KR100269279B1 - Method for manufacturing semiconductor devices - Google Patents

Abstract

PURPOSE: A method for fabricating a semiconductor device is provided to improve the yield and the quality of the semiconductor product by forming a stable thin film without defect by suppressing an abnormal chemical reaction generated in a step of loading a semiconductor wafer. CONSTITUTION: A low pressure chemical vapor deposition method includes a standby step of initializing a reaction condition to form a thin film on a semiconductor wafer(23), and a loading step of loading the semiconductor wafer. And, a pumping and fuzzy step reduces a pressure in a reaction chamber(22) and removes the impurities in the reaction chamber. A deposition step performs a deposition for forming the thin film. The method also includes the first circular fuzzy step to increase the pressure in the reaction chamber and an unloading step of unloading the semiconductor wafer, and the second circular fuzzy step to form the thin film. The internal temperature in the reaction chamber in the fuzzy step and the deposition step and the first circular fuzzy step is set higher than in the other steps.

Description

Semiconductor device manufacturing method

1 is a schematic configuration diagram of a low pressure chemical vapor deposition apparatus.

2 is a schematic step-by-step temperature setting profile (PROFILE) graph of a conventional low pressure chemical vapor deposition process.

3 is a scanning electron microscope (SCANNING ELECTRON MICROSCOPE) photograph of hemispherical surface protruding defect (DEFECT).

4 is a schematic step-by-step temperature setting profile graph in a low pressure chemical vapor deposition process according to the present invention.

BACKGROUND OF THE INVENTION 1. Field 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 for preventing a film quality defect generated in a low pressure chemical vapor deposition process.

Chemical vapor deposition (CVD), which is used in semiconductor device manufacturing processes, decomposes a gaseous compound and then forms a thin film (THIN FILM) or an epilayer (EPITAXIAL LAYER) on a semiconductor substrate by chemical reaction. To form. Chemical vapor deposition is distinguished from other semiconductor fabrication processes because the process of forming a thin film is mainly performed by introducing a gas from outside into a reaction chamber without using a material on a silicon wafer.

Useful chemical vapor deposition occurs over a wide temperature range (approximately 100 ° C to 1200 ° C), and heat, plasma energy from RADIO FREQUENCY power, or light energy from lasers or ultraviolet light are used to decompose incoming gas. In addition, the reaction of atoms or molecules decomposed by heating of the semiconductor substrate may be promoted or the physical properties of the formed thin film may be controlled.

Chemical vapor deposition is sometimes referred to as ATMOSPHERIC PRESSURE CVD and LOW PRESSURE CVD depending on the degree of vacuum in the reaction chamber during the process.

Chemical vapor deposition technology has been rapidly applied in the semiconductor industry for several advantages, such as:

First, various thicknesses and resistances of EPITAXIAL LAYER can be obtained. Second, thin films can be produced at low cost when making polysilicon, silicon nitride, and silicon oxide films. Third, a thin film of a silicon oxide film or a silicon nitride film used as a layer for protecting a silicon device can be made even at a relatively low temperature.

The physicochemical properties of the thin film obtained by chemical vapor deposition are determined by the substrate (amorphous, polycrystalline, crystal) on which the deposition takes place and the deposition conditions (temperature, growth rate, pressure, etc.). In general, these variables affect the structure or properties of the film by affecting the rate of surface movement of the deposited atoms.

In such chemical vapor deposition, the atmospheric pressure chemical vapor deposition has a small capacity of the semiconductor wafer, requires a large amount of carrier gas since the semiconductor wafer is placed in parallel on the susceptor, and a high frequency (RADIO). FREQUENCY) There is a problem that the maintenance cost is high because of the high cost of the generator.

Therefore, low pressure chemical vapor deposition was developed to solve this problem, which increases the semiconductor wafer capacity by placing the semiconductor wafer vertically, the amount of gas used is also greatly reduced, and induced by high frequency power. The heating turns into simple resistive heating, which has the advantage that the system is inexpensive.

A schematic diagram of a low pressure chemical vapor deposition apparatus having such an advantage is shown in FIG.

Referring to FIG. 1, a low pressure chemical vapor deposition apparatus includes a three-zone HEATING FURNACE 21, a reaction chamber 22 disposed in the resistance furnace 21, and the reaction. The semiconductor wafer 23 is vertically densely positioned in the chamber 22, and is opened and closed to load and unload the semiconductor wafer 23 into the reaction chamber 22 and in the reaction chamber 22. End cap (END CAP) 24, a vacuum seal mounted at the end to allow low pressure, and a vacuum pump 25 for exhausting the reaction product and unused gases to the outside of the device.

And the supply tanks 26 of various reaction gases (SOURCE GAS), and a gas control system (GAS CONTROL SYSTEM) 27 for controlling the flow of the reaction gas from the supply tank 26 is provided.

A conventional low pressure chemical vapor deposition process using a low pressure chemical vapor deposition apparatus having such a configuration is performed as follows, and FIG. 2 shows a schematic step-by-step temperature setting profile (PROFILE) graph in the conventional low pressure chemical vapor deposition process. It is.

1. As STAND-BY step 1, the basic conditions for the initialization and stabilization of the low pressure chemical vapor deposition apparatus are set before loading the semiconductor wafer SILICON WAFER 23 into the reaction chamber 22.

2. In the loading step (2), the end cap 24 is opened to load the processed semiconductor wafer 23 into the reaction chamber 22, and the end cap 24 is closed to seal the reaction chamber 22.

3. Pumping step (3), the internal pressure is reduced by the pumping action inside the sealed reaction chamber (22).

4. As a nitrogen purge (N ₂ PURGE) step (4), a step of injecting nitrogen gas into the pressure-reduced inside of the reaction chamber 22 to remove impurities therefrom, which is introduced when the semiconductor wafer 23 is loaded. Oxygen (O ₂ ), water (H ₂ O) and other contaminants in the work environment are removed.

5. DEPOSITION In step (5), SiH ₂ Cl ₂ (DICHLORO SILANE) and NH ₃ (AMMONIA), which are purified reaction gases, are injected to form a silicon nitride film by chemical reaction thereof, or SiH ₄ (SILANE). ) And a polysilicon film is formed on the semiconductor wafer 23 by a chemical reaction by thermal decomposition thereof (Si + 2H ₂ ). At this time, the chemical reaction is performed under a low pressure state, which increases the average free path of the reaction gas to improve the uniformity of the thin film on the semiconductor wafer, and also the chemical reaction is heated. Induces a heterogeneous reaction that occurs on the surface of the semiconductor wafer and then migrates to the semiconductor wafer surface at a stable position (ie, low energy level), resulting in an even film surface resulting in a good film quality. It is to.

6. As a first cycle purge step 6, nitrogen gas is injected into the reaction chamber 22 where desired thin film deposition is completed, and the pressure inside the reaction chamber 22 is elevated to atmospheric pressure.

7. As unloading step 7, the end cap 24 is opened to unload the semiconductor wafer 23 to complete the low pressure chemical vapor deposition process.

8. In the second circulation purge step 8, after unloading the semiconductor wafer 23, unnecessary gases and products remaining in the reaction chamber 22 are cleaned using nitrogen gas.

However, referring to the step-by-step temperature setting profile graph in the conventional low pressure chemical vapor deposition process of FIG. 2, the temperature in the reaction chamber is constant from the standby step, which is the start of the process, to the unloading step, where the deposition temperature is set. Is maintained. That is, in the case of silicon nitride film deposition, the temperature in the reaction chamber is set from 650 to 900 ° C., and in the case of poly silicon film deposition, 610 to 640 ° C. from the standby stage.

As such, the semiconductor wafer is loaded while the inside of the reaction chamber is maintained at a high temperature, which is a deposition temperature, from the atmospheric stage, thereby introducing oxygen, moisture, and other contaminants in the working environment into the reaction chamber.

Oxygen, moisture, and other contaminants in the working environment introduced into the reaction chamber immediately cause their own homogeneous reactions in the reaction chamber under high temperature and atmospheric pressure to cause abnormal reactions on the semiconductor wafer. Causing problems. 3 shows a scanning electron microscope (SCANNING ELECTRON MICROSCOPE) photograph of the hemispherical surface protruding defect (DEFECT) generated in polysilicon film deposition as an example of the abnormal reactant.

The abnormal reactants thus formed act as seeds and cause gradual defects in subsequent processes, resulting in short circuits and disconnection of wires or blockages when impurity ions are implanted. This results in a lower yield of the semiconductor device (YIELD) and poor electrical characteristics.

In order to solve the above problems, an object of the present invention is to suppress the undesired chemical reaction that may occur in the loading step of the semiconductor wafer to form a stable thin film without defects to improve the yield and quality of semiconductor products It is to provide a manufacturing method.

In order to achieve the above object, the present invention, the standby step of initializing the reaction conditions to form a thin film on the semiconductor wafer, the loading step of loading the semiconductor wafer, pumping for decompression and impurities removal inside the reaction chamber And a purge step, a deposition step for forming a film, a first circulation purge step for boosting the inside of the reaction chamber, an unloading step for unloading the semiconductor wafer, and a second circulation step for cleaning the inside of the reaction chamber after unloading. In the low pressure chemical vapor deposition process including a purge step, the internal temperature of the reaction chamber in the purge step, the deposition step for forming the film, and the first circulation purge step is set relatively high compared to the other steps and improves the predetermined time. It is characterized in that to be maintained.

As a specific embodiment, in the waiting step of initializing the device and the loading step when loading the semiconductor wafer into the reaction chamber, the temperature in the reaction chamber is set to 300 to 450 ° C., and the semiconductor wafer is loaded into the reaction chamber, The temperature is increased from 5 to 10 ° C./min from the pumping step, which starts the pumping step, to the nitrogen purge step, and then the nitrogen purge step and the purified reaction gas are injected to cause a desired chemical reaction to form a thin film. The pressure in the step and the reaction chamber is set to a deposition temperature, ie, 650-900 ° C. for silicon nitride film deposition, and 610-640 ° C. for polysilicon film deposition, until a cyclic purge step of raising the atmospheric pressure.

After the thin film is formed, the temperature is lowered to a lower rate of 3-7 ° C./min until the unloading step of unloading the semiconductor wafer and the second circulation purge step in the reaction chamber to lower the initial atmospheric step, 300-450 ° C.

Here, if the upper limit of the temperature in the reaction chamber is set above 500 ° C. in the waiting step and the loading step, the desired value cannot be achieved, and the lower limit of the temperature is set below 300 ° C. and the productivity is low due to the reduction of reproducibility. There is a problem with losing. Thus, the appropriate value is in the range of 300 ~ 450 ℃.

In addition, if the temperature increase rate from the pumping step to the nitrogen purge step is 5 to 10 ° C./min or more, the time required for stabilization to the set deposition temperature is excessively increased. .

In addition, the temperature lowering rate in the unloading step and the second circulation purge step is more than 3-7 ° C./min, which is good. However, this is likely to cause an abnormality in the apparatus. Is emerging.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the illustrated drawings.

Figure 4 schematically shows a step-by-step temperature setting profile graph in the low pressure chemical vapor deposition process according to the present invention.

Referring to this, the semiconductor device manufacturing method according to the present invention is performed as follows.

11. As the standby step 11, basic conditions for the initialization and stabilization of the low pressure chemical vapor deposition apparatus are set before loading the semiconductor wafer 23 into the reaction chamber 22, and the temperature is set to 300 to 450 캜. .

12. As the loading step 12, the end cap 24 of the reaction chamber 22 maintained at a temperature of 300 to 450 DEG C is opened to load the semiconductor wafer 23 to be processed into the reaction chamber 22, and the end The cap 24 is closed to seal the reaction chamber 22.

13. In the pumping step 13, while reducing the internal pressure by the pumping action inside the sealed reaction chamber 22, the temperature rise rate in the reaction chamber 22 is set to 5 to 10 ° C / min to In the case of 650 ~ 900 ℃, polysilicon film deposition is raised to 610 ~ 640 ℃.

14. As the nitrogen purge step 14, by injecting nitrogen gas into the pressure-reduced reaction chamber 22 to maintain a nitrogen atmosphere, oxygen flowing into the semiconductor wafer 23 and remaining in the reaction chamber 22 ( Remove impurities such as O ₂ ), moisture (H ₂ O) and other contaminants. At this time, the temperature in the reaction chamber 22 reaches the deposition temperature of the silicon nitride film or the polysilicon film, thereby activating the film-forming atmosphere by the reaction gas.

15. As the deposition step 15, SiH ₂ Cl ₂ (DICHLORO SILANE) and NH ₃ (AMMONIA), which are purified reaction gases into the reaction chamber 22 maintained at the deposition temperature of the silicon nitride film or the polysilicon film, are deposited. Injecting to form a silicon nitride film by their chemical reaction, or SiH ₄ (SILANE) is injected to form a polysilicon film on the semiconductor wafer 23 by a chemical reaction by thermal decomposition thereof. At this time, the chemical reaction takes place under a reduced pressure state, which lengthens the average free path of the reaction gas so that the chemical reaction takes place on the surface of the heated semiconductor wafer 23 and is again at a stable position, i.e., where the energy level is low. 23) To induce a heterogeneous reaction that migrates to the surface to form the film surface evenly.

16. As the first circulating purge step 16, nitrogen gas or the like is injected into the reaction chamber 22 in a state where deposition of the desired thin film is completed, and the internal pressure is increased to atmospheric pressure. Thereafter, the temperature in the reaction chamber 22 is lowered at a rate of 3-7 ° C./min.

17. As the unloading step 17, the semiconductor wafer 23 in which the desired thin film is formed by opening the end cap 24 from the inside of the reaction chamber 22 which is descending at a temperature of 3-7 ° C./min. Unload to complete the low pressure chemical vapor deposition process.

18. TEMPERATURE RAMP DOWN and the second circulating purge step 18, after unloading the semiconductor wafer 23, the temperature in the reaction chamber 22 is continued and the initial rate is lowered at a rate of 3-7 ° C./min. It is lowered to 300-450 degreeC which is the waiting step 11. At the same time, nitrogen gas is cleaned of unnecessary gas and reaction products remaining in the reaction chamber 22.

Here, the temperature setting when unloading the semiconductor wafer after thin film formation is very low, and after the thin film formation, the generation of chemical reactants due to oxygen, moisture and other contaminants in the working environment is very small, and there is a wet cleaning process. It doesn't matter.

The operation of the semiconductor device manufacturing method according to the present invention having such a configuration is as follows.

In the standby step of setting the basic conditions for the initialization and stabilization of the low pressure chemical vapor deposition apparatus before loading the semiconductor wafer into the reaction chamber and the loading step of loading the semiconductor wafer, the temperature inside the reaction chamber is lowered to 300 to 450 ° C. It suppresses anomalous chemical reactions that may occur in the loading stage early in the low pressure chemical vapor deposition process.

The results of the defects before and after the application of the semiconductor manufacturing method according to the present invention as described above in the horizontal low pressure chemical vapor deposition apparatus experimented with a silicon nitride film are as follows, where the size of the defects is 0.2 to 0.5 μm. And 0.5 ~ 5.0μm were divided into two groups. Data collection was based on one month.

Before application:

① group of defects of 0.2 ~ 0.5μm in size;

Highest: 2876, Lowest: 1156, Range: 1720.

② group of defects of 0.5 ~ 5.0μm in size;

Highest: 575, Lowest: 161, Range: 414.

After application:

③ group of defects of 0.2-0.5 μm in size;

Highest: 208, Lowest: 12, Range: 196.

④ group of defects of size 0.5-5.0 μm;

Maximum: 148, maximum: 2, range: 146.

Obviously, the number of defect groups of two sizes decreased after the application of the present invention, and its spread was also reduced. And this is more effective in the 0.2 ~ 0.5μm defect group.

In the case of polysilicon film, it is not possible to count the number of defects, especially the fine size of defects due to diffuse reflection and grain, by using a PARTICLE COUNTING measuring instrument. ) Can be used to determine the approximate number. As a result of observation through this method, no defects that were abnormal reactants in the polysilicon film were detected.

Although the present invention has been described in connection with the above embodiments, various modifications and changes may be made without departing from the scope and spirit of the present invention.

As described above, according to the present invention, there is provided a method of manufacturing a semiconductor device capable of improving the yield and quality of a semiconductor product by forming a stable thin film free of defects by suppressing undesired chemical reactions that may occur during the loading step of the semiconductor wafer. Will be provided.

Claims (4)

A standby step of initializing reaction conditions to form a thin film on a semiconductor wafer, a loading step of loading the semiconductor wafer, a pumping step for depressurizing the inside of the reaction chamber, a purge step for removing impurities in the reaction chamber, And a deposition step of forming a film on the semiconductor wafer, a first circulation purge step for boosting the pressure inside the reaction chamber, an unloading step for unloading the semiconductor wafer, and a second circulation purge for cleaning the reaction chamber inside after the unloading. In a low pressure chemical vapor deposition process comprising the steps of: And maintaining the internal temperature of the reaction chamber in the atmospheric and loading steps below the internal temperature of the reaction chamber in the purge step to the second circulation purge step for removing impurities in the reaction chamber. The method of claim 1, The method of manufacturing a semiconductor device, characterized in that for maintaining the temperature inside the reaction chamber at 300 ~ 500 ℃, preferably 300 ~ 450 ℃ in the waiting step and the loading step. The method of claim 1, After loading the semiconductor wafer 23 into the reaction chamber 22, the temperature in the reaction chamber 22 from the pumping step 13 to the nitrogen purge step 14 to increase the rate of 5 ~ 10 ℃ / min A semiconductor device manufacturing method characterized by the above-mentioned. The method according to claim 1, wherein After depositing the film, the temperature in the reaction chamber 22 until the unloading step 17 and the temperature drop and the second circulation purge step 18 are lowered to a rate of 3-7 ° C./min. Semiconductor device manufacturing method.