Grid structures of ion beam etching (IBE) systems

An ion beam etching (IBE) system, comprising:

• a plasma chamber configured to provide plasma;
• a screen grid comprising a screen grid element in contact with the plasma chamber;
• an extraction grid comprising an extraction grid element disposed adjacent to and separated from the screen grid element;
• an accelerator grid comprising an accelerator grid element disposed adjacent to and separated from the extraction grid element;
• a decelerator grid comprising a decelerator grid element disposed adjacent to and separated from the accelerator grid element;
• a hole that extends through the screen grid, the extraction grid, the accelerator grid, and the decelerator grid;
• and
• a deflector system comprising at least a first deflector plate and a second deflector plate separated by a gap, wherein the first deflector plate and the second deflector plate are disposed around the hole, wherein the first deflector plate is configured to receive a first deflector voltage, and the second deflector plate is configured to receive a second deflector voltage, and wherein a trajectory of an ion beam through the hole formed by ions extracted from the plasma within the plasma chamber depends on a voltage difference between the first deflector voltage and the second deflector voltage.

A method, comprising:

• placing a wafer onto a rotating fixture within a process chamber of an etching system, wherein the wafer has a tilted angle 0 and a rotated angle a;
• supplying a screen grid voltage to a screen grid element of a screen grid to extract ions from plasma within a plasma chamber of the process chamber to form an ion beam;
• supplying an extraction grid voltage to an extraction grid element of an extraction grid, wherein an ion current density of the ion beam depends on a voltage difference between the screen grid voltage and the extraction grid voltage;
• supplying an accelerator grid voltage to an accelerator grid element of an accelerator grid, wherein an ion beam energy for the ion beam depends on a voltage difference between the extraction grid voltage and the accelerator grid voltage;
• supplying a decelerator grid voltage to a decelerator grid element of a decelerator grid, wherein the screen grid element, the extraction grid element, the accelerator grid element, and the decelerator grid element form a hole that extends through the screen grid, the extraction grid, the accelerator grid, and the decelerator grid, and the ion beam goes through the hole;
• and
• performing directional etching of a dielectric layer on the wafer by the ion beam through the hole to reach the wafer wherein performing the directional etching comprises forming, in the dielectric layer, an opening with a first length along a first direction and a second length along a second direction perpendicular to the first direction, and wherein the first and second directions are along a horizontal plane of the dielectric layer.