US20020046810A1

US20020046810A1 - Processing apparatus

Info

Publication number: US20020046810A1
Application number: US09/982,927
Authority: US
Inventors: Masayuki Tanaka; Sumi Tanaka
Original assignee: Individual
Current assignee: Tokyo Electron Ltd
Priority date: 2000-10-25
Filing date: 2001-10-22
Publication date: 2002-04-25
Also published as: JP2002134596A

Abstract

A processing apparatus of the invention includes: a processing vessel in which a vacuum can be created; a stage disposed in the processing vessel for supporting an object to be processed thereon; a clamping member supported above the stage and capable of pressing down a peripheral part of the object to be processed mounted on the stage to fixedly hold the object to be processed on the stage; an elastic member for giving a force to cause the clamping member to press down the peripheral part of the object to be processed mounted on the stage; and an elastic-member cover substantially entirely covering the elastic member.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a processing apparatus for conducting a predetermined process to an object to be processed, such as a semiconductor wafer.

2. Description of the Related Art

Generally, in a semiconductor integrated circuit manufacturing process, a semiconductor wafer, which is an object to be processed, is subject to various processes including a film-forming process, an etching process, an oxidation diffusion process, an annealing process, a modification process and so on. In a film-forming process, for example, a metal or a metal compound, such as tungsten (W), tungsten silicide (WSi), titanium (Ti), titanium nitride (TiN) or titanium silicide (TiSi), is deposited to form a wiring pattern on a surface of a wafer or to fill up recesses between wiring lines, or an insulating film, such as a SiO ₂film, is deposited.

A generally known conventional single-wafer processing apparatus will be described with reference to FIGS. 4 and 5A to 5C.

FIG. 4 is a schematic sectional view of a generally known conventional single-wafer processing apparatus, and FIGS. 5A to 5C are schematic sectional views of assistance in explaining the operation of an object-to-be-processed holding member (clamping ring). This processing apparatus is provided with a processing vessel 2 in which a vacuum can be created. A showerhead 4 for introducing various necessary gases into the processing vessel 2 is incorporated into a top wall of the processing vessel 2. A thin stage 8 is supported on a cylindrical, reflective support 6 set on a bottom wall of the processing vessel 2. A semiconductor wafer W is mounted on the stage 8. A plurality of heating lamps 10 are disposed under the processing vessel 2. Heat rays emitted by the heating lamps 10 travel through a transparent window 12 attached to the bottom wall of the processing vessel 2 into the processing vessel 2, and heat the stage 8 to heat the wafer W mounted on the stage 8.

Three lifting pins 16 (only two of those are shown in FIG. 4) attached to a circular lifting ring 14 are arranged to extend under the stage 8. The lifting pins 26 are vertically movable so that they can extend through holes 18 formed in the stage 8 and that can come in contact with a lower surface of the wafer W to vertically move the wafer W.

A

lifting rod

22 for vertically moving the lifting ring 14 is vertically extended through an opening formed in the bottom wall of the processing vessel 2 and is connected to the lifting ring 14. The opening formed in the bottom wall of the processing vessel 2 is covered with a bellows 20. The bellows 20 allows the lifting rod 22 to vertically move and also prevents leakage of gases through the opening of the bottom wall.

A

circular clamping ring

24 is pressed down to a peripheral part of the wafer W mounted on the stage 8 to fasten the wafer W tot he stage 8 during a process. More specifically, as shown in FIGS. 5A to 5C, three rods 26 (only two of those rods are shown) are attached to a lower surface of the clamping ring 24 so as to extend downward. Guide members 28, each of which has the shape of an inverted letter L and is provided with an opening 30, are attached to the lifting ring 14 in such a manner that the rods 26 are extended loosely through the openings 30 of the guide members 28, respectively. Each of the rods 26 is provided with a head (stopper) 34 at its lower end. Coil springs 32 are wound around the rods 26 in such a manner that the coil springs 32 are compressed between the guide members 28 and the heads 34 of the rods 26, respectively. Thus, the clamping ring 24 is always biased (forced) downward by resilience of the coil springs 32.

Stopping projections

36 project from upper ends of the guide members 28 to limit a downward movement of the clamping ring 24 relative to the lifting ring 14.

When mounting a wafer W on the

stage

8 of the thus formed processing apparatus, a conveying arm, not shown, holding the wafer W transfers the wafer W onto the lifting pins 16 set at an upper position thereof, and then the lifting ring 14 is lowered together with the lifting pins 16 in order to mount the wafer W on the stage 8 as shown in FIG. 5B. Then, the lifting pins 16 are lowered further to bring the clamping ring 24 into contact with a peripheral part of the wafer W. As the lifting ring 14 is lowered still further, the coil springs 32 are further compressed, whereby the wafer W is held securely on the stage 8 by the resilience of the compressed coil springs 32.

DISCLOSURE OF THE INVENTION

The aforesaid processing of a semiconductor wafer uses various process gases including a highly corrosive gas, such as WF ₆gas (tungsten hexafluoride gas) or Cl₂gas.

An interior of the processing vessel must be periodically or occasionally cleaned by a cleaning process using a cleaning gas (etching gas), such as ClF ₃gas, in order to prevent falling off of unnecessary films deposited on inner surfaces of the processing vessel and thereby production of particles. The cleaning gas also may be highly corrosive.

When such a highly corrosive gas is introduced into the

processing vessel

2, the corrosive gas flows unavoidably into a space around a back surface of the stage 8. Even if a so-called backside gas is supplied into the space around the back surface of the stage 8, the coil springs 32 of a metal exposed to the corrosive gas may be corroded, and hence corrosion products may be scattered as particles to cause metallic contamination.

The present invention has been made in view of the foregoing problems to solve the problems effectively. Accordingly, it is an object of the present invention to provide a processing apparatus provided with an elastic member for biasing an object-to-be-processed holding member (clamping member) and capable of effectively preventing corrosion of the elastic member.

This invention is a processing apparatus comprising: a processing vessel in which a vacuum can be created; a stage disposed in the processing vessel for supporting an object to be processed thereon; a clamping member supported above the stage and capable of pressing down a peripheral part of the object to be processed mounted on the stage to fixedly hold the object to be processed on the stage; an elastic member for giving a force to cause the clamping member to press down the peripheral part of the object to be processed mounted on the stage; and an elastic-member cover substantially entirely covering the elastic member.

According to the invention, the elastic member for giving a force to cause the clamping member to press down the object to be processed is covered by the elastic-member cover. Thus, the elastic member is prevented from touching any corrosive gas, and hence corrosion of the elastic member can be effectively suppressed.

Preferably, the elastic member cover is excellently corrosion-resistant. In the case, corrosion of the elastic-member cover is also prevented.

Preferably, the elastic member cover is formed of a material having a low thermal conductivity. Such an elastic-member cover is effective in suppressing rise of the temperature of the elastic member, and is further effective in suppressing the corrosion of the elastic member.

In addition, preferably, the clamping member has a rod extending downward from a lower surface thereof, the elastic member is a coil spring surrounding the rod, the rod is provided with a spring stopper at a lower end thereof to support a lower end of the coil spring thereon, and an upper end of the coil spring rests on a clamping-member supporting member through which the rod extend and which can support a lower surface of the clamping member.

In addition, preferably, the elastic-member cover is formed integrally with the clamping-member supporting member.

In addition, preferably, the elastic-member cover also covers the lower end of the rod and the spring stopper.

In addition, preferably, the clamping-member supporting member is formed integrally with lifting pins capable of moving through the stage and of vertically moving the object to be processed on the stage.

In addition, preferably, a processing apparatus further comprises: a process-gas supply means for supplying a process gas into the processing vessel, and a heating means for heating the object to be processed mounted on the stage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of a processing apparatus in a preferred embodiment according to the present invention; [0025]
FIG. 2 is a plan view of a lifting ring and an elastic-member cover; [0026]
FIGS. 3A to [0027] 3C are schematic sectional views of assistance in explaining an operation of an object-to-be-processed holding member (clamping ring);
FIG. 4 is a schematic sectional view of a conventional single-wafer processing apparatus; and [0028]
FIGS. 5A to [0029] 5C are schematic sectional views of assistance in explaining an operation of a conventional object-to-be-processed holding member (clamping ring).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A processing apparatus in a preferred embodiment according to the present invention will be described with reference to the accompanying drawings. [0030]
FIG. 1 is a schematic sectional view of a processing apparatus in a preferred embodiment according to the present invention, FIG. 2 is a plan view of a lifting ring and an elastic-member cover, and FIGS. 3A to [0031] 3C are views of assistance in explaining an operation of an object-to-be-processed holding member (clamping ring).
A [0032] processing apparatus 40 has a cylindrical or box-shaped processing vessel 42 made of, for example, aluminum, in which a vacuum can be created by evacuating. A cylindrical reflective support (reflector) 44 having a mirror-finished inner surface is set upright on a bottom wall of the processing vessel 42. A stage 46 for supporting a semiconductor wafer W, i.e., an object to be processed, thereon is supported on the reflective support 44. The reflective support 44 is formed of a material which can transmit heat rays, such as quartz. The stage 46 has a thickness on the order of 1 mm, and is formed of a carbonaceous material or an aluminum compound, such as AlN.
A [0033] clamping ring 47, i.e., an object-to-be-processed holding member, for pressing down a peripheral part of the wafer W and fixing the wafer W onto the stage 46 is supported above a peripheral part of the stage 46. The clamping ring 47 will be described later.
A [0034] transparent window 48 made of a material which can transmit heat rays, such as quartz, is hermetically joined to a portion of the bottom wall of the processing vessel 42 right under the stage 46. A heater case 50 defining a heating chamber is joined to the bottom wall of the processing vessel 42 so as to surround the transparent window 48. A heating unit placed in the heater case 50 includes a plurality of heating lamps 52, and a reflecting rotary table 54 serving also as a reflector and supporting the heating lamps 52. The rotary table 54 is driven for rotation via a shaft attached thereto by a motor 56 held at a bottom wall of the heater case 50. Heat rays emitted by the heating lamps 52 can travel through the transparent window 48 and fall on a lower surface of the stage 46 to heat the same. A resistance-heating element embedded in the stage 46 may be used instead of the heating lamps 52 for heating the stage 46.
A circular current-straightening [0035] plate 58 provided with a plurality of straightening holes 56 is disposed so as to surround an outside periphery of the stage 46. The current-straightening plate 58 is supported on a circular column 60. A circular attachment 62 made of quartz is placed on an inner peripheral part of the current-straightening plate 58. Then, an outer peripheral part of the clamping ring 47 is adapted to come into light contact with an inner peripheral part of the attachment 62. An exhaust port 64 is formed in a portion of the bottom wall below the current-straightening plate 58. An exhaust line 66 connects the exhaust port 64 to a vacuum pump, not shown, that can evacuate the processing vessel 42 to create a vacuum. A gate valve 68 is incorporated into a side wall of the processing vessel 42. The gate valve 68 is opened when carrying a wafer W into and out from the processing vessel 42.
A [0036] showerhead 70 for introducing process gases or the like into the processing vessel 42 is incorporated into a top wall of the processing vessel 42 opposite to the stage 46. More specifically, the showerhead 70 has a body 72 formed of aluminum or the like and having the shape of a cylindrical box. A gas inlet 74 is formed in a top wall of the body 72.
The [0037] gas inlet 74 is connected to gas sources, not shown, which respectively supply necessary process gases, such as WF₆, Ar, SiH₄, H₂, N₂and such. Respective flow rates of those process gases are controllable.
A bottom wall of the [0038] body 72 is provided with many gas-jetting holes 76. The gas jetting holes 76 are distributed over the entire bottom wall in order to jet gases supplied into the body 72 to a processing space S, and hence over the entire surface of the wafer W mounted on the stage 46.
A diffusing [0039] plate 80 provided with many diffusing holes 78 is placed in the body 72 in order to supply the gases much evenly over the surface of the wafer W mounted on the stage 46.
As shown in FIG. 2, a plurality of, for example three L-shaped lifting pins [0040] 84 are attached at substantially equal angular intervals to an annular lifting ring 82, which is arranged below the stage 46, via respective elastic-member covers 96. Upper parts of the lifting pins 84 extend upright. The lifting pins 84 are vertically movable together with the lifting ring 82. That is, the lifting pins 84 can be vertically moved upward so that the upper parts thereof pass through holes 86 formed in the stage 46 and can come into contact with the lower surface of the wafer W to lift up the wafer W. The lifting pins 84 can be also moved downward to lower the wafer W onto the stage 46. Lower parts of the lifting pins 84 extend through slots 85 formed in the reflective support 44 and are capable of vertically moving in the slots 85. A lifting rod 88 connected to the lifting ring 82 extends through an opening formed in the bottom wall of the processing vessel 42, and a lower end of the lifting rod 88 is connected to an actuator 92. The opening of the bottom wall of the processing vessel 42 is covered with a bellows 90. The bellows 90 allows the lifting rod 88 to move vertically and seals the processing vessel 42 hermetically. A substantially circular (annular) clamping ring 47, whose shape conforms to an outline of the wafer W, is disposed above a peripheral part of the stage 46 to press a peripheral part of the wafer W fixedly against the stage 46. The clamping ring 47 is formed of, for example, a ceramic material. A plurality of, for example three rods 94 are attached at substantially equal angular intervals to the clamping ring 47, i.e., an object-to-be-processed holding member, so as to extend vertically downward. The rods 94 are supported by the lifting ring 82 via the respective elastic-member covers 96, which are a feature of the present invention.
More specifically, as shown in FIGS. 3A to [0041] 3C, each of the elastic-member covers 96 is made of a transparent, corrosion-resistant, low heat-conductive material, such as quartz, and has a substantially cylindrical shape. The elastic-member cover 96 is provided with a guide hole 98 of a diameter slightly greater than that of the rod 94 for guiding a vertical movement of the rod 94, in an upper part thereof, and a spring containing hole 100 of a diameter greater than that of the guide hole 98, in a lower part thereof. The guide hole 98 and the spring containing hole 100 are communicated. The rod 94 is extended through the guide hole 98 and the spring containing hole 100. A coil spring 102, i.e., an elastic member, is placed in the spring containing hole 100 so as to surround a lower part of the rod 94. Then, the coil spring 102 is compressed between a spring stopper 104 formed at a lower end of the rod 94 and an upper end surface 100A of the spring containing hole 100 in order to give downward force to the clamping ring 47 at all times.
Thus, each of the coil springs [0042] 102 is substantially entirely covered with the elastic-member cover 96, excluding a lower part thereof.
Stopping [0043] projections 106 project from upper ends of the elastic-member covers 96, respectively, to limit the downward movement of the clamping ring 47 relative to the elastic-member covers 96.
The [0044] edge 98A of each guide hole 98 is beveled (tapered) or rounded to ensure that the rod 94 can smoothly move therethrough.
A process, such as a film deposition process, to be carried out by this processing apparatus will be described by way of example. [0045]
The [0046] gate valve 68 on the side wall of the processing vessel 42 is opened, a carrying arm (not shown) carries a wafer W into the processing vessel 42, the lifting pins 84 are raised, and the wafer W is transferred from the carrying arm onto the lifting pins 84 as shown in FIG. 3A. Subsequently, the lifting pins 84 are lowered to mount the wafer W on the stage 46 as shown in FIG. 3B. As the lifting pins 84 are lowered further, the clamping ring 47 comes into contact with a peripheral part of the wafer W. As the lifting pins 84 are lowered still further, the coil springs 102 are further compressed as shown in FIG. 3C. Consequently, the peripheral part of the wafer W is pressed down by resilience of the coil springs 102 so that the wafer W is fixedly held on the stage 46. In this state, the compressed coil springs 102 are completely contained in the spring containing holes 100, that is, are entirely covered with the elastic-member covers 96, respectively.
Suppose that a tungsten film is to be deposited on the wafer W. Process gases optionally including some or all of WF[0047] ₆gas (source gas), SiH₄gas, H₂gas (reducing gas), Ar gas, N₂gas (diluting gas) or the like are supplied at predetermined flow rates, respectively, into the shower head 70. A mixture of those process gases is jetted substantially uniformly into the processing vessel 42 through the gas jetting holes 76 formed in the bottom wall of the body 72 of the showerhead 70. At the same time, an atmosphere in the processing vessel 42 is exhausted through the exhaust port 64 to create and maintain a predetermined vacuum in the processing vessel 42, the rotary table 54 supporting the heating lamps 52 thereon and disposed below the stage 46 is rotated, and the heating lamps 52 are energized to make the same radiate thermal energy.
Heat rays emitted by the [0048] heating lamps 52 travel through the transparent window 48 and fall on the back surface of the stage 46 to heat the same. Since the stage 46 has a very small thickness on the order of 1 mm, the stage 46 can be quickly heated. Consequently, the wafer W mounted on the stage 46 can be quickly heated to a predetermined temperature. The process gases supplied into the processing vessel 42 undergo predetermined chemical reactions to deposit (form) a tungsten film on the surface of the wafer W according to a film deposition condition. N₂gas or Ar gas, as a so-called backside gas, is supplied into a space around the backside of the stage 46.
One or some highly corrosive process gases including the WF[0049] ₆gas may flow around the stage 46 into the space around the backside of the stage 46 in addition to the processing space S in the processing vessel 42, during this film deposition process. However, the coil springs 102 made of a metal are exposed scarcely to the corrosive gases and hence corrosion of the coil springs 102 is prevented, because the coil springs 102 are substantially entirely contained in the spring containing holes 100, that is, because the coil springs 102 are covered substantially completely with the elastic-member covers 96.
In the embodiment, since the elastic-member covers [0050] 96 are made of a material having an excellent corrosion resistance and a low thermal conductivity, corrosion of the elastic-member covers 96 can be also prevented. In addition, the elastic-member covers 96 can suppress rise of temperature of the coil springs 102 and hence the coil springs 102 can be contained in a less corrosive environment.
Even if the coil springs [0051] 102 should be corroded and hence corrosion products should scatter, the corrosion products can scatter only downward because only lower ends of the spring containing holes 100 are open. Thus, it is scarcely possible that the scattered corrosion products contaminate the wafer W mounted on the stage 46.
Each [0052] rod 94 may be formed in such a length that the spring stopper 104 supporting the lower end of the coil spring 102 can be always completely contained in the spring containing hole 100 and that the lower end of the spring containing hole 100 may be completely closed, which can prevent the exposure of the coil springs 102 to the corrosive gases more effectively.
This effect on controlling the corrosion of the coil springs [0053] 102 is effective also in a cleaning process wherein a highly corrosive cleaning gas is supplied into the processing vessel 42 for cleaning.
The elastic-member covers [0054] 96 may be formed of a ceramic material, such as Al₂O₃, having functions substantially similar to those of quartz.
The object to be processed is not limited to a semiconductor wafer, and the present invention is applicable to an LCD substrate, a glass substrate or the like. [0055]

Claims

What is claimed is:

1. A processing apparatus comprising:

a processing vessel in which a vacuum can be created;

a stage disposed in the processing vessel for supporting an object to be processed thereon;

a clamping member supported above the stage and capable of pressing down a peripheral part of the object to be processed mounted on the stage to fixedly hold the object to be processed on the stage;

an elastic member for giving a force to cause the clamping member to press down the peripheral part of the object to be processed mounted on the stage; and

an elastic-member cover substantially entirely covering the elastic member.

2. A processing apparatus according to claim 1, wherein

the elastic-member cover is highly corrosion-resistant.

3. A processing apparatus according to claim 1, wherein

the elastic-member cover is made of a material having a low thermal conductivity.

4. A processing apparatus according to claim 1, wherein

the clamping member has a rod extending downward from a lower surface thereof,

the elastic member is a coil spring surrounding the rod,

the rod is provided with a spring stopper at a lower end thereof to support a lower end of the coil spring thereon, and

an upper end of the coil spring rests on a clamping-member supporting member through which the rod extend and which can support a lower surface of the clamping member.

5. A processing apparatus according to claim 4, wherein

the elastic-member cover is formed integrally with the clamping-member supporting member.

6. A processing apparatus according to claim 5, wherein

the elastic-member cover also covers the lower end of the rod and the spring stopper.

7. A processing apparatus according to claim 4, wherein

the clamping-member supporting member is formed integrally with lifting pins capable of moving through the stage and of vertically moving the object to be processed on the stage.

8. A processing apparatus according to claim 1 further comprising:

a process-gas supply means for supplying a process gas into the processing vessel; and

a heating means for heating the object to be processed mounted on the stage.