JP3117703B2 - Ion implantation apparatus and ion implantation method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ion implantation apparatus.
The present invention relates to an ion implantation apparatus including an electron supply source in an ion implantation current detection system.

[Conventional technology]

In the ion implantation process, since positively charged ions are implanted into the wafer, the charges of the implanted ions are accumulated in the insulating film on the wafer surface, so that the dielectric breakdown of the semiconductor element and the amount of ion implantation in the wafer surface are not sufficient. This can cause problems with uniformity. This problem frequently occurs particularly when ion implantation is performed with an ion beam current of 1 mA or more. As a method for solving this problem, there has been proposed a charge charge neutralization method in which a source of electrons is provided in the vicinity of a wafer into which ions are implanted, and positive electrons are neutralized by the electrons.

The operation of the conventional ion implantation apparatus including an electron supply source in the ion implantation current detection system will be described with reference to FIG.

Ion beam 1 having positively charged ion beam current IB
Passes through the suppressor 2 and enters the ion implantation current detection system. At this time, the suppressor 2 has a function of removing electrons trapped in the ion beam by an electric force or a magnetic force from the ion beam. The suppressor 2 also functions to confine charges such as secondary electrons generated in the ion implantation current detection system in the system. The ion beam that has passed through the suppressor 2 is injected into the wafer 3, a current corresponding to the injected charge is detected by the injection current measuring device 4, and the value is transmitted to the ion injection controller 5 '. When there is an electrically insulating portion on the surface of the wafer 3 in the ion implantation of the mA order, the charges injected into that portion can hardly be neutralized by electrons from the wafer substrate and are accumulated on the surface.

The low-energy electrons emitted from the electron supplier 6 function to neutralize the positive charges and the space charges of the ion beam accumulated on the surface of the wafer 3. The electrons emitted from the electron supplier 6 include secondary electrons radiated from the metal by projecting primary electrons of several hundreds eV to the metal and electrons generated by generation of plasma. The electron supplier 6 is electrically connected to the Faraday cylinder 7, the shield plate 11, the wafer 3, and the wafer support 8 surrounding the ion implantation current detection system. Faraday barrel 7, wafer support 8 and shield 11
During this time, bias voltages VB and VB 'for controlling the flow of electrons may be applied. Therefore, as long as the electrons emitted from the electron supplier 6 do not leak from the ion implantation current detection system, the current measuring device 4 transmits a signal corresponding to the ion beam current to the ion implantation controller 5 '. The ion implantation amount controller 5 turns on / off the ion beam,
By controlling the scanning of the ion beam or the wafer or the like, a predetermined amount of charge is uniformly injected over the entire surface of the wafer 3.

[Problems to be solved by the invention]

However, in an ion implantation apparatus of a type including an electron supply source such as the electron supply 6 in the ion implantation current detection system,
It is practically difficult to completely prevent the electrons generated in the system from leaking out of the system. As a result, some of the electrons generated in the ion implantation current detection system leak out of the system from the gap between the wafer support base 8 and the Faraday cylinder 7 and the shield plate 11 and the vacuum exhaust port 9 as shown by the broken line. And flows into the inner wall 10 which is the reference potential of the entire ion implantation apparatus. Since this leakage current IL returns to the system through the injection current measuring device 4,
The injection current measuring device 4 detects the ion injection current as if (IB + I
L) and the value is transmitted to the ion implantation amount controller 5 '. Since the ion implantation amount controller 5 'controls scanning and ion beam on / off according to the values, an error shown in Expression 1 occurs between the actual implantation amount and the set implantation amount.

Error [%] = (actual injection amount−set injection amount) / set injection amount × 100 = −IL / (IB + IL) × 100 (1) The leakage current IL is an electron supply amount, an ion beam condition, and a bias voltage. Wear 3 on VB, VB 'and wafer support 8
Scan position, wafer surface condition, wafer support 8
, The surface state of the Faraday cylinder 7, and the surface state of the shield plate 11. Normally, when a new ion implanter is introduced and during periodic maintenance, the leak current IL is adjusted to be a negligibly small value with respect to the normally used minimum ion beam IB. However, the wafer support,
The surface contamination state of the Faraday cylinder and the shield plate changes with the use time, and the leakage current IL increases accordingly with time. Eventually, the leakage current IL becomes a value that cannot be ignored with respect to the beam current IB. This causes a change, and lowers the product yield due to over-ion implantation (overdose).

In view of the above, it is an object of the present invention to provide an ion implantation apparatus that includes an electron supply source in an ion implantation current detection system without reducing the yield of products due to leakage current and without being affected by leakage current. Is what makes it possible.

[Means and actions for solving the problem]

In order to solve the above problem, the present invention provides an ion implantation apparatus with a means for detecting a leakage current from an ion implantation current detection system and a means for stopping the ion implantation when the leakage current is a predetermined value or more.

As a result, when the leakage current increases to the extent that the product yield is reduced, the ion implantation is stopped.
The ion implantation can be performed again.

Further, in the ion implantation apparatus according to the present invention, which includes an electron supply source in the ion implantation current detection system, means for detecting a leakage current corresponding to an ion beam implantation position from the ion implantation current detection system, and a measured ion beam Means is provided for controlling the ion implantation current by correcting the current with the leakage current corresponding to the ion beam implantation position.

As a result, even if there is a leakage current, ion implantation is appropriately performed in accordance with the ion implantation position.

Preferably, the leakage current detecting means detects a leakage current at the ion beam implantation position and a leakage current at a home position, and the control means detects a leakage current at the home position from the measured leakage current at the ion beam implantation position. Leakage current correction according to the ion position is performed based on the difference from the current.

More preferably, the control means controls a scan speed based on the corrected leakage current.

Further, the present invention provides an ion implantation method for performing the above-described processing.

〔Example〕

FIG. 1 shows an example in which the present invention is applied to a batch processing type mechanical scan type ion implanter. Sixth
Portions that overlap with the figure are given the same numbers as in FIG.

In the batch processing type mechanical scanning method, a plurality of wafers are arranged in a circumferential direction on a disk-shaped wafer support table 8, and are rotated at a constant rotation speed around a rotation shaft 13. Direction (radial direction of wafer support table 8)
Scan multiple wafers in a single ion implantation process. At this time, in order to perform ion implantation uniformly over the entire surface of the wafer 3, the scanning speed in the radial direction is controlled according to the ion beam current IB and the radial distance of the wafer support 8 from the position where the ion beam is implanted. There is a need to. The control constant is determined by the set implantation dose, the ion beam current in consideration of the fluctuation, the physical limit of the scan drive system, and the like. This control constant is usually set immediately before starting the ion implantation process.
Is calculated by the ion implantation controller 5 at a scan position where the ion beam is not implanted into the ion beam (hereinafter, referred to as a home position). Thereafter, based on the control constants, the ion implantation controller 5 operates the scan drive system, the ion beam on / off, The supply and the like are controlled, and the ion implantation process is performed under the control.

Hereinafter, the control operation of the ion implanter shown in FIG.
This will be described with reference to the flowchart in FIG.

The leakage current controller 12 first inputs the initial beam current IB (Step 01 (S01)). Next, the ion implantation controller 5 with a built-in CPU switches the electron supply device 6 from off to on before starting the ion implantation process (S02), and after the operation of the electron supply device 6 becomes stable after a certain time τ, for example, several seconds, elapses. (S03), the injection process is started. Next, the leakage current controller 12 reads the beam current value IB 'of the injection current measuring device 4 immediately after the operation of the electron supply device 6 is stabilized (S04), and compares the initial beam current IB with the stabilized beam current IB'. Calculate the difference ΔB = IL = (IB′−IB) (S0
Five). Normally, the time τ during which the electron supply device 6 stabilizes is as short as several seconds, so that the ion beam current IB itself hardly changes during that time, and the value of ΔIB = (IB′−IB) indicates the leakage during the batch processing. It can be regarded as the current value IL. The leakage current controller 12 compares whether this value IL (= ΔIB) does not exceed the allowable limit value LIMIT as shown in FIG.
07), if the allowable limit value LIMIT is exceeded, a process stop signal is sent to the ion implantation amount controller 5, the ion implantation process is stopped via the ion implantation amount controller 5, and a warning signal is sent to the outside (S07). ). This eliminates the need for ion implantation under a leakage current exceeding the allowable limit value LIMIT, and realizes stable ion implantation.

If ΔIB (IL) does not exceed the allowable limit value LIMIT, the ion implantation controller 5 starts the implantation process (S08).

In the example of FIG. 1, the leakage current controller 12 reads the values of the beam currents IB and IB 'from the ion implantation amount controller 5, but as shown by the broken line in FIG. Can also be read.

Further, it is not necessary to provide the leakage current controller 12 independently. For example, the ion implantation controller 5 may include the control processing content of the leakage current controller 12 as software.

Further, it is not necessary to fix the allowable limit value of the leakage current, and the allowable limit value stored in the leak current controller 12 can be changed according to the processing device.

In the above description, the ion beam current IB hardly fluctuates for several seconds until the operation of the electric supply unit 6 is stabilized. However, the reliability of the signal processing can be improved. The following is an example.

a) The leakage current controller 12 repeats the reading of IB, IB 'and ΔIB = (IB'-IB) a plurality of times, and issues a warning when the variation in ΔIB is large.

b) The leakage current controller 12 monitors parameters related to the fluctuation of the ion beam current, for example, the current and voltage drawn from the ion source, the magnetic field of the ion analysis tube, the degree of vacuum, and the like. Beam current, if any
Measure IB and IB 'again.

c) △ IB (IL) or LIMIT is corrected by a parameter relating to the fluctuation of the ion beam current.

Further, the ion beam current IB may be zero. In this case, the electron supply 6 is turned on while the ion beam is off,
The ion beam may be turned on after measuring the leakage current.

As described above, the present invention measures the electron leakage current, controls the ion implantation process based on the measured value, and manages the error of the ion implantation amount due to the leakage current shown in Equation 1, thereby realizing a highly reliable ion implantation process. it can.

FIG. 3 shows the results based on the embodiment of FIG. 1 for a batch processing type high current ion implanter. In FIG.
The horizontal axis shows the passage of days, and the vertical axis shows the relative value of the leakage current IL. Although the leakage current IL per batch increases with time, according to the present invention, before the allowable limit value LIMIT is exceeded, maintenance processing M1 to M1 is performed.
4 have been implemented. The maintenance processing includes decontamination of contaminants attached to the wafer support 8.

In the present invention, not only the method of stopping the ion implantation process depending on the value of the leakage current as shown in FIG.
By subtracting the absolute value | IL | of the leakage current from the beam detection current IB ', it is possible to proceed with the ion implantation process using the beam current (IB' + | IL |) corrected for the leakage current. At this time,
When there is a correlation between the scan position and the leakage current as shown in FIG. 4, correction can be performed in consideration of the correlation equation between the scan position and the leakage current. In FIG. 4, the horizontal axis shows the scan position (moving distance) [mm] when the home position is set to 0, and the vertical axis shows the relative value of the leak current IL when the leak current at the home position is set to 1.0.

FIG. 5 shows an example of an operation flowchart of the ion implantation controller when the leakage current correction is performed. In this case, all controls are performed by the ion implantation controller. The control operation will be described below.

The ion implantation controller 5 reads the current value IB from the injection current measurement device 4 immediately before turning on the electron supply device 6 (S0
1). Next, the electron supply device 6 is turned on (S02), and after a lapse of time until the electron supply state is stabilized (S03), the current value IB '(0) is read from the injection current measurement device 4 (S10), and the home position is set. Calculate the leak current value IL (0) of (S1
1). Thereafter, the ion implantation controller 5 starts the implantation process, periodically reads the scan position information x and the measured current value IB '(x) at the scan position, and, based on the characteristics shown in FIG. Calculate the leak current IL (x) = IL (0) xf (x) and calculate the measured current value.
IB (x) = IB '(x) -IL (x) is corrected (S1
2). The ion implantation controller 5 calculates the corrected IB (x)
The scanning speed is controlled on the basis of the above (S13), and this is repeated until the ion implantation is completed (S14). After ion implantation,
The ion implantation controller 5 turns off the electron supply device 6 (S15) and turns off the beam current (S16). The second
In the example shown in the figure, the leakage current IL is measured at the home position before the start of the ion implantation process. However, the leakage current can be measured anywhere where the ion beam is not implanted into the wafer 3, and the wafer 3 is irradiated with the ion beam. It is possible to make a correction while measuring the leakage current each time it passes. If the electron supply device 6 can be turned on and off at a high speed as in the grid voltage control system, it can be applied to a scan type ion implanter using electromagnetic force. That is, the present invention measures the leakage current of electrons from the ion implantation current detection system and controls the ion implantation process based on the measured value in an ion implantation apparatus including an electron supply source in the ion implantation current detection system. It does not depend on the control method or scan method.

〔The invention's effect〕

As described above, in the present invention, when the leakage current is equal to or more than the predetermined limit value and the yield of the semiconductor product is reduced, the ion implantation is stopped, so that the ion implantation that reduces the yield can be prevented.

Further, in the present invention, by performing ion implantation after correcting the leakage current, it becomes possible to perform ion implantation which is not affected by the leakage current.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a batch processing mechanical scan type ion implanter as one embodiment of the present invention, FIG. 2 is a control processing flowchart of an ion implantation controller and a leakage current controller in FIG. 1, and FIG. Fig. 4 is a graph of the data of the embodiment in Fig. 1, Fig. 4 is a graph showing the dependence of the leakage current on the scan position in Fig. 1, and Fig. 5 is an ion implantation controller and a leakage current controller in Fig. 1. FIG. 6 is a schematic diagram of an ion implantation apparatus including an electron supply source in a conventional ion implantation current detection system. [Explanation of Symbols] 1 ... Ion beam 3 ... Wafer 4 ... Implantation current measuring device 5 ... Ion implantation amount controller 6 ... Electron supply 7 ... Faraday cylinder 8 ... Wafer support 10 ... Ion implantation Equipment inner wall 12 …… Leakage current controller

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-288364 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 14/48 H01J 37/04 H01J 37 / 30-37/36 H01L 21/26-21/268 INSPEC (DIALOG)

Claims (6)

(57) [Claims] 1. An ion implantation apparatus including an electron supply source in an ion implantation current detection system, means for detecting a leakage current from the ion implantation current detection system, and ion implantation when the leakage current is equal to or more than a predetermined value. An ion implantation apparatus comprising: means for stopping the ion implantation. 2. An ion implantation apparatus including an electron supply source in an ion implantation current detection system, means for detecting a leakage current according to an ion beam implantation position from the ion implantation current detection system, and a measured ion beam current. And means for correcting the current with the leakage current corresponding to the ion beam implantation position to control the ion implantation current. 3. The leakage current detection means detects a leakage current at the ion beam implantation position and a leakage current at a home position, and the control means detects a leakage current at the ion beam implantation position at a home position from the measured leakage current at the ion beam implantation position. The ion implantation apparatus according to claim 2, wherein a leak current is corrected according to the ion position based on a difference from the leak current. 4. The ion implantation apparatus according to claim 1, wherein said control means controls a scan speed based on said corrected leakage current. 5. A method for implanting ions into a wafer using an ion implantation apparatus including an electron supply source in an ion implantation current detection system, wherein a leakage current is detected from the ion implantation current detection system, and the leakage current is determined to be a predetermined value. An ion implantation method characterized in that the ion implantation is stopped when the value is equal to or more than the value. 6. A method for implanting ions into a wafer using an ion implantation apparatus including an electron supply source in an ion implantation current detection system, wherein a leakage current corresponding to an ion beam implantation position from the ion implantation current detection system is detected. An ion implantation method characterized in that the ion beam current measured based on the leakage current is corrected according to the ion beam implantation position to control the ion implantation current.