JP2002175986A - Method for manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce damages to quartz member in a furnace and a metal furnace opening, and to prevent particles from being generated after furnace cleaning. SOLUTION: Temperature in a reaction chamber for processing silicon wafer in the furnace is kept at a prescribed film-forming temperature and a gas for forming film is introduced into the reaction chamber and prescribed films, such as Poly-Si film on the wafer are formed. In the film-forming process, the film is deposited on a quartz member on the metal member in the reaction chamber. After the deposition process, the inside of the reaction chamber is kept at a prescribed temperature, and ClF3 gas introduced into the reaction chamber for starting chemical reaction, to remove and clean the deposited film formed on the quartz member or the metal member in the reaction chamber. The prescribed temperature in the cleaning process is set to 450 deg.C or lower, at which the selection ratio between Poly-Si and SiO2 (quartz) varies greatly. The lower limit is set at room temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device having a film forming step and a cleaning step, and more particularly to a method for improving a cleaning step.

[0002]

2. Description of the Related Art Conventionally, self-cleaning for removing a generated film deposited in a furnace of a vertical CVD apparatus is performed by introducing a ClF ₃ gas into the furnace to dry-etch the inside of the furnace without using plasma to clean the furnace. Has been done. At that time, the furnace temperature was around the generation temperature of the film to be removed. This is for the following reason. On the other hand, it is better to perform the temperature inside the furnace at the time of performing the cleaning around the generation temperature of the film to be removed.
The removal of the film is promoted, and the cleaning time can be reduced.
On the other hand, since the film forming process and the cleaning in the processing chamber are repeated, if the cleaning can be performed at a temperature close to the film forming temperature,
The increase / decrease width of the temperature of the processing chamber is reduced, and the throughput is improved. Therefore, in consideration of the temperature at the time of performing the cleaning from the viewpoint of promoting the cleaning and improving the throughput, it is preferable to perform the cleaning at around the generation temperature of the film to be removed.

[0003]

However, if the temperature in the furnace at the time of cleaning is close to the film forming temperature, there is a problem that the damage in the furnace is large. For example, 550 which is a film forming temperature of a polysilicon (Poly-Si) film
When cleaning is performed at a temperature of ° C., a chemical reaction with ClF ₃ gas occurs violently, and the quartz member in the furnace and the metal at the furnace opening are greatly damaged. There is also a problem that particles after cleaning are increased due to the damage.

C used for cleaning with ClF ₃ gas
As a countermeasure against damage to the VD device, some of the metal at the furnace opening is replaced with stainless steel (SUS) instead of Hastelloy, which has high corrosion resistance. However, even Hastelloy could not effectively avoid the damage. .

An object of the present invention is to solve the above-mentioned problems of the prior art, to reduce damage to a quartz member and a metal member, and to reduce generation of particles after cleaning. An object of the present invention is to provide a method for manufacturing a device.

[0006]

According to the present invention, the cleaning temperature is reassessed from the viewpoint of avoiding damage in the furnace, and the cleaning temperature is preferably performed at a temperature lower than the formation temperature of the film to be removed. It was made with the help of According to a first aspect of the present invention, in a method of manufacturing a semiconductor device in a reaction chamber in which a substrate is processed in a reaction chamber having a quartz member or a metal member therein, the temperature in the reaction chamber is maintained at a predetermined film forming temperature. A film forming step of forming a predetermined film on the substrate by supplying a film forming gas into the reaction chamber; and maintaining the temperature in the reaction chamber within a temperature range of 450 ° C. or lower to room temperature. A cleaning step of flowing a ClF ₃ gas to remove a film attached to the quartz member or the metal member in the film forming step.

When the cleaning gas is introduced into the furnace, the cleaning gas causes a chemical reaction with the product film deposited in the furnace, and removes the product film deposited in the furnace. According to the method of manufacturing a semiconductor device of the present invention, the temperature for cleaning the inside of the reaction chamber with the ClF ₃ gas is lowered from 450 ° C. or lower to room temperature, so that the reaction with the ClF ₃ gas is suppressed and the quartz member or the metal member Only the adhered film is selectively removed, so that erosion of the quartz member and corrosion of the metallic member can be reduced.

The invention according to claim 2 is the method of manufacturing a semiconductor device according to claim 1, wherein the film forming step is a step of forming a Poly-Si film on the substrate. . The present invention is particularly suitably used when the film forming step is a step of forming a Poly-Si film.

[0009]

Embodiments of the present invention will be described below. FIG. 10 shows a schematic structure of a vertical CVD apparatus for performing a method of manufacturing a semiconductor device.

An external reaction tube 1 is provided inside a heater 10, and an internal reaction tube 2 constituting a reaction chamber having an open upper end is concentrically disposed inside the external reaction tube 1. The tube 1 and the inner reaction tube 2 are erected on a furnace port flange 3, and the space between the outer reaction tube 1 and the furnace port flange 3 is sealed by an O-ring (not shown). The furnace port flange 3
The lower end is hermetically closed by a seal cap 5, and a boat 6 is erected on the seal cap 5 and inserted into the internal reaction tube 2. Wafers 7 to be processed are loaded on the boat 6 in multiple stages in a horizontal posture. Further, a required number of heat insulating plates 4 are loaded in multiple stages in a horizontal posture in a region below the boat 6.

A gas introduction nozzle 8 communicates with the furnace port flange 3 at a position below the internal reaction tube 2, and a gas introduction nozzle 8 is provided at a lower end of a cylindrical space formed between the external reaction tube 1 and the internal reaction tube 2. The exhaust pipe 9 is connected to the furnace port flange 3 so as to communicate with each other.
It is connected to the.

The boat 6 is lowered by the boat elevator (not shown) through the seal cap 5, the wafer 6 is loaded into the boat 6, and the boat 6 is inserted into the internal reaction tube 2 by the boat elevator. After the seal cap 5 completely seals the lower end of the furnace port flange 3, the inside of the external reaction tube 1 (reaction chamber) is exhausted.

Among the members constituting the above-mentioned vertical CVD apparatus, the reaction tubes 1, 2 and the boat 6 are made of quartz members.
The furnace port members such as the furnace port flange 3 are made of metal members. Here, the furnace port member refers to both the reaction tube side member and the boat side member that constitute the furnace port when the boat 6 is inserted into the internal reaction tube 2. FIG. 11 shows the details of the lower part of the apparatus. The outer reaction tube 1, the inner reaction tube 2, and the boat 6
Columns 6b and the like are made of a quartz member. The furnace port flange 3 which is the furnace port and is exposed to ClF ₃ gas is made of SUS.
The seal flange 12 for sealing the reaction tube, the seal cap 5 of the boat 6, and the cap receiver 11 on the seal cap 5 are each made of a metal member such as Hastelloy C22.

Next, a method of manufacturing a semiconductor device in the case of forming a Poly-Si film on a silicon wafer in the vertical CVD apparatus having the above configuration will be described. The Poly-Si film mentioned here includes a P-doped Poly-Si film doped with an impurity. In a film forming process for forming a Poly-Si film on a silicon wafer,
A gas for film formation is supplied from a gas introduction nozzle 8, and the inside of the internal reaction tube 2 is heated and maintained at a predetermined film formation temperature to form a Poly-Si film on the surface of the wafer 7. The conditions for forming the Poly-Si film are, for example, as follows.

Temperature: 530 ° C. to 620 ° C. Pressure: 0 to several Torr (about 1000 Pa) Gas: SiH ₄ (several tens ccm to several thousand ccm (liter / liter)
min)) After the completion of the film formation, an inert gas is supplied from the gas introduction nozzle 8, and the inside of the reaction tubes 1 and 2 is replaced with the inert gas to return to normal pressure. The wafer 7 after completion of the film is paid out.

After repeating the film forming step once or a plurality of times, a cleaning step of the apparatus is performed. In the cleaning step, a ClF ₃ gas is supplied from a gas introduction nozzle 8 to form a film inside the internal reaction tube 2. While maintaining the temperature from 450 ° C. or lower, which is lower than the temperature, to room temperature, the Poly-Si film adhered to the quartz member or the metal member in the reaction tubes 1 and 2 in the film forming process is removed. At this time, the furnace port is closed with a metal shutter, or an empty boat 6 from which wafers have been discharged is inserted into the reaction tube 1, and the quartz member or metal member constituting the boat 6 is put together. May be cleaned.

As described above, the temperature for cleaning the inside of the reaction chamber with ClF ₃ gas is lowered from 450 ° C. or lower to room temperature, so that the reaction of ClF ₃ gas with a quartz or metal member can be suppressed. . Therefore,
Poly-Si adhered to quartz or metal members
By selectively removing only the film, erosion of the quartz member and corrosion of the metallic member can be reduced. The effect obtained by this is significant from a comprehensive point of view, even if acceleration of cleaning and improvement in throughput are somewhat sacrificed.

[0018]

Next, referring to FIGS. 5 to 9, quartz (SiO ₂ )
An experimental example of the etching characteristics and the cleaning state will be described. The cleaning conditions shown in FIGS.
0 Pa, a ClF ₃ gas flow rate of 1.25 LM, and a diluted N ₂ gas flow rate of 3.5 LM.

FIG. 5 shows the etching rate of SiO ₂ (quartz). The lower horizontal axis of the upper and lower two horizontal axes is 1000 / temperature.
(K), the upper horizontal axis represents temperature (° C.), and the vertical axis represents etching rate (angstrom / min). Since the etching rate decreases as the temperature decreases, 450
It is presumed that the etching rate is lower at 550 ° C. than at 550 ° C., and the etching rate drops considerably at room temperature.

FIG. 6 shows the state of the quartz surface (× 50 k) after the ClF ₃ cleaning for 30 minutes, and FIG.
After cleaning, (B) is after cleaning at 400 ° C. Here, a quartz piece was put into the furnace from the time of forming the Poly-Si film, and ClF ₃ cleaning was performed as it was to remove Po.
The ly-Si film was removed. The quartz piece was placed on the top of the boat (see reference numeral 6a in FIG. 10). In (A), C
Although severely eroded by the 1F ₃ gas, no significant damage is seen on the quartz surface in (B).

FIGS. 7 and 8 show the surface state of the metal sample piece after the metal sample piece (SUS or Hastelloy) constituting the metal at the furnace opening is put into the furnace and the ClF ₃ cleaning is performed. Is shown. The sample input location is on the cap receiver (see reference numeral 11 in FIG. 11).
It is inside the boat pillar 6b. FIG. 7 shows the SUS304 surface state (× 400) after the ClF ₃ cleaning was performed, and (A) shows the state after the cleaning at 550 ° C. for 30 minutes.
(B) shows the results after the cleaning at 400 ° C. for 210 minutes. In FIG. 7 (A), rusting reddish brown discoloration was observed after only 30 minutes of cleaning, but (B)
No significant change was observed even after the cleaning was performed for a total of 210 minutes.

FIG. 8 shows the surface state of Hastelloy C22 (× 400) after the ClF ₃ cleaning, and FIG.
(B) 400 ° C. after 200 minutes of cleaning at 50 ° C.
After cleaning for 210 minutes is shown. FIG.
In (A), corrosion was observed in a total of 200 minutes of cleaning, but in (B), no significant change was observed after a total of 210 minutes of cleaning. FIG.
Is a corrosion-resistant member.

FIGS. 9A and 9B show the state of particle generation after the ClF ₃ cleaning is performed. FIG. 9A shows the state before the cleaning at 550 ° C., FIG. 9B shows the state after the cleaning at 550 ° C. for 120 minutes, FIG. (D) is 4
The results after the cleaning at 00 ° C. for 180 minutes are shown. 9A to 9C show the results after forming a Poly-Si film of 8 μm.
The ClF ₃ cleaning was performed at each temperature setting shown in (D), and then a monitor wafer was loaded during the N ₂ purge sequence to measure particles. Since the cleaning was performed until the Poly-Si film was completely removed, the cleaning time was different.

The following can be said from these experiments. 45
By performing low-temperature ClF ₃ cleaning at 0 ° C. or less, damage to the furnace such as quartz and metal is reduced,
Life can be extended. Further, compared with the case where cleaning is performed at a temperature higher than 450 ° C., quartz (SiO
_Since the etching rate in ₂ ) is reduced from a fraction to a hundredth, it is estimated that the life of the quartz member can be extended several times or more. In addition, due to the reduction in damage to the quartz member, the number of particles increased after cleaning is reduced by a factor of ten, and the metal contamination level is also 3.0 × 10 ^10.
From atoms / cm ² , 1.0 × 10 ¹⁰ atoms / cm ²
cm ² or less.

Next, a description will be given of the fact that the upper limit of the cleaning temperature is preferably 450 ° C. and the dependence of the temperature, pressure and gas flow rate with reference to FIGS. In the figure, TOP, CNT, and BTM indicate the input points of the monitor wafer, and mean the top, center, and bottom on the boat, respectively. AVE indicates an average.

FIG. 1 shows that the cleaning temperature is preferably 450 ° C. or lower, and that the cleaning temperature is not higher than 450 ° C.
Will be described. FIG. 1 shows the selectivity (Poly-Si and SiO _2).
Of shows the temperature dependence of the ClF ₃ ratio of the etch rate by gas), the horizontal axis represents temperature (° C.), the vertical axis represents selectivity ratio (Pol
y-Si / SiO ₂ ). From FIG. 1, the selectivity between Poly-Si and SiO ₂ (quartz) changes remarkably at 450 ° C. as a boundary.
It can be seen that the selectivity can be made very large.
That is, by setting the cleaning temperature to 450 ° C. or lower, cleaning can be performed while reducing damage in the reaction furnace.

The main factors affecting the erosion of the quartz member and the corrosion of the metal at the furnace port are considered to be the cleaning temperature, the cleaning execution pressure, and the ClF ₃ gas flow rate.
As can be seen from FIGS. 2, 3, and 4, the effect of temperature is dominant, and the effects of pressure and flow rate are insignificant. FIG. 2 shows the temperature dependence of the etching rate of the Poly-Si film by the ClF ₃ gas. The horizontal axis represents temperature (° C.), and the vertical axis represents the etching rate (angstrom / min). FIG. 3 shows the pressure dependence of the etching rate of the Poly-Si film by ClF ₃ gas, and the horizontal axis represents the pressure (P
a), the vertical axis is the etching rate (angstrom / m)
in). Figure 4 shows a ClF ₃ gas flow rate dependency of the Poly-Si film etching rate, the horizontal axis represents ClF ₃ flow rate (SLM (standard liters / min)), the vertical axis represents the etching rate (Å / min).

FIGS. 2, 3 and 4 are all based on a basic test using a monitor wafer. In the basic test method, a monitor wafer on which a Poly-Si film has been formed in advance is placed in a furnace, cleaning is performed for a certain period of time, and an etching rate is obtained based on a difference in film thickness before and after. As can be seen from these, the cleaning execution pressure and the ClF ₃ gas flow rate are not so affected as the cleaning temperature. Therefore, the cleaning temperature is preferably 450 ° C. or less.

By setting the temperature in the reaction chamber at 450 ° C. or less at the time of cleaning, damage is reduced, but as shown in FIG. 2, the etching rate is reduced and the time required for etching is increased. I can't deny it. The temperature at which damage during cleaning can be avoided is 450 ° C. or less, but the temperature range that satisfies both damage avoidance and the etching rate is preferably 450 ° C. to room temperature, and more preferably around 400 ° C. .

The method of manufacturing a semiconductor device according to the present invention comprises:
In addition to being applied to self-cleaning in vertical equipment furnaces,
It is needless to say that the present invention can be applied to a horizontal apparatus and a single-wafer apparatus.

[0031]

According to the present invention, the upper limit temperature at the time of performing the ClF ₃ gas cleaning is lowered to 450 ° C., so that the chemical reaction can be performed at a higher temperature than the conventional method of performing the cleaning at a high temperature exceeding the upper limit temperature. The damage to the quartz member and the metal member in the furnace can be greatly reduced. In addition, generation of particles after cleaning can be reduced by reducing damage.

[Brief description of the drawings]

FIG. 1 shows a selection ratio (Poly-Si and S
FIG. 5 is a diagram showing the temperature dependence of the etching rate ratio of iO ₂ to ClF ₃ gas).

FIG. 2 is a diagram illustrating Poly with a ClF ₃ gas according to the embodiment.
FIG. 3 is a diagram showing the temperature dependence of an etching rate of a Si film.

FIG. 3 is a diagram illustrating Poly with a ClF ₃ gas according to the embodiment.
FIG. 3 is a diagram showing pressure dependency of an etching rate of a Si film.

FIG. 4 is a diagram showing a ClF ₃ gas flow rate dependency of a Poly-Si film etching rate according to the embodiment.

FIG. 5 is a characteristic diagram showing an etching rate of SiO _{2 according to} an example.

FIG. 6 is a view showing a quartz surface state (× 50 k) after performing ClF ₃ cleaning for 30 minutes according to the example.

FIG. 7 shows S after ClF ₃ cleaning according to the embodiment.
It is a figure which shows the US304 surface state (x400).

FIG. 8 is a diagram showing a surface state (× 400) of Hastelloy 22 after performing ClF ₃ cleaning according to the example.

FIG. 9 is a diagram illustrating a state of particle generation after performing ClF ₃ cleaning according to the example.

FIG. 10 is a schematic structure of a vertical CVD apparatus for performing a method of manufacturing a semiconductor device according to an embodiment.

FIG. 11 is a detailed view of a lower part of a vertical CVD apparatus according to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 External reaction tube (made of quartz glass) 2 Internal reaction tube (made of quartz glass) constituting a reaction chamber 3 Furnace opening flange (made of SUS) 5 Seal cap (made of SUS) 6 Boat 7 Wafer (substrate) 8 Gas introduction nozzle

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K030 BA29 BB03 CA04 CA12 DA06 JA06 JA10 KA08 KA46 5F004 AA15 BD04 CA04 DA00 DB02 EA34 5F045 AA03 AB03 AD08 AE01 AE19 BB15 DP19 EB06 EC02 HA13

Claims (2)

[Claims] In a method for manufacturing a semiconductor device, wherein a substrate is processed in a reaction chamber having a quartz member or a metal member therein, the temperature in the reaction chamber is maintained at a predetermined film forming temperature, and the temperature in the reaction chamber is reduced. A film forming step of forming a predetermined film on the substrate by supplying a film gas, maintaining the temperature in the reaction chamber within a temperature range of 450 ° C. or less to room temperature, and flowing a ClF ₃ gas into the reaction chamber, A cleaning step of removing a film attached to the quartz member or the metal member in the film forming step. 2. The method according to claim 1, wherein said film forming step is a step of forming a polysilicon film on said substrate.