JP2001127063A - Method of increasing adhesion between copper and silicon nitride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of increasing the adhesion between copper and silicon nitride. SOLUTION: First, a substrate coated with a dielectric layer is prepared. Then, a copper layer is formed on the dielectric layer and a copper phosphide intermediate layer is formed on the copper layer by a PECVD method and then a silicon nitride layer is formed on the copper phosphide intermediate layer. All the copper oxide layers appearing on the surface of the copper layer are turned into a copper phosphide intermediate layer. The copper phosphide intermediate layer has a lower resistance than a copper oxide and has an excellent property of effectively preventing the diffusion of copper into the dielectric layer surrounding copper.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated circuit, and more particularly to an invention using copper.

[0002]

2. Description of the Related Art In a current integrated circuit manufacturing process, an interconnect is usually formed of metal. The metal used must meet certain conditions: low resistance, high electromigration resistance, and high adhesion and low tension of the substrate material.

[0003] Among all metals meeting such conditions,
Aluminum is most widely used in silicon integrated circuit processing. The advantage of aluminum is its low resistance (2.
7 micro ohms / cm) and excellent adhesion to silicon dioxide layers.

As the device dimensions reach the level of deep sub-microns, the drawbacks of aluminum, such as low electromigration resistance and corrosion, become a bottleneck in the process.
That is, it is necessary to form the internal wiring by using another metal instead of aluminum.

[0005] The resistance value of copper (1.7 micro ohm / c)
m) is lower than aluminum and its ability to resist electromigration is higher than aluminum. For this reason, copper has attracted attention as a material for forming internal wiring in an integrated circuit, particularly when the critical dimension of an element has entered the deep submicron level.

However, there is a problem that copper diffuses into the surrounding dielectric layer, and particularly, copper atoms easily diffuse into the silicon dioxide layer. For this reason, it is necessary to prevent the diffusion of copper by the diffusion blocking layer to ensure that the actual contour of the copper internal wiring is equal to the predetermined contour. Generally, any diffusion blocking layer is made of PE
It is composed of a silicon nitride layer formed by a CVD method.

[0007] The use of a silicon nitride layer as a diffusion blocking layer presents two challenges that must be solved for copper applications. One is the poor adhesion between the silicon nitride layer and the copper layer, which makes it easy for silicon nitride to peel off, and the other is that copper is very susceptible to oxidation, which results in an extra process. Unless unnecessary copper oxide is eliminated, the electric resistance of the copper wiring will increase.

As can be seen from the above, in order to form internal wiring by applying copper, it was necessary to develop a method for solving the above two problems. In particular, chemical-mechanical polishing has already been widely applied to eliminate excess copper, and the lack of a proper etching process is no longer a major limitation in copper applications.

[0009] The following is a specific description of a known copper layer (including a copper thin film and a copper conductor) manufacturing process technique.

As shown in FIG. 1, a silicon nitride layer 1
0 is formed between the copper layer 11 and the first dielectric layer 12. This copper layer 11 is formed on a substrate 13 which is covered with a second dielectric layer 15 and comprises at least a FET 14. In addition, the first silicon nitride layer 10
It is used for preventing diffusion into the dielectric layer 12 and the second dielectric layer 15.

When exposed to air, especially oxygen gas, the copper layer 11
Is easily oxidized, and this oxidation reaction is thermodynamically called a spontaneous reaction (spontaneous reaction).
n). During the semiconductor manufacturing process, the wafer is continuously moved from one chamber to another, so that the wafer is exposed to the air, and as shown in FIG. The copper layer 16 is present, and the thickness of the copper oxide layer 16 is approximately 50 ° to 100 °.

The resistance value of the copper oxide layer 16 is clearly
, It is necessary to remove the copper oxide layer 16 before forming the silicon nitride layer 10 without leaving it as it is. For this reason, the manufacturing process of the integrated circuit has become more complicated.

In addition, even after the copper oxide layer 16 has been removed, the well-known process for forming the copper layer 11 has a severe problem. That is, poor adhesion between the copper layer 11 and the silicon nitride layer 10. This problem was particularly severe when the silicon nitride layer 10 was formed by PECVD. For this reason, the silicon nitride layer 10 has peeled off from the copper layer 11 and the diffusion of copper into the surrounding first dielectric layer 12 cannot be effectively prevented.

In this regard, as shown in FIGS. 1 and 2, the silicon nitride layer 10 is on the copper layer 11; however, even if the silicon nitride layer 10 is below or around the copper layer 11, The problems and drawbacks of the above still hold.

[0015]

SUMMARY OF THE INVENTION It is a primary object of the present invention to provide a method for enhancing the adhesion between copper and silicon nitride.

Another object of the present invention is to provide a method capable of reducing the electric resistance between copper and a contact.

It is yet another object of the present invention to provide a method that can effectively prevent copper from diffusing into the surrounding dielectric layer.

Yet another object of the present invention is to provide a method which can be practically used in an integrated circuit manufacturing process.

[0019]

SUMMARY OF THE INVENTION The invention of claim 1 includes providing a substrate coated with a dielectric layer, forming a copper layer on the dielectric layer, and providing a copper phosphide interlayer to the copper layer. , A silicon nitride layer on the copper phosphide intermediate layer, and at least the above steps for enhancing the adhesion between copper and silicon nitride. The invention according to claim 2, wherein the substrate has at least a plurality of structures, and the plurality of structures are located inside and on the surface of the substrate. It is a method of enhancing sex. According to a third aspect of the present invention, there is provided the method of enhancing adhesion between copper and silicon nitride according to the second aspect, wherein the structure includes at least a transistor and a contact. The invention of claim 4 is characterized in that the method of enhancing the adhesion between copper and silicon nitride further comprises the step of forming a copper phosphide intermediate layer on the copper layer and the surrounding dielectric layer. ,
According to a first aspect of the present invention, there is provided a method for enhancing adhesion between copper and silicon nitride. The invention according to claim 5 is characterized in that the copper phosphide intermediate layer is formed by a first PECVD process.
According to a first aspect of the present invention, there is provided a method for enhancing adhesion between copper and silicon nitride. The invention of claim 6, characterized by the use of free of PH ₃ gas in the second 1PECVD process, are copper and the method of adhesion enhancement of silicon nitride according to claim 5. The invention according to claim 7 is characterized in that the first PECV
The method for enhancing adhesion between copper and silicon nitride according to claim 5, wherein the reaction temperature of the process D is set to about 400 ° C. The invention according to claim 8 is characterized in that the first PEC
The method according to claim 5, wherein the reaction pressure of the VD process is about 1 Torr to 10 Torr. According to a ninth aspect of the present invention, there is provided the method for enhancing adhesion between copper and silicon nitride according to the first aspect, wherein the silicon nitride layer is formed by a second PECVD process. The invention according to claim 10, wherein a copper oxide layer is formed on the copper layer, and the copper oxide layer is present on the copper layer before the formation of the copper phosphide intermediate layer, According to a first aspect of the present invention, there is provided a method for enhancing adhesion between copper and silicon nitride. The invention of claim 11 is
11. The method of claim 10, wherein the thickness of the copper oxide layer is about 50 to 100 degrees. According to a twelfth aspect of the present invention, there is provided the method of enhancing adhesion between copper and silicon nitride according to the tenth aspect, wherein the copper oxide layer is removed by a first PECVD process. The invention of claim 13 provides the step of providing a substrate coated with a first dielectric layer and comprising at least one FET, wherein a first layer is formed on the first dielectric layer.
Forming a silicon nitride layer, forming a second dielectric layer on the first silicon nitride layer, partially forming the second dielectric layer by a lithography process and an etching process.
Removing a dielectric layer and a portion of the first silicon nitride layer to form a void on the top surface of the first dielectric layer, covering the second dielectric layer with a copper layer and filling the void with the copper layer; Removing the copper layer other than the copper layer filling the void by a chemical mechanical polishing process;
Forming over the dielectric layer and covering the remaining copper layer with the copper phosphide intermediate layer, forming a second silicon nitride layer over the copper phosphide intermediate layer; A method for forming a copper internal wiring, comprising at least the steps of forming on a silicon nitride layer. According to a fourteenth aspect of the present invention, there is provided the copper internal wiring forming method according to the thirteenth aspect, wherein the copper phosphide intermediate layer is formed by a first PECVD process. According to a fifteenth aspect of the present invention, there is provided the copper internal wiring forming method according to the fourteenth aspect, wherein a liberated PH ₃ gas is used in the first PECVD process. According to a sixteenth aspect of the present invention, there is provided the copper internal wiring forming method according to the fourteenth aspect, wherein the reaction temperature of the first PECVD process is about 400 ° C. The invention of claim 17 is characterized in that the reaction pressure of the first PECVD process is from about 1 Torr to 10 Torr.
(2) Copper internal wiring forming method described in (1). The invention according to claim 18 is characterized in that a copper oxide layer is formed on the copper layer, and the copper oxide layer is present on the copper layer before the formation of the copper phosphide intermediate layer. 13 is a method for forming a copper internal wiring. The invention according to claim 19, wherein the thickness of the copper oxide layer is about 50 ° to 100 °,
A copper internal wiring forming method according to claim 18 is provided. According to a twentieth aspect of the present invention, there is provided the copper internal wiring forming method according to the eighteenth aspect, wherein the copper oxide layer is removed by a first PECVD process.

[0020]

DETAILED DESCRIPTION OF THE INVENTION A first embodiment of the present invention is a method for enhancing the adhesion between copper and silicon nitride. This embodiment includes at least the following steps. First, a substrate coated with a dielectric layer is provided. Further, a copper layer is formed on the dielectric layer. Thereafter, a copper phosphide intermediate layer is formed on the copper layer. Finally, a silicon nitride layer is formed on the copper phosphide intermediate layer. The copper phosphide intermediate layer is formed by using a PH ₃ gas as a reaction gas by a PECVD method.

Obviously, copper very easily reacts with oxygen to form copper oxide on the surface. However copper oxide in PH ₃ plasma is very easily found to be instead of copper phosphide experimentally. And the adhesion between silicon nitride and copper phosphide is clearly better than the adhesion between copper and silicon nitride. For this reason, in the present embodiment, the phosphorus ions react with the copper layer to enhance the adhesion between copper and silicon nitride, and eliminate the need to remove the copper oxide layer by an extra step. In addition, there are two advantages in selecting copper phosphide as the intervening layer between copper and silicon nitride. That is,
Low resistance and effective prevention of copper from diffusing into the surrounding dielectric layer.

The second embodiment of the present invention is a method for forming copper internal wiring. This embodiment includes at least the following steps. Providing a substrate coated with a first dielectric layer. A first silicon nitride layer is formed over the first dielectric layer. A second dielectric layer is formed over the first silicon nitride layer. Removing a portion of the second dielectric layer and a portion of the first silicon nitride layer to form an air gap over the first dielectric layer, covering the second dielectric layer with a copper layer and filling the air gap; . Phosphorus copper intermediate layer by a PECVD method and PH ₃ plasma is formed on the second dielectric layer and to cover the remaining copper layer. A second silicon nitride layer is formed over the copper phosphide intermediate layer. A third dielectric layer is formed over the second silicon nitride.

In summary, a major feature of the present invention is that copper phosphide is used to connect copper and silicon nitride, and that copper oxide on the copper surface is automatically replaced with copper phosphide. For this reason, the adhesion between copper and silicon nitride is enhanced, and the resistance value between copper and the contact does not increase due to the presence of copper oxide.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The above-mentioned objects, features, and advantages of the present invention will be further described below with reference to specific examples and drawings.

The present invention is provided to solve the above-mentioned disadvantages of the prior art, and a first embodiment of the present invention provides a method for enhancing the adhesion between copper and silicon nitride. The method involves at least four steps. This will be described with reference to FIGS.

As shown in FIG. 3, first, the dielectric layer 21
Is provided, the copper layer 24 is provided on the dielectric layer 2.
1 is formed. Among them, the substrate 22 is at least
It comprises a plurality of structures located inside and on the surface of the substrate 22, such as FETs 23, contacts and dielectric layers. In addition, materials that can be used for the dielectric layer 21 include at least silicon dioxide, silicon nitride oxide, and silicon nitride.

FIG. 4 shows a state where there is no copper oxide layer located on the copper layer 24. At this time, the copper layer 24 is made of PECVD.
The PH ₃ plasma 25 is used in the reaction with the copper layer 24 and generates a copper phosphide intermediate layer.

FIG. 5 shows a situation where the copper oxide layer 26 is on the copper layer 24. The copper oxide layer 26 is a by-product of the process of moving a wafer (substrate 22) from one chamber to another during a semiconductor process, and the thickness of the copper oxide layer 26 is generally between 50 ° and 100 °. This PECVD process is used to treat the copper layer 24 and the copper oxide layer 26 overlying the copper layer 24, and the PH ₃ plasma 25 reacts with the copper oxide layer 26 and the copper layer 24 to form phosphorus and copper. Reacts to form a copper phosphide composite, and the oxygen in the copper oxide is easily reduced by hydrogen, whereby copper and phosphorus react to form copper phosphide.

According to the experimental results, the liberated PH ₃ gas efficiently forms a copper phosphide layer, regardless of whether it reacts directly with the copper layer 24 or with the copper oxide layer 26. Therefore, regardless of whether or not the copper oxide layer 26 exists on the copper layer 24, the PECVD method using the liberated PH ₃ gas is an effective method for forming the copper phosphide layer on the copper layer 24. It is.

In connection with this, the reaction temperature of the above-mentioned PECVD method is about 400 ° C., and the reaction pressure is about 1 Torr to 10 Torr.

Finally, as shown in FIG. 6, a copper phosphide intermediate layer 27 is formed on the copper layer 24, and then a silicon nitride layer 28 is formed on the copper phosphide intermediate layer 27. Here, the silicon nitride layer 28 is formed in another PECVD method, free of PH ₃ in this another PECVD process
There is no need to use gas.

Obviously, the emphasis of the above embodiment lies in the separation of the copper layer 24 and the silicon nitride layer 28 by the copper phosphide intermediate layer 27. As a result, the adhesion between the copper layer 24 and the silicon nitride layer 28 combines the adhesion between the copper layer 24 and the copper phosphide intermediate layer 27 and the adhesion between the copper phosphide intermediate layer 28 and the silicon nitride layer 28. It will be.

Here, the interface between the copper phosphide intermediate layer 27, the copper layer 24 and the silicon nitride layer 28 is not flat,
Further, the copper phosphide intermediate layer 27 forms many diffusion bonds on the interface between both the copper layer 24 and the silicon nitride layer 28. Therefore, the adhesion between the copper layer 24 and the silicon nitride layer 28 is effectively enhanced through the copper phosphide intermediate layer 27. This excellent point is demonstrated by a cross-sectional transmission electron microscope (X-TEM).

In addition, the copper oxide layer 26 is effectively removed by the PECVD method for forming the copper phosphide intermediate layer 27.
Thus, the appearance of the copper oxide layer 26 has no effect, and there is no need to remove the copper oxide layer 26 by an additional step. In other words, the removal of the copper oxide layer 26 and the formation of the copper phosphide intermediate layer 27 proceed simultaneously, and the electric resistance of the copper phosphide intermediate layer 27 is lower than the electric resistance of this copper oxide layer. Processing on copper is more efficient and outstanding than processing on copper by known processes.

In addition, another very rough point of the copper phosphide intermediate layer 27 is that the copper phosphide intermediate layer 27 prevents copper from diffusing into the surrounding dielectric layer. That is, the copper phosphide intermediate layer 27 itself serves as a blocking layer, which reduces the demand for the diffusion blocking layer.

Another embodiment of the present invention is a method for forming copper internal wiring. As shown in FIGS. 7 to 12, the method includes at least the following main steps.

As shown in FIG. 7, a substrate 30 is provided and the substrate 30 is coated with a first dielectric layer 31. This substrate 30 comprises at least a FET 32 and may further comprise contacts, isolation and capacitors.

As shown in FIG. 8, a first silicon nitride layer 33 and a second dielectric layer 34 are sequentially formed on a substrate 30. The second dielectric layer 34 covers the first silicon nitride layer 33. The material usable for the second dielectric layer 34 is at least silicon dioxide.

As shown in FIG. 9, a part of the second dielectric layer 34 and a part of the first silicon nitride layer 33 are removed to form a gap 3
5 is formed on the upper surface of the first dielectric layer 33. Here, at least a lithography process and an etching process are used.

As shown in FIG. 10, the second layer
Cover the dielectric layer 34. The copper layer 36 simultaneously fills the gap 35.

As shown in FIG. 11, the copper layer 36 on the surface of the second dielectric layer 34 is removed by chemical mechanical polishing. However, the void 35 is still filled with the copper layer 36.

As shown in FIG. 12, first, a copper phosphide intermediate layer 37 is formed on the second dielectric layer 34. Copper phosphide interlayer 37 overlies all unremoved copper layers 36. After that, a second silicon nitride layer 38 is formed on the copper phosphide intermediate layer 37. The copper phosphide intermediate layer 37 is formed by the PECVD method, using the liberated PH ₃ gas by the PECVD method, the reaction temperature is about 400 ° C., and the reaction pressure is about 1 Torr to 10 Torr.

This embodiment can be provided during the movement of the wafer (substrate 30). Therefore, a copper oxide layer on the copper layer 36 can be formed before forming the copper phosphide intermediate layer 37. The thickness of the copper oxide layer is approximately 50 ° to 100 °.

Of course, the copper oxide layer is not the purpose of this embodiment, but merely one unnecessary by-product. However, the copper oxide layer can be replaced by a copper phosphide intermediate layer by the aforementioned PECVD process, so that the temporary presence of the copper oxide layer does not cause any side effects.

Obviously, in this embodiment, the necessary copper internal wiring can be formed by the copper remaining in the gap 35 by appropriately determining the contour of the gap 35.

Obviously, this embodiment has at least the following advantages. First, the resistance between the copper internal wiring and any conductive structure (for example, a contact) connected to the copper internal wiring is not increased by the copper oxide layer. Second, the copper phosphide intermediate layer 37 is not used. Is to effectively enhance the adhesion between the copper internal wiring and the surrounding dielectric layers.
Second, the copper phosphide intermediate layer 37 effectively prevents the diffusion of copper into the second silicon nitride layer 38 and the third dielectric layer 39 around the copper.

The above is a description of the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Other alterations or modifications which are completed in the spirit of the present invention and have the same effect are described below. , Both of which fall within the scope of the present invention.

[0048]

The present invention provides a method for enhancing the adhesion between copper and silicon nitride. The present invention also provides a method that can reduce the electrical resistance between copper and contacts. The present invention further provides a method that can effectively prevent the diffusion of copper into the surrounding dielectric layer. The present invention further provides a method that can be practically used during the integrated circuit manufacturing process.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a known copper layer manufacturing process.

FIG. 2 is a cross-sectional view showing a known copper layer manufacturing process.

FIG. 3 is a cross-sectional view showing the main steps of the method for enhancing the adhesion between copper and silicon nitride according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view showing the main steps of the method for enhancing the adhesion between copper and silicon nitride according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view showing the main steps of the method for enhancing the adhesion between copper and silicon nitride according to the first embodiment of the present invention.

FIG. 6 is a cross-sectional view showing the main steps of the method for enhancing the adhesion between copper and silicon nitride according to the first embodiment of the present invention.

FIG. 7 is a sectional view showing main steps of a copper wiring forming method according to a second embodiment of the present invention.

FIG. 8 is a sectional view showing main steps of a method for forming a copper internal wiring according to a second embodiment of the present invention.

FIG. 9 is a sectional view showing main steps of a method for forming a copper internal wiring according to a second embodiment of the present invention.

FIG. 10 is a sectional view showing main steps of a copper internal wiring forming method according to a second embodiment of the present invention.

FIG. 11 is a sectional view showing main steps of a method for forming a copper internal wiring according to a second embodiment of the present invention.

FIG. 12 is a sectional view showing main steps of a method for forming a copper internal wiring according to a second embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 10 silicon nitride layer 11 copper layer 12 first dielectric layer 13 substrate 14 FET 15 second dielectric layer 16 copper oxide layer 22 substrate 23 FET 24 copper layer 25 PH ₃ plasma 26 copper oxide layer 27 copper phosphide intermediate layer 28 silicon nitride layer REFERENCE SIGNS LIST 30 substrate 31 first dielectric layer 32 FET 33 first silicon nitride layer 34 second dielectric layer 35 void 36 copper layer 37 copper phosphide intermediate layer 38 second silicon nitride layer 39 third dielectric layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F033 HH11 MM01 MM05 QQ00 QQ09 QQ48 RR01 RR04 RR06 RR08 TT02 WW03 WW05 XX14 XX28 5F058 BA05 BA10 BC08 BE10 BF07 BJ01 BJ02

Claims (20)

[Claims] Providing a substrate coated with a dielectric layer; forming a copper layer on the dielectric layer; forming a copper phosphide intermediate layer on the copper layer; A method for enhancing the adhesion between copper and silicon nitride, comprising: forming on the copper phosphide intermediate layer; 2. The method of claim 1, wherein the substrate comprises at least a plurality of structures, wherein the plurality of structures are located inside and on the surface of the substrate. the method of. 3. The method of claim 2, wherein the structure includes at least a transistor and a contact. 4. The method of enhancing adhesion between copper and silicon nitride, further comprising the step of forming a copper phosphide interlayer on the copper layer and the surrounding dielectric layer. Item 4. The method for enhancing adhesion between copper and silicon nitride according to Item 1. 5. The method of claim 1, wherein the copper phosphide intermediate layer is formed by a first PECVD process. 6. The method of claim 1 wherein said first PECVD process releases P
Characterized by using of H ₃ gas, copper and method for adhesion enhancement of silicon nitride according to claim 5. 7. The method of claim 5, wherein the reaction temperature of the first PECVD process is about 400 ° C. 8. The method of claim 1, wherein the first PECVD process has a reaction pressure of about 1 Torr to 10 Torr.
A method for enhancing adhesion between copper and silicon nitride according to claim 5. 9. The method of claim 1, wherein the silicon nitride layer is formed by a second PECVD process. 10. A copper oxide layer is formed on the copper layer,
The method of claim 1 wherein the copper oxide layer is present on the copper layer prior to the formation of the copper phosphide interlayer. 11. The copper oxide layer has a thickness of about 50 ° to 1 °.
11. The method of claim 10 wherein the adhesion is copper. 12. The method of claim 10, wherein the copper oxide layer is removed by a first PECVD process. 13. Providing a substrate covered with a first dielectric layer and comprising at least one FET; forming a first silicon nitride layer on the first dielectric layer; Forming a second dielectric layer thereon, forming a gap on the upper surface of the first dielectric layer by removing a part of the second dielectric layer and a part of the first silicon nitride layer by a lithography process and an etching process; Covering the second dielectric layer with a copper layer and filling the void with the copper layer; removing a copper layer other than the copper layer filling the void by a chemical mechanical polishing process; copper phosphide Forming an intermediate layer on the second dielectric layer and covering the remaining copper layer with the copper phosphide intermediate layer; forming a second silicon nitride layer on the copper phosphide intermediate layer; The second nitridation of the dielectric layer Forming on the silicon layer, characterized by comprising at least the above steps, the copper internal wiring forming method. 14. The method of claim 1, wherein the copper phosphide intermediate layer is formed by first PECVD.
14. The method according to claim 13, wherein the copper internal wiring is formed by a process. 15. The method of claim 14, wherein a liberated PH ₃ gas is used in the first PECVD process. 16. The method according to claim 14, wherein a reaction temperature of the first PECVD process is about 400 ° C. 17. The method according to claim 14, wherein the reaction pressure of the first PECVD process is about 1 Torr to 10 Torr. 18. The method according to claim 13, wherein a copper oxide layer is formed on the copper layer, and the copper oxide layer is present on the copper layer before forming the copper phosphide intermediate layer. The method for forming a copper internal wiring according to the above description. 19. The method according to claim 19, wherein said copper oxide layer has a thickness of about 50 ° to 1 °.
The method according to claim 18, wherein the angle is 00 °. 20. The method as claimed in claim 18, wherein the copper oxide layer is removed by a first PECVD process.