A method for removing residual glue after dry degumming

Abstract

The present invention discloses a method for removing residual glue after dry degumming, which optimizes the process by combining contact (Pin Up combined with Pin down mode) between the wafer and the hot stage without contact, and at the beginning, water and oxygen are introduced into the etching chamber without adding radio frequency to soften the glue, and then water is introduced into the etching chamber and a microwave source is started at the same time, and the radio frequency power will affect the softening effect of the glue, and finally the microwave source is turned off, and water, oxygen and nitrogen are continuously introduced into the etching chamber, and the operation is repeated to complete degumming. The present invention can be applied in a large-scale integrated circuit industrial manufacturing environment, and degumming is performed by changing the contact between the wafer and the hot stage during the dry degumming process under the action of the radio frequency power of the microwave source, and the wafer and the hot stage are not in contact mode without radio frequency power to soften the glue, and an optimization method in the manufacturing process. The experimental results show that the residual glue on the surface of the wafer is completely removed, and the effect is quite obvious.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor manufacturing, and in particular relates to a method for removing residual glue after dry-process glue removal. Background Art

[0002] The removal of photoresist plays a very important role in the IC manufacturing process, and its cost accounts for about 20% to 30% of the IC manufacturing process. If the photoresist removal effect is too weak and the uniformity is too poor, it will affect the production efficiency, and then affect the yield of the entire product. The traditional mainstream degumming method uses wet degumming, which is low in cost and high in efficiency. However, with the continuous iteration and update of technology, more and more IC manufacturers have begun to adopt dry degumming. The dry degumming process is different from the traditional wet degumming process. It does not require soaking in chemical solvents or drying. The degumming process is easier to control, avoiding excessive substrate counting and improving the product yield. Dry degumming is also called plasma degumming. Its principle is similar to plasma cleaning. It mainly removes photoresist by reacting oxygen nuclei and photoresist in a plasma environment. Since the basic components of photoresist are hydrocarbon organic matter, under the action of radio frequency or microwave, oxygen is ionized into oxygen atoms and reacts chemically with photoresist to generate carbon monoxide, carbon dioxide and water, etc., which are then vacuumed away by a pump to complete the removal of photoresist.

[0003] In the IC manufacturing process, the efficiency of degumming is the main factor in determining the quality of degumming. Temperature, oxygen, RF frequency, RF power, and vacuum are the main factors affecting the degumming effect. In terms of degumming rate and effect, temperature has the greatest impact on the degumming rate. The higher the temperature, the more active the oxygen ions in the reaction chamber, the more violent the chemical reaction, and the better the degumming effect. However, too high a heating temperature may damage the substrate itself and affect the substrate yield. In addition, the RF itself will generate heat, so the degumming heating temperature is usually determined according to the process time and the substrate material. For thin glue (<3μm), the gap between the wafer and the hot plate during dry degumming is as follows: Figure 1 As shown in the figure, it can be observed that the wafer and the hot stage are in close contact with no gap. However, for thick resist (>3μm, <5μm), high temperature alone is not enough. Since the byproducts of the entire front-end etching are very heavy, the thick resist is easy to harden at high temperature. Even if the subsequent debonding time is extended, it is difficult to remove the residual resist completely. The actual debonding effect of the thick resist at this time is as follows: Figure 2 As shown, it can be observed that even after high-temperature debonding, there is still a large amount of residual glue left on the top of the thick glue. Summary of the invention

[0004] In order to solve the problem of residual glue left by thick glue at high temperature (250°C), the present invention provides a method for removing residual glue after dry stripping, which can be applied in a large-scale integrated circuit industrial manufacturing environment. The method removes the glue under the action of microwave source radio frequency power by changing the contact between the wafer and the hot stage during the dry stripping process, softens the glue without radio frequency power in a non-contact mode between the wafer and the hot stage, and optimizes the manufacturing process.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for removing residual glue after dry degumming, comprising the following steps:

[0007] Step 1) placing the wafer in the etching chamber;

[0008] Step 2) the ejector pin rises out of the heat table and lifts up the wafer, so that the heat table and the wafer are spaced apart in the up and down directions;

[0009] Step 3) introducing oxygen and water into the etching chamber in sequence to soften the surface layer of the photoresist;

[0010] Step 4) the ejector pin is lowered from the bottom of the wafer into the heat stage so that the wafer abuts against the heat stage, water is introduced into the etching chamber and a microwave source is started at the same time;

[0011] Step 5) After the reaction is completed, the microwave source is turned off, and water is continued to be introduced into the etching chamber, and oxygen and nitrogen are introduced at the same time to perform a degumming operation.

[0012] Preferably, the method further comprises: step 6) repeating the process from step 4) to step 5) 2 to 3 times to complete the degumming operation.

[0013] Preferably, the reaction pressure of the etching chamber in step 3) is 2 to 2.5 torr.

[0014] Preferably, the flow rate of oxygen gas is 3500-4000 sccm, and the time of oxygen gas introduction is 30-60 s.

[0015] Preferably, the amount of water introduced is 0.5 to 0.6 g, and the time for introducing water is 30 to 60 seconds.

[0016] Preferably, the radio frequency power of the microwave source in step 4) is 800-1400W.

[0017] Preferably, the reaction pressure of the etching chamber is 2000-4000 mtorr.

[0018] Preferably, the amount of water introduced is 0.3-0.6 g, and the time for introducing water is 30-50 s.

[0019] Preferably, in step 5), the flow rate of the oxygen gas introduced is 2000-4000 sccm, the flow rate of the nitrogen gas introduced is 200-800 sccm, and the time for introducing the oxygen gas and the nitrogen gas is 30-50 s.

[0020] Preferably, the amount of water continuously introduced into the etching chamber is 0.3-0.6 g.

[0021] The beneficial effects of the present invention are as follows:

[0022] The present invention removes glue under the action of microwave source radio frequency power by changing the contact between the wafer and the hot stage in the dry degumming process, and softens glue without radio frequency power in the non-contact mode between the wafer and the hot stage. The microwave frequency of 2.45GHz is adopted. When microwaves penetrate into the medium, the microwave energy interacts with the medium to a certain extent, so that the molecules of the medium vibrate 2.4 billion times at high speed, and the molecules of the medium rub against each other, causing the temperature of the medium to rise, so that the inside and outside of the medium material are heated and heated almost at the same time, forming a body heat source state, greatly shortening the heat conduction time in conventional heating, and when the condition is that the dielectric loss factor is negatively correlated with the medium temperature, the material is heated uniformly inside and outside. Water vapor and oxygen are dissociated into ions under the action of microwave source radio frequency, and react with the photoresist on the surface of the wafer at high temperature, and the purpose of nitrogen is to promote ionization, so that the reaction speed is accelerated. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the contact mode between the wafer and the hot stage (Pin down mode);

[0024] Figure 2 This is a diagram showing the actual effect of removing thick glue in the prior art;

[0025] Figure 3 is a flow chart of the method of the present invention;

[0026] Figure 4 Schematic diagram of the non-contact mode between the wafer and the hot stage (Pin up mode);

[0027] Figure 5 This is a picture showing the actual effect of removing the thick glue after step (2) of Example 1 is completed;

[0028] Figure 6 This is a picture showing the final debonding effect of the thick glue after debonding in Example 1;

[0029] Figure 7 is a graph of the rate of degumming in Example 1;

[0030] Figure 8 This is a diagram showing the uniformity of the degumming process in Example 1. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] It is understandable that in the prior art, microwaves refer to electromagnetic waves with wavelengths between infrared rays and radio waves. The frequency range of microwaves is approximately between 300MHz and 300GHz. The corresponding wavelength is between 1m and 1mm. The frequency of microwaves is higher than that of radio waves, and is also commonly referred to as "ultra-high frequency electromagnetic waves". Microwaves, as an electromagnetic wave, also have the dual nature of wave and particle. The basic properties of microwaves are usually presented as three characteristics: penetration, reflection, and absorption. For glass, plastic, and porcelain, microwaves almost pass through without being absorbed. For water and food, they will absorb microwaves and heat themselves, while for metal objects, microwaves will be reflected.

[0033] The present invention changes the contact between the wafer and the hot plate in the dry debonding process to debond under the action of the radio frequency power of the microwave source, and softens the adhesive without radio frequency power in a non-contact mode between the wafer and the hot plate. A microwave frequency of 2.45 GHz is adopted. When the microwave penetrates into the medium, the microwave energy interacts with the medium to a certain extent, so that the molecules of the medium vibrate 2.4 billion times at high speed, and the molecules of the medium rub against each other, causing the temperature of the medium to rise, so that the inside and outside of the medium material are heated and heated almost simultaneously, forming a body heat source state, greatly shortening the heat conduction time in conventional heating, and when the condition is that the dielectric loss factor is negatively correlated with the medium temperature, the material is heated uniformly inside and outside.

[0034] Example 1

[0035] A method for removing residual glue after dry degumming, the process is as follows Figure 3 As shown, the specific steps are as follows:

[0036] (1) Place the wafer in the etching chamber.

[0037] (2) In the dry stripping process, the wafer and the hot plate are not in contact with each other (Pin up mode). The hot plate is in the etching chamber, and the ejector pin is in the hot plate. The ejector pin can be raised and lowered. Figure 4 As shown, a gap is formed between the wafer and the heat stage through a pin, and the pin slowly rises from the heat stage and lifts up the wafer, so that the heat stage and the wafer are separated in the vertical direction.

[0038] (3) Oxygen and water are introduced into the etching chamber in sequence to soften the surface layer of the photoresist.

[0039] Parameter settings: etching chamber pressure is 2-2.5 torr; oxygen flow rate is 3500-4000 sccm, time is 30-60 s; water volume is 0.5-0.6 g, time is 30-60 s.

[0040] The process is optimized by combining non-contact and contact between the wafer and the hot plate (Pin Up and Pin Down modes). In this step, water and oxygen are passed without adding radio frequency to soften the glue.

[0041] The actual degumming effect of the thick glue at this time is as follows Figure 5 As shown, it can be observed that there is still a small amount of residual glue left on the wafer surface.

[0042] (4) The wafer and the hot stage contact mode (Pin down mode) is used again, such as Figure 1 As shown, the ejector pin slowly descends from the bottom of the wafer into the hot stage, so that the wafer abuts against the hot stage, water is introduced into the etching chamber and the microwave source is started at the same time.

[0043] Parameter settings: upper RF power is 800-1400W, frequency is 2.45GHz; etching chamber pressure is 2000-4000mtorr; water volume is 0.3-0.6g, time is 30-50s.

[0044] (5) After the reaction is completed, the microwave source is turned off, and water is continued to be introduced into the etching chamber, and oxygen and nitrogen are introduced at the same time to perform the descaling operation.

[0045] Parameter settings: water volume is 0.3~0.6g; oxygen flow rate is 2000~4000sccm, nitrogen flow rate is 200~800sccm, and time is 30~50s.

[0046] (6) Repeat steps (4) to (5) 2 to 3 times to complete the degumming operation.

[0047] Figure 6 This is the final degumming effect of thick glue. It can be observed that the residual glue on the wafer surface has been completely removed.

[0048] A preferred solution is that on the basis of step (2) and step (3), the number of cycles or time from step (4) to step (5) can be shortened or increased according to the thickness of the glue and the actual effect.

[0049] The process flow of this embodiment is shown in Table 1 below.

[0050] Table 1 Process flow

[0051] project Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step7 Step8 Pin Up Up Down Down Down Down Down Down Time(s) 30 30 40 50 40 50 40 50 <![CDATA[O2(sccm)]]> 4000 - - 3500 - 3500 - 3500 <![CDATA[N2(sccm)]]> - - - 200 - 200 - 200 <![CDATA[H2O(g)]]> - 0.6 0.5 0.3 0.5 0.3 0.5 0.3 Power(W) - - 1400 1400 1400 1400 1400 1400 Frequency (GHz) - - 2.45 2.45 2.45 2.45 2.45 2.45 Pressure (torr) 2.5 2.5 2 2 2 2 2 2

[0052] Table 1 shows the numerical settings of the process parameters of Example 1. The results show that the setting of the degumming rate is high and the uniformity is good. Figure 7 As shown in the figure, a higher degumming rate can improve machine utilization and increase production capacity. Figure 8 As shown, better degumming uniformity ensures the product yield.

[0053] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for removing residual glue after dry degumming, characterized in that: The following steps are involved: Step 1) placing the wafer in the etching chamber; Step 2) the ejector pin rises out of the heat table and lifts up the wafer, so that the heat table and the wafer are spaced apart in the vertical direction; Step 3) introducing oxygen and water into the etching chamber in sequence to soften the surface of the photoresist; Step 4) the ejector pin is lowered from the bottom of the wafer into the heat stage so that the wafer abuts against the heat stage, water is introduced into the etching chamber and a microwave source is started at the same time; the radio frequency of the microwave source is 2.45 GHz; Step 5) After the reaction is completed, the microwave source is turned off, and water, oxygen and nitrogen are continuously introduced into the etching chamber to perform a debonding operation.

2. A method for removing residual glue after dry degumming according to claim 1, characterized in that: The method further comprises: step 6) repeating the process from step 4) to step 5) 2 to 3 times to complete the degumming operation.

3. A method for removing residual glue after dry degumming according to claim 1, characterized in that: Step 3) The reaction pressure of the etching chamber is 2-2.5 torr.

4. A method for removing residual glue after dry degumming according to claim 3, characterized in that: Step 3) The flow rate of the oxygen gas is 3500-4000 sccm, and the time of the oxygen gas is 30-60 s.

5. A method for removing residual glue after dry degumming according to claim 4, characterized in that: In step 3), the amount of water introduced is 0.5-0.6 g, and the time for introducing water is 30-60 s.

6. The method for removing residual glue after dry degumming according to claim 1, characterized in that: Step 4) The radio frequency power of the microwave source is 800~1400W.

7. A method for removing residual glue after dry degumming according to claim 6, characterized in that: Step 4) The reaction pressure of the etching chamber is 2000-4000 mtorr.

8. A method for removing residual glue after dry degumming according to claim 7, characterized in that: In step 4), the amount of water introduced is 0.3-0.6 g, and the time of introducing water is 30-50 s.

9. The method for removing residual glue after dry degumming according to claim 1, characterized in that: Step 5) The flow rate of the oxygen gas is 2000-4000 sccm, the flow rate of the nitrogen gas is 200-800 sccm, and the time for the oxygen gas and the nitrogen gas is 30-50 s.

10. A method for removing residual glue after dry degumming according to claim 9, characterized in that: In step 5), the amount of water continuously introduced into the etching chamber is 0.3-0.6 g.

Images