KR20080006750A - Plasma doping system for fabrication of semiconductor device - Google Patents

Abstract

A plasma doping system for fabricating a semiconductor device is provided to prevent a process error by monitoring the abnormal state of a plasma doping process in a real-time period. A plasma doping system comprises a chamber, a platten for supporting a wafer within the chamber, and an RF generator for applying RF power. A voltage-current detection unit(260) is connected between the RF generator and the platten in order to detect the amount of changing voltage-current between the RF generator and the platten. An optical fiber(270) is installed at a view port of the chamber in order to detect the change of atmosphere of the chamber and the degassing state of a chamber wall. An RF detection unit(280) is installed at the view port in order to detect generation of arcs within the plasma and the change of the atmosphere within the chamber. A data processor(290) receives output signals from the voltage-current detection unit, the optical fiber, and the RF detection unit in order to determine the abnormal state of a plasma dipping process. A system controller(300) controls the plasma doping system on the basis of a determination signal of the data processor.

Description

Plasma doping system for semiconductor device manufacturing {Plasma doping system for fabrication of semiconductor device}

1 is a cross-sectional view schematically showing a conventional glow discharge plasma type plasma doping system.

2 is a cross-sectional view schematically showing an RF plasma plasma doping system according to an embodiment of the present invention.

3 is a view for explaining a method of detecting arcing by the collision rate measured by the RF measuring unit of the RF plasma doping system of the present invention.

4 is a view for explaining a method of detecting the arc generation by the voltage and current change amount using the current-voltage detection unit of the RF plasma doping system of the present invention.

5 is a view for explaining a method of detecting a chamber atmosphere by the collision rate measured by the RF measuring unit of the RF plasma doping system of the present invention.

6 is a view for explaining a method of detecting a degassing state of a chamber wall using an optical fiber of the RF plasma doping system of the present invention.

7A to 7C are diagrams for explaining a method of detecting an abnormality in the flow amount of the doping gas in the chamber using the optical fiber of the RF plasma doping system of the present invention.

Explanation of symbols on the main parts of the drawings

210: chamber 220: RF generator

230: platen 240: plasma

250: wafer 260: voltage-current measuring unit

270 optical fiber 280 RF measurement unit

290: Data Processor 300: System Controller

The present invention relates to a plasma doping system for semiconductor device manufacturing, and more particularly, to a plasma doping system capable of preventing a process defect by detecting the abnormality of the plasma doping process in real time.

Conventionally, an ion implanter is used to ionize desired impurities from an ion source. Ionized ions are accelerated to form an ion beam of predetermined energy, and the ion beam is implanted into the surface of the wafer to be trapped in the crystal lattice in the bulk of the wafer to form an ion implantation region of a desired conductivity type. In order to ensure the operation characteristics of all devices in the wafer, such an ion implantation apparatus must satisfy process conditions such as cumulative ion temperatures implanted on the wafer, implantation depth and dose uniformity on the wafer surface. In addition, excessive damage to the wafer surface due to ion implantation and contamination by particles may destroy structures previously formed on the wafer.

Recently, a plasma doping (PLAD) system has been proposed for manufacturing nanometer scale semiconductor devices requiring ultra shallow junction regions. The plasma doping method is highly applicable to the next-generation semiconductor manufacturing process because it can realize a high dose rate in the ultra low energy band of 0.02 to 20keV.

Plasma doping is a method of doping ions in a plasma formed in a chamber into a wafer to dope it to a desired dose, which not only has the advantage of doping the entire surface of the wafer at a time, but also controlling the doping energy by using a bias applied to the wafer. Can be. The plasma doping method is largely divided into a glow discharge plasma doping method and a high frequency (RF) plasma doping method according to the principle of generating plasma.

1 shows a schematic cross-sectional view of a conventional glue discharge plasma doping system. Referring to FIG. 1, a conventional plasma doping system includes a plasma doping apparatus 100. The plasma doping apparatus 100 is disposed in the chamber 110, the cathode 130 disposed in the chamber 110, on which the wafer 150 is placed, and the anode installed in the chamber 110 opposite to the cathode 130. 120. The plasma doping system is installed in the chamber 110, the dose measuring unit for measuring the dose amount accumulated in the wafer 110 connected to the Faraday cup 160, the Faraday cup 160 for the conversion of the dose amount ( 170 and a power supply unit 180 for applying power to the cathode 130.

When the anode 130 is grounded and a pulsed DC power is applied to the cathode 130 through the power supply unit 180, a plasma 140 is generated in the chamber 110, and the plasma 140 is formed. Ions in the cavities are implanted into the wafer 110 to form a junction region in the wafer 110.

In the doping method using the plasma doping system, since plasma is directly used in the doping process, device characteristics due to arc generation are easily deteriorated, process reproducibility according to the atmosphere of the chamber 110 is difficult, and impurity gas ions other than the doping gas are difficult. For example, co-doping due to degassing ions of the chamber wall, etc. occurs, so that monitoring them in real time is required.

In addition, the conventional plasma doping system 100 includes a Faraday cup 160 and a dose measuring unit 170 connected to the Faraday cup 160 to measure and monitor the dose accumulated on the wafer 110. However, it was not possible to monitor in real time the presence of arcing or abnormality of the chamber atmosphere or to monitor the degassing ions of the chamber wall in real time.

Therefore, the technical problem to be achieved by the present invention is to provide a plasma doping system for semiconductor device manufacturing that can prevent the process failure by monitoring the presence or absence of abnormality in the plasma doping process in real time.

In order to achieve the above technical problem of the present invention, the plasma doping system of the present invention is disposed in the chamber, a platen for supporting a wafer, and a high frequency for plasma generation inside the chamber and installed outside the chamber It is provided with a plasma doping equipment having an RF generator for applying power. The plasma doping system includes: a voltage-current detection unit connected between the RF generator and the platen of the plasma doping apparatus and detecting a voltage-current change amount between the RF generator and the platen; An optical fiber installed in a viewport of the chamber to detect a change in atmosphere of the chamber and to detect a degassing state of the chamber wall; And an RF detector installed in the viewport of the chamber to detect arc generation in the plasma and to detect a change in the chamber atmosphere. The plasma doping system may further include: a data processor configured to input an output signal of the voltage-current detector, the optical fiber, and the RF detector to determine whether a plasma doping process is abnormal; And a system controller for controlling the plasma doping equipment based on the determination signal provided from the data processor.

The data processor inputs the output signal of the voltage-current detector to determine that an arc is generated in the plasma when the value of the current output signal is 10% or more greater than a previous output signal or the RF detector of the RF detector. By inputting an output signal, it is determined that an arc has occurred in the plasma when the current electron collision rate is 10 times larger than the immediately previous electron collision rate.

The data processor inputs the output signal of the optical fiber and compares the emission intensity of the entire wavelength band with a reference value to determine that the atmosphere of the chamber has changed or compares the emission intensity of a specific band with the reference value. Determine that the mood has changed. When boron is doped to the wafer using a BF3 gas, the specific band is 249.8 nm.

The data processor inputs the output signal of the RF detector, and determines that the process is unstable according to the change in the atmosphere of the chamber if the electron collision rate is not within 30% of the reference value.

The data processor inputs an output signal of the optical fiber and compares the spectrum difference in the steady state and the degassing state to determine that an impurity gas in the chamber wall is generated. When comparing the spectral differences, discrimination is made based on the composition change caused by the comparison difference of the peak positions. The data processor determines a key number based on a change in the emission spectrum with respect to the flow rate of the gas injected into the chamber, and determines that an impurity gas in the chamber wall is generated based on the determined key number.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited by the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape and the like of the elements in the drawings are exaggerated to emphasize a more clear description, and the elements denoted by the same reference numerals in the drawings means the same elements.

Figure 2 shows a cross-sectional view of the plasma doping apparatus for manufacturing a semiconductor device according to an embodiment of the present invention.

2, the plasma doping system of the present invention includes a plasma doping apparatus 200. The plasma doping apparatus 200 is installed outside the chamber 210, the platen 230 disposed in the chamber 210, and the chamber 210 to provide an RF power -Vimplant to the platen 230. An RF generator 220 is provided. The wafer 250 is positioned on the platen 230 so that the platen 230 supports the semiconductor wafer 250.

The plasma doping system further includes a voltage-current measuring unit 260 connected between the RF generator 220 and the platen 250. The voltage-current measuring unit 260 measures the voltage-current change between the RF generator 220 and the platen 230 to monitor in real time. The voltage-current variation measured by the voltage-current measuring unit 260 is provided to the data processor 290 and used as a signal for determining the occurrence of an arc.

The plasma doping system further includes an optical fiber 270 installed in the viewport of the chamber 210 and an RF measuring unit 280. The optical fiber 270 measures an optical emission spectrum (OES), and the RF measuring unit 280 measures a self-excited electron resonance spectrum (SEERS). The OES measured by the optical fiber 270 is provided to the data processor 290 to determine whether there is an abnormal process due to the change of the atmosphere of the chamber 210 according to the doping material or to determine the degassing state of the chamber wall. Used as a signal to judge. The SEER measured by the RF measuring unit 280 is provided to the data processor 290 to determine whether an arc is generated based on the electron collision rate or to determine the change in the chamber atmosphere based on the electron collision rate. Used as

The plasma doping system inputs signals provided from the voltage-current detector 260, the optical fiber 270, and the RF measurement unit 280 to detect arc generation, process stability according to a chamber atmosphere, and to remove the chamber walls. And a data controller 290 for determining a gas state and a system controller 300 for inputting a determination signal provided from the data processor 290 to control the plasma doping apparatus 200.

When high frequency power is provided from the RF generator 220 to the platen 230 of the chamber 210, the plasma 240 including the plasma sheath 241 is generated in the reaction space in the chamber 210. Ions in the plasma 240 are implanted across the plasma sheath 241 into the wafer 250 on the platen 230 to form impurity regions.

The method of monitoring in real time the presence or absence of arc generation during the plasma doping process, process stability according to the chamber atmosphere, and degassing state of the chamber wall will be described with reference to FIGS. .

First, an operation of monitoring the occurrence of arc in real time using the RF detector 280 and the voltage-current measurer 260 will be described. The RF detector 280 detects an electron collision rate in real time using Sears, and the detected electron collision rate is provided to the data processor 290. The data processor 290 receives the electron collision rate detected by the RF detector 280 to determine whether an arc is generated.

If, as shown in a2 of FIG. 3, the electron collision rate fluctuates more than a value measured immediately before, for example, 10 times or more, the data processor 290 generates an arc to the system controller 300. It outputs a signal indicating that it is. That is, the data processor 290 recognizes that an arc is generated in the plasma 240 when the instantaneous change in the electron collision rate is more than 10 times. The system controller 300 controls the plasma doping apparatus 200 according to the output signal generated from the data processor 290. A1 in FIG. 3 shows the electron collision rate in the steady state without an arc, and it can be seen that the electron collision rate increases more rapidly than the steady state when the arc is generated.

In addition, the voltage-current detector 260 measures and monitors the voltage-current change between the RF generator 220 and the platen 230 in real time. At this time, when the voltage-current change is detected through the voltage-current detector 260, as shown in b of FIG. You will be judged. That is, the data processor 290 instantly recognizes that an arc has occurred in the plasma 240 when the width of the voltage-current change increases by 10% or more from a reference value. When a signal indicating that an arc is generated as a result of the detection of the voltage-current detector 260 is provided from the data processor 290, the system controller 300 operates the plasma doping apparatus 200 based on the arc generation signal. To control.

As described above, the arc generation in the plasma 240 is monitored in real time through the voltage-current measuring unit 260 and the RF measuring unit 280, and the system controller 300 monitors the plasma according to the monitoring result. By controlling the doping equipment 20, it is possible to prevent a process failure due to the arc generation in the plasma 240.

Next, an operation of detecting an atmosphere change of the chamber 210 using the optical fiber 270 and the RF measuring unit 280 will be described. First, the RF measuring unit 280 monitors the electronic collision rate in real time using Sears, and the data processor 290 determines the change in the atmosphere of the process chamber based on the electronic collision rate monitored in real time. For example, as shown in c2 of FIG. 5, when the electron collision rate is within the range of ㅁ 30%, it is determined that the process is stable. As shown in c1 of FIG. 5, the electron collision rate against the reference value is not less than 30%. In this case, the data processor 290 determines that the process is unstable. In this case, since there is an absolute value of the electron collision rate measured by the RF measuring unit 280, the data processor 290 sets this value as a reference value to determine whether there is an abnormality in the process.

In addition, the optical fiber 270 monitors the OES in real time, and the data processor 180 determines the presence of a process abnormality by measuring the change in the atmosphere of the chamber in real time from the signal provided from the optical fiber 270. . The emission intensity I (λij) in the plasma 240 is expressed by the following equation (1). Here, i and j represent the ground state and the excited state, λij represents the transition wavelength, and N represents the ground state density. Pij is the electron impact excitation function, Aij is the Einstein emission probability, and K is the correction factor.

I (λij) = NPijAij (λij) K ..... (1)

The data processor 290 determines whether there is a process abnormality from the change in emission intensity at the emission wavelength of the doping material, or determines whether there is a process abnormality from the change in emission intensity of the entire 200 to 800 nm band. For example, in the case of using BF3 as the doping gas, it is determined whether there is an abnormal process by detecting the change in the atmosphere of the chamber from the change in the emission intensity at 249.8 nm, which is the emission wavelength of boron.

As described above, the optical fiber 270 and the RF measuring unit 280 monitor the change in the atmosphere of the chamber 210 in real time, and the system controller 300 performs the plasma doping equipment 20 according to the monitoring result. By controlling), it is possible to prevent a process failure due to the change in the atmosphere of the chamber 210.

Next, the operation of detecting the co-doping and the gas flow rate change by the impurity gas through the optical fiber 270 will be described. If an impurity gas, in particular a gas that is degassed in the wall of the chamber 210, is generated, a difference in OES measured through the optical fiber 270 occurs as shown in FIG. Therefore, the optical fiber 270 is used to monitor the degree of degassing in the wall of the chamber 210 based on the emission intensity of the designated wavelength band in real time. The data processor 290 determines whether the degassing gas of the chamber wall has been generated from the emission intensity provided from the optical fiber 270, and the system controller 300 determines that the degassing gas is generated according to the determination result of the data processor 290. The plasma doping equipment 200 is controlled. At this time, when judging the occurrence of degassing gas from the difference between the spectrum under normal conditions and the degassing conditions I and II, the compositional change according to the difference between the peak positions (arrows in FIG. 6) of each spectrum is mainly used. Can be used as a decision factor. In FIG. 6, unlike the normal condition, cogasing may occur when degassing conditions I or II are generated, so that the doping process may be stopped and the walls of the chamber 210 may be cleaned.

7A to 7C are diagrams showing a correlation between O 2 flow rate and OES. 7A and 7B, it can be seen that the emission intensity in the entire band remains different depending on the difference in the O 2 flow rate. Therefore, the key number can be extracted as shown in FIG. 7C in consideration of the full emission spectrum according to the O 2 flow rate. For example, by using a mass floor controller (not shown in the drawing) to the plasma doping apparatus 200, the emission intensity of the OES was monitored in real time during the doping process by supplying an O 2 flow rate of 16 sccm of the key number 0. As a result, when the key number is detected as 50, it is determined that the flow rate of O2 is changed and the system controller 300 controls the mass follower controller to control the gas flow rate supplied to the chamber 210.

In an embodiment of the present invention, a Faraday cup may be installed in the chamber 210, and a dose measuring unit may be connected to the Faraday cup to detect a dose amount accumulated in the wafer 250.

As described above in detail, according to the plasma doping system of the present invention, by monitoring the plasma doping process in real time to determine whether there is an abnormality of the process can prevent the process defects.

Although the present invention has been described in detail with reference to preferred embodiments, the present invention is not limited to the above embodiments, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention. .

Claims (9)

A plasma doping apparatus including a chamber, a platen disposed in the chamber to support a wafer, and an RF generator installed outside the chamber and applying high frequency power for generating plasma in the chamber; A voltage-current detector connected between the RF generator and the platen of the plasma doping apparatus and detecting a voltage-current change amount between the RF generator and the platen; An optical fiber installed in a viewport of the chamber to detect a change in atmosphere of the chamber and to detect a degassing state of the chamber wall; An RF detector installed in the viewport of the chamber to detect arc generation in the plasma and to detect a change in the chamber atmosphere; A data processor configured to input an output signal of the voltage-current detector, the optical fiber, and the RF detector to determine whether a plasma doping process is abnormal; And And a system controller for controlling the plasma doping apparatus based on the determination signal provided from the data processor. The data processor of claim 1, wherein the data processor inputs the output signal of the voltage-current detector to determine that an arc is generated in the plasma when a value of the current output signal is 10% or more greater than a previous output signal. Plasma doping system, characterized in that. The method of claim 1, wherein the data processor inputs the output signal of the RF detector to determine that an arc is generated in the plasma when a current electron collision rate is 10 times greater than a previous electron collision rate. Plasma doping system. The method of claim 1, wherein the data processor inputs the output signal of the optical fiber, and compares the emission intensity of the entire wavelength band with a reference value to determine that the atmosphere of the chamber has changed or the emission intensity of a specific band and the reference value Comparing the atmosphere of the chamber with the plasma doping system. 5. The plasma doping system according to claim 4, wherein when the boron is doped to the wafer using a BF3 gas, the specific band is 249.8 nm. The method of claim 1, wherein the data processor inputs the output signal of the RF detector, and determines that the process is unstable according to the change in the atmosphere of the chamber if the electron collision rate is not within the range of 30% of the reference value. Plasma doping system. 2. The plasma doping of claim 1, wherein the data processor inputs an output signal of the optical fiber and compares a spectrum difference in a steady state and a degassing state to determine that an impurity gas in the chamber wall is generated. system. 8. The plasma doping system according to claim 7, wherein when comparing the spectral differences, the spectral differences are determined based on a change in composition according to a comparison difference between peak positions. 8. The method of claim 7, wherein the data processor determines a key number based on a change in emission spectrum with respect to the flow rate of the gas injected into the chamber, and determines that an impurity gas in the chamber wall is generated based on the determined key number. Plasma doping system.

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