JP6340655B2 - Plasma processing apparatus and plasma processing method - Google Patents

Description

  The present invention relates to a plasma processing apparatus, and more particularly, to a technique effective for plasma processing of a wafer held on a conveyance carrier including an annular frame and a holding sheet.

  As plasma processing apparatuses, those disclosed in Patent Documents 1 and 2 are known. These plasma processing apparatuses are intended for processing a wafer held on a transport carrier including an annular frame and a holding sheet. When the wafer is diced with plasma, the annular frame is prevented from being exposed to plasma by covering the annular frame with a cover.

Japanese Patent No. 4858395 US Application Publication No. 2012/0238073

  However, in the conventional plasma processing apparatus, the annular frame is not directly exposed to the plasma by a covering made of a material having excellent etching resistance such as quartz and ceramics, but the etching is repeatedly performed. As a result of the heat accumulated in the cover ring over time, the holding sheet suffers from heat damage.

  Therefore, an object of the present invention is to prevent thermal damage received by the holding sheet of the transport carrier due to plasma processing.

  According to a first aspect of the present invention, there is provided a plasma processing apparatus for performing a plasma process on a substrate held by a conveyance carrier composed of an annular frame and a holding sheet, and a chamber having a depressurizable internal space; A substantially flat upper surface having a plasma source for generating plasma, a first region provided in the chamber and on which the carrier is placed, and a second region extending outward from the first region And a cover disposed above the stage so as to overlap the second region in plan view, the stage including an electrode portion, and the electrode portion from the first region A plasma treatment comprising a built-in electrostatic adsorption electrode that occupies an area extending to the second area, and cooling means for cooling the electrode section in the second area from the first area. To provide a device.

It is front sectional drawing which shows the outline of the plasma processing apparatus which concerns on this embodiment. It is the elements on larger scale of FIG. FIG. 3 is a plan view of FIG. 2. (A) to (d) is a partial cross-sectional view showing various examples of a protection portion formed on the cover of FIG.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings. In the following description, terms indicating specific directions and positions (for example, terms including “up”, “down”, “side”, “end”) are used as necessary. Is for facilitating understanding of the invention with reference to the drawings, and the technical scope of the present invention is not limited by the meaning of these terms. Further, the following description is merely illustrative in nature and is not intended to limit the present invention, its application, or its use.

  FIG. 1 shows a dry etching apparatus 1 which is an example of a plasma processing apparatus according to an embodiment of the present invention. In this embodiment, the dry etching apparatus 1 performs plasma dicing and subsequent ashing on the wafer (substrate) 2. Plasma dicing is a method in which a wafer 2 on which a plurality of IC parts (semiconductor devices) are formed is cut at a boundary line (street) using dry etching and divided into individual IC parts. Referring to FIG. 2, a wafer 2 that is circular in the present embodiment has a front surface 2a on which an IC portion or the like (not shown) is formed, and a back surface 2b opposite to the front surface 2a (an IC portion or the like is not formed). ). A mask 3 is formed on the upper surface of the wafer 2 with a pattern for plasma dicing.

  The dry etching apparatus 1 includes a chamber 4 having an internal space that can be decompressed. In the chamber 4, the transport carrier 5 can be stored in the internal space through the entrance / exit 4 a. The transport carrier 5 includes a holding sheet 6 that detachably holds the wafer 2. As the holding sheet 6, for example, a so-called UV tape that can be elastically stretched and holds the wafer 2 by adhesive force, but changes its chemical characteristics due to irradiation of ultraviolet rays and greatly reduces the adhesive force can be used. . One surface is an adhesive surface (adhesive surface 6a) and the other is an adhesive surface (non-adhesive surface 6b). The holding sheet 6 is flexible and can be easily bent by itself to maintain a fixed shape. For this reason, a substantially ring-shaped thin frame 7 (annular frame) 7 is attached to the adhesive surface 6 a near the outer peripheral edge of the holding sheet 6. The frame 7 is made of, for example, a metal such as stainless steel or aluminum, or resin, and has a rigidity capable of holding the shape together with the holding sheet 6.

  The wafer 2 is held on the holding sheet 6 of the transport carrier 5 by sticking the back surface 2b to the adhesive surface 6a. As shown in FIG. 3, the wafer 2 is disposed in the center of a circular region 6 c surrounded by the frame 7 on the adhesive surface 6 a of the holding sheet 6. Specifically, the position of the wafer 2 with respect to the holding sheet 6 is such that the center Cs of the circular region 6c and the center Cw of the wafer 2 (center when the wafer 2 is viewed from the front surface 2a or the back surface 2b) are substantially coincident. Is set. By disposing the wafer 2 in the center of the circular region 6 c, a wide annular region 6 d having a constant width is formed between the wafer 2 of the holding sheet 6 and the frame 7. And it is set so that the outer periphery of RF electrode 21 may be located in this annular region 6d in plan view.

  As shown in FIG. 1, an antenna 9 (plasma source) as an upper electrode is disposed above a dielectric wall 8 that closes the top of a chamber 4 (vacuum vessel) of the dry etching apparatus 1. The antenna 9 is electrically connected to the first high frequency power supply unit 10. On the other hand, on the bottom side in the chamber 4, the stage 11 on which the transfer carrier 5 holding the wafer 2 is placed is disposed as described above. A process gas source 12 and an ashing gas source 13 are connected to the gas inlet 8 a of the chamber 4, and a decompression mechanism 14 including a vacuum pump for evacuating the chamber 4 is connected to the exhaust port 4 b.

  As shown in FIG. 2, the stage 11 includes an electrostatic chuck 16A, an electrode portion 15 including an electrode portion main body 16B disposed below the electrostatic chuck 16A, and a base portion disposed below the electrode portion main body 16B. 17 and an exterior part 18 surrounding these outer peripheries. The stage 11 is provided with a cooling device 19.

According to a second aspect of the present invention, there is provided a plasma processing method for performing plasma processing on a substrate held by a carrier made up of an annular frame and a holding sheet , the carrier carrier being carried into a chamber, A stage having a substantially flat upper surface having a second region extending outward from the first region, and a built-in electrostatic chucking electrode occupying a region extending from the first region to the second region A step of placing the cover on the first region, a step of arranging a cover above the stage on which the carrier is placed so as to overlap the second region in plan view, and And a step of cooling the electrode part in the second region by a cooling means .

  The electrode part main body 16B of the electrode part 15 is comprised with the metal (for example, aluminum alloy). A coolant channel 24 is formed in the cooling unit 16.

  The cooling device 19 includes a refrigerant flow path 24 formed in the cooling unit 16 and a refrigerant circulation device 25. The refrigerant circulation device 25 circulates the temperature-controlled refrigerant in the refrigerant flow path 24 and maintains the cooling unit 16 at a desired temperature. In the cooling device 19 in the present embodiment, the first region and the second region of the stage 11 can be cooled, that is, both the transport carrier 5 and the cover 28 can be cooled. As a result, the plasma processing apparatus can be miniaturized and the structure can be simplified.

  The exterior portion 18 is made of an earth shield material (a metal having conductivity and etching resistance). The exterior part 18 protects the electrode part 15, the cooling part 16, and the base part 17 from plasma.

  The transport carrier 5 is placed on the electrode portion 15 of the stage 11 with the surface (adhesive surface 6 a) of the holding sheet 6 holding the wafer 2 facing upward, and the non-adhesive surface 6 b of the holding sheet 6 is the electrode portion 15. Touch the top surface of. The transport carrier 5 is placed at a predetermined position and posture with respect to the electrode portion 15 by a transport mechanism (not shown) (including a rotational angle position around the center Cs of the circular region 6 c of the holding sheet 6). Hereinafter, the predetermined position and posture are referred to as a normal position.

  The transport carrier 5 placed at the regular position is lifted and discharged by the first drive rod 26 after the processing described later. The first drive rod 26 is driven up and down by a first drive mechanism 27 conceptually shown only in FIG. Specifically, the transport carrier 5 can be moved to the raised position shown in FIG. 1 and the lowered position shown in FIG.

  A cover 28 that moves up and down above the stage 11 is provided in the chamber 4. The cover 28 is made of a metal material such as aluminum or an aluminum alloy, or a ceramic material having excellent thermal conductivity such as silicon carbide or aluminum nitride. The cover 28 has a circular outer contour and has a window 32 on the inner diameter side. It is formed into a thin donut shape.

  The outer diameter of the cover 28 is formed sufficiently larger than the outer contour of the transport carrier 5. This is because the holding sheet 6 and the frame 7 of the carrier 5 are covered and protected from plasma during plasma processing.

  The inner diameter of the cover 28 is set in a range of ± 2 mm with respect to the outer diameter of the wafer 2. In the example shown in FIG. 4, the inner diameter dimension of the cover 28 is larger than the outer diameter dimension of the wafer 2, but the inner diameter dimension of the cover 28 is smaller than the outer diameter dimension of the wafer 2 to You may make it cover with the cover 28. FIG.

  When the cover 28 is lowered, the lower surface thereof is brought into surface contact with the upper surface of the second region. This region is on the outer peripheral side of the stage 11, and a sufficient contact area can be ensured. Therefore, the heat of the cover 28 can be easily released to the second region, and the cover 28 can be efficiently cooled. In addition, by bringing the lower surface of the cover 28 into surface contact with the upper surface of the second region close to the frame 7, thermal damage to the transport carrier 5 (sheet, frame, wafer) can be effectively prevented. In particular, it is possible to suppress heating of the frame that is likely to become high temperature due to radiant heat, and to prevent thermal damage of the sheet in contact therewith.

  In order to improve the adhesion between the cover 28 and the second region, an elastic sheet, an O-ring, or the like may be provided on the lower surface of the cover 28 or the upper surface of the second region. Thereby, the cooling effect of the cover 28 can be further improved.

  As shown in FIG. 4A, the upper surface of the cover 28 has a protect portion 28a formed of a material having low reactivity with plasma, such as quartz, alumina, aluminum nitride, aluminum fluoride, silicon carbide, silicon nitride. Yes. A material different from that of the cover 28 is used for the protect portion 28a, but which material should be selected in consideration of the relationship with the process gas to be used. Note that a conductive layer may be formed on the lower surface of the cover 28 (the portion that comes into contact with the electrode unit 15 described later) in order to increase the electrostatic adsorption force (for example, by attaching a conductive sheet).

  The protect part 28a does not necessarily have to be formed in the entire area of the upper surface. For example, as shown in FIG. 4B, the cover 28 may be formed only on the inner peripheral surface of the center hole (window portion 32) and a part of the upper surface connected thereto. Moreover, as shown in FIG.4 (c), the inner peripheral part of the cover 28 may be made into a step shape, and you may make it form the protection part 28a in the part, as shown in FIG.4 (d), From there, it may be formed on the outer diameter side. However, the protection part 28a is formed on the entire upper surface of the cover 28, so that a part of the cover 28 is scattered by the irradiated plasma and adheres to the wafer 2 disposed on the inner diameter side. This is preferable because it can be surely prevented. The protector 28a can be provided on the cover 28 by thermal spraying or assembly. If the material of the cover 28 is a metal material such as aluminum or an aluminum alloy, the protection portion 28a (coating layer) is formed by either a spraying method or an assembling method. Materials that can be used for radiation include quartz, alumina, aluminum nitride, aluminum fluoride, silicon carbide, and silicon nitride. Materials that can be used for assembly include quartz, alumina, aluminum nitride, silicon carbide, and silicon nitride. In the case of assembly, the plate-like material can be attached by bonding, fitting, fastening or the like to the cover 28. If the material of the cover 28 is a ceramic material such as silicon carbide or aluminum nitride, the cover 28 is made of any material of quartz, alumina, aluminum nitride, silicon carbide, or silicon nitride (plate, ring, block). The protection portion 28a is formed by attaching the cover 28 to the upper surface by fitting, fitting, fastening, or the like. In addition, when attaching the protection part 28a to the cover part 28 by an assembly, it is preferable to make the protection part 28a and the cover 28 point contact rather than surface contact. Specifically, by forming irregularities or protrusions on either or both, or by roughening the surface, the contact area between the protect portion 28a and the cover 29 is suppressed, and heat transfer from the protect portion 28a to the cover 28 is difficult. It can be a structure. Thereby, it becomes possible to prevent the heat damage of the conveyance carrier 5 more effectively.

  The outer diameter of the RF electrode 21 is the same as or larger than the outer diameter of the wafer 2. The larger the outer diameter of the RF electrode 21 is, the more advantageous the uniformity of the etching rate is. However, when the RF electrode 21 is too large, the generated plasma sheath region is applied to the cover 28, so that ions colliding with the cover 28 increase. However, there is a problem that the cover 28 is heated more intensely. Accordingly, it is important to appropriately design the outer diameter of the RF electrode 21 in order to achieve uniformity in the etching rate and prevention of overheating of the cover 28 (preventing excessive heating and high temperature). Become. In this embodiment, the outer diameter of the wafer 2, the outer diameter of the RF electrode 21, and the inner diameter of the cover 28 are formed so as to increase in order, thereby achieving uniformity in etching and prevention of overheating of the cover 28. Both are compatible.

  The cover 28 is moved up and down by the second drive rod 29. The cover 28 and the second drive rod 29 are fixed by screws or the like made of a material having excellent thermal conductivity. When the cover 28 is heated, the heat is radiated through the second drive rod 29. The second drive rod 29 is driven up and down by a second drive mechanism 30 conceptually shown only in FIG. The cover 28 is raised and lowered by raising and lowering the second drive rod 29. Specifically, the cover 28 can be moved to the raised position shown in FIG. 1 and the lowered position shown in FIG. Further, the lower surface of the cover 28 comes into contact with the upper surface of the electrode portion 15 of the stage 11 in the lowered position. As described above, the second drive mechanism 30 functions as an elevating unit that elevates and lowers the cover 28 with respect to the stage 11 and also makes contact with and separates the cover 28 from the mounting surface 11a of the stage 11 (the upper surface of the electrode unit 15). It also functions as a separation means.

  As shown in FIG. 1, the cover 28 in the raised position is located above the placement surface 11 a of the stage 11 with a sufficient interval. Therefore, if the cover 28 is in the raised position, the operation of placing the transport carrier 5 (holding the wafer 2) on the upper surface of the electrode portion 15 and the operation of lowering the transport carrier 5 from the upper surface of the electrode portion 15 are performed. It is possible to do.

  As shown in FIG. 2, the cover 28 in the lowered position covers the holding sheet 6 (excluding the portion holding the wafer 2) and the frame 7 of the transport carrier 5 in the normal position. Further, the outer peripheral lower surface of the cover 28 is in contact with the upper surface of the electrode portion 15 and is electrostatically adsorbed by the electrostatic adsorption electrode 20. In this state, the heat of the cover 28 can be radiated from the electrode portion 15, the base portion 17, and the exterior portion 18 to the outside via the chamber 4.

  In a state where the transport carrier 5 is covered with the cover 28, the ceiling surface 28b of the cover 28 has a sufficient gap a (for example, 5 mm) with respect to the frame 7 to prevent thermal influence during plasma processing. Further, the inclined surface 28 c of the cover 28 ensures a sufficient distance from the holding sheet 6 exposed on the inner diameter side of the frame 7. As is clear from the drawing, the cover 28 in the lowered position does not contact any of the frame 7, the holding sheet 6, and the wafer 2.

  A control device 31 schematically shown only in FIG. 1 includes a first high-frequency power supply unit 10, a process gas source 12, an ashing gas source 13, a decompression mechanism 14, a DC power supply 22, a second high-frequency power supply unit 23, and a refrigerant circulation device. 25, the operation of each element constituting the dry etching apparatus 1 including the first drive mechanism 27 and the second drive mechanism 30 is controlled.

  Next, operation | movement of the dry etching apparatus 1 of this embodiment is demonstrated.

  First, the transfer carrier 5 having the wafer 2 attached to the center of the circular area 6 c of the holding sheet 6 is carried into the chamber 4 by a transfer mechanism (not shown), and is placed at a normal position on the stage 11. At this time, the cover 28 is in the raised position (FIG. 1).

  Then, the second drive mechanism 29 is driven by the second drive mechanism 30 to lower the cover 28 from the raised position (FIG. 1) to the lowered position (FIG. 2). When the cover 28 is in the lowered position, the holding sheet 6 and the frame 7 of the transport carrier 5 are covered with the cover 28, and the wafer 2 is exposed from the window 32. Further, the cover 28 contacts the electrode portion 15 in the second region.

  Subsequently, a DC voltage is applied from the DC power source 22 to the electrostatic chucking electrode 20 to hold the wafer 2 on the upper surface of the electrode portion 15 of the stage 11 by electrostatic chucking. At this time, since the electrostatic attraction electrode 20 is disposed in the vicinity of the lower surface of the cover 28, a sufficient electrostatic force can be applied to stabilize the attraction state.

  Furthermore, while introducing a process gas for plasma dicing from the process gas source 12 into the chamber 4, the process gas is exhausted by the decompression mechanism 14, and the inside of the chamber 4 is maintained at a predetermined pressure. Thereafter, high frequency power is supplied from the first high frequency power supply unit 10 to the antenna 9 to generate plasma in the chamber 4 and irradiate the wafer 2 exposed from the window 32 of the cover 28. At this time, a bias voltage is applied to the RF electrode 21 of the stage 11 from the second high frequency power supply unit 23. Further, the stage 11 is cooled by the cooling device 19. In a portion (street) exposed from the mask 3 of the wafer 2, the surface 2a to the back surface 2b are removed by the physicochemical action of radicals and ions in the plasma, and the wafer 2 is divided into individual chips.

  By the way, in the above plasma dicing, the cover 28 is heated by being exposed to plasma, and the cover 28 is made of a material having excellent thermal conductivity. Therefore, the heat by the plasma can be efficiently released to the stage 11 (cooling unit 16), and the transport carrier 5 is not damaged by the heat.

  A protective portion 28a made of a material having low reactivity with plasma is formed on the upper surface of the cover 28. For this reason, the surface of the cover 28 is protected by the plasma and is not damaged. Therefore, a problem that a part of the material constituting the cover 28 scatters and adheres to the wafer 2 on the transfer carrier 5 arranged in the window portion does not occur, and the problem of contamination does not occur.

  Ashing is performed after plasma dicing is completed. While introducing an ashing process gas (for example, oxygen gas) from the ashing gas source 13 into the chamber 4, the pressure is reduced by the decompression mechanism 14 to maintain the inside of the chamber 4 at a predetermined pressure. Thereafter, high frequency power is supplied from the first high frequency power supply unit 10 to the antenna 9 to generate plasma in the chamber 4 and irradiate the wafer 2 exposed from the window 32 of the cover 28. The mask 3 is completely removed from the surface 2a of the wafer 2 by plasma irradiation.

  After ashing, the second drive mechanism 29 is driven by the second drive mechanism 30 to move the cover 28 from the lowered position to the raised position. Thereafter, the first drive rod 27 is driven by the first drive mechanism 27 to move the transport carrier 5 from the lowered position to the raised position, and the transport carrier 5 is carried out of the chamber by a transport mechanism (not shown).

  In addition, this invention is not limited to the structure described in the said embodiment, A various change is possible.

  For example, in the above embodiment, the second drive mechanism 30 (lifting means, contact / separation means) moves the cover 28 up and down with respect to the stage 11 via the second drive rod 29. As a configuration, the stage 11 may be moved up and down with respect to the cover 28 fixed in the chamber 4. Even in this case, since the cover 28 is made of a material having excellent heat conductivity, the heat of the cover 28 exposed to the plasma and heated can be radiated through the chamber 4. Therefore, similarly to the above-described embodiment, it is possible to prevent the occurrence of problems due to the cover 28 becoming hot and the transport carrier 5 being indirectly heated.

  Further, the electrostatic attraction electrode 20 is not limited to the bipolar type as in the embodiment, and may be a monopolar type.

  Further, in the present embodiment, the cover 28 is configured to be electrostatically attracted, but electrostatic adsorption of the cover 28 is not essential, and the electrostatic attracting electrode 20 may be at least in the first region.

  Moreover, the process performed with the dry etching apparatus 1 is not limited to plasma dicing and ashing, For example, normal dry etching may be sufficient. The dry etching apparatus 1 is not limited to the ICP type as in the embodiment, and may be a parallel plate type.

DESCRIPTION OF SYMBOLS 1 ... Dry etching apparatus 2 ... Wafer 3 ... Mask 4 ... Chamber 5 ... Conveyance carrier 6 ... Holding sheet 7 ... Frame 8 ... Dielectric wall 9 ... Antenna 10 ... 1st high frequency power supply part 11 ... Stage 12 ... Process gas source 13 ... Ashing gas source 14 ... Depressurization mechanism 15 ... Electrode part 16A ... Electrostatic chuck 16B ... Electrode part body 17 ... Base part 18 ... Exterior part 19 ... Cooling device (cooling means)
DESCRIPTION OF SYMBOLS 20 ... Electrode for electrostatic attraction 21 ... RF (high frequency) electrode 22 ... DC power supply 23 ... 2nd high frequency power supply part 24 ... Refrigerant flow path 25 ... Refrigerant circulation device 26 ... 1st drive rod 27 ... 1st drive mechanism 28 ... Cover 28a ... Protect part 28b ... Ceiling surface 28c ... Inclined surface 29 ... Second drive rod 30 ... Second drive mechanism 31 ... Control device

Claims (4)

A plasma processing apparatus for performing plasma processing on a substrate held by a carrier carrying an annular frame and a holding sheet,
A chamber having an internal space capable of decompression;
A plasma source for generating plasma in the chamber;
A stage provided in the chamber and having a substantially flat upper surface having a first region on which the carrier is placed and a second region extending outward from the first region;
A cover disposed above the stage so as to overlap the second region in plan view;
The stage includes an electrode part,
The electrode unit includes an electrostatic adsorption electrode that occupies a region extending from the first region to the second region;
A plasma processing apparatus, comprising: cooling means for cooling the electrode portions in the second region from the first region. The inner peripheral edge of the cover is located between the outer peripheral edge of the substrate held by the transport carrier placed on the stage and the inner peripheral edge of the frame in plan view,
The electrode unit includes an RF electrode to which a high frequency is applied, and an outer peripheral edge of the RF electrode is an annular region between the substrate and the frame of the holding sheet in a plan view, and the electrode of the cover The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus is located on an inner peripheral side of the inner peripheral edge. A plasma processing method for performing plasma processing on a substrate held by a carrier carrying an annular frame and a holding sheet,
By loading the transport carrier into the chamber, a first region, it said with the first region comprises a substantially planar upper surface and a second region that has spread outward, the second region from the first region a step you placed on the first region of the stage that incorporates the electrostatic attraction electrode occupying an area of up to,
Disposing a cover above the stage on which the transport carrier is placed so as to overlap the second region in plan view;
Cooling the electrode part in the second region from the first region by a cooling means;
A plasma processing method comprising: The inner peripheral edge of the cover is located between the outer peripheral edge of the substrate held by the transport carrier placed on the stage and the inner peripheral edge of the frame in plan view,
The electrode unit has a built-in RF electrode, the outer peripheral edge of the RF electrode, an annular region between the substrate and the frame of the holding sheet in plan view, the inner peripheral side of the inner peripheral edge of said cover The plasma processing method according to claim 3, wherein high-frequency power is applied to the RF electrode.

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