JP4579451B2 - Semiconductor device manufacturing method and manufacturing apparatus thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a semiconductor device and a manufacturing apparatus thereof that can obtain a desired processed shape when etching a semiconductor member made of silicon.
[0002]
[Prior art]
In recent semiconductor element isolation formation processes, a groove is formed in a semiconductor substrate made of silicon, a silicon oxide film is embedded in the formed groove, and the surface of the embedded silicon oxide film is formed by a CMP (Chemical Mechanical Polishing) method. A method of forming an element isolation structure called an STI (Shallow Trench Isolation) structure by planarization is employed.
[0003]
Hereinafter, a conventional method for manufacturing an element isolation structure in a semiconductor device will be described with reference to FIG.
[0004]
FIG. 17A to FIG. 17D show cross-sectional configurations in the order of steps of a conventional method for manufacturing an element isolation structure in a semiconductor device.
[0005]
First, a first silicon oxide film 102 is formed on the upper surface of a semiconductor substrate 101 made of silicon by thermal oxidation, and then a silicon nitride film 103 is formed on the first silicon oxide film 102. Subsequently, a resist film 104 having a desired separation pattern 104a is formed on the silicon nitride film 103 by using a photolithography technique to obtain the state shown in FIG.
[0006]
Next, as shown in FIG. 17B, the silicon nitride film 103 and the first silicon oxide film 102 are etched by a dry etching method using the resist film 104 as a mask, and then the resist is obtained by ashing and cleaning. The film 104 is removed, and the separation pattern 103 a is transferred to the silicon nitride film 103 and the first silicon oxide film 102.
[0007]
Next, the semiconductor substrate 101 on which the separation pattern 103a is formed is put into a chamber of a dry etching apparatus, and the inside of the chamber is evacuated to a predetermined degree of vacuum. Thereafter, an etching gas (process gas) for the semiconductor substrate 101 is introduced into the chamber, and the process gas is turned into plasma. Etching proceeds by reacting the plasma process gas with the semiconductor substrate 101 to form a volatile reaction product and evacuating the reaction product. In dry etching for silicon, chlorine (Cl₂ Or a mixed gas containing halogen such as hydrogen bromide (HBr).
[0008]
Since etching of the semiconductor substrate 101 requires high processing accuracy due to the miniaturization of the separation pattern 103a, a dual power supply type dry etching apparatus, for example, a source power source for plasma generation and plasma is used as an etching target. Using an inductively coupled (ICP) type plasma etching apparatus having a bias power supply to pull in, the plasma density is 1 × 10¹⁶/ M^Three The above high density plasma is generated. By this plasma etching, a groove portion 101a for forming an element isolation structure is formed in the semiconductor substrate 101, and the deposit formed during the dry etching is removed by cleaning to obtain the state shown in FIG.
[0009]
Next, in order to reduce the surface level of the surface of the groove 101a, the side wall and the bottom of the groove 101a are oxidized by a thermal oxidation method. Thereafter, a second silicon oxide film for element isolation is deposited on the silicon nitride film 103 so as to fill the groove 101a. Subsequently, the deposited second silicon oxide film is planarized by CMP or the like, and the silicon nitride film 103 and the first silicon oxide film 102 are removed by wet etching, as shown in FIG. Then, the element isolation structure 105 made of the second silicon oxide film is formed.
[0010]
[Problems to be solved by the invention]
However, in the conventional dry etching method using high density plasma for the silicon substrate 101, when etching is performed only with chlorine gas, as shown in FIG. 17C, a small groove (local groove) 101b is formed in the lower portion of the side wall of the groove 101a. And a crystal defect is generated in the silicon substrate 101 by the local groove 101b.
[0011]
In addition, when a mixed gas of hydrogen bromide and chlorine is used to suppress the generation of the local groove 101b, there is a problem that the etching rate is reduced.
[0012]
In addition, when hydrogen bromide gas is used for etching, there is a problem in that a high etching selectivity cannot be obtained with respect to the silicon nitride film 103 serving as an etching mask, resulting in poor processing accuracy.
[0013]
The present invention solves the above-mentioned conventional problems, suppresses the formation of local grooves formed in the lower side edge of the opening when dry etching a silicon member, and performs etching while having a high selectivity to the silicon nitride film. The purpose is to make it.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is configured to include chlorine molecules in the high-density plasma used for etching the silicon member.
[0015]
Specifically, in the method for manufacturing a semiconductor device according to the present invention, a first step of forming a mask pattern having an opening on a semiconductor member made of silicon, and a semiconductor member on which the mask pattern is formed are converted to chlorine molecular ions. And a second step of etching using a high-density plasma containing.
[0016]
According to the method for manufacturing a semiconductor device of the present invention, a semiconductor member made of silicon is etched by irradiating a plasma containing chlorine molecular ions that are less reactive than chlorine atom ions, thereby lowering the side edge of the opening. It is possible to suppress local etching that occurs in the process. In addition, etching with plasma containing molecular chlorine ions reduces the reactivity of chlorine plasma to silicon compared to the case of containing many chlorine atom ions, so that a high selectivity to silicon nitride film can be obtained. Can do.
[0017]
In the semiconductor device manufacturing method of the present invention, it is preferable that the second step generates high-density plasma in an atmosphere having a pressure of about 4 Pa or more.
[0018]
In the method for manufacturing a semiconductor device of the present invention, it is preferable that the second step is to generate high-density plasma by adding about 0.3 ml or more oxygen per 1 liter in a standard state.
[0019]
In the method for manufacturing a semiconductor device of the present invention, the second step preferably generates a high-density plasma using a plasma generating power source having a frequency of about 20 MHz or more.
[0020]
In the method for manufacturing a semiconductor device of the present invention, it is preferable that the second step is to selectively accelerate and irradiate the semiconductor member with chlorine molecular ions.
[0021]
In this case, it is preferable that the chlorine molecular ions are selectively accelerated by intermittently applying a bias power having a period of 0.1 μs to 100 μs.
[0022]
Furthermore, in this case, it is preferable that the period in which the bias power is intermittently applied is about the time during which chlorine atom ions can pass through the plasma sheath.
[0023]
In the method for manufacturing a semiconductor device of the present invention, the mask pattern is preferably made of a silicon nitride film.
[0024]
A first semiconductor device manufacturing apparatus according to the present invention generates a plasma including a reaction chamber containing an etching target member made of silicon, and chlorine molecule ions and chlorine atom ions provided in the reaction chamber to irradiate the etching target member. Plasma generating means, ion quantity analyzing means for analyzing the amount of generated chlorine molecular ions and chlorine atom ions, and process parameter control means for adjusting process parameters based on the analysis results of the ion quantity analyzing means And the process parameter control means keeps the value of the ratio between the ion amount of the chlorine molecular ions and the ion amount of the chlorine atom ions at a substantially predetermined value.
[0025]
According to the first semiconductor device manufacturing apparatus, the ion amount analyzing means for analyzing the ion amount of chlorine molecular ions and the ion amount of chlorine atom ions generated by the plasma generating means, and chlorine based on the analysis result of each ion amount A process parameter control means for maintaining the ratio of the ion amount of the molecular ions and the ion amount of the chlorine atom ions at a substantially predetermined value, so that the semiconductor device manufacturing method according to the present invention can be realized. A manufacturing apparatus can be obtained.
[0026]
In the first semiconductor device manufacturing apparatus, the ion content analyzing means is preferably a plasma emission spectroscopic analyzer.
[0027]
A second semiconductor device manufacturing apparatus according to the present invention includes a reaction chamber for storing an etching target member made of silicon, plasma generation means for generating plasma containing chlorine gas for irradiating the etching target member, and Ion separation means for separating chlorine molecular ions from the plasma and ion introduction means for selectively introducing the separated chlorine molecular ions into the reaction chamber.
[0028]
According to the second semiconductor device manufacturing apparatus, the ion separating means for separating the chlorine molecular ions from the plasma generated by the plasma generating means, and the ion introducing means for selectively introducing the separated chlorine molecular ions into the reaction chamber; Therefore, a semiconductor device manufacturing apparatus capable of realizing the semiconductor device manufacturing method according to the present invention can be obtained.
[0029]
A third semiconductor device manufacturing apparatus according to the present invention generates a reaction chamber containing an etching target member made of silicon, and a plasma including chlorine molecular ions and chlorine atom ions that are provided in the reaction chamber and irradiate the etching target member. The ion energy of the chlorine molecular ions is analyzed based on the analysis results of the ion energy analyzing means and the ion energy analyzing means for analyzing the ion energy of the generated chlorine molecular ions and the ion energy of the chlorine atom ions. Pulse control means for adjusting the amplitude, period or duty ratio of the pulse so as to be higher than the ion energy of the atomic ion, and pulse generation for receiving a control signal from the pulse control means and controlling the bias power supply of the plasma generation means Means.
[0030]
According to the third semiconductor device manufacturing apparatus, the ion energy analyzing means for analyzing the ion energy of the chlorine molecular ions and the ion energy of the chlorine atom ions generated by the plasma generating means, and the ion energy of the chlorine molecular ions as the chlorine atom ions And a pulse control means for adjusting the amplitude, period, or duty ratio of the pulse so as to be higher than the ion energy of the semiconductor device, a semiconductor device manufacturing apparatus capable of realizing the semiconductor device manufacturing method according to the present invention. Obtainable.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
A first embodiment of the present invention will be described with reference to the drawings.
[0032]
FIG. 1A to FIG. 1D show cross-sectional structures in the order of steps of a method for manufacturing an element isolation structure in a semiconductor device according to a first embodiment of the present invention.
[0033]
First, a first silicon oxide film 12 is formed on the upper surface of a semiconductor substrate 11 made of silicon by a thermal oxidation method, and then a silicon nitride film 13 is formed on the first silicon oxide film 12 by using a CVD method or the like. Form. Subsequently, a resist film 14 having an isolation pattern 14a, which is a design pattern of an element isolation structure, is formed on the silicon nitride film 13 by photolithography to obtain the state shown in FIG.
[0034]
Next, as shown in FIG. 1B, the silicon nitride film 13 and the first silicon oxide film 12 are etched by dry etching using the resist film 14 as a mask, and then the resist film 14 is etched and washed. Then, a separation pattern 13 a is formed by transferring the separation pattern 14 a to the silicon nitride film 13 and the first silicon oxide film 12.
[0035]
Next, the semiconductor substrate 11 on which the separation pattern 13a is formed is put into a chamber of a dry etching apparatus, for example, an inductively coupled plasma etching apparatus, and the inside of the chamber is evacuated to a predetermined vacuum level. Thereafter, the source power is about 600 W, the bias power is about 200 W, and chlorine (Cl₂ ) Dry etching is performed under the condition of a gas flow rate of about 150 ml / min. At this time, the pressure in the chamber (process pressure) is preferably about 4 Pa or more, and is set to about 7 Pa here, for example. By performing etching under these conditions, the groove portion 11a for forming an element isolation structure is formed in the semiconductor substrate 11 without forming a local groove at the lower side end. Thereafter, when the deposit formed during the dry etching of the semiconductor substrate 11 is removed by cleaning, the result is as shown in FIG. The plasma density is 1 × 10¹⁶/ M^Three In this specification, the plasma in this state is referred to as high density plasma.
[0036]
Next, in order to reduce the surface level of the surface of the groove part 11a, the side wall and the bottom part (hereinafter referred to as a trench side wall) of the groove part 11a are oxidized by a thermal oxidation method. Thereafter, a second silicon oxide film for element isolation is deposited on the silicon nitride film 13 so as to fill the groove 11a by CVD. Subsequently, the upper surface of the deposited second silicon oxide film is flattened by a CMP method or the like, and the silicon nitride film 13 and the first silicon oxide film 12 are removed by wet etching, so that FIG. As shown, an element isolation structure 15 made of a second silicon oxide film is formed.
[0037]
Hereinafter, in the first embodiment, by setting the process pressure to about 4 Pa or more, a local groove is not formed in the lower portion of the side end of the groove portion 11a, and a high selectivity with respect to the silicon nitride film 13 is ensured. Explain why.
[0038]
FIG. 2 shows the dependence of the selectivity of the silicon nitride film on the process pressure and the depth of the local trench. From FIG. 2, it can be seen that the depth of the local groove is drastically lowered by setting the process pressure to about 4 Pa or more, and the selectivity of the silicon nitride film is greatly improved.
[0039]
  FIG. 3 shows the analysis results of the spectral intensity (relative value) of each plasma emission spectrum when the process pressure is 0.7 Pa, 1.3 Pa, 4.0 Pa, and 7.0 Pa, respectively. In FIG. 3, 256 nm and 309 nm represent chlorine molecules (Cl₂ ), And 726 nm, 741 nm, and 755 nm indicate emission peaks due to chlorine atoms (Cl). As can be seen from FIG. 3, as the process pressure is increased, chlorine molecules (Cl₂ )On the contrary, the peak of chlorine atom (Cl) is small.
[0040]
FIG. 4 shows the dependence of the emission intensity ratio between a chlorine atom with a 726 nm emission peak and a chlorine molecule with a 256 nm emission peak on the process pressure. It can be seen from FIG. 4 that when the process pressure is increased, the value of the emission intensity ratio between chlorine atoms and chlorine molecules decreases.
[0041]
Therefore, if the emission intensity ratio between chlorine atoms and chlorine molecules is maintained at about 0.15 or less in FIG. 4, the formation of local grooves is determined from the data of the local groove depth and silicon nitride film selectivity shown in FIG. It can be seen that it can be suppressed and a selection ratio of 40 or more can be secured. That is, it can be seen that the emission intensity ratio between chlorine atoms and chlorine molecules can be adopted as a process parameter between the local groove depth and the silicon nitride film selectivity.
[0042]
Here, the reason why local grooves are formed by chlorine atoms will be described with reference to FIG.
[0043]
When etching the semiconductor substrate 11 made of silicon, chlorine ions 106 having high energy enter the groove 11a. Since the chlorine ions 106 have an incident angle distribution, a part of the chlorine ions 106 collides with the side wall and is reflected. For this reason, the chlorine ions 106 concentrate on the lower side end of the groove 11a. At this time, the chlorine atom ion is more reactive than the chlorine molecule ion, and if the ratio of the chlorine atom to the incident chlorine ion 106 is high, the etching rate at the lower side end of the groove 11a is locally increased. The local groove 11b is formed.
[0044]
Accordingly, the formation of the local groove 11b can be suppressed by increasing the proportion of the chlorine molecular ions in the incident chlorine ions 106. Similarly, a high etching selectivity with respect to the silicon nitride film 13 can be ensured by performing etching while increasing the ratio of chlorine molecular ions.
[0045]
(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.
[0046]
FIG. 6A to FIG. 6D show cross-sectional structures in the order of steps of the method for manufacturing the element isolation structure in the semiconductor device according to the second embodiment of the present invention.
[0047]
First, a first silicon oxide film 12 is formed on the upper surface of a semiconductor substrate 11 made of silicon by a thermal oxidation method, and then a silicon nitride film 13 is formed on the first silicon oxide film 12 by using a CVD method or the like. Form. Subsequently, a resist film 14 having an isolation pattern 14a, which is a design pattern of an element isolation structure, is formed on the silicon nitride film 13 by photolithography to obtain the state shown in FIG.
[0048]
Next, as shown in FIG. 6B, the silicon nitride film 13 and the first silicon oxide film 12 are etched by a dry etching method using the resist film 14 as a mask, and then the resist film 14 is subjected to ashing and cleaning. Then, a separation pattern 13 a is formed by transferring the separation pattern 14 a to the silicon nitride film 13 and the first silicon oxide film 12.
[0049]
Next, the semiconductor substrate 11 on which the separation pattern 13a is formed is put into a chamber of a dry etching apparatus, for example, an inductively coupled plasma etching apparatus, and the inside of the chamber is evacuated to a predetermined vacuum level. Thereafter, the source power is about 600 W, the bias power is about 200 W, the process pressure is about 1.3 Pa, and chlorine (Cl₂ ) Dry etching is performed under the condition of a gas flow rate of about 150 ml / min. Further, as a process gas, 0.3 ml or more of oxygen (O₂ ) Add gas. In the second embodiment, since an etching apparatus having a chamber volume of 26 l is used, for example, oxygen gas of about 8 ml / min is added.
By performing etching under these conditions, the groove portion 11a for forming an element isolation structure is formed in the semiconductor substrate 11 without forming a local groove at the lower side end. Thereafter, when cleaning is performed to remove deposits formed during dry etching of the semiconductor substrate 11, the result is as shown in FIG.
[0050]
Next, in order to reduce the surface level of the surface of the groove 11a, the trench sidewall of the groove 11a is oxidized by a thermal oxidation method. Thereafter, a second silicon oxide film for element isolation is deposited on the silicon nitride film 13 so as to fill the groove 11a by CVD.
Subsequently, the upper surface of the deposited second silicon oxide film is flattened by a CMP method or the like, and the silicon nitride film 13 and the first silicon oxide film 12 are removed by wet etching, so that FIG. As shown, an element isolation structure 15 made of a second silicon oxide film is formed.
[0051]
Hereinafter, in the second embodiment, although the process pressure is set to about 1.3 Pa and set to 4 Pa or less, the groove portion 11a is obtained by adding 0.3 ml or more of oxygen gas per 1 liter of volume to the process gas. The reason why etching can be performed without forming a local groove in the lower side edge of the substrate will be described.
[0052]
FIG. 7 shows the dependence of the emission intensity ratio between the chlorine atom having a light emission peak of 726 nm and the chlorine molecule of 256 nm and the depth of the local groove when the inductively coupled plasma etching apparatus is used. Here, the source power is about 600 W, the bias power is about 200 W, and the process pressure is about 1.3 Pa.
[0053]
As shown in FIG. 7, by adding oxygen gas to chlorine gas, even if the process pressure is 4 Pa or less, the emission intensity ratio can be maintained at 0.15 or less, thereby suppressing the formation of local grooves. can do. This is considered to be because dissociation of chlorine molecules into chlorine atoms is suppressed by oxygen.
[0054]
As described above, unlike the first embodiment, the second embodiment improves the degree of freedom of the process pressure.
[0055]
(Third embodiment)
Hereinafter, a method for manufacturing an element isolation structure in a semiconductor device according to the third embodiment of the present invention will be described with reference to the drawings.
[0056]
FIG. 8 shows an inductively coupled dry etching apparatus having a source power source of 13.56 MHz, which is a general frequency for etching a silicon substrate, and a parallel plate type dry etching apparatus having a source power source of 20 MHz whose frequency is higher than a normal value. The emission intensity ratio between a chlorine atom with a 726 nm and a chlorine molecule with a 256 nm emission peak and a local groove depth are shown in comparison with each other.
[0057]
Here, the source power is about 600 W, the bias power is about 200 W, the process pressure is about 1.3 Pa, and chlorine (Cl₂ ) The gas flow rate is about 150 ml / min.
[0058]
As can be seen from FIG. 8, when the source power source for generating high-density plasma is 20 MHz, which is higher than the normal value, the value of the emission intensity ratio is smaller than that of the normal source power source frequency of 13.56 MHz. It becomes about 0.15. Along with this, the depth of the local groove also decreases, and when the frequency is 20 MHz, the depth of the local groove is 1 nm or less, which is a depth that does not cause a problem.
[0059]
As described above, according to the third embodiment, in the etching of the silicon member, the formation of local grooves is suppressed by setting the power supply frequency for generating plasma to 20 MHz higher than the normal value, or more, for example, 100 MHz. Can do. This is presumably because the degree of dissociation of chlorine molecules into chlorine atoms decreases when the power supply frequency is high. Thereby, the process pressure or the composition ratio of the etching gas can be freely set.
[0060]
(Fourth embodiment)
Hereinafter, a fourth embodiment of the present invention will be described with reference to the drawings.
[0061]
FIG. 9 schematically shows an inductively coupled plasma etching apparatus which is a semiconductor device manufacturing apparatus according to the fourth embodiment of the present invention.
[0062]
As shown in FIG. 9, a dry etching apparatus 50 </ b> A according to the fourth embodiment includes a reaction chamber 51, an induction coil 53 provided above the reaction chamber 51 via a dielectric plate 52, and a reaction chamber 51. And a lower electrode 54 for holding a substrate 70 which is an object to be etched.
[0063]
The induction coil 53 has one end grounded and the other end connected to the source power supply 55.
The lower electrode 54 is connected to a bias power source 57 via a blocking capacitor 56.
[0064]
On the side wall of the reaction chamber 51, there are a gas introduction pipe 58 for introducing process gas and one end of an optical fiber 59 for observing (monitoring) the composition ratio of chlorine atom ions and chlorine molecule ions in the process gas. Is provided.
[0065]
The other end of the optical fiber 59 is connected to an emission analyzer 60 as an ion amount analyzing means, and the emission analyzer 60 is connected to a process parameter control device 61.
[0066]
Hereinafter, the operation of the dry etching apparatus 50A configured as described above will be described.
[0067]
First, the substrate 70 which is an etching target member made of, for example, silicon is held on the lower electrode 54. Next, a process gas, which is an etching gas, is introduced into the reaction chamber 51 through the gas introduction pipe 58, and the process gas is adjusted by the process parameter control device 61 so as to have a predetermined pressure and flow rate. Further, high frequency power is applied from the source power source 55 to the induction coil 53 to discharge chlorine plasma to the reaction chamber 51, and bias power is also applied to the bias power source 56 to start etching of the substrate 70. Here, for example, each process parameter is a process pressure of about 5 Pa, a source power of about 600 W, a bias power of about 200 W, and chlorine (Cl₂ ) The gas flow rate is about 150 ml / min, and oxygen (O₂ ) Etching the substrate 70 with a gas flow rate of about 5 ml / min.
[0068]
During etching, the emission light of chlorine plasma is taken into the spectroscopic analyzer 60 through the optical fiber 59, and a peak intensity value of one wavelength or more is extracted. An operation is performed based on the extracted peak intensity value. For example, in the fourth embodiment, a chlorine atom ion having a wavelength of 726 nm and a chlorine molecular ion having a wavelength of 256 nm are extracted, and the value of the emission intensity ratio (726 nm intensity / 256 nm intensity) is obtained.
[0069]
The calculation result is input from the emission analyzer 60 to the process parameter control device 61, and one or more process parameters are changed by the process parameter control device 61 so that the calculation result satisfies a predetermined condition.
[0070]
For example, the flow rate of oxygen is changed so that the calculation result of the emission intensity ratio becomes 0.10. As described in the second embodiment, since the value of the ratio of 726 nm intensity / 256 nm intensity decreases as the oxygen flow rate is increased, the calculation result is set to a predetermined value, that is, 0.10 by adjusting the oxygen flow rate. Can be maintained.
[0071]
As described above, according to the fourth embodiment, for example, when forming a groove in the substrate 70 made of silicon, it is possible to suppress local grooves generated at the lower side end of the groove due to process variation. The semiconductor device can be stably manufactured on the substrate 70.
[0072]
In the fourth embodiment, the emission spectroscopic method is used for monitoring the plasma generated from the etching gas. However, the present invention is not limited to this, and mass spectrometry, infrared absorption analysis, laser-induced fluorescence, etc. Similar effects can be obtained by using other methods.
[0073]
(Fifth embodiment)
Hereinafter, a fifth embodiment of the present invention will be described with reference to the drawings.
[0074]
FIG. 10 schematically shows an inductively coupled plasma etching apparatus which is a semiconductor device manufacturing apparatus according to the fifth embodiment of the present invention. 10, the description of the same components as shown in FIG. 9 is omitted by retaining the same reference numerals. As shown in FIG. 10, the dry etching apparatus 50B according to the fifth embodiment includes a chlorine atom separation magnet 62 as a mass analyzer and an ion separation means between a reaction chamber 51 and an induction coil 53. It is provided. A plasma generation chamber 63 is provided between the chlorine atom separation magnet 62 and the dielectric plate 52, and a gas introduction pipe 58 is provided in the plasma generation chamber 63.
[0075]
Since the dry etching apparatus 50B according to the fifth embodiment can separate chlorine atom ions from chlorine plasma, an ion amount analyzing means and a process parameter control apparatus are not required.
[0076]
Hereinafter, the operation of the dry etching apparatus 50B configured as described above will be described.
[0077]
First, the substrate 70 which is an etching target member made of, for example, silicon is held on the lower electrode 54. Next, a process gas which is an etching gas is introduced into the plasma generation chamber 63 through the gas introduction pipe 58, and the process gas is adjusted to have a predetermined pressure and flow rate. Further, high frequency power is applied from the source power supply 55 to the induction coil 53 to discharge chlorine plasma into the plasma generation chamber 63. Chlorine atom ions and chlorine molecule ions generated in the plasma generation chamber 63 are incident on a chlorine atom separation magnet 62. Since chlorine atom ions in the plasma are removed by the chlorine atom separation magnet 62, only chlorine molecular ions are introduced into the reaction chamber 51. Thereafter, the chlorine molecular ions accelerated by the electric field formed by the bias power source 57 are incident on the substrate 70, and etching proceeds.
[0078]
FIG. 11 shows the depth of the local groove depending on the presence or absence of the chlorine atom separation magnet 62. Here, as an example of the process parameters, the source power is about 600 W, the bias power is about 200 W, the process pressure is about 1.3 Pa, and chlorine (Cl₂ ) Etching is performed at a gas flow rate of about 150 ml / min. As shown in FIG. 11, in the fifth embodiment, since etching is performed in principle using plasma containing only chlorine molecular ions, no local grooves are generated.
[0079]
(Sixth embodiment)
Hereinafter, a sixth embodiment of the present invention will be described with reference to the drawings.
[0080]
FIG. 12A to FIG. 12D show cross-sectional structures in the order of steps of a method for manufacturing an element isolation structure in a semiconductor device according to a sixth embodiment of the present invention.
[0081]
First, a first silicon oxide film 12 is formed on the upper surface of a semiconductor substrate 11 made of silicon by a thermal oxidation method, and then a silicon nitride film 13 is formed on the first silicon oxide film 12 by using a CVD method or the like. Form. Subsequently, a resist film 14 having an isolation pattern 14a, which is a design pattern of the element isolation structure, is formed on the silicon nitride film 13 by photolithography to obtain the state shown in FIG.
[0082]
Next, as shown in FIG. 12B, the silicon nitride film 13 and the first silicon oxide film 12 are etched by a dry etching method using the resist film 14 as a mask, and then the resist film 14 is etched and washed. Then, a separation pattern 13 a is formed by transferring the separation pattern 14 a to the silicon nitride film 13 and the first silicon oxide film 12.
[0083]
Next, the semiconductor substrate 11 on which the separation pattern 13a is formed is put into a chamber of a dry etching apparatus, for example, an inductively coupled plasma etching apparatus, and the inside of the chamber is evacuated to a predetermined vacuum level.
[0084]
Thereafter, the source power is about 600 W, the bias power is about 200 W, the process pressure is about 1.3 Pa, and chlorine (Cl₂ ) Dry etching is performed under the condition of a gas flow rate of about 150 ml / min. At this time, the bias power applied to the lower electrode is intermittently applied with an appropriate period of 0.1 μs to 100 μs. For example, here, etching is performed by intermittently applying a bias power of 600 W at a period of 4.4 μs. By performing etching under these conditions, the groove portion 11a for forming an element isolation structure is formed in the semiconductor substrate 11 without forming a local groove at the lower side end. Thereafter, when cleaning is performed to remove deposits formed during dry etching of the semiconductor substrate 11, the state shown in FIG. 12C is obtained.
[0085]
Next, in order to reduce the surface level of the surface of the groove 11a, the trench sidewall of the groove 11a is oxidized by a thermal oxidation method. Thereafter, a second silicon oxide film for element isolation is deposited on the silicon nitride film 13 so as to fill the groove 11a by CVD.
Subsequently, the upper surface of the deposited second silicon oxide film is flattened by a CMP method or the like, and the silicon nitride film 13 and the first silicon oxide film 12 are removed by wet etching, so that FIG. As shown, an element isolation structure 15 made of a second silicon oxide film is formed.
[0086]
Hereinafter, in the sixth embodiment, by applying a bias power intermittently at an appropriate period of 0.1 μs to 100 μs, etching can be performed without forming a local groove at the lower side end of the groove. Explain why.
[0087]
FIG. 13 schematically shows the inside of the chamber when dry etching is performed by the semiconductor device manufacturing method according to the sixth embodiment.
[0088]
As shown in FIG. 13, when the source power is applied to the chlorine gas above the substrate 70 that is the object to be etched, a chlorine plasma 72 is generated, and the chlorine gas 72 is ionized in the generated chlorine plasma 72. The chlorine atom ions 72a and the chlorine molecule ions 72b thus formed are included. When bias power is applied by the bias power source 57, an electric field is generated in the plasma sheath 73 generated on the upper side of the substrate 70, and the chlorine atom ions 72a and the chlorine molecular ions 72b incident on the plasma sheath 73 are generated by the generated electric field. Etching proceeds by acquiring high kinetic energy and entering the substrate 70. As described above, the local groove is generated when the chlorine atom ions 72a having high energy enter the substrate 70.
[0089]
By the way, the chlorine molecular ion 72b has a mass twice that of the chlorine atom ion 72a. Therefore, when the bias power supply 57 is continuously applied, the time for which the chlorine molecular ions 72b pass through the plasma sheath 73 is about 1.41 times that of the chlorine atom ions 72a. Accordingly, by setting the application period of the bias power to be approximately the same as the time during which the chlorine atom ions 72a pass through the plasma sheath 73, the chlorine atom ions 72b hardly increase the chlorine atom ions 72a having high energy. Can be selectively accelerated.
[0090]
Hereinafter, the reason why the chlorine molecular ions 72b can be selectively accelerated by setting the application period of the bias power to the same level as the time during which the chlorine atom ions 72a pass through the plasma sheath 73 will be described in detail.
[0091]
14A shows a pulse waveform output from the bias power source 57, and FIG. 14B shows a chlorine atom (Cl) ion and a chlorine molecule (Cl₂ ) Shows the velocity of each ion when a pulse bias is applied to the ion, and FIG. 14C shows the distance traveled by each ion when a pulse bias is applied to the chlorine atom ion and the chlorine molecule ion. 14 (d) shows the ion energy of each ion when a pulse bias is applied to chlorine atom ions and chlorine molecule ions.
[0092]
In the sixth embodiment, the thickness of the plasma sheath 73 is 10 mm, the bias voltage is 495 V, the pulse period of the bias voltage is 4.0 μs, and the duty ratio is 0.5. Thus, the travel distance of chlorine atom ions is made to coincide with the thickness of the plasma sheath 73 in one cycle of the pulse.
[0093]
As shown in FIG. 14B, when the pulse bias is in the on state, that is, in the first half of the pulse, both the chlorine atom ions and the chlorine molecule ions are accelerated by the electric field, and the chlorine atom ions are more than the chlorine molecule ions. Because the mass is small, it is accelerated more and increases in speed.
[0094]
Further, as can be seen from FIG. 14 (c), after one cycle of the pulse bias, the travel distance of chlorine atom ions is 1.0 × 10.^-2Since it reaches m, that is, 10 mm, and reaches the substrate 70, the chlorine atom ions are not accelerated by the electric field due to the ON state in the second period of the bias pulse. On the other hand, since the chlorine molecular ions have not reached the substrate 70 yet because of their low velocity, they are accelerated again by the ON-state electric field in the second period of the bias pulse, and as a result, as shown in FIG. It is possible to obtain energy larger than that of chlorine atom ions.
[0095]
Next, FIGS. 15A to 15C show simulation results when the thickness of the plasma sheath 73 is 10 mm, the bias voltage is 500 V, and the duty ratio is 0.5. Here, FIG. 15A shows the ion velocities of chlorine atom ions and chlorine molecule ions with respect to the pulse period, and FIG. 15B shows the ion energies of chlorine atom ions and chlorine molecule ions with respect to the pulse period. FIG. 15C shows the ratio of the ion energy of chlorine molecular ions and chlorine atom ions to the pulse period.
[0096]
From FIG. 15C, it is most effective to set the pulse cycle of the bias power supply to the time for the chlorine atom ions to reach the end of the plasma sheath (substrate 70), that is, the time to reach the sheath end in one pulse. This simulation result shows that the ion energy of the chlorine molecular ion can be increased to about 1.8 times that of the chlorine atom ion. Moreover, the effect of selectively accelerating chlorine molecular ions cannot be obtained if the pulse period is too long or conversely too short.
[0097]
In the sixth embodiment, the thickness of the plasma sheath is 10 mm, and the sheath electric field is 400V. Since the optimum bias application period at this time is 4.4 μs, the etching can be performed so that no local groove is formed by setting the bias power application period to about 4.4 μs.
[0098]
(Seventh embodiment)
The seventh embodiment of the present invention will be described below with reference to the drawings.
[0099]
FIG. 16 schematically shows an inductively coupled plasma etching apparatus which is a semiconductor device manufacturing apparatus according to the seventh embodiment of the present invention. In FIG. 16, the same components as those shown in FIG.
[0100]
The dry etching apparatus 50C according to the seventh embodiment receives an ion energy analyzer 64 that analyzes the ion energy of the generated plasma and the analysis result from the ion energy analyzer 64, and converts the ion energy of chlorine molecular ions to chlorine. A pulse controller 65 that adjusts the amplitude, period, or duty ratio of the pulse so as to be higher than the ion energy of the atomic ions, and a pulse that controls the bias power supply 57 by receiving a control signal from the pulse controller 65 And a generator 66.
[0101]
The ion energy analyzer 64 is provided on the lower side of the reaction chamber 51. In the ion energy analyzer 64, ions converted into plasma have an opening at the side end portion of the lower electrode 54 in the reaction chamber 51. It is taken in through the sampling orifice 67.
[0102]
Hereinafter, the operation of the dry etching apparatus 50C configured as described above will be described.
[0103]
First, the substrate 70 which is an etching target member made of, for example, silicon is held on the lower electrode 54. Next, a process gas, which is an etching gas, is introduced into the reaction chamber 51 through the gas introduction pipe 58, and the process gas is adjusted to have a predetermined pressure and flow rate. Further, high frequency power is applied from the source power source 55 to the induction coil 53 to discharge chlorine plasma to the reaction chamber 51, and bias power is also applied to the bias power source 56 to start etching of the substrate 70. At this time, the ion energy of each of the chlorine atom ions and the chlorine molecule ions incident through the ion sampling orifice 67 is analyzed using the ion energy analyzer 64. In response to this analysis result, the pulse controller 65 reduces the number of chlorine atom ions having high energy, and the pulse amplitude and pulse so that the ion energy of chlorine molecular ions is higher than the ion energy of chlorine atom ions. And a control signal is output to the pulse generator 66.
[0104]
The pulse generator 66 generates a power pulse based on a control signal from the pulse controller 65, and intermittently applies power by operating the bias power source 57 with the generated power pulse.
[0105]
As described above, according to the seventh embodiment, even when the etching condition is changed and the thickness of the plasma sheath or the sheath electric field changes, the optimum intermittent bias power can be applied. Generation | occurrence | production can be suppressed reliably.
[0106]
【The invention's effect】
According to the method for manufacturing a semiconductor device according to the present invention, when a semiconductor member made of silicon is etched by irradiating plasma containing chlorine molecular ions, the plasma of chlorine plasma with respect to silicon is compared with the case of containing more chlorine atom ions. Since the reactivity is reduced, local etching that occurs at the lower portion of the side edge of the opening can be suppressed. In addition, a high etching selectivity with respect to the silicon nitride film can be obtained.
[Brief description of the drawings]
FIGS. 1A to 1D are cross-sectional structural views showing a manufacturing method of a semiconductor device according to a first embodiment of the present invention.
FIG. 2 shows each dependency of a selection ratio of a silicon nitride film to a process pressure and a depth of a local groove on a process pressure in the semiconductor device manufacturing method according to the first embodiment of the present invention.
FIG. 3 is a graph showing the spectral intensity of each plasma emission spectrum for each process pressure in the semiconductor device manufacturing method according to the first embodiment of the present invention.
FIG. 4 is a graph showing the dependence of the emission intensity ratio between a chlorine atom having a 726 nm emission peak and a chlorine molecule having a 256 nm emission peak on the process pressure in the semiconductor device manufacturing method according to the first embodiment of the present invention;
FIG. 5 is a schematic cross-sectional view illustrating a formation mechanism in which local grooves are formed in a silicon member.
FIGS. 6A to 6D are structural cross-sectional views in order of steps showing a method for manufacturing a semiconductor device according to a second embodiment of the present invention. FIGS.
FIG. 7 shows the dependence of the emission intensity ratio between the chlorine atom with 726 nm and the chlorine molecule with 256 nm emission peak on the oxygen flow rate and the depth of the local groove in the method for manufacturing a semiconductor device according to the second embodiment of the present invention. It is a graph which shows.
FIG. 8 shows an inductively coupled dry etching apparatus having a source power source having a frequency of 13.56 MHz and a parallel plate type having a source power source having a frequency of 20 MHz in the method for manufacturing a semiconductor device according to the third embodiment of the present invention. The emission peak when using a dry etching apparatus is a graph comparing the emission intensity ratio of chlorine atoms of 726 nm and chlorine molecules of 256 nm and the depth of local grooves.
FIG. 9 is a configuration diagram schematically showing a semiconductor device manufacturing apparatus according to a fourth embodiment of the present invention.
FIG. 10 is a configuration diagram schematically showing a semiconductor device manufacturing apparatus according to a fifth embodiment of the present invention.
FIGS. 11A and 11B are graphs showing local groove depths when a chlorine atom separation magnet is used and when not used in a semiconductor device manufacturing apparatus according to a fifth embodiment of the present invention; FIGS.
FIGS. 12A to 12D are structural cross-sectional views in order of steps showing a method for manufacturing a semiconductor device according to a sixth embodiment of the present invention. FIGS.
FIG. 13 is a schematic view showing a state of plasma in a chamber during dry etching for explaining a method for manufacturing a semiconductor device according to a sixth embodiment of the present invention.
FIGS. 14A to 14D show the principle of a semiconductor device manufacturing method according to a sixth embodiment of the present invention, and FIG. 14A is a waveform diagram of pulses output from a bias power source; b) is a graph showing each ion velocity when a pulse bias is applied to chlorine atom ions and chlorine molecule ions, and (c) is each ion when pulse bias is applied to chlorine atom ions and chlorine molecule ions. (D) is a graph showing ion energy of each ion when a pulse bias is applied to chlorine atom ions and chlorine molecule ions.
FIGS. 15A to 15C show simulation results of the semiconductor device manufacturing method according to the sixth embodiment of the present invention, and FIG. 15A shows each of chlorine atom ions and chlorine molecule ions with respect to the pulse period; It is a graph which shows ion velocity, (b) is a graph which shows each ion energy of the chlorine atom ion and chlorine molecular ion with respect to a pulse period, (c) is the ion of chlorine molecular ion and chlorine atom ion with respect to a pulse period. It is a graph which shows ratio with energy.
FIG. 16 is a configuration diagram schematically showing a semiconductor device manufacturing apparatus according to a seventh embodiment of the present invention;
17A to 17D are process cross-sectional views illustrating a method for manufacturing an element isolation structure in a conventional semiconductor device in order of processes.
[Explanation of symbols]
11 Semiconductor substrate
11a Groove
11b Local groove
12 First silicon oxide film
13 Silicon nitride film
13a separation pattern
14 Resist film
14a separation pattern
15 Device isolation structure
106 Chlorine ion
50A dry etching equipment
50B dry etching equipment
50C dry etching equipment
51 reaction chamber
52 Dielectric plate
53 Induction coil (plasma generating means)
54 Lower electrode
55 Source power supply (plasma generating means)
56 Blocking capacitor
57 Bias power supply
58 Gas introduction pipe
59 Optical fiber
60 Emission analyzer (ion content analysis means)
61 Process parameter control device (process parameter control means)
62 Chlorine atom separation magnet (ion separation means)
63 Plasma generation chamber
64 Ion energy analyzer (ion energy analyzer)
65 Pulse control device (pulse control means)
66 Pulse generator (pulse generation means)
70 substrates
72 Chlorine plasma
72a Chlorine atom ion
72b Chlorine molecular ion
73 Plasma sheath

Claims (12)

A first step of forming a mask pattern having an opening on a semiconductor member made of silicon;
Etching the semiconductor member on which the mask pattern is formed using high-density plasma containing chlorine ions, and
The chlorine ions include chlorine molecular ions and chlorine atom ions,
In the high-density plasma, the chlorine molecular ions are included at a higher ratio than the chlorine atom ions, and the ratio of the emission intensity of the chlorine atom ions to the emission intensity of the chlorine molecule ions is 0.15 or less. A method for manufacturing a semiconductor device.   2. The method of manufacturing a semiconductor device according to claim 1, wherein in the second step, the high-density plasma is generated in an atmosphere having a pressure of 4 Pa or more.   2. The method of manufacturing a semiconductor device according to claim 1, wherein in the second step, the high-density plasma is generated by adding 0.3 ml or more of oxygen per 1 liter in a standard state.   2. The method of manufacturing a semiconductor device according to claim 1, wherein in the second step, the high-density plasma is generated using a plasma generation power source having a frequency of 20 MHz or more.   The method of manufacturing a semiconductor device according to claim 1, wherein in the second step, the semiconductor member is selectively accelerated and irradiated with the chlorine molecular ions.   The method of manufacturing a semiconductor device according to claim 5, wherein the chlorine molecular ions are selectively accelerated by intermittently applying a bias power having a period of 0.1 μs to 100 μs.   The method of manufacturing a semiconductor device according to claim 6, wherein the period of intermittently applying the bias power is about the time during which chlorine atom ions can pass through the plasma sheath.   The method for manufacturing a semiconductor device according to claim 1, wherein the mask pattern is made of a silicon nitride film. A reaction chamber containing a member to be etched made of silicon;
A plasma generating means that is provided in the reaction chamber and generates plasma containing chlorine molecular ions and chlorine atom ions to be irradiated to the member to be etched;
An ion amount analyzing means for analyzing the amount of generated chlorine molecular ions and the amount of chlorine atom ions;
A process parameter control means for adjusting a process parameter based on an analysis result of the ion content analysis means,
The plasma generating means generates more chlorine molecule ions than chlorine atom ions,
The ion content analyzing means is a plasma emission spectroscopic analyzer,
It said process parameter control means, while etching the etching object member, a semiconductor device characterized by maintaining the ratio of the emission intensity of the chlorine atom ions to the emission intensity of the molecular chlorine ions 0.15 Manufacturing equipment. A reaction chamber containing a member to be etched made of silicon;
Plasma generating means for generating plasma containing chlorine atom ions and chlorine molecule ions;
Ion separation means for separating the chlorine molecular ions from the generated plasma;
An ion introduction means for selectively introducing the separated chlorine molecule ions into the reaction chamber,
In the reaction chamber, the member to be etched is etched by using the separated chlorine molecular ions. A reaction chamber containing a member to be etched made of silicon;
A plasma generating means that is provided in the reaction chamber and generates plasma containing chlorine molecular ions and chlorine atom ions to be irradiated to the member to be etched;
An ion energy analyzing means for analyzing the ion energy of the generated chlorine molecular ions and the ion energy of the chlorine atom ions;
Based on the analysis result of the ion energy analyzing means, while etching the member to be etched, the pulse amplitude, period or so that the ion energy of the chlorine molecular ions is higher than the ion energy of the chlorine atom ions. Pulse control means for adjusting the duty ratio;
An apparatus for manufacturing a semiconductor device, comprising: a pulse generation unit that receives a control signal from the pulse control unit and controls a bias power source of the plasma generation unit.   The semiconductor device manufacturing apparatus according to claim 9, wherein the etching target member made of silicon is a semiconductor substrate.

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