JP3926977B2 - Semiconductor manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention Semiconductor device In particular, a process gas is introduced into a vacuum vessel to process a substrate to be processed. Semiconductor device It relates to the manufacturing method.
[0002]
[Prior art]
In a semiconductor manufacturing apparatus that generates plasma and decomposes a process gas to process a substrate to be processed, specifically, a plasma etching apparatus or a plasma CVD apparatus, the substrate to be processed is usually processed by the following procedure. First, a process gas or the like is introduced into a processing vessel evacuated to a vacuum, and plasma is generated by applying a high frequency to decompose and excite the gas. The substrate to be processed is processed using the active species thus generated with high reactivity. In such a semiconductor manufacturing apparatus, not all of the process gas introduced into the vacuum container is consumed by the reaction with the substrate. Rather, most of the process gas introduced into the vacuum vessel is not used but is exhausted to the outside by the exhaust device. Therefore, it has been demanded to reduce the cost of the gas in the production cost in the etching or CVD process by improving the gas utilization efficiency.
[0003]
By the way, in the etching process and the CVD process, PFC gas having a high GWP (global warming potential) is used in various amounts and in large quantities as a cleaning gas for treatment and apparatus. In order to suppress global warming, the semiconductor manufacturing industry is required to reduce the amount of PFC gas emitted. However, at present, it is very difficult to find an alternative gas that has a low GWP, is safe, and has a performance equal to or higher than that of PFC gas. Therefore, it has been an important issue to increase the utilization efficiency of the process gas currently in use and to reduce the amount of use.
[0004]
As an effective apparatus for solving this problem, an apparatus described below has been proposed (Japanese Patent Laid-Open No. 9-251981). Here, in a plasma etching apparatus or a plasma CVD apparatus for processing a substrate in a vacuum processing container, a circulation pipe that connects the exhaust pipe and the processing container is provided, and a part of the exhausted gas is returned to the processing container. It is described that it can be reused.
[0005]
Hereinafter, a case where a silicon oxide film is etched while circulating gas using a DRM type plasma etching apparatus having a circulation mechanism will be described.
[0006]
A schematic block diagram of the apparatus used is shown in FIG. As shown in the figure, a parallel plate type plasma generation mechanism composed of a cathode electrode 102 and an anode electrode 103 facing each other is provided in the processing chamber 101, and is parallel to the processing chamber by a magnetic field application mechanism (not shown). A magnetic field is formed. A substrate to be processed 104 is installed on the cathode electrode 102, and a high frequency power source 106 is connected to the cathode electrode via a matching circuit 105. On the other hand, the anode electrode 103 incorporates a shower nozzle 107 for uniformly supplying a process gas to the substrate to be processed. The shower nozzle includes one or more flow control devices 108 and an on-off valve 109 (as required). Gas cylinders 110, which are process gas supply sources, are connected via V1). In the illustrated apparatus, one flow control device 108 and one gas cylinder 110 are shown, but the number thereof can be appropriately determined as necessary.
[0007]
A turbo molecular pump 112 is connected to the processing chamber 101 via an automatic pressure control valve 111 (APC1), and a dry pump 113 is further connected to the exhaust side of the turbo molecular pump. In addition, a circulation pipe 114 that connects the exhaust side of the turbo molecular pump 112 and the processing chamber 101 is provided, and an open / close valve 116 (V2) is provided in the circulation pipe 114 to adjust the circulation amount. An automatic pressure adjustment valve 115 (APC2) is installed on the front side.
[0008]
When processing a substrate to be processed using the apparatus shown in the figure, first, C gas is supplied from the gas cylinder 110 via the flow rate adjusting device 108. _Four F ₈ , CO, Ar and CO ₂ Gas is supplied to the processing chamber 101 at a desired ratio. Here, the flow rate of the gas introduced into the processing chamber is indicated as Q1. At the same time, the opening / closing valve 116 provided in the circulation pipe 114 is opened, and the opening degree of the automatic pressure adjustment valve 115 before the dry pump 113 is reduced. Part of the exhaust gas exhausted from the processing chamber 101 by the turbo molecular pump 112 returns to the processing chamber via the circulation pipe 114. The flow rate of the exhaust gas returning to the processing chamber 101 is indicated as Q2. That is, since the exhausted process gas is reused, the amount of new gas introduced can be reduced by that amount as compared with the case where it is not circulated.
[0009]
Such a process is performed in a procedure (sequence) as shown in FIG. At the time of idle between processes (a in the figure), the on-off valves V1 and V2 are closed, APC1 and APC2 are fully opened, and the pressure P1 in the processing chamber 101 and the pressure P2 in the circulation pipe 114 are reached. Apply vacuum.
[0010]
Next, in the gas introduction / pressure adjustment step (b in the figure), V1 is opened and C is discharged from the gas cylinder 110 via the flow rate control device. _Four F ₈ , CO, Ar and O ₂ While supplying the gas at a desired ratio, the pressure P1 in the processing chamber 101 is adjusted to a desired pressure by the automatic pressure adjustment valve APC1 (111). At the same time, the opening degree of the automatic pressure control valve APC2 (115) is adjusted, and a certain ratio, for example, 80% of the exhaust gas exhausted from the processing chamber 101 by the turbo molecular pump 112 is processed through the circulation pipe 114. Return to the room. When the respective pressures of P1 and P2 are stabilized, high frequency power is applied (c in the figure), and etching is started.
[0011]
When processing is performed for a desired time, high-frequency power is turned off (d in the figure), valves V1 and V2 are closed, APC1 and APC2 are fully opened (e in the figure), and gas is discharged from the processing chamber 101 and the circulation pipe 114. Exhaust completely.
[0012]
According to this method, it is possible to increase the use efficiency of the process gas and reduce the amount of gas used by circulating the exhausted gas to the processing chamber. Moreover, as a result of this, the amount of PFC released could be significantly suppressed. However, it has been found that there are some problems in applying to a plasma treatment process at an actual production site. One is accumulation of sediment in the circulation pipe during long-term running. In plasma CVD processes as well as in etching processes that require high selectivity, such as highly selective oxide film etching, the circulating gas components tend to contain many reactive components with a high probability of adsorption to the solid surface. is there. Most of them adhere to the inner wall of the processing chamber, but some are considered to adhere to the inner wall when passing through the circulation pipe. When the deposit attached to the inner wall peels off and flows into the processing chamber as dust, it may adhere to the wafer and reduce the yield of devices being processed. At present, in order to prevent the deposits from peeling off and flowing into the processing chamber as dust, the entire circulation pipe is replaced at regular intervals. A method of providing a filter in the circulation pipe has also been proposed, but a normal filter is not preferable because it causes a decrease in conductance.
[0013]
Another problem relates to a method for controlling the amount of circulating gas. At present, the amount of circulating gas is controlled as follows. First, when the opening / closing 116 (V2) is closed and the automatic pressure control valve 115 (APC2) is fully opened, that is, when the introduced gas flow rate Q1 = 100 sccm without the gas circulating to the processing chamber 101, the desired pressure is obtained. The automatic pressure control valve 111 (APC1) is adjusted. It is assumed that the position of the valve APC1 at this time becomes 100. Next, when a high frequency power of 1 kW is applied, the process gas is decomposed, so that the valve APC1 is opened to maintain a constant pressure in the processing chamber, and the position becomes 110. Thereafter, the valve APC1 is kept at the position of 110, the flow rate of the introduced gas is set to the first 20%, that is, 20 sccm, the valve V2 is opened until the pressure returns to a desired pressure, and the valve APC2 is squeezed to increase the circulation flow rate. The position of the valve APC2 at this time is stored in the recipe as the position when the circulation rate is 80%.
[0014]
Remember the position of the valve APC2 for each flow rate, pressure, and high-frequency power condition of the introduced gas, and when performing actual processing, set the APC2 in that position in advance, introduce Q1, and operate the valve V2 It was possible to reproduce 80% of the circulation amount. However, the above-described method has a problem in that the position of the valve APC2 has to be checked for each process condition, which is troublesome.
[0015]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, A method of manufacturing a semiconductor device that reduces the amount of process gas used and reduces production costs and environmental burdens while controlling the flow rate of circulating gas with a simple method with good reproducibility. The purpose is to provide.
[0017]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides: A method of manufacturing a semiconductor device for processing a substrate to be processed by supplying a process gas into an exhausted processing container and applying high-frequency power to plasma the process gas to process the substrate, and the process exhausted from the processing container At least part of the gas is reintroduced into the processing container, the reintroduction of the process gas into the processing container is stopped, and then the application of the high-frequency power is stopped. I will provide a.
[0024]
In this case, it is preferable to keep the pressure constant by stopping the reintroduction of the process gas into the processing container and at the same time increasing the flow rate of the process gas supplied to the processing container.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a semiconductor manufacturing apparatus and method of the present invention will be described in detail with reference to the drawings.
[0026]
Example 1
FIG. 3 shows the DRM type plasma etching apparatus of this embodiment.
[0027]
In etching a silicon oxide film while circulating a gas using a DRM type plasma etching apparatus having a circulation mechanism, an example of applying a recipe for SAC used in a conventional apparatus without a circulation mechanism, that is, a circulation rate An example in which is changed will be described.
[0028]
In FIG. 3, the schematic block diagram of the used apparatus is shown. Note that description of portions common to FIG. 1 is omitted. A dust capturing mechanism 117 for capturing a reaction product having a high adhesion rate in the circulating gas is attached at a position near the branch from the circulation pipe 114.
[0029]
FIG. 4 shows an example of the configuration of the capture mechanism 117. The circulation pipe 114 is provided with a detachable U-shaped bent portion as a dust capturing mechanism 117. As shown in the drawing, two opposing glass windows 118a and 118b are provided in the U-shaped bent portion, and a light source 119 is attached to one of them and a light receiving element 120 is attached to the other.
[0030]
In order to examine the effect of the trapping mechanism in this example, first, an oxide film on the semiconductor substrate was etched while circulating gas in an etching apparatus that does not have such a trapping mechanism. As a result, in about 6 months, a thin accumulation of the reaction product that was observable was observed in the entire inside of the circulation pipe. At this time, no dust was generated in the processing chamber, but this circulation pipe was replaced as a whole in a preventive manner.
[0031]
On the other hand, in the etching apparatus provided with the capture mechanism 117 shown in the present embodiment, when the light intensity of the light source 119 detected by the light receiving element 120 is attenuated and falls below the reference value, only this capture mechanism portion is removed. Replaced with cleaned spare parts. The light intensity decreases due to deposits attached to the glass window provided in the bent portion. The degree of this reduction varies depending on the operating rate and use conditions of the apparatus, but in this example, only a portion of the capture mechanism was replaced with a cleaned spare part every other month on average. As a result, even after two years had passed, no deposits were seen in other parts of the circulation pipe 114, and there was no need to replace them.
[0032]
The dust trapping mechanism 117 is not limited to the example shown in FIG. Any member that is detachable and can change the direction of gas flow by 180 ° or more can be used as the dust capturing mechanism 117 in the present invention. For example, a member such as a shape that is combined with a direction changing portion (such as an elbow) of a pipe, a shape that is bent a plurality of times, or a U-shaped or a spiral-shaped bent shape may be used.
[0033]
5 and 6 show another example of the dust trapping mechanism 117. FIG. 5A is a combination of a U-shaped part and a bent part, FIG. 5B is a combination of a spiral and a bent part, and FIG. 5C is a combination of a U-shaped part and a straight part. It is. 6A shows a combination of a spiral and a straight line part, FIG. 6B shows a combination of a U-shaped part and a position changing part, and FIG. 6C shows a U-shaped type. It is the bend part.
[0034]
The shape of the dust trapping mechanism 117 can be selected according to the piping space, cleaning frequency, necessary conductance, etc., but when reused, a curved shape without corners is used from the viewpoint of easy cleaning. preferable.
[0035]
Furthermore, in the present invention, the dust trapping mechanism 117 can be configured by keeping a part of the circulation pipe at a lower temperature than the other parts. Components that may adhere to the inner wall of the pipe and become a dust source are intensively captured by a dust trapping mechanism having a low temperature. In this case, the temperature of the dust trapping mechanism 117 is set to a temperature that does not adsorb a gas component having a high vapor pressure that contributes to etching.
[0036]
Here, with reference to the vapor pressure curves of various etching gases shown in the graph of FIG. 7, the appropriate temperature of the dust holding mechanism 117 will be specifically described. Since the operating pressure in the circulation pipe 114 is 1 to 10 Torr, for example, C required for etching _Four F ₈ It can be seen from this vapor pressure curve that the temperature of the trapping part should be set to approximately −75 ° C. or higher in order to prevent the gas from adsorbing. On the other hand, for example, CF ₂ Is not adsorbed at 150 ° C. or higher, and must be 150 ° C. or lower. Alternatively, SiF that may generate dust in the processing chamber due to plasma decomposition when exhausted and circulated in large quantities _Four In order to adsorb etc., -150 degrees C or less is required.
[0037]
Note that the lower the temperature of the dust trapping mechanism 117, the higher the trapping efficiency and the more compact and effective. However, when the temperature is excessively low, the structure as a device becomes complicated, for example, it is necessary to have a heat insulating structure at room temperature or lower. Therefore, it is desirable to select the temperature of the dust capturing mechanism 117 in consideration of these.
[0038]
FIG. 8 shows an example in which the dust trapping mechanism 117 is installed by providing a low temperature part in the circulation pipe. Specifically, the low-temperature portion was provided in the circulation pipe by attaching the pipe through which the cooling water flowed to the outside or the inside of the circulation pipe. FIG. 8A shows a case where a pipe 122 in which water cooled to about 10 ° C. with a chiller is flowing is attached to the pipe 114, and FIG. 8B shows a similar pipe 122 attached inside the pipe. Is the case. Furthermore, FIG.8 (c) is a case where the same pipe 122 and the above-mentioned U-shaped bending piping are combined.
[0039]
In the case of the configuration shown in FIG. 8B, since the cooled trapping part is provided under reduced pressure, it is only necessary to insulate only the refrigerant supply part. Therefore, it could be kept at −10 ° C. relatively easily as compared with the case of FIG. 8A, and the adsorbed component could be captured with high efficiency. Or the method of winding a heater around piping parts other than a capture part, etc. and keeping the temperature high may make the capture part relatively low temperature. Furthermore, it can also be used in the combination of warming other parts while cooling the capture part.
[0040]
In addition to the method described above, in the present invention, an electrostatic dust collector can be attached inside the circulation pipe and used as a dust trapping mechanism.
[0041]
Here, the electrostatic dust collector 130 will be described in detail with reference to FIGS. 9 to 11. FIG. 9 is an exploded view showing the structure of the electrostatic dust collector 130. As shown in FIG. 9, the electrostatic precipitator has a charging unit 131 for charging dust negatively on the upstream side, and a capturing unit 132 for adsorbing negatively charged dust is provided on the downstream side. It has been. The charging unit 131 includes a thin wire electrode 134 fixed to an insulating frame 133 such as ceramics, and the capturing unit 132 includes a flat plate electrode 135 fixed to an insulating frame 133 such as ceramics.
[0042]
As shown in FIG. 10, the electrostatic precipitator has a lead wire 136a, b for connecting the thin wire electrode and the plate electrode to a high voltage power source (not shown) outside the vacuum pipe. Along with the voltage introduction terminals 137a, b for connecting the electrodes to a high voltage power supply outside the vacuum pipe, they are mounted in the circulation pipe.
[0043]
As shown in FIG. 11, the plate-like electrode 135 constituting the trap part 132 of the electrostatic dust collector is formed by forming electrodes on both surfaces of an insulating plate, and one side of the opposing electrode is a ground electrode. (The same potential as the piping) 138, the other is wired to be the high voltage electrode 139.
[0044]
Such an electrostatic precipitator can be installed in the circulation pipe 114 of the semiconductor manufacturing apparatus shown in FIG. 3, and processing can be performed while circulating gas as follows. For example, −2 kV is applied to the thin wire electrode 134 and 3.5 kV is applied to the high potential side of the plate electrode 135. When passing through the charging unit 131 where the thin wire electrode 134 is installed, the dust is negatively charged by a strong negative electric field, and thereafter is captured by the surface of the high voltage electrode 139 of the downstream capturing unit 132.
[0045]
After the processing is completed, the flow rate adjustment valve V2 (116) is closed, and the gas in the circulation pipe 114 is exhausted by the dry pump 113. At this time, when the thin wire electrode 134 and the flat electrode 135 are returned to 0 V, the dust adsorbed only by the electrostatic force is exhausted without passing through the processing chamber 101. Deposits that remain adsorbed to the electrodes even when the voltage is reduced can be removed by periodically removing the electrostatic precipitator and washing the flat electrode.
[0046]
The electrostatic dust collector is not limited to the above-described one, and any device may be used as long as it is a mechanism that charges and adsorbs dust components in the circulating gas. For example, the charging unit 131 can be a thermoelectron supply mechanism using a W filament. Alternatively, in order to increase the charging rate of dust, the number of fine wire electrodes may be increased as necessary within a range that keeps the distance not to be discharged. In order to further improve the capture efficiency, it is also effective to increase the area by increasing the length of the plate-like electrode. Regardless of which configuration is employed, if the electrostatic precipitator having the above-described configuration is employed, the conductance of the circulation pipe is hardly reduced, so that the performance of the gas circulation mechanism is not hindered.
[0047]
In the semiconductor manufacturing apparatus of the present invention, the dust capturing mechanism 117 as described above is preferably provided at a position close to the branch portion of the circulation pipe 114 in any configuration. This makes it possible to capture dust at an early stage. In addition, the larger the dust trapping mechanism, the greater the trapping capability, but this is accompanied by the disadvantage of a decrease in conductance. Therefore, it is desirable to determine the size in consideration of both dust trapping ability and decrease in conductance.
[0048]
Furthermore, even when any type of trapping mechanism is used, the trapping mechanism can be washed without waste if a glass window is provided in the circulation pipe 117 so that deposits can be monitored visually or by an optical method. .
[0049]
(Example 2)
FIG. 12 shows a schematic configuration diagram of the apparatus used. Note that description of portions common to FIG. 1 is omitted.
[0050]
In the illustrated apparatus, the circulation pipe 114 is provided with an orifice portion 141 and a pressure gauge 142 for measuring the pressure upstream of the orifice. The orifice 141 used in the present invention is designed so that the differential pressure before and after it is always three times or more under the use conditions in the circulation mode of the plasma processing apparatus. Critical pressure r _c Varies depending on the specific heat ratio of the gas, but in a normally used gas, if the pressure ratio is three times or more, a sonic flow is obtained. Thereby, when the gas types are the same, the circulating gas flow rate at the orifice portion 141 becomes a value proportional to the pressure upstream of the orifice.
[0051]
That is, based on the measurement result of the pressure gauge 142, the circulating gas flow rate can be immediately known. For example, the circulating gas flow rate can be easily controlled by adjusting the valve V2 (116).
[0052]
Using such an apparatus including the circulation pipe 114 provided with the orifice part 141 and the pressure gauge 142, the treatment can be performed while circulating gas by the following method, for example. First, similar gas conditions used in processing equipment (for example, CF-based gas / Ar conditions, N ₂ / O ₂ And the like, and then, for each, a proportionality constant κ according to the gas condition in the following formula (1) is obtained.
[0053]
Q2 = κ × P2 (1)
Here, Q2 is the circulating gas flow rate, and P2 is the orifice upstream pressure.
[0054]
Specifically, as shown in the graph of FIG. 13, the circulation gas flow rate Q2 is plotted for each gas condition group against the pressure P2 on the upstream side of the orifice, and the proportionality coefficient κ is obtained from the slope of the straight line.
[0055]
Next, in order to control the gas circulation rate to be 80% for a process in which the introduced gas flow rate Q1 when not circulating is 100 sccm, the following adjustment is performed. First, the flow rate of the introduced gas is set to 20 sccm of 20%, and at the same time, the valve V2 (116) is adjusted so that the upstream pressure P2 of the orifice becomes P2 = 80 (sccm) / κ.
[0056]
At this time, the inside of the processing chamber 101 is automatically adjusted by the pressure adjusting valve V1 (111) so as to have a desired pressure. Furthermore, when plasma is discharged by applying high-frequency power, the pressure in the processing chamber rises due to gas decomposition, so that the position of the pressure adjusting valve 111 automatically changes to maintain a desired pressure. . At the same time, the orifice upstream pressure P2 changes, but the valve V2 (116) moves so as to maintain P2 = Q2 / κ and maintain Q2 at 80 sccm.
[0057]
Thus, by providing a predetermined orifice part and a pressure gauge for measuring the upstream pressure of the orifice in the circulation pipe, it becomes possible to easily control the circulation gas flow rate in accordance with a wide range of conditions. It was.
[0058]
The semiconductor manufacturing apparatus and the semiconductor manufacturing method of the present invention have been described above by taking the etching of the silicon oxide film as an example, but the present invention is not limited to this. For example, the present invention can be applied to a control operation of a CVD apparatus that does not use plasma. FIG. 14 is a schematic diagram showing the configuration of a vertical LPCVD apparatus showing an example of the semiconductor device of the present invention.
[0059]
In the illustrated apparatus, a gas cylinder 159 which is a supply source of a film forming process gas and a cleaning gas is connected to the processing chamber 151 via a flow rate control device 158. As the process gas, for example, SiH _Four , And AsH _Three Etc. are used. In addition, a heater 165 for decomposing the process gas with heat is provided in the processing chamber 151.
[0060]
Further, a dry pump 166 is connected to the processing chamber via a pressure regulating valve V1 ′ (160). The dry pump includes a booster pump 167, a main pump 168, and a flow rate adjustment valve V2 ′ (162) provided between the two pumps. A circulation pipe 161 is provided between the booster pump 167 and the flow rate adjustment valve V2 ′ (162), and this circulation pipe 161 is further connected to the processing chamber 151. The circulation pipe 161 is provided with an orifice 163 and a pressure gauge 164 for measuring the pressure on the upstream side of the orifice 163.
[0061]
A case where cleaning is performed while circulating gas using the vertical LPCVD apparatus having such a configuration will be described. In the CVD apparatus, for example, when a polycrystalline silicon film is formed, silicon is deposited not only on the substrate to be processed but also on the inner wall of the processing chamber 151. Therefore, every time a certain amount of film forming process is performed, the processing chamber 151 must be cleaned to remove the deposited film. To perform the cleaning process, ClF _Three Gas is used. This is an active gas having an etching action without being discharged by plasma.
[0062]
Specifically, simultaneously with the film forming process, first, ClF. _Three The gas was introduced into the processing chamber 151 while being controlled to 200 sccm from the cleaning gas inlet. Next, the opening degree of valve | bulb V1 '(160) was adjusted, and pressure P1' in the process chamber 151 was controlled to process pressure 10Torr. On the other hand, by adjusting the opening degree of the valve V2 ′ (162), the pressure P2 ′ upstream of the orifice of the circulation pipe 161 was adjusted to 100 Torr. At this time, the pressure immediately downstream of the orifice 163 is about 20 Torr, and gradually decreases due to the conductance of the circulation pipe 161 to a value in the vicinity of the processing pressure of 10 Torr in the processing chamber.
[0063]
Further, the opening degree of the valve V1 ′ (160) was adjusted again, and the pressure P1 ′ in the processing chamber 151 was controlled to 10 Torr. Since the circulating gas flow rate Q2 ′ when P2 ′ = 100 Torr is about 1800 sccm, the total gas flow rate introduced into the processing chamber is 2000 sccm.
[0064]
As a result, a cleaning rate equivalent to that obtained when 2000 sccm was introduced into the processing chamber 151 without circulating gas was obtained, and the flow rate of newly introduced gas could be greatly reduced. In the vertical LPCVD apparatus used here, the pressure condition is 2 to 10 Torr, and the introduced gas flow rate is SiH. _Four Film formation is performed under the condition of approximately 500 sccm. Also in the circulation operation during film formation, the circulation flow rate could be controlled promptly in response to the change in the film formation conditions based on the proportional relationship between P2 ′ and Q2 ′ investigated in advance.
[0065]
As described above, even when an exhaust means for exhausting the processing chamber is used, which is composed of a booster pump, a main pump, and a flow rate adjusting valve provided between them, it is three times or more under the operating conditions of the apparatus. By using a circulation pipe equipped with an orifice part that can form a differential pressure and a pressure gauge arranged to measure the pressure upstream of this orifice, the flow rate of the circulation gas can be easily adjusted for a wide range of conditions. It became possible to control.
[0066]
(Example 3)
FIG. 15 shows a mechanism that uses a plasma etching apparatus equipped with a circulation mechanism to cause dust flowing into the processing chamber to adhere to the wafer when etching the wafer while circulating the gas, thereby reducing the yield of devices being processed. Will be described with reference to FIG. Note that description of portions common to FIG. 1 is omitted.
[0067]
In order to perform plasma processing, a process gas is introduced into the processing chamber 101, high-frequency power is supplied from a high-frequency power source 106, and a high-frequency electric field is applied between the anode electrode 103 and the cathode electrode 102 to turn the gas into plasma. At this time, a bulk plasma 201 and a sheath 202 are formed in the space in the processing chamber 101. Note that the bulk plasma 201 is an electrically neutral plasma in which positive charges and negative charges are mixed, and the sheath portion 202 has an electric field formed perpendicular to the cathode electrode 102. In general, while the plasma is being formed, the dust 203 in the plasma is negatively charged and is trapped on the boundary surface between the bulk plasma 201 and the sheath in a form repelled by the electric field of the sheath portion 202 and falls on the wafer. It is thought that it will be exhausted without.
[0068]
However, when the sheath electric field collapses, that is, at the moment when the high-frequency power is dropped, the dust generated in the processing chamber or the dust 203 that flows into the processing chamber and is trapped at the boundary surface between the bulk plasma 201 and the sheath 202. Drops on the wafer and adheres. It is difficult to remove dust once adhering to the wafer, resulting in a decrease in device yield.
[0069]
A procedure (sequence) for performing an etching process according to the present embodiment using the apparatus shown in FIG. 15 will be described with reference to FIG.
[0070]
During idling between processes (a in the figure), the on-off valves V1 and V2 are closed, the automatic pressure control valves APC1 and APC2 are fully opened, the pressure P1 in the processing chamber 101, and the pressure in the circulation pipe 114 Both P2 are at the ultimate vacuum.
[0071]
Next, in the gas introduction / pressure adjustment step (b in the figure), V1 is opened and C is discharged from the gas cylinder 110 via the flow rate control device. _Four F ₈ , CO, Ar and O ₂ While supplying the gas at a desired ratio, the pressure P1 in the processing chamber 101 is adjusted to a desired pressure by the automatic pressure adjustment valve APC1 (111). At the same time, the opening degree of the automatic pressure control valve APC2 (115) is adjusted, and a certain ratio, for example, 80% of the exhaust gas exhausted from the processing chamber 101 by the turbo molecular pump 112 is supplied to the processing chamber through the circulation pipe 114. return. When the respective pressures of P1 and P2 are stabilized, high frequency power is applied (c in the figure), and etching is started.
[0072]
When processing is performed for a predetermined time, the gas to be reintroduced is closed by closing V2 (f in the figure), and then the high frequency power is turned off (d in the figure). The time between these is indicated by t. Further, the valves V1 and V2 are closed, the APC1 and APC2 are fully opened (e in the figure), and the gas is completely exhausted from the processing chamber 101 and the circulation pipe 114.
[0073]
As described above, in this embodiment, before the high-frequency power is stopped, the gas circulation is stopped and the processing is performed. As a result, even if some dust was generated or flowed in, it did not fall and adhere to the wafer. As a result, it was possible to double the frequency of cleaning and replacement of the circulation piping.
[0074]
At this time, as can be seen from FIG. 16, the shorter the time t from when the gas circulation is stopped to when the high-frequency power is stopped, the less influence is exerted on the etching characteristics. On the other hand, in order to enhance the dust prevention effect, t is the gas residence time under the processing conditions (when the processing chamber volume is V (L), the pressure is P (Torr), and the gas flow rate is Q (slm), More preferably, the stay time is equal to or longer than V · P · 60 / (760 · Q) (sec)). This is typically V = 3.1 liters, P = 40 × 10 ^-3 When Torr, Q = 700 slm, the dwell time is 14 μs.
[0075]
Example 4
A procedure (sequence) for performing an etching process according to the present embodiment using the apparatus shown in FIG. 15 will be described with reference to FIG.
[0076]
During idling between processes (a in the figure), the on-off valves V1 and V2 are closed, the automatic pressure control valves APC1 and APC2 are fully opened, the pressure P1 in the processing chamber 101, and the pressure in the circulation pipe 114 Both P2 are at the ultimate vacuum.
[0077]
Next, in the gas introduction / pressure adjustment step (b in the figure), V1 is opened and C is discharged from the gas cylinder 110 via the flow rate control device. _Four F ₈ , CO, Ar and O ₂ While supplying the gas at a desired ratio, the pressure P1 in the processing chamber 101 is adjusted to a desired pressure by the automatic pressure adjustment valve APC1 (111). At the same time, the opening degree of the automatic pressure control valve APC2 (115) is adjusted, and a certain ratio, for example, 80% of the exhaust gas exhausted from the processing chamber 101 by the turbo molecular pump 112 is processed through the circulation pipe 114. Return to the room. When the respective pressures of P1 and P2 are stabilized, high frequency power is applied (c in the figure), and etching is started.
[0078]
When processing is performed for a predetermined time, the gas reintroduced by closing V2 is stopped and the supply flow rate Q1 is increased (f in the figure). Thereafter, the high frequency power is turned off (d in the figure). The time between these is indicated by t. Further, the valves V1 and V2 are closed, the APC1 and APC2 are fully opened (e in the figure), and the gas is completely exhausted from the processing chamber 101 and the circulation pipe 114.
[0079]
Thus, in this embodiment, the Q1 flow rate is increased and compensated in conjunction with closing V2 and stopping the circulating gas. As a result, the pressure fluctuation can be almost eliminated, and the plasma becomes unstable, and for example, damage to the device due to the abnormal discharge can be suppressed.
[0080]
While the present invention has been described with reference to specific examples, various modifications can be made without departing from the spirit of the present invention, and the effects of the present invention can be obtained in any case.
[0081]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to prevent the inflow of dust into the processing chamber or to prevent dust from adhering to the wafer without frequently replacing and cleaning the circulation pipe. A semiconductor manufacturing apparatus that can prevent a reduction and can reduce production cost and environmental load is provided. In addition, according to the present invention, there is provided a method for manufacturing a semiconductor device that reduces the amount of process gas used and reduces the production cost and environmental load while controlling the flow rate of the circulating gas with a simple method with good reproducibility. The
[0082]
INDUSTRIAL APPLICABILITY The present invention is particularly effectively used in a semiconductor manufacturing process for processing a substrate to be processed using plasma such as a plasma etching apparatus or a plasma CVD apparatus, and its industrial value is tremendous.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a conventional semiconductor manufacturing apparatus.
FIG. 2 is a diagram showing a processing sequence in a conventional semiconductor manufacturing apparatus.
FIG. 3 is a schematic configuration diagram showing an example of a semiconductor manufacturing apparatus according to the present invention.
FIG. 4 is a schematic view showing an example of a dust trapping mechanism used in the semiconductor manufacturing apparatus of the present invention.
FIG. 5 is a schematic view showing another example of a dust trapping mechanism used in the semiconductor manufacturing apparatus of the present invention.
FIG. 6 is a schematic view showing another example of a dust trapping mechanism used in the semiconductor manufacturing apparatus of the present invention.
FIG. 7 is a graph showing vapor pressure curves of various etching gases.
FIG. 8 is a schematic view showing another example of a dust trapping mechanism used in the semiconductor manufacturing apparatus of the present invention.
FIG. 9 is an exploded view showing the structure of an electrostatic precipitator used in the present invention.
FIG. 10 is a schematic diagram showing a state of an electrostatic precipitator attached in a circulation pipe.
FIG. 11 is a schematic diagram illustrating a plate electrode used in an electrostatic dust collector.
FIG. 12 is a schematic configuration diagram showing another example of a semiconductor manufacturing apparatus according to the present invention.
FIG. 13 is a graph showing the relationship between the orifice upstream pressure P2 and the circulation flow rate Q2.
FIG. 14 is a schematic configuration diagram showing another example of a semiconductor manufacturing apparatus according to the invention.
FIG. 15 is a schematic configuration diagram showing another example of a semiconductor manufacturing apparatus according to the invention.
FIG. 16 is a diagram showing an example of a procedure (sequence) of an etching process according to the present invention.
FIG. 17 is a diagram showing another example of the procedure (sequence) of the etching process according to the present invention.
[Explanation of symbols]
101 ... Processing chamber
102 ... Cathode electrode
103 ... Anode electrode
104 ... Substrate to be processed
105 ... matching circuit
106 ... High frequency source
107 ... Shower nozzle
108 ... Flow control device
109 ... Opening and closing valve
110 ... Gas cylinder
111 ... Automatic pressure control valve
112 ... Turbo molecular pump
113 ... Dry pump
114 ... circulation piping
115 ... Automatic pressure control valve
116: Circulating gas on-off valve
117 ... Capture mechanism
118a, 118b ... Glass window
119 ... Light source
120. Light receiving element
122 ... Cooling water pipe
130 ... Electrostatic dust collector
131: Charging part
132 ... Capture unit
133: Insulator frame
134 ... Fine wire electrode
135: Flat plate electrode
136 ... Lead wire
137 ... Voltage introduction terminal
138 ... Ground electrode
139 ... high voltage electrode
141 ... Orifice part
142 ... Pressure gauge
151. Processing chamber
158 ... Flow control device
159 ... Gas cylinder
160 ... Pressure adjusting valve
161: Circulating piping
162 ... Flow rate adjusting valve
163: Orifice
164 ... Pressure gauge
165 ... Heater
166 ... Dry pump
167 ... Booster pump
168 ... Main pump
201 ... Bulk plasma
202 ... sheath part
203 ... Dust trapped

Claims (2)

A method of manufacturing a semiconductor device for processing a substrate to be processed by supplying a process gas into an exhausted processing container, applying high frequency power to plasma the process gas,
At least a portion of the process gas exhausted from the processing vessel is reintroduced into the processing vessel;
A method of manufacturing a semiconductor device, wherein re-introduction of the process gas into the processing container is stopped, and then application of the high-frequency power is stopped. 2. The semiconductor device according to claim 1, wherein the re-introduction of the process gas into the processing container is stopped, and at the same time, the flow rate of the process gas supplied to the processing container is increased to keep the pressure constant. Production method.

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