JPH0142628B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application This invention detects the processing state during surface processing of a substrate such as etching processing in the manufacturing process of a photomask, and accurately detects the end point of the processing. It is about the method.

(b) Prior art Photomasks used in the manufacture of semiconductors are usually manufactured through a process in which a photoresist is applied to a substrate such as glass with a thin layer of metal deposited on the surface, and a photoresist film is formed on the substrate. It is created through the steps of patterning the photoresist film by printing a predetermined mask pattern on the film and then developing it with a predetermined developer, and etching the metal thin film exposed by the development process. Among the steps for creating such a photomask,
In particular, since highly accurate processing is required in the etching process, it is necessary to accurately control the end point of the process. Therefore, various attempts have been made to detect the end point of this etching process with high precision. For example, JP-A-56-158872
In this issue, a light transmittance measurement area is provided outside the effective area on the photomask surface to detect the progress of etching, the light transmittance in this area is measured, and the end point of the etching process is detected from the measurement results. A method is proposed.

However, in this prior invention, the method of detecting the end point of the etching process is to take the difference between the two sample values before and after the amount of transmitted light, and then calculate the difference between the two sample values before and after the amount of transmitted light.
This method calculates the end point of the etching process by averaging around 10 points and detecting when the average value approaches zero. If there is an oxide film on the metal thin film that is poorly soluble in the etching solution, there is a risk that the temporary stagnation may be regarded as the end point of the etching process before the etching process reaches its true end point. There is. In addition, the amount of light transmitted through a glass substrate on which a metal thin film is deposited varies depending on the type of metal being deposited, the presence or absence of an oxide film of this metal, the material and thickness of the glass substrate, etc. The etching process has the disadvantage that it is not possible to accurately detect the end point of the etching process.

On the other hand, as a means for holding glass substrates etc. in a rotary processing device (spinner) that performs surface treatment, a vacuum chuck system using a vacuum chuck on the spinner head is generally used. A simple type of fixed holding arm type holding device is known.

When using this simple fixed holding arm type spinner head, the arms that hold the four corners of a glass substrate, etc., intermittently interrupt the light beam used to detect the amount of light transmitted through the substrate. Therefore, in the above-described averaging process, it becomes more difficult to accurately detect the end point of the etching process.

In addition, the applicant of the present application had previously filed the patent application in Japanese Patent Publication No. 62-
No. 40701 and Japanese Unexamined Patent Publication No. 59-215727 have filed applications for methods for detecting the end point of surface treatment similar to the present application, but both methods involve photoelectric conversion of a light beam transmitted (or reflected) through a plate-like object to be treated. It detects whether the level of the detection signal obtained by This was a method in which when the temperature no longer exceeded even after a certain period of time had elapsed, that point was regarded as the end point of the surface treatment.

However, with these methods, it is not possible to check whether the surface treatment is progressing uniformly over the entire surface of the plate-like object to be treated, so it is possible that the surface treatment has progressed only on a part of the plate-like object to be treated. Even in some cases, there was a problem in that the end point of the surface treatment could be mistakenly detected.

(c) Purpose of the Invention This invention was made to solve the disadvantages of the conventional method described above and the difficulties of the invention already filed by the applicant, and it uses the simple fixed holding arm type spinner head described above. It is an object of the present invention to provide a new method that can extremely accurately detect the end point of surface treatment such as etching treatment, regardless of the photomask's characteristics of the amount of transmitted light.

(D) Structure of the Invention The present invention provides that, as shown in FIG. This was done based on the knowledge that as the processing progresses, the characteristics of each transmitted light amount become almost similar.The structure is based on the fact that the amount of transmitted light to the plate-shaped object to be processed is detected by a photoelectric conversion element, and this In the method of detecting the surface treatment state of the plate-like object to be treated from a change in the detection level, it is detected whether the detection level exceeds a predetermined target level a predetermined number of times in a row within a predetermined time, and when the detection level exceeds the target level, , setting a next new target level and repeatedly detecting whether the detection level exceeds this newly set predetermined target level within a predetermined time;
When it is detected that the detection level no longer exceeds a predetermined target level for a predetermined number of consecutive times within a predetermined time, this point is set as the end point of the surface treatment. In addition, in this invention, by detecting a relatively large initial target level at the beginning of processing, the processing state can be accurately detected without being influenced by the transmitted light amount characteristics that change in various ways at the beginning of processing. As the processing progresses, the detection accuracy is increased by setting and detecting finer target levels. When it is detected that the limit is no longer exceeded, the process ends at this point.

(E) Embodiments of the Invention FIGS. 2 and 3 show a schematic configuration of a fixed holding arm type spinner head used in carrying out the present invention, and FIG. 2 shows a plan view of the head. 3 is a side cross-sectional view of the - line cross-section viewed in the direction of the arrow.

In these drawings, a plate-like object 1 to be processed is a glass substrate or a semiconductor substrate G made of silicon, etc., on which a metal thin film is deposited, a photoresist is applied and dried to form a photoresist film on the upper surface, and then a photoresist film is formed. , a predetermined pattern is printed and developed on this photoresist film. The head part has a central part C coaxially connected to the spindle SP,
Arms 2 are arranged radially from the center C at equal angular intervals in a horizontal plane, and a pair of substrate holding pins 3 are formed on the upper surface of the tip of each arm 2.
and a substrate mounting pin 4. The plate-shaped object 1 to be processed is placed on the substrate mounting pin 4, and is placed on a horizontal surface while its four corners are held by the substrate holding pins 3. It is designed so that it can be rotated internally.

Further, as shown in an example in FIG. 4, a disk 17 having the same number of notches 18 as the arms 2 is fixed to the spindle SP, and the notches 18 of the disk 17 are detected. In order to do this, a photo sensor 16 is provided opposite the disc 17.

The light amount detection unit S is connected to the board mounting pin 4 of the arm 2.
A light-receiving fiber 5 and a light-emitting light are arranged opposite to the upper and lower surfaces of the plate-like object 1 to be processed placed horizontally above, and one end of which is connected to a light-receiving element 8 and a light-emitting element 8', respectively. It consists of a fiber 6 and a holder 7 that holds the light receiving end and the light emitting end of these optical fibers 5 and 6, respectively, and is designed to detect the amount of light transmitted to the plate-shaped object 1 to be processed. ing. Incidentally, it is necessary to hold the light-receiving end and the light-emitting end of these optical fibers 5 and 6 so that the etching solution from a spray nozzle (not shown) will adhere to them. Furthermore, the light-emitting fiber 6 may be omitted and the light-emitting element 8' may be provided directly facing the light-receiving end of the light-receiving fiber 5.

FIG. 5 is a schematic diagram of the entire apparatus for carrying out the method according to the present invention. 8 in the same figure is
A photoelectric conversion element converts the transmitted light transmitted by the light-receiving optical fiber 5 into an amount of electricity (voltage) corresponding to the amount of light, and 9 is an amplifier that amplifies the output of the photoelectric conversion element 8. , the output signal amplified by this amplifier 9 is sent to the A/D converter 1
0 and is also input to one terminal of the comparator 11. The output signal from the central processing unit (CPU) 14 is input as a reference voltage to the other terminal of the comparator 11 via the D/A converter 12, and the output signal from the amplifier 9 is higher than this reference voltage. When this happens, the comparator 11 is configured to output a pulse-like discrimination signal Ep.
The discrimination signal Ep output from the comparator 11 is
After being input to the counter circuit 13 and processed as described later, the signal is input from the counter circuit 13 to the CPU 14 as an END signal.

The CPU 14 selects predetermined reference level values E ₁ and E ₂ (E ₁ > E ₂ ), which will be described later and is preset in the built-in memory, according to the detected transmitted light amount level, and for example, V _o1 = V _{(o- 1) Perform a calculation corresponding to 1} +E ₁ (n=2, 3,...), and convert this calculated value to an analog reference voltage (target level) via the D/A converter 12.
Set it to comparator 11 as V _o1 , and
14 and the predetermined time set in the built-in timer,
The processing state of the plate-shaped object 1 to be processed can be detected.

The counter circuit 13 described above can be composed of an AND gate 131, a flip-flop F/F circuit 132, and a counter 133, as shown in FIG. As shown in FIG. 7a, the detection signal is compared with a target level (indicated by a dotted line) in the comparator circuit 11, and only the detection signal exceeding the target level is inputted as a discrimination signal Ep as shown in FIG. 7b. This discrimination signal Ep is output from the AND gate 131 as a pulse-like signal as shown in FIG. 7D only while the AND gate 131 is opened by the gate signal <FIG. 7C> from the photo sensor 16. The output from this AND gate 131 then sets the F/F circuit 132 to "1"<The F/F circuit 132 is reset at the fall of the gate signal>, and a pulse signal as shown in FIG. 7e is generated. These pulse signals output from the F/F circuit 132 are then counted by a counter 133, and when the count reaches a preset number, for example 4, the counter 133 is
Outputs the END signal as shown in . Note that this counter 133 is configured to be reset by a pulse signal corresponding to one revolution of the spinner head.

Next, specific procedures for carrying out the invention using this apparatus will be explained with reference to the flowcharts shown in FIGS. 8 and 9.

First, a plurality of reference level values (level values serving as a guideline for detecting the etching processing state) E ₁ and E ₂ and detection times T ₁ and T ₂ are input to the CPU 14 using an input device (not shown). Set in internal memory (step,).

In this case, the reference levels E ₁ , E ₂ and detection times T ₁ , T ₂ are appropriately determined through experiments, etc., but in this invention, as the etching process progresses, the detection accuracy of the processing state is improved. In order to increase the value, E ₁ ≫ E ₂ is set.

Once this setting is completed, the amount of transmitted light unique to the plate-shaped object 1 to be processed before processing is measured, and the detected signal level V ₁ ' (= V ₁₁ ) at that time is stored in the internal memory of the CPU 14 (step 1). ).

Then, the etching process starts (step).
Activate the timer at the same time (step).

The setting time _T1 of this timer is the plate-like object 1 to be processed.
It is preferable to select the time at which the amount of transmitted light begins to change due to etching of the surface.

Note that this timer may be configured with a counter, and the processing time may be controlled by counting required pulse signals.

When the initial setting time T ₁ has elapsed, the CPU 14
Using the first reference level value E ₁ stored in the internal memory, perform the calculation V ₂₁ =V ₁₁ −E ₁ ,
Using this calculated value as the reference voltage (target level), D/
It is input to one terminal of the comparator 11 via the A converter 12 (step). Also, timer _T2 is set (step).

When the etching process starts in the step,
Since the spinner head rotates at a constant rotational speed as described above, in FIG. It is cut off every 1/4 rotation by the four arms 2 shown in FIG. 2, and as a result, the detection level of the output signal from the photoelectric conversion element 8 changes as shown in FIG. Note that in FIG. 10, V ₀ is the detection level of the output signal from the photoelectric conversion element 8 when the irradiation light beam is interrupted by the arm 2, and V ₁ ′ (=V ₁₁ ) is
This is a detection level corresponding to the amount of light transmitted through the plate-shaped object 1 to be processed before etching processing. As the etching process on the plate-like object 1 progresses, the amount of transmitted light of the light beam irradiated onto the plate-like object 1 gradually increases.
The photoelectric conversion element 8 outputs a pulse signal as shown in FIG. This is a clock pulse-like signal outputted according to the mask pattern applied to the plate-like object 1, that is, the portion where the photoresist remains and the portion from which the resist has been removed. Only the signals from the parts are schematically shown.

When the timer exceeds the set time _T1 , the comparator 11 compares the detected signal level with the target level _V21 , checks whether the detected signal level exceeds the target level _V21 , and sets the target level _V21 . If it exceeds, the comparator 11 outputs a discrimination signal Ep to the counter circuit 13. This counter circuit 13
Now, as mentioned above, the F/F circuit 1 is activated for each area divided by arms, for example, by the discrimination signal Ep.
32 is set to create a pulse signal, and when this pulse signal is input to the counter 133 consecutively, for example four times, the counter circuit 13
Outputs the END signal to the CPU 14 (step).
This is to confirm that the processing is progressing to the same extent in all regions of the plate-like object 1 divided by the arms 2 of the spinner head. If the time t at that time is shorter than the set time T ₂ , the CPU 14 sets the first target level to V ₃₁ =
Reset to V ₂₁ +E ₁ . and at the same time set the timer
Reset to T ₂ (step).

By repeating steps ~ in this way, the time required for the counter 133 of the counter circuit 13 to count the pulse signal <Fig. When t becomes longer than the set time T ₂ ,
Move from step to step. Then, a second target level V _o1 =V _(o-1)1 +E ₂ is set from the first target level (step). Here, E ₂ is a second reference level value that is much smaller than the first reference level value E ₁ .

At the same time, _T2 is set on the timer, the detected signal level and the target level are compared, and when the pulse signal from the F/F circuit 132 of the counter circuit 13 is counted, for example, four times in succession by the counter 133, In other words, when the detection signal level corresponding to the transmitted light amount level of each region of the plate-like object to be processed divided by the arm exceeds the target level for each region, the counter circuit 13 outputs END.
A signal is output to the CPU 14, and if the time t at this time is shorter than the set time _T2 , the process returns from step to step and a new target level is set again.

If the time t is longer than the set time _T2 in the step, the process moves to the step, and that point is set as the end point of the surface treatment, and the surface treatment is stopped.

By the way, in the flowchart of the embodiment, the end point of the surface treatment is detected at the second target level V _o1 =V _(o-1)1 + _E2 , but the third target level and the third target level are detected as necessary. 4 target levels may be further set. Furthermore, the number of arms 2 that hold and fix the plate-like object 1 to be processed shown in FIG.
33 is when the pulse signal from the F/F circuit 132 is counted three times in succession.

In the above embodiment, the end point of the surface treatment is detected based on the change in the amount of light transmitted through the plate-like object to be processed. It is also possible to detect the end point of the surface treatment as described above. Further, in the above-described embodiments, the surface treatment of the plate-like object to be processed was explained as etching treatment, but the method according to the present invention can also be applied to detecting the end point in the development treatment of, for example, a substrate.

(F) Effects of the Invention As explained above, the present invention continuously detects the amount of transmitted light or the amount of reflected light with respect to the plate-like object to be processed using a photoelectric conversion element, and detects the amount of light transmitted or reflected from the plate-like object to be processed based on the change in the detection level. In the method for detecting a surface treatment state, detecting whether the detection signal level exceeds a predetermined target level a predetermined number of times consecutively within a predetermined time, and setting the next target level when the level exceeds the predetermined target level. repeatedly detects changes in the detection signal level, and when it is detected that the detection signal level no longer exceeds a predetermined target level within a predetermined time, a new target level that is finer than the target level is set. Finally, the end point of the surface treatment is the point at which the detection signal level no longer exceeds this new target level within a predetermined time. It is possible to accurately detect whether the detection signal levels of all the divided regions exceed the target level.

In other words, even when surface treatment is carried out on a plate-shaped object to be processed while being held in a simple spinner head using a fixed holding arm, the detection signal level will exceed a predetermined target level consecutively for a predetermined number of times within a predetermined time. Since the end point of this surface treatment is set at the point in time when the particles disappear, it is possible to detect the end point of the treatment over almost the entire area of the plate-like object to be treated.

Furthermore, in the method according to the present invention, if the target level is set high at the beginning of the surface treatment, no matter how the transmitted light amount characteristics of the surface treatment change at the beginning, the treatment state can be maintained accurately without being affected by such changes. can be detected. Furthermore, as the surface treatment progresses, finer target levels are set,
Since this target level is compared with the detection signal level, the accuracy of detecting the end point of surface treatment can be improved.

[Brief explanation of drawings]

Figure 1 is a characteristic curve diagram showing the change in the amount of light transmitted through various plate-like objects as the processing time t elapses, Figure 2 is a plan view of the simple spinner head, and Figure 3 is its 4 is a plan view showing one embodiment of the gate signal generating means provided in the spinner head, and FIG. 5 is a device used to carry out the method according to the present invention. Explanatory diagram showing the configuration of the main part of the example, No. 6
7 are a block diagram and timing chart showing an embodiment of the counter circuit of FIG.
8 and 9 are flowcharts for explaining the embodiment of FIG. 5, and FIG. 10 is a diagram showing an example of the detection signal level as the processing time elapses. 1... Plate-shaped object to be processed (photomask), 8...
Photoelectric conversion element, E ₁ ...first reference level value, E ₂ ...
...Second reference level value, T ₁ , T ₂ ...Setting time.

Claims (1)

[Scope of Claims] 1. A light beam is irradiated onto a predetermined portion of a plate-like object to be surface-treated, and the amount of transmitted light or reflected light of the plate-like object to be processed corresponding to the irradiated light beam is detected, and the level of this detection signal is determined. In a surface treatment method in which the end point of the surface treatment is detected based on a change in and when the detection signal level exceeds the new predetermined target level, a new predetermined target level is set, and the end point of this surface treatment is set at the time when the detection signal level no longer exceeds the new predetermined target level within a predetermined time. A surface treatment method characterized by: 2. The surface treatment method according to claim 1, wherein the target level to be set can be selected depending on the progress of the surface treatment. 3. The surface treatment method according to any one of claims 1 to 2, wherein the surface treatment of the plate-shaped object to be treated is an etching treatment. 4. The surface treatment method according to any one of claims 1 to 2, wherein the surface treatment of the plate-like object to be treated is a development treatment.