WO2001024244A1 - High etch selectivity etchant for doped silicate glass - Google Patents

High etch selectivity etchant for doped silicate glass Download PDF

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Publication number
WO2001024244A1
WO2001024244A1 PCT/US2000/025481 US0025481W WO0124244A1 WO 2001024244 A1 WO2001024244 A1 WO 2001024244A1 US 0025481 W US0025481 W US 0025481W WO 0124244 A1 WO0124244 A1 WO 0124244A1
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WO
WIPO (PCT)
Prior art keywords
etchant
water content
volume
less
silicate glass
Prior art date
Application number
PCT/US2000/025481
Other languages
French (fr)
Inventor
Klaus Penner
Hans-Juergen Kruwinus
Matthias Ilg
Original Assignee
Infineon Technologies North America Corp.
Sez Semiconductor Equipment Zubehor Fur Die Halbleiterfertigung Ag
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Infineon Technologies North America Corp., Sez Semiconductor Equipment Zubehor Fur Die Halbleiterfertigung Ag filed Critical Infineon Technologies North America Corp.
Publication of WO2001024244A1 publication Critical patent/WO2001024244A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
    • H01L21/3105—After-treatment
    • H01L21/311—Etching the insulating layers by chemical or physical means
    • H01L21/31105—Etching inorganic layers
    • H01L21/31111—Etching inorganic layers by chemical means
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02107—Forming insulating materials on a substrate
    • H01L21/02109—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates
    • H01L21/02112—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer
    • H01L21/02123—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon
    • H01L21/02126—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon the material containing Si, O, and at least one of H, N, C, F, or other non-metal elements, e.g. SiOC, SiOC:H or SiONC
    • H01L21/02129—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer the material containing silicon the material containing Si, O, and at least one of H, N, C, F, or other non-metal elements, e.g. SiOC, SiOC:H or SiONC the material being boron or phosphorus doped silicon oxides, e.g. BPSG, BSG or PSG

Definitions

  • the invention generally relates to semiconductor device fabrication and, more particularly, to providing highly selective etching of silicon based oxides.
  • device layers of insulating, semiconducting, and conducting materials are formed on a substrate.
  • the layers are patterned to create features and spaces .
  • the features and spaces are patterned so as to form devices, such as transistors, capacitors, and resistors. These devices are then interconnected to achieve a desired electrical function, creating an integrated circuit (IC) .
  • IC integrated circuit
  • Etch selectivity is defined as the ratio of etch rates between a first material that is to be etched with respect to a second material.
  • silicon-based materials such as silicon-base d oxides are generally employed as, for example, dielectric layers, masks for etch processes as well as etch stop and polish stop layers.
  • Conventional wet etch processes employs a fluoride-based etchant to etch silicon-based materials. Such etchants produce an etch selectivity of less than 15:1.
  • the invention relates to a highly selective etching of silicon-based materials.
  • an etchant comprising sulfuric acid and hydrofluoric acid having a low water content is used for to etch a doped silicate glass with a high selectivity to silicon-based materials such as silicon oxides, silicon nitrides, silicate glass, or polysilicon.
  • the water content of the etchant is less than 20% by volume.
  • the invention relates generally to semiconductor fabrication and particularly to an etchant that provides a high etch selectivity of a first material to a second material on a substrate such as a semiconductor wafer.
  • the first and second materials are silicon-based materials.
  • the silicon-based materials can be formed by techniques such as thermal oxidation, chemical vapor deposition (CVD) , or a combination of thermal oxidation and CVD.
  • the first material comprises a doped silicate glass.
  • Dopants such as boron, phosphorus, or arsenic, are useful to dope the silicate glass.
  • the doped silicate glass comprises, for example boron such as borosilicate glass (BSG) .
  • BSG borosilicate glass
  • Other types of doped silicate glass such as phosphosilicate glass (PSG) are also useful.
  • a doped silicate glass comprising more than one type of dopant, such as borophosphosilicate glass (BPSG) is also useful.
  • BPSG borophosphosilicate glass
  • BPSG borophosphosilicate glass
  • the second silicon-based material comprises silicon oxide, silicon nitride, undoped silicate glass or polysilicon.
  • the polysilicon can be doped or undoped.
  • the second silicon-based material comprises silicon oxide.
  • the silicon-based oxide is formed by thermal oxidation.
  • the etch system etches the doped silicate glass with an etch selectivity to the silicon oxide of greater than about 15:1, preferably greater than about 40:1, more preferably greater than about 70:1, and even more preferably greater than about 100:1.
  • the etchant comprises sulfuric acid and hydrofluoric acid having a low water content to produce a high etch selectivity between silicon-based materials.
  • the etch system comprises a water content of less than about 20% by volume, preferably less than about 15% by volume, more preferably less than about 10% by volume, and even more preferably less than about 5% by volume .
  • the high etch selectivity can be achieved using a wide range of mixing ratio of concentrated sulfuric acid and concentrated hydrofluoric acid.
  • the ratio of the acids affect the etch rate.
  • a higher ratio of sulfuric acid causes the etchant to etch at a lower etch rate and vice-versa.
  • the etchant retains its high etch selectivity characteristics.
  • the etchant comprises sulfuric acid and hydrofluoric acid in a ratio of about 5:1 to about 20:1 by volume. A ratio of greater than 20:1 can also be useful if lower etch rates are desired.
  • the substrate is exposed to the etchant using wet etch tools, such as a bath, a spray tool or a spintech tool .
  • the etchant exhibits high etch selectivity characteristics over a wide range of temperatures.
  • the etchant can be used at temperatures ranging from below room temperature to above 80°C with a high etch selectivity.
  • the temperature does affect the etch rates of the materials.
  • the temperature of the etch can be chosen to produce the desired etch rates on the materials while still retaining the desired high etch selectivity property.
  • the etch rate of the doped silicate glass can be controlled by changing the concentration of the dopants. In particular, the etch rate can be increased or decreased by increasing or decreasing the dopant concentration, respectively, in the doped silicate glass.
  • the doped silicate glass comprises a dopant concentration of at least 3 wt%. A dopant concentration of about 3 - 3.5 wt% has been found to produce an etch selectivity to silicon oxide of about 45:1. Increasing the dopant concentration of the doped silicate glass to above 5 wt% produces an etch selectivity to silicon oxide of greater than about 70:1.
  • the BSG comprises a concentration of B of at least 3 wt%, preferably greater than about 5 wt%.
  • An etchant comprising a mixture of 5 parts sulfuric acid (96%) and 1 part hydrofluoric acid (49%) was used to etch a BSG layer comprising 5 wt% B and a thermal oxide layer.
  • the etchant yielded an etch rate of about 720 nm/min for the BSG layer and only 14 nm/min for the thermal oxide layer, resulting in an etch selectivity of the BSG to the thermal oxide of about 51:1.

Abstract

An etchant for highly selective etching of silicon-based materials. The etchant comprises sulfuric acid and hydrofluoric acid with low water content.

Description

HIGH ETCH SELECTIVITY ETCHANT FOR DOPED SILICATE GLASS
Field Of Invention
The invention generally relates to semiconductor device fabrication and, more particularly, to providing highly selective etching of silicon based oxides.
Background Of Invention
In device fabrication, device layers of insulating, semiconducting, and conducting materials are formed on a substrate. The layers are patterned to create features and spaces . The features and spaces are patterned so as to form devices, such as transistors, capacitors, and resistors. These devices are then interconnected to achieve a desired electrical function, creating an integrated circuit (IC) .
The ability to selectively etch or remove specific layers without attacking others facilitates patterning of the device layers. Etch selectivity is defined as the ratio of etch rates between a first material that is to be etched with respect to a second material. Of particular interest is the selectivity of silicon-based materials. Silicon-based materials such as silicon-based oxides are generally employed as, for example, dielectric layers, masks for etch processes as well as etch stop and polish stop layers. Conventional wet etch processes employs a fluoride-based etchant to etch silicon-based materials. Such etchants produce an etch selectivity of less than 15:1.
As device dimension decreases and complexity increases in the advance IC designs, it is becoming more important to have high selectivity between different types of silicon-based materials. Typically, the etch selectivity of different silicon-based materials required in advance IC designs exceeds that achievable with conventional wet etch processes. This results in reduced manufacturing yields or the loss of process capability at all. On the other hand very high selectivities offer new possibilities in process architecture.
From the above discussion, it is desirable to provide an etch system for silicon based oxides with high etch selectivity for advance IC designs.
Summary of the Invention
The invention relates to a highly selective etching of silicon-based materials. In one embodiment, an etchant comprising sulfuric acid and hydrofluoric acid having a low water content is used for to etch a doped silicate glass with a high selectivity to silicon-based materials such as silicon oxides, silicon nitrides, silicate glass, or polysilicon. The water content of the etchant is less than 20% by volume.
Description of the Invention
The invention relates generally to semiconductor fabrication and particularly to an etchant that provides a high etch selectivity of a first material to a second material on a substrate such as a semiconductor wafer. The first and second materials, in one embodiment, are silicon-based materials. The silicon-based materials can be formed by techniques such as thermal oxidation, chemical vapor deposition (CVD) , or a combination of thermal oxidation and CVD.
In one embodiment, the first material comprises a doped silicate glass. Dopants such as boron, phosphorus, or arsenic, are useful to dope the silicate glass. In one embodiment, the doped silicate glass comprises, for example boron such as borosilicate glass (BSG) . Other types of doped silicate glass such as phosphosilicate glass (PSG) are also useful. A doped silicate glass comprising more than one type of dopant, such as borophosphosilicate glass (BPSG) is also useful. Including other types of dopants, such as phosphorous (P) or arsenic (A) , in the doped silicate glass is also useful. The second silicon-based material comprises silicon oxide, silicon nitride, undoped silicate glass or polysilicon. The polysilicon can be doped or undoped. In one embodiment, the second silicon-based material comprises silicon oxide. The silicon-based oxide is formed by thermal oxidation. The etch system etches the doped silicate glass with an etch selectivity to the silicon oxide of greater than about 15:1, preferably greater than about 40:1, more preferably greater than about 70:1, and even more preferably greater than about 100:1.
In accordance with one embodiment of the invention, the etchant comprises sulfuric acid and hydrofluoric acid having a low water content to produce a high etch selectivity between silicon-based materials. In one embodiment, the etch system comprises a water content of less than about 20% by volume, preferably less than about 15% by volume, more preferably less than about 10% by volume, and even more preferably less than about 5% by volume .
The high etch selectivity can be achieved using a wide range of mixing ratio of concentrated sulfuric acid and concentrated hydrofluoric acid. The ratio of the acids affect the etch rate. A higher ratio of sulfuric acid causes the etchant to etch at a lower etch rate and vice-versa. Although the ratio of sulfuric acid and hydrofluoric acid changes actual etch rates of the materials being etched, the etchant retains its high etch selectivity characteristics. In one embodiment, the etchant comprises sulfuric acid and hydrofluoric acid in a ratio of about 5:1 to about 20:1 by volume. A ratio of greater than 20:1 can also be useful if lower etch rates are desired.
The substrate is exposed to the etchant using wet etch tools, such as a bath, a spray tool or a spintech tool . The etchant exhibits high etch selectivity characteristics over a wide range of temperatures. For example, the etchant can be used at temperatures ranging from below room temperature to above 80°C with a high etch selectivity. The temperature, however, does affect the etch rates of the materials. As such, the temperature of the etch can be chosen to produce the desired etch rates on the materials while still retaining the desired high etch selectivity property.
The etch rate of the doped silicate glass can be controlled by changing the concentration of the dopants. In particular, the etch rate can be increased or decreased by increasing or decreasing the dopant concentration, respectively, in the doped silicate glass. In one embodiment, the doped silicate glass comprises a dopant concentration of at least 3 wt%. A dopant concentration of about 3 - 3.5 wt% has been found to produce an etch selectivity to silicon oxide of about 45:1. Increasing the dopant concentration of the doped silicate glass to above 5 wt% produces an etch selectivity to silicon oxide of greater than about 70:1. In one embodiment, the BSG comprises a concentration of B of at least 3 wt%, preferably greater than about 5 wt%.
Example
An etchant comprising a mixture of 5 parts sulfuric acid (96%) and 1 part hydrofluoric acid (49%) was used to etch a BSG layer comprising 5 wt% B and a thermal oxide layer. The etchant yielded an etch rate of about 720 nm/min for the BSG layer and only 14 nm/min for the thermal oxide layer, resulting in an etch selectivity of the BSG to the thermal oxide of about 51:1.
While the invention has been particularly shown and described with reference to various embodiments, it will be recognized by those skilled in the art that modifications and changes may be made to the present invention without departing from the scope thereof. The scope of the invention should therefore be determined not with reference to the above description but with reference to the appended claims along with their full scope of equivalents.

Claims

What is claimed is :
1. An etchant comprising sulfuric acid and hydrofluoric acid with a low water content to produce a high etch selectivity.
2. The etchant of claim 1 wherein the first material comprises a doped silicate glass and the second material comprises a silicon-based material.
3. The etchant of claim 2 wherein the first material comprises a doped silicate glass and the second material comprises a silicon-based material selected from the consisting of polysilicon, silicate glass, silicon oxide, or silicon nitride.
4. The etchant of claim 3 wherein the doped silicate glass comprises a dopant concentration of greater than 3 wt%.
5. The etchant of claim 4 wherein the water content is less than about 20% by volume.
6. The etchant of claim 4 wherein the water content is less than about 15% by volume.
7. The etchant of claim 4 wherein the water content is less than about 10% by volume.
8. The etchant of claim 4 wherein the water content is less than about 5% by volume.
9. The etchant of claim 3 wherein the doped silicate glass comprises a dopant concentration of greater than 5 wt%.
10. The etchant of claim 9 wherein the water content is less than about 20% by volume.
11. The etchant of claim 9 wherein the water content is less than about 15% by volume.
12. The etchant of claim 9 wherein the water content is less than about 10% by volume.
13. The etchant of claim 9 wherein the water content is less than about 5% by volume.
14. The etchant of claim 3 wherein the doped silicate glass comprises boron.
15. The etchant of claim wherein the doped silicate glass comprises a boron concentration of greater than 3 wt%.
16. The etchant of claim 15 wherein the water content is less than about 20% by volume.
17. The etchant of claim 15 wherein the water content is less than about 15% by volume.
18. The etchant of claim 15 wherein the water content is less than about 10% by volume.
19. The etchant of claim 15 wherein the water content is less than about 5% by volume.
20. The etchant of claim wherein the doped silicate glass comprises a boron concentration of greater than 5 wt%.
21. The etchant of claim 20 wherein the water content is less than about 20% by volume.
22. The etchant of claim 20 wherein the water content is less than about 15% by volume.
23. The etchant of claim 20 wherein the water content is less than about 10% by volume.
24. The etchant of claim 20 wherein the water content is less than about 5% by volume.
25. The etchant of claim 2 wherein the water content is less than about 20% by volume.
26. The etchant of claim 2 wherein the water content is less than about 15% by volume.
27. The etchant of claim 2 wherein the water content is less than about 10% by volume.
28. The etchant of claim 2 wherein the water content is less than about 5% by volume.
29. The etchant of claim 25 wherein the high etch selectivity of the first material to the second material is greater than 15:1
30. The etchant of claim 25 wherein the high etch selectivity of the first material to the second material is greater than 45:1
31. The etchant of claim 25 wherein the high etch selectivity of the first material to the second material is greater than 70:1
32. The etchant of claim 25 wherein the high etch selectivity of the first material to the second material is greater than 100:1
33. A method for wet etching comprising: providing a substrate including first and second materials; and exposing the substrate to an etchant comprising sulfuric acid and hydrofluoric acid with a low water content, the etching etches the first material with a high etch selectivity to the second material .
PCT/US2000/025481 1999-09-24 2000-09-15 High etch selectivity etchant for doped silicate glass WO2001024244A1 (en)

Applications Claiming Priority (2)

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US40490799A 1999-09-24 1999-09-24
US09/404,907 1999-09-24

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10544329B2 (en) 2015-04-13 2020-01-28 Honeywell International Inc. Polysiloxane formulations and coatings for optoelectronic applications

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3751314A (en) * 1971-07-01 1973-08-07 Bell Telephone Labor Inc Silicon semiconductor device processing
US4465549A (en) * 1984-01-26 1984-08-14 Rca Corporation Method of removing a glass backing plate from one major surface of a semiconductor wafer
US5300463A (en) * 1992-03-06 1994-04-05 Micron Technology, Inc. Method of selectively etching silicon dioxide dielectric layers on semiconductor wafers
EP0932187A2 (en) * 1998-01-27 1999-07-28 International Business Machines Corporation Trench etching using borosilicate glass mask
DE19850838A1 (en) * 1998-09-09 2000-03-23 Mosel Vitelic Inc Improving wet etching uniformity during spin-etching of a layer on a semiconductor wafer, by forming a water film on the wafer before acid etching of the layer
EP0989598A2 (en) * 1998-09-25 2000-03-29 Siemens Aktiengesellschaft Process for wet etching a semiconductor structure

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3751314A (en) * 1971-07-01 1973-08-07 Bell Telephone Labor Inc Silicon semiconductor device processing
US4465549A (en) * 1984-01-26 1984-08-14 Rca Corporation Method of removing a glass backing plate from one major surface of a semiconductor wafer
US5300463A (en) * 1992-03-06 1994-04-05 Micron Technology, Inc. Method of selectively etching silicon dioxide dielectric layers on semiconductor wafers
EP0932187A2 (en) * 1998-01-27 1999-07-28 International Business Machines Corporation Trench etching using borosilicate glass mask
DE19850838A1 (en) * 1998-09-09 2000-03-23 Mosel Vitelic Inc Improving wet etching uniformity during spin-etching of a layer on a semiconductor wafer, by forming a water film on the wafer before acid etching of the layer
EP0989598A2 (en) * 1998-09-25 2000-03-29 Siemens Aktiengesellschaft Process for wet etching a semiconductor structure

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10544329B2 (en) 2015-04-13 2020-01-28 Honeywell International Inc. Polysiloxane formulations and coatings for optoelectronic applications

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