JP2000173984A - Etching apparatus and etching method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To achieve high etching process performance stably with high yield. An etching apparatus includes an etching chamber and an evaluation chamber for sample surface, and uses an etching apparatus having a function of transferring a sample between the etching chamber and the evaluation chamber by robot transfer. Based on the sample profile measurement results, correction of the process conditions applied to the subsequent sample and feedback control are performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching apparatus and an etching method, and more particularly to an etching apparatus and an etching method suitable for achieving a high process performance in a process requiring a high process performance. is there.

[0002]

2. Description of the Related Art In order to obtain a desired process performance in an etching process, usually, a confirmation experiment in which a plurality of process conditions are used as parameters is performed in advance to determine an optimum process condition, and the process condition is registered as a recipe in an etching apparatus. I do. In the production line, the etching process is performed by selectively using the recipe for each process. The etching performance at this time is
Ideally, the conditions should be exactly the same as when the conditions were determined in advance, but the etching rate also increases or decreases due to the state of the inner wall of the etching processing chamber, changes over time in the atmosphere, and the like. 2. Description of the Related Art With the recent increase in the degree of integration of LSIs, there is a demand for a process performance capable of coping with a fine processing dimension and a high aspect ratio. As means for stably achieving the process performance, for example, as described in JP-A-8-138887, a plasma measurement technique is used to measure a current value or the like passing through an aperture provided in a chamber during etching. There has been proposed a technique of monitoring and controlling the discharge power and the gas flow rate in a feedback manner.

[0003]

In the above-mentioned conventional example,
The process conditions are fed back based on the results of the plasma measurement. In this case, a certain degree of correlation can be found for macro process characteristics such as the average etching rate in the sample plane, but the process performance in micro regions such as etching of fine contact holes can be found. On the other hand, it is difficult to perform feedback control. In the prior art described in the above publication, an aperture simulating a contact hole is employed.However, in actual etching of a sample, re-incidence of a reaction product to the sample and sputtering on a side surface of the hole occur. Affects micro process characteristics. Therefore, the information from the plasma measurement in the prior art described in the above publication is often not useful for grasping the etching state in an actual micro area.

An object of the present invention is to provide an etching apparatus and an etching method capable of stably realizing high etching process performance at a high yield.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to evaluate an actual profile after etching for each wafer or for each wafer when a plurality of wafers are continuously subjected to the same etching process. This is achieved by performing feedback control on the process conditions applied to the subsequent sample so that the result becomes a desired result, repeating this process, and causing the computer to store and learn. This makes it possible to achieve high process performance at a high yield. Further, a processing chamber for performing plasma etching, and an evaluation chamber for a sample surface provided via the processing chamber and the buffer chamber are provided, and a sample is transferred between the processing chamber and the evaluation chamber by automatic robot conveyance. Achieved by delivery.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, when the same etching process is continuously performed, the sample which has been plasma-etched in the etching processing chamber is continuously evaluated by means of an automatic robot transfer via the buffer chamber. Transfer to the room and evaluate the actual profile. When the evaluation result of the profile is out of the allowable range of the desired profile, correction and feedback control are performed on the process conditions applied to the subsequent sample. As described above, since the desired process performance is directly monitored for each wafer or every plurality of wafers and feedback control is performed, highly reliable etching processing can be performed. Also, by accumulating a huge amount of process evaluation data in-line and learning the effect of feedback by a computer, it is possible to further improve the process and respond to changes over time. In the unlikely event that the process performance fluctuates unexpectedly, it is possible to find a defect at an early stage by in-line evaluation, and to achieve a desired process performance with a high yield.
Hereinafter, embodiments of the present invention will be described.

[Embodiment 1] An embodiment of the present invention will be described with reference to the configuration diagram of an etching apparatus shown in FIG. Loading room 1
After the sample is charged and evacuated, the sample is placed in the etching chamber 102 via the buffer chamber 101 by robot transfer, and is subjected to an etching process under predetermined process conditions. Next, the sample is robot-transported to the sample surface profile evaluation chamber 103 via the buffer chamber 101, and the surface profile is measured using an atomic force microscope (AFM). Figure 2 shows the measurement of the surface profile.
As shown in (1), the sensor unit 200 performs surface profile measurement by AFM at a desired measurement point in the movable area 202 of the sensor unit including the entire area of the sample 201. It is effective to use pattern recognition by an optical monitor in order to quickly identify a measurement location. FIG. 3 shows an example of a sample cross section and profile measurement results after the etching process. In the sample, as shown in FIG. 3A, a first insulating film 301 is etched on a substrate 300 by using a second insulating film mask 302 which is patterned in advance. First
The measurement profile when the etching of the insulating film 301 is completely completed is, as shown in FIG. 3B, the sum of the film thickness of the first insulating film 301 and the film thickness of the second insulating film mask 302. A corresponding concave profile is obtained. However, depending on the state of the apparatus, particularly, a change in the atmosphere in the etching processing chamber 102, a phenomenon may occur in which the etching rate of the first insulating film 301 is reduced or the etching does not progress on the way. As shown in FIG. 3C, the measurement profile at this time can be easily checked because the concave profile is shallower than that in FIG. 3B. When such a state is reached, an alarm is issued and the process conditions for the subsequent sample are corrected, and FIG.
The feedback control is performed so as to obtain the ideal profile shown in FIG. As a means for correction, for example, C ₄ F ₈
In the case where the SiO ₂ film is etched by the / Ar / O ₂ system, a decrease in the etching rate can be prevented by increasing the flow rate of O ₂ , discharge power, bias power to the sample, and the like. For each effect, a method optimized by a statistical method using the control computer 104 can be selected based on the monitoring and feedback control data described above. Also, if the monitored measured profile deviates more than a predetermined level compared to the ideal profile, it is determined that the device is abnormal,
Raises an alarm and interrupts processing of subsequent samples. As a result, a large amount of valuable sample is not wasted due to unexpected equipment trouble. The sample for which the profile measurement has been completed is transferred to the unloading chamber 105 via the buffer chamber 101. Although the surface profile measurement described above is surely performed for all the samples, the time-dependent change in the process performance occurs slowly. Therefore, it is sufficient to perform the measurement for each of a plurality of samples (for example, at an interval of 3 to 5). In this case, if the profile measurement time for one sample is shorter than the time for performing the etching process on two to four samples, the throughput is basically not affected. Therefore, it is possible to perform more detailed measurement on the in-plane distribution of etching performance by increasing the number of measurement points including the central part and the peripheral part in the plane of the specimen than when performing profile measurement on all specimens. Become.

According to this embodiment, since the feedback control is performed while directly monitoring the etching profile, a high process performance can be realized with a high yield. Further, since feedback control is performed in-line, even if a failure occurs, quick recovery is possible, and a defect is not created for each lot.

In this embodiment, the method of correcting the process condition is optimized by a statistical method using a computer based on the data of monitoring and feedback control, but a plurality of types of correction and the effects of the correction are determined by using a neural network. It can also be optimized by learning and optimized correction methods.

In this embodiment, the profile measurement when the etching of the first insulating film 301 is completely completed is monitored in-line. However, the first insulating film 301 is optimized for the purpose of optimizing the process conditions. By stopping the etching before the etching is completed and performing profile measurement, it is also possible to optimize the etching rate or the process conditions suitable for improving the uniformity of the etching rate within the sample surface. .

In this embodiment, an atomic force microscope (A
FM) to measure the profile
Alternatively, a tip made of metal or the like is employed as a probe.
Therefore, when the sample after the etching process is transferred from the processing chamber 102 to the evaluation chamber 103 via the buffer chamber 101, if the etching gas remains on the surface of the sample, the probe is corroded. In order to prevent the corrosion, the buffer chamber 10
The volume of 1 is 1 to 2 liters or less, and the residual gas can be eliminated in a short time by repeatedly purging with an inert gas and evacuating to a high vacuum before transferring the sample to the evaluation chamber 103.
Further, as shown in FIG. 4, the shape of the buffer chamber 400 is reduced in volume in accordance with the shape of the sample 401, and a purge gas inlet 403 and an exhaust port 404 are provided opposite to the sample inlet / outlet 402 in addition to the sample inlet / outlet 402. The gas flow can be exhausted without stagnation.

In this embodiment, profile measurement is performed including the film thickness of the second insulating film mask 302. However, the etching depth of the first insulating film 301 is strictly monitored from the concave profile. For this purpose, before performing the etching process, the thickness of the second insulating film mask 302 is determined in the evaluation chamber 1.
It is effective to measure at 03.

In the above embodiment, the profile is measured using an atomic force microscope (AFM).
Other measuring means, for example, a scanning tunneling microscope, a scanning electron microscope, a laser microscope, and the like can be applied. It is also effective to combine them according to usability. It goes without saying that the measurement in the atmosphere is possible in the case of the atomic force microscope and the laser microscope.

The material to be etched is not limited to the above-described insulating film, and it goes without saying that the present invention is effective for etching other materials such as wiring metal and substrate crystal. .

Embodiment 2 FIG. 5 shows a second embodiment of the present invention.
It will be explained by. FIG. 5 shows a configuration diagram of the etching apparatus. After loading the sample from the load chamber 500 and evacuating,
The sample is placed in the etching chamber 502 via the buffer chamber 501 by robot transfer, and is subjected to an etching process under predetermined process conditions. Next, the sample is transferred to the ashing processing chamber 503 via the buffer chamber 501, and the resist used as a mask in the etching processing is removed. Subsequently, the sample is transferred by robot to the surface profile evaluation chamber 504 via the buffer chamber 501, and the surface profile is measured using an atomic force microscope (AFM). FIG. 6 shows an example of a sample cross section and profile measurement result after the etching process. The measurement profile when the etching of 601 is completely completed is shown in FIG.
As shown in (b), a concave profile corresponding to the thickness of the first insulating film 601 is obtained. However, there is a fear that the etching rate of the first insulating film 601 may be reduced or the etching may not progress on the way due to a change in the state of the apparatus, particularly, the atmosphere in the etching processing chamber 502. The measurement profile at this time is shown in FIG.
As shown in FIG. 6C, the concave profile is shallower than that in FIG. When such a state is reached, an alarm is issued using the control computer 505, and the process conditions for the subsequent sample are corrected so that the ideal profile shown in FIG. 6B is obtained. Perform feedback control. After the profile measurement, the sample is stored in the buffer chamber 501.
Is transferred to the unloading chamber 506 via the.

According to this embodiment, since the feedback control is performed while directly monitoring the etching profile, it is possible to realize a high process performance with a high yield.

Further, with the increasing integration of LSIs and miniaturization of elements, a level of about 0.25 μm is required as an etching dimension. Although the resolution of the AFM is on the order of the atomic level, the shape and size of the probe may hinder the measurement of the profile of the bottom surface of the contact hole having a high aspect ratio. In such a case, as shown in FIG. 7A, profile measurement of contact holes having different dimensions formed in the first insulating film on the substrate 700 is performed. FIG.
From the results of the profile measurement shown in (b), the depth at the center of each hole can be accurately evaluated because it is hardly affected by the shape and size of the probe. From the dependence of the depth of the center of the contact hole on the hole diameter shown in FIG. 7C, it can be determined whether or not the etching has been performed under the process conditions suitable for processing the fine contact hole. Generally, the amount of etching decreases as the contact hole diameter becomes finer. This is called the microloading effect. Of course, (i) in FIG.
It is preferable to apply a process condition with a small contact diameter where the microloading effect as shown in FIG. From the profile measurement result, (ii) in FIG.
If the microloading effect is significant as shown in
Correct the process conditions for subsequent samples. These determinations can be made instantaneously by accumulating and learning data in the control computer. By forming the contact holes having the different dimensions as a TEG (test element group) in the sample, the microloading effect can be quickly evaluated.

Further, as shown in FIG.
When the isolated pattern 801 and the dense pattern 802 are mixedly formed on 0, the side surface of the isolated pattern 801 may have a forward tapered shape, and the pattern size may be larger than that of the dense pattern 802. The profile of the forward tapered shape on the side surface of the isolated pattern 801 can be accurately measured by AFM as shown in FIG. It is possible to provide an allowable range for the forward tapered shape and correct the process conditions in a direction to reduce the forward tapered shape on the side surface of the isolated pattern 801 as shown in FIG.

In recent years, Cu wiring has recently been used as an LSI wiring material.
The process called damascene, which forms wiring by embedding Cu in a wiring groove formed by etching, has been spotlighted. Among them, as shown in FIG. 9A, a contact hole 90 is formed in an insulating film 901 on a substrate 900.
Attention has been paid to a process called dual damascene in which the wiring groove 2 and the wiring groove 903 are formed together. As shown in FIG. 9B, the profile can be measured even for such a slightly complicated shape after etching, so that the present invention can be used.

In the above-described embodiment, the surface measurement is performed in the evaluation chamber 504 provided separately from the etching processing chamber 502 and the ashing processing chamber 503. However, the surface measurement system is used for one or both of these processing chambers. Or in the buffer chamber 501, and it is possible to provide in-line feedback to process conditions based on the results of these surface measurement systems.

[0021]

According to the present invention, since the etching profile is corrected directly and the feedback control is performed while monitoring the etching profile in-line and directly, a high process performance is realized with a high yield. can do. In addition, even if a failure due to aging or a sudden accident occurs, the etching equipment determines the prompt correction of the process conditions for the processing of the subsequent sample or the interruption of the subsequent processing based on the vast data. Can be done automatically. Also, optimization of the process conditions can be performed in a short time by using the learning of the computer only with the etching apparatus.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an etching apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a movement area of a sensor provided in an evaluation room in the apparatus of FIG.

FIG. 3 is a diagram showing a sample cross section and a measurement profile result after processing in an etching processing chamber in the apparatus of FIG. 1;

FIG. 4 is a view schematically showing a buffer chamber in the apparatus shown in FIG.

FIG. 5 is a configuration diagram of an etching apparatus according to a second embodiment of the present invention.

6 is a diagram showing a sample cross section and a measurement profile result after processing in an etching processing chamber in the apparatus of FIG. 5;

FIG. 7 is a diagram showing a contact hole cross section and a measurement profile result after processing in the apparatus of FIG. 5;

FIG. 8 is a diagram showing a cross section of a dense / dense pattern after processing in the apparatus of FIG. 5 and a measurement profile result.

9 is a diagram showing a cross section of a sample for damascene and a measurement profile result after processing in the apparatus of FIG. 5;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 100 ... Load room, 101 ... Buffer room, 102 ... Etching process room, 103 ... Evaluation room, 104 ... Control computer, 105 ... Unload room, 200 ... Sensor part, 2
01: sample, 202: movable area of sensor unit, 300: substrate, 301: first insulating film, 302: second insulating film mask, 400: buffer chamber, 401: sample, 402: entrance of sample, 403: Purge gas inlet, 404 exhaust port, 500 load chamber, 501 buffer chamber, 502
Etching chamber, 503 ... Ashing chamber, 504
... Evaluation room, 505 ... Control computer, 506 ... Unload room, 600 ... Substrate, 601 ... First insulating film, 70
0: substrate, 701: first insulating film, 800: substrate, 80
1 ... isolated pattern, 802 ... dense pattern, 900 ... substrate, 901 ... insulating film, 902 ... contact hole, 903 ...
Wiring groove.

Claims (22)

[Claims] 1. A processing chamber for performing plasma etching, and an evaluation chamber for a sample surface provided via the processing chamber and a buffer chamber, wherein a space between the processing chamber and the evaluation chamber by automatic robot transfer is provided. An etching apparatus having a function of transferring a sample. 2. The method according to claim 1, wherein at least one or more locations in the first processing chamber or the second processing chamber for performing plasma etching are provided.
Alternatively, an etching apparatus comprising a sample surface evaluation system in a buffer chamber. 3. An etching apparatus for measuring a profile of a sample surface in a non-contact manner in the sample room evaluation system or the evaluation system according to claim 1 or 2. 4. An etching apparatus according to claim 3, wherein in the non-contact profile measurement of the sample surface, a surface profile of a desired portion is measured using a sensor head capable of scanning on a plane including the sample to be measured. 5. An etching apparatus according to claim 3, wherein said non-contact profile measurement of the sample surface comprises at least one of an atomic force microscope, a scanning tunnel microscope and a laser microscope. 6. The buffer chamber according to claim 1, wherein said buffer chamber has a volume of one.
An etching apparatus that is not more than 2 liters, and an inlet and an outlet of a purge gas to the buffer chamber are opposed to each other, so that a gas flow can be exhausted without stagnation. 7. A step of measuring and recording a surface profile of a desired portion of a sample to be processed in the evaluation chamber or the evaluation system using the etching apparatus according to claim 1; and transporting the sample to the processing chamber. An etching method comprising: performing plasma etching; and transporting the sample to an evaluation chamber via a buffer chamber, and measuring and recording the surface of the desired portion again. 8. The method according to claim 1, wherein purging of an inert gas or nitrogen gas and evacuation of a high-vacuum gas are repeated one or more times in a state where the sample subjected to the plasma etching is set in a buffer chamber. And after transporting the wafer to the evaluation chamber to measure and record the surface of a desired location. 9. An etching method according to claim 7, wherein the surface profile of the sample to be processed is measured for all samples in one batch or for a plurality of samples. 10. An etching method for determining whether or not a desired etching process has been completed based on a difference between surface profile measurement results before and after the plasma etching step according to claim 7, and recording the result. 11. An etching method for judging and recording whether or not a desired etching process has been completed based on a measurement result of a surface profile of a sample after the plasma etching according to claim 7. 12. An etching method according to claim 11, wherein the measurement result of the surface profile of the sample after the plasma etching is based on the measurement of the etching depth of patterns having different pattern dimensions provided on the sample surface. 13. An etching method according to claim 11, wherein the measurement result of the surface profile of the sample after the plasma etching is based on the profile measurement of dense and fine patterns having different intervals provided on the sample surface. 14. The etching method according to claim 12, wherein the measurement result of the surface profile of the sample after the plasma etching is based on the measurement at the central portion and the peripheral portion of the sample. 15. A determination as to whether the desired etching process has been completed according to claim 10 is based on a difference in a measurement result of a surface profile before and after a step of performing plasma etching or a difference in a surface profile of a sample after plasma etching. If the measurement result is within the first allowable range, the processing is determined to be normal and the processing of the sample is continued, and if the measurement result exceeds the first allowable range and falls within the second allowable range, a first warning is issued. And the processing of the sample is continuously performed, and when the difference between the measurement results exceeds a second allowable range, a second warning is issued and the processing of the subsequent sample is interrupted. 16. A difference between a measurement result of a surface profile before and after the step of performing the plasma etching according to claim 15 or a measurement result of a surface profile of a sample after the plasma etching exceeds a first allowable range and exceeds a first allowable range. An etching method that issues a first warning and corrects processing conditions of a subsequent sample when the value falls within the allowable range of 2. 17. An etching method according to claim 16, wherein the method for correcting the processing conditions of the subsequent sample is an adjustment of an etching processing time. 18. The etching method according to claim 16, wherein the correction method for the processing conditions of the subsequent sample is an adjustment of the power of plasma discharge. 19. An etching method according to claim 16, wherein the correction method for the processing condition of the subsequent sample is an adjustment of a bias power applied to the sample. 20. An etching method according to claim 16, wherein the correction method for the processing conditions of the subsequent sample is a flow rate (ratio) of a process gas or pressure adjustment. 21. The difference between the measurement results of the surface profile before and after the step of performing the plasma etching according to claim 16 or the measurement result of the surface profile of the sample after the plasma etching, wherein the measurement result is within the first allowable range. If the value exceeds and falls within the second allowable range, a plurality of types of corrections are made in advance to the processing conditions of the subsequent sample, and the effects of the corrections are optimized by a statistical method using a computer. An etching method for processing a subsequent sample by the method. 22. The difference between the measurement results of the surface profile before and after the step of performing the plasma etching according to claim 16 or the measurement result of the surface profile of the sample after the plasma etching, wherein the measurement result is within the first allowable range. If it exceeds and falls within the second allowable range, a plurality of types of corrections are previously performed on the processing conditions of the subsequent sample and the effects of the corrections are learned using a neural network and the subsequent correction is performed by a correction method optimized. An etching method for processing a sample.