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US3844858A Expired / Lapsed US ⏱️ 0.0 years remaining

Process for controlling the thickness of a thin layer of semiconductor material and semiconductor substrate

Assignee: Texas Instruments Inc
•
Filing: 1968-12-31
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Granted: 1974-10-29
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Expires: 1988-12-31
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Abstract

Abstract Process permitting control of the thickness of the thin layer of semiconductor material by first forming a slot of a predetermined depth in one surface so that the slot will be exposed during removal of material from the opposite surface should the thickness of the thin layer of semiconductor material become less than the depth of the slot, and a (110) oriented semiconductor substrate having a slot formed therein which is bounded by converging (111) planes. In a preferred embodiment the thickness control is realized by first preparing the slice of semiconductor material so that at least one of its surfaces has a (100) orientation. There is then formed on the surface of the slice having the (100) orientation an etch-resistant mask having a window opened therethrough such that the window defines on the surface of the slice two lines which are parallel to each other and to lines defined by the intersection of (111) planes with the surface of the slice. Semiconductor material is then removed through the windows by etching to produce a slot having a depth greater than thickness to which the single crystal semiconductor material is to be subsequently processed. A vapor deposited support layer may then be produced on the surface of the slice to which the mask was attached during which process it will fill the slot etched in the semiconductor material through the window. Upon removal of the semiconductor material from the opposite surface of the slice, which may be affected by lapping and polishing, the support layer formed in the slot will become exposed, thus indicating that the thickness of the semiconductor material remaining is equal to or less than the depth of the slot etched in the first surface of the semiconductor material. At the time the first depth control slot is formed in the first surface of the semiconductor slice, there may also be performed a plurality of similar slots, the depth of which are controlled by controlling the width of the window in the etch resistant mask. Thus, as semiconductor material is removed from the slice, the thickness of the material remaining after the removal process can be determined by the number of slots exposed during lapping and polishing.

Inventors

  • 👤 K Bean

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-10-25 05:08
CPC Classifications
H; H10; H10P; H10P95/00; H10W; H10W10/00; H10W10/01; H10W10/011; H10W10/019; H10W10/10; Y; Y10; Y10S; Y10S148/00; Y10S148/049; Y10S148/051; Y10S148/085; Y10S148/102; Y10S148/115; Y10S438/00; Y10S438/977

Claims Analysis

Total Claims: 17
Claim 1
Independent Claim 92 words
A METHOD FOR THINING A SEMICONDUCTOR SLICE TO A PRECISELY CONTROLLED THICKNESS COMPRISING THE STEPS OF: FORMING A PLURALITY OF SLOTS IN ONE SURFACE OF SAID SLICE, SAID SLOTS HAVING A PRECISELY KNOWN DEPTH EQUAL TO OR GREATER THAN THE DESIRED THICKNESS OF SAID SLICE; REMOVING MATERIAL FROM THE OPPOSITE SURFACE OF SAID SLICE UNTIL AT LEAST A PORTION OF AT LEAST ONE OF SAID SLOTS IS EXPOSED; AND INTERRUPTING SAID REMOVAL OF SEMICONDUCTOR MATERIAL BASED UPON THE EXPOSURE OF SAID SLOTS AS AN INDICATION OF THE THICKNESS OF THE SEMICONDUCTOR SLICE.
Claim 2
Independent Claim 92 words
A METHOD FOR THINING A SEMICONDUCTOR SLICE TO A PRECISELY CONTROLLED THICKNESS COMPRISING THE STEPS OF: FORMING A PLURALITY OF SLOTS IN ONE SURFACE OF SAID SLICE, SAID SLOTS HAVING A PRECISELY KNOWN DEPTH EQUAL TO OR GREATER THAN THE DESIRED THICKNESS OF SAID SLICE; REMOVING MATERIAL FROM THE OPPOSITE SURFACE OF SAID SLICE UNTIL AT LEAST A PORTION OF AT LEAST ONE OF SAID SLOTS IS EXPOSED; AND INTERRUPTING SAID REMOVAL OF SEMICONDUCTOR MATERIAL BASED UPON THE EXPOSURE OF SAID SLOTS AS AN INDICATION OF THE THICKNESS OF THE SEMICONDUCTOR SLICE.
Claim 3
Dependent Claim 16 words
A method as defined in claim 1 wherein said slots are formed by orientation dependent etching.
Claim 4
Dependent Claim 16 words
A method as defined by claim 1 wherein the respective depths of said slots are unequal.
Claim 5
Independent Claim 137 words
A method for lapping a semiconductor slice having (100) orientation to provide a precisely controlled thickness, comprising the steps of: forming on a surface of said slice an etch-resistant mask having a plurality of windows defining on said surface at least two lines which are parallel to each other and parallel to the intersection of (111) planes with said surface, said windows having unequal widths; subjecting said masked surface to an orientation dependent etch whereby a plurality of slots of precisely determined depths are formed in said slice, said depths being determined by the respective widths of said windows; lapping the opposite surface of said semiconductor slice until one or more of said slots is exposed; and terminating said lapping to provide a precisely determined slice thickness as indicated by the exposure of said slot or slots.
Claim 6
Independent Claim 137 words
A method for lapping a semiconductor slice having (100) orientation to provide a precisely controlled thickness, comprising the steps of: forming on a surface of said slice an etch-resistant mask having a plurality of windows defining on said surface at least two lines which are parallel to each other and parallel to the intersection of (111) planes with said surface, said windows having unequal widths; subjecting said masked surface to an orientation dependent etch whereby a plurality of slots of precisely determined depths are formed in said slice, said depths being determined by the respective widths of said windows; lapping the opposite surface of said semiconductor slice until one or more of said slots is exposed; and terminating said lapping to provide a precisely determined slice thickness as indicated by the exposure of said slot or slots.
Claim 7
Dependent Claim 31 words
A method as defined by claim 4 wherein said etch resistant mask is provided with a plurality of groups of windows, each group comprising a series of windows having unequal widths.
Claim 8
Dependent Claim 18 words
A method as defined in claim 4 wherein the walls of said slots are formed of (111) planes.
Claim 9
Dependent Claim 25 words
A method as defined in claim 4 wherein said slots are filled by a vapor-deposited support layer prior to the lapping of the opposite surface.
Claim 10
Dependent Claim 160 words
In a method for shaping a body of silicon having first and second sides in the formation of dielectrically isolated integrated circuits so that the body has a precise depth, forming by the use of an anisotropic etch at least two generally V-shaped grooves in said body extending inwardly from said first side of the body so that the grooves have apexes which terminate at different depths in said body within predetermined limits, forming a layer of silicon dioxide on said first side and in the apexes of the grooves, forming a polycrystalline silicon support structure upon said layer of silicon dioxide and removing silicon from the second side of the body using said grooves as depth gauges until at least some of the silicon dioxide in at least one of the apexes of the V-shaped grooves is exposed to thereby give an indication of the depth to which siLicon has been removed from said second side of the body.
Claim 11
Dependent Claim 160 words
In a method for shaping a body of silicon having first and second sides in the formation of dielectrically isolated integrated circuits so that the body has a precise depth, forming by the use of an anisotropic etch at least two generally V-shaped grooves in said body extending inwardly from said first side of the body so that the grooves have apexes which terminate at different depths in said body within predetermined limits, forming a layer of silicon dioxide on said first side and in the apexes of the grooves, forming a polycrystalline silicon support structure upon said layer of silicon dioxide and removing silicon from the second side of the body using said grooves as depth gauges until at least some of the silicon dioxide in at least one of the apexes of the V-shaped grooves is exposed to thereby give an indication of the depth to which siLicon has been removed from said second side of the body.
Claim 12
Dependent Claim 22 words
A method as in claim 8, wherein the apexes of the depth gauges differ in depth by approximately 5 microns or less.
Claim 13
Dependent Claim 50 words
A method as in claim 8, including forming more than two of said V-shaped grooves in the body of silicon and wherein silicon is removed from the second side of the body until some of the silicon dioxide in the apexes of at least two of the grooves is exposed.
Claim 14
Dependent Claim 34 words
A method as in claim 8, including forming active and passive devices in the islands and placing a metallization pattern on the body to interconnect the active and passive devices into an integrated circuit.
Claim 15
Dependent Claim 17 words
A method as in claim 8, wherein said silicon is removed from said second side by lapping.
Claim 16
Dependent Claim 87 words
A method as in claim 8, including forming isolation moats by the use of an anisotropic etch, which are generally V-shaped in cross-section and extend inwardly from said first side of the body and have a depth which is greater than the depth of any of the V-shaped grooves and forming a layer of silicon dioxide in said moats so that the silicon dioxide layer in the moats provides dielectrically isolated islands of silicon when at least one of the apexes of the V-shaped grooves is exposed.
Claim 17
Dependent Claim 32 words
A method as in claim 13 wherein the layer of silicon dioxide in the grooves is formed at the same time that the layer of silicon dioxide is formed in the moats.

References Cited (Backward Citations)

US3171762A Cited
US3290753A Cited
US3411200A Cited
US3457123A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1977-10-28 1978-04-29 1978-10-29 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1981-10-28 1982-04-29 1982-10-29 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1985-10-28 1986-04-29 1986-10-29 $7700.00 Window Closed / Lapsed

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