Preventing misshaped solder balls

1. A method of making a semiconductor die contact assembly, the method comprising:

providing a first stage assembly;

removing a photoresist layer from the first stage assembly to yield a second stage assembly; and

removing a portion of a ball limiting metallurgy layer from the second stage assembly to yield a third stage assembly;

wherein:

the first stage assembly includes the ball limiting metallurgy layer, a first thick pad, the photoresist layer, and a first pre-reflow solder structure;

in the first and second stage assemblies, the ball limiting metallurgy layer defines a top surface;

in the first stage assembly, the photoresist layer: (i) is located on top of the top surface of the ball limiting metallurgy layer, (ii) defines a first pocket located over the first thick pad, and (iii) defines a first upstanding wall defining the first pocket;

in the first stage assembly, the pre-reflow solder structure is located within the first pocket and over a portion of a footprint of the first thick pad;

in the first stage assembly, an entirety of the first upstanding wall extends upwards from a first region of the top surface of the ball limiting metallurgy layer;

in the first stage assembly, no portion of the first region of the top surface of the ball limiting metallurgy layer is located on any downward-inclined discontinuity; and

a thickness of the first thick pad is substantially greater than 1 micrometer.

2. The method of claim 1 further comprising:

performing solder reflow on the third stage assembly to yield a fourth stage assembly;

wherein:

the solder reflow causes the first pre-reflow solder structure to be reshaped into a solder ball shape.

3. The method of claim 1 wherein:

in the first stage assembly, the top surface of the ball limiting metallurgy layer includes: (i) a first elevated region located over at least the portion of the footprint of the first thick pad, (ii) a first non-elevated region located away from a vicinity of the footprint of the first thick pad, and (iii) a downward-inclined discontinuity region located between the first elevated region and the first non-elevated region.

4. The method of claim 3 wherein:

the first region of the top surface of the ball limiting metallurgy layer is entirely located within the first elevated region.

5. The method of claim 1 wherein:

the thickness of the first thick pad is at least approximately 4 micrometers.

6. A method of making a semiconductor die contact assembly, the method comprising:

providing a first stage assembly;

removing, from the first stage assembly, an uppermost portion of a passivation layer from a removed passivation layer footprint to yield a second stage assembly;

depositing a ball limiting metallurgy layer over a top surface of the second stage assembly to yield a third stage assembly;

depositing a photoresist layer and a first pre-reflow solder structure over a top surface of the third stage assembly to yield a fourth stage assembly;

removing the photoresist layer from the fourth stage assembly to yield a fifth stage assembly; and

removing a portion of the ball limiting metallurgy layer from the fifth stage assembly to yield a sixth stage assembly;

wherein:

the fourth stage assembly includes a portion of the passivation layer, the ball limiting metallurgy layer, a first thick pad, the photoresist layer, and the first pre-reflow solder structure;

in the fourth stage assembly, the photoresist layer: (i) is located on top of a top surface of the ball limiting metallurgy layer, (ii) defines a first pocket located over the first thick pad, and (iii) defines an first upstanding wall defining the first pocket;

in the fourth stage assembly, the first pre-reflow solder structure is located within the first pocket and over a portion of a footprint of the first thick pad;

in the fourth stage assembly, an entirety of the first upstanding wall extends upwards from the removed passivation layer footprint; and

a thickness of the first thick pad is substantially greater than 1 micrometer.

7. The method of claim 6 further comprising:

performing solder reflow on the sixth stage assembly to yield a seventh stage assembly;

wherein:

the solder reflow causes the first pre-reflow solder structure to be reshaped into a solder ball shape.

8. The method of claim 6 wherein the removing of the uppermost portion of the passivation layer is achieved, at least in part, by chemical-mechanical polishing.

9. The method of claim 6 wherein the removing of the uppermost portion of the passivation layer further removes, an entirety of the passivation layer that is located within the removed passivation layer footprint.

10. The method of claim 9 wherein the removal of the entirety of the passivation layer that is located within the passivation layer footprint includes:

selectively covering a top surface of a portion of passivation layer of the first stage assembly that is outside of the removed passivation layer footprint with a resist layer;

removing the entirety of the passivation layer where the top surface of the passivation layer is not covered by the resist layer; and

removing the resist layer from the top surface of a remaining portion of the passivation layer.

11. The method of claim 6 wherein:

the first thick pad has a thickness substantially equal to 4 micrometers.