Ion implanter and method for implanting substrate

Abstract

An ion implanter and a method for implanting a substrate are provided. The method includes: performing implantation by scanning an ion beam along a first axis over a substrate while scanning a substrate coated with a photoresist layer along a vertical axis using an implantation recipe; measuring an implantation current (I) during implantation using a first detector located on one side of a substrate position; determining a value of a difference ratio (I-B) / (B) based on the implantation current, wherein B is a current measured by the first detector during calibration at a reference pressure; determining multiple values ​​of a current ratio (CR) for multiple moments based on the difference ratio, wherein the current ratio is a ratio of the implantation current to a current measured by a second detector during calibration, wherein the second detector is located above the substrate position; and adjusting scanning of the ion beam, scanning of the substrate, or a combination thereof based on the current ratio.

Description

[0001] Related Applications

[0002] This application claims priority to U.S. Provisional Patent Application Serial No. 62 / 944,811 filed on December 6, 2019 and entitled “Techniques for Determining and correcting for expected dose variation during implantation of photoresist-coated substrates,” and the entire text of the U.S. Provisional Patent Application is incorporated herein by reference. Technical Field

[0003] The present embodiment relates to a processing device and method, and more specifically to a method for controlling beam current in an ion implantation process; in particular, to an ion implanter and a method for implanting an ion implanter into a substrate. Background Art

[0004] Various types of processing devices are used today to treat or process substrates using ions. For processing substrates such as semiconductor substrates, ions may be used to etch layers or features on the substrate. Ions may also be used to deposit layers or structures on a substrate, implant substances into a substrate, or amorphize a substrate. Techniques have also been developed to monitor the processing of a substrate in order to control the processing of the substrate.

[0005] To provide accurate dose control for ion implantation of a substrate using a scanned spot beam, a current monitor (e.g., a Faraday cup monitor) may be provided at or near the substrate. In some ion implanters, the scanned spot beam is monitored in real time to estimate the ion dose provided to the substrate. A current sensor (e.g., a Faraday cup) may be provided adjacent to the substrate to intercept the spot beam scanning back and forth along a first direction while scanning the substrate in a vertical direction. For example, when the ion dose measured at the current sensor does not match the target ion dose, the real-time monitoring may be used to adjust the scanning of the spot beam.

[0006] In some cases, to ensure that the appropriate ion dose is delivered to the substrate during implantation, a current monitor located near the substrate may perform current measurement. In some cases, a closed loop Faraday (CLF) monitor may be located just upstream of the substrate position outside the substrate position, and may intercept the ion beam and be used to measure the integrated current as the ion beam is scanned along a given direction. This integrated current may be compared with the integrated current measured by a monitor located at the substrate plane (e.g., a profile current detector (PF)) to determine the ratio of the integrated CLF current to the integrated PF current. The PF detector may be placed, for example, at a position corresponding to the center position of the substrate. This determined ratio may be used later to ensure repeatability of providing non-uniform ion doses between different substrates, and to control uniformity of upper / lower substrates.

[0007] To ensure that the appropriate beam current or ion dose is delivered to the substrate during ion implantation, the CLF assembly can measure the beam current during the implantation process while being coupled to a beam controller to dynamically adjust the beam current during implantation. Thus, changes in the current measured at the CLF during implantation can trigger a signal for adjusting the beamline assembly to increase or decrease the beam current delivered to the substrate. For example, for a scanned spot beam, changes in the measured CLF current can result in changes in the scanning speed of the substrate to adjust the effective beam current delivered to a given portion of the substrate.

[0008] It should be noted that although variations in the functionality of beamline components located upstream of the substrate may affect the beam current delivered to the substrate during ion implantation, local variations in conditions surrounding the substrate during implantation are generally not taken into account and, therefore, are not corrected by known implant systems that use current monitors to adjust the beam current.

[0009] These and other considerations may require this improvement. Summary of the invention

[0010] In one embodiment, a method is provided. The method may include: performing implantation using a first implantation recipe by scanning an ion beam along a first axis over a substrate coated with a photoresist layer while scanning the substrate along a second axis, the second axis being perpendicular to the first axis; and measuring an implantation current (I) at multiple times during the implantation using a first detector located on one side of a substrate position. The method may include: determining values ​​of a difference ratio based on the implantation current at the multiple times, the difference ratio being represented by (IB) / (B), where B is the current measured by the first detector during calibration at a reference pressure when the substrate is not present. The method may also include: determining multiple values ​​of a current ratio (CR) during the implantation, respectively for the multiple times, based on the difference ratio, the current ratio being the ratio of the implantation current to the current measured by a second detector during the calibration, the second detector being located above the substrate position. The method may include: adjusting the scanning of the ion beam and / or the scanning of the substrate based on the current ratio.

[0011] In another embodiment, an ion implanter may include: an ion source that generates an ion beam according to an implantation recipe; a scanner that scans the ion beam; a first detector and a second detector that measure the current of the ion beam; a substrate stage that scans the substrate; and a controller that controls the ion beam. The controller may be configured to: perform implantation by scanning the ion beam along a first axis over the substrate while scanning the substrate coated with a photoresist layer along a second axis, the second axis being perpendicular to the first axis; and measure the implantation current (I) at multiple times during the implantation using a first detector located on one side of the substrate position. The controller may be configured to: determine values ​​of a difference ratio based on the implantation current at the multiple times, the difference ratio being represented by (IB) / (B), where B is the current measured by the first detector during calibration at a reference pressure when the substrate is not present. The controller may also be configured to: determine multiple values ​​of a current ratio (CR) during the implantation, respectively for the multiple times, based on the difference ratio, the current ratio being the ratio of the implantation current to the current measured by the second detector during the calibration, the second detector being located above the substrate position. The controller may be configured to adjust the scanning of the ion beam, the scanning of the substrate, or a combination thereof based on the current ratio.

[0012] In another embodiment, a method of implanting a substrate may include: performing implantation using a first implantation recipe by scanning an ion beam over the substrate along a first axis while scanning the substrate along a second axis, the second axis being perpendicular to the first axis; and measuring an implantation current (I) during the implantation using a first detector located to one side of a substrate location. The method may include: determining a value of a difference ratio based on the implantation current, the difference ratio being represented by (IB) / (B), where B is the current measured by the first detector during calibration at a reference pressure. The method may also include: determining a value of a current ratio (CR) during the implantation based on the difference ratio, the current ratio being a ratio of the implantation current to a current measured by a second detector during the calibration, the second detector being located over the substrate location; and adjusting the scanning of the ion beam, the scanning of the substrate, or a combination thereof based on the current ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figures 1A to 1F Shown are the variations in beam current monitor parameters as gas pressure in an ion implanter changes during a gas ramp calibration.

[0014] Figure 2A and Figure 2C The results of gas ramp measurements under two different conditions are shown. Figure 2B and Figure 2D Show the use and Figure 2A and Figure 2C Shown is the gas pressure behavior during implantation for the same measurement protocol.

[0015] Figure 3A and Figure 3B Shown are the variations in current during implantation under two different conditions relative to a baseline current measured at a baseline pressure prior to implantation.

[0016] Figure 4A and Figure 4B Horizontal and vertical Rs line scans are shown for a substrate implanted under two different conditions compared to a reference substrate, showing the over-implantation due to the effect of gas pressure.

[0017] Figure 5 An exemplary process flow is shown.

[0018] Figure 6 A top plan view of a beam-line ion implanter according to various embodiments of the present disclosure is shown in block form.

[0019] [Explanation of Symbols]

[0020] 100: Ion implanter

[0021] 102: Ion Source

[0022] 104: Ion Beam

[0023] 106: Analyzer magnet

[0024] 108: Mass Resolving Slit

[0025] 110: Beam Scanner

[0026] 112: Collimator

[0027] 114: Substrate platform

[0028] 116: Substrate

[0029] 118: Current detector

[0030] 119: Substrate area

[0031] 120: Scan adjustment component

[0032] 120-A: Controller

[0033] 120-B: Memory

[0034] 500: Process

[0035] 510, 520, 530, 540, 550, 560, 570, 580: Blocks

[0036] W: Width

[0037] X, Y, Z: direction DETAILED DESCRIPTION

[0038] The present embodiment will now be more fully described below with reference to the accompanying drawings of some embodiments shown therein. The subject matter of the present disclosure may be implemented in many different forms and is not to be considered limited to the embodiments described herein. Rather, these embodiments are provided so that the present disclosure will be comprehensive and complete and will fully convey the scope of the subject matter to those skilled in the art. In the drawings, the same number always refers to the same element.

[0039] Embodiments described herein provide novel processing apparatus and methods for producing controlled ion implantation of substrates.

[0040] In various embodiments, techniques are disclosed that take into account variations in beam current parameters including CLF current and ratios (e.g., CLF current / PF current that may be sensed during implantation of a substrate) where pressure variations may occur near the substrate. As disclosed herein, experiments performed have found that pressure variations caused by implantation of a substrate including a photoresist layer may systematically affect the CLF current and other beam current parameters. According to the present embodiments, by taking these effects into account, the beam current delivered to the substrate may be more accurately controlled.

[0041] Figure 6 A top plan view of a beamline ion implanter (shown as ion implanter 100) according to various embodiments of the present disclosure is shown in block form. The ion implanter 100 includes an ion source 102 configured to produce an ion beam 104. The ion beam 104 can be configured as a spot beam that is scanned along a direction, such as an X direction. In the convention used herein, the Z direction refers to the direction of an axis parallel to the central ray trajectory of the ion beam 104. Therefore, as shown in the figure, the absolute direction of the Z direction and the X direction can vary at different points within the ion implanter 100, where the X direction is perpendicular to the Z direction. The ion beam 104 can travel through an analyzer magnet 106, a mass resolving slit 108 and through a collimator 112 before irradiating a substrate 116 disposed on a substrate platform 114. In some embodiments, the substrate platform 114 can be configured to scan the substrate 116 at least along the Y direction. Figure 6 In the example shown in FIG. 1 , the ion implanter 100 includes a beam scanner 110. When the ion beam 104 is set as a spot beam, the beam scanner 110 can scan the ion beam 104 along the X direction to generate a scanned ion beam, which is also scanned at the substrate along the X direction. The width of the resulting scanned spot beam can be comparable to the width W of the substrate 116.

[0042] In various embodiments, the ion implanter 100 can be configured to deliver an ion beam for "low" energy ion implantation or "medium" energy ion implantation (e.g., a voltage range of 1 kV to 300 kV) corresponding to an implantation energy range of 1 keV to 300 keV for singly charged ions. As described below, the scanning of the ion beam provided to the substrate 116 can be adjusted based on current measurements made for a given scanned ion beam.

[0043] The ion implanter 100 further includes a current detector 118, such as a closed loop current detector and in particular a closed loop Faraday current detector (CLF), to monitor the beam current provided to the substrate 116. The current detector 118 is arranged to intercept the ion beam outside the substrate region 119 and can be configured to record the measured integrated current of the ion beam 104 during the scan of the ion beam 104.

[0044] The ion implanter 100 also includes a scan adjustment component 120. The scan adjustment component 120 can be coupled to the beam scanner 110 and the current detector 118. The scan adjustment component 120 can be coupled to one or more components to adjust the scanning of the ion beam 104, especially in situations where measurements can be performed. The scan adjustment component 120 can include logic to generate adjustment signals for adjusting the scanning of the ion beam 104 based on various inputs. In some cases, the logic of the scan adjustment component 120 can be implemented in hardware, firmware, or a combination of hardware and software. In some examples, the scan adjustment component 120 can include circuitry such as a controller 120-A and a memory 120-B, which is coupled to software to execute instructions for adjusting the scanning of the ion beam 104. The embodiments are not limited to this context.

[0045] The inventors have discovered that, under certain configurations, when ion implantation is performed into a photoresist-coated substrate under closed-loop control in which the current reading obtained from the CLF monitor is used to adjust the implantation, the actual implanted ion dose deviates from the expected ion dose. The photoresist-coated substrate may be partially, mostly, or completely covered with a photoresist layer, which may serve as an implantation mask in some cases. Without being limited to a particular theory, the deviation of the actual implanted dose from the expected implanted dose during the photoresist implantation may be due to local pressure fluctuations in the environment near the substrate 116 and near the current probe 118.

[0046] According to various embodiments of the present disclosure, changes in pressure (e.g., changes in pressure in the substrate end station) due to photoresist implantation are determined and adjusted as described with respect to the following figures. A series of experiments have been conducted to record changes in detected current as ambient pressure changes. It should be noted that it has been observed that during implantation of a photoresist-coated wafer (substrate), the pressure in the substrate end station increases from background pressure to between 1E -5 To 5E -5torr range. According to some embodiments, in order to quickly determine the change of detected current with pressure, gas (for wafer cooling) is deliberately discharged into the substrate platen when there is no substrate. After setting the recipe, the wafer cooling pressure is rapidly ramped up (in some cases approximately one second) without a wafer on the substrate platen until the terminal station pressure reaches a value comparable to the peak value encountered during the substrate implant process (as described above, photoresist is present). The pressure then decreases ramped down. While the pressure in the terminal station is rising ramped up, the ion beam is scanned in the terminal station and the CLF current and the profiler (PF) current are recorded (where the PF monitor is placed at the center of the wafer), so the change in current value includes the CLF current / PF current ratio, and how the ratio changes with the CLF current.

[0047] Go to Figures 1A to 1F , Figures 1A to 1F The variation of beam current monitor parameters with changes in ambient pressure is shown for various cases. The pressure shown on the X axis of the figure is measured at the end station containing the substrate. Figure 1A and Figure 1C The relationship between CLF current and profiler current relative to the terminal pressure during the gas pressure ramp is shown. Figure 1A In , data are taken from the first implant configuration, while in Figure 1C In , data is taken from a second implanter configuration. In both configurations, no gas is exhausted into the implanter at an upstream location (eg, at the beam scanner 110). Figure 1B and Figure 1D Shown respectively for Figure 1A and Figure 1C The change in the CLF / PF current ratio (meaning the CLF current divided by the profiler (PF) current, where the profiler detector is placed at the center of the wafer) for each configuration.

[0048] It is apparent that the detected current and CLF / PF current ratio vary with gas pressure over the range of pressure characteristics of the pressure sensed during implantation of a photoresist coated substrate. Additionally, the variation in current and CLF / PF current ratio in implanter 2 is greater than that in the configuration of implanter 1. The CLF / PF current ratio varies by a few percent on implanter 2 but by <0.5% on implanter 1. Figure 1E and Figure 1F Detected current and current ratio are shown, respectively, for Implanter 2, where gas was vented at a rate of 1 sccm upstream of the end station in the scanner chamber (see beam scanner 110). Increasing venting in the scanner chamber reduced the CLF / PF current ratio variation in Implanter 2 to <0.5%.

[0049] In summary, the above results show a strong dependence of the detected current and CLF / PF current ratio on the end station pressure, implanter configuration, and the presence of gas venting upstream. It should be noted that in situations where gas venting is performed upstream (e.g., in the scanner chamber), energetic contamination of the implanted species at the substrate may increase. Therefore, using no gas venting upstream of the end station often helps to reduce energetic contamination. However, if Figure 1D As shown in , the actual "on-wafer" current increased by approximately 4% over the detected CLF current prediction at the expected peak exhaust pressure during implantation of a photoresist coated wafer (approximately 10 microtorr). These results indicate that an implant process using no gas exhaust on a photoresist coated substrate in Implanter 2 should be performed in a manner that overdoses the substrate by approximately 4% relative to an implant process performed on the same substrate using 1 sccm exhaust to the scanner chamber.

[0050] Figure 2A and Figure 2C Gas ramp calibration measurement results for implanter 2 are shown under no venting and 1 sccm venting conditions shown for two different gas pressure monitors as described above. As discussed in the following description, various calibration curves can be established using controlled gas ramp experiments, including curves representing various entities, including ratios referred to as difference ratios and / or current ratios. Figure 2B and Figure 2D Show the use and Figure 2A and Figure 2C Gas pressure behavior during implantation for the same measurement scheme. These results show that the variation of the upstream pressure relative to the end station pressure (IG3, on the X axis) is similar on Implanter 2 for both the gas ramp calibration and the actual implantation test, for both the no venting case and the 1 sccm venting.

[0051] Figure 3A The measured implant current deviation due to the presence of a photoresist-coated wafer is plotted relative to the current value that would be expected from an ion beam directed into a substrate position in an end station in the absence of the wafer. Specifically, the Y axis plots a ratio known as a difference ratio and is defined as the difference between the instantaneous current (I) measured by the first detector at a given pressure minus a baseline current (B) measured by the first detector at a baseline pressure before the start of the gas ramp, wherein the difference is divided by the baseline current. That is, the difference ratio can be expressed as (IB) / B. In the example, the first detector is a closed-loop Faraday detector (CLF detector). Thus, at a baseline pressure, the pressure in the implanter end station can be between less than 2×10 -6 within the scope of support. Figure 3A The data shown is based on Figure 1C, and represents the situation in which no exhaust gas is introduced upstream of the terminal station as described above. After the substrate is loaded onto the substrate platen coated with photoresist, the implantation current is measured by the CLF detector located on one side of the substrate during implantation of the substrate. In this way, during implantation, a pressure increase may occur due to the outgassing effect of the photoresist. Figure 3A In the data shown in , an ion beam is scanned across a substrate, creating a pressure excursion as the ion beam outgasses photoresist on the substrate into the end station. Figure 3A The data in represent data acquired during implantation of only one wafer (substrate). In general, the pressure in the end station fluctuates with beam position as the ion beam is scanned across the wafer, ranging from slightly less than 2 × 10 -5 The low value of tor increases to approximately 1×10 -5 All data points represent data derived from the instantaneous recording of pressure in the end station and the instantaneous measured beam current recorded by the CLF monitor. Thus, the data shown represent multiple recordings taken over multiple scans of the ion beam across the wafer.

[0052] like Figure 3A As shown in , in this example, the (IB) / B ratio increases monotonically by approximately 0.5% from the lowest pressure to the highest pressure, meaning that the measured implant current is approximately 0.5% higher than expected. Figure 3B In , the difference ratio ((IB) / B ratio) is plotted as a function of the change in current ratio (in this example, the CLF current / contour current ratio), where a negative % represents a decrease in the CLF current / contour current ratio relative to the ratio at the baseline pressure.

[0053] Therefore, based on Figure 3A and Figure 3B When the CLF current is changed while the substrate coated with the photoresist is exposed to the ion beam, the pressure change relative to the reference pressure can be obtained from Figure 3A The % change in the CLF / profile current ratio relative to the baseline ratio can be determined from Figure 3B It should be noted that pressure changes can also be used to correct for neutral effects and can be obtained in the table in the program for correcting for changes in the CLF current / contour current ratio.

[0054] Thus, when a substrate (e.g., a photoresist coated wafer) is exposed to an ion beam (e.g., a scanned ion beam), changes in implant current can be measured in real time by a sensor such as a CLF, wherein such changes in implant current are used to determine changes in pressure at the end station and changes in the CLF current / profile current ratio relative to a reference value. Thus, the current on the wafer will be known. The neutral component of the substance affecting the substrate can be determined from the pressure change based on the implant current change.

[0055] Figure 4A and Figure 4B Horizontal and vertical resistance (Rs) line scans are shown for substrates implanted under two different conditions compared to a reference substrate, showing the overimplantation due to the effect of gas pressure. Figure 4A In FIG. 1 , the upper two curves are shown as the horizontal resistance and vertical resistance for a bare implant substrate as a function of position on the substrate. In this case, the resistance is relatively high. Figure 4A In FIG. 1 , the lower two lines are the horizontal and vertical resistance values ​​of an implanted substrate with photoresist without exhausting upstream of the scanner chamber. As shown, the resistance values ​​are much lower, indicating that the substrate has been overdosed by approximately 5% relative to the target dose, as shown for a bare substrate. Figure 4B In the case of 1 sccm of gas exhaust during implantation, the Rs value of the bare substrate (the upper two curves) is Figure 1A The Rs value of the substrate coated with photoresist is the same as that expected in the above graph, while the Rs value of the substrate coated with photoresist (the two curves below) is slightly lower, indicating that Figure 4A The no-emission case is shown to have a smaller ion excess. The difference in excess between the two cases is predicted from the gas ramp calibration data, e.g. Figure 1D reflected in the data.

[0056] In summary, the above results show that the delivered dose implanted into a substrate with photoresist present matches the prediction of the delivered dose using the CLF current / PF current ratio data derived from the gas ramp calibration, which determines the CLF current / PF current ratio as the gas pressure in the terminal station changes. These results show that the CLF current / PF current ratio data from the gas ramp test calibration can be used to more accurately control the delivered ion dose implanted into the photoresist-coated substrate. In other words, determining the value of the CLF current / PF ratio as the implant current changes with the deviation of the target current can be used to deliver a more accurate dose to the wafer. That is, the % change of the CLF current measured at the reference pressure (reference current) relative to the set current can be used to predict the CLF current / PF current ratio change. This method accordingly excludes the ambient pressure from the equation, so the correction does not rely on the ion gauge accuracy.

[0057] Therefore, according to an embodiment of the present disclosure, during the implantation of at least one wafer (or substrate) in a series coated with photoresist, current measurements can be performed by a CLF monitor, for example at the beginning of the implantation process of each wafer, wherein the current measurement is converted back to the actual implantation current based on the previously measured current ratio (CLF current / PF current ratio).

[0058] Thus, according to the present embodiment, to dose compensate for a given ion implantation recipe, only one correction factor (the "dose compensation" factor) may be used, which is independent of the tuning conditions. This factor takes into account the net effect of the current ratio variation (CLF_current / Profiler_current) and the effect of neutral particles generated by the ions due to charge exchange interactions. The contribution of neutral particles to the variation does not depend on the set conditions, while the current ratio variation does. Thus, in practice, the dose compensation factor may vary as the tuning conditions change. The present embodiment more accurately determines the variable portion of the net dose compensation factor by measuring the variation of the current ratio with pressure for given tuning conditions.

[0059] Figure 5 A process flow 500 is shown in accordance with an embodiment of the present disclosure. At block 510, a controlled gas ramp calibration process is performed, wherein multiple values ​​of a current ratio are measured during the gas ramp calibration. The current ratio represents a ratio of a current measured by a first detector located on one side of a substrate to a current measured by a second detector located above the substrate position. In one example, the current ratio may represent a ratio of a current measured by a closed-loop Faraday detector to a current measured by a profile detector. Multiple measurements are performed as the pressure in an end station housing the substrate varies, the pressure being within a given pressure range. The given pressure range may cover a range of pressures generated when an ion beam is scanned over a photoresist-coated substrate.

[0060] At block 520, during the gas ramp calibration, a plurality of values ​​of a difference ratio are calculated within a given pressure range of the operation shown in block 510, wherein the difference ratio is defined as the difference between the instantaneous current (I) measured by the first detector at a given pressure minus the reference current (B) measured by the first detector at a reference pressure before the gas ramp begins, wherein the difference is divided by the reference current. That is, the difference ratio may be expressed as (IB) / B.

[0061] According to various embodiments of the present disclosure, the operations shown in blocks 510 and 520 may be performed before implanting a given plurality of substrates according to a given ion implantation recipe, and the results may be obtained in the form of a table, graph, or function to represent the variation of the difference ratio (IB) / B with pressure for a given recipe.

[0062] At block 530, a variation of the difference ratio as a function of the current ratio is determined, for example, for a given implant recipe used to generate blocks 510 and 520. In other words, the current ratio may be determined for a given number of pressure values. Specifically, for each pressure value during the gas ramp calibration of blocks 520 and 530, a current ratio measurement is determined and a difference ratio is determined such that each measured current ratio value corresponds to a difference ratio value. For example, at different gas pressures, these different current ratio values ​​and difference ratios may be stored as a table, function, or graph to express the correlation of the difference ratio to the current ratio or the variation of the difference ratio as a function of the current ratio.

[0063] At block 540, an ion beam is scanned over a substrate coated with a photoresist layer. The ion beam may be scanned over a given axis (e.g., an x-axis of a Cartesian coordinate system). At the same time, the substrate may be scanned along a second axis (e.g., a Y-axis) perpendicular to the first axis. The ion beam may be scanned using an implantation recipe employed during the gas ramp calibration of blocks 510 and 520. In some instances, according to some non-limiting embodiments, the ion beam may be scanned back and forth at a given rate (e.g., 0.5 kHz to 5 kHz). At the same time, the substrate may be scanned at a scanning rate where scanning the substrate from one end to the opposite end under the ion beam may require a duration of a few tenths of a second to a few seconds. Thus, the ion beam may be scanned back and forth along the first direction several hundred times during the duration of the substrate being scanned from one end to the opposite end. Thus, during scanning of the substrate (e.g., a circular substrate), outgassing of the photoresist may increase as the substrate moves from a position where only the edge of the substrate is scanned under the ion beam to a position where the widest portion of the substrate is scanned under the ion beam. Thus, during scanning of the substrate from one end to the other, the gas pressure may vary.

[0064] According to various embodiments, the substrate of block 540 and subsequent blocks may be one of a plurality of substrates to be implanted according to the recipe used to generate the information at blocks 510 and 520 .

[0065] At block 550, implant current is measured using a first detector located to one side of the substrate location during scanning of the ion beam over the substrate. During a single scan of the substrate under the ion beam, the implant current may be measured instantaneously at a large number of times, such as tens or hundreds of times. That is, during the one second duration of scanning the substrate along the second axis under the ion beam scanning along the first axis perpendicular to the second axis, the measurement of implant current may be performed by the first detector every several milliseconds.

[0066] At block 560, a value of the difference ratio is determined based on the implant current (I) measured by the first detector during scanning of the substrate and the ion beam. In some non-limiting examples, the value of the difference ratio may be determined for a plurality of implant current values ​​(e.g., for each implant current measurement of block 550). The value of the difference ratio may be determined based on the value of the reference current of block 520. In this operation, the calculation of the difference ratio is generally performed as shown in the calibration operation of block 520, and at block 560, the value of the difference ratio is based on the instantaneous implant current (I) measured by the first detector during the actual implant, wherein the value of B is as described at block 520, and the reference current (B) represents the reference current measured at the beginning of the implantation before scanning the substrate under the ion beam.

[0067] At block 570, a current ratio (CR) between the first detector and the second detector is determined at multiple times during the scan of the ion beam and the substrate by mapping the calculated difference ratio to the difference ratio / current ratio curve or function or table determined at block 530. The current ratio may be determined for multiple times during a given scan, such as determining a current ratio for each implant current measurement collected by the first detector.

[0068] At block 580, a correction current is calculated based on the current ratio measured at multiple times in block 570. Next, the scan of the ion beam is adjusted based on the correction current using the current ratio determined at block 570. For example, during a scan of the substrate, multiple values ​​of CR can be determined at multiple times. During a first scan, these values ​​of CR help determine how far the measured ion current (measured by a first detector located on one side of the substrate) deviates from the current on the substrate. More specifically, for a given scan (or multiple scans), the ion dose on the substrate (scan dose) is proportional to the current on the substrate multiplied by the scan time, where the current on the substrate is calculated based on the current (I) measured by the first detector multiplied by the current ratio. As in known methods, the scan speed of a given scan can be based on the average on-wafer current recorded from a fixed number of previous scans before the given scan. For any given scan, the current on the wafer = (CLF current for the scan) / (CR of the CLF current).

[0069] In summary, the present embodiment provides various advantages for correcting implant conditions, including the first advantage of using only one correction factor to adjust the conditions. Another advantage provided is that the correction of ion dose is independent of ion metering accuracy, since the measurement of the pressure drift over time is already indirectly accounted for in the dose compensation factor.

[0070] The scope of the present disclosure is not limited by the specific embodiments described herein. In fact, through the above description and the accompanying drawings, it will be apparent to those of ordinary skill in the art that, in addition to the embodiments and modifications described herein, various other embodiments of the present disclosure and various modifications to the present disclosure will also be apparent. Therefore, these other embodiments and modifications are intended to fall within the scope of the present disclosure. In addition, although the present disclosure has been described herein in the context of a specific embodiment in a specific environment for a specific purpose, it will be appreciated by those of ordinary skill in the art that the utility of the present disclosure is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Therefore, the claims described above should be understood in light of the full scope and spirit of the present disclosure described herein.

Claims

1. A method for implanting a substrate, comprising: performing an implantation process using a first implantation recipe by scanning an ion beam along a first axis over a substrate coated with a photoresist layer while scanning the substrate along a second axis, the second axis being perpendicular to the first axis; measuring implant current (I) at multiple times during the implant process using a first detector located to one side of the substrate location; determining a value of a difference ratio based on the implant current at the plurality of time instances, the difference ratio being represented by (IB) / (B), where I is the implant current and B is the current measured by the first detector during calibration at a baseline pressure in the absence of the substrate; determining, based on the difference ratio, a plurality of values ​​of a current ratio (CR) for the plurality of times during the implant process, the current ratio being a ratio of the implant current to a current measured by a second detector located above the substrate location during the calibration, wherein the determining the values ​​of the current ratio comprises mapping the difference ratio to a current ratio curve expressing (IB) / (B) as a function of the current ratio (CR); and Based on the current ratio, the scanning of the ion beam, the scanning of the substrate, or a combination thereof is adjusted.

2. The method according to claim 1, wherein the current ratio curve is determined by: measuring, for a plurality of times during a gas ramp calibration, a plurality of values ​​of the current ratio as a function of pressure in an end station housing the substrate, the pressure being within a given pressure range; and For the plurality of time instants, a plurality of values ​​of the difference ratio within the given pressure range are determined. The method of claim 1 , wherein the first detector is a closed-loop current detector.

4. The method of claim 1, wherein the scanning is adjusted by: determining a scanning dose of a first scanning based on the plurality of values ​​of the current ratio (CR); and Based on the scanning dose of the first scanning, a scanning speed of a second scanning subsequent to the first scanning is adjusted.

5. The method of claim 4, wherein the scanning is adjusted by: The scanning speed of the second scanning is adjusted based on the scanning dose of the first scanning and a plurality of scanning doses determined for a predetermined plurality of scannings before the first scanning.

6. An ion implanter comprising: An ion source that produces an ion beam according to the implant recipe; A scanner for scanning the ion beam; A first detector and a second detector for measuring the current of the ion beam; A substrate platform for scanning the substrate; as well as A controller for controlling the ion beam, the controller being configured to: Performing an implantation process by scanning the ion beam over the substrate along a first axis while scanning the substrate coated with a photoresist layer along a second axis, the second axis being perpendicular to the first axis; measuring implant current (I) at multiple times during the implant process using a first detector located to one side of the substrate location; determining a value of a difference ratio based on the implant current at the plurality of time instances, the difference ratio being represented by (IB) / (B), where I is the implant current and B is the current measured by the first detector during calibration at a baseline pressure in the absence of the substrate; determining, based on the difference ratio, a plurality of values ​​of a current ratio (CR) for each of the plurality of times during the implant process, the current ratio being a ratio of the implant current to a current measured by a second detector located above the substrate during the calibration, wherein the value of the current ratio is determined by mapping the difference ratio to a current ratio curve expressing (IB) / (B) as a function of the current ratio (CR); as well as Based on the current ratio, the scanning of the ion beam, the scanning of the substrate, or a combination thereof is adjusted.

7. The ion implanter of claim 6, wherein the current ratio curve is determined by: measuring, for a plurality of times during a gas ramp calibration, a plurality of values ​​of the current ratio as a function of pressure in an end station housing the substrate, the pressure being within a given pressure range; and For the plurality of time instants, a plurality of values ​​of the difference ratio within the given pressure range are determined.

8. The ion implanter of claim 6, wherein the first detector is a closed loop current detector.

9. The ion implanter of claim 6, wherein the scanning is adjusted by: determining a scanning dose of a first scanning based on the plurality of values ​​of the current ratio (CR); and Based on the scanning dose of the first scanning, a scanning speed of a second scanning subsequent to the first scanning is adjusted.

10. The ion implanter of claim 9, wherein the scanning is adjusted by: The scanning speed of the second scanning is adjusted based on the scanning dose of the first scanning and a plurality of scanning doses determined for a predetermined plurality of scannings before the first scanning.

11. A method for implanting a substrate, comprising: performing an implantation process using a first implantation recipe by scanning an ion beam over the substrate along a first axis while scanning the substrate along a second axis, the second axis being perpendicular to the first axis; measuring implant current (I) during the implant process using a first detector located on one side of the substrate location; determining a value of a difference ratio based on the implant current, the difference ratio being represented by (IB) / (B), where I is the implant current and B is the current measured by the first detector during calibration at a baseline pressure; determining a value of a current ratio (CR) during the implant process based on the difference ratio, the current ratio being a ratio of the implant current to a current measured by a second detector located above the substrate location during the calibration, wherein the determining the value of the current ratio comprises mapping the difference ratio to a current ratio curve expressing (IB) / (B) as a function of current ratio (CR); and Based on the current ratio, the scanning of the ion beam, the scanning of the substrate, or a combination thereof is adjusted.

12. The method of claim 11, wherein the current ratio curve is determined by: measuring, for a plurality of times during a gas ramp calibration, a plurality of values ​​of the current ratio as a function of pressure in an end station housing the substrate, the pressure being within a given pressure range; and For the plurality of time instants, a plurality of values ​​of the difference ratio within the given pressure range are determined. The method of claim 11 , wherein the first detector is a closed loop current detector.

14. The method of claim 11, wherein the scanning is adjusted by: determining a scanning dose of a first scanning based on a plurality of values ​​of a current ratio (CR); and Based on the scanning dose of the first scanning, a scanning speed of a second scanning subsequent to the first scanning is adjusted.

15. The method of claim 14, wherein the scanning is adjusted by: The scanning speed of the second scanning is adjusted based on the scanning dose of the first scanning and a plurality of scanning doses determined for a predetermined plurality of scannings before the first scanning.

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