JPH10189535A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a plasma treatment apparatus which prevents an irregularity in the etch rate of an oxide film among wafers as the problem of a continuous treatment in the etching operation of the oxide film by a semiconductor manufacturing apparatus, which prevents an irregularity in the etch rate of an etching mask and a substrate material, which performs a process stably and whose selectivity is high. SOLUTION: Before a plasma treatment, a dummy wafer is conveyed into a treatment chamber, a higher-order fluorocarbon gas which is different from a fluorocarbon gas used for an actual etching operation is used, and a plasma discharge which generates a deposition inside the treatment chamber is executed. After that, the dummy wafer is carried out to the outside of the treatment chamber, a wafer which is used as an object to be treated is carried into the treatment chamber, the plasma treatment is executed, a sidewall state in the treatment chamber for every wafer is made constant, and an irregularity in a process among wafers is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for etching an oxide film or a nitride film on a silicon substrate.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, a plasma C is used.
A plasma device for performing VD and dry etching is indispensable. In plasma CVD, SiH ₄ or Si (O
By exciting and activating C ₂ H ₅ ) _{4 and the} like in plasma, a film forming reaction is promoted, and a desired material thin film is formed on the wafer surface at high speed.

[0003] In the plasma process in which the deposition occurs as described above, a large number of deposition species exist in the processing chamber, and adhere to and deposit on the processing chamber walls and other internal components in addition to the processing substrate. It is known that a deposition film formed in a processing chamber causes generation of particles and instability of processing, and greatly affects semiconductor product quality and a defective rate.

[0004] First, in this deposition, the deposited film thickness increases with the number of times of the plasma processing, and when the deposited film thickness exceeds the limit film thickness, it is peeled off and becomes particles. As a countermeasure, the current plasma apparatus performs a process of removing deposits deposited on the inner walls and components of the processing chamber every unit wafer processing, and removes the deposits before the film thickness exceeds the peeling limit film thickness. As another measure, there is a method of increasing the temperature of the processing chamber. By increasing the temperature of the side wall of the processing chamber, it is possible to suppress the adhesion of the deposited film.

In the method proposed in Japanese Patent Application Laid-Open No. Hei 5-243167, a deposit such that a reaction product adhered to the inside of the plasma processing chamber forms a sublimable product is previously deposited in the processing chamber. A method has been proposed in which after the plasma treatment is completed, the reaction between the reaction product and the deposited layer is promoted by raising the treatment room temperature to remove the product as a sublimate.

In Japanese Patent Application Laid-Open No. 7-201742, a substantial surface area is obtained by subjecting components in a processing chamber to a surface roughening treatment such as a blast treatment or a porous plating treatment having a large number of pores. By increasing the adhesion and increasing the adhesion of the deposited film, a process in which the generation of particles is small and the productivity is improved is realized.

Next, it is known that the reaction products adhering to the processing chamber are necessary for the stability of the continuous wafer processing. In the plasma CVD method disclosed in JP-A-63-129628, fluctuations in film thickness and film quality for each wafer are performed by predeposition processing, that is, by depositing a reaction product in a processing chamber in advance before plasma processing. To achieve a stable process. In addition, by cleaning the inside of the processing chamber after the plasma processing, excessive deposition of reaction products is suppressed, and a stable plasma CVD process with few particles is achieved. As described above, in plasma CVD, the state of adhesion of the deposition film inside the processing chamber has a great effect on the process.

On the other hand, in oxide film etching of dry etching using a plasma apparatus, a fluorocarbon gas such as CF ₄ or CHF ³ is introduced, and the oxide film is etched by ions and radicals excited in the plasma. In the oxide film etching step, it is important to obtain selectivity between the base material and the photoresist as the mask material. In order to secure this selectivity, fluorine generated by exciting a fluorocarbon gas in plasma is used. It is known that a deposition film made of carbon is formed on a base material and a mask material to achieve selective etching. That is, deposition is performed simultaneously with etching. The deposition generated during the etching of the oxide film also adheres to the inner wall of the processing chamber as in the CVD process.

FIG. 4 is a structural view showing a conventional capacitively coupled plasma etching apparatus widely used. FIG.
, 1 is a processing chamber, 2 is a gas introduction pipe, 3 is an exhaust pipe,
4 is a pressure control device, 6 is a lower electrode, 7 is a high frequency power supply, 8
Denotes an upper electrode, and 11 denotes an object to be processed. In this apparatus, the plasma density was as low as about 10 ⁹ to 10 ¹⁰ cm ^−3, and the working pressure range was relatively high as about 100 mTorr to 1 Torr. Therefore, it was possible to confine the plasma between the parallel plate electrodes. Therefore, the interaction with the side wall of the processing chamber was small, and did not affect the stability of the continuous wafer processing.

However, a plasma etching apparatus equipped with a high-density plasma source, which has been used recently, has a high plasma density of 10 ¹¹ to 10 ¹² cm ^-3 and a low operating pressure range of 1 mTorr to 10 mTorr. It becomes difficult and an interaction with the side wall occurs. Therefore, there is a problem that the plasma state changes with the change of the state of the processing chamber side wall, and it is difficult to obtain the process reproducibility during the continuous wafer processing.

Further, because of the high density, the dissociation of the etching gas proceeds, and the fluorocarbon-based gas used in the oxide film etching releases a large amount of fluorine radicals.
Fluorine radicals can etch oxide films, but also etch silicon and mask resists, making it difficult to obtain high selectivity.

[0012]

SUMMARY OF THE INVENTION In semiconductor manufacturing,
It is important to obtain good process reproducibility by suppressing process variations between wafers during continuous processing of wafers. Further, there is a need to realize a process with good characteristics. However, in an oxide film etching process using a high-density plasma source used in a low-pressure region, there is a problem that the process reproducibility is deteriorated due to a change in the temperature of the side wall of the processing chamber and a change in deposition of the side wall state. In addition, since high-density plasma generates a large amount of active fluorine, there is a problem that it is difficult to ensure the selectivity between the underlying material and the resist of the mask.

In order to solve the deterioration of reproducibility due to the change in the temperature and state of the side wall of the processing chamber, the same pre-deposition processing as the CVD process described in JP-A-63-129628 is performed in the plasma etching step. It is necessary to keep the state of the side wall and the temperature constant. The processing chamber side wall temperature rises and stabilizes as the plasma processing start time and the number of sheets advance. For this reason, the plasma state is different immediately after the processing time and at the end of the processing time, and a variation occurs.

Therefore, by performing pre-deposition,
By increasing the side wall temperature to a stable temperature, it is possible to reduce process variations due to temperature changes. On the other hand, regarding the deposition of the side wall, the deposition rate of the deposition is small, about 10 to 20 nm / min, using an etching gas of CF ₄ or the like which has been conventionally used for etching an oxide film. It is impossible to form a thick film.

In addition, the deposition film formed on the side wall is released again into the plasma to form a deposition species.
It has a significant effect on the selectivity with resist and underlying materials.
A gas having a low C / F ratio, such as CF _4, which has been conventionally used for etching an oxide film, forms a deposition film having a high fluorine concentration, so that it is difficult to obtain a high selectivity.

An object of the present invention is to stably perform a process in an oxide film etching step using high-density plasma, which has an unstable process reproducibility and an insufficient selectivity with a photoresist and a base material. Another object of the present invention is to provide a method of manufacturing a semiconductor device which realizes high selectivity.

[0017]

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention includes a pre-deposition step and an etching step, and uses a fluorocarbon gas to dry an oxide film. A method of manufacturing a semiconductor device to be etched, wherein a pre-deposition step is a step of introducing a fluorocarbon gas different from an etching gas into a processing chamber before processing an object to be processed, and depositing a fluorocarbon deposition film in the processing chamber. In the etching step, after completion of the pre-deposition process, an oxide film is etched using a fluorocarbon gas different from the gas used for the pre-deposition.

In the predeposition step, a silicon substrate is used as an object to be processed, and a bias is applied to perform the deposition simultaneously with the silicon etching.

Further, among the fluorocarbon gases used in the predeposition process, a fluorocarbon gas having an n / m ratio represented by CnFm of 3/8 or more is used.

Further, among the fluorocarbon gases used in the predeposition process, n / F expressed by CnHxFm
A fluorocarbon gas having an m ratio of 1/3 or more is used.

[0021]

According to the present invention, when etching is performed using a fluorocarbon gas, the processing chamber is covered with a fluorocarbon deposition made of fluorine and carbon before the processing of the object to be processed, so that the state of the inner wall of the processing chamber is changed according to the number of plasma processing. Is kept constant without change, and a change in the plasma composition due to a change in the processing chamber is suppressed. As a result, it is possible to suppress process variations between wafers when the wafers are continuously processed.

Further, by performing the predeposition until the rise in the side wall temperature due to the plasma discharge is saturated, a more stable process can be performed. In this pre-deposition, C ₄ F ₈
Fluorocarbon gas having a high C / F ratio is used. Thereby, a deposition rate of 100 nm / min or more is achieved. Since the deposition rate is about 10 times that of the conventional CF ₄ gas used as the etching gas, the pre-deposition process can be performed in a short time.

Further, by using a fluorocarbon gas having a high C / F ratio, it is possible to increase the C / F ratio of the deposition type. Deposition species with high carbon concentration
Since the adsorption probability is also increased, the polymerization of fluorocarbon deposition on the inner wall of the processing chamber is promoted. In addition, the deposition species having a high carbon concentration attached to the inner wall of the processing chamber are re-emitted into the plasma during the etching process due to the interaction with the plasma, which affects the composition of the deposition species in the plasma, and the deposition species having a high carbon concentration are affected. Generate

As a result, the carbon concentration of the deposition film deposited on the processing wafer during the etching increases. The relationship between the carbon concentration of the fluorocarbon deposition film generated in the oxide etching plasma and the selective etching of the oxide film with respect to silicon is described by Akim.
oto et al. reported as follows (Jpn. J. Appl. P.
hys. Vol. 33 1994 pp2151). In other words, it is reported that a fluorocarbon deposition film having a high carbon concentration has a high sputtering resistance, protects the underlying silicon from an etchant during etching, and realizes highly selective etching. In other words, by forming a fluorocarbon deposition film having a high carbon concentration by pre-deposition, it is possible to increase the carbon concentration of the deposition species in the plasma, and even when etching the oxide film using a low-pressure high-density plasma, Selectivity is achieved.

As described above, by performing pre-deposition using a fluorocarbon gas having a high C / F ratio different from the etching gas, it is possible to improve the process reproducibility between wafers during continuous processing of wafers. At the same time, highly selective etching becomes possible.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a configuration diagram showing an apparatus for performing a method of manufacturing a semiconductor device according to an embodiment of the present invention.

In FIG. 1, a processing chamber 1 includes a lower electrode 6 provided in the processing chamber 1 on which an object 11 to be processed is placed, and an upper electrode 8 provided opposite thereto. A dielectric line composed of a Teflon plate 9 for introducing microwaves into the processing chamber 1 via a microwave transmitter 5 and a waveguide 10 provided adjacent to the processing chamber 1 and a high frequency connected to a lower electrode 8 It has a power supply 7, a gas introduction pipe 2 for introducing gas into the processing chamber 1, an exhaust pipe 3 for exhausting gas in the processing chamber 1, and a pressure control device 4.

FIG. 2 is a flowchart showing a method for manufacturing a semiconductor device according to the first embodiment of the present invention. First, step S
^{In 1} , a Si substrate, which is a dummy wafer different from the wafer to be processed, is introduced into the processing chamber 1, and the Si substrate is placed on the lower electrode 6. In step S ^2, through the gas inlet tube 2, for introducing a mixed gas of a different gas Hachidoru of butane (C ₄ F ⁸⁾ and carbon monoxide (CO) is an etching gas. The gas condition at this time is C ₄ F ⁸ : 5 scc
m, CO: 75 sccm. Next, the pressure in the processing chamber 1 was controlled to 30 mTorr by the exhaust pipe 3 and the pressure control device 4.

Next, in step S ₃ , the microwave transmitter 5 is transmitted, and the high-frequency power source 7 connected to the lower electrode 6 is transmitted.
To generate plasma in the processing chamber 1. At this time, the microwave power and the high frequency power were 1300 W and 600 W, respectively. By performing the above process for 5 minutes, a fluorocarbon polymer composed of fluorine and carbon is deposited on the surface of the processing chamber 1, and the predeposition is completed. At this time, 1000 nm
Degree of polymer is deposited. Since this polymer uses C ₄ F ⁸ , CO and CO, the fluorine concentration in the plasma decreases due to the fluorine scavenging effect of the CO gas (Proceedings. Of 10th Sym).
Posium on Plasma Processes
ng. 1994. San Francisco P.C. 31
1) A polymer rich in carbon concentration is produced. Further, since the high-frequency power source 7 serving as the substrate bias is applied, Si in the dummy wafer is etched, reacts with fluorine in the plasma, and a Si-F bond is formed and exhausted. Therefore, fluorine in the plasma is removed, and a deposition film with a higher carbon concentration is formed. Also,
By performing this pre-deposition, the side wall temperature increases due to the plasma discharge. The temperature rise rises with the discharge time and stabilizes in a certain time. The conditions for performing the above predeposition are 4 minutes and a stable temperature of 12 minutes.
0 ° C. was reached.

Next, in step S ₄ , after the dummy wafer used for pre-deposition is carried out of the processing chamber 1, the wafer to be processed is introduced into the processing chamber in step S ₅ , and the plasma is generated in steps S ₆ and S ₇ . Perform processing. As an etching gas, a mixed gas of CF ₄ , CHF ³ and Ar was used, and each flow rate was set to CHF ₃ : 20 scc.
m, CF ₄ : 10 sccm, Ar: 50 sccm,
Pressure 30 mTorr, microwave power 1300
W, and the high-frequency power source power was 600 W. In this case, by attaching deposition the pre-deposition in the processing chamber 1 in step S _3, since the side surface temperature reached a stable temperature, it is possible to suppress the variation and side temperature of the processing chamber surface condition during the plasma treatment This makes it possible to reduce process variations among wafers in etch rate, photoresist selectivity, and base selectivity. In addition, since the temperature rise on the inner surface of the processing chamber 1 due to the increase in the number of plasma processing can be controlled by adjusting the predeposition step time, re-emissions from the processing chamber surface are stably supplied, and the plasma state is reduced. Be stabilized. Then after the plasma treatment ends in step S _8, and convey the treated wafer to the outside of the processing room, the removal of reaction products of the process chamber in step S _9. Thereafter, the same flow is repeated for each sheet.

(Embodiment 2) FIG. 3 is a flow chart showing Embodiment 2 of the present invention. In the second embodiment, steps S ₃ and the first sheet of step S ₇ of the plasma treatment of the first sheet of pre-deposition, after performs similarly to Embodiment 1, which then transports the wafer to the process outside the process The second and subsequent wafers are processed without performing the reaction product removal and pre-deposition step in the room, and after finishing the last wafer processing of the lot,
It is characterized in that reaction products in the processing chamber are removed. That is, the pre-deposition is performed for each lot.

In the above-described embodiment, the reaction products are removed by removing the deposition by a certain number of sheets in order to prevent dust generation due to excessive deposition of deposition in the processing chamber. Have gone to prevent.
However, performing many of these steps hinders productivity. Therefore, by performing a roughening treatment such as a plast treatment on the components in the processing chamber, a substantial surface area is increased,
The adhesion of the deposited film can be improved, the cleaning cycle can be extended, and the generation of particles can be prevented.

[0034]

As described above, according to the present invention, in the step of etching an oxide film using plasma,
By providing a step of performing deposition using a fluorocarbon gas different from the gas for processing the object to be processed before the plasma processing, it is possible to reduce the variation between the number of processed wafers in the deposition and temperature state of the inner wall of the processing chamber, and It can be constant.

Further, by using a higher-order fluorocarbon gas, a higher-order fluorocarbon species than the gas is formed by polymerization on the inner wall of the processing chamber, and redissolved into the plasma, so that a higher-order fluorocarbon carbon is formed on the object to be processed. Can promote carbon-rich polymerization, and can realize highly selective etching.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an apparatus for performing a method of manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a method for manufacturing the semiconductor device according to the first embodiment of the present invention.

FIG. 3 is a flowchart illustrating a method for manufacturing a semiconductor device according to a second embodiment of the present invention.

FIG. 4 is a sectional view showing a conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Processing chamber 2 Gas introduction pipe 3 Exhaust pipe 4 Pressure control device 5 Microwave transmitter 6 Lower electrode 7 High frequency power supply 8 Upper electrode 9 Teflon plate 10 Waveguide 11 Object to be processed

Claims (4)

[Claims] 1. A method of manufacturing a semiconductor device, comprising a pre-deposition step and an etching step, wherein an oxide film is dry-etched using a fluorocarbon gas. Before the etching, a fluorocarbon gas different from the etching gas is introduced into the processing chamber, and a fluorocarbon deposition film is deposited in the processing chamber.
A method for manufacturing a semiconductor device, wherein the oxide film is etched using a fluorocarbon gas different from a gas used for pre-deposition. 2. The semiconductor device according to claim 1, wherein in the pre-deposition step, a silicon substrate is used as an object to be processed, and deposition is performed simultaneously with silicon etching by applying a bias. Production method. 3. The semiconductor device according to claim 1, wherein, among the fluorocarbon gases used for the pre-deposition process, a fluorocarbon gas whose n / m ratio represented by CnFm is 3/8 or more is used. Manufacturing method. 4. Among the fluorocarbon gases used for the pre-deposition process, n / m represented by CnHxFm
2. The method according to claim 1, wherein a fluorocarbon gas having a ratio of 1/3 or more is used.