JPH0536617A - Ion beam irradiation method and apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] Ion implantation (implantation) to semiconductor wafers
With respect to the ion beam irradiation method and the ion beam irradiation apparatus, the ion implantation depth and the dose amount should be set to a predetermined value by preventing the adhered deposition layer from being generated on the surface of the irradiation object in the conventional low temperature ion beam implantation. With the goal. An ion beam for irradiating an irradiation object 23 on a supporting device 11 with a cooling function in a vacuum chamber 12, and irradiating the irradiation object with an ion beam 32 while cooling the irradiation object 23 to 0 ° C. or less. In the irradiation method, the surface of the irradiation target is irradiated with ultraviolet rays before the irradiation of the irradiation target with an ion beam. In the ion beam irradiation device,
Ultraviolet irradiation means (mercury lamps) 28 and 29 for irradiating the surface of the object to be irradiated with ultraviolet rays are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion implantation technique, and more particularly to ion implantation (implantation) into a semiconductor wafer.
Ion beam irradiation method and ion beam irradiation device in the above. BACKGROUND ART When manufacturing a semiconductor device (IC, LSI, etc.) using a semiconductor wafer (substrate), introduction of impurities (donor, acceptor) has come to be carried out mainly by an ion implantation method. Further, there is a demand for suppressing thermal diffusion of impurities (expansion of impurity introduction region) due to miniaturization of individual elements of a semiconductor device and complication of structure, so that defects generated in a wafer by ion implantation are annealed (heated). When removing, the heat treatment temperature and heat treatment time are required to be lowered and shortened. However, as a result of lowering the temperature and shortening the time, it becomes difficult to remove the secondary and tertiary complex defects that are formed in the process of heat treatment starting from the defects introduced during ion implantation, and the P-N junction part There was an adverse effect such as an increase in leak current.

[0002]

2. Description of the Related Art In order to lower the annealing temperature after ion implantation and to remove defects and prevent compound defects, it has been proposed to cool a wafer to 0 ° C. or lower during ion implantation into a semiconductor wafer. It is being put to practical use. By cooling, it is possible to reduce the crystal recovery in the ion-implanted layer during the ion-implantation and the local crystal recovery that occurs near the boundary between the ion-implanted layer and the semiconductor crystal thereunder. The local crystal recovery causes a mismatch between the crystal recovery of the entire implanted layer in the annealing treatment after the ion implantation and causes the above-mentioned secondary and tertiary composite defects. Leads to the prevention of.

Therefore, an apparatus as shown in FIG. 1 has been proposed as an ion beam irradiation apparatus capable of low temperature implantation. In such an ion beam irradiation apparatus, a cooler 2 is provided in a vacuum container 1, and an object to be irradiated (semiconductor wafer) 3 is carried on the cooler 2 and cooled. The cooler 2 is a hollow body, in which a refrigerant (for example, liquid nitrogen) 4 is put, and a refrigerant introduction pipe 5 and a refrigerant exhaust pipe 6 are provided. Ion implantation is performed by irradiating an ion beam (phosphorus ion, boron ion, etc.) 8 from an ion beam generator 7 while the object 3 to be irradiated is cooled, and implanting impurities.

[0004]

In the above-mentioned conventional ion beam irradiation apparatus capable of low temperature implantation, only the function of cooling the irradiation object 3 is added, and consideration for the surroundings is insufficient. Met. When the object to be irradiated (wafer) 3 is cooled with liquid nitrogen, the temperature becomes close to 80 ° K, which is a general pressure for ion implantation (10 ^-5 -10 ^-7 Tor).
r), residual gas in the vacuum chamber 1, especially H ₂ O and
CO ₂ condenses on the surface of the irradiation object 3 and adheres as a solid thin film. According to the equilibrium vapor pressure curves of various gases shown in FIG. 2, for example, CO ₂ vapor pressure is 10 ⁻⁷ to 10 ^{−8 at} 80 ° K.
It is about Torr, and it condenses and becomes an adhering matter (adsorbs) on the surface of the irradiation object.

During ion implantation, part of the deposit is heated by impact energy and re-evaporates due to impact (collision) of incident ions. An adhered deposition layer is formed on the surface of the object, and this deposition layer absorbs the energy of the implanted ions a little, so the range of the ions decreases and the ion implantation depth becomes shallower than a predetermined value. Will result in a lack of dose.

An object of the present invention is to prevent the formation of an adhered and deposited layer on the surface of an object to be irradiated in the conventional low temperature ion beam implantation, so that the ion implantation depth and dose amount can be set to predetermined values. Another object of the present invention is to provide a method capable of removing deposits in the condensation solidification of residual gas on the surface of an irradiation object in a method of cooling an irradiation object to a low temperature and performing ion implantation. Another object of the present invention is to provide an ion implantation irradiation apparatus capable of implementing this method.

[0007]

The above-mentioned object is to mount an object to be irradiated on a carrier device having a cooling function in a vacuum chamber, and to cool the object to be irradiated to 0 ° C. or lower, ion the object to be irradiated. The ion beam irradiation method of irradiating a beam is achieved by irradiating the surface of the object to be irradiated with ultraviolet rays before the irradiation of the object to be irradiated with the ion beam. It is also possible to irradiate the surface of the object to be irradiated with ultraviolet rays during the irradiation of the object to be irradiated with an ion beam.

Further, the above-mentioned object is to carry an object to be irradiated, which is provided with a means for cooling the object to be irradiated to 0 ° C. or below, an ion beam generator for irradiating the object to be irradiated with an ion beam, and these objects to be irradiated. An ion beam irradiating device including a material carrier and a vacuum chamber accommodating an ion beam generator, comprising an ultraviolet irradiating means for irradiating the surface of the object to be irradiated with ultraviolet light. Also achieved by.

The object carrier for rotation is in the form of a disk that is rotatable and movable about its axis of rotation, and carries a plurality of objects for irradiation near the outer periphery, and the ion beam generator irradiates the ion beam as a stationary beam. It is preferable that the

[0010]

In the present invention, before the ion implantation (ion beam irradiation) (even during the additional ion implantation), the irradiation object (semiconductor wafer) is irradiated with (irradiates) ultraviolet rays, whereby the energy of the ultraviolet rays (about 3 eV). However, the adhesion (adsorption) energy of the residual gas is 0. It is about an order of magnitude higher than the order of several eV (0.4 eV for H ₂ O), so that the deposit of residual gas can be re-evaporated. After the ion implantation is started, even if the irradiation of ultraviolet rays is stopped, it is heated by the collision energy of the ions, and the ion bombardment also has a sputtering action, so that there is no deposition of residual gas during the ion implantation. Therefore, at the time of ion implantation, the impurities can be ion-implanted into the irradiation target cooled at a low temperature in a state where the adhered deposition layer does not interfere with the implanted ions.

In the ion beam irradiation device, ultraviolet irradiation means (for example, a mercury lamp, a plasma emission source, etc.)
May be provided in the vicinity of an irradiation target carrier provided with a cooling means so as to illuminate the irradiation target before ion implantation. Further, another ultraviolet irradiation means can be provided so as to illuminate the irradiation object at the ion beam irradiation position. In this case, the substance knocked out by the ion beam sputtering effect will fly to the surface of the ultraviolet irradiation means (mercury lamp) near the ion beam irradiation position and the lamp surface will be fogged (dirty). It is desirable to place a UV transparent glass plate in front of the lamp and replace it with a new one if it becomes dirty.

The ion beam irradiation apparatus as shown in FIG. 1 is an experimental apparatus, not a mass production apparatus. Therefore, the irradiation object carrier has a disk-shaped structure that is rotatable and can rotate about the rotation axis, supports a plurality of irradiation objects near the outer periphery, and uses an ion beam generator as a stationary beam (without scanning). If the ion beam is applied, it is possible to process a plurality of sheets at the same time. By rotating the irradiation target carrier, if it is viewed as one irradiation target, it is moved to the position where the ion beam hits and the ion beam does not hit next time, so the heating effect due to ion collision energy disappears. The object to be irradiated is cooled by the cooling effect. It should be noted that when the ion beam is scanned and irradiated as in FIG. 1, it is cooled by the cooler, but the cooling effect may not be sufficient due to ion implantation in the heating affected portion. Since the apparatus according to the present invention is sufficiently cooled by the time of performing one rotation and performing ion implantation again, it is possible to perform ion implantation with a large dose and a high dose amount.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings by way of example embodiments of the present invention. FIG. 3 is a schematic sectional view of an ion beam irradiation apparatus (ion implantation apparatus) according to the present invention.

As shown in FIG. 3, this ion beam irradiation apparatus is provided with an irradiation object carrier 11 which is rotatable and movable in a rotation axis in a vacuum chamber 12. The irradiation target carrier 11 includes a disk-shaped cooling carrier 13, a shaft 14, and a rotation driver (not shown). The shaft 14 is attached to the bearing of the vacuum chamber 12 and the vacuum seal 15. There is. Further, the vacuum chamber 12 is provided with an expansion / contraction part 16 so that the bearing and the vacuum seal 15 and the irradiation target carrier 11 can move in the vertical direction in the drawing. The shaft portion 14 has a cooling gas (for example, He gas) introduction pipe 18 and an exhaust pipe 19
And an introduction pipe 20 for introducing a gas for thermal contact (H ₂ , Ne, N _2, etc.) for the object to be irradiated are concentrically incorporated. Introductory pipe 18
And the exhaust pipe 19 is the ring-shaped space 2 of the cooling carrier 13.
The gas from the introduction pipe 18 is sent to the ring-shaped space 22 to be adiabatically expanded and cooled. The cooling carrier 13 has a clamp ring 24 for holding a plurality of objects to be irradiated (semiconductor wafers) 23 and a platen 2.
5, and is fixed near the outer periphery of the cooling carrier 13. A recess is formed on the exposed surface of the platen 25, and the flow path 26 is formed so that the gas for thermal contact flows therethrough.
Are formed. Further, the platen 25 faces the space 22, is surrounded by the heat insulating material 27, and is cooled effectively and effectively. The heat insulating material 27 may be a space (vacuum) depending on the place. In the vacuum state in the vacuum chamber 12, heat transfer is insufficient because the actual contact area is small by simply placing the irradiation target 23 on the platen 25, and the adiabatic expansion cooling effect is applied via the platen 25. A gas for thermal contact is made to flow between the platen 25 and the object to be irradiated 23 in order to transmit it to the object 23. Further, according to the present invention, an ultraviolet irradiation means (mercury lamp) 28 is provided in the vacuum chamber 12 so as to illuminate the irradiation target 23 which is not in the ion implantation position, and additionally, the ultraviolet irradiation means (mercury lamp) 29 is provided. It is provided to illuminate the irradiation object 23 at the injection position. An ultraviolet transparent glass 30 is provided in front of the latter mercury lamp 29. An ion beam generator 31 is attached to the vacuum chamber 12 so as to irradiate an object 23 to be irradiated with a stationary ion beam 32.

In order to perform ion implantation on the object to be irradiated 23 using the above-mentioned ion beam irradiation apparatus, first, the object to be irradiated (silicon wafer) 23 is attached to the platen 25 of the cooling carrier 13 by the clamp ring 24, and a vacuum is applied. The chamber 12 is evacuated to a predetermined degree of vacuum, and the object carrier 1
1 is rotated and cooling gas is supplied to start cooling. Further, a gas for thermal contact is passed between the platen 25 and the object to be irradiated 23 through the introduction pipe 20 and the flow path 26, and the object to be irradiated 23 is irradiated with ultraviolet rays from the ultraviolet irradiation means (mercury lamp) 28. . It should be noted that the ultraviolet irradiation means (mercury lamp) 28 may be plural. When the irradiation target 23 is cooled to a predetermined temperature of 0 ° C. or lower, the stationary ion beam 32 is irradiated from the ion beam generator 31 toward the irradiation target 23 to perform ion implantation. In this ion beam irradiation apparatus, the irradiation target carrier 11 is moved upward (or downward) in the drawing for several seconds to shift the irradiation position of the irradiation target 23.
It is moved once every several tens of seconds, and ions are implanted into the entire irradiation object 23.

As described above, the object to be irradiated 23 is always cooled, and an adhered and deposited layer of residual gas is formed on the surface of the object to be irradiated. As soon as the deposited layer is formed, it can be vaporized by the energy of the ultraviolet light, and the deposited deposited layer is not formed. Further, when the ion beam is hit, the deposited deposition layer generated by the collision energy of the ion beam itself can be evaporated. When the acceleration energy and dose amount of the ion beam are low, it is considered that an adhered and deposited layer is generated to some extent. At that time, the irradiation object 23 at the ion implantation position is irradiated with ultraviolet rays from the ultraviolet irradiation means (mercury lamp) 29. It will be irradiated. When the UV irradiation means 29 is not used, it is desirable to dispose a protective shutter (not shown) in front of the UV transparent glass 30.

The object carrier 11 is rotated at 1000 rpm, and the irradiation intensity from the ultraviolet irradiation mercury lamp 29 is 10 μW /
When ion implantation was performed after irradiating with cm ² of ultraviolet rays for 5 minutes, it was possible to perform under the condition that there was no deposition layer due to residual gas and the temperature of the irradiated object was about −120 ° C.

[0018]

As described above, in the ion beam irradiation method (apparatus) according to the present invention, the advantages of low temperature implantation are utilized, and ultraviolet rays are irradiated to the object to be irradiated before the ion implantation (and during the ion implantation). By irradiating, the deposited layer (especially H ₂ O and CO ₂ ) attached to the surface of the object to be irradiated can be re-evaporated by cooling, and the ion implantation depth and dose amount can be set to predetermined values. .

With the ion beam irradiation apparatus shown in FIG. 3, the ion implantation process can be mass-produced.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a conventional ion beam irradiation apparatus.

FIG. 2 is an equilibrium vapor pressure curve of various gases.

FIG. 3 is a schematic sectional view of an ion beam irradiation apparatus according to the present invention.

[Explanation of symbols]

11 ... Irradiation object carrier 12 ... Vacuum chamber 13 ... Cooling support section 15 ... Bearing and vacuum seal 22 ... Ring-shaped space 23 ... Irradiation object (semiconductor wafer) 25 ... Platen 28 ... Ultraviolet irradiation means (mercury lamp) 31 ... Ion beam generator 32 ... Ion beam

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H01L 21/26 L 8617-4M

Claims (4)

[Claims] 1. An ion beam irradiation method in which an object to be irradiated is placed on a carrying device with a cooling function in a vacuum chamber, and the object to be irradiated is irradiated with an ion beam while the object to be irradiated is cooled to 0 ° C. or lower. An ion beam irradiation method comprising irradiating the surface of the object to be irradiated with ultraviolet rays before the irradiation of the object to be irradiated (23) with the ion beam. 2. The ion beam irradiation method according to claim 1, wherein the surface of the object to be irradiated is irradiated with ultraviolet rays during the irradiation of the object to be irradiated with the ion beam. 3. An irradiation object carrier provided with means for cooling an irradiation object to 0 ° C. or less, an ion beam generator for irradiating the irradiation object with an ion beam, and these irradiation object carrier and ions. An ion beam irradiation apparatus including a vacuum chamber accommodating a beam generator, comprising an ultraviolet irradiation means (28) for irradiating the surface of the object to be irradiated with ultraviolet rays. 4. The irradiation object carrier (11) is a disk shape that is rotatable and rotatable about a rotation axis, and carries a plurality of the irradiation objects (23) near the outer periphery, and the ion beam generator. (31) is the ion beam (3
2. The ion beam irradiation apparatus according to claim 3, which is for irradiating 2).