Plasma processing equipment

Abstract

To provide a plasma processing apparatus capable of accurately detecting the position of plasma even if there is a fluctuation in the light emission of the plasma itself. [Solution] A plasma processing apparatus comprising a vacuum processing chamber for plasma processing a sample, a plasma generating unit for generating plasma inside the vacuum processing chamber, and a sample stage on which the sample is placed inside the vacuum processing chamber, the plasma processing apparatus also comprising: a first optical sensor for measuring the light intensity of the plasma generated inside the vacuum processing chamber from a direction approximately parallel to the surface of the sample stage; a second optical sensor for measuring the light intensity of the plasma from a direction approximately perpendicular to the surface of the sample stage; and a plasma position calculation unit for calculating the position of the plasma within the vacuum processing chamber based on the ratio of the signal of the light intensity measured by the first optical sensor to the signal of the light intensity measured by the second optical sensor.

Description

[Technical Field]

[0001] The present invention relates to a plasma processing apparatus. [Background technology]

[0002] Driven by market demands for lower power consumption and higher speed, semiconductor devices have continued to shrink in size in accordance with Moore's Law for over 50 years. Currently, miniaturization has reached the limits of cutting-edge lithography patterning, resulting in reduced cost efficiency and significant short-channel effects, making simple reduction of dimensions in two dimensions impossible. Therefore, device structures are moving from miniaturization to three-dimensional integration. The processing precision required for current cutting-edge semiconductor manufacturing has been miniaturized to the 1 nm range or less, and future semiconductor manufacturing processes will need to maintain a corresponding level of stability for the miniaturized processed shapes.

[0003] Therefore, in plasma-based etching techniques, there is a need for a method to reduce the inter-device differences and time-dependent changes in the plasma position (also called "plasma height") within a vacuum processing chamber. To achieve this, a system for detecting the plasma position is first required. Patent Document 1 discloses a method for detecting the plasma position, which involves measuring the ECR height, which is electron cyclotron resonance (ECR) caused by the interaction between high-frequency power and a magnetic field, using a camera that captures images of the plasma from a horizontal or oblique direction, a first spectrometer that acquires the plasma's emission intensity from above the ECR surface, and a second spectrometer that acquires the plasma's emission intensity from below the ECR surface, and calculating the ECR height by determining the emission ratio between the first and second spectrometers. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 012704 Summary of the Invention [Problem to be solved by the invention]

[0005] The first and second spectrometers described in Patent Document 1 both observe from directions that are significantly affected by fluctuations in the plasma position, and fluctuations in the light emission of the plasma itself due to discharge conditions, etc., can cause deviations in the measured ECR height.

[0006] An object of the present invention is to provide a plasma processing apparatus that can accurately detect the position of the plasma even if there is a fluctuation in the light emission of the plasma itself. [Means for solving the problem]

[0007] The present invention has the following configuration to achieve the above object. A plasma processing apparatus comprising a vacuum processing chamber for plasma processing a sample, a plasma generating unit for generating plasma inside the vacuum processing chamber, and a sample stage on which the sample is placed inside the vacuum processing chamber, the plasma processing apparatus also comprising: a first optical sensor for measuring the light intensity of the plasma generated inside the vacuum processing chamber from a direction approximately parallel to the surface of the sample stage; a second optical sensor for measuring the light intensity of the plasma from a direction approximately perpendicular to the surface of the sample stage; and a plasma position calculation unit for calculating the position of the plasma within the vacuum processing chamber based on the ratio of the signal of the light intensity measured by the first optical sensor to the signal of the light intensity measured by the second optical sensor. [Effects of the Invention]

[0008] It is possible to provide a plasma processing apparatus that can accurately detect the plasma position even if there is a fluctuation in the light emission of the plasma itself. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of a plasma processing apparatus according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing an example of the relationship between the emission intensity signal IA measured by the optical sensor A in FIG. 1 and the plasma position. [Figure 3]FIG. 2 is a diagram showing an example of the relationship between the emission intensity signal IB measured by optical sensor B in FIG. 1 and the plasma position. [Figure 4] An example of the relationship between IA / IB and plasma position. [Figure 5] FIG. 10 is a cross-sectional view showing a schematic configuration of a plasma processing apparatus according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Example]

[0011] 1 shows a schematic cross-sectional view of the configuration of a plasma processing apparatus according to a first embodiment of the present invention. In the apparatus of this embodiment, plasma can be generated in vacuum processing chamber 101 by electron cyclotron resonance (ECR) between 2.45 GHz microwaves (high frequency power) supplied from magnetron 102, a high frequency power source, to vacuum processing chamber 101 through dielectric window 103, and the magnetic field generated by solenoid coil 106, a magnetic field generating mechanism. Such a plasma processing apparatus is called an ECR plasma processing apparatus.

[0012] A sample 109 is placed on a sample stage 108. Gas necessary for plasma generation is supplied into the vacuum processing chamber 101 from a gas supply pipe 115. Furthermore, the vacuum processing chamber 101 is connected to a pump 105 via a valve 116, and the internal pressure can be adjusted by changing the opening of the valve 116.

[0013] In this embodiment, the plasma position 113 (height position at which the plasma is generated) depends on the position of the equal magnetic field intensity surface (ECR surface) where ECR is established. Therefore, by controlling the current supplied to the solenoid coil 106 with the coil power supply 107, it is possible to generate plasma at any height within the vacuum processing chamber 101. In this case, the lower limit height for plasma generation is set to 114.

[0014] Optical sensor A (111, also referred to as the "first optical sensor"), which monitors plasma emission from a direction parallel to the surface of sample stage 108, receives plasma emission from an optical lens 117 installed on the wall of the vacuum processing chamber at a position closer to sample stage 108 than the plasma generation lower limit position 114. Optical sensor B (112, also referred to as the "second optical sensor"), which monitors plasma emission from a direction perpendicular to the surface of sample stage 108, receives plasma emission through an optical lens 118 installed at the top of vacuum processing chamber 101. For this reason, the dielectric window must be made of a material that transmits light.

[0015] Any optical sensor can be used as long as it can measure the intensity of light emitted from the plasma, but a photodiode is a typical example. It is also possible to use a CCD or C-MOS sensor to measure the light intensity and also capture a two-dimensional image of the plasma, thereby providing the function of monitoring the plasma generation status.

[0016] The "plasma position" here is defined as "the central position where the emission intensity measured by the optical sensor is at its maximum." Mechanisms such as the magnetron 102, solenoid coil 106, valve 116, pump 105, coil power supply 107, optical sensor A (111), and optical sensor B (112) are controlled by a control device 130 (the dashed lines in FIG. 1 are an illustration of control lines). The control device 130 includes a memory unit for storing various data, a display unit for displaying various data, and an operation unit for inputting various data (none of which are shown).

[0017] Figure 2 shows the characteristics of the signal detected by optical sensor A (111) versus plasma position. Because the height of optical lens 117 is set below the lower limit of plasma generation, the signal exhibits a monotonically decreasing trend as the plasma position rises. Conditions (1) and (2) are shown as examples that reflect the different plasma emission characteristics depending on the plasma generation conditions.

[0018] Figure 3 shows the characteristics of the signal detected by optical sensor B (112) versus plasma position. As with Figure 2, Figure 3 also illustrates conditions (1) and (2) as an example that reflects the different plasma emission characteristics depending on the plasma generation conditions. Optical sensor B (112) shows a smaller change in emission intensity relative to changes in plasma position within the optical lens field of view than optical sensor A (111), and more significantly reflects the difference in emission intensity due to differences in plasma generation conditions.

[0019] Figure 4 shows the characteristics of the ratio of the signals from optical sensor A (111) and optical sensor B (112) versus the plasma position. In Figure 2, the characteristics of the signal detected by optical sensor A (111) versus the plasma height were significantly different under conditions (1) and (2). However, as shown in Figure 4, by taking the ratio of the signals from optical sensor A (111) and optical sensor B (112), the change in signal characteristics due to conditions can be offset, and unique signal characteristics versus the plasma height can be obtained under either condition. Based on the characteristics shown in Figure 4, the plasma height can be estimated from the signals obtained by optical sensor A (111) and optical sensor B (112) under any other conditions.

[0020] 4 is stored in advance in the memory of the control device 130, and the plasma position is estimated based on the light intensity signals obtained from the optical sensor A (111) and the optical sensor B (112) (one of the programs of the control device 130 is a "plasma position calculation" program, and a part of the control device 130 constitutes a "plasma position calculation unit"). The estimated plasma position is used for various controls of the plasma processing apparatus, and the estimated plasma position may also be displayed on the display unit of the control device 130.

[0021] Here, by using an optical lens 117 with a long focal length, the field of view angle can be narrowed and the sensitivity of optical sensor A (111) to the plasma position can be increased. Also, by attaching a hood (attachment) such as a tube or eaves, it is possible to reduce ambient light (stray light) and increase the sensitivity to the plasma position in the same way as narrowing the field of view. In this case, by limiting the direction in which the field of view is narrowed depending on the direction of the eaves, it is also possible to increase the sensitivity to changes in the plasma position in any direction.

[0022] Furthermore, by narrowing the field of view angle by assuming a long focal length, optical lens 118 ensures that there is no change in the optical area in the field of view of optical sensor B (112) caused by changes in the plasma position, or that only a small portion of the change is captured in the field of view. This reduces sensitivity to changes in plasma position, increases the difference in sensitivity to the plasma position with optical sensor A (111), and enhances its function as a reference. The same effect can also be achieved by narrowing the field of view angle using an attachment such as a tube or canopy. Conversely, using an optical lens with a short focal length widens the field of view angle, thereby reducing the influence of changes in the optical area in the field of view caused by changes in the plasma position, and achieving the same effect.

[0023] Furthermore, by using optical lens 117 that reduces the spatial resolution of the emission intensity, such as frosted glass, the emission intensity within the field of view can be made uniform, and the influence of changes in the optical area within the field of view caused by changes in the plasma position can be reduced, thereby achieving the same effect.

[0024] Even if the optical lens 117 is installed above the upper limit of plasma generation, the detection signal from the optical sensor A (111) can produce the same results as in Figure 2. Furthermore, by installing multiple optical lenses 117 and optical sensors A (111) in the direction of the plasma position, the detection accuracy of the plasma position can be further improved and the detection range of the plasma generation height can be expanded. [Example]

[0025] 5 shows a schematic cross-sectional view of the overall configuration of a plasma processing apparatus according to a second embodiment of the present invention. The configuration of the apparatus according to this embodiment, which is related to its function as a plasma processing apparatus, is the same as that of the first embodiment. The apparatus according to this embodiment is a plasma processing apparatus characterized by generating plasma above and below a shielding plate 121. With the same configuration of optical sensor A (111) and optical sensor B (112) as in the first embodiment, or with the configuration of optical sensor A2 (118) and optical sensor B (112) provided above the shielding plate 121, it is possible to detect whether the plasma position 113 is located above or below the shielding plate.

[0026] Even if the optical lens 120 is installed at a position above the upper limit of plasma generation, the detection signal from the optical sensor A2 can produce the same results as in FIG.

[0027] In addition, in order to improve the resolution of position detection in each area above and below the shielding plate, it is also possible to install, for example, both optical sensor A (111) in the area below the shielding plate 121 and optical sensor A2 (118) in the area above the shielding plate 121.

[0028] Furthermore, similar to Example 1, by installing multiple optical lenses 117, optical sensors A (111), and optical sensors A2 (118) in the direction of the plasma position in each of the upper and lower areas of the shielding plate 121, the detection accuracy of the plasma position can be further improved and the detection range of the plasma generation height can also be expanded. [Explanation of symbols]

[0029] 101: vacuum processing chamber, 102: microwave power supply, 103: dielectric window, 105: vacuum pump, 106: solenoid coil, 107: coil power supply, 108: sample stage, 109: sample, 110: plasma, 111: optical sensor A, 112: optical sensor B, 113: plasma position, 114: plasma generation lower limit position, 115: gas supply pipe, 116: vacuum valve, 117: optical lens, 130: control device.

Claims

1. A plasma processing apparatus including: a vacuum processing chamber for plasma processing a sample; a plasma generating unit for generating plasma inside the vacuum processing chamber; and a sample stage for placing the sample inside the vacuum processing chamber, a first optical sensor that measures the amount of light of the plasma generated inside the vacuum processing chamber from a direction substantially parallel to the surface of the sample stage; a second optical sensor that measures the amount of light from the plasma in a direction substantially perpendicular to the surface of the sample stage; a plasma position calculation unit that calculates a position of the plasma in the vacuum processing chamber based on a ratio of a signal of the light amount measured by the first optical sensor and a signal of the light amount measured by the second optical sensor, A plasma processing apparatus characterized by:

2. 2. The plasma processing apparatus according to claim 1, The installation position of the first optical sensor is closer to the sample than the position of the plasma when the plasma is generated at the closest position to the sample. The plasma processing apparatus is characterized by the above.

3. 2. The plasma processing apparatus according to claim 1, the installation position of the first optical sensor is farther from the sample than the position of the plasma when the plasma is generated at the farthest position from the sample; The plasma processing apparatus is characterized by the above.

4. 2. The plasma processing apparatus according to claim 1, a shielding plate is provided in the vacuum processing chamber, and the plasma generating unit can generate the plasma either above or below the shielding plate; The first optical sensor is provided above and / or below the shielding plate. A plasma processing apparatus characterized by:

5. 2. The plasma processing apparatus according to claim 1, the first optical sensor measures the signal of the light amount of the plasma through an optical lens having a focal length equal to or greater than a predetermined value, thereby increasing sensitivity to the plasma in the height direction. A plasma processing apparatus characterized by:

6. 2. The plasma processing apparatus according to claim 1, the first optical sensor measures a signal of the amount of light from the plasma through an optical lens, and the optical lens is provided with an attachment that limits the light receiving direction; A plasma processing apparatus characterized by:

7. 2. The plasma processing apparatus according to claim 1, the second optical sensor measures the signal of the light quantity of the plasma through an optical lens having a focal length equal to or greater than a predetermined value, thereby reducing sensitivity to the height direction of the plasma. A plasma processing apparatus characterized by:

8. 2. The plasma processing apparatus according to claim 1, the first optical sensor measures a signal of the light amount of the plasma through an optical lens, the optical lens having a small spatial resolution and capable of uniforming the light emission intensity within a light receiving field of view; A plasma processing apparatus characterized by:

9. 2. The plasma processing apparatus according to claim 1, The apparatus includes a plurality of the first optical sensors, and the plurality of first optical sensors are provided at different height positions. A plasma processing apparatus characterized by:

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