JP2006510196A - Recrystallization of semiconductor surface film by high energy cluster irradiation and semiconductor doping method - Google Patents

Abstract

Process method by gas cluster ion beam 128 for recrystallizing damaged semiconductor film 308 and / or for activating dopants in semiconductor film 308 by reduced dopant diffusion and formed by the method Semiconductor devices. This method is effective for electrical activation of dopant species after shallow dopant ion implantation, for example, to restore crystallinity and / or to form shallow junctions. In one embodiment of the method, the dopant atoms incorporated into the gas cluster produce a shallow doping of the semiconductor 302, resulting in simultaneous electrical activation of the dopant atoms and recrystallization of the semiconductor.

Description

  The present invention relates generally to doping and / or recrystallization of a semiconductor surface, and more particularly to recrystallization of a semiconductor surface by high energy gas cluster ion irradiation and self-annealing by high energy gas cluster ion irradiation or The present invention relates to impurity doping of a semiconductor surface accompanied by self-activation.

  Effective features of semiconductor materials such as silicon, germanium, and gallium arsenide, and other semiconductors are contingent on the purity and crystal structure of the semiconductor material. Dopant atoms that are incorporated into semiconductor materials for the purpose of changing electrical properties, forming electronic junctions, and others are often introduced into semiconductor surfaces by conventional ion implantation.

  During this conventional ion implantation process, ionized dopant atoms are physically deposited into the crystalline semiconductor material, but in doing so, the semiconductor crystal lattice is damaged by the implantation process. Is well known. In order for the implanted dopant atoms to become electrically active within the semiconductor and restore the desired crystallinity of the semiconductor, the crystal lattice structure of the semiconductor must be restored, and the implanted dopant atoms are replaced by substitution. It must occupy the lattice sites in the restored crystal lattice. Processes typically used to provide crystal lattice restoration and electrical activation of implanted dopant atoms include elevated temperature thermal annealing, pulsed laser beam annealing, and pulsed electron beam annealing.

  For some semiconductor products, an important requirement for introducing dopants into the semiconductor surface is that the maximum depth at which the dopant penetrates after the completion of the lattice recrystallization and dopant activation process is very shallow. In that case it must be kept below only a few hundred angstroms.

  Using conventional ultra-low energy ion implantation, such shallow introduction of dopants can also be achieved by using ultra-low implantation energy of less than about 1000 eV, or even less than 200 eV.

  However, when such conventional low energy implants are recrystallized or activated by well-known prior art, diffusion of shallow dopant atoms redistributes the dopant atoms deeper, thus forming a deeper junction than desired. Result.

  Surface etching, cleaning and smoothing using gas cluster ion beams (GCIB) are well known in the art (see, for example, US Pat. No. 5,814,194 to Deguchi et al.). For the purposes of this discussion, a gas cluster is a nano-sized collection of substances that are gaseous under conditions of standard temperature and pressure. Such clusters can consist of loose or more tightly aggregated bonds with up to one thousand, two thousand to several thousand molecules. The clusters can be ionized by electron bombardment or other means, allowing them to be formed into a controllable energy directed beam.

  Each such ion typically has a positive charge of q · e, where e is the magnitude of the charge of the electron and q is about 1 to 5,6 representing the charge state of the cluster ion. Is an integer). Larger size clusters are often the most effective due to their ability to carry significant energy per cluster ion, but still retain moderate energy in molecular units. The clusters are destroyed by impact and each individual molecule carries only a small portion of the total energy of the cluster. As a result, the impact of large cluster impacts is enormous, but is limited to very shallow surface regions. This makes ion clusters effective for a variety of surface modification processes that do not tend to cause the deeper subsurface damage characteristic of conventional ion beam processes.

  Means for generating and accelerating such GCIB are described in the cited reference (US Pat. No. 5,814,194). Currently available ion cluster sources produce cluster ions with a broad distribution of size N (where N is the number of molecules in each cluster and throughout this discussion a monoatomic gas such as argon In this case, the atom of a monoatomic gas is referred to as either an atom or a molecule, and the ionized atom of such a monoatomic gas is referred to as either an ionized atom, a molecular ion, or simply a monomer ion).

  Accordingly, it is an object of the present invention to provide recrystallization of a semiconductor surface by high energy gas cluster ion irradiation.

  Another object of the present invention is to provide for the implantation of shallowly implanted dopant atoms in a semiconductor material having reduced dopant atom redistribution by activation induced diffusion utilizing high energy gas cluster ions for activation. It is to bring activation.

  A further object of the present invention is to introduce dopant atoms into the ultra-shallow subsurface region of semiconductor material by irradiation with high energy gas cluster ions containing dopant atoms or containing dopant atoms and inert atoms. It is in.

  Yet another object of the present invention is to provide an ultra-shallow junction by introducing dopant atoms into the ultra-shallow subsurface region of a semiconductor material, and to provide a high energy gas containing dopant atoms or containing dopant atoms and inert atoms. It is to bring about activation of a dopant and recrystallization of a semiconductor surface by irradiation of cluster ions.

  The above and further and other objects and advantages of the present invention are achieved by the embodiments of the present invention described below.

When a high energy gas cluster bombards the surface of a solid target, the penetration of the cluster atoms into the target surface is typically due to the penetration depth being determined by the low energy of the individual constituent atoms. It is extremely shallow. The gas clusters dissociate upon impact, and individual gas atoms can freely recoil and escape from the target surface. The total energy of the high energy clusters before impact, except for the energy carried away by the individual gas atoms that escape, accumulates in the impact zone on the target surface. The size of the target impact zone depends on the energy of the cluster, but is almost the size of the cross section of the impacting cluster and is small, for example, in the case of an ion cluster of 1000 atoms, the diameter is about 30 angstroms. . As a result of the accumulation of the majority of the total energy carried by the cluster to a small impact zone on the target, severe thermal transients occur within the target material at the impact site. Thermal transients dissipate deep into the target by conduction as energy is lost from the impact zone. The duration of the thermal transient is determined by the conductivity of the target material, but is typically less than ^10-6 seconds.

  In the vicinity of the cluster impact site, the volume of the target surface can instantaneously reach a temperature of hundreds to thousands of Kelvin degrees. As an example, the impact of a cluster carrying a total energy of 10 keV is estimated to be capable of generating an instantaneous temperature rise of about 2000 Kelvin degrees over a hemispherical zone extending approximately 100 angstroms down from the silicon surface.

  Following the onset of elevated temperature transients in the target volume under the impact site of the high energy cluster, the affected zone cools from below the surface to the surface. If a damaged crystalline lattice state, such as that caused by ion implantation of dopant atoms, is present in the layer close to the target surface, the transient temperature state created by the impact of high energy clusters is It can be used to cause recovery. In order for this to occur, sufficient thermal transients must be generated in the volume from the damaged area to the underlying undamaged silicon crystal. During dissipation of transient temperature conditions, cooling should proceed from the undamaged crystal lattice below the damaged layer to the surface through the damaged layer. When the crystal lattice is restored within the damaged region, the dopant atoms are incorporated into the lattice sites and electrical activation occurs.

  Gases such as, but not limited to, argon, xenon, oxygen, nitrogen, carbon dioxide, etc. should be used to form high energy gas clusters to create the effects of crystal lattice restoration and dopant activation described above. Is possible. In addition, if a gas containing a suitable semiconductor dopant atom, such as boron, is added to or used as the gas to form the high energy gas cluster, the impact of the high energy gas cluster will be the dopant atom. Can be stored in the semiconductor lattice, and at the same time, any damage of the lattice can be restored.

  For some semiconductor products, an important requirement for introducing dopants into the semiconductor surface is that the maximum depth at which the dopant penetrates after the completion of the lattice recrystallization and dopant activation process is very shallow. In that case it must be kept below only a few hundred angstroms. The depth of effect produced by the bombardment of high energy gas clusters can be controlled by controlling the energy of the impinging gas cluster ion beam. As a result, the high energy gas cluster method for semiconductor annealing and dopant activation described above, or the high energy gas cluster method for dopant introduction and self-aligning, can be applied to the dopants that are introduced and activated. It is possible to promote the realization of the final ultra shallow depth.

  In order that the invention and other and further objects of the invention may be better understood, a detailed description will be given below with reference to the accompanying drawings.

FIG. 1 schematically shows the basic elements of a typical configuration of a GCIB process apparatus 100 of a known type in the prior art, but adapted for carrying out the present invention, in which a vacuum vessel 102 has three connections. It can be described that it is divided into a source chamber 104, an ionization / acceleration chamber 106, and a process chamber 108. The three chambers are each evacuated to an appropriate operating pressure by vacuum pump systems 146a, 146b and 146c. Condensable source gas 112 (eg, argon or N ₂ ) stored in gas storage cylinder 111 enters residence chamber 116 under pressure via gas meter plug 113 and gas supply line 114 and was properly shaped. It is ejected through a nozzle 110 into a vacuum, which is a substantially lower pressure. As a result, a supersonic gas jet 118 is generated. The cooling that occurs as a result of jet expansion condenses a portion of the gas jet 118 into clusters of several to thousands of weakly bonded atoms or molecules each. The gas skimmer opening 120 partially separates the cluster jet and gas molecules that are not condensed into the cluster jet, and such higher pressures may be undesirable in downstream regions (e.g., ionizer 122, high Minimize pressure at voltage electrode 126 and process chamber 108). Suitable as condensable source gases 112 include, but are not necessarily limited to, argon, nitrogen, carbon dioxide, oxygen and other gases.

  After the supersonic gas jet 118 containing the gas clusters is formed, the clusters are ionized in the ionizer 122. The ionizer 122 is typically an electron impact ionizer that generates thermal electrons from one or more incandescent filaments 124 and accelerates and directs the electrons to collide with gas clusters in the gas jet 118. It passes through this ionizer 122. Electron bombardment causes electrons to be ejected from the cluster, which causes some of the cluster to carry positive ions. A suitably biased high voltage electrode set 126 extracts cluster ions from the ionizer to form a gas cluster ion beam (GCIB), which is then converted to the desired energy (typically 1 keV to tens of keV). ) And focus to form GCIB128. The filament power supply 136 supplies a filament voltage Vf for heating the ionizer filament 124. The anode power supply 134 accelerates the thermoelectrons emitted from the filament 124 and irradiates them with a cluster including the gas jet 118 to supply an anode voltage VA for generating ions. The extraction power supply 138 biases the high voltage electrode to extract ions from the ionization region of the ionizer 122 and supplies an extraction voltage VE for forming the GCIB 128. The accelerator power supply 140 biases the high voltage electrode with respect to the ionizer 122 and provides an acceleration voltage VAcc to ultimately bring the total GCIB acceleration energy equal to VAcc electron volts (eV). One or more lens power supplies (142 and 144 are illustrated) can be provided to focus the GCIB 128 by biasing the high voltage electrodes with a focusing voltage (eg, VL1 and VL2).

  A workpiece 152, which may be a semiconductor wafer or other workpiece to be processed by the GCIB process, is held on a workpiece holder 150 located in the path of the GCIB 128. Because most applications contemplate processing large workpieces with spatially uniform results, the scanning system scans GCIB128 uniformly over a large area to produce spatially uniform results. It is desirable to do. Two pairs of orthogonally oriented electrostatic scan plates 130 and 132 can be used to generate a raster or other scan pattern over the desired process area. When a beam scan is performed, GCIB 128 is converted to a scan GCIB 148 that scans the entire surface of workpiece 152.

  FIG. 2 schematically illustrates the basic elements of a prior art mechanically scanned GCIB process apparatus 200 adapted for use in the present invention, the apparatus being a mechanically scanned workpiece 152. And a conventional Faraday cup for beam measurement and a conventional thermionic neutralizer. The GCIB configuration is similar to that shown in FIG. 1, but with an optional second storage stored in a gas storage cylinder 221 connected to a residence chamber 116 via a gas supply line 114 with a gas meter plug 223. Two source gases 222 (typically different from the source gas 112) are additionally supplied. This arrangement allows for a controllable choice between two different source gases 112 and 222 for use in forming a gas cluster, or a controllable formation of a mixture of two source gases. Further, in the mechanical scanning type GCIB process apparatus 200 of FIG. 2, the GCIB 128 is fixed (not scanned electrostatically as in the case of the GCIB process apparatus 100), and the workpiece 152 is mechanically connected via the GCIB 128. Scanned and the effect of GCIB 128 is distributed across the surface of workpiece 152.

  X-scan actuator 202 provides linear motion of workpiece holder 150 in the direction of X-scan motion 208 (in and out of the paper). Y-scan actuator 204 provides linear motion of workpiece holder 150 in the direction of Y-scan motion 210 that is typically orthogonal to X-scan motion 208. The combination of X-scan and Y-scan operations allows the workpiece 152 held by the workpiece holder 150 to move in a raster-like scan motion through the GCIB 128 for a uniform process of the workpiece 152. A uniform irradiation of the surface of the workpiece 152 by the GCIB 128 occurs. The workpiece holder 150 positions the workpiece 152 at an angle with respect to the angular axis of the GCIB 128 such that the GCIB 128 has a beam incident angle 206 with respect to the surface of the workpiece 152. The beam incident angle 206 may be 90 degrees or some other angle, but is typically 90 degrees or very close to 90 degrees. During the Y scan, the workpiece 152 held by the workpiece holder 150 moves from the position shown to the alternate position “A” indicated by the indicators 152A and 150A, respectively. Note that in movement between the two positions, the workpiece 152 is scanned through the GCIB 128 and moved completely out of the path of the GCIB 128 in both extreme positions (overscan). Although not explicitly shown in FIG. 2, similar scans and overscans are also performed (typically) in the direction of the orthogonal X scan operation 208 (inside and out of the paper).

  The beam current sensor 218 is positioned beyond the workpiece holder 150 in the GCIB 128 path so that the sample of the GCIB 128 is intercepted when the workpiece holder 150 is scanned out of the GCIB 128 path. The beam current sensor 218 is typically a closed Faraday cup or the like other than the beam entrance opening and is attached to the wall of the vacuum vessel 102 by an electrically isolated mount 212.

  Controller 220, which can be a microcomputer-based controller, connects to X-scan actuator 202 and Y-scan actuator 204 via electrical cable 216 and controls X-scan actuator 202 and Y-scan actuator 204 to control workpiece 152. Is placed inside or outside of the GCIB 128 and the workpiece 152 is scanned uniformly with respect to the GCIB 128 in order for the GCIB 128 to achieve a uniform process of the workpiece 152. The controller 220 receives the sampled beam current collected by the beam current sensor 218 via the lead 214, thereby monitoring the GCIB and from the GCIB 128 when a predetermined desired dose is sent. The GCIB dose received by the workpiece 152 is controlled by removing the piece 152.

  FIG. 3 is a schematic cross-sectional view 300 of a semiconductor wafer portion of thickness 302 having a damaged and / or doped surface coating 308. This figure is not drawn to scale. Bulk semiconductor 304 is typically a single crystal material with a high degree of crystallinity and has a surface 306 with a damaged and / or doped coating having a thickness 310. Damaged and / or doped coating 308 is a common feature of a semiconductor wafer during various processing stages of a typical integrated circuit or semiconductor device. In an illustrative example that is not intended to be limiting, if the semiconductor wafer is in a processing stage immediately after shallow doping by a low energy ion implantation process, there will be approximately 2, 30 near the surface 306 of the semiconductor wafer 302. There is a damaged and / or doped coating 308 having a thickness 310 that can be between -5 and 60 angstroms. Damage in the damaged and / or doped coating 308 arises from radiation damage during the ion implantation step, typically from moderate to extreme, including complete decrystallization of the previous crystalline material. Including crystal lattice damage, which can be any degree. In addition, the coating contains donor or acceptor type dopant atoms deposited by an ion implantation process (eg, if the bulk semiconductor is silicon, some dopants are typically boron, phosphorus, arsenic and antimony). Seeds). Usually, desirably any crystalline damage should be repaired after dopant ion implantation, and the implanted dopant atoms perform their electrical activation in the semiconductor. It should be placed at a substitution site in the repaired crystal lattice. In the prior art, such recrystallization and activation is sometimes referred to as annealing, and typically involves heating in a furnace, treatment with fast light pulses or heat pulses, irradiation with a laser or electron beam, other processes, etc. Has been run by. Typically, such a process results in a period of heating of the finally implanted film, followed by recrystallization of the damaged semiconductor and the majority of the dopant atoms being substituted lattice sites and electrical Attainment activation. These annealing processes have drawbacks in that eventually many of the dopant atoms diffuse to a depth much deeper than the film thickness 310 as it is implanted. Thus, the electrical effects of the dopant atoms can extend beyond the desired depth and / or the semiconductor junction can be formed deeper than the desired depth. A first embodiment of the present invention recrystallizes and electrically activates such damaged and doped coatings with dopant atom depth redistribution control that is significantly improved over prior art methods. Annealing method is provided.

  FIG. 4 is similar to the prior art type shown in FIG. 3, except that the damaged and / or doped is shown in the initial stage of the process of gas cluster ion beam irradiation according to the first embodiment of the invention. 3 is a schematic cross-sectional view 350 of a portion of a semiconductor wafer having a thickness 302 having a coating 308. For simplicity, only a single gas cluster ion 352 and gas cluster ion bombardment region 360 is shown in FIG. During the implementation of the first embodiment of the present invention, a gas cluster ion beam process system, for example of the type shown in FIG. 1 or FIG. Used to orient to. The semiconductor wafer 302 is a workpiece 152 as shown in FIG. 1 or FIG. For example, cluster ions consisting of one or more gases that are not dopants for bulk semiconductor 304 (eg, gas cluster ions 352 shown) are used to form a gas cluster ion beam. For example, gas cluster ions such as gas cluster ions 352 follow a trajectory such as a trajectory 354 and impact the surface 306 of the semiconductor wafer. Such gas cluster ions 352 have energy preselected and controlled by the gas cluster ion beam process system and its operating and control parameters. When the gas cluster ions 352 collide with the surface 306 of the semiconductor wafer 302, a gas cluster ion bombardment region 360 is formed. According to the first embodiment of the present invention, the preselected and controlled energy of gas cluster ions 352 extends into the bulk semiconductor 304 through the damaged and / or doped coating 308. A type that supplies the ion bombardment region 360. The gas cluster ion bombardment region 360 comprises two parts: a gas cluster ion bombardment region portion 356 within the damaged and / or doped coating 308 and a gas cluster ion bombardment region portion 358 within the bulk semiconductor 304. Including.

FIG. 5 is a schematic diagram 400 showing a portion of the semiconductor wafer 302 shown in FIG. The gas cluster ions 352 are composed of a plurality of molecules (one molecule 408 is shown as an example) including one or more gases that are not dopants for the bulk semiconductor 304. Such molecules 408 can be, for example, but not limited to, argon or other inert gas molecules. The gas cluster ion bombardment region 360 has a boundary 402. The volume of gas cluster ion bombardment region 360 and thus its penetration depth of semiconductor surface 306 depends on the preselected and controlled energy of gas cluster ions 352. When high energy gas cluster ions 352 strike the surface 306, the gas cluster ions dissociate and individual gas molecules 408 can freely recoil and escape from the target surface. The total energy of the high energy gas cluster ions, except for the small amount of energy carried away by the individual gas atoms that escape, accumulates in the gas cluster ion bombardment region 360. The size of the gas cluster ion bombardment region 360 depends on the energy of the cluster, but is almost the size of the cross section of the impacting gas cluster ion and is small, for example, depending on the energy of the preselected gas cluster ion. The diameter is about 30 to 100 angstroms. The gas cluster ions 352 accumulate most of the total energy delivered to the smaller gas cluster ion bombardment region 360, resulting in severe thermal transients within the material in the gas cluster ion bombardment region 360. The heat stored in the gas cluster ion bombardment region 360 is dissipated by conduction into direction 404 and deep into the surrounding semiconductor material. The duration of the thermal transient is determined by the conductivity of the surrounding material, but is typically less than ^10-6 seconds.

  In the gas cluster ion bombardment region 360, the material can instantaneously reach temperatures of hundreds to thousands of Kelvin degrees. As an example, the bombardment of gas cluster ions 352 when carrying a total energy of 10 keV momentarily increases the temperature by about 2000 Kelvin degrees over the gas cluster ion bombardment region 360 extending approximately 100 angstroms down from the surface 306 Is estimated to be capable of generating Without being bound by a particular theory, it is believed that during thermal transients, the thermal disturbance is probably high enough to melt the material in the gas cluster ion bombardment region 360. With the cooling by heat conduction in the direction 404 of the gas cluster ion bombardment region 360, the gas cluster ion bombardment region 360 from the original undamaged high crystalline gas cluster ion bombardment region portion 358 to the gas cluster Crystalline regrowth proceeds in the direction 406 through the gas cluster ion bombardment region portion 356 of the ion bombardment region 360. As a result, crystallinity is restored in most of the gas cluster ion bombardment region 360 following the thermal transient resulting from the bombardment of the gas cluster ions 352. Similarly, as a result of the recrystallization of the material in the gas cluster / ion bombardment region 360, many dopant atoms existing in the gas cluster / ion bombardment region portion 356 of the gas cluster / ion bombardment region 360 move to the substitution lattice site. , Become electrically active.

  FIG. 6 is a schematic diagram 450 of a portion of a semiconductor wafer 302 illustrating recrystallization and electrical activation of a region 452 bombarded by gas cluster ions according to a first embodiment of the present invention. Portions 356 and 358 of the gas cluster ion bombardment region 360 of FIG. 5 are all or at least partially recrystallized and the dopant is activated to form region 452.

  FIG. 7 is a schematic diagram 500 of a portion of a semiconductor wafer 302 being processed by a gas cluster ion beam according to the method of the first embodiment of the present invention, showing a surface region bombarded by a number of gas cluster ions. Recrystallization and electrical activation are shown. As the process continues, the original damaged and / or doped coating 308 undergoes recrystallization and electrical activation of dopants in an increasingly larger area 502. The island 504 of the original damaged and / or doped coating 308 contracts and is generally replaced by recrystallized and activated material. The recrystallized and activated region 502 extends down from the surface 306 to a depth 506, which is somewhat larger than the original thickness 310 of the original damaged and / or doped coating 308. . Depth 506 is determined by the energy of the gas clusters in the beam used in the process, and is processed by conventional modeling, or by experimentally processing the energy matrix of the gas cluster ion beam, and finally of the semiconductor integrated circuit or semiconductor device. Can be pre-determined and pre-selected by either selecting gas cluster ion beam energy to provide acceptable recrystallization and activation without resulting in depth 506 exceeding process requirements It is.

  FIG. 8 is a schematic diagram 550 of a portion of a semiconductor wafer 302 illustrating the recrystallization and electrical activation of the surface coating after completion of the gas cluster ion beam process according to the first embodiment of the present invention. A uniformly recrystallized and electrically activated coating 552 having a depth 506 replaces the original damaged and / or doped coating 308.

  FIG. 9 is a schematic diagram 600 illustrating a portion of a semiconductor wafer 602 that has been bombarded by gas cluster ions 606 comprising a mixture of dopant gas and electrically inert gas molecules according to a second embodiment of the present invention. . This figure is not drawn to scale. The semiconductor wafer 602 is a single crystal material having a surface 604 and typically a high degree of crystallinity and may be in any of several stages of the process of processing an integrated circuit or semiconductor device. There is. In this example, and not by way of limitation, by way of example, semiconductor wafer 602 may be used to dope a surface film with acceptor or donor impurities and to electrically activate dopants to form shallow junctions or shallow doped regions. It is in the processing stage that it is desired to do. Gas cluster ions 606 having trajectories 608 are shown impacting the surface 604 of the semiconductor wafer 602, and a gas cluster ion impact region 610 is formed on the surface 604. According to this second embodiment of the invention, the gas cluster ions 606 are formed such that the inclusion of acceptor or donor species of the semiconductor wafer 602 is a gas. For example, if the semiconductor wafer 602 is silicon, this gas may include boron trifluoride, diborane, arsine, arsenic pentafluoride, phosphorus pentafluoride, phosphine, stibine, and others.

  FIG. 10 is a schematic diagram 650 showing an enlarged part of the semiconductor wafer 602 shown in FIG. 9 and adding details. The gas cluster ions 606 include a plurality of molecules of at least one gas that includes dopant atoms for the semiconductor wafer 602. The gas cluster ions 606 may be completely composed of a gas containing a dopant for the semiconductor wafer 602, or may be composed of a mixture of a plurality of gases, at least of two or more gases in the mixture. One type may include dopant atoms for the semiconductor wafer 602. Such gas cluster ions 606 can be formed in a GCIB process apparatus 100 or 200 as shown, for example, or similar to that shown in FIG. 1 or FIG. In the GCIB process equipment, if it is desired that a gas mixture be formed in the gas cluster, a gas pre-mixed with the desired mixture in a single gas storage cylinder 111 (FIG. 1 or FIG. 2). The mixture may be supplied or alternatively, different source gases 112 and 222 are supplied to the gas storage cylinders 111 and 221 (FIG. 2), which are then fed into the residence chamber 116 (FIG. 2). While flowing, it may be mixed in the desired ratio by appropriate adjustment of the gas meter plugs 113 and 223 (FIG. 2). Thus, it is possible to generate a gas cluster ion beam composed entirely of a single gas containing dopant atoms in the molecule, or at least one of which is a gas containing dopant atoms in the molecule and at least It is also possible to generate a gas cluster ion beam with a mixture of two or more gases, one of which is a gas that is not a dopant.

Returning to the examination of FIG. 10, the gas cluster ions 606 display non-dopant molecules (non-dopant molecules 652 are shown as representative examples) and dopant molecules containing dopant atoms (dopant molecules 654 are shown as representative examples). Is included) (illustrative and not intended to be limiting). A wide range of dopant and non-dopant molecule mixtures are useful in the present invention, and the clusters used in the process of the present invention may be formed entirely of dopant gas molecules, and vice versa. The ratio of gas molecules to non-dopant gas molecules is too small, some or many gas cluster ions do not contain any dopant gas molecules, and at least some of the gas cluster ions in the gas cluster ion beam It may be appreciated that may contain one or more molecules of the dopant gas. In the example shown in FIG. 10, the gas cluster ions 606 are formed of a gas mixture having a majority of non-dopant molecules 652 and a small number of dopant molecules 654. For example, when the semiconductor wafer 602 is silicon, the dopant gas may be, for example, diborane containing boron as a dopant atom. The non-dopant gas can be, for example, argon, an inert gas. The gas cluster ion bombardment region 610 has a boundary 656. The volume of the gas cluster ion bombardment region 610 and thus its penetration depth of the semiconductor surface depends on the preselected and controlled energy of the gas cluster ions 606. When high energy gas cluster ions 606 strike the surface 604, the gas cluster ions 606 dissociate and the individual non-dopant molecules 652 and dopant molecules 654 become free. Inert gas molecules typically recoil and escape from the surface 604 of the semiconductor wafer 602. Some molecules, including some of the dopant molecules 654, become embedded in the surface. The total energy of the high energy gas cluster ions 606, except for the small energy carried away by the individual gas atoms that escape, accumulates in the gas cluster ion bombardment region 610. The size of the gas cluster ion bombardment region 610 depends on the energy of the cluster, but is almost the size of the cross section of the impacting gas cluster ion and is small, for example, depending on the energy of the preselected gas cluster ion The diameter is about 30 to 100 angstroms. As the gas cluster ions 606 accumulate most of the total energy delivered to the smaller gas cluster ion bombardment region 610, severe thermal transients occur within the material in the gas cluster ion bombardment region 610. The heat stored in the gas cluster ion bombardment region 610 is dissipated by conduction into direction 658 and deep into the surrounding semiconductor material. The duration of the thermal transient is determined by the thermal conductivity of the surrounding material, but is typically less than ^10-6 seconds.

  In the gas cluster ion bombardment region 610, material can instantaneously reach temperatures of hundreds to thousands of Kelvin degrees. As an example, the impact of gas cluster ions 606 when carrying a total energy of 10 keV momentarily increases the temperature by about 2000 Kelvin degrees over the gas cluster ion impact region 610 extending approximately 100 angstroms down from the surface 604. Is estimated to be capable of generating Without being bound by a particular theory, it is believed that during thermal transients, the thermal disturbance is probably high enough to melt the material in the gas cluster ion bombardment region 610. As the gas cluster ion bombardment region 610 is cooled by heat conduction in the direction 658, crystal regrowth proceeds from the highly crystalline semiconductor wafer 602 to the direction 660 through the gas cluster ion bombardment region 610. As a result, crystallinity is restored in the gas cluster ion bombardment region 610 following the thermal transient of the cluster ions, and some dopant atoms originating from the dopant molecules 654 remain in the semiconductor, resulting in gas cluster ion bombardment. Occupies substitution lattice sites in the semiconductor material in region 610. The dopant atoms present in the gas cluster ion bombardment region 610 are thus brought into an electrically active state. Accordingly, the semiconductor wafer 602 is doped in the gas cluster ion bombardment region 610 and becomes electrically activated and recrystallized. The doping concentration is controlled by pre-selecting and controlling the ratio of dopant molecules to non-dopant molecules in the gas mixture used to form the gas cluster ion beam.

  FIG. 11 is a schematic diagram 700 of a portion of a semiconductor wafer 602 showing doping by recrystallization and electrical activation of a region bombarded by gas cluster ions according to a second embodiment of the present invention. After the gas cluster ion bombardment event described in FIG. 10, when the thermal transient is dissipated, the doped, electrically activated and recrystallized region 702 is taken up by the gas cluster ion bombardment region 610 of FIG. Replace. The doped, electrically activated and recrystallized region 702 extends down from the surface 604 of the semiconductor wafer 602 to a depth 704. FIG. 12 shows a semiconductor wafer 602 showing a doped, electrically activated and recrystallized film 752 formed by the completion of a gas cluster ion beam process according to a second embodiment of the invention. 7 is a partial schematic 750. Additional doped, electrically activated and recrystallized similar to the doped, electrically activated and recrystallized region 702 (FIG. 11) by continuous irradiation of gas cluster ions. Regions are formed, and a doped, electrically activated and recrystallized film 752 is grown that overlaps and eventually extends down to a depth 704 from the surface 604 of the semiconductor wafer 602. A semiconductor surface gas cluster ion beam process using gas cluster ions containing dopant gas molecules is doped, electrically activated and recrystallized on the semiconductor wafer 602 in a single process step. The formed film 752 is formed. By avoiding the need for conventional annealing, undesirable diffusion of dopant atoms is avoided and the coating depth 704 is controlled by the choice of energy of the gas cluster ion beam. Several hundred to several tens of angstroms of a shallow doped semiconductor surface film can be formed, and thus shallow junctions can be formed as well.

  Although the invention has been described with reference to various embodiments, it should be appreciated that the invention is capable of a wide variety of further and other embodiments within the spirit of the invention.

1 is a schematic diagram showing the basic elements of a prior art GCIB process apparatus using an electrostatic scanning beam. 1 is a schematic diagram showing the basic elements of a prior art GCB process apparatus using a fixed beam with mechanical scanning of a workpiece. 1 schematically illustrates a portion of a semiconductor wafer having a damaged and / or doped surface coating. 1 is a schematic diagram showing a portion of a semiconductor wafer having a damaged and doped surface coating during gas cluster ion beam irradiation according to an embodiment of the present invention. FIG. 5 is a schematic view showing a part of the semiconductor wafer of FIG. 4 in an enlarged manner with additional details. 1 is a schematic diagram of a portion of a semiconductor wafer showing recrystallization and electrical activation of a region bombarded by a gas cluster ion beam according to the present invention. 1 is a schematic illustration of a portion of a semiconductor wafer showing recrystallization and electrical activation of a surface region bombarded by a number of gas cluster ions. 1 is a schematic illustration of a portion of a semiconductor wafer showing recrystallization and electrical activation of a surface coating after completion of gas cluster ion beam processing according to the present invention. 1 is a schematic illustration of a portion of a semiconductor wafer being bombarded by gas cluster ions including a molecular mixture of a dopant gas and an electrically inert gas according to one embodiment of the present invention. FIG. 10 is a schematic diagram showing a part of the semiconductor wafer of FIG. 1 is a schematic illustration of a portion of a semiconductor wafer showing doping with recrystallization and electrical activation of a region bombarded by a gas cluster ion beam according to one embodiment of the present invention. 1 is a schematic illustration of a portion of a semiconductor wafer showing doping with recrystallization and electrical activation of a surface coating after completion of a gas cluster ion beam treatment according to an embodiment of the present invention.

Claims (17)

A method for recrystallizing a damaged semiconductor thin film on the surface of a substantially crystalline semiconductor substrate, comprising:
Providing a vacuum chamber including a substrate holder for holding the virtual crystalline semiconductor substrate;
Holding the virtual crystalline semiconductor substrate on the substrate holder in the vacuum chamber;
Selecting energy for the gas cluster ion process;
Generating a gas cluster ion beam in the vacuum chamber;
Accelerating the gas cluster ion beam to the selected energy;
In order to process the film to reduce the extent of damage and improve its crystallinity, the accelerated gas cluster ion beam is directed onto at least a portion of the damaged semiconductor thin film and into the at least a portion of the film. A step of directing. The method of claim 1, wherein the workpiece is a semiconductor substrate that has been subjected to an ion irradiation process of a type that causes irradiation damage to the thin film. The method of claim 2, wherein the ion irradiation process is ion implantation using molecular or atomic ions. The step of selecting energy further includes determining a depth to reduce damage and improve crystallinity, wherein the depth is less than about 200 angstroms, and the beam is within the film consistent with each determination. The method of claim 1, wherein the method is directed to a plurality of levels. The method of claim 1, wherein the directing step further comprises controllably scanning the accelerated cluster ion beam. A method for electrically activating dopant atoms in a doped semiconductor thin film overlying the surface of a virtual crystalline semiconductor substrate, comprising:
Providing a vacuum chamber including a substrate holder for holding the virtual crystalline semiconductor substrate;
Holding the virtual crystalline semiconductor substrate on the substrate holder in the vacuum chamber;
Selecting energy for the gas cluster ion process;
Generating a gas cluster ion beam in the vacuum chamber;
Accelerating the gas cluster ion beam to the selected energy;
Directing the accelerated gas cluster ion beam onto and into at least a portion of the doped semiconductor thin film to electrically activate at least a portion of the dopant atoms; Including methods. 7. The method of claim 6, further comprising receiving the semiconductor substrate from a molecular or atomic ion implantation process to dope the semiconductor thin film with the dopant atoms. The method of claim 6, wherein selecting the energy further comprises determining a depth for electrically activating at least a portion of the dopant atoms, the depth being less than about 200 Angstroms. . The method of claim 6, wherein the directing step further comprises controllably scanning the accelerated cluster ion beam. A method of forming a doped ultra-shallow subsurface region of a semiconductor substrate, comprising:
Providing a vacuum chamber including a substrate holder for holding the semiconductor substrate;
Holding the semiconductor substrate on the substrate holder in the vacuum chamber;
Selecting the ratio of dopant to non-dopant gas molecules or atoms;
Selecting energy for the gas cluster ion process;
Selecting a dose for the gas cluster ion process;
Generating in the vacuum chamber a gas cluster ion beam comprising dopant and non-dopant molecules or atoms in approximately the selected proportion;
Accelerating the gas cluster ion beam to the selected energy;
Irradiating a portion of the surface of the semiconductor substrate with substantially the selected dose of dopant molecules or atoms to form an ultra-shallow subsurface region doped with the accelerated gas cluster ion beam Directing onto a portion of the surface of the substrate. The method of claim 10, wherein selecting the energy further comprises determining a depth of the ultra-shallow subsurface region, wherein the depth is less than about 200 angstroms. The method of claim 10, wherein the selected ratio ranges from about 1: 10,000 to about 1: 1. The method of claim 10, wherein the dopant in the irradiated portion of the semiconductor substrate is at least partially electrically activated. The method of claim 10, wherein the directing step further comprises controllably scanning the accelerated cluster ion beam. A semiconductor device formed in part by the method of claim 1. A semiconductor device formed in part by the method of claim 6. A semiconductor device formed in part by the method of claim 10.

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