JPS61256553A - Ion-beam generator - Google Patents

Abstract

PURPOSE:To improve efficiency, with a scanning electric field independent of an acceleration voltage, by making composition in which a generator of focusing ion beams capable of being scanned, with a high acceleration voltage, is positioned before a beam-scanning part. CONSTITUTION:Ion beams 1 from an ion source 2 are made to pass through condenser lenses 3 and a mass-separator 4, and thereafter being scanned at a beam scanning part 5. Then, they are accelerated to have high energy, and focussed by object lenses 7, and the necessary amount of them are shot into an assigned position on a substrate 8 to shoot ions into, to form an ion-beam generator used in the production of a semiconductor device or the like. A transverse scanning electric field is made to be decided independent of a final acceleration voltage. Therefore, with the scanning electric field being reduced to improve efficiency, high-energy focussing ion beams of good quality, capable of being scanned, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for generating an ion beam used in an ion implantation process in a semiconductor device manufacturing process, and particularly relates to a method for generating an ion beam used in an ion implantation process in a semiconductor device manufacturing process, and in particular, when the accelerating voltage is approximately IMV or higher, conventional techniques The present invention relates to a suitable generating device for a focused ion beam that can be scanned in very high cases compared to the present invention.

[Background of the invention]

Application of ion beams to the impurity implantation process in the semiconductor device manufacturing process, where the acceleration voltage is about IMV or higher, which is extremely high compared to conventional technology (hereinafter referred to as high energy), is at a depth of about 1 μm. Since the impurity concentration in the region can be controlled, the manufacturing process can be simplified, and the amorphous layer can be recrystallized at low temperatures due to the cellphaneel effect, which is faster than the conventional method of several tens to hundreds of KV. It has two advantages not seen with ion beams.

On the other hand, in order to enable ion implantation into minute regions of 1 μm or less and to control the lateral distribution,
For example, Journal of Vacuum Science Technology (Journalof Vacu@5c
ience Technology) 19 (4)
115g (1981) is advantageous. In particular, high-energy ion beams have a long range, so when introducing impurities into a desired position in a semiconductor, a material that blocks ions is conventionally formed on the semiconductor surface to block unwanted ions. In the method of stopping in a blocking material, the mask material is limited, and from this point of view, a convergence that enables maskless operation is desired.

Therefore, as a method for generating a focused ion beam that has high energy and can be scanned, we will first consider a case where the method used for conventional focused ion beams of tens to hundreds of kilovolts is applied as is. Figure 3 is an explanatory diagram of the ion source 2.
．． Condenser lens 3° Mass separator 4. objective lens 7,
It is composed of a beam scanning section 5. If you try to obtain a high-energy focused ion beam by simply increasing the accelerating voltage by applying such a conventional focused ion beam generator configuration as it is, the energy will be high.

Scanning the beam requires a large lateral scanning electric field proportional to its accelerating voltage.

Furthermore, as a result, the transverse velocity component of the output beam increases, and the angle of incidence with respect to the target (wafer) into which ions are implanted deviates from the perpendicular.

This is undesirable because it interferes with accurate ion implantation control. That is, the obliquely implanted ions not only deviate laterally from a predetermined implantation position, but also decrease the implantation position accuracy in the depth direction.

The error in the horizontal position is AX, and the error in the depth direction is Δ2. θ is the deviation angle of the incident ion angle from the vertical.

If the projected range of ions at a certain ion implantation energy is R, then AX, , AZ are given by the following equations.

AX = R, sinθ・(1)
AZ = R, (1-cosθ) - (2
) Therefore, considering that the accuracy required in current integrated circuit technology is about 0.05 μm, the equation (1
), (2), when R2 is about 2 μm, θ is 1.
It is necessary to keep it below 4 degrees.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide a high-energy focused ion beam generator that can scan efficiently and with good quality.

[Summary of the invention]

In conventional focused ion beam generators, the beam scanning section was generally located at the final stage of the device configuration, so a lateral electric field for scanning was required that was proportional to the final accelerating voltage. Ta. Therefore.

The present invention enables a scanning electric field that is independent of the accelerating voltage by bringing the beam scanning section before accelerating the beam, and especially when this method is applied to a high-energy focused ion beam, 4. It is possible to reduce the scanning voltage and improve the quality of the beam (the transverse velocity component is small). FIG. 1 is a diagram showing an example of the configuration of an ion beam generator of the present invention. The ion beam 1 that has passed through the mass separator 4 is first scanned by a beam scanning section 5, then accelerated to high energy by an accelerating section 6, focused by an objective lens 7, and delivered to a substrate 8 into which ions are to be implanted. The required amount is driven into the predetermined position on the top.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail using Examples.

Embodiment 1 FIG. 2 is a diagram schematically showing only the acceleration section and the scanning section of an ion beam generator, in which (a) is the one according to the present invention, and (b) is the conventional device.

After the ions 9 pass through the scanning section 5 and the acceleration section 6,
Reach target 8. Using boron as an ion,
The initial energy V, is 10 K e V.

The final beam kinetic energy V, is 2 M e V
In the figure, when z = Q1 + 02 + 03,
The horizontal electric field E for scanning required to pass y=L, that is, to pass point X, is Ω.

ioam,n,=5am,Q3=30a*,L=2an
In the case of the present invention, the amount can be reduced by 50% compared to the conventional device. Also, looking at the angle at which the final beam enters the target at this time, with the conventional device, it is approximately 3 degrees with respect to the X axis.
In contrast, in the present invention, an excellent beam quality of 0.5° can be obtained.

Next, in FIG. 2, the value of Q2 is further increased, and Q
, = 10 am, the scanning electric field E
It is possible to further reduce the amount of work required, and the value is 7.
A value as low as 0% is sufficient. Also, the direction of the beam is also 0.3°.

Embodiment 2 In this embodiment, the system configuration of an apparatus according to the present invention is shown in FIG. 4, which shows an ion source 2. Condenser lens 3.
Mass separator 4. In a focused ion beam generator consisting of a beam scanning section 5 and a beam accelerating section 6, a beam scanning control section 1
A system is shown in which the beam scanning section 5 is controlled according to pattern information generated by 0, and ions are implanted into the substrate 8.

Here, the ion source 2 is a field emission type liquid metal ion source, which uses a metal such as N1-B alloy or Ga, and releases ions to become donors or acceptors in the semiconductor substrate 8 by field ionization radiation. It is something to do. The optimal extraction voltage of the ion source is about 10 KV.6 Condenser lens 3 and mass separator 4. The beam scanning section 5 is located in the high voltage section 12, and its control is performed from the operating section 14 through the optical fiber 13. Power for their operation is supplied from the isolation transformer 15.

Beam scanning is controlled by a beam scanning control section 10 in an operating section 14. In this embodiment, the beam scanning controller 10
uses H-80E (product name: Newly manufactured by Hitachi Seisakusho), and the data transfer rate is 24 MB/s. The D/A converter used for beam scanning has an accuracy of 18 bits,
This made it possible to obtain an accuracy of about 20 ppm. That is, the field size was set to 2 m, and an accuracy of 0.1 μm was obtained. Beam blanking is performed by the beam scanning section 5.
This was done by

The beam accelerator 6 consists of a normal Cock-Crodt accelerator, and the acceleration voltage range is 0 to 200 KV. Board 8
is placed on a sample stage 16 that is controlled by laser interference, and the sample stage 16 moves under the control of a beam scanning controller IQ. The ion implantation amount control section 11 detects the amount of ions implanted into the substrate 8, and feeds it back to the beam scanning control section 1o, thereby providing an appropriate ion implantation amount. In this example, the implantation amount error could be suppressed to within 1%. These are placed in a vacuum system 17 and are operated by a Talio pump under normal operating conditions.
It is exhausted to 0-'Torr.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, the scanning lateral electric field can be determined independently of the final accelerating voltage, so that the scanning electric field can be reduced in generating a high-energy focused ion beam. becomes possible. moreover,
Since the applied lateral electric field is small, the beam direction is more perpendicular to the target and of excellent quality compared to conventional devices. Therefore, it becomes possible to control the distribution more accurately. Furthermore, according to the present invention, even if the implantation voltage during ion implantation is changed, the scan voltage can be kept constant, so that the electric circuit can be simplified. That is, it is possible to form a desired impurity distribution by performing so-called multiple implantation at the same location while changing the ion implantation energy, which is highly profitable.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of the present invention, and FIGS. 2(a) and 2(b) are diagrams for explaining the acceleration section and scanning section of the present invention and a conventional focused ion beam generator, respectively. FIG. 3 is a diagram showing the configuration of a conventional device, and FIG. 4 is a diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Focused ion beam, 2... Ion source, 3... Condenser lens, 4... Mass separator, 5... Beam scanning unit. 6... Beam accelerator, 7... Objective lens, 8...
Substrate, 9... Ion, 10... Beam scanning controller,
11... Injection amount control section, 12... High voltage section, 13
...optical fiber, 14. ...Operation unit, 15...Isolation ° transformer, 16...Sample stage, 17...
・Vacuum system.

Claims (1)

[Claims] An ion beam generator that can scan an ion beam with a high acceleration voltage, and is characterized in that after scanning an ion beam with a low acceleration voltage, the ion beam is accelerated to a final acceleration voltage.