Wafer chuck designs and methods for retaining a processing liquid on a surface of a semiconductor wafer
Improved wafer chuck designs and methods are provided herein for retaining a processing liquid on a surface of a semiconductor substrate during a puddle process. More specifically, the present disclosure provides various embodiments of wafer chucks that reshape a surface of a semiconductor substrate to ensure that the substrate surface is concave (or completely flat) before a processing liquid is dispensed onto the substrate surface to form a puddle of the processing liquid on the substrate surface. By providing the substrate surface with a concave (or completely flat) shape, the embodiments disclosed herein provide complete chemical coverage across the substrate surface during a puddle process, retain the puddle on the substrate surface and prevent the puddle from spilling over the substrate edge.
1 . A method for retaining a processing liquid on a surface of a semiconductor substrate, the method comprising:
receiving the semiconductor substrate within a first processing chamber, the semiconductor substrate having a frontside surface, a backside surface, a peripheral edge region, a frontside center region that extends from a center of the frontside surface to the peripheral edge region and a backside center region that extends from a center of the backside surface to the peripheral edge region;
mounting the semiconductor substrate onto a wafer chuck disposed within the first processing chamber, the wafer chuck comprising: (i) a central planar region positioned below the backside center region of the semiconductor substrate, and (ii) an edge support region positioned below the peripheral edge region of the semiconductor substrate;
activating the wafer chuck to clamp the backside center region of the semiconductor substrate onto the central planar region of the wafer chuck and elevate the peripheral edge region of the semiconductor substrate above the frontside center region of the semiconductor substrate to ensure that the frontside surface of the semiconductor substrate is concave; and
dispensing a first processing liquid onto the frontside surface of the semiconductor substrate after activating the wafer chuck to form a puddle of the first processing liquid that covers an entirety of the frontside surface;
wherein said activating the wafer chuck retains the puddle of the first processing liquid on the frontside surface by ensuring the frontside surface of the semiconductor substrate is concave.
2 . The method of claim 1 , wherein said activating the wafer chuck comprises applying a vacuum pressure or an electrostatic charge to the wafer chuck.
3 . The method of claim 2 , wherein the wafer chuck activated further comprises a fluid flow channel coupled to the central planar region, wherein the fluid flow channel is used to provide a fluid to, or remove a fluid from, the backside surface of the semiconductor substrate, and wherein the fluid is a gas or a liquid.
4 . The method of claim 3 , wherein said activating the wafer chuck comprises applying a vacuum pressure to the wafer chuck by removing gas from the backside surface of the semiconductor substrate to generate the vacuum pressure.
5 . The method of claim 3 , wherein said activating the wafer chuck comprises applying a vacuum pressure to the wafer chuck by providing a liquid to the backside surface of the semiconductor substrate and subsequently removing the liquid to generate the vacuum pressure.
6 . The method of claim 2 , wherein the edge support region of the wafer chuck comprises an annular support ring or a plurality of support pins, and wherein said activating the wafer chuck further comprises mechanically lifting the annular support ring or the plurality of support pins to elevate the peripheral edge region of the semiconductor substrate above the frontside center region of the semiconductor substrate.
7 . The method of claim 1 , wherein the first processing liquid is dispensed onto the frontside surface of the semiconductor substrate while the wafer chuck is stationary or spinning at a first rotational speed ranging between 0 to 50 rotations per minute (RPM).
8 . The method of claim 7 , further comprising dispersing the puddle of the first processing liquid across the frontside surface of the semiconductor substrate by spinning the wafer chuck at the first rotational speed.
9 . The method of claim 7 , further comprising dispersing the puddle of the first processing liquid across the frontside surface of the semiconductor substrate by tilting the wafer chuck while spinning the wafer chuck at the first rotational speed.
10 . The method of claim 7 , further comprising heating the wafer chuck to ensure that the puddle of the first processing liquid maintains a uniform temperature across the frontside surface of the semiconductor substrate.
11 . The method of claim 7 , further comprising dispensing a second processing liquid onto the frontside surface of the semiconductor substrate while spinning the wafer chuck at a second rotational speed, which is greater than the first rotational speed, to remove the first processing liquid from the frontside surface of the semiconductor substrate.
12 . The method of claim 11 , wherein the first processing liquid comprises an etching solution or a cleaning solution, and wherein the second processing liquid comprises a rinsing solution or a drying solution.
13 . The method of claim 11 , further comprising spinning the wafer chuck to remove the second processing liquid from the frontside surface of the semiconductor substrate and spin-dry the semiconductor substrate.
14 . The method of claim 11 , further comprising deactivating the wafer chuck before, during or after dispensing the second processing liquid onto the frontside surface of the semiconductor substrate to release the backside center region of the semiconductor substrate from the central planar region of the wafer chuck, wherein said deactivating the wafer chuck comprises removing a vacuum pressure or an electrostatic charge applied to the wafer chuck.
15 . The method of claim 14 , wherein the edge support region of the wafer chuck comprises an annular support ring or a plurality of support pins, and wherein said deactivating the wafer chuck further comprises mechanically lowering the annular support ring or the plurality of support pins to release the peripheral edge region of the semiconductor substrate.
16 . The method of claim 14 , further comprising dispensing a third processing liquid onto the backside surface of the semiconductor substrate after deactivating the wafer chuck to clean the backside surface.
17 . The method of claim 16 , wherein the first processing liquid comprises an etching solution or a cleaning solution, wherein the second processing liquid comprises a rinsing solution or a drying solution, and wherein the third processing liquid comprises a cleaning solution.
18 . The method of claim 16 , further comprising spinning the wafer chuck to spin-dry the semiconductor substrate after dispensing the third processing liquid onto the backside surface of the semiconductor substrate.
19 . The method of claim 11 , further comprising dispensing the second processing liquid onto the frontside surface of the semiconductor substrate while the wafer chuck is stationary or spinning at the first rotational speed to form a puddle of the second processing liquid that covers an entirety of the frontside surface.
20 . The method of claim 19 , wherein the first processing liquid comprises an etching solution or a cleaning solution, and wherein the second processing liquid comprises a drying solution.
21 . The method of claim 19 , wherein said dispensing the first processing liquid and said dispensing the second processing liquid are performed within the first processing chamber, and wherein the method further comprises:
transferring the semiconductor substrate from the first processing chamber to a second processing chamber after dispensing the second processing liquid on the frontside surface of the semiconductor substrate to form the puddle of the second processing liquid;
wherein said activating the wafer chuck retains the puddle of the second processing liquid on the frontside surface by ensuring the frontside surface of the semiconductor substrate is concave during said transferring.
22 . The method of claim 21 , wherein the first processing chamber is a wet processing chamber, wherein the second processing chamber is a supercritical processing chamber, and wherein the method further comprises:
treating a surface of the semiconductor substrate with supercritical carbon dioxide (CO 2 ); and
drying the surface of the semiconductor substrate.