JP6014143B2 - Dry etching apparatus and dry etching method - Google Patents

Description

  The present invention relates to a dry etching apparatus and a dry etching method for performing a dry etching process on a substrate such as a silicon wafer.

  2. Description of the Related Art Conventionally, a dry etching apparatus that has a flat mounting surface and performs a dry etching process on a substrate such as a silicon wafer is known (see Patent Document 1). This type of dry etching apparatus is used, for example, in a manufacturing process of a rotary vibration gyro.

JP 2011-188798 A

  By the way, when performing an etching process, as shown in FIG. 8, it is normal to introduce | transduce cooling gas into the back surface of the board | substrate W mounted in the flat mounting surface 23. FIG. In this case, the etching process is performed on the substrate W which is slightly deformed into a circular arc shape protruding upward (see FIG. 8A). For this reason, the etching direction with respect to the substrate is not perpendicular, and the etching direction is tilted (inclined radially outward of the substrate W from the surface of the substrate W to the back) (see FIG. 8B). ). In addition, the code | symbol W1 of FIG. 8 and FIG. 9 shows a resist layer (protective film).

Further, as shown in FIG. 9, ECR type (Electron Cycloton Resonance) ICP type (Inductive Coupling: Inductive Coupling)
In the case of a remote plasma type dry etching apparatus such as Plasma), since the plasma ion traveling direction d spreads outward, the radial direction of the substrate W unless the apparatus (plasma generation region) is considerably larger than the diameter of the substrate W. As it goes outward, plasma ions are obliquely incident on the substrate W placed on the flat placement surface 23. In this case, the etching direction with respect to the substrate W does not become vertical, and tilt occurs (inclination toward the outside in the radial direction of the substrate W from the surface of the substrate W). In addition, when the substrate W has a circular arc shape protruding upward as described above, the tilt angle in the etching direction increases. As described above, it is difficult to perform etching perpendicular to the surface of the substrate W with high accuracy.

  In the etching process of the rotational vibration type gyro described above, when a tilt occurs in the etching direction of the substrate, the cross section of the elongated detection spring and the drive spring is formed in a parallelogram shape. In this case, especially when the cross section of the drive spring is formed in a parallelogram shape, the detection weight generates a vibration (right-angle component error) different from the Coriolis force, which adversely affects the detection of angular velocity (noise). It was.

  An object of the present invention is to provide a dry etching apparatus and a dry etching method capable of performing etching perpendicularly with high accuracy to the surface of a substrate.

The dry etching apparatus of the present invention has a mounting surface formed in a downwardly recessed shape, and a cooling gas introduction channel for introducing a cooling gas into the gap between the back surface of the substrate and the mounting surface. A chamber having an electrostatic adsorption unit that electrostatically adsorbs a substrate to be processed, a plasma generation chamber in which plasma ions are generated, and a processing chamber in which the electrostatic adsorption unit is accommodated, and the substrate is flat or downward And a controller that controls the pressure of the cooling gas in the gap so as to have a concave arcuate cross section .

The dry etching method of the present invention has a mounting surface formed in a downwardly recessed shape, and a cooling gas introduction channel for introducing a cooling gas into the gap between the back surface of the substrate and the mounting surface. In a dry etching apparatus including an electrostatic adsorption unit that performs electrostatic adsorption, a plasma generation chamber in which plasma ions are generated, and a processing chamber in which the electrostatic adsorption unit is accommodated, a cooling gas in a gap It is characterized in that the pressure is controlled and a dry etching process is performed on a substrate that is flat or has a circular arc shape that is recessed downward.

According to this configuration, by electrostatically attracting the substrate to the mounting surface that is recessed downward, the electrostatically attracted substrate can be flat or have a circular arc section (spherical crown shape) that is recessed downward. It becomes possible. For this reason, when the traveling directions of the plasma ions are aligned in parallel, the etching direction with respect to the substrate can be made perpendicular to the entire area of the substrate by making the electrostatically attracted substrate flat. In addition, when the plasma ion travels outward, the electrostatically adsorbed substrate has a cross-sectional arc shape that is recessed downward, so that the etching direction with respect to the substrate can be made vertical throughout the substrate. Become. Therefore, it is possible to perform etching perpendicular to the surface of the substrate with high accuracy.
Further, according to this configuration, when cooling gas is introduced into the gap between the back surface of the substrate and the mounting surface in order to cool the substrate, the substrate is flattened by controlling the pressure of the cooling gas in the gap. It can be made to have a circular arc shape that is recessed downward. That is, when it is desired to flatten the substrate electrostatically attracted to the mounting surface, the cooling gas pressure in the gap may be controlled to a relatively large value. On the other hand, when it is desired to make the substrate electrostatically attracted to the mounting surface into a circular arc shape with a downward recess, the pressure of the cooling gas in the gap may be controlled to a relatively small value.

  In this case, it is preferable that the mounting surface is formed of a spherical crown-shaped concave surface.

According to this configuration, the mounting surface includes a concave portion having a flat bottom surface and a flat portion connected to the periphery thereof via a step portion. The distance becomes closer. For this reason, a board | substrate can be electrostatically adsorbed appropriately.
Note that the placement surface is constituted by a spherical crown-shaped concave surface is not limited to the entire placement surface being constituted by a spherical crown-shaped concave surface, for example, a flat portion is formed on the periphery of the placement surface. It is a concept that includes the one that has been processed or the peripheral edge of which is countersunk.

It is a figure which shows the structure of the dry etching apparatus which concerns on one Embodiment of this invention. It is a figure which shows the structure of the electrostatic chuck and cooling gas introducing | transducing part of a dry etching apparatus. In a dry etching apparatus, it is a figure which shows the state which made the board | substrate electrostatically adsorbed with respect to the mounting surface flat by controlling the pressure of the cooling gas in a board | substrate back side gap to a comparatively big value. The figure which shows the state which made the board | substrate electrostatically adsorbed with respect to the mounting surface into the circular arc shape dented below by controlling the pressure of the cooling gas in the back side gap | interval in a dry etching apparatus to a comparatively small value. It is. It is a figure for demonstrating the amount of dents of a board | substrate. It is a figure which shows the modification of the mounting surface of an electrostatic chuck. It is a figure which shows the rotational vibration type gyro manufactured by performing the dry etching process with respect to a board | substrate with a dry etching apparatus, (a) is the top view, (b) is the sectional drawing. FIG. 5 is a diagram showing that an etching process is performed on a substrate having an arcuate cross section protruding upward in a dry etching apparatus according to a conventional technique. In the dry etching apparatus which concerns on a prior art, it is a figure which shows that an etching process is performed with respect to a flat board | substrate, when the advancing direction of plasma ion spreads outside.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. As shown in FIG. 1, the dry etching apparatus 1 according to the present embodiment is of an ECR type, and includes a chamber 11 including an upper plasma generation chamber 11a and a lower processing chamber 11b, and the periphery of the plasma generation chamber 11a. The electrostatic chuck 13 that electrostatically attracts the substrate W such as a silicon wafer to be etched, and the back side of the substrate W via the electrostatic chuck 13. And a cooling gas introduction part 14 (see FIG. 2) for introducing the cooling gas into the apparatus.

  The coil 12 forms a magnetic field having a magnetic flux density (B = 87.5 mT) that satisfies the ECR condition in the plasma generation chamber 11a. Further, a microwave transmitter (not shown) that generates microwaves (2.45 GHz) having a frequency that satisfies the ECR condition is connected to the upper wall of the plasma generation chamber 11a via the waveguide 15.

  A high frequency power supply 16 for RF (Radio Frequency) bias is connected to the electrostatic chuck 13 via a matching circuit (not shown). A gas supply nozzle 17 for supplying a reactive gas (for example, a fluorine-based gas) is connected to the upper part of the plasma generation chamber 11a. Further, a vacuum pump (not shown) is connected to the lower portion of the processing chamber 11b through an exhaust port 18. The electrostatic chuck 13 and the cooling gas introduction unit 14 will be described later.

  Here, the operation of the dry etching apparatus 1 will be briefly described. First, the substrate W to be etched is set on the electrostatic chuck 13. After the insides of the plasma generation chamber 11a and the processing chamber 11b are evacuated, a reactive gas is supplied from the gas supply nozzle 17 into the plasma generation chamber 11a. Subsequently, the coil 12 is energized to form a magnetic field in the plasma generation chamber 11a. At this time, when a microwave is supplied from the waveguide 15 to the plasma generation chamber 11a, electron cyclotron resonance occurs, and the reactive gas in the plasma generation chamber 11a is ionized by the accelerated electrons, thereby generating plasma ions. The

  Plasma ions generated in the plasma generation chamber 11a are drawn into the processing chamber 11b and applied to the surface of the substrate W by applying an RF bias from the high frequency power supply 16 to the substrate W, and the substrate W is etched. The This etching process is performed while cooling the substrate W by the cooling gas introduction unit 14.

  Next, the electrostatic chuck 13 and the cooling gas introduction unit 14 will be described with reference to FIG. The electrostatic chuck 13 is formed in a disk shape and has a cooling function, a disk-shaped dielectric layer 22 bonded on the metal plate 21, and embedded in the dielectric layer 22. And an internal electrode 24 connected to the power supply circuit 27. The upper surface of the dielectric layer 22 is a mounting surface 23 on which the substrate W is mounted. The mounting surface 23 is slightly recessed downward, that is, a spherical crown-shaped concave surface (circular arc). (In FIG. 2 etc., the dent amount is exaggerated). The internal electrode 24 also has a shape (cross-sectional arc) that follows the mounting surface 23. Although details will be described later, the substrate W electrostatically attracted to the mounting surface 23 is flat or has a cross-sectional arc shape recessed downward.

  Further, the electrostatic chuck 13 is formed with a cooling gas introduction hole 25 that penetrates the metal plate 21 and the dielectric layer 22 and continues to the cooling gas introduction portion 14. In this embodiment, the cooling gas introduction holes 25 are formed at the centers of the metal plate 21 and the dielectric layer 22, but a plurality of cooling gas introduction holes 25 may be formed in the outer peripheral regions of the metal plate 21 and the dielectric layer 22. It may be formed in both the center and the outer peripheral region.

  The cooling gas introduction unit 14 includes a gas source 31 storing a cooling gas, a gas introduction pipe 32 connecting the gas source 31 and the cooling gas introduction hole 25 of the electrostatic chuck 13, and an intervening gas introduction pipe 32. The mass flow controller 33 and the pressure gauge 34 are provided. Then, the cooling gas stored in the gas source 31 passes through the gas introduction pipe 32 and the cooling gas introduction hole 25, and is at the gap between the back surface of the substrate W electrostatically attracted to the electrostatic chuck 13 and the placement surface 23. It is introduced into a certain substrate back side gap 26. Note that an inert gas such as helium can be suitably used as the cooling gas.

  Then, based on the pressure value detected by the pressure gauge 34, the introduction of the cooling gas is intermittently turned on / off by the mass flow controller 33, whereby the pressure of the cooling gas in the substrate back side gap 26 is stabilized at a required value. So that it is controlled. That is, after the required pressure value is reached, the amount of cooling gas introduced into the substrate back side gap 26 is controlled to be equal to the amount of cooling gas flowing out (leakage amount) from the substrate back side gap 26. In this embodiment, the pressure of the cooling gas in the substrate back side gap 26 is controlled by the flow rate of the introduced cooling gas, but may be controlled by the pressure of the introduced cooling gas. In this case, for example, a pressure adjusting valve is provided in the gas introduction pipe 32.

  Then, by controlling the pressure of the cooling gas in the substrate back side gap 26 to a relatively large value, the substrate W electrostatically attracted to the placement surface 23 can be flattened as shown in FIG. . In this way, by making the electrostatically attracted substrate W flat, the etching direction with respect to the substrate W is made vertical in the entire region of the substrate W when the traveling directions of plasma ions are aligned in parallel. Can do.

  On the other hand, by controlling the pressure of the cooling gas in the substrate back side gap 26 to be relatively small, as shown in FIG. 4, a cross section in which the substrate W electrostatically attracted to the mounting surface 23 is recessed downward. It can be deformed into an arc shape. In this way, by making the electrostatically attracted substrate W into a circular arc shape that is recessed downward, the etching direction with respect to the substrate W is made vertical in the entire region of the substrate W even when the plasma ion travels outward. can do.

Here, when the following θ is sufficiently small, the dent amount ΔH of the substrate W can be approximated as follows (see FIG. 5).
ΔH = πrθ / 360
r: radius of the substrate W θ: spread angle in the direction of travel of plasma ions [degrees]
For example, when a 6-inch wafer (r = 75 mm) substrate W is used and θ = 1 degree, ΔH = 654 μm. Therefore, the pressure in the substrate back side gap 26 may be controlled so that the amount of depression ΔH of the substrate W becomes 654 μm. In this case, the mounting surface 23 of the electrostatic chuck 13 is formed in a shape that allows the amount of recess of the substrate W by ΔH = 654 μm.

  In the present embodiment, the mounting surface 23 is configured by a spherical crown-shaped concave surface (circular arc). However, as shown in FIG. 6, a flat portion 23 a is provided on the periphery of the mounting surface 23 of the electrostatic chuck 13. It may be formed (see FIG. 6A) or may be in contact with the substrate W at the flat portion 23a (see FIG. 6B). Further, a counterbore portion 23b that is counterbored may be provided on the periphery of the mounting surface 23, and a flat portion 23a may be formed on the outer edge thereof (see FIG. 6C).

  Furthermore, the mounting surface 23 is not a spherical crown-shaped concave surface, but is constituted by a shallow concave portion 23c having a flat bottom surface and a flat portion 23a connected to the periphery thereof through a step portion, and is in contact with the substrate W by the flat portion 23a. You may make it (refer FIG.6 (d)). However, as in the present embodiment, the placement surface 23 is formed of a spherical crown-shaped concave surface, so that the distance from the placement surface 23 is reduced in the entire substrate W, so that the substrate W is appropriately electrostatically adsorbed. be able to.

  As described above, according to the dry etching apparatus 1 of the present embodiment, the electrostatically attracted substrate W is protruded upward by electrostatically attracting the substrate W to the mounting surface 23 recessed downward. Instead of the circular arc shape, the cross-sectional arc shape can be flat or recessed downward. For this reason, the etching can be performed perpendicularly to the surface of the substrate W with high accuracy.

  In the present embodiment, the dry etching apparatus 1 has been described by taking an ECR type as an example, but the dry etching apparatus 1 is not limited to this, and an ICP type or the like of a remote plasma system is preferably used. it can. In the remote plasma dry etching apparatus 1, plasma is generated at a position (plasma generation chamber 11 a) away from the substrate W, and plasma ions are drawn toward the substrate W therefrom. For this reason, in the remote plasma method, the traveling direction of plasma ions tends to spread outward, but according to the dry etching apparatus 1 of the present embodiment, as described above, even when the traveling direction of plasma ions spreads outward. The etching direction with respect to the substrate W can be made vertical throughout the substrate W.

  And the dry etching apparatus 1 of this embodiment can be used suitably for the manufacturing process of the rotational vibration gyroscope 100 shown in FIG. 7, for example. The rotational vibration type gyro 100 includes an annular driving weight 101 formed on a substrate W (silicon wafer), a disc-shaped detection weight 102 disposed concentrically inside the driving weight 101, and a substrate W. An anchor 103 that supports the driving weight 101 and the detection weight 102, a detection spring 104 that spans between the anchor 103 and the detection weight 102, and functions as a hinge of the detection weight 102 that vibrates, and a driving weight 101 and a detection weight 102, and a drive spring 105 that absorbs rotational vibration of the drive weight 101 and transmits only the Coriolis force to the detection weight 102.

  The rotational vibration gyro 100 rotates and vibrates the driving weight 101 around the Z axis passing through the center of gravity, and swings the detection weight 102 by the Coriolis force generated when an angular velocity is applied around an axis orthogonal to the Z axis. The angular velocity is detected from the change in capacitance due to this peristaltic movement. Then, the drive weight 101, the detection weight 102, the detection spring 104, the drive spring 105, and the like are released and formed through an etching process for the substrate W in several stages.

In the etching process of the rotational vibration gyro 100, when a tilt occurs in the etching direction with respect to the substrate W, the cross section of the detection spring 104 and the drive spring 105 formed in an elongated shape is formed in a parallelogram shape. In this case, in particular, when the cross section of the drive spring 105 is formed in a parallelogram shape, the detection weight 102 is caused to vibrate different from the Coriolis force (right angle component error), which adversely affects the detection of the angular velocity. become. In this respect, according to the dry etching apparatus 1 of the present embodiment, since the etching can be performed perpendicularly to the surface of the substrate W with high accuracy, the drive spring 105 and the like can be formed with a rectangular cross section with high accuracy. Therefore, it is possible to manufacture the rotational vibration gyro 100 that can accurately detect the angular velocity.
The dry etching apparatus 1 can be suitably used for manufacturing processes of other MEMS (Micro Electro Mechanical Systems) devices and semiconductor devices besides the rotational vibration gyroscope 100.

  1: dry etching apparatus, 13: electrostatic chuck, 14: cooling gas introduction section, 23: mounting surface, 26: substrate back side gap, 33: mass flow controller, 34: pressure gauge, W: substrate

Claims (3)

The substrate having a mounting surface formed in a downwardly recessed shape, and a cooling gas introduction channel for introducing a cooling gas into a gap between the back surface of the substrate and the mounting surface, and is subjected to dry etching processing An electrostatic adsorption part that electrostatically adsorbs,
A chamber having a plasma generation chamber in which plasma ions are generated, and a processing chamber in which the electrostatic adsorption unit is accommodated;
A control unit for controlling the pressure of the cooling gas in the gap so that the substrate is flat or has a circular arc shape recessed downwards;
Dry etching apparatus comprising the. The dry etching apparatus according to claim 1, wherein the mounting surface is formed of a spherical crown-shaped concave surface. An electrostatic surface for electrostatically adsorbing the substrate , comprising a mounting surface formed in a downwardly recessed shape, and a cooling gas introduction channel for introducing a cooling gas into the gap between the back surface of the substrate and the mounting surface. An adsorbing part;
In a dry etching apparatus comprising: a plasma generation chamber in which plasma ions are generated; and a chamber having a processing chamber in which the electrostatic adsorption unit is accommodated.
The pressure of the cooling gas to control, to the substrate that has a cross section arcuate recessed flat or downward, dry etching method and performing dry etching process in the gap.

Images