Process for treatment of semiconductor wafer using water vapor containing environment

Semiconductor wafer processing process using a water vapor environment

PROCESS FOR TREATMENT OF SEMICONDUCTOR WAFER USING WATER VAPOR CONTAINING ENVIRONMENT

The present invention relates to a semiconductor wafer processing process using an environment containing water vapor. More specifically, the present invention relates to a process in which water vapor is dispensed into a processing chamber to provide the chamber with a defined atmospheric environment containing water vapor.

This application claims the rights of the U.S. Application No. 12/152,641 named "PROCESS FOR TREATMENT OF SUBSTRATES WITH WATER VAPOR OR STEAM" filed on May 15, 2008, and claims the rights of the U.S. Application No. 12/152,641 filed on November 18, 2008 The rights of US Provisional Application No. 61/199,581 entitled "PROCESS FOR TREATMENT OF SEMICONDUCTOR WAFER USING WATER VAPOR CONTAINING ENVIRONMENT" are incorporated herein by reference in their entirety.

Advances in electronic technology have allowed integrated circuits to be formed on substrates such as silicon wafers with ever-increasing packing densities of active components. The formation of the circuit is carried out by sequential coating, processing and selective removal of various components from the substrate.

Sometimes it is necessary to transfer steam to the semiconductor wafer processing chamber as one aspect of the processing process. US Patent No. 6,837,252 describes a device for treating workpieces by steam and ozone. The disclosure of this patent describes an alternative configuration by which liquid is dispensed into the chamber (as shown in FIG. 4 of the patent), and steam is dispensed as shown in FIG. 5 of the patent. As described there, steam is produced by a steam generator or boiler. See row 15, columns 37 to 56.

In US Patent Application Publication No. 2007/0161248, various methods for introducing water vapor into a processing chamber by generating steam outside the processing chamber are described in paragraphs. Specifically, the disclosure states "For example, water vapor generated from the outside can be supplied to the chamber as a component of gas or a mixture of gases. In one embodiment, it can be passed through a water (preferably heat) Water) column bubbling gas (e.g. N₂) To generate steam. In another embodiment, the gas can pass through the surface of a certain amount of water. In another embodiment, the gas can pass through an irrigation packed column as commonly used in chemical engineering. In another embodiment, substantially pure water vapor can be produced by boiling liquid water. The gaseous product from any of these alternatives can be further heated. Other embodiments are also possible. "

There will be a need to identify alternative technologies and systems for processing semiconductor wafers using water vapor.

It has been found that the processing of temperature-sensitive semiconductor wafers exhibits non-uniformity across the surface of the wafer due to a variety of reasons, including heat transfer to the environment, evaporative cooling, and temperature differences between the wafer and the processing liquid (and related The non-uniform heating/cooling distribution of the joint).

In the present invention, the temperature difference across the surface of the wafer is minimized by using a unique process for processing semiconductor wafers at the target wafer temperature. In the present invention, a process for processing a semiconductor wafer at a target wafer temperature is provided. This process includes the following steps: a) Determine the semiconductor wafers quality during a given wafer processing process step

Target wafer temperature; b) provide a processing chamber in which at least one semiconductor wafer is placed; c) dispense water vapor into the processing chamber in an amount to provide the chamber with a temperature sufficiently close to the target wafer Provide a dew point atmospheric environment with a temperature regulation effect; and

d) Start the given wafer processing process step when the atmospheric environment of the processing chamber is at the dew point of step c).

Although not bound by theory, it is believed that the temperature uniformity across the wafer surface is improved by one or more of the following phenomena in the process of the present invention:<b>temperature control:</b>By adding the dispensed water vapor into the processing chamber to provide an atmospheric environment with a designated dew point, the saturation temperature of the environment (that is, the temperature at which water starts to condense) can be set to the desired processing temperature. In this way, any cool spot on the wafer will tend to condense water from the humid environment, thereby increasing the temperature of the initially cooler spot to the desired temperature.

<b>Evaporation control:</b>Because the atmospheric environment can be set to a humidified environment, wafer processing components (or "chemicals") that are essentially water-containing will tend to stay on the wafer instead of being evaporated. Similarly, the water in the water-containing chemicals at the appropriate location on the wafer will only evaporate from any temperature point until the local temperature of the wafer drops to the dew point. Because evaporation is restricted in the embodiment of the process of the present invention, the associated cooling effect is avoided and the temperature of the wafer tends to be kept relatively uniform.

When the dew point is close enough to the temperature of the wafer, the evaporation and/or condensation of water vapor imparts a temperature regulation effect.

The present invention provides the ease of using a process that gives excellent control over the process conditions, which can lead to excellent uniformity of process results.

The accompanying drawings incorporated into and constituting a part of this application illustrate several aspects of the present invention, and together with the description of the embodiments are used to explain the principle of the present invention.

The embodiments of the present invention described below are not intended to be exhaustive or to limit the present invention to the precise form disclosed in the following detailed description. In fact, one purpose of the selected and described embodiments is to facilitate the understanding and understanding of the principles and practices of the present invention by others who are familiar with the art.

In the process of the present invention, we first determine the target wafer temperature of the semiconductor wafer during a given wafer processing step. In a typical wafer processing process, the temperature of the wafer needs to be raised to a specific predetermined temperature to promote the desired interaction between the wafer and the processing chemicals. It should be understood that it is possible to carry out the reaction within a specific temperature range. When performing the process of the present invention, those skilled in the art can deliberately select a single target temperature as an operating point, or can in fact select the target temperature by establishing tool setting parameters for performing the process, thereby It is determined what the temperature as a target will be without actually recognizing a measured temperature value.

A processing chamber in which at least one semiconductor wafer is placed is provided. The processing chamber may be a chamber designed to accommodate one semiconductor wafer or a plurality of semiconductor wafers at a time. In one embodiment, the processing chamber is a spray processor. Spray processors are generally known and provide the ability to remove liquid by centrifugal force by rotating or rotating the wafer (around its own axis or around a common axis) on a turntable or carousel. Exemplary spray processor machines suitable for adaptation according to the present invention are described in US Patent Nos. 6,406,551 and 6,488,272, which are fully incorporated herein by reference in their entireties. Spray processor type machines can (for example) be under the brand name MERCURY<img file="TWI463547B_D0001.tif" he="41" id="i0001" img-content="character" img-format="tif" inline="no" orientation="portrait" wi="41" />Or ZETA<img file="TWI463547B_D0002.tif" he="40" id="i0002" img-content="character" img-format="tif" inline="no" orientation="portrait" wi="41" />One or more of them were purchased from FSI International, Inc. of Chaska, MN. An example of a single-wafer spray processor system suitable for adaptation according to the present invention is available from SEZ AG, Villach, Austria and sold under the brand name SEZ 323. Another example of a tool system suitable for adaptation according to the present invention is described in a U.S. patent named BARRIER STRUCTURE AND NOZZLE DEVICE FOR USE IN TOOLS USED TO PROCESS MICROELECTRONIC WORKPIECES WITH ONE OR MORE TREATMENT FLUIDS filed on March 15, 2006 Application No. 11/376,996; or as described in U.S. Patent Application Publication No. 2005/0205115.

Once the wafer is provided in the processing chamber, it can be used as appropriate by using any appropriate technology (such as by using radiant heat to heat the chamber; by introducing hot water or other liquid solutions to the wafer, where the processing chemical The heated liquid is generally removed as appropriate before the coating of the substance; and by introducing the heated gas into the chamber; and similar technologies) the wafer is preheated to or close to the above determination Target wafer temperature. In one embodiment of the present invention, one or more wafers can be immersed in a heated liquid bath, quickly draining the contents of the bath (for example, a "quick dumping" procedure) and proceed as follows Describe the remaining processing steps to preheat the wafer. The bath liquid can be, for example, DI water, DI water containing sulfuric acid, sulfuric acid/hydrogen peroxide mixtures, inert fluids (such as fluorocarbons), sulfuric acid/ozone mixtures, and the like. This embodiment can provide substantial benefits in enhancing the throughput of the processing process by heating the wafers more efficiently. An example of a particularly suitable process system that can be used to use this embodiment is Magellan available from FSI International, Chaska, Minnesota<img file="TWI463547B_D0003.tif" he="40" id="i0003" img-content="character" img-format="tif" inline="no" orientation="portrait" wi="41" />system.

The water vapor is dispensed into the processing chamber in an amount effective to provide the chamber with an atmospheric environment having a dew point at the target wafer temperature. For the purpose of the present invention, water vapor is defined as water in a gaseous form, and is distinguished from the small droplets of water commonly referred to as "fog". Because the mist is condensed water in the form of small droplets, there is essentially no pure warming effect corresponding to the heat of vaporization when the mist is on a surface. For the purpose of the present invention, steam is vaporized water at or above the boiling point of water. The boiling point of water depends on the pressure. For example, if the pressure is 1 atmosphere, the boiling point of water is 100°C. When steam is provided at a temperature higher than the boiling point of water, it is called superheated steam. Water vapor may optionally be provided by a composition containing components other than water such as a dissolved gas such as ozone or an inert gas such as nitrogen. It is expected that water vapor can be supplied to the processing chamber in any manner (in essence, pure or in the form of a composition, above or below or at 100°C and having a water vapor pressure or partial pressure above, below or at 1 atmosphere) . The water vapor may further contain additional components as appropriate, such as the oxidizing agent discussed above or components used for wafer cleaning (including NH₄OH, sulfuric acid, HF, ammonium fluoride, H₃PO₄, HCl, peroxide, ozone and combinations thereof). In addition, the incorporation of other ingredients such as surfactants, co-solvents, or the like is expected.

As is commonly known in semiconductor wafer processing technology, water vapor can be provided by a steam generator or boiler. For example, the US Provisional Patent Application No. 61/199,580 named SYSTEM FOR SUPPLYING WATER VAPOR IN SEMICONDUCTOR WAFER TREATMENT filed on November 18, 2008 (for all purposes, the disclosure of this case is incorporated herein by reference) As described in ), depending on the situation, a steam dispenser system can be used to provide wafer steam. The steam dispenser includes: i) a hot water source; ii) a steam separator; iii) a first pipe that fluidly connects the hot water source to the steam separator; iii) a hot water source A fluid control valve in a pipeline that controls the flow of fluid between the hot water source and the steam separator; and iv) a second pipeline that fluidly connects the steam separator to the processing chamber for steam To the inside of the processing chamber.

The dew point is the temperature to which the air must be cooled (under constant pressure and constant water vapor content) in order to reach saturation. When the air in the chamber is maintained at the maximum amount of water vapor that may exist at the existing temperature and pressure, the atmosphere in the processing chamber is saturated. Moisture will condense on any surface at a temperature or below the dew point, thereby transferring energy to that surface.

When the atmospheric environment of the processing chamber is at a dew point close enough to the target wafer temperature to provide a temperature regulation effect, a given wafer processing process step is initiated. In an embodiment of the present invention, the dew point is within about 20°C of the target wafer temperature. In another embodiment, the dew point is within about 10°C of the target wafer temperature. In another embodiment, the dew point is within about 5°C of the target wafer temperature. In another embodiment, when the atmospheric environment of the processing chamber is at the dew point at the target wafer temperature and when the wafer is at the target wafer temperature, the wafer processing step is initiated. In another embodiment, when the temperature of the atmospheric environment of the processing chamber is far away from the target wafer temperature, but the atmospheric temperature and dew point rapidly move to the target wafer temperature (close to the target wafer temperature in a shorter time compared with the processing step length). At the target temperature), the wafer processing process step is initiated. In other words, it is particularly expected that the wafer processing step can be initiated at a certain time before the processing chamber reaches the desired atmospheric temperature and/or dew point, provided that the desired wafer processing is given during a part of the processing step A temperature regulation effect is performed on the wafer.

The wafer processing step can be initiated when the wafer itself is above, below, or at the target wafer temperature. When the wafer is above the target temperature range, the wafer will be in the cooling process during the wafer processing process. In an embodiment of the present invention, the wafer processing process step is initiated when the wafer is at the target wafer temperature. When the wafer is below the target temperature range, the wafer will be in the heating process during the wafer processing process. The present invention provides the benefits of other embodiments by providing enhanced temperature uniformity when the wafer heats up.

It has been further discovered that we can use the process of the present invention to adjust the process uniformity. In a typical center-dispensing semiconductor wafer process where heated chemicals are directly applied to a pre-heated wafer, the edges of the wafer lose heat by evaporating and cooling faster than the center. This situation can lead to a rapid manufacturing process in the center. By rotating the wafer in a humid vapor environment (specifically, an environment where the dew point is close to the temperature of the heated chemical substance), evaporation from the edge can be suppressed. Alternatively, a process is performed while applying heated chemicals to a semiconductor wafer (the wafer has not been preheated to the temperature of the heated chemicals to be applied to the wafer). This process will be fast for the center because the center of the wafer heats up the fastest. If instead the process is performed in a high-moisture vapor environment (specifically, an environment where the dew point is higher than the temperature of the heated chemical substance), the vapor will tend to condense on the edge of the wafer, causing the edge to become hot . The rotating edge of the wafer will tend to heat up more quickly than the rest of the wafer, thereby offsetting the tendency to become a center of rapid processing.

Various amounts and temperatures can be used to provide water vapor as dispensed in the processing chamber. In one embodiment of the present invention, the dew point at the target wafer temperature is achieved by dispensing fully saturated water vapor into the processing chamber until the dew point at the target wafer temperature in the processing chamber is reached. In another embodiment, the dew point at the target wafer temperature is achieved by dispensing incompletely saturated water vapor into the processing chamber until the dew point at the target wafer temperature in the processing chamber is reached. Incompletely saturated water vapor can be provided by operating a water vapor source at less than the full capacity used to prepare a saturated environment, or it can be operated at full capacity but diluted by a non-vapor fluid stream (such as an inert gas). In one embodiment, the water vapor contains nitrogen.

In an embodiment of the present invention, water vapor is provided as steam at a temperature of about 100°C.

Examples of processing compositions that can be used in the present invention include wafer cleaning systems known in the art, such as SC-1 composition (NH₄OH/H₂O₂/Water), SC-2 composition (HCl/H₂O₂/Water), Piranha or SPM composition (sulfuric acid/H₂O₂), SOM (sulfuric acid/ozone) composition, sulfuric acid composition, buffered oxide etchant (HF and ammonium fluoride) composition, and NH₄OH, H₃PO₄, HF, HCl, HCl/H₂O₂Or HF/HCl composition.

You can add N in one bite₂And by adding steam through a separate port, the processing environment of the processing chamber is modified. Optionally, steam can be added via the spray bar or via both the mouth and the spray bar. Can be adjusted by steam and N₂The operating pressure changes the processing chamber environment, thereby changing the amount of each component added to the processing chamber.

<b>Instance</b>

The representative embodiments of the present invention will now be described with reference to the following examples which illustrate the principle and practice of the present invention.

<b>Example 1</b>

A semiconductor wafer (which has oxide on its surface) is provided in the processing chamber. In the control process, the hot ammonium hydroxide/H₂O₂/Water mixture (APM, 1:1:30) is applied to the wafer, where N is introduced through a port under 20 psi₂. This control standard exhibits oxidation etching that is approximately 1 angstrom faster at the center than at the edges. See the data marked "APMN2" in Figure 1.

The same process as described above in steam and N₂In the environment, by which N is introduced through one port at 20 psi₂And the steam is introduced through a spray rod under the boiler pressure of 20 psi. In this inventive process, the difference in the etching rate from the center to the edge of the wafer essentially disappears. See the information marked "APMBOTH" in Figure 1.

Although not bound by theory, the inventive process can be better understood by using the following prospective examples.

<b>Example 2</b>

Figure 2 shows the temperature distribution of a cold wafer placed in a dry atmosphere at the target temperature. The radiant heat transfer mechanism (and in particular the convective heat transfer mechanism) heats the wafer until it reaches equilibrium at the target temperature. However, since these mechanisms are slow, the temperature of the initially cold wafer only slowly approaches the target temperature. (For the sake of brevity, only the convection mechanism will be mentioned in the further discussion.) Figure 2 also shows the slow cooling of the initially hot wafer to the target temperature. The procedure of FIG. 2 is generally used in the semiconductor industry and is not an embodiment of the present invention.

<b>Example 3</b>

Figure 3 shows the most ideal embodiment of the present invention. Figure 3 shows the influence of liquid and vaporized water on the heating and cooling process when the atmospheric temperature and dew point are at the target temperature (usually the dispensing temperature of the processed liquid). For reference, the temperature distribution of the initially hot dry wafer from Figure 2 is repeated. Anhydrous vapor condenses or evaporates from the initially hot dry wafer, so the heat transfer mechanism of the present invention does not work.

By comparison, FIG. 3 also shows the temperature distribution of the initially hot wet wafer (bulk water on the wafer surface) introduced into the atmosphere at the target temperature and dew point. The liquid water evaporates, and the heat of vaporization of the water quickly cools the wafer toward the target temperature. However, when the wafer temperature approaches the dew point of the atmosphere, evaporation and its associated cooling cease. Therefore, the temperature of the initially hot wet wafer quickly reaches the target temperature, but does not exceed the limit and fall below the target temperature. The heat removed by evaporating water cools the wafer to the target temperature much faster than using convection alone.

Figure 3 also shows the result of introducing a dry or wet cold wafer into the atmosphere at the target temperature and dew point. When the wafer temperature is lower than the dew point, water vapor will condense on the wafer, thereby depositing the vaporization heat of the vapor, and quickly heating the wafer to the target temperature. However, when the wafer temperature approaches the dew point, the condensation and its associated heating cease. Therefore, the temperature of the initially cold wet or dry wafer quickly reaches the target temperature, but does not exceed the limit and is higher than the target temperature. The heat added by condensed water heats the wafer to the target temperature much faster than using convection alone.

The heating of the initially cold wet or dry wafer and the cooling of the initially hot wet wafer in the atmosphere where the temperature and dew point of the atmosphere match the target temperature of the wafer represent the most ideal embodiment of the present invention. Although described using only water, it is expected that the liquid vapor balance of other liquids can be used to control temperature. For example, ethylene glycol (boiling point 198°C) can be used for processing at temperatures higher than 100°C under atmospheric pressure. It is also possible to support elevated processing temperatures by using water under high pressure.

<b>Example 4</b>

Figure 4 shows a less desirable embodiment of the present invention. Ideally, the temperature and dew point of the atmosphere match the target temperature of the wafer. When the dew point deviates from the target temperature, the temperature regulation effect of condensation and evaporation decreases. Although the atmospheric temperature and the dew point close to the target temperature represent an embodiment of the present invention, this situation is less ideal than the target temperature. Figure 4 illustrates the result when the dew point is sufficiently lower than the target temperature. For reference, the temperature distribution of the initially hot dry wafer from Figure 2 is repeated.

In FIG. 4, the initially hot wet wafer is rapidly cooled by evaporation in zone I. Unfortunately, the low dew point allows evaporation to continue into zone II, where evaporative cooling cools the wafer to an equilibrium temperature below the target temperature. The evaporation continues through region II until all the water has evaporated from the wafer. In area III, the currently dried wafer is slowly heated toward the target temperature by convection. The amount of thermal undershoot depends on the local rate of evaporation, where the surface receiving a large flow of dry gas cools faster than the surface in the relatively stagnant gas flow, and cools to a lower temperature. This situation leads to non-uniform temperature and therefore non-uniform chemical treatment across the wafer surface.

Figure 4 also shows the temperature distribution of the initially cold wafer. Whether initially wet or dry, water condenses on the cold wafer in zone I, thereby rapidly heating the cold wafer until it reaches the dew point. Above the dew point, the situation is reversed, and the evaporation of water is slowed down to further heating. Only when all the water has evaporated from the wafer does the temperature climb to the target temperature (zone III). Also, changes in local gas flow can cause significant changes in temperature and therefore in the activity of chemical treatments.

A situation similar to that in FIG. 4 but where the atmospheric temperature and the dew point are far away from the target temperature does not represent an embodiment of the present invention. However, a situation similar to FIG. 4 but in which the atmospheric temperature and the dew point are close to the target temperature represents a less desirable but still potentially useful embodiment of the present invention. For example, it is believed that the inventive process used during the "APMBOTH" process example in FIG. 1 represents a situation where the atmospheric temperature and dew point are slightly higher than the target temperature (the temperature of the processed chemical substance), resulting in close to crystallinity. Slightly excessive chemical action at the rounded edge (the gas flow is highest at the edge of the wafer). However, the non-ideal conditions still result in a significantly more uniform treatment than the treatment of the comparative "APMN2" process example in Figure 1 (where no attempt is made to control the water vapor in the atmosphere).

Unless otherwise indicated, all percentages and ratios used herein are weight percentages and ratios. All patents, patent applications (including provisional applications) and publications cited in this text are incorporated herein by reference as if they were individually incorporated for all purposes. In the foregoing description, the numerous features and advantages of the present invention intended to be described by this document have been described. However, it should be understood that although specific forms or embodiments of the present invention have been described, they can be provided without departing from the spirit and scope of the present invention. Under the circumstances, various modifications are made, including modifications to the shape and the configuration of parts and the like.

FIG. 1 is a graph showing the uniformity evaluation of wafers across the process performed in accordance with the present invention compared to a control standard.

Fig. 2 is a graph showing the equilibrium of drying a wafer in a relatively dry atmosphere to the atmospheric temperature.

FIG. 3 is a graph showing the balance of the wet wafer and the dry wafer in the atmosphere where the dew point is close to the atmospheric temperature (close to saturation).

FIG. 4 is a graph showing the balance between wet wafers and dry wafers in the atmosphere where the dew point is lower than the atmospheric temperature (below saturation).