JP4235458B2 - Plasma etching method and plasma etching apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for plasma etching a surface of a plate-like object such as a semiconductor wafer.
[0002]
[Prior art]
A semiconductor wafer on which a plurality of circuits such as IC and LSI are formed on the front surface is polished to a predetermined thickness on the back surface, and then divided into individual semiconductor chips by a dicing apparatus or the like.
[0003]
In recent years, in order to reduce the size and weight of various electronic devices, it has been required that the thickness of a semiconductor chip be as extremely thin as 100 μm or less and 50 μm or less. However, it has been required to grind the back surface until it becomes extremely thin, such as 100 μm or less and 50 μm or less.
[0004]
After grinding the back surface of the semiconductor wafer, there is a problem that a strained layer generated by grinding remains on the back surface of the ground semiconductor wafer, and this strained layer lowers the bending strength of the semiconductor chip. The strained layer is removed by chemical etching.
[0005]
There are two types of chemical etching: wet etching that uses chemical reaction of solution and plasma etching that uses plasma gas to perform etching. Since the influence of etching is small, plasma etching tends to be employed, and an apparatus and a method for performing plasma etching are also disclosed (for example, see Patent Document 1). In this Patent Document 1, a semiconductor wafer is placed on a lower electrode, the inside of the chamber is evacuated in a state where the semiconductor wafer is sucked from a suction hole formed in the lower electrode, an etching gas is supplied into the chamber and an upper portion is supplied. Plasma discharge is generated by applying a high frequency voltage between the electrode and the lower electrode, and the back surface of the semiconductor wafer is etched by the plasma etching effect.
[0006]
[Patent Document 1]
Japanese Patent Laying-Open No. 2001-257248 (FIGS. 8, 9, and 10)
[0007]
[Problems to be solved by the invention]
However, the outer periphery of the holding portion formed on the lower electrode on which the semiconductor wafer is placed is formed slightly inside the outer periphery of the semiconductor wafer in order to avoid being electrically affected by plasma. Therefore, when the protective tape is attached to the circuit surface of the semiconductor wafer and the protective tape side is placed on the lower electrode and the back surface is plasma etched, the non-held portion on the outer peripheral side is slightly lifted because the semiconductor wafer is thin, There is a problem that the etching gas enters there and the protective tape is melted, and the circuit surface of the semiconductor wafer is exposed to the etching gas and damaged.
[0008]
Further, there is a problem that the plasma density becomes relatively high on the outer peripheral side of the semiconductor wafer, the outer peripheral side and the outer peripheral side surface of the back surface of the semiconductor wafer are etched much, and the back surface is not uniformly etched.
[0009]
The above problems are caused by forming a cutting groove corresponding to the finished thickness of the semiconductor chip on the surface of the semiconductor wafer, and then attaching a protective tape to the surface of the semiconductor wafer and grinding the back surface side. This can also occur when plasma etching is performed on the back surface of each semiconductor chip after using a so-called tip dicing technique in which the cutting groove is exposed and divided into individual semiconductor chips.
[0010]
Furthermore, the same problem may occur when plasma etching is performed on other plate-like materials as well as semiconductor wafers.
[0011]
Therefore, in the case of plasma etching a plate-like object, there is a problem in that the exposed surface is etched so that the outer periphery is not lifted and the exposed surface can be uniformly etched.
[0012]
[Means for Solving the Problems]
As specific means for solving the above-described problems, the present invention provides an opening serving as a plate-like material carry-in / out port, a shutter for opening and closing the opening, and a chuck table on which a holding portion for holding the plate-like object is formed. A plasma etching method for etching the exposed surface of the plate using a plasma etching apparatus including at least an etching gas supply means for supplying an etching gas to the exposed surface of the plate held by the chuck table, A plate-like object is a semiconductor wafer held on a chuck table, and the outer peripheral area of the semiconductor wafer is not pressed against the back side of a plurality of circuits formed on the front side of the exposed back side of the semiconductor wafer. is formed by the ring-shaped porous member having pores through which an etching gas on the outer peripheral side provided on the lower surface of the etching gas supply means In a state of being pressed by and with means to provide a performing plasma etching method of plasma etching.
[0013]
In this plasma etching method, a protective member is attached to the front surface of the semiconductor wafer, the front surface side of the semiconductor wafer is held on the chuck table so that the back surface of the semiconductor wafer is exposed, and the outer peripheral area of the back surface of the semiconductor wafer is pressed. The back side of the semiconductor wafer is ground in advance, and the grinding distortion layer generated on the back side of the semiconductor wafer by grinding is removed by plasma etching, and a cutting groove for partitioning a plurality of circuits is formed on the surface of the semiconductor wafer. The back surface of the semiconductor wafer is ground until the cutting groove is exposed from the back surface side and divided into individual semiconductor chips for each circuit, and the grinding distortion layer generated on the back surface of each semiconductor chip by plasma etching is plasma-etched. Is an additional requirement.
[0014]
The present invention also provides an opening serving as a semiconductor wafer carry-in / out opening, a shutter for opening and closing the opening, a chuck table on which a holding unit for holding the semiconductor wafer is formed, and an exposure of a plate-like object held on the chuck table. A plasma etching apparatus including at least an etching gas supply means for supplying an etching gas to a surface, a semiconductor formed by a ring-shaped porous member having pores through which the etching gas passes to the outer peripheral side of the ring and held on a chuck table Plasma etching in which the pressing means for pressing the outer peripheral area of the semiconductor wafer so as not to press the back side of a plurality of circuits formed on the front surface among the exposed back surface of the wafer is disposed on the lower surface of the etching gas supply means Providing equipment.
[0015]
This plasma etching apparatus has an additional requirement that an opening is formed below the pressing means.
[0016]
According to the plasma etching method and the plasma etching apparatus configured as described above, since the plasma etching is performed with the outer peripheral region of the semiconductor wafer not held by the suction portion of the chuck table being pressed by the pressing unit, the outer peripheral region is lifted. Etching is performed. Therefore, the etching gas is not supplied to the surface side. When the protective member is attached to the surface of the semiconductor wafer , the protective member is not melted, so that the circuit on the surface is not etched.
[0017]
In addition, since the pressing means is formed in a ring shape, the pressing means does not contact the back surface of the portion of the semiconductor wafer where the circuit is formed, so that the circuit is not damaged by the pressing force and the etching gas is evenly distributed. By forming the pressing means with a porous member having pores that allow the etching gas to pass to the outer peripheral side, the etching gas flows to the outer peripheral side through the pores, so that the etching gas does not stay inside the ring. .
[0018]
Furthermore, I'll be opening in the lower portion of the pressing means are formed, the etching gas flows to the outer peripheral side, it is possible to etching gas inside is prevented from staying.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
As an example of an embodiment of the present invention, a method and apparatus for plasma-etching a back surface of a semiconductor wafer after grinding the back surface will be described.
[0020]
A semiconductor wafer to be plasma-etched according to the present invention is divided by street S and formed with a plurality of circuits on the surface, such as a semiconductor wafer W shown in FIG. Chip C is obtained. As shown in FIG. 2, a protective member 1 for circuit protection is attached to the front surface W1 of the semiconductor wafer W prior to grinding the back surface.
[0021]
For grinding the back surface of the semiconductor wafer W, for example, a grinding apparatus 10 shown in FIG. 3 is used. The grinding apparatus 10 includes cassettes 11 and 12 for storing semiconductor wafers W having a protective member 1 attached to the surface, and unloading of the semiconductor wafers W from the cassettes 11 and unloading of the semiconductor wafers W into the cassettes 12. Insertion means 13, a center alignment table 14 for aligning the center of the semiconductor wafer W, first transfer means 15 and second transfer means 16 for transferring the semiconductor wafer W, and 4 for holding the semiconductor wafer W by suction. Two holding tables 17, 18, 19, 20, a turntable 21 that rotatably supports the holding tables 17, 18, 19, 20, a first grinding means 22 and a second grinding means for grinding the semiconductor wafer W 23 and cleaning means 24 for cleaning the semiconductor wafer W after grinding.
[0022]
In the cassette 11, the semiconductor wafers W before being ground are accommodated in a plurality of stages, picked up one by one by the loading / unloading means 13, and placed on the centering table 14 with the back surface exposed upward. Is done.
[0023]
Then, after the center position of the semiconductor wafer W is aligned on the centering table 14, the semiconductor wafer W is attracted to the first transport means 15 and transported to the holding table 17 by the turning movement, and the semiconductor wafer W is placed thereon. At this time, the semiconductor wafer W is exposed with its back surface facing upward, and the protection member 1 is held by the holding table 17 and the front surface side is held.
[0024]
Next, the turntable 21 is rotated by a required angle (90 degrees when there are four holding tables as in the illustrated example), and the semiconductor wafer W is positioned directly below the first grinding means 22. At this time, the holding table 18 is automatically positioned at the position where the holding table 17 was located before the turntable 21 is rotated, and the semiconductor wafer W to be ground next is unloaded from the cassette 11 and the centering table 14. After the center position has been aligned, the first transport means 15 transports it to the holding table 18 and places it thereon.
[0025]
The first grinding means 22 can move up and down with respect to the standing wall portion 25, and a pair of rails 26 are provided in the vertical direction on the inner surface of the wall portion 25 and driven by a drive source 27. As the support plate 28 moves up and down along the rail 26, the first grinding means 22 fixed to the support plate 28 moves up and down.
[0026]
In the first grinding means 22, a grinding wheel 31 is mounted on the tip of a spindle 29 that is rotatably supported via a mounter 30, and a grinding wheel 32 for rough grinding is fixed to the lower part of the grinding wheel 31. Has been.
[0027]
When the protective member 1 is adhered to the surface and the semiconductor wafer W held on the holding table 17 is positioned directly below the first grinding means 22, the semiconductor wafer W is rotated by the rotation of the holding table 17, and the spindle 29 As the grinding wheel 32 is rotated by the rotation, the first grinding means 22 is lowered, so that the rotating grinding wheel 32 comes into contact with the back surface of the semiconductor wafer W, and the back surface of the semiconductor wafer W is roughly ground. Here, a cutting groove for partitioning a plurality of circuits is formed on the surface of the semiconductor wafer W, and the back surface of the semiconductor wafer is exposed until the cutting groove is exposed from the back surface side and divided into individual semiconductor chips for each circuit. In the case of so-called tip dicing to be ground, the grinding is finished immediately before the cutting groove appears on the back surface.
[0028]
The roughly ground semiconductor wafer W is positioned directly below the second grinding means 23 by further rotating the turntable 21 by a required angle.
[0029]
The second grinding means 23 can move up and down with respect to the standing wall portion 25, and a pair of rails 33 are provided in the vertical direction on the inner surface of the wall portion 25 and driven by a drive source 34. As the support plate 35 moves up and down along the rail 33, the second grinding means 23 fixed to the support plate 35 moves up and down.
[0030]
In the second grinding means 23, a grinding wheel 38 is mounted on the tip of a spindle 36 that is rotatably supported via a mounter 37, and a grinding wheel 39 for finish grinding is fixed to the lower part of the grinding wheel 38. Has been.
[0031]
When the protective member 1 is adhered to the surface and the semiconductor wafer W is roughly ground, the semiconductor wafer W is rotated by the rotation of the holding table 17 and is ground by the rotation of the spindle 36. The grinding wheel 39 rotating while the grinding wheel 39 rotates while the second grinding means 23 descends contacts the back surface of the semiconductor wafer W, and the back surface of the semiconductor wafer W is finish-ground. Here, in the case of so-called tip dicing, a cutting groove is exposed and separated into individual semiconductor chips.
[0032]
The semiconductor wafer W held on the holding table 17 and finish-ground is positioned in the vicinity of the second transfer means 16 by the rotation of the turntable 21. Then, after being transported to the cleaning means 24 by the second transport means 16 and cleaned, it is carried out by the transport device 40 with the protective member 1 still adhered.
[0033]
In the vicinity of the carry-in / out means 13, a suction part 41 that sucks the semiconductor wafer, an arm part 42 that moves the suction part 41 in the horizontal direction and the vertical direction, and a drive part 43 that drives the arm part 42 are configured. A transfer device 40 is provided, and the semiconductor wafer W after cleaning is sucked by the suction unit 41, and the semiconductor wafer W is transported to the plasma etching device 50 by moving the suction unit 41.
[0034]
As shown in FIG. 3, the plasma etching apparatus 50 is configured by connecting a gas supply unit 51 and a plasma processing unit 52. The gas supply unit 51 includes a tank that stores an etching gas, a pump that sends the etching gas to the plasma processing unit 52, and the like. In the tank, a mixed gas for generating plasma mainly composed of a fluorine-based gas such as CF ₄ and oxygen is stored.
[0035]
As shown in FIG. 4, the plasma processing unit 52 accommodates an etching gas supply means 54 from the upper side of a chamber 53 where plasma etching is performed, and lowers a chuck table 55 that holds a plate-like object to be etched. It is the structure accommodated from.
[0036]
The etching gas supply means 54 supplies etching gas to the exposed surface of the plate-like object held by the chuck table 55, and the shaft portion 54 a is inserted into the chamber 53 through the bearing 56 so as to be movable up and down. In addition, a gas flow hole 57 that communicates with the gas supply part 51 and communicates with the ejection part 57a formed of a porous member is formed inside. The etching gas supply means 54 is configured to move up and down as the ball screw 59 is rotated by being driven by a motor 58 and the elevating unit 60 having a nut screwed to the ball screw 59 is moved up and down.
[0037]
On the other hand, the chuck table 55 has a shaft portion 55a rotatably inserted through a bearing 61, and a suction passage 63 communicating with a suction source 62 and a cooling passage 65 communicating with a cooling portion 64 are formed therein. The suction path 63 communicates with the suction part 63a on the upper surface.
[0038]
An opening 66 serving as a carry-in / out port for the plate-like object to be etched is formed on the side of the chamber 53, and a shutter 67 that opens and closes the opening 66 by raising and lowering is disposed outside the opening 66. The shutter 67 is moved up and down by a piston 69 that is driven by a cylinder 68 to move up and down.
[0039]
An exhaust port 71 communicating with the gas exhaust unit 70 is formed in the lower part of the chamber 53, and used gas can be exhausted from the exhaust port 71. Further, a high frequency power source 72 is connected to the etching gas supply means 54 and the chuck table 55, and a high frequency voltage can be supplied to turn the etching gas into plasma.
[0040]
A pressing unit 73 is disposed on the lower surface of the etching gas supply unit 54. The pressing means 73 has a function of pressing the outer peripheral area not held by the plate-like object suction portion 63 a held by the chuck table 55 from above. The pressing means 73 is preferably formed in a ring shape, for example, as shown upside down in FIG. 5, and is preferably detachable from the etching gas supply means 54. In this case, a plurality of pressing means 73 having different inner diameters and outer diameters are prepared, and can be appropriately selected according to the size of the plate-like object.
[0041]
When the back surface of the semiconductor wafer W shown in FIGS. 1 and 2 is subjected to plasma etching after the back surface grinding, the shutter 67 is lowered to open the opening 66, and the suction portion 41 shown in FIG. Adsorption is released with the semiconductor wafer W exposed to the inside of the chamber 53 and the back surface of the semiconductor wafer W exposed, and placed on the suction portion 63a of the chuck table 55, and the protection member 1 is held on the chuck table 55. . Then, after retracting the suction portion 41 to the outside of the chamber 53, the shutter 67 is returned to its original position, the opening 63 is closed, and the inside is evacuated.
[0042]
Then, the etching gas supply means 54 is lowered, and the outer peripheral region 74 of the semiconductor wafer W is pressed downward by the pressing means 73 as shown in FIG. Here, the outer peripheral area 74 is an area outside the suction portion 63a in the chuck table 55, that is, an area where the semiconductor wafer W is not sucked and held, and only the outer peripheral area 74 may be pressed. A slightly inner region may be pressed.
[0043]
Next, in this state, the etching gas is supplied from the gas supply unit 51 to the gas circulation hole 57, the etching gas is jetted from the jetting part 57 a on the lower surface of the etching gas supply unit 54, and the etching gas supply unit 54 is supplied from the high frequency power source 72. When a high frequency voltage is applied between the chuck table 55 and the etching gas is turned into plasma, the back surface of the semiconductor wafer W is etched by the plasma etching effect, and the grinding distortion layer formed by grinding is removed. Moreover, in the case of the tip dicing, the grinding distortion layer on the back surface of each semiconductor chip is removed. Furthermore, the side surface of the cutting groove is also etched, and the cutting strain layer is removed.
[0044]
In the plasma etching performed as described above, the etching is performed without lifting the outer peripheral region 74 of the semiconductor wafer W, so that the protective tape 1 attached to the surface of the semiconductor wafer W is not melted. Therefore, the surface circuit is not etched and damaged. Further, the plasma density becomes uniform and the back surface is etched uniformly.
[0045]
Furthermore, even if the outer peripheral region 74 of the semiconductor wafer W is not etched by pressing from the back surface side by the pressing means 73, no circuit is formed in the outer peripheral region 74 of the semiconductor wafer W as shown in FIG. Since the area is not required after being divided into individual semiconductor chips, the quality of the semiconductor chip is not affected. In addition, the width | variety of the outer periphery area | region 74 is about 2 mm-4 mm normally.
[0046]
In addition, since the pressing means 73 is formed in a ring shape, the back surface corresponding to the portion where a plurality of circuits are formed is not pressed by the pressing means 73, so that the circuit is not damaged by the pressing force, and the etching gas It is possible to perform etching evenly.
[0047]
The pressing means 73 can also be formed by a porous member. In this case, since the etching gas flows to the outer peripheral side through the pores formed in the pressing means 73, the etching gas does not stay inside the ring.
[0048]
Moreover, it can be set as the structure which provided the suitable opening part 75 in the lower part like the pressing means 73a shown in FIG. Also in this case, since the etching gas flows to the outer peripheral side through the opening 75, it is possible to prevent the etching gas from staying inside the ring, and the back surface corresponding to the portion where a plurality of circuits are formed is Since it is not pressed by the pressing means 73, the etching gas is spread and etching can be performed uniformly without damaging the circuit by the pressing force. In this case, the pressing means 73a may be formed of a porous member.
[0049]
The semiconductor wafer W whose back surface has been subjected to plasma etching in this manner lowers the shutter 67 shown in FIG. 4 to open the opening 66, and the semiconductor wafer W is adsorbed by the adsorbing part 41 shown in FIG. The part 41 is moved and carried out of the chamber 53. Then, the semiconductor wafer W is transferred to the cleaning means 24 of the grinding apparatus 10 shown in FIG. 3, and the etched semiconductor wafer W is cleaned and then stored in the cassette 12 by the loading / unloading means 13. Grinding and plasma etching as described above are performed on all the semiconductor wafers accommodated in the cassette 11, and all the semiconductor wafers are accommodated in the cassette 12.
[0050]
【The invention's effect】
As described above, according to the plasma etching method and the plasma etching apparatus according to the present invention, the plasma etching is performed in a state where the outer peripheral region of the semiconductor wafer not held by the suction portion of the chuck table is pressed by the pressing means. Etching is performed without raising the area. Accordingly, the etching gas is not supplied to the front surface side, the front surface is not etched, the plasma density becomes uniform, and the back surface is etched uniformly. When the protective member is attached to the surface of the semiconductor wafer , the protective member is not melted, so that the circuit on the surface is not etched and damaged.
[0051]
Also, by forming the pressing means in a ring shape, the pressing means does not contact the back surface of the portion of the semiconductor wafer where the circuit is formed, so that the circuit is not damaged by the pressing force, and the etching gas is evenly distributed. By forming the pressing means with a porous member having pores that allow the etching gas to pass to the outer peripheral side, the etching gas flows to the outer peripheral side through the pores, so that the etching gas does not stay inside the ring, Etching can be performed uniformly.
[0052]
Furthermore, I'll be opening in the lower portion of the pressing means are formed, the etching gas flows to the outer peripheral side, it is possible to etching gas inside is prevented from staying, etched uniformly be able to.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of a semiconductor wafer.
FIG. 2 is a front view showing a semiconductor wafer having a protective member attached to its surface.
FIG. 3 is a perspective view showing an example of a grinding device, a transport device, and a plasma etching device.
FIG. 4 is a cross-sectional view showing an example of a structure of a plasma processing unit constituting the plasma etching apparatus.
FIG. 5 is a perspective view showing an example of an etching gas supply unit and a pressing unit constituting the plasma processing unit.
FIG. 6 is a cross-sectional view showing a state where an outer peripheral region of a semiconductor wafer is pressed using a pressing unit.
FIG. 7 is a perspective view showing an outer peripheral region of a semiconductor wafer.
FIG. 8 is a front view showing a second example of the pressing means.
[Explanation of symbols]
W ... Semiconductor wafer S ... Street C ... Semiconductor chip 1 ... Protective member 10 ... Grinding device 11, 12 ... Cassette 13 ... Loading / unloading means 14 ... Centering table 15 ... First transfer means 16 ... Second transfer means 17, 18, 19, 20 ... holding table 21 ... turntable 22 ... first grinding means 23 ... second grinding means 24 ... cleaning means 25 ... wall 26 ... rail 27 ... drive source 28 ... support plate 29 ... spindle 30 ... Mounter 31 ... grinding wheel 32 ... grinding wheel 33 ... rail 34 ... drive source 35 ... support plate 36 ... spindle 37 ... mounter 38 ... grinding wheel 39 ... grinding wheel 40 ... conveying device 41 ... adsorption part 42 ... arm part 43 ... drive part DESCRIPTION OF SYMBOLS 50 ... Plasma etching apparatus 51 ... Gas supply part 52 ... Plasma processing part 53 ... Chamber 54 ... Etching gas supply means 55 Chuck table 56 ... Bearing 57 ... Gas flow hole 57a ... Ejection part 58 ... Motor 59 ... Ball screw 60 Lifting / lowering part 61 ... Bearing 62 ... Suction source 63 ... Suction path 64 ... Cooling part 65 ... Cooling path 66 ... Opening part 67 ... Shutter 68 ... Cylinder 69 ... Piston 70 ... Gas exhaust part 71 ... Exhaust port 72 ... High frequency power supply 73, 73a ... Pressing means 74 ... Outer peripheral region

Claims (6)

An opening serving as an entrance / exit for the plate-like object, a shutter for opening / closing the opening, a chuck table formed with a holding part for holding the plate-like object, and an exposed surface of the plate-like object held by the chuck table A plasma etching method for etching an exposed surface of the plate using a plasma etching apparatus including at least an etching gas supply means for supplying an etching gas to
The plate-like object is a semiconductor wafer held on the chuck table, and the semiconductor wafer is prevented from being pressed against the back side of a plurality of circuits formed on the front side among the back side which is the exposed surface of the semiconductor wafer. Plasma that performs plasma etching in a state where the outer peripheral region of the electrode is pressed by a pressing means provided on the lower surface of the etching gas supply means formed by a ring-shaped porous member having pores through which etching gas passes to the outer peripheral side of the ring Etching method.   The protective member is attached to the surface of the semiconductor wafer, the front surface side of the semiconductor wafer is held by a chuck table so that the back surface of the semiconductor wafer is exposed, and the outer peripheral region of the back surface of the semiconductor wafer is pressed. Plasma etching method.   The plasma etching method according to claim 2, wherein the back surface of the semiconductor wafer is ground in advance, and the grinding strain layer generated on the back surface of the semiconductor wafer by grinding is removed by plasma etching.   A cutting groove for dividing a plurality of circuits is formed on the front surface of the semiconductor wafer, and the back surface of the semiconductor wafer is ground until the cutting groove is exposed from the back surface side and divided into individual semiconductor chips for each circuit. 3. The plasma etching method according to claim 2, wherein the grinding distortion layer generated on the back surface of each semiconductor chip by grinding is removed by plasma etching. An opening serving as a semiconductor wafer carry-in / out opening, a shutter for opening and closing the opening, a chuck table on which a holding unit for holding the semiconductor wafer is formed, and an etching gas on the exposed surface of the semiconductor wafer held on the chuck table An etching gas supply means for supplying at least a plasma etching apparatus comprising:
The back surface side of a plurality of circuits formed on the front surface of the back surface, which is the exposed surface of the semiconductor wafer, formed by a ring-shaped porous member having pores through which the etching gas passes to the outer peripheral side of the ring. A plasma etching apparatus in which pressing means for pressing the outer peripheral region of the semiconductor wafer so as not to press is disposed on the lower surface of the etching gas supply means .   6. The plasma etching apparatus according to claim 5, wherein an opening is formed in a lower portion of the pressing means.

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