JP2006287153A - Substrate treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate treatment apparatus for manufacturing a semiconductor substrate with a high yield, by preventing plasma damages to the substrate and metallic contamination. <P>SOLUTION: By using high-frequency voltage from an oscillator 8, two discharge electrodes 5a, 5b, arranged in a buffer chamber 6, causes plasma electric discharge so that reactive gas introduced into the buffer chamber 6 is excited to treat the substrate 2 in a reactive tube 1. The potential change of the plasma generated from two discharge electrodes 5a, 5b is measured by a monitor electrode 22. As to the potential change of the plasma measured by the monitor electrode 22, the polarity of the potential is reversed by a high frequency transformer 16 and applied to two discharge electrodes 5a, 5b. In this way, the potential change generated by two discharge electrodes 5a, 5b is restricted seemingly. Then, plasma discharge between two discharge electrodes 5a, 5b and a metallic seal chap 3 is made weak, so parasitic plasma is not generated outside the buffer chamber. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a substrate processing apparatus for etching a surface of a substrate such as a silicon wafer or forming a thin film using an ionized reactive gas.

2. Description of the Related Art Conventionally, a substrate processing apparatus that ionizes a reactive gas by plasma discharge and performs a film forming process on a semiconductor substrate (hereinafter simply referred to as a substrate) has been widely known. In such a substrate processing apparatus, plasma is generated by applying a high frequency voltage between a plurality of discharge electrodes in a buffer chamber, and a reactive gas supplied into the buffer chamber is ionized by plasma excitation. Then, the ionized reactive gas is sent into the processing chamber to perform substrate processing such as forming a thin film on the surface of the substrate or etching. As such a substrate processing apparatus, a CVD (Chemical Vapor Deposition) apparatus that performs an annealing process, an oxide film forming process, a diffusion process, or a film forming process on a substrate is known (for example, Patent Document 1). reference).
JP 2003-297818 A

  However, since the bottom of the reaction tube of the substrate processing apparatus is covered with a metal seal cap, plasma discharge is not only generated between the pair of discharge electrodes in the buffer chamber, but also between the pair of discharge electrodes and the seal cap. It may also occur in the space between. Such plasma generated outside the buffer chamber is generally called parasitic plasma. If parasitic plasma is generated outside the buffer chamber in this way, plasma damage is caused to the substrate in the processing chamber, or metal contamination occurs due to the sputtering effect of the parasitic plasma, resulting in a substrate product manufactured by the substrate processing apparatus. Yield is reduced.

  The present invention has been made in view of such problems, and provides a substrate processing apparatus capable of manufacturing a semiconductor substrate having a high product yield by preventing plasma damage and metal contamination to the substrate. With the goal.

  In order to solve the above-described problems, a substrate processing apparatus according to the present invention is applied with a processing chamber for processing a substrate such as a semiconductor substrate, a gas supply means for supplying a reactive gas into the processing chamber, and a high-frequency voltage. Measured by a pair of discharge electrodes for generating a plasma and exciting a reactive gas supplied by the gas supply means by the plasma, a monitor electrode for measuring the potential of the plasma generated by the pair of discharge electrodes, and the monitor electrode A voltage application means for applying a potential having a polarity opposite to the potential of the plasma to the pair of discharge electrodes is employed.

  According to such a configuration, when the monitor electrode measures the potential change of the plasma generated by the pair of discharge electrodes, the potential change of the plasma is applied to the pair of discharge electrodes with the polarity of the potential reversed by the voltage applying means. The Thereby, the potential fluctuation of the plasma generated by the pair of discharge electrodes is apparently suppressed. Therefore, plasma discharge between the pair of discharge electrodes and the metal seal cap covering the bottom of the processing chamber is weakened, and parasitic plasma is not generated. As a result, there is no possibility of causing plasma damage to the substrate in the processing chamber, and the product yield is improved.

  According to the substrate processing apparatus of the present invention, since generation of parasitic plasma outside the buffer chamber that excites the reactive gas by plasma discharge is suppressed, plasma damage to the substrate in the processing chamber can be prevented. . In addition, by suppressing the generation of parasitic plasma outside the buffer chamber, metal contamination from the metal member around the processing chamber can be prevented. Thereby, a substrate processing apparatus having a high product yield of the substrate can be realized.

<< Summary of Invention >>
In the substrate processing apparatus of the present invention, when a pair (two) of discharge electrodes installed in the buffer chamber causes plasma discharge, the reactive gas introduced into the buffer chamber is ionized and introduced into the reaction tube. A semiconductor substrate as a substrate is processed. At this time, the potential change of the plasma generated by the pair of discharge electrodes is measured by the monitor electrode installed in the buffer chamber. Furthermore, the plasma potential change measured by the monitor electrode is converted into a reverse phase voltage by the high frequency transformer (that is, the potential polarity is inverted) and applied to the pair of discharge electrodes. As a result, the potential change of the plasma generated by the pair of discharge electrodes is apparently suppressed, so that the plasma discharge between the pair of discharge electrodes and the metal seal cap is weakened, and parasitic plasma is generated outside the buffer chamber. It can be prevented from occurring. As a result, the product yield of the substrate can be improved.

Embodiment 1
Hereinafter, embodiments of a substrate processing apparatus of the present invention will be described in detail with reference to the drawings. 1A and 1B are structural views of a substrate processing furnace according to an embodiment of the present invention, in which FIG. 1A is an upper cross-sectional view and FIG. 1B is a cross-sectional view along line aa in FIG. That is, (b) is a side sectional view of the substrate processing furnace.

  As shown in FIG. 1, a vertically elongated buffer chamber 6 is provided near the inner wall surface of the reaction tube 1, and the buffer chamber 6 is covered with a dielectric tube 14 and covered with two discharge electrodes 5 a, 5b and one monitor electrode 22 are arranged in the vertical direction. Further, although not shown, the buffer chamber 6 is provided with a gas nozzle (gas supply means).

  A high frequency voltage generated by the oscillator 8 is applied to one discharge electrode end 4a of the two discharge electrodes 5a and 5b via a matching unit 9 and a high frequency transformer (voltage applying means) 16. Are wired like so. The matching unit 9 is for impedance matching of the oscillator 8 and the two discharge electrodes 5a and 5b. Further, the other discharge electrode end portion 4 b of the two discharge electrodes 5 a and 5 b is installed on the ground via the high-frequency transformer 16.

  With this configuration, when a high frequency voltage is applied from the oscillator 8 to the two discharge electrodes 5a and 5b, plasma 11 is generated between the discharge electrodes 5a and 5b in the buffer chamber 6 and supplied from a gas nozzle (not shown). The reactive gas is ionized by plasma excitation. The ionized reactive gas is supplied to the inside of the reaction chamber 1 through a small hole 10 formed in the wall of the buffer chamber 6. As a result, the ionized reactive gas is supplied to the surface of the substrate 2 placed on the boat 12 inside the reaction chamber 1, and the surface of the substrate 2 can be etched or formed into a thin film.

  At this time, plasma discharge may also occur between the two discharge electrodes 5 a and 5 b connected to the oscillator 8 and the metal seal cap 3, and the parasitic plasma 20 may be generated outside the buffer chamber 6. Such parasitic plasma 20 may cause plasma damage to the substrate 2 placed on the boat 12, or metal contamination may occur due to the sputtering effect of the parasitic plasma 20, thereby reducing the product yield of the substrate 2.

  Therefore, in the present invention, as shown in the upper cross-sectional view of FIG. 1A, the monitor electrode 22 for measuring the potential change of the plasma generated by the two discharge electrodes 5a and 5b is provided. By using this monitor electrode 22 to suppress an apparent potential change between the two discharge electrodes 5a and 5b and the seal cap 3, it is possible to prevent the generation of the parasitic plasma 20 outside the buffer chamber 6. is doing.

  That is, the two discharge electrodes 5 a and 5 b and the one monitor electrode 22 are both connected to the high-frequency transformer 16 at the lower part of the reaction tube 1. At this time, the windings 17a and 17b of the high-frequency transformer 16 connected to the two discharge electrodes 5a and 5b are both in-phase winding, but the winding 17c of the high-frequency transformer 16 connected to the monitor electrode 22 is It is a reverse phase winding. That is, when the black circles displayed on the windings 17a, 17b, and 17c of the high-frequency transformer 16 are the winding start of the windings, the discharge electrode end portions 4a and 4b of the two discharge electrodes 5a and 5b are connected to the high-frequency transformer 16, respectively. The windings 17a and 17b are connected to the end of winding (the side without the black circle), but the discharge electrode end 4c of the monitor electrode 22 is connected to the winding start (the side with the black circle) of the winding 17c of the high-frequency transformer 16. ing.

  When the polarities of the windings 17a, 17b and 17c of the high-frequency transformer 16 are connected to the two discharge electrodes 5a and 5b and the monitor electrode 22 as shown in FIG. 1A, for example, the two discharge electrodes 5a and 5b Considering the case where the generated plasma potential changes to the + side, the change in plasma potential is measured by the monitor electrode 22. Then, a positive voltage is induced at the discharge electrode end 4 c of the monitor electrode 22. That is, the winding start (black circle) of the winding 17c of the high-frequency transformer 16 connected to the monitor electrode 22 becomes a positive potential.

  At this time, since the winding 17c on the monitor electrode 22 side of the high-frequency transformer 16 and the windings 17a and 17b of the two discharge electrodes 5a and 5b have opposite polarities, the winding ends of the windings 17a and 17b (black circles) On the other side, a negative potential is induced. That is, if the winding ratio of each winding is the same, each discharge electrode end 4a, 4b of the two discharge electrodes 5a, 5b has a negative potential equal to the positive potential of the discharge electrode end 4c of the monitor electrode 22. Is induced. As a result, the two discharge electrodes 5a and 5b act to suppress a change in + potential. Thereby, the fluctuation of the + potential of the two discharge electrodes 5a and 5b is suppressed, and the parasitic plasma 20 outside the buffer chamber induced by the change of the plasma potential between the two discharge electrodes 5a and 5b and the seal cap 3 is suppressed. Occurrence can be prevented.

  That is, the high-frequency transformer (voltage applying means) 16 applies a potential having a polarity opposite to the plasma potential measured by the monitor electrode 22 to the two discharge electrodes 5a and 5b. The parasitic plasma 20 generated between 5b and the seal cap 3 can be suppressed, and plasma damage to the substrate 2 placed on the boat 12 and metal contamination due to sputtering of the parasitic plasma 20 can be prevented.

  It is most preferable that the winding ratios of the windings 17a, 17b, and 17c in the high-frequency transformer 16 be the same because the potential change of the two discharge electrodes 5a and 5b can be canceled to zero. However, the winding ratios of the windings 17a and 17b on the two discharge electrodes 5a and 5b side and the winding 17c on the monitor electrode 22 side are not necessarily the same. That is, if the winding ratio is different, the potential change of the two discharge electrodes 5a and 5b is canceled by the induced voltage corresponding to the winding ratio. Therefore, the two discharge electrodes 5a and 5b and the seal cap are offset by the potential offset. 3 can be suppressed.

  In summary, the two discharge electrodes 5a and 5b installed in the buffer chamber 6 by the high-frequency voltage from the oscillator 8 cause plasma discharge to ionize the reactive gas introduced into the buffer chamber 6 and react. The substrate 2 in the tube 1 is processed. At this time, the monitor electrode 22 measures the potential change of the plasma generated by the two discharge electrodes 5a and 5b. The plasma potential change measured by the monitor electrode 22 is applied to the two discharge electrodes 5a and 5b with the polarity of the potential reversed by the high-frequency transformer 16. Thereby, the potential fluctuation of the plasma generated by the two discharge electrodes 5a and 5b is apparently suppressed. Therefore, plasma discharge between the two discharge electrodes 5a and 5b and the metal seal cap 3 is weakened, and no parasitic plasma is generated outside the buffer chamber.

<< Embodiment 2 >>
Next, a substrate processing apparatus using the substrate processing furnace of the first embodiment will be described. FIG. 2 is a perspective view of a substrate processing apparatus using the substrate processing furnace of the present invention, and FIG. 3 is a cross-sectional view of the substrate processing apparatus shown in FIG. Accordingly, a substrate processing apparatus to which the substrate processing furnace of the present invention is applied will be described with reference to FIGS.

  A cassette stage 105 is provided on the front side of the inside of the housing 101 as a holding member transfer member that transfers the cassette 100 as a substrate storage container to and from an external transfer device (not shown). Is provided with a cassette elevator 115 as an elevating means, and a cassette transfer machine 114 as a conveying means is attached to the cassette elevator 115. Further, a cassette shelf 109 as a means for placing the cassette 100 is provided on the rear side of the cassette elevator 115, and a spare cassette shelf 110 is also provided above the cassette stage 105. Further, a clean unit 118 is provided above the spare cassette shelf 110 and is configured to distribute clean air through the inside of the casing 101.

  A processing furnace 202 is provided above the rear portion of the casing 101, and below the processing furnace 202, a boat 217 as a substrate holding unit that holds the wafers 200 as substrates in multiple stages in a horizontal posture is raised and lowered to the processing furnace 202. A boat elevator 121 is provided as lifting means. Further, a seal cap 219 as a lid is attached to the tip of the elevating member 122 attached to the boat elevator 121 to support the boat 217 vertically. Further, a transfer elevator 113 as an elevating means is provided between the boat elevator 121 and the cassette shelf 109, and a wafer transfer machine 112 as a transfer means is attached to the transfer elevator 113. Further, a furnace port shutter 116 as a shielding member that has an opening / closing mechanism and closes the lower surface of the processing furnace 202 is provided beside the boat elevator 121.

  In addition, the cassette 100 loaded with the wafers 200 is carried into the cassette stage 105 from an external transfer device (not shown) in an upward posture, and is rotated by 90 ° on the cassette stage 105 so that the wafers 200 are in a horizontal posture. Further, the cassette 100 is transported from the cassette stage 105 to the cassette shelf 109 or the spare cassette shelf 110 by cooperation of the raising / lowering operation of the cassette elevator 115, the transverse operation, the advance / retreat operation of the cassette transfer machine 114, and the rotation operation.

  Further, the cassette shelf 109 has a transfer shelf 123 in which the cassette 100 to be transferred by the wafer transfer device 112 is stored. The cassette 100 used for transferring the wafer 200 includes the cassette elevator 115 and the cassette transfer. It is transferred to the transfer shelf 123 by the machine 114.

  When the cassette 100 is transferred to the transfer shelf 123, the boat 217 in the lowered state from the transfer shelf 123 is cooperated by the advance / retreat operation of the wafer transfer device 112, the rotation operation, and the lifting / lowering operation of the transfer elevator 113. The wafer 200 is transferred to the above.

  Further, when a predetermined number of wafers 200 are transferred to the boat 217, the boat 217 is inserted into the processing furnace 202 by the boat elevator 121, and the processing furnace 202 is airtightly closed by the seal cap 219. The wafer 200 is heated in the hermetically closed processing furnace 202 and a processing gas is supplied into the processing furnace 202 to perform a predetermined process on the wafer 200.

  When the predetermined processing for the wafer 200 is completed, the wafer 200 is transferred from the boat 217 to the cassette 100 of the transfer shelf 123 by the reverse procedure of the operation described above. Further, the cassette 100 is transferred from the transfer shelf 123 to the cassette stage 105 by the cassette transfer device 114, and is carried out of the casing 101 by an external transfer device (not shown). The furnace port shutter 116 closes the lower surface of the processing furnace 202 when the boat 217 is in the lowered state, and prevents outside air from being caught in the processing furnace 202. The transport operation of the cassette transfer device 114 and the like is controlled by the transport control means 124.

<< Embodiment 3 >>
Next, a vertical reactor that further embodies the substrate processing furnace of the first embodiment will be described. First, a film forming process using the ALD method, which is one of the CVD methods, will be briefly described as an example of a process performed on a substrate such as a wafer performed in the vertical reaction furnace according to the third embodiment of the present invention. .

  In the ALD method, two kinds (or more) of raw material gases used for film formation under a certain film formation condition (temperature, time, etc.) are alternately supplied onto the substrate one by one and in units of one atomic layer. This is a technique in which a film is formed by adsorption and surface reaction.

That is, for example, in the case of forming a SiN (silicon nitride) film, the chemical reaction to be used is high-quality formation at a low temperature of 300 to 600 ° C. using DCS (SiH ₂ Cl ₂ , dichlorosilane) and NH ₃ (ammonia) in the ALD method. A film is formed. Further, the gas supply alternately supplies a plurality of types of reactive gases one by one. Furthermore, the film thickness is controlled by the number of reactive gas supply cycles. For example, assuming that the film formation rate is 1 mm / cycle, the process is performed 20 cycles when a film of 20 mm is formed.

Next, an embodiment of the vertical reactor according to the present invention will be described. FIG. 4 is a schematic configuration diagram of a vertical substrate processing furnace according to an embodiment of the present invention, and is a configuration diagram showing a processing furnace portion in a vertical cross section. FIG. 5 is a block diagram showing a cross section of the processing furnace shown in FIG. Therefore, a vertical reactor to which the substrate processing furnace of the present invention is applied will be described with reference to FIGS.
4 and 5 also include the monitor electrode 22 and the high-frequency transformer 16 according to the present invention shown in FIG. 1, but will be omitted for convenience of explanation.

  A reaction tube 203 is provided as a reaction vessel for processing the wafer 200 as a substrate inside a heater 207 as a heating means, and the lower end opening of the reaction tube 203 is an O-ring as an airtight member by a seal cap 219 as a lid. Airtightly closed through 220. At least the processing furnace 202 is formed by the heater 207, the reaction tube 203, and the seal cap 219. A boat 217 as a substrate holding means is erected on the seal cap 219 via a quartz cap 218, and the quartz cap 218 serves as a holding body for holding the boat. Then, the boat 217 is inserted into the processing furnace 202. On the boat 217, a plurality of wafers 200 to be batch-processed are stacked in a multi-stage in the tube axis direction in a horizontal posture. The heater 207 heats the wafer 200 inserted into the processing furnace 202 to a predetermined temperature.

  The processing furnace 202 is provided with two gas supply pipes 232a and 232b as supply pipes for supplying a plurality of types, here two types of gases. Here, a buffer chamber 237 formed in the processing furnace 202, which will be described later, is further provided from the first gas supply pipe 232a through a first mass flow controller 241a that is a flow control means and a first valve 243a that is an on-off valve. Through the second gas supply pipe 232b, a second mass flow controller 241b as a flow rate control means, a second valve 243b as an on-off valve, a gas reservoir 247, and an on-off valve are supplied. The reaction gas is supplied to the processing furnace 202 via a third valve 243c, which is a gas supply unit 249 described later.

  The processing furnace 202 is connected to a vacuum pump 246, which is an exhaust means, via a fourth valve 243d by a gas exhaust pipe 231 which is an exhaust pipe for exhausting gas, and is evacuated. The fourth valve 243d is an open / close valve that can open and close the valve to stop evacuation / evacuation of the processing furnace 202, and can adjust the pressure by adjusting the valve opening.

  The arc-shaped space between the inner wall of the reaction tube 203 and the wafer 200 constituting the processing furnace 202 is a gas dispersion space along the loading direction of the wafer 200 on the inner wall above the lower part of the reaction tube 203. A buffer chamber 237 is provided, and a first gas supply hole 248 a that is a supply hole for supplying a gas is provided at the end of the wall adjacent to the wafer 200 in the buffer chamber 237. The first gas supply hole 248 a opens toward the center of the reaction tube 203. The first gas supply holes 248a have the same opening area from the lower part to the upper part, and are provided at the same opening pitch.

  At the end of the buffer chamber 237 opposite to the end where the first gas supply hole 248 a is provided, a nozzle 233 is also disposed along the stacking direction of the wafer 200 from the lower part to the upper part of the reaction tube 203. Has been. The nozzle 233 is provided with a second gas supply hole 248b which is a supply hole for supplying a plurality of gases. When the differential pressure between the buffer chamber 237 and the processing furnace 202 is small, the second gas supply hole 248b may have the same opening area and the same opening pitch from the upstream side to the downstream side. When the pressure is large, the opening area may be increased from the upstream side toward the downstream side, or the opening pitch may be decreased.

  In the present invention, by adjusting the opening area and opening pitch of the second gas supply holes 248b from the upstream side to the downstream side, first, there is a difference in the gas flow velocity from each of the second gas supply holes 248b, but the flow rate is A gas of approximately the same amount is ejected. Then, the gas ejected from each of the second gas supply holes 248b is ejected into the buffer chamber 237 and once introduced to make the gas flow rate difference uniform.

  That is, in the buffer chamber 237, the gas ejected from each second gas supply hole 248b is ejected from the first gas supply hole 248a to the processing furnace 202 after the particle velocity of each gas is reduced in the buffer chamber 237. During this time, the gas ejected from each of the second gas supply holes 248b could be a gas having a uniform flow rate and flow velocity when ejected from each of the first gas supply holes 248a.

  Further, in the buffer chamber 237, the first rod-shaped electrode 269 that is a first electrode having an elongated structure and the second rod-shaped electrode 270 that is a second electrode are electrodes that are protective tubes that protect the electrode from the top to the bottom. One of the first rod-shaped electrode 269 and the second rod-shaped electrode 270 is connected to a high-frequency power source 273 via a matching device 272, and the other is grounded as a reference potential. It is connected to the. As a result, plasma is generated in the plasma generation region 224 between the first rod-shaped electrode 269 and the second rod-shaped electrode 270.

  The electrode protection tube 275 has a structure in which the first rod-shaped electrode 269 and the second rod-shaped electrode 270 can be inserted into the buffer chamber 237 while being isolated from the atmosphere of the buffer chamber 237. Here, if the inside of the electrode protection tube 275 has the same atmosphere as the outside air (atmosphere), the first rod-shaped electrode 269 and the second rod-shaped electrode 270 inserted into the electrode protection tube 275 are oxidized by the heating of the heater 207. Will be. Therefore, the inside of the electrode protection tube 275 is filled or purged with an inert gas such as nitrogen to keep the oxygen concentration sufficiently low to prevent oxidation of the first rod-shaped electrode 269 or the second rod-shaped electrode 270. A gas purge mechanism is provided.

  Further, a gas supply unit 249 is provided on the inner wall of the reaction tube 203 that is rotated about 120 ° from the position of the first gas supply hole 248a. The gas supply unit 249 is a supply unit that shares the gas supply species with the buffer chamber 237 when a plurality of types of gases are alternately supplied to the wafer 200 one by one in film formation by the ALD method.

  Similarly to the buffer chamber 237, the gas supply unit 249 also has third gas supply holes 248c which are supply holes for supplying gas at the same pitch at positions adjacent to the wafer, and a second gas supply pipe 232b is provided at the lower part. It is connected.

  When the differential pressure between the buffer chamber 237 and the processing furnace 202 is small, the third gas supply hole 248c may have the same opening area and the same opening pitch from the upstream side to the downstream side. If it is larger, the opening area should be increased from the upstream side to the downstream side, or the opening pitch should be reduced.

  A boat 217 for loading a plurality of wafers 200 in multiple stages at the same interval is provided at the center of the reaction tube 203. This boat 217 can enter and exit the reaction tube 203 by a boat elevator mechanism (not shown). It has become. Further, a boat rotation mechanism 267 that is a rotation means for rotating the boat 217 in order to improve the uniformity of processing is provided. By rotating the boat rotation mechanism 267, the boat 217 held by the quartz cap 218 is provided. Is designed to rotate.

  The controller 321 as a control means includes first and second mass flow controllers 241a and 241b, first to fourth valves 243a, 243b, 243c, and 243d, a heater 207, a vacuum pump 246, a boat rotation mechanism 267, and are omitted in the drawing. Connected to the boat lifting mechanism, the high frequency power supply 273, and the matching unit 272, the flow rate adjustment of the first and second mass flow controllers 241a, 241b, the opening / closing operation of the first to third valves 243a, 243b, 243c, 4 valve 243d opening and closing and pressure adjustment operation, heater 207 temperature adjustment, vacuum pump 246 activation / deactivation, boat rotation mechanism 267 rotation speed adjustment, boat elevating mechanism elevating operation control, high frequency power supply 273 power supply control, Impedance control by the matching unit 272 is performed.

Next, an example of film formation by the ALD method will be described using an example of forming a SiN film using DCS and NH ₃ gas. First, a wafer 200 to be deposited is loaded into a boat 217 and loaded into the processing furnace 202. After carrying in, the following three steps are sequentially executed.

[Step 1]
In step 1, NH ₃ gas that requires plasma excitation and DCS gas that does not require plasma excitation are caused to flow in parallel. First, the first valve 243a provided in the first gas supply pipe 232a and the fourth valve 243d provided in the gas exhaust pipe 231 are both opened, and the first mass flow controller 243a is opened from the first gas supply pipe 232a. The NH ₃ gas whose flow rate has been adjusted by the nozzle 233 is jetted from the second gas supply hole 248b of the nozzle 233 to the buffer chamber 237, and the matching device 272 is connected from the high frequency power source 273 between the first rod-shaped electrode 269 and the second rod-shaped electrode 270. Then, high frequency power is applied to excite plasma of NH ₃ and exhaust it from the gas exhaust pipe 231 while supplying it as an active species to the processing furnace 202.

When flowing NH ₃ gas as an active species by plasma excitation, the pressure in the processing furnace 202 is set to 10 to 100 Pa by appropriately adjusting the fourth valve 243d. The supply flow rate of NH ₃ controlled by the first mass flow controller 241a is 1000 to 10000 sccm. The time for exposing the wafer 200 to the active species obtained by plasma excitation of NH ₃ is 2 to 120 seconds. At this time, the temperature of the heater 207 is set to be 300 to 600 ° C. for the wafer. Since NH ₃ has a high reaction temperature, it does not react at the above-mentioned wafer temperature. Therefore, it is made to flow as an active species by plasma excitation. Therefore, the wafer temperature can be kept in a set low temperature range.

When NH ₃ is supplied as an active species by plasma excitation, the second valve 243b on the upstream side of the second gas supply pipe 232b is opened, the third valve 243c on the downstream side is closed, and the DCS is also Make it flow. Thereby, DCS is stored in the gas reservoir 247 provided between the second and third valves 243b and 243c. At this time, the gas flowing in the processing furnace 202 is an active species obtained by plasma-exciting NH ₃ and there is no DCS. Therefore, NH ₃ without causing gas phase reaction, NH ₃ became excited active species by the plasma reacts base film and the surface of the wafer 200.

[Step 2]
In Step 2, the first valve 243a of the first gas supply pipe 232a is closed to stop the supply of NH ₃ , but the supply to the gas reservoir 247 is continued. When a predetermined pressure and a predetermined amount of DCS accumulate in the gas reservoir 247, the second valve 243b on the upstream side is also closed, and the DCS is confined in the gas reservoir 247. Further, the fourth valve 243 d of the gas exhaust pipe 231 is kept open, and the processing furnace 202 is exhausted to 20 Pa or less by the vacuum pump 246, and residual NH ₃ is removed from the processing furnace 202. At this time, if an inert gas such as N ₂ is supplied to the processing furnace 202, the effect of eliminating residual NH ₃ is further enhanced. DCS is stored in the gas reservoir 247 so that the pressure is 20000 Pa or more.

Further, the apparatus is configured such that the conductance between the gas reservoir 247 and the processing furnace 202 is 1.5 × 10 ⁻³ m ³ / s or more. At this time, when considering the ratio between the volume of the reaction tube 203 and the volume of the necessary gas reservoir 247, the volume of the reaction tube 203 is preferably 100 to 300 cc when the volume of the reaction tube 203 is 100 liters. The gas reservoir 247 is preferably 1/1000 to 3/1000 times the reaction chamber volume.

[Step 3]
In step 3, when exhaust of the processing furnace 202 is completed, the fourth valve 243d of the gas exhaust pipe 231 is closed to stop the exhaust. The third valve 243c on the downstream side of the second gas supply pipe 232b is opened. As a result, the DCS stored in the gas reservoir 247 is supplied to the processing furnace 202 at once. At this time, since the fourth valve 243d of the gas exhaust pipe 231 is closed, the pressure in the processing furnace 202 is rapidly increased to about 931 Pa (7 Torr). At this time, the time for supplying DCS was set to 2 to 4 seconds, and then the time for exposure to the increased pressure atmosphere was set to 2 to 4 seconds, for a total of 6 seconds. The wafer temperature at this time is 300 to 600 ° C. as in the case of supplying NH ₃ .

By supplying DCS, NH ₃ and DCS on the base film react with each other to form a SiN film on the wafer 200. After the film formation, the third valve 243c is closed, the fourth valve 243d is opened, and the processing furnace 202 is evacuated to remove the gas after contributing to the film formation of the remaining DCS. At this time, if an inert gas such as N ₂ is supplied to the processing furnace 202, the effect of removing the remaining gas after contributing to the film formation of DCS from the processing furnace 202 is enhanced. Further, the second valve 243b is opened and the supply of DCS to the gas reservoir 247 is started.

  Steps 1 to 3 are defined as one cycle, and this cycle is repeated a plurality of times to form a SiN film having a predetermined thickness on the wafer.

  In the ALD apparatus, gas is adsorbed on the surface of the base film. The amount of gas adsorption is proportional to the gas pressure and the gas exposure time. Therefore, in order to adsorb a desired amount of gas in a short time, it is necessary to increase the gas pressure in a short time. In this respect, in the present embodiment, the DCS stored in the gas reservoir 247 is instantaneously supplied after the fourth valve 243d is closed, so the DCS pressure in the processing furnace 202 is rapidly increased. The desired amount of gas can be instantaneously adsorbed.

Further, in the present embodiment, while DCS is stored in the gas reservoir 247, NH ₃ gas, which is a necessary step in the ALD method, is excited as plasma to be supplied as active species and the processing furnace 202 is exhausted. As a result, no special steps are required to store the DCS. Further, since the inside of the processing furnace 202 is exhausted to remove the NH ₃ gas, DCS is flowed, so that they do not react on the way to the wafer 200. The supplied DCS can be effectively reacted only with NH ₃ adsorbed on the wafer 200.

1A and 1B are structural views of a substrate processing furnace according to an embodiment of the present invention, in which FIG. 1A is an upper cross-sectional view and FIG. 1B is a cross-sectional view along line aa in FIG. That is, (b) is a side sectional view. It is a perspective view of a substrate processing apparatus using a substrate processing furnace of the present invention. It is sectional drawing of the substrate processing apparatus shown in FIG. It is a schematic block diagram of the vertical substrate processing furnace concerning embodiment of this invention, Comprising: It is the block diagram which showed the processing furnace part with the longitudinal cross-section. It is the block diagram which showed the process furnace part shown in FIG. 4 in the cross section.

Explanation of symbols

1 reaction tube, 2 substrate, 3 seal cap, 4, 4a, 4b, 4c discharge electrode end, 5a, 5b discharge electrode, 6 buffer chamber, 8 oscillator, 9 aligner, 10 small hole, 11 plasma, 12 boat, 14 Dielectric tube, 16 high frequency transformer, 17a, 17b, 17c winding, 20 parasitic plasma, 22 monitor electrode, 100 cassette, 101 housing, 105 cassette stage, 109 cassette shelf, 110 spare cassette shelf, 112 wafer transfer machine, 113 Transfer elevator, 114 Cassette transfer machine, 115 Cassette elevator, 116 Furnace port shutter, 118 Clean unit, 121 Boat elevator, 122 Lifting member, 123 Transfer shelf, 124 Transport control means, 200 Wafer, 202 Processing furnace, 203 Reaction tube, 207 heater, 217 218 quartz cap, 219 seal cap, 220 O-ring, 224 plasma generation region, 231 gas exhaust pipe, 232a first gas supply pipe, 232b second gas supply pipe, 233 nozzle, 237 buffer chamber, 241a first 1 mass flow controller, 241b second mass flow controller, 243a first valve, 243b second valve, 243c third valve, 243d fourth valve, 246 vacuum pump, 247 gas reservoir, 248a first gas supply Hole, 248b second gas supply hole, 248c third gas supply hole, 249 gas supply unit, 267 boat rotation mechanism, 269 first rod-shaped electrode, 270 second rod-shaped electrode, 271 ground, 272 aligner, 273 High frequency power supply, 275 electrode protection tube, 321 controller Over La

Claims (1)

A processing chamber for processing the substrate;
Gas supply means for supplying a reactive gas into the processing chamber;
A pair of discharge electrodes for generating plasma by applying a high-frequency voltage and exciting the reactive gas supplied by the gas supply means by the plasma;
A monitor electrode for measuring the potential of plasma generated by the pair of discharge electrodes;
Voltage applying means for applying a potential having a polarity opposite to that of the plasma measured by the monitor electrode to the pair of discharge electrodes;
A substrate processing apparatus comprising:

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