Techniques for processing devices

1. A method of forming a microelectronic assembly, comprising:

preparing a bonding surface of a first substrate, including activating the bonding surface of the first substrate with a first plasma based on a first gas;

forming a bonding surface of a second substrate;

mounting the second substrate to a dicing layer;

singulating the second substrate into a plurality of dies while the second substrate is mounted to the dicing layer, each die of the plurality of dies having a bonding surface comprising a portion of the bonding surface of the second substrate;

processing the plurality of dies while the plurality of dies is mounted to the dicing layer, including cleaning the bonding surface of the dies with a second plasma based on a second gas, different from the first gas;

selecting a die of the plurality of dies; and

directly bonding the bonding surface of the die to the bonding surface of the first substrate without adhesive, and without activating the bonding surface of the die while the die is mounted to the dicing layer.

2. The method of claim 1 , further comprising applying a protective coating to the bonding surface of the second substrate prior to singulating the second substrate.

3. The method of claim 1 , further comprising cleaning one or more surfaces of the plurality of dies or the first substrate using a chemical reagent, a megasonic transducer, and/or a mechanical brush.

4. The method of claim 1 , further comprising processing the die while the die is held by a pick and place tool, the processing including insitu cleaning of the bonding surface of the die.

5. The method of claim 1 , further comprising picking up the die by contacting the bonding surface of the die with a pick and place tool formed from a hydrophobic material or coated with a hydrophobic material.

6. The method of claim 1 , wherein the first plasma comprises a nitrogen plasma.

7. The method of claim 1 , wherein the second plasma comprises an oxygen plasma.

8. A method of forming a microelectronic assembly, comprising:

preparing a bonding surface of a first substrate;

preparing a bonding surface of a second substrate;

mounting the second substrate to a dicing layer;

singulating the second substrate into a plurality of dies while the second substrate is mounted to the dicing layer, each die of the plurality of dies having a bonding surface comprised of a portion of the bonding surface of the second substrate;

processing the plurality of dies while the plurality of dies is mounted to the dicing tape;

selecting a die of the plurality of dies and removing the die from the dicing tape;

activating one of the bonding surface of the first substrate or the bonding surface of the die; and

directly bonding the bonding surface of the die to the bonding surface of the first substrate without adhesive, and without activating the other of the bonding surface of the first substrate or the bonding surface of the die.

9. The method of claim 8 , further comprising cleaning the other of the bonding surface of the first substrate or the bonding surface of the die with an oxygen plasma.

10. The method of claim 8 , wherein the bonding surface of the first substrate or the bonding surface of the die is activated with a nitrogen plasma.

11. The method of claim 8 , wherein the bonding surface of the die is a first bonding surface of the die and wherein the die includes a second bonding surface opposite the first bonding surface of the die, the method further comprising:

activating the second bonding surface of the die, a first bonding surface of an additional die, or the second bonding surface of the die and the first bonding surface of the additional die with a nitrogen plasma; and

directly bonding the first bonding surface of the additional die to the second bonding surface of the die without adhesive.

12. A method of forming a microelectronic assembly, comprising:

preparing a bonding surface of a first substrate;

preparing a bonding surface of a second substrate;

mounting the second substrate to a dicing layer;

singulating the second substrate into a plurality of dies while the second substrate is mounted to the dicing layer, each die of the plurality of dies having a bonding surface comprised of a portion of the bonding surface of the second substrate;

cleaning one of the bonding surface of the first substrate or the bonding surface of one or more dies of the plurality of dies with a first plasma based on a first gas;

activating the other of the bonding surface of the first substrate or the bonding surface of the one or more dies of the plurality of dies with a second plasma based on a second gas; and

directly bonding the bonding surface of the one or more dies to the bonding surface of the first substrate without adhesive.

13. The method of claim 12 , further comprising cleaning the plurality of dies while the plurality of dies is mounted to the dicing layer, wherein activating the bonding surface of the one or more dies of the plurality of dies is performed while the one or more dies are mounted to the dicing layer or after removing the one or more dies from the dicing layer.

14. The method of claim 12 , further comprising rendering the bonding surface of the die hydrophobic prior to directly bonding the bonding surface of the die to the bonding surface of the first substrate.

15. The method of claim 12 further comprising applying a megasonic cleaner to clean the plurality of dies or the first substrate or the plurality of dies and the first substrate.

16. The method of claim 12 , wherein the bonding surfaces of the first substrate and the die include corresponding conductive features that meet when the bonding surfaces of the first substrate and the die are directly bonded.

17. The method of claim 16 , further comprising annealing the first substrate and the die at a high temperature following the directly bonding, to cause the conductive features that meet to permanently join.

18. The method of claim 12 , wherein the microelectronic assembly comprises a stack of multiple directly bonded dies of the plurality of dies, and wherein the microelectronic assembly is annealed after placement of a plurality of dies on the stack.

19. The method of claim 12 , wherein the first plasma comprises an oxygen plasma.

20. The method of claim 12 , wherein the second plasma comprises a nitrogen plasma.

21. A method of forming a microelectronic assembly, comprising:

forming a bonding surface of a first substrate;

forming a bonding surface of a second substrate, the second substrate having a smaller footprint than a footprint of the first substrate, wherein forming the bonding surface of the second substrate comprises cleaning the bonding surface of the second substrate while the second substrate is mounted on a layer;

activating the bonding surface of the first substrate, the bonding surface of the second substrate, or the bonding surfaces of the first and the second substrates; and

directly bonding the bonding surface of the second substrate to the bonding surface of the first substrate without adhesive.

22. The method of claim 21 , wherein the activating comprises exposing the bonding surface of the first substrate, the bonding surface of the second substrate, or the bonding surfaces of the first and the second substrates to plasma or ionized gas while the second substrate is mounted to the layer or after removing the second substrate from the layer.

23. The method of claim 22 , wherein the plasma or ionized gas comprises an oxygen or nitrogen plasma.

24. The method of claim 21 , wherein the layer comprises a grip ring, a dicing sheet or a dicing layer.

25. The method of claim 21 , further comprising annealing the first substrate and the second substrate at a high temperature following the directly bonding, to cause conductive features at the bonding surfaces of the first and the second substrates that mate to permanently join.

26. The method of claim 21 , wherein the bonding surface of the second substrate is a first bonding surface of the second substrate and wherein the second substrate includes a second bonding surface opposite the first bonding surface of the second substrate, the method further comprising:

activating one of the second bonding surface of the second substrate or a first bonding surface of an additional substrate; and

directly bonding the first bonding surface of the additional substrate to the second bonding surface of the second substrate without adhesive.

27. A method of forming a microelectronic assembly, comprising:

forming a bonding surface of a first substrate;

forming a first bonding surface of a second substrate, the second substrate having a smaller footprint than a footprint of the first substrate, wherein forming the first bonding surface of the second substrate comprises cleaning the first bonding surface of the second substrate while the second substrate is mounted on a layer;

removing the second substrate from the layer and forming a second bonding surface of the second substrate, opposite the first bonding surface of the second substrate;

activating the bonding surface of the first substrate or the first and second bonding surfaces of the second substrate;

directly bonding the first bonding surface of the second substrate to the bonding surface of the first substrate without adhesive; and

bonding the first bonding surface of an additional substrate to the second bonding surface of the second substrate.

28. The method of claim 27 , wherein the additional substrate is bonded to the second bonding surface of the second substrate using a direct bonding method without adhesives.

29. The method of claim 27 , further comprising annealing the microelectronic assembly at a temperature higher than an ambient temperature of the microelectronic assembly, to cause conductive features at the bonding surfaces of the first and the second substrates that mate to join permanently.