Method for improving first wafer effect in film deposition process
1. A method for improving the first wafer effect in a film deposition process is characterized by comprising the following steps:
providing a reaction chamber;
forming a first film layer covering the inner wall of the reaction chamber, wherein the first film layer stores heat so as to maintain a stable thermal environment in the reaction chamber;
placing a wafer into the reaction chamber;
and forming a second film layer on the surface of the wafer.
2. The method of claim 1, wherein the step of forming the first layer covering the inner wall of the reaction chamber comprises:
and transmitting a first reaction gas and a second reaction gas to the reaction chamber, wherein the first reaction gas and the second reaction gas react to generate a first film layer covering the inner wall of the reaction chamber.
3. The method of claim 2, wherein the material of the first film layer comprises TiN.
4. The method as claimed in claim 2, wherein the first reactive gas is TiCl4The second reaction gas is NH3。
5. The method of claim 4, wherein a flow ratio of the first reactive gas to the second reactive gas is 1:50 to 1: 150.
6. The method of claim 4, wherein a time ratio of the first reactive gas to the second reactive gas is 1:0.6 to 1: 2.
7. The method as claimed in claim 5, wherein the first reactive gas has a flow rate of 0-100 sccm, and the second reactive gas has a flow rate of 1000-4000 sccm.
8. The method of claim 2, wherein before delivering the first reactive gas and the second reactive gas to the reaction chamber, the method further comprises: delivering a precursor gas to the reaction chamber;
the precursor gas is plasmatized.
9. The method as claimed in claim 8, wherein the precursor gas is H2、He、Ar、N2、O2One or a combination of two or more of them.
10. The method as claimed in claim 8, wherein the precursor gas has a flow rate of 1000sccm to 6000 sccm.
11. The method of claim 8, wherein the RF power in the reaction chamber is 450W-1500W.
12. The method of claim 1, wherein the step of forming the first layer covering the inner wall of the reaction chamber further comprises:
controlling the temperature in the reaction chamber to be 300-700 ℃.
13. The method of claim 2, wherein the first and second layers are made of the same material.
14. The method of claim 13, wherein the step of forming a second film on the wafer surface comprises:
and continuously transmitting the first reaction gas and the second reaction gas to the reaction chamber, wherein the first reaction gas and the second reaction gas react to generate a second film layer covering the surface of the wafer.
15. The method of claim 1, wherein the first layer uniformly covers the entire inner wall of the reaction chamber.
Background
Chemical Vapor Deposition (CVD) is one of the major processes used to form thin film structures during semiconductor processing. However, in the using process of the chemical vapor deposition apparatus, the chamber environment of the chemical vapor deposition apparatus changes due to the influence of different stages, such as process conversion, idle process, and end of maintenance, and the thin film process is also influenced by the first-wafer effect. The first-wafer effect means that, in a batch of wafers to be formed with a thin-film structure, the thickness of the thin film formed on the first wafers is greatly different from a preset thickness, and generally, the thickness of the thin film deposited on the first wafer is relatively thin, and then the thickness of the thin films formed on the plurality of wafers gradually increases until the preset thickness is reached. The existence of the first-wafer effect causes great abnormal fluctuation of the manufacturing process, and the phenomenon is particularly obvious in the actual low-temperature chemical vapor deposition process.
The current main way to deal with the first wafer effect is to use a barrier control wafer, namely, the barrier control wafer is used for warming before the product deposits a film. However, the cost of the control wafer is high, and the warm-up time is long, so that the yield of the machine is reduced.
Therefore, how to effectively reduce the first-chip effect, and avoid the large influence on the yield of the apparatus, and improve the yield of the semiconductor product is a technical problem to be solved.
Disclosure of Invention
The invention provides a method for improving the first wafer effect in a film deposition process, which is used for solving the problem that the first wafer effect is easy to occur in the chemical vapor deposition process in the prior art so as to improve the yield of semiconductor products and the capacity of a machine.
In order to solve the above problems, the present invention provides a method for improving the first-wafer effect in a film deposition process, comprising the following steps:
providing a reaction chamber;
forming a first film layer covering the inner wall of the reaction chamber, wherein the first film layer stores heat so as to maintain a stable thermal environment in the reaction chamber;
placing a wafer into the reaction chamber;
and forming a second film layer on the surface of the wafer.
Optionally, the specific step of forming the first film layer covering the inner wall of the reaction chamber includes:
and transmitting a first reaction gas and a second reaction gas to the reaction chamber, wherein the first reaction gas and the second reaction gas react to generate a first film layer covering the inner wall of the reaction chamber.
Optionally, the material of the first film layer includes TiN.
Optionally, the first reaction gas is TiCl4The second reaction gas is NH3。
Optionally, the flow ratio of the first reaction gas to the second reaction gas is 1: 50-1: 150.
Optionally, the ratio of the introduction time of the first reaction gas to the introduction time of the second reaction gas is 1: 0.6-1: 2.
Optionally, the flow rate of the first reaction gas is 0 to 100sccm, and the flow rate of the second reaction gas is 1000 to 4000 sccm.
Optionally, before the first reactive gas and the second reactive gas are transferred to the reaction chamber, the method further includes the following steps:
delivering a precursor gas to the reaction chamber;
the precursor gas is plasmatized.
Optionally, the precursor gas is H2、He、Ar、N2、O2One or a combination of two or more of them.
Optionally, the flow rate of the precursor gas is 1000sccm to 6000 sccm.
Optionally, the radio frequency power in the reaction chamber is 450W-1500W.
Optionally, the step of forming the first film layer covering the inner wall of the reaction chamber further includes:
controlling the temperature in the reaction chamber to be 300-700 ℃.
Optionally, the first film layer and the second film layer are made of the same material.
Optionally, the specific step of forming the second film layer on the surface of the wafer includes:
and continuously transmitting the first reaction gas and the second reaction gas to the reaction chamber, wherein the first reaction gas and the second reaction gas react to generate a second film layer covering the surface of the wafer.
Optionally, the first film layer uniformly covers the entire inner wall of the reaction chamber.
According to the method for improving the first film effect in the film deposition process, the first film layer covering the reaction chamber is formed in the pre-processing stage before the wafer is placed, the first film layer has the heat storage capacity, and the stable thermal environment in the reaction chamber is recovered and maintained by utilizing the first film layer, so that the influence of the first film effect is reduced or improved to the maximum extent, the yield of semiconductor products is improved, and the capacity of a machine is improved.
Drawings
FIG. 1 is a flow chart of a method for improving the first-wafer effect in a film deposition process according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a reaction chamber according to an embodiment of the present invention;
FIGS. 3A-3B are TiCl in accordance with embodiments of the invention4A schematic of the effect of flow on the first effect;
FIGS. 4A-4B are schematic diagrams illustrating the effect of nitridation on the first-wafer effect in accordance with embodiments of the present invention;
FIGS. 5A-5B are schematic diagrams illustrating the effect of RF power on the first-slice effect in accordance with embodiments of the present invention;
fig. 6A-6B are schematic illustrations of the effect of plasma flow on the bow wave effect in an embodiment of the present invention.
Detailed Description
The following describes in detail a specific embodiment of the method for improving the first-wafer effect in the film deposition process according to the present invention with reference to the accompanying drawings.
The present embodiment provides a method for improving the first-wafer effect in a film deposition process, fig. 1 is a flowchart of the method for improving the first-wafer effect in the film deposition process according to the present embodiment, and fig. 2 is a schematic structural diagram of a reaction chamber according to the present embodiment. As shown in fig. 1 and fig. 2, the method for improving the first-wafer effect in the film deposition process according to the present embodiment includes the following steps:
step S11, providing the reaction chamber 20, as shown in fig. 2.
Specifically, the reaction chamber 20 is used for accommodating a wafer to perform a film deposition process on the surface of the wafer. The reaction chamber 20 in the present embodiment may be a reaction chamber of a chemical vapor deposition process, a reaction chamber of a physical vapor deposition process, or a reaction chamber of an atomic layer deposition process, and those skilled in the art can select the reaction chamber according to actual process requirements. The present embodiment is described by taking the reaction chamber 20 as a reaction chamber of a chemical vapor deposition apparatus as an example. The reaction chamber 20 has a susceptor 22 for supporting a wafer therein, and the susceptor 22 has a heater 23 therein for heating the reaction chamber 20 and/or the wafer. The top of the reaction chamber 20 is provided with a shower head 24. The shower head 24 is used for uniformly transmitting the dispersed gas or plasma to the interior of the reaction chamber 20.
Step S12, forming a first film 21 covering the inner wall of the reaction chamber 20, where the first film 21 stores heat to maintain a stable thermal environment in the reaction chamber 20, as shown in fig. 2.
Step S13, placing a wafer in the reaction chamber 20
Step S14, a second film layer is formed on the surface of the wafer.
In the present embodiment, the first film 21 is formed on the inner wall of the reaction chamber 20 during the pre-process, and the heat stored in the first film 21 is utilized to maintain a stable thermal environment in the reaction chamber 20, so as to reduce or even avoid the influence of the reaction chamber 20 on the environment in the reaction chamber 20 due to the switching of different stages (e.g., process conversion, idle process, machine maintenance), and ensure that the thickness of the second film formed on the surface of the wafer placed in the reaction chamber 20 after the pre-process is finished is closer to the preset thickness, thereby reducing the influence of the first-wafer effect. The pre-process in the present embodiment refers to a process of treating the reaction chamber 20 before the wafer is placed in the reaction chamber 20. The preset thickness is the thickness of a film layer which is theoretically formed on the surface of the wafer in advance. The specific material of the first film 21 and the specific amount of heat stored in the first film 21 can be selected by those skilled in the art according to the actual process requirement, for example, according to the material, thickness, etc. of the second film to be formed on the wafer surface.
Optionally, the specific steps of forming the first film 21 covering the inner wall of the reaction chamber 20 include:
and transmitting a first reaction gas and a second reaction gas to the reaction chamber 20, wherein the first reaction gas and the second reaction gas react to generate a first film layer 21 covering the inner wall of the reaction chamber 20.
Specifically, at the pre-processing stage, the first reactive gas and the second reactive gas are introduced into the reaction chamber 20, and the first reactive gas and the second reactive gas chemically react inside the reaction chamber 20 to generate the first film 21 covering the inner wall of the reaction chamber 20. The thickness of the first film layer 21 can be controlled by adjusting the time, flow rate, and reaction temperature of the first reactive gas and the second reactive gas.
Optionally, the material of the first film layer 21 includes TiN.
Optionally, the first reaction gas is TiCl4The second reaction gas is NH3。
Optionally, the flow ratio of the first reaction gas to the second reaction gas is 1: 50-1: 150.
Hereinafter, the first reaction gas is TiCl4The second reaction gas is NH3And the preset thickness of the second film layer generated on the surface of the wafer is 1 μm. FIGS. 3A-3B are TiCl in accordance with embodiments of the invention4Schematic of the effect of flow on first-order effect. The abscissa in fig. 3A and 3B represents the number of different wafers (the wafers are sequentially placed into the reaction chamber 20 according to the number during the process), and the ordinate represents the thickness (in nm) of the second film formed on the surface of the wafer, and NH is used in fig. 3A and 3B3The flow of TiCl is kept constant4The flow rates of the TiCl gas introduced during the pre-processing are respectively 12sccm, 20sccm and 30sccm4The effect of the flux on the first effect. As can be seen from FIGS. 3A and 3B, the TiCl introduced in advance is followed4The thickness of the second film layer generated on the surfaces of the front wafers in a batch of wafers in the process is closer to the preset thickness, namely the first effect is along with TiCl introduced in the process of the previous process4Is increased and is decreased. This is because of the TiCl introduced during the preceding process4The thickness of the first film layer 21 deposited on the inner wall of the reaction chamber 20 is gradually increased, and the heat storage capacity of the first film layer 21 is correspondingly increased, so that the stability of the thermal environment inside the reaction chamber 20 can be more effectively maintained.
Optionally, the ratio of the introduction time of the first reaction gas to the introduction time of the second reaction gas is 1: 0.6-1: 2.
Optionally, the flow rate of the first reaction gas is 0 to 100sccm, and the flow rate of the second reaction gas is 1000 to 4000 sccm.
Hereinafter, the first reaction gas is TiCl4The second reaction gas is NH3And the preset thickness of the second film layer generated on the surface of the wafer is 1 μm. FIGS. 4A-4B are schematic diagrams illustrating the effect of nitridation on the first-wafer effect in accordance with embodiments of the present invention. The nitridation rate in this embodiment refers to the NH transferred to the interior of the reaction chamber 20 during the pre-process stage3On TiCl4And NH3The mixed gas of (2) is used as a gas mixture. The abscissa in fig. 4A and 4B represents the number of different wafers (the wafers are sequentially placed to the reverse side according to the number during the process)In the chamber 20), the ordinate represents the thickness (in nm) of the second film formed on the wafer surface, and the influence of the nitridation ratio on the first wafer effect in the pre-process is illustrated in fig. 4A and 4B by using nitridation ratios of 1:1, 1:1.2, and 1:1.4 as examples respectively. As can be seen from fig. 4A and 4B, as the nitridation ratio increases during the pre-process, the thickness of the second film formed on the surfaces of the first wafers in the batch of wafers during the process is closer to the predetermined thickness, i.e., the first-wafer effect decreases as the nitridation ratio increases during the pre-process. This is because the relative heat transfer coefficient of metal Ti is larger than that of TiN, and therefore, the heat storage capacity of metal Ti is poor, and heat is more easily lost in metal Ti. Increasing the nitridation ratio in the predetermined process is helpful to increase the TiN content in the product (i.e. the first film 21), so as to increase the heat storage capacity of the first film 21 and further maintain the stability of the thermal environment inside the reaction chamber 21. The nitriding ratio in the pre-process can be realized by adjusting the time ratio of introducing the first gas and the second gas and/or the flow ratio of introducing the first gas and the second gas.
Optionally, the rf power in the reaction chamber 20 is 450W-1500W.
Hereinafter, the first reaction gas is TiCl4The second reaction gas is NH3And the preset thickness of the second film layer generated on the surface of the wafer is 1nm for the example. Fig. 5A-5B are schematic diagrams illustrating the effect of rf power on the first-chip effect in accordance with embodiments of the present invention. The abscissa in fig. 5A and 5B represents the number of different wafers (the wafers are sequentially placed into the reaction chamber 20 according to the number during the process), and the ordinate represents the thickness (unit is nm) of the second film formed on the surface of the wafer, and the influence of the rf power on the first wafer effect during the pre-process is illustrated in fig. 5A and 5B by taking the rf power as 450W, 800W, and 1200W, respectively. As can be seen from fig. 5A and 5B, as the rf power increases during the pre-process, the thickness of the second film formed on the surfaces of the first wafers of the batch of wafers during the process approaches the predetermined thickness, i.e. the first effect follows the first wafer effectThe rf power is increased and decreased during the pre-process. This is because, as the rf power delivered into the reaction chamber 20 increases, NH is generated3NH generated by plasmaxThe more the active groups (x is 1 or 2), the more the nitridation of the metal Ti can be promoted, the more TiN is generated, thereby improving the heat storage capability of the first film layer 21 and the film thickness uniformity of the first film layer 21, and further maintaining the stability of the thermal environment inside the reaction chamber 21.
Optionally, before the first reactive gas and the second reactive gas are transferred to the reaction chamber, the method further includes the following steps:
delivering a precursor gas to the reaction chamber;
the precursor gas is plasmatized.
Optionally, the precursor gas is H2、He、Ar、N2、O2One or a combination of two or more of them.
Optionally, the flow rate of the precursor gas is 1000sccm to 6000 sccm.
Hereinafter, the first reaction gas is TiCl4The second reaction gas is NH3And the preset thickness of the second film layer generated on the surface of the wafer is 1nm for the example. Fig. 6A-6B are schematic illustrations of the effect of plasma flow on the bow wave effect in an embodiment of the present invention. The abscissa in fig. 6A and fig. 6B respectively represents the numbers of different wafers (the wafers are sequentially placed into the reaction chamber 20 according to the numbers during the process), and the ordinate represents the thickness (unit is nm) of the second film layer formed on the surface of the wafer, and the influence of the precursor gas flow rate on the first wafer effect during the pre-process is illustrated in fig. 6A and fig. 6B by taking the precursor gas flow rate as 1500sccm, 3000sccm, or 4500sccm as examples. As can be seen from fig. 6A and 6B, as the precursor gas flow rate increases during the pre-process, the thickness of the second film layer formed on the surfaces of the first wafers in the batch of wafers during the process is closer to the predetermined thickness, i.e., the first effect decreases as the precursor gas flow rate increases during the pre-process. This is because the precursor gas is at radio frequency powerGenerating a precursor plasma, the precursor plasma and NH3Reaction to form NHx(x is 1 or 2) a reactive group. Higher precursor gas flow rate can generate more precursor plasma, thereby promoting more NHxAnd (4) generation of active groups. More NHxThe generation of the active group can promote the nitridation of more metal Ti, and the number of generated TiN is correspondingly increased, so that the heat storage capacity of the first film layer 21 and the film thickness uniformity of the first film layer 21 are improved, and the stability of the thermal environment inside the reaction chamber 21 is further maintained.
In order to ensure the generation and stable coverage of the first film 21 on the inner wall of the reaction chamber 20 and ensure that the heat stored in the first film 21 contributes to further improving the first film effect, optionally, the step of forming the first film covering the inner wall of the reaction chamber 20 further comprises:
the temperature in the reaction chamber 20 is controlled to be 300-700 ℃.
Optionally, the material of the first film layer 21 and the second film layer is the same.
Optionally, the specific step of forming the second film layer on the surface of the wafer includes:
and continuously transmitting the first reaction gas and the second reaction gas to the reaction chamber 20, wherein the first reaction gas and the second reaction gas react to generate a second film layer covering the surface of the wafer.
Specifically, the first reactive gas and the second reactive gas are continuously delivered to the interior of the reaction chamber 20 at the beginning of the pre-process stage until the second film is formed on the surface of one or more batches of wafers.
Optionally, the first film 21 uniformly covers the entire inner wall of the reaction chamber 20.
Specifically, parameter conditions such as the flow rates of the first reactive gas and the second reactive gas introduced in the pre-processing, the introduction time of the first reactive gas and the second reactive gas, and the reaction temperature may be controlled, so that the first film layer 21 is uniformly covered on the entire inner wall of the reaction chamber 20, thereby ensuring the uniformity of the thermal environment inside the entire reaction chamber 20, and further improving the thickness uniformity of the second film layer generated on the surface of the wafer.
In the method for improving the first film effect in the film deposition process provided by the embodiment, the first film layer covering the reaction chamber is formed in the pre-processing stage before the wafer is placed, the first film layer has the heat storage capacity, and the stable thermal environment in the reaction chamber is recovered and maintained by using the first film layer, so that the influence of the first film effect is reduced or improved to the maximum extent, the yield of semiconductor products is improved, and the capacity of a machine is improved.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
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