Abstract:
A method and apparatus for providing particle collection channels in a semiconductor substrate processing chamber. The channels are formed in either a chamber liner or directly into the walls and/or bottom of the chamber. The channels direct trapped particles toward a chamber exhaust port.

Description:
BACKGROUND OF THE DISCLOSURE 
     1. Field of the Invention 
     The present invention relates generally to semiconductor substrate processing systems and, more particularly, the invention relates to a chamber surface for a semiconductor substrate processing chamber having particle collection channels formed in the surface. 
     2. Description of the Background Art 
     In modem fabrication of integrated circuits, features are formed on semiconductor substrates, often silicon wafers, by processing the substrates in enclosed processing chambers, often within a multichamber processing system. Typically, a substrate is robotically introduced into a chamber and secured to a support member, or pedestal, within the chamber. As part of the processing procedure, the processing surface of a substrate may be exposed to gas introduced through a gas inlet and later expelled through a gas outlet, the inlet and outlet being formed in the walls of the chamber. 
     Various types of processing chambers are used to process semiconductor substrates. In a deposition chamber, layers of material are deposited on the processing surface of a substrate that is secured to a support member. Deposition chambers include physical vapor deposition (PVD) chambers and chemical vapor deposition (CVD) chambers. In PVD chambers, particles are typically sputtered from a target to form layers of material on the processing surface of a substrate. In CVD chambers, introduced gas or gases are used to cause chemical reactions, the product of which deposits on the processing surface of a substrate, forming layers thereon. In an etch chamber, features are formed by chemically removing material from the surface of a substrate by exposing the surface to an etchant gas or gases introduced into and later expelled from the chamber. In a plasma enhanced etch chamber, such as a decoupled plasma source (DPS) etch chamber, a plasma is generated within the chamber above the processing surface of the substrate. During the course of a number of processing steps, plasma generation may be cycled on and off a number of times. 
     One persistent problem encountered in various types of processing chambers including PVD, CVD and etch chambers is that particles can be generated in the chamber and cause unwanted deposits on various components within the chamber and on the substrate itself. Unwanted particles in the chamber can contaminate the processing surface of a substrate, causing waste and inefficiency. 
     In plasma enhanced etch chambers, unwanted particle formation within the chamber is practically inevitable. Material removed from the processing surface of the substrate can cause unwanted deposition on surfaces within the chamber before the etchant gas containing the particles can be exhausted. In addition, the plasma can cause chemical reactions and particle film accumulation on surfaces within the chamber, which can eventually crack or flake and generate particles that contaminate the chamber environment and can ultimately deposit on the processing surface of the substrate. When the plasma is cycled off, particles in the chamber environment may settle on surfaces within the chamber, such as the bottom of the chamber, only to be lifted again when gases are flowed into the chamber and the plasma is next cycled on, increasing the chances that the particles will contaminate the processing surface of the wafer. 
     Avoiding the presence of unwanted particles within the chamber is a difficult problem. Various methods of reducing unwanted particulate contamination and deposition in processing chambers are presently utilized. In etch chambers, unwanted deposition can in some cases be reduced by the use of self-cleaning chemistries. This involves introducing chemical agents, such as fluorine- or chlorine-based compounds, into the chamber that reduce unwanted deposition by reacting with and eliminating the unwanted deposits. 
     Another approach in reducing the amount of contaminant particles present in the chamber environment involves taking steps to increase adhesion of particles to the chamber walls, thus trapping some of the particulate material so that it cannot contaminate the substrate. This can be accomplished by keeping the chamber walls cool or the surfaces of the walls rough, in order to increase adhesion. This approach has the disadvantage of causing deposits to build up on the walls of the chamber. As these deposits accumulate, thermally induced stresses within the chamber can eventually cause them to crack or flake off, shedding particles that contaminate the chamber environment. Further, causing adhesion of particles to the chamber walls is especially difficult in silicon etch chambers, where the wide and unpredictable variety of particles generated causes difficulty in selecting an ideal type of surface to promote particle adhesion. 
     Controlling the temperature of the chamber components can sometimes be used to reduce unwanted particulate contamination and deposition within a chamber, depending on the type of chamber and processing circumstances. However, temperature control is at best a partial solution and can be difficult to achieve, particularly considering the difficulty in thermally isolating chamber components during processing steps that require heating the substrate. 
     Removable chamber liners are sometimes used to remove unwanted depositions within the chamber. However, using liners requires frequently removing and replacing contaminated liners. In addition, accumulation of particles within the chamber between changes of the liner remains a problem. 
     As discussed above, while various approaches are presently employed to reduce particulate contamination within a chamber and unwanted deposition on the substrate, none of the approaches provide a completely effective solution. 
     Therefore, there is a need for processing chamber-related equipment that can reduce the amount of particles present in a chamber. 
     SUMMARY OF THE INVENTION 
     The present invention generally provides a chamber surface for a semiconductor substrate processing chamber having particle collection channels formed in the surface. Particles in the chamber are trapped in the channels and thereby prevented from contaminating chamber components or a processing substrate. 
     In one embodiment, the invention provides a liner for the bottom of a plasma etch chamber. Channels formed in the liner lead from an area near a support member to an opening leading to a gas outlet. The channels are sized to prevent plasma from entering the channels and potentially lifting trapped particles out of the channels. Gas flow within the chamber drives particles collected in the channels in the direction of the gas outlet until they are removed through the gas outlet by a vacuum pump. The liner may also have recesses in addition to the channels, to further trap particles and prevent them from contaminating the substrate. Additionally, secondary channels, or tributaries, may be formed in the liner, each tributary connecting to a channel and radiating outwardly therefrom. Particles trapped in the tributaries are driven by gas flow into the channels, where the particles are further driven to the gas outlet. 
     In another embodiment, the invention provides a chamber liner having a sidewall, with particle collection channels formed in the sidewall and sized to prevent plasma from entering the channels and potentially removing the particles. 
     In another embodiment, the invention provides a chamber having a plurality of particle collection channels formed in a chamber bottom. Tributaries and/or recesses may also be formed in the chamber bottom. 
     In still another embodiment, the invention provides a chamber having a plurality of particle collection channels formed in a chamber sidewall. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     So that the manner in which the above recited features, advantages and objects of the present invention are attained can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to the embodiments thereof which are illustrated in the appended drawings. 
     It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
     FIG. 1 is a cross-sectional side view of a substrate processing chamber having a liner; 
     FIG. 2 is a cross-sectional top view of the chamber taken along line  2 — 2  of FIG. 1; 
     FIG. 3 is a cross-sectional side view of the liner taken along line  3 — 3  of FIG. 2 depicting a channel and a recess; 
     FIG. 4 is a cross-sectional view of the liner taken along line  4 — 4  of FIGS. 2 and 3 depicting a channel; 
     FIG. 5 is a top view of a section of another embodiment of a liner depicting channels, recesses and tributaries; 
     FIG. 6 is a cross-sectional side view of another embodiment of a chamber depicting a liner having a bottom and a sidewall; 
     FIG. 6A is a top cross sectional view of the chamber taken along line  6 A— 6 A of FIG.  6 . 
     FIG. 6B is a top cross sectional view of another embodiment of a chamber; 
     FIG. 7 is a cross-sectional side view of another embodiment of a chamber depicting a liner having a sidewall; 
     FIG. 8 is a sectional perspective view of the sidewall of the liner taken along line  8 — 8  of FIG. 6A depicting grooves; 
     FIG. 8A is a sectional perspective view of the sidewall of the liner taken along line  8 A— 8 A of FIG. 6B depicting grooves; 
     FIG. 9 is a cross-sectional side view of the sidewall of the liners of FIGS. 6,  6 A, and  7  depicting grooves; and 
     FIG. 10 is a top view of another embodiment of a liner; 
     FIG. 11 is a cross-sectional side view of another embodiment of a substrate processing chamber; 
     FIG. 12 is a cross-sectional top view of the chamber taken along line  12 — 12  of FIG. 1; and 
     FIG. 13 is a cross-sectional side view of another embodiment of a chamber. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention generally provides a chamber surface for a semiconductor substrate processing chamber having particle collection channels formed in the surface. In one embodiment of the invention, the channels are formed in a chamber liner. In another embodiment of the invention, the channels are formed directly in the chamber walls and/or bottom. Particles in the chamber are trapped in the channels and thereby prevented from contaminating chamber components or a substrate being processed. The invention is particularly useful in plasma-assisted etch chambers, where particulate contamination of the chamber environment and ultimately a processing substrate can be especially difficult to prevent. However, other forms of chambers will benefit from use of the invention. 
     In one embodiment, the channels are sized to prevent plasma from entering therein and lead from an area near a substrate support to an opening in the liner leading to a gas outlet. The sizing of the channels prevents particles contained within the channels from being lifted out by plasma and reintroduced into the chamber environment, where the particles may ultimately contaminate the substrate. Gas flow within the chamber causes particles trapped within the channels to be moved toward and eventually out of the opening in the liner leading to the gas outlet. 
     FIG. 1 is a cross-sectional side view of a substrate processing chamber  100  having a liner  122 . One embodiment of a substrate processing chamber  100  is a metal etch decoupled plasma source (DPS) chamber, manufactured by Applied Materials, Inc. of Santa Clara, Calif., as depicted in FIG.  1 . The invention is discussed in relation to a DPS chamber; however, the invention is useful with respect to any type of substrate processing chamber where particles may cause unwanted deposition within the chamber, including CVD and PVD chambers. 
     The chamber  100  is defined by a dome  106 , a sidewall  102 , and a bottom  104 . One or more gas inlets  108  (two are shown) are formed in the sidewall  102 , and a gas outlet  110  is formed in the bottom  104 . Conductive coils  112  circumscribe the outer circumference of the dome  106  and operate as an antenna to couple energy to the gases within the chamber  100 . The chamber  100  houses a support member  118  on which a substrate  120  is retained. The support member  118  also functions as a cathode. A high powered RF source  116  powers the conductive coils  112  and an RF or DC source  117  powers the support member  118  functioning as a cathode. A liner  122  is disposed on the bottom  104  of the chamber  100 . 
     In operation, the substrate  120  is placed on the support member  118  and gaseous components are supplied through a gas inlet port or ports  108  and eventually expelled through the gas outlet  110 . When plasma is cycled on, plasma is ignited in the process chamber  100  above the processing surface  121  of the substrate  120  by applying RF power from the RF source or sources  116  to both the conductive coils  112  and the support member  118  functioning as a cathode. Plasma may be cycled on and off multiple times during substrate  120  processing. Particles are continually generated in the chamber environment as a result of etching processes performed on the substrate  120  as well as by cracking and flaking of particle film deposits on surfaces within the chamber  100 . The liner  122  traps particles that are free in the chamber environment, keeping them from depositing on and contaminating the substrate  120 . Gas flow within the chamber  100  drives particles trapped in the liner  122  toward and eventually through the gas outlet  110 . 
     To best understand the invention, the reader should simultaneously refer to FIGS. 2,  3 , and  4  while reading the following description. FIG. 2 is a cross-sectional top view of the chamber  100  taken along line  2 — 2  of FIG.  1 . In the embodiment shown, the support member  118  extends through a first opening  202  in the liner  122 , and a second opening  204  in the liner  122  is positioned over the gas outlet  110 . The liner  122  may be made of a corrosion resistant polymeric material including a TEFLON® polymer, ULTEM®, KAPTON®, or VESPEL®. In the embodiment depicted in FIG. 2, the liner  122  has first and second openings  202 ,  204  formed therein. However, other embodiments of the invention are possible wherein the liner does not have either or both openings. 
     A plurality of particle collection channels  200  are formed in the liner  122 , leading at least partially from the support member  118  to the gas outlet  110 . The channels  200  are formed in the liner  122  and extend from the proximity of the first opening  202  until the channels  200  connect to the second opening  204 . The first opening  202  is adapted to receive a support member  118  and the second opening  204  is adapted to be positioned above the gas outlet  110 . 
     FIG. 3 is a cross-sectional side view of the liner taken along line  3 — 3  of FIG.  2 . Each channel  200  is formed in the upper surface  300  of the liner  122 , extending partly through the liner  122 . A channel  200  is shown extending from the proximity of the first opening  202  until the channel  200  connects with the second opening  204 . 
     FIG. 4 is a cross-sectional view of the liner  122  taken along line  4 — 4  of FIGS. 2 and 3 depicting a channel  200 . The width  400  of the mouth  402  of the channel  200  is narrower than the width  404  of the base  406  of the channel  200 . 
     The liner  122  includes a plurality of recesses  206  in addition to the channels  200 . The recesses  206  are formed in the liner  122  in the proximity of the portion of the circumference of the first opening  202  that is furthest from the second opening  204 . The cross-section of the recesses  206  depicted in FIGS. 2 and 3 is similar to the cross-section of the channel  200  depicted in FIG.  4 . 
     In operation, the channels  200  and recesses  206  trap particles that are free in the chamber environment and thereby prevent the particles from contaminating the substrate  120  and chamber components. Additionally, the dynamics of gas flow within the chamber  100  causes particles trapped in the channels  200  to be moved toward the second opening  204  in the liner  122  and eventually exhausted from the chamber  100  via a vacuum pump (not shown). 
     In plasma enhanced etch chambers such as the chamber  100  depicted in FIG. 1, plasma formed within the chamber  100  during substrate  120  processing can lift particles from chamber surfaces and into the chamber environment, where the particles may adhere to and contaminate a substrate  120  or chamber components. Typically, plasma may be cycled on and off a number of times during various processing steps. Each time plasma is cycled on, the plasma lifts particles that have accumulated on surfaces of the chamber  100  including the bottom  104  and into the chamber environment, where the particles may deposit on and thus contaminate the substrate  120  or chamber components. In the embodiment depicted in FIGS. 1 through 4, each channel  200  and recess  206  is sized to prevent entry of the plasma therein. As a result, particles that accumulate in the channels  200  and recesses  206  are prevented from being lifted out by plasma, instead remaining trapped in the channels  200  or recesses  206 . This prevents the particles from re-entering the chamber environment as the result of plasma cycling and potentially depositing on and contaminating the processing surface  121  of the substrate  120 . 
     The channels  200  and recesses  206  are sized so that, when plasma is cycled on during a processing step, the plasma is prevented from reaching into the channel  200  and contacting surfaces in the channel  200 . Plasma has the characteristic that its density dramatically decreases as it approaches a surface. In effect, what is known as a “plasma sheath” is formed in all areas within a certain short distance from all surfaces within the chamber  100 , the plasma sheath being an area nearly free of plasma. Each channel  200  and recess  206  is sized so that the width  400  of the mouth  402  is small enough that the surfaces of the liner  122  that form the mouth  402  are near enough to each other so that the plasma sheath proximate to these surfaces causes the entire area enclosed by the mouth  402  to remain nearly free of plasma. For example, the width  400  of the mouth  402  of the channel  200  may be about 1 millimeter. As a result, very little plasma is admitted into the base of the channel  200  or recess  206 , so that particles trapped in the base of the channel  200  or recess  206  are prevented from being contacted by the plasma and lifted out of the channel  200  or recess  206  when plasma is cycled on. Particles trapped in the channels  200  are eventually exhausted from the chamber  100  in the manner described above, and particles trapped in the recesses  206  remain there until the liner  122  is cleaned or replaced. 
     FIG. 5 is a top view of a section of another embodiment of a liner  500  showing channels  200 , recesses  206  and tributaries  514 . In this embodiment, the tributaries  514  are identical in cross-section to the channels  200 , and are sized to prevent plasma from contacting surfaces therein. Arrow  502  points in the direction of the second opening  204 , adapted to be positioned above the gas outlet  110 . In the embodiment shown in FIG. 5, a plurality of recesses  206  are formed in the liner  500  and positioned such that a tributary  514  is in a linear path between a recess  206  and the second opening  204  (of FIG.  2 ). 
     Each tributary  514  radiates outwardly from a channel  200 . Each tributary  514  has a first end  504  connected to a channel  200  and a second end  506  positioned nearer than the first end  504  to the first opening  202  (of FIG.  2 ). Particles trapped in the channels  200  are moved by gas flow within the chamber through the channel  200  in the direction shown by arrow  508  towards and eventually through the second opening  204 . Particles trapped in the tributaries  514  are moved by gas flow within the chamber in the direction of the channel  200  to which the tributary  514  connects, as shown by arrows  510  and  512 , until the particles flow from the tributary  514  into the connected channel  200 . 
     To best understand the invention, the reader should simultaneously refer to FIGS. 6 and 6A while reading the following description. FIG. 6 is a cross-sectional side view of another embodiment of a chamber  600  having a liner  602  comprising a bottom  604  and a sidewall  606 . FIG. 6A is a top view of the liner  602  taken along line  6 A— 6 A of FIG.  6 . The liner  602  has a bottom  604  that is adapted to be positioned along the bottom  104  of the chamber  600  and a sidewall  606  that is adapted to be positioned along the sidewall  102  of the chamber  600 . The bottom  604  and the sidewall  606  of the liner  602  may be separate or may be a unitary structure. In this embodiment, the bottom  604  of the liner  602  covers substantially all of the chamber bottom  104  (of FIG. 6) and the sidewall  606  of the liner  602  is disposed along the circumference of the chamber bottom  604 . The sidewall  606  of the liner  602  extends completely around the sidewall  102  of the chamber  600 . 
     FIG. 6B shows a top view of another embodiment of a chamber  650  having a liner  706  comprising a bottom  704  and a sidewall  706 . The sidewall  714  of the chamber  650  is curved in the vicinity of the gas outlet  710 . A portion of the circumference of the gas outlet  710  defines a curved portion  720  of the sidewall  714  of the chamber  650 . The sidewall  706  extends around the chamber  650  up to the vicinity of the gas outlet  710 . The liner has a first end  716  and a second end  718 , both positioned in the vicinity of the gas outlet. 
     FIG. 7 is a cross-sectional side view of another embodiment of a chamber  700  depicting a liner  702  consisting of the sidewall  606  positioned along the chamber  700  sidewall  102 . The liner  702  depicted in FIG. 7 has no bottom. 
     A plurality of particle collection grooves  608  (five are shown) are formed in the sidewall  606  of the liners depicted in FIGS. 6,  6 A,  6 B and  7 . The grooves  608  are vertically spaced from one another and extend horizontally along the sidewall  606 . The grooves  608  are sized to prevent plasma from contacting surfaces therein. 
     FIG. 8 is a sectional perspective view of the sidewall of the liner taken along line  8 — 8  of FIG. 6A depicting grooves. In the embodiment depicted in FIG. 8, each groove  608  is formed at a different vertical height on sidewall  606  of the liner and extends horizontally along the sidewall  606  of the liner. 
     FIG. 8A is a sectional perspective view of the sidewall of the liner taken along line  8 A— 8 A of FIG. 6B depicting grooves. In the embodiment depicted in FIG. 8A, the grooves  800  slope slightly downward as the grooves  800  approach the first end  716  end and the second end  718  of the sidewall  706  of the liner  702  in the vicinity of the gas outlet  710  (shown in FIG.  6 B), so that gravity and/or gas flow dynamics within the chamber cause at least a portion of particles trapped in the grooves  800  to eventually reach an end of the grooves  800  at the first end  716  or the second end  718  of the sidewall  706  of the liner  702  and fall into the gas outlet  710 . 
     FIG. 9 is a cross-sectional side view of a sidewall  606  of the liners of FIGS. 6 and 7. In the embodiment depicted in FIG. 9, the sidewall  606  is cylindrically shaped. The grooves  608  extend at a downward angle into the sidewall  606  of the liner. Gravity causes particles that happen to enter into a groove  608  to fall to the bottom  900  of the groove  608 . Each groove  608  is sized to prevent plasma from entering into the groove  608  and contacting surfaces therein, so that particles at the bottom  900  of the groove  608  are trapped there and cannot re-enter the chamber environment and potentially deposit on and contaminate the substrate  120  or chamber components. 
     FIG. 10 is a top view of another embodiment of the invention depicting a liner  1002  positioned in a chamber  1000 . The liner  1002  is disposed on the chamber bottom  104  between the support member  118  and the gas outlet  110  so as to extend from the proximity of the support member  118  to the gas outlet  110 . The liner extends only partly around the support member  118  and the gas outlet  110 , and no openings are formed in the liner  1002 . Particle collection channels  200  formed in the liner  1002  extend from the proximity of the support member  118  to the gas outlet  110 . 
     To best understand the invention, the reader should refer simultaneously to FIGS. 11 and 12 while reading the following description. FIG. 11 is a cross-sectional side view of another embodiment of embodiment of the invention, depicting a chamber  1100  without a liner. FIG. 12 is a cross-sectional top view of the chamber  1100  of FIG. 11 taken along line  12 — 12  of FIG.  11 . As shown in FIG. 12, a plurality of particle collection channels  1200  and recesses  1206  are formed in the chamber bottom  1104 . The particle collection channels  1200  and recesses  1206  formed in the chamber bottom  1104  are similar to and function similarly to the particle collection channels  200  and recesses  206  formed in chamber liner  122 , as described above with reference to FIGS. 2,  3 , and  4 . 
     In another embodiment of the chamber, a chamber bottom may have recesses  1206  and/or tributaries in addition to the particle collection channels  1200  and the recesses  1206  depicted in FIG. 11 that are similar to and function similarly to the recesses  206  and tributaries  514  of the chamber liner  500  depicted and described with reference to FIG.  5 . 
     FIG. 13 is a cross-sectional side view of another embodiment of a chamber  1300 . In the embodiment depicted in FIG. 13, the chamber  1300  has a chamber sidewall  1320  having a plurality of particle collection grooves  1308  formed in the chamber sidewall  1320 , in addition to having a chamber bottom  1104  having a plurality of particle collection channels  1200  and recesses  1206  are formed in the chamber bottom  1104 . The particle collection grooves  1308  formed in the chamber sidewall  1320  are similar to and function similarly to particle collection grooves  608  formed in sidewall  606  of liner  602 , depicted and described with reference to FIG.  6 . In an alternative embodiment, a chamber (not shown) may have a chamber sidewall  1320  having a plurality of particle collection grooves  1308  formed in the chamber sidewall  1320 , and a chamber bottom that does not have a plurality of particle collection channels  1200  and/or recesses  1206  formed in the chamber bottom. 
     While foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.