Semiconductor substrate etching apparatus

A semiconductor substrate etching apparatus for etching a tapered outer circumferential surface of a semiconductor substrate. A semiconductor substrate supply unit, an X-Y stage unit, an etchant applying unit, a cleaning unit, a baking unit, and a semiconductor substrate recovering unit are arranged in a horizontal plane in the described order. Semiconductor substrates are sequentially transferred by a transfer mechanism from the semiconductor substrate supply unit to the semiconductor substrate recovering unit in the described order. A control unit controls the transfer mechanism to perform the transferring of the semiconductor substrate, and controls the X-Y stage unit in response to a position detection signal, outputted from a position detector, for positioning the semiconductor substrate on the X-Y stage unit.

BACKGROUND OF THE INVENTION 
The present invention relates to a semiconductor substrate etching 
apparatus, and particularly relates to a semiconductor substrate etching 
apparatus for automatically etching a beveled outer edge of a 
semiconductor substrate (also referred to as a wafer) having a bevel 
structure. 
A disk-shaped semiconductor substrate having no orientation flat is adopted 
as a wafer for a large-power semiconductor device. Most of the 
semiconductor substrates are tapered or beveled at edges thereof to 
maintain predetermined breakdown voltages. During beveling, cracks and 
defects are produced in the beveled edge of the wafer, and must be removed 
by etching the beveled edge. 
The etching of the beveled edge of the wafer is conventionally achieved by 
the following processing. As illustrated in FIG. 5, one major surface of a 
semiconductor substrate 1 is entirely coated with an antietchant 2 with a 
brush, and then the semiconductor substrate 1 is bonded to a fluoroplastic 
disk 3 having the same diameter as the semiconductor substrate 1. 
Thereafter, the semiconductor substrate 1 is placed on a hot plate 4 
through the fluoroplastic disk 3 for baking for several minutes so that 
the semiconductor substrate 1 and the fluoroplastic disk 3 are adhered to 
each other. After baking, the other major surface or the pattern formation 
surface is coated with an antietchant 5 by a brush, and is then similarly 
baked. Care should be taken not to apply the antietchant to the beveled 
edge 1a during the antietchant applying operations. 
The semiconductor substrate 1 attached to the fluoroplastic disk 3 as 
illustrated in FIG. 5 is picked up by a tweezers 6, and is immersed in an 
etchant 7 for a predetermined time to etch only the beveled edge of the 
semiconductor substrate 1. After etching, the semiconductor substrate 1 is 
cleaned with water, and is then immersed in a boiling organic solution to 
peel off the fluoroplastic disk 3 from the semiconductor substrate 1 as 
well as to remove antietchant 2 and 5. Thereafter, the semiconductor 
substrate 1 is washed in a water flow. After washing, the semiconductor 
substrate 1 is dried by an infrared lamp 8. 
Such an earlier attempt however raised the following problems: great care 
should be taken to apply antietchant on the opposite major surfaces of the 
semiconductor substrate 1 so that the antietchant may not adhere to the 
beveled edge 1a of the semiconductor substrate 1; a fluoroplastic disk 3 
must be bonded to one major surface of the semiconductor substrate 1; 
removal of the antietchant is needed with the accompanying cleaning and 
drying operations; a considerable drop in yield of the semiconductor 
substrate 1 due to nonuniform coating of antietchant 2 and 5; the 
consumption of the etchant is rather increased since the whole wafer is 
immersed in the etchant for etching only the beveled edge 1a of the 
semiconductor substrate 1. 
Another attempt to overcome such problems is disclosed in Japanese 
unexamined patent publication (Kokai) 1(1989)-316936. The semiconductor 
substrate etching apparatus of this publication is, as shown in FIGS. 8 
and 9, provided with a rotary table 9 with a vacuum chuck, and an applying 
roller 11 with a rotary shaft 10, the roller 11 being disposed in parallel 
with the rotary table 9. An etchant 13 is supplied from an etchant supply 
nozzle 12 to an outer circumferential groove 11a of the applying roller 
11. A semiconductor substrate 1 is vacuum chucked by the rotary table 9, 
and the beveled edge 1a fits into the outer circumferential groove 11a of 
the applying roller 11. With such a construction, the etchant 13 is 
supplied from the etchant supplying nozzle 12 to the outer circumferential 
groove 11a of the applying roller 11 while the rotary table 9 and the 
applying roller 11 are rotated. The etchant 13 is held in the outer 
circumferential groove 11a due to surface tension, and adheres to the 
beveled edge of the semiconductor substrate 1 for etching as the applying 
roller 11 is rotated. After completion of the etching of the whole edge of 
the semiconductor substrate 1, the supply of the etchant is discontinued, 
and then pure water is jetted from cleaning nozzles 14 and 15 to clean the 
semiconductor substrate 1. Finally, the semiconductor substrate 1 is 
rotated at a high speed for drying. 
The semiconductor substrate etching apparatus taught in the Japanese 
unexamined patent publication 1-316936 is disadvantageous in the following 
points: it automatizes only the applying of the etchant to the beveled 
edge of the semiconductor substrates and the subsequent washing, and does 
not automate the whole line of the etching processing including 
transferring of semiconductor substrates, applying of the etchant, 
cleaning with water, baking, etc; and nonuniform coating of the etchant 
takes place if the semiconductor substrate 1 is eccentrically placed on 
the rotary table 9. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a 
semiconductor substrate etching apparatus which is capable of uniformly 
applying an etchant over the whole edge of a semiconductor substrate, and 
enables automatization of the whole line of the etching processing of the 
semiconductor substrate, including transferring of semiconductor 
substrates, applying of the etchant, cleaning with water, baking, etc. 
In view of this and other objects in view the present invention provides a 
semiconductor substrate etching apparatus for etching a beveled outer edge 
of a semiconductor substrate, comprising: a semiconductor substrate supply 
means for placing a tray, receiving a semiconductor substrate, therein; 
registration means for registering a semiconductor substrate transferred 
from the semiconductor substrate supply means thereto, the registration 
means including: X-Y stage means for resting the semiconductor substrate 
transferred from the semiconductor substrate supply means thereon for 
positioning in an x-y coordinate system; and position detecting means for 
detecting a position in the x-y coordinate system of the semiconductor 
substrate rested on the X-Y stage means to produce a position detection 
signal; etchant applying means including: a rotary table means for resting 
the semiconductor substrate, transferred from the registration means, 
thereon for rotation; and etchant applying means, arranged in the vicinity 
of the rotary table means, for applying an etchant to the tapered outer 
edge of the semiconductor substrate rested on the rotary table means; 
cleaning means for cleaning the semiconductor substrate transferred from 
the rotary table means thereto and for drying the cleaned semiconductor 
substrate; baking means including: hot plate means for resting a cleaned 
and dried semiconductor substrate, transferred from the cleaning means, 
thereon and for baking the cleaned and dried semiconductor substrate for 
drying; semiconductor substrate recovering means for resting a tray to 
receive the baked semiconductor substrate, transferred from the baking 
means, thereon, the semiconductor substrate supply means, the X-Y stage 
means, the etchant applying means, the cleaning means, the baking means, 
and the semiconductor substrate recovering means being arranged in a 
horizontal plane in the described order; transfer means for sequentially 
transferring the semiconductor substrate in the described order from the 
semiconductor substrate supply means to the semiconductor substrate 
recovering means; and control means for controlling the transfer means to 
perform the transferring of the semiconductor substrate and for 
controlling the X-Y stage means in response to the position detection 
signal for positioning the semiconductor substrate on the X-Y stage means. 
According to the present invention, semiconductor substrates are 
sequentially transferred from the semiconductor substrate supply means to 
the semiconductor substrate recovering means by the transfer means, and 
etching is automatically conduced. The processing time is thus greatly 
reduced. Furthermore, the semiconductor substrates are placed on the 
rotary table means of the etchant applying means at a relatively high 
accuracy since this operation is carried out after the semiconductor 
substrates are registered by the X-Y stage means. This enables the etchant 
to be applied more uniformly than the techniques according to the prior 
art, and the semiconductor substrate etching apparatus of the present 
invention is fairly enhanced in yield.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A semiconductor substrate etching apparatus according to the present 
invention will be described with reference to FIGS. 1 to 4, in which parts 
corresponding to parts in FIGS. 5 to 9 are designated by the same 
reference numerals, and descriptions thereof are omitted or simplified. 
In FIGS. 1 and 2, a clean unit 20 is provided with a base 21, on which a 
semiconductor substrate supply unit 22, a registering unit 23, an etchant 
applying unit 24, a cleaning unit 25, a baking unit 26 having a hot plate 
26a and a semiconductor substrate recovery unit 27 are substantially 
longitudinally aligned in a horizontal plane in the described order. The 
semiconductor substrate supply unit 22 has trays 28 each of which is 
adapted to receive semiconductor substrates 1 at predetermined positions. 
The registering unit 23 includes an X-Y stage 23a and a position detector 
23b which includes an industrial television camera arranged above the X-Y 
stage 23a. 
The etchant applying unit 24 has a construction similar to the 
semiconductor substrate etching apparatus disclosed in the Japanese 
unexamined patent publication 1-316936, that is, in FIGS. 8 and 9. As 
shown in FIG. 4, the etchant applying unit 24 includes a rotary table 29 
with a vacuum chuck function, the rotary table 29 being connected to a 
motor, not shown for rotation. The etchant applying unit 24 is further 
provided with an applying roller 30, connected to another motor also not 
shown, and an etchant feed tube 31 for supplying an etchant to the 
applying roller 30. The applying roller 30 and the etchant feed tube 31 
are constructed so that they may be moved in unison toward and away from 
the rotary table 29. 
Just above the semiconductor substrate supply unit 22, the registering unit 
23, the etchant applying unit 24, the cleaning unit 25, the baking unit 26 
and the semiconductor substrate recovery unit 27, there are arranged first 
to fifth transport arms 32, 33, 34, 35 and 36, respectively. As shown in 
FIG. 3, the transport arms 32, 33, 34, 35 and 36 have vacuum chuck heads 
37 to 41, which are communicated to flexible hoses 42 to 46 to a vacuum 
pump unit not shown, respectively. The transfer arms 32 to 36 are attached 
at rear ends thereof to distal ends of piston rods 47a to 51a of pneumatic 
cylinders 47 to 51, respectively. The pneumatic cylinders 47 to 51 are 
vertically secured to a reciprocal arm 52 so that the transfer arms 32 to 
36 are equispaced, 30 cm in this embodiment. The reciprocal arm 52 is 
supported on the frame of the clean unit 20 for horizontal movement. The 
reciprocal arm 52 is horizontally reciprocally moved by a horizontal 
movement pneumatic cylinder 54, mounted on the frame of the cleaning unit, 
through a lug 53 thereof at a predetermined stroke, 30 cm in this 
embodiment. 
The first transfer arm 32 vacuum chucks a semiconductor substrate 1, which 
is in the semiconductor supply unit 22, by the vacuum chuck head 37, and 
transfers the semiconductor substrate 1 onto the X-Y stage 23a of the 
registering unit 23. The second transfer arm 33 vacuum chucks a 
semiconductor substrate 1, which is on the X-Y stage 23a, by the vacuum 
chuck head 38, and carries the semiconductor substrate 1 onto the rotary 
table 29 (FIG. 4) of the etchant applying unit 24. The third transfer arm 
34 sucks a semiconductor substrate 1 from the rotary table 29 by the 
vacuum chuck head 39, and transfers the semiconductor substrate 1 to the 
cleaning unit 25. The fourth transfer arm 35 vacuum chucks a semiconductor 
substrate 1 in the cleaning unit 25 by the vacuum chuck head 40, and 
transfers it to the baking unit 26. The fifth transfer arm 36 vacuum 
chucks a semiconductor substrate 1 in the baking unit 26 by the vacuum 
chuck head 41, and carries it onto a tray 28 placed in the semiconductor 
recovery unit 27. To prevent the etchant applied surface of every 
semiconductor substrate 1 from being damaged during transfer, the vacuum 
chuck heads 37 to 41 of the third to the fifth transfer arms 32 to 36 are 
formed so that each of the contact edges thereof makes a contact only with 
a central part of each semiconductor substrate 1 and does not make a 
contact with the peripheral portion thereof. More specifically, for this 
purpose each of the vacuum chuck heads 37 to 41 of the third to the fifth 
transfer arms 32 to 36 is formed to be sufficiently smaller in diameter 
than the semiconductor substrate 1 or has a circumferential groove formed 
at a portion thereof corresponding to the outer periphery of the 
semiconductor substrate 1. 
The clean unit 20 has a control unit 55 for controlling each unit thereof, 
and an etchant supply unit 56 incorporated in it. 
In operation, a tray 28 in which semiconductor substrates 1 are received is 
placed in the semiconductor substrate supply unit 22. After one of the 
semiconductor substrates 1 on the tray 28 is vacuum chucked and held by 
the vacuum chuck head 37, the pneumatic cylinder 47 is actuated, so that 
the first transfer arm 32 is raised 10 cm, in this embodiment, with the 
semiconductor substrate 1. Then, the pneumatic cylinder 54 is actuated to 
move the reciprocal arm 52 30 cm in a direction indicated by the arrow in 
FIG. 3, after which the pneumatic cylinder 47 is deactivated to place the 
semiconductor substrate 1 on the X-Y stage 23a of the registering unit 23. 
Then, the pneumatic cylinder 54 is deactivated to return the reciprocal 
arm 52 to the original position shown in FIG. 1. The position detector 23b 
detects marks (not shown) of the peripheral portion and the central 
portion of the semiconductor substrate 1 placed on the X-Y stage 23a to 
produce a detection signal, according to which the control unit 55 
computes an amount of misregistration of the semiconductor substrate 1. On 
the basis of this computed misregistration amount, the control unit 55 
controls the X-Y stage 23a to move x and/or y direction, so that the 
semiconductor substrate 1 is positioned at a predetermined position at 
high accuracy. 
The semiconductor substrate 1 thus positioned is vacuum chucked by the 
vacuum chuck head 33 of the second transfer arm 33, and is then 
transferred onto the rotary table 29 of the etchant applying unit 24 at a 
high accuracy by actuating the pneumatic cylinder 48 and the pneumatic 
cylinder 54 in the same fashion as in the first transfer arm 32. 
The rotary table 29 vacuum chucks the semiconductor substrate 1 placed on 
it, and is then rotated by the motor in the direction of the arrow A in 
FIG. 4, so that the semiconductor substrate 1 is rotated in unison with 
the rotary table 29 in the same direction. The applying roller 30 is 
horizontally moved together with the etchant feed tube 31 so that the 
tapered outer circumferential surface 1a of the semiconductor substrate 1 
is received in a circumferential recess 30a of the applying roller 30. 
During this operation, the applying roller 30 is rotated by the other 
motor in the direction B. The etchant feed tube 31 supplies an etchant to 
the circumferential recess 30a of the applying roller 30, so that the 
etchant is uniformly applied over the tapered edge 1a of the semiconductor 
substrate 1 for etching. Then, the semiconductor substrate 1 is washed 
with pure water for initial purpose. 
The semiconductor substrate 1 applied with the etchant is transferred from 
the rotary table 29 to the cleaning unit 25 with the third transfer arm 34 
by actuating the pneumatic cylinder 54 and the pneumatic cylinder 49 in 
the same manner as in the arms 32 and 33. In the cleaning unit 25, the 
semiconductor substrate 1 is washed with water, and is then dried. 
Thereafter, the semiconductor substrate 1 is transferred from the cleaning 
unit 25 onto the hot plate 26a of the baking unit 26 with the fourth 
transfer arm 35 by actuating the pneumatic cylinder 54 and the pneumatic 
cylinder 50 in the same manner as in the arm 32. 
The hot plate 26a dries the semiconductor substrate 1 at a high 
temperature. The fifth transfer arm 36 vacuum chucks the semiconductor 
substrate 1, which is on the hot plate 26a, and transfers it to a tray 28 
in the semiconductor substrate recovery unit 27 by actuating the pneumatic 
cylinder 54 and the pneumatic cylinder 51 in the same manner as in the arm 
32. 
Although the description has been made about only one semiconductor 
substrate 1, the arms 32-36 and the units 22-27 synchronously performs 
functions previously described on respective semiconductor substrates. 
Thus, the operations previously described are continuously carried out.