Stereolithographic patterning by variable dose light delivery

• US 6,777,170 B1
• Filed: 08/06/2001
• Issued: 08/17/2004
• Est. Priority Date: 08/04/2000
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Kunz, Roderick R., Bloomstein, Theodore M., Palmacci, Stephen T.
• Primary Examiner(s): Huff, Mark F.
• Assistant Examiner(s): Sagar, Kripa
• Application Number:
  US09/922,974
• Time in Patent Office: 1,107 Days
• Field of Search: 430/311, 430/320, 430/321, 430/312, 430/322, 264/401, 250/492.22
• US Class Current: 430/320
• CPC Class Codes: B29C 64/40 Structures for supporting 3D objects during manufacture and intended to be sacrificed after completion thereof
• CPC Class Codes: B29K 2995/0073 smooth
• CPC Class Codes: G03F 7/00 Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor using photoresist structures for special production processes, see the relevant places, e.g. B44C, H01L, e.g. H01L21/00, H05K
• CPC Class Codes: G03F 7/0037 Production of three-dimensional images
• CPC Class Codes: G03F 7/70416 2.5D lithography

Abstract

Methods for the preparation of multilayered resists are described. A first layer of photoresist is deposited onto a substrate. First portions of the first layer are exposed to a first dose of radiant energy. A second layer of photoresist is deposited at atop the first layer and second portions of the second layer are exposed to a second varied dose of radiant energy. The dose is modulated over different portions of a layer to preferentially enhance development within the interior of the structure to reduce total development times.

Claims

1. A method for patterning a multilayer positive tone resist to reduce development time, comprising the steps of

depositing a first layer of resist material onto a substrate;

scanning a beam of radiation to expose a portion of the first layer of resist material;

depositing a second layer of resist material; and

scanning a beam of radiation to expose a portion of the second layer of resist material to radiation; and

varying the dose of radiation delivered to at least one region of the second layer based on the dose delivered to a corresponding region of the first layer,

whereby the development time is reduced.

2. The method of claim 1 wherein the step of varying the dose of radiation further comprises delivering more pulses of radiation to at least one region.

3. The method of claim 1 wherein the step of varying the dose of radiation further comprises delivering radiation for a longer period of time to at least one region.

4. The method of claim 1 wherein the step of varying the dose of radiation further comprises delivering an increased fluence of radiation to at least one region.

5. The method of claim 1 wherein the method further comprises varying the dose of radiation delivered to at least one region of the first resist layer.

6. The method of claim 1 wherein the steps are repeated until a pattern having greater than two layers has been completed.

7. The method of claim 1 wherein the method further comprises treating the layers with a developing solution to remove the exposed portions of resist when resist is a positive resist.

8. The method of claim 1, wherein the method further comprises heating the resist following at least one exposure step.

9. The method of claim 1, wherein the resist material is a novolac resin.

10. The method of claim 1 wherein the step of varying the dose of radiation further comprises delivering an increased fluence of radiation to at least one interior region.

11. The method of claim 1 further comprising:

wherein the second dose is determined as a function of second portion locations that reside atop first portions;

such second portion locations being interior portions;

the dose greater for interior portions than for other second portions.

12. The method according to claim 11, wherein exposing and depositing are repeated a number of times, n, thereby creating an n-layer photoresist preform.

13. The method according to claim 12, wherein modulation of an n-th modulated dose is determined as a function of n th portion locations that reside atop (n−

1)st portions;

the dose greater at n th portion locations that reside atop (n−

1)st portions.

14. A method according to claim 1 further comprising the steps of:

predefining a desired pattern including a vertical profile of exposed and unexposed regions in different layers of a multi-layer resist;

patterning the multilayer resist by repeated depositing layers and exposing portions of each layer to radiation; and

varying a dose of radiation delivered to certain portions of the layers to take into account light penetration between resist layers in order to obtain a uniform predetermined exposure level in each layer.

15. The method of claim 14, wherein the radiation exposure is performed with a laser based vector scanning system.