Improved sputtering processes and equipment

Abstract

A method for sputtering a plurality of IC units, the method comprising the steps of applying a layer to a retaining ring; cutting an array of holes in the layer; transferring the retaining ring to a template located in a placement station; aligning the array of holes with an array of recesses in the template; transferring the IC units to the retaining ring, each IC unit corresponding to the aligned holes and recesses; and applying a sputtering method to the IC units engaged with the retaining ring.

Description

Technical Field

[0001] The present invention relates to processing of integrated circuit (IC) units, and in particular to methods and apparatus for assisting the sputtering of ball grid array (BGA) IC units. Background Art

[0002] Sputtering to deposit thin films of material onto IC cells is an effective method for applying materials with very high melting points. Therefore, sputtering has been widely used given its flexibility in the materials applied.

[0003] Typically, an array of IC units is placed on a substrate and passed through a sputtering chamber to receive a thin layer of material.

[0004] In doing so, the IC units are supported by a stencil adhesively bonded to the ring with double-sided tape. The double-sided tape is laser cut, with the IC units fitting into the holes created by the laser cut. The stencil with the IC units is then removed and sent for sputtering. The units are subsequently ejected and removed from the system.

[0005] However, the use of a stencil is uneconomical because the stencil is expensive to manufacture and difficult to recover after the sputtering step. Therefore, some prior art systems omit the stencil and place the IC unit directly on the tape. The difficulty of using the tape without the support of the stencil is that the flexibility of the tape tends to cause the unit to be misaligned and lacks adequate support during transportation. Summary of the invention

[0006] In a first aspect, the present invention provides a method for sputtering multiple IC units, the method comprising the steps of: applying a layer to a retaining ring; cutting an array of holes in the layer; transferring the retaining ring to a template, the template being located in a placement station; aligning the array of holes with the array of recesses in the template; transferring the IC units to the retaining ring, each IC unit corresponding to the aligned holes and recesses; and applying a sputtering method to the IC units engaged with the retaining ring.

[0007] In a second aspect, the present invention provides a placement station comprising: a template having an array of recesses; the template being arranged to receive a retaining ring having an array of holes; the holes and recesses being arranged to align to receive a plurality of IC units for sputtering.

[0008] Thus, by providing a template mounted or integrally located within a sputtering station, the present invention maintains structural support for the IC unit during sputtering while avoiding the additional cost of manufacturing a disposable template.

[0009] The IC unit may be bonded to the layer bonded to the retaining ring, and the IC unit may be sputtered while located on the layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] It will be convenient to further describe the invention with reference to the accompanying drawings which illustrate possible arrangements of the invention. Other arrangements of the invention are possible, and therefore, the particularity of the accompanying drawings should not be understood as superseding the generality of the preceding description of the invention.

[0011] Figure 1A and Figure 1B is a diagram of a sequence for applying layers to a retaining ring according to one embodiment of the present invention;

[0012] Figure 2A and Figure 2B is a sequence diagram of a laser cutting method according to another embodiment of the present invention;

[0013] Figure 3 and Figure 4 is a sequential diagram of applying a retaining ring to a template according to another embodiment of the present invention; and

[0014] Figure 5 is a front view of a cell located within an aligned hole of a laser cut layer and a recess of a template according to another embodiment of the present invention. DETAILED DESCRIPTION

[0015] Therefore, the present invention provides a reusable template with an array of holes corresponding to IC units. The method starts with inspecting, flipping, aligning and orienting the unit. The inspection, alignment and orientation steps include: performing a top view inspection; then moving the unit to a flipper and then a picker to align the unit. By fixing the template to the sputtering table, the IC unit is directly transferred to the sputtering table to be positioned on the laser cutting tape, which is bonded to a retaining ring, which is in turn placed on the template. After the sputtering method, the unit is ejected, aligned and further inspected before being unloaded.

[0016] Figure 1A and Figure 1B The preparation of the retaining ring 10 before the laser cutting holes is shown. The ring 10 contains a double-sided sputtering tape 15 covering the space in the ring 10. The sputtering tape 15 can be an adhesive layer applied to the retaining ring. A lower layer such as a sub-tape 20 is then attached below the tape 15 to cover any adhesive backing of the sputtering tape 15. Since the template of the prior art is fixed to the sputtering tape 15, the uncut adhesive area is covered. However, considering the removal of the template from the method, the lower layer such as the sub-tape 20 is used as a cover for the adhesive portion.

[0017] It should be understood that a layer having an adhesive portion sufficient to adhere to the periphery of the retaining ring 10 may also be used so that the sub-tape 20 is not required. Figure 1A The peripheral portion 17 is shown to adhere to the ring 10. However, in this separate embodiment, no additional adhesive qualities of the peripheral adhesive layer are required.

[0018] Figure 2A and Figure 2B Corresponding to the laser cutting method 55, the laser cutter 60 cuts holes in the sputtering tape 15 and the sub-tape 20 to produce an array of holes 25 for receiving IC units. Once the array of holes 25 is cut in the tape, the backing tape 22 of the double-sided sputtering tape 15 is removed and is ready for receiving IC units.

[0019] Figure 3 and Figure 4 The next step in the method involving the placement station 30 is shown. The ring 10 having the laser cut holes 25 in the sputtering tape and the sub-tape is lowered onto the placement table 35. In this embodiment, the placement table 35 includes a template 40 having an array of notches 45 corresponding to the laser cut holes 25 in the sputtering tape, which are aligned when the retaining ring 10 is lowered onto the template. Thus, the template 40 replaces the template during the placement method, and a separate template is not required before or after sputtering. Therefore, the cost savings of replacing the template with the template 40 is significant because the template 40 can be reused for each placement method compared to a template that is subsequently discarded.

[0020] Figure 5 The ring 10 is shown in position over the template 40, wherein an IC unit 50 is placed on the sputtering tape 15 over the template notch 45 and thus aligned with the holes 25 as previously described. The unit 50 is engaged by a picker to move the unit to the template and inspect the underside of the unit during transfer by the picker. In this case, the IC unit is a BGA chip located on the adhesive surface of the sputtering tape 15, which is assembled over the template 40. The BGA chip 50 includes solder ball connections 55 surrounding the chip 50 that are assembled within the voids created by the alignment of the notch 45 and the holes 25.

Claims

1. A method for sputtering a plurality of IC units, the method comprising the steps of: applying an adhesive layer and a sub-tape to a retaining ring of a placement station such that the sub-tape is arranged to be attached below the adhesive layer; cutting an array of holes in the adhesive layer and the sub-tape; transferring the retaining ring to a template, the template being located within the placement station; aligning the array of holes with the array of recesses in the template; transferring IC units to the retaining ring, each IC unit corresponding to the aligned holes and recesses; as well as A sputtering method is applied to the IC unit engaged with the retaining ring.

2. The method according to claim 1, wherein: The cutting step includes laser cutting.

3. The method according to claim 2, wherein: The transferring step includes engaging the IC unit with a picker and disengaging the IC unit from the picker to transfer to the holding ring.

4. The method according to claim 3, wherein: The adhesive layer is a double-sided tape.

5. The method according to claim 4, wherein: The cutting step includes: cutting the double-sided tape; and peeling off the backing tape to expose the adhesive surface and remove the cut portion of the double-sided tape.

6. The method according to claim 1, wherein: The transferring step includes engaging the IC unit with a picker and disengaging the IC unit from the picker to be transferred to the holding ring.

7. The method according to claim 1, wherein: The adhesive layer is a double-sided tape.

8. A placement station comprising: a template having an array of notches; as well as a retaining ring arranged to be received on the template, the retaining ring having an adhesive layer and a sub-tape, each of the adhesive layer and the sub-tape having an array of holes, the sub-tape being arranged to be attached below the adhesive layer; Therein, corresponding arrays of holes and recesses are arranged in alignment to accommodate a plurality of integrated circuit IC units for sputtering.

9. The placement station of claim 8, wherein: The IC unit is a ball grid array (BGA) chip, and the size of the hole is set to allow solder balls of the BGA chip to connect through the hole to hold the IC portion of the BGA chip.

10. The placement station of claim 9, wherein: The adhesive layer is a double-sided tape.

11. The placement station of claim 10, wherein: The adhesive layer also has a peripheral adhesive portion sufficient to adhere to the retaining ring.

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