The invention relates to plasma processing systems, and particularly plasma enhanced chemical vapor deposition systems (PECVD), however features of the invention could also be used in other types of plasma processing systems.
PECVD systems are advantageously used, for example, in depositing thin films for flat panel displays, photovoltaic cells or modules, or OLEDs. For example, silicon or silicon compounds such as Si, SiOx, or SiN based films are formed using process gases (e.g., silane, dopants, hydrogen, etc.) that are excited to form a plasma.
Such an arrangement can be used, for example, to deposit silicon compounds on glass substrates, for example, substrates having dimensions of 1100-1300 mm or 1.4 m2, by way of example. As shown, an inter-electrode gap IEG is provided as a space between the two electrodes, while the plasma gap PG is provided between the top of the substrate 4 and the bottom of the upper electrode 2. By way of example, a standard gap size can be approximately 30 mm, however very small gaps of below 10 mm can be desirable. As should be apparent, the plasma gap PG is effectively the IEG minus the thickness of the substrate 4.
Such systems can be in the form of single reactor or single chamber systems, but also can be part of larger systems having multiple reactors which simultaneously perform CVD processes on other substrates in parallel. In addition, such chambers or reactors can be provided in in-line or cluster configurations. Two types of reactor arrangements are also commonly known, including a one-reactor-single-wall chamber type, and a box (or boxes)-in-box arrangement. In the one-reactor-single-wall chamber type, the walls of the reactor or chamber form the vacuum or reduced pressure volume within which the processing takes place, and an ambient or approximately atmospheric pressure surrounds the outside of the reactor. In the box-in-box arrangement, the reactor box provides a processing region that is located within the outer walls of another chamber to form a separate outer enclosure, and the outer enclosure can be maintained at a reduced pressure. In addition, plural reactors can be provided in the outer chamber for batch processing of plural substrates. See, for example, U.S. Pat. Nos. 4,989,543 and 5,693,238.
In such arrangements, it is constantly an objective to provide high quality, consistent and cost effective performance from a standpoint of producing Si and Si compound layers or films having a low occurrence of defects, high throughput and deposition rates, and efficient, cost effective performance from a standpoint of cost of the equipment and cost of operation and/or maintenance. To achieve high deposition rates, high RF power and/or high RF frequencies are used. However, this also intensifies ion bombardment onto the substrate, and thus, could produce defects. In addition, a high deposition rate can require a high concentration of Si atoms in the plasma, for example, with a higher working gas pressure. High process pressures can be advantageous in reducing the intensity of ion bombardment, however particle generation can also be a problem as a result of undeposited Si particles. Particles or other impurities, defects or inhomogeneities can result in poor or unacceptable layers or films.
One variable which can be used to control or improve performance is the inter-electrode gap (IEG). By reducing the inter-electrode gap, for example, to the extent that the order of magnitude of the mean free path for SiHx-radical collisions and Poly-SiH2-molecule collisions become comparable to the gap size, agglomeration of Si atoms to form particles or grains can be avoided. However, there can be mechanical, electrical and other process constraints associated with reducing the gap, particularly when considering the size of the substrates being processed are often one square meter in size or larger. Thus, disadvantages or challenges can also be associated with reducing the IEG. Trade-offs associated with the desire to achieve a smaller gap and the challenges presented have resulted in PECVD systems with an IEG of less than 20 mm but greater than 10 mm.
One problem associated with reducing the gap (IEG) is that the equipment used in loading and unloading of the substrates must have sufficient space to operate. WO 2006/056091 discloses a reactor arrangement in which the reactor is separated horizontally into two parts to allow access by a loading fork. The loading forks insert the substrates into the reactors, lift pins rise to remove the substrates from the forks, and the loading forks are retracted. The lift pins are then retracted to deposit the substrate on a lower electrode for processing. In addition, the two parts of the reactor are moved together to close the processing space. However, such an arrangement can be undesirable for many reasons including the need to move heavy parts, which can be difficult particularly within a vacuum for a box-in-box type system. In addition, such an arrangement can be complicated and/or expensive due to the need to interface movable reactor parts with utilities such as process gas handling, heating/cooling connections, pumping, and RF/VHF power—while keeping the chamber secure from RF/VHF power leakage in the closed position.
An additional problem with prior art arrangements resides in the lift pins used in loading substrates as discussed above. In particular, such pins should be made small in cross-section so as to avoid or reduce any adverse impact on the lower electrode, in terms of the uniformity of electrical properties and/or thermal properties of the lower electrode. However, with the size of the pins kept small, they can wear or fail with repeated use. Lift pins can encounter greater frictional stress as a result of the vacuum environment, and the pins can be subjected to additional stresses as a result of exposure to heat and chemicals, which also can cause premature fatigue or wear. If the pins should become defective, it can lead to a crash or damage to the glass substrate, which is unacceptable. Thus, pins must be able to be replaced. Further, the replacement must be relatively simple and not consume substantial amounts of time, particularly given that a system (having multiple chambers or reactors) could have on the order of 480 lift pins, for example.
The invention provides advantageous arrangements which can be utilized in plasma processing equipment, particularly PECVD equipment. The features of the invention can be particularly advantageous for PECVD equipment used in making photovoltaic or solar cell components, however, features of the invention could also be used in other types of plasma processing equipment or equipment used for other products. The invention is also advantageous for processing large substrates, for example, one square meter or larger, with small gap sizes. For example, the arrangement can be advantageously used with an IEG of 3-10 mm, and a PG of 2-8 mm and more preferably a PG of 3-7 mm. Alternately, for example, the IEG can be 3-16 mm, with a PG of 2-14 mm, and more preferably with a PG of 3-13 mm. However, features of the invention could also be used with different substrate and gap sizes. The invention is also advantageous in a fixed gap system, in which the gap spacing is fixed when the chamber is in the assembled and closed position. However, features of the invention could also be used in a variable gap system in which the gap spacing can be changed or adjusted by an adjusting expedient (e.g., an actuator). In addition, the invention is advantageous for deposition systems such as PECVD systems, however, the invention could also be used with other types of systems such as etching, or cleaning systems, for example.
In accordance with one of the features of a preferred example, a reactor is provided which is vertically separable into two parts (upper and lower), to thereby ease loading and unloading of substrates therein when the parts are separated, while also allowing for a small gap between the upper and lower electrodes when the two parts are brought together and substrates are processed. Such an arrangement is especially advantageous in processing large substrates (e.g., one square meter or larger) while processing with a small inter-electrode gap. With this arrangement, an upper portion of the reactor is moved relative to the lower portion (or vice versa) to allow for loading and unloading of the substrate onto lift pins of the reactor. Once the substrate is loaded, the lift pins can be lowered to set the substrate on the lower electrode, and the two parts of the reactor can be brought together or closed so that processing can proceed with a small inter-electrode gap and a small plasma gap.
In accordance with one preferred example, the upper portion of the reactor is movable while the lower portion is fixed. Thus, the upper portion can be easily moved to provide additional space for loading/unloading of substrates. In accordance with another feature, the same vertical movement or actuation for moving the upper portion of the reactor is also used to move the lift pins. This arrangement ensures coordinated operation, and moreover, can reduce the number of required actuators.
In a particularly preferred example, a system is provided which includes plural reactors stacked one above the other, with each of the stacked reactors coupled to a common actuator which opens or moves the upper portion of each of the reactors at the same time (or at least partially overlapping with the time) the lift pins are raised. Alternately, the lower portions of the reactors could be moved, or a combined movement of both parts could be used, however. A loading fork assembly having plural loading forks thereon (for the respective plural reactors) can then move substrates into the reactors, and the lift pins remove the substrates from the loading forks. The reactors are then closed while the lift pins are lowered.
In accordance with another advantageous aspect of the invention, a mounting arrangement is provided for lift pins, which allows the pins to be easily removed and replaced in a simple, efficient manner which is not time consuming. As a result, the lift pins can be regularly maintained and replaced so that the risk of a glass crash is minimized or reduced, and downtime as a result of maintenance is also reduced.
Additional features and advantages will become apparent from the description herein.
As will be apparent from the description herein, the present invention includes a number of advantageous features. It is to be understood that systems can be constructed which might incorporate certain features but not others, and that variations and modifications can be implemented. The invention is therefore not limited to the particular examples described.
A better appreciation of the invention will become apparent from the description herein, particularly when considered in conjunction with the drawings in which:
A better appreciation of the invention will be apparent from the following detailed description, in which like reference numbers are used for the same or similar parts throughout the different views. It is to be understood that the illustrated embodiments are provided as examples, because variations are possible as would be understood by those skilled in the art. In addition, although the examples are provided as a combination of elements, it is to be understood that the invention could be practiced with a subset of such elements, and therefore, features of the illustrated examples should not be considered as required or essential unless so described.
Although not illustrated in
In the arrangement described above, the lower portion of the reactor moves. However, it also would be possible to have both the upper and lower portions movable. In addition, as discussed below, in accordance with another preferred example, the upper portion of the reactor is movable while the lower portion is fixed. To provide movement, a suitable coupling (such as a rod or bar) is connected to a suitable actuator mechanism, such as a pneumatic or hydraulic actuators, an electric motor, a spindle/gear or rack/pinion, or other actuators can be used for opening and closing of the reactor. Where plural reactors are provided, individual actuators could be utilized for each reactor. However, in accordance with a particularly preferred form, a common actuator is provided for simultaneous movement of the reactor parts relative to each other for a plurality of reactors at the same time. An example of such an arrangement is discussed further hereinafter.
In accordance with the
For loading a substrate, the upper portion of the reactor 50 is in the raised position, and the lift pins 61 are in the raised position. The loading fork is inserted to position a substrate just above the lift pins 61. The lift pins are then raised to remove the substrate from the loading forks, and the loading forks are removed. The lift pins are then lowered to place the substrate on the lower electrode. It is to be understood that different combinations of movement could be used to allow the substrates to be received by the lift pins. For example, as an alternative to the lift pins lifting the substrates from the loading forks, the loading forks could be lowered to place the substrates on raised lift pins. Presently, it is preferred to use the lift pins to lift the substrates from the loading forks. As discussed later, in a preferred form, plural reactors are provided in a stacked arrangement. In this case, a loading system can have plural loading forks to simultaneously load plural substrates into respective plural reactors.
As shown, an upper electrode 51 is associated with the upper reactor box 50 and moves therewith. In the illustrated preferred example, the upper electrode 51 is in the form of a shower head such that process gases exit through a plurality of apertures associated with upper electrode as illustrated by the arrows beneath the upper electrode 51. One or more gas inlet tubes or conduits 52 are provided to supply one or more process gases. The gas supply tube or conduit 52 is preferably flexible to accommodate movement of the upper reactor portion 50. By way of example, a space 53 is provided between the top of the upper electrode 51 and the top inner surface of the upper reactor box portion 50, which allows for pressure equalization to thereby provide a more uniform gas flow from the shower head electrode 51. It is to be understood that, where plural process gases are provided, they can be mixed upstream of the gas inlet tube 52 and supplied by way of the single gas inlet tube 52, or alternately, gases can be provided through plural inlet tubes 52 and mixed within the region 53. It is to be understood that alternate shower head or gas injection configurations could also be used, however, the illustrated arrangement is presently preferred.
A power conductor is provided as shown at 54 so that the upper electrode is a powered electrode in the illustrated example. In the preferred form, the conductor is for RF/VHF power. Due to the requirements to supply a high frequency power, in the illustrated arrangement, a hard or rigid conductor 54 is illustrated, and the movement of the upper reactor box portion 50 is accommodated by one or more articulations as illustrated at 54a, 54b. Alternately, the articulations can be replaced with a flexible or semi-flexible connector, such as a flat ribbon or a flexible plate connector. As should be apparent, although the connectors 52, 54 for gas and electrical power are coupled to the upper reactor box, the gas source and power source themselves are not, and thus can be at a fixed location without needing to move with the upper reactor box. This allows the upper reactor box 50 to be light weight, making movement of same more desirable, particularly where a common actuator moves plural upper reactor box portions as discussed later. The power supply (not shown) can be connected to a flange 54c which is at a fixed location, and at which the power supply is coupled to the conductor 54, and movement of the upper reactor box 50 is accommodated by the articulations 54a, 54b of the conductor 54. The gas supply source (not shown) can also be at a fixed location, and movement of the upper reactor box is accommodated by the flexibility of the flexible tube 52 in the illustrated example.
The upper reactor box 50 includes a top 50a as well as depending side walls 50b which form the side walls enclosing the reactor box in the closed position. In addition, a flange portion 50c can be provided to ensure an adequate seal with the lower portion 60. Suitable seals or interlocking expedients can be associated with the flange 50c and/or the lower portion of the reactor box 60 to ensure a good seal in the closed position. However, as discussed further hereinafter, particularly where the arrangement is in a box-in-box system, it is not necessary to have a completely gas tight seal, because any gases that might escape from the reactor into the outer chamber can be exhausted from the outer chamber which encloses a plurality of such reactors. Another flange is illustrated at 50d, and this flange provides for coupling of the upper reactor box portion to an actuator assembly for moving the upper box portion 50 as discussed hereinafter.
The lower assembly includes lift pins 61 which extend through the lower electrode 62, so that in the open position, the lift pins can be raised to hold a substrate 70.
In the illustrated example, the upper electrode can be powered while the lower electrode 62 is grounded, however alternate arrangements can be provided, for example, in which a lower electrode is powered while the upper electrode is grounded, or alternately, it is possible to supply power to both upper and lower electrodes.
As also shown, exhaust passageways 64 are provided to exhaust gases from the reactor, with the passageways 64 connected to a vacuum pump downstream of the exhaust passageway 64 (not shown). In addition, one or more temperature control expedients are associated with the lower assembly 60. In the illustrated arrangement, at least one channel is provided for the flow of a temperature control medium, such as a liquid coolant, as shown at 65. A thermostat and suitable controllers can also be provided. The temperature control medium flowing through passage 65 can provide for heating and/or cooling. In addition, as an alternative, or in combination with the use of a cooling medium, electrical heating can be provided to supply heat. When both a temperature control medium and electrical heating are provided, the electrical heating can provide tuning (e.g., to improve uniformity and/or more precise control) of the temperature control provided by the cooling medium passing through passageway 65. However, the use of a liquid transfer medium alone is suitable for most or many applications.
Processing temperatures can range, for example, from 50° C. to 300° C. Various temperature control mediums or fluids can be utilized, depending upon the processing temperature. For example, water can be suitable for processes lower than 100° C., while a water-glycol-mixture can be utilized for temperatures up to approximately 160° C. For higher temperatures, oils can be used. Because the bottom or lower portion of the reactor 60, 62 is temperature controlled, but the top is not, the temperature of the upper portion 50 of the reactor can oscillate. Cooling of the reactor top and the dampening of temperature oscillation of the top can be provided by thermally coupling the bottom of a reactor to an adjacent top of another reactor positioned underneath, as will now be discussed with reference to
As discussed earlier, is not necessary for the reactors 11, 12 to be completely gas tight, because any gases which might escape from the reactors enters the volume 15 of the chamber 10. The volume 15 of the chamber 10 can be kept at the same pressure as the pressure in the reactor volumes 13, 14 in the preferred arrangement, so as to minimize the exchange of gases between the volumes. A suitable gas can be pumped through the inlet 20 of the chamber 10, however, as an alternative, only an exhaust pump can be utilized for the exhaust outlet 18. By way of example, an inert gas can be provided in the outer chamber 10, or alternately, one or more gases which are also used as a process gas could be used. Separate pumping and pressure control can be provided for the volumes 13, 14 as compared with the volume 15, or if desired, a common pressure control or exhaust pumping can be utilized. Separate pressure control systems can be desirable, for example, to allow different operations such as for flushing of plasma products or contaminants from the reactors 11, 12 when processing is not being performed. Thus, it is to be understood that alternate pumping arrangements could be used, for example, with one pump used for both the reactors and outer chamber, separate pumps for the outer chamber and the reactors, or with one pump connected only the reactors.
As discussed earlier in connection with
In accordance with an additional advantageous feature of the arrangement of
Although a locking member or locking assembly 126 is provided for each row of lift pins in the illustrated example of
Features of the present invention are particularly advantageous for processing of large substrates, for example, substrates having a size of one square meter or larger. Thus, the substrate supporting surface 124 will have a surface area of one square meter or larger. As should be apparent, to ensure good support of such substrates, a large number of lift pins can be provided. In the arrangement shown, 16 lift pins are provided for one reactor. Thus, where a system includes multiple reactors stacked upon one another, the total number of lift pins in system can become very large. Accordingly, there is a need to be able to efficiently remove and replace the lift pins. Although 16 lift pins are shown in
The assembly 126 further includes an aperture having a first aperture portion 140 and a second aperture portion 141 which is contiguous and extends from the first aperture portion 140. As shown, in the locked position (
The lift pin 125 is coupled to bushing or alignment member 145, which serves to hold and align the lift pin for movement between extended and retracted positions. As discussed earlier, the lift pins are raised to remove a substrate from loading forks, and then are retracted to deposit the substrate on the substrate support or lower electrode 122 (which also serves as the floor of the reactor). As shown in
A spring 146 can be coupled to the lift pin to provide return movement of the lift pin from the raised to the retracted position.
In the unlocked position (
As should be apparent, variations and modifications of the disclosed embodiments are possible. It is to be understood that the invention can be practiced in forms other than described in the examples disclosed herein.
This application claims priority application to provisional applications 61/660,910, filed Jun. 18, 2012 and 61/663,122, filed Jun. 22, 2012, the entirety of which are incorporated herein by reference.
Number | Date | Country | |
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61660910 | Jun 2012 | US | |
61663122 | Jun 2012 | US |