Method for manufacturing memory element and method for manufacturing tungsten layer

Abstract

The invention relates to a manufacturing method of a memory element, which can be applied to a three-dimensional NAND memory element with high capacity and high performance. In the manufacturing of a three-dimensional NAND memory element, the material of a control gate (word line) is tungsten. The tungsten layer forming method comprises a nucleation step and a main body forming step. In at least one of the nucleation step and the host formation step, the flow rate of hydrogen is 1000 to 20000 sccm. After the nucleation step, at least one soaking step can be carried out, and nitrogen soaking is carried out. The grain size of tungsten in the tungsten layer is 70 nm or more.

Description

Technical Field

[0001] The invention relates to a semiconductor device process, and in particular to a manufacturing method of a memory device and a manufacturing method of a tungsten layer. Background Art

[0002] As technology advances, the advancement of electronic devices has increased the need for greater storage capacity. In order to meet the demand for high storage density, memory devices have become smaller and more dense. Therefore, the type of memory devices has evolved from two-dimensional memory devices (2D memory devices) with planar gate structures to three-dimensional memory devices (3D memory devices) with vertical channel (VC) structures.

[0003] For 3D NAND memory devices, using low fluorine tungsten (LFW) as the material for the control gate (word line) can improve the performance of the driving device. Summary of the invention

[0004] The present invention provides a method for manufacturing a memory element, which can manufacture low-fluorine tungsten (LFW) with a large grain size, low resistivity and low fluorine concentration as a word line (control gate) material, which can reduce the control gate drive voltage, reduce the risk of fluorine damaging high dielectric constant materials and floating gates, and can also reduce the threshold voltage (Vth) distribution and improve reliability.

[0005] The invention provides a method for manufacturing a tungsten layer, which can manufacture low-fluorine tungsten (LFW) with a large grain size, low resistivity and low fluorine concentration.

[0006] The present invention provides a method for manufacturing a memory element, comprising the following steps. A substrate is provided. A stacked structure is formed on the substrate, wherein the stacked structure comprises a plurality of first material layers and a plurality of second material layers alternately stacked with each other. The stacked structure is patterned to form a first opening in the stacked structure. A charge storage structure is formed on the sidewall of the first opening. A channel layer is formed on the charge storage structure. A plurality of second material layers are removed to form a plurality of second openings. A tungsten layer is formed in the plurality of second openings, wherein the formation of the tungsten layer comprises: performing a nucleation step and, after the nucleation step, performing a body forming step. The nucleation precursor in the nucleation step comprises tungsten halide, hydrogen, and a reducing agent. The body precursor in the body forming step comprises tungsten halide, hydrogen, and a reducing agent. In at least one of the nucleation step and the body forming step, the flow rate of hydrogen is 1000 to 20000 sccm.

[0007] In one embodiment of the present invention, after the nucleation step, at least one soaking step is further included, soaking in nitrogen (hydrogen, deuterium or ammonia).

[0008] In one embodiment of the present invention, the method further includes performing the main body forming step multiple times.

[0009] In one embodiment of the present invention, the main body forming step is performed three times.

[0010] In one embodiment of the present invention, after the nucleation step, the soaking step is performed twice.

[0011] In an embodiment of the present invention, before forming the tungsten layer in the plurality of second openings, the method further includes forming a barrier layer.

[0012] In one embodiment of the present invention, in the nucleation step, the flow rate of hydrogen is greater than 4000 sccm.

[0013] In one embodiment of the present invention, in the body forming step, the flow rate of hydrogen is greater than 5000 sccm.

[0014] In one embodiment of the present invention, in the soaking step, the flow rate of nitrogen gas is 100-6000 sccm.

[0015] The present invention provides a method for manufacturing a tungsten layer, comprising a nucleation step and a body formation step. The nucleation precursor in the nucleation step comprises a tungsten halide, hydrogen, and a reducing agent. The body precursor in the body formation step comprises a tungsten halide, hydrogen, and a reducing agent. In at least one of the nucleation step and the body formation step, the flow rate of hydrogen is 1000 to 20000 sccm, and the grain size of tungsten in the formed tungsten layer is greater than 70 nm.

[0016] In one embodiment of the present invention, after the nucleation step, at least one soaking step is further included, soaking in nitrogen (hydrogen, deuterium or ammonia).

[0017] In one embodiment of the present invention, the method further includes performing the main body forming step multiple times.

[0018] In one embodiment of the present invention, the main body forming step is performed three times.

[0019] In one embodiment of the present invention, after the nucleation step, the soaking step is performed twice.

[0020] In one embodiment of the present invention, in the nucleation step, the flow rate of hydrogen is greater than 4000 sccm.

[0021] In one embodiment of the present invention, in the body forming step, the flow rate of hydrogen is greater than 5000 sccm.

[0022] In one embodiment of the present invention, in the soaking step, the flow rate of nitrogen gas is 100-6000 sccm.

[0023] In many embodiments of the present invention, increasing the hydrogen flow rate in the nucleation step and the body formation step and reducing the total nitrogen soaking flow rate in the soaking step are both beneficial to obtaining a large tungsten grain size; the tungsten layer formed, as the tungsten grain size increases, the fluorine content in the tungsten layer decreases. The tungsten grain size in the tungsten layer is larger, and the resistivity of tungsten can be reduced due to fewer grain boundaries, and impurities (fluorine) that are easy to damage high dielectric constant materials and floating gates can be reduced, and the threshold voltage (Vth) distribution can be narrowed and the reliability of the memory element can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figures 1A to 1E It is a cross-sectional schematic diagram of a method for manufacturing a three-dimensional memory element according to an embodiment of the present invention.

[0025] Figure 2 FIG. 4 is a flow chart of a method for manufacturing a tungsten layer according to an embodiment of the present invention.

[0026] Figure 3 FIG. 4 is a graph showing the relationship between hydrogen flow rate and tungsten grain size according to an embodiment of the present invention.

[0027] Figure 4 FIG. 4 is a graph showing the relationship between tungsten grain size and resistivity according to an embodiment of the present invention.

[0028] Description of Reference Numerals

[0029] 100: Base

[0030] 101, 101′: laminated structure

[0031] 102: First material layer

[0032] 102T: Insulation layer

[0033] 103: Dielectric layer

[0034] 104: Second material layer

[0035] 106, 121: Opening

[0036] 108: Charge storage structure

[0037] 110: Channel layer

[0038] 112: Insulation column

[0039] 114: Conductor plug

[0040] 115: Insulation top cover

[0041] 122: Barrier layer

[0042] 124: Metal layer

[0043] 126: Gate layer

[0044] 200: Nucleation step

[0045] 202: Soaking Steps

[0046] 204: Steps of forming the main body DETAILED DESCRIPTION

[0047] The present invention provides a method for manufacturing a memory element and a method for manufacturing a tungsten layer, which can be applied to a three-dimensional NAND memory element with high capacity and high performance. Figures 1A to 1E It is a cross-sectional schematic diagram of a method for manufacturing a three-dimensional memory element according to an embodiment of the present invention.

[0048] Please refer to Figure 1A , providing a substrate 100. The substrate 100 may be a semiconductor substrate, such as a silicon-containing substrate. In one embodiment, a doped region may be formed in the substrate 100 according to design requirements. A component layer (not shown) and a metal interconnect structure (not shown) may be formed on the substrate 100. The component layer may include active components or passive components. Active components are, for example, transistors, diodes, etc. Passive components are, for example, capacitors, inductors, etc. The metal interconnect structure may include a dielectric layer, a plug, and a wire.

[0049] Please refer to Figure 1A , a stacked structure 101 is formed on the substrate 100. The stacked structure 101 includes a plurality of first material layers 102 and a plurality of second material layers 104 that are alternately stacked. The first material layer 102 may be an insulating layer, such as silicon oxide. The second material layer 104 may be an insulating layer (such as silicon nitride) or a conductive layer (such as doped polysilicon). In one embodiment, the material of the first material layer 102 includes silicon oxide, and the material of the second material layer 104 includes silicon nitride. In another embodiment, the material of the first material layer 102 includes silicon oxide, and the material of the second material layer 104 includes doped polysilicon. In this embodiment, the bottom layer of the stacked structure 101 is the first material layer 102, and the top layer is the second material layer 104, but the present invention is not limited thereto. In addition, in this embodiment, 4 layers of the second material layer 104 and 4 layers of the first material layer 102 are used for illustration, but the present invention is not limited thereto.

[0050] Next, please refer to Figure 1B, an insulating layer 102T is formed on the stacked structure 101. The material of the insulating layer 102T is different from that of the second material layer 104, and the material of the insulating layer 102T is the same as that of the first material layer 104, such as silicon oxide. The insulating layer 102T and the stacked structure 101 may be collectively referred to as a stacked structure 101'.

[0051] Afterwards, please refer to Figure 1C , the insulating layer 102T, the second material layer 104, the first material layer 102 and the support structure 98 of the stacked structure 101′ are patterned to form one or more openings 106 passing through the stacked structure 101′. In one embodiment, the opening 106 may have a slightly inclined sidewall. In one embodiment, the opening 106 may have a substantially vertical sidewall (not shown). In one embodiment, the opening 106 is also referred to as a vertical channel (VC) hole. A vertical channel column CP is then formed in the opening 106. The vertical channel column CP can be formed by the method described below, but is not limited thereto.

[0052] Please refer to Figure 1C , a charge storage structure 108 is formed on the sidewall of the opening 106. The charge storage structure 108 is in contact with the first material layer 102 and the second material layer 104. The material of the charge storage structure 108 is, for example, an oxide / nitride / oxide (ONO) composite layer. In one embodiment, the charge storage structure 108 is formed on the sidewall of the opening 106 in the form of a spacer, and the bottom surface of the opening 106 is exposed.

[0053] Then, a channel layer 110 is formed on the charge storage structure 108. The material of the channel layer 110 includes, for example, polysilicon. In one embodiment, the channel layer 110 covers the charge storage structure 108 on the sidewall of the opening 106 and covers the bottom surface of the opening 106. Next, an insulating column 112 is formed at the lower portion of the opening 106. In one embodiment, the material of the insulating column 112 includes, for example, silicon oxide. Thereafter, a conductor plug 114 is formed at the upper portion of the opening 106, and the conductor plug 114 is in contact with the channel layer 110. In one embodiment, the material of the conductor plug 114 includes, for example, doped polysilicon. The channel layer 110 and the conductor plug 114 may be collectively referred to as a vertical channel column CP. The charge storage structure 108 surrounds the vertical outer surface of the vertical channel column CP. Next, an insulating cap layer 115 is formed above the stacked structure 101′. The material of the insulating cap layer 115 includes, for example, silicon oxide.

[0054] Please refer to Figure 1D, a selective etching process is performed to remove the second material layer 104 to form a plurality of openings 121. The openings 121 expose a portion of the charge storage structure 108, the first material layer 102, and the insulating layer 102T. The selective etching process may be an isotropic etching process, such as a wet etching process. The etchant used in the wet etching process may be, for example, hot phosphoric acid.

[0055] Please refer to Figure 1E , a conductor layer is formed in the opening 121. The conductor layer includes, for example, a barrier layer 122 and a metal layer 124. In one embodiment, the material of the barrier layer 122 includes aluminum oxide (Al2O3), titanium (Ti), titanium nitride (TiN), tantalum (Ta), tantalum nitride (TaN) or a combination thereof, and the material of the metal layer 124 is tungsten (W). The conductor layer in the opening 121 serves as a gate layer 126.

[0056] Next, the method for manufacturing the metal layer 124 (tungsten layer) of the present invention is described. The method for manufacturing the metal layer 124 (tungsten layer) includes performing a nucleation step, an immersion step, and a body formation step.

[0057] For the nucleation step, if the nucleus size of tungsten is larger, it is conducive to forming a tungsten body with a large grain size. In the nucleation step, the nucleation precursor includes tungsten halide (such as tungsten fluoride), hydrogen (or deuterium), and a reducing agent. The reducing agent is, for example, silane, borane, etc. In the nucleation step, for example, an inert gas including argon, helium, nitrogen, etc. can be added.

[0058] In one embodiment, when the reducing agent flow rate is, for example, less than 2000 sccm, the flow rate of hydrogen (or deuterium) is, for example, 1000 to 20000 sccm. When the flow rate of hydrogen (or deuterium) is greater than 4000 sccm, the tungsten grain size is, for example, greater than 40 nm.

[0059] In another embodiment, when the tungsten halide flow rate is, for example, less than 1000 sccm, the reducing agent flow rate is, for example, less than 1800 sccm, and the hydrogen (or deuterium) flow rate is, for example, 4000 to 12000 sccm, it is easier to obtain tungsten with a grain size of, for example, more than 40 nm.

[0060] In one embodiment, after the nucleation step, at least one soaking step is further performed, wherein nitrogen, hydrogen, deuterium or azane (NHx) is soaked. The soaking flow rate of nitrogen, hydrogen, deuterium or azane is, for example, 6000 sccm or less, and the soaking time is, for example, 200 s or less. The total soaking flow rate (soaking flow rate*soaking time) is, for example, 20000 ml or less. When the total soaking flow rate is 5000 ml or less, it is easier to obtain tungsten with a grain size of, for example, 70 nm or more.

[0061] In one embodiment, the soaking step is performed with nitrogen, hydrogen, deuterium or azane (NHx) for 1 to 3 times. When the soaking step is performed for 2 times or less, it is easier to obtain tungsten with a grain size of, for example, 70 nm or more.

[0062] In one embodiment, when the tungsten halide flow rate is, for example, less than 1000 sccm, the hydrogen (or deuterium) flow rate is, for example, 5000 to 12000 sccm, the total immersion flow rate is less than 5000 ml, and the number of immersion steps is less than 1, it is easier to obtain tungsten with a grain size of, for example, more than 70 nm.

[0063] Regarding the bulk forming step, in the bulk forming step, the bulk forming step precursors include, for example, tungsten halides (such as tungsten fluoride), hydrogen (or deuterium), and reducing agents, etc. In the bulk forming step, for example, inert gases including argon, helium, nitrogen, etc. may be added.

[0064] In one embodiment, when the flow rate of tungsten halide is, for example, less than 1000 sccm and the flow rate of hydrogen (or deuterium) is, for example, 1000 to 20000 sccm, preferably 5000-12000 sccm, it is easier to obtain tungsten with a grain size of, for example, more than 70 nm.

[0065] Figure 2 2 is a flow chart of a method for manufacturing a tungsten layer according to an embodiment of the present invention. In one embodiment, the method for manufacturing a tungsten layer includes performing a nucleation step 200, an immersion step 202, and a main body formation step 204. For example, in the nucleation step 200, diborane (B2H6) and hydrogen, argon, tungsten fluoride (WF6), and argon are sequentially introduced. More detailed operations include, for example, turning on diborane and hydrogen, and then turning off diborane and hydrogen after a predetermined time; turning on argon, and then turning off argon after a predetermined time; turning on tungsten fluoride, and then turning off tungsten fluoride after a predetermined time; turning on argon, and then turning off argon after a predetermined time. The above steps are taken as one cycle, and then multiple (1 to 20) cycles are performed to complete the nucleation step.

[0066] In the soaking step 202, nitrogen is introduced. A more detailed operation is, for example, turning on the nitrogen and then turning off the nitrogen after a predetermined time has passed.

[0067] In the main body forming step 204, hydrogen, argon, tungsten fluoride, and argon are introduced in sequence. A more detailed operation is, for example, turning on hydrogen and then turning off hydrogen after a predetermined time has passed; turning on argon and then turning off argon after a predetermined time has passed; turning on tungsten fluoride and then turning off tungsten fluoride after a predetermined time has passed; turning on argon and then turning off argon after a predetermined time has passed. The above steps are regarded as one cycle, and then multiple cycles (1 to 10,000 times) are performed to complete the main body forming step.

[0068] In one embodiment, the method for manufacturing the metal layer 124 (tungsten layer) of the present invention comprises sequentially performing a nucleation step and a main body forming step more than once. In one embodiment, the method for manufacturing the metal layer 124 (tungsten layer) of the present invention comprises sequentially performing a nucleation step and a main body forming step 2 to 3 times. In one embodiment, the method for manufacturing the metal layer 124 (tungsten layer) of the present invention comprises sequentially performing a nucleation step, a soaking step, and a main body forming step 1 to 2 times. In one embodiment, the method for manufacturing the metal layer 124 (tungsten layer) of the present invention comprises sequentially performing a nucleation step, a soaking step, a main body forming step, a soaking step, and a main body forming step 1 to 2 times. By combining the nucleation step, the soaking step, and the main body forming step, tungsten with a grain size of, for example, more than 120 nm can also be obtained.

[0069] Figure 3 FIG. 1 is a graph showing the relationship between hydrogen flow rate and tungsten grain size according to an embodiment of the present invention. Figure 3 As shown, the same nitrogen soaking condition is used for soaking three times in the soaking step. In the subsequent main body forming step, as the hydrogen volume flow rate increases from 3500sccm to 9000sccm, the grain size of tungsten increases from 33.7nm (symbol: ·) / 39.2nm (symbol: ·) to 46.7nm (symbol: ·) / 49.1nm (symbol: ·). Different nitrogen soaking conditions are used for soaking three times in the soaking step. In the subsequent main body forming step, the same hydrogen flow rate is used. When soaking with 1500sccm nitrogen, the grain size of tungsten is 45.8nm (immersion time 15s, symbol: ·) / 47.5nm (immersion time 10s, symbol: ·), and when soaking with 3000sccm nitrogen, the grain size of tungsten is 42.2nm (immersion time 15s, symbol: ▲) / 43.1nm (immersion time 10s, symbol: ◆). The results show that reducing the nitrogen flow rate in the soaking step will increase the grain size of tungsten.

[0070] Figure 4 FIG. 1 is a graph showing the relationship between tungsten grain size and resistivity according to an embodiment of the present invention. Figure 4 As shown in Figure 1, the grain size of tungsten has an opposite trend to the resistivity. Since large grains have fewer grain boundaries, their resistivity is lower than that of small grains.

[0071] Conductivity: Resistivity (uΩ×cm) = resistance×thickness.

[0072] The resistance and thickness are the result of in-line measurement of the tungsten layer.

[0073] Table 1 discloses experimental data of tungsten grain size, fluorine content, and depth sidewall uniformity (U%) according to an embodiment of the present invention.

[0074] Fluorine concentration: Secondary ion mass spectrometry (SIMS) analysis to quantify the concentration of [F] in the tungsten layer (atom / cm 3 )

[0075] Sidewall uniformity: Scanning electron microscopy (SMS) and transmission electron microscopy (TEM) analysis, U% = standard deviation / average value

[0076] Table 1

[0077]

[0078] In the present invention, the fluorine content in the formed tungsten layer decreases as the tungsten grain size increases. In the present invention, the depth sidewall uniformity of the formed tungsten layer becomes worse as the tungsten grain size increases, but there is no tungsten seam problem under all conditions.

[0079] In the present invention, increasing the hydrogen flow rate in the nucleation step and the body formation step and reducing the total nitrogen soaking flow rate in the soaking step are both beneficial to obtaining a large tungsten grain size.

[0080] In many embodiments of the present invention, increasing the hydrogen flow rate in the nucleation step and the body formation step and reducing the total nitrogen soaking flow rate in the soaking step are both beneficial to obtaining a large tungsten grain size; the tungsten layer formed, as the tungsten grain size increases, the fluorine content in the tungsten layer decreases. The tungsten grain size in the tungsten layer is larger, and the resistivity of tungsten can be reduced due to fewer grain boundaries, and impurities (fluorine) that are easy to damage high dielectric constant materials and floating gates can be reduced, and the threshold voltage (Vth) distribution can be narrowed and the reliability of the memory element can be improved.

Claims

1. A method for manufacturing a memory element, characterized in that: include: providing a substrate; forming a stacked structure on the substrate, wherein the stacked structure comprises a plurality of first material layers and a plurality of second material layers alternately stacked with each other; patterning the stacked structure to form a first opening in the stacked structure; forming a charge storage structure on a sidewall of the first opening; forming a channel layer on the charge storage structure; removing the plurality of second material layers to form a plurality of second openings; as well as forming a tungsten layer in the plurality of second openings, The forming of the tungsten layer comprises: performing a nucleation step, wherein the nucleation precursor in the nucleation step comprises tungsten halide, hydrogen, and a reducing agent, and After the nucleation step, a body forming step is performed, wherein the body precursor in the body forming step comprises tungsten halide, hydrogen, and a reducing agent; In at least one of the nucleation step and the body forming step, a flow rate of hydrogen is 1000 to 20000 sccm.

2. The method for manufacturing a memory device according to claim 1, wherein: After the nucleation step, the method further comprises performing at least one soaking step of soaking in nitrogen, hydrogen, deuterium or ammonia.

3. The method for manufacturing a memory device according to claim 1, wherein: The method also includes performing the body forming step multiple times.

4. The method for manufacturing a memory element according to claim 3, wherein: The main body forming step is performed three times.

5. The method for manufacturing a memory device according to claim 2, wherein: After the nucleation step, the soaking step is further performed twice.

6. The method for manufacturing a memory device according to claim 1, wherein: Before forming the tungsten layer in the plurality of second openings, the method further includes forming a barrier layer.

7. The method for manufacturing a memory device according to claim 1, wherein: In the nucleation step, the flow rate of hydrogen is 4000 sccm or more.

8. The method for manufacturing a memory device according to claim 1, wherein: In the body forming step, a flow rate of hydrogen is 5000 sccm or more.

9. The method for manufacturing a memory device according to claim 2, wherein: In the soaking step, the flow rate of nitrogen gas is 100-6000 sccm.

10. A method for manufacturing a tungsten layer, characterized in that: include: performing a nucleation step, wherein the nucleation precursor in the nucleation step comprises tungsten halide, hydrogen, and a reducing agent; and A plurality of body forming steps are performed, wherein the body precursor in the body forming step comprises tungsten halide, hydrogen, and a reducing agent, wherein in at least one of the nucleation step and the body forming step, the flow rate of hydrogen is 1000 to 20000 sccm.

11. The method for manufacturing a tungsten layer according to claim 10, characterized in that: After the nucleation step, the method further comprises performing at least one soaking step of soaking in nitrogen, hydrogen, deuterium or ammonia.

12. The method for manufacturing a tungsten layer according to claim 10, characterized in that: The main body forming step is performed three times.

13. The method for manufacturing a tungsten layer according to claim 11, characterized in that: After the nucleation step, the soaking step is performed twice.

14. The method for manufacturing a tungsten layer according to claim 10, characterized in that: In the nucleation step, the flow rate of hydrogen is 4000 sccm or more.

15. The method for manufacturing a tungsten layer according to claim 10, characterized in that: In the body forming step, a flow rate of hydrogen is 5000 sccm or more.

16. The method for manufacturing a tungsten layer according to claim 11, characterized in that: In the soaking step, the flow rate of nitrogen gas is 100-6000 sccm.

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