Poly etch without separate oxide decap
AssigneeMicron Technology, Inc.
InventorKevin Shea
Life of this patent
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Abstract
The use of an ammonium hydroxide spike to a hot tetra methyl ammonium hydroxide (TMAH) solution to form an insitu poly oxide decapping step in a polysilicon (poly) etch process, results in a single step rapid poly etch process having uniform etch initiation and a high etch selectivity, that may be used in manufacturing a variety of electronic devices such as integrated circuits (ICs) and micro electromechanical (MEM) devices. The etching solution is formed by adding 35% ammonium hydroxide solution to a hot 12.5% TMAH solution at about 70° C. at a rate of 1% by volume, every hour. Such an etch solution and method provides a simple, inexpensive, single step self initiating poly etch that has etch stop ratios of over 200 to 1 over underlying insulator layers and TiN layers.
Claims26
A method of fabricating an electronic memory, comprising:
- forming a substrate including an array of active electronic devices;
- forming at least one polysilicon layer on the substrate having a patterned photoresist layer on the at least one polysilicon layer;
- and
- patterning the polysilicon layer in a single step etch solution, comprising exposing the substrate having the patterned photoresist layer on the polysilicon layer for a predetermined time period to a liquid chemical etch solution containing at least tetra methyl ammonium hydroxide and water at a preselected temperature and first concentration, and at least a fixed percentage of an ammonium hydroxide solution.
A method of etching an oxide cap layer on a polysilicon layer, comprising:
- adding a first volume of an ammonium hydroxide solution to a second volume of a tetra methyl ammonium hydroxide solution at a first time period;
- immersing the polysilicon layer in the ammonium hydroxide and tetra methyl ammonium hydroxide solution within one hour of the first time period;
- removing the polysilicon layer from the ammonium hydroxide and tetra methyl ammonium hydroxide solution after a first preselected time period to etch both an oxide cap layer and at least a portion of the polysilicon layer;
- washing the polysilicon layer to remove essentially all of the ammonium hydroxide and tetra methyl ammonium hydroxide solution from the polysilicon layer;
- and
- drying the polysilicon layer.
A method of fabricating an electronic memory, comprising:
- forming electronic devices on at least one surface of a substrate;
- forming a polysilicon layer on the substrate;
- forming a patterned photoresist layer on the polysilicon layer;
- etching completely through the polysilicon layer in regions exposed by the patterned photoresist layer in a single step in a single etch solution;
- wherein the etching includes exposing the polysilicon layer for a predetermined time period to a liquid chemical etch solution including tetra methyl ammonium hydroxide in a volume concentration between 10% to 15% in water at a preselected temperature between 60° C. to 80° C. and first volume concentration;
- and
- including an ammonium hydroxide solution having a fixed volume percentage greater than 1% of the volume of the tetra methyl ammonium hydroxide and water solution.
A method of etching an oxide cap layer on a polysilicon layer, comprising:
- forming a polysilicon layer on a substrate;
- forming a oxide cap layer on the polysilicon layer
- forming a patterned photoresist layer on the oxide cap layer;
- adding a first volume of an ammonium hydroxide solution having a volume concentration between 25% to 40% in water to a second volume of a tetra methyl ammonium hydroxide solution having a volume concentration between 10% to 15% in water at a first time period;
- immersing the substrate with the polysilicon layer in the ammonium hydroxide and tetra methyl ammonium hydroxide solution within a fixed time from the first time period;
- removing the substrate with the polysilicon layer from the ammonium hydroxide and tetra methyl ammonium hydroxide solution after a first preselected time period to etch completely through portions of the oxide cap layer and of the polysilicon layer exposed by the patterned photoresist layer;
- washing the substrate to remove essentially all of the ammonium hydroxide and tetra methyl ammonium hydroxide solution from the substrate;
- and
- drying the substrate.
A method of etching a patterned oxide layer on a polysilicon layer in a single chemical etch solution, comprising:
- forming a polysilicon layer having an oxide layer on a substrate;
- forming a patterned photoresist layer on the oxide layer;
- exposing the patterned photoresist layer on the oxide layer to a liquid chemical etch solution containing at least tetra methyl ammonium hydroxide and water at a desired temperature and first volume concentration;
- and
- removing the substrate from the etch solution.
Dependencies are inferred from the claim text.