CN102610516B - Method for improving adhesion force between photoresist and metal/metallic compound surface - Google Patents

Abstract

The invention relates to the field of semiconductor manufacturing, in particular to a method for improving the adhesion between a photoresist and a metal/metal compound surface. The invention discloses a method for improving the adhesion between photoresist and metal/metal compound surface, by adding an oxidation atmosphere in the traditional process flow, oxidizing the metal on the upper surface of the metal/metal compound layer, and An adhesive transition layer is grown to improve the adhesion between the upper surface of the metal/metal compound layer and the photoresist, so as to reduce the risk of photoresist peeling off and process defects, and improve process stability and device yield.

Description

A method of improving adhesion between photoresists and metal/metal compound surfaces

technical field

The invention relates to the field of semiconductor manufacturing, in particular to a method for improving the adhesion between a photoresist and a metal/metal compound surface.

Background technique

With the continuous improvement of semiconductor performance requirements, the size of integrated circuit chips is getting smaller and smaller, and a complete 45nm process chip requires about 40 to 60 photolithography processes depending on the performance requirements, so the photolithography process becomes The core process in chip manufacturing. As the pattern of lithography is shrinking due to the reduction of device size, the thickness of photoresist and the size after lithography are also getting smaller and smaller, that is, lithography has become a precision processing technology. For example, as the chip production process changes from the micron level to the current nano-technology, the wavelength used in lithography is also shrinking with the progress of the chip technology, from the I-series line of mercury, the G-series line to the 193nm ultraviolet light in the ultraviolet region, the extreme Ultraviolet (extreme ultraviolet, EUV for short), and even electron beams.

Currently, chip manufacturing imposes very harsh process conditions on the photolithography process, including edge roughness, size uniformity, photoresist (Photoresist, PR) cross-sectional morphology, defects and so on. Insufficient bonding force between the photoresist and the substrate will cause a series of problems such as photoresist warping, shedding, defects, and etching undercuts. Among them, photoresist shedding is the most serious defect, which will lead to pattern failure and even cause particles. source endangers the surrounding area.

Due to the hydrophilic nature of the metal surface, the photoresist is hydrophobic, which makes it harder for the metal to bind tightly to the photoresist than ordinary oxide or silicon-based films. As the metal-insulator-metal (MIM) capacitor structure is more and more widely used in microwave or radio frequency chips, the upper plate of this capacitor is a metal or a metal compound. Therefore, how to avoid photoresist peeling off simply and effectively has become a very valuable research topic.

To avoid the peeling of the photoresist, the key is to improve the adhesion between the photoresist and the substrate. At present, several methods commonly used to improve adhesion are as follows:

The current common way to enhance the bonding force between photoresist and substrate in the integrated circuit manufacturing industry is to use spin-coated organic surface adhesion promoters, currently commonly used is hexamethyldisilazane (HMDS). Since photoresist is an organic compound, it is hydrophobic, and the surface of the wafer after etching, pickling, washing, drying and other processes in the integrated circuit manufacturing process is usually a hydrophilic metal/metal compound. , so it is difficult to directly form a relatively strong bond with the photoresist.

As shown in Figure 1-3, it is a schematic diagram of the structure of the traditional photolithography process flow. First, on the upper surface of the upper electrode plate 11 of the MIM capacitor structure 1, the surface adhesion promoter HMDS molecular layer 12 of the spin-coating organic is covered the upper pole plate 11, and then the photoresist 13 is spin-coated and the HMDS molecular layer 12 is covered, to light The resist 13 is exposed and developed. HMDS molecular layer 12 is as a kind of surfactant, by coating the HMDS molecular layer 12 of one deck surfactant on the surface of upper electrode plate 11, its thickness is only one or two molecular layers, the upper layer of HMDS molecular layer 12 and photolithography The lower surface of the glue 13 is combined together, and the lower layer of the HMDS molecular layer 12 can also be closely combined with the upper surface of the upper electrode plate 11, thereby improving the bonding performance of the photoresist 13 and the upper electrode plate 11, and avoiding photolithography. The glue 13 falls off; but the adhesion of the HMDS molecular layer is limited, and the gas, liquid, and high temperature in the exposure and development process will have an effect on the remaining photoresist 13 ^1. Since the binding force is not enough to resist the above effects, The remaining photoresist 13 ¹ will lift and fall off, thereby changing the pattern and making the process invalid. At the same time, HMDS will generate amines, which not only have a toxic effect on PR, but also generate additional defects.

Chinese patent (publication number 1166798, amine-free photoresist adhesion promoter for microelectronics) discloses an organic adhesion promoter, the principle of which is similar to the above. But the disadvantage of the surface adhesion promoter method recorded in this patent is that the improved adhesion is limited, and the amount of adhesive must be increased in order to obtain higher bonding performance, and too thick adhesive will affect The development of photolithography and the control of the shape and size of photolithography, and the price of the adhesive are relatively high, resulting in high cost.

U.S. Patent (Patent No. US6251804B1, Method for Enhancing Adhesion of Photo-resist to Silicon Nitride Surfaces) discloses a method for enhancing the surface of polysilicon gate The method of adhesion between silicon nitride and photoresist is mainly to introduce an oxidation process. The oxidant is a mixture of deionized water dissolved in ozone, oxygen plasma or sulfuric acid hydrogen peroxide, and the nitrogen is improved by changing the nitrogen-silicon dangling bond. The binding force between silicon oxide layer and HMDS. However, the invention is for the strengthening of silicon nitride substrates for polysilicon gates, and the metal/metal compound substrates are not described.

US Patent (Patent No. US4332881A, Resist adhesion integrated circuit processing) discloses a process of dividing photoresist into two coatings. First coat a thin layer of photoresist, then bake at high temperature to make the photoresist and the substrate well bonded, and then apply thicker photoresist, thicker photoresist and thinner photoresist can Better combined together, so as to achieve the purpose of improving the binding force. However, this method is affected by the performance of the photoresist, and the adhesion that can be improved is also limited, and due to the need for multiple coatings, it has an adverse effect on the exposure capability of the overall photoresist, such as difficult control of size uniformity, Subsequent deglue brings defects and the like; in addition, this method also requires multiple coatings of photoresist, resulting in a decrease in production efficiency and an increase in process cost.

Since metal-organic bonds are more difficult to form, the metal/metal compound substrate has a weaker bond to the photoresist than silicon or silicide substrates. Although the above-mentioned methods have their advantages, none of them disclose that they can effectively improve the adhesion between the metal/metal compound substrate surface and the photoresist.

With the advancement of technology, more and more metal/metal compound substrates will become the surface in direct contact with photoresist, such as the metal plate layer of capacitors, metal wiring, metal hard mask templates, etc. Therefore, how to find a method that can quickly, cheaply and reliably improve the adhesion between the metal/metal compound surface and the photoresist has become an important technical problem to be solved urgently in the semiconductor industry.

Contents of the invention

The invention discloses a method for improving the adhesion between a photoresist and a metal/metal compound surface. The upper surface of a MIM structure contained in a semiconductor device is provided with a metal/metal compound layer, which includes the following steps:

Step S1: performing an oxidation reaction on the upper surface of the metal/metal compound layer with oxygen-containing gas plasma under high temperature conditions, so that the metal on the upper surface of the metal/metal compound layer is oxidized to metal oxide;

Step S2: treating the metal oxide with plasma of silicon-based organic gas to form a bonding transition layer covering the upper surface of the metal/metal compound layer;

Step S3: After coating the adhesion promotion layer on the bonding transition layer, spin-coat photoresist or directly spin-coat photoresist on the bonding transition layer.

The method for improving the adhesion between the photoresist and the surface of the metal/metal compound, wherein the high temperature in step S1 is in the range of 100-700°C.

The method for improving the adhesion between the photoresist and the surface of the metal/metal compound, wherein the oxygen-containing gas in step S1 is oxygen, ozone, carbon dioxide and the like.

The method for improving the adhesion between the photoresist and the surface of the metal/metal compound, wherein the silicon-based organic gas in step S2 is an organic compound gas containing silicon, carbon, hydrogen, etc., preferably methane, di Methylsilane and other gases.

The method for improving the adhesion between the photoresist and the surface of the metal/metal compound, wherein the thickness of the bonding transition layer in step S2 is several to tens of atomic layers.

The method for improving the adhesion between the photoresist and the surface of the metal/metal compound, wherein the adhesion promotion layer is made of hexamethyldisilamine.

The method for improving the adhesion between the photoresist and the surface of the metal/metal compound, wherein the material of the metal/metal compound layer is aluminum, copper, tantalum, tantalum nitride, titanium, titanium nitride or tungsten wait.

In summary, due to the adoption of the above technical scheme, the present invention proposes a method for improving the adhesion between the photoresist and the surface of the metal/metal compound, by adding an oxidizing atmosphere to the traditional process flow to oxidize the metal/metal The metal on the upper surface of the compound layer, and grow a bonding transition layer on it, thereby improving the adhesion between the upper surface of the metal/metal compound layer and the photoresist, so as to reduce the risk of photoresist peeling off and the generation of process defects, Improve process stability and device yield.

Description of drawings

1-3 are schematic diagrams of the traditional photolithography process flow structure in the background technology of the present invention;

4-7 are schematic flow charts of the method for improving the adhesion between the photoresist and the metal/metal compound surface of the present invention.

detailed description

The specific embodiment of the present invention will be further described below in conjunction with accompanying drawing:

As shown in Figures 4-7, the present invention provides a method for improving the adhesion between the photoresist and the surface of the metal/metal compound. On the substrate 2, a first plate 21, a medium Layer 22. Among them, the first plate 21 can be a reserved copper or aluminum metal interconnection line with a certain pattern, or it can be deposited metal aluminum, copper, tantalum, tantalum nitride, titanium, titanium nitride by physical vapor deposition process. It is equal to the metal/metal compound layer formed on the substrate 2; the dielectric layer 22 is formed by chemical vapor deposition (Chemical Vapor Deposition, CVD for short), atomic layer deposition (Atomic layer deposition, ALD for short) or furnace tube growth process, on the first pole A layer of high dielectric constant insulating dielectric layer containing any one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, silicon carbide nitride, hafnium oxide or aluminum oxide is grown on the plate 21 .

First, the second plate 23 made of metal/metal compounds such as aluminum, copper, tantalum, tantalum nitride, titanium, titanium nitride or tungsten is grown on the surface of the dielectric layer 22 to form a three-layer stacked MIM capacitor mechanism. , under the premise that the temperature is controlled within the range of 100-700°C, use oxygen-containing gas such as oxygen, ozone, carbon dioxide and other gases, and preferably use oxygen to perform a high-temperature oxidation heat treatment process on the upper surface of the second electrode plate 23 to oxidize the second electrode plate 23. The metal on the upper surface of the pole plate 23 is oxidized to a metal oxide. In the actual production process, due to the waiting time from the preparation of the capacitor substrate to the photolithography, particles or other defects may be generated, and there will be certain defects and inhomogeneities in the growth process of the second plate 23, The possible dirt or other defects on the surface of the second electrode plate 23 can be effectively eliminated through the high-temperature oxidation heat treatment process, and the clean surface at the atomic level can be restored. In this embodiment, the preferred high-temperature oxidation heat treatment process using oxygen plasma can enhance the reaction activity, thereby reducing the reaction temperature, shortening the process time, further reducing energy consumption and increasing production. In the actual preparation process, the appropriate oxidation treatment method and parameters are selected according to factors such as reaction speed, device tolerance temperature, and cleaning efficiency.

Then, after the high-temperature oxidation heat treatment process is completed, organic compound gases containing silicon, carbon, and hydrogen, such as methane, dimethylsilane, and other gases, are activated by plasma to combine the above-mentioned organic compound gases with the second electrode plate 23 A layer of metal-silicon-oxygen bonding transition layer 24 is formed on the upper surface, and the thickness of the bonding transition layer 24 is several to tens of atomic layers. At this time, the hydrophilic metal atomic layer on the upper surface of the second pole plate 23 is modified into an adhesive transition layer 24 that is more easily combined with the photoresist or the HMDS adhesion promotion layer 25, thereby greatly enhancing its binding force . In the actual preparation process, the reactants and reaction parameters are selected according to the magnitude of the required binding force improvement.

Finally, spray HMDS steam to form an HMDS adhesion promotion layer 25 covering the adhesion transition layer 24, the thickness of which is the thickness of several molecular layers; spin-coat photoresist 26 to cover the HMDS adhesion promotion layer 25, after exposure and development, prepare The defined pattern structure changes the hydrophilic property of the upper surface of the second electrode plate ²³ , making it difficult for the remaining photoresist 261 to have peeling and peeling defects.

Wherein, the sequence between the high-temperature oxidation heat treatment process and the process for forming the bonding transition layer can be reversed, or only one of the two processes can be used for preparation.

Due to the high-temperature oxidation heat treatment process and the process of forming a bonding transition layer, the bonding force between the photoresist and the metal/metal compound layer is greatly enhanced, so the peeling and peeling of the photoresist is effectively controlled, thereby improving the process. reliability and yield.

Furthermore, the method of the present invention for improving the adhesion between the photoresist and the metal/metal compound surface can also be used in the rework photolithography process. First, the failed exposure and development wafers are subjected to conventional adhesive removal technology, ashing and pickling to remove impurities such as photoresist and HMDS on the wafer surface. Then, adopt similar process steps as in Example 1, undergo high-temperature plasma oxidation treatment, remove possible residual organic stains and acid residues, improve the surface state of the wafer, and obtain a clean surface; thereafter, use silicon, carbon, etc. The organic compound plasma generates a bonding transition layer to improve the bonding force between the photoresist and the reworked metal/metal compound layer, thereby reducing the occurrence of peeling and peeling defects of the photoresist.

In summary, due to the adoption of the above technical scheme, the present invention proposes a method for improving the adhesion between the photoresist and the metal/metal compound surface, and effectively removes the metal/metal compound substrate surface through a high-temperature oxidation heat treatment process. Stain and uneven state, and change the hydrophilic property of the metal/metal compound substrate, then use gas wetting and adsorption, and then plasma reaction to form an adhesive transition layer to improve the metal substrate and photoresist or HMDS Bonding force, reducing defects and photoresist peeling, improving process reliability and yield.

The specific embodiments of the present invention have been described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, equivalent changes and modifications made without departing from the spirit and scope of the present invention shall fall within the scope of the present invention.

Claims (5)

1. improve a method for adhesion between photoresist and metal/metal compound surface, the upper surface of the mim structure that semiconductor device comprises is provided with metal/metal compound layer, it is characterized in that, comprises the steps:

Step S1: utilize the plasma of oxygen-containing gas to carry out oxidation reaction to the upper surface of metal/metal compound layer under the temperature conditions of 100-700 DEG C, makes the burning on the upper surface of metal/metal compound layer be metal oxide;

Step S2: utilize the plasma of silica-based organic gas to process metal oxide, forms the bonding transition zone of the upper surface of covering metal/metal compound layer;

Step S3: apply adhesion-promoting layer on bonding transition zone after, then spin coating photoresist or direct at the spin coating photoresist on transition zone that bonds.

2. the method for adhesion between raising photoresist according to claim 1 and metal/metal compound surface, it is characterized in that, in step S1, oxygen-containing gas is oxygen, ozone, carbon dioxide.

3. the method for adhesion between raising photoresist according to claim 1 and metal/metal compound surface, it is characterized in that, the silica-based organic gas in step S2 is the organic compound gas containing silicon, carbon, hydrogen.

4. the method for adhesion between raising photoresist according to claim 1 and metal/metal compound surface, it is characterized in that, the material of described adhesion-promoting layer is hmds.

5. the method for adhesion between raising photoresist according to claim 1 and metal/metal compound surface, it is characterized in that, the material of described metal/metal compound layer is aluminium, copper, tantalum, tantalum nitride, titanium, titanium nitride or tungsten.