CN1286162C - Method for forming contact window - Google Patents

Abstract

The invention discloses a method for forming a contact window, which comprises the steps of firstly forming a dielectric layer on a substrate and forming a patterned photoresist layer on the dielectric layer. Then, the photoresist layer is used as an etching mask to remove a part of the thickness of the dielectric layer, so as to form a first opening. Then, a first liner layer is formed on the surface of the photoresist layer, and the first liner layer is used as an etching mask to remove part of the thickness of the dielectric layer under the first opening, so as to form a second opening, wherein the range of the second opening covers the first opening. Then, a second liner layer is formed on the photoresist layer to cover the first liner layer, and the dielectric layer under the second opening is removed by using the second liner layer as an etching mask, so as to form a third opening to expose the substrate and cover the second opening. After the second liner layer, the first liner layer and the photoresist layer are removed, a conductive layer is filled in the third opening to form a contact window.

Description

Method of Forming Contact Window

technical field

The invention relates to a method for forming a semiconductor element, and in particular to a method for forming a small-sized contact window (Contact or Via) by using multiple etching steps.

Background technique

With the advancement of semiconductor technology, the size of components is also continuously reduced. However, in the deep sub-micron field, when the integration level of the integrated circuit increases, the surface of the chip cannot provide enough area to fabricate the required interconnects (Interconnects). Therefore, in order to meet the increased demand for interconnection after component shrinkage, the design of multilayer metal interconnection with more than two layers has become a necessary method for very large scale integration (VLSI) technology. In addition, if different metal layers are to be connected, an opening must be dug in the insulating layer between the two metal layers and filled with a conductive material to form a contact window structure for connecting the two metal layers.

A known method for forming a contact window structure is to form a dielectric layer on a substrate on which a first metal interconnection layer has been formed, and then pattern the dielectric layer to form an opening to expose the first metal interconnection layer. The wiring layer is then filled with a metal layer in the opening to form a metal contact window. Subsequently, a second metal interconnection layer is formed on the metal contact window, so that the lower first metal interconnection layer and the second metal interconnection layer can be connected in series.

However, under the premise that the integration level of integrated circuits is gradually increasing, not only the size of components is reduced, but also the sizes of metal interconnections and metal contact windows are relatively reduced. However, it is very difficult to form a contact window with a small bottom due to the limitations of the development process and the etching process. Moreover, it is not easy to fill the small-sized contact openings with high aspect ratios with conductive metal materials.

Contents of the invention

The object of the present invention is to provide a method for forming a contact window to solve the problem in the known method that the contact window with a small bottom cannot be formed due to the limitations of the developing process and the etching process.

Another object of the present invention is to provide a method for forming a contact window, so as to solve the problem in the conventional method that it is difficult to fill the metal conductive layer in the small-sized contact window opening with a high aspect ratio.

The invention proposes a method for forming a contact window. The method firstly forms a dielectric layer on a substrate, and forms a patterned photoresist layer on the dielectric layer. Then, using the photoresist layer as an etching mask to remove part of the thickness of the dielectric layer to form a first opening. Afterwards, a first lining layer is formed on the surface of the photoresist layer, wherein there is an etching selectivity between the first lining layer and the dielectric layer. In the present invention, the material of the first lining layer is, for example, polymer material, and the method of forming the first lining layer is, for example, plasma enhanced chemical vapor deposition (PECVD). Afterwards, using the first liner layer and the photoresist layer as an etching mask, part of the thickness of the dielectric layer under the first opening is removed to form a second opening covering the first opening. Next, a second liner layer is formed on the photoresist layer to cover the first liner layer, wherein there is an etching selectivity between the second liner layer and the dielectric layer. In the present invention, the material of the second lining layer is, for example, a polymer material, and the method of forming the second lining layer is, for example, a plasma-enhanced chemical vapor deposition method. Then, using the second liner layer and the photoresist layer as an etching mask, the dielectric layer under the second opening is removed, and a third opening is formed to expose the base, and the range covers the second opening. Then, after removing the second liner layer, the first liner layer and the photoresist layer, a conductive layer is filled into the third opening to form a contact window. The width of the bottom of the contact window structure formed by the multiple etching steps of the present invention is smaller than the width of the top.

The invention proposes a method for forming a contact window. The method firstly forms a dielectric layer on a substrate, and forms a patterned photoresist layer on the dielectric layer. Afterwards, using the photoresist layer as an etching mask to remove part of the thickness of the dielectric layer to form a first opening. Then, after removing the photoresist layer, a first lining layer is formed on the dielectric layer and in the first opening. Wherein, there is an etching selectivity ratio between the first liner layer and the dielectric layer. In the present invention, the material of the first lining layer is preferably silicon nitride or a metal material. Afterwards, using the first liner layer as an etching mask, part of the thickness of the dielectric layer under the first opening is removed to form a second opening covering the first opening. Next, a second lining layer is formed on the dielectric layer and in the second opening to cover the first lining layer. Wherein, there is an etching selectivity ratio between the second liner layer and the dielectric layer. In the present invention, the material of the second lining layer is preferably silicon nitride or a metal material. Then, using the second liner layer as an etching mask, the dielectric layer under the second opening is removed to form a third opening to expose the base, and the range covers the second opening. Then, after the second liner layer and the first liner layer are removed, a conductive layer is filled into the third opening to form a contact window. However, the width of the bottom of the contact window structure formed by the multiple etching steps of the present invention is smaller than the width of the top. In addition, in the present invention, instead of removing the first liner layer and the second liner layer made of silicon nitride or metal, a conductive layer is directly filled in the third opening to form a contact window. This is because, if the first liner layer and the second liner layer are made of silicon nitride, the first liner layer and the second liner layer can be regarded as a part of the dielectric layer. If the first liner layer and the second liner layer are made of metal conductive material, the first liner layer and the second liner layer can be regarded as a part of the contact window.

The method for forming the contact window of the present invention can overcome the limitations of the current development process and etching process because it uses multiple etching steps to form the contact window with a small bottom.

In the method for forming the contact window of the present invention, since the top of the formed contact window opening is wider than the bottom thereof, the metal conductive layer can be easily filled into the contact window opening.

In the method for forming the contact window of the present invention, since the top of the formed contact window is wider, the resistance value of the entire contact window can be reduced.

Description of drawings

In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the following will be described in detail in conjunction with the accompanying drawings:

1A to 1G are schematic cross-sectional views of the process of forming contact windows according to the first embodiment of the present invention;

2A to 2H are schematic cross-sectional views of the process of forming contact windows according to the second embodiment of the present invention.

The marks in the figure are:

100, 200: base

102, 202: dielectric layer

104, 204: photoresist layer

106, 206: first opening

108, 208: the first lining

110, 210: the second opening

112, 212: second lining

114, 214: the third opening

116, 216: conductive layer

Detailed ways

First embodiment:

1A to 1G are schematic cross-sectional views of the process of forming contact windows according to the first embodiment of the present invention.

Referring to FIG. 1A , firstly, a substrate 100 is provided. Next, a dielectric layer 102 is formed on the substrate 100 . Wherein, the material of the dielectric layer 102 is, for example, silicon oxide. Afterwards, a patterned photoresist layer 104 is formed on the dielectric layer 102 .

After that, referring to FIG. 1B , an anisotropic etching process is performed using the photoresist layer 104 as an etching mask to remove part of the thickness of the dielectric layer 102 to form a first opening 106 .

Then, referring to FIG. 1C, a first lining layer 108 is formed on the surface of the photoresist layer 104, and the formed first lining layer 108 may also be formed on the surface of the dielectric layer 102 exposed by the first opening 106. . Wherein, there is an etching selectivity ratio between the first liner layer 108 and the dielectric layer 102 . In this embodiment, the material of the first lining layer 108 is, for example, a polymer material, and the method of forming the first lining layer 108 is, for example, a plasma-enhanced chemical vapor deposition method. The main component of a reactive gas in this plasma-enhanced chemical vapor deposition method is, for example, difluoromethane (CH ₂ F ₂ ), or a mixture of difluoromethane (CH ₂ F ₂ ) and octafluorobutene (C ₄ F ₈ ). Mixed gas, or a mixed gas of difluoromethane (CH ₂ F ₂ ) and trifluoromethane (CHF ₃ ). In addition, a pressure for performing the plasma-enhanced chemical vapor deposition method is, for example, between 1 and 100 mTorr. And its power is between 500 to 2000W, for example. Furthermore, the self-bias value for performing the plasma-enhanced chemical vapor deposition method is, for example, between 0 and −400 V, and the deposition rate is, for example, between 600 and 6000 angstroms/min. In addition, Argon (Ar), Carbon Monoxide (CO), Oxygen (O ₂ ) and Nitrogen (N ₂ ) can be selectively added to the reaction gas of the plasma-enhanced chemical vapor deposition method.

Next, referring to FIG. 1D, an anisotropic etching process is performed using the first liner layer 108 and the photoresist layer 104 as an etching mask to remove the first liner layer 108 and the first opening at the bottom of the first opening 106. Partial thickness of the dielectric layer 102 under the layer 106 forms a second opening 110 covering the first opening 106 . In this anisotropic etching process, the first liner 108 on the sidewall of the first opening 106 will remain, and the first liner 108 on the top of the photoresist layer 104 may be removed at the same time, but since there is still light Because the resist layer 104 serves as an etching mask, the second opening 110 can still be formed smoothly.

It is particularly worth mentioning that, in the above-mentioned step of forming the first lining layer 108, the present invention can adjust the process parameters so that the thickness of the first lining layer 108 formed on the top of the photoresist layer 104 is thicker than that formed on the first lining layer 108. The thickness of the first lining layer 108 at the bottom of the opening 106 is so thick that even the first lining layer 108 will not be deposited on the surface of the dielectric layer 102 exposed by the first opening 106 . In this way, in the aforementioned anisotropic etching process, the first liner layer 108 on top of the photoresist layer 104 will not be completely removed, but can continue to be used as an etching mask.

Next, referring to FIG. 1E , a second lining layer 112 is formed on the surface of the photoresist layer 104 to cover the first lining layer 108 . Similarly, the formed second liner layer 112 may also be formed on the surface of the dielectric layer 102 exposed by the second opening 110 . Wherein, there is an etching selectivity ratio between the second liner layer 112 and the dielectric layer 102 . In this embodiment, the material of the second lining layer 112 is, for example, a polymer material, and the method of forming the second lining layer 112 is, for example, plasma-enhanced chemical vapor deposition (PECVD). The detailed description is the same as the previous method of forming the first liner layer 108 , and will not be repeated here.

Afterwards, referring to FIG. 1F , an anisotropic etching process is performed using the second liner 112 and the photoresist layer 104 as an etching mask to remove the second liner 112 and the second opening at the bottom of the second opening 110 The dielectric layer 102 under the substrate 110 forms a third opening 114 to expose the substrate 100 and covers the second opening 110 . In this anisotropic etching process, the second liner 112 on the sidewall of the second opening 110 will remain, and the second liner 112 on the top of the photoresist layer 104 may be removed at the same time, but since there is still light Because the resist layer 104 serves as an etching mask, the third opening 114 can still be formed smoothly.

Similarly, if in the above step of forming the second liner 112, the process parameters are adjusted so that the thickness of the second liner 112 formed on the top of the photoresist layer 104 is thicker than that of the second liner 112 formed at the bottom of the second opening 110. The thickness of the layer 112 is so thick that even the second liner layer 112 will not be deposited on the surface of the dielectric layer 102 exposed by the second opening 110 . In this way, in the aforementioned anisotropic etching process, the second liner layer 112 on top of the photoresist layer 104 will not be completely removed, but can continue to be used as an etching mask.

Then, referring to FIG. 1G , the second liner layer 112 , the first liner layer 108 and the photoresist layer 104 are removed. Next, a conductive layer 116 is filled in the third opening 114 to form a contact window. Wherein, the method of filling a conductive layer 116 in the third opening 114 is, for example, to form a conductive material layer (not shown) on the substrate 100 and fill the third opening 114, and then use a back etching process or a chemical mechanical polishing process to remove part of the conductive material layer until the dielectric layer 102 is exposed.

Since the method for forming the contact window of the present invention utilizes multiple etching steps to form the contact window opening (the third opening 114), it can overcome the known difficulty in forming a small-sized contact window due to the limitations of the developing process and the etching process. question. In addition, since the width of the top of the third opening 114 formed in the present invention is greater than the width of the bottom, the conductive layer 116 can be easily filled in the third opening 114, and solve the problem of small holes with high aspect ratios in the conventional method. The size of the contact window has the problem that it is not easy to fill in the metal conductive layer. Furthermore, since the top of the contact window formed by the present invention is wider, the resistance value of the entire contact window can be reduced.

Second embodiment:

2A to 2H are schematic cross-sectional views of the process of forming contact windows according to the second embodiment of the present invention.

Referring to FIG. 2A , firstly, a substrate 200 is provided. Next, a dielectric layer 202 is formed on the substrate 200 . Wherein, the material of the dielectric layer 202 is, for example, silicon oxide. Afterwards, a patterned photoresist layer 204 is formed on the dielectric layer 202 .

After that, referring to FIG. 2B , an etching process is performed using the photoresist layer 204 as an etching mask to remove part of the thickness of the dielectric layer 202 to form a first opening 206 .

Then, referring to FIG. 2C , the photoresist layer 204 is removed. Afterwards, a first lining layer 208 is formed on the dielectric layer 202 and in the first opening 206 . Wherein, there is an etching selectivity ratio between the first liner layer 208 and the dielectric layer 202 . In this embodiment, the material of the first liner layer 208 is preferably silicon nitride or a metal material, and the method of forming the first liner layer 208 can use any known deposition technique. It is particularly worth mentioning that, in the step of forming the first liner layer 208, adjustment of process parameters or other means may be used to control the thickness of the first liner layer 208 formed at the bottom of the first opening 206 to be smaller than the thickness of the first liner layer 208 formed at the bottom of the dielectric layer. The thickness of the first liner 208 on top of 202.

Next, referring to FIG. 2D , an anisotropic etching process is performed using the first liner 208 as an etching mask to remove the first liner 208 at the bottom of the first opening 206 and the dielectric layer under the first opening 206 202 to form a second opening 210 covering the first opening 206 . In the previous step of forming the first liner layer 208 , the thickness of the first liner layer 208 formed at the bottom of the first opening 206 is thinner than the thickness of the first liner layer 208 above the dielectric layer 202 . Therefore, after the anisotropic etching process removes the first liner 208 at the bottom of the first opening 206, the top of the dielectric layer 202 still has the first liner 208 that has not been removed, and can continue to serve as an etching mask. The mold is used so that the second opening 210 can be formed smoothly. Moreover, after the anisotropic etching process, the first liner 208 on the sidewall of the first opening 206 remains.

Next, referring to FIG. 2E , a second lining layer 212 is formed on the dielectric layer 202 and in the second opening 210 . Wherein, there is an etching selectivity between the second liner layer 212 and the dielectric layer 202 . In this embodiment, the material of the second liner layer 212 is preferably silicon nitride or a metal material, and the method of forming the second liner layer 212 can use any known deposition technique. It is particularly worth mentioning that, in the step of forming the second liner layer 212, adjustment of process parameters or other methods can be used to control the thickness of the second liner layer 212 formed at the bottom of the second opening 210 to be smaller than that formed at the bottom of the dielectric layer. The thickness of the second liner 212 on top of 202.

Next, referring to FIG. 2F, an anisotropic etching process is performed using the second liner 212 as an etching mask to remove the second liner 212 at the bottom of the second opening 210 and the dielectric layer under the second opening 210. 202 , forming a third opening 214 to expose the substrate 200 and covering the second opening 210 . In the above step of forming the second liner layer 212 , the thickness of the second liner layer 212 formed at the bottom of the second opening 210 is thinner than the thickness of the second liner layer 212 above the dielectric layer 202 . Therefore, after the second liner 212 at the bottom of the second opening 210 is removed in the anisotropic etching process, the top of the dielectric layer 202 still has the second liner 212 that has not been removed, and can continue to serve as an etching mask. For the purpose of making the third opening 214 can be formed smoothly. Moreover, after the anisotropic etching process, the second liner 212 on the sidewall of the second opening 210 remains.

Then, referring to FIG. 2G , a conductive layer 216 is directly filled in the third opening 214 to form a contact window. Wherein, the method of filling a conductive layer 216 in the third opening 214 is, for example, to form a conductive material layer (not shown) on the substrate 200 and fill the third opening 214, and then use a back etching process or a chemical mechanical polishing process to remove part of the conductive material layer until the dielectric layer 202 is exposed. In the present invention, since the material of the first lining layer 208 and the second lining layer 212 is metal material or silicon nitride, the present invention does not need to remove the first lining layer 208 and the second lining layer 212, and directly A conductive layer 216 is filled in the third opening 214 . If the first liner 208 and the second liner 212 are made of metal, they can be used as part of the contact window. And if the first liner layer 208 and the second liner layer 212 are made of silicon nitride, they can be used as a part of the dielectric layer 202 for insulation and isolation.

Of course, as shown in FIG. 2H , the present invention can also remove the second liner layer 212 and the first liner layer 208 first, and then fill a conductive layer 216 into the third opening 214 to form a contact window.

Because the method for forming the contact window of the present invention uses multiple etching steps to form the contact window opening (the third opening 214), it can overcome the known difficulty in forming a small-sized contact window due to the limitations of the development process and the etching process. The problem. In addition, since the width of the top of the third opening 214 formed in the present invention is greater than the width of the bottom, the conductive layer 216 can be easily filled in the third opening 214, and the conventional method solves the problem of having a high aspect ratio. The small-sized contact window has the problem that it is not easy to fill in the metal conductive layer. Furthermore, since the top of the contact window formed by the present invention is wider, the resistance value of the entire contact window can be reduced.

In the embodiment of the present invention, it is described in detail by performing three etching steps to form the contact opening. However, the present invention is not limited to only use three etching processes to form the contact window opening. The present invention also includes using two or more etching steps to form the contact window opening.

In summary, the present invention has the following advantages:

1. The method for forming a contact window of the present invention can overcome the limitations of the current development process and etching process to form a contact window with a small bottom.

2. The method for forming the contact window of the present invention can solve the problem that it is difficult to fill the opening of the small-sized contact window with the metal conductive layer in the known method.

3. The method for forming the contact window of the present invention can reduce the resistance value of the small-sized contact window.

Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any changes and modifications made by any person familiar with the art without departing from the spirit and scope of the present invention are all Belong to the protection scope of the present invention.

Claims (20)

1. method that forms contact hole is characterized in that: comprising:

In a substrate, form a dielectric layer;

On this dielectric layer, form the photoresist layer of a patterning;

Utilizing this photoresist layer is the segment thickness that an etching mask removes this dielectric layer, to form one first opening;

On the surface of this photoresist layer, form one first lining;

Utilize this first lining and this photoresist layer be an etching mask to remove the segment thickness of this dielectric layer under this first open bottom, to form one second opening, the scope of this second opening contains this first opening;

On this photoresist layer, form one second lining, cover this first lining;

Utilize this second lining and this photoresist layer be an etching mask to remove this dielectric layer under this second open bottom, to form one the 3rd opening, expose this substrate, the scope of the 3rd opening contains this second opening;

Remove this second lining, this first lining and this photoresist layer;

In the 3rd opening, insert a conductive layer, to form a contact hole.

2. the method for formation contact hole according to claim 1 is characterized in that: have an etching selectivity between this first lining and this second lining and this dielectric layer.

3. the method for formation contact hole according to claim 1 is characterized in that: this first lining and this second lining are respectively a polymer material layer.

4. the method for formation contact hole according to claim 1 is characterized in that: the material of this dielectric layer comprises silica.

5. the method for formation contact hole according to claim 1 is characterized in that: the method that forms this first lining and this second lining comprises a plasma enhanced chemical vapor deposition method.

6. the method for formation contact hole according to claim 5 is characterized in that: the main component of the employed reacting gas of this plasma enhanced chemical vapor deposition method comprises CH ₂F ₂Or CH ₂F ₂/ C ₄F ₈Mist or CH ₂F ₂/ CHF ₃Mist.

7. the method for formation contact hole according to claim 5 is characterized in that: the employed selectivity of this plasma enhanced chemical vapor deposition method is added gas and is comprised argon gas, carbon monoxide, oxygen and nitrogen.

8. the method for formation contact hole according to claim 5 is characterized in that: a reaction pressure of this plasma enhanced chemical vapor deposition method is between 1 to 100 milli torr.

9. the method for formation contact hole according to claim 5 is characterized in that: the power of this plasma chemical vapour deposition technique is between 500 to 2000W.

10. method that forms contact hole is characterized in that: comprising:

In a substrate, form a dielectric layer;

On this dielectric layer, form the photoresist layer of a patterning;

Utilizing this photoresist layer is the segment thickness that an etching mask removes this dielectric layer, to form one first opening;

Remove this photoresist layer;

On this dielectric layer with in this first opening, form one first lining;

Utilize this first lining be an etching mask to remove the segment thickness of this dielectric layer under this first open bottom, to form one second opening, the scope of this second opening contains this first opening;

On this dielectric layer, form one second lining, cover this first lining;

Utilize this second lining be an etching mask to remove this dielectric layer under this second open bottom, to form one the 3rd opening, expose this substrate, the scope of the 3rd opening contains this second opening;

In the 3rd opening, insert a conductive layer, to form a contact hole.

11. the method for formation contact hole according to claim 10 is characterized in that: before in the 3rd opening, inserting conductive layer, comprise that further one removes the step of this second lining and this first lining.

12. the method for formation contact hole according to claim 10 is characterized in that: have an etching selectivity between this first lining and this second lining and this dielectric layer.

13. the method for formation contact hole according to claim 10 is characterized in that: the material of this first lining and this second lining comprises silicon nitride.

14. the method for formation contact hole according to claim 10 is characterized in that: the material of this first lining and this second lining comprises a metal.

15. the method for formation contact hole according to claim 10 is characterized in that: the material of this dielectric layer comprises silica.

16. the method for formation contact hole according to claim 10 is characterized in that:

Directly in the 3rd opening, insert a conductive layer, to form a contact hole.

17. the method for formation contact hole according to claim 16 is characterized in that: have an etching selectivity between this first lining and this second lining and this dielectric layer.

18. the method for formation contact hole according to claim 16 is characterized in that: the material of this first lining and this second lining comprises silicon nitride.

19. the method for formation contact hole according to claim 16 is characterized in that: the material of this first lining and this second lining comprises a metal.

20. the method for formation contact hole according to claim 16 is characterized in that: the material of this dielectric layer comprises silica.

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