JP2010238739A - Plasma processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma processing method capable of performing preheating before plasma processing in a short time when performing the plasma processing accompanied by heating of a workpiece. <P>SOLUTION: When a wafer is arranged in a chamber and subjected to the plasma processing while heated, the wafer is preheated (preliminary heating) prior to the processing while irradiated with plasma, and a processing gas is supplied into the chamber after preheating to perform the plasma processing on the wafer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a plasma processing method for performing plasma processing such as nitriding processing or oxidation processing on an object to be processed using plasma, for example, microwave plasma.

  In the manufacture of various semiconductor devices, there are plasma processes performed while heating a wafer such as an oxidation process, a nitriding process, and a film forming process on a semiconductor wafer (hereinafter simply referred to as a wafer) that is a target object.

  For example, as a nitriding process, a nitriding process of a gate oxide film for the purpose of reducing the electrical film thickness of the gate oxide film of a MOS type or MIS type transistor in accordance with the recent demand for miniaturization and high speed of devices. Has attracted attention (for example, Patent Document 1). A process for forming a gate insulating film of a MIS transistor by directly nitriding a silicon substrate is also known (Patent Document 2 etc.).

  As a plasma apparatus for performing such nitriding treatment, a microwave is introduced into the processing chamber by a RLSA (Radial Line Slot Antenna) having a plurality of slots as shown in Patent Document 2 above. An RLSA microwave plasma processing apparatus is known in which microwave plasma is generated by generating plasma and plasma processing is performed on a semiconductor substrate mounted on a mounting table in a chamber. This RLSA microwave plasma processing apparatus can generate plasma with high density and low electron temperature, and can perform processing with low damage and high efficiency.

  By the way, such a nitriding process is performed by heating the susceptor to about 400 to 500 ° C. and placing the wafer thereon, but the purpose is to stabilize the temperature of the wafer and reduce the variation between the wafers in the process. For example, prior to nitriding, the wafer is preheated by introducing gas into the chamber by heat from the susceptor or in addition to heat from the susceptor. By performing preheating, the nitriding rate can be improved.

US Pat. No. 6,660,659 JP 2000-294550 A

  However, when preheating is performed by heat from the susceptor, the chamber is in a reduced pressure state, so that it takes a long time to raise the temperature of the room temperature wafer to stabilize it at a predetermined temperature and to stabilize the condition in the chamber. Will reduce the throughput of processing. Even if gas is introduced into the chamber, the effect of improving the heat transfer is limited, and the preheating time is long.

  Further, not only nitriding but also plasma oxidation used for forming a gate oxide film requires a relatively high temperature of 300 to 800 ° C., and preheating is effective, but there is still a problem with throughput. Arise.

The present invention has been made in view of such circumstances, and provides a plasma processing method capable of performing preheating before processing in a short time when performing plasma processing with heating of an object to be processed. Objective.

In order to solve the above problems, according to a first aspect of the present invention, there is provided a plasma processing method in which a target object is disposed in a processing container, and the target object is subjected to plasma processing while heating the target object. Prior to processing, a process of preheating the target object while irradiating the target object with plasma, and a process of supplying a processing gas into the processing container after the preheating and performing a plasma process on the target object. A plasma processing method is provided.

  In the first aspect, a plasma nitriding process can be used as the plasma process. Further, plasma oxidation treatment can be used as the plasma treatment.

  The plasma treatment can be performed by microwave plasma. In this case, the microwave plasma is generated by a microwave generation mechanism having a planar antenna having a plurality of slots and a microwave introducing means for guiding the microwave into the processing container via the planar antenna. Can be used.

  In the first aspect, the preliminary heating step preferably includes a step of setting the pressure in the processing container to 99 to 1000 Pa.

  Further, prior to the preliminary heating step, the step of gradually increasing the pressure in the processing vessel toward the first pressure to shift to the plasma ignition condition, and the first step when the first pressure is reached. It is preferable to perform a step of igniting plasma with a microwave output of 1, and a step of adjusting the pressure from the first pressure to the second pressure after ignition. In this case, it is preferable that the preheating step is performed by the second pressure. In this case, the plasma processing is performed by changing the first microwave output to the third microwave output and changing the pressure in the processing container from the second pressure to the third pressure. Are preferred.

  According to a second aspect of the present invention, there is provided a storage medium that operates on a computer and stores a program for controlling a plasma processing apparatus. The program is executed by the plasma processing method according to the first aspect at the time of execution. As described above, the present invention provides a storage medium that causes a computer to control the plasma processing apparatus.

  According to the present invention, the object to be processed is preheated while irradiating the object to be processed with plasma prior to the processing, so that the preheating can be performed quickly and the throughput of the process can be increased.

It is sectional drawing which shows the plasma processing apparatus for enforcing the plasma processing method concerning one Embodiment of this invention. It is drawing which shows the structure of the planar antenna member of the plasma processing apparatus of FIG. It is a block diagram which shows schematic structure of the control part of the apparatus of FIG. It is a flowchart which shows the plasma processing method which concerns on one Embodiment of this invention. It is a timing chart which shows the processing sequence of the plasma processing method which concerns on one Embodiment of this invention. It is a figure which shows the wafer temperature curve at the time of changing the pressure in a chamber in the case of preheating. It is a figure which shows a wafer temperature curve at the time of irradiating a plasma to a wafer in the case of preheating. It is a figure which shows the relationship between preheating time and nitrogen concentration at the time of performing a plasma nitriding process after performing preheating, respectively on three conditions, standard conditions, high pressure conditions, and high pressure + plasma irradiation conditions. It is a figure which shows the average value of the nitrogen concentration in the 1st-25th wafer at the time of performing a plasma nitriding process after performing preheating each on standard conditions and high pressure + plasma irradiation conditions. It is a figure which shows the dispersion | variation ((sigma) / Avg.) Of the nitrogen concentration in the 1st-25th wafer at the time of performing a plasma nitridation process after performing preheating each on standard conditions and high pressure + plasma irradiation conditions. It is a figure which shows the number of the particle | grains at the time of performing the process which performs a nitriding process after the preheating of high pressure + plasma irradiation conditions with respect to several wafers continuously. It is the figure which showed the relationship between a pressure and nitrogen concentration for every preheating time when Ar plasma power in the case of preheating is fixed to 2000W. It is the figure which showed the relationship between plasma power and nitrogen concentration at the time of fixing the pressure in the case of preheating to 126.7 Pa (0.95 Torr) for every preheating time. It is the figure which showed the relationship between preheating time and nitrogen concentration for every pressure when Ar plasma power in the case of preheating is fixed to 2000W.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing a plasma processing apparatus for performing a plasma processing method according to an embodiment of the present invention. This plasma processing apparatus introduces microwaves into a processing chamber using a planar antenna having a plurality of slots, particularly an RLSA (Radial Line Slot Antenna) to generate plasma, thereby achieving high density and low electron density. It is configured as an RLSA microwave plasma processing apparatus that can generate microwave plasma at a temperature, and performs plasma nitriding.

  The plasma processing apparatus 100 has a substantially cylindrical chamber 1 that is airtight and grounded. A circular opening 10 is formed at a substantially central portion of the bottom wall 1a of the chamber 1, and an exhaust chamber 11 that communicates with the opening 10 and protrudes downward is provided on the bottom wall 1a. .

  In the chamber 1, there is provided a susceptor (mounting table) 2 made of ceramics such as AlN for horizontally supporting a wafer W as a substrate to be processed. The susceptor 2 is supported by a support member 3 made of ceramic such as cylindrical AlN that extends upward from the center of the bottom of the exhaust chamber 11. A guide ring 4 for guiding the wafer W is provided on the outer edge of the susceptor 2. Further, a resistance heating type heater 5 is embedded in the susceptor 2, and the heater 5 is supplied with power from a heater power source 5 a to heat the susceptor 2, and the wafer W as an object to be processed is heated by the heat. To do. In addition, a thermocouple 6 is inserted into the mounting table 2, and the heating temperature of the wafer W can be controlled in a range from room temperature to 900 ° C., for example. A cylindrical liner 7 made of quartz with few impurities is provided on the inner periphery of the chamber 1 to prevent metal contamination by the material constituting the chamber. A baffle plate 8 having a plurality of holes 8 a for uniformly exhausting the inside of the chamber 1 is provided in an annular shape on the outer peripheral side of the mounting table 2, and the baffle plate 8 is supported by a plurality of support columns 9. ing.

  The susceptor 2 is provided with three (only two are shown) wafer support pins 42 for supporting the wafer W to be moved up and down so as to protrude and retract with respect to the surface of the susceptor 2. It is fixed to the plate 43. The wafer support pins 42 are moved up and down via a support plate 43 by a drive mechanism 44 such as an air cylinder.

An annular gas introduction member 15 is provided on the side wall of the chamber 1, and a gas supply system 16 is connected to the gas introduction member 15. The gas introduction member may be arranged in a shower shape. The gas supply system 16 includes, for example, an Ar gas supply source 17 and an N ₂ gas supply source 18, and these gases reach the gas introduction member 15 through the gas lines 20, respectively. It is introduced into the chamber 1. Each of the gas lines 20 is provided with a mass flow controller 21 and front and rear opening / closing valves 22. In place of the N ₂ gas, for example, NH ₃ gas or a mixed gas of N ₂ and H ₂ can be used. Further, as will be described later, other rare gases such as Kr, He, Ne, and Xe may be used instead of the Ar gas, or the rare gas may not be contained.

  An exhaust pipe 23 is connected to the side surface of the exhaust chamber 11, and an exhaust device 24 including a high-speed vacuum pump is connected to the exhaust pipe 23. Then, by operating the exhaust device 24, the gas in the chamber 1 is uniformly discharged into the space 11 a of the exhaust chamber 11 and exhausted through the exhaust pipe 23. 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.

  On the side wall of the chamber 1, there are a loading / unloading port 25 for loading / unloading the wafer W to / from a transfer chamber (not shown) adjacent to the plasma processing apparatus 100, and a gate valve 26 for opening / closing the loading / unloading port 25. Is provided.

The upper portion of the chamber 1 is an opening, and a ring-shaped lid 27 is provided along the peripheral edge of the opening. The lid 27 is made of an insulating material such as quartz, Al ₂ O ₃ , AlN, or other ceramics, and a microwave transmitting plate 28 that transmits microwaves is airtightly provided through a seal member 29. Therefore, the inside of the chamber 1 is kept airtight.

  A disk-shaped planar antenna 31 is provided above the microwave transmission plate 28 so as to face the susceptor 2. The planar antenna 31 is locked to the upper end of the side wall of the chamber 1. The planar antenna 31 has a slightly larger diameter than the microwave transmitting plate, and is a disk made of, for example, copper, aluminum, or Ni whose surface is silver or gold plated, and a large number of microwave radiation holes 32 (slots) are predetermined. It is the structure formed by penetrating in this pattern.

  As shown in FIG. 2, for example, the microwave radiation holes 32 form a pair, and the pair of microwave radiation holes 32 are typically arranged in a “T” shape. A plurality of pairs are arranged concentrically. The lengths and arrangement intervals of the slots 32 are determined according to the wavelength (λg) of the microwave. For example, the intervals of the microwave radiation holes 32 are arranged to be λg / 4 to λg. In FIG. 2, the interval between adjacent slots 32 formed concentrically is indicated by Δr. Further, the slot 32 may have another shape such as a circular shape or an arc shape. Furthermore, the arrangement form of the slots 32 is not particularly limited, and the slots 32 may be arranged concentrically, for example, spirally or radially.

  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 can be formed of, for example, quartz, ceramics, a resin such as fluorine resin or polyimide. 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 microwave transmission plate 28 and the slow wave member 33 and the planar antenna 31 are arranged in close contact with each other, but may be separated from each other.

  A cover member 34 having a waveguide function made of a metal material such as aluminum, stainless steel, or copper is provided on the upper surface of the chamber 1 so as to cover the planar antenna 31 and the slow wave material 33. The upper surface of the chamber 1 and the cover member 34 are sealed by a seal member 35. A cooling water flow path 34a is formed in the cover member 34, and the cover member 34, the slow wave material 33, the planar antenna 31, and the microwave transmission plate 28 are cooled by allowing the cooling water to flow therethrough, These breakages and deformations are prevented. The cover member 34 is grounded.

  An opening 36 is formed at the center of the upper wall of the cover member 34, and a waveguide 37 is connected to the opening 36. A microwave generator 39 is connected to the end of the waveguide 37 via a matching circuit 38. Thereby, for example, a microwave having a frequency of 2.45 GHz generated by the microwave generator 39 is propagated to the planar antenna 31 through the waveguide 37. Note that the microwave frequency may be 8.35 GHz, 1.98 GHz, or the like.

  The waveguide 37 is connected to a coaxial waveguide 37a having a circular cross section extending upward from the opening 36 of the cover member 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 between the rectangular waveguide 37b and the coaxial waveguide 37a 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 in the center of the coaxial waveguide 37 a, and a lower end portion of the inner conductor 41 is connected and fixed to the center of the planar antenna 31. Thereby, the microwave is uniformly and efficiently propagated to the planar antenna 31 via the inner conductor 41 of the coaxial waveguide 37a.

  Each component of the microwave plasma processing apparatus 100 is connected to and controlled by the control unit 50. As shown in FIG. 3, the control unit 50 includes a process controller 51 including a microprocessor, and a user interface 52 and a storage unit 53 connected to the process controller.

  In the plasma processing apparatus 100, the process controller 51 is configured so that each component, for example, the heater power supply 5a, the process conditions such as temperature, pressure, gas flow rate, microwave output, high frequency power for bias application, and the like become desired. The gas supply system 16, the exhaust device 24, the microwave generator 39, and the like are controlled.

  The user interface 52 includes a keyboard on which an operator inputs commands 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. In addition, the storage unit 53 executes processing on each component of the plasma processing apparatus 100 according to a control program for realizing various processes executed by the plasma processing apparatus 100 under the control of the process controller 51 and processing conditions. A program for processing, that is, a processing recipe is stored.

  Control programs and processing recipes are stored in a storage medium (not shown) in the storage unit 53. The storage medium may be a hard disk or semiconductor memory, or may be portable such as a CDROM, DVD, flash memory or the like. Further, instead of storing in a storage medium, a processing recipe or the like may be appropriately transmitted from another device, for example, via a dedicated line.

  Then, if necessary, an arbitrary processing recipe is called from the storage unit 53 by an instruction from the user interface 52 and is executed by the process controller 51, so that the plasma processing apparatus 100 can control the process under the control of the process controller 51. Desired processing is performed.

  In the RLSA type plasma processing apparatus 100 configured as described above, the nitriding process is performed on the wafer W by the following procedure. The procedure at this time is shown in the flowchart of FIG. 4 and the timing chart of FIG.

  First, in a state where the temperature of the susceptor 2 is heated to, for example, 250 to 800 ° C. by the heater 5, the gate valve 26 is opened, the wafer W is loaded into the chamber 1 from the loading / unloading port 25, and placed on the susceptor 2 (step). 1).

Then, Ar gas is introduced at a flow rate of 100 to 5000 mL / min (sccm) (step 2), and the pressure in the chamber 1 is set to 99 to 200 Pa (0.75 to 1.50 Torr), for example, 126.7 Pa (0. 95 Torr) to shift to ignition conditions (Step 3), and then microwaves are introduced to ignite plasma (Step 4). Subsequently, the pressure in the chamber 1 is 99 to 1000 Pa (0.75 to 7.5 Torr). ), Preferably 126.7 Pa to 400 Pa or less (0.95 Torr to 3 Torr or less), for example, increased to 186.7 Pa (1.4 Torr) (Step 5), and the wafer W is subjected to preheating (preheating) by plasma. Perform (plasma preheating; step 6). This plasma preheating is performed for a predetermined time until the wafer temperature is stabilized. The microwave power in the plasma preheating in step 6 is preferably 1000 to 3000 W, and the power density is preferably 0.5 to 2.0 W / cm ² . In addition, the period of the pressure increase in step 5 is also included in the plasma preheating period. Further, the wafer W is also preheated during the step 3 in which Ar gas is introduced to shift to the ignition condition.

After completion of the plasma preheating in step 6, pressure adjustment is performed to reduce the pressure in the chamber 1 to 6.65 to 300 Pa (0.05 to 2.25 Torr) (step 7), and the microwave output is adjusted to adjust the chamber 1 N ₂ gas is introduced into the wafer (step 8), and a plasma nitriding process is performed on the wafer W (step 9).

  After the nitriding process is finished, the plasma is turned off, and then the nitrogen gas is stopped, and the purge gas is supplied into the chamber 1 from a purge gas supply system (not shown) to purge the chamber 1 (step 10), and then the gate valve 26 is opened and the wafer W is unloaded from the loading / unloading port 25 (step 11). The purging may be performed using Ar gas from the Ar gas supply source 17.

  In the above process, the plasma ignition in step 4 is performed and then the preheat pressure is increased. However, the pressure increase in step 5 can be omitted by performing the plasma ignition at the preheat pressure.

  Conventionally, pre-heating is performed in a state where the pressure in the chamber 1 is 99 to 200 Pa (0.75 to 1.50 Torr), for example, 126.7 Pa (0.95 Torr), and plasma ignition is performed at the pressure to perform nitriding treatment. Had migrated to. However, in the preheating under such conditions, it takes time until the temperature stabilizes. For example, in the case of 126.7 Pa (0.95 Torr), it is about 70 sec, and the nitriding throughput is not sufficient.

  Therefore, in this embodiment, preheating is performed in a state where plasma is generated. Thereby, heating efficiency can be improved by the effect of the heating effect by plasma, and preheating time can be shortened.

  In this case, it is preferable to increase the pressure in the chamber 1 as much as possible so as not to affect the apparatus and processing. Thereby, the heating efficiency can be increased and the preheating time can be further shortened by both the effect of heating by plasma and the effect of increasing the pressure in the chamber 1 to improve heat transfer.

  As described above, the reason why the heating efficiency is enhanced by both the plasma generation and the pressure rise is as follows. That is, the pressure in the chamber 1 naturally has an upper limit due to restrictions on the apparatus and processing, and it may be difficult to obtain an effect sufficient to satisfy the required throughput with only the pressure in the chamber 1. . On the other hand, if it is attempted to satisfy the throughput required only by plasma, the wafer W may be damaged as the microwave output increases. On the other hand, by using these together, it is possible to improve the throughput by reducing the preheating time by increasing the preheating efficiency while preventing such inconvenience.

In the present embodiment, plasma ignition during preheating is performed by turning on the microwave generator 39 and guiding the generated microwaves to the waveguide 37 through the matching circuit 38, the rectangular waveguide 37 b, and mode conversion. The wafer 40 in the chamber 1 through the microwave radiation hole 32 of the planar antenna 31 from the microwave radiation hole 32 of the planar antenna 31 through the container 40 and the coaxial waveguide 37a. This is performed by irradiating the space above W and exciting the Ar gas supplied into the chamber 1. At this time, the microwave propagates in the TE mode in the rectangular waveguide 37b, and the microwave in the TE mode is converted into the TEM mode by the mode converter 40, and the planar waveguide 31 passes through the coaxial waveguide 37a. It is propagated towards. An electromagnetic field is formed in the chamber 1 by the microwave radiated from the planar antenna 31 to the chamber 1 through the microwave transmission plate 28, and Ar gas is excited to be turned into plasma. At this time, from the viewpoint of not damaging the wafer, the microwave power is preferably 1000 to 3000 W and the power density is preferably 0.5 to 2.0 W / cm ² as described above.

The conditions during the nitriding process, Ar gas flow rate 100~5000mL / min (sccm), set the _{N 2} gas flow rate 10~500mL / min (sccm), the pressure in the chamber 6.65～300Pa ( 0.05 to 2.25 Torr), and the temperature of the wafer W is set to room temperature to about 900 ° C.

Further, during the nitriding process, the plasma generated during the preheating is maintained, and at that time, the microwave power is adjusted so that the conditions are suitable for the nitriding process. Preferably, the microwave power is adjusted to 1000 to 3000 W, and the power density is adjusted to about 0.5 to 2.0 W / cm ² .

The microwave plasma has a high density of about 1 × 10 ^{10 to} 5 × 10 ¹² / cm ³ by being radiated from a large number of microwave radiation holes 32 of the planar antenna 31, and is substantially in the vicinity of the wafer W. The plasma becomes a low electron temperature plasma of 1.5 eV or less, further about 1.0 eV or less, and a treatment with little damage to the base mainly composed of radicals can be realized.

  By using microwave plasma having such characteristics, damage to the wafer can be extremely reduced during preheating and nitriding.

  The plasma nitriding treatment of this embodiment can be applied to a process of nitriding the surface of a silicon oxide film or a ferroelectric oxide film, or a direct nitriding process of a silicon substrate. A typical example is the nitriding treatment of the gate insulating film of a MOS type or MIS transistor, and the latter is a nitriding treatment for forming a gate insulating film made of silicon nitride of the MIS transistor. It can also be applied to the surface nitriding treatment of a polysilicon film used for a DRAM capacitor or the like.

Next, test results for confirming the effects of the present invention will be described.
First, the effect of pressure during preheating was confirmed. The set temperature of the susceptor is 400 ° C., a TC wafer (temperature measurement wafer with a thermocouple attached) is loaded into the chamber and set on the susceptor, and Ar gas is 2000 mL / min (sccm) in the chamber. While flowing at a flow rate, the internal pressure of the chamber was 126.7 Pa (0.95 Torr), and the pressures were increased to 186.7 Pa (1.4 Torr) and 333.2 Pa (2.5 Torr). We adjusted the pressures of various types and compared the temperature rise profiles of the wafers. The TC wafer was not brought into contact with the susceptor by first pin-up, the wafer start temperature was set to 270 ° C., and then the TC wafer was placed on the susceptor and the temperature rise profiles immediately thereafter were compared.

  The result is shown in FIG. From this figure, as a result of comparing the time when the temperature is equivalent to 70 sec at 126.7 Pa (0.95 Torr), which is the conventional standard condition, 45 sec at 336.7 Pa (1.4 Torr) is obtained at 186.7 Pa (1.4 Torr). ) Was 30 sec, and the effect of increasing the temperature rise rate by increasing the pressure was confirmed. However, 333.2 Pa (2.5 Torr) cannot be achieved depending on the apparatus, and there is a concern about the stability of the process. Therefore, the pressure in the chamber is preferably about 186.7 Pa (1.4 Torr). It is.

  Next, the influence of plasma irradiation during preheating was confirmed. Here, as in the above test, the set temperature of the susceptor was set to 400 ° C., a TC wafer was loaded into the chamber and set on the susceptor, and Ar gas was flowed into the chamber at a flow rate of 2000 mL / min (sccm). The pressure is adjusted to 126.7 Pa (0.95 Torr) in the first 5 seconds, the microwave is incident in the next 5 seconds to ignite the plasma, and then the pressure is adjusted to 186.7 Pa (1.4 Torr) while maintaining the plasma. Pressure (plasma preheating) and a temperature rise test was conducted. The microwave output was 1300 W and 2000 W. For comparison, a temperature rise test was performed in the same manner with respect to a sample adjusted to 186.7 Pa (1.4 Torr) without being irradiated with plasma. In this test as well, the TC wafer is not brought into contact with the susceptor by being pinned up first, the wafer start temperature is adjusted to 270 ° C., and then the TC wafer is pinned down and the TC wafer is placed on the susceptor. Compared.

  The result is shown in FIG. As shown in this figure, when plasma irradiation is applied, it takes about 15 to 17 seconds to reach the same temperature as in the case of 45 seconds without plasma, and the effect of increasing the temperature rise rate by plasma irradiation was confirmed. . Note that the preheating time in the case of plasma irradiation is obtained by adding the time of the pressure adjustment stage before plasma ignition and the plasma preheating time.

  Next, the wafer on which the oxide film was formed was preheated under three types of preheat conditions, and then subjected to nitriding treatment to confirm the dependency of nitrogen concentration on the preheat conditions. Here, as preheating conditions, (1) pressure: 126.7 Pa (0.95 Torr), no plasma irradiation (reference condition), (2) pressure: 186.7 Pa (1.4 Torr), no plasma irradiation (high pressure condition) ), (3) Pressure: 186.7 Pa (1.4 Torr), plasma irradiation with microwaves 2000 W (high pressure + plasma irradiation conditions) was used.

Specifically, under the standard condition (1), the susceptor temperature is 400 ° C., Ar gas is supplied at 2000 mL / min (sccm), the pressure is adjusted to 126.7 Pa (0.95 Torr), and the wafer is removed. After placing on a susceptor and performing preheating for 30 sec, 50 sec, and 70 sec, while maintaining the pressure, a 2000 W microwave was incident for 5 sec to ignite plasma, and in 5 sec, the pressure of nitriding treatment was 40 Pa (0.3 Torr). After that, with a microwave power of 1800 W and maintaining the plasma, Ar gas was flowed at a flow rate of 1000 mL / min (sccm) and N ₂ gas was flowed at a flow rate of 200 mL / min (sccm) to perform nitriding treatment for 60 seconds. It was.

Under the high pressure condition (2), the susceptor temperature is 400 ° C., Ar gas is supplied at 2000 mL / min (sccm), the pressure is adjusted to 186.7 Pa (1.4 Torr), and the wafer is mounted on the susceptor. After preheating for 25 sec, 45 sec, and 65 sec, the pressure is reduced to 126.7 Pa (0.95 Torr) in 5 sec, the total preheat time is set to 30 sec, 50 sec, and 70 sec, and then a 2000 W microwave is applied in 5 sec. Incidence is ignited and plasma is ignited. Subsequently, the pressure is reduced to 40 Pa (0.3 Torr) which is the nitriding pressure in 5 seconds, and then Ar gas is 1000 mL / min (sccm) while maintaining the plasma by setting the microwave power to 1800 W. , N ₂ gas is flowed at a flow rate of 200 mL / min (sccm) For 60 seconds.

Furthermore, under the high pressure + plasma irradiation condition of (3), the susceptor temperature was set to 400 ° C., and the pressure was adjusted to 126.7 Pa (0.95 Torr) in 5 sec while flowing Ar gas at 2000 mL / min (sccm), and then 5 sec. The plasma was ignited by injecting a microwave of 2000 W, and then the pressure was increased to 186.7 Pa (1.4 Torr) and preheating (plasma preheating) was performed for 25 sec, 45 sec, and 65 sec under plasma irradiation, and the total preheating time was set. 30 sec, 50 sec, and 70 sec. Subsequently, the pressure is reduced to 40 Pa (0.3 Torr), which is the pressure of nitriding in 5 sec, and then Ar gas is 1000 mL / min (sccm) while maintaining the plasma with a microwave power of 1800 W, N ₂ gas at 200 mL / min Nitriding treatment was performed for 60 seconds by flowing at a flow rate of (sccm).

  The result is shown in FIG. FIG. 8 is a graph showing the relationship between the horizontal axis representing the preheat time and the vertical axis representing the nitrogen concentration normalized with the film thickness being 1 when preheating is performed under standard conditions at 70 sec. From this figure, when the standard preheating conditions are 126.7 Pa (0.95 Torr) and 70 sec, it is confirmed that the same nitrogen concentration can be obtained with the preheating of about 50 sec under the high pressure condition (2). It was confirmed that the same nitrogen concentration can be obtained by preheating for 30 sec or less under the high pressure + plasma irradiation condition of (3). From this, it was confirmed that a large preheating time can be shortened under a high pressure + plasma irradiation condition, and the throughput is increased by about 25%.

  Next, when the nitriding treatment is performed after 70 sec preheating is performed under the standard condition (1) above, and in the case of performing the 30 sec preheating under the high pressure + plasma irradiation condition (3) above in the wafer surface of the nitrogen concentration And the variation of nitrogen concentration between wafer surfaces was grasped. The average value (Avg .; arbitrary scale) of the nitrogen concentration in each wafer at that time is shown in FIG. 9, and the in-plane variation (σ / Avg.) Of the nitrogen concentration is shown in FIG.

Nitriding conditions are nitriding temperature: 400 ° C., pressure: 40 Pa (0.3 Torr), Ar gas flow rate: 1000 mL / min (sccm), N ₂ gas flow rate: 200 mL / min (sccm), microwave power: 1800 W, nitriding treatment Time: 60 sec.

  Regarding the variation of the nitrogen concentration in the wafer surface, as shown in FIG. 9, the high pressure + plasma irradiation condition in (3) was equivalent to the standard condition in (1). As for the distance between the wafer surfaces, σ / Avg. Is 0.50, range (R) is 0.25, R / 2Avg. 1.08, and under the high pressure + plasma irradiation condition of (3), σ / Avg. Is 0.72, range (R) is 0.32, R / 2 Avg. Was 1.38, and the high pressure + plasma irradiation condition in (3) was equivalent to the standard condition in (1).

  Next, the influence of preheating particles under the condition of (3) high pressure + plasma irradiation was grasped. Here, after preheating under the condition (3), a nitriding process under the above condition was continuously performed on a plurality of wafers, and the number of particles of> 0.16 μm was grasped. The result is shown in FIG. As shown in this figure, the number of particles was less than the specification up to 12,000 for both lot A and lot B.

Next, the wafer on which the oxide film was formed was subjected to preheating while changing the pressure, Ar plasma power, and time, and then subjected to nitriding treatment to confirm the dependency of nitrogen concentration on the preheating conditions. Here, the susceptor temperature is set to 400 ° C., the pressure is set to three levels of 45 Pa (0.34 Torr), 126.7 Pa (0.95 Torr), and 186.7 Pa (1.4 Torr) in preheating, and the Ar plasma power is 1500 W, Three levels of 2000 W and 2500 W were set, and preheating time (transition time to ignition condition + plasma preheating time) was set to three levels of 30 sec, 50 sec, and 70 sec. In the nitriding treatment, the Ar flow rate was 2000 mL / min (sccm), the N ₂ gas flow rate was 40 mL / min (sccm), the susceptor temperature was 400 ° C., and the plasma power was 1500 W.

  FIG. 12 shows the relationship between pressure and nitrogen concentration for each preheating time when the Ar plasma power during preheating is fixed at 2000 W. The nitrogen concentration is a nitrogen concentration normalized with the film thickness when preheating is performed for 70 seconds under the above standard condition as 1. From this figure, it was confirmed that in any preheating time, the nitrogen concentration increased as the pressure during preheating increased.

  FIG. 13 shows the relationship between plasma power and nitrogen concentration for each preheating time when the pressure during preheating is fixed at 126.7 Pa (0.95 Torr). Also in this figure, the nitrogen concentration is a nitrogen concentration normalized by assuming that the film thickness is 1 when preheating is performed for 70 seconds under the above standard conditions. From this figure, it was confirmed that although there was a tendency for the nitrogen concentration to increase as the plasma power increased, no significant change was observed.

  FIG. 14 shows the relationship between preheating time and nitrogen concentration for each pressure when the Ar plasma power during preheating is fixed at 2000 W. Note that the nitrogen concentration is a nitrogen concentration normalized with the film thickness when preheating is performed for 70 seconds under the above-mentioned standard conditions as in FIG. From this figure, it was confirmed that the nitrogen concentration increases as the preheating time becomes longer at each pressure.

  Further, from FIGS. 12 and 14, when the pressure is below the standard condition, the nitrogen concentration is lower in the preheating time of 30 sec than in the standard condition of 70 sec even if the plasma irradiation is performed. By performing plasma irradiation at a high pressure of 186.7 Pa (1.4 Torr), it was confirmed that the nitrogen concentration was higher than in the case of 70 sec under the standard conditions even when the preheat time was 30 sec.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the idea of the present invention.
For example, in the above-described embodiment, the microwave plasma nitriding process has been described as an example. However, the plasma process is not limited to the microwave plasma, and may be another plasma, and in particular, a self-generated plasma similar to the microwave plasma. Examples of the above-described inductively coupled plasma, surface wave plasma, surface reflected wave plasma, and magnetron plasma can be given.

Further, the present invention can be applied not only to nitriding treatment but also to plasma treatment performed while heating other substrates, for example, oxidation treatment. The oxidation process can be used for, for example, a process of oxidizing a silicon substrate to form a gate oxide film, and is a process of heating to a relatively high temperature of 300 to 800 ° C. As with the nitriding process, a stable process is performed. Preheating is effective to do. Therefore, by applying the present invention, preheating can be shortened, and the processing throughput can be increased. Further, plasma treatment performed while heating the substrate can be applied to other treatments such as a CVD film formation treatment.

  Furthermore, although the case where the semiconductor wafer is processed as the object to be processed has been described in the above embodiment, it is needless to say that the present invention is not limited to this and can be applied to other objects to be processed such as a glass substrate for FPD.

DESCRIPTION OF SYMBOLS 1; Chamber 2; Susceptor 3; Support member 5; Heater 15; Gas introduction member 16; Gas supply system 24; Exhaust device 28; Microwave transmission plate 31; Planar antenna 32; Microwave radiation hole 37; Coaxial waveguide 37b; Rectangular waveguide 39; Microwave generator 40; Mode converter 50; Control unit 51; Process controller 53; Storage unit 100; Plasma processing apparatus W; Wafer (object to be processed)

Claims (10)

A plasma processing method for disposing a target object in a processing container and applying a plasma process to the target object while heating the target object,
A step of preheating the object to be processed while irradiating the object with plasma prior to the treatment;
And a step of supplying a processing gas into the processing container after the preheating and performing a plasma processing on the object to be processed.   The plasma processing method according to claim 1, wherein the plasma processing is plasma nitriding.   The plasma processing method according to claim 1, wherein the plasma processing is plasma oxidation processing.   The plasma processing method according to any one of claims 1 to 3, wherein the plasma processing is performed by microwave plasma.   The microwave plasma is generated by a microwave generation mechanism having a planar antenna having a plurality of slots and a microwave introducing means for guiding the microwave into the processing container through the planar antenna. The plasma processing method according to claim 4.   The plasma processing method according to claim 1, wherein the preliminary heating step includes a step of setting the pressure in the processing container to 99 to 1000 Pa. Prior to the preheating step,
Gradually increasing the pressure in the processing vessel toward the first pressure to shift to plasma ignition conditions;
Igniting a plasma with a first microwave output when the first pressure is reached;
The plasma processing method according to claim 1, further comprising: adjusting the pressure from the first pressure to the second pressure after ignition.   The plasma processing method according to claim 7, wherein the preliminary heating step is performed by the second pressure.   The plasma processing is performed by changing the first microwave output from the first microwave output to the third microwave output and changing the pressure in the processing container from the second pressure to the third pressure. The plasma processing method according to claim 8.   A storage medium that operates on a computer and stores a program for controlling a plasma processing apparatus, wherein the program performs the plasma processing method according to any one of claims 1 to 9 at the time of execution. And a computer that controls the plasma processing apparatus.

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