Electroplating electrical contacts

An electrodeposition apparatus for depositing material on a surface of a substrate. The electrodeposition apparatus includes at least one contact for laterally contacting the substrate and providing electrical connection to the substrate. The at least one contact does not obscure the surface of the substrate to be plated. A voltage source is connected to the at least one contact.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The invention relates to a method and apparatus for electrodepositing on a
 substrate. In particular, the present invention relates to a method and
 apparatus for electrodeposition, electroetching, and/or electropolishing
 in semiconductor device manufacturing.
 2. Description of the Related Art
 In the production of microelectronic devices, metal may be plated on a
 semiconductor for a variety of purposes. The metal may be deposited to
 form vias or conductive lines, such as wiring structures. Typically, metal
 is plated on the substrates and cells of reservoirs that hold a plating
 solution that includes at least one metal and/or alloy to be plated on the
 substrate.
 Plating baths are commonly used in microelectronic device manufacture to
 plate at least one material, such as a metal on a substrate for a wide
 variety of applications. For example, plating baths may be utilized for
 electroplating and/or electroless plating on substrates of one or more
 metals and/or alloys.
 SUMMARY OF THE INVENTION
 The present invention provides an apparatus for depositing material,
 electroetching, and/or electropolishing on a surface of a substrate. The
 apparatus includes at least one contact for laterally contacting the
 substrate and providing an electrical connection to the substrate. The at
 least one contact does not obscure the surface of the substrate to be
 plated. A voltage source is connected to the at least one contact.
 The present invention also includes a method for depositing material on a
 surface of a substrate. The method includes laterally engaging a substrate
 on which a material is to be deposited with at least one contact for
 laterally contacting the substrate and providing electrical connection to
 the substrate without obscuring the surface of the substrate to be plated.
 A voltage source is connected to the at least one contact.
 Still other objects and advantages of the present invention will become
 readily apparent to those skilled in the art from the following detailed
 description, wherein it is shown and described only the preferred
 embodiments of the invention, simply by way of illustration of the best
 mode contemplated of carrying out the invention. As will be realized, the
 invention is capable of other and different embodiments, and its several
 details are capable of modifications in various obvious respects, without
 departing from the invention. Accordingly, the drawings and description
 are to be regarded as illustrative in nature and not as restrictive.

DETAILED DESCRIPTION OF THE INVENTION
 Electrodeposition methods have been developed as a technique to deposit
 metal(s) and alloy(s) on surfaces of semiconductor substrates. Typically,
 for electrodeposition methods to function, reliable and practical
 electrical contact must be made to a substrate. Often, to help prevent
 deposition on side surfaces of a substrate, a region in the vicinity of
 the edge of the substrate is not plated.
 Preventing plating of a region in the vicinity of the edge of the substrate
 may be accomplished by not placing a seed layer in the vicinity of the
 edge of the substrate. Alternatively, a structure may be placed over the
 edge of the substrate to prevent deposition of metals in the vicinity.
 Where edge exclusion is carried out, typically, about 2 to about 5 mm of
 the edge may be excluded. Typically, the primary penalty for not plating
 or not being able to plate in the vicinity of the edge of a semiconductor
 substrate is a decrease in the chip yield from a wafer and a loss of
 flexibility of chip layout.
 According to one example, that of chip interconnection wiring applications,
 a seed layer may be deposited on a structure prior to electrodeposition.
 For example, in the case of copper interconnection wiring structures, a
 thin copper seed layer may be deposited on the substrate. The seed layer
 may not be deposited in the vicinity of the edge of the substrate to avoid
 the side surface plating problem. However, to make reliable contact to a
 substrate to help ensure uniform plating, electrical contact typically is
 made about 3 mm into the seed layer. When the electrical contacts are
 sealed, either in a continuous or discontinuous manner, the excluded
 fraction of the wafer increases further.
 To solve the above and other problems, the present invention provides a new
 method and structure for making electrical contact with semiconductor
 substrates. For example, the present invention helps to eliminate the need
 for edge exclusion from plating or for electrical contact to be made on
 the surface of the wafer or away from the edge of the wafer by as much as
 5 mm. As a result, the present invention permits the entire surface of the
 semiconductor substrate to be plated. Furthermore, the present invention
 can improve chip yields and chip counts on wafers as well as increase
 flexibility of chip layout.
 FIG. 1 illustrates typical arrangement of a semiconductor substrate and a
 plating apparatus. Accordingly, FIG. 1 illustrates a semiconductor
 substrate 1, such as a wafer. A seed layer 3 is formed on the upper
 surface 5 of the substrate 1. As FIG. 1 illustrates, the seed layer does
 not extend all the way to the edge 7 of the substrate 1. Rather, an
 exclusion zone 9 about 1 to about 5 mm is not plated. Contact to the seed
 layer 3 on substrate 1 is made by contacts 11 arranged on the surface of
 the substrate. To help ensure good connection to the seed layer 3,
 typically, as illustrated in FIG. 1, the contacts 11 are arranged well
 into the seed layer 3.
 FIG. 2 illustrates an overhead of the substrate 1 illustrated in FIG. 1. As
 can be seen in FIG. 2, the contacts may be arranged about the substrate 1.
 The number of contacts may vary depending upon the application. For
 example, the number of contacts may depend upon the size of the wafer. It
 may also depend upon the plating operation being carried out. For example,
 on a semiconductor substrate having a diameter of about 200 mm, if the
 electrodeposition operation is part of a C4 process, with a thick seed
 layer, as few as four contacts may be used. On the other hand, if the seed
 layer is thin, such as about 300 .ANG. to about 500 .ANG., the number of
 contacts typically needs to be greater. A thin seed layer may require in
 excess of about 50 contacts. Also, for plating on substrates larger than
 about 200 mm in diameter, the number of contacts many need to exceed about
 400.
 Unlike typical known electrodeposition apparatuses, an apparatus according
 to the present invention does not require creating an exclusion zone
 around the perimeter of a substrate. Therefore, according to the present
 invention, clamps, shadow rings, or other devices utilized to prevent
 deposition in the vicinity in the perimeter of the substrate may be
 removed. Also, according to the present invention, a seed layer may be
 provided, such as by sputtering or being otherwise deposited, on a
 substrate all the way to the edge of the substrate. Rather than making
 contact on the surface of the wafer on the seed layer, the present
 invention provides for making contact on the sides, or minor surfaces, of
 a substrate.
 FIG. 3 illustrates an example of a semiconductor substrate 13 having a seed
 layer 15 deposited on the entire upper surface thereof. Contact is made to
 the substrate in the seed layer through contacts 17 arranged on the side,
 or minor, surface 19 of the semiconductor substrate 13. The region of
 contact 21 between the contacts 17 and the substrate 13 and the seed layer
 15 may be about the side surface(s) of the substrate.
 As can be seen in FIG. 3, the contacts of the present invention laterally
 contact the substrate for providing electrical connection to the
 substrate. An electrodeposition apparatus according to the present
 invention can include any number of contacts to substrate. For example, a
 single contact could provide contact to the substrate. This single contact
 could be a single structure that engages the substrate at a plurality of
 points but still be part of a single contact structure. Such contacts
 could be considered to be continuous.
 Alternatively, a single contact could continuously engage a substrate about
 its perimeter. According to the present invention, a plurality of contacts
 could be arranged around the substrate. The plurality of contacts could
 all be separate structures. Such contacts may considered to be
 discontinuous.
 As can be seen in FIG. 3, contacts according to the present invention can
 provide electrical contact to a substrate without obscuring any of the
 upper surface of the substrate where material is to be electrodeposited.
 This is unlike the contact structures illustrated, for example, in FIGS. 1
 and 2.
 The shape of a contact according to the present invention may vary,
 depending upon the embodiment. FIGS. 4a, 4b and 4c illustrate various
 examples of embodiments of contacts according to the present invention.
 The contacts illustrated in FIGS. 4a, 4b and 4c typically are
 discontinuous contacts, wherein a plurality of contacts such as those
 illustrated in FIGS. 4a, 4b, and 4c are arranged about the side edge of a
 substrate.
 The embodiment illustrated in FIG. 4a may make contact at a single point
 where the contact touches the seed layer or the seed layer in the
 substrate. On the other hand, the embodiment illustrated in FIG. 4b may
 make contact all along its length with the seed layer and the substrate.
 Furthermore, the embodiment illustrated in FIG. 4c may make contact with
 the seed layer and substrate at two points.
 As illustrated by arrows 29, 31, and 33, the contacts 23, 25, and 27 may be
 moved laterally to engage and disengage from a seed layer and/or a
 substrate. To facilitate movement of the contacts, the present invention
 may include at least one spring for biasing the contact or contacts into
 contact, association, or engagement with the substrate/seed layer. The
 contact or contacts may be retractable against the force of the spring.
 Utilizing springs to urge the contacts into engagement with the seed layer
 and/or substrate may help to distribute force on the wafer to decrease
 wafer breakage. However, other means may be utilized to urge the contacts
 into engagement with the substrate and/or seed layer. If the present
 invention does not include a spring for biasing the contacts toward the
 substrate, it may include some sort of motor or other means for moving the
 contacts into and out of engagement with the substrate.
 In addition to varying the number, arrangement, and shape of the contacts,
 the structure of the contacts may also vary. Along these lines, the
 composition of the contacts may vary. According to some embodiments, the
 contacts may be made of copper. According to other embodiments, the
 contacts may be made of stainless steel. The contact or contacts may also
 be made of other materials. Along these lines, the contact(s) may also
 include a mixture of copper and beryllium.
 Additionally, portions of the contacts may be made of other materials. For
 example, the entire contact or just a portion of the contact that contacts
 the substrate and/or seed layer may be coated with another material. For
 example, the contact or portion of the contacts that engage the seed layer
 and/or substrate may have a coating of .alpha.-Ta, nitrides of tantalum,
 gold, rhodium, and/or titanium nitride with Ti overlay, in other words,
 TiN/Ti. Examples of nitrides of tantalum include hexagonal-TaN and
 cubic-TaN.
 Regardless of the composition of the contacts, they may be coated with
 another material. For example, the contacts may be coated with an
 elastomeric coating, such as VITON or polymers, such as PTFE or PVDF and
 their like. The polymer coating may be deposited on the contacts in order
 to prevent wasteful metal deposition in this region.
 Whether a contact is made of copper, stainless steel, or any other
 electrically conductive material(s), such contacts could be coated with
 .alpha.-Ta, nitrides of tantalum, gold, rhodium, and/or titanium nitride
 with Ti overlay, an elastomeric or non-elastomeric polymer coating, and/or
 any other material.
 Contacts according to the present invention may have shapes other than
 those illustrated in FIGS. 4a, 4b and 4c. For example, the present
 invention may include contacts that are arranged in a spirally wound
 spring. FIGS. 7 and 8 illustrate two embodiments of such contacts.
 If the contact or contacts include a spirally wound spring, the spring may
 extend substantially entirely about a semiconductor substrate. On the
 other hand, the spring may extend less than entirely around the substrate.
 For example, the present invention could include two spirally wound spring
 contacts that each extend about one half the distance around a substrate.
 On the other hand, the present invention can include more than two
 spirally wound springs that each extend about a portion of the outside of
 a substrate.
 As can be seen in FIGS. 7 and 8, a spirally wound spring contact may make
 contact at a plurality of locations about a substrate. Such a spirally
 wound spring contact illustrates an example of a continuous contact
 according to the present invention. In other words, even though the
 contacts illustrated in FIGS. 7 and 8 may contact a plurality of locations
 around the substrate, the contacts may be part of a single structure.
 The embodiment of the present invention illustrated in FIG. 7 includes two
 spirally wound springs 37 and 39 engaging a substrate 35. Springs 37 and
 39 may be moved apart to arrange or load the substrate 35 between the
 spirally wound spring contacts prior to an electrodeposition processes.
 The spirally wound spring contacts may then be moved toward each other and
 toward the substrate to make electrical contact with the substrate and/or
 the seed layer. The springs may again be moved apart to unload the
 substrate from between the springs. Movement of the springs is indicated
 by arrows 41 and 43.
 According to some embodiments, rather than making contact laterally with
 the substrate, a spirally wound spring may make contact with the seed
 layer and/or the surface of the substrate that the seed layer is deposited
 on. FIG. 8 illustrates such an embodiment of the present invention. As
 such, FIG. 8 illustrates a substrate 45 with a spirally wound spring
 contact 47 contacting the surface of the substrate that includes the seed
 layer.
 FIG. 9 illustrates a cross-sectional view the substrate and spring 45 and
 47 illustrated in FIG. 8. Accordingly, FIG. 9 illustrates the substrate 45
 and spirally wound spring 47 making contact therewith.
 The backside of the substrate, that side of the substrate that does not
 include the seed layer, may be sealed by seal 49. The seal could also be
 an O-ring type of seal. The seal 49, wafer, and spring may be clamped into
 position by clamp 51. The seal may be utilized to help prevent
 electrolytes from coming into contact with the backside of the substrate.
 The spring contact, such as spring contacts 37 and 47 included in the
 embodiments illustrated in FIGS. 7 and 8 may have an outside diameter of
 about 1 mm to about 4 mm. As depicted in FIGS. 7 and 8, the spring is
 designed to wrap around the edge of the substrate.
 The present invention also includes a plating apparatus. A plating
 apparatus according to the present invention includes at least one contact
 such as those described above. FIG. 5 illustrates an embodiment of a
 plating apparatus according to the present invention including one
 embodiment of contacts according to the present invention. Along these
 lines, FIG. 5 illustrates a substrate 53 on which a seed layer 55 has been
 deposited.
 The electrodeposition apparatus illustrated in FIG. 5 includes contacts 57.
 Contacts 57 include an polymer coating 58. The contacts may be moved into
 and out of engagement with substrate 53 as indicated by arrows 59.
 The embodiment of the plating apparatus illustrated in FIG. 5 includes a
 vacuum 61 to maintain the substrate in place in the electrodeposition
 apparatus. The substrate may be supported by support surface 63 through
 which vacuum 61 may be applied to substrate 53. An electrodeposition
 apparatus according to the present invention may include other substrate
 supports for supporting and/or immobilizing the substrate.
 The substrate support may also immobilize the substrate. Along these lines,
 the electrodeposition apparatus according to the present invention may
 include at least one immobilizer for immobilizing the substrate. For
 example, the at least one immobilizer could include at least one clamp for
 engaging a surface of the substrate. The at least one clamp could engage
 any portion of the surface of the substrate. For example, the at least one
 clamp could engage the surface of the substrate opposite the surface that
 includes the seed layer and/or on which the material is to be
 electrodeposited.
 FIG. 6 illustrates another embodiment of an electrodeposition apparatus
 according to the present invention. A substrate 65 may be arranged on the
 electrodeposition apparatus. The substrate may be arranged on substrate
 support 75. A seed layer 67 has been deposited on substrate 65. The
 apparatus illustrated in FIG. 6 also includes vacuum 73 for urging the
 substrate 65 into engagement with substrate support 75.
 Contacts 69 laterally engage the seed layer on the substrate. Contacts 69
 may be moved into and out of engagement with the substrate as indicated by
 arrows 71. The contacts 57 illustrated in FIG. 5 are insulated. In this
 case, the contacts include an elastomeric coating 58 on the surfaces of
 the contacts that do not engage the substrate and/or the seed layer.
 Contacts according to the present invention may also engage a corner of the
 substrate in addition to laterally engaging at least one side surface of a
 substrate. FIGS. 10, 11 and 12 illustrate an embodiment of the present
 invention that includes contacts that may engage a corner of a substrate.
 Along these lines, FIG. 10 illustrates a semiconductor substrate 77 with a
 seed layer 79 deposited thereon.
 A ring 81 may be arranged about the substrate. A plurality of finger
 contacts 83 may be provided on ring 81 for making contact with the
 substrate 77/seed layer 79. The finger contacts may be attached to the
 ring. Alternatively, the ring and the contacts may be formed together as a
 single unit.
 Finger contacts 83 may make peripheral and edge contact with substrate
 77/seed layer 79. A voltage source 85 may be connected to the ring and
 finger contacts. Although not shown in all of the figures, a voltage
 source typically is connected to all of the contacts according to the
 present invention, regardless of their form/composition/shape etc. The
 contacts may be rendered cathodic relative to the anode.
 FIG. 11 represents a perspective view of a portion of a ring 81 including
 finger contacts 83. FIG. 12 illustrates a close up cross-sectional view of
 an individual finger contact 83 according to the present invention. Finger
 contact 83 may have a height 87 of about 1.2 to about 10 times the
 thickness of the wafer. The side to side thickness of the wafer 89 may be
 about 1 mm. However, the finger contacts may be provided in any dimensions
 necessary to treat the substrate of any size.
 The contacts typically are made of beryllium-copper spring, titanium,
 stainless steel or other suitable materials. The spacing between each
 contact 83 and its neighbor depends on the size of the substrate and the
 thickness of the seedlayer. For a seedlayer greater than about 2,000
 .ANG., the spacing between the contacts may be larger than about 30 mm. On
 the other hand, for a thin seed layer, such as about 300 .ANG., the
 spacing can be smaller than about 10 mm.
 The present invention also includes a method for depositing material on a
 surface of a substrate. The method includes laterally engaging the
 substrate on which material is to be deposited with at least one contact.
 The at least one contact laterally contacts the substrate and provides an
 electrical connection to the substrate without obscuring the surface of
 the substrate to be plated. A voltage source may be connected to the at
 least one contact. The contacts and plating apparatus may be provided
 substantially as described above. The at least one contact may be biased
 into contact with the substrate.
 As stated above, the material being deposited may be deposited over the
 entire surface of the substrate that it is desired the material be
 deposited on. This is at least in part due to the fact that the contacts
 according to the present invention obscure the surface of the substrate on
 which material is being deposited. The at least one contact may be
 retracted. A corner of the substrate may also be engaged by the at least
 one contact. Also, the contact may be used to electroetch or electropolish
 metals on a substrate. In this case, the contacts are rendered anodic.
 The foregoing description of the invention illustrates and describes the
 present invention. Additionally, the disclosure shows and describes only
 the preferred embodiments of the invention, but as aforementioned, it is
 to be understood that the invention is capable of use in various other
 combinations, modifications, and environments and is capable of changes or
 modifications within the scope of the inventive concept as expressed
 herein, commensurate with the above teachings, and/or the skill or
 knowledge of the relevant art. The embodiments described hereinabove are
 further intended to explain best modes known of practicing the invention
 and to enable others skilled in the art to utilize the invention in such,
 or other, embodiments and with the various modifications required by the
 particular applications or uses of the invention. Accordingly, the
 description is not intended to limit the invention to the form disclosed
 herein. Also, it is intended that the appended claims be construed to
 include alternative embodiments.