KR20120005992A - Depositing tungsten into high aspect ratio features - Google Patents

Abstract

PURPOSE: A tungsten deposition method to the inside of a high aspect ratio characteristic part is provided to charge the characteristic part with tungsten including materials, thereby arranging a seam in the inside of the charged characteristic part. CONSTITUTION: An under-layer(113) is deposited on a substrate(103). The under-layer lines a characteristic part hole(105). The under-layer arranges an overhang(115). An unfilled void(129) is arranged under a reference point(125). The size of the void and the position of the reference point are varied according to a parameter of a deposition process, the size of a characteristic part, and the size of the overhang.

Description

Depositing Tungsten into High Aspect Ratio Features {DEPOSITING TUNGSTEN INTO HIGH ASPECT RATIO FEATURES}

This application claims priority based on US Patent Application No. 13 / 016,656 of CHANDRASHEKAR, Anand et al. 09/09/2010 "DEPOSITING TUNGSTEN INTO HIGH ASPECT RATIO FEATURES", and of August 4, 2009 of CHANDRASHEKAR, Anand et al. Part of the patent application No. 12 / 535,464, entitled "DEPOSITING TUNGSTEN INTO HIGH ASPECT RATIO FEATURES," US Patent Application No. 12 / 833,823, entitled "DEPOSITING TUNGSTEN INTO HIGH ASPECT RATIO," issued by CHANDRASHEKAR, Anand et al. Part of FEATURES ".

Deposition of tungsten-containing materials using Chemical Vapor Deposition (CVD) techniques is an important part of many semiconductor manufacturing processes. Such materials can be used for horizontal interconnects, vias between adjacent metal layers, contacts between the first metal layer and the device on a silicon substrate, and for high aspect ratio features. In a conventional deposition process, the substrate is heated to a predetermined process temperature in the deposition chamber, and a thin layer of tungsten-containing material is deposited that functions as a seed or nucleation layer. Thereafter, the remainder of the tungsten-containing material (bulk layer) is deposited on the nucleation layer. In the prior art, by the reduction of tungsten hexafluoride (WF ₆ ) with hydrogen (H ₂ ), a tungsten-containing material is formed. Tungsten-containing material is deposited over the entire exposed surface area of the substrate, including features and field areas.

By depositing tungsten-containing material into small, particularly high aspect ratio features, seams (eg, unfilled voids) can be formed inside the filled features. Large shims can result in high resistance, contamination, loss of charged material, and other performance degradation of other integrated circuits. For example, after the filling process, the shim may extend to near the field region and open during the chemical-mechanical planarization process.

A method and apparatus are provided for filling high aspect ratio features with tungsten-containing material in a substantially void free manner. In a particular embodiment, the method includes depositing an initial layer of tungsten-containing material and selectively removing a portion of the initial layer to form a residual layer, wherein the residual layer is characterized by a high aspect ratio feature. Passively passivated along the depth direction. In certain embodiments, the residual layer is more passivated at the feature opening than inside the feature. The method further includes depositing an additional layer of the same or different material on the remaining layer. The deposition rate during this late deposition step is slower near the feature opening than inside the feature because of the differential passivation of the residual layer. This deposition change helps to prevent premature closure of high aspect ratio features and facilitates filling the features in a substantially void free manner.

In certain embodiments, a method for filling high aspect ratio features provided on a partially fabricated semiconductor substrate includes providing a tungsten-containing precursor and a reducing agent to a process chamber, and a chemical vapor deposition reaction between the tungsten-containing material and the reducing agent. And depositing a layer of tungsten containing material on the substrate through. The deposited layer at least partially fills the feature. The method may introduce an activated etch material into a process chamber and remove a portion of the deposited layer using the activated etch material to form a residual layer. The method then reintroduces the tungsten-containing precursor and reducing agent into the chamber, selectively depositing an additional layer of tungsten containing material for the remaining layer of the substrate imagination through a chemical vapor deposition reaction between the precursor and the reducing agent. The additional deposition layer is thicker inside the feature than near the feature opening. As used herein, the term “inside a feature” is used at about 35% to 75%, specifically about 40% to 60%, of a particular depth measured from the opening of the feature, about the midpoint of the feature along the depth direction of the feature. The middle part of the feature located at%. The term “near feature opening” or “near feature opening” refers to the top surface of a feature located within 25%, specifically 10%, of the opening edge or other element representing the edge of the opening of the feature.

In certain embodiments, when removing a portion of the deposition layer, the process chamber is maintained at a pressure of 5 Torr or less. The process chamber can be maintained at a pressure of 2 Torr or less during this operation. In certain embodiments, the residual layer is selectively, ie, differentially passivated, so as to passivate more near the opening of the feature than inside the feature. Herein, when a layer inhibits the deposition of additional material on its surface, the layer is referred to as a passivated layer. With the more passivated layer, deposition is slower and / or delayed than the less passivated layer. In this and other embodiments, the residual layer is thinner near the feature opening than inside the feature. In some embodiments the residual layer may have a thickness of 10% or less of the feature opening. During removal more tungsten-containing material may be removed near the opening of the feature than inside the feature. For example, the rate of reduction of the thickness of the deposited layer may be about 25% or more higher near the feature opening than inside the feature.

In certain embodiments, selectively depositing additional layers includes filling at least the bottom half of the high aspect ratio features in a substantially void free manner. High aspect ratio features have an aspect ratio of at least about two. In this and other embodiments, the step of removing portions of the deposition layer is performed in a mass transfer manner. An apparatus including a plurality of process chambers may be used to fill high aspect ratio features. In these embodiments, depositing a layer of tungsten-containing material, removing a portion of the deposition layer, and selectively depositing an additional layer of tungsten-containing material are performed in different process chambers maintained at different environmental conditions. Can be. In certain embodiments, the substrate has a second feature that is closed during the deposition step and remains closed after the removal step. High aspect ratio features are closed during the deposition step and open during selective removal.

In a particular embodiment, the method includes applying a photoresist to a partially fabricated semiconductor substrate, exposing the photoresist, patterning the photoresist, creating a pattern, and fabricating the pattern, the partially fabricated semiconductor. Transferring to a substrate.

A method of filling high aspect ratio features provided on a partially fabricated semiconductor substrate is provided. The method includes introducing a tungsten-containing precursor and a reducing agent into the process chamber and depositing a layer of tungsten-containing material on the partially fabricated semiconductor substrate through a chemical vapor deposition reaction between the tungsten-containing precursor and the reducing agent ( The layer partially fills the high aspect ratio features), introducing activated etch material into the process chamber, and selectively removing a portion of the layer of tungsten-containing material to form a remaining layer. Step (the remaining layer has a passivation level that varies along the depth direction of the high aspect ratio feature and is more passivated near the feature opening than inside the feature). The passivation level of the remaining layer at a certain depth correlates with the amount of tungsten-containing material removed from the layer of tungsten-containing material at that particular depth.

A method is provided for processing a partially manufactured semiconductor substrate. The method comprises a process chamber comprising a partially fabricated semiconductor substrate comprising a high aspect ratio feature having a size of less than 50 nanometers and having an aspect ratio of 4 or more, the protective layer being deposited within the high aspect ratio feature. By providing tungsten-containing precursor and reducing agent into the process chamber, and by chemical vapor deposition reaction between the tungsten-containing precursor and reducing agent, the layer of tungsten-containing material is half the size of the high aspect ratio feature. Depositing a layer of tungsten-containing material having a thickness of up to a partially fabricated semiconductor substrate, introducing an activated etch material into the process chamber, and applying the activated etch material to a pressure of 5 Torr or less for a specified time period. Removing a portion of the layer using the method, introducing a tungsten-containing precursor and a reducing agent into the process chamber, Selectively depositing an additional layer of tungsten-containing material on the partially fabricated semiconductor substrate through a chemical vapor deposition reaction between the oil precursor and the reducing agent, wherein the internal deposition rate inside the feature is external deposition near the feature opening. And an optional deposition step that is twice as high as the rate and allows to fill at least the bottom half of the feature. The specific time is determined by the thickness of the layer. The size of the high aspect ratio features is 30 nanometers, the depth of the high aspect ratio features is 250 nanometers, and the duration of the removing step is 1 to 10 seconds. The external deposition rate is less than 100 Angstroms per minute during the initial 30 seconds or more of the selective deposition.

A semiconductor processing apparatus is provided for filling high aspect ratio features on a partially fabricated semiconductor substrate. The apparatus includes a first process chamber, a second process chamber, and a controller, the first process chamber having one or more deposition stations for positioning a substrate, wherein the first process chamber comprises a chemical vapor deposition reaction. And deposit a layer of tungsten-containing material or an additional layer of tungsten-containing material on the partially fabricated semiconductor substrate, wherein the one or more deposition stations include a deposition heating element for controlling the temperature of the substrate during deposition. Wherein the second process chamber has one or more etching stations for positioning the substrate, the second process chamber is configured to selectively remove a portion of the layer, wherein the one or more etching stations adjust the temperature of the substrate during etching. An etching heating element for controlling, wherein the controller directs the tungsten-containing precursor and the reducing agent to the first process chamber. A program instruction, and introducing the tungsten-containing precursor and the reducing agent into the first process chamber, and then introducing an activated etching material into the second process chamber at a pressure of 5 Torr or less for a time of 1 to 10 seconds. And introducing the activated etching material into the second process chamber and then introducing the tungsten-containing precursor and the reducing agent into the first process chamber or another process chamber.

The semiconductor processing apparatus further includes a wafer stepper.

A computer-readable storage medium having recorded thereon program instructions for control of a semiconductor processing apparatus for filling high aspect ratio features provided on a partially fabricated semiconductor substrate, the program instructions comprising removing tungsten-containing precursors and reducing agents. A cord introducing into the first process chamber, a cord introducing the activated etching material into the second process chamber at a pressure of 5 Torr or less for a time between 1 and 10 seconds, and a tungsten-containing precursor and a reducing agent in the first process chamber or Code that introduces it to another process chamber.

A method for filling high aspect ratio features provided on partially fabricated semiconductor substrates, the method comprising introducing a tungsten-containing precursor and a reducing agent into a process chamber and through chemical vapor deposition reaction between the tungsten-containing precursor and the reducing agent Depositing a layer of tungsten-containing material on the partially fabricated semiconductor substrate, the layer of tungsten-containing material partially filling high aspect ratio features, and introducing an activated etching material into the process chamber; Selectively removing a portion of the deposited layer using the activated etching material at process conditions that limit recombination of the activated etching material. The process conditions include the temperature of the partially fabricated semiconductor substrate below 250 ° C. and the pressure in the process chamber below 5 Torr. The rate of decrease of the thickness of the deposited layer near the opening of the high aspect ratio feature is at least 25% greater than the rate of decrease of the thickness of the deposited layer inside the feature of the high aspect ratio. It is carried out in a mass transport regime that removes a portion of the deposited layer. The activated etch material is introduced into the process chamber from a remote plasma generator configured to produce an activated etch material from the initial etch material. The method further includes repeating the deposition step to form a second deposition layer and repeating the selective removal step to form a second etch layer. The selective removal step repeated is carried out at different process conditions than the previous selective removal step. The reduction rate of the thickness of the second deposition layer near the opening of the high aspect ratio feature is at least 10% greater than the reduction rate of the thickness of the second deposition layer inside the high aspect ratio feature. The method further includes depositing a tungsten-containing material on the partially fabricated semiconductor substrate through the chemical vapor deposition reaction between the tungsten-containing precursor and the reducing agent until the high aspect ratio features are closed. Closed high aspect ratio features have seams that end up at least 20% of depth from the field area of the high aspect ratio feature. Deposition and selective removal are performed in different chambers maintained at different environmental conditions.

A semiconductor processing apparatus for filling high aspect ratio features provided on partially fabricated semiconductor substrates is provided. The apparatus includes a first process chamber, a second process chamber, and a controller, the first process chamber having one or more deposition stations for positioning a substrate, the first process chamber through a chemical vapor deposition reaction. And depositing a layer of tungsten-containing material on the partially fabricated semiconductor substrate, wherein the at least one deposition station includes a deposition heating element for controlling the temperature of the substrate during deposition, and the second process chamber is adapted to deposit the substrate. Having at least one etching station for positioning, the second process chamber is configured to selectively remove a portion of the deposited layer, the at least one etching station including an etch heating element for controlling the temperature of the substrate during etching; The controller may be configured to include tungsten-based chemical vapor deposition reaction between a tungsten-containing precursor and a reducing agent. Instructions for depositing a layer of tungsten-containing material on the partially fabricated semiconductor substrate such that the layer of dairy material partially fills the high aspect ratio features, and for introducing the activated etch material into the second process chamber; And selectively removing a portion of the deposited layer using the activated etch material under process conditions that prevent recombination of the etched material.

1 illustrates an example of a semiconductor substrate including high aspect ratio features at different stages of a process in accordance with certain embodiments.
2 is a flow chart illustrating a method of filling high aspect ratio features with a tungsten containing material in accordance with certain embodiments.
3 illustrates a cross-sectional view of the substrate at different stages of the cleaning process according to certain embodiments.
4 illustrates an apparatus according to a particular embodiment for filling high aspect ratio features.
5A illustrates a multi-station device according to a particular embodiment for charging high aspect ratio features.
5B illustrates a multi-chamber arrangement according to certain embodiments for filling high aspect ratio features.
6A illustrates a partially fabricated semiconductor substrate having features deposited with a tungsten-containing layer.
FIG. 6B shows a graph of the thickness distribution of the tungsten containing layer shown in FIG. 6A before and after etching for two different process conditions.
FIG. 7 is a plot of etch rates of fluorine species recombined with activated fluorine species shown as a function of pedestal temperature.
8 is a plot of the etch rate of activated thruolin species as a function of chamber pressure.
9 is a plot of deposition thickness over time for various samples processed using different etching conditions.
FIG. 10 shows a cross-sectional SEM image of 30-nanometer features after initial tungsten, 3-second etch and additional tungsten deposition.
FIG. 11 shows a cross-sectional SEM image of another 30-nanometer feature after the same initial tungsten deposition, one-second etch and the same additional tungsten deposition.

In the following description, numerous specific details are provided to provide a thorough understanding of the present invention. Without some or all of these specific details, the invention may be practiced. In addition, well known process operations have not been described in detail in order not to unnecessarily obscure the present invention. While the invention will be described in connection with specific embodiments, it should be understood that it is not intended to limit the invention to these embodiments.

Introduction

By filling the features with tungsten-containing material, a seam can be formed inside the filled features. In the context of the process chamber, when the layer being deposited on the sidewalls of the features thickens to a point that blocks the void space (ie, also referred to as a pinch point, sealing point), below this point In the seam can be formed. That is, as the deposited layer becomes thicker, the void space is pinched off. This engagement prevents precursors and / or other reactants from entering the void space, leaving the void space uncharged. The void space is typically an elongated seam that extends through a portion of the filled feature along the depth direction of the feature. Such void spaces or shims may be referred to as keyholes because of their shape.

There are many possible causes for the formation of shims. One cause is an overhang that is formed near the feature opening during deposition of a tungsten-containing material, or more generally, another material (eg, a diffusion barrier layer or nucleation layer). 1 illustrates an example of a semiconductor substrate that includes high aspect ratio features during various stages of a semiconductor process, in accordance with certain embodiments. The first cross-sectional view 101 shows a substrate 103 having pre-formed feature holes 105. The substrate may be a silicon wafer, such as a 200 mm wafer, a 300 mm wafer, or a 450 mm wafer. Feature hole 105 may have an aspect ratio of about 2: 1 or greater, or in more specific embodiments, an aspect ratio of about 4: 1 or greater. The feature hole 105 may also have an opening near cross-sectional size (eg, opening diameter, line width, etc.) of about 10 nanometers to 500 nanometers, more specifically, about 25 nanometers to 300 nanometers. have. Feature holes may also be referred to as unfilled features, or simply features.

In the next stage (section 111), a substrate 103 is shown, on which an under-layer 113 lining the feature holes 105 is deposited, the under-layer 113. A diffusion barrier layer, or an adhesion layer, or a nucleation layer, or a combination thereof. Or any other suitable material. Because many deposition processes do not have good step coverage properties, i.e., because more material is deposited near the field region and opening than inside the feature, the under-layer 113 overhangs 115 may be formed. If the overhang 115 is part of the under-layer 113, the layer 113 may be thicker (eg, than inside the feature) near the opening. To illustrate this, "near the opening" is defined as a suitable location or area within a feature (i.e. along the sidewall of the feature) corresponding to about 0-10% of the depth measured from the field area. In a particular embodiment, the area near the opening corresponds to an opening area. In addition, “inside the feature” is defined as the appropriate location or area in the feature that corresponds to about 20-60% of the depth measured from the field area on the top of the feature. In general, when the value of a particular parameter (such as thickness) is specified as “near opening” or “inside a feature,” these values represent the average of a plurality of measurements or measurements taken at this location / area. In certain embodiments, the average thickness of the under-layer near the opening is about 10% or more than inside the feature. In more specific embodiments, the difference may be at least about 25%, or at least about 50%, or at least about 100%. In addition, the distribution of material in the features can be characterized by step coverage. To illustrate this, “step coverage” is defined as the ratio of two thicknesses, ie the thickness of the material inside the feature divided by the thickness of the material near the opening. As a specific example, the step coverage of the under-layer is about 100% or less, or more specifically about 75% or less, even more specifically about 50% or less.

Next cross-sectional view 121 shows a feature hole filled with tungsten-containing material 123. The deposition process may lead to a conformal layer of material 123 that is built for the under-layer 113. This deposited layer follows the shape of the under-layer 113, including overhang 115. In certain specific embodiments, in subsequent stages of the deposition process (eg, just before feature closure), layer 123 may be less conformal, resulting in poor step coverage (ie, opening than inside the feature). More material is deposited nearby). When layer 123 thickens, layer 123 may close the feature and form pinch point 125. Before the deposition process ends, some additional material is deposited over the pinch point 125. Because of the overhang 115, specifically because of the poor step coverage of the layer 123, the closed feature may have an unfilled void 129 (ie, seam) below the reference point 125. The size of the void 129 and the location of the reference point 125 relative to the field region 127 can be determined by the size of the overhang 115, the size of the features, the aspect ratio, the bowing, the parameters of the deposition process, and the like. It depends on other parameters.

Finally, cross-sectional view 131 shows the substrate 133 after chemical-mechanical planarization (CMP) removing the top layer from the substrate 103. CMP may be used to remove overburden in the field area. Typically, the substrate 103 is thinned during CMP, so that the substrate 133 can be formed. As shown in FIG. 1, when pinch point 125 is above the leveling level of the CMP process, shim 129 is opened and exposed to ambient environment through shim opening 135. The problem with open large shims has been described above.

Although not shown in FIG. 1, another cause that may result in seam formation or seam enlargement and moving the reference point near the field area is a curved (ie curved) sidewall of the feature hole (which is also a bowed feature). Also known as). In the curved feature, the cross sectional size of the cavity near the opening is smaller than the cross sectional size inside the feature. The effect of this narrower opening of the curved feature is somewhat similar to the overhang problem mentioned above. In addition, the curved features may also have under-layers with overhangs, and face other causes of seam formation that synthesize the negative effects of seam formation.

It may not be possible or practical to completely remove the shims from features filled with tungsten-containing material. For example, some void space may be left inside the feature due to the large particle size of the material being deposited, mass transport limited during deposition (especially during deposition before feature closure), and for other reasons. However, herein, a novel method is provided that allows for seam size reduction and makes it possible to move the reference point away from the field area. These are collectively referred to as mitigating seam formation.

fair

By introducing one or more intermediate selective removal operations, it has been found that seam formation may be relaxed or, in some embodiments, eliminated. For example, the filling process may begin by forming an initial layer that at least partially fills a high aspect ratio feature. After this operation, partial selective removal of this initial layer is followed, followed by the deposition of additional layers. In a substantially void free manner, this removal-deposition cycle may be repeated until it is fully filled with the feature. Process parameters may be selected to improve step coverage in one or more cycles. In certain embodiments, each cycle improves step coverage. Finally, selective removal is characterized in that more material is removed near the opening than inside the feature. Various process control parameters may be used to determine the results (e.g., removal in mass transfer control, removal control, and / or adsorption rates of different etch components (e.g., activated and recombined species), etch species). Control of the recombination rate, etc.) can be obtained. For the purposes of this application, activated species, such as atomized species, radicals and ions (eg, atomic fluorine), are molecules that contain recombined species (eg, high energy state molecules, such as molecular fluorine). Rin)) and initial etchant species (eg, nitrogen tri-fluoride and other precursors to be described below).

2 shows a general process flow diagram illustrating a method of filling high aspect ratio features with tungsten-containing material, in accordance with certain embodiments. Process 200 begins by placing 201 a substrate containing a high aspect ratio feature on a deposition station inside the process chamber. The substrate may have an under-layer, such as a diffusion barrier layer and / or a tungsten nucleation layer. Details of specific substrates and under-layers are provided in the context of FIG. 1. In certain embodiments, the average thickness of the under-layer near the feature opening is about 25% or more than the average thickness of the under-layer inside the feature (eg, near the feature bottom). More generally, the substrate may have an under-layer that forms an overhang. In some cases, a layer of previously deposited bulk tungsten may be provided in the feature. Features with overhangs tend to form voids during charging.

A diffusion barrier layer can be deposited on the substrate in advance, forming a conformal layer that prevents the material used to fill the feature into the surrounding material of the substrate. Materials for the diffusion barrier layer may include tungsten nitride, titanium, titanium nitride and other materials. The barrier layer may have a thickness of about 10 angstroms to 500 angstroms, and in more specific embodiments, may have a thickness of about 25 angstroms to 200 angstroms. In certain embodiments, the diffusion barrier layer may be unevenly distributed on the substrate surface to form an overhang.

The nucleation layer is typically a thin conformal layer that facilitates the deposition of the bulk tungsten-containing material which will subsequently be formed on itself. In certain embodiments, the nucleation layer is deposited using a pulsed nucleation layer (PNL) technique. In the PNL technique, pulses of reducing agent, purge gas and tungsten-containing precursors are sequentially injected into the reaction chamber and purged from the reaction chamber. The process is repeated cyclically until the desired thickness is obtained. In general, PNL implements any cyclic process, such as atomic layer deposition (ALD), that sequentially adds reactants to react on a semiconductor substrate. PNL techniques for depositing tungsten nucleation layers are described in US patent application Ser. No. 12 / 030,645 filed Feb. 13, 2008, US patent application Ser. No. 11 / 951,236 filed Dec. 05, 2007. Patent Application 12 / 407,541 filed March 19, 2009, the contents of which are incorporated herein by reference. Additional descriptions relating to PNL type processes can be found in US Pat. Nos. 6,635,965, 6,844,258, 7,005,372, 7,141,494, and US Patent Application Nos. 11 / 265,531, the contents of which are herein incorporated by reference. Cited by reference. In certain embodiments, the nucleation layer may be unevenly distributed on the substrate surface, forming an overhang. The method according to the invention is not limited to the specific method of tungsten nucleation layer deposition, but on the tungsten nucleation layer formed by any method (eg, PNL, ALD, CVD, PVD and any other method). Depositing a bulk tungsten film. In addition, in certain embodiments, bulk tungsten can be deposited directly without using a nucleation layer.

In addition, a deposition station may be used to perform certain preliminary operations (eg, deposition of diffusion barrier layers, deposition of nucleation layers) and / or subsequent operations (eg, etching, another deposition, final feature filling). have. In certain embodiments, the deposition station may be specifically designed to perform deposition operation 203. The apparatus may include an additional deposition station for performing task 203. For example, initial deposition can be performed on the first deposition station. The substrate can then be moved to another station to be etched. In certain embodiments, which will be described further below, the etch stations can be located in different chambers to prevent cross-contamination between the deposition environment and the deposition environment using different materials and conditions for each operation. Then, if the process requires another deposition operation 203, the substrate can be returned to the first deposition station or moved to another deposition station. A plurality of deposition stations may also be used to perform parallel deposition operations 203 on a plurality of substrates. Additional details and apparatus embodiments are described below with reference to FIGS. 4 and 5A-B.

The process may begin by depositing a tungsten-containing material on the substrate (step 203). In a particular embodiment, bulk deposition includes a chemical vapor deposition (CVD) process in which tungsten-containing precursors are reduced by hydrogen to deposit tungsten. When tungsten hexafluoride (WF ₆ ) is used, other tungsten precursors (such as, but not limited to tungsten hexachloride (WCl ₆ ), organometallic precursors and fluorine free precursors (eg, MDNOW (methylcyclopentadienyldicarbonylnitosyl-)) tungsten) and ENNOW (ethylcyclopentadienyl-dicarbonylnitrosyl-tungsten))). In addition, during CVD deposition of the bulk tungsten layer, hydrogen is generally used as the reducing agent, but within the scope of the present invention, other reducing agents, such as silane, may be used in place of or with hydrogen. In another embodiment, tungsten hexacarbonyl (W (CO) ₆ ) may be used, with or without a reducing agent. Unlike the PNL process described above, in the CVD technique, WF ₆ and H ₂ or other reactants are introduced simultaneously into the reaction chamber. This results in a continuous chemical reaction of the mixed reactant gas, which continuously forms a tungsten film on the substrate surface. A tungsten film deposition method using chemical vapor deposition (CVD) is described in US patent application Ser. No. 12 / 202,126 (filed Aug. 29, 2008), which is incorporated herein by reference in its entirety. Included for illustration purposes. According to various embodiments, the methods described herein are not limited to specific methods of partially filling features, and may include any suitable deposition technique.

3 shows an example of a cross-sectional view of features at different stages of the filling process. In particular, cross-sectional view 321 shows an example of a feature after completing one of the initial deposition operations 203. In this process stage, the substrate 303 may have a layer 323 of tungsten-containing material deposited over the under-layer 313. For example, because of the overhang 315 of the under-layer 313 and / or poor step coverage of the deposited layer 323, the size of the cavity near the opening may be narrower than the size of the cavity inside the feature. This has been described in detail above with reference to FIG. 1.

Referring again to FIG. 2, deposition operation 203 proceeds until the deposited layer (eg, layer 323) reaches a certain thickness. This thickness may vary depending on the cavity profile and opening size. In certain embodiments, the average thickness of the deposited layer near the opening may be about 5% to 25% of the size of the cross section of the feature comprising such under-layer, if any under-layer is present. In another embodiment, features may be fully closed during deposition operation 203 and later re-opened during selective removal operations.

In certain embodiments, various sensors may be provided in the process chamber so that in-situ metrological measurements may be performed to identify the extent of deposition operation 203 and removal operation 205. Examples of in-drill metrology include optical microscopy and X-ray fluorescence to determine the thickness of the deposited film. In addition, an infrared (IR) spectrometer can be used to detect the amount of tungsten fluoride (WF _X ) generated during the etching operation. Finally, an under-layer, such as a tungsten nucleation layer or a diffusion barrier layer, can be used as the etch-stop layer.

The process continues with selective removal operation 205. Specific details of the etching process are described in Chandrashekar et al., US Patent Application No. 12 / 535,377 filed on Aug. 04, 2009, titled METHOD FOR DEPOSITING TUNGSTEN FILM HAVING LOW RESISTIVITY, LOW ROUGHNESS AND HIGH REFLECTIVITY. The contents of which are incorporated herein by reference. The substrate may be moved from a deposition station to another station, and in a more specific embodiment, another process chamber operating under different conditions may continue processing on the same station, or may be moved first from the deposition station (eg, store Can be returned back to the deposition station for selective removal of the deposited layer.

One way to achieve selective removal (ie, removing more deposition material near the opening than inside the features) is to perform operation 205 in a mass transfer control scheme. In this scheme, the rate of removal within a feature is determined by the amount and / or relative amount of different etchant material components (eg, initial etchant material, activated etchant species and recombined etchant species) that diffuse into the feature. By composition, it is limited. In certain instances, the etch rate depends on the concentration of various etchant components at different locations within the feature. As used herein, the terms “etching” and “removal” are used interchangeably. Selective removal may be performed using any removal technique, such as etching and other techniques.

Mass transfer control conditions can be characterized, in part, by changes in total etchant concentration. In certain embodiments, this concentration is lower inside the feature than in the vicinity of the opening, resulting in a higher etch rate near the opening than inside the feature. Thus, this leads to selective removal. Mass transfer control process conditions can be achieved by supplying a limited amount of etchant into the process chamber (eg, with respect to cavity profile and size) while maintaining a relatively high etch rate to consume some etchant as it diffuses into the features. Using a low etchant flow rate). In certain embodiments, there is a significant concentration gradient that can be generated by relatively high etch kinetic energy and relatively low etch feed rates. In certain embodiments, the etch rate near the opening can be mass controlled, and such conditions are not necessary to obtain selective removal.

In addition to the overall etchant concentration variation inside the high aspect ratio features, selective removal may be affected by the relative concentrations of the different etchant components throughout the feature. These relative concentrations depend on the relative power of separation and recombination of the etch species. As will be described further below, the initial etchant material is affected by delivery through a remote plasma generator, and / or by in-drilling plasma, and can produce activated etchant species (eg, fluorine elements, radicals). It is common to have one. However, activated species tend to recombine with less active recombined etching species (eg, fluorine molecules), and / or react with tungsten-containing materials along the diffusion path. Thus, different portions of the deposited tungsten-containing layer may be exposed to different etchant materials at different concentrations (eg, initial etchant, activated etchant species, recombined etchant species). This provides an additional opportunity to control the selective removal, as described below.

For example, generally, activated fluorine species react better with tungsten-containing materials than initial and recombined etching materials. In addition, as shown in FIG. 7, activated fluorine species are generally less sensitive to temperature fluctuations than recombined fluorine species. Thus, process conditions can be controlled in such a way that removal has a strong effect on the activated fluorine species. In addition, species treatment conditions may cause activated fluorine species to be present at higher concentrations near the feature opening than inside the feature. For example, some activated species may be consumed (eg, reacted with and / or absorbed by the deposited material and / or absorbed on the surface) and / or recombined while deeply diffusing into features (especially small high aspect ratio features). Can be. Recombination of activated species may also occur outside the high aspect ratio features, such as in the showerhead of the process chamber, and depends on the chamber pressure. Thus, chamber pressure can be specifically controlled to adjust the concentration of activated etch species at various points in the chamber and features. From now on these process conditions and other process conditions will be explained in more detail.

In certain embodiments, selective removal operation 205 includes introducing an initial etchant material into the process chamber and selectively removing the deposited layer using the initial etchant material. Etchant selection depends on the material deposited. While the present application focuses on tungsten containing materials such as tungsten and tungsten nitride, it should be understood that other materials may also be used for partial or complete filling of high aspect ratio features. Some examples of these materials are titanium, titanium nitride, tantalum, tantalum nitride, ruthenium and cobalt. These materials may be deposited using physical vapor deposition (PVD), chemical vapor deposition (CVD), atomic layer deposition (ALD), and other deposition techniques. In general, operation 205 may be used to selectively remove any material formed within high aspect ratio features, such as diffusion barrier layers, nucleation layers, and / or fill materials.

Examples of initial etchant materials that may be used for the selective removal of tungsten containing materials and any other materials include, but are not limited to, nitrogen tri-fluoride (NF ₃ ), tetra-fluoro-methane (CF ₄ ), tetrafluoro Roethylene (C ₂ F ₄ ), hexafluoroethane (C ₂ F ₆ ) and octafluoropropane (C ₃ F ₈ ), tri-fluoro-methane (CHF ₃ ), sulfur hexafluoride (SF ₆ ) And molecular fluorine (F ₂ ). Typically, the process involves producing activated species (eg, radicals, ions and / or high energy molecules). For example, the initial material may be introduced via a remote plasma generator or affected by in-situ plasma.

In general, the flow rate of the etchant depends on the size of the chamber, the etch rate, the etch uniformity, and other parameters. Typically, the flow rate is chosen in such a way that more tungsten-containing material is removed near the opening than inside the feature. In certain embodiments, these flow rates result in mass transfer controlled selective removal. For example, the flow rate for a 195 liter chamber per station may be between about 25 sccm and 10,000 sccm, or in more specific embodiments, between about 50 sccm and 1,000 sccm. In certain embodiments, the flow rate is about 2,000 sccm or less, specifically about 1,000 sccm or less, more specifically about 500 sccm or less. It should be noted that these values are provided for one individual station set up to process 300 mm wafer substrates. If those skilled in the art, for example, these flow rates can be scaled according to the substrate size, scaled according to the number of stations in the device (eg 4 times for 4-station devices), and depending on the process chamber volume, It will be appreciated that the ratio may be adjusted according to other factors.

In certain embodiments, the substrate needs to be heated or cooled before the removal operation 205 can proceed. Various devices to bring the substrate to a specified temperature, such as heating (or cooling) elements in a station (such as an electrical resistance heater installed in a pedestal, or heat transfer fluid circulated through the pedestal), and an infrared lamp located above the substrate. Plasma ignition or the like can be used.

In addition to inducing a chemical reaction between the deposited layer and various etchant species, the temperature specified for the substrate is chosen in such a way as to control the rate of the chemical reaction. For example, the temperature may be selected to have a high removal rate such that more material is removed near the opening than inside the feature. In addition, the temperature can be selected to control recombination of activated species (eg, recombination of atomic fluorine to molecular fluorine) and / or to control which species contributes strongly to etching. Eventually, the substrate temperature is based on the chemical composition of the etchant, the desired etch rate, the desired concentration distribution of the activated species, the desired contribution to selective removal by the different species, and other materials and process parameters, Can be selected. In certain embodiments, the substrate is maintained at about 300 ° C. or less, more specifically about 250 ° C. or less, or about 150 ° C. or less, or about 100 ° C. or less. In another embodiment, the substrate is heated to about 300 ° C. to 450 ° C., and in more specific embodiments, to about 350 ° C. to 400 ° C. For other types of etchant, other temperature ranges may be used.

Activated species are not only faster than recombination of these species, but also provide more desirable selective removal. Thus, various approaches have been developed to increase the relative concentration and / or removal contribution of activated species. For example, the activation energy of the activated fluorine species is much smaller than the activation energy of the recombined fluorine species. Thus, by lowering the substrate temperature, it is possible to cause higher removal contributions from activated species. At certain temperatures (other process conditions such as flow rate and chamber pressure), the relative removal contribution of the activated species may exceed the relative removal contribution of the recombined species.

7 is a plot of two etch rates (activated species (line 702) and species recombined (line 704)) as a function of pedestal temperature. Remote plasma generator at 400 sccm for 20 seconds. The etch test was modeled using a nitrogen tri-fluoride precursor supplied to the process chamber (line 702) and a molecular fluorine precursor supplied at 500 sccm for 50 seconds (line 704). The chamber pressure was maintained at 1 Torr during both tests, resulting in that the etch rate (line 704) corresponding to the recombined fluorine molecules can be substantially reduced by lowering the pedestal temperature. The etch rate corresponding to was maintained relatively flat (line 702), ie, the etch rate corresponding to the activated species is not as sensitive to pedestal temperature as line 704.

In certain embodiments, it may be difficult to remove or even substantially minimize recombined species (eg, minimize recombination of activated species) from the contact substrate surface. For example, the apparatus includes a showerhead (described in detail later with reference to FIG. 4), wherein the showerhead substantially recombines previously activated etchant species (eg, flowing through the showerhead from a remote plasma generator). Cause. This may be due, for example, to long residence times and high surface-to-volume ratios in the closed space of the showerhead. Although recombination is still present in the system, the effect of the recombined species of partial removal can be lowered by the substrate temperature during this operation. Atomic fluorine has a much lower activation energy than molecular fluorine (0.33 eV versus 0.55 eV). This relationship is also common for other activated and recombined species. Thus, by lowering the temperature during the etching operation, the etch contribution of the recombined species can be reduced.

Another process parameter that may affect the recombination of activated species is the pressure inside the chamber, more specifically, several other materials that may be present in the chamber (eg, initial etchant material, activated species, recombined). Chemical species, carrier gas, reaction product, etc.). It is common for higher voltage forces (eg, about 10 Torr or higher) to correspond to shorter mean free paths of activated etchant species, which leads to more collisions between species Leads to higher recombination rates. In addition, at low pressure levels, the sticking probability of some recombined species (eg, molecular fluorine) to the tungsten surface or other similar surface may be reduced to the activated species (eg, atomic fluorine). It was found to be lower than the adhesion coefficient of. Low adhesion coefficients tend to improve step coverage.

8 is a plot of etch rate as a function of chamber pressure for the nitrogen tri-fluoride precursor fed to the process chamber at 400 sccm for 20 seconds. The substrate was kept at 300 ° C. during this experiment. The results show that an increase in pressure from 01 Torr to 5 Torr lowers the etch rate. Regardless of any particular theory, the higher the pressure at this level, the faster the activated species recombines into the recombined species that have a lower reactivity and have a lower etch rate. This recombination and low etch reactivity actually offset any increase caused by the high overall etch concentration. If the pressure is increased by more than 5 Torr, higher concentrations of etching material cause a moderate increase in etch rate. Removal is mainly controlled by the species recombined at this pressure level. Thus, in order to have a higher contribution from the activated species, the process chamber needs to be maintained at a lower overall pressure value. In certain embodiments, the process chamber is maintained at about 5 Torr or less, more specifically at about 2 Torr or less, and more specifically at about 1 Torr or less or about 0.1 Torr or less.

Referring again to FIG. 2, as a result of the selective removal operation 205, the average thickness of the deposited layer near the opening may be greater than the average thickness of the layer deposited inside the feature. In certain embodiments, the reduction near the opening is at least about 10%, and in more specific embodiments at least about 25%, than the reduction within the features. Generally, removal operation 205 may be performed up to the point where the substrate or any under-layer (if present) is exposed to the etchant. The remaining layers can be characterized by step coverage. In a feature embodiment, the step coverage of the etched layer is at least about 75%, more specifically at least about 100%, or at least about 125%, even more specifically at least about 150%.

In certain embodiments, the removal operation is performed to form a passivated surface. This surface prevents the tungsten-containing material from being deposited in the next deposition cycle. Forming a passivated surface is described with reference to FIG. 2, but is not so limited, and may be performed in any tungsten deposition process by appropriately using an etching process. Passivation and thus a series of tungsten depositions can be selective or non-selective for feature depth or other geometric regions of the deposition surface by appropriately tuning the etching conditions as described herein.

Referring again to FIG. 2, in certain embodiments, a selective removal operation 205 is performed at certain process conditions to form a layer having a passivated surface, which may be referred to as a remaining layer. In certain embodiments, passivation differs along the depth of the high aspect ratio features because of other etching conditions (eg, concentration of activated species) that vary along this depth, as mentioned above. For example, the process conditions during this operation can be tuned such that there is more passivation in particular near the opening of the feature than inside the feature. In general, these conditions correspond to low pressures (eg, 8 Torr or less, even 5 Torr or less) and extended etching times (eg, usually 1 second or more, even 5 seconds or more for 30-nanometer features). This phenomenon will be explained in more detail below with reference to FIG.

9 is a plot showing the second deposition cycle deposition thickness as a function of time for five wafer sets processed using different etching conditions. This diagram shows the effect of the different passivation levels caused by these etching conditions on the deposition rate. In this experiment, an initial tungsten layer is deposited on the surface of five wafer sets. The same deposition conditions were used for all five sets. Thereafter, each wafer set was processed using different etching conditions. The first wafer set (upper solid line, identified by numerals 133, 354, and 545 in the diagram) corresponding to line 902 in FIG. 9 was not etched at all. That is, after the first deposition cycle, a second deposition cycle is followed which does not have any intermediate etching cycles. The second set of wafers corresponding to line 904 (the dotted line located in the middle identified by number 526. Other numbers are not visible because they are adjacent to the other two lines) were etched at 18 Torr for 7 seconds. The third set of wafers corresponding to line 906 (the lower solid line of the upper group consisting of three lines identified by numbers 126, 344 and 517) were etched at 18 Torr for 17 seconds. The fourth set of wafers (identified by numbers 54, 99 and 149) corresponding to line 908 were etched at 0.8 Torr for 5 seconds. Finally, a fifth set of wafers (identified by numbers 5, 9 and 25) corresponding to line 908 was etched at 0.8 Torr for 10 seconds. These five wafer sets formed additional tungsten layers under the same deposition conditions for three time periods (ie, 5 seconds, 15 seconds and 25 seconds). The final thickness of these additional tungsten layers is provided in FIG. 9.

9 shows the first three wafer sets (ie, wafers that are not etched or etched at 18 Torr), and they are a much thicker second than the other two wafer sets (ie wafers etched at 0.8 Torr). It has an additional tungsten layer that is deposited in the deposition cycle. As described above with reference to FIG. 8, higher pressure levels result in recombination of activated etching species (eg, recombination of atomic fluorine into molecular fluorine) during etching and, to some extent, chemical reaction May cause. The final etched layers processed at different pressure levels during etching may have different properties, such as chemical composition and / or physical structure, on their exposed surfaces. This, in turn, affects the deposition of the later deposited tungsten layer (see FIG. 9). In particular, FIG. 9 shows that the lower the pressure and the longer the time, the more passivation residual layers that prevent deposition of at least the next layer. At the same time, as shown in Figure 8, the more the pressure level sits, the more aggressive the etch results. The combination of pressure and etch duration can be carefully controlled to prevent the initial deposited layer from being completely removed and damaging the diffusion barrier layer located below it.

Some passivation is desirable near the feature opening, but passivation inside the feature is less desirable and should be avoided in certain embodiments. In certain process conditions, it was found that the high aspect ratio features are differentially passivated during etching in such a way that the remaining layer is more passivated near the opening than inside the features. Regardless of any particular theory, etching at low pressure levels can result in mass transfer control states in high aspect ratio features in which there is a higher concentration of activated etchant species near the feature opening than inside the feature. have. While etching the layer near the opening, some other activated etchant species are consumed while some activated species recombine and diffuse into the features.

Passivation near the opening of the feature must also be carefully controlled to prevent excessive passivation near the feature opening and to allow sufficient deposition to fully fill and close the feature for later work. This is reflected in FIGS. 10 and 11. In particular, FIG. 10 shows a Scnning Electron Microscopy (SEM) image of a 30-nanometer feature after initial tungsten deposition followed by a 3-second etch and further tungsten deposition. The lower region of this feature is fully charged but the upper region is left unfilled. A gradual bottom-up fill caused by different passivation prevents premature closure and seam formation of the features, but results in excessive passivation on the unfilled features as shown in FIG. This may be undesirable or may not be acceptable. FIG. 11 likewise shows a cross-sectional SEM image of another 30-nanometer feature after initial tungsten deposition, one-second etching, and the same additional tungsten deposition. The upper part of this feature is fully filled. In some cases, over-passivation is avoided, although some passivation near the feature opening may be desirable.

In view of this, the process conditions can be specifically tuned to obtain the desired process result (eg, full filling of the high aspect ratio features in a substantially void free manner). Some of these process conditions include performing the removal operation at a pressure of 5 Torr or less, or 2 Torr or less, or even 1 Torr or less. In some embodiments, the pressure is maintained at about 0.1 Torr to 5 Torr, more specifically about 0.5 Torr to 3 Torr. The duration of the etch operation generally depends on the thickness of the initial layer, and it is common to keep the thickness of the initial layer below about half the size of the feature to prevent closure of the feature. For example, the initial layer deposited over a substrate surface including 30-nanometer features is typically no greater than 15 nanometers. Such a layer can be etched for about 1 second above, more specifically for at least about 3 seconds, even for at least about 5 seconds, without damaging the underlying layer. In certain embodiments, the duration of the etching operation is about 1 to about 10 seconds, more specifically about 3 to about 5 seconds. Referring to the remaining layer and feature size, etching conditions may also be described. In certain embodiments, the remaining layer has a thickness of 10% or less of the feature opening.

In certain embodiments, the substrate may include one or more features that are closed during deposition operation 203 and remain closed during selective removal operation 205. For example, the substrate can include small size features, medium size features, and large size features. Some small size features may be closed during the initial deposition operation and may not open again. The mid-size features may be closed during later cycles and remain closed while other larger size features are being charged. In some embodiments, features may be located at various vertical levels of the substrate, such as in a dual-damascene arrangement. Features on the low level may close faster than features on the high level.

In certain embodiments, deposition operation 203 may only temporarily close features. Unlike closing a feature during a final filling operation (eg, operation 213 to be described below), or unlike having a plurality of features of different sizes and different vertical positions, the shim during this temporary closure. It may still be too large to allow, or start too close to the field area. In this embodiment, selective removal operation 205 such that the first part of operation 205 is used to re-open the feature, and then the next part of operation 205 is used to selectively remove the deposited material. This can be designed. The process conditions in these two parts may be the same or different from each other. For example, the etchant flow rate is increased during the first part of operation 205, and then decreases as features are reopened.

As represented by decision block 207, the deposition-removal cycle, including deposition operation 203 and selective removal operation 205, may be repeated one or more times. For example, especially for small size features with large overhangs, after one cycle, it may be difficult to achieve the desired step coverage. In determining 207 whether to proceed with another cycle, the overhang size, feature size, feature aspect ratio, feature bowing, shim size, shim location requirements are considered.

In certain embodiments, process parameters may be changed 209 for one or both tasks of the next cycle. For example, because the deposited layer is still a thin layer and there is a high risk of contamination during etching, the net deposition during the initial cycle may need to be greater than that of the next cycle. At the same time, the cavity is initially more open and the risk of closure is lower. For example, an initial deposition cycle may be performed at a slower deposition rate (eg, driven by lower temperature and / or chamber pressure) to better control the amount of tungsten containing material deposited on the partially fabricated substrate. Can be. As mentioned above, slower rates can lead to more conformal deposition, which may be more necessary for certain feature types (eg, small, high aspect ratio features). Subsequent deposition cycles can be performed at faster deposition rates (eg, driven by high temperatures and / or high chamber pressures), since the thickness deposited is less important, and / or the cavity is likely to close prematurely. This is because the previous deposition-etch cycle may have been after modifying the profile of the cavity to be lowered. In other embodiments, late cycle deposition operations can be performed at slower deposition rates because the remaining cavities are smaller and more likely to close prematurely. Likewise, the etching process conditions can be modified cycle-by-cycle, for example, to be performed under less aggressive etching conditions when the deposited layer is still thin, and eventually under more aggressive etching conditions.

Referring again to FIG. 3, cross-sectional view 331 shows features after selective removal. Thus, cross-sectional views 321 and 331 may represent one of a first cycle, or more generally an initial cycle. The layer 323 deposited during this cycle is too thin to fully compensate for or offset various cause of seam formation (eg, overhang 315). For example, after the selective removal operation, the cavity shown in cross-sectional view 331 is still narrower near the opening than inside the feature. In certain embodiments, this difference (how narrower) may be small enough for the process to proceed to the final filling operation without repeating the deposition-removal cycle.

Cross-sectional views 341 and 351 show the substrate 303 during and after a later cycle. First, cross-sectional view 341 illustrates a newly deposited layer 343 formed over the etched layer 333. The features of layer 343 may have an improved profile that reflects the lower step coverage obtained during the previous cycle. However, the profile of the cavity still does not allow progress to final filling, and another etching operation may be needed to further mold this cavity. Sectional view 351 shows the substrate 303 at the final deposition low stage to complete the filling. The cavity is wider near the opening than inside the cavity. In certain embodiments, the step coverage of the newly deposited layer is at least about 10%, more specifically at least about 20%, or at least about 30%, than the step coverage of the initially deposited layer.

Referring again to FIG. 2, in certain embodiments, the deposition operation 203 and the optional removal operation 205 may be performed at the same time, which appear at step 204. For example, precursors and etchant may be introduced simultaneously into the process chamber so that deposition and etching reactions occur simultaneously. In order to obtain a better net deposition rate inside the feature than near the opening, at least initially, the flow rate of the etchant and the tungsten-containing precursor is determined such that the etching reaction is mass transfer control and therefore depends on the etchant concentration. . At the same time, the deposition reaction is not mass transfer control, but proceeds at about the same speed inside the feature and at the opening. During operation 204, the etchant or precursor flow rate, or both, may be adjusted (eg, gradually or stepwise), and at some point the flow of etchant to the process chamber may be stopped. Can be. At this point, the process can be transferred to the final filling operation 213.

After one or more deposition-removal cycles have been performed to partially fill the features and form the feature profiles, the process may proceed to final fill operation 213. This operation may be similar to deposition operation 203 in some aspects. The main difference is that operation 213 proceeds until the feature is fully closed, and is not followed by an etching operation to open the feature. Referring again to FIG. 3, a cross-sectional view 361 after the final filling operation shows an example of the substrate 303. In a particular embodiment, the feature still has a shim 363 (but smaller than in the prior art charging feature shown in FIG. 1), and is a reference point located farther from the field area than in the prior art charging feature. Has In a particular embodiment, the shim 363 ends at about 20% or more from the field region with respect to feature depth (ie, the ratio of D _REF to D _FET is at least about 20%).

In yet another embodiment, the feature is filled by depositing more tungsten inside the feature than near the opening. Different deposition rates can be obtained by inhibiting tungsten-containing material from depositing at different levels on the surface depending on the location in the feature (eg near the opening or within the feature). In particular, the near proximal surface can be suppressed more than the feature inner surface. In certain embodiments, an inhibitor is introduced into the process chamber prior to the deposition operation. The exposed surfaces of the features are treated with these inhibitors in a mass transfer control scheme similar to that described previously in the context of etching. However, unlike etching operations, no material is removed from the surface during suppression (ie no pure etching). For example, at certain process conditions, fluorine-based etching of the deposited layer may result in the formation of residues (eg, residues containing certain tungsten fluorides) on the surface of the residual etching layer. These residues function as inhibitors in the next deposition operation. In addition, under certain process conditions, no material is purely removed from the incremental godine layer, and the deposited layer forms a more general suppression layer near the opening than inside the feature. Filling features using differential deposition rates may be performed in conjunction with, or in place of, the deposition-removal operations described above.

Device

The method of the present invention can be carried out in various types of deposition apparatus available from various manufacturers. Examples of suitable devices include Novellus Concept 2 Altus, Concept-2 Altus-S, Concept 3 Altus Deposition System, Concept 3 Inova Deposition System, or any other commercial use of Novellus System, Inc. of San Jose, CA. There is a possible CVD process system. In some cases, the process may be performed in a single chamber, as described, for example, in US Pat. No. 6,770,714, which is incorporated herein by reference. In some cases the process may be performed sequentially on multiple deposition stations. See US patent 6143082, which is incorporated herein by reference. In some embodiments, the tungsten-rich barrier deposition process is performed at the first station, or at the first and second stations, which are one of two, four, or five, or more deposition stations in a single deposition chamber. do. At the first station, the reducing gas and organometallic precursor can be introduced to the surface of the semiconductor substrate using a separate gas supply system that produces a localized atmosphere at the substrate surface.

6 is a block diagram of a CVD process system suitable for carrying out a tungsten thin film deposition process, in accordance with an embodiment of the present invention. The system 600 includes a transfer module 603. The transport module 603 provides a clean, pressurized environment to minimize the risk of contamination of the substrate as the substrate being processed is moved between various reactor modules. A multi-station reactor 609 capable of performing PNL deposition and CVD according to an embodiment of the present invention is mounted on the transport module 603. Chamber 609 may include a number of stations 611, 613, 615, 617 capable of sequentially performing their tasks. For example, chamber 609 may be configured such that station 611 performs PNL deposition, station 713 performs multi-pulse reducing agent treatment, and stations 615 and 617 perform CVD. .

In addition, one or more single or multiple station modules 607 may be mounted on the transport module 603 suitable for performing plasma, or chemical (non-plasma) pre-clean. The module can also be used for a variety of other processing, for example, post liner tungsten nitride processing, and the system 600 can also be used at least one (in this case 2, where wafers are stored before and after processing). Two wafer source modules (601). In an atmospheric transport chamber 619, an atmospheric robot (not shown) first moves the wafer from the source module 601 to a loadlock 621. A wafer transport device (generally a robot arm unit) in the transport module 603 moves the wafer from the load lock 621 to a module mounted on the transport module 603 and between the mounted modules. .

In certain embodiments, a system controller is used to control process conditions during deposition. Typically, the controller will include one or more memory devices and one or more processors. The processor may include a CPU or computer, or an analog / digital input / output connection, or a stepper motor controller, board, or the like.

The controller can control all the actions of the deposition apparatus. The system controller execution system includes a set of instructions for controlling timing, gas mixture, chamber pressure, chamber temperature, wafer temperature, RF power level, wafer chuck, pedestal position and other specific process parameters. To control the software. In some embodiments, other programs stored in a memory device associated with the controller may be used.

Typically, there will be a user interface associated with the controller. The user interface may include a display screen of the device and / or process status, a graphical software display, and a user input device (eg, pointing device, keyboard, touch screen, microphone, etc.).

Computer program code for controlling deposition and other processes in a process sequence may be written in any conventional computer readable programming language, such as C, C ++ m, Pascal, Fortran, and the like. The processor may execute the compiled object code, or script, to perform the tasks identified in the program.

Controller parameters relate to process conditions such as process gas composition and flow rate, temperature, pressure, plasma state, RF power level, low frequency RF frequency, cooling gas pressure, chamber wall temperature. These parameters are provided to the user in the form of a recipe and can be entered using a user interface.

Signals for monitoring the process may be provided by analog and / or digital input connections to the system controller. The signal for controlling the process is the output according to the analog and digital output connections of the deposition apparatus.

System software can be designed or configured in a variety of different ways. For example, subroutines, or control objects, of various chamber components can be written to control the operation of the chamber components to perform the deposition process of the present invention. Examples of programs, or sections of programs, for this purpose are substrate positioning code, process gas control code, pressure control code, heater control code, and plasma control code.

A substrate positioning program is program code for loading a substrate into a pedestal or chuck and controlling chamber components to control the space between the substrate and the rest of the substrate, such as a gas inlet and / or target. It may include. The process gas control program may include code for controlling gas composition and flow rate, and optionally code for introducing gas into the chamber prior to deposition to stabilize the pressure in the chamber. For example, the pressure control program may include code for controlling the pressure in the chamber by adjusting the throttle valve of the chamber's exhaust system. The heater control program may include code for controlling the current to the heating unit used to heat the substrate. Alternatively, the heater control program may control the transfer of a heat transfer gas, such as helium, to the wafer chuck.

Examples of chamber sensors that can be monitored during deposition include mass flow controllers, pressure sensors (eg, pressure gauges) and thermocouples located on pedestals or chucks. Using data from these sensors, appropriately programmed feedback and control algorithms can be used to maintain the desired process conditions. Embodiments of embodiments of the present invention in single or multi-chamber semiconductor processing tools have been described above.

Experiment

In order to determine the effect of different process conditions on the selective removal of the deposited material and the final shim, a series of experiments were performed. Increasing the substrate temperature and decreasing the etchant flow rate result in mass transport limited etching inside the feature, thereby allowing more material to be removed near the opening than inside the feature. Found.

In one experiment, their effects on different etching conditions and step coverage were evaluated. Substrates were used having openings of about 250 nanometers in cross section and features having aspect ratios of about 10: 1. First, the features were partially filled with tungsten in an argon and address atmosphere, at a substrate temperature of about 395 ° C., and at a flow rate of about 200 sccm of tungsten fluoride (WF6). Thereafter, several substrate cross sections were taken so that the tungsten distribution inside the features could be analyzed. The layer was somewhat thinner inside the feature (on average about 862 angstroms thick) than around the feature opening (on average about 639 angstroms thick), which resulted in about 62% step coverage.

The remaining substrates were divided into two groups. The first group of substrates were etched using reference process conditions: a chamber pressure of about 8 Torr, a substrate temperature of about 350 ° C., a flow rate of nitrogen tri-fluoride (NF 3) of about 2,000 sccm, and an etching duration of about 4 seconds. time. Cross sections of a plurality of substrates in this group were taken, and the tungsten distribution inside the features could be further analyzed. The opening thickness (tungsten layer thickness near the opening) averaged about 497 angstroms, the internal thickness averaged about 464 angstroms, and the step coverage was about 107%.

The second wafer group was etched using different (“improved”) process conditions. It is believed that these new conditions enable the etching of features in a mass-transport limited manner, so that step coverage can be improved even further. The substrate temperature was increased to about 395 ° C. and the etchant flow rate was reduced to about 400 sccm. Etching was performed in a chamber maintained at about 2 Torr for about 12 seconds. The remaining etched layer was significantly thicker inside the features (average about 555 angstroms thick) than near the opening (average about 344 angstroms thick). The calculated step coverage is about 161%.

6A schematically illustrates a feature 601 provided in a partially fabricated semiconductor substrate 603 that includes a tungsten-containing layer 605 formed in the feature 601 under conditions similar to those used in the aforementioned experiments. Illustrated. The figure also shows the measurements at different points of layer thickness. 6B shows a graph of the thickness distribution of the tungsten-containing layer for the previously described experiments before and after etching for two different process conditions. The horizontal axis of this graph corresponds to the measurement point shown in FIG. 6A. The thickness values provided in the graph were normalized to the respective values for the field area (points 1 to 16). Lower thin line 607 shows the thickness distribution inside the feature before any etching. This line shows that after deposition, the layer is somewhat thinner inside the feature than near the opening. The middle thick line 609 shows the thickness distribution for the substrate etched using the reference etch conditions. This distribution represents greater step coverage than the step coverage represented by line 607. Finally, the thin line 611 at the top shows the distribution of tungsten etched using the "improved" condition. It shows an improved step coverage. The thickness at the lowest (deepest) measurement point (points 8, 9 and 10, approximately 30-40% from the bottom of the feature) is near the field area (points 1, 2, 15 and 16). It is almost twice larger than the thickness of.

conclusion

The examples and embodiments herein are described for purposes of illustration, and in this regard, various modifications or changes will be apparent to those skilled in the art. While various details have been omitted for clarity, various design alternatives may be implemented. The examples of the present invention are therefore to be regarded as illustrative in nature and not as restrictive.

Claims (30)

A method of filling a high aspect ratio feature on a partially fabricated semiconductor substrate, the method comprising:
Introducing a tungsten-containing precursor and a reducing agent into the process chamber,
Depositing a layer of tungsten-containing material onto a partially fabricated semiconductor substrate through a chemical vapor deposition reaction between the tungsten-containing precursor and the reducing agent, wherein the layer of tungsten-containing material partially fills the high aspect ratio features. Characterized by a deposition step,
Introducing an activated etching material into the process chamber,
Removing a portion of the layer of tungsten-containing material using an activated etching material to form a remaining layer,
Introducing the tungsten-containing precursor and reducing agent back into the process chamber;
Selectively depositing an additional layer of tungsten-containing material on the partially fabricated semiconductor substrate through a chemical vapor deposition reaction between the tungsten-containing precursor and the reducing agent, wherein the additional layer is thicker inside the feature than near the feature opening. Of additional layer selective deposition step
Method for filling a high aspect ratio feature, characterized in that it comprises a. The method of claim 1, wherein the process chamber is maintained at a pressure of 5 Torr or less during the removing step. The method of claim 1, wherein the residual layer is selectively passivated such that the passivation of the residual layer is more passivated near the feature opening than inside the feature. The method of claim 1, wherein the remaining layer is thinner near the feature opening than inside the feature. 2. The method of claim 1, wherein during the removing step, more tungsten-containing material is removed near the feature opening than inside the feature. 2. The method of claim 1, wherein the further layer selective deposition step comprises filling at least a lower half of the high aspect ratio features in a void free manner. The method of claim 1 wherein the step of removing is performed by a mass transport regime. The method of claim 1, wherein the depositing, removing and selective deposition steps are performed in different process chambers maintained at different environmental conditions. The method of claim 1 wherein the method is
Applying the photoresist to the partially fabricated semiconductor substrate,
Exposing the photoresist,
Patterning the photoresist to form a pattern and transferring the pattern onto the partially fabricated semiconductor substrate
Method for filling a high aspect ratio feature, characterized in that it further comprises. A method of filling a high aspect ratio feature provided on a partially fabricated semiconductor substrate, the method comprising
Introducing a tungsten-containing precursor and a reducing agent into the process chamber,
Depositing a layer of tungsten-containing material on a partially fabricated semiconductor substrate via a chemical vapor deposition reaction between the tungsten-containing precursor and the reducing agent, wherein the layer partially fills high aspect ratio features. Wow,
Introducing an activated etching material into the process chamber,
Selectively removing a portion of the layer of tungsten-containing material to form a remaining layer, wherein the residual layer has a passivation level that varies along the depth direction of the high aspect ratio feature and is more than within a feature. Selective removal step of features that are more passivated near the feature opening
Method for filling a high aspect ratio feature, characterized in that it comprises a. 11. The high aspect ratio feature of claim 10, wherein the passivation level of the remaining layer at a particular depth is correlated with the amount of tungsten-containing material removed from the layer of tungsten-containing material at the particular depth. How to charge wealth. A method for processing a partially fabricated semiconductor substrate, the method comprising
Providing to the process chamber a partially fabricated semiconductor substrate comprising a high aspect ratio feature having a size of less than 50 nanometers and having an aspect ratio of 4 or more, the protective substrate being deposited within the high aspect ratio feature; Wow,
Introducing a tungsten-containing precursor and a reducing agent into the process chamber,
Through chemical vapor deposition reaction between a tungsten-containing precursor and a reducing agent, the layer of tungsten-containing material deposits a layer of tungsten-containing material on a partially fabricated semiconductor substrate having a thickness less than half the size of the high aspect ratio feature. Steps,
Introducing an activated etching material into the process chamber,
Removing a portion of the layer using an etching material activated at a pressure of 5 Torr or less for a certain time;
Introducing a tungsten-containing precursor and a reducing agent into the process chamber,
Selectively depositing an additional layer of tungsten-containing material on the partially fabricated semiconductor substrate through a chemical vapor deposition reaction between the tungsten-containing precursor and the reducing agent, wherein the internal deposition rate within the feature is determined by the proximity of the feature opening. A selective deposition step that is twice as high as an external deposition rate and allows to fill at least the bottom half of the feature
And a method for processing a partially fabricated semiconductor substrate. 13. The method of claim 12, wherein the specific time is determined by the thickness of the layer. 13. The partially fabricated semiconductor of claim 12, wherein the feature of the high aspect ratio is 30 nanometers, the depth of the feature of the high aspect ratio is 250 nanometers, and the duration of the removing step is from 1 second to 10 seconds. Method for processing a substrate. 13. The method of claim 12, wherein the external deposition rate is less than 100 Angstroms per minute during the initial 30 seconds or more of the selective deposition. A semiconductor processing apparatus for filling high aspect ratio features on a partially fabricated semiconductor substrate, the apparatus comprising:
A first process chamber,
A second process chamber,
Controller
Including;
The first process chamber has one or more deposition stations for positioning a substrate, wherein the first process chamber is, through a chemical vapor deposition reaction, a layer of tungsten-containing material or a tungsten-containing material on a partially fabricated semiconductor substrate. Configured to deposit an additional layer of material, wherein the one or more deposition stations include a deposition heating element for controlling the temperature of the substrate during deposition,
The second process chamber has one or more etching stations for positioning the substrate, the second process chamber is configured to selectively remove a portion of the layer, and the one or more etching stations are configured to control the temperature of the substrate during etching. An etching heating element for
The controller,
A program instruction for introducing the tungsten-containing precursor and the reducing agent into the first process chamber,
Introducing the tungsten-containing precursor and the reducing agent into the first process chamber, and then introducing an activated etching material into the second process chamber at a pressure of 5 Torr or less for a time of 1 to 10 seconds;
Introducing the activated etching material into the second process chamber and then introducing the tungsten-containing precursor and reducing agent into the first process chamber or another process chamber.
A semiconductor processing apparatus for filling a high aspect ratio feature, characterized in that to perform. The method of claim 16, wherein the semiconductor processing apparatus
Wafer stepper
A semiconductor processing apparatus for filling a high aspect ratio feature further comprising. A computer readable storage medium having recorded thereon program instructions for controlling a semiconductor processing apparatus for filling high aspect ratio features provided on a partially manufactured semiconductor substrate, the program instructions comprising:
A cord for introducing a tungsten-containing precursor and a reducing agent into the first process chamber,
A cord for introducing the activated etching material into the second process chamber at a pressure of 5 Torr or less for a time of 1 to 10 seconds;
Code for introducing a tungsten-containing precursor and a reducing agent into a first process chamber or another process chamber
And a program command recorded thereon. A method for filling a high aspect ratio feature provided on a partially fabricated semiconductor substrate, the method comprising
Introducing a tungsten-containing precursor and a reducing agent into the process chamber,
Depositing a layer of tungsten-containing material onto a partially fabricated semiconductor substrate through a chemical vapor deposition reaction between a tungsten-containing precursor and a reducing agent, the layer of tungsten-containing material partially filling high aspect ratio features. Characterized by a deposition step,
Introducing an activated etching material into the process chamber,
Selectively removing a portion of the deposited layer using the activated etching material under process conditions that limit recombination of the activated etching material
And a high aspect ratio feature. 20. The method of claim 19, wherein the process conditions include a temperature of a partially fabricated semiconductor substrate of 250 ° C. or less and a pressure of a process chamber of 5 Torr or less. 20. The filling of high aspect ratio features as claimed in claim 19, wherein the rate of decrease of the thickness of the deposited layer near the opening of the high aspect ratio feature is at least 25% greater than the rate of decrease of the thickness of the deposited layer inside the high aspect ratio feature. How to. 20. The method of claim 19, wherein the method is performed in a mass transport regime to remove a portion of the deposited layer. 20. The method of claim 19, wherein the activated etch material is introduced into the process chamber from a remote plasma generator configured to produce an activated etch material from the initial etch material. 20. The method of claim 19, wherein the method is
Repeating the deposition step to form a second deposition layer,
Repeating the selective removal step to form a second etching layer
Further comprising a high aspect ratio feature. 25. The method of claim 24, wherein the repeating selective removal step is performed at different process conditions than the previous selective removal step. 25. The high aspect ratio feature of claim 24, wherein a rate of decrease in thickness of the second deposited layer near the opening of the high aspect ratio feature is at least 10% greater than a rate of decrease of the thickness of the second deposited layer inside the high aspect ratio feature. Method for charging wealth. 20. The method of claim 19, wherein the method is
Depositing a tungsten-containing material on the partially fabricated semiconductor substrate through the chemical vapor deposition reaction between the tungsten-containing precursor and the reducing agent until the high aspect ratio features are closed
Further comprising a high aspect ratio feature. 28. The method of claim 27, wherein the closed high aspect ratio features have a seam ending at at least 20% of the depth from the field region of the high aspect ratio feature. 20. The method of claim 19, wherein the deposition and selective removal steps are performed in different chambers maintained at different environmental conditions. A semiconductor processing apparatus for filling a high aspect ratio feature provided on a partially fabricated semiconductor substrate, the apparatus comprising:
A first process chamber,
A second process chamber,
Controller
Including;
The first process chamber has one or more deposition stations for positioning a substrate, the first process chamber is configured to deposit a layer of tungsten-containing material on a partially manufactured semiconductor substrate via a chemical vapor deposition reaction, The at least one deposition station comprises a deposition heating element for controlling the temperature of the substrate during deposition,
The second process chamber has one or more etching stations for positioning the substrate, the second process chamber is configured to selectively remove a portion of the deposited layer, and the one or more etching stations control the temperature of the substrate during etching. An etching heating element for
The controller,
Through a chemical vapor deposition reaction between the tungsten-containing precursor and the reducing agent, depositing a layer of tungsten-containing material on the partially fabricated semiconductor substrate such that the layer of tungsten-containing material partially fills the high aspect ratio features;
Instructions for introducing the activated etching material into the second process chamber,
Selectively remove a portion of the deposited layer using the activated etching material under process conditions that prevent recombination of the activated etching material
A semiconductor processing apparatus, characterized in that for performing.

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