Dummy stacked structures surrounding TSVs and method forming the same

A method comprising:

• forming a plurality of low-k dielectric layers over a semiconductor substrate;
• forming a first plurality of dummy stacked structures extending into at least one of the plurality of low-k dielectric layers;
• forming a plurality of non-low-k dielectric layers over the plurality of low-k dielectric layers;
• forming a second plurality of dummy stacked structures extending into the plurality of non-low-k dielectric layers, wherein the second plurality of dummy stacked structures are over and connected to corresponding ones of the first plurality of dummy stacked structures, wherein the first plurality of dummy stacked structures comprise a plurality of portions in the at least one of the plurality of low-k dielectric layers, and the plurality of portions are disconnected from each other;
• etching the plurality of non-low-k dielectric layers, the plurality of low-k dielectric layers, and the semiconductor substrate to form a via opening, wherein the via opening is encircled by the first plurality of dummy stacked structures and the second plurality of dummy stacked structures;
• and
• filling the via opening to form a through-via.

A method comprising:

• forming a plurality of low-k dielectric layers over a semiconductor substrate;
• forming a first plurality of dummy stacked structures extending into at least one of the plurality of low-k dielectric layers;
• forming a plurality of non-low-k dielectric layers over the plurality of low-k dielectric layers;
• forming a second plurality of dummy stacked structures extending into the plurality of non-low-k dielectric layers, wherein the second plurality of dummy stacked structures are over and connected to corresponding ones of the first plurality of dummy stacked structures, wherein in a top view of the second plurality of dummy stacked structures, neighboring ones of the second plurality of dummy stacked structures are separated from each other by a substantially uniform spacing;
• etching the plurality of non-low-k dielectric layers, the plurality of low-k dielectric layers, and the semiconductor substrate to form a via opening, wherein the via opening is encircled by the first plurality of dummy stacked structures and the second plurality of dummy stacked structures;
• and
• filling the via opening to form a through-via, wherein in the top view, first ones of the second plurality of dummy stacked structures are aligned to a first ring that encircling the through-via.