JP2011114178A - Plasma processing device and plasma processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma processing device and a plasma processing method that can cool not only a wafer, but also a tray during plasma processing. <P>SOLUTION: The wafer 10 is put in an opening 11a formed in the tray 11 first, and a lower-surface peripheral edge of the wafer 10 is held by a holding member 13 provided on a lower surface of the tray 11. Then the tray 11 and a lower electrode 12 as an electrostatic chuck are put closer to each other to insert the holding member 13 into a recess 14 formed in the lower electrode 12, the tray 11 is mounted on a tray mounting part of the lower electrode 12, and the wafer 10 is mounted on the wafer mounting part. Then while the wafer 10 and tray 11 are held by the electrostatic chuck, the wafer 10 and tray 11 are cooled by a cooling mechanism. When the wafer 10 is subjected to plasma process in this state, the wafer 10 and tray 11 are both cooled during the plasma processing, so that the wafer 10 is unlikely to have a temperature difference between a center part and an outer peripheral part thereof, thereby improving uniformity of etching. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a plasma processing apparatus and a plasma processing method.

  In order to reduce defects at the time of GaN crystal growth or increase the light extraction efficiency of the LED, it is performed to form irregularities in advance on the sapphire substrate before GaN is deposited (Patent Document 1). High-density plasma etching is used as a method for forming the unevenness. However, since the sapphire substrate is hard and difficult to process, it is necessary to perform plasma etching with high power. Then, since a large amount of heat is generated from the sapphire substrate during the plasma processing, it is necessary to discharge the heat and cool the sapphire substrate.

  Since high-density plasma etching is performed in a reduced pressure reaction vessel, heat is mainly discharged through the substrate mounting table. At this time, if the sapphire substrate and the mounting table are not sufficiently adhered to each other, the efficiency of heat transfer is poor and the sapphire substrate becomes hot and the photoresist is deformed or burnt, so that there is a problem that the sapphire substrate cannot be processed according to the pattern. .

  In Patent Documents 2 and 3, a large number of substrates are conveyed to a chuck region on the upper surface of the lower electrode by a perforated tray having a plurality of substrate holding portions whose lower surfaces are opened, and the substrate and the lower electrode are brought into close contact with each other and cooled by Coulomb force. Increasing efficiency is disclosed.

JP 2003-318441 A JP 2006-066417 A Japanese Unexamined Patent Publication No. 2007-109770

  In Patent Documents 2 and 3, cooling the back surface of the wafer is considered, but cooling the back surface of the tray is not considered. Therefore, the temperature difference between the wafer and the tray is increased during the plasma processing, and the outer peripheral portion of the wafer is affected by the heat from the tray. As a result, the photoresist on the outer peripheral portion of the wafer is burnt, or the etching rate varies between the central portion and the outer peripheral portion of the wafer, and uniform etching cannot be performed.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a plasma processing apparatus and a plasma processing method capable of cooling not only the wafer but also the tray during the plasma processing. is there.

The plasma processing apparatus according to the present invention, which has been made to solve the above problems,
In a plasma processing apparatus provided with a transfer tray for transferring a wafer to an electrostatic chuck,
The tray includes an opening in which the wafer is accommodated, and a holding member that is provided on the lower surface of the tray so as to extend downward and holds a lower surface periphery of the wafer accommodated in the opening,
The electrostatic chuck includes a tray placing portion on which the tray is placed, a recess into which the holding member is inserted when the tray is placed on the tray placing portion, and a wafer on which the wafer is placed. A mounting portion;
A cooling mechanism is provided in each of the wafer mounting unit and the tray mounting unit.

In addition, a plasma processing method according to the present invention, which has been made to solve the above problems,
A method of performing plasma processing using the plasma processing apparatus,
Storing the wafer in the opening of the tray and transporting the wafer to the electrostatic chuck;
Placing the tray on the tray placing unit and placing the wafer on the wafer placing unit;
And plasma processing while cooling the tray mounting portion and the wafer mounting portion.

  According to the plasma processing apparatus and the plasma processing method of the present invention, first, the wafer is put into the opening formed in the wafer transfer tray, and the lower surface periphery of the wafer is held by the holding member provided on the lower surface of the tray. Next, the tray and the electrostatic chuck are brought close to each other, a holding member is inserted into the concave portion formed in the electrostatic chuck, the tray is placed on the tray placement portion of the electrostatic chuck, and the wafer is placed on the wafer placement portion. Put. Next, the wafer and the tray are cooled by the cooling mechanism while the wafer and the tray are held by the electrostatic chuck. If the wafer is plasma-treated in this state, both the wafer and the tray are cooled during the plasma treatment, so that a temperature difference hardly occurs between the central portion and the outer peripheral portion of the wafer, and the etching uniformity is improved.

It is a figure explaining the tray and lower electrode of the plasma processing apparatus which is one Example of this invention, (a) is a longitudinal cross-sectional view before tray mounting, (b) is a longitudinal cross-sectional view after tray mounting. . The top view of a tray. The top view of a lower electrode. The expanded longitudinal cross-sectional view of a lower electrode. The transverse cross section of the lower electrode in the position which crosses a crevice.

  Embodiments of a plasma processing apparatus and a plasma processing method according to the present invention will be described below with reference to the drawings. The plasma processing apparatus of this embodiment includes a tray 11 for transporting the wafer 10 and a lower electrode 12 that holds the transported wafer 10 and also functions as an electrode for generating plasma.

  As shown in FIG. 1, the tray 11 for transporting the wafer 10 has three openings 11 a having a diameter substantially the same as the diameter of the wafer 10. For example, three holding members 13 are provided on the lower surface of the tray 11 so as to protrude downward from the peripheral edge of the opening 11a. The front end of the holding member 13 protrudes toward the center of the opening, and the wafer 10 is held by the protruding portion 13a during transfer. Examples of the wafer 10 include a sapphire substrate, a compound semiconductor substrate such as gallium nitride and silicon carbide, a silicon substrate, and a glass substrate.

  The holding member 13 is configured such that the upper surface of the protruding portion 13a is lower than the tray lower surface 11b. As shown in FIG. 2, in this embodiment, the holding member 13 holds a part of the outer periphery of the wafer 10, but it may be annular to hold the entire outer periphery of the wafer 10. However, the holding member 13 and the protruding portion 13a are preferably as small as possible in that a later-described recess 14 provided on the upper surface of the lower electrode 12 can be reduced. If the concave portion 14 is small, a larger number of later-described wafer cooling gas introduction grooves 15 can be formed in the lower electrode 12, so that the cooling effect of the wafer 10 is high.

  As shown in FIG. 3, the upper surface of the lower electrode 12 is divided into a wafer placement portion 16 that is a placement position of the wafer 10 and a tray placement portion 17 that is a region other than that and is a placement position of the tray 11. Their upper surfaces are in the same plane. The wafer placement unit 16 has a recess 14 into which the holding member 13 protruding from the rear surface of the tray 11 is inserted. As shown in FIG. 1B, the recess 14 is deeper than the protruding distance of the holding member 13 protruding from the back surface of the tray 11. For this reason, the lower surface 11 b of the tray 11 can be brought into contact with the upper surface of the lower electrode 12 by inserting the holding member 13 into the recess 14 and lowering the tray 11. At this time, the wafer 10 in the opening 11 a is placed on the wafer placement portion 16 (chuck region) of the lower electrode 12. In this state, the upper surface of the tray 11 and the upper surface of the wafer 10 are preferably in the same plane. Thereby, the etching amount of the center part and the outer peripheral part of the wafer 10 becomes more uniform.

  As shown in FIGS. 3 and 4, each wafer mounting portion 16 of the lower electrode 12 has a wafer cooling gas introduction hole 18 that is an inlet of helium gas for cooling the wafer 10, and a wafer cooling gas introduction hole 18. A wafer cooling gas introduction groove 15 serving as a flow path for the introduced helium gas is provided. Further, the tray mounting portion 17 includes a tray cooling gas introduction hole 19 that is an introduction port for helium gas for cooling the tray 11, and a tray that serves as a flow path for the helium gas introduced from the tray cooling gas introduction hole 19. A cooling gas introduction groove 20 is provided. Thus, by providing a cooling mechanism on the entire upper surface of the lower electrode 12 and cooling the back surfaces of the wafer 10 and the tray 11, a temperature difference between the wafer 10 and the tray 11 can be prevented from occurring during the plasma processing. As a result, the etching uniformity is improved at the center and the outer periphery of the wafer 10.

4 and 5, a comb-shaped electrostatic chuck electrode 21 for electrostatic chucking of the wafer 10 and the tray 11 is embedded in the lower electrode 12. The electrostatic chuck electrode 21 is disposed so as to straddle both the wafer mounting unit 16 and the tray mounting unit 17. In the plasma processing apparatus of this embodiment, since the wafer mounting portion 16 and the tray mounting portion 17 are on the same plane, the layout design of the electrostatic chuck electrode 21 can be facilitated, and the internal structure of the lower electrode 12 can be simplified. .
The electrostatic chuck electrode 21 may be deeper than the bottom surface of the recess 14, and as shown in FIG. 4, the bottom surface of the recess 14 and the surface of the lower electrode 12 (the surfaces of the wafer mounting portion 16 and the tray mounting portion 17. ). However, in the latter case, depending on the arrangement of the electrostatic chuck electrode 21, it is necessary to partially punch the electrostatic chuck electrode 21 in order to avoid the recess 14.
When manufacturing the lower electrode 12, it is only necessary to form the recess 14, the cooling gas introduction grooves 15, 20, etc. on the flat upper surface. Generation of (etching difference) can be suppressed.
In the plasma processing apparatuses described in Patent Documents 2 and 3, since the wafer placement portion is provided in each of the island-like protruding portions on the upper surface of the lower electrode, a separate electrostatic chuck is provided for each wafer placement portion. It is necessary to provide an electrode, and the structure inside the lower electrode is complicated. In addition, it is difficult to process each wafer mounting portion at the same height (projection amount), and there is a problem that etching spots (etching differences) are likely to occur between wafers.

As for the tray 11, the one made of aluminum or the one made of resin lined with metal has a large chucking effect by the electrostatic chuck electrode 21 on the back surface of the tray 11, so that the tray 11 can be in close contact with the tray mounting surface with a strong force. The cooling effect of the tray 11 is improved. As a result, the temperature difference between the wafer 10 and the tray 11 can be made less likely to occur, and the etching uniformity is improved at the center and the outer periphery of the wafer 10.
The tray 11 may be made of ceramic such as alumina. In the conventional plasma processing apparatus, a temperature difference tends to occur between the vicinity of the wafer and other parts of the tray during processing. Therefore, breakage such as cracking is likely to occur in the ceramic tray. Since both the tray and the tray are cooled, the temperature variation of the entire tray can be suppressed, and even a ceramic tray is not easily damaged.

Next, an embodiment when the wafer 10 is etched using the plasma processing apparatus will be described.
A sapphire substrate having a resist pattern of a predetermined shape made of a photoresist on the entire upper surface was used as the wafer 10, and they were accommodated one by one in each opening 11 a of the alumina tray 11.

  Next, the tray 11 is transported above the lower electrode 12 provided in the reaction vessel of the plasma processing apparatus, and the tray 11 is lowered while the holding member 13 of the tray 11 is inserted into the concave portion 14 of the lower electrode 12, and the wafer 10 was placed on the wafer placing portion 16, and the tray 11 was placed on the tray placing portion 17.

  Next, a voltage of 500 V was applied to the electrostatic chuck electrode 21 embedded in the lower electrode 12 to pass a direct current, and the wafer 10 and the tray 11 were fixed to the lower electrode 12 by Coulomb force.

  Next, helium gas of about 2000 Pa is introduced into the cooling gas introduction grooves 15 and 20 from the cooling gas introduction holes 18 and 19 provided in the wafer placement unit 16 and the tray placement unit 17 to cool the wafer 10 and the tray 11. Started.

Next, an etching gas was introduced into the reaction vessel, a predetermined high frequency power was applied to the ICP coil and the lower electrode 12 to turn the gas into plasma, and etching of the wafer 10 was started. As the etching gas, Cl ₂ and SiCl ₄ were used, the flow rate of Cl ₂ was 50 sccm, the flow rate of SiCl ₄ was 5 sccm, and the pressure was 0.6 Pa. The ICP and bias power were 800 W and 500 W, respectively, and the frequency was 13.56 MHz.

  Thereafter, after 165 seconds, the etching process was terminated, and the introduction of the cooling gas and the energization to the electrostatic chuck electrode 21 were stopped. Thereafter, the tray 11 was raised upward to lift the wafer 10, and the tray 11 was transferred out of the reaction vessel.

  When the wafer 10 after the plasma treatment was taken out and the etching amount between the central portion and the outer peripheral portion of the wafer 10 was measured, the difference was within 3%.

  For comparison, the sapphire substrate was also plasma-treated by introducing the cooling gas only to the wafer mounting portion 16 without flowing the cooling gas to the tray mounting portion 17. At this time, the conditions other than the cooling gas were the same as in the above example. In this comparative example, the resist on the outer periphery of the wafer 10 was burned during the plasma processing, and a desired etching process could not be performed on the outer periphery of the wafer 10. This is thought to be because the temperature of the tray 11 rose because the tray 11 was not cooled.

  The present invention is not limited to the above-described embodiments, and appropriate modifications are allowed within the scope of the gist of the present invention. For example, the number of openings 11a opened in the tray 11 is not limited to three, and may be one, two, four or more. Further, the upper surface of the protrusion 13 a of the holding member 13 may be the same height as the lower surface of the tray 11. The recess 14 of the lower electrode 12 may have the same depth as the protruding distance of the holding member 13.

DESCRIPTION OF SYMBOLS 10 ... Wafer 11 ... Tray 11a ... Opening 11b ... Tray lower surface 12 ... Lower electrode 13 ... Holding member 13a ... Projection part 14 ... Recess 15 ... Wafer cooling gas introduction groove | channel 16 ... Wafer mounting part 17 ... Tray mounting part 18 ... Wafer Cooling gas introduction hole 19 ... Tray cooling gas introduction hole 20 ... Tray cooling gas introduction groove 21 ... Electrostatic chuck electrode

Claims (6)

In a plasma processing apparatus provided with a transfer tray for transferring a wafer to an electrostatic chuck,
The tray includes an opening in which the wafer is accommodated, and a holding member that is provided on the lower surface of the tray so as to extend downward and holds a lower surface periphery of the wafer accommodated in the opening,
The electrostatic chuck includes a tray placing portion on which the tray is placed, a recess into which the holding member is inserted when the tray is placed on the tray placing portion, and a wafer on which the wafer is placed. A mounting portion;
A plasma processing apparatus, wherein a cooling mechanism is provided in each of the wafer mounting unit and the tray mounting unit. The holding member is configured such that the lower surface of the wafer held by the holding member is at the same position as or lower than the lower surface of the tray other than the opening and the holding member,
The plasma processing apparatus according to claim 1, wherein height positions of upper surfaces of the tray mounting unit and the wafer mounting unit are the same.   The plasma processing apparatus according to claim 1, wherein a plurality of the holding members are provided at intervals in the circumferential direction of the opening. The cooling mechanism is
A cooling gas introduction groove formed in the wafer mounting portion and the tray mounting portion;
The plasma processing according to claim 1, further comprising: a cooling gas introduction hole provided in the cooling gas introduction groove in order to introduce the cooling gas into the cooling gas introduction groove. apparatus.   The electrostatic chuck electrode of the electrostatic chuck is disposed so as to straddle both the wafer mounting unit and the tray mounting unit. Plasma processing equipment. A method for performing plasma processing using the plasma processing apparatus according to claim 1,
Storing the wafer in the opening of the tray and transporting the wafer to the electrostatic chuck;
Placing the tray on the tray placing unit and placing the wafer on the wafer placing unit;
And plasma processing while cooling the tray mounting section and the wafer mounting section.

Images