JP4519576B2 - Base for plasma etching apparatus and plasma etching apparatus provided with the same - Google Patents

Description

The present invention relates to an improvement of a base using a mechanical clamp, and a helium gas of a heat medium introduced between the wafer and the base is actively flowed so that the wafer having a lowered substrate rigidity expands to the reaction chamber side. thereby improving the cooling ability is prevented from being output, FIG Rukoto plasma etching apparatus for a base as possible uniform in-plane temperature of the wafer, and a plasma etching apparatus having the same.

For manufacturing semiconductor devices using wafers such as silicon, glass and GaAs, and for manufacturing various devices using a micro-electro-mechanical system (hereinafter referred to as MEMS), the wafer material itself or the material thereof is used. Etching is indispensable for etching the oxide film provided on the surface into a required shape, and dry etching using plasma is widely used.

  In the plasma etching method, low-pressure process gas plasma is generated in a reduced-pressure atmosphere, and, for example, silicon is etched by the generated plasma. As an example of the configuration of the apparatus, an inductively coupled plasma apparatus (inductively coupled plasma, ICP) capable of individually controlling plasma generation and plasma drawing is known.

  In this ICP apparatus, an alternating voltage is applied to the coil to generate plasma, an alternating voltage is applied to the substrate electrode on which the wafer is placed, and the plasma generated outside the reaction chamber is drawn into the reaction chamber, Etch the wafer.

  The base for placing the wafer in the reaction chamber is a place where the wafer is placed and fixed by means such as electrostatic adsorption or mechanical clamp, and the base itself is cooled or a heat transfer medium between the base and the wafer. The in-plane temperature of the wafer is uniformly maintained by filling the helium gas.

The plasma etching apparatus employing the conventional mechanical clamping, shaped radiate the base attachment surface comprising an electrode and a circumferential respective cooling gas distribution grooves are plural rows formed, He gas for cooling the base It is configured to be supplied to the groove through a cooling gas supply pipe disposed through the platen. However, in such an apparatus, in the case of a compound semiconductor substrate such as GaAs, there is a problem that the etching depth varies, and this is because the electric field distribution on the base attachment is uneven due to the groove.

Therefore, as disclosed in Patent Document 2, for the purpose of improving the etching depth in-plane uniformity of the dielectric film on the processing placed to that of compound semiconductor wafer, as shown in FIG. 4, group platform and flattened by removing the groove from the attachment 13b surface, Yes and the space 16 provided between the wafer 17 and the base attachment 13b, helium gas of the heat medium is introduced into the same space, helium gas base It is sealed so as not to leak into the reaction chamber 12 in a vacuum atmosphere by an O-ring 19 that is circumferentially arranged at a position directly below the clamp member 18 of the attachment 13b.
JP 2003-77892 A JP 2003-133286 A JP 2004-119448 A

In the base of Patent Document 2 shown in FIG. 4, when a temperature difference occurs on the surface of the wafer 17 placed on the base attachment 13b, the etching processing amount may vary. In particular, when the dielectric film such as SiN film or SiO ₂ film formed on the semiconductor substrate is etched, the above-mentioned variation is remarkable.

  On the other hand, a glass wafer or a silicon wafer having a thin thickness and a reinforcing backing material cannot be electrostatically attracted when placed on a base. In addition, since a silicon wafer or the like that has a large amount of etching processing and has a thickness that becomes extremely thin after processing may be broken at the time of separation after processing by electrostatic attraction, the outer peripheral portion of the wafer is mechanically clamped.

As described above, the etching apparatus having the base 13 having the above-described configuration shown in FIG. 3 has a relatively low vacuum atmosphere reaction chamber as the etching process progresses, depending on the wafer type and processing pattern. The convex deflection amount of the wafer 17 due to the helium gas pressure increases to the side, and the distance between the central portion of the wafer 17 and the base attachment 13b may become too large.

  In this case, heat transfer between the central portion of the wafer 17 and the base attachment 13b is not sufficient, and the temperature distribution of the wafer deteriorates. For example, a temperature difference of 40 ° C. or more is generated between the central portion and the outer peripheral side of the wafer. It will adversely affect process performance.

The present invention, in the plasma etching apparatus Yomotodai, to the base upon using the mechanical clamp and the wafer cooling helium gas, etc. small thickness of the wafer also relatively board rigid with the progress of the process is reduced, Providing a base for a plasma etching apparatus and a plasma etching apparatus provided with the same, which can solve the problem that the deflection of the wafer to the reaction chamber side in a vacuum atmosphere increases and the in-plane temperature of the wafer is not uniform. It is an object.

  In order to achieve uniform temperature in the surface of a wafer to be placed on a base using a mechanical clamp, the inventors provide, for example, a minute convex step near the base outer periphery, As a result of various studies on the method of introducing the helium gas as the heat medium while ensuring a gap in the range where good heat transfer is possible, a number of small-diameter vent holes are provided near the outer periphery of the base, and helium gas is passed through the vent holes. Is uniformly flown at a constant flow rate, so that the helium gas pressure on the backside of the wafer has a required slope between the center and the outer periphery to match the deflection of the wafer, thereby making the temperature distribution in the wafer surface uniform. It was found that it can be maintained.

  Further, the inventors arrange a ring of a porous material such as a metal near the outer periphery of the base with which the mechanical clamp of the wafer contacts to constitute an exhaust system to control the gas pressure in the gas introduction space within a predetermined range. At the same time, the inventors have found that controlling the inclination of the helium gas pressure on the backside of the wafer can prevent excessive deflection of the wafer and in-plane temperature non-uniformity, thereby completing the present invention.

That is, the present invention is a base to which a voltage can be applied, has a clamping means for placing a wafer and mechanically fixing the outer periphery thereof, and has a concave portion or a similar shape to the wafer on the upper surface of the base. form forms a single cooling gas inlet space one ring-shaped convex portion on the back side of the wafer is placed is provided, cooling as cooling gas to the back surface of the wafer to move a cooling gas introduction space while contacting the gas supply It flops plasma etching apparatus for base der provided with holes passage cooling gas exhaust hole passage,
The cooling gas supply passage is formed in the center of the base, and a plurality of the cooling gas exhaust passages are formed in the outer periphery of the base at a required interval, the outer periphery of the base and the introduction of the cooling gas The present invention relates to a base for a plasma etching apparatus, characterized in that a ring-shaped porous material is provided between a space and each cooling gas exhaust hole so as to communicate with each other .

The present invention also provides a processing gas supply means for supplying a processing gas to the chamber by adjusting the flow rate and pressure, and a processing chamber provided with the exhaust means, and a base for the plasma etching apparatus provided in the processing chamber , And a power supply means for applying high-frequency power to the base, and a plasma generating means for applying high-frequency power independently of the base and converting the processing gas supplied into the processing chamber into plasma. according to the plasma etching apparatus according to claim.

According to the present invention, a cooling gas introduction space is formed on the upper surface side of the base for the plasma etching apparatus and on the rear surface side of the wafer , and the helium gas is allowed to flow uniformly at a constant flow rate. By tilting so that the center of the wafer becomes higher and adjusting so that more heat transfer is performed in the center where the deflection of the wafer increases, the temperature distribution of the wafer is improved and the etching process performance is improved. Effect is obtained.

In addition, according to the present invention, the temperature within the wafer surface for wafers that require mechanical clamping, such as wafers that cannot be electrostatically attracted when placed on a base, or silicon wafers that become extremely thin after processing. Plasma etching can be performed without causing variation in distribution, and the amount of processing in any part of the wafer surface is equal, and high-quality processing can be provided.

First, a reference example will be described. The plasma etching apparatus base 1 according to this reference example forms a cooling gas introduction space 3 between the back surface of the wafer 17 placed on the upper surface of the base 1 as shown in FIG. The cooling gas supply system path 4 and the exhaust system path 5 are provided so as to move in the cooling gas introduction space while being in contact with each other. When the base is composed of the base attachment shown in the example of FIG. 4 and the base platen that holds the base attachment, the cooling gas supply system 4 and the exhaust system 5 are provided on both, but the attachment and the platen The same applies to the base constructed integrally, and FIGS. 1 to 2 exemplify the attachment and are simply referred to as the base 1.

  The cooling gas introduction space 3 is formed by providing a concave portion or a ring-shaped convex portion similar to the wafer 17 on the upper surface of the base 1, but the example shown in FIG. A recess having a depth of several tens of μm is formed. A lip seal 2 is arranged on the end circumferential portion 1 a on the upper surface of the base 1 and has a function of sealing between the outer peripheral portion of the wafer 17 pressed by the clamp member 18 and the cooling gas introduction space 3. Yes.

  Here, one cooling gas supply hole 4 is provided in the center of the upper surface of the base 1, and a plurality of cooling gas exhaust holes 5 are provided in the vicinity of the clamp member 18 on the upper surface of the base 1. A valve 6 for controlling the pressure in the cooling gas introduction space 3 is arranged in the cooling gas exhaust passage 5. Accordingly, the introduced cooling gas flows evenly from the center of the base 1 toward the outer periphery of the base 1. Note that a plurality of cooling gas supply holes 4 may be arranged at the center of the upper surface of the base 1.

Such cooling gas inlet space 3 can also be formed by providing a ring-shaped protrusion, such as O-ring wafer 17 and the outer peripheral shape on the base 1 upper surface is arranged in a similar shape.

Next, an embodiment of the present invention will be described with reference to FIG. The cooling gas introduction space 3 shown in FIG. 2 is a cooling gas introduction space 3 in which a porous material 7 is disposed in the vicinity of the clamp member 18 at an end circumferential portion 1a on the upper surface of the base 1 in which a concave portion similar to the wafer 17 is formed. The cooling gas exhaust passage 5 is connected to the porous material 7. The cooling gas introduced from the cooling gas supply hole 4 at the center of the upper surface of the base 1 (not shown) flows evenly toward the ring-shaped porous material 7 arranged on the outer peripheral side of the base 1. When such a porous material 7 is used, there is an effect that the cooling gas flows more evenly than the cooling gas exhaust passage 5 alone. The cooling gas exhaust holes 5 can be arranged at a plurality of locations at required intervals.

Examples of the porous material, known metal, alloy, ceramic, any of resins available, specifically, aluminum, stainless steel, titanium, zirconia and various ceramic such as sintered body of the material, polytetra Examples thereof include a porous body of fluoroethylene. Moreover, a porous body by thermal spraying such as aluminum can be used.

The O-ring and lip seal can be appropriately selected from many known materials such as fluorine rubber, perfluoroelastomer, silicone rubber, and fluorosilicone rubber.

FIG. 3 is an explanatory diagram of the configuration of an inductively coupled plasma (ICP) apparatus for carrying out the wafer etching method according to one embodiment of the present invention. The etching apparatus shown in FIG. 3 includes, as a processing chamber 10, an upper plasma generation chamber 11 that generates plasma, and a base 13 for plasma processing the wafer 17 to be etched by drawing the generated plasma. The lower reaction chamber 12 is provided.

  The exhaust system path 14 as the exhaust means in the processing chamber includes a passage member connected to the reaction chamber 12 and a vacuum pump connected to the passage member. The pressure in the processing chamber 10 is reduced to a required range and controlled by an open / close valve (not shown) having a control mechanism interposed between the vacuum pump, the reaction chamber 12 and the passage member.

For example, the gas supply system 15 for supplying the etching SF ₆ gas, the oxidizing gas containing oxygen, and the protective film forming C ₄ F ₈ gas includes a passage member connected to the upper part of the plasma generation chamber 11. The flow control device and the gas cylinder corresponding to each gas (not shown) are included. Various gases are fed into the plasma generation chamber 11 after the flow rate is adjusted by a flow rate control device from a gas cylinder.

  The plasma generating means includes a coil 20 disposed on the outer periphery of a plasma generating chamber 11 having a cylindrical shape made of ceramic, and a high-frequency power source 22 connected to the coil 20 via a matching unit 21. When the plasma etching apparatus is in operation, AC power having a frequency of 13.56 MHz is applied to the coil 20, and the gas supplied to the processing chamber is turned into plasma.

  A base 13 on which the wafer 17 is placed is accommodated in the reaction chamber 12. In order to actively draw the plasma generated by applying high-frequency power to the coil 20 to the wafer 17, A high frequency power supply 24 having a frequency of 13.56 MHz is connected to the coil 20 via a matching unit 23 separately from the coil 20.

  A control device (not shown) has functions of reactive gas flow rate control, base power control, and coil power control, and controls the gas flow rate control device described above to supply etching gas, oxidizing gas, and protective film forming gas from the gas cylinder. The high frequency power supply 22 and the matching unit 21 are applied to the above-described base 13 by controlling the high frequency power supply 22 and the matching unit 21, and the high frequency power supply 24 and the matching unit 23 are applied to the coil 20. Control and apply high frequency power.

  In particular, the reactive gas flow rate control includes an etching process in which etching is performed by supplying only an etching gas for a predetermined time, a process in which only an oxidizing gas is supplied for a predetermined time, and a protective film is formed by supplying only a protective film forming gas for a predetermined time. The step of depositing the protective film to be formed can be sequentially repeated.

(Comparative example)
In the etching apparatus provided with the base for the plasma etching apparatus of the conventional configuration shown in FIG. 4 , a silicon wafer having an outer diameter of 8 inches was used, and a thermo label was attached thereto and placed on the upper surface of the base during the etching process. The temperature inside the center part of a wafer and the clamp member of an outer peripheral part was measured. As a result, the central portion was 88 to 92 ° C, the outer peripheral portion was 49 to 53 ° C, and the temperature difference was 35 to 43 ° C.

The plasma conditions for measuring the wafer surface temperature were as follows.
Gas type: SF ₆
Coil power (power for plasma excitation): 2000W
Platen power (substrate power ← for plasma pulling): 15W
Gas flow: 300sccm
Chamber pressure: 5Pa

(Reference example)
In the plasma etching apparatus of the present invention shown in FIG. 3 equipped with the base attachment of FIG. 1, a wafer mounted on the upper surface of the base attachment during the etching process using an 8-inch outer diameter silicon wafer as in the comparative example. The temperature inside the center part of this and the inner side of the clamp member of an outer peripheral part was measured. As a result, the central portion was 88 to 92 ° C, the outer peripheral portion was 82 to 87 ° C, and the temperature difference was 1 to 10 ° C.

In the etching apparatus of the comparative example, the temperature distribution difference of the wafer, those were 35 to 43 ° C., in this reference example, is clear to be greatly reduced and 1 to 10 ° C., the uniformity of the wafer surface It can be seen that good etching process performance can be obtained.

  This invention enables plasma etching without causing variations in the temperature distribution in the wafer surface for wafers that require mechanical clamping, such as wafers made of materials that cannot be electrostatically attracted, and silicon wafers that become extremely thin after processing. It can be processed, and the processing amount at any point in the wafer surface is equivalent, can provide high-quality processing, and is optimal for manufacturing various devices by MEMS.

It is a vertical explanatory view showing a configuration of a main part of a base for a plasma etching apparatus according to a reference example . BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal explanatory view showing a configuration of a main part of a base for a plasma etching apparatus according to the present invention. It is explanatory drawing which shows the structural example of the plasma etching apparatus by this invention. It is explanatory drawing which shows the structural example of the conventional plasma etching apparatus.

1 base 2 lip seal
3 Cooling gas introduction space
4 Cooling gas supply passage
5 Cooling gas exhaust passage 6 Valve 7 Porous material
1 0 the processing chamber 11 plasma generation chamber 12 reaction chamber 13 base plate 14 an exhaust pathway 15 reaction gas supply line 16 void 17 wafer 18 clamping member 19 O-ring 20 coil 21 and 23 matching unit 22 high-frequency power source

Claims (3)

A base to which a voltage can be applied, has a clamping means for placing the wafer and mechanically fixing the outer periphery thereof, and has one concave portion or one ring-shaped convex portion similar to the wafer on the upper surface of the base A cooling gas inlet space and a cooling gas exhaust hole are formed so that one cooling gas introduction space is formed on the back surface side of the wafer placed and mounted, and the cooling gas introduction space is moved while the cooling gas is in contact with the back surface of the wafer. A base for a plasma etching apparatus provided with a path ,
While forming the cooling gas supply passage in the center of the base,
A plurality of the cooling gas exhaust holes are formed at a required interval on the outer periphery of the base,
A base for a plasma etching apparatus, characterized in that a ring-shaped porous material is provided on the outer periphery of the base and between the cooling gas introduction space and each cooling gas exhaust passage so as to communicate with each other. table. The porous material is a metal, alloy, ceramic, 1 Symbol placement of the plasma etching apparatus for base claims, characterized in that either the resin. A processing gas supply means for supplying a processing gas to the chamber by adjusting the flow rate and pressure, and a processing chamber provided with the exhaust means ;
The plasma etching apparatus base according to claim 1 or 2, disposed in the processing chamber,
Power supply means for applying high-frequency power to the base ;
A plasma etching apparatus , comprising: plasma generating means for applying high-frequency power independently of the base and converting the processing gas supplied into the processing chamber into plasma .

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