JP4933373B2 - Plasma etching equipment - Google Patents

Description

  The present invention relates to a plasma etching apparatus for performing plasma etching on a workpiece such as a semiconductor wafer.

  In the semiconductor device manufacturing process, a plurality of regions are partitioned by dividing lines called streets formed in a lattice shape on the surface of a substantially wafer-shaped semiconductor wafer, and devices such as ICs, LSIs, etc. are partitioned in these partitioned regions. Form. Then, the semiconductor wafer is cut along the planned dividing line to divide the region where the device is formed to manufacture individual semiconductor chips. The semiconductor wafer is formed to have a predetermined thickness by grinding the back surface of the semiconductor wafer with a grinding device before being divided into individual devices.

However, if the back surface of the wafer is ground as described above, there is a problem in that grinding strain remains on the back surface of the wafer and the bending strength of the divided devices is lowered.
In order to solve such problems, a technique has been proposed in which the grinding distortion generated on the back surface of the wafer is removed by performing plasma etching on the back surface of the wafer, and the bending strength of the device is improved. A plasma etching apparatus that performs etching is disclosed in Patent Document 1 below.
JP 2004-221175 A

  The grinding strain generated on the back surface of the wafer is 1 to 2 [mu] m, and the grinding strain can be removed without causing any other problems because the grinding strain can be removed by etching 1 to 2 [mu] m. On the other hand, the wafer can be formed to a predetermined thickness by plasma etching the back surface of the wafer by several hundred μm without grinding the back surface of the wafer to a predetermined thickness. However, in the experiments by the present inventors, when the back surface of the wafer is plasma etched by several hundred μm, the etching amount at the center of the wafer increases, and the etching amount decreases as it goes to the outer periphery. It was found that a difference of μm occurred.

  The present invention has been made in view of the above facts, and a main technical problem thereof is to provide a plasma etching apparatus capable of etching a workpiece with a uniform thickness.

In order to solve the above-mentioned main technical problem, according to the present invention, a housing having an etching chamber and a workpiece holding portion having a holding surface disposed in the etching chamber and holding a workpiece on the upper surface are provided. The lower electrode unit, and an upper electrode provided with a plurality of jet nozzles that are disposed to face the holding surface of the workpiece holding portion of the lower electrode unit and jet gas for generating plasma toward the holding surface In a plasma etching apparatus comprising: a unit; and a plasma generating gas supply means for supplying a plasma generating gas to the plurality of jet nozzles provided in the upper electrode unit.
A chuck table rotating means for rotating the workpiece holder;
The plurality of jet holes provided in the upper electrode unit are formed such that the distance between the workpiece holding portion and the holding surface gradually decreases from the center toward the outer periphery,
The plasma generating gas supply means is configured such that the flow rate of the plasma generating gas ejected from the plurality of ejection ports provided in the upper electrode unit is increased from the center of the holding surface of the workpiece holding portion toward the outer periphery. Configured to increase,
A plasma etching apparatus is provided.

In the plasma etching apparatus according to the present invention, a chuck table rotating means for rotating the workpiece holding portion is provided, and the plasma generating gas supply means generates plasma that is ejected from a plurality of nozzles provided in the upper electrode unit. Since the flow rate of the working gas increases from the center of the workpiece held on the holding surface of the workpiece holding portion toward the outer periphery, the workpiece held on the holding surface of the workpiece holding portion is The central portion of the workpiece is not etched in a large amount, and is etched substantially uniformly from the center to the outer periphery.
The plasma etching apparatus according to the present invention further includes chuck table rotating means for rotating the workpiece holding unit, and the plurality of jet holes provided in the upper electrode unit are connected to the holding surface of the workpiece holding unit. Since the interval is formed so as to gradually decrease from the center toward the outer periphery, the central portion of the workpiece is not etched in a large amount and is etched substantially uniformly from the center to the outer periphery.

  Hereinafter, a preferred embodiment of a plasma etching apparatus constituted according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a cross-sectional view of a plasma etching apparatus constructed according to the present invention.
The plasma etching apparatus shown in FIG. 1 includes a housing 2 that forms an etching chamber 20. The housing 2 has a bottom wall 21, an upper wall 22, left and right side walls 23, 24, and a rear side wall 25 and a front side wall (not shown). The right side wall 24 has an opening for loading and unloading a workpiece. 241 is provided. Outside the opening 241, the gate 3 for opening and closing the opening 241 is disposed so as to be movable in the vertical direction. The gate 3 is actuated by the gate actuating means 4. The gate actuating means 4 includes an air cylinder 41 and a piston rod 42 connected to a piston (not shown) disposed in the air cylinder 41, and the air cylinder 41 is connected to the bottom of the housing 2 via a bracket 43. It is attached to the wall 21 and the tip (upper end in the figure) of the piston rod 42 is connected to the gate 3. When the gate 3 is opened by the gate operating means 4, the semiconductor wafer 100 as a workpiece can be carried in and out through the opening 241. The bottom wall 21 constituting the housing 2 is provided with an exhaust port 211, and the exhaust port 211 is connected to the gas discharge means 5.

In the etching chamber 20 formed by the housing 2, the lower electrode 6 and the upper electrode 7 are disposed to face each other.
The lower electrode 6 is formed of a conductive material, and includes a disk-shaped workpiece holding portion 61 and a columnar supporting portion 62 formed so as to protrude from the center of the lower surface of the workpiece holding portion 61. It is made up of. Thus, the lower electrode 6 composed of the workpiece holding portion 61 and the columnar support portion 62 is disposed by inserting the support portion 62 through the hole 212 formed in the bottom wall 21 of the housing 2. It is rotatably supported in a state of being sealed by the bottom wall 21 via the insulator 8. Thus, the lower electrode 6 supported on the bottom wall 21 of the housing 2 is electrically connected to the high-frequency power source 10 via the support portion 62.

  A circular fitting recess 611 having an open top is provided at the upper portion of the work piece holding portion 61 constituting the lower electrode 6. The fitting recess 611 is formed of a porous ceramic material and holds the upper surface. A disk-shaped suction holding member 63 serving as a surface is fitted. A chamber 611 a formed below the suction holding member 63 in the fitting recess 611 is communicated with the suction means 9 by a communication path 621 formed in the workpiece holding part 61 and the support part 62. Accordingly, the workpiece is placed on the holding surface which is the upper surface of the suction holding member 63, the suction means 9 is operated, and the communication passage 621 is connected to the negative pressure source, whereby a negative pressure is applied to the chamber 611a, and the suction is performed. The workpiece placed on the holding member 63 is sucked and held. In addition, by operating the suction means 9 to open the communication path 621 to the atmosphere, the suction holding of the workpiece sucked and held on the suction holding member 63 is released.

  A cooling passage 612 is formed in the lower part of the work piece holding part 61 constituting the lower electrode 6. One end of the cooling passage 612 communicates with a refrigerant introduction passage 622 formed in the support portion 62, and the other end of the cooling passage 612 communicates with a refrigerant discharge passage 623 formed in the support portion 62. The refrigerant introduction passage 622 and the refrigerant discharge passage 623 are in communication with the refrigerant supply means 11. Therefore, when the refrigerant supply means 11 is activated, the refrigerant is circulated through the refrigerant introduction passage 622, the cooling passage 612, and the refrigerant discharge passage 623. As a result, heat generated during plasma processing, which will be described later, is transmitted from the lower electrode 6 to the refrigerant, so that an abnormal temperature increase of the lower electrode 6 is prevented.

  The lower electrode 6 configured as described above is configured such that the support portion 62 is connected to the electric motor 12 and is rotated by the electric motor 12.

  The upper electrode 7 is formed of a conductive material, and includes a gas ejection part 71 and a columnar support part 72 formed so as to protrude from the upper surface of the gas ejection part 71. As described above, the upper electrode 7 composed of the gas ejection part 71 and the columnar support part 72 is disposed so as to face the adsorption holding member 63 of the workpiece holding part 61 that constitutes the lower electrode 6. The support 72 is inserted through a hole 221 formed in the upper wall 22 of the housing 2 and supported by the seal member 12 mounted in the hole 221 so as to be movable in the vertical direction. An operation member 73 is attached to the upper end portion of the support portion 72, and this operation member 73 is connected to the elevation drive means 13. The upper electrode 7 is grounded through the support portion 72.

The gas ejection part 71 constituting the upper electrode 7 is formed so as to face the outer peripheral part from the central part of the suction holding member 63 of the workpiece holding part 61 of the lower electrode 6, and a plurality of openings opening on the lower surface thereof. Nozzle outlets 711a, 711b, and 711c are provided. In the illustrated embodiment, the plurality of jet outlets 711a, 711b, and 711c are arranged such that the jet outlet 711a is at the center of the suction holding member 63, and the jet outlet 711b is between the center and the outer periphery of the suction holding member 63. Is arranged so as to face the outer periphery of the suction holding member 63. The plurality of jet outlets 711a, 711b, and 711c formed in this way are communicated with the plasma generating gas supply means 14 via the communication passages 721a, 721b, and 721c formed in the gas jet part 71 and the support part 72, respectively. ing. The plasma generating gas supply means 14 includes a plasma generating mixed gas supply source 141 mainly composed of fluorine gas such as SF ₆ and oxygen, the mixed gas supply source 141 and the communication passages 721a, 721b, 721c. Are connected to the pipes 142a, 142b, 142c, respectively, and electromagnetic on-off valves 143a, 143b, 143c and flow rate adjusting valves 144a, 144b, 144c. The plasma generation gas supply means 14 configured in this way energizes (ON) the electromagnetic on-off valves 143a, 143b, 143c to open the circuit, and controls the voltages applied to the flow rate adjusting valves 144a, 144b, 144c, respectively. Thus, the flow rate of the plasma generating gas supplied to the communication passages 721a, 721b, 721c is adjusted. In the illustrated embodiment, the flow rate adjusting valve 144a is controlled so that the flow rate of the plasma generating gas supplied to the communication path 721a is 1 liter / min, and the flow rate adjusting valve 144b is used for generating plasma supplied to the communication path 721b. The gas flow rate is controlled to be 1.5 liters / minute, and the flow rate adjusting valve 144c is controlled so that the flow rate of the plasma generating gas supplied to the communication path 721c is 2 liters / minute. Therefore, the flow rate of the plasma generating gas ejected from the plurality of ejection ports 711a, 711b, and 711c is gradually increased from the center of the suction holding member 63 of the workpiece holding portion 61 of the lower electrode 6 toward the outer periphery. It has become.

  The plasma etching apparatus in the illustrated embodiment includes an electromagnetic opening / closing of the gate operating means 4, gas discharge means 5, suction means 9, high frequency power supply 10, refrigerant supply means 11, electric motor 12, elevating drive means 13, and gas supply means 14. Control means 15 for controlling the valves 143a, 143b, 143c, the flow rate adjusting valves 144a, 144b, 144c and the like is provided. Data relating to the pressure in the etching chamber 20 formed by the housing 2 from the gas discharge means 5 and data relating to the refrigerant temperature (ie, electrode temperature) from the refrigerant supply means 11 are input to the control means 15. Based on this, the control means 15 outputs a control signal to each of the above means.

The plasma etching apparatus in the illustrated embodiment is configured as described above, and an example of performing plasma etching (dry etching) on the back surface of the semiconductor wafer will be described below.
FIG. 4 shows a perspective view of a semiconductor wafer as a workpiece. A semiconductor wafer 100 shown in FIG. 4 is made of, for example, a silicon wafer having a thickness of 700 μm. A plurality of streets 101 are formed in a lattice shape on the surface 100a, and a plurality of streets partitioned by the plurality of streets 101 are formed. A device 102 such as an IC or LSI is formed in the region. As shown in FIG. 5, a protective tape 110 made of a resin film having a thickness of 100 μm is attached to the surface 100a of the semiconductor wafer 100 thus configured (protective member attaching step). Therefore, the back surface 100b of the semiconductor wafer 100 is exposed.

  In order to form a predetermined thickness by plasma etching (dry etching) on the back surface of the semiconductor wafer 100 formed as described above, first, the gate operating means 4 is operated and the gate 3 is moved downward in FIG. The opening 241 provided in the right side wall 24 of the housing 2 is opened. Next, the above-described semiconductor wafer 100 is transported from the opening 241 to the etching chamber 20 formed by the housing 2 with the back surface 100b upward by unshown loading / unloading means, and the lower electrode 6 is configured as shown in FIG. It is placed on the suction holding member 63 of the workpiece holding part 61. At this time, the raising / lowering drive means 13 is operated and the upper electrode 7 is raised. Then, the semiconductor wafer 100 placed on the suction holding member 63 is sucked and held by operating the suction means 9 to apply a negative pressure to the chamber 611a as described above.

  When the semiconductor wafer 100 is sucked and held on the suction holding member 63, the gate operating means 4 is operated to move the gate 3 upward in FIG. 1 and close the opening 241 provided on the right side wall 24 of the housing 2. . Then, the elevating drive means 13 is operated to lower the upper electrode 7 and held on the lower surface of the gas injection portion 71 constituting the upper electrode 7 and the workpiece holding portion 61 constituting the lower electrode 6 as shown in FIG. The distance between the upper surface of the semiconductor wafer 100 (the back surface 100b: the surface to be etched) is positioned at a predetermined inter-electrode distance (D). This inter-electrode distance (D) is set to 10 mm in the illustrated embodiment.

Next, an etching chamber formed by the housing 2 is operated by operating an electrostatic force generating means (not shown) disposed in the workpiece holding portion 61 to hold the semiconductor wafer 100 with electrostatic force and operating the gas discharging means 5. 20 is exhausted. When the etching chamber 20 is evacuated and decompressed, the control means 15 drives the electric motor 12 to rotate the lower electrode 6 at a rotational speed of, for example, 100 rpm. The control means 15 energizes (ON) the electromagnetic on-off valves 143a, 143b, 143c of the plasma generating gas supply means 14 to open the circuit, and controls the voltages applied to the flow rate adjusting valves 144a, 144b, 144c, respectively. To adjust the flow rate. As a result, from the plasma generation gas supply means 141 of the plasma generation gas supply means 14 through the electromagnetic on-off valves 143a, 143b, 143c, the flow rate adjustment valves 144a, 144b, 144c, the communication passages 721a, 721b, 721c It is ejected from 711a, 711b, 711c toward the back surface 100b of the semiconductor wafer 100 held on the suction holding member 63 of the lower electrode 6. Then, the inside of the etching chamber 20 is maintained at a predetermined gas pressure. In this way, a high frequency voltage is applied between the lower electrode 6 and the upper electrode 7 from the high frequency power supply 10 in a state where the mixed gas for generating plasma is supplied. As a result, SF ₆ plasma is generated in the space between the lower electrode 6 and the upper electrode 7, and the back surface 100b of the semiconductor wafer 100 is etched by the action of the active material generated by this plasma (etching step). In this etching step, the flow rate of the flow rate adjustment valves 144a, 144b, 144c is adjusted to be the smallest as described above, and the flow rate of the flow rate adjustment valve 144b and the flow rate adjustment valve 144c is gradually increased. Therefore, the flow rate of the plasma generating gas ejected from the ejection port 711a opening toward the center of the semiconductor wafer 100 held on the adsorption holding member 63 of the lower electrode 6 is the smallest, and ejection from the ejection port 711b and the ejection port 711c. The flow rate of the plasma generating gas is gradually increased. Accordingly, the central portion of the semiconductor wafer 100 held on the adsorption holding member 63 of the lower electrode 6 is not etched in a large amount and is uniformly etched from the center of the semiconductor wafer 100 to the outer periphery. Even if the semiconductor wafer 100 having a thickness of 700 μm is etched to a thickness of 100 μm, it can be formed to have a substantially uniform thickness.

  A cutting groove having a depth corresponding to the finished thickness of the device is formed from the surface 100b side of the semiconductor wafer 100, and then the etching process is performed to etch the surface 100b of the semiconductor wafer 100. When the semiconductor wafer 100 is divided into individual devices by exposing the surface to the surface 100b, a device having a high bending strength can be obtained.

Next, another embodiment of the upper electrode 7 will be described with reference to FIG. In the embodiment shown in FIG. 3, the same members in the embodiment shown in FIGS. 1 and 2 are denoted by the same reference numerals, and detailed description thereof is omitted.
The upper electrode 7 shown in FIG. 3 adsorbs a region 71 a that faces the center of the suction holding member 63 of the workpiece holding portion 61 in the gas ejection portion 71 and a region 71 b that faces the center of the suction holding member 63 and the middle of the outer periphery. Steps are provided at the height positions of the regions 71 c facing the outer periphery of the holding member 63. That is, the region 71 a in the gas ejection part 71 is set to a position where the distance from the holding surface which is the upper surface of the adsorption holding member 63 is the largest, and the region 71 b and the region 71 c in the gas ejection part 71 are the upper surface of the adsorption holding member 63. The distance from the holding surface is set to gradually decrease. In the gas ejection part 71 formed in this way, an ejection port 711a is provided so as to open on the lower surface of the region 71a, an ejection port 711b is provided so as to open on the lower surface of the region 71b, and an opening is formed on the lower surface of the region 71c. A spout 711c is provided. For this reason, when the plasma generating gas is ejected from the ejection port 711a, the ejection port 711b, and the ejection port 711c toward the workpiece held on the adsorption holding member 63 of the lower electrode 6, the central portion of the workpiece Is not etched in a large amount and is etched substantially uniformly from the center to the outer periphery. When the upper electrode 7 shown in FIG. 3 is implemented, the flow rate adjusting valves 144a, 144b, 144c of the plasma generating gas supply means 14 shown in FIG. 1 need not be provided.

1 is a cross-sectional view of a plasma etching apparatus configured according to the present invention. Sectional drawing which expands and shows the principal part of the lower electrode and upper electrode which comprise the plasma etching apparatus shown in FIG. The principal part expanded sectional view which shows other embodiment of the upper electrode which comprises the plasma etching apparatus shown in FIG. The perspective view of the semiconductor wafer as a to-be-processed object. The perspective view which shows the state which affixed the protective tape on the surface of the semiconductor wafer shown in FIG.

Explanation of symbols

2: Housing 20: Sealed space 221: Exhaust port 241: Opening for carrying in / out the workpiece 3: Gate 4: Gate operating means 5: Gas discharging means 6: Lower electrode 61: Workpiece holding part 612: Cooling passage 62 : Supporting part 622: Refrigerant introduction passage 623: Refrigerant discharge passage 63: Adsorption holding member 7: Upper electrode 71: Gas ejection part 711a, 711b, 711c: Outlet 72: Support part 73: Actuating member 76: Gas injection member 77: Annular partition wall 9: Suction means 10: High frequency power supply 11: Refrigerant supply means 12: Elevating drive means 13: Elevating drive means 14: Gas generating gas supply means 141 1: Supply source of mixed gas for generating plasma 143a, 143b, 143c : Electromagnetic on-off valves 144a, 144b, 144c: Flow rate adjusting valve 15: Control means 100: Semiconductor wafer

Claims (1)

A housing including an etching chamber; a lower electrode unit including a workpiece holding portion disposed in the etching chamber and holding a workpiece on an upper surface; and holding the workpiece of the lower electrode unit An upper electrode unit provided with a plurality of jets arranged to face the holding surface of the unit and jetting plasma generating gas toward the holding surface, and the plurality of jets provided in the upper electrode unit A plasma generating gas supply means for supplying a plasma generating gas to the plasma etching apparatus,
A chuck table rotating means for rotating the workpiece holder;
The plurality of jet holes provided in the upper electrode unit are formed such that the distance between the workpiece holding portion and the holding surface gradually decreases from the center toward the outer periphery ,
The plasma generating gas supply means is configured such that the flow rate of the plasma generating gas ejected from the plurality of ejection ports provided in the upper electrode unit is increased from the center of the holding surface of the workpiece holding portion toward the outer periphery. Configured to increase,
A plasma etching apparatus characterized by that.

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