Tapered edge exposure for removal of material from a semiconductor wafer

1. An edge exposure method for a semiconductor wafer, the method comprising:

setting an inner boundary and an outer boundary for gradient illumination;

forming a first layer of material on a substrate having an outer periphery;

forming a first layer of photoresist on the first layer of material;

exposing the first layer of photoresist near the outer periphery with gradient illumination, resulting in a first exposed photoresist layer, wherein exposing the first layer of photoresist is governed by the inner boundary and the outer boundary;

developing the first exposed photoresist layer, resulting in a first developed photoresist layer having a tapered edge in cross section; and

etching the first developed photoresist layer and the first layer of material, resulting in a first etched layer of material having a tapered edge in cross section.

2. A method according to claim 1 , further comprising forming a second layer of material over the first etched layer of material.

3. A method according to claim 1 , further comprising setting a gradient profile for the gradient illumination, wherein exposing the first layer of photoresist is governed by the gradient profile.

4. A method according to claim 2 , further comprising:

forming a second layer of photoresist on the second layer of material;

exposing the second layer of photoresist near the outer periphery with gradient illumination, resulting in a second exposed photoresist layer;

developing the second exposed photoresist layer, resulting in a second developed photoresist layer having a tapered edge in cross section; and

etching the second developed photoresist layer and the second layer of material, resulting in a second etched layer of material having a tapered edge in cross section.

5. A method according to claim 4 , further comprising controlling the steps of exposing the second layer of photoresist, developing the second exposed photoresist layer, and etching the second developed photoresist layer and the second layer of material such that the tapered edge of the second etched layer of material is continuous with the tapered edge of the first etched layer of material.

6. A method according to claim 4 , wherein:

the tapered edge of the first etched layer of material defines a lower perimeter of the first layer of material, an upper perimeter of the first layer of material, and a sloped surface of the first layer of material between the lower perimeter and the upper perimeter of the first layer of material;

the tapered edge of the second etched layer of material defines a lower perimeter of the second layer of material, an upper perimeter of the second layer of material, and a sloped surface of the second layer of material between the lower perimeter and the upper perimeter of the second layer of material; and

the upper perimeter of the first layer of material corresponds to the lower perimeter of the second layer of material.

7. An edge exposure method for a semiconductor wafer having a substrate, a layer of material formed on the substrate, and a layer of photoresist formed on the layer of material, the method comprising:

obtaining an inner radius and an outer radius for an illumination gradient;

obtaining a gradient profile for the illumination gradient;

exposing a peripheral section of the layer of photoresist with radiation controlled by the illumination gradient; and

creating, in response to the exposing step, an exposed photoresist layer having non-uniform characteristics between the inner radius and the outer radius, the non-uniform characteristics being controlled by the illumination gradient.

8. A method according to claim 7 , further comprising developing the exposed photoresist layer, resulting in a developed photoresist layer having a tapered edge in cross section.

9. A method according to claim 7 , wherein:

the layer of photoresist is formed from a positive photoresist material; and

the gradient profile results in relatively low radiation energy near the inner radius during the exposing step, and relatively high radiation energy near the outer radius during the exposing step.

10. A method according to claim 8 , further comprising etching the developed photoresist layer and the layer of material, resulting in an etched layer of material having a tapered edge in cross section.

11. A method according to claim 10 , further comprising forming an additional layer of material over the etched layer of material.

12. A method according to claim 10 , wherein the inner radius, the outer radius, and the gradient profile influence a slope characteristic of the tapered edge of the etched layer of material.

13. An edge exposure method for a semiconductor wafer having a substrate, a layer of material formed on the substrate, and a layer of photoresist formed on the layer of material, the method comprising:

exposing a peripheral section of the layer of photoresist with radiation having an intensity profile that varies between an inner radial dimension of the semiconductor wafer and an outer radial dimension of the semiconductor wafer, resulting in an exposed photoresist layer;

developing the exposed photoresist layer, resulting in a developed photoresist layer having a tapered peripheral photoresist edge; and

etching the developed photoresist layer and the layer of material, resulting in an etched layer of material having a tapered peripheral material edge.

14. A method according to claim 13 , further comprising forming an additional layer of material over the etched layer of material, wherein the additional layer of material has a contour that follows the tapered peripheral material edge.

15. A method according to claim 13 , further comprising selecting, prior to the exposing step, the inner radial dimension, the outer radial dimension, and the intensity profile.

16. A method according to claim 13 , wherein:

the layer of photoresist is formed from a positive photoresist material; and

the intensity profile results in relatively low radiation energy near the inner radial dimension during the exposing step, and relatively high radiation energy near the outer radial dimension during the exposing step.