JP4580258B2 - Etching composition and etching method - Google Patents

Description

  The present invention relates to a composition for etching hafnium compounds such as hafnium silicate and hafnium aluminate, and more particularly, a hafnium silicate used for semiconductor devices, a composition for etching hafnium aluminate, and a substrate, particularly on a silicon wafer. The present invention relates to a substrate etching method for etching a film made of a hafnium compound.

  In recent years, with the rapid development of information technology, there has been a trend toward large-scale integrated circuits (LSIs, ULSIs, VLSIs) that are miniaturized, densified, and highly integrated, and therefore new materials have been introduced. It is being considered. Along with miniaturization, the insulating film is also thinned, which is a limit in the conventionally used silicon oxide insulating film. Therefore, a so-called High-k material has been studied as a new insulating film. As high-k materials, aluminum oxide, zirconium oxide, and hafnium oxide are candidates, but hafnium silicate and hafnium aluminate are regarded as the most promising.

  In order to finely process a semiconductor circuit, it is necessary to etch after forming these hafnium oxide, hafnium silicate, and hafnium aluminate insulating films. However, hafnium oxide, hafnium silicate, etc. are compounds that cannot be etched easily even with hydrofluoric acid, and these insulating films can be etched at a practical rate without attacking other fragile semiconductor materials. Was very difficult.

  So far, as a method for removing hafnium silicate, for example, an aqueous solution containing hydrofluoric acid and nitric acid has been proposed (Patent Document 1). However, this solution has a problem that the etching performance of hafnium silicate and hafnium aluminate is not always sufficient, and other semiconductor materials (especially silicon oxide) in the vicinity are seriously damaged. An etching solution in which hydrofluoric acid is diluted with an organic solvent has also been proposed (Patent Document 2). However, since this liquid is mostly an organic solvent, it is highly flammable, and it is necessary to make the semiconductor manufacturing apparatus an explosion-proof structure, which is not industrially preferable.

Thus, an optimum etching agent that can sufficiently and selectively process hafnium oxide, hafnium silicate, hafnium aluminate, and the like, which are regarded as promising as semiconductor high-k materials, has not been proposed yet.
JP 2003-229401 A JP 2003-332297 A

  In view of the above problems, an object of the present invention is to provide a non-flammable etching composition that can selectively etch hardly soluble hafnium compounds, particularly hafnium silicate and hafnium aluminate.

As a result of intensive studies on the etching of hafnium silicate, hafnium nitride silicate, hafnium aluminate, and hafnium aluminate nitride, the present inventors have found that etching compositions containing fluorides and chlorides have other oxides such as silicon oxide. It has been found that hafnium silicate, hafnium aluminate, and the like can be selectively etched without damaging the semiconductor material and are nonflammable, and the present invention has been completed.
That is, the present invention is a hafnium silicate or hafnium nitride silicate etching composition comprising 0.1% by weight of ammonium fluoride, 10% by weight of hydrochloric acid and water. Further, 0.06 to 1.5% by weight of fluoride, which is at least one selected from the group consisting of hydrofluoric acid, ammonium fluoride, and hexafluorosilicic acid, and hydrochloric acid and / or ammonium chloride 10 An etching composition for hafnium silicate or nitrided hafnium silicate comprising -30% by weight chloride, 5-10% by weight phosphoric acid, and water.
Further, the above-described etching composition is used when etching a film made of hafnium silicate or nitrided hafnium silicate formed on a substrate.

The etching composition of the present invention can selectively etch hafnium compounds without damaging other semiconductor materials such as silicon oxide, and is nonflammable, so it can be used industrially safely. it can.
In addition, when etching a substrate having a film made of a hafnium compound formed on the surface using the etching composition of the present invention, the hafnium is selectively removed without damaging other semiconductor materials such as silicon oxide. The compound can be etched.

The present invention is described in further detail below.
The fluoride contained in the etching composition of the present invention is preferably at least one selected from the group consisting of hydrofluoric acid, ammonium fluoride, and silicon fluoride. Among these fluorides, ammonium fluoride and silicon fluoride are particularly useful because they cause little damage to the semiconductor material.

  As silicon fluoride used in the etching composition of the present invention, silicon tetrafluoride and hexafluorosilicic acid are particularly preferable. Silicon tetrafluoride is used as a gas, and hexafluorosilicic acid is used as an aqueous solution. These etching compositions containing silicon fluoride can etch hafnium silicate, hafnium aluminate, and the like without damaging other semiconductor materials, particularly silicon and silicon oxide.

  In the etching composition of the present invention, industrially distributed silicon tetrafluoride may be used, or a product produced by reacting silicic acid with hydrofluoric acid may be used. As the hexafluorosilicic acid, one that is commercially available may be used, or one produced by reacting silicon tetrafluoride with water may be used.

  The chloride contained in the etching composition of the present invention is preferably hydrochloric acid and / or ammonium chloride. Other chlorides may be used, but they are not suitable industrially because they are expensive or contain elements that are not suitable for semiconductor manufacturing processes.

  In the etching composition of the present invention, the fluoride content is 0.001 to 10% by weight, preferably 0.01 to 5% by weight, based on the weight of the entire etching composition. If the amount of fluoride is less than 0.001% by weight, the etching rate of the hafnium compound is so slow that it is not industrial, and if the amount of fluoride exceeds 10% by weight, other semiconductor materials are likely to be damaged.

  In the etching composition of the present invention, the chloride content is 0.1 to 70% by weight, preferably 0.1 to 60% by weight, based on the weight of the entire etching composition. If the amount of chloride is less than 0.1% by weight, there is no effect of chloride. If it exceeds 70% by weight, the chloride will not dissolve in the aqueous solution, and even if it exceeds 70% by weight, The improvement in the etching rate of the hafnium compound is small.

  Phosphoric acid can also be added to the etching composition of the present invention. By adding phosphoric acid, the etching rate of hafnium silicate, hafnium aluminate, etc. is improved. The phosphoric acid that can be used is preferably at least one selected from the group consisting of polyphosphoric acids such as orthophosphoric acid, metaphosphoric acid, and pyrophosphoric acid. Although there is no restriction | limiting in particular in content of phosphoric acid, The range of about 1 to 50 weight% is preferable. If it is less than 1% by weight, the effect of adding phosphoric acid is small, and if it exceeds 50% by weight, the improvement in hafnium etching rate is small.

  The etching composition of the present invention can be used as an aqueous solution of fluoride or chloride. Although there is no restriction | limiting in particular in content of water, The range of about 10 to 99 weight% is preferable. Even if the amount of water is less than 10% by weight or more than 99% by weight, the etching rate of the hafnium compound decreases.

  Further, the etching composition of the present invention may contain an organic substance used for the purpose of removing unnecessary organic substances and inorganic substances in the semiconductor manufacturing process. Examples of such organic substances include alcohols, amides, amines, nitriles, carboxylic acids and the like. Since the flammability differs depending on the compound, it is difficult to determine the content of the organic substance, but it is preferable to adjust the content to a range that does not show a flash point.

  The temperature at which the hafnium compound is etched using the etching composition of the present invention is 0 to 100 ° C., preferably 10 to 90 ° C. Below 0 ° C., the etching rate of the hafnium compound is unrealistically low, and at temperatures above 100 ° C., the concentration of water is not constant because of the evaporation of water, which is not industrial.

  The etching composition of the present invention can be used for etching hafnium compounds, particularly for etching hafnium silicate, hafnium nitride silicate, hafnium aluminate, and hafnium aluminate used as an insulating film of a semiconductor device. In semiconductor devices, hafnium compounds are used as so-called High-k materials. A hafnium compound is formed on a semiconductor substrate by a CVD method (chemical vapor deposition) or the like, but it is necessary to remove unnecessary portions by etching in order to form elements and circuits. By using the etching composition of the present invention, these hafnium compounds can be etched without damaging other semiconductor materials such as silicon oxide.

Next, a method for etching a substrate, for example, a silicon wafer, using the etching composition of the present invention will be described with reference to FIGS.
FIG. 1 is a main part schematic front view showing an example of the configuration of a single wafer processing apparatus.
The substrate processing apparatus includes a wafer holding unit 10 that holds a silicon wafer W having a film made of a hafnium compound on its surface in a horizontal posture, and a rotary support shaft 12 that is suspended from the center of the lower surface of the wafer holding unit 10. It has.
The wafer holding unit 10 is rotated in the horizontal plane around the vertical axis by a spin motor (not shown) connected to the rotation support shaft 12. The wafer W held on the wafer holding unit 10 is configured to rotate integrally with the wafer holding unit 10. Although not shown, a cup is disposed around the wafer holding unit 10 so as to surround the side and the lower side of the wafer holding unit 10, and the cup scatters from above the wafer W to the surroundings. Etching solution that flows down or down is collected and collected.

  Above the wafer W held by the wafer holder 10, a nozzle 14 for supplying an etching solution to the upper surface of the wafer W is disposed. The nozzle 14 is connected to an etching solution supply device (not shown) through an etching solution supply pipe. Further, the nozzle 14 can be retreated to the outside of the substrate from the illustrated position, and if necessary, can be swung in a horizontal plane so that the tip discharge port is located between the center position and the peripheral position of the wafer W. Are supported so that the upper surface of the wafer W can be scanned.

  In the substrate processing apparatus having such a configuration, as an etching solution supplied from the etching solution supply device to the nozzle 14, fluorides such as hydrofluoric acid, ammonium fluoride, and silicon fluoride, and hydrochloric acid, ammonium chloride, and the like. The above-mentioned etching composition comprising the above chloride is used. When etching the wafer W by this substrate processing apparatus, the etching liquid is discharged from the tip discharge port of the nozzle 14 to the center of the upper surface of the wafer W while rotating the wafer W around the vertical axis. Is diffused and flowed over the entire upper surface of the wafer W. As a result, the hafnium compound film formed on the wafer W is selectively etched with an etchant containing fluoride and chloride. And the film which consists of other materials, such as a silicon oxide formed in the surface of the wafer W, does not receive a damage.

  When the etching process is completed, the upper surface of the wafer W is cleaned by supplying a cleaning liquid such as pure water to the center of the upper surface of the wafer W while rotating the wafer W around the vertical axis. At this time, if necessary, a cleaning liquid to which ultrasonic waves have been applied is supplied to the wafer W, or a mixed fluid (cleaning liquid droplets) of the cleaning liquid and an inert gas such as nitrogen is supplied to the wafer W using a two-fluid nozzle. Or spout to the top of When the cleaning process for the wafer W is completed, the wafer W is rotated at a high speed and spin-dried.

FIG. 2 is a schematic diagram illustrating an example of the configuration of an immersion type substrate processing apparatus.
The substrate processing apparatus includes a processing tank 18 that is open at the top and stores an etching solution 16. An etching solution supply port 20 is formed in the lower portion of the processing tank 18. An overflow liquid tank 22 into which an etching solution overflowing from the upper part of the processing tank 18 flows is integrally provided on the upper outer periphery of the processing tank 18. In addition, this apparatus includes a lifter 24 that holds a plurality of silicon wafers W, on which a film made of a hafnium compound is formed, in the processing tank 18, and the plurality of wafers W are held by the lifter 24. Are inserted into the processing tank 18 and discharged from the processing tank 18.

An etching solution supply pipe 26 communicates with and is connected to the etching solution supply port 20 of the processing tank 18, and the etching solution supply pipe 26 is connected to a discharge port of a pump 28. The etching solution supply pipe 26 is provided with a filter 30 and a heater 32, respectively. Further, an outflow pipe 34 communicates with the bottom of the overflow liquid tank 22, and the outflow pipe 34 branches into an etching liquid circulation pipe 36 and a drain pipe 38. Open / close control valves 40 and 42 are inserted in the liquid pipe 38, respectively. The etchant circulation pipe 36 is connected to the suction port of the pump 28.
Normally, the opening / closing control valve 40 is opened and the opening / closing control valve 42 is closed, and the etching solution discharged from the processing tank 18 through the overflow liquid tank 22 is etched through the etching liquid circulation pipe 36. The liquid is returned to the liquid supply pipe 26, is supplied again into the processing tank 18 through the etching liquid supply pipe 26, and is circulated. Further, the etching solution is heated by the heater 32 as necessary while circulating the etching solution through the etching solution supply pipe 26, the processing tank 18, and the etching solution circulation pipe 36.

In the substrate processing apparatus having such a configuration, as the etching solution 16 supplied into the processing tank 18, fluorides such as hydrofluoric acid, ammonium fluoride, and silicon fluoride, and hydrochloric acid, ammonium chloride, and the like are used. The above etching composition comprising chloride is used. Then, a plurality of wafers W are immersed in the etching solution 16 stored in the processing tank 18 for a predetermined time, so that the etching solution containing fluoride and chloride is made of another material such as silicon oxide. The hafnium compound film on the wafer W is selectively etched without damaging the film.
In addition, when the etching composition of the present invention is used to etch a hafnium compound, the etching may be promoted by using ultrasonic waves or the like.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In order to simplify the notation, the following abbreviations were used.
SiF: Silicon fluoride (produced by reacting silicic acid with hydrofluoric acid)
AF: ammonium fluoride HCl: hydrochloric acid HF: hydrogen fluoride AC: ammonium chloride PA: phosphoric acid (orthophosphoric acid)
IPA: 2-propanol HfSiOx: Hafnium silicate HfSiONx: Hafnium nitride silicate SiOx: Silicon oxide SiN: Silicon nitride

Examples 1-15, Comparative Examples 1-3
A silicon wafer substrate in which HfSiOx and HfSiONx are formed to a thickness of 10 nm by CVD (chemical vapor deposition), a silicon substrate in which a thermal oxide film (SiOx) is formed to a thickness of 300 nm, and silicon in which SiN is formed to a thickness of 100 nm The board | substrate was each immersed in the composition for an etching of Table 1 put into the polyethylene container (immersion for 10 minutes). Then, after washing with water and drying, the film thicknesses of HfSiOx, HfSiONx, SiOx, and SiN before and after immersion were measured with an optical film thickness measuring device to determine the etching rate. In the composition shown in Table 1, the balance is water.
Moreover, when the flash points of the etching solutions of Examples 1 to 15 and the etching solutions of Comparative Examples 1 to 3 were measured, the etching solutions of Examples 1 to 15 and Comparative Example 1 had no flash point, but Comparative Example 2 The flash point of the etching solution was 12 ° C.

It is a principal part schematic front view which shows an example of a structure of the single wafer type substrate processing apparatus which performs the etching process of a board | substrate using the etching composition of this invention. It is the schematic which shows an example of a structure of the immersion type substrate processing apparatus which performs the etching process of a board | substrate using the etching composition of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Wafer holding part 12 Rotating spindle 14 Nozzle 16 Etching liquid 18 Processing tank 20 Etching liquid supply port 22 Overflow liquid tank 24 Lifter 26 Etching liquid supply pipe 28 Pump 30 Filter 32 Heater 34 Outflow pipe 36 Etching liquid circulation pipe 38 Drainage pipe 40 Open / close control valve 42 Open / close control valve W Silicon wafer

Claims (5)

A composition for etching hafnium silicate or nitrided hafnium silicate comprising 0.1% by weight of ammonium fluoride, 10% by weight of hydrochloric acid and water. 0.06 to 1.5% by weight of fluoride which is at least one selected from the group consisting of hydrofluoric acid, ammonium fluoride and hexafluorosilicic acid, and 10 to 30 which is hydrochloric acid and / or ammonium chloride A composition for etching hafnium silicate or nitrided hafnium silicate, comprising: wt% chloride, 5 to 10 wt% phosphoric acid, and water. In a substrate etching method for etching a film made of hafnium silicate or nitrided hafnium silicate formed on a substrate using an etching composition,
A method for etching a substrate, comprising using, as the etching composition, a composition comprising 0.1% by weight of ammonium fluoride, 10% by weight of hydrochloric acid, and water. In a substrate etching method for etching a film made of hafnium silicate or nitrided hafnium silicate formed on a substrate using an etching composition,
As the etching composition, at least one selected from the group consisting of hydrofluoric acid, ammonium fluoride, and hexafluorosilicic acid, 0.06-1.5 wt% fluoride, hydrochloric acid and / or chloride. A method for etching a substrate, comprising using a composition comprising 10 to 30% by weight of ammonium chloride, 5 to 10% by weight of phosphoric acid, and water.   The substrate etching method according to claim 3 or 4, wherein the etching composition is supplied to a surface of the substrate while the substrate is held in a horizontal posture and rotated around a vertical axis.

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