JP3407488B2 - Ion implanter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to an ion implantation apparatus for irradiating a wafer with an ion beam to perform ion implantation. The present invention relates to a means for easily, surely, and quickly detecting an abnormal rise in the temperature of a wafer. 2. Description of the Related Art FIG. 3 is a plan view partially showing an example of a conventional ion implantation apparatus. This ion implantation apparatus is the same as the apparatus described in Japanese Patent Application Laid-Open No. 3-114127. In this example, the same mechanism is provided on the left and right of the beam line of the ion beam 2 in a substantially symmetrical manner. In the following, description will be made mainly on the right side (right side in the figure) as an example. An ion beam 2 that is electrically scanned in the X direction (ie, by an electric field or a magnetic field) is introduced into an implantation chamber 6 that is evacuated by a vacuum pump (not shown). Two holder driving devices 120 having the same structure are provided on the left and right sides of the injection chamber 6. [0004] Each holder driving device 120 is a motor 1 for rotating a holder 8 holding a wafer 4 as shown by an arrow F.
38, a motor 132 for rotating an arm 136 supporting the motor 138 and the like as shown by an arrow E, and a motor 126 for rotating the main shaft 124 and the motor 132 and the like attached thereto as shown by an arrow D. Motor 1
26, 132 and 138 are reversible direct drive motors in this example. A main shaft 124 is moved by an arrow D
, And the holder 8 attached thereto via the arm 136 or the like is turned upright for ion implantation (see the holder 8 on the right side in the figure) and horizontal for handling the wafer 4. (See the holder 8 on the left side in the figure). Then, in the standing state, the motor 1
When the arm 136 is oscillated and rotated by rotating the arm 32 forward and backward as indicated by an arrow E, the holder 8 attached to the tip of the arm 136 turns the wafer 4 held there toward the ion beam 2 to form an arc. Is mechanically scanned in a Y direction substantially orthogonal to the X direction. Thereby, ion implantation can be performed by irradiating the entire surface of the wafer 4 with the ion beam 2. [0006] Vacuum preparatory chambers 80 for taking in and out the wafers 4 one by one between the inside of the implantation chamber 6 and the atmosphere side are respectively adjacent to the rear left and right bottom portions of the implantation chamber 6. FIG.
As shown in FIG. 7, a vacuum-side valve 88 and an atmosphere-side valve 90 are provided between each vacuum preparatory chamber 80, the injection chamber 6, and the atmosphere. When the wafer 4 is taken in and out, the former is controlled by the air cylinder 86 and the latter is controlled by the air cylinder 10.
2, respectively. At this time, the wafer 4 on the wafer receiver 94 is
00 raises and lowers in two stages. [0007] The holder 8 and the vacuum preparatory chamber 80 are in a horizontal state.
Is transferred by the wafer transfer device 60. Each wafer transfer device 60 includes a transfer arm 61a on the load side (that is, a side for transferring the uninjected wafer 4 to the holder 8) on which the wafer 4 is mounted and a transfer arm 61a on the unload side (that is, the wafer 4 after the injection). Arm 61b), a timing belt 68 and a reversible motor 74 for simultaneously moving them in mutually opposite directions, and guide shafts 6 positioned above and below each other.
2a and 62b. The transfer arm 61a is located above the transfer arm 61b. [0008] The energy of the ion beam 2 applied to the wafer 4 during ion implantation eventually becomes heat, and the temperature of the wafer 4 rises. Since the wafer 4 is held and fixed by a holder 8 having good thermal conductivity, and since the holder 8 is usually cooled by a coolant such as cooling water, heat is transmitted from the wafer 4 to the holder 8 and the temperature of the wafer 4 is increased. Is not going to rise too much. However, in recent years, there has been a tendency to increase the beam current of the ion beam 2 at the time of ion implantation in order to increase the throughput of the apparatus (the number of pieces processed per unit time), thereby increasing the heat input to the wafer 4. Therefore, the temperature of the wafer 4 tends to increase. The heat is transferred from the wafer 4 to the holder 8 by contact between the two surfaces in a vacuum. However, the heat transfer of this method is very unstable, for example, dust of about 1 mm (such as fragments of the wafer 4).
, Between the holder 8 and the wafer 4, almost no heat is transmitted, and the temperature of the wafer 4 rises significantly. A resist is usually applied to the surface of the wafer 4, and the resist deteriorates at a high temperature of 100 ° C. to 120 ° C. or higher. The conventional ion implantation apparatus is not provided with a mechanism for detecting a temperature rise of the wafer 4 at the time of ion implantation. When a predetermined number of ions have been implanted, the inspector visually checks the wafer. The presence or absence of the abnormal temperature rise of No. 4 was inspected by peeling, discoloration and the like of the resist due to burning. More specifically, the wafers 4 before and after the ion implantation are stored in a plurality of cassettes (for example, 25) in a cassette placed near the atmospheric side of the vacuum preparatory chamber 80. At the time when the ion implantation is completed, the inspection is collectively performed visually. However, in the visual inspection, not only is it extremely time-consuming, but if the temperature of the wafer 4 is extremely high (for example, 200 ° C. or more), it can be found that the resist is peeled off. Temperature rise (for example, 150 ° C. to 2
(Approximately 00 ° C.) may not be able to be found due to little discoloration. In addition, even if the temperature of the wafer 4 during ion implantation rises abnormally due to an inconvenience in heat conduction from the first wafer 4, it is not possible to detect the temperature abnormally. After the ion implantation for two cassettes is completed, a large number of defective wafers 4 such as 25 or 50 are generated. SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide an ion implantation apparatus capable of easily, surely and quickly detecting an abnormal rise in the temperature of a wafer during ion implantation. [0015] To achieve the above object, an ion implantation apparatus of the present invention is provided on a transfer path of an ion-implanted wafer removed from a holder in an implantation chamber. A radiation thermometer that measures the temperature of the back surface of the wafer being transported, and outputs a warning signal when the former exceeds the latter by comparing a temperature signal from the radiation thermometer with a preset reference value. And a comparator. The heat radiation of the wafer after ion implantation becomes almost only radiation from the time of removal from the holder. Therefore, the temperature of the wafer after ion implantation in the implantation chamber substantially reflects the temperature of the wafer at the time of ion implantation. ing. The radiation thermometer measures the temperature of the back surface of the wafer being transported in the injection chamber, and if the measured value exceeds the reference value, an alarm signal is output from the comparator. In this manner, an abnormal rise in the temperature of the wafer during the ion implantation can be detected simply and reliably without visual inspection by an inspector, and quickly for each wafer immediately after the ion implantation. FIG. 1 is a plan view partially showing an example of an ion implantation apparatus according to the present invention. FIG. 2 is a cross-sectional view showing the radiation thermometer in FIG. 1 as viewed from the side. Parts that are the same as or correspond to those in the conventional example of FIG. 3 are denoted by the same reference numerals, and differences from the conventional example will be mainly described below. As described above, in this ion implantation apparatus, the wafer 4 ion-implanted on the holder 8
The holder 8 is returned to the horizontal state, and is placed on the unloading transfer arm 61b below the wafer transfer device 60 and transferred to the vacuum preparatory chamber 80. In this embodiment, therefore, in the injection chamber 6, more specifically, on the lower side of the transfer path of the wafer 4 from the holder 8 in a horizontal state to the vacuum preparatory chamber 80, more specifically, in the injection chamber 6.
A viewing window 150 is provided on the bottom surface 7 of the device, and a radiation thermometer 152 is provided outside the viewing window 150. The radiation thermometer 152 is provided through the viewing window 150 so that the wafer 4 after ion implantation is being transported across it. The temperature of the back side is measured. By the way, the transfer arm 61b (the transfer arm 61a
), Since only the peripheral portion of the wafer 4 is supported from below, the wafer 4 placed on the transfer arm 61b is not supported.
Can be measured from below without any problem by the radiation thermometer 152. The radiation thermometer 152 outputs a temperature signal T representing the measured temperature, which is input to the comparator 154.
The comparator 154 compares the temperature signal T with a predetermined reference value R, and outputs an alarm signal S when the temperature signal T exceeds the reference value R. The reference value R may be set to, for example, a temperature at which the resist applied to the surface of the wafer 4 starts to deteriorate, more specifically, about 100 ° C. The radiation thermometer 152 measures the energy radiated from an object to measure the temperature of the object. In this embodiment, as the radiation thermometer 152, an infrared radiation thermometer that detects infrared rays emitted from an object is used. For this reason, it is preferable that the viewing window 150 be made of a material having excellent infrared transmission properties, such as sapphire glass. The transfer of the wafer 4 is controlled.
More specifically, by connecting a controller (not shown) controlling the wafer transfer device 60 to the radiation thermometer 152 or the comparator 154 and exchanging signals with each other, the wafer 4 is connected to the radiation thermometer 152. The above-described comparison may be performed only when entering the measurement range. The heat radiation of the wafer 4 after the ion implantation becomes almost only radiation from the time when the wafer 4 is removed from the holder 8, and the temperature of the wafer 4 hardly decreases. This is because the transfer of the wafer 4 is performed so that the structures such as the transfer arms 61a and 61b do not contact the wafer 4 as much as possible in order to minimize the attachment of dust to the wafer 4. Heat transfer is very low. Further, since the interior of the injection chamber 6 is in a vacuum, there is no heat transfer by convection of gas. Therefore, the temperature during the transfer of the wafer 4 after the ion implantation in the implantation chamber 6 substantially reflects the temperature of the wafer 4 during the ion implantation on the holder 8. If the difference between the temperature of the wafer 4 on the holder 8 and the temperature during the transfer becomes a problem, if the reference value R is set in consideration of the difference, the difference is set. Is no longer a problem. That is, the reference value R may be reduced by an amount corresponding to the difference. The radiation thermometer 152 measures the temperature of the back surface of the wafer 4 being transported in the injection chamber 6, and if the measured value exceeds the reference value R, the comparator 154 outputs an alarm signal S. You. As a result, an abnormal rise in the temperature of the wafer 4 during the ion implantation can be easily and reliably detected without visual inspection by an inspector as in the related art. That is, the temperature rise of the wafer 4 (for example, 15
(About 0 ° C.) can be reliably detected. This can eliminate waste such as finding a defective product in a post-process. Moreover, it is possible to quickly detect each wafer 4 immediately after the ion implantation. Therefore, generation of a large number of defective products can be prevented. As described above, with the radiation thermometer 152,
The reason for measuring the temperature of the back surface of the wafer 4 instead of the front surface is as follows. That is, a device pattern is usually formed on the surface of the wafer 4 and a resist is applied. Since these differ depending on the device to be manufactured, the blackness for measuring the temperature with the radiation thermometer 152 often differs. The radiation thermometer 152 cannot correctly measure the temperature unless the blackness of the object to be measured is set correctly. Therefore, when the temperature of the surface of the wafer 4 is measured by the radiation thermometer 152, the black color of the radiation thermometer 152 is determined for each type of device formed on the surface of the wafer 4, that is, for each type of surface of the wafer 4. It is necessary to set the degree, and the measurement becomes complicated. On the other hand, since no device pattern or the like is formed on the back surface of the wafer 4 unlike the front surface,
The degree of blackness is substantially constant irrespective of the type of the surface of the wafer 4. Therefore, if the temperature of the back surface of the wafer 4 is measured,
The radiation thermometer 152 can eliminate the trouble of resetting the blackness setting for each type of the surface of the wafer 4, so that the measurement becomes easier. When the alarm signal S is output from the comparator 154, the operator may be prompted to stop the ion implantation by displaying the alarm signal S, or may proceed further and respond to the alarm signal S in response to the alarm signal S. Subsequent ion implantation may be automatically stopped. The above is an apparatus of a so-called hybrid scan system in which the ion beam 2 is electrically scanned and the wafer 4 is mechanically scanned. The so-called dual type ion implantation apparatus provided with the apparatus 120 and the like has been described as an example, but the present invention is not limited to such an apparatus. For example, if the ion beam 2 is X
An ion implanter that scans in both Y directions with an electric field or magnetic field, or scans one of XY with an electric field and the other with a magnetic field may be used. This XY represents only two orthogonal directions, and therefore, for example, the X direction may be viewed as a horizontal direction, a vertical direction, or a direction inclined from it. The scanning of the ion beam 2 may be a parallel scan (parallel scan) or a scan having a normal angle. As described above, according to the present invention, since the radiation thermometer and the comparator are provided as described above, the fact that the temperature of the wafer has abnormally increased during the ion implantation is considered. In addition, it is possible to easily and reliably detect each wafer immediately after ion implantation without visual inspection by an inspector. As a result, generation of many defective products can be prevented. In addition, since the radiation thermometer measures the temperature of the back surface of the wafer instead of the front surface,
In the radiation thermometer, the complexity of resetting the blackness setting for each type of wafer surface can be eliminated, and the measurement becomes easier.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view partially showing an example of an ion implantation apparatus according to the present invention. FIG. 2 is a sectional view showing the radiation thermometer in FIG. 1 as viewed from the side. FIG. 3 is a plan view partially showing an example of a conventional ion implantation apparatus. FIG. 4 is a cross-sectional view taken along line II of FIGS. 1 and 3; [Description of Signs] 2 Ion beam 4 Wafer 6 Injection chamber 8 Holder 60 Wafer transfer device 61a, 61b Transfer arm 80 Vacuum preparatory chamber 120 Holder driving device 150 Viewing window 152 Radiation thermometer 154 Comparator

Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) H01J 37/317 H01J 37/244 H01L 21/265 C23C 14/48

Claims (1)

(57) [Claim 1] An apparatus for performing ion implantation by irradiating an ion beam to a wafer held in a holder in an implantation chamber evacuated to a vacuum, wherein the ion removed from the holder is provided. A radiation thermometer that is provided on a transfer path in the implantation chamber of the wafer after implantation and measures the temperature of the back surface of the wafer being transferred therethrough, a temperature signal from the radiation thermometer and a preset reference value. And a comparator that outputs an alarm signal when the former exceeds the latter by comparing the two.