Plasma processing method

Abstract

This invention provides a plasma treatment method capable of forming a deposited film on the walls of a processing chamber and suppressing the diffusion of contaminants into a transport system. The plasma treatment method for plasma treating samples placed on a sample stage within a processing chamber includes: a first step of removing deposits in the processing chamber using plasma; a second step of depositing deposits in the processing chamber using a mixture of hydrofluorocarbon gas and argon (Ar) gas after the first step; a third step of selectively removing deposits from the sample stage using a mixture of oxygen (O2) gas and argon (Ar) gas after the second step; and a fourth step of plasma treating a predetermined number of samples after the third step.

Description

Technical Field

[0001] This invention relates to plasma processing methods. Background Technology

[0002] In recent years, the miniaturization of semiconductor manufacturing, such as integrated circuits, has led to increasingly stringent requirements for product etching. In particular, foreign matter and contamination adhering to wafers significantly reduce yield. Therefore, the development of technologies to reduce foreign matter and contamination is underway. Specifically, when the cause of foreign matter and contamination lies within the processing chamber components, forming a deposited film on these components is effective in reducing foreign matter and contamination.

[0003] Patent Document 1 discloses a processing method comprising a first step of removing residual film in the processing chamber using plasma containing oxygen gas, and a second step of forming a deposited film on the wall surface of the processing chamber using plasma containing fluorinated carbon-based gas or a mixture of gases containing fluorinated carbon-based gas. According to this processing method, the formation of foreign matter caused by the degradation of components in the processing chamber during plasma etching, which is suppressed by the formed deposited film, can be prevented, thus preventing defects in the pattern caused by foreign matter adhering to the product wafer.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2000-91327 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, if the processing method disclosed in Patent Document 1 is performed without placing the wafer on the mounting stage, there is a problem that a deposited film may also form on the mounting stage. If a deposited film forms on the mounting stage, when the wafer for etching is placed on the mounting stage for processing, the deposited film may adhere to the back side of the processed wafer. The deposited film adhering to the processed wafer may separate and detach during transport with the processed wafer, becoming foreign matter, and may then spread through transport robots, thereby potentially contaminating the entire transport system.

[0009] On the other hand, if only the formation of a deposited film on the stage is prevented, it can be said that during the processing method disclosed in Patent Document 1, the dummy wafer is placed on the stage and removed after processing. However, while this method can prevent the formation of a deposited film on the stage, it cannot prevent the formation of a deposited film on the dummy wafer. Therefore, the deposited film remaining on the dummy wafer may separate and detach during transport with the dummy wafer, becoming foreign matter, thus posing a risk of contamination to the transport system.

[0010] The present invention provides a plasma treatment method capable of forming a deposited film on the walls of a treatment room and suppressing the diffusion of contaminants into the transport system.

[0011] Solution for solving the problem

[0012] To achieve the above objectives, one representative plasma treatment method of the present invention involves performing plasma treatment on a sample placed on a sample stage in a treatment chamber. The plasma treatment method is characterized by comprising:

[0013] The first step involves using plasma to remove the buildup inside the processing chamber;

[0014] The second step involves using a mixture of hydrofluorocarbon gas and argon (Ar) gas to deposit the material in the processing chamber after the first step.

[0015] The third step, following the second step, involves selectively removing the deposits on the sample stage using a mixture of oxygen (O2) and argon (Ar) gas; and

[0016] The fourth step involves plasma treatment of a specified number of the samples after the third step.

[0017] Invention Effects

[0018] According to the present invention, a plasma treatment method is provided that can form a deposited film on the inner wall of the treatment chamber and suppress the diffusion of contaminants into the transport system.

[0019] Other issues, structures, and effects not mentioned above will become clear through the following description of the implementation methods. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view schematically illustrating an embodiment of the plasma processing apparatus of the present invention.

[0021] Figure 2 It shows that it was used Figure 1 A flowchart illustrating an example of a plasma processing method using the plasma processing apparatus shown.

[0022] Figure 3 This schematically illustrates the use of a mixture of fluoromethane (CH3F) and argon (Ar) to form CH x A diagram showing the state of plasma treatment of the deposited film.

[0023] Figure 4 This diagram schematically illustrates the state of plasma treatment using a mixture of oxygen (O2) and argon (Ar) to remove deposited films.

[0024] Figure 5 This graph compares the etching rate of a carbon compound deposited film with and without a bias voltage during plasma processing, and with a change in the current value of the solenoid coil. Detailed Implementation

[0025] Specific embodiments of the plasma processing method according to the present invention will be described below with reference to the accompanying drawings.

[0026] (Plasma processing device)

[0027] First, refer to Figure 1 An example of a plasma etching apparatus used to implement the plasma processing method of this embodiment will be described. Figure 1 This is a schematic diagram of an ElectroCyclotron Resonance (hereinafter referred to as ECR) type plasma etching apparatus that utilizes microwaves and magnetic fields as a plasma generation mechanism.

[0028] The ECR-type plasma etching apparatus includes: a processing chamber 101 capable of venting its internal vacuum; a stage 103 housed within the processing chamber 101 and holding a wafer 102 as a sample; a quartz microwave transmission window 104 disposed on the upper surface of the processing chamber 101; a waveguide 105 disposed above the microwave transmission window 104; a magnetron (microwave generating device) 106 for oscillating microwaves; a first high-frequency power supply 112 for supplying high-frequency power to the magnetron 106; solenoid coils 107, 108, and 109 (magnetic field generating devices) arranged along the axial direction around the processing chamber 101; and a gas supply piping 110 for introducing process gas into the processing chamber 101.

[0029] The first high-frequency power supply 112 has the function of pulse modulation of the oscillating microwave.

[0030] During plasma etching, after the wafer 102 is moved from the wafer loading port 111 into the processing chamber 101 by a handling robot, it is electrostatically attracted to the stage 103 by an electrostatic adsorption power source (not shown).

[0031] Next, process gas is introduced into processing chamber 101 from gas supply piping 110. The pressure inside processing chamber 101 is reduced and vented by a vacuum pump (not shown), and adjusted to a specified pressure (e.g., 0.1 Pa - 50 Pa).

[0032] Next, if a specified high-frequency power is supplied to the magnetron 106 from the first high-frequency power supply 112, microwaves with an oscillation frequency of 2.45 GHz from the magnetron 106 are supplied into the processing chamber 101 through the waveguide 105.

[0033] At this time, the process gas is excited by the interaction between the magnetic field generated by the solenoid coils 107, 108, and 109 and the microwave, and plasma 113 is generated in the space above the wafer 102.

[0034] On the other hand, a bias voltage is applied to the stage 103 using a second high-frequency power supply (not shown), and ions in the plasma 113 are vertically accelerated and incident onto the wafer 102. Furthermore, the second high-frequency power supply (not shown) can apply either a continuous bias voltage or a time-modulated bias voltage to the stage 103. Thus, under the influence of free radicals and ions from the plasma 113, the wafer 102 is anisotropically etched.

[0035] The current supplied to solenoid coils 107, 108, and 109 can be controlled. Therefore, the region where ECR is generated can be changed vertically according to each current value.

[0036] (Plasma processing methods)

[0037] Next, referring to the attached diagram, the following was used. Figure 1 The plasma processing method of the plasma etching apparatus shown will be explained. Figure 2 This is a flowchart of a plasma processing method according to an embodiment of the present invention.

[0038] It should be noted that in this specification, gases containing carbon, hydrogen, and fluorine are referred to as CHF-based gases.

[0039] In step 201, in order to prevent the formation of a deposited film on the stage 103, a dummy wafer (dummy sample) that has been moved in from the wafer transfer port 111 by a transfer robot or the like is placed on the stage 103.

[0040] After the dummy wafer is placed, in step 202 (first step), a mixed gas consisting of sulfur hexafluoride (SF6), oxygen (O2), and argon (Ar) is supplied from the gas supply pipe 110 into the processing chamber 101 for plasma treatment, and the residual film (deposits) in the processing chamber 101 are removed.

[0041] As for the plasma treatment conditions, SF6 was supplied at 150 mL / min, O2 at 27 mL / min, and Ar at 60 mL / min. The treatment chamber pressure was set to 0.6 Pa, the microwave power was set to 1000 W, the current values ​​to the upper solenoid coils 107, 108, and 109 were set to 27 / 26 / 0 A, respectively, and the treatment time was set to 60 sec.

[0042] In step 203 (second process), a mixed gas consisting of fluoromethane (CH3F) and argon (Ar) is supplied from the gas supply pipe 110 into the processing chamber 101 for plasma treatment, and CH3F is formed on the inner wall of the processing chamber. x The deposited film.

[0043] Figure 3 This shows the formation of CH on the interior wall surface during processing. x A schematic diagram of the state during film deposition. The plasma treatment in step 203 is performed by applying a bias voltage (high-frequency power) to the stage 103, thereby preventing the deposition film on the dummy wafer from depositing under the action of ion sputtering compared to the deposition film on the inner wall of the processing chamber. In other words, by utilizing the plasma treatment in step 203, both deposition and etching are performed on the dummy wafer, thereby suppressing the deposition rate.

[0044] As for the plasma treatment conditions described above, CH3F was supplied at 100 mL / min and Ar at 100 mL / min, the treatment chamber pressure was set to 0.5 Pa, the microwave power was set to 800 W, the bias power was set to 50 W, the current values ​​to solenoid coils 107, 108, and 109 were set to 27 / 26 / 0 A, respectively, and the treatment time was set to 160 sec. In this embodiment, fluoromethane (CH3F) gas was used, but hydrofluorocarbon gases such as difluoromethane (CH2F2) gas and trifluoromethane (CHF3) gas can also be used in addition to fluoromethane (CH3F) gas.

[0045] In step 204 (third step), high-frequency power is supplied to the mounting stage 103, and a mixed gas consisting of oxygen (O2) and argon (Ar) is supplied from the gas supply pipe 110 into the processing chamber 101 for plasma treatment. On the dummy wafer that has been mounted in step 201, the CH4 formed in step 203 is applied... x The deposited film is selectively removed.

[0046] After the plasma treatment in step 204, in step 205, the dummy wafers placed on the mounting stage 103 are removed by a handling robot or the like. Then, in step 206 (fourth step), a predetermined number of product wafers undergo plasma treatment. This suppresses foreign matter contamination and enables the processing of the product wafers.

[0047] Figure 4 This shows the CH on a virtual wafer. x The diagram shows the state during the removal of the deposited film. The plasma treatment in step 204 is performed by applying a bias voltage to the stage 103, thereby suppressing the removal of the deposited film on the walls of the processing chamber and enabling selective removal of the deposited film on the dummy wafer.

[0048] As for the plasma treatment conditions, O2 was supplied at 30 mL / min and Ar at 150 mL / min, the treatment chamber pressure was set to 0.5 Pa, the microwave power was set to 400 W, the bias power was set to 50 W, the current values ​​to solenoid coils 107, 108, and 109 were set to 27 / 26 / 9 A respectively, and the treatment time was set to 230 sec.

[0049] Figure 5 This graph compares the etching rate of the carbon compound deposit film during the processing in step 204 when the current value of the solenoid coil is changed under conditions of no bias power applied to the stage 103 (no bias) and under conditions of applied bias power (with bias). Specifically, under conditions of no bias and with bias, the current values ​​to the solenoid coils 107, 108, and 109 are common and set to 27 / 26 / 9A. Under conditions of bias, the current values ​​to the solenoid coils 107, 108, and 109 are changed to 27 / 26 / 14A and 27 / 27 / 27A, respectively, and the etching rate is calculated.

[0050] With the current values ​​of solenoid coils 107, 108, and 109 common, the etching rate without bias is 92.64 nm / min, while the etching rate with bias is 159.18 nm / min, indicating that etching proceeds more smoothly under bias. Therefore, by applying bias voltage, the deposited film on the wafer can be selectively removed.

[0051] Furthermore, when comparing the etching rates when the current values ​​of the solenoid coils 107, 108, and 109 were changed, the etching rate was 159.18 nm / min when the current values ​​were 27 / 26 / 9 A, 164.76 nm / min when the current values ​​were 27 / 26 / 14 A, and 172.39 nm / min when the current values ​​were 27 / 27 / 27 A. Therefore, it can be seen that the higher the current value, the higher the etching rate.

[0052] Here, as the current value to the solenoid coil 109 is increased, the region where plasma is generated in step 204 moves closer to the stage 103, thus enabling the removal of more deposited film. That is, by changing the current value to the solenoid coil 109, the amount of deposited film and the amount of etching in step 204 can be arbitrarily adjusted.

[0053] According to this embodiment, by maintaining the deposited film formed on the wall surface of the processing chamber and selectively removing the deposited film formed on the mounting stage, the components in the processing chamber can be protected and foreign matter generation can be prevented. This prevents contamination of the handling system that may occur due to the deposited film forming on the mounting stage. Furthermore, by removing the deposited film on the dummy wafer, the dummy wafer can be reused, thus reducing the cost of the dummy wafer.

[0054] (Modified Example)

[0055] It should be noted that the present invention is applicable even without placing the dummy wafer on the stage (i.e., even if the dummy wafer does not exist). Figure 4 Steps 201 and 205 can also be achieved. More specifically, without placing the dummy wafer on the stage, step 204 can be used to transfer the CH deposited on the stage in step 203. x The deposited film is selectively removed. Depending on the plasma treatment conditions, the CH4 on the stage is... x The amount of deposit and the amount of etching are balanced, so that the amount of deposit before the product wafer is placed on the stage can be set to zero.

[0056] This embodiment is described in detail for the purpose of easily understanding the present invention, and is not necessarily limited to a solution having all the structures described.

[0057] Explanation of reference numerals in the attached figures

[0058] 101 Processing Room

[0059] 102 wafers

[0060] 103 Platform

[0061] 104 Microwaves through the window

[0062] 105 waveguide

[0063] 106 Magnetron

[0064] 107, 108, 109 Solenoid coils

[0065] 110 Gas supply piping

[0066] 111 Wafer Transfer Port

[0067] 112 First high-frequency power supply.

Claims

1. A plasma treatment method, wherein a sample placed on a sample stage is subjected to plasma treatment in a treatment chamber. The plasma processing method is characterized in that... The plasma processing method includes: The first step involves using plasma to remove the buildup inside the processing chamber; The second step involves using a mixture of hydrofluorocarbon gas and argon (Ar) gas to deposit the material in the processing chamber after the first step. The third step, following the second step, involves selectively removing the deposits on the sample stage using a mixture of oxygen (O2) and argon (Ar) gas. as well as The fourth step involves plasma treatment of a specified number of the samples after the third step.

2. The plasma treatment method according to claim 1, characterized in that, The dummy sample is placed on the sample stage in the third process.

3. The plasma treatment method according to claim 2, characterized in that, The hydrofluorocarbon gas is fluoromethane (CH3F) gas.

4. The plasma treatment method according to claim 3, characterized in that, High-frequency power is supplied to the sample stage in the second process.

5. The plasma treatment method according to claim 3, characterized in that, High-frequency power is supplied to the sample stage in the third process.

6. The plasma treatment method according to claim 4, characterized in that, High-frequency power is supplied to the sample stage in the third process.

7. The plasma treatment method according to claim 6, characterized in that, The plasma in the first process is generated by using a mixture of argon (Ar) gas, sulfur hexafluoride (SF6) gas, and oxygen (O2) gas.

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