JP3498238B2 - Ion implantation method and apparatus - Google Patents

Description

Detailed Description of the Invention TECHNICAL FIELD OF THE INVENTION

The present invention relates to an ion implantation method and apparatus, and more particularly to an ion implantation method and apparatus suitable for implanting impurities into a wafer when a device such as a semiconductor or a buried oxide film is formed using the wafer. .

[Prior art]

Conventionally, as an ion implantation apparatus, a plurality of wafer holders arranged in a circular shape on a rotary disk in a vacuum container to hold wafers, a rotary drive device for rotationally driving the rotary disk, and rotation of the rotary disk. What is provided with an ion irradiation source that irradiates ions toward a wafer held by a wafer holder at times is known. In this type of ion implantation apparatus, in order to uniformly irradiate the wafer with ions, the rotating disk is rotated, and while scanning the rotating disk in a substantially semi-circular or linear shape, the wafer on the wafer holder is irradiated with the ions. The method of injection is adopted. At this time, the wafer is fixed to the wafer holder by the centrifugal force generated by the rotation of the rotating disk. The rotation speed of the rotating disk is determined based on the wafer temperature, the uniformity of ion implantation, and the like, and the rotation speed determines the holding force for the wafer.

[Problems to be Solved by the Invention]

In the prior art, the contact resistance (electrical contact) between the wafer and the wafer holder is sufficiently taken into consideration only by adopting the structure in which the wafer is fixed to each wafer holder by the restraining force determined by the rotation speed of the rotating disk. However, the contact resistance between the wafer and the wafer holder cannot be made sufficiently small, the wafer is charged by the injected ion beam, and a discharge occurs between the wafer and the wafer holder due to this charging. Garbage may be generated due to. If dust from the discharge adheres to the wafer,
Pinholes (non-implanted regions) are generated on the wafer, which causes product defects on the wafer and reduces the yield.

An object of the present invention is to provide an ion implantation method and apparatus which can prevent discharge from occurring between a wafer and a wafer holder due to the charging of the wafer.

[Means for Solving the Problems]

In order to achieve the above object, the present invention is a method of mounting a wafer on a wafer holder, rotating the wafer holder on which the wafer is mounted, holding the wafer on the wafer holder when the wafer holder rotates, and holding the wafer on the wafer holder. The contact surface pressure between the wafer and the wafer holder of 150gf
/ Cm ^{2 to} 200 gf / cm ² , the ion implantation method of implanting ions into the wafer is adopted.

Further, according to the present invention, a wafer is mounted on a wafer holder fixed to a rotating plate, the wafer holder on which the wafer is mounted is rotated along with the rotation of the rotating plate, and when the wafer holder is rotated, the wafer is rotated on the rotating surface of the rotating plate. The wafer is held in a state inclined with respect to the wafer holder, and the contact surface pressure between the wafer and the wafer holder when holding the wafer in the wafer holder is 15
This is an ion implantation method in which ions are implanted into the wafer while maintaining the pressure at 0 gf / cm ^{2 to} 200 gf / cm ² .

When adopting each of the above-mentioned ion implantation methods, the following elements can be added.

(1) The contact surface pressure between the wafer and the wafer holder when holding the wafer in the wafer holder is 150 gf /
To maintain the pressure from cm ^{2 to} 200 gf / cm ² , the contact area between the wafer and the wafer holder should be 1 cm ² or less.

(2) The contact surface pressure between the wafer and the wafer holder when holding the wafer in the wafer holder is 150 gf /
To maintain the pressure of cm ^{2 to} 200 gf / cm ² , a part of the wafer is supported by a pressing member, and the pressing member is given an elastic force of an elastic member to press the wafer toward the wafer holder .

Further, according to the present invention, a wafer holder fixed to a rotating plate in a vacuum container to hold a wafer, a rotation driving means for rotating the rotating plate, and a wafer held in the wafer holder when the rotating plate is rotated are provided. a ion irradiating means for irradiating the ion Te, constituting an ion implantation apparatus comprising set to 150gf ^/ cm ² ~200gf / cm 2 of contact surface pressure between the wafer and wafer holder when holding the wafer by the wafer holder It was done.

Further, according to the present invention, a wafer holder fixed to a rotary plate in a vacuum container to hold a wafer, a rotation driving means for rotationally driving the rotary plate, and a wafer held in the wafer holder when the rotary plate is rotated are provided. Ion irradiation means for irradiating ions with the wafer holder, the wafer holder holding the wafer in a state of being inclined with respect to the rotation surface of the rotation plate when the rotation plate is rotated, and holding the wafer by the wafer holder. The contact surface pressure between the wafer and the wafer holder is 150 gf / cm ^{2 to} 200 gf / cm ²
The ion implanter is configured as follows.

In constructing the ion implantation apparatus, the following elements can be added.

(1) A wafer holder fixed to a rotating plate in a vacuum container to hold a wafer, a pressing member for supporting a part of the wafer, and an elastic force applied to the pressing member to press the wafer toward the wafer holder. An elastic member, a rotation driving unit that rotationally drives the rotary plate, and an ion irradiation unit that irradiates the wafer held by the wafer holder with ions when the rotary plate is rotated are provided, and the elastic force of the elastic member is the wafer holder. The contact surface pressure between the wafer and the wafer holder when holding the wafer is 150 gf / cm ² to 2
The value is set to a value of 00 gf / cm ² .

According to the above-mentioned means, since the wafer is fixed to the wafer holder at a contact surface pressure higher than the contact surface pressure at which discharge starts, discharge is prevented from occurring between the wafer and the wafer holder due to ion implantation. Therefore, it is possible to prevent the generation of dust due to the discharge and the reduction in the yield. Furthermore, since ions are injected in a low vacuum, electrons generated in the vicinity of the wafer can be supplied to the charged wafer, and the discharge between the wafer and the wafer holder can be prevented by suppressing the charge on the wafer. Therefore, it is possible to prevent dust from being generated due to the discharge, and it is possible to prevent a decrease in yield.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view of the essential parts of an ion implantation apparatus showing an embodiment of the present invention. In FIG. 1, the ion implantation apparatus includes a rotary disc 10 as a rotary plate in a vacuum container (not shown), and the rotary disc 10 is rotated about a rotation center 12 by a rotary drive device, for example, a motor. And the drive device,
The scanning center 14 is configured to scan in a substantially semi-circular shape. A plurality of wafer holders 16 are arranged in a circular shape on the outer peripheral side of the rotary disk 10, and each wafer holder 16 is tilted with respect to the rotation surface of the rotary disk 10 when the rotary disk 10 rotates, that is, The outer peripheral side of the wafer holder 16 is fixed to the rotating disk 10 in a state of being raised several degrees. Each wafer holder 16 has a wafer 1 for forming semiconductor devices.
Eight is mounted. The wafer 18 is placed on the wafer holder 16 in a state where the wafer holder 16 is parallel to the rotation center 12 of the rotating disk 10. When the rotating disk 10 reaches a set number of rotations, the rotating disk 10 returns to its original position. It is designed to rotate in this state. When the wafer 18 and the wafer holder 16 are rotated, the rotating disk 10 is rotated.
When rotated in a state of being inclined with respect to the rotation surface of, the pressing force acts from the wafer 18 to the wafer holder 16 by the component force of the centrifugal force accompanying the rotation of the rotating disk 10, and this pressing force The wafer 18 is fixed to the wafer holder 16. Then, as the rotating disk 10 rotates, the rotating disk 10 rotates about the rotation center 12, and in the process of scanning left and right around the scan center 14, the wafer 18 on the wafer holder 16 is irradiated with ions. Ions are irradiated from a device (ion irradiation means: not shown). In this case, the wafer 18 on each wafer holder 16 is the rotating disk 10
The wafer is rotated along with the rotation and is scanned left and right, so that ions are uniformly implanted in each wafer 18. When silicon is used as the wafer 18 and oxygen ions are used as ions, the oxygen ion implantation forms an insulating film of silicon dioxide in the silicon. When rotating the rotary disk 10, for example, when the wafer 18 is heated to a high temperature of 600 degrees and ions are implanted, the wafer 18 is externally heated by a heater or the like. The rotation speed of the plate 10 is set to 400 rpm to 500 rpm.

Here, the contact surface pressure between the wafer 18 and the wafer holder 16 (component force acting on the wafer 18 / contact area between the wafer 18 and the wafer holder 16) and the amount of discharge marks formed on the back surface of the wafer 18 by discharge. When the relationship of was measured, the results shown in FIG. 2 were obtained. From FIG. 2, it can be seen that as the contact surface pressure increases, the amount of discharge marks generated on the back surface of the wafer 18 decreases. And the contact surface pressure is 150 gf / cm ² or more, for example, 150 gf / c
It can be seen that the amount of generation of discharge marks disappears at m ^{2 to} 200 gf / cm ² . The amount of generated discharge marks is an arbitrary amount calculated based on the product of the size (area) of discharge marks and the density of discharge marks.

Based on the measurement results shown in FIG. 2, the contact surface pressure between the wafer 18 and the wafer holder 16 was set to 150 gf / cm ^2.
To maintain the above, in the present embodiment, as shown in FIG. 3, the contact area between the wafer 18 and the wafer holder 16 is set to 1
The configuration is set to be cm ² or less. An annular wafer holder 16 is mounted on a base holder 20 fixed to the rotating disk 10, and a ring-shaped protrusion 22 is formed on the upper surface of the wafer holder 16. A disk-shaped wafer 18 is placed on the ring-shaped protrusion 22. The wafer 18 is pressed against the wafer holder 16 by the centrifugal force component F. Therefore, compared to when the wafer 18 is held on the entire surface of the wafer holder 16,
The contact area between the wafer holder 16 and the wafer 18 is reduced, and as a result, the contact surface pressure is increased and the generation of discharge marks can be suppressed. When the contact area of the ring-shaped protrusion 22 with the wafer 18 is set to 1 cm ² or less, for example, the wafer 1
When a 6-inch wafer is used as 8, the wafer holder 16 is tilted 3 degrees with respect to the rotation surface of the rotating plate 10, and the rotation speed of the rotating disk 10 is 500 rpm, the wafer 18 is pressed against the wafer holder 16 with a pressing force of 172 gf. Will be done. At this time, if the ring-shaped protrusion 22 of 0.1 mm is formed at the position of 130 mm in diameter, the wafer 1
The contact surface pressure acting on 8 can be 150 gf / cm ² .

As described above, in the present embodiment, the contact area between the wafer 18 and the wafer holder 16 is 1 cm ² or less, and the contact surface pressure between the wafer 18 and the wafer holder 16 is 150 gf / cm ² or more. It is possible to prevent electric discharge from occurring between the wafer 18 and the wafer holder 16 and to generate dust due to this electric discharge when irradiated with ions, and prevent occurrence of product defects of the wafer 18. In addition, the yield can be prevented from decreasing.

Further, in the above-described embodiment, instead of forming the ring-shaped protrusions 22 on the wafer holder 16, a plurality of rectangular or circular protrusions are dispersedly formed on the surface of the wafer holder 16, and these protrusions and the wafer are formed. Even if the contact area with 18 is 1 cm ² or less, the same effect as in the above embodiment can be obtained.

Next, another embodiment of the present invention will be described with reference to FIG.

In the present embodiment, when the contact surface pressure between the wafer 18 and the wafer holder 16 is set to 150 gf / cm ² or more, the annular wafer holder 16 is arranged on the disk-shaped holder base 20, and the wafer 18 is placed on the wafer holder 16. A ring-shaped wafer retainer 24 is arranged on the outer peripheral side of the wafer 18 as a retaining member for supporting a part of the wafer 18, and the tip side of the bolt 26 penetrating the holder base 20 is attached to the ring-shaped wafer retainer 24. And a spring 30 inserted between the holder base 20 and the head 28 of the bolt 26.
The ring-shaped wafer retainer 24 is fixed to the wafer holder 16 by the repulsive force. At this time, the pressing force of the wafer 18 is determined by the spring constant and the expansion / contraction rate of the spring 30. In the present embodiment, the pressing force of the spring 30 is such that the contact surface pressure between the wafer 18 and the wafer holder 16 is 150 gf / cm ² or more (for example, 150 gf / cm ^2).
˜200 gf / cm ² ).
Since the ring-shaped wafer retainer 24 is disposed on the upper surface of the wafer 18, it is desirable to use a silicon-made one that does not easily generate impurities even when the ring-shaped wafer retainer 24 is hit by the ion beam.

In the present embodiment, since the contact surface pressure between the wafer 18 and the wafer holder 16 is set to 150 gf / cm ² or more, when the ions are implanted into the wafer 18, the wafer 1
It is possible to prevent discharge from occurring between the wafer 18 and the wafer holder 16 due to the electrification of No. 8, and it is possible to prevent generation of dust due to discharge and a reduction in yield.

Next, a third embodiment of the present invention will be described with reference to FIG.

In this embodiment, three plate-shaped wafer retainers 32 are used as pressing members instead of the ring-shaped wafer retainer 24 shown in FIG. 18 is fixed at three places, and the pressing force by the spring 30 is the wafer 1
8 and wafer holder 16 contact surface pressure is 150 gf / cm
² or more (for example, 150 gf / cm ^{2 to} 200 gf / c
m ² ). The plate-shaped wafer retainer 32 is also made of silicon and prevents impurities from being generated from the wafer retainer 32 when the wafer retainer 32 is irradiated with ions. Further, the plate-shaped wafer retainer 32 is the ring-shaped wafer retainer 24.
In comparison with the above, since the portion exposed on the upper surface of the wafer 18 is small, the generation of impurities can be further reduced as compared with the case where the wafer retainer 24 is used.

According to the present embodiment, the contact surface pressure between the wafer 18 and the wafer holder 16 is set to 150 gf / cm ² or more, so that when the ions are implanted into the wafer 18, the wafer 18 is charged and the wafer 18 is charged. And wafer holder 1
It is possible to prevent discharge from occurring during 6 and to prevent dust from being generated due to the discharge to reduce the yield.

In each of the above embodiments, the contact surface pressure between the wafer 18 and the wafer holder 16 is set to 150 gf / cm ^2.
Or more (for example, 150 gf / cm ^{2 to} 200 gf / cm ^{2
Although 2} ) has been described, the amount of discharge traces can be reduced by reducing the degree of vacuum in the vacuum container in which the wafer 18, the wafer holder 16 and the like are housed.

That is, the wafer 18 and the wafer holder 16
When the relationship between the amount of generated discharge marks and the degree of vacuum in the injection chamber (vacuum container) was measured, the results shown in FIG. 6 were obtained. From FIG. 6, it can be seen that the amount of generated discharge marks decreases as the vacuum degree in the injection chamber decreases. This is because the wafer 18 is neutralized by the electrons generated by the collision of the residual gas and the ions in the vicinity of the wafer 18.
This is because no electric charge occurs in the wafer and no discharge occurs between the wafer 18 and the wafer holder 16.

[0029] Thus, the degree of vacuum in the vacuum vessel, for example, as shown in FIG. 6, 5 × ¹⁰ -4 Torr or more, for ^{example, 1.6 × 10 -3 Torr~5 × 10} -4 Tor
By setting the value to r, it is possible to prevent the wafer 18 from being charged, and it is possible to prevent the discharge from occurring between the wafer 18 and the wafer holder 16, so that dust is generated due to the discharge and the yield is reduced. Can be prevented.

【The invention's effect】

As described above, according to the present invention, the contact surface pressure between the wafer and the wafer holder is 150 gf / cm ² to 200, which is higher than the contact surface pressure at which discharge starts.
Since gf / cm ² is used, it is possible to prevent the wafer from being charged and causing discharge between the wafer and the wafer holder when ions are implanted into the wafer, and dust is generated due to the discharge to reduce the yield. Can be prevented.
Furthermore, the degree of vacuum in the vacuum container is set to 1.6 × 10 ⁻³ Tor.
Since it is set to r to 5 × 10 ⁻⁴ Torr, it is possible to prevent the occurrence of discharge between the wafer and the wafer holder due to electrification of the wafer when ions are implanted into the wafer, and dust is generated due to the discharge. As a result, it is possible to prevent the yield from decreasing.

[Brief description of drawings]

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

FIG. 2 is a characteristic diagram showing a relationship between a contact surface pressure and a discharge mark generation amount.

FIG. 3 is a cross-sectional perspective view of essential parts showing a first embodiment of a wafer fixing structure.

FIG. 4 is a cross-sectional perspective view of essential parts showing a second embodiment of a wafer fixing structure.

FIG. 5 is a cross-sectional perspective view of essential parts showing a third embodiment of a wafer fixing structure.

FIG. 6 is a characteristic diagram showing the relationship between the degree of vacuum in the injection chamber and the amount of discharge marks generated.

[Explanation of symbols]

10 rotating disk 12 center of rotation 14 scan center 16 Wafer holder 18 wafers 20 Holder base 22 Ring-shaped protrusion 24 Ring-shaped wafer holder 26 bolts 30 springs 32 plate-shaped wafer holder

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-1-146239 (JP, A) JP-A-2-241024 (JP, A) JP-A-5-13038 (JP, A) JP-A-5- 290788 (JP, A) JP-A-6-84495 (JP, A) JP-A-6-111752 (JP, A) JP-A-7-180053 (JP, A) JP-A-7-201301 (JP, A) JP-A-9-63531 (JP, A) JP-A-9-82687 (JP, A) JP-A-59-86147 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01J 37/317 H01L 21/265

Claims (7)

(57) [Claims] 1. A wafer is mounted on a wafer holder, the wafer holder on which the wafer is mounted is rotated, the wafer is held on the wafer holder when the wafer holder is rotated, and the contact surface pressure between the wafer and the wafer holder when holding the wafer on the wafer holder is set. An ion implantation method in which ions are implanted into a wafer while being maintained at 150 gf / cm ^{2 to} 200 gf / cm ² . 2. A wafer is mounted on a wafer holder fixed to a rotating plate, the wafer holder on which the wafer is mounted is rotated along with the rotation of the rotating plate, and the wafer is inclined with respect to the rotating surface of the rotating plate when the wafer holder is rotated. The wafer is held in this state in the wafer holder, and the contact surface pressure between the wafer and the wafer holder when holding the wafer in the wafer holder is 150 gf / cm ²
An ion implantation method in which ions are implanted into a wafer while being maintained at ˜200 gf / cm ² . 3. The contact surface pressure between the wafer and the wafer holder when holding the wafer in the wafer holder is 150 gf / cm.
The ion implantation method according to claim 1 or 2, wherein the contact area between the wafer and the wafer holder is set to 1 cm ² or less when the pressure is maintained at ² to ²⁰⁰ gf / cm ² . 4. The contact surface pressure between the wafer and the wafer holder when holding the wafer in the wafer holder is 150 gf / cm.
^{2. When} the wafer is maintained at ² to ²⁰⁰ gf / cm2, a part of the wafer is supported by a pressing member, and the pressing member is given an elastic force of an elastic member to press the wafer toward the wafer holder. 2. The ion implantation method described in 2. 5. A wafer holder fixed to a rotating plate in a vacuum container to hold a wafer, a rotation driving means for rotating and driving the rotating plate, and a wafer held in the wafer holder when the rotating plate is rotated, irradiated with ions. And a contact surface pressure between the wafer holder and the wafer holder when holding the wafer by the wafer holder is 150 gf.
/ ^Cm 2 was set to ～200Gf / cm ² formed by ion implantation apparatus. 6. A wafer holder, which is fixed to a rotating plate in a vacuum container to hold a wafer, a rotation driving unit that rotates and drives the rotating plate, and a wafer held in the wafer holder when the rotating plate is rotated, is irradiated with ions. An ion irradiation unit for holding the wafer in a state of being inclined with respect to the rotation surface of the rotating plate when the rotating plate is rotated, and the wafer when holding the wafer by the wafer holder. The contact surface pressure between the wafer and the wafer holder by 15
An ion implanter set to 0 gf / cm ^{2 to} 200 gf / cm ² . 7. A wafer holder fixed to a rotary plate in a vacuum container to hold a wafer, a pressing member for supporting a part of the wafer, and an elasticity for applying an elastic force to the pressing member to press the wafer toward the wafer holder. A member, a rotation driving unit that rotationally drives the rotating plate, and an ion irradiation unit that irradiates the wafer held by the wafer holder with ions when the rotating plate rotates, and the elastic force of the elastic member is controlled by the wafer holder. The contact surface pressure between the wafer and the wafer holder when holding the wafer is 150 gf / cm ² to 200.
An ion implanter set to a value of gf / cm ² .