JPH0322531A - End point detection - Google Patents

Abstract

PURPOSE:To accurately detect the resist removal for enhancing the reliability by a method wherein, in order to remove a resist coated on a sheet type element, the radiation dose rate of infrared rays attaining to specific value when all the resist changed by the removal of the resist radiated from the sheet type element is removed is monitored. CONSTITUTION:A specific amount of developer 15 is fed to the surface of a wafer 2 from a developer feeder 4 through the intermediary of a nozzle 13 to start the development of a circuit pattern exposed to the surface of the wafer 2. In order to perform the development processing, the wafer 2 is spinned by a spin motor 7 if necessary. During the development processing, the infrared rays radiated from the wafer 2 are detected by an infrared ray sensor 16 while the radiation dose rate of infrared rays is monitored by an end point detector 5. The infrared rays detected by the infrared ray sensor 16 are converted into electric signals. The electric signals are amplified by an amplifier 17 and, after being smoothed through a low path filter 18, time-differentiated by a differentiator 19. Finally, the output from the differentiator 19 is inputted to an end point detection device 20 for the end point detection by comparing the electric signals with an end point value Eo as another input.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to an end point detection method.

(Prior Art) In a semiconductor manufacturing process, a resist used as a mask for forming a fine pattern is applied to the surface of a plate-shaped object, such as a semiconductor wafer.

Part or all of the applied resist is removed by a development process after exposure, an ashing process after pattern formation, or the like.

When removing the resist on the surface of the rewafer by such development processing or ashing processing, it is necessary to detect the point in time when a predetermined portion of the resist or all the resist has been removed, that is, the end point of resist removal. For this reason, in the above development process, the end point of development is considered to be the end of a certain period of time after the developer is deposited on the wafer surface, and in the above ashing process, CO2 generated by this ashing is
The (carbon dioxide) concentration is monitored, and the end point of ashing is defined as the point when this CO2 is no longer produced.

(Problem to be Solved by the Invention) However, the end point of the above-mentioned development process is determined by taking into account the size of the wafer and the amount of developer, and determines the time from when the developer is deposited on the wafer surface until the development is completed. , the point at which this time has elapsed is regarded as the end point of development, so it is not necessarily accurate. For example, if the timing of end point detection is too early, the development process will be deemed to have ended before the development is actually completed completely, resulting in development defects such as residual development. In addition, if the end point detection timing is delayed, the development process continues even after development is completed until the end point is detected, resulting in excessive development resulting in an incorrect pattern shape, such as an undercut. Correct any problems such as a decrease in throughput or a decrease in throughput. As described above, there is a problem in that the reproducibility of the pattern shape is poor because the end point detection is not accurate.

Further, the end point detection of the ashing process is accurate and has good reproducibility because it is detected from changes in CO2 concentration, but the C○211JI degree detector is very expensive.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide an end point detection method capable of detecting the end point of resist removal at low cost and with high reliability.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides, when removing a resist adhered to a plate-like object, radiation emitted from the plate-like object and changing as the resist is removed. Obtain an end point detection method characterized by monitoring the infrared emissivity that becomes a constant value when all the resist is removed, and detecting the point when the infrared emissivity becomes a constant value as the end point of resist removal. It is something.

(Operation and Effect) That is, when removing the resist adhered to a plate-like object, the present invention emits radiation from the plate-like object and changes as the resist is removed, and when the resist is completely removed. By monitoring the emissivity of the infrared rays, which is a constant value, and detecting the point at which the emissivity of the infrared rays becomes a constant value as the end point of resist removal, the end point can be directly determined from the emissivity of the infrared rays, which changes as the resist is removed. Detected. Thereby, removal of the resist can be detected accurately and reliability can be improved. Furthermore, infrared emissivity can be detected with an inexpensive configuration and can be realized at low cost.

(Example) Hereinafter, an example in which the method of the present invention was applied to a semiconductor wafer development process will be described with reference to the drawings.

First, the structure of the developing device will be explained.

This developing device (1) is a device for developing a pattern after exposing a photoresist coated on a plate-shaped object, such as a semiconductor wafer, and as shown in FIG.
A rotation processing unit (4) that rotates the wafer (2), a developer supply unit (4) that supplies a developer to the surface of the wafer (2), and a developer supply unit (4) that monitors the emissivity of infrared rays emitted from the wafer (2). It consists of an end point detection section (2) that detects the end point of removing the resist attached to the surface.

The rotation processing section (■) is made of a resin such as Delrin (trade name) that can hold the back side of the wafer (2) by suction.
A chuck 0 manufactured by the manufacturer is provided. A drive mechanism such as a spin motor 0 is connected to the chuck (2), and it is possible to control the rotation of the wafer (2) and the chuck 0 at a predetermined acceleration and rotational speed. Furthermore, a cup (2) is placed around the wafer (2) held by the chuck (2) so as to collect the developer that scatters from the wafer (2) when a developer is supplied to the surface of the wafer (2) and the wafer (2) is rotated. are arranged to form the processing chamber (9). This cup ■ has a bottomed cylindrical shape with a U-shaped cross section that is open at the top, and the portion of the side wall of this cup ■ near where it intersects with the extended surface of the surface of the wafer ■ is at an angle A (A≠90°). ). By tilting the side wall of this cup, the processing liquid splashed from the wafer surface hits the sloped portion and is guided in a direction other than the wafer surface, for example, downward, thereby preventing it from rebounding to the wafer surface. . In addition, the above cup (8
) At the bottom, on the outside from the center, there is a drain pipe (10) for draining the developer, rinse solution, etc. , and an exhaust pipe (11) for exhausting the inside of the processing chamber 0.

In this case, the drainage liquid is exhausted above! (11) An annular separation wall (
12) is provided, and the exhaust pipe (1l) is arranged inside this separation wall (12). Further, the bottom surface of the cup (1) has a gradual slope with the drain pipe (10) at the lowest position so that the drained liquid collects in the drain pipe (10).

Further, the developer supply section (4) is provided with a tank (not shown) for storing a developer, and the tip thereof is connected to the cup so that a predetermined amount of developer can be supplied from the tank to the surface of the wafer (2). (8) The nozzle (13) located above is connected. At this time, a nozzle scanning mechanism (not shown) may be provided for retracting the nozzle (l3) from above the cup (8).

In addition, as shown in FIG. 2, the end point detection part (2) is filled with a developer (15) on the wafer (15) whose surface is coated with a resist (14) to perform the development process. An infrared sensor (l6) such as a thermopile is provided to receive infrared rays emitted from the wafer (2). This infrared sensor (l6) has an amplifier (17) connected in series.
, a low-pass filter (l8) and a differentiator (19) are provided in an electrically connected state.

Furthermore, an end point determiner (20) is provided so that an electrical signal of the infrared emissivity received by the infrared sensor (16) is input. This end point determiner (20) has a semi-variable value E that can be arbitrarily set depending on the object of end point detection (particularly the aperture ratio). is also a configuration that is input, and this E
. The electric signal of the infrared emissivity and the above infrared emissivity are compared to output an end point detection signal. In this way, the developing device (2) is constructed.

Next, the operation and end point detection method of the above-mentioned developing device will be explained.

First, a plate-like object, such as a semiconductor wafer (2), is transported above the processing chamber (9) by a transport mechanism (not shown) such as a hand arm, and placed on the chuck 0, and the rotation center of this chuck 0 and the wafer (2) are transported above the processing chamber (9). Hold, for example, suction, so that the centers of rotation of the two are aligned. In order to facilitate the work of placing the wafer 1 on the chuck 0, it is preferable to lower the cup (8) or raise the chuck 0 during this work.

Then, a predetermined amount of developer (15) is applied to the surface of the wafer.
The development of the circuit pattern exposed on the surface of the wafer (2) is started by supplying the developer through the nozzle (13) from the developer supply section (2). When performing this development process,
-7- -8- Rotate the wafer ■ by the spin motor ω as necessary. During this development process, the infrared sensor (16) detects the infrared rays emitted from the wafer (2).
) and monitors the infrared emissivity at the end point detection section (■). The infrared rays received by the infrared sensor (16) are converted into an electrical signal, and the magnitude of the electrical signal E is determined according to Stefan Boltzmann's law if the reception band of the infrared sensor (16) is sufficiently wide. , ? (Electrical signal) ■ε■■■ Emissivity) ・ (ΔT (difference between wafer temperature and infrared sensor temperature)) 4
Further, assuming that the change in the difference ΔT between the wafer temperature and the infrared sensor temperature during the development process is negligibly small, it can be seen that E (electrical signal) cc ε (emissivity). This electrical signal is then passed through an amplifier (
17), smoothed through a low-pass filter (l8), and then differentiated with respect to time by a differentiator (l9). Here, the emissivity of infrared rays changes as the resist adhered to the surface of the wafer is removed, as shown in FIG.
) and a differentiator (19) to perform signal processing, the characteristics as shown in FIG. 4 are obtained.

The output from this differentiator (19) is input to an end point determiner (20), and another input is the end point value E. The end point is detected by comparing the At this time, the end point determiner (20) 2
If the two inputs are simply compared, the end point detection signal will be output immediately after the start of the development process, so this first signal is automatically canceled inside the end point determiner (20). . And the end point determiner (20)
When an end point detection signal is output from the wafer (2), the development processing of the wafer (2) is stopped, and a rinsing liquid such as pure water is supplied to the surface of the wafer (2) for rinsing. Further, the wafer (2) is rotated at high speed, and the wafer (2) is subjected to a drying process, thereby completing a series of development processes.

In this way, by directly detecting the end point of the development process from the infrared emissivity, it is possible to prevent development defects and save the developer.

In the above embodiment, an example was explained in which an infrared sensor was used to measure the emissivity of infrared rays, but the invention is not limited to this. For example, as shown in FIG. It is also possible to use autopsy. In this case, the specified value of emissivity? Keep it constant. That is, the apparent temperature value of the total radiation thermometer (21) changes with development, and the change approximately follows the following equation.

δT (temperature change) cc δε (emissivity change) Also,
A moving average process or a digital low-pass filtering process may be applied instead of the low-pass filter (18), and a difference machine may be applied instead of the differentiator (in this case, the end point detection process becomes a discrete process). Furthermore, such processing can be carried out using a microcomputer, a general-purpose signal processing device such as a DSP (digital processor), etc.
It may also be realized using a signal processor (signal processor) or the like.

Furthermore, in the above embodiment, detection of the end point of the developing process was explained as an example, but any method may be used as long as the temperature is constant, the emissivity changes with the process, and the emissivity remains constant after the end point. Similar effects can be obtained by applying the present invention to, for example, detecting the end point of register ashing processing. Furthermore, even if a temperature change occurs as a result of processing, the end point can be detected by inputting the temperature change as a correction signal to the end point determiner.

As described above, according to this embodiment, when the resists 1 to 1 applied to the plate-shaped object are removed, the radiation emitted from the plate-shaped object changes as the resist is removed, and the resist is completely removed. By monitoring the infrared emissivity, which becomes a constant value at the time of resist removal, and detecting the point at which this infrared emissivity becomes a constant value as the end point of resist removal, it is possible to detect the infrared radiation that changes as the resist is removed. The end point can be detected directly from the rate. Thereby, removal of the resist can be detected accurately and reliability can be improved.

Furthermore, infrared emissivity can be detected with an inexpensive structure and can be realized at low cost.

[Brief explanation of drawings]

11-12- The construction drawing is a diagram of the structure of the developing device for explaining one embodiment of the method of the present invention, FIG. 2 is an explanatory diagram of the end point detection section of FIG. 1, and FIG. Fig. 4 is a graph showing a characteristic example of differentiating the infrared emissivity shown in Fig. 3, and Fig. 5 is an illustration of another embodiment of the method of the present invention. be. 2...Wafer 14...Resist l6...Sensor 18...Low-pass filter 20...End point determiner 5...End point detection section l5...Developer 17...Amplifier 19...Differentiator 2l・・・Total radiation type thermometer

Claims (1)

[Claims] When removing resist adhered to a plate-shaped object, monitor the emissivity of infrared rays emitted from the plate-shaped object, which changes as the resist is removed, and becomes a constant value when all the resist is removed. An end point detection method characterized in that the point in time when the emissivity of this infrared ray reaches a constant value is detected as the end point of resist removal.