Methods and systems for dry etching
Methods and systems for dry etching are disclosed. The system includes a wafer clamp ring having a central opening through which a substrate may be treated and a plurality of smaller, outer support holes for receiving pins from plunger assemblies. The outer support holes are tapered and change in diameter. The tapered shape reduces horizontal shifting of the wafer clamp ring which can occur as the wafer clamp ring is moved up-and-down during operational use. The reduced shifting increases wafer yield along the edges of the wafer.
1 . A dry etching process, comprising:
placing a wafer substrate on a support pedestal;
moving the support pedestal relative to an upper electrode to reduce a gap between the support pedestal and the upper electrode, causing a wafer clamping assembly to move from a resting height and engage an edge of the wafer substrate and create a plasma treatment volume along a front side of the wafer substrate and a backside cooling volume along a back side of the wafer substrate; and
etching the wafer substrate by generating a plasma in the plasma treatment volume;
wherein the wafer clamping assembly comprises a plurality of plunger assemblies and a wafer clamp ring, each plunger assembly including a pin at an upper end of a plunger assembly body and a cover;
wherein the wafer clamp ring comprises an annular body surrounding a central opening, the annular body including a plurality of outer support holes extending through the annular body;
wherein each outer support hole has a conical or hourglass shape, and the pin of each plunger assembly passes through one outer support hole and engages the cover to secure the wafer clamp ring to the plunger assembly such that the wafer clamp ring and the plunger assembly body move together vertically from the resting height until the edge of the wafer substrate is engaged by the wafer clamp ring, to reduce horizontal movement of the wafer clamp ring.
2 . The process of claim 1 , wherein the annular body of the wafer clamp ring comprises anodized aluminum or a ceramic material.
3 . The process of claim 1 , wherein the wafer clamping assembly is connected to the support pedestal such that the plurality of plunger assemblies move with the support pedestal and not the upper electrode.
4 . The process of claim 1 , wherein the upper electrode and the wafer clamping assembly are connected to a platform above the support pedestal.
5 . The process of claim 1 , wherein each plunger assembly further comprises a piston shaft and a compression spring within the piston shaft, and wherein the plunger assembly body is located within the piston shaft.
6 . The process of claim 5 , wherein the plunger assembly body further comprises a lip at a lower end thereof, and the lip is adapted to engage a stop surface of the piston shaft.
7 . The process of claim 1 , wherein the wafer clamping assembly has a total of three plunger assemblies, and the wafer clamp ring has three outer support holes.
8 . The process of claim 1 , further comprising cooling the wafer substrate by flowing a cooling fluid through the backside cooling volume.
9 . The process of claim 8 , wherein the cooling fluid is a liquid or a gas.
10 . The process of claim 8 , wherein the cooling fluid is helium gas.
11 . The process of claim 1 , wherein the gap between the support pedestal and the upper electrode is from about 1.1 cm to about 1.3 cm.
12 . The process of claim 1 , further comprising:
separating the upper electrode from the support pedestal after etching is complete; and
raising the wafer substrate from the support pedestal.
13 . A dry etching process, comprising:
placing a wafer substrate on a support pedestal;
moving an upper electrode relative to the support pedestal to reduce a gap between the support pedestal and the upper electrode, causing a wafer clamping assembly to move from a resting height and engage an edge of the wafer substrate and create a plasma treatment volume along a front side of the wafer substrate and a backside cooling volume along a back side of the wafer substrate;
etching the wafer substrate by generating a plasma in the plasma treatment volume; and
cooling the wafer substrate by flowing a cooling fluid through the backside cooling volume;
wherein the wafer clamping assembly comprises a plurality of plunger assemblies and a wafer clamp ring, each plunger assembly including a pin at an upper end of a plunger assembly body and a cover;
wherein the wafer clamp ring comprises an annular body surrounding a central opening, the annular body including a plurality of outer support holes extending through the annular body; and
wherein each outer support hole has a circular conical or hourglass shape, and the pin of each plunger assembly passes through one outer support hole and engages the cover to secure the wafer clamp ring to the plunger assembly such that the wafer clamp ring and the plunger assembly body move together vertically from the resting height until the edge of the wafer substrate is engaged by the wafer clamp ring, to reduce horizontal movement of the wafer clamp ring.
14 . The process of claim 13 , wherein the cooling fluid is a liquid or a gas.
15 . The process of claim 13 , wherein the wafer clamping assembly is connected to the support pedestal.
16 . The process of claim 13 , wherein each plunger assembly further comprises a piston shaft and a compression spring within the piston shaft, and wherein the plunger assembly body is located within the piston shaft.
17 . The process of claim 13 , further comprising:
separating the upper electrode from the support pedestal after etching is complete; and
raising the wafer substrate from the support pedestal.
18 . A dry etching process, comprising:
placing a wafer substrate on a support pedestal;
moving an upper electrode downwards towards the support pedestal to reduce a gap between the support pedestal and the upper electrode, causing a wafer clamping assembly to move from a resting height and engage an edge of the wafer substrate and create a plasma treatment volume along a front side of the wafer substrate and a backside cooling volume along a back side of the wafer substrate;
etching the wafer substrate by generating a plasma in the plasma treatment volume;
separating the upper electrode from the support pedestal after etching is complete; and
raising the wafer substrate from the support pedestal;
wherein the wafer clamping assembly comprises a plurality of plunger assemblies and a wafer clamp ring, each plunger assembly including a piston shaft with a stop surface at an upper end thereof, a plunger assembly body having a pin at an upper end and a lip at a lower end, a compression spring within the piston shaft that biases the plunger assembly body towards the upper end of the piston shaft, and a cover;
wherein the wafer clamp ring comprises an annular body surrounding a central opening, the annular body including a plurality of outer support holes extending entirely through the annular body; and
wherein each outer support hole has a circular conical or hourglass shape, and the pin of each plunger assembly passes through one outer support hole and engages the cover to secure the wafer clamp ring to the plunger assembly such that the wafer clamp ring and the plunger assembly body move together vertically from the resting height until the edge of the wafer substrate is engaged by the wafer clamp ring, to reduce horizontal movement of the wafer clamp ring.
19 . The process of claim 18 , wherein the wafer clamping assembly is connected to the support pedestal.
20 . The process of claim 18 , further comprising cooling the wafer substrate by flowing a cooling fluid through the backside cooling volume.