1. A method of forming a contact hole, comprising:
anisotropically etching a layer on a substrate to form a dummy contact hole exposing the substrate; and
isotropically etching a sidewall of the dummy contact hole to form a contact hole, the isotropically etching of the sidewall including alternatively and repeatedly supplying an etching solution including a fluoride salt in a low-polarity organic solvent and deionized water within the dummy contact hole.
2. The method of claim 1, wherein the isotropically etching further includes drying the dummy contact hole after the deionized water is supplied within the dummy contact hole.
3. The method of claim 1, wherein the isotropically etching alternatively and repeatedly supplies each of the etching solution and the deionized water for a time duration with a range of about 1 through 30 seconds.
4. The method of claim 1, wherein the isotropically etching further includes a spinning scheme in which the etching solution and the deionized water are dropped onto the substrate, which is rotating at a speed.
5. The method of claim 4, wherein the substrate is rotated at a speed of 500 rotations per minute.
6. The method of claim 1, wherein the fluoride salt includes at least one of NH4HF2, NaF, and KF.
7. The method of claim 6, wherein the fluoride salt is molten and is about 0.001 weight percent through about 2 weight percent in the low-polarity organic solvent.
8. A method of manufacturing a semiconductor memory device, the method comprising:
forming a transistor on a substrate;
forming a first interlayer insulation film having a first contact hole exposing sourcedrain areas of the transistor;
forming a pad electrode within the first contact hole;
forming a second interlayer insulation film having a second contact hole exposing the pad electrode;
forming a direct contact electrode within the second contact hole;
forming a bit line on the direct contact electrode;
forming a third interlayer insulation film at least partially surrounding the bit line;
forming a contact hole in the second interlayer insulation film and the third interlayer insulation film over a drain area of the transistor exposing the pad electrode, using the method of claim 1;
forming a storage node contact electrode within the third contact hole; and
forming a capacitor on the storage node contact electrode.
9. The method of claim 8, wherein the isotropically etching includes drying the dummy contact hole after the deionized water is supplied within the dummy contact hole.
10. The method of claim 8, wherein the isotropically etching alternatively and repeatedly supplies each of the etching solution and deionized water for a time duration within a range of about 1 through 30 seconds.
11. The method of claim 8, wherein the isotropically etching further includes a spinning scheme in which the etching solution and the deionized water are dropped onto the substrate, which is rotating at a speed.
12. The method of claim 11, wherein the substrate is rotated at a speed of 500 rotations per minute.
13. The method of claim 8, wherein the fluoride salt includes at least one of NH4HF2, NaF, and KF.
14. The method of claim 13, wherein the fluoride salt is molten and is about 0.001 weight percent through about 2 weight percent in the low-polarity organic solvent.
15. The method of claim 1, wherein the layer is silicon oxide layer.
16. The method of claim 2, wherein drying the dummy contact hole includes one of spinning the substrate and supplying one of air and N2 gas to the substrate.
17. The method of claim 16, wherein the substrate is spun at 2000 rotations per minute.
18. The method of claim 9, wherein drying the dummy contact hole includes one of spinning the substrate and supplying one of air and N2 gas to the substrate.
19. The method of claim 18, wherein the substrate is spun at 2000 rotations per minute.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A riding lawn care vehicle comprising:
a frame to which wheels of the riding lawn care vehicle are attachable; and
a steering assembly comprising a steering apparatus operably coupled to at least one of the wheels of the riding lawn care vehicle to provide steering inputs to the at least one of the wheels based on a position of the steering apparatus,
wherein the steering assembly further comprises:
a steering column extending from the steering apparatus to rotate responsive to movement of the steering apparatus;
a pinion assembly disposed along the steering column and comprising at least two pinions of different sizes; and
a rack assembly operably coupled to the frame and the at least one wheel of the riding lawn care vehicle to translate steering inputs from the steering apparatus to the at least one wheel via the pinion assembly, the rack assembly comprising at least two rack portions of different sizes,
wherein the pinion assembly comprises:
a first circular pinion having a first diameter and disposed at a first position along the steering column; and
a second circular pinion having a second diameter and disposed at a second position along the steering column,
wherein the rack assembly comprises:
a first partial rack portion defining a first contact area over which contact with the first pinion is enabled; and
a second partial rack portion defining a second contact area over which contact with the second pinion is enabled,
wherein the first partial rack portion and the second partial rack portion are separate members of the rack assembly, and
wherein the first and second partial rack portions share a common pivot point and have gear teeth at the first and second contact areas, respectively, the first partial rack portion extending from the common pivot point by a third diameter over an entirety of the first contact area and the second partial rack portion extending from the common pivot point by a fourth diameter over an entirety of the second contact area, the first and second partial rack portions each comprising gear teeth disposed at an external periphery thereof to engage gear teeth of the first and second pinions, respectively.
2. The riding lawn care vehicle of claim 1, wherein a difference between the third and fourth diameters is equal to a difference between the first and second diameters.
3. The riding lawn care vehicle of claim 1, wherein only one of the first pinion or the second pinion contacts a corresponding one of the first contact area or the second contact area over an entirety of a range of motion of the steering apparatus.
4. The riding lawn care vehicle of claim 1, wherein the first pinion has a larger diameter than the second pinion and the first pinion is disposed at a distal end of the steering column.
5. The riding lawn care vehicle of claim 1, wherein the first pinion has a smaller diameter than the second pinion and the first pinion is disposed at a distal end of the steering column.
6. The riding lawn care vehicle of claim 1, wherein the first contact area is disposed to correspond to a portion of a range of motion of the steering apparatus proximate to a neutral position of the steering apparatus, and the second contact area is disposed to correspond to portions of the range of motion of the steering apparatus proximate to maximum deflection from the neutral position.
7. The riding lawn care vehicle of claim 1, wherein the second contact area comprises two portions, and wherein respective ones of the two portions extend from opposite ends of the first contact area to define a discontinuous second contact area with the first contact area interposed therebetween.
8. The riding lawn care vehicle of claim 1, wherein the pinion assembly and the rack assembly combine to provide at least two different gear ratios over respective different portions of a full range of motion of the steering apparatus.
9. The riding lawn care vehicle of claim 1, wherein the steering apparatus is a steering wheel or handlebars.
10. A steering assembly for steering control of a riding lawn care vehicle, the steering assembly comprising:
a steering apparatus operably coupled to at least one wheel of the riding lawn care vehicle to provide steering inputs to the at least one wheel based on a position of the steering apparatus;
a steering column extending from the steering apparatus to rotate responsive to movement of the steering apparatus;
a pinion assembly disposed along the steering column and comprising at least two pinions of different sizes; and
a rack assembly operably coupled to a frame to which wheels of the riding lawn care vehicle are attachable, the rack assembly being further operably coupled to the at least one wheel of the riding lawn care vehicle to translate steering inputs from the steering apparatus to the at least one wheel via the pinion assembly, the rack assembly comprising at least two rack portions of different sizes,
wherein the pinion assembly comprises:
a first circular pinion having a first diameter and disposed at a first position along the steering column; and
a second circular pinion having a second diameter and disposed at a second position along the steering column,
wherein the rack assembly comprises:
a first partial rack portion defining a first contact area over which contact with the first pinion is enabled; and
a second partial rack portion defining a second contact area over which contact with the second pinion is enabled,
wherein the first partial rack portion and the second partial rack portion are separate members of the rack assembly, and
wherein the first and second partial rack portions share a common pivot point and have gear teeth at the first and second contact areas, respectively, the first partial rack portion extending from the common pivot point by a third diameter over an entirety of the first contact area and the second partial rack portion extending from the common pivot point by a fourth diameter over an entirety of the second contact area, the first and second partial rack portions each comprising gear teeth disposed at an external periphery thereof to engage gear teeth of the first and second pinions, respectively.
11. The steering assembly of claim 10, wherein a difference between the third and fourth diameters is equal to a difference between the first and second diameters.
12. The steering assembly of claim 10, wherein only one of the first pinion or the second pinion contacts a corresponding one of the first contact area or the second contact area over an entirety of a range of motion of the steering apparatus.
13. The steering assembly of claim 10, wherein the first pinion has a larger diameter than the second pinion and the first pinion is disposed proximate a distal end of the steering column.
14. The steering assembly of claim 10, wherein the first pinion has a smaller diameter than the second pinion and the first pinion is disposed at a distal end of the steering column.
15. The steering assembly of claim 10, wherein the first contact area is disposed to correspond to a portion of a range of motion of the steering apparatus proximate to a neutral position of the steering apparatus, and the second contact area is disposed to correspond to portions of the range of motion of the steering apparatus proximate to maximum deflection from the neutral position.
16. The steering assembly of claim 10, wherein the second contact area comprises two portions, and wherein respective ones of the two portions extend from opposite ends of the first contact area to define a discontinuous second contact area with the first contact area interposed therebetween.
17. The steering assembly of claim 10, wherein the pinion assembly and the rack assembly combine to provide at least two different gear ratios over respective different portions of a full range of motion of the steering apparatus.
18. The steering assembly of claim 10, wherein the first partial rack portion comprises a first partial disc shaped member, the second partial rack portion comprises a second partial disc shaped member, and the first partial disc shaped member and the second partial disc shaped member are separate members.
19. A riding lawn care vehicle comprising:
a frame to which wheels of the riding lawn care vehicle are attachable; and
a steering assembly comprising a steering apparatus operably coupled to at least one of the wheels of the riding lawn care vehicle to provide steering inputs to the at least one of the wheels based on a position of the steering apparatus,
wherein the steering assembly further comprises:
a steering column extending from the steering apparatus to rotate responsive to movement of the steering apparatus;
a pinion assembly disposed along the steering column and comprising at least two pinions of different sizes; and
a rack assembly operably coupled to the frame and the at least one wheel of the riding lawn care vehicle to translate steering inputs from the steering apparatus to the at least one wheel via the pinion assembly, the rack assembly comprising at least two rack portions of different sizes,
wherein the pinion assembly comprises:
a first circular pinion having a first diameter and disposed at a first position along the steering column; and
a second circular pinion having a second diameter and disposed at a second position along the steering column,
wherein the rack assembly comprises:
a first partial rack portion defining a first contact area over which contact with the first pinion is enabled; and
a second partial rack portion defining a second contact area over which contact with the second pinion is enabled,
wherein the first partial rack portion and the second partial rack portion are separate members of the rack assembly, and
wherein the first partial rack portion comprises a first partial disc shaped member, the second partial rack portion comprises a second partial disc shaped member, and the first partial disc shaped member and the second partial disc shaped member are separate members.
20. The riding lawn care vehicle of claim 19, wherein the first and second partial rack portions share a common pivot point and have gear teeth at the first and second contact areas, respectively, the first partial rack portion extending from the common pivot point by a third diameter over an entirety of the first contact area and the second partial rack portion extending from the common pivot point by a fourth diameter over an entirety of the second contact area, the first and second partial rack portions each comprising gear teeth disposed at an external periphery thereof to engage gear teeth of the first and second pinions, respectively, and
wherein a difference between the third and fourth diameters is equal to a difference between the first and second diameters.
21. The riding lawn care vehicle of claim 19, wherein only one of the first pinion or the second pinion contacts a corresponding one of the first contact area or the second contact area over an entirety of a range of motion of the steering apparatus.
22. The riding lawn care vehicle of claim 19, wherein the first pinion has a larger diameter than the second pinion and the first pinion is disposed at a distal end of the steering column.
23. The riding lawn care vehicle of claim 19, wherein the first pinion has a smaller diameter than the second pinion and the first pinion is disposed at a distal end of the steering column.
24. The riding lawn care vehicle of claim 19, wherein the first contact area is disposed to correspond to a portion of a range of motion of the steering apparatus proximate to a neutral position of the steering apparatus, and the second contact area is disposed to correspond to portions of the range of motion of the steering apparatus proximate to maximum deflection from the neutral position.
25. The riding lawn care vehicle of claim 19, wherein the second contact area comprises two portions, and wherein respective ones of the two portions extend from opposite ends of the first contact area to define a discontinuous second contact area with the first contact area interposed therebetween.
26. The riding lawn care vehicle of claim 19, wherein the pinion assembly and the rack assembly combine to provide at least two different gear ratios over respective different portions of a full range of motion of the steering apparatus.