Sputtering method

Abstract

The present invention provides a sputtering method, comprising the following steps: S1, introducing process gas into a reaction chamber; S2, turning on a sputtering power supply, and adjusting the output power of the sputtering power supply loaded on a target material to a first sputtering power value to start plasma formation; S3, increasing the output power to a second sputtering power value according to a first preset rule to deposit a thin film on a substrate; S4, gradually reducing the output power to zero according to a second preset rule; S5, judging whether the thickness of the thin film reaches the target thickness, if so, proceeding to step S6; if not, returning to step S2; S6, turning off the sputtering power supply, and stopping the introduction of process gas into the reaction chamber; wherein, step S4 is performed first, and then step S5; or, step S5 is performed first, and then step S4. The sputtering method provided by the present invention can avoid the generation of micro-sparking and particle contamination, thereby ensuring the performance of the thin film and improving the electrical performance and yield of the device.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a sputtering method. Background Art

[0002] As a multifunctional material, TiN film has been widely used in barrier layer, bonding layer and metal hard mask in integrated circuit manufacturing. TiN film prepared by traditional DC magnetron sputtering technology has become one of the most commonly used physical vapor deposition (PVD) methods in integrated circuit metallization process because of its advantages of high deposition rate, good film uniformity, less pollution and high production capacity. As the material of metal hard mask in Cu interconnection process, the industry has strict requirements on thickness uniformity, resistance uniformity, stress and particle control of TiN film prepared by PVD method.

[0003] The PVD chamber commonly used to prepare TIN thin films is used for magnetron sputtering. The existing sputtering process includes the following steps:

[0004] 1. Introduce process gas into the reaction chamber;

[0005] 2. Turn on the DC power supply and load a small DC power onto the target to start the plasma formation;

[0006] 3. Increase the DC power to deposit a TIN film on the substrate. The thickness of the film is controlled according to the deposition time to meet the process requirements.

[0007] 4. Turn off the DC power supply and stop supplying process gas to the reaction chamber.

[0008] However, the above sputtering process inevitably has the following problems in practical applications, namely: since the DC power supply is turned off when the above step 3 transitions to step 4, that is, the DC power suddenly drops to 0, resulting in unstable plasma in the extinguishing process, and there is a high probability that tiny sparks (Marco-Arcing) will occur, resulting in tiny particles (generally less than 40-50nm) that fall onto the substrate surface, directly leading to a decrease in film performance and affecting the electrical performance and yield of the device. Summary of the invention

[0009] The present invention aims to solve at least one of the technical problems existing in the prior art and proposes a sputtering method for avoiding the generation of micro-sparking and particle pollution, thereby ensuring the performance of the thin film and improving the electrical performance and yield of the device.

[0010] To achieve the above object, the present invention provides a sputtering method, comprising the following steps:

[0011] S1, introducing process gas into the reaction chamber;

[0012] S2, turning on a sputtering power source, and adjusting the output power of the sputtering power source loaded on the target material to a first sputtering power value, so as to initiate plasma formation;

[0013] S3, increasing the output power to a second sputtering power value according to a first preset rule to deposit a thin film on the substrate;

[0014] S4, gradually reducing the output power to zero according to a second preset rule;

[0015] S5, determining whether the thickness of the film reaches the target thickness, if so, proceeding to step S6; if not, returning to step S2;

[0016] S6, turning off the sputtering power supply and stopping the introduction of the process gas into the reaction chamber;

[0017] Wherein, the step S4 is performed first and then the step S5; or, the step S5 is performed first and then the step S4.

[0018] Optionally, in step S4, the second preset rule includes: performing a power reduction process once at a specified time interval until the output power is zero; the power reduction process includes: reducing the current output power by a preset adjustment amount.

[0019] Optionally, the preset adjustment amount adopted in each power reduction process is the same.

[0020] Optionally, the specified time ranges from 0.1 to 0.3 s.

[0021] Optionally, in step S4, the second preset rule includes: gradually reducing the output power to zero according to a preset linear function of time and sputtering power value.

[0022] Optionally, in step S2, the sputtering power supply is turned on, and the output power is directly adjusted to the first sputtering power value; or, step S2 includes the following sub-steps:

[0023] S21, turning on the sputtering power supply, and adjusting the output power to a third sputtering power value; the third sputtering power value is less than the first sputtering power value;

[0024] S22, after a preset time, increasing the output power from the third sputtering power to the first sputtering power value to initiate plasma formation.

[0025] Optionally, the third sputtering power value is half of the first sputtering power value.

[0026] Optionally, the first preset rule includes: directly adjusting the output power from the first sputtering power value to the second sputtering power value; or, the first preset rule includes:

[0027] Increasing the output power from the first sputtering power to a fourth sputtering power value; the fourth sputtering power value is less than the second sputtering power value;

[0028] After a preset time, the output power is increased from the fourth sputtering power to the second sputtering power value.

[0029] Optionally, the value range of the fourth sputtering power value satisfies the following formula:

[0030] M = (Nn) / 2-(N+n) / 2;

[0031] Wherein, M is the fourth sputtering power value; N is the second sputtering power value; and n is the first sputtering power value.

[0032] Optionally, the fourth sputtering power value ranges from 3.5 to 5.5 KW; the first sputtering power value ranges from 0.5 to 2 KW; and the second sputtering power value ranges from 4 to 12 KW.

[0033] Beneficial effects of the present invention:

[0034] The sputtering method provided by the present invention can avoid tiny sparks caused by a sudden drop in power and avoid particle contamination by adding a step of gradually reducing the sputtering power to zero (step S4) before shutting down the sputtering power supply (step S6), thereby ensuring the performance of the thin film and improving the electrical performance and yield of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A flowchart of a sputtering method provided by an embodiment of the present invention;

[0036] Figure 2 This is a flowchart of step S2 adopted in the embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the technical solution of the present invention, the sputtering method provided by the present invention is described in detail below with reference to the accompanying drawings.

[0038] See also Figure 1 , the sputtering method provided by the embodiment of the present invention comprises:

[0039] Step S1, introducing process gas into a reaction chamber.

[0040] Before step S1, first, the susceptor is moved to the process position. The vertical distance between the process position and the target material can be selected according to the requirements of the thickness uniformity of the specific process. For the deposition of titanium nitride film or other metal nitride film, the vertical distance can be controlled at 50-64 mm, preferably 54-60 mm. Then, the reaction chamber is evacuated to reach a high vacuum state (usually the chamber pressure is controlled at 5*10 -7 Torr or less); then, the substrate is introduced into the reaction chamber and placed on a susceptor (the temperature of the susceptor is controlled at 40-60° C.); thereafter, step S1 is performed.

[0041] Optionally, the process gas includes nitrogen and argon, wherein the flow rate of argon is in the range of 0-200 sccm, preferably 25-60 sccm, and the flow rate of nitrogen is in the range of 0-200 sccm, preferably 80-120 sccm.

[0042] During step S1, the chamber pressure is maintained at a specified pressure value, which is in the range of 4-20 mTorr.

[0043] Step S2, turning on the sputtering power supply, and adjusting the output power of the sputtering power supply loaded on the target to a first sputtering power value to initiate plasma formation.

[0044] Optionally, the sputtering power supply is a DC power supply, which is used to load DC power to the target material to form a negative bias voltage on the target material, and the negative bias voltage can enable plasma to bombard the target material.

[0045] In step S2, the first sputtering power value is set to meet the conditions for starting the plasma. Optionally, the first sputtering power value is in the range of 0.5-2KW, preferably 0.5-1KW.

[0046] Optionally, the flow ratio of nitrogen to argon is in the range of 0.3-0.8. Within this flow ratio range, it is beneficial to control the film stress.

[0047] For step S2, in practical applications, two methods can be used to adjust the output power to the first sputtering power value. Specifically, the first method is to turn on the sputtering power supply and directly adjust the output power to the first sputtering power value. The second method is as follows: Figure 2 As shown, step S2 includes:

[0048] Sub-step S21, turning on the sputtering power supply, and adjusting the output power to a third sputtering power value; the third sputtering power value is less than the first sputtering power value;

[0049] Sub-step S22, after a preset time, increasing the output power from the third sputtering power to the first sputtering power value to initiate plasma formation.

[0050] For the second method, the output power is not directly increased to the first sputtering power value, but first adjusted to a smaller third sputtering power value, and then increased from the third sputtering power value to the first sputtering power value. In this way, the ignition process can be made more stable, and a buffer layer can be deposited on the substrate to improve the bonding strength between the film and the substrate, thereby effectively controlling the growth crystal direction of the film.

[0051] Optionally, the third sputtering power value is half of the first sputtering power value. In practical applications, the ratio of the third sputtering power value to the first sputtering power value should not be too high, otherwise it is not conducive to the control of film stress, and it is easy to cause the film to grow too fast, reducing the bonding force between the film and the substrate. Therefore, by making the third sputtering power value half of the first sputtering power value, the bonding force between the film and the substrate can be improved, so that the growth crystal direction of the film can be effectively controlled. Specifically, the value range of the third sputtering power value is 0.5-1KW.

[0052] In practical applications, for the deposition of titanium nitride film or other metal nitride film, the deposition rate of step S2 can be controlled at The film thickness is controlled at

[0053] Step S3, increasing the output power to a second sputtering power value according to a first preset rule to deposit a thin film on the substrate.

[0054] The process of step S3 after the output power reaches the second sputtering power value is the main process of depositing the thin film, and the second sputtering power value meets the conditions for depositing a thin film that meets the performance and thickness requirements. Optionally, the second sputtering power value is in the range of 4-12KW, preferably 6-10KW. Within this range, the internal stress and resistance value of the thin film can be effectively reduced, and the thin film deposition rate can be increased.

[0055] In addition, for the deposition of titanium nitride film or other metal nitride film, the deposition rate of the above main process can be controlled at The film thickness is controlled at

[0056] In step S3, the first preset rule can increase the output power from the first sputtering power value to the second sputtering power value in two ways. The first way is to directly adjust the output power from the first sputtering power value to the second sputtering power value. The second way includes the following sub-steps:

[0057] Increasing the output power from the first sputtering power value to a fourth sputtering power value; the fourth sputtering power value is less than the second sputtering power value;

[0058] After a preset time, the output power is increased from the fourth sputtering power value to the second sputtering power value.

[0059] For the second method, the output power is not directly increased to the second sputtering power value, but first adjusted to a smaller fourth sputtering power value, and then increased from the fourth sputtering power value to the second sputtering power value. In this way, the stability of plasma changes can be controlled, and the tiny sparking phenomenon that may exist due to sudden changes in plasma volume can be avoided, and particle pollution can be avoided.

[0060] The process of increasing the first sputtering power value to the second sputtering power value has no significant contribution to the thickness of the thin film deposition, and the process time of the process can be controlled within 0.1-0.3s.

[0061] Optionally, the value range of the fourth sputtering power value satisfies the following formula:

[0062] M = (Nn) / 2-(N+n) / 2;

[0063] Wherein, M is the fourth sputtering power value; N is the second sputtering power value; and n is the first sputtering power value.

[0064] By changing the fourth sputtering power value, the stability of plasma changes can be effectively controlled, and the tiny sparking phenomenon that may exist due to the sudden change of the plasma amount can be avoided, and particle pollution can be avoided. Specifically, the fourth sputtering power value is in the range of 3.5-5.5KW.

[0065] Step S4, gradually reducing the output power to zero according to a second preset rule;

[0066] With the aid of step S4, tiny sparks caused by a sudden drop in power can be avoided, and particle pollution can be avoided, thereby ensuring the performance of the film and improving the electrical performance and yield of the device.

[0067] Optionally, the second preset rule includes: performing a power reduction process once at a specified interval until the output power is zero; the power reduction process includes: reducing the current output power by a preset adjustment amount. The second preset rule is similar to gradually reducing the output power to zero according to a step function of time and sputtering power value. In this way, the occurrence of micro-sparking can be effectively avoided.

[0068] Optionally, the preset adjustment amount used in each power reduction process is the same. The preset adjustment amount is, for example, 1KW. In this way, the output power can be evenly reduced, making the plasma extinguishing process more stable.

[0069] Step S4 has no significant contribution to the thickness of the thin film deposition, and the process time of step S4 can be controlled within 0.1-0.3 s.

[0070] It should be noted that, in practical applications, the second preset rule may also use other methods to gradually reduce the output power to zero, for example, gradually reducing the output power to zero according to a preset linear function of time and sputtering power value.

[0071] Step S5, determining whether the thickness of the film reaches the target thickness, if so, proceeding to step S6; if not, returning to step S2.

[0072] Step S6, turning off the sputtering power supply and stopping the introduction of process gas into the reaction chamber.

[0073] After step S6, the reaction chamber is evacuated to reach a high vacuum state (usually the chamber pressure is controlled at 5*10 -7 Torr or less).

[0074] Optionally, in step S2 to step S4, the chamber pressure is in the range of 4-20 mTorr, and the flow ratio of nitrogen gas to argon gas is in the range of 0.3-0.8.

[0075] It should be noted that, in this embodiment, step S4 is performed first and then step S5 is performed, but the present invention is not limited to this. In practical applications, step S5 may be performed first and then step S4. The order of step S4 and step S5 can be freely set according to specific needs. The remaining steps are performed in the order of sequence numbers.

[0076] It should also be noted that, in practical applications, the sputtering process provided in the embodiment of the present invention can be applied to the deposition of titanium nitride films or other metal nitride films.

[0077] To summarize, the sputtering method provided in an embodiment of the present invention can avoid tiny sparks caused by a sudden drop in power and avoid particle contamination by adding a step of gradually reducing the sputtering power to zero (step S4) before shutting down the sputtering power supply (step S6), thereby ensuring thin film performance and improving device electrical performance and yield.

[0078] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A sputtering method, It is characterized in that The following steps are involved: S1, introducing process gas into the reaction chamber; S2, turning on the sputtering power supply, and adjusting the output power of the sputtering power supply loaded on the target material to a first sputtering power value, so as to initiate plasma formation and form a buffer layer on the substrate; the step S2 includes the following sub-steps: S21, turning on the sputtering power supply, and adjusting the output power to a third sputtering power value; the third sputtering power value is less than the first sputtering power value; S22, after a preset time, increasing the output power from the third sputtering power to the first sputtering power value; S3, increasing the output power to a second sputtering power value according to a first preset rule to deposit a thin film on the substrate; The first preset rule includes: directly adjusting the output power from the first sputtering power value to the second sputtering power value; or, the first preset rule includes: increasing the output power from the first sputtering power value to a fourth sputtering power value; the fourth sputtering power value is less than the second sputtering power value; after a preset time, increasing the output power from the fourth sputtering power value to the second sputtering power value; S4, gradually reducing the output power to zero according to a second preset rule; in the step S4, the second preset rule includes: performing a power reduction process at a specified interval until the output power is zero; the power reduction process includes: reducing the current output power by a preset adjustment amount; the value range of the fourth sputtering power value satisfies the following formula: M=(Nn) / 2-(N+n) / 2; wherein M is the fourth sputtering power value; N is the second sputtering power value; and n is the first sputtering power value; S5, determining whether the thickness of the film reaches the target thickness, if so, proceeding to step S6; if not, returning to step S2; S6, turning off the sputtering power supply and stopping the introduction of the process gas into the reaction chamber; Wherein, the step S4 is performed first and then the step S5; or, the step S5 is performed first and then the step S4.

2. The sputtering method according to claim 1, It is characterized in that The preset adjustment amount used in each power reduction process is the same.

3. The sputtering method according to claim 1, It is characterized in that The value range of the specified time is 0.1-0.3s.

4. The sputtering method according to claim 1, It is characterized in that In the step S4, the second preset rule includes: gradually reducing the output power to zero according to a preset linear function of time and sputtering power value.

5. The sputtering method according to any one of claims 1 to 4, It is characterized in that The third sputtering power value is half of the first sputtering power value.

6. The sputtering method according to any one of claims 1 to 4, It is characterized in that The fourth sputtering power value ranges from 3.5 to 5.5 KW; the first sputtering power value ranges from 0.5 to 2 KW; and the second sputtering power value ranges from 4 to 12 KW.

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