Tungsten Chemical Vapor Deposition Method

Abstract

The present invention discloses a tungsten chemical vapor deposition method, comprising: step 1, providing a bottom structure with a first adhesion layer and a second barrier layer formed on the surface. Step 2, performing tungsten chemical vapor deposition on the surface of the second barrier layer to form a tungsten layer. The tungsten layer is formed by superposition of a tungsten seed layer and a tungsten main layer. During the deposition of the tungsten seed layer, the process gas is introduced into the reaction chamber in the following steps: step 21, introducing a tungsten-containing precursor and introducing a first reducing agent gas at the same time. Step 22, introducing a second reducing agent gas after a first delay, and forming a tungsten seed layer by a nucleation reaction between the tungsten-containing precursor and the second reducing agent gas. The activity of the first reducing agent gas is less than that of the second reducing agent gas, and is used to prevent the ions of the tungsten-containing precursor from corroding the first adhesion layer when a switching operation failure occurs in the second reducing agent gas. The present invention can prevent abnormal nucleation and thus avoid product scrapping caused by abnormal nucleation, and finally improve the product yield.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a semiconductor integrated circuit, in particular to a tungsten chemical vapor deposition (WCVD) method. Background Art

[0002] Chemical Vapor Deposition (CVD) is a process that deposits a solid film on the surface of a silicon wafer through a chemical reaction of a gas mixture. CVD technology can prepare thin films of various compositions on different substrates, and has the advantages of good film uniformity, high deposition rate, and strong ductility, and is widely used in the production of semiconductor integrated circuits.

[0003] Metal tungsten (Tungsten, W) CVD film has excellent step coverage and gap filling capabilities and good anti-electromigration properties, making it an ideal process choice for filling through holes between metal layers in integrated circuit manufacturing.

[0004] like Figure 1 As shown, the flow chart of the existing tungsten chemical vapor deposition method; the existing tungsten chemical vapor deposition process mainly has three steps, namely:

[0005] Step S101, silane soaking (SiH4 soak); Figure 1 Silane soak is also expressed as SiH4 soak.

[0006] Step S102: nucleation. Figure 1 Nucleation is also expressed by nucleation.

[0007] Step S103: bulk deposition. Figure 1 Bulk deposition is also expressed as bulk deposition.

[0008] The nucleation process of the existing WCVD process is to use SiH4 and WF6 to react at a certain temperature and pressure to generate a thin layer of tungsten, namely the tungsten seed layer, as the growth point for subsequent bulk deposition. During the nucleation process, the flow ratio of SiH4 and WF6 must be strictly controlled, otherwise abnormal nucleation is likely to occur, resulting in the waste of silicon wafers.

[0009] During the nucleation process, the flow ratio of SiH4 and WF6 is strictly controlled and the two are guaranteed to reach the surface of the silicon wafer at the same time. Since WF6 has a larger molecular weight, it needs to be introduced into the reaction chamber slightly in advance. That is, compared with SiH4, the time required for WF6 to reach the nucleation surface from the inlet into the reaction chamber is longer than the time required for SiH4 to reach the nucleation surface from the inlet. Therefore, in order to make WF6 and SiH4 reach the nucleation surface at the same time, WF6 needs to be introduced slightly in advance to compensate for the time difference between the two from the inlet to the nucleation surface. Figure 2 As shown in FIG. 1 , it is a curve of the process gas introduction during the nucleation process of the existing tungsten chemical vapor deposition method; according to the control of the process gas introduction, Figure 1 Step S102 is divided into the following two sub-steps:

[0010] Step S1021, introducing WF6 gas in advance (WF6 FIRST), Figure 1 Step S1021 also uses WF6 FIRST. Figure 2 The middle curve 101 is the WF6 introduction curve. It can be seen that WF6 starts to be introduced from time t0.

[0011] Step S1022: introducing WF6, H2 and SiH4 together. Figure 1 Step S1022 is also represented by WF6+H2+SiH4. Figure 2 The middle curve 102 is the H2 introduction curve, and the curve 103 is the SiH4 introduction curve. It can be seen that both H2 and SiH4 are introduced from t1.

[0012] In the actual operation process, the machine side occasionally has a delay in switching the set operating conditions, that is, SiH4 enters the reaction chamber much later than WF6, making the reaction chamber fluorine-rich. Fluoride ions easily pass through the TiN barrier layer to react with the underlying Ti layer, corroding the underlying structure, resulting in poor nucleation, and in severe cases, causing the silicon wafer to be discarded at a low yield. The chemical equation for the reaction between WF6 and the Ti layer is:

[0013] 2WF6+3Ti→2W(s)+3TiF4(g);

[0014] like Figure 3 FIG. 104 shows a product yield graph formed by an existing tungsten chemical vapor deposition method. There are many defects 105 in the product yield graph 104, which will eventually reduce the product yield. Failure analysis (FA) shows that these defects 105 are related to the corrosion of the Ti layer. Summary of the invention

[0015] The technical problem to be solved by the present invention is to provide a tungsten chemical vapor deposition method, which can prevent abnormal nucleation and thus avoid product scrapping caused by abnormal nucleation, and finally improve product yield.

[0016] In order to solve the above technical problems, the present invention provides a tungsten chemical vapor deposition method comprising the following steps:

[0017] Step 1: providing a bottom layer structure having a first adhesion layer and a second barrier layer formed on the surface.

[0018] Step 2: Perform tungsten chemical vapor deposition to form a tungsten layer on the surface of the second barrier layer.

[0019] The tungsten layer is formed by stacking a tungsten seed layer and a tungsten main layer.

[0020] During the deposition of the tungsten seed crystal layer, the process gas is introduced into the reaction chamber in the following steps:

[0021] Step 21: introducing a tungsten-containing precursor.

[0022] The first reducing agent gas is introduced while the tungsten-containing precursor is introduced.

[0023] Step 22: introducing a second reducing agent gas after a first delay, and using the tungsten-containing precursor and the second reducing agent gas to perform a nucleation reaction to form the tungsten seed crystal layer.

[0024] The molecular weight of the tungsten-containing precursor is greater than the molecular weight of the second reducing agent gas, the rate at which the tungsten-containing precursor reaches the surface of the second barrier layer is less than the rate at which the second reducing agent gas reaches the surface of the second barrier layer, and the first time is set so that the tungsten-containing precursor and the second reducing agent gas arrive at the surface of the second barrier layer at the same time when there is no switching operation failure of the second reducing agent gas.

[0025] The activity of the first reducing agent gas is lower than that of the second reducing agent. The first reducing agent gas is used to react with the ions of the tungsten-containing precursor when a switching operation failure occurs in the second reducing agent gas, causing the second reducing agent gas to arrive on the surface of the second barrier layer later than the tungsten-containing precursor, thereby preventing the ions of the tungsten-containing precursor from passing through the second barrier layer and corroding the first adhesion layer, thereby eliminating nucleation anomalies.

[0026] In some embodiments, in step 1, the material of the first adhesion layer includes Ti.

[0027] In some embodiments, the material of the second barrier layer includes TiN.

[0028] In some embodiments, in step 2, the tungsten-containing precursor includes WF6.

[0029] In some embodiments, in step 2, the first reducing agent gas includes hydrogen.

[0030] In step 2, when the second reducing agent gas reaches the surface of the second barrier layer later than the precursor, the hydrogen gas reacts with the fluorine ions of the tungsten-containing precursor to form hydrogen fluoride byproducts and is removed, thereby preventing the fluorine ions from corroding the first adhesion layer.

[0031] In some embodiments, in step 2, the second reducing agent gas includes silane.

[0032] In some embodiments, the tungsten layer is used as a tungsten line, a contact hole or a via.

[0033] In some embodiments, when the tungsten layer is used as the tungsten connection, in step 1, the underlying structure includes a semiconductor substrate and a bottom metal interconnection structure formed on the semiconductor substrate, and the bottom metal interconnection structure is located between the tungsten layer and the semiconductor substrate.

[0034] In some embodiments, when the tungsten layer is used as the contact hole, in step one, the underlying structure includes a semiconductor substrate and a pre-metal interlayer film formed on the semiconductor substrate, an opening of a contact hole is formed in the pre-metal interlayer film, and the opening of the contact hole will be formed on the semiconductor substrate to expose the surface of the doped region that needs to be led out; in step two, the tungsten layer completely fills the opening of the contact hole.

[0035] In some embodiments, when the tungsten layer is used as the through hole, in step one, the underlying structure includes a semiconductor substrate and a bottom metal interconnection structure and a current interlayer film formed on the semiconductor substrate; the bottom metal interconnection structure is located between the current interlayer film and the semiconductor substrate, and an opening of the through hole is formed in the current interlayer film, and the surface of the metal layer at the bottom of the opening of the through hole is exposed; in step two, the tungsten layer completely fills the opening of the through hole.

[0036] In some embodiments, in step 2, before depositing the tungsten seed crystal layer, the step further includes: silane soaking.

[0037] In some embodiments, in step 2, after forming the tungsten seed layer, the step further includes: performing body deposition to form the tungsten main body layer.

[0038] In some embodiments, the semiconductor substrate includes a silicon substrate.

[0039] The present invention makes a special arrangement for the process gas introduction step in the step of forming the tungsten seed crystal layer. While delaying the introduction of the second reducing agent gas with strong reducing property at the first time so that under normal circumstances the second reducing agent gas and the tungsten-containing precursor can reach the surface of the second barrier layer at the same time, the present invention simultaneously introduces the first reducing agent gas with weaker reducing property and the tungsten-containing precursor at the same time. In this way, when the second reducing agent gas has a switching failure and reaches the surface of the second barrier layer later than the tungsten-containing precursor, the first reducing agent gas can react with the ions of the tungsten-containing precursor and thereby prevent the ions of the tungsten-containing precursor from passing through the second barrier layer and reacting with the first adhesion layer, thereby avoiding nucleation abnormalities caused by corrosion of the first adhesion layer, and finally avoiding product scrapping due to abnormal nucleation, and finally improving product yield.

[0040] Since the activity of the first reducing agent gas is lower than that of the second reducing agent gas, when the second reducing agent gas reaches the surface of the second barrier layer, the tungsten-containing precursor mainly reacts with the second reducing agent gas to form tungsten nuclei. Therefore, the inflow of the first reducing agent gas itself will not have an adverse effect on tungsten nucleation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0042] Figure 1 is a flow chart of an existing tungsten chemical vapor deposition method;

[0043] Figure 2 It is the process gas introduction curve in the nucleation process of the existing tungsten chemical vapor deposition method;

[0044] Figure 3 It is a product yield map formed by the existing tungsten chemical vapor deposition method;

[0045] Figure 4 is a flow chart of a tungsten chemical vapor deposition method according to an embodiment of the present invention;

[0046] Figure 5 is a curve of process gas introduction during the nucleation process of the tungsten chemical vapor deposition method according to an embodiment of the present invention;

[0047] Figure 6 This is a product yield diagram formed by the tungsten chemical vapor deposition method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0048] like Figure 4 FIG. 2 is a flow chart of a tungsten chemical vapor deposition method according to an embodiment of the present invention. The tungsten chemical vapor deposition method according to an embodiment of the present invention comprises the following steps:

[0049] Step 1: providing a bottom layer structure having a first adhesion layer and a second barrier layer formed on the surface.

[0050] In the embodiment of the present invention, the material of the first adhesion layer includes Ti.

[0051] The material of the second barrier layer includes TiN.

[0052] Step 2: Perform tungsten chemical vapor deposition to form a tungsten layer on the surface of the second barrier layer.

[0053] The tungsten layer is formed by stacking a tungsten seed layer and a tungsten main layer.

[0054] In the embodiment of the present invention, before depositing the tungsten seed crystal layer, the process further includes: silane soaking. Figure 4 In the embodiment, the silane soaking corresponds to step S201, and step S201 is also represented by SiH4 soak.

[0055] The deposition process of the tungsten seed layer is a nucleation process, corresponding to Figure 4 In step S202, step S202 is also expressed by nucleation.

[0056] During the deposition of the tungsten seed crystal layer, the process gas is introduced into the reaction chamber in the following steps:

[0057] Step 21: introducing a tungsten-containing precursor.

[0058] The first reducing agent gas is introduced while the tungsten-containing precursor is introduced.

[0059] In an embodiment of the present invention, the tungsten-containing precursor includes WF6.

[0060] The first reducing agent gas includes hydrogen.

[0061] Step 21 corresponds to Figure 4 In step S2021, step S2021 is also expressed by WF6 first (with H2).

[0062] like Figure 5 As shown, it is the introduction curve of process gas in the nucleation process of the tungsten chemical vapor deposition method according to the embodiment of the present invention; curve 201 is the introduction curve of WF6, and curve 202 is the introduction curve of H2. It can be seen that both WF6 and H2 are introduced from time t0.

[0063] Step 22: introducing a second reducing agent gas after a first delay, and using the tungsten-containing precursor and the second reducing agent gas to perform a nucleation reaction to form the tungsten seed crystal layer.

[0064] In an embodiment of the present invention, the second reducing agent gas includes silane.

[0065] Step 22 corresponds to Figure 4In step S2022, step S2022 is also represented by WF6+H2+SiH4.

[0066] Figure 5 In FIG. 2 , curve 203 is a curve of SiH 4 being introduced, and it can be seen that SiH 4 is introduced from time t1. The first time is the difference between t1 and t0.

[0067] The molecular weight of the tungsten-containing precursor is greater than the molecular weight of the second reducing agent gas, the rate at which the tungsten-containing precursor reaches the surface of the second barrier layer is less than the rate at which the second reducing agent gas reaches the surface of the second barrier layer, and the first time is set so that the tungsten-containing precursor and the second reducing agent gas arrive at the surface of the second barrier layer at the same time when there is no switching operation failure of the second reducing agent gas.

[0068] The activity of the first reducing agent gas is lower than that of the second reducing agent. The first reducing agent gas is used to react with the ions of the tungsten-containing precursor when a switching operation failure occurs in the second reducing agent gas, causing the second reducing agent gas to arrive on the surface of the second barrier layer later than the tungsten-containing precursor, thereby preventing the ions of the tungsten-containing precursor from passing through the second barrier layer and corroding the first adhesion layer, thereby eliminating nucleation anomalies.

[0069] In the embodiment of the present invention, the first reducing agent gas is hydrogen. Therefore, when the second reducing agent gas reaches the surface of the second barrier layer later than the tungsten-containing precursor, the hydrogen reacts with the fluorine ions of the tungsten-containing precursor to form hydrogen fluoride byproducts and is removed, thereby preventing the fluorine ions from corroding the first adhesion layer. The chemical reaction equation of WF6 and H2 is:

[0070] WF6+3H2→W(s)+6HF(g);

[0071] As can be seen from the above, in the tungsten chemical vapor deposition process of the embodiment of the present invention, hydrogen H2 is introduced at the same time as the WF6 introduction step, so that the chamber atmosphere is in a hydrogen-rich state before the nucleation reaction. Since the reaction activity of WF6 with hydrogen is less than that of WF6 with SiH4, the introduction of hydrogen at the initial stage of nucleation has no effect on the nucleation process of the reaction of WF6 and SiH4, and hydrogen can react with fluoride ions to generate hydrogen fluoride gas byproducts when SiH4 does not enter the chamber in time, and is discharged, thereby achieving the purpose of protecting the underlying structure.

[0072] In the embodiment of the present invention, the tungsten layer is used as a tungsten connection line, a contact hole or a through hole.

[0073] In some embodiments, when the tungsten layer is used as the tungsten connection, in step 1, the underlying structure includes a semiconductor substrate and a bottom metal interconnection structure formed on the semiconductor substrate, and the bottom metal interconnection structure is located between the tungsten layer and the semiconductor substrate.

[0074] In some embodiments, when the tungsten layer is used as the contact hole, in step one, the underlying structure includes a semiconductor substrate and a pre-metal interlayer film formed on the semiconductor substrate, an opening of a contact hole is formed in the pre-metal interlayer film, and the opening of the contact hole will be formed on the semiconductor substrate to expose the surface of the doped region that needs to be led out; in step two, the tungsten layer completely fills the opening of the contact hole.

[0075] In some embodiments, when the tungsten layer is used as the through hole, in step one, the underlying structure includes a semiconductor substrate and a bottom metal interconnection structure and a current interlayer film formed on the semiconductor substrate; the bottom metal interconnection structure is located between the current interlayer film and the semiconductor substrate, and an opening of the through hole is formed in the current interlayer film, and the surface of the metal layer at the bottom of the opening of the through hole is exposed; in step two, the tungsten layer completely fills the opening of the through hole.

[0076] In some embodiments, the semiconductor substrate includes a silicon substrate.

[0077] In the embodiment of the present invention, in step 2, after forming the tungsten seed crystal layer, the step further includes: performing body deposition to form the tungsten main body layer. Body deposition corresponds to Figure 4 In step S203, step S203 is also represented by bulk deposition.

[0078] The embodiment of the present invention makes a special arrangement for the process gas introduction step in the step of forming the tungsten seed crystal layer. While delaying the introduction of the second reducing agent gas with strong reducing property at the first time so that under normal circumstances the second reducing agent gas and the tungsten-containing precursor can reach the surface of the second barrier layer at the same time, the present invention simultaneously introduces the first reducing agent gas with weaker reducing property and the tungsten-containing precursor at the same time. In this way, when the second reducing agent gas has a switching failure and reaches the surface of the second barrier layer later than the tungsten-containing precursor, the first reducing agent gas can react with the ions of the tungsten-containing precursor and thereby prevent the ions of the tungsten-containing precursor from passing through the second barrier layer and reacting with the first adhesion layer, thereby avoiding nucleation abnormalities caused by corrosion of the first adhesion layer, and finally avoiding product scrapping due to abnormal nucleation, and finally improving product yield.

[0079] Since the activity of the first reducing agent gas is lower than that of the second reducing agent gas, when the second reducing agent gas reaches the surface of the second barrier layer, the tungsten-containing precursor mainly reacts with the second reducing agent gas to form tungsten nuclei. Therefore, the inflow of the first reducing agent gas itself will not have an adverse effect on tungsten nucleation.

[0080] like Figure 6 As shown, it is a product yield graph formed by the tungsten chemical vapor deposition method according to an embodiment of the present invention. It can be seen from the product yield graph 204 that product defects are greatly reduced.

[0081] The present invention has been described in detail above through specific embodiments, but these do not constitute limitations of the present invention. Without departing from the principle of the present invention, those skilled in the art may also make many variations and improvements, which should also be considered as the protection scope of the present invention.

Claims

1. A tungsten chemical vapor deposition method, characterized in that: The steps include: Step 1, providing a bottom layer structure having a first adhesion layer and a second barrier layer formed on the surface; Step 2: performing chemical vapor deposition of tungsten to form a tungsten layer on the surface of the second barrier layer; The tungsten layer is formed by stacking a tungsten seed layer and a tungsten main layer; During the deposition of the tungsten seed crystal layer, the process gas is introduced into the reaction chamber in the following steps: Step 21, introducing a tungsten-containing precursor; While introducing the tungsten-containing precursor, a first reducing agent gas is introduced; Step 22, introducing a second reducing agent gas after a first delay, and using the tungsten-containing precursor and the second reducing agent gas to perform a nucleation reaction to form the tungsten seed crystal layer; The molecular weight of the tungsten-containing precursor is greater than the molecular weight of the second reducing agent gas, the speed at which the tungsten-containing precursor reaches the surface of the second barrier layer is less than the speed at which the second reducing agent gas reaches the surface of the second barrier layer, and the first time is set to allow the tungsten-containing precursor and the second reducing agent gas to reach the surface of the second barrier layer at the same time when there is no switching operation failure of the second reducing agent gas; The activity of the first reducing agent gas is lower than that of the second reducing agent, and the first reducing agent gas is used to react with the ions of the tungsten-containing precursor when the second reducing agent gas fails to switch so that the second reducing agent gas reaches the surface of the second barrier layer later than the tungsten-containing precursor, thereby preventing the ions of the tungsten-containing precursor from passing through the second barrier layer and corroding the first adhesion layer, thereby eliminating nucleation anomalies; The tungsten-containing precursor is WF6; The first reducing agent gas is hydrogen; when the second reducing agent gas reaches the surface of the second barrier layer later than the tungsten-containing precursor, the hydrogen gas reacts with the fluorine ions of the tungsten-containing precursor to form hydrogen fluoride byproducts and is removed, thereby preventing the fluorine ions from corroding the first adhesion layer; The second reducing agent gas is silane.

2. The tungsten chemical vapor deposition method according to claim 1, characterized in that: In step 1, the material of the first adhesion layer includes Ti.

3. The tungsten chemical vapor deposition method according to claim 2, characterized in that: The material of the second barrier layer includes TiN.

4. The tungsten chemical vapor deposition method according to claim 1, characterized in that: The tungsten layer is used as a tungsten wiring, a contact hole or a through hole.

5. The tungsten chemical vapor deposition method according to claim 4, characterized in that: When the tungsten layer is used as the tungsten connection, in step 1, the underlying structure includes a semiconductor substrate and a bottom metal interconnection structure formed on the semiconductor substrate, and the bottom metal interconnection structure is located between the tungsten layer and the semiconductor substrate.

6. The tungsten chemical vapor deposition method according to claim 4, characterized in that: When the tungsten layer is used as the contact hole, in step 1, the underlying structure includes a semiconductor substrate and a pre-metal interlayer film formed on the semiconductor substrate, an opening of a contact hole is formed in the pre-metal interlayer film, and the opening of the contact hole exposes the surface of the doped region to be led out formed on the semiconductor substrate; In step 2, the tungsten layer completely fills the opening of the contact hole.

7. The tungsten chemical vapor deposition method according to claim 4, characterized in that: When the tungsten layer is used as the through hole, in step one, the underlying structure includes a semiconductor substrate and a bottom metal interconnection structure and a current interlayer film formed on the semiconductor substrate; the bottom metal interconnection structure is located between the current interlayer film and the semiconductor substrate, and an opening of the through hole is formed in the current interlayer film, and the surface of the metal layer at the bottom of the opening of the through hole is exposed; in step two, the tungsten layer completely fills the opening of the through hole.

8. The tungsten chemical vapor deposition method according to claim 1, characterized in that: In step 2, before depositing the tungsten seed crystal layer, the method further includes: silane soaking.

9. The tungsten chemical vapor deposition method according to claim 8, characterized in that: In step 2, after forming the tungsten seed crystal layer, the method further includes: performing body deposition to form the tungsten main body layer.

10. The tungsten chemical vapor deposition method according to claim 5, 6 or 7, characterized in that: The semiconductor substrate includes a silicon substrate.

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