JP2010080990A - Insulation film etching apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulation film etching apparatus that effectively prevents particles from depositing onto a substrate and is excellent in performance. <P>SOLUTION: The substrate 9 is held on a substrate holder 2 in a process chamber 1, and gas for etching is introduced by a gas introduction system 3. Plasma is formed in a plasma formation means 4 by a means, and the insulation film on the surface of the substrate 9 is etched by action of active species and ions in the plasma. A control unit 8 introduces gas for cleaning by the gas introduction system 3 after completion of etching, forms plasma by the means 4 for plasma formation, and removes a film deposited on an exposure surface in the process chamber 1 by the action of plasma. A cooling trap 12 provided at a portion lower than a substrate holding surface is cooled forcedly, and a gas molecular having sedimentation is captured to deposit a number of films. The cooling trap 12 is replaceable. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an insulating film etching apparatus for etching an insulating film on a surface of a substrate.

  Surface treatments for substrates are actively performed in the manufacturing process of electronic devices such as LSI (Large Scale Integrated Circuit) and LCD (Liquid Crystal Display). Among these, the process of etching the insulating film on the surface of the substrate is one of the main processes when forming a fine circuit. For example, a resist pattern is formed by photolithography on a silicon substrate whose surface is covered with an insulating film such as a silicon oxide film or a silicon nitride film, and the insulating film is etched in a shape along the resist pattern using this as a mask. Is called. Then, fine wiring is formed by filling tungsten or aluminum into the etched portion.

Insulating film etching apparatuses mainly perform dry etching using plasma. Specifically, a gas is introduced into the process chamber, and plasma is formed by high frequency discharge. The introduced gas is a reactive gas such as CHF ₃ , and etching (reactive ion etching, RIE) is performed by the action of active species generated in the reactive gas plasma and the action of ions.

JP 2000-195830 A JP 2000-150487 A JP 2001-267297 A JP-A-11-150100 Japanese Patent Laid-Open No. 8-022980

  With the background of higher functionality, higher integration, and further improvement in performance of electronic devices, which are products, demands for insulating film etching apparatuses are becoming increasingly severe. In particular, the requirements regarding the cleanliness of the atmosphere in the process chamber are becoming more and more strict against the background of circuit miniaturization. In this respect, a problem in the insulating film etching apparatus is film deposition in the process chamber by the gas used for etching. Hereinafter, this point will be described by taking etching of a silicon oxide film as an example.

When the silicon oxide film is etched, plasma of a fluorinated hydrocarbon gas (CFC gas) such as CHF ₃ is formed. Fluorine liberated in the plasma of the fluorinated hydrocarbon gas reacts with silicon to generate volatile SiF ₄ . In addition, hydrogen and carbon liberated in the plasma react with oxygen to generate volatiles such as water vapor and carbon dioxide. In this way, etching is performed by converting the silicon oxide film into volatiles by reaction.
However, in etching using a fluorinated hydrocarbon-based gas, a carbon-based thin film tends to be deposited on the exposed surface in the process chamber during the etching due to the influence of unreacted gas and undecomposed gas. Film deposition may be caused by residual gas after etching is completed. The deposited film is a polymer film made of a material such as fluorine, carbon, or hydrogen.

  Thus, the film deposited on the exposed surface in the process chamber 1 may be peeled off due to internal stress or its own weight. When the deposited film peels off, fine particles (hereinafter referred to as particles) having a certain size are released. If these particles adhere to the surface of the substrate, in addition to abnormal etching shapes, there is a risk of causing serious defects such as circuit disconnection or short circuit. Further, when the peeled deposited film adheres to the substrate holding surface of the substrate holder, there arises a problem that the contact property between the substrate and the substrate holding surface is lowered in the next etching. If the contact between the substrate and the substrate holding surface is lowered, the temperature of the substrate during etching may become unstable or non-uniform, and the etching characteristics may be deteriorated.

In particular, recently, there are cases where gases having various actions are added and used against the background of miniaturization and high functionality of products, and film deposition tends to be facilitated by the influence of the additive gas. On the other hand, it is required to reduce the amount of particles that affect the etching process as much as possible. In a sense, there are strict demands on the insulating film etching apparatus that conflict with each other.
The invention of the present application has been made in order to solve such problems, and has technical significance to provide an insulating film etching apparatus with excellent performance that effectively prevents adhesion of particles to a substrate.

  In order to solve the above-mentioned problems, an invention according to claim 1 of the present application includes a process chamber having an exhaust system and performing an etching process therein, a substrate holder for holding the substrate at a predetermined position in the process chamber, and an etching action. Gas introduction system for introducing a certain gas into the process chamber, plasma forming means for forming plasma of the introduced gas, untreated substrates are loaded into the process chamber, and processed substrates are unloaded from the process chamber An insulating film etching apparatus that etches an insulating film on the surface of a substrate by the action of species generated in plasma, the substrate being held in the substrate holder in the process chamber A cooling trap for forced cooling is provided so as to occupy a position below the surface. The cooling trap collects gas molecules having a deposition action and deposits more films than other places, and is attached so as to be replaceable. The substrate holds the substrate, the cooling trap is attached to a side surface of the substrate holder, and the plasma forming means includes a counter electrode provided to face the substrate holder, and a counter electrode. A high-frequency power source for plasma formation that applies a high-frequency voltage; and further, ions are extracted from the plasma and made incident on the substrate holder by a self-bias voltage formed by applying the high-frequency voltage to the substrate holder. A bias power supply is connected, and a control unit for controlling the bias power supply is provided. Is the time of packaging processes with operating the bias power supply during the cleaning has a configuration that performs control to operate so that the small self-bias voltage than during the etching.

As described below, according to the invention described in claim 1 of the present application, since the cooling trap collects gas molecules having a depositing action, the deposition amount of the film at a problematic location is relatively reduced.
Further, in addition to the above effects, control is performed to stop the bias power supply and apply a floating potential to the substrate during cleaning, so that cleaning is performed without damaging the substrate holder.

It is the front sectional schematic diagram showing the composition of the principal part of the insulating film etching device of the embodiment of the present invention. It is the top view which showed schematically the whole apparatus shown in FIG. 4 is a flowchart showing an outline of a sequence control program provided in the control unit 8. It is the figure shown about the result of the experiment confirmed about adjustment of distribution of plasma density.

Embodiments of the present invention (hereinafter referred to as embodiments) will be described.
FIG. 1 is a schematic front sectional view showing a configuration of a main part of an insulating film etching apparatus according to an embodiment of the present invention. The apparatus shown in FIG. 1 includes a process chamber 1 having an exhaust system 11 in which etching is performed, a substrate holder 2 that holds a substrate 9 at a predetermined position in the process chamber 1, and an etching action in the process chamber 1. A gas introduction system 3 for introducing a certain gas, plasma forming means 4 for forming plasma of the introduced gas, and an untreated substrate 9 are carried into the process chamber 1 and the treated substrate 9 is loaded into the process chamber 1. And a transport system for unloading.

The process chamber 1 is an airtight vacuum vessel. The process chamber 1 is made of a metal such as stainless steel and is electrically grounded. The exhaust system 11 includes a vacuum pump 111 such as a dry pump and an exhaust speed adjuster 112, and the inside of the process chamber 1 can be maintained at a vacuum pressure of about 10 ⁻³ Pa to 10 Pa.
The substrate holder 2 includes a main holder portion 21 and a substrate holding block 22 provided in contact with the main holder portion 21. The main holder portion 21 is made of a metal such as aluminum or stainless steel. The substrate holding block 22 is made of a dielectric material such as alumina, and its upper surface is a substrate holding surface.
The substrate holder 2 is provided with a substrate adsorption mechanism 28 that adsorbs the substrate 9 by static electricity. The substrate suction mechanism 28 includes a substrate suction electrode 282 provided inside the substrate holding block 22 and a substrate suction power source 281 that applies a predetermined negative DC voltage to the substrate suction electrode 282.
An insulating tube 284 is provided in the substrate holder 2 so as to penetrate the inside and communicate with the substrate holding block 22. An introduction member 283 is inserted inside the insulating tube 284, and one end is connected to the substrate adsorption electrode 282. The other end of the introduction member 283 is connected to the substrate suction power source 281. In some cases, there is no substrate adsorption electrode 282, and the entire main holder 21 is used as an electrostatic adsorption electrode.

The substrate holding block 22 has a convex cross-sectional shape as a whole, and a step is formed in a circumferential shape. The substrate holding surface is the surface of the protruding portion. A correction ring 25 is provided so as to be placed on a step in the peripheral portion of the substrate holding block 22. The correction ring 25 is made of the same material as the substrate 9 such as single crystal silicon.
Regarding the consumption of the etching gas and the generation of reaction products during the etching, the outer portion of the substrate 9 is different from the central portion of the substrate 9. For this reason, the plasma component also differs between the region facing the central portion of the substrate 9 and the region facing the outer portion of the substrate 9. As a result, the etching characteristics may change in the peripheral portion of the surface of the substrate 9. A correction ring 25 is provided for the purpose of correcting such variations in etching characteristics in the peripheral portion.
The correction ring 25 is cooled by the holder cooling mechanism 27 in the same manner as the substrate 9, and the temperature is controlled so as to be the same temperature as the substrate 9. As a result, the correction ring 25 gives heat to the substrate 9 that is commensurate with the heat dissipation from the end face of the substrate 9, and suppresses a temperature drop in the peripheral portion of the substrate 9. If the temperature varies, the generation of reaction products also varies, and the etching characteristics become non-uniform as well, but this is also prevented by the correction ring 25.

The substrate holder 2 includes a heat transfer gas introduction system (not shown) that introduces a heat transfer gas into the gap between the substrate holding surface and the substrate 9. Normally, helium is used as the heat transfer gas.
The substrate holder 2 is attached to the process chamber 1 via an insulating block 26. The insulating block 26 is formed of an insulating material such as alumina, and insulates the main holder portion 21 from the process chamber 1 and protects the main holder portion 21 from plasma. In order to prevent a vacuum leak from occurring in the process chamber 1, sealing members such as an O-ring (not shown) are provided between the substrate holder 2 and the insulating block 26 and between the process chamber 1 and the insulating block 26. Is provided.

  The substrate holder 2 is provided with a cooling mechanism 27. The cooling mechanism (hereinafter referred to as “holder cooling mechanism”) 27 is a mechanism for circulating a refrigerant in a cavity provided in the main holder portion 21. The holder cooling mechanism 27 includes a refrigerant supply pipe 271 that supplies a refrigerant to a cavity in the main holder 21, a refrigerant discharge pipe 272 that discharges the refrigerant from the cavity, a pump or circulator 273 for supplying and discharging the refrigerant, and the like. Has been. As the coolant, for example, Fluorinert (trade name) manufactured by 3M Company having a temperature of about 20 to 80 ° C. is used, and the substrate holder 2 is entirely cooled to the same temperature during the etching process. Thereby, the board | substrate 9 is cooled to about 70-130 degreeC during an etching.

The gas having an etching action (hereinafter referred to as an etching gas) introduced by the gas introduction system 3 is a fluorinated hydrocarbon gas such as C ₄ F ₈ , CF _4, or CHF ₃ . Moreover, argon, oxygen, etc. may be used. The gas introduction system 3 includes a gas cylinder (not shown) that stores an etching gas, a pipe 31 that connects the gas cylinder and the process chamber 1, a valve 32 and a flow rate regulator 33 that are provided on the pipe 31. .

The plasma forming means 4 generates plasma by generating high frequency discharge in the introduced etching gas. The plasma forming means 4 is mainly composed of a counter electrode 41 provided so as to face the substrate holder 2 and a plasma forming high frequency power source 42 for applying a high frequency voltage to the counter electrode 41.
The counter electrode 41 and the substrate holder 2 constitute a so-called parallel plate electrode. The discharge space between the counter electrode 41 and the substrate holder 2 capacitively couples a high-frequency circuit by the plasma-forming high-frequency power source 42. That is, the plasma forming means 4 forms capacitively coupled plasma.

The counter electrode 41 is fitted in an upper wall of the process chamber 1 through an insulating block 44 in an airtight manner. The counter electrode 41 is also used as a gas introduction path by the gas introduction system 3. That is, as shown in FIG. 1, a front plate 411 is fixed to the front surface of the counter electrode 41. The front plate 411 has a hollow cross-sectional shape, and a large number of gas blowing holes are formed on the surface facing the substrate holder 2. The gas introduction system 3 is configured to temporarily store gas in the front plate 411 and then blow it out from each blowing hole.
As the plasma forming high-frequency power source 42, one having a frequency of about 10 MHz to 600 MHz and an output of about 0 to 5000 W is used. A matching unit 421 is provided between the counter electrode 41 and the plasma forming high frequency power source 42.

  The counter electrode 41 is also provided with a cooling mechanism 43. The cooling mechanism (hereinafter referred to as an electrode cooling mechanism) 43 is a mechanism for circulating a refrigerant in a cavity provided in the counter electrode 41. The electrode cooling mechanism 43 includes a refrigerant supply pipe 431 that supplies a refrigerant to the cavity in the counter electrode 41, a refrigerant discharge pipe 432 that discharges the refrigerant from the cavity, a pump or circulator 433 for supplying and discharging the refrigerant, and the like. Has been. Similarly, a fluorinate of about 20 to 80 degrees is used as the coolant, and the counter electrode 41 is cooled to about 90 to 150 degrees during the etching process.

  In the present embodiment, a bias power source 6 is connected to extract ions from the plasma and make them incident on the surface of the substrate by a self-bias voltage formed by applying a high frequency voltage to the substrate holder 2. The bias power source 6 is a high frequency power source different from the plasma forming high frequency power source 42. The bias power source 6 has a frequency of 400 kHz to 13.56 MHz and an output of about 0 to 5000 W. A variable capacitor 61 is provided between the substrate holder 2 and the bias power source 6. A matching unit (not shown) is provided between the bias power source 6 and the substrate holder 2, and the variable capacitor 61 may be a part of the matching unit.

  When a high frequency voltage is applied to the substrate 9 through a capacitance in a state where plasma is formed in the process chamber 1, the potential of the surface of the substrate 9 is negative DC voltage with respect to the high frequency due to the interaction between the plasma and the high frequency electric field. It becomes the change which superimposed. This negative DC component voltage is the self-bias voltage. An electric field from the plasma toward the substrate 9 is formed by the self-bias voltage, and ions in the plasma are extracted by this electric field and efficiently enter the substrate 9.

  FIG. 2 is a plan view schematically showing the entire apparatus shown in FIG. As shown in FIG. 2, in this apparatus, a transfer chamber 50 is provided at the center, and a process chamber 1 and a load lock chamber 7 are provided around the transfer chamber 50. A gate valve 10 is provided at the boundary between the chambers. Although a plurality of process chambers 1 are shown in FIG. 2, there may be a case where the same etching process is performed, and a case where the process before or after the etching process is performed. .

As the transport system, an articulated arm type robot 51 is used in this embodiment. A robot (hereinafter referred to as a transfer robot) 51 holds the substrate 9 at the tip of the arm, and transfers the substrate 9 to an arbitrary position by performing an arm expansion / contraction motion, a rotational motion around a vertical axis, and an arm lifting motion. It is like that.
The transfer robot 51 is provided in the central transfer chamber 50. The unprocessed substrate 9 is carried into the load lock chamber 7 from the atmosphere side. The transfer robot 51 takes out the substrate 9 from the load lock chamber 7, loads it into the process chamber 1, and places it on the substrate holder 2. After the etching process, the transfer robot 51 removes the substrate 9 from the substrate holder 2 and returns it to the load lock chamber 7.
An autoloader 52 is provided outside the load lock chamber 7 (atmosphere side). The autoloader 52 carries the unprocessed substrate 9 from the cassette 53 arranged on the atmosphere side into the load lock chamber 7 and carries the processed substrate 9 from the load lock chamber 7 to the cassette 53 on the atmosphere side.

Further, as shown in FIG. 1, the insulating film etching apparatus includes a control unit 8 that controls each unit. The control unit 8 controls operations of the exhaust system 11, the gas introduction system 3, the substrate adsorption mechanism 28, the plasma forming high frequency power supply 42, the bias power supply 6, the holder cooling mechanism 27, the transport system, and the like.
One of the major features of the apparatus according to the present embodiment is that cleaning for removing a film (hereinafter, deposited film) deposited on an exposed surface in the process chamber 1 during the etching process can be performed. . Hereinafter, this point will be described in detail.

  First, in addition to the etching gas described above, the gas introduction system 3 can introduce a gas having a cleaning action (hereinafter referred to as a cleaning gas). As the cleaning gas, oxygen is used in this embodiment. The gas introduction system 3 opens or closes the valve 32 under the control of the control unit 8 to introduce either the etching gas or the cleaning gas.

  Cleaning is performed by forming a plasma of the introduced oxygen. The oxygen plasma is formed by high frequency discharge as in the etching. In the present embodiment, the plasma forming high-frequency power source 42 is also used for cleaning. When oxygen plasma is formed by the plasma forming high-frequency power source 42, oxygen ions and oxygen active species are actively generated in the plasma. Deposits on the exposed surface in the process chamber 1 are removed by the arrival of these ions and active species.

  More specifically, in the present embodiment, it is assumed that the silicon oxide film is etched as described above, and the etching gas is a fluorocarbon (fluorocarbon) gas. Therefore, the deposited film is made of carbon, hydrocarbon, or the like. Oxygen ions and active oxygen species in the plasma react with these materials to generate volatiles such as carbon dioxide and water vapor. Volatiles are exhausted out of the process chamber 1 by the exhaust system 11.

  In addition, the control unit 8 includes a sequence control program that performs control including optimal control of each part of the apparatus for cleaning. FIG. 3 is a flowchart showing an outline of a sequence control program provided in the control unit 8. Hereinafter, the sequence control program provided in the control unit 8 will be described with reference to FIG.

  When the operation of the apparatus is started, the sequence control program exhausts each chamber by the respective exhaust system and confirms whether or not a predetermined vacuum pressure is obtained. Next, the transport system is operated to carry the first substrate 9 into the process chamber 1 and place it on the substrate holder 2. The controller 8 operates the electrostatic adsorption mechanism 28 to electrostatically adsorb the substrate 9 onto the substrate holder 2 and operates the gas introduction system 3 to introduce the etching gas at a predetermined flow rate. After confirming that the pressure in the process chamber 1 and the flow rate of the etching gas are predetermined values, the plasma forming high frequency power source 42 is operated to form plasma, and the bias power source 6 is operated. Thereby, the insulating film on the surface of the substrate 9 is etched by the action of ions and active species in the plasma. The holder cooling mechanism 27 and the electrode cooling mechanism 43 are basically constantly operating during operation of the apparatus, and the substrate holder 2 and the counter electrode 41 are cooled.

  After the start of etching, the sequence control program starts a timer. When the count of the timer reaches a predetermined value, the operations of the bias power source 6, the electrostatic adsorption mechanism 28, and the plasma forming high frequency power source 42 are stopped in this order. Then, the introduction of the etching gas by the gas introduction system 3 is also stopped, and the inside of the process chamber 1 is exhausted again by the exhaust system 11. Thereafter, the transfer system is controlled to take out the substrate 9 from the process chamber 1 and return it to the load lock chamber 7.

  Next, the sequence control program shifts to control for cleaning. Specifically, the exhaust system 11 is operated to exhaust the process chamber 1 again. After confirming that the exhaust gas is exhausted to a predetermined pressure by a vacuum gauge (not shown), a signal is sent to the gas introduction system 3 to switch the valve 32 to introduce oxygen gas at a predetermined flow rate. After confirming that the amount of oxygen gas introduced and the pressure in the process chamber 1 are maintained at predetermined values, the sequence control program operates the plasma forming high-frequency power source 42 to form plasma. As a result, as described above, the deposited film is removed by the action of oxygen plasma. The sequence control program stops the operations of the holder cooling mechanism 27 and the electrode cooling mechanism 43 almost simultaneously with the operation of the plasma forming high frequency power supply 42. That is, the circulation of the refrigerant is stopped.

The sequence control program starts counting the timer as the cleaning starts, and stops the operation of the plasma-forming high-frequency power source 42 when the timer count reaches a predetermined value. At the same time, the operation of the gas introduction system 3 is stopped. Further, the operations of the holder cooling mechanism 27 and the electrode cooling mechanism 43 are resumed.
Next, the sequence control program prepares for processing the next substrate 9. That is, the exhaust system 11 is operated to exhaust the process chamber 1 again, and after confirming that the process chamber 1 is exhausted to a predetermined pressure, the transport system is operated to carry the next substrate 9 into the process chamber 1. . Thereafter, etching is performed in the same sequence as described above. Then, after the processing is completed, the processing number counter is updated by adding 1.

  In this manner, the substrate 9 is etched by single wafer processing while cleaning is performed for each processing. In the present embodiment, 25 substrates 9 are accommodated in the cassette 53, and when the etching of the 25 substrates 9 is completed, one lot of processing is completed. In the present embodiment, the cleaning is performed before the processing of the next lot. That is, although not shown in FIG. 3, when the processing number counter reaches 25, the sequence control program performs cleaning again before the first substrate 9 of the next lot is carried.

Although not shown in FIG. 3, the sequence control program performs cleaning before starting the processing of the first lot after starting the operation of the apparatus. That is, in this embodiment, cleaning is performed between the processing of each substrate 9 and between the processing of each lot.
Specifically, the control unit 8 is a microcomputer including a CPU, a memory, a hard disk, and the like. The sequence control program described above is installed on the hard disk, and when the apparatus is in operation, it is read from the hard disk, stored in a memory, and executed by the CPU.

In the insulating film etching apparatus of the present embodiment, since the deposited film is removed by cleaning, the generation of particles due to the peeling of the deposited film is suppressed. For this reason, generation | occurrence | production of abnormality, such as a circuit defect, by the particle adhering to the surface of the board | substrate 9 is prevented effectively. Further, since the particles adhere to the substrate holding surface, the temperature of the substrate 9 does not become non-uniform or unstable during the next etching. In particular, in a configuration in which a heat transfer gas such as helium is introduced between the substrate and the substrate holding surface, the heat transfer gas needs to be confined at the interface. There is. In this embodiment, such a heat transfer gas confinement error is also prevented.
By the way, when the plasma-forming high-frequency power source 42 is operated at 60 MHz and 1500 W, oxygen gas is introduced as a cleaning gas at a flow rate of 100 sccm, and cleaning is performed at a pressure of 5 Pa, the particle size of 0.2 μm or more adhering to the substrate 9 is increased. The number of particles can be stably suppressed to less than 20.

In this embodiment, since the cleaning is performed each time the substrate 9 is etched, the above-described effect is enhanced. Further, since the cleaning is performed for each lot, the above effect is further enhanced. That is, if the deposited film cannot be completely removed during the cleaning performed each time the substrate 9 is etched, the deposited film that remains increases as the number of processed sheets increases. Therefore, additional cleaning is performed at the timing when the processing of one lot is completed to completely remove the remaining deposited film.
If the amount of the deposited film deposited in one etching is not so large, the cleaning frequency may be less than that described above. For example, cleaning is performed every several etchings, or only cleaning for each lot is performed.

  After the apparatus has been operating for a long time, the inside of the process chamber 1 may be subjected to wet cleaning. Even in this case, if the dry cleaning as described above is performed, the total time required for the wet cleaning can be remarkably shortened. For example, even in an apparatus that performs wet cleaning after an operating time of 200 hours, if cleaning is performed under the above-described conditions, the total time required for wet cleaning is less than 3 hours, and the operating efficiency of the apparatus is reduced. Is greatly improved.

One of the important points in the configuration of the sequence control program described above is that the holder cooling mechanism 27 and the electrode cooling mechanism 43 are operated during etching, but are not operated during cleaning. This point has the technical significance of improving the cleaning efficiency and ending the cleaning in a short time.
The reason for cooling the substrate holder 2 during the etching is mainly to prevent the substrate 9 from being heated more than the limit by the heat from the plasma. The counter electrode 41 is also heated so as not to be thermally damaged. On the other hand, at the time of cleaning, there is no substrate 9 on the substrate holder 2, and the time required for cleaning is shorter than etching. Since cleaning is based on a reaction with oxygen ions or oxygen active species, the higher the temperature, the higher the effect.

  Therefore, in this embodiment, the operations of the holder cooling mechanism 27 and the electrode cooling mechanism 43 are stopped during cleaning so that the temperature of the substrate holder 2 and the counter electrode 41 is higher than that during etching. A large amount of film is deposited on the surface of the correction ring 25 of the substrate holder 2 and the opposing surface (lower surface) of the counter electrode 41, but these films are exposed to high temperatures and oxygen ions / oxygen-activated species quickly. Removed. In addition to completely stopping the holder cooling mechanism 27 and the electrode cooling mechanism 43 during cleaning, the holder cooling mechanism 27 and the electrode cooling mechanism 43 may be operated with a reduced capability compared to the etching. Decreasing the capacity means increasing the temperature of the refrigerant or decreasing the circulation amount of the refrigerant.

Another important point in the configuration of the sequence control program is that the bias power source 6 is not operated during cleaning. This point has technical significance in protecting the substrate holder 2 by preventing excessive ions from being incident on the substrate holder 2 during cleaning.
As described above, the bias power source 6 has an effect of increasing the etching efficiency by extracting ions from the plasma and making them enter the substrate 9. However, since there is no substrate 9 during cleaning, if the ions are excessively extracted, the substrate holding surface of the substrate holder 2 may be damaged by the incidence of ions. Therefore, the bias power source 6 is not operated during cleaning.

  However, since a film is deposited on the surface other than the substrate holding surface, the bias power source 6 may be operated to some extent. Even in this case, the self-bias voltage generated on the surface of the substrate holder 2 is made smaller than that in the case of etching to the extent that the substrate holding surface is not damaged. The degree of self-bias voltage at which the substrate holding surface is not damaged depends on the pressure. Therefore, it cannot be generally stated, but the self-bias voltage is within the range of 1 to 100 Pa, which is normally considered as the pressure during cleaning. Should be about 0 to 100V.

In addition, the apparatus according to the present embodiment is specially devised so as to suppress a decrease in productivity while performing the above-described cleaning. Hereinafter, this point will be described.
As a technical means for suppressing a decrease in productivity, the apparatus of this embodiment includes a cooling trap 12 that actively deposits a deposited film. The cooling trap 12 is provided at a position below the surface of the substrate 9. Specifically, as shown in FIG. 1, the cooling trap 12 is provided on the side surface of the substrate holder 2.

  In addition, the apparatus includes a refrigerant block 121 as a member for cooling the cooling trap 12. The refrigerant block 121 is a member that is directly cooled by the refrigerant flowing therein. The refrigerant block 121 is a ring-shaped member that surrounds the lower end portion of the substrate holder 2. A refrigerant supply pipe 122 that supplies the refrigerant to the cavity in the refrigerant block 121, a refrigerant discharge pipe 123 that discharges the refrigerant from the cavity, and a pump or circulator 124 for supplying and discharging the refrigerant are provided. A temperature control unit (not shown) is provided for cooling and supplying the discharged refrigerant to a predetermined temperature.

The cooling trap 12 has a cylindrical shape surrounding the substrate holder 2. As shown in FIG. 1, the cooling trap 12 has a flange portion at the lower end portion. The cooling trap 12 is fixed to the refrigerant block 121 with good thermal contact by screwing the flange portion to the refrigerant block 121. A thin sheet member (not shown) (for example, a carbon sheet) is sandwiched between the interfaces so as to further improve the thermal contact between the two. The surfaces of the cooling trap 12 and the refrigerant block 121 are not completely flat but have minute irregularities. Therefore, a minute space is formed at the interface between the two. Since this space is under vacuum pressure, the thermal conductivity is not good. A sheet-like member fills this space and improves heat transferability.

  For example, Fluorinert or Galden is used as the refrigerant, and the temperature of the supplied refrigerant is about 20 to 80 ° C. Thereby, the cooling trap 12 is cooled to about 40-100 degreeC during an etching. The forced cooling of the cooling trap 12 is essential to be performed during etching, but it may be always forcedly cooled during operation of the apparatus.

Film deposition during etching tends to occur on the exposed surface at a low temperature in the process chamber 1. This is a result of the unreacted and undecomposed etching gas molecules having a deposition action being deprived of energy at a low temperature and trapped on the exposed surface. At high temperatures, the depositing gas molecules float again in the process chamber 1 away from the exposed surface to maintain high energy even when the exposed surface is reached.
According to the apparatus of the present embodiment, a large amount of gas molecules having a deposition action are collected in the cooling trap 12 and grow into a film. For this reason, film deposition on other locations in the process chamber 1 is relatively reduced. Therefore, compared to the case where there is no cooling trap 12, the amount of a film (including deposition due to residual gas after etching) deposited in one etching process is reduced. This means that less frequent cleaning is required. That is, according to the present embodiment provided with the cooling trap 12, it is possible to effectively perform a cleaning process with less particles while effectively reducing a decrease in productivity due to an increase in the frequency of cleaning. Has technical significance.

  A thin film is deposited and grown on the surface of the cooling trap 12 by the collected gas molecules. For this reason, the cooling trap 12 is replaced after being used for a certain number of etching processes. The process chamber 1 can be divided by a dividing unit (not shown). When replacing the cooling trap 12, the process chamber 1 is vented to return to atmospheric pressure, and then the process chamber 1 is divided, and the cooling trap 12 is removed from the refrigerant block 121. Then, the cooling trap 12 from which the new or surface deposited film is removed is attached.

  In the present embodiment, the refrigerant is not circulated and cooled directly in the cooling trap 12, but the refrigerant is circulated in the refrigerant block 121 and the cooling trap 12 is detachably attached to the refrigerant block 121. When the coolant is directly circulated through the cooling trap 12, when the cooling trap 12 is replaced, it is necessary to stop the circulation of the refrigerant and to extract the refrigerant from the cooling trap 12. There is no trouble.

Further, the surface of the cooling trap 12 is formed with minute irregularities as shown in an enlarged view in FIG. This unevenness prevents peeling of the deposited film. The deposited film is easy to peel off when the surface is flat, but when unevenness is provided, peeling is prevented because it is caught by the unevenness.
Such unevenness is formed by alumina spraying, for example, by spraying heated and melted alumina. In some cases, the surface of the aluminum is alumite-treated after forming irregularities by sandblasting.

  In any case, the surface of the cooling trap 12 is preferably made of an oxide or an insulator. This is because the deposited film is often organic based on the relationship with the type of gas used for insulating film etching. This is because in the case of an organic film, an oxide or an insulator has higher affinity and less peeling than aluminum or stainless steel. Therefore, the surface of the cooling trap 12 may be coated with a fluororesin. The main body of the cooling trap 12 and the refrigerant block 121 are made of metal such as aluminum, stainless steel, or copper in consideration of thermal conductivity.

The cooling trap 12 is provided at a position below the surface of the substrate 9 in consideration of a problem in the event that particles are emitted from the cooling trap 12. As described above, the cooling trap 12 has less peeling of the deposited film, but the possibility of peeling is not zero. If the deposited film is peeled off, if the cooling trap 12 is positioned higher than the surface of the substrate 9, there is a high possibility that it adheres to the surface of the substrate 9 when dropped. Considering the point of the exhaust path by the exhaust system 11, the cooling trap 12 is preferably provided at a position closer to the surface of the substrate 9 with respect to the exhaust port provided in the wall of the process chamber 1. This is to increase the possibility that particles will not reach the surface of the substrate 9 and be exhausted by the exhaust system 11 even if the deposited film is peeled off. As shown in FIG. 1, the apparatus of this embodiment also satisfies this configuration.

In addition, the apparatus of the present embodiment has a special contrivance for the plasma formation method in order to further increase the cleaning effect. Hereinafter, this point will be described.
As described above, the reason why the deposited film becomes a problem is that particles are generated by peeling and adhere to the surface of the substrate 9. Therefore, a problem is more likely to occur as the deposited film is deposited near the substrate 9 held by the substrate holder 2. In the configuration of the present embodiment, the correction ring 25 surrounding the substrate holding surface of the substrate holder 2 and the film deposited in the vicinity thereof correspond to this. The cleaning is based on the action of oxygen ions or oxygen active species generated in the plasma. For this reason, it is preferable to increase the plasma density in a space that faces the peripheral portion of the substrate holder 2.

  According to the inventor's research, in the parallel plate capacitively coupled high-frequency plasma as in the present embodiment, when the magnitude of the capacitance of the variable capacitor provided between the power source and the electrode is adjusted, the electrode (the counter electrode 41 and the electrode) is adjusted. It has been found that the plasma density distribution in a direction parallel to the substrate holder 2) can be adjusted.

FIG. 4 is a diagram showing the results of an experiment confirming this point. The experiment shown in FIG. 4 was performed under the following conditions. Although the bias power source 6 is operated, the self-bias voltage is smaller than that during etching as described above. “Sccm” is a gas flow rate (standard cubic centimeter par minute) converted to 0 degree and 1 atm.
Plasma forming high frequency power supply 42: frequency 60 MHz, output 1800 W
Bias power supply 6: frequency 1.6 MHz, output 1800 W
Pressure in the process chamber 1: 3.3 Pa
Introduced gas: Oxygen Gas flow rate: 100 sccm

The horizontal axis in FIG. 4 is the position in the direction parallel to the electrode in the discharge space, and the vertical axis is the plasma density (number density of electrons or ions). In FIG. 4, the data plotted with ● is when the capacitance of the variable capacitor 61 is zero, and the data plotted with ▪ is when the capacitance is about 55 pF. Even when the capacitance of the variable capacitor 61 is zero, a certain amount of capacitance exists between the substrate 9 and the ground because of the stray capacitance and the capacitance of the substrate holding block 22.
As shown in FIG. 4, when the capacitance of the variable capacitor 61 is set to about 50 to 60 pF as compared with the case where the capacitance of the variable capacitor 61 is zero, the protrusion of the plasma density in the peripheral portion is confirmed.

  In the present embodiment, in consideration of such points, a variable capacitor 61 is provided between the bias power supply 6 and the substrate holder 2 so that the capacitance can be adjusted so as to obtain a desired plasma density distribution. The degree of capacitance that causes the plasma density to protrude in the peripheral portion depends on the pressure, the frequency and output of the high-frequency power source 42 for forming plasma. Therefore, the capacitance at which plasma density protrusion is observed under optimum cleaning conditions is experimentally examined in advance. Then, the control unit 8 is controlled to perform the cleaning so as to obtain the capacitance. That is, the control unit 8 individually controls the variable capacitors 61 so as to obtain the optimum capacitance for each of etching and cleaning. A variable capacitor may be provided between the plasma forming high-frequency power source 42 and the counter electrode 41 to control this.

  Note that, under the above-described conditions, the capacitance of 55 pF is actually used for the resonance of the high frequency of the plasma-forming high-frequency power source 42 between the substrate holder 2 and the ground portion below. However, the achievement of this resonance is not an essential condition for the above-described protrusion of the plasma density in the peripheral portion.

  In the insulating film etching apparatus of this embodiment described above, a covering member having the same shape and dimension as the substrate 9 may be disposed on the substrate holding surface in order to protect the substrate holding surface of the substrate holder 2 during cleaning. The covering member is kept waiting in the load lock chamber 7 or the like during the etching, and is transported by a transport system during cleaning and is disposed on the substrate holding surface in the same manner as the substrate 9. In this way, the substrate holding surface is protected, and there is no problem even if the ion bias is increased by generating a self-bias voltage comparable to that during etching. The covering member is formed of a material that is not etched by oxygen plasma or a material that does not cause a problem even if it is etched, such as silicon or carbon, so as not to release contaminants.

The insulating film etched by the insulating film etching apparatus of the present invention is not limited to the above-described silicon oxide film or silicon nitride film. In addition to oxygen, N ₂ , H ₂ , NH ₃ , H ₂ O, CF ₄ , CHF ₃ or the like may be used as the cleaning gas.

DESCRIPTION OF SYMBOLS 1 Process chamber 11 Exhaust system 12 Cooling trap 2 Substrate holder 25 Correction ring 27 Holder cooling mechanism 28 Electrostatic adsorption mechanism 3 Gas introduction system 32 Valve 4 Plasma formation means 41 Counter electrode 42 High frequency power supply 43 for plasma formation Electrode cooling mechanism 51 Transfer robot 6 Bias power supply 61 Variable capacitor 7 Load lock chamber 8 Control unit 9 Substrate

Claims (1)

A process chamber having an exhaust system and in which an etching process is performed; a substrate holder that holds the substrate in a predetermined position in the process chamber; and a gas introduction system that introduces an etching gas into the process chamber. A plasma forming means for forming a plasma of a gas, and a transfer system for carrying an untreated substrate into the process chamber and carrying the treated substrate out of the process chamber, by the action of species generated in the plasma. An insulating film etching apparatus for etching an insulating film on a surface of a substrate,
A cooling trap that is forcibly cooled is provided in the process chamber so as to occupy a position below the surface of the substrate held by the substrate holder, and the cooling trap is a gas molecule having a deposition action. It collects more films than other places by collecting, and is attached so that it can be replaced.
The substrate holder is for holding the substrate on the upper surface, and the cooling trap is attached to a side surface of the substrate holder,
The plasma forming means comprises a counter electrode provided so as to face the substrate holder, and a plasma forming high frequency power source for applying a high frequency voltage to the counter electrode,
Further, the substrate holder is connected with a bias power source for extracting ions from the plasma by a self-bias voltage formed by applying a high frequency voltage to the substrate holder, and controlling the bias power source. The control unit operates the bias power source during the etching process and controls the self-bias voltage to be smaller during the cleaning than during the etching. An insulating film etching apparatus that performs the above-described process.

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