System and method for laser patterning an integrated circuit etching mask
View Patent ↗A method is provided for laser patterning an integrated circuit (IC) etching mask. The method provides an IC packaged die with a first region underlying a backside surface of a bulk silicon (Si) layer. An etch-resistant film is formed overlying the backside surface. Alternately, the entire IC die package is conformally coated. A semi-transparent film is formed overlying the etch-resistant film, semi-transparent to light having a first wavelength. In response to irradiating the semi-transparent film with light having a first power density, an IC die first region is located. In response to irradiating the semi-transparent film with a laser light having a second power density, greater than the first power density, an area of etch-resistant film overlying the first region is decomposed. More explicitly, an area of semi-transparent film overlying the first region is ablated, and the etch-resistant film underlying the ablated semi-transparent film is heated.
1. A method for laser patterning an integrated circuit (IC) etching mask, the method comprising:
providing an IC packaged die with a first region underlying a backside surface of a bulk silicon (Si) layer;
forming an etch-resistant film overlying the backside surface;
forming a semi-transparent film overlying the etch-resistant film, semi-transparent to light having a first wavelength;
irradiating the semi-transparent film with light having the first wavelength;
in response to irradiating the semi-transparent film with a first power density, locating the IC die first region; and,
in response to irradiating the semi-transparent film with a laser light having a second power density, greater than the first power density, decomposing an area of etch-resistant film overlying the first region.
2. The method of claim 1 further comprising:
selectively etching the backside surface overlying the IC die first region; and,
exposing the IC die first region.
3. The method of claim 1 wherein irradiating the semi-transparent film with the laser light includes irradiating with light having a first wavelength of greater than 1 micron and less than 2 microns.
4. The method of claim 1 wherein forming the semi-transparent film includes forming a film selected from a group consisting of polyimide and polyethylene terephthalate (boPET) polyester films.
5. The method of claim 1 wherein forming the etch-resistant film includes forming a poly-para-xylylene film.
6. The method of claim 5 wherein decomposing the area of the etch-resistant film includes:
ablating an area of semi-transparent film overlying the first region; and,
heating the etch-resistant film underlying the ablated semi-transparent film.
7. The method of claim 2 wherein forming the etch-resistant film includes isotropically depositing the etch-resistant film overlying the entire IC package.
8. The method of claim 7 wherein selectively etching the backside surface includes:
placing the IC package in an etchant bath; and,
etching the backside surface through the decomposed area of the etchant-resistant film.
9. The method of claim 1 wherein forming the etch-resistant film includes forming a film having an index of refraction about midway between of indices of refraction for air and silicon.
10. The method of claim 1 wherein forming the etch-resistant film includes forming a film having a plano-plano lens shape.
11. The method of claim 1 further comprising:
prior to forming the semi-transparent film, polishing the backside surface; and,
in response to the polishing, thinning the bulk Si layer overlying the IC die first region.
12. The method of claim 1 further comprising:
using an etchant, selectively thinning a backside surface area overlying the IC die first region; and,
sputtering the thinned backside surface area with a focused ion beam (FIB); and,
in response to the FIB, exposing the IC die first region.
13. The method of claim 1 wherein forming the semi-transparent film includes forming a film having an index of refraction about midway between of indices of refraction for air and silicon.
14. The method of claim 2 further comprising:
prior to selectively etching the backside surface overlying the IC die first region, removing the semi-transparent film.
15. A method for exposing a packaged integrated circuit (IC) die region, the method comprising:
providing an IC packaged the with a first region underlying a backside surface of a bulk silicon (Si) layer;
conformally coating the IC die package with an etch-resistant film;
forming a semi-transparent film overlying the etch-resistant film on the backside surface, semi-transparent to light having a first wavelength;
irradiating the semi-transparent film with light having the first wavelength;
in response to irradiating the semi-transparent film with a first power density, locating the IC die first region;
in response to irradiating the semi-transparent film with a laser light having a second power density, greater than the first power density, decomposing an area of etch-resistant film overlying the first region;
selectively etching the backside surface overlying the IC die first region; and,
exposing the IC die first region.
16. A method for selectively etching a packaged integrated circuit (IC) die region, the method comprising:
providing an IC packaged die with a first region underlying a backside surface of a bulk silicon (Si) layer;
forming an etch-resistant film overlying the backside surface;
forming a semi-transparent film overlying the etch-resistant film, semi-transparent to light having a first wavelength;
irradiating the semi-transparent film with light having the first wavelength;
in response to irradiating the semi-transparent film with a first power density, locating the IC die first region;
in response to irradiating the semi-transparent film with a laser light having a second power density, greater than the first power density, decomposing an area of etch-resistant film overlying the first region; and,
selectively etching a backside surface area overlying the IC die first region.