JP2011054767A - Plasma etching method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that, in plasma etching, in order to suppress a temporal change of processing accuracy in a lot, it is required to execute heating before lot processing, consequently, it reduces throughput. <P>SOLUTION: A heater power supply is controlled by calculating values of an applied voltage and an inflow current to a heater 301 of a sample placing electrode of a plasma etching device. The temperature of the placing electrode is controlled by the heater for each wafer in a lot while using a controller for controlling the temperature of a wafer and that of the sample placing electrode. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a plasma etching apparatus, and more particularly to a plasma etching method for improving throughput (the number of etching processes per unit time) or improving etching performance.

  When pattern transfer is performed by etching, since the processing accuracy can be obtained by adjusting the wafer to an optimum temperature during etching, the temperature of the sample mounting electrode is adjusted with a circulating refrigerant. In addition, since the radiant heat generated from the components that make up the chamber changes the surface temperature of the wafer and affects the processing accuracy, a heating process (heating process) of the chamber's components is performed before starting the etching process. ing.

  If the heating process is not performed, the chamber components are gradually heated during the lot process, and the amount of radiant heat generated from the in-chamber components changes. Accordingly, since the wafer surface temperature also changes during lot processing, the processing accuracy during lot processing changes over time. The amount of radiant heat generated from the components in the chamber is small in the initial stage of lot processing and increases in the second half of lot processing.

  Conventionally, the temperature of the components in the chamber is adjusted by performing the heating process before the lot process (before the start of the etching process), and the amount of radiant heat generated from the initial stage to the latter half of the lot process is kept constant. The wafer surface temperature between the wafers was kept constant.

  In addition, after the etching process is completed, when there is an idling (etching process not started) time until the wafer is unloaded from the mounting electrode and the next etching process is started, the heating process is performed before the next etching process is started. However, the heating processing time is based on the idling time. For example, when the idling time is short, the cooling time for the in-chamber component during idling is short, so that the heating time for reaching the desired temperature of the in-chamber component necessary for starting etching may be short.

  On the other hand, when the idling time is long, the cooling time for the in-chamber components is long, so the heating time for reaching the desired temperature of the in-chamber components necessary for starting etching must be increased. However, since it is difficult to manage the heating processing time due to the difference in the idling time, the heating processing time is performed when the idling time is long regardless of the actual idling time.

  In order to suppress a change with time in the processing accuracy in the lot, a heating process must be performed before the lot process, which causes a problem of reducing the throughput.

  The plasma etching processing method of the present invention is a plasma etching processing method using a plasma etching apparatus with a heater on a sample mounting electrode, and controls a heater power source by calculating a voltage applied to the heater and an inflow current value. Using the controller for controlling the temperature of the wafer and the sample mounting electrode, the mounting electrode temperature is controlled by a heater for each wafer in the lot.

  During lot processing, by applying a voltage to the heater resistance in the mounting electrode and changing the wafer surface temperature instantaneously, the wafer surface temperature is changed for each wafer according to the amount of radiant heat generated from the components in the chamber, The wafer surface temperature between the wafers in the lot is kept constant.

  According to the present invention, etching with high throughput and high processing accuracy can be performed as compared with the case of using the conventional technique.

FIG. 1 is a sectional view showing an embodiment of a plasma etching apparatus using the present invention. FIG. 2 is a diagram showing a configuration of an electrode according to an embodiment of the present invention. FIG. 3 is a diagram showing a configuration of an electrode control system according to the embodiment of the present invention. FIG. 4 is a diagram showing etching process conditions. FIG. 5 is a diagram showing the wafer temperature fluctuation in the lot when there is no heating. FIG. 6 is a diagram showing the CD shift amount in the lot when there is no heating. FIG. 7 is a view showing the wafer surface temperature for each wafer processing number obtained from the approximate curve. FIG. 8 shows the wafer application temperature for achieving the same temperature as the 25th sheet in the lot. FIG. 9 shows the in-lot CD shift amount when the technique according to the present invention is used.

  To achieve high-precision processing, CD (Critical Dimension: processing accuracy), CDU (Critical Dimension Uniformity), and ID Bias (Iso.-Dense Bias) are strictly limited. It is necessary to etch while managing.

  In order to realize optimum etching conditions, an etching apparatus capable of controlling various parameters such as electrode temperature distribution, gas flow distribution, and plasma density distribution is required. In particular, the wafer temperature is an important element for controlling the CD and CDU. By setting the wafer temperature to an optimum state, the etching performance and productivity can be greatly improved.

  In addition, since the radiant heat generated from the components constituting the chamber changes the surface temperature of the wafer, and the CD and CDU between the wafers in the lot change over time, the plasma of the components in the chamber due to plasma before the etching process is started. A heating process is performed. By performing the heating process before the start of the etching process, the radiant heat generated from the components in the chamber during the lot process can be kept constant.

  However, there is a problem that throughput is reduced by performing the heating process before the lot process. The heating process time depends on the idling time between lot processes, but the management of the heating process time varies depending on the lot process conditions performed after idling. Regardless of this, a constant condition was used for a long time, which caused a further decrease in throughput.

  The present invention has been made specifically for the purpose of meeting this industrial demand, and its configuration, method of use, and effects will be described below with reference to examples.

  An etching apparatus used as an example will be briefly described with reference to FIG. The microwave output from the microwave source 101 is transmitted through the waveguide 102. A vacuum exhaust system (not shown) and a gas introduction system (not shown) are connected to the processing chamber 103 and can be maintained in an atmosphere and pressure suitable for plasma processing.

  The gas in the processing chamber 103 is turned into plasma by the input microwave, and a predetermined plasma processing can be performed on the sample to be processed (hereinafter referred to as a wafer) 104. The plasma generating means may be plasma generating means using inductive coupling means using high frequency or electrostatic coupling means using high frequency instead of microwaves.

  A sample (wafer) 104 to be processed is placed on a sample mounting electrode 105, and a bias potential can be applied by a connected bias power source 107. As a result, ions in the plasma are drawn into the substrate to be processed, and plasma etching is performed.

  Furthermore, the electrode includes a He introduction system 106 that ensures heat conduction between the sample and the electrode surface, a DC power source 108 for electrostatic chuck, a constant voltage output power source 110 for heater temperature control, and an electrode body base material. A temperature controller 109 is connected to cool and circulate the refrigerant for cooling. The constant voltage output power supply 110 is connected to a temperature control unit 111 that determines an output voltage value.

  FIG. 2 is a detailed schematic cross-sectional view of the sample mounting electrode 105 of FIG. The sample mounting electrode is roughly divided into a head plate 201 and a cooling plate 202. The head plate is made of an insulating material and has a heater resistor 203 for heating embedded therein. A constant voltage output power source 110 shown in FIG. 1 is connected to the heater resistor 203.

  On the other hand, the cooling plate 202 has an internal flow path 204 for circulating the refrigerant whose temperature is adjusted by the temperature controller 109 of FIG. A small diameter hole is machined in a part of the cooling plate 202 and a temperature sensor 205 is embedded.

  FIG. 3 is a block diagram of a temperature control unit that controls the heater power supply. The constant voltage output power source 302 connected to the heater resistor 301 receives the voltage command from the arithmetic unit 304 and applies a voltage to the heater resistor 301 to control the temperature.

  The voltage command of the computing unit 304 outputs a voltage command so that the set temperature 305 is reached by input signals from the current monitor 303 and the temperature sensor 306. As a result, the wafer or the mounting electrode is controlled to a desired temperature. As described above, the temperature control unit is configured by one signal loop.

  In the heater built-in electrode as described above, the response speed when changing the temperature of the electrode surface can be set to 5 to 20 ° C./S according to one design example. In this case, for example, heater power with a maximum of 2000 to 5000 W is used, and by maintaining the coolant temperature of the cooling plate at 0 to 40 ° C., the same response speed can be achieved for both temperature rise and fall.

  Next, during the lot processing of the present invention, a voltage is applied to the heater resistance in the mounting electrode, and the wafer surface temperature is instantaneously changed, so that the wafer surface temperature is changed according to the amount of radiant heat generated from the components in the chamber. An embodiment will be described with respect to a method of keeping the wafer surface temperature constant between the wafers in the lot by changing each time.

  First, idling for a long time until the components in the chamber are sufficiently cooled. Next, one lot (25 sheets) is processed under the processing conditions shown in FIG. At this time, the wafer surface temperature is measured using a wireless thermometer wafer for measuring the wafer surface temperature on the first, fifth, thirteenth, and twenty-fifth sheets during the lot processing.

  FIG. 5 shows the wafer temperature fluctuation in the lot. The wafer surface temperature gradually increases with the number of processed sheets. Since the heating process is not performed before the lot process, the influence of the radiant heat generated from the components in the chamber appears as an increase in the wafer surface temperature for each process wafer.

  FIG. 6 shows the CD shift amount in the lot of the Iso portion when a patterned wafer (film structure is a polysilicon single layer film, film thickness of 120 nm) is lot processed under the etching conditions shown in FIG. Since the heating process is not performed before the lot process, the influence of the radiant heat generated from the components in the chamber appears as a variation in the CD shift amount. Next, the wafer surface temperature in lots other than the first, fifth, thirteenth, and twenty-fifth wafers is calculated from the approximate curve from the result of the wafer surface temperature fluctuation in the lot obtained in FIG.

  FIG. 7 shows the wafer surface temperature for each wafer processing number obtained from the approximate curve. Using this calculated value, the deviation between the wafer surface temperature of the 25th lot processing and the previous (1st to 24th) wafers is calculated, and the difference in the placement electrode necessary for obtaining the same wafer surface temperature as the 25th wafer The temperature applied by the heater is calculated. FIG. 8 shows the temperature applied to each wafer to achieve the same temperature as the 25th sheet.

  FIG. 9 shows the CD shift amount (sparse part) in the lot when the lot processing is performed using each wafer application temperature obtained in FIG. Etching conditions other than the wafer application temperature are the same as in FIG. From this result, even when the heating process is not performed, the wafer temperature during the lot process is measured in advance, and the wafer surface temperature is changed for each wafer according to the amount of radiant heat generated from the components in the chamber. By keeping the wafer surface temperature at a constant value, the CD shift amount in the lot to be shifted in accordance with the change of the idle time can be made constant.

101 Microwave source 102 Waveguide 103 Processing chamber 104 Substrate to be processed (wafer)
105 Sample Placement Electrode 106 He Supply System 107 Bias Power Supply 108 Electrostatic Adsorption Power Supply 109 Temperature Controller 110 Constant Voltage Power Supply 111 Controller 201 Head Plate 202 Cooling Plate 203 Heater Resistor 204 Refrigerant Flow Channel 205 Temperature Sensor 301 Heater Resistance 302 Constant Voltage power supply 303 Current monitor 304 Calculator 305 Temperature setting 306 Temperature sensor

Claims (2)

A plasma etching processing method using a plasma etching apparatus with a heater on a sample mounting electrode,
The applied voltage to the heater and the inflow current value are calculated to control the power supply for the heater, and the controller for controlling the temperature of the wafer and the sample mounting electrode is used. A plasma etching processing method characterized by controlling the temperature.   2. The plasma etching processing method according to claim 1, wherein a wafer surface temperature for each wafer processing number calculated from an approximate curve of wafer temperature fluctuations in the lot is used, and a predetermined number of wafer surface temperatures in the lot processing and earlier. And calculating and controlling the temperature applied by the heater in the sample mounting electrode necessary to obtain the same wafer surface temperature as the predetermined number of sheets.

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