Selective etching process
AssigneeIowa State University Research Foundation, Inc.
InventorSteve D. Braymen
Life of this patent
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Abstract
A process for selectively etching silicon comprises preparing a solution of etchant which is a non-selective etch for at least silicon and aluminum. The prepared solution is preconditioned by adding atomic silicon to the solution and aging the solution after the addition of silicon for at least 30 minutes. Then, silicon substrates carrying aluminum are immersed in the preconditioned solution to etch the silicon while leaving the aluminum substantially unaffected.
Claims15
A process for selectively etching silicon comprising the steps of:
- preparing a solution of etchant which is a non-selective etch for at least silicon and aluminum;
- preconditioning the prepared solution by adding atomic silicon to the solution and aging the solution after the addition of silicon for at least 30 minutes;
- and
- immersing silicon substrates carrying aluminum in the preconditioned solution to etch the silicon while leaving the aluminum substantially unetched.
A process for fabricating an electronic device on a silicon substrate, the device having a patterned conductor and an etched aperture in the substrate, the process comprising the steps of:
- providing a silicon substrate;
- forming the electronic device on the substrate, the forming step including the step of depositing and patterning at least one aluminum pattern, at least part of the aluminum pattern being exposed to an etchant solution and serving as an etchant stop;
- providing the etchant solution comprising an aqueous solution of hydrazine and quinoxaline, and preconditioning the etchant solution by treating the solution with silicon and aging the treated solution, thereby rendering the preconditioned etchant solution selective to silicon;
- and
- utilizing the etchant solution to etch an aperture in the silicon substrate to remove an area of the substrate without removal of the exposed aluminum pattern.
A process for fabricating a thin film resonator comprising the steps of:
- providing a silicon substrate having first and second surfaces;
- depositing alternating metallization layers and piezoelectric layers on the first surface of the substrate, with the metallization layers being the first and last deposited layers;
- etching an aperture in the second surface of the silicon substrate to remove an area of the substrate from below the resonating portion of the thin film resonator, the step of etching comprising immersing the substrate in a selective etchant solution comprising an aqueous solution of hydrazine and quinoxaline, and preconditioning the etchant solution by inserting a sample of silicon in the solution for at least five minutes and aging the solution after removal of the sample of silicon for at least 30 minutes, thereby rendering the preconditioned etchant solution selective to silicon in the presence of the metallization or piezoelectric material of the resonator;
- and
- terminating the etching step when the etching reaches the first deposited layer.
A process for fabricating a thin film stacked crystal filter, comprising the steps of:
- providing a planar silicon substrate with generally planar opposed first and second surfaces;
- employing DC sputtering to deposit on the first surface of the substrate three aluminum electrode layers and two aluminum nitride piezoelectric layers, the layers being deposited in alternation, with the first, third, and fifth layers being aluminum and the second and fourth layers being aluminum nitride;
- etching a via in the second surface of the silicon substrate to remove an area of the substrate from below the resonating portion of the stacked crystal filter, the step of etching comprising immersing the substrate in a selective etchant which is selective to silicon in the presence of the metallization or piezoelectric material of the resonators;
- and
- terminating the etching when the etching reaches the first deposited layer.
Dependencies are inferred from the claim text.