Method for producing a semiconductor substrate having an epitaxially deposited layer
The process of susceptor oxidation forms an oxide layer to prevent reactive gas deposition on semiconductor substrates, addressing substrate deterioration and maintaining quality for electronic components without complex susceptor modifications.
Patent Information
- Application Number
- JP2025540854
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-02-07
- Filing Date
- 2024-02-06
- Publication Date
- 2026-01-29
AI Technical Summary
Existing epitaxial deposition processes face issues with reactive gas deposition on the rear surface of semiconductor substrates, leading to substrate deterioration and unsuitability for electronic component manufacturing, and the use of susceptors with gas channels complicates the process and requires major equipment modifications.
A process involving susceptor oxidation using an oxygen-containing gas mixture forms an oxide layer between the susceptor and substrate, preventing reactive gas deposition on the rear surface, and includes steps like chamber etching, coating, and firing to manage substrate quality.
Prevents reactive gas deposition on the rear surface of semiconductor substrates, maintaining substrate quality for electronic components and avoiding complex susceptor modifications.
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Abstract
Description
[Technical Field]
[0001] The field of the invention is that of processes for producing semiconductor substrates comprising epitaxially deposited layers. [Background technology]
[0002] Description of Related Art The process of epitaxial deposition on semiconductor substrates is described, for example, in U.S. Pat. No. 7,479,187. U.S. Pat. No. 7,479,187 discloses that, for example, during the deposition of silicon on semiconductor substrates, it is advantageous, and often necessary, to remove residues that have accumulated on the surfaces of the epitaxy reactor in an uncontrolled manner. This step, called "chamber etching," may be performed more or less frequently depending on the level of contamination and quality requirements. In some cases, it is appropriate to perform chamber etching after deposition of an epitaxial layer on a semiconductor substrate and before a subsequent epitaxial deposition on another semiconductor substrate. In other cases, chamber etching may be performed less frequently, for example, every 2 to 8 epitaxial depositions on a semiconductor substrate.
[0003] U.S. Patent No. 7,479,187 further provides for coating the etched surface with a thin silicon film in the epitaxy reactor by flowing deposition gases into the epitaxy reactor. The thin silicon film seals the surface and prevents contaminants diffusing from the surface from entering the growing epitaxial layer during subsequent epitaxial deposition. The deposition of the thin silicon film on the surface of the epitaxy reactor after chamber etching is referred to as "chamber coating."
[0004] The epitaxial deposition process requires a susceptor, e.g., a graphite susceptor, which includes one or more circular recesses, called pockets, e.g., made of silicon carbide, formed at the respective locations where the substrates are to be placed. Passage of reactive gases between the pockets and the rear surface of a substrate placed over the pockets can result in deposition of reactive gases on the rear surface of the substrate. Such deposition tends to deteriorate the surface condition of the rear surface of the substrate. This deteriorated surface condition can render the substrate unsuitable for use in processes for the manufacture of electronic components, particularly CMOS circuits.
[0005] To overcome this problem, it is known, for example from US Pat. No. 7,601,224, to use a susceptor with gas channels to enable a trickle of gas to be directed towards the rear surface of the substrate, thereby preventing reactive gas from flowing underneath the substrate and thus preventing unwanted deposition of reactive gas on the rear surface of the substrate.
[0006] The use of such susceptors tends to disrupt the flow of reactive gases within the chamber, which can lead to non-uniform epitaxial deposition, and is also complex, expensive, and requires major equipment modifications. Summary of the Invention
[0007] (Brief Description of the Invention) The present invention aims to overcome the above-mentioned drawbacks of susceptors with gas channels while avoiding deposition of reactive gases on the rear surface of a substrate during epitaxial deposition on the front surface of the substrate.
[0008] Therefore, the present invention provides a process for producing a semiconductor substrate including an epitaxially deposited layer, the process comprising, in order, the steps of etching a susceptor of an epitaxy reactor, coating the susceptor, placing a semiconductor substrate on the susceptor, and depositing an epitaxial layer on the semiconductor substrate. The process additionally includes, after the coating step and before the depositing step, exposing the susceptor to an oxygen-containing gas mixture. This exposure step results in oxidation of the susceptor, resulting in the formation of an oxide layer. This oxide layer is found to be interposed between the susceptor and the rear surface of the substrate during the step of depositing an epitaxial layer on the front surface of the substrate, and allows for the prevention of deposition of reactive gases on the rear surface of the substrate. The process additionally includes, after the step of placing the semiconductor substrate on the susceptor and before the step of depositing an epitaxial layer on the semiconductor substrate, a step of firing the semiconductor substrate, which removes the oxide layer formed by exposure of the susceptor to the oxygen-containing gas mixture, except from the underside of the semiconductor substrate.
[0009] Some preferred, but non-limiting aspects of this process are as follows: The oxygen-containing gas mixture is a mixture of hydrogen and argon containing 0.1% to 10% O2; O2 is introduced into the epitaxy reactor at a flow rate of 0.1 to 10 slm; a step of exposing the susceptor to an oxygen-containing gas mixture occurs after the step of coating and before the step of placing; the oxide layer formed on the surface of the susceptor by exposing the susceptor to the oxygen-containing gas mixture has a thickness of less than 10 Å; the steps of placing the semiconductor substrate on the susceptor and depositing an epitaxial layer on the semiconductor substrate are repeated for at least one other semiconductor substrate without etching, coating, or oxidizing the susceptor therebetween; a step of exposing the susceptor to an oxygen-containing gas mixture occurs after the step of placing and before the step of depositing; the step of exposing the susceptor to the oxygen-containing gas mixture is performed while ramping the temperature of the epitaxy reactor to an epitaxial deposition temperature; The steps of placing the semiconductor substrate on the susceptor, exposing the susceptor to an oxygen-containing gas mixture, and depositing an epitaxial layer on the semiconductor substrate are repeated for at least one other semiconductor substrate without etching and coating the susceptor in between. [Brief explanation of the drawings]
[0010] Other aspects, objects, advantages and features of the present invention will become more clearly apparent from a reading of the following detailed description of preferred embodiments of the invention, given by way of non-limiting example and made with reference to the accompanying drawings, in which:
[0011] [Figure 1] 1 is a diagram illustrating a schematic diagram of the temperature evolution in an epitaxy reactor during an epitaxial deposition process according to the prior art; [Figure 2] FIG. 2 shows a schematic diagram of the evolution of temperature in an epitaxy reactor during an epitaxial deposition process according to a first embodiment of the present invention. [Figure 3] FIG. 5 shows a schematic diagram of the evolution of temperature in an epitaxy reactor during an epitaxial deposition process according to a second embodiment of the present invention. [Figure 4] 1A-1D show schematic diagrams of stages in an epitaxial deposition process according to a first embodiment of the present invention; [Figure 5] 5A-5D show schematic diagrams of stages in an epitaxial deposition process according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION
[0012] (Detailed Description of the Invention) The present invention relates to a process for producing a semiconductor substrate containing an epitaxially deposited layer, which process involves exposing a susceptor of an epitaxy reactor to an oxygen-containing gas mixture.
[0013] The present invention therefore uses an epitaxy reactor into which an oxygen-containing gas mixture can be introduced so as to expose the materials placed therein to the oxygen-containing gas mixture and thus oxidize them in situ. This natural oxidation results in the formation of an oxide layer. This oxide layer is found interposed between the susceptor and the rear surface of the substrate during deposition of the epitaxial layer on the front surface of the substrate, making it possible to prevent deposition of reactive gases on the rear surface of the substrate.
[0014] As mentioned below, exposing the susceptor to the oxygen-containing gas mixture occurs after "chamber coating" and before forming an epitaxial layer. By way of example, exposing the susceptor to the oxygen-containing gas mixture can be performed after "chamber coating" and before placing a semiconductor substrate on the susceptor on which an epitaxial layer is to be deposited, or after placing a semiconductor substrate on the susceptor and before performing epitaxial deposition on the semiconductor substrate.
[0015] 1 is a diagram illustrating a schematic diagram of the change in temperature T in an epitaxy reactor over time t during an epitaxial deposition process according to the prior art. As shown in FIG. 1, after one or more epitaxial depositions EPI (in the illustrated example, four epitaxial positions EPI) on a semiconductor substrate performed in the epitaxy reactor, the susceptor is etched during a chamber etching stage ETCH and coated with a silicon layer during a chamber coating stage COAT. One or more additional epitaxial depositions EPI can then be performed before repeating the chamber etching ETCH and chamber coating COAT.
[0016] 2 and 3 are diagrams showing the evolution of temperature T in an epitaxy reactor over time t during an epitaxial deposition process according to an embodiment of the present invention. As shown in these figures, the process of the present invention includes a stage of exposure of the susceptor to an oxygen-containing gas mixture, denoted ISO. This stage ISO is performed after the chamber coating COAT and before the epitaxial deposition EPI.
[0017] 4 shows the stages of a process for producing a semiconductor substrate comprising an epitaxially deposited layer according to a first embodiment of the invention. This process requires a susceptor S of an epitaxy reactor, for example a graphite susceptor, which includes one or more circular recesses P, called pockets, for example made of silicon carbide, each formed at the location of the placement of a substrate.
[0018] During step (a), the susceptor is subjected to a chamber etching step, for example in H2 and HCl. H2 may be introduced into the epitaxy reactor at a flow rate of 3 to 100 slm (standard liters per minute), while HCl may be introduced into the epitaxy reactor at a flow rate of 5 to 20 slm. The chamber etching step may be carried out at a temperature of 1050°C to 1200°C for a period of 20 to 400 seconds.
[0019] During step (b), the susceptor is subjected to a chamber coating step to form a silicon film 10 thereon, e.g., a polycrystalline silicon film. The chamber coating step can include introducing a mixture of H2 and TCS (trichlorosilane) into the epitaxy reactor. H2 can be introduced into the epitaxy reactor at a flow rate of 3 to 100 slm (standard liters per minute), while TCS can be introduced into the epitaxy reactor at a flow rate of 10 to 19 slm. The chamber coating step can be performed at a temperature of 1000°C to 1150°C for a period of 10 to 100 seconds.
[0020] During step (c), the coated susceptor is exposed to an oxygen-containing gas mixture. This exposure results in the formation of an oxide layer 20 on the surface of the susceptor. The thickness of this oxide layer is, for example, less than 10 Å. More specifically, as mentioned above, this step (c) performs a natural oxidation of the susceptor. The oxygen-containing gas mixture introduced into the epitaxy reactor reacts in situ with the coated susceptor, thereby forming the oxide layer 20. In FIG. 2, these three steps (a), (b), and (c) are designated ETCH, COAT, and ISO, respectively.
[0021] The step of exposing the susceptor to the oxygen-containing gas mixture can be carried out at a temperature of 900°C to 1100°C for a period of 5 to 100 seconds. The oxygen-containing gas mixture to which the susceptor is exposed during natural oxidation can contain hydrogen and argon as carrier gases, with 0.1% to 10% O2. In one possible embodiment, natural oxidation involves introducing oxygen into the epitaxy reactor at a flow rate of 0.1 to 10 slm together with carrier gas H2 at a flow rate of 5 to 100 slm.
[0022] The process continues with step (d) of placing one or more semiconductor substrates 30 on the oxide layer 20 of the susceptor S (more precisely at the position(s) for placing the substrates corresponding to the pocket(s)). The oxide layer 20 is thus interposed between the susceptor and the rear face of each of the substrate(s), thus preventing diffusion of reactive gases between the susceptor and the rear face of the substrate(s) during subsequent steps.
[0023] The process then includes step (e) of baking the semiconductor substrate(s) 30 on the susceptor S, which removes the oxide layer 20 except from the underside of the semiconductor substrate(s) 30 (i.e., the oxide layer still exists between the rear surface of the substrate(s) and the susceptor), and step (f) of depositing an epitaxial layer 40 on the front surface of each of the semiconductor substrate(s) 30. In FIG. 2, these two steps (e) and (f) are designated BAKE and EPI, respectively. As shown in FIG. 2, baking typically occurs after the temperature is increased, and epitaxial deposition occurs after the bake, after which the temperature is decreased. For simplicity of illustration, only one baking step, BAKE, is shown in FIG. 2, but it will be understood that this type of baking step precedes each epitaxial deposition EPI.
[0024] The baking step BAKE may be carried out in H2 introduced at a flow rate of 3 to 100 slm, at a temperature of 950°C to 1200°C, for a period of 5 to 100 seconds.
[0025] The epitaxial deposition EPI step is carried out using a reactive gas for epitaxial deposition, such as TCS, in H2. TCS may be introduced at a flow rate of 5-50 slm, while the carrier gas H2 may be introduced at a flow rate of 3-100 slm. The epitaxial deposition EPI step may be carried out at a temperature of 950°C to 1200°C for a period of 10 seconds to 1000 seconds.
[0026] According to a possible alternative to this first embodiment, the steps of placing a semiconductor substrate on a susceptor, firing the semiconductor substrate, and depositing an epitaxial layer on the semiconductor substrate are repeated for at least one other semiconductor substrate without etching, coating, and natively oxidizing the susceptor between them. By way of example, four to six epitaxial depositions may be performed before the susceptor is subjected to a new sequence of etching, coating, and natively oxidizing. In FIG. 2, four epitaxial depositions (EPI) are performed between two susceptor etching, coating, and natively oxidizing sequences.
[0027] 5 shows stages of a process for producing a semiconductor substrate comprising an epitaxially deposited layer according to a second embodiment of the present invention. Stages (a) and (b) are respectively a chamber etching stage and a chamber coating stage, as mentioned above with respect to FIG. 4. After coating, the process includes stage (c) of placing one or more semiconductor substrates 30 on the susceptor S (more precisely, at the substrate placement position(s) corresponding to the pocket(s)). As shown schematically in FIG. 5, the semiconductor substrate 30 may exhibit a reduced local flatness value in its edge region.
[0028] Subsequently, in step (d), the coated susceptor is exposed to an oxygen-containing gas mixture, during which the oxygen-containing gas mixture introduced into the epitaxy reactor reacts in situ with the coated susceptor by natural oxidation, thereby forming an oxide layer 25 located not only on the front surface of the semiconductor substrate but also on the rear surface of the semiconductor substrate between the semiconductor substrate and the coated susceptor. The thickness of this oxide layer is, for example, less than 10 Å. In Figure 3, this natural oxidation is designated ISO.
[0029] The oxygen-containing gas mixture to which the susceptor is exposed during natural oxidation may contain hydrogen and argon as carrier gases, with 0.1% to 10% O. In one possible embodiment, natural oxidation involves the introduction of oxygen into the epitaxy reactor at a flow rate above 0.1 slm to ensure layer contact on the coated susceptor, while the carrier gas H is introduced at a flow rate of 5 to 100 slm.
[0030] After the natural oxidation of the susceptor, the oxide layer 25 is removed except from the underside of the semiconductor substrate(s) 30 (i.e., an oxide layer still exists between the rear surface of the substrate(s) and the susceptor), followed by step (e) of baking one or more semiconductor substrate(s) 30 on the susceptor S, and step (f) of depositing an epitaxial layer 40 on each of the semiconductor substrate(s) 30. In FIG. 3, these two steps (e) and (f) are designated BAKE and EPI, respectively. As shown in FIG. 3, baking typically occurs after the temperature is increased, and epitaxial deposition occurs after the bake, after which the temperature is decreased. For simplicity of illustration, only one baking step, BAKE, is shown in FIG. 3, but it will be understood that this type of baking step precedes each epitaxial deposition EPI.
[0031] According to this second embodiment, the natural oxidation ISO of the susceptor can be performed during the temperature ramp, i.e., while the temperature of the epitaxy reactor is increased until the temperature of the epitaxial deposition is reached. For example, the natural oxidation ISO of the susceptor can be performed during the temperature ramp up to a temperature of 600°C to 1100°C at a ramp rate of 3 to 10°C / s. Its duration can be 5 to 200 seconds.
[0032] The baking step BAKE may be carried out in H2 introduced at a flow rate of 3 to 100 slm. This may be carried out at a temperature of 950°C to 1200°C for a period of 5 to 100 seconds. The epitaxial deposition EPI step is carried out in H2 using a reactive gas for epitaxial deposition, such as TCS. TCS may be introduced at a flow rate of 5 to 50 slm, while the carrier gas H2 may be introduced at a flow rate of 3 to 100 slm. The epitaxial deposition EPI step may be carried out at a temperature of 950°C to 1200°C for a period of 10 to 1000 seconds.
[0033] According to a possible alternative to this second embodiment, the steps of placing a semiconductor substrate on a susceptor, exposing the susceptor to an oxygen-containing gas mixture, baking the semiconductor substrate, and depositing an epitaxial layer on the semiconductor substrate are repeated for at least one other semiconductor substrate without etching or coating the susceptor during these steps. By way of example, four to six epitaxial depositions may be performed before the susceptor is subjected to a new sequence of etching, etching, and coating. In FIG. 3, four epitaxial depositions of this type are performed between two susceptor etching, etching, and coating sequences, with each epitaxial deposition being preceded by a natural oxidation of the susceptor.
Claims
1. 1. A process for producing a semiconductor substrate including an epitaxially deposited layer, comprising: Etching (ETCH) the susceptor (S) of the epitaxy reactor; coating the susceptor; placing a semiconductor substrate (30) on the susceptor; depositing (EPI) an epitaxial layer (40) on the semiconductor substrate (30); Additionally, after the coating step and before the depositing step, a step of exposing (ISO) the susceptor to an oxygen-containing gas mixture, which results in the formation of an oxide layer (20, 25) on the surface of the susceptor, resulting in oxidation of the susceptor, and which oxide layer (20, 25) can be seen interposed between the susceptor and the rear surface of the semiconductor substrate during the step of depositing the epitaxial layer on the front surface of the semiconductor substrate; Additionally, after the step of placing and before the step of depositing (EPI), baking the semiconductor substrate (30) to remove the oxide layer (20, 25) except for the underside of the semiconductor substrate (30). The process includes:
2. The oxygen-containing gas mixture ２ 2. The process of claim 1, wherein the hydrogen and argon mixture contains 0.1% to 10% of
3. O ２ is introduced into the epitaxy reactor at a flow rate of 0.1 to 10 slm.
4. The process according to any one of claims 1 to 3, wherein the oxide layer (20, 25) formed by the step of exposing (ISO) the susceptor to the oxygen-containing gas mixture exhibits a thickness of less than 10 Å.
5. The process according to any one of claims 1 to 4, wherein the exposing (ISO) step is carried out after the coating (COAT) step and before the setting step.
6. 6. The process of claim 5, wherein the steps of placing a semiconductor substrate on the susceptor and depositing an epitaxial layer on the semiconductor substrate are repeated for at least one other semiconductor substrate without exposing the susceptor to an etching, coating, or oxygen-containing gas mixture therebetween.
7. The process of any one of claims 1 to 4, wherein the exposing (ISO) step is performed after the providing step and before the depositing step.
8. 8. The process of claim 7, wherein the exposing step occurs while the temperature of the epitaxy reactor is ramped up to an epitaxial deposition temperature.
9. 9. The process of claim 7 or 8, wherein the steps of placing a semiconductor substrate on the susceptor, exposing the susceptor, and depositing an epitaxial layer on the semiconductor substrate are repeated for at least one other semiconductor substrate without etching and coating the susceptor in between.