JPH11102902A - Semiconductor device thin film forming device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent overetching from occurring at the boundaries of a laminated film by a method wherein reaction auxiliary gas is stopped from being fed before reaction gas is stopped from being fed above a spot where gases are mixed together. SOLUTION: A mixed gas inlet pipe 4 used for introducing a mixed gas of reaction gas and reaction auxiliary gas is connected to a shower head 3, and a reaction gas inlet pipe 5 for introducing reaction gas and a reaction auxiliary gas inlet pipe 6 for introducing reaction auxiliary gas are connected at a mixing part 11 located above the mixed gas inlet pipe 4. A shut-off valve 7 which is used only for stopping the reaction auxiliary gas 2 to 10 seconds, preferably 4 to 6 seconds, before the reaction gas is stopped by a valve 8 is provided in the inlet pipe 6. When a prescribed film forming time elapses after a silicon oxide film starts depositing on the surface of a substrate, the reaction auxiliary gas is stopped from being fed by the shut-off valve 7 a few seconds before the reaction gas stops.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention belongs to the technical field of a thin film forming apparatus and a thin film forming method for forming a thin film for a semiconductor device represented by a semiconductor memory such as a DRAM.

[0002]

2. Description of the Related Art A process for manufacturing a semiconductor device such as a DRAM includes a process for forming a transistor and a process for forming a capacitor or a multilayer wiring.

Among these, when forming a capacitor or a multilayer wiring, PSG (phosphorus-doped silicon oxide film), B
SG (boron-doped silicon oxide film), BPSG
(Silicon oxide film doped with phosphorus and boron) may be formed in a single film-forming apparatus, or may be stacked in large numbers.

[0004]

Since such a film is used, for example, as an etching mask when forming a capacitor, it is cleaned with hydrofluoric acid (HF). FIG. 7 shows the state of the laminated film when the cleaning with hydrofluoric acid is performed after the formation of the five PSG films, and a polycrystalline silicon film is deposited so as to cover the PSG films. As shown in FIG. 7, over-etching occurs at the boundary between the stacked thin films at this time,
As a result, when a polycrystalline silicon film covering this laminated film is formed, a defective shape of the polycrystalline silicon film occurs. This causes the reliability of the device to deteriorate.

An object of the present invention is to provide a thin film forming apparatus and a thin film forming method for a semiconductor device in which overetching hardly occurs at a boundary portion of a laminated film.

[0006]

According to the present invention, there is provided a thin film forming method and apparatus for forming a thin film for a semiconductor device, wherein a reaction gas is supplied upstream of a portion where a plurality of gases are mixed before shutting off a supply of a reactive gas. It is characterized in that the supply of the auxiliary gas is shut off and a valve for that is provided.

[0007]

FIG. 1 is a schematic diagram showing a thin film forming apparatus according to an embodiment of the present invention. A substrate holder 1 for holding a semiconductor wafer 2 as a substrate with a film-forming surface facing down and heating the semiconductor wafer 2 as a substrate to a predetermined temperature in a space surrounded by an exhaustable chamber 10 and a reaction gas and a reaction auxiliary gas Is provided with a gas blowing shower head 3 for introducing the gas. A mixed gas introduction pipe 4 for introducing a mixed gas of a reaction gas and a reaction auxiliary gas is connected to the shower head 3, and a reaction gas for introducing the reaction gas in the mixing section 11 is provided upstream of the mixed gas introduction pipe 4. An introduction pipe 5 and a reaction aid gas introduction pipe 6 for introducing a reaction aid gas are connected. In the present embodiment, the supply of the reaction aid gas to the introduction pipe 6 is stopped for 2 seconds to 10 seconds, more preferably 4 to 6 seconds before the supply of the reaction gas is stopped by the valve 8. A shut-off valve 7 dedicated to the process is provided.

The film forming process is as follows.

First, the inside of the chamber 10 is once evacuated by the exhaust pump 9 connected to the exhaust port, and
Heat to 0 ° C. A gas containing Si, such as Si (OC ₂ H ₅ ) _4, ie, TEOS (tetraethoxysilane) or SiH _4, is supplied from a reaction gas introduction pipe 5 through a valve 8 to 0.1 to 4.0 g /
At a flow rate of about min, (C ₂ H ₅ O) ₃ B, ie, TEB (triethyl borate) or (CH ₃ O) ₃ B, ie, TMB (trimethyl borate) or (CH ₃ O) ₃ PO, ie, TMOP (trimethyl phosphate) , a gas containing P and B, such as B ₂ H ₆ and PH ₃
A mixed gas mixed at a flow rate of 0.1 to 1.0 g / min is introduced into the chamber 10. At the same time as the introduction of these mixed gases, the introduction of oxygen-containing gas such as oxygen gas or gas containing ozone (O ₃ ) from the reaction aid gas introduction pipe 6 via the valve 7 is started. The flow rate of the gas containing O is, for example, 5 to 10
It is about slm. Thus, the deposition of the silicon oxide film doped with phosphorus and / or boron by normal pressure CVD is started on the substrate. When a predetermined film formation time has elapsed, supply of a reaction auxiliary gas is performed several seconds before the supply of the gas containing Si and P (and / or B) is shut off using the valve 8 provided in the reaction gas supply system. Is shut off using the shut-off valve 7. Such control of the opening / closing timing of the valve can be easily performed by mechanically connecting the two valves or electrically controlling the opening / closing timing of the two valves (for example, a delay circuit or control means by a computer program). Can be executed.

According to the present embodiment, PSG, BSG and BPSG films having a uniform composition can be obtained by suppressing segregation of B and P.

By repeating the above steps a plurality of times, it is possible to form a laminated film free of B and P segregation at the interface.

FIG. 2 is a schematic diagram showing a thin film forming apparatus according to another embodiment of the present invention. This apparatus has five film formation regions 10A to 10E, and is suitable for stacking five films.

A common reaction gas supply pipe 15 is provided for each film formation area.
, A mixed gas of a gas containing Si and a gas containing P and / or B is supplied through five valves 8A to 8E provided in each branch pipe. A mixed gas supply valve 16 has a gas source 17 of a gas containing Si, a gas source 18 of a gas containing P, and a gas source 19 of a gas containing B upstream thereof.
And are connected.

A reaction auxiliary gas containing O, such as oxygen or ozone, is supplied from a gas source 14 via a supply valve 13 to a common supply pipe 12 through each of the open shutoff valves 7A to 7B.
It is supplied to five film formation areas 10A to 10E via 7E. If the substrates are sequentially transferred to the five regions to form a continuous film, a laminated film can be obtained on the same substrate. Stacking a film formed in a plurality of regions in this manner improves processing throughput and reliability, as compared with stacking a film in one region.

At the end of film formation in each region, these valves are controlled so as to close the reaction assistant gas shutoff valves 7A to 7E several seconds before closing the valves 8A to 8E as in the above-described embodiment. Then, the valves 13 and 16 are closed simultaneously or sequentially.

FIG. 3 shows still another embodiment.
In FIG. 3, five wafer susceptors 21 capable of heating a wafer as a substrate are provided on a table 22, and the five film forming regions 10A, 10B, 10C, 10D, 10E are rotated by rotating the table 22 clockwise. Is a thin film forming apparatus for forming a thin film. Although each film forming region is in the chamber 10 and the atmosphere communicates with each other, each region is provided with a shower head similar to that shown in FIG. The mixed gas is blown toward the wafer, and chemical vapor deposition is performed. The gas supply system to the shower head is the same as that shown in FIG. 2, and is controlled by valves 7A to 7E so as to shut off the supply of the reaction aid gas before shutting off the supply of the reaction gas. With this apparatus, five wafers are formed in the film formation areas 10A to 10A.
After 10E, a five-layer laminated film is formed. Since the five films are made of the same material, they cannot be distinguished into five. In other words, they can be called a single film. 2
Reference numeral 3 denotes a case where the wafer is placed on the susceptor 21 or the susceptor 2
This is a wafer transfer robot that can be removed from the wafer transfer robot.

Also in this embodiment, in order to further reduce the number of particles, the film may be formed with the surface on which the film is formed facing downward as in FIG.

Example 1 A thin film forming apparatus according to the present invention shown in FIG. 3 was prepared.

As reaction gases, TEOS and TMOP were prepared. Ozone and oxygen gas were prepared as reaction aid gases. Wafer susceptor 2 using Si wafer as substrate
1 and the inside of the chamber 10 was once depressurized. And
The heater of the wafer susceptor was energized so that the substrate temperature became 400 ° C.

Oxygen containing 0.1 to 4.0 g / min of TEOS gas from the gas source 17 to each film formation region, 0.1 to 1.0 g / min of TMOP gas from the gas source 18 and 1 to 5 mol% of ozone. A gas was introduced from the gas source 14 at a flow rate of 7.5 slm into each film formation region. 80 to 100 film thickness from the start of gas introduction
After continuously supplying the reaction gas and the reaction assistant gas until the thickness reaches nm, the valves 7A to 7E are first closed, and after a few seconds, the valve 8A
8E was closed, and then valves 13 and 16 were closed to terminate the film formation.

The same processing was performed by rotating the table 22 to move the wafer to the next film formation area. Then, PSG was formed in five regions.

FIG. 4 schematically shows a state in which five layers of the thus obtained PSG films are patterned, washed with hydrofluoric acid, and polycrystalline silicon is formed.

As can be seen from a comparison with FIG.
Overetching is prevented at the interface of the laminated film,
It was found that the defective shape of the polycrystalline silicon disappeared.

Embodiment 2 A thin film forming apparatus according to the present invention shown in FIG. 3 was prepared.

As the reaction gas, TEOS, TMOP, T
MB was prepared. Ozone and oxygen gas were prepared as reaction aid gases. A Si wafer as a substrate was mounted on the wafer susceptor 21, and the inside of the chamber 10 was once depressurized.
Then, the heater of the wafer susceptor 21 was energized so that the substrate temperature became 400 ° C.

The TEOS gas is supplied from the gas source 17 to each of the film forming regions at 0.1 to 4.0 g / min, the TMOP gas is supplied from the gas source 18 to 0.1 to 1.0 g / min, and the TMB gas is supplied from the gas source 19.
Oxygen gas containing 0.1 to 1.0 g / min and 1 to 5 mol% of ozone is introduced from the gas source 14 to the reaction gas and the reaction aid until the thickness of each film formation region becomes 80 to 100 nm by introducing 7.5 slm. After supplying the gas, the valves 7A to 7E were closed first, and after a few seconds, the valves 8A to 8E were closed to form a thin film. The same processing was performed by rotating the table 22 to move the wafer to the next film formation area. Then, BPSG was formed in five regions.

The atomic composition of one BPSG film obtained by processing a plurality of wafers was analyzed.

FIG. 5 shows a graph in which the BPSG film was subjected to SIMS analysis and the contents of Si, B and P elements were measured.

(Comparative Example) Using the apparatus shown in FIG. 3, film forming conditions other than the valve opening / closing timing were set in the same manner as in Example 2, and a film was formed. In this comparative example, the timing of closing the shut-off valves 7A to 7E of the reaction auxiliary gas was made to coincide with the timing of closing the shut-off valves 8A to 8E of the reaction gas, and the BPS
A laminated film in which five G films were laminated was formed.

FIG. 6 shows that the thus obtained BPSG film is
The graph which measured the content of Si, B, and P element by performing the IMS analysis is shown.

As is clear from the data shown in FIGS. 5 and 6, it can be seen that in the method of the comparative example, the B and P concentrations increase at the interface of the BPSG thin film. Due to such segregation of phosphorus and boron, the etching rate by hydrofluoric acid at the interface is higher than the etching rate at portions other than the interface, and it seems that overetching occurs. this is,
It is considered that an abnormal film-forming phenomenon occurred immediately after the end of the supply of the reaction gas due to the influence of the gas containing P and B adsorbed in the chamber.

On the other hand, according to the present embodiment, the supply of the reaction aid gas which promotes the decomposition of the gas and promotes the incorporation of P and B into the film is performed by the supply of the reaction gas. A few seconds before the shutoff, the relative concentration of the reaction assistant gas in the chamber is temporarily reduced to shut off using the dedicated shutoff valve 7 (7A to 7E). Is suppressed, and a film having a uniform composition in the film thickness direction can be obtained. In this way, partial over-etching is prevented even when the hydrofluoric acid treatment is performed, and the defective shape of polycrystalline silicon formed thereafter is suppressed.

[0033]

According to the present invention, segregation of impurities such as B and / or P is suppressed, and a uniform single film or laminated film can be formed in the film thickness direction, and over-etching hardly occurs on the surface or the boundary portion. Become. In this way, the shape defect of the film formed thereafter is eliminated, and the reliability of the device is improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a thin film forming apparatus according to a preferred embodiment of the present invention.

FIG. 2 is a schematic view of a thin film forming apparatus according to another preferred embodiment of the present invention.

FIG. 3 is a schematic view of a thin film forming apparatus according to still another preferred embodiment of the present invention.

FIG. 4 shows a method for forming a PSG film using the thin film forming apparatus according to the present invention.
FIG. 5 is a schematic diagram showing a state in which five layers are stacked and patterned, and then washed with hydrofluoric acid to form a polycrystalline silicon film.

FIG. 5 shows B obtained using the thin film forming apparatus according to the present invention.
FIG. 4 is a diagram showing an atomic composition ratio of a PSG film.

FIG. 6 is a view showing an atomic composition ratio of a BPSG film obtained in a comparative example.

FIG. 7 is a schematic diagram showing a state in which five layers of PSG films are stacked and patterned using a conventional thin film forming apparatus, and then washed with hydrofluoric acid to form polycrystalline silicon.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate holder 2 Substrate 3 Shower head 4 Mixed gas introduction pipe 5 Reaction gas introduction pipe 6 Reaction assistant gas introduction pipe 7 Shutoff valve 8 Valve 9 Exhaust pump 10 Chamber 11 Mixing part

Claims (8)

[Claims] In a thin film forming apparatus for forming a thin film for a semiconductor device having a laminated film composed of a plurality of thin films, a reaction assist gas is supplied before shutting off a supply of a reactive gas upstream of a portion where a plurality of gases are mixed. A thin film forming apparatus for a semiconductor device, comprising a valve for shutting off supply of a chemical gas. 2. The thin film for a semiconductor device according to claim 1, wherein the reaction gas is a gas containing Si and at least one of P and B, and the reaction auxiliary gas is a gas containing O. Forming equipment. 3. A thin film forming apparatus for forming a thin film for a semiconductor device, wherein a supply of a reaction auxiliary gas is stopped before a supply of a reaction gas is stopped upstream of a portion where a plurality of gases are mixed. A thin film forming apparatus for a semiconductor device, comprising a valve. 4. The thin film for a semiconductor device according to claim 3, wherein the reaction gas is a gas containing Si and at least one of P and B, and the reaction auxiliary gas is a gas containing O. Forming equipment. 5. A thin film forming method for forming a thin film for a semiconductor device having a stacked film composed of a plurality of thin films by introducing a plurality of gases into a reaction chamber, wherein the supply of the reaction gas is stopped to complete the film formation. A method for forming a thin film for a semiconductor device, wherein the supply of the reaction assistant gas is interrupted beforehand. 6. The thin film for a semiconductor device according to claim 5, wherein the reaction gas is a gas containing Si and at least one of P and B, and the reaction auxiliary gas is a gas containing O. Method. 7. A thin film forming method for forming a thin film for a semiconductor device in which a plurality of gases are introduced into a reaction chamber to form a thin film. A method for forming a thin film for a semiconductor device, comprising shutting off a gas supply. 8. The thin film for a semiconductor device according to claim 7, wherein the reaction gas is a gas containing Si and at least one of P and B, and the reaction auxiliary gas is a gas containing O. Forming method.