WO2018218612A1

WO2018218612A1 - Extend ground straps lifetime in pecvd process chamber

Info

Publication number: WO2018218612A1
Application number: PCT/CN2017/086853
Authority: WO
Inventors: Xiaoming Su; Zeren SHANG; Yi GUI; Robin L. Tiner; Shih Yao SUN
Original assignee: Applied Materials, Inc.
Priority date: 2017-06-01
Filing date: 2017-06-01
Publication date: 2018-12-06
Also published as: CN110730829A

Abstract

A substrate processing chamber (102) includes a plurality of ground straps (130) coupled to the substrate support (118) and chamber floor. A first end (234) of the ground strap (130) is vertically offset from a second end (236) of the ground strap (130). A substrate processing chamber (102) includes one or more ceramic plates (590) coupled to an outer perimeter of the substrate support (118) to reduce film deposition on the chamber walls (106), substrate support (118), and ground straps (130). A substrate processing chamber (102) includes one or more ground straps (130) coupled to the substrate support (118) and chamber floor. Each ground strap (130) includes an L-type block (462, 472) at one or both ends to reduce the exposed length of the ground strap (130). The apparatus extend ground strap lifetime, improve overall chamber performance, and reduce RF frequency variation in the chamber.

Description

EXTEND GROUND STRAPS LIFETIME IN PECVD PROCESS CHAMBER

BACKGROUND Field

Examples of the present disclosure generally relate to apparatus and methods for extending the lifetime of ground straps in a substrate processing chamber， such as a plasma enhanced chemical vapor deposition (PECVD) chamber.

Description of the Related Art

PECVD is used for processing substrates， such as solar substrates， display substrates， and semiconductor substrates. PECVD generally includes introducing precursor gases into a vacuum chamber in which a substrate is placed on a substrate support. The precursor gases are directed into the vacuum chamber through a gas distribution plate， typically situated near the top of the chamber， and are energized by radio frequency (RF) power applied to the gas distribution plate to generate plasma between the gas distribution plate and the substrate on the substrate support. The excited gas reacts to form a thin film layer on the substrate positioned on the substrate support.

During processing， the substrate support needs to be RF grounded to eliminate any voltage drop across the substrate support， which would affect deposition uniformity. If the substrate support is not properly RF grounded and there is high impedance， parasitic plasma generally deposits on the substrate support and chamber walls. The substrate support is typically grounded to the chamber body by ground straps to form an RF current return path.

The lifetime of a ground strap is measured by the number of substrates processed. Conventional ground straps are generally thin， flexible strips of aluminum， which are susceptible to breakage， especially over time and as the substrate support is moved between a home and processing position， or when they are exposed to plasma leakage. Each ground strap breakage results in chamber downtime for maintenance and costs to replace the ground strap.

Therefore， there is a need for improved substrate processing chambers having ground straps with extended lifetimes.

SUMMARY

The present disclosure relates to methods and apparatus for extending ground strap lifetime. In one example， a substrate processing chamber includes a plurality of ground straps coupled to the substrate support and chamber floor. A first end of the ground strap is vertically offset from a second end of the ground strap. In another example， a substrate processing chamber includes one or more ceramic plates coupled to an outer perimeter of the substrate support to reduce film deposition on the chamber walls， substrate support， and ground straps. In yet another example， a substrate processing chamber includes one or more ground straps coupled to the substrate support and chamber floor. Each ground strap includes an L-type block at one or both ends to reduce the exposed length of the ground strap. The apparatus and methods extend ground strap lifetime， improve overall chamber performance， and reduce RF frequency variation in the chamber.

In one example a substrate processing chamber is disclosed. The chamber includes a chamber body having one or more chamber walls and a chamber bottom having a first bottom connector and a second bottom connector， a substrate support disposed in the chamber body， the substrate support having at least a first support connector， a second support connector， and a third support connector， a first ground strap having a first end and a second end， the first end being coupled to the substrate support at the first support connector， and the second end being coupled to the chamber bottom at the second bottom connector， and a second ground strap having a first end and a second end， the first end being coupled to the substrate support at the second support connector， and the second end being coupled to the chamber bottom at the third bottom connector.

In another example， a substrate processing chamber is disclosed. The substrate processing chamber includes a chamber body having one or more chamber walls and a chamber bottom， a substrate support disposed in the chamber body， the substrate support having an outer perimeter facing the one or more chamber walls， one or more ground straps having a first end and a second end， the first end being coupled to the substrate support and the second end being coupled to the chamber bottom， and one or more ceramic plates coupled to the outer perimeter of the substrate support.

In yet another example， a substrate processing chamber is disclosed. The substrate processing chamber includes a chamber body having one or more chamber walls and a chamber bottom， a substrate support disposed in the chamber body， one or more ground straps having a first end and a second end， the first end being coupled to the substrate support and the second end being coupled to the chamber bottom， a first L-block and clamp at the first end and a second L-block and clamp at the second end， each of the first L-block and the second L-block having a first portion and a second portion intersecting at an angle greater than about 90 degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the present disclosure can be understood in detail， a more particular description of the disclosure， briefly summarized above， may be had by reference to examples， some of which are illustrated in the appended drawings. It is to be noted， however， that the appended drawings illustrate only exemplary examples and are therefore not to be considered limiting of its scope， may admit to other equally effective examples.

Figure 1 is a cross-sectional view of a substrate processing system having one or more ground straps therein.

Figure 2 is a top view of an exemplary ground strap.

Figure 3 is a cross-sectional view of a portion of the substrate processing chamber of Figure 1.

Figure 4A is a cross-sectional view of a portion of the substrate processing chamber of Figure 1.

Figure 4B is a cross-sectional view of a portion of the substrate processing chamber of Figure 1.

Figure 4C is a cross-sectional view of a portion of the substrate processing chamber of Figure 1.

Figure 5A is a cross-sectional view of a substrate processing system having one or more ceramic plates therein.

Figure 5B is a schematic view of the one or more ceramic plates of Figure 5A.

To facilitate understanding， identical reference numerals have been used， where possible， to designate identical elements that are common to the figures. It is contemplated that elements and features of one example may be beneficially incorporated in other examples without further recitation.

DETAILED DESCRIPTION

Figure 1 is a cross-sectional view of a substrate processing system 100， such as a PECVD chamber. The substrate processing system 100 includes a substrate processing chamber 102 coupled to a gas source 104. The substrate processing chamber 102 comprises chamber walls 106 and a chamber bottom 108 (collectively， a chamber body 101) that partially define a process volume 110. The process volume 110 is generally accessed through a slit valve 112 in the chamber walls 106 that facilitates movement of a substrate 114 into and out of the substrate processing chamber 102. The chamber walls 106 and chamber bottom 108 are generally fabricated from a unitary block of aluminum or other suitable material for substrate processing. The chamber walls 106 support a lid assembly 116.

A gas distribution plate 126 is suspended in the substrate processing chamber 102 from a backing plate 128 that is coupled to the lid assembly 116. In other examples， the gas distribution plate 126 and backing plate 128 are manufactured from a unitary block of material. The gas distribution plate 126 is generally perforated such that precursor gases are uniformly distributed into the substrate processing chamber 102.

A substrate support 118 is generally centrally disposed within the substrate processing chamber 102. The substrate support 118 supports the substrate 114 during processing. Generally， the substrate support 118 is fabricated from conductive materials， such as aluminum， that encapsulates at least one temperature control device， which controllably heats or cools the substrate support 118 to maintain the substrate 114 at a predetermined temperature during processing.

The substrate support 118 has a first surface 120 and a second surface 122. The first surface 120 is opposite the second surface 122， and a third surface 121， which couples the first surface 120 to the second surface 122， is perpendicular to the first surface 120 and the second surface 122. The first surface 120 supports the substrate 114. The second surface 122 has a stem 124 coupled thereto. The stem 124 couples the substrate support 118 to a lift system (not shown) that moves the substrate support 118 between an elevated processing position (as shown) and a lowered position that facilitates substrate transfer into and out of the substrate processing chamber 102. The stem 124 also provides a conduit for electrical and thermocouple leads between the substrate support 118 and other components of the substrate processing system 100.

Any suitable number of ground straps 130 ground the substrate support 118 to the chamber bottom 108 to form a low-impedance RF current return path between the substrate support 118 and the chamber bottom 108 of the chamber body 101.

In operation， when precursor gases are introduced to the substrate processing chamber 102 and excited into plasma， the generated plasma forms a thin film on the substrate 114. In addition to depositing a thin film on the substrate， the generated plasma generally leaks to other parts of the chamber， becoming parasitic plasma that forms undesired films on various chamber components， such as chamber walls 106， chamber bottom 108， substrate support 118， and the ground straps 130.

Figure 2 is a top view of an exemplary ground strap 130. The body 232 of ground strap 130 is generally a rectangular piece of thin， flexible aluminum material having a first end 234 and a second end 236， with a slit 238 centrally located along the body 232 between the first end 234 and the second end 236. In one example， the ground strap 130 is further manufactured with one or more folds 240 centrally located between the first end 234 and the second end 236 and along the slit 238. In another example， the one or more folds 240 occur during processing when the substrate support 118 is raised from a lower， home position to a higher， processing position， thus bending the ground straps 130 and creating the one or more folds 240. Figure 2 illustrates just one example of a ground strap 130. The ground strap 130 is generally any suitable size， shape， and material conducive to substrate processing.

Figure 3 is a cross-sectional view of a portion 300 of the substrate processing chamber 102 of Figure 1， according to one example. As shown in Figure 3， the substrate support 118 comprises one or more support connectors 350 coupled thereto. A first， second， third， fourth， and fifth support connector， 350a-350e， respectively， are shown in Figure 3. The chamber bottom 108 includes one or more bottom connectors 352. A first， second， third， fourth， and fifth bottom connector， 352a-352e， respectively， are shown. In one example， the first support connector 350a and the first bottom connector 352a are aligned in a substantially vertical plane (y) . In another example， the first bottom connector 352a is vertically offset from the first top connector 350a.

Each of the ground straps 130 (three are shown as 130a， 130b， and 130c) is coupled to the substrate support 118 at a first end 234 and to the chamber bottom 108 at a second end 236.

According to one example of the present disclosure， shown in Figure 3， the first end 234a of the first ground strap 130a is coupled to the first support connector 350a； however， the second end 236a is coupled to the second bottom connector 352b such that the second end 236a is vertically offset from the first end 234a. The first end 234b of the second ground strap 130b is coupled to the second support connector 350b and the second end 236b is coupled to the third bottom connector 352c such that the second end 236b is vertically offset from the first end 234b. The first end 234c of the third ground strap 130c is coupled to the third support connector 350c and the second end 236c is coupled to the fourth bottom connector 352d such that the second end 236c is vertically offset from the first end 234c. While three ground straps 130 are shown in Figure 3， the vertically offset positions of the first ends 234 and the second ends 236 is applicable to any number of ground straps 130. A distance between each of the bottom connectors 352 along an horizontal axis (x) is generally any suitable distance， for example， between about 5 inches and about 10 inches， such as between about 6 inches and about 9 inches.

According to another example of the present disclosure， the first end 234a of the first ground strap 130a is coupled to the first support connector 350a； however， the second end 236a is coupled to the third bottom connector 352c such that the second end 236a is more vertically offset from the first end 234a. The first end 234b of the second ground strap 130b is coupled to the second support connector 350b and the second end 236b is coupled to the fourth bottom connector 352d such that the second end 236b is more vertically offset from the first end 234b. The first end 234c of the third ground strap 130c is coupled to the third support connector 350c and the second end 236c is coupled to the fifth bottom connector 352e such that the second end 236c is more vertically offset from the first end 234c.

While the examples described above contemplate the first ends 234 being offset from the second ends 236 by one or two bottom connector positions， it is also contemplated that the second ends 236 are vertically offset by any suitable distance along the x axis， for example， by three or more bottom connector positions， or less than one bottom connector position.

Conventionally， the first end 234a of the first ground strap 130a is coupled to the first support connector 350a and the second end 236a is coupled to the first bottom connector 352a. Under the conventional positioning， the one or more folds 240 are centrally located between the substrate support 118 and the chamber bottom 108. Accordingly， during processing， the center portion of the ground strap 130 having the one or more folds 240 is exposed to parasitic plasma 354， which reduces the lifetime of the ground straps 130.

Generally， according to the present disclosure， the second ends 236 of the one or more ground straps 130 are installed one or more bottom connector 352 positions in a counter-clockwise direction (when viewed from above) from the position directly， or substantially vertically， below the corresponding support connector. Under the vertically offset positioning of the present disclosure， the one or more folds 240 are located proximal to the chamber bottom 108， for example greater than 50％away from the substrate support in the y direction. In another example， one or more folds are within 40％in the y direction adjacent the chamber bottom 108. In another example， the one or more of folds 240 are positioned greater than fifty percent distal the first end 234. In operation， the vertically offset position of the first ends 234 from the second ends 236 of the respective ground straps 130 reduces the exposure of the one or more folds 240 to parasitic plasma 354 generated during processing. As shown in Figure 3， the parasitic plasma 354 is proximal the substrate support 118. The reduced exposure to parasitic plasma 354 extends the lifetime of the ground straps 130. As an additional benefit， the offset positioning of the present disclosure increases film deposition uniformity.

Figure 4A is a cross-sectional view of a portion 400 of the substrate processing chamber 102 of Figure 1. As shown in Figure 4A， the substrate processing chamber 102 further includes a first L-block and clamp assembly 460 and a second L-block and clamp assembly 470. The one or more ground straps 130 (one is shown) are coupled to the substrate support 118 through the first L-block and clamp assembly 460， and are coupled to the chamber bottom 108 through the second L-block and clamp assembly 470. Figure 4B is an enlarged cross-sectional view of the first L-block and clamp assembly 460. Figure 4C is an enlarged cross-sectional view of the second L-block and clamp assembly 470.

As shown in Figure 4B， the first L-block and clamp assembly 460 generally includes a first L-block 462 and a first clamp 464. The first L-block 462 is coupled to the substrate support 118 via a first coupling mechanism 466. In one example， the first coupling mechanism 466 is a screw； however， the first coupling mechanism 466 is generally any suitable coupling mechanism. The first clamp 464 is coupled to the first L-block 462 via a second coupling mechanism 468. In one example， the second coupling mechanism 468 is a screw； however， the second coupling mechanism 468 is generally any suitable coupling mechanism. The first L-block 462 further includes a first portion 462a and a second portion 462b. The first portion 462a and the second portion 462b intersect an angle (∠A) greater than about 90°. In one example， the ∠A is between about 100° and about 120°， for example， about 116.5°. The first clamp 464 intersects the substrate support 118 at an angle (∠B) less than about 90°. In one example， the ∠B is between about 60° and about 80°， for example， about 63.5°. A space 469 is formed between the first L-block 462 and the first clamp 464. The space 469 is generally configured to hold a first end 234 of the ground strap 130， such that the first end 234 of the ground strap 130 slides in between the first L-block 462 and the first clamp 464. In one example， the first end 234 of the ground strap 130 is coupled to the first L-block 462 and the first clamp 464， for example， through the second coupling means 468. In another example， the space 469 between the first L-block 462 and the first clamp 464 is sized to tightly hold the first end 234 of the ground strap 130 therebetween.

The second L-block and clamp assembly 470， shown in Figure 4C， is substantially similar to the first L-block and clamp assembly 470. The second L-block and clamp assembly 470 generally includes a second L-block 472 and a second clamp 474. The second L-block 472 is coupled to the chamber bottom 108 via a first coupling mechanism 476. In one example， the first coupling mechanism 476 is a screw； however， the first coupling mechanism 476 is generally any suitable coupling mechanism. The second clamp 474 is coupled to the second L-block 472 via a second coupling mechanism 478. In one example， the second coupling mechanism 478 is a screw； however， the second coupling mechanism 478 is generally any suitable coupling mechanism. The second L-b`ock 472 further includes a first portion 472a and a second portion 472b. The first portion 472a and the second portion 472b intersect an angle (∠A) greater than about 90°. In one example， the ∠A is between about 100° and about 120°， for example， about 116.5°. The second clamp 474 intersects the chamber bottom 108 at an angle (∠B) less than about 90°. In one example， the ∠B is between about 60° and about 80°， for example， about 63.5°. A space 479 is formed between the second L-block 472 and the second clamp 474. The space 479 is generally configured to hold a second end 236 of the ground strap 130， such that the second end 236 of the ground strap 130 slides in between the second L-block 472 and the second clamp 474. In one example， the second end 236 of the ground strap 130 is coupled to the second L-block 472 and the second clamp 474， for example， through the second coupling means 478. In another example， the space 479 between the second L-block 472 and the second clamp 474 is sized to tightly hold the second end 236 of the ground strap 130 therebetween.

In one example， the first L-block and clamp assembly 460 and the second L-block and clamp assembly 470 reduce an exposed portion 480 of the ground strap 130. In another example， the ground strap 130 is manufactured to a shorter length because the first L-block and clamp assembly 460 and the second L-block and clamp assembly 470 reduce a length of the ground strap 130 needed to couple ground the substrate support 118 to the chamber bottom 108. In one example， the first L-block and clamp assembly 460 and the second L-block and clamp assembly 470 reduce the overall length， or exposed length， of the ground strap 130 by about 25％. For example， the length over the one or more ground straps 130 is between about 30 centimeters (cm) and about 50 cm， such as between about 40 cm and about 45 cm. The reduced length of the exposed portion 480， or overall length， of the ground strap 130 extends the life time of the ground strap 130 by improving the RF grounding efficiency and reducing the impedance between the substrate support 118 and the chamber bottom 108. Additionally， the strength of the parasitic plasma is reduced because there is a reduced potential accumulation on the substrate support 118.

Figure 5A is a cross-sectional view of a substrate processing system 500. The substrate processing system 500 is similar to the substrate processing system 100. Similar to substrate processing system 100， the substrate processing system 500 includes a substrate support 118 having a first surface 120 for supporting a substrate 114， a second surface 122， which is opposite the first surface 120， and a third surface 121， which is perpendicular to the first surface 120 and the second surface 122； however， substrate processing system 500 further includes one or more ceramic plates 590 coupled to the substrate support 118. Additionally， the substrate support 118 may include one or more L-blockers 594 coupled to the substrate support 118 proximal to the third surface 121. The one or more L-blockers 594 generally include a first portion and a second portion perpendicular to the first portion. In one example， the first portion of the one or more L-blockers 594 is coupled to the second surface 122 of the substrate support 118.

Figure 5B is a schematic view of the one or more ceramic plates 590 coupled to the substrate support 118. In one example， the one or more ceramic plates 590 are coupled to the third surface 121， which corresponds to the outer perimeter， of the substrate support 118. In another example， the one or more ceramic plates 590 are coupled to the one or more L-blockers 594， which are coupled to the substrate support 118. As shown in Figure 5B， the one or more ceramic plates 590 are coupled to the substrate support 118 via one or more fastening mechanisms 596 (two are shown for each of the one or more ceramic plates 590) . In the example shown in Figure 5B， the one or more fastening mechanisms 596 are screws； however， any suitable fastening mechanism may be used， such as a rivet or bolt.

In one example， the one or more ceramic plates 590 are rectangular having a length (I) and a width (w) . The width of the one or more ceramic plates 590 generally extends below the second surface 122 of the substrate support 118. For example， the length of each of the one or more ceramic plates 590 is between about 4 inches and about 6 inches， such as about 5 inches， and the width of each of the one or more ceramic plates 590 is between about 3 inches about and about 5 inches， such as about 4 inches. In another example， the one or more ceramic plates 590 are square. In further examples， the width and length of the one or more ceramic plates 590 are generally any length and width suitable for the substrate processing chamber. For example， the width of the one or more ceramic plates 590 may be greater than 6 inches to cover a larger portion of the one or more ground straps 130.

In operation， the one or more ceramic plates 590 separate the parasitic plasma between the substrate support 118 and the various components of the substrate processing chamber 102， including the chamber walls 106 and the chamber bottom 108， and reduce parasitic plasma leakage in the substrate processing system 500. By reducing the parasitic plasma leakage， the amount of parasitic plasma induced film deposition on the components of the substrate processing system 500， including the chamber body 101， the substrate support 118， and the ground straps 130， is reduced or eliminated. Additionally， the one or more ceramic plates 590 shield at least a portion of the one or more ground straps 130 during processing. The one or more ceramic plates 590 extend the life time of the one or more ground straps 130.

While the above description discusses various apparatus and methods for extending the lifetime of one or more ground straps in turn， the disclosed apparatus and methods can be used alone or in any combination.

Benefits of the present disclosure include extension of the lifetime of ground straps by up to or more than 200％， for example， to greater than 12，000 processed substrates， and thus， reduced chamber component consumption and maintenance costs. Additionally， the disclosed apparatus and methods provide for better substrate processing chamber performance， for example， by less byproduct film formation on the chamber body， and reduced RF frequency variation in the substrate processing chamber.

While the foregoing is directed to examples of the present disclosure， other and further examples of the disclosure may be devised without departing from the basic scope thereof， and the scope thereof is determined by the claims that follow.

Claims

A substrate processing chamber comprising：

a chamber body， the chamber body comprising：

one or more chamber walls； and

a chamber bottom having a first bottom connector and a second bottom connector；

a substrate support disposed in the chamber body， the substrate support having at least a first support connector， a second support connector， and a third support connector；

a first ground strap having a first end and a second end， the first end being coupled to the substrate support at the first support connector， and the second end being coupled to the chamber bottom at the second bottom connector； and

a second ground strap having a first end and a second end， the first end being coupled to the substrate support at the second support connector， and the second end being coupled to the chamber bottom at the third bottom connector.
The chamber of claim 1， wherein a distance along a horizontal axis between the first bottom connector and the second bottom connector is between about 6 and about 9 inches.
The chamber of claim 1， wherein the second end of the first ground strap is vertically offset from the first end of the first ground strap， and wherein the second end of the second ground strap is vertically offset from the first end of the second ground strap.
The chamber of claim 1， wherein the first ground strap and the second ground strap further comprise one or more folds， and wherein the one or more folds are positioned greater than fifty percent distal the first end.
The chamber of claim 4， wherein the one or more folds are positioned within forty percent adjacent the second end.
A substrate processing chamber comprising：

a chamber body， the chamber body comprising：

one or more chamber walls； and

a chamber bottom；

a substrate support disposed in the chamber body， the substrate support having a first surface， a second surface， and a third surface perpendicular to the first surface and the second surface and facing the one or more chamber walls；

one or more ground straps having a first end and a second end， the first end being coupled to the substrate support and the second end being coupled to the chamber bottom； and

one or more ceramic plates coupled to the substrate support， each ceramic plate having a length and a width， the width being parallel to the third surface， and the ceramic plate extending below the second surface.
The chamber of claim 6， further comprising an L-blocker coupled to the substrate support， and wherein the one or more ceramic plates are coupled to the L-blocker.
The chamber of claim 6， wherein each of the one or more ceramic plates is rectangular， wherein the length of each of the one or more ceramic plates is between about 4 inches and about 6 inches， and wherein the width of the one or more ceramic plates is between about 3 inches and about 5 inches.
The chamber of claim 6， wherein each of the one or more ceramic plates is square.
The chamber of claim 6， wherein the one or more ceramic plates separate the one or more chamber walls from at least a portion of the one or more ground straps.
A substrate processing chamber comprising：

a chamber body， the chamber body comprising：

one or more chamber walls； and

a chamber bottom；

a substrate support disposed in the chamber body；

one or more ground straps having a first end and a second end， the first end being coupled to the substrate support and the second end being coupled to the chamber bottom；

a first L-block and clamp at the first end； and

a second L-block and clamp at the second end， each of the first L-block and the second L-block having a first portion and a second portion intersecting at an angle greater than about 90 degrees.
The chamber of claim 11， wherein the angle is between about 100 degrees and about 140 degrees.
The chamber of claim 11， wherein an exposed length of each of the one or more ground straps is between about 40 centimeters and about 45 centimeters.
The chamber of claim 11， wherein the chamber bottom further comprises a first bottom connector and a second bottom connector， and wherein the substrate support further comprises a first support connector and a second support connector.
The chamber of claim 14， wherein the first L-block is coupled to the first support connector， wherein the second L-block is coupled to the second bottom connector， and wherein the second L-block is vertically offset from the first L-block.