Method for depositing silicon nitride on side wall of groove structure

Abstract

The invention provides a method for depositing silicon nitride on the side wall of a groove structure, and belongs to the technical field of semiconductor manufacturing. The method comprises the following steps of: depositing carbon-containing barrier layers on the top, the side wall and the bottom of a groove structure by utilizing inductively coupled plasma enhanced chemical vapor deposition, and then carrying out directional etching on the side wall of the groove by utilizing ammonia plasma bombardment, so that the carbon-containing barrier layers on the side wall of the groove are accurately removed, and the barrier layers in the top and bottom areas are kept complete; and finally, using inductively coupled plasma to enhance atomic layer deposition, and selectively depositing a silicon nitride film in the side wall area of the groove. The method does not need to depend on traditional photoetching and etching steps, non-target area deposition is avoided, the technological process is simplified, the deposition precision and the critical dimension control capability are improved, and the method has the dual control effects of precise directional etching and selective deposition.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of semiconductor manufacturing, and particularly relates to a method for depositing silicon nitride on the sidewall of a trench structure. BACKGROUND

[0002] With the development of semiconductor technology towards nanometer and smaller technology nodes, the complexity and integration of device structures are continuously improved, and higher requirements are put forward for the deposition selectivity and precise control of materials. In high aspect ratio trench structures (usually with an aspect ratio of 2:1 to 10:1), the deposition requirements of different regions (such as sidewall, top and bottom) are not the same. In particular, when depositing a silicon nitride film on the sidewall of a trench, it is required to achieve high-precision sidewall deposition without affecting the top and bottom.

[0003] Traditional deposition methods (such as physical vapor deposition and chemical vapor deposition) often have difficulty in achieving high-selectivity deposition in specific regions of the trench structure. These methods simultaneously deposit throughout the trench structure, resulting in material attachment in the top, bottom and sidewall regions, which cannot meet the requirement of independent sidewall deposition. Such global deposition leads to uneven distribution of the film layer, increasing the waste of materials, and in some cases, affecting the physical and electrical properties of the trench. In addition, current selective deposition processes rely on photolithography and etching steps for structure control, selectively removing material deposition in non-target regions through masks and subsequent etching. However, photolithography and etching processes not only take a long time and are costly, but also have difficulty in meeting the requirements of high aspect ratio trenches in terms of precision, which can easily cause alignment errors on the sidewall of the trench, increasing the deposition and surface damage in non-target regions.

[0004] There is a prior art that proposes a method for regionally selective deposition by filling the gap between the mask plate and the substrate with a liquid sealing layer. This method suppresses the deposition in non-target regions through a physical barrier, but there are problems in the adaptability of the thickness control and fluidity of the liquid sealing layer to fine trench structures. Essentially, it cannot achieve in-situ control of the deposition material, and cannot accurately control the regionally selectivity of deposition in high-precision nanodevices. SUMMARY

[0005] The purpose of the present application is to provide a method for depositing silicon nitride on the sidewall of a trench structure. The present application removes the carbon-containing barrier layer on the sidewall of the trench structure by ammonia plasma bombardment, and then deposits silicon nitride, achieving deposition of silicon nitride only in the sidewall region of the trench structure, with the dual control of precise directional etching and selective deposition.

[0006] In order to achieve the purpose of the present application, the present application provides the following technical solutions:

[0007] A method for depositing silicon nitride on the sidewall of a trench structure, comprising the following steps:

[0008] depositing a carbon-containing barrier layer on the top, sidewall and bottom of the trench structure; the depositing is inductively coupled plasma enhanced chemical vapor deposition, and the carbon source is methane;

[0009] performing directional etching on the sidewall of the trench structure by ammonia plasma bombardment to remove the carbon-containing barrier layer on the sidewall; the angle of the ammonia plasma bombardment is perpendicular to the bottom;

[0010] depositing silicon nitride on the surface of the sidewall from which the carbon-containing barrier layer is removed by using plasma enhanced atomic layer deposition with a silicon precursor and nitrogen plasma as co-reactants.

[0011] Preferably, in the inductively coupled plasma enhanced chemical vapor deposition, the gas flow rate of methane is 5-10 sccm; the carrier gas is argon, and the gas flow rate of argon is 200-300 sccm; the plasma power is 20-40 W; the deposition temperature is 200-300℃, the pressure is 4-6 Pa, the rate is 0.05-0.15 nm / s, and the time is 30-140 s.

[0012] Preferably, the thickness of the carbon-containing barrier layer is 3-50 nm.

[0013] Preferably, the power of the ammonia plasma bombardment is 200-300 W.

[0014] Preferably, in the plasma enhanced atomic layer deposition, the deposition temperature is 300-400℃, the carrier gas is argon, and the gas flow rate of argon is 200-300 sccm; the nitrogen flow rate is 100-200 sccm; the plasma power is 300-500 W; the temperature of the silicon precursor is 40-60℃; and the deposition cycle is 10-150.

[0015] Preferably, the silicon precursor includes a silane precursor and / or a silazane precursor.

[0016] Preferably, the deposition thickness of the silicon nitride is 1-20 nm.

[0017] Preferably, the ammonia plasma bombardment and the deposition of silicon nitride are both performed in the reaction chamber of the plasma enhanced atomic layer deposition; the ammonia plasma bombardment and the deposition of silicon nitride are sequentially performed or automatically continuously performed without the need to take out the reaction chamber again.

[0018] Preferably, the aspect ratio of the trench structure is 2:1-10:1.

[0019] The application provides a method for depositing silicon nitride on the sidewall of a trench structure, comprising the following steps: depositing a carbon-containing barrier layer on the top, sidewall and bottom of the trench structure; the deposition is inductively coupled plasma enhanced chemical vapor deposition, and the carbon source is methane; directional etching is performed on the sidewall of the trench structure by using ammonia plasma bombardment to remove the carbon-containing barrier layer on the sidewall; the angle of the ammonia plasma bombardment is perpendicular to the bottom; silicon nitride is deposited on the sidewall surface from which the carbon-containing barrier layer has been removed by using plasma enhanced atomic layer deposition with silicon precursor and nitrogen plasma as co-reactants.

[0020] Firstly, the application uses an inductively coupled plasma enhanced chemical vapor deposition system (PECVD) to deposit a carbon-containing barrier layer on the top, sidewall and bottom of the trench structure, and the carbon-containing barrier layer has high density and strong chemical inertness, which can effectively block the growth of the subsequent silicon nitride film, especially forming a uniform barrier layer in the top area of the trench, thereby creating conditions for selective deposition in the sidewall area.

[0021] Secondly, the application uses ammonia plasma bombardment to perform directional etching on the sidewall of the trench, and by combining chemical reaction with physical bombardment, the carbon-containing barrier layer in the sidewall area of the trench is accurately removed, while the barrier layer in the top and bottom areas remains intact. The ammonia plasma has directionality and high energy characteristics, which realizes the exposure of only the sidewall area for subsequent deposition, avoids the damage to the top and bottom areas, ensures the high-selective deposition of the subsequent silicon nitride, and provides good substrate conditions for the selective deposition of the silicon nitride film, which is suitable for complex trench structures with micron to nanometer aspect ratio, and has wide application prospects in the trench filling of semiconductor devices, the preparation of insulating isolation layers and device passivation layers.

[0022] Finally, the application uses an inductively coupled plasma enhanced atomic layer deposition system (PEALD) to selectively deposit a silicon nitride film in the sidewall area of the trench by using double silicon precursors and nitrogen plasma as co-reactants. Due to the inhibitory effect of the carbon-containing barrier layer, silicon nitride cannot be deposited in the top and bottom areas, thereby achieving the purpose of selectively depositing a silicon nitride film only in the sidewall area. The application does not need to rely on traditional photolithography and etching steps, avoids non-target area deposition, simplifies the process flow, improves deposition accuracy and critical dimension control capability, and has the dual control effects of precise directional etching and selective deposition. At the same time, the process has low energy consumption, which is convenient for industrial production. Moreover, the ammonia plasma bombardment treatment is directly performed in the PEALD chamber, without the need to take out the chamber again, avoiding the process of taking out, transporting, breaking the vacuum and placing again in the chamber, simplifying the process flow, reducing the pollution and loss risk, and improving the stability and efficiency of the overall process. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0024] Figure 1 Flow chart of the method for depositing silicon nitride on the sidewall of the trench structure in the present application;

[0025] Figure 2 Variation chart of the relationship between methane treatment time and deposition thickness of carbon-containing barrier layer;

[0026] Figure 3 Variation chart of the relationship between ammonia plasma bombardment time and removal thickness of carbon-containing barrier layer;

[0027] Figure 4 Effect chart of directional removal of carbon-containing barrier layer on the sidewall after deposition of 12nm carbon-containing barrier layer and ammonia plasma bombardment;

[0028] Figure 5 Surface topography chart of carbon-containing barrier layer;

[0029] Figure 6 Variation chart of 3nm carbon-containing barrier layer under 50 PEALD cycle periods;

[0030] Figure 7 Variation chart of 10.21nm carbon-containing barrier layer under 180 PEALD cycle periods. DETAILED DESCRIPTION

[0031] The present application provides a method for depositing silicon nitride on the sidewall of a trench structure, comprising the following steps:

[0032] Depositing a carbon-containing barrier layer on the top, sidewall and bottom of the trench structure; the deposition is inductively coupled plasma enhanced chemical vapor deposition, and the carbon source is methane;

[0033] Directionally etching the sidewall of the trench structure by ammonia plasma bombardment to remove the carbon-containing barrier layer on the sidewall; the angle of the ammonia plasma bombardment is perpendicular to the bottom;

[0034] Using silicon precursor and nitrogen plasma as co-reactants, depositing silicon nitride on the sidewall surface from which the carbon-containing barrier layer has been removed by plasma enhanced atomic layer deposition.

[0035] In the present application, unless otherwise specified, the raw materials or instruments used are commercially available products well known to those skilled in the art.

[0036] The carbon-containing barrier layer is deposited on the top, sidewall and bottom of the trench structure. In the present application, the trench structure can be a trench structure of a semiconductor device, and the aspect ratio is 2:1-10:1.

[0037] In the present application, the deposition is inductively coupled plasma enhanced chemical vapor deposition, and the carbon source is methane. In the inductively coupled plasma enhanced chemical vapor deposition, the gas flow of methane is 5-10 sccm, and in specific embodiments, it can be 6.5 or 8 sccm; the carrier gas is argon, and the gas flow of argon is 200-300 sccm, and in specific embodiments, it can be 250 sccm; the plasma power is 20-40 W, and in specific embodiments, it can be 25 or 30 W; the deposition temperature is 200-300℃, and in specific embodiments, it can be 230 or 250℃; the pressure is 4-6 Pa, and in specific embodiments, it can be 5 Pa; the rate is 0.05-0.2 nm / s, and in specific embodiments, it can be 0.094 nm / s or 0.12 nm / s; and the time is 30-140 s, and in specific embodiments, it can be 60, 90, 110 or 130 s.

[0038] In the present application, methane (CH4) is used as the carbon source gas, and argon (Ar) is used as the auxiliary gas. In a low-pressure high-energy plasma environment, methane molecules generate active groups (such as ·CH3 and C2H2) through a dissociation process, and then undergo a polymerization reaction to deposit a carbon-containing barrier layer. The carbon-containing barrier layer has high compactness and strong chemical inertness, can effectively block the growth of subsequent silicon nitride, and especially forms a uniform carbon-containing barrier layer in the top region of the trench, thereby creating conditions for selective deposition in the sidewall region. Moreover, the present application uses a low-temperature (260℃) deposition method, which can adjust the thickness according to actual needs. The process is simple and controllable, and can achieve uniform deposition under low temperature and low pressure conditions, thereby breaking through the limitation of traditional methods that it is difficult to deposit a high-stability barrier layer on the surface of a complex trench structure.

[0039] In the present application, the thickness of the carbon-containing barrier layer is 3-50 nm, and in specific embodiments, it can be 5 nm, 10.2 nm, 12 nm, 20 nm or 35 nm.

[0040] After depositing the carbon-containing barrier layer, the present application uses ammonia plasma to bombard the sidewall of the trench structure for directional etching to remove the carbon-containing barrier layer on the sidewall. In the present application, the angle of the ammonia plasma bombardment is perpendicular to the bottom; the power of the ammonia plasma bombardment is 200-300 W, and the time is 10-30 s, and in specific embodiments, it can be 15, 20 or 25 s.

[0041] The ammonia plasma decomposes to generate hydrogen active groups (·H) and amino groups (·NH2) under high-energy conditions, which chemically react with and physically bombard the carbon-containing barrier layer, and due to the three-dimensional structure of the trench, the reaction of the ammonia plasma has directionality, and can achieve efficient removal in the sidewall area, while the carbon-containing barrier layer in the top and bottom areas is limitedly bombarded and remains intact.

[0042] After the carbon-containing barrier layer of the sidewall is removed, the active surface is exposed, and the present application uses a silicon precursor and a nitrogen plasma as co-reactants to deposit silicon nitride on the sidewall surface from which the carbon-containing barrier layer is removed by plasma-enhanced atomic layer deposition. Since the carbon-containing barrier layer in the top area is not removed, it blocks the adsorption and reaction of silicon precursor molecules, thereby inhibiting the deposition of the silicon nitride film; and ensures the high-selective deposition of the silicon nitride film.

[0043] In the present application, in the plasma-enhanced atomic layer deposition, the deposition temperature is 300-400℃, the carrier gas is argon, the argon gas flow rate is 200-300sccm; the nitrogen plasma flow rate is 100-200sccm; the plasma power is 300-500W; the silicon precursor temperature is 40-60℃; and the deposition cycle is 10-150.

[0044] In the present application, the plasma-enhanced atomic layer deposition is performed by alternately supplying a pulsed silicon precursor and plasma purging, and a single-layer nanoscale silicon nitride film is formed in each reaction cycle; the parameters of each deposition cycle include: silicon precursor pulse 0.1-1s, waiting 1-5s, purging 2-10s; nitrogen plasma and argon are introduced, the nitrogen plasma acts for 30s, and purging is performed for 13s, which is one deposition.

[0045] In the present application, the silicon precursor includes a silane precursor and / or a silylamine precursor; the silane precursor is one or more of bis(tert-butylamino)silane (BTBAS), hexachlorodisilane, trichlorosilane, and dichlorosilane; and the silylamine precursor is trimethylsilylamine.

[0046] In the present application, the deposition thickness of the silicon nitride is 1-20nm, and in specific embodiments, it can be 5nm or 8nm.

[0047] The method for selectively depositing silicon nitride on the sidewall of a trench structure provided by the present application can be applied to complex trench structures with a micron-to-nanoscale aspect ratio, and is particularly suitable for the filling of trench structures of semiconductor devices, the preparation of insulating isolation layers, and the preparation of device passivation layers.

[0048] In order to further illustrate the present application, the method for depositing silicon nitride on the sidewall of a trench structure provided by the present application is described in detail below in conjunction with the accompanying drawings and examples, but they should not be understood as limiting the scope of protection of the present application.

[0049] Example 1

[0050] According to the flow chart shown in the trench structure sidewall deposition of silicon nitride, the specific steps are as follows: Figure 1

[0051] The semiconductor structure piece (aspect ratio of 2:1) with trench structure was placed in the inductively coupled plasma enhanced chemical vapor deposition device, and the deposition parameters were as follows: deposition temperature 260℃, deposition rate 0.094nm / s, system pressure 6Pa, ICP power 30W, methane gas flow 5sccm, argon gas flow 300sccm. A layer of carbon-containing barrier layer was deposited on the whole surface of the trench (top, bottom and sidewall), and after the deposition was completed, the semiconductor structure piece was taken out for standby;

[0052] The above semiconductor structure piece was placed in the inductively coupled plasma enhanced atomic layer deposition (PEALD) device chamber, the chamber temperature was set to 400℃, the ammonia plasma bombardment direction was perpendicular to the trench structure, the ammonia plasma power was 300W, and the ammonia plasma bombardment was carried out to remove the carbon-containing barrier layer in the sidewall area of the trench;

[0053] After removing the sidewall barrier layer, BTBAS and nitrogen plasma were used as co-reactants, argon was used as carrier gas, the BTBAS source bottle temperature was set to 55℃, the plasma power was 300W, the chamber temperature was 400℃, and the silicon nitride was deposited according to the plasma power, BTBAS flow and cycle number described in Table 1; the parameters of each deposition cycle were as follows: BTBAS pulse 0.15s, waiting 4s, purging 2s, nitrogen (flow rate 100sccm) and argon (flow rate 300sccm) were introduced, nitrogen plasma was applied for 30s, and purging was carried out for 13s.

[0054] Table 1 Thickness control parameters and experimental results of selective deposition of silicon nitride on sidewall

[0055]

[0056] As can be seen from the results in Table 1, with the increase of deposition cycle number, the deposition thickness of the sidewall region increases stably, showing a good linear trend; under the condition of keeping other parameters unchanged, the increase of BTBAS flow can slightly increase the film formation rate of silicon nitride, but at the same time, the risk of non-target deposition in the top region also needs to be controlled; the increase of plasma power can increase the reactivity, but too high may cause slight deposition or surface damage in the upper region

[0057] Figure 2 is the relationship between the methane treatment time and the deposition thickness of the carbon-containing barrier layer; from Figure 2 ​The results show that in the inductively coupled plasma enhanced chemical vapor deposition, the methane treatment time and the deposition thickness of the carbon-containing barrier layer have a monotonic growth trend, the deposition rate is 0.094 nm / s, the thickness of the barrier layer can be accurately controlled, and the thickness control precision is within ±1.5 nm.

[0058] Figure 3 Figure 1 is a graph showing the relationship between ammonia plasma bombardment time and carbon-containing barrier layer removal thickness; Figure 3 The results show that the ammonia plasma bombardment time and the barrier layer removal thickness have an approximate linear relationship, which proves that the present application can realize accurate sidewall thickness control and directional selective removal of the carbon-containing barrier layer.

[0059] According to the above inductively coupled plasma enhanced chemical vapor deposition parameters, the carbon-containing barrier layer is deposited, the deposition time is 130 s, the thickness of the carbon-containing barrier layer is 12 nm, and the carbon-containing barrier layer is removed by ammonia plasma bombardment;

[0060] Figure 4 Figure 4 is an effect diagram after the 12 nm carbon-containing barrier layer is deposited and the sidewall barrier layer is directionally removed after ammonia plasma bombardment; as shown in Figure 4 After directional removal by ammonia plasma, only the barrier layer in the sidewall region is removed, the barrier layer at the top and bottom is still retained, and a selectively exposed surface is formed, which provides a good window for subsequent silicon nitride deposition.

[0061] Figure 5 Figure 5 is a surface topography diagram of the carbon-containing barrier layer, which shows that Figure 5 The carbon-containing barrier layer has high compactness. Figure 4 It can be known that the deposited carbon-containing barrier layer has strong chemical inertness and lacks active sites for silicon precursor adsorption, which can effectively block the growth of the subsequent silicon nitride film, especially forming a uniform barrier layer in the trench top region, thereby creating conditions for selective deposition in the sidewall region.

[0062] Test example

[0063] According to the above inductively coupled plasma enhanced chemical vapor deposition parameters, the carbon-containing barrier layer is deposited, the deposition time is 30 s, and the thickness of the carbon-containing barrier layer is 3 nm.

[0064] Figure 6 Figure 6 is a transformation diagram of the 3 nm carbon-containing barrier layer under 50 PEALD cycle periods, wherein WCA is the water droplet contact angle, None is the previous value without deposition of the carbon-containing barrier layer, and CH4 treat is the step of depositing the carbon-containing barrier layer in PEVCD. Figure 6As shown in the figure, after the deposition of the carbon-containing barrier layer on the silicon nitride substrate by methane treatment (i.e. CH4 treat step), the thickness of the substrate is increased by 3 nm, and the increased thickness is the thickness of the barrier layer. Then, the silicon nitride deposition is carried out in the PEALD system. During the silicon nitride deposition cycle, the barrier layer is etched under the plasma action while the growth of the silicon nitride on the surface of the barrier layer is inhibited, which proves that the deposition of the 3 nm carbon-containing barrier layer can effectively inhibit the growth of the silicon nitride under 50 PEALD cycle periods, thereby realizing the selective deposition control of the non-target area.

[0065] Figure 7 The transformation graph of the 10.21 nm carbon-containing barrier layer under 180 PEALD cycle periods is shown in the figure. Figure 7 As shown in the figure, after the deposition of the 10.21 nm carbon barrier layer on the silicon nitride substrate by methane treatment, the silicon nitride film deposition is carried out in the PEALD system, which can effectively inhibit 150 PEALD deposition cycle periods.

[0066] Although the above embodiment has made a detailed description of the present application, it is only a part of the embodiments of the present application, but not all the embodiments. Other embodiments can be obtained according to the present embodiment without creativity, which all belong to the protection scope of the present application.

Claims

1. A method for depositing silicon nitride on the sidewall of a trench structure, characterized in that: The following steps are involved: depositing a carbon-containing barrier layer on the top, sidewalls, and bottom of the trench structure; The deposition is inductively coupled plasma enhanced chemical vapor deposition, and the carbon source is methane; bombarding the sidewalls of the trench structure with ammonia plasma to perform directional etching to remove the carbon-containing barrier layer on the sidewalls; The angle of the ammonia plasma bombardment is perpendicular to the bottom; Silicon nitride is deposited on the sidewall surface from which the carbon-containing barrier layer is removed by plasma-enhanced atomic layer deposition using a silicon precursor and nitrogen plasma as co-reactants.

2. The method according to claim 1, characterized in that In the inductively coupled plasma enhanced chemical vapor deposition, the gas flow rate of methane is 5 to 10 sccm; the carrier gas is argon, and the gas flow rate of argon is 200 to 300 sccm; the plasma power is 20 to 40 W; the deposition temperature is 200 to 300° C., the pressure is 4 to 6 Pa, the rate is 0.05 to 0.15 nm / s, and the time is 30 to 140 s.

3. The method according to claim 1 or 2, characterized in that The thickness of the carbon-containing barrier layer is 3-50 nm.

4. The method according to claim 1, wherein The power of the ammonia plasma bombardment is 200-300W.

5. The method according to claim 1, wherein In the plasma-enhanced atomic layer deposition, the deposition temperature is 300-400° C., the carrier gas is argon, the gas flow rate of argon is 200-300 sccm; the nitrogen flow rate is 100-200 sccm; the plasma power is 300-500 W; the silicon precursor temperature is 40-60° C.; and the deposition cycle is 10-150.

6. The method according to claim 1, characterized in that The silicon precursor includes a silane precursor and / or a silanamine precursor.

7. The method according to claim 1, characterized in that The deposition thickness of the silicon nitride is 1 to 20 nm.

8. The method according to claim 1, characterized in that The ammonia plasma bombardment and the deposition of silicon nitride are both performed in a plasma enhanced atomic layer deposition reaction chamber; the ammonia plasma bombardment and the deposition of silicon nitride are performed sequentially or automatically and continuously without having to be taken out of the reaction chamber again.

9. The method according to claim 1, characterized in that The aspect ratio of the trench structure is 2:1 to 10:1.

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