JP2005229028A - Method of manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing semiconductor devices capable of sufficiently planarizing an insulating film of the semiconductor devices at a temperature of ≤800°C by high-pressure water vapor without increasing process steps as compared to the existing process steps, and capable of reducing the time for removing the moisture in the insulating film after the high-pressure water-vapor treatment. <P>SOLUTION: The method of manufacturing semiconductor devices includes a film-forming step for forming an insulating film on a semiconductor substrate; a reflow step (S2) for planarizing the insulating film by heat-treating the semiconductor substrate in an atmosphere containing water vapor at a pressure of 1 MPa or higher; and after the reflow step; and a moisture removal step (S4) for removing the moisture in the insulating film, by heat-treating the semiconductor substrate in an inert gas atmosphere at a pressure lower than the atmospheric pressure of the reflow step. In the moisture removal step, the heat treatment temperature is preferably ≥400°C, and the atmospheric pressure is preferably the ambient pressure or a negative pressure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a semiconductor device having an insulating film such as a BPSG film on a semiconductor substrate (wafer). More specifically, the present invention relates to a method for manufacturing a semiconductor device that can planarize the insulating film at a low temperature and in a short time and can effectively remove moisture in the insulating film in a short time.

  As miniaturization associated with high integration progresses in a semiconductor device, the aspect ratio of the structure (ratio of the dimension in the depth direction to the lateral dimension of the structure) increases, and the step of the structure tends to increase in the manufacturing process. For example, in the manufacturing process of a semiconductor device, a gate electrode of a MOSFET is formed so as to protrude on a semiconductor substrate, so that a recess is formed between adjacent gate electrodes, and there are unevenness and level difference between the gate electrode and the gate electrode. it can. When this level difference becomes large, defocusing occurs when drawing a wiring pattern due to exposure, or when the wiring is crossed, the lap part of the crossing portion becomes thin and causes disconnection. Problems that lead to defects occur. As a method of eliminating such a step, a flattening step is required in which an interlayer insulating film such as a BPSG film or a PSG film is formed on the step and then the insulating film is flattened (flattened) by some method. .

  Conventionally, planarization of an insulating film of a semiconductor device is performed by heat-treating the semiconductor device on which the insulating film has been formed at a temperature of 900 ° C. in an inert gas atmosphere at normal pressure (0.1 MPa) or at normal pressure. The insulating film has been fluidized by heat treatment at a temperature slightly lower than 900 ° C. in an oxygen or water vapor atmosphere, and planarization has been performed by the planarization effect by flow. The following Patent Documents 1 and 2 are disclosed as prior art relating to planarization of such an insulating film.

  Patent Document 1 “Method for planarizing insulating film of semiconductor device” aims at effectively reflowing the BPSG film of the semiconductor device at a relatively low temperature in a short time, on the uneven surface on the substrate of the semiconductor device. In the method of planarizing the formed insulating film by heat flow, the heat flow is performed under a pressure of 3 atm or more in an atmosphere containing oxygen or water vapor. By this method, the amount of oxygen diffused in the insulating film and the diffusion rate thereof are increased, and a good reflow of the BPSG film is realized at a lower temperature and in a shorter time than in the past.

  The “method for manufacturing a semiconductor device” in Patent Document 2 aims to obtain sufficient flatness by low-temperature processing, and forms an element on a semiconductor substrate, forms a silicon nitride film on the element, and forms an element on the element. A BPSG film containing boron and phosphorus is formed, and an SOG film containing at least one of boron and phosphorus is formed thereon by a coating method. Then, the substrate is heat-treated in a high-pressure atmosphere containing water vapor. As a result, the SOG film is gelled, and pressure is applied to the film itself by a high pressure from the outside to flatten the film.

JP-A-5-67607 JP-A-10-275805

  However, in the above-described “planarization method of insulating film of semiconductor device” in Patent Document 1, heat treatment can be performed at 800 ° C. lower than the conventional planarization temperature, but the element characteristics at the miniaturization level have an adverse effect. It is a temperature, and further reduction in the planarization temperature is desired.

  Further, in the “semiconductor device manufacturing method” of Patent Document 2, although the planarization temperature can be set to 700 ° C. or less, the number of steps for forming an oxide film by a coating method is increased and complicated. In addition, if moisture remains in the insulating film while performing the steam treatment, it may adversely affect the stability and life of the device, so that sufficient moisture removal is required. In the SOG curing process, nitrogen gas or the like remains in a high pressure atmosphere. Since the treatment is performed in an inert atmosphere, there is a problem in that moisture is hardly diffused in the insulating film and the treatment time is increased.

  The present invention has been made to solve the above-described problems. That is, an object of the present invention is to sufficiently planarize an insulating film of a semiconductor device at a temperature of 800 ° C. or lower with high-pressure steam without increasing the number of processes as compared with the conventional process, and to perform insulation after high-pressure steam treatment. An object of the present invention is to provide a method of manufacturing a semiconductor device that can shorten the time for removing moisture in the film.

  In order to achieve the above object, the present invention provides a method of manufacturing a semiconductor device having an insulating film on a semiconductor substrate, the film forming step for forming the insulating film on the semiconductor substrate, and the semiconductor substrate with water vapor. A reflow step of flattening the insulating film by heat treatment in an atmosphere of 1 MPa or higher, and after the reflow step, the insulating film is heat-treated in an inert gas atmosphere having a pressure lower than the atmospheric pressure of the reflow step. And a moisture removal step of removing moisture in the inside (claim 1).

According to the present invention, the heat treatment is performed in a high-pressure steam atmosphere of 1 MPa or higher that can maintain the moisture concentration in the atmosphere at a high level, so that the water vapor diffuses into the insulating film and the moisture concentration in the insulating film increases. The decrease in the viscosity of the insulating film is due to the (—Si—O—Si—) network structure in the insulating film being cut by water molecules H ₂ O. According to the present invention, Since the moisture concentration is increased, cutting of the network structure can be promoted, and the viscosity of the insulating film can be reduced as compared with the conventional method. Therefore, the processing time for obtaining the same flatness as the conventional one can be shortened. In addition, when processing is performed for the same processing time as in the prior art, the processing temperature for obtaining the same viscosity can be lowered, so that the processing temperature can be lowered (eg, 700 ° C.). In addition, voids (bubbles) in the insulating film can be eliminated by lowering the clay of the insulating film.
In addition, by performing a planarization treatment in a high-pressure steam atmosphere and then performing a heat treatment in a low-pressure inert gas atmosphere, the water vapor partial pressure is lowered in a low-pressure atmosphere, so that moisture in the insulating film is shortened. It can be effectively removed in time. Therefore, moisture does not remain in the processed insulating film, and deterioration due to moisture diffusion into the semiconductor device can be prevented.

  In the present invention, it is preferable that an insulating film is formed by a chemical vapor deposition method or a coating method in the film forming step.

  Moreover, in the said invention, it is preferable that the heat processing temperature in the said water removal process is 400 degreeC or more (Claim 3).

  Moreover, in the said invention, it is preferable that the atmospheric pressure in the said water removal process is atmospheric pressure or a negative pressure (Claim 4).

  Further, the present invention preferably includes a step of forming a barrier layer made of silicon nitride between the object to be insulated and the insulating film.

  In the present invention, the insulating film is preferably composed of a silicon oxide film, and the silicon oxide film preferably contains at least one of phosphorus, arsenic, boron, and halide. .

  In the present invention, the insulating film is preferably an interlayer insulating film.

  As described above, according to the present invention, the insulating film of the semiconductor device can be sufficiently flattened at a temperature of 800 ° C. or lower with high-pressure steam without increasing the number of processes, and the high-pressure steam. It is possible to obtain excellent effects such as shortening the time for removing moisture in the insulating film after processing.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In each figure, the same portions are denoted by the same reference numerals, and redundant description is omitted.

  In the method for manufacturing a semiconductor device of the present invention, for example, a high-pressure steam annealing apparatus as shown in FIG. 1 is used. The high-pressure steam annealing apparatus 10 is an apparatus that can perform heat treatment in a high-pressure steam atmosphere, and includes a wafer loading boat 12, a processing vessel 13, a heater 14, a pressure vessel 15, a pure water boiler 16, and a pure water supply line. 17, a water vapor line 18, an inert gas supply line 19, a processing vessel exhaust line 20, and a pressure vessel supply / exhaust line 21.

  The wafer loading boat 12 can mount a large number (for example, about 100 to 150) of semiconductor devices (processed wafers) 11 side by side. The processing vessel 13 is made of quartz glass having an empty cross section and a dome shape at the top, and can accommodate the wafer loading boat 12 therein. The heater 14 has a cylindrical shape and is provided in a plurality of stages in the vertical direction so as to surround the outside of the processing container 13, thereby heating the semiconductor device 11.

  The pure water boiler 16 is a device that evaporates pure water supplied from the pure water supply line 17 to generate water vapor, and the generated water vapor is introduced into the processing vessel 13 through the water vapor line 18. An inert gas supply line 19 is connected to the processing container 13 so that an inert gas such as nitrogen gas can be introduced into the processing container 13. The water vapor or the inert gas introduced into the processing container 13 is discharged from the processing container exhaust line 20. Thereby, the inside of the processing container 13 is configured to be able to replace the water vapor atmosphere and the inert gas atmosphere.

  In addition, a pressure vessel supply / exhaust line 21 is connected to the pressure vessel 15, and gas (air or the like) is supplied into the pressure vessel 15 or discharged from the pressure vessel 15. The pressure is adjusted.

  Next, the semiconductor device manufacturing method of the present invention will be specifically described. The manufacturing method according to the present invention includes a film forming step for forming an insulating film on a semiconductor substrate, a flattening step for flattening the insulating film, and a water removing step for removing water in the insulating film. Hereinafter, each step will be described.

  First, the film forming process will be described. 2A and 2B show a cross-sectional shape of the semiconductor device according to the embodiment of the present invention. As shown in FIG. 2, an unevenness (trench) 1 made of a wiring structure 7 such as a gate insulating film and a gate electrode formed on a semiconductor substrate 11 is formed on an interlayer by chemical vapor deposition (CVD) or coating. A film forming process for forming the insulating film 2 is performed. The insulating film 2 is, for example, a silicon oxide film, and is a BPSG film, a PSG film, or the like containing at least one of phosphorus, arsenic, boron, halide, and the like. At this time, irregularities are formed on the insulating film 2 as shown in FIG. Further, as shown in FIG. 2B, voids (bubbles) 3 may be generated in the insulating film 2.

  Further, as shown in FIG. 3, a silicon nitride film 4 is preferably formed between the insulating film 2 and an object to be insulated such as the wiring structure 7 by CVD or the like. The silicon nitride film 4 functions as a protective film (barrier layer) for preventing moisture due to processing in a later process from entering the device.

  Next, a planarization process and a water | moisture-content removal process are demonstrated with reference to FIG. 4A and 4B show a temperature profile (a) and a pressure profile (b) in each step. 4A and 4B, the horizontal axis indicates time, and the vertical axis indicates processing temperature (° C.) and processing pressure (MPa), respectively.

  First, the inside of the processing vessel 13 of the high-pressure steam annealing apparatus 10 shown in FIG. Next, a flattening step for flattening the insulating film 2 is started (S2). In the planarization step, the necessary processing time (about 1 hour) is maintained. As a result, the viscosity of the insulating film 2 is reduced by the diffusion of moisture into the insulating film 2 and the heat treatment, and the unevenness on the insulating film 2 is relaxed or flattened (see FIG. 5) and is present in the insulating film. The void 3 disappears (see FIG. 6).

Here, the correlation between the viscosity of silica glass and the moisture content will be described. FIG. 7 is a correlation graph between the viscosity of silica glass and the moisture content, with the horizontal axis representing the reciprocal of absolute temperature (10 ⁴ / T [K]) and the vertical axis representing the viscosity of silica glass (Log η [Poise]). Have taken. In the figure, the marks “▲”, “×”, “●”, and “◯” indicate the water (H ₂ O) concentration in the silica glass, respectively, and “▲” indicates 0.0003 wt%, “ “X” indicates 0.027 wt%, “●” indicates 0.04 wt%, and “◯” indicates 0.12 wt%. As can be seen from the figure, the viscosity of the glass tends to decrease as the moisture concentration increases and the temperature increases. This is because the network structure of (—Si—O—Si—) in silica glass is cut by water molecules (H ₂ O). That is, by increasing the moisture concentration in the insulating film, cutting of the network structure can be promoted, and the viscosity of the insulating film can be reduced.

On the other hand, when heating is performed in a water vapor atmosphere maintained at atmospheric pressure, the water vapor concentration in the atmosphere decreases due to the ideal gas law (Boicharle's law), and sufficient water introduction into the glass cannot be expected. (From the water concentration ∝PV / RT, when the temperature T is increased, the water concentration decreases). FIG. 8 shows the water molecule concentration distribution when a 1 μm thick SiO ₂ film is treated at a temperature of 700 ° C. for 1 hour in a water vapor atmosphere. The horizontal axis indicates the depth (μm) from the surface of the insulating film. The vertical axis represents the concentration of water molecules (pieces / cm ³ ) in the insulating film. In the figure, “▲”, “×”, “●”, “△”, “■” marks indicate treatment conditions, respectively, “▲” indicates 700 ° C./2.0 MPa, and “×” indicates 700 ° C. and 1.0 MPa, “●” indicates 700 ° C. and 0.5 MPa, “Δ” indicates 700 ° C. and 0.3 MPa, and “■” indicates 700 ° C. and 0.1 MPa. As shown in the figure, the water concentration at a depth of 1 μm is 7.33 × 10 ¹⁸ pieces / cm ³ in the steam treatment at atmospheric pressure (0.1 MPa), whereas the water vapor at 2.0 MPa. Since the treatment is 1.47 × 10 ²⁰ pieces / cm ³ , when comparing the atmospheric pressure (0.1 MPa) water vapor treatment with the 2.0 MPa water vapor treatment, 2.0 MPa is about 20 times moisture content. The result is a higher concentration.

  Therefore, in the planarization step (S2) of the insulating film in FIG. 4, as a method for introducing more moisture into the insulating film 2, the semiconductor substrate 11 is heat-treated in an atmosphere of 1 MPa or more containing water vapor, and the moisture in the atmosphere A method was adopted in which the concentration was high and more moisture was introduced into the insulating film 2. As a result, the viscosity of the insulating film 2 can be reduced as compared with the conventional method by increasing the moisture concentration in the insulating film 2 due to the pressurized steam and heating, and the processing time for obtaining the same flatness as the conventional method. Can be shortened. In addition, when processing is performed for the same processing time as in the prior art, the processing temperature for obtaining the same viscosity can be set to 700 ° C. or lower, so that the processing temperature can be lowered. Further, it is possible to perform flattening without using recoating or the like as in the prior art described above. Further, as described above, the void 3 in the insulation can be eliminated by the decrease in the viscosity of the insulating film 2.

  When moisture remains in the insulating film 2 after the planarization process (S2), moisture diffuses into the semiconductor device 11 over time, and the semiconductor device 11 deteriorates, so that stability becomes a problem. For this reason, it is necessary to prevent moisture from remaining in the processed insulating film 2.

FIG. 9 shows the water in the insulating film when a 1 μm thick SiO ₂ film is heat treated in a 2.0 MPa water vapor atmosphere at a temperature of 700 ° C. for 1 hour and then heat treated in an inert gas atmosphere of 0.1 MPa for 1 hour. It shows molecular concentration distribution. In the figure, the horizontal axis represents the depth (μm) from the surface of the insulating film, and the vertical axis represents the concentration of water molecules (pieces / cm ³ ) in the insulating film. In the figure, the marks “◯”, “●”, “×”, “□”, “■”, “▲” indicate processing conditions, respectively, “○” indicates 200 ° C./0.1 MPa, “●” is 350 ° C./0.1 MPa, “×” is 400 ° C./0.1 MPa, “□” is 450 ° C./0.1 MPa, “■” is 500 ° C./0.1 MPa, “▲” is 700 ° C. -0.1 MPa is shown. As shown in the figure, the moisture concentration at a depth of 1 μm is 7.33 × 10 ¹⁸ pieces / cm ³ in the heat treatment at 700 ° C., whereas it is 1.09 × 10 ^{20 in} the heat treatment at 350 ° C. because it is pieces / cm ^3, when comparing the 700 ° C. and 350 ° C., if better heat treatment of 700 ° C. and treated with about 1/15, and the lower atmospheric pressure than the heat treatment at 350 ° C., in the film The result was that the moisture concentration was lower. This shows that there is a tendency that the moisture removal rate tends to be higher when the processing atmosphere pressure and the water vapor partial pressure are lower and the processing temperature is higher.

  Therefore, in order to use the tendency that the moisture removal rate is higher when the processing atmosphere pressure and the water vapor partial pressure are lower and the processing temperature is higher, the processing temperature is maintained after the flattening processing (S2) as shown in FIG. While reducing the atmospheric pressure to a predetermined pressure (0.1 MPa), the processing atmosphere is replaced with an inert gas (S3), and a moisture removing step (S4) for removing moisture in the insulating film 2 is performed. As the inert gas, nitrogen gas, argon gas, helium gas or the like is used. At this time, it is preferable that the atmospheric pressure is lower. Accordingly, in this embodiment, the inert gas atmosphere pressure is atmospheric pressure (0.1 MPa), but may be negative pressure (less than 0.1 MPa). In this embodiment, the temperature of the treatment atmosphere in the moisture removal step (S4) is 700 ° C. However, according to FIG. 9, it can be seen that a sufficient moisture removal effect can be obtained at 400 ° C. or higher. The temperature is preferably 400 ° C. or higher.

  By this moisture removal step (S4), moisture in the insulating film 2 after the planarization treatment can be effectively removed in a short time, and deterioration due to diffusion of moisture into the semiconductor device 11 can be prevented. .

  After the moisture removing step (S4), the processing temperature is lowered and the atmospheric pressure is reduced, and the processing ends (S5). After the treatment, an etch bag by a dry etching method or the like may be performed to appropriately adjust the film pressure of the insulating film on the element.

As described above, according to the present invention, the following effects can be obtained.
(1) Since the heat treatment is performed in a high-pressure steam atmosphere of 1 MPa or more that can maintain the moisture concentration in the atmosphere at a high level, the moisture concentration in the insulating film increases due to the diffusion of water vapor into the insulating film, and the viscosity of the insulating film Can be reduced as compared with the conventional method. Therefore, the processing time for obtaining the same flatness as the conventional one can be shortened. In addition, when processing is performed at a processing time comparable to that of the prior art, the processing temperature for obtaining the same viscosity can be lowered, so that the processing temperature can be lowered to 800 ° C. or lower (eg, 700 ° C.). In addition, voids (bubbles) in the insulating film can be eliminated by lowering the viscosity of the insulating film.
(2) Heat treatment at a high temperature (400 ° C. or higher) in an inert gas atmosphere at a low pressure (atmospheric pressure or negative pressure) reduces the water vapor partial pressure in a low-pressure atmosphere, so moisture in the insulating film Can be effectively removed in a short time. Therefore, no moisture remains in the insulating film after the planarization treatment, and deterioration due to diffusion of moisture into the semiconductor device can be prevented.

  In addition, this invention is not limited to embodiment mentioned above, Of course, a various change can be added in the range which does not deviate from the summary of this invention.

It is a schematic block diagram of the high pressure steam annealing apparatus used for implementation of this invention. It is sectional drawing which shows the structure of the semiconductor device in embodiment of this invention. It is sectional drawing which shows another structure of the semiconductor device in embodiment of this invention. (A) is a figure which shows the temperature profile in each process of this invention, (b) is a figure which shows the pressure profile of each process. It is a figure which shows the planarization of the unevenness | corrugation (trench) by this invention, (a) is before a process, (b) is after a process. It is a figure which shows disappearance of the void (bubble) by this invention, (a) is before a process, (b) is after a process. It is a figure which shows the correlation of the viscosity of a silica glass, and a containing water | moisture content. It is a figure which shows water molecule concentration distribution in the insulating film during water vapor | steam pressurization. It is a figure which shows the water molecule concentration distribution in the insulating film at the time of moisture removal.

Explanation of symbols

1 Unevenness (trench)
2 Insulating film 3 Void 4 Silicon nitride film 7 Wiring structure 10 High-pressure steam annealing device 11 Semiconductor device 12 Wafer mounting boat 13 Processing vessel 14 Heater 15 Pressure vessel 16 Pure water boiler 17 Pure water supply line 18 Water vapor line 19 Inert gas Supply line 20 Processing vessel exhaust line 21 Pressure vessel supply / exhaust line

Claims (7)

A method of manufacturing a semiconductor device having an insulating film on a semiconductor substrate,
A film forming step of forming an insulating film on the semiconductor substrate;
A planarization step of planarizing the insulating film by heat-treating the semiconductor substrate in an atmosphere of 1 MPa or more containing water vapor;
And a moisture removal step of removing moisture in the insulating film by performing heat treatment in an inert gas atmosphere at a pressure lower than the atmospheric pressure of the planarization step after the planarization step. Manufacturing method.   2. The method of manufacturing a semiconductor device according to claim 1, wherein in the film forming step, an insulating film is formed by a chemical vapor deposition method or a coating method.   The method for manufacturing a semiconductor device according to claim 1, wherein a heat treatment temperature in the moisture removing step is 400 ° C. or higher.   4. The method of manufacturing a semiconductor device according to claim 1, wherein the atmospheric pressure in the moisture removing step is atmospheric pressure or negative pressure.   5. The method of manufacturing a semiconductor device according to claim 1, further comprising a step of forming a silicon nitride film between an object to be insulated and the insulating film.   6. The insulating film according to claim 1, wherein the insulating film is made of a silicon oxide film, and the silicon oxide film contains at least one of phosphorus, arsenic, boron, and halide. Semiconductor device manufacturing method. The method for manufacturing a semiconductor device according to claim 1, wherein the insulating film is an interlayer insulating film.

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