Method for forming a charge layer using vapor and liquid phase coating - Patents.com

Abstract

A method for tuning the work function of a structure in a substrate utilizes near-surface doping. In some embodiments, the method for tuning the work function of a structure in a substrate may include coating a surface of the structure to form a doping layer in a non-solid phase containing a dopant on the surface of the structure, and performing a dopant diffusion process using an oxidation process to drive the dopant through the surface of the structure to embed the dopant in the structure to form an abrupt junction profile and form an oxide layer on the surface of the structure to tune the work function of the structure near the surface. Coating the surface of the structure may be performed using a gas phase process or a liquid phase process.

Description

[Technical field]

[0001] FIELD OF THE PREFERRED EMBODIMENTS Embodiments of the present principles relate generally to semiconductor processing of semiconductor substrates. [Background technology]

[0002] As part of building semiconductor devices, structures such as trenches are often formed on a substrate. Bulk processing and high temperatures are typically used to modify the work function of the structures. However, the inventors have discovered that during such processes, high temperatures can damage the surrounding devices and also cause areas of large charge gradients to form in the structures, reducing the area available for other device layers and causing significant degradation in performance.

[0003] Thus, the inventors have provided an improved process for forming a charge layer that significantly enhances the performance and quantum efficiency of the structure without requiring surface modification prior to carrying out the process. Summary of the Invention

[0004] Provided herein are methods and structures for improved charge layers using vapor and liquid phase coating.

[0005] In some embodiments, a method of tuning a work function of a structure on a substrate may include coating a surface of the structure to form a doping layer in a non-solid phase containing a dopant on the surface of the structure, and performing a dopant diffusion process using an oxidation process to drive the dopant through the surface of the structure to embed the dopant in the structure to tune the work function of the structure near the surface, forming an abrupt junction profile and forming an oxide layer on the surface of the structure.

[0006] In some embodiments, the method includes: the oxidation process is a dry oxidation process; the oxidation process is a wet oxidation process; the method is performed without prior modification of the crystalline formation of the surface of the structure; the surface of the structure is coated using a vapor phase coating; the surface of the structure is coated using a liquid phase coating; the method is performed at a temperature less than 450 degrees Celsius; the dopant diffusion process is at most plus or minus about 1e16 / cm 3 ~About 1e20 / cm 3 The method may further include forming the structure using an etching process that results in a charge on a surface of the structure; forming a sacrificial oxide layer on the surface of the structure by a dry oxidation process at a temperature less than about 450 degrees Celsius with a controllable oxidation thickness of about 1 nm to about 15 nm; selectively removing the sacrificial oxide layer from the surface of the structure prior to coating the surface of the structure to form the doping layer; the dry oxidation process being performed in a plasma oxidation chamber; and / or etching the structure into a substrate to a high aspect ratio of greater than about 75:1.

[0007] In some embodiments, a method for adjusting a work function of a structure on a substrate may include coating a surface of the structure with a plasma-based process to form a gas-phase doping layer containing a dopant on the surface of the structure, and performing a dopant diffusion process using a dry oxidation process to drive the dopant through the surface of the structure to embed the dopant in the structure to adjust the work function of the structure near the surface and form an oxide layer on the surface of the structure, where the dopant diffusion process is performed at less than about 450 degrees Celsius and forms a charge layer with an abrupt junction profile.

[0008] In some embodiments, the method further comprises the step of: the dopant diffusion process is at most plus or minus about 1e16 / cm 3 ~About 1e20 / cm 3the dopant is P-type or N-type; the method is performed in a back-end-of-line (BEOL) process; the method is performed without prior alteration of the crystalline formation of the surface of the structure; and / or the method may further include forming the structure using an etching process; forming a sacrificial oxide layer on the surface of the structure by a dry oxidation process at a temperature less than about 450 degrees Celsius with a controllable oxide thickness of about 1 nm to about 15 nm; and selectively removing the sacrificial oxide layer from the surface of the structure prior to coating the surface of the structure to form the gas phase doping layer.

[0009] In some embodiments, a non-transitory computer readable medium having instructions stored thereon that, when executed, cause a method for tuning a work function of a structure in a substrate to be performed, the method may include coating a surface of the structure to form a doping layer in a non-solid phase containing a dopant on the surface of the structure, and performing a dopant diffusion process using an oxidation process to drive the dopant through the surface of the structure to embed the dopant in the structure to tune the work function of the structure near the surface, forming an abrupt junction profile and forming an oxide layer on the surface of the structure.

[0010] In some embodiments, the non-transitory computer readable medium is configured to provide a dopant diffusion process having a dopant diffusion rate of up to plus or minus about 1e16 / cm 3 ~About 1e20 / cm 3 In one embodiment, the method further comprises generating a charge on a surface of the structure to form a step-like junction profile, and / or the surface of the structure is coated using a vapor or liquid phase coating.

[0011] Other and further embodiments are disclosed below.

[0012] Embodiments of the present principles, briefly summarized above and described in more detail below, can be understood by reference to exemplary embodiments of the principles that are illustrated in the accompanying drawings, which, however, depict only typical embodiments of the present principles, and therefore should not be considered limiting in scope, since the present principles may admit of other equally effective embodiments. [Brief description of the drawings]

[0013] [Figure 1] 1 is a diagram of a method for adjusting a charge layer on a surface of a structure on a substrate, according to some embodiments of the present principles; [Figure 2A] 1A-1C are cross-sectional views of structures after an etching process, in accordance with some embodiments of the present principles. [Figure 2B] 1A-1C are cross-sectional views of structures after an optional dry oxidation process, in accordance with some embodiments of the present principles. [Figure 2C] 1A-1C are cross-sectional views of structures after an optional selective oxide removal process, in accordance with some embodiments of the present principles. [Figure 2D] 1 is a cross-sectional view of a structure after forming a coating or doping layer, according to some embodiments of the present principles. [Figure 2E] 1 is a cross-sectional view of a structure after oxidation, according to some embodiments of the present principles. [Figure 2F] 4A-4C are cross-sectional views of structures after formation of an oxide layer, in accordance with some embodiments of the present principles. [Diagram 3] FIG. 1 illustrates an integration tool according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] For ease of understanding, the same reference numbers have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0015] The method provides a high performance charge layer formation solution that dramatically increases the charge manipulation capability at the surface of a structure. The method provides innovative dopant and junction formation using gas and liquid phase processes with precise profile control without the thermal budget and surface state constraints found in older processes. The technique allows for abrupt junction formation of charge near the surface with ultra-high activation doping without crystal damage. Additionally, the technique allows for use in back-end-of-line (BEOL) processes without thermal damage to existing structures on the substrate. The method is also compatible with the surfaces of high aspect ratio structures, greater than 50:1. The principle technique allows for low to high activation doping levels while maintaining a low thermal budget of less than 450 degrees Celsius and is insensitive to surface states. Additionally, the gas phase process allows for high conformality in high aspect ratio structures.

[0016] In the following examples, trenches are used as "structures" for simplicity, however, other structures may benefit from the methods of the present principles, and therefore the use of trenches in the examples is not limiting. For example, the techniques of the present principles may also be used for planar structures. FIG. 1 is a method 100 of adjusting a charge layer or work function of a structure 204 in a substrate 202, according to some embodiments. At block 102, in some embodiments, an etching process forms a structure 204 in the substrate 202, for example, as shown in view 200A of FIG. 2A. The etching process typically uses a hard mask layer 212 that protects areas from the etching process. In some embodiments, the aspect ratio of the structure 204 is at least about 50:1. In some embodiments, the aspect ratio of the structure 204 is at least about 75:1. In some embodiments, the aspect ratio of the structure 204 is at least about 100:1. As a side effect of the etching process, damage 208 occurs to a surface 206 of the structure 204. The damage 208 may include crystalline damage in the substrate material, contaminants or residues from the etching process, and / or dangling bonds in the substrate material, etc. The hard mask layer 212 is removed after the etching process is completed. The method of the present principles has the advantage and ability to proceed directly onto a damaged or unclean surface of the structure 204 (perform block 102 of method 100 and move directly to block 108). However, for completeness, the method may also be performed on an undamaged and clean surface, as described in optional blocks 104 and 106.

[0017] To further prepare the structure 204 in optional block 104, in some embodiments, an oxide layer 216 is formed on the substrate 202 as a sacrificial layer using a dry oxidation process. As shown in view 200B of FIG. 2B, the field 214 or top surface of the substrate 202 and the surface 206 of the structure 204 undergo a dry oxidation process to form an oxide layer 216, which partially consumes the material of the substrate 202, including damaged portions. The dry oxidation process is performed at a temperature below 450 degrees Celsius and may result in less contamination and residue when compared to a wet oxidation process. Furthermore, the dry oxidation process may be used on much higher aspect ratio structures (e.g., greater than 100:1 aspect ratio) than wet oxidation (e.g., less than 50:1 aspect ratio). In some embodiments, the dry oxidation process is performed with a plasma oxidation chamber with or without a remote plasma source. The dry oxidation process is performed to repair the damage to the surface 206 and to reduce the stress-induced leakage current (SILC) and interface trap density (D it ) to facilitate embedding oxygen in the surface 206 of the structure 204.

[0018] The dry oxidation process can also be controlled to provide different thicknesses of the oxide layer 216. Parameters such as exposure time, plasma density, temperature, etc. can facilitate determining the oxidation rate. The thickness is then controlled by the duration of the dry oxidation process. In conventional methods such as wet oxidation, the oxidation process is self-limiting (wet oxidation processes are self-terminating) and the oxide layer thickness cannot be adjusted. Wet oxidation generally stops at a saturation point at a thickness of 1 nm to 2 nm (self-limiting). Dry oxidation does not have a saturation point, is not self-limiting, and allows any level of thickness to be obtained. In some embodiments, the dry oxidation process can achieve conformality in the structure 204 of greater than 95% for structures with aspect ratios greater than 100:1, enabling scaling of isolated structures using the present principles.

[0019] In optional block 106, in some embodiments, the oxide layer 216 is selectively removed from the surface 206 and the field 214 of the structure 204 of the substrate 202, as shown in view 200C of FIG. 2C. In some embodiments, a plasma-based chamber may be used to selectively remove the oxide layer 216, for example, with a selectivity ratio of greater than 50:1 (e.g., oxide with respect to Si or SiGe). The selective removal of the oxide layer 216 removes all of the oxide layer 216 without damaging any of the materials underlying the substrate 202 or creating contaminants / residues, thereby leaving an undamaged and clean surface of the structure 204. In block 108, the surface 206 of the structure 204 is coated by using a gas-phase or liquid-phase process to form a doping layer 210 with dopants 222 on the surface of the structure 204, as shown in view 200D of FIG. 2D. As previously described, the coatings and processes are insensitive to surface conditions and can be applied to damaged or unclean surfaces of structure 204 (e.g., surface 206 in FIG. 2A ), as well as undamaged and clean surfaces of structure 204 (e.g., surface 206 in FIG. 2C ).

[0020] The surface insensitivity of the process allows for great flexibility without adding complexity to the process when not required. In some embodiments, a gas phase process can be performed by using a plasma-based process and process gases to deposit the dopant 222 on the surface 206 of the structure 204. The gas phase dopant development on the surface 206 is limited to a subsequent dry oxidation process to diffuse the dopant 222 into the surface 206. The gas phase dopant development provides greater conformality on the surface 206, especially in high aspect ratio structures. The pressure can be adjusted to allow the gas phase dopant to form on the surface with greater conformality as the pressure increases. In some embodiments, a liquid phase process results in a wet layer of the dopant 222 on the surface 206 of the structure 204. The liquid phase dopant development on the surface 206 is compatible with subsequent dry and wet oxidation processes to diffuse the dopant 222 into the surface 206. The coating or doping layer 210 on the surface 206 may have a thickness 232 of less than one nanometer and up to an atomic layer thickness.

[0021] The dopant 222 species (P-type species shown but not limited to) can be incorporated to form positive or negative charges on the substrate 202 (e.g., silicon doped with boron, gallium, phosphor, arsenic, etc.). The dopant 222 density and / or dopant 222 type can be adjusted to provide a given positive or negative charge level as required for the structure 204. In block 110, the structure 204 is oxidized to diffuse the dopant 222 to the surface 206 to adjust the work function of the structure 204 and to form an oxide layer. The work function of the structure 204 is adjusted by varying the dopant density, dopant type, and dopant depth. The dopant 222 density and / or dopant 222 type can be adjusted to provide a given positive or negative charge level and a given work function as required for the structure 204. A higher work function near the surface can facilitate or increase carrier mobility inside adjacent structures, such as pixel structures, reducing sensitivity to surface recombination. The above techniques allow for considerable flexibility in engineering the work function through dopant depth, density, and type tuning, while increasing adjacent structure area by using an abrupt junction profile.

[0022] After deposition of the dopant using a gas or liquid phase process, a dopant diffusion process 224 is performed on the structure 204 as shown in the view 200E of FIG. 2E. In some embodiments, the dopant diffusion process 224 can be a dry oxidation process performed in a plasma oxidation chamber or the like. The dry oxidation process is compatible with the gas and liquid phase processes for the diffusion of the dopant to the surface 206 of the structure 204. In some embodiments, the dopant diffusion process 224 can be a wet oxidation process that is compatible with the liquid phase process for the diffusion of the dopant to the surface 206 of the structure 204. In practice, the doping layer 210 results in the liner layer 230 and the buried charge layer 226 without an annealing process as shown in the view 200F of FIG. 2F.

[0023] The dopant diffusion process 224 creates an abrupt charge boundary or abrupt junction profile or abrupt composition transition in the material of the substrate 202 that increases the effective area of ​​adjacent structures (e.g., pixel structure area, etc.) in contrast to conventional techniques that create gradient charge regions that require more area to be used adjacent the structures, reducing the performance of the adjacent structures. An abrupt junction, as used herein, is, by definition, a junction in which the doping concentration changes over a very small distance from the surface compared to the spatial extent over which the doping can be diffused. In some embodiments, the charge layer 226 has a doping concentration of plus or minus about 1e16 / cm, depending on the allowable temperature and pressure. 3 ~About 1e20 / cm 3 The charge layer 226 of the present principles can achieve a level of activation such that it can be processed without the need for post-activation processing. In optional block 112, an additional back-end-of-line (BEOL) compatible thermal or annealing process can be performed after oxidation. In some embodiments, the above process can be performed without an air break to prevent surface impurities, contaminants, and / or particle generation.

[0024] The methods described herein may be implemented in individual process chambers, which may be provided in a stand-alone configuration or as part of a cluster tool, for example, an integrated tool 300 (i.e., a cluster tool) described below with respect to FIG. 3. An advantage of using an integrated tool 300 is that there is no vacuum break and therefore no requirement to degas and pre-clean the substrate prior to processing in the chamber. For example, in some embodiments, the inventive methods described above may be advantageously implemented in an integrated tool with limited or no vacuum breaks between processes to limit or prevent contamination of the substrate. The integrated tool 300 includes a vacuum-tight processing platform 301, a factory interface 304, and a system controller 302. The processing platform 301 includes multiple processing chambers, such as 314A, 313B, 314C, 314D, 314E, and 314F, operably coupled to a vacuum substrate transfer chamber (transfer chambers 303A, 303B). The factory interface 304 is operably coupled to the transfer chamber 303A by one or more load lock chambers (two load lock chambers, such as 306A and 306B shown in FIG. 3).

[0025] In some embodiments, the factory interface 304 includes at least one docking station 307 and at least one factory interface robot 338 to facilitate transfer of semiconductor substrates. The docking station 307 is configured to receive one or more front opening unified pods (FOUPs). Four FOUPs, such as 305A, 305B, 305C, and 305D, are shown in the embodiment of FIG. 3. The factory interface robot 338 is configured to transfer substrates from the factory interface 304 to the processing platform 301 through the load lock chambers, such as 306A and 306B. Each of the load lock chambers 306A and 306B has a first port coupled to the factory interface 304 and a second port coupled to the transfer chamber 303A. The load lock chambers 306A and 306B are coupled to a pressure control system (not shown) that pumps down and vents the load lock chambers 306A and 306B to facilitate the transfer of substrates between the vacuum environment of the transfer chamber 303A and the substantially ambient (e.g., atmospheric) environment of the factory interface 304. The transfer chambers 303A, 303B have vacuum robots 342A, 342B disposed therein. The vacuum robot 342A can transfer substrates 321 between the load lock chambers 306A, 306B, the processing chambers 314A and 314F, and the cooling station 340 or pre-cleaning station 342. The vacuum robot 342B can transfer substrates 321 between the cooling station 340 or pre-cleaning station 342 and the processing chambers 314B, 314C, 314D, and 314E.

[0026] In some embodiments, the processing chambers 314A, 314B, 314C, 314D, 314E, and 314F are coupled to the transfer chambers 303A, 303B. The processing chambers 314A, 314B, 314C, 314D, 314E, and 314F may comprise, for example, atomic layer deposition (ALD) process chambers, physical vapor deposition (PVD) process chambers, chemical vapor deposition (CVD) chambers, annealing chambers, and the like. The chambers may include any chamber suitable for performing all or part of the methods described herein, as described above, such as dry oxide removal or pre-cleaning chambers, and etching and deposition chambers. In some embodiments, one or more optional service chambers (shown as 316A and 316B) may be coupled to the transfer chamber 303A. The service chambers 316A and 316B may be configured to perform other substrate processes, such as degassing, orientation, substrate metrology, cooling, and the like.

[0027] The system controller 302 controls the operation of the tool 300 using direct control of the process chambers 314A, 314B, 314C, 314D, 314E, and 314F, or alternatively, by controlling the computers (or controllers) associated with the process chambers 314A, 314B, 314C, 314D, 314E, and 314F and the tool 300. During operation, the system controller 302 enables data collection and feedback from the respective chambers and systems to optimize the performance of the tool 300. The system controller 302 generally includes a central processing unit (CPU) 330, a memory 334, and support circuits 332. The CPU 330 may be any form of general-purpose computer processor that may be used in an industrial setting. The support circuits 332 are conventionally coupled to the CPU 330 and may include cache, clock circuits, input / output subsystems, power supplies, etc. Software routines, such as the methods described above, when stored in memory 334 and executed by CPU 330, may transform CPU 330 into a special purpose computer (system controller) 302. Software routines may also be stored and / or executed by a second controller (not shown) located remotely from tool 300.

[0028] Embodiments according to the present principles may be implemented in hardware, firmware, software, or any combination thereof. Embodiments may also be implemented as instructions stored using one or more computer-readable media, which may be read and executed by one or more processors. A computer-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing platform, or a "virtual machine" running on one or more computing platforms). For example, a computer-readable medium may include any suitable form of volatile or non-volatile memory. In some embodiments, a computer-readable medium may include a non-transitory computer-readable medium.

[0029] While the forgoing is directed to embodiments of the present principles, other and further embodiments of the present principles may be devised without departing from the basic scope thereof.

Claims

1. 1. A method for adjusting a work function of a structure on a substrate, comprising: coating the surface of the structure to form a non-solid phase doping layer containing a dopant on the surface of the structure, the structure having an aspect ratio of at least 50:1; performing a dopant diffusion process using an oxidation process to drive the dopant through the surface of the structure to embed the dopant in the structure to form an abrupt junction profile and to form an oxide layer on the surface of the structure to adjust the work function of the structure proximate the surface; A method comprising:

2. The method of claim 1 , wherein the oxidation process is a dry oxidation process.

3. The method of claim 1 , wherein the oxidation process is a wet oxidation process.

4. The method of claim 1 , performed without prior modification of the crystalline formation of the surface of the structure.

5. The method of claim 1 , wherein the surface of the structure is coated using a vapor phase coating.

6. The method of claim 1 , wherein the surface of the structure is coated using a liquid phase coating.

7. 10. The method of claim 1 carried out at a temperature below 450 degrees Celsius.

8. The dopant diffusion process has a maximum of plus or minus about 1e16 / cm ３ to about 1e20 / cm ３ The method of claim 1 , further comprising:

9. forming said structure using an etching process; forming a sacrificial oxide layer on a surface of the structure by a dry oxidation process at a temperature less than about 450 degrees Celsius with a controllable oxide thickness of about 1 nm to about 15 nm; selectively removing the sacrificial oxide layer from a surface of the structure prior to coating the surface of the structure to form the doping layer; The method of claim 1 further comprising:

10. The method of claim 9 , wherein the dry oxidation process is performed in a plasma oxidation chamber.

11. Etching said structure into said substrate to a high aspect ratio of greater than about 75:

1. The method of claim 9 further comprising:

12. 1. A method for adjusting a work function of a structure on a substrate, comprising: coating a surface of the structure by a plasma-based process to form a gas-phase doping layer on the surface of the structure comprising a dopant; performing a dopant diffusion process using a dry oxidation process to drive the dopant through the surface of the structure to embed the dopant into the structure to adjust the work function of the structure proximate the surface and form an oxide layer on the surface of the structure, the dopant diffusion process being performed at a temperature less than about 450 degrees Celsius and forming a charge layer with an abrupt junction profile; A method comprising:

13. The dopant diffusion process has a maximum of plus or minus about 1e16 / cm ３ to about 1e20 / cm ３ The method of claim 12, further comprising:

14. The method of claim 12 , wherein the dopant is P-type or N-type.

15. The method of claim 12 , wherein the method is performed in a back-end-of-line (BEOL) process.

16. 13. The method of claim 12, performed without prior modification of the crystalline formation of the surface of the structure.

17. forming said structure using an etching process; forming a sacrificial oxide layer on a surface of the structure by a dry oxidation process at a temperature less than about 450 degrees Celsius with a controllable oxide thickness of about 1 nm to about 15 nm; selectively removing the sacrificial oxide layer from a surface of the structure prior to coating the surface of the structure to form the gas-phase doping layer; The method of claim 12 further comprising:

18. 1. A non-transitory computer readable medium having stored thereon instructions that, when executed, cause a method for tuning a work function of a structure in a substrate to be performed, the method comprising: coating a surface of the structure to form a doping layer in a non-solid phase containing a dopant on the surface of the structure; performing a dopant diffusion process using an oxidation process to drive the dopant through the surface of the structure to embed the dopant in the structure to form an abrupt junction profile and to form an oxide layer on the surface of the structure to adjust the work function of the structure proximate the surface; A non-transitory computer readable medium comprising:

19. The dopant diffusion process has a maximum of plus or minus about 1e16 / cm ３ to about 1e20 / cm ３ 20. The non-transitory computer readable medium of claim 18, wherein the first and second electrodes are connected to a first electrode and a second electrode are connected to a second electrode.

20. 20. The non-transitory computer readable medium of claim 18, wherein the surface of the structure is coated using a vapor phase coating or a liquid phase coating.

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