TW492905B - Method of chemical-mechanical planarization - Google Patents

Abstract

The present invention relates to a method of chemical-mechanical planarization (CMP), which is applicable to polishing silicon oxide layer on a wafer using a silicon nitride layer as a stop layer, and comprises the following steps: (a) providing a planarization liquid having a first pH value and a polishing pad; (b) delivering the planarization liquid having the first pH value to the polishing pad; (c) pressing the wafer and the polishing pad with a pressure; (d) at least relatively moving the wafer or the polishing pad to perform a first stage polishing; and (e) changing the first pH value of the planarizatiion liquid to a second pH value and performing a second stage polishing.

Description

492905 V. Description of the invention (1) Field of the invention: This case is about a chemical-mechanical planarization (CMP) method.

I specifically refers to a chemical-mechanical planarization (CM P) method of polishing a silicon dioxide layer with a silicon nitride layer as a stop layer. Background of the invention:

! With the miniaturization of semiconductor devices, the control of semiconductor processes also becomes very important. Taking the planarization process as an example, the conventional spin-on glass method! (Sp i n-On G 1 ass) and Etch Back have been difficult to meet the requirements of process flatness, so chemical mechanical planarization Mechanical Planarization (CMP)

i At present the most noticeable planarization process, chemical mechanical planarization |

(Chemical-Mechanical Planarization, CMP) can be applied to Shallow Trench Isolation (STI), Inter-Layer Dielectrics (ILD), and Inter-Metal Dielectrics,丨 I MD) silicon dioxide layer can also be applied to the tungsten, aluminum and copper layers of metal wires. Compared with the conventional spin-on glass method and Etch Back, Chemical-Mechanical Planarization (CMP) is already possible

Page 4 492905 丨 V. Description of the invention (2) To achieve the purpose of global planarization of wafers 0 Please refer to the first figure, which is a chemical mechanical planarization of a wafer 13 (Chemical- Mechanical Planarization (CMP)

In Figure I, a chemical mechanical polishing machine table 10 includes a polishing table 17, a wafer holder 16, a polishing pad 15, and a planarizing liquid 14. For Chemical-Mechanical Planarization (CMP)

Before I, the wafer holder 16 first grasps the back of the wafer 13 and then presses the front side of the wafer 13 on the polishing pad 15 of the polishing table 17 and then injects a flattening liquid 1 4 In order to perform so-called chemical mechanical grinding. When grinding is performed, in addition to the drive system 11 itself can rotate in the A direction, the drive system 11 can also move in other directions (such as the B direction), and the transmission mechanism 12 can rotate in the C direction besides itself. You can move in other directions (such as the d direction). In fact, the planarizing liquid 14 also contains chemical auxiliaries (such as oxidants) to help the chemical mechanical planarization (Chemi cal-Mechanical Planarization, CMP), and during grinding, it will follow the transport: Or in other ways, the flattening liquid 14 is continuously supplied to the polishing pad 15 of the grinding table 17. Chemical mechanical planarization

I

(Chemical-Mechanical Planarization, CMP) is to use the chemical reaction provided by the chemical assistant in the planarizing liquid 14 to mechanically polish the wafer 1 3 on the polishing pad 15 to place the wafer 13 on Protruded deposition: A flattening process in which layers are slowly forced σ to remove. The polishing pad 15 can be a traditional polishing pad made of a non-abrasive material (such as PU), or an abrasive particle.

Page 5 492905 V. Description of the invention (3) A new fixed abrasive pad (Fixed-Abrasive ρ 1 i s h i n g P a d) uniformly dispersed and fixed therein. The flattening liquid 14 can be a traditional slurry containing abrasive particles and chemical additives, or a solution containing no abrasive particles. Generally speaking, the traditional slurry containing Abrasive Particle I is used in traditional polishing pads, while the flattening fluid system without Abrasive Particle is used in Fixed-Abrasive Polishing Pad). Because traditional polishing pads (S 1 urry) tend to be concentrated around the wafer during polishing, the polishing speed around the wafer is higher than the polishing speed at the center of the wafer. This problem causes poor flatness, and It may also scratch or deform the wafer. Replaced by a fixed polishing pad (Fixed-Abrasive Po 1 i sh i ng Pad), because the abrasive particles | (Abrasive Particle) is uniformly dispersed and fixed in the polishing pad, so as to avoid poor flatness or around the wafer Scratching and deformation problems. However, 'the Chemical-Mechanical Planarization (CMP) method of the Fixed-Abrasive Polishing I Pad has its shortcomings, especially the polishing dioxide using a silicon nitride layer as a stop layer. Chemical mechanical planarization of silicon layers (such as applied to ground shallow trench isolation (S ha 1 1 0w Trench Isolation, STI), one of inter-Layer Dielectrics (ILD) ^ gasification stone layer ) Has the following disadvantages of poor grinding control ability: 1 · As shown in the second figure, when grinding wafer patterns with high differences,

V. Description of the invention (4) j ^ Grinding-after the oxide stone layer 21 is exposed to the silicon nitride layer 22, there will be two remaining emulsified stone layers 23 = the wafer pattern at a lower height, which will reduce Good product. Although the residual dioxide dioxide 23 can be removed by over-polishing (〇verp〇1 ish), at the same time, because the choice between the silicon oxide layer 2 丨 and the silicon nitride layer 22 is low, the nitride nitride is caused. The layer 22 is reduced from the original thickness a to the subsequent thickness b, and the too thin thickness b often cannot meet the requirements of the specification (Spec ·) in the manufacturing process. ^ 2 · Due to the problem of silicon dioxide residue in the first point above, the conventional technique also uses the so-called reversed raask etch and deglaze steps to compensate for the absence of poor grinding control ability. For this reason, in view of the lack of known technology, the present invention has learned the test and a persevering research spirit, and finally developed the method of mechanical flattening in this case. " However, one more step will increase the production cost, and also reduce the production capacity. The probability of product failure will also increase the heart rate. Brief description of the invention: The main purpose of this case is to provide _ a kind of lifting force chemical mechanical flatness. Method. The secondary purpose of this case is to provide a method for chemical mechanical planarization of residues. Another object of this case is a method of mechanical planarization. Is to provide a chemical machine to increase productivity

Page 7 492905 V. Description of the invention (5) (Chemical-Mechanical Planarization, CMP) method is applied to a wafer with a silicon nitride layer with a silicon nitride layer as a stop layer on a polished silicon dioxide layer, which includes the following steps: (A) providing a flattening liquid having a first pH value and a polishing pad; (b) distributing the flattening liquid having the first pH value onto the polishing pad; (c) pressing the crystal with a pressure And the grinding pad, (d) moving at least one of the wafer and the polishing pad relative to perform a first stage polishing; and (e) changing the first pp value of the planarizing liquid to one The second p threshold value and a second stage of grinding.

According to the above-mentioned concept, the polishing pad is a fixed-abrasive polishing pad I. According to the above-mentioned concept, the flattening liquid system is a solution containing no abrasive particles. According to the above concept, wherein the step (e) changes the first PH value by adding a member selected from the group consisting of deionized water, potassium hydroxide, ammonium hydroxide, cesium hydroxide, and tetramethylammonium hydroxide TMAH), one of a mixed liquid of potassium hydroxide and tetramethylammonium hydroxide, and one of a mixed liquid group of potassium hydroxide and ammonium hydroxide was completed in the flattening liquid.

j According to the above concept, the flattening liquid further includes a buffer I agent to stabilize the first pH value and the second pH value of the flattening liquid. According to the above-mentioned concept, wherein the planarizing liquid further includes a chemical auxiliary agent to help chemical mechanical planarization by chemical action. According to the above concept, wherein the first pH value is higher than U. According to the above concept, the grinding time of the first stage is

492905 V. Description of the invention (6) The point detection system (EPD System) detects a terminal debt controlled by S i g n a 1). I according to the above concept, wherein the second pH value is lower than 1 1 according to the above concept, wherein the second stage of grinding is according to the above concept, wherein the first p Η value is lower than 1] according to the above concept, wherein the first stage The EPD System detects an end point detection i

Signal). According to the above concept, wherein the second pH is higher than 1] According to the above concept, wherein the second stage of grinding is according to the above concept, wherein the first pH value is lower than 1] According to the above concept, wherein the first stage of grinding second. According to the above concept, wherein the second pH value is higher than 1] | According to the above concept, wherein the second stage of polishing is based on the above purpose, another aspect of the present case provides a chemical-mechanical planarization method, which is applied to a wafer It has a silicon nitride layer as the final silicon oxide layer, which includes the following steps: (a) performing a wafer and a polishing pad under a first-tanning liquid and (b) changing the planarizing liquid The second PH value of the first PH value, and the second stage of the wafer and the polishing pad according to the above-mentioned concept, wherein the polishing pad is a fixed (Abrasive Polishing Pad).

Measure time (EPD 〇 time is 40 seconds. 〇 time is based on a final test signal (EPD time is 10 seconds. 〇 time is 100 time is 10 seconds. Chemical mechanical flat CMP) stop polishing Two-pH one level grinding in one stage; & one second pH grinding. Grinding 塾 492905 V. Description of the invention (7) According to the above concept, wherein the flattening liquid system is a solution containing no abrasive particles; It is envisaged that, in step (b), the first pH value can be changed by adding a compound selected from the group consisting of deionized water, potassium hydroxide, ammonium hydroxide, hydroxide, and tetramethyl nitrogen monoxide (TMAH). ), One of the mixed solution of potassium hydroxide and tetramethylammonium hydroxide, and one of the mixed liquid group of potassium hydroxide and ammonium hydroxide is completed in the flattened liquid. According to the above concept, where The flattening liquid further includes a buffering agent to stabilize the first pH value and the second pH value of the flattening liquid.

According to the above-mentioned concept, the planarizing liquid further includes a chemical i additive to assist chemical mechanical planarization by chemical action.

I According to the above concept, the grinding time of the first stage is controlled by an end point detection signal (EPD S i g n a 1) detected by an end point detection system (EPD System). This case, as well as its further purposes and effects, will refer to the detailed description of a preferred embodiment and the accompanying drawings for a deeper understanding. Description of the preferred embodiment:

As mentioned earlier, the chemical-mechanical planarization (CMP) method of the fixed-abrasive polishing pad has its shortcomings, especially for polishing using a silicon nitride layer as a stop layer. Silicon oxide

Page 10 Outside 2905 V. Description of the invention (8) ~-The chemical mechanical planarization of the layer has the lack of poor grinding control ability. Therefore, the present invention provides a chemical mechanical planarization method for improving polishing control ability. According to the present invention, different levels of removal rates can be obtained by grinding the same material layer with flattening liquids of different pH values. Of course, under different pH values, the removal selectivity between layers is also different. There is a linear relationship. When polishing at pH = 1 0 · 8, the removal selectivity is silicon dioxide · silicon nitride = 1 0 0 0: 1 and when polishing at pH = 12, the removal selectivity is silicon dioxide: nitrogen Siliconization = 3.5 ... In other words, the higher the pH value, the lower the removal ratio of di-emulsified silicon to silicon nitride. In the present invention, the pH value of the Hiragaki liquid is adjusted, and at the same time, the endpoint detection mode (EpD Mode) and time mode (Time Mode) are used, through the first stage of polishing (Polish) and the second stage of polishing (〇verp〇Hsh) to improve the grinding control ability. Please refer to the descriptions of the following three embodiments to understand the invention applied to the flattening process in detail. Example one

^ Grind the wafer to the end point detection under the flattening liquid of pH > 11 · 5. After the end point detection signal (EpD Signal) is detected by the system,

Flatten and grind the wafer for 40 seconds under the liquid. This embodiment is mainly applied to the polishing of wafer patterns with no difference in degree of reversal. The first stage of rapid polishing is performed at a high pH value until the silicon nitride layer has been exposed in some areas of the wafer pattern. After the end point detection signal, one of the second stage is performed at a lower pH value.

492905 V. Description of the invention (9) (Overpol ish) to remove the silicon dioxide layer that has not been completely ground. In the second embodiment, the wafer is polished under the pH < 10 flattening liquid, and the wafer is polished to the endpoint detection system to detect the end point detection signal (EPD Signal), and then the crystal is polished on the pH > 11. 5 flattening liquid. Circle 10 seconds. This embodiment is mainly applied to the polishing of wafer patterns with high differences (as shown in the third figure). The first stage of polishing with a higher silicon dioxide to silicon nitride selection ratio is performed at a lower pp value. After the silicon nitride layer 32 has been exposed in a part of the wafer pattern and the final i-point debt measurement signal is detected, the second stage of rapid over-polishing (Over pol ish) is performed at a higher pH value to remove The thickness of the silicon dioxide layer 31 that has not been completely polished, the thickness of the silicon nitride layer after over-polishing (〇verp〇1 ish) _ The thickness of the silicon nitride layer c before over-polishing is approximately equal, which can meet the process specifications (Spec ·) requirements. Compared with conventional technology, during the second stage of over-polishing, the silicon dioxide has a high selectivity to silicon nitride, so the stone dioxide can be removed. This embodiment can avoid the problem shown in the second figure. The problem of silicon dioxide residue does not require a reversed imask etch step or repeated deglaze steps to compensate for the shortcomings of poor grinding control. Example 3 First, the wafer was ground for 1000 seconds under a flattening liquid of pH < 10, and then

Page 12 492905 V. Description of the invention (~)-~ p H > 1 1 · 5 in a flattening liquid, the wafer is polished for 10 seconds. This embodiment is similar to the second embodiment, and is also applied to the polishing of wafer patterns with high differences. The difference between the two embodiments is that the polishing time control in the first stage is controlled by the end point detection mode (EPD Mode) of the second embodiment. Instead of the time mode (T i me Mode) of this embodiment, when the endpoint detection system fails, it can also achieve a good control effect by this embodiment. As in the second embodiment, this embodiment also The problem of silicon dioxide residue can be avoided, and a reflective mask etch step (reversed mask etch) or repeated removal step (deglaze) step is not needed to make up for the disadvantage of poor grinding control ability. The above two consecutive examples are used as examples, and which embodiment should be applied in which product process depends on different wafer patterns, and the leveling solution ^ pH value should also be adjusted appropriately to achieve good control ability. When changing the ρΗ value, other chemical mechanical planarization parameters can also be adjusted at the same time (such as polishing pad or crystal | circle = rotation speed, moving speed of polishing pad or wafer, pressure between polishing pad and wafer) to achieve polishing effect optimize. The value of the flattening liquid can be adjusted by adding deionized water, acidic agents or alkaline agents. Preferably, the alkaline agent is potassium hydroxide, ammonium argon oxide, t oxide planer or tetra | fluorenyl ammonium hydroxide? "It is a mixture that does not produce a chemical reaction with each other," for example, a mixed solution of potassium lice and tetramethylammonium hydroxide, or a mixed solution of oxidized money with nitrogen). The flattening liquid can also contain!, A lotion to stabilize the pH value of the flattening liquid, and chemical additives to help chemical and mechanical planarization by the effect of & Γ. Of course, Abras i ve Par t i c 1 e)

492905 V. Description of the invention (π) It is made of rhenium dioxide material that is conventionally used in chemical-mechanical planarization of fixed-abrasive polishing pads. With the invention of this case, the problem of residual silicon dioxide can be avoided, and a reversed mask etch or deglaze step can be reduced, which can improve the grinding control ability, reduce production costs and increase production capacity. . This case may be modified by any person skilled in the art, but none of them can be protected as attached to the scope of patent application.

% Page 14 492905 Schematic description of the diagram: First diagram: Schematic diagram of Chemical-Mechanical Planarization (CMP); Second diagram: Schematic diagram of polishing silicon dioxide layer using conventional technology; and FIG. 3 is a schematic diagram of a process for polishing a silicon dioxide layer according to the present invention. Description of drawing number: 1 1: Drive system 1 3: Wafer 1 5: Polishing pad 17: Polishing table 2 1: Silicon dioxide layer 2 3: Silicon dioxide residue 3 2: Silicon nitride layer

1 0: Chemical mechanical polishing machine 1 2: Transmission mechanism 1 4: Flattening liquid 1 6: Wafer holder 18: Transport tube 2 2: Silicon nitride layer 3 1 Silicon dioxide layer

Page 15

Claims (1)

492905 VI. Application Patent Scope 1. A chemical-mechanical planarization (CMP) method is applied to a wafer with a silicon nitride layer as a stop layer for grinding and oxidizing. A silicon layer including the following steps: (a) providing a planarizing liquid having a first pH value and a polishing pad; (b) distributing the planarizing liquid having the first pH value onto the polishing pad; (c) ) Pressing the wafer and the polishing pad with a pressure; (d) relatively moving at least one of the wafer and the polishing pad to perform a first stage polishing; and (e) changing the first pH value of the planarizing liquid to a second pH value and performing a second Stage of grinding. 2. The method as described in item 1 of the scope of the patent application, wherein the polishing pad is a fixed-abrasive polishing pad. 3. The method according to item 2 of the scope of patent application, wherein the flattening liquid is a solution containing no abrasive particles. 4. The method according to item 1 of the scope of patent application, wherein the step (e) changes the first pH value by adding a member selected from the group consisting of deionized water, potassium hydroxide, ammonium hydroxide, cesium hydroxide, and Tetra Methy 1 Ammonium Hydroxide (TMA Η), a mixed solution of oblique hydroxide and tetramethylammonium hydroxide, and a mixed solution of potassium hydroxide and ammonium hydroxide This is done in a flattening liquid. I 5 The method as described in item 4 of the scope of patent application, wherein the flattening liquid further comprises a buffering agent to stabilize the first pH of the flattening liquid Page 16 492905 I Sixth, the scope of patent application and the second pH value. 6. The method according to item 5 of the scope of patent application, wherein the flattening liquid further comprises a chemical assistant to assist chemical mechanical flattening by chemical action. 7. The method according to item 1 of the scope of patent application, wherein the first pH value is higher than 1 8 8. The method according to item 7 of the scope of patent application, wherein the grinding time of the first stage is determined by an end point The detection system (EPD System) detects an endpoint detection signal (EPDS igna 1) to control it. 9. The method according to item 8 of the scope of patent application, wherein the second pH value is lower than U.OilO. The method according to item 9 of the scope of patent application, wherein the grinding time of the second stage I i is 4 0 seconds. 11. The method according to item 1 of the patent application range, wherein the first pH value is lower than 11. 1 2. The method according to item 11 of the scope of patent application, wherein the grinding time in the first stage is controlled by an endpoint detection signal (EPD S i g n a 1) detected by an endpoint detection system (EPD System). + 13. The method according to item 12 of the scope of patent application, wherein the second pH value! 丨 higher than 1 b 1 4. The method according to item 13 of the scope of patent application, wherein the second stage of grinding The time is 10 seconds. 15. The method according to item 1 of the scope of patent application, wherein the first p 第一 value is lower than 11. Page 17 492905 6. Scope of patent application 16 · The method as described in item 15 of the scope of patent application, wherein the grinding time in the first stage is 1000 seconds. 17. The method according to item 16 of the scope of patent application, wherein the second pH value is higher than 11. 18 · The method as described in item 17 of the scope of patent application, wherein the grinding time in the second stage is 10 seconds. 19. A chemical-mechanical planarization (CMP) method, which is applied to a wafer with a polished silicon dioxide layer having a silicon nitride layer as a termination layer, which includes the following steps: (a) performing the first stage polishing of the wafer and a polishing pad under a planarizing liquid of a first pH value; and (b) changing the first pH value of the planarizing liquid to a second pH I value, and the second stage polishing of the wafer and the polishing pad is performed. 2 0. The method according to item 19 of the scope of patent application, wherein the polishing pad is a fixed-abrasive polishing pad. 2 1. The method as described in item 20 of the scope of the patent application, wherein the planarizing solution 1 丨 is a solution containing no abrasive particles. f 22. The method according to item 19 of the scope of application for a patent, wherein the step (b |) changes the first pH value by adding selected from the group consisting of deionized water, potassium hydroxide, ammonium hydroxide, hydroxide planer, Tetra Methyl Ammonium Hydroxide (TMAH), a mixed solution of potassium hydroxide and tetramethylammonium hydroxide, and a mixed solution of potassium hydroxide and ammonium hydroxide This is done in a chemical fluid. I 2 3 · The method according to item 22 of the scope of patent application, wherein the flattening liquid Page 18 492905 6. Scope of patent application The body further includes a buffering agent to stabilize the first pH value and the second pH value of the flattening liquid. 24. The method according to item 23 of the scope of patent application, wherein the planarizing liquid further includes a chemical assistant to help chemical mechanical planarization by chemical action. 25. The method as described in item 19 of the scope of patent application, wherein the grinding time in the first stage is controlled by an endpoint detection signal (EPDS igna 1) detected by an endpoint detection system (Epd System) . 26. A chemical-mechanical planarization (CMP) method is applied to a wafer with an abrasive silicon dioxide layer with a nitrided layer as a gastric termination layer, which includes the following steps: (a) providing a flattening liquid having a first pH value and a polishing pad; (b) distributing the flattening liquid having the first pH value to the polishing pad; (c) pressing the crystal with a pressure Round and the polishing pad; (d) relatively moving at least one of the wafer and the polishing pad to perform a first-stage polishing; and I (e) changing the first pH value of the pingyuan liquid to a second The pH value is I, and a second stage of polishing is performed; I, wherein the 5H polishing pad is a fixed polishing potential (Fixed-Abrasive jPolishing Pad), and the flattening liquid system is a solution containing no abrasive particles. 2 7 · The method described in item 26 of the patent application park, wherein the step (e 492905 VI, scope of patent application) of changing the first pH value can be added by selecting from deionized water, potassium hydroxide, Ammonium hydroxide, hydroxide hydroxide, Tetra Methyl Ammonium Hydroxide (TMAH), a mixed solution of potassium hydroxide and tetramethylammonium hydroxide, and a mixed solution of potassium hydroxide and hydroxide One of the groups is done in the flattening liquid. 28. The method according to item 27 of the scope of patent application, wherein the flattening liquid further comprises a buffering agent to stabilize the first pH value and the second pH value of the flattening liquid. 29. The method according to item 28 of the scope of patent application, wherein the planarizing liquid further comprises a chemical assistant to help chemical mechanical planarization by chemical action. 30. The method as described in item 26 of the scope of patent application, wherein the grinding time in the first stage is controlled by an end point detection system (EPD System) detecting an i end point detection signal (EPD Signal) . Page 20