JP4565480B2 - Dry etching method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for performing stable dry etching by preventing generation of contaminants inside an etching apparatus in dry etching of a solid thin film. In particular, HI (hydrogen iodide) gas, HBr (hydrogen bromide) gas, Cl₂In dry etching of an indium compound thin film using (chlorine) gas, the present invention relates to a method for performing stable dry etching of an indium compound thin film by preventing generation of contaminants inside the etching apparatus.
[0002]
[Prior art]
An indium-tin oxide (hereinafter referred to as ITO) thin film, which is representative of an indium compound thin film, is used as a pixel electrode of a liquid crystal display, but needs to be patterned in order to provide a predetermined area and shape. . Currently, wet etching methods using acids such as hydrochloric acid, oxalic acid, ferric chloride, etc. are mainly used, but the need for further fine processing has arisen in response to the demand for higher definition of liquid crystal displays. Yes.
[0003]
In response to the demand for higher definition, it is currently expected that the processing width, which is about several μm, will need to be reduced to about 1 μm. It is extremely difficult. Therefore, it is expected that a dry etching process will be used as used in the manufacture of LSI.
[0004]
The dry etching of ITO is caused by plasma by using a capacitively coupled 13.56MHz high frequency power supply and setting a substrate to be etched on the applied electrode, and by self-bias voltage formed by discharge. The RIE (Reactive Ion Etching) method in which the etching reaction is advanced by inducing ions to the substrate and promoting the chemical reaction is the mainstream.
[0005]
When HI gas is used for dry etching of ITO, it is known that an RIE type apparatus can be used to achieve an etching rate exceeding 1000 Å / min, and a clean etching process that does not leave any residue on the substrate can be achieved. It can be said that this is an excellent etching method. The dry etching of ITO using HI has been introduced in many documents so far and is well known. For example, J. Electrochem. Soc., Vol. 136, No. 6, June 1989 p1839 describes the dry etching characteristics of ITO using HI. In Sputtering & Plasma Processes Vol.11 No.5 held on December 11, 1996, many reports on dry etching of ITO using HI gas have been made. Further, a method is disclosed in which not only HI gas alone is used for dry etching of ITO, but also other gases are mixed and used. For example, Japanese Patent Laid-Open No. 5-251400 discloses a method of using an HI gas mixed with an etching species or hydrogen gas. In JP-A-6-151380, although it is a batch etching method with an Al thin film, BCl_ThreeA method using a mixed gas with a gas is disclosed. Further, JP-A-8-97190 discloses a dry etching method for ITO by mixing with Ar gas. Although the dry etching method of ITO using HI gas has excellent characteristics, it is also a fact that it has a problem that contaminants adhere to the inner wall of the chamber.
[0006]
Further, as a gas used for dry etching of ITO, etching using not only HI gas but also other gases has been studied. A method using chlorine gas, a method using hydrogen bromide (HBr) gas, and the like have been proposed. Lam Resarch Corp. has reported on etching of ITO using HBr gas using ICP discharge in the content published in the May issue of Solid State Technology 1996. However, these gases also have a problem that residues remain on the inner wall of the chamber, like the HI gas.
[0007]
As a gas used for dry etching of ITO, methane (CH_FourGas and hydrogen or chlorine (Cl₂) Has been proposed. The above-mentioned Sputtering & Plasma Processes Vol.11 No.5 also discloses an ITO dry etching method using methane gas. When methane gas is used, there is a problem that by-products remain on the substrate to be etched.
[0008]
[Problems to be solved by the invention]
As described above, the dry etching method for ITO has a problem in that contaminants adhere to the inner wall of the chamber even if the etching gas to be used is selected so that no residue remains on the substrate to be etched. It is also true that This is The 20 It is also reported in th Symposium on Dry Process p123. Therefore, in order to achieve a higher yield and operating rate, it is an issue that must be solved by all means to prevent contaminants from adhering to the inner wall of the chamber. The 20 It is shown in th Symposium on Dry Process p123. However, the previous method is a method using nitrogen trifluoride gas, and it has been desired to develop a method for suppressing the formation of pollutants without using another kind of gas.
[0009]
Problems to be solved by the present invention are HI gas, HBr gas, Cl₂An object of the present invention is to provide a fundamental method for continuously performing dry etching without generating contaminants generated in dry etching of an indium compound thin film such as ITO using gas in an etching chamber. This method gives a solution by finding a fundamental solution to suppress the adhesion of pollutants while examining the origin of pollutants generated by dry etching of ITO using HI gas. There is.
[0010]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors have conducted intensive studies in consideration of the surface material of the chamber inner wall and the operating conditions during etching, and the like. The inventors have found a method that allows dry etching to proceed without forming a substance.
[0011]
That is, the present invention
(A) In dry etching of a solid material using an etching gas,
Use a material with a specific surface area of 5 or less for the inner wall material of the chamber, and perform the etching under the condition that the water vapor pressure in the chamber is kept at 0.003 Pa or lower with the chamber inner wall heated at 80 ° C or higher. It relates to a dry etching method,
(B) The chamber inner wall material is a transition metal, a silicon metal or an oxide, nitride, or carbide of a transition metal and a silicon metal, and relates to the dry etching method according to (A),
(C) The dry etching method according to (A) or (B), wherein the solid material is an indium compound.
(D) The etching gas is one of hydrogen iodide gas, hydrogen bromide gas, and chlorine gas, and relates to the dry etching method according to any one of (A) to (C),
The dry etching method of ITO disclosed by the present invention can be applied to an RIE type or ICP type etching apparatus which is performed by applying a high frequency electric field of 13.56 MHz. It can also be used for an ECR type apparatus.
In the case of an RIE type apparatus, it is usual to use an apparatus in which a discharge is formed between an applied electrode (cathode electrode) and a counter electrode (anode electrode), but the counter electrode is grounded. In some cases, it is common to place the substrate on the applied electrode side. Further, in the case where a bias voltage (which may be applied by high frequency) is applied to the counter electrode, a substrate may be provided on the counter electrode side. The frequency of the applied electrode used for dry etching of the indium compound thin film including RIE type ITO disclosed in the present invention is 5 MHz or more and 200 MHz or less, and covers the range of so-called RF discharge to VHF discharge. The frequency in the case of using the ICP type discharge is within the range of 1 MHz to 100 MHz on the applied electrode side.
[0012]
The inventors have determined that the basic substance constituting the pollutant is InI_Three(M. Sadamoto et.al. The 20th symposium on dry process p123). As a result of further intensive studies, this InI_ThreeAs a result of repeated experiments and discussions on the mechanism of how molecules adhere to the inner wall surface of the chamber, we have succeeded in obtaining strong evidence that suggests that the presence of water molecules is the origin of depot generation. Invented.
[0013]
The dry etching of ITO using HI is usually performed in the range of about 4 to 10 Pa. At this time, the temperature of the inner wall of the chamber is about 20 ° C. when the minimum temperature is taken into consideration, but it is usually raised to about 40 ° C. due to the influence of plasma. InI_ThreeHas a very high value of about 1000 Pa at 20 ° C., and considering the vapor pressure data, it is unlikely that the vapor pressure adheres to the inner wall of the chamber.
[0014]
The inventors paid attention to the water present in the chamber, and investigated the use of a polymer material as the inner wall material under conditions of high and low water vapor pressure existing in the chamber. As a study condition, the surface material temperature is controlled between 25 ° C and 120 ° C, and at the same time, the water vapor pressure existing on the inner wall of the chamber is examined under different conditions. I was able to find.
[0015]
As a result of intensive studies by these inventors, the following findings were obtained. It is also an important requirement that the specific surface area of the inner wall surface material is 5 or less. This specific surface area is also an index of the roughness of the material surface, but when the adsorption to the surface is considered, it is better to use the specific surface area as a reference. More preferably, the specific surface area is 3 or less, and most preferably 2 or less. This specific surface area is preferably used in a BET method using nitrogen gas. Furthermore, it has been found that the temperature of the inner wall surface material has the largest change in the amount of contaminants deposited, and the higher the temperature, the smaller the amount of contaminants deposited. Furthermore, it was also confirmed that there was a difference in the amount of pollutant generated due to the level of water vapor pressure. The lower the water vapor pressure, the smaller the amount of contaminants attached to the inner wall surface material. It was confirmed that the surface temperature and the water vapor pressure in the chamber were strongly influenced by the material used for the inner wall. That is, it was also confirmed that the roughness of the surface has a great influence on the water vapor pressure, and in turn causes a large difference in the amount of the pollutant deposited. That is, it was confirmed that the adhesion amount of pollutants tends to decrease under high temperature and low water vapor pressure conditions, and greatly decreases by making the chamber inner wall surface as smooth as possible.
[0016]
The material of the chamber usually used is SUS or aluminum whose surface is anodized, but recently, aluminum tends to be preferred from the viewpoint of weight reduction. However, the alumite-treated surface contains innumerable microscopic pores and naturally has an uneven shape. As a result, in addition to having a large surface area, alumite itself has a high affinity for water molecules, so that it can be said that there are many water molecules or O—H groups on the surface. Result, InI_ThreeSuch a substance having a high interaction with water, which is symbolized by exhibiting deliquescence, results in a large amount of adhesion to the anodized surface and can easily be expected to become a polluted substance.
[0017]
Therefore, by removing adsorbed water molecules from the chamber inner wall surface, InI_ThreeIt prevents molecular adsorption and subsequent chemical changes and thus prevents the formation of deposits. The inventors have found that it is preferable to reduce the water vapor pressure in the chamber as much as possible in order to reduce the amount of moisture present on the surface of the material and consequently reduce the amount of adhering contaminants, and complete the invention. succeeded in.
[0018]
Also, water molecules adsorbed on the surface are not necessarily only chemically adsorbed, but are often subject to physical adsorption based on van der Waals forces. In particular, physical adsorption plays a major role in the adsorption phenomenon at low temperatures. Therefore, in order to avoid the adsorption of water molecules, it is an important requirement to create conditions that prevent the physical adsorption of water molecules by heating the material surface.
[0019]
Therefore, the temperature of the chamber inner wall surface material needs to be heated to 80 ° C. or higher. More preferably, heating to 100 ° C. or higher is preferable. And it is more preferable to heat to 120 ° C. or higher. And most preferably, heating to 130 ° C. or higher is preferable. And these chamber heating needs to be performed on the pressure conditions of 0.004 Pa or less. Thus, by heating the inside of the chamber in a vacuum atmosphere, it is possible to greatly reduce the water molecules present on the inner wall of the chamber.
[0020]
As a result, it is desirable to reduce the water vapor pressure in the chamber before etching to 0.003 Pa or less, and more desirably to 0.002 Pa or less. Most preferably, even better results can be obtained if the pressure is reduced to 0.001 Pa or less. When the water vapor pressure in the chamber is low, the number of water molecules adsorbed on the wall surface is reduced, and as a result, adhesion of pollutants can be inhibited.
[0021]
However, even if the adsorbed moisture on the surface of the material is reduced, there is an unsuitable one in the sense of preventing adhesion of pollutants. The inner wall surface material has InI generated when dry etching of ITO is performed._ThreeIt is necessary that the molecule does not cause a reaction. On the other hand, it is difficult to say that a highly reactive metal material or the like is a preferable material. Moreover, it cannot be said that a substance that easily reacts with an etching gas used for etching is also preferable. For example, aluminum cannot be said to be preferable as the inner wall surface material. Aluminum itself is known to spontaneously react with chlorine gas to be removed by etching, and has high reactivity with a halogen-based gas, which is not preferable as an etching chamber material. For this reason, it is used after alumite treatment, but a method such as anodic oxidation for alumite treatment is used, but many fine pores are formed for this purpose, which significantly increases the surface area. Result. Since the inner wall of the chamber having a significantly increased surface area is in a state where a large amount of water vapor is adsorbed, the formation of pollutants is increased.
[0022]
Furthermore, it is a necessary requirement not only to be used as a surface material but also to have a low water absorption rate. The water absorption is preferably 1% or less, more preferably 0.8% or less. More preferably, it is 0.6% or less, and most preferably 0.4% or less.
[0023]
And it is necessary that these conditions are fused. That is, the water pressure inside the chamber is 0.004 Pa or less, the chamber inner wall surface material is 80 ° C. or higher, the material used for the chamber inner wall has a heat resistant temperature of 130 ° C. or higher, and the moisture content is 1%. It is the following. When all of these conditions are satisfied, the most effective case in the present invention is to suppress the adhesion of contaminants generated when hydrogen iodide gas is used for dry etching of ITO.
[0024]
Further, the chamber inner wall material is preferably made of a transition metal, silicon metal, transition metal or silicon metal oxide, nitride, or carbide. In particular, a material which is difficult to cause dry etching and which is difficult to be etched is a suitable material because reactivity with a pollutant is low. SUS or the like is a compound made of a transition metal such as iron, nickel, or chromium, and is suitable as a chamber inner wall material.
Carbon steel and the like are also suitable materials.
[0025]
Furthermore, ITO is expected to exert the highest effect as a solid material for dry etching, but the same effect was confirmed when etching other metals and oxides including indium. it can. For example, an oxide such as indium-zinc oxide, and a thin film such as indium-phosphorus as a semiconductor material can also be expected to have the same effect in the present invention.
[0026]
As an etching gas, hydrogen iodide gas can be expected to exhibit the highest effect, but a similar effect can be confirmed in an etching gas containing halogen. The same applies to hydrogen bromide gas containing bromine and chlorine gas containing chlorine. When etching indium compounds such as ITO using hydrogen bromide gas, indium tribromide (InBr_Three) Is the main etching product. When etching indium compounds such as ITO using chlorine gas, indium trichlorine (InCl_Three) Is the main etching product.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a diagram of an experimental apparatus used in the present invention. The apparatus of the present invention is composed of a normal RIE apparatus. Specifically, a chemical dry pump 12 and a turbo molecular pump 13 for exhaust are attached to the etching chamber 11 so that a high vacuum up to 0.002 Pa or less can be obtained. Since the electrode is an RIE type, it is composed of a parallel plate electrode, and is composed of an applied electrode 14 capable of supplying a high frequency power of 13.56 MHz and a counter electrode 15 which is grounded. A substrate having a solid material to be etched can be placed on the upper surface of the applied electrode. In this system, a glass plate and an ITO plate used as a sputtering target were used as etching objects. The apparatus used in the present invention is equipped with a partial pressure vacuum gauge sensor 23 and a partial pressure vacuum gauge main body 24, and can measure the water vapor pressure in the chamber as a pressure component corresponding to a mass number of 18. . The measured pressure can be read by the partial pressure gauge main body, but the pressure range that can be measured is 0.000001 Pa or more and 0.1 Pa.
[0028]
The etching gas is supplied from the counter electrode via the mass flow controller 20. Using this device, when etching an ITO thin film with a thickness of 10,000 mm set on a glass substrate under the conditions of HI gas 50 sccm, pressure 6.5 Pa, and RF output 100 W, 700 mm / sec or more in a temperature range from room temperature to 80 ° C. An etching rate of 1000mm / sec is obtained.
[0029]
In this experimental apparatus, it can be recognized that the pollutant 21 adheres to the inner wall of the chamber. However, the adhesion position is close to the plasma region formed in the part surrounded by the high-frequency electrode surrounded by two electrodes, and the generation of pollutants is not possible at a position more than 10 cm away from the plasma region. There are few if any.
[0030]
A test piece 17 is fixed to the inner wall of the chamber for the purpose of confirming the amount of pollutant generated. Further, the sample fixed to the inner wall of the chamber is provided with a planar heater 18 on the back surface, and the test piece can be heated and temperature controlled by this heater. These test pieces have a thickness of 1mm or less and an area of 4cm.²Within. This is because it is desirable to make the test piece itself as light as possible in order to accurately confirm the contaminants attached to the test piece by the gravimetric method. The electronic balance used for confirmation by the gravimetric method was Shimadzu semi-micro electronic analytical balance AEL-40SM manufactured by Shimadzu Corporation. Using this balance, it is possible to measure up to a weight of 0.001 mg.
[0031]
In addition, for the purpose of heating the entire chamber used for the test and controlling the temperature, the chamber temperature was uniformly controlled by the external heater 19. The temperature at which the control is performed by the external heater is the same as the temperature attached to the test piece, so that the pollutant is generated at the same conditions everywhere in the chamber.
[0032]
In order to examine whether or not the test piece is a material suitable for the inner wall material using such experimental equipment, the inventors set the surface temperature of the test piece as a parameter by controlling the temperature of the heater installed in the test piece. In addition, the adhesion amount of the pollutant was measured under the condition of water vapor pressure measured by a partial pressure vacuum gauge.
[0033]
In the experiment, an aluminum plate, an anodized aluminum plate, a SUS plate, a SiOx thin film formed by sputtering on the SUS plate was deposited (SiOx / SUS plate), and a quartz plate was examined. The result shown in 5 was obtained. FIG. 2 shows the amount of contaminants attached on the aluminum plate, FIG. 3 shows the amount of contaminants attached on the anodized aluminum plate, and FIG. 4 shows the amount of contaminants attached on the SUS plate. Furthermore, the amount of contaminants formed on the SiOx / SUS plate is shown in FIG. 5, and the amount of contaminants deposited on the quartz plate is shown in FIG.
[0034]
As shown in FIGS. 4, 5, and 6, when the adhesion amount of the pollutant is measured using the SUS plate, the SiOx / SUS plate, and the quartz plate as a test piece, the adherence amount of the pollutant decreases as the surface temperature increases. There was a trend. And in the temperature range of 80 degreeC or more, it turned out that a pollutant tends to fall with the fall of water vapor pressure. When the water vapor pressure is 0.004 Pa or less and the etching is continuously performed for 3 hours, the adhesion amount of the pollutant is 0.01 [mg / cm²It was confirmed that the level reached almost no problem. The specific surface area of the SUS plate was 3, and the specific surface area of the SiOx / SUS plate was 4.5. The specific surface area of the quartz plate was 1.8.
[0035]
On the other hand, the aluminum plate and the one using the anodized aluminum plate as the test piece showed a tendency significantly different from the case of using the SUS plate and the SiOx / SUS plate. In the case of using an aluminum plate, it was observed that the pollutant was reduced as the temperature increased, as in the case of using an SUS plate. No reduction was observed. Further, the weight of the anodized aluminum plate was greatly reduced by evacuation, but when the surface thereof was observed, the adhesion of pollutants could be clearly confirmed. Thus, the weight reduction of the alumite-treated surface material can be considered to be due to the detachment of the adsorbed component from the pores due to evacuation, and it can be predicted that the majority will be water molecules. Therefore, it can be judged that the aluminum plate which performed the aluminum and the alumite process is not a preferable material from a viewpoint of preventing adhesion of a pollutant. The specific surface area of each aluminum plate was 3, and the specific surface area of the aluminum plate subjected to the anodizing treatment was 30 or more. However, it is possible to judge that the amount of contaminants deposited can be kept low for a high-temperature condition of 80 ° C. or higher and a low water vapor pressure condition for an aluminum surface formed by depositing a SiOx thin film.
[0036]
These polymer materials may be used as they are for the inner wall material of the chamber, or may be deposited by some method. Further, it may be processed into a plate shape and installed as a protective plate on the inner wall of the chamber. The diagram shown in FIG. 7 is a schematic diagram of an apparatus for reducing pollutants. This apparatus uses a surface material with a planar heater mounted on the back surface and is mounted on the inner wall of the etching chamber. For example, when installing as a protective plate, a surface heater may be provided behind the protective plate.
[0037]
【Example】
Hereinafter, embodiments of the present invention will be described in detail.
A discharge was formed in a state where a glass substrate was placed on the applied electrode of a dry etching apparatus equipped with a capacitively coupled high-frequency electrode and an ITO plate used as a sputtering target was placed. The ITO plate used is of a square type with a side of about 5 cm. The plasma used for discharge is 13.56 MHz. Further, a 2 cm square SUS plate was used as a test piece inside the chamber. The surface temperature of the SUS substrate can be controlled by attaching the SUS substrate to the planar heater and separately controlling the temperature of the planar heater.
[0038]
After making these preparations, the inside of the chamber is evacuated and at the same time, the inside of the chamber is heated. Further, the temperature of the SUS substrate was also controlled independently to keep the temperature of the entire chamber and the SUS substrate constant. The evacuation was performed by connecting a turbo molecular pump and a chemical dry pump in series. The degree of vacuum obtained was set to 0.002 Pa or less. Furthermore, the partial pressure of water vapor was measured with a partial pressure gauge immediately before etching. The SUS substrate surface temperature and the water vapor partial pressure were individually controlled, and various studies were made as etching conditions. The water vapor partial pressure was controlled by the chamber vacuum time. When the partial pressure of water vapor is high, the time for evacuation prior to etching is short, and for a long time in order to lower the partial water vapor pressure.
[0039]
The gas used was HI gas manufactured by Mitsui Chemicals, and 50 sccm was supplied through the mass flow controller. The pressure when supplying HI gas is 6.5 Pa. The RF power to be input was 100W. Electrode area is 78.5cm²The resulting power density is 1.27 W / cm²It is a numerical value slightly higher than the input power density at the time of ITO etching generally used.
[0040]
The etching was continued for 3 hours. 3 hours later, vacuuming is performed for about 10 minutes, the HI gas in the chamber is exhausted sufficiently, the chamber is opened, and at the same time, the weight change before and after etching is measured using an electronic balance capable of measuring up to 0.001 mg. By doing so, the deposit amount was measured. The measurement results are shown in FIG. As a result, when the surface temperature of the test piece was set to 80 ° C. or higher and the water vapor partial pressure was set to 0.003 Pa or lower, it was confirmed that the adhesion amount of the pollutant was extremely low.
[0041]
【The invention's effect】
According to the present invention, deposits attached to the inner wall of the chamber can be reduced extremely effectively, contributing to greatly improving the productivity of dry etching of indium compound thin films using hydrogen iodide gas, hydrogen bromide gas, and chlorine gas. can do.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an experimental apparatus used in the present invention.
[Fig. 2] Experimental results of the amount of contaminants deposited on an aluminum plate when the surface material temperature and water vapor pressure are changed
FIG. 3 shows the experimental results of the amount of pollutant adhering on an aluminum plate subjected to alumite treatment when the surface material temperature and water vapor pressure were changed.
FIG. 4 shows the experimental results of the amount of pollutant adhering on the SUS plate when the temperature of the surface material and the water vapor pressure are changed.
FIG. 5 shows the experimental results of the amount of contaminants deposited on the SiOx / SUS plate when the surface material temperature and water vapor pressure are changed.
FIG. 6 shows the experimental results of the amount of pollutant adhering on the quartz plate when the temperature of the surface material and the water vapor pressure are changed.
FIG. 7 is a schematic diagram of an apparatus for reducing pollutants.
[Explanation of symbols]
11 Etching chamber
12 Chemical dry pump
13 Turbo molecular pump
14 High frequency electrode
15 RF counter electrode
16 Substrate to be etched or glass plate and ITO plate
17 Test piece
18 Test piece heater
19 Chamber external heater
20 Mass flow controller
21 Pollutant
22 Gate valve
23 partial pressure gauge sensor
24 partial pressure gauge
25 High frequency power supply
30 Surface material with a planar heater on the back

Claims (2)

In the dry etching of the solid material containing indium compound with an etching gas, the specific surface area in the inner wall of the chamber material Ri der 5 or less, a transition metal, silicon metal or transition metal oxide or silicon metal, nitride or carbide A dry etching method characterized in that etching is carried out using a material comprising the above, and heating the inner wall of the chamber at 80 ° C. or higher while maintaining the water vapor pressure in the chamber at 0.003 Pa or lower. 2. The dry etching method according to claim 1 , wherein the etching gas is any one of hydrogen iodide gas, hydrogen bromide gas, and chlorine gas.

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