JP2007208169A - Substrate processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate processing method with which film thickness uniformity within a substrate surface can be improved. <P>SOLUTION: The substrate processing method for generating plasma by incurring magnetron discharge within a processing vessel by an electric field and a magnetic field, and for performing plasma processing on a substrate using the plasma includes the steps of: carrying the substrate into the processing vessel; forming a film on the substrate through activation using plasma by feeding gases into the processing vessel; and carrying the treated substrate out of the processing vessel. In the film forming step, the exhaustion of gases from the processing vessel is reduced so as not to affect film thickness uniformity of the film formed on the substrate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a substrate processing method for processing a substrate using plasma, and more particularly to an improved exhaust in a film forming process.

Conventionally, as a substrate processing apparatus for processing a substrate using plasma, a substrate such as a wafer is processed using a modified magnetron type plasma source that can generate high-density plasma by an electric field and a magnetic field. A processing furnace (hereinafter referred to as an MMT apparatus) is known.
In this MMT apparatus, a substrate is installed in a processing container that ensures airtightness, a reaction gas is introduced into the processing container through a shower head, the inside of the processing container is maintained at a certain pressure, and a high frequency is applied to the discharge electrode. Electric power is supplied to form an electric field and a magnetic field to cause magnetron discharge. Since the electrons emitted from the discharge electrode continue to circulate while continuing the cycloid motion while drifting, the lifetime becomes longer and the ionization rate is increased, so that high-density plasma can be generated. In this way, the substrate can be subjected to various plasma treatments such as diffusion treatment such as oxidation or nitridation by exciting and decomposing the reaction gas, or forming a thin film on the substrate surface, or etching the substrate surface.
Here, the pressure control for keeping the pressure in the processing container constant is mainly performed by adjusting the exhaust amount with an automatic pressure control valve (APC valve) (see, for example, Patent Document 1).
JP 2002-359236 A

However, in the MMT apparatus, when the pressure inside the processing container is controlled by adjusting the exhaust amount, the in-plane uniformity of the film thickness formed on the substrate is deteriorated by the influence of the gas flow caused by the exhaust. There was a problem.
An object of the present invention is to provide a substrate processing method capable of solving the above-described problems of the prior art and improving the film thickness uniformity in the substrate surface.

A first invention is a substrate processing method for generating a plasma by generating a magnetron discharge in a processing container by an electric field and a magnetic field, and plasma processing the substrate using the plasma, and the substrate is carried into the processing container A step of forming a film on the substrate by supplying a gas into the processing container and activating the plasma, and a step of unloading the processed substrate from the processing container. Is a substrate processing method characterized in that the exhaust of gas from the processing container is reduced so as not to affect the film thickness uniformity of the film formed on the substrate.
In the substrate processing method using plasma, if the gas exhaust from the processing container is reduced, the gas flow in the processing container becomes gentle and the gas density becomes uniform. Will improve.

According to a second aspect of the present invention, in the first aspect of the present invention, in the film formation step, the gas uniformity is supplied to the processing container so as not to affect the film thickness uniformity of the film formed on the substrate. A substrate processing method characterized by reducing gas exhaust from a processing container.
When performing such a process of reducing exhaust gas, gas is consumed particularly by magnetron discharge, so that the pressure in the processing vessel changes, thereby affecting the quality of the film formed on the substrate. However, according to the present invention, by supplying the gas, the consumption gas and the supply gas can be balanced, so that the pressure in the processing container can be stabilized, and the above-described problems can be solved. can be solved.

A third invention is a substrate processing method according to the first or second invention, wherein the exhaust of gas from the processing container is controlled by an automatic pressure control valve.
When performing such a process of reducing exhaust gas, the problem that the pressure in the processing container becomes unstable is likely to occur. However, according to the present invention, since the exhaust of gas is controlled by the APC valve, the processing container The pressure stability inside can be ensured, and the above problems can be solved.

According to a fourth aspect, in the third aspect, the opening of the automatic pressure control valve is set to 0%, and gas is supplied into the processing container so that the pressure in the processing container is constant. A substrate processing apparatus.
If the opening degree of the APC valve is 0%, the APC valve is not completely sealed, but the exhaust of gas can be minimized. Therefore, if the opening of the APC valve is set to 0% and the gas is supplied into the processing container so that the pressure in the processing container is constant, the exhaust of the gas from the processing container is reduced, and the inside of the processing container Since the gas flow becomes more gentle and the gas density becomes more uniform, the film thickness uniformity in the substrate surface is further improved.

  According to the present invention, since the gas density becomes uniform, the film thickness uniformity within the substrate surface can be improved.

  Embodiments of the present invention will be described below.

FIG. 2 shows a configuration example of an in-line type semiconductor manufacturing apparatus according to the embodiment of the present invention. The in-line type semiconductor manufacturing apparatus can be divided into a vacuum side and an atmosphere side.
On the vacuum side, two process modules 107 connected in-line and two vacuum transfer chambers 105 are provided. Each vacuum transfer chamber 105 is provided with one vacuum robot 106, and the wafer 200 can be transferred independently between the process module 107 and the vacuum transfer chamber 105.
On the atmosphere side, an atmosphere loader 102 connected to the vacuum transfer chamber 105 constituting the substrate processing module and two load ports 101 connected to the atmosphere loader 102 are provided. The atmospheric loader 102 is provided with one atmospheric robot 104 so that the wafer 200 can be transferred between the vacuum transfer chamber 105 and the load port 101. In the atmospheric loader 102, an aligner 109 for aligning the wafer 200 is provided. Further, a control box 103 in which a controller for controlling the apparatus is housed outside the atmospheric loader 102 is provided.

In each vacuum transfer chamber 105, the transfer is performed independently. The wafer 200 is received from the wafer holding unit 108 in the vacuum transfer chamber 105 by the vacuum robot 106, loaded into the process module 107, and film formation processing of the wafer 200 is performed. When the processing of the wafer 200 is completed, the processed wafer 200 is received by the vacuum robot 105, held in the wafer holding unit 108, and the wafer 200 is cooled. The vacuum transfer chamber 105 is returned to atmospheric pressure, the cooled wafer 200 is taken out from the vacuum transfer chamber 105 by the atmospheric robot 104, and discharged to the load port 101 via the atmospheric loader 102.
After unloading, the unprocessed wafer 200 is loaded into the vacuum transfer chamber 105 from the load port 101 by the atmospheric robot 104, and the above-described processing is repeated.

The process module 107 that performs the film forming process described above is configured by an MMT apparatus.
FIG. 3 shows a schematic configuration diagram of such an MMT apparatus. The MMT apparatus has a processing container 203, which is formed by a dome-shaped upper container 210 as a first container and a bowl-shaped lower container 211 as a second container. Is covered on the lower container 211. The upper container 210 is made of a non-metallic material such as aluminum oxide or quartz, and the lower container 211 is made of aluminum. Further, by configuring the susceptor 217 which is a heater-integrated substrate holder (substrate holding means), which will be described later, with a non-metallic material such as aluminum nitride, ceramics or quartz, metal contamination taken into the film during processing can be prevented. Reduced.

  The shower head 236 is provided in the upper part of the processing chamber 201, and includes a cap-shaped lid 233, a gas inlet 234, a buffer chamber 237, an opening 238, a shielding plate 240, and a gas outlet 239. Yes. The buffer chamber 237 is provided as a dispersion space for dispersing the gas introduced from the gas introduction port 234.

  A gas supply pipe 232 for supplying gas is connected to the gas inlet 234. The gas supply pipe 232 is connected via a valve 243a as an on-off valve and a mass flow controller 241 as a flow rate controller (flow rate control means). It is connected to the gas cylinder of the reaction gas 230 not shown in the figure. The reaction gas 230 is supplied from the shower head 236 to the processing chamber 201, and the exhaust for exhausting the gas to the side wall of the lower container 211 so that the gas after substrate processing flows from the periphery of the susceptor 217 toward the bottom of the processing chamber 201. A mouth 235 is provided. A gas exhaust pipe 231 for exhausting gas is connected to the exhaust port 235, and the gas exhaust pipe 231 is connected to a vacuum pump 246 as an exhaust device via an APC 242 as a pressure regulator and a valve 243b as an on-off valve. Has been.

  As a discharge mechanism (discharge means) that excites the supplied reaction gas 230, a cylindrical electrode 215 that is a first electrode formed in a cylindrical shape, for example, a cylindrical shape, is provided. The cylindrical electrode 215 is installed on the outer periphery of the processing vessel 203 (upper vessel 210) and surrounds the plasma generation region 224 in the processing chamber 201. The cylindrical electrode 215 is connected to a high frequency power source 273 that applies high frequency power via a matching unit 272 that performs impedance matching.

  Moreover, the cylindrical magnet 216 which is a cylinder, for example, the magnetic field formation mechanism (magnetic field formation means) formed in the shape of a cylinder is a cylindrical permanent magnet. The cylindrical magnet 216 is disposed near the upper and lower ends of the outer surface of the cylindrical electrode 215. The upper and lower cylindrical magnets 216 and 216 have magnetic poles at both ends (inner and outer peripheral ends) along the radial direction of the processing chamber 201, and the magnetic poles of the upper and lower cylindrical magnets 216 and 216 are set in opposite directions. Has been. Therefore, the magnetic poles in the inner peripheral portion are different from each other, and thereby magnetic lines of force are formed in the cylindrical axis direction along the inner peripheral surface of the cylindrical electrode 215.

  A susceptor 217 is disposed at the bottom center of the processing chamber 201 as a substrate holder (substrate holding means) for holding the wafer 200 as a substrate. The susceptor 217 is formed of, for example, a non-metallic material such as aluminum nitride, ceramics, or quartz, and a heater (not shown) as a heating mechanism (heating means) is integrally embedded therein to heat the wafer 200. It can be done. The heater is adapted to heat the wafer 200 to about 700 ° C. by applying electric power.

  The susceptor 217 is also equipped with a second electrode that is an electrode for changing the impedance, and the second electrode is grounded via the impedance variable mechanism 274. The impedance variable mechanism 274 is composed of a coil and a variable capacitor, and the potential of the wafer 200 can be controlled 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 at least a processing chamber 201, a processing vessel 203, a susceptor 217, a cylindrical electrode 215, a cylindrical magnet 216, a shower head 236, and an exhaust port. The wafer 200 can be subjected to plasma processing in the processing chamber 201.

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

  The susceptor 217 is insulated from the lower container 211 and is provided with a susceptor elevating mechanism (elevating means) 268 for elevating and lowering the susceptor 217. The susceptor 217 is provided with through holes 217a, and at the bottom of the lower container 211, wafer push-up pins 266 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 217a and the wafer up pin are arranged such that the wafer push-up pin 266 penetrates the through-hole 217a in a non-contact state with the susceptor 217. 266 is arranged.

  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 mechanism (transfer means) not shown in the drawing. The process chamber 201 can be hermetically closed when closed.

  Further, the controller 121 as a control unit (control means) includes the APC 242, the valve 243b, and the vacuum pump 246 through the signal line A, the susceptor lifting mechanism 268 through the signal line B, the gate valve 244 through the signal line C, and the signal line D. The matching device 272, the high-frequency power source 273, the mass flow controller 241 and the valve 243a are controlled through the signal line E, and the heater and the impedance variable mechanism 274 embedded in the susceptor are controlled through the signal line (not shown).

  Next, using the MMT apparatus configured as described above, a predetermined plasma treatment is performed on the surface of the wafer 200 or the surface of the base film formed on the wafer 200 as one step of the semiconductor device manufacturing process. A method will be described. In the following description, the operation of each unit constituting the substrate processing apparatus is controlled by the control unit 121.

  The wafer 200 is loaded into the processing chamber 201 by a transfer mechanism (not shown) that transfers the wafer from the outside of the processing chamber 201 that constitutes the processing furnace 202, and is transferred onto the susceptor 217 (loading step).

  The details of this transport operation are as follows. The susceptor 217 is lowered to the substrate transfer position, and the tip of the wafer push-up pin 266 passes through the through hole 217a of the susceptor 217. At this time, the push-up pin 266 is protruded by a predetermined height from the surface of the susceptor 217. Next, the gate valve 244 provided in the lower container 211 is opened, and the wafer 200 is placed on the tip of the wafer push-up pin 266 by a transfer mechanism not shown in the drawing. When the transfer mechanism is retracted out of the processing chamber 201, the gate valve 244 is closed. 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 raised to a position where the wafer 200 is processed.

  The heater embedded in the susceptor 217 is preheated, and heats the loaded wafer 200 to a predetermined wafer processing temperature within a range of room temperature to 700 ° C. The pressure of the processing chamber 201 is maintained at a predetermined pressure within the range of 0.1 to 250 Pa using the vacuum pump 246 and the APC 242.

For example, when a nitride compound thin film is formed on a SiO ₂ film on a Si wafer, when the temperature of the wafer 200 reaches the processing temperature and stabilizes, the gas ejection holes 239 of the shielding plate 240 are opened from the gas introduction port 234. Then, N ₂ gas or NH ₃ gas, which is a reactive gas, is introduced toward the upper surface (processing surface) of the wafer 200 disposed in the processing chamber 201. The gas flow rate at this time is a predetermined flow rate within a range of 120 to 1000 sccm. 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. The power to be applied is a predetermined output value within the range of 100 to 500W. At this time, the impedance variable mechanism 274 is controlled in advance so as to have a desired impedance value.

  Magnetron discharge is generated under the influence of the magnetic field of the cylindrical magnets 216 and 216, charges are trapped in the upper space of the wafer 200, and high-density plasma is generated in the plasma generation region 224. A thin film of a nitride compound is formed on the surface of the wafer 200 on the susceptor 217 by the generated high-density plasma (film formation process).

  The wafer 200 that has been subjected to the plasma processing is carried out of the processing chamber 201 using a transport mechanism (not shown) in the reverse order of substrate loading (unloading step).

  By the way, in the above film forming process, the film thickness of the film formed on the wafer may be affected by the flow of gas due to the exhaust, which may cause the film thickness in-plane uniformity to deteriorate. When the gas flow due to the exhaust is steep, the present inventor observes an increase in film thickness on the exhaust port 235 side. Therefore, to make the gas flow as uniform as possible, the film thickness uniformity in the substrate surface Found to improve. In this embodiment, the film thickness uniformity is improved by the following substrate processing method.

In the film forming process, a film forming gas is supplied into the processing vessel 203 and the gas is activated by plasma to form a film on the wafer 200. In the step of forming this film, the exhaust of gas from the processing container 203 is reduced to the extent that the film thickness uniformity of the film formed on the wafer 200 is not affected.
When the exhaust of gas from the processing container 203 is reduced in this way, the gas flow in the processing container 203 becomes gentle and the gas density becomes uniform, so that the film thickness uniformity in the wafer surface is improved.

Further, in this embodiment mode, gas supply from the processing container 203 is reduced so as not to affect the film thickness uniformity of the film formed on the wafer while supplying the gas.
When performing the process of reducing the exhaust of gas as described above, the gas is consumed by the magnetron discharge, so the pressure in the processing container changes, thereby affecting the film quality formed on the substrate. Such a problem is likely to occur. Therefore, in the embodiment, by continuing the supply without stopping the supply of the gas, the gas lost due to the discharge is balanced with the supply gas that compensates for this. As a result, the pressure is as stable as that during APC control. Therefore, there is no effect on film quality and film thickness.

  It is preferable that the amount of gas exhausted from the processing vessel 203 is reduced. For that purpose, the opening degree of the APC valve 242 is preferably narrowed. In order to minimize gas exhaust, the opening degree of the APC valve 242 is set to 0%. Even if the opening degree of the APC valve 242 is 0%, the APC valve 242 is not completely sealed, but gas exhaust can be minimized. If the opening degree of the APC valve 242 is 3% or more, the in-plane uniformity becomes 1% or more, and the request for in-plane uniformity cannot be met. If the opening is 0%, the in-plane uniformity can be made less than 1%, and the request for in-plane uniformity can be met. Therefore, the opening degree of the APC valve 242 is preferably in the range of 0% to 3%.

  In particular, plasma oxidation is being applied to an oxide film, which is a gate insulating film of flash memory. However, the film thickness uniformity within the conventional wafer surface is about 2%, which satisfies the required less than 1%. The current situation is not done. In this respect, the MMT apparatus according to the present embodiment can meet this requirement. In addition to the plasma oxidation process, the present invention can be applied to a high temperature plasma nitridation process.

  As described above, in the embodiment, in the MMT plasma processing apparatus, during plasma processing, the gas flow is moderated as much as possible by suppressing gas exhausting as much as possible without affecting the film thickness uniformity, and making the gas density as uniform as possible. By doing so, the uniformity of the in-plane film thickness is increased. As a result, the flow of the supplied gas can be made uniform, and as a result, processing with good film thickness uniformity within the substrate surface can be performed.

[Example]
Next, examples and comparative examples applied to nitriding treatment and oxidation treatment using the MMT apparatus shown in FIG. 3 will be described. Usually, the MMT apparatus is used as suitable for low-temperature nitridation and high-temperature nitridation, but here, high-temperature nitridation and high-temperature oxidation are performed on the premise of thick film formation.

A nitride film was formed on the wafer (high temperature nitriding treatment). The processing conditions were a wafer temperature of 700 ° C., a power of 300 W supplied to the cylindrical electrode 215, a processing time of 300 seconds, and a pressure in the processing container 203 of 200 Pa. The flow rate of N ₂ gas supplied into the processing container 203 was 450 sccm. At this time, the opening degree of the APC valve 242 was set to 0%. As a result, the film thickness of the nitride film formed on the wafer was 5 nm, and the wafer in-plane uniformity was 0.6%.

Comparative Example 1

A nitride film was formed on the wafer under the same conditions as in Example 1 except that the flow rate of N ₂ gas was 500 sccm and the opening degree of the APC valve 242 was 3%. As a result, the film thickness of the nitride film formed on the wafer was 5 nm, and the wafer in-plane uniformity was 1.0%.

An oxide film was formed on the wafer using the MMT apparatus shown in FIG. 3 (high temperature oxidation treatment). The processing conditions were such that the wafer temperature was 700 ° C., the power supplied to the cylindrical electrode was 350 W, the processing time was 240 seconds, and the pressure in the processing container 203 was 200 Pa. The flow rate of O ₂ gas supplied into the processing vessel 203 was 450 sccm. The opening degree of the APC valve 242 at that time was 0%. As a result, the film thickness of the oxide film formed on the wafer was 4 nm, and the wafer in-plane uniformity was 7.0%.

Comparative Example 2

An oxide film was formed on the wafer under the same conditions as in Example 2 except that the flow rate of O ₂ gas was 500 sccm and the opening degree of the APC valve 242 was 3%. As a result, the thickness of the oxide film formed on the wafer was 4 nm, and the wafer in-plane uniformity was 8.0%.

  In Example 2, the uniformity within the wafer surface is as bad as 7.0%. However, as shown in Comparative Example 2, data with poor uniformity was originally taken and a significant difference from Comparative Example 2 was obtained. This was done to make it easier to understand the effects of the invention.

  FIG. 1 is an explanatory diagram of an APC opening degree in which the comparative example is B and the example is A in the above-described event, particularly, the event from pressure adjustment to discharge stabilization. Here, the gas flow rate is the same when the pressure is adjusted and when the discharge is stable. In Example A, since the exhaust gas flow rate is adjusted so that APC = 0% when the discharge is stable, the pressure adjustment is higher than in Comparative Example B where the exhaust gas flow rate is adjusted so that APC = 3% when the discharge is stable. At this point, the exhaust flow rate has already decreased. Therefore, the APC opening degree of Example A at the time of pressure adjustment is smaller than that of Comparative Example B as illustrated.

An oxide film was formed on the wafer under the same conditions as in Example 2 except that the flow rate of O ₂ gas was 200 or 150 sccm, the processing time was 600 seconds, and the pressure was 50 Pa (high-temperature oxidation treatment). As a result, the film thickness of the oxide film formed on the wafer was 7 nm, and the wafer in-plane uniformity was 0.9%.

Comparative Example 3

  An oxide film was formed on the wafer under the same conditions as in Example 3 except that the opening degree of the APC valve 242 was set to 3%. As a result, the film thickness of the oxide film formed on the wafer was 7 nm, and the wafer in-plane uniformity was 1.0%.

It is explanatory drawing of the APC opening degree of the comparative example and Example in the event from pressure adjustment to discharge stabilization. 1 shows a configuration example of an in-line type semiconductor manufacturing apparatus as a substrate processing apparatus in an embodiment. It is a schematic block diagram of the MMT apparatus in embodiment.

Explanation of symbols

200 wafer (substrate)
203 Processing vessel 235 Exhaust pipe (exhaust port)
234 Gas inlet 242 APC

Claims (1)

A substrate processing method in which a magnetron discharge is generated in a processing container by an electric field and a magnetic field to generate plasma, and the substrate is subjected to plasma processing using this plasma,
Carrying the substrate into the processing container;
Supplying a gas into the processing vessel and activating it with the plasma to form a film on the substrate;
And a step of unloading the processed substrate from the processing container,
In the film forming step, the exhaust of gas from the processing container is reduced so as not to affect the film thickness uniformity of the film formed on the substrate.

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