JPS63161620A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To shorten the etching treating time by regulating the temperature of a substrate so that the predetermined etching ratio of a plurality of workpieces on the surface of the substrate is obtained and etching the workpieces. CONSTITUTION:The etching ratio of a plurality of workpieces (including semiconductor substrate 1 itself and a coating film formed onto the substrate 1) on the surface of the substrate 1 is adjusted by regulating the temperature of the substrate 1 (a sample), and the the workpieces are etched. Since the rates of changes by a temperature of the etching rates of a plurality of the workpieces (such as an insulating or conductive film 3 and a coating film 4 such as a photoresist) on the surface of the substrate 1 each differ, the temperature of the substrate 1 is regulated in a process in which the surface of the substrate 1 is plasma-etched in a decompression atmosphere, thus controlling the etching rates of a plurality of the workpieces. That is, the both etching rates can be brought to the same extent or only at least one kind of a certain material can be etched selectively.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing a semiconductor device.

The present invention relates to a method of manufacturing a semiconductor device that performs planarization etching or selective etching of a workpiece on the surface of a semiconductor substrate.

[Conventional technology]

In the manufacturing process of semiconductor devices, a workpiece such as a semiconductor substrate or a film deposited on the substrate is etched. Etching processes include planarization etching by etchback of a workpiece on the surface of a substrate, and selective etching in which only a certain workpiece is selectively removed.

For flattening etching, for example, Japanese Patent Application Laid-Open No. 52-13147
As described in No. 1, in order to fill the step difference that occurs during the manufacturing process, the etching rate must be the same as that of the material making the step (that is, the etching ratio (etching speed difference) with the step material should be A coating film of a material (approximately 1) is formed to have a flat surface, and the surface of the substrate placed in a reduced pressure atmosphere is etched with gas plasma to remove the coating film and the convex portions of the steps at the same time to flatten the semiconductor substrate.

In selective etching, etching is performed under conditions where the etching ratio of a plurality of workpieces on the surface of the substrate is high, thereby selectively removing only the workpieces with a high etching rate. (Refer to "rMO5LST Manufacturing Technology" edited by Makoto Tokuyama and Naoto Hashimoto, published in 1985, Nikkei McGraw-Hill Publishing, p. 177) [Problems to be solved by the invention] In the conventional planarization etching and selective etching methods, No consideration was given to temperature-dependent changes in the etching rate of the semiconductor substrate itself or of the film deposited on the substrate.

That is, in the conventional method, the etching rate (etching ratio) is adjusted by changing the etching conditions over time during etching. This method has the problem that it is very troublesome to operate and at the same time requires a long processing time.

In addition, in order to adjust the etching rate, it is necessary to adjust the mixture ratio of atmospheric gases and gas pressure.Especially in selective etching, the etching selection ratio can be set due to slight fluctuations in the mixture ratio or gas pressure. However, there was a problem in that it caused product defects.

In addition, in order to prevent the temperature of the coated film on the substrate from rising due to the impact of the gas plasma and changing the film quality, methods such as reducing the power for plasma excitation and etching at a low etching rate are used. Because there are
There was a problem that the processing time was long.

Furthermore, there is a restriction that a material with high heat resistance must be used in order to suppress the temperature rise of the coated film due to plasma.

SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma etching method that is high-speed and allows easy control of the etching ratio.

[Means for solving problems]

In order to achieve the above object, in a method for manufacturing a semiconductor device in which the surface of a substrate placed in a reduced pressure atmosphere is etched by gas plasma, a plurality of coatings on the surface of the substrate (sample) are removed by adjusting the temperature of the substrate (sample). The gist of this method is to etch a workpiece (including the semiconductor substrate itself and a deposited film formed on the substrate) by adjusting the etching ratio.

When performing planarization etching, after forming a coating film flat on the substrate having a step, the temperature of the substrate is adjusted so that the etching ratio of the coating film and the other workpiece is approximately 1. Adjust and perform etching.

When selective etching is performed, the temperature of the substrate is adjusted so that the etching ratio of the plurality of workpieces is increased.

[Effect]

Since the rate of change in etching rate of multiple workpieces on the substrate surface (e.g., insulating or conductive coatings and coated coatings such as photoresist) differs depending on the temperature, the process of plasma etching the substrate surface in a reduced pressure atmosphere is necessary. In this method, the etching rate of a plurality of workpieces can be controlled by adjusting the temperature of the substrate. In other words, it is possible to make the etching rates of both the same or to selectively etch only at least one type of material.

The method of the present invention, which controls the etching ratio by controlling the substrate temperature, differs from conventional methods in that the etching conditions are changed over time during etching, and in order to prevent changes in the film quality of the applied film due to temperature rise. Since it is not necessary to perform etching under conditions of low etching speed, it is possible to achieve higher etching speed than in the past.

Furthermore, since the etching ratio can be controlled by controlling the substrate temperature, it is not necessary to make strict adjustments to the gas mixture ratio, gas pressure, etc., and an extremely stable etching method can be provided.

〔Example〕

Example 1 A first example of the present invention will be described below with reference to FIGS. 1(a) and 1(b). This embodiment shows an example in which planarization etching is performed.

FIGS. 1(a) and 1(b) are schematic process cross-sectional views of an example of a semiconductor device to be processed by the method of the present invention.

In the figure, 1 is a semiconductor substrate, 2 is a step formed on the semiconductor substrate 1 and is made of, for example, a conductive film, 3 is an Sio film formed on the step 2, and 4 is a layer for filling the step. This is a sample of an organic photoresist 1 coated on a film 3 with a flat surface.

That is, as shown in FIG. 2(a), after forming a 5in2 film 3 on a semiconductor substrate 1 having a stepped portion 2 on its surface, the semiconductor device coated with an organic photoresist film 4 is subjected to parallel plate high frequency discharge plasma etching. The semiconductor device was placed on a sample stand of the apparatus at a temperature of 15.degree. C., and the sample stand was cooled to adjust the temperature of the semiconductor device, and etching was performed.

In this example, the temperature of the sample was controlled at -80°C, and the atmospheric gases were CF4 and 0.5°C. Using a mixture of gases,
Gas pressure is 100 m Torr, CF4 gas vs. 02
The gas mixing ratio (pressure ratio) is 1:1, and the input power is 30
Plasma etching was performed for 3 minutes at 0W.

As a result, as shown in FIG. 3B, it was found that the surface of the semiconductor device, that is, the surface of the photoresist film 4 and the Sin, [3, was planarized.

Note that the etching rate is 50 On for the photoresist film 4.
+m/a+in, SiO, Ff93 is 480nm/m
Flattening was achieved in approximately the same amount of time as in, and approximately 1/2 or less of the time required by the conventional method.

FIG. 2 is a diagram showing the relationship between the substrate (sample) temperature ('C) and etching rate (nm/mjn) of the photoresist film 4 and the SiO film 3 under the above etching conditions of this example. be. As is clear from this figure, when the temperature of the sample is changed, the etching rates of both types change at different rates. It was found that in order to perform planarization etching under the etching conditions of this example, it is sufficient to control the sample temperature to -85±20°C.

On the other hand, by changing the gas pressure, mixing ratio, input power, etc., the etching speed of the 5xO2 film and the photoresist film changes, but under the above etching conditions and other etching conditions, the etching rate is between -10 and -190°C. It was found that the etching ratio was less than ±20%, and planarization etching was possible.

In other words, no matter what gas pressure, mixing ratio, or input power is used to generate plasma, by controlling the sample temperature, the etching speed of both can be made to be the same, making planarization etching possible. was completed. In addition to the above-mentioned mixed gas of CF4 and 02, the atmospheric gas for flattening and etching the Sin film and the photoresist film was 5in2.
CHF, , C, which is a gas that can be used for film etching.
Fs.

Fluorocarbon gases such as C and F, fluoride gases, and 02 and F gases that can be used for etching resist films.
A mixed gas with 2, N, , H, (Q2) or each of the above gases alone can be applied.By controlling the temperature of the sample with each gas type, a flat surface as shown in Figure 1(b) can be applied. It was possible to

In the planarization etching of this example, unlike the conventional method, the etching conditions are changed over time during etching,
In order to prevent changes in the film quality of the coated film due to temperature rise, the electric power for plasma excitation is reduced, and etching is not required under conditions of low etching speed, resulting in approximately 2 times faster etching than before.
We were able to achieve double the speed of etching. Furthermore, strict adjustment of etching conditions such as gas mixture ratio and gas pressure is not required. Furthermore, in this example, etching was carried out at a low temperature, so it was possible to prevent the temperature of the coating film from rising due to plasma as in the conventional method, and it was possible to perform etching at a low etching rate and use a material with high heat resistance. There is no need to do this, and the degree of freedom in etching conditions can be increased.

Example 2 This example is also an example of planarization etching. Instead of the SiO□ film 3 shown in FIG.
In the case of coating, a mixed gas of chloride gas, fluoride gas, 02 gas, inert gas such as N2, or a single gas can be used as the atmospheric gas. CCL and Ar(5
CCf
The mixing ratio of 14 and Ar is 1:1, and the gas pressure is 200 m
Torr, when the input power is 400W, the substrate temperature dependence of the etching rate of the photoresist film and the An film is as follows.
It was found that the result was as shown in Fig. 3. That is, −
By maintaining the substrate temperature at 30±lθ℃, All
It was possible to make the etching speed of the photoresist and the photoresist about the same, and it was possible to planarize the etching of both.

When N2 gas is used instead of Ar gas in the above atmospheric gas, the etching rate of the photoresist film increases. In this case, when the partial pressure of CCa4 (or Ca1) was increased, the etching rate of the A-layer film also increased, making it possible to perform faster processing. Its effective temperature range varied depending on gas pressure and input power, and was 0 to -60°C.

In this example, the same effects as in the first example were obtained.

Example 3 This example is also an example of planarization etching. When a SiN film is used in place of the 5102 film 3 shown in FIG. Planarization etching is possible using a gas or a single gas.

When using a mixed gas of CF4+O□ (mixing ratio 1:1),
Under the conditions of a gas pressure of 200 mTorr and an input power of 300 W, the dependence of the etching rate of the SiN film and photoresist film on the substrate humidity as shown in FIG. 4 was revealed. That is, under these five conditions, the etching rates of the SiN film and the photoresist film are approximately the same at -10±10° C., and planarization etching is possible.

In the above atmospheric gas, when the partial pressure of CF is reduced, the etching rate of 5iNlli is reduced, and the effective temperature range in planarization etching is lowered. By changing the partial pressure of CF4 under the above etching conditions, the effective temperature range was -10 to -200°C.

Also, the insulation on the half-body board! (Indicated by reference numeral 3 in FIG. 1) is SiO□ shown in the above embodiment.

In addition to SiN, PSG, SOG, 5iON, RPSG, etc. can be applied, and as the conductive film (also denoted by reference numeral 3 in FIG. 1), in addition to M shown in the above embodiment, W, Mo, TiN, etc.
, A (L-Si alloy (Af1 silicide).

^ Q-Cu-3i alloy etc. can be applied, and materials such as photoresist, organic resin, SOG etc. can be applied as the coating material [(numeral 4 in Fig. 1), and any combination of these can be applied. By controlling the substrate temperature between -10 and -200°C and using a single gas or a mixture of these gases for etching each material, planarization can be performed more than twice as fast as conventional methods. , it was possible to reduce manufacturing costs. In addition, the same effects as in the above-mentioned example were obtained in this example as well.

On the other hand, as shown in FIG. 4, an etching ratio of 5 or more can be obtained when the substrate temperature is lower, around 150.degree. That is, in the case of this example, selective etching was possible under the same etching conditions as above by simply lowering the substrate temperature.

Example 4 This example is an example of selective etching according to the present invention.

Figure 5 shows the Si substrate and photoresist film when a patterned photoresist film (AZ1350J) is formed on a Si (silicon) substrate and the Si substrate is etched using only CF4 gas plasma using the photoresist film as a mask. This figure shows the dependence of the etching rate on the substrate temperature. As is clear from the figure, the lower the temperature of the board, the lower the temperature.

A large etching ratio between the Si substrate and the photoresist film could be obtained, and the Si substrate, which had a higher etching rate than the photoresist film, could be selectively etched with respect to the photoresist film. In addition, from the point of view of desirable anisotropic processing that does not cause side etching, -100 to -1
20°C was effective.

By controlling the temperature of the substrate in this way, highly selective etching becomes possible. In addition to the above CF4, S
Highly selective etching is also possible using etching gases such as FG, Ccc, and CB r F 1.

Polycrystalline Si films can also be selectively etched with respect to photoresist films and Sun films. When the substrate was kept at -90° C. or lower using SF gas, the etching rate of the polycrystalline Si film was more than 30 times that of the photoresist film, Sin. This selectivity ratio can also be changed by changing the substrate temperature.

Example 5 This example is also an example of selective etching. SF of tungsten (W) Ill formed on a Si substrate.

When etching with a gas, the etching rate of the W film at room temperature is compared with etching at room temperature and etching with the substrate cooled to 0°C, -30°C, and -70°C. If it is 1, then in the case of 0℃, it is 2/3. -30°C: l/3° -70°C: 1
/8. Therefore, by controlling the temperature of the substrate to such a low temperature, selective etching can be performed in which only the Si substrate is etched without etching the W film.

In addition to W, conductive materials such as AM and Mo, SiO, S
Highly selective etching of the same type was possible with insulating materials such as iN, Ta2O, etc., and semiconductor materials such as Si, GaAs, etc., by using the substrate temperature dependence of the etching rate according to the present invention.

In each of the above embodiments, the temperature of the substrate is controlled to a low temperature range to enable planarization etching or selective etching.

In conventional plasma etching, the substrate is usually placed on a water-cooled sample stage and etched. At this time, the substrate is heated by the ion incidence from the plasma and the reaction heat of the light radiation 1, and its temperature increases. The temperature rise depends on the input power and the thermal contact coefficient between the substrate and the sample stage. Generally, the temperature of the substrate is set at the water cooling temperature (approximately 2
It is about 10 to 50 degrees Celsius higher than 0 degrees Celsius (about 5 degrees Celsius in winter). This temperature rise can be controlled and reproduced at a constant level by adjusting the input power and taking measures against thermal contact.
Etching characteristics can be stabilized.

In the above example, it was confirmed that flattening etching and selective etching were possible by controlling the temperature of the sample to about freezing temperature or lower, including this temperature increase.

At higher temperatures, the etching rate of each workpiece increases. However, when the temperature is above about freezing and below the deterioration temperature of the mask material, the speed of side etching also increases, which is not desirable for selective microfabrication.

However, it is not necessarily necessary to cool the substrate to a low temperature range and perform etching as in the above embodiment, and it is also possible to set the substrate in a different temperature range and adjust the etching ratio to perform etching. It's no good.

〔Effect of the invention〕

As explained above, according to the present invention, planarization etching or selective etching can be performed at high speed under stable etching conditions, so the etching processing time can be reduced and manufacturing costs can be reduced. There is. Further, in selective etching, a high selectivity can be obtained, which is effective in reducing the occurrence of manufacturing defects.

[Brief explanation of the drawing]

1(a) and 1(b) are process cross-sectional views of a semiconductor device according to an embodiment of the present invention, and FIGS. 2 to 5 each show the substrate temperature dependence of the etching rate of a plurality of workpieces. It is a diagram. l... Semiconductor substrate 2... Step portion 3... 5i02 film 4... Photoresist film Representative patent attorney Junnosuke Nakamura Junior High School 1 Figure (Q) (b) 4 Small trace) - Yoshino 12 Picture base level (°C) Sai3 picture base ↓ 1 °C) Base connection return (°C)

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device in which the surface of a substrate placed in a reduced pressure atmosphere is etched using gas plasma,
A method of manufacturing a semiconductor device, characterized in that the temperature of the substrate is adjusted and etched so that a predetermined etching ratio of a plurality of workpieces on the surface of the substrate is obtained. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the etching is performed by controlling the temperature of the substrate to a low temperature below freezing temperature. 3. After forming a flat coating film on the substrate having a step, etching is performed at the temperature of the substrate such that the etching ratio of the coating film to the other workpiece is approximately 1, and the surface of the workpiece is etched. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the semiconductor device is planarized. 4. The semiconductor device manufacturing method according to claim 1, wherein selective etching of the plurality of workpieces is performed by etching at a temperature of the substrate at which an etching ratio of the plurality of workpieces is large.