JP7708515B2 - Plasma etching apparatus and plasma etching method - Google Patents

Description

This disclosure relates to a plasma etching apparatus and a plasma etching method.

The plasma etching apparatus described in Patent Document 1 includes a vacuum chamber, an electrostatic chuck table, a nozzle, a nozzle oscillating means, and a control means. The electrostatic chuck table holds a workpiece in the vacuum chamber. The nozzle supplies plasma etching gas to a portion of the workpiece held on the electrostatic chuck table. The nozzle oscillating means oscillates the nozzle so as to trace a horizontal arc-shaped trajectory. The control unit controls the amount of rotation of the electrostatic chuck and the position of the nozzle to supply plasma etching gas to any portion of the workpiece.

JP 2016-219594 A

One aspect of the present disclosure provides a technique for adjusting the thickness of a substrate.

A plasma etching apparatus according to one aspect of the present disclosure includes a substrate holding unit, a plasma generating unit, a nozzle, an electrode, a high-frequency power supply, a moving unit, and a control unit. The substrate holding unit holds a substrate inside a processing chamber. The plasma generating unit converts an etching gas for etching the substrate into plasma outside the processing chamber. The nozzle supplies the plasma-converted etching gas to a portion of the substrate held by the substrate holding unit. The electrode is provided on the substrate holding unit. The high-frequency power supply applies a bias high-frequency power to the electrode. The moving unit moves the supply position of the plasma-converted etching gas on the substrate. The control unit controls the plasma generating unit, the high-frequency power supply, and the moving unit. The control unit changes the voltage of the high-frequency power according to the supply position.

According to one aspect of the present disclosure, the thickness of the substrate can be adjusted.

FIG. 1 is a diagram showing a plasma etching apparatus according to an embodiment. FIG. 2 is a diagram illustrating an example of the operation of the moving unit in FIG. FIG. 3 is a flow chart showing an example of a substrate processing method. FIG. 4 is a diagram showing an example of a substrate before being thinned. FIG. 5 is a diagram showing an example of a grinding device used to thin a substrate. FIG. 6 is a diagram showing an example of a trajectory of the grindstone. FIG. 7 is a diagram showing a first example of the arrangement of the discharge nozzles. FIG. 8 is a diagram showing a second example of the arrangement of the discharge nozzles. FIG. 9 is a diagram showing a third example of the arrangement of the discharge nozzles. FIG. 10 is a diagram showing a fourth example of the arrangement of the discharge nozzles.

Embodiments of the present disclosure will be described below with reference to the drawings. Note that the same or corresponding configurations in each drawing are given the same reference numerals, and descriptions thereof may be omitted. In this specification, the X-axis direction, the Y-axis direction, and the Z-axis direction are perpendicular to each other. The X-axis direction and the Y-axis direction are horizontal directions, and the Z-axis direction is vertical.

First, a plasma etching apparatus 1 according to one embodiment will be described with reference to Figures 1 and 2. The plasma etching apparatus 1 etches a substrate W using an etching gas that has been converted into plasma. In this embodiment, the plasma etching apparatus 1 is a vacuum plasma apparatus, but may also be an atmospheric pressure plasma apparatus.

The plasma etching apparatus 1 includes, for example, a processing vessel 10, an exhaust section 15, a substrate holding section 20, a plasma generating section 30, a nozzle 40, an electrode 50, a high-frequency power supply 51, a moving section 60, and a control section 90.

The processing vessel 10 has a processing chamber 11 inside. The processing vessel 10 has a loading/unloading port 12 for the substrate W and a gate valve 13 that opens and closes the loading/unloading port 12.

The exhaust unit 15 reduces the pressure in the processing chamber 11 by exhausting the gas in the processing chamber 11. The exhaust unit 15 includes a pipe 16 connected to the processing vessel 10. Although not shown, the exhaust unit 15 includes an opening/closing valve provided in the middle of the pipe 16 and a pressure controller provided in the middle of the pipe 16.

When a reduced pressure source such as a vacuum pump is activated and the on-off valve opens the pipe 16, the pipe 16 sucks in the gas in the processing chamber 11. The gas pressure in the processing chamber 11 is controlled by a pressure controller. The pressure controller includes a pressure adjustment valve such as a butterfly valve.

The substrate holding unit 20 holds the substrate W inside the processing chamber 11. The substrate holding unit 20 is, for example, an electrostatic chuck. The electrostatic chuck can adsorb the substrate W under a reduced pressure atmosphere. Note that when the plasma etching apparatus 1 etches the substrate W under atmospheric pressure, the substrate holding unit 20 may be a vacuum chuck.

The plasma generating unit 30 converts an etching gas for etching the substrate W into plasma outside the processing chamber 11. The etching gas that has been converted into plasma contains radicals. The radicals include, for example, ions. The radicals collide with the first main surface Wa of the substrate W to etch the substrate W. Although not shown, the plasma generating unit 30 includes, for example, an electrode for generating plasma and a high-frequency power supply that supplies high-frequency power to the electrode.

The plasma generating unit 30 converts the etching gas into plasma, for example, using microwaves. The frequency of the microwaves is, for example, 2.45 GHz. The plasma is not limited to microwave plasma, and may be capacitively coupled plasma or inductively coupled plasma, etc. Any plasma that can generate radicals may be used. The high-frequency power used for generating the plasma has a frequency of, for example, 450 kHz to 2.45 GHz, and a voltage of, for example, 0.5 kV to 5 kV.

Although not shown, the plasma generating unit 30 has a gas supply chamber in which an electrode for plasma generation is provided, and converts the etching gas into plasma in the gas supply chamber. The etching gas may be a mixed gas, for example, a mixed gas of _SF6 gas and _O2 gas. In addition to the etching gas, a dilution gas for diluting the etching gas may be supplied to the gas supply chamber. An inert gas such as Ar gas is used as the dilution gas.

The plasma generating unit 30 includes, for example, an individual pipe for each type of gas, an on-off valve provided in the middle of the individual pipe, and a flow controller provided in the middle of the individual pipe. When the on-off valve opens the individual pipe, gas is supplied from the supply source to the gas supply chamber. The supply amount is controlled by the flow controller. On the other hand, when the on-off valve closes the individual pipe, the supply of gas from the supply source to the gas supply chamber is stopped.

The nozzle 40 supplies the etching gas that has been converted into plasma by the plasma generating unit 30 to a portion of the substrate W held by the substrate holding unit 20. The nozzle 40 has a discharge nozzle 41 that discharges the etching gas that has been converted into plasma. The discharge nozzle 41 discharges the etching gas that has been converted into plasma, for example, perpendicular to the first main surface Wa of the substrate W. The discharge nozzle 41 has a discharge port 41a at its lower end.

The flow rate and supply time of the plasmatized etching gas are controlled, for example, using a flow rate controller and an on-off valve of the plasma generating unit 30. The higher the flow rate of the plasmatized etching gas, the faster the etching speed. Also, the longer the supply time of the plasmatized etching gas, the greater the amount of etching.

The nozzle 40 may have a suction nozzle 42 surrounding the discharge nozzle 41. The discharge nozzle 41 and the suction nozzle 42 form a double tube. The suction nozzle 42 narrows the area to be etched on the substrate W by sucking in the plasma etching gas. The suction port 42a at the lower end of the suction nozzle 42 is installed, for example, lower than the discharge port 41a at the lower end of the discharge nozzle 41.

The electrode 50 is provided on the substrate holding part 20. For example, the electrode 50 is embedded inside the substrate holding part 20. When the substrate holding part 20 holds the substrate W horizontally, the electrode 50 has a size equal to or larger than that of the substrate W when viewed from the vertical direction. A high-frequency power source 51 is electrically connected to the electrode 50.

The high frequency power supply 51 applies high frequency power to the electrode 50. This high frequency power is for drawing radicals of the etching gas that has been turned into plasma into the substrate W, and is also bias power for controlling the energy of the radicals. The high frequency bias power has a frequency of, for example, 0.1 MHz to 100 MHz, and a voltage of, for example, 0.5 kV to 5 kV. The high frequency bias power is controlled independently of the high frequency power for generating plasma.

The high frequency power supply 51 applies high frequency power to the electrode 50 to generate a sheath region near the first main surface Wa of the substrate W. The sheath region is a region where radicals such as ions repeatedly collide with the first main surface Wa of the substrate W. The collision of the radicals etches the first main surface Wa of the substrate W. The higher the voltage of the high frequency power, the higher the radical energy and the faster the etching rate.

The moving unit 60 moves the supply position of the plasmatized etching gas on the substrate W. The moving unit 60 has, for example, a rotational moving unit 61 and a linear moving unit 62. The rotational moving unit 61 rotates the substrate holding unit 20. The rotational moving unit 61 includes, for example, a motor. The linear moving unit 62 moves the substrate holding unit 20 in a direction perpendicular to the center line of rotation of the substrate holding unit 20. The linear moving unit 62 includes, for example, a motor and a ball screw that converts the rotational motion of the motor into linear motion.

When the substrate holding unit 20 holds the substrate W horizontally, the rotational movement unit 61 rotates the substrate holding unit 20 around a vertical rotation center line, and the linear movement unit 62 moves the substrate holding unit 20 horizontally. Note that the movement unit 60 only needs to move the substrate holding unit 20 and the nozzle 40 relatively, and may also move the nozzle 40. The movement unit 60 may also move the nozzle 40 in a swiveling manner, as in Patent Document 1.

The control unit 90 is, for example, a computer, and includes a CPU (Central Processing Unit) 91 and a storage medium 92 such as a memory. The storage medium 92 stores programs that control various processes executed in the plasma etching apparatus 1. The control unit 90 controls the operation of the plasma etching apparatus 1 by having the CPU 91 execute the programs stored in the storage medium 92.

Next, a substrate processing method using the plasma etching apparatus 1 shown in Figs. 1 and 2 will be described with reference to Fig. 3. The substrate processing method includes, for example, steps S101 to S103 shown in Fig. 3. The plasma etching apparatus 1 performs step S103.

In step S101 of FIG. 3, the substrate W is thinned. The substrate W is, for example, a silicon wafer, but may also be a compound semiconductor wafer. The substrate W may also be a glass substrate. As shown in FIG. 4, the substrate W has a first main surface Wa and a second main surface Wb facing opposite to the first main surface Wa.

The first main surface Wa of the substrate W is etched by the plasma etching apparatus 1. A device (not shown) is formed on the second main surface Wb of the substrate W. The device is, for example, an electronic circuit, and is formed in each area partitioned by a plurality of streets shown by dashed lines in FIG. 4. After step S103, the substrate W is cut along the plurality of streets and divided into a plurality of chips.

A protective film F for protecting devices may be formed on the second main surface Wb of the substrate W. The protective film F protects the devices while the substrate W is being thinned. The protective film F covers the entire second main surface Wb of the substrate W. The protective film F is removed after the substrate W is thinned. Instead of forming the protective film F on the second main surface Wb of the substrate W, a second substrate separate from the substrate W may be bonded. The second substrate is a silicon wafer, a compound semiconductor wafer, or a glass substrate. Devices may also be formed on the surface of the second substrate facing the substrate W.

To thin the substrate W, for example, a grinding device 100 shown in FIG. 5 is used. The grinding device 100 includes, for example, a flange 101, a spindle shaft 102, a first rotary motor 103, a chuck 104, and a second rotary motor 105.

The flange 101 is provided at the lower end of the spindle shaft 102. A grinding tool D is attached to the flange 101. The grinding tool D includes, for example, a disk-shaped grinding wheel D1 and a plurality of grinding stones D2 arranged in a ring shape on the lower surface of the grinding wheel D1. The first rotary motor 103 rotates the spindle shaft 102 about the rotation center line R1, thereby rotating the grinding tool D.

The chuck 104 holds the substrate W from below with the first main surface Wa of the substrate W facing upward. The suction surface of the chuck 104 that suctions the substrate W, i.e., the upper surface of the chuck 104, may be a conical surface that is symmetrical about the rotation center line R2 of the chuck 104. The thickness distribution in the radial direction of the substrate W can be adjusted by adjusting the inclination angle of the rotation center line R2 of the chuck 104. The second rotation motor 105 rotates the chuck 104 about the rotation center line R2, thereby rotating the substrate W.

As shown in FIG. 6, the trajectory E of the multiple grinding wheels D2 arranged in a ring shape is set to pass through the center of the upper surface of the substrate W. In addition, the substrate W is attracted to the chuck 104 so that the center of the upper surface of the substrate W passes through the rotation center line R2 of the chuck 104. As the substrate W rotates together with the chuck 104, the entire upper surface of the substrate W is ground by the grinding wheels D2.

After grinding, the substrate W has a thickness distribution. The thickness variation is expressed, for example, as the difference between the maximum and minimum thickness values (TTV: Total Thickness Variation). The thickness variation is caused, for example, by the relative speed difference between the grinding wheel D2 and the substrate W on the trajectory E of the grinding wheel D2 shown in FIG. 6. When a protective film F is used, the thickness variation increases due to deformation of the protective film F.

A laser processing device (not shown) may be used to thin the substrate W. The laser processing device forms a modified layer inside the substrate W. A plurality of modified layers are formed at intervals in the radial and circumferential directions of the substrate W. The substrate W can be thinned by dividing the substrate W starting from the plurality of modified layers. In this case, the substrate W after thinning has a thickness distribution.

In step S102 in FIG. 3, the thickness distribution of the thinned substrate W is measured. The measuring device 200 shown in FIG. 1 is used to measure the thickness distribution of the substrate W. The location where the thickness distribution of the substrate W is measured may be inside the grinding device 100 or the laser processing device, inside the plasma etching device 1, or along the transport path that transports the substrate W from the grinding device 100 or the laser processing device to the plasma etching device 1.

The measuring device 200 may be either a non-contact type or a contact type, but is preferably a non-contact type. The non-contact type measuring device 200 measures the thickness distribution of the substrate W, for example, by using infrared light that transmits through the substrate W and utilizing the interference between the light reflected from the first main surface Wa of the substrate W and the light reflected from the second main surface Wb of the substrate W. The non-contact type measuring device 200 may measure the thickness distribution of the substrate W by measuring the distance to the substrate W using a capacitance type displacement sensor or a laser displacement sensor.

The measuring device 200 transmits measurement data of the thickness distribution of the substrate W to the plasma etching device 1. The transmitted measurement data includes coordinates on the first main surface Wa of the substrate W and the thickness of the substrate W for each coordinate. The control unit 90 of the plasma etching device 1 receives the measurement data transmitted by the measuring device 200, and controls the etching of the substrate based on the received measurement data of the thickness distribution of the substrate W, thereby performing control to reduce thickness unevenness of the substrate W.

In step S103 in FIG. 3, plasma etching is performed on the substrate W. For plasma etching of the substrate W, the plasma etching apparatus 1 shown in FIG. 1 and FIG. 2 is used. The control unit 90 of the plasma etching apparatus 1 performs control to change the voltage of the bias high frequency power according to, for example, the supply position of the plasmatized etching gas. This makes it possible to adjust the thickness distribution of the substrate W.

Specifically, for example, the control unit 90 acquires measurement data of the thickness distribution of the substrate W, and performs control to change the voltage of the bias high frequency power based on the acquired measurement data. The control unit 90 sets the voltage of the bias high frequency power higher at positions where the substrate W is thicker, for example, based on the minimum thickness of the substrate W. This makes it possible to reduce unevenness in the thickness of the substrate W.

In addition, the control unit 90 may control the flow rate or supply time of the plasmatized etching gas instead of or in addition to controlling the voltage of the bias high-frequency power. For example, the control unit 90 uses the minimum thickness of the substrate W as a reference and sets a higher flow rate or a longer supply time for positions on the substrate W where the thickness is thicker. This can reduce unevenness in the thickness of the substrate W.

The thickness distribution of the substrate W has the same tendency, for example, for each lot of the substrate W. Therefore, the control unit 90 may perform control to reduce unevenness in the thickness of the substrate W by previously storing the supply position of the plasmatized etching gas in correspondence with the voltage of the high-frequency bias power, etc., and controlling the etching of the substrate W according to the stored data.

Next, the number and arrangement of the discharge nozzles 41 will be described with reference to Figures 7 to 10. In Figures 7 to 10, the black circle indicates the center of the first main surface Wa of the substrate W. As shown in Figure 7, when there is one discharge nozzle 41, the substrate W is rotated around the Z axis and moved in the X axis direction so that the supply position of the plasmatized etching gas is displaced over the entire first main surface Wa of the substrate W.

As shown in Figure 8, even when multiple discharge nozzles 41 are arranged in the radial direction of the substrate W, the substrate W rotates around the Z axis and moves in the X axis direction. The more discharge nozzles 41 are used, the shorter the movement distance of the substrate W in the X axis direction can be, improving throughput. As shown in Figures 9 and 10, it is also possible to reduce the movement distance of the substrate W in the X axis direction to zero.

The multiple discharge nozzles 41 can independently control the flow rate and supply time of the plasmatized etching gas. The control unit 90 controls to change the flow rate or supply time of the plasmatized etching gas for each discharge nozzle 41 independently. The control unit 90 controls to change the flow rate or supply time for each discharge nozzle 41 independently depending on the thickness of the substrate W at the discharge position of the discharge nozzle 41.

The control unit 90 sets a higher flow rate or a longer supply time for the discharge nozzle 41 located at a position where the thickness of the substrate W is thicker, for example, based on the minimum thickness of the substrate W. This makes it possible to reduce unevenness in the thickness of the substrate W. When the minimum thickness of the substrate W is the target value, it is preferable to perform control so that etching gas is not discharged from the discharge nozzle 41 located at the position where the thickness of the substrate W is minimum.

The control unit 90 may control the voltage of the bias high frequency power instead of, or in addition to, changing the flow rate or supply time of the plasmatized etching gas. Specifically, the control unit 90 controls the voltage of the bias high frequency power to be set higher at positions where the thickness of the substrate W is thicker, for example, based on the minimum thickness of the substrate W. This reduces unevenness in the thickness of the substrate W. When the minimum thickness of the substrate W is the target value, it is preferable to control so that the etching gas is not discharged from the discharge nozzle 41 arranged at the position where the thickness of the substrate W is the minimum.

As shown in FIG. 9, multiple discharge nozzles 41 may be arranged in a staggered manner, or as shown in FIG. 10, multiple discharge nozzles 41 may be arranged randomly. If there is a discharge port 41a with the same width as each of the multiple regions A1 to A4 formed by radially dividing the first main surface Wa of the substrate W directly above each of the multiple regions A1 to A4, then plasmatized etching gas can be supplied to the entire first main surface Wa of the substrate W simply by rotating the substrate W around the Z axis.

Although the embodiments of the plasma etching apparatus and plasma etching method according to the present disclosure have been described above, the present disclosure is not limited to the above embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. Naturally, these also fall within the technical scope of the present disclosure.

Reference Signs List 1 Plasma etching apparatus 11 Processing chamber 20 Substrate holder 30 Plasma generator 40 Nozzle 50 Electrode 51 High frequency power source 60 Moving unit 90 Control unit W Substrate

Claims (10)

a substrate holder for holding a substrate within the processing chamber;
a plasma generating unit that generates plasma from an etching gas for etching the substrate outside the processing chamber;
a nozzle that supplies the etching gas in the plasma form to a portion of the substrate held by the substrate holder;
An electrode provided on the substrate holder;
a high frequency power supply that applies high frequency bias power to the electrode;
a moving unit that moves a supply position of the etching gas plasma on the substrate;
A control unit that controls the plasma generating unit, the high frequency power supply, and the moving unit;
Equipped with
The control unit performs control to change the voltage of the high frequency power in accordance with the supply position. The plasma etching apparatus of claim 1, wherein the control unit acquires measurement data of the thickness distribution of the substrate and performs control to change the voltage of the high frequency power based on the acquired measurement data. The plasma etching device according to claim 1 or 2, wherein the control unit performs control to change the flow rate or supply time of the plasmatized etching gas depending on the supply position. a substrate holder for holding a substrate within the processing chamber;
a plasma generating unit that generates plasma from an etching gas for etching the substrate outside the processing chamber;
a nozzle that supplies the etching gas in the plasma form to a portion of the substrate held by the substrate holder;
a moving unit that moves a supply position of the etching gas plasma on the substrate;
A control unit that controls the plasma generating unit and the moving unit;
Equipped with
the plasma generating unit includes a flow rate controller that controls a flow rate of the etching gas that has been converted into plasma and is discharged from the nozzle;
The control unit controls the flow rate controller to change a flow rate of the etching gas plasma discharged from the nozzle in accordance with the supply position. 5. The plasma etching apparatus according to claim 4 , wherein the control unit acquires measurement data of a thickness distribution of the substrate, and controls the flow rate controller to change the flow rate based on the acquired measurement data. the moving unit includes a rotation moving unit that rotates the substrate holding unit to rotate the substrate,
6. The plasma etching apparatus according to claim 1, further comprising a plurality of the nozzles in a radial direction of the substrate. holding a substrate on a substrate holder inside a processing chamber;
generating a plasma of an etching gas for etching the substrate outside the processing chamber;
discharging the etching gas plasma from a nozzle and supplying the etching gas to a portion of the substrate held by the substrate holder;
applying a high frequency bias power to an electrode provided on the substrate holding unit;
moving a supply position of the etching gas plasma on the substrate;
changing a voltage of the high frequency power in accordance with the supply position;
The plasma etching method comprises: The plasma etching method according to claim 7, comprising acquiring measurement data of the thickness distribution of the substrate, and changing the voltage of the high frequency power based on the acquired measurement data. The plasma etching method according to claim 7 or 8, wherein a plurality of the nozzles are arranged in the radial direction of the substrate. A plasma etching method , comprising: etching the substrate by using the plasma etching apparatus according to claim 4 or 5 .