KR100664512B1 - Plasma processing method and apparatus - Google Patents

Abstract

In the present invention, in processing a wafer using plasma, the wafer is processed with high reproducibility by suppressing fluctuations in processing dimensions for each wafer without lowering throughput.

A plasma is generated in the vacuum processing chamber 20 and a high frequency voltage is applied to the lower electrode 27 on which the wafer is placed, and a high frequency voltage applied to the lower electrode 27 is periodically turned on and off and processed. The wafer 32 is plasma-processed by controlling the duty ratio of the high frequency voltage on / off for each wafer or a plurality of wafers.

Description

Plasma treatment method and apparatus {PLASMA PROCESSING METHOD AND APPARATUS}

1 is an overall configuration diagram showing an example of a plasma processing apparatus to which the present invention is applied;

FIG. 2 is a longitudinal cross-sectional view showing the detailed configuration of an etching apparatus section in the apparatus of FIG. 1; FIG.

FIG. 3 is a diagram showing a relationship between the duty ratio of on / off of a high frequency voltage applied to a sample when using the apparatus shown in FIG. 2 and the etching characteristics of CD gain, selectivity, and uniformity;

4 is a view showing an example of the measurement (monitor) value of the cross-sectional shape of the sample subjected to the etching treatment;

5 is a flow chart showing a method of controlling a process using the apparatus of FIG. 2;

Fig. 6 is a diagram showing an example of the initial value of CD gain in the plasma processing chamber and the CD gain characteristics after N sheet processing obtained as a result of the monitor;

7 is a longitudinal sectional view showing a configuration of an etching apparatus section according to a second embodiment of the present invention;

8 is a flow chart showing a control method of a process using the apparatus of FIG.

9 is a flow chart showing a control method of the third embodiment of the present invention;

10 is a diagram showing a method of applying a high frequency voltage in a fourth embodiment of the present invention;                 

11 is a flowchart illustrating a control method of the embodiment of FIG. 10;

12 is a diagram showing the relationship between the duty ratio and CD gain of the high frequency voltage, the amplitude and selectivity of the high frequency voltage, and the duty ratio and the etching rate of the high frequency voltage in the high frequency power of FIG. 10;

13 is a flowchart showing a control method of the fifth embodiment;

14 is an overall configuration diagram showing another example of the plasma processing apparatus to which the present invention is applied;

15 is an overall configuration diagram showing another example of the plasma processing apparatus to which the present invention is applied.

※ Explanation of symbols for main parts of drawing

1: vacuum processing apparatus 2a to 2d: plasma processing chamber

3: vacuum conveying room 4a, 4b: lock room

5: conveying apparatus 6: conveying robot

7: cassette stand 8: cassette

9: Inspection device 10, 10a: Control device

11: aligner (Oripra fit) 20, 20a, 20b: vacuum processing chamber

21: dielectric window 22: antenna

23: coaxial waveguide 24: matching device

25, 72, 81: high frequency power supply 26: magnetic field coil

27, 27a, 27b: lower electrode 28, 28a, 28b: high frequency bias power supply

29: ESC power supply 30: exhaust port

31: gas supply device 32: wafer

33: high frequency voltage waveform 34: emission monitor

71: induction coil 82: upper electrode

100: etching condition adjusting unit

The present invention relates to a plasma processing method and apparatus, and more particularly, to a plasma processing method and apparatus suitable for etching a substrate such as a semiconductor wafer using plasma.

As a technique for maintaining the etching performance, as described in Japanese Patent Laid-Open No. 9-129594, plasma is generated in a gas containing a reaction gas by applying electric power to the first electrode, thereby performing light emission analysis of plasma and a substance in the plasma. The plasma state during etching by one or more of these methods, such as mass spectrometry, measurement of the magnetic bias voltage of the plasma, measurement of the impedance of the plasma, and the like to control the bias voltage according to the detected plasma state. BACKGROUND ART A technique is known in which high control properties and excellent pattern dimensions and pattern cross-sectional shapes are obtained.

On the other hand, as a technique for enabling device processing of a processing dimension of 1 μm or less in accordance with the miniaturization of semiconductor devices, conventionally, for example, as described in Japanese Patent Application Laid-Open No. H11-297679, a sample table installed in a vacuum container is used. Placing the sample, supplying the processing gas into the vacuum vessel to make a plasma, applying a high frequency bias at a frequency of 100 kHz or more to the sample stage independently of the plasma generation, modulating the high frequency bias at a frequency of 100 Hz to 10 kHz to achieve the same etching rate. It is known to perform a surface treatment of a sample on and off of a high frequency bias voltage to which a Vpp value having a value larger than the Vpp value is applied to a Vpp value of a continuous high frequency bias voltage at which is obtained.

In recent years, as the speed of semiconductor devices increases, the processing dimensions of LSIs (large scale integrated circuits) have now become 0.1 µm. The machining precision of the electrode and wiring part of an element is required to be ± 0.01 μm or less.

On the other hand, in the etching apparatus using the plasma, there is a problem that the processing dimensions vary slightly for each wafer. In the etching apparatus, for example, the plasma is affected by the state of the inner wall of the vacuum vessel. In other words, when etching the Si wafer, the reaction product of Si gradually adheres to the inner wall, whereby the plasma composition changes due to the change of the surface state of the inner wall or the re-emission of the deposit from the wall. As a result, when the wafers are continuously processed one by one, even if the processing conditions of the wafer such as gas flow rate and pressure are constantly maintained, there is a slight deviation in the processing line width for each wafer. With the recent miniaturization of devices, there has been a problem that it is difficult to satisfy the required machining accuracy due to this dimensional variation, which has not been a problem at the 0.1 占 퐉 machining dimension, at a 0.1 占 퐉 machining dimension.

As a method of solving such a problem, there is a method in which sheet cleaning is performed to clean the processing chamber for each wafer. However, this method is not only effective for all plasma treatments at the same time as it is a factor of lowering throughput. As another method, it is conceivable to perform the plasma treatment while correcting the processing conditions for each wafer or every sheet. As such a method, there is a method of feedback control as shown in the above-described prior art.

As described above, in the prior art in which the bias voltage is controlled by various kinds of information from the plasma, the selectivity during etching changes due to the change of the bias voltage, which may not be suitable for a sample having a thin thickness of a mask or an underlying film. .

Moreover, in the related art of controlling the high frequency bias voltage on and off, it is not considered about controlling the on and off of the high frequency bias voltage according to the change of the process processing during the processing. When the bias voltage, that is, the on / off voltage value (Vpp) is controlled based on the information, the influence on the selection ratio is less than that of the continuous bias. It is not enough for selection ratio yet.

SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma processing method and apparatus which can be processed with high reproducibility while suppressing fluctuations in the processing dimension for each wafer in a device processing having a processing dimension of 1 μm or less, without reducing the throughput. .

The above object is to independently control the generation of the plasma and the bias applied to the substrate, and periodically modulate the output (amplitude) of the high frequency voltage applied to the sample stage in the method of plasma processing the substrate, and for each substrate to be processed. Alternatively, this is achieved by changing the duty ratio (percentage of time when a large voltage occupies one cycle) of periodic time modulation for a plurality of substrates.

The above object is a plasma processing apparatus for generating a plasma in a vacuum vessel and simultaneously applying a high frequency voltage to a sample stage installed in the vacuum vessel to process a substrate disposed on the sample stage, the high frequency power source connected to the sample stage and a high frequency. It is achieved by including modulation means for periodically on / off-modulating the high frequency voltage from the power supply and control means for changing the duty ratio of on / off for each substrate to be processed or for a plurality of substrates.

In addition, the duty ratio is changed by measuring the line width after wafer processing, and if the deviation is from a specified value, the duty ratio is changed in a direction for correcting the duty ratio. Alternatively, monitor the condition of the device correlated with the processing dimensions of the plasma light, and change the duty ratio to enter the normal range when the monitor amount is out of the normal value.

In addition, in the method of monitoring the variation of the apparatus state and feeding back the etching conditions in order to stabilize one of the etching characteristics (e.g., processing dimensions), the etching conditions are changed by changing predetermined conditions (e.g., wafer surface uniformity of etching rate). It is necessary to prevent sex change. In the present invention, the output (amplitude) of the high frequency voltage applied to the sample is changed in time, and the duty ratio is changed to change only the incident ion amount and the radical deposition amount so as not to affect other etching characteristics such as plasma composition, plasma distribution, and processing dimensions. The fluctuation of can be suppressed.

EMBODIMENT OF THE INVENTION Hereinafter, the Example which applied this invention is demonstrated using each figure.

(Example 1)

First, Example 1 of this invention is demonstrated with reference to FIGS. In the first embodiment, the wafer processing dimension by etching is measured for one sheet or a plurality of wafers, and the etching conditions are changed according to this value. As the etching conditions, in this case, the high frequency voltage applied to the wafer serving as the substrate is turned on and off, and the duty ratio (ratio of on time occupied in one cycle) to be turned on and off is changed. This suppresses the variation in the machining dimension.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the whole structure of the plasma processing apparatus for implementing the plasma processing method of this invention in Example 1. FIG. In this case, the vacuum processing apparatus 1 consists of four plasma processing chambers 2a-2d, the vacuum conveyance chamber 3, and the lock chambers 4a, 4b. Plasma processing chambers 2a and 2b and lock chambers 4a and 4b are arranged around the vacuum transfer chamber 3. The plasma processing chambers 2a to 2d are, for example, etching chambers, and the plasma processing chambers 2c and 2d are, for example, ashing chambers. On the lock chambers 4a and 4b side of the vacuum processing apparatus 1, the conveying apparatus 5 which has the conveying robot 6 is arrange | positioned, and the cassette stand which can arrange | position multiple cassette 8 with the conveying apparatus 5 in between. (7) is arranged. In addition, the aligner 11 and the inspection apparatus 9 are provided around the conveying apparatus 5 together with the vacuum processing apparatus 1. The measurement result by the inspection device 9 is introduced into the control device 10, and the wafer processing in the plasma processing chambers 2a and 2b is performed by the etching condition adjusting unit 100 of the control device 10 based on the measurement result. Adjust the conditions. In addition, the control apparatus 10 is comprised by the computer provided with a CPU, a memory, a program, an external memory | storage device, an input / output means, etc., and controls the vacuum processing apparatus 1, for example. Among them, the etching condition adjusting unit 100 is based on the measurement result, and is executed by a program that executes run-to-run control for changing the duty ratio of the high frequency bias for each sample or lot unit, or a memory device that holds various data required for the control. Is realized.

Here, the cassette 8 is accommodated in a sealed container and conveyed by the conveyance robot 6 of the conveying apparatus 5. It is preferable that the moving space of the transport robot 6 is maintained in a clean gas atmosphere, and between the cassette 8 and the aligner 11, between the aligner 11 and the lock chambers 4a and 4b or the cassette ( It is preferable to isolate | separate from the atmosphere in a clean room between 8) and the lock chambers 4a and 4b, and between the lock chambers 4a and 4b and the inspection apparatus 9. In addition, when the cleanliness of the atmosphere in the clean room is high, the above-mentioned isolation is not necessary.

In the above-described plasma processing apparatus, the wafer etched in the vacuum processing apparatus 1 is transferred from the lock chamber 4a or 4b by the transfer robot 6 to a side scanning type electron microscope (hereinafter referred to as "side length SEM"). It is sent to the inspection apparatus 9 which measures a process line width. In the inspection apparatus 9, the thickness amount (henceforth "CD gain") from a design value of a process line | wire width is measured by a measurement SEM. This measurement is performed for each wafer or every predetermined number of sheets as necessary, and the data is accumulated in the storage device in the control device 10. The CD gain has a predetermined allowable value, and the initial etching condition, that is, the etching process condition at the start of the load process, is set so that the CD gain falls within this allowable value. Here, several wafers are continuously processed, and if the CD gain exceeds the allowable value, this data signal is sent to the etching condition adjusting unit 100 in the control apparatus 10 so that the CD gain is changed according to the etching condition adjusting unit 100. The condition is automatically adjusted so as to fall within the allowable value, and the control apparatus 10 changes and adjusts the etching processing conditions in the plasma processing chamber 2a or 2b of the vacuum processing apparatus.

FIG. 2A is a cross-sectional view of the plasma processing chambers 2a and 2b of the vacuum processing apparatus 1. The vacuum processing apparatus 1 in this embodiment is an ECR type plasma etching apparatus which generates a plasma by interacting with a magnetic field by radiating electromagnetic waves from an antenna. An antenna 22 made of Al is disposed on the vacuum processing chamber 20 that is a plasma processing chamber via the dielectric window 21. The antenna 22 is connected to a high frequency power source 25 for generating UHF electromagnetic waves (for example, frequency 450 MHz) via the coaxial waveguide 23 and the matching unit 24. The dielectric window 21 can transmit electromagnetic waves from the high frequency power supply 25. A magnetic field coil 26 (in this case, a two-stage coil) for forming a magnetic field in the vacuum processing chamber 20 is wound around the outer peripheral portion of the vacuum processing chamber 20.

In the vacuum processing chamber 20, a lower electrode 27 serving as a sample stage for placing the wafer 32 serving as the sample facing the antenna 22 is provided. A space is formed between the dielectric window 21 and the lower electrode 27 to generate a plasma therein. The lower electrode 27 includes a high frequency bias power supply 28 for applying incident energy to the wafer 32 to ions in the plasma, and an ESC power supply 29 for electrostatically adsorbing the wafer 32 to the lower electrode 27. Connected. There is no restriction | limiting in particular in the frequency of the high frequency bias power supply 28, Usually, the range of 200kHz-20MHz is used. In this case, the frequency of the high frequency bias power supply 28 is 400 kHz.

In addition, the voltage waveform 33 of the high frequency voltage applied to the lower electrode by the high frequency bias power supply 28 controls the output of the high frequency on / off to control the on and off periods as shown in FIG. It is set to 1 cycle and is repeatedly controlled at an arbitrary cycle, for example, 1 kHz. This on / off control may be performed as run-to-run control for each sample or in a lot unit or other suitable unit.

In addition, instead of turning on / off the high frequency output by run-to-run control, the high frequency voltage has a large amplitude (value in the range where etching progresses) and a small value (value in the range where etching does not proceed). You may make it control. In this case, the high frequency bias application method is applied periodically by dividing the time t1 and the time t2 into another high frequency bias voltage within one cycle.

The exhaust port 30 is provided in the lower part of the vacuum processing chamber 20, and the exhaust apparatus which is not shown in figure is connected. 31 is a gas supply device for supplying processing gas into the vacuum processing chamber 20 and is connected to a plurality of gas supply holes (not shown) provided in the dielectric window 21.

In the plasma processing apparatus configured as described above, the UHF electromagnetic waves output from the high frequency power supply 25 pass through the dielectric window 21 from the antenna 22 portion through the matching unit 24 and the coaxial waveguide 23, and then the vacuum processing chamber ( Supplied within 20). On the other hand, a magnetic field by the magnetic field coil 26 is formed in the vacuum processing chamber 20. By the interaction between the electric field of the electromagnetic wave and the magnetic field of the magnetic field coil, the etching gas introduced into the vacuum processing chamber 20 is efficiently converted into plasma. The plasma is subjected to a predetermined etching process on the wafer 32 on the lower electrode 27. In the etching process, the incident energy of ions in the plasma entering the wafer 32 by the high frequency bias power supply 28 is controlled to obtain a desired etching process.

Fig. 3 shows the results obtained by experiments of the relationship between the CD gain, selectivity, and etching rate of the underlying oxide film of the polycrystalline silicon wiring etched using this plasma processing apparatus and the duty ratio of the high frequency bias. It is a figure which shows. In addition, CD gain means the increase amount of CD, and a selection ratio is a ratio of the etching rate of polycrystal silicon and an underlying oxide film.

Usually, in gate processing of transistors, it is necessary to selectively etch polycrystalline silicon with respect to a thin oxide film of a few nm, which is an underlying film. For this reason, in addition to the CD gain, the selectivity with the underlying oxide film and the uniformity of the etching rate of the underlying oxide film become important. In addition, the etching conditions that is the basis of the data of Figure 3 is, and as a process gas using a mixture of _{Cl 2 (18cc), HBr (} 82cc), O 2 (3cc) to the processing pressure 0.4Pa. Moreover, the output of the high frequency bias power supply 28 is set to 35W, and electric power is controlled uniformly. When the high frequency is turned on and off, the peak value of the power is changed so that the average of one cycle is 35W. For example, when the duty ratio is 50%, the average value is 35W by controlling the peak value of the power to be the output of the peak value when the continuous output is 70W.

As can be seen from Fig. 3, when the output of the high frequency bias is made constant, that is, the duty ratio is controlled with the average power of ON and OFF being constant, the CD gain is changed depending on the duty ratio. In other words, it can be seen that the CD gain is large at the duty ratio of 100% (that is, the continuous bias), but the CD gain is decreased when the value of the duty ratio is reduced. This is because, when the power is constant, the duty ratio is reduced as compared with when the duty is 100%, and thus the amplitude of the high frequency voltage is increased, so that the incident energy to the wafer applied to the ions in the plasma is increased. It was also found that the selectivity and uniformity depend little on the duty ratio. That is, the output (power) of the high frequency bias is made constant, and the high frequency applied to the sample is turned on and off, and the duty ratio is changed to change the selectivity and the uniformity of the etching rate of the underlying oxide film, which greatly affect the processing of the wiring. In other words, only CD gain can be changed without sacrificing performance of selectivity and uniformity.

According to the present invention, the run-to-run control of the etching is performed by using the characteristics of the duty ratio as shown in FIG. 3, whereby the variation in the processing dimension of the sample can be suppressed.

This point is demonstrated concretely below. 4 shows a cross-sectional shape in the case where the sample having the mask 311 is etched on the Poly-Si film 312 which is a gate material. 4A is a target shape (CD value is L1), and (b) is an example of a case where the processing shape is thickened due to a change in etching characteristics or the like (CD value is L2). The variation amount L2-L1 of the processing dimension of the sample is kept below a predetermined value by the duty ratio feedback control.

5 shows the Nth wafer from the processed wafers with the inspection device 9, and the etching condition adjusting unit 100 of the control device 10 compares the Nth wafer with the measured CD gain of the processed line width. The run-to-run control for controlling the duty ratio of the N + m (m = 1, 2 ...) wafers to be processed later, in this case, the duty ratio feedback control. The CD of the Nth wafer etched by the etching apparatus is measured by the length measurement SEM of the inspection apparatus 9 (502). The difference between the CD value and the target value (the variation amount L2-L1 in FIG. 4) is obtained (504), and it is determined whether the variation amount is within the standard value (506). Next, the next new N + m-th wafer is processed (508). If the variation is outside the standard value, the duty ratio is changed (510) to process the next new N + m-th wafer (508). The completion of the N + m-th etching process is performed by using an etching end point determination device (512).

Fig. 6 shows an example of the initial value of the CD gain in the plasma processing and the CD gain characteristics after the N sheet processing obtained as a result of the monitor. As shown in Fig. 6, the CD gain has a predetermined allowable value (standard value), and the initial etching condition, that is, the etching process condition at the start of the lot processing, is set so that the CD gain falls within this allowable value. On the other hand, after several wafers, for example, Si wafers, are continuously processed, the reaction product of Si gradually adheres to the inner wall of the plasma processing chamber, thereby changing the inner wall surface state. As a result, the plasma is affected and the CD gain changes even if the etching conditions are the same. Therefore, when the CD gain exceeds the allowable value, the data signal is sent to the etching condition adjusting unit 100 in the control device 10, and the condition is automatically set by the etching condition adjusting unit 100 so that the CD gain falls within the allowable value. The control apparatus 10 changes and adjusts the etching treatment conditions in the plasma processing chamber 2a or 2b of the vacuum processing apparatus.

This change and adjustment amount is obtained as shown in FIG. For example, at an initial value, CD target value is 0.23 micrometers, and the duty ratio at that time is set to 50%. When the CD variation amount specification is ± 5 nm, when the CD variation amount after etching becomes 7 nm thick, it can be seen that the CD gain decreases by 7 nm when the duty ratio is made about 10% smaller than the characteristics of FIG. Therefore, the duty ratio is set to 40% by the duty ratio feedback control to process the next wafer. By the feedback control of the duty ratio, the CD value of the next wafer can be returned to the target value of 0.23 mu m.

The relationship between the CD gain and the duty ratio as shown in FIG. 6 changes when the structure and etching conditions of the wafer to be processed change. Therefore, in practice, it is necessary to make a database in which data corresponding to each process is stored in advance, or to accumulate data for each wafer process to construct a database and make it available to the control apparatus 10.

Further, even in the method of applying high frequency continuously and increasing the power, the ion energy increases, so that the thickness of the shape, that is, the CD gain can be reduced. However, in this case, since only the ion energy is large and there is no off period of the bias that does not accelerate the ions, the etching rate of the oxide film also increases at the same time, resulting in a problem that the underlying oxide film becomes shallow because the selectivity becomes small.

  As described above, according to the present embodiment, the duty ratio of the high frequency bias power supply is changed according to the CD gain value for the slight deviation of the processing line width for each wafer due to the plasma composition change or variation in the vacuum processing chamber caused by the repetition of the wafer processing. By feedback control, the processing line width of the wafer can be made the optimum value, and the required processing precision can be satisfied. Thereby, there is an effect that processing can be performed with good reproducibility by suppressing fluctuations in machining dimensions for each wafer.

The change in duty ratio can facilitate the adjustment of the CD gain in several nm units, and is suitable for the processing of fine semiconductor devices having a level of 0.1 µm to 0.05 µm in which variation in the processing dimension for each wafer becomes a problem.

In addition, when run-to-run control starts to change in the CD gain value before the CD gain value after wafer processing exceeds the allowable range, the duty ratio of the high frequency bias is always adjusted based on the data accumulated in the etching condition adjusting unit 100 described above. The feed forward control may be performed to maintain the feed.

A measuring SEM is generally used as an apparatus for measuring a processing dimension. However, since the measuring SEM observes the shape from above, when the shape is thin, that is, the width of the polycrystalline silicon is smaller than that of the resist, the width of the polycrystalline silicon can be measured. There is no problem. As a method for determining the deviation or change in the width of the processed wire in place of the measured SEM, the method of measuring the electrical resistance of the wire to obtain the deviation from the design value of the processed dimension, or the method of estimating the shape of the wire from the reflection or diffraction of light, etc. have. By using these in the inspection apparatus 9 and applying the feedback control or the feed forward control to the etching conditions, the duty ratio is adjusted, which makes it possible to correct the case where the processing shape is thinned.

The run-to-run control, i.e., the process of measuring the machining size and adjusting the etching conditions can be set for each wafer or once for a plurality of sheets, but the process can be set according to the processing state of the wafer.

The etching conditions adjusted by the etching condition adjusting unit 100 according to the variation of the CD gain are at least a duty ratio, and in addition to the duty ratio, other conditions such as gas pressure and gas composition may be finely adjusted.                     

Example 2

Next, a second embodiment of the present invention will be described with reference to Figs. In FIG. 7, the same code | symbol as FIG. 2 shows the same member, and abbreviate | omits description. The present embodiment differs from the embodiment of FIG. 2 in that a means for monitoring plasma light is provided in place of the inspection apparatus 9 so as to control the duty ratio and the like in accordance with the change of the plasma generation state. That is, a skylight window is provided for lighting plasma light corresponding to the plasma generating portion of the vacuum processing chamber 20, and a light emission monitor 34 for measuring the light emission spectrum of the plasma light is connected to the skylight through an optical fiber. The light emission spectrum measured by the light emission monitor 34 is converted into an electrical signal and input to the control device 10a.

As a cause of the change in the etching shape for each wafer, a reaction product such as Si chloride may adhere to the inner wall of the vacuum processing chamber 20 to change the state of the plasma. For example, when the reaction product attached to the inner wall is re-released and attached to the wafer 32, the CD gain increases. At the same time, the plasma emission intensity is measured with respect to the wavelength of light, that is, when the emission spectrum is measured, the change corresponding to the increase of the reaction product is measured. The change pattern varies depending on the gas composition and the material to be etched, but the relationship between the CD gain and the emission spectrum of the plasma is measured in advance, and the data is input to the etching condition adjusting unit 100. The etching condition adjusting unit 100 converts the change in the output of the light emitting monitor 34 into an adjustment amount of the duty ratio, thereby changing the duty ratio of the high frequency bias power supply 28 by the controller 10a.

In this manner, the etching condition adjusting unit 100 of the control apparatus 100a inputs and stores data relating to the relationship between the light emission spectrum and the CD gain value in advance or accumulates data for each processing of the wafer.

In the apparatus configured as described above, the emission spectrum of the plasma is measured by the emission monitor 34 for each wafer process, and the small duty ratio or the large duty ratio is selected so that the CD gain falls within the allowable range according to the etching condition adjusting unit 100. Alternatively, a signal for calculating and adjusting the duty ratio of the high frequency bias power supply 28 and the output peak value (amplitude) of the power is sent from the control device 10a to the high frequency bias power supply 28, and the duty ratio of the high frequency bias power supply 28 and Adjust the peak voltage. As a result, the controller 10a can adjust the duty ratio of the high frequency bias from the high frequency bias power supply in real time in accordance with the variation in the emission spectrum of each wafer process.

The above processing flow is shown in FIG. When etching starts (802), the value from the light emission monitor 34 is measured (804), and how much the measured value changes with respect to the previous monitor value is determined (806). It is determined whether the obtained change amount is within the allowable range with respect to the previous monitor value (808), and if it is within the range, processing is performed without changing the condition as it is. When it is determined out of the range in step 808, the duty control of the on / off repetition of the high frequency bias, that is, the control of changing the duty ratio, is performed (810). After these controls, when the etching process of the wafer has not yet finished (812), the measurement of the monitor value 804 is continued and the above flow is repeated. Thereafter, if the end of the etching is determined in step 812, the wafer is taken out and collected. If the predetermined number of wafer processes are completed, the process ends (814).

As described above, according to the second embodiment, the duty ratio of the high frequency bias power supply can be adjusted according to the emission spectrum and, in other words, according to the CD gain value, so that the processing line width of the wafer can be made optimal as in the above-described embodiment. It can satisfy the required machining precision. As a result, similarly to the first embodiment described above, there is an effect that processing can be performed with good reproducibility by suppressing fluctuations in processing dimensions for each wafer. Moreover, it is suitable for the processing of the fine semiconductor element of 0.05 micrometer-0.01 micrometer level which the fluctuation | variation of the processing dimension for every wafer becomes a problem.

In addition, the signal of the emission spectrum of the plasma may be treated as the signal intensity of a specific wavelength, and by using a principal analysis method generally known as a multivariate analysis method, the principal component most correlated with the CD gain, or a combination of several principal components. It may be converted to the parameter to be obtained and handled.

In this embodiment, the light emission spectrum of the plasma is used. However, in addition to the light emission spectrum of the plasma, the plasma emission power spectrum uses the impedance of the plasma and power supply circuits, the voltage waveform height of the high frequency bias power supply 28, and the like. It is thought too.

Example 3

Next, a third embodiment of the present invention will be described. In the case where the emission spectrum of the plasma or the other monitor values suddenly change within the range capable of plasma treatment, abnormalities due to hard changes of the device, for example, wear or deterioration of components on the electrical circuit that have undergone the plasma, are recognized. First, the bias voltage may be optimized to prevent the wafer during processing from being defective, and for this purpose, the control may be performed by varying and optimizing the power value of the constant power control during the on / off control. In addition, the apparatus configuration of this embodiment is the same as that of the second embodiment except for the etching condition adjusting unit 100.

9 shows a control flow of the etching condition adjusting unit 100 in the third embodiment. When etching is started (902), the value from the light emission monitor 34 is measured (904), and how much the measured value changes with respect to the previous monitor value is determined (906). It is determined whether the obtained change amount is within a range of the set value (allowed value) with respect to the previous monitor value (908), and if it is within the range, the duty control of repetition of normal high frequency bias on / off is performed (910). If etching after these control has not yet finished (912), the measurement 904 of the monitor value is continued and the above flow is repeated. After the end of the etching is determined, the etching is finished and the wafer is taken out and recovered (914). On the other hand, if it is determined in step 908 that it is out of range, that is, if the amount of change obtained exceeds the range of the set value (allowed value) for the previous monitor value, a change in the hardware of the device, for example, abrasion of components on the electric circuit through plasma, An abnormality due to deterioration or the like is considered. In this case, control is performed to optimize the bias voltage so as to optimize the bias voltage so that the wafer during the processing is not defective within the range in which plasma processing is possible, and change the output value during the on / off control, that is, the power value (916). If such control is likely to exceed the range of the set value (allowed value) for the monitor value continuously (918), it is possible to think that there is an abnormality in the device or the processing condition. Let's wait for the specific treatment by the operator.

Also in this case, the relationship between the change amount of the monitor value and the output value of the high frequency bias and the conditions for generating an alarm are inputted as data in advance, or data is accumulated and processed for each process.

Example 4

Next, a fourth embodiment of the present invention will be described. In the first embodiment, the high frequency voltage is turned on and off as shown in Fig. 2 (b). However, in this embodiment, the period is divided into three or more regions and set as time (T1, T2, ... Tm). At the same time, the applied power (or amplitude) of each high frequency wave is changed into P1, P2,... It is controlled by setting to Pm.

This embodiment will be described using FIGS. 10 to 12. FIG. 10 shows a case where one subdivision is divided into three sub-regions in this case. FIG. 11 shows a flow in the case of processing using the high frequency power shown in FIG. First, the dividing number m for each cycle is m = 3, and T1, T2, T3 and P1, P2, and P3 corresponding thereto are determined (1102), and the etching process is started. For example, set P1 to 100W, P2 to 10W, and P3 to 30W. The wafer which has been etched is measured for the CD value, the selection ratio, and the etching rate by the above-described measurement inspection apparatus or the like (1104, 1106, 1108), and if the condition is within the standard value (1112), no condition is changed. After the control value is set in the state (1114), the next wafer is processed, but if the variation amount deviates from the standard value, one of T1, T2, T3 and P1, P2, P3 in the sub area is set and changed (1116). The wafer is then processed.

For example, as shown in FIG. 10, when one period is divided into three sections, characteristics as shown in FIG. 12 are obtained. The section T1 having the largest amplitude is a section controlling the maximum ion energy, and the ratio of this section becomes the dominant factor of the CD. Therefore, the CD is adjusted by controlling the ratio of the section T1 as shown in FIG. In other words, the amplitude of the section T2 having the smallest amplitude is changed small, in other words, by changing the applied power, fine adjustment of the selection ratio becomes possible as shown in Fig. 12B. Of course, even if the amplitude of the other section is changed, the selection ratio changes, but in this case, the selection ratio is large, so that the control becomes difficult, and the CD or the like also changes at the same time. Therefore, it is suitable to slightly change the amplitude of the section T2 in order to suppress the influence of other factors such as CD as much as possible and to finely adjust the selection ratio. In addition, the section T3 having an intermediate amplitude can be used to adjust the etching rate of Poly-Si. For this reason, the amplitude of the section T3 is set slightly higher than the threshold at which wafer deposition occurs, which affects the etching rate of Poly-Si, but it is necessary to adjust the amplitude so as not to affect the oxide film rate as much as possible. Under this adjustment, the etching rate of Poly-Si can be controlled by changing the ratio of the section T3 as shown in FIG.

Specifically, if the CD fluctuates by [Delta] CD after processing N sheets as shown in Fig. 12A, the next wafer is processed by changing the ratio of T1 by [Delta] T1 to return the CD to the target value. If the selectivity is shifted by ΔS as shown in Fig. 12B, by changing the amplitude of the period T2 by ΔP2 and processing the next wafer, the selectivity can be maintained at the target value. Similarly, when the etching rate of Poly-Si is shifted by ΔR, the ratio of the section T3 is changed by ΔT3 as shown in FIG. 12 (c) to maintain the poly-Si etching rate as the target value.

Also in this embodiment, the width of the control that can change only the factor that you want to control while keeping other factors approximately constant is not so large. However, when the same product is processed in large quantities under the same conditions, the shape and the like do not change as it is. In this case, the present invention is effective because it aims to adjust a slight change occurring over time.

Example 5

Next, a fifth embodiment of the present invention will be described. In this embodiment, the number m of sub-areas is changed during processing to independently control one or both of the time T1, T2 ... Tm in one cycle and the applied power P1, P2 ... Pm of high frequency.

Fig. 13 illustrates the processing flow of this embodiment. First, time T1, T2, T3 and applied powers P1, P2, P3 are set as initial settings (1302), and etching is started (1304). After the start of etching, the monitor value of plasma emission intensity during etching is measured (1306). The change amount for the monitor value is obtained (1308), and it is determined whether the change amount is within the allowable range (1310), and if it is within the allowable range, etching processing by duty ratio feedback control is performed (1312) under the same condition. When etching is completed (1314), the wafer is taken out and recovered (1316). In step 1310, if there is a deviation from the allowable range, the number (m) of sub-areas is changed (1318), and the time (T1, T2, ... Tm) and the applied power (P1, P2, ... Pm) are set (1320). To change the duty ratio. If such a setting change cannot be processed well even after repeating a plurality of times (1322), an alarm sounds (1324). Since the amount of change is changed when the structure or etching conditions of the wafer to be processed change, it is necessary to actually make a database in which data corresponding to each process is stored in advance or to build a database by accumulating data for each wafer process. Done.

In addition, in the present embodiment, a method of monitoring and controlling the plasma emission intensity during etching has been described. However, as shown in the embodiment shown in Fig. 5, the wafer after the end of etching is inspected by the inspection apparatus, and based on the measurement data, Judgment may be made. As the determination condition of step 1310, the CD value, the selection ratio, and the etching rate may be determined as in the embodiment shown in FIG.

Example 6

Next, a sixth embodiment of the present invention will be described. In the present embodiment, the plasma processing apparatus using the inductively coupled plasma source is switched to the ECR plasma apparatus of the first embodiment, and the high frequency voltage for plasma generation is turned on and off by the on / off control of the high frequency voltage. This embodiment will be described with reference to FIG. A high frequency power of 13.56 MHz is applied to the induction coil 71 provided outside the vacuum processing chamber 20a by on / off control by the high frequency power supply 72 to generate plasma in the vacuum processing chamber 20a. A high frequency bias power supply 28a for accelerating ions is connected to the lower electrode 27a on which the sample is installed.

In the on period of the high frequency power supply 72, ions are generated in the plasma, ions are accelerated by the high frequency bias power supply 28a for bias, and are vertically incident on the wafer to proceed vertical etching of the wafer. In the off period of the high frequency power supply 72, the ions in the plasma disappear and the etching in the vertical direction stops, and the reaction product contained in the gas diffuses and deposits on the wafer. That is, the same effect as that of the on / off control of the high frequency voltage applied to the lower electrode 27a is produced. By this effect, the shape (CD) of etching can be controlled by maintaining uniformity and selectivity.                     

The on / off control of the high frequency power supply 72 can be controlled in the same manner as shown in the first to fifth embodiments described above. In addition, of course, in the apparatus of this embodiment, the high frequency voltage applied to the lower electrode 27a may be controlled on and off.

Example 7

Next, a seventh embodiment of the present invention will be described. In this embodiment, the plasma processing apparatus is a capacitive coupling type plasma processing apparatus. This embodiment will be described with reference to FIG. Two parallel plate electrodes are provided in the vacuum processing chamber 20b, a high frequency power supply 81 for plasma generation is connected to the upper electrode 82, and a high frequency bias power supply for ion acceleration to the lower electrode 27b where the wafer is placed. 28b is connected. Also in the present embodiment, as in the sixth embodiment, any one of the high frequency power supplies may be turned on and off and controlled as shown in the above first to fifth embodiments.

As described above, according to these embodiments of the present invention, there is an effect that the wafer can be processed with good reproducibility by suppressing the variation in the processing dimension for each wafer without reducing the throughput.

In addition, the data of the etching process in these Examples may be stored in the control apparatus of a plasma processing apparatus, or may be stored in the upper control apparatus which controls a semiconductor manufacturing line. Further, the semiconductor manufacturing company and the manufacturing apparatus manufacturer may be connected by a network using the Internet to use the data accumulated in the manufacturing apparatus manufacturer.

Claims (14)

In the plasma processing method of processing a sample using a high frequency voltage, The high frequency voltage is composed of a sub-region divided into a plurality of times within one cycle, and each sub-region has a different amplitude, It is possible to independently control the applied power to one or more sub-regions of the plurality of sub-regions, And controlling the applied power of the one or more sub-areas for each unit for processing the sample. The method of claim 1, It is possible to control the amplitude and duty ratio of the high frequency voltage for one or more sub-regions of the plurality of sub-regions, and to control the amplitude and duty ratio of the high frequency voltage of the one or more sub-regions for each unit for processing the sample. Plasma treatment method, characterized in that. The method of claim 1, It is possible to control the amplitude and duty ratio of the high frequency voltage with respect to one or more areas of the plurality of sub-areas, and the ratio of time of the sub-area having a large amplitude of at least one cycle is changed for each unit for processing the sample. Plasma treatment method. In the plasma processing method of processing a sample using a high frequency voltage, The high frequency voltage is composed of a sub-region divided into a plurality of times within one cycle, and is configured to independently control the applied power to each sub-region and the duty ratio of each sub-region. Monitoring the processing state of the sample, and controlling the applied power of each sub-region to the duty ratio of each sub-region for each unit processing the sample according to the change of the processing state. . The method of claim 4, wherein Monitor the processing state of the sample and control the applied power of each sub-region to the duty ratio of each sub-region for each unit processing the sample so as to maintain the processing characteristic for the sample according to the change of the processing state. Plasma processing method characterized in that. The method of claim 4, wherein Measuring the machining dimension after the treatment and changing the duty ratio of the high frequency voltage in accordance with the value. The method of claim 4, wherein And measuring the plasma emission intensity and changing the duty ratio of the high frequency voltage according to the variation of the measured value. The method of claim 4, wherein The first sub-area is a period for performing feedback control of CD gain, the second sub-area for feedback control of selection ratio, and the third sub-area for feedback control of CD gain and selection ratio. And setting a larger value to change the duty ratio (T1 / T) according to the CD gain. In the plasma processing apparatus for processing a sample using a high frequency voltage, The high frequency voltage is composed of a sub-region divided into a plurality of times within one cycle, and is configured to be capable of independently controlling the applied power to each sub-region. And an etching condition adjusting unit for controlling the applied power of each sub-region for each unit for processing the sample. The method of claim 9, It is comprised so that the amplitude and duty ratio of the said high frequency voltage with respect to each said sub area can be controlled independently, and is provided with the etching condition adjustment part which controls the amplitude and duty ratio of the said high frequency voltage for every unit which processes the said sample. Plasma processing apparatus, characterized in that. The method of claim 9, The high frequency voltage is composed of a sub-region divided into a plurality of times within one cycle, and is configured to independently control the applied power to each sub-region and the duty ratio of each sub-region, and for each unit for processing the sample, And an etching condition adjusting unit for controlling the applied power of each sub region and the duty ratio of each sub region. The method of claim 9, A plasma processing apparatus for generating a plasma in a vacuum vessel and applying a high frequency voltage to a sample stage installed in the vacuum vessel to process a substrate disposed on the sample stage, comprising: a high frequency power source connected to the sample stage and the high frequency power source; And a control means for periodically on / off-modulating the high frequency voltage from the control unit and a control means for changing the duty ratio of the on / off for each substrate to be processed or for a plurality of substrates. The method of claim 12, And said control means measures a machining dimension after said substrate processing and changes the duty ratio of said high frequency voltage in accordance with said value. The method of claim 12, And the control means measures the plasma emission intensity and changes the duty ratio of the high frequency voltage according to the variation of the measured value.

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