JP2012009243A - Plasma processing apparatus and semiconductor device manufacturing method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing apparatus to which a sensor for detecting abnormal discharge can be easily attached without remodeling, and to provide a semiconductor device manufacturing method using the plasma processing apparatus.SOLUTION: On a side wall 8 of a chamber 2 of a plasma processing apparatus 1, an earth wire 9 is attached which fixes the chamber 2 at a ground potential. In the vicinity of the portion of the side wall 8 where the earth wire 9 is connected, a current sensor 10 is attached which measures a return current flowing from plasma generated in the chamber 2 to the ground potential. An abnormal discharge detection unit 14 is electrically connected to the current sensor 10 so as to determine whether or not abnormal discharge has been generated based on the return current thus measured.

Description

  The present invention relates to a plasma processing apparatus and a method of manufacturing a semiconductor device using the same, and more particularly to a plasma processing apparatus applied to sputtering or etching processing, and a method of manufacturing a semiconductor device using such a plasma processing apparatus. It is about.

  In manufacturing a semiconductor device, for example, there is a step of applying a plasma processing apparatus such as a sputtering process or a dry etching process. In the plasma processing apparatus, foreign matter may be generated by abnormal discharge occurring in the plasma generated in the chamber. When the generated foreign matter falls on the surface of the wafer, it becomes a factor of reducing the yield of the semiconductor device.

  In order to eliminate such a decrease in yield due to abnormal discharge, development for detecting abnormal discharge in a plasma processing apparatus has been conventionally performed. For example, a technique is used in which a sensor is incorporated in a power supply line that supplies high-frequency power to a chamber of a plasma processing apparatus, current or voltage is detected, and abnormal discharge is detected from the change. There is also a method of monitoring a sensor in a matching box provided on the power supply side. Patent Document 1 proposes a method for detecting abnormal discharge from a change in DC bias voltage generated by plasma. There is also a method for detecting abnormal discharge by changing the light emission state of plasma. Furthermore, Patent Document 2 proposes a technique for detecting ultrasonic waves generated by abnormal plasma discharge. Patent Document 3 proposes a method of detecting electromagnetic waves generated by abnormal plasma discharge.

JP 2003-234332 A JP 2003-173896 A JP 2003-243367 A

  However, the conventional method for detecting abnormal plasma discharge has the following problems.

  First, in the method of incorporating a sensor in the power supply side line of the plasma processing apparatus, there is a problem in that it is not easy to attach the sensor because large power flows through the power supply side line. In addition, since the current generated by the abnormal discharge is a minute current of about several mV, for example, in a state where a voltage of 1000 V or more is applied, such a minute change in current is detected from the S / N ratio. Is also very difficult. Furthermore, if a sensor is to be incorporated into an existing plasma processing apparatus, the plasma processing apparatus needs to be modified and the plasma processing apparatus must be stopped.

  Further, in the method for detecting abnormal discharge from the change in the light emission state of plasma and the method for detecting electromagnetic waves generated by abnormal discharge, a window is required in the chamber. For this reason, it is difficult to detect a change in the light emission state or to detect an electromagnetic wave in a structure in which plasma is covered with a metal shield as in a sputtering apparatus. In addition, it is practically impossible to provide windows by modifying the existing plasma processing apparatus.

  Furthermore, in the method of detecting ultrasonic waves generated by abnormal discharge, the generated ultrasonic waves are greatly attenuated by an elastic member such as an O-ring used for sealing of the plasma processing apparatus and a minute gap. For this reason, it is necessary to attach a sensor in the vicinity of the location where abnormal discharge occurs, and the place where the sensor is installed is limited. Moreover, it is not easy to attach such a sensor to an existing plasma processing apparatus.

  The present invention has been made to solve the above-described problems, and one object of the present invention is to provide a plasma processing apparatus in which a sensor for detecting abnormal discharge can be easily attached without modification. Another object is to provide a method of manufacturing a semiconductor device using such a plasma processing apparatus.

  A plasma processing apparatus according to an embodiment of the present invention includes a chamber, a power supply unit, a return current measurement unit, and an abnormal discharge detection unit. In the chamber, a predetermined plasma treatment is performed on the semiconductor substrate. The power supply unit supplies predetermined power for generating plasma in the chamber. The return current measurement unit is installed in contact with a return current path flowing from the plasma generated in the chamber toward the ground potential, and measures the return current by a magnetic field generated by the return current. The abnormal discharge detection unit detects the occurrence of abnormal discharge by comparing the return current measured by the return current measurement unit with the return current measured when no abnormal discharge has occurred.

  A method for manufacturing a semiconductor device according to an embodiment of the present invention includes the following steps. In order to perform a predetermined plasma process on the semiconductor substrate, the semiconductor substrate is carried into a chamber of a plasma processing apparatus. Plasma is generated in the chamber. The semiconductor substrate is subjected to plasma treatment by exposing the semiconductor substrate to plasma generated in the chamber. The semiconductor substrate for which the plasma treatment has been completed is carried out of the chamber. An abnormal discharge of the plasma is detected by measuring a return current flowing from the plasma toward the ground potential between the generation of the plasma in the chamber and the completion of the plasma treatment.

  According to the plasma processing apparatus of one embodiment of the present invention, it is determined whether or not an abnormal discharge has occurred by measuring a return current flowing from the plasma toward the ground potential, and measuring the return current. The current measuring unit is installed in a manner in contact with the return current path. Accordingly, the return current measuring unit can be easily installed in the plasma processing apparatus as a sensor for detecting abnormal discharge.

  According to the method for manufacturing a semiconductor device of one embodiment of the present invention, the return current flowing from the plasma toward the ground potential is measured between the generation of the plasma in the chamber and the completion of the plasma processing. By detecting the abnormal discharge of the plasma by the above, the yield of the semiconductor device due to the abnormal discharge can be minimized.

It is sectional drawing which shows the 1st example of the plasma processing apparatus which concerns on Embodiment 1 of this invention. In the same embodiment, it is a perspective view which shows the structure of the current sensor applied to a plasma processing apparatus. In the same embodiment, it is a graph which shows the relationship between the distance from the surface where the electric current flows, and the strength of a magnetic field. In the same embodiment, it is sectional drawing which shows the relationship between a current sensor and a magnetic field. In the same embodiment, it is a 1st graph which shows the relationship between the direction of an electric current, and the output of a current sensor. In the same embodiment, it is a 2nd graph which shows the relationship between the direction of an electric current, and the output of a current sensor. FIG. 6 is a cross-sectional view for explaining the operation of the plasma processing apparatus in the same embodiment. In the embodiment, it is a first partial cross-sectional view showing a state in which a return current flows through an outer wall portion of a chamber. In the same embodiment, it is a graph which shows an example of the return current which was measured by the current sensor and in which abnormal discharge has not occurred. In the same embodiment, it is the 2nd partial sectional view showing signs that return current flows through the outer wall part of a chamber. In the same embodiment, it is a graph which shows an example of the return current in which abnormal discharge has occurred, which is measured by a current sensor. In the same embodiment, it is a top view which shows the attachment position of the current sensor for evaluating the dependence of the installation position of the current sensor in a chamber. 13 is a graph showing a return current measured at a point A shown in FIG. 12 in the same embodiment. 13 is a graph showing a return current measured at a point B shown in FIG. 12 in the same embodiment. 13 is a graph showing a return current measured at a point C shown in FIG. 12 in the same embodiment. 13 is a graph showing a return current measured at a point D shown in FIG. 12 in the same embodiment. 13 is a graph showing a return current measured at a point E shown in FIG. 12 in the same embodiment. 13 is a graph showing a return current measured at a point F shown in FIG. 12 in the same embodiment. In the same embodiment, it is sectional drawing which shows the plasma processing apparatus which concerns on the modification 1. FIG. In the same embodiment, it is sectional drawing which shows the plasma processing apparatus which concerns on the modification 2. FIG. FIG. 10 is a cross-sectional view for explaining the operation of the plasma processing apparatus according to modification 2 in the same embodiment. In the same embodiment, it is sectional drawing which shows the plasma processing apparatus which concerns on the modification 3. FIG. FIG. 11 is a cross-sectional view for explaining the operation of the plasma processing apparatus according to modification 3 in the same embodiment. In the same embodiment, it is sectional drawing which shows the sputtering device as a plasma processing apparatus. It is a figure for demonstrating the method to detect the abnormal discharge of the plasma processing apparatus based on Embodiment 2 of this invention. In the same embodiment, it is a graph which shows the voltage value measured in a normal plasma processing apparatus, and its count number. In the same embodiment, it is a graph which shows the voltage value measured in the plasma processing apparatus in which abnormal discharge generate | occur | produces, and the count number. 5 is a first flowchart for explaining a flow for detecting abnormal discharge of the plasma processing apparatus in the embodiment. In the same embodiment, it is a 2nd flowchart for demonstrating the flow which detects the abnormal discharge of a plasma processing apparatus. In the same embodiment, it is a 3rd flowchart for demonstrating the flow which detects the abnormal discharge of a plasma processing apparatus. In the same embodiment, it is a graph which shows a voltage value and the count number when the signal by abnormal discharge can be judged clearly. In the same embodiment, it is a graph which shows a voltage value and the count number when the signal by abnormal discharge cannot be judged clearly. In the same embodiment, it is a first graph showing a voltage value and its count number when only signals higher than a predetermined threshold voltage are integrated. In the same embodiment, it is the 2nd graph which shows a voltage value at the time of integrating only a signal higher than a predetermined threshold voltage and its count number. In the embodiment, it is a third graph showing the voltage value and the count number when only signals higher than a predetermined threshold voltage are integrated. It is sectional drawing which shows 1 process of the manufacturing method of the semiconductor device using the plasma processing apparatus based on Embodiment 3 of this invention. FIG. 37 is a cross-sectional view showing a step performed after the step shown in FIG. 36 in the same embodiment. FIG. 38 is a cross-sectional view showing a step performed after the step shown in FIG. 37 in the same embodiment. FIG. 39 is a cross-sectional view showing a step performed after the step shown in FIG. 38 in the same embodiment. FIG. 40 is a cross-sectional view showing a step performed after the step shown in FIG. 39 in the same embodiment. FIG. 41 is a cross-sectional view showing a process performed after the process shown in FIG. 40 in the same embodiment. FIG. 42 is a cross-sectional view showing a process performed after the process shown in FIG. 41 in the same Example. FIG. 43 is a cross-sectional view showing a step performed after the step shown in FIG. 42 in the same embodiment. FIG. 44 is a cross-sectional view showing a step performed after the step shown in FIG. 43 in the same embodiment. FIG. 45 is a cross-sectional view showing a step performed after the step shown in FIG. 44 in the same embodiment.

Embodiment 1
Here, a plasma processing apparatus will be described. As shown in FIG. 1, a stage 3 on which a wafer is placed is provided in a chamber 2 of a plasma processing apparatus 1. The stage 3 is connected to a high frequency power supply unit 4 for generating plasma. A matching box 5 for impedance matching is connected to the power cable 4a of the high frequency power supply unit 4. A gas supply unit 6 for feeding a predetermined gas into the chamber 2 is provided at the upper part of the chamber 2. A gas exhaust port 7 for exhausting the gas in the chamber 2 is provided at the lower portion of the chamber 2. An earth wire 9 for fixing the chamber 2 to the ground potential is attached to the outer wall portion 8 of the chamber 2.

  A current sensor 10 is attached in the vicinity of the portion of the outer wall 8 to which the ground wire 9 is connected. The current sensor 10 measures the return current that flows from the plasma generated in the chamber 2 toward the ground potential. An abnormal discharge detector 14 is electrically connected to the current sensor 10 and, as will be described later, it is determined whether or not an abnormal discharge has occurred based on the measured return current. In the current sensor 10, the current generated by the magnetic field formed by the return current is output as a voltage signal based on the principle of the current transformer. As shown in FIG. 2, the current sensor 10 includes an iron core 11 as a core and a coil 12 wound around the iron core 11. The iron core 11 and the coil 12 are accommodated in a predetermined case 13.

  As shown in FIG. 3, the strength of the magnetic field generated by the flow of current decreases exponentially as the distance from the current flow path increases. For this reason, it is desirable to attach the current sensor 10 so as to be in contact with the surface of the outer wall portion 8 through which the return current flows. Further, the current flowing through the coil 12 depends on the relative positional relationship between the magnetic field and the coil 12. As shown in FIG. 4, in the coil 12 wound in the longitudinal direction of the iron core 11, the longitudinal direction of the iron core 11 can be made substantially orthogonal to the flowing direction of the return current (skin current 31) flowing through the skin of the conductor portion. desirable. As a result, the magnetic field 32 formed by the return current has the highest component 33 passing through the coil 12, the voltage value output from the current sensor is the highest, and abnormal discharge can be detected more reliably.

  FIG. 5 and FIG. 6 are the results showing the dependence of the arrangement of the current sensor on the return current flow direction measured by the inventors. FIG. 5 shows the current almost perpendicular to the return current flow direction. FIG. 6 is a graph when the sensor is arranged (case A), and FIG. 6 is a graph when the current sensor is arranged in parallel to the direction in which the return current flows (case B). As shown in FIGS. 5 and 6, in case A, a voltage about 10 times that in case B is measured. Thus, the current sensor 10 can capture the current waveform of the return current as a change with time in voltage.

  The material of the portion of the current sensor 10 that contacts the outer wall portion 8 of the chamber 2 is preferably an insulator that passes a magnetic field and does not generate eddy currents due to a high-frequency electromagnetic field, and the outer wall portion of the chamber is a heater. Heat-resistant ceramics and the like are more desirable because they often reach a relatively high temperature due to heat.

  Further, when installing the current sensor 10 (see FIG. 1 and the like), the current sensor 10 is brought into close contact with the outer wall portion 8 so that there is no gap between the current sensor 10 and the outer wall portion 8, and the return current is set. It is desirable to install so that 22 is almost perpendicular to the flowing direction. For this reason, when the surface of the part of the outer wall part 8 to be installed is a curved surface, it is desirable to form the surface of the part of the current sensor 10 in contact with the outer wall part 8 into a curved surface corresponding to the curved surface. Further, the current sensor 10 is fixed so that the current sensor 10 does not move during measurement, and the current sensor 10 is directed toward the outer wall 8 with a constant force so that the distance between the current sensor 10 and the outer wall 8 does not change. It is desirable to energize.

  Further, the jig for fixing the current sensor 10 to the outer wall portion 8 or the like needs to be electrically insulated from the main body portion of the current sensor 10. In particular, it is necessary to prevent the connector (not shown) of the coaxial cable for signal output of the current sensor 10 from coming into contact with the jig. This is because the return current to be measured is affected by such contact, and accurate measurement cannot be performed.

  Next, operation | movement of the plasma processing apparatus 1 mentioned above is demonstrated. As shown in FIG. 7, the chamber 2 is first depressurized to a predetermined pressure by exhausting from the gas exhaust port 7. Next, in this state, for example, argon (Ar) gas is introduced into the chamber 2 from the gas supply unit 6 as a gas for generating plasma. Next, predetermined high frequency power is supplied into the chamber 2 by the high frequency power supply unit 4. Argon (Ar) gas is dissociated by the high frequency power supplied into the chamber 2, and a plasma 21 is generated in the space between the stage 3 and the gas supply unit 6. Thereafter, a predetermined gas for etching is sent from the gas supply unit 6 toward the plasma 21, so that the gas is dissociated and the semiconductor substrate (wafer) 51 placed on the stage 3 is subjected to an etching process. It will be.

  During the plasma processing, a return current 22 flows from the generated plasma 21 through the chamber 2 toward the grounded ground wire 9. At this time, as shown in FIG. 8, the return current 22 flowing from the plasma 21 through the outer wall 8 of the chamber 2 flows near the surface of the outer wall 8 of the chamber 2 due to the skin effect. The skin effect refers to a phenomenon in which when the frequency of current flowing through a conductor increases, the current collects and flows on the surface of the conductor. For example, if the power supply frequency is 13.56 MHz, when the material of the chamber 2 is aluminum (Al), a current flows in a region having a depth of about 22.4 μm from the surface. When the abnormal discharge has not occurred, the current accompanying the abnormal discharge is not measured in the current waveform of the return current 22 measured by the current sensor 10. An example of the measured current waveform of the return current (voltage change with time) is shown in FIG.

  On the other hand, when an abnormal discharge has occurred, as shown in FIG. 10, the current associated with the abnormal discharge 23 also flows near the surface of the outer wall portion 8 of the chamber 2 toward the ground wire 9. In this case, a pulsed current accompanying abnormal discharge is measured. An example of the actually measured current waveform is shown in FIG. As shown in FIG. 11, in the current waveform in which abnormal discharge has occurred, it can be seen that the pulse current 25 that is not found in the current waveform in which abnormal discharge has not occurred (see FIG. 9) is measured.

  In the plasma processing apparatus 1 described above, the return current 22 flowing from the plasma 21 toward the ground wire (ground potential) 9 is measured by the current sensor 10 installed so as to be in contact with the outer wall portion 8 of the chamber 2. Detect discharge. Accordingly, the current sensor can be easily attached without using a special jig or the like as compared with the case where the sensor is incorporated in the power supply line of the high frequency power supply unit. Further, in order to attach the sensor to the plasma processing apparatus, it is not necessary to make modifications such as stopping the operation of the plasma processing apparatus and providing a window, and the operating rate of the plasma processing apparatus is not lowered. Furthermore, since abnormal discharge is detected by measuring the return current, there are few restrictions on the position where the current sensor 10 is installed, and the current sensor 10 can be installed at a place where abnormal discharge is expected to occur, which is more reliable. An abnormal discharge can be detected.

(Modification 1)
It is desirable to install the current sensor at a location where abnormal discharge is expected to occur. However, depending on the plasma processing apparatus, it may be difficult to specify the location where abnormal discharge occurs. If the current sensor is installed in the opposite circumferential direction position with respect to the circumferential position of the outer wall of the chamber where abnormal discharge occurs, the current associated with the abnormal discharge is detected by the current sensor. It becomes difficult.

  Even when it is difficult to identify the location where such abnormal discharge occurs, the return current flowing from the plasma to the outer wall of the chamber eventually flows toward the ground line (ground potential), so the current sensor is grounded. It has been found by the inventors' evaluation that the sensitivity of detecting abnormal discharge can be increased by installing the wire near the portion of the outer wall portion to which the wire is connected.

  The inventors measured the current waveform by using a plasma processing apparatus that is likely to generate abnormal discharge and installing current sensors at six circumferential positions on the outer wall of the chamber as shown in FIG. The current waveforms are shown in FIGS. 13, 14, 15, 16, 17, and 18, respectively. As shown in FIGS. 13 to 18, the current waveform (voltage value) measured increases as the outer wall portion 8 to which the ground wire 9 is connected approaches the circumferential position, and the ground wire 9 is connected. It turns out that it is the largest in the circumferential position. From this evaluation result, as shown in FIG. 19, it is possible to increase the sensitivity of detecting the abnormal discharge 23 by installing the current sensor 10 in the vicinity of the portion of the outer wall 8 to which the ground wire 9 is connected. found.

(Modification 2)
As described above, the return current flowing from the plasma through the outer wall portion of the chamber finally flows toward the ground line (ground potential). Therefore, as shown in FIG. 20, the current sensor 10 may be installed so as to be in contact with the ground wire 9. In this case, as shown in FIG. 21, the return current 22 accompanying the abnormal discharge 23 generated in the chamber 2 flows through the ground wire 9 through the outer wall portion 8 of the chamber 2. Even if it is not possible to clearly identify the location where the discharge occurs, the abnormal discharge 23 can be detected more reliably.

(Modification 3)
Depending on the plasma processing apparatus, the ground wire may not be provided. In such a plasma processing apparatus, as shown in FIG. 22, it is desirable to install the current sensor 10 in such a manner that it contacts the ground path of the power cable 4 a of the high frequency power supply unit 4. For example, you may install the current sensor 10 so that the metal connector part of the power cable 4a connected to the chamber 2 may be contacted. Moreover, you may install a current sensor so that the matching box 5 made from metal which matches impedance may be contacted. In this case, as shown in FIG. 23, it becomes easy to detect the abnormal discharge 23 generated particularly in the vicinity of the semiconductor substrate (wafer) 51 placed on the stage 3.

  In the plasma processing apparatus described above, the current sensor 10 is exemplified by a current sensor including an iron core and a coil using the principle of a current transformer. In addition to such a current sensor, a method of measuring the return current using the Faraday effect of insulating glass or the like may be used. The Faraday effect is a phenomenon in which when a magnetic field is applied to a substance, the plane of polarization rotates when linearly polarized light is transmitted in a direction parallel to the magnetic field. In this case, insulative optical fiber can be used for the input and output of light to the glass instead of the coaxial cable for signal output, and the return due to contact between the connector of the coaxial cable for signal output and the jig etc. The influence on the current can be eliminated.

Alternatively, a method of measuring return current using a crystal having a Pockels effect may be used. The Pockels effect is a phenomenon in which, when an electric field is applied to a dielectric isotropic crystal, the refractive index of the isotropic crystal changes in proportion to the strength of the electric field and exhibits birefringence. In this case, as the isotropic crystal, ammonium dihydrogen phosphate (ADP: ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ )) or potassium dihydrogen phosphate (KDP: potassium dihydrogen phosphate (KH ₂ PO ₄₎ )) Crystals can be used. In particular, crystals of bismuth germanium oxide (BGO: Bismuth Germanium Oxide (Bi ₁₂ GeO ₂₀ )) do not have deliquescence and are suitable for measurement. Moreover, the influence on return current can be eliminated by using an insulating optical fiber to obtain light to the crystal.

  In the plasma processing apparatus 1 described above, the etching apparatus has been described as an example. However, as the plasma processing apparatus, there is a plasma processing apparatus applied to a film forming process in addition to the etching process. For example, there is a plasma CVD apparatus that introduces a predetermined material gas into a chamber and forms a predetermined film by chemical vapor deposition. There is also a sputtering device. As shown in FIG. 24, in the sputtering apparatus as the plasma processing apparatus 1, a sputtering material target 15 is arranged on the side facing the stage 3 on which the semiconductor substrate 51 is placed. A DC power supply 16 is connected to the target 15 and is electrically insulated from the chamber 2 by a shield flange 17. A ground shield 18 is provided in the chamber 2. Stage 3 is connected to ground potential. Also in the sputtering apparatus, the current sensor 10 is installed so as to be in contact with the vicinity of the portion of the outer wall portion 8 of the chamber 2 to which the ground wire 9 is connected, or it is in contact with the ground wire connected to the stage 3. By installing the current sensor 10 as described above, it is possible to reliably detect abnormal discharge.

Embodiment 2
Here, an example of an abnormal discharge determination method provided in the abnormal discharge detection unit 14 (see FIG. 1 and the like) of the plasma processing apparatus 1 will be described. Abnormal discharge is determined by whether or not the return current, which is regarded as a change with time in voltage, exceeds a predetermined threshold voltage.

  First, how to determine the threshold voltage will be described. First, for a plasma processing apparatus in which abnormal discharge has not occurred and is determined to be normal, a return current is measured by installing a current sensor on the outer wall of the chamber. The abnormal discharge current usually has a pulsed waveform. Therefore, the voltage of the current pulse is obtained by a pulse height analyzer based on the waveform of the return current to be measured, and the number of times the voltage value is measured is counted. The principle of converting the waveform of the measured return current into a voltage value and a count number is schematically shown in FIG. In FIG. 25, the voltage value at each peak of the waveform of the return current and the counted voltage value are indicated by the same hatching.

  FIG. 26 is a graph showing the voltage value and count number of the return current of a normal plasma processing apparatus actually measured by the inventors. A maximum voltage value is obtained from this graph, and a threshold voltage is set based on the maximum value. For example, a voltage value obtained by adding a voltage value of 10% of the maximum value to the maximum voltage value is set as the threshold voltage.

  Next, the return current is measured under the same conditions as in a normal plasma processing apparatus for a plasma processing apparatus in which abnormal discharge is assumed to have occurred. At this time, if a signal (voltage) higher than the threshold voltage is measured, it can be determined that an abnormal discharge has been detected. FIG. 27 is a graph showing the voltage value and count number of the return current actually measured for the plasma processing apparatus in which abnormal discharge occurs. As shown in FIG. 27, it can be seen that a signal (voltage) higher than the threshold voltage is measured. In this way, the threshold voltage is determined in advance.

  Next, a method for determining whether or not abnormal discharge has occurred based on the determined threshold voltage will be described with reference to a flowchart. As shown in FIG. 28, first, in step S1, measurement for detecting abnormal discharge is started in response to a signal for starting measurement from the plasma processing apparatus, and in step S2, based on the return current measured by the current sensor. Output signal data is captured. Next, in step S3, it is determined whether or not it is within a predetermined time required to process, for example, one wafer after the measurement is started. If the predetermined time is exceeded, the measurement is terminated. If the predetermined time has not elapsed, the measurement is continued and the voltage value is measured. Further, the number of times that the voltage value is measured is integrated.

  Next, in step S5, it is determined whether or not the measured voltage value has a voltage value exceeding the threshold voltage. If a voltage value exceeding the threshold voltage is not measured, it is determined in step S6 that no abnormal discharge has occurred, and the process returns to step S1 and measurement is continued. On the other hand, when a voltage value exceeding the threshold voltage is measured, it is determined in step S7 and subsequent steps how high the voltage value is with respect to the threshold voltage. If the measured voltage value is, for example, a voltage value exceeding 10 times the threshold voltage, plasma processing is stopped and an error signal is generated in step S8 because a large abnormal discharge has occurred.

  On the other hand, if the measured voltage value does not exceed 10 times the threshold voltage, as shown in FIG. 29, in step S9, the measured voltage value is, for example, 2 of the threshold voltage. It is determined whether or not it is more than twice and less than 10 times. If the measured voltage value is not less than 2 times and less than 10 times the threshold voltage, in step S10, the measured voltage value is divided by the threshold voltage and normalized, and in step S11, the standard value is Accumulated values are calculated by integrating the converted values for N. Next, in step S12, it is determined whether or not the calculated cumulative value is 50 or more, for example. If the calculated cumulative value is 50 or more, it is determined in step S13 that an abnormal discharge affecting the yield has occurred, and the plasma processing is stopped after the current plasma processing is completed. Is generated. On the other hand, if the calculated cumulative value does not exceed 50, the process returns to step S2 and measurement is continued.

  If the measured voltage value in step S9 is not less than 2 times the threshold voltage and not less than 10 times, the measured voltage value in step S14 is the threshold value as shown in FIG. It is determined whether or not the value voltage is 1 time or more and less than 2 times. If the measured voltage value is not less than 1 and not more than twice the threshold voltage, the process returns to step S2 and measurement is continued. On the other hand, if the measured voltage value is greater than or equal to one time and less than twice the threshold voltage, in step S15, the measured voltage value is divided by the threshold voltage and normalized, and in step S16. The accumulated value is calculated by adding N normalized values. Next, in step S17, it is determined whether or not the calculated cumulative value is 20 or more, for example. If the calculated cumulative value is 20 or more, it is determined in step S18 that a minute abnormal discharge that does not affect the yield has occurred, and an alarm signal is generated while plasma processing is continued. On the other hand, if the calculated cumulative value does not exceed 20, the process returns to step S2 and measurement is continued.

  In the above-described determination method, first, the threshold voltage is set based on the voltage value of the return current measured for a normal plasma processing apparatus. Next, while measuring the return current of the target plasma processing device under the same conditions, the voltage value when the return current voltage exceeds the threshold voltage and the threshold voltage are exceeded. Are stored as data. If the number of times that the threshold voltage has been exceeded is greater than the predetermined number of times, it is determined that an abnormal discharge has occurred in the plasma processing apparatus to be inspected.

  Thereby, it is possible to reliably detect abnormal discharge of the plasma processing apparatus without misjudgment in a semiconductor factory having a lot of noise from other semiconductor manufacturing apparatuses. When abnormal discharge is detected, it is possible to prevent the yield of the semiconductor device from being reduced by foreign matter generated by abnormal discharge by taking appropriate measures such as stopping the plasma processing apparatus and performing maintenance. it can.

  Even if the return current voltage value exceeds the threshold voltage only once, but the return current voltage value is higher than the threshold voltage by, for example, one digit or more, the object to be inspected It can be determined that a relatively large abnormal discharge has occurred in the plasma processing apparatus, and measures such as immediately stopping the plasma processing apparatus are taken, so that a decrease in the yield of the semiconductor device due to the large abnormal discharge can be suppressed.

  By the way, when determining the threshold voltage, it is assumed that the threshold voltage cannot be easily determined due to the influence of noise or the like in actual measurement. That is, it is assumed that a signal associated with abnormal discharge cannot be clearly distinguished from measurement data of a plasma processing apparatus in which abnormal discharge has not occurred.

  FIG. 31 shows a measurement result when a signal associated with abnormal discharge can be clearly distinguished from measurement data of a normal plasma processing apparatus measured by the inventors. As shown in FIG. 31, it can be seen that a signal higher than the threshold voltage due to abnormal discharge is measured. On the other hand, FIG. 32 shows the measurement in the case where the signal associated with the abnormal discharge cannot be clearly distinguished from the measurement data of the normal plasma processing apparatus despite the occurrence of the abnormal discharge. Results are shown. As shown in FIG. 32, it can be seen that there is a signal associated with abnormal discharge in the signal of a normal plasma apparatus, and it is difficult to distinguish the two. In such a case, it is possible that the current sensor is not installed at an appropriate position with respect to the flow of the return current. Therefore, it is desirable to change the position where the current sensor is attached for measurement.

  Further, when the return current is measured, the relatively low voltage value is counted more than the relatively high voltage value, so that it is assumed that the count number overflows before the measurement is completed. In order to prevent such overflow, the voltage value smaller than the voltage value (maximum voltage value) measured for the normal plasma processing apparatus may not be counted. The results measured by such a method are shown in FIGS. 33, 34 and 35, respectively. FIG. 33 shows a measurement result when abnormal discharge occurs continuously, and the pulse count number is 379. In FIG. 34, the measurement result when the abnormal discharge occurs intermittently is shown, and the pulse count number was 21 pieces. FIG. 35 shows the measurement results when no abnormal discharge occurs, and the pulse count number was zero.

Embodiment 3
Here, an example of a method for manufacturing a semiconductor device to which the above-described plasma processing apparatus is applied will be described. As shown in FIG. 36, element formation regions RP and RN are defined by first forming an element isolation insulating film from the surface of the semiconductor substrate 51 to a predetermined depth. An n-type well region 52 is formed in the element formation region RP. Next, in the element formation region RP, a p-channel field effect transistor T1 having a gate electrode GP and a pair of source / drain regions PSD and PSD is formed. In the element formation region RN, the gate electrode GN and a pair of pairs are formed. An n-channel field effect transistor T2 having source / drain regions NSD and NSD is formed. Next, an interlayer insulating film 60 such as a silicon oxide film is formed on the surface of the semiconductor substrate 51 so as to cover the p-channel field effect transistor T1 and the n-channel field effect transistor T2.

First, the semiconductor substrate 51 on which the p-channel field effect transistor T1 and the n-channel field effect transistor T2 are formed is placed on the stage 3 in the chamber 2 of the plasma CVD apparatus as the plasma processing apparatus described above. (See, for example, FIG. 1). Next, an argon gas is introduced in a state where the pressure in the chamber 2 is reduced to a predetermined pressure, and plasma is generated by supplying high-frequency power. For example, a monosilane (SiH ₄ ) -based gas or the like, or a TEOS (Tetra Ethyl Ortho Silicate glass) -based gas is fed into the plasma, and the gas is dissociated. An interlayer insulating film 60 is deposited on the surface of 51.

  While the interlayer insulating film 60 is deposited, the return current is measured by the current sensor 10, and determination processing for determining whether or not abnormal discharge has occurred is performed in parallel according to the flowchart described above. When no abnormal discharge occurs through the film forming process, an interlayer insulating film 60 is formed so as to cover the p-channel field effect transistor T1 and the n-channel field effect transistor T2, as shown in FIG. The

  On the other hand, if the return current exceeds the threshold voltage and abnormal discharge occurs during the film formation process, the voltage value exceeding the threshold voltage and the threshold voltage are exceeded. Predetermined measures are taken based on the number of times As described above, for example, when the voltage value exceeds 10 times the threshold voltage, the plasma processing is stopped because a large abnormal discharge has occurred. In this case, if it is determined that the semiconductor substrate (wafer) whose film formation process has been stopped can be relieved, the remaining plasma CVD apparatus or the like other than the plasma CVD apparatus in which the abnormal discharge has occurred can be used. By performing the film forming process, an interlayer insulating film is formed.

  Further, when the voltage value is a voltage value that does not exceed 10 times the threshold voltage, the film forming process is continued as it is based on the voltage value and the number of times the threshold voltage is exceeded, or Although the film forming process is continued, measures such as stopping the plasma CVD apparatus are taken when the film forming process of the semiconductor substrate is completed. Thus, a decrease in the yield of the semiconductor device due to foreign matters caused by abnormal discharge can be minimized.

  Next, as shown in FIG. 37, a resist pattern 70 is formed by performing a predetermined photoengraving process for forming a contact hole in the interlayer insulating film 60. Next, the interlayer insulating film 60 is etched using the resist pattern 70 as a mask. First, the semiconductor substrate 51 on which the resist pattern 70 is formed is placed on the stage 3 in the chamber 2 of the etching apparatus as the plasma processing apparatus described above (see, for example, FIG. 1). Next, an argon gas is introduced in a state where the pressure in the chamber 2 is reduced to a predetermined pressure, and plasma is generated by supplying high-frequency power. For example, by supplying a gas for fluorocarbon etching toward the plasma, the etching gas is dissociated, and the portion of the interlayer insulating film 60 not covered with the resist pattern 70 is etched.

  While the interlayer insulating film 60 is subjected to the etching process, the return current is measured by the current sensor 10, and the process for determining whether or not an abnormal discharge has occurred is performed in parallel according to the flowchart described above. When no abnormal discharge occurs through the etching process, contact holes 60a exposing the surfaces of the source / drain regions PSD and NSD are formed as shown in FIG.

  On the other hand, during the etching process, if the return current voltage exceeds the threshold voltage and abnormal discharge occurs, the voltage value exceeding the threshold voltage and the threshold voltage are exceeded. Predetermined measures are taken based on the number of times. As described above, for example, when the voltage value exceeds 10 times the threshold voltage, the plasma processing is stopped because a large abnormal discharge has occurred. In this case, if it is determined that the semiconductor substrate (wafer) whose etching process has been stopped midway can be repaired, the remaining etching process is performed by an etching apparatus other than the etching apparatus in which the abnormal discharge has occurred. By doing so, a contact hole is formed.

  Further, when the voltage value is a voltage value that does not exceed 10 times the threshold voltage, the etching process is continued as it is based on the voltage value and the degree of the number of times the threshold voltage is exceeded, or Although the etching process is continued, measures such as stopping the etching apparatus are taken when the etching process of the semiconductor substrate is completed. Thus, a decrease in the yield of the semiconductor device due to foreign matters caused by abnormal discharge can be minimized.

  After the contact hole 60a is formed in the interlayer insulating film 60, the resist pattern 70 (see FIG. 38) is removed as shown in FIG. Next, a barrier metal film such as titanium nitride is formed in the contact hole 60a. First, the plasma processing apparatus described above is placed on the stage 3 in the chamber 2 of the sputtering apparatus (see FIG. 24). Next, argon gas is introduced in a state where the inside of the chamber 2 is reduced to a predetermined pressure, and a predetermined voltage is applied between the stage 3 and the target 15 to generate plasma (glow discharge). A barrier metal material (titanium nitride) sputtered by colliding the dissociated argon (argon ions) with the target 15 is deposited on the surface of the semiconductor substrate 51.

  While the barrier metal film of titanium nitride is being deposited, the return current is measured by the current sensor 10, and in accordance with the above-described flowchart, determination processing for determining whether or not abnormal discharge has occurred is performed in parallel. When abnormal discharge does not occur through the sputtering process, as shown in FIG. 40, a barrier metal film 61 is formed so as to cover the bottom and side surfaces of the contact hole 60a.

  On the other hand, during the sputtering process, if the return current exceeds the threshold voltage and abnormal discharge occurs, the voltage value exceeding the threshold voltage and the threshold voltage are exceeded. Predetermined measures are taken based on the number of times. As described above, for example, when the voltage value exceeds 10 times the threshold voltage, the plasma processing is stopped because a large abnormal discharge has occurred. In this case, if it is determined that the semiconductor substrate (wafer) on which the sputtering process has been stopped can be relieved, a desired film thickness can be obtained using a sputtering apparatus other than the sputtering apparatus in which abnormal discharge has occurred. A barrier metal film is formed by performing the sputtering process until it becomes.

  When the voltage value is a voltage value that does not exceed 10 times the threshold voltage, the sputtering process can be continued as is based on the voltage value and the number of times the threshold voltage has been exceeded, or Although the sputtering process is continued, a measure such as stopping the sputtering apparatus is taken when the sputtering process of the semiconductor substrate is completed. Thus, a decrease in the yield of the semiconductor device due to foreign matters caused by abnormal discharge can be minimized.

  Next, as shown in FIG. 41, a tungsten film 62 is formed by, for example, a CVD (Chemical Vapor Deposition) method so as to be in contact with the surface of the barrier metal film 61. Next, leaving the portion of the barrier metal film 61 and the portion of the tungsten film 62 located in the contact hole 60a, the portion of the tungsten film 62 and the portion of the barrier metal film 61 located on the upper surface of the interlayer insulating film 60 are It is removed by chemical mechanical polishing (CMP). In this way, as shown in FIG. 42, the plug 63 is formed in the contact hole 60a.

  Next, a first wiring layer is formed on the surface of the interlayer insulating film 60. First, the plasma processing apparatus described above is placed on the stage 3 in the chamber 2 of the sputtering apparatus (see FIG. 24). Next, argon gas is introduced in a state where the inside of the chamber 2 is reduced to a predetermined pressure, and a predetermined voltage is applied between the stage 3 and the target 15 to generate plasma (glow discharge). A wiring material (tungsten) sputtered by colliding the dissociated argon (argon ions) with the target 15 is deposited on the surface of the interlayer insulating film 60.

  While the tungsten wiring material is being deposited, the return current is measured by the current sensor 10, and in accordance with the above-described flowchart, determination processing for determining whether or not abnormal discharge has occurred is performed in parallel. When no abnormal discharge occurs through the sputtering process, a tungsten film 64 is formed so as to be in contact with the surface of the interlayer insulating film 60 as shown in FIG. On the other hand, if the return current exceeds the threshold voltage and abnormal discharge occurs during the sputtering process, the threshold voltage is set in the same manner as described for the barrier metal film. Based on the voltage value at the time of exceeding and the number of times of exceeding the threshold voltage, measures such as performing the sputtering process until the desired film thickness is reached or continuing the sputtering process are taken. .

  Next, a titanium nitride film is formed on the surface of the tungsten film 64 as an antireflection film. This titanium nitride film is also formed in a chamber of a predetermined sputtering apparatus. While titanium nitride is being deposited, a process for determining whether or not an abnormal discharge has occurred is performed in parallel as in the case of the tungsten film. When abnormal discharge does not occur through the sputtering process, a titanium nitride film 65 as an antireflection film is formed so as to come into contact with the surface of the tungsten film 64 as shown in FIG. On the other hand, if the return current exceeds the threshold voltage and abnormal discharge occurs during the sputtering process, the threshold voltage is set in the same manner as described for the barrier metal film. Based on the voltage value at the time of exceeding and the number of times of exceeding the threshold voltage, measures such as performing the sputtering process until the desired film thickness is reached or continuing the sputtering process are taken. .

  Next, as shown in FIG. 44, a predetermined resist pattern 71 for patterning the first wiring layer is formed. Next, using the resist pattern 71 as a mask, the tungsten film 64 and the like are etched. First, the plasma processing apparatus described above is placed on the stage 3 in the chamber 2 of the etching apparatus (see FIG. 1). Next, an argon gas is introduced in a state where the pressure in the chamber 2 is reduced to a predetermined pressure, and plasma is generated by supplying high-frequency power. By sending a predetermined gas for etching tungsten or the like toward the plasma, the etching gas is dissociated, and the titanium nitride film 65 portion and the tungsten film 64 portion not covered with the resist pattern 71 are dissociated. Etching is performed.

  While the tungsten film 64 and the like are being etched, the return current is measured by the current sensor 10, and a process for determining whether or not an abnormal discharge has occurred is performed in parallel according to the flowchart described above. If no abnormal discharge occurs through the etching process, the first wiring layer M1 is formed as shown in FIG.

  On the other hand, if the voltage value of the return current exceeds the threshold voltage and an abnormal discharge occurs during the etching process, the threshold voltage is set in the same manner as described for the etching of the interlayer insulating film. Predetermined measures are taken based on the voltage value when the threshold voltage is exceeded and the number of times the threshold voltage is exceeded. For example, when the voltage value exceeds 10 times the threshold voltage, the plasma processing is stopped because a large abnormal discharge has occurred. In this case, if it is determined that the semiconductor substrate (wafer) whose etching process has been stopped midway can be repaired, the remaining etching process is performed by an etching apparatus other than the etching apparatus in which the abnormal discharge has occurred. By doing so, the first wiring layer M1 is formed.

  Further, when the voltage value is a voltage value that does not exceed 10 times the threshold voltage, the etching process is continued as it is based on the voltage value and the degree of the number of times the threshold voltage is exceeded, or Although the etching process is continued, measures such as stopping the etching apparatus are taken when the etching process of the semiconductor substrate is completed. Thus, the first wiring layer M1 is formed. Thereafter, if necessary, an interlayer insulating film is further formed, and a second wiring layer and the like are formed. Thus, the main part of the semiconductor device is formed.

  In the semiconductor device manufacturing method described above, when the return current measured while performing plasma processing exceeds the threshold voltage when performing etching processing or sputtering processing by the plasma processing apparatus, the voltage value and threshold value are measured. Whether or not abnormal discharge has occurred is determined based on the number of times the voltage has been exceeded. In the event of abnormal discharge, by taking desired measures according to the voltage value and the number of times the threshold voltage has been exceeded, it is possible to minimize the decrease in yield of semiconductor devices due to abnormal discharge. it can.

  In the plasma CVD apparatus as the plasma processing apparatus, the case where it is applied to the formation of an interlayer insulating film such as a silicon oxide film or a silicon nitride film has been described as an example, but it is also applied to the formation of a passivation film or an antireflection film. Is possible. It can also be applied to the formation of a titanium (Ti) -based barrier metal film.

  The embodiment disclosed this time is an example, and the present invention is not limited to this. The present invention is defined by the terms of the claims, rather than the scope described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention is effectively used for a plasma processing apparatus applied to manufacture of a semiconductor device.

  DESCRIPTION OF SYMBOLS 1 Plasma processing apparatus, 2 chamber, 2a flange part, 3 stage, 4 high frequency power supply part, 4a power supply cable, 5 matching box, 6 gas supply part, 7 gas exhaust port, 8 outer wall part, 9 earth wire, 10 current sensor, 11 Iron Core, 12 Coil, 13 Case, 14 Abnormal Discharge Detection Unit, 15 Target, 16 DC Power Supply, 17 Shield Flange, 18 Earth Shield, 21 Plasma, 22 Return Current, 23 Abnormal Discharge, 25 Current Associated with Abnormal Discharge, 31 Skin Current, 32 magnetic field, 33 components, 51 semiconductor substrate, 52 n-type well region, 53 element isolation insulating film, 54 gate insulating film, 55 polysilicon film, 56 sidewall insulating film, 57 metal silicide film, 58 metal silicide film, GN gate electrode, GP gate electrode, RN element Child formation region, RP element formation region, T1 n-channel type MISFET, T2 p-channel type MISFET, NSD n-type source / drain region, PSD p-type source / drain region, 60 interlayer insulating film, 60a contact hole, 61 barrier Metal film, 62 tungsten film, 63 plug, 64 tungsten film, 65 antireflection film, 70 resist pattern, 71 resist pattern.

Claims (16)

A chamber for performing a predetermined plasma treatment on a semiconductor substrate;
A power supply for supplying predetermined power for generating plasma in the chamber;
A return current measuring unit that is installed in contact with a path of return current flowing from the plasma generated in the chamber toward the ground potential, and that measures the return current by a magnetic field generated by the return current;
The return current measured by the return current measurement unit comprises an abnormal discharge detection unit that detects the occurrence of abnormal discharge by comparing the return current measured when no abnormal discharge has occurred, Plasma processing equipment.   The plasma processing apparatus according to claim 1, wherein the return current measuring unit is disposed so as to contact a conductor portion through which the return current flows.   The plasma processing apparatus according to claim 1, wherein the return current measurement unit is disposed so as to contact an outer wall portion of the chamber.   The return current measuring unit is installed at a position corresponding to a circumferential position where the path from the chamber to the ground potential is connected to the chamber among the circumferential positions of the outer wall of the chamber. The plasma processing apparatus as described.   The plasma processing apparatus according to claim 1, wherein the return current measurement unit is installed in a portion where a path from the chamber to the ground potential is connected to the chamber.   The plasma processing apparatus according to claim 1, wherein the return current measurement unit is installed so as to contact a portion of a path from the chamber to the ground potential.   The plasma processing apparatus according to claim 1, wherein the return current measurement unit is installed so as to be in contact with a ground potential portion in the power supply unit.   The abnormal discharge detection unit captures the measured return current as a voltage value, and the measured voltage value is set based on the voltage value of the return current measured when no abnormal discharge occurs. The plasma processing apparatus according to any one of claims 1 to 7, comprising a function of determining that an abnormal discharge has occurred when a predetermined threshold voltage is exceeded.   The abnormal discharge detection unit captures the measured return current as a voltage value, and the measured voltage value is set based on the voltage value of the return current measured when no abnormal discharge occurs. 9. The method according to claim 1, further comprising a function of determining that an abnormal discharge has occurred based on the number of times a predetermined threshold voltage has been exceeded and the voltage value when the threshold voltage has been exceeded. A plasma processing apparatus according to claim 1. A step of carrying the semiconductor substrate into a chamber of a plasma processing apparatus in order to perform a predetermined plasma treatment on the semiconductor substrate;
Generating plasma in the chamber;
Subjecting the semiconductor substrate to plasma treatment by exposing the semiconductor substrate to the plasma generated in the chamber;
A step of unloading the semiconductor substrate from which the plasma treatment has been completed from the chamber,
A semiconductor comprising a step of detecting an abnormal discharge of plasma by measuring a return current flowing from the plasma toward a ground potential between generation of plasma in the chamber and completion of the plasma processing. Device manufacturing method.   11. The method of manufacturing a semiconductor device according to claim 10, wherein in the step of detecting the abnormal discharge of the plasma, the plasma processing apparatus detects the abnormal discharge by a predetermined sensor installed so as to be in contact with a conductor portion through which the return current flows.   In the step of detecting an abnormal discharge of the plasma, the return current is regarded as a voltage value, and the measured voltage value is set based on the voltage value of the return current measured when no abnormal discharge occurs. 12. The method of manufacturing a semiconductor device according to claim 10, wherein it is determined that an abnormal discharge has occurred when a predetermined threshold voltage is exceeded.   In the step of detecting an abnormal discharge of the plasma, the return current is regarded as a voltage value, and the measured voltage value is set based on the voltage value of the return current measured when no abnormal discharge occurs. 13. It is determined that an abnormal discharge has occurred based on the number of times when the predetermined threshold voltage is exceeded and the voltage value when the threshold voltage is exceeded. The manufacturing method of the semiconductor device of description.   The method for manufacturing a semiconductor device according to claim 10, wherein the plasma treatment includes an etching treatment.   The method for manufacturing a semiconductor device according to claim 10, wherein the plasma treatment includes a film formation treatment by sputtering.   The method for manufacturing a semiconductor device according to claim 10, wherein the plasma treatment includes a film formation process by a chemical vapor deposition method.

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