JP3198525B2 - Polishing apparatus, polishing method, and semiconductor device manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing apparatus and a polishing apparatus.
And a method for manufacturing a semiconductor device . INDUSTRIAL APPLICABILITY The present invention can be used as a means for performing polishing for flattening a surface, for example, when flattening irregularities on a substrate when forming an electronic material such as a semiconductor device . It can be used when a semiconductor device is formed by a polishing technique .

[0002]

2. Description of the Related Art The application field of the polishing technique is wide, and it has been used, for example, for flattening irregularities generated on a substrate such as a semiconductor substrate in the manufacture of a semiconductor device (for example, Japanese Patent Laid-Open Publication No. 60-39835).

[0003] On the other hand, in the field of semiconductor devices, the capacity of devices has been increasing, but a multilayer wiring technique is necessary to reduce the chip area as much as possible to increase the capacity.
In this multi-layer wiring technology, it is important to flatten the base in order to prevent disconnection of the multi-layer wiring. This is because if the base has irregularities, a so-called disconnection occurs in which the wiring is cut on a step caused by the unevenness. In order to perform this flattening satisfactorily, the flattening from the initial step is important. For this reason, for example, flat trench isolation or the like has been considered. What is trench isolation?
An insulating material is buried in a trench (trench) formed in a semiconductor substrate to perform element isolation. This is advantageous because it can be formed finely, but after embedding the groove, remove the protrusion made of the embedding material deposited on the part other than the groove,
It needs to be planarized. As a method of forming this flat trench isolation, there is a method shown in FIG.
In this method, first, the grooves 41 to 43 formed in the base 1 such as a substrate are filled with a filling material 5 by a deposition means such as CVD to obtain a structure shown in FIG. In this structure, the embedding material 5 is thickly deposited in portions other than the grooves 41 to 43, and the convex portions 51 are generated. Therefore, this convex portion 51
Is removed by polishing and flattened as shown in FIG. In the figure, reference numeral 2 denotes a polish stopper layer, which is formed of, for example, a silicon nitride film having a lower polish rate if the filling material is SiO ₂ .

However, a problem with this technique is that there is no means for determining the end point of polishing. Generally, polishing is performed at a set time. However, if the removal rate by polishing becomes slow, the SiO ₂ or the like as the filling material 5 cannot be sufficiently polished, and the filling material to be removed remains as shown in FIG. Conversely, if the removal rate is increased, the base is polished to the state shown in FIG. 6B. Increasing the thickness of the stopper layer 2 itself increases the margin for the change in the removal rate due to polishing, but increases the aspect ratio of the trench, making it difficult to fill the trench by CVD or the like. Therefore, in such circumstances,
There is a need for an effective endpoint determination technique for polishing.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and provides a polishing apparatus, a polishing method, and a polishing method capable of effectively determining the end point of polishing.
It is an object of the present invention to provide a method for manufacturing a semiconductor device .

[0006]

The basic structure of the present invention is to monitor the sound generated at the time of polishing and determine the end point of the polishing by changing the monitor sound by removing the material to be polished. . That is, the polishing apparatus according to the present invention is a polishing apparatus used for forming an electronic material for removing and planarizing a material to be polished on a stopper layer, and a pickup apparatus for picking up vibration noise generated during polishing. A high- period during the vibrating sound generated when the polished material layer is removed and the lower stopper layer, which is a material layer having a lower polishing speed than the polished material layer, is exposed.
A change in which a wave component appears is detected by the pickup device,
A polishing apparatus characterized in that an end point of polishing is determined based on the detection result, thereby achieving the above object. A polishing method according to the present invention is a polishing method used for forming an electronic material for planarizing by removing a polished material layer on a stopper layer, wherein the polished material layer is polished to form the polished material layer. Exposing a lower stopper layer, which is a material layer having a lower polishing rate, and a high-frequency component included in a vibration sound generated when the stopper layer is exposed.
Detecting a change that appears , based on the detection result,
Determining the end point of polishing, thereby achieving the above object. The method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device, the method comprising at least a filling step of filling a groove formed in a base with a filling material and a step of removing a filling material on the base by polishing. As a layer, a material layer having a polishing speed lower than that of a material to be polished made of an embedding material is formed in advance, and vibration generated when the polish exposes the stopper layer in the embedding material removing step on the substrate by the polish. High frequency in sound
A method for manufacturing a semiconductor device, characterized by detecting the appearance of a component and determining the end point of polishing based on the detection result, thereby achieving the above object.

[0007]

According to the present invention, when the polished material portion to be polished is removed, the underlying material starts to be polished. At that time, the sound generated during polishing differs depending on the material. It is possible to know that polishing of the material to be polished has been completed. Therefore, this makes it possible to correctly determine the end point of the polish.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. However, needless to say, the present invention is not limited by the following examples.

Embodiment 1 Reference is made to FIGS. In the present embodiment, a polisher having a sound monitoring mechanism was used, and polishing was performed so that the end point could be determined.

The material to be polished in this embodiment is shown in FIG.
As shown in FIG. 1, a substrate 1 (here, a silicon semiconductor substrate)
The grooves 41 to 43 formed in
It is embedded with iO ₂ , and at this time, a convex portion is formed. In the figure, reference numeral 2 denotes a polished stopper layer made of silicon nitride. This is a structure in the middle of trench isolation formation, and a structure in which a silicon nitride film is formed as a stopper layer 2 on a silicon substrate is patterned to form grooves 41 to 43, which are formed, for example, by bias ECR-CVD. By law
It is buried with a burying material 5 of iO ₂ (irrespective of a forming means, any other may be used).

In this embodiment, as shown in FIG.
Polished material placed on sample stage 74 (see FIG. 3)
Is polished with a polish plate P. In the figure, 7
Reference numeral 3 denotes a rotation axis of the polish plate P. In this embodiment, during polishing, a sound E generated by the polishing is monitored. FIG. 3 shows sound pickup means. As this pickup means, for example, a sound collecting microphone can be used, and the polished sound is picked up at a position slightly away from the place where the polishing is performed, but not so far away. Generally, at the time of polishing, a polished plate P and a material to be polished 10
Since both the (sample stage 74) rotate, the pickup means is not usually provided in the rotating portion. However, it is arranged on the sample stage 74 or the like by embedding or the like, and the vibration noise is directly detected, converted into a signal, and monitored. It may be sent to the department.

In this embodiment, first, SiO _{2 as the} filling material 5 is polished. Next, when the polishing of SiO ₂ is completed, the stopper layer 2 of polished Si ₃
N ₄ layer is exposed. At this time, since the sound during polishing differs depending on the material to be polished, the waveform of the sound of the SiO ₂ polish changes to the waveform of the Si ₃ N ₄ polish. This change is detected, and the time of the change is set to SiO
Judge as the end point of ₂ polish.

Usually, when a polish stopper layer is formed, a material which is less polished than the upper material is used, that is, a material having a lower polishing speed is used to make it difficult for polishing to proceed. Is used. Generally, a hard material has a high sound when polished and changes to a sound close to a metallic sound. Therefore, by knowing this point accurately and quickly, it is possible to determine an appropriate polishing end point. This is a means that can be used universally when judging when the polish has reached the base material and judging the end point of the polish because the polish sound changes when the material changes, regardless of whether the base is a polish stopper layer or not. It is.

[0014] In this embodiment, as schematically shown in FIG. 2, the embedding material 5 is a time of etching (b) SiO ₂ in the etching as shown in FIG. 2 (A), such as code Although a relatively low frequency sound is generated as shown by I, when the etching reaches the etching stopper layer 2 and becomes (b) Si ₃ N ₄ etching as shown in FIG. , High frequency components appear. Therefore, this change is monitored to make a determination. If the generated high-frequency component is known in advance, the end point can be determined when the high-frequency component exceeds a certain threshold. This threshold value is generally 20 KHz or slightly lower.
If a component that reaches this threshold value occurs, it can be determined that it is the end point.

Alternatively, the background waveform I is subtracted from the waveform II, the remaining component (high-frequency component) is monitored, or it is detected whether or not the component exceeds a threshold value to determine the end point. You can also do so. For example, it can be set as appropriate, such as stopping the polish by one minute after this component appears.

The polishing means that can be used in this embodiment is arbitrary, and for example, an apparatus illustrated in FIG. 9 can be used. In FIG. 9, reference numeral 1 denotes a silicon substrate (wafer) as a material to be polished, and P denotes a polishing plate (polishing head).
It is. Reference numeral 71 denotes a slurry introduction pipe, 72 denotes a slurry containing abrasive particles, 73 denotes a rotation axis of the polishing plate P, 74 denotes a wafer holding sample table that supports the workpiece 1 to be polished, and 75 denotes a rotation axis of the wafer holding sample table. Reference numeral 76 denotes a polishing pressure, which should be appropriately adjusted.

According to this embodiment, since the polisher having a mechanism for monitoring the sound generated during polishing is used, it is possible to determine the appropriate end point of the polishing by utilizing the difference in sound depending on the material to be polished.

Embodiment 2 Next, Embodiment 2 will be described with reference to FIG. In this example, a concavo-convex structure to which the polishing means of the present invention can be preferably applied is provided during the formation. Specifically,
In the formation of the trench isolation, a convex portion made of a filling material formed in a place other than the groove (trench) is polished.

Since the conventional LOCOS structure has a limit in integration due to its bird's beak, when a trench isolation structure is formed instead, a polishing method is applied at that time as shown in FIGS. Technology is conceivable. FIG.
In the method shown in FIG. 7, a conformal CVD-SiO ₂ is deposited as a filling material 5 in the filling of the grooves 41 and 42 (FIG. 7A), and this is polished as shown in FIG. 7B. Causes a step between the wide groove 41 and the narrow groove 42 by the thickness of the oxide thin film 11 such as SiO ₂ and the polish stopper layer 2 (FIG. 7 (c); AB in the figure is a step).

In the method shown in FIG. 8, a resist is applied on conformal CVD-SiO ₂ , which is the filling material 5, and is patterned to form a block resist 61, and further a resist layer 62 is coated ( FIG.
(A)) and then polishing to obtain the structure of FIG. 8 (b). In this method, although there is no difference in the buried film thickness after polishing, the number of steps is increased and the productivity is reduced due to the presence of a plurality of photoresist patterning steps.

On the other hand, in this embodiment, the bias EC
The trench isolation is formed by a process including a trench filling process by the R-CVD method, a filling material (SiO ₂ ) removing process by polishing, and a process of forming Si ₃ N ₄ as a stopper layer at the time of polishing.

Specifically, as shown in FIG. 4, in this embodiment, first, a pad-Si
As O ₂ 11, a 100 ° SiO ₂ film is formed by a thermal oxidation method. Then, a Si ₃ N ₄ film is LP-coated as a stopper layer 2.
It is formed to a thickness of 1500 ° by the CVD method. Next, photoresist patterning for forming a desired trench pattern is performed to obtain a resist pattern 6. This is the structure shown in FIG.

Next, a trench 4 is formed by etching.
1, 42 are formed. For example, using an ECR plasma etcher, gas used: C ₂ Cl ₃ F ₃ (F113) / SF ₆ = 6
0/10 SCCM pressure: 10 mTorr Microwave power: 850 W RF bias: 150 W Thus, the structure shown in FIG. 4B is obtained. One of the grooves 41 and 42 in this example is a wide trench (groove 41), and the other is a narrow trench (groove 42).

Next, an SiO ₂ film is formed by a bias ECR-CVD method until the SiO ₂ film becomes the same as the trench depth. The conditions may be as follows. Using gas _{system: SiH 4 / N 2 O =} 21 / 35SCCM pressure: 7 × 10 ^-4 Torr microwave power: 1000W RF bias: 300 W Thus, embedded SiO ₂ is buried material deposited FIG 4 (c ). Next, polishing is performed by a polisher (FIG. 4D). The polishing conditions are shown in Table 1 below. The structure of the polisher used is that shown in FIG.

[Table 1] The main component of the slurry is silica (particle size: 10 to several 100 μm) KOH water

Here, the polished SiO ₂ and Si ₃
Since the ratio of the etching rate of N ₄ is 5: 1,
The i ₃ N ₄ layer functions as the stopper layer 2 and the Si
All O ₂ can be removed. In addition, the underlying Si is not etched, and the thickness of SiO _{2 in} the isolation portion is maintained. At this time, the generated sound is monitored to determine the end point. The obtained structure is shown in FIG.

Next, the Si ₃ N ₄ of the stopper layer 2 is removed with hot phosphoric acid, and the pad SiO ₂ layer 11 is removed by light etching to form isolation. Thus, the structure shown in FIG. The embedding material 5 slightly protrudes from the surface of the base 1, thereby improving the pressure resistance.

According to this embodiment, both the wide groove 41 and the narrow groove 42 can be buried with the same buried film thickness. In addition, a complicated plurality of resist steps are not required, and the process is easy.

[0028]

The polishing apparatus and the polisher according to the present invention.
Method, and a method of manufacturing a semiconductor device using the same,
This has the effect that the end point of the polish can be effectively determined.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of Example-1.

FIG. 2 is a view showing a process of Example-1.

FIG. 3 is a sectional view showing a material to be polished in Example-1.

FIG. 4 is a process chart of Example-2.

FIG. 5 is a diagram showing a background art.

FIG. 6 is a diagram showing a problem.

FIG. 7 is a diagram showing a conventional technique.

FIG. 8 is a diagram showing a conventional technique.

FIG. 9 is a configuration diagram of an example of a polishing apparatus used in the embodiment.

[Reference Numerals] P ... polished plates, sound generated at the time of E ... polish, 2 ... stopper layer, 5 ... the Porisshi <br/> Interview material layer (filling material), 10 ...・ Polished material (wafer).

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 21/304 B24B 37/04

Claims (3)

(57) [Claims] 1. A polishing apparatus used for forming an electronic material for flattening by removing a material layer to be polished on a stopper layer, comprising: a pickup device for picking up a vibration sound generated during polishing. The vibration material generated when the polish material layer is removed and the lower stopper layer, which is a material layer having a lower polishing rate than the material layer to be polished, is exposed.
A polishing apparatus characterized in that a change in appearance of a minute is detected by the pickup device, and an end point of polishing is determined based on the detection result. 2. A polishing method for forming an electronic material for removing and planarizing a material layer to be polished on a stopper layer, wherein the material layer to be polished is polished more than the material layer to be polished. A step of exposing a lower stopper layer, which is a material layer having a low speed, and a step of exposing a high frequency during a vibration sound generated when the stopper layer is exposed.
A polishing method, comprising: detecting a change in which a component appears ; and determining an end point of polishing based on the detection result. 3. A method for manufacturing a semiconductor device, comprising at least a filling step of filling a groove formed in a base with a filling material, and a step of removing a filling material on the base by polishing. A material layer having a lower polishing rate than the material layer to be polished is formed, and in the step of removing the buried material on the substrate by the polish , a high frequency component is generated in a vibration sound generated when the stopper layer is exposed by the polish. A method for manufacturing a semiconductor device, comprising: detecting an appearing change ; and determining an end point of polishing based on the detection result.