Poly etch without separate oxide decap
AssigneeMicron Technology, Inc.
InventorKevin Shea
Life of this patent
Estimating the term…
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.
Claims27
A method of etching a polysilicon layer on an integrated circuit substrate, 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;
- immersing the substrate in the ammonium hydroxide and tetra methyl ammonium hydroxide solution within one hour of the first time;
- removing the substrate after expiration of a preselected time period;
- removing essentially all of the ammonium hydroxide and tetra methyl ammonium hydroxide solution from the substrate;
- and
- drying the substrate.
A method of etching a polysilicon layer on an integrated circuit substrate in a single chemical etch solution, comprising:
- exposing a substrate having a patterned photo-resist layer disposed on a polysilicon layer to a liquid chemical etch solution containing at least tetra methyl ammonium hydroxide and water at a preselected temperature and first volume concentration;
- removing the substrate from the etch solution after a preselected time period;
- removing the liquid chemical etch solution from the polysilicon layer;
- and
- removing the patterned photo-resist layer from the polysilicon layer.
A method of etching a polysilicon layer on an integrated circuit substrate in a single chemical etch solution, comprising:
- adding a first volume of an ammonium hydroxide solution having a volume concentration approximately 35% in water, to a second volume of a tetra methyl ammonium hydroxide solution having a volume concentration between 7.5% and 15% in water;
- immersing at least one surface of a polysilicon layer having a patterned photo-resist mask in the ammonium hydroxide and tetra methyl ammonium hydroxide solution, the solution having a preselected temperature in a range from 55° C. to 85° C.;
- and
- removing the polysilicon layer after a preselected time period.
Dependencies are inferred from the claim text.