JP3332063B2 - Method for forming SiNx / PSG laminated structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a method for forming an iNx / PSG laminated structure, and more particularly, to a method for forming a PSG layer on a SiNx film by CVD.
The present invention relates to a method for forming a SiNx / PSG laminated structure improved so that a SiO ₂ film is not locally locally grown.

[0002]

2. Description of the Related Art PS is used as an interlayer insulating film of a semiconductor device.
When a G (Phospho-Silicate Glass) film was used, stress often occurred in the PSG film, causing cracks and hillocks in the lower aluminum (Al-Si 1% alloy) wiring layer in many cases. Therefore, in order to solve these problems, a SiNx / PSG stacked structure including a SiNx film as an interlayer insulating film and a PSG film formed thereon has been developed. As the SiNx film, for example, Si ₃ N ₄
There is. In a conventional method for forming a SiNx / PSG laminated structure, first, a plasma CVD method is performed on an aluminum wiring layer formed on a reflow oxide film formed as an insulating film on a semiconductor substrate, and thus on the reflow oxide film. Causes a chemical reaction between a SiH ₄ (silane) -based gas and a nitrogen-containing gas such as NH ₃ (ammonia) to form a SiNx film. Next, SiH is formed on the SiNx film by a normal pressure CVD method.
Chemical reaction between ₄ gas, PH ₃ gas and O ₂ gas
A G film is formed.

In order to prevent the occurrence of stress in the PSG film and the occurrence of hillocks in the aluminum wiring layer, an S
It is necessary to shorten the heating time when forming the iNx film and the PSG film, and to keep the heating temperature low. For that, PS
The density of the G film was sacrificed to some extent.

[0004]

By the way, the conventional Si
In the method of forming the Nx / PSG laminated structure, the underlying SiNx
At the time of film formation, the concentration of unreacted Si—H groups locally increases, which causes a phenomenon that the upper PSG film locally grows at an increased rate. For this reason, the flatness of the wiring layer formed on the PSG film is deteriorated, and the diameter of the wiring is changed, so that a certain region becomes thick and a certain region becomes thin. As a result, the product yield decreases, and the product reliability decreases. The local increase in the concentration of unreacted Si-H groups is
It accompanies the formation of the iNx film, and specifically,
For example, a silicon hydride compound of unreacted SiH ₄ at the time of forming the SiNx film adheres as particles to the surface of the reflow oxide film on the base substrate or the surface of the SiNx film during formation.

Hereinafter, this phenomenon will be described in more detail with reference to FIG. FIGS. 3A, 3B, and 3C are cross-sectional views of a substrate for each step of a conventional method for forming a SiNx / PSG stacked structure. To form the SiNx / PSG laminated structure, first, a SiNx film is formed on a reflow oxide film formed on a semiconductor substrate (not shown) by a plasma CVD method. At this time, the silicon hydride compound particles 12 adhere to the reflow oxide film 14, for example, as shown in FIG. Since the silicon hydride compound particles 12 contain excess hydrogen, the excess hydrogen is degassed during the SiNx film forming process. As a result, the surface of the silicon hydride particles 12 is SiNx
Since the film 16 is not formed, even when the formation of the SiNx film 16 is completed, a part of the attached silicon hydride compound particles 12 is exposed on the surface. FIG. 3B is a cross-sectional view showing the above state.

However, in the conventional method of forming a SiNx / PSG laminated structure, the silicon hydride particles 12
The PSG film 18 is formed on the SiNx film 16 with the exposed portions as shown in FIG. The PSG film 18
For example, it is formed by a normal pressure CVD method. Therefore, P
During the formation of the SG film 18, the silicon hydride compound particles 12 in which O ₂ in the reaction gas is exposed are oxidized to expand the volume of the silicon hydride compound particles 12 from about 1.5 to 2 times. As a result, in the PSG film 18 formed on the SiNx film 16, as shown in FIG. 3C, only the region above the portion where the silicon hydride compound particles 12 adhere is swelled like a protrusion. This protruding bulge 1
No. 9 raises the aluminum wiring layer in a step of forming an aluminum wiring layer to be formed on the PSG film thereafter, thereby deteriorating the flatness of the wiring and causing a variation in the wire diameter.

In view of the above circumstances, an object of the present invention is to form a SiNx / PSG laminated structure by forming a SiNx film and a PSG layer sequentially on a semiconductor substrate.
CVD-SiO ₂ is to provide a method of forming a locally accelerated growth not improved SiNx / PSG laminate structure as.

[0008]

Means for Solving the Problems The present inventor has attempted various measures to solve the above-mentioned object. For example, the present inventor has searched for a plasma CVD manufacturing apparatus in which silicon hydride compound particles are unlikely to be generated. However, when such an apparatus is used, the ability to form a SiNx / PSG laminated structure is reduced and productivity is low. I understood. Also, SiNx
An attempt was made to increase the thickness of the film, but the device speed was reduced due to an increase in interlayer capacitance. Further, an attempt was made to reduce the amount of protrusion-like swelling by lowering the deposition rate of the PSG film, but this was not preferable because hillock growth increased in the lower aluminum wiring layer. Then, the inventor focused on the surface nitridation of the SiNx film, and completed the present invention after repeated experiments.

[0009] In order to solve the above-mentioned object, according to the present invention, the S
A method for forming an iNx / PSG laminated structure (hereinafter, referred to as a first invention method) includes a step of forming a SiNx film by a plasma CVD method and a step of forming a PSG film. , SiNx film and PSG film to form SiN
x / PSG lamination structure, a method of forming a SiNx
The method is characterized in that a step of nitriding the surface of the SiNx film is provided after the step of forming the film and before the step of forming the PSG film.

In the method of the present invention, the step of forming a SiNx film is performed by using a known plasma CVD apparatus to form a PSG.
The process of forming the film uses a known atmospheric pressure CVD device,
Each is performed under the same film forming conditions as the conventional method. In the present invention, the SiNx film means a silicon nitride film, for example, Si ₃ N ₄ . By nitriding the surface of the SiNx film, the locally increased concentration of the Si—H group can be reduced, and thus the PSG film formed on the SiNx film can be reduced.
Accelerated growth of the film is prevented.

According to a preferred embodiment of the present invention, in the step of nitriding the surface of the SiNx film, the temperature of the SiNx film is set at 5 ° C.
It is characterized in that the surface of the SiNx film is nitrided by nitrogen plasma treatment or ammonia plasma treatment at a low temperature of 0 ° C. to 150 ° C. Thereby, the influence on the SiNx film and the lower aluminum wiring layer is reduced, and
The occurrence of stress in the iNx film and the occurrence of hillocks in the aluminum wiring layer can be prevented.

Also, another SiNx / PSG according to the present invention
A method for forming a laminated structure (hereinafter, referred to as a second invention method) is as follows.
Forming a SiNx film by a plasma CVD method;
And forming a PSG film on the substrate.
In the method of forming the SiNx / PSG stacked structure by forming the iNx film and the PSG film, in the step of forming the SiNx film, the thickness of the SiNx film is suppressed to a range of 10 nm to 70 nm, and then 700 ° C. The method is characterized in that a step of thermally nitriding the surface of the SiNx film by a nitrogen annealing method or an ammonia annealing method at the following temperature is provided.

In the method of the present invention, a nitrogen annealing method such as rapid thermal nitridation (RTN) or an ammonia annealing method is used as a surface nitriding method. In the present invention, since the film thickness of the SiNx film is reduced, the film forming time is shortened, and the temperature of the thermal nitridation treatment is lowered, the influence on the SiNx film and the lower aluminum wiring layer is small.

In any of the above methods, SiNx
The silicon hydride compound particles exposed on the surface of the film are nitrided to reduce the concentration of Si-H groups, and when forming the PSG film, O ₂ in the reaction gas oxidizes the particles and expands the volume. Can be prevented. Therefore, P
Since no volume expansion of the particles occurs during the formation of the SG film, it is possible to prevent the occurrence of the projection-like swelling on the PSG film as in the related art.

Further, still another SiNx / P according to the present invention
Method for forming SG laminated structure (hereinafter, referred to as a third invention method)
Has a step of forming a SiNx film by a plasma CVD method and a step of forming a PSG film, and sequentially forms a SiNx film and a PSG film on a substrate to form a SiNx / PS
In the method of forming the G laminated structure, following the step of forming the SiNx film, before the step of forming the PSG film,
The method is characterized by including a step of cleaning the SiNx film with a cleaning liquid and performing surface etching and surface oxidation.

In the method of the present invention, the high-concentration Si-H groups exposed on the surface of the SiNx film are washed with a cleaning solution, and the surface is etched and oxidized to reduce the concentration of the Si-H groups. I have. The cleaning liquid used in the present invention performs a surface etching treatment and a surface oxidation treatment by cleaning,
There is no particular limitation as long as the concentration of the Si-H group can be reduced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in more detail below with reference to the drawings. Embodiment 1 Embodiment 1 is an embodiment of the first invention method.
(A), (b), and (c) are sectional views of the substrate in each step of Example 1. In this embodiment, first, a SiNx film 22 was formed on a reflow oxide film 20 formed on a semiconductor substrate by a plasma CVD method. At that time, FIG.
It is assumed that the silicon hydride compound particles 24 adhere to the reflow oxide film 20 at the initial stage when the SiNx film 22 is formed, and the formation of the SiNx film 22 ends with the silicon hydride compound particles 24 remaining attached.

In forming the SiNx film 22, a parallel plate type plasma CVD apparatus capable of batch processing eight sheets simultaneously was used to form the SiNx film 22 at a temperature of 250 ° C. and a pressure of 100 Pa. The kind and flow rate of the gas used were 100 sccm for SiH ₄ and 300 for NH _3.
sccm and N ₂ were 4000 sccm. The RF output of the plasma CVD apparatus was 500 W, and the time required for formation was 420 seconds. As a result, the formed SiNx film 2
2 had a thickness of 100 nm, and the hydrogen component in the film was 20 to 25 in atomic percent.

Next, the substrate was immediately transferred to a chamber of another 8-plate batch processing type parallel plate type plasma CVD apparatus, and the surface of the SiNx film 22 was subjected to nitrogen plasma treatment to nitride the surface of the SiNx film 22. Processing pressure is 100P
a, the processing temperature is 50 ° C. lower than the temperature at the time of forming the SiNx film.
To 150 ° C. which is lower by about 150 ° C. Nitrogen flow is 10
00 sccm, the RF output during processing was 120 W, and the processing time was 120 seconds. By the above processing, the SiNx film 2
The SiNx film 2 is kept
2 is nitrided to form a nitrided layer 26. Further, in this embodiment, in order to promote the surface nitridation of the SiNx film 22, the nitrogen plasma treatment was performed immediately after the SiNx film 22 was formed.

After the nitrogen plasma treatment, a PSG film 28 was formed on the SiNx film 22. Using a parallel plate type normal pressure CVD apparatus of 8 batch processing type, the pressure is normal pressure and the temperature is 450
° C. The gas used was 100 scc of SiH ₄
m, 0.05% PH ₃ (phosphine) 300 scc
m and O ₂ were 4000 sccm and N ₂ was 4000 sccm. The time required for forming the PSG film was 300 seconds. The thickness of the formed PSG film 28 was 350 nm, and the phosphorus component in the film was 4.5% by weight.

The S of Example 1 formed as described above
In the iNx / PSG laminated structure, the bulging part 30 of the PSG film 28 is formed as shown in FIG.
(See FIG. 3 (c)).

Embodiment 2 This embodiment is an embodiment of the second invention method.
The cross section of the substrate in each step of FIG.
Shown by (b) and (c). In the present embodiment, first, the SiNx film 22 was formed on the reflow oxide film 20 under the same film forming conditions except for the deposition time, using the same plasma CVD apparatus as in the first embodiment. At this time, as shown in FIG. 1A, the silicon hydride compound particles 24 adhere to the reflow oxide film 20 at the initial stage of the formation of the SiNx film 22, and the SiNx film 22 It is assumed that the formation is completed. However, unlike the first embodiment, the deposition time is set to 100 to make the thickness of the SiNx film 22 50 nm.
Seconds. Note that the hydrogen concentration of the SiNx film 22 was determined in Example 1.
Was the same as

Next, a rapid thermal nitridation treatment was performed on the surface of the SiNx film 22 using a single-wafer lamp heating type nitriding annealing apparatus. The pressure is 1400m, slightly higher than normal pressure
Bar and the processing temperature were 550 ° C. The kind and flow rate of the gas used were 400 sccm for NH ₃ and 100 for N _2.
It was 0 sccm. Processing time was 30 seconds. Thereby, the SiNx film 22 becomes, as shown in FIG.
Only the surface is nitrided to form a nitrided layer 26, SiNx
The composition of the components inside the film did not change.

After the rapid thermal nitridation, a PSG film 28 was formed on the SiNx film 22 in the same manner as in Example 1 using an atmospheric pressure CVD apparatus. However, the forming time was slightly longer than that of the first embodiment and was 275 seconds, and the thickness of the formed PSG film 28 was 400 nm, which was thicker than that of the first embodiment.

The S of Example 2 formed as described above
In the iNx / PSG laminated structure, the bulging part 30 of the PSG film 28 is formed as shown in FIG.
(See FIG. 3 (c)).

Embodiment 3 This embodiment is an embodiment of the third invention method.
FIGS. 9A, 9B, and 9C are cross-sectional views of the substrate in each step of the method for forming a laminated structure in Example 3. FIGS. In this embodiment, first, as in the first embodiment, the reflow oxide film 40
An SiNx film 42 is formed thereon. At this time, as shown in FIG. 2A, silicon hydride compound particles 44 adhere to the reflow oxide film 40 at the initial stage of the formation of the SiNx film 42, and the SiNx film 42 It is assumed that the formation is completed. The thickness and the hydrogen concentration of the SiNx film 42 were the same as in Example 1.

Next, using a sulfuric acid / hydrogen peroxide cleaning apparatus, the SiN
The surface of the x film 42 was subjected to a sulfuric acid / hydrogen peroxide cleaning treatment at a treatment temperature of 80 ° C. for 300 seconds. Sulfuric acid peroxide had a volume ratio of sulfuric acid to hydrogen peroxide solution of 15: 1. By this process, silicon hydride compound particles are removed as shown in FIG.
Remained.

After the sulfuric acid / hydrogen peroxide cleaning treatment, the SiNx film 4 was formed using the same atmospheric pressure CVD apparatus as in Example 1 under the same film forming conditions.
A PSG film 48 was formed on 2. The thickness of the PSG film 48,
The phosphorus concentration was the same as in Example 1.

The S of Example 3 formed as described above
In the iNx / PSG laminated structure, no bulge is formed on the PSG film 48, and rather a shallow recess 50 that does not affect the formation of the aluminum wiring layer is formed as shown in FIG. 2C. That was confirmed.

Although the present invention has been described based on the preferred embodiments, the method of forming the present invention is not limited only to the configuration of the above-described embodiments. Forming methods in which various modifications and changes have been made from the configuration of the above embodiment are also included in the scope of the present invention.

[0031]

According to the present invention, when forming a SiNx / PSG laminated structure, any one of nitrogen plasma treatment, thermal nitridation treatment, and etching / oxidation treatment by cleaning is performed on the surface of the SiNx film. In addition, when the PSG film is formed, it is possible to prevent the PSG film from locally growing at a high speed by economic means. As a result, it is possible to prevent the occurrence of a protruding shape defect on the interlayer film without changing the device structure and maintaining the conventional procedure for forming the SiNx / PSG laminated structure. In addition, the flattening of the aluminum wiring layer can be improved, and the fluctuation of the wire diameter can be prevented, so that the product yield and the product reliability can be improved.
Further, since the method of the present invention can be carried out by only slightly changing the manufacturing process, there is almost no increase in cost associated with the implementation of the method of the present invention.

[Brief description of the drawings]

FIGS. 1A, 1B, and 1C are cross-sectional views of a substrate in each step of Embodiments 1 and 2 of a method for forming a laminated structure according to the present invention.

FIGS. 2A, 2B, and 2C are cross-sectional views of a substrate in each step of a third embodiment of the method of forming a laminated structure according to the present invention.

3 (a), 3 (b) and 3 (c) are cross-sectional views of a substrate in each step of a conventional laminated structure forming method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 12 silicon hydride compound particles 14 reflow oxide film 16 SiNx film 18 PSG film 19 bulging portion 20 reflow oxide film 22 SiNx film 24 silicon hydride compound particles 26 nitride layer 28 PSG film (phosphorus silicon glass film) 30 bulging portion 40 reflow oxide film 42 SiNx film 44 Silicon hydride compound particles 46 Depression 48 PSG film 50 Depression

Claims (4)

(57) [Claims] A step of forming a SiNx film by a plasma CVD method and a step of forming a PSG film, wherein a SiNx film and a PSG film are sequentially formed on a substrate to form a SiNx film.
In the method for forming an x / PSG laminated structure, a step of nitriding the surface of the SiNx film is provided after the step of forming the SiNx film and before the step of forming the PSG film. A method for forming a laminated structure. 2. The step of nitriding the surface of the SiNx film,
2. The SiNx / PSG multilayer structure according to claim 1, wherein the surface of the SiNx film is nitrided by performing a nitrogen plasma treatment or an ammonia plasma treatment at a temperature lower than the deposition temperature of the SiNx film by 50 to 150 [deg.] C. Method. A step of forming a SiNx film by a plasma CVD method and a step of forming a PSG film, wherein a SiNx film and a PSG film are sequentially formed on a substrate to form a SiNx film.
In the method of forming the x / PSG laminated structure, in the step of forming the SiNx film, the thickness of the SiNx film is set to 1
0 nm to 70 nm range, then 700 ° C
A method for forming a SiNx / PSG laminated structure, comprising a step of thermally nitriding the surface of a SiNx film by a nitrogen annealing method or an ammonia annealing method at the following temperature. 4. A step of forming a SiNx film by a plasma CVD method and a step of forming a PSG film, wherein a SiNx film and a PSG film are sequentially formed on a substrate to form a SiNx film.
The method for forming an x / PSG laminated structure includes a step of performing a surface etching and a surface oxidation by cleaning the SiNx film with a cleaning liquid before the step of forming the PSG film, following the step of forming the SiNx film. A method for forming a SiNx / PSG laminated structure, characterized in that: