JPS6057922A - Implantation of ion micro-beam - Google Patents

Abstract

PURPOSE:To enlarge the extent of the quantity of ions implanted largely with high accuracy, and to manufacture a semiconductor element, etc. having high performance by intermittently operating ion micro-beams and changing the intermittent time ratio of the beams. CONSTITUTION:Ion micro-beams 2 from an ion source 1 are accelerated and focussed by electrostatic lenses 3, 3', and reach on a sample to be implanted 4 such as a semiconductor substrate. A mass separator 5 and a blanker 6 are mounted between the electrostatic lenses 3, 3' and an ion beam deflector 7 after the electrostatic lens 3'. Ion micro-beams 2 are turned ON-OFF electrically in a short time by using the blanker 6 driven by a control power supply 8 and an implanted concentration control circuit 10 to effectively reduce ion-beam current density, and ions are implanted at a desired position in desired concentration. The time ratio of ON-OFF operation of the blanker is changed, and ions in low concentration can be implanted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method of directly implanting a predetermined amount of ions into a predetermined region of a sample such as a semiconductor substrate by scanning an ion microbeam. The present invention relates to widening the range of implantation amount in this method of implantation.

[Background of the invention]

In the ion implantation method using an ion microbeam, the ion implantation fD is usually 1011 to 10"71o.
ns/(-d. Conventionally, the ion implantation amount is controlled by changing the scanning speed of the ion beam on the sample. In other words, the current density J of the ion beam is usually 10 The scanning speed of the ion beam on the sample vCcrn/IIec] can be calculated from the following equation.

V=(J/1.axxo-”)・(dxio-')/D
(1) However, here, for simplicity, the ion beam shape is assumed to be a square with one side of 6 μm.

In order to increase the accuracy of the ion beam position, the ion beam position and υ deflection signals are handled digitally. At this time, if the degree of the ion beam is taken to be l/n of the diameter d of the ion beam, the time t [μS] per bit for electrically processing the deflection signal is calculated by the following equation.

t=(dXlo-4/n)XIO'/V (2) Substituting equation (1) into this, it becomes t=1.6xlO"-D/(n-J) (3).

Now, let n = 5 and J = 0. IA/cr
1012i ons/crI with 1 ion beam
When attempting to perform ion implantation of i, t=0.3 μs. This value is the response time t' (= several μ
s) If the length was much shorter, ion implantation with such specifications would be impossible. The condition under which ion implantation is possible is t>t'. For example, if t'=3 μs, there is a disadvantage that ion implantation is limited to a region that satisfies the condition of the following equation (4).

[Purpose of the invention]

Therefore, an object of the present invention is to provide an ion implantation method that allows ion implantation to be performed with high precision and high positional accuracy even in regions where the amount of ion implantation is low, rather than in regions where the amount of ion implantation is still low.

[Summary of the invention]

In order to achieve the above object, in the present invention, in an ion implantation method in which ions are directly implanted into a sample by scanning an ion microbeam, the ion microbeam is operated intermittently and a predetermined amount is implanted into the sample by changing the intermittent time ratio. It is characterized by implanting ions.

Furthermore, the present invention is characterized in that the ion microbeam is operated intermittently, and a predetermined amount of ions are implanted into the sample by changing the intermittent time ratio and at the same time changing the scanning speed of the ion microbeam. There is.

By using such a characteristic method of the present invention, it has become possible to greatly expand the range of ion implantation amount by high-quality counterfeiting while maintaining the accuracy of the ion implantation position and keeping fc. As a result, by applying this ion implantation method, it becomes possible to manufacture high-performance semiconductor devices.

[Embodiments of the invention]

First, the basic principle of the present invention will be explained in detail.

In conventional ion lychrobe beam implantation methods, it has been difficult and rare to perform ion implantation with high accuracy in a concentration region where there are few ion implanters while maintaining the positional accuracy of the ion beam. The difficulty is, for example, the formula (
As shown in 3), the higher the ion beam current density J is, the larger it tends to be. Therefore, when implanting to a low concentration region with high positional accuracy, it is necessary to lower the ion beam current density J. Although it is possible to lower the ion beam current density J by adjusting the ion beam optical system, for example, adjusting many factors such as the ion extraction voltage of the ion source, lens voltage, and aperture, it is possible to lower the ion beam current density J. , (1) IAI
(II) conversion between high current density and low current density cannot be done in a short time; Gi
Since it is difficult to arbitrarily select the Dm current density, it is not practical to select the ion beam current density J by adjusting the ion beam optical system. Therefore, in the present invention, for example, a plunker is used to electrically turn on and off the ion beam in a short period of time, to allow the ion beam to pass through, and to stop the ion beam to effectively control the ion beam current density. By lowering J, ions can be implanted at desired locations and at desired concentrations.

In other words, while the settling time of the deflection circuit control power supply system, which requires #J precision, is on the order of a few μs, the response of the plunker control power supply can be from several ns to several 1001 S. By changing the time ratio of the on/off operation of the plunker within a short period of about several microseconds, it is possible to implant ions at a particularly low concentration.

Furthermore, by combining this on/off operation of the ion beam with the conventional method of changing the scanning speed, it becomes possible to consistently perform ion implantation from high to low concentration regions. .

Next, one embodiment of the present invention will be explained with reference to FIG. 1st
The figure schematically shows an ion implantation apparatus for carrying out the ion microbeam implantation method according to the present invention. In the figure, an ion microbeam 2 extracted from an ion source 1, such as a liquid metal ion source, is accelerated by a pair of electrostatic lenses 3.degree. 3', and reaches an implanted sample 4, such as a semiconductor substrate. Between the electrostatic lenses 3 and 3',
mass separator 5, plunker 6, and electrostatic lens 3'
An ion beam deflector 7 is provided after the ion beam deflector 7, and a control power source 8.9 is connected to the ion beam deflector 6 and the deflector 7, respectively.
An implant density control circuit 10 controls both of these.
are connected to both control power supplies 8 and 9. In addition, 11. l
1' and 11'' are respective diaphragms.

FIGS. 2(a) to 2(d) show the ion microbeam 2 of the planker 6 driven by the control power source 8 and the control circuit 1o.
This figure shows examples of temporal changes in passing (on) and stopping (off). In FIGS. 2(a) to 2(d), the time during which the ion microbeam 2 is in the passing (on) state is 1/2 of the total time ((a) in FIG. 2), respectively.
((b) in the same figure), 1/3 ((C) in the same figure), 1/3
4 ((d) in the same figure), the effective ion microbeam current density J is as shown in (b), (C), (d) in the same figure.
In the case of FIG. Now, for example, the pulse width ts in the on state is 100 ns in (b), (C), and (d) in the same figure, and when expressed as the period Ttl - NtB, N is 2 and 3.4, respectively. .

In FIG. 2, the implanted ion concentration is changed by changing the pulse period T while keeping the on-state pulse width ts constant. On the other hand, as shown in FIGS. 3(a) to 3(d), the same effect can be achieved by keeping the pulse period T constant and changing the on-state pulse width ts.

In Figures 3 (a) to (d), (a) and (b)
, (CL (d) are respectively t++ /'r=o, s
, o, s, 0.25, 0.05. Of course, a method combining the methods shown in FIG. 2 and FIG. 3 is also possible.

In addition, in FIG. 3, good results can be obtained if the pulse period is T, which is made equal to the changing period of the deflection voltage of the beam deflector control power source 9, or is made a fraction of an integer.

By the way, in the conventional method of controlling the ion implantation concentration using only the ion microbeam scanning speed V, the settling time t per bit for electrically processing the deflection signal of the deflector 7 is The response time of the electric circuit element could only be shortened to t'.

On the other hand, in the present invention, in order to maintain the same driving accuracy as in the conventional method, T x t' must be achieved. In this example, t' = 3 μs and ts = 100 nB, so
N≦30. Furthermore, according to the present invention, the lowest value of the ion implantable concentration given by equation (4) can be further reduced to 1/30.

In this example, ion implantation was performed using a 30 KeV boron beam, and at this time, J = 0. IA/cr/l
However, the lower limit of the concentration that can be implanted with ions is from 10"1ons/- to 10"1ons/- in the conventional method.
(To J (9) Much improved.

The ion microbeam current density ffJ is constant within the range of the path diameter of the ion beam from 0.1 to 3 μm, and the above-mentioned depth modification value is satisfied within this range.

Next, an example of a combination of the on/off operation of the ion microbeam and the control of the scanning speed will be described.

When a deflection voltage with a sinusoidal waveform (sin wl ) is applied to the beam deflector 7, the scanning speed of the ion beam changes to a cosine waveform (sin wl ).
cos wt ). Here, W is the angular frequency (=2
πf, f is frequency). In this example, ion implantation is performed using the same boron beam as in the previous example, and f=
I took it to 50H2. This made it possible to change the amount of ion implantation on sample 4 in proportion to cos'' (2ot).

By simultaneously controlling the scanning speed of the ion beam and the on/off operation of the ion beam in the above embodiment, the lower limit of the concentration that can be implanted based on the location average can be reduced to 10 tm 1 ons/crt using the conventional method.
l to 3 X 10” i ons /(:J to (
10) Greatly improved.

〔Effect of the invention〕

As described above, according to the present invention, in the method of performing ion implantation by scanning an ion microbeam, it is possible to implant ions not only in areas with high ion implantation concentration but also in areas with low ion implantation concentration with high accuracy and high positional accuracy. Using this, it becomes possible to manufacture semiconductor sintering elements with good sieving performance. Also,
Unexploded Lllj can also be applied to ion beam exposure of resist.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an ion microbeam implantation apparatus for carrying out the ion microbeam implantation method according to the present invention, FIGS. 2(a) to (d), and FIGS. 3(a) to 3.
(d) Each is a time chart showing the temporal operation state of the plunker in FIG. 1... Ion source, 2... Ion microbeam, 3
゜3'... Electrostatic lens, 4... Sample, 5... JR
3t separator, 6... Plunker, 7... Beam deflector. 8... Plunker control power supply, 9... Beam deflector control power supply, 10... Implant density control circuit section, 11.
11', 11" (11) (12) d 3S resistance +', ,

Claims (1)

[Claims] 1. In an ion implantation method in which ions are directly implanted into a sample by scanning an ion microbeam, a predetermined amount of ions is implanted into the sample by intermittent operation of the ion microbeam and by changing the intermittent time ratio. An ion microbeam implantation method characterized in that the ion microbeam is implanted. 2. The ion microbeam implantation method according to item 1, wherein the intermittent operation of the ion microbeam is performed by a plunker provided on the trajectory of the ion microbeam. 3. In an ion implantation method in which ions are directly implanted into a sample by scanning an ion microbeam, by intermittent operation of the ion microbeam and changing the intermittent time ratio, at the same time, changing the scanning speed of the ion microbeam. An ion microbeam implantation method characterized by implanting a predetermined amount of ions into a sample.