KR20070093199A - Ion-implanting apparatus - Google Patents

Abstract

A plasma ion implanter is provided to prevent the generation of corrosion at a conventional wafer loading unit by preventing a wafer loading electrode from being exposed to plasma in a vacuum chamber using an insulator capable of shielding the wafer loading electrode. A plasma ion implanter includes a vacuum chamber(10) for keeping a vacuum state, a plasma generating unit, a wafer loading unit, a high voltage pulse supply unit, and a gas supply unit. The plasma generating unit is attached to an outer portion of a dielectric plate of the vacuum chamber to generate plasma. The wafer loading unit(40) is shielded by using an insulator in the vacuum chamber. The wafer loading unit is used for loading a wafer. The high voltage pulse supply unit(50) is used for supplying an AC type high voltage pulse to the wafer loading unit. The gas supply unit(60) is used for supplying a plasma gas into the vacuum chamber.

Description

Plasma ion implantation device {ION-IMPLANTING APPARATUS}

1 is a cross-sectional view showing the structure of a plasma ion implantation apparatus according to an embodiment of the present invention.

2 is a view for explaining the shape of the AC high-voltage pulse applied to the wafer mounting base according to an embodiment of the present invention.

3 is a diagram illustrating a relationship between a synchronized pulsed RF power and a high voltage pulse according to an embodiment of the present invention.

<Description of Symbols for Major Parts of Drawings>

1: plasma ion implantation apparatus according to an embodiment of the present invention

10: vacuum chamber 20: RF antenna

30: pulse RF generator 40: wafer mounting table

44 conductor 46 insulating film

50: high voltage pulse supply 60: gas supply

72: refrigerant circulation flow path 80: vacuum pump

W: Wafer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma ion implantation apparatus, and more particularly, to a plasma ion implantation apparatus that performs ion implantation in a manufacturing process of a semiconductor using a high voltage pulse applied to an inductively coupled plasma and a wafer mounting table.

In general, an ion implantation method using an ion beam has been most widely used as an impurity doping method such as boron (B), phosphorus (P), or arsenic (As) in a thin film such as silicon. However, as the degree of integration of semiconductors increases, the ion implantation depth of impurities requires a low implantation depth of several tens of nanometers or less. To do this, the ion beam energy of the ion implanter must be lowered from 10 keV to several hundred eV. However, when the ion implanted at such a low energy, since the amount of ions is reduced due to the phenomenon called 'Child-Langmuir current limit', the ion implantation speed is significantly reduced. In addition, an ion beam dispersing device is required for uniform ion implantation into a large area wafer, and a device for preventing charge concentration because thin insulating films in an ultra-high density semiconductor are destroyed at the time of ion implantation due to the charging phenomenon caused by the ion beam. Additionally required. Therefore, the ion implantation equipment using the ion beam has a disadvantage that the price of the equipment is very expensive.

On the other hand, plasma ion implantation technology using plasma and high voltage pulses (US Pat. No. 4,764,394, Republic of Korea Patent No. 137,704) is a technology capable of surface modification by uniformly injecting ions into the surface of a large-area three-dimensional sample. Impurity doping is also very advantageous over ion implantation using conventional ion beams. In other words, it uses plasma and high voltage pulse, so it is not limited to 'Child-Langmuir current limit'. Therefore, uniform ion implantation into a large area wafer can be realized very quickly, and an ion beam dispersing device or the like is not required. In addition, there is no charge concentration phenomenon on the wafer surface, and since the device is simple, it has the advantage of excellent clustering with other semiconductor processing equipment and a very low equipment cost.

On the other hand, the conventional semiconductor doping technique using plasma, accelerates the ions in the plasma using a continuous plasma generated by the gas such as B ₂ H ₆ , BF ₃ , PH ₃ , AsH ₃ and high voltage pulse to the wafer surface The basic method of ion implantation is used. However, when continuous plasma is used, plasma is generated not only during the time when the high voltage pulse is applied but also during the time when the pulse is not applied, thereby forming impurities such as a thin film on the wafer surface. This seriously degrades the ion implantation characteristics.

In order to compensate for the shortcomings of the continuous plasma, a method of directly generating a plasma using a high voltage pulse applied to a wafer and simultaneously performing ion implantation (US Pat. No. 5,654,043), generates a plasma using a pulse cold cathode discharge. By devising a method (US Pat. No. 5,354,381) or a method of generating plasma using an auxiliary electrode (Korean Patent No. 2002-0047294), etc., it was intended to generate the plasma only during a time when a high voltage pulse was applied. However, in the case of using the pulse cold cathode, the cold cathode material may act as a wafer contamination source. Plasma generation using a high voltage pulse or auxiliary electrode basically uses a DC voltage, so that plasma cannot be generated under low pressure. Works on Therefore, the ion implantation energy is reduced and diversified by the collision of the injected ions with the gas.

As a method of generating plasma even at low pressure and increasing ion implantation energy, a method of doping semiconductors and a system using a pulsed inductively coupled plasma using a pulsed inductively coupled plasma and a system thereof (Korean Patent No. 2005-67116) have been devised. have. However, in the case of using such a pulsed inductively coupled plasma, a negative voltage pulse of a direct current type is used. Therefore, in order to inject ions into the wafer, the wafer holder must be composed of electrodes exposed to the plasma, and arcing can be easily performed in the space between the wafer and the wafer holder unless the wafer is closely adhered to the entire holder. There is a problem that occurs. In addition, the temperature of the wafer rises very high because the heat generated during the ion implantation process cannot be effectively removed, and when the temperature of the wafer rises, the photoresist formed on the wafer is damaged. It has the disadvantage of being easily corroded.

SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma ion implantation apparatus in which an electrode used for wafer placement in a vacuum chamber of a plasma ion implantation apparatus is shielded with an insulator so as not to be exposed to plasma.

In order to achieve the above object, the present invention provides a vacuum chamber, the inside of which maintains a vacuum state; A plasma generator installed on an upper portion of the vacuum chamber; An RF antenna for applying RF power to an RF antenna inside the plasma generator through an RF matching unit; A pulse RF generator for supplying pulsed RF power to the RF antenna through an RF matching unit; A wafer mounting table provided with a conductive material shielded by an insulator inside the vacuum chamber, and having a wafer mounted thereon; A high voltage pulse supply unit supplying an alternating current type high voltage pulse to a wafer mounting table; It provides a plasma ion implantation device comprising a; gas supply unit for supplying a gas to be plasmaized to the vacuum chamber.

Hereinafter, with reference to the accompanying drawings will be described in detail a specific embodiment of the present invention.

Plasma ion implantation apparatus 1 according to the present embodiment, as shown in Figure 1, the vacuum chamber 10; A plasma generator 14; RF antenna 20; A pulse RF generator 30; Wafer placement table 40; A high voltage pulse supply unit 50; Gas supply unit 60; is configured to include.

First, the vacuum chamber 10 refers to an airtight holding chamber whose interior maintains a vacuum state, and various components are provided in combination with the interior and exterior thereof. One surface of the vacuum chamber 10 is made of a dielectric plate 12. In general, as shown in FIG. 1, the top surface of the chamber 10 is made of a dielectric 12.

As described above, the plasma generator 14 is mounted outside the chamber surface of the dielectric 12, and the RF antenna 20 is mounted inside the plasma generator 14. The RF antenna 20 serves to apply pulsed RF power to the dielectric 12. In addition, the RF antenna 20 is connected to the pulse RF generator 30 for generating and supplying pulsed RF power. At this time, it is preferable that a matching unit 32 is further provided between the pulse RF generator 30 and the RF antenna 20 to electrically match both. In this case, as shown in FIG. 3, the RF power generated by the RF generator is preferably time modulated by an external or self-generated pulse signal. In addition, the pulse and the high voltage pulse applied to the wafer mounting table are preferably synchronized with each other in time.

The wafer mounting base 40 is provided with a conductor 44 inside the vacuum chamber 10, and the conductor 44 is coated with an insulating material 46 or made of an insulator thin plate so as not to be exposed to the inside of the vacuum chamber. Surrounded to maintain electrical insulation with the plasma in the vacuum chamber. The wafer W on which the process is to be processed is mounted on the wafer placing table. The wafer placing table 40 is generally provided at a position opposite to the surface on which the dielectric 12 is provided. In this embodiment, the wafer 12 is provided on the upper surface of the vacuum chamber 10. Base 40 is disposed on the bottom surface of chamber 10. The wafer placement table 40 is electrically insulated and mounted in the vacuum chamber 10 so that an alternating current high voltage pulse can be applied. The wafer placement table 40 is made larger than the diameter of the wafer W to achieve uniform doping of the wafer. In addition, the wafer mounting table 40 is integrated with a current measuring device (not shown) such as a Faraday cup capable of measuring the amount of ion implantation.

In this embodiment, an alternating current high voltage pulse is applied to the wafer placement table 40. Here, the "AC high voltage pulse" refers to a high voltage pulse reciprocating with a constant amplitude of a positive (Vo) value and a negative (-V) value, as shown in FIG. 2B. In this embodiment, the high voltage pulse supply unit 50 is connected to the wafer mounting table 40 to apply an AC high voltage pulse. The high voltage pulse supply unit 50 is configured to generate an AC high voltage pulse as shown in FIG. 2B by increasing a reference value by a predetermined value Vo relative to the chamber ground in a general negative high voltage pulse as shown in FIG. 2A. It is preferable to generate.

A gas supply unit 60 is further provided to supply the gas to be plasmaized to the vacuum chamber 10. This gas supply part 60 is a component which plasmas and supplies the raw material gas used for the process of a wafer.

In the present embodiment, the wafer mounting table 40 may be configured as an electrostatic chuck. At this time, the electrostatic chuck is preferably made of ceramic, which has a strong plasma resistance. The wafer is strongly adhered to the wafer by electrostatic power, thereby facilitating cooling the wafer, and preventing arcing from occurring in the space between the wafer and the wafer holder. .

In this embodiment, the coolant circulates inside the wafer placement table 40, and thus, the cooling unit 70 may be further provided to cool the wafer placement table and the wafer. In the case where ion implantation is performed on the wafer using plasma, the temperature of the wafer generally rises to 100 ° C or higher. Therefore, it is necessary to cool the wafer to an appropriate temperature in order to protect a mask or the like formed on the wafer. Therefore, in the present embodiment, as shown in FIG. 1, a circulation pump for forming a coolant circulation flow path 72 through which coolant can be circulated inside the mounting table 40 and circulating the coolant in the coolant circulation flow path 72. (Not shown in the figure) by indirectly controlling the temperature of the wafer.

In addition, it is preferable that a heat transfer medium supply unit (not shown) is further provided to supply the heat transfer medium to the space between the wafer placement table 40 and the wafer W to facilitate cooling of the wafer. Between the wafer W and the wafer mounting table 40, point contact or separation spaces exist from the microscopic point of view. Therefore, in the plasma ion implantation apparatus 1 according to the present embodiment which performs ion implantation under a low pressure close to a vacuum, since there is no medium capable of effectively transferring the heat of the wafer, the temperature of the wafer may rise even if the temperature of the wafer mounting table is low. There is a possibility. Accordingly, the wafer is smoothly cooled by supplying a heat transfer medium such as helium gas at a constant pressure to the space between the wafer and the wafer mounting table.

According to the present invention, it is possible to solve the problem that the wafer mounting table is corroded when using a conventional DC pulse by providing the wafer mounting table as a method of shielding with an insulator or an electrostatic chuck. In addition, the wafer is in close contact with the wafer mounting table to enable temperature control, and thus, there is an advantage of facilitating ion energy control and ion density control.

Claims (7)

A vacuum chamber whose interior maintains a vacuum state; A plasma generator that is mounted outside a dielectric plate, which is one surface of the vacuum chamber, to generate plasma; A wafer mounting table that is shielded with an insulator inside the vacuum chamber and has a wafer mounted thereon; A high voltage pulse supply unit supplying an AC high voltage pulse to the wafer mounting base; And a gas supply unit for supplying a gas to be plasmaized to the vacuum chamber. The method of claim 1, wherein the plasma generating unit, Plasma ion implantation device, characterized in that for generating a plasma by the RF power source synchronized in time by a pulse signal of a frequency lower than the high voltage pulse generator. The method of claim 2, wherein the pulse signal, Plasma ion implantation apparatus, characterized in that synchronized with the high voltage pulse applied to the wafer mounting stage. The method of claim 1, wherein the wafer mounting table, Plasma ion implantation apparatus, characterized in that the electrostatic chuck to suck the wafer by the electrostatic force. The wafer mounting base according to claim 4, Plasma ion implantation apparatus, characterized in that the coolant is circulated through the inside of the wafer mounting stage and the cooling unit for cooling the wafer is further provided. The method of claim 5, And a heat transfer medium supply unit for supplying a heat transfer medium to the space between the wafer mounting table and the wafer to facilitate cooling of the wafer. The method of claim 1, wherein the high voltage pulse supply unit, Plasma ion implantation device characterized in that the ac high voltage pulse is obtained by raising the reference of the negative high voltage pulse to the ground of the whole chamber.

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