Method for fabrication of multi-step structures using embedded etch stop layers

A method of forming a four-phase Fresnel lens for use in acoustic printing, the method comprising steps of:

• depositing a first layer of a first material comprised of a plurality of compounds supplied in first proportions, the first material being etchable at a first rate;
• altering the first proportions of the plurality of compounds to obtain a second material comprised of the plurality of compounds supplied in second proportions, the second material being etchable at a second rate less than the first rate;
• depositing a first layer of the second material on the first layer;
• altering the second proportions to obtain the first material;
• depositing a second layer of the first material on the first layer of the second material;
• altering the first proportions to obtain the second material;
• depositing a second layer of the second material on the second layer of the first material;
• altering the second proportions to obtain the first material;
• depositing a third layer of the first material on the second layer of the second material, the first, second and third layers of the first material and the first and second layers of the second material comprising a block;
• masking a first pattern on the third layer of first material leaving areas of the first material exposed;
• etching portions of the first material corresponding to the exposed areas and underlying portions of the second layer of the second material until all of the first material corresponding to the exposed areas is removed;
• masking a second pattern on the third layer of the first material and the second layer of the second material leaving areas of the second layer of the second material exposed;
• etching portions of the second material corresponding to the exposed areas, underlying portions of the second layer of the first material, and underlying portions of the first layer of the second material until all of the second material corresponding to the exposed areas and the underlying first material is removed;
• masking a third pattern on the third layer of the first material, the second layer of the second material, the second layer of the first material and the first layer of the second material leaving areas of the first layer of the second material exposed;
• and,
• etching portions of the second material corresponding to the exposed areas and underlying portions of the first layer of the first material until all of the underlying first material is removed.

A method of forming an n-phase Fresnel lens for use in acoustic printing, the method comprising steps of:

• (a) depositing a layer of a first material comprised of a plurality of compounds supplied in first proportions, the first material being etchable at a first rate;
• (b) altering the first proportions of the plurality of compounds to obtain a second material comprised of the plurality supplied in second proportions, the second material being etchable at a second rate less than the first rate;
• (c) depositing a layer of the second material on the first layer;
• (d) altering the second proportions to obtain the first material;
• (e) depositing another layer of the first material on the layer of the second material;
• (f) repeating steps (b) through (e) (n−3) times to form a block;
• and,
• (g) selectively masking and etching the block to form the n-phase lens.

A method of forming a Fresnel lens for use in acoustic printing, the method comprising steps of:

• depositing a first layer of a first material, the first material being etchable at a first rate;
• forming a first patterned layer of a second material on the first layer, the second material being etchable at a second rate less than the first rate;
• depositing a second layer of the first material over the first patterned layer of the second material;
• forming a second patterned layer of the second material on the second layer of the first material;
• depositing a third layer of the first material on the second patterned layer of the second material, the first, second and third layers of the first material and the first and second patterned layers of the second material comprising a block;
• and,
• selectively masking and etching the block to form the lens.

A method of forming an n-phase microlithographic structure, the method comprising steps of:

• (a) depositing a layer of a first material comprised of a plurality of compounds supplied in first proportions, the first material being etchable at a first rate;
• (b) altering the first proportions of the plurality of compounds to obtain a second material comprised of the plurality supplied in second proportions, the second material being etchable at a second rate less than the first rate;
• (c) depositing a layer of the second material on the first layer;
• (d) altering the second proportions to obtain the first material;
• (e) depositing another layer of the first material on the layer of the second material;
• (f) repeating steps (b) through (e) (n−3) times to form a block;
• and,
• (g) selectively masking and etching the block to form the n-phase structure.

A method of forming a multi-step microlithographic structure, the method comprising steps of:

• depositing a first layer of a first material, the first material being etchable at a first rate;
• forming a first patterned layer of a second material on the first layer, the second material being etchable at a second rate less than the first rate;
• depositing a second layer of the first material over the first patterned layer of the second material;
• forming a second patterned layer of the second material on the second layer of the first material;
• depositing a third layer of the first material on the second patterned layer of the second material, the first, second and third layers of the first material and the first and second patterned layers of the second material comprising a block;
• and,
• selectively masking and etching the block to form the structure.