Patent Grant
11691244
Embodiments of the present disclosure generally relate to an apparatus and method for polishing and/or planarization of substrates. More particularly, embodiments of the disclosure relate to retaining assemblies for carrier heads utilized for chemical mechanical polishing (CMP).
During fabrication of a semiconductor device, various layers such as oxides and copper for example, require polishing to remove steps or undulations before formation of subsequent layers. Polishing is useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches, and contaminated layers or materials. Polishing is also useful in forming features on a substrate by removing excess deposited material used to fill the features and to provide an even surface for subsequent levels of metallization and processing.
Polishing is typically performed mechanically, chemically, and/or electrically using processes such as chemical mechanical polishing (CMP) or electro-chemical mechanical polishing (ECMP).
CMP removes material from the surface of a substrate in the presence of a slurry through a combination of mechanical and chemical interaction. During CMP, the slurry is delivered on to a rotating polishing pad, and the substrate is pressed against the polishing pad by a carrier head. The carrier head may also rotate and move the substrate relative to the polishing pad. As a result of the motion between the carrier head and the polishing pad and chemicals included in the slurry, the substrate surface is planarized.
The carrier head includes a membrane having a plurality of different radial zones that contact the substrate. In some embodiments, the membrane may include three or more zones, such as from 3 zones to 11 zones, for example, 3, 5, 7 or 11 zones. Using the different radial zones, pressure applied to a chamber bounded by the backside of the membrane may be selected to control the center to edge profile of force applied by the membrane to the substrate, and consequently, to control the center to edge profile of force applied by the substrate against the polishing pad. The zones are typically labeled from outer to inner (e.g., from zone 1 on the outside to zone 11 on the inside for an 11 zone membrane). A common problem in CMP is occurrence of an edge effect (i.e., the over- or under-polishing of the outermost 5-10 mm of a substrate). In an effort to remove the edge effect, the outer zones (typically referred to as zones 1 and 2) of the membrane are spaced more closely together than the inner zones (typically referred to as zones 10 and 11) to provide more precise pressure control over a shorter radial distance at the outer edge. However, such close spacing can add complexity to the design of the outer zones making manufacturing of the carrier head more difficult.
A retaining ring is secured to the carrier head to retain the semiconductor substrate and improve the resulting finish and flatness of the substrate surface (e.g., by minimizing the edge effect). The retaining ring has a bottom surface for contacting the polishing pad during polishing and a top surface which is secured to the carrier head. The bottom surface can pre-compress the polishing pad to move a high-pressure region at the leading edge off the substrate. The bottom surface includes a plurality of grooves to facilitate transport of a polishing slurry from outside the retaining ring to the substrate even when the bottom surface is contacting the polishing pad. Existing retaining rings have a fixed number of grooves, fixed groove shape, and fixed groove dimensions making it difficult to improve and/or optimize slurry intake and retention within the ring during processing. As existing retaining rings wear down with normal use, groove height will be reduced, which causes the amount of slurry intake and retention to gradually change over time. Existing retaining ring designs can also suffer from a scraping effect, which can increase overall slurry consumption. Thus, existing designs exhibit pronounced shortcomings with respect to slurry use, and since slurry is an expensive aspect of CMP process, it is desirable to lower overall slurry consumption by reducing waste.
Therefore, there is a need for an apparatus and method to overcome the problems described above.
Embodiments of the present disclosure generally relate to an apparatus and method for polishing and/or planarization of substrates. More particularly, embodiments of the disclosure relate to retaining assemblies for carrier heads utilized for chemical mechanical polishing (CMP).
In one embodiment, a retaining ring assembly is configured to be attached to a carrier head. The retaining ring assembly includes a retaining ring including a lower surface, an inner surface, an outer surface and a plurality of grooves, where the lower surface is configured to contact a polishing pad during a polishing process, and each of the plurality of grooves are formed in the lower surface and extend from the inner surface to the outer surface. The retaining ring assembly includes a plurality of retainers, each retainer including a movable tooth at least partially disposed in a respective groove of the retaining ring and moveable relative to the lower surface.
In another embodiment, a system for polishing a substrate includes a housing including a plurality of stationary magnets, a carrier head disposed adjacent to the housing, and a retaining ring assembly attached to the carrier head. The retaining ring assembly includes a retaining ring including a lower surface, an inner surface, an outer surface and a plurality of grooves, where the lower surface is configured to contact a polishing pad during a polishing process, and each of the plurality of grooves are formed in the lower surface and extend from the inner surface to the outer surface. The retaining ring assembly includes a movable magnet disposed within a magnetic field of a first stationary magnet of the plurality of stationary magnets. The retaining ring assembly includes a movable tooth coupled to the movable magnet and disposed within a groove of the plurality of grooves.
In yet another embodiment, a method for polishing a substrate includes disposing the substrate in a polishing system. The polishing system includes a housing including a plurality of stationary magnets, a carrier head disposed adjacent to the housing, and a retaining ring assembly attached to the carrier head. The retaining ring assembly includes a retaining ring including a lower surface, an inner surface, an outer surface and a plurality of grooves, where the lower surface is configured to contact a polishing pad during a polishing process, and each of the plurality of grooves are formed in the lower surface and extend from the inner surface to the outer surface. The retaining ring assembly includes a movable magnet and a movable tooth coupled to the movable magnet and disposed within a groove of the plurality of grooves. The method includes rotating the carrier head to a first angular position relative to the housing, where the retainer has a first vertical position when the carrier head is in the first angular position and rotating the carrier head to a second angular position relative to the housing, where the second angular position is different from the first angular position, and where the retainer moves to a second vertical position different from the first vertical position.
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 embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, may admit to other equally effective embodiments.
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 embodiment may be beneficially incorporated in other embodiments without further recitation.
Before describing several exemplary embodiments of the apparatus and methods, it is to be understood that the disclosure is not limited to the details of construction or process steps set forth in the following description. It is envisioned that some embodiments of the present disclosure may be combined with other embodiments.
One or more embodiments of the present disclosure are directed towards an apparatus and method for polishing and/or planarization of substrates, such as semiconductor substrates. In some embodiments, a system may comprise a stationary housing including a plurality of stationary magnets, a carrier head disposed adjacent to the stationary housing, and a retainer movably attached to the carrier head. In some embodiments, the retainer may include a movable magnet disposed within a magnetic field of a first stationary magnet of the plurality of stationary magnets and a movable tooth fixedly attached to the movable magnet. In one or more embodiments, as the carrier head rotates, the movable magnet can align with the first stationary magnet causing the movable magnet to move relative to the first stationary magnet.
In one or more embodiments, a gap between a bottom surface of the movable tooth and a polishing pad is configured to convey a polishing slurry. In one or more embodiments, the gap between each movable tooth and the polishing pad can be adjusted to precisely control transport of polishing slurry to and from a substrate being polished. For example, retaining assemblies at a trailing edge of the carrier head may be lowered to restrict polishing slurry from exiting the retaining ring holding the substrate while retaining assemblies at a leading edge of the carrier head may be raised to admit fresh polishing slurry to the substrate. Precise control of polishing slurry transport can reduce overall consumption of the polishing slurry.
Conventional CMP processes can have high polishing rates at the edge of the substrate caused by deflection and rebound of the pad resulting in non-uniform pressure being applied by the pad to all regions of to be polished surface of the substrate. However, in one or more other embodiments of the present disclosure, a downforce of each movable tooth of the retaining ring assembly on the polishing pad can be independently controlled. Independent control of downforce can improve wafer edge uniformity and profile (e.g., by reducing and/or eliminating non-uniformity at the edge caused by high polishing rates), and independent control of downforce can also enable simplified membrane design (e.g., in outer zones 1 and 2).
The polishing system 100 generally comprises a polishing station 110, a carrier head 120, a retaining ring 150, and a housing 180. The housing 180 includes one or more stationary magnets 184. In addition, the polishing system 100 also includes one or more retaining assemblies 200 movably attached to the carrier head 120 and/or the retaining ring 150. Each of the retaining assemblies 200 includes a movable magnet 210 and a movable tooth 220. In at least one embodiment, the polishing system 100 has a single polishing station 110. In another embodiment, the polishing system 100 includes multiple polishing stations 110 and multiple carrier heads 120. For example, the polishing station 110 may be disposed on a system base having multiple platens and the carrier head 120 may be supported by a rotatable carousel having multiple carrier heads identical or similar to the carrier head 120. In some embodiments, the carrier head 120 may move a substrate 10 from one polishing station 110 to another polishing station configured to perform a different polishing step to the substrate 10. In one or more embodiments, the housing 180 may be an upper pneumatics assembly (UPA).
The polishing station 110 generally comprises a rotatable platen 112 on which a polishing pad 114 is placed. The rotatable platen 112 and the polishing pad 114 are generally larger than a semiconductor substrate 10 being processed. In at least one embodiment, the platen 112 is a rotatable aluminum plate connected by a aluminum drive shaft 116 to a platen drive motor (not shown), which rotates the platen 112 and polishing pad 114 during processing. In one or more embodiments, the platen 112 may be directly or indirectly driven by the platen drive motor.
The polishing pad 114 has a roughened polishing surface 118 configured to polish the substrate 10. In at least one embodiment, the polishing pad 114 may be attached to the platen 112 by a pressure-sensitive adhesive layer. The polishing pad 114 is generally consumable and may be replaced.
The polishing station 110 may further comprise a polishing composition supply tube (not shown) configured to provide a polishing composition (e.g., slurry) to the polishing pad 114. The polishing composition generally contains a reactive agent, abrasive particles, and a chemical-reactive catalyzer. In one or more embodiments, a chemistry of the polishing composition may depend on the type of CMP process being performed. In some embodiments, the polishing composition can be or include a basic chemistry for planarizing oxide layers (e.g., dielectrics). For example, a basic polishing composition may include deionized water, metal oxide powder, and potassium hydroxide. In addition, CMP processes performed on oxide layers are primarily mechanically driven, whereby control of downforce (e.g., pressure applied to the substrate during polishing) is a primary polishing rate and uniformity control mechanism.
In some other embodiments, the polishing composition can be or include an acidic chemistry for planarizing metal layers. For example, an acidic polishing composition may include deionized water, metal oxide power, and carboxylic acid. In addition, CMP processes performed on metal layers are primarily chemically driven, whereby control of slurry intake and retention is a primary polishing rate and uniformity control mechanism. Therefore, use of one or more of the apparatus and methods disclosed herein can be especially advantageous for use in metal CMP polishing processes.
The polishing station 110 may further comprise a pad conditioner (not shown) configured to maintain the polishing pad 114 in a state that effectively polishes the substrate 10. In at least one embodiment, the pad conditioner may comprise a rotatable arm holding an independently rotating conditioner head.
The carrier head 120 is suspended from and/or positioned below the housing 180. The carrier head 120 is generally configured to press the substrate 10 against the polishing pad 114 during polishing. In one example, the carrier head 120 includes a housing 122, a base assembly 124, and a gimbal 126. The base assembly 124 is vertically movable with respect to the housing 122 and together therewith defines a loading chamber 128. The vertical position of the base assembly 124 relative to the polishing pad 114 may be controlled by changing the pressure within the loading chamber 128. For example, the loading chamber 128 is typically pressurized during polishing to exert a downward force on the base assembly 124 which brings the retaining ring 150 into contact with the polishing pad 114. Before and after polishing, the pressure in the loading chamber 128 is reduced and/or a vacuum is applied to the loading chamber 128 so that the base assembly 124, is moved and/or pulled upward and away from the polishing pad 114. Once the base assembly 124 is moved upward and away from the polishing pad 114, the carrier head 120 may be moved, e.g., swung, away therefrom, such as to a second polishing platen (not shown) and/or to a substrate loading station, e.g., a load cup (not shown), for subsequent polishing and/or substrate loading/unloading handling operations respectively.
The housing 122 is generally circular in shape and can be connected to a spindle 130 to rotate and/or sweep then carrier head 120 across the polishing pad 114 during polishing. The base assembly 124 is a vertically movable assembly located beneath the housing 122. The gimbal 126 slides vertically to provide a vertical motion of the base assembly 124. The gimbal 126 also permits the base assembly 124 to pivot with respect to the housing 122 so that the retaining ring 150 may remain substantially parallel with the polishing surface 118 of the polishing pad 114.
The carrier head 120 includes a membrane 138 that contacts the substrate 10 (e.g., the membrane 138 illustrated in
The carrier head 120 includes a plurality of pneumatic ports 140 for supplying pressurized air to respective chambers of the carrier head 120 (e.g., 5 pneumatic ports 140 are illustrated in
The carrier head 120 includes a plurality of thru-holes 142, each thru-hole 142 being configured to receive a retainer 200. In one or more embodiments, the thru-holes 142 may be disposed on a common radius. In some embodiments, the thru-holes 142 may be formed by drilling, machining, or other suitable technique. In some embodiments, the thru-holes 142 may be evenly spaced between adjacent screw holes 136. In one or more embodiments, the thru-holes 142 may be evenly spaced by a radial angle of 20 degrees.
The retaining ring 150 comprises a top surface 152 having a plurality of blind-holes 154 having internal threads for receiving a plurality of fasteners (e.g., machine screws) to attach the retaining ring 150 to the carrier head 120. The top surface 152 contacts the bottom surface 132 of the carrier head 120 when the retaining ring 150 is installed on the carrier head 120. The top surface 152 can comprise stainless steel, molybdenum, aluminum, other suitable metals, composites, and plastics, among other suitable material. The blind-holes 154 can be spaced by a radial angle α0. In some embodiments, the radial angle α0 can be from about 15 degrees to about 60 degrees, such as about 15 degrees, alternatively about 20 degrees, alternatively about 30 degrees, alternatively about 60 degrees. In the example depicted in
The retaining ring 150 includes a plurality of thru-holes 156 formed in the top surface 152, each thru-hole 156 being configured to receive a retainer 200. In one or more embodiments, the thru-holes 156 may be disposed on a common radius. In some embodiments, the thru-holes 156 may be formed by drilling, machining, or other suitable technique. In some embodiments, the thru-holes 156 may be evenly spaced between adjacent blind-holes 154. In one or more embodiments, the thru-holes 156 may be evenly spaced by a radial angle of 20 degrees. In one or more embodiments, each thru-hole 156 of the retaining ring 150 is aligned with a respective thru-hole 142 of the carrier head 120 when the retaining ring 150 is installed on the carrier head 120.
Each of the plurality of fixed teeth 158 has an inner surface 162 facing toward a centerline of the retaining ring 150 and an outer surface 164 opposite the inner surface 162. In some embodiments, the inner and outer surfaces 162, 164 may be curved surfaces matching the curvature of the retaining ring 150. In some other embodiments, the inner and outer surfaces 162, 164 may be straight. In some embodiments, a radial distance R1 between the inner and outer surfaces 162, 164 may be from about 5 mm to about 50 mm, such as from about 20 mm to about 30 mm. Each of the plurality of fixed teeth 158 has first and second lateral surfaces 166. In some embodiments, the first and second lateral surfaces 166 may be non-parallel as shown in
In one or more embodiments, the retaining ring 150 can include from about 6 to about 24 fixed teeth, such as from about 12 to about 18 fixed teeth. In some other embodiments, the retaining ring 150 can include about 12 fixed teeth or less, such as from about 6 to about 12 fixed teeth. In some other embodiments, the retaining ring 150 can include about 18 fixed teeth or more, such as from about 18 to about 24 fixed teeth.
In some embodiments, a maximum arc length α1 of each of the fixed teeth 158 (i.e., a central angle corresponding to a maximum arc length selected from the group of arc lengths between the inner surface 162 and the outer surface 164 of each of the fixed teeth 158) may be from about 10 degrees to about 20 degrees, such as from about 10 degrees to about 15 degrees, alternatively from about 15 degrees to about 20 degrees. In some other embodiments, the maximum arc length α1 of each of the fixed teeth 158 may be from about 1 degree to about 10 degrees, such as from about 1 degree to about 5 degrees, alternatively from about 5 degrees to about 10 degrees. In some other embodiments, the maximum arc length α1 of each of the fixed teeth 158 may be from about 20 degrees to about 30 degrees, such as from about 20 degrees to about 25 degrees, alternatively from about 25 degrees to about 30 degrees.
In some embodiments, a minimum arc length α2 of each of the fixed teeth 158 may be from about 10 degrees to about 20 degrees, such as from about 10 degrees to about 15 degrees. In some other embodiments, the minimum arc length α2 of each of the fixed teeth 158 may be from about 5 degrees to about 10 degrees.
A plurality of grooves 168 are formed between opposing first and second lateral surfaces 166 of adjacent fixed teeth 158, wherein the plurality of grooves 168 are configured to convey a polishing slurry from outside the retaining ring 150 to the substrate 10. The groove 168 includes a shoulder 170 intersecting a respective one of the thru-holes 156. Each of the grooves 168 may be aligned with a respective one of the thru-holes 156. In one or more embodiments, each thru-hole 156 may be evenly spaced between the lateral surfaces 166. In some other embodiments, each thru-hole 156 may be offset relative to the lateral surfaces 166.
The upper portion 204 may have a length L1, measured from the shoulder 208 to the movable magnet 210, selected based on one or more of the depth D1 of the upper portion 144 of the thru-hole 142 in the carrier head 120, the vertical clearance between the carrier head 120 and the housing 180, the height of the stationary magnets 184, a working distance between the movable magnet 210 and one or more of the stationary magnets 184, or combinations thereof. In one or more embodiments, the length L1 may be from about 10 mm to about 60 mm, such as from about 30 mm to about 60 mm. The lower portion 206 may have a length L2, measured from the shoulder 208 to the movable tooth 220, selected based on one or more of the depth D2 of the lower portion 146 of the thru-hole 142 in the carrier head 120, the depth D4 of the thru-hole 156 in the retaining ring 150, a height H2 of the movable tooth 220, a gap between the fixed tooth and the polishing pad 114, or combinations thereof. In one or more embodiments, the length L2 may be from about 10 mm to about 60 mm, such as from about 30 mm to about 60 mm.
In some embodiments, the movable magnet 210 attached to the upper portion 204 of the shaft 202 is at least partially disposed above the top surface 134 of the carrier head 120, such that the movable magnet 210 may be vertically positioned within a magnetic field of one or more of the stationary magnets 184 attached to the housing 180. In some embodiments, the movable magnet 210 may be any suitable permanent magnet, such as a neodymium magnet. In some alternative embodiments, the movable magnet 210 can be or include a ferromagnetic material. In one or more embodiments, the ferromagnetic material may include iron, nickel, cobalt, or combinations thereof. In some embodiments, the ferromagnetic material may be in the form of a coating over a non-magnetic or magnetic material. Thus, the movable magnet 210 can be defined as any magnetic material including permanent magnets or ferromagnetic materials. Some suitable ferromagnetic materials can be or include iron, nickel, cobalt, or combinations thereof. The movable magnet 210 can have any suitable size and shape depending on a vertical clearance between the stationary magnets 184 and the carrier head 120 and other spatial constraints. In some embodiments, the size and shape of the movable magnet 210 may match the size and shape of the stationary magnets 184, such that the corresponding magnetic fields may be aligned. In one or more embodiments, the movable magnet 210 may be cylindrical having a diameter of from about 5 mm to about 25 mm, such as from about 10 mm to about 20 mm, and a height of from about 2 mm to about 10 mm, such as from about 2 mm to about 5 mm, alternatively from about 5 mm to about 10 mm. The movable magnet 210 may have a top surface 212 facing one or more of the stationary magnets 184. In some embodiments, a distance Z1, measured between the top surface 212 of the movable magnet 210 and the bottom surface 186 of one or more of the stationary magnets 184, may be about 20 mm or less, such as about 10 mm or less, such as from about 1 mm to about 10 mm, such as from about 1 mm to about 5 mm.
In some embodiments, a lower stop shoulder 214 may be formed on the upper portion 204 of the shaft 202. In one or more embodiments, contact between the lower stop shoulder 214 and the top surface 134 of the carrier head 120 can limit downward movement of the retainer 200. In one or more embodiments, a spring 216 may be disposed between shoulder 148 of the carrier head 120 and the shoulder 208 of the retainer 200 to bias the retainer toward a lower position. In some embodiments, the spring 216 can be or include any suitable compression spring (e.g., a coil spring or flat spring). In some other embodiments, the spring 216 may be omitted and the retainer 200 may be biased to the lower position by gravity.
In some embodiments, the retainer 200 may start in the lower position under the downward bias force with the lower stop shoulder 214 contacting the top surface 134 as shown on the left side of
In some embodiments, a height H2 of the movable tooth 220, measured from the bottom surface 222 to an opposing top surface 230 may be about equal to a height H1 of each of the fixed teeth 158 or greater, such as from about 3 mm or greater, such as from about 3 mm to about 60 mm, such as from about 3 mm to about 30 mm. In some embodiments, the movable tooth 220 may be fixedly attached to the lower portion of the shaft 202. In some embodiments, the movable tooth 220 is at least partially disposed in the groove 168 of the retaining ring 150, such that vertical movement of the movable tooth 220 may adjust a gap Z2 between a bottom surface 222 of the movable tooth 220 and the polishing pad 114. In some embodiments, a stroke length of the movable tooth 220 may be about 20 mm or less, such as from about 3 mm to about 20 mm, such as from about 5 mm to about 12 mm. In some embodiments, the stroke length may be about 10 mm or less, such as about 7 mm or less. In some embodiments, the gap Z2 in the lower position of the retainer 200 is equal to about 0 mm. In some embodiments, the gap Z2 in the upper position of the retainer 200 may be from about 3 mm to about 20 mm, such as from about 5 mm to about 12 mm, such as from about 7 mm to about 10 mm, such as about 7 mm. In some embodiments, the gap Z2 in the intermediate position of the retainer 200 can about 15 mm or less, such as about 10 mm or less, such as from about 0 mm to about 10 mm, such as from about 1 mm to about 9 mm, alternatively from about 0 mm to about 7 mm, such as from about 1 mm to about 6 mm.
In some embodiments, the gap Z2 may be controlled to control polishing slurry intake. For example, increasing or decreasing the gap Z2 on a leading edge 190 of the retaining ring 150 can increase or decrease, respectively, a cross-sectional flow area for conveying the polishing slurry from outside the retaining ring 150 to the substrate 10. In some embodiments, the gap Z2 may be controlled to control polishing slurry retention. For example, increasing or decreasing the gap Z2 on a trailing edge 192 of the retaining ring 150 can increase or decrease, respectively, a cross-sectional flow area for conveying the polishing slurry from the substrate 10 to outside the retaining ring 150. In some embodiments, the cross-sectional area is linearly proportional to the gap Z2. In some embodiments, a maximum volume of polishing slurry can be conveyed through the grooves 168 when the retainer 200 is in the upper position. Likewise, a minimum volume of polishing slurry can be conveyed through the grooves 168 when the retainer 200 is in the lower position.
In one or more embodiments, each movable tooth 220 may have a width W2 measured between the first and second lateral surfaces 228. In some embodiments, the width W2 may be selected to provide a suitable clearance between each of the first and second lateral surfaces 228 and lateral surfaces 166 of adjacent fixed teeth 158. In some embodiments, a radial distance R2 between the inner and outer surfaces 224, 226 may be about equal to the radial distance R1 between the inner and outer surfaces 162, 164 of each of the fixed teeth 158.
In this example, the polishing system 100 has 12 evenly distributed retaining assemblies 200 installed therewith, although any suitable number and distribution of retaining assemblies may be used as described herein. The retaining assemblies 200 are disposed in positions 1-12 as shown. In one or more embodiments, the housing 180 may have magnets disposed only along the leading edge 190 (e.g., positions 1-6) while the trailing edge 192 (e.g., positions 7-12) is free of stationary magnets 184. In this example, the housing 180 includes 6 magnets in positions 1-6 along the leading edge 190, although any suitable number and distribution of stationary magnets 184 may be used as described herein.
In some alternative embodiments, to be described later, the retainer 200 may be biased to the upper position, and the magnetic force may repel the movable magnet 210, pushing the retainer 200 down instead of attracting the movable magnet 210 to lift the retainer 200 up. In some other embodiments, the retainer 200 may be biased to an intermediate position between the upper and lower positions. The same general principles of operation can apply to each embodiment described herein.
In some embodiments, permanent and/or electromagnetic stationary magnets 184 may have different magnetic field strengths to induce gradual lifting to various intermediate positions between the upper and lower positions.
In some embodiments, the stationary magnets 184 may be closely spaced such that the magnetic force is continuous between positions 1 and 2. In some other embodiments, the stationary magnets 184 in positions 1 and 2 may be spaced such that the magnetic fields are strongest in the vertical direction and weakest in the horizontal direction. In other words, the magnetic force on the movable magnet 210 will decrease as the movable magnet 210 moves away from vertical alignment with one or more of the magnets 184; however, the magnetic fields may overlap in the region between adjacent magnets 184, such that an adequate magnetic field can exist to continuously maintain the retainer 200 during transition from position 1 to position 2.
In some other embodiments, the retainer 200 may be continuously maintained in the upper position between position 1 and position 2 simply because the retainer 200 is moved between positions faster than a time required for the retainer 200 to lower from the upper position once the magnetic attraction force is removed.
In some embodiments, the housing 180 may have stationary magnets 184 in positions 1-5 and 12. This arrangement may account for a time required for lifting the retainer 200 to the upper position (e.g., at position 12) and for lowering the retainer to the lower position (e.g., at position 5). In other words, when the retainer 200 is lifted by the stationary magnet 184 in position 12, the retainer 200 may not fully reach the upper position until closer to position 1.
In some other embodiments, the housing 180 may include 5 stationary magnets 184 or less, such as 5 or less, such as 4 or less, such as 3 or less, such as 2 or less, such as 1. In one or more embodiments, the housing 180 may include 4 stationary magnets 184 in positions 2-5, alternatively in positions 1-4. In some other embodiments, the housing 180 may include 3 stationary magnets 184 in positions 2-4. In some other embodiments, the housing 180 may include 2 stationary magnets 184 in positions 3 and 4. In some other embodiments, the housing 180 may include from 6 to about 12 stationary magnets 184, such as 9 stationary magnets.
In one or more embodiments, when the polishing system 100 includes 18 fixed teeth 158 and 18 retaining assemblies 200 as shown in
It will be appreciated that many other numbers and positions of stationary magnets 184 and retaining assemblies 200 are within the scope of this disclosure, and the present disclosure is not intended to be limiting beyond what is specifically recited in the claims that follow.
In some embodiments, the polishing system 100 of
In this example, the polishing system 100 has 12 evenly distributed retaining assemblies 200 installed therewith, although any suitable number and distribution of retaining assemblies may be used as described herein. The retaining assemblies 200 are disposed in positions 1-12 as shown. In one or more embodiments, the housing 180 may have magnets disposed along the leading edge 190 (e.g., positions 1-6) and along the trailing edge 192 (e.g., positions 7-12). In this example, the housing 180 includes 12 magnets in positions 1-12 along both the leading and the trailing edges 190, 192, although any suitable number and distribution of stationary magnets 184 may be used as described herein.
During rotation, as each retainer 200 and corresponding movable magnet 210 passes under and/or through at least part of a magnetic field of one or more of the stationary magnets 184, a controllable magnetic field can be applied to lift the retainer 200. In some embodiments, the magnetic field can be controlled to lift the retainer 200 to the upper position as shown on the right side of
In one or more embodiments, the stationary magnets 184 on the leading edge 190 (e.g., positions 1-6) may be controlled to have a magnetic field strength and orientation to maintain the retainer 200 in the upper position, and the stationary magnets 184 on the trailing edge 192 may be controlled to have a magnetic field strength and orientation to maintain the retainer 200 in the intermediate position. In some other embodiments, the stationary magnets 184 on the trailing edge 192 may be controlled to have a magnetic field strength and orientation to maintain the retainer 200 in the lower position.
In some embodiments, an alternating pattern may be applied where every other stationary magnet 184 (e.g., positions 1, 3, 5, 7, 9, and 11) may be controlled to maintain the retainer 200 in the upper position, and the remaining stationary magnets 184 (e.g., positions 2, 4, 6, 8, 10, and 12) may be controlled to maintain the retainer 200 in the lower position. Thus, the alternating pattern can induce a snake-like motion of the retaining assemblies 200 during rotation of the carrier head 120. In some other embodiments, the stationary magnets 184 may be controlled to move the retaining assemblies 200 in a sinusoidal pattern.
In some other embodiments, the stationary magnets 184 may be controlled to continuously vary the gap Z2 around the circumference of the carrier head 120. For example, the gap Z2 may have a maximum value at positions 3 and 4, and the gap Z2 may decrease at each subsequent position moving CCW from position 4 to position 9 and moving CW from position 3 to position 10, such that the gap Z2 has a minimum value at positions 9 and 10. Gradual lifting of the retaining assemblies 200 around the circumference of the carrier head 120 may also be applied to other embodiments described herein.
It will be appreciated that many other control strategies of the stationary magnets 184 are within the scope of this disclosure, and the present disclosure is not intended to be limiting beyond what is specifically recited in the claims that follow.
In some embodiments, the polishing system 100 of
In some embodiments, an alternating pattern may be applied where every other stationary magnet 184 (e.g., positions 1, 3, 5, 7, 9, and 11) may be controlled to apply a minimum downforce, and the remaining stationary magnets 184 (e.g., positions 2, 4, 6, 8, 10, and 12) may be controlled to apply a maximum downforce. Thus, the alternating pattern can induce a low frequency oscillating downforce by the retaining assemblies 200 on the polishing pad 114.
As illustrated in
In some other embodiments, the spring 216 may be disposed to bias the retainer 200 toward the lower position. In some other embodiments, the spring 216 may be omitted.
In one or more embodiments, a magnetic field orientation of the stationary magnets 184 may be controlled to apply a downforce to the retainer 200. In some embodiments, from a top-down perspective, the magnetic field of the stationary magnets 184 may be oriented N-S when the movable magnets 210 are oriented S-N. In some other embodiments, also from a top-down perspective, the magnetic field of the stationary magnets 184 may be oriented S-N when the movable magnets 210 are oriented N-S. In either case, the magnetic field of the stationary magnets 184 will repel the movable magnets 210.
In one or more embodiments, the movable teeth 220 may contact the substrate 10, acting as retaining teeth to retain the substrate 10. In one or more embodiments, the movable teeth 220 may apply a downforce to the polishing pad 114. In some other embodiments, the plurality of fixed teeth 158 may retain the substrate 10 and/or apply a downforce to the polishing pad 114. In other words, the vertical positions of the plurality of fixed teeth 158 and the movable teeth 220 may be reversed relative to some other embodiments, such that grooves are formed between lateral surfaces of adjacent movable teeth 220 to convey the polishing slurry. In one or more embodiments, the grooves may have width a about equal to a conventional retaining ring groove width. In some embodiments, the width may be from about 3 mm to about 25 mm, such as from about 3 mm to about 13 mm, such as about 6 mm.
In one or more embodiments, each of the fixed teeth 158 may be vertically spaced from the polishing pad 114 by a gap Z2 about equal to a conventional retaining ring groove depth. In some embodiments, the gap Z2 may be from about 5 mm to about 12 mm, such as from about 7 mm to about 10 mm, such as about 7 mm. In some embodiments, each of the fixed teeth 158 may be spaced from the polishing pad 114 by a distance about equal to a thickness of the substrate 10 or greater.
In some embodiments, as a downforce is applied by each movable tooth 220 on the polishing pad 114, an equal and opposite reaction force may be applied by the movable magnet 210 on the stationary magnets 184. The upward reaction force can be measured by one or more of the strain gauges 188 to provide real-time feedback of the magnitude of the downforce applied by each respective movable tooth 220 on the polishing pad 114. Thus, by using the strain gauges 188, the applied downforce can be continuously monitored and adjusted.
In some embodiments, the polishing system 100 of
Embodiments of the present disclosure using magnetic control offer contactless operation, among other advantages. In particular, the interactions between the stationary magnets 184 and the movable magnets 210 are contactless. In other words, vertical forces are applied to the retaining assemblies 200 without allowing the mating parts, which can be blocked or coated with debris during operation, to come into physical contact with each other.
In one or more embodiments, the retaining assemblies 200 may be controlled using a pneumatic system. In some embodiments, in place of the stationary magnets 184 and the movable magnets 210, a plurality of pneumatic supply lines may be used to supply air pressure to move each of the retaining assemblies 200. In one or more embodiments, a slip-ring may be used to couple the pneumatic supply lines between the housing 180 and the retaining assemblies 200. In one or more embodiments, a single pneumatic supply line may supply air pressure to move each retainer 200 in a first direction and a spring 216 may be used to bias each retainer 200 in the opposite direction. In some other embodiments, a first pneumatic supply line may supply air pressure to move each retainer 200 in a first direction and a second pneumatic supply line may supply air pressure to move each retainer 200 in the opposite direction. In some embodiments, the pneumatic system may have a response time of about 250 ms or greater.
In one or more embodiments, the polishing system 100 may include a closed-loop control system, which may be generally referred to as a feedback control system. In one or more embodiments, the closed-loop control system may operate in real-time. In some embodiments, the closed-loop control system may independently monitor and control a downforce applied by each movable tooth 220. In some embodiments, the closed-loop control system may independently monitor and control a gap Z2 between each movable tooth 220 and the polishing pad 114. In one or more embodiments, the closed-loop control system may receive inputs from eddy current sensors and/or optical sensors to measure wafer thickness and/or wafer non-uniformity in situ. In some embodiments, sensors on or within the platen 112 may sense the wafer thickness. In some embodiments, the in situ measurements can be used to control membrane pressure and/or downforce. For example, membrane pressure can be adjusted across various zones of the membrane 138 in order to more evenly polish the wafer.
In some embodiments, the closed-loop control system can perform active control of downforce of the retaining assemblies 200. In some embodiments, the closed-loop control system can receive signals from each of the strain gauges 188 providing real-time feedback of the magnitude of the downforce applied by each respective movable tooth 220 on the polishing pad 114. In addition, the closed-loop control system can receive signals from the one or more eddy current sensors and/or optical sensors, which are positioned to detect the thickness of a material layer formed on the wafer and are used to detect the thickness profile of the wafer 10 and/or edge profile of the wafer 10. In some embodiments, the foregoing signals can be utilized to continuously monitor and adjust the applied downforce of each movable tooth 220. In some embodiments, optimal downforce can depend on parameters including pressure of the membrane 138, rotation rate of the polishing pad 114, rebound rate of the polishing pad 114, rotation rate of the wafer 10, and slurry composition. In some embodiments, the optimal downforce can be determined experimentally.
In one example of CMP process, when the closed-loop control system determines a non-uniformity in thickness at the edge of the wafer 10 resulting from excess downforce, the closed-loop control system may actively reduce the downforce of each movable tooth 220. Alternatively, when the closed-loop control system determines a non-uniformity in thickness at the edge of the wafer 10 resulting from inadequate downforce, the feedback control system may actively increase the downforce of each movable tooth 220. In some embodiments, the non-uniformity may be corrected by independently adjusting the downforce of one or more of the movable teeth 220, and in some cases adjust the downforce of one or more of the movable teeth 220 and the pressure applied by an outer zone of the polishing head. In some embodiments, a magnitude of the downforce applied by each movable tooth 220 may be precisely controlled to reduce non-uniformity in real-time. In some embodiments, the downforce of each movable tooth 220 can be selected in order to limit decompression of the polishing pad 114 in a gap between the movable tooth 220 and the edge of wafer 10.
In some other embodiments, the closed-loop control system can perform active control of the gap Z2 between the bottom surface 222 of each movable tooth 220 and the polishing pad 114. In some embodiments, the closed-loop control system can receive signals from sensors coupled to one or more of the retaining assemblies 200, movable teeth 220, carrier head 120 or retaining ring 150 providing real-time feedback of the gap Z2 between each respective movable tooth 220 and the polishing pad 114. In addition, the closed-loop control system can receive signals from the one or more eddy current sensors and/or optical sensors indicating thickness profile of the wafer 10 and/or edge profile of the wafer 10. In some embodiments, the depth D3 of each groove 168 may be reduced as the bottom surfaces 160 of the fixed teeth 158 wear down during use. In some embodiments, the depth D3 may be proportional to the usage of the retaining ring 150. Thus, the usage history of the retaining ring 150 may be another input to the closed-loop control system. In some embodiments, the foregoing signals can be utilized to continuously monitor and adjust the gap Z2 of each movable tooth 220 in order to control slurry intake and/or retention.
For example, when the closed-loop control system determines a non-uniformity in thickness that may be corrected by adjusting slurry intake and/or retention, the closed-loop control system may actively adjust the gap Z2 of each movable tooth 220 in order to correct the non-uniformity. Alternatively, when the closed-loop control system determines a change in the depth D3 of one or more of the grooves 168, the closed-loop control system may actively adjust the gap Z2 of each movable tooth 220 to compensate for the change. In some embodiments, the gap Z2 of each movable tooth 220 can be selected in order to conserve polishing slurry.
While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 63/049,609, filed on Jul. 8, 2020, the entirety of which is herein incorporated by reference.
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