JP7466432B2 - Plasma processing apparatus and method for measuring consumption amount - Google Patents

Description

This disclosure relates to a plasma processing apparatus and a method for measuring wear.

Conventionally, plasma processing apparatuses have been known that use plasma to perform plasma processing on a workpiece, such as a wafer. Such plasma processing apparatuses have, for example, a mounting stage that holds the workpiece and also serves as an electrode, in a processing vessel that can form a vacuum space. The plasma processing apparatus applies a predetermined high-frequency power to the mounting stage, thereby performing plasma processing on the workpiece placed on the mounting stage.

JP 2015-115541 A

This disclosure provides a technology that can accurately measure the wear of a conductive member without opening the chamber.

A plasma processing apparatus according to one aspect of the present disclosure is a plasma processing apparatus having a processing vessel and a conductive member, and includes a plasma generating unit configured to generate plasma in the processing vessel, a power application unit configured to apply DC power to the conductive member while plasma is being generated in the processing vessel by the plasma generating unit, a measurement unit configured to measure a physical quantity related to the DC power applied by the power application unit, and a calculation unit configured to calculate the amount of wear of the conductive member by using the measured physical quantity related to the DC power in a correlation function between the amount of wear of the conductive member and the physical quantity related to the DC power.

The present disclosure has the advantage of being able to accurately measure the amount of wear of the conductive member without opening the chamber.

FIG. 1 is a schematic cross-sectional view showing the configuration of a plasma processing apparatus according to an embodiment. FIG. 2 is a diagram showing an example of a state of electrical coupling of the upper electrode when plasma is generated. FIG. 3 is a diagram showing an example of the state of electrical coupling of the upper electrode after it has been worn away. FIG. 4 is a diagram showing an example of a relationship between DC voltage V and DC current I when an upper top plate having each consumption amount is disposed. FIG. 5 is a diagram showing an example of a correlation function between the amount of wear of the upper top plate and the I/V ratio. FIG. 6 is a flow chart showing an example of the flow of a plasma etching process using wear amount measurement by the plasma processing apparatus. FIG. 7 is a diagram showing an example of an electrical coupling state of the focus ring when plasma is generated. FIG. 8 is a diagram showing an example of the state of electrical coupling of the focus ring after it has been worn out. FIG. 9 is a diagram showing an example of the relationship between the amount of wear of the upper top plate and the DC current corresponding to the DC voltage. FIG. 10 is a diagram showing an example of the relationship between the amount of wear of the upper top plate and the etching rate of the wafer.

The following describes in detail an embodiment of the plasma processing apparatus and the wear amount measuring method disclosed in the present application with reference to the drawings. Note that the same or corresponding parts in each drawing are given the same reference numerals. Furthermore, the plasma processing apparatus and the wear amount measuring method disclosed in this embodiment are not limited to these. The same or corresponding parts in each drawing are given the same reference numerals. Furthermore, the terms "upper" and "lower" are based on the state shown in the drawings and are for convenience.

In recent years, attempts have been made to cancel the effects of process shifts caused by parts wear and tear by changing various control parameters through feedback control. In particular, the upper electrode (CEL) among the parts that make up the chamber has a large effect on its characteristic values due to wear. Therefore, in order to restore the etching rate shift caused by wear and improve the deteriorated uniformity of the product, it is desirable to accurately grasp the amount of wear on the upper electrode and control it with an appropriate amount of control.

Normally, to measure the exact amount of wear on a part, it is necessary to open the chamber and remove the part in question, then measure it with a vernier caliper or to request an external company to measure it, which can reduce productivity. There is also a method that does not require opening the chamber, but estimates the amount of wear from the RF cumulative time, but because the amount of wear on a part varies depending on the conditions, it is difficult to adjust the knob control amount.

(Embodiment)
[Configuration of Plasma Processing Apparatus]
FIG. 1 is a schematic cross-sectional view showing the configuration of a plasma processing apparatus 100 according to an embodiment. The plasma processing apparatus 100 includes a processing vessel 1 that is airtight and electrically grounded. The processing vessel 1 is cylindrical and made of, for example, aluminum. The processing vessel 1 defines a processing space in which plasma is generated. A mounting table 2 is provided in the processing vessel 1 to horizontally support a semiconductor wafer (hereinafter, simply referred to as a "wafer") W, which is a workpiece to be processed. The mounting table 2 includes a substrate (base) 2a and an electrostatic chuck (ESC) 6. The substrate 2a is made of a conductive metal, for example, aluminum, and functions as a lower electrode. The electrostatic chuck 6 has a function of electrostatically attracting the wafer W. The mounting table 2 is supported by a support table 4. The support table 4 is supported by a support member 3 made of, for example, quartz. A focus ring 5 is provided on the outer periphery above the mounting table 2. The focus ring 5 is a conductive member, and is formed of, for example, a silicon-containing material. Examples of the silicon-containing material include silicon (Si) and silicon carbide (SiC). Further, a cylindrical inner wall member 3 a made of, for example, quartz is provided in the processing chamber 1 so as to surround the periphery of the mounting table 2 and the support table 4.

The first RF power supply 10a is connected to the substrate 2a via a first matching device 11a, and the second RF power supply 10b is connected via a second matching device 11b. The first RF power supply 10a is mainly for generating plasma, and is configured to supply high-frequency power of a predetermined frequency selected from the range of 150 MHz to 10 MHz to the substrate 2a of the mounting table 2. The second RF power supply 10b is mainly for attracting ions (bias), and is configured to supply high-frequency power of a predetermined frequency selected from the range of 40 MHz to 100 KHz, which is lower than that of the first RF power supply 10a, to the substrate 2a of the mounting table 2. In this way, the mounting table 2 is configured to be able to apply a voltage.

The frequency of the first RF power supply 10a not only generates plasma but also attracts ions to a certain extent, and the lower the frequency, the greater the proportion of the ion attracting effect. The frequency of the second RF power supply 10b not only attracts ions but also generates plasma to a certain extent, and the higher the frequency, the greater the proportion of the plasma generating effect.

Meanwhile, a shower head 16 that functions as an upper electrode is provided above the mounting table 2 so as to face the mounting table 2 in parallel. The shower head 16 and the mounting table 2 function as a pair of electrodes (upper electrode and lower electrode).

The electrostatic chuck 6 is configured with an electrode 6a interposed between the insulators 6b, and a DC power supply 12 is connected to the electrode 6a. When a DC voltage is applied from the DC power supply 12 to the electrode 6a, the wafer W is attracted by Coulomb force.

A coolant flow path 2d is formed inside the mounting table 2, and a coolant inlet pipe 2b and a coolant outlet pipe 2c are connected to the coolant flow path 2d. The mounting table 2 is configured to be able to be controlled to a predetermined temperature by circulating an appropriate coolant, such as cooling water, through the coolant flow path 2d. In addition, a gas supply pipe 30 is provided that passes through the mounting table 2, etc., to supply a gas for transferring heat and cold (backside gas), such as helium gas, to the backside of the wafer W, and the gas supply pipe 30 is connected to a gas supply source (not shown). With these configurations, the wafer W, which is attracted and held by the electrostatic chuck 6 on the upper surface of the mounting table 2, is controlled to a predetermined temperature.

The focus ring 5, which is provided on the upper outer periphery of the mounting table 2, is also controlled to a predetermined temperature. A heater may be provided inside the mounting table 2 or the electrostatic chuck 6, and the wafer W and focus ring 5 may be controlled to the predetermined temperature by heating the heater to the predetermined temperature.

The mounting table 2 is provided with a plurality of, for example, three pin through holes 200 (only one is shown in FIG. 1), and a lifter pin 61 is disposed inside each of these pin through holes 200. The lifter pin 61 is connected to a drive mechanism 62 and is moved up and down by the drive mechanism 62.

The shower head 16 is provided on the ceiling of the processing vessel 1. The shower head 16 includes a main body 16a and an upper top plate 16b that serves as an electrode plate, and is supported on the upper part of the processing vessel 1 via an insulating member 95. The main body 16a is made of a conductive material, such as aluminum whose surface has been anodized, and is configured so that the upper top plate 16b can be detachably supported on its lower part. The upper top plate 16b is a conductive material, and is formed of, for example, a silicon-containing material. Examples of silicon-containing materials include silicon (Si) and silicon carbide (SiC).

The main body 16a has a gas diffusion chamber 16c inside. The main body 16a has a number of gas flow holes 16d formed in the bottom so as to be located below the gas diffusion chamber 16c. The upper top plate 16b has gas inlet holes 16e formed to penetrate the upper top plate 16b in the thickness direction so as to overlap with the gas flow holes 16d. With this configuration, the processing gas supplied to the gas diffusion chamber 16c is dispersed in a shower-like manner and supplied into the processing vessel 1 through the gas flow holes 16d and the gas inlet holes 16e.

The main body 16a is formed with a gas inlet 16g for introducing a processing gas into the gas diffusion chamber 16c. One end of a gas supply pipe 15a is connected to the gas inlet 16g. The other end of the gas supply pipe 15a is connected to a processing gas supply source (gas supply unit) 15 for supplying the processing gas. The gas supply pipe 15a is provided with a mass flow controller (MFC) 15b and an on-off valve V2 in this order from the upstream side. Processing gas for plasma etching is supplied from the processing gas supply source 15 through the gas supply pipe 15a to the gas diffusion chamber 16c. Processing gas is supplied from the gas diffusion chamber 16c through the gas flow hole 16d and the gas introduction hole 16e in a shower-like dispersion manner into the processing vessel 1.

A variable DC power supply 72 is electrically connected to the shower head 16 as the upper electrode via a low pass filter (LPF) 71. The variable DC power supply 72 is configured so that power supply can be turned on and off by an on/off switch 73. The current and voltage of the variable DC power supply 72 and the on/off of the on/off switch 73 are controlled by a control unit 90 described later. As described later, when high frequency power is applied to the mounting table 2 from the first RF power supply 10a and the second RF power supply 10b to generate plasma in the processing space, the control unit 90 turns on the on/off switch 73 as necessary, and a predetermined DC voltage is applied to the shower head 16 as the upper electrode.

A cylindrical ground conductor 1a is provided so as to extend from the side wall of the processing vessel 1 above the height position of the shower head 16. This cylindrical ground conductor 1a has a ceiling wall at its upper part.

An exhaust port 81 is formed at the bottom of the processing vessel 1. A first exhaust device 83 is connected to the exhaust port 81 via an exhaust pipe 82. The first exhaust device 83 has a vacuum pump, and is configured so that the inside of the processing vessel 1 can be depressurized to a predetermined vacuum level by operating this vacuum pump. Meanwhile, a transfer port 84 for the wafer W is provided on the side wall inside the processing vessel 1, and a gate valve 85 is provided at this transfer port 84 to open and close the transfer port 84.

A deposit shield 86 is provided along the inner wall surface on the inside of the side of the processing vessel 1. The deposit shield 86 prevents etching by-products (deposits) from adhering to the processing vessel 1. A conductive member (GND block) 89, whose potential to the ground is controllably connected, is provided at approximately the same height as the wafer W on the deposit shield 86, thereby preventing abnormal discharge. The GND block 89 is a conductive member, and is formed of, for example, a silicon-containing material. Examples of silicon-containing materials include silicon (Si) and silicon carbide (SiC). A deposit shield 87 is provided at the lower end of the deposit shield 86, extending along the inner wall member 3a. The deposit shields 86, 87 are detachable.

The operation of the plasma processing apparatus 100 configured as described above is generally controlled by a control unit 90. The control unit 90 includes a process controller 91 that has a CPU and controls each part of the plasma processing apparatus 100, a user interface 92, and a memory unit 93.

The user interface 92 is composed of a keyboard through which the process manager inputs commands to manage the plasma processing device 100, a display that visualizes and displays the operating status of the plasma processing device 100, etc.

The memory unit 93 stores recipes that store control programs (software) and process condition data for implementing various processes performed by the plasma processing device 100 under the control of the process controller 91. Then, as necessary, an arbitrary recipe is called up from the memory unit 93 by instructions from the user interface 92, and executed by the process controller 91, so that the desired process is performed by the plasma processing device 100 under the control of the process controller 91. In addition, recipes such as control programs and process condition data can be used in a state stored in a computer-readable computer storage medium (e.g., a hard disk, a CD, a flexible disk, a semiconductor memory, etc.), or can be used online by transmitting them from other devices at any time, for example, via a dedicated line.

[Measurement of wear amount of upper electrode]
Next, the measurement of the wear amount of the upper electrode will be described. When plasma etching is performed, the upper top plate 16b, which is the electrode plate of the shower head 16 that is actually the upper electrode, is worn away. In the following description, the wear amount of the upper top plate 16b will be described, but if the main body 16a and the upper top plate 16b are considered as an integrated shower head, the wear amount of the upper top plate 16b can also be said to be the wear amount of the upper electrode (CEL).

Figure 2 is a schematic diagram showing an example of the electrical coupling state of the upper electrode when plasma is generated. As shown in Figure 2, when plasma P is generated in the processing vessel 1, the shower head 16, which is the upper electrode (CEL), is electrically coupled to the GND block 89 at ground potential via the plasma P. The shower head 16 and the plasma P can be electrically regarded as resistors R1 and R2, respectively. Therefore, when plasma P is generated in the processing vessel 1, the space in the processing vessel 1 can be regarded as a series circuit in which the resistors R1 and R2 are connected in series. The variable DC power supply 72 applies DC power to the shower head 16 via a low pass filter (LPF) 71 to measure the DC voltage and DC current related to the series circuit including the resistors R1 and R2. The variable DC power supply 72 outputs the measurement result to the process controller 91.

When plasma etching is performed, the upper top plate 16b of the shower head 16, which is the upper electrode (CEL), is worn out. When the upper top plate 16b is worn out, the values of the resistances R1 and R2 change. FIG. 3 is a schematic diagram showing an example of the electrical coupling state of the upper electrode after it is worn out. As shown in FIG. 3, when the upper top plate 16b is worn out, the value of the resistance R1 of the upper top plate 16b decreases. On the other hand, as the upper top plate 16b is worn out, the processing space in which the plasma P is generated in the processing vessel 1 expands, and the value of the resistance R2 of the plasma P increases. Here, the combined resistance R of the series circuit including the resistances R1 and R2 is expressed by the following formula (1).

R = R1 + R2 + Rothers ... (1)
Here, Rothers is the resistance of other parts including the GND block 89, and is a constant value.

If the DC voltage and DC current for the series circuit including resistors R1 and R2 are V and I, respectively, Ohm's law gives the following equation (2).

V = R * I ... (2)
By modifying equation (2), the following equation (3) is obtained.

I/V=1/R (3)
From equation (3), it can be seen that the combined resistance R of the series circuit including the resistors R1 and R2 changes with the change in I/V. And from equations (1) and (3), the combined resistance R and I/V of the series circuit including the resistors R1 and R2 change with the change in the values of the resistors R1 and R2 due to wear of the upper top plate 16b. Therefore, the plasma processing apparatus 100 according to this embodiment obtains a plurality of DC currents I for a plurality of DC voltages V, measures the change in I/V, that is, the I/V ratio indicating the ratio of the change in the DC current I to the change in the DC voltage V, and obtains the wear amount of the upper top plate 16b. The wear amount measurement process will be described in detail below.

First, the process controller 91 receives an instruction from the user interface 92 and executes a reference data acquisition process to acquire reference data to be used in calculating the wear amount. Specifically, the process controller 91 applies RF power to generate plasma to the mounting table 2 using a measurement recipe stored in the memory unit 93. Then, while plasma is being generated in the processing vessel 1, the process controller 91 applies DC power to the shower head 16 to acquire the reference data. The process controller 91 executes the reference data acquisition process with a wafer placed on the mounting table 2 as a protective cover for the mounting table 2.

For example, in the reference data acquisition process, an unused upper top plate 16b, an upper top plate 16b with a pseudo-wear of 0.2 mm, and an upper top plate 16b with a pseudo-wear of 2.0 mm are sequentially placed in the plasma processing apparatus 100. The unused upper top plate 16b has a wear amount of 0 mm and is an example of a reference conductive member having a specified thickness. The upper top plate 16b with a pseudo-wear of 0.2 mm and an upper top plate 16b with a pseudo-wear of 2.0 mm have wear amounts of 0.2 mm and 2.0 mm, respectively, and are examples of consumable conductive members having a thickness thinner than the specified thickness.

For each of the upper top plates 16b of each consumable amount, the process controller 91 applies DC power to the shower head 16 while plasma is being generated in the processing vessel 1, and obtains multiple DC currents I for multiple DC voltages V. Then, for each of the upper top plates 16b of each consumable amount, the process controller 91 obtains a relational equation showing the relationship between the DC voltage V and the DC current I, and obtains the slope of each obtained relational equation as the change in I/V, that is, the ratio of the change in the DC current I to the change in the DC voltage V. Hereinafter, the ratio of the change in the DC current I to the change in the DC voltage V, which is obtained as reference data during the reference data acquisition process, is referred to as the reference I/V ratio.

Figure 4 is a diagram showing an example of the relationship between DC voltage V and DC current I when upper top plates 16b with various wear amounts are arranged. In (A) to (C) of Figure 4, graphs 301, 302, and 303 show the relationship between DC voltage V and DC current I when upper top plates 16b with wear amounts of 0 mm, 0.2 mm, and 2.0 mm are arranged, respectively. These relationship formulas can be obtained by linear approximation using the least squares method for three points where the DC voltage V is changed to -150 V, -300 V, and -450 V. In the example of Figure 4, the relationship formula for the upper top plate 16b with a wear amount of 0 mm is the following formula (4), the relationship formula for the upper top plate 16b with a wear amount of 0.2 mm is the following formula (5), and the relationship formula for the upper top plate 16b with a wear amount of 2.0 mm is the following formula (6).

y = 0.001036x + 0.371621 ... (4)
y = 0.001035x + 0.372512 ... (5)
y = 0.000997x + 0.342981 ... (6)
The process controller 91 obtains the slope of 0.001036 in the above formula (4) as the reference I/V ratio for the upper top plate 16b with a wear amount of 0 mm. The process controller 91 obtains the slope of 0.001035 in the above formula (5) as the reference I/V ratio for the upper top plate 16b with a wear amount of 0.2 mm. The process controller 91 obtains the slope of 0.000997 in the above formula (6) as the reference I/V ratio for the upper top plate 16b with a wear amount of 2.0 mm.

Then, the process controller 91 uses the reference I/V ratio for each wear amount of the upper top plate 16b to obtain a correlation function that indicates the relationship between the wear amount of the upper top plate 16b and the I/V ratio. Then, the process controller 91 stores the obtained correlation function in the memory unit 93.

For example, the process controller 91 plots the reference I/V ratio for each amount of wear on the upper top plate 16b on a two-dimensional plane with the wear amount and I/V ratio of the upper top plate 16b as the dimensions, and obtains an approximation of a linear function as the correlation function. The correlation function can be obtained by performing linear approximation using the least squares method for three points where the wear amount is 0 mm, 0.2 mm, and 2.0 mm, for example.

Figure 5 is a diagram showing an example of a correlation function between the wear amount of the upper top plate 16b and the I/V ratio. Figure 5 shows a correlation function that represents the relationship between the wear amount of the upper top plate 16b and the reference I/V ratio, which is the slope of the above equations (4) to (6). In the example of Figure 5, the correlation function is expressed by the following equation (7).

y = -0.0000208x + 0.0010384 ... (7)
Then, the process controller 91 performs plasma etching. The process controller 91 periodically executes a wear data acquisition process to acquire wear data using the installed upper top plate 16b used in the plasma etching, using a measurement recipe. Specifically, the process controller 91 functions as a plasma generating unit and a power applying unit, applies RF power to generate plasma to the mounting table 2 using the measurement recipe, and applies DC power to the shower head 16 while plasma is being generated in the processing chamber 1. The process controller 91 functions as a measuring unit, and acquires the I/V ratio measured for the worn shower head 16 as the wear I/V ratio. The process controller 91 functions as a calculating unit, and calculates the wear amount of the upper top plate 16b corresponding to the wear I/V using a correlation function indicating the relationship between the wear amount of the upper top plate 16b and the I/V ratio stored in the storage unit 93. For example, when the correlation function is expressed by the above formula (7), the process controller 91 substitutes the I/V ratio during wear for "y" in formula (7) to obtain "x", which is the amount of wear of the upper top plate 16b.

Next, the process controller 91 compares the calculated wear amount of the upper top plate 16b with a predetermined wear amount threshold to determine whether the wear amount is within an allowable value. For example, the process controller 91 stores the wear amount threshold as 2 mm.

If the calculated wear amount of the upper top plate 16b is equal to or greater than the wear amount threshold, the process controller 91 determines that the wear amount has exceeded the allowable value. The process controller 91 then notifies the administrator of the plasma processing apparatus 100 of the occurrence of the abnormality, for example by displaying an alert on the display of the user interface 92. The administrator receives the alert and replaces the upper top plate 16b. After replacing the upper top plate 16b, the process controller 91 measures the I/V ratio when worn to calculate the wear amount, and determines that the upper top plate 16b is normal if the calculated wear amount is within the allowable value. The process controller 91 then waits for instructions from the user interface 92, and if an instruction is received, performs plasma etching according to the instruction.

In contrast, if the calculated wear amount of the upper top plate 16b is less than the wear amount threshold, the process controller 91 determines that the wear amount is within the allowable value. Then, the process controller 91 calculates the knob control amount according to the calculated wear amount of the upper top plate 16b and reflects it in the recipe when plasma etching is performed. Thereafter, the process controller 91 performs plasma etching using the corrected recipe.

Next, the flow of a plasma etching process using wear amount measurement by the plasma processing apparatus 100 according to this embodiment will be described with reference to FIG. 6. FIG. 6 is a flow chart showing an example of the flow of a plasma etching process using wear amount measurement by the plasma processing apparatus.

The process controller 91 acquires reference data including information on the reference I/V ratio for each wear amount of the upper top plate 16b, and calculates the correlation function between the wear amount of the upper top plate 16b and the I/V ratio (step S1).

Then, the process controller 91 executes plasma etching by the plasma processing device 100 (step S2) and, for example, determines whether the accumulated time of the plasma etching process has elapsed a certain time (step S3). If the certain time has not elapsed (step S3: No), the process controller 91 returns to step S2 and continues the plasma etching.

On the other hand, if a certain period of time has elapsed (step S3: Yes), the process controller 91 decides to calculate the consumption amount. Then, the process controller 91 measures the consumption I/V ratio for the installed upper top plate 16b using the measurement recipe (step S4).

Next, the process controller 91 calculates the wear amount of the installed upper top plate 16b by using the I/V ratio at the time of wear to the correlation function between the wear amount of the upper top plate 16b and the I/V ratio (step S5).

Then, the process controller 91 compares the calculated wear amount with the wear amount threshold value to determine whether the wear amount is within the allowable value (step S6).

On the other hand, if the amount of wear falls within the allowable value (step S6: Yes), the process controller 91 adjusts the control amount of the knob control in accordance with the amount of wear (step S7). For example, the process controller 91 adjusts the DC voltage V applied to the shower head 16 from the variable DC power supply 72 in accordance with the amount of wear of the upper top plate 16b. The adjustment of the DC voltage V in accordance with the amount of wear of the upper top plate 16b will be described later.

Then, the process controller 91 returns to step S2 and performs plasma etching using a recipe that includes corrections to the control amount of the knob control.

If the consumption amount exceeds the allowable value (step S6: No), the process controller 91 notifies the administrator with an alert (step S8).

Then, the process controller 91 determines whether or not to stop the operation of the plasma processing device 100 depending on whether or not an instruction to stop operation has been received from the user interface 92 (step S9).

If the operation is not stopped (step S9: No), the administrator who received the alert replaces the upper top plate 16b (step S10). After that, the plasma etching process using the wear amount measurement by the process controller 91 returns to step S4.

On the other hand, if it is determined that the operation should be stopped (step S9: Yes), the process controller 91 stops the operation of the plasma processing device 100.

[DC voltage adjustment according to the wear amount of the upper top plate]
Here, adjustment of the DC voltage V according to the wear amount of the upper top plate 16b will be described with reference to Fig. 9 and Fig. 10. Fig. 9 is a diagram showing an example of the relationship between the wear amount of the upper top plate 16b and the DC current I corresponding to the DC voltage V. In Fig. 9, "New" indicates the measured value of the DC current I when the wear amount of the upper top plate 16b is 0 mm. Also, "Cons." indicates the measured value of the DC current I when the wear amount of the upper top plate 16b is a value greater than 0 (for example, 2.0 mm). In the measurement of "New" and "Cons.", the DC voltage V applied to the shower head 16 from the variable DC power supply 72 was set to -300 V, and the corresponding DC current I was measured.

As shown in FIG. 9, it was confirmed that the DC current I flowing through the shower head 16 decreased from an initial value of 0.133 A to 0.119 A as the wear of the upper top plate 16b increased.

Figure 10 is a diagram showing an example of the relationship between the wear amount of the upper top plate 16b and the etching rate of the wafer W. In Figure 10, "New" indicates the measured value of the etching rate of the wafer W when the wear amount of the upper top plate 16b is 0 mm. Also, "Cons." indicates the measured value of the etching rate of the wafer W when the wear amount of the upper top plate 16b is a value greater than 0 (e.g., 2.0 mm). Note that, in measuring "New" and "Cons.", the DC voltage V applied to the shower head 16 from the variable DC power supply 72 was set to -300 V, and the corresponding etching rate was measured.

As shown in FIG. 10, it was confirmed that the etching rate of the wafer W increased from an initial value of 36.09 nm/min to 37.01 nm/min as the wear amount of the upper top plate 16b increased. This is believed to be because the processing space in the processing vessel 1 expanded due to wear of the upper top plate 16b, resulting in a decrease in the electron density of the plasma in the processing vessel 1. The decrease in the electron density of the plasma in the processing vessel 1 appears as a decrease in the DC current I flowing through the shower head 16, as shown in FIG. 9.

Therefore, the process controller 91 adjusts the DC voltage V applied to the shower head 16 from the variable DC power supply 72 according to the wear amount of the upper top plate 16b so that the decrease in the DC current I is eliminated. For example, by performing an experiment or the like, correspondence information that associates the wear amount of the upper top plate 16b with the adjustment value of the DC voltage V is obtained in advance. The correspondence information that associates the wear amount of the upper top plate 16b with the adjustment value of the DC voltage V may be stored in the storage unit 93. Then, the process controller 91 may read out the adjustment value corresponding to the wear amount of the upper top plate 16b from the correspondence information, and adjust the DC voltage V to the adjustment value. Also, for example, the process controller 91 may adjust the DC voltage V according to the wear amount of the upper top plate 16b so that the DC current I after the decrease returns to its initial value.

In FIG. 9, the measured value of the DC current I after the DC voltage V applied to the upper top plate 16b with a wear amount of 2.0 mm is adjusted from -300 V to -348 V is shown as "DCS 348 V." By adjusting the DC voltage V from -300 V to -348 V, the process controller 91 can return the corresponding DC current I from 0.119 A to the initial value of 0.133 A.

In Figure 10, the etching rate of the wafer W after the DC voltage V applied to the upper top plate 16b with a wear amount of 2.0 mm is adjusted from -300 V to -348 V is shown as "DCS 348 V." As can be seen from Figure 10, by adjusting the DC voltage V, the etching rate of the wafer W can be corrected from 37.01 nm/min to 36.39 nm/min, which is close to the initial value of 36.09 nm/min.

As described above, the plasma processing apparatus according to one embodiment is a plasma processing apparatus having a processing vessel and a conductive member (e.g., upper top plate 16b), and has a plasma generation unit, a power application unit, a measurement unit, and a calculation unit. The plasma generation unit generates plasma in the processing vessel. The power application unit applies DC power to the conductive member while plasma is being generated in the processing vessel by the plasma generation unit. The measurement unit measures a physical quantity related to the DC power applied by the power application unit (e.g., I/V ratio at the time of consumption). The calculation unit uses the measured physical quantity related to the DC power in a correlation function between the consumption amount of the conductive member and the physical quantity related to the DC power to calculate the consumption amount of the conductive member. This allows the plasma processing apparatus to accurately measure the consumption amount of the conductive member without opening the processing vessel (chamber).

In addition, in one embodiment of the plasma processing apparatus, the conductive member is provided in a position facing the plasma inside the processing vessel. This allows the plasma processing apparatus to accurately measure the amount of wear of the conductive member facing the plasma without opening the processing vessel.

In addition, in one embodiment of the plasma processing apparatus, the conductive member is formed from a silicon-containing material. This allows the plasma processing apparatus to accurately measure the amount of wear of the conductive member formed from a silicon-containing material.

The plasma processing apparatus according to one embodiment further includes another conductive member (e.g., GND block 89) that is disposed in the processing chamber at a position facing the plasma and is set to ground potential. This allows the plasma processing apparatus to accurately measure the amount of wear of the conductive member that is electrically coupled to the other conductive member at ground potential via the plasma.

In addition, in a plasma processing apparatus according to an embodiment, the calculation unit measures a first physical quantity (e.g., a reference I/V ratio) related to the DC power applied to the reference conductive member when a reference conductive member having a specified thickness (e.g., an upper top plate 16b with a consumption amount of 0 mm) is used as the conductive member. The calculation unit measures a second physical quantity (e.g., a reference I/V ratio) related to the DC power applied to the consumable conductive member when a consumable conductive member having a thickness thinner than the specified thickness (e.g., an upper top plate 16b with a consumption amount of 0.2 mm or 2.0 mm) is used as the conductive member. The plasma processing apparatus then calculates a correlation function based on the first physical quantity and the second physical quantity. This allows the plasma processing apparatus to appropriately calculate the correlation function between the consumption amount of the conductive member and the physical quantity related to the DC power.

In addition, the plasma processing apparatus according to one embodiment further includes a notification unit that issues an alert when the determined wear amount of the conductive member is equal to or greater than a threshold value. This allows the plasma processing apparatus to notify the administrator of the plasma processing apparatus of the time to replace the conductive member.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The above embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims.

For example, in the above embodiment, the I/V ratio of the DC power applied to the shower head 16, i.e., the ratio of the change in DC current I to the change in DC voltage V, is measured, but the ratio of the change in DC voltage V to the change in DC current I may also be measured. Furthermore, if the measurement accuracy of the DC voltage V and the DC current I is high, the ratio of the DC current I to the DC voltage V or the ratio of the DC voltage V to the DC current I may also be measured. These ratios are examples of physical quantities related to the applied DC power.

In the above embodiment, the wear amount of the shower head 16, which is the upper electrode (CEL), was measured, but the wear amount of a conductive member other than the upper electrode may also be measured. For example, when a variable DC power supply is connected to the focus ring 5, which is a conductive member, the wear amount of the focus ring 5 may be measured using the I/V ratio of the DC power applied from the variable DC power supply to the focus ring 5.

Figure 7 is a schematic diagram showing an example of the electrical coupling state of the focus ring 5 when plasma is generated. In the plasma processing apparatus shown in Figure 7, a variable DC power supply 172 is connected to the focus ring 5, which is a conductive member, via an LPF (not shown). As shown in Figure 7, when plasma P is generated in the processing vessel 1, the focus ring 5 is electrically coupled to the GND block 89 at the ground potential via the plasma P. The focus ring 5 and the plasma P can be electrically regarded as resistors R3 and R4, respectively. Therefore, when plasma P is generated in the processing vessel 1, the space in the processing vessel 1 can be regarded as a series circuit in which the resistors R3 and R4 are connected in series. The variable DC power supply 172 applies DC power to the focus ring 5 via the LPF and measures the DC voltage and DC current related to the series circuit including the resistors R3 and R4. The variable DC power supply 172 outputs the measurement result to the process controller 91.

When plasma etching is performed, the focus ring 5 is worn. As the focus ring 5 is worn, the values of the resistances R3 and R4 change. FIG. 8 is a schematic diagram showing an example of the state of electrical coupling of the focus ring 5 after it is worn. As shown in FIG. 8, as the focus ring 5 is worn, the value of the resistance R3 of the focus ring 5 decreases. On the other hand, as the focus ring 5 is worn, the processing space in which the plasma P is generated in the processing vessel 1 expands, and the value of the resistance R4 of the plasma P increases. Here, the combined resistance R of the series circuit including the resistances R3 and R4 is expressed by the following equation (8).

R = R3 + R4 + Rothers ... (8)
Here, Rothers is the resistance of other parts including the GND block 89, and is a constant value.

If the DC voltage and DC current for the series circuit including resistors R3 and R4 are V and I, respectively, Ohm's law gives us the following equation (9).

V = R * I ... (9)
By modifying equation (9), the following equation (10) is obtained.

I/V=1/R (10)
From equation (9), it is seen that the combined resistance R of the series circuit including the resistors R3 and R4 changes with the change in I/V. From equations (8) and (10), the combined resistance R and I/V of the series circuit including the resistors R3 and R4 change with the change in the values of the resistors R3 and R4 due to wear of the focus ring 5. Therefore, the plasma processing apparatus obtains a plurality of DC currents I for a plurality of DC voltages V, and measures the change in I/V, i.e., the I/V ratio indicating the ratio of the change in the DC current I to the change in the DC voltage V, to obtain the wear amount of the focus ring 5. The outline of the process for measuring the wear amount of the focus ring 5 is similar to the process for measuring the wear amount of the upper top plate 16b described in the above embodiment.

For example, when a variable DC power supply is connected to the GND block 89, which is a conductive member, the wear of the GND block 89 may be measured using the I/V ratio of the DC power applied from the variable DC power supply to the GND block 89.

Reference Signs List W: Wafer 1: Processing chamber 2: Mounting table 16: Shower head 16a: Main body 16b: Upper top plate 91: Process controller 92: User interface 93: Storage unit 100: Plasma processing apparatus

Claims (10)

A plasma processing apparatus having a processing vessel and a conductive member,
a plasma generating unit configured to generate plasma in the processing vessel;
a power application unit configured to apply DC power to the conductive member while plasma is generated in the processing chamber by the plasma generation unit;
a measurement unit configured to measure a physical quantity related to the DC power applied by the power application unit;
and a calculation unit configured to calculate a wear amount of the conductive member by using the measured physical quantity related to the DC power in a correlation function between a wear amount of the conductive member and the physical quantity related to the DC power. The plasma processing apparatus according to claim 1, wherein the conductive member is provided in the processing vessel at a position facing the plasma. The plasma processing apparatus according to claim 1 or 2, wherein the conductive member is an upper electrode or a focus ring. The plasma processing apparatus according to any one of claims 1 to 3, wherein the conductive member is formed from a silicon-containing material. The plasma processing apparatus according to any one of claims 1 to 4, further comprising another conductive member disposed in the processing chamber at a position facing the plasma and set to a ground potential. The calculation unit is
2. The plasma processing apparatus of claim 1, configured to measure a first physical quantity related to the DC power applied to a reference conductive member having a specified thickness when the conductive member is used as the reference conductive member, measure a second physical quantity related to the DC power applied to the consumable conductive member when the conductive member is used as a consumable conductive member having a thickness thinner than the specified thickness, and calculate the correlation function based on the first physical quantity and the second physical quantity. The calculation unit is
7. The plasma processing apparatus of claim 6, wherein when a plurality of consumable conductive members having different thicknesses thinner than the specified thickness are used as the conductive members, a plurality of second physical quantities related to the DC power applied to the plurality of consumable conductive members are measured, and the correlation function is calculated based on the first physical quantity and the plurality of second physical quantities. The plasma processing apparatus according to any one of claims 1 to 7, further comprising a notification unit configured to notify an alert when the determined wear amount of the conductive member is equal to or greater than a threshold value. The plasma processing apparatus according to any one of claims 1 to 8, wherein the physical quantity related to the DC power is at least one of the ratio of the amount of change in DC current to the amount of change in DC voltage, the ratio of the amount of change in DC voltage to the amount of change in DC current, the ratio of DC current to DC voltage, and the ratio of DC voltage to DC current. In a plasma processing apparatus having a processing vessel and a conductive member,
generating a plasma in the processing vessel;
applying DC power to the conductive member while plasma is being generated in the processing chamber;
measuring a physical quantity related to the applied DC power;
a wear amount measuring method for determining the wear amount of the conductive member by using the measured physical quantity related to the DC power in a correlation function between the wear amount of the conductive member and the physical quantity related to the DC power.

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