JP3264988B2 - Ion implanter - Google Patents

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.

[0002]

2. Description of the Related Art An ion implantation technique is a method in which impurity ions generated in an ion source are accelerated by a high electric field, and impurities are mechanically introduced into a semiconductor wafer by using the kinetic energy thereof. This is a very effective method in that the total amount of the impurities thus obtained can be accurately measured as a charge amount.

Conventionally, such ion implantation is performed, for example, by referring to FIG.
Is performed using the apparatus shown in FIG. That is, a gas or solid vapor is turned into plasma in the ion source 7, positive ions in the plasma are extracted with a constant energy by the extraction electrode 71, and then mass analysis is performed on the ion beam by the mass analyzer 72. The desired ions are separated, and the ions are completely separated by the decomposition slit 73. Then, the ion beam of the separated desired ions is accelerated to the final energy through the accelerating tube 74 and then irradiated to the wafer W, thereby introducing a desired impurity to the surface of the wafer W.

Reference numeral 75 denotes a Faraday cup for accurately measuring the amount of ion implantation by confining secondary electrons generated when ions are implanted into the surface of the wafer so as not to flow out. .

When an ion beam is applied to the wafer W, the insulating film exposed on the surface of the wafer W is charged with positive charges of ions. When the amount of charge exceeds the dielectric breakdown charge, the insulating film is destroyed. The device becomes defective.

For this reason, conventionally, as shown in FIG. 6, a plasma generator 76 is provided near the wafer W at a position facing the ion beam, and electrons in the plasma generated by the plasma generator 76 are transferred to the plasma generator 76. The surface of the wafer W is attracted to the surface of the wafer W by a potential gradient between the wafer W and the surface of the wafer W, thereby neutralizing the positive charges on the surface of the wafer W, thereby suppressing the charge amount of the insulating film on the wafer W.

[0007]

In the plasma generating section, a filament made of tungsten is provided in a plasma generating chamber made of, for example, molybdenum, and the filament is heated and its thermal electrons collide with argon gas to generate plasma. However, a small amount of filament vapor and sputtered particles on the inner wall of the plasma generation chamber due to the plasma are present in the plasma generation chamber. For this reason, heavy metal particles such as tungsten and molybdenum jump out of the plasma generation chamber, and a part thereof adheres to the surface of the wafer W, thereby causing contamination (contamination).

[0008] DRAM is 4M to 16M, 64M
If the device is further miniaturized as the capacity is increasing, there is a problem that even such a small amount of heavy metal particles adversely affects the characteristics of the device.

The present invention has been made under such circumstances, and an object of the present invention is to provide an ion implantation apparatus capable of suppressing contamination of an object to be processed.

[0010]

According to the first aspect of the present invention, there is provided an image processing apparatus comprising:
Ions that irradiate the body with ion beams and implant ions
In an implantation apparatus, an ion beam near the object to be processed is provided.
The discharge gas is supplied outside the passage area of
Plasma generation chamber for generating plasma and this plasma
Passing electrons in the plasma in the generation chamber through the ion beam
The micro-hole formed in the plasma generation chamber to discharge to the area
A first opening having a small opening width and facing the first opening
Line-of-sight regulating member for forming a second opening at a position
And the first plasma generator from the inside of the plasma generation chamber.
An ion implantation apparatus, characterized in that a line-of-sight region, which is formed by a combination of an opening and a second opening and looks out of a plasma outlet, is outside of the object to be processed.

[0011]

For example, when the metal particles of the filament in the plasma generation section are vaporized and scatter from the filament, or when the inner wall of the plasma generation chamber is sputtered by the plasma and the metal particles are scattered, these metal particles are neutral,
Since the inside of the Faraday cup 75 has a vacuum atmosphere of, for example, 10 ⁻⁴ Pa or less, the metal particles that have jumped out of the plasma generation chamber go straight. Therefore, the metal particles (neutral particles) that fly out in this way fly from the inside of the plasma generation chamber into the line-of-sight region looking out of the plasma outlet.
Since this line-of-sight region is out of the object, the metal particles do not directly reach the object,
Contamination can be suppressed.

[0012]

FIG. 1 is a schematic structural view showing an entire ion implantation apparatus according to an embodiment of the present invention. Briefly describing the entire apparatus with reference to FIG. 1, reference numeral 1 denotes an ion source, which converts, for example, a gas sublimated from a solid material in a vaporizer 11 into plasma. It is extracted as an ion beam to the outside by an extraction voltage applied between the ion source 12 and the main body of the ion source 1. On the downstream side of the extraction electrode 12, a mass analyzer 14 is arranged via a slit 13 and only desired ions are extracted therefrom.
5 and into the accelerator 16. The ion is an accelerator 1
After being accelerated by the accelerating voltage at 6, it was passed through the Faraday cup 2, and was placed and held on a rotating disk 17 (the lower portion of the rotating disk 17 is cut away in FIG. 1) rotated by a spin motor 18. It is implanted into an object to be processed, for example, a semiconductor wafer W.

The Faraday cup 2 is a "prior art"
As described in the section, the secondary electrons generated at the time of ion implantation are confined so as not to flow out, and the amount of ion implantation is accurately measured. Further, outside the Faraday cup 2, As described in detail, a plasma generator 3 is provided to neutralize the electric charge on the surface of the wafer W.

Next, the periphery of the Faraday cup 2 and the plasma generator 3 will be described in detail with reference to FIG.
On the entry side of the ion beam IB of the Faraday cup 2, a suppress electrode 21 to which a voltage Es of, for example, -1000V is applied is provided so that secondary electrons do not fly out of the Faraday cup 2.

The plasma generating section 3 is constituted by providing a filament 32 made of, for example, tungsten in a plasma generating chamber 31 made of, for example, carbon or molybdenum. A gas supply pipe 33 to which, for example, an argon gas, a xenon gas, a krypton gas, or the like is supplied from a source is connected, and plasma is supplied to the wall of the plasma generation chamber 31 facing the Faraday cup 2. An opening 41 is formed so that it can flow out.

In the Faraday cup 2, an opening 42 is formed in the tube wall facing the opening 41. The tube wall serves as a line-of-sight restricting member for restricting the line-of-sight region from the inside to the outside of the plasma generation chamber 31, and these openings 41 and 42.
Constitutes a plasma outlet 4 in this embodiment. The opening 41 of the plasma generation chamber 31 has an opening width on the inner side (left and right opening widths in FIG. 2) of, for example, about 1 mm and an It is formed in a shape that expands toward the side. The entirety of the openings 41 and 42, that is, the plasma outlet 4, is configured such that the line-of-sight region S that looks out of the plasma outlet 4 from the inside of the plasma generation chamber 31 is separated from the wafer W as shown in FIG. 3. . That is, of the straight lines L extending from the left end a in FIG. 3 of the opening 41 toward the wafer W side, the straight line L that can be extended through the plasma outlet 4 is located outside the peripheral edge of the wafer W. Is configured.

At both ends of the filament 32, power supply members 34 and 35 each comprising a combination of a terminal, a power supply plate, a power supply rod, and the like are connected, and a filament voltage Ef is applied between the power supply members 34 and 35. And a power supply for connecting the discharge voltage Ed is connected between the filament 32 and the wall of the plasma generation chamber 31. The plasma generating unit 3 may be a unit that generates plasma using an RF ion source or the like in addition to a unit using a filament.

As shown in FIGS. 2 and 4, the plasma generating chamber 3 is housed in a cooling block 5 made of, for example, aluminum.
A cooling water passage (not shown) is formed inside to cool the plasma generation chamber 3, and cooling water pipes 51 and 52 are connected to circulate the cooling water in the cooling water passage.

In the block 5, a filament 32 is provided.
By increasing the probability of collision between electrons from the gas and the gas,
In order to generate plasma more efficiently, permanent magnets 5 are provided on both side walls of plasma generation chamber 31 so as to face each other.
3 and 54 are provided, and these permanent magnet bodies 53 and 5 are provided.
No. 4 is magnetized so that the inner side (the plasma generation chamber 31 side) becomes the N pole and the outer side becomes the S pole. In addition, the permanent magnet body 5
When a magnetic field is formed in the Faraday cup 2 by the Faraday cups 3 and 54, the direction of movement of the electrons extracted from the plasma generating unit 3 is regulated by the magnetic field, so that it is difficult to supply the electrons to the surface of the wafer W that needs to be neutralized. Therefore, a magnetic shield cover 55 is provided to cover the front surface (the surface on the Faraday cup 2 side) and side surfaces of the block body 5.

On the back side of the plasma generation chamber 31 (the side opposite to the Faraday cup 2), a power supply member 34,
A large current flows therethrough and is heated to a high temperature of, for example, about 800 ° C. Therefore, when the components are heated to a high temperature in this manner, the wafer surface may be contaminated by contaminants released from the surface, and the circuit pattern on the wafer surface may be thermally deformed. Therefore, in order to prevent such a situation, a heat shield plate 6 is provided so as to separate the wafer W from the back side of the plasma generation chamber 31 as shown in FIGS. The manner of disposing the heat shield plate 6 may be determined according to the apparatus. However, the heat shield plate 6 should be disposed so that any wafer on the rotating disk cannot be seen from components heated to a high temperature. Must be provided.

Next, the operation of the above embodiment will be described. An ion beam extracted from the ion source 1 and containing ions of impurities such as phosphorus and arsenic is mass-analyzed by a mass analyzer 14, further accelerated by an acceleration tube 16, passes through the Faraday cup 2, The wafer W placed and held on the rotating disk 17 is irradiated, and the impurities are driven into the wafer W.

The filament 32 in the plasma generation chamber 31 is heated by the voltage Vf to generate thermoelectrons. The discharge voltage Vd between the filament 32 and the plasma generation chamber 31 causes argon introduced from the gas supply pipe 33 to flow. Thermoelectrons excite a discharge gas such as a gas, and a permanent magnet 5
Since a magnetic field is formed in the plasma generating chamber 31 by 3 and 54, plasma is generated efficiently. On the other hand, when the surface of the wafer W is charged with positive charges by the irradiation of the ion beam, a potential gradient is generated between the plasma generation chamber 31 and the surface of the wafer W. It is drawn to the surface of the wafer W through the openings 41 and 42) and neutralizes the positive charges on the surface.

The inner wall of the plasma generating chamber 31 is sputtered by the plasma, and the sputtered particles, for example, carbon and molybdenum particles jump out into the Faraday cup 2 through the plasma outlet 4, and the sputtered particles, such as tungsten particles, are also heated by the filament 32. Pops out. Since the outside of the plasma outlet 4 of the plasma generation chamber 31, that is, the inside of the Faraday cup 2 and the region where the wafer W is placed is in a vacuum atmosphere of, for example, 10 ⁻⁴ Pa or less, these particles fly linearly. Here, since the plasma outlet 4 is formed so that the line of sight from the inside to the outside deviates from the wafer W as described above, the particles do not directly collide with the surface of the wafer W. Contamination of the wafer W by particles is suppressed. Therefore, as the degree of integration of devices increases, the level of contamination that adversely affects the characteristics of the device becomes increasingly lower, and it is necessary to avoid even a slight contamination in a series of processes. The plasma generating portion for neutralizing the electric charge on the surface of W is also a very significant and effective means in view of the contamination source and taking measures against it.

In the above description, the ion beam is often applied to a region slightly outside the peripheral edge of the wafer W so that the uniformity of the impurity concentration near the peripheral edge of the wafer W is not reduced. Preferably, the plasma outlet 4 is formed such that the line-of-sight region from the inside is further outside the irradiation region of the ion beam protruding from the wafer W. The reason is that, when sputtered particles from the plasma generating section 3 or particles from the filament adhere to the protruding region, these adhered particles are sputtered by the ion beam and adhere to the surface of the wafer W. .

The plasma outlet 4 of the plasma generation chamber 31
Is an opening 41 formed in the wall of the plasma generation chamber 31.
It is desirable that the opening is formed by a combination of a line of sight and an opening 42 formed in the line-of-sight regulating member (corresponding to the tube wall of the Faraday cup 2 in this example). That is, if it is attempted to regulate the line-of-sight area only by the opening 41 in the wall of the plasma generation chamber 31, the opening width inside the opening 41 becomes, for example, 1
In addition to the fact that it is very narrow, on the order of mm, it is difficult to perform accurate processing on the wall, but when combined with the line-of-sight restriction member, the shape of the opening 41 may be rough, which is a good measure in design. . However, in the present invention, the plasma outlet 4 may be constituted only by the opening 41 of the wall.

As the object to be implanted with ions,
Not limited to semiconductor wafers, various types can be applied. The present invention can also be applied to a device without the accelerating tube 16 or a device in which the Faraday cup 2 is arranged on the back side of the rotating disk 17.
The present invention can also be applied to an apparatus for introducing a wafer into a vacuum processing chamber one by one.

[0027]

According to the present invention, when the plasma generating portion is provided to neutralize the positive charges on the surface of the object, the line-of-sight region relating to the plasma outlet is out of the object. It is possible to suppress contamination of the object to be processed due to sputtered particles in the generation chamber.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an overall configuration of an ion implantation apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a main part of the embodiment of the present invention.

FIG. 3 is an explanatory diagram for explaining an operation of the embodiment.

FIG. 4 is an exploded perspective view showing peripheral members of a plasma generation unit.

FIG. 5 is a perspective view showing an appearance of a main part of the embodiment.

FIG. 6 is a schematic explanatory view showing a conventional ion implantation apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ion source 14 Mass spectrometer 16 Accelerator tube 2 Faraday cup 3 Plasma generating part 31 Plasma generating chamber 4 Plasma outlet 41, 42 Opening S S Viewing area 5 Cooling block 6 Heat shield plate

Continuation of front page (56) References JP-A-3-25846 (JP, A) JP-A-3-93141 (JP, A) JP-A-3-167745 (JP, A) JP-A-2-297856 (JP) , A) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01J 37/317

Claims (1)

(57) [Claims] An object to be processed is irradiated with an ion beam to emit ions.
In an ion implantation apparatus for implanting an ion beam, an ion beam passing through an ion beam passing region near the object to be processed is provided.
Provided to supply discharge gas and generate plasma
And the electrons in the plasma in the plasma generation chamber
Into the plasma generation chamber for discharge into the beam passage area
A first opening having a small opening width formed and a second opening formed at a position facing the first opening.
A line-of-sight regulating member for the first opening and the second opening from the inside of the plasma generation chamber.
An ion implantation apparatus characterized in that a line-of-sight region that looks out of a plasma outlet formed by a combination of the two openings is deviated from the object to be processed.