JP4032740B2 - Semiconductor polishing apparatus and semiconductor substrate polishing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a monitoring device in a semiconductor polishing apparatus.
[0002]
[Prior art]
Along with the high integration of semiconductor devices, a technique for polishing and flattening a semiconductor element structure with high precision during a semiconductor manufacturing process has recently become important. Among the planarization technique, CMP (C hemical M echanical P olish) technology is an excellent method capable of realizing global planarization, the excess left on the substrate during planarization or isolation form the interlayer insulating film It is used for polishing oxide films.
[0003]
FIG. 9 shows the basic principle and apparatus configuration of planarization by CMP.
[0004]
1 is a load cell, 2 is a servo valve, 14 is a bell bud, 15 is a semiconductor substrate, 16 is a slurry nozzle, 17 is a conditioner, 18 is a polishing head, and 19 is a load control circuit. The CMP apparatus is composed of a combination of a polishing head 18 and a table that rub against each other. A solution in which an abrasive is dispersed between a polishing head 18 to which a semiconductor substrate 11 is attached and a table to which a polishing cloth (beld pad 14) is attached ( While the slurry) is being supplied from the slurry nozzle 16 and the surface of the pad pad 14 is activated by the conditioner 17, the polishing head 18 and the table rotate independently of each other, and the surface of the semiconductor substrate is balanced by mechanical polishing and chemical action. Polishing is performed.
[0005]
The polishing state during CMP strongly depends on the mechanical contact state between the polishing cloth and the substrate. Therefore, in order to polish the semiconductor substrate over the entire surface with high accuracy, it is indispensable to control apparatus parameters such as the pressure (load) applied to the polishing cloth in the non-polished part and the slurry supply flow rate.
[0006]
In recent years, monitoring of device parameters of semiconductor polishing equipment has shifted to a method in which the display values on the monitor screen of the equipment are electrically monitored by the manufacturing operator once a week or once a month. It is being done. By using such a new monitoring method, continuous monitoring over a long period of time becomes possible, and quick monitoring is possible for changes in polishing characteristics and changes over time.
[0007]
[Problems to be solved by the invention]
However, the conventional semiconductor polishing apparatus and its monitoring apparatus mostly utilize the function of collecting apparatus parameters attached to commercially available data loggers and semiconductor polishing apparatuses as they are, and contact failure of the probe connected to the data logger and semiconductor polishing Due to the influence of the system noise of the device itself, there is a problem that accurate monitoring cannot be performed unlike the monitored signal and the control signal actually used by the device.
[0008]
The present invention solves the above-described problems, and provides a monitoring apparatus for a semiconductor polishing apparatus that can quickly and accurately monitor polishing characteristic fluctuations and changes over time, and can improve manufacturing yield and productivity. There is to do.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, Oite the semiconductor polishing equipment according to claim 1 of the present invention, a first signal line for control is branched from the first signal line and the first signal line A second signal line that does not have a feedback circuit, a noise removal circuit inserted in the second signal line, and a load measurement terminal provided in the second signal line Therefore, since system noise caused by the host computer can be removed, the apparatus parameters can be monitored with high accuracy. A method for polishing a semiconductor substrate according to claim 5 of the present invention is a method for polishing a semiconductor substrate with a semiconductor polishing apparatus, and the semiconductor substrate is applied to a polishing cloth by a load control circuit provided in the semiconductor polishing apparatus. A step of polishing the semiconductor substrate while controlling the load; and a step of monitoring the value of the load. The load control circuit is branched from the first signal line for control, the first signal line, and the first signal line A second signal line that does not have a feedback circuit to the signal line, a noise removal circuit inserted in the second signal line, and a load measurement terminal provided in the second signal line The monitoring step includes a step of monitoring a load value from a load measurement terminal.
[0010]
Oite the semiconductor polishing equipment according to claim 2, since the band-pass filter circuit for passing the frequency band set pre Me is characterized in that it is inserted in the second signal line peeling of the polishing pad and belt motor It is possible to monitor the vibration of the machine.
[0011]
Due to the provision Oite the semiconductor polishing equipment according to claim 3, the data processing unit for Fourier transform processing the signals obtained from the second signal line, rapidly cause investigation in the presence of noise It is possible to reduce the manufacturing loss of the semiconductor device and improve the productivity of the semiconductor polishing apparatus.
[0012]
Oite the semiconductor polishing equipment according to claim 4, a data decision unit for matching the strength and standard value of the frequency set in advance in the Fourier transform data processed in the data processing unit, the intensity of the frequency set in advance Since the device has a function of outputting an alarm when the value exceeds the standard value , it is possible to quickly catch the device abnormality, and thus it is possible to prevent a manufacturing loss of the semiconductor device.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
The present invention relates to noise countermeasures for a load control circuit of a semiconductor polishing apparatus.
[0014]
Embodiments of the present invention will be described below with reference to the drawings.
[0015]
FIG. 1 shows a load control circuit of a semiconductor polishing apparatus according to the first embodiment of the present invention. In FIG. 1, 1 is a load cell, 2 is a servo valve, 3 is a control signal line, 4 is an amplifier 1, 5 is a measurement terminal, 6 is a host computer, 7 is an amplifier 2, 8 is an amplifier 3, and 9 is a noise removing capacitor. It is.
[0016]
First, a circuit for controlling the load value of the load cell 1 will be described. The set value is input from the host computer 6 as the load value, and the set value is amplified by the amplifier 2 (7). The value obtained by converting the load into voltage from the load cell 1 (: voltage value) is compared with the set value by the amplifier 1 (4), the difference is fed back to the servo valve 2, and the set value and the data from the load cell 1 are compared. Control is performed so that the load value becomes the set value while amplifying with the servo amplifier so that the difference becomes zero. Since such a feedback circuit is easily affected by noise, the load value is monitored from a signal line that does not have a feedback circuit to the control signal line 3 by a signal line branched from the control signal line from the amplifier 3 (8). Monitoring terminal 5 must be provided for monitoring. Otherwise, if an abnormality such as noise occurs in the monitoring system, the control circuit will be affected and trouble will occur in the polishing process.
[0017]
FIG. 2 shows a change over time in the waveform of the load value depending on whether or not a noise removal capacitor is inserted in a signal line branched from the control signal line and having no feedback circuit to the control signal line. 2A is a waveform of a load value when a noise removing capacitor is not inserted (conventional case), FIG. 2B is a waveform of a load value when a noise removing capacitor of 0.1 μF is inserted, and FIG. c) is a waveform of the load value when the noise removing capacitor 1.0 μF is inserted, and FIG. 2D is a waveform of the load value taken out from the control signal line. Here, when comparing the average values of the load values as A1, B1, C1, and D1, respectively,
A1 = −0.538, B1 = −0.533,
C1 = −0.556, D1 = 0.580
There is no large difference between D1 and D1. Incidentally, although A1, B1, and C1 are reversed in polarity by the amplifier 3 (8) shown in FIG. 1, they return to the host computer 6 and thus do not affect the load control.
[0018]
Next, when the load value variation (3σ) is compared as A2, B2, C2, and D2, respectively,
A2 = 0.343, B2 = 0.119,
C2 = 0.092, D2 = 0.093
It can be seen that A2 is more than three times larger than B2, C2, and D2. Since no noise removing capacitor is inserted, the load value during polishing processing varies greatly due to the influence of system noise from the host computer, making it difficult to accurately grasp the apparatus state. Further, when the value of the capacitor to be inserted is increased to 10 μF, the variation in the load value is reduced and is equivalent to the value taken out from the control signal line. At this time, the upper limit of the capacitance value of the capacitor is determined by the delay time of the signal. The delay time is the product of the capacitance value and the resistance. In the first embodiment of the present invention, 10 kΩ is used as the resistance value, so the delay time at 100 μF is 1 second. Since the load value sampling time is 1 second, this delay time can be considered as the upper limit. Therefore, a 10 μF capacitor is preferable. In addition, since the capacitance value of the capacitor may be various, it is not limited to 100 μF or less.
[0019]
Therefore, when monitoring the load value, etc., it is possible to remove the signal from the control signal line by inserting a noise removal circuit such as a capacitor at a location that branches off from the control signal line and does not feed back to the control signal line. It is equivalent to the extracted value, and it is possible to accurately grasp the device state.
[0020]
(Second Embodiment)
The second embodiment of the present invention relates to the monitoring of mechanical vibration in the monitoring method of the semiconductor polishing apparatus.
FIG. 3 shows a waveform of a load value in the monitoring method of the present invention. E1 and E2 indicate the load value during normal polishing and the variation with respect to the load value. F1 and F2 indicate the waveform of the load value and the variation with respect to the load value during the polishing process in which the polishing pad peeling occurred. Load values E1 and F1 during the polishing process are respectively
E1 = 4.61PSi, F1 = 4.65PSi
Although there is no particular difference, the variation with respect to the load value (3σ) E2, F2 is E2 = 0.11PSi, F2 = 0.35PSi
And E2 are more than three times as large as F2.
[0021]
Here, as described in the first embodiment of the present invention, the noise removal circuit is inserted in the signal line that does not have the feedback circuit to the control signal line 3 by the signal line branched from the control signal line. Despite removal of system noise from the host computer, pulsation is observed in the waveform of the load value shown in FIG. 3 when the polishing pad is peeled off. This waveform pulsation is due to mechanical vibration.
[0022]
FIG. 4 is a diagram obtained by Fourier transforming the load value monitored according to the present invention.
[0023]
4A is a Fourier transform diagram before application of the bandpass filter, and FIG. 4B is a Fourier transform diagram after application of the bandpass filter. For example, in FIG. 4A in which noise exists in the low frequency band, the load value signal at the time of peeling of the polishing pad is 30 MHz or more. Therefore, a filter that allows passage of only a signal of 30 MHz or more is attached. When the signal is attenuated, the signal in the low frequency band does not pass as shown in FIG. 4B, so that highly accurate monitoring with less noise is possible. Therefore, in the present invention, it is possible to pass an output signal only in an arbitrary frequency band by inserting a band pass filter into a signal line that is branched from the control signal line and does not have a feedback circuit to the control signal line 3. Therefore, it is possible to quickly monitor mechanical vibration such as polishing pad peeling and belt motor vibration by removing system noise.
[0024]
(Third embodiment)
The present invention has a function of quickly Fourier-transforming the monitored load value. It should be noted that there is a specific frequency pattern in the trouble of the semiconductor polishing apparatus. As described in the second embodiment of the present invention, it can be seen that the load value signal is 30 MHz or more when the polishing pad is peeled off. Since it is difficult to monitor the confirmation of the noise generation status, a function of Fourier transform processing has been added.
[0025]
A third embodiment of the present invention will be described with reference to the drawings.
[0026]
FIG. 5 shows a connection configuration diagram having a Fourier transform function in the present monitoring method. 10 is a data logger, 11 is a data storage unit, and 12 is a data processing unit. The data logger 10 automatically transfers the sampled device parameter results to the data storage unit 11, and the data processing unit 12 performs a Fourier transform process on the measured load value. Thereafter, the result of Fourier transform is transferred to the host computer 6. In order to have a Fourier transform function of the load value, in the existing apparatus configuration, if the Fourier transform processing function, the arithmetic processing unit, the setting value instruction, and the like are collectively performed by the host computer 6, each operation of the apparatus and the set value are performed. May cause a malfunction, and it is difficult to process quickly. Therefore, in the present invention, it is determined that it is necessary to provide the data processing unit 12 and the data storage unit 11 dedicated to the Fourier transform function, and the configuration shown in FIG.
[0027]
FIG. 6 shows the result of Fourier transform of the load value by the monitoring method of the present invention. FIG. 6A shows the waveform of the load value, and FIG. 6B shows the result of Fourier transform of FIG. 6A. By performing the Fourier transform process quickly in this way, it is possible to quantitatively check the noise, and thus it is possible to quickly grasp the apparatus abnormality.
[0028]
(Fourth embodiment)
The present invention provides means for determining whether a semiconductor polishing apparatus is normal or abnormal from the result of Fourier transform of a monitored load value. A fourth embodiment of the present invention will be described with reference to the drawings.
[0029]
FIG. 7 shows a connection configuration diagram having a Fourier transform function in the present monitoring method. Reference numeral 13 denotes a data determination unit. The method of performing the Fourier transform by monitoring the load value according to the present invention is the same as that of the third embodiment. A Fourier transform process of the load value measured by the data processing unit 12 is performed. After that, the data determination unit 13 compares the standard value of the frequency intensity set in advance to determine normality or abnormality, and transfers the result to the host computer 6. Output.
[0030]
FIG. 8 shows a flowchart of alarm output of the apparatus due to noise abnormality based on the Fourier transform of the monitored load value.
[0031]
The load value is monitored by the data logger 10 during the polishing process, and the collected results are stored in the data storage unit 11 and the data processing unit 12 performs a Fourier transform process. The data judgment unit 13 collates with the standard value of the intensity of the frequency set in advance, and if normal, the judgment result is transferred to the host computer 7 and the next wafer is processed. In the case of an abnormality, the determination result is similarly transferred to the host computer 7, but an alarm is output to notify the abnormality. By providing the above function in the semiconductor polishing apparatus, it is possible to quickly grasp the apparatus abnormality, and it is possible to reduce the manufacturing loss and improve the productivity of the semiconductor device.
[0032]
In the first to fourth embodiments described above, the semiconductor polishing apparatus has been described. However, the present invention can be applied to other semiconductor substrate processing apparatuses such as a plasma etching apparatus, a plasma CVD apparatus, a cleaning apparatus, and an ion implantation apparatus. Needless to say.
[0033]
【The invention's effect】
As described above, according to the present invention, in a semiconductor polishing apparatus, a signal line branched from a control signal line is inserted into a signal line that does not have a feedback circuit to the control signal line, whereby a host computer or the like Since system noise can be reduced, device parameters can be monitored with an accuracy equal to or better than that of control signals, improving the yield of semiconductor devices, early detection of abnormalities in semiconductor manufacturing equipment, and improving the productivity of semiconductor manufacturing equipment. A great effect is obtained.
[Brief description of the drawings]
FIG. 1 is a load control circuit diagram of a semiconductor polishing apparatus according to the present invention. FIG. 2 is a diagram showing a monitoring waveform of a load value of the semiconductor polishing apparatus according to the present invention. FIG. 4 is a diagram showing a monitoring waveform of the load value of the semiconductor polishing apparatus according to the present invention. FIG. 5 is a connection configuration diagram having a Fourier transform function in the monitoring method of the semiconductor polishing apparatus according to the present invention. FIG. 7 is a diagram showing a Fourier analysis waveform of a load value of the semiconductor polishing apparatus in the invention. FIG. 7 is a connection configuration diagram having a Fourier transform function in the monitoring method of the semiconductor polishing apparatus in the invention. Flowchart of performing Fourier transform in method FIG. 9 is a block diagram of a conventional semiconductor polishing apparatus Description]
1 Load cell 2 Servo valve 3 Control signal line 4 Amplifier 1
5 Measurement terminal 6 Host computer 7 Amplifier 2
8 Amplifier 3
9 Noise Eliminating Capacitor 10 Data Logger 11 Data Storage Unit 12 Data Processing Unit 13 Data Determination Unit 14 Belt Pad 15 Semiconductor Substrate 16 Slurry Nozzle 17 Conditioner 18 Polishing Head 19 Load Control Circuit

Claims (5)

A semiconductor polishing apparatus for polishing a semiconductor substrate ,
A polishing cloth, and a load control circuit for controlling a load on the polishing cloth of the semiconductor substrate,
The load control circuit includes a first signal line for control , a second signal line branched from the first signal line and having no feedback circuit to the first signal line, and the second signal line A noise removing circuit inserted in the signal line, a load measuring terminal provided in the second signal line,
A semiconductor polishing apparatus comprising: The semiconductor polishing apparatus according to claim 1, wherein the band-pass filter circuit for passing the frequency band set Me pre is inserted into the second signal line. 2. The semiconductor polishing apparatus according to claim 1, further comprising a data processing unit for performing a Fourier transform process on a signal obtained from the second signal line . A data determination unit for collating a preset frequency intensity and a standard value in the data subjected to Fourier transform processing in the data processing unit, and an alarm is output when the preset frequency intensity exceeds the standard value features and semiconductor polishing apparatus according to claim 3, wherein a. A method of polishing a semiconductor substrate with a semiconductor polishing apparatus,
Polishing the semiconductor substrate while controlling the load on the polishing cloth of the semiconductor substrate by a load control circuit provided in the semiconductor polishing apparatus;
Monitoring the value of the load,
The load control circuit includes a first signal line for control, a second signal line branched from the first signal line and having no feedback circuit to the first signal line, and the second signal line A noise removal circuit inserted into the signal line, and a load measurement terminal provided on the second signal line,
The method of polishing a semiconductor substrate, wherein the monitoring step includes a step of monitoring the load value from the load measurement terminal.

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