JPS6387762A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve accuracy of a resistance value and integration by forming a resistor layer after burying a polycrystal silicon layer in a field oxide film, thereby forming a resistor after levelling the surface. CONSTITUTION:A field oxide film 2 is formed on a semiconductor substrate 1 and a recessed part 6 is formed with a photoetching process and then a polycrystal silicon layer with an N-or a P-type impurity added is laminated and furthermore, a photoresist layer 9 is deposited on an upper part of the polycrystal silicon layer 7 to form a flat surface. Subsequently, an anisotropy etching is performed with a gas having an almost identical etching rate on the polycrystal silicon layer 7 and the photoresist layer 9 and, when the above photoresist layer 9 and the silicon layer 7 are removed, a resistor layer 7A consisting of polycrystal silicon is left as it is. After an insulating layer 4 is selectively formed on the resistor layer 7A, the resistor 4 is completed by attaching lead-out metals 5 for electrodes to both ends of the resistor layer 7A.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of manufacturing a resistor using polycrystalline silicon.

[Conventional technology]

Conventionally, resistors used in semiconductor devices are roughly divided into, for example, diffused resistors formed in a single crystal region in a silicon substrate, and polycrystalline silicon resistors that use polycrystalline silicon on the substrate as a resistor. As higher frequencies and higher integration progress, polycrystalline silicon resistors, which are advantageous in terms of parasitic capacitance and occupied area, have come into widespread use.

FIG. 2 shows an example of a polycrystalline silicon resistor.

In FIG. 2, 1 is a semiconductor substrate, 2 is a field oxide film on the substrate, 7A is a resistor layer made of a polycrystalline silicon layer doped with N-type or P-type impurities, and 4 is on the resistor layer 7A. An insulating layer 5 is made of a silicon oxide film or the like, and 5 is an electrode lead metal for making electrical contact with the resistor layer 7A.

[Problem that the invention seeks to solve]

However, the conventional polycrystalline silicon resistor described above has the following drawbacks. That is, (1) Generally, in order to ensure the accuracy of the resistance value, it is desirable that the cross-sectional shape of the resistor layer be as vertical as possible, as shown in Figure 2. Since the step 8 is formed, the coverage of the metal 5 for leading out the electrode is deteriorated, and wire breakage and the like occur, which poses a serious problem in terms of reliability.

(2) Furthermore, in order to achieve higher integration, it is necessary to reduce the element size and the element spacing. However, the thickness of the resistor layer 7A made of polycrystalline silicon is usually 2,000 to 3,000 µm, and the thickness of the insulating layer 4 on the polycrystalline resistor layer 7A is also 2,000 to 3,000 µm. The total thickness reaches 4,000 to 6,000 people.

Therefore, if the distance between adjacent elements is not kept at least -100 cm, interference of light during the photoresist process will result in defective punching and errors in dimensional accuracy, which is critical when forming fine patterns. This becomes a major hindrance, and ultimately becomes a cause of hindering high integration.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems and provide a method for manufacturing a highly integrated semiconductor device having a resistor with a highly accurate resistance value.

[Means for solving problems]

The method of manufacturing a semiconductor device of the present invention includes the steps of forming a field oxide film on a semiconductor substrate, selectively forming a recess in the oxide film, and depositing an impurity-doped polycrystalline silicon layer at least in the recess. The process of laminating layers beyond the depth,
By stacking an organic material film on the polycrystalline silicon layer and flattening the surface, and by dry etching using a gas having approximately the same etching rate for the polycrystalline silicon and the organic material film, the areas other than the recessed areas are etched. a process of removing the polycrystalline silicon layer and the organic material film;

At least the step of selectively forming an insulating film on the polycrystalline silicon layer in the recessed region, and the step of forming a metal layer making electrical contact with the polycrystalline silicon layer in the recessed region. Ru.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1A to 1E are cross-sectional views of a semiconductor chip shown in the order of steps for explaining an example of the present invention.

First, as shown in FIG. 1(a), a field oxide film 2 is formed on a semiconductor substrate 1, and four parts 6 are formed by photolithography.
form.

Next, as shown in FIG. 1(b), a polycrystalline silicon layer doped with N or P type impurities is laminated, and then a photoresist layer 9 is deposited on top of this polycrystalline silicon layer 7 to form a flat layer. Form on the surface. At this time, the thickness of the polycrystalline silicon layer 7 may be at least the depth of the recess 6. Further, the layer above the polycrystalline silicon layer 7 may be made of an organic material other than photoresist as long as it has an appropriate viscosity and can flatten the surface, such as polyimide.

Next, as shown in FIG. 1(C), a polycrystalline silicon layer 7
and photoresist layer 9 with almost the same etching process.
When the photoresist layer 9 and the polycrystalline silicon layer 7 are removed by anisotropic etching using a gas having a certain rate, for example, a mixed gas of CCe4 and 02, a resistor layer 7A made of polycrystalline silicon is left in the four parts 6. .

Next, as shown in FIG. 1(d), after selectively forming an insulating layer 4 (for example, an oxide film) on the resistor layer 7A, electrode lead metals 5 are attached to both ends of the resistor layer 7A. As a result, a resistor made of polycrystalline silicon is completed. .

As shown in FIG. 1(e), an insulating film 4A such as an oxide film or a nitride film is laminated on the entire surface of the field oxide film 2 including on the resistor layer 7A, and a contact opening is formed. After that, a metal 5A for drawing out the electrode may be provided.

〔Effect of the invention〕

As explained above, the present invention has the following effects as a result of forming a resistor layer by burying a polycrystalline silicon layer in a field oxide film and flattening the surface to form a resistor.

(1) Not only can the step difference in the resistance layer, which is a problem in conventional manufacturing methods, be eliminated, but also the cross-sectional shape can be maintained as it is, so a semiconductor device equipped with a resistor having a highly accurate resistance value can be obtained.

(2) Light interference during exposure in the photoresist process due to the polycrystalline silicon resistor can be eliminated;
The element region can be formed very close to the resistor, and high integration of the semiconductor device can be realized.

[Brief explanation of the drawing]

FIGS. 1(a) to (e) are cross-sectional views of a semiconductor chip shown in the order of steps for explaining an embodiment of the present invention, and FIG. 2 is a cross-sectional view for explaining an example of a conventional semiconductor device. be. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 2... Oxide film for field, 4
゜4A...Insulating layer, 4,5A...Metal for electrode extraction, 6...Concave portion, 7...Polycrystalline silicon layer, 7A...
- Resistor layer, 8... Step, 9... Photoresist layer. Otsu I! I name p Kaya/Ki

Claims (1)

[Claims] A step of forming a field oxide film on a semiconductor substrate, a step of selectively forming a recess in the oxide film, and a step of stacking a polycrystalline silicon layer doped with impurities over the entire surface to a depth at least equal to or greater than the depth of the recess. The recessed portion is formed by stacking an organic material film on the polycrystalline silicon layer and flattening the surface, and dry etching using a gas having substantially the same etching rate for the multilayer crystalline silicon and the organic material film. a step of removing the polycrystalline silicon layer and an organic material film other than the region; a step of selectively forming an insulating film on at least the polycrystalline silicon layer in the recessed region; and a step of selectively forming an insulating film on the polycrystalline silicon layer in the recessed region. 1. A method of manufacturing a semiconductor device, comprising: forming a metal layer for making electrical contact with the semiconductor device.