon oxide (SiO: F) film, and a fluorine-containing silicon oxynitride (SiON: F) film. Item 3. The electronic device according to Item 1 or 2.   4. The electronic device according to claim 1, wherein the first film is an etch stop film, and the second film is a passivation film. 5.   The electronic device according to any one of claims 1 to 4, wherein the metal oxide film contains at least zinc oxide or IGO as a constituent element. An electronic device comprising a metal oxide film forming an oxide semiconductor, a first film adjacent to the metal oxide film, and a second film facing the metal oxide film with the first film interposed therebetween a method of production,
Previous SL second film constituted by fluorine-containing film, is diffused from該弗-containing film a fluorine atom to the metal oxide film,
The concentration of the fluorine atoms at the boundary of the first film and the metal oxide film, the metal oxide film a fluorine atom in high and the second layer than the concentration of the fluorine atoms in the portion other than the boundary of the The manufacturing method of the electronic device characterized by being lower than the density | concentration of . An electronic device manufacturing method comprising a metal oxide film forming an oxide semiconductor and a fluorine-containing film adjacent to the metal oxide film with another film interposed therebetween,
A channel is formed in the metal oxide film, and the other film and the fluorine-containing film are insulating films,
Forming the fluorine-containing film by CVD (Chemical Vapor Deposition) using a fluoride gas and a gas containing at least one of oxygen atoms and nitrogen atoms ;
By diffusing fluorine atoms from the fluorine-containing film, the concentration distribution of fluorine atoms in the other film decreases toward the boundary in a portion other than the boundary with the metal oxide film in the other film. A method of manufacturing an electronic device having a concentration gradient increasing at the boundary, wherein the concentration of fluorine atoms increased at the boundary is lower than the concentration of fluorine atoms in the fluorine-containing film . The method for manufacturing an electronic device according to claim 7, wherein any gas used for the CVD does not contain hydrogen atoms. The CVD is ICP (Inductively Coupled Plasma), or a method of manufacturing an electronic device according to claim 7 or 8, wherein the executed by the plasma processing apparatus using a microwave plasma. The fluorine-containing film is made of a fluorine-containing silicon nitride (SiN: F) film, and the gas used in the CVD contains silicon tetrafluoride (SiF ₄ ) gas and nitrogen (N ₂ ) gas. Item 10. The method for manufacturing an electronic device according to any one of Items 7 to 9 . The fluorine-containing film is made of a fluorine-containing silicon oxide (SiO: F) film, and gases used in the CVD are silicon tetrafluoride gas, oxygen (O ₂ ) gas, and nitrous oxide (N ₂ O) gas. the method of manufacturing an electronic device according to any one of claims 7 to 9, characterized in that it comprises at least one of. The fluorine-containing film is a fluorine-containing silicon oxynitride (SiON: F) film, and the gas used in the CVD contains at least one of silicon tetrafluoride gas, nitrogen gas, oxygen gas, and nitrous oxide gas. the method of manufacturing an electronic device according to any one of claims 7 to 9, characterized in that. An electronic device manufacturing apparatus comprising: a metal oxide film that forms an oxide semiconductor; and a fluorine-containing film adjacent to the metal oxide film with another film interposed therebetween,
A channel is formed in the metal oxide film, and the other film and the fluorine-containing film are insulating films,
Forming the fluorine-containing film by CVD using a fluoride gas and a gas containing at least one of oxygen atoms and nitrogen atoms ;
By diffusing fluorine atoms from the fluorine-containing film, the concentration distribution of fluorine atoms in the other film decreases toward the boundary in a portion other than the boundary with the metal oxide film in the other film. An apparatus for manufacturing an electronic device having a concentration gradient increasing at the boundary, wherein the concentration of fluorine atoms increased at the boundary is lower than the concentration of fluorine atoms in the fluorine-containing film . The apparatus for manufacturing the device ICP, or microwave electronic device manufacturing apparatus according to claim 13, characterized in that it is realized by a plasma processing apparatus using plasma.