Real-time photoresist outgassing control system and method

Abstract

A system and method for controlling the amount of outgassing caused by implanting ions into photoresist disposed on a workpiece. The amount of outgassing is based on, among other effects, the species being implanted, the type of photoresist, the implant energy, and the dose already implanted. By controlling the effective beam current, the amount of outgassing can be kept below a predetermined threshold. By developing and utilizing a relationship between the effective beam current, the total dose already dosed, and the rate of outgassing, the effective beam current can be more precisely controlled to implant the workpiece in the most efficient manner while remaining below a predetermined outgassing threshold.

Description

[Technical Field]

[0001] This application claims priority to U.S. Patent Application No. 17 / 582,655, filed January 24, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0002] SUMMARY Embodiments of the present disclosure relate to systems and methods for controlling outgassing caused by implanting species into photoresist disposed on a workpiece. [Background technology]

[0003] Ion implantation is a common technique for introducing impurities into a workpiece to affect the electrical conductivity of portions of the workpiece. For example, ions containing Group III elements such as boron, aluminum, and gallium can be used to create P-type regions in a silicon workpiece. Ions containing Group V elements such as phosphorus and arsenic can be used to create N-type regions in a silicon workpiece.

[0004] To implant these ions into selected portions of the workpiece, photoresist is typically applied to the surface of the workpiece in areas where ions are not to be implanted. This process may be known as patterning the workpiece. The photoresist typically reduces the number of ions that can be implanted into the workpiece below the photoresist. In this way, ions are implanted only in areas not covered by the photoresist.

[0005] However, in certain embodiments, outgassing may occur during the process of implanting ions into the photoresist. In certain systems, a maximum allowable outgassing rate may occur. The beam current is reduced to fall below this maximum allowable outgassing rate. This results in reduced utilization and reduced throughput.

[0006] Therefore, it would be advantageous to have a system and method for implanting ions into patterned workpieces in a more efficient manner. Summary of the Invention

[0007] A system and method for controlling the amount of outgassing caused by implanting ions into photoresist disposed on a workpiece. The amount of outgassing is based on, among other influences, the species being implanted, the type of photoresist, the implant energy, and the dose already implanted. By controlling the effective beam current, the amount of outgassing can be maintained below a predetermined threshold. By developing and utilizing a relationship between the effective beam current, the total dose already dosed, and the rate of outgassing, the effective beam current can be more precisely controlled to implant the workpiece in the most efficient manner while remaining below a predetermined outgassing threshold.

[0008] According to one embodiment, a method for implanting ions of a specific species into a workpiece coated with a photoresist material to maintain a rate of outgassing below a threshold is disclosed. The method includes identifying a relationship between an effective beam current, a total dose already dosed, and a rate of outgassing; using this relationship to identify an effective beam current to be used for one or more passes when implanting ions into the workpiece based on the total dose already dosed; implanting ions using the effective beam current during one or more passes; and repeating the using and implanting multiple times. In some embodiments, ions are extracted from an ion source and the using and implanting are repeated until the effective beam current is equal to or greater than a maximum beam current that can be extracted from the ion source. In some embodiments, after the effective beam current is equal to or greater than the maximum beam current, the method further includes implanting ions using the maximum beam current until a desired dose is implanted. In certain embodiments, ions are extracted from the ion source and the effective beam current is changed after each pass until the effective beam current is equal to or greater than the maximum beam current that can be extracted from the ion source. In some embodiments, ions are extracted from an ion source and the effective beam current is varied without changing process parameters of the ion source. In some embodiments, a workpiece is placed on a movable workpiece holder and the effective beam current is varied by modifying a workpiece scan speed of the movable workpiece holder. In some embodiments, a blocker can be moved into the path of the ions and is configured such that the effective beam current is varied by moving the blocker into the path of the ions to block some or all of the ions. In some embodiments, a scanner is used to generate a ribbon ion beam from a spot beam and the effective beam current is varied by modifying the beam scan frequency of the scanner. In some embodiments, the relationship is identified using a calibration process.In certain embodiments, the calibration process includes implanting an ion beam of a particular species into a workpiece, the workpiece being coated with a photoresist material, the ion beam comprising a beam current; measuring a pressure at the workpiece during implantation, the pressure indicative of a rate of outgassing; measuring the pressure at the workpiece during implantation; calculating an implanted amount in the workpiece after each pass of the ion beam; repeating the directing, measuring, and calculating for a plurality of workpieces, each workpiece being implanted using a different beam current; and determining a relationship between the effective beam current, the total dose already dosed, and the rate of outgassing based on the calculated implanted amount, pressure, and beam current of each ion beam.

[0009] According to another embodiment, an ion implantation system is disclosed. The ion implantation system includes an ion source, a mass analyzer, a mass resolving device, a collimator, a movable workpiece holder, and a controller. The controller includes a memory device containing instructions. When executed by the controller, the instructions enable the ion implantation system to use a previously determined relationship between the effective beam current, the rate of outgassing, and the total dose already administered to determine an effective beam current to be used for one or more passes when ions are implanted into a workpiece coated with a photoresist material, to implant ions of a particular species using the effective beam current during the one or more passes, and to repeat the determining and implanting multiple times. In some embodiments, the controller repeats the determining and implanting until the effective beam current is equal to or greater than a maximum beam current that can be extracted from the ion source. In certain embodiments, after the effective beam current is equal to or greater than the maximum beam current, the controller implants ions using the maximum beam current until the desired dose is implanted. In some embodiments, the controller changes the effective beam current after each pass until the effective beam current is equal to or greater than the maximum beam current that can be extracted from the ion source. In some embodiments, the workpiece is disposed on a movable workpiece holder, and the controller varies the effective beam current by modifying a workpiece scanning speed of the movable workpiece holder. In certain embodiments, the ion source generates a spot beam, the ion implantation system includes a scanner for generating a ribbon ion beam from the spot beam, and the controller varies the effective beam current by modifying a beam scanning frequency of the scanner. In some embodiments, the ion implantation system further includes a blocker, the blocker being movable into the path of the ions, and the controller configured to vary the effective beam current by moving the blocker into the path of the ions to block some or all of the ions. In some embodiments, the previously determined relationship is determined by the controller by performing a calibration process.In certain embodiments, the calibration process involves directing an ion beam of a particular species onto a workpiece. towards and determining a relationship between the effective beam current, the total dose already dosed, and the rate of outgassing based on the calculated implanted dose, the pressure, and the beam current of each ion beam. In some embodiments, the controller varies the effective beam current without changing process parameters of the ion source.

[0010] For a better understanding of the present disclosure, reference is made to the accompanying drawings, which are incorporated herein by reference. [Brief explanation of the drawings]

[0011] [Figure 1] 1 illustrates an ion implanter utilizing a spot beam according to one embodiment. [Figure 2] 1 illustrates an ion implanter utilizing a ribbon ion beam according to one embodiment. [Figure 3] 1 shows a graph illustrating the relationship between beam current and total dose already administered to achieve an acceptable rate of outgassing. [Figure 4] The graph in Figure 3 is used to illustrate the beam current used to implant the workpiece. [Figure 5] 1 illustrates a flowchart that may be used to implant a photoresist-coated workpiece according to one embodiment. [Figure 6]1 shows a comparison of throughput utilization for various injection methods. DETAILED DESCRIPTION OF THE INVENTION

[0012] FIG. 1 illustrates a spot beam ion implantation system that may be used to implant ions into a patterned workpiece using a spot beam, according to one embodiment.

[0013] The spot beam ion implantation system includes an ion source 100 comprising a plurality of chamber walls defining an ion source chamber. In certain embodiments, the ion source 100 may be an RF ion source. In this embodiment, an RF antenna may be positioned against a dielectric window. The dielectric window may comprise part or all of one of the chamber walls. The RF antenna may comprise a conductive material, such as copper. An RF power source is in electrical communication with the RF antenna. The RF power source may provide an RF voltage to the RF antenna. The power provided by the RF power source may be between 0.1 and 10 kW and any suitable frequency, such as between 1 and 100 MHz. Furthermore, the power provided by the RF power source may be pulsed.

[0014] In another embodiment, a cathode is positioned within the ion source chamber. A filament is positioned behind the cathode and is energized to emit electrons. These electrons are attracted to the cathode, which in turn emits the electrons into the ion source chamber. This cathode may be referred to as an indirectly heated cathode (IHC) because it is indirectly heated by the electrons emitted from the filament.

[0015] Other embodiments are possible, for example, the plasma may be generated in different ways, such as by a Bernas ion source, a capacitively coupled plasma (CCP) source, a microwave ion source, or an electron-cyclotron-resonance (ECR) ion source, etc. The manner in which the plasma is generated is not limited by this disclosure.

[0016] One chamber wall, referred to as the extraction plate, includes an extraction aperture. The extraction aperture may be an opening through which ions 1 generated in the ion source chamber are extracted and directed to the workpiece 10. The extraction aperture may be any suitable shape. In certain embodiments, the extraction aperture may be oval or rectangular, with one dimension, referred to as the width (x-dimension), being much larger than a second dimension, referred to as the height (y-dimension).

[0017] The extraction optics 110 are positioned outside and near the extraction aperture of the ion source 100. In certain embodiments, the extraction optics 110 include one or more electrodes. Each electrode may be a single conductive component with an aperture disposed therein. Alternatively, each electrode may be composed of two conductive components spaced apart to create an aperture between them. The electrodes may be a metal, such as tungsten, molybdenum, or titanium. One or more of the electrodes may be electrically grounded. In certain embodiments, one or more of the electrodes may be biased using an electrode power supply. The electrode power supply can be used to bias one or more of the electrodes relative to the ion source to attract ions through the extraction aperture. The extraction aperture and the aperture in the extraction optics are oriented such that ions pass through both apertures.

[0018] Downstream of the extraction optics 110 is a mass analyzer 120. The mass analyzer 120 uses a magnetic field to guide the path of the extracted ions 1. The magnetic field influences the flight path of the ions according to their mass and charge. A mass resolving device 130 having a resolving aperture 131 is located at the output (i.e., distal) end of the mass analyzer 120. By appropriately selecting the magnetic field, only ions 1 having a selected mass and charge will be guided through the resolving aperture 131. Other ions will collide with the mass resolving device 130 or the walls of the mass analyzer 120 and will not be able to travel further within the system. Ions passing through the mass resolving device 130 may form a spot beam.

[0019] The spot beam may then enter a scanner 140 located downstream from the mass resolving device 130. The scanner 140 fans out the spot beam into multiple diverging beamlets. The scanner 140 may be electrostatic or magnetic. In certain embodiments, a collimator 150 then converts these diverging beamlets into multiple parallel beamlets that are directed toward the workpiece 10. In other embodiments, the collimator 150 may not be employed.

[0020] The workpiece 10 is placed on a movable workpiece holder 160 .

[0021] In certain embodiments, the direction of the ion beam may be referred to as the Z direction, the direction perpendicular and horizontal to this direction may be referred to as the X direction, and the direction perpendicular and vertical to the Z direction may be referred to as the Y direction. In this example, it is assumed that the scanner 140 scans the spot beam in the X direction, while the movable workpiece holder 160 translates in the Y direction. The rate at which the movable workpiece holder 160 moves in the Y direction may be referred to as the workpiece scan rate. The rate at which the scanner 140 scans the spot beam in the X direction may be referred to as the beam scan frequency.

[0022] The movable workpiece holder 160 moves in the Y direction from a first position to a second position. The first position can be above the ion beam. The second position can be below the ion beam. The movable workpiece holder 160 then moves from the second position back to the first position. Thus, at the first and second positions, the workpiece may not be affected by the ion beam. However, the workpiece 10 is affected as the movable workpiece holder 160 moves between these two positions.

[0023] A pass may be defined as the period during which the movable workpiece holder 160 is moving from a first position to a second position, or from a second position to a first position, or in other words, the period during which the entire workpiece 10 is exposed to the ion beam once.

[0024] A controller 180 is also used to control the system. The controller 180 has a processing unit 181 and an associated memory device 182. The memory device 182 contains instructions 183 that, when executed by the processing unit, enable the system to perform the functions described herein. The memory device 182 may be any non-transitory storage medium, including non-volatile memory, such as flash ROM, electrically erasable ROM, or other suitable devices. In other embodiments, the memory device 182 may be volatile memory, such as RAM or DRAM. In certain embodiments, the controller 180 may be a general-purpose computer, an embedded processor, or a specially designed microcontroller. The actual implementation of the controller 180 is not limited by this disclosure. The controller 180 may be in communication with the ion source 100, the scanner 140, and the movable workpiece holder 160 and may be configured to modify process parameters of these components.

[0025] Figure 2 shows an ion implantation system using a ribbon ion beam. Components having the same function as those shown in Figure 1 are given the same reference designations. An ion source 100 is used to generate ions. Any of the ion sources described with reference to Figure 1 may be used. Unlike Figure 1, the extraction aperture 100 may be a slit having a width significantly greater than its height. In this way, the extracted ions 2 take the form of a ribbon ion beam. Extraction optics 110 are located outside and near the extraction aperture of the ion source 100.

[0026] Downstream of the extraction optics 110 is a mass analyzer 120. The mass analyzer 120 uses a magnetic field to guide the path of the extracted ions 2. The magnetic field influences the flight path of the ions according to their mass and charge. A mass resolving device 130 having a resolving aperture 131 is located at the output (i.e., distal) end of the mass analyzer 120. The mass resolving device 130 is located at the crossover point of the ribbon ion beam. By appropriately selecting the magnetic field, only ions 2 with a selected mass and charge will be guided through the resolving aperture 131. Other ions will collide with the walls of the mass resolving device 130 or the mass analyzer 120 and will not be able to travel further within the system.

[0027] A collimator 150 may be positioned downstream from the mass resolving device 130. The collimator 150 accepts ions 2 that have passed through a resolving aperture 131 and produces a ribbon ion beam made up of multiple parallel or nearly parallel beamlets. The output (i.e., distal end) of the mass analyzer 120 and the input (i.e., proximal end) of the collimator 150 may be separated by a fixed distance. The mass resolving device 130 is positioned in the space between these two components.

[0028] An acceleration / deceleration stage 190 may be located downstream from the collimator 150. The acceleration / deceleration stage 190 may be referred to as an energy purity module. An energy purity module is a beamline lens component configured to independently control the deflection, deceleration, and focus of the ion beam. For example, the energy purity module may be a vertical electrostatic energy filter (VEEF) or an electrostatic filter (EF). A movable workpiece holder 160 is located downstream from the acceleration / deceleration stage 190.

[0029] A controller 180 is also used to control the system. The controller 180 has a processing unit 181 and an associated memory device 182. The memory device 182 contains instructions 183 that, when executed by the processing unit, enable the system to perform the functions described herein. The controller 180 may be in communication with the ion source 100 and the moveable workpiece holder 160 and may be configured to modify process parameters of these components.

[0030] It has been found that a relationship between outgassing rate, effective beam current, and total dose already dosed exists for each type of workpiece, where the workpiece is coated with a particular photoresist material and implanted with a particular species. Stated differently, the outgassing rate is a function of the total dose already dosed, the effective beam current, the photoresist material, and the species being implanted.

[0031] In other words, the rate of outgassing is related to the photoresist material and the species implanted into that photoresist material. Furthermore, as larger doses are administered, the rate of outgassing typically decreases because less trapped gas remains within the outgassed photoresist material. Thus, if a maximum rate of outgassing is specified, a graph can be constructed that depicts the relationship between the maximum effective beam current that can be used and the total dose already dispensed.

[0032] One such graph is shown in Figure 3. In this particular example, a beam of boron was implanted into a photoresist-coated workpiece. The beam energy was set to 130 kV and the boron was implanted at a 0 degree angle.

[0033] The horizontal axis represents the total dose already administered, while the vertical axis represents the effective beam current in milliamps. Line 300 represents the effective beam current that can be utilized without exceeding the maximum velocity of outgassing.

[0034] In one embodiment, these relationships may be developed by performing a calibration process. In the calibration process, a pressure sensor may be placed near a workpiece. One or more workpieces having a photoresist coating may be utilized. The ion implantation system may be configured to provide an ion beam with specific parameters, such as a desired species, beam energy, and implant angle. One or more workpieces may then be implanted using the ion beam with these specific parameters and different beam currents. When the ion beam strikes the photoresist, gas is generated and may be detected by a pressure sensor. Furthermore, when ions are implanted into the workpiece, the total dose already administered is determined. Using the beam current, the total dose already administered, and pressure sensor readings, the amount of outgassing at a specific beam current and dose may be determined.

[0035] By performing this procedure using multiple workpieces and beam currents, data is obtained showing outgassing as a function of the total dose already dosed for different beam currents, which can then be interpolated to identify the maximum effective beam current that can be utilized at each dose for that implant without exceeding the outgassing limit.

[0036] It should be noted that the rate of outgassing is also a function of the percentage of the workpiece that the photoresist material is disposed on. For example, if the photoresist covers 25% of the workpiece, the rate of outgassing may be approximately 50% of the rate of outgassing experienced by a workpiece with 50% of its surface covered by photoresist. In certain embodiments, the relationship between the percentage of photoresist coverage and the rate of outgassing is approximately linear. In other embodiments, a different relationship may exist based on other effects, such as cryopump response or other factors.

[0037] In another embodiment, the relationship between these parameters can be theoretically calculated, for example, collecting a large amount of data allows for the generation of a theoretical model that can be used to estimate the relationship between effective beam current, total dose already administered, and rate of outgassing.

[0038] Once a graph similar to that shown in FIG. 3 has been created, an ion implantation process can be performed. In one embodiment, this graph is used to create an equation that calculates effective beam current versus total dose already dosed for a particular implant species, implant angle, photoresist coverage percentage, and photoresist material. This graph may be created using least squares or some other technique. The controller 180 may then use this graph or this equation to control the implantation system. In another embodiment, data is used to create the equation without generating a graph.

[0039] The effective beam current can be controlled in several ways. For example, in an IHC ion source, the power supplied to the cathode or filament can be varied by the controller 180 to vary the density of the plasma in the ion source. In an RF ion source, the power supplied to the antenna can be varied by the controller 180 to vary the density of the plasma in the ion source. This is applicable to the implantation systems shown in Figures 1 or 2.

[0040] In certain embodiments, the process parameters of the ion source 100 remain unchanged to minimize the time to tune the ion source. Rather, other techniques for varying the effective beam current are used that do not involve changing the process parameters of the ion source.

[0041] For example, the effective beam current can be varied by changing the workpiece scanning speed of the movable workpiece holder 160. This is applicable to the implantation systems shown in FIG. 1 or FIG. 2. For example, a faster workpiece scanning speed results in a smaller amount of ions being implanted during each pass, which is effectively a decrease in beam current. Conversely, a slower workpiece scanning speed results in a larger amount of ions being implanted during each pass, which is effectively an increase in beam current.

[0042] Alternatively, or in addition, the effective beam current can be varied by changing the beam scanning frequency of the scanner 140. For example, a faster beam scanning frequency results in a smaller amount of ions being implanted during each pass, which is effectively a decrease in beam current. Conversely, a slower beam scanning frequency results in a larger amount of ions being implanted during each pass, which is effectively an increase in beam current. This is applicable to the implantation system shown in FIG. 1.

[0043] Alternatively, or in addition, the block member 171 may be configured to be movable into the path of the ion beam. In certain embodiments, as shown in FIG. 1, the block member 171 may be positioned near the entrance to the mass analyzer 120. In other embodiments, as shown in FIG. 2, the block member 171 may be positioned near the end of the beamline, such as at the output of the collimator 150. In other embodiments, the block member 171 may be positioned near the resolving aperture 131, such as just before or just after the resolving aperture 131. To vary the effective beam current, the block member 171 may be moved into the ion path to block some or all of the ions in the path. Note that while FIG. 1 shows the block member 171 positioned near the ion source 100, other placements may be possible. Similarly, while FIG. 2 shows the block member 171 positioned near the end of the beamline, other placements may be possible.

[0044] In addition to physically blocking the ion beam, the ion beam can also be diverted electrically. For example, a diverter can be located within the acceleration / deceleration stage 190. This diverter can be used to divert the ion beam away from the workpiece 10 through the application of an AC voltage. This diverter can be located within another component in the beamline or can be a separate part.

[0045] In one embodiment, the controller 180 may configure the ion source 100 to extract a maximum amount of beam current, which may result in an unacceptable rate of outgassing during earlier passes of the workpiece. Therefore, during earlier passes, the controller 180 may reduce the effective beam current by manipulating the workpiece scan speed, manipulating the beam scan frequency, using a diverter, and / or inserting a blocking member to achieve an acceptable rate of outgassing.

[0046] 5 shows a flow chart illustrating the operations of the injection system, which are performed by a controller 180 executing instructions 183 located in a memory device 182.

[0047] First, as shown in box 500, for a particular implant species, implant angle, photoresist material, and implant energy, the relationship between effective beam current, total dose already dosed, and outgassing rate is determined. In certain embodiments, this relationship is determined by performing the calibration process described above. In other embodiments, this relationship is determined theoretically based on previously collected data.

[0048] It should be noted that in certain embodiments, the calibration process is performed by the controller 180 associated with the implant system performing the implant process. However, in other embodiments, the calibration process may be performed using a separate controller. For example, the calibration process may be performed by the system vendor or by using a reference system. In this embodiment, the relationship identified during the calibration process is provided to the controller 180 associated with the implant system performing the implant process. In another embodiment, the predetermined relationship may be theoretically identified and provided to the controller 180. Thus, in embodiments, the controller 180 utilizes a previously identified relationship between the effective beam current, the total dose already administered, and the rate of outgassing.

[0049] Next, as illustrated in box 510, controller 180 uses this relationship to identify an appropriate effective beam current that does not exceed an acceptable rate of outgassing. As one example, no ions are implanted so that the total dose already administered is set to zero. Controller 180 then identifies an appropriate beam current that does not exceed an acceptable rate of outgassing.

[0050] Next, as illustrated in box 520, the controller 180 then performs an implantation of the workpiece using the effective beam current. This effective beam current may be used for a single pass or multiple passes, such as 2 passes, 4 passes, 10 passes, 25 passes, 50 passes, 100 passes, etc. As discussed above, a pass is defined as the period during which the movable workpiece holder 160 moves from a first position to a second position, or from the second position to the first position, thereby exposing the entire workpiece to the ion beam once.

[0051] After each pass or set of passes, the system returns to box 510, and controller 180 may then identify a new effective beam current that achieves an acceptable rate of outgassing based on the total amount already dosed. Controller 180 then adjusts the effective beam current by performing one or more of the actions described above.

[0052] After identifying the new effective beam current, the controller then performs another pass or set of passes using the new effective beam current, as illustrated in box 520. In some embodiments, the effective beam current is changed after each pass. In other embodiments, the effective beam current is changed after two passes, four passes, ten passes, twenty-five passes, fifty passes, or one hundred passes. This process of identification and implantation may be repeated until the maximum amount of beam current being extracted from the ion source results in an acceptable rate of outgassing. In other words, the controller 180 may repeat boxes 510 and 520 until the effective beam current, as identified based on the relationship, exceeds the maximum beam current that can be supplied by the implantation system. The controller 180 may then simply allow the implantation process to continue to completion without any further manipulation of the effective beam current, as illustrated in box 530. This process is repeated until the desired amount is implanted, as illustrated in box 540. Thus, in certain embodiments, the effective beam current is changed at least twice during the implantation process. In other embodiments, the effective beam current is changed at least three times during the implantation process.

[0053] One example of this process is shown in FIG. 4. In FIG. 4, line 400 represents the effective beam current applied as ions are implanted into the workpiece. Until time 401, the effective beam current is constrained by controller 180 using one or more of the techniques described above or another technique. However, after time 401, the maximum beam current that can be extracted from ion source 100 is injected into the workpiece. In this example, the maximum extracted current was assumed to be 12 mA. If the actual maximum extracted current were smaller, time 401 could be shifted to the left. If the actual maximum extracted current were larger, time 401 could be shifted to the right, with line 400 following the contour of line 300 until time 401.

[0054] The embodiments described above in this application may have many advantages: In many conventional implantation systems, the entire implantation is performed at a lower beam current, whereby the beam current never causes the rate of outgassing to exceed a threshold.

[0055] 6 is a graph showing a comparison of throughput utilization for various doses using this conventional method and the method disclosed herein. Line 600 shows the throughput utilization illustrating the present method. In this example, the beam current follows the graph of FIG. 3 until the allowable beam current reaches the maximum extraction current from the ion source. Line 601 represents the throughput utilization of the conventional method. For this illustration, assume that the conventional method performs extraction at 50% of the maximum current that can be extracted from the ion source so that the rate of outgassing does not exceed a predetermined threshold.

[0056] If the desired concentration is 1 x 10 15 and 2×10 15 Note that for injections between: the present method achieves an improvement in throughput utilization of at least 15% to 30% when compared to line 601;

[0057] Furthermore, in certain embodiments, the present disclosure changes the effective beam current without changing the process parameters of the ion source, which allows for very fast path-to-path switching, in contrast to changing the process parameters of the ion source, which typically requires a tuning process that can take several seconds to minutes.

[0058] The scope of the present disclosure is not limited to the specific embodiments described herein. Indeed, various other embodiments and modifications of the present disclosure, in addition to those described herein, will be apparent to those skilled in the art from the foregoing description and accompanying drawings. Accordingly, such other embodiments and modifications are intended to be included within the scope of the present disclosure. Moreover, while the present disclosure has been described herein in the context of particular implementations in particular environments for particular purposes, those skilled in the art will recognize that its utility is not limited thereto, and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in accordance with the broadest possible scope and spirit of the disclosure as described herein.

Claims

1. 1. A method of implanting ions of a specific species into a workpiece coated with a photoresist material so as to maintain a rate of outgassing below a threshold value, comprising: determining the relationship between the total amount of ions already dosed and the maximum effective beam current that can be utilized without exceeding the threshold rate of outgassing; using the relationship to identify an effective beam current to be used for one or more passes when implanting ions into the workpiece based on a total amount of ions already dosed, the effective beam current not exceeding the maximum effective beam current; implanting the ions using the effective beam current during the one or more passes; and repeating the determining and injecting of the effective beam current a plurality of times while increasing the effective beam current from an initial value of the effective beam current. A method comprising:

2. 10. The method of claim 1, wherein the ions are extracted from an ion source and the determining and injecting steps are repeated until the effective beam current reaches a maximum beam current that can be extracted from the ion source.

3. 3. The method of claim 2, after the effective beam current reaches the maximum beam current, the method further comprising implanting the ions using the maximum beam current until a desired amount is implanted.

4. 2. The method of claim 1, wherein the ions are extracted from an ion source and the effective beam current is varied after each pass until the effective beam current reaches a maximum beam current that can be extracted from the ion source.

5. 10. The method of claim 1, wherein the ions are extracted from an ion source and the effective beam current is varied without changing a processing parameter of the ion source.

6. 10. The method of claim 1, wherein the workpiece is disposed on a movable workpiece holder, and the effective beam current is varied by modifying a workpiece scanning velocity of the movable workpiece holder.

7. 10. The method of claim 1, wherein the blocker is configured such that the blocker can be moved into the path of the ions, and by moving the blocker into the path of the ions to block some or all of the ions, the effective beam current is changed.

8. The method of claim 1 , wherein a scanner is used to generate a ribbon ion beam from a spot beam, and the effective beam current is varied by modifying a beam scan frequency of the scanner.

9. The method of claim 1 , wherein the relationship is determined using a calibration process.

10. The calibration process comprises: directing the specific species ion beam toward a workpiece, the workpiece being coated with the photoresist material, the ion beam comprising a beam current; measuring a pressure at the workpiece during said directing, said pressure being indicative of a rate of said outgassing; calculating the implanted dose in the workpiece after each pass of the ion beam; repeating said directing, said measuring, and said calculating for a plurality of workpieces, each workpiece being implanted using a different beam current; and determining a relationship between effective beam current, total amount of ions already dosed, and rate of outgassing based on the calculated implanted dose, the pressure, and the beam current of each ion beam; 10. The method of claim 9, comprising:

11. ion source, mass spectrometer, mass decomposition device, Collimator, A movable workpiece holder, and 1. An ion implantation system comprising: a controller; The controller includes a memory device containing instructions that, when executed by the controller, cause the ion implantation system to: using a pre-specified relationship between the total amount of ions already dosed and a maximum effective beam current that can be utilized without exceeding an acceptable threshold for outgassing, to identify an effective beam current to be used for one or more passes when ions are implanted into a workpiece coated with a photoresist material, the effective beam current not exceeding said maximum effective beam current; implanting ions of a particular species using the effective beam current during the one or more passes; and An ion implantation system that enables the steps of identifying and implanting to be repeated multiple times while increasing the effective beam current from an initial value of the effective beam current.

12. 12. The ion implantation system of claim 11, wherein the controller repeats the identifying and implanting until the effective beam current reaches a maximum beam current that can be extracted from the ion source.

13. 13. The ion implantation system of claim 12, wherein after the effective beam current reaches the maximum beam current, the controller implants the ions using the maximum beam current until a desired amount is implanted.

14. 12. The ion implantation system of claim 11, wherein the controller varies the effective beam current after each pass until the effective beam current reaches a maximum beam current that can be extracted from the ion source.

15. 12. The ion implantation system of claim 11, wherein the workpiece is disposed on the movable workpiece holder, and the controller varies the effective beam current by modifying a workpiece scanning speed of the movable workpiece holder.

16. 12. The ion implantation system of claim 11, wherein the ion source generates a spot beam, the ion implantation system includes a scanner for generating a ribbon ion beam from the spot beam, and the controller varies the effective beam current by modifying a beam scan frequency of the scanner.

17. 12. The ion implantation system of claim 11, further comprising a blocker that can be moved into a path of the ions, the controller configured to vary the effective beam current by moving the blocker into the path of the ions to block some or all of the ions.

18. The ion implantation system of claim 11 , wherein the pre-specified relationship is determined by the controller by performing a calibration process.

19. The calibration process comprises: directing the specific species ion beam toward a workpiece, the workpiece being coated with the photoresist material, the ion beam comprising a beam current; measuring a pressure at the workpiece during said directing, said pressure being indicative of a rate of said outgassing; calculating the implanted dose in the workpiece after each pass of the ion beam; repeating said directing, said measuring, and said calculating for a plurality of workpieces, each workpiece being implanted using a different beam current; and determining a relationship between an effective beam current, a total amount of ions already administered, and a rate of outgassing based on the calculated implanted amount, the pressure, and the beam current of each ion beam; 20. The ion implantation system of claim 18.

20. 12. The ion implantation system of claim 11, wherein the controller varies the effective beam current without changing a process parameter of the ion source.

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