Patent Application
20060240680
The invention relates generally to semiconductor processing equipment. In particular, the invention relates to a platform to which multiple processing chambers are attached.
Much of modern commercial semiconductor processing is performed in single-wafer processing chambers attached to a central transfer chamber through respective vacuum slit valves. The transfer chamber and much of the associated control and vacuum equipment is referred to as a platform, which can be combined with different types of processing chambers. Different processing chambers allowing sputtering, etching, chemical vapor deposition (CVD), and rapid thermal processing (RTP). The transfer chamber is held at a reduced pressure to prevent contamination and perhaps oxidation of the wafers between processing steps and to allow the processing chambers to always be held at reduced pressure, which for etching may be in the milliTorr range and for sputtering in the microTorr range. A robot arm within the transfer chamber can transfer wafers from a wafer cassette in a vacuum load lock to any of the processing chambers and can also transfer wafers between chambers for different processing steps.
Although multi-chamber platforms including a vacuum transfer chamber are very effective, they are large and relatively expensive. Further, they occupy large amounts of floor space in very expensive clean rooms. That is, they have a large foot print. Also, their size requires that the platform and its chambers be shipped separately with much of the plumbing and wiring disconnected. As a result, even if the system has been assembled and tested at the equipment factory, it needs to be disassembled for shipment and reassembled and retested at the wafer fabrication line. Accordingly, the lead time between ordering a system and putting it into production may be significantly long. Therefore, in some applications, may and simpler platforms may be useful.
Rapid thermal processing (RTP) is one application not greatly benefitting from a vacuum transfer chamber. In RTP, an array of high-intensity lamps can quickly heat a wafer to a high temperature, for example, 700° C. or even above 1250° C., to thermally activate a process such as annealing or oxidation. After a relatively short time at the elevated temperature, the lamps are turned off and the wafer quickly cools, thereby reducing the thermal budget. RTP is typically performed at atmospheric pressure or at a relatively relaxed vacuum, for example, in the Torr range. Tam et al. in U.S. Patent Application Publication 2003/0186554, incorporated herein by reference in its entirety, describe an RTP platform of the general sort available as the Vantage platform from Applied Materials, Inc. of Santa Clara, Calif. An RTP system 10 illustrated in the orthographic view of
The illustrated system 10 does not include a vacuum load lock for the cassettes and the RTP chambers 12, 14 are opened to the atmosphere of the clean room between wafer cycles. The RTP chambers 12, 14 conventionally used with this system are not vacuum pumped but operate at substantially atmospheric pressure. Processing gases are sufficiently pressurized to be forced into an exhaust line. This limitation simplifies the platform since there is no vacuum pump and the high-intensity lamps can operate at atmospheric pressure with minimal pressure differential across the lamp window. The system is small enough that the system mounted on the frame 16 may be shipped intact and quickly installed at the fab line adjacent the factory interface 26.
Tam et al. address the problem in an atmospheric factory interface of preventing contaminants in the clean room from flowing into the chamber during wafer transfer. They maintain a slightly positive pressure of an inert gas within the chamber when the slit valve is opened so that the inert gas flows into the factor interface rather than the atmosphere of the clean room flowing into the chamber.
A multi-chamber substrate processing platform includes a factory interface operating at atmospheric pressure for holding substrate cassettes and a plurality of processing chambers connected to the factory interface through respective valved slits. A robot can transfer substrates between the cassettes and the processing chambers. At least one of the processing chambers can operate at reduced pressures, for example, less than 200 Torr or be capable of vacuum pumping to remove processing gases, especially toxic gases.
The processing chamber may be configured for rapid thermal processing (RTP) including an array of incandescent lamps directing radiant energy through a window to the vacuum process chamber holding the substrate being thermally processed. A thermal transfer gas, for example, of helium is supplied into a lamp head cavity enclosing the array and is vacuum pumped to a reduced pressure, preferably approximating the pressure within the vacuum process chamber. A single vacuum pump can pump the lampheads of multiple RTP chambers.
The invention includes a multi-step process to be performed in an RTP chamber, especially one vented to atmosphere for substrate transfer, in which different steps are performed at different processing pressures and temperatures.
One aspect of the invention includes a manifold adjacent an RTP chamber for mixing oxygen and hydrogen that are metered in a gas panel and distributed to the manifold by separate gas lines.
A further aspect of the invention includes a gas sheet of inert gas that may be formed on the port between the factory interface and the slit valve, particularly when the slit valve is opened, to prevent the back flow of processing gas into the factory interface.
The platform of the general sort illustrated in
The RTP chambers 42, 44 may include features previously used only when the chamber was attached to a vacuum pumped transfer chamber. One embodiment of the reduced-pressure RTP chamber 42, 44, schematically illustrated in cross section in
The vacuum chamber 52 includes a main chamber body 71, which supports the window 60. O-rings 72, 73 seal the window 60 to the main chamber body 68 and the lamp body 64 when clamps 74 or other fixing means such as screws or bolts press them together. An annular channel 76 is formed in the main chamber body 71, in which is disposed a magnetic rotor 78, which can rotate about the central axis 62 in the annular channel 76. A magnetic stator 80 is driven by an unillustrated motor to rotate about the central axis 62 and is magnetically coupled through the main chamber body 71 to the magnetic rotor 78 to both support it in the vertical direction and to drive it to rotate about the central axis 62. The magnetic rotor 78 supports a tubular riser 81, which in turn supports an edge ring 82 having an annular lip 84 supporting at its tip the periphery of the wafer 56. A typical width of the lip 84 is about 4 mm. Thereby, the wafer 56 is rotated about the central axis 62, for example, at a speed of about 240 rpm. The tubular riser 81 is typically formed of silica while the edge ring 82 may be formed of silicon, silicon carbide, or silicon coated quartz. The inside of a bottom wall 86 of the main chamber body 71 underlying the wafer may be highly polished to form a black body cavity 88 below the wafer 56 for the thermal radiation emitted by the wafer 56 as the lamphead 58 radiantly heats it. An exemplary height of the black body cavity 71 is about 4.3 mm
Multiple pyrometers 90, for example, seven, are coupled by light pipes 92 disposed in holes 94 formed in the bottom wall 86 at different radial positions to receive radiation from different radial portions of the wafer 56 or edge ring 82 to measure the radial distribution of temperature or other thermal property as the edge ring 82 and supported wafer 56 rotate about the central axis 62. A power supply controller 96 receives the outputs of the pyrometers 90 and accordingly adjusts the power delivered to the incandescent lamps 66. The power is varied to control the heating rate and is further differentially supplied to the radial heating zones, for example, 13 zones across a 300 mm wafer, to improve the radial temperature distribution across the wafer 56.
A processing space 100 is formed between the window 60 and the top surface of the wafer 56, for example, having a thickness of 36 mm. A processing gas, such as a mixture of hydrogen and oxygen may be supplied from an oxygen source 102 and from a hydrogen source 104 respective mass flow controllers 106, 108 to a gas inlet 110 to the processing space 100. Oxygen and hydrogen are used for an oxidation process referred to as in situ steam generation. That is, oxygen and hydrogen react to form water vapor within a chamber held at reduced pressure of, for example, between 5 and 20 Torr. However, other processing gases may be used if the invention is applied to other production processes, such as ozone oxidation, nitridation, hydrogen annealing, and chemical vapor deposition. Typically, an inert gas such as argon is supplied from a source 112 through another mass flow controller 114 for use as a purge gas or a diluent. For gas flows which do not need to be metered, a restricted flow orifice and a valve may be substituted for a mass flow controller.
A vacuum pump 120 is connected through a valve 122 to a pump port 124 on the side of the processing space 100 to exhaust the processing gas and reaction by products and to pump the processing space 100 to a sub-atmospheric pressure. In the case of toxic or flammable gases, the pump 120 should be remote from the system 40 of
A thermal transfer gas, such as helium, is supplied from a gas source 130 through a passive restricted flow orifice 131, for example, passing 50 sccm of helium, which then passes through a valve 132 and past a pressure release vent 133 to a gas manifold 135 in back of the lamp holes 68. Both the valve 132 and the pressure release vent 133 are controlled by a gas controller 134, associated with the power supply controller 90, to regulate the absolute supply and the pressure of the helium being supplied to the gas manifold 135 of the lamphead 58. Bulbs 136 of the lamps 66 loosely fit within the lamp holes 68 and porous potting material fix the backs of the bulbs 136 to the tops of the lamp holes 68. The thermal transfer gas flows from the manifold 135 into the gaps between the lamp bulbs 136 and the sides of the lamp holes 68 to promote cooling of the lamps 46.
The common lamphead vacuum pump 46 is connected through a lamphead outlet 138 and the respective exhaust line 48, 50 to the volume surrounding the bulbs 136 within the sealed chamber of the lamphead body 64 to control the pressure at the backside of the window 60 and reduce the pressure differential across the window 60. A valve 139 can block the flow on the respective exhaust hose 48, 50 and a pressure relief vent 140 can regulate the pressure on the outlet 138 and accordingly within the lamphead 58. A manometer 141 or other pressure sensor connected to the main pump port 124 measures the pressure within the process space 100. The gas controller 134 receiving the pressure signal from the manometer 141 over unillustrated electrical line and controls the two valves 132, 139 and the two pressure relief vents 133, 140 over yet other unillustrated electrical lines to suitably control the lamphead pressure.
Ideally, the pressure of the helium on the back side of the window 60 in the lamphead approximately equals the pressure of the processing or purge gases or atmosphere in the processing space 100 on the front side of the window 60 during atmospheric wafer transfer, during pump down, during processing, and during purging. If necessary, the lamphead pressure may be raised above atmospheric pressure relying upon the pressure of the helium source 130. Pressure differentials of more than 5 Torr between the lamphead 58 and the processing space 100, that is, across the window 60, should be avoided. If both chambers 42, 44 are reduced-pressure chambers, only the single vacuum pump 46 may be connected to the respective chambers 42, 44 through respective outlet ports 138, and valves 139. The gas flow controller 141 controls the various mass flow controllers, valves, vents, and pumps over unillustrated electrical lines to control the flow of the gases and the back side and front side pressures during different phases of the processing cycle.
Cooling channels 142 are formed in the lamphead body 64 to convey cooling water supplied through an inlet 144 and exhausted through an outlet 146. The cooling channels 142 surround the lamp holes 68 and thereby cool the lamps 64 with the assistance of the thermal transfer gas. Helium is used as the thermal transfer gas to increase the thermal coupling at the reduced pressures used for some RTP processes. In contrast, for atmospheric processes, helium is not required as the thermal transfer gas and an atmospheric air ambient provides adequate thermal transfer within the lamphead 58.
Thus, the reduced-pressure RTP chambers 42, 44 require a new lamphead vacuum pump 46, new processing vacuum pumps 120, plumbing for the helium from the gas panel supplying the chamber, elements not required for an atmospheric RTP chamber.
Facility gas supply lines 152, 154, 156 illustrated in
Another drawback of the atmospheric factory interface 26 is that toxic or flammable gases used in the processing chamber may flow back into the factory interface 26 and from there directly into the clean room. However, the additional vacuum capability of the reduced-pressure chamber 42, 44 of
Tam et al. in the aforecited printed application disclose additional chamber purging in the presence of toxic processing gases. Another technique applicable to both atmospheric and reduced-pressure chambers creates an inert gas curtain at the chamber slit when the slit valve is opened. As illustrated in the orthographic view of
An inert gas such as argon supplied from the argon source 112 through another mass flow controller or valve and restricted flow orifice and is thus selectively supplied to a gas supply manifold 208 having an unillustrated gas inlet slit to the side of the port 202 beneath and outside of the wafer slit 206. A gas outlet slit 210 is formed in the side of the port 202 opposite and parallel to and longer than the gas inlet slit fed from the gas manifold 208. The gas outlet slit 210 extends across the entire width of the wafer slit 206 and farther. An unillustrated gas exhaust manifold receives the gas from the gas outlet slit 210 and feeds it to an exhaust port 212. A separate vacuum pump or the chamber pump 120 may pump the exhaust port 212. Alternatively, a strong purge pressure may be sufficient to exhaust the gas through an exhaust line. Just before the chamber slit valve is opened when a toxic or flammable processing gas has been used, the inert gas is supplied to the gas supply manifold 208 and the valve to the associated vacuum pump is opened to thereby form a curtain of inert gas flow across the face of the opened slit 206. Thereby, any toxic or inert gas back flowing from the processing chamber 200 towards the factory interface 26 is pumped out of the system away from the factory interface 26 to be neutralized or otherwise processed or vented according to well known procedures. Furthermore, the gas curtain largely prevents the atmosphere of the clean room and factory interface and from flowing into the opened RTP chamber 200, thereby reducing contaminants in the RTP processing space. When the slit valve is closed, the gas curtain can be turned off if desired. The wafer paddle and any supported wafer may pass through the gas curtain without interrupting its flow.
The factory interface 26 is schematically illustrated in the plan view of
The factory interface also includes a cooling chuck 228 accessible by both blades 222, 224. In one mode of operation, while a wafer 56 is being thermally processed in one of the chambers 42, 44, the cold blade 224 removes an unprocessed wafer from either of the cassettes 30. At the completion of thermal processing, the slit valve 220 is opened, the hot blade 222 removes the hot processed wafer 56 from the RTP chamber 42, 44 and the cold blade immediately places the unprocessed wafer 56 in the same RTP chamber. The slit valve 220 is then closed and the RTP chamber 42, 44 begins to process the new wafer 56. The hot blade 222 places the hot processed wafer onto the cooling chuck 228 and leaves it there a sufficient time to allow it to cool to a temperature low enough for the cassettes 30, which are typically made of plastic. The cold blade 224 removes the cooled wafer 56 from the cooling chuck 228 and places it into one of the cassettes 30 and then removes an unprocessed wafer 56 from one of the cassettes 30. The process may alternate between the two RTP chambers 42, 44 with the use of a single robot and single cooling chuck.
Although a two-chamber system has found great commercial success, the inventive system may include more than two chambers served by a common factory interface.
The invention thus allows the simple atmospheric factory interface to be used for reduced pressure RTP, such as the in situ steam generation. In another example of radical oxidation processes, ozone may be used as the oxidizing gas. For safety reasons, ozone should be maintained at a pressure of less than 20 milliTorr. Other processes involving reaction of radicals typically require low pressures to increase the lifetimes of the radicals. The invention also permits the use of toxic processing gases such as NH3 and NO2 since the chamber may be pumped out and backfilled with N2 before the slit valve is opened. The invention also allows a high-temperature hydrogen anneal. The use of the inventive chambers with a toxic or flammable processing gas may include a near atmospheric process with the processing gas followed by a vacuum pump down to remove the deleterious gas from the processing chamber prior to opening it to the atmospheric factory interface.
High temperature processes are facilitated by modifying the chamber 44 of
Other processes enabled by the reduced-pressure chamber include low-temperature oxidation, plasma-assisted oxidation, forming gas anneals, chemical vapor deposition as well as others. The reduced-pressure chamber also enables a multi-step process, such as that generally illustrated in the timing diagram of
The two-chamber system of the prior art of
The invention thus allows a significant increase in the capability of a small and simple system with small increases in the complexity and size of the system.
