Structure and method for overlay marks
AssigneeTaiwan Semiconductor Manufacturing Company, Ltd.
InventorsHsien-Cheng Wang, Ming-Chang Wen, Chun-Kuang Chen, Yao-Ching Ku
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Abstract
The overlay mark and method for making the same are described. In one embodiment, a semiconductor overlay structure includes gate stack structures formed on the semiconductor substrate and configured as an overlay mark, and a doped semiconductor substrate disposed on both sides of the gate stack structure that includes at least as much dopant as the semiconductor substrate adjacent to the gate stack structure in a device region. The doped semiconductor substrate is formed by at least three ion implantation steps.
Claims20
A method for processing a semiconductor substrate that includes a device region and an overlay region, the method comprising:
- performing a first ion implantation to the semiconductor substrate within the device region and the overlay region;
- forming a first polysilicon gate stack in the device region and a second polysilicon gate stack in the overlay region;
- performing a second ion implantation to the semiconductor substrate;
- performing a third ion implantation to the semiconductor substrate;
- replacing the first and second polysilicon gate stacks with metal gate stacks;
- and
- measuring an overlay error using the metal gate stacks in the overlay region and another overlay layer,
- wherein a total boron ion implantation dosage to the semiconductor substrate within the overlay region is greater than about 2×1015 ions/cm2.
A method of forming an overlay mark, the method comprising:
- performing a first ion implantation in an overlay region of a semiconductor substrate, wherein the overlay region is free of active devices;
- forming a plurality of gate stacks configured as a periodic grating structure;
- enhancing a contrast between the semiconductor substrate and the gate stacks of the plurality of gate stacks by performing a second ion implantation in the overlay region;
- and
- replacing at least one gate stack of the plurality of gate stacks with at least one metal gate stack,
- wherein performing the second ion implantation comprises providing a boron dosage greater than about 2×1015 ions/cm2.
A method of forming a semiconductor device, the method comprising:
- simultaneously forming a first active device in a device region of a semiconductor substrate and forming a first dummy device in an overlay region of the semiconductor substrate, wherein the overlay region is free of active devices;
- and
- simultaneously forming a second active device in the device region and forming a second dummy device in the overlay region,
- wherein the second dummy device is surrounded by the first dummy device when viewed from above, and the first dummy device is a dummy oxide layer around the second dummy device to form a box-in-box overlay mark.
Dependencies are inferred from the claim text.