JP3892744B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device capable of efficiently removing reaction products remaining in a processing chamber.
[0002]
[Prior art]
Known examples (patent publication or literature)
"JP-A-5-144799", "JP-A-7-153751"
As semiconductor devices have been highly integrated in recent years, circuit patterns have been increasingly miniaturized, and the required processing dimension accuracy has become increasingly severe. In such a situation, process reproducibility becomes important.
[0003]
For example, in an etching process that requires high processing accuracy, a process of performing etching while protecting a sidewall with a polymer generated by etching is used to realize anisotropic etching. In this process, the production state of the polymer serving as the protective film changes depending on the amount of etching products remaining in the processing chamber and the temperature of the wafer. Therefore, if the remaining amount of the reaction product in the processing chamber changes for each processing, the deposition state of the side wall protective film made of polymer varies between wafers, and the reproducibility of the etching shape deteriorates. In recent semiconductor manufacturing processes, even a variation in processing dimensions of about 10 nm or less may cause a device failure, and the deterioration of reproducibility is a serious problem.
[0004]
Further, the etching product remaining in the processing chamber forms a deposited film on the inner wall of the apparatus, and when the film thickness reaches a certain level, the etching product may peel off and adhere to the wafer. When these exfoliations called foreign substances adhere to the wafer, they become a mask during etching and cause etching residue, causing a major cause of product defects.
[0005]
As a method for coping with such an etching product, for example, in Japanese Patent Laid-Open No. 5-1447979, the film quality of the deposited film deposited on the inner wall of the processing chamber is modified to a film quality that is difficult to peel off and etching is continued. It is shown. Japanese Patent Application Laid-Open No. 7-153751 discloses that a dry cleaning process using plasma of a mixed gas of oxygen gas and chlorine gas is inserted as a separate process between etching processes.
[0006]
[Problems to be solved by the invention]
According to the method disclosed in Japanese Patent Laid-Open No. 5-144779, it is difficult to peel off the deposited film on the inner wall of the processing chamber. However, since this technique is based on the assumption that the deposit remains, the etching performance varies depending on the deposit, and a reduction in reproducibility cannot be avoided.
[0007]
Further, the method disclosed in Japanese Patent Application Laid-Open No. 7-153751 is a technique for removing etching products at certain processing intervals and preventing the remaining reaction products in the processing chamber from exceeding a certain amount. The deposition film is prevented from being formed on the inner wall of the processing chamber, and the reproducibility of the etching shape is within a specified value. However, productivity is deteriorated because a plasma cleaning process, which is a process not involved in wafer production, is inserted between the etching processes.
[0008]
The present invention has been made in view of these problems, and provides a manufacturing method and a manufacturing apparatus capable of efficiently removing reaction products remaining in a processing chamber.
[0009]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above problems.
[0010]
An etching processing chamber, a substrate stage on which a semiconductor substrate disposed in the etching processing chamber is placed, a plasma generating means for generating plasma in the etching processing chamber, and a processing gas introducing means for introducing a processing gas into the etching processing chamber In the method of manufacturing a semiconductor device, the semiconductor substrate is processed by a processing condition consisting of a single step or a plurality of continuous steps using the plasma processing apparatus.
After over-etching , which is the final step of the etching , conditions for reducing the processing pressure and / or lowering the wafer application bias among the final step processing conditions were added.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram for explaining a method of manufacturing a semiconductor device according to the first embodiment of the present invention. FIG. 2 is a diagram showing a dry etching apparatus used for carrying out the manufacturing method of the present invention.
[0012]
In FIG. 1, 1 is a silicon substrate, 2 is a polysilicon film formed on the silicon substrate 1 by CVD (Chemical Vapor Deposition) or the like, and 3 is a photoresist having an opening in a region to be processed by an etching process.
[0013]
FIG. 2 is a diagram showing a dry etching apparatus used for carrying out the manufacturing method of the present invention. In FIG. 2, 5 is an etching chamber, 6 is a waveguide for introducing a microwave into the chamber, 8 is a gas introducing tube for introducing an etching gas, 10 is a substrate stage on which a substrate is placed, and 14 is a vacuum. This is an exhaust port for exhausting.
[0014]
In the etching process, first, after evacuating, an etching gas is introduced from the gas introduction pipe 8 and adjusted to a predetermined pressure. Next, a microwave generated by a magnetron (not shown) is introduced into the processing chamber 5 through the waveguide 6. The introduced microwave turns the gas in the processing chamber into plasma by resonance with the magnetic field formed by the solenoid coil 7, and etching is performed using this plasma 4. The high frequency power source 12 applies anisotropic bias to the substrate stage 10 and performs anisotropic etching by drawing ions in the plasma. Thereby, a processing shape can be controlled.
[0015]
The substrate 1 is attracted to the substrate stage 10 by electrostatic attraction, and the substrate stage 10 includes a temperature adjusting mechanism 11 that controls the temperature of the substrate. The substrate 1 is electrostatically adsorbed on the substrate stage 10, and the temperature adjustment mechanism 11 adjusts the temperature of the refrigerant supplied to the substrate stage 10, thereby making the temperature in the substrate surface being processed uniform. The etching rate and etching shape can be made uniform. That is, by adsorbing the substrate 1 onto the substrate stage 10, the thermal conductivity between the substrate stage 10 and the substrate 1 can be increased, and the temperature control of the substrate can be performed reliably. The shower hole 9 is a hole for uniformly introducing the etching gas into the processing chamber 5.
[0016]
As described above, in an etching process that requires high processing accuracy, anisotropic etching is realized by performing etching while protecting the side wall with a polymer generated by etching. By the way, the production of the polymer serving as the protective film for the etching is influenced by the amount of etching products remaining in the processing chamber 5, and the degree of the influence becomes more sensitive as the processing pattern becomes finer. For example, if there are many remaining etching products, the protective film is too attached and the processed shape, for example, the dimension d shown in FIG. 1 tends to increase. Since the total amount of etching products remaining in the processing chamber 5 increases as the number of processed wafers increases, the processing shape changes as the processing proceeds even if processing is continued under the same conditions. .
[0017]
For example, when the polysilicon film 2 shown in FIG. 1 is etched using the photoresist 3 as a mask, the etching gas is a mixed gas of hydrogen bromide HBr, chlorine Cl ₂ , oxygen O ₂ , or chlorine Cl ₂ and oxygen. In general, a mixed gas of O _2, a mixed gas of hydrogen bromide HBr and oxygen O ₂ , or the like is used. In this case, a product by etching such as SiCl, SiH, SiO, and SiBr is generated and adheres to the processing chamber wall surface 5 ′, which affects the etching characteristics. In recent state-of-the-art devices, the processing dimension is about to reach 0.1 μm or less, and therefore satisfactory characteristics may not be obtained even if the amount of change in the dimension d is about several nanometers.
[0018]
In the present embodiment, an etching process including two steps of hydrogen bromide HBr, chlorine Cl ₂ , oxygen O ₂ mixed gas, and chlorine Cl ₂ and oxygen O ₂ mixed gas will be described as an example. First, in step 1, the polysilicon 2 is etched by plasma of a mixed gas of HBr, Cl ₂ and O ₂ . That is, the etching is advanced by chemically changing polysilicon to SiCl, SiH, SiO, SiBr in addition to Si. At this time, anisotropic etching is realized by performing etching while protecting the side wall with a polymer made of SiCl, SiH, SiO, SiBr or the like generated by etching. Step 2 using a mixed gas of chlorine Cl ₂ and oxygen O ₂ is a step called “over-etching”, which is a step of removing a slight amount of polysilicon remaining in the etching of step 1 such as a step in the device.
[0019]
In this embodiment, after step 2, the step of turning off the RF bias 12 and continuing the discharge for 15 seconds is added among the conditions of step 2. Here, the added step is called step 3. The reason for turning off the RF bias is to prevent the underlying 1 from being etched or the resist mask 3 from being excessively etched after the polysilicon 2 is etched. As a result, it was possible to prevent the d dimension from increasing as the wafer processing continued. Since the condition of step 2 originally vaporizes the Si compound, the discharge of the condition of step 2 is continued as step 3 in this way, and is generated by the process of step 1 and adheres to and accumulates on the inner wall 5 ′ of the apparatus. The etched etching product can be vaporized and exhausted. That is, by making it possible to remove etching products carried over to the next process, it is possible to eliminate the influence on the etching result of the next wafer and to perform etching processing with good reproducibility. Further, since the etching product is not accumulated on the inner wall 5 ′ of the apparatus, low foreign matters can be realized and the maintenance frequency can be reduced. Further, productivity does not decrease unlike the conventional method in which a cleaning process is provided separately from the etching process.
[0020]
In this embodiment, since the pressure in step 2 was performed under a sufficiently low condition of 0.2 Pa, only the wafer bias was turned off in the condition of step 3. If the pressure is low, the product remaining in the processing chamber 5 is easily exhausted and removed, so that the influence on the next etching process can be reduced. Therefore, when the etching condition is a relatively high pressure of about several Pa, it is desirable that the step 3 to be added has a low pressure.
[0021]
Note that the plasma generation position can be controlled by the position of the solenoid coil 7 shown in FIG. 2 and the value of the current flowing through the solenoid coil. As already described, by adding a processing step to the original etching process, the underlayer 1 and the resist mask 3 after the polysilicon 2 etching are additionally etched. In the case where the selection ratio is insufficient or the film thickness of the base film or resist is thin, the adverse effect can be suppressed by controlling the current value flowing through the solenoid coil to move the plasma generation position away from the substrate. .
[0022]
The above has been described with reference to an example in which a photoresist is used as a mask for processing. However, a similar effect can be obtained even with a so-called hard mask using a silicon oxide film or silicon nitride as a mask.
[0023]
As described above, since the influence of the etching product generated by the previous wafer process can be efficiently removed during the etching process, an etching process with good reproducibility is possible. Further, since the etching product does not accumulate on the inner wall of the apparatus, a low foreign substance apparatus can be realized. Furthermore, high productivity can be achieved as compared with a conventional method in which a cleaning process is provided between etching processes.
[0024]
【The invention's effect】
As described above, according to the present invention, it is possible to remove the influence of the etching product generated by the previous wafer processing during the etching processing, so that it is possible to perform highly efficient etching processing with high reproducibility.
[Brief description of the drawings]
FIG. 1 is a view for explaining a method of manufacturing a semiconductor device according to a first embodiment of the invention.
FIG. 2 is a view showing a dry etching apparatus used for carrying out the manufacturing method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Polysilicon 3 Photoresist 4 Plasma 5 Etching processing chamber 5 'Processing chamber wall surface 6 Waveguide 7 Solenoid coil 8 Etching gas introduction tube 9 Shower hole 10 Substrate stage 11 Temperature control mechanism 12 High frequency power source 13 DC power source 14 Vacuum Exhaust port 15 Ground

Claims (3)

An etching processing chamber, a substrate stage on which a semiconductor substrate disposed in the etching processing chamber is placed, a plasma generating means for generating plasma in the etching processing chamber, and a processing gas introducing means for introducing a processing gas into the etching processing chamber In the method of manufacturing a semiconductor device, using the plasma processing apparatus, the polysilicon deposited on the semiconductor substrate is etched according to processing conditions consisting of a single stage or a plurality of continuous stages.
A method for manufacturing a semiconductor device, comprising adding a step of turning off a wafer bias and continuing a discharge in an overetching process condition after the overetching step. An etching processing chamber, a substrate stage on which a semiconductor substrate disposed in the etching processing chamber is placed, a plasma generating means for generating plasma in the etching processing chamber, and a processing gas introducing means for introducing a processing gas into the etching processing chamber In the method of manufacturing a semiconductor device, using the plasma processing apparatus, the polysilicon deposited on the semiconductor substrate is etched according to processing conditions consisting of a single stage or a plurality of continuous stages.
A method of manufacturing a semiconductor device, characterized in that, after the over-etching process step, a step of reducing pressure in the over-etching process condition and turning off the wafer application bias and continuing the discharge are added. The method of manufacturing a semiconductor device according to claim 1 or claim 2 wherein, the method of manufacturing a semiconductor device characterized in that set away plasma generation position from the semiconductor substrate in the step of adding after the overetching process.

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