Microwave plasma processing apparatus having a vacuum pump located under a susceptor

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a microwave plasma processing apparatus and, more particularly, to a microwave plasma processing apparatus having a vacuum chamber in which an object to be processed such as a semiconductor wafer is subjected to plasma processing.

2. Description of the Related Art

Recently, in a semiconductor device manufacturing process, plasma processing apparatuses have been used to perform semiconductor producing processes such as a deposition process, an etching process or an ashing or stripping process since high-density integration and fine structure are required for semiconductor devices. Particularly, a microwave plasma processing apparatus has become popular since the microwave plasma processing apparatus is capable of generating stable plasma at a relatively low vacuum of 0.1 millitorr (mTorr) to several tens of mTorr. The microwave plasma processing apparatus generates high-density plasma by using a microwave or a combination of a microwave and a magnetic field generated by a ring-like coil.

In a typical microwave plasma processing apparatus, a 2.45 GHz microwave is introduced into a process chamber via a waveguide and a slot electrode. A reaction gas is also introduced into the process chamber, which is maintained at a predetermined negative pressure. The reaction gas introduced into the process chamber is changed into active radicals and ions by the microwave so as to produce plasma. An object to be processed such as a semiconductor wafer is placed in the process chamber so that a predetermined process such as an etching process is performed on the object by utilizing the action of the plasma.

FIG. 1

is an illustration of a structure of a conventional plasma processing apparatus. The conventional plasma processing apparatus

1

shown in

FIG. 1

comprises: a process chamber

2

in which an object W to be processed is placed; a microwave generator

4

which generates a microwave to be introduced into the process chamber

2

; and vacuum pumps

6

connected to the process chamber

2

for maintaining the process chamber

2

at a predetermined negative pressure.

The object W to be processed is placed on a susceptor

8

provided in the process chamber

2

. The susceptor

8

is supported by a rod

10

which is moved up and down by a vertical moving mechanism

12

. The rod

10

extends out of the process chamber

2

with a bellows

14

provided on the bottom of the process chamber

2

so as to hermetically seal the process chamber

12

.

It should be noted that

FIG. 1

is a schematic illustration for mainly explaining the vertical movement of the susceptor

8

and the positions of the vacuum pumps

6

, and other members such as a gate connected to other cluster chambers or a reaction gas supply port are omitted for the sake of simplification of the figure.

The susceptor

8

provided in the process chamber

2

shown in

FIG. 1

can be moved up and down by the vertical moving mechanism

12

via the rod

10

so that a processing speed of the object W to be processed can be adjusted by changing a process condition of the object W since the processing speed varies depending on a vertical position of the object W within the process chamber

2

. For example, when the plasma processing is managed in accordance with a time period during which the object W is subjected to the plasma processing, the vertical position of the object W to be processed must be adjusted so as to obtain a desired degree of plasma processing within a predetermined time period.

The process chamber

2

has the bellows

14

on the bottom thereof, and the rod

10

extends to the vertical moving mechanism through the bellows

14

so as to maintain a hermetic seal between the rod

10

and the process chamber

2

. If the rod

10

horizontally extends within the process chamber

2

and the vertical moving mechanism

12

is provided on the side of the process chamber

2

, the hermetic seal of the process chamber

2

cannot be achieved by the bellows

14

since the direction of movement of the rod

10

is perpendicular to the direction of deformation of the bellows

14

. Accordingly, in order to move the susceptor

8

up and down and achieve a hermetic seal between the rod

10

and the process chamber

2

, it is preferable that the bellows

14

be positioned on the bottom of the process chamber

2

as shown in FIG.

1

. In this case, the length of the rod

10

can be short since the vertical moving mechanism

12

is positioned directly underneath the susceptor

8

, and a smooth movement of the rod

10

can be achieved.

The vacuum pumps

6

are directly connected to the bottom of the process chamber

2

. That is, each of the vacuum pumps

6

is mounted on the process chamber without any connecting pipe therebetween. The structure shown in

FIG. 1

can achieve a better vacuum characteristic, as long as maintenance of a high-vacuum condition is concerned, than a structure of the plasma processing apparatus in which a vacuum pump is connected to a process chamber via a connecting pipe.

Two or more vacuum pumps

6

are provided symmetrically around the bottom of the process chamber

2

so as to uniformly evacuate air or gas from the process chamber

2

so that a uniform plasma density can be achieved in the process chamber

2

. This is because, if the plasma in the process chamber

2

is locally concentrated, the degree of the plasma processing on the object W will vary according to the said local concentration.

However, the plasma processing apparatus

1

shown in

FIG. 1

must be large in its size and complex in its structure since the plurality of vacuum pumps

6

are provided diagonally around the periphery of the bottom of the process chamber

2

. Accordingly, a manufacturing cost of the plasma processing apparatus

1

is high.

Additionally, the structure of the plasma processing apparatus

1

in which the plurality of vacuum pumps

6

are provided still has a problem in that the plasma density cannot be completely uniform in the process chamber

2

since the number of vacuum pumps

6

which can be connected to the periphery of the bottom of the process chamber

2

is limited. The inventors found that a uniform plasma density can be achieved by a single vacuum pump being provided in the center of the bottom of the process chamber

2

. However, in the structure shown in

FIG. 1

, the vacuum pump

6

cannot be moved to the center of the bottom of the process chamber

2

since the rod

10

and the vertical moving mechanism

12

are positioned in the center of the bottom of the process chamber

2

.

SUMMARY OF THE INVENTION

It is a general object of the present invention to provide an improved and useful microwave plasma processing apparatus in which the above-mentioned problems are eliminated.

A more specific object of the present invention is to provide a microwave plasma processing apparatus having a process chamber in which a susceptor is movable by a vertical moving mechanism having a simple structure while a vacuum pump is positioned in the center of the bottom of the process chamber.

In order to achieve the above-mentioned objects, there is provided according to one aspect of the present invention a microwave plasma processing apparatus, comprising: a process chamber in which an object to be processed is subjected to plasma processing under a predetermined negative pressure environment; a susceptor provided in the process chamber, the susceptor being configured to hold the object thereon; a susceptor moving member connected to the susceptor; a first bellows provided to a bottom of the process chamber, the first bellows being connected to the susceptor moving member so as to allow a vertical movement of the susceptor moving member while providing a hermetic seal to the process chamber to maintain the predetermined negative pressure environment in the process chamber; a susceptor moving mechanism provided outside the process chamber, the susceptor moving mechanism moving the susceptor moving member in the vertical direction so as to move the susceptor in the vertical direction within the process chamber; and a vacuum pump provided to the bottom of the process chamber so that an inlet opening of the vacuum pump substantially aligns with the susceptor in the vertical direction.

According to the above-mentioned invention, the susceptor moving member is movable in the vertical direction in the process chamber while the first bellows maintains the process chamber hermetically sealed. Additionally, since the vacuum pump is provided to the bottom of the process chamber and is aligned with the susceptor in the vertical direction. Thereby, uniform evacuation can be achieved in the process chamber by positioning the susceptor and the vacuum pump substantially in the center of the process chamber. Thus, there is no need to provide a plurality of vacuum pumps around the periphery of the bottom of the process chamber, resulting in reduced size and cost of the microwave plasma processing apparatus.

Additionally, there is provided according to another aspect of the present invention a microwave plasma processing apparatus comprising: a process chamber in which an object to be processed is subjected to plasma processing under a predetermined negative pressure environment; a susceptor provided in the process chamber, the susceptor being configured to hold the object thereon; an object moving member configured to move the object relative to the susceptor in the vertical direction; a bellows provided to the bottom of the process chamber, the bellows being connected to the object moving member so as to allow a vertical movement of the object moving member while providing a hermetic seal between the object moving member and the process chamber to maintain the predetermined negative pressure environment in the process chamber; an object moving mechanism provided outside the process chamber, the object moving mechanism moving the object moving member in the vertical direction so as to move the object in the vertical direction within the process chamber; and a vacuum pump provided to the bottom of the process chamber so that an inlet opening of the vacuum pump substantially aligns with the susceptor in the vertical direction.

According to this invention, the object moving member is movable in the vertical direction in the process chamber while the bellows maintains the process chamber hermetically sealed. Additionally, the vacuum pump is provided to the bottom of the process chamber and is aligned with the susceptor in the vertical direction. Thereby, uniform evacuation can be achieved in the process chamber by positioning the susceptor and the vacuum pump substantially in the center of the process chamber. Thus, there is no need to provide a plurality of vacuum pumps around the periphery of the bottom of the process chamber, resulting in reduced size and cost of the microwave plasma processing apparatus.

Additionally, there is provided according to another aspect of the present invention a cluster tool comprising: a plasma processing apparatus having a process chamber in which an object to be processed is subjected to plasma processing at a predetermined temperature higher than a room temperature; a preheating section in which the object is preheated, the preheating section being provided outside the process chamber; and a conveyor conveying the object between the preheating section and the process chamber.

According to this invention, the object to be processed is preheated in the preheating section before the object to be processed is placed in the process chamber. Accordingly, the temperature of the object can be quickly raised to the predetermined temperature after the object is placed in the process chamber, resulting in a reduced time period for heating the object in the process chamber. Thus, the plasma processing can be quickly started after the object is placed in the process chamber.

Additionally, there is provided according to another aspect of the present invention a cluster tool comprising: a plasma processing apparatus having a process chamber in which an object to be processed is subjected to plasma processing at a predetermined temperature higher than a room temperature; a cooling section in which the object is cooled, the cooling section being provided outside the process chamber; and a conveyor conveying the object between the cooling section and the process chamber.

According to this invention, the object to be processed is cooled in the cooling section after the object is processed in the process chamber. Accordingly, the temperature of the object can be quickly decreased after the object is taken out of the process chamber, resulting in a reduced time period for preparing the object for a subsequent process. Thus, the subsequent process can be quickly started after the object is taken out of the process chamber.

Additionally, there is provided according to another aspect of the present invention a plasma processing method performed by a cluster tool, comprising the steps of: conveying an object to be processed to a preheating section outside a process chamber; preheating the object in the preheating section; conveying the preheated object to the process chamber; applying a plasma process to the object in the process chamber; conveying the processed object to a cooling section outside the process chamber; and cooling the processed object in the cooling section.

According to this invention, the object to be processed is preheated in the preheating section before the object to be processed is placed in the process chamber. Accordingly, the temperature of the object can be quickly raised to the predetermined temperature after the object is placed in the process chamber, resulting in a reduced time period for heating the object in the process chamber. Thus, the plasma processing can be quickly started after the object is placed in the process chamber. Additionally, the object is cooled in the cooling section after the object is processed in the process chamber. Accordingly, the temperature of the object can be quickly decreased after the object is taken out of the process chamber, resulting in a reduced time period for preparing the object for a subsequent process. Thus, the subsequent process can be quickly started after the object is taken out of the process chamber.

Other objects, features and advantages of the present invention will become more apparent from the following detailed descriptions when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is an illustration of a structure of a conventional plasma processing apparatus;

FIG. 2

is an illustration of an entire structure of a microwave plasma processing apparatus according to a first embodiment of the present invention;

FIG. 3

is a cross-sectional view of a susceptor having a baffle plate;

FIG. 4

is a plan view of the susceptor shown in

FIG. 3

on which the object to be processed is placed;

FIG. 5

is a cross-sectional view of an upper part of the microwave plasma processing apparatus shown in

FIG.2

;

FIG. 6

is a plan view of a slot electrode;

FIG. 7

is an enlarged cross-sectional view of a shower plate;

FIG. 8

is an enlarged cross-sectional view of a nozzle part of the shower plate;

FIG. 9

is a cross-sectional view of a first example of a nozzle member;

FIG. 10

is a cross-sectional view of a second example of the nozzle member;

FIG. 11

is a cross-sectional view of a third example of the nozzle member;

FIG. 12

is an illustration for explaining a mounting structure of a view port;

FIG. 13

is a cross-sectional view of a microwave blocking member;

FIG. 14

is a plan view of the microwave blocking member shown in

FIG. 12

; and

FIG. 15

is an illustration of a structure of a cluster tool to which the microwave plasma processing apparatus shown in

FIG. 2

is applied.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A description will now be given of a microwave plasma processing apparatus according to a first embodiment of the present invention.

FIG. 2

is an illustration of an entire structure of the microwave plasma processing apparatus

100

according to the first embodiment of the present invention. The microwave plasma processing apparatus

100

according to the present embodiment serves as a chemical vapor deposition (CVD) apparatus.

The microwave plasma processing apparatus

100

according to the present invention comprises: a process chamber

102

provided with a susceptor

104

on which an object W to be processed is placed; a vacuum pump

108

connected to the process chamber

102

; a susceptor moving system

130

for moving the susceptor

104

up and down in the process chamber

102

; a lifter pin moving system

140

in the process chamber

102

; a reaction gas supply system

150

for introducing a reaction gas into the process chamber

102

; a view port

160

provided to the process chamber

102

; and a microwave generator

110

for generating a microwave to be introduced into the process chamber

102

. It should be noted that a control system for controlling operations of the microwave plasma processing apparatus

100

is not shown in the figure.

The process chamber

102

has a side wall and a bottom wall which are made of a conductive material such as aluminum. The process chamber

102

has a hollow shape having a bottom part larger than a top opening. The process chamber

2

can be maintained at a negative pressure or vacuum by a vacuum pump

108

. In this embodiment, the vacuum pump

108

is a high vacuum pump which can generate a high vacuum. The susceptor

104

is provided in the process chamber

102

so that the object W to be processed can be placed thereon. It should be noted that an electrostatic chuck and a clamp mechanism for fixing the object W to the susceptor

104

are not show in

FIG.2

for the sake of simplification of the figure.

The susceptor

104

controls a temperature of the object W to be processed in the process chamber

102

. For example, the object W is maintained at a temperature of about 450° C. for the CVD process. If an etching process is performed by the microwave plasma processing apparatus

100

, the object W is maintained at a temperature lower than 80° C. In either case, the object W to be processed is maintained at a temperature at which a water component, an impurity, does not adhere to the object W. A method of controlling the temperature can be achieved by any methods known in the art such as a combination of a temperature sensor and a heater as described later.

The susceptor

104

may be replaced with a susceptor

192

shown in

FIGS. 3 and 4

.

FIG. 3

is a cross-sectional view of the susceptor

192

having a baffle plate

194

, and

FIG. 4

is a plan view of the susceptor

192

on which the object W to be processed is placed.

As shown in

FIG. 3

, the susceptor

192

has a step part

193

on the periphery thereof, and the baffle plate

194

fits to the step part

103

of the susceptor

192

. In this case, the susceptor

192

moves up and down together with the baffle plate

194

. Alternatively, the baffle plate

194

may be configured to be brought into engagement with the susceptor

192

when the susceptor

192

is moved to a process position as described later. The baffle plate

194

separates a process space in which the object W is present from an exhaust space underneath the process space so as to maintain the process space at a predetermined potential to attract the microwave to the process space and to maintain the process space at a predetermined vacuum, for example, 50 mTorr.

The baffle plate

194

is made of pure aluminum, and has a disk-like shape having a center hole. The thickness of the baffle plate

194

is about 2 mm. The baffle plate

194

has a lot of small holes

196

arranged at random as shown in

FIG.4

so that an opening ratio is more than 50%. Alternatively, the baffle plate

194

may have a meshed structure. If possible, the baffle plate

194

may have a function to prevent a reverse flow from the exhaust space to the process space or a function to create a pressure difference between the exhaust space and the process space.

The side wall of the process chamber

102

is provided with a gas supply nozzle

158

of the reaction gas supply system

150

. The gas supply nozzle

158

is made of a quartz pipe, and is connected to a reaction gas source

151

by a gas supply line via a mass flow controller

154

and a stop valve

152

. For example, in order to deposit a silicon nitride film, NH

3

or SiH

4

is mixed with a mixture gas of N

2

, H

2

and one of neon, xenon, argon, helium, radon and krypton. It should be noted that a variation of the reaction gas supply system

150

will be described later.

In the present embodiment, the vacuum pump

108

is a turbo molecular pump (TMP), and is connected to the process chamber

102

via a pressure adjust valve

106

. The pressure adjust valve

106

is a valve which is known in the art as a conductance valve, a gate valve or a high-vacuum valve. The pressure adjust valve

106

is closed when it is not used, and is opened so as to maintain the process chamber

102

by the vacuum pump

108

at a predetermined negative pressure in the range of 0.1 mTorr to 10 mTorr.

In the present embodiment, in order to achieve a uniform exhaust or evacuation, the maximum opening area S

1

of the pressure adjust valve

106

and the minimum horizontal cross-sectional area S of the process chamber

102

satisfy a relationship S

1

<S. The minimum horizontal cross-sectional area S is a horizontal cross-sectional area of the process chamber

102

in which the cross-sectional area of component parts such as a vertical moving member

132

provided in the process chamber

102

is excluded.

It should be noted that, as shown in

FIG.2

, according to the present embodiment, the vacuum pump

108

is directly connected to the process chamber

102

. That is, the vacuum pump

108

is connected to the process chamber

102

without any connecting pipe therebetween although the pressure adjust valve

106

is provided between the vacuum pump

108

and the process chamber

102

.

Since the vacuum pump

108

is connected to the bottom of the process chamber

102

underneath the susceptor

104

, the vacuum pump

108

can uniformly evacuate air or gas from the entire process chamber

102

. Accordingly, a uniform plasma density can be maintained in the process chamber

102

, and, therefore, the degree of plasma processing of the object W to be processed is prevented from varying due to a local concentration of the plasma density. Additionally, there is no need to provide a plurality of vacuum pumps as in the plasma processing apparatus

1

shown in FIG.

1

. The plasma processing apparatus

100

according to the present embodiment can be reduced in its size and cost.

In the present embodiment, the microwave generator

110

comprises a magnetron, which can generate, for example, a 2.45-GHz, 5-kW microwave. The microwave generated by the microwave generator

110

is converted into a TM mode, a TE mode or a TEM mode by a mode converter (not shown in the figure). It should be noted that, in

FIG.2

, an isolator for absorbing a microwave returning to the microwave generator

110

and a stub tuner for load matching are not shown for the sake of simplification of the figure.

The antenna member

120

comprises, as shown in

FIG. 5

, a temperature control plate

122

, an antenna accommodating member

123

and a dielectric plate

126

. The temperature control plate

122

is connected to a temperature control unit

121

. The antenna accommodating member

123

accommodates a wavelength reducing member

124

and a slot electrode

125

which contacts the wavelength reducing member

124

. The dielectric plate

126

is positioned under the slot electrode

125

. The antenna accommodating member

123

is made of a material having a high heat conductivity such as stainless steel. A temperature of the antenna accommodating member

123

can be controlled nearly equal to the temperature of the temperature control plate

122

.

The wavelength reducing member

124

is made of a material having a predetermined permittivity to reduce the wavelength of the microwave transmitted therethrough. The material of the wavelength reducing member

124

also has a high heat conductivity. As shown in

FIG. 6

, many slits

200

must be formed in the slot electrode

125

so as to achieve uniform plasma density in the process chamber

102

. The wavelength reducing member

124

has a function to allow many slits

200

to be formed in the slot electrode

125

.

Ceramics such as SiN or AlN can be used for the wavelength reducing member

124

. For example, the specific permittivity ε

t

of AlN is about

9

and, thus, the wavelength reducing rate n is 0.33 (n=1/(ε

t

)

½

=0.33). Accordingly, the transmission rate of the microwave after passing through the wavelength reducing member

124

becomes 0.33 times the original transmission rate, and, thus, the wavelength also becomes 0.33 times the original wavelength. Accordingly, a distance between adjacent slits

200

can be reduced, resulting in a larger number of slits

200

being provided in the slot electrode

125

.

The slot electrode

125

is formed of a copper plate having a circular shape whose diameter is, for example, about 50 cm and thickness is less than 1 mm. The slot electrode

125

is fixed to the wavelength reducing member

124

by screws. As shown in

FIG. 6

, the slot electrode

125

has many T-slits

200

that are arranged along a spiral which starts near the center O of the slot electrode

125

and extends toward the periphery in about two turns.

In the present embodiment, each T-slit

200

comprises a pair of slits

202

and

204

forming a T shape with a predetermined distance therebetween. More specifically, each of the slits

202

and

204

has a length L

1

which is in the range of about one half of the wavelength λ

0

of the microwave to 2.5 times a free space wavelength. The width of each of the slits

202

and

204

is about 1 mm. A distance L

2

between two adjacent pairs of slits along a radial direction is approximately equal to the wavelength λ

0

. That is, the length L

1

of each of the slits

202

and

204

is set to satisfy the following relationship.

(λ

0

/2×1/{square root over (ε

t

+L )})≦L

1

≦(λ

0

×2.5)

By setting each of the slits

202

and

204

to the above-mentioned structure, a uniformly distributed microwave can be achieved in the process chamber

102

.

A radiation element

206

having a width of about 1 mm is provided outside the spirally arranged T-slits

200

so as to prevent reflection of the microwave transmitted toward the periphery of the slot electrode

125

. The radiation element

206

is provided for increasing an antenna efficiency of the slot electrode

125

. It should be noted that the configuration of the pair of slits

202

and

204

is not limited to the above-mentioned T shape, and, for example, L-shaped slits may be used for the slot electrode

125

.

The temperature control plate

122

serves to control the temperature change of the antenna accommodating member

123

and component parts near the antenna accommodating member

123

to fall within a predetermined range. A temperature sensor and a heater unit (both not shown in the figure) are connected to the temperature control plate

122

. The temperature control unit

121

controls a temperature of the temperature control plate

122

to be a predetermined temperature by introducing a cooling water or a coolant such as alcohol, gulden or flon into the temperature control plate

122

. The temperature control plate

122

is made of a material such as stainless steel, which has a high heat conductivity and can be machined to form a fluid passage for the coolant therein.

The temperature control plate

122

contacts the antenna accommodating member

123

, and each of the antenna accommodating member

123

and the wavelength reducing member

124

has a high heat conductivity. Accordingly, the temperature of each of the wavelength reducing member

124

and the slot electrode

125

can be controlled by merely controlling the temperature of the temperature control plate

122

.

The temperature of each of the wavelength reducing member

124

and the slot electrode

125

is increased due to energy absorption when the microwave of the microwave generator

110

is supplied thereto for a long period of time. As a result, each of the wavelength reducing member

124

and the slot electrode

125

may deform due to thermal expansion.

For example, if the slot electrode

125

thermally deforms, the length of each slit is changed, which results in a decrease in the plasma density or localization of the plasma in the process chamber

102

. The decrease in the plasma density may slow down a plasma processing speed such as an etching rate or a film deposition rate. As a result, if the plasma processing is controlled based on a processing time, there may be a case in which a desired result of the plasma processing (such as plasma etching depth or plasma deposition thickness) cannot be obtained when the plasma processing is applied for a predetermined time period (for example, two minutes), that is, for example, if the object W is processed for a predetermined time (for example, two minutes) and thereafter removed from the process chamber

102

. Additionally, if the plasma density in the process chamber

102

is localized, the magnitude of plasma processing applied to the semiconductor wafer may vary. As mentioned above, if a deformation occurs in the slot electrode

125

, the quality of plasma processing may deteriorate.

Further, if the temperature control plate

122

is not provided, the slot electrode

125

may warp since the wavelength reducing member

124

and the slot electrode

125

are different from each other and the both members are fixed to each other by screws. In such a case, the quality of plasma processing may deteriorate for a reason similar to the above-mentioned reason.

A dielectric material member

126

is provided between the slot electrode

125

and the process chamber

102

so as to close the top opening of the process chamber

102

. The slot electrode

125

is tightly joined to the surface of the dielectric material member

126

by brazing. Alternatively, the slot electrode

125

can be formed by a copper plate applied to the surface of the dielectric material member

126

.

It should be noted that the function of the temperature control plate

122

may be provided to the dielectric material member

126

. That is, the temperature of the dielectric material member

126

can be controlled by integrally forming a temperature control plate with the dielectric material member

126

, which temperature control plate has a coolant passage near the side of the dielectric material member

126

. By controlling the temperature of the dielectric material member

126

, the temperature of the wavelength reducing member

124

and the slot electrode

125

can be controlled. The dielectric material member

126

is mounted to the process chamber

102

with an O-ring provided therebetween. Accordingly, the temperature of the dielectric material member

126

can be controlled by controlling a temperature of the O-ring, and, thereby controlling the temperature of the wavelength reducing member

124

and the slot electrode

125

.

The dielectric material member

126

is made of a dielectric material such as aluminum nitride (AlN). The dielectric material member

126

prevents the slot electrode

125

from being deformed due to a negative pressure generated in the process chamber

102

. Additionally, the dielectric material member

126

prevents the slot electrode

125

from being exposed to the atmosphere inside the process chamber

102

so that the environment inside the process chamber

102

is prevented from being contaminated by copper. If necessary, the dielectric material member

126

may be formed of a dielectric material having a low heat conductivity so as to prevent the slot electrode

125

from being influenced by heat from the process chamber

102

.

A description will now be given of the susceptor moving system

130

. As shown in

FIG. 2

, the susceptor moving system

130

comprises a vertical moving member

132

, a bellows

134

and a vertical moving unit

136

provided outside the process chamber

102

.

The vertical moving member

132

is formed as a single member made of aluminum. Alternatively, the vertical moving member

132

may have a mechanical structure such as a hinge mechanism. In such a case, care must be taken to prevent the process chamber

102

from being contaminated by a lubricant if the mechanical structure requires lubrication.

The vertical moving member

132

is provided for moving the susceptor

104

by being driven by the vertical moving unit

136

. One end of the vertical moving member

132

is connected to the susceptor

104

, and the other end is connected to the vertical moving unit

136

. The vertical moving member

132

comprises a first vertical part

132

a

, a first horizontal part

132

b

, a second vertical part

132

c

and a second horizontal part

132

d.

The second horizontal part

132

d

is connected to the vertical moving unit

136

, and the second horizontal part

132

d

is vertically moved along the side of the process chamber

102

. Since the bottom of the process chamber

102

is expanded and the vacuum pump

108

is located in the center of the bottom of the process chamber

102

, there is a space to provide the vertical moving unit

136

under the bottom of the process chamber

102

. Thus, the vertical moving unit

136

may be located under the bottom of the process chamber. Alternatively, a third vertical part may be provided at the end of the second horizontal part

132

d

, and the vertical moving unit

136

may be connected to the third vertical part.

In the present embodiment, the vacuum pump

108

is located in the center of the bottom of the process chamber

102

instead of locating the vertical moving unit

136

in the center of the bottom of the process chamber

102

. This is because the vacuum pump

108

being located in the center of the bottom of the process chamber

102

allows a uniform evacuation of air or gas from the process chamber

102

. This structure can be achieved by locating the bellows

134

on the periphery of the bottom of the process chamber

102

and providing the vertical moving member

132

having the first horizontal part

132

b

extending in the horizontal direction from the center to the periphery of the process chamber

102

. Additionally, the direction of deformation of the bellows

134

is the same as the direction of movement of the second vertical part

132

c

of the vertical moving member

132

. Thus, the bellows

134

can provide an effective seal between the vertical moving member

132

and the bottom of the process chamber

102

. It should be noted that as a variation of the present embodiment, the first horizontal part

132

b

of the vertical moving member

132

may be connected to a side of the susceptor

104

.

The vertical moving unit

136

moves the vertical moving member

132

while controlling a travel distance of the vertical moving member

132

by using a known technique such as a mechanical means, an electric means, a magnetic means or an optical means or a combination of the foregoing. A sensor including an optical sensor such as a photodiode can be preferably used to detect a travel distance of the vertical moving member

132

.

The susceptor

104

moves up and down between a home position and a process position. The susceptor

104

is moved to the home position when the plasma processing apparatus

100

is turned off or in a waiting mode. At the home position, the susceptor

104

receives the object W to be processed from a conveyor arm of a cluster tool

170

described later. The object W is inserted into the process chamber

102

through a gate valve

179

provided on the side wall of the process chamber

102

. A receiving position may be set at which the object W to be processed is placed on the susceptor

104

. A travel distance of the susceptor

104

can be controlled by a control unit of the vertical moving unit

136

or a control unit of the microwave plasma processing apparatus

100

. A position of the susceptor

104

can be observed through the view port

160

.

A description will now be given of a lifter pin moving system

140

. Similar to the susceptor moving system

130

, the lifter pin moving system

140

comprises a vertical moving member

142

, a bellows

144

and a vertical moving unit

146

. One end of the vertical moving member

142

is connected to three lifter pins (not shown in the figure) located at vertices of an equilateral triangle, respectively. The lifter pins penetrate through the susceptor

104

from the bottom side to the top side so as to lift the object W from the top surface of the susceptor

104

. The lifter pins are moved when the object W is inserted into the process chamber

102

and when the object W is transferred to the conveyor arm of the cluster tool

170

.

In the present embodiment, the bellows

144

for sealing the vertical moving member

142

is also provided to the bottom of the process chamber

102

. The direction of deformation of the bellows

142

is the same as the direction of movement of the vertical moving member

142

. Thus, the bellows

144

can provide an effective seal between the vertical moving member

142

and the bottom of the process chamber

102

.

The vertical moving unit

146

may be configured so as to allow the lifter pins to move only when the susceptor

104

is at a predetermined position such as a home position. The travel distance of the lifter pins can be controlled by a control unit of the vertical moving unit

146

or a control unit of the microwave plasma processing apparatus

100

. Additionally, the movement of the lifer pins can be observed through the view port

160

.

The reaction gas supply system

150

has a structure in which a nozzle

158

is provided to the side wall of the process chamber

102

so as to supply a reaction gas (process gas) to the process chamber

102

. Accordingly, the flow of the reaction gas may traverse in a space above the object W. Even if a plurality of nozzles

158

are provided symmetrically with respect to the center of the susceptor

104

, the density of the reaction gas cannot be uniform. Thus, a uniform plasma density cannot be achieved. In order to solve this problem, it can be considered to provide a shower head in a position above the susceptor

104

. Such a shower head can be made of a glass tubing so that an electric field generated in the process chamber

102

is not disturbed by the shower head. However, such a shower head is not practical since a plasma may be undesirably generated within the shower head. In order to prevent a plasma from being generated within the shower head, the present inventors conceived a new shower plate

220

.

A description will now be given, with reference to

FIGS. 7 and 8

, of the shower plate

220

provided in the microwave plasma processing apparatus

100

according the present embodiment.

FIG. 7

is an enlarged cross-sectional view of the shower plate

220

.

FIG. 8

is an enlarged cross-sectional view of a nozzle part of the shower plate

220

.

The shower plate

220

is mounted to a dielectric material plate

250

, which corresponds to the dielectric material plate

126

shown in FIG.

5

. The dielectric material plate

250

is made of an aluminum nitride (AlN) plate having a thickness of about 30 mm. The dielectric material plate

250

has gas inlet ports

252

and

254

connected to the gas supply line

156

. In this case, the nozzle

158

shown in

FIG. 2

is removed, and the gas supply line

156

is connected to each of the gas inlet ports

252

and

254

. The reaction gas introduced into the gas inlet ports

252

and

254

is lead to a plurality of nozzles

222

formed in the shower plate

220

.

The shower plate

220

is made of an aluminum nitride (AlN) plate having a thickness of about 6 mm. The shower plate

220

has a plurality of nozzles

222

. As shown in

FIG. 8

, each of the nozzles

222

is constituted by a nut

236

and a screw comprising a screw head

232

and a screw part

234

.

The screw head

232

has a height of about 2 mm. A pair of ejecting passages

239

are formed in the screw head

232

. Each of the ejecting passages

239

extends from the center of the screw head

232

in a direction inclined 45 degrees with respect to the bottom surface

226

of the shower plate

220

. An end of each of the ejecting passages

239

is connected to a passage

238

formed in the screw part

234

. Each of the ejecting passages

239

has a diameter of about 0.1 mm. The ejecting passages

239

are inclined so as to achieve a uniform introduction of the reaction gas. Accordingly, the number of the ejecting passages

239

and their angle with respect to the shower plate

220

may be changed so as to achieve uniform distribution of the reaction gas. It should be noted that, according to experiments conducted by the inventors, uniform distribution of the reaction gas was not achieved by a single ejecting passage extending in a direction perpendicular to the surface

226

of the shower plate

220

. It was found that the ejecting passage is preferably inclined as shown in

FIG. 8

to achieve uniform distribution of the reaction gas.

The passage

238

formed in the screw part

234

has a diameter of about 1 mm, and extends in a longitudinal direction of the screw part

234

. An end of the passage

238

is open to a gap space

240

formed between the dielectric material plate

250

and the shower plate

220

. The screw part

234

is inserted into a through hole formed in the shower plate

220

, and the screw is fastened to the shower plate

220

by the nut

236

being engaged with the end of the screw part

234

. The nut

236

is accommodated in a depression

256

formed on the surface of the dielectric material plate facing the shower plate

220

.

The gap space

240

is provided for preventing generation of plasma. The thickness of the gap space

240

required for preventing generation of plasma varies according to a pressure of the reaction gas. That is, for example, the thickness of the gap space

240

is set to about 0.5 mm when the pressure is 10 Torr. In this case, the process space under the shower plate

220

in the process chamber

102

is set to a pressure of about 50 mTorr. The reaction gas is introduced into the process chamber

102

at a predetermined speed by controlling the pressure difference between the reaction gas and the atmosphere in the process chamber

102

.

According to the shower plate

220

provided in the present embodiment, the reaction gas can be uniformly introduced and distributed in the process space in the process chamber

102

without generation of plasma before reaching the process space. An amount of flow of the reaction gas can be controlled according to the pressure difference between the gap space

240

and the process space in the process chamber

102

, the number of ejecting passages

239

, the inclination angle of the ejecting passages

239

and the size of each of the ejecting passages

239

.

The passage

238

and/or the ejecting passages

239

can be provided by nozzle members being inserted into through holes formed in the shower plate

220

, respectively.

FIGS. 9

,

10

and

11

are cross-sectional views of examples of the nozzle member replaceable with the screw and nut arrangement shown in FIG.

8

.

FIG. 9

shows a nozzle member

300

a

that is a first example of the nozzle member that can replace the screw and nut arrangement shown in FIG.

8

. The nozzle member

300

a

has a single straight passage

302

a

in a longitudinal direction of the nozzle member

300

a

.

FIG. 10

shows a nozzle member

300

b

that is a second example of the nozzle member that can replace the screw and nut arrangement shown in FIG.

8

. The nozzle member

300

b

has a single straight passage

302

b

connected to a pair of branch passages

304

b

at one end thereof.

FIG. 11

shows a nozzle member

300

c

that is a third example of the nozzle member that can replace the screw and nut arrangement shown in FIG.

8

. The nozzle member

300

c

has a single straight passage

302

c

connected to three branch passages

304

c

at on end of thereof.

A description will now be given, with reference to

FIG. 12

, of the view port

160

for observing the interior of the process chamber

102

.

FIG. 12

is an illustration for explaining a structure and a mounting structure of the view port

160

. The view port

160

is mounted to a side wall of the process chamber

102

. The view port

160

is made of glass so that the object W placed on the susceptor

104

can be observed from outside the process chamber

102

.

Conventionally, the view port is mounted to the side wall of the process chamber

102

by securing a punching metal from the inner side of the process chamber

102

by means of screws. The punching metal refers to a metal plate having a plurality of through holes formed by punching. The punching metal contacts the inner surface of the process chamber

102

so as to maintain a uniform potential in the process chamber

102

. However, it is inconvenient to secure the punching mental to the inner surface of the process chamber

102

.

Accordingly, in the present embodiment, the view port

160

is fit in an opening

103

A provided in the wall of the process chamber. The view port

160

comprises a punching metal

162

and a pair of mounting parts

164

. Each of the mounting parts

164

is made of metal, and includes a vertical part

165

and an engaging parts

166

extending from an end of the vertical part

165

. The engaging part

166

is elastically urged in directions indicated by arrows in FIG.

12

. That is, the vertical parts

165

are urged so as to be away from each other. In order to mount the view port

160

to the process chamber

102

, the punching metal

162

is inserted into the opening

103

A while pressing the mounting parts

164

in directions opposite to the direction of urging. The punching metal

162

is fixed inside the opening

103

A by an elastic urging force of the mounting parts

164

, and the mounting parts contact the inner wall of the opening

103

A so as to provide an electromagnetic shielding effect

It should be noted that although the view port

160

is sealed with respect to the process chamber

102

, the structure of the seal is not shown in FIG.

12

. The glass late is also not shown in the figure. The mounting parts

164

are not always required to provide the elastic urging force by themselves. That is, an elastically urging means may be provided separately from the mounting parts

164

. Additionally, the engaging parts

166

are not always required.

As mentioned above, the view port

160

shown in

FIG. 12

does not require the punching metal plate

162

to be fixed to the inner surface of the process chamber

102

by means of screws. This achieves an easy mounting operation of the view port

160

.

A description will now be given, with reference to

FIGS. 13 and 14

, of a microwave blocking member provided above the pressure adjust valve

106

located in the center of the bottom of the process chamber

102

.

FIG. 13

is a cross-sectional view of the microwave blocking member

280

.

FIG. 14

is a plan view of the microwave blocking member

280

.

The microwave blocking member

280

comprises a base plate

282

that is fixed to the bottom of the process chamber

102

so as to cover the pressure adjust valve

106

located above the vacuum pump

108

. The base plate

282

is fixed to the inner side of the process chamber

102

by a bolt

284

and nut

286

arrangement at a plurality of positions along the periphery of the base plate

282

. Alternatively, the base plate

282

may be fixed to the outer side of process chamber

102

.

The base plate

282

has a number of openings

288

at random or in a predetermined arrangement. The base plate

282

is bent in a convex shape so as to absorb a strain due to thermal expansion and prevent generation of particles. The base plate

282

can be formed by a punching metal plate. A diameter of each of the openings

288

is determined based on a harmonic wave of the microwave to be passed therethrough. For example, if the fifth harmonic wave of a 2.45 GHz microwave (the fifth harmonic wave has a frequency of 122.5 GHz (24.5/5) is to be allowed to pass through the microwave blocking member

280

, the diameter of each of the openings

288

is set to about 6 mm (122.5/5/4=6.125). It should be noted that the number of order of the harmonic wave is not limited to 5, and any number n can be used. It should be noted that at least one of the nuts

286

may be grounded so as to maintain the base plate

282

at the ground level. Alternatively, the base plate itself may be grounded by contacting a ground line to a side of the base plate

282

. It is preferable that the base plate

282

be bent to be in a convex shape or concave shape as mentioned above. However, the bent configuration is not always required.

The microwave blocking member

280

prevents the microwave and the harmonic wave thereof from entering the vacuum pump

108

. Especially, before the reaction gas is converted into a plasma, a large amount of microwave is introduced into the process chamber

102

from the microwave generator

110

. If such a large amount of microwave enters the vacuum pump, the vacuum pump may run out of control and may be damaged. However, the microwave blocking member

280

blocks the microwave while maintaining vacuum action by the vacuum pump

108

. That is, the microwave blocking member

280

can prevent the vacuum pump

108

from being damaged due to the microwave while maintaining a sufficient area of opening provided for the vacuum pump

108

. The microwave blocking member

280

protects the vacuum pump

108

irrespective of the presence of the baffle plate

194

shown in FIG.

3

.

A description will now be given, with reference to

FIG. 15

, of a cluster tool having the microwave plasma processing apparatus

100

serving as a part thereof.

FIG. 15

is an illustration of a cluster tool

170

to which the microwave plasma processing apparatus

100

is applied.

As mentioned above, the temperature of the object W can be controlled by the susceptor

104

. However, in a CVD process, it takes a considerable time to raise the temperature of the object W from a room temperature to 450° C. by the susceptor

104

. In order to eliminate such a problem, the cluster tool

170

heats the object W prior to providing the object W to the process chamber

102

of the microwave plasma processing apparatus

100

. Similarly, it takes a considerable time to decrease the temperature of the object W from 450° C. to a room temperature by the susceptor

104

after the plasma processing is completed. In order to eliminate such a problem, the cluster tool

170

cools the object W prior to starting another process after the object W is taken out of the process chamber

102

of the microwave plasma processing apparatus

100

.

As shown in

FIG. 15

, the cluster tool

170

comprises: a conveyor section

172

including a conveyor arm which holds and conveys the object W to be processed; a preheating section

174

for heating the object W; a cooling section

176

for cooling the object W; and load-lock (L/L) chambers

178

. In

FIG. 15

, two process chambers

102

A and

102

B are shown. Each of the process chambers

102

A and

102

B can be the process chamber

102

of the microwave plasma processing apparatus

100

shown in FIG.

2

. The number of process chambers provided in the cluster tool

170

is not limited to two.

The conveyor section

172

is provided with the conveyor arm which holds the object W and a rotating mechanism for rotating the conveyor arm. The preheating section

174

is provided with a heater so as to heat the object W to a temperature close to a process temperature before the object W is placed in the process chamber

102

A or

102

B. The cooling section

176

is provided with a cooling chamber which is cooled by a coolant so as to cool the object W taken out of the process chamber

102

A or

102

B to a room temperature before the object W is conveyed to a subsequent apparatus such as an ion implantation apparatus or an etching apparatus.

Preferably, the cluster tool

170

comprises a rotational angle sensor, a temperature sensor, at least one control unit and a memory for storing control programs so as to control the rotation of the conveyor arm of the conveyor section

172

and control a temperature of each of the preheating section

174

and cooling section

176

. Such a sensor, a control unit and a control program are known in the art, and descriptions thereof will be omitted. Additionally, the conveyor arm of the conveyor section

172

places the object W in the process chamber

102

A or

102

B through the gate valve

179

.

A description will now be given of an operation of the microwave plasma processing apparatus

100

shown in FIG.

2

.

First, the conveyor arm of the conveyor section

172

shown in

FIG. 15

holds the object W to be processed so as to place the object W in the process chamber

102

(in

FIG. 15

, one of the process chambers

102

A and

102

B corresponds to the process chamber

102

). It is assumed that the object W is subjected to a CVD process in the process chamber

102

. In such as case, the control unit (not shown in the figure) of the cluster tool

170

sends an instruction to the conveyor section

172

to heat the object W to a temperature of 450° C. before placing the object W in the process chamber

102

.

Upon receiving the instruction, the conveyor section

172

moves the object W to the preheating section

174

so as to heat the object W. When the temperature sensor (not shown in the figure) of the cluster tool

170

detects that the object W to be processed is heated to a temperature of about 450° C., the control unit of the cluster tool

170

sends an instruction to the conveyor section

172

to move the object W to be processed from the preheating section

174

to the process chamber

102

through the gate valve

179

. Accordingly, the conveyor arm of the conveyor section

172

conveys the heated object W to the process chamber

102

through the gate valve

179

.

When the heated object W reaches a position above the susceptor

104

in the process chamber

102

, the vertical moving unit

146

of the lifter pin moving system

140

moves the vertical moving member

142

upward so as to support the object W by the three lifter pins (not shown in the figure) protruding from the upper surface of the susceptor

104

. After the object W is transferred from the conveyor arm to the lifter pins, the conveyor arm returns through the gate vale

179

. The conveyor arm may be moved to a home position (not shown in the figure).

After the object W is transferred to the lifter pins, the vertical moving unit

146

moves the vertical moving member

142

downward so as to return the lifter pins inside the susceptor

104

and place the object W on the susceptor

104

. At this time, the susceptor moving member

142

can be moved while maintaining the hermetic seal of the process chamber

102

by the bellows

144

. The susceptor

104

heats the object W placed thereon to a temperature of 450° C. At this time, since the object W is preheated, it takes a short time to completely heat the object W to a desired temperature (450° C.).

Thereafter, the vacuum pump

108

(normally a high-vacuum pump is used) maintains the pressure in the process chamber

102

at 50 mTorr by being controlled by the pressure adjust valve

106

. In the microwave plasma processing apparatus

100

, since the vacuum pump

108

is positioned directly under the susceptor

104

, that is, the opening of the vacuum pump

108

is aligned with the susceptor

104

in a vertical direction in the center of the bottom of the process chamber

102

, a uniform evacuation can be achieved in the process chamber

102

.

The vertical moving unit

136

of the susceptor moving system

130

moves the susceptor moving member

134

upward so as to move the susceptor

104

and the object W from the home position to a process position at which a predetermined process condition is satisfied. At this time, the susceptor moving member

134

can be moved while hermetic seal of the process chamber

102

is maintained by the bellows

134

.

Thereafter, the reaction gas is introduced into the process chamber

102

from the reaction gas source

151

via the mass flow controller

154

and the stop valve

152

while the flow of the reaction gas is controlled. The reaction gas may be a mixture of helium, nitride and hydrogen and NH

3

as an additional mixture component.

If the shower plate

220

shown in

FIG. 7

is used, the reaction gas is supplied from the reaction gas source

151

to the dielectric material plate

250

via the mass flow controller

154

and the stop valve

152

. The reaction gas passes through the gap space

240

shown in FIG.

8

and is introduced into the process chamber

102

via the passage

238

and branch passages

239

of the nozzle member

230

. The reaction gas is not converted into plasma in the gap space

240

, and is introduced into the process chamber

102

with a uniform density and accurately controlled flow. The process space in the process chamber

102

is maintained at a temperature of about 450° C.

At the same time, a microwave is generated by the microwave generator

110

. The microwave is supplied to the wavelength reducing member

124

of the antenna member

120

in a TEM mode via a square waveguide or a coaxial waveguide. The microwave passing through the wavelength reducing member

124

is reduced in its wavelength, and enters the slot electrode

125

. The microwave is then introduced into the process chamber

102

via the slits

200

and the dielectric material plate

126

. Since a temperature of the wavelength reducing member

124

and the slot electrode

125

is controlled, there is no deformation due to thermal expansion. Accordingly, an optimum length of the slits

200

can be maintained. Thus, the microwave can be introduced into the process chamber

102

at a desired density without local concentration.

Thereafter, the process gas in the process chamber

102

is converted into plasma by the microwave, and a plasma CVD process is performed on the object W placed on the susceptor

104

. If the baffle plate

194

shown in

FIGS.3 and 4

is used, the baffle plate

194

maintains the potential in the process space so as to prevent the microwave from exiting the process space. Thus, a desired process speed can be maintained.

If a temperature of the temperature control plate

122

is raised higher than a predetermined upper limit temperature due to continuous use, the temperature control plate

122

is cooled by the temperature control unit

121

. On the other hand, if the temperature of the temperature control plate

122

is below a predetermined lower limit temperature at an initial stage of the operation of the apparatus or when the temperature control plate

122

is over cooled, the temperature control unit

121

heats the temperature control plate

122

.

The plasma CVD process is continued for a predetermined period of time. Thereafter, the vertical moving unit

136

moves the susceptor moving member

132

downward so as to return the susceptor

104

and the object W to the home position. Then, the object W is taken out of the process chamber

102

by being held by the conveyor arm of the cluster section

172

.

Since the microwave is uniformly supplied to the process chamber

102

with a predetermined density, a film having a desired thickness is formed on the object W to be processed. Additionally, since the temperature of the process chamber

102

is maintained in the predetermined range so that a water component (an impurity) does not enter the object W, the deposited film can be maintained at a desired quality.

The object W taken out of the process chamber

102

is transferred to the cooling section

176

and the object W is cooled to a room temperature in a short time. Then, if necessary, the object W is conveyed to a next stage apparatus such as an ion implantation apparatus.

It should be noted that the microwave plasma processing apparatus

100

can utilize an electron cyclotron resonance, and therefore, an electromagnetic coil may be provided so as to generate a magnetic field in the process chamber

102

. Additionally, although the microwave plasma processing apparatus

100

according to the present embodiment performs the plasma CVD process as plasma processing, the plasma processing is not limited to the plasma CVD process. That is, for example, a plasma etching process or a plasma ashing or stripping process may be performed by the microwave plasma processing apparatus

100

.

Additionally, the object W to be processed by the microwave plasma processing apparatus

100

is not limited to the wafer for producing a semiconductor device, and the microwave plasma processing apparatus

100

may be used to process an LCD substrate or a glass substrate.

The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention.

The present application is based on Japanese priority applications No. 11-119002 filed on Apr. 27, 1999 and No. 11-118889 filed on Apr. 27, 1999, the entire contents of which are hereby incorporated by reference.

Number	Date	Country	Kind
11-118889	Apr 1999	JP
11-119002	Apr 1999	JP

Number	Name	Date	Kind
5413688	Crowley	May 1995	A
5575883	Nishikawa	Nov 1996	A
5587205	Saito et al.	Dec 1996	A
6093281	Wise et al.	Jul 2000	A
6120609	Selyutin et al.	Sep 2000	A
6178919	Li et al.	Jan 2001	B1

Number	Date	Country
8-264462	Oct 1996	JP
11-297672	Oct 1999	JP

Microwave plasma processing apparatus having a vacuum pump located under a susceptor

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

Priority Claims (2)

US Referenced Citations (6)

Foreign Referenced Citations (2)