JPS6240701B2 - - Google Patents

Description

[Detailed description of the invention] (a) Industrial application field This invention is a method for detecting the processing state during surface processing of a substrate, such as etching processing when manufacturing a photomask, and automatically detecting 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, followed by the required development. It is created through a process of patterning a photoresist film by developing it with a solution, 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 measuring area for detecting the progress of etching is provided outside the effective area on the photomask surface, and the light transmittance in that area is measured. A method for detecting the end point has been proposed.

However, in this prior invention, the method of detecting the end point of etching is to detect two points before and after the amount of transmitted light.
Take the difference between the sample values for 10 consecutive
Since a point-based averaging method is used, if the progress of etching temporarily stagnates, for example, if a poorly soluble oxide film exists under a thin metal film that has been deposited, There is a risk that the above-mentioned temporary stagnation may be seen as the end point of the etching process before the etching process reaches its true end point. In addition, the amount of light transmitted through a glass substrate on which a thin metal film is deposited varies depending on the type of metal, the presence or absence of an oxide film on the metal, the material and thickness of the glass substrate, etc. The 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 a glass substrate etc. to a rotating processing device (spinner) during surface treatment,
A vacuum suction method using a vacuum chuck at the spinner head is common, but a simple fixing and holding frame method that fixes and holds the four corners of a glass substrate, etc., is also known. When using such a simple fixed holding frame type, the frames for holding the four corners of the glass substrate, etc., intermittently block the light beam for detecting the amount of light transmitted through the substrate, etc. Therefore, it becomes 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 was devised to solve the inconveniences in the conventional method, and even when using the above-mentioned simple fixed holding frame, or even when the above-mentioned degree of progress of etching is 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 even when stagnation occurs, and even when the photomask has any transmitted light amount characteristics.

(d) Structure of the invention This invention takes the following technical means to achieve the above object, and its gist is to detect the amount of light transmitted through the object to be processed using a photoelectric conversion element. In the method of detecting the surface treatment state of the object from changes in the detection level, it is determined at each step whether or not the detection level exceeds a predetermined target level set in stages within a predetermined time. If a predetermined target level is exceeded at a certain stage, the target level plus a predetermined level is set as the new target level for the next stage, and the detection level is increased again. It is characterized in that it detects whether or not the new target level has been exceeded within a predetermined time, and if the detected level does not exceed the predetermined target level within a predetermined time, the processing ends at that point in time. It is something to do. In other words, detecting whether the detection level has changed by a predetermined level width within a predetermined time, and if it has changed, further detecting whether the detection level has changed by a next predetermined level width within a predetermined time, In this way, changes in the detection level within a predetermined width are sequentially detected within a predetermined time limit, and when the detection level can no longer exceed the next predetermined level width, that point is the end point of the process. It is. In this manner, the present invention detects the processing state of the object to be processed based on the target level and processing time that are set in stages, and therefore can accurately detect the end point of the processing. Therefore, for example, as shown in FIG. 1, even when the characteristics of the amount of transmitted light to the object to be treated vary as shown in the diagrams A to D, it is possible to accurately detect the end point of the surface treatment.

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

In these figures, the object to be processed 1 is a metal thin film deposited on the surface of a semiconductor substrate G such as a glass substrate or silicon, a photoresist coated on the upper surface and dried, and then a desired pattern is printed on the photoresist. This is a developed image. The head part 2 includes a central part C coupled to a spindle SP, and arms B extending equidistantly in four directions from the central part C in a horizontal plane.
is formed at the tip of each arm B. It is composed of a pair of substrate holding pins 3 and substrate mounting pins 4, and the workpiece 1 is placed on the substrate mounting pins 4, and its four corners are held by the substrate holding pins 3. It is designed so that it can be rotated within a horizontal plane. The light amount detection unit S includes a pair of light-receiving fibers 5 and light-emitting fibers 6, which are disposed opposite to each other on the upper and lower surfaces of the plate-shaped workpiece 1, and a holder that holds one end of these fibers 5 and 6. 7, 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, and in this figure, reference numeral 8 denotes a photovoltaic device 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. 2, when the amount of light received by the light-receiving fiber 5 increases, the conversion element 8
is configured to be low active so that its output voltage decreases. Reference numeral 9 denotes an amplifier that amplifies the output of the conversion element 8, and its output _V1 is sent to the A/D converter 10.
It is also input to one terminal of the comparator 11. The other terminal of the comparator 11 has
The output V ₂ of the D/A converter 12 is input as a reference voltage, and when the output V ₁ becomes equal to or lower than the reference voltage V ₂ , a determination signal E _P is output. Further, the discrimination signal E _P is transmitted to the latch circuit 13
After being held for a predetermined time, it is input to the CPU 14 as an END signal, which will be described later. The CPU 14 reads a predetermined level value E set in advance in a built-in memory (not shown), performs an operation corresponding to V ₂ =V ₁ -E, and converts this to the D/A converter 12 as described above. The analog reference voltage V ₂ is output to the comparator 11 through the analog reference voltage V 2 , while the end point of the processing of the object 1 can be detected by the input END signal, control program, timer, and the like.

Next, specific procedures for carrying out the present invention using the apparatus having such a configuration will be explained based on the flowcharts shown in FIGS. 6 and 7.

First, use an input device (not shown) to
The predetermined level value E that should become the first target level value and the detection time T are stored in the memory device of the CPU 14.
and _E (steps A and B). In this case, the predetermined level value E and the detection time T _E should be appropriately selected in advance through experiments, etc., but for example, as shown in FIG. If there is a temporary stagnation during the operation, the stagnation time must be longer than the relevant stagnation time T _D.

When the setting by the input device is completed, the specific amount of transmitted light of the object 1 before processing is measured, and the detection level V ₁ ' at that time is stored in the memory device of the CPU 14 (step C). Next CPU1
4 uses the set predetermined level value E,
The calculation V ₂₁ =V ₁ '-E is performed, and the calculated value is input to the comparator 11 via the D/A converter 12 as the detection level as the target level to be reached (step D). Next, a surface treatment, for example an etching treatment, for the object 1 to be treated is started (step E). In this case, since the spinner head section 2 is rotated at a constant speed, the light beam irradiated from the light projection fiber 6 is interrupted every 1/4 rotation by the arm B that constitutes the head section 2. As a result, the detection level output from the photoelectric conversion element 8 changes periodically between V ₀ and V ₁ ', as shown in FIG. In this figure, V ₀ is the detection level of the photoelectric conversion element 8 output when the arm B blocks the irradiation light from the light emitting fiber 6, and
V ₁ ' is the detection level of the photoelectric conversion element 8 output when the light beam from the projection fiber 6 passes through the object 1 to be processed before etching. As the etching process on the object 1 progresses, the amount of light transmitted through the object 1 gradually increases, and as a result, a pulse signal as shown in FIG. 2 is detected. This is output at intervals corresponding to the mask pattern applied to the object to be processed 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 a built-in register as an initial value for counting the END signals from the latch circuit 13 based on a command from the program (step F), and then The presence or absence of a signal is checked repeatedly (step G). Then, as the etching process progresses, the level of the pulse signal changes as shown in Figure 2.
When the value of V ₂₁ =V ₁ '-E is exceeded, the comparator 11 outputs a discrimination signal E _P , which is sent to the latch circuit 13.
After being latched, as an END signal
It is input to the CPU 14. CPU14 is this END
When it is detected that a signal has been input, the contents of the register are decreased by 1 in the next step H, and then the latch circuit 13 is reset (step). This causes the latch circuit 13 to
The input of the END signal to 4 is stopped. Next, it is checked whether the content of the register in the CPU 14 has become 0 (step J), and if it has not become 0, the process returns to step G and the END
Check for presence of signal. Also, if the contents of the register are 0, the next target level
As V ₂₂ , the calculation of V ₂₂ =V ₂₁ -E is performed, and the calculated value is input to the comparator 11 via the D/A converter 12 (step K). Subsequently, the step F
Similarly, for example, "3" is set as the initial value for counting the END signal (step L),
In the following step M, a timer is set to a predetermined time _TE . This means that the subsequent change in the amount of transmitted light is
This is because the detection is performed within a limited period of time, which is the detection time T _E mentioned above. As a result, even when the amount of transmitted light to the object 1 changes as shown in FIG. 1B, the detection time T
By setting _E to be longer than the temporary stagnation time T _D , the end point of the etching process will not be detected incorrectly, and the end point of the etching process can be accurately detected even when the workpiece 1 has arbitrary transmitted light amount characteristics. can be detected.

Next, the CPU 14 performs the following steps in the same manner as in step G above.
The presence or absence of the END signal is checked (step N), and if the END signal is latched in the latch circuit 13, the same processing as in steps H, I, and J is executed (steps O, P, and Q). As a result of the check in step Q, if the contents of the register are 0, the timer is reset and the process returns to step K again. At this time, V ₂₃ =V ₂₂ -E is calculated as the next target level, and this is input to the comparator 11 as the next target level value in the same manner as described above.

Also, as a result of the check in step N,
If the END signal is not latched in the latch circuit 13, it is checked in the next step S whether or not a time has elapsed, and if not, the process returns to step N and repeats the above-mentioned check.

In this way, the aforementioned _target level is updated one after another (V ₂₁ →V ₂₂ →V ₂₃ →……
→V _2o ), and the processes corresponding to each of the above steps K to R are repeatedly executed.

Then, as a result of the check in step S,
If the operating time of the timer exceeds the detection time _TE , it can be assumed that the etching process has been completed, so this point is considered as the end point of the process (step T). In the following step U, the etching process etc. are stopped.

In addition, in order to apply the method of the present invention to various types of workpieces whose transmitted light quantity characteristics change variously as shown in FIG. This can be dealt with by shifting it accordingly. Further, in this embodiment, a case has been described in which a constant value is set as the level value E necessary for calculating the target level value at each stage, but the invention is not limited to this. For example, E ₁ ≧ E ₂ ≧E ₃ ≧E ₄ ≧E ₅ ……≧
Various level values such as E _o are set, and these are adjusted depending on the type of object to be treated, the characteristics of the amount of transmitted light, etc.
Various selections may be made for use.

Further, in the above-mentioned 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.

Further, in the embodiment described above, the end point of the surface treatment is detected by checking whether or not a predetermined target level set in stages has been exceeded under the limit of the detection time _TE . As another method, for example, the time from the start to the end of etching for a normal photomask is experimentally determined in advance, and the detection level remains at a predetermined target level even after the elapse of the time obtained by adding the detection time _TE to the time. It is also possible to set the end point of the etching process to a point that does not exceed this point.

(F) Effects of the Invention As explained above, the present invention detects whether the detection level has changed by a predetermined level width within a predetermined time, and if it has changed, the detection level further changes the next predetermined level width by a predetermined amount. As in the case of detecting whether or not there has been a change within a certain period of time, changes in a predetermined width of the detection level are detected step by step and sequentially within a predetermined time limit, and the detection level no longer reaches the next predetermined level width for a predetermined time. The process is repeated until it cannot be exceeded within a certain period of time, and that point is set as the end point of the treatment, so that the end point of the surface treatment material on the object to be treated can be detected very accurately.

[Brief explanation of the drawing]

FIG. 1 is a characteristic curve diagram showing the change characteristics of the amount of transmitted light for various objects to be processed, FIG. 2 is a diagram showing the waveform of the detection signal output from the photoelectric conversion element, and FIG. 3 is a diagram showing the method of the present invention. FIG. 4 is a side sectional view of the spinner head, FIG. 5 is a schematic explanatory view of the overall structure of the device, and FIGS. The figure is a flowchart showing one embodiment of the present invention. Object to be processed...1, Photoelectric conversion element...8, Target level... _V21 , _V22 , _V23 , Predetermined level...E, Predetermined time... _TE .

Claims (1)

[Claims] 1. A method of detecting the amount of light transmitted through a workpiece and detecting a surface treatment state of the workpiece based on a change in the detection level, wherein the detection level is:
Whether or not a predetermined target level set in stages has been exceeded within a predetermined time is sequentially detected at each step, and if the detected level does not exceed the target level at that step within a predetermined time, the point in time is detected. A surface treatment method characterized in that the end point of the treatment is smearing. 2. The surface treatment method according to claim 1, wherein the surface treatment of the object to be treated is an etching treatment. 3. The surface treatment method according to claim 1, wherein the surface treatment of the object to be treated is a development treatment.