JP2010097993A - Plasma treatment method - Google Patents

Abstract

The present invention provides a plasma processing method capable of reducing the amount of initial metal contamination after startup and maintenance of an apparatus without being affected by the environment and cleaning parts.
An initial metal contamination prevention process is provided before a product wafer production process (main process) after a new apparatus start-up process and / or after a maintenance re-operation process. The initial metal contamination prevention process includes a step of performing plasma discharge while supplying a gas containing nitrogen gas to the processing chamber without placing the product wafer on the susceptor provided in the processing chamber, and a product wafer on the susceptor provided in the processing chamber. The step of performing plasma discharge while supplying a gas containing oxygen gas to the processing chamber without mounting is performed, and the nitrogen plasma processing step and the oxygen plasma processing step are repeatedly performed according to the state of initial metal contamination.
[Selection] Figure 2

Description

  The present invention relates to a plasma processing method in which the amount of contamination of a processing substrate is improved.

In general, a substrate processing apparatus for manufacturing a device has a processing chamber for processing a substrate. The substrate is loaded into the processing chamber from the outside of the processing chamber, and the substrate is processed by exhausting while supplying a gas. The substrate is unloaded from the processing chamber to the outside of the processing chamber.
The substrate is preferably not contaminated with metal in the processing chamber. This is because the characteristics of the device deteriorate when the metal is contaminated.

By the way, the initial contamination amount in the processing chamber at the time of commissioning after newly manufacturing the substrate processing apparatus and at the time of restarting after maintenance of the substrate processing apparatus constitutes the environment of the clean room and the processing chamber It depends on how the parts (cleaning parts) are cleaned. For this reason, the cleanliness of the clean room environment is increased, and the cleaning degree of the cleaning parts at the time of maintenance is increased.
Therefore, it was considered that the initial contamination at the time of starting up the apparatus or at the time of restarting after maintenance was not contamination from the clean room environment and cleaned components, but contamination from another route.
For this reason, conventionally, when starting up the equipment or restarting after maintenance, after processing several dummy substrates in the processing chamber (initial contamination prevention processing), the process proceeds to product substrate production processing (main processing). It was.

  However, it has been found that the contamination of the substrate is affected by the environment of the clean room, the method of transporting the cleaning parts after maintenance, and the transport time. For this reason, as in the prior art described above, when only a few dummy substrates are processed at the time of starting up the apparatus or restarting after maintenance, contamination of the substrate cannot be effectively prevented. When the number of sheets is increased, there is a problem that productivity decreases.

Therefore, as a substrate processing method that can reduce the amount of contamination after startup and maintenance without being affected by the environment and cleaning parts, a substrate is not mounted on a substrate mounting table provided in the processing chamber. A substrate processing method has been proposed in which a gas containing nitrogen (N ₂ ) gas is exhausted while being discharged and plasma discharged, and then a substrate is mounted on a substrate mounting table to process a product substrate. For example, see Patent Document 1.
JP 2006-5287 A

  However, the above-described substrate processing method has a problem that initial metal contamination cannot be sufficiently prevented when the apparatus is started up or when it is restarted after maintenance.

  An object of the present invention is to provide a plasma processing method capable of sufficiently preventing initial metal contamination.

Typical means for solving the above-described problems are as follows.
(1) performing plasma discharge while supplying a gas containing nitrogen gas to the processing chamber without mounting the substrate on a mounting table provided in the processing chamber;
Plasma discharge while supplying a gas containing oxygen gas to the processing chamber without placing the substrate on the mounting table provided in the processing chamber;
A plasma processing method comprising:
(2) The plasma processing method according to (1), wherein the plasma discharge step while supplying the oxygen gas and the plasma discharge step while supplying the nitrogen gas are repeatedly performed.

  According to this substrate processing method, it is possible to sufficiently prevent initial metal contamination when the apparatus is started up and when the apparatus is restarted after maintenance.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In the present embodiment, the plasma processing method according to the present invention is a substrate processing apparatus for plasma processing a substrate such as a wafer using a modified magnetron type plasma source that can generate high-density plasma by an electric field and a magnetic field. (Hereinafter referred to as an MMT apparatus).

  In this MMT apparatus, a substrate is installed in a processing chamber that ensures airtightness, a reaction gas is introduced into the processing chamber via a shower plate, the processing chamber is maintained at a certain pressure, and high-frequency power is supplied to the discharge electrode. As a result, an electric field is formed and a magnetron discharge is generated by applying a magnetic field. Since the electrons emitted from the discharge electrode continue to circulate while continuing the cycloid motion while drifting, the lifetime is increased and the ionization generation rate is increased, so that high-density plasma can be generated. In this way, the reaction gas is excited and decomposed to subject the substrate surface to diffusion treatment such as oxidation or nitridation, or to various plasma treatments such as forming a thin film on the substrate surface or etching the substrate surface. be able to. Since this MMT apparatus is excellent in uniformity of oxidation treatment and nitriding treatment, it is used as an oxynitriding apparatus.

FIG. 1 shows a schematic configuration diagram of such an MMT apparatus.
In the MMT apparatus, a processing chamber 201 is formed of a lower container 211 that is a second container and an upper container 210 that is a first container that covers the lower container 211. The upper container 210 is made of dome-shaped aluminum oxide or quartz, and the lower container 211 is made of aluminum.
Further, the susceptor 217, which is a heater-integrated substrate holding means described later, is made of aluminum nitride, ceramics, or quartz, thereby reducing metal contamination taken into the film during processing.

A shower head 236 that forms a buffer chamber 237 that is a gas dispersion space is provided on the upper side of the upper container 210, and a gas introduction port 234 that is an introduction port for introducing gas is provided on the upper wall of the shower head 236. . The lower wall is composed of a shower plate 240 having a gas ejection hole 234a which is an ejection hole for ejecting gas. The gas introduction port 234 is a valve 243a which is an open / close valve by a gas supply pipe 232 which is a supply pipe which supplies gas. The gas is connected to a gas cylinder of a reaction gas 230 (not shown in the figure) via a mass flow controller 241 which is a flow rate control means.
A gas exhaust port 235, which is an exhaust port for exhausting gas, is provided on the side wall of the lower container 211, the reaction gas 230 is supplied from the shower head 236 to the processing chamber 201, and the gas after the substrate processing is supplied from the periphery of the susceptor 217. It is provided to flow toward the bottom of the processing chamber 201. The gas exhaust port 235 is connected to a vacuum pump 246, which is an exhaust device, via an APC 242, which is a pressure regulator, and a valve 243b, which is an on-off valve, by a gas exhaust pipe 231 which is an exhaust pipe for exhausting gas.
In addition to the gas supply pipe 232 for supplying the reaction gas 230, the plasma processing furnace is provided with a gas supply pipe (gas line) for supplying oxygen gas (O ₂ ) and nitrogen (N ₂ ) gas.

  The discharge means for exciting the supplied reaction gas 230 has a cylindrical cross section, and a cylindrical electrode 215 that is preferably a cylindrical first electrode is provided. The cylindrical electrode 215 is installed on the outer periphery of the processing chamber 201 and surrounds the plasma generation region 224 in the processing chamber 201. A high frequency power supply 273 that applies high frequency power is connected to the cylindrical electrode 215 via a matching unit 272 that performs impedance matching.

  Further, the cross section is cylindrical, and preferably the cylindrical magnetic field forming means 216 is made of, for example, a cylindrical permanent magnet. The magnetic field forming means 216 forms magnetic lines of force in the cylindrical axis direction along the inner peripheral surface of the cylindrical electrode 215.

  A susceptor 217 is disposed in the center of the bottom side of the processing chamber 201 as a substrate holding means for holding the wafer 200 as a substrate. The susceptor 217 can heat the wafer 200. The susceptor 217 is made of, for example, aluminum nitride, and a heater (not shown) as a heating unit is integrally embedded therein. The heater can heat the wafer 200 to about 500 ° C. by applying high-frequency power.

  The susceptor 217 is also equipped with a second electrode that is an electrode for varying the impedance, and the second electrode is grounded via the impedance varying mechanism 274. The impedance variable mechanism 274 is composed of a coil and a variable capacitor, and can control the potential of the wafer 200 via the electrode and the susceptor 217 by controlling the number of coil patterns and the capacitance value of the variable capacitor.

  A processing furnace 202 for processing the wafer 200 by magnetron discharge with a magnetron type plasma source includes a processing chamber 201, a susceptor 217, a cylindrical electrode 215, a magnetic field forming means 216, a shower head 236, and an exhaust port 235. The wafer 200 can be subjected to plasma processing in the processing chamber 201.

  Around the cylindrical electrode 215 and the magnetic field forming means 216, an electric field and a magnetic field formed by the cylindrical electrode 215 and the magnetic field forming means 216 are applied so as not to adversely affect the external environment and other processing furnaces. A shielding plate 223 that effectively shields the magnetic field is provided.

The susceptor 217 is insulated from the lower container 211 and is provided with a susceptor elevating mechanism 268 that is an elevating means for elevating and lowering the susceptor 217. The susceptor 217 has a through-hole 217a, and at the bottom of the lower container 211, wafer push-up pins 266 that are substrate push-up means for pushing up the wafer 200 are provided in at least three places.
Then, when the susceptor 217 is lowered by the susceptor elevating mechanism 268, the through hole 217 a and the wafer up pin are arranged so that the wafer push-up pin 266 penetrates the through-hole 217 a without contacting the susceptor 217. 266 is provided.

  Further, a gate valve 244 serving as a gate valve is provided on the side wall of the lower container 211. When the gate valve 244 is open, the wafer 200 is loaded into or unloaded from the processing chamber 201 by a transfer means (not shown), and when it is closed, the processing is performed. The chamber 201 can be closed airtight.

  The controller 121 as a control means includes a high-frequency power source 273, a matching unit 272, a valve 243a, a mass flow controller 241, an APC 242, a valve 243b, a vacuum pump 246, a susceptor lifting mechanism 268, a gate valve 244, and a heater embedded in the susceptor. It is connected to a high-frequency power source that applies electric power, and each is controlled.

  A method for performing a predetermined plasma process on the surface of the wafer 200 or the surface of the base film formed on the wafer 200 using the MMT apparatus having the above configuration will be described.

The wafer 200 is loaded into the processing chamber 201 by a transfer means (not shown) that transfers the wafer from the outside (clean room) of the processing chamber 201 constituting the processing furnace 202, and is transferred onto the susceptor 217. The details of this transport operation are as follows.
First, the susceptor 217 is in a lowered state, and the tip of the wafer push-up pin 266 passes through the through-hole 217a of the susceptor 217 and protrudes by a predetermined height from the surface of the susceptor 217. The gate valve 244 provided in the container 211 is opened, and the wafer 200 is placed on the tip of the wafer push-up pin by a transfer means (not shown). When the transfer means retreats out of the processing chamber 201, the gate valve 244 is closed, and when the susceptor 217 is raised by the susceptor lifting mechanism 268, the wafer 200 can be placed on the upper surface of the susceptor 217, and further up to a position where the wafer 200 is processed. To rise.

  The heater embedded in the susceptor 217 is preheated, and heats the loaded wafer 200 to a wafer processing temperature within a range of room temperature to 500 ° C. The pressure of the processing chamber 201 is maintained within a range of 0.1 to 100 Pa using the vacuum pump 246 and the APC 242.

When the wafer 200 is heated to the processing temperature, the reaction gas is directed from the gas inlet 234 to the upper surface (processing surface) of the wafer 200 disposed in the processing chamber 201 via the gas ejection holes 234a of the shower plate 240. To introduce.
At the same time, high frequency power is applied to the cylindrical electrode 215 from the high frequency power supply 273 via the matching unit 272. At this time, the impedance variable mechanism 274 is controlled in advance to a desired impedance value.

  Magnetron discharge is generated under the influence of the magnetic field of the magnetic field forming means 216, and charges are trapped in the upper space of the wafer 200 to generate high-density plasma in the plasma generation region 224. Then, the surface of the wafer 200 on the susceptor 217 is subjected to plasma processing by the generated high density plasma. The wafer 200 that has been subjected to the surface treatment is transferred to a clean room outside the processing chamber 201 by a transfer procedure (not shown) in the reverse order of the wafer loading.

  The controller 121 turns on / off the power of the high-frequency power supply 273, adjusts the matching unit 272, opens / closes the valve 243a, the flow rate of the mass flow controller 241, the valve opening of the APC 242, opens / closes the valve 243b, starts / stops the vacuum pump 246, The susceptor elevating mechanism 268 is controlled to be moved up and down, the gate valve 244 is opened and closed, and power ON / OFF to a high frequency power source that applies high frequency power to a heater embedded in the susceptor is controlled.

  As described above, in the MMT apparatus, when a new apparatus is started up or restarted after maintenance, only a few dummy substrates or the like are processed in the processing chamber. Even if the environment is highly cleaned and the cleaning parts are kept highly clean, if the wafer is plasma-oxidized or plasma-nitrided, the plasma-treated wafer may be contaminated with metal. This is presumed to be caused by being influenced by the environment of the clean room and the method and time of carrying the cleaning parts after maintenance.

Therefore, in the present embodiment, as shown in FIG. 2, the initial metal before the product wafer production process (main process) process P3 after the new apparatus startup process P1 and / or the post-maintenance restart process P2. The contamination prevention process P4 was provided.
In the initial metal contamination prevention process P4, plasma discharge is performed while supplying a gas containing nitrogen gas to the processing chamber 201 without placing the wafer (hereinafter referred to as a product wafer) 200 on the susceptor 217 provided in the processing chamber 201. Step (referred to as a nitrogen plasma treatment step) S1 and a step (oxygen discharge) while supplying a gas containing oxygen gas to the processing chamber 201 without placing the product wafer 200 on the susceptor 217 provided in the processing chamber 201. S2) (referred to as plasma processing step).
The nitrogen plasma processing step S1 and the oxygen plasma processing step S2 are repeatedly performed according to the state of initial metal contamination.

  The fact that the initial metal contamination prevention process P4 before the product wafer production process (main process) process P3 after the new apparatus startup process P1 and / or the post-maintenance restart process P2 reduces the initial metal contamination amount of the wafer. The experiment to evaluate was performed using the MMT apparatus.

First, in order to investigate the model of the initial metal contamination occurrence, the metal contamination characteristics in the nitrogen plasma treatment step were confirmed. FIG. 3 is a graph showing this characteristic.
As shown in FIG. 3, sodium (Na) contamination occurs only when RF is turned on and off when a high-frequency power supply (hereinafter referred to as RF) is turned on and off. Based on this fact, it is presumed that sodium existing on the surface of quartz (susceptor, heater, etc.) is scattered in the processing chamber by plasma.
As shown in FIG. 4, the metal contamination can be reduced only slightly when the RF on time is long. From this fact, it is presumed that sodium scattered by the plasma is exhausted by the pressure control gas.
As shown in FIG. 5, as a result of confirming the temperature dependence, the higher the temperature, the more metal contamination. From this fact, it is estimated that sodium is also precipitated from the quartz.
It can be seen that sodium can be positively precipitated by raising the heater temperature.

In order to positively discharge the separated sodium, an oxygen plasma treatment step was performed in which the gas species was changed to oxygen gas, and metal contamination was measured. FIG. 6 shows the result.
According to FIG. 6, it was found that sodium can be efficiently removed by performing the oxygen plasma treatment step.
From the above results, it was verified that initial metal contamination can be efficiently reduced by repeatedly performing the nitrogen plasma treatment step S1 and the oxygen plasma treatment step S2.

The mechanism (principle) for reducing the initial metal contamination by repeatedly performing the nitrogen plasma treatment step S1 and the oxygen plasma treatment step S2 will be described with reference to FIG.
As shown in FIG. 7A, in the nitrogen plasma treatment step S1, sodium in the quartz is precipitated on the quartz surface by separating the sodium on the quartz surface into the plasma. The precipitated sodium is separated into the plasma by nitrogen plasma treatment. Dissociates sodium into the plasma efficiently.
As shown in FIG. 7B, the detached sodium is efficiently discharged as an oxide by oxidative coupling with oxygen plasma in the oxygen plasma treatment step S2.

  As described above, in the present embodiment, the initial metal contamination prevention process P4 includes the nitrogen plasma processing step S1 and the oxygen plasma processing step S2, and the nitrogen plasma processing step S1 and the oxygen plasma processing step S2 are performed as initial metal contamination. By repeating the process according to the degree, the initial metal contamination can be sufficiently and efficiently reduced.

  Therefore, in the MMT apparatus, initial metal contamination can be reliably prevented after the new apparatus start-up process P1 and / or the post-maintenance restart process P2 and before the product wafer production process (main process) process P3. The stability of the productivity of the MMT apparatus can be improved.

  According to the present embodiment, it is not necessary to use a dummy wafer, and it is only necessary to increase the number of dummy discharges, so that resources can be effectively used.

  Needless to say, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

  In the above embodiment, the substrate processing method using the MMT apparatus has been described. However, the present invention can be applied to other plasma processing methods or substrate processing methods that do not use plasma. In general, when an electric or electronic device is manufactured, the characteristics of the electric or electronic device are deteriorated when the metal is contaminated. However, the present invention can prevent the metal contamination.

Preferred embodiments of the present invention will be additionally described.
(1) a treatment chamber capable of decompression;
A heater for heating the quartz part;
An electrode disposed on one side of the quartz part and applied with a positive electrode of a direct current voltage;
A substrate processing apparatus comprising:
(2) The substrate processing apparatus according to (1), further including an electrode to which a negative electrode of a DC voltage is applied facing the electrode.

1 is a schematic configuration diagram of a substrate processing apparatus in which an embodiment of the present invention is implemented. It is a flowchart which shows the substrate processing method which is one Embodiment of this invention. It is a graph which shows the relationship between RF on / off and sodium precipitation amount. It is a graph which shows the relationship between RF on time and the amount of sodium precipitation. It is a graph which shows the relationship between heater temperature and sodium precipitation amount. It is a graph which compares the amount of sodium precipitation of nitrogen plasma processing and oxygen plasma processing. It is each schematic diagram which shows the mechanism of initial stage metal contamination reduction, (a) has shown the nitrogen plasma processing step, (b) has shown the oxygen plasma processing step.

Explanation of symbols

200 wafer (substrate)
201 processing chamber 217 susceptor (substrate mounting table)
224 Plasma generation region 232 Gas supply pipe

Claims (1)

Plasma discharge while supplying a gas containing nitrogen gas to the processing chamber without mounting the substrate on a mounting table provided in the processing chamber;
Plasma discharge while supplying a gas containing oxygen gas to the processing chamber without placing the substrate on the mounting table provided in the processing chamber;
A plasma processing method comprising:

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