Advances in plasma processing have facilitated growth in the semiconductor industry. Plasma processing may involve different plasma generating technologies, for example, inductively coupled plasma processing systems, capacitively-coupled plasma processing systems, microwave generated plasma processing systems and the like. Manufacturers often employ capacitively-coupled plasma processing systems in processes that involve etching and/or depositing of materials to manufacture semiconductor devices.
Next-generation semiconductor devices being fabricated with new advanced materials, complex stacks of dissimilar materials, thinner layers, smaller features, and tighter tolerances may require plasma processing systems with more exact control and wider operating windows for plasma process parameters. Thus, an important consideration for plasma processing of substrates involves capacitively-coupled plasma processing systems possessing capabilities to control a plurality of plasma related process parameters. Prior art methods to control plasma related process parameters may include an external radio frequency (RF) generator or an external DC power source.
To facilitate discussion, FIG. 1 shows a simplified schematic of a prior art plasma processing system 100 with an external RF generator 124 coupled to an upper electrode 104. Plasma processing system 100 may be a single, double (DFC), or triple frequency RF capacitively discharge system. In an example, radio frequencies may include, but are not limited tot 2, 27 and 60 MHz. Plasma processing system 100 may be configured to include a substrate 108 being disposed above a lower electrode 106.
Consider the situation wherein, for example, substrate 108 is being processed. During plasma processing, an RF generator 120 with a path to ground may supply a low RF bias power to lower electrode 106 through an RF match 118. In an example, RF match 118 may be used to maximize power deliver), to the plasma system. The power from RF generator 120 tends to interact with a gas to ignite plasma (the gas and the plasma are not shown to simplify schematic) between upper electrode 104 and lower electrode 106. The plasma may be used to etch and/or deposit materials onto substrate 108 to create electronic devices.
In the example of FIG. 1, lower electrode 106 is electrically isolated from a grounded bottom-extension 114 through a bottom insulator 116. Upper electrode 104 is electrically isolated from a grounded upper outer electrode 110 through an upper insulator 112.
Consider the situation, wherein, for example, a manufacturer may want to adjust the voltage of upper electrode 104 during plasma processing to provide additional control over plasma processing parameters. The voltage of upper electrode 104 may be adjusted by an external generator 124 through an RF match 122 with a path to ground. External generator 124, in the example of FIG. 1, may be a high RF powered generator.
In addition, FIG. 2 shows a simplified schematic of a prior art plasma processing system 200 with an external DC power source 224 connected to an upper electrode 104. Plasma processing system 200 of FIG. 2 is similar to the aforementioned multi-frequency capacitively-couple plasma processing system 100 of FIG. 1.
In the example of FIG. 2, external DC power source 224 is coupled to upper electrode 104 through an RF filter 222 with a path to ground. RF filter 222 is generally used to provide attenuation of unwanted harmonic RF energy without introducing losses to DC power source 224. Unwanted harmonic RF energy is generated in the plasma discharge and may be kept from being returned to the DC power source by RF filter 222.
Consider the situation, wherein, for example, a manufacturer may want to adjust the DC potential of upper electrode 104 during plasma processing to provide additional control over plasma processing parameters. The DC potential of upper electrode 104, in the example of FIG. 2, may be adjusted by employing external DC power source 224.
Unfortunately, the aforementioned plasma processing systems require employing an external RF power supply to change the voltage on an upper electrode or an external DC power supply to change the DC potential on an upper electrode to attain additional control over plasma related parameters. The requirement of external power sources may be expensive to implement and add undesirable operational costs for device manufacturers.