JPS59230242A - Ion implantation device - Google Patents

Abstract

PURPOSE:To enable homogeneous implantation to be performed on a wafer by using a mass-separating magnet as a reducing system and a deflecting magnet as a magnifying system and synchronously scanning the field intensities of both magnets and the position of a mass-separating slit. CONSTITUTION:Ion beams 4 discharged through the discharge slit 31 of an ion source 1 are deflected by the magnetic field of a mass-separatig magnet 32 before specified ions are selected by a mass-separating slit 33. Ion beams of a specific mass discharged from the slit 33 becomes incident upon a deflecting magnet 34 to make parallel beams which are then imaged upon an imaging position 35. These ion beams irradiate wafers 7 placed in the periphery of a rotary disk 9 located in front of the position 35. A magnetic-field power source 37, a motor 38 for moving the slit 33 and a deflecting magnetic-field power source 39 are controlled by a controlling part 40, thereby delivering signals synchronous with the field scanning of a magnet 32 to the motor 38 and the power source 39. As a result, homogeneous implantation can be performed on the wafers 7 by selecting ions of a desired mass.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an ion implantation apparatus for wafers, and particularly to an ion implantation apparatus of a type in which a wafer is fixed and an ion beam is moved.

[Background of the invention]

As the demand for semiconductor devices increases, increasing the efficiency of ion implantation into wafers, which are the raw material for semiconductor devices, has become an important issue, and various ion implantation devices are being developed that aim to improve productivity and implantation accuracy.

For example, a device that scans and implants an ion beam onto a rotating disk with a large number of wafers mounted on the same circumference, or a device that rotates a rotating disk with a large number of wafers mounted on the same circumference and directs the ion beam in the diametrical direction. This is a system in which the ion beam is moved back and forth while the ion beam is fixed. These ion implantation devices have advantages and disadvantages, but the latter ion implantation device, which uses a fixed ion beam, is large and has a complicated structure due to the movement of the rotating disk.

FIG. 1 is a principle diagram showing the basic configuration of an ion implantation device. 1 is an ion source, 2 is an ion source housing, and 3 is an electromagnet. An ion beam 4 emitted and accelerated from the ion source 1 is mass-separated by the electromagnet 3. Of the separated ions, only desired ions are selected by a slit 6 attached to the analysis tube 5 and implanted into the wafer 7 in the implantation chamber 8.

Ions of different masses are implanted by changing the magnetic force of the electromagnet 3, but in order to increase the amount of ions, a suitable gas is introduced into the ion source housing 2. Note that the interiors of the ion source housing 2, analysis tube 5, and implantation chamber 8 are evacuated to a high vacuum state so that movement of the ion beam 4 cannot be prevented.

Since the ion beam 4 that has arrived at the wafer 7 passes through the slit 6, it has a rectangular cross section that is long in the direction perpendicular to the plane of the paper. Therefore, in order to uniformly implant ions into the wafer 7, it is necessary to scan the ion beam 4 or move the wafer 7 back and forth.

FIG. 2 is a sectional view of a main part of a conventional wafer moving type ion implantation apparatus. In this apparatus, a large number of wafers 7 are mounted on the same radius of a rotating disk 9, and ions are implanted by rotating the rotating disk 9 and simultaneously reciprocating the rotating shaft 11 in the Y-Y' force direction. The wafer 7 is inserted into the cassette 25,
It is attached to the rotating disk 9 by a spring 26. A rotating shaft 11 directly connected to the rotating disk 9 is rotated by a pulse motor 16 via a shaft 15 and a pair of bevel gears 13 .

Further, the rotating shaft 11 penetrates a rotating vacuum seal 10 attached to the gear housing 12 to maintain the vacuum in the driving chamber 8.

The gear housing 12 has a ball bearing 20 mounted on a 7 flange 21 attached to the driving chamber 8 by a bellows 14.23.
A female screw plate 24 is movably coupled through the gear housing 12 and the bellows 23 and is airtightly fixed between the gear housing 12 and the bellows 23.
A threaded rod 22 is screwed together. That is, the driving chamber 8 is kept under vacuum by the rotary vacuum seal 10 and the bellows 14, 23, and the gear housing 12 is configured to be able to reciprocate in the Y-Y' force direction by the bellows 14, 23. Therefore, the volume of the driving chamber 8 needs to be large enough to allow for movement.

An outline of the operation of such an ion implantation device will be explained below. When the pulse motor 19 is rotated, the threaded rod 22 rotates and moves the gear housing 12 and the rotating disk 9 in the Y-Y' force direction, thereby increasing the R dimension, which is the distance between the center of the ion beam 4 and the center of the rotating shaft 11. change. Moreover, when the pulse motor 16 is rotated, the rotating disk 9 can be rotated.

Therefore, if the pulse motors 16 and 19 are rotated simultaneously, uniform ion implantation can be performed on a large number of wafers 7 at the same time. Since 25 wafers 7 are normally attached to the rotating disk 9, 25 implanted wafers 7 can be obtained by one implanting operation.

However, since the gear housing 12 is provided in the driving chamber 8 and movably connected to it by bellows 14, 23, the structure becomes complicated and the volume of the driving chamber 8 becomes large. Therefore, the evacuation time when replacing the rotary disk 9 is long, and the production efficiency is reduced accordingly. Furthermore, since the rotating shaft 11 is driven by the bevel gear 13, it is difficult to employ a direct cooling method such as providing a water pipe on the rotating shaft 11 and cooling the rotating disk 9 with water. Furthermore, since the wafer 7 is mounted using the cassette 25 and the spring 26, there are drawbacks such as the troublesome mounting of the wafer 7.

In addition, in the conventional device, when replacing the wet cloth, the rotating disk 9
, the drive mechanism including the gear housing 12, motor 16, 19, etc. is opened using a large-scale opening/closing mechanism to expose the wafer 7, and the weight of the moving parts becomes large and it takes time to open/close the opening/closing operation. However, there were problems such as requiring a large installation floor space.

A further disadvantage of the mechanical scanning method is that it has a short lifespan. Since the bellows 14, 23 repeatedly move up and down to perform scanning, their deterioration cannot be avoided.

They must be replaced as appropriate, but this requires a great deal of cost and time. A conventional device in which the wafer 7 is fixed and the ion beam 4 is scanned by a magnetic field is composed of a separation magnetic field for separating ions and a deflection magnetic field for irradiating the separated and selected ions onto the wafer 7. A correction magnetic field is separately installed to prevent changes in the beam width on the wafer 7 caused by scanning the ion beam, and the large magnetic field is
This has drawbacks such as the need for multiple units, resulting in an increase in the size of the device.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above, and to provide an ion implantation device that is small, easy to operate, and operates with high efficiency and precision.

[Summary of the invention]

The feature of the present invention is that the mass separation magnet is a reduced system,
In addition to using a deflection magnet as an enlargement system, the magnetic field strength of the mass separation magnet and deflection magnet and the position of the mass separation slit are scanned in synchronization, so that the ions emitted from the ion source are uniformly implanted into the wafer. It is in.

[Embodiments of the invention]

FIG. 3 is an ion optical system diagram of an ion implantation apparatus which is an embodiment of the present invention. The ion beam 4 emitted from the exit slit 31 of the ion source 1 is deflected by the magnetic field of the mass separation magnet 32, and specific ions are selected by the mass separation slit 33. The ion beam of a specific mass that has exited this slit is incident on the deflection magnet 34, and the ion beam deflected here becomes a parallel beam and is imaged at the imaging position 35.

The wafer 7 placed around the rotating disk 9 in front of the imaging position 35 is irradiated with this ion beam.

The rotating disk 9 is rotated by a drive motor 36, and a magnetic field power supply 37 for changing the magnetic field of the mass separation magnet 32 moves the mass separation slit 33.
38, deflection magnetic field power supply 3 that changes the magnetic field of the deflection magnet 34
9 etc. are controlled by signals from the control section 40.

That is, by sending a signal synchronized with the magnetic field scanning of the mass separation magnet 32 to the motor 38 and the deflection magnet power supply 39, ions of a desired mass are selected and uniformly implanted into the wafer 7.

Note that when the magnetic field strength is B1, the magnetic field radius is rl, and the ion acceleration voltage is V1, the ion mass number is M, the following relationship is obtained.

Br-144VvV This can be understood as the trajectory of the ion beam when M and V are kept constant and the magnetic field strength B is changed as a change in the magnetic field radius r. Furthermore, it can be understood that the magnetic field strength B changes in proportion to the output currents of the separation magnet power supply 37 and the deflection magnet power supply 39, and that the magnetic field radius r is inversely proportional to the magnet strength B by expanding the above equation.

When a specific ion among the ions emitted from the exit slit 31, which is the object point S of the ion source, is deflected by the magnetic field of the mass separation magnet 32, it follows a trajectory with magnetic field radii R1, R2, and Rs, and reaches the surface of the mass separation slit 33. Pl, P2, P on top
Create an image point of s.

Then, the mass separation slit 33 is moved and the magnetic field strength of the mass separation magnet 32 is changed.

Furthermore, when the ion beam is deflected by the deflection magnet 34, it is performed in synchronization with the magnetic field sweep of the mass separation magnet 32, so that the ion beam is emitted in parallel through a trajectory of '1 e r2 * rl, and is focused at the imaging position 35. Image formed on the same plane Pl'l P
2' and Ps' are obtained.

Wafer 7 is imaged P! ' , P2' * Ps"
Since the ion beam 4 is placed in front of the wafer 7, the shape of the ion beam 4 is constant on any surface of the wafer 7. Furthermore, in order to obtain uniformity of the ion beam, the deflection magnet 34 is an expanding system. For example, if the width of the slit (9) of the exit slit 31 is 2 mm and the reduction ratio of the mass separation magnet 32 is 172, the imaging width of Pt I P2 s p3 will be 1 m (within 2 WIR even including the amount of aberration). . Magnify this by 10
Image formation of double deflection magnet 34 P1' * P2' + P3
'The imaging width is 10mm (20mm even if aberration is added)
Even when two wafers are placed in front of the wafer, it is extremely easy to keep the distance within the image on the wafer 7 surface within 30 m.

In the apparatus of this embodiment, the mass separation slit 33 is the only mechanical scanning section, but this slit is essential to all ion implantation apparatuses and is not particularly added. Only the control for moving this mass separation slit 33 in synchronization with magnetic field scanning is added. Note that the mass separation slit 33 is a small component that can be easily moved in a straight line.

In order to uniformly implant ions into the wafer 7, magnetic field scanning is performed at a speed inversely proportional to the radius R of the rotating disk 9 on which the wafer 7 is mounted. Further, at this time, the scanning of the mass separation slit 33 and the deflection magnetic field (10), which are performed synchronously, is also performed at a speed inversely proportional to R. In this way, completely uniform ion implantation becomes possible.

The ion implantation apparatus of this embodiment has the following effects.

1. Since the rotating disk 9 to which the wafer 7 is attached only rotates the rotating shaft 11 without moving it laterally, the implanting chamber 8 becomes smaller, the evacuation time is shortened, and implanting efficiency is improved. .

2. The driving chamber 8 must be clean, but since there is no mechanical system for moving the rotary shaft 11 laterally as described above, contaminants will not be diffused.

3. Since only one deflection magnet 34 is required and the correction magnetic field required in the conventional magnetic field scanning method is not required, a relatively inexpensive and compact device can be obtained.

4. Since the rotating disk 9 has a simple structure, the wafer 7 can be cooled easily.

[Effects of the Invention] The ion implantation apparatus of the present invention can carry out uniform ion implantation (11) while moving the ion beam to the wafer on the rotating disk, so it has the advantage of being small and highly efficient. is obtained.

[Brief explanation of drawings]

Fig. 1 is a principle diagram showing the basic configuration of an ion implantation device, Fig. 2 is a sectional view of main parts of a conventional wafer movement type ion implantation device, and Fig. 3 is an ion implantation device according to an embodiment of the present invention. FIG. 3 is an ion optical system diagram of the implantation device. DESCRIPTION OF SYMBOLS 1... Ion source, 4... Ion beam, 7... Wafer, 8... Implanting chamber, 9... Rotating disk, 31...
Output slit, 32... Mass separation magnet, 33... Mass separation slit, 34... Deflection magnet, 35... Imaging position, 36... Drive motor, 37... Separation magnet power supply, 38 ... Slit motor, 39 ... Deflection magnet power supply, 40 ... Control unit. Agent Patent attorney Hiroo Nagasaki (and 1 other person) (12) Figure 2

Claims (1)

[Claims] 1. It has an ion source, a mass separation magnet and a mass separation slit that separate the ions emitted from the ion source, a deflection magnet that displaces the ion flow, and an ion implantation chamber that implants the separated ions into the wafer. In the ion implantation device, the mass separation magnet is used as a reduction system and the deflection magnet is used as an enlargement system, and the magnetic field intensities of the mass separation magnet and the deflection magnet and the position of the mass separation slit are scanned in synchronization with each other, An ion implantation apparatus characterized in that the ion implantation apparatus is configured to uniformly implant ions emitted from the ion source into the wafer.