JP5166231B2 - Plasma treatment device - Google Patents

Description

  The present invention relates to a plasma treatment apparatus, and more particularly to a plasma treatment apparatus capable of obtaining a desired plasma distribution in a processing chamber.

  In a plasma processing apparatus used in a semiconductor device manufacturing process, a processing gas introduced into a vacuum processing chamber is turned into plasma and becomes ions or radicals. In a plasma etching apparatus, which is a kind of plasma processing apparatus, the wafer is etched by reacting these ions or radicals with the wafer.

  For this reason, in the plasma processing apparatus, the distribution of ions and radicals in the vacuum processing chamber is the main factor that determines the uniformity of the processing performance. The following documents are known as techniques for measuring the distribution of such ions or radicals.

Patent Document 1 discloses a measurement system that measures a plasma emission distribution in a processing chamber by installing a plasma light receiving portion in a vacuum processing chamber and rotating the light receiving portion. In Patent Document 2, a lens and a plasma emission detector are provided outside a window provided in a vacuum processing chamber, and the focal position is changed by moving the emission detector with a linear motor. A method for measuring the plasma emission distribution is shown.
JP 2006-313847 A JP 2006-310371 A

  In the method of Patent Document 1, since the light receiving unit exists in the processing chamber, accurate measurement is possible, but the configuration is not suitable for a mass production apparatus. Further, in the method of Patent Document 2, it takes time to measure all points in the wafer surface by driving the linear motor and moving the plasma emission detector.

  The present invention has been made in view of these problems, and provides a plasma treatment apparatus capable of measuring plasma distribution (emission intensity distribution) in a vacuum processing chamber at high speed with a simple configuration.

  In order to solve the above problems, the present invention employs the following means.

  Plasma processing comprising a vacuum processing chamber, a sample stage for placing and holding a sample in the vacuum processing chamber, and a plasma generating means for generating plasma by supplying high-frequency energy to a process gas introduced into the vacuum processing chamber In the apparatus, a light receiving device that receives light emitted from the generated plasma outside the vacuum processing chamber, and is provided between the light receiving device and the vacuum processing chamber, and is introduced into the light receiving device out of the light emitted from the plasma. And a control device for controlling the plasma processing apparatus based on the amount of light received by adjusting the light receiving adjuster to change the light receiving range by the light receiving device.

  Since the present invention has the above configuration, the plasma distribution in the vacuum processing chamber can be measured at high speed with a simple configuration.

  Hereinafter, the best embodiment will be described with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a plasma processing apparatus according to an embodiment of the present invention. The plasma processing apparatus 1 includes a vacuum processing chamber 2, a mass flow controller 3 that supplies a processing gas to the vacuum processing chamber 2, a plasma-generating high-frequency power source 4 that converts the processing gas supplied to the vacuum processing chamber 2 into plasma, and a vacuum A gas exhaust system 5 for exhausting the gas in the processing chamber 2 is provided.

  A wafer 6 that is a substrate to be processed is placed on a sample stage 7 disposed in the vacuum processing chamber 2 of the plasma processing apparatus 1.

  A processing gas used for the plasma processing is introduced into the apparatus through the mass flow controller 3, and the introduced processing gas is turned into plasma by the high frequency energy supplied from the plasma generating high frequency power source 4. Charged particles (ions) in the plasma 8 are accelerated by a bias electric field formed by a bias high-frequency power source 9 connected to the sample stage 7 and are drawn into the surface of the wafer 6 placed on the sample stage 7.

  As a result, the surface of the wafer 6 is activated, and the reactive gas in the plasma 8 and the surface of the wafer 6 chemically react to perform plasma processing.

  The pressure in the vacuum processing chamber 2 is adjusted by comparing the measured value from the pressure gauge 10 with a reference value and adjusting the opening / closing angle of the variable conductance valve 11 based on the comparison result to adjust the exhaust speed. Therefore, it can be kept constant.

  The light emission intensity of the plasma 8 is observed by the light receiver 13 through the observation window 12. A light reception adjuster 14 is disposed between the observation window 12 and the light receiver 13. The light receiving adjuster 14 has at least two light receiving lenses. By moving at least one of the light receiving lenses up and down, the observation range of the plasma 8 is concentrically expanded / reduced.

  The emission intensity of the plasma 8 observed by the light receiver 13 is transmitted to the monitor device 15 where the plasma distribution is measured. The control unit 16 that controls the plasma processing apparatus 1 corrects the process data in the plasma processing, for example, according to the degree of the plasma distribution measured by the monitor device 15 or issues an alarm to stop the processing.

  FIG. 2 is a diagram for explaining the principle of measuring the plasma distribution. As described above, in the present invention, the observation range of the plasma 8 can be expanded or reduced concentrically by moving the light receiving lens in the light receiving adjuster 14 up and down. Further, the distribution of plasma emission intensity can be measured using a plurality of measured values of plasma emission intensity acquired by expanding or reducing the observation range.

  Hereinafter, a method for measuring the plasma distribution will be described using FIG. 2 as an example in which the observation range (21 to 24) of the plasma 8 is changed in four stages according to time (t1 to t4). Note that the number of steps for changing the observation range of the plasma 8 may be two or more, but it is desirable to change the number of steps depending on the size of the wafer 6 or the required plasma processing performance.

  First, at time t1, the light receiving lens position of the light receiving adjuster 14 is adjusted so as to observe the plasma range (observation range 21) over the entire wafer 6, and the plasma emission intensity is observed. Subsequently, the observation range 22 → the observation range 23 → the observation range 24 and the observation range are narrowed concentrically, for example, every time time t2 → t3 → t4, and the plasma emission intensity in each observation range is observed. To do.

  Subsequently, by taking the difference between the plasma emission intensity in the observation range 21 observed at time t2 and the plasma emission intensity in the observation range 22 observed at time t1, the plasma emission in a ring-shaped range as shown in the observation range 31 is obtained. Calculate the intensity. Similarly, the plasma emission intensity in the observation range 32 is calculated from the difference between the observation range 22 and the observation range 23, and the plasma emission intensity in the observation range 33 is calculated from the difference between the observation range 23 and the observation range 24.

Then, by combining the plasma emission intensity of the plasma emission intensity and the observation range 24 of the observation area 31, 32, 33 and the calculated, it is possible to obtain a plasma distribution 35.

  The in-plane distribution of the plasma processing performance such as the etching rate of the wafer 6 often shows a sharper change in the outer peripheral portion than in the central portion of the wafer 6. For this reason, it is desirable to narrow the ring width of the observation range 31 that is a ring on the outer peripheral portion, and gradually increase the ring width of the observation range as the observation ranges 32 and 33 are advanced. For example, the observation areas 24, 31, 32, and 33 may have the same area.

  FIG. 3 is a flowchart showing a procedure for measuring the plasma distribution (plasma emission intensity distribution). Each step will be described below in order.

  First, in step 41, the plasma processing apparatus 1 performs plasma processing. In step 42, the plasma emission intensity in each of the observation ranges 21 to 24 is acquired during the plasma processing.

  In step 43, only the emission intensity of one or more wavelengths set in advance is selected and extracted from the acquired plasma emission intensity of each observation range. For example, when etching polysilicon with a chlorine-based gas, the emission intensity of wavelengths such as Si emission wavelengths of 251 nm and 288 nm, SiCl emission wavelengths of 390 nm, Cl emission wavelengths of 726 nm and 838 nm, and the like. It is good to extract.

  In addition, when silicon nitride is etched with a fluorocarbon-based gas, light emission with a wavelength such as 359 nm and 387 nm as CN emission wavelengths, 470 nm and 517 nm as C2 emission wavelengths, and 703 nm and 775 nm as F emission wavelengths. Choose strength. In addition, when argon is added as a dilution gas, it is preferable to select emission intensity of wavelengths such as 420 nm, 603 nm, and 752 nm, which are emission wavelengths of Ar. When oxygen is added as an additive gas, the emission intensity of a wavelength such as 777 nm or 845 nm, which is the emission wavelength of O 2, may be selected.

  In step 44, the product of the emission intensity of the extracted wavelength and the area of the observation range is calculated. The purpose of calculating the product is as follows. Since the plasma emission intensity observed by the light receiver 13 is an average value of the plasma emission intensity in the observation range, for example, when the plasma distribution is exactly the same in the surface of the wafer 6, the emission intensity in the observation range 21 and the observation are observed. The emission intensity in the range 22 is the same, and the difference between the two observation ranges is zero. Therefore, by calculating the product of the area of each observation range, the plasma emission intensity in the observation range 31 can be obtained when the difference between the two observation ranges is calculated.

  In step 45, the plasma emission intensity in the ring-shaped observation range can be acquired by calculating the difference between the product of the wavelength intensity and the area in each calculated observation range.

  In step 46, the plasma emission intensity in the ring-shaped observation range is divided by the area in the ring-shaped observation range. Thereby, the average value of the plasma emission intensity in the ring-shaped observation range can be obtained. Thereby, for example, even when the observation areas 24, 31, 32, and 33 have different areas, the light emission intensities (average values) in the observation ranges can be compared.

In addition, the process in steps 44, 45, and 46 can be represented by Formula (1). Equation (1) represents the emission intensity I ₃₁ in the observation range 31.

_{I 31 = (I 21 * S} 21 -I 22 * S 22) / (S 21 -S 22) (1)
I ₂₁ : Plasma emission intensity measured in observation range 21 I ₂₂ : Plasma emission intensity measured in observation range 22 S ₂₁ : Area of observation range 21 S ₂₂ : Area of observation range 22 In step 47, the calculated observation range Based on the plasma emission intensities (average values) of 24, 31, 32, and 33, a plasma emission intensity distribution 35 (see FIG. 2) for each wavelength is created.

  By the above procedure, the plasma emission intensity distribution for each wavelength can be obtained as a map, for example.

  FIG. 4 is a flowchart showing a procedure for searching for a processing condition capable of obtaining an optimum plasma distribution. Each step will be described below step by step.

  First, in step 51, initial values of plasma processing conditions such as gas flow rate, pressure value, high frequency power supply output value, sample stage temperature, parameters to be changed, parameter change range, desired plasma distribution, etc. are set.

  In step 52, plasma processing is started based on the processing conditions.

  In step 53, the plasma distribution during the plasma processing is measured according to the procedure of steps 42 to 47 in FIG.

  In step 54, after the plasma distribution measurement, the plasma processing is terminated.

  In step 55, it is determined whether or not all plasma processing within the parameter change range has been completed.

  If it is determined that all the processing conditions have been completed, the process proceeds to step 57 where the plasma distributions in all the processing conditions are compared. Thereafter, the processing conditions close to the desired plasma distribution set in step 51 are listed in order and displayed on a display device (not shown).

  If it is determined that all the processing conditions have not ended, the process proceeds to step 56, the processing conditions are changed according to the changed parameter setting set in step 51, and the plasma processing in step 52 is started again.

  By the above procedure, processing conditions close to a desired plasma distribution can be obtained. In normal plasma processing, in order to obtain a desired processing result, processing conditions (recipe) such as gas flow rate, pressure value, high-frequency power source output value, and sample stage temperature are determined in advance.

  Conventionally, in order to determine the optimum processing conditions, a large part depends on the intuition and experience of engineers.For example, in plasma etching processing, after determining a temporary recipe, the processing performance such as the etching rate is evaluated, and the processing performance In general, the processing conditions are tuned so as to be optimal. For this reason, much labor and a wafer for processing performance evaluation are consumed.

  However, by carrying out the processing according to the flowchart of FIG. 4, it is possible to semi-automatically search for processing conditions that can obtain a desired plasma distribution. Thereby, it becomes possible to reduce the labor of an engineer and the waste of the wafer for processing performance evaluation.

  As described above, the processing conditions for generating a desired plasma distribution can be obtained by executing the procedure of FIG. However, in normal plasma processing, the plasma distribution may change over time due to deposits of reaction products in the vacuum processing chamber 2 or wear of parts in the vacuum processing chamber 2, and the plasma processing performance may deteriorate. is there. For this reason, in order to perform stable plasma processing, it is important to maintain the plasma distribution over a long period of time.

  FIG. 5 is a flowchart showing a procedure for maintaining an optimal plasma distribution. Each step will be described below step by step.

  First, in step 61, the processing conditions determined in the procedure of FIG. 4, the desired plasma distribution, the allowable range of the plasma distribution, and the like are set.

  In step 62, plasma processing is started based on the processing conditions.

  In step 63, it is determined whether or not to end the plasma processing. If it is determined that the plasma processing is not terminated, the process proceeds to step 64, and the plasma distribution during the plasma processing is measured based on the procedure of steps 42 to 47 in FIG.

  In step 65, it is determined whether or not the measured plasma distribution is within the allowable range set in step 61. If it is within the allowable range, the plasma processing is continued, and the process returns to step 63. If the plasma distribution exceeds the allowable range, the process proceeds to step 66.

  In step 66, the processing conditions are changed. The change of the processing conditions is preferably selected from the processing conditions (plurality) close to the desired plasma distribution acquired in FIG. Further, a database may be created from the plurality of processing conditions and the plasma distribution at the time of the processing, and the processing conditions may be determined using the database.

  If it is determined in step 63 that the plasma process is to be terminated, the process proceeds to step 67 and the plasma process is terminated.

  With the above procedure, an optimal plasma distribution can be maintained.

  As described above, according to the present embodiment, plasma is observed from the upper part of the vacuum processing chamber, and the plasma emission intensity is observed while changing the plasma observation range concentrically. Also, by taking the difference between the data acquired in each observation range, the radial distribution of the plasma emission intensity can be measured. Further, by moving the light receiving lens in the light receiving adjuster 14, the observation range of the plasma 8 can be expanded or reduced concentrically. For this reason, the plasma distribution in the vacuum processing chamber can be measured at high speed with an easy configuration.

  In the above example, the plasma observation range is changed concentrically by moving at least one of the plurality of lenses and changing the focal length between the light receiver 13 and the lens. It is also possible to change the plasma observation range to be concentric by configuring the light receiving element such as a CCD and changing the light receiving range itself constituted by the aggregate.

It is a figure explaining the plasma processing apparatus concerning an embodiment. It is a figure explaining the principle which measures plasma distribution. It is a figure explaining the procedure which measures plasma distribution (intensity distribution of plasma light emission). It is a figure explaining the procedure which searches the process conditions which can obtain optimal plasma distribution. It is a figure explaining the procedure for maintaining optimal plasma distribution.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plasma processing apparatus 2 Vacuum processing chamber 3 Mass flow controller 4 High frequency power supply for plasma generation 5 Gas exhaust system 6 Wafer 7 Sample stage 8 Plasma 9 High frequency power supply for bias 10 Pressure gauge 11 Variable conductance valve 12 Observation window 13 Light receiver 14 Light receiving controller 15 Monitor device 16 Control unit

Claims (5)

Plasma processing comprising a vacuum processing chamber, a sample stage for placing and holding a sample in the vacuum processing chamber, and a plasma generating means for generating plasma by supplying high-frequency energy to a process gas introduced into the vacuum processing chamber In the device
A photoreceiver that receives light emitted from the generated plasma outside the vacuum processing chamber;
A light receiving adjuster that is provided between the light receiver and a vacuum processing chamber, and that adjusts a range of concentric plasma introduced into the light receiver among light emitted from the plasma;
A plasma distribution is obtained by synthesizing the amount of light received by the light receiver and the amount of light received by adjusting the light reception adjuster to change the light reception range by the light receiver, and a plasma processing apparatus based on the acquired plasma distribution The plasma processing apparatus provided with the control apparatus which controls this. Plasma processing comprising a vacuum processing chamber, a sample stage for placing and holding a sample in the vacuum processing chamber, and a plasma generating means for generating plasma by supplying high-frequency energy to a process gas introduced into the vacuum processing chamber In the device
A photoreceiver that receives light emitted from the generated plasma outside the vacuum processing chamber;
A light reception adjuster for adjusting a range of concentric plasma introduced between the light receiver and the vacuum processing chamber and being emitted from the plasma into the light receiver;
Adjusting the light receiving adjuster to change the light receiving range by the light receiver to concentric multiple stages, obtain the plasma distribution by synthesizing the received light amount at each changed stage , and based on the acquired plasma distribution A plasma processing apparatus, further comprising a control device that changes processing conditions of the plasma processing apparatus. The plasma processing apparatus according to claim 1,
The said control apparatus adjusts the high frequency electric power supplied to the said plasma production | generation means or the said sample stand, The plasma processing apparatus characterized by the above-mentioned. The plasma processing apparatus according to claim 1,
The light receiving adjuster is configured to change the range of the plasma introduced into the light receiver in multiple stages concentrically and in the radial direction of concentric plasma emission based on the received light amount obtained by the change. A plasma processing apparatus characterized by obtaining a distribution and controlling the plasma processing apparatus based on the obtained radial distribution. The plasma processing apparatus according to claim 1,
Plasma processing is performed by changing the processing conditions of the plasma processing apparatus, and the radial distribution of plasma emission when the processing conditions of the plasma processing apparatus are changed is detected, and the optimal processing conditions are determined based on the detected results. A plasma processing apparatus.

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