JPH11121454A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a semiconductor device, by which conductive material is buried in a contact hole, plug loss is suppressed without leaving the conductive material outside of the contact hole and without lowering its productivity to thereby form a highly-reliable buried wiring layer. SOLUTION: An insulating film 20 is formed on a wiring layer formed on a substrate 10, and a contact hole for exposure of the wiring layer is made in the insulating film 20. Next, a conductive layer 30 is formed at a first film deposition rate in the contact hole and on the insulating film 20, the layer 30 being formed at a film deposition rate higher than the first rate. Thereafter, the conductive layer 30 outside of the hole is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device having a contact hole.

[0002]

2. Description of the Related Art As the integration and performance of semiconductor devices have advanced as seen in recent VLSIs and the like, fine processing of semiconductor devices has become an essential condition. In order to finely process a semiconductor device, for example, it is necessary to finely process a wiring portion while reducing a gate width of a gate electrode of a transistor and an area occupied by a capacitor in a DRAM or the like.

For example, in a contact hole connecting a lower wiring and an upper wiring, the diameter of the hole is reduced due to fine processing, while the interlayer insulating film between the lower wiring and the upper wiring tends to be thicker. The aspect ratio of holes is increasing. In order to connect the lower-layer wiring and the upper-layer wiring, a method called a polyplug process in which polysilicon containing a conductive impurity such as phosphorus is buried in the contact hole is well known.

A method of embedding polysilicon containing a conductive impurity in a contact hole in the above conventional method will be described. FIG. 4 is a sectional view of a semiconductor device formed by this method. Silicon semiconductor substrate 10
A semiconductor element such as a transistor or a diffusion layer (not shown) is formed thereon, and an upper layer of the semiconductor substrate 10 is covered with an insulating film 20 made of, for example, silicon oxide. The insulating film 20 has a contact hole C reaching the semiconductor substrate 10.
H is opened, and a buried wiring layer 30a made of polysilicon containing a conductive impurity such as phosphorus is buried in the contact hole.

Hereinafter, a method for manufacturing the above semiconductor device will be described. First, as shown in FIG. 5A, after semiconductor elements such as transistors and diffusion layers (not shown) are formed on a silicon semiconductor substrate 10, these elements are covered and, for example, silicon oxide is formed by atmospheric pressure CVD or the like. Deposited by reflow, etchback, or CMP (Chem
The insulating film 20 is formed by flattening using an ical mechanical polishing method.

[0006] Next, as shown in FIG.
A resist film R having an opening pattern of a contact hole is formed as an upper layer by photolithography. Next, using the resist film R as a mask, etching such as RIE (reactive ion etching) is performed to form the insulating film 2.
0, and a contact hole CH reaching the semiconductor substrate 10 is opened.

Next, as shown in FIG. 5C, for example, low pressure chemical vapor deposition (Low Pressure Chemical Vapor Depo).
A conductive layer 30 is formed by burying polysilicon containing a conductive impurity such as phosphorus by burying the contact hole CH by an LPCVD method.

Next, the entire surface is etched back by etching such as RIE to remove the conductive layer 30 outside the contact hole CH and form a buried wiring layer 30a in the contact hole CH, as shown in FIG. To semiconductor devices. Subsequent steps include the embedded wiring layer 30a.
A desired semiconductor device is formed, for example, by forming an upper wiring connected to the semiconductor device.

[0009]

However, in the method of embedding polysilicon containing a conductive impurity in the contact hole in the above-mentioned conventional method, the opening diameter of the contact hole is reduced and the thickness of the insulating film is increased. As the aspect ratio of the contact hole increases, it becomes more difficult to fill the hole with a conductive material. For example, as shown in FIG. The concave portion H occurs. Due to the recess H, the plug loss PL of the buried wiring layer 30a formed by removing the conductive layer 30 outside the contact hole CH in the next step increases. When the plug loss PL is large, there arises a problem that the reliability of the wiring is greatly reduced and the flattening of the upper layer is adversely affected. In order to suppress the plug loss, if the amount of over-etching when removing the conductive layer 30 outside the contact hole CH is reduced, a conductive layer which may cause a short circuit outside the contact hole due to a problem of uniformity of etching. There is a problem that the material is left.

There is a trade-off between the filling characteristics of polysilicon as described above and the deposition rate of the polysilicon layer, and the plug loss PL can be suppressed by reducing the deposition rate of the conductive layer 30. . In a process requiring burying characteristics, such as the process of forming the buried wiring layer, the film forming speed is set low. However, in order to suppress the above-described plug loss PL, it is necessary to deposit a conductive layer having a certain thickness even after completion of filling with a conductive material inside the contact hole. Since the layers are also deposited at a low deposition rate, the time for the step of filling the inside of the contact hole with polysilicon has been long, resulting in low productivity.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. Accordingly, an object of the present invention is to provide a method of manufacturing a semiconductor device in which a conductive material is buried in a contact hole. It is an object of the present invention to provide a method of manufacturing a semiconductor device capable of forming a highly reliable embedded wiring layer by suppressing plug loss without leaving a conductive material or reducing productivity.

[0012]

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention comprises the steps of: forming an insulating film on a wiring layer formed on a substrate; A step of opening a contact hole for exposing a wiring layer, a step of forming a conductive layer in the contact hole and on the insulating film at a first film forming rate, and a step of forming a second layer faster than the first film forming rate A step of increasing the thickness of the conductive layer at a film forming speed, and a step of removing the conductive layer outside the contact hole.

In the above-described method for manufacturing a semiconductor device, an insulating film is formed on a wiring layer formed on a substrate, and a contact hole for exposing the wiring layer is formed in the insulating film. Next, a conductive layer is formed at a first deposition rate in the contact hole and on the insulating film, and the thickness of the conductive layer is increased at a second deposition rate higher than the first deposition rate. After that, the conductive layer outside the contact hole is removed.

According to the above-described method for manufacturing a semiconductor device, after opening the contact hole, a conductive layer is first formed by burying a conductive material in the contact hole at a slow first deposition rate. Since the thickness of the conductive layer is increased at a second film forming speed higher than the film forming speed of 1, the film forming speed is reduced at the stage where the burying property is required so that the concave portion of the conductive layer above the contact hole is reduced. The film formation speed is increased at the point where the process moves to a stage where the embedding property is not required, so that the total time required for forming the conductive layer can be reduced. In addition, after the filling of the inside of the contact hole with the conductive material is completed, it is possible to deposit a conductive layer having a certain thickness without lowering the productivity, thereby suppressing plug loss and reducing the amount of over etching. By performing the etch back, it is possible to prevent a conductive layer material that may cause a short circuit from being left outside the contact hole.

Preferably, the method of manufacturing a semiconductor device includes a step of forming a conductive layer at the first film forming rate and a step of thickening the conductive layer at the second film forming rate.
It is performed continuously in the same film forming apparatus. Thus, the productivity can be further improved, and a film formation process in which the speed is easily controlled by changing the film formation conditions or the like can be performed.

In the method of manufacturing a semiconductor device, preferably, the step of forming the conductive layer at the first film forming rate and the step of thickening the conductive layer at the second film forming rate are performed. Then, a conductive layer made of polysilicon is formed and the thickness is increased. Preferably, in the step of forming a conductive layer at the first film forming rate and the step of thickening the conductive layer at the second film forming rate, the step of forming the conductive layer by a reduced pressure chemical vapor deposition method. A conductive layer is formed and the thickness is increased. As a conductive material, polysilicon is formed by low pressure chemical vapor deposition (Low Pressure).
The film forming speed in the chemical vapor deposition (LPCVD) method can control the film forming speed.

Preferably, in the method of manufacturing a semiconductor device, the step of forming the conductive layer at the first film forming rate and the step of thickening the conductive layer at the second film forming rate are performed. The first film forming rate and the second film forming rate are controlled by controlling the pressure in a film forming apparatus in the low pressure chemical vapor deposition method. It is possible to easily control the film forming rate by controlling the pressure in the film forming apparatus among the film forming conditions in the low pressure chemical vapor deposition method, and the pressure ranges from 10 ⁻² to 10 torr. It can be preferably controlled within.

Preferably, in the method of manufacturing a semiconductor device, the step of forming the conductive layer at the first film forming rate and the step of thickening the conductive layer at the second film forming rate are performed. The first film forming rate and the second film forming rate are controlled by controlling the film forming temperature in the low pressure chemical vapor deposition method. It is possible to easily control the film forming rate by controlling the film forming temperature among the film forming conditions in the low pressure chemical vapor deposition method. By controlling the amount of heating, the film formation temperature can be easily controlled.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

First Embodiment FIG. 1 is a sectional view of a semiconductor device according to the first embodiment .
For example, a semiconductor element such as a transistor or a diffusion layer (not shown) is formed on a silicon semiconductor substrate 10, and an upper layer of the semiconductor substrate 10 is covered with an insulating film 20 made of, for example, silicon oxide. The semiconductor substrate 1 is formed on the insulating film 20.
A contact hole CH reaching 0 is opened, and a buried wiring layer 30a made of polysilicon containing a conductive impurity such as phosphorus is buried in the contact hole CH.

Such a semiconductor device is a semiconductor device having a highly reliable contact bonding with an embedded wiring layer in which plug loss is suppressed.

Hereinafter, a method for manufacturing the above semiconductor device will be described. First, as shown in FIG. 2A, after semiconductor elements such as transistors and diffusion layers (not shown) are formed on a silicon semiconductor substrate 10, these elements are covered and, for example, silicon oxide is formed by atmospheric pressure CVD or the like. Deposited by reflow, etchback, or CMP (Chem
The insulating film 20 is formed by flattening using an ical mechanical polishing method.

Next, as shown in FIG.
A resist film R having an opening pattern of a contact hole is formed as an upper layer by photolithography. Next, using the resist film R as a mask, etching such as RIE (reactive ion etching) is performed to form the insulating film 2.
0, and a contact hole CH reaching the semiconductor substrate 10 is opened. Next, the natural oxide film at the bottom of the contact hole is removed by, for example, hydrofluoric acid wet cleaning.

Next, as shown in FIG.
PCVD (Low Pressure Chemical Vapor Deposition)
Polysilicon containing a conductive impurity such as phosphorus is buried in the contact hole CH and deposited over the entire surface by a method to form the conductive layer 30. The CVD conditions at this time include, for example, (film formation temperature: 550 ° C., film formation pressure: 0.5 T
orr, reaction gas and flow rate: SiH ₄ / PH ₃ (1%, based on N ₂ ) =
1000/50 sccm, film formation rate: 2 nm / min).

Next, as shown in FIG.
In the PCVD apparatus, the LP is continuously formed at a higher film forming rate than the LPCVD method without taking the wafer out of the apparatus.
The polysilicon is deposited by the CVD method, and the conductive layer 30 is deposited.
Is thickened. As the CVD conditions at this time, the above C
The film forming speed is increased by changing only the film forming pressure from the VD condition, for example, (film forming temperature: 550 ° C., film forming pressure: 3 to
4 Torr, reaction gas and flow rate: SiH ₄ / PH ₃ (1%, N ₂ base) = 1000/50 sccm, deposition rate: 10 nm / min). The control of the deposition pressure can be performed instantaneously and accurately.
It is possible to easily control the film forming speed.

Next, the entire surface is etched back by etching such as RIE, the conductive layer 30 outside the contact hole CH is removed, and a buried wiring layer 30a is formed in the contact hole CH, as shown in FIG. To semiconductor devices. Subsequent steps include the embedded wiring layer 30a.
A desired semiconductor device is formed, for example, by forming an upper wiring connected to the semiconductor device.

According to the method of manufacturing a semiconductor device of the present embodiment, when the burying characteristic is required, the film forming speed is reduced so that the concave portion of the conductive layer above the contact hole is reduced, and the film is formed. At the point when the process shifts to the stage where the embedding property is not required, the film formation speed can be increased, and the total time required for forming the conductive layer can be reduced. Also,
After the filling of the contact hole with the conductive material is completed, it is possible to deposit a conductive layer having a certain thickness without lowering the productivity, thereby suppressing plug loss and providing a sufficient amount of over-etching. By performing the etch-back, a conductive layer material that may cause a short circuit outside the contact hole can be prevented from being left.

Second Embodiment A semiconductor device according to the second embodiment is substantially the same as the first embodiment, and a cross-sectional view thereof is shown in FIG. For example, a semiconductor element such as a transistor or a diffusion layer (not shown) is formed on a silicon semiconductor substrate 10, and an upper layer of the semiconductor substrate 10 is covered with an insulating film 20 made of, for example, silicon oxide. A contact hole CH reaching the semiconductor substrate 10 is opened in the insulating film 20, and a buried wiring layer 30a made of polysilicon containing a conductive impurity such as phosphorus is buried in the contact hole.

Such a semiconductor device is a semiconductor device having a highly reliable contact bonding by an embedded wiring layer in which plug loss is suppressed.

Hereinafter, a method of manufacturing the above semiconductor device will be described. First, as shown in FIG. 2A, after semiconductor elements such as transistors and diffusion layers (not shown) are formed on a silicon semiconductor substrate 10, these elements are covered and, for example, silicon oxide is formed by atmospheric pressure CVD or the like. The insulating film 20 is formed by flattening by reflow, etch back, CMP, or the like.

Next, as shown in FIG.
A resist film R having an opening pattern of a contact hole is formed as an upper layer by photolithography. Next, etching such as RIE is performed by using the resist film R as a mask to penetrate the insulating film 20 so that the semiconductor substrate 10
Is opened. Next, the natural oxide film at the bottom of the contact hole is removed by, for example, hydrofluoric acid wet cleaning.

Next, as shown in FIG.
Polysilicon containing conductive impurities such as phosphorus is buried in the contact holes CH and deposited over the entire surface by PCVD to form the conductive layer 30. The CVD conditions at this time include, for example, (film formation temperature: 550 ° C., film formation pressure:
0.5 Torr, reaction gas and flow rate: SiH ₄ / PH ₃ (1%, N ₂
(Base) = 1000/50 sccm, deposition rate: 2 nm / min). Further, by using a lamp heating type CVD apparatus, the film formation temperature can be controlled.

Next, as shown in FIG.
In the PCVD apparatus, the LP is continuously formed at a higher film forming rate than the LPCVD method without taking the wafer out of the apparatus.
The polysilicon is deposited by the CVD method, and the conductive layer 30 is deposited.
Is thickened. As the CVD conditions at this time, the above C
By changing only the film forming temperature from the VD condition, the film forming speed is increased, for example, (film forming temperature: 650 ° C., film forming pressure: 0.
5 Torr, reaction gas and flow rate: SiH ₄ / PH ₃ (1%, N ₂ base) = 1000/50 sccm, deposition rate: 10 nm / min). When a lamp heating type CVD apparatus is used, by controlling the amount of heating of the lamp, the film forming temperature can be accurately controlled in a short time, and the film forming speed can be easily controlled. It is possible.

Next, the entire surface is etched back by etching such as RIE to remove the conductive layer 30 outside the contact hole CH and form a buried wiring layer 30a in the contact hole CH, as shown in FIG. To semiconductor devices. Subsequent steps include the embedded wiring layer 30a.
A desired semiconductor device is formed, for example, by forming an upper wiring connected to the semiconductor device.

According to the method of manufacturing a semiconductor device of the present embodiment, as in the first embodiment, in the method of manufacturing a semiconductor device in which a conductive material is embedded in a contact hole, the conductive material outside the contact hole is formed. The plug loss can be suppressed and a highly reliable embedded wiring layer can be formed without leaving any material or reducing productivity.

The present invention can be applied to any semiconductor device having a contact hole, such as a MOS transistor semiconductor device, a bipolar semiconductor device, or an A / D converter. It is possible to provide fine and highly reliable bonding to a semiconductor device whose device has been miniaturized and miniaturized without lowering productivity.

The present invention is not limited to the above embodiment. For example, the lower wiring connected to the buried wiring layer by a contact is not particularly limited, such as a diffusion layer in a semiconductor substrate, a lower wiring formed on the substrate (for example, a gate electrode of a transistor), or the like. The conductive material used for the buried wiring layer may be any material other than polysilicon, as long as the material can control the burying characteristics depending on the deposition rate. The conductive impurities used in the polysilicon are n
It may be either a p-type or a p-type. Also, by forming a sidewall on the inner wall of the contact hole as a layer serving as a mask for opening the contact hole and narrowing the diameter of the contact hole and opening it, it is suitable for high integration and high performance by a fine contact hole. Semiconductor device. Further, the insulating film may have a multilayer structure. In particular, when a gate electrode of a transistor is formed on a semiconductor substrate and a connection is made to a source / drain diffusion layer of the transistor formed in the substrate by a contact, the gate electrode is covered with an offset insulating film or the like. And the insulating film is made of, for example, silicon oxide,
By providing an etching stopper layer of, for example, silicon nitride between the insulating film and the offset insulating film covering the gate electrode, the opening of the contact hole is once stopped at the surface of the etching stopper layer, and then the source / drain in the substrate is newly formed. It is also possible to combine a self-aligned contact method of opening a contact hole reaching the diffusion layer. In addition, various changes can be made without departing from the spirit of the present invention.

[0038]

According to the present invention, in a method of manufacturing a semiconductor device in which a conductive material is buried in a contact hole, plug loss is suppressed without leaving a conductive material outside the contact hole or reducing productivity. As a result, a highly reliable embedded wiring layer can be formed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a semiconductor device according to the present invention.

FIGS. 2A and 2B are cross-sectional views illustrating a manufacturing process of a method for manufacturing a semiconductor device according to the present invention, in which FIG. 2A illustrates up to a step of forming an insulating film, and FIG.

FIG. 3 is a sectional view showing a step subsequent to that of FIG. 2;
(D) shows up to the step of forming the conductive layer, and (b) shows the step up to the step of thickening the conductive layer.

FIG. 4 is a sectional view of a conventional semiconductor device.

5A to 5C are cross-sectional views illustrating a manufacturing process of a conventional method for manufacturing a semiconductor device. FIG. 5A is a diagram illustrating an insulating film forming process, FIG. 5B is a diagram illustrating a contact hole opening process, and FIG.
Indicates the steps up to the step of forming the conductive layer.

[Explanation of symbols]

10 semiconductor substrate, 20 insulating film, 30 conductive layer, 3
0a: embedded wiring layer, R: resist film, CH: contact hole, H: concave portion, PL: plug loss.

Claims (8)

[Claims] A step of forming an insulating film on a wiring layer formed on a substrate; a step of opening a contact hole exposing the wiring layer in the insulating film; and a step in the contact hole and on the insulating film. Forming a conductive layer at a first film forming rate; thickening the conductive layer at a second film forming rate higher than the first film forming rate; Removing the conductive layer. 2. The method according to claim 1, wherein the step of forming the conductive layer at the first film forming rate and the step of thickening the conductive layer at the second film forming rate are performed continuously in the same film forming apparatus. Item 2. A method for manufacturing a semiconductor device according to Item 1. 3. The step of forming a conductive layer at the first film forming rate and the step of thickening the conductive layer at the second film forming rate include forming a conductive layer made of polysilicon, The method for manufacturing a semiconductor device according to claim 1, wherein the thickness is increased. 4. The step of forming a conductive layer at the first film forming rate and the step of thickening the conductive layer at the second film forming rate are performed by a reduced pressure chemical vapor deposition method. 2. The method for manufacturing a semiconductor device according to claim 1, wherein a layer is formed and the film is thickened. 5. The step of forming a conductive layer at the first film forming rate and the step of thickening the conductive layer at the second film forming rate are performed in the low pressure chemical vapor deposition method. The method of manufacturing a semiconductor device according to claim 4, wherein the first film forming speed and the second film forming speed are controlled by controlling a pressure in a film device. 6. The step of forming a conductive layer at the first film-forming rate and the step of thickening the conductive layer at the second film-forming rate. 6. The method of manufacturing a semiconductor device according to claim 5, wherein the first film forming speed and the second film forming speed are controlled by controlling a pressure in a film device within a range of 10 ^-2 to 10 torr. 7. The step of forming a conductive layer at the first film-forming rate and the step of thickening the conductive layer at the second film-forming rate. The method of manufacturing a semiconductor device according to claim 4, wherein the first film forming speed and the second film forming speed are controlled by controlling a film temperature. 8. A lamp heating type chemical vapor deposition apparatus in the step of forming a conductive layer at the first deposition rate and the step of thickening the conductive layer at the second deposition rate. 8. A film forming temperature in the low-pressure chemical vapor deposition method is controlled by controlling a heating amount of the lamp using the method.
The manufacturing method of the semiconductor device described in the above.