JP2000200772A - Plasma processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing method capable of preventing the generation of an etching stop without causing damage to a photoresist film layer. SOLUTION: A processing gas including C4F8, CO, and Ar is introduced into the processing chamber 102 of an etching device 300 and then plasma is produced to etch a SiO2 film layer formed on a wafer W on a bottom electrode 106. An analyzer 302 measures the amounts of the etchant and the by- products in the plasma from infrared laser beams passing the plasma by an infrared laser absorption analyzing method. A controller 156 controls the dose of O2 gas so that the amounts of the etchant and the by-product measured are equal to those previously set according to an increase in the aspect ratio of the contact hole to dope the processing gas with the O2 gas, wherein the dose of the O2 gas is increased according to an increase in the aspect ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a plasma processing method.

[0002]

2. Description of the Related Art Conventionally, a plasma in which a lower electrode also serving as a mounting table for an object to be processed, for example, a semiconductor wafer (hereinafter, referred to as a "wafer"), and a grounded upper electrode are arranged in an airtight processing chamber. An etching apparatus has been proposed. In this apparatus, a wafer is first placed on the lower electrode, and then a predetermined processing gas is introduced into the processing chamber, and the processing chamber is evacuated to maintain a predetermined reduced-pressure atmosphere. Next, by applying a high-frequency power to the lower electrode, the processing gas is dissociated to generate plasma, and the plasma is used to perform etching on, for example, a SiO ₂ film layer formed on the surface to be processed of the wafer, thereby forming a plasma. A contact hole is formed.

When a contact hole is formed in the SiO ₂ film layer, at least CF 3 is used as a processing gas.
A gas containing (fluorocarbon) -based gas and O ₂ , for example, a mixed gas of C ₄ F ₈ , CO, Ar and O ₂ is used. When C ₄ F ₈ dissociates, F ^* (fluorine radical) and C
Radicals such as F ^* (fluorocarbon radical), ions and electrons are generated, and the SiO ₂ film layer is etched by a competitive reaction between the radicals and ions therein. Since C ₄ F ₈ is a gas containing carbon (C),
During the treatment, reaction products such as carbon and CF-based compounds are generated. Therefore, when the reaction product adheres to and deposits on the photoresist film layer formed on the SiO ₂ film layer, particularly on the shoulder of the opening of the etching pattern, the shoulder is protected from ion bombardment by the reaction product. Therefore, the opening of the pattern does not widen, and a predetermined narrow contact hole is formed.

The above-mentioned O ₂ is added to the processing gas in order to suppress the occurrence of the etch stop. That is, it has been empirically found that adding O ₂ to the processing gas has at least an action of removing the above reaction products, and adding an appropriate amount of O ₂ to the processing gas causes the bottom of the contact hole to be removed. Of the above reaction products is reduced,
The occurrence of etch stop can be prevented. However, if O ₂ is excessively added to the processing gas, not only the reaction products deposited on the bottom of the contact hole but also the reaction products deposited on the photoresist film layer are removed, and the shoulder is etched and the pattern is removed. The opening diameter of is widened. Therefore, for example, C ₄ F ₈ , CO and Ar are added to the processing gas so as to prevent the occurrence of an etch stop and to reduce the amount of shaving of the shoulder portion of the photoresist film layer.
Flow rates of 10 sccm, 50 sccm and 200 sccm, respectively.
In the case of sccm, the etching process is performed by constantly adding 5 sccm of O ₂ .

[0005]

However, with the recent trend toward ultra-miniaturization and ultra-high integration of semiconductor devices,
When forming a contact hole having a so-called high aspect ratio having a relatively small inner diameter with respect to the depth of the contact hole, even if O ₂ is added to the processing gas as described above,
An etch stop may occur. Also, if the added amount of O ₂ is increased in order to eliminate the etch stop, the photoresist film layer and the shoulder are eroded as described above, so that the inner diameter of the contact hole is widened and so-called CD loss (critical dimension). loss) occurs,
Before the required amount of etching of the SiO ₂ film layer, the photoresist film layer is completely removed, so that a narrow contact hole cannot be formed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to prevent the occurrence of an etch stop without damaging a mask pattern, and to achieve a high level of performance. An object of the present invention is to provide a new and improved plasma processing method capable of forming a contact hole having an aspect ratio.

[0007]

According to a first aspect of the present invention, there is provided a processing apparatus including at least a fluorocarbon introduced into a processing chamber according to the first aspect of the present invention. In a plasma processing method in which a gas is converted into plasma and a plasma processing is performed on a silicon oxide film layer formed on an object to be processed disposed in a processing chamber, oxygen is intermittently added to the processing gas. A plasma processing method is provided.

According to this configuration, since oxygen is intermittently added to the processing gas, the occurrence of an etch stop can be prevented when, for example, a plasma etching process is performed on the SiO ₂ film layer to form a contact hole. Amount of O ₂
Is added to the processing gas, the photoresist film layer formed on the SiO ₂ film layer and the shoulder thereof are hardly damaged.
For example, when etching is performed with a process gas containing C ₄ F _8, even with the addition of the conventional number of O ₂ than the etching method in order to prevent the occurrence of an etch stop during the addition of O _2, O _Since reaction products can be deposited on the photoresist film layer when ₂ is not added, the photoresist film layer and its shoulder can be protected. As a result, since the opening diameter of the pattern formed in the photoresist film layer does not increase and no etch stop occurs, a contact hole having a high aspect ratio can be formed.

Further, when oxygen is added to the processing gas periodically (pulse-wise), for example, as in the second aspect of the present invention, the occurrence of the etch stop and the deposition of the reaction product can be improved. This can be performed reliably, and the addition control of O ₂ can be easily performed.

Further, if the time for adding oxygen is relatively shorter than the time for not adding oxygen, for example, as in the third aspect of the present invention, the total amount of O ₂ introduced (input amount) can be reduced. Even if the total amount is less than the total amount in the case of the continuous introduction, it is possible to prevent the etch stop from occurring while minimizing the damage to the photoresist film layer and its shoulder.

In the process of forming a contact hole in a silicon oxide film layer, an etch stop tends to occur in proportion to an increase in the aspect ratio. Therefore, for example, when a contact hole is formed in a silicon oxide film layer by plasma treatment as in the invention of claim 4, if the amount of added oxygen is increased in accordance with the increase in the aspect ratio of the contact hole, Even if the aspect ratio increases with the progress of etching, the occurrence of etch stop can be reliably prevented. In addition, in the initial stage of processing having a small aspect ratio, the amount of added O ₂ can be reduced, so that damage to the photoresist film layer can be prevented. In this specification, the aspect ratio refers to the ratio (b / a) between the inner diameter (width) a and the depth (height) b of the contact hole.

Further, according to the invention, for example, the relationship between the change in the aspect ratio and the change in the plasma component can be determined in advance, and the amount of oxygen added can be adjusted according to the change in the plasma component. . The change in the aspect ratio is difficult to measure during processing, but the present invention can adjust the amount of added O ₂ based on the change in the plasma component corresponding to the change in the aspect ratio. the amount adjustment of the O ₂ in response to changes in aspect ratio can be easily and reliably.

In general, even if O ₂ is added after plasma stabilization as in the invention of claim 6,
Since the above-mentioned etch stop occurs after the etching has progressed to some extent, it does not affect the processing.

According to a second aspect of the present invention, as in the invention according to claim 7, the processing gas containing at least fluorocarbon introduced into the processing chamber is turned into plasma and placed in the processing chamber. In a plasma processing method for performing plasma processing on a silicon oxide film layer formed on a processing object, oxygen is added to a processing gas,
Characterized by relatively increasing or decreasing the amount of oxygen added,
A plasma processing method is provided.

According to this configuration, the amount of O ₂ added to the processing gas is relatively increased or decreased.
Similarly to the invention described in (1), the occurrence of etch stop is prevented when the O ₂ addition amount is relatively large, and the reaction product is added to the photoresist film layer when the O ₂ addition amount is relatively small. Can be deposited to protect the photoresist film layer, so that a contact hole with a high aspect ratio can be formed.

If the amount of added oxygen is increased or decreased periodically, for example, as in the eighth aspect of the present invention, it is possible to prevent the occurrence of an etch stop in the same manner as in the second aspect of the present invention. In addition, the protection of the photoresist film layer can be reliably performed, and the addition amount of O ₂ can be easily controlled.

Further, if the increasing time of the added amount of oxygen is set to be relatively shorter than the decreasing time of the added amount of oxygen, for example, as in the ninth aspect of the present invention, the invention according to the third aspect is provided. Similarly to the above, it is possible to prevent an etch stop from occurring while minimizing damage to the photoresist film layer.

In the case where a contact hole is formed in a silicon oxide film layer by plasma treatment, for example, according to the present invention, the amount of added oxygen is increased in accordance with an increase in the aspect ratio of the contact hole. In this way, even when the aspect ratio increases with the processing, the occurrence of the etch stop can be reliably prevented without damaging the photoresist film, similarly to the invention of the fourth aspect.

Furthermore, if the relationship between the change in the aspect ratio and the change in the plasma component is determined in advance and the amount of added oxygen is adjusted in accordance with the change in the plasma component as in the invention of the eleventh aspect, Similarly to the fifth aspect, the addition amount of O ₂ can be easily and reliably adjusted according to the aspect ratio.

Further, the increase or decrease of the amount of addition may be determined by, for example,
If performed after stabilization of the plasma, as in the invention described in
Similarly to the above-described invention, it is possible to reliably generate plasma and to reliably prevent the occurrence of etch stop without causing adverse effects on the process due to instability of plasma. Can be.

According to a third aspect of the present invention, the processing gas containing at least fluorocarbon introduced into the processing chamber is turned into plasma and disposed in the processing chamber, as in the invention according to claim 13. In a plasma processing method for performing plasma processing on a silicon oxide film layer formed on an object to be processed, oxygen is added to a processing gas, and the amount of oxygen added depends on a contact amount formed on the silicon oxide film layer. A plasma processing method is provided, which is increased as the aspect ratio of a hole is increased.

According to this structure, the amount of O ₂ added is increased in accordance with the increase in the aspect ratio, and the amount of O ₂ introduced into the bottom of the contact hole can be increased. Can be reliably prevented. Further, when the aspect ratio is small, the amount of O ₂ added is small, and the total amount of O ₂ can be reduced as compared with the conventional case, so that the photoresist film layer and the shoulder thereof can be prevented from being damaged.

Further, the relationship between the change in the aspect ratio and the change in the plasma component is determined in advance and the amount of added oxygen is adjusted according to the change in the plasma component. Similarly to the fifth and eleventh aspects of the present invention, the addition amount of O ₂ can be easily and reliably adjusted according to the increase in the aspect ratio.

Further, the amount of oxygen to be added is, for example,
When the aspect ratio is increased continuously as in the invention described in the above, or in a stepwise manner as in the invention according to the sixteenth aspect, the O ₂ is increased in a desired state according to the increase in the aspect ratio. It can be added to the processing gas.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a plasma processing method according to the present invention is applied to an etching method will be described below with reference to the accompanying drawings.

First Embodiment (1) Overall Configuration of Etching Apparatus First, an etching apparatus 100 to which the etching method of the first embodiment is applied will be described with reference to FIG. Processing chamber 10 of etching apparatus 100 shown in FIG.
2 is formed in a conductive airtight processing vessel 104, in which a conductive lower electrode 106 also serving as a mounting table for the wafer W is disposed. Further, on the lower electrode 106, an electrostatic chuck 108 for sucking and holding the wafer W is provided.
Is connected to a high-voltage DC power supply 110 that outputs a high-voltage DC voltage. Further, on the lower electrode 106, a focus ring 112 is provided so as to surround the periphery of the wafer W mounted on the electrostatic chuck 108.

A baffle plate 114 is attached to the lower electrode 106 so as to surround the periphery of the lower electrode 106. The processing chamber 102 and the processing vessel 104 are formed through a plurality of through holes 114a formed in the baffle plate 114. An exhaust pipe 116 connected inward and downward communicates. Further, a vacuum pump (not shown) is connected to the exhaust pipe 116.
Further, a high-frequency power supply 120 that outputs high-frequency power via a matching unit 118 is connected to the lower electrode 106.
Further, a magnet 122 that forms a magnetic field in the processing chamber 102 is provided outside the processing chamber 102.

A conductive upper electrode 124 is disposed on the ceiling of the processing chamber 102 facing the mounting surface of the lower electrode 106. In the example shown in FIG. I have. Further, a number of gas discharge holes 124 a are formed in the upper electrode 124, and the gas discharge holes 124 a communicate with a gas diffusion chamber 130 connected to the first gas supply pipe 126 and the second gas supply pipe 128. are doing. The first gas supply pipe 126 has a first gas supply source 136 via a first open / close valve 132 and a first flow control valve (mass flow controller) 134, a second open / close valve 138, and a second flow control valve 140. Through the second gas supply source 142 and the third gas supply source 1 through the third opening / closing valve 144 and the third flow control valve 146.
48 are connected. Further, in the illustrated example, C ₄ F ₈ is supplied from the first gas supply source 136, CO is supplied from the second gas supply source 142, and Ar is supplied from the third gas supply source 148.

Further, a fourth gas supply source 154 for supplying O ₂ is connected to the second gas supply pipe 128 via a fourth opening / closing valve 150 and a fourth flow control valve 152. Further, the first to fourth flow control valves 134, 14
Controllers 156 for controlling the flow rates of the respective gases are connected to 0, 146, and 152.

(2) Phenomenon of Elimination of Etch Stop by Addition of O ₂ Next, referring to FIG. 2, a description will be given of a phenomenon that the etch stop does not occur by the addition of O ₂ to the processing gas. According to the findings of the inventors, the following two theories can be considered as the main reasons why the etch stop is eliminated by the addition of O ₂ .

(A) First theory For example, using a mixed gas of C ₄ F ₈ , CO and Ar to which O ₂ is not added, as shown in FIG. SiO ₂ film layer 202 formed on
To the contact hole 20
4 is formed. At this time, the positive ions (I ⁺ ) are accelerated by the sheath and enter the contact holes 204, but the electrons (e ⁻ ) are isotropically incident. Therefore, when the hole diameter (inner diameter) of the contact holes 204 is reduced. Some of the contact holes 204 may or may not enter the contact hole 204, and the lower side wall of the contact hole 204 is charged to a positive (plus) charge.

When the amount of positive charge exceeds a certain level, ions cannot enter the contact hole 204 and the ions cannot reach the bottom of the contact hole 204. As a result, the balance between radicals and ions is lost, and an etch stop occurs. However, when the aspect ratio is small, the charge is hardly charged to a positive charge, so that the balance between radicals and ions is not broken, and no etch stop occurs. On the other hand, when the aspect ratio is large, ions cannot reach the bottom of the contact hole 204 as described above, the ratio of ions to radicals changes, and an etch stop occurs.

Therefore, when O ₂ is added to the processing gas, O ₂ is dissociated to generate O ^* (oxygen radical) and negative ions. When the negative ions of O enter the contact hole 204, the negative ions of O are generated. The positive charge is eliminated by the action of ions and O ^* . Therefore, the inner diameter is approximately 0.18μ.
Even when a very narrow contact hole 204 of not more than m is formed, ions reach the bottom of the contact hole 204. Then, ions, C _x F _y radicals and Si
O ₂ reacts with an appropriate balance, and the SiO ₂ film layer 202 at the bottom of the contact hole 204 is appropriately etched, thereby preventing the occurrence of an etch stop.

[0034] (b) a second theory deposition species is greater solid angle of incidence, as shown in FIG. 2 (b), easily deposited on the upper portion of the side wall of the contact hole 204, CF _x polymer (sediment) 210 Is formed.
Further, ions (I ⁺ ) collide with the CF _x polymer 210, and a component having a high C / F ratio is sputtered downward in the contact hole 204. That, CF _x polymer 210 repeats sputter and redeposit, C-rich sediments (reaction product) 212 is formed. Then, this deposit 212 is deposited in the fine contact hole 204 by S
This is a main cause of a decrease in the etching rate of the iO ₂ film layer 202. Therefore, it is important to form the side wall of the contact hole 204 vertically in consideration of such a cause.

Therefore, if O ₂ is added to the processing gas, O ^* generated by dissociation of O ₂ as described above reacts with the deposit 212 at the bottom of the contact hole 204, for example, C 2
It becomes O, CO ₂ , COF _x, etc. to form a contact hole 20.
4 is discharged outside. As a result, contact hole 2
04 Difficult-to-etch deposit 212 deposited on bottom
Is removed, the etching balance of the ratio between the ions 210 and the radicals becomes appropriate, and the occurrence of an etch stop can be prevented.

As described above, regardless of which theory is employed, etch stop can be prevented by adding O ₂ to the processing gas. However, in order to reliably prevent the occurrence of the etch stop, it is necessary to increase the amount of added O ₂ with the increase (narrowing) of the aspect ratio of the contact hole 204. If O ₂ is constantly added to the processing gas in a constant amount as in the etching method, the photoresist film layer 206 formed on the SiO ₂ film layer 202 and its shoulder are also etched. Therefore, this embodiment is
As will be described later, by adding O ₂ to the processing gas while alternately switching between adding and not adding O ₂ at predetermined intervals, an amount of O ₂ that can reliably prevent the occurrence of an etch stop is added to the processing gas. The contact hole 204 having a high aspect ratio is formed without damaging the photoresist film layer 206 and its shoulder.

(3) Structure for Controlling Etching Step and Addition of O ₂ Next, the structure for controlling the etching step and the addition amount (flow rate) of O ₂ will be described with reference to FIGS. First, as shown in FIG. 1, the wafer W is placed on the electrostatic chuck 108 of the lower electrode 106 set at, for example, 20 ° C. and held by suction. As shown in FIG. 2, this wafer W has a SiO ₂ film layer 202 formed on a Si substrate 200 and a photoresist film layer 206 on which the upper surface of the SiO ₂ film layer 202 has a predetermined pattern. Covered by The temperature of the inner wall surface of the processing chamber 102 and the temperature of the upper electrode 124 shown in FIG. 1 are set to, for example, 60 ° C.

Next, the controller 156 appropriately adjusts the first to third flow control valves 134, 140, and 146,
For example, a mixed gas composed of C ₄ F ₈ , CO and Ar is introduced into the processing chamber 102 at flow rates of 10 sccm, 50 sccm and 200 sccm, respectively. At this time, the fourth flow control valve 152 is closed, and the supply of O ₂ is stopped. The inside of the processing chamber 102 is evacuated through the through hole 114a of the baffle plate 114 and the exhaust pipe 116, and is maintained at a pressure of, for example, 40 mTorr. Then, for example, 13.56 MHz at 17
When a high-frequency power of 00 W is applied, plasma is generated between the upper electrode 124 and the lower electrode 106, and a predetermined etching process is performed on the SiO ₂ film layer 202 by ions and radicals in the plasma.

The generation state of the plasma is monitored by, for example, a sensor that detects the emission spectrum of the plasma, and information from this sensor is transmitted to the controller 156. If the controller 156 determines that the plasma has been stabilized and the SiO ₂ film layer 202 has been subjected to a stable etching process, the controller 156 applies a predetermined pulse voltage to the fourth flow control valve 152. The fourth flow control valve 152 opens the valve when the pulse voltage is on to supply O ₂ into the gas diffusion chamber 130, and closes the valve when the pulse voltage is off to supply O ₂ . Stop. As a result, as shown in FIG. 3, O ₂ is added to the processing gas staying in the gas diffusion chamber 130 in synchronization with the on / off of the pulse voltage, and the processing gas is supplied through the gas discharge holes 124a. , Are supplied into the processing chamber 102.

The maximum flow rate at the time of adding O ₂ is set to be higher than the flow rate of O _{2 in} the above-mentioned conventional etching method, and is set to, for example, 10 sccm in the present embodiment. Further, 1 addition time of O ₂ of per period, the number m of seconds to several 10m seconds, is set to, for example, 5m sec ~10m seconds, also without addition time of O ₂ is set to be longer than the addition time of the O ₂ Have been. Therefore, since the addition time of the O ₂ is very small in comparison with the additive-free time, the amount would photoresist layer 206 is shaved if added at all times O ₂ O
₂ is added to the processing gas,
A reaction product (protective film) such as a CF-based compound can be formed on the photoresist film layer 206 which is easily damaged.
The shoulders are not cut off. Furthermore, since the total amount of O ₂ introduced is less than the total amount of conventional continuous introduction, the above-mentioned damage can be reliably prevented.

The present embodiment is configured as described above. Since the addition and the non-addition of O ₂ added to the processing gas are switched at a predetermined period, the pattern formed on the photoresist film layer 206 is initialized. While maintaining the state of
It is possible to prevent the charging phenomenon on the inner side wall of the contact hole 204 and suppress the deposition of the reaction products (deposits) 208 and 212 on the bottom 204 of the contact hole, thereby preventing the occurrence of the etch stop.

(Second Embodiment) Next, an etching method according to a second embodiment will be described. Since the etching apparatus to which this embodiment can be applied is the same as the etching apparatus 100 described in the first embodiment,
For components having almost the same function and configuration,
Repetitive description will be omitted by giving the same reference numerals. However, in the first embodiment, O ₂ is intermittently added to the processing gas, whereas in the present embodiment, the amount of O ₂ added is relatively increased or decreased.

That is, in the present embodiment, a mixed gas composed of C ₄ F ₈ , CO and Ar is supplied into the processing chamber 102 before plasma generation, for example, at 10 sccm and 50 sccc, respectively.
In addition to the introduction of m and a flow rate of 200 sccm, for example, O ₂ having a flow rate of 5 sccm is simultaneously introduced. At this time, the flow rate of each gas is controlled by the controller 156 from the controller 156 as in the first embodiment.
It is adjusted by the voltage applied to 0,146,152. In the case of this embodiment, although the addition before the plasma generating the O ₂ in the process gas, the amount of O ₂ not affect because trace the generation and photoresist layer 206 of the plasma Absent.

Next, a predetermined high frequency power is applied to the lower electrode 106 to generate plasma in the processing chamber 102. When the controller 156 confirms that the plasma has stabilized, similarly to the first embodiment, the controller 156 adjusts the opening degree of the fourth flow control valve 152 from the controller 156 to thereby control the gas diffusion chamber 130. The flow rate of O ₂ introduced into the chamber, that is, the amount of O ₂ added to the processing gas is increased or decreased as shown in FIG. In the case of this embodiment, the flow rate of O ₂ is 5 scc
It is configured to repeat the increase and decrease between m and 10 sccm. In this embodiment, the time for supplying O ₂ at a high flow rate, for example, 10 sccm, into the gas diffusion chamber 130 is several milliseconds to several tens of milliseconds, for example, 5 milliseconds to 10 milliseconds.
It is set to m seconds. In contrast, the gas diffusion chamber 13
The time for supplying O ₂ at a low flow rate within 0, for example, 5 sccm, is set longer than the time for supplying O ₂ at a high flow rate.

The present embodiment is configured as described above, and the amount of O ₂ added to the processing gas is increased or decreased in a predetermined cycle, so that the processing gas does not always contain a large amount of O _2. . As a result, the contact hole 204 having a predetermined high aspect ratio can be formed without generating an etch stop while maintaining the pattern formed in the photoresist film layer 206 in the initial state. Also,
Since O ₂ is added to the processing gas before and after the plasma generation, the processing can be performed under substantially the same conditions as in the conventional processing process. Furthermore, since O ₂ is constantly added to the processing gas during processing, the occurrence of etch stop can be more reliably prevented.

(Third Embodiment) Next, an etching method according to a third embodiment will be described. Note that the present embodiment is different from the first and second embodiments in that the addition amount of O ₂ is adjusted according to the change in the plasma component corresponding to the change in the aspect ratio of the contact hole 204.

(1) Overall Configuration of Etching Apparatus First, an etching apparatus 300 to which the etching method of the present embodiment is applied will be described with reference to FIG. Note that components having substantially the same functions and configurations as those of the above-described etching apparatus 100 are denoted by the same reference numerals, and redundant description will be omitted. An analyzer 302 that measures a change in plasma component in the processing chamber 102 by, for example, infrared laser absorption spectroscopy (IR-LAS) is connected to the controller 156 of the etching apparatus 300 shown in FIG. The analyzer 302 transmits an infrared laser beam, which is output from a light source (not shown) and passes through the plasma generated in the processing chamber 102, to a light-transmissive detection window 304 provided on the side wall of the processing chamber 102. It is arranged so that it is inputted to the light receiving section of the spectroscope 302 through the through hole 306 provided in the magnet 122.

(2) Relationship between Change in Aspect Ratio of Contact Hole and Change in Plasma Component Next, referring to FIGS. 6 and 7, the relationship between change in the aspect ratio of the contact hole 204 and change in plasma component will be described. Will be described. C ₄ F without O ₂ added
₈ and the processing gas composed of CO and Ar
When the etching process is performed on the iO ₂ film layer 202, FIG.
As shown in FIG. 3A, when a predetermined etching time has elapsed, that is, when the aspect ratio of the contact hole 204 formed in the SiO ₂ film layer 202 has exceeded a predetermined size, the etching rate decreases, and finally the etching rate decreases. Stops progressing.

At this time, as shown in FIG. 6, in the section (A) where a substantially constant etching rate is secured,
A contact hole 204 of a so-called μ-trench shown in FIG. 7A is formed in the O ₂ film layer 202. In the section (B) where the etching proceeds and the etching rate decreases,
The etching state of the SiO ₂ film layer 202 becomes unstable, and the bottom of the contact hole 204 becomes uneven as shown in FIG. 7B. Further, in the section (C) where the etching rate becomes substantially zero, as shown in FIG.
08 and the sediment 212 (hereinafter referred to as “reaction products 208, 2
12 ". ) Is deposited and the contact hole 20
4 Etch stop occurs due to the charging phenomenon of the inner side wall.

Next, the etching time (aspect ratio) and the reaction products 208 and 2 at the bottom of the contact hole 204 are determined.
Focusing on the relationship with the accumulation amount of No. 12, FIG.
As shown in FIG. 7, the reaction products 208 and 212 are deposited on the bottom of the contact hole 204 from the initial stage of etching, that is, the stage with a small aspect ratio. A predetermined etching is performed as shown in a). In addition, reaction products and the like 20
FIG. 7 shows that the accumulation amount in the section (B) is 8,212.
It affects the etching as shown in FIG. Further, when the deposition amount in the section (C), that is, the etch stop boundary amount at the boundary between the section (B) and the section (C), is exceeded, an etch stop is caused as shown in FIG.

As described above, the increase of the aspect ratio (etching time), the etching rate, the etching shape, the reaction product 208 at the bottom of the contact hole 204, etc.
There is a close relationship with the amount of 212 deposited. Therefore, if the addition amount of O _{2 is} increased according to the increase of the aspect ratio,
In addition to preventing the occurrence of an etch stop, a desired etching rate and a desired etching shape can be obtained. In the early stage of processing with a small aspect ratio, O
₂ can reduce the amount of photoresist film layer 2
06 and pattern shoulder damage can be minimized. Further, since the total amount of O ₂ introduced (input amount) can be made equal to or less than the total amount of conventional continuous introduction, the shoulder portion of the photoresist film layer 206 can be reliably prevented from being scraped. Further, since the amount of O ₂ added in the initial stage of the treatment is reduced, the amount of O ₂ can be further added later than that described above, so that the occurrence of etch stop can be reliably prevented.

However, it is very difficult to measure the actual aspect ratio of the contact hole 204 during the etching process. Therefore, in the present embodiment, the addition amount of O ₂ is adjusted based on the change in the component of the plasma that changes in accordance with the increase in the aspect ratio. Here, the relationship between the increase in the aspect ratio and the change in the component of the plasma will be described. As shown in FIG. 6C, in the section (A) where the above-described predetermined etching is performed, the etchant is in the plasma. The total content of CF, CF ₂ and CF ₃ (hereinafter, referred to as “CF total content”) is constant. Further, the content of SiF ₂ , which is one of the by-products (biproducts) generated by etching the SiO ₂ film layer 202, is constant. Further, in the section (B) where the etching does not easily proceed, the total content of CFs increases and the Si content increases.
The content of F ₂ is reduced. Further, in the section (C) where the etching does not substantially proceed, the total content of CFs becomes constant, and the content of SiF ₂ becomes almost zero.

As described above, the change in the aspect ratio and the etching shape of the contact hole 204 and the change in the etching
The change in CF acids total content and the content of SiF ₂ in the plasma in 2, because the correlation, at the time of actual processing to measure the components change in the plasma, the process gas in accordance with the components change by adjusting the amount of O ₂ to be added, it is possible to perform substantially the same control as when adjustment of quantity added of O ₂ in accordance with the aspect ratio and the etching shape.

(3) Configuration for Controlling Etching Step and Addition of O ₂ Next, the configuration for controlling the etching step and the addition of O ₂ will be described with reference to FIGS. 5, 6C, and 8. The same steps as in the first embodiment will not be described. An infrared laser beam output from a light source (not shown) is input to the analyzer 302.
When plasma is generated in the processing chamber 102 by the start of the etching process, the infrared laser light passes through the plasma. The analyzer 302 calculates the above-mentioned contents of CF, CF ₂ and CF _{3 and} the content of SiF ₂ among the components contained in the plasma by infrared laser absorption spectroscopy from the infrared laser light passing through the plasma. And outputs the respective content information to the controller 156.

In the controller 156, change information of the total content of CFs and the content of SiF _{2 in} the plasma according to the increase of the aspect ratio shown in FIG. 6C is set in advance. Therefore, the controller 156 increases the total content of CF, CF ₂ , CF ₃ (total content of CFs) and the content of SiF ₂ input from the analyzer 302, that is, the total content of CFs increases. When the content of SiF ₂ decreases, O ₂
Adjust the flow rate. With this configuration, as shown in FIG. 8, the addition amount of O ₂ is continuously increased substantially as the aspect ratio of the contact hole 204 is increased, and the introduction amount of O ₂ into the bottom of the contact hole 204 is increased. Thus, the contact hole 204 having a high aspect ratio can be formed without damaging the photoresist film layer 206 and its shoulder and without causing an etch stop.

Although the preferred embodiments of the present invention have been described with reference to the accompanying drawings, the present invention is not limited to such configurations. In the scope of the technical idea described in the claims, those skilled in the art
Various changes and modifications can be conceived, and it is understood that these changes and modifications also belong to the technical scope of the present invention.

For example, in the first and second embodiments, a fixed amount of O ₂ is intermittently provided at predetermined intervals.
Although an example has been described in which the configuration is added to the processing gas while increasing or decreasing it, the present invention is not limited to such a configuration. For example, as shown in FIG. 9, O ₂ is intermittently (pulsed) as shown in FIG. 9 while increasing the aspect ratio, that is, increasing the amount of O ₂ added in accordance with a change in the plasma component, as in the third embodiment. or or or added pulsed manner to increase or decrease the O ₂ as shown in FIG. 10 added, FIG. 1
As shown in Fig. 1, if O ₂ is added in a curved manner,
The same effects as in the third embodiment can be obtained. Further, according to the change of the component of the plasma, FIG.
As shown in ( ₂₎ , the same effect as described above can be obtained even if the amount of added O ₂ is continuously and linearly increased.

In the third embodiment, O
While continuously configured to increase the amount of ₂ has been described, the present invention is not limited to such a configuration, for example, as shown in FIG. 12, O ₂ in accordance with the component change of the plasma The same effect can be obtained by employing a configuration in which the addition amount of is increased stepwise (multiple steps).

Further, in the third embodiment,
The configuration in which the addition amount of O ₂ is adjusted based on the change in the composition of the plasma has been described as an example. However, the flow rate of the processing gas other than O ₂ , the pressure in the processing chamber, the high-frequency power applied to the electrode, the electrode Also, the temperature of the inner wall of the processing chamber can be adjusted according to the change in the component of the plasma.

Further, in the third embodiment, a configuration for measuring a change in plasma components by infrared laser absorption analysis has been described as an example. However, the present invention is not limited to such a configuration. , For example, laser-induced fluorescence (L
IF), emission spectroscopy (OES), quadrupole mass spectrometry, etc., the present invention can be implemented even if the content of the plasma component is determined. It is also possible to adjust the amount of O ₂ to be added.

Further, in the third embodiment,
Although the configuration in which the addition amount of O ₂ is adjusted according to the measured change in the composition of the plasma has been described as an example, the present invention is not limited to such a configuration, and the aspect ratio of the contact hole is increased and the etching time is increased. The present invention can also be implemented by adopting a configuration in which the relationship is determined in advance and the addition amount of O ₂ is increased as the etching time elapses.

In the first to third embodiments, the mixed gas of C ₄ F ₈ , CO and Ar is used as the processing gas.
_Although the configuration in which ₂ is added has been described as an example, the present invention is not limited to such a configuration, and the present invention can be implemented even if another processing gas is used as long as it is a processing gas containing at least fluorocarbon. be able to.

Further, in the above-described first to third embodiments, an example in which O ₂ and other processing gases are introduced into the gas diffusion chamber and then supplied into the processing chamber through the gas discharge holes will be described. As described above, the present invention is not limited to such a configuration, and the present invention can be implemented by directly supplying O ₂ into the processing chamber.

In the first to third embodiments, the flow rate (addition amount) of O ₂ has been described by taking as an example a configuration in which the flow rate adjusting valve for adjusting the opening degree by the voltage is used. The present invention is not limited to such a configuration, and the present invention can be implemented using other flow rate adjusting means as long as the flow rate of O ₂ can be appropriately adjusted.

Further, in the first to third embodiments, the configuration in which the state of plasma is detected by the optical sensor has been described as an example. However, the present invention is not limited to such a configuration. The present invention can also be implemented by adopting a configuration in which the time during which the plasma is stabilized is determined in advance, and the amount of O ₂ added is controlled based on the time during actual processing.

In the first to third embodiments, the etching apparatus for applying high-frequency power only to the lower electrode has been described as an example. However, the present invention is not limited to such a configuration. For example, the present invention can be applied to a plasma processing apparatus having a configuration in which high-frequency power is applied to both the upper electrode and the lower electrode or only the upper electrode.
Further, the present invention can be applied not only to the etching apparatus having the above-described magnet but also to a plasma processing apparatus not having such a magnet.

[0067]

According to the present invention, with the addition of O ₂ to intermittently process gas, or because the amount of O ₂ performs processing while relatively decreasing, minimizing damage to the etching mask It can be stopped and, for example, the reaction products deposited on the bottom of the contact hole can be removed to prevent the occurrence of charging phenomenon on the inner wall surface of the contact hole.
The occurrence of etch stop can be prevented. As a result, it is possible to form an ultrafine contact hole having a high aspect ratio in a desired shape. In addition, since the processing can be performed while increasing the amount of added O ₂ according to the increase in the aspect ratio, the occurrence of an etch stop can be more reliably prevented, and the total input amount of O ₂ can be reduced, thereby damaging the etching mask. Nothing.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an etching apparatus to which the present invention can be applied.

FIG. 2A is a schematic explanatory view for explaining a first theory of a phenomenon of eliminating an etch stop by adding O ₂ , and FIG. 2B is a diagram schematically illustrating a phenomenon of eliminating an etch stop by adding O ₂ ; It is a schematic explanatory view for explaining the second theory.

FIG. 3 is a schematic explanatory diagram for explaining a control configuration of an added amount of O ₂ applied to the etching apparatus shown in FIG. 1;

FIG. 4 is a schematic explanatory diagram for explaining another control configuration of the added amount of O ₂ .

FIG. 5 is a schematic sectional view showing another etching apparatus to which the present invention can be applied.

6A is a schematic explanatory view for explaining a relationship between an etching time (aspect ratio of a contact hole) and an etching rate, and FIG. 6B is a diagram schematically illustrating an etching time (aspect ratio of a contact hole); It is a schematic explanatory view for explaining the relation between the deposition amount of reaction products and the like at the bottom of the contact hole, and (c) shows the relation between the etching time (aspect ratio of the contact hole) and the content of the plasma component. FIG. 4 is a schematic explanatory diagram for describing.

7A is a schematic cross-sectional view showing a shape of a contact hole in a section (A) shown in FIGS. 6A to 6C, and FIG. 7B is a sectional view of FIG. 6A to 6C are schematic cross-sectional views showing the shapes of contact holes in a section (B) shown in FIG. 6C, and FIG. 6C is a sectional view in a section (C) shown in FIGS. 6A to 6C. FIG. 4 is a schematic cross-sectional view showing the shape of the contact hole of FIG.

FIG. 8 is a schematic explanatory diagram for explaining a control configuration of an added amount of O ₂ applied to the etching apparatus shown in FIG. 5;

FIG. 9 is a schematic explanatory diagram for explaining another control configuration of the added amount of O ₂ .

FIG. 10 is a schematic explanatory diagram for explaining another control configuration of the added amount of O ₂ .

FIG. 11 is a schematic explanatory diagram for explaining another control configuration of the added amount of O ₂ .

FIG. 12 is a schematic explanatory diagram for explaining another control configuration of the added amount of O ₂ .

FIG. 13 is a schematic explanatory diagram for explaining another control configuration of the added amount of O ₂ .

[Explanation of symbols]

100, 300 Etching apparatus 102 Processing chamber 106 Lower electrode 124 Upper electrode 124a Gas discharge holes 126, 128 First and second gas supply pipes 130 Gas diffusion chambers 134, 140, 146, 152 First to fourth flow control valves 136, 142, 148, 154 First to fourth gas supply sources 156 Controller 202 SiO ₂ film layer 204 Contact hole 206 Photoresist film layer 302 Analyzer W Wafer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Ishihara 2381 Kita Shimojo, Fujii-machi, Nirasaki City, Yamanashi Prefecture Inside Tokyo Electron Yamanashi Co., Ltd. 1 F term in Tokyo Electron Yamanashi Co., Ltd. (Reference) 4K057 DA11 DA12 DA20 DB20 DD03 DD08 DE06 DE14 DE20 DG07 DJ02 DJ03 DJ06 DM02 DM03 DM08 DM22 DM23 DM35 DN01 5F004 AA00 AA01 BA04 BA08 BA09 BA13 BB11 BB18 BB22 BB28 DA03 DB03 DA03 EB01

Claims (16)

[Claims] 1. A plasma processing method for converting a processing gas containing at least fluorocarbon introduced into a processing chamber into plasma and performing a plasma processing on a silicon oxide film layer formed on an object to be processed disposed in the processing chamber. 3. The plasma processing method according to claim 1, wherein oxygen is intermittently added to the processing gas. 2. The plasma processing method according to claim 1, wherein the oxygen is periodically added to the processing gas. 3. The method of claim 1, wherein the time of adding oxygen is relatively shorter than the time of not adding oxygen.
Or the plasma processing method according to any one of 2. 4. The method according to claim 1, wherein a contact hole is formed in the silicon oxide film layer, and an amount of the oxygen added increases as an aspect ratio of the contact hole increases. 4. The plasma processing method according to any one of 2 and 3. 5. The method according to claim 4, wherein the relationship between the change in the aspect ratio and the change in the component of the plasma is obtained in advance, and the amount of the oxygen added is adjusted according to the change in the component of the plasma. Plasma processing method. 6. The method according to claim 1, wherein the oxygen is added after the plasma is stabilized.
6. The plasma processing method according to any one of 4 and 5. 7. A plasma processing method for converting a processing gas containing at least fluorocarbon introduced into a processing chamber into plasma and performing a plasma processing on a silicon oxide film layer formed on an object to be processed disposed in the processing chamber. Wherein oxygen is added to the processing gas and the amount of oxygen is relatively increased or decreased.
Plasma treatment method. 8. The plasma processing method according to claim 7, wherein the increase or decrease in the amount of added oxygen is performed periodically. 9. The plasma processing method according to claim 7, wherein the increasing time of the added amount of oxygen is relatively shorter than the decreasing time of the added amount of oxygen. 10. The method according to claim 7, wherein a contact hole is formed in the silicon oxide film layer, and an amount of the oxygen added is increased according to an increase in an aspect ratio of the contact hole. 10. The plasma processing method according to any one of 8 and 9. 11. The method according to claim 10, wherein the relationship between the change in the aspect ratio and the change in the component of the plasma is obtained in advance, and the amount of the oxygen added is adjusted according to the change in the component of the plasma. Plasma processing method. 12. The method according to claim 7, wherein the increase or decrease of the addition amount is performed after stabilization of the plasma.
12. The plasma processing method according to any one of 9, 10, and 11. 13. A plasma processing method in which a processing gas containing at least fluorocarbon introduced into a processing chamber is turned into plasma, and plasma processing is performed on a silicon oxide film layer formed on an object to be processed placed in the processing chamber. In the method, oxygen is added to the processing gas, and an amount of the oxygen added is increased according to an increase in an aspect ratio of a contact hole formed in the silicon oxide film layer. Plasma treatment method. 14. The method according to claim 13, wherein a relationship between the change in the aspect ratio and the change in the component of the plasma is obtained in advance, and the amount of the oxygen added is adjusted according to the change in the component of the plasma. Plasma processing method. 15. The plasma processing method according to claim 13, wherein the amount of added oxygen is continuously increased. 16. The plasma processing method according to claim 13, wherein the amount of oxygen added is increased stepwise.