Method of fabricating a suspension microstructure

• US 7,829,364 B2
• Filed: 10/02/2008
• Issued: 11/09/2010
• Est. Priority Date: 12/14/2007
• Status: Expired due to Fees

• Current Assignee: Memsmart Semiconductor Corporation
• Original Assignee: Memsmart Semiconductor Corporation
• Inventors: Tan, Siew-Seong
• Primary Examiner(s): Chambliss, Alonzo
• Application Number:
  US12/243,972
• Publication Number:
  US 20090243084A1
• Time in Patent Office: 768 Days
• Field of Search: None
• US Class Current: 438/51
• CPC Class Codes: B81C 1/00182 Arrangements of deformable or non-deformable structures, e.g. membrane and cavity for use in a transducer
• CPC Class Codes: B81C 1/00801 Avoid alteration of functional structures by etching, e.g. using a passivation layer or an etch stop layer B81C1/00595, B81C1/00468 take precedence

Abstract

A suspension microstructure and its fabrication method, in which the method comprises the steps of: forming at least one insulation layer with inner micro-electro-mechanical structures on an upper surface of a silicon substrate, the micro-electro-mechanical structure includes at least one microstructure and a plurality of metal circuits that are independent from each other, the micro-electro-mechanical structures have an exposed portion on the surface of the insulation layer, and the exposed portion is provided with through holes or stacked metal-via layers correspondingly to the predetermined etching spaces of the micro-electro-mechanical structures, the above predetermined etching spaces and the stacked metal-via layers only penetrate the insulation layer; forming a photoresist with an opening on the upper surface of the exposed portion, and the opening of the photoresist is located outside all the through holes or the stacked metal-via layers; subsequently, conducting etching to realize the suspension of the microstructures.

Claims

1. A method for fabricating a suspension microstructure comprising the steps of:

forming an insulation layer including inner micro-electro-mechanical structures on an upper surface of a silicon substrate, the micro-electro-mechanical structure including at least one microstructure and a plurality of metal circuits that are independent from each other, the micro-electro-mechanical structures having an exposed portion on a surface of the insulation layer, the exposed portion being provided with through holes correspondingly to predetermined etching spaces of the micro-electro-mechanical structures, which only penetrates the insulation layer without contacting the micro-electro-mechanical structures;

next, forming a photoresist with an opening on the insulation layer, the opening of the photoresist being located outside the through holes of the exposed portion;

subsequently, conducting an etching from the through holes of the exposed portion downwards to form etching spaces which only penetrate the insulation layer, the microstructures of the micro-electro-mechanical structures being clad in the insulation layer; and

realizing suspension of the microstructures by etching.

2. The method for fabricating a suspension microstructure as claimed in claim 1 further comprising the steps of:

forming a barrier layer with an opening on a lower surface of the silicon substrate, the opening of the barrier layer being located correspondingly to the microstructures of the micro-electro-mechanical structures;

subsequently, conducting a deep reactive ion etching from the opening of the barrier layer and quickly etching a space in the silicon substrate; and

removing the barrier layer.

3. The method for fabricating a suspension microstructure as claimed in claim 1 further comprising the step of:

removing a part of the exposed portion within the opening of the photoresist by etching.

4. The method for fabricating a suspension microstructure as claimed in claim 3, wherein the step of realizing suspension of the microstructures by etching further comprises:

conducting a deep reactive ion etching from the etching spaces to the space in the silicon substrate to form through spaces, the respective spaces connect with each other to realize the suspension of the microstructures of the micro-electro-mechanical structures.

5. The method for fabricating a suspension microstructure as claimed in claim 1 further comprising removing the photoresist in the step of realizing suspension of the microstructures by etching.

6. A method for fabricating a suspension microstructure comprising the steps of:

forming an insulation layer including inner micro-electro-mechanical structures on an upper surface of a silicon substrate, the micro-electro-mechanical structure including at least one independent microstructure, the micro-electro-mechanical structures having an exposed portion on a surface of the insulation layer, under the exposed portion being provided a plurality of mutually-conducted stacked metal-via layers correspondingly to predetermined etching spaces, the stacked metal-via layers reaching the upper surface of the silicon substrate and only penetrating the insulation layer without contacting the micro-electro-mechanical structures;

next, forming a photoresist with an opening on the insulation layer, the opening of the photoresist being located outside the exposed portion;

subsequently, removing the exposed portion and all the stacked metal-via layers by etching to form etching spaces only penetrating the insulation layer; and

conducting an etching from the etching spaces downwards to realize suspension of the microstructures.

7. The method for fabricating a suspension microstructure as claimed in claim 6 further comprising the steps of:

forming a barrier layer with an opening on a lower surface of the silicon substrate, the opening of the barrier layer being located correspondingly to the microstructures of the micro-electro-mechanical structures;

subsequently, conducting a deep reactive ion etching from the opening of the barrier layer and quickly etching a space in the silicon substrate; and

removing the barrier layer.

8. The method for fabricating a suspension microstructure as claimed in claim 6 further comprising removing the photoresist in the step of conducting the etching downwards to realize suspension of the microstructures.

9. The method for fabricating a suspension microstructure as claimed in claim 6 further comprising in the step of conducting the etching downwards to realize suspension of the microstructures:

conducting a deep reactive ion etching from the etching spaces to the space in the silicon substrate to form through spaces, the respective spaces connect with each other to realize the suspension of the microstructures of the micro-electro-mechanical structures.

10. A method for fabricating a suspension microstructure comprising the steps of:

forming an insulation layer including inner micro-electro-mechanical structures on an upper surface of a silicon substrate, the micro-electro-mechanical structure including at least one microstructure and a plurality of metal circuits that are independent from each other, the micro-electro-mechanical structures having an exposed portion and an embedded portion, the exposed portion being provided with through holes correspondingly to predetermined etching spaces of the micro-electro-mechanical structures, the embedded portion being lower than the exposed portion and located in a predetermined etching space of the through holes, which only penetrates the insulation layer without contacting the micro-electro-mechanical structures;

next, forming a photoresist with an opening on the insulation layer, the opening of the photoresist being located outside all the through holes of the exposed portion;

subsequently, conducting an etching from the through holes of the exposed portion downwards to etch etching spaces in the insulation layer, the embedded portion is lower than the exposed portion and located in the predetermined etching space of the through holes, so that a sunken space is etched above the embedded portion, the etching spaces and the sunken space only penetrate the insulation layer without contacting the micro-electro-mechanical structures;

removing a part of the exposed portion within the opening of the photoresist and the exposed embedded portion; and

etching a predetermined space toward the silicon substrate to realize suspension of the microstructures of micro-electro-mechanical structures.

11. The method for fabricating a suspension microstructure as claimed in claim 10 further comprising the steps of:

forming a space in the silicon substrate;

next, conducting a dry reactive ion etching (RIE) from the through holes of the exposed portion downwards;

removing the exposed portion and the embedded portion by etching; and

conducting a deep reactive ion etching from the etching space toward the space in the silicon substrate.

12. The method for fabricating a suspension microstructure as claimed in claim 10 further comprising the steps of:

forming a barrier layer with an opening on a lower surface of the silicon substrate, the opening of the barrier layer being located correspondingly to the microstructures of the micro-electro-mechanical structures;

subsequently, conducting a deep reactive ion etching from the opening of the barrier layer and quickly etching the space in the silicon substrate; and

removing the barrier layer.

13. The method for fabricating a suspension microstructure as claimed in claim 10 further comprising the step of:

covering a protective cap outside the opening of the photoresist.