WO1997024754A1 - Preferential etch of semiconductor substrate with respect to epitaxial layers - Google Patents
Preferential etch of semiconductor substrate with respect to epitaxial layers Download PDFInfo
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- WO1997024754A1 WO1997024754A1 PCT/IB1996/001399 IB9601399W WO9724754A1 WO 1997024754 A1 WO1997024754 A1 WO 1997024754A1 IB 9601399 W IB9601399 W IB 9601399W WO 9724754 A1 WO9724754 A1 WO 9724754A1
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- substrate
- etching
- solvent
- etchant
- approximately
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- 239000000758 substrate Substances 0.000 title claims abstract description 77
- 239000004065 semiconductor Substances 0.000 title claims abstract description 32
- 238000005530 etching Methods 0.000 claims abstract description 65
- 239000008139 complexing agent Substances 0.000 claims abstract description 45
- 239000000203 mixture Substances 0.000 claims abstract description 42
- 239000002904 solvent Substances 0.000 claims abstract description 23
- 150000001875 compounds Chemical class 0.000 claims abstract description 16
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 15
- 238000004519 manufacturing process Methods 0.000 claims abstract description 7
- 238000000034 method Methods 0.000 claims description 28
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 24
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical group [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- FEWJPZIEWOKRBE-JCYAYHJZSA-N Dextrotartaric acid Chemical compound OC(=O)[C@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-JCYAYHJZSA-N 0.000 claims description 10
- 239000000908 ammonium hydroxide Substances 0.000 claims description 8
- 235000006408 oxalic acid Nutrition 0.000 claims description 7
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical group [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 claims description 6
- PANJMBIFGCKWBY-UHFFFAOYSA-N iron tricyanide Chemical compound N#C[Fe](C#N)C#N PANJMBIFGCKWBY-UHFFFAOYSA-N 0.000 claims description 6
- 239000011591 potassium Substances 0.000 claims description 6
- 229910052700 potassium Inorganic materials 0.000 claims description 6
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric acid Natural products [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 claims description 5
- 235000002906 tartaric acid Nutrition 0.000 claims description 5
- 239000011975 tartaric acid Substances 0.000 claims description 5
- JBRZTFJDHDCESZ-UHFFFAOYSA-N AsGa Chemical compound [As]#[Ga] JBRZTFJDHDCESZ-UHFFFAOYSA-N 0.000 description 16
- 229910052733 gallium Inorganic materials 0.000 description 13
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 12
- 239000000243 solution Substances 0.000 description 11
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 8
- IPCGGVKCDVFDQU-UHFFFAOYSA-N [Zn].[Se]=S Chemical compound [Zn].[Se]=S IPCGGVKCDVFDQU-UHFFFAOYSA-N 0.000 description 7
- PTFCDOFLOPIGGS-UHFFFAOYSA-N Zinc dication Chemical compound [Zn+2] PTFCDOFLOPIGGS-UHFFFAOYSA-N 0.000 description 6
- -1 for example Substances 0.000 description 6
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000011701 zinc Substances 0.000 description 5
- 229910052725 zinc Inorganic materials 0.000 description 5
- 230000009471 action Effects 0.000 description 4
- 239000005083 Zinc sulfide Substances 0.000 description 2
- VBIXEXWLHSRNKB-UHFFFAOYSA-N ammonium oxalate Chemical compound [NH4+].[NH4+].[O-]C(=O)C([O-])=O VBIXEXWLHSRNKB-UHFFFAOYSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 125000000896 monocarboxylic acid group Chemical group 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000003908 quality control method Methods 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 229910052984 zinc sulfide Inorganic materials 0.000 description 2
- UQMZPFKLYHOJDL-UHFFFAOYSA-N zinc;cadmium(2+);disulfide Chemical compound [S-2].[S-2].[Zn+2].[Cd+2] UQMZPFKLYHOJDL-UHFFFAOYSA-N 0.000 description 2
- ZPEJZWGMHAKWNL-UHFFFAOYSA-L zinc;oxalate Chemical compound [Zn+2].[O-]C(=O)C([O-])=O ZPEJZWGMHAKWNL-UHFFFAOYSA-L 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- DMNSJGKZWRRIOO-UHFFFAOYSA-N S=[Se].[Mg].[Zn] Chemical compound S=[Se].[Mg].[Zn] DMNSJGKZWRRIOO-UHFFFAOYSA-N 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 238000003486 chemical etching Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000001493 electron microscopy Methods 0.000 description 1
- 230000003028 elevating effect Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 229910021513 gallium hydroxide Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000012876 topography Methods 0.000 description 1
- 238000004627 transmission electron microscopy Methods 0.000 description 1
- 229940100888 zinc compound Drugs 0.000 description 1
- 150000003752 zinc compounds Chemical class 0.000 description 1
- DRDVZXDWVBGGMH-UHFFFAOYSA-N zinc;sulfide Chemical compound [S-2].[Zn+2] DRDVZXDWVBGGMH-UHFFFAOYSA-N 0.000 description 1
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
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
- H01L21/30604—Chemical etching
- H01L21/30612—Etching of AIIIBV compounds
-
- 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
- H01L21/34—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 not provided for in groups H01L21/0405, H01L21/0445, H01L21/06, H01L21/16 and H01L21/18 with or without impurities, e.g. doping materials
- H01L21/46—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/428
- H01L21/461—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/428 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/469—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/428 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After-treatment of these layers
- H01L21/471—Inorganic layers
- H01L21/473—Inorganic layers composed of oxides or glassy oxides or oxide based glass
Definitions
- Fig. 1 is partial, schematic view, in cross-section and not to scale, of an exemplary semiconductor structure
- an exemplary semiconductor structure 8 comprises a substrate 10 and a plurality of epitaxial layers 12.
- the substrate 10, in processing, can be exposed either at the interface 14 formed between the epitaxial layers 12 and the substrate 10 or at the back 16 of the substrate 10 opposite the epitaxial layers 12. Processing often calls for removal of some, or substantially all, of the substrate 10 relative to the epitaxial layers 12, while leaving these layers substantially intact. In particular, processing may require removal of the substrate 10 at the interface 14 or at the back 16, or both.
- the etching composition according to the present invention comprises a solvent, an etchant and first and second complexing agents.
- the etchant has a redox potential intermediate between the redox potential of the substrate and the redox potential of at least one of the epitaxial layers. Thence, the etchant is capable of preferentially etching the substrate with respect to the at least one epitaxial layer.
- the etchant preferably is soluble in the solvent.
- the first complexing agent is reactive with the substrate so as to accelerate the rate at which the etchant etches the substrate.
- the complexing agent preferably is selected to take up gallium ions [Ga 3+ ].
- the first complexing agent preferably is soluble in the solvent.
- the second complexing agent preferably is selected to take up zinc ions [Zn 2+ ] removed by the etchant, so as to form a compound or compounds that are highly insoluble in water so as to reach saturation in the solvent and limit further etching of the layer by establishing the above-described equilibrium.
- the etching composition yields a relatively optimized etch rate, e.g., O.45 ⁇ m per minute, for a substrate comprising gallium arsenide [GaAs], while maintaining at substantially zero the etch rate for an epitaxial layer comprising zinc selenium sulfide [ZnSeS].
- the etch rate of a gallium arsenide substrate has been found to be approximately only a few microns per hour.
- Etching performed in other then stagnant application accelerates the etch rate of gallium arsenide substrate, without changing the etch rate of the zinc-compound epitaxial layer.
- mat stirring can increase the etch rate of gallium arsenide substrate approximately three-fold.
- Other mechanical operations, such as agitation, are thought to have similar results.
- the first embodiment of the etching composition it has been determined that elevating the temperature to approximately 50°C results in an etch rate of approximately l ⁇ m/min for the substrate, while maintaining the etch rate of the zinc selenium sulfide [ZnSeS] at approximately OA/min.
- the second embodiment of the etching composition it has been determined that the etch rate of such an epitaxial layer remains acceptably low even where this etch is performed at a temperature of approximately 65 °C. It is to be recognized, however, that the temperature at which the etch occurs generally will have some optimum range, the range being factors dependent. The factors can include, for example and without limitation, the type of substrate, the desired etch rate of the substrate, the type of epitaxial layer or layers, and the level of acceptable epitaxial layer damage.
- the etching composition preferably is substantially similar to that described above, including employment of an acidity adjustment agent.
- the acidity adjustment agent preferably is added after mixing the solvent, the etchant and the first and second complexing agents, and before immersion of the substrate. In this manner, the mixed components are brought fully into solution and the acidity of the solution is established prior to immersion.
- One advantage of this order is that the etch of the substrate is subject to greater control.
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- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Weting (AREA)
Abstract
A method of manufacturing a semiconductor whereby a semiconductor structure comprising a substrate and one or more epitaxial layers is etched in an etching composition comprising a solvent, an etchant, and first and second complexing agents, the etchant and complexing agents being soluble in the solvent. The etchant preferentially etches the substrate with respect to at least one epitaxial layer. The first complexing agent is reactive with the substrate so as to accelerate the rate at which the etchant etches the substrate. The second complexing agent is reactive with a component of the at least one epitaxial layer so as to form a resulting compound with the component. This reaction establishes an equilibrium between the resulting compound, the second complexing agent and the component, the equilibrium precluding significant etching of the at least one epitaxial layer. The etching composition preferably comprises an agent which provides for adjusting the acidity of the solution, and thereby provides for adjusting the etch rate of the substrate while maintaining the composition's etching characteristics with respect to the at least one epitaxial layer.
Description
Preferential etch of semiconductor substrate with respect to epitaxial layers.
This invention relates to a method of manufacturing a semiconductor device, whereby a semiconductor structure comprising a semiconductor substrate and one or more epitaxial layers is etched.
In semiconductor and integrated circuit fabrication, processing generally includes forming epitaxial layers on a substrate. Moreover, processing often calls for removal of some, or substantially all, of the substrate relative to the epitaxial layers, while leaving the epitaxial layers substantially intact. In particular, removal of the substrate has been found desirable both at the substrate's interface with the epitaxial layers and from the back of the substrate opposite the epitaxial layers. In the former case, removal of the substrate is directed at creating topographies useful in the manufacture of specific devices, such as vertical cavity surface emitting lasers. Removal can also be directed to increasing device density
In the latter case, removal of the substrate is to accomplish various processing ends, including, as examples (i) eliminating of substances that can interfere with the performance of the semiconductor and integrated circuit devices, (ii) thinning the substrate prior to dividing it into individual devices, (iii) preparing the backside for subsequent processing, and (iv) quality control.
Quality control includes removal of the substrate to enable study of the epitaxial layers. This study generally is performed to identify the layers' physical properties, as well as their chemical and crystallographic purity. For example, this study typically includes evaluation, for one or more layers, of (i) the layer thickness, (ii) the concentration of desirable and undesirable impurities, (iii) the density and distribution of defects and (iv) any variation of these parameters over a selected surface area. This study typically is performed using electron microscopy, including transmission electron microscopy. Ultimately, this study is performed toward advancing understanding the fabrication process and the operation of the semiconductor and integrated circuit devices to be produced. Such understanding typically leads to improvement in fabrication, device performance or both.
Techniques for removing substrate are known, each of which has associated problems. For example, it is known to mechanically remove selected portions of the substrate, which process is known as lapping. Lapping, however, tends to damage the crystalline structure of the remaining substrate. Moreover, lapping is undesirably inexact: it can leave behind substrate sought to be removed and it can remove substrate sought to be retained. In some applications, lapping results in one or more epitaxial layers being damaged or removed.
It is also known to remove substrate using chemical etching compositions and techniques. Generally, these etching compositions and techniques are preferential, being selected to etch the substrate while leaving the epitaxial layers undamaged. However, known preferential etching techniques can be undesirably slow or fast. When the etch rate is relatively slow, processing is impeded. When the etch rate is relatively fast, the etch can be difficult to control, leading to the removal of an incorrect amount of substrate.
Moreover, the etching composition is often somewhat reactive with one or more of the epitaxial layers, notwithstanding that the composition is selected to be relatively nonreactive with such layers. This reactivity tends to result in not insignificant etching of one or more epitaxial layers. For example, if a relatively large amount of the substrate is to be removed, the overall etch time can be relatively long. A longer etch time for the substrate, in turn, means a longer time for the etching composition to react with epitaxial layers. Over a sufficiently long time, the etching composition tends to etch one or more of the layers in an amount that is not insignificant.
Accordingly, a need exists for an improved etching composition and method for preferentially etching a semiconductor substrate with respect to one or more epitaxial layers. Moreover, a need exists for an improved etching composition and method for preferentially etching a gallium arsenide semiconductor substrate, with respect to one or more epitaxial layers, including with respect to layers comprising II-VI materials.
An object of the invention is to provide an improved etching composition and method for removing some, or substantially all, of a substrate with respect to one or more epitaxial layers, while leaving the epitaxial layers substantially unetched.
A further object of the invention is to provide an improved preferential etching composition and method for etching a gallium arsenide substrate with respect to one or more epitaxial layers, including layers comprising II-VI materials.
A specific object of the invention is to provide a preferential etching composition and method that etches a gallium arsenide substrate at a selectable rate, the etching composition etching an epitaxial layer in an amount that is not significant.
According to one aspect of the invention, an etching composition is provided for use in etching a semiconductor structure, the semiconductor structure comprising a substrate and one or more epitaxial layers. The composition comprises a solvent, an etchant and first and second complexing agents. The etchant preferentially etches me substrate with respect to at least one epitaxial layer. The first complexing agent is reactive with the substrate so as to accelerate the rate at which the etchant etches the substrate. The second complexing agent is reactive with a component of at least the one epitaxial layer so as to form a resulting compound with the component. The reaction between the second complexing agent and the component, however, is such that the resulting compound, the second complexing agent and the component exist in equilibrium in the solution. In mis way, the second complexing agent provides that the at least one epitaxial layer is etched in an amount that is not significant and that is substantially independent of the etching duration.
In another aspect of the invention, a method is provided for etching a semiconductor structure, the semiconductor structure comprising a substrate and one or more epitaxial layers. The method comprises the steps of selecting a solvent, an etchant, and first and second complexing agents; mixing these elements to form a solution; immersing a portion of the semiconductor structure in the solution, whereby the substrate of that portion is preferentially etched with respect to the portion's epitaxial layers.
In this second aspect, the etching composition preferably is substantially similar to that described above, including employment of an acidity adjustment agent. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be made to the accompanying drawings and descriptive matter in which its preferred embodiments are illustrated and described, wherein like reference numerals identify the same or similar elements.
In the drawings:
Fig. 1 is partial, schematic view, in cross-section and not to scale, of an
exemplary semiconductor structure; and
Fig. 2 is a flow chart of a method for etching a semiconductor structure having a substrate and one or more epitaxial layers, in accordance with the invention.
As shown in Figure 1, an exemplary semiconductor structure 8 comprises a substrate 10 and a plurality of epitaxial layers 12. The substrate 10, in processing, can be exposed either at the interface 14 formed between the epitaxial layers 12 and the substrate 10 or at the back 16 of the substrate 10 opposite the epitaxial layers 12. Processing often calls for removal of some, or substantially all, of the substrate 10 relative to the epitaxial layers 12, while leaving these layers substantially intact. In particular, processing may require removal of the substrate 10 at the interface 14 or at the back 16, or both.
This invention contemplates an etching composition and method for use in etching the semiconductor structure 8 and, in particular, for preferentially etching the substrate 10 with respect to one or more of the epitaxial layers 12. The etching composition described hereinafter is generally applicable to substrates 10 comprising gallium arsenide [GaAs] and epitaxial layers 12 formed of II-VI materials, including, for example, zinc sulfide [ZnS], zinc selenium sulfide [ZnSeS], zinc magnesium selenium sulfide [ZnMgSeS] and zinc cadmium sulfide [ZnCdS]. However, it is to be recognized that the substrate can be formed of materials other than GaAs and the epitaxial layers may be formed by other than the above materials, without departing from the principles of the invention.
The etching composition according to the present invention comprises a solvent, an etchant and first and second complexing agents. The etchant has a redox potential intermediate between the redox potential of the substrate and the redox potential of at least one of the epitaxial layers. Thence, the etchant is capable of preferentially etching the substrate with respect to the at least one epitaxial layer. The etchant preferably is soluble in the solvent.
The first complexing agent is reactive with the substrate so as to accelerate the rate at which the etchant etches the substrate. For example, where the substrate is gallium arsenide, the complexing agent preferably is selected to take up gallium ions [Ga3+]. The first complexing agent preferably is soluble in the solvent.
The second complexing agent is reactive with a component of the at least one epitaxial layer so as to form a resulting compound with the component. More specifically, the second complexing agent reacts with the component such that the resulting
compound, the second complexing agent and the component exist in equilibrium in the solvent. In this manner, the etching composition is precluded from significantly etching the at least one epitaxial layer because the component can dissolve in the solvent in only acceptably minute amounts before equilibrium is established. In particular, to minimize the etch of the at least one epitaxial layer, the second complexing agent preferably is selected so that the resulting compound is highly insoluble in the solvent. To illustrate, where the at least one epitaxial layer comprises zinc and the solvent comprises water, the second complexing agent preferably is selected to take up zinc ions [Zn2+] removed by the etchant, so as to form a compound or compounds that are highly insoluble in water so as to reach saturation in the solvent and limit further etching of the layer by establishing the above-described equilibrium.
Therefore, the second complexing agent provides that the etching composition etches the at least one epitaxial layer in an amount that is not significant. Moreover, the second complexing agent provides that the amount of etching of that layer is substantially independent of the etching duration.
It is to be recognized that the first and second complexing agents can be the same or different, without departing from the principles of the invention.
The etching composition preferably comprises an acidity adjustment agent. The acidity adjustment agent provides for adjusting the acidity of the solution, and thereby provides for adjusting the etch rate of the substrate while maintaining the etching characteristics of the etching composition with respect to the at least one epitaxial layer. The acidity adjustment agent also preferably advances dissolution of the first and second complexing agents in the solvent.
In one specific embodiment, it has been determined that acceptable etch results are achieved in etching a semiconductor structure having a gallium arsenide substrate and a zinc selenium sulfide epitaxial layer, the following etching composition being employed: the solvent comprises approximately 50 ml of water, the etchant comprises approximately 7.5 gm of potassium ferric cyanide [K3Fe(CN)6 at 0.5 Mol/1], and the first and second complexing agents comprise approximately 1.25 gm of oxalic acid [(COOH)2 at 0.2 Mol/1].
That is, particularly in the case of semiconductor structures comprising gallium and epitaxial layers comprising zinc, oxalic acid is a preferred complexing agent. Indeed, it is believed that oxalic acid can be used for the first and second complexing agents because it takes up not only gallium ions [Ga3+], but also zinc ions [Zn2+]. In the former
action, gallium oxalate is formed, this compound being substantially soluble in water so that additional gallium ions can be etched by the etchant. In the latter action, zinc oxalate is formed, this compound being highly insoluble in water so that the above-described equilibrium is established without significant etching of the epitaxial layer. It is believed that other oxalate-providing complexing agents may also be used, including zinc oxalate, gallium oxalate and ammonium oxalate, each without departing from the principles of the invention. It is to be recognized, however, that use of these other oxalate-providing complexing agents generally may implicate additional changes in the etching composition. In this embodiment, the results were obtained using an acidity adjustment agent comprising ammonium hydroxide [NH4OH] in an amount calculated to adjust the pH to a selected level. This acidity adjustment agent was also found to bring undissolved oxalic acid into solution.
For example, it has been determined that, at room temperature (approximately 25°C), by adding ammonium hydroxide [NH4OH] to establish the pH within a range of approximately 7.0 to 8.0, the etching composition yields a relatively optimized etch rate, e.g., O.45 μm per minute, for a substrate comprising gallium arsenide [GaAs], while maintaining at substantially zero the etch rate for an epitaxial layer comprising zinc selenium sulfide [ZnSeS]. By comparison, in the absence of the first complexing agent, the etch rate of a gallium arsenide substrate has been found to be approximately only a few microns per hour.
The following describes the chemistry of this example. In an aqueous solution, the potassium ferric cyanide [K3Fe(CN)6] etchant dissociates, as follows: K3Fe(CN)6 3K+ + Fe(CN)6 3"
The Fe(CN)6 3\ so formed, reacts with gallium arsenide [GaAs] as follows: 6Fe(CN)6 3' + GaAs ≠ 6Fe(CN)6*- + Ga3+ + As3+
However, Ga3+ is almost insoluble as Ga(OH)3. The addition of oxalic acid [COOH)2] forms gallium oxalate which has a solubility of approximately 0.15 mol/1 at pH = 8. Moreover, when ammonium hydroxide [NH„OH] is added to the solution, gallium ammonium oxalate is formed, which has a solubility of approximately 0.27 mol/1 at pH=8.
The following table summarizes experimental results obtained when etching a semiconductor structure comprising a gallium arsenide [GaAs] substrate and a zinc
selenium sulfide [ZnSeS] epitaxial layer. The results reflect stagnant etching at room temperature (approximately 25 °C) using the etching composition of the above-described first embodiment, together with an acidity adjustment agent comprising ammonium hydroxide [NH4OH] added in an amount calculated to adjust the pH to selected levels.
Vtlcll-ZnSeS V^-GaAs
EH (A/min) ( /min) 4.1 0 0.25
5.1 0 0.36 6.1 0 0.25
7.2 0 0.45
8.0 0 0.45
8.5 5 0.45
9.0 40 0.45
Etching performed in other then stagnant application accelerates the etch rate of gallium arsenide substrate, without changing the etch rate of the zinc-compound epitaxial layer. In particular, it has been determined mat stirring can increase the etch rate of gallium arsenide substrate approximately three-fold. Other mechanical operations, such as agitation, are thought to have similar results.
In a second specific embodiment, it has been determined that acceptable etch results are achieved in etching a semiconductor structure having a gallium arsenide substrate and a zinc selenium sulfide epitaxial layer, the following etching composition being employed: the solvent comprises approximately 50 ml of water, the etchant comprises approximately 7.5 gm of potassium ferric cyanide [K3Fe(CN)6], and the first and second complexing agents comprise approximately 1.5 gm of tartaric acid [C4H6O6].
That is, particularly in the case of semiconductor structures comprising gallium and epitaxial layers comprising zinc, tartaric acid is a preferred complexing agent. Indeed, it is believed that tartaric acid can be used for the first and second complexing agents because it takes up not only gallium ions [Ga3+], but also zinc ions [Zn2+]. In the former action, gallium tartarate is formed, this compound being substantially soluble in water so that additional gallium ions can be etched by the etchant. In the latter action, zinc tartarate is formed, this compound being highly insoluble in water so that the above-described equilibrium is established without significant etching of the epitaxial layer.
It is believed that other tartarate-providing complexing agents may also be used, including zinc tartarate, gallium tartarate and ammonium tartarate, each without departing from the principles of the invention. It is to be recognized, however, that use of these other tartarate-providing complexing agents generally may implicate additional changes in the etching composition.
In this second embodiment, the results were obtained using an acidity adjustment agent comprising ammonium hydroxide [NH4OH] in an amount calculated to adjust the pH to a selected level. This aspect of the etching composition is described above and, therefore, is not repeated here. It has been determined that, using the two embodiments, a temperature increase from room temperature to approximately 50 °C increases the etch rate as to a gallium arsenide [GaAs] substrate while not appreciable affecting the etch rate of a zinc selenium sulfide [ZnSeS] epitaxial layer. Using the first embodiment of the etching composition, it has been determined that elevating the temperature to approximately 50°C results in an etch rate of approximately lμm/min for the substrate, while maintaining the etch rate of the zinc selenium sulfide [ZnSeS] at approximately OA/min. Moreover, using the second embodiment of the etching composition, it has been determined that the etch rate of such an epitaxial layer remains acceptably low even where this etch is performed at a temperature of approximately 65 °C. It is to be recognized, however, that the temperature at which the etch occurs generally will have some optimum range, the range being factors dependent. The factors can include, for example and without limitation, the type of substrate, the desired etch rate of the substrate, the type of epitaxial layer or layers, and the level of acceptable epitaxial layer damage.
Turning to Figure 2, a flow chart is shown of a method for etching a semiconductor structure having a substrate and one or more epitaxial layers is, the etching composition and method being in accordance with the invention. The method comprises the steps of selecting a solvent, an etchant, and first and second complexing agents; mixing these elements to form a solution; immersing a portion of the semiconductor structure in the solution, whereby the substrate of that portion is preferentially etched with respect to the portion's epitaxial layers.
In this method, the etching composition preferably is substantially similar to that described above, including employment of an acidity adjustment agent. The acidity adjustment agent preferably is added after mixing the solvent, the etchant and the first and second complexing agents, and before immersion of the substrate. In this manner, the mixed
components are brought fully into solution and the acidity of the solution is established prior to immersion. One advantage of this order is that the etch of the substrate is subject to greater control.
Moreover, the method preferably comprises the step of selecting whether or not to operate mechanically on at least one of the solution or the semiconductor structure while the portion of the semiconductor structure is immersed. As described above, this step, performed for example by stirring or agitating the etching composition, generally accelerates the etch rate of the substrate.
The method also preferably comprises the step of selecting the temperature at which etching occurs. As described above, temperature generally affects the etch rate of the substrate while not causing any appreciable increase in the etch rate of the epitaxial layers.
While the invention has been described in connection with preferred embodiments, it will be understood that modifications thereof within the principles outlined above will be evident to those skilled in the art and thus the invention is not limited to the preferred embodiments but is intended to encompass such modifications.
Claims
1. A method of manufacturing a semiconductor device, whereby a semiconductor structure comprising a substrate and one or more epitaxial layers, is etched in an etching composition comprising a solvent and an etchant soluble in the solvent, the etchant having a redox potential intermediate between the redox potential of the substrate and the redox potential of at least one of the epitaxial layers so as to preferentially etch the substrate with respect to the at least one epitaxial layer; characterized in that the composition further comprises a first complexing agent soluble in the solvent, the first complexing agent being reactive with the substrate so as to accelerate the rate at which the etchant etches the substrate and a second complexing agent soluble in the solvent, the second complexing agent being reactive with a component of the at least one epitaxial layer so as to form a resulting compound with the component, the reaction being such that the resulting compound, the second complexing agent and the component exist in equilibrium in the solution so that the at least one epitaxial layer is etched in an amount that is not significant and that is substantially independent of the etching duration.
2. Method as in claim 1, characterized in that the composition further comprises an acidity adjustment agent soluble in the solvent, the acidity adjustment agent being selected so as to adjust the acidity of the solution, and thereby so as to adjust the etch rate of the substrate while maintaining the etching characteristics respecting the at least one epitaxial layer.
3 Method as in claim 2, characterized in that the acidity adjustment agent is ammonium hydroxide [NH4OH], the solvent is water and the acidity adjustment agent is added in an amount to adjust the pH to within a range of approximately 7.0 to 8.0.
4. Method as in claim 1-3, characterized in that the etchant is potassium ferric cyanide [K3Fe(CN)6].
5. Method as in claim 1-4, characterized in that the first and second complexing agents are oxalic acid, or tartaric acid.
6. Method as in claim 5, characterized in that first and second complexing agents are the same chemical compound.
7. Method as in claim 1-6, characterized in that the composition comprises approximately 50 ml of water, approximately 7.5 gm of potassium ferric cyanide [K3Fe(CN)6], approximately 1.25 gm of oxalic acid, and ammonium hydroxide [NH4OH]. 8 Method as claimed in claim 1-6, characterized in that composition comprises approximately 50 ml of water, approximately 7.5 gm of potassium ferric cyanide [K3Fe(CN)6], approximately 1.5 gm of tartaric acid, and ammonium hydroxide [NH4OH].
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9524144A JPH11502975A (en) | 1995-12-29 | 1996-12-09 | Preferential etching of semiconductor substrates for epitaxial layers |
| EP96939275A EP0815585B1 (en) | 1995-12-29 | 1996-12-09 | Preferential etch of semiconductor substrate with respect to epitaxial layers |
| DE1996633616 DE69633616D1 (en) | 1995-12-29 | 1996-12-09 | SELECTIVE ETCHING OF SEMICONDUCTIVE SUBSTRATE RELATING TO EPITACTIC LAYERS |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/581,233 US5756403A (en) | 1995-12-29 | 1995-12-29 | Method of preferentially etching a semiconductor substrate with respect to epitaxial layers |
| US08/581,233 | 1995-12-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1997024754A1 true WO1997024754A1 (en) | 1997-07-10 |
Family
ID=24324384
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/IB1996/001399 WO1997024754A1 (en) | 1995-12-29 | 1996-12-09 | Preferential etch of semiconductor substrate with respect to epitaxial layers |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5756403A (en) |
| EP (1) | EP0815585B1 (en) |
| JP (1) | JPH11502975A (en) |
| DE (1) | DE69633616D1 (en) |
| WO (1) | WO1997024754A1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6419554B2 (en) * | 1999-06-24 | 2002-07-16 | Micron Technology, Inc. | Fixed abrasive chemical-mechanical planarization of titanium nitride |
| JP3858888B2 (en) * | 2003-12-02 | 2006-12-20 | ソニー株式会社 | Etching method and semiconductor device manufacturing method |
| TWI363891B (en) * | 2006-11-14 | 2012-05-11 | Lg Display Co Ltd | Manufacturing method of the flexible display device |
| DE102007006151B4 (en) * | 2007-02-07 | 2008-11-06 | Siltronic Ag | A method of reducing and homogenizing the thickness of a semiconductor layer located on the surface of an electrically insulating material |
| CA2736927A1 (en) | 2008-10-03 | 2010-04-08 | Nestec S.A. | User-friendly interface for a beverage machine |
| AU2010317053B2 (en) | 2009-11-05 | 2015-07-02 | Nestec S.A. | Remote diagnosis of beverage preparation machines |
| AU2010101537A4 (en) | 2009-12-02 | 2016-04-14 | Nestec S.A. | Beverage preparation machine comprising an extended user-advisory functionality |
| US8876000B2 (en) | 2009-12-02 | 2014-11-04 | Nestec S.A. | Beverage preparation machine with touch menu functionality |
| WO2011067232A1 (en) | 2009-12-02 | 2011-06-09 | Nestec S.A. | Beverage preparation machine supporting a remote service functionality |
| JP2013512697A (en) | 2009-12-02 | 2013-04-18 | ネステク ソシエテ アノニム | Beverage preparation machine with card reader |
| ES2433084T3 (en) | 2009-12-02 | 2013-12-09 | Nestec S.A. | Beverage preparation machine with virtual purchase functionality |
| EP2507773A1 (en) | 2009-12-02 | 2012-10-10 | Nestec S.A. | Beverage preparation machine with ambience emulation functionality |
| JP5881683B2 (en) | 2010-05-21 | 2016-03-09 | ネステク ソシエテ アノニム | Ergonomic dispenser interface |
| ES2474593T3 (en) | 2010-05-21 | 2014-07-09 | Nestec S.A. | Beverage machine with ergonomic water management |
| EP2571404B2 (en) | 2010-05-21 | 2017-10-25 | Nestec S.A. | Ergonomic handle & user-interface |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0617458A2 (en) * | 1993-03-19 | 1994-09-28 | Mitsubishi Denki Kabushiki Kaisha | Etching solution and etching method for semiconductor therefor |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3237235C2 (en) * | 1982-10-07 | 1986-07-10 | Wacker-Chemitronic Gesellschaft für Elektronik-Grundstoffe mbH, 8263 Burghausen | Process for polishing III-V semiconductor surfaces |
| US5071510A (en) * | 1989-09-22 | 1991-12-10 | Robert Bosch Gmbh | Process for anisotropic etching of silicon plates |
| CA2028899C (en) * | 1989-10-31 | 1997-03-04 | Teturo Ijichi | Semiconductor laser elements and method for the production thereof |
| US5015346A (en) * | 1990-04-10 | 1991-05-14 | United States Department Of Energy | Electrochemical method for defect delineation in silicon-on-insulator wafers |
| US5110765A (en) * | 1990-11-30 | 1992-05-05 | At&T Bell Laboratories | Selective etch for GaAs-containing group III-V compounds |
| US5279704A (en) * | 1991-04-23 | 1994-01-18 | Honda Giken Kogyo Kabushiki Kaisha | Method of fabricating semiconductor device |
| JP3135185B2 (en) * | 1993-03-19 | 2001-02-13 | 三菱電機株式会社 | Semiconductor etching solution, semiconductor etching method, and method for determining GaAs surface |
| US5811839A (en) * | 1994-09-01 | 1998-09-22 | Mitsubishi Chemical Corporation | Semiconductor light-emitting devices |
-
1995
- 1995-12-29 US US08/581,233 patent/US5756403A/en not_active Expired - Fee Related
-
1996
- 1996-12-09 JP JP9524144A patent/JPH11502975A/en not_active Abandoned
- 1996-12-09 EP EP96939275A patent/EP0815585B1/en not_active Expired - Lifetime
- 1996-12-09 DE DE1996633616 patent/DE69633616D1/en not_active Expired - Fee Related
- 1996-12-09 WO PCT/IB1996/001399 patent/WO1997024754A1/en active IP Right Grant
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0617458A2 (en) * | 1993-03-19 | 1994-09-28 | Mitsubishi Denki Kabushiki Kaisha | Etching solution and etching method for semiconductor therefor |
Non-Patent Citations (1)
| Title |
|---|
| PATENT ABSTRACTS OF JAPAN, Vol. 10, No. 386, E-467; & JP,A,61 176 122 (FUJITSU LTD), 7 August 1986. * |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH11502975A (en) | 1999-03-09 |
| DE69633616D1 (en) | 2004-11-18 |
| EP0815585A1 (en) | 1998-01-07 |
| US5756403A (en) | 1998-05-26 |
| EP0815585B1 (en) | 2004-10-13 |
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