JP3330759B2 - Ion implantation apparatus and ion implantation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation apparatus and an ion implantation method, and more particularly to an improvement in a setup mechanism for initially setting an ion implantation amount.

[0002]

2. Description of the Related Art Generally, an ion implantation apparatus is used as an apparatus for introducing impurities in a semiconductor device manufacturing process because it can precisely control the amount of impurities to be introduced and can perform processing while grasping the number of ions. Have been.

In this ion implantation apparatus, a gas such as a halogen compound is brought into a plasma state, ions are extracted by applying an electric field to an electrode provided in the plasma, and a predetermined magnetic field is applied to the extracted ion beam. As a result, mass spectrometry for extracting only predetermined ions while eliminating impurity ions is performed, and the energy of the extracted ions is increased or decreased to be implanted into the object to be processed.

[0004] This will be specifically described with reference to FIG.
FIG. 4 is a schematic configuration diagram showing a general ion implantation apparatus. As shown in the figure, the ion implantation apparatus 2 has an ion source 4 for converting a supply gas into a plasma, and the ion source 4 is connected to a gas box 6 for supplying a halogen gas or the like required for the supply by a pipe 8. Connected through. An extraction electrode 10 is provided on the outlet side to extract positive ions from the ion source 4. The extracted ion beam B1 is accelerated and passes through a mass analyzer 12 having a strong electromagnetic magnet. The direction is bent by about 90 °, where only predetermined necessary ions are taken out and impurity ions are eliminated. The extracted ions are further accelerated or decelerated by the multi-stage accelerating electrodes 14 and pass through the mask 16 and then attached to a rotatable wafer disk 18 as a rotatable workpiece holder in a disk chamber. Is injected into the semiconductor wafer W. In addition, since the degree of vacuum greatly affects the performance of the ion implantation apparatus, the inside of the portion through which the ion beam B1 passes is, for example, 10 ⁻⁶ by a turbo molecular pump, a cryopump, or the like.
A high vacuum of about Torr is maintained.

To extract the ion beam B1, an ion source 4 is connected to an extraction power source 20 variably provided so as to output a high voltage DC of, for example, about 60 KV at a maximum, and the other poles are connected via a shunt resistor R1. And is connected to the extraction electrode 10. Further, between the acceleration electrode 14 and the terminal 22, for example, an acceleration power source 24 variably connected so as to output a high voltage of about 140 KV at maximum is connected, so that ion implantation can be performed at an energy of 200 KV at maximum. ing. By the way, when implanting ions such as phosphorus and boron into a wafer, the amount of implantation must be controlled with high accuracy in order to keep the electrical characteristics of the IC chip when it is commercialized and to obtain good characteristics. . For this purpose, a setup mechanism 26 called a Faraday setup flag is provided between the wafer disk 18 and the mask 16 so that the setup mechanism 26 can be turned upside down.

FIG. 5 is a sectional view showing a setup mechanism, and FIG. 6 is a schematic view of the setup mechanism shown in FIG. The set-up mechanism 26 is fixed to the rotatable support shaft 28 as described above, and by rotating the support shaft 28, the set-up mechanism 26 can be freely moved in and out of the ion beam path. This setup mechanism 26 is used when initial setting of the ion implantation amount is performed before the ions are actually implanted into the wafer. Once the ion implantation amount is set, the setup mechanism 26 is overturned. Then, the ion beam is removed from the ion beam path, and then ions are implanted into the surface of the wafer W. As described above, since the ion implantation apparatus is very excellent in the reproducibility of the ion implantation amount, if the beam current value or the like determined at the time of initial setting is held, an accurate ion amount is implanted in the subsequent ion implantation operation. be able to.

To enable such an initial setting operation, the setup mechanism 26 includes a ring-shaped first bias plate 30, a ring-shaped beam collector 32, and a ring-shaped second bias from the ion beam entering direction. A plate 34 and a disc-shaped center cup 36 are sequentially arranged. In FIG. 5, only the first bias plate 30 is configured as a separate body, the second bias plate 34 and the center cup 36 are housed in a cup-shaped casing 38, and the beam collector is 32 is shown. The beam collector 32 is electrically connected to the wafer disk 18 and has the same potential, and a minute focus adjustment hole 32A for focus adjustment is provided at the center of the collector. The opening area of the focus adjustment hole 32A is very small as compared with the surface area of the beam collector 32, and is set to, for example, about 1/100.

The first and second bias plates 30 and 34 disposed on both sides of the beam collector 32 are formed with relatively large-diameter ion passage holes 30A and 34A for passing an ion beam, respectively. 3
The negative poles of the DC power supply 40 are commonly connected to 0 and 34 to have a negative potential. By setting the bias plate to a negative potential in this manner, the first bias plate 30
The secondary electrons E1 struck out by irradiating the beam collector 32 with ions at the time of the initial setting are returned to the beam collector 32 again, and the second bias plate 34 leaks out of the plate 34 at the time of the initial setting to the center cup 36. The function is performed so that the secondary electrons E2 hit by the arriving ions are returned to the center cup 36 again and do not reach the beam collector 32. Thereby, an implantation amount measuring unit 4 connected to the beam collector 32 for measuring the amount of ion implantation.
The charge count value of 2 is prevented from being adversely affected by the above-mentioned secondary electrons, and an accurate ion implantation amount can be measured. The center cup 36 receives the ion beam that has passed through the focus adjustment hole 32A of the beam collector 32.

The injection amount measuring section 42 connected to the beam collector 32 of the setup mechanism 26 is configured as shown in FIG. That is, the beam collector 32 includes
Current-to-voltage converter 4 that converts the current flowing into this to voltage
4 is connected, and this output is input to the integrator 46 to remove the AC component and output only the DC component. And
The output of the integrator 46 is input to a voltage / frequency converter 48 to output a signal having a frequency corresponding to the voltage value, and this frequency is counted by a charge counter 50 to indirectly determine the ion implantation amount. It has become. And
The output of the charge counter 50 is input to a control unit 52 composed of, for example, a microprocessor or the like, and controls the entire apparatus.

In order to perform the initial setting of the ion implantation amount prior to the ion implantation operation to the wafer by using the set-up mechanism 26 of the ion implantation apparatus configured as described above, first, in FIG. This is erected as shown by the dashed line to face the ion beam path. Then, the ion beam B1 is irradiated with the setup mechanism 26 standing up, the beam focus, the beam acceleration state, the overscan amount, and the like are set to optimal values, and the current flowing through the beam collector 32 is supplied to the implantation amount measurement unit 42. The beam current is counted, and the beam current is set so that this becomes a desired value. In the implantation mode in which an actual ion implantation operation is performed, the above-described set-up mechanism 26 is tilted sideways as shown by a solid line in FIG. 4, and ion implantation is performed by flowing a beam current value set at the time of the initial setting.

[0011]

As apparent from the circuit configuration shown in FIG. 6, the beam collector 32 and the first
And the second bias plates 30 and 34 and the beam collector 32 are insulated from the ground of the apparatus main body. Therefore, when the ion beam is not supplied in the initial setting, the current is normally supplied to the beam collector 32. Should not flow and the charge counter value should be zero. However, as the apparatus is used, for example, dirt is formed on the surface of each plate or deposits adhere thereto, resulting in poor insulation, a discharge phenomenon occurring on the plate, and a leak current flowing. For example, when insulation failure occurs between the beam collector 32 and the bias plates 30 and 34, a negative leak current flows through the beam collector 32, and insulation failure occurs between the beam collector 32 and the ground of the apparatus body. And a negative or positive leakage current flows.

When such a leak current is generated, the beam current value measured due to the leak current is adversely affected at the time of initial setting, and the charge counter 50
An error occurs between the ion implantation amount counted in step 1 and the amount of ions actually implanted. As a result, a predetermined amount of ions cannot be implanted, thereby deteriorating the electrical characteristics of the IC chip or increasing the yield. Was causing the decrease.

The present invention focuses on the above problems,
It was created to solve this effectively. An object of the present invention is to provide an ion implantation apparatus and an ion implantation method capable of detecting a leak current and determining whether or not the current is appropriate.

[0014]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to an object to be processed held by an object holder after passing an ion beam extracted from an ion source through a mass analyzer. An ion implantation apparatus, in the course of the ion beam for performing initial setting of the ion implantation amount,
A setup mechanism consisting of a beam collector, a center cup, and a bias plate is provided so that it can appear and disappear in the beam path
In an ion implantation apparatus in which an implantation amount measuring unit for measuring an ion implantation amount is connected to the set-up mechanism, a comparison unit for determining whether a leak current of the setup mechanism is within an allowable range, And a controller for controlling whether to continue or stop the ion implantation operation based on the output.

[0015]

The present invention has the above-described structure,
Prior to the initial setting, it is detected whether or not a current is flowing to the beam collector in a state where no ion beam is flowing, and the detected value at this time is compared with a preset allowable range value by a comparing unit. . Based on the comparison result, if the leakage current is within the allowable range, the control unit performs an initial setting operation by flowing an ion beam, and then performs actual ion implantation on the object in the implantation mode.

On the other hand, if the leak current value is out of the allowable range, it means that the accurate ion implantation amount cannot be counted. Therefore, a command is issued to stop the subsequent ion implantation operation to the object. Emit. This makes it possible to prevent an implantation operation with an incorrect ion implantation amount.
A window comparator circuit can be used as the comparison unit that determines whether the leak current is appropriate. The allowable range of the voltage-converted leak current is, for example, ± 3 with respect to 0V.
Set within the range of%.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an ion implantation apparatus and an ion implantation method according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram showing an electric circuit of a setup mechanism of an ion implantation apparatus according to the present invention. FIG. 2 is a circuit configuration diagram of a comparison unit shown in FIG. 1, and FIG. It is a figure showing an example.

The ion implantation apparatus according to the present invention is different from the ion implantation apparatus shown in FIG.
Since the configuration is the same as that shown in FIG.
The structure of the setup mechanism 26 is the same as the structure shown in FIGS. 5 and 6, but will be briefly described to facilitate understanding of the present invention.

As shown in FIGS. 5 and 6, the set-up mechanism 26 is provided so as to be able to move up and down, and can be protruded and retracted as needed along the ion beam path. The setup mechanism 26 has a focus adjustment hole 32A at the center.
And a first bias plate 3 disposed on both sides of the collector 32 in the ion beam direction.
0 and a second bias plate 34. Each of the bias plates 30 and 34 has ion adjustment holes 30A and 34A formed at the center thereof for passing an ion beam. The beam collector 32 leaks from the second bias plate 34 downstream of the ion beam. A center cup 36 is provided for trapping the ions.

First and second bias plates 30, 3
4, a negative electrode of a DC power supply 40 is connected to have a negative potential, and acts to return secondary electrons E1 and E2 struck out of the beam collector 40 and the center cup 36 by an ion beam to a source. And prevents adverse effects due to secondary electrons. The beam collector 32 is electrically connected to the wafer disk 18 as an object-to-be-processed holder and has the same potential. Is connected.

As shown in FIG. 1, the injection amount measuring section 42 includes a current / voltage converter 44 for converting a current flowing through the beam collector 32 into a voltage, and an AC component from an output of the converter 44 to remove a DC component. An integrator 46 for extracting only the component;
It is mainly constituted by a voltage / frequency converter 48 for outputting a signal of a frequency corresponding to the voltage value of the output of the integrator 46, and a charge counter 50 for counting the frequency to indirectly determine the ion implantation amount. I have. With this configuration, the value of the current flowing through the beam collector 32 is converted into a DC value by the current / voltage converter 44 and the integrator 46, and this is frequency-converted to indirectly determine the ion implantation amount. Then, the injection amount measuring unit 4 thus configured
Second, a comparison unit 54, which is a feature of the present invention, for determining whether or not the leak current of the setup mechanism 26 is within an allowable range, and controls the ion implantation operation based on the output of the comparison unit 54. The control unit 56 is connected.

FIG. 2 shows a specific circuit configuration of the comparing section 54. The comparing section 54 is connected to the output side of the integrator 46. The comparison unit 54 includes a first and a second two comparators 5.
8 and 60, and an OFF circuit 62 for calculating the logical sum of the outputs of these two comparators 58 and 60, thereby forming a so-called wind comparator circuit. That is, the first
The output of the integrator 46 is input to the-input terminal of the comparator 58 via the resistor R10, and the output of the integrator 46 is input to the + input terminal of the second comparator 60 via the resistor R11. Have been. The + input terminal of the first comparator 58 is connected to a positive power supply having a potential of + Vcc via resistors R12 and R13, and the-input terminal of the second comparator 60 is connected to a resistor R14, It is connected to a negative power supply having a potential of -Vcc via R15. R16 is a variable resistor for changing the reference voltage input to the + input terminal of the first comparator 58 and the-input terminal of the second comparator 60.

Here, as shown in FIG. 3, for example, assuming that the allowable current is within a range of ± 3% of the standard beam current (assuming ± 1 V in voltage conversion), the first comparator A reference voltage of +1 V is input to the plus terminal input of 58, and a reference voltage of -1 V is input to the-input terminal of the second comparator 60. Thereby, the output of the integrator 46, for example, the voltage value corresponding to the leak current is changed from + 1V to-
If it is within the range of 1 V, negative logic is output from the OR circuit 62, and otherwise, positive logic is output.

This output is input to the control unit 56. If the leak current is out of the allowable range, the operation of the end station, for example, the driving unit of the transfer system of the semiconductor wafer W, is stopped to stop the subsequent ion implantation operation. And a program on software is configured to stop the power supply and the power supply driving unit of the ion beam source.

Next, an ion implantation method which is an operation of the present embodiment configured as described above will be described. First, since the ion implantation amount of the ion implantation apparatus is very good in reproducibility, a beam current corresponding to a desired ion implantation amount is obtained prior to an actual ion implantation operation on a wafer, and beam focusing or the like is performed. Make initial settings to adjust. At the time of this initial setting, the setup mechanism 2
If a leak current exceeding the allowable amount occurs in 6, the measurement is performed in a state where the leak current is added to or subtracted from the actual beam current, and the initial setting is determined based on this. With the set beam current, ions different in amount from the desired ion implantation amount are implanted into the wafer.

Therefore, in the present invention, prior to the initial setting, it is checked whether or not the leak current of the setup mechanism falls within an allowable range. That is, first, the setup mechanism 26 is erected as shown by a two-dot chain line in FIG. 4 and is interposed in the ion beam path. Then, a current flowing through the beam collector 32 in a state where the ion beam B1 does not flow at all while the setup mechanism 26 is standing up, that is, a leak current is detected.
If there is an insulation failure between the beam collector 32 and the bias plates 30, 34 or between the beam collector 32 and the apparatus main body, a leak current flows through the beam collector 32 even when the ion beam B1 is not irradiated at all.

This leakage current is supplied to the current / voltage converter 44
And the integrator 46 converts the voltage value into a voltage. The comparator 54 determines whether the voltage value falls within an allowable range.
Here, for the sake of simplicity, it is assumed that the allowable range when the leak current is converted to a voltage is within the range of ± 1.0 V (± 3%). In this case, in the circuit shown in FIG. 2, a positive voltage of +1.0 V is input to the + input terminal of the first comparator 58 as described above, and -A negative voltage of -1.0 V is input to the input terminal. The time when the output of the window comparator circuit is, for example, negative logic is defined as the ion implantation stop signal. Here, the integrator 4
When the output voltage of No. 6 is in the range of +1.0 V to -1.0 V, the first and second comparators 58 and 60 both have positive logic because the leakage current is within the allowable range. Is transmitted to the control unit 56.

The control unit 56 that has received this signal subsequently performs an initial setting operation because the leak current is within the normal range. That is, with the setup mechanism 26 standing up in the ion beam path as described above, the ion source 4 (see FIG. 4) is driven to emit the ion beam B1, and this is emitted to the beam collector 32 of the setup mechanism 26.
Irradiated. At this time, the current flowing through the beam collector 32 is detected by the implantation amount measuring unit 42 and converted into a voltage and a frequency, as described above, and then counted by the charge counter 50 so that the ion implantation amount with respect to the beam current at that time is indirectly measured. Required.

At this time, the ion implantation amount D is obtained by the following equation. D = i · t / (A · e) Incidentally, i is the emission current, t is the irradiation time, A is irradiated area, e is a single charge quantity electron (1.6 × 10- ¹⁹ coulombs). Here, the beam current, irradiation time, and the like at that time are obtained for the implantation mode to be performed later so that the desired ion implantation amount is obtained. In this case, as described above, the leak current included in the detected beam current is very small and within the allowable range. Therefore, if the ion implantation is performed on the wafer with the beam current value set at this time, the implantation is performed. There is almost no amount error, and a substantially desired amount of ions can be implanted into the wafer.

In this initial setting operation, the focus of the ion beam is set by the current value flowing through the beam collector 40 and the focus adjustment hole 32 of the collector 40.
The control is performed by controlling the ratio of the beam passing through A to the center cup 36 and the current value generated.
As described above, when the initial setting operation is completed, the setup mechanism 26 is tilted as shown by the solid line in FIG. 4 to open the ion beam path, and the ion beam B1 having the previously set beam current is caused to flow. Ion implantation is performed in the wafer.

On the other hand, when the leak current is large and the output voltage of the integrator 46 is higher than +1.0 V, or-
When the voltage is smaller than 1.0 V, the output of the OR circuit 62 becomes negative logic because the leak current is out of the allowable range.
For example, when the output of the integrator 46 is larger than +1.0 V, the output of the first comparator 58 becomes negative logic, and as a result, the output of the OR circuit 56 also becomes negative logic. In this case, the output of the second comparator 60 remains positive logic. Conversely, when the output of the integrator 46 is smaller than -1.0 V, the output of the second comparator 60 becomes negative logic, and as a result, the output of the OR circuit 56 also becomes negative logic. In this case, the output of the first comparator 58 is of a positive logic.

This negative logic signal (ion implantation stop signal)
Is input to the control unit 56, and the control unit 56
Is to stop the driving unit of the transfer system for transferring the wafer W to the wafer disk to stop the ion implantation operation,
Alternatively, the drive unit of the ion source 4 is stopped, or the end station is interlocked. When the ion implantation is stopped due to a large leak current, the fact is displayed on an operator panel (not shown) at the same time as the stop operation. Such an initial setting operation may be performed, for example, for each batch processing of 25 wafers as one unit, or after completion of analog offset removal after each wafer injection.

As described above, when the leak current exceeds the allowable range, the ion implantation operation is stopped by interlocking, so that the ion implantation amount is reliably prevented from becoming inaccurate. be able to. In the above-described embodiment, the leak current is measured with the setup mechanism 26 upright. However, the leak current may be measured with the setup mechanism 26 overturned.
In addition, the circuit configuration of the comparison unit 54 and the allowable range set here are merely examples, and are not limited to this.

[0034]

As described above, according to the ion implantation apparatus and the ion implantation method of the present invention, the following excellent operational effects can be exhibited. A comparison unit is provided to determine the leak current of the setup mechanism and determine whether the leak amount is within the allowable range. If the leak amount is out of the allowable range, the ion implantation operation is performed. Since the interlock is applied so as to stop the operation, it is possible to prevent an ion implantation operation with an incorrect implantation amount from being performed. Therefore, an appropriate amount of ions can be implanted, and the yield of products can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electric circuit of a setup mechanism of an ion implantation apparatus according to the present invention.

FIG. 2 is a circuit configuration diagram of a comparison unit shown in FIG. 1;

FIG. 3 is a diagram illustrating an example of an allowable range of a voltage in a comparison unit illustrated in FIG. 2;

FIG. 4 is a schematic configuration diagram showing a general ion implantation apparatus.

FIG. 5 is a sectional view showing a setup mechanism.

FIG. 6 is a schematic diagram of the setup mechanism shown in FIG.

FIG. 7 is a block diagram showing an injection amount measuring unit.

[Explanation of symbols]

 2 Ion implanter 4 Ion source 12 Mass analyzer 18 Wafer disk (substrate to be processed) 26 Setup mechanism 30 First bias plate 32 Beam collector 34 Second bias plate 36 Center cup 42 Injection amount measurement unit 44 Current / Voltage converter 46 Integrator 48 Voltage / frequency converter 50 Charge counter 54 Comparison unit 56 Control unit 58 First comparator 60 Second comparator 62 OR circuit B1 Ion beam W Semiconductor wafer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-221282 (JP, A) JP-A-63-128543 (JP, A) JP-A-4-132151 (JP, A) JP-A-2- 295051 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 37/317 C23C 14/48 H01L 21/265

Claims (4)

(57) [Claims] An apparatus for injecting an ion beam extracted from an ion source through a mass spectrometer and then implanting the ion beam into an object held on an object holder for initial setting of an ion implantation amount. In the ion implantation apparatus, a setup mechanism including a beam collector, a center cup, and a bias plate is provided in the beam path in the middle of the path of the ion beam so as to be able to protrude and retract from the beam path. A comparison unit for determining whether the leak current of the setup mechanism is within an allowable range, and a control unit for controlling whether to continue or stop the ion implantation operation based on the output of the comparison unit. An ion implantation apparatus characterized by comprising: 2. The injection amount measuring unit is formed by sequentially connecting a current / voltage converter, an integrator, a voltage / frequency converter, and a charge counter for counting charges based on a frequency. The ion implanter according to claim 1, wherein the comparator is configured to be connected to an output of the integrator. 3. The comparison unit according to claim 1, wherein the comparison unit includes a window comparator circuit.
An ion implanter according to any one of the preceding claims. 4. An apparatus for injecting an ion beam extracted from an ion source through a mass spectrometer and then implanting the ion beam into an object to be processed held on an object to be inspected, for performing initial setting of an ion implantation amount. In the middle of the path of the ion beam, a setup mechanism including a beam collector, a center cup, and a bias plate is provided so as to be able to protrude and retract in the beam path. the ion implantation method using, characterized in that the leakage current of the set-up mechanism compares determines whether it is within the allowable range, that is to continue the ion implantation operation, or stop to on the basis of the comparison determination result Ion implantation method.