Solution for electrochemical dissolution of silicon

FIELD: electronic engineering; treatment of semiconductor materials including semiconductor silicon wafers.

SUBSTANCE: proposed solution for electrochemical dissolution of silicon has ammonia chloride and urea used as solvent, their proportion being as follows, mass percent: ammonia chloride, 7 - 10; urea, 90 - 93. Provision is made for controlling rate of silicon etching at current output close to 100%.

EFFECT: ability of controlling silicon etching rate and of eliminating environmentally detrimental substances in solution.

1 cl

 

The invention relates to the electronics industry, in particular to the processing of semiconductor materials, and can be used in the processing of semiconductor wafers of silicon.

A known solution for the processing of semiconductor materials, primarily silicon, including a salt of hydrofluoric acid, nitric acid and metal salt of group 1B (French Patent 517308, CL SC, publ. 1968).

The disadvantage of the solution is relatively low removal rate of silicon, the instability of the solution in time, associated with the precipitation of the fluorides of copper and allow for uncontrolled corrosion of the surface due to temperature increase during processing, as well as impossibility of adequate etching the surface of a heterogeneous areas of silicon wafers.

Closest to the proposed solution is based on glycerol containing hydrofluoric acid or its salts (Efimov E.A., Erusalimsky IG Russ germanium and silicon. M Goschimizdat, 1963).

The disadvantage of this solution is that it contains poisonous substances, namely hydrofluoric acid.

A common disadvantage of the known solutions are difficult to conduct local and precision etching of silicon, expressed in dotted dissolution of the surface and the appearance of her various films PE the temporal composition, as well as the content in their composition of harmful and toxic substances such as fluoride and nitrogen compounds. During the chemical etching of the additional difficulties arise in connection with ekzotermicheskie process that leads to a dramatic and often unmanaged growth rate.

The objective of the invention is to provide controlled electrochemical dissolution of semiconductor silicon at high current output.

The technical result - the ability to control the etching rate of the semiconductor material when the output current is close to 100%, and exclusion from a solution of environmentally harmful substances.

This is achieved by the fact that the solution for the electrochemical dissolution of silicon containing salt and the solvent of organic origin, as salt includes ammonium chloride, and the solvent - urea in the following ratio, wt.%:

urea90-93
ammonium chloride7-10

Ammonium chloride and urea used in the proposed solution, are known compounds. Ammonium chloride is a salt of inorganic origin, which in the melt of urea can dissociate with the advent of ions. The appearance of chlorine ions and ammonium in raspravivshiy leads to lower resistance of the electrolyte and the possibility of improving the power flowing current during the etching of silicon. Urea is an organic compound, which is in the molten state manifests alkaline properties, which contributes to the dissolution of silicon and its oxides. The appearance of chlorine ions in the melt contributes during anodic etching of silicon for the formation of silicon tetrachloride (boiling temperature of 56.7° (C)that is removed from the treated surface due to the diffusion.

Removal of silicon depends almost only on the duration of the electrolysis process at a given current density obeys the law of Faraday, linking mass released or dissolved substances with the power of the flowing current and the time of his passing.

In the proposed solution, the electrochemical etching of silicon (n - and p-type) may be carried out at an anode current density within 5-10 A/DM2, the voltage of 5-10 V and a temperature of 150-160°C. Anode current output is from 90 to 100% in terms of tetravalent silicon.

Example 1. The solution-melt urea 100%, the ammonium chloride is missing. The current output of 60-70% at the current density of the silicon processing 5-10 A/ DM2.

Example 2. The solution-melt urea, wt.% - 93, ammonium chloride - 7. Output but current 100% at the current density of the silicon processing 5-10 A/DM2.

Example 3. The solution-melt urea, wt.% - 90, ammonium chloride - 10. The current output 100% at the current density clicks the processing of silicon 5-10 A/DM 2.

Example 4. The solution-melt urea, wt.% - 90, ammonium chloride - 10 at a current density of 5 A/DM2the current efficiency of 100%.

Example 5. The solution-melt urea, wt.% - 90, ammonium chloride - 10. At current density of 10 A/DM2the current efficiency of 100%.

When the current density is less than 5 A/DM2to decrease correspondingly the speed of the electrochemical dissolution of silicon. When the current density in excess of 10 A/DM2there complications during electrochemical dissolution of silicon associated with the slow removal of the etching products from treated surfaces.

In the absence in the solution of the melt of urea, ammonium chloride is sharply reduced the number of ions vector current, thereby increasing the resistance of the solution, the decrease in the rate of etching and current output, and the difficulty of removal from the surface of the silicon products of its dissolution. Therefore, when the content of ammonium chloride is less than 7% of the current output of dissolution of silicon is reduced to 60-70% with a corresponding high resistance solution. To improve the content of ammonium chloride over 10% impractical, since increasing the viscosity of the melt begins to impede inadvertent removal of the products of dissolution of silicon without stirring. The solution for electrochemical etching of semiconductor silicon can be used to conduct hostage etching silicon n - and p-type.

The solution for the electrochemical dissolution of silicon containing salt and the solvent of organic origin, characterized in that the quality of the salt includes ammonium chloride, and the solvent urea in the following ratio, wt.%:

urea90-93
ammonium chloride7-10



 

Same patents:

FIELD: technology for producing semi-penetrable membranes for molecular filtration of gas flows and for division of reaction spaces in chemical reactors.

SUBSTANCE: method for producing gas-penetrable membrane includes two-sided electro-chemical etching of monocrystalline plate made of composition AIIIBV of n conductivity type or of semiconductor AIV with width of forbidden zone E≥1,0 electron volts and alloying level 1017-1020 1/cm3. Modes of aforementioned etching are set, providing for generation of simultaneously porous layers, while etching process is performed until moment of spontaneous stopping of electro-chemical process and generation of solid separating layer of stationary thickness on given part of plate area, determined using sharp bend on the curve of temporal dependence of anode current.

EFFECT: gas membrane, produced in accordance to method, has increased penetrability for molecules of light gases and increased selectivity characteristics at room temperature.

2 cl, 3 dwg, 3 ex

The invention relates to a process for electrochemical treatment of semiconductor wafers and can be used to create silicon substrates with surfaces that are applicable as emitters ions in analytical instruments, in particular the mass-spectrometers

The invention relates to electronic equipment, namely the processes of electrochemical processing of semiconductor wafers, in particular to the operations of electropolishing and thinning of the plates, the formation of anodic oxide films or layers of porous silicon (forming a porous silicon includes several simultaneously occurring processes: electrochemical etching and polishing and anodic oxidation)

FIELD: technology for producing semi-penetrable membranes for molecular filtration of gas flows and for division of reaction spaces in chemical reactors.

SUBSTANCE: method for producing gas-penetrable membrane includes two-sided electro-chemical etching of monocrystalline plate made of composition AIIIBV of n conductivity type or of semiconductor AIV with width of forbidden zone E≥1,0 electron volts and alloying level 1017-1020 1/cm3. Modes of aforementioned etching are set, providing for generation of simultaneously porous layers, while etching process is performed until moment of spontaneous stopping of electro-chemical process and generation of solid separating layer of stationary thickness on given part of plate area, determined using sharp bend on the curve of temporal dependence of anode current.

EFFECT: gas membrane, produced in accordance to method, has increased penetrability for molecules of light gases and increased selectivity characteristics at room temperature.

2 cl, 3 dwg, 3 ex

FIELD: electronic engineering; treatment of semiconductor materials including semiconductor silicon wafers.

SUBSTANCE: proposed solution for electrochemical dissolution of silicon has ammonia chloride and urea used as solvent, their proportion being as follows, mass percent: ammonia chloride, 7 - 10; urea, 90 - 93. Provision is made for controlling rate of silicon etching at current output close to 100%.

EFFECT: ability of controlling silicon etching rate and of eliminating environmentally detrimental substances in solution.

1 cl

FIELD: electric engineering.

SUBSTANCE: invention relates to electric engineering equipment and may be used for application of coatings by electrochemical process. The device for one-side treatment of semiconductor plates comprises a galvanic bath with anode and a substrate holder with a set of electrode conducting contacts and support posts whereto a semiconductor plate is pressed. The device incorporates additionally a horizontal support frame with an angular flange and three needle-type stops with ring-like marks, the substrate holder being provided with a guiding angular recess and mounted on the support frame flange. Also, the device comprises the current source control unit and a system of forced mixing of electrolyte made up of a magnetic mixer with a shielding plate.

EFFECT: increased quality of galvanic treatment of semiconductor plates, simpler design of the device.

5 dwg

FIELD: technological processes.

SUBSTANCE: invention concerns selective membrane production for molecular gas mix filtering and can be applied in compact fuel cells. Method of gas-permeable membrane production includes vacuum sputtering of a metal displaying chemical stability in concentrated hydrogen fluoride solutions in anode polarisation conditions onto monocrystalline silicon plate in closed pattern, and further double-side electrochemical etching of the plate area limited by the mentioned closed pattern. Etching process is performed until its spontaneous cease determined by break of time function curve of anode current on the plate surface not covered by sputtered metal.

EFFECT: increased thickness homogeneity of solid monocrystalline filtering silicon layer, improved membrane durability at higher gas permeability.

31 cl, 9 dwg, 2 ex

FIELD: nanotechnologies.

SUBSTANCE: invention relates to the field of membrane technologies and industry of nanosystems, and may be used in production of micro- and nanofluid filters, biosensor devices, medical diagnostics instruments. Concept of the invention is as follows: in method for production of silicon microchannel membrane in monolithic framing, anode etching of single-crystal silicon plate of hole type with seed pits on surface in solution of electrolytes, containing ions of hydrogen and fluoride is interrupted with electric polishing and further removal of sacrificial microchannel membrane, afterwards anode etching is restored.

EFFECT: improved coefficient of transparency and mechanical strength of membranes, better operational characteristics and expanded assortment of items.

4 cl, 5 dwg, 2 ex

FIELD: physics.

SUBSTANCE: invention relates to membrane membrane technology and can be used to produce micro- and nano-fluid filters, biosensors, medical diagnosis devices, as well as in making elements of electro-optical converters and X-ray optics. In the method of producing a silicon microchannel matrix, anodic etching of a p-type microcrystalline silicon wafer with inoculating cavities on the surface in an aqueous solution of electrolytes which contains hydrogen and fluoride ions is carried out in conditions with time variation of electric current density according to a third-order hyperbolic law. An exponential law holds if a surfactant or alcohol is added to the solution. The law includes three fixed coefficients which depend on the type of solution of the electrolyte and structural parameters of the microchannel matrix.

EFFECT: improved operational characteristics of silicon microchannel matrices by endowing the microchannels with the required profile.

8 dwg

FIELD: machine building.

SUBSTANCE: proposed method comprises anode etching of single-crystal p-type silicon with seed holes on surface in solution of electrolytes containing ions of hydrogen and fluorine, stopping opened micro channels by plugs of silicon dioxide nanoparticles to perform low-temperature deposition of porous-silicon film on matrix continuous surface and produce channels from pores of said silicon in entire nanometre range.

EFFECT: decreased transverse sizes of channels, expanded range of products, lower costs.

7 cl, 6 dwg

FIELD: chemistry.

SUBSTANCE: in canal matrix in addition to plate of monocrystalline silicon of hole type with opened canals and deposited material on frontal surface of this plate intermediate dielectric layer of silicon dioxide is created and metal film is applied on the frontal surface of plate with opened canals which have specified diametrical dimension.

EFFECT: improvement of exploitation characteristics by introduction of electrodes and application of electrokinetic and electrophysiological control, which makes it possible to extend nomenclature of membrane equipment products based on biocompatible and highly technological silicon.

8 cl, 8 dwg

Up!