JP6230184B2 - Film forming apparatus, film forming method, and metal oxide thin film manufacturing method - Google Patents

Description

  The present invention relates to, for example, a film forming apparatus, a film forming method, and a metal oxide thin film manufacturing method capable of controlling the oxygen concentration in a film with high accuracy.

  Semiconductor memory includes volatile memory such as DRAM (Dynamic Random Access Memory) and non-volatile memory such as flash memory. A NAND flash memory or the like is known as a non-volatile memory, but ReRAM (Resistance RAM) has attracted attention as a device that can be further miniaturized.

  ReRAM uses a variable resistor whose resistance value is changed by receiving a pulse voltage as a resistance element. This variable resistor is typically a metal oxide layer of two or more layers having different degrees of oxidation, that is, resistivity, and has a structure in which these are sandwiched between upper and lower electrodes. As a method of forming oxide layer structures having different degrees of oxidation, a method of forming a metal oxide by so-called reactive sputtering in which a metal target is sputtered in an oxygen atmosphere is known. For example, Patent Document 1 describes a method of laminating a metal oxide layer on a substrate by so-called reactive sputtering in which a metal target is sputtered in an oxygen atmosphere.

JP 2008-244018 A

  However, since the resistivity change of the metal oxide layer with respect to the oxygen flow rate change is large, it is generally difficult to uniformly form a metal oxide layer having a desired resistivity on the substrate. For example, it is often difficult to form a metal oxide layer with a target oxygen concentration by adsorption of introduced oxygen on the surface of the target or the shield (protection plate). In particular, if the oxygen flow rate to be controlled is a flow rate level that cannot be controlled with high accuracy by an MFC (mass flow controller) or a flow rate that is included in the transition region of reactive sputtering, the desired film quality can be stably formed. It was almost impossible to film.

  In view of the circumstances as described above, an object of the present invention is to form a film forming apparatus, a film forming method, and a film forming method capable of stably forming a thin film having a desired film quality by controlling the flow rate of a reactive gas with high accuracy. It is providing the manufacturing method of a metal oxide thin film.

In order to achieve the above object, a film forming apparatus according to one embodiment of the present invention includes a vacuum chamber, an exhaust line, a gas introduction line, and a control valve.
The exhaust line includes a vacuum pump capable of exhausting the inside of the vacuum chamber.
The gas introduction line is connected to the exhaust line and introduces a process gas including a reactive gas into the vacuum chamber.
The control valve is disposed between a connection point between the exhaust line and the gas introduction line and the vacuum chamber, and is introduced into the vacuum chamber from the exhaust speed of the vacuum chamber by the vacuum pump and the gas introduction line. The flow rate of the process gas is controllable.

A film forming method according to an embodiment of the present invention includes exhausting the inside of a vacuum chamber with a vacuum pump via a control valve capable of controlling an exhaust speed.
A process gas including a reactive gas is exhausted by the vacuum pump through the gas introduction line connected between the control valve and the vacuum pump, and introduced into the vacuum chamber through the control valve. Is done.
A metal target thin film is formed on the substrate by sputtering a metal target with the plasma of the process gas in the vacuum chamber.

The manufacturing method of the metal oxide thin film which concerns on one form of this invention includes exhausting the inside of a vacuum chamber with a vacuum pump through the control valve which can control an exhaust speed.
A process gas containing oxygen is introduced into the vacuum chamber through the control valve while being exhausted by the vacuum pump through a gas introduction line connected between the control valve and the vacuum pump. .
A metal oxide thin film is formed on the substrate by sputtering a metal target with the plasma of the process gas in the vacuum chamber.

It is a schematic sectional drawing which shows one structural example of the variable resistance element which concerns on one Embodiment of this invention. It is an experimental result which shows the relationship between the ON current value of the said resistance change element, and the oxygen composition ratio of a low resistance metal oxide layer. It is an experimental result which shows the current-voltage characteristic of the said resistance change element, (A) shows when an oxygen composition ratio is 1, and (B) shows when an oxygen composition ratio is 1.5, respectively. It is an experimental result which shows the switching characteristic of the said resistance change element, (A) shows when oxygen composition ratio is 1, and (B) shows when oxygen composition ratio is 1.5, respectively. It is a schematic sectional side view of the film-forming apparatus which concerns on one Embodiment of this invention. It is a [A]-[A] line direction sectional view in Drawing 5.

A film forming apparatus according to an embodiment of the present invention includes a vacuum chamber, an exhaust line, a gas introduction line, and a control valve.
The exhaust line includes a vacuum pump capable of exhausting the inside of the vacuum chamber.
The gas introduction line is connected to the exhaust line and introduces a process gas including a reactive gas into the vacuum chamber.
The control valve is disposed between a connection point between the exhaust line and the gas introduction line and the vacuum chamber, and is introduced into the vacuum chamber from the exhaust speed of the vacuum chamber by the vacuum pump and the gas introduction line. The flow rate of the process gas is controllable.

  The film forming apparatus is configured such that the process gas can be introduced into the vacuum chamber via the control valve functioning as an exhaust valve. Most of the process gas introduced at this time is exhausted by the vacuum pump. By optimizing the opening of the control valve, the amount of process gas introduced, etc., the process gas diffused into the vacuum chamber The amount can be finely controlled. As a result, the flow rate of the reactive gas can be controlled with high accuracy to stably form a thin film having the desired film quality.

The film forming apparatus may further include a cylindrical partition and a gas flow path.
The partition wall is disposed inside the vacuum chamber, and divides the inside of the vacuum chamber into a film forming chamber and an exhaust chamber connected to the exhaust line.
The gas flow path is provided between the bottom wall of the vacuum chamber and the partition wall, and supplies the process gas introduced into the exhaust chamber to the film formation chamber.
According to the above configuration, since the partition wall that partitions the film formation chamber is formed in a cylindrical shape, the process gas is supplied isotropically from the exhaust chamber to the film formation chamber. As a result, variation in the concentration distribution of the reactive gas on the substrate can be suppressed, and a metal compound layer having desired film characteristics can be uniformly formed in the substrate surface.

  As the reactive gas, a gas containing oxygen, nitrogen, and carbon is applicable, and is appropriately selected according to the type and film characteristics of the target metal compound layer. For example, when forming a metal oxide layer, oxygen can be used as a reactive gas, and the resistivity of the metal oxide layer can be adjusted in accordance with the amount of oxygen to be added. As the process gas, a mixed gas of the above various reactive gases and a rare gas such as argon as a sputtering gas can be used.

The film formation chamber may include a stage that is installed on the bottom wall portion and has a support surface for supporting a substrate, and a sputtering target that is installed on the top plate and faces the stage. In this case, the gas flow path is provided closer to the bottom wall portion than the support surface.
As a result, the process gas can be supplied to the film formation chamber from a position farther from the target, so that variations in the degree of oxidation of the target surface can be reduced, and the surface of the metal compound layer to be sputtered The internal uniformity can be further increased.

A film forming method according to an embodiment of the present invention includes exhausting the inside of a vacuum chamber with a vacuum pump via a control valve capable of controlling an exhaust speed.
A process gas including a reactive gas is exhausted by the vacuum pump through the gas introduction line connected between the control valve and the vacuum pump, and introduced into the vacuum chamber through the control valve. Is done.
A metal target thin film is formed on the substrate by sputtering a metal target with the plasma of the process gas in the vacuum chamber.

  According to the film forming method, the amount of process gas diffused into the vacuum chamber can be finely controlled by optimizing the opening of the control valve, the amount of process gas introduced, and the like. As a result, the flow rate of the reactive gas can be controlled with high accuracy to stably form a thin film having the desired film quality.

The vacuum chamber may have a film forming chamber formed inside a cylindrical partition and an exhaust chamber formed outside the partition. In this case, the process gas is introduced into the film forming chamber through a gas flow path formed between the exhaust chamber, the partition wall, and the vacuum chamber.
Since the process gas is supplied isotropically from the exhaust chamber to the film forming chamber, variation in the concentration distribution of the reactive gas on the substrate can be suppressed, and a metal compound layer having desired film characteristics can be uniformly distributed on the substrate surface. It becomes possible to form.

The manufacturing method of the metal oxide thin film which concerns on one Embodiment of this invention includes exhausting the inside of a vacuum chamber with a vacuum pump via the control valve which can control an exhaust speed.
A process gas containing oxygen is introduced into the vacuum chamber through the control valve while being exhausted by the vacuum pump through a gas introduction line connected between the control valve and the vacuum pump. .
A metal oxide thin film is formed on the substrate by sputtering a metal target with the plasma of the process gas in the vacuum chamber.

  According to the method for producing a metal oxide thin film, it is possible to finely control the amount of process gas diffusing into the vacuum chamber by optimizing the opening of the control valve, the amount of process gas introduced, and the like. Become. This makes it possible to stably form a metal oxide thin film having a desired resistivity by controlling the oxygen flow rate with high accuracy.

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

  FIG. 1 is a schematic cross-sectional view showing a configuration example of a variable resistance element according to an embodiment of the present invention. In the present embodiment, a film forming apparatus and a film forming method used for forming a metal oxide layer constituting the variable resistance element will be described as an example.

[Resistance change element]
First, a schematic configuration of the variable resistance element will be described. As shown in FIG. 1, the resistance change element 1 includes a substrate 2, a lower electrode layer 3, a first metal oxide layer 4, a second metal oxide layer 5, and an upper electrode layer 6.

  The substrate 2 is made of, for example, a silicon substrate, but is not limited thereto, and other substrate materials such as a glass substrate may be used.

  The lower electrode layer 3 is formed on the substrate 2 and is formed of Pt (platinum) in the present embodiment. The material is not limited to this. For example, Hf (hafnium), Zr (zirconium), Ti (titanium), Al (aluminum), Fe (iron), Co (cobalt), Mn (manganese), Sn (tin) , Zn (zinc), Cr (chromium), V (vanadium), W (tungsten), transition metals such as Ta (tantalum), or alloys thereof (silicon alloys such as TaSi, WSi, TiSi, TaN, WN, TiN) Nitrogen compounds such as TiAlN, carbon alloys such as TaC, etc.) can be used.

  The first metal oxide layer 4 is formed on the lower electrode layer 3. The second metal oxide layer 5 is formed on the first metal oxide layer 4. The metal oxide constituting the first and second metal oxide layers 4 and 5 is not particularly limited. For example, ZrOx, HfOx, TiOx, AlOx, SiOx, FeOx, NiOx, CoOx, MnOx, SnOx, ZnOx, VOx Binary oxides of transition metals such as WOx and CuOx can be used. In the present embodiment, the first and second metal oxide layers 4 and 5 are each composed of TaOx.

Here, TaOx constituting the first metal oxide layer 4 is an oxide having a lower degree of oxidation than TaOx constituting the second metal oxide layer 5 and containing many oxygen vacancies, and its resistivity is For example, it is greater than 1 Ωcm and less than 10 ⁶ Ωcm. On the other hand, TaOx constituting the second metal oxide layer 5 is an oxide close to the stoichiometric composition, and its resistivity is, for example, a value larger than 10 ⁶ Ωcm.

  The first and second metal oxide layers 4 and 5 are not limited to being composed of oxides made of the same metal, but may be composed of oxides made of different metals. In this embodiment, the first and second metal oxide layers 4 and 5 are formed by reactive sputtering. The sputtering method is not particularly limited, and an appropriate method such as DC sputtering, pulse DC sputtering, or RF sputtering can be employed.

In the resistance change element 1 of the present embodiment, the first metal oxide layer 4 has a lower degree of resistivity than the second metal oxide layer 5 because the first metal oxide layer 4 has a lower degree of oxidation than the second metal oxide layer 5. Have. Here, when a negative voltage is applied to the upper electrode layer 6 and a positive voltage is applied to the lower electrode layer 3, oxygen ions (O ²⁻ ) in the second metal oxide layer 5 having a high resistance are low in resistance. The first metal oxide layer 4 diffuses and the resistance of the second metal oxide layer 5 decreases (low resistance state). On the other hand, when a negative voltage is applied to the lower electrode layer 3 and a positive voltage is applied to the upper electrode layer 6, oxygen ions (O ²⁻ ) diffuse from the first metal oxide layer 4 to the second metal oxide layer 5. Again, the degree of oxidation of the second metal oxide layer 5 increases and the resistance increases (high resistance state).

  That is, the second metal oxide layer 5 reversibly switches between the low resistance state and the high resistance state by controlling the voltage between the lower electrode layer 3 and the upper electrode layer 6. Furthermore, since the low resistance state and the high resistance state are maintained even when no voltage is applied, the resistance change element 1 can be used as a nonvolatile memory element.

  A resistance change element (ReRAM) is one of next-generation memory candidates, and is most expected in recent years in terms of high-speed operation and low power consumption. Therefore, in a resistance change element, the smaller the on-current that flows during the switching operation (when transitioning to the low resistance state or the low resistance state), the lower the power consumption and the larger number of elements can be activated at one time. Therefore, a highly integrated memory is expected. In addition, it was found that the electrical characteristics gradually deteriorate due to the diffusion of oxygen ions by repeating switching, and there was a problem to be improved from the viewpoint of reliability toward mass production of devices.

  In the present embodiment, the above problem is solved by controlling the oxygen composition of the oxygen-deficient metal oxide layer (first metal oxide layer 4). That is, when the oxygen composition ratio with respect to the metal component of the first metal oxide layer 4 is Roxy (O / Ta), 1.2 ≦ Roxy ≦ 1.8 is achieved, thereby reducing the current of the device and improving the reliability. Improvements can be realized.

  FIG. 2 shows the dependence of the oxygen composition ratio (O / Ta; Roxy) of the first metal oxide layer 4 on the on-current. It can be seen that the on-current value decreases as Roxy increases. And when Roxy is less than 1.2, the on-current value exceeds 1 mA, and when Roxy exceeds 1.8, the on-current value is much less than 10 μA, and it is buried in the noise at the time of reading. If the resistance ratio (difference between the low resistance and the high resistance) becomes small, there is a possibility that a read error occurs. Therefore, a suitable oxygen composition ratio that can reduce the current of the device and prevent occurrence of read errors is 1.2 or more and 1.8 or less.

  FIG. 3A shows one experimental result showing the IV characteristic of the resistance change element when the oxygen composition ratio (Roxy) of the first metal oxide layer 4 is 1. FIG. FIG. 3B shows one experimental result showing the IV characteristic of the resistance change element when the oxygen composition ratio (Roxy) of the first metal oxide layer 4 is 1.5. It was confirmed that the on-current value when Roxy = 1.5 was reduced by about two digits with respect to the on-current value when Roxy = 1.

FIG. 4A shows one experimental result showing the switching characteristics of the variable resistance element when the oxygen composition ratio (Roxy) of the first metal oxide layer 4 is 1. FIG. FIG. 3B shows one experimental result showing the switching characteristics of the variable resistance element when the oxygen composition ratio (Roxy) of the first metal oxide layer 4 is 1.5. In the figure, the horizontal axis is the number of switching repetitions, the vertical axis is the resistance value when 0.5 V is applied, the black circle is the on state, that is, the resistance value when the on current flows, and the white circle is the off state, that is, the off current flows Each resistance value is shown. When Roxy = 1, the high resistance state decreases by repeating switching, whereas when Roxy = 1.5, the high resistance state varies, but the on / off current ratio exceeds a certain level. It was confirmed that switching of 10 ¹⁰ times or more can be realized while maintaining the above.

  As described above, by controlling the oxygen composition ratio (Roxy) of the first metal oxide layer 4, it is possible to realize low power consumption of the device, thereby enabling a large number of devices to be activated at one time. Integration can be achieved. In addition, by controlling the oxygen composition ratio (Roxy) of the first metal oxide layer 4, the switching durability of the element can be improved, thereby improving the reliability of the device.

  In the present embodiment, the first and second metal oxide layers 4 and 5 are formed by a reactive sputtering method in which a Ta metal target is sputtered in an oxygen atmosphere. The oxygen concentration in the film is typically controlled by the flow rate of oxygen introduced into the film formation chamber.

  However, since the resistivity change of the metal oxide layer with respect to the oxygen flow rate change is large, it is generally difficult to uniformly form a metal oxide layer having a desired resistivity on the substrate. For example, it is often difficult to form a metal oxide layer with a target oxygen concentration by adsorption of introduced oxygen on the surface of the target or the shield (protection plate). In particular, if the oxygen flow rate to be controlled is a flow rate level that cannot be controlled with high accuracy by an MFC (mass flow controller) or a flow rate that is included in the transition region of reactive sputtering, the desired film quality can be stabilized. It was almost impossible to form a film.

  Therefore, in the present embodiment, the first and second metal oxide layers 4 and 5 are formed using the film forming apparatus shown in FIGS. Details of the film forming apparatus will be described below.

[Film deposition system]
5 and 6 are schematic configuration diagrams showing a film forming apparatus according to an embodiment of the present invention. FIG. 5 is a side sectional view, and FIG. 6 is a sectional view in the [A]-[A] line direction in FIG. It is. The film forming apparatus 100 of this embodiment is configured as a sputtering apparatus for forming the first and second metal oxide layers 4 and 5 in the manufacturing process of the resistance change element 1, for example.

  The film forming apparatus 100 includes a vacuum chamber 10. The vacuum chamber 10 is made of a metal material such as aluminum or stainless steel, and is connected to the ground potential. The vacuum chamber 10 includes a bottom wall portion 11, a top plate portion 12, and a side wall portion 13, and is configured to be able to maintain the inside in a predetermined vacuum atmosphere.

  Inside the vacuum chamber 10, a stage 30 having a support surface 31 for supporting the substrate W and a target unit 40 including a metal target 41 (Ta target in the present embodiment) are arranged. The stage 30 is provided on the bottom wall portion 11 of the vacuum chamber 10, and the target unit 40 is provided on the top plate portion 12 of the vacuum chamber 10. The stage 30 and the target unit 40 are arranged so as to face each other.

  The stage 30 may be provided with a chucking mechanism for electrostatically or mechanically holding the substrate W on the support surface 31, a temperature control unit for heating or cooling the substrate W to a predetermined temperature, or the like. Good.

  The target unit 40 may include a backing plate that supports the target 41, a magnetic circuit that forms a magnetic field on the surface of the target 41, and the like. The target unit 40 is connected to a power source for supplying predetermined power (direct current, alternating current, or high frequency) to the backing plate. The power source may be configured as a part of the target unit 40 or may be configured separately from the target unit 40.

  The film forming apparatus 100 includes a cylindrical partition wall 20 that divides the inside of the vacuum chamber 10 into a film forming chamber 101 and an exhaust chamber 102. In the present embodiment, the partition wall 20 has a first end portion 21 fixed to the top plate portion 12 and a second end portion 22 facing the bottom wall portion 11, for example, a metal plate made of aluminum or stainless steel. Consists of.

  The partition wall 20 has a cylindrical shape large enough to accommodate the stage 30 and the target unit 40 therein, and forms a film forming chamber 101 inside the partition wall 20. The film forming chamber 101 is further provided with a cylindrical deposition preventing plate 23 so as to surround the periphery of the region between the stage 30 and the target unit 40.

  An exhaust chamber 102 is formed outside the partition wall 20. The inside of the vacuum chamber 10 including the film forming chamber 101 and the exhaust chamber 102 is exhausted to a predetermined vacuum pressure by an exhaust line 50 connected to the vacuum chamber 10. The exhaust line 50 includes an exhaust valve 51 and a vacuum pump 52 connected to the exhaust chamber 102 via the exhaust valve 51. The exhaust valve 51 is composed of a flow rate control valve whose opening degree can be adjusted. For example, a turbo molecular pump is used as the vacuum pump 52, and an auxiliary pump is additionally connected as necessary.

  The film forming apparatus 100 has a gas introduction line 60 for introducing a process gas for film formation. The gas introduction line 60 is connected to the exhaust line 50, and more specifically, is connected between the exhaust valve 51 and the vacuum pump 52.

  That is, the exhaust valve 51 functions as a control valve disposed between the connection point J between the exhaust line 50 and the gas introduction line 60 and the vacuum chamber 10. The exhaust valve 51 is configured to be able to control the exhaust speed of the vacuum chamber 10 (exhaust chamber 102) by the vacuum pump 52 and the flow rate of the process gas introduced from the gas introduction line 60 into the vacuum chamber 10 (exhaust chamber 102). The

  In the present embodiment, a mixed gas of argon gas as a sputtering gas and oxygen as a reactive gas is used as the process gas. The gas introduction line 60 includes a main valve 61 and an argon introduction line 62a and an oxygen introduction line 62b connected to the exhaust line 50 via the main valve. These introduction lines 62a and 62b include a plurality of valves, a mass flow controller, a gas source, and the like.

  The film forming chamber 101 and the exhaust chamber 102 communicate with each other through a gas flow path 80. The gas flow path 80 includes an annular passage portion 81 formed between the side wall 13 of the vacuum chamber 10 and the outer peripheral surface of the partition wall 20, and a flow passage portion 82 communicating with the passage portion 81 and formed around the partition wall 20. Including.

  In the present embodiment, the flow path portion 82 is configured by a plurality of holes, but may be configured by an arc-shaped slit or the like formed over the entire circumference of the partition wall 20. Further, the flow path portion 82 may be configured by an annular gap between the second end portion 22 of the partition wall 20 and the bottom wall portion 11 of the vacuum chamber 10. The size (width or height) of the hole, slit, or gap is not particularly limited, and is set to about 0.1 mm to 1 mm, for example.

  The formation position of the flow path portion 82 is not particularly limited, but the reactive gas (provided to the film formation chamber 101 through the flow path portion 82 is provided by providing the flow path portion 82 at a position further away from the target 41. Surface reaction (oxidation) of the target 41 due to (oxygen) can be suppressed. In the present embodiment, the flow path portion 82 is provided closer to the bottom wall portion 11 side of the vacuum chamber 10 than the support surface 31 of the stage 30.

  The film forming apparatus 100 further includes a controller 70. The controller 70 is typically configured by a computer, and controls operations of the target unit 40, the exhaust line 50 (exhaust valve 51, vacuum pump 52), the gas introduction line 60, and the like.

[Film formation method]
Next, the film forming method according to the present embodiment will be described together with an operation example of the film forming apparatus 100.

  First, the substrate W is placed on the support surface 31 of the stage 30. Here, the substrate 2 (FIG. 1) having the lower electrode layer 3 formed on the upper surface is used as the substrate W. Next, the controller 70 drives the exhaust line 50 to evacuate the film forming chamber 101 formed inside the partition wall 20 and the exhaust chamber 102 formed outside the partition wall 20 to a predetermined reduced pressure atmosphere. The film forming chamber 101 is exhausted by the exhaust line 50 through the gas flow path 80 and the exhaust chamber 102.

  After the film formation chamber 101 and the exhaust chamber 102 reach a predetermined vacuum pressure, the controller 70 drives the gas introduction line 60 to introduce process gas into the exhaust chamber 102 via the exhaust valve 51.

  At this time, the vacuum pump 52 is continuously driven. Therefore, most of the introduced process gas is exhausted by the vacuum pump 52, but the degree of opening of the exhaust valve 51 and the process so that the process gas can diffuse into the exhaust chamber 102 via the exhaust line 50. The amount of gas introduced is set. As a result, it is possible to introduce a predetermined flow rate of process gas into the exhaust chamber 102 while finely controlling the amount of process gas diffused into the exhaust chamber 102.

  For example, by setting the exhaust speed of the vacuum pump 52 to 800 L / sec and the opening degree of the exhaust valve 51 to 4 to 16%, the gas introduction amount of 1.0 sccm is set to about 0 into the exhaust chamber 102. A process gas having a flow rate of .1 to 0.40 sccm can be introduced. For example, when the opening degree of the exhaust valve 51 is set to 10% and the gas introduction amount is set to 1.0 sccm, a process gas of about 0.25 sccm can be introduced into the exhaust chamber 102.

  In this embodiment, a mixed gas of argon and oxygen is used as the process gas. The mixing ratio of argon and oxygen is not particularly limited, and the amount of oxygen added is adjusted by the resistivity of the metal oxide layer to be formed. As described above, the film forming apparatus 100 is used for forming the first and second metal oxide layers 4 and 5 in the resistance change element 1 shown in FIG.

  In the present embodiment, when the first metal oxide layer 4 is formed, an oxygen flow rate (first flow rate) at which a tantalum oxide having an oxygen composition ratio (Roxy) of 1.2 to 1.8 can be formed. When the second metal oxide 5 is formed, the oxygen flow rate (second flow rate) at which a tantalum oxide having a stoichiometric composition can be formed is set. The first and second flow rates are set by the oxygen introduction line 62b, and the flow rate setting by the oxygen introduction line 62b is controlled by the controller 70.

  As an example of the first flow rate, the oxygen flow rates when the oxygen composition ratio (Roxy) is 1.2, 1.5, and 1.8 are 10.0 sccm, 10.2 sccm, and 10.4 sccm, respectively. On the other hand, the second flow rate is, for example, 15 sccm. Note that a target made of tantalum oxide having a stoichiometric composition (not shown) may be provided, and the second metal oxide layer may be formed at an oxygen flow rate of 10 sccm, for example.

  The process gas introduced into the exhaust chamber 102 is supplied to the film forming chamber 101 via the gas flow path 80. By introducing the process gas into the exhaust chamber 102, the film formation chamber 101 has a lower pressure than the exhaust chamber 102. While maintaining this state, the process gas introduced into the exhaust chamber 102 is formed into a film via a gas flow path 80 (passage section 81, flow path section 82) formed between the vacuum chamber 10 and the partition wall 20. It diffuses isotropically into the chamber 101.

  On the other hand, the controller 70 controls the target unit 40 to form process gas plasma in the film forming chamber 101. Argon ions in the plasma sputter the target 41, sputtered particles jumping out of the target 41 react with oxygen, and the generated tantalum oxide particles are deposited on the surface of the substrate W. Thereby, a tantalum oxide (TaOx) layer is formed on the substrate W.

  The controller 70 switches the film formation target from the first metal oxide layer 4 to the second metal oxide layer 5 by controlling the flow rate of the exhaust valve 51. In the present embodiment, the first metal oxide layer 4 is formed by setting the oxygen flow rate to the first flow rate, and the second metal is set by setting the oxygen flow rate to the second flow rate. An oxide layer 5 is formed. As a result, it is possible to continuously form the first metal oxide layer 4 and the second metal oxide layer having different resistivities in the same vacuum chamber 10 and improve productivity.

  As described above, in the present embodiment, since the process gas can be introduced into the vacuum chamber 10 through the exhaust valve 51, the process gas conductance with respect to the exhaust valve 51, the exhaust speed of the exhaust line 50, and the like. A corresponding amount of process gas is introduced into the vacuum chamber 10. Thereby, fine flow control can be realized with high accuracy. Accordingly, it is possible to stably form a thin film having a desired resistivity by controlling the flow rate of the reactive gas with high accuracy.

  In the present embodiment, the process gas is supplied from the exhaust chamber 102 to the film forming chamber 101 via the gas flow path 80 using the pressure difference between the film forming chamber 101 and the exhaust chamber 102. At this time, since the partition wall 20 is formed in a cylindrical shape, the process gas is supplied isotropically from the exhaust chamber 102 to the film formation chamber 101. As a result, variation in the concentration distribution of oxygen in the process gas on the substrate W is suppressed, and a metal compound layer having desired film characteristics can be formed uniformly in the plane of the substrate W.

  Further, in the present embodiment, the process gas is supplied to the film forming chamber 101 through a flow path portion 82 formed between the partition wall 20 and the bottom wall portion 11 of the vacuum chamber 10. As a result, the process gas can be supplied to the film forming chamber 101 from a position farther from the target 41 installed on the top plate portion 12 of the vacuum chamber 10, so that contact with oxygen in the process gas is possible. Oxidation of the target 41 due to is suppressed. Thereby, variation in the degree of oxidation on the surface of the target 41 can be reduced, and the in-plane uniformity of the resistivity of the metal oxide layer formed by sputtering can be improved.

  The embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

  For example, in the variable resistance element 1 according to the above embodiment, the oxygen composition of the first metal oxide layer 4 is less than the stoichiometric amount, and the oxygen composition of the second metal oxide layer 5 is the stoichiometric amount. However, instead of this, the oxygen composition of the first metal oxide layer 4 is stoichiometric and the oxygen composition of the second metal oxide layer 5 is less than the stoichiometric amount. It may be configured.

  In the above embodiment, oxygen is used as the reactive gas added to the process gas, but the type of reactive gas can be appropriately selected according to the type and film characteristics of the target metal compound layer. A gas containing nitrogen (for example, ammonia) is selected when forming the metal nitride layer, and a gas (for example, methane) containing carbon can be selected when forming the metal carbide layer.

  In the above embodiment, the film forming apparatus 100 including the partition wall 20 that partitions the film forming chamber 101 and the exhaust chamber 102 has been described as an example. However, the partition wall 20 may be omitted as necessary.

  In the above embodiment, the film forming apparatus provided with the single exhaust line 50 and the gas introduction line 60 has been described as an example. However, the present invention is not limited to this, and the exhaust line 50 and / or the gas introduction line 60 is not limited thereto. A plurality may be provided.

  Further, in the above embodiment, the sputtering apparatus has been described as an example of the film forming apparatus. However, the present invention is not limited to this, and film formation is performed in a vacuum using a process gas including a reactive gas, such as a CVD apparatus or a vacuum evaporation apparatus. The present invention is also applicable to various film forming apparatuses and film forming methods.

DESCRIPTION OF SYMBOLS 1 ... Resistance change element 4,5 ... Metal oxide layer 10 ... Vacuum chamber 20 ... Partition 30 ... Stage 40 ... Target unit 50 ... Exhaust line 51 ... Exhaust valve 52 ... Vacuum pump 60 ... Gas introduction line 70 ... Controller 80 ... Gas Flow path 81 ... Passage section 82 ... Flow path section 100 ... Film forming apparatus 101 ... Film forming chamber 102 ... Exhaust chamber

Claims (7)

A vacuum chamber;
An exhaust line including a vacuum pump introduced into the vacuum chamber and exhausting a process gas including a reactive gas ;
Connected to said exhaust line, and a gas introduction line for introducing a pre Kipu Rosesugasu between said vacuum pump and said vacuum chamber,
Disposed between the connection point of the exhaust line and the gas introduction line and the vacuum chamber, the exhaust speed of the vacuum chamber by the vacuum pump and the process gas introduced into the vacuum chamber from the gas introduction line And a control valve capable of controlling the flow rate. The film forming apparatus according to claim 1,
A cylindrical partition that is disposed inside the vacuum chamber and divides the interior of the vacuum chamber into a film forming chamber and an exhaust chamber connected to the exhaust line;
A film forming apparatus, further comprising: a gas flow path that is provided between a bottom wall portion of the vacuum chamber and the partition wall and supplies the process gas introduced into the exhaust chamber to the film forming chamber. The film forming apparatus according to claim 2,
The film formation chamber includes a stage having a support surface for supporting a substrate that is installed on the bottom wall, and a sputtering target that is installed on a top plate of the vacuum chamber and faces the stage.
The gas channel is provided on the bottom wall side of the support surface. The film forming apparatus according to claim 3,
The partition has a first end fixed to the top plate and a second end facing the bottom wall through the gas flow path.
Deposition device. A process gas including a reactive gas introduced into the vacuum chamber is exhausted by a vacuum pump through a control valve capable of controlling an exhaust speed,
Via the connection gas introduction line between the vacuum pump and the control valve, while exhausting the process gas by the vacuum pump, through the control valve is introduced into the interior of the vacuum chamber,
A film forming method for forming a metal compound thin film on a substrate by sputtering a metal target with plasma of the process gas in the vacuum chamber. The film forming method according to claim 5 ,
The vacuum chamber has a film formation chamber formed inside a cylindrical partition and an exhaust chamber formed outside the partition,
The process gas is introduced into the film forming chamber through a gas flow path formed between the exhaust chamber, the partition wall, and the vacuum chamber. A process gas containing oxygen introduced into the vacuum chamber is exhausted by a vacuum pump through a control valve capable of controlling the exhaust speed,
Via the connection gas introduction line between the vacuum pump and the control valve, while exhausting the process gas by the vacuum pump, through the control valve is introduced into the interior of the vacuum chamber,
A method for producing a metal oxide thin film, comprising forming a metal oxide thin film on a substrate by sputtering a metal target with plasma of the process gas in the vacuum chamber.

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