JP2660701B2 - Ion implanter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ion implantation apparatus used to implant ions into a wafer, for example. [Prior Art and Problems Thereof] FIG. 2 shows a conventional ion implantation apparatus. In the figure, an ion beam (1) is formed by an opening (2a) of a mask (2) and a Faraday bias plate (3). ) Is introduced into the Faraday box (5) under reduced pressure through the opening (3a) as shown by the arrow. A negative potential is applied to the Faraday bias plate (3) by a bias power supply (4) to prevent electrons in the Faraday box (5) from being emitted outward. The ion beam (1) introduced into the Faraday box (5) collides with the wafer (11) disposed in the Faraday box (5) and is injected. When the charge is charged up, the injection effect is reduced or the characteristics of the thin film formed on the surface of the wafer are degraded. As shown in the figure, the water is discharged into the Faraday box (5). This collides with the inner wall of the Faraday box (5) as shown by a broken line, thereby generating secondary electrons (6) '(6) ". The ion beam (1) is an electron shower (6). Is partially neutralized when passing through, and after passing through, it is also neutralized by secondary electrons (6) ′ (6) ″ before reaching the wafer (11). Further, electrons are present in high density near the surface of the wafer (11), and when injected, are neutralized and injected into the wafer (11). Note that reference numeral (12) denotes an ammeter which measures the current based on the amount of ions implanted into the wafer (11), that is, the amount of ions implanted. The current source (13) is composed of an extraction electrode (7), a filament (8), a filament power supply (9) and an extraction power supply (10), and the filament power supply (9) heats the filament (8). Thermal electrons are emitted,
This is accelerated by the extraction electrode (7) given a positive potential by the extraction power supply (10), and passes through the opening (5a) formed in a part of the wall of the Faraday box (5) as shown by the broken line. As shown by a broken line, an electron shower (6) is generated. Then, as described above, this collides with the upper wall of the Faraday box (5) and emits secondary electrons (6) ′ (6) ″ toward the respective parts from this. The apparatus is configured as described above. The amount of electrons may be an appropriate amount in order to prevent charge-up of the wafer (11) by the ion beam (1). On the contrary, if the number is too large, the wafer (11) is charged up to electrons, that is, a negative potential, which also deteriorates the characteristics of the wafer. Points] The present invention has been made in view of the above points, and the wafer (1) can be used regardless of the intensity of the ion beam (1).
An object of the present invention is to provide an ion implantation apparatus capable of appropriately preventing the charge-up of 1) and obtaining a high-quality wafer. [Means for Solving the Problems] The above object is to irradiate a wafer disposed in a wafer processing chamber under reduced pressure with an ion beam and introduce an electron shower from an electron source into the wafer processing chamber. In the ion implantation apparatus, a bias plate having a negative potential is provided on an ion beam implantation side of the wafer processing chamber in order to prevent the wafer from being charged and to confine electrons in the wafer processing chamber. Wherein the amount of electrons generated from the electron source is controlled in accordance with the current flowing through the ion implantation apparatus. [Operation] The number of positive ions generated in the wafer processing chamber increases in proportion to the intensity of the ion beam introduced into the chamber. The intensity of the ion beam is indirectly detected by the flow of the ion beam to the bias plate, and the amount of electrons generated from the electron source is controlled based on the detected intensity. Therefore, charge-up of the wafer is prevented. [Embodiment] Hereinafter, an ion implantation apparatus according to an embodiment of the present invention will be described with reference to FIG. 1. In the figure, parts corresponding to FIG. It shall be omitted. That is, according to the present embodiment, the electron source (20) includes the extraction electrode (7), the filament (8), and the like, as in the related art, but further includes an extraction voltage controller (15). A resistor (16) is connected to the Faraday bias plate (3) ', and both ends of the resistor (16) are connected to the above-mentioned extraction voltage controller (15).
That is, the voltage generated at both ends of the resistor (16) changes depending on the magnitude of the current flowing through the Faraday bias plate (3) ', and this voltage is supplied to the extraction voltage controller (15) as a detection output. The extraction voltage controller (15) generates an extraction voltage in accordance with the magnitude of the detected voltage, and supplies this to the extraction electrode (7). The ion implantation apparatus according to the embodiment of the present invention is configured as described above. Next, the operation, effects, and the like will be described. Positive ions (14) generated secondarily in the vicinity of the Faraday bias plate (3) 'due to the intensity of the ion beam (1) externally introduced into the Faraday box (5).
Are generated according to the intensity of the ion beam (1). The current generated by the positive ions flows through the resistor (16) to generate a voltage at both ends of the resistor, which is applied to the extraction voltage controller (15). The controller (15) generates a positive DC voltage proportional to the voltage generated across the resistor (16), and this is supplied to the extraction electrode (7). Therefore, if the intensity of the ion beam (1) is high, an electron shower (60) having a corresponding intensity is emitted from the current source (20) into the Faraday box (5). Then, secondary electrons are also generated according to the strength. Therefore, the ion beam (1) introduced into the Faraday box (5) is injected into the wafer (11), but electrons corresponding to the intensity are present in the Faraday box (5). Properly neutralized to prevent wafer (11) charge-up,
At the same time, charge-up due to electrons is prevented, and a wafer having excellent characteristics can be obtained. Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention. For example, in the above embodiment, a DC voltage is generated by the extraction voltage controller (15) in accordance with the voltage generated in the resistor (16) connected to the Faraday bias plate (3) ', and this is applied to the extraction electrode (7). Instead, the bias power supply for the extraction electrode (7) is kept constant as in the prior art, and the DC voltage of the filament power supply (9) of the filament (8) is replaced with the extraction voltage controller ( 15). [Effects of the Invention] As described above, according to the ion implantation apparatus of the present invention,
The intensity of the electron shower can be changed in accordance with the intensity of the ion beam introduced into the wafer processing chamber under reduced pressure. A good quality wafer can be obtained without being charged up negatively.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of an ion implantation apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic view of a conventional ion implantation apparatus. In the figure, (15) ... Pull-out voltage controller (16) ... Resistance (20) ... Electron source

Claims (1)

(57) [Claims] The wafer disposed in the wafer processing chamber under reduced pressure is irradiated with an ion beam, and a shower of electrons from an electron source is introduced into the wafer processing chamber, thereby preventing charging of the wafer and preventing the wafer processing. In an ion implantation apparatus provided with a negative potential bias plate on the ion beam implantation side of the wafer processing chamber in order to confine electrons in the chamber, electrons generated from the electron source in accordance with a current flowing through the bias plate are provided. An ion implantation apparatus wherein the amount of shower is controlled.