JP2011243450A - Ion implanter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion implanter comprising a beam current measuring unit which can measure the value of a substantial beam current, with which a target is irradiated, depending on the pressure variation in a processing chamber changing every moment, and can measure an accurate beam current without being affected by a fluctuation caused by the charge up of a target.SOLUTION: An ion implanter 1 comprises a pressure gauge 8 which measures pressure in a processing chamber 7, a beam current measuring unit 6 arranged between an ion source 2 and a target 9 in order to partially measure the beam current of an ion beam 3, and a controller 12 which adjusts ion implantation parameters so that the target 9 is irradiated with a specified quantity of ion beam based on at least the measurement result from the beam current measuring unit 6 when the measurement by the pressure gauge 8 reaches a predetermined reference value.

Description

  The present invention relates to an ion implantation apparatus capable of implanting a desired amount of ions even when the pressure in a processing chamber fluctuates.

  In the ion implantation apparatus, the beam current of the ion beam or the target is monitored so that a desired amount of ions is implanted into the target by monitoring the beam current of the ion beam using a monitoring means such as a Faraday cup arranged in the vicinity of the target. The scanning speed is controlled.

  When a substance that easily volatilizes upon irradiation with an ion beam (for example, a photoresist) exists on the target surface, the substance is volatilized by irradiation of the ion beam onto the target, and becomes a gas to be a pressure in the processing chamber Becomes higher. When an ion beam collides with such a gas, ions in the ion beam become neutral particles by charge conversion.

  Since the ions that have become neutral particles have no electric charge, they cannot be detected by a monitoring means such as a Faraday cup. Therefore, such neutralization of ions has been regarded as a problem in controlling the beam current and the like for injecting a desired amount of ions into the target as described above. Therefore, as a technique for solving this problem, a technique such as Patent Document 1 has been proposed.

  In Patent Document 1, the gas pressure in the target chamber is measured by an ionization meter. The beam current of the ion beam is measured by a Faraday gauge through a groove provided in the disk every time the disk supporting the workpiece placed in the target chamber makes one rotation. Finally, it is disclosed that the beam current of a substantial ion beam applied to the workpiece is calculated by substituting these measurement results into a predetermined formula.

Japanese Patent Laid-Open No. 61-16456 (FIG. 1)

  In the technique described in Patent Document 1, measurement of the beam current by the Faraday gauge requires one rotation of the disk, so that the workpiece is irradiated corresponding to the pressure fluctuation in the processing chamber that changes every moment. The actual beam current value cannot be calculated. Therefore, it is impossible to accurately inject a desired amount of ions into the workpiece.

  Further, when the workpiece is charged up by being irradiated with the ion beam, a Faraday gauge is arranged on the downstream side (the side on which the ion beam travels) from the workpiece as in Patent Document 1. Then, fluctuations in the measured value of the beam current at the Faraday gauge occur (temporal fluctuations in the measured values due to fluctuations in space potential).

  This fluctuation of the measured value is considered to be caused by a change in the space potential generated due to the charged workpiece being scanned or the charge-up state of the workpiece being changed. This fluctuation makes it difficult to accurately measure the beam current, which in turn affects the substantial calculation of the beam current.

  Therefore, according to the present invention, it is possible to calculate the value of a substantial beam current irradiated to the target according to the pressure fluctuation in the processing chamber that changes from time to time, and the influence of fluctuations caused by target charge-up. An object of the present invention is to provide an ion implantation apparatus including a beam current measuring device that enables accurate beam current measurement without being subjected to the above.

  That is, an ion implantation apparatus according to the present invention includes an ion source, a target irradiated with an ion beam extracted from the ion source, a processing chamber in which the target is disposed, and a pressure for measuring a pressure in the processing chamber. And at least one of the ion beams that are disposed between the ion source and the target so as not to interfere with an irradiation region of the ion beam that is irradiated onto the target. The ion implantation parameters are set so that a predetermined amount of ions are implanted into the target when the measured value by the pressure gauge exceeds a predetermined reference value. And a control device for adjustment.

  As described above, a beam current measuring device is arranged between the ion source and the target so as not to interfere with the irradiation region of the ion beam irradiated on the target, and one of the ion beams not irradiated on the target. Since the fluctuation of the beam current of the ion beam is detected using the unit, the beam current of a part of the ion beam is always measured while the ion beam is irradiated toward the target. It becomes possible. As a result, it is possible to calculate the value of the substantial beam current irradiated to the target immediately in accordance with the pressure fluctuation that changes every moment in the processing chamber.

  The ion implantation apparatus further includes a holder for holding the target and holder driving means for driving the holder, and the implantation parameter is a speed at which the holder is driven by the holder driving means. It is desirable that

  The holder drive speed can be changed quickly compared to changing the ion beam current or the like. In addition, since the changed value is not affected by degassing from the target, ions of a desired implantation amount can be accurately implanted into the target.

  Furthermore, it is desirable to provide a function capable of turning on and off the function of the control device. By doing so, when it is not necessary to use the control device, it is possible to keep the function of the control device from working so that the processing in the control device can be omitted and the unit time in the ion implantation device. The number of targets processed per hit can be increased.

  The beam current measuring device provided in the ion implantation apparatus of the present invention is configured to always measure the beam current of a part of the ion beam while the ion beam is irradiated toward the target. The value of the substantial beam current irradiated to the target can be calculated according to the pressure fluctuation in the processing chamber that changes every moment. Furthermore, since the beam current measuring device is disposed between the ion source and the target, it is possible to accurately measure the beam current without being affected by fluctuations caused by the charge-up of the target.

It is a top view which shows the ion implantation apparatus which concerns on one Example of this invention. The state when the beam current measuring device 6 shown in FIG. 1 is viewed from the direction opposite to the X direction is shown.

  An example of an ion implanter of the present invention is shown in FIG.

  In the ion implantation apparatus 1, mass analysis is performed using the mass analysis magnet 4 and the analysis slit 5 so that only desired ions are irradiated from the ion beam 3 extracted from the ion source 2. In FIG. 1, only the center trajectory on the XY plane of the ion beam 3 is drawn by a one-dot chain line.

  In the processing chamber 7, the target 9 is supported by a holder 10 and is reciprocated and conveyed in the direction of arrow A by a driving mechanism (not shown). During this reciprocal transfer, the ion beam 3 introduced into the processing chamber 7 is traversed to perform ion implantation processing on the entire surface of the target 9. A conventional drive mechanism may be used.

  For example, a ball screw that can be rotated in the forward and reverse directions by a motor provided outside the processing chamber 7 is introduced into the processing chamber 7 through a vacuum seal, and the rotational motion is linearly moved to the ball screw. A ball nut to be converted is screwed, and finally this ball nut and the holder 10 are connected to each other so that the holder 10 can be transported in the direction of the arrow A or provided outside the processing chamber 7. A shaft that can be moved along the direction of arrow A by a motor is introduced into the processing chamber 7 via a vacuum seal, and the holder 10 is supported at the end of this shaft, so that This is the mechanism that enables the holder 10 to be transported.

  A beam current measuring device 11 for measuring the beam current density distribution of the ion beam 3 is provided on the side wall in the processing chamber 7. The beam current measuring device 11 is used when adjusting the beam current density distribution in the Z direction (long side direction of the ion beam) of the ion beam 3 extracted from the ion source 2. Therefore, the beam current measuring instrument 11 has a dimension larger than at least the dimension of the ion beam 3 described later in FIG. 2 in the Z direction. The beam current measuring device 11 may be a measuring device in which a plurality of Faraday cups as conventionally used are arranged along the Z direction.

  The pressure gauge 8 is attached to the processing chamber 7 in order to measure the pressure in the processing chamber 7, and degassing from the target 9 generated in the processing chamber 7 based on the measurement result by the pressure gauge 8. The pressure fluctuation in the processing chamber 7 is detected.

  Examples of the target 9 include a semiconductor substrate, more specifically, a silicon wafer and a glass substrate. A glass substrate has an area irradiated with an ion beam several tens of times larger than that of a silicon wafer. Accordingly, the variation of the space potential that occurs when the charged glass substrate is transferred is larger than the variation of the space potential that occurs when the charged silicon wafer is moved. Therefore, when the present invention is applied to an ion implantation apparatus that performs ion implantation into a glass substrate, it can be said that the effect is great.

  Of course, when the target 9 is irradiated with the ion beam 3 and the resist provided on the surface of the target 9 is volatilized, degassing occurs from the target 9. It doesn't matter what it is.

  In detecting the actual pressure fluctuation, a reference value of a predetermined pressure is prepared, and when the pressure value measured by the pressure gauge 8 exceeds this reference value, there is a pressure fluctuation in the processing chamber 7. to decide.

  After this determination, adjustment of injection parameters, which will be described later, is performed. If the injection parameters are adjusted without detecting the pressure fluctuation, the filament of the ion source 2 may be broken.

  The reason for this will be described. Prior to the adjustment of the implantation parameters, the beam current of the ion beam 3 is measured by the beam current measuring device 6 arranged on the downstream side of the analysis slit 5. At this time, it is erroneously recognized that the value of the beam current is smaller than an assumed value due to the pressure fluctuation in the processing chamber 7, and a predetermined amount of ion implantation to the target 9 is achieved. Assume that the amount of current flowing through the filament of the ion source 2 is increased. In this case, if the result of measurement by the beam current measuring device 6 has actually decreased due to the fact that the filament of the ion source has been tapered due to sputtering or the like, a large amount of the filament that has become thinner Therefore, the filament may be broken.

  However, by detecting the pressure fluctuation in the processing chamber 7 with the pressure gauge 8, it is possible to know whether or not the beam current of the ion beam 3 has decreased due to at least degassing from the target 9. The risk of operations such as increasing the amount of current flowing through the filament of the ion source 2 unnecessarily can be reduced. It also helps to analyze the factors that cause the beam current to decrease.

  When it is detected by the pressure gauge 8 that the pressure in the processing chamber 9 has changed due to degassing, the beam current of the substantial ion beam irradiated to the target by the controller 12 based on the measurement result by the beam current measuring device 6. Is calculated. The substantial ion beam beam current referred to here is not only the beam current caused by ions having a charge measurable with an amperometer, but also neutralized particles contained in the ion beam irradiated to the target 9. It means a beam current that takes into account the beam current caused by ions.

  The beam current measuring device 6 detects a variation in the beam current of the ion beam by using a part of the ion beam that is not irradiated to the target 9. This is illustrated in FIG. The beam current measuring device 6 may be a conventional Faraday cup.

  FIG. 2 shows a state when the beam current measuring device 6 shown in FIG. 1 is viewed from the direction opposite to the X direction.

  The ion beam 3 shown in FIG. 2 is an ion beam 3 that has passed through the analysis slit 5 and includes only a desired ion species that is irradiated onto the target 9. In the YZ plane, the cross section has a substantially rectangular shape. As described above, since the target 9 is reciprocated in the direction of arrow A (Y direction) so as to cross the ion beam 3, the entire surface of the target 9 can be irradiated with the ion beam 3.

  In this case, not all of the ion beam 3 is irradiated on the target 9. In order to clarify the positional relationship among the ion beam 3, the beam current measuring device 6, and the target 9 that is reciprocally conveyed, the trajectory of the reciprocal conveyance of the target 9 in the processing chamber 7 is drawn in broken lines in FIG. .

  9A and 9B in FIG. 2 show the outer shape of the target. Here, the target 9 is assumed to be a rectangular glass substrate. The target 9 is reciprocated between the targets indicated by 9A and 9B along the Y direction. At that time, it is understood that a part of the ion beam 3 is not irradiated on the target 9 in the Z direction. A beam current measuring device 6 measures a beam current of a part of the ion beam not irradiated on the target 9.

  Since the beam current measuring device 6 is disposed at a position as shown in FIG. 2, the irradiation of the ion beam 3 to the target 9 is not hindered. Further, since the beam current measuring device 6 is arranged upstream of the target 9 in the traveling direction of the ion beam 3, the beam current is not affected by the variation of the space potential caused by the charged target 9. Can be measured.

  The measurement result of the beam current by the beam current measuring device 6 is transmitted to the control device 12 shown in FIG. The control device 12 adjusts ion implantation parameters related to the implantation amount based on the beam current generated by the pressure fluctuation in the processing chamber 7 so that the implantation amount of ions implanted into the target 9 becomes a desired one. To do.

  Specifically, the adjustment of the injection parameters is performed as follows. Before the pressure fluctuation in the processing chamber 7 occurs, the beam current is measured by the beam current measuring device 6, and this value is stored in the control device 12. On the other hand, the beam current measuring device 11 measures the value of the beam current of the entire ion beam 3 before the pressure fluctuation in the processing chamber 7 occurs, and this value is also stored in the control device 12. deep.

  When the pressure fluctuation does not occur from the ratio of the measurement value obtained by the beam measuring device 6 measured when the pressure fluctuation occurs and the measurement value obtained by the beam measuring device 6 measured before the pressure fluctuation occurs. The total beam current value (I) of the ion beam 3 when the pressure fluctuation occurs is calculated using the value of the total beam current of the ion beam 3.

  Based on the calculated value (I) of the beam current and the measured value (P) of the pressure gauge 8 in the processing chamber 7, the value is substituted into the following formula, and the target 9 is substantially irradiated. Calculate the value of the correct beam current.

 In the above mathematical formula, K is a correction coefficient determined by the ion species irradiated to the target and the configuration of the ion implantation apparatus, and It indicates a substantial beam current irradiated to the target 9.

  By calculating It, it is possible to know the substantial beam current of the ion beam applied to the target 9, and based on this result, the beam current of the ion beam 3 and the driving during the reciprocal conveyance of the target 9 are performed. By appropriately changing the speed, it is possible to finally achieve ion implantation of a desired implantation amount for the target 9.

  Although the beam current and the driving speed of the holder 10 that supports the target 9 are given as the implantation parameters, other parameters may be used as long as they are parameters related to the amount of ions implanted into the target 10. . For example, if the ion implantation apparatus is of a type that scans a spot-like ion beam using a magnetic field or an electric field, the scanning speed of the ion beam may be adjusted.

  However, it takes time to control the ion beam parameters (beam current and scanning speed) so that the ion beam characteristics become the desired characteristics. In addition, under the influence of degassing from the target 9, the adjusted value may change again.

  On the other hand, the drive speed of the holder 10 that supports the target 9 has good control responsiveness and is not affected by degassing from the target 9. Therefore, it is desirable that the injection parameter to be adjusted is the driving speed of the holder 10 that supports the target 9.

  Furthermore, in addition to the method of calculating the substantial beam current using the above formula, there is also a method of calculating the drive speed to be adjusted directly using the following formula.

  In the above formula, V is the driving speed of the holder 10 to be adjusted, and Vo is the driving speed of the holder 10 before the pressure fluctuation in the processing chamber 7 occurs. I is a beam current value measured by the beam current measuring device 6 after the pressure fluctuation in the processing chamber 7 occurs, and Io is a beam current measuring device before the pressure fluctuation in the processing chamber 7 occurs. 6 is the value of the beam current measured in 6. Similarly, P is the pressure in the processing chamber 7 after the pressure fluctuation measured by the pressure gauge 8, and Po is the pressure in the processing chamber 7 before the pressure fluctuation. K is a correction coefficient determined by the ion species irradiated to the target and the configuration of the ion implantation apparatus, as in the previous mathematical expression.

  Depending on the ion implantation conditions and the type of target, it may not be necessary to adjust the ion implantation parameters by the controller 12. Therefore, you may comprise so that the function of the control apparatus 12 can be turned on and off according to the characteristic of the device on the target manufactured by the ion implantation apparatus 1. FIG. Before manufacturing a full-scale device, a small amount of target 9 is processed in the ion implantation apparatus 1 as a prototype. In this prototype stage, the function of the control device 12 provided in the ion implantation apparatus 1 is not used. In other words, in the case of turning on and off, it is in a cut state. Then, the characteristics (threshold voltage and the like) of the device manufactured in such a trial production stage are inspected to confirm whether or not a desired device has been manufactured.

  In the above-described confirmation, a reference range is provided for a predetermined device characteristic, and it is confirmed whether the manufactured device characteristic is within this range. If there is a device characteristic within this range, the function of the control device 12 is not used during full-scale device manufacturing. That is, the function of the control device 12 is turned off. On the other hand, when there is no device characteristic within the range, the function of the control device 12 is made to work at the time of full-scale device manufacture. That is, the function of the control device 12 is kept on.

  In this way, when the control device 12 is configured so that the function of the control device 12 can be turned on and off as necessary in consideration of the device characteristics when the device is manufactured on the target 9 as a prototype, the ion implantation apparatus The number of targets 9 processed per unit time can be increased. This is because the calculation time and the like by the control device 12 can be omitted as much as the function of the control device 12 is not used.

The control device 12 can be switched on and off by providing a user interface that allows the operation of the control device 12 so that the operator of the ion implantation apparatus 1 can perform the on / off operation. Alternatively, the control device 12 may be provided with physical means such as a switch so that the functions of the control device 12 can be turned on and off.
<Other variations>

  The ion implantation apparatus to which the present invention is applied is not limited to the above-described embodiment. For example, an ion implantation apparatus that does not include the mass analysis magnet 4 and the analysis slit 5 may be used. Alternatively, the ion implantation apparatus may be of a type in which the target 9 is fixed and the ion beam 3 having a size larger than that of the target 9 is used to irradiate the entire surface of the target 9 with the ion beam 3.

  In addition, a spot-like ion beam is extracted from the ion source, and is scanned in one plane so that the ion beam spreads in a direction orthogonal to the traveling direction of the ion beam by a magnetic field or an electric field, and the scanned ion beam is applied to the magnetic field. Alternatively, an ion implantation apparatus configured to irradiate the target through a collimator that is substantially parallelized in the plane by an electric field may be used. In that case, for example, the beam current measuring device 6 described in the above embodiment may be arranged between the collimator and the target.

  Furthermore, the beam current measuring device 6 may be configured to be movable along the Z direction so that the function of the beam current measuring device 11 can also be used. Specifically, the ion beam 3 is irradiated into the processing chamber 7 before the ion implantation process. At this time, the beam current of the ion beam 3 is measured while moving the beam current measuring device 6 in the Z direction. In addition, about the structure which moves the beam current measuring device 6, what reduced the drive mechanism of the holder 10 should just be used.

  In the previous embodiment, the beam current measuring device 6 measures only the lower part in the Z direction of the ion beam 3 as shown in FIG. Another beam current measuring device may be prepared for measurement. In addition, a value obtained by averaging the measurement results obtained by the respective beam current measuring devices may be used as the measured value of the beam current. By configuring in this way, it is possible to more appropriately deal with the influence of degassing spreading over the entire ion beam 3.

  In addition to the above, it goes without saying that various improvements and modifications may be made without departing from the scope of the present invention.

1. Ion implantation apparatus 2. 2. ion source Ion beam4. 4. Mass analysis magnet Analysis slit6. 6. Beam current measuring instrument Processing chamber 8. Pressure gauge9. Target 10. Holder 12. Control device

Claims (4)

An ion source;
A target irradiated with an ion beam extracted from the ion source;
A processing chamber in which the target is disposed;
A pressure gauge for measuring the pressure in the processing chamber;
At least a part of the ion beam that is disposed between the ion source and the target and that is not irradiated on the target so as not to interfere with an irradiation region of the ion beam irradiated on the target A beam current measuring device for measuring current;
A control device that adjusts ion implantation parameters so that a predetermined amount of ions is implanted into the target when a value measured by the pressure gauge exceeds a predetermined reference value. Ion implantation equipment. The ion implantation apparatus includes:
A holder for holding the target;
A holder driving means for driving the holder;
The ion implantation apparatus according to claim 1, wherein the implantation parameter is a speed at which the holder is driven by the holder driving means.   The ion implantation apparatus according to claim 1, wherein the target is a glass substrate. The ion implantation apparatus according to claim 1, wherein a function capable of turning on and off the function of the control device is provided.