KR100854082B1 - Seasoning using a plasma etching device - Google Patents

Abstract

The present invention discloses a seasoning method using a plasma etching apparatus. The seasoning method includes measuring a process temperature of the chamber; Determining whether the measured temperature is within a preset temperature range; If the measured temperature is not within the preset temperature range, starting a seasoning process to measure the density of ions or radicals using a light emission analysis method and obtaining dissociation rate and ionization rate therefrom; Among the plasma process variables affecting the dissociation rate and the ionization rate, determining whether the value of the plasma process variable of the current process is within a range of the value of the plasma process variable under a predetermined normal condition; As a result of the determination, when the value of the plasma process variable of the current process is not within the range of the value of the plasma process variable of a predetermined normal condition, the plasma process variable of the current process is maintained until the inside of the chamber is maintained in the main etchable atmosphere. Controlling the value of the feedback; And if the value of the plasma process variable of the current process is within the range of the plasma process variable under a predetermined normal condition, maintaining the inside of the chamber in a main etchable atmosphere and ending the seasoning process. do.

Description

Plasma Etching Apparatus and Method for Seasoning using the Same}

1 is a longitudinal sectional view showing a plasma etching apparatus according to the present invention;

2 is a flowchart illustrating a seasoning method using a plasma etching apparatus according to the present invention.

3 is a graph illustrating a feedback control of an internal temperature of a chamber in a seasoning method using a plasma etching apparatus according to the present invention.

Figure 4 is a graph showing the plasma radical density change during the plasma discharge, when the control of the internal temperature of the chamber
FIG. 5 is a view illustrating an etching rate and an etching profile of a wafer when feedback control of an internal temperature of a chamber is performed;

delete

* Explanation of symbols for the main parts of the drawings

delete

delete

100: plasma etching device

110: chamber

111: liner

112: gas inlet

120: stage

130: coil

140,150: RF Power Supply

170: temperature sensor

180: optical fiber

190: Spectroscope

W: Wafer

The present invention relates to a seasoning method using a plasma etching apparatus, and more particularly, feedback control of plasma process variables that have an important effect on plasma characteristics to shorten the time required for stabilization of a chamber and to prevent changes in etching characteristics in advance. The present invention relates to a seasoning method using a plasma etching apparatus.

In general, a semiconductor manufacturing process forms a photoresist film which is removed by chemical reaction with light on a pure silicon wafer, and then scans light to a portion of the photoresist film to form a desired pattern. A photo process for selectively opening only a desired portion of the photoresist film, an etching process for etching the opened portion to a predetermined depth, an ion implantation process for implanting desired impurities, and another in the opened portion And a deposition process for depositing a thin film having characteristics.

Among these semiconductor manufacturing processes, the etching process is a process requiring particularly precision compared to other processes. Therefore, in recent years, dry etching is more actively used than wet etching for more precise etching.

Wet etching has been widely used in the LSI era when the minimum line width of devices is in the range of hundreds to tens of microseconds, but VLSI and ULSI devices are rarely used because of the limited integration density.

In the plasma etching process, the atmosphere in the chamber is not stabilized when the main etching process is performed immediately after the initial operation of the chamber, immediately after cleaning, or immediately after the idle time of the chamber. The so-called first wafer effect, a process failure, is likely to occur.

The seasoning process refers to a process that refers to a process for forming an atmosphere inside the chamber under the same process conditions as the main etching process before the main etching process is performed in the same chamber.

In the midst of continuous production of wafers, it is necessary to continuously diagnose chamber conditions and prevent defects in advance. Plasma diagnostic equipments include plasma etching using plasma and plasma enhanced chemical vapor deposition (PECVD) deposition equipment. It is used for analyzing the kind and concentration of radicals or compounds formed in the inside, and the kind and concentration of charged particles.

Langmuir probes have been mainly used to measure the properties of such particles, but in the case of Langmuir probes, it is impossible to measure the mass and ion energy distribution of charged particles formed in the plasma. An error occurs because the effective current-collecting area is not the actual surface area of the probe but the surface area of the sheath formed around the probe.

For reference, the sheath means a cover and refers to a positive charge space generated on the surface in contact with the plasma.

In addition, after the preliminary main etching process is performed using the preliminary seasoning recipe for the seasoning, the standard deviation of the end point detection time is calculated to perform the seasoning process, and the seasoning effect by DC bias. A control method, a seasoning method of forming an atmosphere in a chamber using a seasoning wafer patterned with a photoresist, a method of measuring and seasoning a ratio of radiation intensities of chemical species present in a chamber before performing a plasma process, etc. There is this.

However, these methods have the disadvantage of not accurately detecting the plasma parameters that are sensitive to the etching results and the decrease in the production efficiency due to the defective processing of the used wafers, and it is difficult to be a fundamental solution because only the process results are monitored and presented. there was.

Accordingly, the present invention has been made to solve the above problems, in which the density of ions or radicals is measured using a light emission analysis method during the initial operation of the chamber, after the chamber is cleaned, or when the chamber is restarted, and the dissociation rate therefrom. And controlling the plasma process parameters of the current process so that the inside of the chamber is maintained at a normal condition by obtaining an ionization rate, thereby reducing the time required for stabilizing the chamber for the plasma etching process and improving the semiconductor yield. The present invention relates to a seasoning method using an apparatus.

In order to achieve the above technical problem, the seasoning method using a plasma etching apparatus according to the present invention, measuring the process temperature of the chamber; Determining whether the measured temperature is within a preset temperature range; If it is determined that the measured temperature is not within the preset temperature range, starting the seasoning process, measuring the density of ions or radicals using light emission analysis, and obtaining dissociation rate and ionization rate therefrom; Among the plasma process variables affecting the dissociation rate and the ionization rate, determining whether the value of the plasma process variable of the current process is within the range of the value of the plasma process variable of a predetermined normal condition; As a result of the determination, when the value of the plasma process variable of the current process is not within the range of the value of the plasma process variable of a predetermined normal condition, the plasma process variable of the current process is maintained until the inside of the chamber is maintained in the main etchable atmosphere. Controlling the value of the feedback; And as a result of the determination, when the value of the current process plasma process variable is within a range of the value of the plasma process variable under a predetermined normal condition, maintaining the interior of the chamber in a main etchable atmosphere and ending the seasoning process. do.

On the other hand, the plasma etching apparatus according to the present invention includes a chamber having a closed space for the plasma process to proceed, and a liner for maintenance; A stage located in the chamber and in which a wafer to be etched is seated; A coil installed at an outer circumference of the chamber; RF power supply for supplying power to the coil to convert the reaction gas injected into the chamber into a plasma state; A temperature sensor in contact with the liner of the chamber to measure the process temperature of the chamber; And an optical fiber installed in the chamber to send light from the plasma to the spectrometer.

Hereinafter, a plasma etching apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a longitudinal sectional view showing a plasma etching apparatus according to the present invention.

As shown in FIG. 1, the plasma etching apparatus 100 according to the present invention has a sealed space for the plasma process to proceed and includes a chamber 110 in which a liner 111 for maintenance is installed. The liner 111 may be formed of an aluminum (Al) material whose surface is anodized. The gas inlet 112 for introducing the reaction gas is formed in the chamber 110.

In the chamber 110, a stage 120 on which the wafer W to be etched is seated is installed to be lifted and lowered by a lifter (not shown).

A coil 130 is installed at the outer circumference of the chamber 110 to form an electromagnetic field in the chamber 110. The coil 130 is electrically connected to an RF power supply 140 that supplies power to the coil 130 to convert the reaction gas injected into the chamber 110 into a plasma state. An RF power supply 150 is connected to the stage 120.

The RF power supply 140 for supplying power to the coil 130 and the RF power supply 150 connected to the stage 120 are all matched through a matching box (not shown).

The temperature sensor 170 is installed at the liner 111 to measure the process temperature of the chamber 110.

Since the liner 111 is separated from the chamber 110 during maintenance, the temperature sensor 170 is electrically connected to the control unit installed at the outside of the chamber 110 at this time. It consists of a contact structure.

That is, the temperature sensor 170 may be electrically connected to and in contact with the wire 171 installed in the chamber 110. Of course, the wire 171 is electrically connected to a control unit (not shown) installed outside the chamber 110.

In addition, the chamber 110 is provided with an optical fiber 180 to send light from the plasma to the spectrometer 190.

Although not shown in the figure, a vacuum pump is connected to the lower portion of the chamber 110, and an exhaust port is formed. Since the vacuum pump and the exhaust port have a conventional structure, detailed description thereof will be omitted.

In the plasma etching apparatus configured as described above, the high-frequency power (power) is supplied from the RF power supply device 140 to the coil 130 to form an electromagnetic field, thereby reacting gas introduced into the gas inlet 112 of the chamber 110. To generate plasma.

The stage 120 supplies high frequency power from the RF power supply 140 to accelerate plasma ions toward the wafer (W).

The seasoning method using the plasma etching apparatus according to the present invention measures the process temperature of the chamber. Then it is determined whether the measured temperature is within the preset temperature range. As a result of the determination, the seasoning process is performed only when the measured temperature is not within the preset temperature range. At this time, the density of ions or radicals is measured by using light emission analysis, and the dissociation rate and ionization rate are obtained therefrom. Then, the plasma etching process variable of the current process, that is, the feedback control of the plasma etching process variable of the current process so that the process temperature is within the range of normal conditions.

Hereinafter, a seasoning method using the plasma etching apparatus according to the present invention will be described in more detail with reference to the accompanying drawings.

2 is a flowchart illustrating a seasoning method using a plasma etching apparatus according to the present invention, and FIG. 3 is a feedback method of an internal temperature of an etching chamber in a seasoning method using a plasma etching apparatus according to the present invention. A graph describing the control.

1 and 2, in the seasoning method using the plasma etching apparatus according to the present invention, the chamber 110 is monitored by using a temperature sensor 170 while monitoring the inside of the chamber 110. The process temperature is measured (S210). Next, it is determined whether the measured temperature is within a preset temperature range (S220).

As a result of the determination, only when the measured temperature is not within the preset temperature range, the seasoning process is performed (S230). At this time, the density of ions or radicals is measured by using light emission analysis, and the dissociation rate and ionization rate are obtained therefrom.

For reference, dissociation is a basic reaction in forming chemically reactive radicals in the plasma. Dissociative reactions are formed by heat, light, and impact processes, but only at the collision in low temperature plasmas. The dissociation due to the collision action can be divided into the one due to the electron impact and the sequential action, but the overall dissociation can be thought of as the sum of the two mechanisms. It is greatly affected by the pressure of the reaction gas and the input power.

In addition, the diagnostic method of least disturbing the plasma is an optical diagnostic method for diagnosing the plasma using light. Such optical diagnostic methods include optical emission spectroscopy (OES), absorption spectroscopy, and laser induced fluorescence.

Among these, the above-described light emission analysis method analyzes the spectrum of light emitted from the plasma, and is most widely used for diagnosis and monitoring of plasma processes. By measuring the wavelength and intensity of the light emitted, the presence of neutral species and ions can be identified. The spectrum of light emitted from the plasma gives us insight into the chemical and physical processes taking place in the plasma.

That is, as shown in FIG. 1, when the light emitted from the plasma enters the external spectrometer 190 directly or through the optical fiber 180 installed in the chamber 110, diffraction occurs at the diffraction grating of the spectroscope 190. This spreads, and only light having a predetermined wavelength passes through the gap in the exit chamber to reach the PM detector, which causes an optical current to flow in proportion to the intensity. This principle is used to obtain information about chemical and physical processes occurring in plasma and to obtain dissociation and ionization rates from the information.

Next, among the various plasma process variables affecting the dissociation rate, it is determined whether the plasma process variable of the current process, that is, the temperature of the process temperature is within the range of the plasma process variable under a predetermined normal condition (S240). . In this case, the value of the plasma process variable under a predetermined normal condition refers to the value of the plasma process variable set through the existing data to maintain the atmosphere in which the main plasma etching is possible without the first wafer effect.

As a result of determination, when the value of the plasma process variable of the current process is not within the range of the value of the plasma process variable of the preset normal condition, it means that the current process condition does not satisfy the normal condition. Until the etchable atmosphere is maintained, feedback is controlled while adjusting the value of the plasma process parameter of the current process (S250).

Here, as shown in FIG. 3, since the temperature of the liner of the chamber (graph 1) gradually rises, in consideration of the increase of the chamber set temperature (graph 2), the feedback of the liner temperature of the chamber (graph 1) is continuously fed. Control. This is because, in the current structure, the temperature sensor does not directly measure the temperature of the plasma seasoning, but indirectly determines the temperature of the plasma seasoning by measuring the liner of the chamber. Therefore, in the present invention, the set temperature (graph 2) of the chamber is adjusted by the feedback temperature (graph 3).

As a result of the determination, when the value of the plasma process variable of the current process is within the range of the value of the plasma process variable of the preset normal condition, it means that the current process condition satisfies the normal condition. Maintaining the main etchable atmosphere is terminated (S260).

On the other hand, Figure 4 is a graph showing the plasma radical density change during the plasma discharge, when the feedback control of the chamber internal temperature, Figure 5 shows the etching rate and etching profile of the wafer, when the feedback control of the chamber internal temperature Drawing.
When the feed back control of the chamber internal temperature is not controlled, the etching rate is changed, so that the etching profile is not vertically formed but tapered on the first wafer, resulting in a poor etching profile.
On the other hand, in the case of feedback control of the internal temperature of the chamber, as shown in FIGS. 4 and 5, among the various reaction gases, in the case of CF ₂ , the density of radicals increases as the process proceeds, thereby causing an etching rate. By maintaining the etching rate uniformly, the etching profile is vertically formed on the second wafer so that the defect of the etching profile does not occur.

delete

delete

As described above, according to the present invention, by monitoring the seasoning process or chamber state change after wet cleaning with minimal investment in the existing plasma equipment, defects caused by the initial operation such as the first wafer effect or the change of the chamber state during the process Can be effectively prevented.

In addition, the yield is expected to increase due to the reduction of the semiconductor manufacturing time and the increase of the chamber cleaning cycle, thereby realizing a reduction in manufacturing cost.

In addition, the user can easily access the system configuration for determining the seasoning, thereby maximizing user convenience.

Claims (6)

Measuring a process temperature of the chamber; Determining whether the measured temperature is within a preset temperature range; If it is determined that the measured temperature is not within the preset temperature range, starting the seasoning process, measuring the density of ions or radicals using light emission analysis, and obtaining dissociation rate and ionization rate therefrom; Among the plasma process variables affecting the dissociation rate and the ionization rate, determining whether the value of the plasma process variable of the current process is within a range of the value of the plasma process variable under a predetermined normal condition; As a result of the determination, when the value of the plasma process variable of the current process is not within the range of the value of the plasma process variable of a predetermined normal condition, the plasma process variable of the current process is maintained until the inside of the chamber is maintained in the main etchable atmosphere. Controlling the value of the feedback; And If the value of the plasma process variable of the current process is within the range of the plasma process variable of a preset normal condition, maintaining the interior of the chamber in a main etchable atmosphere and ending the seasoning process; Seasoning using a plasma etching apparatus. The method of claim 1, Seasoning using a plasma etching apparatus, characterized in that for measuring the process temperature of the chamber using a temperature sensor installed in the chamber. The method of claim 1, And wherein said plasma process variable is a process temperature. The method of claim 1, A method of seasoning using a plasma etching apparatus by controlling process temperature, input RF power, and process pressure to feedback control the dissociation rate and ionization rate. delete delete

Images