Method for expanding deposition window of metal tungsten
Through hydrogen plasma etching and SiCoNi pre-cleaning technology, the problem of volume loss of metal layer and uneven contact surfaces before deposition of metal tungsten and copper is solved, and a larger deposition window and higher quality metal tungsten deposition are achieved.
Patent Information
- Application Number
- CN202411216101.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-30
- Publication Date
- 2024-12-17
AI Technical Summary
In the chip manufacturing process, before metal tungsten and copper are deposited, the existing argon sputtering cleaning methods lead to loss of metal layer volume, uneven contact surfaces and narrowing of process windows, affecting contact resistance and deposition quality.
Using hydrogen plasma etching and SiCoNi pre-cleaning technology, the oxide layer on the surface of the metal layer is removed to form a flat contact surface, and a titanium/titanium nitride layer is deposited on the inner wall of the through hole to expand the deposition window.
The metal layer volume loss and uneven contact surfaces are avoided, the process window for metal tungsten deposition is increased, the contact surface smoothness and deposition quality are improved, and the contact resistance is reduced.
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Figure CN119153397A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of semiconductor technology, and in particular to a method for expanding a deposition window of metal tungsten. Background Art
[0002] In the chip manufacturing process, metal tungsten (W) has a wide range of applications as a filling material for wires and contact holes. For example, in the preparation process of memory devices such as dynamic random access memory and three-dimensional NAND flash memory devices, metal tungsten materials are widely used in the interconnect structure after the copper process.
[0003] In the subsequent interconnection process after the metal tungsten and copper process, before the deposition of metal tungsten and copper, the previous metal layer, or the metal copper layer formed after the copper process, needs to be pre-cleaned to remove the previous oxide. When the previous oxide is a metal oxide, the cleaning method using argon sputtering will cause the loss of volume of the copper metal layer, resulting in an uneven surface of the copper metal layer. The volume loss of the metal and the uneven contact surface will cause the contact surface to fail, which will increase the metal contact resistance. Therefore, the pre-cleaning and pre-cleaning before the metal tungsten / copper deposition process are required to be high. In addition, the re-sputtering of the side wall by argon sputtering can easily cause the side wall to overhang, which ultimately leads to a narrow metal film deposition process window.
[0004] It should be noted that the information disclosed in the background technology section of the invention is only intended to deepen the understanding of the general background technology of the invention, and should not be regarded as an admission or suggestion in any form that the information constitutes prior art already known to those skilled in the art. Summary of the invention
[0005] The purpose of the present invention is to provide a method for expanding the deposition window of metal tungsten to solve the problems of through holes formed on the surface of the metal layer, volume loss of the metal layer, unevenness on the surface of the metal layer, and narrowing of the process window when depositing metal tungsten.
[0006] In order to solve the above technical problems, the present invention provides a method for expanding the deposition window of metal tungsten, comprising:
[0007] A semiconductor structure is provided, wherein a through hole and a first isolation layer are formed on the surface of the semiconductor structure, a metal oxide layer is formed on the bottom of the through hole, and the first isolation layer includes a silicon oxide layer and a barrier layer;
[0008] Etching the semiconductor structure using hydrogen plasma;
[0009] After etching, the semiconductor structure is subjected to SiCoNi pre-cleaning;
[0010] After depositing a second isolation layer on the inner wall of the through hole and the surface of the first isolation layer, metal tungsten is filled in the through hole.
[0011] Preferably, the reaction formula for etching the semiconductor structure using hydrogen plasma is as follows:
[0012] H / H*+YO x →Y+H2O……(1),
[0013] SiO x +H / H*→SiH4+H2O……(2),
[0014] SiH4+H2O→SiO2+H2……(3).
[0015] Preferably, a heating treatment is performed when the semiconductor structure is etched using hydrogen plasma, and the heating temperature range is 25° C. to 100° C.
[0016] Preferably, the reaction formula for performing SiCoNi pre-cleaning on the semiconductor structure is:
[0017] NF3+NH3(RPS)→NH4F+NH4F . HF……(4),
[0018] NH4F+NH4F . HF+SiO2(heat)→(NH4)2SiF6+H2O……(5),
[0019] (NH4)2SiF6+H2O(heat)→SiF4+NH3……(6).
[0020] Preferably, when the semiconductor structure is subjected to SiCoNi pre-cleaning, the reaction gas is a mixed gas of NF3 and NH3, and the flow rate of the mixed gas is 1000 sccm to 2000 sccm, and the reaction temperature ranges from 150°C to 210°C.
[0021] Preferably, the etching of the semiconductor structure using hydrogen plasma, the SiCoNi pre-cleaning of the semiconductor structure and the deposition of titanium and titanium nitride layers are performed using the same machine.
[0022] Preferably, etching the semiconductor structure using hydrogen plasma, performing SiCoNi pre-cleaning on the semiconductor structure, and depositing titanium and titanium nitride layers are performed using different machines.
[0023] Preferably, the second isolation layer includes a titanium layer and a titanium nitride layer deposited on the surface of the titanium layer.
[0024] Preferably, the material used for the barrier layer is silicon nitride.
[0025] Preferably, the first isolation layer includes a first silicon oxide layer, a silicon nitride layer deposited on a surface of the first silicon oxide layer, and a second silicon oxide layer deposited on a surface of the silicon nitride layer.
[0026] Compared with the prior art, the method for expanding the deposition window of metal tungsten of the present invention has the following advantages:
[0027] The method for expanding the deposition window of metal tungsten provided by the present invention is to firstly etch the semiconductor structure using hydrogen plasma before depositing metal tungsten / copper in the through hole. Since the hydrogen plasma reacts with the silicon oxide in the previous metal layer, reduced metal and silicon dioxide are generated on the surface of the metal layer. Then, the semiconductor structure after the etching treatment is subjected to SiCoNi pre-cleaning to remove the silicon dioxide on the surface of the metal layer. Finally, metal tungsten is deposited in the through hole to interconnect the metal layer with the metal tungsten. Such a process will not cause the loss of the volume of the previous metal layer, making the contact surface between the metal layer and the metal tungsten / copper smoother, and at the same time will not cause the top of the side wall to overhang, thereby increasing the process window for subsequent metal tungsten deposition. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 is a schematic diagram of a structure for forming a through hole in a semiconductor structure;
[0029] Figure 2 It is a schematic diagram of a structure formed by processing a semiconductor structure by argon sputtering;
[0030] Figure 3 is a schematic diagram of the structure after argon sputtering treatment and deposition of metal tungsten in the through hole;
[0031] Figure 4 is a flow chart of a method for expanding a deposition window of metal tungsten provided in one embodiment of the present invention;
[0032] Figure 5 is a schematic diagram of a structure formed by performing a first etching process on a semiconductor structure using hydrogen plasma in one embodiment of the present invention;
[0033] Figure 6 In one embodiment of the present invention, Figure 5 A schematic diagram of a structure formed after SiCoNi pre-cleaning is performed on the semiconductor structure;
[0034] Figure 7 In one embodiment of the present invention Figure 6 Schematic diagram of the structure of the semiconductor structure after metal tungsten is deposited;
[0035] In the figure,
[0036] 100-first silicon oxide layer; 200-barrier layer;
[0037] 300-second silicon oxide layer; 400-through hole;
[0038] 500-metal layer; 510-metal oxide layer;
[0039] 520-interface; 600-metal tungsten;
[0040] 700 - Titanium / Titanium nitride layer. DETAILED DESCRIPTION
[0041] In order to make the purpose, advantages and features of the present invention clearer, the method for expanding the deposition window of metal tungsten proposed by the present invention is further described in detail below in combination with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. It should be understood that the drawings in the specification do not necessarily show the specific structure of the present invention in proportion, and the illustrative features used to illustrate certain principles of the present invention in the drawings in the specification will also adopt a slightly simplified drawing method. The specific design features of the present invention disclosed herein include, for example, specific dimensions, directions, positions and shapes, which will be determined in part by the specific application and use environment. And, in the embodiments described below, sometimes the same figure mark is used in common between different drawings to represent the same part or a part with the same function, and its repeated description is omitted. In this specification, similar numbers and letters are used to represent similar items, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.
[0042] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.
[0043] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.
[0044] Ginseng Figures 1 to 3 As shown, in the prior art, after the contact hole process (i.e., after forming the metal layer 500) and before depositing the metal tungsten 600, the semiconductor structure needs to be pre-cleaned to remove the metal oxide layer 510 on the surface of the metal layer 500. The method of pre-cleaning the semiconductor structure in the prior art is as follows: Figure 2 As shown in FIG. 1 , argon gas is used to sputter the through hole 400. However, after the argon gas sputtering treatment, Figure 2 It can be seen from the dotted line a that the volume of the metal layer 500 is lost. And the interface 520 of the metal layer 500 is uneven. In addition, the re-sputtering of the side wall of the through hole 400 by argon sputtering is likely to cause the top of the side wall of the through hole 400 to overhang, which ultimately leads to the narrowing of the metal film deposition process window (i.e., the top of the through hole 400). After the metal tungsten is deposited in the through hole 400, the formed Figure 3 In the structure shown, the contact surface fails due to the volume loss of the metal layer 500 and the unevenness of the contact interface 520, which results in an increase in the metal contact resistance.
[0045] The core idea of the present invention is to provide a method for expanding the deposition window of metal tungsten, which can avoid the loss of volume of the metal layer 500. At the same time, it can ensure that the contact surface between the metal layer 500 and the titanium / titanium nitride 700 and the metal tungsten 600 is flat and smooth. It can also further solve the technical problem of narrowing the top of the through hole 400.
[0046] In order to realize the above idea, the present invention provides a method for expanding the deposition window of metal tungsten. Figure 1 , Figures 4 to 7 A specific implementation of a method for expanding a deposition window of metal tungsten is disclosed. The method for expanding a deposition window of metal tungsten includes the following steps S1 to S4.
[0047] Step S1 : providing a semiconductor structure, wherein a through hole 400 and a first isolation layer are formed on the surface of the semiconductor structure, a metal oxide layer 510 is formed at the bottom of the through hole 400 , and the first isolation layer includes a silicon oxide layer and a barrier layer 200 .
[0048] Specifically, refer to Figure 1 and Figure 4 As shown, the semiconductor structure is a semiconductor structure after devices such as CMOS have been manufactured. And metal copper is formed on the surface of the semiconductor structure by a copper process. That is, the metal layer 500 is a copper metal layer. There is a naturally formed metal oxide layer 510 at the bottom of the through hole 400. A first isolation layer is deposited around the metal layer 500 to play an insulating and protective role. The oxide layer can be an oxide layer containing silicon. That is, the first isolation layer includes a first silicon oxide layer 100, a barrier layer 200 and a second silicon oxide layer 300. A barrier layer 200 is deposited on the surface of the first silicon oxide layer 100. A second silicon oxide layer 300 is deposited on the surface of the barrier layer 200. The first silicon oxide layer 100 and the second silicon oxide layer 300 serve as insulating layers between metal connections, playing an isolating role to prevent short circuits. The barrier layer 200 can prevent metal copper from diffusing into surrounding materials. The first silicon oxide layer 100 and the second silicon oxide layer 300 can be oxides containing silicon such as silicon dioxide. The barrier layer 200 can be silicon nitride, etc. The metal oxide layer 510 may be an oxide layer containing a metal, such as CuO, CoOx, TiOx, etc. A through hole 400 is formed in the first isolation layer, and the through hole 400 exposes the metal copper.
[0049] Step S2: using hydrogen plasma to perform etching on the semiconductor structure.
[0050] Specifically, refer to Figure 4 and Figure 5 As shown, the semiconductor structure is etched using hydrogen plasma. When the metal oxide layer 510 is a metal oxide, CuOx is taken as an example. The reaction formula for etching the semiconductor structure using hydrogen plasma is as follows:
[0051] H / H*+CuO x →Cu+H2O……(1),
[0052] SiO x +H / H*→SiH4+H2O……(2),
[0053] SiH4+H2O→SiO2+H2……(3).
[0054] The semiconductor structure is etched by using hydrogen plasma, so that the metal oxide formed on the surface of the copper metal layer is reduced to metal and H2O under the action of hydrogen plasma. Then, the hydrogen plasma reacts with SiOx (silicon oxide) on the side wall to generate SiH4. Finally, SiH4 and H2O generate SiO2 on the metal surface.
[0055] Furthermore, in order to further improve the removal effect of the metal oxide on the surface of the copper metal layer, when the semiconductor structure is etched using hydrogen plasma, a heater with a heating function can be used in conjunction to obtain a better effect. The temperature of the heater is 25°C to 100°C. That is, the reaction temperature when the semiconductor structure is first etched using hydrogen plasma can be 25°C, 40°C, 50°C, 70°C, 80°C, or any value within the range of 25°C to 100°C.
[0056] Step S3: After etching, SiCoNi pre-cleaning is performed on the semiconductor structure.
[0057] Specifically, refer to Figure 4 and Figure 6 As shown, after etching, SiCoNi pre-cleaning is performed on the semiconductor structure to remove silicon dioxide at the bottom of the through hole 400. When SiCoNi pre-cleaning is performed on the semiconductor structure, the reaction gas is a mixed gas of NF3 and NH3. The reaction formula for performing SiCoNi pre-cleaning on the semiconductor structure is:
[0058] NF3+NH3(RPS)→NH4F+NH4F . HF……(4),
[0059] NH4F+NH4F . HF+SiO2(heat)→(NH4)2SiF6+H2O……(5),
[0060] (NH4)2SiF6+H2O(heat)→SiF4+NH3……(6).
[0061] Wherein, the flow rate of the mixed gas of NF3 and NH3 is 1000sccm to 2000sccm. That is, the flow rate of the mixed gas can be 1500sccm, 1600sccm, 1700sccm, 1800sccm, 1900sccm, 2000sccm, or any value within the range of 1000sccm to 2000sccm. The RPS (Rermove Plasma Source) in reaction formula (4) indicates that when the SiCoNi pre-cleaning is performed, the excitation source is located outside the reaction chamber. The reaction temperature of reaction formula (5) and the reaction temperature of reaction formula (6) are 150℃ to 210℃.
[0062] The etching of the semiconductor structure using hydrogen plasma, the pre-cleaning of SiCoNi on the semiconductor structure, and the deposition of titanium and titanium nitride layers are performed using the same machine. The etching of the semiconductor structure using hydrogen plasma, the pre-cleaning of SiCoNi on the semiconductor structure, and the deposition of titanium and titanium nitride layers can also be performed using different machines.
[0063] Pre-cleaning of the semiconductor structure using SiCoNi forms Figure 6 The structure shown. Figure 6 It can be seen that the surface of the copper metal layer at the bottom of the through hole 400 is not uneven. At the same time, there is no volume loss of the copper metal layer at the bottom of the through hole 400. In addition, the width of the top of the through hole 400 does not become narrower, that is, the process window for depositing the metal tungsten 600 does not become narrower.
[0064] Step S4 : after depositing a second isolation layer on the inner wall of the through hole 400 and the surface of the first isolation layer, filling the through hole 400 with metal tungsten 600 .
[0065] Specifically, refer to Figure 4 and Figure 7 As shown, after the above steps, deposition can be performed to form a second isolation layer. The second isolation layer includes an insulating layer and an adhesion layer, and is generally made of Ti / TiN or TaN. That is, a titanium / titanium nitride layer 700 is deposited on the inner wall of the through hole 400 and the surface of the insulating layer. Metal tungsten 600 is deposited in the through hole 400 by using a chemical vapor deposition process or a physical vapor deposition process to achieve metal interconnection between the copper metal layer and the metal tungsten 600, forming a Figure 7 It should be noted that for the copper metal layer (ie, Figure 7 The Metal (hereinafter referred to as "M") shown in the figure may be the first copper metal layer, the second copper metal layer, or the third copper metal layer. Figure 7 It can be seen from the structure shown that there is no unevenness at the interface between the copper metal layer and the tungsten metal surface, and there is no loss of the copper metal layer. In addition, the process window at the top of the through hole 400 will not be narrowed due to the re-sputtering of the side wall of the through hole 400.
[0066] The method for expanding the deposition window of metal tungsten disclosed in this embodiment is to first etch the semiconductor structure using hydrogen plasma before depositing metal tungsten 600 in the through hole 400. Since hydrogen plasma reacts with silicon oxide in the previous metal layer, reduced metal and silicon dioxide are generated on the surface of the metal layer. Then, the semiconductor structure after the etching treatment is subjected to SiCoNi pre-cleaning to remove silicon dioxide on the surface of the copper metal layer. Finally, after depositing the titanium / titanium nitride layer 700 on the inner wall of the through hole 400 and the surface of the insulating layer, metal tungsten 600 is deposited in the through hole 400 to interconnect the copper metal layer with the metal tungsten 600. Such a process will not cause the loss of the volume of the previous copper metal layer, making the contact surface between the copper metal layer and the metal tungsten 600 smoother, and will not cause the top of the side wall to overhang, thereby increasing the process window for the subsequent deposition of metal tungsten 600.
[0067] In summary, the above embodiments have described in detail the different configurations of the method for expanding the deposition window of metal tungsten. Of course, the above description is only a description of the preferred embodiments of the present invention, and is not any limitation to the scope of the present invention. The present invention includes but is not limited to the configurations listed in the above embodiments. Those skilled in the art can draw inferences based on the contents of the above embodiments. Any changes and modifications made by ordinary technicians in the field of the present invention based on the above disclosure are within the scope of protection of the claims.
Claims
1. A method for expanding the deposition window of metal tungsten, characterized in that: include: A semiconductor structure is provided, wherein a through hole and a first isolation layer are formed on the surface of the semiconductor structure, a metal oxide layer is formed on the bottom of the through hole, and the first isolation layer includes a silicon oxide layer and a barrier layer; Etching the semiconductor structure using hydrogen plasma; After etching, the semiconductor structure is subjected to SiCoNi pre-cleaning; After depositing a second isolation layer on the inner wall of the through hole and the surface of the first isolation layer, metal tungsten is filled in the through hole.
2. The method for expanding the deposition window of metal tungsten according to claim 1, characterized in that: The reaction equation for etching the semiconductor structure using hydrogen plasma is as follows: H / H*+ME x →Y+H2O……(1), SiO x +H / H*→SiH4+H2O……(2), SiH4+H2O→SiO2+H2……(3).
3. The method for expanding the deposition window of metal tungsten according to claim 2, characterized in that: When the semiconductor structure is etched by hydrogen plasma, a heating treatment is performed, and the heating temperature range is 25° C. to 100° C.
4. The method for expanding the deposition window of metal tungsten according to claim 1, characterized in that: The reaction formula for performing SiCoNi pre-cleaning on the semiconductor structure is: NF3+NH3(RPS)→NH4F+NH4F . HF……(4), NH4F+NH4F . HF+SiO2(heat)→(NH4)2SiF6+H2O……(5), (NH4)2SiF6+H2O(heat)→SiF4+NH3……(6).
5. The method for expanding the deposition window of metal tungsten according to claim 4, characterized in that: When the semiconductor structure is subjected to SiCoNi pre-cleaning, the reaction gas is a mixed gas of NF3 and NH3, and the flow rate of the mixed gas is 1000 sccm to 2000 sccm, and the reaction temperature ranges from 150°C to 210°C.
6. The method for expanding the deposition window of metal tungsten according to claim 1, characterized in that: The semiconductor structure is etched by hydrogen plasma, SiCoNi is pre-cleaned and the titanium and titanium nitride layers are deposited by the same machine.
7. The method for expanding the deposition window of metal tungsten according to claim 1, characterized in that: The semiconductor structure is etched by hydrogen plasma, SiCoNi is pre-cleaned and titanium and titanium nitride layers are deposited by different machines.
8. The method for expanding the deposition window of metal tungsten according to claim 1, characterized in that: The second isolation layer includes a titanium layer and a titanium nitride layer deposited on the surface of the titanium layer.
9. The method for expanding the deposition window of metal tungsten according to claim 1, characterized in that: The material used for the barrier layer is silicon nitride.
10. The method for expanding the deposition window of metal tungsten according to claim 9, characterized in that: The first isolation layer includes a first silicon oxide layer, a silicon nitride layer deposited on a surface of the first silicon oxide layer, and a second silicon oxide layer deposited on a surface of the silicon nitride layer.