JPH0338031A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce the difference of film thickness of a tungsten layer by forming a tungsten wiring by a selective CVD-tungsten method constituted of two stages. CONSTITUTION:A silicon substrate 8 has an element on the surface, which element is previously formed of an tungsten based layer 2B and layers 3, 4 formed of N<+> Si and/or P<+> Si; an insulating layer 5 is formed on the substrate; by etching the insulating layer 5, a contact hole is formed, which reaches the tungsten based layer 2B and the layers 3, 4 of N<+> Si and/or P<+> Si. A tungsten wiring is formed in the contact hole by selective CVD-tungsten method constituted of two stages. The first stage is performed under the following conditions; the flow rate ratio of WF6 and SiH4 is so set that an alpha crystal tungsten layer 7 is formed on all layers and the growth speed is constant. The second stage is performed at the flow rate ratio lower than the first stage. Thereby tungsten can be deposited at nearly equal growth speeds in the contact holes of different base material, and the growth of unstable beta crystal tungsten can be surely restrained.

Description

[Detailed description of the invention] (b) Industrial application fields The present invention relates to a method for manufacturing a semiconductor device.

More specifically, the present invention relates to a method of forming an electrically conductive portion.

(b) Conventional technology In recent years, with the miniaturization of semiconductor devices, the diameter of contact holes has also become smaller, and the ratio of the depth to diameter of contact holes (aspect ratio)
are becoming larger and larger, and it is becoming difficult to coat the inside of the contact hole with the wiring material using the normal thin film forming method using sputtering. Conventionally, a chemical vapor deposition method (hereinafter referred to as CVD method) of a high melting point metal such as tungsten has been used to solve this problem. Tungsten has a so-called selective growth feature in which it does not grow on insulating films but only on Si, silicide, and metals by appropriately selecting conditions when forming by the CVD method, and this property can be used to By growing tungsten in the contact hole, the contact hole is buried, the aspect ratio is reduced, and the wiring layer is planarized.

(c) Selection of the problem to be solved by the invention CVD-Tungsten
A tungsten layer is formed by reduction with 4, but its growth rate largely depends on the flow rate ratio of WF and SiH+, and the growth rate in the initial process differs depending on the underlying material. When the film is formed under conventional conditions, the initial growth rate is tungsten silicide >N'-S i > P”
−S i increases in order. Differences in growth rate due to differences in the underlying material that occur during the initial growth process have the drawback of causing differences in the thickness of the resulting tungsten film.

The difference in initial growth rate due to this difference in substrate is WF, 5
As the flow rate ratio of iHa is increased, the problem is solved, but on the other hand, the problem arises that the growth rate decreases and the throughput decreases. Moreover, this selective CVD-tungsten method can be applied to tungsten silicide, N'-St and P''-Si.
, and the depth of the tungsten silicide contact is N''-St and p''-s.
When applied to filling contact holes in highly integrated devices such as semiconductor memories that are shallower than the t-contact depth, the thickness of the grown film on the tungsten silicide layer, ? +<N”-
The deeper N''-Si and P because it is larger than the film thickness grown on the Si and P'-Si layers.

Since the tungsten layer formed at the contact portion on Si is thinner than the film on the tungsten silicide, a problem arises in that the aspect ratio cannot be reduced sufficiently.

This invention was made in view of the above problems, and
Tungsten-based layer and N''-Si and/or P''-Si
The purpose of this invention is to reduce the difference in the thickness of a tungsten layer grown by a selective CVD (tungsten) method on a base layer containing a mixture of layers.

(d) Means for solving the problem The inventor has developed a method for selecting C using various different base materials.
After intensive research on the growth behavior of a tungsten layer using the VD-tungsten method, we found that the flow rates of W F s and Si H4 were adjusted to 30 s under the specified range of temperature, pressure, etc.
When ccsSl is 7 sccm, the difference in the thickness of the grown film on the tungsten silicide layer and the P”-Si layer is approximately 0.15μ.
m, and by increasing only the SiH flow rate, WF, and S
iH+flow and 30 sec.

18seca and when the SiH4 flow rate ratio was increased, abnormally fast growth of unstable β-crystal W was observed only on tungsten silicide, and the thickness of the tungsten grown between the N''-5i layer and the P''-Si layer was The difference also increased. On the contrary, S
i The dependence of the grown film thickness on the substrate decreases as the H4 flow rate decreases, and the flow rate of WF and SiH is reduced to 305 ccrn115.
The fact that when sccm is set, the difference becomes zero,
Furthermore, the inventors discovered the fact that lowering the S r H4 flow rate makes it difficult to form unstable β-crystalline tungsten, leading to the present invention.

According to this invention, a tungsten-based layer and an N'-S
An insulating layer is formed on a silicon substrate having an element formed with a layer of i and/or P''-Si on its surface, and this insulating layer is etched to form a layer of tungsten and N''-S.
A contact hole leading to the i and/or P"-Si layer is formed, and the flow rate ratio of WF and S r Ha is adjusted in this contact hole so that an α-crystalline tungsten layer is formed on all the layers and the growth rate is high. Selective CVD consisting of a first stage performed under constant conditions and a second stage performed at a flow rate lower than the first stage.
- A method of manufacturing a semiconductor device is provided, which is characterized in that tungsten wiring is formed by a tungsten method.

This tungsten wiring is connected to the tungsten-based layer and the N
A tungsten layer is formed by selective CVD-tungsten method into the contact hole leading to these layers, which is for inputting or outputting a signal to an element formed with "-Si and/or P"-5i layer. can be formed by laminating them.

This contact hole is made in advance with a tungsten-based layer and an N”-
An insulating layer is formed on the element formed with the Si and/or P"-Si layer, and this insulating layer is etched to form the tungsten-based layer and the N'-Si and/or P"-Si layer. It can be fabricated by forming holes leading to elements formed by layers.

This selective CVD-tungsten method uses WFs and SiH,
Tungsten is deposited in the contact hole in the first step, which is carried out at a flow rate ratio of 1, under conditions such that an α-crystalline tungsten layer is formed on all layers and the growth rate is constant, and in the second step, which is carried out at a flow rate lower than the first step. This can be done by laminating layers.

The conditions of the first step selective CVD-tungsten method are that on the base of each contact hole the base is a tungsten-based layer and a layer of N'-Si and/or P''-Si.
For depositing a base layer of tungsten layer made of similar thin alpha crystals, a short deposition time can be adopted with a flow rate ratio of WF and 5iHa in the range of 30/15 to 30/14. .

If this flow rate ratio is less than 30/18, the growth of unstable β crystal tungsten cannot be suppressed. In addition, when the flow rate ratio is 30/17 to 30/16, the deposition rate of the tungsten layer that grows in the contact hole with a tungsten layer as the base is lower than that in the contact hole with the N"-Si and P"-Si layers as the base. This is not preferable because the deposition rate is higher than that of the tungsten layer that grows, the base of the tungsten layer becomes thicker, and the difference in depth between the undeposited portions of each contact hole becomes large. The selective CVD-tungsten process conditions for the second stage were similar to those deposited in the first stage.
This is for efficiently depositing a tungsten layer in each contact hole having a tungsten layer underlying layer made of crystal, and the flow rate ratio of WF and S I H4 is set to the first
It is suitable to do it lower than the stage, usually 3G/1
It is preferably 8 or less, particularly 3G/18 to 30/19, and can increase the deposition rate of the tungsten layer.

In this invention, specifically, a semiconductor device can be manufactured by the following method. A tungsten-based layer and NoSi and/or P”-S are used as materials for semiconductor devices.
A silicon substrate having an element consisting of i layers is used.

Examples of this tungsten-based layer include tungsten silicide, which forms the surface of the gate electrode of PET.

Examples of the N''-Si and P''-Si layers include the source and drain of an FET.

Next, on the silicon substrate, usually l, θ ~ 1.5μ
An insulating layer having a thickness of m is formed. This insulating layer can be formed using, for example, an oxide film or the like by, for example, a CVD method. Next, this insulating layer is etched by a method such as photolithography, so that the tungsten-based layer and the N''-Si and/or P''-
A contact hole is formed leading to the Si layer. These contact holes usually have a diameter of 07-0.8 μm, a depth of 1, 0
A material having a shape of ~1.5μ can be used. Next, the substrate with these contact holes formed is subjected to CV
WF and Si
H, flow rate ratio of 30/15 or more (usually 30/15 to 3G/
As step 14), a base layer of α-crystalline tungsten with a thickness of usually 0.05 to 0.1 Alm is deposited in each contact hole, typically for 30 to 40 seconds. Next, W
A second stage process is performed with the flow rate ratio of F and S i Ha smaller than the first stage (usually 3G/18 to 30/19) for usually 80 to 90 seconds, and a tungsten layer is laminated in the contact hole. tungsten wiring is formed. Furthermore, wiring, elements, etc. can be formed on this to manufacture a semiconductor device.

(e) The selective CVD-tungsten process, which is performed with the flow rate ratio of WF and SiH+ in a specific range, forms a base consisting of a tungsten layer and a layer of N''-Si and/or P'-5t. A tungsten layer base having a similar thickness is deposited in the contact hole to suppress the deposition of β crystals.

(f) 5th example Embodiments of the invention will be described with reference to the drawings.

Example 1 A semiconductor manufacturing method using the selective CVD-tungsten method for embedding contacts in an SRAM will be described. As shown in FIG. 1, on a silicon substrate 8, there is a gate electrode 2 consisting of a stacked structure of an element isolation region 11, a tungsten silicide layer 2B, and a polysilicon layer 2A, an N"-Si layer 3, and a P"
- After forming the element consisting of the Si layer 4, an interlayer insulating film 5 of an oxide film is deposited by the CVD method, and this interlayer insulating film 5 is etched by the photolithography method.
Contact holes are formed on the layer 3, the P"-St layer and on the tungsten silicide layer 2B of the gate electrode 2. At this time, the contact holes each have a diameter of 1.0 μm and a depth of 1.5 μm. , 1.5 μm and 1.0 μm.

Next, as shown in FIG. 2, the film formation temperature was 300°C and the pressure was 0.
The tungsten layer was grown for 30 seconds until the contact surface was covered with tungsten at 1 Torr and the flow rates of WFs and S i 84 were 30 secI11 and 15 secIm, respectively (first stage), and the S i H4 flow rate was subsequently increased to increase the throughput. , WF, and 5iHa flow rates of 30 scc and 18 sec, respectively.
The growth rate was increased by setting +a, and the second stage growth was performed for 90 seconds.

As a result, as shown in FIG. 3, a tungsten layer having a similar thickness is formed in the contact hole with the tungsten silicide layer 2B, the N"-Si layer 3, and the P+-Si layer 4 as the base, and the tungsten silicide layer β on 2B
Generation of crystalline tungsten was reliably suppressed.

Comparative Example 1 In Example 1, the flow rate of SiH + was changed to 18 seconds instead of 15 seconds, and tungsten wiring was formed in the contact hole using the selective CVD-tungsten method in the same manner as in Example 1 except for this.

As a result, as shown in FIG. 4, an unstable β-crystalline tungsten layer 6 grew in the contact hole with the tungsten silicide layer 2B of the gate electrode 2 as the base.

Comparative Example 2 Example 2 Here, the flow rate of SiH+ was changed to 17 sec- instead of 15 sec-11, and tungsten wiring was formed in the contact hole using the selective CVD-tungsten method in the same manner as in Example 1. Ta.

As a result, as shown in Fig. 5, in addition to the difference in depth of the contact hole of 0.5μ-, the thickness of the tungsten layer grown in the contact hole with the P"-Si layer as the base is the same as that of the tungsten silicate 2B as the base. Since the contact hole is thinner than that of the contact hole, a step difference of 0.15 μm was generated, and sufficient flattening could not be achieved.

(G) Effects of the Invention According to this invention, tungsten can be deposited at the same growth rate in contact holes made of different underlying materials, and the growth of unstable β-crystal tungsten can be reliably suppressed, resulting in improved reliability. High tungsten wiring can be created.

[Brief explanation of drawings]

1 to 3 are explanatory diagrams of the manufacturing process of a semiconductor device manufactured in an embodiment of the present invention, and FIGS. 4 to 5 are explanatory diagrams of the manufacturing process of a conventional semiconductor device. 1...Element isolation region, 2...Gate electrode, 2A...Polysilicon layer, 2B...Tungsten silicide layer, 3...
...N''-Si layer, 4...P''-Si layer, 5...Interlayer insulating film, 6...β crystal tungsten layer, 7...
...Tungsten layer, 8...Nlicon substrate. Filled Senshin Flute Stomach

Claims (1)

[Claims] 1. Tungsten-based layer and N^+-Si and/or P^
An insulating layer is formed on a silicon substrate having an element formed with a layer of +-Si on its surface, and this insulating layer is etched to separate the tungsten-based layer and N^-Si and/or P^+. - A first step in which a contact hole leading to the Si layer is formed, and the flow rate ratio of WF_8 and SiH_4 is applied to the contact hole under conditions such that an α-crystalline tungsten layer is formed on all layers and the growth rate is constant. A method for manufacturing a semiconductor device, characterized in that tungsten wiring is formed by a selective CVD-tungsten method comprising a second stage performed at a lower flow rate than the first stage.