Etching residue-resistant method

Abstract

The invention provides an etching anti-residue method, which comprises the following steps: in a chip packaging process, directly covering a passivation layer on a topmost metal layer, and after the passivation layer is etched to expose the topmost metal layer, carrying out a pre-cleaning step, namely introducing a first oxygen-containing gas and a first inert gas into a reaction chamber under a plasma excitation condition, carrying out ion bombardment cleaning; under the plasma excitation condition, first reducing gas and second inert gas are introduced into the reaction chamber, and reduction reaction treatment is carried out on the etched surface; under the plasma excitation condition, second reducing gas and third inert gas are introduced into the reaction cavity, residues are removed, and the cavity environment is purified; and connecting the lead to the topmost metal layer. According to the invention, the reducing gas is introduced into the non-volatile etching by-products for reduction to generate volatile products, the volatile products are effectively removed in the subsequent steps, and meanwhile, a cleaner reaction chamber environment is created, so that a favorable environment is created for the subsequent reaction.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, in particular to a method for etching anti-residue. Background Art

[0002] The passivation layer is the last step in the wafer manufacturing process, used to protect the entire chip. The film layer structure is usually SiN / OX / TiN / AL. Due to the excellent electrical conductivity of Cu, it has good performance in automotive-grade electronic applications. Chip manufacturers eliminate the top aluminum pad process and directly cover the passivation layer on the surface of the top copper metal layer (M1 Cu) (this saves a layer of holes and the top aluminum pad process). After the passivation layer is etched, the leads are connected to the top copper metal layer (M1 Cu).

[0003] The process is difficult because conventional etching creates trenches that connect to holes, leaving only a 2%-5% window area in the passivation layer. This trench-to-trench process, which directly connects to the top copper metal layer, creates a passivation window area greater than 10%. This results in the carbon-doped nitride layer in the passivation layer being opened, exposing a large area of copper. During the etching process, dissociated electrons bombard both Cu and SIN. Etching SIN can form a severe N / F / O polymer, which adheres to the sidewalls and bottom, affecting package reliability. It can also adhere to the cavity surface, hindering subsequent wafer etching.

[0004] In order to solve the above problems, a new etching anti-residue method needs to be proposed. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the object of the present invention is to provide a method for etching anti-residue, which is used to solve the problem in the prior art that the passivation layer is directly covered on the surface of the top metal layer (such as M1 Cu) (which can save a layer of holes and the top aluminum pad process), the passivation layer window area is large, the etching by-products affect the packaging reliability, and at the same time will adhere to the cavity surface, affecting the subsequent wafer etching.

[0006] To achieve the above-mentioned and other related purposes, the present invention provides a method for etching an anti-residue, comprising:

[0007] Step 1: In the chip packaging process, a passivation layer is directly covered on the top metal layer. After the passivation layer is etched to expose the top metal layer, a pre-cleaning step is performed. The pre-cleaning step includes introducing a first oxygen-containing gas and a first inert gas into the reaction chamber under plasma excitation conditions to perform ion bombardment cleaning;

[0008] Step 2: Under plasma excitation conditions, a first reducing gas and a second inert gas are introduced into the reaction chamber to perform a reduction reaction on the etched surface;

[0009] Step 3: Under plasma excitation conditions, a second reducing gas and a third inert gas are introduced into the reaction chamber to remove residues and purify the chamber environment;

[0010] Step 4: Connect the leads to the top metal layer.

[0011] Preferably, the material of the passivation layer in step 1 includes a nitride layer and an oxide layer.

[0012] Preferably, the material of the topmost metal layer in step 1 is Cu.

[0013] Preferably, the etching by-product in step 1 is a copper-containing fluorine-nitrogen polymer.

[0014] Preferably, the open area of the passivation layer in step 1 is greater than 10%.

[0015] Preferably, in step 1, the first oxygen-containing gas is O2, and the first inert gas is N2.

[0016] Preferably, in the pre-cleaning step in step 1, the flow rate of O2 is 200-300 sccm, and the flow rate of N2 is 700-900 sccm.

[0017] Preferably, in step 1, ion bombardment cleaning is performed at a pressure of 200-300 mT and a power of 400-600 W.

[0018] Preferably, in step 2, the first reducing gas is CO, and the second inert gas is CO2.

[0019] Preferably, in step 2, the flow rate of CO is 100-200 sccm, and the flow rate of CO2 is 25-75 sccm.

[0020] Preferably, in step 2, the etched surface is subjected to a reduction reaction treatment at a pressure of 150-250 mT and a power of 1000-1500 W.

[0021] Preferably, the second reducing gas in step three is CO, and the third inert gas is N2.

[0022] Preferably, in step 3, the flow rate of CO is 80-120 sccm, and the flow rate of N2 is 700-900 sccm.

[0023] Preferably, in step three, the residues are removed and the cavity environment is purified at a pressure of 5-20 mT and a power of 800-1200 W.

[0024] As described above, the etching anti-residue method of the present invention has the following beneficial effects:

[0025] The present invention introduces reducing gas to reduce the non-volatile etching by-products to generate volatile products, which are effectively removed in subsequent steps, while creating a cleaner reaction chamber environment, thereby creating a favorable environment for subsequent reactions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Shown is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0027] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present invention.

[0028] See also Figure 1 To achieve the above-mentioned and other related purposes, the present invention provides a method for etching an anti-residue, comprising:

[0029] Step 1: In the chip packaging process, a passivation layer is directly covered on the top metal layer. After the passivation layer is etched to expose the top metal layer, a pre-cleaning step is performed. The pre-cleaning step includes introducing a first oxygen-containing gas and a first inert gas into the reaction chamber under plasma excitation conditions to perform ion bombardment cleaning;

[0030] In some embodiments, the material of the passivation layer in step 1 includes a nitride layer and an oxide layer.

[0031] In some embodiments, the material of the topmost metal layer in step 1 is Cu.

[0032] In some embodiments, the etching byproduct in step 1 is a copper-containing fluorine-nitrogen polymer.

[0033] In some embodiments, the open area of the passivation layer in step 1 is greater than 10%.

[0034] In some embodiments, the first oxygen-containing gas in step 1 is O2, and the first inert gas is N2. O2 is ionized to O + , O -High-energy ions bombard the surface with oxygen free radicals (·O), breaking the CN / F bonds in the CuxNyFz polymer attached to the copper layer and sidewalls, decomposing it into volatile small molecules such as CO, CO2, and NO. The oxygen plasma reacts with the polymer remaining in the cavity, reducing the impact of cavity contamination on subsequent processes. N2, as a non-reactive gas, dilutes the O2 concentration to prevent localized excessive oxygen concentrations from leading to copper surface oxidation (Cu→CuO / Cu2O). It also acts as a carrier gas to enhance plasma fluidity and help expel decomposition products. The ionization properties of N2 help maintain plasma stability and avoid process inconsistencies caused by power fluctuations.

[0035] In some embodiments, in the pre-cleaning step in step 1, the flow rate of O2 is 200-300 sccm, and the flow rate of N2 is 700-900 sccm. For example, the flow rate of O2 is 250 sccm, the flow rate of N2 is 700-900 sccm, and the flow rate of N2 is 800 sccm.

[0036] In some embodiments, in step 1, ion bombardment cleaning is performed at a pressure of 200-300 mT and a power of 400-600 W, for example, a pressure of 250 mT and a power of 500 W.

[0037] Step 2: Under plasma excitation conditions, a first reducing gas and a second inert gas are introduced into the reaction chamber to perform a reduction reaction on the etched surface;

[0038] In some embodiments, the first reducing gas in step 2 is CO and the second inert gas is CO2. CO is dissociated into C + and O - , where C + As a strong reducing agent, CO combines with metallic copper (Cu) and fluorine (F) in CuxNyFz to form gaseous copper fluoride (CuFz) and COx. The reducing properties of CO neutralize trace amounts of CuO that may be produced in the previous step (O2 cleaning), protecting the copper surface.

[0039] In some embodiments, the CO flow rate in step 2 is 100-200 sccm, and the CO2 flow rate is 25-75 sccm. For example, the CO flow rate is 150 sccm and the CO2 flow rate is 50 sccm. CO2 is decomposed into CO and O2 in the plasma, with O2 assisting in cleaning residual debris, while the added CO further strengthens the reducing atmosphere, forming a dynamic equilibrium. By adjusting the CO / CO2 ratio, carbon deposition (e.g., residual carbon) caused by excessive CO can be suppressed.

[0040] In some embodiments, in step 2, the etched surface is subjected to a reduction reaction treatment at a pressure of 150-250 mT and a power of 1000-1500 W, for example, a pressure of 200 mT and a power of 1200 W.

[0041] Step 3: Under plasma excitation conditions, a second reducing gas and a third inert gas are introduced into the reaction chamber to remove residues and purify the chamber environment;

[0042] In some embodiments, the second reducing gas in step three is CO, and the third inert gas is N2. The CO plasma can further dissociate the CuFz that has not been completely removed into Cu atoms and gaseous F2, which is then discharged with the carrier gas. CO reacts with the copper surface to form a thin layer of carbide (Cu-C), which inhibits the oxidation tendency of copper in subsequent processes. N2 molecules act as a high-speed carrier gas, rapidly evacuating reaction byproducts (such as COx and NOy) from the chamber via a vacuum pump. The high ionization rate of N2 helps maintain plasma density under low-pressure conditions, avoiding process interruptions or fluctuations.

[0043] In some embodiments, the flow rate of CO in step 3 is 80-120 sccm, and the flow rate of N2 is 700-900 sccm. For example, the flow rate of CO is 100 sccm, and the flow rate of N2 is 800 sccm.

[0044] In some embodiments, in step three, the residue is removed and the chamber environment is purified at a pressure of 5-20 mT and a power of 800-1200 W, for example, a pressure of 10 mT and a power of 1000 W.

[0045] Step 4. Connect the leads to the top metal layer.

[0046] In other embodiments, CO can be partially replaced by H2 (hydrogen): H2 also has reducing properties, but may affect reliability due to hydrogen embrittlement (hydrogen atoms penetrate into the copper lattice), so CO is preferred; CO2 can be added with Ar (argon) to assist ionization: Ar as an inert gas can enhance plasma density, but because it has no chemical reaction activity, it needs to be used in combination with CO.

[0047] It should be noted that the illustrations provided in this embodiment are only used to schematically illustrate the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0048] In summary, the present invention introduces a reducing gas to reduce non-volatile etching byproducts, generating volatile products that are effectively removed in subsequent steps. This also creates a cleaner reaction chamber environment, fostering a favorable environment for subsequent reactions. Therefore, the present invention effectively overcomes the shortcomings of existing technologies and possesses high industrial value.

[0049] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for etching anti-residue, characterized in that: At least: Step 1: In the chip packaging process, a passivation layer is directly covered on the top metal layer. After the passivation layer is etched to expose the top metal layer, a pre-cleaning step is performed. The pre-cleaning step includes introducing a first oxygen-containing gas and a first inert gas into the reaction chamber under plasma excitation conditions to perform ion bombardment cleaning; Step 2: Under plasma excitation conditions, a first reducing gas and a second inert gas are introduced into the reaction chamber to perform a reduction reaction on the etched surface; Step 3: Under plasma excitation conditions, a second reducing gas and a third inert gas are introduced into the reaction chamber to remove residues and purify the chamber environment; Step 4: Connect the leads to the top metal layer.

2. The method for etching anti-residue according to claim 1, characterized in that: The material of the passivation layer in step 1 includes a nitride layer and an oxide layer.

3. The method for etching anti-residue according to claim 1, characterized in that: The material of the topmost metal layer in step 1 is Cu.

4. The method for etching anti-residue according to claim 3, characterized in that: The etching by-product in step 1 is a copper-containing fluorine-nitrogen polymer.

5. The method for etching anti-residue according to claim 1, characterized in that: The open area of the passivation layer in step 1 is greater than 10%.

6. The method for etching anti-residue according to claim 1, characterized in that: In step 1, the first oxygen-containing gas is O2, and the first inert gas is N2.

7. The method for etching anti-residue according to claim 6, characterized in that: In the pre-cleaning step in step 1, the flow rate of O2 is 200-300 sccm, and the flow rate of N2 is 700-900 sccm.

8. The method for etching anti-residue according to claim 1, characterized in that: In step 1, ion bombardment cleaning is performed at a pressure of 200-300 mT and a power of 400-600 W.

9. The method for etching anti-residue according to claim 1, characterized in that: In step 2, the first reducing gas is CO, and the second inert gas is CO2.

10. The method for etching anti-residue according to claim 9, characterized in that: In step 2, the flow rate of CO is 100-200 sccm, and the flow rate of CO2 is 25-75 sccm.

11. The method for etching anti-residue according to claim 1, characterized in that: In step 2, the etched surface is subjected to a reduction reaction treatment at a pressure of 150-250 mT and a power of 1000-1500 W.

12. The method for etching anti-residue according to claim 1, characterized in that: In step 3, the second reducing gas is CO, and the third inert gas is N2.

13. The method for etching anti-residue according to claim 12, characterized in that: In step 3, the flow rate of CO is 80-120 sccm, and the flow rate of N2 is 700-900 sccm.

14. The method for etching anti-residue according to claim 1, characterized in that: In step 3, the residue is removed and the cavity environment is purified at a pressure of 5-20 mT and a power of 800-1200 W.

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