JPS62272536A - Dry ashing apparatus - Google Patents

Abstract

PURPOSE:To largely suppress an etching with fluorine radical on a base part without so decelerating an ashing velocity by switching gas fed into a plasma light emitting chamber from a mixture gas of CF4 and O2 to only oxygen when the intensity of a light emitting spectrum of a specific wavelength becomes a preset predetermined value or higher. CONSTITUTION:When a resist is ashed by an oxygen radical, a CO light emitting spectrum is generated. Then, a spectrochemical analyzer 17 detects only the intensity of the CO light emitting spectrum, and outputs a detection signal of a level responsive to the detecting intensity. When the intensity of the input detection signal spectrum arrives at a predetermined value, a comparator 18 supplies a control signal of a logic level different from that supplied so far since the input detection signal level becomes a first reference signal level or lower from an input terminal 19 to close a conduit 10 by a solenoid valve 11. Thus, the input of Freon gas (CF4) to a plasma light emitting chamber 6 is stopped, but only oxygen (O2) is fed into the chamber 6 to eliminate an etching with fluorine radical (F*) on the base of a sample 14.

Description

[Detailed Description of the Invention] a Detailed Description of the Invention (Summary) The present invention provides a dry ashing device for photoresist that controls the flow field of Freon gas (CFJ) mixed with oxygen gas to remove resist on a sample. Etching on other parts of the base is kept to a minimum.

[Industrial application field]

TECHNICAL FIELD The present invention relates to a dry ashing device, and particularly to a down 70 type dry ashing device.

Dry ashing equipment is widely used to remove unnecessary resist after processing the base using resist as a mask. However, it is required that the underlying portion other than the resist is not etched.

[Conventional technology]

As one of the conventional dry ashing devices, a down 70 type dry ashing device is known.

This is configured so that only radicals in the plasma emitted in the plasma emission chamber are introduced into the ashing chamber to ash (ash) the resist on the sample in the ashing chamber.

According to this type of dry ashing device, since the sample is not directly exposed to plasma, there is no fear of damage and the required ashing can be performed.

[Problem that the invention seeks to solve]

However, the above-mentioned conventional dry ashing equipment uses Freon gas (CF4) to increase the ashing speed.
) was used by mixing it with oxygen (02).

Therefore, as shown in FIG. 3, the sample in the ashing chamber is deposited on the substrate 1. In the case where resist 3 is formed through oxygen radical 2, resist 3 is oxygen radical (01)
At the same time, the underlying portion 4 on the substrate 1, which is made of Si or 5iiNs, where there is no resist 3, is also attacked by fluorine radicals (F8).
There was a problem in that it reacted with Fl) and was etched.

Therefore, the present invention was created in view of the above points.
To provide a dry ashing device which minimizes etching of a base portion as much as possible.

[Means for solving problems]

The dry ashing device of the present invention is a device that ashes resist on a sample by introducing only radicals into an ashing chamber, and detects the intensity of an emission spectrum of a specific wavelength that occurs when there is resist on the sample. a detection means for outputting a detection signal of a level corresponding to the plasma emission chamber; a valve means for controlling the flow rate of Freon gas flowing into the plasma emission chamber; and a valve means for controlling the valve means after the detection intensity exceeds a preset constant intensity. and a comparator that outputs a control signal to prevent Freon gas from flowing into the plasma emission chamber.

[Effect]

Only radicals in the plasma generated in the plasma emission chamber using a mixed gas of oxygen and 7 Leon gas are introduced into the ashing chamber and 7 ts the resist on the sample in the ashing chamber.

At this time, the detection means detects the intensity of the emission spectrum at a specific wavelength, the emission intensity of which varies greatly depending on the presence or absence of the resist. The detection (No. 3) taken out from this detection means is supplied to a comparator and compared in level with a reference signal.

This reference signal is selected to correspond to the detection signal level obtained when the intensity of the emission spectrum of the specific wavelength is a preset constant intensity, so the comparator detects that the detection signal is at a higher level than the reference signal. After that, that is, after the intensity of the emission spectrum of the specific wavelength exceeds a predetermined intensity, a signal at a predetermined logic level is output.

The output signal of this comparator is supplied as a control signal to valve means to prevent Freon gas from flowing into the plasma emission chamber.

As a result, when the intensity of the emission spectrum of the specific wavelength exceeds a predetermined intensity, the gas flowing into the plasma emission chamber is switched from the mixed gas to only oxygen gas.

(Embodiment) Fig. 1 shows a block diagram of an embodiment of the device of the present invention.
The microwave guided by is introduced through a microwave transmission window 8 made of a dielectric material or the like, and oxygen gas (O2) is introduced through a conduit 9, and
Freon gas (CF4) is introduced through a conduit 10 which is provided with a solenoid valve 11 along the way.

By introducing microwaves into a submerged plate into which a mixed gas of oxygen and Freon gas (CFs) has been introduced, plasma is generated in the plasma emission chamber 6, and oxygen radicals <01
) and fluorine radicals (Fl) are respectively dissociated.

Between the plasma-emitting seedlings 6 and the ashing chamber 13, there is a window 1 made of metal, for example, that does not allow plasma to pass through but only allows radicals to pass through.
2, the ashing chamber 13
Inside are the oxygen radicals (O*) and fluorine radicals (
F8) is introduced.

A sample 14 having a resist to be ashed is placed in the ashing chamber 13, and ashing of unnecessary resist is started. Note that 15 is an exhaust port.

A quartz window 16 is provided in a part of the ashing chamber 13, and light generated by the ashing is incident on the spectroscopic analyzer 17 through the quartz window 16.

Here, when the resist is ashed with oxygen radicals,
An emission spectrum of CO is generated. Therefore, in this embodiment, the spectroscopic analyzer 17 is configured to detect only the intensity of the CO emission spectrum and output a detection signal of a level corresponding to the detected intensity.

The output detection signal of the spectroscopic analyzer 17 is supplied to a comparator 18, where the levels are compared with a first reference signal from an input terminal 19 and a second reference signal from an input terminal 20, respectively. The first reference signal is selected to have the same level as the output detection signal level of the spectroscopic analyzer 17 obtained when the intensity of the 00 emission spectrum reaches a predetermined value. This predetermined value is, for example, the value shown by 11 in FIG. 2, which is the optimum value in consideration of the condition that the etching G due to fluorine radicals (Fl) of the base is below the specified value and the condition of shortening the ashing time. is set in advance.

The second reference signal mentioned above is selected to correspond to the detection signal level when all the resist has been ashed, and the intensity of the 00 emission spectrum at this time is the CO emission intensity shown at 12 in Figure 2. This is when the end point is detected.

When ashing is started as described above, the intensity of the 00 emission spectrum increases with the passage of time, as shown by the solid line ■ in FIG. 2, and the output detection signal level of the spectroscopic analyzer 17 also increases correspondingly. do.

The comparator 18 is configured such that the level of the input detection signal is lower than the first reference signal from the start of ashing. During the period up to the time indicated by , a control signal to open the solenoid valve 11 is being sent. Therefore, a mixed gas of oxygen (O2) and Freon gas (CF4) continues to be introduced into the plasma emission chamber 6 until time 1.

Conventionally, as described above, the above-mentioned mixed gas continues to be introduced into the plasma emission chamber 6 until the end point is detected, but in this case, the CO emission spectrum intensity changes as shown by the dashed line ■. , the end point is detected in a short time, but m becomes large as the base of sample F114 is etched by fluorine radicals (Fl).

In contrast, in this embodiment, when the intensity of the emission spectrum of the GO reaches a predetermined value shown by 11 in FIG. Therefore, once the comparator 18 enters this state, it supplies the solenoid valve 11 with a control signal of a logic level different from that before, and the solenoid valve 11
to close the conduit 10.

As a result, the intensity of the emission spectrum 1- of co reaches the predetermined li+ shown in FIG. 2 at time 1. From then on, the Freon gas (CFJ) is prevented from flowing into the plasma emission chamber 6, and only oxygen (02) is allowed to flow into the plasma emission chamber 6.

As a result, time 1. From then on, only oxygen radicals (0*) will be introduced into the ashing chamber 13, so
Etching by fluorine radicals (Fl) of the base of sample 14 is not performed, and only the resist continues to be ashed.

As a result, the intensity of the emission spectrum of co changes as shown by the solid line ■ in FIG. 2 after time t in this embodiment. At the time indicated by tl in FIG. 2, the comparator 18
is a signal that detects that the input detection signal level has become lower than the second reference signal level, detects the end point, and turns off the power source, etc. of the microwave generation source (not shown) via the terminal 21. Output.

Note that immediately after the start of ashing, the input detection signal of the comparator 18 is lower than the second reference signal level, but the comparator 18 is made not to operate for a certain period of time immediately after the start of ashing (or there is a delay before it starts operating). (there is a time limit), and at the time when the comparator 18 starts the level comparison operation, the detection level is always higher than the second reference signal level.

In this way, as can be seen from FIG. 2, according to this embodiment, time 1. From then on, ashing is performed using only oxygen radicals, so the ashing speed will be slightly slower than before, but test F! Etching m of the base portion other than the resist in V14 is at time t. This can be suppressed to a very small amount due to the previous period.

〔Effect of the invention〕

As described above, according to the present invention, when the intensity of the emission spectrum of a specific wavelength exceeds a preset certain intensity, the gas flowing into the plasma emission chamber is replaced with Freon gas (CF4).
) and oxygen (02) to only oxygen, the etching caused by fluorine radicals on the underlying part of the sample where there is no resist is significantly suppressed without significantly reducing the ashing speed. As a result, it has the advantage of being able to perform resist ashing, which greatly contributes to improving device characteristics.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the apparatus of the present invention, FIG. 2 is a diagram showing an example of the relationship between ashing time and CO emission intensity, and FIG. 3 is a cross-sectional view of an example of the main part of a sample. . In the figure, 6 is a plasma emission chamber, 9.10 is a pipe, 11 is a solenoid valve, 12 is a window, 13 is an ashing chamber, 14 is a sample, 16 is a quartz window, 17 is a spectroscopic analyzer, 18 is a comparator, Reference numerals 19 and 20 are reference signal input terminals. at figure 2

Claims (1)

[Claims] Only the radicals in the plasma generated in the plasma emission chamber (6) using a mixed gas of oxygen and Freon gas are introduced into the ashing chamber (13) to remove the resist on the sample (14). In a dry ashing device that performs ashing, the intensity of an emission spectrum of a specific wavelength that occurs when resist is present on the sample (14) in the ashing chamber (13) is detected, and a detection signal of a level corresponding to the intensity is output. detection means (16, 17) for controlling the flow rate of the Freon gas flowing into the plasma emission chamber; and a valve means (11) for controlling the flow rate of the Freon gas flowing into the plasma emission chamber, and comparing the levels of the output detection signal of the detection means and a reference signal, respectively, and detecting the It is characterized by comprising a comparator (18) that outputs a control signal that controls the valve means to prevent the Freon gas from flowing into the plasma emission chamber after the intensity exceeds a preset certain level. Dry ashing equipment.