Patent Application
20110226739
A plasma processing apparatus generates a plasma in a process chamber for treating a workpiece supported by a platen in the process chamber. A plasma processing apparatus may include, but not be limited to, doping systems, etching systems, and deposition systems. The plasma is generally a quasi-neutral collection of ions (usually having a positive charge) and electrons (having a negative charge). The plasma has an electric field of about 0 volts per centimeter in the bulk of the plasma. In some plasma processing apparatus, ions from the plasma are attracted towards a workpiece. In a plasma doping apparatus, ions may be attracted with sufficient energy to be implanted into the physical structure of the workpiece, e.g., a semiconductor substrate in one instance.
Turning to
The plasma doping apparatus 100 may further includes a gas pressure controller 116 that is electrically connected to the mass flow controller 106, the pressure gauge 108, and the exhaust valve 114. The gas pressure controller 116 may be configured to maintain a desired pressure in the process chamber 102 by controlling either the exhaust conductance with the exhaust valve 114 or a process gas flow rate with the mass flow controller 106 in a feedback loop that is responsive to the pressure gauge 108.
The process chamber 102 may have a chamber top 118 that includes a first section 120 formed of a dielectric material that extends in a generally horizontal direction. The chamber top 118 also includes a second section 122 formed of a dielectric material that extends a height from the first section 120 in a generally vertical direction. The chamber top 118 further includes a lid 124 formed of an electrically and thermally conductive material that extends across the second section 122 in a horizontal direction.
The plasma doping apparatus further includes a source 101 configured to generate a plasma 140 within the process chamber 102. The source 101 may include a RF source 150 such as a power supply to supply RF power to either one or both of the planar antenna 126 and the helical antenna 146 to generate the plasma 140. The RF source 150 may be coupled to the antennas 126, 146 by an impedance matching network 152 that matches the output impedance of the RF source 150 to the impedance of the RF antennas 126, 146 in order to maximize the power transferred from the RF source 350 to the RF antennas 126, 146.
The plasma doping apparatus may also include a bias power supply 190 electrically coupled to the platen 134. The plasma doping system may further include a controller 156 and a user interface system 158. The controller 156 can be or include a general-purpose computer or network of general-purpose computers that may be programmed to perform desired input/output functions. The controller 156 may also include communication devices, data storage devices, and software. The user interface system 158 may include devices such as touch screens, keyboards, user pointing devices, displays, printers, etc. to allow a user to input commands and/or data and/or to monitor the plasma doping apparatus via the controller 156. A shield ring 194 may be disposed around the platen 134 to improve the uniformity of implanted ion distribution near the edge of the workpiece 138. One or more Faraday sensors such as Faraday cup 199 may also be positioned in the shield ring 194 to sense ion beam current.
In operation, the gas source 104 supplies a primary dopant gas containing a desired dopant for implantation into the workpiece 138. The source 101 is configured to generate the plasma 140 within the process chamber 102. The source 101 may be controlled by the controller 156. To generate the plasma 140, the RF source 150 resonates RF currents in at least one of the RF antennas 126, 146 to produce an oscillating magnetic field. The oscillating magnetic field induces RF currents into the process chamber 102. The RF currents in the process chamber 102 excite and ionize the primary dopant gas to generate the plasma 140.
The bias power supply 190 provides a pulsed platen signal having a pulse ON and OFF periods to bias the platen 134 and hence the workpiece 138 to accelerate ions 109 from the plasma 140 towards the workpiece 138. The ions 109 may be positively charged ions and hence the pulse ON periods of the pulsed platen signal may be negative voltage pulses with respect to the process chamber 102 to attract the positively charged ions. The frequency of the pulsed platen signal and/or the duty cycle of the pulses may be selected to provide a desired dose rate. The amplitude of the pulsed platen signal may be selected to provide a desired energy.
Particles may be generated on the sidewalls of the process chamber 102 during plasma processing. These particles may be of any composition and may include, but are not limited to, silicon, carbon, silicon oxide and aluminum oxide. These particles also may be caused by sputtering of the workpiece or the tool itself. In some embodiments, a liner 193 may be introduced which protects the sidewalls of the process chamber 102. This liner 193 typically extends the height of the process chamber 102 sidewalls, reaching first section 120, and along the floor or the process chamber 102. However, particles may still accumulate on the side surfaces 197 of the liner 193. Over time, these particles may be subject to external forces that may be greater than the adhesive strength holding them to the side surface 197 of the liner 193. These external forces may include, but are not limited to, electrostatic forces, shock waves from sudden changes in pressure, and gravitational forces due to continued deposition on the sidewalls or liner 193.
When the adhesive strength of these particles is overcome, they free themselves from the sidewalls (or liner 193) and may become suspended in the plasma (if active), or fall due to the gravitational force. In some cases, these particles fall atop the workpiece 138, thereby affecting the functionality of at least a portion of the workpiece 138 and possibly resulting in lower device yields. In other cases, these particles may fall to the floor of the process chamber 102. However, even in this case, the electrostatic forces caused by the plasma may attract the particles upward from the floor of the process chamber 102. This force causes the particles to become suspended again in the volume within the chamber and increases the possibility that the particles will ultimately land atop the workpiece 138, thereby affecting the processing of the workpiece 138 and the device yield.
One way to minimize the yield decreases of the workpieces 138 is to clean the sidewalls and floor of the process chamber 102 more regularly. Another method requires regular cleaning or replacement of the liner 193. However, these steps result in additional downtime for the plasma doping apparatus 100, which lowers the effective yield of the apparatus.
Therefore, there exists a need for an apparatus that will reduce the possibility of particles landing atop the workpiece and the possibility of particles lowering the device yield.
According to a first aspect of the disclosure, an apparatus for use within a process chamber is provided. The apparatus includes a liner adapted to cover the sidewalls of the process chamber, with apertures corresponding to various inlets and outlets in the process chamber. In addition, the liner has one or more apertures on its bottom surface, which allow particles to pass through the liner. The liner is designed to be shorter in height than the sidewalls of the process chamber. This allows the liner to be placed within the chamber such that its bottom surface is above the floor of the process chamber. This minimizes the possibility of particles that have fallen onto the process chamber floor becoming re-suspended at a later time. In some embodiments, the apertures in the bottom surface have a width that is less than the thickness of the bottom surface.
According to a second aspect of the disclosure, a bottom liner is provided. This liner has one or more apertures and can be used in conjunction with a conventional liner and in a process chamber without a liner. The bottom liner is held above the bottom of the process chamber, such as by one or more spacers.
For a better understanding of the present disclosure, reference is made to the accompanying drawings, in which like elements are referenced with like numerals, and in which:
As described above, traditional plasma processing apparatus may generate particles that adhere to the sidewalls of the process chamber 102. As described above, a liner 193 may be used to eliminate adhesion to sidewalls of the process chamber 102, however adhesion to the liner 193 may still present yield issues due to particle buildup and subsequent separation.
Currently, as shown in
According to one embodiment of the present disclosure, a liner is defined as shown in
The spacers 210 are preferably constructed of an electrically conductive material. The spacers 210 may be aluminum bushings, or another structure, and there may be one or more spacers 210 used to support the liner 200. The height of the spacer may be between 0.25″ and 1.00″ inches tall. In some embodiments, it is preferable that the bottom surface 201 of the liner 200 is no higher than the platen 134.
Referring to
As described above, the bottom surface 201 of the liner 200 is preferably annular in shape, where the inner diameter may be greater than or equal to the diameter of the platen 134, so that the liner 200 fits around the platen 134 in the process chamber 102. In some embodiments, the inner diameter is between 15.5″ and 16.0″ inches. The outer diameter of the annular bottom surface 201 may be made to be roughly the same as the diameter of the process chamber 102, so that the side surfaces 202 of the liner 200 are in close proximity to the sidewalls of the process chamber 102 during normal operation, such as less than 0.125″ away. The outer diameter may be between 21.5″ and 22.0″ inches.
In addition to being elevated from the floor of the process chamber 102, the liner 200 also has apertures 309 on its bottom surface 201. These apertures 309 allow particles to fall through the bottom surface 201 and become trapped in the volume 310 defined between the floor of the process chamber 102 and the bottom surface 202 of the liner 200. In some embodiments, the spacers 210 are affixed to the bottom surface 201 of the liner 200, such as by fasteners 207 that pass through one or more fastener holes 307. In one embodiment, the fasteners 207 are screws.
The apertures 309 can be configured in a variety of ways. For example,
Once particles falls into the volume 310 between the bottom surface 201 of the liner 200 and the floor of the process chamber 102, it is beneficial that these particles remain trapped within this volume. The constant changes in pressure in the process chamber 102 may cause the particles to be agitated and float upward from the floor of the process chamber 102. In some embodiments, the apertures are designed to minimize the possibility of particles floating upward through the apertures. In some embodiments, this is achieved by controlling the ratio of the thickness of the bottom surface 201 of the liner 200 to the width of the aperture 309, also referred to as the aspect ratio of the aperture. For example, in some embodiments, the width of the apertures 309 is about 0.125 inches, while the thickness of the bottom surface of the liner is 0.25 inches. In this case, the ratio of surface thickness to aperture width is 2. In other embodiments, ratios of greater than 1 are suitable. In a two dimensional aperture 309, the characteristic dimension is typically the smaller dimension. For example, the characteristic dimension of the aperture 309 may be defined as its diameter (in the case of circular apertures 309) or its width (in the case of slotted apertures 309).
By creating an aspect ratio greater than 1, the possibility of a particle floating upward and passing through the aperture is reduced. This reduces the number of particles that fall atop the workpiece 138, and consequently improve the device yield of the apparatus.
In another embodiment, the liner comprises only a bottom surface.
In other embodiments, liner 700 can be used without a pre-existing liner 193. In this embodiment, the liner 700 is fastened to the floor of the process chamber 102 using fasteners through spacers 210.
In the embodiments employing liner 700, a volume 310 is still created between the floor of the process chamber 102 and the bottom surface of the liner 700. In addition, the bottom surface of liner 700 comprises a plurality of apertures, as described above with respect to liner 200. Thus, particles pass through the apertures in liner 700 and become trapped in the volume 310. In some embodiments, the apertures comprise over 40% of the area of the liner 700. In some embodiments, the aspect ratio of the apertures is greater than 1.
Furthermore, the liner 700 has dimensions similar to the bottom surface of liner 200. In other words, it is annular in shape with an inner diameter of between about 15.5″ and 16.0″ and an outer diameter of between about 21.5″ and 22.0″. The apertures of liner 700 may be of any pattern, such as those shown in
The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Further, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure as described herein.
