Method for filling deep trench epitaxy of super junction device

Abstract

The invention provides a filling method for deep trench epitaxy of a super junction device, and the method comprises the steps: enabling a second epitaxial layer of a second conductive type to be formed in a deep trench in a first epitaxial layer of a first conductive type in an epitaxy manner through introducing a silicon source gas, a hydrogen chloride gas, a doping gas and hydrogen, and enabling the flow of the hydrogen to meet the following formula: Flow = k * x. According to the method, the flow of the hydrogen in the epitaxial growth process of the second epitaxial layer is dynamically adjusted by adjusting the initial flow x of the hydrogen and the hydrogen flow coefficient k value, and then the deposition rate and the resistivity of the second epitaxial layer are adjusted, so that the optimal deep trench filling effect and PN concentration matching degree are achieved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor manufacturing technology, and in particular to a method for filling deep trench epitaxy of a super junction device. Background Art

[0002] Power semiconductors are the core components of power systems such as switching power supplies, smart cars, and smart grids. Super junction (SJ) technology, with its advantages such as lower power consumption, is highly consistent with the current needs of high-power fast-charging power supplies, LED lighting power supplies, etc.

[0003] Deep trench etching and epitaxial filling, as the core of super junction devices, have very high requirements on the process. Among them, the quality of epitaxial filling and the matching of the doping concentration of the P column and the N column (PN concentration for short) are very important parts.

[0004] In order to complete defect-free, high-quality epitaxial filling faster and more safely, it is necessary to gradually reduce the epitaxial growth rate during the filling process; and in order to meet the needs of deep trench etching and epitaxial filling, the lateral size of the deep trench often gradually increases from the bottom to the top, so the epitaxial growth method with a slightly higher epitaxial concentration at the bottom of the deep trench and a slightly lighter epitaxial concentration at the top of the deep trench is more conducive to PN concentration matching.

[0005] However, there are mainly the following problems in practical applications:

[0006] While the epitaxial growth rate is slowed down by adjusting the flow rate of silicon source gas or HCl gas, if the doping gas (doping gas is, for example, B2H6) is kept unchanged so that the epitaxial growth rate from the bottom to the top of the trench gradually decreases, the inventors found that the epitaxial resistivity also gradually decreases, which is contrary to the ideal filling mode; in addition, the epitaxial filling method in which the epitaxial growth rate is reduced by adjusting the flow rate of silicon source gas or HCl gas and the flow rate of doping gas (for example, B2H6) is reduced also has the problem that the doping concentration is affected by the epitaxial growth rate and the amount of doping gas, and the two influences are in opposite directions, which causes certain difficulties for the parallel expansion of the deep trench epitaxial filling method for different products. Summary of the invention

[0007] The present application provides a method for filling deep trench epitaxy of a super junction device, which can solve the problem that traditional epitaxial filling methods cannot take into account both deep trench filling effect and PN concentration matching.

[0008] The embodiment of the present application provides a method for filling deep trench epitaxy of a super junction device, comprising:

[0009] A substrate is provided, on which a first epitaxial layer of a first conductivity type is formed, a deep trench is formed in the first epitaxial layer, wherein the opening of the deep trench gradually increases from the bottom end to the top end of the deep trench;

[0010] Passing silicon source gas, hydrogen chloride gas, doping gas and hydrogen gas to epitaxially form a second epitaxial layer of a second conductivity type in the deep trench, wherein the second epitaxial layer fills the deep trench;

[0011] Wherein, the flow rate of the hydrogen satisfies the following formula:

[0012] Flow = k*x;

[0013] Wherein, Flow is the flow rate of hydrogen, k is the hydrogen flow coefficient, and x is the initial flow rate of the hydrogen.

[0014] Optionally, in the deep trench epitaxial filling method of the super junction device, the value range of k is 0 to 2, wherein the value of k gradually decreases from the bottom to the top of the deep trench.

[0015] Optionally, in the deep trench epitaxial filling method of the super junction device, in the process of epitaxially forming a second epitaxial layer of the second conductivity type, at the bottom of the deep trench, the value of k is 1.2; at the top of the deep trench, the value of k is 0.8.

[0016] Optionally, in the deep trench epitaxial filling method of the super junction device, the smaller the value of k is from the bottom to the top of the deep trench, the lower the epitaxial growth rate of the second epitaxial layer is.

[0017] Optionally, in the deep trench epitaxial filling method of the super junction device, the initial flow rate x of the hydrogen gas is in the range of 15 slm to 60 slm.

[0018] Optionally, in the deep trench epitaxial filling method of the super junction device, in the process of epitaxially forming a second epitaxial layer of the second conductivity type, the flow rate of the silicon source gas is 200 sccm to 3000 sccm; the flow rate of the hydrogen chloride gas is 200 sccm to 4000 sccm; and the flow rate of the doping gas is 100 sccm to 2500 sccm.

[0019] Optionally, in the deep trench epitaxial filling method of the super junction device, the silicon source gas is DCS; and the doping gas is B2H6.

[0020] Optionally, in the deep trench epitaxial filling method of the super junction device, the flow rates of the silicon source gas, the hydrogen chloride gas and the doping gas are all kept constant from the bottom to the top of the deep trench.

[0021] Optionally, in the deep trench epitaxial filling method of the super junction device, the first conductivity type is N-type and the second conductivity type is P-type.

[0022] The technical solution of this application has at least the following advantages:

[0023] The present application provides a method for filling deep trench epitaxy of a super junction device, wherein a second epitaxial layer of a second conductivity type is epitaxially formed in a deep trench in a first epitaxial layer of a first conductivity type by introducing silicon source gas, hydrogen chloride gas, doping gas and hydrogen, wherein the flow rate of hydrogen satisfies the following formula: Flow = k*x. The present application dynamically adjusts the flow rate of hydrogen during epitaxial growth of the second epitaxial layer by adjusting the initial flow rate x of hydrogen and the value of the hydrogen flow coefficient k, thereby adjusting the deposition rate and resistivity of the second epitaxial layer, thereby achieving the best deep trench filling effect and PN concentration matching. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 is a flow chart of a method for filling deep trench epitaxy of a super junction device according to an embodiment of the present invention;

[0026] Figure 2 is a schematic diagram of a semiconductor structure after deep trenches are formed according to an embodiment of the present invention;

[0027] Figure 3 is a schematic diagram of a semiconductor structure after forming a second epitaxial layer according to an embodiment of the present invention;

[0028] Figure 4 is a schematic diagram of the relationship between the k value and the epitaxial growth rate of the second epitaxial layer in an embodiment of the present invention;

[0029] Figure 5 is a schematic diagram of the relationship between the k value and the resistivity of the second epitaxial layer in an embodiment of the present invention;

[0030] The reference numerals are described as follows:

[0031] 10 - substrate, 20 - first epitaxial layer, 21 - deep trench, 30 - second epitaxial layer. DETAILED DESCRIPTION

[0032] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0033] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0034] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0035] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0036] The present application embodiment provides a method for filling deep trench epitaxy of a super junction device, referring to Figure 1 , Figure 1 1 is a flow chart of a method for filling a deep trench epitaxy of a super junction device according to an embodiment of the present invention, wherein the method for filling a deep trench epitaxy of a super junction device comprises:

[0037] Step S1: Reference Figure 2 A substrate 10 is provided, on which a first epitaxial layer 20 of a first conductivity type is formed, and a deep trench 21 is formed in the first epitaxial layer 20, wherein the opening of the deep trench 21 gradually increases from the bottom end to the top end of the deep trench 21.

[0038] Step S2: Reference Figure 3, silicon source gas, hydrogen chloride gas, doping gas and hydrogen are introduced to epitaxially form a second epitaxial layer 30 of a second conductivity type in the deep trench 21, and the second epitaxial layer 30 fills the deep trench 21; wherein the flow rate of the hydrogen satisfies the following formula:

[0039] Flow=k*x; wherein Flow is the flow rate of hydrogen, k is the hydrogen flow coefficient, and x is the initial flow rate of the hydrogen.

[0040] Furthermore, the value range of k is 0 to 2, wherein the value of k gradually decreases from the bottom to the top of the deep trench 21 .

[0041] In this embodiment, the value of k ranges from 0.8 to 1.2. In the process of epitaxially forming the second epitaxial layer 30 of the second conductivity type, at the bottom of the deep trench, the value of k is 1.2; at the top of the deep trench, the value of k is 0.8.

[0042] In this embodiment, the first conductivity type is N type, and the second conductivity type is P type, so the first epitaxial layer 20 after forming the deep trench 21 can be called an N column, and the second epitaxial layer 30 formed by epitaxy can be called a P column.

[0043] It is noteworthy that hydrogen is used as a reactant for the decomposition of the silicon source gas and is also used as a carrier gas for the entire reaction system.

[0044] Preferably, the initial flow rate x of hydrogen is in the range of 15 slm to 60 slm.

[0045] Preferably, in the process of epitaxially forming the second conductivity type second epitaxial layer 30, the flow rate of the silicon source gas is 200 sccm to 3000 sccm; the flow rate of the hydrogen chloride gas is 200 sccm to 4000 sccm; and the flow rate of the doping gas is 100 sccm to 2500 sccm.

[0046] It is worth noting that the flow rate of the doping gas may vary depending on the actual raw material concentration in different factories and the machine range. Therefore, the flow rate of the doping gas described in the present application can be determined according to the actual raw material concentration in different factories and the machine range, and can be within the range of 100 sccm to 2500 sccm or outside this flow rate range.

[0047] Furthermore, from the bottom to the top of the deep trench 21 , the flow rates of the silicon source gas, the hydrogen chloride gas, and the doping gas remain unchanged.

[0048] In this embodiment, the silicon source gas is DCS (dichlorosilane); the doping gas is B2H6.

[0049] refer to Figure 4 and Figure 5 , the inventors have found through experiments that, from the bottom to the top of the deep trench 21, the smaller the value of k, the lower the epitaxial growth rate of the second epitaxial layer 30, and the doping concentration of the second epitaxial layer 30 decreases, and the resistivity increases. The present application gradually reduces the epitaxial growth rate of the second epitaxial layer 30, that is, gradually reduces the rate of epitaxial filling, and improves the overall filling efficiency and filling quality of the deep trench. Further, for concentration matching, the structure is observed laterally. Due to the non-vertical structure of the deep trench, the width (lateral dimension) below the deep trench is narrow, and the width (lateral dimension) above the deep trench is large, and the PN matching is essentially the matching of the number of PN atoms, so the width below the deep trench is narrow and the concentration is high, and the width above the deep trench is large and the concentration is low, so from the bottom to the top of the deep trench 21, the doping concentration of the second epitaxial layer 30 decreases, and the resistivity increases.

[0050] The present application dynamically adjusts the flow rate of hydrogen during the epitaxial growth of the second epitaxial layer by adjusting the initial flow rate x of hydrogen and the hydrogen flow coefficient k value, thereby adjusting the deposition rate and resistivity of the second epitaxial layer, thereby achieving the best deep trench filling effect and PN concentration matching.

[0051] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection created by this application.

Claims

1. A method for filling deep trench epitaxy of a super junction device, characterized in that: include: A substrate is provided, on which a first epitaxial layer of a first conductivity type is formed, a deep trench is formed in the first epitaxial layer, wherein the opening of the deep trench gradually increases from the bottom end to the top end of the deep trench; Passing silicon source gas, hydrogen chloride gas, doping gas and hydrogen gas to epitaxially form a second epitaxial layer of a second conductivity type in the deep trench, wherein the second epitaxial layer fills the deep trench; Wherein, the flow rate of the hydrogen satisfies the following formula: Flow = k*x; Wherein, Flow is the flow rate of hydrogen, k is the hydrogen flow coefficient, and x is the initial flow rate of the hydrogen.

2. The method for filling deep trench epitaxy of a super junction device according to claim 1, characterized in that: The value range of k is 0-2, wherein the value of k gradually decreases from the bottom to the top of the deep trench.

3. The method for filling deep trench epitaxy of a super junction device according to claim 2, characterized in that: In the process of epitaxially forming the second epitaxial layer of the second conductivity type, at the bottom of the deep trench, the value of k is 1.2; at the top of the deep trench, the value of k is 0.

8.

4. The method for filling deep trench epitaxy of a super junction device according to claim 1, characterized in that: In a direction from the bottom end to the top end of the deep trench, the smaller the value of k is, the lower the epitaxial growth rate of the second epitaxial layer is.

5. The method for filling deep trench epitaxy of a super junction device according to claim 1, characterized in that: The value range of the initial flow rate x of hydrogen is 15slm to 60slm.

6. The method for filling deep trench epitaxy of a super junction device according to claim 1, characterized in that: In the process of epitaxially forming the second epitaxial layer of the second conductivity type, the flow rate of the silicon source gas is 200 sccm to 3000 sccm; the flow rate of the hydrogen chloride gas is 200 sccm to 4000 sccm; and the flow rate of the doping gas is 100 sccm to 2500 sccm.

7. The method for filling deep trench epitaxy of a super junction device according to claim 1 or 6, characterized in that: The silicon source gas is DCS; the doping gas is B2H6.

8. The method for filling deep trench epitaxy of a super junction device according to claim 1, characterized in that: From the bottom to the top of the deep trench, the flow rates of the silicon source gas, the hydrogen chloride gas and the doping gas remain unchanged.

9. The method for filling deep trench epitaxy of a super junction device according to claim 7, characterized in that: The first conductivity type is N type, and the second conductivity type is P type.

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