Patent Application
20160042945
The present disclosure relates to substrate processing methods and more particularly to methods for depositing film on a substrate.
The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Fabrication of substrates such as semiconductor wafers typically requires multiple processing steps that may include material deposition, planarization, feature patterning, feature etching, and feature cleaning. These processing steps are typically repeated one or more times during processing of the substrate.
As semiconductor devices continue to scale down to smaller feature sizes, high aspect ratio (HAR) structures are increasingly required to achieve desired device performance objectives. The use of the HAR structures creates challenges for some of the substrate processing steps. For example, wet processes such as etch and clean pose problems for the HAR structures due to capillary forces that are generated during drying of the substrate. The strength of the capillary forces depends upon surface tension, a contact angle of the etch, clean, or rinse fluids that are being dried, feature spacing and/or an aspect ratio of the features. If the capillary forces generated during drying are too high, the HAR features will become strained or collapse onto each other and stiction may occur, which severely degrades device yield.
To solve this problem, one approach uses rinsing liquids that have a lower surface tension than deionized water to prevent the features from collapsing. While generally successful for relatively low aspect ratio structures, this approach has the same collapse and stiction issues as methods that use deionized water. The rinse fluids still possess a finite amount of surface tension that generates forces during drying that are still too strong for the fragile HAR structures.
An alternative approach for drying HAR structures involves dissolving and flushing the rinsing fluid with a supercritical fluid. Supercritical fluids are free of surface tension when processed correctly. However, several technical and manufacturing challenges arise when using the supercritical fluids. The challenges include high equipment and safety costs, long process times, variable solvent quality during the process, extreme sensitivity due to the diffuse and tunable nature of the fluid, and wafer defectivity/contamination issues arising from the interaction of the supercritical fluid with components of the processing chamber.
Another approach for preventing collapse of the HAR structures during processing is to add a mechanical brace. However, this approach typically has higher cost and process complexity that negatively impact throughput and yield. Furthermore, the mechanical braces are limited to certain types of patterned features.
A method includes depositing a film solution onto a patterned feature of a semiconductor substrate after wet cleaning the semiconductor substrate and without performing a drying step after the wet cleaning. The film solution includes a dielectric film precursor or a dielectric film precursor and at least one of a reactant, a solvent, a surfactant and a carrier fluid. The method includes baking at least one of solvent and unreacted solution out of a film formed by the film solution by heating the substrate to a baking temperature.
In other features, the method includes, prior to depositing the film solution and after wet cleaning, rinsing the patterned feature with a rinsing fluid. The rinsing fluid comprises at least one of water, aqueous alcohol and a polar solvent.
In other features, the method includes curing the substrate after baking the film. The curing comprises at least one of heating, thermal annealing, ultraviolet (UV) curing, plasma curing or chemically reactive curing. A curing temperature of the curing is greater than the baking temperature.
In other features, the method includes applying the film solution to the patterned feature using a spin-on approach.
In other features, depositing the film solution includes pre-wetting the semiconductor substrate with a first solution, displacing the first solution using the film solution and spinning the substrate using a spin coater. The displacing and the spinning occur sequentially, simultaneously or overlapping.
In other features, the dielectric film precursor of the film solution includes a polysilazane. The patterned feature includes at least one high aspect ratio (HAR) feature. An aspect ratio of the at least one high aspect ratio (HAR) feature is greater than or equal to 8.
A method includes rinsing a patterned feature of a semiconductor substrate with a rinsing fluid after wet cleaning the semiconductor and without performing a drying step after the wet cleaning. The method includes at least partially displacing the rinsing fluid on the patterned feature using a film solution. The film solution includes a dielectric film precursor or a dielectric film precursor and one of a reactant, a solvent, surfactant and a carrier fluid. The method includes baking at least one of solvent and unreacted solution out of film formed by the film solution by heating the substrate to a baking temperature. The method includes curing the substrate after baking the film.
In other features, the rinsing fluid comprises at least one of water, aqueous alcohol and a polar solvent. The curing comprises at least one of heating, thermal annealing, ultraviolet (UV) curing, plasma curing or chemically reactive curing. A curing temperature of the curing is greater than the baking temperature.
In other features, the method includes applying the film solution to the patterned feature using a spin-on approach. The dielectric film precursor of the film solution includes a polysilazane. The patterned feature includes at least one high aspect ratio (HAR) feature. An aspect ratio of the at least one high aspect ratio (HAR) feature is greater than or equal to 8.
Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.
The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein:
In the drawings, reference numbers may be reused to identify similar and/or identical elements.
Systems and methods according to the present disclosure enable collapse-free feature fill of HAR structures using spin-on film deposition after a wafer wet clean step and without a prior drying step. By keeping the surface wet after wet cleaning and transitioning to a liquid precursor for a spin-on film, the method eliminates a vapor/liquid interface between the HAR features that occurs during drying. The capillary forces that are generated during drying are eliminated and the HAR structures can be filled using spin-on film without collapse or stiction.
For example only, the method for film deposition can be performed on a clean track. After wet cleaning, the substrate may be rinsed with a post rinse fluid. In some examples, the post rinse fluid includes water, aqueous alcohol or polar solvent, which remains on the surface with the HAR features. A spin-coater can be used to spin-on a film solution including a film precursor or a film precursor and at least one of a solvent, a reactant, a surfactant or a carrier liquid. If used, the reactant chemical reacts with the film precursor to create a solid film.
For example only, a hot plate or another curing approach can be used to drive out excess or unreacted liquids in the film. In some examples, the deposited film may be a dielectric film. For example only, the solution may be a dielectric solution that includes a dielectric film precursor in an aqueous alcohol solution. The wetted volume on the substrate is displaced by the film solution. The film solution is selected to diffuse through the wetted surface to provide bottom-up fill. In some examples, the film solution operates in a regime that favors gap-fill, such as in shallow trench isolation (STI), pre-metal dielectric (PMD) or inter-metal dielectric (IMD) applications. In an alternative method, only the film precursor is deposited and a diffusion/reaction occurs through the wetted layer.
As can be appreciated, the methods described herein allow deposition of a film such as a dielectric film onto a patterned surface of a substrate such as a semiconductor wafer after wet cleaning and without first drying the surface on which the film is deposited. This approach avoids the problem of having the HAR features collapse or become strained during drying after wet cleaning. This approach also increases process throughput by reducing steps that are required to dry the substrate.
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In some examples, the film solution is a dielectric film solution. In some examples, the dielectric film may be a silicon oxide, a silicon nitride, silicon carbide, silicon carbon nitride, aluminum oxide, hafnium oxide, low-k dielectric, or porous dielectric. In some examples, the film solution is a spin-on film solution. In some examples, the film precursor includes one or more polysilazanes, although other film precursors may be used. In some examples, the film solution may include other reactants that will chemically react with the film precursor, such as water, peroxides, or alcohols. In some examples, the film solution may also include catalysts or inhibitors that may, respectively, speed up or slow down the chemical reaction with the film precursor. In some examples, the carrier fluid may include water, aqueous alcohol, solvent, surfactant, or other carrier fluid.
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In some examples, the solvent baking of the substrate may occur at a lower temperature than the subsequent curing step. For example only, curing may include heating, thermal annealing, ultraviolet (UV) curing, plasma curing or chemically reactive curing. For example only, the substrate may be cured at high temperature (such as at temperatures ≧300 C-800 C) and/or in the presence of oxygen, ozone, steam or other oxygen-containing gases. For example only, the solvent baking may be performed at a temperature between 75 C and 300 C, such as 150 C.
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For example only, hydrolyzed precursor may be used to form Si(OH)3R′ in solution with H2O or alcohol. The hydrolyzed precursor is diffused into solution onto the pre-wetted substrate. Polymerization occurs on the wetted substrate to form SiCOH film. For example only, hydrolyzed precursor may be used to form Si(OH)4 in solution with H2O. The hydrolyzed precursor is diffused into solution onto the pre-wetted substrate. Polymerization occurs on the wetted substrate to form SiO2 or SiOxHy film. For example only, an unhydrolyzed precursor may be used which then reacts with H2O or alcohol in the film solution. Hydrolysis and polymerization occurs on the wetted substrate to form the film. In these examples the film solution reacts to form a sol, gel or solid film on the wetted substrate.
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The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.” It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure.
