JPS62177848A - Ion implanting control method - Google Patents

Abstract

PURPOSE:To make it possible to control the implanting amount accurately and implant evenly, by detecting the ion beam amount radiated from an ion source, and controlling only when the amount of the ion beams and the amount of the implanting ion beams separated by a mass separating electromagnet are converted at the same time. CONSTITUTION:Without controlling the mechanical scanning control and the implanting control of an implanting chamber depending on only the implanting ion current value I, the radiant ion current value A from the ion source 1 is also compared. In other words, both the radiated ion current A from the ion source 1 and the implanting ion current I are observed, and only when the both values are converted, the implanting is controlled by the implanting ion current I. In such a way, even though the vacuum degree in the implanting chamber is converted by the implanting, causing to neutralize a part of the implanting ions, errors thereby are not disturb to control the implanting accurately, and a good quality of semiconductor elements can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an ion implantation control method, particularly to an ion implantation control method used as an impurity doping method in a semiconductor manufacturing process.

[Background of the invention]

In recent semiconductor manufacturing processes, it is required to apply a photoresist mask to the wafer surface and directly implant an ion beam with a large current of 2 mA or more onto the mask.

Figure 2 is an explanatory diagram of a conventional high-current ion implantation device used in the ion implantation control method. In this diagram, 1 is an ion source that accelerates ions, 2 is an acceleration power source, and 3 is an exit ion beam. , 4 is a current meter for the ejected ion beam, 5 is an electromagnet for mass separation, 6 is a specific mass-separated implanted ion beam, 7
8 is a rotating disk for attaching targets, 8 is a plurality of targets (wafers),
9 is a vacuum evacuation system for the ion source, 10 is a vacuum evacuation system for the beam line, 11 is an implantation chamber vacuum container, 12 is a rotating disk motor, 13 is an ammeter for the implantation ion beam, and 14 is an implantation drive control. It shows the system.

There are various driving control methods for uniformly driving a predetermined driving amount into a target, and the method shown in FIG. 2 shows an example in which a rotating disk is mechanically scanned.

In the ion implantation control method using this large current ion implantation device, ions generated from ion g1 are accelerated by an acceleration power source 2, and the accelerated ions are used as an output ion beam 3 by an ion source vacuum evacuation system 9. The evacuated vacuum is guided into the magnetic field of the mass separation electromagnet 5. Here, the mass-separated and selected specific ion species are introduced into the implantation chamber vacuum chamber 11 as the implantation ion beam 6 and implanted into the target 8. A plurality of targets 8 are mounted around the rotating disk 7, and are mechanically scanned back and forth from side to side while rotating at high speed in a vacuum evacuated by the beam line vacuum M1 gas system 10, so that the beam is uniformly scanned. irradiated. In this case, if the amount of the implanted ion beam 6 changes, the implanted ion beam current is always received by the rotating disk 7 or a detector near it to drive the implant, in order to control the speed of mechanical scanning accordingly. The control system 14 provides feedback.

In recent semiconductor processes, a method of directly implanting a high-current ion beam into a photoresist mask is being developed to simplify the process. In this type of implantation, since the photoresist mask is made of a thin organic material, the surface is heated by the high-current ion beam implantation, and organic matter is released in gaseous form, reducing the degree of vacuum around the implantation chamber. let Therefore, the implanted ion beam collides with the gas molecules, generating electrons e, which neutralizes the ion beam and is not detected as an ion current. It is observed by the beam ammeter 13. Figure 2 schematically shows this situation. The horizontal and vertical axes show the implantation time and ion current, respectively, and the amount of ions emitted from the ion source and the implantation in the implantation chamber. The amount of ions is an indication.

In other words, the amount of ions implanted in the implantation chamber decreases from the start of implantation step 1, and returns to the original value when the scan in FIG. The tendency to do so is measured. However, the amount of ions emitted from the ion source does not change during implantation, but in this way, the amount of implanted ions decreases! ! ! If this is the case, it is determined that there is insufficient implantation, and the implantation scanning speed is controlled to be slow to compensate for this.

In the mechanical scanning method, the scanning speed V of the rotating disk is controlled to a value expressed by the following equation to maintain uniformity.

(1) where K is a constant, (2) is the implanted ion current, and R is the distance from the center of the rotating disk to the irradiation position of the ion beam.

If the implanted ion current is actually changing, the scanning speed V must of course be changed according to equation (1).
Even if a change in the implanted ion current is detected, as shown in Figure 3, if the amount of ions emitted from the ion source remains unchanged, a portion (~10%) of the implanted ions will be Even if it is neutralized in the driving chamber and has changed in appearance, it is accelerated at high speed, so even if it is neutralized, it will still be driven into the target, so it will scan according to Equation 1 (1). There is no need to change the speed V.

In other words, in the conventional ion implantation control method, which performs implantation control simply based on the measurement results of the implanted ion current in the implantation chamber, the implantation is controlled by the beam neutralization effect of the gas generated during implantation. There were also phenomena that impaired the amount of implantation and the uniformity of implantation.

In addition, Ion Implantation Technique; Springer-Fuellag Berlin Heidelberg New York, 1982 (Ion Implantat
ionTechniques: Springar-
VerlagBerlin Heidalberg N
ew Work, 1982), pp. 319-342; Development and results of the Tsuba NV-10 Predep TM Implanter (G, Ryding:
Evolution and Performance
of the Nova NV-10Predap
TM Implanter) shows the relationship between the vacuum degree of the implantation chamber and the implantation current.

[Purpose of the invention]

It is an object of the present invention to provide an ion implantation control method that eliminates these problems and enables accurate control of the implantation amount and uniform implantation.

[Summary of the invention]

The present invention separates ions of a specific mass number from an ion beam emitted by an ion source that accelerates ions using a mass separation electromagnet, detects the amount of the separated ion beam, and uniformly implants a predetermined amount into the target. In the ion implantation control method, the amount of ion beam emitted from the ion source is detected, and the amount of the ion beam and the amount of the implanted ion beam separated by the mass separation electromagnet change simultaneously. The present invention is characterized in that the control is performed only when the above conditions are met.

That is, the present invention detects the amount of ion beams emitted from the ion source in addition to the amount of implanted ion beams separated by the mass separation electromagnet, and even if the amount of implanted ion beams that are mass separated changes, If the amount of ion beams emitted from the ion source does not change, the implanted ion beam is assumed to remain unchanged, and implantation is performed only when the amount of ion beams emitted from the ion source and the amount of mass-separated implanted ion beams change at the same time. The intended purpose was achieved by controlling the integrated control system.

[Embodiments of the invention]

Examples will be described below.

FIG. 1 is an explanatory diagram of the configuration of an ion implantation control device used to implement an embodiment of the ion implantation control method of the present invention.
The same parts as those in the figure are given the same reference numerals. In this diagram, 1
5 is a feed screw, 16 is a control power source for disk rotation, 17 is a disk scanning motor, 18 is a disk scanning control Wt source, and 19 is a scanning position detector.

20a and 20b are amplifiers, 21 is a divider, 22 is a comparison value setter, 23 is a binary comparator (window comparator),
24 indicates a scanning velocity (V) calculator.

The difference between this ion implantation control device and the conventional device shown in Fig. 2 is that the mechanical scanning control and implantation control of the implantation chamber were conventionally controlled solely based on the implantation ion current (I) value. On the other hand, the emitted ion current (A) from the ion source 1
The point is that changes in values are also compared.

During implantation, the exit ion beam current A flowing through the accelerating power source 2 is amplified by the amplifier 20 a and input to the divider 21 .

On the other hand, the implanted ion beam 6 is irradiated onto a plurality of targets 8 and flows through the target mounting rotary disk 7 to the implanted ion beam ammeter 13 .

The implanted ion current is amplified by the amplifier 20b, and the divider 2
1, and also input the scanning speed (V) as calculation data.
It is also input to the arithmetic unit 24. The respective values at time to before the start of implantation are (Ao, Io).

The value at each time t1 after the start of driving is (A1
．． Then, the comparison value ε1 is arbitrarily set by the comparison value setter 22, and the binary comparator 23 generates a signal that can be recognized by the scanning speed (V) calculator 24 at times other than the comparison value tx. input.

Along with the driving operation, the rotary disk 7 for attaching the target rotates and performs mechanical scanning by the feed screw 15 directly connected to the motor 17 for scanning one disk. At the same time, a scanning position detector 19 directly connected to the one-disc scanning motor 17 sends out position data R.

The scanning speed (V) calculator 24 monitors the signal from the binary comparator 23 every time the minimum resolution unit of this position data R changes, and if it is less than the comparison value E1, the implanted ion current E is used. Calculate the scanning speed V, otherwise calculate the scanning speed V at Io, ignoring the implantation ion current step 1.
A speed command is issued to the disk scanning control source 18.

In this way, even if the implanted ion current is partially neutralized and reduced by outgas, as in implantation from above a photoresist mask, if the ejected ion current A does not change, the implanted ion current will change. It is possible to judge that the drive is not done and control the drive.

Note that the emitted ion current A from the ion source 1 does not change significantly even if the degree of vacuum in the implantation chamber changes slightly. For being.

This is because the degree of vacuum on the ion source side is not affected by the degree of vacuum on the implantation chamber side.

As in this embodiment, if both the ejected ion current from the ion source and the implanted ion current are monitored and the implantation amount is determined based on the implanted ion current only when both change, the implantation amount can be changed in the implantation chamber.
Even if the degree of vacuum changes during implantation and some of the implanted ions become neutral particles, accurate implantation control is possible without any additional error, resulting in semiconductor elements of good quality. be able to.

〔Effect of the invention〕

The present invention makes it possible to provide an ion implantation control method that enables accurate control of the implantation amount and uniform implantation, and has great industrial effects.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of an ion implantation control device used to implement an embodiment of the ion implantation control method of the present invention, FIG. 2 is an explanatory diagram of a conventional ion implantation control device, and FIG. 3 is an explanatory diagram of a conventional ion implantation control device. 2 is an explanatory diagram of ion current during implantation in the ion implantation control device of FIG. 2. FIG. DESCRIPTION OF SYMBOLS 1... Ion source, 2... Acceleration power supply, 4... Current meter for exit ion beam, 5... Electromagnet for mass separation, 6...
... Implanting ion beam, 7... Rotating disk, 8... Target, 12... Motor for rotating disk, 13... Ammeter for implanting ion beam, 17... Disc scanning motor, 18
... Control power supply for disk scanning, 21... Divider, 23.
・Binary comparator, 51, + concave

Claims (1)

[Claims] 1. Ions with a specific mass number are separated from the ion beam emitted by the ion source that accelerates ions using a mass separation electromagnet, the amount of separated ion beam is detected, and based on the detection results, the ions are placed on the target. In an ion implantation control method that controls the implantation amount to be uniform, an ion beam amount emitted from the ion source is detected, and the ion beam amount is separated from the mass separation electromagnet by the mass separation electromagnet. An ion implantation control method characterized in that the control is performed only when the amount of implanted ion beams changes at the same time.