Wafer flatness control using backside compensation structure
Embodiments of semiconductor structures for wafer flatness control and methods for using and forming the same are disclosed. In an example, a model indicative of a flatness difference of a wafer between a first direction and a second direction is obtained. The flatness difference is associated with one of a plurality of fabrication stages of a plurality of semiconductor devices on a front side of the wafer. A compensation pattern is determined for reducing the flatness difference based on the model. At the one of the plurality of the fabrication stages, a compensation structure is formed on a backside opposite to the front side of the wafer based on the compensation pattern to reduce the flatness difference.
1. A method for controlling wafer flatness, comprising:
obtaining a model indicative of a flatness difference of a wafer between a first direction and a second direction, the flatness difference being associated with one of a plurality of fabrication stages of a plurality of semiconductor devices on a front side of the wafer;
determining a compensation pattern for reducing the flatness difference based on the model;
at the one of the plurality of the fabrication stages, forming a compensation structure on a backside opposite to the front side of the wafer based on the compensation pattern to reduce the flatness difference; and
removing at least part of the compensation structure from the backside of the wafer.
2. The method of claim 1 , wherein the flatness difference comprises a difference of wafer bow.
3. The method of claim 1 , wherein the first direction is perpendicular to the second direction.
4. The method of claim 1 , wherein the plurality of semiconductor devices comprise a plurality of three-dimensional (3D) memory devices.
5. The method of claim 4 , wherein
each of the 3D memory devices comprises a plurality of slit structures nominally parallel to one another; and
the first direction is the same as a direction in which the slit structures extend.
6. The method of claim 5 , wherein the compensation structure comprises a plurality of strips each extending in the first direction.
7. The method of claim 1 , wherein obtaining the model comprises:
obtaining an initial model of simulation indicative of the flatness difference based on a design of the semiconductor devices and the fabrication stages of the semiconductor devices;
obtaining a measurement result of the flatness difference at the one of the plurality of the fabrication stages; and
adjusting the initial model based on the measurement result to obtain the model.
8. The method of claim 1 , wherein the compensation pattern is associated with at least one of a layout, a thickness, and a material of the compensation structure.
9. The method of claim 8 , wherein the material associated with the compensation pattern is determined based on the model and the one of the plurality of the fabrication stages.
10. The method of claim 1 , wherein removing at least the part of the compensation structure is performed after filling openings of the plurality of semiconductor devices.
11. The semiconductor structure of claim 1 , wherein the at least part of the compensation structure is removed from the backside of the wafer before an end of the respective fabrication process.
12. A method for forming a semiconductor structure, comprising:
forming a plurality of semiconductor structures on a front side of a wafer;
depositing a film on a backside opposite to the front side of the wafer;
patterning the deposited film on the backside of the wafer to form a compensation structure partially covering the backside of the wafer, such that a flatness difference of the wafer between a first direction and a second direction is reduced; and
removing at least part of the compensation structure from the backside of the wafer.
13. The method of claim 12 , wherein a thickness of the compensation structure is not greater than about 5 μm.
14. The method of claim 12 , wherein a layout of the compensation structure comprises at least one of parallel straight lines, parallel wave lines, radial strips, and lattice.
15. The method of claim 12 , wherein a material of the compensation structure comprises at least one of silicon oxide, silicon nitride, polysilicon, and an organic material.
16. The method of claim 12 , wherein
the plurality of semiconductor structures comprise a plurality of slit structures nominally parallel to one another; and
the first direction is the same as a direction in which the slit structures extend.
17. A semiconductor structure, comprising:
a wafer having a front side and a backside opposite to the front side;
a plurality of semiconductor devices on the front side of the wafer; and
a compensation structure partially covering the backside of the wafer and configured to reduce a flatness difference of the wafer between a first direction and a second direction,
wherein a layout of the compensation structure comprises at least one of parallel wave lines, radial strips, or lattice.
18. The semiconductor structure of claim 17 , wherein a thickness of the compensation structure is not greater than about 5 μm.
19. The semiconductor structure of claim 17 , wherein a material of the compensation structure comprises at least one of silicon oxide, silicon nitride, polysilicon, and an organic material.
20. The semiconductor structure of claim 17 , wherein the plurality of semiconductor devices comprise a three-dimensional (3D) memory device, the 3D memory device comprising at least one structure extending along the same direction as the compensation structure.
21. The semiconductor structure of claim 17 , wherein the plurality of semiconductor devices comprise a 3D memory device, the 3D memory device comprising a through-array contact (TAC) in a dielectric stack which comprises interleaved a plurality of first dielectric layers and a plurality of second dielectric layers surrounded by a barrier structure.