JP2005150623A - Method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor device which can surely make a semiconductor substrate come off from a lower electrode. <P>SOLUTION: The substrate is attracted by electrostatic force and fixed to a substrate support part capable of supplying a gas to the rear face of the substrate. Then, the substrate is subjected to processings, such as etching, and the flow rate of the gas is measured, while the gas is supplied to the rear face of the substrate from the substrate support part on which the substrate is fixed. Then, the measured flow rate of the gas is decided whether it is higher than or equal to a predetermined standard flow rate. If the measured flow rate of the gas is higher than or equal to the predetermined standard flow rate, the coming-off of the substrate from the substrate supporting part is completed. Thus, the transfer trouble resulting from detachment defect can be suppressed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method of manufacturing a semiconductor device in which a semiconductor substrate is fixed to a holding part by electrostatic adsorption in a chamber and processed, and more specifically, the semiconductor substrate is fixed to a holding part such as an electrode by electrostatic adsorption force. The present invention relates to a method for removing a semiconductor substrate without causing a transportation trouble.

  In plasma processing such as dry etching and plasma CVD in the manufacturing process of a semiconductor integrated circuit, the technology for fixing a semiconductor substrate to a lower electrode by electrostatic attraction is a process characteristic such as an etching rate and a processing dimension in a semiconductor substrate having a large diameter. This technique is essential for improving the uniformity of the image.

  FIG. 1 is a cross-sectional view of a conventional semiconductor substrate fixing portion that mechanically fixes a semiconductor substrate to a lower electrode. As shown in the figure, the semiconductor substrate 2 is mechanically fixed to the lower electrode 3 by a fixing member 1 (clamp ring or the like) located at the upper part of the reaction chamber capable of depressurization of the semiconductor manufacturing apparatus. However, in such a method, there is a problem that the uniformity of the plasma is lowered due to the influence of the member 1, and the uniformity of the etching rate, dimensions, and the like is also lowered in the dry etching.

FIG. 2 shows a cross-sectional view of a semiconductor substrate fixing portion in which the semiconductor substrate is fixed to the lower electrode by electrostatic attraction for the purpose of improving the uniformity of the etching rate, dimensions, and the like. The semiconductor substrate 2 is electrically fixed to the lower electrode 4 by a lower electrode 4 capable of generating an electrostatic adsorption force. For the purpose of controlling the temperature of the semiconductor substrate, helium gas 5 flows between the semiconductor substrate 2 and the lower electrode 4 from the pores provided in the lower electrode 4 into the chamber as indicated by the arrows, and the temperature of the back surface of the semiconductor substrate 2 is reduced. It comes to control. The temperature of the semiconductor substrate 2 is kept uniform by the helium gas 5. By using such a technique, the uniformity of the etching rate, dimensions, etc. is improved. Such improvement of the electrostatic adsorption method is described in Patent Document 1.
Japanese Patent Laid-Open No. 08-236604

  However, when the dry etching process using plasma is completed and the semiconductor substrate is detached from the lower electrode, charges that existed to be adsorbed and fixed to the lower electrode may remain on the lower electrode or the semiconductor substrate. Desorption is incomplete due to this residual charge. That is, although not shown in FIG. 2, push pins are provided at, for example, four places on the surface of the lower electrode, and when the processing is completed, the push pins rise from the lower electrode and push the semiconductor substrate 2 up from the electrode. It has become. At this time, if electric charges remain on the semiconductor substrate or the like, it will be pushed up against the residual electrostatic force, so that there is a problem that a transport trouble such as the substrate jumps up and falls into the chamber occurs. Was. Such a conveyance trouble due to a detachment failure causes a loss of the semiconductor substrate or a reduction in operating rate due to a recovery operation of the semiconductor substrate dropped in the semiconductor manufacturing apparatus. In order to solve this problem, it is necessary to detach the semiconductor substrate from the lower electrode without fail. On the other hand, although the above-mentioned Patent Document 1 proposes assisting desorption, no proposal has been made regarding reliable charge removal / desorption confirmation.

  In order to solve the above-described conventional problems, the present invention provides a method for manufacturing a semiconductor device in which a semiconductor substrate is reliably detached from a lower electrode.

According to a first method of manufacturing a semiconductor device of the present invention, a substrate is supported by an electrostatic force on a substrate support that can supply gas to the back surface of the substrate, and the substrate is processed.
Measure the flow rate of the gas while supplying the gas from the substrate support part to which the substrate is fixed to the back surface of the substrate,
Determining whether the measured gas flow rate is greater than or equal to a predetermined standard flow rate value;
When the measured gas flow rate becomes equal to or higher than the standard flow rate value, the substrate detachment from the substrate support portion is completed.

According to a second method of manufacturing a semiconductor device of the present invention, the substrate is adsorbed and fixed by an electrostatic force on a substrate support that can supply gas to the back surface of the substrate, and the substrate is processed.
Measure the increasing gas flow rate while supplying gas from the substrate support part to which the substrate is fixed to the back surface of the substrate,
Determining whether the measured gas flow rate has reached or exceeded a predetermined standard flow rate value;
A step of completing the desorption of the substrate from the substrate support portion when the measured gas flow rate is equal to or higher than the standard flow rate value,
Before the gas flow rate reaches the standard value, it is determined whether or not the gas flow rate has reached each of one or more predetermined standard flow rate values which are smaller than the standard flow rate value and different from each other. It is characterized by that.

In a third method of manufacturing a semiconductor device according to the present invention, the substrate is adsorbed and fixed by an electrostatic force on a substrate support that can supply gas to the back surface of the substrate, and the substrate is processed.
Supplying gas to the back surface of the substrate from the substrate support portion to which the substrate is fixed, pressing the back surface of the substrate, and separating at least a part of the back surface of the substrate from the substrate support portion;
Measure the flow rate of the gas while pressing the back surface of the substrate,
When the measured gas flow rate is equal to or higher than a predetermined standard flow rate value, after removing the pressure, the flow rate variation from the measured gas flow rate is substantially measured,
When the flow rate change amount is within a predetermined flow rate change amount, the substrate detachment from the substrate support portion is completed.

  As described above, the present invention provides a substrate support portion such as a lower electrode in a step of detaching a substrate such as a semiconductor substrate fixed on the lower electrode by electrostatic attraction after processing of the semiconductor substrate such as dry etching. A step for measuring the flow rate of the gas flowing out into the chamber for substrate processing and a standard for the gas flow rate in a state in which the electrostatic adsorption force is almost removed are provided, and when the gas flow rate reaches the standard, the next step is performed. By proceeding to the substrate transportation such as a semiconductor after the substrate is detached, it is possible to suppress the transportation trouble caused by the separation failure.

  In the present invention, in the step of detaching the semiconductor substrate fixed on the lower electrode by electrostatic adsorption force after the semiconductor substrate processing such as dry etching, a plurality of gas flows flowing from the lower electrode to the inside of the chamber for substrate processing. Due to the detachment failure by setting the gas flow rate standard for each step and each step, and when the gas flow rate reaches the standard in all measurements, the process proceeds to the next process of semiconductor substrate transport after detachment It becomes possible to suppress the conveyance trouble to carry out.

  Further, in the process of detaching the substrate fixed on the lower electrode by electrostatic adsorption force after processing the semiconductor substrate such as dry etching, the present invention slightly lifts and lowers the substrate from the lower electrode for the purpose of detachment assistance. Measure the amount of gas flow reduction at the time, and when the amount of gas flow reduction falls within the standard, proceed to the next step, the semiconductor substrate transport after desorption, which is a transportation trouble due to defective desorption. Can be suppressed.

  By using the method as described above, a stable semiconductor device can be produced, which can greatly contribute to the manufacture of an ultra-high density integrated circuit.

  In the first to third methods of the present invention, it is preferable that the substrate support portion is provided with a push-up pin for lifting the substrate from the support portion, and the pressing is performed by the push-up pin. As the gas, a gas for controlling the temperature of the substrate can be used. In addition, it is preferable that the standard flow rate value determined in advance is substantially the gas flow rate value when the substrate is placed on the substrate support portion under its own weight only, in order to completely desorb the substrate. The measurement of the gas flow rate may be performed after removing the voltage applied to the substrate support in order to adsorb the substrate by electrostatic force.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 3 is a process flow diagram showing the processing steps of the semiconductor device according to the first embodiment of the present invention. First, a semiconductor substrate to be subjected to plasma processing such as dry etching is transported and installed on a lower electrode inside a chamber that can be decompressed. This lower electrode allows helium gas to flow between the installed semiconductor substrate and the lower electrode surface from a large number of pores provided on the surface in order to control the substrate temperature during plasma processing. The gas is maintained at a substantially constant pressure during processing. In addition, the lower electrode is provided with push-up pins that support, for example, four places on the back surface of the substrate and lift it upward from the electrode in order to transport the semiconductor substrate to the outside of the chamber after the processing is completed.

  Next, a DC voltage is applied to the lower electrode and the semiconductor substrate is fixed to the lower electrode by electrostatic adsorption. Then, the semiconductor substrate is subjected to plasma treatment and then the process of detaching the semiconductor substrate from the lower electrode is started. However, the desorption method is a method in which a weak plasma of an inert gas such as Ar is generated, for example, except for the DC voltage that has been electrostatically adsorbed. You can use either method.

  The substrate desorption process of the present invention is characterized in that it is performed while monitoring the flow rate value of the helium gas for controlling the substrate temperature. FIG. 4 is a diagram showing a change in the flow rate of helium gas from the adsorption fixation of the semiconductor substrate to the plasma processing and the desorption of the substrate. The unit of the vertical axis is cc / min. It is. First, when the semiconductor substrate is adsorbed on the lower electrode, the flow rate of helium gas decreases and is maintained at a constant value (about 9 cc / min.). After 55 seconds, the plasma treatment is finished and the desorption process is started. As the electric charges are discharged from the semiconductor substrate and the lower electrode, the adsorptive power decreases. On the other hand, the flow rate increases because the helium gas pressure is constant, but the desorption period is from 55 seconds to 80 seconds. FIG. 5 is an enlarged view of the desorption process portion of FIG. 4, and after 80 seconds of FIG. 5, the state of complete desorption with almost no adsorption force between the lower electrode and the semiconductor substrate, that is, electrostatic adsorption It shows a state where the semiconductor substrate is simply on the lower electrode without using force.

  In the flow chart of FIG. 3, the helium gas flow rate value is always measured, and the flow rate increases as shown in FIG. 5 as desorption progresses, but it is determined whether the flow rate has reached a predetermined standard value. If the flow rate exceeds the standard value flow rate, the semiconductor substrate is lifted and transferred by the push-up pin, and the next semiconductor substrate to be processed is transferred to the lower electrode. If the standard value is not reached, the desorption process is continued and the flow rate is judged again.

  Here, the predetermined flow rate standard value will be described. When the semiconductor substrate starts desorption from the lower electrode in the desorption process, the helium gas flow rate value increases from 2.0 seconds (increase coefficient a = helium gas flow rate change / second) as shown in FIG. Increase in 75 seconds. After that, as shown in FIG. 5, a slight charge remains at 75 seconds when the gas flow rate changes to an increase factor of 0.1, but the semiconductor substrate is actually detached. Therefore, the helium gas flow rate at the time when the increase coefficient is changed from 2.0 to 0.1 is 27 cc / min. Is set as a standard for completing the detachment, and at this point, the push-up pin is raised for conveyance.

  According to the present embodiment, the state of the semiconductor substrate detachment from the electrode is monitored by monitoring the helium gas flow rate, and is transported when the flow rate standard value is satisfied. It is possible to prevent an accident that the semiconductor substrate sometimes falls into the chamber. Actually, the number of conveyance troubles per 10000 semiconductor substrates was 10 times in the past, but has been reduced to 5 times after the present invention is implemented.

(Second Embodiment)
FIG. 6 is a process flow diagram showing the processing steps of the semiconductor device according to the second embodiment of the present invention. First, a semiconductor substrate to be subjected to plasma processing such as dry etching is transported and installed on a lower electrode inside a chamber that can be decompressed. This lower electrode has the same structure as in the first embodiment. Next, after applying a DC voltage or the like to the lower electrode and fixing the semiconductor substrate to the lower electrode by electrostatic adsorption, the semiconductor substrate is subjected to plasma treatment, and then the semiconductor is removed except for the DC voltage that has been electrostatically adsorbed. The process of desorbing the substrate from the lower electrode is started. In this process, the helium gas flow rate is monitored or measured a plurality of times.

  FIG. 7 is an enlarged view of the semiconductor substrate desorption process portion in the change in the helium gas flow rate from the adsorption fixation of the semiconductor substrate to the plasma processing and the desorption of the substrate. The time up to 65 seconds is the plasma treatment period of the substrate. After 65 seconds, the semiconductor substrate desorption process is started, and the charge discharge causes the adsorption power between the lower electrode and the substrate to weaken with time. It will increase. As shown in FIG. 7, the increase coefficient of the flow rate of helium gas flowing out from the lower electrode into the chamber for processing the semiconductor substrate is 0.0 at the time of processing the semiconductor substrate, and when the desorption process is started, the increase coefficient of the flow rate is 0.1. → 0.5 → 2.0 → 0.1

  In the present embodiment, the gas flow rate standard value in the desorption process is 13 cc / min. And 26 cc / min. Then, as shown in the flowchart of FIG. 6, the first helium gas flow rate measurement is performed in the time from about 70 seconds to about 72 seconds. The gas flow rate is the first standard value 13 cc / min. Whether or not the above is satisfied is determined. If satisfied, the process proceeds to the final desorption process. If not satisfied, the gas flow rate value is determined again.

  Next, in the final desorption step, the second helium gas flow rate measurement is performed at a time around 75 seconds, and the second standard value 26 cc / min. Judgment is made if the above is satisfied, and if satisfied, the push-up pin of the electrode is raised, the semiconductor substrate is transferred out of the chamber, and the next semiconductor substrate to be processed is transferred onto the electrode in the chamber To do. In the vicinity of the second standard value, the charge still remains on the semiconductor substrate or the electrode, but it is very weak and there is no problem in transportation. If the second standard value is not satisfied, the helium gas flow rate is measured again, and a comparison with the standard value is made.

  As described above, in the present embodiment, the helium gas flow rate value at the change point of the increase coefficient of the helium gas flow rate in the desorption process is 13 cc / min. 26 cc / min. Is set as a standard, and it is confirmed that the helium gas flow rate value increases stepwise, and the semiconductor substrate is detached from the lower electrode. That is, the helium gas flow rate value is constantly monitored in each step of the desorption process, and when the standard is reached, the process proceeds to the next step. By confirming the flow rate value a plurality of times, the desorption process can be made even more reliable, and accidents during substrate transport after substrate processing can be prevented.

  The above is a set of two standard values, but each stage shown in FIG. 13 cc / min. 26 cc / min. 27 cc / min. 4 This standard value is set, and the helium gas flow rate value 27 sccm when the increase coefficient of the helium gas flow rate finally shows 0.1 is set as the standard for ending the semiconductor substrate processing conditions, and the standard has been reached. The semiconductor substrate conveyance may be started at the time. In this embodiment, the conveyance trouble per 10000 semiconductor substrates processing was 0 times compared with the conventional 10 times, so it can be said that this is an excellent method compared with the first embodiment.

(Third embodiment)
FIG. 8 is a process flow diagram showing the processing steps of the semiconductor device according to the third embodiment of the present invention. First, a semiconductor substrate to be subjected to plasma processing such as dry etching is transported and installed on a lower electrode inside a chamber that can be decompressed. This lower electrode has the same structure as in the first embodiment. Next, after applying a DC voltage or the like to the lower electrode and fixing the semiconductor substrate to the lower electrode by electrostatic adsorption, the semiconductor substrate is subjected to plasma treatment, and then the semiconductor is removed except for the DC voltage that has been electrostatically adsorbed. The desorption process from the lower electrode of the substrate is started. In this embodiment, first, the push-up pin provided in the lower electrode is operated, and the back surface of the semiconductor substrate that is electrostatically attracted is pressed with a pressure that does not completely detach from the lower electrode, and is lifted slightly. Is a feature. This is because when a large pressure is used, the substrate jumps abruptly as in the prior art.

  FIG. 9 is a schematic diagram showing the structure of the lower electrode 4, showing the state where the push-up pin 10 is raised and the semiconductor substrate 2 is completely lifted up, and the flow rate of the helium gas 5 increases from the surface of the lower electrode and flows out to the periphery. Yes. In the substrate pressing performed at the initial stage of detachment, the substrate is not completely separated from the lower electrode 4 as shown in FIG. 9, and only the central portion pushed up by the pin 10 is lifted by about 0.2 mm, and the peripheral portion remains in contact. is there.

  FIG. 10 is an enlarged view showing the semiconductor substrate desorption process portion in the change in the helium gas flow rate from the adsorption fixation of the semiconductor substrate to the plasma processing and the desorption of the substrate. The time t1 second is the plasma processing period of the substrate, and the time t1 to t2 is the period during which the semiconductor substrate is pressed. The substrate is gradually separated from the lower electrode by pressing for a certain time, and the helium gas flow rate increases. It becomes constant at a certain time. This constant time is the time when the substrate is almost completely separated from the lower electrode, and the flow rate of 27 cc / min. Is a first flow rate standard value.

  As the desorption confirmation, the helium gas flow rate value is constantly monitored. When the helium gas flow rate reaches the standard, it is determined that the desorption of the semiconductor substrate is completed. If the standard value has not been reached, the helium gas flow rate is measured again after a certain period of time as shown in FIG. 8 and compared with the standard flow rate value.

  Thereafter, in FIG. 9, the semiconductor substrate 2 is again lowered to the lower electrode 4 and the flow rate of helium gas is measured. FIG. 11 shows fluctuations in the normal flow rate of the helium gas during the descent. As shown in FIG. 11, the amount of decrease is 1 cc / min. If the flow rate variation is within a certain standard value, it is determined that the semiconductor substrate is completely detached from the lower electrode. This is because the electrostatic force does not work unless the electric charges of the lower electrode or the semiconductor substrate are almost discharged and remain, and the flow rate of helium gas is reduced only by the weight of the substrate, so that the reduction amount is slight.

  On the other hand, when desorption is incomplete, if the substrate is lowered again to the lower electrode, a considerable amount of electric charge still remains and adsorption force works, so the flow rate of helium gas after the semiconductor substrate is lowered is 12, 1 cc / min. As a result, the voltage drops to about 9 sccm, which is equivalent to that during processing of the semiconductor substrate. In the desorption process of FIG. 8, when the standard is not satisfied, the automatic processing by the plasma processing apparatus is stopped here, the chamber is opened to the atmosphere, and the substrate is collected. When it is determined that the flow rate change amount satisfies the standard and the removal of the substrate is completed, the push-up pin is raised to transport the semiconductor substrate out of the chamber, and the next substrate to be processed is transported.

  In the third embodiment of the present invention, the semiconductor substrate is slightly lifted mechanically and forcibly from the lower electrode in advance to assist in the detachment, and the charge is substantially removed, while further confirming the change in the helium gas flow rate. Since it is desorbed, there is an advantage that desorption can be surely performed and the desorption time can be shortened by the amount of adopting the forcible desorption step. Table 1 shows the results in the case of processing a semiconductor substrate using this embodiment.

表１から明らかな通り、従来半導体基板処理１００００枚毎に１０回発生していた搬送トラブルを０回に抑制することが可能となった。また、半導体基板の脱離にかかる時間が１０秒短縮され、基板処理時間も１０秒短縮されるので１時間当たりの基板処理枚数が３６枚から４０枚へ増加させることを達成した。

As is apparent from Table 1, it has become possible to suppress the transport trouble that has occurred 10 times for every 10000 wafers processed in the past to 0 times. Further, the time required for desorption of the semiconductor substrate is reduced by 10 seconds, and the substrate processing time is also reduced by 10 seconds, so that the number of processed substrates per hour can be increased from 36 to 40.

  As described above, the substrate detachment method according to the present invention can be applied not only to dry etching and plasma CVD processes, but also to manufacturing using other apparatus for fixing a substrate by electrostatic adsorption.

The figure which shows the conventional electrode structure of the system which fixes a semiconductor substrate to a lower electrode mechanically. The figure which shows the electrode structure of the system which fixes a semiconductor substrate to a lower electrode using the conventional electrostatic attraction force. The process flowchart of the board | substrate removal | desorption process by the 1st Embodiment of this invention. The graph which shows the helium gas flow rate change from a semiconductor substrate process to a board | substrate removal | desorption process. The graph which shows the helium gas flow rate change in the semiconductor substrate removal | desorption process at the time of a semiconductor substrate process. The process flowchart of the board | substrate removal | desorption process by the 2nd Embodiment of this invention. The graph which shows the helium gas flow rate change in the semiconductor substrate removal | desorption process at the time of a semiconductor substrate process. The process flowchart of the board | substrate removal | desorption process by the 3rd Embodiment of this invention. The figure which shows the structure of the lower electrode which has a push-up pin similarly. The graph which shows a helium gas flow rate value change when a semiconductor substrate detachment | desorption process is used. FIG. 6 is a graph showing a change in helium gas flow rate when the semiconductor substrate is mechanically raised in the semiconductor substrate detachment process during semiconductor substrate processing and then lowered again to the lower electrode to complete the detachment. FIG. 6 is a graph showing a change in helium gas flow rate when the semiconductor substrate is mechanically raised in the semiconductor substrate detachment process during processing of the semiconductor substrate and then lowered again to the lower electrode to cause detachment failure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing member 2 Semiconductor substrate 3 Lower electrode 4 Lower electrode 5 Helium gas 10 Push-up pin

Claims (7)

A substrate support that can supply gas to the backside of the substrate is fixed by adsorbing the substrate by electrostatic force, processing the substrate,
Measure the flow rate of the gas while supplying the gas from the substrate support part to which the substrate is fixed to the back surface of the substrate,
Determining whether the measured gas flow rate is greater than or equal to a predetermined standard flow rate value;
A method of manufacturing a semiconductor device, comprising: completing the desorption of the substrate from the substrate support portion when the measured gas flow rate becomes equal to or higher than the standard flow rate value. A substrate support that can supply gas to the backside of the substrate is fixed by adsorbing the substrate by electrostatic force, processing the substrate,
Measure the increasing gas flow rate while supplying gas from the substrate support part to which the substrate is fixed to the back surface of the substrate,
Determining whether the measured gas flow rate has reached or exceeded a predetermined standard flow rate value;
A step of completing the desorption of the substrate from the substrate support portion when the measured gas flow rate is equal to or higher than the standard flow rate value,
Before the gas flow rate reaches the standard value, it is determined whether or not the gas flow rate has reached each of one or more predetermined standard flow rate values which are smaller than the standard flow rate value and different from each other. A method for manufacturing a semiconductor device. A substrate support that can supply gas to the backside of the substrate is fixed by adsorbing the substrate by electrostatic force, processing the substrate,
Supplying gas to the back surface of the substrate from the substrate support portion to which the substrate is fixed, pressing the back surface of the substrate, and separating at least a part of the back surface of the substrate from the substrate support portion;
Measure the flow rate of the gas while pressing the back surface of the substrate,
When the measured gas flow rate is equal to or higher than a predetermined standard flow rate value, after removing the pressure, the flow rate variation from the measured gas flow rate is substantially measured,
A method of manufacturing a semiconductor device, comprising: completing the desorption of the substrate from the substrate support portion when the flow rate change amount is within a predetermined flow rate change amount.   The method for manufacturing a semiconductor device according to claim 1, wherein the gas is a gas for controlling a temperature of the substrate.   The semiconductor device manufacturing method according to claim 1, wherein the predetermined standard flow rate value is the gas flow rate value when the substrate is placed on the substrate support portion under substantially its own weight. Method.   The method of manufacturing a semiconductor device according to claim 3, wherein the substrate support portion is provided with a push-up pin for lifting the substrate from the support portion, and the pressing is performed by the push-up pin.   The method of manufacturing a semiconductor device according to claim 1, wherein the measurement of the gas flow rate is performed after removing a voltage applied to the substrate support portion in order to adsorb the substrate by electrostatic force.

Images