JP4975569B2 - Plasma oxidation treatment method and silicon oxide film formation method - Google Patents

Description

  The present invention relates to an oxidation processing technique using plasma that can be used when a silicon oxide film is formed in a process of manufacturing a CMOS device, for example.

In an n-channel MOS transistor, carriers that contribute to conduction are electrons, so the mobility of carriers is larger than that of a p-channel MOS transistor. Normally, when the gate oxide film thickness is the same and the transistor size is the same (that is, the channel length and the channel width are the same), the n-channel MOS transistor has a drive current (I _on current) as compared to the p-channel MOS transistor. ) Can be taken large. For this reason, an n-channel MOS transistor is used as a switching transistor for processing a Key trigger signal in order to operate an LSI digital circuit at a high speed. However, when a digital circuit is composed of only n-channel MOS transistors, there is a problem that the power consumption increases although the speed is high. In order to solve this, a system (CMOS circuit configuration) is generally employed in which a p-channel MOS transistor is arranged on the Vcc (power supply voltage) side and a mechanism for interrupting unnecessary current from Vcc is added. .

When designing an LSI with a CMOS circuit, it is necessary that the transistors constituting the circuit satisfy the following requirements. First, the state of the signal line of the trigger signal that determines the operation speed of the circuit in the digital circuit needs to match the speed at which the signal shifts from Low to High and the switching speed at which the signal shifts from High to Low. Therefore, when a CMOS inverter circuit is assembled, V _th (threshold voltage) of the pull-up p-channel MOS transistor on the Vcc side and the pull-down n-channel MOS transistor on the GND side have the same value in a +/− symmetry. And the drive current ( _Ion current) of both transistors is required to be equal.

In order to satisfy the above requirements, conventionally, the channel width of a p-channel MOS transistor paired with an n-channel MOS transistor has been designed to be large. That is, in order to complement the drive current ( _Ion current) of the p-channel MOS transistor, the channel width of the p-channel MOS transistor is generally designed to be about 1.5 to 2 times larger than that of the n-channel MOS transistor.

  In the future, in a CMOS device aiming at high-speed operation while reducing power consumption, in consideration of reducing the transistor size, the p-channel MOS transistor can be miniaturized as well as the n-channel MOS transistor. Efforts to improve drive current are required. The reason why the technology tends to shift from the conventional buried channel type p-channel MOS transistor to the surface channel type p-channel MOS transistor is as described above.

In a p-channel MOS transistor, the larger the drive current (I _on current), the better, and the smaller the leak current characteristic (I _off ), the better. Since the leakage current characteristic (I _off ) is sometimes more important than the drive current characteristic (I _on ), it is difficult to forcibly reduce the threshold voltage (V _th ) in consideration of the leakage current characteristic (I _off ). It is. The thickness of the gate oxide film should be as thin as possible unless the leakage current from the upper part of the gate toward the substrate becomes a problem level. That is, the transistor performance [that is, drive current characteristics (I _on ) And the leakage current characteristics (I _off )] are advantageously improved. In addition, it is considered that the optimization of the gate oxide film thickness in the n-channel MOS transistor and the p-channel MOS transistor is ideally performed independently. A p-channel MOS transistor has both I _on and I _off characteristics smaller than those of an n-channel MOS transistor when the gate oxide film has the same thickness. Thus, there is sufficient room for forming the gate oxide film of the p-channel MOS transistor thinner than the gate oxide film of the n-channel MOS transistor.

However, in the actual CMOS transistor formation process, it is often avoided to independently adjust the thicknesses of the n-channel and p-channel gate oxide films. The reason is that the formation process of the gate oxide film is inevitably complicated, and adverse effects such as an increase in manufacturing cost and a decrease in device reliability occur.
That is, in order to form silicon oxide films having different thicknesses in the n-channel formation region (conductivity type is p-type) and the p-channel formation region (conductivity type is n-type) in the prior art, silicon oxide is temporarily formed in these regions. After the film is formed, a photoresist mask is selectively formed in the region where the oxide film is to be formed thick, and the oxide film in other portions is removed by wet etching using a dilute hydrofluoric acid (HF) aqueous solution. After that, a complicated process of performing another oxidation treatment to form a thin oxide film is necessary. If the gate oxide film forming process is complicated as described above, the cost is increased and cross contamination in the process is likely to occur, which may reduce the stability and reliability of the transistor performance.

  Incidentally, as a typical technique for forming a silicon oxide film as a gate oxide film, a thermal oxidation method, a plasma oxidation method, and the like are known. For example, Patent Document 1 proposes a technique for forming a uniform and high-quality silicon oxide film independent of the plane orientation on the silicon surface by performing plasma oxidation using a rare gas such as Kr and oxygen. . In the case of plasma oxidation treatment, it has been considered important to ensure the uniformity of the treatment within the silicon substrate surface (that is, the in-plane uniformity of the oxide film thickness) by making the plasma uniform.

JP 2002-261091 A

  In the conventional plasma oxidation treatment, it is aimed to realize a uniform oxidation treatment on the same silicon substrate surface, and it has not been studied to form a silicon oxide film with a different film thickness depending on the part. However, if there is a method capable of forming the silicon oxide film in the n-type diffusion region thinner than the silicon oxide film in the p-type diffusion region without requiring a complicated process, the gate in the p-channel MOS transistor as described above can be obtained. It is possible to reduce the thickness of the insulating film and the size of the transistor. Further, there is a possibility that downsizing and improvement in integration can be realized while maintaining low power consumption and high speed operation in the CMOS device.

  The present invention has been made in view of the above circumstances, and does not require a complicated process, so that silicon oxides having different thicknesses can be formed in p-type diffusion regions and n-type diffusion regions formed in the same silicon layer. An object of the present invention is to provide a plasma oxidation processing method capable of forming a film.

The plasma oxidation treatment method according to the first aspect of the present invention includes:
Introducing a processing gas containing an oxygen-containing compound and an inert gas into the processing chamber of the plasma processing apparatus;
Introducing a microwave into the processing chamber by a planar antenna having a plurality of holes to generate plasma;
A plasma oxidation process for oxidizing the surface of the silicon layer with the plasma;
A plasma oxidation treatment method comprising:
A first region having a first conductivity type and a second region having a second conductivity type opposite to the first conductivity type are exposed on the surface of the silicon layer. In the first region and the second region, the oxidation rate in the first region is 1.2 to 2.0 times the oxidation rate in the second region. Thus, the oxidation treatment is performed.

  In the plasma oxidation method according to the first aspect of the present invention, the thickness of the silicon oxide film formed in the first region is larger than the thickness of the silicon oxide film formed in the second region. It may be 1.2 to 2.0 times.

In the plasma oxidation treatment method of the first aspect of the present invention, the oxygen-containing compound is oxygen, the inert gas is argon, and the flow rate ratio O ₂ / Ar is 0.001 or more and 0.00. It may be within a range of 2 or less.

  Further, in the plasma oxidation treatment method of the first aspect of the present invention, the treatment pressure in the plasma oxidation treatment step is either in the range of 1.3 Pa or more and less than 6.7 Pa, or in the range of more than 667 Pa and 1333 Pa or less. May be.

In the first aspect of the plasma oxidation processing method of the present invention, the power density of the microwave in the plasma oxidation process is, even within a range of less than 0.08 W / cm ² or more 0.42 W / cm ² Good.

The plasma oxidation treatment method according to the second aspect of the present invention is as follows.
Introducing a processing gas containing an oxygen-containing compound and an inert gas into the processing chamber of the plasma processing apparatus;
Introducing a microwave into the processing chamber by a planar antenna having a plurality of holes to generate plasma;
A plasma oxidation process for oxidizing the surface of the silicon layer with the plasma;
A plasma oxidation treatment method comprising:
The silicon layer has a first region having a first conductivity type and a second region having a second conductivity type opposite to the first conductivity type on the surface. It is exposed and provided
The plasma oxidation treatment step includes a first oxidation treatment step for performing an oxidation treatment such that an oxidation rate for the first region is higher than an oxidation rate for the second region;
A second oxidation treatment step for performing an oxidation treatment after the first oxidation treatment step so that an oxidation rate for the first region and an oxidation rate for the second region are approximately the same;
It is characterized by including.

  In the plasma oxidation processing method of the second aspect of the present invention, in the first oxidation processing step, the oxidation rate in the first region is 1.2 to 2.0 times the oxidation rate in the second region. It may be.

  In the plasma oxidation method according to the second aspect of the present invention, in the first oxidation treatment step, the thickness of the silicon oxide film formed in the first region is formed in the second region. It may be 1.2 to 2.0 times the thickness of the silicon oxide film.

Moreover, in the plasma oxidation treatment method of the second aspect of the present invention, the oxygen-containing compound in the first oxidation treatment step is oxygen, the inert gas is argon, and a flow rate ratio O ₂ / Ar may be in the range of 0.001 to 0.25, and the processing pressure may be in the range of 1.3 Pa to less than 6.7 Pa, or in the range of more than 667 Pa to 1333 Pa.

In the second aspect of the plasma oxidation processing method of the present invention, the power density of the microwaves in the first oxidation treatment step, there in the range of less than 0.08 W / cm ² or more 0.42 W / cm ² May be.

In the plasma oxidation treatment method of the second aspect of the present invention, the oxygen-containing compound in the second oxidation treatment step is oxygen, the inert gas is argon, and a flow rate ratio O ₂ / Ar may be in the range of 0.0025 to 0.4, and the processing pressure in the second oxidation treatment step may be in the range of 6.7 Pa to 667 Pa.

In the second aspect of the plasma oxidation processing method of the present invention, the power density of the microwave in the second oxidation step is a by 0.42 W / cm ² or more 4.19W / cm ² within the range May be.

  In the plasma oxidation processing method of the second aspect of the present invention, the first region may be a p-type diffusion region and the second region may be an n-type diffusion region.

Moreover, in the plasma oxidation treatment method of the second aspect of the present invention, the boron concentration in the p-type diffusion region is in the range of 1 × 10 ^{16 to} 5 × 10 ¹⁸ cm ⁻³ , and the n-type diffusion region The concentration of phosphorus may be in the range of 1 × 10 ^{16 to} 5 × 10 ¹⁸ cm ⁻³ .

A method for forming a silicon oxide film according to a third aspect of the present invention includes a step of introducing a processing gas containing an oxygen-containing compound and an inert gas into a processing chamber of a plasma processing apparatus, and a planar antenna having a plurality of holes. A step of introducing a microwave into the processing chamber to generate plasma, and a plasma oxidation treatment step of oxidizing the surface of the silicon layer with the plasma to form a silicon oxide film ,
In the plasma oxidation treatment step, the oxidation rate for the first region having the first conductivity type provided on the surface of the silicon layer is a second conductivity type opposite to the first conductivity type. A first oxidation treatment step for performing an oxidation treatment so as to be larger than an oxidation rate for the second region having the conductivity type;
A second oxidation treatment step for performing an oxidation treatment after the first oxidation treatment step so that an oxidation rate for the first region and an oxidation rate for the second region are approximately the same;
It is characterized by including .

A method of manufacturing a CMOS device according to the fourth aspect of the present invention is as follows.
A method of manufacturing a CMOS device comprising an n-channel transistor and a p-channel transistor,
Forming a first region having a first conductivity type and a second region having a second conductivity type opposite to the first conductivity type in the silicon layer; ,
A silicon oxide film forming step of forming a silicon oxide film on the surface of each of the first region and the second region;
Forming gate electrodes on the silicon oxide film formed in the first region and the silicon oxide film formed in the second region, respectively;
With
The silicon oxide film forming step includes
Introducing a processing gas containing an oxygen-containing compound and an inert gas into a processing chamber of the plasma processing apparatus; and introducing a microwave into the processing chamber by a planar antenna having a plurality of holes to generate plasma. , by the plasma, possess a plasma oxidation process for oxidizing the surface of the silicon layer, and
The plasma oxidation treatment step includes a first oxidation treatment step for performing an oxidation treatment such that an oxidation rate for the first region is higher than an oxidation rate for the second region;
A second oxidation treatment step for performing an oxidation treatment after the first oxidation treatment step so that an oxidation rate for the first region and an oxidation rate for the second region are approximately the same;
It is characterized by including .

A computer-readable storage medium according to the fifth aspect of the present invention is provided.
A storage medium storing a control program that runs on a computer,
The control program controls the plasma processing apparatus so that the plasma oxidation processing method is performed in the processing chamber of the plasma processing apparatus at the time of execution.
The plasma oxidation treatment method includes:
Introducing a processing gas containing an oxygen-containing compound and an inert gas into the processing chamber; introducing a microwave into the processing chamber by a planar antenna having a plurality of holes; generating plasma; and And a plasma oxidation process for oxidizing the surface of the silicon layer,
In the plasma oxidation treatment step, the oxidation rate for the first region having the first conductivity type provided on the surface of the silicon layer is a second conductivity type opposite to the first conductivity type. A first oxidation treatment step for performing an oxidation treatment so as to be larger than an oxidation rate for the second region having the conductivity type;
A second oxidation treatment step for performing an oxidation treatment after the first oxidation treatment step so that an oxidation rate for the first region and an oxidation rate for the second region are approximately the same;
It is characterized by including .

A plasma processing apparatus according to a sixth aspect of the present invention provides:
A processing chamber for processing an object to be processed using plasma;
A planar antenna having a plurality of holes for introducing microwaves into the processing chamber;
A gas supply mechanism for supplying gas into the processing chamber;
An exhaust mechanism for exhausting the processing chamber under reduced pressure;
A first region having a first conductivity type provided on the surface of the silicon layer by introducing a processing gas containing an oxygen-containing compound and an inert gas and a microwave into the processing chamber to generate plasma; A control unit for controlling the second region having a second conductivity type opposite to the first conductivity type to perform a plasma oxidation process for oxidizing each of the second regions .
The plasma oxidation treatment step includes a first oxidation treatment step for performing an oxidation treatment such that an oxidation rate for the first region is higher than an oxidation rate for the second region;
A second oxidation treatment step for performing an oxidation treatment after the first oxidation treatment step so that an oxidation rate for the first region and an oxidation rate for the second region are approximately the same;
It is characterized by including .

  According to the plasma oxidation processing method of the present invention, the first conductivity type first region and the second conductivity type second region are oxidized at different oxidation rates, so that photolithography, etching, etc. It is possible to form silicon oxide films having different thicknesses in the first region and the second region, respectively, while reducing the number of steps compared to the conventional method. Therefore, for example, in the process of manufacturing a CMOS transistor, the degree of freedom in designing the thickness of the gate insulating film formed in the p-type diffusion region for forming the n-channel and the n-type diffusion region for forming the p-channel is greatly increased. It becomes possible to raise. As a result, in a semiconductor device such as a CMOS element, it is possible to cope with miniaturization and high integration while maintaining excellent reliability.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 to 3 are explanatory views showing an outline of the plasma oxidation processing method according to the first embodiment of the present invention. As shown in FIG. 1, on the silicon layer 101, a p-type diffusion region 103 doped with a p-type impurity as a first region having a first conductivity type, and a second conductivity type having a second conductivity type. As a region, an n-type diffusion region 105 doped with an n-type impurity is formed. Examples of the p-type impurity include trivalent elements such as boron (B), aluminum (Al), gallium (Ga), and indium (In). Examples of the n-type impurity include pentavalent elements such as phosphorus (P), arsenic (As), and antimony (Sb). Both p-type diffusion region 103 and n-type diffusion region 105 may have impurity concentration distributions.

  The p-type diffusion region 103 is not limited to one type of p-type impurity, and may include two or more types of p-type impurities. Similarly, the n-type diffusion region 105 is not limited to one type of n-type impurity, and may include two or more types of n-type impurities. Furthermore, since the p-type diffusion region 103 only needs to have p-type predominance, the p-type diffusion region 103 is not limited to containing only p-type impurities, and may contain both p-type impurities and n-type impurities. Similarly, the n-type diffusion region 105 may include both n-type impurities and p-type impurities, as long as the n-type is dominant, not only including n-type impurities.

  1 to 3, for convenience of explanation, the p-type diffusion region 103 and the n-type diffusion region 105 are illustrated as being provided separately in the silicon layer 101. However, for example, the n-type silicon layer 101 is not provided. The second region may be provided with a p-type diffusion region 103 as a first region in a part thereof, or the p-type silicon layer 101 as a first region and a second part thereof. An n-type diffusion region 105 as the region may be provided. The silicon layer 101 may be a polycrystalline silicon layer, an amorphous silicon layer, or a single crystal silicon substrate.

  As shown in FIG. 2, the surface of the silicon layer 101 is subjected to plasma oxidation using plasma P of an oxygen-containing gas. This plasma oxidation treatment includes a step of oxidizing the p-type diffusion region 103 and the n-type diffusion region 105 at different oxidation rates. Then, the plasma oxidation process is performed so that the thickness of the silicon oxide film formed in the p-type diffusion region 103 is larger than the thickness of the silicon oxide film formed in the n-type diffusion region 105. The plasma processing apparatus and plasma oxidation processing conditions used for this plasma oxidation processing will be described in detail later.

FIG. 3 shows a state in which the silicon oxide film 107 is formed on the surface of the silicon layer 101 by the plasma oxidation process. The silicon oxide film 107 includes a thick film portion 107 a formed on the surface of the p-type diffusion region 103 and a thin film portion 107 b formed on the surface of the n-type diffusion region 105 and having a thickness smaller than that of the thick film portion 107 a. Have. That is, the thickness _{T 1} of the thick portion 107a, the relationship between the thickness _{T 2} of the thin section 107b _{is T} 1> T _2.

  As described above, the plasma oxidation treatment method of this embodiment is a method in which the thick film portion 107a and the thin film portion 107b having different film thicknesses can be formed in the same substrate surface (in the silicon layer 101). By using the thick film portion 107a and the thin film portion 107b of the silicon oxide film 107 formed in this way as gate insulating films, gate insulation having different thicknesses within the same substrate surface (within the silicon layer 101). A plurality of transistors having a film can be manufactured. Accordingly, as will be described later, a CMOS device having an n-channel transistor and a p-channel transistor formed by gate insulating films having different thicknesses can be easily manufactured.

  Next, a plasma processing apparatus 100 that can be suitably used in the plasma oxidation processing method of the present embodiment will be described with reference to FIGS. FIG. 4 is a cross-sectional view schematically showing a schematic configuration of a plasma processing apparatus 100 that can be used for the plasma oxidation process. FIG. 5 is a plan view showing a planar antenna of the plasma processing apparatus 100 of FIG. Further, FIG. 6 is a diagram illustrating a configuration example of a control unit of the plasma processing apparatus 100 of FIG.

The plasma processing apparatus 100 generates plasma by introducing microwaves into a processing chamber using a planar antenna having a plurality of slot-shaped holes, particularly RLSA (Radial Line Slot Antenna). In addition, it is configured as an RLSA microwave plasma processing apparatus capable of generating microwave-excited plasma having a low electron temperature. In the plasma processing apparatus 100, processing with plasma having a plasma density of 1 × 10 ^{10 to} 5 × 10 ¹² / cm ³ and a low electron temperature of 0.7 to 2 eV is possible. Therefore, the plasma processing apparatus 100 can be suitably used for the purpose of forming a silicon oxide film by oxidizing silicon in the manufacturing process of various semiconductor devices.

  The plasma processing apparatus 100 includes, as main components, an airtight chamber (processing chamber) 1, a gas supply mechanism 18 for supplying gas into the chamber 1, and an exhaust mechanism for evacuating the chamber 1 under reduced pressure. An exhaust device 24, a microwave introduction mechanism 27 for introducing a microwave into the chamber 1, and a control unit 50 for controlling each component of the plasma processing apparatus 100. Yes.

  The chamber 1 is formed of a substantially cylindrical container that is grounded. The chamber 1 may be formed of a rectangular tube container. The chamber 1 has a bottom wall 1a and a side wall 1b made of a material such as aluminum.

  Inside the chamber 1 is provided a mounting table 2 for horizontally supporting a silicon wafer (hereinafter simply referred to as “wafer”) W which is an object to be processed. The mounting table 2 is made of a material having high thermal conductivity, such as ceramics such as AlN. The mounting table 2 is supported by a cylindrical support member 3 extending upward from the center of the bottom of the exhaust chamber 11. The support member 3 is made of ceramics such as AlN, for example.

Further, the mounting table 2 is provided with a cover ring 4 that covers the outer edge portion thereof and guides the wafer W. The cover ring 4 is an annular member made of a material such as quartz, AlN, Al ₂ O ₃ , or SiN.

  In addition, a resistance heating type heater 5 as a temperature adjusting mechanism is embedded in the mounting table 2. The heater 5 is heated by the heater power supply 5a to heat the mounting table 2 and uniformly heats the wafer W, which is a substrate to be processed, with the heat.

  The mounting table 2 is provided with a thermocouple (TC) 6. By measuring the temperature with the thermocouple 6, the heating temperature of the wafer W can be controlled in a range from room temperature to 900 ° C., for example.

  The mounting table 2 is provided with wafer support pins (not shown) for supporting the wafer W and raising and lowering it. Each wafer support pin is provided so as to protrude and retract with respect to the surface of the mounting table 2.

  A cylindrical liner 7 made of quartz is provided on the inner periphery of the chamber 1. A quartz baffle plate 8 having a large number of exhaust holes 8a is annularly provided on the outer peripheral side of the mounting table 2 in order to uniformly exhaust the inside of the chamber 1. The baffle plate 8 is supported by a plurality of support columns 9.

  A circular opening 10 is formed in a substantially central portion of the bottom wall 1 a of the chamber 1. An exhaust chamber 11 that communicates with the opening 10 and protrudes downward is provided on the bottom wall 1a. An exhaust pipe 12 is connected to the exhaust chamber 11 and is connected to an exhaust device 24 via the exhaust pipe 12.

  An annular upper plate 13 is joined to the upper portion of the chamber 1. The inner periphery of the upper plate 13 protrudes toward the inner side (chamber inner space) to form an annular support portion 13a.

  An annular gas introduction portion 15 is provided on the side wall 1 b of the chamber 1. The gas introduction unit 15 is connected to a gas supply mechanism 18 that supplies an oxygen-containing gas and a plasma excitation gas. The gas introduction part 15 may be provided in a nozzle shape or a shower shape.

  Further, on the side wall 1b of the chamber 1, a loading / unloading port 16 for loading / unloading the wafer W between the plasma processing apparatus 100 and a transfer chamber (not shown) adjacent to the plasma processing apparatus 100, and the loading / unloading port 16 are provided. And a gate valve 17 for opening and closing.

  The gas supply mechanism 18 includes, for example, an inert gas supply source 19a and an oxygen-containing gas (O-containing gas) supply source 19b. The gas supply mechanism 18 includes, as gas supply sources (not shown) other than those described above, for example, a purge gas supply source used when replacing the atmosphere in the chamber 1, a cleaning gas supply source used when cleaning the inside of the chamber 1, and the like. It may be.

As the inert gas, for example, N ₂ gas or rare gas can be used. As the rare gas, for example, Ar gas, Kr gas, Xe gas, He gas, or the like can be used. Among these, it is particularly preferable to use Ar gas because it is economical. As the oxygen-containing gas, for example, oxygen gas (O ₂ ), water vapor (H ₂ O), nitric oxide (NO), or the like can be used.

  The inert gas and the oxygen-containing gas reach from the inert gas supply source 19a and the oxygen-containing gas supply source 19b of the gas supply mechanism 18 to the gas introduction unit 15 through the gas line 20, and from the gas introduction unit 15 into the chamber 1. To be introduced. Each gas line 20 connected to each gas supply source is provided with a mass flow controller 21 and front and rear opening / closing valves 22. With such a configuration of the gas supply mechanism 18, the supplied gas can be switched and the flow rate can be controlled.

  The exhaust device 24 as an exhaust mechanism includes a high-speed vacuum pump such as a turbo molecular pump. As described above, the exhaust device 24 is connected to the exhaust chamber 11 of the chamber 1 through the exhaust pipe 12. The gas in the chamber 1 flows uniformly into the space 11a of the exhaust chamber 11, and is further exhausted to the outside through the exhaust pipe 12 by operating the exhaust device 24 from the space 11a. Thereby, the inside of the chamber 1 can be depressurized at a high speed to a predetermined degree of vacuum, for example, 0.133 Pa.

  Next, the configuration of the microwave introduction mechanism 27 will be described. The microwave introduction mechanism 27 includes a transmission plate 28, a planar antenna 31, a slow wave material 33, a shield lid 34, a waveguide 37, a matching circuit 38, and a microwave generator 39 as main components.

The transmission plate 28 that transmits microwaves is disposed on a support portion 13 a that protrudes to the inner peripheral side of the upper plate 13. The transmission plate 28 is made of a dielectric, for example, ceramics such as quartz, Al ₂ O ₃ , and AlN. A gap between the transmission plate 28 and the support portion 13a is hermetically sealed through a seal member 29. Therefore, the inside of the chamber 1 is kept airtight.

  The planar antenna 31 is provided above the transmission plate 28 so as to face the mounting table 2. The planar antenna 31 has a disk shape. The shape of the planar antenna 31 is not limited to a disk shape, and may be a square plate shape, for example. The planar antenna 31 is locked to the upper end of the upper plate 13.

  The planar antenna 31 is made of, for example, a copper plate or an aluminum plate having a surface plated with gold or silver. The planar antenna 31 has a number of slot-shaped microwave radiation holes 32 that radiate microwaves. The microwave radiation holes 32 are formed through the planar antenna 31 in a predetermined pattern.

  Each microwave radiation hole 32 has an elongated rectangular shape (slot shape), for example, as shown in FIG. And typically, the adjacent microwave radiation holes 32 are arranged in a “T” shape. Further, the microwave radiation holes 32 arranged in combination in a predetermined shape (for example, T shape) are further arranged concentrically as a whole.

  The length and arrangement interval of the microwave radiation holes 32 are determined according to the wavelength (λg) of the microwave. For example, the interval between the microwave radiation holes 32 is arranged to be λg / 4, λg / 2, or λg. In FIG. 5, the interval between the adjacent microwave radiation holes 32 formed concentrically is indicated by Δr. Note that the microwave radiation hole 32 may have another shape such as a circular shape or an arc shape. Furthermore, the arrangement form of the microwave radiation holes 32 is not particularly limited, and may be arranged in a spiral shape, a radial shape, or the like in addition to a concentric shape.

  A slow wave material 33 having a dielectric constant larger than that of a vacuum is provided on the upper surface of the planar antenna 31. The slow wave material 33 has a function of adjusting the plasma by shortening the wavelength of the microwave because the wavelength of the microwave becomes longer in vacuum.

  The planar antenna 31 and the transmission plate 28 and the slow wave member 33 and the planar antenna 31 may be brought into contact with or separated from each other, but they are preferably brought into contact with each other.

  A shield lid 34 is provided on the upper portion of the chamber 1 so as to cover the planar antenna 31 and the slow wave material 33. The shield lid 34 is made of a metal material such as aluminum or stainless steel. The upper end of the upper plate 13 and the shield lid 34 are sealed by a seal member 35. A cooling water passage 34 a is formed inside the shield lid 34. By passing cooling water through the cooling water channel 34a, the shield lid 34, the slow wave material 33, the planar antenna 31 and the transmission plate 28 can be cooled. The shield lid 34 is grounded.

  An opening 36 is formed in the center of the upper wall (ceiling part) of the shield lid 34, and a waveguide 37 is connected to the opening 36. A microwave generator 39 that generates microwaves is connected to the other end of the waveguide 37 via a matching circuit 38.

  The waveguide 37 is connected to a coaxial waveguide 37a having a circular cross section extending upward from the opening 36 of the shield lid 34, and an upper end portion of the coaxial waveguide 37a via a mode converter 40. And a rectangular waveguide 37b extending in the horizontal direction. The mode converter 40 has a function of converting the microwave propagating in the TE mode in the rectangular waveguide 37b into the TEM mode.

  An inner conductor 41 extends at the center of the coaxial waveguide 37a. The inner conductor 41 is connected and fixed to the center of the planar antenna 31 at its lower end. With such a structure, the microwave is efficiently and uniformly propagated radially and uniformly to the planar antenna 31 via the inner conductor 41 of the coaxial waveguide 37a.

  By the microwave introduction mechanism 27 having the above configuration, the microwave generated by the microwave generator 39 is propagated to the planar antenna 31 through the waveguide 37 and further introduced into the chamber 1 through the transmission plate 28. It has come to be. For example, 2.45 GHz is preferably used as the frequency of the microwave, and 8.35 GHz, 1.98 GHz, or the like can also be used.

  Each component of the plasma processing apparatus 100 is connected to and controlled by the controller 50. As shown in FIG. 6, the control unit 50 includes a process controller 51 having a CPU, a user interface 52 connected to the process controller 51, and a storage unit 53. In the plasma processing apparatus 100, the process controller 51 is a component related to process conditions such as temperature, pressure, gas flow rate, and microwave output (for example, the heater power supply 5a, the gas supply mechanism 18, the exhaust device 24, the microwave). This is a control means for controlling the generator 39 and the like in an integrated manner.

  The user interface 52 includes a keyboard on which a process manager manages command input to manage the plasma processing apparatus 100, a display that visualizes and displays the operating status of the plasma processing apparatus 100, and the like. The storage unit 53 stores a recipe in which a control program (software) for realizing various processes executed by the plasma processing apparatus 100 under the control of the process controller 51 and processing condition data are recorded. Yes.

  If necessary, an arbitrary recipe is called from the storage unit 53 according to an instruction from the user interface 52 and is executed by the process controller 51, so that the process controller 51 controls the inside of the chamber 1 of the plasma processing apparatus 100. The desired process is performed. The recipes such as the control program and processing condition data may be stored in a computer-readable storage medium such as a CD-ROM, a hard disk, a flexible disk, a flash memory, a DVD, or a Blu-ray disk. Alternatively, it may be transmitted from other devices as needed via, for example, a dedicated line and used online.

  In the plasma processing apparatus 100 configured as described above, it is possible to perform damage-free plasma processing on the base film or the like at a low temperature of 800 ° C. or lower. In addition, since the plasma processing apparatus 100 is excellent in plasma uniformity, process uniformity can be realized.

  Next, plasma oxidation processing using the RLSA type plasma processing apparatus 100 will be described. First, the gate valve 17 is opened, and the wafer W is loaded into the chamber 1 from the loading / unloading port 16 and mounted on the mounting table 2. Note that a p-type diffusion region 103 as a first diffusion region and an n-type diffusion region 105 as a second diffusion region are formed on the wafer W (see FIGS. 1 to 3).

  Next, while the chamber 1 is evacuated under reduced pressure, the oxygen introduction gas and the inert gas are respectively supplied from the inert gas supply source 19a and the oxygen-containing gas supply source 19b of the gas supply mechanism 18 at a predetermined flow rate. Through the chamber 1. In this way, the inside of the chamber 1 is adjusted to a predetermined pressure.

  Next, a microwave having a predetermined frequency, for example, 2.45 GHz, generated by the microwave generator 39 is guided to the waveguide 37 via the matching circuit 38. The microwave guided to the waveguide 37 sequentially passes through the rectangular waveguide 37 b and the coaxial waveguide 37 a and is supplied to the planar antenna 31 through the inner conductor 41. That is, the microwave propagates in the TE mode in the rectangular waveguide 37b, and the TE mode microwave is converted into the TEM mode by the mode converter 40, and the inside of the coaxial waveguide 37a is directed to the planar antenna 31. Will be propagated. Then, the microwave is radiated to the space above the wafer W in the chamber 1 through the transmission plate 28 from the slot-shaped microwave radiation hole 32 formed through the planar antenna 31. The microwave output at this time can be selected according to the purpose from the range of 100 to 5000 W, for example, when processing a wafer W having a diameter of 200 mm or more.

An electromagnetic field is formed in the chamber 1 by the microwave radiated from the planar antenna 31 to the chamber 1 through the transmission plate 28, and the inert gas and the oxygen-containing gas are turned into plasma. The microwave-excited plasma has a high density of about 1 × 10 ^{10 to} 5 × 10 ¹² / cm ³ and a vicinity of the wafer W when microwaves are radiated from a large number of microwave radiation holes 32 of the planar antenna 31. Then, it becomes a low electron temperature plasma of about 1.5 eV or less. The microwave-excited high-density plasma formed in this way has little plasma damage due to ions or the like on the underlying film. Then, the silicon surface of the wafer W is oxidized by the action of active species such as radicals or ions in the plasma, and a thin film of silicon oxide film SiO ₂ is formed.

  In the plasma processing apparatus 100, the formation rate of the silicon oxide film (that is, the oxidation rate of silicon) can be controlled to a desired size by selecting the plasma processing conditions. For example, the following conditions can be given as plasma processing conditions for preferentially oxidizing the p-type diffusion region 103 and oxidizing the n-type diffusion region 105 only slightly.

<Plasma oxidation treatment conditions>
In the present embodiment, the concentration of impurities (for example, boron) in the p-type diffusion region 103 is in the range of 1 × 10 ¹⁶ cm ^{−3 to} 5 × 10 ¹⁸ cm ⁻³ , and the n-type diffusion region 105 has an impurity A case where the concentration of (for example, phosphorus) is in the range of 1 × 10 ¹⁶ cm ^{−3 to} 5 × 10 ¹⁸ cm ⁻³ will be described as an example.

As the processing gas, it is preferable to use Ar gas as a rare gas and O ₂ gas as an oxygen-containing gas. In this case, the flow ratio of _{O 2} gas to the Ar gas _{(O 2} gas flow rate / Ar flow rate) is, in view of enhancing the plasma stability, it is preferably in the range of 0.001 to 0.2. For example, when processing a wafer W having a diameter of 200 mm or more, the flow rate of Ar gas is in the range of 500 mL / min (sccm) to 5000 mL / min (sccm) and the flow rate of O ₂ gas is 5 mL / min (sccm) or more. The flow rate ratio can be set within the range of 100 mL / min (sccm) or less.

  Moreover, it is preferable to set processing pressure in the range of 1.3 Pa or more and less than 6.7 Pa, or in the range of more than 667 Pa and 1333 Pa or less.

The power density of the microwave, increase the plasma stability, and from the standpoint of controlling the oxidation rate, it is preferable to 0.08 W / cm ² or more 0.42 W / cm ² less than the range. In the present invention, the microwave power density means the microwave power per 1 cm ² area of the transmission plate 28 (see FIG. 4) facing the plasma formation space. For example, when processing a wafer W having a diameter of 200 mm or more, it is preferable to set the microwave power within the range of 100 W or more and less than 500 W.

  In addition, the heating temperature of the wafer W is preferably set, for example, in the range of 300 ° C. to 800 ° C., more preferably in the range of 400 ° C. to 600 ° C. as the temperature of the mounting table 2.

  Furthermore, the gap (interval from the lower surface of the transmission plate 28 to the upper surface of the mounting table 2) G in the plasma processing apparatus 100 is set within a range of, for example, 50 mm or more and 200 mm or less from the viewpoint of controlling the plasma density and the oxidation rate. Is preferred.

  The above conditions are stored as a recipe in the storage unit 53 of the control unit 50. The process controller 51 reads the recipe and sends a control signal to each component of the plasma processing apparatus 100, such as the gas supply mechanism 18, the exhaust device 24, the microwave generator 39, the heater power supply 5a, etc. Plasma oxidation treatment under conditions is realized.

  The plasma oxidation process under the above conditions is performed until a silicon oxide film having a desired thickness is formed in the p-type diffusion region 103. The end point of the oxidation treatment can be determined from the oxidation rate and time, for example. Alternatively, for example, the end point can be detected by installing a film thickness monitoring device in the chamber 1 and monitoring the film thickness of the silicon oxide film in real time.

  Under the above conditions, the wafer W (silicon layer 101) on which the p-type diffusion region 103 and the n-type diffusion region 105 are formed is subjected to plasma oxidation treatment, so that silicon in the p-type diffusion region 103 is preferentially oxidized, A silicon oxide film thicker than the n-type diffusion region 105 can be formed. That is, under the above conditions, the p-type diffusion region 103 is oxidized quickly, but the progress of oxidation in the n-type diffusion region 105 is slower than that of the p-type diffusion region 103. For example, the oxidation rate in the p-type diffusion region 103 is 1.2 to 2.0 times, preferably 1.6 to 2.0 times that of the n-type diffusion region 105. be able to. Due to the difference in oxidation rate, the thickness of the silicon oxide film of the p-type diffusion region 103 formed in the same oxidation processing time is 1.2 to 2.0 compared to the n-type diffusion region 105. The film can be formed thick within a range of twice, preferably within a range of 1.6 to 2.0 times.

<Action>
Conventional plasma oxidation treatment has been aimed at forming a uniform silicon oxide film within the surface of the wafer W by increasing the density of radicals in the plasma and performing oxidation treatment mainly of radicals. Therefore, a method for forming a silicon oxide film having a different film thickness by actively changing the oxidation rate depending on the part within the surface of the wafer W has not been studied. The inventors select specific plasma generation conditions in the plasma processing apparatus 100 that generates plasma by introducing microwaves into the chamber 1 using the planar antenna 31 having a plurality of microwave radiation holes 32. Thus, it has been found that a difference in oxidation rate occurs in a plurality of regions having different conductivity types formed in silicon. As described above, the cause of the difference in the oxidation rate is not yet clear, but is estimated as follows. Differences in the polarity of silicon in each region occur due to differences in the conductivity type of silicon. Due to this difference in polarity, the p-type diffusion region 103 is slightly more easily oxidized than the n-type diffusion region 105. The slight difference in “easiness of oxidation” appears as a difference in oxidation rate when the oxidation treatment is performed under oxidation treatment conditions with a limited weak oxidation power.

In the present invention, by utilizing the above phenomenon, for example, by performing plasma oxidation treatment on a silicon surface having a p-type diffusion region and an n-type diffusion region, silicon oxides having different thicknesses are formed in the p-type diffusion region and the n-type diffusion region. It has been found that the film can be easily formed.
That is, in order to form silicon oxide films having different thicknesses in the p-type diffusion region and the n-type diffusion region formed on one wafer W in the conventional technique, after forming the silicon oxide film in these regions once, Then, a photoresist mask is selectively formed in the region where the oxide film is to be formed thick, and the oxide film in the other part is removed by wet etching using a dilute hydrofluoric acid (HF) aqueous solution, and then oxidized once again. A complicated procedure of forming a thin oxide film by performing the treatment is necessary. In this way, in order to give a difference in film thickness using photolithography technology, many steps such as resist coating, exposure, development, etching, and washing are required, and at least two oxidation treatment steps are required. Met. In contrast, in the present embodiment, silicon oxide films having different film thicknesses can be formed in the p-type diffusion region and the n-type diffusion region only by the plasma oxidation treatment step, so the number of steps is greatly increased compared to the conventional method. There is a remarkable effect that it can be reduced. By using the silicon oxide film thus formed as a gate insulating film of, for example, a CMOS device, the degree of freedom in designing the film thickness of the gate insulating film is eliminated while minimizing adverse effects on device performance with a simple process. Can be increased.

[Second Embodiment]
Next, a plasma oxidation method according to the second embodiment of the present invention will be described with reference to FIGS. In the plasma oxidation processing method according to the present embodiment, the conditions under which both the p-type diffusion region 103 and the n-type diffusion region 105 can be oxidized after the plasma oxidation treatment is performed mainly under the condition that the p-type diffusion region 103 is oxidized. The second embodiment is different from the first embodiment in that a two-step oxidation process is performed. Accordingly, the following description will be focused on differences from the first embodiment, and illustration and description of the same contents as those of the first embodiment will be omitted.

  FIG. 7 is a flowchart showing an example of a procedure in the second embodiment. As shown in FIG. 7, in the present embodiment, after the first plasma oxidation process performed under the condition of oxidizing only the p-type diffusion region 103, the oxidizing power is higher than that of the first plasma oxidation process. The second plasma oxidation treatment process is performed under strong conditions. In the second plasma oxidation treatment step, the oxidation treatment is preferably performed so that the oxidation rate for the p-type diffusion region 103 and the oxidation rate for the n-type diffusion region 105 are approximately the same.

  First, in step S <b> 1, the wafer W is loaded into the chamber 1 of the plasma processing apparatus 100 by a transfer device (not shown) and mounted on the mounting table 2. The wafer W is provided with a p-type diffusion region 103 and an n-type diffusion region 105.

Next, in step S2, Ar gas and O ₂ gas are introduced into the chamber 1 from the gas supply mechanism 18 at a predetermined flow rate. In step S3, the exhaust device 24 is operated to reduce the pressure in the chamber 1 to a predetermined pressure and stabilize it.

  Next, in step S4, the power of the microwave generator 39 is turned “ON” to generate a microwave having a predetermined frequency, for example, 2.45 GHz, and a first plasma oxidation process is performed. Microwaves generated by the microwave generator 39 are introduced into the internal space of the chamber 1 through the matching circuit 38, the waveguide 37 and the planar antenna 31, and oxygen-containing plasma is generated in the chamber 1. With this oxygen-containing plasma, silicon on the surface of the wafer W is subjected to plasma oxidation to form a silicon oxide film. In this first plasma oxidation treatment step, the silicon in the p-type diffusion region 103 is oxidized, but the weak oxidizing power is selected so that the silicon in the n-type diffusion region 105 is hardly oxidized.

<First plasma oxidation treatment condition>
In the present embodiment, the concentration of the impurity (for example, phosphorus) in the p-type diffusion region 103 is 1 × 10 ^{16 to} 5 × 10 ¹⁸ cm ⁻³ , and the concentration of the impurity (for example, boron) is used as the n-type diffusion region 105. Will be described taking as an example the case of 1 × 10 ^{16 to} 5 × 10 ¹⁸ cm ⁻³ .

As the processing gas, it is preferable to use Ar gas as a rare gas and O ₂ gas as an oxygen-containing gas. In this case, the flow ratio of _{O 2} gas to the Ar gas _{(O 2} gas flow rate / Ar flow rate) is, in view of enhancing the plasma stability, it is preferably in the range of 0.001 to 0.2. For example, when processing a wafer W having a diameter of 200 mm or more, the flow rate of Ar gas is in the range of 100 mL / min (sccm) to 5000 mL / min (sccm), preferably 100 mL / min (sccm) to 500 mL / min ( sccm) or less, or 2000 mL / min (sccm) or more and 5000 mL / min (sccm) or less, and the flow rate of O ₂ gas is 0.1 mL / min (sccm) or more and 500 mL / min (sccm) or less. Preferably, the flow rate ratio is set within the range from 1 mL / min (sccm) to 5 mL / min (sccm) or from 200 mL / min (sccm) to 500 mL / min (sccm). be able to.

  Moreover, it is preferable to set processing pressure in the range of 1.3 Pa or more and less than 6.7 Pa, or in the range of more than 667 Pa and 1333 Pa or less.

The power density of the microwave, increase the plasma stability, and from the standpoint of controlling the oxidation rate, it is preferable to 0.08 W / cm ² or more 0.42 W / cm ² less than the range. For example, when processing a wafer W having a diameter of 200 mm or more, it is preferable to set the microwave power within the range of 100 W or more and less than 500 W.

  In addition, the heating temperature of the wafer W is preferably set, for example, in the range of 300 ° C. to 800 ° C., more preferably in the range of 400 ° C. to 600 ° C. as the temperature of the mounting table 2.

  Furthermore, the gap (interval from the lower surface of the transmission plate 28 to the upper surface of the mounting table 2) G in the plasma processing apparatus 100 is set within a range of, for example, 50 mm or more and 200 mm or less from the viewpoint of controlling the plasma density and the oxidation rate. Is preferred.

  The above conditions are stored as a recipe in the storage unit 53 of the control unit 50. The process controller 51 reads the recipe and sends a control signal to each component of the plasma processing apparatus 100, such as the gas supply mechanism 18, the exhaust device 24, the microwave generator 39, the heater power supply 5a, etc. Plasma oxidation treatment under conditions is realized.

After the processing time specified by the recipe has elapsed, the microwave power is turned “off” in step S5, and the first plasma oxidation process is completed. This first plasma oxidation treatment step, as shown in FIG. 8, the surface of the p-type diffusion region 103 is a silicon oxide film 106 is formed by oxidizing a predetermined thickness T _3, n-type diffusion region The surface of 105 is hardly oxidized, and the silicon oxide film is formed only with a thickness (not shown) that is almost negligible.

  After the end of step S5, the gas flow rate is adjusted in step S6 and the pressure in the chamber is adjusted in step S7 toward the second plasma oxidation process.

  Next, in step S8, the power of the microwave generator 39 is turned “ON” again to generate a microwave having a predetermined frequency, for example, 2.45 GHz, and a second plasma oxidation process is performed. Oxygen-containing plasma is generated in the chamber 1 by microwaves introduced into the space in the chamber 1, and silicon on the surface of the wafer W is plasma-oxidized by the oxygen-containing plasma to form a silicon oxide film. In the second plasma oxidation treatment step, a condition having a stronger oxidizing power than that in the first plasma oxidation treatment step (step S4) is selected. As a result, in the second plasma oxidation process, the oxidation reaction proceeds at the same oxidation rate in the p-type diffusion region 103 and the n-type diffusion region 105.

<Second plasma oxidation treatment condition>
As the processing gas, it is preferable to use Ar gas as a rare gas and O ₂ gas as an oxygen-containing gas. In this case, the flow ratio of _{O 2} gas to the Ar gas _{(O 2} gas flow rate / Ar flow rate) is, in view of enhancing the plasma stability, it is preferably in the range of 0.0025 to 0.4. For example, when processing a wafer W having a diameter of 200 mm or more, the flow rate of Ar gas is in the range of 500 mL / min (sccm) to 2000 mL / min (sccm), and the flow rate of O ₂ gas is 5 mL / min (sccm) or more. The flow rate ratio is set within the range of 200 mL / min (sccm) or less.

  Moreover, it is preferable to make processing pressure into the range of 6.7 Pa or more and 667 Pa or less.

The power density of the microwave, increase the plasma stability, and from the standpoint of controlling the oxidation rate, it is preferable to 0.42 W / cm ² or more 4.19W / cm ² within the following ranges. For example, when processing a wafer W having a diameter of 200 mm or more, it is preferable that the microwave power is in the range of 500 W to 5000 W.

  In addition, the heating temperature of the wafer W is preferably set, for example, in the range of 300 ° C. to 800 ° C., more preferably in the range of 400 ° C. to 600 ° C. as the temperature of the mounting table 2.

  Further, the gap (interval from the lower surface of the transmission plate 28 to the upper surface of the mounting table 2) G in the plasma processing apparatus 100 is set within a range of, for example, 70 mm or more and 150 mm or less from the viewpoint of controlling the plasma density and the oxidation rate. Is preferred.

  The conditions for the second plasma oxidation process are stored as a recipe in the storage unit 53 of the control unit 50, as in the first plasma oxidation process (step S4). Then, under the control of the process controller 51, the second plasma oxidation process under a desired condition is realized. After the processing time defined by the recipe has elapsed, the microwave power is turned “off” in step S9, and the second plasma oxidation processing step is terminated.

By selecting the above conditions, the second plasma oxidation process differs from the first plasma oxidation process in that the oxidation rate for the p-type diffusion region 103 and the oxidation rate for the n-type diffusion region 105 are approximately the same. is there. Here, the “same degree of oxidation rate” means that the oxidation rate of the p-type diffusion region 103 is within a range of 1 to 1.1 times the oxidation rate of the n-type diffusion region 105, for example. Accordingly, not only the p-type diffusion region 103 but also the n-type diffusion region 105 is formed with a silicon oxide film having a predetermined thickness. As shown in FIG. 9, in the p-type diffusion region 103, oxidation proceeds further than in the state shown in FIG. 8, and a thick silicon oxide film 107a is formed. Thickness T ₄ of the silicon oxide film 107a has a thickness of the first film thickness T ₃ of the silicon oxide film 106 formed by the plasma oxidation step, the second oxide film formed by plasma oxidation process Is the sum of On the other hand, the n-type diffusion region 105, because it was not nearly silicon oxide film is formed in the first plasma oxidation step, the silicon oxide film 107b having a small thickness T ₅ that is formed in the second plasma oxidation process Is formed. That is, film thickness T ₄ > film thickness T ₅ .

  After completion of the second plasma oxidation process, the pressure in the chamber is increased in step S10, and the supply of process gas is stopped in step S11. In step S12, the wafer W is unloaded from the chamber 1 and the process for one wafer W is completed.

As described above, in the present embodiment, the first plasma oxidation process in which the silicon in the p-type diffusion region 103 is oxidized and the silicon in the n-type diffusion region 105 is hardly oxidized, the silicon in the p-type diffusion region 103 and the n A silicon oxide film having different thicknesses is formed in the p-type diffusion region 103 and the n-type diffusion region 105 by performing a second plasma oxidation process step of oxidizing the silicon in the type diffusion region 105 at a substantially equivalent oxidation rate. be able to. In other words, by performing the first plasma oxidation process and the second plasma oxidation process, the p-type diffusion region 103 is formed in the first plasma oxidation process compared to the n-type diffusion region 105. silicon oxide film of an amount corresponding large thickness T ₄ corresponding to the thickness of the silicon oxide film is formed.

Other configurations, operations, and effects in the present embodiment are the same as those in the first embodiment.
In FIG. 7, the first plasma oxidation process in step S4 and the second plasma oxidation process in step S8 are performed in the same chamber. However, the first plasma oxidation process and the second plasma oxidation process are performed in the same chamber. The plasma oxidation process can be performed in a separate chamber. When the first plasma oxidation treatment step and the second plasma oxidation treatment step are performed in different chambers, there is an advantage that it is easy to perform the treatment with different gaps G.

[Example of application to semiconductor device manufacturing process]
Next, an example of manufacturing a semiconductor device using the plasma oxidation processing method of the present invention will be described. 10 to 13 show an example in which the plasma oxidation processing method of the present invention is applied to the formation of a gate insulating film in the process of manufacturing a CMOS device including an n-channel transistor and a p-channel transistor.

First, an element isolation film 202 made of silicon oxide (SiO ₂ ) is formed on the surface of the silicon substrate 201 by, eg, STI (Shallow Trench Isolation; STI) method or LOCOS (Local Oxidation of Silicon) method. The element isolation film 202 partitions the nMOS formation region 220 and the pMOS formation region 221. Next, boron ions are selectively implanted into the silicon substrate 201 exposed in the nMOS formation region 220, and phosphorus ions or arsenic ions are selectively implanted into the silicon substrate 201 exposed in the pMOS formation region 221. In this way, as shown in FIG. 10, the p-well 203 that is a p-type diffusion region is formed in the nMOS formation region 220, and the n-well 205 that is an n-type diffusion region is formed in the pMOS formation region 221. Although illustration is omitted, in order to determine the threshold voltage of the transistor, channel doping may be performed on a channel formation scheduled portion. In the case of the present embodiment, channel doping is performed, for example, by ion-implanting impurities having the same conductivity type as each well into the channel formation scheduled sites near the surface of the p well 203 and the n well 205. In another embodiment, ions of a conductivity type opposite to each well may be implanted during channel doping.

  Next, using the plasma processing apparatus 100, the silicon substrate 201 having the nMOS formation region 220 and the pMOS formation region 221 is subjected to plasma oxidation treatment. As a result, as shown in FIG. 11, a silicon oxide film 207a is formed on the surface of the p well 203, and a silicon oxide film 207b thinner than the silicon oxide film 207a is formed on the surface of the n well 205. In this embodiment, the silicon oxide films 207a and 207b having different film thicknesses may be formed by a single plasma oxidation process as in the first embodiment, or in the second embodiment. As in the embodiment, a two-step plasma oxidation process may be performed. A silicon oxynitride film (SiON film) may be formed by nitriding the silicon oxide films 207a and 207b formed as described above.

  In the prior art, in order to form silicon oxide films with different thicknesses in the p-well 203 and the n-well 205, a silicon oxide film is once formed to a predetermined thickness, and then the nMOS formation region 220 and Of the pMOS formation region 221, it is necessary to form a mask by using a photolithographic technique on the one where it is desired to leave a thick film, remove the remaining oxide film, and then oxidize again to form a thin film. there were. On the other hand, in this embodiment, by performing selective plasma oxidation using the plasma processing apparatus 100, the photolithography process, the etching process, and the like can be reduced. Therefore, there is an advantage that the silicon oxide film 207a of the p-well 203 can be formed thicker than the silicon oxide film 207b of the n-well 205 by only the plasma oxidation process with a smaller number of processes than the prior art.

  Next, a polysilicon layer is formed on the silicon oxide film 207 by, eg, CVD. Then, a mask having a predetermined pattern is formed on the polysilicon layer by photolithography, and the polysilicon layer and the silicon oxide film 207 are sequentially etched. As a result, as shown in FIG. 12, a gate electrode 210a in which a polysilicon electrode layer 209a is stacked on the gate insulating film 208a is formed on the p-well 203. On the n well 205, a gate electrode 210b in which a polysilicon electrode layer 209b is stacked on the gate insulating film 208b is formed. Note that the gate electrodes 210a and 210b may have a stacked structure including an electrode layer made of a metal such as tungsten or a silicide thereof, and an insulating layer such as a silicon nitride film, in addition to the polysilicon electrode layers 209a and 209b.

  Next, sidewalls (spacers) 211 made of silicon nitride are formed on the side surfaces of the gate electrodes 210a and 210b as shown in FIG. In addition, phosphorus is selectively implanted into the upper portion of the p well 203 in the nMOS formation region 220 to form n-type source / drain regions 212 on both sides of the gate electrode 210a, and the n well 205 in the pMOS formation region 221. The p-type source / drain regions 213 are formed on both sides of the gate electrode 110b by selectively implanting boron into the upper portion of the gate electrode 110b. Thereafter, by forming a contact, wiring, etc. (not shown) using a known method, a CMOS device having an n-channel MOSFET in the p-well 203 and a p-channel MOSFET in the n-well 205 can be formed. Although there are many variations in the form of the CMOS device and the manufacturing method thereof, a silicon oxide film having different thicknesses can be formed on the surface of the p-well 203 and the surface of the n-well 205 according to the present invention. The plasma oxidation processing method can also be applied to other forms of CMOS devices and manufacturing processes thereof.

  As mentioned above, although embodiment of this invention was described, this invention is not restrict | limited to the said embodiment, A various deformation | transformation is possible. For example, in the first embodiment, as a p-type diffusion region 103 and an n-type diffusion region 105 to be subjected to plasma oxidation processing, a twin well structure in which a p well and an n well are formed in a silicon layer 101 is taken as an example. However, the present invention is not limited to this. For example, a combination of a p-type silicon substrate (or p-type silicon layer) as a p-type diffusion region and an n-well as an n-type diffusion region formed therein, or an n-type silicon substrate as an n-type diffusion region Similarly, the plasma oxidation processing method of the present invention can be applied to a combination of (or an n-type silicon layer) and a p-well as a p-type diffusion region formed therein.

  The p-type diffusion region 103 and the n-type diffusion region 105 are not limited to wells, but are regions (including part of the wells) doped with impurities at a higher concentration than the wells, for example, for the purpose of channel doping. There may be. The plasma oxidation processing method of the present invention is applied to the silicon layer 101 (silicon substrate) having a plurality of p-type diffusion regions 103 having different impurity concentrations and a plurality of n-type diffusion regions 105 having different impurity concentrations. By doing so, it is possible to provide a film thickness difference of three or more steps within the same substrate surface.

It is explanatory drawing which shows the cross-sectional structure of the silicon surface vicinity used as the object of the plasma oxidation process which concerns on the 1st Embodiment of this invention. It is explanatory drawing which drew the mode of the plasma oxidation process typically. It is explanatory drawing which shows the state in which the silicon oxide film was formed by the plasma oxidation process. It is a schematic sectional drawing which shows an example of the plasma processing apparatus suitable for a plasma oxidation process. It is drawing which shows the structure of a planar antenna. It is explanatory drawing which shows the structure of a control part. It is a flowchart which shows the outline | summary of the procedure of the plasma oxidation process which concerns on the 2nd Embodiment of this invention. It is explanatory drawing which shows the cross-sectional structure of the silicon surface vicinity after a 1st plasma oxidation treatment process. It is explanatory drawing which shows the cross-sectional structure of the silicon surface vicinity after a 2nd plasma oxidation treatment process. It is explanatory drawing which shows the cross-sectional structure of the silicon surface vicinity for demonstrating the manufacturing process of a CMOS element. It is explanatory drawing which shows the cross-sectional structure of the silicon surface vicinity after forming a silicon oxide film in the manufacturing process of a CMOS element. It is explanatory drawing which shows the cross-sectional structure of the silicon surface vicinity after forming a gate electrode in the manufacturing process of a CMOS element. It is explanatory drawing which shows schematic structure of the manufactured CMOS element.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Chamber (processing chamber), 2 ... Mounting stand, 3 ... Support member, 5 ... Heater, 12 ... Exhaust pipe, 15 ... Gas introduction part, 16 ... Carry-in / out port, 17 ... Gate valve, 18 ... Gas supply mechanism, 19a DESCRIPTION OF SYMBOLS ... Inert gas supply source, 19b ... Oxygen-containing gas supply source, 24 ... Exhaust device, 27 ... Microwave introduction mechanism, 28 ... Transmission plate, 29 ... Seal member, 31 ... Planar antenna, 32 ... Microwave radiation hole, 37 DESCRIPTION OF SYMBOLS ... Waveguide, 37a ... Coaxial waveguide, 37b ... Rectangular waveguide, 39 ... Microwave generator, 50 ... Control part, 51 ... Process controller, 52 ... User interface, 53 ... Memory | storage part, 100 ... Plasma processing Device: 101 ... Silicon layer, 103 ... p-type diffusion region, 105 ... n-type diffusion region, 107 ... silicon oxide film, 107a ... thick film portion, 107b ... thin film portion, W ... semiconductor wafer (substrate)

Claims (18)

Introducing a processing gas containing an oxygen-containing compound and an inert gas into the processing chamber of the plasma processing apparatus;
Introducing a microwave into the processing chamber by a planar antenna having a plurality of holes to generate plasma;
A plasma oxidation process for oxidizing the surface of the silicon layer with the plasma;
A plasma oxidation treatment method comprising:
A first region having a first conductivity type and a second region having a second conductivity type opposite to the first conductivity type are exposed on the surface of the silicon layer. In the first region and the second region, the oxidation rate in the first region is 1.2 to 2.0 times the oxidation rate in the second region. plasma oxidation process wherein the oxidizing treatment as.   The film thickness of the silicon oxide film formed in the first region is 1.2 to 2.0 times the film thickness of the silicon oxide film formed in the second region. The plasma oxidation treatment method according to claim 1. The oxygen-containing compound is oxygen, the inert gas is argon, and the flow rate ratio O ₂ / Ar is in the range of 0.001 to 0.2. The plasma oxidation treatment method according to claim 2 . The plasma within the processing pressure is below than 1.3 Pa 6.7 Pa in the oxidation treatment step, or 667Pa any of claims 1 to 3, characterized in that either the super 1333Pa the range 1 The plasma oxidation treatment method according to item. The power density of the microwave in the plasma oxidation process is, in any one of claims 1 to 4, characterized in that in the range of less than 0.08 W / cm ² or more 0.42 W / cm ² The plasma oxidation treatment method described. Introducing a processing gas containing an oxygen-containing compound and an inert gas into the processing chamber of the plasma processing apparatus;
Introducing a microwave into the processing chamber by a planar antenna having a plurality of holes to generate plasma;
A plasma oxidation process for oxidizing the surface of the silicon layer with the plasma;
A plasma oxidation treatment method comprising:
The silicon layer has a first region having a first conductivity type and a second region having a second conductivity type opposite to the first conductivity type on the surface. It is exposed and provided
The plasma oxidation treatment step includes a first oxidation treatment step for performing an oxidation treatment such that an oxidation rate for the first region is higher than an oxidation rate for the second region;
A second oxidation treatment step for performing an oxidation treatment after the first oxidation treatment step so that an oxidation rate for the first region and an oxidation rate for the second region are approximately the same;
A plasma oxidation treatment method comprising: The plasma according to claim 6 , wherein, in the first oxidation treatment step, an oxidation rate in the first region is 1.2 to 2.0 times an oxidation rate in the second region. Oxidation method. In the first oxidation treatment step, the film thickness of the silicon oxide film formed in the first region is 1.2 to 2.2 compared to the film thickness of the silicon oxide film formed in the second region. The plasma oxidation processing method according to claim 6 , wherein the plasma oxidation processing method is 0 times. In the first oxidation treatment step, the oxygen-containing compound is oxygen, the inert gas is argon, and the flow rate ratio O ₂ / Ar is in the range of 0.001 to 0.25. And the processing pressure is in the range of 1.3 Pa or more and less than 6.7 Pa, or in the range of more than 667 Pa and 1333 Pa or less, according to any one of claims 6 to 8 . Plasma oxidation treatment method. In the first oxidation step, the power density of the microwave, claim 9 claim 6, characterized in that in the range of less than 0.08 W / cm ² or more 0.42 W / cm ² 2. The plasma oxidation treatment method according to item 1. In the second oxidation treatment step, the oxygen-containing compound is oxygen, the inert gas is argon, and a flow rate ratio O ₂ / Ar is within a range of 0.0025 to 0.4. The plasma oxidation treatment method according to any one of claims 6 to 10 , wherein a treatment pressure in the second oxidation treatment step is in a range of 6.7 Pa to 667 Pa. In the second oxidizing step, the power density of the microwave, claim 11 claim 6, characterized in that in the range 0.42 W / cm ² or more 4.19W / cm ² or less of 2. The plasma oxidation treatment method according to item 1. The plasma oxidation treatment method according to any one of claims 1 to 12 , wherein the first region is a p-type diffusion region, and the second region is an n-type diffusion region. The boron concentration in the p-type diffusion region is in the range of 1 × 10 ^{16 to} 5 × 10 ¹⁸ cm ⁻³ , and the phosphorus concentration in the n-type diffusion region is 1 × 10 ^{16 to} 5 × 10 ¹⁸ cm ^−3. The plasma oxidation treatment method according to claim 13 , wherein the plasma oxidation treatment method is within the range. Introducing a processing gas containing an oxygen-containing compound and an inert gas into a processing chamber of the plasma processing apparatus; and introducing a microwave into the processing chamber by a planar antenna having a plurality of holes to generate plasma. A plasma oxidation treatment step of oxidizing the surface of the silicon layer with the plasma to form a silicon oxide film ,
In the plasma oxidation treatment step, the oxidation rate for the first region having the first conductivity type provided on the surface of the silicon layer is a second conductivity type opposite to the first conductivity type. A first oxidation treatment step for performing an oxidation treatment so as to be larger than an oxidation rate for the second region having the conductivity type;
A second oxidation treatment step for performing an oxidation treatment after the first oxidation treatment step so that an oxidation rate for the first region and an oxidation rate for the second region are approximately the same;
A method for forming a silicon oxide film. A method of manufacturing a CMOS device comprising an n-channel transistor and a p-channel transistor,
Forming a first region having a first conductivity type and a second region having a second conductivity type opposite to the first conductivity type in the silicon layer; ,
A silicon oxide film forming step of forming a silicon oxide film on the surface of each of the first region and the second region;
Forming gate electrodes on the silicon oxide film formed in the first region and the silicon oxide film formed in the second region, respectively;
With
The silicon oxide film forming step includes
Introducing a processing gas containing an oxygen-containing compound and an inert gas into a processing chamber of the plasma processing apparatus; and introducing a microwave into the processing chamber by a planar antenna having a plurality of holes to generate plasma. And a plasma oxidation treatment step of oxidizing the surface of the silicon layer with the plasma,
The plasma oxidation treatment step includes a first oxidation treatment step for performing an oxidation treatment such that an oxidation rate for the first region is higher than an oxidation rate for the second region;
A second oxidation treatment step for performing an oxidation treatment after the first oxidation treatment step so that an oxidation rate for the first region and an oxidation rate for the second region are approximately the same;
A method of manufacturing a CMOS device. A computer-readable storage medium storing a control program that runs on a computer,
The control program controls the plasma processing apparatus so that the plasma oxidation processing method is performed in the processing chamber of the plasma processing apparatus at the time of execution.
The plasma oxidation treatment method includes:
Introducing a processing gas containing an oxygen-containing compound and an inert gas into the processing chamber; introducing a microwave into the processing chamber by a planar antenna having a plurality of holes; generating plasma; and And a plasma oxidation process for oxidizing the surface of the silicon layer,
In the plasma oxidation treatment step, the oxidation rate for the first region having the first conductivity type provided on the surface of the silicon layer is a second conductivity type opposite to the first conductivity type. A first oxidation treatment step for performing an oxidation treatment so as to be larger than an oxidation rate for the second region having the conductivity type;
A second oxidation treatment step for performing an oxidation treatment after the first oxidation treatment step so that an oxidation rate for the first region and an oxidation rate for the second region are approximately the same;
Including a computer-readable storage medium. A processing chamber for processing an object to be processed using plasma;
A planar antenna having a plurality of holes for introducing microwaves into the processing chamber;
A gas supply mechanism for supplying gas into the processing chamber;
An exhaust mechanism for exhausting the processing chamber under reduced pressure;
A first region having a first conductivity type provided on the surface of the silicon layer by introducing a processing gas containing an oxygen-containing compound and an inert gas and a microwave into the processing chamber to generate plasma; A control unit for controlling the second region having a second conductivity type opposite to the first conductivity type to perform a plasma oxidation process for oxidizing each of the second regions .
The plasma oxidation treatment step includes a first oxidation treatment step for performing an oxidation treatment such that an oxidation rate for the first region is higher than an oxidation rate for the second region;
A second oxidation treatment step for performing an oxidation treatment after the first oxidation treatment step so that an oxidation rate for the first region and an oxidation rate for the second region are approximately the same;
The plasma processing apparatus according to claim, comprises a.

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