JP4147699B2 - Ion implanter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ion implantation apparatus that performs ion implantation by irradiating a substrate with an ion beam extracted from an ion source having a plurality of filaments, and more specifically, a beam current of an ion beam extracted from the ion source is a predetermined value. In addition, the present invention relates to an improvement in means for controlling the uniformity.
[0002]
[Prior art]
A plurality of beam current measuring devices and a filament current flowing through each filament based on the beam current measured by the beam current measuring device are controlled at least once. An ion implantation apparatus capable of controlling the beam current of an ion beam to a predetermined value and having good uniformity while preventing deterioration of uniformity due to changes over time of the filament, etc. It has been previously proposed by the same applicant (Japanese Patent Application No. 11-123974). One example thereof will be described with reference to FIGS.
[0003]
The ion implantation apparatus shown in FIG. 4 is also called an ion doping apparatus (or non-mass separation type ion implantation apparatus), and a wide ion beam 12 drawn from the ion source 2 is directly used as a substrate without passing through a mass separator. 14 is configured to perform ion implantation on the substrate 14.
[0004]
The substrate 14 is held on a substrate holder 13 that is somewhat larger than the substrate 14, and both are reciprocally scanned in the direction of arrow D within the irradiation region of the ion beam 12 extracted from the ion source 2 by the holder scanning mechanism 15.
[0005]
The substrate holder 13 and the substrate 14 have a square shape (square or rectangular shape) as shown in FIG. 5, for example. The planar shape of the ion beam 12 is, for example, an elongated rectangle as shown in FIG.
[0006]
The ion source 2 is also called a bucket type ion source (or a multipole magnetic field type ion source), and a plurality of (for example, three) filaments 6 are provided in the plasma generation container 4. An arc discharge is generated between the generation container 4 and the ion source gas is ionized to generate plasma 8, and the ion beam 12 is extracted from the plasma 8 by the extraction electrode system 10. Illustration of a magnet for forming a multipolar magnetic field is omitted.
[0007]
In this example, a filament power source 16 is connected to each filament 6, and a filament current IF for heating each filament 6 can flow independently from each other from each filament power source 16 to each filament 6. it can.
[0008]
In order to control the beam current of the ion beam 12 extracted from the ion source 2 to a predetermined value, the ion implantation apparatus further receives the ion beam 12 and supplies the beam current to a plurality of downstream sides of the scanning region of the substrate holder 13. Based on a plurality of (for example, 24) beam current measuring instruments 18 that are measured at the position and larger than the number of filaments 6 and the beam current IB measured by the beam current measuring instrument 18, And a control device 20 that controls a filament current IF flowing through each filament 6.
[0009]
As shown in FIG. 5, the beam current measuring devices 18 are arranged, for example, in a line in the irradiation region of the ion beam 12 and downstream of the scanning region of the substrate holder 13.
[0010]
As shown in FIG. 6, the control device 20 repeats the current value control routine (step 30) and the uniformity control routine (step 31) one or more times.
[0011]
An example of the current value control routine is shown in FIG. FIG. 9 shows a schematic example of a beam profile before and after the control, and FIG. 9 is also referred to in the following description. Note that 1 to 24 on the horizontal axis in FIG. 9 indicate numbers from the ends of the 24 beam current measuring devices 18.
[0012]
First, each beam current measuring device 18 measures the beam current of the ion beam 12 (step 50). Thereby, for example, the beam profile A in FIG. 9 is obtained. Next, an average value AVE of all the measured beam currents IB is calculated (step 51).
[0013]
It is determined whether or not the average value AVE is within the stop range STP for the set value SET (step 52). The stop range STP is, for example, a range of ± 3% of the set value SET. If it is within the stop range STP, the purpose of the average value control has already been achieved, and the process proceeds to the uniformity control routine shown below.
[0014]
When the average value AVE is not within the stop range STP, the routine proceeds to step 53, where it is determined whether or not the average value AVE is larger than the set value SET. If the filament current IF is decreased by a predetermined amount, and if it is smaller, the process proceeds to step 55, and the filament current IF flowing through all the filaments 6 is increased by a predetermined amount. In this example, the amount of the increase or decrease is the same (including the same) amount for all the filaments 6. By increasing or decreasing the filament current IF, the amount of electrons emitted from each filament 6 increases or decreases, thereby increasing or decreasing the density of the plasma 8 in the vicinity of each filament 6, and the ion beam 12 extracted from the region corresponding to each filament 6. The beam current increases or decreases.
[0015]
By the current value control routine, the average value AVE of the beam current of the ion beam 12 drawn from the ion source 2 is controlled so as to approach the set value SET. Thereby, for example, the beam profile B in FIG. 9 is obtained. In this state, since the uniformity control routine has not yet been executed, the beam profile B has a shape similar to the original beam profile A, and the beam profile A is almost translated. .
[0016]
Subsequently, the process proceeds to the uniformity control routine. An example is shown in FIG.
[0017]
Here, the 24 beam current measuring devices 18 (measurement points) are grouped into the number of filaments 6, that is, three (step 60). Specifically, as shown in FIG. 9, the 1st to 8th beam current measuring devices 18 are group 1, the 9th to 16th beam current measuring devices 18 are group 2, and from the 17th The beam current measuring instruments 18 up to the 24th are grouped as 3.
[0018]
Then, the maximum value MAX and the minimum value MIN are searched from all the measurement values obtained by all the beam current measuring devices 18 (step 61), and the groups to which the maximum value MAX and the minimum value MIN belong are determined (step 62). . In the example of FIG. 9, the maximum value MAX belongs to the group 1 and the minimum value MIN belongs to the group 3.
[0019]
Then, the filament current IF flowing through the filament 6 corresponding to the group 1 to which the maximum value MAX belongs is decreased by a predetermined amount (step 63), and the filament current IF flowing through the filament 6 corresponding to the group 3 to which the minimum value MIN belongs is determined by a predetermined amount. (Step 64). As a result, the beam current of group 1 decreases and the beam current of group 3 increases.
[0020]
By this uniformity control routine, the beam current of the group 1 to which the maximum value MAX of the beam profile B belongs is decreased and the beam current of the group 3 to which the minimum value MIN belongs is increased, so that the uniformity of the beam current is good. Is controlled in the direction. Thereby, for example, a beam profile C shown in FIG. 9 is obtained.
[0021]
The uniformity of the beam current can be defined by (MAX−MIN) / (MAX + MIN) using, for example, the maximum value MAX and the minimum value MIN of the beam current at all measurement points.
[0022]
According to this ion implantation apparatus, since the current value control routine and the uniformity control routine as described above are performed at least once by the control device 20, the deterioration of uniformity due to a change in the filament 6 over time or the like is prevented, It is possible to control the beam current of the ion beam 12 to a predetermined value (that is, to the set value SET) and to have good uniformity.
[0023]
Moreover, according to the two-stage control of the current value control routine and the uniformity control routine as described above, unlike the conventional technique described in Japanese Patent Laid-Open No. 3-134937, the control causes hunting. Stable control can be performed without causing the problem of non-convergence.
[0024]
[Problems to be solved by the invention]
However, in the ion implantation apparatus of the preceding example, as shown in FIG. 5, while the substrate holder 13 is scanned and the substrate 14 is irradiated with the ion beam 12 and the ion implantation is performed on the substrate 14, Since the beam 12 is blocked by the substrate holder 13 and is not incident on the beam current measuring device 18, the beam current measuring device 18 does not output the measurement value of the beam current IB. The above-described control of the 12 current values and uniformity cannot be performed.
[0025]
The time required for one reciprocating scan of the substrate holder 13 is relatively short, for example, about 3 to 20 seconds. If the time is within such a short time, the ion beam 12 is uniform due to the difference with time of each filament 6 of the ion source 2. Although the decrease in the characteristics can be ignored, the current value of the ion beam 12 can change from moment to moment depending on the state of the plasma 8 in the ion source 2, so that the specific value can be obtained even during ion implantation into the substrate 14. It is preferable that the current value of the ion beam 12 can be controlled even when the substrate holder 13 is shielding the beam current measuring device 18. By doing so, it becomes possible to perform ion implantation amount (dose amount) control on the substrate 14 with higher accuracy.
[0026]
Therefore, the present invention further improves the ion implantation apparatus as described above, and controls the ion beam current value extracted from the ion source to a predetermined value even while the substrate holder shields the beam current measuring device. The main purpose is to provide an injection device.
[0027]
[Means for Solving the Problems]
An ion implantation apparatus according to the present invention receives an ion beam extracted from the ion source and measures a beam current thereof. The ion implantation apparatus is disposed outside a scanning region of the substrate holder and is scanned by the substrate holder during scanning. An unshielded non-shielded beam current measuring device is further provided.
[0028]
In addition, the control device constituting the ion implantation apparatus according to the present invention includes a pre-scan control that repeats the current value control routine and the uniformity control routine a predetermined number of times before the substrate holder starts scanning, and scanning of the substrate holder. The measurement value obtained by the non-shielded beam current measuring instrument immediately before the start is stored as a target value, and each filament is measured so that the measured value obtained by the non-shielded beam current measuring instrument approaches the target value during scanning of the substrate holder. Scanning control for increasing and decreasing the filament currents to be supplied by substantially the same amount is performed for each reciprocating scan of the substrate holder.
[0029]
According to the above configuration, before starting the scanning of the substrate holder, the current value control routine and the uniformity as described above are based on the beam currents measured by a plurality of beam current measuring devices, as in the case of the preceding example. The control routine is repeated a predetermined number of times (control before starting scanning). As a result, the beam current of the ion beam extracted from the ion source can be controlled to a predetermined value and with good uniformity.
[0030]
On the other hand, during the scanning of the substrate holder, the filament current passed through each filament of the ion source is controlled so that the measured value by the non-shielded beam current measuring instrument approaches the target value stored immediately before the scanning of the substrate holder is started ( Control during scanning). Therefore, even when the substrate holder shields the beam current measuring device, the beam current value of the ion beam drawn from the ion source can be controlled to a predetermined value.
[0031]
Moreover, since the control before the start of scanning and the control at the time of scanning as described above are performed for each reciprocating scan of the substrate holder, the ion beam is accurately applied to the substrate with an accurate beam current value and a uniform ion beam. An injection can be performed.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a view showing an example of an ion implantation apparatus according to the present invention. FIG. 2 is a plan view around the substrate holder of the apparatus of FIG. Portions that are the same as or correspond to those of the preceding example described above are denoted by the same reference numerals, and differences from the preceding example will be mainly described below.
[0033]
The ion implantation apparatus receives an ion beam 12 extracted from the ion source 2 and measures the beam current IB. The ion implantation apparatus is arranged outside the scanning region of the substrate holder 13 and is scanning. One unshielded beam current measuring device 24 that is not shielded by the substrate holder 13 is further provided. The non-shielded beam current measuring device 24 is also composed of, for example, a Faraday cup, like the beam current measuring devices 18.
[0034]
Further, this ion implantation apparatus includes the following control device 22 as an alternative to the control device 20 in the preceding example.
[0035]
In this example, the control device 22 is based on the beam current IB measured by each of the beam current measuring devices 18 and the non-shielded beam current measuring device 24 and based on the scanning information of the substrate holder 13 by the holder scanning mechanism 15. Thus, the pre-scan start control in steps 30 to 32 and the scan time control in steps 33 to 39 shown in FIG. 3 are performed for each reciprocating scan of the substrate holder 13.
[0036]
More specifically, first, before starting the scanning of the substrate holder 13, as in the case of FIG. 6, the current value control routine (step 30) and the uniformity control routine (step 31) are performed one or more predetermined times. Repeatedly (steps 30 to 32). An example of this current value control routine is as shown in FIG. 7, and an example of the uniformity control routine is as shown in FIG.
[0037]
By this control before the start of scanning, the beam current of the ion beam 12 drawn out from the ion source 2 can be controlled to a predetermined value and with good uniformity as in the case of the previous example.
[0038]
Next, the measurement value (beam current IB) measured by the non-shielding beam current measuring instrument 24 immediately before the start of scanning of the substrate holder 13 is stored as a target value (step 33), and scanning of the substrate holder 13 is started (step 34).
[0039]
While scanning the substrate holder 13, it is determined whether or not the measured value by the non-shielded beam current measuring device 24 is larger than the target value (step 35). If larger, the process proceeds to step 36 and the filament current flowing through all the filaments 6. Decrease IF by a predetermined amount. If it is not larger, the routine proceeds to step 37, where it is determined whether or not the measured value is smaller than the target value. If smaller, the routine proceeds to step 38 where the filament current IF flowing through all the filaments 6 is increased by a predetermined amount. In this example, the amount of the increase or decrease is the same (including the same) amount for all the filaments 6. By increasing or decreasing the filament current IF, the amount of electrons emitted from each filament 6 increases or decreases, thereby increasing or decreasing the density of the plasma 8 in the vicinity of each filament 6, and the ion beam 12 extracted from the region corresponding to each filament 6. The beam current increases or decreases.
[0040]
The processes in steps 35 to 38 are performed until one reciprocating scan of the substrate holder 13 is completed (step 39).
[0041]
By this control at the time of scanning, during scanning of the substrate holder 13, that is, during ion implantation into the substrate 14, the measurement value by the non-shielding beam current measuring instrument 24 approaches the target value stored immediately before the substrate holder 13 starts scanning. Controlled. That is, the current value of the ion beam 12 drawn from the ion source 2 can be controlled to a predetermined value even while the substrate holder 13 is shielding the beam current measuring device 18. Therefore, the dose amount control for the substrate 14 can be performed with higher accuracy than in the case of the previous example.
[0042]
The pre-scan start control and the scan control are performed for each reciprocating scan of the substrate holder 13. That is, in step 40, it is determined whether or not the substrate holder 13 has been reciprocated a predetermined number of times. If the predetermined number of reciprocating scans are completed, the control is terminated. If not completed, the process returns to the current value control routine in step 30. The above control is repeated.
[0043]
Although the uniformity control of the ion beam 12 is not performed during the reciprocating scanning of the substrate holder 13, as described above, such a decrease in the uniformity of the ion beam 12 within a short time can be ignored. Since it can, there is no particular problem. In addition, since the uniformity control routine of step 31 is performed every time the substrate holder 13 is reciprocated, the uniformity of the ion beam 12 can be kept good.
[0044]
As described above, according to this ion source, the control before the start of scanning and the control at the time of scanning as described above are performed for each reciprocating scan of the substrate holder 13, so that an accurate beam current value can be obtained. With the good ion beam 12, ion implantation can be performed on the substrate 14.
[0045]
The uniformity control routine in step 31 in FIG. 3 may be as shown in FIG. The difference from FIG. 8 will be mainly described. In the uniformity control routine of FIG. 10, a plurality of beam current measuring devices 18 (measurement points) are set to the number of filaments 6 as in step 60 of FIG. The group is divided into three groups (step 70), the average values of the measurement beam currents in the groups 1 to 3 are calculated (step 71), and the group having the maximum average value (in the example of FIG. 1) and the group having the minimum average value (group 3 in the example of FIG. 9) are respectively determined (step 72), and the filament current IF flowing through the filament 6 corresponding to the group 1 having the maximum average value is decreased (step 73). ) Increase the filament current IF passed through the filament 6 corresponding to the group 3 having the minimum average value (step 74).
[0046]
By adopting such a uniformity control routine, even if a small number of singular values and noise are included in a plurality of beam current measurement values by a plurality of beam current measuring devices 18, an average value for each group is obtained. Since the control is based on the beam current, the beam current can be controlled while suppressing the influence of the singular value and noise. In other words, even if there is a single singular point or noise, it is possible to prevent the entire control from being dragged and to control the beam current of the entire ion beam more correctly.
[0047]
Note that the plurality of filament power supplies 16 are not necessarily separate, and may be combined into one filament power supply that can flow the filament current IF to each filament 6 independently of each other. good.
[0048]
Further, the number of the beam current measuring devices 18 is, for example, an integer multiple of 2 or more of the number of filaments 6, but is not necessarily an integer multiple. Further, the number of beam current measuring instruments 18 belonging to each group is not necessarily the same. The number of beam current measuring instruments 18 in a group to be controlled more finely may be increased than the others.
[0049]
The control as in the above example by the control device 22 can be said to be an ion implantation device control method, an ion source control method, or an ion beam current automatic control method, as a control method.
[0050]
【The invention's effect】
As described above, according to the present invention, the current value control routine and the uniformity control routine are repeatedly performed a predetermined number of times based on the beam currents measured by the plurality of beam current measuring devices before the substrate holder starts scanning. Therefore, it is possible to control the beam current of the ion beam extracted from the ion source to a predetermined value and to have good uniformity.
[0051]
On the other hand, during scanning of the substrate holder, the filament current flowing through each filament of the ion source is controlled so that the measurement value by the non-shielding beam current measuring instrument approaches the target value stored immediately before the scanning of the substrate holder is started. Even when the substrate holder shields the beam current measuring device, the beam current value of the ion beam drawn from the ion source can be controlled to a predetermined value.
[0052]
Moreover, since the control before the start of scanning and the control at the time of scanning as described above are performed for each reciprocating scan of the substrate holder, the ion beam is accurately applied to the substrate with an accurate beam current value and a uniform ion beam. An injection can be performed.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of an ion implantation apparatus according to the present invention.
FIG. 2 is a plan view around a substrate holder of the apparatus of FIG.
FIG. 3 is a flowchart showing an example of control contents by the control device in FIG. 1;
FIG. 4 is a view showing a preceding example of an ion implantation apparatus.
5 is a plan view around a substrate holder of the apparatus of FIG. 4. FIG.
6 is a flowchart showing an example of control content by the control device in FIG. 4; FIG.
7 is a flowchart showing an example of a current value control routine in the control device in FIGS. 1 and 4. FIG.
8 is a flowchart showing an example of a uniformity control routine in the control device shown in FIGS. 1 and 4. FIG.
FIG. 9 is a diagram showing a schematic example of a beam profile before and after control.
FIG. 10 is a flowchart showing another example of the uniformity control routine in the control device shown in FIGS. 1 and 4;
[Explanation of symbols]
2 Ion source 6 Filament 12 Ion beam 13 Substrate holder 14 Substrate 15 Holder scanning mechanism 16 Filament power source 18 Beam current measuring instrument 22 Controller 24 Unshielded beam current measuring instrument

Claims (1)

An ion source having a plurality of filaments, one or more filament power sources for supplying filament currents independently to each filament of the ion source, a substrate holder for holding a substrate to be ion-implanted, and the substrate holder as the ion source A holder scanning mechanism for reciprocating scanning within the irradiation region of the ion beam extracted from the ion source, and measuring a beam current of the ion beam extracted from the ion source at a plurality of positions downstream of the scanning region of the substrate holder. A plurality of beam current measuring devices larger than the number of filaments, and an apparatus for controlling the filament currents flowing from the filament power source to the filaments based on the beam current measured by the beam current measuring device. Calculate the average value of all beam currents measured by the beam current measuring instrument A current value control routine for increasing or decreasing filament currents flowing through the filaments by substantially the same amount so that the average value approaches a set value, and the plurality of beam current measuring devices are grouped into the number of filaments, In an ion implantation apparatus comprising: a controller that repeats a uniformity control routine for controlling the uniformity of a beam current by increasing or decreasing a filament current flowing through a filament corresponding to
A non-shielded beam current measuring device which receives an ion beam extracted from the ion source and measures the beam current, and is arranged outside the scanning region of the substrate holder and is not shielded by the substrate holder during scanning. In addition,
And the controller controls the current value control routine and the uniformity control routine to repeat the predetermined times before the substrate holder starts scanning, and the unshielded beam current measurement immediately before the substrate holder starts scanning. The measured value by the measuring device is stored as a target value, and the filament currents to be passed through the filaments are substantially the same amount so that the measured value by the non-shielded beam current measuring device approaches the target value during the scanning of the substrate holder. An ion implantation apparatus characterized in that the scanning control for increasing / decreasing is performed for each reciprocating scan of the substrate holder.

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