JP2009260001A - Etching method and etching endpoint decision device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately decide the etching endpoint. <P>SOLUTION: A process gas containing HF as a reactive component is blown off from a blow-off port 21 into contact with a treated object 90 to etch a silicon film 93. Part of the processed gas sucked up through a suction port 22 is introduced into an analysis part 51 to analyze the concentrations of the reactive component and a generated component. The endpoint of etching is decided by a decision part 52 based on changes in concentration of the two components. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an etching method and apparatus, and more particularly to a method and apparatus for determining whether etching has reached an end point.

For example, in plasma etching of a silicon film or the like, the thickness of the remaining film is optically measured by polarization analysis, reflection analysis, etc., and the etching end point is detected (see Patent Document 1). An etching end point is detected by analyzing plasma emission.
In Patent Document 2, impurities are doped in the uppermost layer, and the etching end point is determined by detecting impurities in the gas.
In Patent Document 3, the concentration of the object to be etched in the gas is analyzed, and the etching is stopped when the object to be etched disappears.
In Patent Document 4, the etching depth is determined from the concentration ratio of two elements constituting the substrate in the gas.
In Patent Document 5, when the inside of a chamber is cleaned by plasma etching in silicon oxide film formation, the degree of cleaning is determined by analyzing the concentration of SiF ₄ in exhaust gas.
JP 2008-41974 A JP 05-055578 A Japanese Patent Laid-Open No. 06-120172 JP 06-163469 A (paragraph 0016) JP 2007-14018 A

In the method of measuring the film thickness by polarization analysis or reflection analysis, the measurement error increases as the film thickness decreases. For this reason, it may be determined that the etching target film still remains but the end point, or the end point determination is delayed even though the etching target film disappears, and the underlying protective film may be etched.
In the plasma emission analysis, it is necessary that the etching apparatus to be applied is a so-called direct type plasma etching apparatus in which an object to be processed is arranged inside the plasma space. For this reason, it cannot be used in a so-called remote plasma etching apparatus in which an object to be processed is arranged outside the plasma space and plasma gas is ejected from the plasma space toward the object to be processed, and the application range is limited.
In any of the methods described in Patent Documents 2 to 5, the etching end point is determined from the concentration of only the components mixed in the gas by the etching reaction. Therefore, it is difficult to ensure accuracy when an atmospheric gas or the like is mixed in the etching gas.

  The present invention has been made in view of the above circumstances, and the error does not increase even when the thickness of the film to be etched is reduced. Furthermore, the determination accuracy is ensured even if there is a disturbance such as mixing of atmospheric gas. It is an object to provide an end point determination means that can be used.

In order to solve the above-described problem, an etching method according to the present invention brings a processing gas containing a reaction component having reactivity with the film into contact with an object to be processed including a film to be etched,
The end point of etching of the film is determined based on the reaction component in the processed gas after the processing gas contacts the object to be processed and the concentration change of the generated component due to the reaction between the film and the reaction component. It is characterized by doing.
Thereby, even if the thickness of the film to be etched is reduced, the error does not increase, and the etching end point can be accurately determined. Even if there is a disturbance such as atmospheric gas mixed in the processing space, the determination accuracy can be ensured.

The film is silicon or silicon oxide, the reaction component is HF, the generated component is SiF ₄ , and the determination is performed based on the concentration change of HF and SiF ₄ in the treated gas. It is preferable to do so.
Thereby, the end point of the etching of silicon or silicon oxide can be accurately and reliably determined.

It is preferable to perform the determination based on whether or not the ratio of the HF concentration to the SiF ₄ concentration in the treated gas has reached a predetermined value.
As a result, even if an external atmospheric gas or the like is involved in the treated gas and the concentration of each component is reduced, the end point of etching can be reliably determined without being affected by it.

An etching end point determination apparatus according to the present invention is provided in an etching apparatus for contacting a processing object including a film to be etched with a processing gas containing a reactive component having reactivity with the film, and determines the etching end point of the film. A device for determining,
An analysis unit for analyzing the concentration of the reaction component in the treated gas after the treatment gas has contacted the object to be treated and the concentration of the component produced by the reaction between the membrane and the reaction component;
A determination unit that determines an end point of etching of the film based on a concentration change of the reaction component and the generation component;
It is provided with.
As a result, even if the thickness of the film to be etched is reduced, the error does not increase, and the etching end point can be accurately determined. Even if there is a disturbance such as atmospheric gas mixed into the processing space, the determination accuracy can be ensured.

The analysis unit is preferably an infrared spectrometer.
Thereby, the concentration analysis of the reaction component and the product component can be reliably performed.

A detection path is branched from a suction path for sucking the processed gas of the etching apparatus through a branch section, the analysis section is connected to the detection path, and conductance of at least a portion near the branch section of the detection path Is preferably smaller than the conductance of the suction path,
As a result, the processed gas that has been branched from the suction path to the detection path can be accelerated, reach the analysis section in a short time, and the responsiveness of the concentration analysis and consequently the end point determination can be enhanced.

The present invention is suitable for plasma etching under substantially atmospheric pressure (normal pressure). Here, substantially under atmospheric pressure (substantially normal pressure) refers to a range of 1.013 × 10 ^{4 to} 50.663 × 10 ⁴ Pa, and considering the ease of pressure adjustment and the simplification of the device configuration, 1.333 × 10 ^{4 to} 10.664 × 10 ⁴ Pa are preferable, and 9.331 × 10 ^{4 to} 10.9797 × 10 ⁴ Pa are more preferable.

  According to the present invention, the error does not increase even when the thickness of the film to be etched is reduced, and the end point of etching can be accurately determined. Even if there is a disturbance such as atmospheric gas mixed in the processing space, the determination accuracy can be ensured.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the workpiece 90 includes, for example, flat panel display glass as a substrate 91, and a base film 92 made of silicon nitride (SiNx) is formed on the substrate 91. A silicon film 93 made of amorphous silicon is laminated on the base film 92. The silicon film 93 may be polysilicon or single crystal silicon instead of amorphous silicon.

The silicon film 93 of the workpiece 90 is etched by the etching apparatus 1.
The etching apparatus 1 includes a support unit 10 and a nozzle head 20. A workpiece 90 is supported by the support unit 10. The support unit 10 includes a stage, a roller conveyor, and the like. A movement mechanism is added to the support unit 10 so that the workpiece 90 is reciprocated in the left-right direction indicated by the two white arrows in FIG.

  The nozzle head 20 is disposed above the support portion 10. The nozzle head 20 is formed with one or more outlets 21 and one or more suction ports 22. Here, one outlet 21 is disposed at the center of the nozzle head 20, and suction ports 22 are disposed on both sides of the outlet 21. The blowout port 21 and the suction port 22 are formed in a slit shape extending in a direction orthogonal to the paper surface of FIG.

A supply path 31 extends from the processing gas supply source 30. This supply path 31 is connected to the outlet 21. The processing gas supply source 30 sends the processing gas to the supply path 31. The processing gas contains HF (fluorine-based reactive component) and O ₃ (oxidizing reactive component) as reactive components having reactivity with the silicon film 93. HF can be generated, for example, by adding water (H ₂ O) to a fluorocarbon such as CF ₄ to form plasma. O ₃ can be generated by, for example, an ozonizer. HF and O ₃ may be simultaneously generated by one plasma generation apparatus by converting the mixed gas of CF ₄ , H ₂ O, and O ₃ into plasma.

  A suction path 41 extends from the suction port 22 of the nozzle head 20. The suction path 41 is connected to the suction pump 40 (suction means). The suction pump 40 is provided with an exhaust gas treatment facility (not shown) such as a scrubber.

  The etching apparatus 1 is provided with an etching end point determination device 50 in order to determine whether or not the etching of the silicon film 93 has reached the end point. The etching end point determination device 50 includes an analysis unit 51 and a determination unit 52. The analysis unit 51 is composed of a Fourier transform infrared spectrometer (FTIR), and spectrally analyzes the composition of the sampled gas with infrared rays, and consequently analyzes the concentration of each gas component.

The analysis unit 51 is connected to the suction path 41 as follows.
The detection path 53 is branched from the suction path 41 via the branch portion 41b. The flow path cross-sectional area of the detection path 53 is sufficiently smaller than the flow path cross-sectional area of the suction path 41. An analysis unit 51 is provided in the detection path 53. A suction pump 54 is provided at the downstream end of the detection path 53. A throttle valve 55 is provided on the upstream side of the analysis section 51 in the detection path 53 and near the branch section 41b.

A determination unit 52 is connected to the analysis unit 51. The determination unit 52 is configured by a microprocessor. As is well known, the microprocessor includes a CPU, a program ROM, a RAM, and an input / output interface. The determination unit 52 determines the end point of etching based on the analysis result of the analysis unit 51.
The analysis result of the analysis unit 51 and the determination result by the determination unit 52 are displayed on a monitor (not shown).

A method of etching the silicon film 93 by the etching apparatus 1 having the above configuration will be described focusing on the end point determination of etching.
A processing gas containing HF and O ₃ from the processing gas supply source 30 is sent to the nozzle head 20 through the supply path 31 and blown out from the outlet 21 to be brought into contact with the workpiece 90. Thereby, an etching reaction of the silicon film 93 occurs. Specifically, silicon is oxidized by O ₃ to become silicon oxide, and this silicon oxide and HF react to generate volatile SiF ₄ .

The processed gas after the processing gas contacts the workpiece 90 is sucked into the suction ports 22, passes through the suction path 41, and is exhausted from the suction pump 40. The treated gas contains a component generated by an etching reaction such as SiF ₄ and a reaction component such as HF that has not been used for the etching reaction.

  A part of the processed gas is diverted from the branch part 41 b to the detection path 53 by driving the suction pump 54. Since the detection channel 53 has a smaller channel cross-sectional area than the suction channel 41, the flow rate of the processed gas in the detection channel 53 can be made larger than the flow rate of the processed gas in the suction channel 41. Moreover, since the detection path 53 downstream of the throttle valve 55 is lowered by the throttle valve 55, the flow rate of the processed gas in the detection path 53 can be further increased. As a result, the treated gas can be introduced into the analysis unit 51 in a short time.

The analysis unit 51 made of FTIR quantitatively analyzes the composition of the processed gas. Specifically, the concentration of HF (reaction component) and the concentration of SiF ₄ (product component) in the treated gas are detected.

Analysis data from the analysis unit 51 is input to the determination unit 52 as needed. The determination unit 52 determines whether the etching of the silicon film 93 has reached the end point based on the analysis data. Specifically, end point determination is performed based on changes in the concentrations of HF and SiF ₄ in the treated gas.

For example, the determination unit 52 calculates the concentration ratio r of HF and SiF _{4 by} calculating the following formula.
r = [HF] / [SiF ₄ ] (Formula 1)
In Equation 1, [HF] is the concentration of HF, and [SiF ₄ ] is the concentration of SiF ₄ . The ROM of the determination unit 52 stores a threshold value r0 (predetermined value) of the density ratio r. The determination unit 52 determines whether or not the calculated concentration ratio r has reached the threshold value r0.

At the stage where the silicon film 93 remains on the surface of the workpiece 90, the amount of HF consumed in the processing gas is large and the amount of SiF ₄ produced is large. Therefore, the HF concentration in the treated gas is relatively low and the SiF ₄ concentration is relatively high. Therefore, the density ratio r is below the threshold value r0.
r <r0 (Formula 2)
At this time, the determination unit 52 determines that the etching end point has not yet been reached.

When the silicon film 93 is removed, the underlying silicon nitride film 92 is exposed. Silicon nitride has a lower reaction rate than amorphous silicon. Therefore, the amount of HF consumed is smaller than that in the stage where the silicon film 93 remains, and the amount of SiF ₄ generated is reduced. Therefore, the HF concentration in the treated gas increases and the SiF ₄ concentration decreases. Thereby, the density ratio r exceeds the threshold value r0.
r ≧ r0 (Formula 3)
At this time, the determination unit 52 determines that the etching has reached the end point. As a result, the etching can be completed at the time when the silicon film 93 is removed or immediately after that, and the base film 93 can be prevented from being etched excessively.

According to the present invention, unlike the conventional end point determination by polarization analysis or reflection analysis, the measurement error does not increase as the thickness of the silicon film 93 decreases. Therefore, the etching end point can be accurately determined. Since the determination is made based on the ratio r of the two components (HF and SiF ₄ ) in the processed gas, the atmosphere gas (air or the like) is mixed into the processed gas from the outside, and the above components (HF and SiF) are mixed. _{Even if} the density of ₄ ) is lowered, the determination accuracy is not affected.
Moreover, if it etches by processing gas containing reaction components, such as HF, on a to-be-processed object, it can apply universally and an application range is not limited. Even in a so-called remote plasma etching apparatus in which an object to be processed 90 is disposed outside the plasma space, a processing gas is blown from the plasma space and sprayed onto the object to be processed 90, the object 90 is disposed inside the plasma space, The present invention can also be applied to a so-called direct type plasma etching apparatus in which a plasma processing gas is directly applied to the workpiece 90.
When the processed gas is diverted from the suction path 41 to the detection path 53, the gas is accelerated and reaches the analysis unit 51 in a short time. Therefore, the etching state of the workpiece 90 can be detected with almost no time delay, and the determination response is improved. Can do.

The present invention is not limited to the above embodiment, and various modifications can be made.
For example, instead of the concentration ratio threshold r0, the determination unit 52 stores the HF concentration threshold and the SiF ₄ threshold in the ROM, and determines whether or not the HF concentration and the SiF ₄ concentration exceed the corresponding threshold values. The etching end point may be determined.
Not limited to two components (for example, HF and SiF ₄ ) in the treated gas, three or more components (for example, HF, O ₃ , SiF _4, etc.) may be quantitatively analyzed, or only one component may be quantitatively analyzed. May be.
The etching target film is not limited to silicon, and may be silicon oxide. In that case, the reaction component in the processing gas may be only a fluorine-based reaction component such as HF, and an oxidizing reaction component such as O ₃ is unnecessary.
Furthermore, the etching target film is not limited to silicon or silicon oxide, but may be another insulating film such as silicon nitride or a semiconductor film. The reaction component of the processing gas and the component to be quantitatively analyzed by the etching end point determination device 50 may be appropriately selected according to the film to be etched.
The etching reaction only needs to change the concentration of the reaction component and the generated component of the processed gas when the etching of the etching target film is completed, and the etching end-point determination device 50 can analyze the change in the concentration. Good.
The analyzer 51 is not limited to FTIR as long as it can analyze the gas concentration.
The determination unit 52 may be configured by an analog circuit instead of the microprocessor.
The end point determination of the present invention can be applied universally as long as the processing gas containing a reaction component is sprayed on the object to be processed and etched.

Examples will be described. The present invention is not limited to this embodiment.
As shown in FIG. 2, three workpieces 90 </ b> A, 90 </ b> B, and 90 </ b> C are arranged side by side on the stage-like support portion 10. The base film 92 of each of the workpieces 90A to 90C was silicon nitride, and the etching target film 93 was amorphous silicon. The initial thickness of the film 93 of each workpiece 90A to 90C was not measured and was unknown. The horizontal dimension of each workpiece 90A to 90C was 250 mm, and the total horizontal dimension of the three workpieces 90A to 90C was 750 mm. Saddle plates 94L and 94R made of polyimide resin are disposed on the left and right outer sides of the workpieces 90A to 90C, respectively. The thicknesses of the attachment plates 94L and 94R are the same as the workpieces 90A to 90C, and the upper surfaces of the attachment plates 94L and 94R and the workpieces 90A to 90C are aligned.

The configuration of the etching apparatus 1 is the same as that of the embodiment. A processing gas containing HF and O ₃ was blown from the nozzle head 20 and the support portion 10 was reciprocated left and right. A part of the treated gas was diverted from the suction passage 41 to the detection passage 53 and quantitatively analyzed by the analysis unit 51 to detect the HF concentration and the SiF ₄ concentration in the treated gas. Based on this detection data, the determination unit 52 calculates the concentration ratio r = [HF] / [SiF ₄ ] shown in Equation 1. The concentration of SiF ₄ was substituted into Equation 1 after subtracting the detected value at the start of operation (0 [sec] on the horizontal axis in FIG. 3).

  FIG. 3 shows changes with time in detected concentration and concentration ratio. In the concentration ratio line, the peaks 90A, 90B, 90C, 94L, and 94R of the samples are attached to the peaks that are considered to be data of the samples 90A, 90B, 90C, 94L, and 94R.

In the stage where the silicon film 93 remains in any of the objects 90A to 90C (before time 300 [sec]), the HF concentration in the processed gas is low, the SiF ₄ concentration is high, and the concentration ratio r is small. became. When the supporting plates 94L and 94R were processed, no reaction occurred, so the HF concentration increased, the SiF ₄ concentration decreased, and the concentration ratio r increased.

When the operation time is close to 330 [sec], the HF concentration becomes high, the SiF ₄ concentration becomes low, the concentration ratio r becomes large, and 300 [sec. ] The behavior was clearly different from before. Therefore, it has been clarified that the etching end point can be determined by observing the concentration change of the reaction component and the generated component of the treated gas. It was found that the threshold value r0 of the density ratio r should be set to about r0 = 1 from the fluctuation of the peak of the sample 90B. On the other hand, when the concentration ratio r reaches r = 1, there is a possibility that the portion reaching the etching end point does not reach the entire surface of the object to be processed. Therefore, the threshold value r0 is set to r0 = 5, for example. Also good. Thereby, the whole surface of a to-be-processed object can be etched reliably. After the concentration ratio r reaches r = 1, the concentration ratio r becomes about r = 5 by merely moving the object to be processed one way or reciprocating about one time with respect to the nozzle head 20. Therefore, the amount of overetching during this period is small, and a suitable etching end point can be set.

When it is determined whether it is during the processing of the workpieces 90A to 90C or the processing of the attachment plates 94L and 94R from the relative position of the support unit 10 and the nozzle head 20, and when it is during the processing of the attachment plates 94L and 94R May be ignored even if the density ratio r exceeds the threshold value r0.
In FIG. 3, the peak after 350 [sec] is presumed to be due to etching of the underlying silicon nitride film 92.

  The present invention can be applied to an etching process in a manufacturing process of a glass substrate or a semiconductor substrate for a flat panel display, for example.

It is a schematic block diagram of the etching apparatus containing the etching end point determination apparatus which concerns on one Embodiment of this invention. 1 is a schematic configuration diagram of an etching apparatus and a sample used in Example 1. FIG. 3 is a graph showing the results of Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Etching apparatus 10 Support part 20 Nozzle head 21 Blowing port 22 Suction port 30 Process gas supply source 31 Supply path 40 Suction pump (suction means)
41 Suction path 41b Branching section 50 Etching end point determination device 51 Analysis section (infrared spectrometer)
52 Determination Unit 53 Detection Path (Conductance Reduction Unit)
54 Suction pump 55 Throttle valve (conductance reduction part)
90 Workpiece 91 Substrate 92 Base film 93 Silicon film (etching target film)
94L, 94R side plate

Claims (6)

A processing gas containing a reactive component having reactivity with the film is brought into contact with an object including the film to be etched;
The end point of etching of the film is determined based on the reaction component in the processed gas after the processing gas contacts the object to be processed and the concentration change of the generated component due to the reaction between the film and the reaction component. Etching method characterized by performing. The film is silicon or silicon oxide, the reaction component is HF, the generated component is SiF ₄ , and the determination is performed based on the concentration change of HF and SiF ₄ in the treated gas. The etching method according to claim 1, wherein the etching method is performed. The etching method according to claim 2, wherein the determination is performed based on whether or not a ratio of the HF concentration to the SiF ₄ concentration in the processed gas has reached a predetermined value. An apparatus for determining an end point of etching of the film, provided in an etching apparatus for bringing a processing gas including a reaction component having reactivity with the film into contact with an object to be processed including the film to be etched,
An analysis unit for analyzing the concentration of the reaction component in the treated gas after the treatment gas has contacted the object to be treated and the concentration of a component produced by the reaction between the membrane and the reaction component;
A determination unit that determines an end point of etching of the film based on a concentration change of the reaction component and the generated component;
An etching end point determination apparatus comprising:   The etching end point determination apparatus according to claim 4, wherein the analysis unit is an infrared spectrometer.   A detection path is branched from a suction path for sucking the processed gas of the etching apparatus through a branch section, the analysis section is connected to the detection path, and conductance of at least a portion near the branch section of the detection path The etching end point determination apparatus according to claim 4, wherein the etching end point is smaller than a conductance of the suction path.

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