Method and means for handling semiconductor and similar electronic devices

Method and apparatus for handling semiconductor chips and the like are disclosed which include the use of a flat flexible film which is attached to the face of a base member. The face of the base member is formed with recesses covered by the flat flexible film. Chips are loaded onto the flat flexible film in good surface contact therewith whereby they are securely held in position by interfacial, adhesive, or other forces between the chips and film. To facilitate removal of chips from the film, the recesses are connected to a vaccuum source, drawing portions of the flexible film into said recesses and providing the film with a texturized, or undulating, surface. The area of contact between the chips and film is thereby reduced which, in turn, results in a reduction in the force by which the chips are attached to the film, thereby enabling removal of the chips by conventional techniques.

BACKGROUND OF THE INVENTION 
The manufacture of semiconductor and other electronic devices including 
wafers, die, substrates, chips, and the like, includes steps such as 
breaking, sorting, inspection, bonding, shipping, storage and additional 
processing. A number of apparatus and methods are commonly employed by 
processors of such devices in the handling thereof. One such method 
involves the use of carriers, or trays, which are formed with a plurality 
of cavities in the face thereof in which the chips are loaded. 
Typical disadvantages in the use of cavity trays include: 
(a) Many different cavity sizes are needed to accommodate the multitude of 
chip sizes that are available. 
(b) Unless the chip size and cavity size are very closely matched, the chip 
can rotate within the cavity and make subsequent automatic pickup systems, 
which require precise chip locations, more difficult. 
(c) Chips may turn over within the cavities during shipment, and thus 
require re-orientation prior to subsequent processing. 
(d) Chips may break as they move within the cavities during shipment. 
(e) Chips tend to be difficult to place within a cavity, particularly small 
chips, by automatic equipment, since the chips tend to bounce out. 
(f) Chips, particularly small chips, tend to easily dislodge and fly out of 
the tray, unless particular care is exercised, when the cavity tray is 
opened. 
Other methods for holding and handling chips include: 
(a) A film that contains a pressure sensitive adhesive mounted in a frame. 
Such frames are often difficult to handle and require special equipment to 
remove chips from the adhesive film. Commonly, this includes a probe from 
the bottom of the film to push the chip from the adhesive, and a vacuum 
tool from the top to capture and remove the chip. 
(b) A non-adhesive elastomeric film that holds chips in place because of 
intimate surface contact between film and chip. Such films are ordinarily 
mounted on rigid substrates. Predominantly, small chips are handled on 
this type of system since larger ones, with increased surface contact 
area, are difficult to remove by ordinary vacuum techniques. 
(c) A system similar to (b) where the surface of the elastomer has been 
texturized to reduce the surface contact between chip and elastomer, and 
thus allow for the removal of larger chips. This system is disclosed in 
copending U.S. patent application Ser. No. 168,031 filed July 14, 1980, 
U.S. Pat. No. 4,395,451 issued July 26, 1984 entitled Semiconductor Wafer 
and Die Handling Method and Means by Victor E. Althouse, one of the 
present co-inventors. While this system has a number of advantages, it is 
sometimes difficult to control the degree of texturization so that 
sufficient surface contact is maintained to retain chips in place. 
SUMMARY AND OBJECTS OF THE INVENTION 
An object of this invention is the provision of method and means for 
handling semiconductor and other electronic devices which avoid the 
above-mentioned and other shortcomings of prior art arrangements. 
An object of this invention is the provision of a carrier for handling 
semiconductor die, wafers, chips, or like devices, upon which the devices 
are retained in desired position during handling, yet are readily removed 
from the carrier using conventional vacuum collets, tweezers, or the like. 
An object of this invention is the provision of an improved carrier which 
includes a flexible plastic film which allows for high surface contact 
between the film and chip for maximum retention prior to chip removal, and 
the reduction in surface contact by withdrawal of a portion of the 
flexible film from the chip during chip removal. 
The above and other objects and advantages of this invention are achieved 
by use of a base member having a substantially flat upper face formed with 
recess means inside the perimeter thereof. A thin flexible film is 
supported on the face of the base member in sealing engagement with the 
base member about the perimeter thereof. Chips, or the like, to be handled 
are supported on the upper face of the thin flexible film in full surface 
contact with the film. Frictional, interfacial adhesive and/or other 
forces tightly hold the chips in position on the film. To allow for 
removal of chips from the film, the film is drawn downwardly into the 
recess means by reducing the gas pressure in the recess means thereby 
reducing the surface contact between the chip and film which, in turn, 
reduces the force by which the chip is attached to the film. If desired, 
the flexible film may be resilient so as to return to a flat condition in 
preparation for reuse of the carrier when gas pressure is returned to 
normal; i.e. restored to ambient pressure. The base member may be adapted 
for support on a vacuum chuck, or table, to facilitate connection of the 
recess means to a source of reduced gas pressure.

Reference first is made to FIGS. 1 and 2 of the drawings wherein one form 
of a novel carrier 10 embodying this invention is shown, which carrier is 
adapted for use in handling semiconductor chips, wafers, or other such 
smooth-surfaced articles. The illustrated carrier comprises a base member 
12 formed of a suitable rigid material such as glass, plastic, metal, or 
the like. The base member 12 has an upper face 14 formed with flat 
marginal edges 16 and a recess 18 therewithin. 
A cover 20 in the form of a thin flexible film, or sheet, is attached to 
the face 14 of the base member 12, a portion of which cover is shown 
broken away in FIG. 1 for clarity. A plurality of cover-supporting 
protuberances 22 are located within the margin edges of the base, the 
upper faces of which protuberances are provided in the plane of the 
margins 16. The protuberances 22 in the carrier illustrated in FIGS. 1-4 
have an elongated horizontal cross-sectional shape, and are arranged in 
the form of a two-dimensional array in which adjacent protuberances extend 
at right angles to each other. Preferably, the protuberances are 
dimensioned such that the recess 18 is made up of only short straight line 
segments, with no long segments extending, say, between opposite margins 
of the carrier at any angle. The purpose of this arrangement of 
protuberances is described below in a further description of FIG. 4. 
The cover sheet 20 is arranged to the upper face of the base member 12 in 
sealing engagement therewith, which attachment may be effected by any 
suitable means including, for example, the use of an adhesive, not shown, 
or simply by non-adhesive frictional and interfacial forces between the 
smooth flat upper face of the base member and the marginal edges of the 
cover. With the cover sheet 20 attached to the base member 12, an air 
chamber, or cavity is defined between the recess 18 in the base member and 
the attached cover sheet 20, which chamber is adapted for connection to a 
low air pressure, or vacuum, source through a passageway 24 formed in the 
base member 12. 
As noted above, the novel carrier is adapted for use in handling 
semiconductor chips, wafers, die, or other such smooth-surfaced articles. 
In FIGS. 1-4, a semiconductor chip 26 is shown resting on the surface of 
the flexible sheet 20. The cover sheet 20 may, for example, comprise an 
elastomeric member having a smooth upper face to provide for high 
interfacial retention forces between the sheet and the smooth-faced device 
26 supported thereon. Alternatively, a pressure sensitive adhesive, not 
shown, may be provided at the upper face of the cover sheet 20 for 
adhesive retention of the device 26 thereon. In any event, means are 
provided for securely holding the device 26 on the cover sheet 20 through 
attachment of their adjacent faces such that the device can not be readily 
removed using conventional tweezers or vacuum techniques while the sheet 
20 is in a flat position illustrated in FIGS. 1-3. 
To facilitate removal of the device 26 from the cover sheet 20 the surface 
contact between the cover sheet and device is reduced by drawing portions 
of the cover sheet 20 adjacent the recess 18 downwardly into the recess. 
To pull portions of the cover sheet which are adjacent the recess 
downwardly into said recess, the air chamber defined between the recess 
and cover is connected to a vacuum, or low pressure, source. During chip 
removal operation, the base member 12 may be supported on a vacuum chuck, 
or table, 30 which is provided with vertical walls 32 to define a recess 
34 in the upper face thereof. Downwardly extending walls 36 on the base 
member 12 surround the walls 32 of the chuck when the base member 12 is 
positioned on the chuck, and a substantially fluid tight chamber is 
defined between the bottom of the base member 12 and recess 34 in the 
chuck. A passageway 40 in the vacuum chuck is provided for connection of 
the recess 34 to a vacuum, or low pressure, source through a control valve 
42. Low pressure in the chamber between the chuck 30 and base member 12 is 
communicated through the passageway 24 in the base member 12 to the recess 
18 in the face of the base member whereupon the flexible cover sheet 20 is 
drawn downwardly into the recess, as shown in FIG. 4. Surface contact 
between the chip 26 and supporting sheet 20 is reduced by withdrawal of 
portions of the sheet 20 into the recess 18 thereby reducing the magnitude 
of the force by which the chip is attached to the film thereby allowing 
ready removal of the chip by a vacuum needle, tweezer, or the like. 
With the present invention, the surface of the chip supporting sheet 20 is 
converted from a flat condition, for full surface contact with the device 
26, to a wavy or undulating condition for a reduction in the surface 
contact between the sheet 20 and devices supported thereon. The invention 
is adapted for use with a wide variety of chip sizes; with the number and 
size of protuberances 22 employed in the base member 12 being selected in 
relation to the size of the chips 26 to be handled. The relative 
dimensions are such that the chip is supported through the cover sheet 20 
in a level condition by one or more of the protuberances, and remains 
level when portions of the sheet are drawn downwardly into the recess in 
the base member 12. A chip which is too small for proper use with the 
carrier 10 could be drawn down with the cover sheet 20 into a recess, 
which would not facilitate removal of the chip from the carrier. 
With the protuberances array shown in the embodiment of FIGS. 1-4, the 
resultant recess includes only short straight line segments to avoid 
creation of a long straight line crease in the cover sheet 20 when 
portions of the sheet are drawn into the recess 18. This helps to avoid 
adhesion of the surface along an entire edge of a chip with the depressed 
portion of the cover sheet and resultant tilting of the chip on the 
carrier. 
As noted above, the flexible cover member 20 may comprise an elastomeric 
film which returns to a smooth, flat, condition upon release of the vacuum 
in the recess 18 for reuse of the carrier including the member 20. An 
elastomeric member may be formed using a suitable curable liquid polymer 
such as Sylgard 184 (Dow-Corning), a curable two part silicone elastomer 
material which may be formed with smooth opposite faces. Use of an 
elastomer having a Shore A hardness of from about 15 to about 90 is 
practical, with a range of between about 30 to 65 Shore A being preferred. 
Obviously, other factors including thickness of the film 20, configuration 
of the recess 18, and vacuum employed also determine the degree of 
texturing, or waviness, which is obtained. In one arrangement, a Sylgard 
184 elastomeric film about 1/64 in. thick and having a Shore A hardness of 
35 was used in a system employing a vacuum of approximately 20 psi. With 
this elastomeric material, retention forces between the bottom face of the 
film 20 and the smooth upper face of the base member 12 normally are 
sufficiently great such that no adhesive or other such bonding means are 
required to provide an adequate seal therebetween to obtain the necessary 
vacuum. Also, chips 26, or the like, which are placed on the flat film 20 
with a slight pressure to assure good contact between the film and chip, 
are tightly held in position on the film by frictional and interfacial 
forces so long as the film remains in the flat condition. Even when the 
tray is turned over, chips remain attached to the film and are not readily 
removed by a vacuum needle. 
If desired, a flexible but substantially non-resilient film 20 may be used 
in the carrier, such as Mylar or other such film, in which case the cover 
20 is replaced following every use, after a vacuum has been applied and 
chips removed therefrom. 
Obviously, the invention is not limited to use of a carrier in which the 
recess 18 has the pattern illustrated in FIGS. 1-4. Reference now is made 
to FIG. 5 wherein a carrier 10A is shown comprising a base member 12A of 
the same general type as base member 12 shown in FIGS. 1-4 and described 
above, together with a flexible cover sheet 20 only a portion of which is 
shown in FIG. 5. The upper face of the base member 12A is formed with a 
plurallity of intersecting grooves 50 which define a two-dimensional array 
of protuberances, or pads 52, the upper faces of which lie in the plane of 
the margins 16A of the face. The flexible cover 20 is attached to the face 
of the base member 12A, overlying the grooves 50. The chamber defined by 
the grooves 50 and flexible cover 20 is adapted for connection to a vacuum 
source, not shown, through a passageway 54 in the base member. A vacuum 
chuck, such as a vacuum chuck 30 shown in FIG. 2, may be used for 
connection of the carrier to a vacuum source. When a vacuum is drawn, 
portions of the film, or cover, 20 are drawn into the grooves thereby 
reducing the contact between chips 26 supported on the film and the film, 
and allowing for ready removal of the chips from the film as by use of a 
vacuun needle, tweezers, or the like. With this arrangement, care 
generally must be taken to avoid locating an edge of a chip directly over 
a groove in alignment therewith, thereby avoiding possible tilting of the 
chip when a vacuum is applied. Obviously, the chip must be of sufficient 
size to overlie one or more grooves to obtain a reduction in surface 
contact when the film is withdrawn into the grooves. 
In another embodiment of this invention, shown in FIG. 6, a modified form 
of base member 12B is employed which is of the same general type as base 
members 12 and 12A, described above. As seen in FIG. 6, base member 12B 
has a smooth upper face 60 which is covered by a flexible cover sheet 20 
attached thereto. A plurality of holes, or passageways, 62 are formed 
through the base member 12B extending from the face 60 to the bottom 
thereof. As with the other carriers, the base member 12B is adapted for 
operation with a vacuum chuck, or the like, such as chuck 30 shown in FIG. 
2, for connection of the passageways 62 to a vacuum source. With a reduced 
pressure in the passageways, portions of the flexible cover 20 are drawn 
downwardly into the passageways 62 to reduce surface contact between the 
film 20 and chips 26 supported thereon. With this arrangement, care must 
be taken to avoid complete overlay of a passageway by a chip to avoid 
formation of a vacuum between the chip and adjacent portion of the 
flexible cover 20 drawn downwardly into the passageway. 
The novel carrier of this invention is well adapted for use in a shipping 
container for shipping semiconductor chips, wafers, etc. In FIG. 7, to 
which reference now is made, there is shown a carrier 10, which may be of 
the same type shown in FIGS. 1-4 and described above, which is provided 
with a cover 70. Chips 26 to be transported are shown supported on the 
flexible sheet 20 of the carrier, and a resilient foam plastic layer 72 is 
shown placed over the chips to further hold them in place when the cover 
70 is attached to the carrier 10. The force of the foam plastic layer 72 
on the chips adds to the retention forces between the chips and sheet 20 
to maintain the chips in position on the sheet during handling and/or 
shipping of the container. At the destination, the cover 70 and foam 
plastic layer 72 are removed from the carrier, and the base member 12 is 
attached to a vacuum chuck for drawing of a vacuum in the recess between 
the flexible film 20 and base member 12. As described above, this causes 
the film 20 to be drawn into the recess, or cavity, in the face of the 
base member which, in effect, imposes a texture or waviness on the film 
thereby reducing the surface contact between the chip and film. Retention 
forces between the chips and film are thereby reduced whereupon the chips 
are readily removable by a vacuum needle, tweezers, or the like. Since 
chips remain in position on the carrier without relative movement during 
handling and shipping, the carrier of this invention is well adapted for 
use with automated chip-handling equipment since oriention of the chips on 
the carrier is a known factor. 
The invention having been described in detail in accordance with 
requirements of Patent Statutes, various other changes and modifications 
will suggest themselves to those skilled in the art. For example, a 
laminated cover sheet may be employed to provide for desired film 
properties. Reference is made to FIG. 8 wherein an enlarged fragmentary 
sectional view which is similar to that of FIG. 3 is shown, comprising a 
base member 12 with a modified form of cover sheet 80 attached to the face 
thereof for support of chips, such as chip 26. The cover sheet 80 
comprises a laminated member which includes upper and lower layers 80A and 
80B, respectively. The upper layer 80A comprises an elastomer having a 
smooth upper face to which chips, or the like, tightly adhere when pressed 
into intimate surface contact therewith. A silicone elastomer is preferred 
since it retains desired properties over a wide range of conditions, 
including use at high temperatures. The lower layer 80B comprises a 
plastic flexible film affixed to the upper layer 80A and having a smooth 
bottom face for intimate engagement with the upper face of the associated 
base member 12. A suitable plastic for this use includes polyethylene 
terephthalate (Mylar) which has high strength over a wide range of 
temperatures. As in other embodiments, the laminated sheet 80 is supported 
in a flat condition on the associated base member to provide for high 
surface contact between the sheet and chips supported thereon. The sheet 
is sufficiently flexible to allow for withdrawal of portions thereof into 
the recess 18 in the face of the base member when the recess is connected 
to a vacuum source, for reduction of the surface contact between the sheet 
and chips supported thereon when chip removal is required. It is intended 
that the above and other such changes and modifications shall fall within 
the spirit and scope of the invention defined in the appended claims.