JPH04218250A - Ion implantation device - Google Patents

Abstract

PURPOSE:To neutralize electrified ions completely by arranging an electron current control device to control electron quantity to neutralize the ions electrified on a semiconducting substrate. CONSTITUTION:A semiconducting substrate is housed in a chamber 2, and an ion gun 1 generates ions to be implanted into one main surface of this substrate, and electrons are generated from an electron gun 3 so as to neutralize the ions electrified on the substrate. Here, an electron current control circuit 11 is connected to a vacuum gage 10 to measure degree of vacuum in the chamber 2, and also controls flow rate of the electrons generated by means of the electron gun 3 according to the degree of vacuum in the chamber 2. An emission electric current to flow into a cathode of the electron gun 3 is set to flow abundantly as the degree of vacuum rises while following up the degree of vacuum. Thereby, the rise in the degree of vacuum and the generation of the ions can be neutralized by outgassing from an organic material coat by showering the electrons more abundantly.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation apparatus used for implanting impurity ions into a semiconductor substrate in the manufacturing process of semiconductor devices.

0002

2. Description of the Related Art FIG. 4 is a block diagram showing an example of a conventional ion implantation apparatus. Conventionally, as shown in FIG. 4, this type of ion implantation apparatus conventionally includes a chamber 4 in which a wafer 2, which is a semiconductor substrate, is mounted on a stage 5 and housed therein; An ion gun 1 that generates ions to be implanted into the wafer 2, an electron gun 3 that generates electrons to neutralize the ions charged in the wafer 2, and an evacuation system 6 that evacuates the chamber 2 to a predetermined degree of vacuum. There is. Further, the ion gun 1 is composed of an ion source 1a and a mass separator 1b, and is connected to an ion beam controller 9 and a dose controller 8 outside the device, which control the amount of ions generated. Further, the electron gun 3 is connected to an electron controller 7 that controls the electron flow.

Next, the operation of this ion implantation apparatus will be explained. First, the wafer 2 on which a pattern has been formed with an organic material film is placed in the chamber 4 and mounted on the stage 5 . Next, the chamber 4 is heated to a predetermined degree of vacuum, for example, 1
．． Exhaust to about 3 mPa. Next, predetermined ion energy and impurity amount are set using the ion beam controller 9 and the dose controller 8 to generate an ion beam, and the wafer 2 is irradiated with the ion beam while moving. On the other hand, the electron gun 3 exposes the wafer to electrons to neutralize the charged ions. Next, after irradiating the entire surface of the wafer 2 with an ion beam, the vacuum in the chamber 4 is released, and the wafer 2 is taken out of the chamber 4.

[0004] As described above, when ion implantation into a wafer is performed, the ion beam conditions and electron irradiation conditions are set in advance.

[0005]

In the conventional ion implantation apparatus described above, when the ion beam bombards the organic material coating, gas is generated from the organic material coating and the degree of vacuum deteriorates. Furthermore, the generation of gas molecules neutralizes the irradiated electrons, and in fact, the number of electrons that contribute to neutralizing the ions charged on the organic material coating decreases, causing the organic material coating to become electrically charged. For this reason, there is a problem in that the ions to be implanted are repelled, making it impossible to implant a predetermined dose of impurities into the wafer.

SUMMARY OF THE INVENTION An object of the present invention is to provide an ion implantation apparatus capable of more completely neutralizing charged ions and implanting a predetermined dose of impurities into a semiconductor substrate in order to solve this problem.

[0007]

[Means for Solving the Problems] The ion implantation apparatus of the present invention includes a chamber that houses a semiconductor substrate, an ion gun that generates ions to be implanted into one main surface of the semiconductor substrate, and an ion gun that generates charged ions of the semiconductor substrate. The ion implantation apparatus includes an electron flow control circuit that adjusts an electron flow rate of the electron gun depending on the degree of vacuum of the chamber. Further, another pre-electron flow control device of an ion implantation apparatus is characterized in that the electron flow rate follows the degree of vacuum, and the electron flow rate is adjusted to be large when the pressure is high. Furthermore, another ion implantation apparatus is characterized in that the electron flow control circuit tracks the electron flow rate with the degree of vacuum, holds it at predetermined time intervals, and varies it stepwise.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an ion implantation apparatus showing an embodiment of the present invention. As shown in the figure, the ion implantation apparatus in this embodiment is connected to a vacuum gauge 10 that measures the degree of vacuum in a chamber 2, and an electron flow that controls the flow rate of electrons generated by an electron gun 3 according to the degree of vacuum in the chamber 2. This is because the control circuit 11 is provided. Other than that, it is the same as before. This is to neutralize charged ions, which increase as the gas pressure increases, by exposing them to more electrons.

FIG. 2 is a graph showing the relationship between the degree of vacuum and the emitter current of the electron gun, for explaining one embodiment of the method of controlling the electron flow in the electron gun depending on the degree of vacuum in the ion implantation apparatus shown in FIG. In the ion implantation apparatus of this embodiment, as shown in the figure, the electron flow control circuit 11 controls the emission current (
In this graph, the emission current is used instead of the amount of electron charge) to follow the degree of vacuum, and to flow more as the degree of vacuum increases. This makes it possible to neutralize the increase in the degree of vacuum and the generation of ions due to gas release from the organic material coating by exposing it to more electrons. Also, this gas release is most intense at the beginning;
As the injection time elapses, it decreases.

In order to obtain this phenomenon, for example, if the vacuum gauge 10 uses an ionization vacuum gauge, the electronic current control circuit 11 detects the ionized ion current generated from the vacuum gauge 10 and controls the electron gun controller 7. This can be achieved by controlling the current of the emission power supply. Furthermore, if the electron gun is a triode, it is sufficient to control the grid bias power supply instead of the emission power supply.

FIG. 3 is a graph showing the relationship between the degree of vacuum and the emitter current of the electron gun, for explaining another embodiment of the method of controlling the electron flow in the electron gun depending on the degree of vacuum in the ion implantation apparatus shown in FIG. In the ion implantation apparatus of this embodiment, the electron flow rate controlled by the electron flow control device 11 is followed by the degree of vacuum, and the electron flow rate is held for a predetermined time interval and changed in steps.

In this control method, as shown in FIG. 3, a program for setting stepwise emission current values according to the degree of vacuum is installed in the electron flow control circuit 11 in advance, and the ionization from the vacuum gauge 10 is It detects the ion current value and flows a step-like emission current depending on the detected ion current value. This is because the detection sensitivity of the vacuum gauge 10 or the gas generation situation changes depending on the workpiece, so in order to more reliably neutralize the workpiece, check the gas generation situation from the film thickness, material, pattern opening, etc. A program was created that predicts the emission current, temporarily holds the emission current at a predetermined value, and then varies the current in steps. This embodiment is advantageous in that ions can be implanted more accurately than the previously described embodiments for repeated ion implantation operations into semiconductor substrates.

[0014]

Effects of the Invention As explained above, the present invention provides an electron flow control circuit that controls the amount of electrons that neutralize charged ions on a semiconductor substrate, thereby neutralizing charged ions more completely and reducing implantation. Since it is possible to prevent ions from being repelled, it is possible to obtain an ion implantation device that can implant impurities at a predetermined dose.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an ion implantation apparatus showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the degree of vacuum and the emitter current of the electron gun for explaining an example of a method of controlling the electron flow of the electron gun depending on the degree of vacuum in the ion implantation apparatus of FIG. 1;

3 is a graph showing the relationship between the degree of vacuum and the emitter current of the electron gun for explaining another embodiment of the method of controlling the electron flow of the electron gun depending on the degree of vacuum in the ion implantation apparatus of FIG. 1; FIG.

FIG. 4 is a block diagram showing an example of a conventional ion implantation device.

[Explanation of symbols]

1 Ion gun 1a Ion source 1b Mass separator 2 Chamber 3 Electron gun 4 Wafer 5 Stage 6 Vacuum exhaust system 7 Electron gun controller 8 Dose controller 9 Ion beam controller 10 Vacuum gauge 11 Electron flow control circuit

Claims (3)

[Claims] 1. A chamber for storing a semiconductor substrate, an ion gun for generating ions to be implanted into one principal surface of the semiconductor substrate, and an electron gun for generating electrons for neutralizing charged ions in the semiconductor substrate. An ion implantation apparatus comprising: an electron flow control circuit that adjusts an electron flow rate of the electron gun according to the degree of vacuum of the chamber. 2. The ion implantation apparatus according to claim 1, wherein the electron flow control circuit adjusts the electron flow rate to follow the degree of vacuum and increases the electron flow rate when the pressure is high. 3. The ion implantation apparatus according to claim 1, wherein the electron flow control circuit tracks the degree of vacuum and holds the electron flow rate at predetermined time intervals to vary it stepwise.