Patent Application
20090206281
This invention relates to the generation and delivery of vapor to vapor-receiving devices within high vacuum chambers. It also relates to delivery of ionizable vapor to high voltage ion sources that provide ion beams for ion implantation in the manufacture of semi-conductor devices and materials. It has particular relevance to systems and methods for vaporizing and ionizing materials that form molecular ions containing multiple atoms of a species of interest.
In industry it is frequently desired to deliver highly toxic, unstable material in vapor form to devices or substrate materials within a high vacuum system. It is necessary to periodically service such devices for cleaning or replacement of parts and to refill or replace the vapor sources and perform maintenance service. Each instance of refilling or service requires disengagement and re-engagement of vacuum seals and performance of re-qualification tests to ensure safety.
A particularly important example of such vapor delivery, having many stringent requirements, is the handling of doping materials for production of semiconductor devices. In this case it is necessary to produce vapor streams at accurately controlled flow from highly toxic solid materials that have low vapor pressure at room temperature. This requires careful heating of the solids to produce sublimation, and careful handling of the vapors because of risks of disassociation, unwanted condensation in the flow path and reaction of the vapors if brought in contact with other substances. Provisions to ensure personnel safety are also required. Improved systems for such vapor delivery are needed.
In particular there is need for improved vapor delivery for ion beam implantation systems in which the vapors ionized in an ion source produce an ion beam which is accelerated, mass-analyzed, and transported to a target substrate. With such ionization systems, it is especially desired to meet all requirements while prolonging the uptime, i.e. the time between required servicing. An advantageous way of doing this is by providing in situ cleaning of components of the system using highly reactive agents, but this introduces further safety concerns.
There is also need for safe and reliable vapor delivery systems that enable the same equipment to be employed with a number of different source materials that have differing vaporization temperatures.
There is further a need for a way to progress efficiently and safely from delivery of feed material obtained from a vendor to connection to a vapor receiving system of a vaporizer charged with the feed material. It is preferable that this be done in a standardized manner, to ensure familiarity to personnel.
Among the situations having all of the foregoing needs is the case of providing flows of decaborane and octadecaborane vapor, and vapor of carboranes, to an ion source at flows suitable to perform ion beam implantation to produce boron implants.
The needs also arise, more generally, in providing vapor flows of large molecules for semiconductor manufacturing. Examples include vapor flows: of large molecules for n-type doping, e.g. of arsenic and phosphorus; of large molecules of carbon for co-implanting processes in which the carbon inhibits diffusion of an implanted doping species, or getters (traps) impurities, or amorphizes crystal lattice of the substrate; of large molecules of carbon or other molecules for so-called “stress engineering” of crystal structure (e.g., to apply crystal compression for PMOS transistors, or crystal tension for NMOS transistors); and of large molecules for other purposes including reduction of the thermal budget and unwanted diffusion during annealing steps in semiconductor manufacture.
These needs apply to implementations employing ion beam implantation, and, where applicable, also to large molecule deposition of boron and other species for atomic layer deposition or producing other types of layers or deposits. Techniques for this may employ: plasma immersion, including PLAD (plasma doping), PPLAD (pulsed plasma doping) and PI3 (plasma immersion ion implantation); atomic layer deposition (ALD); or chemical vapor deposition (CVD), for example.
The needs just described and the inventive aspects now to be described apply importantly to the manufacture of high density semiconductor devices at shallow depth in semiconductor substrates, including CMOS and NMOS transistors and memory ICs, in the manufacture of computer chips, computer memory, flat panel displays, photovoltaic devices, and other products.
Other procedures in industry involving the generation and delivery of vapors or process gases to a vapor or gas consuming device can also benefit from features presented here.
According to one aspect of invention, a flow interface device is provided in the form of a thermally conductive valve block which defines at least one vapor passage, the passage associated with at least first and second vapor transfer interfaces, one interface comprising a vapor inlet located to receive vapor from a vaporizer of solid feed material and communicating with an inlet portion of the passage, and the other interface comprising a vapor outlet for delivery of vapor from an outlet portion of the passage to a vapor-receiving device, the valve block having at least one vapor valve and constructed to heat the passage and deliver vapor from the vaporizer to the vapor-receiving device.
Implementations of this aspect may have one or more of the following features:
A vapor valve is a flow control valve for regulating the flow of vapor to a vapor-receiving device in the form of an ion source.
A vapor valve system enables vapor flow to an ion source of vapor entering through the vapor inlet and another flow to the ion source.
A flow enabled is flow of vapor from another vapor inlet defined by the valve block.
A flow enabled is flow to the ion source of a reactive cleaning gas.
Valves provided in the valve block comprise a first valve system enabling vapor flow to the ion source of vapor entering through a vapor inlet, and enabling flow to the ion source of vapor from another vapor inlet defined by the valve block, and a selector valve system enabling flow of vapor from a vapor inlet defined by the valve block, or, alternatively, closing all vapor flow and permitting flow to the ion source of a reactive cleaning gas.
At least two vapor inlets are defined by the valve block and located to receive vapor from respective vaporizers, the two vapor inlets associated with respective inlet passage portions, flows through the inlet passage portions being enabled by the first valve system, the inlet passage portions merging following the first valve system into a common passage portion, and the second valve system is arranged to selectively enable flow through the common passage portion to the vapor-receiving device, or, alternatively, flow of the reactive cleaning gas to the vapor-receiving device.
A further valve comprises a flow control valve associated with the common passage portion for regulating flow of vapor to the vapor-receiving device.
A valve of the valve system comprises a spool valve acting as a selector to permit only one of the flows at a time.
The valve block is associated with a heater controlled to maintain the temperature of the valve block higher than that of a vaporizer from which it receives vapor.
The valve block defines a mounting region constructed to receive and support a vaporizer.
Thermal insulation insulates the valve block from a vaporizer to define respective separate thermal control regions to enable maintenance of valve block temperature higher than that of the vaporizer.
A connector is constructed and arranged so that mounting motion of a vaporizer with respect to the valve block causes the connector to mate with a matching connector of the vaporizer, for connecting the vaporizer electrically to a heating control system.
The valve block defines a receptacle having support surfaces for receiving a support projection of a vaporizer to thereby support the vaporizer during vaporizer heating and vapor transfer.
The support projection is a lateral projection defining a lateral vapor flow passage, the projection having a peripheral side surface and an end surface, and peripheral and end thermal insulation portions are provided to enable thermal isolation of the valve block from the projection of the vaporizer.
The receptacle of the valve block is constructed to receive the support projection of the vaporizer by linear sliding motion of the projection, the flow interface device mounting an electrical connector that is constructed, with mounting motion of a vaporizer relative to the valve block, to slideably mate with a matching electrical connector of the vaporizer for connecting the vaporizer electrically to a control and heating system.
The electrical connector includes a pneumatic connector for supplying controllable compressed air to the vaporizer for selectively actuating a valve of the vaporizer.
The vapor valve is a flow control valve, the interface device being associated with a power supply and heating system for receiving sensed temperature signal from a vaporizer and for applying electric heating current to the vaporizer to cause the vaporizer to heat sufficiently to produce vapor of the solid feed material of pressure greater than that required by the vapor-receiving device, and in the range that enables the flow control valve to regulate vapor flow to the ion source.
The flow interface device is combined with a vaporizer, the vaporizer containing solid feed material capable of producing ionizable vapor.
The vapor-receiving device in the form of an ion source is constructed to produce ions for use in semiconductor manufacture.
The flow interface device is combined with an ion beam implanter in which the vapor-receiving device comprises a high voltage ion source capable of ionizing vapor to produce a beam of ions for ion implantation.
Solid feed material vaporized by the vaporizer comprises a cluster compound capable of producing vapor for the production of cluster ions.
The solid feed material comprises a cluster boron compound.
The compound comprises a borane or a carborane.
The cluster compound comprises B10H14, B18H22, C2B10H12 or C4B18H22.
The cluster compound comprises a cluster carbon compound.
The cluster compound comprises C14H14, C16H10, C16H12, C16H20, C18H14 or C18H38.
The cluster compound comprises a compound for N-Type doping.
The compound comprises an arsenic, phosphorus or antimony cluster compound.
The compound comprises an arsenic or phosphorus compound capable of forming ions of the form AnHx+ or AnRHx+, where n and x are integers with n greater than 4 and x greater than or equal to 0, and A is either As or P and R is a molecule not containing phosphorus or arsenic and which is not injurious to the implantation process.
The compound comprises a phosphorus compound selected from the group consisting of phosphanes, organophosphanes and phosphides.
The compound is P7H7.
The compound comprises an antimony compound that comprises a trimethylstibine.
The compound comprises Sb(CH3)C3.
The flow interface device and vaporizer are provided in combination with an ion beam implanter in which the vapor-receiving device comprises a high voltage ion source capable of ionizing vapor produced from the solid feed material for ion implantation.
A vapor-receiving-device is in the form of a high voltage ion source and the flow-interface device is mounted for support upon an electrical insulator.
The insulator is an insulator bushing that also supports the ion source to which the vapors are delivered.
The flow interface device is in combination with an ion beam implanter in which the vapor-receiving device comprises a high voltage ion source capable of ionizing the vapor to produce a beam of ions for ion implantation.
The flow interface device includes a gas purge system for removing vapor from the vapor inlet passage of the valve block prior to disconnecting the vaporizer from the valve block.
The valve block defines a delivery passage for a process gas.
The flow interface device is constructed so that a process gas is selectively directed through a passage through which reactive cleaning gas is at other times directed.
The valve block includes a delivery extension defining at least two flow paths to the vapor-receiving device, at least one of which is constructed to convey vapor from solid feed material and another is constructed to deliver a process gas or a reactive cleaning gas.
The flow control valve is a throttle type valve.
The valve system permits only one of the vapor flows at a time.
The valve system comprises a spool valve.
The flow interface device, for use with vaporizers containing the same feed material, comprises a valve system that permits flow from at least two vaporizers simultaneously. In some cases the valve system is constructed for a second mode of action in which the valve system permits only one of the vapor flows at a time.
According to another aspect of invention, a flow interface device for an ion source is constructed for use as the ion source for an ion beam implanter, the interface device being in the form of a thermally conductive valve block which defines at least one vapor passage, the passage associated with at least first and second vapor transfer interfaces, one interface comprising a vapor inlet located to receive vapor from a vaporizer and communicating with an inlet portion of the passage, and the other interface comprising a vapor outlet for delivery of vapor from an outlet portion of the passage to the ion source, the valve block constructed to heat the passage and deliver vapor from the vaporizer to the ion source, a flow control valve associated with the passage for regulating the flow of vapor to the ion source, and a valve system that enables vapor flow to the ion source of vapor entering through the inlet and another enables flow to the ion source.
Implementations of this aspect may employ one or more of the following features.
The flow interface device is associated with a power supply and control system for causing the vaporizer to heat sufficiently to produce vapor of the solid feed material of pressure greater than that required by the ion source, and in the range controllable by the flow control valve.
The flow control valve is a butter-fly type valve.
Another flow enabled is flow of vapor from another vapor inlet defined by the valve block.
Another flow enabled is flow to the ion source of a reactive cleaning gas.
The flow interface device includes at least two valve systems in the valve block that enable flow, a first valve system enabling vapor flow to the ion source of vapor entering through the vapor inlet, and enabling another flow to the ion source of vapor from another vapor inlet defined by the valve block, and a selector valve system enabling flow of vapor from a vapor inlet defined by the valve block, or, alternatively, closing all vapor flow and enabling flow to the ion source of a reactive cleaning gas.
The flow interface has vapor inlet passages associated with at least two vapor inlets located to receive vapor from respective vaporizers, controlled by a first valve system, following which inlet passage portions merge into a common passage, and the second valve system selectively controls flow through the common passage portion to the ion source, or alternatively flow of the reactive cleaning gas to the ion source, the flow control valve being associated with the common passage for regulating flow of vapor to the ion source.
A flow selection valve comprises a spool valve.
The valve block is associated with a heater controlled to maintain the temperature of the valve block higher than that of a vaporizer from which it receives vapor.
Another aspect of invention comprises the generation, delivery and utilization of vapor from solid material comprising solid feed material capable of forming ionizable vapor that comprises a cluster molecule.
Another aspect of invention comprises the generation, delivery and utilization of vapor from solid material comprising a cluster molecule.
Another aspect of invention comprises the generation, delivery and utilization of vapor from solid material comprising C14H14, C16H10, C16H12, C16H20, C18H14 or C18H38.
Another aspect of invention comprises the generation, delivery and utilization of vapor from solid material comprising N-Type doping.
Another aspect of invention comprises the generation, delivery and utilization of vapor from solid material comprising an arsenic, phosphorus or antimony cluster compound.
Another aspect of invention comprises the generation, delivery and utilization of vapor from solid material comprising arsenic or phosphorus compound capable of forming ions of the form AnHx+ or AnRHx+ where n and x are integers with n greater than 4 and x greater than or equal to 0, and A is either As or P and R is a molecule not containing phosphorus or arsenic and which is not injurious to an ion implantation process.
Another aspect of invention comprises the generation, delivery and utilization of vapor from solid material comprising a phosphorus compound selected from the group consisting of phosphanes, organophosphanes and phosphides.
Another aspect of invention comprises the generation, delivery and utilization of vapor from solid material comprising P7H7.
Another aspect of invention comprises the generation, delivery and utilization of vapor from solid material comprising an antimony compound that comprises a trimethylstibine.
Another aspect of invention comprises the generation, delivery and utilization of vapor from solid material comprising Sb(CH3)C3.
Another aspect of invention comprises a method of treating a semiconductor device or material comprising using the systems of any of the foregoing description to produce cluster ions, and using the ions in the treatment, especially a treatment comprising ion implantation and especially ion beam implantation.
According to another aspect of invention, a method of producing vapor employs the device or combination of any of the preceding disclosure.
Another aspect of invention comprises a system for producing vapor along a flow path from a group of vaporizers at mounting stations of a vapor delivery system comprising subgroups of vaporizers, one of the subgroups containing at least two vaporizers containing the same solid feed material and another group containing at least one vaporizer containing a different solid feed material, at least one vaporizer of the group containing material comprising a cluster molecule, the system including a control system enabling the subgroup of vaporizers containing the same solid feed material to simultaneously provide vapor along the path and preventing simultaneous flow through the path of vapor from the other subgroup.
In one implementation the system is an electro-mechanical control system.
In one implementation the system includes a vapor flow control that includes two variable conductance flow devices in series along the flow path, the down-stream device comprising a throttle valve and the up-stream device enabling adjustment of pressure of the vapor reaching the throttle valve.
Another aspect of invention is a system for producing vapor along a flow path from a group of vaporizers at mounting stations of a vapor delivery system comprising at least two vaporizers containing the same solid feed material of a cluster molecule wherein a control system is constructed to enable the two vaporizers to operate simultaneously.
In one implementation the system, and also useful with a single vaporizer, the system includes a vapor flow control that includes two variable conductance flow devices in series along the flow path, the down-stream device comprising a throttle valve and the up-stream control enabling adjustment of pressure of the vapor reaching the throttle valve.
Another aspect of invention is a method of producing ions for implantation comprising ionizing vapor received from any of the systems just described.
In one implementation the ions produced are formed into a beam for ion implantation.
The details of one or more implementations of the foregoing features are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Referring to
Vaporizer 14 is of canister type having a bottom section, which contains a charge of solid feed material to be vaporized, and a removable top member. The top member is associated with a vaporizer heater shown diagrammatically at 19. The interface system includes a heater control circuit 33 which controls power P14 to the vaporizer heater which produces vapor from the feed material. A vapor flow path 16 extends in the interface device 10 from the vaporizer via the interface I, through an adjacent stop valve 15, thence through portion 8 and extension 9. The extension 9 is sealed to the housing of vacuum chamber 20 at vacuum-tight seal 21.
A sealed disengageable connection is formed between extension 9 and vapor-receiving device 22 within the high vacuum chamber. This point of connection is referred to as interface II.
With this arrangement, ready removal and servicing of both the external vaporizer 14 and the vapor-receiving device 22 is made possible without disturbance of the seal 21 at the connection of the flow interface device 10 to the housing of high vacuum chamber 20. Despite repeated flow disconnection and reconnection at interface II for performing service on vapor-receiving device 22, interface II does not present a potential leak hazard to workers because of its location. To any extent that leak may occur, the leakage is confined within high vacuum chamber 20 and is removed by its vacuum pump and associated effluent treatment system 25.
In preferred implementations of the system, at interface II, the connection is made within the high vacuum chamber by installation movement of the vapor-receiving device. In the example of
Flow interface device 10′ is in the form of a thermally conductive block that defines a vapor flow passage. It includes a collar 6 constructed to mount the block upon housing flange 20F in vacuum tight manner. A neck member 7 joined and sealed to block 10′, defines an extension of the vapor passage. Neck member 7 protrudes from the collar 6, through chamber flange 20F, into the high vacuum chamber 20′.
A spring-loaded connector seal member 5, e.g. of Teflon, has a tubular stem 5A closely fitted inside a cylindrical portion of the passage in neck member 7. The stem 5A extends upwardly into the installation path of vapor receiving device 22′, terminating in a top head 5B that defines a horizontal upwardly directed sealing surface. Head 5B has a corner cam surface 5C, disposed to be engaged by a corresponding cam surface 22C of device 22.
In
For removal of the vapor-receiving device 22′, the motions are reversed.
It will be understood by those skilled that other docking configurations can be employed, one example being engaging surfaces that are axially-aligned, e.g. surfaces of conical or pyramidal connectors. In other cases, after the vacuum-receiving device has been seated, a reversible actuator mechanism may be activated to complete a sealed connection between the parts within the vacuum housing.
Referring again to
In preferred implementations, flow interface device 10 comprises a thermally conductive body, formed for instance of machined aluminum block-forming parts. When valves are installed, the thermally conductive block serves effectively as valve body for the valves. A vacuum-tight vapor path through the heated body extends from interface I to interface II. The body is in thermal contact with a heater shown diagrammatically at 11, controlled by circuit 13. Circuit 13 has temperature inputs T14 from vaporizer 14 and T10 from the conductive body of flow interface device 10. Circuit 13 is adapted to control heater 11 to maintain the conductive body at a controlled temperature, for instance, to a temperature above the temperature of the respective vaporizer 14, but below a safety temperature, e.g., a temperature below disassociation temperature of a respective material being vaporized.
The heaters of the system may be of various forms, for instance conventional electric cartridge or band heaters, and may be arranged in one or more than one heating zone. For instance, advantageously, there may be a heating zone 1 for heating the vaporizer to T1, heating zone 2 for heating the interface body 10 and heating zone 3 for the vapor-receiving device 22. The heating zones are comprised of respective heater elements and temperature sensors, that, in one arrangement, increase in temperature from T1 to T2 along the path from vaporizer to interface II in the vapor receiving device, i.e. T1<T2<T3 where all of these temperatures are limited to a temperature T4 below a safety limit for the material to be vaporized.
Referring to
Advantageously, only the top member of the vaporizer unit is electrically heated. Solid material within the canister body is heated to a major extent by heat transfer through the joint between the detachable top and bottom sections and through the side and bottom walls of the bottom section which are heated by conduction from the heater. In this manner it is ensured that the temperature T1 of the vapor passage through the top member exceeds the temperature of the solid source material being sublimated.
As previously mentioned, placement of the heater in the detachable top closure section of a vaporizer-canister unit, whereas the charge of material to be vaporized at varying temperature is located in the bottom of the unit, might not appear to be good practice to those of ordinary skill. Thermal resistance of the interface between the detachable top and the bottom sections and the distance for the heat travel with associated thermal mass and slowness of response as well as heat loss to the exterior would appear undesirable. However, it is found that significant advantages are obtainable with this arrangement and what might seem to be inherent disadvantages are found avoidable or inconsequential in suitable implementations.
Thus the system ensures that vapors produced from the material encounter passages of increasing temperature while moving from the point of generation through valve V1 and to and through flow interface device 10. Similarly the part of the vapor-receiving device 22 that precedes the point of vapor utilization may define another heating zone adapted to be held at a temperature incrementally above that of the flow interface device 10.
Referring now to the plan view of
Individual flow path segments 16A and 16B extend partially through the length of portion 8 of the thermally conductive body of device 10A, respectively, from the mounting stations 12A and 12B. Paths 16A and 16B merge at junction X. A common vapor flow path segment 16C extends through the remainder of portion 8A and through extension 9 of interface device 10A to interface II where the vapor is delivered to vapor-receiving device 22. Stop valves 15A and 15B in device 10 are associated with the individual flow paths 16A and 16B. As indicated by link 17, valves 15A and 15B are interlocked. This is done, in the case shown, in a manner that ensures each valve must be closed before the other can be opened. This prevents simultaneous flows from paths 16A and 16B.
The flow interface device 10A thus provides ready access for removal and servicing of two vaporizers without disturbance of the sealed connection 21 of interface device 10A with the high vacuum chamber 20; it permits one vaporizer to be serviced or filled, while another, containing the same source material, produces vapor and permits vaporizers of two different species to be installed for selective use. By providing, at Interface I, thermal isolation of the vaporizer-canister from the remainder of the system, an inactive unit is enabled to cool so that any charge of material remaining in the unit does not substantially degrade.
Referring to
The flow control device 24 in common path C may comprise a throttle valve such as a butterfly valve that varies the vapor conductance of the passage. The control system may be constructed to operate in accordance with the protocol described in the patent application WO 2005/060602 published 7 Jul. 2005, entitled “Controlling the Flow of Vapors Sublimated from Solids”, the entire contents of which are hereby incorporated by reference.
In particular, the operation of such a throttle valve to deliver a desired flow depends upon there being a desired pressure of vapor in the region immediately upstream of the throttle valve. It is to be noted that at a given vaporizer temperature, the amount of the vapor generated and hence its pressure, is dependent upon the amount of the charge of feed material that remains in position to be heated to vaporization temperature. To compensate for progressive depletion of the original charge of material, the control system senses delivered pressure and increases the temperature of the vaporizing chamber accordingly. It is advantageous for the vaporizer system to be capable of achieving the increased temperature without great delay. This is important during operation and is especially important during start-up when the operating pressure and heating system is being tuned to achieve desired performance of the overall system.
The single flow control device 24, being situated in the common path segment 16C, is capable of selectively controlling flows from two or more vaporizers at respective mounting stations. By interlocks, including the selected position of linked valves 15A and 15B as described in
Referring to
If implemented according to
The reactive cleaning gas source 40 may be a container of reactive gas or a means for generating a reactive gas from a gaseous or solid feed material.
The interface device 10C of
Referring to
A reactive gas source in the specific form of a reactive cleaning gas generator 40A has a feed line 41 for a material, for instance a gaseous fluoride compound capable of being disassociated. The cleaning gas generator is constructed to provide disassociating conditions by which a reactive cleaning gas is generated, for instance, fluorine or fluorine ions. Its output is introduced to feed passage 42 in interface device 10D. As in
The system of
Referring to
The schematic of
The vapor system of
The system shown schematically in
All connections to the canisters are formed at Interface I. This includes electrical power connections for powering the vaporizer heaters, signal connectors for signaling temperature and other parameters of vaporizer status and compressed air, for controlling the pneumatic valve within each vaporizer canister.
Like
For enabling flow from the vaporizers, the strict controls needed to prevent mixing of dangerous combinations of vapors can be subject to pre-established protocols, implemented by control logic in an electro-mechanical control system. Similarly, mechanical interlocking mechanisms may have provisions for altering modes of operation. In some cases, controls are established that absolutely prevent communication between vaporizers, or between selected vaporizers. They may on the other hand implement permission for simultaneous flow of some vaporizers. A case where this is appropriate and useful is where the vaporizers contain the same feed material. For example, a simultaneous flow may be employed when a charge in one vaporizer is nearing depletion and while it is desired for economic reasons to utilize the entire charge, it is also desired to commence use of a replacement vaporizer. Such strategy has advantage in ensuring a plentiful supply of vapor, while not pushing the heating limits of a nearly-spent vaporizer. Referring to
In the implementation shown in
As shown in
Incorporated in the valve block 130 are cartridge heaters and valves that perform the safety and flow heating and control functions of the heater and valves described with respect to the previous figures. A sheet metal enclosure 140 surrounds this delivery assembly, and has covers, including vaporizer cover 142, that can be opened for access. This enclosure is supported from the floor by feet comprising high voltage insulators. Thus the entire vapor delivery system is adapted to be maintained at the high voltage potential of the ion source.
It will be understood that numerous other physical arrangements are possible that still provide the actions described at one or the other sides of a mounting ring connected to the insulator and still out of the path of installation and removal of the ion source.
Referring to
The heater 19 of this vaporizer preferably comprises a set of cartridge heater elements fit into receptacles formed in the top member 14B. Importantly, this heater, located in the detachable top member is found to provide sufficient heat to vaporize the solids properly. By its location, it serves to maintain the valve of the top closure member at temperature higher than the temperature to which the solid material is heated. Advantageously, for this purpose, the body of valve V1 is comprised of thermally conductive aluminum and disposed in conductive heat transfer relationship with the heater, via the aluminum top member to maintain the vapor passage through the valve substantially at heater temperature.
In preferred implementations, there is only one controlled heating zone for the vaporizer. With these features in combination, it is found that the heater located in the top section of the vaporizer-canister can produce efficient vaporization of the remote charge in the lower section as the charge is consumed. The construction is found to have a sufficiently low thermal mass so that acceptably fast equilibration to a set temperature can occur. This permits proper operation and sufficiently rapid change in temperature setting as an operator adjusts parameters to initiate or tune the operation of the overall system.
In particular, the unit is found useful with pressure-based throttle valve vapor flow control 24, implemented e.g. with a butterfly valve, in which the vaporization temperature must be gradually increased as the charge of feed material is consumed to maintain the pressure upstream of the throttle valve, see
Furthermore, and very importantly, the positive temperature gradient from bottom to top of the vaporizer unit that is attainable with this heat transfer arrangement prevents condensation of the vapor and build-up of disadvantageous deposits in the vapor valve V1 (located at the transition from vertical to horizontal flow) and the vapor delivery passage (upward inlet passage and horizontal delivery passage). These features are strategically located close to the heater, with temperature dependably being higher than the temperature of the charge of material in the bottom of the remote vaporization cavity.
In more detail, the rising passage terminates at a horizontal valve seat. The horizontal vapor passage then extends from the valve. Top part 14B houses pneumatic bellows valve (V1 in
Cartridge heaters of suitable type may be employed in the top section 14B of the vaporizer and in the valve block flow interface device 10.
Suitable RTDs (resistive thermal detectors) are located at the bottom of the vaporizer-canister unit and elsewhere in the system. A conductive lead for signal from the bottom sensor extends to a connector at the interface with the top section 14B. This connector is laterally aligned with a mating connector of the top section by bringing the overall mounting devices of the unit into alignment with those of the bottom section, and movement of the aligned top section down to engage the bottom section engages the connector.
The top of the regulated temperature range for the RTD temperature sensor, controlled by the remote thermal control unit, in one example, may be set at 40 C for B10H14 and 120 C for B18H22, and, for one example, an over-temperature limit switch in the top of the vaporizer-canister unit may be set at 50 C for a B10H14 vaporizer-canister and 140 C for a B18H22 vaporizer-canister. Similar temperature settings are employed with other feed materials, the particular values being dependent upon the vaporizing properties of the chosen material
As previously indicated, separate thermal zones are established to prevent heat migration between the vaporizer canister and the vapor-receiving device, accomplished by introduction of a substantial thermal break. This prevents heat entering the vaporizer unit from the vapor-receiving device and interfering with the thermal control system of the vaporizer-canister unit. Also, because of presence of this thermal break, a mounted vaporizer-canister unit can cool relatively quickly after being de-energized and its outer thermal insulation removed, despite the vapor-receiving device to which it is mounted being hot and continuing operation at temperature with another attached vaporizer unit. Despite continued heated state of the flow interface device (valve block), workmen can soon handle a de-energized vaporizer-canister unit for removal and replacement. Alternatively, the cooled unit may be left in place while avoiding substantial thermal degradation of remaining charge of feed material that otherwise would occur due to heat from the interface device.
The system described is suitable for safe production of ion beams from large molecule feed materials, including boron containing compounds such as decaborane (B10H14) and octadecaborane (B18H22).
As described, the system of
A. Applications
In general, any material which can provide a flow at least in the 1 sccm range, at temperature between about 20 C and 150 C is a candidate material for use in the vaporizer units and with the vapor delivery system constructed according to principles described above.
The embodiments of vaporizer and vapor delivery system specifically described have been demonstrated to be particularly effective for providing flows of decaborane and octadecaborane vapor and the vapor of carboranes to an ion source at flows suitable to perform ion beam implantation, to implant boron which achieving a degree of amorphization.
The principles are applicable more generally to providing vapor flows of large molecules of many descriptions in a host of applications in semiconductor manufacturing. Examples include vapor flows: of large molecules for n-type doping, e.g. of arsenic and phosphorus; of large molecules of carbon for co-implanting processes in which the carbon inhibits diffusion of an implanted doping species, or getters (traps) impurities, or amorphizes crystal lattice of the substrate; of large molecules of carbon or other molecules for so-called “stress engineering” of crystal structure (e.g., to apply crystal compression for PMOS transistors, or crystal tension for NMOS transistors); and of large molecules for other purposes including reduction of the thermal budget and unwanted diffusion during annealing steps in semiconductor manufacture. The principles have been demonstrated in the laboratory to apply to boranes, carbon clusters, carboranes, trimethylstibines, i.e., Sb(CH3)C3, arsenic and phosphorus materials, and other materials.
The principles apply to implementations in ion beam implantation systems, and to systems for large molecule deposition of boron and other species for atomic layer deposition or producing other types of layers or deposits, for instance by plasma immersion, including PLAD (plasma doping), PPLAD (pulsed plasma doping) and PI3 (plasma immersion ion implantation), Atomic Layer Deposition (ALD) or Chemical Vapor Deposition (CVD), for example.
B. Feed Materials for Cluster Ion Sources, in General
It is useful for efficiently implanting molecular ions which contain multiple atoms of an electrical dopant species such as the elements B, P, As, Sb, and In which lie in the periodic table on either side of the group IV elements of C, Si, Ge, and Sn, and also for efficiently implanting molecular ions which contain multiple atoms of elements such as C, Si, or Ge useful for modifying a semiconductor substrate to effectuate, for example, amorphization, dopant diffusion control, stress engineering, or defect gettering. Such molecular ions can be useful for fabricating integrated circuits with critical dimensions of 60 nm and less. Hereinafter, such ions will be collectively referred to as “cluster” ions.
The chemical composition of a singly charged cluster ion has the general form
MmDnRxHy+ (1)
where M is an atom such as C, Si, or Ge useful for material modification of the substrate; D is a doping atom such as B, P, As, Sb, or In (from group III or IV of the Periodic Table) for implanting a charge carrier in to the substrate; R is a radical, ligand, or molecule; and H is a hydrogen atom. Generally, R or H are present simply as part of the complete chemical structure needed to produce or form a stable ion and are not specifically required for the implant process. In general H is not significantly detrimental to the implant process. The same should be true for R. For example it would be undesirable for R to contain a metallic atom such as Fe, or an atom such as Br. In the above equation m, n, x, and y are all integers greater than or equal to zero, with the sum of m and n greater than or equal to two, i.e, m+n≧2. Of particular interest in ion implantation are cluster ions with a high M and/or D atomic multiplicity, i.e those with m+n≧4, because of their improved efficiency for low energy, high dose implants.
Examples of cluster ions that can be used for material modification are those derived from adjoining benzene rings such as C7Hy+, C14Hy+, C16Hy+, and C18Hy+. Examples of cluster ions that can be used for doping are:
One of ordinary skill in the art can appreciate the possibility of using cluster ions other than those listed in the examples above, including: ions containing Si and Ge for material modification, ions with different amounts and different isotopes of dopant atoms, and ions with different isomeric structures. Doubly charged cluster ions are also generally formed with a much smaller yield in which case they are not as useful for high dose, low energy implantation.
For example, the method of cluster implantation and cluster ion sources with respect to decaborane has been described by Horsky et al. in U.S. Pat. No. 6,452,338 and U.S. Pat. No. 6,686,595 hereby incorporated by reference. The use of B18Hx+ in making PMOS devices is disclosed in Horsky et al. in pending U.S. patent application Ser. No. 10/251,491, published as U.S. Patent Application No. U.S. 2004/0002202 A1, hereby incorporated by reference.
C. Large Carborane Molecules
The nature of these boron-containing materials and their ions is explained in the literature, see for instance Vasyukova, N. I. [A. N. Neseyanov Institute of Heteroorganic Compounds, Academy of Sciences of the USSR, Moscow. Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1337-1340, June, 1985. Original article submitted Mar. 13, 1984. Plenum Publishing Corporation.]
The cluster molecule o-C2B10H12 has been successfully vaporized and ionized, see
D. Large Molecules of Carbon
In general, any hydrocarbon with a chemical formula of the form CnHy, where n≧4 and y≧0 will increase the effective carbon dose rate into the silicon, and provide varying degrees of amorphization, in all cases being more beneficial than a monomer carbon implant. Flouranthane, C16H10, vaporizes at a temperature of 100 C, well suited to use in an electron impact ion source. Its vaporization temperature is similar to that of B18H22. A beam current of 0.5 mA enables the equivalent of 8 mA of carbon to be implanted on the wafer, at very low energy (about 1 keV per carbon atom). Ion beam currents of >1 mA are easily realized. Other carbon cluster materials are useful. For example, the following hydrocarbons may potentially be used:
E. Large Molecules for N-Type Doping
As, P, and Sb are N-type dopants, i.e., “donors”.
For Sb, trimethystibines are good large molecule candidate feed materials, for instance Sb(CH3)C3.
For As and P, the ions are of the form AnHx+ or AnRHx+ where n and x are integers with n greater than 4 and x greater than or equal to 0, and A is either As or P, and R is a molecule not containing phosphorus or arsenic, which is not injurious to the implantation process.
The compounds phosphanes, organophosphanes and phosphides are seen to be potential sources for cluster phosphorus molecules and the subsequent ions for N-type doping. Examples include (1) phosphane, e.g., Heptaphosphane, P7H3, and Cyclopentaphosphane, P5H5, (2) Organophosphane, e.g., Tetra-tertbutylhexaphosphane, tBu4P6, Pentamethylheptaphosphane, Me5P7, (3) Phosphide, e.g., Polyphosphides: Ba3P14, Sr3P14 or Monophosphides: Li3P7, Na3P7, K3P7, Rb3P7, Cs3P7.
Cyclic phosphanes appear to be the most effective source of dopant clusters favorable to ionization and subsequent implantation with Heptaphosphane, P2H3, appearing to have the greatest potential of providing a simple cluster source for ion beam implantation.
Phosphorus-containing species and supporting synthesis techniques are theorized to allow direct substitution of the phosphorus atoms with arsenic to form similar arsenic species, due to similarity in the outer shell electron configuration and similar chemistry reactivity that same group elements exhibit. Molecular prediction software also indicates the similarity in substituting arsenic for phosphorus. The predicted molecular structure for As7H3 is nearly identical to P7H3 with differences being limited to the individual atomic radii of phosphorus and arsenic. Synthesis Pathways for P7H3 and As7H3 are analogous and interchangeable. In addition, since both Si and H are not injurious to devices formed on silicon wafers, the compounds As7(SiH3)3 and As5(SiH3)5 are very attractive, and are predicted to be stable compounds.
Furthermore, materials in the form of AnRHx may be formulated in a manner to allow selective removal of the phosphorus or arsenic containing portion independently of the remaining molecular structure, R. This characteristic may be employed to increase the level of safe transportation in that the complex feed material is less volatile, hence less susceptible to emissions than the pure component. The residual material may be left in the transport container and “recharged” in normal cycle operations. Furthermore, the R molecular portion may be removed prior to the targeted dopant containing species, discarded or recycled to provide an increased margin of safety during transportation. Synthesis pathways to develop numerous organometallic compounds are well documented and known within the art.
In addition to the 6-membered ring in (P/As)6, 5-membered rings have been obtained with R═Me, Et, Pr, Ph, CF3, SiH3, GeH3 and 4-membered rings occur with R═CF3, Ph.” (N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, Butterworth and Heinemann Ltd, 1984, pgs 637-697). Thus, carbonyl groups are directly interchangeable with silicon hydrides, as well known in the art. In addition, a silicon phosphide has also been identified: Si12P5. This material is seen to be extremely useful in ultra-shallow junction formation of Halos and S/D Extensions, and also for Poly Gate doping. The mass of Si12P5 is about 491 amu. Thus, extremely shallow implants can be per formed with this compound. In addition, since Si is routinely used for pre-amorphization prior to conducting the N-type drain extension implant, the Si12P5 implant would be self-amorphizing. It is likely there would not be deleterious end-of-range defects created by this implant, since the silicon would have about the same range as the P atoms, keeping damage very shallow. Such defects can be annealed out very effectively, since they tend to diffuse to the surface, when they annihilate.
A number of implementations of the inventive aspects have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other implementations are within the scope of the following claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US07/71010 | 6/12/2007 | WO | 00 | 11/14/2008 |
| Number | Date | Country | |
|---|---|---|---|
| 60804555 | Jun 2006 | US | |
| 60860631 | Nov 2006 | US |
