JPH0142627B2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field The present invention is a technology that detects the processing status during surface processing of a substrate such as etching processing when manufacturing photomasks, and automatically detects the end point. It is related to.

(b) Prior art Photomasks used in the manufacture of semiconductors usually involve a process of applying a photoresist to a substrate such as glass on which a metal is vapor-deposited, and then printing a mask pattern onto the photoresist film, and then applying the required pattern. It is created through a process of patterning a photoresist film by developing it with a developer, and a process of etching the metal thin film exposed by the development process. Among the photomask manufacturing steps, particularly the etching step requires highly accurate processing, and accurate control of the end point is required. For this reason, various attempts have been made to detect the end point of this etching process with high precision. For example, in JP-A-56-158872, a light transmittance measurement area is provided outside the effective area on the photomask surface to detect the degree of progress of etching, and the light transmittance in that area is measured. A method has been proposed for detecting the end point of etching from the results.

However, in this prior invention, the method of detecting the end point of etching is to take the difference between two sample values before and after the amount of transmitted light and average it over about 10 consecutive points. In cases where the progress of etching temporarily stagnates, for example, when there is a poorly soluble oxide film on the deposited metal thin film, etching may be performed with the above stagnation before reaching the true end point of the etching process. There is a risk that it will be seen as the end point of the process. In addition, the amount of light transmitted through a glass substrate on which a metal thin film is deposited is
Since it varies depending on the type of metal, the presence or absence of an oxide film of the metal, the material and thickness of the glass substrate, etc., it is difficult to accurately detect the end point of the etching process with the above-mentioned averaging process. There is a drawback that it cannot be done.

On the other hand, as a means of holding a glass substrate, etc. to a rotating processing device (spinner) during surface treatment, a vacuum chuck system using a vacuum chuck on the spinner head is generally used. A simple fixed-holding machine system that holds the device fixedly is known. When using such a simple fixed holding device, the device for holding the four corners of the glass substrate, etc., intermittently blocks the light beam for detecting the amount of light transmitted through the substrate, etc. Therefore, it becomes even more difficult to accurately detect the end point of the etching process using the above-described averaging process.

(C) Purpose of the Invention The present invention has been devised to solve the inconveniences of the conventional method, and even when using the above-mentioned simple fixed holding device, or with a photomask having any transmitted light quantity characteristics. Another object of the present invention is to provide a new method that can extremely accurately detect the end point of surface treatment such as etching treatment.

(D) Structure of the Invention This invention provides that, as shown in FIG. This was done based on the knowledge that the light intensity characteristics are almost similar, and the structure is such that the amount of transmitted light to the object to be processed is detected by a photoelectric conversion element, and the amount of light transmitted to the object to be processed is detected by the change in the detection level. In the method of detecting the surface treatment state of
The target level is set in detail one after another, and changes in the detection level are repeatedly detected. When it is detected that the detection level no longer exceeds the target level within a predetermined time, surface treatment is started at that point. It is characterized in that it is the end point of . That is, in the present invention, by increasing the initial target level and performing detection at the beginning of processing, it is possible to accurately detect the processing state without being influenced by the transmitted light amount characteristics that change in various ways at the beginning of processing. As processing progresses, detection accuracy is increased by setting and detecting more detailed target levels, and when it is detected that the detection level no longer exceeds a predetermined target level within a predetermined time. , this point in time is the end point of the process.

(E) Embodiments of the Invention Figures 3 and 4 show a schematic configuration of a fixed-holding type spinner head used in carrying out the present invention, of which Figure 3 shows a plan view of the head. and FIG. 4 shows a side sectional view thereof.

In these drawings, an object to be processed 1 is a metal thin film deposited on the surface of a glass substrate or a semiconductor substrate G made of silicon, etc., a photoresist is coated on the upper surface, and after drying, a desired pattern is formed on the photoresist. It is printed and developed. The head part 2 includes a central part C coupled to a spindle SP, arms B extending equidistantly in all directions in a horizontal plane from the central part C, and a pair of substrate holding pins formed on the upper surface of the tip of each arm B. 3 and a substrate mounting pin 4, the workpiece 1 is placed on the substrate mounting pin 4, and is moved in a horizontal plane while its four corners are held by the substrate holding pins 3. It is designed so that it can be rotated. The light amount detection unit S includes a pair of light-receiving fibers 5 and light-emitting fibers 6, which are arranged to face the upper and lower surfaces of the workpiece 1 placed horizontally on the substrate mounting pins 4 of the arm B. , and a holder 7 for holding the light-receiving end faces and light-emitting end faces of these fibers 5 and 6, and is adapted to detect the amount of light transmitted to the object 1 to be processed.

FIG. 5 shows a schematic diagram of the entire structure including the spinner head section 2. As shown in FIG. In this figure, reference numeral 8 denotes a photoelectric conversion element that converts the light transmitted by the light-receiving fiber 5 into an amount of electricity proportional to the amount of light. In this embodiment, as shown in FIG. When the amount of light received by 5 increases, the conversion element 8
The output voltage of is configured to decrease. 9
is an amplifier that amplifies the output of the conversion element 8, and its output V ₁ is input to the A/D converter 10 and also to one terminal of the comparator 11. The output V ₂ of the D/A converter 12 is input as a reference voltage to the other terminal of the comparator 11, and the output V ₁
is configured to output a discrimination signal Ep when the voltage becomes equal to or less than the reference voltage _V2 . Also, the discrimination signal
Ep is held in the latch circuit 13 for a predetermined time and is input to the CPU 14 as an END signal, which will be described later.
The CPU 14 selects from predetermined reference level values E ₁ , E ₂ , E ₃ preset in the built-in memory according to the detected amount of transmitted light level, and calculates V _o+1 = Vn.
-E Performs calculations corresponding to _{1 to 3} , and converts the calculated values to the analog reference potential via the D/A converter 12.
It is output to the comparator 11 as V _o+1 , and the corresponding
The processing state of the object to be processed 1 can be detected based on the END signal inputted to the CPU 14 and a predetermined time set in a built-in timer.

Next, specific procedures for implementing the present invention using such an apparatus will be explained based on the flowcharts shown in FIGS. 6 to 8.

First, a plurality of reference level values (level values serving as a guideline for detecting the processing state) E ₁ to E ₃ and detection times T ₁ and T ₂ are set using an input device (not shown) (step). . In this case, the reference level values E ₁ to _{E 3} and the detection times T ₁ and T ₂ should be appropriately selected through experiments, etc., but in this invention, as the etching process progresses, the processing state is changed. In order to increase detection accuracy, E ₁ > E ₂ > E ₃ T ₁ > T ₂ are set.

Once these settings are completed, next is the workpiece 1 before processing.
The specific amount of transmitted light corresponding to is measured, and the detection level V ₁ ' at that time is stored in the memory of the CPU 14 (step). Next, the etching process is started (step) and a timer is activated at the same time. (step). The setting time _T1 of this timer is, for example, the time when each transmitted light amount characteristic is almost stabilized, as shown in Figure 2.
It is preferable to select T ₁ .

Note that this timer may be configured with an appropriate counter.

Next, the reference level value E ₁ stored in the built-in memory of the CPU 14 is used to calculate V ₂ ′=V ₁ ′−E ₁ , and the calculated value is used as the reference voltage (target level) for the D/A converter. 12 to one terminal of the comparator 11 (step).

At this time, since the spinner head section is being rotated at a constant speed due to the start of the etching process, the light beam from the light source 8' irradiated from the projection fiber 6 is halved by the arm B shown in FIG. It is periodically interrupted every 4 rotations, and as a result, the photoelectric conversion element 8
The detection level of the output signal from the sensor changes periodically as shown in FIG. Furthermore, in this figure 9
V ₀ is the detection level of the output signal from the photoelectric conversion element 8 when the irradiation light beam is blocked by arm B, and V 1 is the detection level of the output signal from the photoelectric conversion element 8 when the irradiation light beam is blocked by arm B, and V _{1 is the detection level of the output signal from the photoelectric conversion element 8 when the irradiation light beam is interrupted by arm B, and V 1} is the detection level of the output signal from the photoelectric conversion element 8 when the irradiation light beam is interrupted by arm B, and V 1 is the detection level of the output signal from the photoelectric conversion element 8 when the irradiation light beam is blocked by arm B. Time photoelectric conversion element 8
is the detection level of the output signal from. As the etching process on the object 1 progresses, the amount of transmitted light of the light beam irradiated onto the object 1 gradually increases, and as a result, the photoelectric conversion element 8 outputs a pulse signal as shown in FIG. . This is output at intervals corresponding to the mask pattern applied to the object 1, that is, the portion where the photoresist remains and the portion from which the resist has been removed.

Next, the CPU 14 sets, for example, "3" in the built-in register as an initial value for counting the END signals latched in the latch circuit 13 based on the control program (step), and then
Repeatedly checks the presence or absence of the END signal (step). Then, as the etching process progresses, the level of the pulse signal output from the photoelectric conversion element 8 reaches the target level V ₂ '=V ₁ '-E ₁ as shown in FIG.
When the signal level exceeds , the comparator 11 outputs a discrimination signal Ep, which is latched by the latch circuit 13 and inputted to the CPU 14 as the END signal. When the CPU 14 detects this END signal,
In the next step, the initial value "3" set in the register in the CPU 14 is decreased by "1", and then the latch circuit 13 is reset in response to a command from the CPU 14 (step). Next, it is checked (step) whether the contents of the register have become ``0'', and if it is not ``0'', the process returns to the step again and the presence or absence of the END signal is checked.
On the other hand, if the contents of the register are "0", the CPU 14 sets an E flag in a predetermined register indicating that the first target level V ₂ ' has been completely exceeded (step). In this case, it is desirable that the output pulse signal continuously exceed the target level. In the next step, it is checked whether the T flag is set. This T flag is set by interrupt processing when the timer stops.
This is set by the CPU 14 (step). At this time, the CPU 14 also checks whether or not the E flag is set (step). If the E flag is set, the CPU 14 ignores the previous processing and proceeds to the step described below. If the E flag is not set, the process moves to step processing.
Similarly, as a result of the check in the above step,
If the T flag is not set, the process jumps to the step described below, and if the T flag is set, the process moves to the next step. That is, as shown in FIG. 2, the detection level for the object 1 is
If the first target level V ₂ ' is exceeded before time T ₁ has elapsed, the step jumps to a narrower reference level E ₃ corresponding to the amount of transmitted light, as shown in Figure 2. Check the change in the detection level, and if the detection level does not exceed the first target level V ₂ ' even after T ₁ hour as shown in Figure 2, increase the above reference level step by step. It is made smaller (E ₂ →E ₃ ) and the change in detection level corresponding to the amount of transmitted light is checked. This makes it possible to detect the process status in detail according to the speed of progress of the etching process.

Returning to the flowchart of FIG. 7, if the T flag is set as a result of the check in step, the CPU 14 calculates V ₂ ''=V ₂ '-E ₂ as the next target level V ₂ ''. The calculated value is input to the comparator 11 via the D/A converter 12 (step). Subsequently, the process proceeds to the step shown in FIG. 8 through a process similar to the process from step to step described above. In this step, calculate V ₂ = V ₂ ″−E ₂ as the next target level V ₂ .
The CPU 14 performs the calculation, and inputs the calculated value to the comparator 11 via the D/A converter 12 in the same manner as in the previous step. Thereafter, for example, "3" is set in the register of the CPU 14 as an initial value for counting the END signal (step 〓〓), and then the timer is activated (step). this is,
This is because, as shown in FIG. 2, the change in the detection level with respect to the amount of light transmitted through the object 1 to be processed thereafter is limited to a detection time of T ₂ to detect the processing state.

Next, the CPU 14 controls the latch circuit 13.
Check the presence or absence of the END signal (step 〓〓),
If the END signal is output, the same processing as that from step to step is executed from step to step. If the result of the check in step <<> is that the content set in the register is "0", the timer is reset and the process returns to step processing again. And at this time the next target level V ₂
As ``V ₂ ''''=V ₂ -E ₃ is calculated by the CPU 14, and the calculated value is input to the comparator 11.

Also, as a result of the check in step 〓〓,
If the END signal is not latched in the latch circuit 13, it is checked in the next step 〓〓 whether or not a time has elapsed, and if the time has not exceeded, the process returns to step 〓〓 and checks the presence or absence of the END signal.

In this way, until the amount of light transmitted to the object 1 hardly changes, in other words, until the END signal latched to the latch circuit 13 in response to the discrimination signal Ep from the comparator 11 is no longer output, The steps from the above steps are performed while updating the reference values that have been set to lower level values sequentially.
Repeat each process up to .

Then, the result of the check in step 〓〓 is
If the operation time of the timer exceeds the detection time _T2 mentioned above, the etching process can be considered to have ended, so this point is considered the end point (step) of the process, and the etching process is stopped in the following step. let

In the above embodiment, the end point of surface treatment such as etching is detected based on the change in the amount of light transmitted through the object to be processed. From the change, it is also possible to detect the end point of the surface treatment as described above.

Furthermore, in the above-described embodiments, the surface treatment of the object to be treated is described as etching treatment, but the method according to the present invention can also be applied to, for example, detection of the end point in development treatment of a substrate or the like.

Furthermore, in the above embodiment, CPU1
The new target level calculated in step 4 was created by selecting and subtracting the reference level value E ₂ or E ₃ from the target level, but the method according to the present invention is limited to such a method of creating the target level. For example, the CPU 14 detects the pulse signal level output during surface treatment, as shown in FIG. 9, and subtracts the reference level value E ₂ or E ₃ from the minimum level of the pulse signal levels. It is also possible to set the target level as a new target level, and in that case, there is an advantage that the target level can be set very efficiently. In other words, in the above embodiment, only the number of pulses exceeding the target level is detected, but the level is not detected, so the level of the pulse signal has already exceeded the target level to be set next. If the level of the pulse signal already exceeds the target level to be set next without checking whether the target level is the same or not, there is no point in setting the target level. Therefore,
When setting a new target level, it is more practical to subtract the reference level value E ₂ or E ₃ from the minimum level of the pulse signal that exceeded the previous target level to set the next new target level. I can say that there is.

In addition, in the method according to the present invention described above, the pulse signal level output according to the amount of transmitted or reflected light from the object to be processed is divided by the arm B of the head section 2 (in the case of the embodiment of the present invention). 4 pieces)
For example, when the averaged pulse signal exceeds a predetermined target level four times in a row, a new required target level is set, and the setting of the target level is repeated as necessary. Thereafter, when the target level is no longer exceeded, for example, four times in a row within a predetermined period of time, the end point of the surface treatment can be determined at that point.

(f) Effects of the Invention As explained above, the present invention continuously detects the amount of light transmitted through the object to be treated using a photoelectric conversion element, and detects the surface treatment state of the object from changes in the detection level. In the method, it is detected whether the detection level exceeds a predetermined target level within a predetermined time, and when it changes, the target level is sequentially set finely, and the change in the detection level is repeatedly detected, and the detection level is set. When it is detected that the level no longer exceeds a predetermined target level within a predetermined time, that point is considered as the end point of surface treatment, so the initial target level is set high at the beginning of surface treatment. By doing so, no matter how much the transmitted light quantity characteristics of the surface treatment change at the beginning, the treatment state can be accurately detected without being affected by such changes. Further, as the surface treatment progresses, a finer target level is set and the detection level is detected, so the accuracy of detecting the end point of the surface treatment can be further improved. In addition, since it is configured to change the size of the target level that is determined thereafter depending on the amount of change in the detection level from the start of surface treatment until the elapse of a predetermined time, it is possible to It is also possible to perform appropriate detection.

[Brief explanation of drawings]

FIG. 1 is a characteristic curve diagram showing the change characteristics of the amount of transmitted light for various processing objects, FIG. 2 is a characteristic curve diagram also showing the change characteristics of the amount of transmitted light, and FIG. FIG. 4 is a plan view of the spinner head section of an example of the device used, FIG. 5 is a plan view of the spinner head section, FIG. is a flowchart showing an embodiment of the present invention, No. 9.
The figure is a waveform characteristic diagram of a detection signal output by a photoelectric conversion element. Object to be processed...1, Photoelectric conversion element...8.

Claims (1)

[Scope of Claims] 1. In a method of detecting the amount of transmitted or reflected light on a workpiece and detecting the surface treatment state of the workpiece based on a change in the detection level, after a predetermined detection time has elapsed from the start of surface treatment. , characterized in that a required target level is repeatedly set when a predetermined target level is exceeded, and when the target level is no longer exceeded within a predetermined time, the end point of the surface treatment is determined. Surface treatment method. 2. According to claim 1, the state of the detection level after a predetermined time has elapsed from the start of surface treatment is detected, and the target level to be set next can be selected according to the state of the detection level. , surface treatment method. 3. The target level that is repeatedly set is constant.
A surface treatment method according to claim 1. 4. A flat surface processing method according to claim 1, wherein the repeatedly set target level is calculated each time according to the amount of transmitted or reflected light from the object to be processed. 5. The surface treatment method according to any one of claims 1 to 4, wherein the surface treatment of the object to be treated is an etching treatment. 6. The surface treatment method according to any one of claims 1 to 4, wherein the surface treatment of the object to be treated is a development treatment.