JP3437961B2 - Apparatus and method for monitoring substrate bias during plasma processing of a substrate - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates generally to the processing of substrates utilizing plasma in the production of integrated circuits. More particularly, it relates to the determination of substrate bias parameters in plasma processing systems, such as plasma processing systems that utilize an electrostatic chuck to secure a substrate to a susceptor during processing.

[0002]

BACKGROUND OF THE INVENTION Gas plasmas are widely used in a variety of integrated circuit manufacturing processes, including plasma etching and plasma deposition applications such as PECVD. Generally, a plasma is created in a processing chamber by introducing a low pressure process gas into the chamber and then directing electrical energy into the chamber to create an electric field within the chamber. The electric field creates an electron flow in the chamber. The electron flow ionizes individual gas molecules by transferring kinetic energy to the molecules by collision of the individual electrons with the gas molecules. The electrons are accelerated in the electric field and efficiently ionize gas molecules. The ionized particles and free electrons of the gas collectively form what is called a gas plasma.

Gas plasmas are useful in a variety of different processes. One commonly used plasma process is the plasma etching process, which removes or "etches" a layer of material from the surface of a substrate. In the etching process, the ionized gas molecules of the plasma are generally positively charged and the substrate is negatively biased, so the positively ionized plasma particles are attracted to the substrate surface and impinge on the surface to cause the substrate surface To etch. For example, after etching the substrate to remove unwanted material layers or coatings on the substrate, another layer is deposited. Such a pre-deposition etching process is often referred to as etching cleaning of the substrate.

Another common plasma process involves deposition, which deposits a layer of material on a substrate. Chemical vapor deposition (ch
In electrical vapor deposition or CVD, for example, typically a material gas is introduced into a processing chamber where the gas chemically reacts to form a material layer or coating on the exposed substrate surface. Gas plasmas can be used to enhance chemical reactions. Such C using plasma
VD deposition process is plasma enhanced
It is called CVD or PECVD. Plasma is used to supply energy to the process to enhance deposition quality and deposition rate. Other plasma deposition processes exist, as will be appreciated by those of ordinary skill in the art.

During plasma processing of semiconductor substrates, it is often useful to apply an accelerating voltage to the surface of the substrate.
An accelerating voltage or substrate bias is utilized to accelerate the ions or other charged particles in the plasma to the substrate surface. In the etching process, charged plasma particles are attracted to the surface of the substrate and actually strike the surface to perform the etching as described above. In a deposition process such as PECVD,
Utilizing the energy provided by the impact of such charged particles, the deposition rate is further improved as described above,
Improves deposition quality.

In general, the biasing of a substrate in a plasma-enhanced etching and deposition process exposes the RF field from the electrode within the processing chamber through the substrate to accept the layer of material to be etched or deposited. It is performed by capacitively coupling to the surface of the formed substrate.
Specifically, the electrodes placed in the susceptor or substrate support are biased with an RF feeder to create an RF electric field. The RF field is then capacitively coupled through the susceptor and the substrate to form a relatively uniform DC bias potential across the exposed substrate surface. The DC bias on the substrate surface enhances the etching or deposition process by affecting the plasma as described above.

Within a plasma processing system, the plasma is usually associated with certain non-uniformities. For example, plasma density often has a maximum at the center of the plasma. this is,
This is due to the edge effect near the side of the processing chamber. Non-uniformities in the plasma translate into inconsistencies in the plasma-based etching and deposition processes. For example, there may be undesirable variations in the etch rate such that the etch rate near the center of the substrate is greater than the etch rate near the outer lip of the substrate. Furthermore, in plasma-enhanced deposition processes, the effects of deposition may differ near the center of the substrate and at the edges of the substrate,
As a result, radially non-uniform deposition layers and non-uniform deposition rates may occur across the substrate.

[0008]

Attempts have been made by those skilled in the art to address such plasma non-uniformities in plasma processing systems. For example, US patent application filed May 4, 2000, "Improved Apparatus and Method for Plasma Processing of Substrates Utilizing Electrostatic Chuck" (Improved Apparatus and Method).
Method for Plasma Procedures
sing of a SubstrateUtilize
ing an Electrostatic Chuc
In k), a plasma processing system is disclosed that selectively adjusts the bias on the substrate to cancel the non-uniformity of the plasma in the system. This application is incorporated herein by reference in its entirety. Although the system improves the overall plasma process, it has been difficult to achieve precise selectivity in changing the substrate bias. Therefore, one object of the present invention is to provide a finer adjustment to the substrate bias in a plasma processing system to address plasma non-uniformities.

According to another aspect of the invention, it is desirable to provide precise bias control even in systems utilizing electrostatic chucks. Especially during the manufacture of integrated circuits, the substrate being processed is supported in the processing chamber by a substrate support or susceptor. The substrate is often physically fixed on the susceptor during processing. This is for example to improve the heat transfer between the substrate and the susceptor. One method of fixing the substrate is an electrostatic chuck (ESC: ele).
a ctrostatic chuck). The electrostatic chuck electrostatically attracts and fixes the substrate to the susceptor by applying a DC bias to the substrate. Electrostatic chucks are known to those skilled in the art, and suitable designs are described in the above-referenced U.S. patent application filed May 4, 2000, "Improved for Plasma Processing of Substrates Utilizing Electrostatic Chuck. Apparatus and Method "(Improved
Apparatus and Method for
Plasma Processing of a Su
bstrate Utilizing an Elec
Trostatic Chuck), and US Pat. No. 5,117,121. The latter U.S. patents are also incorporated herein by reference. Electrostatic chucks typically use the same electrodes that are used to bias the substrate. This practice has made even more difficult the precise measurement of substrate surface bias levels due to the effects of electrostatic clamping voltage on such measurements. Therefore, another object of the present invention is to provide a more precise substrate bias to utilize an electrostatic chuck to address plasma non-uniformities in a processing system.

Yet another object of the present invention is to address the aforementioned objectives without adversely affecting the desired bias of the substrate required for plasma processing.

[0011]

According to the principles of the present invention,
The processing system has improved substrate bias control,
More precise monitoring of the substrate bias in the plasma processing system. Further, the system of the present invention, in combination with a system utilizing an electrostatic chuck, makes such precise bias measurements. For more uniform or selectively varying plasma treatments, measurements obtained from the system can be used to vary the bias across selected portions of the exposed substrate surface.

To that end, the processing system includes a processing chamber for containing a plasma. A substrate support is mounted within the chamber to support the substrate in proximity to the plasma. A plurality of electrodes, such as first and second electrodes, are coupled to the substrate support and are located proximate the support surface. The electrodes are electrically isolated from each other. An RF power source is coupled to each electrode to bias the electrodes with RF electrical energy. The biased electrode may work with the substrate support to create a DC bias on the exposed surface of the substrate located on the support surface of the substrate support.

According to one aspect of the invention, a plurality of comparators are utilized to monitor the bias on individual electrodes for the purpose of selectively varying the bias. More specifically, the first comparator has first and second inputs electrically coupled to one electrode. An isolation element coupled between the first input and the second input is operable to isolate the first input from the bias on the monitored electrode created by the RF power source. The first comparator has an output that reflects the voltage difference between the first input and the second input caused by the electrode DC bias created by the RF power supply. Since the first input is isolated from the electrode bias created by the RF power supply, the first comparator reflects the electrode RF bias.

The second comparator provides an indication of the voltage bias difference between the first electrode and the second electrode. By coupling the output from the first comparator to one electrode and the output of the second comparator between both electrodes, the bias level of each individual electrode can be obtained. In particular, the second comparator has a first input coupled to the first electrode and a second input coupled to the second electrode. The second comparator has an output that reflects the voltage difference between the first input and the second input resulting from the bias difference between the first electrode and the second electrode. From the signal reflecting the bias on one electrode and the signal reflecting the bias difference between the two electrodes, the relative bias of the other non-measurement electrode can be obtained. In this way, the bias can be optimally adjusted by monitoring the relative bias on the first and second electrodes.

By utilizing the monitored output of the comparator to determine the relative bias of the electrodes, the bias can be adjusted as desired for the plasma process. For that purpose, a variable capacitor is coupled between the RF power supply and the electrodes. By changing the capacitance of the capacitor, the bias created on the substrate by at least one of the plurality of electrodes is changed relative to the bias created on the substrate by the other electrode of the plurality of electrodes. In this way, the influence of the plasma on one part of the substrate can be selectively changed with respect to the influence of the plasma on the other part of the substrate.

According to another aspect of the invention, at least one of the inputs of the comparator is coupled to the electrode via a voltage divider circuit. The voltage divider circuit includes a variable resistor that can be selectively adjusted to change the voltage level at the comparator input. When the processing system utilizes an electrostatic chuck, a DC power source is coupled to each electrode in addition to the RF power source. The DC power supply provides the voltage difference at each electrode needed to electrostatically clamp the substrate to the susceptor. By selectively changing the variable resistance, the effect of clamping DC bias on the electrodes of the comparator input can be eliminated. In this way, the comparator output is directly related to the difference between the inputs resulting in the DC bias on the electrodes created by the RF power supply.

In accordance with another aspect of the invention, another comparator is utilized that has first and second inputs respectively coupled to the first and second electrodes. The output of the comparator reflects the voltage difference between the first and second inputs caused by the bias difference between the first and second electrodes. However, the output is coupled to an autotuning element, eg a servomotor, which is in turn coupled to a variable resistor. The servomotor automatically changes the resistance value of the variable resistor to adjust one of the inputs and zero the comparator output. The comparator output drives the servo and variable resistor until the output is zero. When this is done with the DC power supply on and the RF power supply off, the bias measurement is essentially an effect of the DC power supply because the comparator inputs coupled to both electrodes are adjusted to produce zero output. Do not receive Since the comparator input that automatically adjusts the variable resistance is the same as the comparator input that measures the different bias between the electrodes, the output of one comparator is automatically zeroed to the output of the other comparator. Is also zero. A disable switch is coupled between the output of each comparator and the self-adjusting element. The disable switch is coupled to the RF power supply and is operable to disable the self-regulating element when RF power is applied to the electrodes. Therefore, the output of a comparator coupled to both electrodes cannot be further altered to bring its output to zero, so that the comparator will reduce the voltage difference between its first and second inputs. Measure and provide an output signal that reflects the bias difference between the electrodes.

Therefore, a signal is produced at the comparator output which reflects the individual bias level of the electrodes due to the RF power supply. In this way, the variable capacitor can be adjusted to achieve the desired electrode bias between the two electrodes. Therefore, the bias of the substrate can likewise be selectively changed to achieve the desired result in the plasma process. The present invention will be described with respect to two electrodes,
Multiple electrodes may be utilized and their bias levels can be similarly measured using the present invention.

These and other features and advantages of the present invention are described in further detail below with reference to the accompanying drawings.

The accompanying drawings, which are included in and constitute a part of this specification, illustrate embodiments of the invention and, together with the following general description of the invention, serve to explain the principles of the invention. Fulfill.

[0021]

1 illustrates one embodiment of a plasma processing system that may be utilized in accordance with the principles of the present invention. Plasma processing systems generally include processing chamber 12
including. The processing chamber 12 includes a base portion 14 formed of a suitable metal such as stainless steel and a dielectric portion 16 formed of a suitable metal such as quartz. A plasma generating assembly 18 is coupled to the dielectric portion 16 of the processing chamber 12. A substrate support or susceptor 20 is disposed in the processing chamber 12 and is configured to support a semiconductor wafer or substrate 22 therein for plasma processing. The process chamber 12, and in particular the dielectric portion 16, has therein a process space 26 for containing a plasma 28.
Determine. In the embodiment of FIG. 1, the substrate 22 is located below the process space 26 and the plasma 28.

In one embodiment of the invention, the processing system may be a stand alone plasma processing system utilized for an isolated plasma process. In another embodiment, the processing system is incorporated into a multi-process system having a plurality of other processing systems and a centrally located substrate transfer module (not shown) for moving substrates between the various systems. Can be configured as. Such multi-chamber multi-process systems are known to those skilled in the art.

Due to the plasma treatment, the process space 26 must generally be a vacuum. Therefore, the processing chamber 12 is coupled to a suitable vacuum system 30. Vacuum system 30
Includes suitable vacuum pumps and valves as known to those skilled in the art to provide the desired vacuum pressure in process space 26. The processing chamber 12 is suitably configured to provide the necessary openings to create a vacuum in the space 26 as known to those skilled in the art.

A plasma producing assembly 18 is shown in FIG. 1 and is electrically coupled to the dielectric portion 16 of the processing chamber 12. The plasma generating assembly 18 forms a plasma 28 in the process space 26 above the substrate support assembly 20 by inductively coupling electrical energy into the dielectric portion 16, often referred to by those of ordinary skill in the art as a "glass bell." (See FIG. 1). The dielectric portion or enclosure 16 is mounted on a flange 32 of the base 14 that surrounds an open top surface 34 of the base 14. Appropriate O-ring seals and other seals (not shown) are typically placed between the base 14 and the dielectric portion 16 to properly vacuum seal the various portions of the processing chamber.

In order to form a plasma in the space 26, a process gas is introduced into the space 26 and electric energy is electrically coupled to the space, whereby the gas particles are ionized to form a plasma. For that purpose, the processing chamber is coupled to a suitable process gas source 36 and a suitable process gas is introduced to form a plasma 28. Any suitable gas distribution element (not shown) may be coupled to the gas source 36 to uniformly introduce a process gas, such as argon, into the space 26 to form a uniform, dense plasma. Good. The gas source 36 may include multiple gases mixed together in the chamber 12, such as for chemical vapor deposition.

In order to ignite and sustain the plasma in the space 26, the plasma-generating assembly, as shown in FIG.
It includes an inductive element in the form of a helical coil 38 wrapped around the dielectric section 16. The coil 38 is essentially an elongated conductor formed in the shape of a helical coil sized to fit around the dielectric portion 16 and the outer wall surface 17 of the enclosure. Coil 38 is electrically coupled to plasma power supply 40. The plasma power supply 40 is
It includes an RF power supply and a suitable RF matching circuit for efficiently coupling RF power to the coil 38. RF electrical energy from power supply 40 is inductively coupled to process space 26 by coil 38 to excite the process gas and form plasma 28. Inductively coupled plasmas and the formation of such plasmas are known to those skilled in the art, and process space 2
A variety of different configurations can be utilized to inductively couple energy to 6. Accordingly, FIG. 1 discloses, in a broad conceptual form, only one possible embodiment for inductively coupling a plasma to the processing chamber 12.

Further, as will be readily appreciated by those of ordinary skill in the art, a plasma processing system suitable for use in the present invention may take any one of a number of different forms.
It may include processing chambers of different configurations. For example,
In another inductively coupled plasma processing system,
Energy is coupled through a dielectric window on the top of the processing chamber utilizing a flat coil (as opposed to a helical coil) located on the top of the processing chamber. Further, the plasma may be formed not capacitively but capacitively. In such a capacitively coupled system, an electrode element in the process space 26, eg, an electrically biased gas distribution showerhead (not shown) may be coupled to another electrode, eg, a biased substrate support assembly. Used in combination with 20 and substrate 22. The electric field between the electrodes sustains the plasma near the substrate. Accordingly, the present invention may be incorporated with a variety of different plasma processing systems that use inductively coupled plasma or capacitively coupled plasma, or systems that otherwise form a plasma for processing semiconductor substrate 22. .

In the present invention, multiple electrodes are used to shape the plasma to improve process results. As shown in FIG. 1, embodiments of the present invention include multiple electrodes. The plurality of electrodes includes a first electrode 44 coupled to the substrate support 20 and a second electrode 46 proximate to the first electrode 44 and also coupled to the substrate support. As shown, electrodes 44 and 46 are embedded in substrate support 20. The second electrode 46 is generally spaced from the first electrode 44 and electrically insulated from the first electrode 44. The present invention envisions the use of multiple electrodes to create a DC bias on the substrate surface 23 and selectively vary the DC bias. Accordingly, the disclosed invention has at least two electrodes,
However, it will probably include systems that utilize a greater number of electrodes, and the claims include such multiple electrode processing systems. For ease of reference herein when describing the invention, the illustrated electrodes are sometimes referred to as first electrode 44 and second electrode 46. However, as mentioned above, other embodiments of the present invention may utilize third, fourth, and other electrodes. Furthermore, the names of the first electrode and the second electrode may be interchanged. For example, in the embodiment shown in FIGS. 1 and 2, the multi-electrode includes an outer annular electrode 44, labeled the first electrode, and an inner flat discoid electrode 46, labeled the second electrode. Be done. But,
Such names may be reversed, eg electrode 44
May be named the second electrode, and the electrode 46 may be named the first electrode.

According to another aspect of the invention, the DC bias on the electrodes formed by the RF power supply 48 is selectively varied between the electrodes. For that purpose, the bias of one electrode may be selectively varied with respect to the constant bias on the other electrode, and vice versa.
Alternatively, both (or more) electrodes may be selectively changed from each other in accordance with the principles of the present invention. Therefore, naming the electrodes in the drawings as first and second electrodes for the purpose of describing the invention should not be considered as limiting the invention in any way.

In one embodiment of the present invention, as shown, the first and second electrodes 44, 46 are embedded within the substrate support or susceptor 20. The substrate support 20 is preferably formed of a dielectric material such as aluminum nitride. The electrodes can be made of a suitable electrically conductive material such as molybdenum. Appropriate electrodes 44, 46 are from N.M. G. K. Available as a 120 micron thick molybdenum electrode. Other suitable electrode materials may be utilized in accordance with the principles of the present invention.

Electrodes 44 and 46 as described below
Is electrically coupled to an RF power supply that includes a suitable RF power supply for providing RF power to the electrodes. In one embodiment of the invention, the electrodes 44, 46 connect the substrate 22 to the substrate support 20.
Also used to electrostatically clamp to. For that purpose, the electrodes 44, 46 are coupled to a clamping DC power supply 50. Clamping DC power supply 50 is DC on the electrode
An appropriate electric field is formed by inducing a bias. This electric field clamps the substrate 22 according to the well-known electrostatic clamping principle. Biased electrodes 44, 4
An RF power source 48 in combination with 6 creates an RF generated DC bias on the substrate 22, especially on the upper surface 23 of the substrate facing the plasma 28. The bias on the substrate surface 23 accelerates the ions and other charged particles in the plasma 28 onto the surface 23. Such substrate bias on surface 23 enhances the plasma etching process. Or using such a substrate bias on surface 23,
Enhances deposition, for example in PECVD. Power supply 50
The clamping DC bias formed on the substrate by is generally limited away from surface 23 and does not significantly affect the DC substrate bias created at the RF of surface 23 that interacts with the plasma. Biasing the substrate in such a manner is known to enhance the etching and deposition processes, but generally there is little control over such bias, and the plasma process is in process space 26. It is left to the control of the plasma 28 formed in the.

US Patent Application filed May 4, 2000, incorporated herein by reference, "Improved Apparatus for Plasma Processing of Substrates Utilizing Electrostatic Chuck and Method "(Improv
ed Apparatus and Method fo
r Plasma Processing of S
upstrate Utilizing an Ele
The invention of ctrostatic chuck) is the electrode 4
The problem is addressed by selectively varying the DC bias created by the RF on the substrate surface with a selective bias of 4,46. The present invention allows for more precise tuning of the bias by allowing the measurement of the specific relative bias created on each electrode to allow for more selective plasma treatment.

FIG. 2 illustrates one embodiment of the present invention, showing a cutaway perspective view of the first and second electrodes 44,46. The first and second electrodes 44, 46 are coupled to an RF power source 48. The RF power source 48 includes an RF power supply 54 that can generate a suitable RF signal to bias the electrodes. According to one aspect of the invention, the electrically capacitive structure 5
6, 58 are electrically coupled between the RF power source 48 and the electrodes 44, 46, and one or more of the electrically capacitive structures 56, 58 has a variable or adjustable capacitance, The DC bias created by the at least one on the substrate surface 23 is varied with respect to the DC bias created by the at least one of the other electrodes on the substrate. In the embodiment shown in FIG. 2, the first electrode 44 is coupled to a first electrically capacitive structure 56 with a variable capacitance. That is, the capacitance of the capacitive structure 56 can be adjusted to increase or decrease. The second electrode 46 is coupled to the RF power source 48 by the second capacitive structure 58. In the embodiment shown in FIG. 2, the second capacitive structure also has a variable capacitance. Suitable capacitive structures to be used in the present invention are conventional variable capacitors such as variable air capacitors or vacuum capacitors.

As mentioned above, with respect to the naming of the first and second electrodes, the capacitors 56, 58 are likewise named for the purposes of the present description. Since it is possible to utilize more than two electrodes, more than two capacitors may be utilized to couple the various electrodes to the RF power supply 48, all of which may be variable capacitors or fixed capacitors. It can be a combination of capacitors. Therefore, reference herein to capacitors as first and second capacitors should not be construed as limiting the scope of the invention in any way.

According to one aspect of the present invention, by utilizing variable capacitors 56, 58, a capacitively coupled DC is created on substrate surface 23 by one of the electrodes.
The bias is varied with respect to the DC bias created on the substrate surface by another of the electrodes. In detail,
The mutual electrical bias of each electrode can be selectively varied by changing the electrical capacitance of a capacitor coupled between the particular electrode and the RF power supply 48. For example, one electrode may be biased at a higher bias voltage than the other electrode, depending on how the plasma is affected. As noted above, the plasma density in a confined space plasma, such as plasma 28 in processing chamber 12, is generally non-uniform. In particular, the greatest density is most at the center of the substrate, rather than at the center of the chamber 12, and thus at the outer lip of the substrate. Thus, changes in etch rate, deposition rate, and other plasma-affected parameters can vary radially across the substrate surface 23. The present invention can be used to address such plasma non-uniformities, as well as radial changes in corresponding plasma parameters, including etch rate and deposition rate. In one embodiment of the invention described herein, the electrodes 44, 46 are interdigitated to address the problem of greater plasma density at the center of the plasma and substrate surface 23 than at the outer edge of the surface 23. Subject to different biases. As will be readily appreciated by those of ordinary skill in the art, various other plasma non-uniformities associated with a particular processing system also include:
This can be addressed in the present invention by varying the capacitance of the capacitor and manipulating the DC bias created by the RF on one or more of the electrodes, and thus on the substrate surface 23.

In FIG. 2, the first capacitor 56 has a variable capacitance that can be increased or decreased as necessary. To address the low plasma density at the edges outside the substrate, the first electrode 44 is biased at a higher bias level so that more plasma particles are outside the substrate surface 23 in the annular or surrounding edges. Should be attracted to. Reducing the capacitance of capacitor 56 increases the bias level of electrode 44. For example, if both electrodes 44, 46 are similarly biased by an RF power supply 48 having a power level in the range of 300 to 400 watts, both electrodes will experience a bias level of about -100 volts DC to ground potential. It will be. In this way, the electrodes are on the surface 23 of the substrate 22.
A nearly uniform D in the range of about -100 volts DC across
C bias will be added. At this time, the substrate surface 2
A uniform DC bias across 3 will experience non-uniformities in plasma 28. The amount of power provided to the various electrodes 44,46 is dependent on the capacitance characteristics of the respective capacitors 56,58 coupled between those electrodes and the RF power supply 48. In one aspect of the invention, by reducing the capacitance of the variable capacitor 56, more power is provided to the first or outer electrode 44, so that the electrode 44 is outside the substrate surface 23, ie, the annular portion. , Maintaining a higher DC bias level. Of course, increasing the capacitance of the variable capacitor 56 has the opposite effect, providing more power to the second or central electrode 46 than the first electrode 44. At this time, the electrode 46
Are maintained at a relatively higher bias than electrodes 44, so that the central portion of substrate surface 23 is maintained at a higher bias level than the outer annular portion of surface 23. Substrate surface 23
Maintaining a higher bias level in the outer annulus of the cathode addresses the decrease in plasma density that would normally occur at the outer edge of the plasma 28, ensuring a uniform etch or deposition rate across the substrate surface 23. Desirable to achieve.

The second capacitor 58 can also be varied to achieve a somewhat similar effect, and to increase the bias level of the outer electrode 44 relative to the center electrode 46. In this way, if the capacitance of the second capacitor 58 is increased, the amount of electric power supplied to the electrode 46 is reduced, so that the bias level of the electrode 46 is lowered. This substantially increases the bias level closer to the annulus outside the substrate surface 23 as compared to the bias level inside the substrate surface 23, ie, the central portion. Still further, both capacitors 56, 58 may be changed. In this case, the capacitances of capacitors 56 and 58 are adjusted to increase or decrease relative to each other to provide the desired relative bias level adjustment across electrodes 44 and 46 and across surface 23.
For example, to increase the relative bias level external to electrode 46, ie on first electrode 44,
Either reduce the capacitance of the capacitor 56, increase the capacitance of the capacitor 58, or satisfy both conditions at the same time. As shown in FIG. 2, the capacitors 56, 58 may be physically connected together by a linkage 57 so that their capacitance changes synchronously.

The invention described with reference to FIG. 2 can be utilized in a plasma processing chamber with or without a substrate support including an electrostatic chuck. Figure 2
7 illustrates components that can be used to provide electrostatic chuck functionality on a substrate support that utilizes first and second electrodes 44,46. More specifically, the clamping DC power source 50
Are coupled to the electrodes 44, 46 and provide a DC potential difference between the electrodes to electrostatically clamp the substrate to the support 20 according to well known electrostatic clamping principles. Clamping DC power supplies generally include a clamping DC power supply with a positive terminal 61 and a negative terminal 62 coupled to the electrodes. In the embodiment shown in FIG. 2, the positive terminal 61 is coupled to the outer or first electrode 44 and the negative terminal 62 is coupled to the inner or second electrode 46. But D
The C-clamping bias voltage may be reversed for the electrodes and the electrostatic chuck works equally well. When using the present invention with an electrostatic chuck, an RF filter 6
4, 66 are used to protect the clamping DC power supply 50 from damage due to the RF signal from the power supply 54. Figure 2
The capacitors 56, 58 shown in the example of FIG. 2 are both variable, so changing the capacitance of each causes the DC bias formed from the RF created on one of the electrodes by one electrode on the substrate to the other. The electrodes can vary with respect to the DC bias created on the substrate. Capacitors 56, 58 also provide isolation from the DC signal of power supply 50 to RF power supply 54 when an electrostatic clamping function is also incorporated with the present invention.

As mentioned above, it may be desirable to change the capacitance of capacitors 56, 58 simultaneously and in synchronism. To that end, the capacitors can be arranged to be adjusted synchronously by being coupled together like a linkage 57. For example, it may be desirable to maintain a somewhat constant power load on the RF power feeder 54 during processing. Therefore, by physically coupling or interlocking the variable capacitors 56 and 58, their capacitance values can be simultaneously adjusted in a synchronous manner to provide a somewhat constant power load. More specifically, the interlocking capacitor is adjusted to reduce the capacitance of the first capacitor 56 and increase the capacitance of the second capacitor 58 by a similar amount, so that the second or inner electrode 46 is A larger bias level can be applied to the first or outer electrode 44. Since the capacitors 56, 58 are electrically coupled in parallel to the power supply 54, their capacitances are mathematically added in series to represent the overall capacitive load on the power supply. Therefore, the capacitor is the power feeding device 5
The total power load given to 4 is capacitors 56, 5
It is the sum of the capacitances of 8. Therefore, increasing one capacitor can reduce the other capacitor by the same amount, maintaining a constant load. Therefore, by interlocking the adjustment mechanism with respect to the variable capacitors 56 and 58, the electrodes 44 and 4
It is possible to maintain a relatively constant power load on the RF power feeder while varying and adjusting the relative differential DC bias between 6 as described above.

Referring again to FIG. 2, one embodiment of the present invention will be described in more detail. The present invention provides a system and method for measuring the DC bias produced capacitively on each electrode by an RF power source 48. To that end, the present invention provides a system for monitoring the DC bias created by at least one of the electrodes by the RF feeder 54 and the DC bias difference measured between the two electrodes. The bias from one electrode and the differential bias measurement between the two electrodes can be used to determine the bias measurement from the other unmeasured electrode. The present invention allows for precise measurement of the bias on each electrode so that precise and selective adjustments to the variable capacitors 56 and 58 can be made to obtain the desired DC bias at the substrate surface 23. Since the embodiment shown in FIG. 2 utilizes an electrostatic clamp, the electrodes are biased with RF from RF source 48 and DC signal from DC source 50.

More specifically, the first comparator U1 has a first input 70 and a second input 72.
The first comparator U1 has an output 73, which is represented in FIG. 2 as the bias voltage output. The first and second inputs 70, 72 of the comparator U1 are electrically coupled to one electrode, eg electrode 46. Terminal 62 of clamping DC power supply 50 is coupled to electrode 46 and comparator inputs 70, 72 are electrically coupled between electrode 46 and power supply 50. A voltage divider circuit 74 is electrically coupled between power supply 50 and input 70 to provide an input signal to component U1. The voltage dividing circuit includes a resistor R1 and a variable resistor VR2. The input 70 is connected between the resistors R1 and VR2 of the voltage dividing circuit 74. The RF filter 66 isolates the input 70 from the RF signal of the RF power supply 54.

The input 72 is connected to the electrode 46 via the voltage dividing circuit 76.
And power supply 50. The voltage dividing circuit 76 has a resistor R3.
And R4. Input 72 is connected between resistors R3 and R4. The RF filter 77 inputs the input 72 to the power feeding device 5
Isolate from 4 RF signal. Comparator U1 may be configured utilizing a differential operational amplifier to provide a difference signal at output 73 based on the difference in voltage levels between inputs 70 and 72.

An isolation element such as diode D1 is electrically coupled between first input 70 and second input 72. More specifically, D1 is connected to the negative terminal 62 of the power source 50,
It is coupled in the orientation shown in FIG. Isolation element D1 is utilized to provide a differential voltage signal to inputs 70, 72 in accordance with the principles of the present invention. Specifically, the RF power source 48
In order to measure the bias voltage of the electrode 46 from the power source 48 turned off and the DC power source 50 turned on,
V so that both inputs 70 and 72 have the same input voltage
The resistance of R2 can be changed. The fixed value of resistors R3 and R4 and voltage divider circuit 76 fixes the input voltage at input 72. Therefore, VR2 is adjusted so that input 70 equals input 72 and produces essentially no output voltage at output 73 of comparator U1. When inputs 70 and 72 are equal, comparator U1 produces an output voltage that is essentially zero or very small. When VR2 is adjusted to zero the output of the comparator U1, the RF power supply 48 is turned on and the electrode 46
Form a DC bias created by RF. D created on the electrode 46 by the blocking diode D1
C-bias is prevented from producing a current in voltage divider circuit 74. However, the RF DC bias of electrode 46 causes a current in voltage divider circuit 76, resulting in a voltage drop across resistor R4. On the other hand, the input 72 is less affected by the RF power source 48, so the input 72 is different from the input 70. As described above, the influence of the clamping DC power supply 50 is canceled by the change in the resistance of VR2, and the output 73 of the comparator U1 becomes zero. Thus, the voltage difference between the inputs 70, 72 and the resulting output voltage 73 is almost simply the result of a DC bias created at RF from the power supply 48. Therefore, the output 73 of the comparator U1 is the power source 48.
Is proportional to the DC bias voltage on electrode 46 created by. Insulation element, namely blocking diode D
1 is operable to isolate the first input 70 from the bias on the electrode 46 created by the RF power supply. Electrode 4
Similar measurements can be made with electrode 44 instead of 6.

The second comparator U2 is utilized to determine the bias difference between the first electrode 44 and the second electrode 46 due to the RF power source. For that purpose, a second comparator U2
Has an input 78 electrically coupled to electrode 44 and an input 80 electrically coupled to electrode 46. Figure 2
Then, the second input is coupled to the electrode 46 via the voltage divider circuit 76 and the RF filter 77, like the input 72. The input 78 is a voltage dividing circuit 82 including a resistor R5 and a variable resistor VR6.
Is coupled to the electrode 44 via. RF filter 83 isolates input 78 from the RF signal of power supply 48. Voltage dividing circuit 8
The effect of the clamping DC voltage from the power supply 50 also affects the input 78, 80 of the comparator U2 by adjusting the voltage of 2 to obtain an essentially zero output signal from the output 86 of the comparator U2.
Effectively removed from. By changing the resistance VR6, the signal level from the voltage dividing circuit 82 is changed. Output 86
2 is designated as the delta voltage output in FIG. 2 because it reflects the bias difference between electrodes 44 and 46. By adjusting VR6 with power supply 50 on, output 86 is essentially zero. The RF power supply 48 is then turned on and a DC bias is created on both electrodes 44 and 46. The DC bias created by RF causes current to flow in the voltage divider circuits 76 and 82, causing a voltage drop across resistors R4 and VR6. The voltage difference between inputs 78 and 80 is reflected in output 86, representing different bias levels on both electrodes. The output of comparator U2 is proportional to the DC voltage difference between inner electrode 46 and outer electrode 44 because the circuit is preconditioned to remove the effects of the DC clamping voltage from power supply 50.

Relative DC of one electrode, eg electrode 46
Knowing the bias and the differential bias between electrodes 44 and 46 allows mathematical determination of the relative, unmeasured relative bias level on electrode 44. In alternative embodiments of the invention, of course, electrode 44
Can be measured to determine mathematically the bias level of electrode 46. Capacitors 56 and 58 are varied to provide the desired precision electrodes 44 and 46.
Experimental bias data for achieving the relative bias of the substrate surface 23 and the relative bias of the substrate surface 23.
Is obtained using a typical output voltage signal from For example, it may be desirable to bias one electrode to twice the height of the other electrode. Output signal 7
3, 86 reflect the relative bias voltage levels on electrodes 44 and 46. The data from the output is used to set a particular bias level difference between electrodes 44 and 46 by experimentally adjusting the variable capacitances of capacitors 56 and 58, ie at both electrodes and finally to the substrate. A uniform bias level can be obtained at the surface.

Alternatively, the present invention can be utilized to balance clamping voltages. To that end, the selection of the resistance values utilized in the voltage divider circuits 76 and 82 determines the delta voltage due to the clamping DC power supply 50 and adjusts the signal from the power supply 50 to provide the electrodes 44 and 4.
A balanced or equal clamping voltage of 6 can be achieved.

According to another aspect of the present invention, another comparator U3 is constructed similarly to the comparator U2, and the electrode 4
The voltage difference between 4 and 46 can be measured and the output of the comparator U2 automatically zeroed. The output of the comparator U3 is coupled to an automatic adjustment element, which is a variable resistor VR.
Is combined with 6. As shown by the dashed line 90, the self-adjusting element automatically changes the resistance of the variable resistor VR6. Therefore, the automatic adjusting element 92 performs such an operation,
It can be suitably mechanically or electrically coupled to the variable resistor VR6. To that end, the output 94 of the comparator U3
Is coupled to the servomotor 92 and drives the servomotor to automatically zero the voltage at the output 94 from the comparator U3. Therefore, because comparators U2 and U3 are essentially coupled in parallel to electrodes 44 and 46, output 86 of comparator U2 is also automatically driven to zero. Electrode 44
A disable switch, for example STR1, is coupled between the output 94 of the comparator U3 and the servomotor 92 to make a measurement of the delta voltage between V and 46. STR
1 is also operatively coupled to the RF power supply via line 96. This causes STR1 to open when the RF power is on and RF power is applied to electrodes 44 and 46, and the servomotor is unable to further adjust resistance VR6. In this way, the effect of the DC clamping voltage on the comparators U2 and U3 is zeroed by the servomotor 92. When RF power supply 54 is turned on, servo motor 92 is disabled and comparators U2 and U
3 measures the bias difference created between electrodes 44 and 46 by RF feeder 54 and the resulting DC bias due to RF.

As mentioned above, the comparators U1, U2 and U3
Output provides experimental data for adjusting variable capacitors 56 and 58 to obtain desired relative DC bias voltage levels on electrodes 44 and 46. Output 73, 8
The differential voltage signals of 6 and 94 can be used directly to determine how the capacitors 56, 58 should be adjusted. Alternatively, a table or chart may be created from the various output voltages to produce the various capacitance levels required to obtain the desired DC bias level on the electrodes 44 and 46 and, finally, the substrate surface 23. Good.

The present invention is not limited to use with electrodes having the particular concentric embodiments shown in FIGS. 1 and 2, but for various geometric configurations bias voltage between multiple electrodes. Can be used to change For example, an electrode configuration, often referred to as a double D configuration, that utilizes two electrodes with a gap in between may be used with the present invention. Since such an arrangement is often utilized with electrostatic clamps, it can be used with the present invention to address plasma non-uniformities, for example, on one side of the process chamber relative to the other side of the chamber. For this reason, it may also be suitable to vary the bias level near one side of the substrate with respect to the other side of the substrate. Other electrode configurations are suitable for use with the present invention, as will be readily appreciated by those of ordinary skill in the art. Moreover, more than two electrodes can be used to further adapt the bias on the substrate to address non-uniformities in the plasma processing system. For example, three or four concentric electrodes may be utilized similar to the arrangements of Figures 1 and 2 to further tailor the effect on the plasma. At this time, various voltage levels on the electrodes are measured in accordance with the principles of the invention described herein.

While the invention has been shown and described in considerable detail by the description of the examples, it is not the intention of the inventor to limit the scope of the claims to such details in any way. . Additional advantages and variations will readily occur to those of ordinary skill in the art. Accordingly, the invention in its broader aspects is not limited to the specific details of the exemplary apparatus and method, as well as the examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the inventor's overall inventive concept.

[Brief description of drawings]

1 is a side cross-sectional view of a plasma processing system that may be utilized in accordance with the principles of the present invention.

FIG. 2 is a perspective view and a schematic view of an embodiment of the present invention.

[Explanation of symbols]

12 Processing chamber 20 Substrate support assembly 22 plates 28 Plasma 44 First electrode 46 Second electrode 48 RF power supply 50 Clamping DC power supply 56 First capacitance structure 58 Second capacitance structure 70 First Input of First Comparator 72 Second input of first comparator 73 Output of the first comparator 74 voltage divider 78 First input of second comparator 80 Second input of second comparator 82 voltage divider 86 Output of second comparator 92 Servo motor 94 Output of third comparator D1 insulation element STR1 disable switch U1 comparator U2 comparator U3 comparator VR2 variable resistor VR6 variable resistor

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor William Di, Jones USA Arizona, Phoenix, West Palm Lane 934 (72) Inventor Craigty, Baldwin USA Arizona, Chandler, N, Federal Street 375, Number 334 ( 56) References JP-A-6-334024 (JP, A) JP-A-5-322967 (JP, A) JP-A-8-316212 (JP, A) International Publication 97/37382 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/3065 C23C 16/52 H01L 21/205

Claims (26)

(57) [Claims] 1. A processing system for processing a substrate with a plasma, the substrate in a chamber having a processing chamber configured to contain the plasma, and a supporting surface for supporting the substrate in proximity to the plasma. A support and first and second electrodes coupled to the substrate support, each of which is positioned proximate to the support surface and electrically isolated from each other; An RF power supply coupled to each electrode for biasing the electrodes, the biased electrodes creating a DC bias thereon and operating to create a DC bias on a substrate disposed on a supporting surface. A first comparator having an RF power source and first and second inputs electrically coupled to one of the electrodes for measuring a DC bias of the electrode, the first comparator comprising: Input and the second An isolation element coupled to an input is operable to isolate the first input from a DC bias on the one electrode created by the RF power source, and the electrode created by the RF power source. A first comparator having an output that reflects a voltage difference between the first input and the second input caused by a DC bias; a first input coupled to the first electrode; A second comparator having a second input coupled to a second electrode, the DC being between the first electrode and the second electrode.
A second comparator having an output that reflects the voltage difference between the first input and the second input resulting from a bias difference, and RF at the first electrode and the second electrode. A processing system in which the DC bias level can be optimally adjusted by monitoring the relative DC bias level created. 2. The processing system of claim 1, further comprising a first capacitor electrically coupled between the RF power source and at least one of the plurality of electrodes, wherein the first capacitor is Providing a variable capacitance for varying a DC bias created on the substrate by the at least one electrode with respect to a DC bias created on the substrate by at least one of the other electrodes of the plurality of electrodes, A modified DC bias changes the effect of plasma on one part of the substrate to the effect of plasma on another part of the substrate, a processing system. 3. The processing system of claim 2, wherein the DC bias created by at least two electrodes of the plurality of electrodes is varied relative to one another. The processing system further comprising a second capacitor coupled to the one electrode. 4. The processing system of claim 1, wherein the substrate support is formed of a dielectric material and the electrodes are embedded within the dielectric material. 5. The processing system of claim 1, further comprising a DC power supply coupled to the electrodes, the DC between the two electrodes for electrostatically clamping the substrate to a supporting surface of the substrate support. A processing system, wherein the DC power supply is operable to create a potential difference. 6. The processing system of claim 1, wherein at least one of the inputs of the first comparator is coupled to an electrode via a voltage divider circuit, the voltage divider circuit changing the voltage level of the comparator input. A processing system with a variable resistance that can be adjusted to change. 7. The processing system of claim 1, wherein at least one of the inputs of the second comparator is coupled to an electrode via a voltage divider circuit, the voltage divider circuit changing the voltage level of the comparator input. A processing system with a variable resistance that can be adjusted to change. 8. The processing system of claim 7, further comprising an automatic adjustment element coupled to the variable resistor for automatically changing a resistance value of the variable resistor, the second comparator. A processing system in which the self-adjusting element is coupled to the output of the second comparator so that the resistance of the variable resistor is changed based on the output of 9. The processing system of claim 7, further comprising another comparator having a first input coupled to the first electrode and a second input coupled to the second electrode. An output of the other comparator reflects a voltage difference between the first input and the second input caused by a bias difference between the first electrode and the second electrode, Processing system. 10. The processing system of claim 8, further comprising a disable switch operatively coupled to the RF power source and the self-adjusting element, the automatic switch when RF power is applied to the electrodes by the RF power source. A processing system, wherein the disable switch is operable to disable a tuning element. 11. The processing system of claim 1, wherein the isolation element is a diode. 12. A processing system for processing a substrate with a plasma, the substrate in a chamber comprising a processing chamber configured to contain the plasma, and a supporting surface for supporting the substrate in proximity to the plasma. A support and first and second electrodes coupled to the substrate support, each of which is positioned proximate to the support surface and electrically isolated from each other; A DC power supply coupled to each electrode, the DC power supply operable to create a DC potential difference between the two electrodes for electrostatically clamping the substrate to the supporting surface of the substrate support; An RF power supply coupled to each electrode at the same time as the DC power supply for biasing, wherein the RF biased electrode creates a DC bias thereon and a DC bias on a substrate disposed on a support surface. An RF power source and a first comparator electrically coupled to one electrode, the first comparator having first and second inputs for measuring a DC bias of the electrode. And an isolation element coupled between the first input and the second input operates to isolate the first input from a DC bias on the one electrode created by an RF power source. Can be said RF
A first comparator having an output that reflects the voltage difference between the first input and the second input caused by an electrode DC bias created by a power supply; and a first comparator coupled to the first electrode. A second comparator having one input and a second input coupled to the second electrode, the DC between the first electrode and the second electrode.
A second comparator having an output reflecting a voltage difference between the first input and the second input resulting from a bias difference, at least one of the inputs of the first comparator being a voltage divider. A voltage divider circuit coupled to the electrodes through the voltage divider circuit, the voltage divider circuit having a variable resistor adjustable to change the voltage level of the comparator input, wherein at least one of the second comparator inputs is coupled through the voltage divider circuit. Coupled to an electrode, the voltage divider circuit includes a variable resistor that can be adjusted to change the voltage level at the comparator input, and the first electrode and the second electrode are RF-relative relative to each other. A processing system in which the DC bias level can be optimally adjusted by monitoring the DC bias level. 13. The processing system according to claim 12, wherein:
Further comprising an auto-adjusting element coupled to the variable resistor for automatically changing a resistance value of the variable resistor, the self-adjusting element coupled to the variable resistor based on an output of the second comparator. The processing system wherein the self-adjusting element is coupled to the output of the second comparator such that the resistance of the variable resistor is changed. 14. The processing system of claim 12, wherein:
There is further included another comparator having a first input coupled to the first electrode and a second input coupled to the second electrode, between the first electrode and the second electrode. The processing system in which the output of the other comparator reflects the voltage difference between the first input and the second input caused by the bias difference in. 15. The processing system according to claim 13, wherein:
A disable switch operably coupled to the RF power source and the self-adjusting element is further included, the disable switch operating to disable the self-adjusting element when RF power is applied to the electrodes by the RF power source. Get the processing system. 16. The processing system according to claim 12, wherein:
The processing system, wherein the isolation element is a diode. 17. A method of treating a substrate with a plasma, the method comprising: disposing the substrate on a supporting surface of a substrate support in a processing chamber; and forming a plasma in the processing chamber proximate to the substrate. And providing first and second electrodes coupled to the substrate support, each of the first and second electrodes disposed proximate to the support surface and electrically isolated from one another. , Coupling an RF power source to each electrode and biasing each electrode to create a DC bias on the substrate disposed on the support surface of the substrate support; Created by an RF power source by measuring the DC bias of the electrodes by electrically coupling one and a second input and coupling an insulating element between the first and second inputs. One of the electrodes A step of insulating the first input from the DC bias, by monitoring the output of said first comparator, said R
Determining a voltage difference between the first input and the second input that reflects an electrode bias created on the one electrode by an F power source; and a first input of a second comparator. Electrically coupling to the first electrode and electrically coupling the second input of the second comparator to the second electrode, and monitoring the output of the second comparator. Therefore, the R
Determining a voltage difference between the first input and the second input that reflects an electrode DC bias created on the first electrode and the second electrode by an F power source; Determining the DC bias of the first electrode and the second electrode based on the outputs of the one comparator and the second comparator, wherein the first electrode and the second electrode A treatment method that allows the bias to be optimally adjusted by monitoring the relative bias. 18. The method of claim 17, further comprising electrically coupling a first capacitor having a variable capacitance between the RF power source and at least one of the plurality of electrodes. DC created on the substrate by the at least one electrode by changing the capacitance of the first capacitor based on the output of at least one comparator of the first comparator and the second comparator. Changing the bias to a DC bias created on the substrate by the other electrode, thereby changing the effect of the plasma on one part of the substrate to the effect of the plasma on another part of the substrate; A processing method including. 19. The method of claim 18, further comprising electrically coupling a second capacitor having a variable capacitance between the RF power source and the other electrode, the first comparison. A DC bias created on the substrate by the at least one electrode by varying the capacitance of the second capacitor based on the output of the at least one comparator of the capacitor and the second comparator. Further varying with respect to the DC bias created on the substrate by the one electrode. 20. The processing method according to claim 19, further comprising the step of synchronously changing the capacitances of the first capacitor and the second capacitor. 21. The method of claim 17, further comprising coupling a DC power source to the first and second electrodes, a DC potential difference between the first electrode and the second electrode. Electrostatically clamping the substrate to the support surface of the substrate support by creating a substrate. 22. The method of claim 17, further comprising at least one of the inputs of the first comparator having a variable resistance adjustable to change the voltage level of the comparator input. A method of processing comprising coupling to an electrode via a. 23. The method according to claim 17, further comprising a variable resistor capable of adjusting at least one of the inputs of the second comparator to change the voltage level of the comparator input. A method of processing comprising coupling to an electrode via a. 24. The processing method according to claim 23, further comprising: coupling an automatic adjustment element to the variable resistor to automatically change a resistance value of the variable resistance; Coupling to the output of a second comparator and changing the resistance of the variable resistor based on the output. 25. The processing method of claim 17, further comprising electrically coupling a first input of a third comparator to the first electrode, the second input of the third comparator. Electrically coupling an input to the second electrode, and monitoring the output of the third comparator to create an electrode bias created by an RF power source on the first electrode and the second electrode. And determining a voltage difference between the first input and the second input that reflects the. 26. The method of claim 24, further comprising coupling a disable switch to the RF power supply and the self-adjusting element, the self-tuning when RF power is applied to the electrodes by the RF power supply. Disabling the device.