Method for pattern reduction using a staircase spacer

A method of patterning a substrate, the method comprising:

• forming a first stack of layers on the substrate, the first stack including a first layer deposited over the substrate, a second layer deposited over the first layer, a third layer deposited over the second layer and a fourth layer deposited over the third layer, each of the layers of the first stack having an initial width that is equal;
• forming a first relief pattern on the stack of layers, by:
• executing a first trimming etch process on the fourth layer, the first trimming etch process being an isotropic etch that etches material of the fourth layer without etching material of the second layer and without etching material of the third layer, the first trimming first etch process being executed until the initial width of the fourth layer is reduced to a first line of a first desired line width;
• executing a second trimming etch process on the third layer, the second trimming etch process being an isotropic etch that etches material of the third layer without etching material of the fourth layer and without etching material of the second layer, the second trimming etch process being executed until the initial width of the fourth layer is reduced to a second line having a line width which is three times the first desired line width;
• executing a third trimming etch process on the second layer, the third trimming etch process being an isotropic etch that etches material of the second layer without etching material of the first layer and the third layer, the third trimming etch process being executed until the initial width of the second layer is reduced to a third line having a line width which is five times the first desired line width;
• depositing a first fill material on the fourth, third and second layers;
• etching a portion of the first fill material to expose a top of the first line;
• etching the first line through the fourth, third and second layers down to the substrate, thus forming a first central bore;
• removing, by etching, the third layer and the fourth layer;
• depositing a second fill material in the first central bore;
• removing a portion of the first fill material to expose a part of the second layer;
• selectively etching through the part of the second layer not covered by the second fill material and through portions of the first layer not covered by the first fill material;
• removing the first fill material and the second fill material;
• and
• removing, by etching, the second layer, resulting in the first layer having a second relief pattern of four lines with line-to-space pitch ratio of 1:1, wherein each line and each space has a width of one fifth of the first desired line width.

A method of patterning a substrate, the method comprising:

• forming a first stack of layers on a substrate, the first stack including a memorization layer deposited over the substrate, a first nitride layer deposited over the memorization layer, a first amorphous carbon layer deposited over the first nitride layer and a first oxide layer deposited over the first amorphous carbon layer;
• forming a second stack of layers over the first stack of layers, the second stack including a second nitride layer deposited over the first oxide layer, a second amorphous carbon layer deposited on the second nitride layer, a second oxide layer deposited over the second amorphous carbon layer, an organic planarization layer deposited over the second oxide layer and a silicon anti-reflective coating deposited over the organic planarization layer, wherein each of the layers of the first stack and second stack have equal initial width;
• depositing a photoresist relief pattern of lines over the silicon anti-reflective coating;
• transferring, by selective anisotropic etching, the photoresist relief pattern of lines into the silicon anti-reflective coating, the organic planarization layer, the second oxide layer, and the second amorphous carbon layer, then removing the photoresist, the anti-reflective coating and the organic planarization layer;
• executing a first trimming etch process on the second oxide layer, the first trimming etch process being an isotropic etch that etches material of the second oxide layer without etching material of the second amorphous carbon layer and without etching material of the second nitride layer, the first trimming etch process being executed until the initial width of each line of the second oxide layer is reduced to one seventh of a line width of each line of the photoresist relief pattern;
• executing a second trimming etch process on the second amorphous carbon layer, the second trimming etch process being an isotropic etch that etches material of the amorphous carbon layer without etching material of the second oxide layer and without etching material of the second nitride layer, the second trimming etch process being executed until the initial width of each line of the amorphous carbon layer is reduced to three eighths of the line width of each line the photoresist relief pattern;
• depositing a first fill material on the second oxide layer, the amorphous carbon layer and the second nitride layer;
• etching a portion of the first fill material to expose a top of the lines of the second oxide layer;
• etching the lines of the second oxide layer down through the second amorphous carbon layer, then removing the first fill material, the lines of the second amorphous carbon layer forming a second relief pattern;
• transferring, by selective anisotropic etching, the second relief pattern into the second nitride layer, the first oxide layer, and the first amorphous carbon layer, then removing the second amorphous carbon layer and the second nitride layer;
• executing a fourth trimming etch process on the first oxide layer, the fourth trimming etch process being an isotropic etch that etches material of the first oxide layer without etching material of the first amorphous carbon layer or material of the first nitride layer, the fourth trimming etch process being executed until the width of the lines of the first oxide is reduced to one third of the line width of the second relief pattern;
• depositing a second fill material on the first oxide layer, the first amorphous carbon layer and the first nitride layer;
• etching a portion of the second fill material to expose a top of the lines of the first oxide layer;
• etching the lines of the first oxide layer down through the first amorphous carbon layer, then removing the second fill material, thus forming a third relief pattern;
• transferring, by selective anisotropic etching, the third relief pattern into the first nitride layer, then removing the first amorphous carbon layer, thus forming a fourth relief pattern;
• transferring, by selective anisotropic etching, the fourth relief pattern into the memorization layer, then removing the first nitride layer, resulting in the memorization layer having a pattern of four lines with line-to-space pitch ratio of 1:1, wherein each line and each space has a width of one eighth of the initial line width.